bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasma‐related phonon‐sideband emission in semiconductors
Authors: Chernikov Alexej , Böttge Christoph N. , Feldtmann Thomas , Chatterjee Sangam , Koch Martin , Kira Mackillo , Koch Stephan W. 
Published: February 2011

AbstractThe phonon‐assisted recombination in bulk II‐VI semi‐conductors is analyzed by means of time‐resolved photoluminescence spectroscopy. Experimental results on both CdS and CdSe clearly indicate that phonon‐sideband emission is not exclusively attributed to the presence of excitons. The contributions of Coulombcorrelated electron‐hole plasma to the phonon assisted recombination may be significant, depending on the excitation conditions. This observation is supported by a microscopic many‐particle theory of interacting electrons, phonons, and photons. Our theoretical approach generalizes previous investigations by including both correlated and uncorrelated luminescence sources. Our findings contradict and expand the traditional picture of phonon‐sideband emission. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of motion on exciton magnetic properties
Authors: Kochereshko Vladimir P. , Davies John J. , Smith Lowenna C. , Wolverson Daniel , Mariette Henri , Boukari Hervé , Wiater Maciej , Karczewski Grzegorz , Wojtowicz Tomasz J. 
Published: February 2011

AbstractIn this paper we demonstrate that the magnetic moment of the exciton increases due to its motion along the magnetic field, and the diamagnetic shift decreases. These effects were observed for a set of quantum well structures with different well widths and based on a variety of semiconductor compounds. The reason for these effects is mixing of the exciton’s center of mass motion and the internal motion of the electron and hole in the exciton. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coulomb correlations in quantum dots and their signatures in single dot femtosecond pump‐probe signals
Authors: Huneke J. , D'Amico I. , Machnikowski P. , Thomay T. , Bratschitsch R. , Leitensdorfer A. , Kuhn T. 
Published: February 2011

AbstractWe present a theoretical study of femtosecond pump‐probe experiments on a negatively charged single quantum dot and analyze the influence of Coulomb correlation effects on the lowest trion absorption line. The Coulomb correlated states as well as their corresponding oscillator strengths are calculated by a full diagonalization approach. The dynamics induced by the laser pulses are determined numerically by solving the Liouville‐von Neumann equation in the basis of the calculated few‐particle states. In agreement with the experiment, we demonstrate that Coulomb interactions and carrier relaxations noticeably affect the lowest trion absorption line. For negative and short positive delay times between pump and probe pulse instantaneous Coulomb renormalizations dominate the signal while for longer delay times the signal is governed by carrier relaxations. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Semiclassical theory for a nonequilibrium steady state in microcavity semiconductor lasers
Authors: Kamide Kenji , Ogawa Tetsuo 
Published: February 2011

AbstractSemiclassical equations for microcavity semiconductor lasers based on Maxwell‐semiconductor‐Bloch equations are solved for on‐lasing state (nonequilibrium steady state) with a steady state condition for eigenfrequencies. Results for a single mode operation can account for input‐output curves for laser operation, gain saturation accompanied by the spectral hole‐burning in the carrier distribution, and the shift of laser frequency.We found nonmonotonic dependency of the laser frequency on the pump intensity (excited carrier density) when the cavity mode is close to the exciton level. Effects of Coulomb interaction, and phase‐space filling are also discussed with reference to the case of homogeneously and inhomogeneously broadened two‐level atom lasers. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Silicon based light emitter utilizing tunnel injection of excess carriers via MIS structure
Authors: Arguirov Tzanimir , Wenger Christian , Lukosius Mindaugas , Mchedlidze Teimuraz , Reiche Manfred , Kittler Martin 
Published: February 2011

AbstractWe report on electro‐luminescence from metal‐insulator‐semiconductor diodes (MISLED). MISLEDs prepared on silicon with HfO2 layers of different thicknesses were investigated and their properties compared with such prepared by using SiO2 insulator layer. The role of the insulator layer was studied in view of the efficiency of the band‐to‐band radiation from silicon. We show that the luminescence efficiency depends on the dielectric constant of the insulator as well as on its ability to conduct carriers by tunnelling. Efficiency enhancement of 3.3 times was detected when the SiO2 insulator was substituted by HfO2 in the MIS emitter. Optimal injection current exists, which leads to a maximal efficiency of the luminescence. The optimal current depends strongly on the thickness of the oxide. We relate the existence of an optimal current with the depth at which the injected minority carriers recombine radiatively. Thus the electric field in the semiconductor and the surface recombination are the factors determining the optimal injection (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of dislocation behavior in Si‐ and C‐face 4H‐SiC
Authors: Chen Bin , Matsuhata Hirofumi , Sekiguchi Takashi , Ohyanagi Takasumi , Kinoshita Akimasa , Okumura Hajime 
Published: February 2011

AbstractThe dislocation behavior in C‐face 4H‐SiC homoepitaxial films was studied by using electron‐beam‐induced current (EBIC) technique and is compared with that in Si‐face ones. For the basal plane dislocations (BPDs) with the same line shape appearing in the EBIC images, the mobile partial dislocations (PDs) originated from the dissociation of such BPDs move in two opposite directions, while they move in one direction in the Si‐face samples. The difference of the PD movement between two faces is discussed (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect luminescence at grain boundaries in multicrystalline silicon
Authors: Dreckschmidt Felix , Möller Hans‐Joachim 
Published: February 2011

AbstractMulticrystalline silicon is characterised by extended defects like dislocations and grain boundaries. Grain boundaries in this material can show radiative recombination in the near infrared (NIR) region even at room temperature (Dreckschmidt et al., Proc. 23rd European Photovoltaic Solar Energy Conference, Valencia, Spain, 2008, p. 407. [1]). Here we present results of further investigations by the electroluminescence method regarding these phenomena. It turned out that carrier recombination at these centres is negligible. From temperature dependent measurements activation energies of the different centres were determined. Defect schemes for the grain boundary luminescence are proposed (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fast electron beam charge injection and switching in dielectrics
Authors: Fitting Hans‐Joachim , Touzin Matthieu , Schreiber Erik 
Published: February 2011

AbstractBasic investigations of secondary electrons (SE) relaxation and attenuation are made by means of Monte Carlo simulations using ballistic electron scattering and interactions with optical and acoustic phonons as well as impact ionization of valence band electrons. Then the electron beam induced selfconsistent charge transport and secondary electron emission in insulators are described by means of an electron‐hole flight‐drift model (FDM). Ballistic secondary electrons and holes, their attenuation and drift, as well as their recombination, trapping, and field‐ and temperature‐dependent Poole‐Frenkel detrapping are included. Whereas the initial switching‐on of the secondary electron emission proceeds over milli‐seconds due to long‐lasting selfconsistent charging, the switching‐off process occurs much faster, even over femto‐seconds.Thus a rapid electron beam switching becomes possible with formation of ultra‐short electron beam pulses offering an application in stroboscopic electron microscopy and spectroscopy. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
EPR spectroscopy of weak exchange interactions between Co2+ ions in ZnO
Authors: Azamat D. V. , Dejneka A. , Trepakov V. A. , Jastrabik L. , Fanciulli M. , Ivanov V. Y. , Godlewski M. , Sokolov V. I. , Rosa J. , Badalyan A. G. 
Published: February 2011

AbstractElectron paramagnetic resonance (EPR) is used to identify the next nearest neighbour Co2+ pairs coupled by spin–spin interaction in Co‐doped ZnO single crystals grown by the hydrothermal technique. These dimer centers are described by a spin Hamiltonian with exchange coupling terms written as interaction between identical effective spins Seff = 1/2 of the lowest ground state Kramers doublets of the two Co2+ ions. The exchange parameters of weakly ferromagnetically coupled next nearest neighbor Co2+ pairs are estimated. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of ice particles in convective clouds observed over the Black Forest mountains during COPS
Authors: Huang Yahui , Blyth Alan M. , Brown Philip R. A. , Cotton Richard , Crosier Jonathan , Bower Keith N. , Gallagher Martin W. , Jones Hazel , Gadian Alan M. , Choularton Tom W. , Cardwell John , Coe Hugh , Mobbs Stephen D. , Hagen Martin 
Published: February 2011

AbstractA combination of modelling studies and ground‐based and aircraft measurements is used to examine the development of ice particles in convective clouds observed over the Black Forest mountains during the Convective and Orographically‐induced Precipitation Study (COPS). High concentrations of relatively small ice particles were observed in the weaker northern cell that developed on convergence lines over the mountains in the much‐studied 15 July 2007 case. The conditions in the cloud were not conducive for the Hallett–Mossop process. Instead, the explanation for such high concentrations of ice is likely associated with the type of ice nuclei ingested into the cloud. Biological nuclei, oxidised organic aerosol particles in the polluted air vented from the Murg valley into the cloud base, and desert dust are all possible candidates. A model sensitivity test with biological nuclei produced similar concentrations of ice particles to the observations. In contrast, the high concentration of ice particles measured in clouds that advected over the Black Forest mountains on 11 July 2007 were likely due to the Hallett–Mossop process. The deep convective cell at the southern end of the COPS domain on 15 July 2007 developed in less polluted air than the shallower northern cloud. A model sensitivity test with lower aerosol loading produced a more vigorous cloud with a higher top, more precipitation, and greater reflectivity, more similar to the radar observations. The results suggest that aerosol particles vented out of the valleys could have a significant impact on orographically induced precipitation. Copyright © 2011 Royal Meteorological Society and Crown copyright, the Met Office
The Convective and Orographically‐induced Precipitation Study (COPS): the scientific strategy, the field phase, and research highlights
Authors: Wulfmeyer Volker , Behrendt Andreas , Kottmeier Christoph , Corsmeier Ulrich , Barthlott Christian , Craig George C. , Hagen Martin , Althausen Dietrich , Aoshima Fumiko , Arpagaus Marco , Bauer Hans‐Stefan , Bennett Lindsay , Blyth Alan , Brandau Christine , Champollion Cédric , Crewell Susanne , Dick Galina , Di Girolamo Paolo , Dorninger Manfred , Dufournet Yann , Eigenmann Rafael , Engelmann Ronny , Flamant Cyrille , Foken Thomas , Gorgas Theresa , Grzeschik Matthias , Handwerker Jan , Hauck Christian , Höller Hartmut , Junkermann Wolfgang , Kalthoff Norbert , Kiemle Christoph , Klink Stefan , König Marianne , Krauss Liane , Long Charles N. , Madonna Fabio , Mobbs Stephen , Neininger Bruno , Pal Sandip , Peters Gerhard , Pigeon Grégoire , Richard Evelyne , Rotach Mathias W. , Russchenberg Herman , Schwitalla Thomas , Smith Victoria , Steinacker Reinhold , Trentmann Jörg , Turner David D. , van Baelen Joel , Vogt Siegfried , Volkert Hans , Weckwerth Tammy , Wernli Heini , Wieser Andreas , Wirth Martin 
Published: February 2011

AbstractWithin the framework of the international field campaign COPS (Convective and Orographically‐induced Precipitation Study), a large suite of state‐of‐the‐art meteorological instrumentation was operated, partially combined for the first time. This includes networks of in situ and remote‐sensing systems such as the Global Positioning System as well as a synergy of multi‐wavelength passive and active remote‐sensing instruments such as advanced radar and lidar systems. The COPS field phase was performed from 01 June to 31 August 2007 in a low‐mountain area in southwestern Germany/eastern France covering the Vosges mountains, the Rhine valley and the Black Forest mountains. The collected data set covers the entire evolution of convective precipitation events in complex terrain from their initiation, to their development and mature phase until their decay. Eighteen Intensive Observation Periods with 37 operation days and eight additional Special Observation Periods were performed, providing a comprehensive data set covering different forcing conditions. In this article, an overview of the COPS scientific strategy, the field phase, and its first accomplishments is given. Highlights of the campaign are illustrated with several measurement examples. It is demonstrated that COPS research provides new insight into key processes leading to convection initiation and to the modification of precipitation by orography, in the improvement of quantitative precipitation forecasting by the assimilation of new observations, and in the performance of ensembles of convection‐permitting models in complex terrain. Copyright © 2010 Royal Meteorological Society
Latent heat flux measurements over complex terrain by airborne water vapour and wind lidars
Authors: Kiemle Christoph , Wirth Martin , Fix Andreas , Rahm Stephan , Corsmeier Ulrich , Di Girolamo Paolo 
Published: February 2011

AbstractVertical profiles of the latent heat flux in a convective boundary layer (CBL) are obtained for the first time over complex terrain with airborne water vapour differential absorption lidar and Doppler wind lidar. During the Convective and Orographically‐induced Precipitation Study (COPS) over the Black Forest mountains in south‐western Germany both lidars were installed nadir‐viewing onboard the Falcon research aircraft of the Deutsches Zentrum für Luft‐ und Raumfahrt (DLR). On 30 July 2007, additional in situ measurements by the Karlsruhe Institute of Technology (KIT) were performed with a Dornier‐128 aircraft that flew below the Falcon. This unique instrument configuration allows us to validate the lidar‐derived fluxes and to assess lidar‐specific issues such as instrument noise and data gaps that impinge on the results. The cospectra of in situ humidity and vertical velocity peak at wavelengths between 1 and 3 km and reveal that the dominant scales of turbulent transport are larger than 700 m in dimension. Consequently the airborne lidars' horizontal and vertical resolution of ∼ 200 m is sufficient to capture most of the flux. The lidar and in situ fluxes of five collocated 45 km flight legs agree within ±20%; the average difference over the total distance of 225 km is 3%. A flux comparison with ground‐based water vapour Raman and wind lidars shows agreement within the instruments' accuracies under low‐wind conditions. All latent heat fluxes vary between 100 and 500 W/m2 in the CBL and have small vertical divergences. Vertical velocity spectra in the mid‐CBL enable us to estimate the dissipation rate of turbulent kinetic energy that amounts to 5 × 10−4 m2 s−3 in the Rhine Valley and 10−3 m2 s−3 over the Black Forest mountains. This new airborne lidar instrumentation proves to be a valuable tool for the study of CBL processes and variability, particularly over complex terrain. Copyright © 2011 Royal Meteorological Society
On stability analysis of systems featuring a multiplicative combination of nonlinear and linear time‐invariant feedback
Authors: Kulkarni Vishwesh V. , Pao Lucy Y. , Safonov Michael G. 
Published: February 2011

AbstractWe show that sufficient conditions for the finite‐gain stability of certain systems featuring a multiplicative combination of memoryless nonlinear feedback and linear time‐invariant feedback, as encountered in some systems' biology prototype applications, can be obtained by building on the Rantzer multipliers. These results are obtained by observing that for all finite energy signals x, the time‐truncated inner product 〈x, H(x)N(x)〉T is positive for all T>0 if N belongs to a subclass of positive memoryless monotone nonlinearities and if, in addition, H is a Rantzer multiplier. Copyright © 2011 John Wiley & Sons, Ltd.
Backstepping control design for motion coordination of self‐propelled vehicles in a flowfield
Authors: Mellish Rochelle , Napora Seth , Paley Derek A. 
Published: February 2011

AbstractMotion coordination of autonomous vehicles has applications from target surveillance to climate monitoring. Previous research has yielded stabilizing control laws for a self‐propelled vehicle model with first‐order rotational dynamics, but this model does not adequately describe the rotational dynamics of vehicles in the atmosphere or ocean. This paper describes the design of backstepping algorithms for the decentralized control of self‐propelled vehicles with second‐order rotational dynamics. We design backstepping controls for parallel and circular formations in the absence of a flowfield and in the presence of a steady, uniform flowfield. These controls extend prior results to a more realistic vehicle model. Aside from the addition of new sensing and communication requirements, the second‐order control laws are demonstrated to have comparable performance to the first‐order controllers. Copyright © 2011 John Wiley & Sons, Ltd.
Cellular analysis by open‐source software for affordable cytometry
Authors: Mittag Anja , Pinto Fernanda E. , Endringer Denise C. , Tarnok Attila , Lenz Dominik 
Published: February 2011

AbstractImage cytometry is an important technique in affordable healthcare and cellular research. Some efforts toward establishing a personal, low‐cost cytometer have been described in the literature. However, a self‐assembled fluorescence microscope requires software for cytometric analysis. There are some open‐source image‐based software analysis applications available. However, for a quantitative analysis of images, software that can generate data comparable to those of previously evaluated cytometric analyses programs is required. Hence, the aim of this study is to compare results of a commercially available image cytometry program to data obtained using the open‐source software CellProfiler (CP). Leukocytes and fluorescent bead images obtained using a Laser Scanning Cytometer were analyzed by CP and the results compared with those of conventional cytometric analyses' programs. Algorithms were developed enabling the analysis of leukocytes and beads by CP. CP provided similar results to those obtained by the cytometer software. Hallmark parameters, including cell count and fluorescence intensity, revealed a high correlation in the analysis of both programs. Therefore, CP is appropriate for cellular analysis on a self‐assembled microscope, thereby enabling affordable cytometry. SCANNING 33: 33–40, 2011. © 2011 Wiley Periodicals, Inc.
Chronic Work Stress and Depressive Symptoms: Assessing the Mediating Role of Teacher Burnout
Authors: Steinhardt Mary A. , Smith Jaggars Shanna E. , Faulk Kathryn E. , Gloria Christian T. 
Published: February 2011

AbstractA conceptual model of the relationship between stress, the mediating role of burnout, and depressive symptoms was examined. Results indicated that teachers (n = 267) experiencing greater stress were more burned out. The subscale emotional exhaustion was moderately related to depressive symptoms, whereas depersonalization and reduced personal accomplishment had small positive relationships. After controlling for burnout and demographics, the relationship between stress and depressive symptoms was small but significant. Emotional exhaustion mediated the association between stress and depressive symptoms. The total effect of stress on depressive symptoms, taking together the direct and indirect effects via burnout, accounted for 43% of the total variance. Copyright © 2011 John Wiley & Sons, Ltd.
An Important Role for CDK2 in G1 to S Checkpoint Activation and DNA Damage Response in Human Embryonic Stem Cells
Authors: Neganova Irina , Vilella Felipe , Atkinson Stuart P. , Lloret Maria , Passos João F. , von Zglinicki Thomas , O'Connor José-Enrique , Burks Deborah , Jones Richard , Armstrong Lyle , Lako Majlinda 
Published: February 2011

AbstractA precise understanding of mechanisms used by human embryonic stem cells (hESCs) to maintain genomic integrity is very important for their potential clinical applications. The G1 checkpoint serves to protect genomic integrity and prevents cells with damaged DNA from entering S-phase. Previously, we have shown that downregulation of cyclin-dependent kinase 2 (CDK2) in hESC causes G1 arrest, loss of pluripotency, upregulation of cell cycle inhibitors p21 and p27 and differentiation toward extraembryonic lineages. In this study, we investigate in detail the role of CDK2 in cellular processes, which are crucial to the maintenance of genomic stability in hESC such as G1 checkpoint activation, DNA repair, and apoptosis. Our results suggest that downregulation of CDK2 triggers the G1 checkpoint through the activation of the ATM-CHK2-p53-p21 pathway. Downregulation of CDK2 is able to induce sustained DNA damage and to elicit the DNA damage response (DDR) as evidenced by the formation of distinct γ-H2.AX and RAD52-BRCA1 foci in hESC nuclei. CDK2 downregulation causes high apoptosis at the early time points; however, this is gradually decreased overtime as the DDR is initiated. Our mass spectrometry analysis suggest that CDK2 does interact with a large number of proteins that are involved in key cellular processes such as DNA replication, cell cycle progression, DNA repair, chromatin modeling, thus, suggesting a crucial role for CDK2 in orchestrating a fine balance between cellular proliferation, cell death, and DNA repair in hESC.
Evo Devo and cognitive science
Authors: Ploeger Annemie , Galis Frietson 
Published: February 2011

AbstractEvo Devo (evolutionary developmental) biology forges a synthesis of evolutionary and developmental processes. Evo Devo is the result of collaborative work of evolutionary and developmental biologists after the discovery of regulatory genes that human beings share with many other animals, including fruit flies, frogs, and rats. Compared to traditional evolutionary biologists, Evo Devo biologists focus on processes underlying the generation of evolutionary novelties, rather than on how natural selection changes gene frequencies in populations and how organisms are adapted to their environment. Evo Devo biologists try to answer questions such as: How do novel structures arise? Which mechanisms facilitate or constrain evolutionary change? In this article we argue that insights from Evo Devo research can contribute to the understanding of the evolution and development of cognition, and of the origin of neurocognitive disorders. We discuss three major Evo Devo topics: modularity, evolvability, and developmental constraints. We argue that each of these topics are relevant for research in cognitive science, and we argue that interdisciplinary research is necessary in order to unravel the evolutionary and developmental mechanisms of cognitive traits and disorders.WIREs Cogni Sci2011 2 429–440 DOI: 10.1002/wcs.137This article is categorized under:Cognitive Biology > Evolutionary Roots of Cognition