bluuebunny/crossref_metadata_2025 huggingface dataset:
Nocardia globerulaNHB-2: a versatile nitrile-degrading organism
Authors: Bhalla Tek Chand , Kumar Harish
Published: October 2005

A versatile nitrile-degrading bacterium was isolated by enrichment culture from the soil of a forest near Manali, Himachal Pradesh, India, and was identified as Nocardia globerula. This organism contains 3 enzymes with nitrile-degrading activity: nitrilase, nitrile hydratase, and amidase. Nocardia globerula NHB-2 cells grown on nutrient broth supplemented with 1% glucose and 0.1% yeast extract exhibited nitrile hydratase–amidase activity specific for saturated aliphatic nitriles or amide, while addition of acetonitrile in nutrient broth yielded cells with nitrile hydratase–amidase that in addition to saturated aliphatic nitriles–amide also hydrolyzed aromatic amide. Nocardia globerula NHB-2 cultivated on nutrient broth containing propionitrile exhibited nitrilase activity that hydrolyzed aromatic nitrile and unsaturated aliphatic nitrile. The versatility of this organism in the hydrolysis of various nitriles and amides makes it a potential bioresource for use in organic synthesis.Key words: Nocardia globerula NHB-2, nitrilase, nitrile hydratase, amidase, nitrile–amide degradation.
Effects of selected pharmaceuticals on riverine biofilm communities
Authors: Lawrence John R , Swerhone George D.W , Wassenaar Leonard I , Neu Thomas R
Published: October 2005

Although pharmaceutical and therapeutic products are widely found in the natural environment, there is limited understanding of their ecological effects. Here we used rotating annular bioreactors to assess the impact of 10 µg·L–1of the selected pharmaceuticals ibuprofen, carbamazepine, furosemide, and caffeine on riverine biofilms. After 8 weeks of development, community structure was assessed using in situ microscopic analyses, fluor-conjugated lectin binding, standard plate counts, fluorescent in situ hybridization, carbon utilization spectra, and stable carbon isotope analyses. The biofilm communities varied markedly in architecture although only caffeine treated biofilms were significantly thicker. Cyanobacteria were suppressed by all 4 compounds, whereas the nitrogen containing caffeine, furosemide, and carbamazepine increased algal biomass. Ibuprofen and carbamazepine reduced bacterial biomass, while caffeine and furosemide increased it. Exopolymer content and composition of the biofilms was also influenced. Significant positive and negative effects were observed in carbon utilization spectra. In situ hybridization analyses indicated all treatments significantly decreased the gamma-proteobacterial populations and increased beta-proteobacteria. Ibuprofen in particular increased the alpha-proteobacteria, beta-proteobacteria, cytophaga-flavobacteria, and SRB385 probe positive populations. Caffeine and carbamazepine additions resulted in significant increases in the high GC354c and low GC69a probe positive cells. Live–dead analyses of the biofilms indicated that all treatments influenced the ratio of live-to-dead cells with controls having a ratio of 2.4, carbamazepine and ibuprofen being 3.2 and 3.5, respectively, and furosemide and caffeine being 1.9 and 1.7, respectively. Stable isotope analyses of the biofilms indicated δ13C values shifted to more negative values relative to control biofilms. This shift may be consistent with proportional loss of cyanobacteria and relative increase in algal biomass rather than incorporation of pharmaceutical carbon into microbial biofilm. Thus, at 10 ug·L–1levels pharmaceuticals exhibit both nutrient-like and toxic effects on riverine microbial communities.Key words: carbamazepine, ibuprofen, furosemide, caffeine, laser microscopy, digital imaging, in situ hybridization, stable isotopes.
The effect of farnesol on amino acid incorporation by a wild-type and cell-wall variant strain ofCandida albicans
Authors: Braun Phyllis C
Published: October 2005

Farnesol, a quorum sensing (QS) signal, is produced by Candida albicans during high density growth and has been found to inhibit morphogenesis. This QS auto-inducing signal was discovered to increase amino acid incorporation by C. albicans when concentrations of farnesol increased to 10 µg/mL in yeast nitrogen broth. Farnesol concentrations greater than 10 µg/mL abolished the enhanced incorporation, and the magnitude of the increased incorporation was dependent on cell-surface hydrophobicity.Key words: Candida albicans, farnesol, amino acid incorporation.
Isolation, characterization, and identification ofGeobacillus thermodenitrificansHRO10, an α-amylase and α-glucosidase producing thermophile
Authors: Ezeji Thaddeus C , Wolf Arite , Bahl Hubert
Published: October 2005

Thermophilic and amylolytic aerobic bacteria were isolated from soil through a selective enrichment procedure at 60 °C with starch as the carbon source. One of the isolates designated as HRO10 produced glucose aside from limit dextrin as the only hydrolysis product from starch and was characterized in detail. The starch-degrading enzymes produced by strain HRO10 were determined to be α-amylase and α-glucosidase. Whereas the α-amylase activity was detected exclusively in the culture supernatant, α-glucosidase occurred intracellular, extracellular, or on the surface of the bacteria depending on the growth phase. The optimum temperature and pH required for the growth of strain HRO10 were about 50 °C and pH 6.5 to 7.5. The strain used different carbohydrates as the carbon source, but the maximum production of α-amylase occurred when 1.0% (w/v) starch or dextrin was used. The use of organic vs. inorganic nitrogen favored the production of α-amylase in strain HRO10. The metal ions Li+, Mg2+, and Mn2+stimulated the production of both enzymes. Identification of strain HRO10 by physiological and molecular methods including sequencing of the 16S rDNA showed that this strain belongs to the species Geobacillus thermodenitrificans. Biochemically, strain HRO10 differs from the type strain DSM 465 only in its ability to hydrolyze starch.Key words: thermophilic, amylolytic, α-amylase, α-glucosidase, Geobacillus thermodenitrificans.
OPTIMAL DISCRETE STOPPING TIMES FOR RELIABILITY GROWTH TESTS
Authors: QUIGLEY JOHN
Published: October 2005

Often, the duration of a reliability growth development test is specified in advance and the decision to terminate or continue testing is conducted at discrete time intervals. These features are normally not captured by reliability growth models. This paper adapts a standard reliability growth model to determine the optimal time for which to plan to terminate testing. The underlying stochastic process is developed from an Order Statistic argument with Bayesian inference used to estimate the number of faults within the design and classical inference procedures used to assess the rate of fault detection. Inference procedures within this framework are explored where it is shown the Maximum Likelihood Estimators possess a small bias and converges to the Minimum Variance Unbiased Estimator after few tests for designs with moderate number of faults. It is shown that the Likelihood function can be bimodal when there is conflict between the observed rate of fault detection and the prior distribution describing the number of faults in the design. An illustrative example is provided.
ROBUST TIME WEIGHTED CONTROL CHARTS FOR THE PROCESS VARIANCE
Authors: KHOO MICHAEL B. C.
Published: October 2005

The statistical quality control of a process consists of two phases. In phase I, preliminary data of 20–30 samples of about 5 units each are collected to construct control charts, such as [Formula: see text] and R charts. The limits computed from these preliminary samples are referred to as trial control limits and they enable us to determine whether the process is in-control when the initial samples are selected. These control charts are then used to monitor for problems in a future process (i.e., phase II monitoring) such as outliers or excess variability in the subgroups which may indicate the presence of an assignable cause. The presence of outliers in the preliminary samples will stretch the trial limits of conventional charts such as [Formula: see text] and R charts, making them difficult in detecting these outliers. As a result, a bulk of these outliers will be included in the estimation of the trial limits so that the computed limits become wider and less meaningful. Thus, the detection of any out-of-control (o.o.c.) behaviour in phase II becomes slower and more difficult. In this paper, two time weighted robust control charts for the process variance which allow quicker detection of outliers and increased sensitivity to other types of o.o.c. signals when outliers are present are presented. These new approaches use a weighted average and an unweighted moving average as the charts' statistics. A robust estimator of scale, i.e., the sample interquartile range is used in the computation of the control limits. It is shown that overall better performances are provided by these two charts in comparison to that of the existing robust chart for process variance which uses the same estimator of scale.
MODELING THIN CURVED FERROMAGNETIC FILMS
Authors: ZORGATI HAMDI
Published: October 2005

The behavior of a thin film made of a ferromagnetic material in the absence of an external magnetic field is described by an energy depending on the magnetization of the film verifying the saturation constraint. The free energy consists of an induced magnetostatic energy and an energy term with density including the exchange energy and the anisotropic energy. We study the behavior of this energy when the thickness of the curved film goes to zero. We show that the minimizers of the free energy converge to the minimizers of a local energy depending on a two-dimensional magnetization by Γ-convergence arguments.
NON-MONOTONIC TRAVELING WAVES IN VAN DER WAALS FLUIDS
Authors: BEDJAOUI N. , CHALONS C. , COQUEL F. , LeFLOCH P. G.
Published: October 2005

We investigate the existence and properties of traveling wave solutions for the hyperbolic-elliptic system of conservation laws describing the dynamics of van der Waals fluids. The model is based on a constitutive equation of state containing two inflection points and incorporates nonlinear viscosity and capillarity terms. A global description of the traveling wave solutions is provided. We distinguish between classical and non-classical trajectories and, for the latter, the existence and properties of kinetic functions is investigated. An earlier work in this direction (cf. [4]) was restricted to dealing with one inflection point only. Specifically, given any left-hand state and any shock speed (within some admissible range), we prove the existence of a non-classical traveling wave for a sequence of parameter values representing the ratio of viscosity and capillarity. Our analysis exhibits a surprising lack of monotonicity of traveling waves. The behavior of these non-classical trajectories is also investigated numerically.
DATA CRYSTALLIZATION: CHANCE DISCOVERY EXTENDED FOR DEALING WITH UNOBSERVABLE EVENTS
Authors: OHSAWA YUKIO
Published: October 2005

This paper introduces the concept of chance discovery, i.e. discovery of an event significant for decision making. Then, this paper also presents a current research project on data crystallization, which is an extension of chance discovery. The need for data crystallization is that only the observable part of the real world can be stored in data. For such scattered, i.e. incomplete and ill-structured data, data crystallizing aims at presenting the hidden structure among events including unobservable ones. This is realized with a tool which inserts dummy items, corresponding to unobservable but significant events, to the given data on past events. The existence of these unobservable events and their relations with other events are visualized with KeyGraph, showing events by nodes and their relations by links, on the data with inserted dummy items. This visualization is iterated with gradually increasing the number of links in the graph. This process is similar to the crystallization of snow with gradual decrease in the air temperature. For tuning the granularity level of structure to be visualized, this tool is integrated with human's process of chance discovery. This basic method is expected to be applicable for various real world domains where chance-discovery methods have been applied.
HUMAN CHAT AND SELF-ORGANIZED CRITICALITY: A CHANCE DISCOVERY APPLICATION
Authors: MONTERO CALKIN A. S. , ARAKI KENJI
Published: October 2005

It has been said that there is something deeply touching about creating something and then having a chat with it. Machines in general, and more specifically computers, are not the exception to that tendency. In fact, since the Turing dissertation "Computing Machinery and Intelligence", machines' ability to perform a human-like conversational behavior has been regarded as the basis to consider the machines as "intelligent entities". In this paper, we propose the idea of the discovery of critically self-organized interaction, using its inherent structure as the basis to modeling computer chat.
CHANCE DISCOVERY IN STOCK INDEX OPTION AND FUTURES ARBITRAGE
Authors: TSANG EDWARD , MARKOSE SHERI , ER HAKAN
Published: October 2005

The prices of the option and futures of a stock both reflect the market's expectation of futures changes of the stock's price. Their prices normally align with each other within a limited window. When they do not, arbitrage opportunities arise: an investor who spots the misalignment will be able to buy (sell) options on the one hand, and sell (buy) futures on the other and make risk-free profits. Historical data suggest that option and futures prices on the LIFFE Market do not align occasionally. Arbitrage chances are rare. Besides, they last for seconds only before the market adjusts itself. The challenge is not only to discover such chances, but to discover them ahead of other arbitragers. In the past, we have introduced EDDIE as a genetic programming tool for forecasting. This paper describes EDDIE-ARB, a specialization of EDDIE, for forecasting arbitrage opportunities. As a tool, EDDIE-ARB was designed to enable economists and computer scientists to work together to identify relevant independent variables. Trained on historical data, EDDIE-ARB was capable of discovering rules with high precision. Tested on out-of-sample data, EDDIE-ARB out-performed a naive ex ante rule, which reacted only when misalignments were detected. This establishes EDDIE-ARB as a promising tool for arbitrage chances discovery. It also demonstrates how EDDIE brings domain experts and computer scientists together.
KNOWLEDGE REUSE THROUGH CHANCE DISCOVERY FROM AN ENTERPRISE DESIGN-BUILD ENTERPRISE DATA STORE
Authors: FRUCHTER RENATE , OHSAWA YUKIO , MATSUMURA NAOHIRO
Published: October 2005

This paper explores the possibilities of chance discovery in building design and construction knowledge towards knowledge reuse from past project experiences captured in a enterprise data store. The proposed approach leverages two innovative technologies, (1) ThinkTank™, a web-based asynchronous collaboration technology developed at the Project Based Learning Lab at Stanford University that provides many of the advantages of face-to-face team meetings combined with the utility of e-mail and the organization of content in a database; and (2) Techniques of chance discovery, composed of the Double Helix process of chance discovery, and KeyGraph, a method of visualizing the content of human communications, developed in the laboratory of Chance Discovery at the University of Tsukuba. An overview of the ThinkTank™ and KeyGraph is presented. The validation testbed is described and a concrete scenario of chance discovery of reusable knowledge from a past project is presented to illustrate the value of linking an enterprise data store such as ThinkTank™ and KeyGraph. The paper concludes with a discussion of the importance of the double helix concept, i.e. first helix represented by the KeyGraph computer processing of the ThinkTank™ data, and the second helix represented by human interpretation and exploration of the KeyGraph representation of ThinkTank™ data. We emphasize that without the second helix, i.e. the human interpretation, contextualization and exploration of the results, the KeyGraph would offer only a visual representation of the data, but would not provide valuable input for decision making or knowledge reuse.
A Low Temperature Preparation of BaTiO3 Thin Film by Sol-Gel-Hydrothermal Treatment below 210°C
Authors: Naoyama Takuji , Sakioka Youji , Noda Minoru , Okuyama Masanori , Saito Keisuke
Published: October 2005

BaTiO3 thin films with a perovskite structure have been prepared by the hydrohermal treatment of TiO2 gel films at temperatures below 210°C. The TiO2 gel films were produced at 200°C by the sol-gel method and then were transformed into crystalline BaTiO3 thin films with the hydrothermal treatment in Ba(OH)2 alkaline aqueous solutions below 210°C. The hydrothermal crystallization of BaTiO3 thin films depends remarkably on the prebaking temperature of the TiO2 gel film, and the morphology depends on the Ba(OH)2 concentration, but the crystalline structure is not changed according to the results of XRD θ-2θ and reciprocal space mapping measurements. The microscopic structure is columnar for BaTiO3 thin films treated in Ba(OH)2 solutions greater than 0.3 M and is granular for those treated in solutions less than 0.2 M. The morphology of the BaTiO3 thin film treated in 0.2 M Ba(OH)2 solution is an island structure near the surface and granular near the bottom. The BaTiO3 thin film treated at 210°C for 3 h in 0.2 M Ba(OH)2 solution has a hysteresis loop showing 5 µC/cm2 at zero electric field.
Microstructure Control and Dielectric/Piezoelectric Properties of Alkoxy-Derived Ba(Ti,Zr)O3 Thin Films
Authors: Tanaka Kiyotaka , Suzuki Kazuyuki , Nishizawa Kaori , Miki Takeshi , Kato Kazumi
Published: October 2005

Lead-free ferroelectric Ba(Ti1-x
Zr
x
)O3 (BTZ, x=0.00–0.50) thin films were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates by the chemical solution deposition (CSD) process using complex alkoxide solutions. When the Zr content x was increased, the crystallinity of BTZ thin films was changed from the typical random orientation to the (111) preferred orientation. From the composition dependence of the dielectric constant ε
r and piezoelectric constant d
33, the pinching region at room temperature of BTZ thin films consisting of nano-crystals appeared around x=0.20. For the BTZ thin film (x=0.20) fabricated using an alkoxide solution with partial hydrolysis, the grain and crystallite size were increased, and the ε
r and d
33 were improved to 253 and 8.9 pm/V, respectively.
Piezo- and Ferroelectric Properties of Self-Assembled PbTiO3 Nanoisland Structures Fabricated by Metalorganic Chemical Vapor Deposition
Authors: Okaniwa Mamoru , Fujisawa Hironori , Shimizu Masaru , Niu Hirohiko , Honda Koichiro
Published: October 2005

Self-assembled PbTiO3 nanoisland structures were fabricated on Pt/SiO2/Si at 400°C by metalorganic chemical vapor deposition. The average width and height were 35 and 1.9 nm for PbTiO3 grown for 10 s, and 35 and 3.6 nm for that grown for 20 s, respectively. In-plane X-ray diffraction showed that PbTiO3 nanoisland structures had a tetragonal structure and only c-domains. Piezoresponse force microscopy revealed that the piezoresponse signal decreased with a decrease in the height of nanoisland structures. The minimum height and width of PbTiO3 nanoisland structures showing a piezoelectric hysteresis loop were 1.2 and 27 nm, respectively.
Stress Control and Ferroelectric Properties of Lead Zirconate Titanate (PZT) Thin Film on Si Substrate with Buffer Layers
Authors: Fujito Keisuke , Wakiya Naoki , Mizutani Nobuyasu , Shinozaki Kazuo
Published: October 2005

Lead zirconate titanate (PZT) thin films were grown on a Si substrate with an epitaxial relationship by introducing yttria-stabilized zirconia (YSZ), CeO2, and (La,Sr)CoO3 (LSCO) buffer layers. The buffer layers, which facilitated the growth of the epitaxial PZT thin film and controlled the residual stress, were deposited by pulsed laser deposition (PLD). The PZT thin films were fabricated on [A]: LSCO*/CeO2/YSZ/Si and [B]: LSCO*/PZT*/LSCO/CeO2/YSZ/Si by pulsed metalorganic chemical vapor deposition. The respective thicknesses of the LSCO* and PZT* layers were changed to control the residual stress in the PZT thin films. The relationship between residual stress and the ferroelectric properties of the PZT thin films was investigated. Residual tensile stresses in the PZT thin films were maximum in [A] as LSCO* thickness changed. Increasing the PZT* layer thickness at a fixed thickness of LSCO* of 188 nm changed the residual tensile stress in the PZT thin films from 2.92 GPa to 2.67 GPa. Consequently, remanent polarization (2Pr) was increased from 15 µC/cm2 to 27 µC/cm2, suggesting that residual stress may be controlled by introducing buffer layers and that ferroelectric properties may be improved.
Enhancement of Polarization Property of PZT Film by Ion-Substitution Using Rare-Earth Elements
Authors: Nakaki Hiroshi , Uchida Hiroshi , Nishida Ken , Osada Minoru , Funakubo Hiroshi , Katoda Takashi , Koda Seiichiro
Published: October 2005

Rare-earth-substituted lead zirconate titanate thin films were synthesized to improve the ferroelectric properties of lead zirconate titanate through the enhancement of its crystal anisotropy. Thin films of Pb1.00-(3x/2)RE
x
(Zr0.40Ti0.60)O3 [RE-PZT(A)] and Pb1.00RE
x
(Zr0.40Ti0.60)1-(3x/4)O3 [RE-PZT(B)] with RE=La or Dy were deposited on (111)Pt/Ti/SiO2/(100)Si substrates by chemical solution deposition (CSD). Rare-earth-substitution did not affect the crystal orientation of the PZT-based films where the PZT(111) plane was oriented along the surface-normal direction. Dy3+ substitution based on Dy-PZT(B) up to x=0.02 enhanced the crystal anisotropy (c/a) and remanent polarization (P
r) of PZT films simultaneously, while both c/a and P
r values of Dy-PZT(A) decreased as x increased continuously. On the other hand, La3+ substitution degraded the ferroelectric properties gradually in both the case of La-PZT(A) and (B). The Dy3+ ion could be substituted for a B-site in a PZT crystal preferentially, and that promoted the crystal anisotropy and the ferroelectric properties of PZT films.
All-Epitaxial Trilayered Ferroelectric (Bi,La)4Ti3O12/Pb(Zr0.4Ti0.6)O3/(Bi,La)4Ti3O12Thin Films on SrTiO3Substrates by Pulsed Laser Deposition
Authors: Bao Dinghua , Zhu Xinhua , Alexe Marin , Hesse Dietrich
Published: October 2005

Trilayered ferroelectric (Bi,La)4Ti3O12(BLT)/Pb(Zr,Ti)O3(PZT)/(Bi,La)4Ti3O12thin films were grown epitaxially on SrTiO3(STO) substrates by pulsed laser deposition. The epitaxial relationships between BLT, PZT and STO were identified to be BLT(001)∥PZT(001)∥STO(001) and BLT[110]∥PZT[100]∥STO[100] for the trilayered thin films on (001)-oriented STO substrates, whereas for the trilayered thin films on (011)-oriented STO substrates, the epitaxial relationships were BLT(118)∥PZT(011)∥STO(011) and BLT[110]∥PZT[100]∥STO[100]. The morphology of the BLT/PZT interfaces and of the surface of the trilayered thin films depended largely on the orientation of the film layers. A rather large remanent polarization as well as a high fatigue resistance of up to 1010switching pulse cycles was obtained for the trilayered thin films deposited on SrRuO3-coated STO substrates.
Electrical Characterization of Germanium Oxide/Germanium Interface Prepared by Electron-Cyclotron-Resonance Plasma Irradiation
Authors: Fukuda Yukio , Ueno Tomoo , Hirono Shigeru , Hashimoto Satoshi
Published: October 2005

We have found excellent electrical characteristics in germanium oxide grown by plasma oxidation for germanium metal-insulator-semiconductor gate dielectric applications. An oxygen plasma stream generated by electron cyclotron resonance was used to oxidize a germanium surface without substrate heating. A transmission electron microscope observation revealed that the obtained germanium oxide/germanium interface is atomically smooth. The energy distribution of interface trap density (D
it) in the upper half of the p-type germanium band gap was measured by the ac conductance method. It is shown that the D
it at the midgap is ∼6 ×1010 cm-2·eV-1 and increases exponentially as the energy increases to the conduction-band edge.
Preparation and Curie Temperatures of Nanosized (Pb,Sr)TiO3 Powders
Authors: Zhang Fan , Karaki Tomoaki , Adachi Masatoshi
Published: October 2005

Nanosized perovskite lead strontium titanate (Pb
x
Sr1-x
)TiO3 (PST) powders were successfully prepared by a simple coprecipitation method. A lead-strontium titanyl oxalate (PSTO) precursor was first synthesized at room temperature and the precursor was then calcined at various temperatures to produce the PST powders ranging from 10 to 200 nm in size. The effects of PST particle size on Curie temperature and dielectric constant have been investigated. High-temperature X-ray diffraction results showed that the Curie temperature of Pb0.7Sr0.3TiO3 powder with a size of 10 nm decreased from 290 to 120–130°C.
Effects of Ca Substitution for Sr on Ferroelectric Properties and Crystal Structure of (Sr1-xCax)Bi3Ti2NbO12
Authors: Ogawa Hirotaka , Yokoi Atsushi , Taketani Hidekazu
Published: October 2005

The effects of substituting Ca for Sr in (Sr1-x
Ca
x
)Bi3Ti2NbO12 compounds on the ferroelectric properties and the weight fraction of the orthorhombic phase were investigated in this study. Mixtures of orthorhombic and tetragonal phases of (Sr1-x
Ca
x
)Bi3Ti2NbO12 compounds were obtained in the composition ratio range of x=0–0.4. The weight fraction of the orthorhombic phase calculated by Rietveld analysis increased from 89.66 to 92.83 wt % as the composition ratio x increased from 0 to 0.25. The remanent polarization (P
r) of the samples in the composition ratio range of 0–0.25 was greatly improved by the substitution of Ca for Sr, and the maximum value of P
r was 9.31 µC/cm2 at x=0.25. These results suggest that the P
r values of (Sr1-x
Ca
x
)Bi3Ti2NbO12 compounds are related to the weight fraction of the orthorhombic phase, because the variation in remanent polarization showed the same tendency as the variation in the weight fraction of the orthorhombic phase. Moreover, the Curie temperature (T
c) increased as the tolerance factor (t) of the pseudo-perovskite block (SrBiTi2NbO10)2- decreased; it is suggested that the increase in T
c is connected to the structural distortion of the pseudo-perovskite block.
Ferroelectric Nanodomain Properties in Near-Stoichiometric and Congruent LiNbO3 Crystals Investigated by Scanning Force Microscopy
Authors: Liu Xiaoyan , Terabe Kazuya , Kitamura Kenji
Published: October 2005

The properties of ferroelectric nanodomains in LiNbO3 crystals were investigated using scanning force microscopy. In particular, we found differences in the domain shape, domain-wall sharpness, and lateral growth rate of domains in near-stoichiometric and congruent LiNbO3 crystals. In the near-stoichiometric LiNbO3 crystal, the domain dots are hexagonal and linear domains with smooth walls can be engineered parallel to one of the crystallographic Y-axes. The shape of the linear domains engineered at an angle to the crystallographic Y-axis changes when a small bias is applied during scanning, and various domain shapes are obtained after being stabilized by scanning. However, in the congruent LiNbO3 crystal, the domain dots are roughly circular and there is no change in the shape of the linear domains, which have rough domain walls. The lateral growth rate of domains in the congruent LiNbO3 crystal is smaller than that in the near-stoichiometric LiNbO3 crystal.
Growth and Characterization of a New Nonlinear Borate Crystal: LiRbB6O10
Authors: Kamiuto Kei , Fukuda Masayuki , Ikeda Ko , Komatsu Ryuichi
Published: October 2005

A newly developed nonlinear optical crystal, LiRbB6O10, has been successfully grown by the Czochralski (CZ) method. The major problem in growing this crystal is that it becomes pulverized during cooling after growth. Growth conditions that would allow us to avoid such pulverization have been investigated in association with the hydrous reaction between a grown crystal and the water in it or in the growth atmosphere. The optical properties of a grown crystal are also investigated and compared with those of Li2B4O7.
Giant Piezoelectricity on k31 Mode in Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals
Authors: Ogawa Toshio , Matsushita Mitsuyoshi , Iwasaki Yosuke
Published: October 2005

The giant k
31 and piezoelectric d
31 constant in Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMNT) single-crystal plates with dimensions of 13L×4.0W×0.34T/0.47T mm were investigated via the poling field dependence of the ferroelectric properties and by impedance response analysis on the k
31 mode. Giant k
31 over 86% was realized for (110) PMNT single-crystal plates under the conditions of a poling temperature of 40°C (pseudo-cubic phase), DC poling fields over 200 V/mm, and a poling time of 10 min. P–E hysteresis loops in (110) PMNT plates with giant k
31 became asymmetric when the bipolar triangle pulse field exceeded 800 V/mm, which corresponds to the coercive field to obtain giant k
31. The frequency response of impedance in (110) PMNT plates with giant k
31 consisted of a single vibration in the length direction. Furthermore, since there were two frequency constants, 680 Hz-m on k
31 (length direction) mode and 1425 Hz-m on k
32 (width direction) mode, a single domain structure in the (110) PMNT single-crystal plate was confirmed by an anisotropy of their frequency constants. A mechanism to realize giant k
31 can be explained by the relationship between the crystal plane and poling direction. The existence of a giant d
31 constant was proven by the strain measurement as well as by the impedance measurement.
Study of Multilayer Ceramic Photonic Crystals in THz Region
Authors: Matsumoto Naoki , Nakagawa Takuji , Ando Akira , Sakabe Yukio , Kirihara Soshu , Miyamoto Yoshinori
Published: October 2005

We have fabricated one-dimensional photonic crystals with a conventional ceramic layering process and investigated their terahertz wave transmission properties by terahertz time-domain spectroscopy (THz-TDS). In one-dimensional photonic crystals with a structural defect, a narrow transmission band (i.e., a defect mode) appears within the band gap. However, the dielectric losses of the ceramic materials significantly suppress the transmission intensity of the defect mode. The observed low transmission is mainly associated with the absorption loss of the defect layer material. Since the internal multiple reflections enhance the absorption loss, tuning the periodicity of the photonic crystal from a high reflectivity condition is effective for improving the transmission intensity of the defect mode. The measured highest peak transmission is -4.5 dB when periodicity is changed from a quarter-wavelength stack.
First-Principles Predictions of Giant Electric Polarization
Authors: Uratani Yoshitaka , Shishidou Tatsuya , Ishii Fumiyuki , Oguchi Tamio
Published: October 2005

Giant electric polarization of more than 150 µC/cm2 is predicted for PbVO3 and BiCoO3 on the basis of the first-principles Berry-phase method. The stable crystal structure is tetragonally distorted with a large c/a ratio and significant ionic displacements breaking centrosymmetry. In PbVO3, the key factor that stabilizes such a highly distorted structure and realizes an insulating electronic structure, leading to giant polarization, is the coexistence of ferro-orbital and antiferro-spin orderings in the V4+ d1 configuration. It is shown that the same electronic mechanism works also for BiCoO3 with Co3+ d6 configuration.
High-Energy SR Powder Diffraction Evidence of Multisite Disorder of Pb Atom in Cubic Phase of PbZr1-xTixO3
Authors: Kuroiwa Yoshihiro , Terado Yoshihiro , Kim Su Jae , Sawada Akikatsu , Yamamura Yasuhisa , Aoyagi Shinobu , Nishibori Eiji , Sakata Makoto , Takata Masaki
Published: October 2005

High-energy synchrotron-radiation (SR) powder diffraction experiments have been carried out to investigate the relationship between the crystal structure of the paraelectric phase in PbZr1-x
Ti
x
O3 (PZT) and phase transition. The Rietveld refinement adopting the split-atom method reveals that the Pb atom in PZT, except PbTiO3 (x=1), is settled at multisites in relevant directions from the corner site of an ideal cubic structure. Namely, the Pb atom is found to be disordered at 12 sites in the <110 > directions in PbZrO3 (x=0), and at 8 sites in the <111 > directions in the Zr-rich region (0<x<0.5). The disordered motion of the Pb atom markedly changes at x=0.5, and the <110 > disorder is preferable in the Ti-rich region (0.5<x<1). The disordered characteristics of the Pb atom and the structural boundary observed at x=0.5 in the paraelectric phase are significant for understanding of the mechanism of the order-disorder phase transition and appearance of a morphotropic phase boundary (MPB) in PZT.
Crystallization and Raman Spectra of Langasite-Type Phases in Glasses of La3Ga5GeO14–Ba3Ga2Ge4O14 System
Authors: Takahashi Yoshihiro , Kitamura Kenji , Inoue Satoru , Benino Yasuhiko , Fujiwara Takumi , Komatsu Takayuki
Published: October 2005

Crystallization of the langasite-type La3Ga5GeO14–Ba3Ga2Ge4O14 mixed crystals in the stoichiometric corresponding glasses was studied by differential thermal and X-ray diffraction analyses, and by Raman spectroscopy. Although the glasses used in this study were multicomponent systems (BaO–La2O3–Ga2O3–GeO2), the langasite-type phases were singly crystallized in the corresponding glasses. The Raman spectroscopic study revealed the structural similarity on the scale of short-range order between the langasite-type phase and the corresponding glasses. This also strongly suggested the coexistence of Ga and Ge with six-coordination in the gallogermanate glasses.
Effects of an Electrically Conducting Layer at the Zinc Oxide Surface
Authors: Schmidt Oliver , Kiesel Peter , Walle Chris G. Van de , Johnson Noble M. , Nause Jeff , Döhler Gottfried H.
Published: October 2005

Measurements of the electrical properties of high-resistivity zinc oxide (ZnO) are strongly influenced by the sample ambient. Temperature-dependent Hall-effect measurements were performed on Li- and Cu-doped bulk crystals in both air and vacuum. Repeating the measurements under a given test ambient produced stable results. Changing the ambient systematically changed the measured results. We explain this behavior in terms of a surface conducting channel that exists in vacuum but is destroyed upon exposure to air. We propose that the surface conducting layer is eliminated in air due to changes of the surface condition. This feature of the untreated ZnO surface may relate to reports of large scatter and poor reproducibility of electrical data onp-type ZnO samples.
Electronic Properties of Amorphous and Crystalline Ge2Sb2Te5 Films
Authors: Kato Takayuki , Tanaka Keiji
Published: October 2005

Optical and electrical properties of sputtered Ge2Sb2Te5 films in amorphous and crystalline states have been studied. The optical band-gaps of amorphous, cubic (NaCl-type), and hexagonal Ge2Sb2Te5 are 0.74, 0.5, and 0.5 eV, respectively. Electrically, the amorphous and cubic states behave as semiconductors with activation energies of 0.45 and 0.14 eV, while the hexagonal state is metallic. The resistivity decreases slightly at the melting point of ∼600°C. All the states show p-type thermoelectric power, in which the amorphous and the cubic state have the activation energies of 0.3 and 0.14 eV. Carrier parameters and electronic densities-of-states are estimated and considered.
Deposition of Cd1-xZnxS (0 ≤x ≤1) Alloys by Photochemical Deposition
Authors: Gunasekaran Muniappan , Ichimura Masaya
Published: October 2005

Cd1-x
Zn
x
S alloys were successfully deposited on indium–tin oxide (ITO)-coated glass substrates from an aqueous solution containing Cd2+, Zn2+ and S2O3
2- ions by photochemical deposition (PCD). The concentrations of Cd2+ and Zn2+ ions were varied to obtain the entire range of compositions from x=0 to 1. Raman scattering studies were carried out for the as-deposited and annealed films. The alloy composition x was determined from the longitudinal optical phonon frequency observed from Raman spectroscopy. The composition of the alloy was also calculated by X-ray diffraction analysis and compared with the composition calculated from Raman spectra.
Flat (1120) GaN Thin Film on Precisely Offset-Controlled (1102) Sapphire Substrate
Authors: Imura Masataka , Hoshino Akira , Nakano Kiyotaka , Tsuda Michinobu , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu
Published: October 2005

A high-quality thin (1120) GaN layer with an atomically flat surface has been successfully grown on a precisely offset-angle-controlled (1102) sapphire substrate by metal-organic vapor phase epitaxy. The insertion of an AlGaN layer between the underlying AlN layer and the GaN layer was found to improve the crystalline quality of the upper GaN layer.
Photoelectrochemical Properties of InGaN for H2 Generation from Aqueous Water
Authors: Fujii Katsushi , Kusakabe Kazuhide , Ohkawa Kazuhiro
Published: October 2005

The photoelectrochemical properties of In
x
Ga1-x
N (x=0.02 and 0.09) were compared with those of GaN. The band-edge potentials of In
x
Ga1-x
N were determined by the Mott–Schottky plot for the first time. The gas generation from a counterelectrode using the In0.02Ga0.91N working electrode was the highest of the three samples. Band-edge potentials and the light absorption of a working photoelectrode presumably affect the gas generation efficiency.
Extended Finite Difference Time Domain Analysis of Induced Phase Modulation and Four-Wave Mixing between Two-Color Femtosecond Laser Pulses in a Silica Fiber with Different Initial Delays
Authors: Nakamura Shinki , Takasawa Naoya , Koyamada Yahei , Sone Hiroyasu , Xu Lin , Morita Ryuji , Yamashita Mikio
Published: October 2005

Experimental results of nonlinear propagation with the induced-phase modulation (IPM) effect of two-color 120 fs laser pulses with three different initial delays in a silica fiber were analyzed with finite-difference time domain (FDTD) calculations, including self-phase modulation (SPM), IPM, and degenerate four-wave mixing (DFWM) in the fused-silica fiber. Initial delay dependence by the FDTD qualitatively agrees with the previous experimental results. An ultrabroad spectrum induced by IPM mostly agrees with the previous experimental results that had the optimum initial delay. A Fourier transform of this spectrum yields a 4 fs optical pulse, which agrees with the previous experimental results. The spectral phases of two different pulses with three different initial delays are connected continuously. The IPM spectral phase obtained by the extended FDTD shows that the DFWM occurs. To the best of our knowledge, this is the first observation of DFWM with IPM by the FDTD simulation.
Ultrasonic-Assisted Synthesis of Poly(3-hexylthiophene)/TiO2 Nanocomposite and Its Photovoltaic Characteristics
Authors: Feng Wei , Feng Yiyu , Wu Zigang
Published: October 2005

The nanocomposites of poly(3-hexylthiophene) (PAT6) encapsulating titanium oxide (TiO2) with different TiO2 weight fractions were synthesized by in situ ultrasonic-assisted polymerization, and investigated in terms of their optical properties, microstructures and photoconductivity. The interaction between PAT6 and TiO2 and the nature of chain growth were investigated and explained according to the results of Fourier transform infrared spectroscopy (FTIR). The increase in conjugation length of the polymer and the improvement of crystallinity with an increase in TiO2 weight fraction were investigated and explained according to the results of UV–vis absorption spectroscopy, photoluminescence spectroscopy and X-ray diffractometry (XRD). Particle dimensions were measured and the nature of association between the components was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The photoconductivity of the PAT6/TiO2 composite increased markedly and was discussed by taking the photoinduced charge transfer between PAT6 and TiO2 into consideration.
A Study on the Orientational Ordering Deformation in Ferroelectric Liquid Crystal during Bending of the Plastic Substrate
Authors: Lee Ji-Hoon , Son Ock-Soo , Jang Chi-Woong , Lim Tong-Kun
Published: October 2005

The change in the orientational order of ferroelectric liquid crystal molecules during the bending of the plastic cell substrate was studied with a polarizing optical microscope and birefringence data. The optic axis of neighboring striped domains gets widen while optic axis of one striped domain rotates more than that of the adjacent one does as a radius of curvature of the substrate gets shortened. Also the width of each stripe is increased and the liquid crystals in each domain orients more coherently. By the measurements of birefringence for the obliquely incident light, the liquid crystal molecules are found to rotate to the surface normal direction, too.
Comparison of DC and RF Sputtered Zinc Oxide Films with Post-Annealing and Dry Etching and Effect on Crystal Composition
Authors: Schuler Leo P. , Alkaisi Maan M. , Miller Paul , Reeves Roger J. , Markwitz Andreas
Published: October 2005

Zinc oxide (ZnO) thin films were deposited on Silicon substrates by DC and RF sputtering deposition. Thermal annealing was performed at up to 900°C in N2for 30 min. The samples were dry etched for 30 min using CHF3plasma. The effect of different sputtering techniques, annealing and reactive ion etching (RIE) were investigated using X-ray diffraction, Rutherford backscattering (RBS), photoluminescence (PL) spectra, atomic force microscopy (AFM), scanning electron microscopy (SEM), and piezoelectric measurements. The PL response improved considerably during annealing and was further enhanced after RIE process. RBS traced a C rich surface layer on all etched samples, which is possibly caused by the etching gas.
Vibrational Spectroscopic Study of the Interface of SiO2/Si(100) Fabricated by Highly Concentrated Ozone: Direct Evidence for Less Strained Si–O–Si Bond Angle
Authors: Nakamura Ken , Ichimura Shingo
Published: October 2005

The interface structure of SiO2/Si(100) synthesized with a highly concentrated ozone gas was analyzed by Fourier-transformed infrared absoption spectroscopy (FT-IR). The position of a transverse optical (TO) phonon peak of Si–O–Si asymmetric stretching vibration, which is a function of a Si–O–Si bond angle, remains constant at 1065 cm-1 within a ∼2 nm thickness of an ozone-oxide film. This result indicates that the thickness of structural transition layers at this interface where the Si–O–Si angle is distorted due to the stress at the interface is considerably limited, which is in contrast to a thermal oxide film on Si(100) showing the existence of structural transition layers.
Production of Radicals and Particulates by Interaction between High-Density Hydrogen Plasma and Graphite Plate
Authors: Sasaki Koichi , Maeda Toshiki , Takada Noriharu , Aramaki Mitsutoshi , Goto Motoshi , Muto Sadatsugu , Morita Shigeru
Published: October 2005

Laser-induced fluorescence was employed to detect CH, C2 and H radicals in high-density H2 plasma interacting with a graphite plate. The densities of the radicals were examined as functions of the gas pressure, the temperature of the graphite plate, and the radial distance from the plasma center. In addition, we observed the formation of particulates on the graphite plate irradiated by the high-density plasma column. By considering the experimental results, we conclude that the interaction between the high-density hydrogen plasma and the graphite plate is governed by a mechanism similar to reactive ion etching.
Rubbed Polyimide Layers Studied by Rotating Sample and Compensator Spectroscopic Ellipsometry
Authors: Kyoung Jaesun , Bang Kyungyoon , Oh Hyekeun , Lee Iksoo , Kim Hochul , Jeon Dong Ryul , An Ilsin
Published: October 2005

Rotating compensator spectroscopic ellipsometry was used to study the optical properties of a rubbed polyimide layer. Two operating modes in the transmission configuration were studied. One was a conventional mode of `polarizer–sample–rotating compensator–analyzer'. The other was a dual rotation mode of `polarizer–rotating sample–rotating compensator–analyzer'. We found that calibration is not possible in the conventional mode due to the extremely small retardance and non-dichroic nature of the sample. Meanwhile, in dual rotation mode which we developed, a retardance smaller than 0.5° could be measured without calibration. Using this technique, the variation in retardance with rubbing could be easily determined over a range of 320–800 nm. The optical axis could also be determined with high precision for this sample, and this optical axis was found to be parallel to the direction of rubbing.
Photoluminescence Characteristics of Mn- and Pr-doped ZnS Nanoparticles Optically Annealed with UV Illumination
Authors: Lee Jun Woo , Cho Kyoungah , Kim Hyunsuk , Kim Jin-Hyoung , Park Byoungjun , Noh Taeyong , Kim Sung Hyun , Kim Sangsig
Published: October 2005

Undoped, Mn-doped, Pr-doped, and Mn- and Pr-codoped ZnS nanoparticles were synthesized by a wet chemical method, and these nanoparticles were optically annealed in air or vacuum. In the photoluminescence (PL) spectra of the optically annealed nanoparticles, a sulfur–vacancy-related PL band at around 420 nm, a PL band associated with the 4T1→6A1 transition of Mn2+, and PL peaks associated with Pr-related complexes were investigated during optical annealing. The integrated PL intensities for the nanoparticles annealed in air increased more markedly with the optical annealing time than those for the nanoparticles annealed in vacuum. This increase may be explained by the photooxidation of the surface, the enhancement of the crystal quality, and the gradual diffusion of luminescent ions into the crystal lattice.
Fabrication of Nanocomposites by Filling Nanoholes in Highly Ordered Anodic Porous Alumina by Vacuum Deposition of Metal
Authors: Yasui Kenji , Nishio Kazuyuki , Masuda Hideki
Published: October 2005

Nanocomposite structures of a metal and an alumina matrix were prepared by depositing a metal into holes in anodic porous alumina using vacuum deposition. The process, which was composed of sequences of metal deposition into straight holes and then peeling of the deposit on the surface, induced an almost uniform filling of the holes that had aspect ratio of 4.
First-Principles Materials Design of CuAlO2 Based Dilute Magnetic Semiconducting Oxide
Authors: Kizaki Hidetoshi , Sato Kazunori , Yanase Akira , Katayama-Yoshida Hiroshi
Published: October 2005

The electronic structures and the magnetic properties of dilute magnetic semiconductors (DMSs) based on transparent semiconducting oxide CuAlO2 are calculated by using the Korringa–Kohn–Rostoker method combined with the coherent potential approximation within the local density approximation. We see from the results that we can expect to obtain the half-metallic and high-spin ferromagnetic state is expected to be stable in Mn-, Fe-, Co- and Ni-doped CuAlO2.
Crystal Structure and Electrical Properties of Epitaxial BiFeO3 Thin Films Grown by Metal Organic Chemical Vapor Deposition
Authors: Ueno Risako , Okaura Shingo , Funakubo Hiroshi , Saito Keisuke
Published: October 2005

BiFeO3 thin films with various thicknesses were grown on (100)
c
SrRuO3∥(100)SrTiO3 substrates at 620°C by metalorganic chemical vapor deposition (MOCVD) for the first time. X-ray diffraction analysis revealed cube-on-cube epitaxial growth of phase-pure BiFeO3 films with (001) orientation irrespective of the film thickness. Out-of-plane lattice parameter decreased with increasing the film thickness up to 100 nm, however this change with the film thickness became small above this thickness. The well saturated hysteresis loops with the remanent polarization and the coercive field values of 51 µC/cm2 and 166 kV/cm, respectively were obtained at 80 K up to 400 kV/cm for the 480-nm-thick film.