TY - THES A1 - Liepertz, Sven Christian T1 - Zusammenhang zwischen dem Professionswissen von Physiklehrkräften, dem sachstrukturellen Angebot des Unterrichts und der Schülerleistung T2 - Studien zum Physik- und Chemielernen ; 224 Y1 - 2017 SN - 978-3-8325-4480-5 PB - Logos CY - Berlin ER - TY - JOUR A1 - Leussu, R. A1 - Usoskin, IIlya G. A1 - Valliappan, Senthamizh Pavai A1 - Diercke, Andrea A1 - Arlt, Rainer A1 - Denker, Carsten A1 - Mursula, K. T1 - Wings of the butterfly BT - sunspot groups for 1826-2015 JF - Astronomy and astrophysics : an international weekly journal N2 - The spatio-temporal evolution of sunspot activity, the so-called Maunder butterfly diagram, has been continously available since 1874 using data from the Royal Greenwich Observatory, extended by SOON network data after 1976. Here we present a new extended butterfly diagram of sunspot group occurrence since 1826, using the recently digitized data from Schwabe (1826-1867) and Sporer (1866-1880). The wings of the diagram are separated using a recently developed method based on an analysis of long gaps in sunspot group occurrence in different latitude bands. We define characteristic latitudes, corresponding to the start, end, and the largest extent of the wings (the F, L, and H latitudes). The H latitudes (30 degrees-45 degrees) are highly significantly correlated with the strength of the wings (quantified by the total sum of the monthly numbers of sunspot groups). The F latitudes (20 degrees-30 degrees) depict a weak tendency, especially in the southern hemisphere, to follow the wing strength. The L latitudes (2 degrees-10 degrees) show no clear relation to the wing strength. Overall, stronger cycle wings tend to start at higher latitudes and have a greater wing extent. A strong (5-6)-cycle periodic oscillation is found in the start and end times of the wings and in the overlap and gaps between successive wings of one hemisphere. While the average wing overlap is zero in the southern hemisphere, it is two to three months in the north. A marginally significant oscillation of about ten solar cycles is found in the asymmetry of the L latitudes. The new long database of butterfly wings provides new observational constraints to solar dynamo models that discuss the spatio-temporal distribution of sunspot occurrence over the solar cycle and longer. KW - Sun: activity KW - sunspots KW - history and philosophy of astronomy Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629533 SN - 1432-0746 VL - 599 PB - EDP Sciences CY - Les Ulis ER - TY - THES A1 - Kayser, Markus T1 - Wechselwirkung der atmosphärischen Grenzschicht mit synoptisch–skaligen Prozessen während der N-ICE2015 Kampagne N2 - Die Arktis erwärmt sich schneller als der Rest der Erde. Die Auswirkungen manifestieren sich unter Anderem in einer verstärkten Erwärmung der arktischen Grenzschicht. Diese Arbeit befasst sich mit Wechselwirkungen zwischen synoptischen Zyklonen und der arktischen Atmosphäre auf lokalen bis überregionalen Skalen. Ausgangspunkt dafür sind Messdaten und Modellsimulationen für den Zeitraum der N-ICE2015 Expedition, die von Anfang Januar bis Ende Juni 2015 im arktischen Nordatlantiksektor stattgefunden hat. Anhand von Radiosondenmessungen lassen sich Auswirkungen von synoptischen Zyklonen am deutlichsten im Winter erkennen, da sie durch die Advektion warmer und feuchter Luftmassen in die Arktis den Zustand der Atmosphäre von einem strahlungs-klaren in einen strahlungs-opaken ändern. Obwohl dieser scharfe Kontrast nur im Winter existiert, zeigt die Analyse, dass der integrierte Wasserdampf als Indikator für die Advektion von Luftmassen aus niedrigen Breiten in die Arktis auch im Frühjahr geeignet ist. Neben der Advektion von Luftmassen wird der Einfluss der Zyklonen auf die statische Stabilität charakterisiert. Beim Vergleich der N-ICE2015 Beobachtungen mit der SHEBA Kampagne (1997/1998), die über dickerem Eis stattfand, finden sich trotz der unterschiedlichen Meereisregime Ähnlichkeiten in der statischen Stabilität der Atmosphäre. Die beobachteten Differenzen in der Stabilität lassen sich auf Unterschiede in der synoptischen Aktivität zurückführen. Dies lässt vermuten, dass die dünnere Eisdecke auf saisonalen Zeitskalen nur einen geringen Einfluss auf die thermodynamische Struktur der arktischen Troposphäre besitzt, solange eine dicke Schneeschicht sie bedeckt. Ein weiterer Vergleich mit den parallel zur N-ICE2015 Kampagne gestarteten Radiosonden der AWIPEV Station in Ny-Åesund, Spitzbergen, macht deutlich, dass die synoptischen Zyklonen oberhalb der Orographie auf saisonalen Zeitskalen das Wettergeschehen bestimmen. Des Weiteren werden für Februar 2015 die Auswirkungen von in der Vertikalen variiertem Nudging auf die Entwicklung der Zyklonen am Beispiel des hydrostatischen regionalen Klimamodells HIRHAM5 untersucht. Es zeigt sich, dass die Unterschiede zwischen den acht Modellsimulationen mit abnehmender Anzahl der genudgten Level zunehmen. Die größten Differenzen resultieren vornehmlich aus dem zeitlichen Versatz der Entwicklung synoptischer Zyklonen. Zur Korrektur des Zeitversatzes der Zykloneninitiierung genügt es bereits, Nudging in den unterstem 250 m der Troposphäre anzuwenden. Daneben findet sich zwischen den genudgten HIRHAM5-Simulation und den in situ Messungen der gleiche positive Temperaturbias, den auch ERA-Interim besitzt. Das freie HIRHAM hingegen reproduziert das positive Ende der N-ICE2015 Temperaturverteilung gut, besitzt aber einen starken negativen Bias, der sehr wahrscheinlich aus einer Unterschätzung des Feuchtegehalts resultiert. An Beispiel einer Zyklone wird gezeigt, dass Nudging Einfluss auf die Lage der Höhentiefs besitzt, die ihrerseits die Zyklonenentwicklung am Boden beeinflussen. Im Weiteren wird mittels eines für kleine Ensemblegrößen geeigneten Varianzmaßes eine statistische Einschätzung der Wirkung des Nudgings auf die Vertikale getroffen. Es wird festgestellt, dass die Ähnlichkeit der Modellsimulationen in der unteren Troposphäre generell höher ist als darüber und in 500 hPa ein lokales Minimum besitzt. Im letzten Teil der Analyse wird die Wechselwirkung der oberen und unteren Stratosphäre anhand zuvor betrachteter Zyklonen mit Daten der ERA-Interim Reanalyse untersucht. Lage und Ausrichtung des Polarwirbels erzeugten ab Anfang Februar 2015 eine ungewöhnlich große Meridionalkomponente des Tropopausenjets, die Zugbahnen in die zentrale Arktis begünstigte. Am Beispiel einer Zyklone wird die Übereinstimmung der synoptischen Entwicklung mit den theoretischen Annahmen über den abwärts gerichteten Einfluss der Stratosphäre auf die Troposphäre hervorgehoben. Dabei spielt die nicht-lineare Wechselwirkung zwischen der Orographie Grönlands, einer Intrusion stratosphärischer Luft in die Troposphäre sowie einer in Richtung Arktis propagierender Rossby-Welle eine tragende Rolle. Als Indikator dieser Wechselwirkung werden horizontale Signaturen aus abwechselnd aufsteigender und absinkender Luft innerhalb der Troposphäre identifiziert. N2 - The Arctic warms faster than the rest of the earth. The causes and effects of this arctic amplification are manifested in the arctic atmosphere, especially in the atmospheric boundary layer, which plays a key role in the exchange processes of the atmosphere, ocean and sea ice. This work highlights the importance of synoptic cyclones in the Arctic North Atlantic region. For this purpose, the influence of synoptic cyclones on the Arctic boundary layer as well as their interactions with different regions within the Arctic atmosphere on local to supraregional scales is investigated. The starting point for this are measurement data and model simulations for the period of the NICE2015 expedition, which took place in the Arctic North Atlantic region from early January to late June 2015. On the basis of radiosonde measurements, the effects of synoptic cyclones are most noticeable in the winter because, by the advection of warm and humid air masses into the Arctic, the condition of the atmosphere changes from a radiative clear to opaquely cloudy. Although this sharp contrast only exists in winter, the analysis shows that integrated water vapor is an indicator for the advection of air masses from low latitudes into the Arctic even in the spring. In addition to the advection of air masses, the influence of cyclones on static stability is characterized. Comparing the N-ICE2015 observations with the SHEBA campaign (1997/1998), which took place over thicker ice, similarities are found in the static stability of the atmosphere despite the different sea ice regimes. The observed differences in stability can be attributed to differences in synoptic activity. A further comparison with the radiosondes of the AWIPEV station in Ny-Åesund, Spitzbergen, which were launched parallel to the N-ICE2015 campaign, shows that synoptic cyclones determine the course of the winter months. In addition, the effects of vertically-varying nudging on the development of cyclones is examined for February 2015 using the hydrostatic regional climate model HIRHAM5. It is shown that the differences between the eight model simulations are increasing with decreasing number of nudged levels. The greatest differences are mainly due to the temporal offset of the development of synoptic cyclones. To correct the time offset of the cyclone initiation, it is sufficient to use nudging in the lowest troposphere. The free HIRHAM reproduces the positive end of the N-ICE2015 temperature distribution well, but has a strong negative bias which most likely results from an under-estimation of the moisture content. An example of a cyclone shows that nudging has an influence on the position of the high altitude lows, which in turn influences cyclone development on the ground. Furthermore, a statistical estimate of the effect of nudging on the vertical is made by means of a variance measure suitable for small ensemble sizes. It is found that the similarity of model simulations in the lower troposphere is generally higher than above and has a local minimum in 500 hPa. In the last part of the analysis, the interaction of the upper troposphere and the lower stratosphere is investigated with data from the ERA interim reanalysis using previously examined cyclones. The position and orientation of the polar vortex produced an unusually large meridional component of the tropopause jets, which favored passage of low pressure systems into the central Arctic from the beginning of February 2015 onwards. Using a cyclone as an example, the synoptic development is compared with the theoretical assumptions about the downward impact of the stratosphere on the troposphere. The non-linear interaction between Greenland’s orography, an intrusion of stratospheric air into the troposphere, and a Rossby wave propagating in the direction of the Arctic play a key role in the selected time frame. As an indicator of this interaction, horizontal signatures are identified from alternately ascending and descending air within the troposphere. KW - arktische Grenzschicht KW - Arctic boundary layer KW - synoptische Zyklone KW - synoptic cyclones KW - thermodynamische Struktur KW - thermodynamic structure KW - regional climate simulations KW - regionale Klimasimulationen KW - nudging Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-411124 ER - TY - JOUR A1 - Kayser, Markus A1 - Maturilli, Marion A1 - Graham, Robert M. A1 - Hudson, Stephen R. A1 - Rinke, Annette A1 - Cohen, Lana A1 - Kim, Joo-Hong A1 - Park, Sang-Jong A1 - Moon, Woosok A1 - Granskog, Mats A. T1 - Vertical thermodynamic structure of the troposphere during the Norwegian young sea ICE expedition (N-ICE2015) JF - Journal of geophysical research-atmosheres N2 - The Norwegian young sea ICE (N-ICE2015) expedition was designed to investigate the atmosphere-snow-ice-ocean interactions in the young and thin sea ice regime north of Svalbard. Radiosondes were launched twice daily during the expedition from January to June 2015. Here we use these upper air measurements to study the multiple cyclonic events observed during N-ICE2015 with respect to changes in the vertical thermodynamic structure, moisture content, and boundary layer characteristics. We provide statistics of temperature inversion characteristics, static stability, and boundary layer extent. During winter, when radiative cooling is most effective, we find the strongest impact of synoptic cyclones. Changes to thermodynamic characteristics of the boundary layer are associated with transitions between the radiatively "clear" and "opaque" atmospheric states. In spring, radiative fluxes warm the surface leading to lifted temperature inversions and a statically unstable boundary layer. Further, we compare the N-ICE2015 static stability distributions to corresponding profiles from ERA-Interim reanalysis, from the closest land station in the Arctic North Atlantic sector, Ny-Alesund, and to soundings from the SHEBA expedition (1997/1998). We find similar stability characteristics for N-ICE2015 and SHEBA throughout the troposphere, despite differences in location, sea ice thickness, and snow cover. For Ny-Alesund, we observe similar characteristics above 1000 m, while the topography and ice-free fjord surrounding Ny-Alesund generate great differences below. The long-term radiosonde record (1993-2014) from Ny-Alesund indicates that during the N-ICE2015 spring period, temperatures were close to the climatological mean, while the lowest 3000 m were 1-3 degrees C warmer than the climatology during winter. Plain Language Summary The Norwegian young sea ICE (N-ICE2015) expedition was designed to investigate the atmosphere-snow-ice-ocean interactions in the young and thin sea ice regime north of Svalbard. Radiosondes were launched twice daily during the expedition from January to June 2015. Here we use these upper air measurements to study the multiple cyclonic events observed during N-ICE2015 with respect to changes in the vertical thermodynamic structure, moisture content, and the atmospheric boundary layer characteristics. During winter, we find the strongest impact of synoptic cyclones, which transport warm and moist air into the cold and dry Arctic atmosphere. In spring, incoming solar radiation warms the surface. This leads to very different thermodynamic conditions and higher moisture content, which reduces the contrast between stormy and calm periods. Further, we compare the N-ICE2015 measurements to corresponding profiles from ERA-Interim reanalysis, from the closest land station in the Arctic North Atlantic sector, Ny-Alesund, and to soundings from the SHEBA expedition (1997/1998). We find similar stability characteristics for N-ICE2015 and SHEBA throughout the troposphere, despite differences in location, sea ice thickness, and snow cover. The comparisons highlight the value of the N-ICE2015 observation and show the importance of winter time observations in the Arctic North Atlantic sector. Y1 - 2017 U6 - https://doi.org/10.1002/2016JD026089 SN - 2169-897X SN - 2169-8996 VL - 122 IS - 20 SP - 10855 EP - 10872 PB - American Geophysical Union CY - Washington ER - TY - GEN A1 - Fraschetti, Federico A1 - Pohl, Martin T1 - Two-zone model for the broadband crab nebula spectrum BT - microscopic interpretation T2 - The European physical journal : Web of Conferences : proceedings N2 - We develop a simple two-zone interpretation of the broadband baseline Crab nebula spectrum between 10(-5) eV and similar to 100 TeV by using two distinct log-parabola energetic electrons distributions. We determine analytically the very-high energy photon spectrum as originated by inverse-Compton scattering of the far-infrared soft ambient photons within the nebula off a first population of electrons energized at the nebula termination shock. The broad and flat 200 GeV peak jointly observed by Fermi/LAT and MAGIC is naturally reproduced. The synchrotron radiation from a second energetic electron population explains the spectrum from the radio range up to similar to 10 keV. We infer from observations the energy dependence of the microscopic probability of remaining in proximity of the shock of the accelerating electrons. Y1 - 2017 U6 - https://doi.org/10.1051/epjconf/201713602009 SN - 2100-014X VL - 136 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Schubert, Marcel A1 - Frisch, Johannes A1 - Allard, Sybille A1 - Preis, Eduard A1 - Scherf, Ullrich A1 - Koch, Norbert A1 - Neher, Dieter T1 - Tuning side chain and main chain order in a prototypical donor-acceptor copolymer BT - implications for optical, electronic, and photovoltaic characteristics JF - Elementary Processes in Organic Photovoltaics N2 - 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. KW - Aggregate states KW - All-polymer heterojunctions KW - Alternating copolymers KW - Ambipolar charge transport KW - Ambipolar materials KW - Backbone modifications KW - Bilayer solar cells KW - Charge separation KW - Conformational disorder KW - Crystalline phases KW - Donor-acceptor copolymers KW - Electron traps KW - Energetic disorder KW - Energy-level alignment KW - Fermi-level alignment KW - Fermi-level pinning KW - Interface dipole KW - Interlayer KW - Intrachain order KW - Intragap states KW - Microscopic morphology KW - Mobility imbalance KW - Mobility relaxation KW - Monte Carlo simulation KW - Multiple trapping model KW - Nonradiative recombination KW - OFET KW - Open-circuit voltage KW - Optoelectronic properties KW - Partially alternating copolymers KW - Photo-CELIV KW - Photocurrent KW - Photovoltaic gap KW - Polymer intermixing KW - Recombination losses KW - Spectral diffusion KW - Statistical copolymers KW - Stille-type cross-coupling KW - Structure-property relationships KW - Time-dependent mobility KW - Time-of-flight (TOF) KW - Transient photocurrent KW - Ultraviolet photoelectron spectroscopy KW - Vacuum-level alignment KW - X-ray photoelectron spectroscopy Y1 - 2016 SN - 978-3-319-28338-8 SN - 978-3-319-28336-4 U6 - https://doi.org/10.1007/978-3-319-28338-8_10 SN - 0065-3195 VL - 272 SP - 243 EP - 265 PB - Springer CY - Berlin ER - TY - JOUR A1 - Cherstvy, Andrey G. A1 - Vinod, Deepak A1 - Aghion, Erez A1 - Chechkin, Aleksei V. A1 - Metzler, Ralf T1 - Time averaging, ageing and delay analysis of financial time series JF - New journal of physics N2 - We introduce three strategies for the analysis of financial time series based on time averaged observables. These comprise the time averaged mean squared displacement (MSD) as well as the ageing and delay time methods for varying fractions of the financial time series. We explore these concepts via statistical analysis of historic time series for several Dow Jones Industrial indices for the period from the 1960s to 2015. Remarkably, we discover a simple universal law for the delay time averaged MSD. The observed features of the financial time series dynamics agree well with our analytical results for the time averaged measurables for geometric Brownian motion, underlying the famed Black–Scholes–Merton model. The concepts we promote here are shown to be useful for financial data analysis and enable one to unveil new universal features of stock market dynamics. KW - time averaging KW - diffusion KW - geometric Brownian motion KW - financial time series Y1 - 2017 U6 - https://doi.org/10.1088/1367-2630/aa7199 SN - 1367-2630 VL - 19 SP - 1 EP - 11 PB - IOP CY - London ER - TY - GEN A1 - Cherstvy, Andrey G. A1 - Vinod, Deepak A1 - Aghion, Erez A1 - Chechkin, Aleksei V. A1 - Metzler, Ralf T1 - Time averaging, ageing and delay analysis of financial time series N2 - We introduce three strategies for the analysis of financial time series based on time averaged observables. These comprise the time averaged mean squared displacement (MSD) as well as the ageing and delay time methods for varying fractions of the financial time series. We explore these concepts via statistical analysis of historic time series for several Dow Jones Industrial indices for the period from the 1960s to 2015. Remarkably, we discover a simple universal law for the delay time averaged MSD. The observed features of the financial time series dynamics agree well with our analytical results for the time averaged measurables for geometric Brownian motion, underlying the famed Black–Scholes–Merton model. The concepts we promote here are shown to be useful for financial data analysis and enable one to unveil new universal features of stock market dynamics. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 347 KW - diffusion KW - financial time series KW - geometric Brownian motion KW - time averaging Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400541 ER - TY - JOUR A1 - Sun, Ning-Chen A1 - de Grijs, Richard A1 - Subramanian, Smitha A1 - Cioni, Maria-Rosa L. A1 - Rubele, Stefano A1 - Bekki, Kenji A1 - Ivanov, Valentin D. A1 - Piatti, Andrés E. A1 - Ripepi, Vincenzo T1 - The VMC Survey. XXII. Hierarchical star formation in the 30 Doradus-N158-N159-N160 star-forming complex JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - 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. KW - galaxies: clusters: general KW - infrared: stars KW - Magellanic Clouds KW - stars: formation Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/835/2/171 SN - 0004-637X SN - 1538-4357 VL - 835 IS - 2 PB - Institute of Physics Publ. CY - Bristol ER - TY - JOUR A1 - Almeida, Leonardo A. A1 - Sana, H. A1 - Taylor, W. A1 - Barbá, Rodolfo A1 - Bonanos, Alceste Z. A1 - Crowther, Paul A1 - Damineli, Augusto A1 - de Koter, A. A1 - de Mink, Selma E. A1 - Evans, C. J. A1 - Gieles, Mark A1 - Grin, Nathan J. A1 - Hénault-Brunet, V. A1 - Langer, Norbert A1 - Lennon, D. A1 - Lockwood, Sean A1 - Maíz Apellániz, Jesús A1 - Moffat, A. F. J. A1 - Neijssel, C. A1 - Norman, C. A1 - Ramírez-Agudelo, O. H. A1 - Richardson, N. D. A1 - Schootemeijer, Abel A1 - Shenar, Tomer A1 - Soszyński, Igor A1 - Tramper, Frank A1 - Vink, J. S. T1 - The tarantula massive binary monitoring BT - I. Observational campaign and OB-type spectroscopic binaries JF - Astronomy and astrophysics : an international weekly journal N2 - 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⊙. KW - stars: early-type KW - stars: massive KW - binaries: spectroscopic KW - binaries: close Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629844 SN - 1432-0746 VL - 598 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Shenar, Tomer A1 - Richardson, N. D. A1 - Sablowski, Daniel P. A1 - Hainich, Rainer A1 - Sana, H. A1 - Moffat, A. F. J. A1 - Todt, Helge Tobias A1 - Hamann, Wolf-Rainer A1 - Oskinova, Lida A1 - Sander, Andreas Alexander Christoph A1 - Tramper, Frank A1 - Langer, Norbert A1 - Bonanos, Alceste Z. A1 - de Mink, Selma E. A1 - Gräfener, G. A1 - Crowther, Paul A1 - Vink, J. S. A1 - Almeida, Leonardo A. A1 - de Koter, A. A1 - Barbá, Rodolfo A1 - Herrero, A. A1 - Ulaczyk, Krzysztof T1 - The tarantula massive binary monitoring BT - II. First SB2 orbital and spectroscopic analysis for the Wolf-Rayet binary R145 JF - Astronomy and astrophysics : an international weekly journal N2 - We present the first SB2 orbital solution and disentanglement of the massive Wolf-Rayet binary R145 (P = 159 d) located in the Large Magellanic Cloud. The primary was claimed to have a stellar mass greater than 300 M-circle dot, making it a candidate for being the most massive star known to date. While the primary is a known late-type, H-rich Wolf-Rayet star (WN6h), the secondary has so far not been unambiguously detected. Using moderate-resolution spectra, we are able to derive accurate radial velocities for both components. By performing simultaneous orbital and polarimetric analyses, we derive the complete set of orbital parameters, including the inclination. The spectra are disentangled and spectroscopically analyzed, and an analysis of the wind-wind collision zone is conducted. The disentangled spectra and our models are consistent with a WN6h type for the primary and suggest that the secondary is an O3.5 If*/WN7 type star. We derive a high eccentricity of e = 0 : 78 and minimum masses of M-1 sin(3) i approximate to M-2 sin(3) i = 13 +/- 2 M-circle dot, with q = M-2/M-1 = 1.01 +/- 0.07. An analysis of emission excess stemming from a wind-wind collision yields an inclination similar to that obtained from polarimetry (i = 39 +/- 6 degrees). Our analysis thus implies M-1 = 53(-20)(+40) and M2 = 54(-20)(+40) M-circle dot, excluding M-1 > 300 M-circle dot. A detailed comparison with evolution tracks calculated for single and binary stars together with the high eccentricity suggests that the components of the system underwent quasi-homogeneous evolution and avoided mass-transfer. This scenario would suggest current masses of approximate to 80 M-circle dot and initial masses of M-i,M-1 approximate to 10(5) and M-i,M-2 approximate to 90 M-circle dot, consistent with the upper limits of our derived orbital masses, and would imply an age of approximate to 2.2 Myr. KW - binaries: spectroscopic KW - stars: Wolf-Rayet KW - stars: massive KW - Magellanic Clouds KW - stars: individual: R 145 KW - stars: atmospheres Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629621 SN - 1432-0746 VL - 598 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Xiong, Hui A1 - Mignolet, Benoit A1 - Fang, Li A1 - Osipov, Timur A1 - Wolf, Thomas J. A. A1 - Sistrunk, Emily A1 - Gühr, Markus A1 - Remacle, Francoise A1 - Berrah, Nora T1 - The Role of Super-Atom Molecular Orbitals in Doped Fullerenes in a Femtosecond Intense Laser Field JF - Scientific reports N2 - The interaction of gas phase endohedral fullerene Ho3N@C-80 with intense (0.1-5 x 10(14) W/cm(2)), short (30 fs), 800 nm laser pulses was investigated. The power law dependence of Ho3N@C-80(q+), q = 1-2, was found to be different from that of C-60. Time-dependent density functional theory computations revealed different light-induced ionization mechanisms. Unlike in C-60, in doped fullerenes, the breaking of the cage spherical symmetry makes super atomic molecular orbital (SAMO) states optically active. Theoretical calculations suggest that the fast ionization of the SAMO states in Ho3N@C-80 is responsible for the n = 3 power law for singly charged parent molecules at intensities lower than 1.2 x 10(14) W/cm(2). Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-00124-9 SN - 2045-2322 VL - 7 PB - Nature Publ. Group CY - London ER - TY - THES A1 - Feulner, Georg T1 - The influence of solar radiation changes on the energy budget of Earth's climate Y1 - 2017 ER - TY - GEN A1 - Parsons, R. D. A1 - Schüssler, F. A1 - Garrigoux, T. A1 - Balzer, A. A1 - Füssling, Matthias A1 - Hoischen, Clemens A1 - Holler, M. A1 - Mitchell, A. A1 - Pühlhofer, G. A1 - Rowell, G. A1 - Wagner, S. A1 - Bissaldi, E. A1 - Tam, P. H. T. T1 - The HESS II GRB Observation Scheme T2 - AIP conference proceedings / American Institute of Physics N2 - Gamma-ray bursts (GRBs) are some of the Universe’s most enigmatic and exotic events. However, at energies above 10 GeV their behaviour remains largely unknown. Although space based telescopes such as the Fermi-LAT have been able to detect GRBs in this energy range, their photon statistics are limited by the small detector size. Such limitations are not present in ground based gamma-ray telescopes such as the H.E.S.S. experiment, which has now entered its second phase with the addition of a large 600 m2 telescope to the centre of the array. Such a large telescope allows H.E.S.S. to access the sub 100-GeV energy range while still maintaining a large effective collection area, helping to potentially probe the short timescale emission of these events. We present a description of the H.E.S.S. GRB observation programme, summarising the performance of the rapid GRB repointing system and the conditions under which GRB observations are initiated. Additionally we will report on the GRB follow-ups made during the 2014-15 observation campaigns. Y1 - 2017 SN - 978-0-7354-1456-3 U6 - https://doi.org/10.1063/1.4968980 SN - 0094-243X SN - 1551-7616 VL - 1792 IS - 1 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Reese, Ronja A1 - Gudmundsson, Gudmundur Hilmar A1 - Levermann, Anders A1 - Winkelmann, Ricarda T1 - The far reach of ice-shelf thinning in Antarctica JF - Nature climate change N2 - Floating ice shelves, which fringe most of Antarctica’s coastline, regulate ice flow into the Southern Ocean1,2,3. Their thinning4,5,6,7 or disintegration8,9 can cause upstream acceleration of grounded ice and raise global sea levels. So far the effect has not been quantified in a comprehensive and spatially explicit manner. Here, using a finite-element model, we diagnose the immediate, continent-wide flux response to different spatial patterns of ice-shelf mass loss. We show that highly localized ice-shelf thinning can reach across the entire shelf and accelerate ice flow in regions far from the initial perturbation. As an example, this ‘tele-buttressing’ enhances outflow from Bindschadler Ice Stream in response to thinning near Ross Island more than 900 km away. We further find that the integrated flux response across all grounding lines is highly dependent on the location of imposed changes: the strongest response is caused not only near ice streams and ice rises, but also by thinning, for instance, well-within the Filchner–Ronne and Ross Ice Shelves. The most critical regions in all major ice shelves are often located in regions easily accessible to the intrusion of warm ocean waters10,11,12, stressing Antarctica’s vulnerability to changes in its surrounding ocean. Y1 - 2017 U6 - https://doi.org/10.1038/s41558-017-0020-x SN - 1758-678X SN - 1758-6798 VL - 8 IS - 1 SP - 53 EP - 57 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Dzhanoev, Arsen R. A1 - Sokolov, Igor M. T1 - The effect of the junction model on the anomalous diffusion in the 3D comb structure JF - Chaos, solitons & fractals : applications in science and engineering ; an interdisciplinary journal of nonlinear science N2 - The diffusion in the comb structures is a popular model of geometrically induced anomalous diffusion. In the present work we concentrate on the diffusion along the backbone in a system where sidebranches are planes, and the diffusion thereon is anomalous and described by continuous time random walks (CTRW). We show that the mean squared displacement (MSD) in the backbone of the comb behaves differently depending on whether the waiting time periods in the sidebranches are reset after the step in the backbone is done (a rejuvenating junction model), or not (a non-rejuvenating junction model). In the rejuvenating case the subdiffusion in the sidebranches only changes the prefactor in the ultra-slow (logarithmic) diffusion along the backbone, while in the non-rejuvenating case the ultraslow, logarithmic subdiffusion is changed to a much faster power-law subdiffusion (with a logarithmic correction) as it was found earlier by Iomin and Mendez [25]. Moreover, in the first case the result does not change if the diffusion in the backbone is itself anomalous, while in the second case it does. Two of the special cases of the considered models (the non-rejuvenating junction under normal diffusion in the backbone, and rejuvenating junction for the same waiting time distribution in the sidebranches and in junction points) were also investigated within the approach based on the corresponding generalized Fokker-Planck equations. (c) 2017 Elsevier Ltd. All rights reserved. KW - Comb model KW - Comb-lattice model KW - Cylindrical comb KW - Junction model KW - Anomalous diffusion Y1 - 2017 U6 - https://doi.org/10.1016/j.chaos.2017.12.001 SN - 0960-0779 SN - 1873-2887 VL - 106 SP - 330 EP - 336 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Gout, Julien A1 - Quade, Markus A1 - Shafi, Kamran A1 - Niven, Robert K. A1 - Abel, Markus T1 - Synchronization control of oscillator networks using symbolic regression JF - Nonlinear Dynamics N2 - Networks of coupled dynamical systems provide a powerful way to model systems with enormously complex dynamics, such as the human brain. Control of synchronization in such networked systems has far-reaching applications in many domains, including engineering and medicine. In this paper, we formulate the synchronization control in dynamical systems as an optimization problem and present a multi-objective genetic programming-based approach to infer optimal control functions that drive the system from a synchronized to a non-synchronized state and vice versa. The genetic programming-based controller allows learning optimal control functions in an interpretable symbolic form. The effectiveness of the proposed approach is demonstrated in controlling synchronization in coupled oscillator systems linked in networks of increasing order complexity, ranging from a simple coupled oscillator system to a hierarchical network of coupled oscillators. The results show that the proposed method can learn highly effective and interpretable control functions for such systems. KW - Dynamical systems KW - Synchronization control KW - Genetic programming Y1 - 2017 U6 - https://doi.org/10.1007/s11071-017-3925-z SN - 0924-090X SN - 1573-269X VL - 91 IS - 2 SP - 1001 EP - 1021 PB - Springer CY - Dordrecht ER - TY - GEN A1 - Loupos, Konstantinos A1 - Damigos, Yannis A1 - Amditis, Angelos A1 - Gerhard, Reimund A1 - Rychkov, Dmitry A1 - Wirges, Werner A1 - Schulze, Manuel A1 - Lenas, Sotiris-Angelos A1 - Chatziandreoglou, Christos A1 - Malliou, Christina A1 - Tsaoussidis, Vassilis A1 - Brady, Ken A1 - Frankenstein, Bernd T1 - Structural health monitoring system for bridges based on skin-like sensor T2 - IOP conference series : Materials science and engineering N2 - Structural health monitoring activities are of primal importance for managing transport infrastructure, however most SHM methodologies are based on point-based sensors that have limitations in terms of their spatial positioning requirements, cost of development and measurement range. This paper describes the progress on the SENSKIN EC project whose objective is to develop a dielectric-elastomer and micro-electronics-based sensor, formed from a large highly extensible capacitance sensing membrane supported by advanced microelectronic circuitry, for monitoring transport infrastructure bridges. Such a sensor could provide spatial measurements of strain in excess of 10%. The actual sensor along with the data acquisition module, the communication module and power electronics are all integrated into a compact unit, the SENSKIN device, which is energy-efficient, requires simple signal processing and it is easy to install over various surface types. In terms of communication, SENSKIN devices interact with each other to form the SENSKIN system; a fully distributed and autonomous wireless sensor network that is able to self-monitor. SENSKIN system utilizes Delay-/Disruption-Tolerant Networking technologies to ensure that the strain measurements will be received by the base station even under extreme conditions where normal communications are disrupted. This paper describes the architecture of the SENSKIN system and the development and testing of the first SENSKIN prototype sensor, the data acquisition system, and the communication system. Y1 - 2017 U6 - https://doi.org/10.1088/1757-899X/236/1/012100 SN - 1757-8981 VL - 236 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Müller, B. R. A1 - Cooper, R. C. A1 - Lange, A. A1 - Kupsch, Andreas A1 - Wheeler, M. A1 - Hentschel, M. P. A1 - Staude, A. A1 - Pandey, A. A1 - Shyam, A. A1 - Bruno, Giovanni T1 - Stress-induced microcrack density evolution in beta-eucryptite ceramics BT - experimental observations and possible route to strain hardening JF - Acta materialia N2 - In order to investigate their microcracking behaviour, the microstructures of several beta-eucryptite ceramics, obtained from glass precursor and cerammed to yield different grain sizes and microcrack densities, were characterized by laboratory and synchrotron x-ray refraction and tomography. Results were compared with those obtained from scanning electron microscopy (SEM). In SEM images, the characterized materials appeared fully dense but computed tomography showed the presence of pore clusters. Uniaxial tensile testing was performed on specimens while strain maps were recorded and analyzed by Digital Image Correlation (DIC). X-ray refraction techniques were applied on specimens before and after tensile testing to measure the amount of the internal specific surface (i.e., area per unit volume). X-ray refraction revealed that (a) the small grain size (SGS) material contained a large specific surface, originating from the grain boundaries and the interfaces of TiO2 precipitates; (b) the medium (MGS) and large grain size (LGS) materials possessed higher amounts of specific surface compared to SGS material due to microcracks, which decreased after tensile loading; (c) the precursor glass had negligible internal surface. The unexpected decrease in the internal surface of MGS and LGS after tensile testing is explained by the presence of compressive regions in the DIC strain maps and further by theoretical arguments. It is suggested that while some microcracks merge via propagation, more close mechanically, thereby explaining the observed X-ray refraction results. The mechanisms proposed would allow the development of a strain hardening route in ceramics. KW - Beta-eucryptite KW - Microcracked ceramics KW - X-ray refraction KW - Tensile load KW - Strain hardening Y1 - 2017 U6 - https://doi.org/10.1016/j.actamat.2017.10.030 SN - 1359-6454 SN - 1873-2453 VL - 144 SP - 627 EP - 641 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Gorobtsov, O. Yu. A1 - Mercurio, G. A1 - Brenner, G. A1 - Lorenz, Ulf A1 - Gerasimova, N. A1 - Kurta, R. P. A1 - Hieke, F. A1 - Skopintsev, P. A1 - Zaluzhnyy, I. A1 - Lazarev, S. A1 - Dzhigaev, D. A1 - Rose, M. A1 - Singer, A. A1 - Wurth, W. A1 - Vartanyants, I. A. T1 - Statistical properties of a free-electron laser revealed by Hanbury Brown-Twiss interferometry JF - Physical review : A, Atomic, molecular, and optical physics N2 - We present a comprehensive experimental analysis of statistical properties of the self-amplified spontaneous emission free-electron laser (FEL) FLASH by means of Hanbury Brown and Twiss interferometry. The experiments were performed at FEL wavelengths of 5.5, 13.4, and 20.8 nm. We determined the second-order intensity correlation function for all wavelengths and different operation conditions of FLASH. In all experiments a high degree of spatial coherence (above 50%) was obtained. Our analysis performed in spatial and spectral domains provided us with the independent measurements of an average pulse duration of the FEL that were below 60 fs. To explain the complicated behavior of the second-order intensity correlation function we developed an advanced theoretical model that includes the presence of multiple beams and external positional jitter of the FEL pulses. By this analysis we determined that in one of the experiments external positional jitter was about 25% of the beam size. We envision that methods developed in our study will be used widely for analysis and diagnostics of FEL radiation. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevA.95.023843 SN - 2469-9926 SN - 2469-9934 VL - 95 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Couto, Rafael C. A1 - Cruz, Vinicius V. A1 - Ertan, Emelie A1 - Eckert, Sebastian A1 - Fondell, Mattis A1 - Dantz, Marcus A1 - Kennedy, Brian A1 - Schmitt, Thorsten A1 - Pietzsch, Annette A1 - Guimaraes, Freddy F. A1 - Agren, Hans A1 - Odelius, Michael A1 - Kimberg, Victor A1 - Föhlisch, Alexander T1 - Selective gating to vibrational modes through resonant X-ray scattering JF - Nature Communications N2 - 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. Y1 - 2017 U6 - https://doi.org/10.1038/ncomms14165 SN - 2041-1723 VL - 8 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Kiethe, Jan A1 - Heuer, Axel A1 - Jechow, Andreas T1 - Second-order coherence properties of amplified spontaneous emission from a high-power tapered superluminescent diode JF - Laser physics letters N2 - We study the degree of second-order coherence of the emission of a high-power multi-quantum well superluminescent diode with a lateral tapered amplifier section with and without optical feedback. When operated in an external cavity, the degree of second-order coherence changed from the almost thermal case of g((2))(0)approximate to 1.9 towards the mostly coherent case of g((2)) (0) approximate to 1.2 when the injection current at the tapered section was increased. We found good agreement with semi-classical laser theory near and below threshold while above laser threshold a slightly higher g((2))(0) was observed. As a free running device, the superluminescent diode yielded more than 400 mW of optical output power with good spatial beam quality of M-slow(2) < 1.6. In this case, the degree of second-order coherence dropped only slightly from 1.9 at low powers to 1.6 at the maximum output power. To our knowledge, this is the first investigation of a high-power tapered superluminescent diode concerning the degree of second-order coherence. Such a device might be useful for real-world applications probing the second order coherence function, such as ghost imaging. KW - photon statistics KW - incoherent light KW - superluminescent diodes Y1 - 2017 U6 - https://doi.org/10.1088/1612-202X/aa772c SN - 1612-2011 SN - 1612-202X VL - 14 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Mahata, Khadak Singh A1 - Panday, Arnico Kumar A1 - Rupakheti, Maheswar A1 - Singh, Ashish A1 - Naja, Manish A1 - Lawrence, Mark T1 - Seasonal and diurnal variations in methane and carbon dioxide in the Kathmandu Valley in the foothills of the central Himalayas JF - Atmospheric Chemistry and Physics N2 - The SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley-Atmospheric Brown Clouds) international air pollution measurement campaign was carried out from December 2012 to June 2013 in the Kathmandu Valley and surrounding regions in Nepal. The Kathmandu Valley is a bowl-shaped basin with a severe air pollution problem. This paper reports measurements of two major greenhouse gases (GHGs), methane (CH4) and carbon dioxide (CO2), along with the pollutant CO, that began during the campaign and were extended for 1 year at the SusKat-ABC supersite in Bode, a semi-urban location in the Kathmandu Valley. Simultaneous measurements were also made during 2015 in Bode and a nearby rural site (Chanban) similar to 25 km (aerial distance) to the southwest of Bode on the other side of a tall ridge. The ambient mixing ratios of methane (CH4), carbon dioxide (CO2), water vapor, and carbon monoxide (CO) were measured with a cavity ring-down spectrometer (G2401; Picarro, USA) along with meteorological parameters for 1 year (March 2013-March 2014). These measurements are the first of their kind in the central Himalayan foothills. At Bode, the annual average mixing ratios of CO2 and CH4 were 419.3 (+/- 6.0) ppm and 2.192 (+/- 0.066) ppm, respectively. These values are higher than the levels observed at background sites such as Mauna Loa, USA (CO2: 396.8 +/- 2.0 ppm, CH4: 1.831 +/- 0.110 ppm) and Waliguan, China (CO2: 397.7 +/- 3.6 ppm, CH4: 1.879 +/- 0.009 ppm) during the same period and at other urban and semi-urban sites in the region, such as Ahmedabad and Shadnagar (India). They varied slightly across the seasons at Bode, with seasonal average CH4 mixing ratios of 2.157 (+/- 0.230) ppm in the pre-monsoon season, 2.199 (+/- 0.241) ppm in the monsoon, 2.210 (+/- 0.200) ppm in the post-monsoon, and 2.214 (+/- 0.209) ppm in the winter season. The average CO2 mixing ratios were 426.2 (+/- 25.5) ppm in the pre-monsoon, 413.5 (+/- 24.2) ppm in the monsoon, 417.3 (+/- 23.1) ppm in the postmonsoon, and 421.9 (+/- 20.3) ppm in the winter season. The maximum seasonal mean mixing ratio of CH4 in winter was only 0.057 ppm or 2.6% higher than the seasonal minimum during the pre-monsoon period, while CO2 was 12.8 ppm or 3.1% higher during the pre-monsoon period (seasonal maximum) than during the monsoon (seasonal minimum). On the other hand, the CO mixing ratio at Bode was 191% higher during the winter than during the monsoon season. The enhancement in CO2 mixing ratios during the pre-monsoon season is associated with additional CO2 emissions from forest fires and agro-residue burning in northern South Asia in addition to local emissions in the Kathmandu Valley. Published CO = CO2 ratios of different emission sources in Nepal and India were compared with the observed CO = CO2 ratios in this study. This comparison suggested that the major sources in the Kathmandu Valley were residential cooking and vehicle exhaust in all seasons except winter. In winter, brick kiln emissions were a major source. Simultaneous measurements in Bode and Chanban (15 July-3 October 2015) revealed that the mixing ratios of CO2, CH4, and CO were 3.8, 12, and 64% higher in Bode than Chanban. The Kathmandu Valley thus has significant emissions from local sources, which can also be attributed to its bowl-shaped geography that is conducive to pollution build-up. At Bode, all three gas species (CO2, CH4, and CO) showed strong diurnal patterns in their mixing ratios with a pronounced morning peak (ca. 08:00), a dip in the afternoon, and a gradual increase again through the night until the next morning. CH4 and CO at Chanban, however, did not show any noticeable diurnal variations. These measurements provide the first insights into the diurnal and seasonal variation in key greenhouse gases and air pollutants and their local and regional sources, which is important information for atmospheric research in the region. Y1 - 2017 U6 - https://doi.org/10.5194/acp-17-12573-2017 SN - 1680-7316 SN - 1680-7324 VL - 17 IS - 20 SP - 12573 EP - 12596 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Shprits, Yuri Y. A1 - Angelopoulos, V. A1 - Russell, C. T. A1 - Strangeway, R. J. A1 - Runov, A. A1 - Turner, D. A1 - Caron, R. A1 - Cruce, P. A1 - Leneman, D. A1 - Michaelis, I. A1 - Petrov, V. A1 - Panasyuk, M. A1 - Yashin, I. A1 - Drozdov, Alexander A1 - Russell, C. L. A1 - Kalegaev, V. A1 - Nazarkov, I. A1 - Clemmons, J. H. T1 - Scientific Objectives of Electron Losses and Fields INvestigation Onboard Lomonosov Satellite JF - Space science reviews N2 - The objective of the Electron Losses and Fields INvestigation on board the Lomonosov satellite ( ELFIN-L) project is to determine the energy spectrum of precipitating energetic electrons and ions and, together with other polar-orbiting and equatorial missions, to better understand the mechanisms responsible for scattering these particles into the atmosphere. This mission will provide detailed measurements of the radiation environment at low altitudes. The 400-500 km sun-synchronous orbit of Lomonosov is ideal for observing electrons and ions precipitating into the atmosphere. This mission provides a unique opportunity to test the instruments. Similar suite of instruments will be flown in the future NSF-and NASA-supported spinning CubeSat ELFIN satellites which will augment current measurements by providing detailed information on pitch-angle distributions of precipitating and trapped particles. KW - Magnetospheric physics KW - Observations KW - Particles precipitating KW - Particles trapped KW - Radiation belts Y1 - 2017 U6 - https://doi.org/10.1007/s11214-017-0455-4 SN - 0038-6308 SN - 1572-9672 VL - 214 IS - 1 PB - Springer CY - Dordrecht ER - TY - THES A1 - Kornhuber, Kai T1 - Rossby wave dynamics and changes in summertime weather extremes T1 - Rossby Wellendynamik und Veränderungen von Extremwetter im Sommer N2 - Extreme weather events like heatwaves and floods severely affect societies with impacts ranging from economic damages to losses in human lifes. Global warming caused by anthropogenic greenhouse gas emissions is expected to increase their frequency and intensity, particularly in the warm season. Next to these thermodynamic changes, climate change might also impact the large scale atmospheric circulation.Such dynamic changes might additionally act on the occurence of extreme weather events, but involved mechanisms are often highly non-linear. Therefore, large uncertainty exists on the exact nature of these changes and the related risks to society. Particularly in the densely populated mid-latitudes weather patterns are governed by the large scale circulation like the jet-streams and storm tracks. Extreme weather in this region is often related to persistent weather systems associated with a strongly meandering jet-stream. Such meanders are called Rossby waves. Under specific conditions they can become slow moving, stretched around the entire hemisphere and generate simultaneaous heat- and rainfall extremes in far-away regions. This thesis aims at enhancing the understanding of synoptic-scale, circumglobal Rossby waves and the associated risks of dynamical changes to society. More specific, the analyses investigate their relation to extreme weather, regions at risk, under which conditions they are generated, and the influence of anthropogenic climate change on those conditions now, in the past and in the future. I find that circumglobal Rossby waves promoted simultaneous occuring weather extremes across the northern hemisphere in several recent summers. Further, I present evidence that they are often linked to quasiresonant-amplification of planetary waves. These events include the 2003 European heatwave and the Moscow heatwave of 2010. This non-linear mechanism acts on the upper level flow through trapping and amplification of stationary synoptic scale waves. I show that this resonance mechanism acts in both hemispheres and is related to extreme weather. A main finding is that circumglobal Rossby waves primarily occur as two specific teleconnection patterns associated with a wave 5 and wave 7 pattern in the northern hemisphere, likely due to the favourable longitudinal distance of prominent mountain ridges here. Furthermore, I identify those regions which are particularly at risk: The central United States, western Europe and the Ukraine/Russian region. Moreover, I present evidence that the wave 7 pattern has and extreme weather in these regions. My results suggest that the increase in frequency can be linked to favourable changes in large scale temperature gradients, which I show to be largely underestimated by model simulations. Using surface temperature fingerprint as proxy for investigating historic and future model ensembles, evidence is presented that anthropogenic warming has likely increased the probability for the occurence of circumglobal Rossby waves. Further it is shown that this might lead to a doubling of such events until the end of the century under a high-emission scenario. Overall, this thesis establishes several atmosphere-dynamical pathways by which changes in large scale temperature gradients might link to persistent boreal summer weather. It highlights the societal risks associated with the increasing occurence of a newly discovered Rossby wave teleconnection pattern, which has the potential to cause simultaneaous heat-extremes in the mid-latitudinal bread-basket regions. In addition, it provides further evidence that the traditional picture by which quasi-stationary Rossby waves occur only in the low wavenumber regime, should be reconsidered. N2 - Extreme Wetterereignisse haben oft katastrophale Folgen für Menschen und Umwelt. Die zuletzt beobachtete Zunahme von Hitzewellen und Überschwemmungen im Sommer lässt sich zum Teil mit dem Klimawandel, verursacht durch den Ausstoß von Treibhausgasen aus fossilen Brennstoffen, erkären. Allerdings übetrafen einige Extremereignisse der jüngeren Vergangenheit in ihrer Intensität, das was allein durch die Erwärmung im globalen Mittel zu erwarten wäre. Der Klimawandel wirkt sich ebenfalls auf die atmosphärische Zirkulation, wie beispielsweise den Jetstream aus. Es wird hier vermutet, dass Änderungen in der Dynamik Extrem-Ereignisse verstärken, indem sie beispielsweise langanhaltender werden. Allerdings sind die entsprechenden Mechanismen komplex und stark nicht-linear, was die Unsicherheiten in Bezug auf zuünftige Risiken vergrößert. Ein Mechanismus der mit extremen Wetter in den mittleren Breiten in Verbindung gebracht wurde, ist ein stark mäandernder Jet-Stream. Dieser führt zu ungewöhnlichen Temperaturen in den mittleren Breiten weile dies Mänder, genannt Rossby-Wellen, den Transport von ungewöhnlich warmer beziehungsweise kalter Luft entlang der Breiten erlauben. Unter bestimmten Bedingungen erstrecken sich diese Rossby Wellen über die gesamte Hemisphäre und führen zum synchronen auftreten von Wetterextremen entlang den mittleren Breiten. Extreme treten insbesondere dann auf wenn sie lang über bestimmten Regionen verharren. Diese Dissertation erforscht den Zusammenhang dieser quasi-stationären Rossby-Wellen und Wetter-Extremen: In welchem Maße können diese durch Rossby-Wellen erklärt werden, welche Regionen sind besonders betroffen und welchen Bedingungen sind für ihr Entstehen förderlich und wie wirkt sich der Klimawandel auf diese Bedingungen aus? Ich zeige, dass einige der verheerendsten Wetterextreme der jüngeren Vergangenheit durch hemisphärische Rossby-Wellenmuster erzeugt wurden und dass diese zumeist synchron mit anderen ungewöhnlichen Wettersituationen in den mittleren Breiten auftraten. Desweiteren zeige ich, dass einige dieser Ereignisse mit dem resonanten Aufschaukeln einiger Wellenkomponenten erklärt werden könnnen (engl. Quasi-resonant Amplification of Planetary Waves, kurz: QRA). Diesem nicht-linearen Mechanismus zufolge verhindert ein starker Jet, dass bestimmte Wellen ihre Energie in Richung Äquator oder Pol verlieren und so förmlich in den mittleren Breiten gefangen werden. Diese Wellen können dann resonant mit dem stationären thermischen und orographischen Störungen interagieren und gewinnen so an Intensität. Ich zeige, dass dieser Mechanismus sowohl in der Nord- als auch in der Südhemisphäre wirkt. Desweiteren zeige ich, dass die Rossby-Wellen in der Nordhemisphäre als zwei wiederkehrende örtlich festgelegte Wellenmuster, charakterisiert durch Welle 5 und Welle 7, auftreten. Dies erkläre ich mit dem relativen Abstand markanter Gebirgskämme entlang der Längengrade in den mittleren Breiten. Dieses Ergebnis ermöglicht es jene Regionen zu identifizieren, welche während solcher Ereignisse besonders gefährdet sind: das Zentrum der USA, Westeuropa und die Region Ukraine / Russland. Ich zeige, dass das Welle-7-Muster in den letzten Jahrzehnten in seiner Häufigkeit zugenommen hat, was die beobachtete Zunahme von extremen Wetter in diesen Regionen erklären könnte. Diese Zunahme führe ich auf die Veränderungen der groß-skaligen Temperaturgradienten entlang der Längen und Breitengrade zurück. Ich zeige zudem, dass diese Veränderungen durch Modelle weitestgehend unterschätzt werden. Über ein charakteristisches Temperaturprofil als Proxy untersuchen wir Modeldaten von historische und Projektionen. Diese Analyse zeigt, dass die anthropogene Erwärmung mit einiger Wahrscheinlichkeit die Bedingungen für die erzeugung solcher Rossby-Wellen verändert hat. Desweiteren kommt es unter der Annahme ungestoppter Emissionen vermutlich zu einer Verdopplung dieser Ereignisse führen zum Ende des Jahrhunderts. In dieser Dissertation zeige ich auf wie die Veränderung großskaliger Oberflächen-Temperatur-Gradienten mit dem vermehrten Aufkommen langanhaltender und oft extremen Wetterereignisse zusammenhängt. Ich indentifiziere die Regionen, die durch das Welle 7 Muster besonders gefärdet sind. Desweiteren, geben meine Ergebnisse weitere Hinweise darauf, dass die traditionell Sicht, aus der quasi-stationäre-Rossby-Wellen nur in Form von niedrigen Wellenzahlen vorkommen, überdacht werden muss. KW - Telekonnektionen KW - Atmosphärendynamik KW - Jetstream KW - Klimawandel KW - Hitzewellen KW - teleconnections KW - atmosphere dynamics KW - jet stream KW - climate change KW - heatwaves Y1 - 2017 ER - TY - JOUR A1 - Fandrich, Artur A1 - Buller, Jens A1 - Memczak, Henry A1 - Stoecklein, W. A1 - Hinrichs, K. A1 - Wischerhoff, E. A1 - Schulz, B. A1 - Laschewsky, André A1 - Lisdat, Fred T1 - Responsive Polymer-Electrode Interface-Study of its Thermo- and pH-Sensitivity and the Influence of Peptide Coupling JF - Electrochimica acta : the journal of the International Society of Electrochemistry (ISE) N2 - This study introduces a thermally responsive, polymer-based electrode system. The key component is a surface-attached, temperature-responsive poly(oligoethylene glycol) methacrylate (poly(OEGMA)) type polymer bearing photoreactive benzophenone and carboxy groups containing side chains. The responsive behavior of the polymer in aqueous media has been investigated by turbidimetry measurements. Polymer films are formed on gold substrates by means of the photoreactive 2(dicyclohexylphosphino)benzophenone (DPBP) through photocrosslinking. The electrochemical behavior of the resulting polymer-substrate interface has been investigated in buffered [Fe(CN)6](3-)/[Fe (CN)6](4-)solutions at room temperature and under temperature variation by cyclic voltammetry (CV). The CV experiments show that with increasing temperature structural changes of the polymer layer occur, which alter the output of the electrochemical measurement. Repeated heating/cooling cycles analyzed by CV measurements and pH changes analyzed by quartz crystal microbalance with dissipation monitoring (QCM-D) reveal the reversible nature of the restructuring process. The immobilized films are further modified by covalent coupling of two small biomolecules - a hydrophobic peptide and a more hydrophilic one. These attached components influence the hydrophobicity of the layer in a different way the resulting change of the temperature-caused behavior has been studied by CV indicating a different state of the polymer after coupling of the hydrophobic peptide. KW - Stimuli-responsive materials KW - electroanalysis KW - modified electrode KW - bioreceptors KW - peptides KW - surface modification KW - cyclic voltammetry KW - IR ellipsometry KW - quartz crystal microbalance Y1 - 2017 U6 - https://doi.org/10.1016/j.electacta.2017.01.080 SN - 0013-4686 SN - 1873-3859 VL - 229 SP - 325 EP - 333 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Waldrip, S. H. A1 - Niven, Robert K. A1 - Abel, Markus A1 - Schlegel, M. T1 - Reduced-Parameter Method for Maximum Entropy Analysis of Hydraulic Pipe Flow Networks JF - Journal of hydraulic engineering N2 - A maximum entropy (MaxEnt) method is developed to predict flow rates or pressure gradients in hydraulic pipe networks without sufficient information to give a closed-form (deterministic) solution. This methodology substantially extends existing deterministic flow network analysis methods. It builds on the MaxEnt framework previously developed by the authors. This study uses a continuous relative entropy defined on a reduced parameter set, here based on the external flow rates. This formulation ensures consistency between different representations of the same network. The relative entropy is maximized subject to observable constraints on the mean values of a subset of flow rates or potential differences, the frictional properties of each pipe, and physical constraints arising from Kirchhoff’s first and second laws. The new method is demonstrated by application to a simple one-loop network and a 1,123-node, 1,140-pipe water distribution network in the suburb of Torrens, Australian Capital Territory, Australia. KW - Maximum entropy method KW - Water distribution systems KW - Hydraulic networks KW - Pipe networks KW - Hydraulic models KW - Nonlinear analysis KW - Probability Y1 - 2017 U6 - https://doi.org/10.1061/(ASCE)HY.1943-7900.0001379 SN - 0733-9429 SN - 1943-7900 VL - 144 IS - 2 PB - American Society of Civil Engineers CY - Reston ER - TY - JOUR A1 - Ramos, Antonio M. T. A1 - Builes-Jaramillo, Alejandro A1 - Poveda, German A1 - Goswami, Bedartha A1 - Macau, Elbert E. N. A1 - Kurths, Jürgen A1 - Marwan, Norbert T1 - Recurrence measure of conditional dependence and applications JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - Identifying causal relations from observational data sets has posed great challenges in data-driven causality inference studies. One of the successful approaches to detect direct coupling in the information theory framework is transfer entropy. However, the core of entropy-based tools lies on the probability estimation of the underlying variables. Herewe propose a data-driven approach for causality inference that incorporates recurrence plot features into the framework of information theory. We define it as the recurrence measure of conditional dependence (RMCD), and we present some applications. The RMCD quantifies the causal dependence between two processes based on joint recurrence patterns between the past of the possible driver and present of the potentially driven, excepting the contribution of the contemporaneous past of the driven variable. Finally, it can unveil the time scale of the influence of the sea-surface temperature of the Pacific Ocean on the precipitation in the Amazonia during recent major droughts. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevE.95.052206 SN - 2470-0045 SN - 2470-0053 VL - 95 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Sysoev, Ilya V. A1 - Ponomarenko, Vladimir I. A1 - Pikovskij, Arkadij T1 - Reconstruction of coupling architecture of neural field networks from vector time series JF - Communications in nonlinear science & numerical simulation N2 - We propose a method of reconstruction of the network coupling matrix for a basic voltage-model of the neural field dynamics. Assuming that the multivariate time series of observations from all nodes are available, we describe a technique to find coupling constants which is unbiased in the limit of long observations. Furthermore, the method is generalized for reconstruction of networks with time-delayed coupling, including the reconstruction of unknown time delays. The approach is compared with other recently proposed techniques. KW - Network reconstruction KW - Time series KW - Neurooscillators KW - Time delay Y1 - 2017 U6 - https://doi.org/10.1016/j.cnsns.2017.10.006 SN - 1007-5704 SN - 1878-7274 VL - 57 SP - 342 EP - 351 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Goychuk, Igor T1 - Quantum ergodicity breaking in semi-classical electron transfer dynamics JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - 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. Y1 - 2016 U6 - https://doi.org/10.1039/c6cp07206b SN - 1463-9076 SN - 1463-9084 VL - 19 SP - 3056 EP - 3066 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schwarzl, Maria A1 - Godec, Aljaž A1 - Metzler, Ralf T1 - Quantifying non-ergodicity of anomalous diffusion with higher order moments JF - Scientific reports N2 - Anomalous diffusion is being discovered in a fast growing number of systems. The exact nature of this anomalous diffusion provides important information on the physical laws governing the studied system. One of the central properties analysed for finite particle motion time series is the intrinsic variability of the apparent diffusivity, typically quantified by the ergodicity breaking parameter EB. Here we demonstrate that frequently EB is insufficient to provide a meaningful measure for the observed variability of the data. Instead, important additional information is provided by the higher order moments entering by the skewness and kurtosis. We analyse these quantities for three popular anomalous diffusion models. In particular, we find that even for the Gaussian fractional Brownian motion a significant skewness in the results of physical measurements occurs and needs to be taken into account. Interestingly, the kurtosis and skewness may also provide sensitive estimates of the anomalous diffusion exponent underlying the data. We also derive a new result for the EB parameter of fractional Brownian motion valid for the whole range of the anomalous diffusion parameter. Our results are important for the analysis of anomalous diffusion but also provide new insights into the theory of anomalous stochastic processes. Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-03712-x VL - 7 PB - Macmillan Publishers Limited CY - London ER - TY - GEN A1 - Schwarzl, Maria A1 - Godec, Aljaž A1 - Metzler, Ralf T1 - Quantifying non-ergodicity of anomalous diffusion with higher order moments N2 - Anomalous diffusion is being discovered in a fast growing number of systems. The exact nature of this anomalous diffusion provides important information on the physical laws governing the studied system. One of the central properties analysed for finite particle motion time series is the intrinsic variability of the apparent diffusivity, typically quantified by the ergodicity breaking parameter EB. Here we demonstrate that frequently EB is insufficient to provide a meaningful measure for the observed variability of the data. Instead, important additional information is provided by the higher order moments entering by the skewness and kurtosis. We analyse these quantities for three popular anomalous diffusion models. In particular, we find that even for the Gaussian fractional Brownian motion a significant skewness in the results of physical measurements occurs and needs to be taken into account. Interestingly, the kurtosis and skewness may also provide sensitive estimates of the anomalous diffusion exponent underlying the data. We also derive a new result for the EB parameter of fractional Brownian motion valid for the whole range of the anomalous diffusion parameter. Our results are important for the analysis of anomalous diffusion but also provide new insights into the theory of anomalous stochastic processes. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 382 Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-402109 ER - TY - JOUR A1 - Kunnus, Kristjan A1 - Josefsson, I. A1 - Schreck, Simon Frederik A1 - Quevedo, W. A1 - Miedema, P. S. A1 - Techert, S. A1 - de Groot, F. M. F. A1 - Föhlisch, Alexander A1 - Odelius, M. A1 - Wernet, Ph. T1 - Quantifying covalent interactions with resonant inelastic soft X-ray scattering BT - case study of Ni2+ aqua complex JF - Chemical physics letters N2 - 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. KW - Transition-metal ion KW - Aqueous solution KW - Covalent interaction KW - Resonant inelastic X-ray scattering KW - Ligand-field state KW - Charge-transfer state Y1 - 2016 U6 - https://doi.org/10.1016/j.cplett.2016.12.046 SN - 0009-2614 SN - 1873-4448 VL - 669 SP - 196 EP - 201 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Popovych, Oleksandr V. A1 - Lysyansky, Borys A1 - Rosenblum, Michael A1 - Pikovskij, Arkadij A1 - Tass, Peter A. T1 - Pulsatile desynchronizing delayed feedback for closed-loop deep brain stimulation JF - PLoS one N2 - High-frequency (HF) deep brain stimulation (DBS) is the gold standard for the treatment of medically refractory movement disorders like Parkinson’s disease, essential tremor, and dystonia, with a significant potential for application to other neurological diseases. The standard setup of HF DBS utilizes an open-loop stimulation protocol, where a permanent HF electrical pulse train is administered to the brain target areas irrespectively of the ongoing neuronal dynamics. Recent experimental and clinical studies demonstrate that a closed-loop, adaptive DBS might be superior to the open-loop setup. We here combine the notion of the adaptive high-frequency stimulation approach, that aims at delivering stimulation adapted to the extent of appropriately detected biomarkers, with specifically desynchronizing stimulation protocols. To this end, we extend the delayed feedback stimulation methods, which are intrinsically closed-loop techniques and specifically designed to desynchronize abnormal neuronal synchronization, to pulsatile electrical brain stimulation. We show that permanent pulsatile high-frequency stimulation subjected to an amplitude modulation by linear or nonlinear delayed feedback methods can effectively and robustly desynchronize a STN-GPe network of model neurons and suggest this approach for desynchronizing closed-loop DBS. Y1 - 2017 U6 - https://doi.org/10.1371/journal.pone.0173363 SN - 1932-6203 VL - 12 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Acero, F. A1 - Aloisio, R. A1 - Amans, J. A1 - Amato, Elena A1 - Antonelli, L. A. A1 - Aramo, C. A1 - Armstrong, T. A1 - Arqueros, F. A1 - Asano, Katsuaki A1 - Ashley, M. A1 - Backes, M. A1 - Balazs, C. A1 - Balzer, A. A1 - Bamba, Aya A1 - Barkov, Maxim A1 - Barrio, J. A. A1 - Benbow, Wystan A1 - Bernloehr, K. A1 - Beshley, V. A1 - Bigongiari, C. A1 - Biland, A. A1 - Bilinsky, A. A1 - Bissaldi, Elisabetta A1 - Biteau, J. A1 - Blanch, O. A1 - Blasi, P. A1 - Blazek, J. A1 - Boisson, C. A1 - Bonanno, G. A1 - Bonardi, A. A1 - Bonavolonta, C. A1 - Bonnoli, G. A1 - Braiding, C. A1 - Brau-Nogue, S. A1 - Bregeon, J. A1 - Brown, A. M. A1 - Bugaev, V. A1 - Bulgarelli, A. A1 - Bulik, T. A1 - Burton, Michael A1 - Burtovoi, A. A1 - Busetto, G. A1 - Bottcher, M. A1 - Cameron, R. A1 - Capalbi, M. A1 - Caproni, Anderson A1 - Caraveo, P. A1 - Carosi, R. A1 - Cascone, E. A1 - Cerruti, M. A1 - Chaty, Sylvain A1 - Chen, A. A1 - Chen, X. A1 - Chernyakova, M. A1 - Chikawa, M. A1 - Chudoba, J. A1 - Cohen-Tanugi, J. A1 - Colafrancesco, S. A1 - Conforti, V. A1 - Contreras, J. L. A1 - Costa, A. A1 - Cotter, G. A1 - Covino, Stefano A1 - Covone, G. A1 - Cumani, P. A1 - Cusumano, G. A1 - Daniel, M. A1 - Dazzi, F. A1 - De Angelis, A. A1 - De Cesare, G. A1 - De Franco, A. A1 - De Frondat, F. A1 - Dal Pino, E. M. de Gouveia A1 - De Lisio, C. A1 - Lopez, R. de los Reyes A1 - De Lotto, B. A1 - de Naurois, M. A1 - De Palma, F. A1 - Del Santo, M. A1 - Delgado, C. A1 - della Volpe, D. A1 - Di Girolamo, T. A1 - Di Giulio, C. A1 - Di Pierro, F. A1 - Di Venere, L. A1 - Doro, M. A1 - Dournaux, J. A1 - Dumas, D. A1 - Dwarkadas, Vikram V. A1 - Diaz, C. A1 - Ebr, J. A1 - Egberts, Kathrin A1 - Einecke, S. A1 - Elsaesser, D. A1 - Eschbach, S. A1 - Falceta-Goncalves, D. A1 - Fasola, G. A1 - Fedorova, E. A1 - Fernandez-Barral, A. A1 - Ferrand, Gilles A1 - Fesquet, M. A1 - Fiandrini, E. A1 - Fiasson, A. A1 - Filipovic, Miroslav D. A1 - Fioretti, V. A1 - Font, L. A1 - Fontaine, Gilles A1 - Franco, F. J. A1 - Freixas Coromina, L. A1 - Fujita, Yutaka A1 - Fukui, Y. A1 - Funk, S. A1 - Forster, A. A1 - Gadola, A. A1 - Lopez, R. Garcia A1 - Garczarczyk, M. A1 - Giglietto, N. A1 - Giordano, F. A1 - Giuliani, A. A1 - Glicenstein, J. A1 - Gnatyk, R. A1 - Goldoni, P. A1 - Grabarczyk, T. A1 - Graciani, R. A1 - Graham, J. A1 - Grandi, P. A1 - Granot, Jonathan A1 - Green, A. J. A1 - Griffiths, S. A1 - Gunji, S. A1 - Hakobyan, H. A1 - Hara, S. A1 - Hassan, T. A1 - Hayashida, M. A1 - Heller, M. A1 - Helo, J. C. A1 - Hinton, J. A1 - Hnatyk, B. A1 - Huet, J. A1 - Huetten, M. A1 - Humensky, T. B. A1 - Hussein, M. A1 - Horandel, J. A1 - Ikeno, Y. A1 - Inada, T. A1 - Inome, Y. A1 - Inoue, S. A1 - Inoue, T. A1 - Inoue, Y. A1 - Ioka, K. A1 - Iori, Maurizio A1 - Jacquemier, J. A1 - Janecek, P. A1 - Jankowsky, D. A1 - Jung, I. A1 - Kaaret, P. A1 - Katagiri, H. A1 - Kimeswenger, S. A1 - Kimura, Shigeo S. A1 - Knodlseder, J. A1 - Koch, B. A1 - Kocot, J. A1 - Kohri, K. A1 - Komin, N. A1 - Konno, Y. A1 - Kosack, K. A1 - Koyama, S. A1 - Kraus, Michaela A1 - Kubo, Hidetoshi A1 - Mezek, G. Kukec A1 - Kushida, J. A1 - La Palombara, N. A1 - Lalik, K. A1 - Lamanna, G. A1 - Landt, H. A1 - Lapington, J. A1 - Laporte, P. A1 - Lee, S. A1 - Lees, J. A1 - Lefaucheur, J. A1 - Lenain, J. -P. A1 - Leto, Giuseppe A1 - Lindfors, E. A1 - Lohse, T. A1 - Lombardi, S. A1 - Longo, F. A1 - Lopez, M. A1 - Lucarelli, F. A1 - Luque-Escamilla, Pedro Luis A1 - Lopez-Coto, R. A1 - Maccarone, M. C. A1 - Maier, G. A1 - Malaguti, G. A1 - Mandat, D. A1 - Maneva, G. A1 - Mangano, S. A1 - Marcowith, Alexandre A1 - Marti, J. A1 - Martinez, M. A1 - Martinez, G. A1 - Masuda, S. A1 - Maurin, G. A1 - Maxted, N. A1 - Melioli, Claudio A1 - Mineo, T. A1 - Mirabal, N. A1 - Mizuno, T. A1 - Moderski, R. A1 - Mohammed, M. A1 - Montaruli, T. A1 - Moralejo, A. A1 - Mori, K. A1 - Morlino, G. A1 - Morselli, A. A1 - Moulin, Emmanuel A1 - Mukherjee, R. A1 - Mundell, C. A1 - Muraishi, H. A1 - Murase, Kohta A1 - Nagataki, Shigehiro A1 - Nagayoshi, T. A1 - Naito, T. A1 - Nakajima, D. A1 - Nakamori, T. A1 - Nemmen, R. A1 - Niemiec, Jacek A1 - Nieto, D. A1 - Nievas-Rosillo, M. A1 - Nikolajuk, M. A1 - Nishijima, K. A1 - Noda, K. A1 - Nogues, L. A1 - Nosek, D. A1 - Novosyadlyj, B. A1 - Nozaki, S. A1 - Ohira, Yutaka A1 - Ohishi, M. A1 - Ohm, S. A1 - Okumura, A. A1 - Ong, R. A. A1 - Orito, R. A1 - Orlati, A. A1 - Ostrowski, M. A1 - Oya, I. A1 - Padovani, Marco A1 - Palacio, J. A1 - Palatka, M. A1 - Paredes, Josep M. A1 - Pavy, S. A1 - Persic, M. A1 - Petrucci, P. A1 - Petruk, Oleh A1 - Pisarski, A. A1 - Pohl, Martin A1 - Porcelli, A. A1 - Prandini, E. A1 - Prast, J. A1 - Principe, G. A1 - Prouza, M. A1 - Pueschel, Elisa A1 - Puelhofer, G. A1 - Quirrenbach, A. A1 - Rameez, M. A1 - Reimer, O. A1 - Renaud, M. A1 - Ribo, M. A1 - Rico, J. A1 - Rizi, V. A1 - Rodriguez, J. A1 - Fernandez, G. Rodriguez A1 - Rodriguez Vazquez, J. J. A1 - Romano, Patrizia A1 - Romeo, G. A1 - Rosado, J. A1 - Rousselle, J. A1 - Rowell, G. A1 - Rudak, B. A1 - Sadeh, I. A1 - Safi-Harb, S. A1 - Saito, T. A1 - Sakaki, N. A1 - Sanchez, D. A1 - Sangiorgi, P. A1 - Sano, H. A1 - Santander, M. A1 - Sarkar, S. A1 - Sawada, M. A1 - Schioppa, E. J. A1 - Schoorlemmer, H. A1 - Schovanek, P. A1 - Schussler, F. A1 - Sergijenko, O. A1 - Servillat, M. A1 - Shalchi, A. A1 - Shellard, R. C. A1 - Siejkowski, H. A1 - Sillanpaa, A. A1 - Simone, D. A1 - Sliusar, V. A1 - Sol, H. A1 - Stanic, S. A1 - Starling, R. A1 - Stawarz, L. A1 - Stefanik, S. A1 - Stephan, M. A1 - Stolarczyk, T. A1 - Szanecki, M. A1 - Szepieniec, T. A1 - Tagliaferri, G. A1 - Tajima, H. A1 - Takahashi, M. A1 - Takeda, J. A1 - Tanaka, M. A1 - Tanaka, S. A1 - Tejedor, L. A. A1 - Telezhinsky, Igor O. A1 - Temnikov, P. A1 - Terada, Y. A1 - Tescaro, D. A1 - Teshima, M. A1 - Testa, V. A1 - Thoudam, S. A1 - Tokanai, F. A1 - Torres, D. F. A1 - Torresi, E. A1 - Tosti, G. A1 - Townsley, C. A1 - Travnicek, P. A1 - Trichard, C. A1 - Trifoglio, M. A1 - Tsujimoto, S. A1 - Vagelli, V. A1 - Vallania, P. A1 - Valore, L. A1 - van Driel, W. A1 - van Eldik, C. A1 - Vandenbroucke, Justin A1 - Vassiliev, V. A1 - Vecchi, M. A1 - Vercellone, Stefano A1 - Vergani, S. A1 - Vigorito, C. A1 - Vorobiov, S. A1 - Vrastil, M. A1 - Vazquez Acosta, M. L. A1 - Wagner, S. J. A1 - Wagner, R. A1 - Wakely, S. P. A1 - Walter, R. A1 - Ward, J. E. A1 - Watson, J. J. A1 - Weinstein, A. A1 - White, M. A1 - White, R. A1 - Wierzcholska, A. A1 - Wilcox, P. A1 - Williams, D. A. A1 - Wischnewski, R. A1 - Wojcik, P. A1 - Yamamoto, T. A1 - Yamamoto, H. A1 - Yamazaki, Ryo A1 - Yanagita, S. A1 - Yang, L. A1 - Yoshida, T. A1 - Yoshida, M. A1 - Yoshiike, S. A1 - Yoshikoshi, T. A1 - Zacharias, M. A1 - Zampieri, L. A1 - Zanin, R. A1 - Zavrtanik, M. A1 - Zavrtanik, D. A1 - Zdziarski, A. A1 - Zech, Alraune A1 - Zechlin, Hannes A1 - Zhdanov, V. A1 - Ziegler, A. A1 - Zorn, J. T1 - Prospects for Cherenkov Telescope Array Observations of the Young Supernova Remnant RX J1713.7-3946 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We perform simulations for future Cherenkov Telescope Array (CTA) observations of RX J1713.7-3946, a young supernova remnant (SNR) and one of the brightest sources ever discovered in very high energy (VHE) gamma rays. Special attention is paid to exploring possible spatial (anti) correlations of gamma rays with emission at other wavelengths, in particular X-rays and CO/H I emission. We present a series of simulated images of RX J1713.7-3946 for CTA based on a set of observationally motivated models for the gamma-ray emission. In these models, VHE gamma rays produced by high-energy electrons are assumed to trace the nonthermal X-ray emission observed by XMM-Newton, whereas those originating from relativistic protons delineate the local gas distributions. The local atomic and molecular gas distributions are deduced by the NANTEN team from CO and H I observations. Our primary goal is to show how one can distinguish the emission mechanism(s) of the gamma rays (i.e., hadronic versus leptonic, or a mixture of the two) through information provided by their spatial distribution, spectra, and time variation. This work is the first attempt to quantitatively evaluate the capabilities of CTA to achieve various proposed scientific goals by observing this important cosmic particle accelerator. KW - cosmic rays KW - gamma rays: ISM KW - ISM: individual objects (RX J1713.7-3946, G347.3-0.5) Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/aa6d67 SN - 0004-637X SN - 1538-4357 VL - 840 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - GEN A1 - Gudowska-Nowak, Ewa A1 - Lindenberg, Katja A1 - Metzler, Ralf T1 - Preface: Marian Smoluchowski’s 1916 paper—a century of inspiration T2 - Journal of physics : A, Mathematical and theoretical Y1 - 2017 U6 - https://doi.org/10.1088/1751-8121/aa8529 SN - 1751-8113 SN - 1751-8121 VL - 50 IS - 38 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Buschhüter, David A1 - Spoden, Christian A1 - Borowski, Andreas T1 - Physics knowledge of first semester physics students in Germany BT - a comparison of 1978 and 2013 cohorts JF - International journal of science education N2 - 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. KW - University physics KW - entrance test KW - generational comparison Y1 - 2017 U6 - https://doi.org/10.1080/09500693.2017.1318457 SN - 0950-0693 SN - 1464-5289 VL - 39 IS - 9 SP - 1109 EP - 1132 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Schimka, Selina A1 - Lomadze, Nino A1 - Rabe, Maren A1 - Kopyshev, Alexey A1 - Lehmann, Maren A1 - von Klitzing, Regine A1 - Rumyantsev, Artem M. A1 - Kramarenko, Elena Yu. A1 - Santer, Svetlana T1 - Photosensitive microgels containing azobenzene surfactants of different charges JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - 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. Y1 - 2016 U6 - https://doi.org/10.1039/c6cp04555c SN - 1463-9076 SN - 1463-9084 VL - 19 SP - 108 EP - 117 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Schimka, Selina A1 - Lomadze, Nino A1 - Rabe, Maren A1 - Kopyshev, Alexey A1 - Lehmann, Maren A1 - von Klitzing, Regine A1 - Rumyantsev, Artem M. A1 - Kramarenko, Elena Yu. A1 - Santer, Svetlana T1 - Photosensitive microgels containing azobenzene surfactants of different charges T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 461 KW - ph-responsive microgels KW - co-monomer content KW - drug-delivery KW - photoresponsive surfactants KW - metal nanoparticles KW - swelling behavior KW - temperature KW - particles KW - collapse KW - hydrogels Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-413528 SN - 1866-8372 IS - 461 ER - TY - JOUR A1 - Malyar, Ivan V. A1 - Gorin, Dmitry A. A1 - Santer, Svetlana A1 - Stetsyura, Svetlana V. T1 - Photo-assisted adsorption of gold nanoparticles onto a silicon substrate JF - Applied physics letters N2 - We report on a photo-assisted adsorption of gold nanoparticles on a silicon substrate studied using atomic-force microscopy and secondary ion mass-spectrometry. Depending on a silicon conductivity type (n-Si or p-Si), the amount of photo-assisted adsorbed gold nanoparticles either increases (n-Si) or decreases (p-Si) on irradiation. In addition, the impacts of a cationic polyelectrolyte monolayer and adsorption time were also revealed. The polyelectrolyte layer enhances the adsorption of the gold nanoparticles but decreases the influence of light. The results of the photo-assisted adsorption on two types of silicon wafer were explained by electron processes at the substrate/solution interface. This work was supported by the German-Russian Interdisciplinary Science Center (G-RISC) funded by the German Federal Foreign Office via the German Academic Exchange Service (DAAD), Project No. P-2014b-1, and Russian foundation for basic research, Project No. 16-08-00524_a. Y1 - 2017 U6 - https://doi.org/10.1063/1.4979082 SN - 0003-6951 SN - 1077-3118 VL - 110 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Niebuhr, Mario A1 - Heuer, Axel T1 - Phase measurement and far-field reconstruction on externally coupled laser diode arrays JF - Optics express N2 - Passive coherent combination of several discrete low power laser diodes is a promising way to overcome the issue of degrading beam quality when scaling single emitters to > 10W output power. Such systems would be an efficient alternative to current high power sources, yet they suffer from fatal coherence loss when operated well above threshold. We present a new way to obtain detailed coherence information for laser diode arrays using a spatial light modulator to help identify the underlying decoherence processes. Reconstruction tests of the emitted far-field distribution are conducted to evaluate the performance of our setup. Y1 - 2017 U6 - https://doi.org/10.1364/OE.25.014317 SN - 1094-4087 VL - 25 IS - 13 SP - 14317 EP - 14322 PB - Optical Society of America CY - Washington, DC ER - TY - GEN A1 - Niebuhr, Mario A1 - Heuer, Axel T1 - Phase measurement and far-field reconstruction on externally coupled laser diode arrays N2 - Passive coherent combination of several discrete low power laser diodes is a promising way to overcome the issue of degrading beam quality when scaling single emitters to > 10W output power. Such systems would be an efficient alternative to current high power sources, yet they suffer from fatal coherence loss when operated well above threshold. We present a new way to obtain detailed coherence information for laser diode arrays using a spatial light modulator to help identify the underlying decoherence processes. Reconstruction tests of the emitted far-field distribution are conducted to evaluate the performance of our setup. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 383 Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-402140 ER - TY - THES A1 - Thielemann-Kühn, Nele T1 - Optically induced ferro- and antiferromagnetic dynamics in the rare-earth metal dysprosium T1 - Optisch induzierte ferro- und antiferromagnetische Dynamik im Seltenerdmetall Dysprosium N2 - Approaching physical limits in speed and size of today's magnetic storage and processing technologies demands new concepts for controlling magnetization and moves researches on optically induced magnetic dynamics. Studies on photoinduced magnetization dynamics and their underlying mechanisms have been primarily performed on ferromagnetic metals. Ferromagnetic dynamics bases on transfer of the conserved angular momentum connected with atomic magnetic moments out of the parallel aligned magnetic system into other degrees of freedom. In this thesis the so far rarely studied response of antiferromagnetic order to ultra-short optical laser pulses in a metal is investigated. The experiments were performed at the FemtoSpex slicing facility at the storage ring BESSY II, an unique source for ultra-short elliptically polarized x-ray pulses. Laser-induced changes of the 4f-magnetic order parameter in ferro- and antiferromagnetic dysprosium (Dy), were studied by x-ray methods, which yield directly comparable quantities. The discovered fundamental differences in the temporal and spatial behavior of ferro- and antiferrmagnetic dynamics are assinged to an additional channel for angular momentum transfer, which reduces the antiferromagnetic order by redistributing angular momentum within the non-parallel aligned magnetic system, and hence conserves the zero net magnetization. It is shown that antiferromagnetic dynamics proceeds considerably faster and more energy-efficient than demagnetization in ferromagnets. By probing antiferromagnetic order in time and space, it is found to be affected along the whole sample depth of an in situ grown 73 nm tick Dy film. Interatomic transfer of angular momentum via fast diffusion of laser-excited 5d electrons is held responsible for the out-most long-ranging effect. Ultrafast ferromagnetic dynamics can be expected to base on the same origin, which however leads to demagnetization only in regions close to interfaces caused by super-diffusive spin transport. Dynamics due to local scattering processes of excited but less mobile electrons, occur in both magnetic alignments only in directly excited regions of the sample and on slower pisosecond timescales. The thesis provides fundamental insights into photoinduced magnetic dynamics by directly comparing ferro- and antiferromagnetic dynamics in the same material and by consideration of the laser-induced magnetic depth profile. N2 - Die Geschwindigkeit und Datendichte in heutigen Technologien zur magnetischen Datenspeicherung und -verarbeitung erreichen allmählich physikalische Grenzen. Neue Konzepte zur Manipulation von Magnetisierung sind deshalb erforderlich, was die Forschung an optisch induzierter Magnetodynamik motiviert. Studien zur magnetischen Dynamik ausgelöst durch Femtosekunden-Laserpulse und die ihr zugrunde liegenden Mechanismen stützen sich vorwiegend auf ferromagnetische Metalle. Die Manipulation ferromagnetischer Ordnung basiert aufgrund physikalischer Erhaltungssätze auf dem Transfer des mit atomaren magnetischen Momenten verknüpften Drehimpulses, in andere Freiheitsgrade wie das Gitter oder räumlich in Bereiche mit anderen magnetischen Eigenschaften. Gegenstand dieser Arbeit ist die bisher weniger umfassend untersuchte Reaktion antiferromagnetischer Ordnung auf optische Anregung. Die hier vorgestellten Experimente wurden an der FemtoSpex Slicing Facility, einer einzigartigen Quelle für ultrakurze elliptisch polarisierte Röntgenpulse am Elektronenspeicherring BESSY II durchgeführt. Im 4f-Metall Dysprosium (Dy), das je nach Temperatur ferro- oder antiferromagnetisch ist, wurden optisch induzierte Änderungen der magnetischen Ordnung mit Röntgenmethoden untersucht, aus denen sich der jeweilige 4f-Ordnungsparameter direkt vergleichbar ableiten lässt. Es wird ein sowohl zeitlich als auch räumlich fundamental unterschiedliches Verhalten der ferro- und antiferromagnetischen Dynamik im Femtosekundenbereich nachgewiesen: Antiferromagnetische Ordnung wird wesentlich schneller und energieeffizienter reduziert als ferromagnetische Ordnung. Zeit- und tiefenaufgelöste Messungen an antiferromagnetischem Dy zeigen, dass dieser Effekt zudem äußerst weitreichend ist und die magnetische Ordnung entlang der gesamten Probentiefe eines 73 nm dicken in situ gewachsenen Dy-Films reduziert. Verantwortlich dafür ist ein hier identifizierter Kanal für Drehimpulstransfer, der es aufgrund der nicht-parallelen Orientierung der atomaren magnetischen Momente in Antiferromagneten erlaubt, die entsprechende Ordnung durch eine Umverteilung des Drehimpulses innerhalb des magnetischen Systems zu reduzieren. Dieser Kanal wird zugänglich durch schnelle Diffusion von laserangeregten 5d-Elektronen, die interatomar Drehimpuls übertragen. Die Experimente deuten darauf hin, dass ultraschnelle ferromagnetische Dynamik ebenfalls stark auf Diffusion mobiler Elektronen basiert. Allerdings sorgt der Effekt hier ausschließlich für Demagnetisierung in grenzflächennahen Bereichen durch Spintransport in magnetisch andersartige Gebiete. Auf längeren Picosekundenzeitskalen wird magnetische Dynamik in der antiferro- und voraussichtlich auch in der ferromagnetischen Phase von Dy durch lokale Streuprozesse angeregter aber weniger beweglicherer Elektronen, zum Beispiel mit Phononen hervorgerufen, allerdings nur in direkt angeregten Teilen der Probe. Die vorliegende Arbeit gibt durch den direkten Vergleich ferro- und antiferromagnetischer Dynamik und der Berücksichtigung des optisch induzierten magnetischen Tiefenprofils Einblicke in die fundamentalen Ursprünge optisch induzierter magnetischer Dynamik. KW - antiferromagnetism KW - ferromagnetism KW - ultrafast phenomena KW - x-ray magnetic circular dichroism (XMCD) KW - x-ray magnetic resonant diffraction (XMRD) KW - rare-earth metals KW - pump-probe experiment KW - optically induced dynamics KW - Antiferromagnetismus KW - Ferromagnetismus KW - ultraschnelle Phänomene KW - magnetischer Zirkulardichroismus KW - magnetische resonante Beugung KW - seltene Erden KW - Anregungs-Abfrage-Experiment KW - optisch induzierte Dynamik Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-402994 ER - TY - THES A1 - Kiani Alibagheri, Bahareh T1 - On structural properties of magnetosome chains T1 - Auf strukturellen Eigenschaften von Magnetosomenketten N2 - Magnetotaktische Bakterien besitzen eine intrazelluläre Struktur, die Magnetosomenkette genannt wird. Magnetosomenketten enthalten Nanopartikel von Eisenkristallen, die von einer Membran umschlossen und entlang eines Zytoskelettfilaments ausgerichtet sind. Dank der Magnetosomenkette ist es magnetotaktischen Bakterien möglich sich in Magnetfeldern auszurichten und entlang magnetischer Feldlinien zu schwimmen. Die ausführliche Untersuchung der strukturellen Eigenschaften der Magnetosomenkette in magnetotaktischen Bakterien sind von grundlegendem wissenschaftlichen Interesse, weil sie Einblicke in die Anordnung des Zytoskeletts von Bakterien erlauben. In dieser Studie haben wir ein neues theoretisches Modell entwickelt, dass sich dazu eignet, die strukturellen Eigenschaften der Magnetosomenketten in magnetotaktischen Bakterien zu erforschen. Zuerst wenden wir uns der Biegesteifigkeit von Magnetosomenketten zu, die von zwei Faktoren beeinflusst wird: Die magnetische Wechselwirkung der Magnetosomenpartikel und der Biegesteifigkeit des Zytoskelettfilaments auf welchem die Magnetosome verankert sind. Unsere Analyse zeigt, dass sich die lineare Konfiguration von Magnetosomenpartikeln ohne die Stabilisierung durch das Zytoskelett zu einer ringörmigen Struktur biegen würde, die kein magnetisches Moment aufweist und daher nicht die Funktion eines Kompass in der zellulären Navigation einnehmen könnte. Wir schlussfolgern, dass das Zytoskelettfilament eine stabilisierende Wirkung auf die lineare Konfiguration hat und eine ringförmige Anordnung verhindert. Wir untersuchen weiter die Gleichgewichtskonfiguration der Magnetosomenpartikel in einer linearen Kette und in einer geschlossenen ringförmigen Struktur. Dabei beobachteten wir ebenfalls, dass für eine stabile lineare Anordnung eine Bindung an ein Zytoskelettfilament notwendig ist. In einem externen magnetischen Feld wird die Stabilität der Magnetosomenketten durch die Dipol-Dipol-Wechselwirkung, über die Steifheit und die Bindungsenergie der Proteinstruktur, die die Partikel des Magnetosomen mit dem Filament verbinden, erreicht. Durch Beobachtungen während und nach der Behandlung einer Magnetosomenkette mit einem externen magnetischen Feld, lässt sich begründen, dass die Stabilisierung von Magnetosomenketten durch Zytoskelettfilamente über proteinhaltige Bindeglieder und die dynamischen Eigenschaften dieser Strukturen realisiert wird. Abschließend wenden wir unser Modell bei der Untersuchung von ferromagnetischen Resonanz-Spektren von Magnetosomenketten in einzelnen Zellen von magnetotaktischen Bakterien an. Wir erforschen den Effekt der magnetokristallinen Anistropie in ihrer dreifach-Symmetrie, die in ferromagnetischen Ressonanz Spektren beobachtet wurden und die Besonderheit von verschiedenen Spektren, die bei Mutanten dieser Bakterien auftreten. N2 - Magnetotactic bacteria possess an intracellular structure called the magnetosome chain. Magnetosome chains contain nano−particles of iron crystals enclosed by a membrane and aligned on a cytoskeletal filament. Due to the presence of the magnetosome chains, magnetotactic bacteria are able to orient and swim along the magnetic field lines. A detailed study of structural properties of magnetosome chains in magnetotactic bacteria has primary scientific interests. It can provide more insight into the formation of the cytoskeleton in bacteria. In this thesis, we develop a new framework to study the structural properties of magnetosome chains in magnetotactic bacteria. First, we address the bending stiffness of magnetosome chains resulting from two main contributions: the magnetic interactions of magnetosome particles and the bending stiffness of the cytoskeletal filament to which the magnetosomes are anchored. Our analysis indicates that the linear configuration of magnetosome particles without the stabilisation to the cytoskeleton may close to ring like structures, with no net magnetic moment, which thus can not perform as a compass in cellular navigation. As a result we think that one of the roles of the filament is to stabilize the linear configuration against ring closure. We then investigate the equilibrium configurations of magnetosome particles including linear chain and closed−ring structures. We notably observe that for the formation of a stable linear structure on the cytoskeletal filament, presence of a binding energy is needed. In the presence of external stimuli the stability of the magnetosome chain is due to the internal dipole−dipole interactions, the stiffness and the binding energy of the protein structure connecting the magnetosome particles to the filament. Our observations, during and after the treatment of the magnetosome chain with the external magnetic field substantiates the stabilisation of magnetosome chains to the cytoskeletal filament by proteinous linkers and the dynamic feature of these structures. Finally, we employ our model to study the FMR spectra of magnetosome chains in a single cell of magnetotactic bacteria. We explore the effect of magnetocrystalline anisotropy in three-fold symmetry observed in FMR spectra and the peculiarity of different spectra arisen from different mutants of these bacteria. KW - magnetotactic bacteria KW - magnetosome chains KW - structural properties KW - magnetotaktische Bakterien KW - Magnetosomen-Ketten KW - strukturelle Eigenschaften Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-398849 ER - TY - JOUR A1 - Wolf, Thomas J. A. A1 - Holzmeier, Fabian A1 - Wagner, Isabella A1 - Berrah, Nora A1 - Bostedt, Christoph A1 - Bozek, John A1 - Bucksbaum, Philip H. A1 - Coffee, Ryan A1 - Cryan, James A1 - Farrell, Joe A1 - Feifel, Raimund A1 - Martinez, Todd J. A1 - McFarland, Brian A1 - Mucke, Melanie A1 - Nandi, Saikat A1 - Tarantelli, Francesco A1 - Fischer, Ingo A1 - Gühr, Markus T1 - Observing Femtosecond Fragmentation Using Ultrafast X-ray-Induced Auger Spectra JF - Applied Sciences N2 - Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymine′s neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes. KW - ultrafast dynamics KW - Auger electron spectroscopy KW - photofragmentation KW - photochemistry Y1 - 2017 U6 - https://doi.org/10.3390/app7070681 SN - 2076-3417 VL - 7 IS - 7 PB - MDPI CY - Basel ER - TY - GEN A1 - Wolf, Thomas J. A. A1 - Holzmeier, Fabian A1 - Wagner, Isabella A1 - Berrah, Nora A1 - Bostedt, Christoph A1 - Bozek, John A1 - Bucksbaum, Philip H. A1 - Coffee, Ryan A1 - Cryan, James A1 - Farrell, Joe A1 - Feifel, Raimund A1 - Martinez, Todd J. A1 - McFarland, Brian A1 - Mucke, Melanie A1 - Nandi, Saikat A1 - Tarantelli, Francesco A1 - Fischer, Ingo A1 - Gühr, Markus T1 - Observing Femtosecond Fragmentation Using Ultrafast X-ray-Induced Auger Spectra N2 - Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymine′s neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 386 KW - Auger electron spectroscopy KW - photochemistry KW - photofragmentation KW - ultrafast dynamics Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-402692 ER - TY - JOUR A1 - Olson, R. A1 - An, Soon-Il A1 - Fan, Y. A1 - Evans, J. P. A1 - Caesar, Levke T1 - North Atlantic observations sharpen meridional overturning projections JF - Climate dynamics : observational, theoretical and computational research on the climate system N2 - Atlantic Meridional Overturning Circulation (AMOC) projections are uncertain due to both model errors, as well as internal climate variability. An AMOC slowdown projected by many climate models is likely to have considerable effects on many aspects of global and North Atlantic climate. Previous studies to make probabilistic AMOC projections have broken new ground. However, they do not drift-correct or cross-validate the projections, and do not fully account for internal variability. Furthermore, they consider a limited subset of models, and ignore the skill of models at representing the temporal North Atlantic dynamics. We improve on previous work by applying Bayesian Model Averaging to weight 13 Coupled Model Intercomparison Project phase 5 models by their skill at modeling the AMOC strength, and its temporal dynamics, as approximated by the northern North-Atlantic temperature-based AMOC Index. We make drift-corrected projections accounting for structural model errors, and for the internal variability. Cross-validation experiments give approximately correct empirical coverage probabilities, which validates our method. Our results present more evidence that AMOC likely already started slowing down. While weighting considerably moderates and sharpens our projections, our results are at low end of previously published estimates. We project mean AMOC changes between periods 1960-1999 and 2060-2099 of -4.0 Sv and -6.8 Sv for RCP4.5 and RCP8.5 emissions scenarios respectively. The corresponding average 90% credible intervals for our weighted experiments are [-7.2, -1.2] and [-10.5, -3.7] Sv respectively for the two scenarios. KW - Atlantic Meridional Overturning Circulation KW - Climate modeling KW - Bayesian Model Averaging KW - Model structural error KW - Probabilistic projections Y1 - 2017 U6 - https://doi.org/10.1007/s00382-017-3867-7 SN - 0930-7575 SN - 1432-0894 VL - 50 IS - 11-12 SP - 4171 EP - 4188 PB - Springer CY - New York ER - TY - JOUR A1 - Warren, Donald C. A1 - Ellison, Donald C. A1 - Barkov, Maxim V. A1 - Nagataki, Shigehiro T1 - Nonlinear Particle Acceleration and Thermal Particles in GRB Afterglows JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The standard model for GRB afterglow emission treats the accelerated electron population as a simple power law, N(E) proportional to E-p for p greater than or similar to 2. However, in standard Fermi shock acceleration, a substantial fraction of the swept-up particles do not enter the acceleration process at all. Additionally, if acceleration is efficient, then the nonlinear back-reaction of accelerated particles on the shock structure modifies the shape of the nonthermal tail of the particle spectra. Both of these modifications to the standard synchrotron afterglow impact the luminosity, spectra, and temporal variation of the afterglow. To examine the effects of including thermal particles and nonlinear particle acceleration on afterglow emission, we follow a hydrodynamical model for an afterglow jet and simulate acceleration at numerous points during the evolution. When thermal particles are included, we find that the electron population is at no time well fitted by a single power law, though the highest-energy electrons are; if the acceleration is efficient, then the power-law region is even smaller. Our model predicts hard-soft-hard spectral evolution at X-ray energies, as well as an uncoupled X-ray and optical light curve. Additionally, we show that including emission from thermal particles has drastic effects (increases by factors of 100 and 30, respectively) on the observed flux at optical and GeV energies. This enhancement of GeV emission makes afterglow detections by future gamma-ray observatories, such as CTA, very likely. KW - acceleration of particles KW - cosmic rays KW - gamma-ray burst: general KW - shock waves KW - turbulence Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/aa56c3 SN - 0004-637X SN - 1538-4357 VL - 835 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Henkel, Carsten T1 - Nanoscale Thermal Transfer BT - an Invitation to Fluctuation Electrodynamics JF - Zeitschrift für Naturforschung A N2 - 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. KW - Heat Transfer KW - Near-Field Optics KW - Thermal Radiation Y1 - 2017 U6 - https://doi.org/10.1515/zna-2016-0372 SN - 0932-0784 SN - 1865-7109 VL - 72 IS - 2 SP - 99 EP - 108 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Heydari, Esmaeil A1 - Pastoriza-Santos, Isabel A1 - Liz-Marzan, Luis M. A1 - Stumpe, Joachim T1 - Nanoplasmonically-engineered random lasing in organic semiconductor thin films JF - Nanoscale horizons N2 - We demonstrate plasmonically nano-engineered coherent random lasing and stimulated emission enhancement in a hybrid gainmedium of organic semiconductors doped with core-shell plasmonic nanoparticles. The gain medium is composed of a 300 +/- 2 nm thin waveguide of an organic semiconductor, doped with 53 nm gold nanoparticle cores, isolated within silica shells. Upon loading the nanoparticles, the threshold of amplified spontaneous emission is reduced from 1.75 mu J cm(-2) x 10(2) for an undoped gain medium, to 0.35 mu J cm(-2) x 10(2) for a highly concentrated gain medium, and lasing spikes narrower than 0.1 nm are obtained. Most importantly, selection of silica shells with thicknesses of 10, 17 and 21 nm enables engineering of the plasmon-exciton energy coupling and consequently tuning of the laser slope efficiency. With this approach, the slope efficiency is increased by two times by decreasing the silica shell from 21 nm down to 10 nm, due to the enhancement of the localized electric field. Y1 - 2017 U6 - https://doi.org/10.1039/c7nh00054e SN - 2055-6756 SN - 2055-6764 VL - 2 SP - 261 EP - 266 PB - Royal Society of Chemistry CY - Cambridge ER -