bluuebunny/crossref_metadata_2025 huggingface dataset:
A PHENOMENOLOGICAL MONTE CARLO SIMULATION OF A TWO-STEP DIMER/MONOMER SURFACE REACTION
Authors: KRIM L. , BOUFERGUENE A. , HOGGAN P. E. , HAMMOUTENE D.
Published: August 2011

In the past few years stochastic models have been extensively used to describe the adsorption and reaction of molecules on metallic surfaces. One such model was due to Ziff, Gulari and Barshad (ZGB) which despite its simplicity was able to capture some important features of surface reactions such as steady state, phase transition and surface poisoning. However, in all the contributions that used the ZGB model the reactants were assumed to occupy similar sites on the metallic surface. The intent of this contribution is to investigate a more complicated two-step monomer/dimer model reaction of the form A2 + B → (AB)ads + B → A2B in which the reacting species adsorb on distinct sites on the metallic surface, e.g. four-fold hollow- and bridge-bonding. In this context, it was found that the lack of correlation between surface concentrations leads to a dramatic breakdown of the site approximation which did not occur when only equivalent surface sites are used.
LIFESPAN ESTIMATES FOR SOLUTIONS OF POLYHARMONIC KIRCHHOFF SYSTEMS
Authors: AUTUORI GIUSEPPINA , COLASUONNO FRANCESCA , PUCCI PATRIZIA
Published: August 2011

In mathematical physics we increasingly encounter PDEs models connected with vibration problems for elastic bodies and deformation processes, as it happens in the Kirchhoff–Love theory for thin plates subjected to forces and moments. Recently Monneanu proved in Refs. 26 and 27 the existence of a solution of the nonlinear Kirchhoff–Love plate model. In this paper we treat several questions about non-continuation for maximal solutions of polyharmonic Kirchhoff systems, governed by time-dependent nonlinear dissipative and driving forces. In particular, we are interested in the strongly damped Kirchhoff–Love model, containing also an intrinsic dissipative term of Kelvin–Voigt type. Global non-existence and a priori estimates for the lifespan of maximal solutions are proved. Several applications are also presented in special subcases of the source term f and the nonlinear external damping Q.
ANALYSIS ON FRACTALS IN FUZZY METRIC SPACES
Authors: EASWARAMOORTHY D. , UTHAYAKUMAR R.
Published: August 2011

In this paper, we investigate the fractals generated by the iterated function system of fuzzy contractions in the fuzzy metric spaces by generalizing the Hutchinson-Barnsley theory. We prove some existence and uniqueness theorems of fractals in the standard fuzzy metric spaces by using the fuzzy Banach contraction theorem. In addition to that, we discuss some results on fuzzy fractals such as Collage Theorem and Falling Leaves Theorem in the standard fuzzy metric spaces with respect to the standard Hausdorff fuzzy metrics.
A Fuzzy Ontology-Based Semantic Data Integration System
Authors: Yaguinuma Cristiane A. , Afonso Gustavo F. , Ferraz Vinícius , Borges Sérgio , Santos Marilde T. P.
Published: August 2011

Data integration becomes even more necessary given the increasing availability of data from distributed and heterogeneous sources. To address such heterogeneity, crisp ontologies have been employed in order to represent the semantics of integrated data. However, it is interesting to use fuzzy logic concepts in these ontologies for a more expressive representation of vague information relevant to some domains. In this context, this paper presents DISFOQuE system for data integration based on fuzzy ontology, which provides a homogeneous view of data sources and also performs query expansions in order to retrieve more comprehensive answers for the user. We have executed a real experiment in the domain of watershed analysis, which provided a homogeneous view of the watershed data sources and more effective answers to researchers.
ALTERNATIVE DECOMPOSITION OF TWO-QUTRIT PURE STATES AND ITS RELATION WITH ENTANGLEMENT INVARIANTS
Authors: GU RUI-JUAN , ZHANG FU-LIN , FEI SHAO-MING , CHEN JING-LING
Published: August 2011

Based on maximally entangled states in the full- and sub-spaces of two-qutrits, we present an alternative decomposition of two-qutrit pure states in a form [Formula: see text]. Similar to the Schmidt decomposition, all two-qutrit pure states can be transformed into the alternative decomposition under local unitary transformations, and the parameter p1 is shown to be an entanglement invariant.
Novel Ring Protection Architecture for Fiber Sensor System
Authors: Peng Peng-Chun , Chen Jing-Fu , Sun Jen-Wei
Published: August 2011

We develop a novel ring protection architecture for fiber sensor systems. The architecture can perform a reconfigurable function under fiber link failure. Such a reconfigurable function is realized using a ring topology and remote nodes. A linear cavity fiber laser is applied in this network to increase the signal-to-noise ratio of the entire system. The experimental results reveal the feasibility of the proposed architecture. The architecture increases the reliability and capacity of the fiber sensor system.
Surface Structural and Magnetic Properties of Cobalt Bilayer Deposited on Pt(111) with Ni Buffer Layer
Authors: Ho Huei-Ying , Shern Ching-Song
Published: August 2011

A cobalt bilayer film was deposited on a monolayer (ML) Ni/Pt(111) surface at room temperature. The dependencies of the structural and magnetic properties of the surface on the annealing temperature were investigated. During the annealing, it was found that the formation of Co–Ni alloy occurs before the formation of Co–Ni–Pt alloy. After high-temperature annealing, the surface consisted of Co–Ni–Pt alloys with a Pt-rich phase. We found that the perpendicular magnetic anisotropy (PMA) contribution of the Co–Ni–Pt alloy at the surface was greater than that of the Co–Pt alloy below. The ultraviolet photoelectron spectrum (UPS) of the 2 ML Co/1 ML Ni/Pt(111) system showed a redistribution of electron density on the surface after annealing. The UPS peak height near the Fermi edge was mostly dependent on the surface composition. However, the change in the work function was not dependent on the PMA after high-temperature annealing. The strength of the PMA of this system can be tuned to a desired level by annealing without affecting the work function.
Study of the Effect of Volume Fraction Concentration and Particle Materials on Thermal Conductivity and Thermal Diffusivity of Nanofluids
Authors: Ali Faris Mohammed , Yunus W. Mahmood Mat
Published: August 2011

Nanofluids, a mixture of nanoparticles and fluids, have exceptional potential to improve their effective thermal conductivity and thermal diffusivity, aluminum and aluminum oxide nanofluids with five different volume fractions of nanoparticle suspensions in different base fluids, i.e., distilled water, ethylene glycol (EG), and ethanol were prepared by mixing nanopowder and base fluids. Sonication with high-powered pulses was used to ensure the dispersion of nanoparticles in good uniformity in the base fluids. The hot wire-laser beam displacement technique was used to measure thermal conductivity and thermal diffusivity of the prepared nanofluids. The effects of the volume fraction concentration and particle materials on the thermal conductivity and thermal diffusivity of nanofluids were determined. The results showed that the thermal conductivity and thermal diffusivity increased linearly with increasing volume fraction concentration of nanoparticles in the respective base fluids. In addition, the thermal conductivity and thermal diffusivity increased faster in the Al2O3 nanofluids than in all the three base fluids.
Schottky-Barrier-Induced AC Surface Photovoltages in Au-Precipitated n-Type Si(001) Surfaces
Authors: Shimizu Hirofumi , Sanada Yuji
Published: August 2011

We have studied the behavior of Au clusters on the top surface of a SiO2film and/or at the SiO2/Si interface as a function of oxidation temperature between room temperature (RT) and 500 °C in conjunction with a Schottky-barrier-induced AC surface photovoltage (SPV) and an enhanced SiO2growth due to Au at 500 °C. Upon rinsing an n-type Si(001) wafer in a Au-contaminated aqueous solution, precipitated Au atoms are observed as clusterlike Au granules on the top surface of SiO2(Au surface concentration, 2.3 ×1015atoms/cm2). In thermally oxidized Au-contaminated n-type Si(001) wafers between 100 and 500 °C, a Au cluster of a similar shape is also observed. Chemical analysis gives evidence that Au existed at the SiO2/Si interface, which produced Au/n-Si Schottky-barrier-type AC SPV between 100 and 500 °C as well as at both RT and higher temperatures, indicating that the Au/n-Si Schottky barrier remains in a similar manner. In the Au-contaminated n-Si thermally oxidized at 500 °C, the catalytic action of Au atoms enhances SiO2growth as well as the case at high temperatures between 750 and 900 °C. The mechanism of the enhanced growth is proposed.
Improvement of Photoelectrochemical Properties by Surface Modification with Iron Oxide on p-Type Si Electrodes for Hydrogen Evolution from Water
Authors: Lu Xuwang , Minegishi Tsutomu , Kubota Jun , Domen Kazunari
Published: August 2011

Surface modifications using platinum (Pt) particles and iron oxides (FeO
x
) were found to lead to a significant improvement in the current–potential (J–E) properties for hydrogen evolution from water in p-type silicon (p-Si) electrodes. The onset potential and cathodic photocurrent for hydrogen evolution from the Pt/p-Si(100) electrode were, respectively, 0.50 VRHE and 0.28 mA/cm2 at 0 VRHE (RHE: reversible hydrogen electrode). When the p-Si(100) electrode was coated with iron oxide followed by Pt particles [Pt/FeO
x
/p-Si(100)], it showed an onset potential and photocurrent of 0.85 VRHE and 2.45 mA/cm2 at 0 VRHE, respectively. A detailed study of surface morphology and a comparative study between (100) plane and (111) plane p-Si electrodes revealed that the dramatic improvement in J–E properties was the result of a change in the surface structure and tailing of FeO
x
in p-Si.
Two-Dimensional Patterning of Inorganic Particles in Resin Using Ultrasound-Induced Plate Vibration
Authors: Tuziuti Toru , Masuda Yoshitake , Yasui Kyuichi , Kato Kazumi
Published: August 2011

The fabrication of a two-dimensional millimeter-sized pattern of micrometer-sized titanium dioxide particles in UV-reactive acrylic resin using 1.93 MHz ultrasound is demonstrated. A mixture of particles and resin is set in a thin layer between square glass plates of which one plate is irradiated with ultrasound. Both vibration normal to the plate and the wave propagating in the mixture form standing waves to provide a two-dimensional pattern of the particles. Scanning electron microscopy and X-ray diffraction analysis of the UV-hardened pattern indicate that the titanium dioxide particles are embedded in the resin.
Effect of Dispersing Ag Micro Particles on Enhancing Surface Potential of CYTOP Electret Film
Authors: Takahashi Tomokazu , Suzuki Masato , Hirata Tetsuya , Aoyagi Seiji
Published: August 2011

Polymer CYTOP is known as a good electret material that traps electrons semipermanently. It realizes a high surface potential, making it possible to be used for a micro power generator recently besides a microphone. We note that electrons are liable to be trapped at the interface between different materials. Ag micro particles are dispersed inside a CYTOP film for making interfaces. As a result, a surface potential that is two times higher than that of a pure film was experimentally achieved. The film preparation, the electron charging method, and the charge holding property are also reported.
Estimations of Electron Temperature and Electron Density in Argon-Containing Reactive Plasma Based on Diode Laser Absorption Spectroscopy
Authors: Sasaki Koichi , Asaoka Ryota
Published: August 2011

We propose an optical method for estimating both the electron temperature and the electron density in an argon-containing reactive plasma. This method is based on density measurements of the two metastable states of argon in the plasma. Diode laser absorption spectroscopy is utilized for measuring the metastable densities. A population-kinetics model is used for finding the electron temperature and the electron density for which the measured densities of the metastable states are realized. This method has a potential application for thein-situmonitoring of plasma processing tools in factories because of the low cost, small footprint, and maintenance-free operation of a diode laser. We demonstrated this method in an inductively coupled Ar/N2mixture plasma.
Spatial Diagnostics of Hg/Ar and Hg/Xe Discharge Lamps by Means of Tomography
Authors: Denisova Natalia , Revalde Gita , Skudra Atis , Skudra Janis
Published: August 2011

In this work, the diagnostics using tomography in Hg/Xe and Hg/Ar capillary lamps is presented. First, the imaging of the lamps was performed using selected emission lines of mercury, argon and xenon in different operation conditions. Thus the tomographic reconstruction was made, to determine the spatial distribution of the emitting Hg and rare gas atoms. Significant differences of the distribution of the emitting atoms have been found in vertical and horizontal operation positions. The emitting mercury atoms in the state 73S1 were differently distributed within the lamp in the vertical and horizontal lamp positions. The radial profile has demonstrated a substantial depletion of the population density from the lamp centre in the vertical operating position, whereas the profile had a flat top shape in the horizontally operating lamp. A theoretical hypothesis is proposed to explain the observed phenomenon. Strong inhomogeneous structure of the argon atom distribution was found as well.
Particle Simulations of Sheath Dynamics in Low-Pressure Capacitively Coupled Argon Plasma Discharges
Authors: Takao Yoshinori , Matsuoka Kenji , Eriguchi Koji , Ono Kouichi
Published: August 2011

A numerical study of low-pressure capacitively coupled plasma (CCP) discharges in Ar has been performed including the transport of ions in a sheath onto a substrate. We employ a two-dimensional axisymmetric particle-in-cell with a Monte Carlo collision (PIC-MCC) method for an asymmetric capacitive discharge with an external electrical circuit containing a blocking capacitor and an rf power supply. The PIC-MCC results show that for the gas pressure (5–100 mTorr), rf voltage (50–500 V), and frequency (6.78–40.68 MHz) ranges examined for a single-frequency CCP, the peak plasma density increases linearly with gas pressure, rf voltage, and frequency squared. With a decrease in pressure or increases in plasma density and sheath potential, the sheath becomes less collisional and thus significant peaks at high energies of ion energy distributions appear and narrow ion angular distributions are obtained. The tendency is in a reasonable agreement with experimental results.
New Simulation Approach to Controlling Plasma Uniformities
Authors: Tsuji Akihiro , Yasaka Yasuyoshi
Published: August 2011

Plasma simulations have never been used for tool tuning in the field of semiconductor manufacturing because existing plasma simulations cannot inversely calculate input parameters such as power and gas distributions from output parameters such as the distribution of electron densityne. One of the solutions is to reconstruct the framework of simulations as an inverse problem. A new simulation system has been developed as the first step. It has two key points. One is to introduce a power coupling coefficientapas an index of the tool tuning, and the other is to add some functions to inversely calculateapfrom the targetnedistribution. In the verification of a two-dimensional model, it is shown that the error between the distribution ofnecalculated by a check simulation and the target is sufficiently small. Therefore, this approach can be one of the solutions to control plasma uniformities.
Temperature-Dependent Current-Induced Magnetization Switching in Fe3Si/FeSi2/Fe3Si Trilayered Films
Authors: Hirakawa Shin-ichi , Sonoda Takayuki , Sakai Ken-ichiro , Takeda Kaoru , Yoshitake Tsuyoshi
Published: August 2011

Fe3Si/FeSi2/Fe3Si trilayered films were grown on Si(111) substrates at a substrate temperature of 300 °C by facing-targets direct-current sputtering, and current-induced magnetization switching in current-perpendicular-to-plane geometry was studied for the films wherein an antiferromagnetic interlayer coupling perpendicular to the plane was probably formed at room temperature. The appearance of a hysteresis loop in the electrical resistance–injection current curve well coincided with that of a hysteresis loop in the magnetization curve perpendicular to the plane. In addition, the hysteresis loop in the electrical resistance–injection current curve disappeared under large magnetic fields. The origin of the change in the electrical resistance for the injection current might be the change in the interlayer coupling.
Deposition of MgF2 Thin Films by Pulsed Laser Ablation Technique
Authors: Lorusso Antonella , Gontad Francisco , Perrone Alessio
Published: August 2011

In this paper, we report the successful growth of MgF2 thin films on Si and sapphire (Al2O3) substrates at room temperature by direct laser ablation of a pure MgF2 target. The irradiations were performed in high vacuum (10-5 Pa) using the fourth harmonic of a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (λ= 266 nm, τFWHM = 7 ns) with energy density of about 10 J/cm2. Uniform films, with a good adhesion on the substrate were obtained. The average ablation and deposition rates resulted to be 1.1 µg/pulse and 0.03 Å/pulse, respectively. Different diagnostic techniques were used to study the morphology and chemical composition of deposited films. Time-resolved mass spectrometry studies of the laser ablated material indicate a strong correlation between the chemical species present in the plume and the residual gas. Present interest in the deposition of MgF2 thin films by laser ablation technique is related to their potential application as protecting coating in photocathodes.
Addition of Si-Containing Gases for Anisotropic Etching of III–V Materials in Chlorine-Based Inductively Coupled Plasma
Authors: Gatilova Lina , Bouchoule Sophie , Patriarche Gilles , Guilet Stephane
Published: August 2011

We discuss the possibility of obtaining high-aspect-ratio etching of InP materials in Cl2- and HBr-based inductively coupled plasmas (ICP) with the addition of Si-containing gases (SiH4or SiCl4). A vertical and smooth etching profile is demonstrated in SiCl4/H2plasma. The effect of adding of a small amount of SiH4to a previously optimised Cl2/H2chemistry is presented, and new SiH4/Cl2and SiH4/HBr chemistries are proposed.Ex-situenergy-dispersive X-ray spectroscopy coupled to transmission electron microscopy (EDX–TEM) is used to analyze the composition of the thin passivation layer deposited on the etched sidewalls. We show that it consists of a Si-rich silicon oxide (Si/O∼1) in Cl2/H2/SiH4chemistry, and is changed to nano-crystalline (nc-) Si in SiH4/Cl2chemistry depending on the SiH4percentage. Moreover, we show that deep anisotropic etching of InP independent of the electrode coverplate material can be obtained via a SiOxpassivation mechanism with the addition of Si-containing gases.
Development of Nanostructured Black Metal by Self-Growing Helium Bubbles for Optical Application
Authors: Kajita Shin , Saeki Tsubasa , Hirahata Yuki , Yajima Miyuki , Ohno Noriyasu , Yoshihara Reiko , Yoshida Naoaki
Published: August 2011

When tungsten is exposed to a helium plasma under specific conditions, fiberform nanostructures grow from the surface, and optical properties significantly alter. It is shown that the optical absorptivity increases significantly by the helium irradiation from visible to near-infrared wavelength range. The optical absorptivity became almost 100% from visible to near infrared wavelength range after the nanostructure was formed on the surface. The result indicates that the emissivity of radiation in visible and near infrared wavelength range also increases significantly by the helium irradiation. The emissivity around 1550 nm is 4.4 times higher than the initial value, while it is twice at the visible wavelength range. The helium fluence dependences of the specular and total optical reflectances and the morphology change observed by transmission electron microscope (TEM) are revealed.
SiNx Double Layer Antireflection Coating by Plasma-Enhanced Chemical Vapor Deposition for Single Crystalline Silicon Solar Cells
Authors: Gong Daeyeong , Lee Youn-Jung , Ju Minkyu , Ko Jisoo , Yang Doohwan , Lee Yongwoo , Choi Gyuho , Kim Sin , Yoo Jinsu , Choi Byoungdeog , Yi Junsin
Published: August 2011

Double layer antireflection (DLAR) coatings have significant advantages over single-layer antireflection (SLAR) coatings owing to their coverage of a broad solar spectral range. In this study, the properties of SiN
x
are examined. DLAR coatings using two thin films of SiN
x
with different refractive indices are presented. Using the same materials is more cost-effective than using different materials. The total thickness of SiN
x
/SiN
x
films is kept at 80 nm. The top SiN
x
film has a refractive index of 1.9, while the bottom layer has a refractive index of 2.3. Single crystalline solar cells are fabricated with different thicknesses for the top and bottom layers. The solar cell with 60 nm/20 nm SiN
x
DLAR coatings has 18.3% efficiency, while that with 80 nm SiN
x
SLAR coating has 17.6% efficiency. The improvement of efficiency is due to the effect of better passivation and better antireflection of DLAR.
Reactive Sputter Deposition of SiOxNy Films under Ar–CO2–N2 Atmosphere
Authors: Ashida Toru , Omoto Hideo , Tomioka Takao , Takamatsu Atsushi
Published: August 2011

Amorphous SiO
x
N
y
films were deposited by pulsed-dc reactive magnetron sputtering using a boron-doped Si target under Ar–CO2–N2 atmosphere. The refractive index (n) varied continuously between 1.54 and 2.0 with the CO2 flow ratio [CO2/(CO2+ N2)], maintaining a high transparency in the visible range. Furthermore, the variations in the cathode voltage and deposition rate revealed that the target surface was progressively oxidized with increasing CO2 flow ratio. Thus, the films deposited with the CO2 gas exhibited a gradual n shift and a high deposition rate as compared with that deposited with the O2 gas. On the other hand, these films had the typical composition and structure of SiO
x
N
y
films prepared by reactive sputtering. These results indicate that the CO2 gas is an effective reactive gas for controlling the n of the SiO
x
N
y
films.
Photoassisted Kelvin Probe Force Microscopy on Multicrystalline Si Solar Cell Materials
Authors: Takahashi Takuji
Published: August 2011

A multicrystalline Si solar cell material has been investigated through photovoltaic measurements by photoassisted Kelvin probe force microscopy (P-KFM). Photovoltage distributions mapped by P-KFM exhibited an abrupt change in photovoltage near the Σ3 grain boundary, and those distributions are well related to intrinsic surface potential profiles. In addition, the diffusion length and lifetime of minority carriers were evaluated from the dependence of photovoltage on incident light wavelength and from the temporally averaged photovoltage as a function of modulation frequency, respectively, indicating the reductions in both minority carrier diffusion length and lifetime around the grain boundary. Those results strongly suggest that the grain boundary in the multicrystalline Si material acts as a carrier recombination site and/or a leakage path, which may degrade the overall solar cell performance.
Nanometer-Scale Deposition of Metal Plating Using a Nanopipette Probe in Liquid Condition
Authors: Ito So , Iwata Futoshi
Published: August 2011

We describe a novel technique of a local metal plating using an atomic force microscope (AFM) with a nanopipette probe in liquid condition. A glass nanopipette, filled with CuSO4 electrolyte solution, was used as the AFM probe. An electrode wire inside the electrolyte-filled nanopipette and the conductive surface of a Au-sputtered glass slide were employed as the anode and the cathode, respectively. To avoid drying of the nanopipette solution and clogging of the probe-edge aperture, the edge of the nanopipette was immersed in the same electrolyte solution in a liquid cell placed on the Au substrate. As for controlling the distance between the probe edge and the surface in the liquid, the nanopipette probe glued on a tuning fork quartz crystal resonator was vertically oscillated to use a method of frequency modulation in tapping-mode. By utilizing the probe–surface distance control during the deposition, nanometer-scale Cu dots were successfully deposited on the Au surfaces without diffusion of the deposition even in the liquid condition. This technique of local deposition in a liquid would be applicable for various fields such as the fabrication of micro/nanometer-scale devices and the arrangement of biological samples.
Tissue length modulates “stimulated actin polymerization,” force augmentation, and the rate of swine carotid arterial contraction
Authors: Tejani Ankit D. , Walsh Michael P. , Rembold Christopher M.
Published: August 2011

“Stimulated actin polymerization” has been proposed to be involved in force augmentation, in which prior submaximal activation of vascular smooth muscle increases the force of a subsequent maximal contraction by ∼15%. In this study, we altered stimulated actin polymerization by adjusting tissue length and then measured the effect on force augmentation. At optimal tissue length (1.0 Lo), force augmentation was observed and was associated with increased prior stimulated actin polymerization, as evidenced by increased prior Y118 paxillin phosphorylation without changes in prior S3 cofilin or cross-bridge phosphorylation. Tissue length, per se, regulated Y118 paxillin, but not S3 cofilin, phosphorylation. At short tissue length (0.6 Lo), force augmentation was observed and was associated with increased prior stimulated actin polymerization, as evidenced by reduced prior S3 cofilin phosphorylation without changes in Y118 paxillin or cross-bridge phosphorylation. At long tissue length (1.4 Lo), force augmentation was not observed, and there were no prior changes in Y118 paxillin, S3 cofilin, or cross-bridge phosphorylation. There were no significant differences in the cross-bridge phosphorylation transients before and after the force augmentation protocol at all three lengths tested. Tissues contracted faster at longer tissue lengths; contractile rate correlated with prior Y118 paxillin phosphorylation. Total stress, per se, predicted Y118 paxillin phosphorylation. These data suggest that force augmentation is regulated by stimulated actin polymerization and that stimulated actin polymerization is regulated by total arterial stress. We suggest that K+ depolarization first leads to cross-bridge phosphorylation and contraction, and the contraction-induced increase in mechanical strain increases Y118 paxillin phosphorylation, leading to stimulated actin polymerization, which further increases force, i.e., force augmentation and, possibly, latch.
Growth factor regulation of neural chemorepellent Sema3A expression in satellite cell cultures
Authors: Do Mai-Khoi Q. , Sato Yusuke , Shimizu Naomi , Suzuki Takahiro , Shono Jun-ichi , Mizunoya Wataru , Nakamura Mako , Ikeuchi Yoshihide , Anderson Judy E. , Tatsumi Ryuichi
Published: August 2011

Successful regeneration and remodeling of the intramuscular motoneuron network and neuromuscular connections are critical for restoring skeletal muscle function and physiological properties. The regulatory signals of such coordination remain unclear, although axon-guidance molecules may be involved. Recently, satellite cells, resident myogenic stem cells positioned beneath the basal lamina and at high density at the myoneural junction regions of mature fibers, were shown to upregulate a secreted neural chemorepellent semaphorin 3A (Sema3A) in response to in vivo muscle-crush injury. The initial report on that expression centered on the observation that hepatocyte growth factor (HGF), an essential cue in muscle fiber growth and regeneration, remarkably upregulates Sema3A expression in early differentiated satellite cells in vitro [Tatsumi et al., Am J Physiol Cell Physiol 297: C238–C252, 2009]. Here, we address regulatory effects of basic fibroblast growth factor (FGF2) and transforming growth factor (TGF)-βs on Sema3A expression in satellite cell cultures. When treated with FGF2, Sema3A message and protein were upregulated as revealed by reverse transcription-polymerase chain reaction and immunochemical studies. Sema3A upregulation by FGF2 was dose dependent with a maximum (8- to 1-fold relative to the control) at 2.5 ng/ml (150 pM) and occurred exclusively at the early differentiation stage. The response was highly comparable in dose response and timing to effects of HGF treatment, without any additive or synergistic effect from treatment with a combination of both potent upregulators. In contrast, TGF-β2 and -β3 potently decreased basal Sema3A expression; the maximum effect was at very low concentrations (40 and 8 pM, respectively) and completely cancelled the activities of FGF2 and HGF to upregulate Sema3A. These results therefore encourage the prospect that a time-coordinated increase in HGF, FGF2, and TGF-β ligands and their receptors promotes a programmed strategy for Sema3A expression that guarantees successful intramuscular motor reinnervation by delaying sprouting and reattachment of motoneuron terminals onto damaged muscle fibers early in regeneration pending restoration of muscle fiber contractile integrity.
Truncated IRAG variants modulate cGMP-mediated inhibition of human colonic smooth muscle cell contraction
Authors: Werder Alexander von , Mayr Martina , Schneider Günter , Oesterle Daniela , Fritsch Ralph M. , Seidler Barbara , Schlossmann Jens , Hofmann Franz , Schemann Michael , Allescher Hans D. , Schmid Roland M. , Saur Dieter
Published: August 2011

Nitric oxide (NO) induces relaxation of colonic smooth muscle cells predominantly by cGMP/cGMP-dependent protein kinase I (cGKI)-induced phosphorylation of the inositol 1,4,5-trisphosphate receptor (IP3R)-associated cGMP kinase substrate (IRAG), to block store-dependent calcium signaling. In the present study we analyzed the structure and function of the human IRAG/MRVI1 gene. We describe four unique first exon variants transcribed from individual promoters in diverse human tissues. Tissue-specific alternative splicing with exon skipping and alternative splice donor and acceptor site usage further increases diversity of IRAG mRNA variants that encode for NH2- and COOH-terminally truncated proteins. At the functional level, COOH-terminally truncated IRAG variants lacking both the cGKI phosphorylation and the IP3RI interaction site counteract cGMP-mediated inhibition of calcium transients and relaxation of human colonic smooth muscle cells. Since COOH-terminally truncated IRAG mRNA isoforms are widely expressed in human tissues, our results point to an important role of IRAG variants as negative modulators of nitric oxide/cGKI-dependent signaling. The complexity of alternative splicing of the IRAG gene impressively demonstrates how posttranscriptional processing generates functionally distinct proteins from a single gene.
G protein-coupled estrogen receptor 1-mediated effects in the rat myometrium
Authors: Tica Andrei A. , Dun Erica C. , Tica Oana S. , Gao Xin , Arterburn Jeffrey B. , Brailoiu G. Cristina , Oprea Tudor I. , Brailoiu Eugen
Published: August 2011

G protein-coupled estrogen receptor 1 (GPER), also named GPR30, has been previously identified in the female reproductive system. In this study, GPER expression was found in the female rat myometrium by reverse transcriptase-polymerase chain reaction and immunocytochemistry. Using GPER-selective ligands, we assessed the effects of the GPER activation on resting membrane potential and cytosolic Ca2+ concentration ([Ca2+]i) in rat myometrial cells, as well as on contractility of rat uterine strips. G-1, a specific GPER agonist, induced a concentration-dependent depolarization and increase in [Ca2+]i in myometrial cells. The depolarization was abolished in Na+-free saline. G-1-induced [Ca2+]i increase was markedly decreased by nifedipine, a L-type Ca2+ channel blocker, by Ca2+-free or Na+-free saline. Intracellular administration of G-1 produced a faster and transitory increase in [Ca2+]i, with a higher amplitude than that induced by extracellular application, supporting an intracellular localization of the functional GPER in myometrial cells. Depletion of internal Ca2+ stores with thapsigargin produced a robust store-activated Ca2+ entry; the Ca2+ response to G-1 was similar to the constitutive Ca2+ entry and did not seem to involve store-operated Ca2+ entry. In rat uterine strips, administration of G-1 increased the frequency and amplitude of contractions and the area under the contractility curve. The effects of G-1 on membrane potential, [Ca2+]i, and uterine contractility were prevented by pretreatment with G-15, a GPER antagonist, further supporting the involvement of GPER in these responses. Taken together, our results indicate that GPER is expressed and functional in rat myometrium. GPER activation produces depolarization, elevates [Ca2+]i and increases contractility in myometrial cells.
Mast cells function as an alternative modulator of adipogenesis through 15-deoxy-delta-12, 14-prostaglandin J2
Authors: Tanaka Akane , Nomura Yoshihiro , Matsuda Akira , Ohmori Keitaro , Matsuda Hiroshi
Published: August 2011

Mast cells are one of the major producers of prostaglandins (PGs). The final metabolite of PGs 15-deoxy-delta-12,14-PGJ2 (15-deoxy-delta PGJ2) is the endogenous ligand of the peroxisome proliferator-activated receptor (PPAR) γ. PPARγ modulates adipocyte differentiation; therefore, we attempted to investigate whether PGs derived from mast cells influenced on adipogenesis. We found the increase of mast cell numbers in fat tissue of obese mice fed with a high-fat diet allowed us to speculate contributions of mast cells to adipogenesis. Mast cell-mediated induction of adipogenesis was evaluated by using 3T3 L1 cells. Supernatants obtained from mast cells stimulated with calcium ionophore or the high-glucose condition contained 15-deoxy-delta PGJ2 and induced adipogenesis of 3T3 L1 cells. Agonistic activity of PGJ2 from the supernatants on PPARγ was confirmed by a reporter gene assay. Culture medium collected from calcium ionophore-stimulated bone marrow-derived cultured mast cells (BMCMC) activated PPAR-responsive element in NIH3T3 fibroblasts, and the specific inhibitor of PPARγ canceled the activation. Contribution of mast cells to obesity was evaluated by using mast cell-deficient mice fed with a Western diet. Weight gain of mast cell-deficient mice during high-fat feeding was impaired compared with their littermate wild-type mice; on the other hand, transplantation of bone marrow-derived cultured mast cells to mast cell-deficient mice restored the weight gain by intake of a high-fat diet. In this study, we clearly demonstrated that mast cells produced PGs in response to the high-glucose condition and induced adipocyte differentiation and possibly obesity. This is the first study that provides evidence for a novel role of mast cells in adipogenesis via PPARγ activation.
MicroRNA-1 transfected embryonic stem cells enhance cardiac myocyte differentiation and inhibit apoptosis by modulating the PTEN/Akt pathway in the infarcted heart
Authors: Glass Carley , Singla Dinender K.
Published: August 2011

microRNAs (miRs) have emerged as critical modulators of various physiological processes including stem cell differentiation. Indeed, miR-1 has been reported to play an integral role in the regulation of cardiac muscle progenitor cell differentiation. However, whether overexpression of miR-1 in embryonic stem (ES) cells (miR-1-ES cells) will enhance cardiac myocyte differentiation following transplantation into the infarcted myocardium is unknown. In the present study, myocardial infarction (MI) was produced in C57BL/6 mice by left anterior descending artery ligation. miR-1-ES cells, ES cells, or culture medium (control) was transplanted into the border zone of the infarcted heart, and 2 wk post-MI, cardiac myocyte differentiation, adverse ventricular remodeling, and cardiac function were assessed. We provide evidence demonstrating enhanced cardiac myocyte commitment of transplanted miR-1-ES cells in the mouse infarcted heart as compared with ES cells. Assessment of apoptosis revealed that overexpression of miR-1 in transplanted ES cells protected host myocardium from MI-induced apoptosis through activation of p-AKT and inhibition of caspase-3, phosphatase and tensin homolog, and superoxide production. A significant reduction in interstitial and vascular fibrosis was quantified in miR-1-ES cell and ES cell transplanted groups compared with control MI. However, no statistical significance between miR-1-ES cell and ES cell groups was observed. Finally, mice receiving miR-1-ES cell transplantation post-MI had significantly improved heart function compared with respective controls ( P < 0.05). Our data suggest miR-1 drives cardiac myocyte differentiation from transplanted ES cells and inhibits apoptosis post-MI, ultimately giving rise to enhanced cardiac repair, regeneration, and function.
Ca2+ sensitization of cardiac myofilament proteins contributes to exercise training-enhanced myocardial function in a porcine model of chronic occlusion
Authors: Sarin Vandana , Muthuchamy Mariappan , Heaps Cristine L.
Published: August 2011

Exercise training has been shown to improve cardiac dysfunction in both patients and animal models of coronary artery disease; however, the underlying cellular and molecular mechanisms have not been completely understood. We hypothesized that exercise training would improve force generation in the myocardium distal to chronic coronary artery occlusion via altered intracellular Ca2+ concentration ([Ca2+]i) cycling and/or Ca2+ sensitization of myofilaments. Ameroid occluders were surgically placed around the proximal left circumflex coronary artery of adult female Yucatan pigs. Twenty-two weeks postoperatively, the myocardium was isolated from nonoccluded (left anterior descending artery dependent) and collateral-dependent (formerly left circumflex coronary artery dependent) regions of sedentary (pen confined) and exercise-trained (treadmill run, 5 days/wk for 14 wk) pigs. Force measurements in myocardial strips showed that the percent change in force at stimulation frequencies of 3 and 4 Hz relative to 1 Hz was significantly higher in exercise-trained pigs compared with sedentary pigs. β-Adrenergic stimulation with dobutamine significantly improved force kinetics in myocardial strips of sedentary but not exercise-trained pigs at 1 Hz. Additionally, time to peak and half-decay of intracellular Ca2+ (340-to-380-nm fluoresence ratio) responses at 1 Hz were significantly decreased in the collateral-dependent region of exercise-trained pigs with no difference in peak [Ca2+]i between groups. Furthermore, the skinned myocardium from exercise-trained pigs showed an increase in Ca2+ sensitivity compared with sedentary pigs. Immunoblot analysis revealed that the relative levels of cardiac troponin T and β1-adrenergic receptors were decreased in hearts from exercise-trained pigs independent of occlusion. Also, the ratio of phosphorylated to total myosin light chain-2, basal phosphorylation levels of cardiac troponin I (Ser23 and Ser24), and cardiac myosin binding protein-C (Ser282) were unaltered by occlusion or exercise training. Thus, our data demonstrate that exercise training-enhanced force generation in the nonoccluded and collateral-dependent myocardium was associated with improved Ca2+ transients, increased Ca2+ sensitization of myofilament proteins, and decreased expression levels of β1-adrenergic receptors and cardiac troponin T.
Transactivated EGFR mediates α1-AR-induced STAT3 activation and cardiac hypertrophy
Authors: Li Yan , Zhang Hui , Liao Wenqiang , Song Yao , Ma Xiaowei , Chen Chao , Lu Zhizhen , Li Zijian , Zhang Youyi
Published: August 2011

Li Y, Zhang H, Liao W, Song Y, Ma X, Chen C, Lu Z, Li Z, Zhang Y. α1-Adrenergic receptor (α1-AR) is a crucial mediator of cardiac hypertrophy. Although numerous intracellular pathways have been implicated in α1-AR-induced hypertrophy, its precise mechanism remains elusive. We aimed to determine whether α1-AR induces cardiac hypertrophy through a novel signaling pathway-α1-AR/epidermal growth factor receptor (EGFR)/signal transducer and activator of transcription 3 (STAT3). The activation of STAT3 by α1-AR was first demonstrated by tyrosine phosphorylation, nuclear translocation, DNA binding, and transcriptional activity in neonatal Sprague-Dawley rat cardiomyocytes. Activated STAT3 showed an essential role in α1-AR-induced cardiomyocyte hypertrophic growth, as assessed by treatment with STAT3 inhibitory peptide and lentivirus-STAT3 small interfering RNA. The results were further confirmed by in vivo experiments involving intraperitoneal injection of the STAT3 inhibitor WP1066 significantly inhibiting phenylephrine-infusion-induced heart hypertrophy in male C57BL/6 mice. Furthermore, the α1-AR-activated STAT3 was associated with transactivation of EGFR because inhibition of EGFR with the selective inhibitor AG1478 prevented α1-AR-induced STAT3 tyrosine phosphorylation and its transcriptional activity, as well as cardiac hypertrophy. In summary, these results suggest that α1-AR induces the activation of STAT3, mainly through transactivation of EGFR, which plays an important role in α1-AR-induced cardiac hypertrophy.
Differential interaction of dicarboxylates with human sodium-dicarboxylate cotransporter 3 and organic anion transporters 1 and 3
Authors: Kaufhold Marcel , Schulz Katharina , Breljak Davorka , Gupta Shivangi , Henjakovic Maja , Krick Wolfgang , Hagos Yohannes , Sabolic Ivan , Burckhardt Birgitta C. , Burckhardt Gerhard
Published: August 2011

Organic anions are taken up from the blood into proximal tubule cells by organic anion transporters 1 and 3 (OAT1 and OAT3) in exchange for dicarboxylates. The released dicarboxylates are recycled by the sodium dicarboxylate cotransporter 3 (NaDC3). In this study, we tested the substrate specificities of human NaDC3, OAT1, and OAT3 to identify those dicarboxylates for which the three cooperating transporters have common high affinities. All transporters were stably expressed in HEK293 cells, and extracellularly added dicarboxylates were used as inhibitors of [14C]succinate (NaDC3), p-[3H]aminohippurate (OAT1), or [3H]estrone-3-sulfate (OAT3) uptake. Human NaDC3 was stably expressed as proven by immunochemical methods and by sodium-dependent uptake of succinate ( K0.5for sodium activation, 44.6 mM; Hill coefficient, 2.1; Kmfor succinate, 18 μM). NaDC3 was best inhibited by succinate (IC5025.5 μM) and less by α-ketoglutarate (IC5069.2 μM) and fumarate (IC5095.2 μM). Dicarboxylates with longer carbon backbones (adipate, pimelate, suberate) had low or no affinity for NaDC3. OAT1 exhibited the highest affinity for glutarate, α-ketoglutarate, and adipate (IC50between 3.3 and 6.2 μM), followed by pimelate (18.6 μM) and suberate (19.3 μM). The affinity of OAT1 to succinate and fumarate was low. OAT3 showed the same dicarboxylate selectivity with ∼13-fold higher IC50values compared with OAT1. The data 1) reveal α-ketoglutarate as a common high-affinity substrate of NaDC3, OAT1, and OAT3 and 2) suggest potentially similar molecular structures of the binding sites in OAT1 and OAT3 for dicarboxylates.
Angiotensin-converting enzyme inhibitor limits pulse-wave velocity and aortic calcification in a rat model of cystic renal disease
Authors: Ng Keith , Hildreth Cara M. , Avolio Alberto P. , Phillips Jacqueline K.
Published: August 2011

The effect of angiotensin-converting enzyme inhibition on function and structure of the aorta was studied in the Lewis polycystic kidney (LPK) rat model of cystic renal disease and Lewis controls. Pulse-wave velocity (PWV) was recorded under urethane anesthesia (1.3 g/kg ip) in mixed-sex animals aged 6 and 12 wk and in 12-wk-old animals treated with perindopril (3 mg·kg−1·day−1po) from age 6–12 wk. Tail-cuff systolic pressures were recorded over the treatment period. After PWV measurements, animals were euthanized and the aorta was removed for histomorphological and calcium analysis. Hypertension in LPK at 6 and 12 wk was associated with a shift of the PWV curve upward and to the right, indicating a decrease in aortic compliance, which was significantly reduced by perindopril. LPK demonstrated greater aortic calcification (6 wk: 123 ± 19 vs. 65 ± 7 and 12 wk: 406 ± 6 vs. 67 ± 6 μmol/g, P < 0.001, LPK vs. Lewis, respectively). This was reduced by treatment with perindopril (172 ± 48 μmol/g, 12 wk LPK P < 0.001). Medial cross-sectional area and elastic modulus/wall stress of the aorta were greater in LPK vs. Lewis control animals at 6 and 12 wk of age and showed an age-related increase that was prevented by treatment with perindopril ( P < 0.001). Perindopril also ameliorated the degradation of elastin, increase in collagen content, and medial elastocalcinosis seen in 12-wk LPK. Overall, perindopril improved the structural and functional indices of aortic stiffness in the LPK rats, demonstrating a capacity for angiotensin-converting enzyme inhibition to limit vascular remodeling in chronic kidney disease.
CCL2 has similar excitatory effects to TNF-α in a subgroup of inflamed C-fiber axons
Authors: Richards Natalie , Batty Thomas , Dilley Andrew
Published: August 2011

Peripheral nerve inflammation can cause neuronal excitability changes that have been implicated in the pathogenesis of chronic pain. Although the neuroimmune interactions that lead to such physiological changes are unclear, in vitro studies suggest that the chemokine CCL2 may be involved. This in vivo study examines the effects of CCL2 on untreated and inflamed neurons and compares its effects with those of TNF-α. Extracellular recordings were performed in the anesthetized rat on isolated neurons with C-fiber axons. On untreated neurons, CCL2, as well as TNF-α, had negligible effects. Following neuritis, both cytokines transiently caused the firing of action potentials in 27–30% of neurons, which were either silent or had background (ongoing) activity. The neurons with ongoing activity, which responded to either cytokine, had significantly slower baseline firing rates {median = 3.0 spikes/min [interquartile range (IQR) 3.0]} compared with the nonresponders [median = 24.4 spikes/min (IQR 24.6); P < 0.001]. In an additional group, 26–27% of neurons, which were sensitized due to repeated noxious mechanical stimulation of the periphery, also responded to the effects of both cytokines. Neither cytokine caused axons to become mechanically sensitive. Immunohistochemistry confirmed that the cognate CCL2 receptor, CCR2, is mainly expressed on glia and is therefore not likely to be an axonal target for CCL2 following inflammation. In contrast, the cognate TNF-α receptor (TNFR), TNFR1, was present on untreated and inflamed neurons. In summary, CCL2 can excite inflamed C-fiber neurons with similar effects to TNF-α, although the underlying mechanisms may be different. The modulatory effects of both cytokines are limited to a subgroup of neurons, which may be subtly inflamed.