bluuebunny/crossref_metadata_2025 huggingface dataset:
State-of-the-Science Symposium on Postacute Rehabilitation: Setting a Research Agenda and Developing an Evidence Base for Practice and Public Policy—Executive Summary
Authors: Heinemann Allen W.
Published: October 2007

Purpose

The Rehabilitation Research and Training Center on Measuring Rehabilitation Outcomes and Effectiveness along with academic, professional, provider, and accreditor organizations sponsored a symposium with the aim of serving as a catalyst for expanded research on postacute care (PAC) rehabilitation. The goals were to describe the state of our knowledge regarding utilization, organization, and outcomes of postacute rehabilitation settings, identify methodological and measurement challenges, foster the exchange of ideas among stakeholders, and identify researchable questions.

Method

The symposium was organized around 4 themes: (a) the need for improved
measurement
of rehabilitation variables and
methods
to collect and analyze this information, (b) factors that influence
access
to rehabilitation care, (c) similarities and differences in services across PAC
settings,
and (d)
effectiveness
of rehabilitation services.

Results

Key themes included the need for improved measures, particularly of case-mix factors and treatment ingredients; the need for a uniform and coherent system of PAC; the need to attend to under- and overutilization of rehabilitation services; the need for cooperation among stakeholders to advance an effectiveness research agenda; and the desire to develop payment policies that are based on research evidence.

Conclusions

The symposium articles appear in the November 2007 issue of
Archives of Physical Medicine and Rehabilitation.
Developing a Clinician-Friendly Aphasia Test
Authors: Marshall Robert C. , Wright Heather Harris
Published: October 2007

Purpose

The Kentucky Aphasia Test (KAT) is an objective measure of language functioning for persons with aphasia. This article describes materials, administration, and scoring of the KAT; presents the rationale for development of test items; reports information from a pilot study; and discusses the role of the KAT in aphasia assessment.

Method

The KAT has 3 parallel test batteries, KAT-1, KAT-2, and KAT-3. Each battery contains the same orientation test and 6 subtests, each with 10 items, assessing expressive and receptive language functions. Subtests for KAT-1, KAT-2, and KAT-3 systematically increase in difficulty so that it is possible to assess individuals with severe, moderate, and mild aphasia, respectively. The KAT was administered to 38 participants with aphasia and 31 non-brain-damaged (NBD) participants.

Results

Results with the KAT clearly differentiated the language performance of individuals with and without aphasia. NBD participants made few errors, and overall scores on the test for individuals with aphasia were rarely within 1
SD
of the NBD group. Performance of the participants with aphasia administered KAT-1, KAT-2, and KAT-3 suggested that the 3 versions of the test represent a hierarchy of difficulty.

Conclusions

The KAT remains in its early stages of development. However, it does appear to meet the requirements for a “clinician-friendly” aphasia test and, as such, offers a rapid, convenient means of obtaining an objective score to determine changes in language functioning during the early postonset period.
Communication Disorders: Prevalence and Comorbid Intellectual Disability, Autism, and Emotional/Behavioral Disorders
Authors: Pinborough-Zimmerman Judith , Satterfield Robert , Miller Judith , Bilder Deborah , Hossain Shaheen , McMahon William
Published: October 2007

Purpose

To determine a population-based estimate of communication disorders (CDs) in children; the co-occurrence of intellectual disability (ID), autism, and emotional/behavioral disorders; and the impact of these conditions on the prevalence of CDs.

Method

Surveillance targeted 8-year-olds born in 1994 residing in 2002 in the 3 most populous counties in Utah (
n
= 26,315). A multiple-source record review was conducted at all major health and educational facilities.

Results

A total of 1,667 children met the criteria of CD. The prevalence of CD was estimated to be 63.4 per 1,000 8-year-olds (95% confidence interval = 60.4–66.2). The ratio of boys to girls was 1.8:1. Four percent of the CD cases were identified with an ID and 3.7% with autism spectrum disorders (ASD). Adjusting the CD prevalence to exclude ASD and/or ID cases significantly affected the CD prevalence rate. Other frequently co-occurring emotional/behavioral disorders with CD were attention deficit/hyperactivity disorder, anxiety, and conduct disorder.

Conclusions

Findings affirm that CDs and co-occurring mental health conditions are a major educational and public health concern.
Analysis and prediction of absorption band shapes, fluorescence band shapes, resonance Raman intensities, and excitation profiles using the time-dependent theory of electronic spectroscopy
Authors: Petrenko Taras , Neese Frank
Published: October 2007

A general method for the simulation of absorption (ABS) and fluorescence band shapes, resonance-Raman (rR) spectra, and excitation profiles based on the time-dependent theory of Heller is discussed. The following improvements to Heller’s theory have been made: (a) derivation of new recurrence relations for the time-dependent wave packet overlap in the case of frequency changes between the ground and electronically excited states, (b) a new series expansion that gives insight into the nature of Savin’s preresonance approximation, (c) incorporation of inhomogeneous broadening effects into the formalism at no additional computational cost, and (d) derivation of a new and simple short-time dynamics based equation for the Stokes shift that remains valid in the case of partially resolved vibrational structure. Our implementation of the time-dependent theory for the fitting of experimental spectra and the simulation of model spectra as well as the quantum mechanical calculation of the model parameters is discussed. The implementation covers all electronic structure approaches which are able to deliver ground- and excited-state energies and transition dipole moments. The technique becomes highly efficient if analytic gradients for the excited-state surface are available. In this case, the computational cost for the simultaneous prediction of ABS, fluorescence, and rR spectra is equal to that of a single excited-state geometry optimization step while the limitations of the short-time dynamics approximation are completely avoided. As a test case we discuss the well-known case of the strongly allowed 1Ag1→1Bu1 transition in 1,3,5 trans-hexatriene in detail using method ranging from simple single-reference treatments to elaborate multireference electronic structure approaches. At the highest computational level, the computed spectra show the best agreement that has so far been obtained with quantum chemical methods for this problem.
Calculation of the zero-field splitting tensor on the basis of hybrid density functional and Hartree-Fock theory
Authors: Neese Frank
Published: October 2007

The zero-field splitting (ZFS) (expressed in terms of the D tensor) is the leading spin-Hamiltonian parameter for systems with a ground state spin S>1∕2. To first order in perturbation theory, the ZFS arises from the direct spin-spin dipole-dipole interaction. To second order, contributions arise from spin-orbit coupling (SOC). The latter contributions are difficult to treat since the SOC mixes states of different multiplicities. This is an aspect of dominant importance for the correct prediction of the D tensor. In this work, the theory of the D tensor is discussed from the point of view of analytic derivative theory. Starting from a general earlier perturbation treatment [F. Neese and E. I. Soloman, Inorg. Chem. 37, 6568 (1998)], straightforward response equations are derived that are readily transferred to the self-consistent field (SCF) Hartree-Fock (HF) or density functional theory (DFT) framework. The main additional effort in such calculations arises from the solution of nine sets of nonstandard coupled-perturbed SCF equations. These equations have been implemented together with the spin-orbit mean-field representation of the SOC operator and a mean-field treatment of the direct spin-spin interaction into the ORCA electronic structure program. A series of test calculations on diatomic molecules with accurately known zero-field splittings shows that the new approach corrects most of the shortcomings of previous DFT based methods and, on average, leads to predictions within 10% of the experimental values. The slope of the correlation line is essentially unity for the B3LYP and BLYP functionals compared to ∼0.5 in previous treatments.
Non-Spitzer return currents in intense laser-plasma interactions
Authors: Sherlock M. , Bell A. R. , Kingham R. J. , Robinson A. P. L. , Bingham R.
Published: October 2007

The propagation of an intense (1019Wcm−2) laser-produced hot electron distribution through overdense, long scale-length plasma is modeled using the one-dimensional relativistic electron Vlasov-Fokker-Planck code KALOS [Bell et al., Plasma Phys. Control. Fusion 48, R37 (2006)]. The initial density profile is chosen to be relevant to the coronal region in fast ignition fusion scenarios in which the density rises from around 10ncr to solid density over 35μm. Under these conditions, the return current transport is intermediate between that of collisional Spitzer transport characterized by strong resistivity and that of collisionless transport characterized by electron inertia. It is shown that the isotropic component of the distribution function of the return-current-carrying electrons becomes doubly peaked. Strong anisotropic pressure inhomogeneities can drive additional contributions to the return current not considered in Spitzer’s transport equations. As a result the electric field can become an order-of-magnitude greater than its classical (Spitzer) value.
Current carrying blob filaments and edge-localized-mode dynamics
Authors: Myra J. R.
Published: October 2007

The model of blob-filament propagation in the scrape-off layer (SOL) of a tokamak is extended to include objects that carry a large net unidirectional current parallel to the magnetic field. Under experimentally realistic conditions, the blob-filament structure and propagation are influenced by magnetostatic forces. Some aspects of the model may be relevant to the SOL propagation of edge-localized modes.
Nonlinear generation mechanism for the vortical electric field in magnetized plasma media
Authors: Aburjania G. D.
Published: October 2007

A physical mechanism and nonlinear mathematical formalism for study of generation and further amplification of the vortical electric field in the magnetized plasma are proposed. A modulation instability process in a plasma medium is considered in a strong constant magnetic field. The plasmon condensate is modulated not by a low-frequency ionic sound as is usually done, but by the beating of two high-frequency transverse electromagnetic waves propagating along the external magnetic field. Conditions in which aperiodic instability occurs are found and its increment is defined. This instability leads to a decrease in the scale of Langmuir turbulence along the external magnetic field and to the generation of electromagnetic fields. Dissipative property of the medium increases an amplitude threshold of the pumping waves. It is shown that for sufficiently large amplitudes of pumping waves the effect described in the paper is the defining nonlinear process.
Simulations of plasma confinement in an antihydrogen trap
Authors: Gomberoff K. , Fajans J. , Friedman A. , Grote D. , Vay J.-L. , Wurtele J. S.
Published: October 2007

The three-dimensional particle-in-cell (3-D PIC) simulation code WARP is used to study positron confinement in antihydrogen traps. The magnetic geometry is close to that of a UC Berkeley experiment conducted, with electrons, as part of the ALPHA collaboration [W. Bertsche et al., AIP Conf. Proc. 796, 301 (2005)]. In order to trap antihydrogen atoms, multipole magnetic fields are added to a conventional Malmberg-Penning trap. These multipole fields must be strong enough to confine the antihydrogen, leading to multipole field strengths at the trap wall comparable to those of the axial magnetic field. Numerical simulations reported here confirm recent experimental measurements of reduced particle confinement when a quadrupole field is added to a Malmberg-Penning trap. It is shown that, for parameters relevant to various antihydrogen experiments, the use of an octupole field significantly reduces the positron losses seen with a quadrupole field. A unique method for obtaining a 3-D equilibrium of the positrons in the trap with a collisionless PIC code was developed especially for the study of the antihydrogen trap; however, it is of practical use for other traps as well.
Projection formalism for constrained dynamical systems: From Newtonian to Hamiltonian mechanics
Authors: Kneller Gerald R.
Published: October 2007

The Hamiltonian of a holonomically constrained dynamical many-particle system in Cartesian coordinates has been recently derived for applications in statistical mechanics [G. R. Kneller, J. Chem. Phys. 125, 114107 (2006)]. Using the same projector formalism, we show here the equivalence of the corresponding equations of motion with those obtained from a Newtonian and a Lagrangian description. In the case of Newtonian mechanics, the general case of nonholonomic constraints is considered, too.
Nonlinear excitations in Debye bi-crystals
Authors: Farokhi B. , Kourakis I. , Shukla P. K.
Published: October 2007

The nonlinear dynamics of longitudinal dust lattice waves propagating in a dusty plasma bi-crystal is investigated. A “diatomic”-like one-dimensional dust lattice configuration is considered, consisting of two distinct dust grain species with different charges and masses. Two different frequency dispersion modes are obtained in the linear limit, namely, an optical and an acoustic wave dispersion branch. Nonlinear solitary wave solutions are shown to exist in both branches, by considering the continuum limit for lattice excitations in different nonlinear potential regimes. For this purpose, a generalized Boussinesq and an extended Korteweg de Vries equation is derived, for the acoustic mode excitations, and their exact soliton solutions are provided and compared. For the optic mode, a nonlinear Schrödinger-type equation is obtained, which is shown to possess bright- (dark-) type envelope soliton solutions in the long (short, respectively) wavelength range. Optic-type longitudinal wavepackets are shown to be generally unstable in the continuum limit, though this is shown not to be the rule in the general (discrete) case.
Self-fields in a planar wiggler and axial magnetic field
Authors: Esmaeilzadeh Mahdi , Ghafouri Vahid , Najafi Mehrdad , Taghavi Amin , Namvar Esmaeil
Published: October 2007

A theory for self-fields induced by charge and current densities of the electron beam in a free-electron laser with planar wiggler and axial magnetic field is presented. Mutual influence of the electron velocity and self-magnetic field is considered to account for the total self-magnetic field. The quasisteady-state orbits and their stability under the influence of self-fields are derived and discussed. The function Φ which determines the rate of change of axial velocity with energy is then derived. It is shown that for a planar wiggler, the wiggler-induced self-magnetic has two components. The first one is perpendicular to the wiggler magnetic field and the second is parallel (or antiparallel) to the wiggler magnetic field. The wiggler-induced self-magnetic field has a diamagnetic effect for group I orbits, while for group II orbits it has a paramagnetic effect. Some interesting effects of self-fields on electron dynamics include the generation of a negative singularity for function Φ and creation of new unstable orbits for group II which are not found in the absence of self-fields.
The coaxial gyrotron with two electron beams. II. Dual frequency operation
Authors: Liu Shenggang , Yuan Xuesong , Liu Diwei , Yan Yang , Zhang Yaxin , Li Hongfu , Zhong Renbin
Published: October 2007

The dual frequency operation (DFO) of the coaxial gyrotron with two electron beams (CGTB) has been investigated in this part by means of both linear theory and computer simulation. In such an operation, the cavity is at degeneration and one beam works at the first harmonic while another at high harmonic. Making use of the coupled-mode theory, the dispersion equation considering the coupling of two beams and two modes has been obtained. The results of the numerical calculation and the particle in cell simulation show that CGTB with DFO can obtain high output power at two different frequencies simultaneously. In addition, the power of the high harmonic can be enhanced due to the nonlinear coupling between two beams, and some interesting and important phenomena of CGTB with DFO revealed in the paper are of significance in physics.
Spectroscopic determination of the singly ionized helium density in low electron temperature plasmas mixed with helium in a linear divertor plasma simulator
Authors: Nishijima D. , Doerner R. P. , Baldwin M. J. , Hollmann E. M. , Seraydarian R. P. , Ueda Y.
Published: October 2007

The spectroscopic method is developed to obtain the He+ ion density nHe+ in low electron temperature, Te=5–20eV, plasmas mixed with He. Plasmas were produced in the PISCES-B linear divertor plasma simulator [R. P. Doerner et al., Phys. Scr. T111, 75 (2004)] where the electron densities are ne=(1−15)×1018m−3 and the ionization degree is ∼1–10%. In the method, the He I line intensity IHeI at λ=447.1nm is used, instead of the He II line intensity in the conventional method. The radial confinement time of He+ ions is requisite, and is measured to be at a level of the Bohm confinement time. The He+ ion concentration, nHe+∕ne, is found to be proportional to IHeI, and to weakly depend on ne and Te. Because of the higher ionization energy of He than other species (D2, Ne, and Ar), the measured nHe+∕ne becomes systematically lower than the He gas pressure fraction, and agrees with data from an omegatron mass spectrometer. The omegatron measurement and estimates of the He+ ion loss rates indicate that the influences of vibrationally excited deuterium molecules on the particle balance of He+ ions are small at Te⩾10eV.
Theoretical study of the wave dispersion relation for a two-dimensional strongly coupled Yukawa system in a magnetic field
Authors: Jiang Ke , Song Yuan-Hong , Wang You-Nian
Published: October 2007

A theoretical model is presented to investigate the wave dispersion relation of a two-dimensional (2D) strongly coupled Yukawa system, taking into account a constant magnetic field pointing perpendicular to the 2D Yukawa system, within the framework of the quasilocalized charge approximation. Numerical results represent the dependence of the dispersion relation on the magnetic field strength, the coupling parameter, and the screening parameter. Both the high-frequency and low-frequency branches are shown as a result of the coupling of the longitudinal and transverse modes due to the Lorenz effect. The results obtained from the theoretical analysis agreed well with the molecular-dynamics simulation.
Efficient density-functional theory integrations by locally augmented radial grids
Authors: Gräfenstein Jürgen , Cremer Dieter
Published: October 2007

Standard density-functional theory integration grids have proven insufficient for the meta generalized gradient approximation description of weakly bound complexes [E. R. Johnson et al., Chem. Phys. Lett. 394, 334 (2004)]. This is caused by an insufficient radial resolution in the valence region of frequently used standard grids. We present an algorithm for the construction of locally augmented radial grids, which allows us to enhance the resolution of a given radial grid in a specified region, thus increasing the accuracy of the standard grid in a cost-efficient way. Test calculations with the Van Voorhis-Scuseria exchange and correlation functional for the Ar dimer confirm that a suitably constructed, locally augmented radial grid with 100 points provides an accuracy competitive to that of a 250-point nonaugmented grid. Time savings and possible applications for locally augmented radial grids are discussed.
Influence of the focal point position on the properties of a laser-produced plasma
Authors: Kasperczuk A. , Pisarczyk T. , Badziak J. , Miklaszewski R. , Parys P. , Rosinski M. , Wolowski J. , Stenz CH. , Ullschmied J. , Krousky E. , Masek K. , Pfeifer M. , Rohlena K. , Skala J. , Pisarczyk P.
Published: October 2007

This paper deals with investigations of the influence of the focusing lens focal point position on the properties of a plasma produced by a defocused laser beam. The experiment was carried out at the Prague Asterix Laser System iodine laser [K. Jungwirth, A. Cejnarova, L. Juha, B. Kralikova, J. Krasa, E. Krousky, P. Krupickova, L. Laska, K. Masek, T. Mocek, M. Pfeifer, A. Prag, O. Renner, K. Rohlena, B. Rus, J. Skala, P. Straka, and J. Ullschmied, Phys. Plasmas 8, 2495 (2001)] by using the third harmonic of laser radiation (λ=0.438μm), laser energy of 70J, pulse duration of 250ps (full width at half-maximum), and beam spot radii of 250 and 400μm. Cu and Ta were chosen as target materials. The experimental data were obtained by means of a three-frame interferometric system, ion collectors, and crater replica techniques. The reported results allow formulating an important hypothesis that the laser-produced plasma modifies strongly the laser intensity distribution. It is shown how such a modification depends on the relative position and distance of the focal point to the target surface. Of particular importance is whether the focal point is located inside or in front of the target. The irradiation geometry is crucial for the possibility of generating plasma jets by laser radiation. Well-formed jet-like plasma structures can be created if an initially homogeneous laser intensity distribution is transformed in the plasma to an annular one.
Double dielectric relaxations in SnO2 nanoparticles dispersed in conducting polymer
Authors: Dutta Kousik , De S. K.
Published: October 2007

The tetragonal phase of SnO2 and the conducting form of polyaniline are characterized by x-ray diffraction and Fourier transform infrared spectroscopy. The electrical conductivity and the dielectric properties of tin dioxide (SnO2)-polyaniline hybrid nanocomposites have been investigated as a function of temperature and frequency for different concentrations of polyaniline. Electrical conductivity has been derived from the simple equivalent circuit pertaining to inhomogeneous polycrystalline materials. Grain and grain boundary conductivities follow an Arrhenius type of electrical conduction. The nanocomposites possess an extraordinarily high dielectric constant of about 103. Different conductivities of the grain and grain boundary give rise to a large dielectric constant in nanocomposites. The dielectric loss spectra reveal two peaks in the measured frequency interval for the maximum concentration of the SnO2 nanoparticles. The peaks are ascribed to interfacial polarization and the intrinsic oxygen defects in nanosized SnO2.
A unified approach to the Darwin approximation
Authors: Krause Todd B. , Apte A. , Morrison P. J.
Published: October 2007

There are two basic approaches to the Darwin approximation. The first involves solving the Maxwell equations in Coulomb gauge and then approximating the vector potential to remove retardation effects. The second approach approximates the Coulomb gauge equations themselves, then solves these exactly for the vector potential. There is no a priori reason that these should result in the same approximation. Here, the equivalence of these two approaches is investigated and a unified framework is provided in which to view the Darwin approximation. Darwin’s original treatment is variational in nature, but subsequent applications of his ideas in the context of Vlasov's theory are not. We present here action principles for the Darwin approximation in the Vlasov context, and this serves as a consistency check on the use of the approximation in this setting.
Gradient theory computation of the radius-dependent surface tension and nucleation rate for n-nonane clusters
Authors: Hrubý J. , Labetski D. G. , van Dongen M. E. H.
Published: October 2007

The Van der Waals-Cahn-Hilliard gradient theory (GT) is applied to determine the structure and the work of formation of clusters in supersaturated n-nonane vapor. The results are analyzed as functions of the difference of pressures of the liquid phase and vapor phase in chemical equilibrium, which is a measure for the supersaturation. The surface tension as a function of pressure difference shows first a weak maximum and then decreases monotonically. The computed Tolman length is in agreement with earlier results [L. Gránásy, J. Chem. Phys. 109, 9660 (1998)] obtained with a different equation of state. A method based on the Gibbs adsorption equation is developed to check the consistency of GT results (or other simulation techniques providing the work of formation and excess number of molecules), and to enable an efficient interpolation. A cluster model is devised based on the density profile of the planar phase interface. Using this model we analyze the dependency of the surface tension on the pressure difference. We find three major contributions: (i) the effect of asymmetry of the density profile resulting into a linear increase of the surface tension, (ii) the effect of finite thickness of the phase interface resulting into a negative quadratic term, and (iii) the effect of buildup of a low-density tail of the density profile, also contributing as a negative quadratic term. Contributions (i)–(iii) fully explain the dependency of the surface tension on the pressure difference, including the range relevant to nucleation experiments. Contributions (i) and (ii) can be predicted from the planar density profile. The work of formation of noncritical clusters is derived and the nucleation rate is computed. The computed nucleation rates are closer to the experimental nucleation rate results than the classical Becker-Döring theory, and also the dependence on supersaturation is better predicted.
Grand canonical Monte Carlo simulation of the adsorption isotherms of water molecules on model soot particles
Authors: Moulin F. , Picaud S. , Hoang P. N. M. , Jedlovszky P.
Published: October 2007

The grand canonical Monte Carlo method is used to simulate the adsorption isotherms of water molecules on different types of model soot particles. The soot particles are modeled by graphite-type layers arranged in an onionlike structure that contains randomly distributed hydrophilic sites, such as OH and COOH groups. The calculated water adsorption isotherm at 298K exhibits different characteristic shapes depending both on the type and the location of the hydrophilic sites and also on the size of the pores inside the soot particle. The different shapes of the adsorption isotherms result from different ways of water aggregation in or/and around the soot particle. The present results show the very weak influence of the OH sites on the water adsorption process when compared to the COOH sites. The results of these simulations can help in interpreting the experimental isotherms of water adsorbed on aircraft soot.
Classical and quantum studies of the photodissociation of a HX (X=Cl,F) molecule adsorbed on ice
Authors: Woittequand S. , Duflot D. , Monnerville M. , Pouilly B. , Toubin C. , Briquez S. , Meyer H.-D.
Published: October 2007

The photodissociation dynamics of a HX (X=Cl,F) molecule adsorbed on a hexagonal ice surface at T=0K is studied using time-dependent quantum wave packets and quasiclassical trajectories. The relevant potential energy surfaces are calculated using high-level ab initio methods. We present here two dimensional calculations for the dynamics of the hydrogen photofragment for both HCl and HF molecules. The purpose of this paper is to compare the photodissociation dynamics of the two molecules which are adsorbed on the ice surface with different equilibrium geometries. The total photodissociation cross section and the angular distribution are calculated. The comparison with classical trajectory calculations provides evidence for typical quantum effects and reveals rainbow structures.
A time-dependent wave packet quantum scattering study of the reaction HD+(v=–3;j=1)+He→HeH+(HeD+)+D(H)
Authors: Tang Xiaonan , Houchins Cassidy , Lau Kai-Chung , Ng C. Y. , Dressler Rainer A. , Chiu Yu-Hui , Chu Tian-Shu , Han Ke-Li
Published: October 2007

Time-dependent wave packet quantum scattering (TWQS) calculations are presented for HD+(v=0–3;j0=1)+He collisions in the center-of-mass collision energy (ET) range of 0.0–2.0eV. The present TWQS approach accounts for Coriolis coupling and uses the ab initio potential energy surface of Palmieri et al. [Mol. Phys. 98, 1839 (2000)]. For a fixed total angular momentum J, the energy dependence of reaction probabilities exhibits quantum resonance structure. The resonances are more pronounced for low J values and for the HeH++D channel than for the HeD++H channel and are particularly prominent near threshold. The quantum effects are no longer discernable in the integral cross sections, which compare closely to quasiclassical trajectory calculations conducted on the same potential energy surface. The integral cross sections also compare well to recent state-selected experimental values over the same reactant and translational energy range. Classical impulsive dynamics and steric arguments can account for the significant isotope effect in favor of the deuteron transfer channel observed for HD+(v<3) and low translational energies. At higher reactant energies, angular momentum constraints favor the proton-transfer channel, and isotopic differences in the integral cross sections are no longer significant. The integral cross sections as well as the J dependence of partial cross sections exhibit a significant alignment effect in favor of collisions with the HD+ rotational angular momentum vector perpendicular to the Jacobi R coordinate. This effect is most pronounced for the proton-transfer channel at low vibrational and translational energies.
Dissociation of ground and nσ* states of CF3Cl using multireference configuration interaction with singles and doubles and with multireference average quadratic coupled cluster extensivity corrections
Authors: Lucena Juracy R. , Ventura Elizete , do Monte Silmar A. , Araújo Regiane C. M. U. , Ramos Mozart N. , Fausto Rui
Published: October 2007

Extended complete active space self-consistent field (CASSCF), multireference configuration interaction with singles and doubles (MR-CISD), and multireference average quadratic coupled cluster (MR-AQCC) calculations have been performed on the ground (S0) and first excited (nσ*,S1) states of the CF3Cl molecule. Full geometry optimizations have been carried out for S0 as well as “relaxed” potential energy calculations for both states, along the C–Cl bond distance. Vertical excitation energies (ΔEvertical), dissociation energies (ΔEdiss), dissociation enthalpies (ΔHdiss), and the oscillator strength (f) have also been computed. Basis set effects, basis set superposition error (BSSE), and spin-orbit and size-extensivity corrections have also been considered. The general agreement between theoretical and available experimental results is very good. The best results for the equilibrium geometrical parameters of S0 (at MR-AQCC∕aug-cc-pVTZ+d level) are 1.762 and 1.323Å, for the C–Cl and C–F bond distances, respectively, while the corresponding experimental values are 1.751 and 1.328Å. The ∠ClCF and ∠FCF bond angles are in excellent agreement with the corresponding experimental values (110.3° and 108.6°). The best calculated values for ΔEvertical, ΔHdiss, and f are 7.63eV [at the MR-AQCC∕aug-cc-pV(T+d)Z level], 3.59eV[MR-AQCC∕aug-cc-pV(T+d)Z level+spin-orbit and BSSE corrections], and 2.74×10−3 (MR-CISD/cc-pVTZ), in comparison with the corresponding experimental values of 7.7±0.1eV, 3.68eV, and 3.12×10−3±2.50×10−4. The results concerning the potential energy curves for S0 and S1 show a tendency toward the nonoccurrence of crossing between these two states (in the intermediate region along the C–Cl coordinate), as the basis set size increases. Such tendency is accompanied by a decreasing well depth for the S1 state. Dynamic electronic correlation (especially at the MR-AQCC level) is also an important factor toward an absence of crossing along the C–Cl coordinate. Further investigations of a possible crossing using gradient driven techniques (at CASSCF and MR-CISD levels) seem to confirm its absence.
Origin of efficiency droop in GaN-based light-emitting diodes
Authors: Kim Min-Ho , Schubert Martin F. , Dai Qi , Kim Jong Kyu , Schubert E. Fred , Piprek Joachim , Park Yongjo
Published: October 2007

The efficiency droop in GaInN∕GaN multiple-quantum well (MQW) light-emitting diodes is investigated. Measurements show that the efficiency droop, occurring under high injection conditions, is unrelated to junction temperature. Furthermore, the photoluminescence output as a function of excitation power shows no droop, indicating that the droop is not related to MQW efficiency but rather to the recombination of carriers outside the MQW region. Simulations show that polarization fields in the MQW and electron blocking layer enable the escape of electrons from the MQW region and thus are the physical origin of the droop. It is shown that through the use of proper quaternary AlGaInN compositions, polarization effects are reduced, thereby minimizing droop and improving efficiency.
Fingerprint detection using full-field swept-source optical coherence tomography
Authors: Dubey Satish Kumar , Anna Tulsi , Shakher Chandra , Mehta Dalip Singh
Published: October 2007

We report the application of full-field swept-source optical coherence tomography for fingerprint detection. This system consists of a superluminescent diode as broadband light source and an acousto-optic tunable filter as wavelength-tuning device. The conventional optical coherence tomographic system was modified by coating aluminum oxide on one side of the beam splitter which is used as reference mirror and fingerprints on the glass slide as object. Low-coherence interferometry, nonmechanical scanning, and compactness are the main advantages of the proposed system over conventional fingerprint detection techniques. The present technique is noninvasive in nature and does not require any physical or chemical processing.
Strain characterization of strained silicon on insulator including the effects of rotational misalignment
Authors: Zoo Yeongseok , Theodore N. D. , Alford T. L.
Published: October 2007

High resolution x-ray diffraction (XRD) techniques were used to characterize the perpendicular and parallel strains in strained Si-on-insulator (SSOI) layers. XRD profiles generated from the crystalline SSOI layer provided a direct measurement of the layer’s strain components. Calculated strain values, such as the compressive perpendicular and tensile parallel strains, were consistent with expected values. In addition, we have demonstrated that the rotational misalignment (Δϕ) between the layer and the substrate can be incorporated within the biaxial strain equations for epitaxial layers. Strain components calculated using the modified equations showed 1%–5% increase with respect to values obtained using typical strain relations. We observed an interesting phenomenon in that the tensile parallel strains increased from 0.56% to 0.7% upon annealing. This behavior was contrary to unconstrained strain relaxation but was consistent with layer constraint and the existence of finite stresses at the Si∕SiO2 interface, resulting from the difference in coefficients of thermal expansion between Si and SiO2. Since both the overlying strained Si and underlying substrate maintained a stressed state in the buried SiO2, the compressively strained oxide retained the lattice expansion of the overlying strained Si and resulted in increasing parallel strains after annealing. These results are consistent with a balanced strain structure between the strained Si overlayer and the underlying thermally grown oxide and with the related strain evolution during heat treatment.
Thermodynamics of mono- and di-vacancies in barium titanate
Authors: Erhart Paul , Albe Karsten
Published: October 2007

The thermodynamic and kinetic properties of mono- and di-vacancy defects in cubic (para-electric) barium titanate BaTiO3 are studied by means of density-functional theory calculations. It is determined which vacancy types prevail for given thermodynamic boundary conditions. The calculations confirm the established picture that vacancies occur in their nominal charge states almost over the entire band gap. For the dominating range of the band gap the di-vacancy binding energies are constant and negative. The system, therefore, strives to achieve a state in which, under metal-rich (oxygen-rich) conditions, all metal (oxygen) vacancies are bound in di-vacancy clusters. The migration barriers are calculated for mono-vacancies in different charge states. As oxygen vacancies are found to readily migrate at typical growth temperatures, di-vacancies can be formed at ease. The key results of the present study with respect to the thermodynamic behavior of mono- and di-vacancies influence the initial defect distribution in the ferroelectric phases and therefore the conditions for aging.
Theoretical study of new superhard materials: B4C3
Authors: Gao Faming , Klug Dennis D. , Tse John S.
Published: October 2007

The structural, energetic, mechanical, and elastic properties of B4C3 polymorphs have been predicted from first-principles calculations. Results that indicate α-B4C3, β-B4C3, and pseudocubic B4C3 can be stable at ambient conditions, and their hardness is comparable to that of cubic BN. In particular, an extension of the Hall-Petch relation is established for the study of the hardness of nanocrystalline B4C3. It is predicted that the hardness of nanocrystalline β-B4C3 can approach that of diamond. The calculated energetic shows that the α- and β-B4C3 phases could potentially be prepared under high pressure and are promising superhard materials. The calculated band structure of β-B4C3 indicates that it may be transparent.
An improved process for fabricating high-mobility organic molecular crystal field-effect transistors
Authors: Micolich A. P. , Bell L. L. , Hamilton A. R.
Published: October 2007

In this paper we present an improved process for producing elastomer transistor stamps and high-mobility organic field-effect transistors (FETs) based on semiconducting acene molecular crystals. In particular, we have removed the need to use a silanized Si wafer for curing the stamps and to handle a fragile micron thickness polydimethylsiloxane (PDMS) insulating film and laminate it, bubble-free, against the PDMS transistor stamp. We find that despite the altered design, rougher PDMS surface, and lamination and measurement of the device in air, we still achieve electrical mobilities of the order of 10cm2∕Vs, comparable to the current state of the art in organic FETs. Our device shows hole conduction with a threshold voltage of the order of −9V, which corresponds to a trap density of 1.4×1010cm−2.
A hydrogen sensor based on tunneling between palladium clusters
Authors: van Lith J. , Lassesson A. , Brown S. A. , Schulze M. , Partridge J. G. , Ayesh A.
Published: October 2007

We describe nanocluster based tunneling sensors for detecting hydrogen. Pd clusters with diameters ranging from 3.5to6nm are deposited between a pair of contacts until a predetermined resistance between the contacts is obtained. We demonstrate that the conduction through the cluster film is dominated by tunneling gaps. Upon exposure to hydrogen, the clusters expand, reducing the average size of the gaps and reducing the measured resistance. The sensor response as a function of external hydrogen pressure is described, for different cluster sizes and different operating temperatures, by a simple model with a single physically meaningful fitting parameter.
An ultrathin (∼100μm thick) flexible light plate fabricated using self-alignment and lift-off techniques
Authors: Chiang Cheng-Chung , Wuu Dong-Sing , Horng Ray-Hua
Published: October 2007

An ultrathin (∼100μm thick) flexible light plate was designed and fabricated on a parylene template using a combination of self-alignment and lift-off techniques. The solid-state InGaN light-emitting diodes (LEDs) (λp=465nm) was used as the light source to overcome the problem of conventional organic light-emitting devices which require perfect encapsulation against the permeation of water and oxygen. After the sidewalls of LEDs were passivated by the photodefinable polymer, the LED chip array can be further sandwiched by the indium-tin oxide (ITO) and Al electrodes to form a thin-film package with all the processing temperatures below 250°C. The ITO-coated transparent parylene template can be peeled off from the glass carrier after forming the ultrathin LED light plate. The flexible light plates present no damage even after they were flexed 1000 times around a 3-cm-diameter cylinder. The present self-alignment or mask-less process is a very promising approach to flexible backlight applications.
Noise and scale effects on the signal-to-noise ratio in magnetoelectric laminate sensor/detection units
Authors: Xing Zengping , Li Jiefang , Viehland D.
Published: October 2007

We have investigated the output noise level (Eno) and signal-to-noise ratio (SNR) for various magnetoelectric (ME) laminate composites. Our findings show (i) that Eno is nearly independent of materials couple or operational mode and practically determined by the laminate capacitance C and (ii) that the SNR has a scale effect, where it is limited by the volume (V) of the piezoelectric layer. Relations between SNR, V, and the magnetoelectric coefficient (αME) give insights into how to construct ME sensors with enhanced sensitivity to small magnetic variation.
Soft magnetism, magnetostriction, and microwave properties of FeGaB thin films
Authors: Lou J. , Insignares R. E. , Cai Z. , Ziemer K. S. , Liu M. , Sun N. X.
Published: October 2007

A series of (Fe100−yGay)1−xBx (x=0–21 and y=9–17) films were deposited; their microstructure, soft magnetism, magnetostrictive behavior, and microwave properties were investigated. The addition of B changes the FeGaB films from polycrystalline to amorphous phase and leads to excellent magnetic softness with coercivity <1Oe, high 4πMs, self-biased ferromagnetic resonance (FMR) frequency of 1.85GHz, narrow FMR linewidth (X band) of 16–20Oe, and a high saturation magnetostriction constant of 70ppm. The combination of these properties makes the FeGaB films potential candidates for tunable magnetoelectric microwave devices and other rf/microwave magnetic device applications.
Wetting behavior of molten In–Sn alloy on bulk amorphous and crystalline Cu40Zr44Al8Ag8
Authors: Ma G. F. , Zhang H. F. , Li H. , Hu Z. Q.
Published: October 2007

Using the sessile-drop method, the wettability of the molten In–Sn alloy on bulk amorphous and crystalline Cu40Zr44Al8Ag8 alloy was studied at different temperatures. It was found that the equilibrium contact angle of In–Sn alloy melt on bulk amorphous substrate was smaller than that of the crystalline one. An intermetallic compound existed at the interface of In–Sn alloy on amorphous Cu40Zr44Al8Ag8, while no intermediate reaction layer was formed at the interface of In–Sn alloy on crystalline Cu40Zr44Al8Ag8 in the temperature range studied.
Series resistance imaging of solar cells by voltage dependent electroluminescence
Authors: Hinken David , Ramspeck Klaus , Bothe Karsten , Fischer Bernhard , Brendel Rolf
Published: October 2007

This letter introduces a method based on electroluminescence imaging to determine mappings of the local series resistance of large area semiconductor devices such as solar cells. The method combines the local electroluminescence emission Φi(U) and its derivative Φi′(U) with respect to the applied voltage U. The combined analysis of these two quantities yields the local series resistance Rise and proves the physical validity of the used current transport model and thus the physical relevance of the determined Rise value. The method is verified on a monocrystalline silicon solar cell with local shunts and local series resistance problems.
Enhanced visibility of graphene: Effect of one-dimensional photonic crystal
Authors: Chang Kai , Liu J. T. , Xia J. B. , Dai N.
Published: October 2007

We investigate theoretically the light reflectance of a graphene layer prepared on the top of one-dimensional Si∕SiO2 photonic crystal (1DPC). It is shown that the visibility of the graphene layers is enhanced greatly when 1DPC is added, and the visibility can be tuned by changing the incident angle and light wavelengths. This phenomenon is caused by the absorption of the graphene layer and the enhanced reflectance of the 1DPC.
Ultrawide range dielectric spectroscopy of BaTiO3-based perovskite dielectrics
Authors: Tsurumi T. , Li J. , Hoshina T. , Kakemoto H. , Nakada M. , Akedo J.
Published: October 2007

Ultrawide range dielectric spectra from the kilohertz to terahertz range of BaTiO3 (BT), Ba(Zr0.25Ti0.75)O3 (BZT), (Ba0.6Sr0.4)TiO3 (BST), and SrTiO3 ceramics were presented by analyzing dielectric permittivity and IR reflectivity data. It was found that the permittivity of the ST was determined only by the ionic polarization while that of the BT was determined by the ionic polarization as well as the dipole polarization due to the domain contribution. The high permittivity of the BZT ceramics was attributed to the dipole polarization of polar nanoregions in the relaxors. The dipole and ionic polarizations overlapped in the BST.
Nanoparticle films as sensitive strain gauges
Authors: Herrmann J. , Müller K.-H. , Reda T. , Baxter G. R. , Raguse B. , de Groot G. J. J. B. , Chai R. , Roberts M. , Wieczorek L.
Published: October 2007

We demonstrate that thin films consisting of cross-linked nanoparticle aggregates function as highly sensitive strain gauges. The sensors exploit the exponential dependence of the interparticle tunnel resistance on the particle separation. Their sensitivity (gauge factor) is two orders of magnitude higher than that of conventional metal foil gauges and rivals that of state-of-the-art semiconductor gauges. We describe the strain gauge behavior in a tunneling model that predicts the dependence of the gauge factor on several parameters, in particular, the nanoparticle size, the interparticle separation gap, and the conductance of the linker molecules.
Influence of electromechanical boundary conditions on elasticity of zinc oxide nanowires
Authors: Desai A. V. , Haque M. A.
Published: October 2007

Uniaxial tensile experiments were performed on single crystal zinc oxide nanowires with a custom microfabricated tool. The measured Young’s modulus is about 30%—40% of the bulk value for specimens with 200–400nm in diameter, which cannot be explained with classical elasticity formulations. We discuss this anomaly in light of the enhanced electromechanical coupling due to static mechanical and isolated electrical boundary conditions that can significantly contribute to the softening of the material, irrespective of the length scale.