bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations from a Yakutat eddy in the northern Gulf of Alaska
Authors: Ladd C. , Kachel N. B. , Mordy C. W. , Stabeno P. J.
Published: February 2005

The impingement of deep basin eddies on the shelf in the Gulf of Alaska has been implicated as an important mechanism for cross‐shelf exchange. The influence of eddies on biological processes has been confirmed with data from the Sea‐viewing Wide Field‐of‐view Sensor showing elevated chlorophyll associated with eddies. Altimetry data suggest that an eddy formed in the winter of 2003 near Yakutat, Alaska, and propagated along the shelf break, reaching the head of the gulf by spring. This eddy was sampled during May and September of 2003. The eddy core water was warm, salty, and high in nitrate relative to basin water of the same density but was similar to historical water properties from the shelf near Yakutat. This suggests a shelf origin for the eddy core water.
Stimulus‐dependent glucocorticoid‐resistance of GM‐CSF production in human cultured airway smooth muscle
Authors: Tran Thai , Fernandes Darren J , Schuliga Michael , Harris Trudi , Landells Linda , Stewart Alastair G
Published: February 2005

For a subpopulation of asthmatics, symptoms persist even with high doses of glucocorticoids. Glucocorticoids reduce the levels of the proinflammatory and fibrogenic cytokine, granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) produced by human cultured airway smooth muscle (ASM). We have contrasted the effects of a synthetic glucocorticoid, dexamethasone, on thrombin‐ and IL‐1α‐stimulated GM‐CSF production in human ASM cells.

Although IL‐1α stimulated three‐fold higher levels of GM‐CSF mRNA and protein compared to thrombin, dexamethasone concentration‐dependently reduced IL‐1α‐stimulated GM‐CSF more potently and to a greater extent than the response to thrombin. This pattern of glucocorticoid regulation was also observed at the GM‐CSF mRNA level and was reproduced with other glucocorticoids such as fluticasone propionate.

IL‐1α and thrombin stimulated NF‐κB‐dependent luciferase expression equally. Dexamethasone treatment reduced luciferase expression stimulated by both IL‐1α and thrombin.

The GM‐CSF mRNA half life was markedly prolonged by IL‐1α compared to thrombin. This IL‐1α‐induced GM‐CSF mRNA stability was prevented by either dexamethasone or the p38MAPK inhibitor, SB203580, neither of which influenced GM‐CSF mRNA stability in thrombin‐treated cells. Dexamethasone inhibited p38MAPK phosphorylation in IL‐1α‐stimulated ASM, whereas thrombin does not stimulate p38MAPK phosphorylation.

These data suggest that the mechanism underlying the greater potency and efficacy of glucocorticoids in reducing GM‐CSF synthesis stimulated by IL‐1α depends on inhibition of the involvement of p38MAPK‐induced increases in GM‐CSF message stability.

British Journal of Pharmacology (2005) 145, 123–131. doi:10.1038/sj.bjp.0706174
Expansion dynamics and equilibrium conditions in a laser ablation plume of lithium: Modeling and experiment
Authors: Stapleton M. W. , McKiernan A. P. , Mosnier J.-P.
Published: February 2005

The gas dynamics and atomic kinetics of a laser ablation plume of lithium, expanding adiabatically in vacuum, are included in a numerical model, using isothermal and isentropic self-similar analytical solutions and steady-state collisional radiative equations, respectively. Measurements of plume expansion dynamics using ultrafast imaging for various laser wavelengths (266–1064nm), fluences (2–6.5Jcm−2), and spot sizes (50–1000μm) are performed to provide input parameters for the model and, thereby, study the influence of laser spot size, wavelength, and fluence, respectively, on both the plume expansion dynamics and atomic kinetics. Target recoil pressure, which clearly affects plume dynamics, is included in the model. The effects of laser wavelength and spot size on plume dynamics are discussed in terms of plasma absorption of laser light. A transition from isothermal to isentropic behavior for spot sizes greater than 50μm is clearly evidenced. Equilibrium conditions are found to exist only up to 300ns after the plume creation, while complete local thermodynamic equilibrium is found to be confined to the very early parts of the expansion.
Ordered Ni nanowire tip arrays sticking out of the anodic aluminum oxide template
Authors: Meng Guowen , Cao Anyuan , Cheng Ju-Yin , Vijayaraghavan Aravind , Jung Yung Joon , Shima Mutsuhiro , Ajayan Pulickel M.
Published: February 2005

We present a method for making highly ordered arrays of Ni nanowire (NW) tips fully exposed over the surface of anodic aluminum oxide (AAO) templates with uniform exposed lengths. Ni NWs are electrochemically deposited in the nanochannels of the AAO templates, and the templates surface is selectively etched to expose Ni NW tips of uniform lengths, which can be tuned by adjusting the etching time. The magnetic domain structure and magnetic hysteresis of the Ni NW tips were studied at room temperature, and the results indicate strong magnetic anisotropy for the NW arrays and magnetic coercivities significantly larger than that of bulk Ni. The ordered NW tips fully exposed over the surface of the AAO templates with uniform lengths could have various practical applications.
Electric-field-induced orthorhombic to rhombohedral phase transition in [111]C-oriented 0.92Pb(Zn1∕3Nb2∕3)O3−0.08PbTiO3
Authors: Davis Matthew , Damjanovic Dragan , Setter Nava
Published: February 2005

Strain-field measurements and in situ polarized light microscopy have been used to evidence a hysteretic, irreversible electric-field-induced transition to a quasimonodomain rhombohedral phase in [111]C-oriented, pseudo-orthorhombic PZN−8PT [0.92Pb(Zn1∕3Nb2∕3)O3−0.08PbTiO3]. This first-order transition most likely occurs following the simplest path O-MB-R, i.e., via polarization rotation in the (10-1)C plane. The measured strain-field loops are compared to those for rhombohedral, [111]C-oriented PMN−28PT [0.72Pb(Mg1∕3Nb2∕3)O3−0.28PbTiO3] and PMN−33PT [0.67Pb(Mg1∕3Nb2∕3)O3−0.33PbTiO3] where no electric-field-induced transition is possible.
Secondary barriers in CdS–CuIn1−xGaxSe2 solar cells
Authors: Pudov A. O. , Kanevce A. , Al-Thani H. A. , Sites J. R. , Hasoon F. S.
Published: February 2005

Previous work on CdS–CuInSe2 (CIS) solar cells, which reported distortions of their current-voltage (J–V) curves under red illumination, is expanded in this work to include CdS–CuIn1−xGaxSe2 cells with variable Ga and CIS cells with variable CdS thickness. Different amounts of J–V distortion were observed in these cells under red light. The details are in good agreement with predictions of a photodiode model, in which a secondary barrier caused by the positive conduction-band discontinuity (spike) at the buffer–absorber interface is responsible for the current limitation. The illumination of the cell with high-energy photons lowers the barrier due to buffer photoconductivity, and thus removes the J–V distortion.
Spin detectors operating in the medium-energy range
Authors: Drouhin Henri-Jean
Published: February 2005

Solid-state spin filters consisting of ultrathin ferromagnetic layers can be used as convenient spin polarimeters. A few years ago, a good sensitivity was demonstrated using a Pd∕Fe bilayer deposited onto a n-type ozonized GaAs substrate, the spin detector being operated around 800eV primary energy. From the analysis of the experimental data, a spin-dependent transport scheme is proposed. This provides keys for the practical development of spin filters in the keV range, an energy domain which is well suited for application, and opens perspectives in the study of hot-electron transport in metals.
A molecular dynamics simulation of the adsorption of water molecules surrounding an Au nanoparticle
Authors: Ju Shin-Pon
Published: February 2005

This study uses molecular dynamics simulations performed in a parallel computing environment to investigate the adsorption of water molecules surrounding Au nanoparticles of various sizes. An observation of the oxygen and hydrogen atom distributions reveals that the adsorption of the water molecules creates two shell-like formations of water in close vicinity to the Au nanoparticle surface. These shell-like formations are found to be more pronounced around smaller Au nanoparticles. The rearrangement of water molecules in this region reduces the local hydrogen bond strength to below that which is observed in the bulk region. Finally, the simulation results indicate that the absolute value of the interaction energy between the water molecules and the Au nanoparticle is reduced when the water molecules surround a nanoparticle of larger diameter. This observation implies that a stronger adsorption effect exists between smaller Au nanoparticles and water molecules. Hence, the value of the adsorption constant increases for smaller Au nanoparticles.
Small para-hydrogen clusters doped with carbon monoxide: Quantum Monte Carlo simulations and observed infrared spectra
Authors: Moroni S. , Botti M. , De Palo S. , McKellar A. R. W.
Published: February 2005

The structures and rotational dynamics of clusters of a single carbon monoxide molecule solvated in para-hydrogen, (paraH2)N–CO, have been simulated for sizes up to N=17 using the reptation Monte Carlo technique. The calculations indicate the presence of two series of R(0) rotational transitions with J=1←0 for cold clusters, similar to those predicted and observed in the case of HeN–CO. Infrared spectra of these clusters have been observed in the region of the C–O stretch (≈2143cm−1) in a pulsed supersonic jet expansion using a tunable diode laser probe. With the help of the calculations, the observed R(0) rotational transitions have been assigned up to N=9 for the b-type series and N=14 for the a-type series. Theory and experiment agree rather well, except that theory tends to overestimate the b-type energies. The (paraH2)12–CO cluster is calculated to be particularly stable and (relatively) rigid, corresponding to completion of the first solvation shell, and it is observed to have the strongest a-type transition.
Ab initio calculation of the C∕D ratio of magnetic circular dichroism
Authors: Seth Michael , Ziegler Tom , Autschbach Jochen
Published: February 2005

A procedure for calculating the magnetic circular dichroism C∕D ratio from density functional theory calculations is discussed. The method is simplified considerably through the application of group theory and the irreducible-tensor method and only requires integrals of the magnetic dipole moment operator over a few orbitals and published tables of symmetry factors. The implementation of the method is tested through application to several small and medium-sized molecules.
Pressure dependent study of the solid-solid phase change in 38-atom Lennard-Jones cluster
Authors: Sabo Dubravko , Freeman David L. , Doll J. D.
Published: February 2005

Phase change phenomena in clusters are often modeled by augmenting physical interaction potentials with an external constraining potential to handle evaporation processes in finite temperature simulations. These external constraining potentials exert a pressure on the cluster. The influence of this constraining pressure on phase change phenomena in 38-atom Lennard-Jones clusters is investigated, and it is demonstrated that modest changes in the parameters of the constraining potential can lead to an order of magnitude change in the constraining pressure. At sufficiently high pressures the solid to solidlike phase change region in the 38-atom Lennard-Jones cluster is completely eliminated.
Application of the Wolf damped Coulomb method to simulations of SiC
Authors: Ma Y. , Garofalini S. H.
Published: February 2005

A multibody interatomic potential is developed for bulk SiC using a modification of the Wolf et al. summation technique [D. Wolf, P. Keblinski, S. R. Phillpot, and J. Eggebrecht, J. Chem. Phys. 110, 8254 (1999)] for the electrostatic interaction. The technique is modified to account for the short-range nonpoint charge effect. The nonelectrostatic interaction is modeled by a simple Morse-stretch term. This potential is then applied to β-SiC to calculate various bulk properties using molecular dynamics simulations. The simulated x-ray diffraction pattern, radial distribution functions, lattice constant, elastic constants, and defect energy agree well with experimental data.
Three-dimensional instabilities of liquid-lined elastic tubes: A thin-film fluid-structure interaction model
Authors: White Joseph P. , Heil Matthias
Published: February 2005

We develop a theoretical model of surface-tension-driven, three-dimensional instabilities of liquid-lined elastic tubes—a model for pulmonary airway closure. The model is based on large-displacement shell theory, coupled to the equations of lubrication theory, modified to ensure the exact representation of the system’s equilibrium configurations. The liquid film that lines the initially uniform, axisymmetric tube can become unstable to a surface-tension-driven instability. We show that, if the surface tension of the liquid lining is sufficiently large (relative to the tube’s bending stiffness), the axisymmetric redistribution of fluid by this instability can increase the wall compression to such an extent that the system becomes unstable to a secondary, nonaxisymmetric instability which causes the tube wall to buckle. We establish the conditions for the occurrence of the nonaxisymmetric instability by a linear stability analysis and use finite element simulations to explore the system’s subsequent evolution in the large-displacement regime. The simulations show that nonaxisymmetric instabilities allow the formation of occluding liquid bridges in situations in which the volume of fluid is insufficient to occlude the tube in its axisymmetric state. Finally, we discuss the implications of our results for the physiological problem of pulmonary airway closure.
Spiral shear layers: Roll-up and incipient instability
Authors: Lepage Christophe , Leweke Thomas , Verga Alberto
Published: February 2005

The structure and roll-up of thin shear layers generated by the impulsive motion of a plate is investigated through experiments and numerical computations. At large Reynolds numbers, the shear layer rolls up into a self-similar spiral, compatible with a power-law geometry, to which an oscillation is superimposed. This modulation is also manifest in the distributions of the circulation density and the strain rate, which are found to be nonmonotonic along the layer. A sequence of stretching and compression regions is observed, critical for the stability of the sheet.
Flow and deformation of the capillary glycocalyx in the wake of a leukocyte
Authors: Damiano Edward R. , Stace Thomas M.
Published: February 2005

An analysis is presented of the axisymmetric axial and radial flow and deformation fields throughout the endothelial-cell glycocalyx surface layer in the wake region behind a leukocyte moving steadily through a capillary. The glycocalyx, modeled as a thin poroelastic surface layer lining the capillary wall, is assumed to consist of a binary mixture of a linearly viscous fluid constituent and an isotropic, highly compressible, linearly elastic solid constituent having a vanishingly small solid-volume fraction. Invoking the asymptotic approximations of lubrication theory in a frame of reference translating with the leukocyte, closed-form solutions are obtained to the leading-order boundary-value problems governing the axial and radial flow and deformation fields throughout the glycocalyx as well as the axial and radial flow fields throughout the free capillary lumen within the wake. A simple asymptotic expression is obtained for the length lchar of the wake region in terms of the translational speed U0 of the leukocyte, and the equilibrium thickness h0, permeability k0, and aggregate elastic modulus HA of the glycocalyx. The predicted wake length, as seen from an observer moving in a reference frame attached to the leukocyte, is consistent with the recovery time predicted from a one-dimensional analysis of glycocalyx deformation through a quiescent inviscid fluid. The two-dimensional fluid dynamical analysis presented here thus provides the appropriate relationships for extracting estimates of the mechanoelectrochemical properties of the glycocalyx from physiologically realistic constitutive models developed under simplified one-dimensional flow regimes. The directly measurable quantities lchar,U0, and h0, which are obtainable from in vivo observations of the wake region behind a leukocyte moving steadily through a capillary, can therefore be connected, through the results of this analysis, to estimates of the mechanoelectrochemical properties of the glycocalyx on vascular endothelial cells.
Linear stability analysis of axisymmetric perturbations in imperfectly conducting liquid jets
Authors: López-Herrera J. M. , Riesco-Chueca P. , Gañán-Calvo A. M.
Published: February 2005

A discussion is presented on the role of limited conductivity and permittivity on the behavior of electrified jets. Under certain conditions, significant departures with respect to the perfect-conductor limit are to be expected. In addition, an exploration is undertaken concerning the validity of one-dimensional average models in the description of charged jets. To that end, a temporal linear modal stability analysis is carried out of poor-conductor viscous liquid jets flowing relatively to a steady radial electric field. Only axisymmetric perturbations, leading to highest quality aerosols, are considered. A grounded coaxial electrode is located at variable distance. Most available studies in the literature are restricted to the perfect-conductor limit, while the present contribution is an extension to moderate and low electrical conductivity and permittivity jets, in an effort to describe a situation increasingly prevalent in the sector of small-scale free-surface flows. The influence of the electrode distance b, a parameter α defined as the ratio of the electric relaxation time scale to the capillary time scale, and the relative permittivity β on the growth rate has been explored yielding results on the stability spectrum. In addition, arbitrary viscosity and electrification parameters are contemplated. In a wide variety of situations, the perfect-conductor limit provides a good approximation; however, the influence of α and β on the growth rate and most unstable wavelength cannot be neglected in the general case. An interfacial boundary layer in the axial velocity profile occurs in the low-viscosity limit, but this boundary layer tends to disappear when α or β are large enough. The use of a one-dimensional (1D) averaged model as an alternative to the 3D approach provides a helpful shortcut and a complementary insight on the nature of the jet’s perturbative behavior. Lowest-order 1D approximations (average model), of widespread application in the literature of electrified jets, are shown to be inaccurate in low-viscosity imperfect-conductor jets.
Ferrofluid pipe flow in an oscillating magnetic field
Authors: Krekhov Alexei P. , Shliomis Mark I. , Kamiyama Shinichi
Published: February 2005

Ferrofluid pipe flow in an oscillating magnetic field along the pipe axis is studied theoretically in a wide range of the flow rate. The field-dependent part of viscosity (it can be positive or negative) reveals significant dependence on the flow vorticity, i.e., ferrofluids exhibit non-Newtonian behavior. This is manifested in an alteration of the velocity profile—it ceases to be parabolic—and deviation of the flow rate from the value prescribed by Poiseuille’s formula. The presented model based on the conventional ferrohydrodynamic equations and an assumption of the ferrofluid structure fits well experimental data recently obtained by Schumacher, Sellien, Konke, Cader, and Finlayson [“Experiment and simulation of laminar and turbulent ferrofluid pipe flow in an oscillating magnetic field,” Phys. Rev. E 67, 026308 (2003)].
Nucleation and spinodal decomposition of liquid mixtures
Authors: Lamorgese Andrea G. , Mauri Roberto
Published: February 2005

We simulated the phase segregation of a metastable deeply quenched binary mixture. Our theoretical approach follows the diffuse interface model, where convection and diffusion are coupled via a nonequilibrium capillary force, expressing the tendency of the demixing system to minimize its free energy. As this driving force induces a material flux which, for liquid mixtures, is much larger than that due to pure molecular diffusion, the ratio of thermal to viscous forces is assumed to be of order 103, in agreement with experimental data. Using a pseudospectral method, we integrated the equations of motion in two dimensions, showing that the metastability of the system can be characterized through a critical radius, as in Gibbs’ treatment, or through the (finite) intensity of a white noise superposed on the initial uniform concentration field. This critical intensity grows exponentially as the mean composition of the mixture approaches its equilibrium value. In addition we showed that, in general, the value of the critical radius decreases as the number density of the nucleating drops becomes very large, so that nuclei have the chance to coalesce and grow before being reabsorbed.
On-shell description of stationary flames
Authors: Kazakov Kirill A.
Published: February 2005

The problem of nonperturbative description of stationary flames with arbitrary gas expansion is considered. On the basis of the Thomson circulation theorem an implicit integral of the flow equations is constructed. With the help of this integral, a simple explicit expression for the vortex mode of the burnt gas flow near the flame front is obtained. Furthermore, a dispersion relation for the potential mode at the flame front is written down, thus reducing the initial system of bulk equations and jump conditions for the flow variables to a set of integrodifferential equations for the flame front position and the flow velocity at the front. The developed approach is applied to the case of thin flames. Finally, an asymptotic expansion of the derived equations is carried out in the case θ→1 where θ is the gas expansion coefficient, and a single equation for the front position is obtained in the second post-Sivashinsky approximation. It is demonstrated, in particular, how the well-known problem of correct normalization of the front velocity is resolved in our approach. It is verified also that in the first post-Sivashinsky approximation, the equation reduces to the Sivashinsky–Clavin equation corrected according to Cambray and Joulin. Analytical solutions of the derived equations are found, and compared with the results of numerical simulations.
Numerical study of the decay of enstrophy in a two-dimensional Navier–Stokes fluid in the limit of very small viscosities
Authors: Dmitruk Pablo , Montgomery David C.
Published: February 2005

The rate of enstrophy decay in two-dimensional Navier–Stokes turbulence is explored numerically with high resolution pseudospectral simulations. Initial conditions and all other physical parameters are held fixed while viscosity is decreased through about three orders of magnitude, while increasing the numerical resolution as required to resolve the smallest scales that develop. The attempt is to discern whether or not a regime is being approached in which the behavior of the vorticity decay could be approximated as ideal and nondissipative. Although the enstrophy decay shows a (logarithmic) tendency to go to zero as the viscosity is decreased, at fixed times, the extrapolated values of viscosity to approach a zero enstrophy decay regime lie many orders of magnitude out of our currently available numerical resolution.
The stabilization of arginine’s zwitterion by dipole-binding of an excess electron
Authors: Xu Shoujun , Zheng Weijun , Radisic Dunja , Bowen Kit H.
Published: February 2005

The arginine parent anion was generated by a newly developed, infrared desorption-electron photoemission hybrid anion source. The photoelectron spectrum of the arginine anion was recorded and interpreted as being due to dipole binding of the excess electron. The results are consistent with calculations by Rak, Skurski, Simons, and Gutowski, who predicted the near degeneracy of arginine’s canonical and zwitterionic dipole bound anions. Since neutral arginine’s zwitterion is slightly less stable than its canonical form, this work also demonstrates the ability of an excess electron to stabilize a zwitterion, just as ions and solvent molecules are already known to do.
Effects of body forces on electro- and magnetorheological fluids
Authors: Klingenberg D. J. , Ulicny J. C. , Smith A.
Published: February 2005

Body forces in electro- and magnetorheological fluids are typically small compared to the magnitudes of the field-induced electric and magnetic forces. Using particle-level simulations, we show that these relatively small forces can have large effects on the rheological response of these fluids in shear flow.
Correlation of nanochemistry and electrical properties in HfO2 films grown by metalorganic molecular-beam epitaxy
Authors: Moon Tae-Hyoung , Ham Moon-Ho , Myoung Jae-Min
Published: February 2005

We present the annealing effects on nanochemistry and electrical properties in HfO2 dielectrics grown by metalorganic molecular-beam epitaxy. After the postannealing treatment of HfO2 films in the temperature range of 600–800°C, the thicknesses and chemical states of the films were examined by high-resolution transmission electron microscopy and angle-resolved x-ray photoelectron spectroscopy. By comparing the line shapes of core-level spectra for the samples with different annealing temperatures, the concentrations of SiO and Hf-silicate with high dielectric constant are found to be highest for HfO2 film annealed at 700°C. This result supports that the accumulation capacitance of the sample annealed at 700°C is not deteriorated in spite of a steep increase in interfacial layer thickness compared with that of the sample annealed at 600°C.
Raman active phonon modes and heat capacities of Ti2AlC and Cr2AlC ceramics: first-principles and experimental investigations
Authors: Wang Jingyang , Zhou Yanchun , Lin Zhijun , Meng Fanling , Li Feng
Published: February 2005

Raman active phonon frequencies and corresponding vibrational eigenmodes are reported for two M2AlC ceramics, Ti2AlC and Cr2AlC, by means of first-principles calculations. The theoretical modes are approved by the experimental Raman spectrum for Ti2AlC. Compared with that of the Ti3SiC2 counterpart, the number of Raman active modes is definitely determined by the chemical formula of transition-metal carbide layers; for example, TiC0.67 in Ti3SiC2 and TiC0.5 in M2AlC. All active modes originate from stretching and bending of Al–M–C covalent bond chains, whereas the vibration of M–C bond localized inside the M6C octahedra is not Raman active. The differences in vibration characteristics between Ti2AlC and Cr2AlC are discussed in terms of atomic force constants. By including the phonon and electron contributions, trends in heat capacities as a function of temperature were illustrated and compared.
Optical nanofountain: A biomimetic device that concentrates optical energy in a nanometric region
Authors: Kawazoe Tadashi , Kobayashi Kiyoshi , Ohtsu Motoichi
Published: February 2005

We have proposed and demonstrated a nanophotonic device, which concentrates optical energy in a nanometric region. We call this device an “optical nanofountain,” which uses the energy transfer among quantum dots and acts like a light-harvesting photosynthetic system. We experimentally concentrated optical energy in a nanometric area less than 20 nm by using the optical nanofountain which was composed of CuCl quantum dots embedded in a NaCl matrix. Its focal diameter of 20 nm corresponds to the numerical aperture of 12.
Modification of the electric conduction at the pentacene∕SiO2 interface by surface termination of SiO2
Authors: Yagi Iwao , Tsukagoshi Kazuhito , Aoyagi Yoshinobu
Published: February 2005

A surface treatment method has been developed for the SiO2∕Si substrate to control the electrical properties of pentacene thin-film transistors (TFTs). The surface treatment is performed by spin-coating 1,1,1,3,3,3-hexamethyldisilazane liquid, resulting in a drastic improvement of the off current although the surface treatment never shows a pronounced morphological change in the pentacene channel in comparison with the one on the nontreated substrate. The off current improvement directly enhances the transistor performance especially in the TFTs with a few monolayers channel thickness. The off current suppression could be caused by the reduction of the interfacial floating charge trapped at the pentacene∕SiO2 interface.
High pressure study of Ti4AlN3 to 55 GPa
Authors: Manoun Bouchaib , Saxena S. K. , Barsoum M. W.
Published: February 2005

Using a synchrotron radiation source and a diamond anvil cell, we measured the pressure dependence of the lattice parameters of a polycrystalline Ti4AlN3 sample up to a pressure of 55 GPa. No phase transformations were observed. As observed in Ti3SiC2,Ti3Si0.5Ge0.5C2, and Zr2InC, the compressibility of Ti4AlN3 along the c axis was larger than along the a axis which leads to a decrease in the c∕a ratio with increasing pressure. The bulk modulus is 216±2GPa, with a pressure derivative of 3.84±0.06.
Interband cascade detectors with room temperature photovoltaic operation
Authors: Li Jian V. , Yang Rui Q. , Hill Cory J. , Chuang Shun Lien
Published: February 2005

We investigated mid-infrared interband cascade laser structures as photodetectors, which are sensitive to normal incidence and operate in photovoltaic mode at room temperature. The proposed operation principle of these interband cascade detectors is based on the unique combination of interband photoexcitation and the much faster intersubband relaxation as well as interband tunneling recombination, which allows for the efficient collection of the photoexcited carriers. Peak responsivity and detectivity of 21 mA/W and 7.1×108cmHz1∕2∕W at λ=4.0μm are obtained for a device with cutoff wavelength of 4.4μm. Peak responsivity and detectivity of 46 mA/W and 1.4×109cmHz1∕2∕W at λ=3.0μm are obtained for another device with cutoff wavelength of 3.3μm. These detectors exhibit low noise (4.8×10−13A∕Hz1∕2) and a large product of the differential resistance and active area (19Ωcm2) at room temperature.
High transparency of Ag∕Zn–Ni solid–solution ohmic contacts for GaN-based ultraviolet light-emitting diodes
Authors: Leem Dong-Seok , Song June-O , Hong Woong-Ki , Maeng Jeong-Tae , Kwak J. S. , Park Y. , Seong Tae-Yeon
Published: February 2005

Ag ∕ Zn – Ni solid–solution scheme has been investigated to produce transparent ohmic contacts for ultraviolet (UV) light-emitting diodes (LEDs). The Ag∕Zn–Ni solid–solution contacts annealed at 430 °C for 1 min in air show high transmittance of 67%–69% at 340 nm, which is much better than that (53%) of the conventional Ni∕Au contact. The annealed contacts give specific contact resistance of 8.2×10−5 and 4.8×10−5Ωcm2. Further, near UV LEDs (300×300μm2) made with the annealed contact layers produce a forward-bias voltage of 3.32–3.46 V at 20 mA. Possible explanations are given to describe the annealing-induced improvement of the ohmic behaviors of the Ag∕Zn–Ni solid–solution contacts.
Raman scattering and field-emission properties of RuO2 nanorods
Authors: Cheng C. L. , Chen Y. F. , Chen R. S. , Huang Y. S.
Published: February 2005

We report Raman scattering and field emission properties of rutile RuO2 nanorods obtained by metalorganic chemical vapor deposition. The RuO2 nanorods have lengths up to several micrometers and diameters in the range of 10–50 nm. The nanosize dependencies of the peak shift and the broadening of the three first-order Raman modes agree well with those calculated on the basis of the phonon confinement model. The unique geometrical features of RuO2 nanorods exhibit a strong effect on field enhancement (β∼1153), which results in a low threshold field (Eth∼4.9V∕μm) defined at the beginning of emission. The low turn-on field for driving a current of 10μA∕cm2 is about 10.3V∕μm, which is comparable with amorphous carbon film. Our results indicate that RuO2 nanorods provide an excellent alternative for field emitter due to several advantages, including nanometer structure, natural conductor, enhanced resistance to oxidation, and long-term stability.
In vitro stimulation of neurons by a planar Ti–Au-electrode interface
Authors: Reiher A. , Günther S. , Krtschil A. , Witte H. , Krost A. , Opitz T. , de Lima A. , Voigt T.
Published: February 2005

We report on the realization of a planar large area electrode interface which reproducibly allows the global excitation of neurons and the generation of stimulated network activity. The interface is formed by two double finger-shaped Ti–Au-electrodes without any isolating coating deposited by electron beam evaporation on microscope cover slips. Dissociated nerve cells from embryonic rat cerebral cortex were cultured on these electrodes forming electrophysiologically active networks within seven days of culture. These networks were electrically excited by application of voltage pulses, resulting either in an activity of single neurons or in a stimulated synchronous network activity in dependence on the pulse parameters. The impact of these parameters, such as the number of pulses, the pulse amplitude and the delay between distinct pulse events, on the stimulation success was systematically investigated. We found threshold values for the voltage pulse amplitude of 1.8–2.2 V and for the voltage pulse duration of 1 ms to reproducibly obtain stimulation success with our system. These results are repeated for differently aged cell cultures and at different sections of the whole network. The stimulation procedure does not significantly damage the nerve cells.
Optically probed wetting layer in InAs/InGaAlAs/InP quantum-dash structures
Authors: Rudno-Rudziński W. , Sęk G. , Ryczko K. , Kudrawiec R. , Misiewicz J. , Somers A. , Schwertberger R. , Reithmaier J. P. , Forchel A.
Published: February 2005

Photoluminescence and photoreflectance measurements have been performed to investigate molecular-beam-epitaxy-grown InAs/InGaAlAs/InP structures with different-size InAs quantum dashes. Optical features related to all relevant parts of the structure have been detected and recognized, including a line which has been attributed to the ground-state wetting layer quantum well transition. The spectral position of the latter is independent of the nominal InAs layer thickness in contrast to quantum-dash emission peak, which shifts sequentially to the red due to an increase of the islands’ size. The interpretation has been supported by energy level calculations showing that the wetting layer has to be approximately 2 ML thick and that only one state is confined in such a thin well for each kind of carriers, i.e., electrons, heavy, and light holes.
Extremely low frequency response of magnetoelectric multilayer composites
Authors: Dong Shuxiang , Zhai Junyi , Xing Zhengping , Li Jie-Fang , Viehland D.
Published: February 2005

A promising generation of extremely low frequency magnetic field sensors, based on multilayer composites (MLCs) of magnetostrictive Terfenol-D (Tb1−xDyxFe2−y) and piezoelectric Pb(Mg1∕3Nb2∕3)O3–PbTiO3, has been developed. Our MLC magnetoelectric sensor presently shows a limit in (i) working frequency of ∼5×10−3Hz; and (ii) magnetic field sensitivity of 10−7,10−9, and 10−11T for frequencies of f=10−2, 1, and 102Hz, respectively. The results open up possibilities for sensitive low frequency passive magnetic anomaly detection.
Growth, chemical composition, and carbon isotope discrimination of pistachio (Pistacia vera L.) rootstock seedlings in response to salinity
Authors: Hokmabadi H. , Arzani K. , Grierson P. F.
Published: February 2005

Pistachio is considered a potential crop for many semi-arid regions affected by salinisation. We examined the effects of salinity on growth of 3 pistachio rootstocks: Badami-e-zarand, Sarakhs, and Ghazvini. Rootstocks were grown in soil in 8-L polyethylene pots and irrigated every 3 days with treatments of 0, 75, 150, or 225 mm NaCl. We measured above-ground biomass, allocation of C to root systems and foliage, and carbon isotope discrimination (Δ) and proline accumulation after 30 days and again after 60 days. Relative growth rate (RGR) decreased with time for all treatments and rootstocks. RGR and net assimilation rates (NARw) decreased with increasing salinity. In all rootstocks, NARw, but not leaf weight ratio (LWR), was significantly correlated with RGR, indicating that NARw was an important factor underlying growth responses among rootstocks. Increased salinity did not affect leaf water potential (Ψleaf), even though proline concentrations increased with increasing NaCl concentration, particularly in the Ghazvini rootstocks. Both Cl– and Na+ concentrations in leaves increased from 30 to 60 days but not in roots and stems. The Sarakhs rootstocks accumulated more of Cl– and Na+ compared with other rootstocks. K+ concentration in the roots and stems of all rootstocks also decreased with increasing salinity at both 30 and 60 days. Concentrations of Ca2+ in stems and root systems, but not in leaves, were also reduced by increased salinity in all rootstocks but only after 60 days. Carbon isotope discrimination (Δ) decreased with increased salinity in the leaves, stems, and roots; however, there was no significant difference in carbon isotope discrimination among rootstocks. We conclude that the Ghazvini rootstock was the most salt tolerant among the rootstocks tested. Carbon isotope discrimination in pistachio rootstocks may be a useful indicator of cumulative salinity history of the plant but is not a suitable indicator for pre-screening of pistachio rootstocks for salinity resistance.
Fibre diameter and staple strength of sheep selected for divergent clean fleece weight when subjected to an increase in intake or an increase in intake and diet change
Authors: Friend M. A. , Robards G. E.
Published: February 2005

Merino wethers with a high (fleece plus, Fl+) or low (fleece minus, Fl–) potential for wool growth were offered a restricted intake of either oat grain or lucerne chaff for 8 weeks followed by ad libitum lucerne chaff for 4 weeks. The Fl– sheep that were fed oats then lucerne had a lower (P < 0.05) intake during the first 2 weeks of ad libitum feeding than all other groups. Staple strength of Fl+ sheep (37.5 ± 2.2 N/ktex) was less (P < 0.05) than that of Fl– sheep (44.5 ± 2.4 N/ktex), and dietary treatment did not significantly affect staple strength. Wool growth rate was unaffected by dietary treatment, but was greater (P < 0.001) for Fl+ (6.4 ± 0.2 µg/mm2.day) than for Fl– (4.0 ± 0.2 µg/mm2.day) sheep. Along-fibre variation in diameter was greater (P < 0.001) in Fl+ (15.6 ± 0.5%) than in Fl– (9.9 ± 0.5%) sheep. Between-fibre variation in diameter was greater (P < 0.001) in Fl+ (16.5 ± 0.5%) than in Fl– (13.2 ± 0.5%) sheep, and between-fibre variation in diameter was affected (P < 0.05) by dietary treatment in Fl+ sheep. Staple strength was significantly correlated (P < 0.05) with along-fibre variation in diameter (r = –0.48), and stepwise regression analysis indicated that along-fibre variation in diameter, wool growth rate during early restricted feeding, and minimum fibre diameter explained 63% of the variance in staple strength. The results are discussed in relation to the lower staple strength of Fl+ sheep.
Agronomic evaluation of a tiller inhibition gene (tin) in wheat. I. Effect on yield, yield components, and grain protein
Authors: Duggan B. L. , Richards R. A. , van Herwaarden A. F. , Fettell N. A.
Published: February 2005

Reduced tillering cereals have been proposed as being advantageous under terminal drought conditions through their reported reduction in non-productive tiller number and reduced soil water use prior to anthesis. This study was conducted to determine whether wheat (Triticum aestivum L.) lines containing the tiller inhibition (tin) gene have a yield penalty over their commercial near-isogenic counterparts. A terminal drought was experienced in all experiments. The effects of the tin gene were investigated in 4 different near-isogenic pairs of lines grown at 2 sowing densities at 4 locations in the eastern Australian wheatbelt over a 3-year period. Averaged over all experiments and lines, grain yield was unaffected by the presence of the tin gene. However, the highest yielding line contained the tin gene and its yield was 5% higher than all other lines. Averaged across the different genetic backgrounds, the tin gene decreased fertile spike number by 11%, increased the number of kernels/spike by 9%, and there was a 2% increase in kernel weight. The tin gene increased the harvest index by an average of 0.02, whereas above-ground biomass was reduced by 7%. Increasing sowing density from 50 to 100 kg/ha had little influence on yield or yield-related characteristics in both the restricted tillering and freely tillering lines. There was an interaction between sowing rate and the presence of the tin gene on yield, with tin lines yielding 0.2 t/ha more than the freely tillering lines at the higher sowing rate, whereas there was no effect at the lower sowing rate. The response of several lines containing the tin gene to nitrogen fertiliser was also investigated at 2 sites. Nitrogen increased spike number in all lines but the number remained around 20% less than in the freely tillering cultivars. The yield of wheat lines containing the tin gene was 6% greater than their near-isogenic pairs where nitrogen status was high in the presence of terminal drought. Grain protein concentration was unaffected by the presence of the tin gene at high grain protein sites, whereas at lower grain protein sites it had a positive effect.
An identification tool for the Australian weedy Sporobolus species based on random amplified polymorphic DNA (RAPD) profiles
Authors: Shrestha Sangita , Adkins Stephen W. , Graham Glenn C. , Loch Donald S.
Published: February 2005

Based on morphological features alone, there is considerable difficulty in identifying the 5 most economically damaging weed species of Sporobolus [viz. S. pyramidalis P. Beauv., S. natalensis (Steud.) Dur and Schinz, S. fertilis (Steud.) Clayton, S. africanus (Poir.) Robyns and Tourney, and S. jacquemontii Kunth.] found in Australia. A polymerase chain reaction (PCR)-based random amplified of polymorphic DNA (RAPD) technique was used to create a series of genetic markers that could positively identify the 5 major weeds from the other less damaging weedy and native Sporobolus species. In the initial RAPD profiling experiment, using arbitrarily selected primers and involving 12 species of Sporobolus, 12 genetic markers were found that, when used in combination, could consistently identify the 5 weedy species from all others. Of these 12 markers, the most diagnostic were UBC51490 for S. pyramidalis and S. natalensis; UBC43310, 2000, 2100 for S. fertilis and S. africanus; and OPA20850 and UBC43470 for S. jacquemontii. Species-specific markers could be found only for S. jacquemontii. In an effort to understand why there was difficulty in obtaining species-specific markers for some of the weedy species, a RAPD data matrix was created using 40 RAPD products. These 40 products amplified by 6 random primers from 45 individuals belonging to 12 species, were then subjected to numerical taxonomy and multivariate system (NTSYS pc version 1.70) analysis. The RAPD similarity matrix generated from the analysis indicated that S. pyramidalis was genetically more similar to S. natalensis than to other species of the ‘S. indicus complex’. Similarly, S. jacquemontii was more similar to S. pyramidalis, and S. fertilis was more similar to S. africanus than to other species of the complex. Sporobolus pyramidalis, S. jacquemontii, S. africanus, and S. creber exhibited a low within-species genetic diversity, whereas high genetic diversity was observed within S. natalensis, S. fertilis, S. sessilis, S. elongates, and S. laxus. Cluster analysis placed all of the introduced species (major and minor weedy species) into one major cluster, with S. pyramidalis and S. natalensis in one distinct subcluster and S. fertilis and S. africanus in another. The native species formed separate clusters in the phenograms. The close genetic similarity of S. pyramidalis to S. natalensis, and S. fertilis to S. africanus may explain the difficulty in obtaining RAPD species-specific markers. The importance of these results will be within the Australian dairy and beef industries and will aid in the development of integrated management strategy for these weeds.
Salinity-induced changes in the nutritional status of expanding cells may impact leaf growth inhibition in maize
Authors: Neves-Piestun Beatriz G. , Bernstein Nirit
Published: February 2005

Salinity-induced excess or deficiency of specific nutrients are often hypothesised to operate as causes of growth inhibition and to trigger primary responses, which directly affect growth. Information concerning salinity effects on microelement nutrition in the growing cells is limited. In this study, salinity-(80 mm NaCl) inflicted alterations in spatial profiles of essential elements (N, P, K, S, Ca, Mg, Fe, Zn, Mn, Cu) and the salinity source (Na and Cl) were studied along the growing zone of leaf 4 of maize (Zea mays L.). Correlations between spatial profiles of growth and nutritional status of the tissue were tested for evaluation of the hypothesis that a disturbance of specific mineral nutritional factors in the growing cells might serve as causes of salt-induced growth inhibition. Examined nutritional elements exhibited unique distribution patterns, all of which were disturbed by salinity. With the exception of Na, Cl and Fe, the deposition rates of all the studied mineral elements were reduced by salinity throughout the elongating tissue. Localised contents of Ca, K and Fe in the growing tissue of the salt-stressed leaf were highly correlated with the intensity of localised tissue volumetric expansion, suggesting reduced levels of Ca and K, and toxic levels of Fe as possible causes of growth inhibition. Na and Cl accumulation were not correlated with growth inhibition under salinity.
A new group of plant-specific ATP-dependent DNA ligases identified by protein phylogeny, hydrophobic cluster analysis and 3-dimensional modelling
Authors: Bonatto Diego , Brendel Martin , Henriques João Antonio Pêgas
Published: February 2005

The eukaryotic ATP-dependent DNA ligases comprise a group of orthologous proteins that have distinct roles in DNA metabolism. In contrast with the well-known DNA ligases of animal cells, the DNA ligases of plant cells are poorly described. Until now, only two DNA ligases (I and IV) genes of Arabidopsis thaliana (L.) Heynh were isolated and characterised. Use of the complete genomic sequences of Oryza sativa L. and A. thaliana, as well as the partially assembled genomic data of Medicago truncatula L. and Brassica spp., allowed us to identify a new family of ATP-dependent DNA ligases that are found only in the Viridiplantae kingdom. An in-depth phylogenetic analysis of protein sequences showed that this family composes a distinct clade, which shares a last universal common ancestor with DNA ligases I. In silico sequence studies indicate that these proteins have distinct physico-chemical properties when compared with those of animal and fungal DNA ligases. Moreover, hydrophobic cluster analysis and 3-dimensional modelling allowed us to map two conserved domains within these DNA ligases I-like proteins. Additional data of microsynteny analysis indicate that these DNA ligases I-like genes are linked to the S and SLL2 loci of Brassica spp. and A. thaliana, respectively. Combining the results of all analyses, we propose the creation of the DNA ligases VI (LIG6) family, which is composed by plant-specific DNA ligases.