@article{YazmaciyanStolterfohtBurnetal.2018, author = {Yazmaciyan, Aren and Stolterfoht, Martin and Burn, Paul L. and Lin, Qianqian and Meredith, Paul and Armin, Ardalan}, title = {Recombination losses above and below the transport percolation threshold in bulk heterojunction organic solar cells}, series = {Advanced energy materials}, volume = {8}, journal = {Advanced energy materials}, number = {18}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1614-6832}, doi = {10.1002/aenm.201703339}, pages = {8}, year = {2018}, abstract = {Achieving the highest power conversion efficiencies in bulk heterojunction organic solar cells requires a morphology that delivers electron and hole percolation pathways for optimized transport, plus sufficient donor:acceptor contact area for near unity charge transfer state formation. This is a significant structural challenge, particularly in semiconducting polymer:fullerene systems. This balancing act in the model high efficiency PTB7:PC70BM blend is studied by tuning the donor:acceptor ratio, with a view to understanding the recombination loss mechanisms above and below the fullerene transport percolation threshold. The internal quantum efficiency is found to be strongly correlated to the slower carrier mobility in agreement with other recent studies. Furthermore, second-order recombination losses dominate the shape of the current density-voltage curve in efficient blend combinations, where the fullerene phase is percolated. However, below the charge transport percolation threshold, there is an electric-field dependence of first-order losses, which includes electric-field-dependent photogeneration. In the intermediate regime, the fill factor appears to be limited by both first- and second-order losses. These findings provide additional basic understanding of the interplay between the bulk heterojunction morphology and the order of recombination in organic solar cells. They also shed light on the limitations of widely used transport models below the percolation threshold.}, language = {en} } @article{YeZhangWarbyetal.2022, author = {Ye, Fangyuan and Zhang, Shuo and Warby, Jonathan and Wu, Jiawei and Gutierrez-Partida, Emilio and Lang, Felix and Shah, Sahil and Saglamkaya, Elifnaz and Sun, Bowen and Zu, Fengshuo and Shoaee, Safa and Wang, Haifeng and Stiller, Burkhard and Neher, Dieter and Zhu, Wei-Hong and Stolterfoht, Martin and Wu, Yongzhen}, title = {Overcoming C-60-induced interfacial recombination in inverted perovskite solar cells by electron-transporting carborane}, series = {Nature Communications}, volume = {13}, journal = {Nature Communications}, number = {1}, publisher = {Nature Publishing Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/s41467-022-34203-x}, pages = {12}, year = {2022}, abstract = {Inverted perovskite solar cells still suffer from significant non-radiative recombination losses at the perovskite surface and across the perovskite/C-60 interface, limiting the future development of perovskite-based single- and multi-junction photovoltaics. Therefore, more effective inter- or transport layers are urgently required. To tackle these recombination losses, we introduce ortho-carborane as an interlayer material that has a spherical molecular structure and a three-dimensional aromaticity. Based on a variety of experimental techniques, we show that ortho-carborane decorated with phenylamino groups effectively passivates the perovskite surface and essentially eliminates the non-radiative recombination loss across the perovskite/C-60 interface with high thermal stability. We further demonstrate the potential of carborane as an electron transport material, facilitating electron extraction while blocking holes from the interface. The resulting inverted perovskite solar cells deliver a power conversion efficiency of over 23\% with a low non-radiative voltage loss of 110mV, and retain >97\% of the initial efficiency after 400h of maximum power point tracking. Overall, the designed carborane based interlayer simultaneously enables passivation, electron-transport and hole-blocking and paves the way toward more efficient and stable perovskite solar cells. Effective transport layers are essential to suppress non-radiative recombination losses. Here, the authors introduce phenylamino-functionalized ortho-carborane as an interfacial layer, and realise inverted perovskite solar cells with efficiency of over 23\% and operational stability of T97=400h.}, language = {en} } @article{YeZhangWarbyetal.2022, author = {Ye, Fangyuan and Zhang, Shuo and Warby, Jonathan and Wu, Jiawei and Gutierrez-Partida, Emilio and Lang, Felix and Shah, Sahil and Saglamkaya, Elifnaz and Sun, Bowen and Zu, Fengshuo and Shoai, Safa and Wang, Haifeng and Stiller, Burkhard and Neher, Dieter and Zhu, Wei-Hong and Stolterfoht, Martin and Wu, Yongzhen}, title = {Overcoming C₆₀-induced interfacial recombination in inverted perovskite solar cells by electron-transporting carborane}, series = {Nature Communications}, volume = {13}, journal = {Nature Communications}, number = {1}, publisher = {Springer Nature}, address = {London}, issn = {2041-1723}, doi = {10.1038/s41467-022-34203-x}, pages = {12}, year = {2022}, abstract = {Inverted perovskite solar cells still suffer from significant non-radiative recombination losses at the perovskite surface and across the perovskite/C₆₀ interface, limiting the future development of perovskite-based single- and multi-junction photovoltaics. Therefore, more effective inter- or transport layers are urgently required. To tackle these recombination losses, we introduce ortho-carborane as an interlayer material that has a spherical molecular structure and a three-dimensional aromaticity. Based on a variety of experimental techniques, we show that ortho-carborane decorated with phenylamino groups effectively passivates the perovskite surface and essentially eliminates the non-radiative recombination loss across the perovskite/C₆₀ interface with high thermal stability. We further demonstrate the potential of carborane as an electron transport material, facilitating electron extraction while blocking holes from the interface. The resulting inverted perovskite solar cells deliver a power conversion efficiency of over 23\% with a low non-radiative voltage loss of 110 mV, and retain >97\% of the initial efficiency after 400 h of maximum power point tracking. Overall, the designed carborane based interlayer simultaneously enables passivation, electron-transport and hole-blocking and paves the way toward more efficient and stable perovskite solar cells.}, language = {en} } @article{YeKurthHospodarskyetal.2018, author = {Ye, S. -Y. and Kurth, William S. and Hospodarsky, George B. and Persoon, Ann M. and Gurnett, Don A. and Morooka, Michiko and Wahlund, Jan-Erik and Hsu, Hsiang-Wen and Seiss, Martin and Srama, Ralf}, title = {Cassini RPWS dust observation near the Janus/Epimetheus orbit}, series = {Journal of geophysical research : Space physics}, volume = {123}, journal = {Journal of geophysical research : Space physics}, number = {6}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1029/2017JA025112}, pages = {4952 -- 4960}, year = {2018}, abstract = {During the Ring Grazing orbits near the end of Cassini mission, the spacecraft crossed the equatorial plane near the orbit of Janus/Epimetheus (similar to 2.5 Rs). This region is populated with dust particles that can be detected by the Radio and Plasma Wave Science (RPWS) instrument via an electric field antenna signal. Analysis of the voltage waveforms recorded on the RPWS antennas provides estimations of the density and size distribution of the dust particles. Measured RPWS profiles, fitted with Lorentzian functions, are shown to be mostly consistent with the Cosmic Dust Analyzer, the dedicated dust instrument on board Cassini. The thickness of the dusty ring varies between 600 and 1,000 km. The peak location shifts north and south within 100 km of the ring plane, likely a function of the precession phase of Janus orbit.}, language = {en} } @article{YeKurthHospodarskyetal.2018, author = {Ye, Shengyi and Kurth, William S. and Hospodarsky, George B. and Persoon, Ann M. and Sulaiman, Ali H. and Gurnett, Don A. and Morooka, Michiko and Wahlund, Jan-Erik and Hsu, Hsiang-Wen and Sternovsky, Zoltan and Wang, Xu and Horanyi, M. and Seiss, Martin and Srama, Ralf}, title = {Dust Observations by the Radio and Plasma Wave Science Instrument During}, series = {Geophysical research letters}, volume = {45}, journal = {Geophysical research letters}, number = {19}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2018GL078059}, pages = {10101 -- 10109}, year = {2018}, abstract = {Plain Language Summary Cassini flew through the gap between Saturn and its rings for 22 times before plunging into the atmosphere of Saturn, ending its 20-year mission. The radio and plasma waves instrument on board Cassini helped quantify the dust hazard in this previously unexplored region. The measured density of large dust particles was much lower than expected, allowing high-value science observations during the subsequent Grand Finale orbits.}, language = {en} } @article{YeldesbayPikovskijRosenblum2014, author = {Yeldesbay, Azamat and Pikovskij, Arkadij and Rosenblum, Michael}, title = {Chimeralike states in an ensemble of globally coupled oscillators}, series = {Physical review letters}, volume = {112}, journal = {Physical review letters}, number = {14}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.112.144103}, pages = {5}, year = {2014}, abstract = {We demonstrate the emergence of a complex state in a homogeneous ensemble of globally coupled identical oscillators, reminiscent of chimera states in nonlocally coupled oscillator lattices. In this regime some part of the ensemble forms a regularly evolving cluster, while all other units irregularly oscillate and remain asynchronous. We argue that the chimera emerges because of effective bistability, which dynamically appears in the originally monostable system due to internal delayed feedback in individual units. Additionally, we present two examples of chimeras in bistable systems with frequency-dependent phase shift in the global coupling.}, language = {en} } @article{YestePrimusAlcantaraetal.2020, author = {Yeste, Maria Pilar and Primus, Philipp-Alexander and Alcantara, Rodrigo and Cauqui, Miguel Angel and Calvino, Juan Jose and Pintado, Jos{\´e} Mar{\´i}a and Blanco, Ginesa}, title = {Surface characterization of two Ce0.62Zr0.38O2 mixed oxides with different reducibility}, series = {Applied surface science : a journal devoted to applied physics and chemistry of surfaces and interfaces}, volume = {503}, journal = {Applied surface science : a journal devoted to applied physics and chemistry of surfaces and interfaces}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2019.144255}, pages = {9}, year = {2020}, abstract = {This paper presents a study of the surface properties of two Ce/Zr mixed oxides with different reducibility, obtained by applying distinct thermal ageing treatments to an oxide with the composition Ce0.62Zr0.38O2. The surface composition was investigated by XPS. Chemical reactivity of the surface was studied by adsorption of the probe molecules CO2, D-2 and methanol. Nanostructural characterization was carried out by XRD, Raman and high-resolution Eu3+ spectroscopy (FLNS). The characterization showed only slight variations in surface composition and bulk Ce-Zr distribution, but hardy differences concerning the type and strength of acidic surface centres, as well as strong differences in the ability to dissociate hydrogen. Structural variations between both samples were identified by comparing the optical spectra of Eu3+ in surface doped samples.}, language = {en} } @article{YilmazWirgesBauerGogoneaetal.1997, author = {Yilmaz, S{\"u}kr{\"u} and Wirges, Werner and Bauer-Gogonea, Simona and Bauer, Siegfried and Gerhard, Reimund and Michelotti, F. and Toussaere, E. and Levenson, R. and Liang, J. and Zyss, Joseph}, title = {Dielectric, pyroelectric and electro-optic monitoring of the cross-linking process and photo-induced poling of Red Acid Magly}, year = {1997}, language = {en} } @article{YinInhesterVeeduetal.2017, author = {Yin, Zhong and Inhester, Ludger and Veedu, Sreevidya Thekku and Quevedo, Wilson and Pietzsch, Annette and Wernet, Philippe and Groenhof, Gerrit and F{\"o}hlisch, Alexander and Grubmueller, Helmut and Techert, Simone}, title = {Cationic and Anionic Impact on the Electronic Structure of Liquid Water}, series = {The journal of physical chemistry letters}, volume = {8}, journal = {The journal of physical chemistry letters}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.7b01392}, pages = {3759 -- 3764}, year = {2017}, abstract = {Hydration shells around ions are crucial for many fundamental biological and chemical processes. Their local physicochemical properties are quite different from those of bulk water and hard to probe experimentally. We address this problem by combining soft X-ray spectroscopy using a liquid jet and molecular dynamics (MD) simulations together with ab initio electronic structure calculations to elucidate the water ion interaction in a MgCl2 solution at the molecular level. Our results reveal that salt ions mainly affect the electronic properties of water molecules in close vicinity and that the oxygen K-edge X-ray emission spectrum of water molecules in the first solvation shell differs significantly from that of bulk water. Ion-specific effects are identified by fingerprint features in the water X-ray emission spectra. While Mg2+ ions cause a bathochromic shift of the water lone pair orbital, the 3p orbital of the Cl- ions causes an additional peak in the water emission spectrum at around 528 eV.}, language = {en} } @article{YinRajkovicKubiceketal.2014, author = {Yin, Zhong and Rajkovic, Ivan and Kubicek, Katharina and Quevedo, Wilson and Pietzsch, Annette and Wernet, Philippe and F{\"o}hlisch, Alexander and Techert, Simone}, title = {Probing the Hofmeister effect with ultrafast core-hole spectroscopy}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {118}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {31}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/jp504577a}, pages = {9398 -- 9403}, year = {2014}, abstract = {In the current work, X-ray emission spectra of aqueous solutions of different inorganic salts within the Hofmeister series are presented. The results reflect the direct interaction of the ions with the water molecules and therefore, reveal general properties of the salt-water interactions. Within the experimental precision a significant effect of the ions on the water structure has been observed but no ordering according to the structure maker/structure breaker concept could be mirrored in the results indicating that the Hofmeister effect if existent may be caused by more complex interactions.}, language = {en} } @article{YinRajkovicVeeduetal.2015, author = {Yin, Zhong and Rajkovic, Ivan and Veedu, Sreevidya Thekku and Deinert, Sascha and Raiser, Dirk and Jain, Rohit and Fukuzawa, Hironobu and Wada, Shin-ichi and Quevedo, Wilson and Kennedy, Brian and Schreck, Simon and Pietzsch, Annette and Wernet, Philippe and Ueda, Kyoshi and F{\"o}hlisch, Alexander and Techert, Simone}, title = {Ionic solutions probed by resonant inelastic X-ray scattering}, series = {Zeitschrift f{\"u}r physikalische Chemie : international journal of research in physical chemistry and chemical physics}, volume = {229}, journal = {Zeitschrift f{\"u}r physikalische Chemie : international journal of research in physical chemistry and chemical physics}, number = {10-12}, publisher = {De Gruyter}, address = {Berlin}, issn = {0942-9352}, doi = {10.1515/zpch-2015-0610}, pages = {1855 -- 1867}, year = {2015}, abstract = {X-ray spectroscopy is a powerful tool to study the local charge distribution of chemical systems. Together with the liquid jet it becomes possible to probe chemical systems in their natural environment, the liquid phase. In this work, we present X-ray absorption (XA), X-ray emission (XE) and resonant inelastic X-ray scattering (RIXS) data of pure water and various salt solutions and show the possibilities these methods offer to elucidate the nature of ion-water interaction.}, language = {en} } @article{YochelisBetaGov2020, author = {Yochelis, Arik and Beta, Carsten and Gov, Nir S.}, title = {Excitable solitons}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {101}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, number = {2}, publisher = {American Physical Society}, address = {Melville, NY}, issn = {2470-0045}, doi = {10.1103/PhysRevE.101.022213}, pages = {6}, year = {2020}, abstract = {Excitable pulses are among the most widespread dynamical patterns that occur in many different systems, ranging from biological cells to chemical reactions and ecological populations. Traditionally, the mutual annihilation of two colliding pulses is regarded as their prototypical signature. Here we show that colliding excitable pulses may exhibit solitonlike crossover and pulse nucleation if the system obeys a mass conservation constraint. In contrast to previous observations in systems without mass conservation, these alternative collision scenarios are robustly observed over a wide range of parameters. We demonstrate our findings using a model of intracellular actin waves since, on time scales of wave propagations over the cell scale, cells obey conservation of actin monomers. The results provide a key concept to understand the ubiquitous occurrence of actin waves in cells, suggesting why they are so common, and why their dynamics is robust and long-lived.}, language = {en} } @article{YoonLopezVafinetal.2017, author = {Yoon, P. H. and Lopez, R. A. and Vafin, Sergei and Kim, S. and Schlickeiser, R.}, title = {Spontaneous emission of Alfvenic fluctuations}, series = {Plasma physics and controlled fusion}, volume = {59}, journal = {Plasma physics and controlled fusion}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0741-3335}, doi = {10.1088/1361-6587/aa77c3}, pages = {8}, year = {2017}, abstract = {Low-frequency fluctuations are pervasively observed in the solar wind. The present paper theoretically calculates the steady state spectra of low-frequency electromagnetic (EM) fluctuations of the Alfvenic type for thermal equilibrium plasma. The analysis is based upon a recently formulated theory of spontaneously emitted EM fluctuations in magnetized thermal plasmas. It is found that the fluctuations in the magnetosonic mode branch is constant, while the kinetic Alfvenic mode spectrum is dependent on a form factor that is a function of perpendicular wave number. Potential applicability of the present work in the wider context of heliospheric research is also discussed.}, language = {en} } @article{YoonLangerScheithauer2004, author = {Yoon, S.-C. and Langer, Norbert and Scheithauer, S.}, title = {Effects of rotation on the helium burning shell source in accreting white dwarfs}, issn = {0004-6361}, year = {2004}, abstract = {We investigate the effects of rotation on the behavior of the helium-burning shell source in accreting carbon- oxygen white dwarfs, in the context of the single degenerate Chandrasekhar mass progenitor scenario for type la supernovae (SNe Ia). We model the evolution of helium-accreting white dwarfs of initially 1 M-circle dot, assuming four different constant accretion rates (2, 3, 5 and 10 x 10(-7) M-circle dot/yr). In a one-dimensional approximation, we compute the mass accretion and subsequent nuclear fusion of helium into carbon and oxygen, as well as angular momentum accretion, angular momentum transport inside the white dwarf, and rotationally induced chemical mixing. Our models show two major effects of rotation: a) The helium-burning nuclear shell source in the rotating models is much more stable than in corresponding non-rotating models - which increases the likelihood that accreting white dwarfs reach the stage of central carbon ignition. This effect is mainly due to rotationally induced mixing at the CO/He interface which widens the shell source, and due to the centrifugal force lowering the density and degeneracy at the shell source location. b) The C/O-ratio in the layers which experience helium shell burning - which may affect the energy of an SN Ia explosion - is strongly decreased by the rotationally induced mixing of a-particles into the carbon-rich layers. We discuss implications of our results for the evolution of SNe la progenitors}, language = {en} } @article{YorkJacksonBrowneetal.2005, author = {York, T. and Jackson, N. and Browne, Ian W. A. and Wucknitz, Olaf and Skelton, J. E.}, title = {The Hubble constant from the gravitational lens CLASS B0218+357 using the Advanced Camera for Surveys}, issn = {0035-8711}, year = {2005}, abstract = {We present deep optical observations of the gravitational lens system CLASS B0218 + 357, from which we derive an estimate for the Hubble constant (H-0). Extensive radio observations using the VLA, MERLIN, the VLBA and VLBI have reduced the degeneracies between H-0 and the mass model parameters in this lens to one involving only the position of the radio-quiet lensing galaxy with respect to the lensed images. B0218 + 357 has an image separation of only 334 mas, so optical observations have, up until now, been unable to resolve the lens galaxy from the bright lensed images. Using the new Advanced Camera for Surveys (ACS), installed on the Hubble Space Telescope in 2002, we have obtained deep optical images of the lens system and surrounding field. These observations have allowed us to determine the separation between the lens galaxy centre and the brightest image, and so estimate H-0. We find an optical galaxy position, and hence an H0 value, that varies depending on our approach to the spiral arms in B0218 + 357. If the most prominent spiral arms are left unmasked, we find H-0 = 70 +/- 5 km s(-1) Mpc(-1) (95 per cent confidence). If the spiral arms are masked out, we find H-0 = 61 +/- 7 km s(-1) Mpc(-1) (95 per cent confidence)}, language = {en} } @article{YoungUedaGuehretal.2018, author = {Young, Linda and Ueda, Kiyoshi and G{\"u}hr, Markus and Bucksbaum, Philip H. and Simon, Marc and Mukamel, Shaul and Rohringer, Nina and Prince, Kevin C. and Masciovecchio, Claudio and Meyer, Michael and Rudenko, Artem and Rolles, Daniel and Bostedt, Christoph and Fuchs, Matthias and Reis, David A. and Santra, Robin and Kapteyn, Henry and Murnane, Margaret and Ibrahim, Heide and Legare, Francois and Vrakking, Marc and Isinger, Marcus and Kroon, David and Gisselbrecht, Mathieu and W{\"o}rner, Hans Jakob and Leone, Stephen R.}, title = {Roadmap of ultrafast x-ray atomic and molecular physics}, series = {Journal of physics : B, Atomic, molecular and optical physics}, volume = {51}, journal = {Journal of physics : B, Atomic, molecular and optical physics}, number = {3}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0953-4075}, doi = {10.1088/1361-6455/aa9735}, pages = {45}, year = {2018}, abstract = {X-ray free-electron lasers (XFELs) and table-top sources of x-rays based upon high harmonic generation (HHG) have revolutionized the field of ultrafast x-ray atomic and molecular physics, largely due to an explosive growth in capabilities in the past decade. XFELs now provide unprecedented intensity (10(20) W cm(-2)) of x-rays at wavelengths down to similar to 1 Angstrom, and HHG provides unprecedented time resolution (similar to 50 attoseconds) and a correspondingly large coherent bandwidth at longer wavelengths. For context, timescales can be referenced to the Bohr orbital period in hydrogen atom of 150 attoseconds and the hydrogen-molecule vibrational period of 8 femtoseconds; wavelength scales can be referenced to the chemically significant carbon K-edge at a photon energy of similar to 280 eV (44 Angstroms) and the bond length in methane of similar to 1 Angstrom. With these modern x-ray sources one now has the ability to focus on individual atoms, even when embedded in a complex molecule, and view electronic and nuclear motion on their intrinsic scales (attoseconds and Angstroms). These sources have enabled coherent diffractive imaging, where one can image non-crystalline objects in three dimensions on ultrafast timescales, potentially with atomic resolution. The unprecedented intensity available with XFELs has opened new fields of multiphoton and nonlinear x-ray physics where behavior of matter under extreme conditions can be explored. The unprecedented time resolution and pulse synchronization provided by HHG sources has kindled fundamental investigations of time delays in photoionization, charge migration in molecules, and dynamics near conical intersections that are foundational to AMO physics and chemistry. This roadmap coincides with the year when three new XFEL facilities, operating at Angstrom wavelengths, opened for users (European XFEL, Swiss-FEL and PAL-FEL in Korea) almost doubling the present worldwide number of XFELs, and documents the remarkable progress in HHG capabilities since its discovery roughly 30 years ago, showcasing experiments in AMO physics and other applications. Here we capture the perspectives of 17 leading groups and organize the contributions into four categories: ultrafast molecular dynamics, multidimensional x-ray spectroscopies; high-intensity x-ray phenomena; attosecond x-ray science.}, language = {en} } @article{YuanZhangQiuetal.2022, author = {Yuan, Jun and Zhang, Chujun and Qiu, Beibei and Liu, Wei and So, Shu Kong and Mainville, Mathieu and Leclerc, Mario and Shoaee, Safa and Neher, Dieter and Zou, Yingping}, title = {Effects of energetic disorder in bulk heterojunction organic solar cells}, series = {Energy \& environmental science}, volume = {15}, journal = {Energy \& environmental science}, number = {7}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1754-5692}, doi = {10.1039/d2ee00271j}, pages = {2806 -- 2818}, year = {2022}, abstract = {Organic solar cells (OSCs) have progressed rapidly in recent years through the development of novel organic photoactive materials, especially non-fullerene acceptors (NFAs). Consequently, OSCs based on state-of-the-art NFAs have reached significant milestones, such as similar to 19\% power conversion efficiencies (PCEs) and small energy losses (less than 0.5 eV). Despite these significant advances, understanding of the interplay between molecular structure and optoelectronic properties lags significantly behind. For example, despite the theoretical framework for describing the energetic disorder being well developed for the case of inorganic semiconductors, the question of the applicability of classical semiconductor theories in analyzing organic semiconductors is still under debate. A general observation in the inorganic field is that inorganic photovoltaic materials possessing a polycrystalline microstructure exhibit suppressed disorder properties and better charge carrier transport compared to their amorphous analogs. Accordingly, this principle extends to the organic semiconductor field as many organic photovoltaic materials are synthesized to pursue polycrystalline-like features. Yet, there appears to be sporadic examples that exhibit an opposite trend. However, full studies decoupling energetic disorder from aggregation effects have largely been left out. Hence, the potential role of the energetic disorder in OSCs has received little attention. Interestingly, recently reported state-of-the-art NFA-based devices could achieve a small energetic disorder and high PCE at the same time; and interest in this investigation related to the disorder properties in OSCs was revived. In this contribution, progress in terms of the correlation between molecular design and energetic disorder is reviewed together with their effects on the optoelectronic mechanism and photovoltaic performance. Finally, the specific challenges and possible solutions in reducing the energetic disorder of OSCs from the viewpoint of materials and devices are proposed.}, language = {en} } @article{ZablBoucheSchroetteretal.2019, author = {Zabl, Johannes and Bouche, Nicolas F. and Schroetter, Ilane and Wendt, Martin and Finley, Hayley and Schaye, Joop and Conseil, Simon and Contini, Thierry and Marino, Raffaella Anna and Mitchell, Peter and Muzahid, Sowgat and Pezzulli, Gabriele and Wisotzki, Lutz}, title = {MusE GAs FLOw and Wind (MEGAFLOW)}, series = {Monthly notices of the Royal Astronomical Society}, volume = {485}, journal = {Monthly notices of the Royal Astronomical Society}, number = {2}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stz392}, pages = {1961 -- 1980}, year = {2019}, abstract = {We use the MusE GAs FLOw and Wind (MEGAFLOW) survey to study the kinematics of extended disc-like structures of cold gas around z approximate to 1 star-forming galaxies. The combination of VLT/MUSE and VLT/UVES observations allows us to connect the kinematics of the gas measured through MgII quasar absorption spectroscopy to the kinematics and orientation of the associated galaxies constrained through integral field spectroscopy. Confirming previous results, we find that the galaxy-absorber pairs of the MEGAFLOW survey follow a strong bimodal distribution, consistent with a picture of MgII absorption being predominantly present in outflow cones and extended disc-like structures. This allows us to select a bona-fide sample of galaxy-absorber pairs probing these discs for impact paramometers of 10-70 kpc. We test the hypothesis that the disc-like gas is co-rotating with the galaxy discs, and find that for seven out of nine pairs the absorption velocity shares the sign of the disc velocity, disfavouring random orbits. We further show that the data are roughly consistent with inflow velocities and angular momenta predicted by simulations, and that the corresponding mass accretion rates are sufficient to balance the star formation rates.}, language = {en} } @article{ZachariasChenWagner2017, author = {Zacharias, Michael and Chen, Xuhui and Wagner, Stefan}, title = {Attenuation of TeV gamma-rays by the starlight photon field of the host galaxy}, series = {Monthly notices of the Royal Astronomical Society}, volume = {465}, journal = {Monthly notices of the Royal Astronomical Society}, number = {3}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stw3032}, pages = {3767 -- 3774}, year = {2017}, abstract = {The absorption of TeV gamma-ray photons produced in relativistic jets by surrounding soft photon fields is a long-standing problem of jet physics. In some cases, the most likely emission site close to the central black hole is ruled out because of the high opacity caused by strong optical and infrared photon sources, such as the broad-line region. Mostly neglected for jet modelling is the absorption of gamma-rays in the starlight photon field of the host galaxy. Analysing the absorption for arbitrary locations and observation angles of the gamma-ray emission site within the host galaxy, we find that the distance to the galaxy centre, the observation angle, and the distribution of starlight in the galaxy are crucial for the amount of absorption. We derive the absorption value for a sample of 20 TeV-detected blazars with a redshift z(r) < 0.2. The absorption value of the gamma-ray emission located in the galaxy centre may be as high as 20 per cent, with an average value of 6 per cent. This is important in order to determine the intrinsic blazar parameters. We see no significant trends in our sample between the degree of absorption and host properties, such as starlight emissivity, galactic size, half-light radius, and redshift. While the uncertainty of the spectral properties of the extragalactic background light exceeds the effect of absorption by stellar light from the host galaxy in distant objects, the latter is a dominant effect in nearby sources. It may also be revealed in a differential comparison of sources with similar redshifts.}, language = {en} } @article{ZaikinGarciaOjalvoSchimanskyGeier1999, author = {Zaikin, Alexei A. and Garcia-Ojalvo, Jordi and Schimansky-Geier, Lutz}, title = {Nonequilibrium first-order phase transition inducd by additive noise}, year = {1999}, language = {en} } @article{ZaikinGarciaOjalvoSchimanskyGeieretal.2002, author = {Zaikin, Alexei A. and Garc{\´i}a-Ojalvo, Jordi and Schimansky-Geier, Lutz and Kurths, J{\"u}rgen}, title = {Noise induced propagation in monostable media}, year = {2002}, abstract = {We show that external fluctuations are able to induce propagation of harmonic signals through monostable media. This property is based on the phenomenon of doubly stochastic resonance, where the joint action of multiplicative noise and spatial coupling induces bistability in an otherwise monostable extended medium, and additive noise resonantly enhances the response of the system to a harmonic forcing. Under these conditions, propagation of the harmonic signal through the unforced medium i observed for optimal intensities of the two noises. This noise-induced propagation is studied and quantified in a simple model of coupled nonlinear electronic circuits.}, language = {en} } @article{ZaikinKurths2001, author = {Zaikin, Alexei A. and Kurths, J{\"u}rgen}, title = {Additive noise in noise-induced nonequilibrium transitions}, issn = {1054-1500}, year = {2001}, language = {en} } @article{ZaikinKurths2000, author = {Zaikin, Alexei A. and Kurths, J{\"u}rgen}, title = {Additive noise and noise-induced nonequilibrium phase transitions}, isbn = {1-563-96826-6}, year = {2000}, language = {en} } @article{ZaikinKurths1999, author = {Zaikin, Alexei A. and Kurths, J{\"u}rgen}, title = {Modeling Cognitive Control in Simple Movements}, isbn = {1-563-96863-0}, year = {1999}, language = {en} } @article{ZaikinKurthsSchimanskyGeier2000, author = {Zaikin, Alexei A. and Kurths, J{\"u}rgen and Schimansky-Geier, Lutz}, title = {Doubly stochastic resonance}, year = {2000}, abstract = {We report the effect of doubly stochastic resonance which appears in nonlinear extended systems if the influence of noise is twofold: A multiplicative noise induces bimodality of the mean field of the coupled network and an independent additive noise governs the dynamic behavior in response to small periodic driving. For optimally selected values of the additive noise intensity stochastic resonance is observed, which is manifested by a maximal coherence between the dynamics of the mean field and the periodic input. Numerical simulations of the signal-to-noise ratio and theoretical results from an effective two state model are in good quantitative agreement.}, language = {en} } @article{ZaikinLopezBaltanasetal.2002, author = {Zaikin, Alexei A. and L{\´o}pez, L and Baltan{\´a}s, J. P. and Kurths, J{\"u}rgen and Sanjuan, Miguel Angel Fern{\´a}ndez}, title = {Vibrational resonance in noise-induced structure}, year = {2002}, abstract = {We report on the effect of vibrational resonance in a spatially extended system of coupled noisy oscillators under the action of two periodic forces, a low-frequency one (signal) and a high-frequency one (carrier). Vibrational resonance manifests itself in the fact that for optimally selected values of high-frequency force amplitude, the response of the system to a low-frequency signal is optimal. This phenomenon is a synthesis of two effects, a noise- induced phase transition leading to bistability, and a conventional vibrational resonance, resulting in the optimization of signal processing. Numerical simulations, which demonstrate this effect for an extended system, can be understood by means of a zero-dimensional "effective" model. The behavior of this "effective" model is also confirmed by an experimental realization of an electronic circuit.}, language = {en} } @article{ZaikinMuraliKurths2001, author = {Zaikin, Alexei A. and Murali, K. and Kurths, J{\"u}rgen}, title = {Simple electronic circuit model for doubly stochastic resonance}, year = {2001}, abstract = {We have recently reported the phenomenon of doubly stochastic resonance [Phys. Rev. Lett. 85, 227 (2000)], a synthesis of noise-induced transition and stochastic resonance. The essential feature of this phenomenon is that multiplicative noise induces a bimodality and additive noise causes stochastic resonance behavior in the induced structure. In the present paper we outline possible applications of this effect and design a simple lattice of electronic circuits for the experimental realization of doubly stochastic resonance.}, language = {en} } @article{ZaikinRosenblumLandaetal.1998, author = {Zaikin, Alexei A. and Rosenblum, Michael and Landa, Polina S. and Kurths, J{\"u}rgen}, title = {On-off itermittency phenomena in a pendulum with a randomly vibrating suspension axis}, year = {1998}, language = {en} } @article{ZaikinRosenblumLandaetal.1997, author = {Zaikin, Alexei A. and Rosenblum, Michael and Landa, Polina S. and Kurths, J{\"u}rgen}, title = {Control of noise-induced oscillations of a pendulum with a rondomly vibrating suspension axis}, year = {1997}, language = {en} } @article{ZaikinRosenblumScheffczyketal.1997, author = {Zaikin, Alexei A. and Rosenblum, Michael and Scheffczyk, Christian and Engbert, Ralf and Krampe, Ralf-Thomas and Kurths, J{\"u}rgen}, title = {Modeling qualitative changes in bimanual movements}, year = {1997}, language = {en} } @article{ZaikinSchimanskyGeier1999, author = {Zaikin, Alexei A. and Schimansky-Geier, Lutz}, title = {Ordering role of additive noise in extended media}, issn = {1373-5411}, year = {1999}, language = {en} } @article{ZaikinTopajGarciaOjalvo2002, author = {Zaikin, Alexei A. and Topaj, Dmitri and Garcia-Ojalvo, Jordi}, title = {Noise-enhanced propagation of bichromatic signals}, year = {2002}, abstract = {We examine the influence of noise on the propagation of harmonic signals with two frequencies through discrete bistable media. We show that random fluctuations enhance propagation of this kind of signals for low coupling strengths, similarly to what happens with purely monochromatic signals. As a more relevant finding, we observe that the frequency being propagated with better efficiency can be selected by tuning the intensity of the noise, in such a way that for large noises the highest frequency is transmitted better than the lower one, whereas for small noises the reverse holds. Such a noise-induced frequency selection can be expected to exist for general multifrequency harmonic signals.}, language = {en} } @article{ZaikinKurthsSaparinetal.2005, author = {Zaikin, Alexei and Kurths, J{\"u}rgen and Saparin, Peter and Gowin, W. and Prohaska, Steffen}, title = {Modeling bone resorption in 2D CT and 3D mu CT images}, issn = {0218-1274}, year = {2005}, abstract = {We study several algorithms to simulate bone mass loss in two-dimensional and three-dimensional computed tomography bone images. The aim is to extrapolate and predict the bone loss, to provide test objects for newly developed structural measures, and to understand the physical mechanisms behind the bone alteration. Our bone model approach differs from those already reported in the literature by two features. First, we work with original bone images, obtained by computed tomography (CT); second, we use structural measures of complexity to evaluate bone resorption and to compare it with the data provided by CT. This gives us the possibility to test algorithms of bone resorption by comparing their results with experimentally found dependencies of structural measures of complexity, as well as to show efficiency of the complexity measures in the analysis of bone models. For two-dimensional images we suggest two algorithms, a threshold algorithm and a virtual slicing algorithm. The threshold algorithm simulates bone resorption on a boundary between bone and marrow, representing an activity of osteoclasts. The virtual slicing algorithm uses a distribution of the bone material between several virtually created slices to achieve statistically correct results, when the bone-marrow transition is not clearly defined. These algorithms have been tested for original CT 10 mm thick vertebral slices and for simulated 10 mm thick slices constructed from ten I mm thick slices. For three-dimensional data, we suggest a variation of the threshold algorithm and apply it to bone images. The results of modeling have been compared with CT images using structural measures of complexity in two- and three-dimensions. This comparison has confirmed credibility of a virtual slicing modeling algorithm for two-dimensional data and a threshold algorithm for three-dimensional data}, language = {en} } @article{ZaikinKurths2006, author = {Zaikin, Alexey and Kurths, J{\"u}rgen}, title = {Optimal length transportation hypothesis to model proteasome product size distribution}, series = {Journal of biological physics : emphasizing physical principles in biological research ; an international journal for the formulation and application of mathematical models in the biological sciences}, volume = {32}, journal = {Journal of biological physics : emphasizing physical principles in biological research ; an international journal for the formulation and application of mathematical models in the biological sciences}, number = {3-4}, publisher = {Springer}, address = {Dordrecht}, issn = {0092-0606}, doi = {10.1007/s10867-006-9014-z}, pages = {231 -- 243}, year = {2006}, abstract = {This paper discusses translocation features of the 20S proteasome in order to explain typical proteasome length distributions. We assume that the protein transport depends significantly on the fragment length with some optimal length which is transported most efficiently. By means of a simple one-channel model, we show that this hypothesis can explain both the one- and the three-peak length distributions found in experiments. A possible mechanism of such translocation is provided by so-called fluctuation-driven transport.}, language = {en} } @article{ZajnulinaBoggioBoehmetal.2015, author = {Zajnulina, Marina and Boggio, Jose M. Chavez and B{\"o}hm, Michael and Rieznik, A. A. and Fremberg, Tino and Haynes, Roger and Roth, Martin M.}, title = {Generation of optical frequency combs via four-wave mixing processes for low- and medium-resolution astronomy}, series = {Applied physics : B, Lasers and optics}, volume = {120}, journal = {Applied physics : B, Lasers and optics}, number = {1}, publisher = {Springer}, address = {New York}, issn = {0946-2171}, doi = {10.1007/s00340-015-6121-1}, pages = {171 -- 184}, year = {2015}, abstract = {We investigate the generation of optical frequency combs through a cascade of four-wave mixing processes in nonlinear fibres with optimised parameters. The initial optical field consists of two continuous-wave lasers with frequency separation larger than 40 GHz (312.7 pm at 1531 nm). It propagates through three nonlinear fibres. The first fibre serves to pulse shape the initial sinusoidal-square pulse, while a strong pulse compression down to sub-100 fs takes place in the second fibre which is an amplifying erbium-doped fibre. The last stage is a low-dispersion highly nonlinear fibre where the frequency comb bandwidth is increased and the line intensity is equalised. We model this system using the generalised nonlinear Schrodinger equation and investigate it in terms of fibre lengths, fibre dispersion, laser frequency separation and input powers with the aim to minimise the frequency comb noise. With the support of the numerical results, a frequency comb is experimentally generated, first in the near infra-red and then it is frequency-doubled into the visible spectral range. Using a MUSE-type spectrograph, we evaluate the comb performance for astronomical wavelength calibration in terms of equidistancy of the comb lines and their stability.}, language = {en} } @article{ZajnulinaBoehmBlowetal.2015, author = {Zajnulina, Marina and B{\"o}hm, Michael and Blow, K. and Rieznik, A. A. and Giannone, Domenico and Haynes, Roger and Roth, Martin M.}, title = {Soliton radiation beat analysis of optical pulses generated from two continuous-wave lasers}, series = {Chaos : an interdisciplinary journal of nonlinear science}, volume = {25}, journal = {Chaos : an interdisciplinary journal of nonlinear science}, number = {10}, publisher = {American Institute of Physics}, address = {Melville}, issn = {1054-1500}, doi = {10.1063/1.4930316}, pages = {6}, year = {2015}, abstract = {We propose a fibre-based approach for generation of optical frequency combs (OFCs) with the aim of calibration of astronomical spectrographs in the low and medium-resolution range. This approach includes two steps: in the first step, an appropriate state of optical pulses is generated and subsequently moulded in the second step delivering the desired OFC. More precisely, the first step is realised by injection of two continuous-wave (CW) lasers into a conventional single-mode fibre, whereas the second step generates a broad OFC by using the optical solitons generated in step one as initial condition. We investigate the conversion of a bichromatic input wave produced by two initial CW lasers into a train of optical solitons, which happens in the fibre used as step one. Especially, we are interested in the soliton content of the pulses created in this fibre. For that, we study different initial conditions (a single cosine-hump, an Akhmediev breather, and a deeply modulated bichromatic wave) by means of soliton radiation beat analysis and compare the results to draw conclusion about the soliton content of the state generated in the first step. In case of a deeply modulated bichromatic wave, we observed the formation of a collective soliton crystal for low input powers and the appearance of separated solitons for high input powers. An intermediate state showing the features of both, the soliton crystal and the separated solitons, turned out to be most suitable for the generation of OFC for the purpose of calibration of astronomical spectrographs.}, language = {en} } @article{ZakharovaKurthsVadivasovaetal.2011, author = {Zakharova, Anna and Kurths, J{\"u}rgen and Vadivasova, Tatyana and Koseska, Aneta}, title = {Analysing dynamical behavior of cellular networks via stochastic bifurcations}, series = {PLoS one}, volume = {6}, journal = {PLoS one}, number = {5}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0019696}, pages = {12}, year = {2011}, abstract = {The dynamical structure of genetic networks determines the occurrence of various biological mechanisms, such as cellular differentiation. However, the question of how cellular diversity evolves in relation to the inherent stochasticity and intercellular communication remains still to be understood. Here, we define a concept of stochastic bifurcations suitable to investigate the dynamical structure of genetic networks, and show that under stochastic influence, the expression of given proteins of interest is defined via the probability distribution of the phase variable, representing one of the genes constituting the system. Moreover, we show that under changing stochastic conditions, the probabilities of expressing certain concentration values are different, leading to different functionality of the cells, and thus to differentiation of the cells in the various types.}, language = {en} } @article{ZakharovaVadivasovaAnishchenkoetal.2010, author = {Zakharova, Anna and Vadivasova, Tatjana and Anishchenko, Vadim S. and Koseska, Aneta and Kurths, J{\"u}rgen}, title = {Stochastic bifurcations and coherencelike resonance in a self-sustained bistable noisy oscillator}, issn = {1539-3755}, doi = {10.1103/Physreve.81.011106}, year = {2010}, abstract = {We investigate the influence of additive Gaussian white noise on two different bistable self-sustained oscillators: Duffing-Van der Pol oscillator with hard excitation and a model of a synthetic genetic oscillator. In the deterministic case, both oscillators are characterized with a coexistence of a stable limit cycle and a stable equilibrium state. We find that under the influence of noise, their dynamics can be well characterized through the concept of stochastic bifurcation, consisting in a qualitative change of the stationary amplitude distribution. For the Duffing-Van der Pol oscillator analytical results, obtained for a quasiharmonic approach, are compared with the result of direct computer simulations. In particular, we show that the dynamics is different for isochronous and anisochronous systems. Moreover, we find that the increase of noise intensity in the isochronous regime leads to a narrowing of the spectral line. This effect is similar to coherence resonance. However, in the case of anisochronous systems, this effect breaks down and a new phenomenon, anisochronous-based stochastic bifurcation occurs.}, language = {en} } @article{ZakrevskyyKopyshevLomadzeetal.2011, author = {Zakrevskyy, Yuriy and Kopyshev, Alexey and Lomadze, Nino and Morozova, Elena and Lysyakova, Liudmila and Kasyanenko, Nina and Santer, Svetlana}, title = {DNA compaction by azobenzene-containing surfactant}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {84}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, number = {2}, publisher = {American Physical Society}, address = {College Park}, issn = {1539-3755}, doi = {10.1103/PhysRevE.84.021909}, pages = {9}, year = {2011}, abstract = {We report on the interaction of cationic azobenzene-containing surfactant with DNA investigated by absorption and fluorescence spectroscopy, dynamic light scattering, and atomic force microscopy. The properties of the surfactant can be controlled with light by reversible switching of the azobenzene unit, incorporated into the surfactant tail, between a hydrophobic trans (visible irradiation) and a hydrophilic cis (UV irradiation) configuration. The influence of the trans-cis isomerization of the azobenzene on the compaction process of DNA molecules and the role of both isomers in the formation and colloidal stability of DNA-surfactant complexes is discussed. It is shown that the trans isomer plays a major role in the DNA compaction process. The influence of the cis isomer on the DNA coil configuration is rather small. The construction of a phase diagram of the DNA concentration versus surfactant/DNA charge ratio allows distancing between three major phases: colloidally stable and unstable compacted globules, and extended coil conformation. There is a critical concentration of DNA above which the compacted globules can be hindered from aggregation and precipitation by adding an appropriate amount of the surfactant in the trans configuration. This is because of the compensation of hydrophobicity of the globules with an increasing amount of the surfactant. Below the critical DNA concentration, the compacted globules are colloidally stable and can be reversibly transferred with light to an extended coil state.}, language = {en} } @article{ZakrevskyyRichterZakrevskaetal.2012, author = {Zakrevskyy, Yuriy and Richter, Marcel and Zakrevska, Svitlana and Lomadze, Nino and von Klitzing, Regine and Santer, Svetlana}, title = {Light-controlled reversible manipulation of microgel particle size using azobenzene-containing surfactant}, series = {Advanced functional materials}, volume = {22}, journal = {Advanced functional materials}, number = {23}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1616-301X}, doi = {10.1002/adfm.201200617}, pages = {5000 -- 5009}, year = {2012}, abstract = {The light-induced reversible switching of the swelling of microgel particles triggered by photo-isomerization and binding/unbinding of a photosensitive azobenzene-containing surfactant is reported. The interactions between the microgel (N-isopropylacrylamide, co-monomer: allyl acetic acid, crosslinker: N,N'-methylenebisacrylamide) and the surfactant are studied by UV-Vis spectroscopy, dynamic and electrophoretic light scattering measurements. Addition of the surfactant above a critical concentration leads to contraction/collapse of the microgel. UV light irradiation results in trans-cis isomerization of the azobenzene unit incorporated into the surfactant tail and causes an unbinding of the more hydrophilic cis isomer from the microgel and its reversible swelling. The reversible contraction can be realized by blue light irradiation that transfers the surfactant back to the more hydrophobic trans conformation, in which it binds to the microgel. The phase diagram of the surfactant-microgel interaction and transitions (aggregation, contraction, and precipitation) is constructed and allows prediction of changes in the system when the concentration of one or both components is varied. Remote and reversible switching between different states can be realized by either UV or visible light irradiation.}, language = {en} } @article{ZakrevskyyRoxlauBrezesinskietal.2014, author = {Zakrevskyy, Yuriy and Roxlau, Julian and Brezesinski, Gerald and Lomadze, Nino and Santer, Svetlana}, title = {Photosensitive surfactants: Micellization and interaction with DNA}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {140}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {4}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4862678}, pages = {8}, year = {2014}, abstract = {Recently, photosensitive surfactants have re-attracted considerable attention. It has been shown that their association with oppositely charged biologically important polyelectrolytes, such as DNA or microgels, can be efficiently manipulated simply by light exposure. In this article, we investigate the self-assembly of photosensitive surfactants as well as their interactions with DNA by calorimetric and spectroscopic methods. Critical micelle concentration (CMC), standard micellization enthalpy, entropy, and Gibbs energy were determined in different conditions (ionic strengths and temperatures) for a series of cationic surfactants with an azobenzene group in their tail. It is shown, that aggregation forces of photosensitive units play an important role in the micellization giving the major contribution to the micellization enthalpy. The onset of the aggregation can be traced from shift of the absorption peak position in the UV-visible spectrum. Titration UV-visible spectroscopy is used as an alternative, simple, and sensitive approach to estimate CMC. The titration UV-visible spectroscopy was also employed to investigate interactions (CAC: critical aggregation concentration, precipitation, and colloidal stabilization) in the DNA-surfactant complex.}, language = {en} } @article{ZakrevskyyTitovLomadzeetal.2014, author = {Zakrevskyy, Yuriy and Titov, Evgenii and Lomadze, Nino and Santer, Svetlana}, title = {Phase diagrams of DNA-photosensitive surfactant complexes: Effect of ionic strength and surfactant structure}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {141}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {16}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4899281}, pages = {8}, year = {2014}, abstract = {Realization of all-optically controlled and efficient DNA compaction is the major motivation in the study of interactions between DNA and photosensitive surfactants. In this article, using recently published approach of phase diagram construction [Y. Zakrevskyy, P. Cywinski, M. Cywinska, J. Paasche, N. Lomadze, O. Reich, H.-G. Lohmannsroben, and S. Santer, J. Chem. Phys. 140, 044907 (2014)], a strategy for substantial reduction of compaction agent concentration and simultaneous maintaining the light-induced decompaction efficiency is proposed. The role of ionic strength (NaCl concentration), as a very important environmental parameter, and surfactant structure (spacer length) on the changes of positions of phase transitions is investigated. Increase of ionic strength leads to increase of the surfactant concentration needed to compact DNA molecule. However, elongation of the spacer results to substantial reduction of this concentration. DNA compaction by surfactants with longer tails starts to take place in diluted solutions at charge ratios Z < 1 and is driven by azobenzene-aggregation compaction mechanism, which is responsible for efficient decompaction. Comparison of phase diagrams for different DNA-photosensitive surfactant systems allowed explanation and proposal of a strategy to overcome previously reported limitations of the light-induced decompaction for complexes with increasing surfactant hydrophobicity. (C) 2014 AIP Publishing LLC.}, language = {en} } @article{ZaksParkKurths2000, author = {Zaks, Michael A. and Park, Eun Hyoung and Kurths, J{\"u}rgen}, title = {On phase synchronization by periodic force in chaotic oscillators with saddle equilibria}, year = {2000}, language = {en} } @article{ZaksPikovskij2019, author = {Zaks, Michael A. and Pikovskij, Arkadij}, title = {Synchrony breakdown and noise-induced oscillation death in ensembles of serially connected spin-torque oscillators}, series = {The European physical journal : B, Condensed matter and complex systems}, volume = {92}, journal = {The European physical journal : B, Condensed matter and complex systems}, number = {7}, publisher = {Springer}, address = {New York}, issn = {1434-6028}, doi = {10.1140/epjb/e2019-100152-2}, pages = {12}, year = {2019}, abstract = {We consider collective dynamics in the ensemble of serially connected spin-torque oscillators governed by the Landau-Lifshitz-Gilbert-Slonczewski magnetization equation. Proximity to homoclinicity hampers synchronization of spin-torque oscillators: when the synchronous ensemble experiences the homoclinic bifurcation, the growth rate per oscillation of small deviations from the ensemble mean diverges. Depending on the configuration of the contour, sufficiently strong common noise, exemplified by stochastic oscillations of the current through the circuit, may suppress precession of the magnetic field for all oscillators. We derive the explicit expression for the threshold amplitude of noise, enabling this suppression.}, language = {en} } @article{ZaksPikovskij2017, author = {Zaks, Michael A. and Pikovskij, Arkadij}, title = {Chimeras and complex cluster states in arrays of spin-torque oscillators}, series = {Scientific reports}, volume = {7}, journal = {Scientific reports}, publisher = {Macmillan Publishers Limited}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-017-04918-9}, year = {2017}, abstract = {We consider synchronization properties of arrays of spin-torque nano-oscillators coupled via an RC load. We show that while the fully synchronized state of identical oscillators may be locally stable in some parameter range, this synchrony is not globally attracting. Instead, regimes of different levels of compositional complexity are observed. These include chimera states (a part of the array forms a cluster while other units are desynchronized), clustered chimeras (several clusters plus desynchronized oscillators), cluster state (all oscillators form several clusters), and partial synchronization (no clusters but a nonvanishing mean field). Dynamically, these states are also complex, demonstrating irregular and close to quasiperiodic modulation. Remarkably, when heterogeneity of spin-torque oscillators is taken into account, dynamical complexity even increases: close to the onset of a macroscopic mean field, the dynamics of this field is rather irregular.}, language = {en} } @article{ZaksPikovskijKurths1999, author = {Zaks, Michael A. and Pikovskij, Arkadij and Kurths, J{\"u}rgen}, title = {On the generalized dimensions for the fourier spectrum of the thue-morse sequence}, year = {1999}, language = {en} } @article{ZaksPikovskijKurths1998, author = {Zaks, Michael A. and Pikovskij, Arkadij and Kurths, J{\"u}rgen}, title = {Symbolic dynamics behind the singular continuous power spectra of continuous flows}, year = {1998}, language = {en} } @article{ZaksPikovskijKurths1997, author = {Zaks, Michael A. and Pikovskij, Arkadij and Kurths, J{\"u}rgen}, title = {On the correlation dimension of the spectral measure for the Thue-Morse sequence}, year = {1997}, language = {en} } @article{ZaksRosenblumPikovskijetal.1997, author = {Zaks, Michael A. and Rosenblum, Michael and Pikovskij, Arkadij and Osipov, Grigory V. and Kurths, J{\"u}rgen}, title = {Phase synchronization of chaotic oscillations in terms of periodic orbits}, issn = {1054-1500}, year = {1997}, language = {en} } @article{ZaksTomov2016, author = {Zaks, Michael A. and Tomov, Petar}, title = {Onset of time dependence in ensembles of excitable elements with global repulsive coupling}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {93}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, publisher = {American Physical Society}, address = {College Park}, issn = {2470-0045}, doi = {10.1103/PhysRevE.93.020201}, pages = {5}, year = {2016}, abstract = {We consider the effect of global repulsive coupling on an ensemble of identical excitable elements. An increase of the coupling strength destabilizes the synchronous equilibrium and replaces it with many attracting oscillatory states, created in the transcritical heteroclinic bifurcation. The period of oscillations is inversely proportional to the distance from the critical parameter value. If the elements interact with the global field via the first Fourier harmonics of their phases, the stable equilibrium is in one step replaced by the attracting continuum of periodic motions.}, language = {en} } @article{ZaksPikovskij2017, author = {Zaks, Michael and Pikovskij, Arkadij}, title = {Chimeras and complex cluster states in arrays of spin-torque oscillators}, series = {Scientific reports}, volume = {7}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-017-04918-9}, pages = {10}, year = {2017}, abstract = {We consider synchronization properties of arrays of spin-torque nano-oscillators coupled via an RC load. We show that while the fully synchronized state of identical oscillators may be locally stable in some parameter range, this synchrony is not globally attracting. Instead, regimes of different levels of compositional complexity are observed. These include chimera states (a part of the array forms a cluster while other units are desynchronized), clustered chimeras (several clusters plus desynchronized oscillators), cluster state (all oscillators form several clusters), and partial synchronization (no clusters but a nonvanishing mean field). Dynamically, these states are also complex, demonstrating irregular and close to quasiperiodic modulation. Remarkably, when heterogeneity of spin-torque oscillators is taken into account, dynamical complexity even increases: close to the onset of a macroscopic mean field, the dynamics of this field is rather irregular.}, language = {en} } @article{ZaldenQuirinSchumacheretal.2019, author = {Zalden, Peter and Quirin, Florian and Schumacher, Mathias and Siegel, Jan and Wei, Shuai and Koc, Azize and Nicoul, Matthieu and Trigo, Mariano and Andreasson, Pererik and Enquist, Henrik and Shu, Michael J. and Pardini, Tommaso and Chollet, Matthieu and Zhu, Diling and Lemke, Henrik and Ronneberger, Ider and Larsson, J{\"o}rgen and Lindenberg, Aaron M. and Fischer, Henry E. and Hau-Riege, Stefan and Reis, David A. and Mazzarello, Riccardo and Wuttig, Matthias and Sokolowski-Tinten, Klaus}, title = {Femtosecond x-ray diffraction reveals a liquid-liquid phase transition in phase-change materials}, series = {Science}, volume = {364}, journal = {Science}, number = {6445}, publisher = {American Assoc. for the Advancement of Science}, address = {Washington, DC}, issn = {0036-8075}, doi = {10.1126/science.aaw1773}, pages = {1062 -- 1067}, year = {2019}, abstract = {In phase-change memory devices, a material is cycled between glassy and crystalline states. The highly temperature-dependent kinetics of its crystallization process enables application in memory technology, but the transition has not been resolved on an atomic scale. Using femtosecond x-ray diffraction and ab initio computer simulations, we determined the time-dependent pair-correlation function of phase-change materials throughout the melt-quenching and crystallization process. We found a liquid-liquid phase transition in the phase-change materials Ag4In3Sb67Te26 and Ge15Sb85 at 660 and 610 kelvin, respectively. The transition is predominantly caused by the onset of Peierls distortions, the amplitude of which correlates with an increase of the apparent activation energy of diffusivity. This reveals a relationship between atomic structure and kinetics, enabling a systematic optimization of the memory-switching kinetics.}, language = {en} } @article{ZamponiAnsarivonKorffSchmisingetal.2009, author = {Zamponi, Flavio and Ansari, Zunaira and von Korff Schmising, Clemens and Rothhardt, Philip and Zhavoronkov, Nickolai and Woerner, Michael and Elsaesser, Thomas and Bargheer, Matias and Trobitzsch-Ryll, Timo and Haschke, Michael}, title = {Femtosecond hard X-ray plasma sources with a kilohertz repetition rate}, issn = {0947-8396}, doi = {10.1007/s00339-009-5171-9}, year = {2009}, abstract = {Laser-driven plasma sources of femtosecond hard X-ray pulses have found widespread application in ultrafast X- ray diffraction. The recent development of plasma sources working at kilohertz repetition rates has allowed for diffraction experiments with strongly improved sensitivity, now revealing subtle fully reversible changes of the geometry of crystal lattices. We provide a brief review of this development and present a novel plasma source with an optimized mechanical and optical design, providing a high flux of several 10(10) photons/s at the Cu-K alpha energy of 8.04 keV and a pulse duration of a parts per thousand currency sign300 fs. First experiments, including the generation of Debye-Scherrer diffraction patterns from Si powder, demonstrate the high performance of this source.}, language = {en} } @article{ZamponiPenfoldNachtegaaletal.2014, author = {Zamponi, Flavio and Penfold, Thomas J. and Nachtegaal, Maarten and Luebcke, Andrea and Rittmann, Jochen and Milne, Chris J. and Chergui, Majed and van Bokhoven, Jeroen A.}, title = {Probing the dynamics of plasmon-excited hexanethiol-capped gold nanoparticles by picosecond X-ray absorption spectroscopy}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {42}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c4cp03301a}, pages = {23157 -- 23163}, year = {2014}, abstract = {Picosecond X-ray absorption spectroscopy (XAS) is used to investigate the electronic and structural dynamics initiated by plasmon excitation of 1.8 nm diameter Au nanoparticles (NPs) functionalised with 1-hexanethiol. We show that 100 ps after photoexcitation the transient XAS spectrum is consistent with an 8\% expansion of the Au-Au bond length and a large increase in disorder associated with melting of the NPs. Recovery of the ground state occurs with a time constant of similar to 1.8 ns, arising from thermalisation with the environment. Simulations reveal that the transient spectrum exhibits no signature of charge separation at 100 ps and allows us to estimate an upper limit for the quantum yield (QY) of this process to be <0.1.}, language = {en} } @article{ZapataArteagaMarinaZuoetal.2022, author = {Zapata-Arteaga, Osnat and Marina, Sara and Zuo, Guangzheng and Xu, Kai and D{\"o}rling, Bernhard and Alberto P{\´e}rez, Luis and Sebasti{\´a}n Reparaz, Juan and Mart{\´i}n, Jaime and Kemerink, Martijn and Campoy-Quiles, Mariano}, title = {Design rules for polymer blends with high thermoelectric performance}, series = {Advanced energy materials}, volume = {12}, journal = {Advanced energy materials}, number = {19}, publisher = {Wiley}, address = {Weinheim}, issn = {1614-6832}, doi = {10.1002/aenm.202104076}, pages = {11}, year = {2022}, abstract = {A combinatorial study of the effect of in-mixing of various guests on the thermoelectric properties of the host workhorse polymer poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) is presented. Specifically, the composition and thickness for doped films of PBTTT blended with different polymers are varied. Some blends at guest weight fractions around 10-15\% exhibit up to a fivefold increase in power factor compared to the reference material, leading to zT values around 0.1. Spectroscopic analysis of the charge-transfer species, structural characterization using grazing-incidence wide-angle X-ray scattering, differential scanning calorimetry, Raman, and atomic force microscopy, and Monte Carlo simulations are employed to determine that the key to improved performance is for the guest to promote long-range electrical connectivity and low disorder, together with similar highest occupied molecular orbital levels for both materials in order to ensure electronic connectivity are combined.}, language = {en} } @article{ZaragozaCardielGomezGonzalezMayyaetal.2022, author = {Zaragoza-Cardiel, Javier and G{\´o}mez-Gonz{\´a}lez, V{\´i}ctor Mauricio Alfonso and Mayya, Yalia Divakara and Ramos-Larios, Gerardo}, title = {Nebular abundance gradient in the Cartwheel galaxy using MUSE data}, series = {Monthly notices of the Royal Astronomical Society}, volume = {514}, journal = {Monthly notices of the Royal Astronomical Society}, number = {2}, publisher = {Oxford University Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stac1423}, pages = {1689 -- 1705}, year = {2022}, abstract = {We here present the results from a detailed analysis of nebular abundances of commonly observed ions in the collisional ring galaxy Cartwheel using the Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) data set. The analysis includes 221 H II regions in the star-forming ring, in addition to 40 relatively fainter H a-emitting regions in the spokes, disc, and the inner ring. The ionic abundances of He, N, O, and Fe are obtained using the direct method (DM) for 9, 20, 20, and 17 ring H II regions, respectively, where the S++ temperature-sensitive line is detected. For the rest of the regions, including all the nebulae between the inner and the outer ring, we obtained O abundances using the strong-line method (SLM). The ring regions have a median 12 + log O/H = 8.19 +/- 0.15, log N/O = -1.57 +/- 0.09 and log Fe/O = -2.24 +/- 0.09 using the DM. Within the range of O abundances seen in the Cartwheel, the N/O and Fe/O values decrease proportionately with increasing O, suggesting local enrichment of O without corresponding enrichment of primary N and Fe. The O abundances of the disc H II regions obtained using the SLM show a well-defined radial gradient. The mean O abundance of the ring H II regions is lower by similar to 0.1 dex as compared to the extrapolation of the radial gradient. The observed trends suggest the preservation of the pre-collisional abundance gradient, displacement of most of the processed elements to the ring, as predicted by the recent simulation by Renaud et al., and post-collisional infall of metal-poor gas in the ring.}, language = {en} } @article{ZaritskyCourtoisMunozMateosetal.2014, author = {Zaritsky, Dennis and Courtois, Helene and Munoz-Mateos, Juan-Carlos and Sorce, Jenny and Erroz-Ferrer, S. and Comeron, S. and Gadotti, D. A. and Gil De Paz, A. and Hinz, J. L. and Laurikainen, E. and Kim, T. and Laine, J. and Menendez-Delmestre, K. and Mizusawa, T. and Regan, M. W. and Salo, H. and Seibert, M. and Sheth, K. and Athanassoula, E. and Bosma, A. and Cisternas, M. and Ho, Luis C. and Holwerda, B.}, title = {The baryonic Tully-Fisher relationship for S(4)G galaxies and the "condensed" baryon fraction of galaxies}, series = {The astronomical journal}, volume = {147}, journal = {The astronomical journal}, number = {6}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-6256}, doi = {10.1088/0004-6256/147/6/134}, pages = {11}, year = {2014}, abstract = {We combine data from the Spitzer Survey for Stellar Structure in Galaxies, a recently calibrated empirical stellar mass estimator from Eskew et al., and an extensive database of Hi spectral line profiles to examine the baryonic Tully-Fisher (BTF) relation. We find (1) that the BTF has lower scatter than the classic Tully-Fisher (TF) relation and is better described as a linear relationship, confirming similar previous results, (2) that the inclusion of a radial scale in the BTF decreases the scatter but only modestly, as seen previously for the TF relation, and (3) that the slope of the BTF, which we find to be 3.5 +/- 0.2 (Delta log M-baryon/Delta log v(c)), implies that on average a nearly constant fraction (similar to 0.4) of all baryons expected to be in a halo are "condensed" onto the central region of rotationally supported galaxies. The condensed baryon fraction, M-baryon/M-total, is, to our measurement precision, nearly independent of galaxy circular velocity (our sample spans circular velocities, vc, between 60 and 250 km s(-1), but is extended to v(c) similar to 10 km s(-1) using data from the literature). The observed galaxy-to-galaxy scatter in this fraction is generally <= a factor of 2 despite fairly liberal selection criteria. These results imply that cooling and heating processes, such as cold versus hot accretion, mass loss due to stellar winds, and active galactic nucleus driven feedback, to the degree that they affect the global galactic properties involved in the BTF, are independent of halo mass for galaxies with 10 < v(c) < 250 km s(-1) and typically introduce no more than a factor of two range in the resulting M-baryon/M-total. Recent simulations by Aumer et al. of a small sample of disk galaxies are in excellent agreement with our data, suggesting that current simulations are capable of reproducing the global properties of individual disk galaxies. More detailed comparison to models using the BTF holds great promise, but awaits improved determinations of the stellar masses.}, language = {en} } @article{ZbilutMitchellGiulianietal.2004, author = {Zbilut, J. P. and Mitchell, J. C. and Giuliani, A. and Colosimo, A. and Marwan, Norbert and Webber, C. L.}, title = {Singular hydrophobicity patterns and net charge : a mesoscopic principle for protein aggregation/folding}, issn = {0378-4371}, year = {2004}, abstract = {A statistical model describing the propensity for protein aggregation is presented. Only amino-acid hydrophobicity values and calculated net charge are used for the model. The combined effects of hydrophobic patterns as computed by the signal analysis technique, recurrence quantification, plus calculated net charge were included in a function emphasizing the effect of singular hydrophobic patches which were found to be statistically significant for predicting aggregation propensity as quantified by fluorescence studies obtained from the literature. These results suggest preliminary evidence for a mesoscopic principle for protein folding/aggregation. (C) 2004 Elsevier B.V. All rights reserved}, language = {en} } @article{ZehbeKolloscheLardongetal.2016, author = {Zehbe, Kerstin and Kollosche, Matthias and Lardong, Sebastian and Kelling, Alexandra and Schilde, Uwe and Taubert, Andreas}, title = {Ionogels Based on Poly(methyl methacrylate) and Metal-Containing Ionic Liquids: Correlation between Structure and Mechanical and Electrical Properties}, series = {International journal of molecular sciences}, volume = {17}, journal = {International journal of molecular sciences}, publisher = {MDPI}, address = {Basel}, issn = {1422-0067}, doi = {10.3390/ijms17030391}, pages = {16}, year = {2016}, abstract = {Ionogels (IGs) based on poly(methyl methacrylate) (PMMA) and the metal-containing ionic liquids (ILs) bis-1-butyl-3-methlimidazolium tetrachloridocuprate(II), tetrachloride cobaltate(II), and tetrachlorido manganate(II) have been synthesized and their mechanical and electrical properties have been correlated with their microstructure. Unlike many previous examples, the current IGs show a decreasing stability in stress-strain experiments on increasing IL fractions. The conductivities of the current IGs are lower than those observed in similar examples in the literature. Both effects are caused by a two-phase structure with micrometer-sized IL-rich domains homogeneously dispersed an IL-deficient continuous PMMA phase. This study demonstrates that the IL-polymer miscibility and the morphology of the IGs are key parameters to control the (macroscopic) properties of IGs.}, language = {en} } @article{ZehbeMochalesRadziketal.2016, author = {Zehbe, Rolf and Mochales, Carolina and Radzik, Daniela and Mueller, Wolf-Dieter and Fleck, Claudia}, title = {Electrophoretic deposition of multilayered (cubic and tetragonal stabilized) zirconia ceramics for adapted crack deflection}, series = {Journal of the European Ceramic Society}, volume = {36}, journal = {Journal of the European Ceramic Society}, publisher = {Elsevier}, address = {Oxford}, issn = {0955-2219}, doi = {10.1016/j.jeurceramsoc.2015.08.022}, pages = {357 -- 364}, year = {2016}, abstract = {The electrophoretic deposition process was used to produce multi-layered ceramics consisting of alternating layers of fully stabilized cubic zirconia and partially stabilized tetragonal zirconia to make use of their different mechanical behaviour, investigating the possibility to deflect advancing cracks at the interfaces of the different layers. This crack deflection is apparently impacted by a toughening mechanism only found in the tetragonal stabilized zirconia polymorph and is characterized by the stress induced transformation of the metastable tetragonal phase into the monoclinic one, which is accompanied by a volume increase resulting in a closing mechanism for advancing cracks. While improving the electrophoretic deposition process, we investigated the transformation toughening mechanism at the layer interfaces and their effect on crack propagation. Investigations involved a combination of different imaging methods, including light microscopy, white light interferometry, atomic force microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. (C) 2015 Elsevier Ltd. All rights reserved.}, language = {en} } @article{ZehbeMochalesRadziketal.2015, author = {Zehbe, Rolf and Mochales, Carolina and Radzik, Daniela and Mueller, Wolf-Dieter and Fleck, Claudia}, title = {Electrophoretic deposition of multilayered (cubic and tetragonal stabilized) zirconia ceramics for adapted crack deflection}, series = {Journal of the European Ceramic Society}, volume = {36}, journal = {Journal of the European Ceramic Society}, number = {2}, publisher = {Elsevier}, address = {Oxford}, issn = {0955-2219}, doi = {10.1016/j.jeurceramsoc.2015.08.022}, pages = {357 -- 364}, year = {2015}, abstract = {The electrophoretic deposition process was used to produce multi-layered ceramics consisting of alternating layers of fully stabilized cubic zirconia and partially stabilized tetragonal zirconia to make use of their different mechanical behaviour, investigating the possibility to deflect advancing cracks at the interfaces of the different layers. This crack deflection is apparently impacted by a toughening mechanism only found in the tetragonal stabilized zirconia polymorph and is characterized by the stress induced transformation of the metastable tetragonal phase into the monoclinic one, which is accompanied by a volume increase resulting in a closing mechanism for advancing cracks. While improving the electrophoretic deposition process, we investigated the transformation toughening mechanism at the layer interfaces and their effect on crack propagation. Investigations involved a combination of different imaging methods, including light microscopy, white light interferometry, atomic force microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy.}, language = {en} } @article{ZehbeZaslanskyMochalesetal.2016, author = {Zehbe, Rolf and Zaslansky, Paul and Mochales, Carolina and Mueller, Wolf-Dieter and Fleck, Claudia}, title = {Synchrotron micro tomographic evaluation of multilayered zirconia ceramics-Volumetric effects after indentation}, series = {Journal of the European Ceramic Society}, volume = {36}, journal = {Journal of the European Ceramic Society}, publisher = {Elsevier}, address = {Oxford}, issn = {0955-2219}, doi = {10.1016/j.jeurceramsoc.2015.09.015}, pages = {171 -- 177}, year = {2016}, abstract = {Electrophoretic deposition was used to produce zirconia specimen consisting of alternating layers of fully stabilized cubic zirconia and partially stabilized tetragonal zirconia. In this configuration, the tetragonal stabilized zirconia layers can undergo transformation toughening upon mechanical induced stresses, while the cubic stabilized layers can act as confining element. To understand the volumetric changes due to transformation toughening in these layered materials after indentation, we used an advanced synchrotron-based X-ray mu CT setup and compared the results with surface sensitive methods like Raman spectroscopy, AFM and white light interferometry. The high spatial resolution and the adapted beam energy between the absorption edges of zirconia and yttria allowed discriminating between individual layers due to differences in their yttria content. Furthermore we were able to identify single indents and link volume changes to different physical effects in the different stabilized zirconia parts and visualize the three dimensional volume around only few micrometre sized indents. (C) 2015 Elsevier Ltd. All rights reserved.}, language = {en} } @article{ZehbeZehbe2016, author = {Zehbe, Rolf and Zehbe, Kerstin}, title = {Strontium doped poly-epsilon-caprolactone composite scaffolds made by reactive foaming}, series = {The European journal of the history of economic thought}, volume = {67}, journal = {The European journal of the history of economic thought}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0928-4931}, doi = {10.1016/j.msec.2016.05.045}, pages = {259 -- 266}, year = {2016}, abstract = {In the reconstruction and regeneration of bone tissue, a primary goal is to initiate bone growth and to stabilize the surrounding bone. In this regard, a potentially useful component in biomaterials for bone tissue engineering is strontium, which acts as cationic active agent, triggering certain intracellular pathways and acting as so called dual action bone agent which inhibits bone resorption while stimulating bone regeneration. In this study we established a novel processing for the foaming of a polymer (poly-epsilon-caprolactone) and simultaneous chemical reaction of a mixture of calcium and strontium hydroxides to the respective carbonates using supercritical carbon dioxide. The resultant porous composite scaffold was optimized in composition and strontium content and was characterized via different spectroscopic (infrared and Raman spectroscopy, energy dispersive X-ray spectroscopy), imaging (SEM, mu CT), mechanical testing and in vitro methods (fluorescence vital staining, MTT-assay). As a result, the composite scaffold showed good in vitro biocompatibility with partly open pore structure and the expected chemistry. First mechanical testing results indicate sufficient mechanical stability to support future in vivo applications. (C) 2016 Elsevier B.V. All rights reserved.}, language = {en} } @article{ZeimerBaumbachGrenzeretal.1999, author = {Zeimer, Ute and Baumbach, Tilo and Grenzer, J{\"o}rg and L{\"u}bbert, Daniel and Mazuelas, A. and Pietsch, Ullrich and Erbert, G.}, title = {In-situ characterization of strain distribution in broad-area high-power lasers under operation by high- resolution x-ray diffrcation and topography using synchrotron radiation}, year = {1999}, language = {en} } @article{ZeimerBuggeGramlichetal.2000, author = {Zeimer, Ute and Bugge, F. and Gramlich, S. and Smirnitzki, V. and Weyers, Markus and Tr{\"a}nkle, G. and Grenzer, J{\"o}rg and Pietsch, Ullrich and Cassabois, G. and Emiliani, V. and Lienau, C.}, title = {Evidence for strain-induced lateral carrier confinement in InGaAs quantum wells by low-temperature near-field spectroscopy}, year = {2000}, language = {en} } @article{ZeimerBuggeGramlichetal.2001, author = {Zeimer, Ute and Bugge, F. and Gramlich, S. and Smirnitzki, V. and Weyers, Markus and Tr{\"a}nkle, G. and Grenzer, J{\"o}rg and Pietsch, Ullrich and Cassabois, G. and Emiliani, V. and Linau, Christoph}, title = {Evidence of strain-induced lateral carrier confinement in InGaAs-quantum wells by low-temperature near-field spectroscopy}, year = {2001}, language = {en} } @article{ZeimerGrenzerPietschetal.2001, author = {Zeimer, Ute and Grenzer, J{\"o}rg and Pietsch, Ullrich and Bugge, F. and Smirnitzki, V. and Weyers, Markus}, title = {Investigation of strain-modulated InGaAs-nanostructures by grazing-incidence x-ray diffraction and photoluminescence}, year = {2001}, language = {en} } @article{ZeimerPietschGrenzeretal.2005, author = {Zeimer, Ute and Pietsch, Ullrich and Grenzer, Joerg and Fricke, J. and Knauer, A. and Weyers, Markus}, title = {Optimised two layer overgrowth of a lateral strain-modulated nanostructure}, issn = {0925-8388}, year = {2005}, abstract = {Recently it has been shown that lateral carrier confinement in an InGaAs quantum well (QW) embedded in GaAs can be achieved by using a laterally patterned InGaP stressor layer on top of the heterostructure. To exploit this effect in a device the structure has to be planarized by a second epitaxial step. It has been shown that the lateral strain modulation almost vanishes after overgrowth with GaAs, whereas overgrowth with a single ternary layer of opposite strain compared to the stressor layer suffers from strain induced decomposition. Here we show that the lateral carrier confinement of the initially free standing nanostructure can almost be maintained using a two step process for overgrowth, where a strained thin ternary layer is grown first followed by GaAs up to complete planarization of the patterned structure. Thickness and composition of the ternary layer are adjusted on the basis of finite element calculations of the strain distribution (FEM). The strain field achieved after overgrowth is probed by X-ray grazing- incidence diffraction (GID). (c) 2005 Elsevier B.V. All rights reserved}, language = {en} } @article{ZeiskeSandbergKurpiersetal.2022, author = {Zeiske, Stefan and Sandberg, Oskar J. and Kurpiers, Jona and Shoaee, Safa and Meredith, Paul and Armin, Ardalan}, title = {Probing charge generation efficiency in thin-film solar cells by integral-mode transient charge extraction}, series = {ACS photonics}, volume = {9}, journal = {ACS photonics}, number = {4}, publisher = {American Chemical Society}, address = {Washington}, issn = {2330-4022}, doi = {10.1021/acsphotonics.1c01532}, pages = {1188 -- 1195}, year = {2022}, abstract = {The photogeneration of free charges in light-harvesting devices is a multistep process, which can be challenging to probe due to the complexity of contributing energetic states and the competitive character of different driving mechanisms. In this contribution, we advance a technique, integral-mode transient charge extraction (ITCE), to probe these processes in thin-film solar cells. ITCE combines capacitance measurements with the integral-mode time-of-flight method in the low intensity regime of sandwich-type thin-film devices and allows for the sensitive determination of photogenerated charge-carrier densities. We verify the theoretical framework of our method by drift-diffusion simulations and demonstrate the applicability of ITCE to organic and perovskite semiconductor-based thin-film solar cells. Furthermore, we examine the field dependence of charge generation efficiency and find our ITCE results to be in excellent agreement with those obtained via time-delayed collection field measurements conducted on the same devices.}, language = {en} } @article{ZeiskeSandbergZarrabietal.2022, author = {Zeiske, Stefan and Sandberg, Oskar J. and Zarrabi, Nasim and Wolff, Christian Michael and Raoufi, Meysam and Pe{\~n}a-Camargo, Francisco and Gutierrez-Partida, Emilio and Meredith, Paul and Stolterfoht, Martin and Armin, Ardalan}, title = {Static disorder in lead halide perovskites}, series = {The journal of physical chemistry letters}, volume = {13}, journal = {The journal of physical chemistry letters}, number = {31}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.2c01652}, pages = {7280 -- 7285}, year = {2022}, abstract = {In crystalline and amorphous semiconductors, the temperature-dependent Urbach energy can be determined from the inverse slope of the logarithm of the absorption spectrum and reflects the static and dynamic energetic disorder. Using recent advances in the sensitivity of photocurrent spectroscopy methods, we elucidate the temperature-dependent Urbach energy in lead halide perovskites containing different numbers of cation components. We find Urbach energies at room temperature to be 13.0 +/- 1.0, 13.2 +/- 1.0, and 13.5 +/- 1.0 meV for single, double, and triple cation perovskite. Static, temperature-independent contributions to the Urbach energy are found to be as low as 5.1 ?+/- 0.5, 4.7 +/- 0.3, and 3.3 +/- 0.9 meV for the same systems. Our results suggest that, at a low temperature, the dominant static disorder in perovskites is derived from zero-point phonon energy rather than structural disorder. This is unusual for solution-processed semiconductors but broadens the potential application of perovskites further to quantum electronics and devices.}, language = {en} } @article{ZeitzHaackerDongesetal.2022, author = {Zeitz, Maria and Haacker, Jan M. and Donges, Jonathan and Albrecht, Torsten and Winkelmann, Ricarda}, title = {Dynamic regimes of the Greenland Ice Sheet emerging from interacting melt-elevation and glacial isostatic adjustment feedbacks}, series = {Earth system dynamics}, volume = {13}, journal = {Earth system dynamics}, number = {3}, publisher = {Copernicus Publ.}, address = {G{\"o}ttingen}, issn = {2190-4979}, doi = {10.5194/esd-13-1077-2022}, pages = {1077 -- 1096}, year = {2022}, abstract = {The stability of the Greenland Ice Sheet under global warming is governed by a number of dynamic processes and interacting feedback mechanisms in the ice sheet, atmosphere and solid Earth. Here we study the long-term effects due to the interplay of the competing melt-elevation and glacial isostatic adjustment (GIA) feedbacks for different temperature step forcing experiments with a coupled ice-sheet and solid-Earth model. Our model results show that for warming levels above 2 degrees C, Greenland could become essentially ice-free within several millennia, mainly as a result of surface melting and acceleration of ice flow. These ice losses are mitigated, however, in some cases with strong GIA feedback even promoting an incomplete recovery of the Greenland ice volume. We further explore the full-factorial parameter space determining the relative strengths of the two feedbacks: our findings suggest distinct dynamic regimes of the Greenland Ice Sheets on the route to destabilization under global warming - from incomplete recovery, via quasi-periodic oscillations in ice volume to ice-sheet collapse. In the incomplete recovery regime, the initial ice loss due to warming is essentially reversed within 50 000 years, and the ice volume stabilizes at 61 \%-93 \% of the present-day volume. For certain combinations of temperature increase, atmospheric lapse rate and mantle viscosity, the interaction of the GIA feedback and the melt-elevation feedback leads to self-sustained, long-term oscillations in ice-sheet volume with oscillation periods between 74 000 and over 300 000 years and oscillation amplitudes between 15 \%-70 \% of present-day ice volume. This oscillatory regime reveals a possible mode of internal climatic variability in the Earth system on timescales on the order of 100 000 years that may be excited by or synchronized with orbital forcing or interact with glacial cycles and other slow modes of variability. Our findings are not meant as scenario-based near-term projections of ice losses but rather providing insight into of the feedback loops governing the "deep future" and, thus, long-term resilience of the Greenland Ice Sheet.}, language = {en} } @article{ZeitzLevermannWinkelmann2020, author = {Zeitz, Maria and Levermann, Anders and Winkelmann, Ricarda}, title = {Sensitivity of ice loss to uncertainty in flow law parameters in an idealized one-dimensional geometry}, series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, volume = {14}, journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, number = {10}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1994-0416}, doi = {10.5194/tc-14-3537-2020}, pages = {3537 -- 3550}, year = {2020}, abstract = {Acceleration of the flow of ice drives mass losses in both the Antarctic and the Greenland Ice Sheet. The projections of possible future sea-level rise rely on numerical ice-sheet models, which solve the physics of ice flow, melt, and calving. While major advancements have been made by the ice-sheet modeling community in addressing several of the related uncertainties, the flow law, which is at the center of most process-based ice-sheet models, is not in the focus of the current scientific debate. However, recent studies show that the flow law parameters are highly uncertain and might be different from the widely accepted standard values. Here, we use an idealized flow-line setup to investigate how these uncertainties in the flow law translate into uncertainties in flow-driven mass loss. In order to disentangle the effect of future warming on the ice flow from other effects, we perform a suite of experiments with the Parallel Ice Sheet Model (PISM), deliberately excluding changes in the surface mass balance. We find that changes in the flow parameters within the observed range can lead up to a doubling of the flow-driven mass loss within the first centuries of warming, compared to standard parameters. The spread of ice loss due to the uncertainty in flow parameters is on the same order of magnitude as the increase in mass loss due to surface warming. While this study focuses on an idealized flow-line geometry, it is likely that this uncertainty carries over to realistic three-dimensional simulations of Greenland and Antarctica.}, language = {en} } @article{ZeitzReeseBeckmannetal.2021, author = {Zeitz, Maria and Reese, Ronja and Beckmann, Johanna and Krebs-Kanzow, Uta and Winkelmann, Ricarda}, title = {Impact of the melt-albedo feedback on the future evolution of the Greenland Ice Sheet with PISM-dEBM-simple}, series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, volume = {15}, journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, number = {12}, publisher = {Copernicus}, address = {Katlenburg-Lindau}, issn = {1994-0416}, doi = {10.5194/tc-15-5739-2021}, pages = {5739 -- 5764}, year = {2021}, abstract = {Surface melting of the Greenland Ice Sheet contributes a large amount to current and future sea level rise. Increased surface melt may lower the reflectivity of the ice sheet surface and thereby increase melt rates: the so-called melt-albedo feedback describes this self-sustaining increase in surface melting. In order to test the effect of the melt-albedo feedback in a prognostic ice sheet model, we implement dEBM-simple, a simplified version of the diurnal Energy Balance Model dEBM, in the Parallel Ice Sheet Model (PISM). The implementation includes a simple representation of the melt-albedo feedback and can thereby replace the positive-degree-day melt scheme. Using PISM-dEBM-simple, we find that this feedback increases ice loss through surface warming by 60 \% until 2300 for the high-emission scenario RCP8.5 when compared to a scenario in which the albedo remains constant at its present-day values. With an increase of 90 \% compared to a fixed-albedo scenario, the effect is more pronounced for lower surface warming under RCP2.6. Furthermore, assuming an immediate darkening of the ice surface over all summer months, we estimate an upper bound for this effect to be 70 \% in the RCP8.5 scenario and a more than 4-fold increase under RCP2.6. With dEBM-simple implemented in PISM, we find that the melt-albedo feedback is an essential contributor to mass loss in dynamic simulations of the Greenland Ice Sheet under future warming.}, language = {en} } @article{ZellmeierBrennerJanietzetal.2018, author = {Zellmeier, M. and Brenner, Thomas J. K. and Janietz, Silvia and Nickel, N. H. and Rappich, J.}, title = {Polythiophenes as emitter layers for crystalline silicon solar cells}, series = {Journal of applied physics}, volume = {123}, journal = {Journal of applied physics}, number = {3}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-8979}, doi = {10.1063/1.5006625}, pages = {5}, year = {2018}, abstract = {We investigated the influence of the emitter (amorphous-Si, a-Si, or polythiophene derivatives: poly(3-hexylthiophene), P3HT, and poly(3-[3,6-dioxaheptyl]-thiophene), P3DOT) and the interface passivation (intrinsic a-Si or SiOX and methyl groups or SiOX) on the c-Si based 1 × 1 cm2 planar hybrid heterojunction solar cell parameters. We observed higher short circuit currents for the P3HT or P3DOT/c-Si solar cells than those obtained for a-Si/c-Si devices, independent of the interface passivation. The obtained VOC of 659 mV for the P3DOT/SiOX/c-Si heterojunction solar cell with hydrophilic 3,6-dioxaheptyl side chains is among the highest reported for c-Si/polythiophene devices. The maximum power conversion efficiency, PCE, was 11\% for the P3DOT/SiOX/c-Si heterojunction solar cell. Additionally, our wafer lifetime measurements reveal a field effect passivation in the wafer induced by the polythiophenes when deposited on c-Si.}, language = {en} } @article{ZemanovaZhouKurths2006, author = {Zemanova, Lucia and Zhou, Changsong and Kurths, J{\"u}rgen}, title = {Structural and functional clusters of complex brain networks}, series = {Physica, D, Nonlinear phenomena}, volume = {224}, journal = {Physica, D, Nonlinear phenomena}, number = {1-2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-2789}, doi = {10.1016/j.physd.2006.09.008}, pages = {202 -- 212}, year = {2006}, abstract = {Recent research using the complex network approach has revealed a rich and complicated network topology in the cortical connectivity of mammalian brains. It is of importance to understand the implications of such complex network structures in the functional organization of the brain activities. Here we study this problem from the viewpoint of dynamical complex networks. We investigate synchronization dynamics on the corticocortical network of the cat by modeling each node (cortical area) of the network with a sub-network of interacting excitable neurons. We find that the network displays clustered synchronization behavior, and the dynamical clusters coincide with the topological community structures observed in the anatomical network. Our results provide insights into the relationship between the global organization and the functional specialization of the brain cortex.}, language = {en} } @article{ZenBilgeGalbrechtetal.2006, author = {Zen, Achmad and Bilge, Askin and Galbrecht, Frank and Alle, Ronald and Meerholz, Klaus and Grenzer, J{\"o}rg and Neher, Dieter and Scherf, Ullrich and Farrell, Tony}, title = {Solution processable organic field-effect transistors utilizing an alpha,alpha '-dihexylpentathiophene- based swivel cruciform}, doi = {10.1021/Ja0573357}, year = {2006}, language = {en} } @article{ZenNeherBaueretal.2002, author = {Zen, Achmad and Neher, Dieter and Bauer, C. and Asawapirom, Udom and Scherf, Ullrich and Hagen, R. and Kostromine, S. and Mahrt, R. F.}, title = {Polarization-sensitive photoconductivity in aligned polyfluorene layers}, year = {2002}, language = {en} } @article{ZenNeherSilmyetal.2005, author = {Zen, Achmad and Neher, Dieter and Silmy, Kamel and Hollander, A. and Asawapirom, Udom and Scherf, Ullrich}, title = {Improving the performance of organic field effect transistor by optimizing the gate insulator surface}, year = {2005}, abstract = {The effect of oxygen plasma treatment and/or silanization with hexamethyldisilazane (HMDS) on the surface chemistry and the morphology of the SiO2-gate insulator were studied with respect to the performance of organic field effect transistors. Using X-ray photoelectron spectroscopy (XPS), it is shown that silanization leads to the growth of a polysiloxane interfacial layer and that longer silanization times increase the thickness of this layer. Most important, silanization reduces the signal from surface contaminations such as oxidized hydrocarbon molecules. In fact, the lowest concentration of these contaminations was found after a combined oxygen plasma/silanization treatment. The results of these investigations were correlated with the characteristic device parameters of polymer field effect transistors with poly(3-hexylthiophene)s as the semiconducting layer. We found that the field effect mobility correlates with the concentration of contaminations as measured by XPS. We, finally, demonstrate that silanization significantly improves the operational stability of the device in air compared to the untreated devices}, language = {en} } @article{ZenPflaumHirschmannetal.2004, author = {Zen, Achmad and Pflaum, J. and Hirschmann, S. and Zhuang, W. and Jaiser, Frank and Asawapirom, Udom and Rabe, J. P. and Scherf, Ullrich and Neher, Dieter}, title = {Effect of molecular weight and annealing of poly (3-hexylthiophene)s on the performance of organic field-effect transistors}, year = {2004}, abstract = {The optical, structural, and electrical properties of thin layers made from poly(3-hexylthiophene) (P3HT) samples of different molecular weights are presented. As reported in a previous paper by Kline et al., Adv. Mater 2003, 15, 1519, the mobilities of these layers are a strong function of the molecular weight, with the largest mobility found for the largest molecular weight. Atomic force microscopy studies reveal a complex polycrystalline morphology which changes considerably upon annealing. X-ray studies show the occurrence of a layered phase for all P3HT fractions, especially after annealing at 1.50 degreesC . However, there is no clear correlation between the differences in the transport properties and the data from structural investigations. In order to reveal the processes limiting the mobility in these layers, the transistor properties were investigated as a function of temperature. The mobility decreases continuously with increasing temperatures; with the same trend pronounced thermochromic effects of the P3HT films occur. Apparently, the polymer chains adopt a more twisted, disordered conformation at higher temperatures, leading to interchain transport barriers. We conclude that the backbone conformation of the majority of the bulk material rather than the crystallinity of the layer is the most crucial parameter controlling the charge transport in these P3HT layers. This interpretation is supported by the significant blue-shift of the solid-state absorption spectra with decreasing molecular weight, which is indicative of a larger distortion of the P3HT backbone in the low-molecular weight P3HT layers}, language = {en} } @article{ZenSaphiannikovaNeheretal.2005, author = {Zen, Achmad and Saphiannikova, Marina and Neher, Dieter and Asawapirom, Udom and Scherf, Ullrich}, title = {Comparative study of the field-effect mobility of a copolymer and a binary blend based on poly(3- alkylthiophene)s}, issn = {0897-4756}, year = {2005}, abstract = {The performance of highly soluble regioregular poly[ (3-hexylthiophene)-co-(3-octylthiophetie)] (P3HTOT) as a semiconducting material in organic field-effect transistors (OFETs) is presented in comparison to that of the corresponding homopolymers. Transistors made from as-prepared layers of P3HTOT exhibit a mobility of ca. 7 x 10(-3) cm(2) V-1 s(-1), which is comparable to the performance of transistors made from as-prepared poly(3-hexylthiophene) (P3HT) and almost 6 times larger than the mobility of transistors prepared with poly(3-octylthiophene) (P3OT). On the other hand, the solubility parameter delta(p) of P3HTOT is close to that of the highly soluble P3OT. Moreover, compared to a physical blend of poly(3-hexylthiophene) and poly(3-octylthiophene), the mobility of P3HTOT devices is almost twice as large and the performance does not degrade upon annealing at elevated temperatures. Therefore, the copolymer approach outlined here may be one promising step toward an optimum balance between a Sufficient processability of the polymers from common organic solvents, a high solid state order, and applicable OFET performances}, language = {en} } @article{ZersonNeumannSteyrleuthneretal.2016, author = {Zerson, Mario and Neumann, Martin and Steyrleuthner, Robert and Neher, Dieter and Magerle, Robert}, title = {Surface Structure of Semicrystalline Naphthalene Diimide-Bithiophene Copolymer Films Studied with Atomic Force Microscopy}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {49}, journal = {Macromolecules : a publication of the American Chemical Society}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/acs.macromol.6b00988}, pages = {6549 -- 6557}, year = {2016}, language = {en} } @article{ZeuschnerMatternPudelletal.2021, author = {Zeuschner, Steffen Peer and Mattern, Maximilian and Pudell, Jan-Etienne and Reppert, Alexander von and R{\"o}ssle, Matthias and Leitenberger, Wolfram and Schwarzkopf, Jutta and Boschker, Jos and Herzog, Marc and Bargheer, Matias}, title = {Reciprocal space slicing}, series = {Structural dynamics}, volume = {8}, journal = {Structural dynamics}, number = {1}, publisher = {AIP Publishing LLC}, address = {Melville, NY}, issn = {2329-7778}, doi = {10.1063/4.0000040}, pages = {10}, year = {2021}, abstract = {An experimental technique that allows faster assessment of out-of-plane strain dynamics of thin film heterostructures via x-ray diffraction is presented. In contrast to conventional high-speed reciprocal space-mapping setups, our approach reduces the measurement time drastically due to a fixed measurement geometry with a position-sensitive detector. This means that neither the incident (ω) nor the exit (2θ) diffraction angle is scanned during the strain assessment via x-ray diffraction. Shifts of diffraction peaks on the fixed x-ray area detector originate from an out-of-plane strain within the sample. Quantitative strain assessment requires the determination of a factor relating the observed shift to the change in the reciprocal lattice vector. The factor depends only on the widths of the peak along certain directions in reciprocal space, the diffraction angle of the studied reflection, and the resolution of the instrumental setup. We provide a full theoretical explanation and exemplify the concept with picosecond strain dynamics of a thin layer of NbO2.}, language = {en} } @article{ZeuschnerWangDebetal.2022, author = {Zeuschner, Steffen Peer and Wang, Xi-Guang and Deb, Marwan and Popova, Elena and Malinowski, Gregory and Hehn, Michel and Keller, Niels and Berakdar, Jamal and Bargheer, Matias}, title = {Standing spin wave excitation in Bi}, series = {Physical review : B, Condensed matter and materials physics}, volume = {106}, journal = {Physical review : B, Condensed matter and materials physics}, number = {13}, publisher = {American Physical Society}, address = {College Park}, issn = {2469-9950}, doi = {10.1103/PhysRevB.106.134401}, pages = {9}, year = {2022}, abstract = {Based on micromagnetic simulations and experimental observations of the magnetization and lattice dynamics after the direct optical excitation of the magnetic insulator Bi : YIG or indirect excitation via an optically opaque Pt/Cu double layer, we disentangle the dynamical effects of magnetic anisotropy and magneto-elastic coupling. The strain and temperature of the lattice are quantified via modeling ultrafast x-ray diffraction data. Measurements of the time-resolved magneto-optical Kerr effect agree well with the magnetization dynamics simulated according to the excitation via two mechanisms: the magneto-elastic coupling to the experimentally verified strain dynamics and the ultrafast temperature-induced transient change in the magnetic anisotropy. The numerical modeling proves that, for direct excitation, both mechanisms drive the fundamental mode with opposite phase. The relative ratio of standing spin wave amplitudes of higher-order modes indicates that both mechanisms are substantially active.}, language = {en} } @article{ZhangHenkelHalleretal.2005, author = {Zhang, B. and Henkel, Carsten and Haller, E. and Wildermuth, S. and Hofferberth, S. and Kruger, P. and Schmiedmayer, J{\"o}rg}, title = {Relevance of sub-surface chip layers for the lifetime of magnetically trapped atoms}, year = {2005}, abstract = {We investigate the lifetime of magnetically trapped atoms above a planar, layered atom chip structure. Numerical calculations of the thermal magnetic noise spectrum are performed, based on the exact magnetic Green function and multi layer reflection coefficients. We have performed lifetime measurements where the center of a side guide trap is laterally shifted with respect to the current carrying wire using additional bias fields. Comparing the experiment to theory, we find a fair agreement and demonstrate that for a chip whose topmost layer is metallic, the magnetic noise depends essentially on the thickness of that layer, as long as the layers below have a, much smaller conductivity; essentially the same magnetic noise would be obtained with a metallic membrane suspended in vacuum. Based on our theory we give general scaling laws of how to reduce the effect of surface magnetic noise on the trapped atoms}, language = {en} } @article{ZhangHenkel2007, author = {Zhang, Bo and Henkel, Carsten}, title = {Magnetic noise around metallic microstructures}, issn = {0021-8979}, doi = {10.1063/1.2800174}, year = {2007}, abstract = {We compute the local spectrum of the magnetic field near a metallic microstructure at finite temperature. Our main focus is on deviations from a plane-layered geometry for which we review the main properties. Arbitrary geometries are handled with the help of numerical calculations based on surface integral equations. The magnetic noise shows a significant polarization anisotropy above flat wires with finite lateral width, in stark contrast to an infinitely wide wire. Within the limits of a two-dimensional setting, our results provide accurate estimates for loss and dephasing rates in so-called `atom chip traps' based on metallic wires. A simple approximation based on the incoherent summation of local current elements gives qualitative agreement with the numerics, but fails to describe current correlations among neighboring objects.}, language = {en} } @article{ZhangLideGrijsetal.2015, author = {Zhang, Chaoli and Li, Chengyuan and de Grijs, Richard and Bekki, Kenji and Deng, Licai and Zaggia, Simone and Rubele, Stefano and Piatti, Andres E. and Cioni, Maria-Rosa L. and Emerson, Jim and For, Bi-Qing and Ripepi, Vincenzo and Marconi, Marcella and Ivanov, Valentin D. and Chen, Li}, title = {The vmc survey. XVIII. radial dependence of the Low-Mass, 0.55-0.82M(circle dot) stellar mass function in the galactic globular cluster 47 tucanae}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {815}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/815/2/95}, pages = {9}, year = {2015}, language = {en} } @article{ZhangHuHuetal.2002, author = {Zhang, H. and Hu, B. and Hu, G. and Ouyang, Q. and Kurths, J{\"u}rgen}, title = {Turbulence control by developing a spiral wave with a periodic signal injection in the complex Ginzburg-Laundau equation}, year = {2002}, language = {en} } @article{ZhangChenBoettcher2014, author = {Zhang, Haocheng and Chen, Xuhui and Boettcher, Markus}, title = {Synchrotron polarization in blazars}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {789}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/789/1/66}, pages = {16}, year = {2014}, abstract = {We present a detailed analysis of time-and energy-dependent synchrotron polarization signatures in a shock-in-jet model for gamma-ray blazars. Our calculations employ a full three-dimensional radiation transfer code, assuming a helical magnetic field throughout the jet. The code considers synchrotron emission from an ordered magnetic field, and takes into account all light-travel-time and other relevant geometric effects, while the relevant synchrotron self-Compton and external Compton effects are handled with the two-dimensional Monte-Carlo/Fokker-Planck (MCFP) code. We consider several possible mechanisms through which a relativistic shock propagating through the jet may affect the jet plasma to produce a synchrotron and high-energy flare. Most plausibly, the shock is expected to lead to a compression of the magnetic field, increasing the toroidal field component and thereby changing the direction of the magnetic field in the region affected by the shock. We find that such a scenario leads to correlated synchrotron + synchrotron-self-Compton flaring, associated with substantial variability in the synchrotron polarization percentage and position angle. Most importantly, this scenario naturally explains large polarization angle rotations by greater than or similar to 180 degrees, as observed in connection with gamma-ray flares in several blazars, without the need for bent or helical jet trajectories or other nonaxisymmetric jet features.}, language = {en} } @article{ZhangChenBoettcheretal.2015, author = {Zhang, Haocheng and Chen, Xuhui and B{\"o}ttcher, Markus and Guo, Fan and Li, Hui}, title = {Polarization swings reveal magnetic energy dissipation in blazars}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {804}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/804/1/58}, pages = {11}, year = {2015}, abstract = {The polarization signatures of blazar emissions are known to be highly variable. In addition to small fluctuations of the polarization angle around a mean value, large (greater than or similar to 180 degrees) polarization angle swings are sometimes observed. We suggest that such phenomena can be interpreted as arising from light travel time effects within an underlying axisymmetric emission region. We present the first simultaneous fitting of the multi-wavelength spectrum, variability, and time-dependent polarization features of a correlated optical and gamma-ray flaring event of the prominent blazar 3C279, which was accompanied by a drastic change in its polarization signatures. This unprecedented combination of spectral, variability, and polarization information in a coherent physical model allows us to place stringent constraints on the particle acceleration and magnetic field topology in the relativistic jet of a blazar, strongly favoring a scenario in which magnetic energy dissipation is the primary driver of the flare event.}, language = {en} } @article{ZhangYan2018, author = {Zhang, Heshou and Yan, Huirong}, title = {Polarization of submillimetre lines from interstellar medium}, series = {Monthly notices of the Royal Astronomical Society}, volume = {475}, journal = {Monthly notices of the Royal Astronomical Society}, number = {2}, publisher = {Oxford University Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stx3164}, pages = {2415 -- 2420}, year = {2018}, abstract = {Magnetic fields play important roles in many astrophysical processes. However, there is no universal diagnostic for the magnetic fields in the interstellar medium (ISM) and each magnetic tracer has its limitation. Any new detection method is thus valuable. Theoretical studies have shown that submillimetre fine-structure lines are polarized due to atomic alignment by ultraviolet photon-excitation, which opens up a new avenue to probe interstellar magnetic fields. We will, for the first time, perform synthetic observations on the simulated three-dimensional ISM to demonstrate the measurability of the polarization of submillimetre atomic lines. The maximum polarization for different absorption and emission lines expected from various sources, including star-forming regions are provided. Our results demonstrate that the polarization of submillimetre atomic lines is a powerful magnetic tracer and add great value to the observational studies of the submilimetre astronomy.}, language = {en} } @article{ZhangYanRichter2018, author = {Zhang, Heshou and Yan, Huirong and Richter, Philipp}, title = {The influence of atomic alignment on absorption and emission spectroscopy}, series = {Monthly notices of the Royal Astronomical Society}, volume = {479}, journal = {Monthly notices of the Royal Astronomical Society}, number = {3}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/sty1594}, pages = {3923 -- 3935}, year = {2018}, abstract = {Spectroscopic observations play essential roles in astrophysics. They are crucial for determining physical parameters in our Universe, providing information about the chemistry of various astronomical environments. The proper execution of the spectroscopic analysis requires accounting for all the physical effects that are compatible to the signal-to-noise ratio. We find in this paper the influence on spectroscopy from the atomic/ground state alignment owing to anisotropic radiation and modulated by interstellar magnetic field, has significant impact on the study of interstellar gas. In different observational scenarios, we comprehensively demonstrate how atomic alignment influences the spectral analysis and provide the expressions for correcting the effect. The variations are even more pronounced for multiplets and line ratios. We show the variation of the deduced physical parameters caused by the atomic alignment effect, including alpha-to-iron ratio ([X/Fe]) and ionization fraction. Synthetic observations are performed to illustrate the visibility of such effect with current facilities. A study of Photodissociation regions in rho Ophiuchi cloud is presented to demonstrate how to account for atomic alignment in practice. Our work has shown that due to its potential impact, atomic alignment has to be included in an accurate spectroscopic analysis of the interstellar gas with current observational capability.}, language = {en} } @article{ZhangChenArminetal.2017, author = {Zhang, Kai and Chen, Zhiming and Armin, Ardalan and Dong, Sheng and Xia, Ruoxi and Yip, Hin-Lap and Shoaee, Safa and Huang, Fei and Cao, Yong}, title = {Efficient large area organic solar cells processed by blade-coating with single-component green solvent}, series = {Solar Rrl}, volume = {2}, journal = {Solar Rrl}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2367-198X}, doi = {10.1002/solr.201700169}, pages = {9}, year = {2017}, abstract = {While the performance of laboratory-scale organic solar cells (OSCs) continues to grow, development of high efficiency large area OSCs remains a big challenge. Although a few attempts to produce large area organic solar cells (OSCs) have been reported, there are still challenges on the way to realizing efficient module devices, such as the low compatibility of the thickness-sensitive active layer with large area coating techniques, the frequent need for toxic solvents and tedious optimization processes used during device fabrication. In this work, highly efficient thickness-insensitive OSCs based on PTB7-Th:PC71BM that processed with single-component green solvent 2-methylanisole are presented, in which both junction thickness limitation and solvent toxicity issues are simultaneously addressed. Careful investigation reveals that this green solvent prevents the evolution of PC71BM into large area clusters resulting in reduced charge carrier recombination, and largely eliminates trapping centers, and thus improves the thickness tolerance of the films. These findings enable us to address the scalability and solvent toxicity issues and to fabricate a 16 cm(2) OSC with doctor-blade coating with a state-of-the-art power conversion efficiency of 7.5\% using green solvent.}, language = {en} } @article{ZhangHayerAlSutietal.2006, author = {Zhang, Ning and Hayer, Anna and Al-Suti, Mohammed K. and Al-Belushi, Rayya A. and Khan, Muhammad S. and K{\"o}hler, Anna}, title = {The effect of delocalization on the exchange energy in meta- and para-linked Pt-containing carbazole polymers and monomers}, doi = {10.1063/1.2200351}, year = {2006}, abstract = {A series of novel platinum-containing carbazole monomers and polymers was synthesized and fully characterized by UV-VIS absorption, luminescence, and photoinduced absorption studies. In these compounds, a carbazole unit is incorporated into the main chain via either a para- or a meta-linkage. We discuss the effects of linkage and polymerization on the energy levels of S-1, T-1, and T-n. The S-1-T-1 splitting observed for the meta-linked monomer (0.4 eV) is only half of that in the para-linked monomer (0.8 eV). Upon polymerization, the exchange energy in the para- linked compound reduces, yet still remains larger than in the meta-linked polymer. We attribute the difference in exchange energy to the difference in wave function overlap between electron and hole in these compounds. (c) 2006 American Institute of Physics}, language = {en} } @article{ZhangHosseiniGunderetal.2019, author = {Zhang, Shanshan and Hosseini, Seyed Mehrdad and Gunder, Rene and Petsiuk, Andrei and Caprioglio, Pietro and Wolff, Christian Michael and Shoaee, Safa and Meredith, Paul and Schorr, Susan and Unold, Thomas and Burn, Paul L. and Neher, Dieter and Stolterfoht, Martin}, title = {The Role of Bulk and Interface Recombination in High-Efficiency Low-Dimensional Perovskite Solar Cells}, series = {Advanced materials}, volume = {31}, journal = {Advanced materials}, number = {30}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0935-9648}, doi = {10.1002/adma.201901090}, pages = {11}, year = {2019}, abstract = {2D Ruddlesden-Popper perovskite (RPP) solar cells have excellent environmental stability. However, the power conversion efficiency (PCE) of RPP cells remains inferior to 3D perovskite-based cells. Herein, 2D (CH3(CH2)(3)NH3)(2)(CH3NH3)(n-1)PbnI3n+1 perovskite cells with different numbers of [PbI6](4-) sheets (n = 2-4) are analyzed. Photoluminescence quantum yield (PLQY) measurements show that nonradiative open-circuit voltage (V-OC) losses outweigh radiative losses in materials with n > 2. The n = 3 and n = 4 films exhibit a higher PLQY than the standard 3D methylammonium lead iodide perovskite although this is accompanied by increased interfacial recombination at the top perovskite/C-60 interface. This tradeoff results in a similar PLQY in all devices, including the n = 2 system where the perovskite bulk dominates the recombination properties of the cell. In most cases the quasi-Fermi level splitting matches the device V-OC within 20 meV, which indicates minimal recombination losses at the metal contacts. The results show that poor charge transport rather than exciton dissociation is the primary reason for the reduction in fill factor of the RPP devices. Optimized n = 4 RPP solar cells had PCEs of 13\% with significant potential for further improvements.}, language = {en} } @article{ZhangStolterfohtArminetal.2018, author = {Zhang, Shanshan and Stolterfoht, Martin and Armin, Ardalan and Lin, Qianqian and Zu, Fengshuo and Sobus, Jan and Jin, Hui and Koch, Norbert and Meredith, Paul and Burn, Paul L. and Neher, Dieter}, title = {Interface Engineering of Solution-Processed Hybrid Organohalide Perovskite Solar Cells}, series = {ACS applied materials \& interfaces}, volume = {10}, journal = {ACS applied materials \& interfaces}, number = {25}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/acsami.8b02503}, pages = {21681 -- 21687}, year = {2018}, abstract = {Engineering the interface between the perovskite absorber and the charge-transporting layers has become an important method for improving the charge extraction and open-circuit voltage (V-OC) of hybrid perovskite solar cells. Conjugated polymers are particularly suited to form the hole-transporting layer, but their hydrophobicity renders it difficult to solution-process the perovskite absorber on top. Herein, oxygen plasma treatment is introduced as a simple means to change the surface energy and work function of hydrophobic polymer interlayers for use as p-contacts in perovskite solar cells. We find that upon oxygen plasma treatment, the hydrophobic surfaces of different prototypical p-type polymers became sufficiently hydrophilic to enable subsequent perovskite junction processing. In addition, the oxygen plasma treatment also increased the ionization potential of the polymer such that it became closer to the valance band energy of the perovskite. It was also found that the oxygen plasma treatment could increase the electrical conductivity of the p-type polymers, facilitating more efficient charge extraction. On the basis of this concept, inverted MAPbI(3) perovskite devices with different oxygen plasma-treated polymers such as P3HT, P3OT, polyTPD, or PTAA were fabricated with power conversion efficiencies of up to 19\%.}, language = {en} } @article{ZhangZhangYouetal.2014, author = {Zhang, Xiaoqing and Zhang, Xinwu and You, Qiong and Sessler, Gerhard M.}, title = {Low- cost, large- area, stretchable piezoelectric films based on irradiation- crosslinked poly ( propylene)}, series = {Macromolecular materials and engineering}, volume = {299}, journal = {Macromolecular materials and engineering}, number = {3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1438-7492}, doi = {10.1002/mame.201300161}, pages = {290 -- 295}, year = {2014}, abstract = {Low cost, large area, lightweight, stretchable piezoelectric films, based on space-charge electret with a foam structure (i.e., ferroelectrets or piezoelectrets), have been fabricated by using commercially available irradiation cross-linked poly(propylene) (IXPP) foam sheets. Piezoelectric d(33) coefficients are as high as 100pCN(-1). The piezoelectric performance in such IXPP films is well preserved for repeated strains of less than 10\%. Piezoelectric d(33) coefficients are frequency independent in the range from 2 to 100Hz. Such new class materials may be applied in sensory skins, smart clothing, bio-inspired systems, microenergy harvesters, and so on.}, language = {en} } @article{ZhangPikovskijLiu2017, author = {Zhang, Xiyun and Pikovskij, Arkadij and Liu, Zonghua}, title = {Dynamics of oscillators globally coupled via two mean fields}, series = {Scientific reports}, volume = {7}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-017-02283-1}, pages = {16}, year = {2017}, abstract = {Many studies of synchronization properties of coupled oscillators, based on the classical Kuramoto approach, focus on ensembles coupled via a mean field. Here we introduce a setup of Kuramoto-type phase oscillators coupled via two mean fields. We derive stability properties of the incoherent state and find traveling wave solutions with different locking patterns; stability properties of these waves are found numerically. Mostly nontrivial states appear when the two fields compete, i.e. one tends to synchronize oscillators while the other one desynchronizes them. Here we identify normal branches which bifurcate from the incoherent state in a usual way, and anomalous branches, appearance of which cannot be described as a bifurcation. Furthermore, hybrid branches combining properties of both are described. In the situations where no stable traveling wave exists, modulated quasiperiodic in time dynamics is observed. Our results indicate that a competition between two coupling channels can lead to a complex system behavior, providing a potential generalized framework for understanding of complex phenomena in natural oscillatory systems.}, language = {en} } @article{ZhaoDunlopQiuetal.2014, author = {Zhao, Qiang and Dunlop, John William Chapman and Qiu, Xunlin and Huang, Feihe and Zhang, Zibin and Heyda, Jan and Dzubiella, Joachim and Antonietti, Markus and Yuan, Jiayin}, title = {An instant multi-responsive porous polymer actuator driven by solvent molecule sorption}, series = {Nature Communications}, volume = {5}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/ncomms5293}, pages = {8}, year = {2014}, abstract = {Fast actuation speed, large-shape deformation and robust responsiveness are critical to synthetic soft actuators. A simultaneous optimization of all these aspects without trade-offs remains unresolved. Here we describe porous polymer actuators that bend in response to acetone vapour (24 kPa, 20 degrees C) at a speed of an order of magnitude faster than the state-of-the-art, coupled with a large-scale locomotion. They are meanwhile multi-responsive towards a variety of organic vapours in both the dry and wet states, thus distinctive from the traditional gel actuation systems that become inactive when dried. The actuator is easy-to-make and survives even after hydrothermal processing (200 degrees C, 24 h) and pressing-pressure (100 MPa) treatments. In addition, the beneficial responsiveness is transferable, being able to turn 'inert' objects into actuators through surface coating. This advanced actuator arises from the unique combination of porous morphology, gradient structure and the interaction between solvent molecules and actuator materials.}, language = {en} } @article{ZhaoYanLiuetal.2022, author = {Zhao, Siqi Q. and Yan, Huirong and Liu, Terry Z. and Liu, Mingzhe and Wang, Huizi}, title = {Multispacecraft analysis of the properties of magnetohydrodynamic fluctuations in Sub-Alfvenic solar wind turbulence at 1 au}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {937}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/1538-4357/ac822e}, pages = {14}, year = {2022}, abstract = {We present observations of three-dimensional magnetic power spectra in wavevector space to investigate the anisotropy and scalings of sub-Alfvenic solar wind turbulence at magnetohydrodynamic (MHD) scale using the Magnetospheric Multiscale spacecraft. The magnetic power distributions are organized in a new coordinate determined by wavevectors ((kappa) over cap) and background magnetic field ((b) over cap (0)) in Fourier space. This study utilizes two approaches to determine wavevectors: the singular value decomposition method and multispacecraft timing analysis. The combination of the two methods allows an examination of the properties of magnetic field fluctuations in terms of mode compositions without any spatiotemporal hypothesis. Observations show that fluctuations (delta B-perpendicular to 1) in the direction perpendicular to (kappa) over cap and (b) over cap (0) prominently cascade perpendicular to (b) over cap (0), and such anisotropy increases with wavenumbers. The reduced power spectra of 6.8 11 follow Goldreich-Sridhar scalings: (P) over cap (k(perpendicular to)) proportional to k(perpendicular to)(-5/3) and (P) over cap (k(parallel to)) proportional to k(parallel to)(-2). In contrast, fluctuations within the (k) over cap(b) over cap (0) plane show isotropic behaviors: perpendicular power distributions are approximately the same as parallel distributions. The reduced power spectra of fluctuations within the (k) over cap(b) over cap (0) plane follow the scalings (P) over cap (k(perpendicular to)) proportional to k(perpendicular to)(-3/2) and (P) over cap (k(parallel to)) proportional to k(parallel to)(-3/2). Comparing frequency-wavevector spectra with theoretical dispersion relations of MHD modes, we find that delta B-perpendicular to 1 are probably associated with Alfven modes. On the other hand, magnetic field fluctuations within the (k) over cap(b) over cap (0) plane more likely originate from fast modes based on their isotropic behaviors. The observations of anisotropy and scalings of different magnetic field components are consistent with the predictions of current compressible MHD theory. Moreover, for the Alfvenic component, the ratio of cascading time to the wave period is found to be a factor of a few, consistent with critical balance in the strong turbulence regime. These results are valuable for further studies of energy compositions of plasma turbulence and their effects on energetic particle transport.}, language = {en} } @article{ZhaoSarhanEljarratetal.2022, author = {Zhao, Yuhang and Sarhan, Radwan Mohamed and Eljarrat, Alberto and Kochovski, Zdravko and Koch, Christoph and Schmidt, Bernd and Koopman, Wouter-Willem Adriaan and Lu, Yan}, title = {Surface-functionalized Au-Pd nanorods with enhanced photothermal conversion and catalytic performance}, series = {ACS applied materials \& interfaces}, volume = {14}, journal = {ACS applied materials \& interfaces}, number = {15}, publisher = {American Chemical Society}, address = {Washington, DC}, issn = {1944-8244}, doi = {10.1021/acsami.2c00221}, pages = {17259 -- 17272}, year = {2022}, abstract = {Bimetallic nanostructures comprising plasmonic and catalytic components have recently emerged as a promising approach to generate a new type of photo-enhanced nanoreactors. Most designs however concentrate on plasmon-induced charge separation, leaving photo-generated heat as a side product. This work presents a photoreactor based on Au-Pd nanorods with an optimized photothermal conversion, which aims to effectively utilize the photo-generated heat to increase the rate of Pd-catalyzed reactions. Dumbbell-shaped Au nanorods were fabricated via a seed-mediated growth method using binary surfactants. Pd clusters were selectively grown at the tips of the Au nanorods, using the zeta potential as a new synthetic parameter to indicate the surfactant remaining on the nanorod surface. The photothermal conversion of the Au-Pd nanorods was improved with a thin layer of polydopamine (PDA) or TiO2. As a result, a 60\% higher temperature increment of the dispersion compared to that for bare Au rods at the same light intensity and particle density could be achieved. The catalytic performance of the coated particles was then tested using the reduction of 4-nitrophenol as the model reaction. Under light, the PDA-coated Au-Pd nanorods exhibited an improved catalytic activity, increasing the reaction rate by a factor 3. An analysis of the activation energy confirmed the photoheating effect to be the dominant mechanism accelerating the reaction. Thus, the increased photothermal heating is responsible for the reaction acceleration. Interestingly, the same analysis shows a roughly 10\% higher reaction rate for particles under illumination compared to under dark heating, possibly implying a crucial role of localized heat gradients at the particle surface. Finally, the coating thickness was identified as an essential parameter determining the photothermal conversion efficiency and the reaction acceleration.}, language = {en} }