bluuebunny/crossref_metadata_2025 huggingface dataset:
Glucose is a key metabolic regulator of osteoclasts; glucose stimulated increases in ATP/ADP ratio and calmodulin kinase II activity
Authors: Larsen Kirsten I , Falany Marina , Wang Wei , Williams John P
Published: October 2005

Glucose-stimulated increases in osteoclast activity are mediated, at least in part, by transcriptional regulation of H+-ATPase expression through a mechanism involving p38 mitogen-activated protein kinase. We hypothesized that early events in the glucose-dependent signaling pathway would be similar to those identified in other glucose-sensitive cells, such as islet β-cells, including rapid changes in the cellular ATP/ADP ratio and mobilization of intracellular Ca2+. We demonstrate that glucose stimulates a prolonged 50% increase in the ATP/ADP ratio that was maximal 30 s after glucose concentrations were increased. Glucose stimulated a transient 30% increase in calcium/calmodulin-dependent kinase II (CaMK II) activity that was maximal 3 min after the glucose concentration was increased. CaMK II was activated maximally by 3 mmol D-glucose/L in 3-min assays. Activation of CaMK II in the presence of the nonmetabo lizable glucose analog 2-deoxyglucose was 2-fold greater than with D-glucose but was unchanged by glucosamine. Pretreatment of osteoclasts with the intracellular Ca2+chelator BAPTA-AM inhibited glucose transport by 75%. BAPTA-AM treatment also prevented glucose-dependent stimulation of CaMK II. The data indicate that osteoclasts utilize a glucose-sensing mechanism similar to that of β-cells and that glucose-stimulated signaling in osteoclasts involves changes in the ATP/ADP ratio and mobilization of intracellular Ca2+, resulting in activation of CaMK II.Key words: osteoclast, metabolism, glucose transport, calmodulin kinase II.
Cytochromeaa3in facultatively aerobic and hyperthermophilic archaeonPyrobaculum oguniense
Authors: Nunoura Takuro , Sako Yoshihiko , Wakagi Takayoshi , Uchida Aritsune
Published: October 2005

We partially purified and characterized the cytochrome aa3from the facultatively aerobic and hyperthermophilic archaeon Pyrobaculum oguniense. This cytochrome aa3showed oxygen consumption activity with N, N, N′, N′-tetramethyl-1,4-phenylenediamine and ascorbate as substrates, and also displayed bovine cytochrome c oxidase activity. These enzymatic activities of cytochrome aa3were inhibited by cyanide and azide. This cytochrome contained heme As, but not typical heme A. An analysis of trypsin-digested fragments indicated that 1 subunit of this cytochrome was identical to the gene product of subunit I of the SoxM-type heme – copper oxidase (poxC). This is the first report of a terminal oxidase in hyperthermophilic crenarchaeon belonging to the order Thermoproteales.Key words: aerobic respiratory chain, terminal oxidase, Archaea, hyperthermophile, Pyrobaculum.
Variation in antibiosis ability, against potato pathogens, of bacterial communities recovered from the endo- and exoroots of potato crops produced under conventional versus minimum tillage systems
Authors: Sturz A V , Peters R D , Carter M R , Sanderson J B , Matheson B G , Christie B R
Published: October 2005

The culturable component of bacterial communities found in the endoroot and associated exoroot (root zone soil) was examined in potatoes (Solanum tuberosum L.) grown under either conventional or minimum tillage systems. Bacterial species – abundance relationships were determined and in vitro antibiosis ability investigated to discover whether tillage practice or bacteria source (endo- or exoroot) influenced bacterial community structure and functional versatility. Antibiosis abilities against Phytophthora erythroseptica Pethyb. (causal agent of pink rot of potatoes), Streptomyces scabies (Thaxt.) Waksm. and Henrici) (causal agent of potato common scab), and Fusarium oxysporum Schlecht. Emend. Snyder and Hansen (causal agent of fusarium potato wilt) were selected as indicators of functional versatility. Bacterial community species richness and diversity indices were significantly greater (P = 0.001) in the exoroot than in the endoroot. While both endo- and exoroot communities possessed antibiosis ability against the phytopathogens tested, a significantly greater proportion (P = 0.0001) of the endoroot population demonstrated antibiosis ability than its exoroot counterpart against P. erythroseptica and F. oxysporum. Tillage regime had no significant influence on species-abundance relationships in the endo- or exoroot but did influence the relative antibiosis ability of bacteria in in vitro challenges against S. scabies, where bacteria sourced from minimum tillage systems were more likely to have antibiosis ability (P = 0.0151). We postulate that the difference in the frequency of isolates with antibiosis ability among endoroot versus exoroot populations points to the adaptation of endophytic bacterial communities that favour plant host defence against pathogens that attack the host systemically.Key words: antibiosis, bacterial endophytes, Fusarium oxysporum, Phytophthora erythroseptica, Streptomyces scabies, potatoes.
A simple procedure for elimination of fungal contamination for enumeration of iron-oxidizing bacteria from bioleaching matrix of sewage sludge
Authors: Gu X Y , Wong Jonathan W.C
Published: October 2005

Enumeration of iron-oxidizing bacteria from the bioleaching matrix of sewage sludge is always confronted by fungal contamination. The objective of the present study was to find a reliable and simple method to remove fungal growth and to shorten the incubation time for facilitating enumeration of the iron-oxidizers from complex sludge samples. The results demonstrated that filtering the sludge sample through sterile No. 5 Whatman filter paper before serial dilution was effective in eliminating the fungal growth on agarose media. Both the counts and the incubation time required for enumeration were highly dependent on the medium pH, with maximum counts at pH 2.5–2.75. Medium prepared at pH values outside of this range led to lower counts and a longer lag time for colony formation. However, the introduction of heterotrophic microorganisms into the solid medium did not show further improvement in enumeration efficiency and shortening of the incubation period. By incorporating the optimal conditions obtained, the incubation time could be reduced to 7 and 10 d for pure cultures and sludge samples, respectively.Key words: Acidithiobacillus ferrooxidans, iron-based bioleaching process, growth media, sewage sludge.
In vitro inhibition ofHelicobacter pyloribyEnterococcus faeciumGM-1
Authors: Kang J H , Lee M S
Published: October 2005

A strain of Enterococcus faecium that exhibits antibacterial activity against Helicobacter pylori was isolated from the feces of newborn babies. This strain was selected for its ability to inhibit the growth of H. pylori and to withstand harsh environmental conditions, such as acidic pH and high bile concentration. Biochemical tests and 16S rRNA sequencing specific for Enterococcus faecium GM-1 were used to identify the isolated bacterial strain. In vitro studies were used to investigate the inhibitory effects of E. faecium GM-1 on H. pylori. These results showed that the culture supernatant of E. faecium GM-1 significantly decreased the viability and urease activity of H. pylori. This inhibitory activity remained after adjustment of pH of culture supernatant to neutral. However, treatment with proteolytic enzymes reduced the anti-H. pylori activity of GM-1. Therefore, some substance(s) of E. faecium GM-1 other than pH and lactic acid might be associated with this inhibitory activity. Analysis by electron microscopy also demonstrated that the addition of GM-1 destroyed the cell structure of H. pylori. Additional studies suggested that the binding of H. pylori to human colonial cells decreased in the presence of GM-1.Key words: Enterococcus faecium, Helicobacter pylori, inhibition, human fecal strain, proteinaceous substance(s).
Effects of the twin-arginine translocase on the structure and antimicrobial susceptibility ofEscherichia colibiofilms
Authors: Harrison Joe J , Ceri Howard , Badry Erin A , Roper Nicole J , Tomlin Kerry L , Turner Raymond J
Published: October 2005

In this descriptive study, we used Escherichia coli twin-arginine translocase (tat) mutants to distinguish antibiotic tolerance from the formation of mature biofilm structure. Biofilm formation by wild-type and Δtat strains of E. coli was evaluated using viable cell counts, scanning electron microscopy, and confocal laser-scanning microscopy. Escherichia coli Δtat mutants had an impaired ability to form biofilms when grown in rich or minimal media. These mutants produced disorganized layers and cell aggregates with significantly decreased cell density relative to the wild-type strain. In contrast, wild-type E. coli grown under similar test conditions formed highly structured, surface-adherent communities. We thus determined if this decreased biofilm formation by E. coli Δtat mutants may result in lowered tolerance to antimicrobials. When grown in rich media, planktonic Δtat mutants were hypersensitive to some metals, detergents, and antibiotics. However, the corresponding biofilms were about as resilient as the wild-type strain. In contrast, both planktonic cells and biofilms of the ΔtatABC strain grown in minimal media were hypersensitive to many antimicrobials. Remarkably, these biofilms remained up to 365 times more tolerant to β-lactams than corresponding planktonic cells. Our data suggest that the twin-arginine translocase may play a contributing role in the antimicrobial tolerance, structural organization, and formation of mature E. coli biofilms under nutrient-limited conditions. However, the high tolerance of the ΔtatABC strain to bactericidal concentrations of antimicrobials indicates that mature biofilm structure may not be required for surface-adherent E. coli to survive exposure to these lethal factors.Key words: biofilm structure, twin-arginine translocase (tat), Escherichia coli, antimicrobial susceptibility/tolerance.
Effects of electron transport inhibitors and uncouplers on the oxidation of ferrous iron and compounds interacting with ferric iron inAcidithiobacillus ferrooxidans
Authors: Chen Yongqiang , Suzuki Isamu
Published: October 2005

Oxidation of Fe2+, ascorbic acid, propyl gallate, tiron, L-cysteine, and glutathione by Acidithiobacillus ferrooxidans was studied with respect to the effect of electron transport inhibitors and uncouplers on the rate of oxidation. All the oxidations were sensitive to inhibitors of cytochrome c oxidase, KCN, and NaN3. They were also partially inhibited by inhibitors of complex I and complex III of the electron transport system. Uncouplers at low concentrations stimulated the oxidation and inhibited it at higher concentrations. The oxidation rates of Fe2+and L-cysteine inhibited by complex I and complex III inhibitors (amytal, rotenone, antimycin A, myxothiazol, and HQNO) were stimulated more extensively by uncouplers than the control rates. Atabrine, a flavin antagonist, was an exception, and atabrine-inhibited oxidation activities of all these compounds were further inhibited by uncouplers. A model for the electron transport pathways of A. ferrooxidans is proposed to account for these results. In the model these organic substrates reduce ferric iron on the surface of cells to ferrous iron, which is oxidized back to ferric iron through the Fe2+oxidation pathway, leading to cytochrome oxidase to O2. Some of electrons enter the uphill (energy-requiring) electron transport pathway to reduce NAD+. Uncouplers at low concentrations stimulate Fe2+oxidation by stimulating cytochrome oxidase by uncoupling. Higher concentrations lower Δp to the level insufficient to overcome the potentially uphill reaction at rusticyanin-cytochrome c4. Inhibition of uphill reactions at complex I and complex III leads to Δp accumulation and inhibition of cytochrome oxidase. Uncouplers remove the inhibition of Δp and stimulate the oxidation. Atabrine inhibition is not released by uncouplers, which implies a possibility of atabrine inhibition at a site other than complex I, but a site somehow involved in the Fe2+oxidation pathway.Key words: Acidithiobacillus ferrooxidans, electron transport, uncouplers, uphill electron transport pathway.
INCORPORATING FAULT-TOLERANT FEATURES IN VLIW PROCESSORS
Authors: CHEN YUNG-YUAN
Published: October 2005

In recent years, very long instruction word (VLIW) processor has attracted much attention in that it offers a high instruction level parallelism and reduces the hardware design complexity. In this paper, we present two fault-tolerant schemes for VLIW processors. The first one is termed as test-instruction scheme which is based on the concept of instruction duplication to detect the errors. The process of test-instruction scheme consists of the error detection, error rollback recovery and reconfiguration. The second approach is called self-checking scheme which adopts the concept of self-checking logic to detect the errors. A real-time error recovery procedure is developed to conquer the errors. We implement the proposed designs of fault-tolerant VLIW processor in VHDL and employ the fault injection and fault simulation to validate our schemes. The main contribution of this research is to present the complete frameworks from error detection to error recovery for fault-tolerant design of VLIW processors. Experience learned from this investigation is that the issues of error detection and error recovery entail considering together. Without taking both issues into account simultaneously, the outcomes may lead to the improper conclusions.
LEARNING RATES FOR DENSITY LEVEL DETECTION
Authors: SCOVEL CLINT , HUSH DON , STEINWART INGO
Published: October 2005

In this paper, we address learning rates for the density level detection (DLD) problem. We begin by proving a "No Free Lunch Theorem" showing that rates cannot be obtained in general. Then, we apply a recently established classification framework to obtain rates for DLD support vector machines under mild assumptions on the density.
STABILITY RESULTS IN LEARNING THEORY
Authors: RAKHLIN ALEXANDER , MUKHERJEE SAYAN , POGGIO TOMASO
Published: October 2005

The problem of proving generalization bounds for the performance of learning algorithms can be formulated as a problem of bounding the bias and variance of estimators of the expected error. We show how various stability assumptions can be employed for this purpose. We provide a necessary and sufficient stability condition for bounding the bias and variance for the Empirical Risk Minimization algorithm, and various sufficient conditions for bounding bias and variance of estimators for general algorithms. We discuss settings in which it is possible to obtain exponential bounds, and we prove an extension of the bounded-difference inequality for "almost always" stable algorithms.
Orientation Dependence of Epitaxial and One-Axis-Oriented (Ba0.5Sr0.5)TiO3 Films Prepared by RF Magnetron Sputtering
Authors: Ito Sinichi , Takahashi Kenji , Okamoto Shoji , Koutsaroff Ivoyl P. , Cervin-Lawry Andrew , Funakubo Hiroshi
Published: October 2005

The dependences of electrical properties on (111) and (100) orientations were investigated for (Ba0.5Sr0.5)TiO3 films with in-plane random (one-axis-oriented films) and aligned orientations (epitaxial films) prepared by RF magnetron sputtering. Epitaxial films with (100) and (111) orientations were grown on (100)cSrRuO3∥(100)SrTiO3 and (111)cSrRuO3∥(111)SrTiO3 substrates, while one-axis-oriented films were grown on (100)
c
SrRuO3/(100)cLaNiO3/(111)Pt/TiO2/SiO2/Al2O3 and (111)
c
SrRuO3/(111)Pt/TiO2/SiO2/Al2O3 substrates, respectively. Films with the (111) orientation had larger relative dielectric constants, ε
r, measured at an oscillation of 20 mV and 100 kHz under an applied dc bias electric field of 0 kV/cm and a larger tunability against the dc bias electric field than (100)-oriented films for both epitaxial and one-axis orientations. These data show the dependences of ε
r and tunability on orientation were existed, irrespective of the in-plane orientation and the thermal strain caused in the film by the substrates.
Evaluation of Imprint Property of (111)-Highly Oriented Lead Zirconate Titanate (PZT)-Base Ferroelectric Material
Authors: Hamada Yasuaki , Kijima Takeshi , Miyazawa Hiromu , Shimoda Tatsuya
Published: October 2005

We have investigated the mechanism of static imprint failure in (111)-highly oriented lead zirconate titanate (PZT)-base ferroelectric material by examining the change in the leakage current density. We prepared Pt/Pb(Zr,Ti,Nb)O3 (PZTN)/Pt capacitors. Our capacitors passed the static imprint test at 150°C for 1280 h with a write/read voltage of 3 V or higher. After the static imprint test we measured the leakage current densities of capacitors. All capacitors showed an increase in leakage current density on one side and a decrease on the other side. The side on which leakage current increased depended on the voltage polarity of the write pulse. The changes in leakage current density of capacitors with various write/read voltages indicate that static imprint failure has at least two mechanisms, the contributions of which change according to the write/read voltage. When the write/read voltage is lower, capacitors show diode-like behavior after static imprinting.
Electronic Structure of (Pb,La)(Zr,Ti)O3 Thin Film Probed by Soft-X-Ray Spectroscopy
Authors: Higuchi Tohru , Tsukamoto Takeyo , Hattori Takeshi , Honda Yoshihisa , Yokoyama Shintaro , Funakubo Hiroshi
Published: October 2005

The electronic structure of (Pb,La)(Zr,Ti)O3 (PLZT) thin film was studied by X-ray absorption spectroscopy and soft-X-ray emission spectroscopy (SXES). The Ti 3d and O 2p partial densities of states in the valence band region were observed in O 1s and Ti 2p SXES spectra. The energy position of the Ti 3d state overlapped with that of the O 2p state, indicating the occurrence of the hybridization effect between the Ti 3d and O 2p states. The hybridization effect of PLZT thin film is lower than that of Pb(Zr,Ti)O3 thin film. This finding indicates that the hybridization effect is closely related to the change in the bond length between Ti and O ions.
Annealing Effect on 0.5Pb(Ni1/3Nb2/3)O3-0.5Pb(Zr0.3Ti0.7)O3 Thick Film Deposited By Aerosol Deposition Method
Authors: Kawakami Yoshihiro , Aisawa Shuji , Akedo Jun
Published: October 2005

The aerosol deposition method (ADM) is the unique thick film technology based on consolidification by impacting powder particles on a substrate. We prepared a powder of a relaxor ferroelectric material with the composition 0.5Pb(Ni1/3Nb2/3)O3-0.5Pb(Zr0.3Ti0.7)O3 (PNN-PZT) using a solid state reaction process. A PNN-PZT film 10 µm thick was deposited on a YSZ (3 mol % Y2O3-stabilized ZrO2) substrate at room temperature by ADM. The prepared films were annealed from 600 to 900°C to investigate the annealing effect. The PNN-PZT film showed a pure perovskite phase without pyrochlore. As a result of transmission electron microscope (TEM) observation, the mean grain sizes of films annealed at 600 and 850°C were measured to be 83 and 254 nm, respectively. After annealing at 850°C, the values of the piezoelectric constant d
31 and the dielectric constant at 1 kHz of the PNN-PZT film were measured to be -164 pm/V and 2530, respectively.
Fabrication and Electrical Properties of (Bi,La)4Ti3O12 Thin Films Deposited with Electric-Field-Assisted Annealing
Authors: Nakayama Hiroshi , Sugiyama Osamu , Mano Tsuyoshi , Shibuya Yoshio , Hoshi Yusuke , Suzuki Hisao
Published: October 2005

Bi3.35La0.75Ti3O12 (BLT) thin films were deposited with electric-field-assisted annealing (EFA-A) by chemical solution deposition (CSD) to increase the degree of the preferred orientation. The X-ray diffraction intensities of (200)/(020) planes in the BLT films were increased by EFA-A, compared with those in the BLT film annealed without EFA-A. The remanent polarization (P
r) for the film deposited with EFA-A exhibited a higher value than that for the film deposited without EFA-A. The P
r value for the BLT film deposited without EFA-A was 21 µC/cm2. On the other hand, the P
r value for the BLT film deposited with EFA-A was as high as 28 µC/cm2. The enhancement of the polarization in the film deposited with EFA-A was ascribed to the increase in the number of grains in the film oriented in the direction of the polarized axis. In addition, the pyroelectric and piezoelectric properties of the resulting films were measured to investigate the effect of the EFA-A. The pyroelectric coefficient and the effective d
33 value of the films were also improved by EFA-A. The tendencies of the pyroelectric and piezoelectric properties of the BLT films were in good agreement with the P–E hysteresis loops of the films.
Ultrahigh-Density Ferroelectric Data Storage with Low Bit Error Rate
Authors: Hiranaga Yoshiomi , Cho Yasuo
Published: October 2005

Actual information data were recorded on a LiTaO3 single-crystal medium using a data storage system based on scanning nonlinear dielectric microscopy. For increasing recording density and reducing bit error rate, conductive-diamond-coated probes with a sharp tip and thin recording media were prepared. The domain-switching characteristics of virgin and prepolarized recording media were compared. The conditions of pulse voltage for writing were optimized. As a result, actual information data containing 128 ×128 bits were recorded at an areal density of 258 Gbit/inch2 without bit errors; thus, the bit error rate was calculated to be less than 1 ×10-4.
Pulsed-Laser Deposition of Ferroelectric NaNbO3 Thin Films
Authors: Saito Takehisa , Adachi Harumi , Wada Takahiro , Adachi Hideaki
Published: October 2005

High-quality NaNbO3 (NN) thin films were epitaxially grown on a (100)SrTiO3 substrate by pulsed-laser deposition. NN films with a flat surface morphology were obtained, when the films were grown slowly at high substrate temperatures, high oxygen partial pressures, and low laser energy densities. In order to characterize their dielectric properties, the NN films were epitaxially grown on (100)SrRuO3∥(100)SrTiO3 substrates. The relative dielectric constant, ε
r, and dielectric loss, tan
δ of the film were 252 and 0.03 at 1 kHz, respectively. When the temperature dependence of ε
r was measured, ε
r was found to suddenly increase at 377°C, which corresponds to the transition temperature of NN between the antiferroelectric and paraelectric phases. The P–E hysteresis loop of the NN films exhibited characteristic ferroelectric behavior.
Preparation of KNbO3 Thin Film by Self-Assembly of Perovskite Nanosheet
Authors: Toda Kenji , Sugawara Akira , Uematsu Kazuyoshi , Sato Mineo
Published: October 2005

Potassium niobate thin films with a perovskite structure were prepared by a new nanosheet self-assembly technique on a SiO2 glass substrate. A homogeneous nanosheet precursor solution was obtained by dissolving layered perovskite K2NbO3F in water at room temperature without any modifier. It was confirmed by X-ray diffraction that the films have a pseudocubic perovskite structure and show continuous transformation from layered perovskite K2NbO3F to perovskite KNbO3. The ultraviolet-visible absorption spectra of the films showed an increase in absorbance with the thickness of thin films, suggesting the growth of a self-assembled multilayer consisting of perovskite nanosheets and K+ ions.
Low-Temperature Growth and Characterization of Epitaxial YMnO3/Y2O3/Si MFIS Capacitors with Thinner Insulator Layer
Authors: Haratake Kohei , Shigemitsu Norimichi , Nishijima Masanori , Yoshimura Takeshi , Fujimura Nirufumi
Published: October 2005

YMnO3/Y2O3/Si capacitors were fabricated using an improved pulsed laser deposition (PLD) system with a dense YMnO3 target and a semiconductor laser heating system to solve the compositional distribution problem along the thickness of the YMnO3 films. As a result, the deposition temperature of the YMnO3 epitaxial films on Y2O3/Si could be lowered from 800 to 740°C. The epitaxial YMnO3/Y2O3/Si capacitors showed a ferroelectric capacitance–voltage (C–V) hysteresis loop with a memory window of 2.1 V, although the memory window did not saturate. To improve the electrical properties of the YMnO3/Y2O3/Si capacitors, the relationship between the thicknesses of the YMnO3 and Y2O3 layers and the applied voltage to each layer was calculated. The result indicates that a thickness less than 10 nm is required for the Y2O3 layer to bias the YMnO3 and Y2O3 layers equally. In this report, we discuss the fabrication of epitaxial YMnO3/Y2O3/Si capacitors with a 5-nm-thick Y2O3 layer using an improved PLD system. As a result of the optimization of the deposition conditions, epitaxial YMnO3(200 nm)/Y2O3(5 nm)/Si capacitors with a ferroelectric C–V hysteresis loop was obtained.
Oxygen Stability and Leakage Current Mechanism in Ferroelectric La-Substituted Bi4Ti3O12 Single Crystals
Authors: Noguchi Yuji , Soga Masayuki , Takahashi Masatake , Miyayama Masaru
Published: October 2005

We have investigated the effects of La substitution on the oxygen stability, defects, leakage current and polarization properties in ferroelectric bismuth titanate (Bi4Ti3O12) by measuring the properties of single crystals and by ab initio electronic structure calculations. It is shown that electron holes arising from the incorporation of oxygen at oxygen vacancies act as detrimental carriers for leakage current at room temperature for the crystals of BiT and La-substituted BiT. La substitution is effective for reducing oxygen vacancies and thus electron holes, which is attributed to an excellent insulating property observed for La-substituted crystals. High-pressure oxygen annealing is demonstrated to improve the remanent polarization of La-substituted crystals.
Vibration-Stress Dependence of Electromechanical Characteristics for Electrostrictive Pb(Mg1/3Nb2/3)O3–Based Ceramics
Authors: Hayano Shuji , Takahashi Sadayuki , Umeda Mikio , Wada Takahiro
Published: October 2005

The mechanical quality factor Q
m of a normal ferroelectric, piezoelectric ceramic vibrator decreases and heat is given off, when the vibrator is continuously driven at a high level of vibration-stress under a resonant mode. It has been thought that irreversible motions of ferroelectric non-180° domain walls cause this behavior. The effect of ferroelectric domain structure on the vibration-stress dependence of electromechanical characteristics was studied using relaxor ferroelectric electrostrictive (1-x)PbTiO3-xPb(Mg1/3Nb2/3)O3 (x=1.00, 0.95, 0.90) ceramics. The Q
m for the paraelectric crystal phase composition at room temperature is about five times higher than that for hard lead zirconate titanate (PZT) and the decrease of Q
m with vibration-stress is suppressed at high stress levels. The piezoelectric d
31 constant is almost the same as that of hard PZT. Electrostrictive ceramics are therefore superior electromechanical vibrator materials for high power applications.
Material Design of High-Dielectric-Constant and Large-Electromechanical-Coupling-Factor Relaxor-Based Piezoelectric Ceramics
Authors: Hosono Yohachi
Published: October 2005

Material design to achieve a f high dielectric constant of ε
33
T/ε
0>5,000 and a large planar-mode electromechanical coupling factor (EMCF) of k
p>65% near the morphotropic phase boundary (MPB) in the multicomponent system of Pb(Sc1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-Pb(Ni1/3Nb2/3)O3-(Pb,Ba,Sr)(Zr,Ti)O3 (PSN-PMN-PNN-PBSZT) ceramics was investigated. To obtain the MPB composition of the multicomponent system, a smart material design was applied to predict Curie temperature (T
c) and exact TiO2 content in the system. In addition, to realize a high dielectric constant and a large EMCF, a low-mass (LM) B-site ion model and a B-site disordering model in lead perovskite were applied. To enhance disordering of the B-site ions, we focused on the complex perovskite system ceramics PSN-PMN-PNN-PBSZT, which consist of three A-site ions, Pb, Ba and Sr, and six LM B-site ions, those of Sc, Mg, Ni, Nb, Ti and Zr. Dielectric constants of ε
33
T/ε
0=5,500, a planar-mode EMCF of k
p=72%, a piezoelectric constant of d
33=850 pC/N and T
c=153°C were confirmed in the PSN-PMN-PNN-PBSZT ceramics near the MPB by utilizing the material design procedure.
Piezoelectric Properties of Vanadium-Substituted Strontium Bismuth Niobate
Authors: Aoyagi Rintaro , Inai Shinya , Hiruma Yuji , Takenaka Tadashi
Published: October 2005

Vanadium-substituted strontium bismuth niobate, SrBi2Nb1.95V0.05O9 (SBNV), ceramics were synthesized by a low-temperature process, and the detailed piezoelectric properties of the SBNV ceramics were characterized. Dense SBNV ceramics were obtained at a sintering temperature of 950°C, which is 200°C lower than that for nonsubstituted (SBN) ceramics. With the substitution of vanadium cations for niobium the ferroelectric D–E hysteresis loops were observed at room temperature and the remanent polarization, P
r, and coercive field, E
c, obtained were 5.4 µC/cm2 and 105 kV/cm, respectively. The independent electromechanical coupling factors obtained, which were characterized by the resonance-antiresonance method, were as follows: k
p=0.074, k
31=0.045, k
33=0.175, k
15=0.106, and k
t=0.140. The mechanical quality factor, Q
m, of the SBNV ceramics in the (33)-mode was 5500, which was about three times that of SBN. The temperature dependences of the resonance frequency (TCF) in the length extensional vibration mode of the SBNV and SBN ceramics were 42.1 ppm/°C and 34.6 ppm/°C, respectively.
Dielectric, Elastic and Piezoelectric Constants of Lanthanum Calcium Oxoborate Single Crystals with Monoclinic Structure of Point Group m
Authors: Shimizu Hiroyuki , Nishida Takashi , Nishida Masahiro , Takeda Hiroaki , Shiosaki Tadashi
Published: October 2005

In this study, we propose using the d33 mode of a d33/d31 meter, new cuts and vibration modes to evaluate electroacoustical constants (dielectric, elastic and piezoelectric constants) of a piezoelectric crystal belonging to point group m. All material constants at room temperature of lanthanum calcium oxoborate LaCa4O(BO3)3 single crystals were thereby determined. The piezoelectric constants d
11 and d
33 measured by the d33 meter were 2.1 and 1.5 pC/N, respectively. The others were determined by the resonance-antiresonance method using various cuts in which the length-extensional mode and/or face-shear mode can be generated. The elastic compliances s
44

E
, s
55

E
and s
66

E
were 35×10-12, 18×10-12 and 18×10-12 m2/N, respectively. Moreover, in order to investigate the dependence of the Rayleigh surface acoustic wave (RSAW) velocity and coupling coefficient k
2 on propagation direction, theoretical analysis by computer simulations was carried out for the Z-cut using the elastic compliances obtained in this study. The dependence of RSAW velocity on propagation direction calculated using the elastic compliances obtained did not agree with measurement results, but the calculated results were significantly improved and closer to measurement results.
High-Speed Optical Microscanner Driven with Resonation of Lam Waves Using Pb(Zr,Ti)O3 Thick Films Formed by Aerosol Deposition
Authors: Akedo Jun , Lebedev Maxim , Sato Harumichi , Park Jaehyuk
Published: October 2005

A high-performance optical microscanner with a resonance frequency over 20 kHz and a scan angle (peak-to-peak value) over 30° in atmospheric ambient, was successfully fabricated by deposit piezoelectric materials at a high rate by the AD method onto a metal scanner structure, which was fabricated by mechanical machining. The scanner is applicable to SVGA high-resolution display of 800×600 or more. This method is a powerful tool for realizing ceramic integration with metal components.
Absolute Measurement of Surface Potential and Discharge Power Distributions for Piezoelectric Transformer-Based Plasma Reactor
Authors: Teranishi Kenji , Itoh Haruo
Published: October 2005

A new method for absolute measurement of surface potential distributions on a Rosen-type piezoelectric transformer (PT) was investigated using a sensing electrode proposed in this study. The sensing electrode consists of a dielectric layer having striped back electrodes arrayed in the longitudinal direction of the PT, which is basically similar to the electrode for generating a dielectric barrier discharge (DBD). An equivalent circuit was defined for each striped electrode and a constant in the circuit necessary for the estimations of the absolute surface potential distributions was determined experimentally. The absolute measurements of the surface potential distributions of the PT were performed at (1/2)λ mode vibration both with and without a potential divider (PD) connected to the secondary terminal. Surface potential distribution without the PD connected, i.e., the unloaded condition of the PT, is in good agreement with the theoretical curve of the surface potential distribution. Moreover, the surface potential distribution while the DBD appears and the discharge power distribution of the DBD generated by the PT was also determined at absolute values using the same electrode configurations.
Cation Substitution for BaTiO3 Phase in Low-Fired Glass-Ceramics for Tunable Microwave Applications
Authors: Takahashi Junichi , Kageyama Keisuke , Kiyono Hajime , Nakano Hiroshi , Itoh Hidenobu
Published: October 2005

Cation substitution for the Ba2+ and Ti4+ sites in the BaTiO3 structure was attempted in low-fired glass-ceramics derived from glass powders that have perovskite phase compositions corresponding to (BaTiO3:REAlO3) = 9:1 and 8:2 (RE=La, Nd and Sm) to control the Curie temperature (T
c) of the ferroelectric glass-ceramics. The La3+-substituted (9:1) sample heated at 950°C for 24 h showed a broadened ε
r–temperature relationship with substantial lowering in T
c to ∼-55°C. The Ba:La ratio in the perovskite particles was estimated to be in the range of 4:1–6.7:1, whereas very little Al3+ was incorporated into the same particles. It was found that the T
c of the glass-ceramics fabricated in our serial study could be adjusted by A-site cation substitution in BaTiO3. Tailored glass-ceramic samples with room temperature ε
r of 200–300 and T
c of around 0°C had good microwave tunability of 30–40% under dc bias voltage of 10–50 kV/cm. The high tuning sensitivity of the low-fired glass-ceramics was confirmed by comparative examination of the dielectric properties of well-crystallized ceramics and thin films.
Microwave Dielectric Properties of Textured BaLa4Ti4O15 Ceramics with Layered Perovskite Structure
Authors: Wada Kensuke , Fukami Yuko , Kakimoto Ken-ichi , Ohsato Hitoshi
Published: October 2005

Textured ceramics of BaLa4Ti4O15 (BaLT) with layered perovskite structure have been investigated by characterizing their dielectric properties at MHz and GHz frequencies. The highly grain-oriented ceramics were obtained by a templated grain growth technique. Hexagonal {001}-platelet BaLT particles prepared in molten salt were used as the template. The sintered ceramics containing template powders of 10 wt % exhibited a degree of <001>-orientation of 80% for the casting plane, whereas the plane perpendicular to the casting direction showed a degree of <h
k0>-orientation of 76%. The effect of grain orientation on the dielectric properties was observed as an anisotropy between the directions of parallel and perpendicular to the c-axis. As a result of the anisotropy, enhanced microwave dielectric properties (ε
r=53, Q·f=41,400 GHz and τf=-1 ppm/°C) compared with those of a randomly oriented ceramics were obtained in the TE011 mode for a cylindrical specimen with a {001} grain-orientation in the circular plane.
Dependence of Microwave Properties of BaxSr1-xTiO3 Thin Films on Substrate
Authors: Bhakdisongkhram Gun , Yamashita Youji , Nishida Takashi , Shiosaki Tadashi
Published: October 2005

Ba
x
Sr1-x
TiO3 (x=0.5) (BST) films were deposited on MgO, c-cut sapphire, r-cut sapphire and Si substrates by rf sputtering. A coplanar waveguide line was fabricated as a transmission line for microwave signals. Both the phase shift and loss tangent of the samples were measured using the on-wafer through-reflect-line (TRL) calibration comparison method. An external bias of 200 V was applied to the coplanar waveguide line fabricated on the BST layer. The phase of the line changes according to the dependence of BST permittivity on bias. The phase of the line was found to vary according to the crystalline quality of the films. The films were epitaxially grown on the MgO and c-cut sapphire substrates. The phase shifts of the samples were 58.4°, 4.4°, 1.5° and 0.7° for samples with films grown on Si, MgO, c-cut sapphire and r-cut sapphire, respectively. The dielectric loss tangents were 0.008, 0.016 and 0.026 for the films grown on MgO, r-cut sapphire and c-cut sapphire, respectively.
Measurement of Pockels Effect in Piezoelectric Chiral Polymer Film
Authors: Tsukiji Mitsuo , Kowa Hiroyuki , Muraki Kanae , Umeda Norihiro , Tajitsu Yoshiro
Published: October 2005

The possibility has been indicated that a piezoelectric polymer with helical chirality (chiral polymer) such as poly-L-lactic acid (PLLA) shows a large linear electrooptical constant (Pockels effect). However, the linear electrooptical constant of a PLLA film may be very small because such a film fabricated by the conventional method has a complex high-order structure with intermingled crystalline and amorphous regions. In order to measure the small linear electrooptical constant of a PLLA film, we developed a new measurement system, which is based on the heterodyne interferometry principle. In this system, the accuracy of retardation is 0.08 nm and the measurement time is 0.1 s. In our attempt to realize a PLLA film with a large linear electrooptical constant, we fabricated a PLLA film, which was heated to 120°C under 320 MPa. Finally, using our new measurement system, we obtained a linear electrooptical constant of 0.070 pm/V in the PLLA film, which is very small compared with those of other famous Pockels materials. However, the linear electrooptical constant of the PLLA film is clarified in this study for the first time.
ab initio Study of Strain-Induced Ferroelectricity in SrTiO3
Authors: Hashimoto Takatoshi , Nishimatsu Takeshi , Mizuseki Hiroshi , Kawazoe Yoshiyuki , Sasaki Atsushi , Ikeda Yoshiaki
Published: October 2005

Valley lines on total-energy surfaces for the zone-center distortions of free-standing and in-plane strained SrTiO3 are investigated with a newly developed first-principles structure optimization technique [Jpn. J. Appl. Phys. 43 (2004) 6785]. The results of numerical calculations confirmed that ferroelectricity is induced and the Curie temperature is increased by applying biaxial compressive or tensile strains. Along the distortion, strong nonlinear coupling between the soft- and hard-modes is demonstrated.
Microstructures Associated with Dielectric and Magnetic Properties in (1-x)BiFeO3-xBaTiO3
Authors: Horibe Yoichi , Nakayama Maki , Hosokoshi Yuko , Asaka Toru , Matsui Yoshio , Asada Toshihiro , Koyama Yasumasa , Mori Shigeo
Published: October 2005

We have investigated microstructures associated with the magnetic and dielectric properties of multiferroic mixed-perovskite compounds of the formula (1-x)BiFeO3-xBaTiO3by transmission electron microscopy (TEM) combined with conventional dielectric and magnetic measurements. TEM observation revealed that there exist complicated ferroelectric (FE) domains 20–30 nm in size in the FE phase of BiFeO3. It was also found that, in anx=0.25 compound, a weak spontaneous magnetization appears in the FE phase at 20 K. From the results of the X-ray and electron diffraction experiments, it is suggested that this weak spontaneous magnetization is closely associated with the decrease in the extent of rhombohedral distortion by a partial substitution of BaTiO3for BiFeO3.
Orientational Field-Induced Effects in Brillouin Spectra of Lead Magnesium Niobate Crystals
Authors: Lushnikov Sergey G. , Fedoseev Alexander I. , Ko Jae Hyeon , Kojima Seiji
Published: October 2005

The Brillouin light scattering studies of hypersonic acoustic phonons as a function of applied electric field in relaxor ferroelectric PbMg1/3Nb2/3O3-PMN in the temperature range 100–300 K are reported. The orientational dependence of the electroacoustic effect has been studied. It has been shown that the dependence of the velocity of quasilongitudinal hypersonic phonons (QLA) on dc applied electric field direction manifests itself below T
crit≈235 K. Field-induced changes in the Brillouin scattering spectra of the PbMg1/3Nb2/3O3 (PMN) relaxor ferroelectric have been examined in the vicinity of a diffuse phase transition under a dc electric field oriented along the [111] direction. It has been established that the transition into an electric-field-induced ferroelectric phase is accompanied by anomalies in the behavior of the QLA phonon propagating along the [110] direction at T
B≈160 K. The changes in QLA velocity at the ferroelectric phase transition were found to be either reversible or irreversible in different regions of the induced ferroelectric phase. The experimental results are compared with E–T phase diagrams.
Cooling-Rate-Dependence of Dielectric Constant and Domain Structures in (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 Single Crystals
Authors: Okino Hirotake , Sakamoto Junichi , Yamamoto Takashi
Published: October 2005

The relationship between the dielectric constant and domain structure was investigated on PMN-xPT (x: 0.27, 0.32 and 0.34) single crystals. As Yan et al. already reported, the cooling rate across the freezing temperature (the relaxor-ferroelectric phase transition temperature) affected the dielectric constant in the ferroelectric phase. In this study, it was found that the lead titanate compositions x affected the cooling-rate dependences of the dielectric constant. The dependences of domain structures on cooling-rate and on the composition x corresponded with the dielectric constant behavior. That is, the average domain size decreased as the dielectric constant was reduced. The relationship between the dielectric constant and domain structure is discussed from the viewpoint of the evolution of polar nanosized regions during the relaxor to ferroelectric phase transition.
Fingerprint Pattern and Dielectric Property in Pb(Zn1/3Nb2/3)O3
Authors: Iwata Makoto , Hasegawa Yusuke , Maeda Masaki , Yasuda Naohiko , Ishibashi Yoshihiro
Published: October 2005

The effects of an electric field on the fingerprint pattern of the relaxor Pb(Zn1/3Nb2/3)O3 (PZN) were investigated using atomic force microscopy (AFM). It was found that the pattern of the domain wall structure in the relaxor, called the fingerprint pattern, strongly depends on the dc field strength, and disappears for a weak field of 0.2 kV/cm, which is about 1/10 of the coercive field in the D–E hysteresis loop. The dc field dependence of the dielectric constant in PZN was also investigated. It was found that the dielectric constant under the dc field, being of the same order as the coercive field, gradually decreases to 84% with time, and the characteristic dispersion of the relaxor becomes remarkably small with the appearance of the piezoelectric response. We discussed the contribution from the small domain wall structure to the dielectric property of the relaxor.
Investigation of Three-Dimensional Domain Structure in LiTaO3 by Scanning Nonlinear Dielectric Microscopy
Authors: Sugihara Tomoyuki , Cho Yasuo
Published: October 2005

The three-dimensional domain configuration of multidomain LiTaO3 is revealed by scanning nonlinear dielectric microscopy (SNDM). SNDM can measure the polarization components both perpendicular and parallel to the surface of a specimen. These techniques are applied to both congruent and stoichiometric LiTaO3 crystals. The images obtained by SNDM measurements allow us to confirm the various domain features of LiTaO3 and to understand both similarities and differences between congruent and stoichiometric compositions.
Structural Phase Transition and Domain Structures in YMn1-xTixO3
Authors: Mori S. , Tokunaga J. , Horibe Y. , Aikawa Y. , Katsufuji T.
Published: October 2005

We investigated changes in domain structures induced by a partial substitution of Ti for Mn in multiferroic YMnO3 by transmission electron microscopy (TEM). In the ferroelectric phase of YMnO3 at room temperature, there exist 180-degree ferroelectric (FE) domain structures of a micrometer size. On substituting Ti for Mn, the size of FE domains becomes fragile and, at approximately x=0.175 in YMn1-x
Ti
x
O3, the size can be estimated to be 10–20 nm. On further substitution, it is found that a structural phase transition from a hexagonal P63 cm structure to a new rhombohedral R3c one takes place at approximately x=0.20. In YMn1-x
Ti
x
O3 with 0.20<x<0.40, these two distinct structures (the hexagonal P63 cm and rhombohedral R3c structures) coexist and this coexistence should have some strong effect on the ferroelectric properties such as the magnetocapacitance effect found in Ti-substituted YMnO3.
Brillouin Scattering and Domain Observation of TlNO3 Crystals
Authors: Takagi Yasunari , Kono Hiroyuki , Takeuchi Yoshio
Published: October 2005

The structural phase transition in TlNO3 crystals has been investigated by Brillouin scattering. Brillouin shift frequencies were almost unchanged at 79°C (=T
2), but they jumped at 144°C (=T
1), and the intensities varied at T
2. The transverse modes were not softened. Domain observations were performed in order to be certain that the orthorhombic phase at room temperature was “ferroelastic”. It was found that the domains were only created under stress on the crystal. From this result, this crystal was judged to be not ferroelastic, but ferrobielastic according to Aizu's terminology.
Strong Room-Temperature Near-Ultraviolet Emission from In-Rich InGaN/GaN Nanostructures Grown by Metalorganic Chemical Vapor Deposition
Authors: Kwon Soon-Yong , Kim Hee Jin , Kim Young-Woon , Yoon Euijoon
Published: October 2005

We report the successful growth of In-rich InGaN/GaN nanostructures such as multiple quantum wells (MQWs) and quantum dots (QDs) by metalorganic chemical vapor deposition (MOCVD). Introduction of a relatively high growth temperature (730°C) made it possible to grow In-rich InGaN/GaN QWs, and growth interruption (GI) was effectively used to improve the structural and optical properties of the QWs. To enhance thermal characteristics, an artificial formation of In-rich InGaN/GaN QDs was made at a relatively lower growth temperature (650°C) than that of QWs. The well width of the In-rich InGaN/GaN QWs and the dot height of the In-rich InGaN/GaN QDs were both approximately 1 nm, and we obtained strong room-temperature near-ultraviolet (UV) emission from these In-rich InGaN/GaN nanostructures. This strongly suggests that ultrathin In-rich InGaN nanostructures can be a new candidate for a near-UV source, which might replace the conventional low-indium-content (<10%), thicker InGaN QW.
Junction Temperature in Ultraviolet Light-Emitting Diodes
Authors: Xi Yangang , Gessmann Thomas , Xi Jingqun , Kim Jong Kyu , Shah Jay M. , Schubert E. Fred , Fischer Arthur J. , Crawford Mary H. , Bogart Katherine H. A. , Allerman Andrew A.
Published: October 2005

The junction temperature and thermal resistance of AlGaN and GaInN ultraviolet (UV) light-emitting diodes (LEDs) emitting at 295 and 375 nm, respectively, are measured using the temperature coefficient of diode-forward voltage. An analysis of the experimental method reveals that the diode-forward voltage has a high accuracy of ±3°C. A comprehensive theoretical model for the dependence of diode-forward voltage (V
f) on junction temperature (T
j) is developed taking into account the temperature dependence of the energy gap and the temperature coefficient of diode resistance. The difference between the junction voltage temperature coefficient (dV
j/dT) and the forward voltage temperature coefficient (dV
f/dT) is shown to be caused by diode series resistance. The data indicate that the n-type neutral regions are the dominant resistive element in deep-UV devices. A linear relationship between junction temperature and current is found. Junction temperature is also measured by the emission-peak-shift method. The high-energy slope of the spectrum is explored in the measurement of carrier temperature.