bluuebunny/crossref_metadata_2025 huggingface dataset:
Heterodyne Detection for the Extraction of the Probe-Scattering Signal in Scattering-Type Scanning Near-Field Optical Microscope
Authors: Sasaki Yasuo , Sasaki Hiroko
Published: October 2002

We propose that heterodyne detection is useful for the scattering-type scanning
near-field optical microscope (SNOM) to effectively remove the scattering from various
sources on the sample which causes deterioration of the image resolution. First, we
show in a simple model that this sample scattering cannot be completely removed by
ac-mode detection of the SNOM signal for samples with high reflectivity, while only the
probe-scattering signal can be extracted by heterodyne detection. Next, we show
experimental results which compare the ac-mode and heterodyne images, and
demonstrate the effectiveness of heterodyne detection.
Low-Temperature and Low-Activation-Energy Process for the Gate Oxidation of Si Substrates
Authors: Ueno Tomo , Morioka Ayuka , Chikamura Shingo , Iwasaki Yoshitaka
Published: October 2002

A low-temperature and low-activation-energy process for the gate oxidation of
Si substrates has been proposed. Using the energy-controlled excited oxygen generated
in rare-gas and O2 molecule mixture plasma, the enhancement of the oxidation
rates was achieved. In addition, the oxidation rates and kinetics drastically change
with the type of mixed rare gas in the plasma. Using Kr as the mixed rare gas, the
interface trap density near the mid gap [D
it(mid)] of the SiO2/Si
interface grown at 500°C was 2.6×1011/cm2/eV, which was
comparable to that of the as-grown one using conventional thermal oxidation at a
higher temperature. For this process, the oxidation rates were shown to be hardly
dependent on the substrate temperature, and the activation energy of B, which is the
parabolic rate constant, was found to be low, 0.14 eV.
Low Temperature Growth of GaAs on Si Substrate by Chemical Beam Epitaxy
Authors: Mitsuhiro Adachi Mitsuhiro Adachi , Yasunori Fujii Yasunori Fujii , Takashi Egawa Takashi Egawa , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno
Published: October 2002

We report on the growth of GaAs on Si substrates without a high temperature process over 500°C using chemical beam epitaxy (CBE). First, the epilayer grown on Si was preheated for 5 min at 400, 500 and 600°C, respectively, and it was found that the preheating at 500°C was sufficient to remove an oxide on the Si surface. The dependence of the surface morphology on the growth condition during the nucleation stage was investigated. As a result, it was found that a high growth rate and a high V/III ratio in the initial stage are required to grow high-quality GaAs on a Si substrate, and the quality of GaAs on Si grown in this research was better than that grown by metalorganic chemical vapor deposition.
Pulsed Laser Deposition of Crystalline Indium Tin Oxide Films at Room Temperature by Substrate Laser Irradiation
Authors: Adurodija Frederick O. , Izumi Hirokazu , Ishihara Tsuguo , Yoshioka Hideki , Motoyama Muneyuki , Murai Kensuke
Published: October 2002

Crystalline tin (Sn)-doped indium oxide (ITO) films grown at room temperature
(RT) using pulsed laser deposition (PLD) coupled with laser irradiation of the growing
films are discussed. The energy of the laser irradiation beam was
∼0.07 J·cm-2. The films were deposited from Sn-doped
(0–10 wt%) In2O3 targets under oxygen pressure (P
O2
) of
10-2 Torr. At RT, the laser-irradiated and nonirradiated portions of the films
yielded resistivities of ∼1.2×10-4 and
∼2.5×10-4 Ω·cm, respectively. At 200°C,
a resistivity of 8.9×10-5 Ω·cm was observed for the
laser-irradiated part of the ITO films.
Solar-Blind UV Photodetectors Based on GaN/AlGaN p-i-n Photodiodes
Authors: Pernot Cyril , Hirano Akira , Iwaya Motoaki , Detchprohm Theeradetch , Amano Hiroshi , Akasaki Isamu
Published: October 2002

We report on the fabrication and characterization of n-Al0.44Ga0.56N/i-Al0.44Ga0.56N/p-GaN ultraviolet
solar-blind photodetectors. The diodes were fabricated by organometallic vapor phase epitaxy on
low-defect-density AlGaN layers using a low-temperature interlayer technique. They present a long
cutoff wavelength at 270 nm with high rejection of solar light and a responsivity of 12 mA/W. Low
dark currents between 4 and 35 pA/mm2 at -5 V have been measured. A photocurrent decay time of
14 µs has been estimated in unbiased diodes. Due to the large dynamic resistance of the diode at 0 V
bias, the detector itself shows a detectivity of 1.2×1013 cm·Hz1/2·W-1.
Low-Frequency Noise of High Tc Superconducting Quantum Interference Device (SQUID) Magnetometer Fabricated on Bicrystal Substrate
Authors: Minotani Tadashi , Hotta Masahiro , Enpuku Keiji
Published: October 2002

The excess low-frequency noise of a high T
c superconducting quantum interference
device (SQUID) magnetometer fabricated on bicrystal substrate is studied. Direct-coupled
magnetometers are fabricated using different geometries of the pickup coil, and
the relationship between the geometry of the pickup coil and the low-frequency noise of
the magnetometer is studied. It is shown that the weak superconducting region in the
pickup coil, which is automatically formed on top of the grain boundary of the bicrystal
substrate, is one of the main sources of the excess noise. By selecting an appropriate
geometry of the pickup coil, we can significantly decrease the excess noise of the
magnetometer without decreasing its effective area.
Fabrication of (La0.8Sr0.2)MnO3/(La1-xSrx)CrO3 Spin Frustrated Superlattices and Their Electrical Magnetic Properties
Authors: Kanki Teruo , Tanaka Hidekazu , Kawai Tomoji
Published: October 2002

We have fabricated ferromagmetic [La0.8Sr0.2MnO3
(LSMO), T
C=270 K]/antiferromagnetic
[La0.8Sr0.2CrO3 (LSCO), T
N=270 K]
spin-frustrated superlattices on SrTiO3 (001)
substrates by the laser molecular-beam epitaxy
technique. [(LSMO)5 unit cell/(LSCO)1 unit cell]
superlattices exhibit a magnetoresistance
ratio of 23%, higher than that of LSMO single-phase film (18%) at
8000 Oe. In addition, [(LSMO)5/(LaCrO3)1] superlattices
exhibited a magnetoresistive property superior to LSMO/LSCO superlattices within
a magnetic field of 5000 Oe. This enhancement of magnetoresistance can
be explained by the spin-frustrative effect between a ferromagnetic
layer and an antiferromagnetic layer.
Performance of a Laser-Diode End-Pumped Nd:Sr5(VO4)3F/Nd:YVO4 Hybrid-Crystal Laser
Authors: Deyuan Shen Deyuan Shen , Jie Song Jie Song , Cheng Li Cheng Li , Siu-Chung Tam Siu-Chung Tam , Namseong Kim Namseong Kim , Kenichi Ueda Kenichi Ueda
Published: October 2002

A laser-diode end-pumped continuous wave hybrid Nd:Sr5(VO4)3F and Nd:YVO4 laser is demonstrated. The two crystals are combined to construct a hybrid crystal having a broader effective absorption bandwidth than a single crystal. The hybrid laser can operate efficiently without controlling the temperature of the pump diode. In a combination wherein the c-axes of the two crystals are perpendicular to each other, the polarization states of the laser output can be selected by changing the pumping wavelength of the laser diode.
High-Temperature Electrical Behaviors of Li2ZrO3 Thick Films
Authors: Park Jin-Seong , Hong Jin-Who , Lee Eun-Goo , Kim Jae-Yeoul , Kim Si-Wouk , Akbar Sheikh A.
Published: October 2002

The electrical behavior of Li2ZrO3 ceramics was
studied as a function of temperature and CO2 concentration. The
phases of Li2ZrO3 were synthesized by the solid-state
reaction of ZrO2 and Li2CO3 at 1300°C for 6 h. The specimens were made by the thick film fabrication process on 96% alumina
substrates. The electrical resistance readily responded to CO2
concentrations ranging from 0.1% to 100% at 550°C. The variation
of the electrical behavior is related to the change of the phases
and conducting path. Li2ZrO3 decomposed into Li2CO3 and
ZrO2 after the reaction with CO2 below 650°C, and Li2CO3 decomposed into Li2O and CO2 at and above 650°C.
Superconducting T′-La2-xCexCuO4 Films Grown by Molecular Beam Epitaxy
Authors: Naito Michio , Hepp Markus
Published: October 2002

In this letter we report the synthesis of superconducting
T′-La2-x
Ce
x
CuO4 on SrTiO3(001) by molecular beam
epitaxy. Although T′-La2-x
Ce
x
CuO4 with a very limited range
of x can be prepared by bulk synthesis using rather complicated techniques, this
compound is very easy to obtain by thin film synthesis. Crucial to our success was the
use of SrTiO3 substrates, which seems to stabilize the formation of the
T′ structure by an epitaxial effect. The best T
c was
∼30 K by onset and ∼28 K by zero resistance, which was obtained for
x=0.109. The resistivity showed a metallic temperature dependence, and the film's
overall behavior was similar to that for the best (Nd, Ce)2CuO4 or
(Pr, Ce)2CuO4 films. Moreover, the single phase of the T′
structure formed for a composition range of 0.09<x<0.22, which is much wider than
for previously reported bulk synthesis.
Heavily Boron-Doped Silicon Single Crystal Growth: Constitutional Supercooling
Authors: Taishi Toshinori , Huang Xinming , Kubota Masayoshi , Kajigaya Tomio , Fukami Tatsuo , Hoshikawa Keigo
Published: October 2002

Constitutional supercooling in the heavily boron-doped Czochralski (CZ) silicon
crystal growth has been investigated. It was found that cellular growth occurred first
in the center of the crystal. The cellular growth changed gradually to facet growth and
finally became polycrystalline growth. This process is quite different from the
well-known mechanism of polycrystallization in the silicon crystal growth. The
cellular growth occurred when the boron concentration in the crystal was
approximately 3×1020 atoms/cm3 with the growth rate of about
1 mm/min. In the theoretical analysis using an equation for occurrence of the
constitutional supercooling, it is found that the condition for the occurrence is
satisfied by considering that the segregation coefficient of boron decreases with
increasing boron concentration in the heavily boron-doped silicon crystal growth.
Thermal Properties of BaFCl Crystals Simulated by Molecular Dynamics
Authors: Toshio Kurobori Toshio Kurobori , Shuichi Kozake Shuichi Kozake , Tomonori Kawamoto Tomonori Kawamoto , Yukio Hirose Yukio Hirose
Published: October 2002

The thermal properties of BaFCl crystals by molecular dynamics
simulation have been examined using the Born-Mayer-Huggins
potential. The c/a ratio, density, and the linear thermal expansion
coefficient along the directions parallel (α||
) and
perpendicular (α⊥) to the tetragonal axis have been
calculated from the temperature dependence of the lattice parameters
(a and c). It was found that both α||
and
α⊥
are of the order of (2-4) ×10-5 K-1
and show a change of curvature around 500 K. These results were in
good agreement with the experimental results.
Sub-Doppler Spectroscopy of Molecular Iodine at 531 nm Using a Frequency-Doubled α-Distributed Feedback Laser
Authors: Huang Tong-Long , Cheng Wang-Yau , Lin Yan-Rung , Shy Jow-Tsong , Liu Hai-Pei
Published: October 2002

We report, for the first time, the observation of the iodine hyperfine transitions
at 531 nm using a frequency-doubled α-distributed feedback (α-DFB)
laser. The moderate high power of the α-DFB laser allows us to
generate the second harmonic light by a periodically-poled LiNbO3 single-pass
frequency doubler. We can stabilize this laser frequency to the hyperfine component
a
10 of R(94) 34-0 or R(70) 33-0 I2 line, and the preliminary frequency
stability was about 5×10-11. This laser system is an attractive frequency
standard at 531 nm due to its compact size, high reliability, and low cost.
A Study of the Effect of Deuterium on Stress-Induced Leakage Current
Authors: Mitani Yuichiro , Satake Hideki , Ito Hitoshi , Toriumi Akira
Published: October 2002

The effect of deuterium incorporation into SiO2 on the stress-induced
leakage current (SILC) of the gate oxide was investigated using deuterium pyrogenic
oxidation and deuterium annealing. As a result, we found that the SILC is reduced by
deuterium pyrogenic oxidation under Fowler-Nordheim (F-N) electron injection from the
substrate, and that the SILC is not improved by deuterium annealing, although a large
amount of deuterium is contained in the SiO2 film.
Metastable Domain Structures of Ferromagnetic Microstructures Observed by Soft X-Ray Magnetic Circular Dichroism Microscopy
Authors: Shin Imada Shin Imada , Shigenori Ueda Shigenori Ueda , Ranju Jung Ranju Jung , Yuji Saitoh Yuji Saitoh , Masato Kotsugi Masato Kotsugi , Wolfgang Kuch Wolfgang Kuch , Jörg Gilles Jörg Gilles , Shishou Kang Shishou Kang , Francesco Offi Francesco Offi , Jürgen Kirschner Jürgen Kirschner , Hiroshi Daimon Hiroshi Daimon , Takashi Kimura Takashi Kimura , Junichi Yanagisawa Junichi Yanagisawa , Kenji Gamo Kenji Gamo , Shigemasa Suga Shigemasa Suga
Published: October 2002

The benefit of combining soft X-ray magnetic circular dichroism and photoelectron microscopy is demonstrated by applying this combination to the observation of the magnetic domain structures of rectangular microstructures. The size and aspect-ratio dependence of the transformation of the domain structures by magnetic field pulses is investigated. The switching mechanism, which is very important in the application to magnetic storage, is discussed in terms of transformation between saturated and vortex domain structures.
Observation of O K-Edge X-Ray Magnetic Circular Dichroism of CO Adsorbed on an Ultrathin Co/Cu(001) Film
Authors: Kenta Amemiya Kenta Amemiya , Toshihiko Yokoyama Toshihiko Yokoyama , Yoshiki Yonamoto Yoshiki Yonamoto , Mariko Miyachi Mariko Miyachi , Yoshinori Kitajima Yoshinori Kitajima , Toshiaki Ohta Toshiaki Ohta
Published: October 2002

We have for the first time observed K-edge X-ray magnetic circular dichroism
of submonolayer amounts of adsorbates on ferromagnetic thin metal films.
The O K-edge X-ray magnetic circular dichroism (XMCD) of CO adsorbed on fcc Co grown epitaxially on Cu(001)
showed a positive sign for the O1s →2 π* transition, which implies
an opposite orbital moment of O to the Co magnetization.
Irradiance-Dependence of the Current–Voltage Characteristics of Crystalline Silicon Solar Cells
Authors: Hishikawa Yoshihiro , Imura Yoshihiro , Oshiro Toshimitsu
Published: October 2002

Variations in the current–voltage characteristics I
out(V) of crystalline silicon solar cells under different levels of irradiance (E) are experimentally investigated. It is demonstrated that the I
out(V) can be well approximated by the sum of a dark current and a voltage-dependent “photocurrent,” which is proportional to E. Using this result, the I
out(V) at any E can be calculated from those at two different Es with better accuracy than by the conventional procedure based on the shifted approximation.
In Situ Gravimetric Monitoring of Decomposition Rate from GaN Epitaxial Surface
Authors: Miho Mayumi Miho Mayumi , Fumitaka Satoh Fumitaka Satoh , Yoshinao Kumagai Yoshinao Kumagai , Kikurou Takemoto Kikurou Takemoto , Akinori Koukitu Akinori Koukitu
Published: October 2002

Decomposition of GaN on its surface was investigated under atmospheric pressure using the in situ gravimetric monitoring (GM) method. Weight change of the GaN substrate both in the H2 carrier gas and in the He carrier gas ambient was monitored at temperatures ranging from 600°C to 950°C with and without the presence of NH3 flow. It was found that the GaN decomposition did not occur in the presence of NH3 flow both in the H2 carrier gas and in the He carrier gas. However, without NH3 flow, the decomposition rate of GaN drastically increased as the temperature increased in the H2 carrier gas, whereas the decomposition of GaN was negligible in the He carrier gas. Dependence of the decomposition rate on the H2 partial pressure in the carrier gas (P

H
2
) was also investigated, and it was found that the decomposition rate is proportional to the P

H
2

3/2. These results indicate that the decomposition is governed by the reaction of GaN(surface)+3/2H2(g)→Ga(surface)+NH3(g).
Thin-Film Deposition of Cu2O by Reactive Radio-Frequency Magnetron Sputtering
Authors: Ishizuka Shogo , Maruyama Takahiro , Akimoto Katsuhiro
Published: October 2002

Deposition conditions of cuprous oxide (Cu2O) thin films on glass substrates by reactive radio-frequency (rf) magnetron sputtering method were studied. The substrate temperature was found to be important for obtaining high-quality films, and the optimum substrate temperature was about 500°C. The Cu2O deposited at 500°C shows a band-gap energy of about 2.0 eV and a typical hole concentration of the order of 1015 cm-3 with a Hall mobility of 60 cm2/V·s, which is the highest mobility reported thus far.
Improvement of Gate Oxide Reliability for Direct Tungsten-Gate Using Denudation of WNx
Authors: Han Chang Hee , Sohn Dong Kyun , Lee Byung Hak , Park Ji-Soo , Bae Jong-Uk , Park Jin Won
Published: October 2002

We investigated a gate oxide reliability of metal-oxide-semiconductor capacitors with W and denuded WN
x
gate. A 5.5 nm-thick SiO2 was used as gate dielectric. The W gate was deposited by D.C. magnetron sputtering and the denuded WN
x
gate was formed by N2 annealing following the deposition of WN
x
. The leakage current and charge-to-breakdown results indicate that the denuded WN
x
gate shows improved gate oxide reliability comparing with pure W gate. It is believed to be due to the segregation of nitrogen atoms at the interface of W and SiO2 film. It is also observed that the sputtering power must be reduced to improve the roughness of metal/SiO2 interface.
All-Optical Divided-Clock Extractor Using an Ultrafast All-Optical Symmetric-Mach-Zehnder-Type Semiconductor Switch Embedded in an Optical Loop
Authors: Ueno Yoshiyasu , Nakamura Shigeru , Tajima Kazuhito
Published: October 2002

We propose an ultrafast all-optical divided-clock extractor in which an all-optical symmetric-Mach-Zehnder (SMZ)-type semiconductor switch and a passive energy-distribution Mach-Zehnder interferometer are embedded in an optical loop. The extractor generates ultrashort optical clock pulses at a divided clock frequency (f
0/N, N=1, 2, 3, 4, \dots) from optical-time-division-multiplexed (OTDM) input packets at a bit frequency, f
0. Numerical results reveal that the phase of 40 GHz 1 ps clock pulses locks within 20 ns (which corresponds to 3,000 bits of a 160 Gb/s signal) to that of the 160 Gb/s pseudorandomly encoded input pulses.
Use of Poly(9-vinylcarbazole) as Host Material for Iridium Complexes in High-Efficiency Organic Light-Emitting Devices
Authors: Yang Moon-Jae , Tsutsui Tetsuo
Published: October 2002

Using poly(9-vinylcarbazole)(PVCz) as a host material for tris(2-phenylpyridine)iridium (Ir(ppy)3) guest emitter, double-layer and triple-layer organic light-emitting devices were fabricated. Tris(8-hydroxyquinolino)aluminum (Alq3) and 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene (OXD-7) were used for electron-transporting layers. The insertion of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as a hole-blocking layer was also tested. The double-layer device composed of PVCz doped with 6.8 wt% Ir(ppy)3 and OXD-7 gave the highest external quantum efficiency of 7.5% and power luminous efficiency of 5.8 lm/W at the luminance of 106 cd/m2 (current density of 0.40 mA/cm2 and drive voltage of 14.5 V).
Nonlinear Effects Excitonic Emission from High Quality Homoepitaxial Diamond Films
Authors: Watanabe Hideyuki , Okushi Hideyo
Published: October 2002

A nonlinear relationship between the intensity of the free-exciton emission (235 nm) and the electron-beam current has been observed in cathodoluminescence (CL) spectra from homoepitaxial diamond films for the first time at room temperature. For high quality diamond films grown using a low concentration of CH4 in microwave plasma assisted chemical vapor deposition (CVD) using CH4, the excitonic emission intensity increases linearly with the electron bean current in the low excitation region but increases super-linearly in the high excitation region above a threshold value of about 30 µA at room temperature. These results strongly suggest that the free-exciton emission from high quality diamond films is able to apply as a light souse for deep-ultraviolet (235 nm) of light emitting diodes and laser diodes.
Visualization of Immobilized Microparticles in Fractured Polymer Gel Surfaces by Atomic Force Microscopy
Authors: Suzuki Atsushi , Suzuki Hiromichi
Published: October 2002

Fractured surface images of polymer gels in water were obtained by atomic force microscopy. The gel is a three-dimensional network of N-isopropylacrylamide (NIPA) polymers which is immobilized by NIPA microparticles of submicrometer diameter. The fractured surface structure associated with the aggregated guest particles in the host network strongly depends on the amount of particles: in the cases of smaller and larger amounts, the surface roughness is small, in contrast to the rough surface observed for intermediate concentrations. The distribution of particles and its effect on the fractured surface structure are presented with references to the domain of the aggregated guest particles in the host homogeneous network. It is also shown, for the first time, that the guest gel particles in the fractured surface can swell and shrink in response to temperature change.
Diffusion Simulation of Ultra-Low-Energy Implanted Boron in Silicon
Authors: Uematsu Masashi
Published: October 2002

We have simulated the diffusion of boron (B) after ultra-low-energy implantation in silicon during post-implantation annealing, based on our model [M. Uematsu: Jpn. J. Appl. Phys. 38 (1999) 3433]. When the B concentration is not so high (\lesssim1×1021 cm-3), the experimental B depth profiles are fitted using the model with taking into account B segregation to silicon oxide at the surface. When the B concentration is very high (\gtrsim1×1021 cm-3), however, the simulation underestimates the diffusion, which is attributable to boron-enhanced diffusion. The self-interstitial emission from a silicon boride layer in the high B concentration region is taken into account, and the simulation well reproduces the experimental profiles.
GaP/Si Heterojunction with Ohmic Conduction Fabricated by Wafer Fusion Technique
Authors: Akitaka Soeno Akitaka Soeno , Daisuke Kajita Daisuke Kajita , Jun Suda Jun Suda , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

In this letter, we report the fabrication of a GaP/Si heterojunction with ohmic conduction by a wafer fusion technique. After a hydrophilic pretreatment, GaP and Si wafers were brought in contact and annealed at 500°C in a flowing forming gas for 30 min. The electrical properties of n-GaP/n+-Si and p+-GaP/n+-Si junctions fabricated by this procedure were investigated. The n-GaP/n+-Si junction exhibited potential barriers for both directions, indicating Fermi-level pinning due to high-density interface states at the fused interface. For the p+-GaP/n+-Si junction, ohmic conduction (10–20 Ω·cm2) was observed. This may be due to carrier transport by a tunneling process. The wafer fusion technique of GaP/Si is applicable to optoelectronic integrated circuits (OEICs) and high-efficiency tandem-type solar cells.
Cu/CaF2/Diamond Metal-Insulator-Semiconductor Field-Effect Transistor Utilizing Self-Aligned Gate Fabrication Process
Authors: Umezawa Hitoshi , Taniuchi Hirotada , Arima Takuya , Tachiki Minoru , Tsugawa Kazuo , Yamanaka Sadanori , Takeuchi Daisuke , Okushi Hideyo , Kawarada Hiroshi
Published: October 2002

High-performance metal-insulator-semiconductor field-effect transistors (MISFET) on hydrogen-terminated homoepitaxial diamond films are demonstrated. The gate insulator is evaporated CaF2 which does not cause interface states. This is the first study of a CaF2/diamond MISFET fabricated by a self-aligned gate fabrication process by which the gate length and the source gate spacing are effectively reduced. The maximum transconductance is 86 mS/mm, which is the highest value in diamond MISFETs at present.
Electrical Characteristics of GaAs Bonded to Si Using SeS2 Technique
Authors: Arokiaraj Jesudoss , Okui Hiroki , Taguchi Hironori , Soga Tetsuo , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

We have developed a new technique for bonding GaAs on Si susbtrates; called surface modification by chemical treatment. The treatment of selenium sulphide (SeS2) with GaAs produces a reconstructed surface which helps in strong fusion between GaAs and Si at lower temperatures and without weights. The current–voltage (I–V) characteristics of both n-GaAs/n-Si and p-GaAs/p-Si were measured at room temperature. The I–V curve did not show a rectifying behaviour when GaAs was bonded to Si with SeS2 because of the formation of a high-resistance layer at the interface. The characteristics were greatly improved by small additions of Sn to SeS2 during the bonding process. Sn forms localized islands in addition to the Ga–Se and Se–S, and acts as shunt resistance between GaAs and Si.
Cluster Magnetic Fields
Authors: Carilli C. L. , Taylor G. B.
Published: October 2002

▪ Abstract  Magnetic fields in the intercluster medium have been measured using a variety of techniques, including studies of synchrotron relic and halo radio sources within clusters, studies of inverse Compton X-ray emission from clusters, surveys of Faraday rotation measures of polarized radio sources both within and behind clusters, and studies of cluster cold fronts in X-ray images. These measurements imply that most cluster atmospheres are substantially magnetized, with typical field strengths of order 1 μGauss with high areal filling factors out to Mpc radii. There is likely to be considerable variation in field strengths and topologies both within and between clusters, especially when comparing dynamically relaxed clusters to those that have recently undergone a merger. In some locations, such as the cores of cooling flow clusters, the magnetic fields reach levels of 10–40 μG and may be dynamically important. In all clusters the magnetic fields have a significant effect on energy transport in the intracluster medium. We also review current theories on the origin of cluster magnetic fields.
PATHOGEN POPULATION GENETICS, EVOLUTIONARY POTENTIAL, AND DURABLE RESISTANCE
Authors: McDonald Bruce A. , Linde Celeste
Published: October 2002

▪ Abstract  We hypothesize that the evolutionary potential of a pathogen population is reflected in its population genetic structure. Pathogen populations with a high evolutionary potential are more likely to overcome genetic resistance than pathogen populations with a low evolutionary potential. We propose a flexible framework to predict the evolutionary potential of pathogen populations based on analysis of their genetic structure. According to this framework, pathogens that pose the greatest risk of breaking down resistance genes have a mixed reproduction system, a high potential for genotype flow, large effective population sizes, and high mutation rates. The lowest risk pathogens are those with strict asexual reproduction, low potential for gene flow, small effective population sizes, and low mutation rates. We present examples of high-risk and low-risk pathogens. We propose general guidelines for a rational approach to breed durable resistance according to the evolutionary potential of the pathogen.
Cholesterol Depletion Disrupts Caveolae and Differentially Impairs Agonist-Induced Arterial Contraction
Authors: Dreja Karl , Voldstedlund Marianne , Vinten Jørgen , Tranum-Jensen Jørgen , Hellstrand Per , Swärd Karl
Published: October 2002

Objective—

This study assessed the role of cholesterol-rich membrane regions, including caveolae, in the regulation of arterial contractility.

Methods and Results—

Rat tail artery devoid of endothelium was treated with the cholesterol acceptor methyl-β-cyclodextrin, and the effects on force and Ca
2+
handling were evaluated. In cholesterol-depleted preparations, the force responses to α
1
-adrenergic receptors, membrane depolarization, inhibition of myosin light chain phosphatase, and activation of G proteins with a mixture of 20 mmol/L NaF and 60 μmol/L AlCl
3
were unaffected. In contrast, responses to 5-hydroxytryptamine (5-HT), vasopressin, and endothelin were reduced by >50%. The rise in global intracellular free Ca
2+
concentration in response to 5-HT was attenuated, as was the generation of Ca
2+
waves at the cellular level. By electron microscopy, cholesterol depletion was found to disrupt caveolae. The 5-HT response could be restored by exogenous cholesterol, which also restored caveolae. Western blots showed that the levels of 5-HT
2A
receptor and of caveolin-1 were unaffected by cholesterol extraction. Sucrose gradient centrifugation showed enrichment of 5-HT
2A
receptors, but not α
1
-adrenergic receptors, in the caveolin-1–containing fractions, suggesting localization of the former to caveolae.

Conclusions—

These results show that a subset of signaling pathways that regulate smooth muscle contraction depends specifically on cholesterol. Furthermore, the cholesterol-dependent step in serotonergic signaling occurs early in the pathway and depends on the integrity of caveolae.
Potentiated Sympathetic Nervous and Renin-Angiotensin Systems Reduce Nonlinear Correlation Between Sympathetic Activity and Blood Pressure in Conscious Spontaneously Hypertensive Rats
Authors: Sakata Katsufumi , Kumagai Hiroo , Osaka Motohisa , Onami Toshiko , Matsuura Tomokazu , Imai Masaki , Saruta Takao
Published: October 2002

Background

—

Patients with a reduced nonlinear component of heart rate regulation have a poorer outcome.

Methods and Results

—

We investigated whether a nonlinear correlation between renal sympathetic nerve activity (RSNA) and blood pressure or renal blood flow is reduced in conscious, spontaneously hypertensive rats (SHR) by comparing them with normotensive Wistar-Kyoto rats (WKY). We also determined the linearity and nonlinearity of the correlation in SHR who were given an angiotensin II receptor blocker, candesartan, orally for 2 weeks. The RSNA value was higher in SHR than in WKY, and coherence peaks of transfer function were found at 0.05 and 0.80 Hz (ie, below respiratory- and cardiac-related fluctuations). The coherence (linearity) of the transfer function was significantly higher and gain was smaller in SHR than in WKY. Because mutual information values (linear and nonlinear correlation) were similar in both strains, we found the nonlinear correlation to be lower in SHR than in WKY. Time delay values calculated by the mutual information method demonstrated that RSNA preceded blood pressure and renal blood flow by 0.5 to 1.0 s. In SHR given candesartan, the RSNA value was lower, and the linearity was lower and nonlinearity higher than SHR given vehicle.

Conclusions

—

Linear correlation between RSNA and blood pressure or renal blood flow was higher in SHR than in WKY, whereas the nonlinear correlation was lower. Oral treatment with candesartan increased the nonlinearity and reduced the linearity in SHR. Increased RSNA and the renin-angiotensin system may be responsible for the lower nonlinearity and higher linearity in hypertension.
Postsystolic Shortening in Ischemic Myocardium
Authors: Skulstad Helge , Edvardsen Thor , Urheim Stig , Rabben Stein Inge , Stugaard Marie , Lyseggen Erik , Ihlen Halfdan , Smiseth Otto A.
Published: October 2002

Background

—

Postsystolic shortening in ischemic myocardium has been proposed as a marker of tissue viability. Our objectives were to determine if postsystolic shortening represents active fiber shortening or passive recoil and if postsystolic shortening may be quantified by strain Doppler echocardiography (SDE).

Methods and Results

—

In 15 anesthetized dogs, we measured left ventricular (LV) pressure, myocardial long-axis strains by SDE, and segment lengths by sonomicrometry before and during LAD stenosis and occlusion. Active contraction was defined as elevated LVP and stress during postsystolic shortening when compared with the fully relaxed ventricle at similar segment lengths. LAD stenosis decreased systolic shortening from 10.4±1.2% to 5.9±0.9% (
P
<0.05), whereas postsystolic shortening increased from 1.1±0.3% to 4.2±0.7% (
P
<0.05). In hypokinetic and akinetic segments, LV pressure–segment length and LV stress–segment length loop analysis indicated that postsystolic shortening was active. LAD occlusion resulted in dyskinesis, and postsystolic shortening increased additionally to 8.2±1.0% (
P
<0.05). After 3 to 5 minutes with LAD occlusion, the dyskinetic segment generated no active stress, and the postsystolic shortening was attributable to passive recoil. Elevation of afterload caused hypokinetic segments to become dyskinetic, and postsystolic shortening remained partly active. Postsystolic shortening by SDE correlated well with sonomicrometry (
r
=0.83,
P
<0.01).

Conclusions

—

Postsystolic shortening is a relatively nonspecific feature of ischemic myocardium and may occur in dyskinetic segments by an entirely passive mechanism. However, in segments with systolic hypokinesis or akinesis, postsystolic shortening is a marker of actively contracting myocardium. SDE was able to quantify postsystolic shortening and might represent a clinical method for identifying actively contracting and hence viable myocardium.
Anticoagulant Responses to Thrombin Are Enhanced During Regression of Atherosclerosis in Monkeys
Authors: Lentz Steven R. , Miller Francis J. , Piegors Donald J. , Erger Rochelle A. , Fernández José A. , Griffin John H. , Heistad Donald D.
Published: October 2002

Background—

Diet-induced atherosclerosis in monkeys produces abnormal anticoagulant responses to thrombin, including decreased generation of activated protein C (APC). We tested the hypothesis that anticoagulant responses to thrombin increase toward normal during regression of atherosclerosis.

Methods and Results—

Six cynomolgus monkeys were fed a high-fat atherogenic diet for 44 months and then a low-fat regression diet for 8 months. Serum total cholesterol decreased from 417±44 to 68±6 mg/dL (mean±SEM) and LDL cholesterol decreased from 375±44 to 27±5 mg/dL after the regression diet. In response to infusion of thrombin, the activated partial thromboplastin time (APTT) increased by 11±3 seconds before the regression diet and by 41±22 seconds after the regression diet (
P
=0.01). The peak level of circulating plasma APC was 52±9 ng/mL before the regression diet and 88±17 ng/mL after the regression diet (
P
=0.01). The APC sensitivity of plasma factor V was identical before and after the regression diet. Three additional atherosclerotic monkeys that remained on the high-fat diet for 8 months demonstrated no change in APTT or activation of protein C in response to thrombin.

Conclusions—

Short-term dietary regression of atherosclerosis produces enhanced anticoagulant responses to thrombin in vivo.
Elevated Remnant-Like Particles in Heterozygous Familial Hypercholesterolemia and Response to Statin Therapy
Authors: de Sauvage Nolting Pernette R. W. , Twickler Marcel B. , Dallinga-Thie Geesje M. , Buirma Rudolf J.A. , Hutten Barbara A. , Kastelein John J.P.
Published: October 2002

Background—

Remnant lipoproteins (RLP-C) are considered important in atherogenesis. Hence, this study was designed to assess RLP-C levels and the effect of statin therapy in patients with familial hypercholesterolemia (FH). Elevated RLP-C levels have been associated with the presence and progression of atherosclerotic disease, and their presence in FH patients has been proposed but never established in a large cohort, nor has their response to statin therapy been confirmed.

Methods and Results—

FH patients were recruited from 36 lipid clinics. After a washout period of 6 weeks, all patients were started on monotherapy with 80 mg of simvastatin for 2 years. RLP-C levels were assessed by an immune-separation assay. In 327 FH patients, RLP-C measurements could be performed before and after treatment. Mean total cholesterol (10.55±2.17 mmol/L), mean LDL cholesterol (8.40±2.13 mmol/L), and median RLP-C (0.47 mmol/L) levels were all severely elevated at baseline. After treatment, RLP-C levels were reduced by 49% (0.24 mmol/L;
P
<0.0001). Even patients with normal triglyceride levels had elevated RLP-C levels at baseline, and those with high RLP-C levels were generally characterized by a very atherogenic lipoprotein profile.

Conclusions—

Baseline RLP-C levels are severely elevated in FH patients and are reduced by simvastatin but do not return to normal. These elevated RLP-C levels could be the consequence of impaired function of the LDL receptor in FH. RLP-C levels in FH contribute to an atherogenic lipoprotein profile and could identify patients who require additional treatment.
Renal Perfusion in Blacks
Authors: Price Deborah A. , Fisher Naomi D.L. , Lansang M. Cecilia , Stevanovic Radomir , Williams Gordon H. , Hollenberg Norman K.
Published: October 2002

We have reported that an increased intrarenal renin-angiotensin system activity may be responsible for the reduction in renal plasma flow (RPF) in apparently healthy blacks in comparison to healthy whites during high salt balance. To ascertain whether these differences only exist in the high salt state, we performed the following study, concentrating on the manipulation of the renin system during low salt intake. We measured in 19 healthy blacks and 22 healthy whites para-aminohippurate and inulin clearances as an indication of RPF and glomerular filtration rate, respectively, on both high (200 mmol/d) and low (10 mmol/d) salt balance in random order. A subset of 11 blacks and 12 whites additionally received an angiotensin II infusion while in low salt balance (3 ng/kg per minute for 45 minutes) and captopril to assess differences in RPF response to a converting enzyme inhibitor. The 19 whites had significantly higher RPF when compared with blacks (
P
=0.033) when studied on high salt. However, during low salt balance, the RPFs were comparable in the 2 groups. Plasma renin activity was similar in the 2 groups on both diets. In the subset that received angiotensin II and captopril while in low salt balance, the renal vascular response was not different in whites and blacks. These data provide additional support for the concept that the intrarenal tissue renin system is more active in blacks than whites on a typical (high salt) diet and that the difference reflects primarily incomplete tissue renin suppression with an increase in salt intake. The mechanism involved may contribute to the increased susceptibility to renal injury in blacks.
Sphingosylphosphorylcholine Is a Novel Messenger for Rho-Kinase–Mediated Ca
2+
Sensitization in the Bovine Cerebral Artery
Authors: Shirao Satoshi , Kashiwagi Shiro , Sato Masafumi , Miwa Saori , Nakao Fumiaki , Kurokawa Tetsu , Todoroki-Ikeda Natsuko , Mogami Kimiko , Mizukami Yoichi , Kuriyama Shinichi , Haze Kyousuke , Suzuki Michiyasu , Kobayashi Sei
Published: October 2002

Although recent investigations have suggested that a Rho-kinase–mediated Ca
2+
sensitization of vascular smooth muscle contraction plays a critical role in the pathogenesis of cerebral and coronary vasospasm, the upstream of this signal transduction has not been elucidated. In addition, the involvement of protein kinase C (PKC) may also be related to cerebral vasospasm. We recently reported that sphingosylphosphorylcholine (SPC), a sphingolipid, induces Rho-kinase–mediated Ca
2+
sensitization in pig coronary arteries. The purpose of this present study was to examine the possible mediation of SPC in Ca
2+
sensitization of the bovine middle cerebral artery (MCA) and the relation to signal transduction pathways mediated by Rho-kinase and PKC. In intact MCA, SPC induced a concentration-dependent (EC
50
=3.0 μmol/L) contraction, without [Ca
2+
]
i
elevation. In membrane-permeabilized MCA, SPC induced Ca
2+
sensitization even in the absence of added GTP, which is required for activation of G-proteins coupled to membrane receptors. The SPC-induced Ca
2+
sensitization was blocked by a Rho-kinase inhibitor (Y-27632) and a dominant-negative Rho-kinase, but not by a pseudosubstrate peptide for conventional PKC, which abolished the Ca
2+
-independent contraction induced by phorbol ester. In contrast, phorbol ester–induced Ca
2+
sensitization was resistant to a Rho-kinase inhibitor and a dominant-negative Rho-kinase. In primary cultured vascular smooth muscle cells, SPC induced the translocation of cytosolic Rho-kinase to the cell membrane. We propose that SPC is a novel messenger for Rho-kinase–mediated Ca
2+
sensitization of cerebral arterial smooth muscle and, therefore, may play a pivotal role in the pathogenesis of abnormal contraction of the cerebral artery such as vasospasm. The SPC/Rho-kinase pathway functions independently of the PKC pathway.
Knockout Mice for Pharmacological Screening
Authors: Reuter Hannes , Henderson Scott A. , Han Tieyan , Matsuda Toshio , Baba Akemichi , Ross Robert S. , Goldhaber Joshua I. , Philipson Kenneth D.
Published: October 2002

The role of the Na
+
-Ca
2+
exchanger as a major determinant of cell Ca
2+
is well defined in cardiac tissue, and there has been much effort to develop specific inhibitors of the exchanger. We use a novel system to test the specificity of two putative specific inhibitors, KB-R7943 and SEA0400. The drugs are applied to electrically stimulated heart tubes from control mouse embryos or embryos with the Na
+
-Ca
2+
exchanger knocked out. We monitored effects of the drugs on Ca
2+
transients. Both drugs depress the Ca
2+
transients at low concentrations even in the absence of any Na
+
-Ca
2+
exchanger. KB-R7943 and SEA0400 are not completely specific and should be used with caution as Na
+
-Ca
2+
exchange inhibitors.
Cardiac Microstructure
Authors: Hooks Darren A. , Tomlinson Karl A. , Marsden Scott G. , LeGrice Ian J. , Smaill Bruce H. , Pullan Andrew J. , Hunter Peter J.
Published: October 2002

Our understanding of the electrophysiological properties of the heart is incomplete. We have investigated two issues that are fundamental to advancing that understanding. First, there has been widespread debate over the mechanisms by which an externally applied shock can influence a sufficient volume of heart tissue to terminate cardiac fibrillation. Second, it has been uncertain whether cardiac tissue should be viewed as an electrically orthotropic structure, or whether its electrical properties are, in fact, isotropic in the plane orthogonal to myofiber direction. In the present study, a computer model that incorporates a detailed three-dimensional representation of cardiac muscular architecture is used to investigate these issues. We describe a bidomain model of electrical propagation solved in a discontinuous domain that accurately represents the microstructure of a transmural block of rat left ventricle. From analysis of the model results, we conclude that (1) the laminar organization of myocytes determines unique electrical properties in three microstructurally defined directions at any point in the ventricular wall of the heart, and (2) interlaminar clefts between layers of cardiomyocytes provide a substrate for bulk activation of the ventricles during defibrillation.
Near-Infrared Spectroscopic Topography as a Tool to Monitor Motor Reorganization After Hemiparetic Stroke
Authors: Kato Hiroyuki , Izumiyama Masahiro , Koizumi Hideaki , Takahashi Akira , Itoyama Yasuto
Published: October 2002

Background and Purpose

—

Motor functional recovery from stroke can occur, but the mechanisms underlying this restorative process remain to be elucidated. We used near-infrared spectroscopic (NIRS) topography in comparison with functional MRI (fMRI) to evaluate the compensatory motor activation of cortical regions in patients who recovered from hemiparesis after cortical cerebral infarction.

Methods

—

We examined 6 right-handed patients who suffered cerebral infarction of the middle cerebral artery territory with minimal or mild residual contralateral hemiparesis (4 men and 2 women, 59 to 79 years old, all had left hemiparesis). Both fMRI and NIRS were studied during a hand movement task at chronic stages. Five right-handed, normal subjects (3 men and 2 women, 44 to 81 years old) served as controls.

Results

—

fMRI and NIRS detected very similar cerebral cortical activation, although NIRS detected only superficial activation. The spatial resolution of NIRS was less than that of fMRI, but NIRS provided a dynamic profile of activation. Normal subjects activated predominantly the contralateral primary sensorimotor cortex and supplementary motor areas during each hand movement. All the stroke patients exhibited the normal activation pattern during normal hand movement. On affected hand movement, the stroke patients showed extended activation not only in the contralateral motor cortex but also in the ipsilateral motor cortex (primary motor cortex and supplementary motor areas).

Conclusions

—

Both fMRI and NIRS studies provided evidence for the contribution of ipsilateral motor cortical compensation or reorganization to the recovery from poststroke hemiparesis. The result demonstrated that NIRS was a unique tool to monitor poststroke alterations in cortical motor functions.
Color Doppler Flow Imaging of the Superior Ophthalmic Vein in Dural Arteriovenous Fistulas
Authors: Kawaguchi Shoichiro , Sakaki Toshisuke , Uranishi Ryunosuke
Published: October 2002

Background and Purpose

—

This article evaluates the intracranial venous hemodynamics of dural arteriovenous fistula (DAVF) on the basis of data from color Doppler flow imaging (CDFI) findings of the superior ophthalmic vein (SOV) and discusses the clinical application of the SOV CDFI to the DAVFs.

Methods

—

We examined the diameter, flow direction, flow waveform, and flow velocity of the SOV using CDFI in 20 patients with intracranial DAVF. Six patients were asymptomatic; the other 14 patients were symptomatic. Angiographic retrograde cortical venous filling was seen in 14 patients.

Results

—

In the DAVFs, the average SOV diameter was 2.95±1.15 mm, which was significantly broad compared with that of the control subjects (
P
<0.05). The flow direction was reversed in 2 patients and normal in the other 18 patients. Three patients showed an abnormal waveform. A reversed pulsatile waveform was observed in 2 patients, and a normograde pulsatile waveform was seen in 1 patient. The other 17 patients showed normal waveform. The average SOV diameter and resistance index values were significantly higher (
P
<0.05) in patients with clinical symptoms, angiographic retrograde cortical venous fillings, or large DAVFs compared with those in the other patients.

Conclusions

—

The SOV CDFI findings in DAVFs correlated well with the patient’s clinical symptoms, angiographic findings, and DAVF size. These findings were useful to evaluate the intracranial venous hemodynamics in DAVFs.
Delegation, Comitology, and the Separation of Powers in the European Union
Authors: Ballmann Alexander , Epstein David , O'Halloran Sharyn
Published: October 2002

Although relatively unknown outside of Europe, comitology committees are an object of considerable controversy in the European Union (EU). Controversy stems from their pivotal role in overseeing policy implementation authority delegated from the Council of Ministers (Council) to the European Commission (Commission). In this article, we employ a game-theoretic model to analyze the influence of these, committees on policy outcomes. Our analysis provides three important insights. First, we show that, contrary to the conventional wisdom, comitology committees move outcomes toward theCommission'spreferred policies rather than the Council's. Second, we demonstrate that the possibility of a Council veto may also move outcomes away from Council members' policy preferences and toward the Commission's. Third, the 1999 changes to the comitology procedures, designed to enhance the Commission's autonomy in policymaking, may have had the exact opposite effect. Paradoxically, we conclude that comitology serves to enhance the Commission's role in policy implementation and thereby strengthens the separation of powers within the EU.