@article{BetaKruse2017, author = {Beta, Carsten and Kruse, Karsten}, title = {Intracellular oscillations and waves}, series = {Annual review of condensed matter physics}, volume = {8}, journal = {Annual review of condensed matter physics}, publisher = {Annual Reviews}, address = {Palo Alto}, isbn = {978-0-8243-5008-6}, issn = {1947-5454}, doi = {10.1146/annurev-conmatphys-031016-025210}, pages = {239 -- 264}, year = {2017}, abstract = {Dynamic processes in living cells are highly organized in space and time. Unraveling the underlying molecular mechanisms of spatiotemporal pattern formation remains one of the outstanding challenges at the interface between physics and biology. A fundamental recurrent pattern found in many different cell types is that of self-sustained oscillations. They are involved in a wide range of cellular functions, including second messenger signaling, gene expression, and cytoskeletal dynamics. Here, we review recent developments in the field of cellular oscillations and focus on cases where concepts from physics have been instrumental for understanding the underlying mechanisms. We consider biochemical and genetic oscillators as well as oscillations that arise from chemo-mechanical coupling. Finally, we highlight recent studies of intracellular waves that have increasingly moved into the focus of this research field.}, language = {en} } @article{UsanovaShprits2017, author = {Usanova, Maria E. and Shprits, Yuri Y.}, title = {Inner magnetosphere coupling}, series = {Journal of geophysical research : Space physics}, volume = {122}, journal = {Journal of geophysical research : Space physics}, number = {1}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1002/2016JA023614}, pages = {102 -- 104}, year = {2017}, abstract = {The dynamics of the inner magnetosphere is strongly governed by the interactions between different plasma populations that are coupled through large-scale electric and magnetic fields, currents, and wave-particle interactions. Inner magnetospheric plasma undergoes self-consistent interactions with global electric and magnetic fields. Waves excited in the inner magnetosphere from unstable particle distributions can provide energy exchange between different particle populations in the inner magnetosphere and affect the ring current and radiation belt dynamics. The ionosphere serves as an energy sink and feeds the magnetosphere back through the cold plasma outflow. The precipitating inner magnetospheric particles influence the ionosphere and upper atmospheric chemistry and affect climate. Satellite measurements and theoretical studies have advanced our understanding of the dynamics of various plasma populations in the inner magnetosphere. However, our knowledge of the coupling processes among the plasmasphere, ring current, radiation belts, global magnetic and electric fields, and plasma waves generated within these systems is still incomplete. This special issue incorporates extended papers presented at the Inner Magnetosphere Coupling III conference held 23-27 March 2015 in Los Angeles, California, USA, and includes modeling and observational contributions addressing interactions within different plasma populations in the inner magnetosphere (plasmasphere, ring current, and radiation belts), coupling between fields and plasma populations, as well as effects of the inner magnetosphere on the ionosphere and atmosphere.}, language = {en} } @article{SchubertFrischAllardetal.2017, author = {Schubert, Marcel and Frisch, Johannes and Allard, Sybille and Preis, Eduard and Scherf, Ullrich and Koch, Norbert and Neher, Dieter}, title = {Tuning side chain and main chain order in a prototypical donor-acceptor copolymer}, series = {Elementary Processes in Organic Photovoltaics}, volume = {272}, journal = {Elementary Processes in Organic Photovoltaics}, publisher = {Springer}, address = {Berlin}, isbn = {978-3-319-28338-8}, issn = {0065-3195}, doi = {10.1007/978-3-319-28338-8_10}, pages = {243 -- 265}, year = {2017}, abstract = {The recent development of donor-acceptor copolymers has led to an enormous improvement in the performance of organic solar cells and organic field-effect transistors. Here we describe the synthesis, detailed characterisation, and application of a series of structurally modified copolymers to investigate fundamental structure-property relationships in this class of conjugated polymers. The interplay between chemical structure and optoelectronic properties is investigated. These are further correlated to the charge transport and solar cell performance, which allows us to link their chemical structure to the observed physical properties.}, language = {en} } @article{DahlkeMaturilli2017, author = {Dahlke, Sandro and Maturilli, Marion}, title = {Contribution of atmospheric advection to the amplified winter warming in the arctic north atlantic region}, series = {Advances in meteorology}, journal = {Advances in meteorology}, publisher = {Hindawi Publ. Corp.}, address = {New York}, issn = {1687-9309}, doi = {10.1155/2017/4928620}, pages = {8}, year = {2017}, abstract = {Arctic Amplification of climate warming is caused by various feedback processes in the atmosphere-ocean-ice system and yields the strongest temperature increase during winter in the Arctic North Atlantic region. In our study, we attempt to quantify the advective contribution to the observed atmospheric warming in the Svalbard area. Based on radiosonde measurements from Ny-{\AA}lesund, a strong dependence of the tropospheric temperature on the synoptic flow direction is revealed. Using FLEXTRA backward trajectories, an increase of advection from the lower latitude Atlantic region towards Ny-{\AA}lesund is found that is attributed to a change in atmospheric circulation patterns. We find that about one-quarter (0.45 K per decade) of the observed atmospheric winter near surface warming trend in the North Atlantic region of the Arctic (2 K per decade) is due to increased advection of warm and moist air from the lower latitude Atlantic region, affecting the entire troposphere.}, language = {en} } @article{BuschhueterSpodenBorowski2017, author = {Buschh{\"u}ter, David and Spoden, Christian and Borowski, Andreas}, title = {Physics knowledge of first semester physics students in Germany}, series = {International journal of science education}, volume = {39}, journal = {International journal of science education}, number = {9}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {0950-0693}, doi = {10.1080/09500693.2017.1318457}, pages = {1109 -- 1132}, year = {2017}, abstract = {Over the last decades, the percentage of the age group choosing to pursue university studies has increased significantly across the world. At the same time, there are university teachers who believe that the standards have fallen. There is little research on whether students nowadays demonstrate knowledge or abilities similar to that of the preceding cohorts. However, in times of educational expansion, empirical evidence on student test performance is extremely helpful in evaluating how well educational systems cope with the increasing numbers of students. In this study, we compared a sample of 2322 physics freshmen from 2013 with another sample of 2718 physics freshmen from 1978 at universities in Germany with regard to their physics knowledge based on their results in the same entrance test. Previous results on mathematics knowledge and abilities in the same sample of students indicated that there was no severe decline in their average achievement. This paper compares the physics knowledge of the same two samples of students. Contrary to their mathematics results, their physics results showed a substantial decrease in physics knowledge as measured by the test.}, language = {en} } @article{Richter2017, author = {Richter, Philipp}, title = {Gas accretion onto the Milky Way}, series = {Astrophysics and space science library}, volume = {430}, journal = {Astrophysics and space science library}, editor = {Fox, Andrew J. and Dav{\´e}, Romeel}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-52512-9}, issn = {0067-0057}, doi = {10.1007/978-3-319-52512-9_2}, pages = {15 -- 47}, year = {2017}, abstract = {The Milky Way is surrounded by large amounts of gaseous matter that are slowly being accreted over cosmic timescales to support star formation in the disk. The corresponding gas-accretion rate represents a key parameter for the past, present, and future evolution of the Milky Way. In this chapter, we discuss our current understanding of gas accretion processes in the Galaxy by reviewing past and recent observational and theoretical studies. The first part of this review deals with the spatial distribution of the different gas phases in the Milky Way halo, the origin of the gas, and its total mass. The second part discusses the gas dynamics and the physical processes that regulate the gas flow from the outer Galactic halo to the disk. From the most recent studies follows that the present-day gas accretion rate of the Milky Way is a few solar masses per year, which is sufficient to maintain the Galaxy's star-formation rate at its current level.}, language = {en} } @article{MorgnerBennemannCywińskietal.2017, author = {Morgner, Frank and Bennemann, Mark and Cywiński, Piotr J. and Kollosche, Matthias and G{\´o}rski, Krzysztof and Pietraszkiewicz, Marek and Geßner, Andr{\´e} and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Elastic FRET sensors for contactless pressure measurement}, series = {RSC Advances : an international journal to further the chemical sciences}, volume = {7}, journal = {RSC Advances : an international journal to further the chemical sciences}, publisher = {RSC Publishing}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c7ra06379b}, pages = {50578 -- 50583}, year = {2017}, abstract = {Contactless pressure monitoring based on Forster resonance energy transfer between donor/acceptor pairs immobilized within elastomers is demonstrated. The donor/acceptor energy transfer is employed by dispersing terbium(III) tris[(2-hydroxybenzoyl)-2-aminoethyl] amine complex (LLC, donor) and CdSe/ZnS quantum dots (QD655, acceptor) in styrene-ethylene/buthylene-styrene (SEBS) and poly(dimethylsiloxane) (PDMS). The continuous monitoring of QD luminescence showed a reversible intensity change as the pressure signal is alternated between two stable states indicating a pressure sensitivity of 6350 cps kPa(-1). Time-resolved measurements show the pressure impact on the FRET signal due to an increase of decay time (270 ms up to 420 ms) for the donor signal and parallel drop of decay time (170 mu s to 155 mu s) for the acceptor signal as the net pressure applied. The LLC/QD655 sensors enable a contactless readout as well as space resolved monitoring to enable miniaturization towards smaller integrated stretchable opto-electronics. Elastic FRET sensors can potentially lead to developing profitable analysis systems capable to outdo conventional wired electronic systems (inductive, capacitive, ultrasonic and photoelectric sensors) especially for point-of-care diagnostics, biological monitoring required for wearable electronics.}, language = {en} } @article{RaetzelWilkensMenzel2017, author = {R{\"a}tzel, Dennis and Wilkens, Martin and Menzel, Ralf}, title = {Effect of polarization entanglement in photon-photon scattering}, series = {Physical review : A, Atomic, molecular, and optical physics}, volume = {95}, journal = {Physical review : A, Atomic, molecular, and optical physics}, number = {1}, publisher = {American Physical Society}, address = {College Park}, issn = {2469-9926}, doi = {10.1103/PhysRevA.95.012101}, pages = {6}, year = {2017}, abstract = {It is found that the differential cross section of photon-photon scattering is a function of the degree of polarization entanglement of the two-photon state. A reduced general expression for the differential cross section of photon-photon scattering is derived by applying simple symmetry arguments. An explicit expression is obtained for the example of photon-photon scattering due to virtual electron-positron pairs in quantum electrodynamics. It is shown how the effect in this explicit example can be explained as an effect of quantum interference and that it fits with the idea of distance-dependent forces.}, language = {en} } @article{SchimkaLomadzeRabeetal.2017, author = {Schimka, Selina and Lomadze, Nino and Rabe, Maren and Kopyshev, Alexey and Lehmann, Maren and von Klitzing, Regine and Rumyantsev, Artem M. and Kramarenko, Elena Yu. and Santer, Svetlana}, title = {Photosensitive microgels containing azobenzene surfactants of different charges}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {19}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c6cp04555c}, pages = {108 -- 117}, year = {2017}, abstract = {We report on light sensitive microgel particles that can change their volume reversibly in response to illumination with light of different wavelengths. To make the anionic microgels photosensitive we add surfactants with a positively charged polyamine head group and an azobenzene containing tail. Upon illumination, azobenzene undergoes a reversible photo-isomerization reaction from a trans- to a cis-state accompanied by a change in the hydrophobicity of the surfactant. Depending on the isomerization state, the surfactant molecules are either accommodated within the microgel (trans- state) resulting in its shrinkage or desorbed back into water (cis-isomer) letting the microgel swell. We have studied three surfactants differing in the number of amino groups, so that the number of charges of the surfactant head varies between 1 and 3. We have found experimentally and theoretically that the surfactant concentration needed for microgel compaction increases with decreasing number of charges of the head group. Utilization of polyamine azobenzene containing surfactants for the light triggered remote control of the microgel size opens up a possibility for applications of light responsive microgels as drug carriers in biology and medicine.}, language = {en} } @article{SafdariCherstvyChechkinetal.2017, author = {Safdari, Hadiseh and Cherstvy, Andrey G. and Chechkin, Aleksei V. and Bodrova, Anna and Metzler, Ralf}, title = {Aging underdamped scaled Brownian motion}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {95}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, publisher = {American Physical Society}, address = {College Park}, issn = {2470-0045}, doi = {10.1103/PhysRevE.95.012120}, pages = {15}, year = {2017}, abstract = {We investigate both analytically and by computer simulations the ensemble- and time-averaged, nonergodic, and aging properties of massive particles diffusing in a medium with a time dependent diffusivity. We call this stochastic diffusion process the (aging) underdamped scaled Brownian motion (UDSBM). We demonstrate how the mean squared displacement (MSD) and the time-averaged MSD of UDSBM are affected by the inertial term in the Langevin equation, both at short, intermediate, and even long diffusion times. In particular, we quantify the ballistic regime for the MSD and the time-averaged MSD as well as the spread of individual time-averaged MSD trajectories. One of the main effects we observe is that, both for the MSD and the time-averaged MSD, for superdiffusive UDSBM the ballistic regime is much shorter than for ordinary Brownian motion. In contrast, for subdiffusive UDSBM, the ballistic region extends to much longer diffusion times. Therefore, particular care needs to be taken under what conditions the overdamped limit indeed provides a correct description, even in the long time limit. We also analyze to what extent ergodicity in the Boltzmann-Khinchin sense in this nonstationary system is broken, both for subdiffusive and superdiffusive UDSBM. Finally, the limiting case of ultraslow UDSBM is considered, with a mixed logarithmic and power-law dependence of the ensemble-and time-averaged MSDs of the particles. In the limit of strong aging, remarkably, the ordinary UDSBM and the ultraslow UDSBM behave similarly in the short time ballistic limit. The approaches developed here open ways for considering other stochastic processes under physically important conditions when a finite particle mass and aging in the system cannot be neglected.}, language = {en} } @article{GongKlumpp2017, author = {Gong, Chen Chris and Klumpp, Stefan}, title = {Modeling sRNA-Regulated Plasmid Maintenance}, series = {PLoS one}, volume = {12}, journal = {PLoS one}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0169703}, pages = {19}, year = {2017}, abstract = {We study a theoretical model for the toxin-antitoxin (hok/sok) mechanism for plasmid maintenance in bacteria. Toxin-antitoxin systems enforce the maintenance of a plasmid through post-segregational killing of cells that have lost the plasmid. Key to their function is the tight regulation of expression of a protein toxin by an sRNA antitoxin. Here, we focus on the nonlinear nature of the regulatory circuit dynamics of the toxin-antitoxin mechanism. The mechanism relies on a transient increase in protein concentration rather than on the steady state of the genetic circuit. Through a systematic analysis of the parameter dependence of this transient increase, we confirm some known design features of this system and identify new ones: for an efficient toxin-antitoxin mechanism, the synthesis rate of the toxin's mRNA template should be lower that of the sRNA antitoxin, the mRNA template should be more stable than the sRNA antitoxin, and the mRNA-sRNA complex should be more stable than the sRNA antitoxin. Moreover, a short half-life of the protein toxin is also beneficial to the function of the toxin-antitoxin system. In addition, we study a therapeutic scenario in which a competitor mRNA is introduced to sequester the sRNA antitoxin, causing the toxic protein to be expressed.}, language = {en} } @article{CoutoCruzErtanetal.2017, author = {Couto, Rafael C. and Cruz, Vinicius V. and Ertan, Emelie and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Guimaraes, Freddy F. and Agren, Hans and Odelius, Michael and Kimberg, Victor and F{\"o}hlisch, Alexander}, title = {Selective gating to vibrational modes through resonant X-ray scattering}, series = {Nature Communications}, volume = {8}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/ncomms14165}, pages = {7}, year = {2017}, abstract = {The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations.}, language = {en} } @article{MardoukhiMardoukhiHokkaetal.2017, author = {Mardoukhi, Ahmad and Mardoukhi, Yousof and Hokka, Mikko and Kuokkala, Veli-Tapani}, title = {Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite}, series = {Philosophical Transactions of the Royal Society of London, Series A : Mathematical, Physical and Engineering Sciences}, volume = {375}, journal = {Philosophical Transactions of the Royal Society of London, Series A : Mathematical, Physical and Engineering Sciences}, number = {2085}, publisher = {Royal Society}, address = {London}, issn = {1364-503X}, doi = {10.1098/rsta.2016.0179}, pages = {11}, year = {2017}, abstract = {This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates.}, language = {en} } @article{Goychuk2017, author = {Goychuk, Igor}, title = {Quantum ergodicity breaking in semi-classical electron transfer dynamics}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {19}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c6cp07206b}, pages = {3056 -- 3066}, year = {2017}, abstract = {Can the statistical properties of single-electron transfer events be correctly predicted within a common equilibrium ensemble description? This fundamental in nanoworld question of ergodic behavior is scrutinized within a very basic semi-classical curve-crossing problem. It is shown that in the limit of non-adiabatic electron transfer (weak tunneling) well-described by the Marcus-Levich-Dogonadze (MLD) rate the answer is yes. However, in the limit of the so-called solvent-controlled adiabatic electron transfer, a profound breaking of ergodicity occurs. Namely, a common description based on the ensemble reduced density matrix with an initial equilibrium distribution of the reaction coordinate is not able to reproduce the statistics of single-trajectory events in this seemingly classical regime. For sufficiently large activation barriers, the ensemble survival probability in a state remains nearly exponential with the inverse rate given by the sum of the adiabatic curve crossing (Kramers) time and the inverse MLD rate. In contrast, near to the adiabatic regime, the single-electron survival probability is clearly non-exponential, even though it possesses an exponential tail which agrees well with the ensemble description. Initially, it is well described by a Mittag-Leffler distribution with a fractional rate. Paradoxically, the mean transfer time in this classical on the ensemble level regime is well described by the inverse of the nonadiabatic quantum tunneling rate on a single particle level. An analytical theory is developed which perfectly agrees with stochastic simulations and explains our findings.}, language = {en} } @article{KunnusJosefssonSchrecketal.2017, author = {Kunnus, Kristjan and Josefsson, I. and Schreck, Simon Frederik and Quevedo, W. and Miedema, P. S. and Techert, S. and de Groot, F. M. F. and F{\"o}hlisch, Alexander and Odelius, M. and Wernet, Ph.}, title = {Quantifying covalent interactions with resonant inelastic soft X-ray scattering}, series = {Chemical physics letters}, volume = {669}, journal = {Chemical physics letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0009-2614}, doi = {10.1016/j.cplett.2016.12.046}, pages = {196 -- 201}, year = {2017}, abstract = {We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L-3-edge allows to determine that the Ni 3d orbitals have on average 5.5\% of water character. We propose that 2p3d RIXS at the Ni L-3-edge can be utilized to quantify covalency in Ni complexes without the use of external references or simulations.}, language = {en} } @article{VandewalBenduhnSchellhammeretal.2017, author = {Vandewal, Koen and Benduhn, Johannes and Schellhammer, Karl Sebastian and Vangerven, Tim and R{\"u}ckert, Janna E. and Piersimoni, Fortunato and Scholz, Reinhard and Zeika, Olaf and Fan, Yeli and Barlow, Stephen and Neher, Dieter and Marder, Seth R. and Manca, Jean and Spoltore, Donato and Cuniberti, Gianaurelio and Ortmann, Frank}, title = {Absorption Tails of Donor}, series = {Journal of the American Chemical Society}, volume = {139}, journal = {Journal of the American Chemical Society}, number = {4}, publisher = {American Chemical Society}, address = {Washington}, issn = {0002-7863}, doi = {10.1021/jacs.6b12857}, pages = {1699 -- 1704}, year = {2017}, abstract = {In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D A complexes occur at photon energies below the optical gaps of both the donors and the C-60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C-60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes.}, language = {en} } @article{Henkel2017, author = {Henkel, Carsten}, title = {Nanoscale Thermal Transfer}, series = {Zeitschrift f{\"u}r Naturforschung A}, volume = {72}, journal = {Zeitschrift f{\"u}r Naturforschung A}, number = {2}, publisher = {De Gruyter}, address = {Berlin}, issn = {0932-0784}, doi = {10.1515/zna-2016-0372}, pages = {99 -- 108}, year = {2017}, abstract = {An electromagnetic theory of thermal radiation is outlined, based on the fluctuation electrodynamics of Rytov and co-workers. We discuss the basic concepts and the status of different approximations. The physical content is illustrated with a few examples on near-field heat transfer.}, language = {en} } @article{SundeGrijsSubramanianetal.2017, author = {Sun, Ning-Chen and de Grijs, Richard and Subramanian, Smitha and Cioni, Maria-Rosa L. and Rubele, Stefano and Bekki, Kenji and Ivanov, Valentin D. and Piatti, Andr{\´e}s E. and Ripepi, Vincenzo}, title = {The VMC Survey. XXII. Hierarchical star formation in the 30 Doradus-N158-N159-N160 star-forming complex}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {835}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {Institute of Physics Publ.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/1538-4357/835/2/171}, pages = {10}, year = {2017}, abstract = {We study the hierarchical stellar structures in a similar to 1.5 deg(2) area covering the 30. Doradus-N158-N159-N160 starforming complex with the VISTA Survey of. Magellanic Clouds. Based on the young upper main-sequence stars, we find that the surface densities cover a wide range of values, from log(Sigma.pc(2))less than or similar to -2.0 to log(Sigma. pc(2)) greater than or similar to 0.0. Their distributions are highly non-uniform, showing groups that frequently have subgroups inside. The sizes of the stellar groups do not exhibit characteristic values, and range continuously from several parsecs to more than 100. pc; the cumulative size distribution can be well described by a single power law, with the power-law index indicating a projected fractal dimension D-2 = 1.6 +/- 0.3. We suggest that the phenomena revealed here support a scenario of hierarchical star formation. Comparisons with other star-forming regions and galaxies are also discussed.}, language = {en} } @article{KoopmanNataliDonatietal.2017, author = {Koopman, Wouter-Willem Adriaan and Natali, Marco and Donati, Giovanni P. and Muccini, Michele and Toffanin, Stefano}, title = {Charge-exciton interaction rate in organic field-effect transistors by means of transient photoluminescence electromodulated spectroscopy}, series = {ACS photonics}, volume = {4}, journal = {ACS photonics}, number = {2}, publisher = {American Chemical Society}, address = {Washington, DC}, issn = {2330-4022}, doi = {10.1021/acsphotonics.6b00573}, pages = {282 -- 291}, year = {2017}, abstract = {Organic light-emitting transistors (OLETs) offer a huge potential for the design of highly integrated multifunctional optoelectronic systems and of intense nano scale light sources, such as the long-searched-for electrically pumped organic laser. In order to fulfill these promises, the efficiency and brightness of the current state-of-the-art devices have to be increased significantly. The dominating quenching process limiting the external quantum efficiency in OLETs is charge-exciton interaction. A comprehensive understanding of this quenching process is therefore of paramount importance. The present article reports a systematic investigation of charge-exciton interaction in organic transistors employing time resolved photoluminescence electro-modulation (PLEM) spectroscopy on the picosecond time scale. The results show that the injected charges reduce the exciton radiative recombination in two ways: (i) charges may prevent the generation of excitons and (ii) charges activate a further nonradiative channel for the exciton decay. Moreover, the transient PLEM measurements clearly reveal that not only trapped charges, as already reported in literature, but rather the entire injected charge density contributes to the quenching of the exciton population.}, language = {en} } @article{AlmeidaSanaTayloretal.2017, author = {Almeida, Leonardo A. and Sana, H. and Taylor, W. and Barb{\´a}, Rodolfo and Bonanos, Alceste Z. and Crowther, Paul and Damineli, Augusto and de Koter, A. and de Mink, Selma E. and Evans, C. J. and Gieles, Mark and Grin, Nathan J. and H{\´e}nault-Brunet, V. and Langer, Norbert and Lennon, D. and Lockwood, Sean and Ma{\´i}z Apell{\´a}niz, Jes{\´u}s and Moffat, A. F. J. and Neijssel, C. and Norman, C. and Ram{\´i}rez-Agudelo, O. H. and Richardson, N. D. and Schootemeijer, Abel and Shenar, Tomer and Soszyński, Igor and Tramper, Frank and Vink, J. S.}, title = {The tarantula massive binary monitoring}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {598}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201629844}, pages = {36}, year = {2017}, abstract = {Context: Massive binaries play a crucial role in the Universe. Knowing the distributions of their orbital parameters is important for a wide range of topics from stellar feedback to binary evolution channels and from the distribution of supernova types to gravitational wave progenitors, yet no direct measurements exist outside the Milky Way. Aims: The Tarantula Massive Binary Monitoring project was designed to help fill this gap by obtaining multi-epoch radial velocity (RV) monitoring of 102 massive binaries in the 30 Doradus region. Methods: In this paper we analyze 32 FLAMES/GIRAFFE observations of 93 O- and 7 B-type binaries. We performed a Fourier analysis and obtained orbital solutions for 82 systems: 51 single-lined (SB1) and 31 double-lined (SB2) spectroscopic binaries. Results: Overall, the binary fraction and orbital properties across the 30 Doradus region are found to be similar to existing Galactic samples. This indicates that within these domains environmental effects are of second order in shaping the properties of massive binary systems. A small difference is found in the distribution of orbital periods, which is slightly flatter (in log space) in 30 Doradus than in the Galaxy, although this may be compatible within error estimates and differences in the fitting methodology. Also, orbital periods in 30 Doradus can be as short as 1.1 d, somewhat shorter than seen in Galactic samples. Equal mass binaries (q> 0.95) in 30 Doradus are all found outside NGC 2070, the central association that surrounds R136a, the very young and massive cluster at 30 Doradus's core. Most of the differences, albeit small, are compatible with expectations from binary evolution. One outstanding exception, however, is the fact that earlier spectral types (O2-O7) tend to have shorter orbital periods than later spectral types (O9.2-O9.7). Conclusions: Our results point to a relative universality of the incidence rate of massive binaries and their orbital properties in the metallicity range from solar (Z⊙) to about half solar. This provides the first direct constraints on massive binary properties in massive star-forming galaxies at the Universe's peak of star formation at redshifts z ~ 1 to 2 which are estimated to have Z ~ 0.5 Z⊙.}, language = {en} }