bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of an Archaeal Medium-Chain Acyl Coenzyme A Synthetase fromMethanosarcina acetivorans
Authors: Meng Yu , Ingram-Smith Cheryl , Cooper Leroy L. , Smith Kerry S.
Published: September 2010

Short- and medium-chain acyl coenzyme A (acyl-CoA) synthetases catalyze the formation of acyl-CoA from an acyl substrate, ATP, and CoA. These enzymes catalyze mechanistically similar two-step reactions that proceed through an enzyme-bound acyl-AMP intermediate. Here we describe the characterization of a member of this enzyme family from the methane-producing archaeonMethanosarcina acetivorans. This enzyme, a medium-chain acyl-CoA synthetase designated MacsMa, utilizes 2-methylbutyrate as its preferred substrate for acyl-CoA synthesis but cannot utilize acetate and thus cannot catalyze the first step of acetoclastic methanogenesis inM. acetivorans. When propionate or other less favorable acyl substrates, such as butyrate, 2-methylpropionate, or 2-methylvalerate, were utilized, the acyl-CoA was not produced or was produced at reduced levels. Instead, acyl-AMP and PPiwere released in the absence of CoA, whereas in the presence of CoA, the intermediate was broken down into AMP and the acyl substrate, which were released along with PPi. These results suggest that although acyl-CoA synthetases may have the ability to utilize a broad range of substrates for the acyl-adenylate-forming first step of the reaction, the intermediate may not be suitable for the thioester-forming second step. The MacsMastructure has revealed the putative acyl substrate- and CoA-binding pockets. Six residues proposed to form the acyl substrate-binding pocket, Lys256, Cys298, Gly351, Trp259, Trp237, and Trp254, were targeted for alteration. Characterization of the enzyme variants indicates that these six residues are critical in acyl substrate binding and catalysis, and even conservative alterations significantly reduced the catalytic ability of the enzyme.
Calcium and Iron Regulate Swarming and Type III Secretion inVibrio parahaemolyticus
Authors: Gode-Potratz Cindy J. , Chodur Daniel M. , McCarter Linda L.
Published: September 2010

Here, we probe the response to calcium during growth on a surface and show that calcium influences the transcriptome and stimulates motility and virulence ofVibrio parahaemolyticus.Swarming (but not swimming) gene expression and motility were enhanced by calcium. Calcium also elevated transcription of one of the organism's two type III secretion systems (T3SS1 but not T3SS2) and heightened cytotoxicity toward host cells in coculture. Calcium stimulation of T3SS gene expression has not been reported before, although low calcium is an inducing signal for the T3SS of many organisms. EGTA was also found to increase T3SS1 gene expression and virulence; however, this was demonstrated to be the consequence of iron rather than calcium chelation. Ectopic expression ofexsA, encoding the T3SS1 AraC-type regulator, was used to define the extent of the T3SS1 regulon and verify its coincident induction by calcium and EGTA. To begin to understand the regulatory mechanisms modulating the calcium response, a calcium-repressed, LysR-type transcription factor named CalR was identified and shown to repress swarming and T3SS1 gene expression. Swarming and T3SS1 gene expression were also demonstrated to be linked by LafK, a σ54-dependent regulator of swarming, and additionally connected by a negative-feedback loop on the swarming regulon propagated by ExsA. Thus, calcium and iron, two ions pertinent for a marine organism and pathogen, play a signaling role with global consequences on the regulation of gene sets that are relevant for surface colonization and infection.
A
Rhodobacter capsulatus
Member of a Universal Permease Family Imports Molybdate and Other Oxyanions
Authors: Gisin Jonathan , Müller Alexandra , Pfänder Yvonne , Leimkühler Silke , Narberhaus Franz , Masepohl Bernd
Published: September 2010

Molybdenum (Mo) is an important trace element that is toxic at high concentrations. To resolve the mechanisms underlying Mo toxicity,
Rhodobacter capsulatus
mutants tolerant to high Mo concentrations were isolated by random transposon Tn
5
mutagenesis. The insertion sites of six independent isolates mapped within the same gene predicted to code for a permease of unknown function located in the cytoplasmic membrane. During growth under Mo-replete conditions, the wild-type strain accumulated considerably more Mo than the permease mutant. For mutants defective for the permease, the high-affinity molybdate importer ModABC, or both transporters,
in vivo
Mo-dependent nitrogenase (Mo-nitrogenase) activities at different Mo concentrations suggested that ModABC and the permease import molybdate in nanomolar and micromolar ranges, respectively. Like the permease mutants, a mutant defective for ATP sulfurylase tolerated high Mo concentrations, suggesting that ATP sulfurylase is the main target of Mo inhibition in
R. capsulatus
. Sulfate-dependent growth of a double mutant defective for the permease and the high-affinity sulfate importer CysTWA was reduced compared to those of the single mutants, implying that the permease plays an important role in sulfate uptake. In addition, permease mutants tolerated higher tungstate and vanadate concentrations than the wild type, suggesting that the permease acts as a general oxyanion importer. We propose to call this permease PerO (for oxyanion permease). It is the first reported bacterial molybdate transporter outside the ABC transporter family.
The Methanogen-Specific Transcription Factor MsvR Regulates the
fpaA-rlp-rub
Oxidative Stress Operon Adjacent to
msvR
in
Methanothermobacter thermautotrophicus
Authors: Karr Elizabeth A.
Published: September 2010

Methanogens represent some of the most oxygen-sensitive organisms in laboratory culture. Recent studies indicate that they have developed mechanisms to deal with brief oxygen exposure. MsvR is a transcriptional regulator that has a domain architecture unique to a select group of methanogens. Here, runoff
in vitro
transcription assays were used to demonstrate that MsvR regulates transcription of the divergently transcribed
fpaA-rlp-rub
operon in
Methanothermobacter thermautotrophicus
in addition to transcription from its own promoter. The protein products of the
fpaA-rlp-rub
operon have previously been implicated in oxidative stress responses in
M. thermautotrophicus
. Additionally, electrophoretic mobility shift assays (EMSAs) and DNase I footprinting were used to confirm a binding site inferred by bioinformatic analysis. Sequence mutations within these binding sites did not significantly alter EMSA shifting patterns on longer templates but did on shorter 50-bp fragments encompassing only the region containing the binding sites. Footprinting confirmed that the regions protected for the longer mutant templates are at different positions within the intergenic region compared to those seen in the intact intergenic region. Oxidized and reduced preparations of MsvR demonstrated different EMSA binding patterns and regions of protection on the intergenic sequence, suggesting that MsvR may play a role in detecting the redox state of the cell.
Characterization of Pgp3, aChlamydia trachomatisPlasmid-Encoded Immunodominant Antigen
Authors: Chen Ding , Lei Lei , Lu Chunxue , Galaleldeen Ahmad , Hart P. John , Zhong Guangming
Published: September 2010

Human antibody recognition ofChlamydia trachomatisplasmid-encoded Pgp3 protein is dependent on the native conformation of Pgp3. The structural basis for the conformation dependence and the function of Pgp3 remain unknown. Here, we report that Pgp3 trimerization is required for the recognition of Pgp3 by human antibodies. In a native polyacrylamide gel, Pgp3 purified from a bacterial expression system migrated as stable trimers that were dissociated into monomers only by treatment with urea or sodium dodecyl sulfate (SDS) but not nonionic detergents. Human antibodies recognized trimeric but not monomeric Pgp3, suggesting that Pgp3 is presented to the human immune system as trimers duringC. trachomatisinfection. The endogenous Pgp3 secreted into the chlamydial outer membrane complex or host cell cytosol is always trimerized. Intact Pgp3 trimers were eluted from the outer membrane complex by a combination of nonionic detergents with reducing agents but not by the presence of either alone. These observations have provided important information for further understanding the role of Pgp3 in chlamydial pathogenesis and potentially optimizing Pgp3 as a subunit vaccine candidate antigen.
Complete Genome Sequence of the Cellulolytic Thermophile
Caldicellulosiruptor obsidiansis
OB47
T
Authors: Elkins James G. , Lochner Adriane , Hamilton-Brehm Scott D. , Davenport Karen Walston , Podar Mircea , Brown Steven D. , Land Miriam L. , Hauser Loren J. , Klingeman Dawn M. , Raman Babu , Goodwin Lynne A. , Tapia Roxanne , Meincke Linda J. , Detter J. Chris , Bruce David C. , Han Cliff S. , Palumbo Anthony V. , Cottingham Robert W. , Keller Martin , Graham David E.
Published: September 2010

Caldicellulosiruptor obsidiansis
OB47
T
(ATCC BAA-2073, JCM 16842) is an extremely thermophilic, anaerobic bacterium capable of hydrolyzing plant-derived polymers through the expression of multidomain/multifunctional hydrolases. The complete genome sequence reveals a diverse set of carbohydrate-active enzymes and provides further insight into lignocellulosic biomass hydrolysis at high temperatures.
Genome Sequence of the Polymyxin-Producing Plant-Probiotic Rhizobacterium
Paenibacillus polymyxa
E681
Authors: Kim Jihyun F. , Jeong Haeyoung , Park Soo-Young , Kim Seong-Bin , Park Yon Kyoung , Choi Soo-Keun , Ryu Choong-Min , Hur Cheol-Goo , Ghim Sa-Youl , Oh Tae Kwang , Kim Jae Jong , Park Chang Seuk , Park Seung-Hwan
Published: September 2010

Paenibacillus polymyxa
E681, a spore-forming, low-G+C, Gram-positive bacterium isolated from the rhizosphere of winter barley grown in South Korea, has great potential for agricultural applications due to its ability to promote plant growth and suppress plant diseases. Here we present the complete genome sequence of
P. polymyxa
E681. Its 5.4-Mb genome encodes functions specialized to the plant-associated lifestyle and characteristics that are beneficial to plants, such as the production of a plant growth hormone, antibiotics, and hydrolytic enzymes.
A QUANTUM CRYPTOGRAPHIC SOLUTION TO THE PROBLEM OF ACCESS CONTROL IN A HIERARCHY
Authors: NAGY NAYA , AKL SELIM G.
Published: September 2010

Access control in a hierarchy refers to a selective access to a database. A large number of users work with the same database. These users are organized in a hierarchical structure and therefore have different access rights to the data. This paper offers a solution to the problem of access control in a hierarchy based on quantum cryptography. Each user has two keys: a classical key and a quantum key. Our scheme offers several security advantages over the classical schemes to date. It protects users from identity theft and prevents collusion attacks. Most importantly though, our scheme adapts to dynamic changes of the user hierarchy: users may join, leave, or change position in the hierarchy, without affecting the rest of the user structure.
NEUTRINO MASS AND GRAND UNIFICATION OF FLAVOR
Authors: MOHAPATRA R. N.
Published: September 2010

The problem of understanding quark mass and mixing hierarchies has been an outstanding problem of particle physics for a long time. The discovery of neutrino masses in the past decade, exhibiting mixing and mass patterns so very different from the quark sector has added an extra dimension to this puzzle. This is specially difficult to understand within the framework of conventional grand unified theories which are supposed to unify the quarks and leptons at short distance scales. In the paper, I discuss a recent proposal by Dutta, Mimura and this author that appears to provide a promising way to resolve this puzzle. After stating the ansatz, we show how it can be realized within a SO(10) grand unification framework. Just as Gell-Mann's suggestion of SU(3) symmetry as a way to understand the hadronic flavor puzzle of the sixties led to the foundation of modern particle physics, one could hope that a satisfactory resolution of the current quark-lepton flavor problem would provide fundamental insight into the nature of physics beyond the standard model.
LOCALITY PRESERVING NONNEGATIVE MATRIX FACTORIZATION WITH APPLICATION TO FACE RECOGNITION
Authors: ZHANG TAIPING , FANG BIN , TANG YUAN Y. , SHANG ZHAOWEI
Published: September 2010

In this paper, we propose a Locality Preserving Nonnegative Matrix Factorization (LPNMF) method to discover the manifold structure embedded in high-dimensional face space that is applied for face recognition. It is done by incorporating locality preserving constraints inside the cost function of NMF, then a new decomposition of a face with locality preserving can be obtained. As a result, the proposed LPNMF method shares some properties with the Locality Preserving Projection (LPP) such that it can effectively discover the manifold structure embedded in a high-dimensional face space. Experimental results show that LPNMF provides a better representation and achieves higher recognition rates in face recognition.
SHEARLET TRANSFORMS AND DIRECTIONAL REGULARITIES
Authors: LAKHONCHAI P. , SAMPO J. , SUMETKIJAKAN S.
Published: September 2010

In an effort to characterize uniform and pointwise Hölder regularities, we obtain necessary decay rates and sufficient decay rates of continuous and discrete shearlet transform across scales. They are the same rates as those of the Hart Smith and continuous curvelet transforms. We then consider the situation where the regularity on a line in a non-parallel direction is significantly lower than the directional regularity along the line in a neighborhood of the line. Similar to that of the Hart Smith and continuous curvelet transforms, a set of necessary conditions for this direction of singularity is that the continuous shearlet transform decays half an order faster in directions "away" from the direction of the line and that the decay rate in directions "near" the line depends also on the horizontal distance from the line to the parallel line containing the center of the shearlet function. These similarities among the three transforms call for a general theory of transforms "with parabolic scaling."
Highly Uniform Characteristics of GaN Nanorods Grown on Si(111) by Metalorganic Chemical Vapor Deposition
Authors: Ra Yong-Ho , Navamathavan Rangaswamy , Park Ji-Hyeon , Song Ki-Young , Lee Young-Min , Kim Dong-Wook , Jun Baek Byung , Lee Cheul-Ro
Published: September 2010

Gallium nitride (GaN) nanorod (NR) arrays were grown on a gold-coated Si(111) substrate by metalorganic chemical vapor deposition (MOCVD). The synthesized single GaN NRs were characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and cathodoluminescence (CL) analysis. The HR-TEM images and selected area electron diffraction (SAED) patterns demonstrated that the GaN NRs were of high quality with a single-crystal wurtzite structure and free from defects. The GaN NRs were observed to have a uniform diameter ranging from 40 to 70 nm, length of up to 1 µm, and a sharp symmetrical pyramid-like tip at the top. The pyramid-like tip was attributed to the dissociation of nitrogen atoms by the cracking of ammonia (NH3) at the elevated growth temperature. Furthermore, there was no sign of any metal or alloy cluster at the end of the NRs. Thus, the growth of the GaN NRs does not occur by the typical vapor–liquid–solid (VLS) mechanism.
Depth Profile of Nitrogen Atoms in Silicon Oxynitride Films Formed by Low-Electron-Temperature Microwave Plasma Nitridation
Authors: Murakawa Shigemi , Ishizuka Shu-ichi , Nakanishi Toshio , Suwa Tomoyuki , Teramoto Akinobu , Sugawa Shigetoshi , Hattori Takeo , Ohmi Tadahiro
Published: September 2010

Angle-resolved photoelectron spectroscopy study was performed on the depth profile of nitrogen atoms in silicon oxynitride (SiON) films formed by the plasma nitridation of silicon dioxide using low-electron-temperature microwave plasma. The depth profile of nitrogen near the SiON surface was confirmed to increase and its peak position moves into SiON films with an increase in the nitridation time, which improves boron immunity. A new transport and reaction model of plasma nitridation is proposed to explain the time evolution of nitrogen concentration and its depth profile in the films. Here, the density of radical nitrogen atoms decreases exponentially with an increase in the distance from the surface, and the nitrogen concentration incorporated in the SiON film is approximately proportional to the logarithmic time of plasma nitridation. It was newly found that post-nitridation annealing strongly enhances the pile-up of nitrogen atoms at the Si–SiON interface owing to their diffusion from the inward tail of the nitrogen depth profile near the surface. It is deduced that the pile-up of nitrogen atoms induces Si–H bonds at the interface, which become the main trigger for the degradation of the negative bias temperature instability of p-channel metal–oxide–silicon transistors.
Equivalent Refractive Index of Multilayer-Type Photonic Crystals
Authors: Ohtera Yasuo , Yamada Hirohito
Published: September 2010

Method of calculating the equivalent refractive index of multilayer-type photonic crystals is proposed. The equivalent index here refers to the Herpin's index which has been conventionally utilized for the design of antireflective (AR) coatings on flat multilayer filters. The index is directly connected to the Fresnel reflection coefficient between the ambient media and photonic crystals. The procedure of calculating the equivalent index of autocloning-type photonic crystals, which consists of multilayer of zigzag cross section, is described. Difference between the indices of photonic crystals and flat multilayer is also discussed.
Attaching Thiolated Superconductor Grains on Gold Surfaces for Nanoelectronics Applications
Authors: Valladares Luis De Los Santos , Dominguez Angel Bustamante , Llandro Justin , Suzuki Seiichi , Mitrelias Thanos , Quispe Richard Bellido , Barnes Crispin H. W. , Majima Yutaka
Published: September 2010

We report that the high critical temperature superconductor (HTCS) LaCaBaCu3O7 in the form of nanograins can be linked to Au(111) surfaces through self assembled monolayers (SAMs) of HS–C8H16–HS [octane (di)thiol]. We show that La1113 particles (100 nm mean diameter) can be functionalized by octane (di)thiol without affecting their superconducting critical temperature (T
C=80 K). X-ray photoemission spectroscopy (XPS) analysis reveals that the thiol functional heads link the superconducting grain surfaces creating sulfonates and we deduce that bonding between the S atoms and Cu(1) atoms of the La1113 structure would be formed. We suggest a design for a superconducting transistor fabricated by immobilized La1113 nanograins in between two gold electrodes which could be controlled by an external magnetic field gate.
Facile Combustion Route for Low-Temperature Preparation of Sr2SiO4:Eu2+ Phosphor and Its Photoluminescence Properties
Authors: Lei Bingfu , Machida Ken-ichi , Horikawa Takashi , Hanzawa Hiromasa
Published: September 2010

Uniform and nanosized phosphors of Sr2SiO4:Eu2+ were successfully synthesized by a simple, inexpensive, and relatively low-temperature synthesis route using the combustion method. Through the chemical reaction of Sr(NO3)2, Eu(NO3)3, and fumed silica, the pure phase of nanosized Sr2SiO4:Eu2+ was obtained by sintering at 800 °C for 3 min. The crystallinity and morphology of the as-synthesized Sr2SiO4:Eu2+ powders were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The particle size of the Sr2SiO4:Eu2+ powders was distributed in a range of 30–50 nm. Furthermore, their photoluminescence and luminescence decay properties were also systemically discussed and compared with those of Sr2SiO4:Eu2+ phosphor prepared by a conventional high-temperature solid-state reaction method. The luminescence decay curves indicated that the distribution of Eu2+ ions in the nanosized Sr2SiO4 powders was in a nearly homogeneous average local environment.
Growth Mechanism of Large-Size Rubrene Single Crystals Grown by a Solution Technique
Authors: Zhang Pengqiang , Zeng Xionghui , Deng Jiancheng , Huang  , Bao Feng , Qiu Yongxin , Xu Ke , Zhang
Published: September 2010

Large-size and high-quality rubrene single crystals have been grown by a solution technique. The biggest crystal has 4 mm dimension. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy both indicate that the crystals obtained are pure rubrene and did not incorporate the solvent at the detection level. The morphology of surface and transect of the rubrene single crystals was observed by optical microscope, atomic force microscope (AFM), and scanning electron microscope (SEM). Three-dimensional nucleation was happened on the surface of single crystals. The array of small and large straight steps was observed on the surface of the rubrene single crystals. Layer-like structures were also observed on the cross-section of single crystals. All results indicate that each large step is most probably formed from the piling of small steps and the growth mechanism of rubrene crystals grown from solution is probably a three-dimensional nucleation–layer-by-layer periods growth.
Studies of Defects and Thermal Conductivity of Mixed Polytype in 6H-SiC Single Crystal by Polarized Optical Microscopy, Light Scattering Tomography, and Thermal Microscopy
Authors: Wutimakun Passapong , Morimoto Jun , Toyoda Taro
Published: September 2010

This study was performed to investigate the defects and thermal conductivity of a mixed polytype of 6H-SiC single crystal using polarized optical microscopy (POM), light scattering tomography (LST), and thermal microscopy. First, we used Raman scattering spectroscopy to identify the mixed polytype, and we observed 15R-SiC mixed in a 6H-SiC single crystal. Next, as POM enables color distinction, we could clearly examine the defects in the mixed polytype area and border of 6H-SiC and 15R-SiC. Furthermore, we successfully presented defects that existed in the mixed polytype area and border in three-dimensional (3D) display by 3D light scattering tomography (3D-LST). Finally, we confirmed that there is a difference between the thermal conductivities of mixed polytypes of a 6H-SiC single crystal by thermal microscopy. The thermal conductivities of 6H-SiC, 15R-SiC, and their mixture were 475, 427, and 396 W m-1 K-1, respectively. These differences in thermal conductivity are caused by the existence of defects and the difference in carrier mobility between all polytypes.
Leakage Current Reduction and Ferroelectric Property of BiFe1-xCoxO3 Thin Films Prepared by Chemical Solution Deposition Using Iterative Rapid Thermal Annealing at Approximately 520 °C
Authors: Tho Nguyen Truong , Kanashima Takeshi , Okuyama Masanori
Published: September 2010

Ferroelectric Bi1.1Fe0.9Co0.1O3 (BFCO) thin films of 100 nm thickness have been prepared on Pt/TiO2/SiO2/Si substrates by chemical solution deposition (CSD) using iterative rapid thermal annealing (RTA) at 510–560 °C. A thin film prepared at 520 °C shows low leakage currents of about 6 ×10-3 and 2 ×10-2 A/cm2 at 80 K and room temperature (RT) at a high electric field of 2 MV/cm, respectively. However, the leakage current is above 10-2 A/cm2 at high applied electric fields from 1 to 2 MV/cm so that P–E hysteresis loops of the thin film seem to be unsaturated at RT. As a result, the difference in polarizations at the zero field of the BFCO film prepared at 520 °C is 150 µC/cm2 at an applied electric field of 3 MV/cm and RT, which is larger than that of 120 µC/cm2 at an applied electric field of 4 MV/cm and 80 K.
Effect of Femtosecond Prepulse with Threshold Intensity for Optical Field Ionization on Electron Acceleration and Propagation of Intense Laser Pulse in Plasma
Authors: Masuda Shin-ichi , Miura Eisuke
Published: September 2010

The effect of a prepulse with femtosecond duration, which precedes an intense laser pulse by 4 ns, on electron acceleration and propagation of an intense laser pulse in a plasma is investigated using a helium gas jet. When the prepulse intensity exceeds 1015W/cm2, which is close to the threshold intensity for optical field ionization of helium, the maximum energy and number of accelerated electrons are significantly reduced. In addition, the amplitude of the plasma wave is relatively small, and the propagation length of the laser pulse is short. These results suggest that the preformed plasma produced by the femtosecond prepulse affects the electron acceleration and laser propagation. To investigate the effects of a preformed plasma, two-dimensional particle-in-cell simulations are carried out. The simulation results support the experimental results.
Forty-Five Degree Micromirror Fabrication Using Silicon Anisotropic Etching with Surfactant-Added Tetramethylammonium Hydroxide Solution
Authors: Yagyu Hiroyuki , Yamaji Tadahiro , Nishimura Makoto , Sato Kazuo
Published: September 2010

Flat and smooth 45° micromirrors were successfully fabricated on a 4-in. silicon wafer by means of wet anisotropic etching at the industrially practical temperature of 80 °C using tetramethylammonium hydroxide (TMAH) solution with added NCW-1002, a nonionic surfactant with little environmental load. The effects of the TMAH concentration and the amount of NCW-1002 added were extensively investigated, and it was found that a high TMAH concentration (25 wt %) and a very low amount of NCW-1002, approximately 10 vol ppm, are the optimum conditions to fabricate optically smooth and geometrically flat micromirrors. The mechanism underlying the effects of the concentration of the surfactant is discussed in relation to the clouding point of the surfactant-added TMAH solution.
Improvement of Frequency Locking Algorithm for Atomic Frequency Standards
Authors: Park Young-Ho , Kang Hoonsoo , Lee Soo Heyong , Park Sang Eon , Lee Jong Koo , Lee Ho Seong , Kwon Taeg Yong
Published: September 2010

The authors describe a novel method of frequency locking algorithm for atomic frequency standards. The new algorithm for locking the microwave frequency to the Ramsey resonance is compared with the old one that had been employed in the cesium atomic beam frequency standards such as NIST-7 and KRISS-1. Numerical simulations for testing the performance of the algorithm show that the new method has a noise filtering performance superior to the old one by a factor of 1.2 for the flicker signal noise and 1.4 for random-walk signal noise. The new algorithm can readily be used to enhance the frequency stability for a digital servo employing the slow square wave frequency modulation.
Confocal Imaging Using Ultra Wideband Antenna Array on Si Substrates for Breast Cancer Detection
Authors: Kubota Shinichi , Xiao Xia , Sasaki Nobuo , Kayaba Yasuhisa , Kimoto Kentaro , Moriyama Wataru , Kozaki Takahiro , Hanada Maiko , Kikkawa Takamaro
Published: September 2010

A Si on-chip bow-tie antenna array was developed for transmitting Gaussian monocycle pulses (GMPs) whose center frequency was 15 GHz. The length and flare angle of the bow-tie antenna were 7.16 mm and 53°, respectively. GMPs were emitted from the antenna to the substrate whose dielectric constant was 7 and reflected at the target whose dielectric constant was 30. A minimum dielectric target size of 3×3 mm2 at a depth of 20 mm in the dielectric substrate was detected and a two-dimensional cross-sectional image of a dielectric target in a dielectric substrate was reconstructed by confocal imaging algorithm.
A-Site-Modified Perovskite Nanosheets and Their Integration into High-κ Dielectric Thin Films with a Clean Interface
Authors: Li Bao-Wen , Osada Minoru , Ozawa Tadashi C. , Akatsuka Kosho , Ebina Yasuo , Ma Renzi , Ono Kanta , Funakubo Hiroshi , Sasaki Takayoshi
Published: September 2010

We investigated dielectric properties of La1-x
Eu
x
Nb2O7 perovskite nanosheets in order to study the effect of A-site modification on dielectric properties. Langmuir–Blodgett deposition was employed to fabricate multilayer nanofilms of perovskite nanosheets. In these nanosheets, A-site modification with Eu3+ ions improves the leakage current characteristics and, at the same time, reduces permittivity. The slight modification with Eu3+ ions in La0.95Nb2O7 nanosheets causes a 50% reduction in ε
r value. We also discuss the high-κ properties of La0.95Nb2O7 nanosheets by performing detailed investigations based on first-principles calculations and interfacial structures.
Orientation Dependence of Shear Mode Piezoelectric Properties of Epitaxial Pb(Zrx,Ti1-x)O3 Thin Films
Authors: Akama Kenji , Kanno Isaku , Yokokawa Ryuji , Wasa Kiyotaka , Kotera Hidetoshi
Published: September 2010

The orientation dependence of shear mode piezoelectric properties has been investigated for epitaxial Pb(Zr,Ti)O3 (PZT) thin films with composition near the morphotropic phase boundary. (101)- and (111)-oriented PZT films were epitaxially grown on SrTiO3 (STO) substrates by rf magnetron sputtering and microfabricated into rectangular-shaped specimens to apply a horizontal electric field using lateral electrodes. The application of a sinusoidal input voltage of 100 kHz generated in-plane shear vibration, which was measured using a laser Doppler vibrometer. In-plane displacement proportionally increased with applied voltage for each PZT film. When a horizontal electric field was applied to (101)PZT along the directions parallel and perpendicular to [110]STO, the shear piezoelectric coefficient d
15 was calculated to be 110 and 305 pm/V, respectively. On the other hand, d
15 of (111)PZT under the electric field parallel to [110]STO was calculated to be 160 pm/V. These results indicate that the shear mode piezoelectric coefficients of the epitaxial PZT films not only show large values compatible with bulk ceramics, but also strongly depend on the crystallographic orientation and the direction of the electric field.
Preparation and Characterization of Alkoxide-Derived Lead-Free Piezoelectric Barium Zirconate Titanate Thin Films with Different Compositions
Authors: Ohno Tomoya , Uchida Kazuhisa , Sakamoto Naonori , Fu Desheng , Wakiya Naoki , Matsuda Takeshi , Suzuki Hisao
Published: September 2010

Lead-free barium zirconate titanate Ba(Zr1-x
Ti
x
)O3; BZT100x 0≤x≤0.1) thin films were deposited on lanthanum nickel oxide (LNO)/Pt/SiO2/Si substrate by chemical solution deposition (CSD). The Zr content was changed up to x=0.1 to determine the effect of composition on the electrical properties. An LNO buffer layer was selected to control the crystal orientation of BZT thin films. The use of the LNO seeding layer resulted in the highly (100) and (001) oriented BZT100x films for all compositions. The dielectric and ferroelectric properties of the BZT100x thin films depend on the compositions. The d
33 values of the BZT100x thin films measured using the piezoelectric force microscope (PFM) changed in accordance with the crystal symmetry change. The maximum d
33 value was approximately 45 pm/V at BZT3 composition, showing the possibility of lead-free piezoelectric barium zirconate titanate thin films obtained by CSD.
Annealing and Composition Effects of (BaxSr1-x)Ta2O6 Thin Films Fabricated by Sol–Gel Method
Authors: Lu Li , Nishida Takashi , Echizen Masahiro , Uchiyama Kiyoshi , Uraoka Yukiharu
Published: September 2010

The annealing atmosphere effects and composition effects on the electrical properties of five compositions of (Ba
x
Sr1-x
)Ta2O6 thin films were investigated. O2 atmosphere annealing prevented the diffusion of Ti from the substrates into thin films and thus improved the dielectric properties of thin films. Thin films of all compositions show dielectric constants higher than 60 and loss tangents lower than 1%. Sr substituted for Ba in BaTa2O6 thin films showed a strong influence on the material properties. Among the samples, (Ba0.75Sr0.25)Ta2O6 thin film shows good bias stability, a high dielectric constant of about 65, low loss tangent of about 0.9% and low leakage current of about 10-7 A/cm2, and is regarded as the most promising for application in next-generation miniaturization.
Local Piezoelectric and Conduction Properties of BiFeO3 Epitaxial Thin Films
Authors: Ujimoto Katsuya , Yoshimura Takeshi , Fujimura Norifumi
Published: September 2010

The innate leakage current mechanisms of epitaxial BiFeO3 epitaxial thin films were investigated by current–voltage (I–V) measurements in a microscopic region by a scanning probe microscopy (SPM) using a conductive probe to exclude the effect of the microstructure of the films such as the conduction at the grain boundary. The ferroelectric property for the microscopic region was also characterized using the piezoelectric response. It was found that the leakage current mechanisms of the films exhibiting electrostrictive response and piezoelectric response are Pool–Frenkel emission and Schottky emission, respectively. This result suggests that the innate electric conduction mechanism of BiFeO3 is Schottky emission conduction.
High-Performance Ferroelectric Bi4Ti3O12 Single Crystals Grown by Top-Seeded Solution Growth Method under High-Pressure Oxygen Atmosphere
Authors: Kitanaka Yuuki , Noguchi Yuji , Miyayama Masaru
Published: September 2010

The top-seeded solution growth (TSSG) method under high oxygen pressure (P
O2
) atmosphere has been developed to obtain large high-performance single crystals of ferroelectric Bi4Ti3O12. Crystals grown at 960 °C at a P
O2
of 0.9 MPa exhibited well-saturated hysteresis with a remanent polarization of 48 µC/cm2 and a coercive field of 29 kV/cm. The results of piezoresponse force microscopy indicate that polarization switching is accomplished throughout the crystals. Electric-field-induced strain measurements along the a axis yield a piezoelectric constant d
11
* of 37 pm/V for Bi4Ti3O12.
Low-Temperature Sintering of Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 Ceramics via Single-Step Calcination Process without Sintering Additives
Authors: Hayano Shuji , Shike Ryota , Shoji Kazuo , Ochiai Hiroshi , Kimura Osamu , Maiwa Hiroshi
Published: September 2010

Low-temperature sintering of 0.375Pb(Ni1/3Nb2/3)O3–0.25PbZrO3–0.375PbTiO3 was investigated. Raw material powders of high-purity NiO, Nb2O5, PbO, TiO2, and ZrO2 were mixed and ground to 0.2 µm on average, calcined at 850 °C for 2 h to obtain pyrochlore-free calcined powder, ground again, and finally sintered at 925 °C for 4 h, without adding sintering additives. The sintered sample showed a relative density = 99%, an electromechanical coupling factor planar mode k
p = 0.61, a piezoelectric constant d
33 = 600 pm/V, and a Curie temperature T
c = 189 °C. Accordingly, a multilayered actuator with pure Ag internal electrodes was prepared using the calcined powder.
Structural Property and Electric Field Response of a Single Perovskite PbTiO3 Nanowire Using Micro X-ray Beam
Authors: Yamada Tomoaki , Wang Jin , Sakata Osami , Tanaka Hidenori , Ehara Yoshitaka , Yasui Shintaro , Setter Nava , Funakubo Hiroshi
Published: September 2010

The structural property and electric field response of a single perovskite PbTiO3 nanowire were investigated by means of synchrotron X-ray diffraction (XRD) with a micro X-ray beam. XRD θ–2θ patterns and Raman spectra confirmed the formation of the perovskite phase of PbTiO3 by annealing the PX-phase of Pb–Ti–O nanowires at 600 °C. In addition, the obtained nanowires showed multi-domain/grain features. By focusing the micro X-ray beam on a single perovskite PbTiO3 nanowire, both ends of which are connected to electrodes, the lattice distortion under the electric field was observed.
High-Power Piezoelectric Characteristics of Bi4Ti3O12–SrBi4Ti4O15-Based Ferroelectric Ceramics
Authors: Noumura Yoji , Hiruma Yuji , Nagata Hajime , Takenaka Tadashi
Published: September 2010

The high-power piezoelectric characteristics of lead-free piezoelectric ceramics based on a mixed bismuth layer-structured ferroelectric, Bi4Ti3O12–SrBi4Ti4O15 (abbreviated as BIT–SBTi) were studied. In addition, MnCO3-doped BIT–SBTi (abbreviated as BIT–SBTi + Mn x wt %) were prepared to improve their high-power piezoelectric properties such as the mechanical quality factor Q
m. In the case of pure BIT–SBTi, its vibration velocity v
0–p at 5 V/mm field is 1.5 m/s. The v
0–p values of the BIT–SBTi + Mn 0.2 and 0.4 wt % ceramics were above 2.0 m/s at 5 V/mm. Also, we observed that the mechanical quality factor Q
m at a large amplitude of BIT–SBTi + Mn 0.4 wt % was maintained higher than 4000 at v
0–p of 2.0 m/s. The high-power characteristics of BIT–SBTi + Mn x wt % were superior to those of hard Pb(Zr,Ti)O3 (abbreviated as PZT) at a vibration velocity v
0–p>1.0 m/s. Therefore, Mn-doped BIT–SBTi-based ceramics are a promising candidate for lead-free high-power applications.
Optical and Nonlinear Optical Investigations of Phase Transition of Pb(Zn1/3Nb2/3)O3–9%PbTiO3 Single Crystals
Authors: Kaneshiro Junichi , Uesu Yoshiaki
Published: September 2010

Successive phase transitions of Pb(Zn1/3Nb2/3)O3–9%PbTiO3 single crystals with the morphotropic phase boundary composition are investigated using polarization and scanning-type second-harmonic generation (SHG) microscopes. Clear phase transitions between monoclinic and tetragonal, and tetragonal and cubic phases are observed with temperature hysteresis. A three-dimensional domain structure with a domain boundary consistent with the m3m
F
m( p) transition is observed with the SHG microscope at room temperature. Monoclinic domains develop with a long relaxation time in the zero-field cooling process.
Electronic, Structural, and Piezoelectric Properties of BiFe1-xCoxO3
Authors: Miura Kaoru , Kubota Makoto , Azuma Masaki , Funakubo Hiroshi
Published: September 2010

The electronic, structural, and piezoelectric properties of perovskite BiFe1-x
Co
x
O3 (BFCO) have been investigated using a first-principles calculation with optimized structures. Our calculated results show that the most stable structure changes from rhombohedral to monoclinic to tetragonal as x increases and that piezoelectric constants show maximums at the rhombohedral structure. These results are qualitatively in good agreement with the experimental results. However, even with the randomness of Fe and Co atoms, the piezoelectric constants do not show maximums at the monoclinic structure. This result suggests that the morphotropic phase boundary (MPB) does not appear in BFCO owing to a much larger c/a ratio in monoclinic and tetragonal structures.
Charge Density Study of Metastable State in BaTi2O5 with Fivefold Coordinated Ti
Authors: Moriyoshi Chikako , Miyoshi Satoru , Kuroiwa Yoshihiro , Yu Jianding , Arai Yasutomo , Masuno Atsunobu
Published: September 2010

The crystal structure of BaTi2O5 in metastable β-state synthesized by the containerless method is derived at the charge density levels by analyzing high-energy synchrotron-radiation powder-diffraction data. The characteristic features are revealed in terms of chemical bonding of the two types of Ti–O polyhedra with fivefold oxygen coordination: a trigonal-bipyramid-type Ti–O5 and a square-pyramid-type Ti–O5. We consider that the structures of metastable states observed in BaTi2O5, including the glass, are distinguished by the formation of the Ti–O5 trigonal bipyramid.
Self-Consistent Anharmonic Theory and Its Application to the Isotope Effect on Ferroelectric Phase Transition in BaTiO3 Crystal
Authors: Aikawa Yutaka , Sakashita Tatsuo , Suzuki Toshimasa
Published: September 2010

The isotope effect on ferroelectric phase transition is studied by the variational principle method using a self-consistent anharmonic model. A trial Hamiltonian was devised using the terms of the anharmonic oscillator and arbitrary potential energy between atoms. The isotope effects on BaTiO3 ferroelectric phase transition, especially on the cubic-to-tetragonal transition, are given through a function consisting of the optical phonon. It is revealed that a heavy-isotope-enriched crystal shows a lower T
C than a light-isotope crystal, which is in agreement with the experimental Ti-isotope effects in BaTiO3.
The geochemistry and petrography of the Coastal Batholith of Peru, Lima segment
Authors: Mccourt W.J.
Published: September 2010

SUMMARY: The Coastal Batholith of Peru, Lima segment, is a composite batholith made up of at least 8 time-separated magmatic events. The evolution of the batholith is such that the amount of granitic magma apparently increases with decreasing age, which is reflected in an overall basic to acid sequence of intrusion. High-level differentiation, involving plagioclase and hornblende as the major precipitating phases, is the prime cause of the chemical variation within each suite of rocks, all of which are distinguished by strong calc-alkaline character. The geochemical and petrographical evidence suggests that the batholith magmas were undersaturated with respect to water throughout most of their crystallization histories. Preliminary isotopic studies indicate that the parent magmas to individual super-units originated by partial melting, either in the mantle or in a crustal underplate zone.
Erythrocyte-dependent regulation of human skeletal muscle blood flow: role of varied oxyhemoglobin and exercise on nitrite, S-nitrosohemoglobin, and ATP
Authors: Dufour Stéphane P. , Patel Rakesh P. , Brandon Angela , Teng Xinjun , Pearson James , Barker Horace , Ali Leena , Yuen Ada H. Y. , Smolenski Ryszard T. , González-Alonso José
Published: September 2010

The erythrocyte is proposed to play a key role in the control of local tissue perfusion via three O2-dependent signaling mechanisms: 1) reduction of circulating nitrite to vasoactive NO, 2) S-nitrosohemoglobin (SNO-Hb)-dependent vasodilatation, and 3) release of the vasodilator and sympatholytic ATP; however, their relative roles in vivo remain unclear. Here we evaluated each mechanism to gain insight into their roles in the regulation of human skeletal muscle blood flow during hypoxia and hyperoxia at rest and during exercise. Arterial and femoral venous hemoglobin O2 saturation (O2Hb), plasma and erythrocyte NO and ATP metabolites, and leg and systemic hemodynamics were measured in 10 healthy males exposed to graded hypoxia, normoxia, and graded hyperoxia both at rest and during submaximal one-legged knee-extensor exercise. At rest, leg blood flow and NO and ATP metabolites in plasma and erythrocytes remained unchanged despite large alterations in O2Hb. During exercise, however, leg and systemic perfusion and vascular conductance increased in direct proportion to decreases in arterial and venous O2Hb ( r2 = 0.86–0.98; P = 0.01), decreases in venous plasma nitrite ( r2 = 0.93; P < 0.01), increases in venous erythrocyte nitroso species ( r2 = 0.74; P < 0.05), and to a lesser extent increases in erythrocyte SNO ( r2 = 0.59; P = 0.07). No relationship was observed with plasma ATP ( r2 = 0.01; P = 0.99) or its degradation compounds. These in vivo data indicate that, during low-intensity exercise and hypoxic stress, but not hypoxic stress alone, plasma nitrite consumption and formation of erythrocyte nitroso species are associated with limb vasodilatation and increased blood flow in the human skeletal muscle vasculature.
Activation of host tissue trophic factors through JAK-STAT3 signaling: a mechanism of mesenchymal stem cell-mediated cardiac repair
Authors: Shabbir Arsalan , Zisa David , Lin Huey , Mastri Michalis , Roloff Gregory , Suzuki Gen , Lee Techung
Published: September 2010

We recently demonstrated a cardiac therapeutic regimen based on injection of bone marrow mesenchymal stem cells (MSCs) into the skeletal muscle. Although the injected MSCs were trapped in the local musculature, the extracardiac cell delivery approach repaired the failing hamster heart. This finding uncovers a tissue repair mechanism mediated by trophic factors derived from the injected MSCs and local musculature that can be explored for minimally invasive stem cell therapy. However, the trophic factors involved in cardiac repair and their actions remain largely undefined. We demonstrate here a role of MSC-derived IL-6-type cytokines in cardiac repair through engagement of the skeletal muscle JAK-STAT3 axis. The MSC IL-6-type cytokines activated JAK-STAT3 signaling in cultured C2C12 skeletal myocytes and caused increased expression of the STAT3 target genes hepatocyte growth factor (HGF) and VEGF, which was inhibited by glycoprotein 130 (gp130) blockade. These in vitro findings were corroborated by in vivo studies, showing that the MSC-injected hamstrings exhibited activated JAK-STAT3 signaling and increased growth factor/cytokine production. Elevated host tissue growth factor levels were also detected in quadriceps, liver, and brain, suggesting a possible global trophic effect. Paracrine actions of these host tissue-derived factors activated the endogenous cardiac repair mechanisms in the diseased heart mediated by Akt, ERK, and JAK-STAT3. Administration of the cell-permeable JAK-STAT inhibitor WP1066 abrogated MSC-mediated host tissue growth factor expression and functional improvement. The study illustrates that the host tissue trophic factor network can be activated by MSC-mediated JAK-STAT3 signaling for tissue repair.
The role of collagen in extralobar pulmonary artery stiffening in response to hypoxia-induced pulmonary hypertension
Authors: Ooi Chen Yen , Wang Zhijie , Tabima Diana M. , Eickhoff Jens C. , Chesler Naomi C.
Published: September 2010

Hypoxic pulmonary hypertension (HPH) causes extralobar pulmonary artery (PA) stiffening, which potentially impairs right ventricular systolic function. Changes in the extracellular matrix proteins collagen and elastin have been suggested to contribute to this arterial stiffening. We hypothesized that vascular collagen accumulation is a major cause of extralobar PA stiffening in HPH and tested our hypothesis with transgenic mice that synthesize collagen type I resistant to collagenase degradation (Col1a1R/R). These mice and littermate controls that have normal collagen degradation (Col1a1+/+) were exposed to hypoxia for 10 days; some were allowed to recover for 32 days. In vivo PA pressure and isolated PA mechanical properties and collagen and elastin content were measured for all groups. Vasoactive studies were also performed with U-46619, Y-27632, or calcium- and magnesium-free medium. Pulmonary hypertension occurred in both mouse strains due to chronic hypoxia and resolved with recovery. HPH caused significant PA mechanical changes in both mouse strains: circumferential stretch decreased, and mid-to-high-strain circumferential elastic modulus increased ( P < 0.05 for both). Impaired collagen type I degradation prevented a return to baseline mechanical properties with recovery and, in fact, led to an increase in the low and mid-to-high-strain moduli compared with hypoxia ( P < 0.05 for both). Significant changes in collagen content were found, which tended to follow changes in mid-to-high-strain elastic modulus. No significant changes in elastin content or vasoactivity were observed. Our results demonstrate that collagen content is important to extralobar PA stiffening caused by chronic hypoxia.