bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of HLA-B*81-Associated Mutations in HIV-1 Gag on Viral Replication Capacity
Authors: Wright Jaclyn K. , Naidoo Vanessa L. , Brumme Zabrina L. , Prince Jessica L. , Claiborne Daniel T. , Goulder Philip J. R. , Brockman Mark A. , Hunter Eric , Ndung'u Thumbi
Published: January 2012

HIV-1 attenuation resulting from immune escape mutations selected in Gag may contribute to slower disease progression in HIV-1-infected individuals expressing certain HLA class I alleles. We previously showed that the protective allele HLA-B*81 and the HLA-B*81-selected Gag T186S mutation are strongly associated with a lower viral replication capacity of recombinant viruses encoding Gag-protease derived from individuals chronically infected with HIV-1 subtype C. In the present study, we directly tested the effect of this mutation on viral replication capacity. In addition, we investigated potential compensatory effects of various polymorphisms, including other HLA-B*81-associated mutations that significantly covary with the T186S mutation. Mutations were introduced into a reference subtype B backbone and into patient-derived subtype C sequences in subtype B and C backbones by site-directed mutagenesis. The exponential-phase growth of mutant and wild-type viruses was assayed by flow cytometry of a green fluorescent protein reporter T cell line or by measurement of HIV-1 reverse transcriptase activity in culture supernatants. Engineering of the T186S mutation alone into all patient-derived subtype C sequences failed to yield replication-competent viruses, while in the subtype B sequence, the T186S mutation resulted in impaired replication capacity. Only the T186S mutation in combination with the T190I mutation yielded replication-competent viruses for all virus backbones tested; however, these constructs replicated slower than the wild type, suggesting that only partial compensation is mediated by the T190I mutation. Constructs encoding the T186S mutation in combination with other putative compensatory mutations were attenuated or defective. These results suggest that the T186S mutation is deleterious to HIV-1 subtype C replication and likely requires complex compensatory pathways, which may contribute to the clinical benefit associated with HLA-B*81.
Control of Innate Immune Signaling and Membrane Targeting by the Hepatitis C Virus NS3/4A Protease Are Governed by the NS3 Helix α
0
Authors: Horner Stacy M. , Park Hae Soo , Gale Michael
Published: January 2012

Hepatitis C virus (HCV) infection is sensed in the host cell by the cytosolic pathogen recognition receptor RIG-I. RIG-I signaling is propagated through its signaling adaptor protein MAVS to drive activation of innate immunity. However, HCV blocks RIG-I signaling through viral NS3/4A protease cleavage of MAVS on the mitochondrion-associated endoplasmic reticulum (ER) membrane (MAM). The multifunctional HCV NS3/4A serine protease is associated with intracellular membranes, including the MAM, through membrane-targeting domains within NS4A and also at the amphipathic helix α
0
of NS3. The serine protease domain of NS3 is required for both cleavage of MAVS, a tail-anchored membrane protein, and processing the HCV polyprotein. Here, we show that hydrophobic amino acids in the NS3 helix α
0
are required for selective cleavage of membrane-anchored portions of the HCV polyprotein and for cleavage of MAVS for control of RIG-I pathway signaling of innate immunity. Further, we found that the hydrophobic composition of NS3 helix α
0
is essential to establish HCV replication and infection. Alanine substitution of individual hydrophobic amino acids in the NS3 helix α
0
impaired HCV RNA replication in cells with a functional RIG-I pathway, but viral RNA replication was rescued in cells lacking RIG-I signaling. Therefore, the hydrophobic amphipathic helix α
0
of NS3 is required for NS3/4A control of RIG-I signaling and HCV replication by directing the membrane targeting of both viral and cellular substrates.
Complete Genome Sequence of a Dengue Virus Serotype 4 Strain Isolated in Roraima, Brazil
Authors: Naveca Felipe G. , Souza Victor C. , Silva George A. V. , Maito Rodrigo M. , Granja Fabiana , Siqueira Thalita , Acosta Pablo O. A.
Published: January 2012

Dengue is the most important arboviral disease worldwide. We report the complete genome sequence of a dengue virus serotype 4, genotype II strain isolated in 2010 from a patient with classical dengue fever in Boa Vista, Roraima, Brazil.
Varicella-Zoster Virus ORF12 Protein Triggers Phosphorylation of ERK1/2 and Inhibits Apoptosis
Authors: Liu XueQiao , Li Qingxue , Dowdell Kennichi , Fischer Elizabeth R. , Cohen Jeffrey I.
Published: January 2012

Mitogen-activated protein kinases (MAPKs) are a family of serine-threonine protein kinases involved in many cellular processes, including cell proliferation, differentiation, inflammation, and cell death. Activation of several MAPKs, including extracellular signal-regulated kinase 1 and 2 (ERK1/2), p38, and c-Jun N-terminal kinase (JNK), results in stimulation of activator protein 1 (AP-1), which promotes gene transcription. Previous studies have demonstrated that varicella-zoster virus (VZV) infection activates ERK1/2, p38, and JNK to promote viral replication, but the underlying mechanism(s) is unclear. To identify viral proteins responsible for the activation of MAPK, we used a proteomic approach to screen viral proteins for AP-1 promoter activation by an AP-1–luciferase reporter assay. We found that VZV ORF12 protein, located in the tegument of virions, enhances AP-1 reporter activity. This effect of ORF12 protein was markedly inhibited by a MAPK/ERK kinase 1 and 2 (MEK1/2) inhibitor (U0126), partially blocked by a p38 inhibitor (SB202190), but not inhibited by a JNK inhibitor (SP600125). Expression of VZV ORF12 protein in cells resulted in phosphorylation of ERK1/2 and p38 but not JNK. Infection of cells with a VZV ORF12 deletion mutant resulted in reduced levels of phosphorylated ERK1/2 (p-ERK1/2) compared to infection with wild-type VZV. Furthermore, deletion of ORF12 rendered VZV-infected cells more susceptible to staurosporine-induced apoptosis. In conclusion, VZV ORF12 protein activates the AP-1 pathway by selectively triggering the phosphorylation of ERK1/2 and p38. Cells infected with a VZV ORF12 deletion mutant have reduced levels of p-ERK1/2 and are more susceptible to apoptosis than cells infected with wild-type VZV.
Superconductivity: 100th Anniversary of Its Discovery and Its Future
Authors: Kitazawa Koichi
Published: January 2012

Superconducting technologies are reviewed as the integration of various technologies by considering its research history, present status, future prospects, and the application to energy, transportation, and communications. Superconductivity involves a persistent current, perfect diamagnetism, and the Josephson effect, and is a unique phenomenon that cannot be imitated. After the discovery of superconductivity 100 years ago, as long as half a century was required to clarify its difficult mechanism. To date, the applications of superconductivity have been limited to specific purposes that require ultimate performance. The reason for this undoubtedly lies in the cooling penalty. In addition, to exploit the advantages of superconductivity, it has been necessary to wait until elaborated composite materials, whose fabrication requires nanotechnologies, reached the desired level. Spurred on by the discovery of high-temperature superconductivity, this year, we celebrate the 100th anniversary of the discovery of superconductivity, which is predicted to play a key role in realizing a sustainable global environment and in human society in the future.
Efficient Pump Beam Multiplexer Based on Single-Mode Fibers
Authors: Seo Hong-Seok , Ahn Joon Tae , Park Bong Je , Song Jung-Ho , Chung Woonjin
Published: January 2012

An efficient pump beam combining technique using single-mode fibers was introduced. Well-defined modes formed from a single-mode fiber bundle were efficiently coupled into an output multimode fiber. The coupling rate can be maintained up to an input fiber number of 331. The total power of a multimode output fiber combined with single-mode fibers can greatly exceed the output power of a multimode laser diode pigtailed with the same multimode fiber.
Magnetic Anisotropy and Chemical Order of Artificially Synthesized L10-Ordered FeNi Films on Au–Cu–Ni Buffer Layers
Authors: Kojima Takayuki , Mizuguchi Masaki , Koganezawa Tomoyuki , Osaka Keiichi , Kotsugi Masato , Takanashi Koki
Published: January 2012

L10-FeNi films were grown by alternate monatomic layer deposition on Au–Cu–Ni buffer layers at several substrate temperatures (T
s), and the relation between the uniaxial magnetic anisotropy energy (K
u) and the long-range chemical order parameter (S) was investigated. A large K
u of (7.0 ±0.2) ×106 erg/cm3 and S of 0.48 ±0.05 were obtained. The value of K
u was larger than those reported previously for artificially synthesized FeNi films. It was first found that both K
u and S increased with T
s, and K
u was roughly proportional to S.
Accurate Determination of Iron Density in Large Helical Device Based on Absolute Intensity Profile Measurement of Extreme Ultraviolet Spectral Lines
Authors: Dong Chunfeng , Morita Shigeru , Goto Motoshi , Wang Erhui , Murakami Izumi , Yamamoto Norimasa
Published: January 2012

An iron density profile is accurately determined in Large Helical Device (LHD) using a space-resolved extreme ultraviolet (EUV) spectrometer, the absolute intensity calibration of which is carried out by bremsstrahlung continuum measurement. The effective intensity coefficients R (eV cm3 s-1) of FeXV to FeXXIV are precisely calculated on the basis of a collisional-radiative model for iron density determination. The total iron density at the plasma center is found to be almost 4 or 5 orders of magnitude smaller than the electron density. The application of the present result to the study of impurity transport demonstrates a new way of examining the radial structure of transport coefficients and of determining the total impurity density.
Attractive Polarization Effects on Binary Atomic Si–Si Collisions
Authors: Kim Chang-Geun , Jung Young-Dae
Published: January 2012

Attractive polarization effects are investigated in binary atomic Si–Si collisions. The eikonal method and effective potentials are used to obtain the phase shifts and cross sections for the atomic collisions as functions of the impact parameter and collision energy. The results show that the attractive polarization effect suppresses the phase shift and cross section. It is found that the maximum positions of the differential cross section approach the collision center owing to the attractive polarization effects. It is also found that the attractive polarization effects on the total eikonal cross section decrease with increasing collision energy.
Effect of Nickel Concentration on Bias Reliability and Thermal Stability of Thin-Film Transistors Fabricated by Ni-Metal-Induced Crystallization
Authors: Lai Ming-Hui , Wu YewChung Sermon , Huang Jung-Jie
Published: January 2012

Ni-metal-induced crystallization (MIC) of amorphous Si (α-Si) has been employed to fabricate low-temperature polycrystalline silicon (poly-Si) thin-film transistors (TFTs). Although the high leakage current is a major issue in the performance of conventional MIC-TFTs since Ni contamination induces deep-level state traps, it can be greatly improved by using well-known technologies to reduce Ni contamination. However, for active-matrix organic light-emitting diode (AMOLED) display applications, the bias reliability and thermal stability are major concerns especially when devices are operated under a hot carrier condition and in a high-temperature environment. It will be interesting to determine how the bias reliability and thermal stability are affected by the reduction of Ni concentration. In the study, the effect of Ni concentration on bias reliability and thermal stability was investigated. We found that a device exhibited high immunity against hot-carrier stress and elevated temperatures. These findings demonstrated that reducing the Ni concentration in MIC films was also beneficial for bias reliability and thermal stability.
Effects of Metal Electrode on the Electrical Performance of Amorphous In–Ga–Zn–O Thin Film Transistor
Authors: Yim Jung-Ryoul , Jung Sung-Yup , Yeon Han-Wool , Kwon Jang-Yoen , Lee Young-Joo , Lee Je-Hun , Joo Young-Chang
Published: January 2012

Effects of metal electrode on the electrical performance of amorphous In–Ga–Zn–O (a-IGZO) thin film transistor (TFT) have been studied. Electrical performances and interface stability between Mo, Al, and Cu electrode and a-IGZO semiconductor have been investigated before and after air-annealing. No inter-diffusion and interfacial reaction has been observed between Mo and a-IGZO and the turn-on voltage of the Mo electrode TFT was 0 V after annealing. As for Al, Al oxide was formed at the interface, and the number of conduction electrons in a-IGZO increased. Thus, a negative turn-on voltage was observed after air-annealing. As for Cu, Cu diffused into a-IGZO during air-annealing and acted as an acceptor. Therefore the a-IGZO TFT with a Cu electrode had a positive turn-on voltage and sub-threshold slope increased after air-annealing. These results indicate that the transistor performance can be affected by the metal types due to inter-diffusion or interfacial reaction between metal and a-IGZO.
Effects of Polarization on Mechanical Properties of Lead Zirconate Titanate Ceramics Evaluated by Modified Small Punch Tests
Authors: Deng Qihuang , Fan Yuchi , Wang Lianjun , Xiong Zhi , Wang Hongzhi , Li Yaogang , Zhang Qinghong , Kawasaki Akira , Jiang Wan
Published: January 2012

Pb(Zr,Ti)O3(PZT) ceramics were prepared by the conventional mixed oxide method, and the strength of the resultant PZT ceramics was evaluated using modified small punch (MSP) tests. Load–displacement curve test results showed that the crack-initiation and fracture strengths of PZT ceramics decreased after polarization. The effect of the polarization accelerated the fatigue properties of PZT ceramics. Scanning electron microscopy (SEM) results showed that microcracks were formed before the maximum load in the MSP test, and the first load drop corresponded to crack initiation.
Optical and Electric Properties of Bi0.5Na0.5TiO3-Based Thin Films Grown on Indium–Tin-Oxide-Coated Glass Substrates
Authors: Zhang Shan-Tao , Chen Y. B. , Gu Zheng-Bin
Published: January 2012

0.85(0.94Bi0.5Na0.5TiO3–0.06BaTiO3)–0.15K0.5Na0.5NbO3 thin films have been prepared on indium–tin-oxide-coated glass substrates by pulsed laser deposition. Both X-ray diffraction and transmission electron microscopy reveal that the films have tetragonal crystal structure with columnar-like grains. The films show excellent optical transmittance of 90% and the band gap is calculated to be 3.61 eV. The slim polarization-electron filed hysteresis loop indicates the weak ferroelectricity, which is consistent with the capacitor-electric field curves. These results may be helpful for searching transparent ferroelectric materials.
Role of Sintering Temperature on the Phase Stability and Electrical Properties of 0.94(K0.5Na0.5NbO3)–0.06(LiSbO3) Ceramics
Authors: Palei Prakash Kumar , Kumar Pawan
Published: January 2012

Lead-free 0.94(K0.5Na0.5NbO3)–0.06(LiSbO3) (KNN–LS) ceramics were prepared by conventional solid-state reaction route (CSSR). For single perovskite phase formation the calcination was done at 850 °C for 6 h. Whereas for obtaining dense morphology the sintering of KNN–LS ceramics was carried out at 1060, 1080, 1100, and 1120 °C temperatures for 4 h, respectively. The structural study revealed that with the increase in sintering temperature the structure of the ceramic transformed from pure tetragonal to pseudocubic phase. Scanning electron microscopy (SEM) micrographs indicated that the optimum sintering temperature of the ceramic was found to be 1080 °C. The Curie temperature (Tc) of the KNN–LS ceramic was found to decrease at higher sintering temperature. The development of typical hysteresis loop confirmed the ferroelectric and piezoelectric nature of the KNN–LS ceramics sintered at different temperatures. The KNN–LS ceramics sintered at 1080 °C showed better ferroelectric and piezoelectric properties i.e., remnant polarization (Pr)∼17.2 µC/cm2, coercive field (Ec)∼13.5 kV/cm, piezoelectric coefficient (d33)∼161 pC/N, coupling coefficient (kp)∼0.36 and remnant strain ∼0.06% were obtained.
Effect of Chemical Modifications on the Electronic Transport Properties of the Optical Molecular Switch
Authors: Xia Cai-Juan , Liu De-Sheng , Liu Han-Chen , Zhang Ying-Tang
Published: January 2012

Using first-principles density functional theory and nonequilibrium Green's function formalism, we investigate the effect of chemical modifications on the electronic transport properties of the dihydroazulene optical molecular switch. The molecule that comprises the switch can convert between the closed and the open forms upon photoexcitation. Theoretical results show that the chemical modifications play an important role in determining the switching behavior of such molecular device. This result reflects that the current ratio can be manipulated with the careful selection of the substituents and can provide fundamental guidelines for the design of functional molecular devices.
Vertical InGaN Multiple Quantum Wells Light-Emitting Diodes Structures Transferred from Si(111) Substrate onto Electroplating Copper Submount with Through-Holes
Authors: Luo Ruihong , Rao Wentao , Chen Tufu , Xiang Peng , Liu Minggang , Yang Weimin , Wang Yunqian , Yang Yibin , Wu Zhisheng , Liu Yang , Jiang Hao , Zhang Baijun
Published: January 2012

Vertical InGaN multiple quantum wells light-emitting diodes (LEDs) with through-holes structure were transferred from Si(111) substrate onto the electroplating copper submount successfully. The additional series resistances induced by the AlN buffer layer and other interlayer were shorted by the metals filled through-holes. The LED with through-hole structure shows a low vertical conducting operating voltage and a small series resistance. Combining with substrate removal and copper electroplating technique, the operating voltage at 350 mA and series resistances of the LED were reduce from 5.6 to 5.1 V and 7 to 4 Ω, in comparison with through-hole LED before substrate removal. At the same time, the light output intensity was improved by 75%, which was mainly attributed to both the removal of light absorptive substrate and the substitution for highly thermal conductive copper submount with metal reflector.
Effect of Initial Bow of Sapphire Substrate on Substrate Curvature during InGaN Growth Stage of Light Emitting Diode Epitaxy
Authors: Aida Hideo , Lee Dong S. , Belousov Mikhail , Sunakawa Kazuhiko
Published: January 2012

A systematic study to understand the relationship between wavelength uniformity and substrate curvature during InGaN growth is described in relation to the initial bow of sapphire substrate. The initial bow of the substrate acted as the offset parameter for its curvature throughout the stages of the epitaxy process. Substrate flatness during InGaN growth was found to be important for achieving high wavelength homogeneity. The impact of n-GaN layer thickness and InGaN growth temperature on the substrate curvature shape was investigated to obtain a perfectly flat substrate shape at the InGaN growth stage. Temperature adjustment showed a strong impact on substrate curvature at the InGaN growth stage. The best initial bow was found as a function of InGaN growth temperature, and the importance of the initial bow of the sapphire substrate for obtaining high homogeneity in light emitting diode (LED) wavelength was experimentally verified.
Thermal Diffusivity along X-Axis of Periodically Poled Mg-Doped Near-Stoichiometric LiTaO3 Device with Domain-Inverted Period of 8.0 µm
Authors: Nakamura Masaru , Takekawa Shunji , Kitamura Kenji
Published: January 2012

To clarify whether the thermal diffusivity along the X-axis of a periodically poled Mg 1-mol %-doped near-stoichiometric LiTaO3 (PPMgSLT) frequency-conversion device is the same as that of bulk-MgSLT crystal, we measured the thermal diffusivity along the X-axis (the direction perpendicular to the domain-wall) of a PPMgSLT device with a domain-inverted period of 8.0 µm by using a modified AC calorimetric method (laser-heating Ångström method) at room temperature. We found that the thermal diffusivity [(1.98±0.06)×10-6 m2/s] was almost the same as that of bulk-MgSLT crystal [(2.09±0.04)×10-6 m2/s]. This means that domain-walls are not phonon scattering centers with respect to thermal diffusivity and that domain-walls do not affect thermal diffusivity at room temperature. Consequently, the thermal diffusivity of bulk-MgSLT crystal is acceptable for PPMgSLT devices.
Size Dependence Effect in MgO-Based CoFeB Tunnel Junctions with Perpendicular Magnetic Anisotropy
Authors: Chenchen Jacob Wang , Akhtar Mohamed Akbar Khan Bin , Sbiaa Rachid , Hao Meng , Sunny Lua Yan Hwee , Kai Wong Seng , Ping Luo , Carlberg Patrick , Arthur Ang Khoon Siah
Published: January 2012

We examine the effect of junction sizes on the magnetization reversal process and spin-transfer torque switching of the MgO-based CoFeB magnetic tunnel junctions (MTJs) with perpendicular magnetic anisotropy (PMA). From the magnetic field transport measurements, it was found that the miniaturization of MTJs inherently enhances the switching asymmetry and the PMA of the soft layer. Our micromagnetic simulations confirmed that the dipolar field from the hard layer is responsible for the switching asymmetry and the increase in perpendicular shape anisotropy induces improvement of the PMA. It was further revealed that this additional anisotropy gained from the smaller MTJ sizes is not sufficient to sustain the thermal stability to meet the long-term information storage at the state-of-the-art complementary-metal–oxide semiconductor technology node. The pulsed spin-transfer torque measurements showed that a higher current density is needed to switch the magnetization of the soft layer in MTJ with smaller lateral dimensions, which is attributed to the increase in PMA.
Thermal Conductance of Buckled Carbon Nanotubes
Authors: Nishimura Fumio , Shiga Takuma , Maruyama Shigeo , Watanabe Kazuyuki , Shiomi Junichiro
Published: January 2012

Knowledge of thermal conductance of carbon nanotubes under mechanical deformation is important to characterize the robustness of carbon nanotube heat conduction. In this study, using molecular dynamics simulations, we have calculated thermal conductance of an elastically buckled single-walled carbon nanotube. A local buckle was formed by mechanically bending a carbon nanotube at an angle of 60°, and thermal conductance through the buckle was calculated by a nonequilibrium molecular dynamics approach. The thermal conductance exhibits strong diameter dependence, correlated with the strain energy generated in the buckle. Despite the highly strained deformation, the thermal resistance across a buckle is similar to that of a point defect and heterotube junction, revealing a robust nature of carbon nanotube heat conduction to buckling deformation.
Transparent Conducting Nb-Doped TiO2Electrodes Activated by Laser Annealing for Inexpensive Flexible Organic Solar Cells
Authors: Lee Jung-Hsiang , Lin Chia-Chi , Lin Yi-Chang
Published: January 2012

A KrF excimer laser (λ= 248 nm) has been adopted for annealing cost-effective Nb-doped TiO2(NTO) films. Sputtered NTO layers were annealed on SiO2-coated flexible poly(ethylene terephthalate) (PET) substrates. This local laser annealing technique is very useful for the formation of anatase NTO electrodes used in flexible organic solar cells (OSCs). An amorphous NTO film with a high resistivity and a low transparency was transformed significantly into a conductive and transparent anatase NTO electrode by laser irradiation. The 210 nm anatase NTO film shows a sheet resistance of 50 Ω and an average optical transmittance of 83.5% in the wavelength range from 450 to 600 nm after annealing at 0.25 J/cm2. The activation of Nb dopants and the formation of the anatase phase contribute to the high conductivity of the laser-annealed NTO electrode. Nb activation causes an increase in the optical band gap due to the Burstein–Moss effect. The electrical properties are in agreement with the material characteristics determined by X-ray diffraction (XRD) analysis and secondary ion mass spectrometry (SIMS). The irradiation energy for the NTO electrode also affects the performance of the organic solar cell. The laser annealing technique provides good properties of the anatase NTO film used as a transparent electrode for flexible organic solar cells (OSCs) without damage to the PET substrate or layer delamination from the substrate.
Fabrication and Electrical Properties of Ba(Zr,Ti)O3 Textured Ceramics by Templated Grain Growth
Authors: Bai Wangfeng , Shen Bo , Fu Fang , Zhai Jiwei
Published: January 2012

The (h00) textured Ba(Zr0.085Ti0.915)O3 (BZT) ceramics were fabricated by templated grain growth using anisotropically shaped BaTiO3 (BT) templates. A high orientation degree (Lotgering's factor) of 85% calculated from X-ray diffraction (XRD) patterns was obtained. The dielectric, ferroelectric, piezoelectric properties of the random and textured BZT ceramics have been studied. The Curie temperature of the textured BZT ceramics was 94 °C, which was higher than that of the random BZT ceramics. The textured BZT ceramics exhibited excellent piezoelectric performance with the piezoelectric coefficient d
33 = 234 pC/N, strain levels of 0.22% at 40 kV/cm, normalized strain (S
max/E
max) level of 550 pm/V calculated from the unipolar strain–electric field (S–E) hysteresis loops and remnant polarization P
r = 11.46 µC/cm2 sintered at 1450 °C for 4 h with 85% of Lotgering's factor.
Origin of Device Performance Degradation in InGaZnO Thin-Film Transistors after Crystallization
Authors: Ahn Byung Du , Shin Hyun Soo , Kim Dong Lim , Lee Seung Min , Park Jin-Seong , Kim Gun Hee , Kim Hyun Jae
Published: January 2012

This paper reports the crystallization of amorphous InGaZnO (a-IGZO) films using solid-phase crystallization and discusses the mechanisms responsible for degradation of device performance after crystallization. The field-effect mobility (µFE) and subthreshold gate swing (S) value of the nanocrystallite embedded-IGZO thin-film transistors (TFTs) were significantly degraded to 3.12 cm2 V-1 s-1 and 1.26 V/decade, respectively, compared to those (13.72 cm2 V-1 s-1 and 0.38 V/decade) for the a-IGZO TFTs. The decreased µFE is explained based on indium deficiency by diffusion of its atoms in the channel layer and grain-boundary trapping of mobile carriers. The predominant mechanism of increasing S value has been attributed to increased interface and grain-boundary trapping.
X-ray Photoemission Spectroscopy Study of Low-Temperature Nitridation of GaAs(001) Surface Using RF Radical Source
Authors: Naritsuka Shigeya , Mori Midori , Takeuchi Yoshitaka , Monno Yohei , Maruyama Takahiro
Published: January 2012

The nitridation mechanism of the GaAs(001) surface using an RF-radical source at a low temperature of 350 °C was systematically studied by changing the As supply and nitridation time to obtain a smooth nitrided layer without the formation of Ga droplets. Atomic force microscopy (AFM) measurements indicated that supplying As is useful in suppressing the re-evaporation of As atoms and in maintaining a smooth surface. However, the degree of nitridation was decreased with increasing As pressure in the samples nitrided for 30 min. In contrast, the time dependence of nitridation indicated that the degree of nitridation increases with nitridation time. After optimizing the conditions, a two-monolayer-thick GaN layer was successfully obtained by nitridation for 120 min, regardless of the supply of the As molecular beam. The structure of the nitrided layers was also investigated using angle-resolved X-ray photoemission spectroscopy, and a thin layer that contains As and N atoms was found to cover the nitrided GaN layer.
Characteristics of Silicon/Nitrogen-Incorporated Diamond-Like Carbon Films Prepared by Plasma-Enhanced Chemical Vapor Deposition
Authors: Nakazawa Hideki , Miura Soushi , Kamata Ryosuke , Okuno Saori , Enta Yoshiharu , Suemitsu Maki , Abe Toshimi
Published: January 2012

We have deposited silicon/nitrogen-incorporated diamond-like carbon (Si–N-DLC) films by radio-frequency plasma-enhanced chemical vapor deposition (PECVD) using methane (CH4), argon (Ar), and hexamethyldisilazane [(CH3)3Si]2NH as the Si and N source, and investigated the structure and the mechanical and tribological properties of the films. We compared the properties of the Si–N-DLC films with those of the Si-incorporated DLC (Si-DLC) films prepared by PECVD using monomethylsilane (CH3SiH3) as the Si source. It was found that the N incorporation together with Si into DLC was effective in further decreasing the internal stress and increasing the adhesion strength. The friction coefficients of the Si–N-DLC films containing 4.0% N or less were as low as those of the Si-DLC films. We also found that the Si–N-DLC film containing 10.0% Si and 4.0% N had a higher wear resistance than the Si-DLC film containing 10.8% Si. The wear rate was comparable to that of the undoped DLC film.
Scanning Tunneling Spectroscopy Observation of Electronic Resonances Originating from 1 ×1 Potential on the Dense Pb Overlayer on Si(111)
Authors: Lu Shin-Ming , Chan Wen-Yuan , Chou Hsing-Yi , Chiu Ya-Ping , Su Wei-Bin , Chu Pei-Hong , Jiang Chi-Lun , Chang Chia-Seng , Hsiao Hsi-Lien , Tsong Tien Tzou
Published: January 2012

We use scanning tunneling spectroscopy (STS) to investigate the electronic structures of dense Pb overlayers of three phases grown on the Si(111) surface: the 1 ×1, √7 ×√3, and stripe incommensurate (SIC) phases. Although their atomic structures are all very different, the STS spectra of all three phases show nearly identical oscillatory features with two resonance peaks. These resonances are not common quantum-well states; they are energy bands originating from the dominant 1 ×1 potential in these phases. However, the local electronic states found by STS show that the resonance peaks are modulated with the superstructure of the √7 ×√3 phase, and that the resonance energy varies with the domains and the domain walls in the SIC phase.
High-Density Electron-Beam Recording of Circumferentially Aligned Dots by Using Substrates with Low Atomic Numbers
Authors: Okada Takeru , Aida Makoto , Fujimori Jiro , Katsumura Masahiro , Iida Tetsuya
Published: January 2012

Reducing proximity effects is a key factor for achieving a higher resolution in electron-beam lithography and realizing the mastering of patterned media. The effect of substrate materials on backscattering electrons was investigated by simulation and experiment, and resolution enhancement was demonstrated. In Monte Carlo simulations with 100 keV incident electrons, the intensity of backscattering electrons decreased with decreasing atomic number of substrates. On the other hand, both the density of substrates and the existence of 10 nm thin films had negligible effects on the intensity of backscattering electrons. The measured exposure distributions from line-scanned electron beams supported the results of simulations. The intensity of backscattering electrons was reduced by using a carbon substrate, and circumferentially aligned high-density patterns of 878 Gbit/in.2 were resolved.
Effect of Inserting Teflon as a Surface Modification Layer on Bottom-Contact Pentacene-Based Organic Thin-Film Transistors
Authors: Fan Ching-Lin , Yang Tsung-Hsien , Chiu Ping-Cheng
Published: January 2012

This study reports the effect of poly(tetrafluoroethylene) (Teflon) as a surface modification layer, which was deposited on the surface of gate insulator and source/drain (S/D) electrodes, on bottom-contact pentacene-based organic thin-film transistors (OTFTs). The inserted 1.5-nm-thick Teflon layer can enhance the device performance because of the improved molecular orientation in pentacene film and reduced contact resistance (RC) between the pentacene film and the S/D electrodes. The improved molecular orientation of pentacene film is caused by the hydrophobic and smooth Teflon layer surface. The reducedRCis a result of the tunneling process at the Au/pentacene interface. This study also found that the device performance decreased as the Teflon layer increased in thickness. This is because of the increasedRCand decreased carrier injection efficiency between the pentacene film and the S/D electrodes. Compared to devices without a Teflon layer, the drain current and field-effect mobility of devices with a 1.5-nm-thick Teflon layer increased by 93 and 105%, respectively.
Architecture of kangaroo rat inner medulla: segmentation of descending thin limb of Henle's loop
Authors: Urity Vinoo B. , Issaian Tadeh , Braun Eldon J. , Dantzler William H. , Pannabecker Thomas L.
Published: January 2012

We hypothesize that the inner medulla of the kangaroo rat Dipodomys merriami , a desert rodent that concentrates its urine to more than 6,000 mosmol/kgH2O water, provides unique examples of architectural features necessary for production of highly concentrated urine. To investigate this architecture, inner medullary nephron segments in the initial 3,000 μm below the outer medulla were assessed with digital reconstructions from physical tissue sections. Descending thin limbs of Henle (DTLs), ascending thin limbs of Henle (ATLs), and collecting ducts (CDs) were identified by immunofluorescence using antibodies that label segment-specific proteins associated with transepithelial water flux (aquaporin 1 and 2, AQP1 and AQP2) and chloride flux (the chloride channel ClC-K1); all tubules and vessels were labeled with wheat germ agglutinin. In the outer 3,000 μm of the inner medulla, AQP1-positive DTLs lie at the periphery of groups of CDs. ATLs lie inside and outside the groups of CDs. Immunohistochemistry and reconstructions of loops that form their bends in the outer 3,000 μm of the inner medulla show that, relative to loop length, the AQP1-positive segment of the kangaroo rat is significantly longer than that of the Munich-Wistar rat. The length of ClC-K1 expression in the prebend region at the terminal end of the descending side of the loop in kangaroo rat is about 50% shorter than that of the Munich-Wistar rat. Tubular fluid of the kangaroo rat DTL may approach osmotic equilibrium with interstitial fluid by water reabsorption along a relatively longer tubule length, compared with Munich-Wistar rat. A relatively shorter-length prebend segment may promote a steeper reabsorptive driving force at the loop bend. These structural features predict functionality that is potentially significant in the production of a high urine osmolality in the kangaroo rat.
Hyperthermia induces injury to the intestinal mucosa in the mouse: evidence for an oxidative stress mechanism
Authors: Oliver S. R. , Phillips N. A. , Novosad V. L. , Bakos M. P. , Talbert E. E. , Clanton T. L.
Published: January 2012

Loss of the intestinal barrier is critical to the clinical course of heat illness, but the underlying mechanisms are still poorly understood. We tested the hypothesis that conditions characteristic of mild heatstroke in mice are associated with injury to the epithelial lining of the intestinal tract and comprise a critical component of barrier dysfunction. Anesthetized mice were gavaged with 4 kDa FITC-dextran (FD-4) and exposed to increasing core temperatures, briefly reaching 42.4°C, followed by 30 min recovery. Arterial samples were collected to measure FD-4 concentration in plasma (in vivo gastrointestinal permeability). The small intestines were then removed to measure histological evidence of injury. Hyperthermia resulted in a ≈2.5-fold elevation in plasma FD-4 and was always associated with significant histological evidence of injury to the epithelial lining compared with matched controls, particularly in the duodenum. When isolated intestinal segments from control animals were exposed to ≥41.5°C, marked increases in permeability were observed within 60 min. These changes were associated with release of lactate dehydrogenase, evidence of protein oxidation via carbonyl formation and histological damage. Coincubation with N-acetylcysteine protected in vitro permeability during hyperthermia and reduced histological damage and protein oxidation. Chelation of intracellular Ca2+ to block tight junction opening during 41.5°C exposure failed to reduce the permeability of in vitro segments. The results demonstrate that hyperthermia exposure in mouse intestine, at temperatures at or below those necessary to induce mild heatstroke, cause rapid and substantial injury to the intestinal lining that may be attributed, in part, to oxidative stress.
Natriuretic effect of bufalin in isolated rat kidneys involves activation of the Na+-K+-ATPase-Src kinase pathway
Authors: Arnaud-Batista Francisco J. , Costa Graciana T. , de Oliveira Ilana Mara Barbosa , Costa Paula P. C. , Santos Cláudia F. , Fonteles Manassés C. , Uchôa Daniel E. , Silveira Edilberto R. , Cardi Bruno A. , Carvalho Krishnamurti M. , Amaral Luciana S. , Pôças Elisa S. C. , Quintas Luis E. M. , Noël François , Nascimento Nilberto R. F.
Published: January 2012

Bufadienolides are structurally related to the clinically relevant cardenolides (e.g., digoxin) and are now considered as endogenous steroid hormones. Binding of ouabain to Na+-K+-ATPase has been associated, in kidney cells, to the activation of the Src kinase pathway and Na+-K+-ATPase internalization. Nevertheless, whether the activation of this cascade also occurs with other cardiotonic steroids and leads to diuresis and natriuresis in the isolated intact kidney is still unknown. In the present work, we perfused rat kidneys for 120 min with bufalin (1, 3, or 10 μM) and measured its vascular and tubular effects. Thereafter, we probed the effect of 10 μM 3-(4-chlorophenyl)1-(1,1-dimethylethyl)-1H-pyrazolo[3,4-d]pyrimidin-4amine (PP2), a Src family kinase inhibitor, and 1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio] butadiene (UO126), a highly selective inhibitor of both MEK1 and MEK2, on bufalin-induced renal alterations. Bufalin at 3 and 10 μM profundly increased several parameters of renal function in a time- and/or concentration-dependent fashion. At a concentration that produced similar inhibition of the rat kidney Na+-K+-ATPase, ouabain had a much smaller diuretic and natriuretic effect. Although bufalin fully inhibited the rat kidney Na+-K+-ATPase in vitro, its IC50(33 ± 1 μM) was threefold higher than the concentration used ex vivo and all its renal effects were blunted by PP2 and UO126. Furthermore, the phosphorylated (activated) ERK1/2 expression was increased after bufalin perfusion and this effect was totally prevented after PP2 pretreatment. The present study shows for the first time the direct diuretic, natriuretic, and kaliuretic effects of bufalin in isolated rat kidney and the relevance of Na+-K+-ATPase-mediated signal transduction.
Erythropoietin prevents sepsis-related acute kidney injury in rats by inhibiting NF-κB and upregulating endothelial nitric oxide synthase
Authors: de Souza Ana Carolina C. Pessoa , Volpini Rildo A. , Shimizu Maria Heloísa , Sanches Talita Rojas , Camara Niels Olsen Saraiva , Semedo Patrícia , Rodrigues Camila Eleutério , Seguro Antonio Carlos , Andrade Lúcia
Published: January 2012

The pathophysiology of sepsis involves complex cytokine and inflammatory mediator networks, a mechanism to which NF-κB activation is central. Downregulation of endothelial nitric oxide synthase (eNOS) contributes to sepsis-induced endothelial dysfunction. Erythropoietin (EPO) has emerged as a major tissue-protective cytokine in the setting of stress. We investigated the role of EPO in sepsis-related acute kidney injury using a cecal ligation and puncture (CLP) model. Wistar rats were divided into three primary groups: control (sham-operated); CLP; and CLP+EPO. EPO (4,000 IU/kg body wt ip) was administered 24 and 1 h before CLP. Another group of rats received N-nitro-l-arginine methyl ester (l-NAME) simultaneously with EPO administration (CLP+EPO+l-NAME). A fifth group (CLP+EPOtreat) received EPO at 1 and 4 h after CLP. At 48 h postprocedure, CLP+EPO rats presented significantly higher inulin clearance than did CLP and CLP+EPO+l-NAME rats; hematocrit levels, mean arterial pressure, and metabolic balance remained unchanged in the CLP+EPO rats; and inulin clearance was significantly higher in CLP+EPOtreat rats than in CLP rats. At 48 h after CLP, creatinine clearance was significantly higher in the CLP+EPO rats than in the CLP rats. In renal tissue, pre-CLP EPO administration prevented the sepsis-induced increase in macrophage infiltration, as well as preserving eNOS expression, EPO receptor (EpoR) expression, IKK-α activation, NF-κB activation, and inflammatory cytokine levels, thereby increasing survival. We conclude that this protection, which appears to be dependent on EpoR activation and on eNOS expression, is attributable, in part, to inhibition of the inflammatory response via NF-κB downregulation.
mPGES-1 deletion potentiates urine concentrating capability after water deprivation
Authors: Jia Zhanjun , Liu Gang , Downton Maicy , Dong Zheng , Zhang Aihua , Yang Tianxin
Published: January 2012

PGE2 plays an important role in the regulation of fluid metabolism chiefly via antagonizing vasopressin-induced osmotic permeability in the distal nephron, but its enzymatic sources remain uncertain. The present study was undertaken to investigate the potential role of microsomal PGE synthase (mPGES)-1 in the regulation of urine concentrating ability after water deprivation (WD). Following 24-h WD, wild-type (WT) mice exhibited a significant reduction in urine volume, accompanied by a significant elevation in urine osmolality compared with control groups. In contrast, in response to WD, mPGES-1 knockout (KO) mice had much less urine volume and higher urine osmolality. Analysis of plasma volume by measurement of hematocrit and by using a nanoparticle-based method consistently demonstrated that dehydrated WT mice were volume depleted, which was significantly improved in the KO mice. WD induced a twofold increase in urinary PGE2 output in WT mice, which was completely blocked by mPGES-1 deletion. At baseline, the KO mice had a 20% increase in V2 receptor mRNA expression in the renal medulla but not the cortex compared with WT controls; the expression was unaffected by WD irrespective of the genotype. In response to WD, renal medullary aquaporin-2 (AQP2) mRNA exhibited a 60% increase in WT mice, and this increase was greater in the KO mice. Immunoblotting demonstrated increased renal medullary AQP2 protein abundance in both genotypes following WD, with a greater increase in the KO mice. Similar results were obtained by using immunohistochemistry. Paradoxically, plasma AVP response to WD seen in WT mice was absent in the KO mice. Taken together, these results suggest that mPGES-1-derived PGE2 reduces urine concentrating ability through suppression of renal medullary expression of V2 receptors and AQP2 but may enhance it by mediating the central AVP response.
Smad3 mediates ANG II-induced hypertensive kidney disease in mice
Authors: Liu Zhen , Huang Xiao R. , Lan Hui Y.
Published: January 2012

Although Smad3 is a key mediator for fibrosis, its functional role and mechanisms in hypertensive nephropathy remain largely unclear. This was examined in the present study in a mouse model of hypertension induced in Smad3 knockout (KO) and wild-type (WT) mice by subcutaneous angiotensin II infusion and in vitro in mesangial cells lacking Smad3. After angiotensin II infusion, both Smad3 KO and WT mice developed equally high levels of blood pressure. However, disruption of Smad3 prevented angiotensin II-induced kidney injury by lowering albuminuria and serum creatinine ( P < 0.01), inhibiting renal fibrosis such as collagen type I and IV, fibronectin, and α-SMA expression (all P < 0.01), and blocking renal inflammation including macrophage and T cell infiltration and upregulation of IL-1β, TNF-α, and monocyte chemoattractant protein-1 in vivo and in vitro (all P < 0.001). Further studies revealed that blockade of angiotensin II-induced renal transforming growth factor (TGF)-β1 expression and inhibition of Smurf2-mediated degradation of renal Smad7 are mechanisms by which Smad3 KO mice were protected from angiotensin II-induced renal fibrosis and NF-κB-driven renal inflammation in vivo and in vitro. In conclusion, Smad3 is a key mediator of hypertensive nephropathy. Smad3 promotes Smurf2-dependent ubiquitin degradation of renal Smad7, thereby enhancing angiotensin II-induced TGF-β/Smad3-mediated renal fibrosis and NF-κB-driven renal inflammation. Results from this study suggest that inhibition of Smad3 or overexpression of Smad7 may be a novel therapeutic strategy for hypertensive nephropathy.
Modulation of LTP at rat hippocampal CA3-CA1 synapses by direct current stimulation
Authors: Ranieri F. , Podda M. V. , Riccardi E. , Frisullo G. , Dileone M. , Profice P. , Pilato F. , Di Lazzaro V. , Grassi C.
Published: January 2012

Transcranial direct current stimulation (tDCS) can produce a lasting polarity-specific modulation of cortical excitability in the brain, and it is increasingly used in experimental and clinical settings. Recent studies suggest that the after-effects of tDCS are related to molecular mechanisms of activity-dependent synaptic plasticity. Here we investigated the effect of DCS on the induction of one of the most studied N-methyl-d-aspartate receptor-dependent forms of long-term potentiation (LTP) of synaptic activity at CA3-CA1 synapses in the hippocampus. We show that DCS applied to rat brain slices determines a modulation of LTP that is increased by anodal and reduced by cathodal DCS. Immediate early genes, such as c-fos and zif268 ( egr1/NGFI-A/krox24), are rapidly induced following neuronal activation, and a specific role of zif268 in the induction and maintenance of LTP has been demonstrated. We found that both anodal and cathodal DCS produce a marked subregion-specific increase in the expression of zif268 protein in the cornus ammonis (CA) region, whereas the same protocols of stimulation produce a less pronounced increase in c-fos protein expression in the CA and in dentate gyrus regions of the hippocampus. Brain-derived neurotrophic factor expression was also investigated, and it was found to be reduced in cathodal-stimulated slices. The present data demonstrate that it is possible to modulate LTP by using DCS and provide the rationale for the use of DCS in neurological diseases to promote the adaptive and suppress the maladaptive forms of brain plasticity.