bluuebunny/crossref_metadata_2025 huggingface dataset:
Using partial site aggregation to reduce bias in random utility travel cost models
Authors: Lupi Frank , Feather Peter M.
Published: February 2004

We propose a “partial aggregation” strategy for defining the recreation sites that enter choice sets in random utility models. Under the proposal, the most popular sites and sites that will be the subject of policy analysis enter choice sets as individual sites while remaining sites are aggregated into groups of similar sites. The scheme balances the desire to include all potential substitute sites in the choice sets with practical data and modeling constraints. Unlike fully aggregate models, our analysis and empirical applications suggest that the partial aggregation approach reasonably approximates the results of a disaggregate model. The partial aggregation approach offers all of the data and computational advantages of models with aggregate sites but does not suffer from the same degree of bias as fully aggregate models.
Seasonal runoff forecast for northern South America: A statistical model
Authors: Uvo Cíntia Bertacchi , Graham Nicholas E.
Published: February 2004

The variability of water availability in the Amazon Basin is highly related to the sea surface temperature (par;SST) pattern over the Atlantic and the Pacific Oceans. The possibility of forecasting this variability one season in advance is a necessity for the correct management of water in the region for water supply, energy production, and flood control. Here we present the development of a statistical model to forecast seasonal discharge, one season in advance, at 12 sites in northeastern South America from Pacific and Atlantic Ocean SSTs. Results show that the model has a better capacity to forecast discharge at some sites than at others and that different oceanic regions have different influences over the basins. Discharge at subbasins in the northern part of the Amazon Basin are better forecasted from Pacific Ocean SSTs while discharges at subbasins in the southern part are better forecasted from Atlantic Ocean SSTs.
Systemic anti‐inflammatory fibrosis suppression in threatened trabeculectomy failure
Authors: Vote Brendan , Fuller J Robert , Bevin Tui H , Molteno Anthony CB
Published: February 2004

Purpose: To provide a rationale for the use of systemic anti‐inflammatory fibrosis suppression in the postoperative management of threatened early trabeculectomy bleb failure.

Methods: A review of the literature and of the authors’ own experiences was conducted.

Results: The most important cause of persistent elevation of intraocular pressure after trabeculectomy is unduly marked or persistent inflammation with deposition of fibrous tissue, which prevents the formation of an adequately draining bleb. It was found that a clinically useful degree of suppression of bleb inflammation and fibrosis can be obtained with a 4−6 week course of the combined systemic administration of prednisone (10 mg t.i.d.), a non‐steroidal anti‐inflammatory agent (e.g. diclofenac 100 mg SR daily) and colchicine (0.25 mg or 0.3 mg t.i.d.), which was termed anti‐inflammatory fibrosis suppression. Topical atropine 1% t.i.d. and adrenaline 1% t.i.d. eye drops can also be considered in addition to routine postoperative topical steroids.

Conclusions: Despite advances in surgical techniques and methods to control fibrosis, anti‐inflammatory fibrosis suppression is a valuable tool to have available in the post­operative period for management of trabeculectomies that threaten failure. This regime produces a diffuse bleb, which has a very low risk of late infection or bleb perforation. It is recommend that this regime be added to the list of therapies that are considered when clinical features suggestive of a failing bleb are confronted early in the post­operative course.
Clinical Case Notes
Authors: Sharma Vidushi , Kashyap Seema , Betharia Subhash M , Gupta Somesh , Pathak Harish
Published: February 2004

Lipoid proteinosis is a rare disorder seen even more rarely by ophthalmologists. The interesting clinical and histopathological features of this disease are described in a brother and sister who presented predominantly with lid lesions, without any systemic complaints. Knowledge of the typical lid lesions may help to diagnose this disorder.
Attenuation of MPTP‐induced dopaminergic neurotoxicity by TV3326, a cholinesterase‐monoamine oxidase inhibitor
Authors: Sagi Yotam , Weinstock Marta , Youdim Moussa B. H.
Published: February 2004

(R)‐[(N‐propargyl‐(3R) aminoindan‐5‐yl) ethyl methyl carbamate] (TV3326) is a novel cholinesterase and brain‐selective monoamine oxidase (MAO)‐A/‐B inhibitor. It was developed for the treatment of dementia co‐morbid with extra pyramidal disorders (parkinsonism), and depression. On chronic treatment in mice it attenuated striatal dopamine depletion induced by MPTP and prevented the reduction in striatal tyrosine hydroxylase activity, like selective B and non‐selective MAO inhibitors. TV3326 preferentially inhibits MAO‐B in the striatum and hippocampus, and the degree of MAO‐B inhibition correlates with the prevention of MPTP‐induced dopamine depletion. Complete inhibition of MAO‐B is not necessary for full protection from MPTP neurotoxicity. Unlike that seen after treatment with other MAO‐A and ‐B inhibitors, recovery of striatal and hippocampal MAO‐A and ‐B activities from inhibition by TV3326 did not show first‐order kinetics. This has been attributed to the generation of a number of metabolites by TV3326 that cause differential inhibition of these enzymes. Inhibition of brain MAO‐A and ‐B by TV3326 resulted in significant elevations of dopamine, noradrenaline and serotonin in the striatum and hippocampus. This may explain its antidepressant‐like activity, resembling that of moclobemide in the forced‐swim test in rats.
Protective effects of the antioxidant selenium on quinolinic acid‐induced neurotoxicity in rats:in vitroandin vivostudies
Authors: Santamaría Abel , Salvatierra‐Sánchez Raquel , Vázquez‐Román Beatriz , Santiago‐López Dario , Villeda‐Hernández Juana , Galván‐Arzate Sonia , Jiménez‐Capdeville María E. , Ali Syed F.
Published: February 2004

Quinolinic acid (QUIN), a well known excitotoxin that produces a pharmacological model of Huntington's disease in rats and primates, has been shown to evoke degenerative events in nerve tissue via NMDA receptor (NMDAr) overactivation and oxidative stress. In this study, the antioxidant selenium (as sodium selenite) was tested against different markers of QUIN‐induced neurotoxicity under bothin vitroandin vivoconditions. In thein vitroexperiments, a concentration‐dependent effect of selenium was evaluated on the regional peroxidative action of QUIN as an index of oxidative toxicity in rat brain synaptosomes. In thein vivoexperiments, selenium (0.625 mg per kg per day, i.p.) was administered to rats for 5 days, and 2 h later animals received a single unilateral striatal injection of QUIN (240 nmol/µL). Rats were killed 2 h after the induction of lesions with QUIN to measure lipid peroxidation and glutathione peroxidase (GPx) activity in striatal tissue. In other groups, the rotation behavior, GABA content, morphologic alterations, and the corresponding ratio of neuronal damage were all evaluated as additional markers of QUIN‐induced striatal toxicity 7 days after the intrastriatal injection of QUIN. Selenium decreased the peroxidative action of QUIN in synaptosomes both from whole rat brain and from the striatum and hippocampus, but not in the cortex. A protective concentration‐dependent effect of selenium was observed in QUIN‐exposed synaptosomes from whole brain and hippocampus. Selenium pre‐treatment decreased thein vivolipid peroxidation and increased the GPx activity in QUIN‐treated rats. Selenium also significantly attenuated the QUIN‐induced circling behavior, the striatal GABA depletion, the ratio of neuronal damage, and partially prevented the morphologic alterations in rats. These data suggest that major features of QUIN‐induced neurotoxicity are partially mediated by free radical formation and oxidative stress, and that selenium partially protects against QUIN toxicity.
Estimating entropies from molecular dynamics simulations
Authors: Peter Christine , Oostenbrink Chris , van Dorp Arthur , van Gunsteren Wilfred F.
Published: February 2004

While the determination of free-energy differences by MD simulation has become a standard procedure for which many techniques have been developed, total entropies and entropy differences are still hardly ever computed. An overview of techniques to determine entropy differences is given, and the accuracy and convergence behavior of five methods based on thermodynamic integration and perturbation techniques was evaluated using liquid water as a test system. Reasonably accurate entropy differences are obtained through thermodynamic integration in which many copies of a solute are desolvated. When only one solute molecule is involved, only two methods seem to yield useful results, the calculation of solute–solvent entropy through thermodynamic integration, and the calculation of solvation entropy through the temperature derivative of the corresponding free-energy difference. One-step perturbation methods seem unsuitable to obtain entropy estimates.
Intermolecular interactions in solution: Elucidating the influence of the solvent
Authors: Gora Robert W. , Bartkowiak Wojciech , Roszak Szczepan , Leszczynski Jerzy
Published: February 2004

A new approach for the analysis of intermolecular interactions in a solution is proposed. The changes in the interaction energy components due to the solvent effects are estimated on the basis of the interaction energy calculated in the presence of the electric field induced in a polarizable medium, or in the field of the effective fragment potentials. Obtained results indicate a significant increase in stabilization resulting from electrostatic interactions as a result of the cooperative interactions between interacting subsystems and solvent molecules.
High resolution measurements of kinetic energy release distributions of neon, argon, and krypton cluster ions using a three sector field mass spectrometer
Authors: Głuch K. , Matt-Leubner S. , Michalak L. , Echt O. , Stamatovic A. , Scheier P. , Märk T. D.
Published: February 2004

Using a newly constructed three sector field mass spectrometer (resulting in a BE1E2 field configuration) we have measured the kinetic energy release distributions of neon, argon, and krypton cluster ions. In the present study we used the first two sectors, B and E1, constituting a high resolution mass spectrometer, to select the parent ions in terms of mass, charge, and energy, and studied the decay of those ions in the third field free region. Due to the improved mass resolution we were able to extend earlier studies carried out with a two sector field machine, where an upper size limit arose from the fact that several isotopomers contribute to a decaying parent ion beam when the cluster size exceeds a certain value. Furthermore we developed a new data analysis. It allows us to model also fragment ion peaks that are a superposition of different decay reactions and thus we can determine the average kinetic energy release for all decay reactions of a given cluster ion. In a further step we used these results to determine the binding energies of cluster ions Rgn (n⩾10) by applying finite heat bath theory. The smaller sizes have not been included in this analysis, because the validity of finite heat bath theory becomes questionable below n≈10. The present average kinetic energy releases and binding energies are compared with other experiments and various calculations.
The surface temperature dependence of the inelastic scattering and dissociation of hydrogen molecules from metal surfaces
Authors: Wang Z. S. , Darling G. R. , Holloway S.
Published: February 2004

High-dimensional, wave packet calculations have been carried out to model the surface temperature dependence of rovibrationally inelastic scattering and dissociation of hydrogen molecules from the Cu(111) surface. Both the molecule and the vibrating surface are treated fully quantum-mechanically. It is found, in agreement with experimental data, that the surface temperature dependence of a variety of dynamical processes has an Arrhenius form with an activation energy dependent on molecular translational energy and on the initial and final molecular states. The activation energy increases linearly with decreasing translational energy below the threshold energy. Above threshold the behavior is more complex. A quasianalytical model is proposed that faithfully reproduces the Arrhenius law and the translational energy dependence of the activation energy. In this model, it is essential to include quantized energy transfer between the surface and the molecule. It further predicts that for any process characterized by a large energy barrier and multiphonon excitation, the linear change in activation energy up to threshold has slope-1. This explains successfully the universal nature of the unit slope found experimentally for H2 and D2 dissociation on Cu.
Molecular dynamics study of the surface tension of a binary immiscible fluid
Authors: Simmons V. , Hubbard J. B.
Published: February 2004

The planar interface between two liquids having two degrees of affinity to mix has been studied by molecular dynamics simulations. The surface tension is calculated from the normal, PN, and transverse, PT, components of the pressure tensor P for a wide range of temperatures. An unusual increase in surface tension with increasing temperature is attributed to a pressure induced void transfer mechanism that is justified by basic thermodynamic arguments. This effect is diminished on the addition of a modest attractive potential between the two species, and there is a turnover point at higher temperatures beyond which the surface tension decreases with increasing temperature. An order parameter is identified as the gradient of the mole fraction distribution through the interfacial region. An additional effect is the dramatic inversion of the kinetic and potential contributions to the PN profile as the temperature is varied. It is found that a commonly used approximation for P, the Irving–Kirkwood 1 or IK1 method, results in a relatively modest unphysical variability in PN that weakly violates the condition of local mechanical stability. However, this artifact does not prevent the IK1 method from producing an interfacial tension which is nearly identical to that derived from the complete IK formula with no additional approximations.
Coupled-cluster singles and doubles for extended systems
Authors: Hirata So , Podeszwa Rafał , Tobita Motoi , Bartlett Rodney J.
Published: February 2004

Coupled-cluster theory with connected single and double excitation operators (CCSD) and related approximations, such as linearized CCSD, quadratic configuration interaction with single and double excitation operators, coupled-cluster with connected double excitation operator (CCD), linearized CCD, approximate CCD, and second- and third-order many-body perturbation theories, are formulated and implemented for infinitely extended one-dimensional systems (polymers), on the basis of the periodic boundary conditions and distance-based screening of integrals, density matrix elements, and excitation amplitudes. The variation of correlation energies with the truncation radii of short- and long-range lattice sums and with the number of wave vector sampling points in the first Brillouin zone is examined for polyethylene, polyacetylene, and polyyne, and is shown to be a function of the degree of π-electron conjugation or the fundamental band gaps. The t2 and t1 amplitudes in the atomic orbital (AO) basis are obtained by first computing the t amplitudes in the Bloch-orbital basis and subsequently back-transforming them into the AO basis. The plot of these AO-based t amplitudes as a function of unit cells also indicates that the t2 amplitudes of polyacetylene and polyyne exhibit appreciably slower decay than those of polyethylene, although the asymptotic decay behavior is invariably 1/r3. The AO-based t1 amplitudes appear to correlate strongly with the electronic structure, and they decay seemingly exponentially for polyethylene whereas they stay at a constant magnitude across the seventh nearest neighbors of polyacetylene and polyyne, which attests to far reaching effects of nondynamical electron correlation mediated by orbital rotation. Nonetheless, the unit cell contributions to the correlation energies taper below 10−6 hartree after 15 Å for all three polymers. The basis set dependence of the decay behavior of t2 amplitudes is also examined for linear hydrogen fluoride polymer (HF)∞ and linear beryllium polymer (Be)∞ employing the STO-3G, 6-31G, and 6-31G* basis sets, and proves to be rather small.
Electric-field-induced g/u mixing of the E0g+(3P2) and D0u+(3P2) ion-pair states of jet-cooled I2 observed using optical triple resonance
Authors: Sjödin A. Marica , Ridley Trevor , Lawley Kenneth P. , Donovan Robert J.
Published: February 2004

Electric-field-induced electronic state g/u mixing of nearly isoenergetic rovibrational levels of the E0g+(3P2) and D0u+(3P2) ion-pair states of I2 has been observed using optical triple resonance combined with resonance ionization. Detectable mixing with applied fields of 1 kV/cm occurs over a range of energy level separations of ⩽0.3 cm−1.
Phase separation in mixtures of Yukawa and charged Yukawa particles from Gibbs ensemble Monte Carlo simulations and the mean spherical approximation
Authors: Kristóf Tamás , Boda Dezsö , Henderson Douglas
Published: February 2004

The phase equilibrium of mixtures of Yukawa and charged Yukawa particles is studied by means of Gibbs ensemble Monte Carlo (GEMC) simulation method and the mean spherical approximation (MSA). The strength of the Coulomb energy compared to that of the Yukawa attraction is characterized by a coupling constant. For low coupling constants a classical vapor–liquid phase separation appears with a good agreement between GEMC and the MSA. For high coupling constant, a phase separation between a salt poor and a salt rich phase occurs that resembles the phase equilibrium behavior of the solvent primitive model.
Organic field effect transistors based on modified oligo-p-phenylevinylenes
Authors: Gorjanc T. C. , Lévesque I. , D’Iorio M.
Published: February 2004

We report on an organic field effect transistor device based on a modified oligomer oligo-p-phenylevinylene, 1,4-bis[4-(4-octylphenyl)styryl]-benzene. The effect of growth temperature on the morphology of the organic films and their electrical properties was investigated. Substrates coated with hexamethyldisilazane prior to organic film deposition showed improved electrical characteristics, but a negligible difference with respect to film morphology. A maximum hole mobility of μ=0.12 cm2/V s with an on–off current ratio Ion/off>106 were measured in films deposited at a substrate temperature of 150 °C.
Rimming flows with an axially varying viscosity
Authors: Jin Bo , Acrivos Andreas
Published: February 2004

We consider rimming flows in the presence of an axially varying viscosity but with inertia and surface tension effects being negligible. First, we find that a modified lubrication analysis (MLA) presented earlier [M. Tirumkudulu and A. Acrivos, Phys. Fluids 13, 14 (2001)] can predict accurately the thickness of the film profile over the whole range of Ω, the angular velocity of the rotating cylinder, even when the fill fraction F is as large as 0.36, where the film is far from thin. This is also the case with the analysis due to Benjamin et al. [T. B. Benjamin, W. G. Pritchard, and S. J. Tavener (preprint, 1993)] except that, here, F cannot exceed 0.29. On the basis of this MLA, we propose a model to describe the three-dimensional free surface shape of rimming flows with an axially varying viscosity and show that the free surface profiles thereby obtained agree with those determined by solving numerically the three-dimensional Stokes equations. In the accompanying article, this model will be used as the basis of a stability analysis which will explain the origin of the observed particle band formation in rimming flows of suspensions containing neutrally buoyant particles [M. Tirumkudulu, A. Mileo, and A. Acrivos, Phys. Fluids 12, 1615 (2000)].
Dynamic stretching of a planar liquid bridge
Authors: Mehring C. , Xi J. , Sirignano W. A.
Published: February 2004

A thin incompressible viscous planar free liquid film in a void and under zero gravity is analyzed by means of a reduced-dimension (lubrication) approach. Linear analysis focuses on films with harmonic modulations in the axial film velocity enforced at the ends of the planar bridge. Effects of changes in the problem parameters on the overall distortion characteristics of the film are discussed. Nonlinear film distortion and break-up are investigated for the case of temporally increasing velocity at the end of the film resulting in continuous film stretching eventually leading to film rupture. Implementation of the employed numerical model is validated for the linear limit by comparison with the analytical linear solutions and for harmonically modulated film-end velocities. Within the nonlinear analysis of the continuously stretched film bridge, several distinct film topologies are identified depending on liquid Weber number and Reynolds number, i.e., the magnitude of the stretching rate (end velocity) compared to signal propagation rates through the liquid via capillary waves and viscous action. That is, the Weber number is the square of the ratio of stretching rate to capillary wave velocity while the Reynolds number is the ratio of stretching rate to the characteristic viscous velocity. Here, film topology is typically characterized by three distinct regions, i.e., a film wedge forming at the pulling end(s), the film center region and a transition region. The size and shape of these regions greatly depend on the particular case under investigation. Film distortion characteristics observed for continuously compressed planar films conform with observations made by other authors for the similar case of contracting free liquid films.
Effect of thermal variations on the Knudsen forces in the transitional regime
Authors: Lereu A. L. , Passian A. , Warmack R. J. , Ferrell T. L. , Thundat T.
Published: February 2004

When objects are maintained at different temperatures and separated by distances of the order of the mean free path of the surrounding host gas molecules, gas kinetic forces called Knudsen forces may be involved. The understanding of this effect may result in some improvements in microelectromechanical devices and measurement systems. We present the thermal dependence of these forces in the transitional regime for different gases. In this mode, the Knudsen effect can be significant and, therefore, become a problem in microscale devices. For this study, a silicon microcantilever, mounted close to a substrate, is used and changes in temperature are observed by measuring bending of the microcantilever.
Force on a sphere via the generalized reciprocal theorem
Authors: Leshansky A. M. , Brady J. F.
Published: February 2004

An approach based on the generalized reciprocal theorem is presented to derive the well-known result for the drag force exerted on a rigid sphere translating in a viscous fluid in an arbitrary manner. The use of generalized reciprocal theorem allows one to bypass the calculation of stress distribution over the particle surface in order to compute the force.
The quasi-cylindrical description of submerged laminar swirling jets
Authors: Revuelta Antonio , Sánchez Antonio L. , Liñán Amable
Published: February 2004

The quasi-cylindrical approximation is used to describe numerically the structure of a submerged swirling jet for subcritical values of the swirl ratio S⩽Sc. The emerging flow structure is affected by the swirling motion, which enhances the entrainment rate of the jet and induces an adverse pressure gradient that reduces its momentum flux. The effect is more pronounced as the swirl ratio S is increased, yielding for sufficiently large values of S a jet with an annular structure. The integration describes the smooth transition towards the far-field self-similar solution for all values of S smaller than a critical value S=Sc, at which the numerical integration fails to converge at a given downstream location. The comparisons with previous experimental results confirm the correspondence between the onset of vortex breakdown and the failure of the quasi-cylindrical approximation.
Degradation in blue-emitting conjugated polymer diodes due to loss of ohmic hole injection
Authors: Khan Rizwan U. A. , Bradley Donal D. C. , Webster Matthew A. , Auld James L. , Walker Alison B.
Published: February 2004

We report studies of the evolution of the hole injection and transport characteristics of fluorene-based polymer diodes subjected to electrical stressing. Dark injection (DI) transient measurements show that the polyethylenedioxythiophene/polystyrenesulphonate (PEDOT:PSS)-topolymer contact is initially ohmic, but as stressing proceeds, the transients shift to longer times and lose their characteristic temporal profile. A comparison with time-of-flight transient photocurrent measurements led us to conclude that the DI transient is modified by a loss of ohmic injection. Electroabsorption measurements show a drastic reduction in the built-in potential from 1.4 V to 0.6 V. Device simulation shows this to be consistent with a change in the PEDOT:PSS work function, and the introduction of an interfacial resistance at the PEDOT:PSS-to-polymer contact.
Electrical measurements on praseodymium metal to 179 GPa using designer diamond anvils
Authors: Velisavljevic Nenad , MacMinn Kirkland M. , Vohra Yogesh K. , Weir Samuel T.
Published: February 2004

The electrical and magnetic properties of light rare-earth metals and trans-plutonium actinide metals are of interest to study the f-shell delocalization phenomenon under high compressions. Using designer diamond anvil technology, sensitive electrical four-probe measurements were performed on light rare-earth metal praseodymium to pressures of 179 GPa at room temperature. We document an average drop in resistivity of 53% at a pressure of 20 GPa in a series of high-pressure experiments. This large drop in resistivity provides the strongest experimental evidence yet for the view that the 20 GPa phase transition is indeed associated with f-electron delocalization. Our results show that the precise electrical measurements are ideally suited for f-delocalization studies, especially where structural data do not provide clear evidence of this transition.
Propagation loss measurement for surface plasmon-polariton modes at metal waveguides on semiconductor substrates
Authors: Goto Touichiro , Katagiri Yoshitada , Fukuda Hiroshi , Shinojima Hiroyuki , Nakano Yoshiaki , Kobayashi Ikutaro , Mitsuoka Yasuyuki
Published: February 2004

Propagation losses were measured for surface plasmon-polariton (SPP) modes at metal waveguides on semiconductor substrates. The waveguides are simple strips of Au or Al deposited on InP substrates or 300-nm-thick SiO2 film covering the InP substrates. We used a direct method that can clearly discriminate SPP modes in vidicon-camera images, thereby allowing quantitative measurements. The loss coefficients measured at a wavelength of 1.55 μm were, as predicted by theory, in the range of 8.5–17 dB/mm, which shows the waveguides are feasible for practical applications.
Optical spectroscopy of single, site-selected, InAs/InP self-assembled quantum dots
Authors: Chithrani D. , Williams R. L. , Lefebvre J. , Poole P. J. , Aers G. C.
Published: February 2004

We present optical spectroscopy measurements on a single InAs/InP quantum dot emitting around λ=1.55 μm. The dot is produced using a nanotemplate deposition technique that allows precise a priori control of quantum dot position and electronic configuration. Clear evidence of excitonic shell structure and many-body renormalization effects are observed.
Study on the strength and elongation of free-standing Al beams for microelectromechanical systems applications
Authors: Lee Hoo-Jeong , Zhang Ping , Bravman John C.
Published: February 2004

This letter reports a study on the strength and elongation of Al in the form of micrometer-scale, free-standing beams. We fabricated microtensile specimens of Al beams by using a simple micromachining process and carried out uniaxial tensile tests in a mechanical test system with a piezoelectric actuator that controls the displacement as small as a few nanometers. The results of the tests suggest that, if the grain size remains the same, the yield strength does not change with the thickness whereas the elongation varies with it very sensitively. In addition, the yield strength of the Al beams is found to be much smaller than that of Al films bonded onto Si substrates but somewhat larger than that of the bulk Al estimated for a comparable grain size from the Hall–Petch relation.
Investigation of the mean passive scalar field in zero-net-mass-flux jets in cross-flow using planar-laser-induced fluorescence
Authors: Gordon M. , Cater J. E. , Soria J.
Published: February 2004

Planar-laser-induced fluorescence (PLIF) measurements have been used to investigate the mean passive scalar field in round zero-net-mass-flux jets in cross-flow (ZNMF-JICF). The ZNMF-JICF are formed in a working fluid without net transfer of mass across the system boundary during one period of oscillation. Ensemble-averaged PLIF images of sixteen different ZNMF-JICF are studied and compared. Two distinct flow regimes are observed; single trajectory ZNMF-JICF and multiple trajectory ZNMF-JICF. Single trajectory ZNMF-JICF demonstrate mixing of the bulk of the fluid outside the upstream boundary layer, while multiple trajectory ZNMF-JICF can penetrate more deeply into the ambient cross-flow. A critical Strouhal number of Stcrit=0.02 was found for the generation apparatus that can be used to distinguish between these two regimes. The penetration of the single trajectory ZNMF-JICF does not exhibit the same dependence on velocity ratio observed in the measurements of continuous JICF.
NEW METHOD OF OBSERVING ELECTRON PENETRATION PROFILES IN SOLIDS
Authors: Hatzakis M.
Published: February 2004

Electron penetration and scattering in solids can be measured by electron beam exposure of a positive electron resist. The beam profile is obtained by exposing a long line of controlled width in a thick layer of poly-(methyl methacrylate) resist. The cross section of the developed line which can be examined in the scanning electron microscope represents the beam density profile.
HOLOGRAPHIC STORAGE IN DOPED BARIUM SODIUM NIOBATE (Ba2NaNb5O15)
Authors: Amodei J. J. , Staebler D. L. , Stephens A. W.
Published: February 2004

This paper describes the results obtained using doped crystals of Ba2NaNb5O15 for phase holographic storage. Very short-lived holograms with less than 1% diffraction efficiencies were obtained in nominally pure crystals. Doping with Fe and Mo yields holograms with much longer decay times and diffraction efficiencies of 67% in a 0.32-cm-thick crystal. The energy density required to reach 40% diffraction efficiency was 6 J/cm2.
FORMATION OF SiC IN SILICON BY ION IMPLANTATION
Authors: Borders J. A. , Picraux S. T. , Beezhold W.
Published: February 2004

The production of SiC in single-crystal silicon by C12+ implantation to fluences of 1017/cm2-side followed by annealing has been detected by the characteristic infrared absorption of the TO phonon of SiC. Immediately following room-temperature implantation and after 20-min isochronal anneals up to temperatures ≤ 825°C, a previously unreported broad absorption band centered at 700–725 cm−1 is observed. SiC is observed to form at temperatures ≈ 850°C. For anneals ≥ 850°C, most of the broad absorption band shifts into the SiC-TO phonon absorption band. From the infrared absorption measurements together with the results of He+ backscattering, we conclude that about half of the implanted atoms are incorporated into microregions of SiC which are surrounded by bulk silicon.
SENSITIVE TECHNIQUE FOR STUDYING ION-IMPLANTATION DAMAGE
Authors: EerNisse E. P.
Published: February 2004

The lattice damage created by ion implantation is investigated by measuring the stresses lateral to the implanted surface which are caused by the specific volume expansion inherent with lattice damage. A cantilever beam-shaped sample is implanted on one side and the position of the free end is monitored by measuring the capacitance between it and a fixed electrode. Results are presented for various 220-keV noble ion implants into Si. A new region is observed at very low fluences (1011 cm−2 of 20Ne), where damage is introduced linearly with fluence. The distinct maximum in the stress which appears at higher fluences is attributed to an elastic-plastic transformation.
AN EPR STUDY OF A SMECTIC C LIQUID CRYSTAL: A NEW METHOD FOR DETERMINING THE TILT ANGLE
Authors: Gelerinter Edward , Fryburg George C.
Published: February 2004

We have aligned the liquid crystal molecules of 4, 4′-di-n-heptyloxyazoxybenzene in the smectic C mesophase by means of a magnetic field. With the aid of a paramagnetic probe, we have studied the effect of rotation of the aligned sample in the magnetic field of the EPR spectrometer. Interpretation of the results enables us to determine the tilt angle of the liquid crystal, and to predict that smectic C liquid crystals would not lend themselves to NMR orientation studies because of molecular reorientations.
A TRANSVERSE FLOW cw HCl CHEMICAL LASER
Authors: Glaze James A. , Finzi Jack , Krupke William F.
Published: February 2004

A cw HCl chemical laser utilizing fast flow and transverse geometry is described. The reaction Cl + HI → HCl + I + 32 kcal/mole is used to achieve gains in excess of 2%/cm. Up to 70 mW of multiline power on several P branch lines of the 2→1 and 1→0 vibrational transitions has been observed.
QUANTITATIVE ANALYSIS OF THE DEPENDENCE OF CO2 LASER PERFORMANCE ON ELECTRIC DISCHARGE PROPERTIES
Authors: Fowler M. C.
Published: February 2004

Reported values of electron-molecule energy transfer rate constants are combined with atom/molecule-molecule and radiative energy transfer rate constants in an analysis of the conversion of electron energy to optical energy at 10.6μ in an electric discharge containing CO2, N2, and He. The small-signal gain and the saturation intensity are calculated as functions of the electron density and gas temperature in the discharge. The calculated values of these quantities are consistent with experimentally determined values. The detrimental effect of high gas temperature on small-signal gain is found to be the single most important factor influencing the efficiency of the discharge plasma as an energy conversion medium.
LEAD IODIDE NUCLEAR PARTICLE DETECTORS
Authors: Roth S. , Willig W. R.
Published: February 2004

Semiconductor nuclear particle detectors have been made from lead iodide. α particles and γ quanta have been counted in the temperature range from −200 to +130°C. From α-particle pulse height the μτ+ product has been estimated to be 2×10−8 cm2/V.
Cathodrochromic Properties of Sodalite
Authors: Bolwijn P. T. , Schipper D. J. , van Doorn C. Z.
Published: February 2004

The coloration and bleaching behavior of undoped bromide sodalite prepared by solid-state reaction and by various low-temperature hydrothermal reactions is studied. A high coloration sensitivity is obtained; for instance, a charge density of 0.5 μC/cm2 at 10 kV yields a contrast ratio of 2:1. The coloration and optical bleaching behavior is strongly dependent on the preparation method. A relation between bleaching rate and bromide deficit is found. A relation is suggested between residual coloration and the presence of oxygen on bromine sites. The effect of the doping with transition-metal ions on the bleaching behavior is studied. The doping with Fe, Ni, and Cu causes a considerable increase in bleaching rate.
Light-Sensitive Defect Formation by Electron and Neutron Irradiation of n- and p-type Germanium near 80 °K
Authors: Stein H. J.
Published: February 2004

Measurements of the electrical conductivities and Hall coefficients for neutron-irradiated (76 °K) and electron-irradiated (80 °K) n- and p-type Ge have been made as a function of illumination and isochronal annealing (80–700 °K) to investigate the characteristics of neutron-produced defect clusters in Ge. For p-type Ge there is no effect of illumination immediately following either electron or neutron irradiation but such a dependence is observed after the 140 °K annealing period. This illumination dependence anneals out between 200 and 240 °K. For n-type Ge the effect of illumination on the electrical properties is significantly larger following neutron irradiation than following electron irradiation. Eighty percent of the neutron-produced illumination sensitivity anneals out between 200 and 400 °K. The electrical conductivity in neutron-irradiated n-type Ge is near a degradation maximum after annealing to 240 °K, whereas it is essentially recovered to the preirradiation value in p-type Ge. Furthermore, reverse effects in neutron-irradiated n-type Ge for annealing between 150 and 220 °K contrast with a 100–200 °K recovery after electron irradiation. These results are interpreted as evidence for the neutron formation of high-resistivity p-type defect clusters which increase their p-type character upon annealing to ∼ 200 °K, and recover by vacancy liberation between ∼ 200 and 450 °K. Annealing effects between 400 and 600 °K are interpreted to involve defect-impurity complexes in both electron- and neutron-irradiated n-type Ge.
Prebreakdown Behavior of Long Gold-Doped Germanium n+pp+ Diodes
Authors: Ham W. E. , Ashley K. L.
Published: February 2004

Current-voltage and spatial potential distribution measurements were made on long p-type Au-doped Ge double-injection diodes over the temperature range 65–300 °K. The existing theory for these devices which is based on extensive approximations for the Ohm's-law and power-law region is extended to include the transition region. It is shown that it can occupy several decades of current and hence dominate the prebreakdown injection mode. An excellent fit with experiment is obtained for devices which are provided with probes to permit measuring of the bulk characteristics exclusive of contact drops. Also, the region where the field dependence of mobility and electron lifetime cause the behavior to depart from the low-field theory is clearly manifested. The potential distribution between the contacts was also found to be consistent with the theory. The electron-capture coefficients for neutral and singly charged Au atoms were determined in the temperature range 65–200 °K and were shown to be only slightly temperature dependent.
Molten Tin Bath for the Precision Determination of Activation Volumes
Authors: Buescher B. J. , Gilder H. M.
Published: February 2004

A system is described in which a small-pressure vessel containing diffusion specimens is submerged in a well-stirred and regulated tin bath for diffusion-coefficient measurements in the temperature range 250–450°C up to pressures of 10 kbar. Temperature reproducibility attained is typically 0.1°C, which in combination with a negligible warm-up correction results in activation-volume measurements precise to about 1%.
Amplification in an Amorphous Semiconductor Diode
Authors: Rockstad Howard K.
Published: February 2004

Employing the negative differential resistance region of an amorphous semiconductor point-contact diode, ac voltage amplification is described.
Vapor Growth and Properties of ScAs and ScP
Authors: Yim W. M. , Stofko E. J. , Smith R. T.
Published: February 2004

Single-crystal epitaxial layers of ScAs and ScP have been prepared from the vapor phase on Si substrates. Optical absorption and Hall-effect measurements at 300 °K showed that these compounds are semiconductors with the energy gap of 0.7 eV for ScAs and 1.1 eV for ScP, and that both are highly n type, with carrier concentrations in the range of (2–6)×1021/cm3 and corresponding Hall mobilities of 30−10 cm2/V sec. X-ray results indicate that ScAs and ScP form complete solid-solution alloys.
Negative Absorption near the Electron Cyclotron Harmonics in Weakly Ionized Gases
Authors: Idehara Toshitaka
Published: February 2004

Negative absorption of radio frequency waves is observed near the electron cyclotron harmonics (f=nfc) in weakly ionized plasma. The voltage gains near f=fc and f=2fc are about 7 and 4 dB, respectively. The emissions near f=nfc ascribed to this phenomenon are observed up to n=4 in Xe plasma, up to n=2 in Kr plasma, and only at n=1 in Ar plasma. Their powers are stronger by several tens of dB than those corresponding to thermal noise. The frequency shift from f=nfc as a function of the electron-neutral collision frequency is measured and compared with the theoretical result where the electron distribution function is assumed to be a δ function.
Fracture by Shear Waves
Authors: Steverding B. , Lehnigk S. H.
Published: February 2004

The equation of motion and the stability conditions for cracks interacting with transversal waves and surface waves are given. Threshold conditions for crack propagation relate the crack to a critical duration of the pulse and a second condition gives a relation between initial pulse amplitude and crack length. For surface waves the influence of the length is overshadowed by the penetration depth of the wave. For longitudinal, as well as for transversal pulses, the pulse must have a least-action density in order to propagate a crack. This law loses its meaning for surface waves. Some applications of the derived results to fracture by earthquakes are indicated.
Transformation Twinning of B2(CsCl)-Type Structure Based on an Inhomogeneous Shear Model
Authors: Wang Frederick E.
Published: February 2004

It is shown that in addition to the heretofore accepted homogeneous (simple) shear model, there is yet another mechanism that is inhomogeneous which can bring about mechanical twins in an A2(bcc) structure. In martensitic transformations where the cause for transformation is primarily internal, inhomogeneous-but-cooperative shear may take place in preference to homogeneous shear. Application of the inhomogeneous-but-cooperative shear model to a B2(CsCl)-type structure leads to a triclinic structure. In the course of this structural transformation, two modes of transformation twinning and one mode of trilling are possible.
Electromagnetic surface fields produced by a pulse-excited loop buried in the earth
Authors: Wait James R. , Hill David A.
Published: February 2004

A transient excited magnetic dipole immersed in a conducting half-space is considered. Explicit results for the field waveforms observed on the surface are obtained for the case where the exciting current is an exponential time function. It is shown that the shape of the waveform is diagnostic of the relative location of the buried source. The results have possible application in mine rescue operations.
Infrared absorption study of Li-diffused Mg-doped GaAs
Authors: Leung P. C. , Skolnik L. H. , Allred W. P. , Spitzer W. G.
Published: February 2004

The infrared absorption of Mg-doped GaAs compensated by Li diffusion is measured and the results are compared with those of similar material compensated by electron irradiation and for double-doped material. The absorption bands observed in the GaAs : Mg–Li are consistent with a model in which there is only one type of (Mg–Li) pair defect and one Li paired with each Mg. The (Mg–Li) pair has orthorhombic or lower symmetry with the pair axis probably in a 〈001〉 direction. The Li is in an interstitial position. In GaAs : Mg–Li there is no measurable concentration of Mg which is not paired with Li. Unpaired MgGa absorption is observed in electron-irradiated and in double-doped samples. The ωL values are 331, 326, and 321.5 cm−1 for 24MgGa, 25MgGa, and 26MgGa, respectively. At liquid-nitrogen temperature, the unpaired MgGa has an absorption cross section of σ(24MgGa)≈1.0×10−17 cm2. There is no evidence for pairing between MgGa and any defect centers produced by electron irradiation. The existence of Mg–Te and Mg–Se pairs, probably with C3v symmetry, has been established for impurity concentrations ∼ 1019 cm−3.
Auger recombination in InAs, GaSb, InP, and GaAs
Authors: Takeshima Masumi
Published: February 2004

The Auger recombination lifetimes of the excess carriers in p-type InAs, GaSb, InP, and GaAs are calculated. The calculation is carried out along the line of Beatie and Smith taking into account spin split-off band effect. It is concluded that the spin split-off band effect plays a very important role on the Auger recombination in p-type InAs, GaSb, InP, and GaAs whose spin split-off energies are nearly equal to or smaller than the band-gap energies.
Appearance potential spectroscopy
Authors: Tracy J. C.
Published: February 2004

The dependence of total soft x-ray fluorescence on electron excitation energy is known as appearance potential spectroscopy (APS). The various processes of importance in APS are examined in detail. These include excitation at the threshold for core-hole production, x-ray emission during deexcitation, and x-ray detection by photoelectric emission. The excitation at threshold is controlled by the local density of unfilled states, the position and width (lifetime) of the core-hole state the appropriate transition probabilities, and the energy spread of the incident electrons. While these parameters completely determine the shape of appearance potential thresholds, they do not completely specify the magnitude. The probability of x-ray emission (fluorescence yield) also directly influences the magnitude of the thresholds. These various effects lead to strong variations of both the threshold shape and magnitude as a function of Z. Thus while APS is quite sensitive to the 3d transition metals, it is relatively insensitive to semiconductors and insulators and to 4d transition metals.
Calculation of electromechanical performance of Alnico magnet materials in electrical motors and generators
Authors: Edson A. P. , Peters D. T.
Published: February 2004

A ``maximum electromechanically useful energy product'' (MEP) is proposed as a basis for comparisons among magnet materials for use in electrical motors and generators. This parameter accomodates effects of the operating permeance coefficient and the shape of the electromagnetic field generated by the machine, and relates directly to the maximum machine torque obtainable from a unit volume of the magnet material. A method is presented for approximate calculation of MEP from conventional data for Alnico magnet materials.
Comment on the microwave ``dielectric constant'' of ice
Authors: Gough S. R.
Published: February 2004

The microwave permittivity of 1.9 for ice reported by Perry and Straiton is inconsistent with published infrared and dielectric data. The correct value is 3.2.
Theoretical model for x-ray emission and absorption, bond breaking, and point-defect production in SiO2
Authors: Ruffa A. R.
Published: February 2004

An analysis of the effects of radiation damage in SiO2 is made within the framework of the valence-bond approximation. According to this model, the less energetic and intense satellite in the oxygen Ka emission spectrum results from the breaking of an Si–O bond. The calculated energy separation and intensity ratio of the two lines agree favorably with experiment. The model further indicates that the end result of the radiative processes is the production of transient paramagnetic point defects in the pure material and permanent defects in the impure material. In this sense, this model goes a step further than the usual molecular orbital or band pictures in that it provides a different description of the ionized and un-ionized states. Some implications of these conclusions are discussed in detail.