bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Impurities on the Performance of Doped-Well GaInAs/InP Resonant Tunneling Diodes
Authors: Sekiguchi Tomonori , Yasuyuki Miyamoto Yasuyuki Miyamoto , Kazuhito Furuya Kazuhito Furuya
Published: February 2005

The influence of well impurity doping on the performance of GaInAs/InP resonant tunneling diodes (RTDs) was investigated. For undoped diodes, the peak-to-valley (P/V) current ratio was 9.7, at 2×1017 cm-3 it was 10.8, and at 2×1018 cm-3 it was 4.0. The maximum at 2×1017 cm-3 can be explained by potential bending, and the decrease at 2×1018 cm-3 can be explained by scattering. A change in the current-voltage characteristics at a doping level of 2×1018 cm-3 can be explained by potential bending in the well. Moreover, the variation in the observed width of the resonance level can explain the change in P/V ratios.
(01n)-Oriented BiSrCaCuO Thin Films Formed on CeO2 Buffer Layers
Authors: Tanimura Junji , Kuroda Ken'ichi , Kataoka Masayuki , Wada Osamu , Takami Tetsuya , Kojima Kazuyoshi , Tetsuo Ogama Tetsuo Ogama
Published: February 2005

With the use of RF magnetron sputtering, (01n)-oriented BiSrCaCuO superconducting films were first formed using MgO(110) substrates with CeO2(110) buffer layers. The film obtained using the just MgO(110) substrate had (01n)- and (01̄n)-preferred orientations with the c-axis tilted 45° against the surface of the CeO2 buffer layer. Moreover, with the use of an off-oriented MgO(110) substrate, a uniquely oriented BiSrCaCuO film with the c-axis not perpendicular to the substrate surface was obtained without twin boundaries.
Control of Superconducting Properties of LnBa2Cu3Oy (Ln=Y, Eu) Thin Film Microbridges by Visible Light Irradiation
Authors: Tanabe Keiichi , Kubo Syugo , Teherani Ferechteh Hosseini , Hidefumi Asano Hidefumi Asano , Minoru Suzuki Minoru Suzuki
Published: February 2005

The effects of visible light irradiation on the superconducting properties of LnBa2Cu3O
y
(Ln=Y, Eu) thin film microbridges (13 µm wide constrictions) are examined using a He-Ne laser light which is coupled into an optical fiber with a power density of up to 60 W/cm2. A clear T
c enhancement and a decrease in the normal resistivity both induced by the irradiation are observed even for thin films with a T
c as high as 82 K and larger effects are observed for lower-T
c films. The time dependence of the resistivity decrease almost obeys the logarithmic law. It is demonstrated that the normal resistance and the critical current value of the microbridges can be well controlled by the product of irradiation power and time, namely, the cumulative photon dose.
Stability of Feedback-Type Neural Networks Having Nonsymmetric Interconnections
Authors: Hitoshi Mada Hitoshi Mada
Published: February 2005

A Hopfield network has symmetric interconnections that carry many patterns of memory. Dynamics of the Hopfield model are explained with the energy function constructed by a quadratic form of input vectors and interconnections. However, it is difficult to implement complete symmetric interconnection with practical hardwares. Neural networks having nonsymmetric interconnections cannot be discussed using the energy function. This paper describes a method to treat stability of a Hopfield model having nonsymmetric interconnections. The discussed mathematical forms are analogous to nonequilibrium thermodynamics. A stable condition is theoretically obtained for nonsymmetrically interconnected neural networks.
Electron Tunneling Process between the Two Ground States in Coupled Quantum Well Structure
Authors: Shimizu Naofumi , Furuta Tomofumi , Takao Waho Takao Waho , Takashi Mizutani Takashi Mizutani
Published: February 2005

We have studied the electron tunneling process between the two ground states in a coupled quantum well structure at various temperatures using time-resolved photoluminescence spectroscopy. Two tunneling processes are observed: LO-phonon assisted tunneling and ground-to-ground-state tunneling. The ground-to-ground-state tunneling transfer rate is found to increase as the temperature decreases from 40 K to 6 K. This marked increase in the transfer rate causes the dominant tunneling process to change from LO-phonon assisted tunneling at 40 K to ground-to-ground-state tunneling at 6 K.
Magnetic Properties of CoPt Alloy Films Sputtered on Pt Underlayers
Authors: SHIOMI Shigeru , OKAZAWA Hironori , NAKAKITA Tomoki , Tadashi KOBAYASHI Tadashi KOBAYASHI , Morio MASUDA Morio MASUDA
Published: February 2005

CoPt alloy films have been sputtered on room-temperature glass slides. It has been found that effective perpendicular anisotropy K
⊥ depends on the film composition and reaches a maximum in films with M
s∼850 emu/cm3, and that K
⊥ is greatly enhanced by the application of substrate bias and the deposition of a Pt underlayer. K
⊥ increases with increasing CoPt layer thickness d(CoPt), becoming almost constant beyond d(CoPt)=100 nm in films sputtered on 100-nm-thick Pt underlayers. It has also been found that sputtering at higher Ar gas pressure without substrate bias greatly enhances coercivity, though K
⊥ is somewhat reduced.
Atomic-Layer Control in GaP Growth by Laser-Triggered Chemical Beam Epitaxy
Authors: Yoshimoto Masahiro , Vaccaro Pablo , Hashimoto Tadao , Atsushi Kajimoto Atsushi Kajimoto , Hiroyuki Matsunami Hiroyuki Matsunami
Published: February 2005

Control of GaP growth at the atomic-layer level has been achieved by laser-triggering in chemical beam epitaxy (CBE) under a simultaneous supply of triethylgallium (TEGa) and thermally cracked PH3. The growth rate of GaP was enhanced at low substrate temperatures by ultraviolet (UV) light emitted from a N2 laser. The growth rate is controlled by either the TEGa supply between laser pulses or the photon number, and it shows saturation with a high TEGa supply. This preliminary result will open a new atomic-layer epitaxial mode by means of UV-laser irradiation without an alternating supply of source gases in CBE.
Electron Spin Resonance Centers and Light-Induced Effects in Porous Silicon
Authors: Yokomichi Haruo , Kondo Hideyuki Takakura
Published: February 2005

The nature of defects in porous silicon has been investigated by electron spin resonance measurements. The main defect has trigonal symmetry with a principal axis along the <111> axis, and the principal values of the g-tensors, g// and g
⊥, are 2.0022 and 2.0078, respectively. This defect is identified as a silicon dangling bond located at the surface or at the interface between c-Si and SiO2. Light-induced defect creation and accompanying photoluminescence fatigue have been observed. These changes are partly, but not completely, recovered by thermal annealing, unlike hydrogenated amorphous silicon. Consequently, it is suggested that the light-emitting region of porous silicon is mainly the single-crystal phase.
Light Soaking of a-Si:H at 77 K
Authors: Zhang Qing , Minoru Kumeda Minoru Kumeda , Tatsuo Shimizu Tatsuo Shimizu
Published: February 2005

Light-induced metastable changes in the defect density and the photoconductivity in hydrogenated amorphous silicon for light soaking at 77 K are compared with those at room temperature (RT). Using the power law and the stretched exponential law to fit the data, we found that data for the 77 K light soaking deviate from the (time)1/3×(carrier generation rate)2/3 law for the RT light soaking, and the stretched exponential exponent β is around 0.7 in contrast to the value of about 0.45 for the RT light soaking.
Experimental Derivation of Resonant Tunneling Transit Time Using a Coupled-Quantum-Well Base Transistor
Authors: Takao Waho Takao Waho , Takashi Mizutani Takashi Mizutani
Published: February 2005

We derive the base transit time in a GaAs/AlAs coupled-quantum-well (CQW) base transistor through its high-frequency characteristics. The estimated time should be equivalent to the resonant tunneling transit time, since the collector current in this transistor is the resonant tunneling current flowing through the CQW base and is controlled by the CQW's potential. It is found that the experimentally derived time for 2-nm AlAs barriers (3.2±0.8 ps) agrees reasonably well with the theoretically predicted one.
Influence of the OH Content on Second Harmonic Generation from Electrically Polarized SiO2 Glasses
Authors: Nasu Hiroyuki , Okamoto Hideki , Mito Akihiro , Jun Matsuoka Jun Matsuoka , Kanichi Kamiya Kanichi Kamiya
Published: February 2005

The influence of the OH content in the SiO2 glasses on the intensity of second harmonic generation was investigated. The SiO2 glasses containing various amounts of OH were electrically polarized by applying 3 kV at 300°C. The intensity of the second harmonic generation was dependent on the OH content, and the largest χ33
(2), which was nearly 2% of the χ33
(2) value of LiNbO3, was obtained for sol-gel-derived SiO2 glass containing the largest amount of OH.
Relationship between Barrier Thickness and Crystal Quality in InGaAs/InGaAsP Strained Multi-Quantum Well Structure
Authors: Suzaki Shinzo , Ravikumar Katare Gopalrao , Sekiguchi Toshisada , Takuya Aizawa Takuya Aizawa , Ryozo Yamauchi Ryozo Yamauchi
Published: February 2005

The barrier layer thickness dependence on crystal quality of the multi-quantum well (MQW) structure with compressively strained InGaAs wells and InGaAsP (λg=1.15 µm) barriers is investigated. The lattice mismatch Δa/a for a 15-period MQW structure with a 1%-strained 5 nm InGaAs (In0.68Ga0.32As) well layer is improved by increasing the thickness of the barrier layer, and it becomes saturated over 15 nm to around 0.2%. The X-ray diffraction peak intensity becomes saturated over 10 nm. The strongest exciton peak intensity and the sharpest peak width are observed for a 10 nm barrier. The optimum well volume ratio for a MQW, shown as W/(W+B), is around 0.3 from the results of the X-ray diffraction peak intensity and the exciton peak width and intensity (W: well thickness, B: barrier thickness).
New Concepts for Material Characterizations and Optical Devices: Positive and Negative Hybrid Logics and Self-Induced Photonic Oscillators
Authors: Bruno Ullrich Bruno Ullrich
Published: February 2005

Signal treatments via fibers will replace the common technique using wires. Thus, devices which can process light signals directly in convenient technical ways become more and more interesting. Some future aspects and preliminary experimental findings demonstrated on thin CdS films are presented.
Measurements of Diffusion Coefficiens of Water in Electron Cryclotron Resonance Plasma SiO2
Authors: Takahashi Yasuo , Namatsu Hideo , Katsuyuki Machida Katsuyuki Machida , Kazushige Minegishi Kazushige Minegishi
Published: February 2005

This work proposes a method for measureing the diffusion coefficients of water in the ECR (electron cyclotron resonance) plasma CVD SiO2 used for inter-metal dielectrics. The diffusion coefficients are calculaterd from TPD (temperature programmed desorption) spectra of water measured for a sample SiO2/SOG (spin of glass)/Si structure. In this method, the SOG film is used for a water source. The water diffusion coefficient in ECR SiO2 films measured using this method points to large water blocking power comparing with fused silica.
Ar Ion Laser-Assisted Metalorganic Molecular Beam Epitaxy of InGaAsP
Authors: Iga Ryuzo , Takeshi Yamada Takeshi Yamada , Hideo Sugiura Hideo Sugiura
Published: February 2005

Selective growth of InGaAsP by Ar ion laser-assisted metalorganic molecular beam epitaxy is studied. Laser irradiation during the In1-x
Ga
x
As1-y
P
y
(x=0.28, y=0.4) growth suppresses the growth rate by about 30% of the growth rate in the nonirradiated area and the Ga composition x to about one-tenth that in the nonirradiated area at 510°C. It is found that the rise in the substrate temperature causes the suppression of both the growth rate and the Ga composition of the In1-x
Ga
x
As1-y
P
y
film. The photoluminescence (PL) wavelength of the InGaAsP/InP multiple quantum well shifts to a longer wavelength with laser irradiation during InGaAsP well growth.
GaAs/AlAs and AlAs/GaAs Interface Formation Process Studied by Coaxial Impact-Collision Ion Scattering Spectroscopy: Comparison between Alternating and Simultaneous Source Supply
Authors: Saitoh Tohru , Joyce E. Palmer Joyce E. Palmer , Masao Tamura Masao Tamura
Published: February 2005

Real time observation of GaAs/AlAs and AlAs/GaAs heterointerface formation by molecular beam epitaxy with an alternating source supply and a conventional simultaneous source supply has been performed using coaxial impact-collision ion scattering spectroscopy. A He+ ion beam of 2 keV was incident on the sample surface and the scattering intensity from Ga and As atoms was measured in situ while Ga (Al) and As4 beams were alternately or simultaneously irradiated on the AlAs (GaAs) surface. The time-resolved variations in the scattering intensity show the behavior of Ga atoms in relation to droplet formation and surface segregation when growth is carried out by an alternating source supply, while the intensity variations are consistent with a simple layer-by-layer growth process in the case of simultaneous source supply.
Electron Spin Resonance Spectra of KxC60 Films Prepared by Electrochemical Doping
Authors: Araki Hisashi , Yamasaki Nobuo , Kawai Tsuyoshi , Zakhidov Anver A. , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

We have found that K-doped C60 films can be prepared by the electrochemical doping technique using a solid electrolyte. From these films, we obtained four electron spin resonance (ESR) peaks at a temperature below 50 K. The intensity of one peak in the high field region was extremely sensitive to slight changes in temperature below 10 K and in microwave power. Spin-lattice relaxation time gives a major effect on the power dependence of the increasing rate of the intensity. The ESR center giving this anomalous peak is tentatively interpreted to be related to the superconducting state.
Self-Starting Threshold for Additive Pulse Mode Locking in Nd:YLF Laser
Authors: Kyeong Koo Chi Kyeong Koo Chi , Hong Jin Kong Hong Jin Kong
Published: February 2005

The self-starting condition for the additive pulse mode locking in an arc lamp pumped cw Nd:YLF laser was investigated experimentally. With variation in the coupling between the main cavity and the external cavity, the threshold power for self-starting additive pulse mode locking was measured. A comparison is made between the experimental results and the previously reported results for the cavity mode correlation time.
Nanofabrication of Titanium Surface by Tip-Induced Anodization in Scanning Tunneling Microscopy
Authors: Sugimura Hiroyuki , Uchida Tatsuya , Noboru Kitamura Noboru Kitamura , Hiroshi Masuhara Hiroshi Masuhara
Published: February 2005

A titanium (Ti) surface was arbitrarily oxidized by a scanning tunneling microscope (STM). Oxidation of the Ti surface was induced by scanning an STM tip with the sample (Ti) bias of more than +3 V, and a dot or line pattern of oxide was fabricated on Ti with the spatial resolution of 70 nm. The results were discussed in terms of tip-induced anodization of Ti due to water adsorbed on the surface.
Electrical Properties of Boron-Implanted Homoepitaxial Diamond Films
Authors: Mori Yusuke , Deguchi Masahiro , Okada Takashi , Eimori Nobuhiro , Yagi Hiromasa , Hatta Akimitsu , Nishimura Kazuhito , Kitabatake Makoto , Ito Toshimichi , Hirao Takashi , Takatomo Sasaki Takatomo Sasaki , Akio Hiraki Akio Hiraki
Published: February 2005

Electrical properties produced by boron implantation in homoepitaxial diamond films grown by chemical vapour deposition (CVD) have been studied. Two techniques were employed to anneal out implantation damage: thermal annealing and hydrogen plasma treatment. A large difference in electrical properties between boron-implanted CVD and high-pressure synthesized (HPS) diamonds after thermal annealing has been observed. Hydrogen plasma treatment has a substantial advantage concerning the electrical properties of implanted diamond compared with thermal annealing.
Possible Existence of a Surplus (Oxygen-Excess) Ga Oxide in the Thermal Oxide of GaAs
Authors: Toshifumi Ishikawa Toshifumi Ishikawa , Hideaki Ikoma Hideaki Ikoma
Published: February 2005

With the use of X-ray photoelectron spectroscopy (XPS), a surplus (oxygen-excess) Ga oxide was observed in the thermal oxides of GaAs grown at temperatures between 400°C and 550°C in dry oxygen. The surplus oxides are probably GaO2. A possible mechanism of formation of such an excess oxide is briefly discussed. Advanced Ga oxides such as Ga2O3 and GaO2 begin to desorb and evaporate from the surface during oxidation at 550°C for 10 min. Ga suboxides such as GaO and Ga2O showed no evidence of desorption or evaporation. No surplus (oxygen-excess) oxide of As was observed.
Bulk Growth of Single-Crystal Cubic Silicon Carbide by Vacuum Sublimation Method
Authors: Furukawa Katsuki , Tajima Yoshimitsu , Saito Hajime , Fujii Yoshihisa , Akira Suzuki Akira Suzuki , Shigeo Nakajima Shigeo Nakajima
Published: February 2005

Bulk single crystals of cubic silicon carbide up to 4 mm in length have been obtained by means of the modified sublimation method. Growth temperature and pressure were examined in order to increase the growth rate. The temperatures of seed crystal and source material and the temperature gradient were 1750°C, 2250°C and 100°C·cm-1, respectively. The pressure was ∼10-2 Pa. The growth rate obtained was 0.8 mm·h-1, which is one order of magnitude larger than previously reported values. Raman spectroscopy, reflectoin high-energy electron diffraction analysis and molten KOH etching show that bulk crystals grown on 6H(0001) and 3C(111) seed crystals were 3C(111) single crystals. The crystal on the 6H(0001) showed no double positioning boundaries.
Wide Composition Range of T*-Phase Compound Pr1.6-xYxSr0.4CuOy (0≤x≤0.6)
Authors: Manabu Kishi Manabu Kishi
Published: February 2005

Measurements of X-ray diffraction, magnetic susceptibility and electric resistivity have been carried out for the Pr1.6-x
Y
x
Sr0.4CuO
y
system. The T* phase is obtained in the composition range 0≤x≤0.6. T* phases are also obtained in Nd1.6-x

L
n

x
Sr0.4CuO
y
systems (Ln; Y, Ho, Er, Tm, Yb and Lu), but in a narrow x range such as that of other known T*-phase compounds. The electric resistivity of the Pr system shows systematic rises accompanied by an increase in Pr concentration. This behavior is similar to that of (Pr-Ln)Ba2Cu3O7 in a higher Pr concentration region. Both the wide composition range and the rise of resistivity may be due to the same factor.
Grain Size Effect of CuFeTe2 Response to Oxygen
Authors: Kishiro Koichi , Hisao Kuriyaki Hisao Kuriyaki , Kazuyoshi Hirakawa Kazuyoshi Hirakawa
Published: February 2005

The electrical resistivity of the layered semiconductor CuFeTe2 is created in response to oxygen concentration intercalated into the van der Waals gaps. An oxygen gas sensor operating around room temperature has been fabricated using this property. The resistivity response to oxygen has been improved by the use of crystal grains of uniform size. The specimen consisting of grains with diameters of 20∼53 µm responds to 20% oxygen mixed into nitrogen in 2 min.
Measurements of the CF, CF2 and CF3 Radicals in a CHF3 Electron Cyclotron Resonance Plasma
Authors: Takahashi Kunimasa , Hori Masaru , Maruyama Koji , Shigeru Kishimoto Shigeru Kishimoto , Toshio Goto Toshio Goto
Published: February 2005

The CF, CF2 and CF3 radicals were investigated in an on-off modulated electron cyclotron resonance (ECR) plasma employing a CHF3 gas using infrared diode laser absorption spectroscopy (IRLAS). The microwave power dependences of the radical densities were measured at a CHF3 pressure of 0.4 Pa in the microwave power range from 50 W to 800 W. Moreover, the extinction processes of the radicals were discussed on the basis of the decay curve analysis of the radical densities after termination of the discharge.
Extrinsic Base Surface Recombination Current in GaInP/GaAs Heterojunction Bipolar Transistors with Near-Unity Ideality Factor
Authors: William Liu William Liu
Published: February 2005

Devices demonstrating near-ideal I-V characteristics are fabricated to examine the ideality factor for extrinsic base surface recombination in GaInP/GaAs HBTs. These HBTs with various emitter areas have either passivated or exposed extrinsic base surfaces. Comparison of the passivated and unpassivated devices' characteristics indicate that the ideality factor value of the surface recombination is as close to unity as 1.05. The ideality factor value is bias dependent, decreasing to values of 1.6 at lower base-emitter biases.
Simultaneous Manipulation and Lasing of a Polymer Microparticle Using a CW 1064 nm Laser Beam
Authors: Misawa Hiroaki , Fujisawa Ryo , Sasaki Keiji , Noboru Kitamura Noboru Kitamura , Hiroshi Masuhara Hiroshi Masuhara
Published: February 2005

Simultaneous optical manipulation and lasing of a rhodamine 640-doped polystyrene latex particle in water was demonstrated through irradiation of a single focused 1064 nm CW Nd:YAG laser beam. Lasing of the particle resulting from two-photon absorption was confirmed from periodically spaced peaks in the emission spectrum and from nonlinear (more than quadratic) dependence of the emission intensity upon the incident laser power.
Photoluminescence of Eu3+ in CaS:Eu Phosphor
Authors: Fukumoto Shigeru , Hayashi Yasufumi , Ibuki Sumiaki , Abe Kazunori , Ohnishi Hidetomi
Published: February 2005

New emission lines from Eu3+ centers aside from the main broad-band emission from Eu2+ in CaS-doped EuF3 were found at 10 K. The intensity of these emission lines increases after annealing in a mixed gas of Ar and O2. The origin of the emission might be related to interstitial O2- or F-.
Pulling Technique of a Homogeneous GaInSb Alloy under Solute-Feeding Conditions
Authors: Watanabe Akiyoshi , Akira Tanaka Akira Tanaka , Tokuzo Sukegawa Tokuzo Sukegawa
Published: February 2005

Stable growth under solute-feeding conditions was realized using a two-chamber (growth and source) crucible, in which a small hole connecting the two chambers was used to control the solute supply from the source region. A piston mechanism pushed up the solute source in the source chamber to keep the volume in the growth region constant during growth. With use of a GaSb seed crystal, a GaInSb bulk alloy of 13 mm diameter and 12 mm length with uniform InSb content of 3 mol% was successfully pulled from GaSb-InSb pseudo-binary solution at a constant temperature of 677°C.
A Semi-Analytical Approach to Compute the Decay of Optically Generated Carriers in Silicon Wafer
Authors: Morin Michel , Mitsu Koyanagi Mitsu Koyanagi , Masataka Hirose Masataka Hirose
Published: February 2005

A diffusion model is applied to the recombination dynamics of photogenerated carriers created by laser beam incident to a silicon slab. This analysis yields excess carrier density as an analytical function of time and depth, allowing a fast modeling of excess carrier decay with multi-parameter tuning capability such as excess carrier diffusion coefficient, wafer thickness, surface recombination velocity, bulk lifetime, excitation light absorption coefficient and pulse duration of the excitation laser beam.
Preparation and Transport Properties of TlBa2Ca2Cu3Oy Thin Films by Metalorganic Deposition
Authors: Koike Shuichi , Toshihide Nabatame Toshihide Nabatame , Izumi Hirabayashi Izumi Hirabayashi
Published: February 2005

Thin films of the TlBa2Ca2Cu3O
y
(Tl-(1223)) system were successfully prepared on SrTiO3(100) substrates by means of the deposition of a Ba-Ca-Cu-O precursor by the metalorganic deposition (MOD) method with the reaction of Tl2O3 vapor. The films (1 µm thickness) were composed entirely of the (1223) phase and had a highly c-axis-oriented structure. The films had T
c zero=106 K and showed a high transport critical current (I
c) of 6.3 A with a 1-mm-wide bridge, which corresponds to the transport critical current density (J
c) of 6.3×105 A/cm2 at 77 K in a zero magnetic field. When the magnetic field was applied perpendicular to the a-b plane, the J
c values were 2.0×104 and 6.0×105 A/cm2 at 77 and 40 K in a 1 T field, respectively. Moreover, the history effect of J
c in the magnetic field was not observed at 77 K below 0.1 T. These results indicate that the Tl-(1223) film, formed by the MOD method, has strong magnetic flux pinning characteristics and good intergranular connectivity.
Preparation and Magnetic Property of Sintered Sm2Fe17NxMaterials under High-Pressure Conditions
Authors: Machida Ken-ichi , Nakatani Yoshitaka , Onodera Akifumi , Gin-ya Adachi Gin-ya Adachi
Published: February 2005

Sm2Fe17Nxmaterials were sintered from the corresponding powder under high-pressure conditions of 1.5-30 kb and 300-800°C without any binding material such as zinc or epoxy resin. The sintering characteristics were improved with increase of the applied pressure and temperature, and the sample prepared at 30 kb and 550°C exhibited a good mechanical strength for use as magnet materials, but decomposition to SmN and α-Fe took place under conditions of 30 kb and 800°C.
Saturable Absorption in Ion-Exchanged CdSxSe1-x-Doped Glass Waveguides
Authors: Shimomura Kenkichi , Murata Hiroshi , Masayuki Izutsu Masayuki Izutsu , Tadasi Sueta Tadasi Sueta
Published: February 2005

We have fabricated single-mode channel waveguides using Na+/K+ ion exchange in CdS
x
Se1-x
-doped glasses. Optically induced saturable absorption in these waveguides has been found in the mW guided power range at 514.5 nm wavelength. Observation of apparent time delay on the order of 100 ns between input and output light pulses and its extinction is also reported.
The Problem of Polarization in the Spectral Reflectance Measurement of Textured Crystalline Si Solar Cells
Authors: Shimokawa Ryuichi , Nagamine Fumiaki , Tsuboi Hideyuki
Published: February 2005

This is the first observation of the polarization effect on the spectral reflectance of textured crystalline Si solar cells. It was found that the reflectance of such cells, especially microgrooved solar cells, depends on the polarization of the incident light from the grating monochromator. Also, we have developed two different techniques for measuring the nonpolarization reflectance of such cells. One involves circularly polarized light produced through a quarter-wave multiple-order plate. The other involves the newly developed calcite Lyot depolarizer.
Dependence of Photoluminescence Intensity Enhancement due to Sulfide Treatment on Carrier Concentration and Conduction Type of GaAs
Authors: Kenji Uchida Kenji Uchida , Shin'ichi Nakatsuka Shin'ichi Nakatsuka
Published: February 2005

We find that the photoluminescence intensity enhancement associated with sulfide treatment strongly depends on the carrier concentration and conduction type. The band bending of p-type GaAs decreases, and that of n-type GaAs increases. Surface states are more markedly reduced between the midgap and the conduction band minimum, than between the valence band maximum and the midgap. It is considered that donor-like surface states which capture the electrons are distributed between the midgap and the conduction band maximum, explaining the large intensity enhancement of p-type GaAs with high carrier concentrations, and the very small enhancement of n-type GaAs with high carrier concentration.
Laue-Case Plane Wave Topography Using Synchrotron Radiation to Reveal Microdefects in a Thinned Silicon Crystal
Authors: Suzuki Yoshifumi , Chikaura Yoshinori , Imai Masato , Ishikawa Tetsuya
Published: February 2005

X-ray plane-wave topography in a Laue-transmission case has been widely used to observe microdefects in otherwise perfect silicon crystals. To show the experimental effect of specimen thickness, plane-wave topographic observations were conducted before and after the stepwise chemical etching of the specimen crystal. The observations showed a heightening of the strain sensitivity when reducing the specimen thickness to less than several times the extinction distance of the relevant diffraction. The thickness effect was interpreted through X-ray dynamical diffraction theory for distorted crystals (Takagi-Taupin theory). The computer simulations of the diffraction theory proved that correlations exist amongst the divergence of the incident X-ray beams, the crystal thickness, and the quantity of the minute strain.
Substrate Misorientation Effects on Silicon-Doped AlGaAs Layers Grown on GaAs(111)A by Molecular Beam Epitaxy
Authors: Fujita Kazuhisa , Yamamoto Teiji , Toshihiko Takebe Toshihiko Takebe , Toshihide Watanabe Toshihide Watanabe
Published: February 2005

Silicon-doped Al0.3Ga0.7As layers were grown on GaAs(111)A misoriented 0-19.5° toward (100) by molecular beam epitaxy (MBE). The surface morphology was strongly affected by the off-angle of the substrates; a mirror surface was obtained when the off-angle was over 5°. Occupation sites of Si atoms were dependent on the flux ratio; at a ratio of 2, most Si atoms occupied As sites, whereas at ratios above 5, most Si atoms occupied Ga sites although there was greater compensation. The results show that the off-angle of GaAs(111)A substrates is an important factor for controlling the surface morphology and the impurity concentration of AlGaAs.
Characterization of Surface Conductive Diamond Layer Grown by Microwave Plasma Chemical Vapor Deposition
Authors: Mori Yusuke , Show Yoshiyuki , Deguchi Masahiro , Yagi Hiromasa , Yagyu Hiroyuki , Eimori Nobuhiro , Okada Takashi , Hatta Akimitsu , Nishimura Kazuhito , Kitabatake Makoto , Ito Toshimichi , Hirao Takashi , Izumi Tomio , Takatomo Sasaki Takatomo Sasaki , Akio Hiraki Akio Hiraki
Published: February 2005

The electronic structure of the surface and defect density in diamond films as-grown and cooled in an oxygen ambient after deposition have been investigated by means of electron energy loss and electron spin resonance spectroscopies. As-grown diamond films contain an amorphous carbon phase and a larger amount of defects in the surface region compared with the bulk region.
Werner Goldsmith: Life and Work (1924–2003)
Authors: Berger Stanley A. , King Albert I. , Lewis Jack L.
Published: February 2005

▪ Abstract  Werner Goldsmith, one of the foremost authorities on the mechanics of impact and the biomechanics of head and neck injuries, died peacefully at home in Oakland, California, on August 23, 2003, at age 79 after a short, courageous battle with leukemia, ending a long and very distinguished career in mechanics, dynamics, and biomechanics, and an almost six-decades-long association with the University of California, Berkeley. He was one of the pioneering, eminent solid and fluid mechanicians who made an early transition to biomechanics, and in rising to equal distinction in their new fields, added great credibility to biomechanics as a discipline in its own right. He was also a distinguished and influential figure in bioengineering education at his own institution, and, more broadly, in the United States and abroad. An emeritus professor for over a decade, he continued to be active in research and teaching until the very last days of his life.
A new polymorphism in the type II deiodinase gene is associated with circulating thyroid hormone parameters
Authors: Peeters Robin P. , van den Beld Annewieke W. , Attalki Hayat , Toor Hans van , de Rijke Yolanda B. , Kuiper George G. J. M. , Lamberts Steven W. J. , Janssen Joop A. M. J. L. , Uitterlinden Andre G. , Visser Theo J.
Published: February 2005

Type II deiodinase (D2) is important in the regulation of local thyroid hormone bioactivity in certain tissues. D2 in skeletal muscle may also play a role in serum triiodothyronine (T3) production. In this study, we identified a polymorphism in the 5′-UTR of the D2 gene (D2-ORFa-Gly3Asp). We investigated the association of D2-ORFa-Gly3Asp, and of the previously identified D2-Thr92Ala polymorphism, with serum iodothyronine levels. D2-ORFa-Gly3Asp was identified by sequencing the 5′-UTR of 15 randomly selected individuals. Genotypes for D2-ORFa-Gly3Asp were determined in 156 healthy blood donors (age 46.3 ± 12.2 yr) and 349 ambulant elderly men (age 77.7 ± 3.5 yr) and related to serum iodothyronine and TSH levels. D2-ORFa-Asp3had an allele frequency of 33.9% in blood bank donors and was associated with serum thyroxine (T4; Gly/Gly vs. Gly/Asp vs. Asp/Asp = 7.06 ± 0.14 vs. 6.74 ± 0.15 vs. 6.29 ± 0.27 μg/dl, P = 0.01), free T4(1.22 ± 0.02 vs. 1.16 ± 0.02 vs. 1.06 ± 0.04 ng/dl, P = 0.001), reverse T3( P = 0.01), and T3/T4ratio ( P = 0.002) in a dose-dependent manner, but not with serum T3( P = 0.59). In elderly men, D2-ORFa-Asp3had a similar frequency but was not associated with serum iodothyronine levels. This new polymorphism in the 5′-UTR of D2 is associated with iodothyronine levels in blood donors but not in elderly men. We hypothesize that this might be explained by the decline in skeletal muscle size during aging, resulting in a relative decrease in the contribution of D2 to serum T3production.
Effect of Electrical Coupling on Ionic Current and Synaptic Potential Measurements
Authors: Rabbah Pascale , Golowasch Jorge , Nadim Farzan
Published: February 2005

Recent studies have found electrical coupling to be more ubiquitous than previously thought, and coupling through gap junctions is known to play a crucial role in neuronal function and network output. In particular, current spread through gap junctions may affect the activation of voltage-dependent conductances as well as chemical synaptic release. Using voltage-clamp recordings of two strongly electrically coupled neurons of the lobster stomatogastric ganglion and conductance-based models of these neurons, we identified effects of electrical coupling on the measurement of leak and voltage-gated outward currents, as well as synaptic potentials. Experimental measurements showed that both leak and voltage-gated outward currents are recruited by gap junctions from neurons coupled to the clamped cell. Nevertheless, in spite of the strong coupling between these neurons, the errors made in estimating voltage-gated conductance parameters were relatively minor (<10%). Thus in many cases isolation of coupled neurons may not be required if a small degree of measurement error of the voltage-gated currents or the synaptic potentials is acceptable. Modeling results show, however, that such errors may be as high as 20% if the gap-junction position is near the recording site or as high as 90% when measuring smaller voltage-gated ionic currents. Paradoxically, improved space clamp increases the errors arising from electrical coupling because voltage control across gap junctions is poor for even the highest realistic coupling conductances. Furthermore, the common procedure of leak subtraction can add an extra error to the conductance measurement, the sign of which depends on the maximal conductance.
Dollars and Deficits - The US Current Account Deficit and its Exchange Rate Consequences
Authors: Al-Eyd Ali , Barrell Ray , Pomerantz Olga
Published: February 2005

In the past three years the US dollar has been declining whilst the US current account deficit has expanded, and these two developments are clearly linked. However, the causes of the decline in the dollar and the solution to the US deficit may not be as closely related as at first may appear. The emergence of a sustained deficit does not automatically necessitate a fall in the exchange rate, and a fall in the exchange rate may not correct such a deficit. Deficits can exist if the currency moves above its sustainable real exchange rate, and a real depreciation can remove such a deficit. Deficits caused by exchange rate movements are likely to be more temporary than those that either emerge for long-term structural reasons or result from structural imbalances in the economy. A structural deficit can be the consequence of low domestic saving or high domestic government borrowing. If domestic investment is very profitable then even high levels of domestic saving may still result in a savings shortfall, and the high returns may induce a structural capital inflow which will produce a sustainable current account deficit as a consequence. All these factors have influenced the increase in the US deficit in the past decade, and it is difficult to see how a correction to the deficit can occur without one of the domestic drivers changing in some way. Here we present a set of simulations using NiGEM to examine the impacts of alternative adjustment scenarios and their global implications. Before adding to the debate about the possible remedies, we will attempt to establish the sources of the current conjuncture, as the alternative adjustment paths for deficits and for the dollar depend on the sources of misalignment.
The Sterling Effective Exchange Rate and Other Measures of UK Competitiveness
Authors: Barrell Ray , Choy Amanda , Holland Dawn , Riley Rebecca
Published: February 2005

Movements in exchange rates attract much attention, both for the signals they may contain about future inflation prospects and for their implications for the competitiveness of firms. However, movements in bilateral exchange rates, for instance in sterling against the dollar or the euro, do not convey enough information for either policymakers or for firms except in relation to specific bilateral transactions. It is useful to construct summary measures of exchange rate movements, and there are a number of ways of doing this. The choice of measure depends upon the use to which it is to be put. Some measures, such as the effective exchange rate, are summary indicators, whilst others such as export competitive indices are more relevant when evaluating the prospects for export developments. Some indicators weight together nominal exchange rates. Others are measures of real exchange rates, weighting together exchange rate adjusted relative prices. The indicators chosen should be seen in the context in which they are used.
Stakeholder Participation in Voluntary Environmental Agreements: Analysis of 10 Project XL Case Studies
Authors: Murdock Barbara Scott , Wiessner Carol , Sexton Ken
Published: February 2005

This article examines stakeholder involvement and influence as part of voluntary environmental agreements between regulatory agencies and companies. Ten pilot projects that were part of the U.S. Environmental Protection Agency’s Project XL (excellence and leadership) were examined to evaluate process goals (fairness and competence) and outcome goals (trust and incorporation of public values in decisions). The ten case studies encompass a range of businesses, locations, and ideas for regulatory “reinvention” projects, and they span a spectrum of stakeholder participation processes and outcomes. Although results point to numerous problems in implementation, they also indicate that in several cases, stake holder groups significantly affected the final project agreement (FPA) and enforceable permit. The evidence suggests that companies can work collaboratively and constructively with residents of local communities, members of national environmental organizations and other interest groups, and government regulatory officials to craft voluntary environmental agreements that are cooperative and environmentally beneficial.
Green Chemistry as Social Movement?
Authors: Woodhouse Edward J. , Breyman Steve
Published: February 2005

Are there circumstances under which scientists and engineers doing their ordinary jobs can be thought of as participants in a social movement? The technoscientists analyzed in this article are at the forefront of a new way of doing chemistry; they are attempting to redesign chemical products and synthesis pathways to significantly reduce health effects and environmental damage from industrial chemicals. Green chemistry practitioners and entrepreneurs now constitute a small minority of chemists and chemical engineers in the university, government, and corporate sectors, but the innovators gradually are institutionalizing their efforts and winning converts. Drawing on concepts from social movement theory, the authors argue that examining green chemistry as a social movement sheds light on the intentional social organization of emerging scientific and engineering disciplines, advances thinking about the role of expertise in social change, and uncovers a possible pathway toward reconstructing chemical technologies on a more environmentally sustainable basis. The article closes with questions about potential coalitions among green chemists and engineers, regulators, and activist sectors of civil society.
Farnesyltransferase inhibitor R115777 (Zarnestra, Tipifarnib) synergizes with paclitaxel to induce apoptosis and mitotic arrest and to inhibit tumor growth of multiple myeloma cells
Authors: Zhu Kuichun , Gerbino Elvira , Beaupre Darrin M. , Mackley Paul A. , Muro-Cacho Carlos , Beam Craig , Hamilton Andrew D. , Lichtenheld Mathias G. , Kerr William G. , Dalton William , Alsina Melissa , Sebti Saïd M.
Published: February 2005

Despite major advances, multiple myeloma (MM) remains an incurable malignancy. Recently we have found that disease stabilization was achieved in 64% of patients with advanced MM treated with the farnesyltransferase inhibitor R115777 (Zarnestra) in a phase 2 clinical trial. In order to enhance R115777 antitumor activity in MM, we examined the combination of this novel agent with other anticancer drugs in MM cell lines. In this study, R115777 was found to synergize with paclitaxel and docetaxel, but not with other chemotherapy agents, including doxorubicin, 5-fluorouracil, cisplastin, melphalan, mitoxantrone, and dexamethasone. R115777 synergized with paclitaxel to inhibit MM cell proliferation and to induce apoptosis. Synergism in the induction of apoptosis was accompanied by increase in cytochrome c release and caspase-3 activation. Furthermore, flow cytometry analysis also showed that paclitaxel and R115777 synergized to induce G2/M cell-cycle arrest. Importantly, synergism was observed in taxane- and R115777-resistant MM cells. In the human severe combined immunodeficient (SCID-hu) bone model of myeloma growth, the ability of paclitaxel to inhibit tumor growth in vivo was enhanced by R115777. Combination of paclitaxel or docetaxel with R115777 in the treatment of MM cells from patients with multiple myeloma was more beneficial than treatment with single agents. Our results provide the basis for combination therapy clinical trials with paclitaxel or docetaxel with R115777 in MM patients. (Blood. 2005;105:4759-4766)
An inducible caspase 9 safety switch for T-cell therapy
Authors: Straathof Karin C. , Pulè Martin A. , Yotnda Patricia , Dotti Gianpietro , Vanin Elio F. , Brenner Malcolm K. , Heslop Helen E. , Spencer David M. , Rooney Cliona M.
Published: February 2005

The efficacy of adoptive T-cell therapy as treatment for malignancies may be enhanced by genetic modification of infused cells. However, oncogenic events due to vector/transgene integration, and toxicities due to the infused cells themselves, have tempered enthusiasm. A safe and efficient means of removing aberrant cells in vivo would ameliorate these concerns. We describe a “safety switch” that can be stably and efficiently expressed in human T cells without impairing phenotype, function, or antigen specificity. This reagent is based on a modified human caspase 9 fused to a human FK506 binding protein (FKBP) to allow conditional dimerization using a small molecule pharmaceutical. A single 10-nM dose of synthetic dimerizer drug induces apoptosis in 99% of transduced cells selected for high transgene expression in vitro and in vivo. This system has several advantages over currently available suicide genes. First, it consists of human gene products with low potential immunogenicity. Second, administration of dimerizer drug has no effects other than the selective elimination of transduced T cells. Third, inducible caspase 9 maintains function in T cells overexpressing antiapoptotic molecules. These characteristics favor incorporation of inducible caspase 9 as a safety feature in human T-cell therapies.
The hydration state of human red blood cells and their susceptibility to invasion by Plasmodium falciparum
Authors: Tiffert Teresa , Lew Virgilio L. , Ginsburg Hagai , Krugliak Miriam , Croisille Laure , Mohandas Narla
Published: February 2005

In most inherited red blood cell (RBC) disorders with high gene frequencies in malaria-endemic regions, the distribution of RBC hydration states is much wider than normal. The relationship between the hydration state of circulating RBCs and protection against severe falciparum malaria remains unexplored. The present investigation was prompted by a casual observation suggesting that falciparum merozoites were unable to invade isotonically dehydrated normal RBCs. We designed an experimental model to induce uniform and stable isotonic volume changes in RBC populations from healthy donors by increasing or decreasing their KCl contents through a reversible K+ permeabilization pulse. Swollen and mildly dehydrated RBCs were able to sustain Plasmodium falciparum cultures with similar efficiency to untreated RBCs. However, parasite invasion and growth were progressively reduced in dehydrated RBCs. In a parallel study, P falciparum invasion was investigated in density-fractionated RBCs from healthy subjects and from individuals with inherited RBC abnormalities affecting primarily hemoglobin (Hb) or the RBC membrane (thalassemias, hereditary ovalocytosis, xerocytosis, Hb CC, and Hb CS). Invasion was invariably reduced in the dense cell fractions in all conditions. These results suggest that the presence of dense RBCs is a protective factor, additional to any other protection mechanism prevailing in each of the different pathologies. (Blood. 2005; 105:4853-4860)
CNS activity of Pokeweed Anti-viral Protein (PAP) in mice infected with Lymphocytic Choriomeningitis Virus (LCMV)
Authors: Uckun Fatih M , Rustamova Larisa , Vassilev Alexei O , Tibbles Heather E , Petkevich Alexander S
Published: February 2005

Background

Others and we have previously described the potent in vivo and in vitro activity of the broad-spectrum antiviral agent PAP (Pokeweed antiviral protein) against a wide range of viruses. The purpose of the present study was to further elucidate the anti-viral spectrum of PAP by examining its effects on the survival of mice challenged with lymphocytic choriomeningitis virus (LCMV).

Methods

We examined the therapeutic effect of PAP in CBA mice inoculated with intracerebral injections of the WE54 strain of LCMV at a 1000 PFU dose level that is lethal to 100% of mice within 7–9 days. Mice were treated either with vehicle or PAP administered intraperitoneally 24 hours prior to, 1 hour prior to and 24 hours, 48 hours 72 hours and 96 hours after virus inoculation.

Results

PAP exhibits significant in vivo anti- LCMV activity in mice challenged intracerebrally with an otherwise invariably fatal dose of LCMV. At non-toxic dose levels, PAP significantly prolonged survival in the absence of the majority of disease-associated symptoms. The median survival time of PAP-treated mice was >21 days as opposed to 7 days median survival for the control (p = 0.0069).

Conclusion

Our results presented herein provide unprecedented experimental evidence that PAP exhibits antiviral activity in the CNS of LCMV-infected mice.