bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local Hall measurement of magnetization reversal and magnetic interaction in Fe/Au/Fe trilayer rings
Authors: Miyawaki T. , Kohda M. , Fujita A. , Nitta J. 
Published: November 2007

AbstractMagnetization reversal process of ring‐shaped Fe/Au/Fe pseudo‐spin valve is investigated with different Au thickness by local Hall effect (LHE) using semiconductor two dimensional electron gas. The Hall resistance shows clear hysteresis loop with four different transition fields. By comparing the single‐layer Fe rings, four steps are due to the onion (voretex)‐to‐vortex (onion) transitions both in the top and the bottom rings. The LHE measurement enables us to measure the distinct characterization of the magnetization reversal between the top and bottom Fe rings. Magnetic interactions between two Fe rings are measured as a function of Au thickness. The variation of the onion‐to‐vortex transition field is explained by the displacement of the domain walls in the onion state due to the stray field from the ring edge. The vortex‐to‐onion transition fields are shifted to the lower field in both Fe layers with decreasing Au thickness due to the reduction of entire magnetostatic energy in PSV rings. One possible explanation is the absorption of the stray field between two Fe rings. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Resonant energy transfer in electron‐driven proton pumps
Authors: Smirnov A. Yu. , Mourokh L. G. , Nori Franco 
Published: November 2007

AbstractWe examine proton and electron transport in living cell membranes and show that the Coulomb interaction leads to a resonant energy transfer, from the electrons to protons during their simultaneous tunnelings, which allows the proton pump to work. The proton pump efficiency is controlled by the electron voltage build‐up, external temperature, and the molecular electrostatics driving the electron and proton energies to their resonant conditions. We also show that physiological (e.g., human body) temperatures are optimal for the operation of this proton pump. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wigner ensemble Monte‐Carlo simulation of nano‐MOSFETs in degenerate conditions
Authors: Querlioz D. , Saint‐Martin J. , Do V.‐N. , Bournel A. , Dollfus P. 
Published: November 2007

AbstractWigner quasi‐distribution function is an appropriate quantum mechanics formulation to study the transition from semi‐classical to quantum transport in nano‐devices since it can accurately describe quantum transport including the decoherence due to scatterings. We have recently developed an efficient approach to solving the Wigner transport equation using a Monte Carlo (MC) algorithm that has been applied to Resonant Tunnelling Diodes and nano‐MOSFET simulation. The approach is here extended to incorporate degeneracy effects that are important in highly doped MOSFETs. The calculation is compared with Non Equilibrium Green's Function and the semi‐classical Boltzmann equation. Relative importance of quantum transport and decoherent scattering is discussed at low and room temperatures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Limiting factors for high temperature operation of THz quantum cascade lasers
Authors: Jirauschek C. , Lugli P. 
Published: November 2007

AbstractWe theoretically investigate the temperature performance of GaAs‐based resonant phonon depopulation THz quantum cascade lasers, using an ensemble Monte Carlo simulation which includes both carrier‐carrier and carrier‐phonon scattering. By evaluating the temperature dependence of the different carrier transport paths, we identify the factors restricting high temperature operation. As a major detrimental effect, a strongly increased occupation of the lower laser level is found due to a less efficient depletion at elevated temperatures, which can mainly be attributed to the resonant nature of the depletion process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron transport through single self‐assembled InAs quantum dots coupled to superconducting nanogap electrodes
Authors: Shibata K. , Buizert C. , Oiwa A. , Hirakawa K. , Tarucha S. 
Published: November 2007

AbstractWe have fabricated superconductor‐quantum dot‐superconductor (SC‐QD‐SC) junctions by using SC aluminum electrodes with narrow gaps laterally contacting a single self‐assembled InAs QD. By adopting an appropriate metal deposition sequence we avoided electrical contact through natural oxides on the Al surfaces, and fabricated SC‐QD‐SC junctions with low sample resistance of the order of 4–500 kΩ at room temperature. These junctions exhibit clear Cou‐ lomb staircases at T = 40 mK. Coulomb oscillations are also observed when the backgate voltages are swept. Furthermore, clear suppression in conductance is observed for |VSD| < 2Δ /e, where Δ is the SC energy gap of Al, reflecting the superconductivity in the Al leads. The suppressed conductance disappears at higher temperatures (T ≥ 1 K) or at high magnetic fields (B ≥ 100 mT). These results indicate that SC‐QD‐SC junctions have been successfully fabricated for the first time in the self‐assembled InAs QD system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
3D Monte Carlo simulation of transport in electro‐statically confined silicon nanochannels
Authors: Mohamed Mohamed , Martin Pierre , Ravaioli Umberto 
Published: November 2007

AbstractThis study investigates transport and electrostatic behavior of quasi 1D nanowires adopting a relatively simple planar fabrication technique. The confined conduction channel is created by etching an oxide trench, realizing a T‐gate structure. Since multiple channels are normally needed to realize sufficient current drive in practical applications, the behavior of single and coupled adjacent silicon nanowires is characterized using a 3D quantum corrected Monte Carlo approach. Results indicate that a single T‐gate structure provides over 27% increase in current drive compared to conventional MOSFET at a drain voltage of 1V. In addition, design consideration and recommendation is presented. Cross section of a T‐gate MOSFET. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phonon scattering of hot electrons in intense mid‐infrared laser fields
Authors: Furuse H. , Mori N. , Kubo H. , Momose H. , Kondow M. 
Published: November 2007

AbstractWe calculated intravalley and intervalley phonon scattering rates of accelerated electrons under intense midinfrared laser fields. We extended the Keldysh theory, which assumes oscillatory motion of Bloch electrons driven by intense laser fields, to phonon scattering of electrons in semiconductors. We find that phonon emission is possible even if the initial electron energy is less than the phonon energy due to multi‐photon absorption processes. We also find that the scattering rates increase with electric field strength and wavelength. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and theoretical investigation of terahertz optical‐beating detection by plasma waves in high electron mobility transistors
Authors: Marinchio H. , Torres J. , Sabatini G. , Nouvel P. , Palermo C. , Chusseau L. , Varani L. , Teppe F. , Shiktorov P. , Starikov E. , Gružinskis V. , Shchepetov A. , Bollaert S. , Roelens Y. 
Published: November 2007

AbstractA photomixed laser beam of two 1.55 mm cw lasers is used to obtain interband photoexcitation at the difference frequency and at room temperature in submicron gate‐length InAlAs/InGaAs transistors. Results show the clear excitation of plasma oscillation modes in the transistor channel. Fundamental plasma resonant frequency and its odd harmonics can be tuned with the applied gate voltage. Numerical simulations have also been performed using a hydrodynamic approach coupled to a pseudo‐2D Poisson equation. Numerical results are in qualitative agreement with experiments and confirm optical beating detection at terahertz frequencies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two level mixing effects probed by resonant tunnelling through vertically coupled quantum dots
Authors: Amaha S. , Payette C. , Gupta J. A. , Hatano T. , Ono K. , Kodera T. , Tokura Y. , Austing D. G. , Tarucha S. 
Published: November 2007

AbstractWe study the magnetic (B ‐) field evolution of single‐particle levels in one dot by observing resonant tunnelling (RT) between two weakly coupled vertical quantum dots in series. The B ‐field dependence of the RT current peaks in the spectrum follows closely that of the states of a circular two dimensional harmonic potential. Several prominent two‐level anti‐crossing features are revealed. The RT current changes dramatically on passing through the anti‐crossing point. This can be assigned to the nature of inter‐dot RT though intra‐dot level‐mixed states. (a) Schematic diagram of our device. (b) Measured anti‐cross in the resonant current induced by intra‐dot two level mixing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
All‐optical injection of ballistic electrical currents in unbiased silicon
Authors: Betz M. , Costa L. , Spasenovic M. , Bristow A. D. , van Driel H. M. 
Published: November 2007

AbstractThe absorption of phase‐related near‐infrared fundamental (ω) and second harmonic (2ω) femtosecond pulses results in ballistic electrical currents in clean bulk silicon at room temperature. The ultrafast charge motion is directly monitored via a time‐resolved analysis of the emitted THz bursts of radiation. The vector direction of the current is precisely controlled by the polarization of the two‐color pump field and the relative phase ΔΦ = 2Φω – Φ2ω . The current generation process relies on a third order optical nonlinearity. Microscopically, current injection can be understood as arising from the quantum interference of one‐ and two‐photon absorption processes. Surprisingly, the efficiency of the current injection is relatively high despite the multitude of possible phonon‐assisted absorption channels in the multi‐valley band structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier spin relaxation in undoped GaAs double quantum wells
Authors: Lu S. L. , Ushiyama T. , Tackeuchi A. , Muto S. 
Published: November 2007

AbstractCarrier spin relaxation in undoped GaAs/AlGaAs asymmetric double quantum wells (QWs) at room temperature was studied by spin‐dependent pump and probe reflection measurements. The electron tunneling, which occurs between the two lowest conduction bands in the narrow and wide QWs, has a negligible effect on the electron spin relaxation. The most striking feature is that a long hole spin relaxation time was directly observed in the case of fast electron tunneling while it was not observed in the case of relatively slow electron tunneling. The hole that remains in the QWs due to the escape of the electron tunneling out makes the direct observation of hole spin relaxation possible. The measured hole spin relaxation time varies from 107 ps to 80 ps when the excitation power changes from 10 mW to 40 mW. This study provides direct experimental evidence of the important effect of the interaction between electrons and holes on the hole spin relaxation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic nuclear polarization in a double quantum dot device: electrical induction and detection
Authors: Baugh Jonathan , Kitamura Yosuke , Ono Keiji , Tarucha Seigo 
Published: November 2007

AbstractWe quantify the magnitude, buildup and relaxation dynamics of dynamic nuclear polarization (DNP) in a vertical GaAs double quantum dot device. This is accomplished using electrical techniques in the two‐electron spin‐blockade regime. Measurements are based on realtime electrical control of the relevant two‐electron spindependent energy levels, and observation of DNPinduced current step features at finite external magnetic fields. A simple phenomenological picture is presented to discuss the factors that limit maximum polarization in this system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of electron‐electron interaction on the diffusion current of spin‐polarized electrons
Authors: Takahashi Yutaka , Inaba Nobuyuki , Hirose Fumihiko 
Published: November 2007

AbstractElectron‐electron interaction modifies carrier transport in the spin‐polarized system. The effects are investigated in the two‐dimensional electron gas in semiconductor heterostructures. We find that the diffusion currents of spin‐up and spin‐down electrons are reduced, compared to the non‐interacting values, by the momentum exchange between spin‐up and spin‐down electrons through their collisions (Spin Drag), and also by the electron energy renormalization arising from the manyparticle correlations. We numerically calculate the diffusion coefficients of spin‐up and spin‐down electrons separately in high‐quality heterostructures of GaAs at low temperatures, including the effect of finite spin life time. Our calculations show that the diffusion coefficients are reduced down to less than half of their non‐interacting values. We also find the negative diffusivity at low temperatures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier acceleration under very high fields in bulk GaAs investigated by time‐domain terahertz spectroscopy
Authors: Zhu Y. M. , Unuma T. , Shibata K. , Hirakawa K. , Ino Y. , Kuwata‐Gonokami M. 
Published: November 2007

AbstractNonequilibrium electron transport in bulk GaAs under very high electric fields up to 300 kV/cm has been investigated by time‐domain terahertz (THz) spectroscopy. It is found that when applied electric field, F, is above 50 kV/cm, the initial acceleration signal in THz emission waveforms starts decreasing with increasing F. This result suggests that the effective acceleration mass of electrons significantly increases with increasing F, most likely due to strong band mixing under very high fields. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Density functional computations of the cyclopropanation of ethene catalyzed by iron (II) carbene complexes Cp(CO)(L)FeCHR, L = CO, PMe3, R = Me, OMe, ph, CO2Me
Authors: Wang Fen , Meng Qingxi , Li Ming 
Published: November 2007

AbstractDensity functional theory has been used to study the Fe‐catalyzed cyclopropanation of Fe‐carbene complexes with ethene. All the intermediates and transition states were optimized completely at the B3LYP/6‐31+G(d,p) level. Calculation results confirm that the cyclopropanation of Fe‐carbene complexes with ethene involves the two reaction paths I and II. In the reaction path I, the double bond of ethene attacks directly on the carbene carbon of Fe‐carbene complexes to generate the cyclopropane. In the reaction path II, ethene substitution for PMe3 or CO in the Fe‐carbene complexes leads to the complexes M2; and the attack of one carbon of ethene on the carbene carbon results in the complexes M3 with a FeCCC four‐membered ring, and then generates the cyclopropane via the elimination reaction. For Fe‐carbene complexes A, C, D, E, and H, the main reaction mode is the reaction path I; for Fe‐carbene complexes B, F, and G, the main reaction mode is the reaction path II. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Bonding analysis for NgAuOH (Ng = Kr, Xe)
Authors: Zhang Ping Xia , Zhao Yong Fang , Hao Feng You , Li Xin Ying 
Published: November 2007

AbstractNoble‐gas‐noble‐metal hydroxides NgAuOH (Ng = Kr, Xe) are investigated at the MP2 theoretical level. All species are found to be in Cs symmetry with an approximate linear NgAuO moiety. The noble‐gas‐noble‐metal bond lengths are comparable with covalent limits, and the corresponding binding energies have been computed to be 59.6 and 83.4 kJ/mol for KrAuOH and XeAuOH, respectively. Except the charge‐induced dipole contribution to the binding energies, the remainder could be ascribed to the higher‐order charge‐induction energies, dispersion energies, the contributions of multipole moments on AuOH and covalent effects. The title species are sufficiently chemical bound and are expected to be stable species theoretically. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Analysis of biologically active compounds in water by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry
Authors: Farré Marinella , Gros Meritxell , Hernández Belen , Petrovic Mira , Hancock Peter , Barceló Damià 
Published: November 2007

AbstractA new method based on ultra‐performance liquid chromatography (UPLC) quadrupole time‐of‐flight mass spectrometry ((Q‐ToF)‐MS) was developed for the analysis of 32 biologically active compounds including anti‐inflammatories, analgesics, lipid regulators, psychiatric drugs, anti‐ulcer agents, antibiotics, beta‐blockers and phytoestrogens. This new method allows chromatographic analysis in 14 min, with instrumental detection limits from 2 to 84 pg, and limits of quantification ranging from 0.1 to 15 ng/L in tap water, and from 2 to 300 ng/L in wastewater.The potential of liquid chromatography with triple quadrupole mass spectrometry (LC/QqQ‐MS) was compared with that of UPLC/(Q‐ToF)‐MS for the analysis of biologically active compounds in water samples. LC/Q‐ToF provides accurate mass information and a significantly higher mass resolution than quadrupole analyzers. The available mass resolution of ToF instruments diminishes the problem of isobaric interferences and helps the analysis of trace compounds in complex samples.In this work UPLC/Q‐ToF chromatograms were recorded containing full scan spectral data. The m/z values of analytes were extracted from the total ion chromatogram (TIC) and the accurate masses of the compounds were obtained. In addition, to increase the selectivity of ToF measurements a narrow accurate mass interval (20 m m/z units mass window) was used to reconstruct the chromatographic traces.However, regarding quantitative performance in terms of dynamic range and limits of detection (LODs), typical LODs achieved by QqQ instruments operating in multiple‐reaction monitoring (MRM) mode ranged from 1 to 50 ng/L in wastewater, and the linear response for QqQ instruments generally covers three orders of magnitude. This is an important advantage over ToF instruments and one of the reasons why QqQ instruments are widely used in quantitative environmental analysis. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of N‐glycosylation sites and site heterogeneity in a monoclonal antibody by electrospray quadrupole ion‐mobility time‐of‐flight mass spectrometry
Authors: Olivova Petra , Chen Weibin , Chakraborty Asish B. , Gebler John C. 
Published: November 2007

AbstractThis paper presents an improved analytical method for glycosylation structural characterizations of a monoclonal antibody (mAb) using a newly developed quadrupole ion‐mobility time‐of‐flight (ESI‐Q‐IM‐TOF) mass spectrometer. Using this method, high‐resolution mass spectra were acquired to produce the overall glycosylation profile of the mAb. Additionally, the light and heavy chains from the reduced antibody were separated in the gas phase by the ion mobility functionality of the instrument, allowing accurate mass measurement of each subunit. Furthermore, the glycan sequences, as well as the glycosylation site, were determined by a two‐step sequential fragmentation process using the unique dual‐collision‐cell design of the instrument, thus providing detailed characterizations of the glycan structures. Copyright © 2007 John Wiley & Sons, Ltd.
A binary matrix of 2,5‐dihydroxybenzoic acid and glycerol produces homogenous sample preparations for matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Soltwisch Jens , Berkenkamp Stefan , Dreisewerd Klaus 
Published: November 2007

AbstractWe introduce a two‐component matrix for ultraviolet matrix‐assisted laser desorption/ionization mass spectrometry (UV‐MALDI‐MS) that consists of 2,5‐dihydroxybenzoic acid (DHB) and glycerol. Upon slow evaporation of residual water/methanol solvents in a pre‐vacuum chamber sample preparations are obtained that exhibit a homogeneous morphology with analyte‐matrix crystals evenly distributed over the whole sample spot. At a molar DHB/glycerol ratio of ∼1:5, the crystals range in length from ∼100 to 300 µm and are about 15–30 µm wide. Mass spectra of peptides, proteins, and an oligosaccharide are presented and compared with those recorded from standard dried‐droplet DHB matrix. The ion signals show a reproducibility of the order of 10–15% when scanning the surface of an individual sample or even different samples that contain the same amount of peptide, A close to linear relationship between peptide concentration and the corresponding peptide ion signal is found over three orders of magnitude of sample prepared. However, when a fixed position is irradiated with a large number of laser pulses, a monotonous decay of peptide ion signal with time is observed. Potentially, the binary matrix will be especially useful for the analysis of samples that are stabilized in buffered aqueous glycerol solution and preliminary results addressing this aspect are shown. Copyright © 2007 John Wiley & Sons, Ltd.
Otter predation in a trout fish farm of Central–East Portugal: preference for ‘fast‐food’?
Authors: Marques C. , Rosalino L. M. , Santos‐Reis M. 
Published: November 2007

AbstractThe Eurasian otter (Lutra lutra) is a known piscivorous predator throughout its distribution range, although in some regions a more generalist behaviour emerged, such as in southern European latitudes. We evaluated otter feeding preference/avoidance towards the elements of the fish guild inhabiting a Mediterranean environment (Côa River, Central Portugal) and assessed the influence of proximity to a surplus of trophic resources (a rainbow trout production farm) on the species diet. Almost two years of collected spraints revealed that otters subsisted by consuming almost exclusively fish (94% of consumed biomass), especially the rainbow trout (87% of consumed biomass), although in summer this consumption is complemented with reptiles and amphibians. Due to the presence of the trout farm, and the consequent constancy in the availability of trout, the observed otter specialization in rainbow trout represents an extreme opportunistic behaviour. Copyright © 2007 John Wiley & Sons, Ltd.
INCA: New statistic for estimating the number of clusters and identifying atypical units
Authors: Irigoien I. , Arenas C. 
Published: November 2007

AbstractThis paper presents a solution to two problems that arise in the classification of data such as types of tumor, samples of gene expression profiles or general biomedical data. First, to estimate the real number of clusters in a data set and second to decide whether a new unit belongs to one of these previously identified clusters or it is an outlier or atypical unit. We propose a new statistic which allows us to solve these problems. As our approach is based on a measure of distance or dissimilarity between any pair of units, it can be applied to any kind of multivariate data (continuous, binary or multi‐attribute data) and it has applications in many biomedical fields. We validated the approach in simulated examples and applied it to the diagnosis of dermal diseases and to the analysis of lymphatic cancer data, showing the good performance of our approach. Copyright © 2007 John Wiley & Sons, Ltd.