bluuebunny/crossref_metadata_2025 huggingface dataset:
Stem Cell Self-Renewal Controlled by Chromatin Remodeling Factors
Authors: Xi Rongwen , Xie Ting
Published: December 2005

The self-renewing ability of a stem cell is controlled by its specialized micro-environment or niche, whereas epigenetic regulation of gene expression by chromatin remodeling factors underlies cell fate determination. Here we report that the adenosine triphosphate–dependent chromatin remodeling factors ISWI and DOM control germline stem cell and somatic stem cell self-renewal in the
Drosophila
ovary, respectively. The
iswi
mutant germline stem cells are lost rapidly because of defects in responding to bone morphogenetic protein niche signals and in repressing differentiation, whereas the
dom
mutant somatic stem cells are lost because of defective self-renewal. This work demonstrates that different stem cell types can use different chromatin remodeling factors to control cell self-renewal.
Still Worthy of Our Land?
Authors: Greenberg Joel
Published: December 2005

Return to Wild America
. A Yearlong Search for the Continent's Natural Soul.
By Scott Weidensaul

North Point Press, New York, 2005. 422 pp. $26, C$36.50. ISBN 0-86547-688-8.

The author surveys the natural world of North America through a consideration of the gains and losses at sites Roger Tory Peterson and James Fisher visited on the 1953 tour described in their classic Wild America.
A Well-Preserved
Archaeopteryx
Specimen with Theropod Features
Authors: Mayr Gerald , Pohl Burkhard , Peters D. Stefan
Published: December 2005

A nearly complete skeleton of
Archaeopteryx
with excellent bone preservation shows that the osteology of the urvogel is similar to that of nonavian theropod dinosaurs. The new specimen confirms the presence of a hyperextendible second toe as in dromaeosaurs and troodontids.
Archaeopteryx
had a plesiomorphic tetraradiate palatine bone and no fully reversed first toe. These observations provide further evidence for the theropod ancestry of birds. In addition, the presence of a hyperextendible second toe blurs the distinction of archaeopterygids from basal deinonychosaurs (troodontids and dromaeosaurs) and challenges the monophyly of Aves.
Crowing About Culture
Authors: Dally Joanna
Published: December 2005

In the Company of Crows and Ravens
.
By John M. Marzluff and Tony Angell

Yale University Press, New Haven, CT, 2005. 404 pp. $30, £18.95. ISBN 0-300-10076-0.

Writing for a broad audience, Marzluff and Angell explore the interactions between people and crows and the influences each has had on the other.
Radar Soundings of the Subsurface of Mars
Authors: Picardi Giovanni , Plaut Jeffrey J. , Biccari Daniela , Bombaci Ornella , Calabrese Diego , Cartacci Marco , Cicchetti Andrea , Clifford Stephen M. , Edenhofer Peter , Farrell William M. , Federico Costanzo , Frigeri Alessandro , Gurnett Donald A. , Hagfors Tor , Heggy Essam , Herique Alain , Huff Richard L. , Ivanov Anton B. , Johnson William T. K. , Jordan Rolando L. , Kirchner Donald L. , Kofman Wlodek , Leuschen Carlton J. , Nielsen Erling , Orosei Roberto , Pettinelli Elena , Phillips Roger J. , Plettemeier Dirk , Safaeinili Ali , Seu Roberto , Stofan Ellen R. , Vannaroni Giuliano , Watters Thomas R. , Zampolini Enrico
Published: December 2005

The martian subsurface has been probed to kilometer depths by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument aboard the Mars Express orbiter. Signals penetrate the polar layered deposits, probably imaging the base of the deposits. Data from the northern lowlands of Chryse Planitia have revealed a shallowly buried quasi-circular structure about 250 kilometers in diameter that is interpreted to be an impact basin. In addition, a planar reflector associated with the basin structure may indicate the presence of a low-loss deposit that is more than 1 kilometer thick.
Evolutionary Genetics of the Accessory Gene Regulator (
agr
) Locus in
Staphylococcus aureus
Authors: Robinson D. Ashley , Monk Alastair B. , Cooper Jessica E. , Feil Edward J. , Enright Mark C.
Published: December 2005

The accessory gene regulator (
agr
) locus influences the expression of many virulence genes in the human pathogen
Staphylococcus aureus
. Four allelic groups of
agr
, which generally inhibit the regulatory activity of each other, have been identified within the species. Interference in virulence gene expression caused by different
agr
groups has been suggested to be a mechanism for isolating bacterial populations and a fundamental basis for subdividing the species. To test the hypothesis that the species is phylogenetically structured according to
agr
groups, we mapped
agr
groups onto a clone phylogeny inferred from partial sequences of 14 genes from 27 genetically diverse strains. Shimodaira-Hasegawa and parametric bootstrap tests rejected the hypotheses that the species is subdivided into three or five monophyletic
agr
groups but failed to reject the hypothesis that the species is subdivided into two groups that each consist of multiple clonal complexes and multiple
agr
groups. Additional evidence for
agr
recombination is found from clustered polymorphisms in complete
agr
sequences. However,
agr
recombination has not occurred frequently or randomly through time, because the topology and branch lengths of the clone phylogeny are reflected within each
agr
group. To account for these observations, we propose a new evolutionary model that involves a genetically polymorphic ancestral population of
S. aureus
that horizontally transferred
agr
groups between two subspecies groups near the time that these subspecies groups diverged.
The Maltodextrin System ofEscherichia coli: Glycogen-Derived Endogenous Induction and Osmoregulation
Authors: Dippel Renate , Bergmiller Tobias , Böhm Alex , Boos Winfried
Published: December 2005

Strains ofEscherichia colilacking MalQ (maltodextrin glucanotransferase or amylomaltase) are endogenously induced for the maltose regulon by maltotriose that is derived from the degradation of glycogen (glycogen-dependent endogenous induction). A high level of induction was dependent on the presence of MalP, maltodextrin phosphorylase, while expression was counteracted by MalZ, maltodextrin glucosidase. Glycogen-derived endogenous induction was sensitive to high osmolarity. This osmodependence was caused by MalZ.malZ, the gene encoding this enzyme, was found to be induced by high osmolarity even in the absence of MalT, the central regulator of allmalgenes. The osmodependent expression ofmalZwas neither RpoS nor OmpR dependent. In contrast, themalPQoperon, whose expression was also increased at a high osmolarity, was partially dependent on RpoS. In the absence of glycogen, residual endogenous induction of themalgenes that is sensitive to increasing osmolarity can still be observed. This glycogen-independent endogenous induction is not understood, and it is not affected by altering the expression of MalP, MalQ, and MalZ. In particular, its independence from MalZ suggests that the responsible inducer is not maltotriose.
A Relative-Entropy Algorithm for Genomic Fingerprinting Captures Host-Phage Similarities
Authors: Robins Harlan , Krasnitz Michael , Barak Hagar , Levine Arnold J.
Published: December 2005

The degeneracy of codons allows a multitude of possible sequences to code for the same protein. Hidden within the particular choice of sequence for each organism are over 100 previously undiscovered biologically significant, short oligonucleotides (length, 2 to 7 nucleotides). We present an information-theoretic algorithm that finds these novel signals. Applying this algorithm to the 209 sequenced bacterial genomes in the NCBI database, we determine a set of oligonucleotides for each bacterium which uniquely characterizes the organism. Some of these signals have known biological functions, like restriction enzyme binding sites, but most are new. An accompanying scoring algorithm is introduced that accurately (92%) places sequences of 100 kb with their correct species among the choice of hundreds. This algorithm also does far better than previous methods at relating phage genomes to their bacterial hosts, suggesting that the lists of oligonucleotides are “genomic fingerprints” that encode information about the effects of the cellular environment on DNA sequence. Our approach provides a novel basis for phylogeny and is potentially ideally suited for classifying the short DNA fragments obtained by environmental shotgun sequencing. The methods developed here can be readily extended to other problems in bioinformatics.
1-Deoxy-
d
-Xylulose 5-Phosphate Reductoisomerase (IspC) from
Mycobacterium tuberculosis
: towards Understanding Mycobacterial Resistance to Fosmidomycin
Authors: Dhiman Rakesh K. , Schaeffer Merrill L. , Bailey Ann Marie , Testa Charles A. , Scherman Hataichanok , Crick Dean C.
Published: December 2005

1-Deoxy-
d
-xylulose 5-phosphate reductoisomerase (IspC) catalyzes the first committed step in the mevalonate-independent isopentenyl diphosphate biosynthetic pathway and is a potential drug target in some pathogenic bacteria. The antibiotic fosmidomycin has been shown to inhibit IspC in a number of organisms and is active against most gram-negative bacteria but not gram positives, including
Mycobacterium tuberculosis
, even though the mevalonate-independent pathway is the sole isopentenyl diphosphate biosynthetic pathway in this organism. Therefore, the enzymatic properties of recombinant IspC from
M. tuberculosis
were characterized. Rv2870c from
M. tuberculosis
converts 1-deoxy-
d
-xylulose 5-phosphate to 2-
C
-methyl-
d
-erythritol 4-phosphate in the presence of NADPH. The enzymatic activity is dependent on the presence of Mg
2+
ions and exhibits optimal activity between pH 7.5 and 7.9; the

K
m

for 1-deoxyxylulose 5-phosphate was calculated to be 47.1 μM, and the

K
m

for NADPH was 29.7 μM. The specificity constant of Rv2780c in the forward direction is 1.5 × 10
6
M
−1
min
−1
, and the reaction is inhibited by fosmidomycin, with a 50% inhibitory concentration of 310 nM. In addition,
Rv2870c
complements an inactivated chromosomal copy of
IspC
in
Salmonella enterica
, and the complemented strain is sensitive to fosmidomycin. Thus,
M. tuberculosis
resistance to fosmidomycin is not due to intrinsic properties of Rv2870c, and the enzyme appears to be a valid drug target in this pathogen.
The Shiga Toxin 1-Converting Bacteriophage BP-4795 Encodes an NleA-Like Type III Effector Protein
Authors: Creuzburg Kristina , Recktenwald Jürgen , Kuhle Volker , Herold Sylvia , Hensel Michael , Schmidt Herbert
Published: December 2005

In this study, the complete DNA sequence of Shiga toxin 1-converting bacteriophage BP-4795 was determined. The genome of BP-4795 consists of 85 open reading frames, including two complete IS
629
elements and three morons at the end of its late regulatory region. One of these morons encodes a type III effector that is translocated by the locus of enterocyte effacement-encoded type III secretion system into HeLa cells, where it localizes with the Golgi apparatus.
An α/β-Fold C—C Bond Hydrolase Is Involved in a Central Step of Nicotine Catabolism by
Arthrobacter nicotinovorans
Authors: Sachelaru Paula , Schiltz Emile , Igloi Gabor L. , Brandsch Roderich
Published: December 2005

The enzyme catalyzing the hydrolytic cleavage of 2,6-dihydroxypseudooxynicotine to 2,6-dihydroxypyridine and γ-
N
-methylaminobutyrate was found to be encoded on pAO1 of
Arthrobacter nicotinovorans
. The new enzyme answers an old question about nicotine catabolism and may be the first C—C bond hydrolase that is involved in the biodegradation of a heterocyclic compound.
Characterization of the DNA Gyrase from the Thermoacidophilic Archaeon
Thermoplasma acidophilum
Authors: Yamashiro Kan , Yamagishi Akihiko
Published: December 2005

Thermoplasma acidophilum
is sensitive to the antibiotic drug novobiocin, which inhibits DNA gyrase. We characterized DNA gyrases from
T. acidophilum
strains in vitro. The DNA gyrase from a novobiocin-resistant strain and an engineered mutant were less sensitive to novobiocin. The novobiocin-resistant gyrase genes might serve as
T. acidophilum
genetic markers.
HERSCHEL–BULKLEY FLUIDS: EXISTENCE AND REGULARITY OF STEADY FLOWS
Authors: MÁLEK J. , RŮŽIČKA M. , SHELUKHIN V. V.
Published: December 2005

The equations for steady flows of Herschel–Bulkley fluids are considered and the existence of a weak solution is proved for the Dirichlet boundary-value problem. The rheology of such a fluid is defined by a yield stress τ* and a discontinuous constitutive relation between the Cauchy stress and the symmetric part of the velocity gradient. Such a fluid stiffens if its local stresses do not exceed τ*, and it behaves like a non-Newtonian fluid otherwise. We address here a class of nonlinear fluids which includes shear-thinning p-law fluids with 9/5 < p ≤ 2. The flow equations are formulated in the stress-velocity setting (cf. Ref. 25). Our approach is different from that of Duvaut–Lions (cf. Ref. 10) developed for classical Bingham visco-plastic materials. We do not apply the variational inequality but make use of an approximation of the Herschel–Bulkley fluid with a generalized Newtonian fluid with a continuous constitutive law.
ASYMPTOTIC APPROXIMATION FOR THE SOLUTION TO THE ROBIN PROBLEM IN A THICK MULTI-LEVEL JUNCTION
Authors: DE MAIO U. , DURANTE T. , MEL'NYK T. A.
Published: December 2005

We consider a mixed boundary-value problem for the Poisson equation in a plane two-level junction Ωε, which is the union of a domain Ω0 and a large number 2N of thin rods with variable thickness of order [Formula: see text]. The thin rods are divided into two levels depending on their length. In addition, the thin rods from each level are ε-periodically alternated. The Robin conditions are given on the lateral boundaries of the thin rods. Using the method of matched asymptotic expansions, we construct the asymptotic approximation for the solution as ε → 0 and prove the corresponding estimates in the Sobolev space H1(Ωε).
Recent Topics in High-Tc Superconductive Electronics
Authors: Tonouchi Masayoshi , Fujimaki Akira , Tanabe Keiichi , Enpuku Keiji , Nikawa Kiyoshi , Kobayashi Takeshi
Published: December 2005

This paper reports selected recent topics in high-T
c superconductive electronics. Improved process technology for high-T
c digital electronics, the development of a sampling oscilloscope, magnetic immunoassay using a high-T
c superconducting quantum interference device (SQUID), scanning laser-SQUID for integrated circuits testing, terahertz radiation from high-T
c superconductors, and optical control of vortices are reviewed.
Effect of Nitrogen on Diffusion in Silicon Oxynitride
Authors: Uematsu Masashi , Kageshima Hiroyuki , Shiraishi Kenji
Published: December 2005

The effect of nitrogen (N) on diffusion in silicon oxynitride was investigated through the simulation of silicon oxynitridation. We assumed that the incorporation of N reduces the SiO diffusivity in SiO2 because oxynitride layers retard B penetration, or B diffusion, which is enhanced by SiO. In order to validate this assumption, we simulated the thickness of thermally grown oxynitride. The simulation was based on our oxidation model in which SiO molecules emitted to the oxide during oxidation modulate the oxidation rate. The assumption that the SiO diffusivity exponentially decreases with increasing N concentration was introduced to our oxidation model. The simulation results fit the experimental oxynitride thickness, and this indicates the validity of our assumption of the N effect on diffusion. During oxynitridation, the diffusion of SiO molecules generated at the interface is strongly retarded by the N atoms, which are incorporated and piled up at the interface. This retardation increases the SiO concentration in SiO2 near the interface as oxynitridation proceeds, which decreases the oxynitridation rate with time. The formation of Si3≡N bonds, which should block the reconstruction of Si–O bonds, is most likely the cause of the retardation of SiO diffusion in SiO2.
Agglomerated Large Particles under Various Slurry Preparation Conditions and Their Influence on Shallow Trench Isolation Chemical Mechanical Polishing
Authors: Kim Dae-Hyeong , Kang Hyun-Goo , Kim Sang-Kyun , Paik Ungyu , Park Jea-Gun
Published: December 2005

The effects of various slurry manufacturing conditions, such as suspension pH, abrasive contents, and the calcination temperature of abrasive ceramic particles on the formation of agglomerated large particles of ceria slurry were investigated. The agglomerated large particles in slurry have much influence on the micro-scratches on the wafer surface in shallow trench isolation chemical mechanical polishing (STI CMP). The formation of large agglomerated particles is affected by the conformation of the organic additives in the slurry as a function of the suspension pH and the specific surface area of the abrasive particle. Regarding the solid content, abrasive particles are more easily dispersed at lower solid loading, which prevents additional agglomeration even under acidic conditions. The influence of agglomerated large particles on STI CMP was investigated through a polishing experiment with plasma-enhanced tetra-ethyl-ortho-silicate (PETEOS) and a low-pressure chemical vapor deposition (LPCVD) nitride layer.
Amorphous Silicon Film Deposition from SiH4 by Chemical Vapor Deposition with Argon Excimer Lamp
Authors: Toshikawa Kiyohiko , Yokotani Atsushi , Kurosawa Kou
Published: December 2005

We have deposited amorphous silicon thin films from monosilane (SiH4) gas by photochemical vapor deposition using a vacuum ultraviolet excimer lamp (VUV-CVD). We used an argon excimer lamp (λ=126 nm, hν=9.8 eV) whose photons are strongly absorbed by SiH4 gas. The substrate temperatures were changed from 25 to 300°C. When the temperature was lower than 150°C, the films included H–Si–H units and H2 molecules in its structure. When it was higher than 150°C, the main structural unit was Si–H.
Quantum-Corrected Monte Carlo and Molecular Dynamics Simulation on Electron-Density-Dependent Velocity Saturation in Silicon Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Tsuchiya Hideaki , Oda Azusa , Ogawa Matsuto , Miyoshi Tanroku
Published: December 2005

The effects of electron–electron Coulomb scattering on electron quantum transport under high electric fields in silicon metal–oxide–semiconductor field-effect transistors (MOSFETs) has been studied based on a quantum-corrected Monte Carlo and molecular dynamics simulation, where the electron–electron Coulomb interaction is split into short-range and long-range interactions. The short-range interaction is included using a molecular dynamics approach, while the long-range electron–plasmon interaction is treated in two different ways: an analytical model based on quantum mechanics, and a numerical model within semiclassical treatment. The electron velocity in the inversion layer was calculated as a function of tangential electric field using a high-resistive gate MOSFET and compared with the experimental results reported by Takagi et al., which indicated that the saturation velocity depends on surface electron concentration. The analytical model for describing the long-range interaction qualitatively agrees with the experimental results in the high electric field regime. We also evaluated the role of the plasmon scattering and short-range Coulomb scattering.
Surface Texturing of Silicon by Hydrogen Radicals
Authors: Nagayoshi Hiroshi , Konno Keita , Nishimura Suzuka , Terashima Kazutaka
Published: December 2005

The surface texturing method for crystalline Si using hydrogen radicals generated by a tungsten hot filament was developed. We found that tungsten particles supplied from a tungsten filament work as an etching mask against hydrogen radicals. The surface morphology and feature size of the texture structure could be controlled by the particle deposition condition on the Si(100) surface. An inverted pyramid structure was obtained when the particle density was high, suggesting that the etching reaction induced by hydrogen radicals is anisotropic. The reflectance spectra of hydrogen-treated Si surface using this method showed a very low surface reflectance of less than 1% in the range from 200 to 900 nm without any antireflection coatings. The particles on the silicon surface can easily be removed using HF+HNO3 solution. This method is also effective for the texturing of Si(111) wafer, having a potential for the texturing of multicrystalline silicon.
High-Speed Rotating-Disk Chemical Vapor Deposition Process for In-Situ Arsenic-Doped Polycrystalline Silicon Films
Authors: Terai Fujio , Kobayashi Hiroaki , Katsui Shuji , Tamaoki Naoki , Nagatomo Takao , Homma Tetsuya
Published: December 2005

We have developed high-speed rotating-disk chemical vapor deposition (CVD) equipment for polycrystalline silicon (poly-Si) films. This CVD equipment has an enhanced ability to reduce the boundary layer thickness at a given temperature above a wafer surface, and to suppress vapor-phase reactions. We investigated in-situ arsenic-doped poly-Si film deposition using silane (SiH4), arsine (AsH3) and nitrogen (N2) in a high-speed rotating-disk CVD as functions of AsH3 flow rate and deposition temperature. Both the deposition rate and resistivity decreased with increasing AsH3 flow rate. A deposition rate of 120 nm/min, a resistivity of 16 mΩ·cm, a film thickness nonuniformity of ±5%, and a number of particles of less than 20 (over 200 nm in diameter) were achieved at a deposition temperature of 680°C for in-situ arsenic-doped poly-Si deposition on a 200-mm-diameter silicon (Si) wafer. Moreover, it was confirmed that the concentration of As in the poly-Si film was low at the initial stage of deposition, and that this process has a high gap filling capability in a hole of 0.18 µm width and 7 µm depth. It was also confirmed that there were conditions for a high step coverage of more than 1. These properties are inferred to be due to the adsorbed AsH3 preventing the adsorption of SiH4.
High Temperature Characteristics of Insulated-Gate AlGaN/GaN Heterostructure Field-Effect Transistors with Ultrathin Al2O3/Si3N4 Bilayer
Authors: Wang Chengxin , Maeda Narihiko , Hiroki Masanobu , Kobayashi Takashi , Enoki Takatomo
Published: December 2005

The device performance of AlGaN/GaN-based metal–insulator–semiconductor heterostructure field-effect transistors (MIS-HFETs) with an ultrathin (1 nm/0.5 nm) Al2O3/Si3N4 bilayer has been investigated at elevated temperatures up to 200°C. The devices exhibited excellent transconductance characteristics with high maximum transconductances and ultralow gate current leakages under reverse gate bias conduction at both room and high temperatures due to the employment of an ultrathin bilayer with large dielectric constants and the large conduction band offset between Al2O3 and nitrides. The excellent characteristics observed at high temperatures might indicate the very high interfacial quality between nitrides and bilayer insulator. The results in this report demonstrate that Al2O3/Si3N4 bilayer insulator is a superior candidate for nitride-based MIS-HFET devices operating at high temperatures.
Band Offsets of InN/GaN Interface
Authors: Shih Chuan-Feng , Chen Nie-Chuan , Chang Pen-Hsiu , Liu Kuo-Shung
Published: December 2005

In this paper, we report on the band discontinuities of the wurtzite-InN/GaN interface. X-ray photoemission spectroscopy studies reveal that the offset ratios of conduction bands and valence bands are approximately 80 and 20%, respectively. The valence band offset (0.5 eV) is close to the theoretical value determined on the basis of the density functional theory from first principle that was reported by Wei and Zunger [Appl. Phys. Lett. 69 (1996) 2719]. The photoluminescence signals of InN/GaN quantum wells were also studied. The luminescence of the wells showed a 60 meV quantum confinement shift from the bulk InN signal. The finite potential well model of quantum mechanics is used to show that this shift supports the above results.
Nanocrystalline Mn-doped ZnO Prepared by Chemical Route
Authors: Pal Manisha , Pal Mrinal
Published: December 2005

Nanocrystalline dilute magnetic semiconductor, Mn-doped ZnO, has been prepared by chemical route. The amorphous nature of the as-prepared sample was confirmed by X-ray diffraction analysis. Reitveld analysis of the annealed sample heated at 500°C for 30 min shows it is an anisotropic nanocrystalline phase. Transmission electron microscopy also confirms the anisotropic growth of Mn-doped ZnO. Saturation magnetization around 0.2 emu/gm has been achieved for the same sample, which is substantially higher than previously reported value. A decrease in magnetization with increasing annealing temperature is observed, which might be related to the effect of particle size.
Electrical Behavior of Germanium Oxide/Germanium Interface Prepared by Electron-Cyclotron-Resonance Plasma Oxidation in Capacitance and Conductance Measurements
Authors: Fukuda Yukio , Ueno Tomoo , Hirono Shigeru
Published: December 2005

In this letter, we describe the electrical behavior of the GeO
x
and p-type Ge interface on the basis of capacitance and conductance measurements. The primary conclusion of this work is that when the Ge surface is biased in the depletion region, the frequency response of interface traps in the lower half of the Ge band-gap is so fast that there is no significant frequency dispersion observed in the capacitance measurements over a typical frequency range of ≤ 1 MHz. As a result, the density and energy distributions of the interface traps cannot be determined by a conventional method of combined high-frequency and low-frequency capacitance measurements. Instead, a comparison of the measured capacitance with a theoretical capacitance calculated for a system with no interface traps must be conducted to obtain information on the interface traps. Furthermore, the conductance method provides information on the interface traps in the upper half of the p-type Ge band-gap.
Lowering the Lasing Threshold by Introducing Cholesteric Liquid Crystal Films to Dye-Doped Cholesteric Liquid Crystal Cell Surfaces
Authors: Amemiya Kazuhiro , Song Myoung Hoon , Takanishi Yoichi , Ishikawa Ken , Nishimura Suzushi , Toyooka Takehiro , Takezoe Hideo
Published: December 2005

The effect of the introduction of polymer cholesteric liquid crystal (PCLC) films on the threshold of dye-doped cholesteric liquid crystal (CLC) distributed feedback (DFB) cavity lasing has been investigated. A PCLC film used to reflect a pump beam brings about the efficient use of incident energy, whereas a PCLC film used to reflect the emission contributes to amplifying the stimulated emission. As a result, the cell, in which both PCLC films are introduced, gains about a 60% reduction in the lasing threshold. It is also found that a lasing threshold exists not only for the excitation energy but also for the emission intensity. Namely, the lasing starts to occur at a certain emission level irrespective of the cell structures.
Experimental Investigations of Z Dependence of External Magnetic Field on Magnetic Excitation of CuBr Laser
Authors: Ghomi Hamid , Latifi Hamid
Published: December 2005

In this paper, the effects of an axial longitudinal movable external magnetic field (EMF) on a CuBr laser tube have been explored. Results show that applying a DC EMF on the cathode area of the laser induces a significant effect on its performance. With the application of the EMF to the cathode area, the laser output power increases, the power decreases when the EMF is placed on the anode region. Application of the EMF between the anode and cathode does not have a significant effect on the laser output power.
Integrated-Optic Add/Drop Multiplexing of Free-Space Waves for Intra-Board Chip-to-Chip Optical Interconnects
Authors: Ohmori Junpei , Imaoka Yoshitaka , Ura Shogo , Kintaka Kenji , Satoh Ryohei , Nishihara Hiroshi
Published: December 2005

In order to construct future optical interconnecting board providing ultra-broadband chip-to-chip signal transmission, integrated-optic configuration from two-dimensional array of surface emitting lasers to two-dimensional array of photodiodes was discussed with wavelength-division-multiplexing technique. TE0 guided mode was used for signal transmission while TE1 mode was used for input/output coupling of free-space waves to/from waveguide. Guided-mode-selective focusing grating coupler and different-guided-mode-coupling distributed Bragg reflector were integrated in thin-film waveguide to form free-space-wave add/drop multiplexer. Two-channel multi-/demultiplexing function was experimentally demonstrated for the first time with 5 nm wavelength spacing around 850 nm wavelength, although insertion loss and crosstalk noise were estimated to be not sufficient but -30 and -5 dB, respectively.
Evaluations of Phases and Vacancy Formation Energies in KNbO3 by First-Principles Calculation
Authors: Shigemi Akio , Wada Takahiro
Published: December 2005

In order to clarify thermodynamic relationships of the various phases of KNbO3, enthalpies of formation for cubic (P
m3m), tetragonal (P4m
m), orthorhombic (B
m
m2) and rhombohedral (R3m) phases of KNbO3 were calculated using a plane-wave pseudopotential method within a density functional formalism. The KNbO3 phase with the lowest symmetry was found to have the lowest enthalpy of formation. Moreover, we quantitatively evaluated the formation energies of neutral vacancies in KNbO3 as functions of the atomic chemical potentials of the constituent elements by the use of the same procedure. Relaxation of the first- and the second-neighbor atoms around the vacancy was considered in a 40-atom supercell. The formation energy of a K vacancy was found to be the lowest under an oxidizing atmosphere and that of an O vacancy was found to be the lowest under a reducing atmosphere. The formation energy of a Nb vacancy was the highest under both oxygen-rich and -poor conditions. These results are in agreement with the empirical rule that B site defects in perovskite-type oxide do not exist. These results are discussed on the basis of the band structure of KNbO3.
Electrooptical Responses of Carbon Nanotube-Doped Liquid Crystal Devices
Authors: Huang Chi-Yen , Hu Chao-Yuan , Pan Hung-Chih , Lo Kuang-Yao
Published: December 2005

The electrooptical characteristics of carbon nanotube-doped liquid crystal (LC) devices were investigated. Two complementary operation modes of the liquid crystal cells were fabricated. The measured results reveal that anisotropic carbon nanosolids modify the dielectric anisotropy and the viscosity of the liquid crystal carbon nanotube mixture, hence significantly modifying the threshold voltage and the switching behavior of a liquid crystal device. Doping a small amount of carbon nanotubes into the liquid crystal mixture is effective in improving the electrooptical characteristics of an LC device when the employed LC mixture is viscous.
Dynamic Stability of Liquid Crystal Depending on Shape of Pixel Edge in the Fringe Field Switching Mode
Authors: Kim M. S. , Seen S. M. , Jung Y. H. , Kim H. Y. , Kim S. Y. , Lee K. H. , Lim Y. J. , Lee S. H.
Published: December 2005

We studied the voltage–dependent liquid crystal (LC) dynamic stability corresponding to the pixel edge shape in the fringe field switching (FFS) mode. LC dynamics is very unstable near the edge of the pixel slit, where there is a horizontally different field direction compared with the active region, particularly when the slit angle decreases to 3°. Actually, there are strong field competitions near the edge of the pixel slit due to the patterned pixel shape. Also, a dark disclination line (D/L) at the domain boundary is generated with increasing operation voltage and the D/L extends into the active area at a high applied voltage. It is possible to control LC dynamics near the pixel edge by using different pixel edge shapes. In this paper, we propose an advanced edge shape. This shape has no reverse twist region, unlike the conventional structure, and therefore, LC dynamics is very stable near the edge of the pixel slit. This result indicates that a pixel edge shape with no reverse twist is very important in the design of a high-image-quality FFS mode.
Molecular Dynamics Study of Compressibility of Vitreous Silica
Authors: Kuzuu Nobu , Nagai Ken , Tanaka Mitsuya , Tamai Yoshinori
Published: December 2005

The temperature dependence of the isothermal compressibility of vitreous silica has been studied by molecular dynamics simulation. The compressibility discontinuously jumps from ≈2×10-11 to ≈6×10-11 Pa-1 with a change in temperature up to ≈3200 K at which the thermal expansivity changes from positive to negative. The compressibility values were on the same order as that obtained by the light scattering experiment in the literature reported previously.
Thermally Induced Reorganization of Redshifted Band in Merocyanine–Cd Arachidate Mixed Langmuir–Blodgett Films
Authors: Miyata Junpei , Morita Shin-ichi , Miura Yasuhiro F. , Sugi Michio
Published: December 2005

The effect of heat treatment at 60–70°C has been studied for merocyanine (MS)–Cd arachidate mixed Langmuir–Blodgett (LB) films. MS chromophores are found to be reorganized by the heat treatments to form a novel phase of a redshifted band with spectra sharper than those of the J-band in the as-deposited films. The reorganization of MS seems to be closely related with the mobility of alkyl chains in the LB system, suggesting that the mild heat treatments will introduce another possible method of modifying the properties of films.
Fast Numerical Calculation for a Set of Nonlinear Rate Equations: Application to Rapid Ionizaton Phase in Plasma
Authors: Oda Toshiatsu , Namba Shinichi , Takiyama Ken , Furukane Utaro
Published: December 2005

To make a useful contribution to the development of the compact X-ray laser, a modified quasi-steady-state approximation is applied to the fast numerical calculation of rate equations for the rapid ionization phase of a laser-produced plasma, to which the usual quasi-steady-state model by Bates et al. is not applicable. The set of nonlinear rate equations for the excited level populations coupled with the electron density and temperature for the plasma are numerically calculated with sufficient accuracy for their temporal evolution. The calculation also shows that a suitable combination is possible between the power and pulse width of a heating laser so that a high-density plasma can be obtained as the X-ray laser medium. The mathematical meaning of our approximation is briefly mentioned and its applicability is discussed.
Novel Internal Linear Inductively Coupled Plasma Source for Flat Panel Display Applications
Authors: Kim Kyong Nam , Jung Seung Jae , Yeom Geun Young
Published: December 2005

In this study, using two different types of linear internal type inductively coupled plasma sources with a serpentine-type antenna and a novel double-comb type antenna having the size of 1020×830 mm2, the characteristics of their plasmas were compared as the application to the flat panel display manufacturing. The use of the double-comb type antenna instead of the serpentine-type antenna showed two times higher plasma and radical densities, and more stable plasma when rf power higher than 2000 W was applied. By the application of 5000 W of rf power with 15 mTorr Ar, a high plasma density of 2.2×1011/cm3 with the plasma uniformity of 8% could be obtained for the double-comb type antenna. The increase of plasma density, radical density, and plasma stability for the double-comb type antenna compared to the serpentine-type antenna appears from the higher inductive coupling and less standing wave effect compared to the serpentine-type antenna.
Decomposition of Halide Compounds by Nonequilibrium Discharge
Authors: Gotou Toyokazu , Wada Noboru , Kurahashi Masato , Kuzumoto Masaki , Kitamura Akira
Published: December 2005

A narrow-gap silent discharge has been successfully applied to the resolution of halide compounds (CCl2F2 and CF4) diluted in mixed gases of H2O, O2, N2 and Ar with a varied composition at an atmospheric pressure. The optimum composition of the discharge gas is discussed in terms of an effective decomposition energy E
d defined as the energy necessary for e
-1-fold reduction of the halide concentration. Efficient decomposition of CF4 gas is realized with the use of Ar gas as the dilution gas; the minimum value of E
d approaches 760 eV/CF4-molecule, which must be compared with the value of 18 keV/CF4 obtained when N2 is used as the dilution gas.
Fast Response Polypyrrole Actuators with Auxiliary Electrodes
Authors: Zama Tetsuji , Hara Susumu , Takashima Wataru , Kaneto Keiichi
Published: December 2005

Electrochemical polypyrrole (PPy) actuators, prepared electrochemically from a methyl benzoate solution of tetra-n-butylammonium trifluoromethanesulfonate (TBACF3SO3), have been studied to improve the response rate by two methods; 1) a PPy film attached with plural auxiliary electrodes of thin Au coils, 2) a PPy film equipped with a compliant Au electrode on one side of the film. With increasing the number of auxiliary electrodes for the first method, the film responded faster as if it were a shorter film. These results are due to the decrease in the IR voltage drop along the film from the electrodes and also due to the increased current to the whole film via plural electrodes. The PPy film with the Au thin layer (the second method) exhibited up to 8.8%/s strain rate, which was much faster than that (0.5%/s) without the auxiliary electrodes, keeping the maximum strain of 12–13%. The auxiliary electrodes improved not only the response speed of the PPy actuators but also the durability upon cycling electrochemically.
Novel Packaging Technology for Microelectromechanical-System Devices
Authors: Urano Masami , Sakata Tomomi , Shimamura Toshishige , Ishii Hiromu , Chino Mitsuru , Shimada Teruo , Tazawa Hiroshi , Machida Katsuyuki
Published: December 2005

In this paper, we describe a novel packaging technology for use in microelectromechanical-system (MEMS) device fabrication and its application to an optical MEMS micromirror array that consists of a mirror chip and an electrode chip that controls the micromirrors. Chip-on-chip technology, which involves the selective deposition of silver paste by screen printing, is used to join the two chips. The experimental results ensure a high production yield and heat cycle test results indicate good reliability.
Air Flow in Square Quartz Plate Spin Cleaner
Authors: Habuka Hitoshi , Pan Hairong , Fujita Ko , Kato Masayuki , Takeuchi Takashi , Aihara Masahiko
Published: December 2005

Computational fluid dynamics is used in order to clarify the air flow in a spin cleaner for a square quartz plate (150×150×10 mm3), which is used as a mask substrate. The influences of the rotation rate and the distance between the square quartz plate and its support plate on the air flow are studied. When the distance between the two rotating plates is small, 15 mm, air simply flows downward around the square quartz plate; only a small amount of air enters the region below the rotating square quartz plate. However, by increasing the distance between the plates, air tends to enter the region below the rotating square quartz plate. Such a complicated air flow easily transports very small water droplets or mist existing in the air to the region below the square quartz plate; thus water marks are formed at the surface. Therefore, water mark formation can be reduced by optimizing the air flow in the spin cleaner.
Experimental and Computational Studies on Water Mist Flow in the Horizontal Bore of a Superconducting Magnet: Example of Magnetic Force Application on Micron-Sized Objects
Authors: Wang Xian , Lu ShuShen , Hirano Hiroyuki , Tagawa Toshio , Ozoe Hiroyuki
Published: December 2005

The effect of a magnetic field on water mist (diamagnetic) is studied both experimentally and numerically. The water mist is produced by ultrasonic atomizers and is fed to a Plexiglas pipe (90 mm inner diameter and 1 m long) which is horizontally placed in a horizontal bore (d=100 mm) of a superconducting magnet (10 T at the magnet center). The water mist is found to flow out of the other end of the pipe opening when there is no magnetic field (b=0 T). At b=8 and 10 T, the mist is stopped at an intermediate location in the pipe and flows out from the inlet opening. In the computation, the water mist is simulated with 1000 particles of 0.01–5 µm in diameter. Brownian motion is considered and the Langevin equation is solved. Various magnitudes of magnetic strength, particle diameters and pressure gradients for air flow are numerically tested. The magnetic effect is obvious for particles with diameters larger than 1 µm. For example, for 3 µm particles, only a small amount of particles are able to pass through the weak magnetic field near the cylinder axis to the downstream and sediment over the downward pipe wall.
Biological Imaging by X-ray Phase Tomography Using Diffraction-Enhanced Imaging
Authors: Koyama Ichiro , Momose Atsushi , Wu Jin , Lwin Thet Thet , Takeda Tohoru
Published: December 2005

A feasibility test of phase tomography using diffraction-enhanced imaging (DEI) was performed with biological tissues consisting of not only soft tissues but also cartilages and bones. Reconstructed three-dimensional images indicated that phase tomography using DEI has an advantage from a biological viewpoint over phase tomography using a crystal X-ray interferometer, which cannot be applied to samples involving marked refractive index changes at boundaries between soft tissues and bones or cartilages.
Bipolar Room Temperature Ferromagnetic Semiconductor LaMnOP
Authors: Motomitsu Eiji , Hirano Masahiro , Yanagi Hiroshi , Kamiya Toshio , Hosono Hideo
Published: December 2005

Negated
Improvement of Magnetic Recording Characteristics by Narrowing the Array Pitch of Nanohole Patterned Media
Authors: Oshima Hirotaka , Kikuchi Hideyuki , Nakao Hiroshi , Morikawa Takeshi , Matsumoto Koji , Nishio Kazuyuki , Masuda Hideki , Itoh Ken-ichi
Published: December 2005

Dynamic magnetic recording properties of Co-filled nanohole arrays were successfully investigated as perpendicular magnetic media via a flying giant-magnetoresistive head. By narrowing the Co nanopillar pitch, we observed suppression of the magnetic transition width and increase of the signal-to-noise ratio. The dynamic signals reflect magnetic field variation caused by the nanopillar arrangement on the tens of nanometers scale. These characteristics and the signal behavior suggest their possible application to ultrahigh-density magnetic recording.
Observation of Small Sub-Pulses Out of the Delayed-Interference Signal-Wavelength Converter
Authors: Sakaguchi Jun , Nielsen Mads L. , Ohira Takashi , Suzuki Rei , Ueno Yoshiyasu
Published: December 2005

The generation of small sub-pulses in the delayed-interference signal-wavelength converter (DISC), which has been studied for use in future 160-Gb/s optical time division multiplexing–wavelength division multiplexing (OTDM–WDM) communication systems, was recently predicted as a potential problem. In this work, we have experimentally verified the generation of such pulses and its mechanism. In the experiments we used 3.8-ps-long 1.56-µm input pulses with repetition frequencies from 12.5 to 25.0 GHz and a cross-correlation monitoring system with a time resolution of approximately 2 ps.
Slip Generation in Si Wafers due to Friction-Induced Stress and Its Suppression Technique
Authors: Nakamura Iwao , Sasajima Ryota , Yamazaki Keishin , Nakamura Naoto , Nakashima Sadao
Published: December 2005

Slip-free 300 mm wafers annealed at temperatures higher than 1000°C have been investigated. It has been found that friction-related stress must be introduced to explain slip generation experimentally in addition to gravitationally induced bending stress, compressive stress and thermally induced stress. Slip-free 300 mm wafers annealed at 1350°C are obtained by appropriately controlling the surface roughness of the supporting disk.
Light Emission from Organic Single-Crystal Field-Effect Transistors
Authors: Nakamura Kiyoshi , Ichikawa Musubu , Fushiki Rei , Kamikawa Taketomi , Inoue Masamitsu , Koyama Toshiki , Taniguchi Yoshio
Published: December 2005

We have demonstrated electroluminescence from field-effect transistors (FETs) of an organic single crystal. We used top-contact-configuration FETs with Au and Al (or MgAg) as source and drain electrodes, respectively. The devices exhibited p-type unipolar behavior and light emission depending on gate voltages and metal species of the drain contact. Moreover, the light intensity increased in the saturation region of drain current.
Nucleation of Oxides during Dry Oxidation of Si(001)-2×1 Studied by Scanning Tunneling Microscopy
Authors: Togashi Hideaki , Asaoka Hidehito , Yamazaki Tatsuya , Suemitsu Maki
Published: December 2005

Morphological development of oxide islands on Si(001)-2×1 surfaces during the initial stage of dry oxidation has been studied using scanning tunneling microscopy. The oxidation was conducted at a substrate temperature of 560°C under an oxygen pressure of 6.7×10-5 Pa. The initial oxide islands grow one-dimensionally until the number of oxygen atoms within an island reaches four, at which point the growth is converted into a two-dimensional growth mode.
Hall Effect of Quasi-Hole Gas in Organic Single-Crystal Transistors
Authors: Takeya Jun , Tsukagoshi Kazuhito , Aoyagi Yoshinobu , Takenobu Taishi , Iwasa Yoshihiro
Published: December 2005

Hall effect is detected in organic field-effect transistors, using appropriately shaped rubrene (C42H28) single crystals. It turned out that inverse Hall coefficient, having a positive sign, is close to the amount of electric-field induced charge upon the hole accumulation. The presence of the normal Hall effect means that the electromagnetic character of the surface charge is not of hopping carriers but resembles that of a two-dimensional hole-gas system.
Influence of Anisotropic Diffusion of Ga Atoms on GaAs Growth on Alternately Inverted (100) Substrates
Authors: Yamamura Takuji , Matsushita Tomonori , Koitabashi Tsutomu , Kondo Takashi
Published: December 2005

Growth-rate distributions of GaAs on alternately inverted GaAs substrates have been investigated. Periodic thickness variations of GaAs grown by molecular beam epitaxy (MBE) on planarized surfaces of alternately inverted GaAs(100) substrates are caused by the anisotropic surface diffusion of Ga atoms. Simulation based on a simple diffusion-equation analysis that takes account of the anisotropic diffusion agrees quite well with the measured temperature dependence of the growth-rate distribution. We have also shown that practically flat GaAs surfaces can be attained by MBE growth at 300°C, where diffusion anisotropy is negligibly small.
Defect Structures of AlN on Sapphire (0001) Grown by Metalorganic Vapor-Phase Epitaxy with Different Preflow Sources
Authors: Kawaguchi Kenichi , Kuramata Akito
Published: December 2005

Two types of AlN defect structures directly grown on sapphire (0001) by metalorganic vapor-phase epitaxy with different initial growth sequences were studied. One was a domain structure with arrays of threading edge dislocations aligned along the [1-210] direction, observed in AlN with NH3 preflow. The other was threading dislocations with screw components located randomly, observed in AlN with TMA preflow. It was also confirmed that threading dislocations caused the surface depression of AlN. A model for the formation of domain structures based on the geometrical aspects and dislocation types is proposed.