bluuebunny/crossref_metadata_2025 huggingface dataset:
Blood–brain equilibration kinetics of levo‐α‐acetyl‐methadol using a chronically instrumented sheep preparation
Authors: Foster David J R , Jensen Mette L , Upton Richard N , Somogyi Andrew A , Grant Cliff , Martinez Allison
Published: November 2005

The delayed onset and long duration of action of the opioid agonist levo‐α‐acetyl‐methadol (LAAM) has been attributed to the formation of active metabolites. However, at present, little is known about the time course of blood–brain equilibration of LAAM itself.

The cerebral kinetics of LAAM were quantified using physiologically based kinetic models and a conscious chronically instrumented sheep preparation. Seven sheep were administered 4 min intravenous infusions of 30 mg LAAM. Concentrations of LAAM andN‐demethylated metabolites (nor‐LAAM and di‐nor‐LAAM) in whole blood (0–75 min) were measured using a validated HPLC assay.

LAAM did not alter cerebral blood flow, mean arterial pressure or cause significant respiratory depression. Cardiac output was similar to baseline at 4 min, but decreased by 30% at 10 min and remained at this level for the duration of the 75 min study period.

Cerebral kinetics were best described by a membrane‐limited model, with a relatively slow blood–brain tissue equilibration half‐life of 22 min due to intermediate permeability (56 ml min−1) and a large cerebral distribution volume (724 ml).

In conclusion, pharmacokinetic–pharmacodynamic modelling of LAAM should account for the large equilibration delay between brain and blood caused by slow equilibration kinetics. This may account for some of the delay in onset of effect previously attributed to the delayed appearance of active metabolites in blood.

British Journal of Pharmacology(2006)147, 209–217. doi:10.1038/sj.bjp.0706470
Inflammatory events in a vascular remodeling model induced by surgical injury to the rat carotid artery
Authors: Rinaldi Barbara , Romagnoli Paolo , Bacci Stefano , Carnuccio Rosa , Maiuri Maria Chiara , Donniacuo Maria , Capuano Annalisa , Rossi Francesco , Filippelli Amelia
Published: November 2005

The aim of our study was to gain insight into the molecular and cellular mechanisms of the inflammatory response to arterial injury in a rat experimental model.

Rats (five for each experimental time) were subjected to brief clamping and longitudinal incision of a carotid artery and monitored for 30 days. Subsequently, Nuclear Factor‐kappaB (NF‐κB) expression was measured by electrophoretic mobility shift assay. Heat shock protein (HSP) 27, HSP47 and HSP70 were evaluated by Western blot. Morphological changes of the vessel wall were investigated by light and electron microscopy.

In injured rat carotid artery NF‐κB activity started immediately upon injury, and peaked between 2 and 3 weeks later. Western blot showed a significant increase of HSP47 and HSP70 7 days after injury. At 2 weeks postinjury, HSP27 expression peaked. Ligth microscopy showed a neointima formation, discontinuity of the media layer and a rich infiltrate. Among infiltrating cells electron microscopy identified dendritic‐like cells in contact with lymphocytes.

Our model of surgical injury induces a significant inflammatory process characterized by enhanced NF‐κB activity and HSPs hyperexpression. Dendritic‐like cells were for the first time identified as a novel component of tissue repair consequent to acute arterial injury.

British Journal of Pharmacology (2006) 147, 175–182. doi:10.1038/sj.bjp.0706472
Retrograde jejunale Invagination nach Billroth-II-Resektion
Authors: Muehlenberg K , Wiedmann K. H.
Published: November 2005

Die 78-jährige Patientin hat seit Jahren wiederholt über Stunden anhaltende Oberbauchschmerzen und Erbrechen angedauter Speisen. Vor vielen Jahren war wegen rezidivierender Ulcera ventriculi eine Billroth-II-Magenteil-resektion erfolgt. Neben dem Bauchnabel ist jetzt linksseitig eine Walze tastbar. Die während der Schmerzepisode durchgeführte Gastroskopie zeigt in der abführenden Dünndarmschlinge drei pathologische Befunde. Welche sind das?

Erlauben diese Befunde eine Diagnose? Wenn ja, welche?

Sind Differenzialdiagnosen möglich? Wenn ja, welche?
Simulation of a complex spectrum: Interplay of five electronic states and 21 vibrational degrees of freedom in C5H4+
Authors: Markmann Andreas , Worth Graham A. , Mahapatra Susanta , Meyer Hans-Dieter , Köppel Horst , Cederbaum Lorenz S.
Published: November 2005

Using a five-state, all-mode vibronic coupling model Hamiltonian derived in a previous publication [A. Markmann et al., J. Chem. Phys. 122, 144320 (2005)], we have calculated the photoelectron spectrum of the pentatetraene cation in the neighborhood of the B̃E2 state, which can be represented with charge-localized components. To this end, quantum nuclear dynamics calculations were performed using the multiconfiguration time-dependent Hartree method, taking all 21 vibrational normal modes into account. Compared to experiment, the main features are reproduced but higher accuracy experiments are necessary to gauge the accuracy of the predictions for the vibronic progressions at the rising flank of the spectrum.
Photoelectron spectroscopy as a structural probe of intermediate size clusters
Authors: Guliamov Olga , Kronik Leeor , Jackson Koblar A.
Published: November 2005

We examine the utility of photoelectron spectroscopy (PES) as a structural probe of Sin− in the n=20–26 size range by determining isomers and associated photoelectron spectra from first principles calculations. Across the entire size range, we consistently obtain a good agreement between the theory and experiment [Hoffmann et al., Eur. Phys. J. D 16, 9 (2001)]. We find that PES can almost invariably distinguish between structurally distinct isomers at a given cluster size, but that structurally similar isomers usually cannot be reliably distinguished by PES. For many, but not all, sizes the isomer giving the best match to experiment is the lowest-energy one found theoretically. Thus, combining theory with PES experiments emerges as a useful source of structural information even for intermediate size clusters.
Bi-modal hetero-aggregation rate response to particle dosage
Authors: Olsen Aaron , Franks George , Biggs Simon , Jameson Graeme J.
Published: November 2005

The rate of flocculation of cationic polystyrene latex (PSL) particles by smaller, anionic PSL particles has been measured using a low-angle static light scattering technique. The rate of aggregate growth has been investigated as a function of particle size ratio and relative concentration of each particle species (for a constant dose of cationic particles). Contrary to many previous reports, two peaks in the flocculation rate were observed as a function of dose. It is speculated that the peak observed at the lower particle concentration coincides with the dose yielding maximum constant collision efficiency in the steady-state regime, a condition which is attained only after complete adsorption of the smaller particles onto the larger particle species. The peak at the higher particle concentration is believed to be related to the maximum collision rate constant upon reaching the steady-state regime, the value of which corresponds to maximum degree of aggregation and therefore the maximum mean collision efficiency prior to reaching this condition. From classical collision kinetics, the rate of aggregate growth may be represented as being proportional to the product of the collision rate constant and collision efficiency at any given time. Given then that the maximum value of these two variables coincides with different particle concentrations, the product of the response of each to particle dosage can in some cases yield a net bi-modal aggregation rate response to particle dosage.
Ideality criterion for unilateral constraints in time-dependent impulsive mechanics
Authors: Pasquero Stefano
Published: November 2005

We construct a new geometric framework based on the concepts of left and right jet-bundles of a classical space-time V in order to analyze the impulsive behavior of a unilateral constraint S. The setup allows deep insights into how one can choose an ideality criterion for the constraint S when the hypothesis of conservation of kinetic energy is assumed. We show that the conservation of kinetic energy alone univocally determines the impulsive reaction when the codimension of S is 1, and that it leaves the impulsive reaction partially undetermined when the codimension of S is greater than 1. If the codimension of S is greater than 1, we prove that an additional minimality requirement determines a physically meaningful constitutive characterization of S. We show that both the Newton-like and the Poisson-like approaches to the description of the reactive impulse are equivalent, in the sense that both give the same results about the ideality criterion. Moreover, we prove that the same results hold using the classical approach based on reflection operators, possible only in case of codimension 1. We present also several physically meaningful examples.
Brownian dynamics of mixed surfactant micelles
Authors: Bourov Geuorgui K. , Bhattacharya Aniket
Published: November 2005

We investigate micelle formation in a system containing two or more different amphiphiles with different geometries using a stochastic molecular-dynamics (MD) simulation method. For a binary system containing two amphiphiles, we calculate the critical micelle concentration (CMC) and cluster distribution for the mixture at several mole fractions and compare the simulation results with those predicted by analytic theories in the dilute limit and with experiments. We find that the CMC obtained from molecular mean-field theory agrees well with our simulation results. Motivated by the industrial use of mixed surfactant systems, we then extend our studies to a system containing six different chain lengths drawn from a Poisson distribution. We find that unlike a binary mixture of amphiphiles, the different species cancel the effects of each other so that the cluster distribution for the mixture has a shape of a system consisted entirely of amphiphiles of length equal to the mean chain length of the Poisson distribution.
Layered interfaces between immiscible liquids studied by density-functional theory and molecular-dynamics simulations
Authors: Geysermans P. , Elyeznasni N. , Russier V.
Published: November 2005

We present a study of the structure in the interface between two immiscible liquids by density-functional theory and molecular-dynamics calculations. The liquids are modeled by Lennard-Jones potentials, which achieve immiscibility by supressing the attractive interaction between unlike particles. The density profiles of the liquids display oscillations only in a limited part of the simple liquid-phase diagram (ρ,T). When approaching the liquid-vapor coexistence, a significant depletion appears while the layering behavior of the density profile vanishes. By analogy with the liquid-vapor interface and the analysis of the adsorption this behavior is suggested to be strongly related to the drying transition.
Spintronics birefringence with an extended molecular loop-wire or spiral coupling
Authors: Ovchinnikov Igor V. , Neuhauser Daniel
Published: November 2005

A ring with spin-orbit effects coupled to a conducting wire is shown to exhibit a phase delay which is spin dependent. The key is that the coupling of the ring to the wire is over an extended spatial range and not just along a single point; this breaks the symmetry and makes the ring states couple differently to forward and backward moving wire states. This results, for properly injected spin states, in a spin-flipping probability which is dependent on the energy of the injected electron and can therefore be easily controlled. Several systems are presented and shown to exhibit this effect including the basic ring which couples to a wire as well as a ring which mediates between two wires, and a spiral between two wires.
Effect of adsorbed concentration on the radiative rate enhancement of photoexcited molecules embedded in single microspheres
Authors: Sandeep P. , Bisht Prem Ballabh
Published: November 2005

The variation of the molecular density in a single microcavity and its influence on the radiative rate enhancement (RRE) are reported here. The quality factors of the observed morphology-dependent resonances (MDRs) of the microcavity remain unchanged in the absence of any absorbing effects. In contrast, the MDRs tend to disappear in the presence of strong absorption even due to the self-absorption by the molecule. Time-resolved fluorescence studies reveal the fact that the value of RRE decreases with an increase in the adsorbed concentration of the molecules. The results have been explained in terms of a detuning parameter, which is a function of the refractive index of the microcavity. The increased dispersing capability of the microsphere upon increasing its molecular density has been found to be responsible for the observed decrease in RRE.
Photovoltaic properties of (Pb,La)(Zr,Ti)O3 films with different crystallographic orientations
Authors: Ichiki M. , Furue H. , Kobayashi T. , Maeda R. , Morikawa Y. , Nakada T. , Nonaka K.
Published: November 2005

Photovoltaic (Pb,La)(Zr,Ti)O3 films in a layered structure of different crystallographic orientations are fabricated by an optimized metalorganic deposition method. Such films of (001) orientation exhibit a photovoltaic electrical power of approximately 20 times higher than that of random films. The anisotropic optical properties of the oriented films, including dark conductivity, photoconductivity, and photovoltaic tensor surfaces, are obtained quantitatively. These results show that the photovoltaic output current and power of the oriented films are highly improved to be equal to those of semiconductors and suitable for application in the optical sensor of microelectromechanical systems.
Influence of shock-wave profile shape on dynamically induced damage in high-purity copper
Authors: Koller D. D. , Hixson R. S. , Gray G. T. , Rigg P. A. , Addessio L. B. , Cerreta E. K. , Maestas J. D. , Yablinsky C. A.
Published: November 2005

Studies of the creation of damaged regions leading to failure are conducted using flat-top and triangular shock waves generated in gas-gun experiments as well as quasi-isentropic ramp waves. Shock waves are used to generate release waves, both behind the shock and on reflection at the free surface. It is the interaction of these release waves that places the material in a state of tension which can ultimately result in damage and possibly complete failure. The peak tensile stress and its location in the material are determined by the wave shape. Damage evolution processes and localized behavior are studied under flat-top, triangular, and ramp wave loading∕unloading using time-resolved free-surface velocity interferometry and post-experiment metallurgical analysis of the soft recovered samples.
An investigation of nodal structures and the construction of trial wave functions
Authors: Bressanini Dario , Morosi Gabriele , Tarasco Silvia
Published: November 2005

The factors influencing the quality of the nodal surfaces, namely, the atomic basis set, the single-particle orbitals, and the configurations included in the wave-function expansion, are examined for a few atomic and molecular systems. The following empirical rules are found: the atomic basis set must be fairly large, complete active space and natural orbitals are usually better than Hartree-Fock orbitals, multiconfiguration expansions perform better than single-determinant wave functions, but only few configurations are effective and their choice is suggested by symmetry considerations, while too long determinantal expansions spoil the nodal surfaces. These rules allow us to reduce the nodal error and to compute the best fixed node-diffusion Monte Carlo energies for a series of dimers of first-row atoms.
Channel-independent and sensor-independent stimulus representations
Authors: Levin David N.
Published: November 2005

This paper shows how a machine, which observes stimuli through an uncharacterized, uncalibrated channel and sensor, can glean machine-independent information (i.e., channel- and sensor-independent information) about the stimuli. This is possible if the following two conditions are satisfied by the observed stimulus and by the observing device, respectively: (1) the stimulus’ trajectory in the space of all possible configurations has a well-defined local velocity covariance matrix; (2) the observing device’s sensor state is invertibly related to the stimulus state. The first condition guarantees that the statistical properties of the stimulus time series endow the stimulus configuration space with a differential geometric structure (a metric and parallel transfer procedure), which can then be used to represent relative stimulus configurations in a coordinate-system-independent manner. This requirement is satisfied by a large variety of physical systems, and, in general, it is expected to be satisfied by stimulus trajecteries that densely cover stimulus state space and that have velocity distributions varying smoothly across that space. The second condition implies that the machine defines a specific coordinate system on the stimulus state space, with the nature of that coordinate system depending on the machine’s channels and detectors. Thus, machines with different channels and sensors “see” the same stimulus trajectory through state space, but in different machine-specific coordinate systems. It is shown that this requirement is almost certainly satisfied by any device that measures more than 2d independent properties of the stimulus, where d is the number of stimulus degrees of freedom. Taken together, the two conditions guarantee that the observing device can record the stimulus time series in its machine-specific coordinate system and then derive coordinate-system-independent (and, therefore, machine-independent) representations of relative stimulus configurations. The resulting description is an “inner” property of the stimulus time series in the sense that it does not depend on extrinsic factors such as the observer’s choice of a coordinate system in which the stimulus is viewed (i.e., the observer’s choice of channels and sensors). In other words, the resulting description is an intrinsic property of the evolution of the “real” stimulus that is “out there” broadcasting energy to the observer. This methodology is illustrated with analytic examples and with a numerically simulated experiment. In an intelligent sensory device, this kind of representation “engine” could function as a “front end” that passes channel- and sensor-independent stimulus representations to a pattern recognition module. After a pattern recognizer has been trained in one of these devices, it could be used without a change in other devices having different channels and sensors.
Generating inherent structures of liquids: Comparison of local minimization algorithms
Authors: Chakravarty Charusita , Debenedetti Pablo G. , Stillinger Frank H.
Published: November 2005

Properties of minima obtained by two different local minimization algorithms, the conjugate gradient and the limited-memory Broyden-Fletcher-Goldfarb-Shanno, are compared for a liquid whose particles interact via a modified Lennard-Jones pair interaction. The average properties of inherent structures obtained by the two minimization procedures are shown to agree within statistical error, though for a given starting configuration the two algorithms may not quench to identical minima.
Nonlinear drag force in dusty plasmas
Authors: Tsytovich V. N. , de Angelis U. , Ivlev A. V. , Morfill G. E. , Khrapak S.
Published: November 2005

The condition for large angle scattering in ion-grain collisions, which determine the nonlinear part of the ion drag force, coincides with the condition for the grain screening to be nonlinear (∣eϕ∣∕Ti>1 where ϕ is the electrostatic grain potential and Ti is the ion mean energy), a condition met in many laboratory experiments. A self-consistent treatment of the nonlinear ion-drag force therefore requires a correct treatment of nonlinear screening. A model to account for the nonlinearity is presented and the drag force calculated, showing that it can be substantially larger than that for linear screening. An important physical feature found in the present investigation is that nonlinear screening corresponds to almost full screening inside a finite radius and that large angle scattering occurs only inside this radius. The nonlinear ion-drag force is found to have a strong dependence on the grain size, ratio of ion to electron temperatures, and ion density.
Linear and nonlinear dynamics of a dust bicrystal consisting of positive and negative dust particles
Authors: Kourakis I. , Shukla P. K. , Morfill G. E.
Published: November 2005

A dusty plasma crystalline configuration consisting of charged dust grains of alternating charge sign (⋯∕+∕−∕+∕−∕+∕⋯) and mass is considered. Both charge and mass of each dust species are taken to be constant. Considering the equations of longitudinal motion, a dispersion relation for linear longitudinal vibrations is derived from first principles and then analyzed. Two harmonic modes are obtained, namely, an acoustic mode and an inverse-dispersive optic-like one. The nonlinear aspects of acoustic longitudinal dust grain motion are addressed via a generalized Boussinesq (and, alternatively, a generalized Korteweg–de Vries) description.
Coherent structure dynamics upstream of a long rectangular block at the side of a large aspect ratio channel
Authors: Paik Joongcheol , Sotiropoulos Fotis
Published: November 2005

Chrisohoides and Sotiropoulos [Phys. Fluids 15, L25 (2003)] recently developed an experimental technique for visualizing and extracting the time scale of coherent Lagrangian structures in turbulent, free-surface flows. They applied their technique to visualize the rich dynamics of the flow in the upstream recirculating region of a long, rectangular, surface-piercing obstacle mounted on the side wall of a shallow open channel at a Reynolds number of 4.2×105 and a Froude number of 0.35. In this paper, detached eddy simulation is carried out for a similar geometrical configuration but using the flat, rigid-lid (zero Froude number) assumption to model the free surface in order to verify and explain for the first time the experimental observations. The calculated flow at the surface in the recirculating zone is found to be dominated by multiple, slowly evolving, large-scale eddies whose structure, dynamics, and Lagrangian time scales are shown to be in good agreement with those reported in the experiment at the free surface. Analysis of the computed solutions shows that the resolved flow in this region is quasiperiodic and that its spatial and temporal richness is due to the complex interaction of the slowly moving recirculating flow and the shear layer that forms at its interface with the fast-moving outer flow. The computed solutions also provide the first comprehensive insight into the highly three-dimensional structure of this flow.
Observation of core electron temperature rise in response to an edge cooling in toroidal helical plasmas
Authors: Tamura N. , Inagaki S. , Ida K. , Shimozuma T. , Kubo S. , Tokuzawa T. , Tanaka K. , Neudatchin S. V. , Itoh K. , Kalinina D. , Sudo S. , Nagayama Y. , Ohkubo K. , Kawahata K. , Komori A. ,   LHD Experimental Group
Published: November 2005

The first observation of a significant rise of core electron temperature in response to edge cooling in a helical plasma has been made on the Large Helical Device [O. Motojima et al., Phys. Plasmas 6, 1843 (1999)]. When the phenomenon occurs, the electron heat diffusivity in the core region is reduced abruptly without changing local parameters in the region of interest. Therefore the phenomenon can be regarded as a so-called “nonlocal” electron temperature rise observed so far only in many tokamaks.
Relativistic Raman backscattering in an electron beam with ion-channel guiding and its application in free-electron laser
Authors: Kordbacheh A. A. , Maraghechi B. , Farokhi B. , Willett J. E.
Published: November 2005

A theory for Raman backscattering, in the rest frame of an electron beam with ion-channel guiding, is presented when the electrons are making small amplitude betatron oscillations. A relativistic theory of this problem is also presented when the electrons are moving through relativistic and helical trajectories. The relativistic theory is used to find the growth rate of a free-electron laser in Raman regime. The wiggler effects, on the linear dispersion relations of the space-charge wave and radiation, are included in the analysis. The growth rate and free-space wavelength of the radiation are studied numerically at different operating regimes corresponding to small and large ion-channel densities. An improved dispersion relation for a free-electron laser without any guiding is derived.
Polarization behaviors of (Bi3.15Nd0.85)Ti3O12 thin films deposited by radio-frequency magnetron sputtering
Authors: Gao X. S. , Xue J. M. , Wang J.
Published: November 2005

Ferroelectric (Bi3.15Nd0.85)Ti3O12 (BNdT) thin films of random orientation have been successfully deposited on Pt∕Ti∕SiO2∕Si(001) by radio-frequency magnetron sputtering, followed by rapid thermal annealing at 700 °C. They exhibit a remanent polarization 2Pr of 23.2μC∕cm2 and a coercive field EC of 112kV∕cm at an applied voltage of 10 V. These BNdT films also show a switchable polarization (ΔP=Psw−Pns) of 12.9μC∕cm2 at 5 V, together with an almost fatigue-free behavior up to 1.4×1010 switching cycles at both 100 and 150 °C. They demonstrate desirable retention and imprint behaviors at 100 °C, while a further increase in temperature up to 150 °C led to an acceleration in both retention loss and imprint behavior, which can be accounted for by the thermally assisted redistribution of defects and space charges. Studies of the ac dependence of relative permittivity suggest the occurrence of domain-wall pinning, which is a commonly observed phenomenon in oxide ferroelectric thin films.
Thermal convection with a freely moving top boundary
Authors: Zhong Jin-Qiang , Zhang Jun
Published: November 2005

In thermal convection, coherent flow structures emerge at high Rayleigh numbers as a result of intrinsic hydrodynamic instability and self-organization. They range from small-scale thermal plumes that are produced near both the top and the bottom boundaries to large-scale circulations across the entire convective volume. These flow structures exert viscous forces upon any boundary. Such forces will affect a boundary which is free to deform or change position. In our experiment, we study the dynamics of a free boundary that floats on the upper surface of a convective fluid. This seemingly passive boundary is subjected solely to viscous stress underneath. However, the boundary thermally insulates the fluid, modifying the bulk flow. As a consequence, the interaction between the free boundary and the convective flow results in a regular oscillation. We report here some aspects of the fluid dynamics and discuss possible links between our experiment and continental drift.
Resistive and viscous dynamics of finite-amplitude shear waves at a magnetic X-point
Authors: Craig I. J. D. , Litvinenko Yuri E.
Published: November 2005

The dynamics and dissipation of axial shear waves, superposed on a planar magnetic X-point in a resistive viscous incompressible plasma, are analyzed numerically and analytically. The interplay of viscous and resistive effects is demonstrated by deriving solutions for various values of the scalar coefficients of viscosity and resistivity. These solutions show that viscous-resistive coupling can dramatically affect the global energy dissipation. When either viscosity or resistivity vanishes, the solutions are characterized by oscillatory decaying eigenmodes that maintain equipartition between the magnetic and kinetic energies. This behavior persists when resistivity is the dominant dissipation mechanism. When viscosity is the dominant dissipation mechanism, initial oscillations are followed by exponential decay at sufficiently long times. The applicability of the results to flares in solar active regions, where the viscous Reynolds number can be much smaller than the resistive one, is discussed.
Electron and ion kinetic effects in the saturation of a driven ion acoustic wave
Authors: Riconda C. , Heron A. , Pesme D. , Huller S. , Tikhonchuk V. T. , Detering F.
Published: November 2005

The role of ion and electron kinetic effects is investigated in the context of the nonlinear saturation of a driven ion acoustic wave (IAW) and its parametric decay into subharmonics. The simulations are carried out with a full–particle-in-cell (PIC) code, in which both ions and electrons are treated kinetically. The full-PIC results are compared with those obtained from a hybrid-PIC code (kinetic ions and Boltzmann electrons). It is found that the largest differences between the two kinds of simulations take place when the IAW is driven above the ion wave-breaking limit. In such a case of a strong drive, the hybrid-PIC simulations lead to a Berstein-Greene-Kruskal-like nonlinear IAW of a large amplitude, while in the full-PIC the IAW amplitude decays to a small level after a transient stage. The electron velocity distribution function is significantly flattened in the domain of small electron velocities. As a result the nonlinear frequency shift due to the electron kinetic effects compensates partly the nonlinear frequency shift due to the ion kinetic effects, allowing then for the parametric decay of the driven IAW into subharmonics. These observations lead to the conclusion that electron kinetic effects become important whenever the nonlinear effects come into play.
Pressure-dependent photoluminescence of ZnO nanosheets
Authors: Chen S. J. , Liu Y. C. , Shao C. L. , Xu C. S. , Liu Y. X. , Wang L. , Liu B. B. , Zou G. T.
Published: November 2005

Photoluminescence and Raman spectra of ZnO single-crystal nanosheets have been studied as a function of applied hydrostatic pressure using the diamond-anvil-cell technique at room temperature. The ZnO nanosheets synthesized via a vapor transport process have uniform plane surfaces with lateral dimensions up to several microns and thickness of ∼100nm. In terms of Raman results, the ZnO nanosheets underwent a transition from wurtzite to rock-salt structure with an increase of pressure, and the phase-transition pressure was measured to be about 11.2 GPa. However, a strong near-band-edge UV emission of ZnO nanosheets was observed with the applied pressure up to 20.0 GPa. Simultaneously, the emission peak shifted to higher-energy side with increasing pressure. By examining the dependence of the near-band-edge emission peak on the applied pressure, the pressure coefficient of the direct Γ band gap in the wurtzite ZnO nanosheets was determined.
Synthesis and characterization of metallic TaSi2 nanowires
Authors: Chueh Y. L. , Chou L. J. , Cheng S. L. , Chen L. J. , Tsai C. J. , Hsu C. M. , Kung S. C.
Published: November 2005

TaSi 2 nanowires have been synthesized by annealing FeSi2 thin film and nanodots grown on a Si substrate in an ambient containing Ta vapor. The TaSi2 nanowires are formed in three steps; segregation of Si atoms from the FeSi2 underlayer to form Si base, growth of TaSi2 nanodots on Si base, and elongation of TaSi2 nanowire along the growth direction. Strong field-emission properties promise future electronics and optoelectronics applications.
Photoemission-induced charging of self-assembled Au nanoparticles on GaN substrates and the effect on surface band bending
Authors: Kim Hwa Kyung , Jang Ho Won , Lee Jong-Lam
Published: November 2005

The effects of Au nanoparticles on the electronic properties of a GaN surface were investigated using synchrotron radiation photoelectron spectroscopy (SRPES). A 30-Å-thick Au film on GaN was transformed to nanoparticles by annealing at 300 °C. Ga 3d core level peak as well as Au 4f for p-GaN shifted towards higher binding energies with the formation of Au nanoparticles, while peak shifts in the SRPES spectra for n-GaN were negligible. Poor conductivity of the p-GaN substrate and high resistance between Au nanoparticles and the p-GaN led to positive charges being distributed on the p-GaN surface, suggesting that Au nanoparticles on p-GaN strongly affect the evaluation of surface band bending and the measurement of Schottky barrier heights by photoemission spectroscopy.
Magnetic capture of a single magnetic nanoparticle using nanoelectromagnets
Authors: Kim H. K. , Hong S. H. , Hwang S. W. , Hwang J. S. , Ahn D. , Seong S. , Park T. H.
Published: November 2005

We demonstrate the fabrication of nanoelectromagnets and the magnetic capture of a single magnetic nanoparticle. The magnetic nanoparticles are extracted from magnetotactic bacteria and their diameter is approximately 50 nm. We show that a single nanoparticle is captured at each corner of the serpentine-shaped nanoelectromagnet, and the maximum magnetic field of 35 mT (and the maximum magnetic-field gradient of 4×105T∕m) is shown to be created at the capture spots of the nanoelectromagnet. It is also shown that there is a crossover between the magnetic force and the diffusion force at several hundred nm away from the magnet. This distance is comparable to the average interparticle distance.
Collisionless reversed magnetic shear trapped electron instability and contribution of sidebands to anomalous transport
Authors: Rogister André L. , Singh Raghvendra
Published: November 2005

By keeping account of the trapped electron ∇B and curvature drifts, it is found that the spatial decay of the collisionless electron drift wave is governed either by the trapped electron response or by the resonant interaction of ions with the sidebands of the primary oscillation. In the former case, pairs of spatially bounded unstable and damped solutions are obtained for negative magnetic shear (ŝ<0) if, as usual, LTe=1∕∂rlnTe<0; there are no bounded solutions if ŝLTe<0. In the latter case, there is either a set of bounded damped solutions if ηi>0 or a set of bounded unstable solutions if ηi<0. The unstable modes have a radiating character and the growth rates are γ∼(2n+1)1+2q2∣ŝ∣∣LNωe*∕qR∣ (n is the Hermite polynomial solution index, q the safety factor, ŝ the magnetic shear parameter, R the major radius, ωe* the electron diamagnetic frequency, LN=1∕∂rlnNe, and ηi=LN∕LTi).The sidebands are responsible for unusually large ratios Qe∕TeΓe, where Qe and Γe are the anomalous electron energy flux and the particle flux. These results may explain the box-type Te profile observed in lower hybrid current drive reversed magnetic shear plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) [H. Ninomiya and the JT-60U Team, Phys. Fluids B 4, 2070 (1992)]. It is finally demonstrated that the ballooning hypothesis generally leads to conflicting requirements: it is thus hardly relevant for the electron drift branch! The “radiating” boundary condition that has formerly been imposed on the slab solution is finally discussed.
Styrenic polymers as gate dielectrics for pentacene field-effect transistors
Authors: Nunes G. , Zane S. G. , Meth J. S.
Published: November 2005

The effect of the chemical structure of the dielectric layer in organic thin-film transistors was examined by evaporating pentacene onto five different styrenic polymer dielectrics: poly(styrene), poly(4-hydroxystyrene), poly(4-methylstyrene), poly(4-vinylpyridine), and poly(2-vinylnaphthalene). We find that the polymer has a significant effect, with measured field-effect mobilities ranging from between 0.1 and 1cm2∕Vs. This variation appears uncorrelated with either the polymer suface morphology or the observed pentacene crystallite size. The distribution of mobility, threshold voltage, on/off ratio, and subthreshold swing observed for each of the polymer dielectrics is presented.
Solitary kinetic Alfvén waves in bi-ion plasmas
Authors: Yang L. , Wu D. J.
Published: November 2005

A Sagdeev equation is provided for the solitary kinetic Alfvén waves (SKAWs) in a low-β (me∕mi⪡β⪡1 or mi∕me⪢α⪢1), three-component (electrons, protons, and heavy ions) plasma. Then we get the numerical solution of the equation. It is found that the density humps of SKAWs can exist in the sub-Alfvénic region. The heavy ion density amplitude and the width of the SKAWs rise with the increase in the initial density of heavy ions nb0 in such bi-ion plasmas. The perturbed electromagnetic fields Ez, Ex, and By are also studied further to discuss the effects of heavy ions on them. Also, numerical outcomes have been offered for cases with several different parameters to illustrate these results.
Nanoscale stress analysis of strained-Si metal-oxide-semiconductor field-effect transistors by quantitative electron diffraction contrast imaging
Authors: Li J. , Anjum D. , Hull R. , Xia G. , Hoyt J. L.
Published: November 2005

A technique that uses quantitative electron diffraction contrast imaging (EDCI) to measure stress with a spatial resolution on the order of 10nm and sensitivity on the order of tens of MPa is applied to strained-Si metal-oxide-semiconductor field-effect transistors. This is accomplished by utilizing transmission electron microscopy and focused ion beam micromachining in conjunction with finite element modeling and electron diffraction contrast simulations. Our techniques enable quantitative interpretation of EDCI intensity, as a function of the magnitude of the local stress field. Analysis shows that the stress distribution in the strained-Si channel is very sensitive to the stress state of the surrounding materials, especially TiSi2, which can modify the stress distribution in the channel by well over 100MPa.
Microwave-cut silicon layer transfer
Authors: Thompson D. C. , Alford T. L. , Mayer J. W. , Hochbauer T. , Nastasi M. , Lau S. S. , Theodore N. David , Henttinen K. , Suni llkka , Chu Paul K.
Published: November 2005

Microwave heating is used to initiate exfoliation of silicon layers in conjunction with the ion-cut process for transfer of silicon layers onto insulator or heterogeneous layered substrates. Samples were processed inside a 2.45 GHz, 1300 W cavity applicator microwave system for time durations as low as 12 s. This is a significant decrease in exfoliation incubation times. Sample temperatures measured by pyrometry were within previous published ranges. Rutherford backscattering spectrometry and cross-sectional transmission electron microscopy were used to determine layer thickness and crystallinity. Surface quality was measured by using atomic force microscopy. Hall measurements were used to characterize electrical properties as a function of postcut anneal time and temperature.
Effect of aluminum substitution on microwave absorption properties of barium hexaferrite
Authors: Qiu Jianxun , Zhang Qiguo , Gu Mingyuan , Shen Haigen
Published: November 2005

Aluminum substituted barium hexaferrites were prepared by the self-propagating combustion method and subsequent calcination at 850 °C. The crystalline structure, complex permittivity, complex permeability, and hyperfine parameters of BaFe12−xAlxO19 (x varies from 1.5 to 2.3 in steps of 0.2) were measured with x-ray diffraction (XRD), vector network analyzer and Mössbauer spectroscopy. The XRD results show that all Al3+ ions enter into the lattice of hexagonal barium ferrite. The substitution of Al3+ ions can greatly affect the complex permittivity and permeability of barium ferrite. With increasing substitution, the real part of complex permittivity increases gradually, and the peaks of the imaginary part of complex permeability shift into higher frequency band. When the substitution amount x is 1.9, the largest movement of the peaks is 1.95 GHz, which indicates that the ferromagnetic resonant frequency of barium ferrite increases by 1.95 GHz. The Al3+ ions preferentially occupy the 4f2, 2a, 4f1, and 12k sites in the subcrystalline structure up to x=1.9, and then the Al3+ ions mainly occupy 12k sites. This change also results in 2b sites with a large quadrupole splitting. These occupations lead to a variable magnetocrystalline anisotropy field.
Dynamic accessibility of inflow and outflow reconnective solutions
Authors: Tassi E. , Titov V. S. , Hornig G.
Published: November 2005

An analysis of the accessibility properties of exact stationary solutions of the resistive magnetohydrodynamics equations is presented. The issue is raised of whether such solutions, which describe a particular type of magnetic reconnection, can be obtained as the final state of a time-dependent evolution of the magnetic- and velocity-field disturbances superimposed onto background fields possessing a null point. Numerical experiments indicate that, whereas for the solutions of inflow type with super-Alfvénic background flow the imposed boundary conditions are sufficient to determine the accessed steady-state solution, in the case of outflow solutions with sub-Alfvénic background flow the final steady-state turns out to depend on the initial disturbance as well. It is found that the directions of the characteristic curves of the evolution equations and an implicit condition on the vorticity at the stagnation point are responsible for this behavior. Implications for the maximum current density attained in the final state are discussed. An argument to explain the appearance of damped oscillations in the evolution of the disturbance fields for the outflow case, as opposed to the flux pileup characterizing the inflow case, is also provided.
In situ Auger electron spectroscopy studies of the growth of p-type microcrystalline silicon films on ZnO-coated glass substrates for microcrystalline silicon p-i-n solar cells
Authors: Fujibayashi Takashi , Kondo Michio
Published: November 2005

In situ Auger electron spectroscopy has been applied to investigate the growth process of hydrogenated microcrystalline Si (μc-Si:H)p layers on ZnO-coated glass substrates in plasma-enhanced chemical vapor deposition and the state of ZnO∕p interface. A high hydrogen dilution induces a ZnO∕p interface layer consisting of Si–O bonds to increase an induction period for the film growth and promotes a relaxation of strained Si–Si bond to result in a change in film growth mode from island to layer growth and a highly porous film for a nucleation of crystallites. Such changes in the initial growth influences a short circuit current of μc-Si:Hp-i-n solar cells.
Directed integration of ZnO nanobridge devices on a Si substrate
Authors: Conley John F. , Stecker Lisa , Ono Yoshi
Published: November 2005

We demonstrate the directed assembly and integration of ZnO nanobridges into working devices on silicon-on-insulator substrates. The “pick and place” method of nanowire integration is avoided and metal catalysts are not used. ZnO nanowires (NWs) were grown selectively via a vapor-solid method using a patterned ZnO thin-film seed layer that was deposited on Si trench sidewalls via atomic layer deposition. ZnO NWs grew to span the trench and self-terminate on the opposing surface, effectively forming electrically accessible horizontal ZnO nanobridge devices. Vertical bridge devices were also constructed using undercut islands. Directly grown horizontal ZnO nanobridge devices were operated as gas and UV sensors, demonstrating that this method represents a significant step towards practical large-scale integration of nanodevices into Si microelectronics.
Conducting polymer and hydrogenated amorphous silicon hybrid solar cells
Authors: Williams Evan L. , Jabbour Ghassan E. , Wang Qi , Shaheen Sean E. , Ginley David S. , Schiff Eric A.
Published: November 2005

An organic-inorganic hybrid solar cell with a p-i-n stack structure has been investigated. The p-layer was a spin coated film of PEDOT:PSS [poly(3,4-ethylenedioxythiophene) poly (styrenesulfonate)]. The i-layer was hydrogenated amorphous silicon (a-Si:H), and the n-layer was microcrystalline silicon (μc-Si). The inorganic layers were deposited on top of the organic layer by the hot-wire chemical vapor deposition technique at 200°C. These hybrid devices exhibited open circuit voltages (VOC) as large as 0.88V and solar conversion efficiencies as large as 2.1%. Comparison of these devices with those incorporating a-SiC:H:B p-layers indicates that the organic layer is acting as an electrically ideal p-layer.
Investigation of work function tuning using multiple layer metal gate electrodes stacks for complementary metal-oxide-semiconductor applications
Authors: Jha Rashmi , Lee JaeHoon , Majhi Prashant , Misra Veena
Published: November 2005

Metal gate electrodes consisting of three layered stacks of metals are investigated for complementary metal-oxide-semiconductor device applications. It was observed that the effective work function of the entire gate electrode stack was dominated by the work function of the first metal layer (50Å of tantalum nitride) contacting the gate dielectric. No significant difference in the effective oxide thickness was observed in devices with and without the initial tantalum nitride layer. The potential reasons for this, based on the penetration of an electron wave function from the gate electrode to the gate dielectric and gate depletion due to longer Debye length of electrons in tantalum nitride, will be discussed.
Ultrashort, high-power pulse generation from a master oscillator power amplifier based on external cavity mode locking of a quantum-dot two-section diode laser
Authors: Choi Myoung-Taek , Lee Wangkuen , Kim Ji-Myung , Delfyett Peter J.
Published: November 2005

We investigate an external cavity curved two-section mode-locked diode laser system based on quantum-dot (QD) gain media near 1.3μm. Pulses are generated from the external laser cavity at a 5-GHz repetition rate and amplified using a multilayer quantum-dot semiconductor optical amplifier. The pulses are compressed with a dual-grating dispersion compensator. The shortest, near transform-limited pulses are obtained when the mode-locked pulses are positive (up) chirped. The compressed pulses are 1.2ps in duration, with a pulse energy of 1.46pJ, implying a peak power of 1.22W.
Fe
–
Ga
∕
Pb
(
Mg
1
∕
3
Nb
2
∕
3
)
O
3
–
Pb
Ti
O
3
magnetoelectric laminate composites
Authors: Dong Shuxiang , Zhai Junyi , Wang Naigang , Bai Feiming , Li JieFang , Viehland D. , Lograsso T. A.
Published: November 2005

We have found large magnetoelectric (ME) effects in long-type laminate composites of Fe–20%Ga magnetostrictive alloys and piezoelectric Pb(Mg1∕3Nb2∕3)O3–PbTiO3 single crystals. At lower frequencies, the ME voltage coefficient of a laminate with longitudinally magnetized and longitudinally polarized (i.e., L-L mode) layers was 1.41V∕Oe (or 1.01V∕cmOe). Near the natural resonant frequency (∼91kHz) of the laminate, the ME voltage coefficients were found to be dramatically increased to 50.7V∕Oe (36.2V∕cmOe) for the L-L mode. In addition, the laminate can detect a minute magnetic field as low as ∼2×10−12T at resonance frequency, and ∼1×10−10T at lower frequencies.
Time-resolved photoluminescence from ZnO nanostructures
Authors: Kwok W. M. , Djurišić A. B. , Leung Y. H. , Chan W. K. , Phillips D. L.
Published: November 2005

Different ZnO nanostructures (tetrapods, shells, rods, and highly faceted rods) were characterized by photoluminescence (PL) and time-resolved PL measurements. It was found that different nanostructures exhibit very different optical properties in terms of defect emission and decay times of the spontaneous emission. No correlation was found between the PL decay times and defect emission intensities and defect emission positions. The short decay times of the UV emission are most likely due to nonradiative defects that are correlated with the crystalline quality and do not contribute to the visible emission. Neither short PL decay times nor intense defect emissions rule out achievement of stimulated emission.
Picosecond third-order nonlinearity of lead-oxide glasses in the infrared
Authors: de Araújo Cid B. , Falcão-Filho E. L. , Humeau A. , Guichaoua D. , Boudebs G. , Kassab Luciana R. P.
Published: November 2005

Heavy metal-oxide glasses containing lead and bismuth were prepared, and their picosecond third-order nonlinear (NL) optical characteristics were investigated. NL refractive indices of ≈10−18m2∕W at 1064nm were measured. Negligible NL absorption was verified and, as a consequence, the samples present a good factor-of-merit for photonic applications.