bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transient negative cyclotron absorption due to partially‐inverted distribution of photoexcited electrons
Authors: Romanets P. N. , Vasko F. T. , Ryzhii V. I. 
Published: October 2007

AbstractThe transient magnetoresponse of electrons with partially‐inverted distribution excited by an ultrashort optical pulse in bulk GaAs and InSb is considered. A huge transient amplification of a probe microwave or THz field due to negative cyclotron absorption is described using the kineticequation and the wave equation. A quantum picture of THz emission due to transitions between the Landau levels with different broadenings is suggested. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Feasibility of sequential multiphoton absorption for terahertz radiation detection
Authors: Castellano Fabrizio , Iotti Rita Claudia , Rossi Fausto 
Published: October 2007

AbstractMultilevel architectures based on semiconductor nanostructures appear as promising designs for unipolar midinfrared detectors. In this paper we theoretically investigate their feasibility in the terahertz frequency range. Here, the performances of common quantum‐well photodetectors, based on a single bound subband, are severely hindered by high dark current and low Tblip values. We will demonstrate that, in this respect, the multi‐subband scheme represents a better alternative to the conventional design. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonequilibrium carrier corrections to the optical gain in semiconductor quantum well structures
Authors: Weetman Philip , Wartak Marek S. 
Published: October 2007

AbstractWe report on the development of a novel self‐consistent nano‐scale semiconductor laser model where Wigner functions are used to model carrier dynamics and boundary conditions. The technique allows one to add a new non‐equilibrium correction term to standard formulations of optical As an example, the formalism susceptibility. is applied in the calculation of gain for a single quantum well laser. The conventional component of the gain uses a 4Ł 4 Luttinger‐Kohn bandstructure approximation and the non‐equilibrium correction term is calculated with a parabolic bandstructure approximation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time‐resolved spectroscopy in an undoped GaN (1‐101)
Authors: Kim Eunhee , Hikosaka Toshiki , Honda Yoshio , Yamaguchi Masahito , Sawaki Nobuhiko 
Published: October 2007

AbstractTime‐resolved photoluminescence spectroscopy was performed at 77 K in a GaN (1‐101) grown on a 7 degree off‐axis (001) Si substrate. The sample was grown by metal‐organic‐vapour‐phase‐epitaxy (MOVPE) and was un‐intentionally doped with O, C and Si. By using photoluminescence intensity correlation method, the energy relaxation process of the photogenerated carriers near the band edge was investigated in pico‐second regime. The correlation signal was represented by a single exponential decay curve and the energy relaxation time was determined, which depended strongly on the kinetic energy of the excess carriers. At low energies, the relaxation time was around 700 ps, while it was as short as a few ps at the highest energy under study. The correlation signals obtained for carriers of which kinetic energy was less than 80 meV showed an anti‐correlation behaviour suggesting the occurrence of carrier accumulation. The time constants for the accumulation were of several picoseconds depending on the kinetic energy, which was nearly equal to the decay time constants determined at high energies. This fact shows that the energy relaxation at high energies is controlled by the emission of an LO phonon. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of a measurement system for quantum shot noise at low temperatures
Authors: Hashisaka M. , Nakamura S. , Yamauchi Y. , Kasai S. , Kobayashi K. , Ono T. 
Published: October 2007

AbstractThe noise power spectral density of the mesoscopic devices was measured at low temperatures with two homemade systems for low‐ and high‐frequency ranges. By measuring the noise of the devices at finite bias voltages in the low‐freqiency setup, we estimated a typical cut‐off frequency to avoid the 1/f noise. We developed a high‐frequency measurement system with an cryogenic amplifier and a resonant circuit and calibrated it by measuring the Johnson‐Nyquist noise. We compare these two systems and discuss the advantage of the high‐frequency measurement system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron decoherence in a semiconductor due to electron‐phonon scattering
Authors: Buscemi Fabrizio , Cancellieri Emiliano , Bordone Paolo , Bertoni Andrea , Jacoboni Carlo 
Published: October 2007

AbstractA quantitative analysis of the electron decoherence is performed in the case where an electron interacts with an environment consisting of a phonon bath at a given temperature T. In particular we study the decoherence in terms of the entanglement formation between the electron, initially described by a Gaussian wavepacket, and the environment by using the linear entropy written in terms of the Wigner function. In our work we evaluate, in a rigorous fully quantum mechanical approach, the electron‐phonon interaction using the Wigner‐function formalism. The problem is numerically solved for different time steps, up to the lowest order in the Neumann expansion. Our numerical procedure allows to analyze the system in different conditions and to understand the effect of the electron velocity and of the phonon momenta on the entanglement formation. Results are obtained in a one‐dimensional silicon system but they can be considered indicative of a more general behaviour. The Wigner function describing the electron and the phonon bath is evaluated by means of Neumann series, whose terms may be graphically represented by the so‐called Wigner paths. They are orbits in the Wigner phase‐space and are formed by ballistic free flights separated by scattering processes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transport in narrow minigap superlattices with inter‐Wannier‐Stark level tunneling
Authors: Andronov A. A. , Dodin E. P. , Nozdrin Yu. N. , Zinchenko D. I. 
Published: October 2007

AbstractLow temperature electron transport under interminiband Zener tunneling and LO‐phonon scattering in the second and higher minibands in GaAs/Alx Ga1¡x As superlattices with weak barriers has been studied. At low electric fields multiple negative differential low‐frequency conductivity regions and effects of complicated electron transport have been found. In stronger fields peculiarities of current ‐ voltage curves attributed to resonant tunneling between Wannier‐Stark levels of different minibands have been separated basing on calculated wavefunctions and energies of the levels. Calculated value of optical matrix element for inter‐Wannier‐Stark transitions is promising to achieve negative conductivity at these transitions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Roughness effect on electron transport through quantum wires
Authors: Cancellieri E. , Rosini M. , Bordone P. , Jacoboni C. 
Published: October 2007

AbstractIn the present work we study, by means of numerical simulations, the coherent propagation of electrons in quantum wires and focus on the effect of the introduction of roughness along the channel. We study the electron evolution both in single and coupled quantum wires in the case where the electron freely move through the channel and in the case where transport is assisted by surface acoustic waves. It has been shown that systems of coupled quantum wires can realize a complete set of quantum logic gates.However, its physical implementation is severely limited by the spreading of the wave packet and by the presence of interface roughness. Our results show that the potential of the surface acoustic wave succeeds in confining the electron wavefunction and in driving it along the channels also when interface roughness is introduced. This suggests that electron transport assisted by surface acoustic waves could be a very efficient way to realize quantum solid state devices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oxygen exchange between (de)nitrification intermediates and H2O and its implications for source determination of NO and N2O: a review
Authors: Kool D. M. , Wrage N. , Oenema O. , Dolfing J. , Van Groenigen J. W. 
Published: October 2007

AbstractStable isotope analysis of oxygen (O) is increasingly used to determine the origin of nitrate (NO) and nitrous oxide (N2O) in the environment. The assumption underlying these studies is that the 18O signature of NO and N2O provides information on the different O sources (O2 and H2O) during the production of these compounds by various biochemical pathways. However, exchange of O atoms between H2O and intermediates of the (de)nitrification pathways may change the isotopic signal and thereby bias its interpretation for source determination. Chemical exchange of O between H2O and various nitrogenous oxides has been reported, but the probability and extent of its occurrence in terrestrial ecosystems remain unclear. Biochemical O exchange between H2O and nitrogenous oxides, NO in particular, has been reported for monocultures of many nitrifiers and denitrifiers that are abundant in nature, with exchange rates of up to 100%. Therefore, biochemical O exchange is likely to be important in most soil ecosystems, and should be taken into account in source determination studies. Failing to do so might lead to (i) an overestimation of nitrification as NO source, and (ii) an overestimation of nitrifier denitrification and nitrification‐coupled denitrification as N2O production pathways. A method to quantify the rate and controls of biochemical O exchange in ecosystems is needed, and we argue this can only be done reliably with artificially enriched 18O compounds. We conclude that in N source determination studies, the O isotopic signature of especially N2O should only be used with extreme caution. Copyright © 2007 John Wiley & Sons, Ltd.
A new membrane inlet interface of a vacuum ultraviolet lamp ionization miniature mass spectrometer for on‐line rapid measurement of volatile organic compounds in air
Authors: Hou Keyong , Wang Junde , Li Haiyang 
Published: October 2007

AbstractA novel membrane inlet interface coupled to a single‐photon ionization (SPI) miniature time‐of‐flight mass spectrometer has been developed for on‐line rapid measurement of volatile organic compounds (VOCs). The vacuum ultraviolet (VUV) light source for SPI was a commercial krypton discharge lamp with photon energy of 10.6 eV and photon flux of 1010 photons/s. The experimental results showed that the sensitivity was 5 times as high as obtained with the traditional membrane inlet. The enrichment efficiency could be adjusted in the range of 10 to 20 times for different VOCs when a buffer cell was added to the inlet interface, and the memory effect was effectively eliminated. A detection limit as low as 25 parts‐per‐billion by volume (ppbv) for benzene has been achieved, with a linear dynamic range of three orders of magnitude. The rise times were 6 s, 10 s and 15 s for benzene, toluene and p‐xylene, respectively, and the fall time was only 6 s for all of these compounds. The analytical capacity of this system was demonstrated by the on‐line analysis of VOCs in single puff mainstream cigarette smoke, in which more than 50 compounds were detected in 2 s. Copyright © 2007 John Wiley & Sons, Ltd.
Microelectrospray interface with coaxial sheath flow for high‐resolution capillary electrophoresis/mass spectrometry separation
Authors: Hashimoto Masahiko , Ishihama Yasushi , Tomita Masaru , Soga Tomoyoshi 
Published: October 2007

AbstractWe have fabricated a coaxial sheath liquid flow microelectrospray ionization (µESI) interface for capillary electrophoresis coupled with mass spectrometry (CE/MS). The ESI interface, which features a reduced probe diameter (130 µm i.d. × 174 µm o.d.) with a nebulizer‐free format, can relatively easily electrospray a large amount of make‐up sheath liquid (5–10 µL/min) over the long term (more than 80 runs) with a high degree of stability. The interface also provides higher separation qualities and improved detection sensitivities compared with a conventional ion spray (IS) interface. Copyright © 2007 John Wiley & Sons, Ltd.
Characterization of new phenolic compounds from leaves of Olea europaea L. by high‐resolution tandem mass spectrometry
Authors: Di Donna Leonardo , Mazzotti Fabio , Salerno Raffaele , Tagarelli Antonio , Taverna Domenico , Sindona Giovanni 
Published: October 2007

AbstractA set of minor constituents of Olea europaea L. leaves have been identified and characterized by electrospray ionization tandem mass spectrometry (ESI‐MS/MS) and high‐resolution measurements (HRMS). Most of them are modified hydroxytyrosol species conjugated to a hexose unit. When possible, the structures of the new phenolic compounds present in Olea europaea L. have been confirmed by matching their MS/MS spectra with those of authentic standards isolated from other plants of the oleaceae family. The knowledge of the presence of new phenolic species in Olea europaea L. could provide tools for a full understanding of the secondary metabolism of this plant in relation to the biosynthesis of the phenolic species. Copyright © 2007 John Wiley & Sons, Ltd.
Delay‐range‐dependent robust stability and stabilization for uncertain systems with time‐varying delay
Authors: Li Tao , Guo Lei , Zhang Yuming 
Published: October 2007

AbstractThis paper concerns delay‐range‐dependent robust stability and stabilization for time‐delay system with linear fractional form uncertainty. The time delay is assumed to be a time‐varying continuous function belonging to a given range. On the basis of a novel Lyapunov–Krasovskii functional, which includes the information of the range, delay‐range‐dependent stability criteria are established in terms of linear matrix inequality. It is shown that the new criteria can provide less conservative results than some existing ones. Moreover, the stability criteria are also used to design the stabilizing state‐feedback controllers. Numerical examples are given to demonstrate the applicability of the proposed approach. Copyright © 2007 John Wiley & Sons, Ltd.
Adaptive designs: Looking for a needle in the haystack—A new challenge in medical research
Authors: Bauer Peter 
Published: October 2007

AbstractThe statistical principles of fully adaptive designs are outlined. The options of flexibility and the price to be paid in terms of statistical properties of the test procedures are discussed. It is stressed that controlled inference after major design modifications (changing hypotheses) will include a penalty: Intersections among all the hypotheses considered throughout the trial have to be rejected before testing individual hypotheses. Moreover, feasibility in terms of integrity and persuasiveness of the results achieved after adaptations based on unblinded data is considered as the crucial issue in practice. In the second part, sample size adaptive procedures are considered testing a large number of hypotheses under constraints on total sample size as in genetic studies. The advantage of sequential procedures is sketched for the example of two‐stage designs with a pilot phase for screening promising hypotheses (markers) and controlling the false discovery rate. Finally, we turn to the clinical problem how to select markers and estimate a score from limited samples, e.g. for predicting the response to therapy of a future patient. The predictive ability of such scores will be rather poor when investigating a large number of hypotheses and truly large marker effects are lacking. An obvious dilemma will show up: More optimistic selection rules may be superior if in fact effective markers exist, but will produce more nuisance prediction if no effective markers exist compared with more cautious strategies, e.g. aiming at some control of type I error probabilities. Copyright © 2007 John Wiley & Sons, Ltd.
Strategic human resource management, institutionalization, and employment modes: an empirical study in China
Authors: Li Ji , Lam Kevin , Sun James J. M. , Liu Shirley X. Y. 
Published: October 2007

AbstractThis study compares the predictions of institutional theory with those of the contingency perspective of strategic human resource management (SHRM) on the selection of an employment mode. Empirical data were collected from multinational enterprises, including the electronics and garment industries, that operate in China to test the relative importance of the determinants of the selection of an employment mode. The results provide greater support for the SHRM predictions than for the institutional theory predictions. The implications of the findings for researchers and practitioners are discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Exploring the debate on short‐termism: a theoretical and empirical analysis
Authors: Marginson David , McAulay Laurie 
Published: October 2007

AbstractThe debate on short‐termism has focused on the economic factors of capital markets and performance measurement systems. Laverty (1996) has advocated the inclusion of individual and organizational dimensions to extend the debate. We reorient Laverty's extended debate by drawing upon a broad management and accounting literature and thereby develop testable theoretical explanations of short‐termism. The resulting hypotheses are tested in a telecommunications company. Our findings provide support for Laverty's (1996) argument that individual and organizational factors are important determinants of short‐termism. Copyright © 2007 John Wiley & Sons, Ltd.
Relaxor Behavior, Polarization Buildup, and Switching in Nanostructured 0.92 PbZn1/3Nb2/3O3–0.08 PbTiO3 Ceramics
Authors: Algueró Miguel , Hungría Teresa , Amorín Harvey , Ricote Jesús , Galy Jean , Castro Alicia 
Published: October 2007

AbstractThe relaxor‐type behavior, electrical polarization buildup, and switching in 0.92Pb(Zn1/3Nb2/3)O3–0.08PbTiO3 nanostructured ceramics with a grain size of ≈20 nm is reported for the first time. This composition presents the highest‐known piezoelectric coefficients, yet phase stability is an issue. Ceramics can only be obtained by the combination of mechanosynthesis and spark‐plasma sintering. The results raise the possibility of using nanoscale, perovskite‐relaxor‐based morphotropic‐phase‐boundary materials for sensing and actuation in nanoelectromechanical systems.
Surfactantless Synthesis of Silver Nanoplates and Their Application in SERS
Authors: Sun Yugang , Wiederrecht Gary P. 
Published: October 2007

AbstractSilver nanoplates with thicknesses of 50–70 nm and edge lengths ranging from 200 nm to 1 μm have been grown on semiconductor wafers at room temperature through a simple galvanic reaction between an aqueous solution of AgNO3 and n‐type GaAs. The as‐grown Ag structures have chemically clean surfaces due to no surfactant or coordinating molecules being involved in the synthesis. Electron microscopy characterizations indicate that each Ag plate has rough surfaces and a half‐moon morphology with one straight edge and one arclike edge. Systematic studies on varying reaction conditions reveal that the oxide (i.e., Ga2O3 and As2O3) layers of GaAs, generated in situ in the reactions, play an important role in assisting the growth of anisotropic nanoplates. The cleanliness of the surfaces of the Ag nanoplates is beneficial to attachment of interesting molecules on their surfaces for various applications, such as plasmonic‐enhanced photophysical and photochemical processes and surface‐enhanced spectroscopies.
Approximate boundary conditions for diffraction by thin transmissive media
Authors: Rawlins A.D. 
Published: October 2007

AbstractThe object of this note is to describe a method that can be used to obtain useful boundary conditions to model various situations that arise in diffraction theory. In particular when wanting to apply the Wiener‐Hopf technique to diffraction problems that involve thin transmissive media. Transmissive here means that the thin layer medium suffers a change in the physical quantities of density, acoustic velocity, and wave number from the surrounding medium. The present approach can be used to obtain approximate boundary conditions for other physical applications where thin strata of transmissive material arise.
Individual behavioral variation in predator–prey models
Authors: Okuyama Toshinori 
Published: October 2007

AbstractThe role of individual behavioral variation in community dynamics was studied. Behavioral variation in this study does not refer to differences in average responses (e.g., average response between presence and absence of antipredator behavior). Rather it refers to the variation around the average response that is not explained by trivial experimental treatments. First, the effect of behavioral variation was examined based on Jensen's inequality. In cases of commonly used modeling framework with type II functional response, neglecting behavioral variation (a component of encounter rate) causes overestimation of predation effects. The effect of this bias on community processes was examined by incorporating the behavioral variation in a commonly used consumer‐resource model (Rosenzweig–MacArthur model). How such a consideration affects a model prediction (paradox of enrichment) was examined. The inclusion of behavioral variation can both quantitatively and qualitatively alter the model characteristics. Behavioral variation can substantially increase the stability of the community with respect to enrichment.
Thermal and Textural Properties of Organogels Developed by Candelilla Wax in Safflower Oil
Authors: Toro‐Vazquez J. F. , Morales‐Rueda J. A. , Dibildox‐Alvarado E. , Charó‐Alonso M. , Alonzo‐Macias M. , González‐Chávez M. M. 
Published: October 2007

AbstractWe investigated organogel formation in dispersions of CW in safflower oil (SFO). Candelilla wax (CW) has as its main component hentriacontane (78.9%), a n‐alkane with self assembly properties in organic solvents (i.e., vegetable oils). Results showed that, independent of the cooling rate (i.e., 1 °C/min and 10 °C/min) and gel setting temperature (Tset), the CW organogels observed a thermoreversible behavior. This was evaluated by the behavior of thermal parameters that characterized organogel formation (gelation temperature, Tg; heat of gelation, ΔHg) and melting (melting temperature, Tp; heat of melting, ΔHM) after two heating‐cooling cycles. For a given CW concentration (i.e., 0.5, 1.0, and 3%), the magnitude of ΔHM and Tp and the structural organization of the organogel, depended on the cooling rate, the thermodynamic drive force for gelation, and the annealing process occurring at high Tset (i.e., 25 °C). At Tset of 25 °C the microplatelet units that formed the organogel aggregated as a function of storage time, a process that resulted in an increase in organogel hardness. In contrast, at Tset of 5 °C annealing occurred in a limited extent, but gels had higher solid fat content and microplatelet units of a smaller size than the gels obtained at 25 °C. The result was a three‐dimensional network with greater hardness than the one obtained at 25 °C. The 3% CW organogels showed no phase separation up to 3 months at room temperature, with textures of potential use by the food industry.