bluuebunny/crossref_metadata_2025 huggingface dataset:
A common variant of the eNOS gene (E298D) is an independent risk factor for left ventricular hypertrophy in human essential hypertension
Authors: Xin Ying , Song Xiaodong , Xue Hao , Liu Zhe , Wang Xiaojian , Wang Hu , Sun Kai , Bai Yongyi , Liu Junhao , Hui Rutai
Published: January 2009

eNOS (endothelial NO synthase) plays a critical role in the development of ventricular remodelling and cardiac hypertrophy. The purpose of the present study was to determine whether three common variants in NOS3 (the eNOS gene) are associated with the risk of LVH [LV (left ventricular) hypertrophy] in patients with essential hypertension. Three NOS3 genetic variants, −T786C (rs2070744), eNOS4a/b and +G894T (rs1799983), were genotyped in two independent case-control studies: the first study consisted of 1061 hypertensive patients with LVH and 1118 hypertensive patients without LVH, and the second sample consisted of 120 patients with LVH and 223 patients without LVH. Echocardiographic measurements were obtained in all of the hypertensive patients. Only the +G894T (E298D) variant of NOS3 was associated with a higher risk of LVH {OR (odds ratio), 1.67 [95% CI (confidence interval), 1.19–2.36]; P<0.01} in the first population, and replicated in the second population [OR, 1.41 (95% CI, 1.01–2.28); P<0.05] in a recessive model. Compared with carriers of the G allele (GT+GG), patients carrying the TT genotype had increased septal wall thickness (16.2%, P<0.01 and 11.7%, P<0.01 respectively), LV posterior wall thickness (8.3%, P<0.01 and 7.1%, P<0.01 respectively), LV mass index (14.0%, P<0.01 and 25.1%, P<0.01 respectively) and relative wall thickness (13.1%, P<0.01 and 16.2%, P<0.01 respectively) in the first and second populations. The results of the present study support that homozygosity for +G894T (E298D) in NOS3 is a genetic risk factor for the development of LVH in patients with hypertension.
Adiabatic invariance along the reaction coordinate
Authors: Lorquet J. C.
Published: January 2009

In a two-dimensional space where a point particle interacts with a diatomic fragment, the action integral ∮pθdθ (where θ is the angle between the fragment and the line of centers and pθ its conjugate momentum) is an adiabatic invariant. This invariance is thought to be a persistent dynamical constraint. Indeed, its classical Poisson bracket with the Hamiltonian is found to vanish in particular regions of the potential energy surface: asymptotically, at equilibrium geometries, saddle points, and inner turning points, i.e., at remarkable situations where the topography of the potential energy surface is locally simple. Studied in this way, the adiabatic decoupling of the reaction coordinate is limited to disjoint regions. However, an alternative view is possible. The invariance properties of entropy (as defined in information theory) can be invoked to infer that dynamical constraints that are found to operate locally subsist everywhere, throughout the entire reactive process, although with a modified expression.
Magnetotransport of La0.5Ba0.5MnO3
Authors: Pȩkała M. , Drozd V. , Fagnard J. F. , Vanderbemden Ph. , Ausloos M.
Published: January 2009

Physical properties of polycrystalline La0.5Ba0.5MnO3 are reported from low temperature (10 K) up to above room temperature. An aim has been to obtain microscopic parameters and to search for the characteristic lengths in terms of which one can discuss the interplay between magnetic, electric, and phonon excitations. The structural and magnetotransport measurements reveal a set of relatively high transition temperatures (near 300 K) between ferromagnetic/metallic and paramagnetic/semiconducting phases. It is found, in particular, that the so-called localization length increases from 0.085 to 0.24 nm when the magnetic field varies from 0 to 8 T. Moreover a “special field value” ∼0.03 T is observed in the description of the electrical resistance. It cannot be presently distinguished whether it is the signature of a spin reorientation transition in the canted phase or a mere saturation field for aligning magnetic domains. The relatively high magnetoresistance effect (≃55% at 8 T and 10 K) makes the La0.5Ba0.5MnO3 a very interesting material for among others sensor applications.
Conceptual design of International Linear Collider damping ring wiggler based on a hybrid technology
Authors: Smirnov Alexei V.
Published: January 2009

A magnetic design of a failure-free damping ring wiggler with 100% duty factor, 55.6 mm gap, and field exceeding 1.6 T is proposed. The insertion device is based on permanent magnets and specially shimmed poles that capable to meet the requirements of the International Linear Collider (ILC) damping rings (including positron one), with field quality and gap comparable to that projected for ILC using superconducting wiggler. Performance improvement of the modified hybrid design is attained due to yoke reduction down to six separated strips and maximized packaging of the midgrade (or high-grade) parallelepiped magnet blocks surrounding the Permendur poles. Economical efficiency is demonstrated on the base of calculated amount of magnetic material. A cryogenic variant of the hybrid design may certainly provide good sustainability to harsh radiation environment and further enhancement of the design efficiency within the state of the art.
Abnormal crystal structure stability of nanocrystalline Sm2Co17 permanent magnet
Authors: Song Xiaoyan , Lu Nianduan , Seyring Martin , Rettenmayr Markus , Xu Wenwu , Zhang Zhexu , Zhang Jiuxing
Published: January 2009

Abnormal crystal structure stability is discovered in the single-phase nanocrystalline Sm2Co17 permanent magnet. Three kinds of crystal structures, namely the rhombohedral Th2Zn17-type (2:17 R), the hexagonal TbCu7-type (1:7 H), and the hexagonal Th2Ni17-type (2:17 H), are claimed to exist at room temperature in the Sm2Co17 alloy system. The strong dependence of the magnetic properties on the structure characteristics in the single-phase Sm2Co17 alloy is interpreted in view of the atom space occupancy and the exchange coupling between substructures especially in the nanocrystalline alloy.
Hybrid binomial Langevin-multiple mapping conditioning modeling of a reacting mixing layer
Authors: Wandel Andrew P. , Lindstedt R. Peter
Published: January 2009

A novel, stochastic, hybrid binomial Langevin-multiple mapping conditioning (MMC) model—that utilizes the strengths of each component—has been developed for inhomogeneous flows. The implementation has the advantage of naturally incorporating velocity-scalar interactions through the binomial Langevin model and using this joint probability density function (PDF) to define a reference variable for the MMC part of the model. The approach has the advantage that the difficulties encountered with the binomial Langevin model in modeling scalars with nonelementary bounds are removed. The formulation of the closure leads to locality in scalar space and permits the use of simple approaches (e.g., the modified Curl’s model) for transport in the reference space. The overall closure was evaluated through application to a chemically reacting mixing layer. The results show encouraging comparisons with experimental data for the first two moments of the PDF and plausible results for higher moments at a relatively modest computational cost.
Striped domains at the pentacene:C60 interface
Authors: Dougherty Daniel B. , Jin Wei , Cullen William G. , Reutt-Robey Janice E. , Robey Steven W.
Published: January 2009

Scanning tunneling microscopy observations of the initial growth stages of the first layer of pentacene on a monolayer film of C60 on Ag(111) are presented. Pentacene films nucleate and grow with molecules standing up at the pentacene:C60 interface similar to thin film phases observed on weakly interacting substrates such as SiO2. Unlike reported thin film pentacene phases, those on 1 monolayer C60/Ag(111) exhibit a striated morphology with domains of 4 nm nominal width. This long range pattern of periodic pentacene displacements relative to the substrate is the response to stress induced in the pentacene film by its interaction with the rigid C60 support.
Nonholonomic constraints: A new viewpoint
Authors: Grabowski J. , de León M. , Marrero J. C. , Martín de Diego D.
Published: January 2009

The purpose of this paper is to show that, at least for Lagrangians of mechanical type, nonholonomic Euler–Lagrange equations for a nonholonomic linear constraint D may be viewed as nonconstrained Euler–Lagrange equations but on a new (generally not Lie) algebroid structure on D. The proposed novel formalism allows us to treat in a unified way a variety of situations in nonholonomic mechanics and gives rise to a version of Noether theorem producing actual first integrals in the case of symmetries.
Principal realization of the Yangian Y(gl(n))
Authors: Bai Cheng-Ming , Ge Mo-Lin , Jing Naihuan
Published: January 2009

Motivated to simplify the structure of tensor representations we give a new set of generators for the Yangian Y(sl(n)) using the principal realization in simple Lie algebras. The isomorphism between our new basis and the standard Cartan–Weyl basis is also given. We show by example that the principal basis simplifies the Yangian action significantly in the tensor product of the fundamental representation and its dual.
Exact traveling solutions of some nonlinear evolution equation by (G′/G)-expansion method
Authors: Ganji D. D. , Abdollahzadeh M.
Published: January 2009

In this paper, we establish exact solutions for some nonlinear evolution equations. The (G′/G)-expansion method was used to construct traveling wave solutions of Ramani’s equations. In this method we take the advantages of the general solutions of the second order LODE to solve effectively many nonlinear evolution equations. The (G′/G)-expansion method presents a wider applicability for handling nonlinear wave equations.
Influence of aluminum nanoparticle surface treatment on the electrical properties of polyethylene composites
Authors: Huang Xingyi , Kim Chonung , Jiang Pingkai , Yin Yi , Li Zhe
Published: January 2009

In this study, we investigated the influence of the surface treatment of Al nanoparticles on the electrical properties of linear low density polyethylene composites. Octyl-trimethoxysilane was used as a nonpolar silane coupling agent for the surface treatment of Al nanoparticles. It was found that the incorporation of nonpolar octyl groups onto the surface of Al nanoparticles not only increased the percolation threshold and the resistivity but also improved the dielectric properties as compared to the composites filled with unsurface-treated nanoparticles. The surface treatment makes it possible to easily control the frequency and concentration dependences of dielectric constant and provided an excellent approach able to considerably reduce the dielectric loss of the nanocomposites, which is of great significance from the viewpoint of practical application of the polymer/metal nanocomposites in the electrical and electronic industries. It is concluded that the improved electrical properties could be directly ascribed to the good dispersion and special electrical feature of the surface-treated nanoparticles in the polymer matrix.
Stability analysis of thin film flow along a heated porous wall
Authors: Thiele Uwe , Goyeau Benoît , Velarde Manuel G.
Published: January 2009

The time evolution of a thin liquid film flowing down a heated solid porous substrate is investigated. Using the Navier–Stokes and Darcy–Brinkman equations in the film and the porous layer, respectively, the problem is reduced to the study of the evolution equation for the free surface of the liquid film derived through a long-wave approximation. A linear stability analysis of the base flow is performed and the critical Reynolds and Marangoni numbers are obtained. A nonlinear analysis using continuation techniques shows that the base flow yields to stationary surface structures ranging from surface waves to large amplitude structures resembling sliding drops or ridges. It is also shown under what conditions the porous layer can be replaced by an effective slip boundary condition at the liquid-solid interface. Then, the corresponding slip length is calculated from the porous layer characteristics (thickness, porosity, and Darcy number).
Resonant generation of the rectification electric mode in suddenly created cold lossless magnetized plasma. transversal propagation
Authors: Trifkovic Zoran M. , Osmokrovic Predrag V.
Published: January 2009

The nonlinear transformation of the linearly polarized source electromagnetic wave into electron and electromagnetic plasma oscillations, stationary (rectification and space-varying) modes, and traveling electron and electromagnetic plasma waves due to weak nonlinearity has been analyzed by means of the second order perturbation theory with the radio approximation. The efficiency of excitation of the transversal stationary, spatially nonperiodical (rectification) electric mode has been studied for different values of source wave frequency, taking electron cyclotron frequency as a parameter.
Intrinsic phase separation in a single crystal of La0.98Pb0.02Mn0.74Co0.25O3
Authors: Zhao B. C. , Sun Y. P. , Song W. H. , Wang L.
Published: January 2009

Systematic studies of magnetic, electrical, and thermal transport properties have been performed on a single crystal of La0.98Pb0.02Mn0.74Co0.25O3. From 5 to 500 K, the material system shows three distinct magnetic states, a low-temperature glassing state (from 5 to 185 K), a Griffiths-like ferromagnetic state (from 185 to 326 K), and a single paramagnetic phase above 326 K. The sample shows a semiconducting electrical transport behavior in the whole studied temperature range. With decreasing temperature, magnetoresistance increases rapidly from 290 K and reaches a maximum at 185 K and then decreases continuously with a broad peak in the vicinity of 100 K. Magnetothermopower also presents obvious anomalies at these characteristic temperatures. Both the magnetic and transport properties suggest an intrinsic phase separation in the single crystal.
Penning ionization electron spectra of pyrene, chrysene, and coronene in collision with metastable He(2 3S) atoms in the gas phase
Authors: Yamakita Yoshihiro , Yamauchi Masayo , Ohno Koichi
Published: January 2009

Penning ionization electron spectra (PIES) of pyrene (C16H10), chrysene (C18H12), and coronene (C24H12) in the gas phase are recorded using metastable He∗(2 3S) atoms. The assignments of PIES are presented based on the outer valence Green’s function calculations with the correlation consistent polarized valence triple-ζ basis sets and the exterior electron density calculations of contributing molecular orbitals. The definite positions of all of the π bands in the PIES are identified making use of the large PIES cross sections. Broad bands are observed in low-electron-energy regions for chrysene and coronene and are ascribed to ionization processes of non-Koopmans types from σ orbitals. The anisotropic interaction potential energy surfaces for the colliding systems are obtained from ab initio model potentials for the related systems with similar outer valences Li(2 2S)+C16H10, C18H12, and C24H12, respectively. The attractive well depths in the out-of-plane directions are found to be similar between these molecules, and the repulsive walls embrace the in-plane perimeters uniformly. Collision energy dependencies for partial Penning ionization cross sections and negative peak shifts in PIES for chrysene support these anisotropic interactions. Effects from thermal populations in low-frequency vibrational modes are estimated to be minor in one-electron ionization processes.
Curvature dependence of the electrolytic liquid-liquid interfacial tension
Authors: Bier Markus , de Graaf Joost , Zwanikken Jos , van Roij René
Published: January 2009

The interfacial tension of a liquid droplet surrounded by another liquid in the presence of microscopic ions is studied as a function of the droplet radius. An analytical expression for the interfacial tension is obtained within a linear Poisson–Boltzmann theory and compared with numerical results from nonlinear Poisson–Boltzmann theory. The excess liquid-liquid interfacial tension with respect to the pure salt-free liquid-liquid interfacial tension is found to decompose into a curvature-independent part due to short-ranged interfacial effects and a curvature-dependent electrostatic contribution. Several curvature-dependent regimes of different scalings of the electrostatic excess interfacial tension are identified. Symmetry relations of the interfacial tension upon swapping droplet and bulk liquid are found to hold in the low-curvature limit, which, e.g., lead to a sign change of the excess Tolman length. For some systems a low-curvature expansion up to the second order turns out to be applicable if and only if the droplet size exceeds the Debye screening length in the droplet, independent of the Debye length in the bulk.
Strain-relaxed structure in (001)/(100)-oriented epitaxial Pb(Zr,Ti)O3 films grown on (100) SrTiO3 substrates by metal organic chemical vapor deposition
Authors: Nakaki Hiroshi , Kim Yong Kwan , Yokoyama Shintaro , Ikariyama Rikyu , Funakubo Hiroshi , Nishida Ken , Saito Keisuke , Morioka Hitoshi , Sakata Osami , Han Hee , Baik Sunggi
Published: January 2009

Epitaxial (100)/(001)-oriented tetragonal Pb(Zr,Ti)O3 films above 1 μm thick were grown on (100)SrTO3 substrates by pulsed metal organic chemical vapor deposition, and the films with Zr/(Zr+Ti) ratios up to 0.43 were found to have a strain-relaxed domain structure. The domain structure determined by the volume fraction of (001) orientation (mainly decided by the thermal strain above the Curie temperature) and the lattice parameters dependent on the Zr/(Zr+Ti) ratio are explained by a geometrical model consistent with previous results for PbTiO3 films [J. Appl. Phys. 104, 064121 (2008)].
Novel methodology for estimating the enhancement factor for tip-enhanced Raman spectroscopy
Authors: Roy Debdulal , Wang Jian , Williams Craig
Published: January 2009

Enhancement factor and spatial resolution are two of the most important metrological parameters defining the quality of a tip-enhanced Raman spectrometer. A high degree of variability in the reported values of enhancement factor is highlighted in this work, and the possible reasons for the discrepancies are discussed. A methodology for estimating enhancement factor in tip-enhanced Raman imaging using a one-dimensional nanostructure such as single wall carbon nanotube is suggested. This methodology is verified using tip-enhanced Raman images from our laboratory, and an image from another group published previously.
Extension of analytical model for conduction band nonparabolicity to transport analysis of nanoscale metal-oxide-semiconductor field-effect transistor
Authors: Omura Yasuhisa
Published: January 2009

This paper reconsiders the mathematical formulation for the conventional nonparabolic band model and discusses how the nonparabolicity of the conduction band impacts the effective masses of electrons that are confined within the barriers. Since the conventional simplified model for band nonparabolicity does not include the external potential effect as a perturbation, it is examined whether this perturbation can be implemented into the conventional model for usefulness. When the perturbation energy is smaller than the unperturbed energy, the insertion of the perturbation energy term into the conventional expression for the nonparabolic band model is reasonably valid. It is demonstrated that this approximation is actually accurate given a sub-10-nm-thick Si layer surrounded by an SiO2 layer. A major part of this discussion is focused on the low-dimensionality electron system confined with insulator barriers so this study contributes to the analysis of future electron devices. To support this consideration, this paper proposes an analytical expression for the conduction-band effective mass of electrons including the term of band nonparabolicity.
Photothermal actuation in nanomechanical waveguide devices
Authors: Pernice Wolfram H. P. , Li Mo , Tang Hong X.
Published: January 2009

We analyze the photothermal response of nanoelectromechanical systems (NEMS) integrated in a silicon photonic circuit over a wide frequency range. The dynamic response of NEMS devices is studied using a two-color pump-probe scheme in an on-chip photonic Mach–Zehnder interferometer. The measured response is composed of three contributions: (i) the mechanical response of the NEMS device, (ii) the thermal response of the substrate due to diffusive heating, and (iii) self-heating of the NEMS beam. Analytical and numerical studies of the self-heating effect reveal a first-order thermal roll-off behavior in close agreement with experimental results. Device actuation due to self-heating of the beam is shown to dominate other effects at low frequencies, while an exponential roll-off with 20 dB per decade at high frequencies is observed.
Magnetization reversals in a disk-shaped small magnet with an interface
Authors: Silva R. L. , Pereira A. R. , Moura-Melo W. A.
Published: January 2009

We consider a nanodisk possessing two coupled materials with different ferromagnetic exchange constants. The common borderline of the two media crosses at the disk center, dividing the system exactly in two similar half-disks. The vortex core motion crossing the interface is investigated using a two-dimensional model, which mimics a very thin, real material with such a line defect. The main result of this study is that, depending on the magnetic coupling which connects the media, the vortex core can be dramatically and repeatedly flipped up to down by the interface. This phenomenon produces a burstlike emission of spin waves each time the switching process takes place.
Tunable terahertz radiation from a tunnel ionized magnetized plasma cylinder
Authors: Liu C. S. , Tripathi V. K.
Published: January 2009

A scheme of producing tunable terahertz radiation using a short pulse laser to tunnel ionize a gas jet immersed in a magnetic field is examined. The free electrons born inside the laser pulse retain a finite transverse drift after the passage of the pulse, setting themselves in transverse oscillations at frequencies ωR,ωL=[(2ωp2+ωc2)1/2±ωc]/2, shifted from that without magnetic field at ωp/2, where ωp is the electron plasma frequency and ωc is the cyclotron frequency. The oscillating electron cylinder emits coherent terahertz radiation with ambient magnetic field providing the frequency tunability. The presence of an axial density ripple controls the angular orientation of the emitted radiation.
Self-diffusion coefficient in smoothed dissipative particle dynamics
Authors: Litvinov Sergey , Ellero Marco , Hu Xiangyu , Adams Nikolaus A.
Published: January 2009

Smoothed dissipative particle dynamics (SDPD) is a novel coarse grained method for the numerical simulation of complex fluids. It has considerable advantages over more traditional particle-based methods. In this paper we analyze the self-diffusion coefficient D of a SDPD solvent by using the strategy proposed by Groot and Warren [J. Chem. Phys. 107, 4423 (1997)]. An analytical expression for D in terms of the model parameters is developed and verified by numerical simulations.
Anisotropic etching of amorphous perfluoropolymer films in oxygen-based inductively coupled plasmas
Authors: Ono Takao , Akagi Takanori , Ichiki Takanori
Published: January 2009

An amorphous perfluoropolymer, “Cytop™” (Asahi Glass Co., Ltd.), is a preferable material for the fabrication of micro total analysis system devices because of its superior optical transparency over a wide wavelength range and low refractive index of 1.34, which is almost the same as that of water, as well as excellent chemical stability. To establish the precise microfabrication technology for this unique resin, the dry etching of the amorphous perfluoropolymer in Ar/O2 low-pressure inductively coupled plasma has been studied. A relatively high etch rate of approximately 6.3 μm/min at maximum and highly anisotropic etched features was attained. Plasma measurements by a single Langmuir probe technique and actinometry revealed that etching is dominated by ion-assisted surface desorption above a 10% O2 mixing ratio, whereas the supply of active oxygen species is the rate-limiting process below 10%. Moreover, angled x-ray photoelectron spectroscopy measurements of an etched trench pattern revealed that a high anisotropy is attributed to the formation of a carbon-rich sidewall protection layer.
Photopumped green lasing on BeZnSeTe double heterostructures grown on InP substrates
Authors: Nomura Ichirou , Kishino Katsumi , Ebisawa Tomoya , Sawafuji Yutaka , Ujihara Rieko , Tasai Kunihiko , Nakamura Hitoshi , Asatsuma Tsunenori , Nakajima Hiroshi
Published: January 2009

Double heterostructures (DHs) consisting of BeZnSeTe active and MgSe/BeZnTe superlattice cladding layers were fabricated on InP substrates by molecular beam epitaxy. By photoexciting the DHs, green lasing emissions at 548 nm were obtained at room temperature. The threshold excitation power density was 70 kW/cm2, from which we estimated the threshold carrier density and threshold current density assuming a green laser diode (LD) with a BeZnSeTe active layer to be (1.4–4.6)×1018 cm−3 and 0.22–0.73 kA/cm2, respectively. The experiment proved the applicability of BeZnSeTe as an active layer of green LDs.
Low-field and high-field electron transport in zinc blende InN
Authors: Polyakov V. M. , Schwierz F. , Fuchs F. , Furthmüller J. , Bechstedt F.
Published: January 2009

We report on the electron transport in zinc blende InN simulated by the ensemble Monte Carlo method. To obtain the relevant band structure parameters, ab initio calculations have been carried out. Then, Monte Carlo transport simulations at room temperature and over a wide range of carrier concentrations have been performed. We obtain a steady-state peak drift velocity around 3.3×107 cm/s at an electric field of 55 kV/cm. For low-doped material, a room-temperature low-field mobility of about 6000 cm2/V s is calculated. A comparison with wurtzite InN does not reveal an advantage for the zinc blende InN phase regarding the electron transport.
Soft magnetic FeSiBPCu heteroamorphous alloys with high Fe content
Authors: Makino Akihiro , Men He , Yubuta Kunio , Kubota Takeshi
Published: January 2009

Fe–Si–B amorphous alloys with less than 80 at. % Fe are now in practical use because of their excellent magnetic softness and rather high magnetization (Js) basically owing to the lack of intrinsic magnetic anisotropy and the high Fe content, respectively. A strict upper limit of the Fe content (about 80 at. %) for the formation of a single amorphous phase with good magnetic softness hinders the improvement in Js of the Fe-based amorphous alloys. The alloys with the high Fe content exceeding the limit commonly have the as-quenched structure consisting of coarse α-Fe grains in an amorphous matrix, which inevitably results in inferior magnetic softness. The simultaneous addition of proper amounts of P and Cu is found to be significantly effective in decreasing the grain size of α-Fe phase, formed in an amorphous matrix in the as-quenched Fe82Si9B9 amorphous alloys with high Fe content exceeding the limit. Fe-rich Fe81.7Si9B7P2Cu0.3 heteroamorphous alloy with an as-quenched structure consisting of extremely small α-Fe-like clusters of about 3 nm or smaller in diameter, randomly dispersed within the amorphous matrix, exhibits the lower coercivity of 7 A m−1 and the higher Js of 1.56 T than the typical Fe-based monolithic amorphous alloy at an as-quenched state.
MgB
2
grain boundary nanobridges prepared by focused ion beam
Authors: Lee Soon-Gul , Hong Sung-Hak , Kang Won Nam , Kim Dong Ho
Published: January 2009

We have fabricated MgB2 grain boundary nanobridges by focused-ion-beam etch and studied their transport properties. Nanobridges with a nominal width and length of 100 nm were patterned across naturally formed single grain boundaries in the microbridges, which were prepatterned by a standard argon ion milling technique. We have studied current-voltage (I-V) characteristics, the temperature-dependent critical current, and the normal-state resistance. The measured properties were interpreted based on a flux flow model. In the I-V curves, a typical resistively shunted-junction characteristic was observed near Tc, however, as temperature decreases, flux-flow behavior became dominant, in accordance with the crossover of the ratio of the bridge length to the coherence length from the single-phased regime to the flux-flow regime. The temperature-dependent critical current was Ic(T)∼(1−T/Tc)1–1.5, similar to that of a superconducting film. The normal-state resistance increased steeply as temperature approaches Tc, in agreement with the flux-flow theory.
Tunable ambipolar Coulomb blockade characteristics in carbon nanotubes-gated carbon nanotube field-effect transistors
Authors: Li Hong , Zhang Qing
Published: January 2009

A single-walled carbon nanotube field-effect transistor has been fabricated with two single-walled carbon nanotube bundles as its top gates and a heavily doped p-type silicon substrate as its global back gate. The channel conductance is found to oscillate significantly as a function of the top- and back-gate voltages when the device is measured at 100 K or below. “Diamond”-shaped current forbidden regions can be clearly observed under both positive and negative top-gate voltages. A single-electron transistor model is proposed to qualitatively explain the observations.
Light extraction from GaN-based light emitting diode structures with a noninvasive two-dimensional photonic crystal
Authors: Truong T. A. , Campos L. M. , Matioli E. , Meinel I. , Hawker C. J. , Weisbuch C. , Petroff P. M.
Published: January 2009

A noninvasive fabrication process involving soft nanoimprint lithography is used to pattern a photonic crystal (PhC) in titania film for enhanced light extraction from a GaN light emitting diode (LED). This technique avoids damaging the LED structure by the etching process, while photoluminescence measurements show extracted modes emitted from the quantum wells which agree well with modeling. A light extraction improvement of 1.8 times is measured using this noninvasive PhC.
Thermoelectric power measurements of wide band gap semiconducting nanowires
Authors: Lee Chul-Ho , Yi Gyu-Chul , Zuev Yuri M. , Kim Philip
Published: January 2009

We investigated the temperature-dependent thermoelectric power (TEP) of individual wide band gap ZnO and GaN semiconducting nanowires by fabricating the devices with good Ohmic contacts. In the temperature range of 10–300 K, the measured TEP of both nanowires was linearly dependent on temperature, indicating the degenerate doping nature of these nanowires. The room temperature TEP value of ZnO nanowires was as high as −400 μV/K while an order of magnitude smaller TEP value was observed in GaN. The negative sign of TEP values shows that electrons are the majority carriers in these wide band gap nanowires. More importantly, in comparison with gate-dependent transport measurements of the nanowire field effect transistors, analysis of temperature-dependent TEP measurements provides a reliable way of estimating the majority carrier concentration of nanowires, where conventional Hall effect measurements cannot be used.
Frequency and amplitude modulation in terahertz-sideband generation in quantum wells
Authors: Kim Dong Kwon , Citrin D. S.
Published: January 2009

A narrow-band optical beam incident on a quantum well modulated at terahertz frequencies results in the formation of terahertz sidebands, i.e., optical signals at the input optical frequency plus integer multiples of the modulation frequency. The terahertz sidebands originate in the modulated complex optical susceptibility. In this study, we analyze theoretically terahertz-sideband generation in the context of frequency and amplitude modulations of the incident optical beam. We find that, at the optimum bias field, the frequency and amplitude modulations contribute almost equally to the maximum first-order sideband. The theoretical approach could offer simple yet useful tools for further engineering and optimization of modulator-type sideband-generation or wavelength-conversion devices.
Atmospheric plasma jet array in parallel electric and gas flow fields for three-dimensional surface treatment
Authors: Cao Z. , Walsh J. L. , Kong M. G.
Published: January 2009

This letter reports on electrical and optical characteristics of a ten-channel atmospheric pressure glow discharge jet array in parallel electric and gas flow fields. Challenged with complex three-dimensional substrates including surgical tissue forceps and sloped plastic plate of up to 15°, the jet array is shown to achieve excellent jet-to-jet uniformity both in time and in space. Its spatial uniformity is four times better than a comparable single jet when both are used to treat a 15° sloped substrate. These benefits are likely from an effective self-adjustment mechanism among individual jets facilitated by individualized ballast and spatial redistribution of surface charges.
Investigation of field-induced ferromagnetism in Pd–Ni–Fe–P metallic glass by x-ray magnetic circular dichroism
Authors: Yu D. H. , Duriavig J. , Loh N. , Woodward R. , Lin H. J. , Chang F. H. , Kilcoyne S. H. , Stampfl A. , Robinson R. A.
Published: January 2009

We have applied x-ray magnetic circular dichroism to investigate the field-induced ferromagnetism in Pd40Ni22.5Fe17.5P20 alloy. The experiment revealed that both Ni and Fe were in a divalent state and that the magnetic properties of the material were determined by the localized 3d electrons of the transition metals. No clear evidence of Ruderman–Kittel–Kasuya–Yosida-type interaction among magnetic clusters was observed. It is believed that the detailed balance of fundamental spin-orbit and exchange interactions as a function of temperature and applied magnetic field determine the different magnetic properties of the alloy.
Effect of laser-induced double-step ionization of a gas on vacuum electron acceleration
Authors: Gupta Devki Nandan , Jang Hyo Jae , Suk Hyyong
Published: January 2009

The effect of laser-induced double ionization of a helium gas on electron acceleration is investigated. The optical field ionization of a gas of sufficient density can significantly change its refractive index, which makes the incident laser pulse diverge. For an enough laser intensity, the helium gas can be found doubly ionized and it strengthens the divergence of the pulse. As a result, electrons feel a very low laser intensity at the trailing part of the laser pulse. Hence, there is not much electron deceleration at the trailing part of the pulse. Therefore, a significant enhancement in electron energy by the laser acceleration may be observed.
Transverse surface waves in a functionally graded piezoelectric substrate coated with a finite-thickness metal waveguide layer
Authors: Qian Zheng-Hua , Jin Feng , Lu Tian-Jian , Kishimoto Kikuo
Published: January 2009

An analytical study on transverse surface waves propagating in a functionally graded piezoelectric substrate carrying a metal layer of finite thickness was carried out. Dispersion relations for the existence of the waves were obtained and the effects of material gradient on wave propagation were quantified. Numerical examples show that the presence of the material gradient affects significantly the fundamental mode but has only negligible effects on the higher order modes. Depending on whether the surface wave velocity is smaller or greater than the bulk shear wave velocity in the metal layer, three different types of the dispersion behavior are discussed.
Wafer-bonded single-crystal silicon slot waveguides and ring resonators
Authors: Briggs Ryan M. , Shearn Michael , Scherer Axel , Atwater Harry A.
Published: January 2009

We fabricated horizontal Si slot waveguides with a 25 nm SiO2 slot layer by bonding thin Si-on-insulator wafers. After removing the Si substrate and buried oxide from one side of the bonded structure, grating-coupled waveguides and ring resonators were partially etched into the Si/SiO2/Si device layers. The gratings exhibit efficiencies of up to 23% at 1550 nm and the ring resonators were measured to have loaded quality factors near 42 000 for the lowest-order transverse-electric mode, corresponding to a propagation loss of 15 dB/cm. The leaky lowest-order transverse-magnetic mode was also observed with a propagation loss of 44 dB/cm.
High band gap poly(9,9-dihexylfluorene-alt-bithiophene) blended with [6,6]-phenyl C61 butyric acid methyl ester for use in efficient photovoltaic devices
Authors: Schulz Gisela L. , Chen Xiwen , Holdcroft Steven
Published: January 2009

This paper reports a study of a high band gap conjugated polymer poly(9,9-dihexylfluorene-alt-bithiophene) (F6T2) in an organic photovoltaic device. F6T2 blended with [6,6]-phenyl C61 butyric acid methyl ester (1:4 weight ratio) produced films exhibiting phase segregated domains ∼5 nm in size, and possessing a hole mobility of 3×10−8 m2/V s. Open circuit voltages of photovoltaic devices were greater than 1 V, and power conversion efficiencies of 2.7% based on AM 1.5 G illumination were measured. External quantum efficiencies of up to 48 %, and internal quantum efficiencies of up to 87 % were calculated.
Optimum quantum well width for III-nitride nonpolar and semipolar laser diodes
Authors: Kisin Mikhail V. , Brown Robert G. W. , El-Ghoroury Hussein S.
Published: January 2009

The advantage of using wider quantum wells in III-nitride lasers offered by nonpolar/semipolar technology is limited by narrower valence subband separation, thermal hole redistribution, and resulting optical gain degradation in wider wells. We show that corresponding increase in radiative carrier lifetime in wider quantum wells can lower the laser threshold, thus inferring the existence of an optimum quantum well width for laser design.
Sense of Agency Primes Manual Motor Responses
Authors: Longo Matthew R , Haggard Patrick
Published: January 2009

Perceiving the body influences how we perceive and respond to stimuli in the world. We investigated the respective effects of different components of bodily representation—the senses of ownership and agency—on responses to simple visual stimuli. Participants viewed a video image of their hand on a computer monitor presented either in real time, or with a systematic delay. Blocks began with an induction period in which the index finger was (i) brushed, (ii) passively moved, or (iii) actively moved by the participant. Subjective reports showed that the sense of ownership over the seen hand emerged with synchronous video, regardless of the type of induction, whereas the sense of agency over the hand emerged only following synchronous video with active movement. Following induction, participants responded as quickly as possible to the onset of visual stimuli near the hand by pressing a button with their other hand. Reaction time was significantly speeded when participants had a sense of agency over their seen hand. This effect was eliminated when participants responded vocally, suggesting that it reflects priming of manual responses, rather than enhanced stimulus detection. These results suggest that vision of one's own hand—and, specifically, the sense of agency over that hand—primes manual motor responses.
Aging-related loss of the chromatin protein HMGB2 in articular cartilage is linked to reduced cellularity and osteoarthritis
Authors: Taniguchi Noboru , Caramés Beatriz , Ronfani Lorenza , Ulmer Ulrich , Komiya Setsuro , Bianchi Marco E. , Lotz Martin
Published: January 2009

Osteoarthritis (OA) is the most common joint disease and typically begins with an aging-related disruption of the articular cartilage surface. Mechanisms leading to the aging-related cartilage surface degeneration remain to be determined. Here, we demonstrate that nonhistone chromatin protein high-mobility group box (HMGB) protein 2 is uniquely expressed in the superficial zone (SZ) of human articular cartilage. In human and murine cartilage, there is an aging-related loss of HMGB2 expression, ultimately leading to its complete absence. Mice genetically deficient in HMGB2 (
Hmgb2
−/−
) show earlier onset of and more severe OA. This is associated with a profound reduction in cartilage cellularity attributable to increased cell death. These cellular changes precede glycosaminoglycan depletion and progressive cartilage erosions. Chondrocytes from
Hmgb2
−/−
mice are more susceptible to apoptosis induction
in vitro
. In conclusion, HMGB2 is a transcriptional regulator specifically expressed in the SZ of human articular cartilage and supports chondrocyte survival. Aging is associated with a loss of HMGB2 expression and reduced cellularity, and this contributes to the development of OA.
Aag-initiated base excision repair drives alkylation-induced retinal degeneration in mice
Authors: Meira Lisiane B. , Moroski-Erkul Catherine A. , Green Stephanie L. , Calvo Jennifer A. , Bronson Roderick T. , Shah Dharini , Samson Leona D.
Published: January 2009

Vision loss affects >3 million Americans and many more people worldwide. Although predisposing genes have been identified their link to known environmental factors is unclear. In wild-type animals DNA alkylating agents induce photoreceptor apoptosis and severe retinal degeneration. Alkylation-induced retinal degeneration is totally suppressed in the absence of the DNA repair protein alkyladenine DNA glycosylase (Aag) in both differentiating and postmitotic retinas. Moreover, transgenic expression of Aag activity restores the alkylation sensitivity of photoreceptors in
Aag
null animals.
Aag
heterozygotes display an intermediate level of retinal degeneration, demonstrating haploinsufficiency and underscoring that
Aag
expression confers a dominant retinal degeneration phenotype.
Photoresponsive nanoscale columnar transistors
Authors: Guo Xuefeng , Xiao Shengxiong , Myers Matthew , Miao Qian , Steigerwald Michael L. , Nuckolls Colin
Published: January 2009

This study reports a general methodology for making stable high-performance photosensitive field effect transistors (FET) from self-assembled columns of polycyclic aromatic hydrocarbons by using single-walled carbon nanotubes (SWNTs) as point contacts. In particular, the molecules used in this work are liquid crystalline materials of tetra(dodecyloxy)hexabenzocoronenes (HBCs) that are able to self-organize into columnar nanostructures with a diameter similar to that of SWNTs and then form nanoscale columnar transistors. To rule out potential artifacts, 2 different structural approaches were used to construct devices. One approach is to coat thin films of HBCs onto the devices with the SWNT–metal junctions protected by hydrogensilsesquioxane resin (HSQ), and the other is to place a droplet of HBC exactly on the nanogaps of SWNT electrodes. Both types of devices showed typical FET behaviors, indicating that SWNT–molecule–SWNT nanojunctions are responsible for the electrical characteristics of the devices. After thermally annealing the devices, HBC molecules assembled into columnar structures and formed more efficacious transistors with increased current modulation and higher gate efficiency. More interestingly, when the devices were exposed to visible light, photocurrents with an on/off ratio of >3 orders of magnitude were observed. This study demonstrates that stimuli-responsive nanoscale transistors have the potential applications in ultrasensitive devices for environmental sensing and solar energy harvesting.
Dual biosynthetic pathways to phytosterol via cycloartenol and lanosterol in
Arabidopsis
Authors: Ohyama Kiyoshi , Suzuki Masashi , Kikuchi Jun , Saito Kazuki , Muranaka Toshiya
Published: January 2009

The differences between the biosynthesis of sterols in higher plants and yeast/mammals are believed to originate at the cyclization step of oxidosqualene, which is cyclized to cycloartenol in higher plants and lanosterol in yeast/mammals. Recently, lanosterol synthase genes were identified from dicotyledonous plant species including
Arabidopsis
, suggesting that higher plants possess dual biosynthetic pathways to phytosterols via lanosterol, and through cycloartenol. To identify the biosynthetic pathway to phytosterol via lanosterol, and to reveal the contributions to phytosterol biosynthesis via each cycloartenol and lanosterol, we performed feeding experiments by using [6-
13
C
2
H
3
]mevalonate with
Arabidopsis
seedlings. Applying
13
C-{
1
H}{
2
H} nuclear magnetic resonance (NMR) techniques, the elucidation of deuterium on C-19 behavior of phytosterol provided evidence that small amounts of phytosterol were biosynthesized via lanosterol. The levels of phytosterol increased on overexpression of
LAS1
, and phytosterols derived from lanosterol were not observed in a
LAS1
-knockout plant. This is direct evidence to indicate that the biosynthetic pathway for phytosterol via lanosterol exists in plant cells. We designate the biosynthetic pathway to phytosterols via lanosterol “the lanosterol pathway.”
LAS1
expression is reported to be induced by the application of jasmonate and is thought to have evolved from an ancestral cycloartenol synthase to a triterpenoid synthase, such as β-amyrin synthase and lupeol synthase. Considering this background, the lanosterol pathway may contribute to the biosynthesis of not only phytosterols, but also steroids as secondary metabolites.
Tetherless thermobiochemically actuated microgrippers
Authors: Leong Timothy G. , Randall Christina L. , Benson Bryan R. , Bassik Noy , Stern George M. , Gracias David H.
Published: January 2009

We demonstrate mass-producible, tetherless microgrippers that can be remotely triggered by temperature and chemicals under biologically relevant conditions. The microgrippers use a self-contained actuation response, obviating the need for external tethers in operation. The grippers can be actuated en masse, even while spatially separated. We used the microgrippers to perform diverse functions, such as picking up a bead on a substrate and the removal of cells from tissue embedded at the end of a capillary (an in vitro biopsy).
Arginine racemization by coupled catabolic and anabolic dehydrogenases
Authors: Li Congran , Lu Chung-Dar
Published: January 2009

d
-Amino acids exist in living organisms as specialized components of many different machineries. Biosynthesis of
d
-amino acids from racemization of predominant
l
-enantiomers is catalyzed by a single enzyme. Here, we report the finding of a novel 2-component amino acid racemase for
d
-to-
l
inversion in
d
-arginine metabolism of
Pseudomonas aeruginosa
. From DNA microarray analysis, the putative
dauBAR
operon (for
d
-arginine utilization) of unknown functions was found to be highly induced by
d
-arginine. The importance of the
dau
operon in
d
-arginine metabolism was demonstrated by the findings that strains with a lesion at
dauA
or
dauB
failed to use
d
-arginine as sole carbon source. Two lines of evidence suggest that DauA and DauB are required for
d
-to-
l
racemization of arginine. First, growth complementation of an
l
-arginine auxotroph by
d
-arginine was abolished by a lesion at
dauA
or
dauB
. Second,
d
-arginine induced
l
-arginine-specific genes in the parental strain PAO1 but not in its
dauA
or
dauB
mutants. This hypothesis was further supported by activity measurements of the purified enzymes: DauA catalyzes oxidative deamination of
d
-arginine into 2-ketoarginine and ammonia, and DauB is able to use 2-ketoarginine and ammonia as substrates and convert them into
l
-arginine in the presence of NADPH or NADH. Thus, we propose that DauA and DauB are coupled catabolic and anabolic dehydrogenases to perform
d
-to-
l
racemization of arginine, which serves as prerequisite of
d
-arginine utilization through
l
-arginine catabolic pathways.