bluuebunny/crossref_metadata_2025 huggingface dataset:
High-pressure studies of thermoluminescence of doped ZnS phosphors
Authors: Hook III J. W. , Drickamer H. G.
Published: February 2003

Thermoluminescence measurements have been made as a function of pressure to 40 kbars on three ZnS phosphors, two doped with Cu+ and Cl−, and one doped with Ag+ and Cl−. The apparatus is briefly described. The major features of the thermoluminescent spectra were a low-temperature peak which shifted to lower temperature with increasing pressure and a high-temperature peak which shifted rapidly to higher temperature. The entire spectrum decreased in intensity, which is consistent with House’s measurements of the steady-state intensity. Data from three different heating rates gave consistent values for the trap depth. The change in energy of the electron trap with pressure obtained from these thermoluminescence measurements was quantitatively consistent with House’s calculations based on steady-state data.
Explanation of up-conversion and optical storage in CdS: Spatially modulated band structure
Authors: Perry Percival B. , Schmidt Martin
Published: February 2003

Red-green up-conversion and optical storage are measured in CdS crystals containing deep impurities such as P, N, Fe, and others. The presence of cadmium vacancies favors the formation of centers of self-activated luminescence which reduce the up-conversion efficiency considerably. Spatial fluctuations of the conduction- and valence-band energies with respect to the Fermi level causes electrons and holes to separate after excitation and to populate distant islands in the crystal. The temperature limit of the up-conversion and storage is determined by the energy barrier between the electron and hole islands.
A simple method for growing V3Si single crystals
Authors: Callaghan T. , Schwanebeck J. , Toth L. , Dayan M. , Goldman A. M.
Published: February 2003

V3Si crystals have been grown by electron-beam melting using a procedure simpler than previous methods. The resultant crystals are of high quality with a low oxygen content and with a superconducting-transition temperature of 16.9 K, a resistivity ratio of 40, and a martensitic transformation at 21.7 K.
Experimental analysis of dielectrophoretic forces
Authors: Benguigui L. , Lin I. J.
Published: February 2003

We performed a direct measurement of dielectrophoretic forces on particles immersed in a fluid, in a given electrode configuration which permits particle levitation. We show that the force on several neighboring particles is much larger than that acting on an isolated particle in the same field distribution. We discuss the consequences of the measurements on the use of dielectrophoresis for material separation.
Simplified theory of a multipass cw gasdynamic laser cavity
Authors: Brunné M. , Zieliński A.
Published: February 2003

The paper concerns a simplified analysis of the problem of the power extraction from the multipass cavity of the cw gasdynamic laser. Analytical formulas for the laser output and the resonator efficiency are given relating them to the cavity geometric features, cavity losses, number of the cavity passes, and gain and population inversion of a flowing optically activated medium. The analysis is oriented toward application of the obtained results for a rapid estimation of the power characteristics of a CO2 (or N2O)/N2/(additives) cw gasdynamic lasers. The interaction between gain and radiation field is treated in terms of the rate-equation formalism.
Acoustic-wave absorption/amplification in nonparabolic degenerate semiconductors
Authors: Sharma S. S. , Sharma S. K.
Published: February 2003

Theory for the absorption/amplification coefficient of acoustic waves in nonparabolic degenerate semiconductors is developed using the modified collision term. Ionized impurity scattering is considered to be the sole mechanism of scattering of electrons. It is noted that an increase either in the nonparabolicity factor or in the electron concentration leads to a decrease in the threshold value of the drift velocity of electrons.
Dynamic loading of a single-stage ferromagnetic liquid seal
Authors: Perry M. P. , Jones T. B.
Published: February 2003

Experiments are performed with a single-stage magnetic fluid rotary feed-through seal to determine the influence of shaft rotation, seal fluid inventory, seal clearance, magnetic field intensity, and magnetic field distribution on the maximum seal capacity or burst pressure. For small magnetic fluid inventories, the seal exhibits very low static capacity, a maximum capacity near 20 Hz, and a slowly decreasing capacity for higher shaft speeds. For larger inventories, the effect of motion is small. Under a constant inventory condition, the larger clearance seals are less sensitive to shaft motion than the smaller clearance seals. As the seal clearance is increased, inevitable fluid loss due to rotation becomes more pronounced and the seal becomes weaker. For decreased magnetic field intensity in the gap, the seal capacity exhibits increased sensitivity to shaft speed. Several hypotheses are proposed to explain the observed behavior. Certain design-related implications are discussed.
XeO* production through collisional electronic energy transfer from two-photon excited Xe atoms
Authors: Kligler D. , Pritchard D. , Bischel W. K. , Rhodes C. K.
Published: February 2003

The observation of electronic energy transfer to XeO(1Σ+) from xenon atoms excited by two-photon absorption is reported. Electronically excited xenon atoms in the 5p56p configuration are produced through two-photon excitation at 248.4 nm (KrF*). Subsequent energy transfer from excited rare-gas atoms to N2O leads to the appearance of XeO(1Σ+), which is identified by the detection of its characteristic green emission band. These measurements are in accord with estimates of the relevant two-photon amplitudes for Xe and N2O. Kinetic studies utilizing these techniques provide a flexible method for the study of selective excitation and energy transfer in a wide class of atomic and molecular materials.
The angular distribution of synchrotron-Čerenkov radiation
Authors: Rynne T. M. , Baumgartner G. B. , Erber T.
Published: February 2003

High-energy charged particles emit synchrotron-Čerenkov radiation under the joint action of external magnetic fields and ambient media. The angular and spectral characteristics of this radiation have been derived by classical and quantum-mechanical methods. The experimental significance of the angular distribution—particularly features associated with striations—are considered in some detail.
Optimal timing and power enhancement observed in a double-pulse fast-discharge-driven XeF laser
Authors: Akins Robert P. , Innis George , Lin Shao-Chi
Published: February 2003

A surprisingly long delay time (of the order of 10 μsec) is found necessary for maximum enhancement of the output power and energy from the main pulse of a 0.1-liter-volume Blumlein-driven XeF excimer laser when another fast-discharge pulse of about 0.1-μsec duration and 10% of the main discharge energy is used to preionized or otherwise ’’precondition’’ the gas mixture. At such optimal timing, a factor-of-5 enhancement of the UV laser output (3510<λ<3537 Å) has been observed in a He : Xe : NF3 mixture at an overall generation efficiency of 1.3%.
The microstructural location of the intergranular metal-oxide phase in a zinc oxide varistor
Authors: Clarke David R.
Published: February 2003

High-resolution electron microscopy of a commerical ZnO-based varistor reveals that the Bi-rich intergranular phase is found at all three- and four-grain junctions and that the majority of the ZnO grains are not surrounded by an oxide-barrier film as previously believed.
Capacitance spectroscopy of degraded GaAsP light-emitting diodes
Authors: Tell B. , van Opdorp C.
Published: February 2003

We employ the technique of deep-level transient spectroscopy to study a series of rapidly degraded GaAs0.6P0.4 LED’s. We observe a dramatic increase in the density of defects, two of which appear to be effective recombination centers. The cross-section measurements for these centers are equipment limited, but even these values limit the nonradiative minority-carrier lifetime to less than 20 ns.
TEM observation in cross section of defects in a long-term-degraded Ga1−xAlxAs double-heterostructure injection laser diode
Authors: Proto G. R. , Vermaak J. S.
Published: February 2003

A degraded Ga1−xAlxAs double-heterostructure injection cw laser diode with a lifetime of 1070 h was examined in cross section by TEM. The device contains defects whose contrast is identical to that produced by coherent or partially coherent precipitates and/or by prismatic dislocation loops. They have not previously been observed either in undegraded Ge- or Sn-doped material or in devices degraded by DLD formation. These defects were observed in the top p (Ge) -GaAs layer as well as in the p (Ge) -Ga1−xAlxAs layer adjacent to it. There is a tendency for these defects to decorate the interface between these two layers as well as the interface between the active region and the p (Ge) -Ga1−xAlxAs layer. Furthermore, these defects seem to cluster in regions adjacent and above these two interfaces. These defects have not, however, been observed in the active, the n- (Sn) -Ga1−xAlxAs, and the n-GaAs substrate regions.
Propagation characteristics of moving isotropic homogeneous and inhomogeneous lossy plasma-filled waveguide
Authors: Tiwari G. N.
Published: February 2003

The propagation and attenuation characteristics of electromagnetic waves through a waveguide filled with moving isotropic lossy homogeneous (TEmn modes), as well as inhomogeneous (TEm0 modes) plasma for the appropriate modes, have been theoretically studied. The expressions for the propagation and attenuation constants for TE and TM modes are found to be the same and dependent on waveguide dimension, plasma parameters, and drift velocity. The propagation characteristics near the waveguide walls are seen to be similar to the free-space waveguide. For special cases, the effect of the inhomogeneity of the plasma medium has also been discussed. The power flow and field components existing in waveguides are also discussed in brief.
Smooth and continuous Ohmic contacts to GaAs using epitaxial Ge films
Authors: Anderson W. T. , Christou A. , Davey J. E.
Published: February 2003

Ohmic contacts to n-type GaAs have been developed using epitaxial Ge films on GaAs alloyed with Ni overlayers by solid-state diffusion at temperatures of 450–550 °C. The contacts are smooth and continuous, showing no evidence of phase separation or other surface structure. Interdiffusion at the Ge-GaAs and Ni/Ge-GaAs interfaces was examined by Auger electron spectroscopy (AES) sputter profiling techniques. An abrupt profile is observed at both the as-deposited and sintered Ge-GaAs interface. With the presence of a Ni overlayer, significant interdiffusion between Ge and GaAs is revealed by AES profiles. These results, together with the current-voltage (I-V) characteristics of similar contacts prepared on p-type GaAs, indicate the presence of a Ge-doped n+ layer at the Ni/Ge-GaAs interface.
Electrostatic-spray theory
Authors: Kelly A. J.
Published: February 2003

The statistical equilibrium model for the electrostatic spraying of liquids, previously described by the author, is compared with the available experimental data for Woods’s metal, octoil, and glycerine. The model’s Lagrangian multipliers α′, β′, and δ′ have been evaluated for these fluids. In the two instances where the ratio α′/β′ could be determined (Woods’s metal and octoil), the same value −10−17±15% J was obtained. A tentative expression for this ratio is presented and it is proposed that all practical electrostatic-spray systems are dominated by electron-emission-limited processes. Discontinuities in mean specific charge as a function of droplet radius are predicted and shown to be consistent with the available data. Best correspondence with limited data indicates α′ to be proportional to an inverse fluid property capillary number. In addition, an expression for the pulsed system Lagrangian multiplier δ′ is developed for steady-state systems. The detailed characteristics of a pulsed benzene spray appropriate for use in internal-combustion engines are described.
Rigorous bounds on the conductivity of isotropic one-dimensional polycrystals
Authors: Kassman A. J.
Published: February 2003

The prediction of the effective electrical conductivity of a one-dimensional polycrystal constructed from an anisotropic single crystal is described. The least upper and greatest lower bounds on the effective conductivity are derived for the isotropic polycrystal. The upper bound is equal to or less than the arithmetic mean of the principal conductivities, and the lower bound is equal to or greater than the geometric mean of the principal conductivities.
Compensation of residual boron impurities in extrinsic indium-doped silicon by neutron transmutation of silicon
Authors: Thomas R. N. , Braggins T. T. , Hobgood H. M. , Takei W. J.
Published: February 2003

Infrared-sensitive focal plane arrays based on extrinsic silicon, which integrate the detection and signal-processing functions onto a single chip, are currently being developed at several laboratories. For imaging in the 3–5-μm atmospheric window, highly doped Si : In is a leading candidate due to its spectral range, quantum efficiency, and moderate cooling requirements (50–60 K). The effects of residual boron impurities in the Si : In detector must, however, be compensated by donor concentrations to achieve these operational temperatures, so that precision compensation is a key factor for the production of uniform high-responsivity detector material. We report here the successful use of thermal-neutron irradiation for transmuting a small fraction of the silicon atoms into a known concentration of phosphorus donors in order to compensate Si : In detector material. Czochralski-grown Si : In starting material of 〈100〉 orientation was evaluated by variable-temperature Hall effect studies to contain NIn=2.5×1017 cm−3, NB=1.6×1014 cm−3, and NP=0.6×1014 cm−3. Samples were irradiated in a light-water reactor and then thermally annealed for lattice damage recovery. Detector measurements indicate detectivities D* which approach background-limited performance at temperatures of 55 K at a photon flux of 1015 cm−2 sec−1. Maximum photoconductive lifetimes of 3 nsec were determined from responsivity measurements and are consistent with the known phosphorus concentration (2.2×1014 cm−3) introduced by the transmutation of silicon and the measured impurity concentrations in Czochralski starting material. No attempts were made to optimize the compensation density to produce improved responsivity material, but the absence of any anomalous behavior is encouraging for future efforts at more precise compensation. Measurements of thermal-carrier concentrations in both conventionally compensated and neutron-compensated material also reveal an additional deep-lying acceptor level at 0.11 eV above the valence band edge in Si : In. Concentrations of (3–6) ×1014 cm−3 were observed. A spectral dependence beyond the indium cutoff wavelength which can be attributed to a 0.11-eV level in the Si : In material is observed.
Random walk calculation of diffusion coefficient of hot electrons in two-valley semiconductors
Authors: Gupta Madhu S.
Published: February 2003

The electric-field-dependent longitudinal diffusion coefficient for charge carriers in a two-valley semiconductor is calculated by modeling the carrier movement as two simultaneous coupled random walks. The first random walk represents carrier scattering from one valley to another, and the second describes the motion of a carrier within a single valley, with the carrier position in the first walk determining the parameters of the second walk. The calculated intervalley transfer diffusion coefficient Dtr contains earlier calculations of Dtr as special cases. An agreement between calculated and measured low-field diffusion coefficients for electrons in n-GaAs at room temperature is obtained when the random time interval that a carrier spends in a valley is assumed to have a gamma distribution.
Thermoelectric power of Cu-based dilute alloy films
Authors: Chopra K. L. , Thakoor A. P.
Published: February 2003

The thermoelectric power (TEP) of structurally characterized Cu-based dilute alloy films containing 1, 2, and 5 at.% Al, Ge, or Sn has been studied in the temperature range 80–350 K. The TEP of alloy films increases with thickness to reach a saturation value at ≳2800 Å. The addition of impurities reduces the magnitude of the TEP of copper films while its sign remains positive. The temperature dependence of the TEP is affected markedly by the presence of impurities. Structural disorder, impurity, and phonon-drag contributions to the TEP have been separated by using the Nordheim-Gorter relation. Contribution of the Fermi-surface distortions (and thus change in the neck radius of the Fermi surface) to the TEP has been estimated.
Small-angle x-ray scattering from oriented ellipsoidal voids in pyrolytic graphite
Authors: Bose S. , Bragg R. H.
Published: February 2003

Small-angle x-ray scattering from oriented voids in pyrolytic graphite has been studied. The scattering is found equivalent to that from a dilute dispersion of ellipsoids of revolution called ’’Guinier spheres’’ of radius of gyration R=[(3/5) H]1/2=[(3/5)(a2 sin2γ+b2 cos2γ)]1/2, where γ is the angle between the common axis of revolution (semiminor axis b) and the scattering vector h. Analysis of the data using Hamzeh and Bragg’s theory provides values of a, b, and a/b from the ’’Guinier’’ and the ’’Porod’’ regions, independently, with good agreement. The theoretically predicted angular dependence of H using ’’best-fit’’ values of a and b is in good agreement with the experimentally determined value of H, γ varying from 0° to 180°.
Initiation of laser-supported-detonation (LSD) waves
Authors: Walters C. T. , Barnes R. H. , Beverly III R. E.
Published: February 2003

Experimental results of plasma diagnostic measurements taken during the early development of laser-supported-detonation (LSD) waves in TEA-CO2 laser irradiations of solid surfaces in air are reported. Photographic and sample examination results for irradiations of practical aluminum surfaces indicate that the initiation process is highly local at surface features which are heated preferentially. The intensity dependence of time to plasma initiation was measured using target-electron emission, target-hole transmission, and electrostatic-probe response as indicators of the initiation event timing. The initiation time for aluminum was found to be in the range 25–70 nsec for peak-power densities in the range 0.4 to 4×108 W/cm2. Emission-spectroscopy results indicate the presence of neutral aluminum vapor at late times in the pulse, but no ionized aluminum was detected at atmospheric pressure. The experimental results for aluminum are found to be consistent with a simple theoretical model, wherein electrons are thermionically emitted at preferentially heated surface features. The emitted electrons serve as priming electrons in a cascade air breakdown. A limited amount of data on metals other than aluminum are also presented.
Time dependence of copper-atom concentration in ground and metastable states in a pulsed CuCl laser
Authors: Tenenbaum J. , Smilanski I. , Gabay S. , Erez G. , Levin L. A.
Published: February 2003

We have measured the time dependence of the concentration of copper atoms in the ground and metastable states in a pulsed CuCl laser by monitoring the absorption of atomic copper lines. We found that the ground-state population rises from a very small value at the end of the dissociation pulse to a maximum and decreases slowly after about 160 μsec. The metastable population reaches a maximum after about 40 μsec and then decreases relatively rapidly. We conclude that the minimum and optimum delay times in a double-pulse copper halide laser are determined primarily by the slow buildup of the copper-atom ground-state concentration. This concentration then decays by recombination.
Acoustic resonances in cylindrical high-pressure arc discharges
Authors: Witting Harald L.
Published: February 2003

Acoustic resonances were observed in high-pressure (600 Torr) sodium-mercury-xenon discharges operated with ac input at power frequencies of 2–120 kHz. Three sizes of cylindrical sapphire arc tubes were operated at constant average powers of 400, 250, and 150 W, respectively. The observed resonance frequencies and arc shapes agree well with a simple analysis of standing pressure waves in cylinders. The results indicate that transverse resonances effectively average the gas temperature across the arc, while longitudinal resonances mainly involve the hot core of the discharge.
Approximate theory of magnetoelastic surface-wave convolution
Authors: Robbins William P.
Published: February 2003

Expressions are developed for the internal efficiencies of magnetoelastic Rayleigh-wave convolvers. A bulk-wave formalism is used to express the nonlinear magnetization components m responsible for the convolution, as the square of the input signals 𝒮1 and 𝒮2, i.e., m=η (𝒮1+𝒮2)2. The resulting expressions for η have a resonance-type denominator of the form ω2−ω20, where ω0 is the gyrofrequency. Such a resonance does not occur with surface magnetoelastic waves. The results are adapted to the surface-wave case by means of an approximation to estimate the nonzero value of the denominator. Experimental values of η range from 1.2×105 to 4.7×105 Wb/m2 for the best convolvers reported to date. Corresponding theoretical values range from 9.5×104 to 1.58×105 Wb/m2. Uncertainties in the experimental and theoretical estimates are discussed.
Laser scattering from dense plasmas
Authors: Kimberlin S. R. , Chan P. W. , Hazelton R. C. , Yadlowsky E. J.
Published: February 2003

Although Thomson scattering of laser light from plasmas has become a widely accepted laboratory diagnostic technique, many experiments involving high-density low-temperature plasmas suffer from a masking of the incoherent scattered radiation by bremsstrahlung radiation and by reflected and refracted light signals; consequently, few accurate measurements have been made on laser-produced plasmas. To a large extent these disadvantages have been removed from the present work wherein a high-density (∼1019/cm3) low-temperature (∼10–15 eV) plasma has been generated in 300-Torr pressure of helium by a 3-J CO2 TEA laser, while scattering measurements have been performed with a separate pulsed ruby laser system operating at 0.15 J. Specifically, the frequency spectrum of the incoherent light scattered at 90° from the plasma has been obtained allowing temperatures to be measured in the plasma with a spatial resolution of 250 μm. Holographic interferograms have also been obtained. From the central-ion feature of the scattered-light spectrum, the plasma was inferred to be in thermal equilibrium with equal electron and ion temperatures. The maximum value of the temperature is 17 eV±11%. Additionally, the value of the electron number density from scattering measurements and that found from plasma holograms differ by less than 30%. The scattering results agree well with theoretical predictions for scattering from thermal fluctuations in an equilibrium plasma. The experiment also shows that the calculated values for bremsstrahlung emission approach the observed plasma noise for electron densities near 1019/cm3, but that other noise sources determine the signal-to-noise ratio at lower number densities. The techniques of this paper can be used to study nonequilibrium plasmas where instabilities dominate the scattered-light spectrum.
Electromigration and diffusion in thin films: A new technique
Authors: Beniere F. , Reddy K. V. , Kostopoulos D. , Le Traon J. Y.
Published: February 2003

A new technique has been realized for studying metal migration induced by an electric field in thin metallic stripes. The same experiment allows one to determine the diffusion coefficient, the drift mobility, and the effective charge in the same conditions. A sectioning technique and radiotracers are used. Due to the high sensitivity, the data can be obtained down to the temperatures which are of practical interest for the electronic components.
Effect of morphology on helium mobility in soda-lime-silica glasses
Authors: Shelby J. E.
Published: February 2003

Helium permeability has been measured for a wide range of soda-lime-silica glasses. The results have been used to define the interconnectivity and miscibility limits for this glass-forming system. Results of heat-treatment studies have also been used to determine the interconnectivity boundary temperature for the 2Na2O⋅CaO⋅XSiO2 compositional line. It has also been shown that the replacement of Na2O by CaO substantially reduces the mobility of helium in those glasses lying outside the immiscible region.
Quasistatic approximation to the scattering of elastic waves by a circular crack
Authors: Domany E. , Krumhansl J. A. , Teitel S.
Published: February 2003

The elastic-wave scattering by a flat crack can be represented by an integral expression involving displacement and strain on the surface of the crack. We have explored the use of a modified static solution as an approximation to the displacement field of a penny-shape crack in the long-wavelength regime and then studied numerically how well it connects with the low-freqency limit of the diffraction regime. Comparisons between this and several other existing approximations are made. We conclude that this quasistatic approximation is useful practically in both the long-wavelength and beginning diffraction regime.
Enrichment of hydrogen isotopes using the low-temperature glow-discharge technique
Authors: Geosling C. E. , Manuccia T. J.
Published: February 2003

Deuterium enrichments are reported for flowing methane/hydrogen mixtures subjected to a glow discharge at low temperatures. Dependence of the enrichment factor on initial D/H ratios, flow rates, system pressure, discharge energies, and translational temperature of the reacting gas mixture was studied. In addition to enrichment measurements, details of the estimate of energy requirements for enrichment of deuterium from natural abundance are included.
Measurement of molecular stopping cross sections of aldehydes and ketones and calculation of the atomic stopping cross section of oxygen in double-bonded and three-membered ring-structure C-H-O compounds
Authors: Chau E. K. L. , Powers D.
Published: February 2003

The molecular stopping cross sections of butyraldehyde, acetone, 2-butanone, and 3-pentanone have been measured for 0.3–2.0-MeV He+ ions with probable random errors of 0.6–0.7%. The stopping cross sections of cyclopropane and ethylene have also been remeasured in order that the stopping cross sections of oxygen in aldehydes and ketones [εDB(O)] and in epoxides [εRING(O)] can be extracted. It is found that εDB(O) ≳εRING(O) ≳εSB(O) for E<0.7 MeV, where the subscripts DB, RING, and SB refer to oxygen in a double bond, in a three-membered ring, and in a straight-chained single bond, respectively.
Electron mean free path in a thin metal film
Authors: Ijaz-ur-Rahman  , Ahmed K.
Published: February 2003

The mean free path of an electron in a thin metal film is calculated assuming an exponential probability distribution of the free paths of conduction electrons and a surface specularity parameter p. The calculation differs from that of Fuchs in that no Boltzmann transport equation is used.
Internal quantum efficiency measurements for GaAs light-emitting diodes
Authors: Lastras-Martínez A.
Published: February 2003

Internal quantum efficiency values at room temperature are given for single-heterojunction Zn-diffused GaAs diodes with substrate doping concentrations of ∼1×1018 and (2–3) ×1017/cm3. The internal quantum efficiency temperature dependence for diodes with a substrate doping concentration of (2–3) ×1017/cm3 is also given in the range 200–323 K. Internal quantum efficiency values have been calculated from external quantum efficiency measurements. The conditions under which these calculations are possible have been established. Internal quantum efficiency is found to be ∼60% at room temperature, for diodes with a substrate doping concentration of ∼1×1018/cm3. Internal efficiency variations of ∼60% are observed as we go from 323 to 223 K, for diodes with substrate doping concentrations of (2–3) ×1017/cm3.
Flatband potential of a p-type phosphide electrode
Authors: Horowitz G.
Published: February 2003

Differential-capacitance measurements have been performed on p-type GaP in order to determine its flatband potential in buffered electrolytic solutions at various pH. The reproducibility of the flatband-potential determination is greatly improved by chemical etching of the semiconductor surface. The slope of the flatband-potential–vs–pH curve is that predicted by the Nernst equation. Deriving the acceptor concentration is hampered by the unreliable measurement of the effective area of the electrode which is in contact with the electrolyte.
Magnetic guidance of drug-carrying microspheres
Authors: Senyei Andrew , Widder Kenneth , Czerlinski George
Published: February 2003

Physical laws underlying the intravascular magnetic guidance of a novel drug carrier are discussed. The drug carrier is a magnetically responsive drug-bearing microsphere measuring approximately 1 μm in diameter. The microspheres consist of an albumin matrix in which a prototype drug (adriamycin HCl) and ultrafine Fe3O4 particles are entrapped. An in vitro analog of the human circulatory system is used to test both bipolar and unipolar magnetic arrangements which can retain microspheres flowing in aqueous suspension in the area of applied magnetic field. Retention of the microspheres by the magnetic field is shown to vary with the linear velocity of the viscous suspending medium and to be dependent on the magnitude of the applied magnetic force. This system permits extracorporeal control over the distribution of intravascular soluble chemotherapeutic agents and allows their concentration at specified body sites.
Radiation pressure due to plane electromagnetic waves obliquely incident on moving media
Authors: Kalluri D. , Shrivastava R. K.
Published: February 2003

The mechanical power which has to be supplied to a conducting or dielectric medium to keep it moving uniformly against the radiation pressure of an obliquely incident plane electromagnetic wave is studied in detail for the entire velocity range.
Observation of bulk waves and surface waves through side planes of several cuts of LiNbO3 SAW devices
Authors: Togami Yuji , Chiba Takao
Published: February 2003

The radiation patterns of bulk waves excited by an interdigital transducer have been observed for five cuts of LiNbO3 crystals using a frequency-shift holographic method. The observation of surface acoustic waves through side planes was also done.
The determination of voltage in exploding-foil experiments
Authors: Logan J. D.
Published: February 2003

A basic problem in exploding-foil experiments is the placement of the voltage probes since they cannot be located at the ideal position where the voltage drop shoud be measured. As a result, they are placed so that they introduce error into the measurements. Therefore, knowing how much experimental error exists in these voltage measurements is quite important. In this study, a theoretical determination of the potential drop in a nonlinear conductor is made using both steady-state and dynamic models. Estimates of the magnitude of experimental errors are calculated.
Spatially varied activation of ion-implanted As during the regrowth of amorphous layers in Si
Authors: Ohmura Y. , Inoue T. , Yamamoto Y.
Published: February 2003

He backscattering technique and sheet-resistivity measurements show that the electrical activation of As implanted in (100) and (111) Si and annealed at relatively low temperatures (500–600 °C) takes place from the vicinity of the crystalline substrate Si in the As profile. This is accompanied by the regrowth of the implantation-induced amorphous layer. The annealing temperature required for both the activation and the regrowth is dose dependent. No defect-induced diffusion of As has been observed in these annealing processes.
A refraction correction for RHEED patterns from amorphous surfaces
Authors: Matysik K. J.
Published: February 2003

A method for correcting for refraction effects in RHEED patterns from amorphous surfaces is described. An ’’effective’’ mean inner potential is constructed and used to determine the shift in location of diffuse peaks.
Evidence of damage at gallium arsenide–insulator interfaces
Authors: Lum W. Y. , Messick L. , Zeisse C. R.
Published: February 2003

Photoluminescence (PL) measurements at 77 K have been used to study the interfaces between gallium arsenide and dielectrics grown by anodic and pyrolytic processes. The observed changes in the PL spectra after the deposition of the dielectrics suggest that damage is introduced in both cases during the growth process.
Tunneling spectroscopy of single-crystal Pb1−xSnxTe (x=0, 0.2, 0.3)
Authors: Suzuki Morio , Komorita Kazunori
Published: February 2003

Dependences of the band structure and phonon energies in Pb1−xSnxTe on a tin concentration x were studied by the tunneling measurements using the Pb-SiO2-Pb1−xSnxTe (x=0, 0.2, 0.3) junctions at 4.2 K. From these results, it was found that the value of the energy gap Eg in Pb1−xSnxTe decreased with increasing tin concentration x obeying Eg=180−480x +0.43T meV. This agreed with the results of the optical measurements. The phonon energies in Pb1−xSnxTe were independent of the tin concentrations within the experimental error. No phenomenon accompanying the cubic-rhombohedral phase transition was found, such as a change in the band structure and a phonon softening.
Photoinjection of holes from amorphous selenium into a molecularly doped photoconductor
Authors: Mey William , Borsenberger Paul M. , Chowdry Arun
Published: February 2003

The photoconductive response of a sensitized molecularly doped photoconductor is reported. The photoconductor consists of triphenylamine dispersed in a bisphenol-A-polycarbonate polymer, sensitized by a thin layer of vacuum-deposited amorphous selenium. The wavelength and field dependence of the photoinjection efficiency has been measured using photoinduced discharge techniques. An efficiency of 0.7 was measured at a field of 6.4×105 V/cm.
Current amplification by vibrating membranes of piezoresistive semiconductors
Authors: Lal M. N. , Das B. L.
Published: February 2003

This paper deals with the vibration of a rectangular membrane of a piezoresistive semiconductor under a low steady voltage applied between two parallel sides. An alternating current varying in phase with the vibrations of the membrane in a direction normal to its plane is found. Numerical calculations have been made for both p- and n-type germanium and silicon, which show that the rms value of the transverse current in Ge is about 200 times larger than the direct current in the plane of the membrane. The feasibility of using this magnified current in piezoresistive microphones and acoustic pulse detectors has also been suggested.
Electrochemical effects as the source of electromotive force in metal(1) –polymer–metal(2) systems
Authors: Vijh Ashok K.
Published: February 2003

It has been pointed out that the metal–polyethylene-terephthalate–metal, M1-PET-M2, systems employed in the study of thermally stimulated currents behave as primary batteries. The open-circuit voltages largely arise from the electrode reactions likely to occur at these high temperatures, especially the oxide formation on the negative electrode of this battery, although some contribution to the voltage is made by the series internal resistance of the PET itself. The open-circuit voltages, when corrected for the potential drop due to the internal resistance of the PET and other effects, correspond mainly to the electrode potentials of the metal–metal-oxide couples. This analysis is developed and verified on the basis of the recent experimental data of Ieda and co-workers on the M1-PET-M2 systems. It appears that proper attention to the appropriate electrode reactions at metals which sandwich the polymer in M1- (polymer) -M2 systems would perhaps lead to more satisfactory interpretations of the open-circuit voltages observed during investigations of thermally stimulated currents in these systems.
The refractive-index distribution of LiTaO3 after surface lapping
Authors: Kitayama Tadayoshi , Hashimoto Masahiro , Nakahara Shojiro
Published: February 2003

The approximate theory of the refractive-index distribution of LiTaO3 after surface lapping is presented. A simple formula is given whereby the index distribution can be determined, assuming that the residual stress caused by lapping is known. The results are shown to be in good agreement with the experimental data.
Leaky SAW and guided light Bragg interaction in LiNbO3
Authors: Freyre F. , Wang W. C.
Published: February 2003

The results of a theoretical analysis of Bragg interaction of optically guided light and Leaky surface waves are presented. These results are compared to those of a similar analysis for YZ Rayleigh waves. For TM optical modes, X-propagating Leaky waves on metallized 64° rotated Y-cut LiNbO3 interact nearly twice as strongly at the surface as the free-surface Rayleigh waves. However, X-propagating Leaky waves on free-surface 41° rotated Y-cut LiNbO3 have near zero interaction for both TM and TE modes.
Determination of the hardening temperature using a pulsed laser
Authors: Chan P. W. , Chan Y. W. , Hui F. K. , Ng H. S.
Published: February 2003

A simple method is reported for determining the hardening temperature of a metal by measuring the depths of hardening at different intensities of a pulsed ruby laser. The value of 834 °C obtained for S45C steel agrees well with the reported value of 850 °C.
Electron trapping in electron-beam irradiated SiO2
Authors: Aitken J. M. , Young D. R. , Pan K.
Published: February 2003

In addition to the well-known positive space charge, electron irradiation of MOS capacitors with 25-keV electrons is shown to introduce additional uncharged electron traps into the oxide layer. These traps persist after most of the positively charged defects have been removed by the usual low-temperature (? °C) anneals. Their presence after this anneal is determined by injecting hot electrons into the oxide where they are captured by existing defects. The effective trap densities increase with increasing electron fluence and are reduced by forming-gas anneals at temperatures in excess of 500 °C. Observed electron-capture cross sections are between 10−15 and 10−18 cm2. The residual radiation damage in oxides exposed to 10−4 C cm−2 of 25-keV electrons and subsequently annealed at 400 °C results in an additional neutral density of 5×1011 traps cm−2 with cross sections distributed over the above range. Electron-trapping cross sections and effective trap densities associated with this damage are found to be identical at 77 and 295 K. The traps are possibly associated with dipolar defects formed when valence electrons localize around an ion after the bonds are broken.
Intrinsic voltage in insulating films in aluminum–barium-stearate–aluminum structures
Authors: Singal C. M. , Gupta S. K. , Kapil A. K. , Srivastava V. K.
Published: February 2003

Studies and measurements of internal voltage in a metal-insulator-metal structure with similar electrodes, when the insulator molecules have dipole moments all oriented parallel to each other, have been reported here. The measured voltage has been shown to be directly related to the dipole moment of the carboxylic group in the barium-stearate molecule. The work reported provides a method of measuring the dipole moment of suitably orientable molecules. The transient behavior of the currents at zero bias through the above system has also been studied.
Current transfer in multifilamentary superconductors. I. Theory
Authors: Ekin J. W.
Published: February 2003

In short-specimen critical current measurements, inadequate separation between current and voltage contacts results in a finite linear slope in the measured voltage-current characteristic at low currents. A simple approximate analytic expression is developed for estimating the magnitude of this slope from wire parameters. Current-transfer lengths are evaluated for multifilamentary NbTi and Nb3Sn composite superconductors.
Dynamic magnetization in ferrofluids
Authors: Bogardus H. , Krueger D. A. , Thompson D.
Published: February 2003

A pulsed-field (1 μsec–3 msec) inductive magnetometer has been constructed that measures the magnetic moment of a ferrofluid as a function of time. After the applied field is removed, the magnetization is characterized by a fast decay (<1 μsec) and a gradual decay that can be as long as 4 msec. The magnitude of the magnetization for each component versus applied field can be fit to a Langevin function, and the calculated particle sizes agree well with those measured in the electron microscope. The slow component of magnetization may be due to particle rotation; however, a simple model predicts particle sizes that are not consistent with other measurements. Extending the model to include dimers and trimers in the form of aggregates with an increased local viscosity may explain the slow relaxation.
Microstructure and magnetism in amorphous rare-earth–transition-metal thin films. I. Microstructure
Authors: Leamy H. J. , Dirks A. G.
Published: February 2003

A microscopic examination of vapor- or sputter-deposited amorphous rare-earth–transition-metal thin films reveals that they possess anisotropic microstructure. The morphology of the structure is similar in all of the films. It consists of small (50–250 Å in diameter) rod-shaped regions of high density that are surrounded by a network of less-dense material (10–25 Å thickness). The column axes are mutually parallel and are oriented at an angle β that is described by the relationship: tanβ= (1/2)  tanα, where α is the angle of incidence of the vapor beam, measured with respect to the substrate normal. The columnar structure is formed during deposition by self-shadowing of the incident atoms by the atoms in the growing film. The columnar structure persists when multiple or distributed vapor sources are used to deposit the film. The structure is stable upon heating to temperaures in excess of the crystallization temperature of the amorphous deposits. Vapor deposition at large α leads to the formation of rowlike column aggregates in a direction perpendicular to the plane of incidence.
Exchange-anisotropy field in disordered nickel-manganese alloys
Authors: Satoh T. , Goldfarb R. B. , Patton C. E.
Published: February 2003

Magnetization data for disordered and weakly ordered Ni-Mn alloys from 22.1 to 32.1 at.% Mn have been obtained upon warming from 4.2 to 300 K, for measuring fields up to 100 kOe, after first cooling from 300 to 4.2 K in zero field or in 100 kOe. The measurements show that there is a minimum measuring field for which the data for zero-field cooling match the data for field cooling. This field, for the disordered alloy, increases from 10 kOe at 22.1 at.% Mn to 90 kOe at 32.1 at.% Mn. Partial atomic ordering reduces this coupling field. The coupling field is smaller than expected from previous studies. The data are qualitatively explained by a recently proposed local-environment model which considers explicitly the nearest-neighbor environment of Mn atoms in the alloy.
Mössbauer study of Fe2O3 crystallite formation in B2O3 glass
Authors: Sekhon S. S. , Kamal R.
Published: February 2003

Mössbauer spectroscopy has been used to identify the crystallites of Fe2O3 in B2O3 glass. Mössbauer spectra observed are different from those observed by earlier workers in complex borate glasses. A high-spin Fe2+ state is observed in B2O3 glass containing 0.05 wt% Fe2O3. The result in Na2O⋅2B2O3 doped with a very low concentration of Fe2O3 is also different from that in B2O3 doped with similar amounts of Fe2O3.
Magneto-optical properties of KTb3F10 and LiTbF4 crystals
Authors: Weber M. J. , Morgret R. , Leung S. Y. , Griffin J. A. , Gabbe D. , Linz A.
Published: February 2003

Single crystals of KTb3F10, LiTbF4, LiTb0.5Y0.5F4 and LiTb0.25Gd0.75F4 were prepared and the wavelength, temperature, and magnetic field dependence of the Faraday rotation measured. Optical-absorption spectra and refractive indices are also reported. The Faraday effect in these materials is described by a paramagnetic rotation with the primary oscillator strength arising from 4f8→4f75d electronic transitions of the Tb3+ ions. Whereas LiTbF4 orders ferromagnetically at low temperatures, the mixed crystals exhibited no ordering at T?1.25 K. Low-temperature Faraday rotation measurements of KTb3F10 do not indicate ferromagnetic order above 1.66 K. KTb3F10 and LiTbF4 crystals have large Verdet constants, are transparent in the visible and near infrared and have small nonlinear refractive-index coefficients. These materials are therefore useful for optical rotators and in high-power laser applications.
Photostructural change of lattice-vibrational spectra in Se-Ge chalcogenide glass
Authors: Utsugi Yasushi , Mizushima Yoshihiko
Published: February 2003

Far-infrared absorption spectra of amorphous-chalcogenide semiconductors were measured in the frequency region 500–80 cm−1. A reversible change in the lattice-vibrational spectra of amorphous Se-Ge films at room temperature due to photoirradiation and heat treatment is first reported. A peak in the 256.4-cm−1 absorption band is broadened and weakened by light photoirradiation and recovers by heat treatment, an effect which is associated with the ’’photodarkening effect’’ in amorphous-chalcogenide films. By photoirradiation, no changes were observed in Raman scattering spectrum for amorphous Se-Ge. It is indicated that photoirradiation enhances further disorder in the atomic configurations and induces a decrease in band-gap energy. Broadening and weakening are caused by an increased fluctuation in the Se-Ge bond angle by photoirradiation, wherein the increased fluctuation degree corresponds to a frozen-in state of the thermally excited fluctuation. Through the Grüneisen parameter, correlation with several macroscopic properties, such as volume expansion, is discussed.
Ultrafine chromium particles for photothermal conversion of solar energy
Authors: Granqvist C. G. , Niklasson G. A.
Published: February 2003

Individually isolated chromium particles were prepared by evaporation onto KBr plates in a mixture of argon and air. Such coatings were taken as a model substance simulating the properties of electrodeposited chromium black—a well-known material for efficient photothermal conversion of solar energy. Median diameters of the particles were 5–13 nm; their shapes were spherical or cubelike. Optical transmittance at normal incidence was recorded by spectrophotometry in the interval 0.3–25 μm. Excellent spectral selectivity was documented with high absorptance over the wavelength range for solar radiation and high transmittance further out in the infrared. The optical data were interpreted within the Maxwell Garnett theory, which was generalized so as to encompass dipole-dipole coupling among aggregated spheres, cubelike shapes, and oxide pellicles. Agreement between theory and experiments was achieved by considering aggregation of spherical particles into linear chains. The effects of having cubic particles, as well as oxide-coated spherical ones, were calculated and found to be rather unimportant for understanding the spectral selectivity.
Dynamics of a pistonless engine capable of utilizing solar energy
Authors: Bhargava S. C. , Rup Raj , Saxena R. P. , Srivastava P. K.
Published: February 2003

The dynamics of a liquid piston engine capable of working at low temperature differences is discussed in detail. Two working fluids have been considered, viz., dry air and air saturated with water vapor. A resonance condition for the length of the liquid columns is obtained by solving the linearized equations of motion. In a study of the complete equations of motion, it is found that the engine using wet air is capable of delivering about 70% of its kinetic energy every second while operating at a temperature difference of only 40 °C. It is also found that the dry-air engine operates at only very high temperature differences.