bluuebunny/crossref_metadata_2025 huggingface dataset:
Low concentrations of neuroactive steroids alter kinetics of [3H]ifenprodil binding to the NMDA receptor in rat frontal cortex
Authors: Johansson Tobias , Frändberg Per‐Anders , Nyberg Fred , Le Grevès Pierre
Published: September 2005

The modulatory effects of the two neurosteroids pregnenolone sulphate (PS) and pregnanolone sulphate (3α5βS) on [3H]ifenprodil binding to the N‐methyl‐D‐aspartate (NMDA) receptor in rat frontal cortex were studied.

The binding for [3H]ifenprodil itself displayed monophasic kinetics in all experiments. None of the neurosteroids displaced the radioligand from its binding site on the NR2B subunit of the NMDA receptor. However, their continual presence at nanomolar concentrations had significant effects on ligand binding kinetics, interacting through distinct sites in saturation, competition and dissociation experiments.

PS at 30 nM enhanced the specific binding to about 150% of that in its absence and enhanced the dissociation rate three‐fold indicating a positive modulation of [3H]ifenprodil binding to the NMDA receptor. Furthermore, PS increased Bmax and decreased Kd suggesting that the neurosteroid exposes new [3H]ifenprodil binding sites with altered properties.

In contrast, 3α5βS (30 nM) decreased specific [3H]ifenprodil binding to approximately 40% of that determined for the radioligand alone. The presence of 3α5βS at nanomolar concentrations induced biphasic curve fits in saturation, competition as well as dissociation experiments.

In conclusion, the present study show that the allosteric modulators PS or 3α5βS change [3H]ifenprodil binding kinetics in a way indicating conformational alteration of its binding site on the NR2B subunit.

British Journal of Pharmacology (2005) 146, 894–902. doi:10.1038/sj.bjp.0706397
Studying vocal fold vibrations in Parkinson’s disease with a nonlinear model
Authors: Zhang Yu , Jiang Jack , Rahn Douglas A.
Published: September 2005

A nonlinear model is applied to study pathologic vocal vibratory characteristics and voice treatments of Parkinson’s disease. We find that a number of pathologic vocal characteristics commonly observed in Parkinson’s disease, including reduced vibratory intensity, incomplete vocal closure, increased phonation threshold pressure, glottal tremor, subharmonics, and chaotic vocal fold vibrations, can be studied with this nonlinear model. We also find that two kinds of clinical voice treatments for Parkinson’s disease, including respiratory effort treatment and Lee Silverman voice treatment can be studied with this computer model. Results suggest that respiratory effort treatment, in which subglottal pressure is increased, might aid in enhancing vibratory intensity, improving glottal closure, and avoiding vibratory irregularity. However, the Lee Silverman voice treatment, in which both subglottal pressure and vocal fold adduction are increased, might be better than respiratory effort treatment. Increasing vocal fold thickness would be further helpful to improve these pathologic characteristics. The model studies show consistencies with clinical observations. Computer models may be of value in understanding the dynamic mechanism of disordered voices and studying voice treatment effects in Parkinson’s disease.
Genetic mapping of the distribution of minima on the potential energy surface of disordered systems
Authors: Mohn Chris E. , Stølen Svein
Published: September 2005

We show that genetic algorithms and energy minimizations in combination provide a highly efficient tool for mapping low-energy minima on the erratic and complex potential-energy surfaces of grossly disordered materials. The distribution of energy minima mimics with sufficient accuracy the low-energy portion of the parent distribution of minima and allows accurate calculation of configurational Boltzmann averaged structural and thermodynamic properties in cases where a small fraction of the minima is thermally accessible. The distribution of energy minima obtained using genetic algorithms is biased, and consequently the properties converge slowly at high temperatures. In contrast, an optimized set of a few randomly chosen configurations provides a statistical representable selection for the accurate calculation of configurational-averaged properties at high temperatures, but gives a poor description of the low-energy portion of minima. Thus the properties calculated using the random algorithm are hampered by the presence of systematic errors in cases where a small fraction of the minima is thermally accessible. The inherently slow convergence of both the genetic algorithm and the random selection at intermediate temperatures is tackled by combining the lower fraction of the distribution of minima obtained using genetic algorithms with the intermediate and upper fraction from the random (nonbiased) selection of configurations. For this purpose we introduce a cut-and-scale-type scheme. The resulting combined distribution allows accurate calculation of properties at all temperatures.
Stochastic Liouville equations for hydrogen-bonding fluctuations and their signatures in two-dimensional vibrational spectroscopy of water
Authors: Jansen Thomas la Cour , Hayashi Tomoyuki , Zhuang Wei , Mukamel Shaul
Published: September 2005

The effects of hydrogen-bond forming and breaking kinetics on the linear and coherent third-order infrared spectra of the OH stretch of HOD in D2O are described by Markovian, not necessarily Gaussian, fluctuations and simulated using the stochastic Liouville equations. Slow (0.5ps) fluctuations are represented by a collective electrostatic coordinate, whereas fast (<100fs) frequency fluctuations are described using either a second collective electrostatic coordinate or a four-state jump (FSJ) model for hydrogen-bonding configurations. Parameters for both models were obtained using a 1-ns molecular-dynamics trajectory calculated using the TIP4P force field combined with an electrostatic ab initio map. The asymmetry of the photon-echo spectra (larger linewidth on the blue side than on the red side) predicted by the FSJ is in better agreement with recent experiments.
Modeling signal transduction networks: A comparison of two stochastic kinetic simulation algorithms
Authors: Pettigrew Michel F. , Resat Haluk
Published: September 2005

Computational efficiency of stochastic kinetic algorithms depend on factors such as the overall species population, the total number of reactions, and the average number of nodal interactions or connectivity in a network. These size measures of the network model can have a significant impact on computational efficiency. In this study, two scalable biological networks are used to compare the size scaling efficiencies of two popular and conceptually distinct stochastic kinetic simulation algorithms—the random substrate method of Firth and Bray (FB), and the Gillespie algorithm as implemented using the Gibson-Bruck method (GGB). The arithmetic computational efficiencies of these two algorithms, respectively, scale with the square of the total species population and the logarithm of the total number of active reactions. The two scalable models considered are the size scalable model (SSM), a four compartment reaction model for a signal transduction network involving receptors with single phosphorylation binding sites, and the variable connectivity model (VCM), a single compartment model where receptors possess multiple phosphorylation binding sites. The SSM has fixed species connectivity while the connectivity between species in VCM increases with the number of phosphorylation sites. For SSM, we find that, as the total species population is increased over four orders of magnitude, the GGB algorithm performs significantly better than FB for all three SSM compartment models considered. In contrast, for VCM, we find that as the overall species population decreases while the number of phosphorylation sites increases (implying an increase in network linkage) there exists a crossover point where the computational demands of the GGB method exceed that of the FB.
Calculation of nuclear magnetic shieldings using an analytically differentiated relativistic shielding formula
Authors: Kudo K. , Fukui H.
Published: September 2005

Two expressions for nuclear-magnetic-shielding tensor components based on analytically differentiating the electronic energy of a system are presented. The first is based on a second-order Douglas-Kroll-Hess approach, in which the off-diagonal block terms of the transformed Dirac Hamiltonian are diminished to second order with respect to both the electrostatic nuclear attraction potential V and the magnetic vector potential A. The second expression is based on the method of Barysz-Sadlej-Snijders, in which the off-diagonal block terms in the transformed Dirac Hamiltonian are completely eliminated with respect to purely V terms, while they are diminished to second order with respect to terms including A. The two approaches are applied to the calculation of nuclear magnetic shieldings of HX (X=F,Cl,Br,I), H2X (X=O,S,Se,Te), and noble gas X (X=He,Ne,Ar,Kr,Xe) systems with common gauge origins. The results show that relativistic corrections of higher than second order are negligibly small, except for the paramagnetic parts of I, Te, and Xe shieldings. The present calculations yield very large positive values for the anisotropy of proton shielding, Δσ(H)=σ‖(H)−σ⊥(H), of HI compared to previous reports. Unfortunately, no experimental values for the anisotropy of proton shielding in HI are available for verification.
Calculation of optical rotation with time-periodic magnetic-field-dependent basis functions in approximate time-dependent density-functional theory
Authors: Krykunov Mykhaylo , Autschbach Jochen
Published: September 2005

We report the implementation of a method for the calculation of optical rotation. This method is based on the time-dependent density-functional theory and utilizes time-periodic magnetic-field-dependent basis functions. The calculations are based on a density fit. It is demonstrated that additional terms in the analytical expression appearing from derivatives of the approximated Coulomb potential are necessary to provide the gauge-origin independence of the results within a given numerical accuracy. Contributions from these terms also restore the symmetry between the electric and magnetic perturbations in the optical rotation tensor.
Exploring the Jahn-Teller and pseudo-Jahn-Teller conical intersections in the ethane radical cation
Authors: Venkatesan T. S. , Mahapatra S.
Published: September 2005

We report a theoretical account on the static and dynamic aspects of the Jahn-Teller (JT) and pseudo-Jahn-Teller (PJT) interactions in the ground and first excited electronic states of the ethane radical cation. The findings are compared with the experimental photoionization spectrum of ethane. The present theoretical approach is based on a model diabatic Hamiltonian and with the parameters derived from ab initio calculations. The optimized geometry of ethane in its electronic ground state (A1g1) revealed an equilibrium staggered conformation belonging to the D3d symmetry point group. At the vertical configuration, the ethane radical cation belongs to this symmetry point group. The ground and low-lying electronic states of this radical cation are of Eg2, A1g2, Eu2, and A2u2 symmetries. Elementary symmetry selection rule suggests that the degenerate electronic states of the radical cation are prone to the JT distortion when perturbed along the degenerate vibrational modes of eg symmetry. The A1g2 state is estimated to be ∼0.345eV above the Eg2 state and ∼2.405eV below the Eu2 state at the vertical configuration. The symmetry selection rule also suggests PJT crossings of the A1g2 and the Eg2 electronic states of the radical cation along the vibrational modes of eg symmetry and such crossings appear to be energetically favorable also. The irregular vibrational progressions, with numerous shoulders and small peaks, observed below 12.55 eV in the experimental recording are manifestations of the dynamic (E⊗e)-JT effect. Our findings revealed that the PJT activity of the degenerate vibrational modes is particularly strong in the Eg2–A1g2 electronic manifold which leads to a broad and diffuse structure of the observed photoelectron band.
Computational spectroscopy of helium-solvated molecules: Effective inertia, from small He clusters toward the nanodroplet regime
Authors: Paolini Stefano , Fantoni Stefano , Moroni Saverio , Baroni Stefano
Published: September 2005

Accurate computer simulations of the rotational dynamics of linear molecules solvated in He clusters indicate that the large-size (nanodroplet) regime is attained quickly for light rotors (HCN) and slowly for heavy ones (OCS, N2O, and CO2), thus challenging previously reported results. Those results spurred the view that the different behavior of light rotors with respect to heavy ones—including a smaller reduction of inertia upon solvation of the former—would result from the lack of adiabatic following of the He density upon molecular rotation. We have performed computer experiments in which the rotational dynamics of OCS and HCN molecules was simulated using a fictitious inertia appropriate to the other molecule. These experiments indicate that the approach to the nanodroplet regime, as well as the reduction of the molecular inertia upon solvation, is determined by the anistropy of the potential, more than by the molecular weight. Our findings are in agreement with recent infrared and/or microwave experimental data which, however, are not yet totally conclusive by themselves.
A computational study of some electric and magnetic properties of gaseous BF3 and BCl3
Authors: Rizzo Antonio , Cappelli Chiara , Junquera-Hernández José Miguel , Sánchez de Merás Alfredo M. J. , Sánchez-Marín José , Wilson David J. D. , Helgaker Trygve
Published: September 2005

We present the results of an extended computational study of the electric and magnetic properties connected to Cotton-Mouton birefringences, on the trifluoro- and trichloroborides in the gas phase. The electric dipole polarizabilities, magnetizabilities, quadrupole moments, and higher-order hypersusceptibilities—expressed as quadratic and cubic frequency-dependent response functions—are computed within Hartree-Fock, density-functional, and coupled-cluster response theories employing singly and doubly augmented correlation-consistent basis sets and London orbitals in the magnetic property calculations. The results, which illustrate the capability of time-dependent density-functional theory for electron-rich systems, are compared with available experimental data. Revised values of both experimentally derived quadrupole moment of BF3, 2.72±0.15a.u., and magnetizability anisotropy of BCl3, −0.45±0.09a.u., both obtained in birefringence experiments that neglect the effects of higher-order hypersusceptibilities, are presented. In the theoretical limit the traceless quadrupole moments of BF3 and BCl3 are determined to be 3.00±0.01 and 0.71±0.01a.u., respectively.
Molecular-dynamics simulations for nonclassical kinetics of diffusion-controlled bimolecular reactions
Authors: Sung Bong June , Yethiraj Arun
Published: September 2005

Molecular-dynamics simulations are presented for the diffusion-controlled bimolecular reaction A+B⇔C in two and three dimensions. The reactants and solvent molecules are modeled as spheres interacting via continuous potential-energy functions. The interaction potential between two reactants contains a deep well that results in a reaction. When the solvent concentration is low and the reactant dynamics is essentially ballistic, the system reaches equilibrium rapidly, and the reaction follows classical kinetics with exponential decay to the equilibrium. When the solvent concentration is high the particles enter the normal diffusion regime quickly and nonclassical behavior is observed, i.e., the reactant concentrations approach equilibrium as t−d∕2 where d is the dimensionality of space. When the reaction well depth is large, however, the reaction becomes irreversible within the simulation time. In this case the reactant concentrations decay as t−d∕4. Interestingly this behavior is also observed at intermediate times for reversible reactions.
Conductivity of molten sodium chloride in an arbitrarily weak dc electric field
Authors: Delhommelle Jerome , Cummings Peter T. , Petravic Janka
Published: September 2005

We use nonequilibrium molecular-dynamics (NEMD) simulations to characterize the response of a fluid subjected to an electric field. We focus on the response for very weak fields. Fields accessible by conventional NEMD methods are typically of the order of 109Vm−1, i.e., several orders of magnitude larger than those typically used in experiments. Using the transient time-correlation function, we show how NEMD simulations can be extended to study systems subjected to a realistic dc electric field. We then apply this approach to study the response of molten sodium chloride for a wide range of dc electric fields.
Free isotropic-nematic interfaces in fluids of charged platelike colloids
Authors: Bier Markus , Harnau Ludger , Dietrich S.
Published: September 2005

Bulk properties and free interfaces of mixtures of charged platelike colloids and salt are studied within the density-functional theory. The particles are modeled by hard cuboids with their edges constrained to be parallel to the Cartesian axes corresponding to the Zwanzig model. The charges of the particles are concentrated in their center. The density functional is derived by functional integration of an extension of the Debye-Hückel pair distribution function with respect to the interaction potential. For sufficiently small macroion charges, the bulk phase diagrams exhibit one isotropic and one nematic phase separated by a first-order phase transition. With increasing platelet charge, the isotropic and nematic binodals are shifted to higher densities. The Donnan potential between the coexisting isotropic and nematic phases is inferred from bulk structure calculations. Nonmonotonic density and nematic order parameter profiles are found at a free interface interpolating between the coexisting isotropic and nematic bulk phases. Moreover, electrically charged layers form at the free interface leading to monotonically varying electrostatic potential profiles. Both the widths of the free interfaces and the bulk correlation lengths are approximately given by the Debye length. For fixed salt density, the interfacial tension decreases upon increasing the macroion charge.
Experimental characterization of water flow through smooth rectangular microchannels
Authors: Baviere R. , Ayela F. , Le Person S. , Favre-Marinet M.
Published: September 2005

This article presents experimental results obtained in water flows through smooth rectangular microchannels. The experimental setup used in the present study enabled the investigation of both very small length scales (21–4.5μm) and a wide range of Reynolds numbers (0.1–300). The evolution of the friction coefficient was inferred from pressure drop versus flow-rate measurements for two types of water with different electrical conductivities. The channels were made of a silicon engraved substrate anodically bonded to a Pyrex cover. In these structures, pressure losses were measured internally with micromachined Cu–Ni strain gauges. When compared to macroscale correlations, the results demonstrate that in smooth silicon-Pyrex microchannels larger than 4μm in height, the friction law is correctly predicted by the Navier-Stokes equations with the classical no-slip boundary conditions, regardless of the water electrical conductivity (>0.1μScm−1).
Direct experimental observation of a general pattern at the beginning of brittle fracture
Authors: Emmerich Francisco G.
Published: September 2005

The failures of brittle and ductile materials are governed by the microscopic response around a flaw extremity; but the experimental access to this region of atomic dimensions is extremely difficult. Here we access experimentally this region by using a developed magnetic solid with atomistic characteristics that simulate the crack tip of brittle materials. We show that the general pattern for the beginning of all the ruptures is the reaching of a specific maximum value of the local stress between the unit cells at the extremity of the critical flaw. This work may help simulations of brittle fracture where a criterion is needed to determine when a bond is broken, corresponding to an experimental foundation to those works that use the criterion of a critical atomic snapping distance, starting from which the bond is considered broken.
Microphotoluminescence mapping of laterally overgrown GaN layers on patterned Si (111) substrates
Authors: Macht L. , Hageman P. R. , Haffouz S. , Larsen P. K.
Published: September 2005

Spatial distribution of optical properties of GaN layers grown on patterned Si (111) substrates by maskless metalorganic chemical vapor deposition has been investigated. The Si substrates were prepared with a pattern of 1.5μm diameter holes at a 3.5μm distance from each other. The holes were overgrown by GaN until coalescence, creating GaN areas with no substrate underneath. Microphotoluminescence mapping measurements with 0.8μm lateral resolution show a five-fold increase in luminescence intensity coming from the overhang areas as compared to the layer directly over the substrate. This is accompanied by a slight redshift of the luminescence peak wavelength. Photoelectrochemical etching shows that the dislocation density is much lower in those areas while the photoluminescence redshift is attributed to lesser strain relaxation resulting from a lower dislocation density.
Taking the horizontal fields intrinsically into account in magneto-optical microscopy
Authors: Paturi P.
Published: September 2005

A method that takes intrinsically the horizontal field into account for calculating the current densities of the superconducting sample from magneto-optical (MO) imaging is presented. This effectively removes the “spikes” seen in the current density at the edges of the superconducting sample. The method is also found to take only twice the time of the fastest method presented so far. The effect caused by the finite thickness of the MO layer is also calculated.
White-light emission of polyvinyl alcohol∕ZnO hybrid nanofibers prepared by electrospinning
Authors: Sui X. M. , Shao C. L. , Liu Y. C.
Published: September 2005

Polyvinyl alcohol∕ZnO (PVA∕ZnO) hybrid nanofibers were prepared by the electrospinning technique. The structural and spectral information of the nanofibers was characterized by scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, resonant Raman, and photoluminescence (PL). The results indicate that ZnO were successfully embedded in the one-dimensional hybrid fibers via chemical interactions between ZnO and PVA. PL results show the PVA∕ZnO nanofibers have an intense white-light emission, which originates from the simultaneous emission of three bands covering from the UV to visible range. A possible PL mechanism was proposed accordingly.
Embeddable wireless strain sensor based on resonant rf cavities
Authors: Chuang J. , Thomson D. J. , Bridges G. E.
Published: September 2005

In this article we describe a type of sensor to monitor strain. The strain sensor is a passive device that can be embedded or attached to a structure and then remotely interrogated though a wireless interface. Such a system has the advantage of requiring no permanent physical connection, either electrical or optical, to an interrogation system. The sensor is a conducting coaxial electromagnetic cavity that is embedded in or bonded to the structure in which strain is to be measured. The cavity will exhibit resonance for electrical wavelengths two times the cavity length. Changes in the structure’s dimensions will be reflected in changes in the dimensions of the cavity, and will result in a shift of the resonant frequency of the cavity. The sensor incorporates an antenna so that the resonant frequency of the cavity can be determined by remote interrogation. The acquired resonant frequency is then used to calculate the strain in the structure. The sensor presented in this article operates at a frequency of approximately 2.45 GHz, and exhibits a shift in resonance of 2.45 kHz per microstrain (με). We have demonstrated a strain sensitivity of less than 1με with a bandwidth of 25 Hz. This class of embeddable sensor is expected to have the greatest application in monitoring the health of, and assessing damage in, civil structures.
Development of a virtual probe tip with an application to high aspect ratio microscale features
Authors: Bauza Marcin B. , Hocken Robert J. , Smith Stuart T. , Woody Shane C.
Published: September 2005

Nondestructive measurement of microscale features remains a challenging metrology problem. For example, to assess a high aspect ratio small hole it is currently common to cut a cross section and measure the features of interest using an atomic force microscope, scanning probe microscope, or scanning electron microscope. Typically, these metrology tools may be suitable for surface finish measurement but often lack the capability for dimensional metrology. The aim of this article is to discuss the development of a high aspect-ratio microscale probe for measurement of microscale features. A 700:1 high aspect ratio probe shank is fabricated with a 7μm diameter, and attached at one end to an oscillator. The oscillator produces a standing wave in the oscillating probe shank as opposed to conventional probes that use a microscale sphere on the end of a comparatively rigid shank. As a result of the standing wave formed in steady state vibration, the free end of the shank generates an amplitude of oscillation greater than the probe shank diameter. Thus, the probe does not require a spherical ball to serve as the contact point and simply uses the contact diameter of the free end of the vibrating shank. This methodology is referred to as a virtual probe tip. The virtual probe tip in conjunction with a nanopositioning scanner is used to measure surface profile measurements over traverse lengths of 130μm. In this article, results from profiles of a 500 nm step height and a ruby sphere of diameter 1 mm are presented. Experiments in this article indicate the ability to repeatedly resolve surface features of less than 5 nm while maintaining bandwidths greater than 1 kHz. Furthermore, adhesion problems often encountered with micrometer scaled probes were not observed during profile measurements with this virtual probe.
Pseudospark electron beam as an excitation source for extreme ultraviolet generation
Authors: Jiang Chunqi , Kuthi Andras , Gundersen Martin A. , Hartmann Werner
Published: September 2005

A xenon pseudospark device is used to generate energetic and intense electron beams (e-beams) that induce extreme ultraviolet (EUV) emission in the range of 11–17 nm. This e-beam-based EUV source is compact, and the device is of interest because it has potentially attractive EUV conversion efficiency and pulse energy requirement, with potential for long lifetime and high repetition-rate operation. The role of e-beam-induced inelastic electronic collisions is considered.
Effect of multistep ionizations on the electron temperature in an argon inductively coupled plasma
Authors: Lee Min-Hyong , Chung Chin-Wook
Published: September 2005

Electron energy distribution functions (EEDFs) are measured in an argon inductively coupled plasma. It is observed that the measured EEDFs are nearly Maxwellian distributions, and the electron temperature derived from the EEDFs decreases with increasing input radio-frequency (rf) power. It appears that additional ionization processes exist. To investigate this decrease in the electron temperature, multistep ionizations are taken into account. An analytical particle balance equation, including the multistep ionizations, are derived. According to the new balance equation, to balance between the total volume ionization and the total surface particle loss, the electron temperature should be decreased with increasing rf power. The comparison between the model and the experiment are presented, and the model agrees well with the experiment.
Bends and splitters in metal-dielectric-metal subwavelength plasmonic waveguides
Authors: Veronis Georgios , Fan Shanhui
Published: September 2005

We investigate the performance of bends and splitters in metal-dielectric-metal subwavelength plasmonic waveguides. We show that bends and splitters with no additional loss over a very wide frequency range can be designed for metal-dielectric-metal waveguides with center layer thickness small compared to the wavelength. We also introduce the concept of characteristic impedance for such systems to account for their behavior.
A technique to study the lattice location of hydrogen atoms in silicon by channeling elastic recoil detection analysis
Authors: Shao Lin , Wang Yongqiang , Lee J. K. , Nastasi M. , Thompson Phillip E. , Theodore N. David , Mayer J. W.
Published: September 2005

By combining elastic recoil detection analysis with the channeling technique, energy analysis of forward-scattered H1 permits determination of the H1 lattice location. We have used this technique to study the lattice location of hydrogen in a crystalline Si containing a buried boron-doped layer. We showed that hydrogen atoms are trapped at the boron-doped Si layer after hydrogenation and that the majority of the trapped hydrogen atoms are located near bond-center sites.
Angular dependence of the magnetization reversal in exchange-biased Fe∕MnF2
Authors: Arenholz Elke , Liu Kai
Published: September 2005

A detailed study of exchange-biased Fe∕MnF2 bilayers using magneto-optical Kerr effect shows that the magnetization reversal occurs almost fully through domain wall nucleation and propagation for external fields parallel to the exchange-bias direction. For finite angles ϕ between bias and external field, the magnetization is aligned perpendicular to the cooling-field direction for a limited field range for decreasing fields. For external fields perpendicular to the bias direction, the magnetization aligns with the cooling-field direction for descending and ascending fields before fully reversing. The field range for which the magnetization is close to perpendicular to the external field can be estimated using a simple effective-field model.
Effect of Brownian coagulation on the microstructure evolution in rapidly solidified immiscible alloys
Authors: Zhao J. Z. , Gao L. L. , He J.
Published: September 2005

The microstructure evolution during a liquid-liquid phase transformation was calculated. The effect of Brownian coagulation on the microstructure development was investigated. The results indicate that Brownian coagulation has a weak effect on the nucleation of the minority phase droplets. For a given alloy composition, its effect on the coalescence of droplets increases with the cooling rate until a critical cooling rate is reached. After that, its effect decreases with the cooling rate. Brownian coagulation leads to a wider and multipeak size distribution of minority phase droplets.
Room temperature continuous wave operation of a heterojunction bipolar transistor laser
Authors: Feng M. , Holonyak N. , Walter G. , Chan R.
Published: September 2005

Continuous wave laser operation at 25°C, with simultaneous electrical gain, of an InGaP–GaAs heterojunction bipolar transistor laser, with AlGaAs optical confining layers and an InGaAs recombination quantum well incorporated into the p-type base region, is demonstrated. At laser threshold (IB=40mA, VCB=0, 25°C), the transistor current gain β=ΔIC∕ΔIB in common-emitter operation changes abruptly (2.3→1.2,β>1), with laser modes developing at wavelength λ∼1006nm. Direct three-port modulation of the transistor laser at 3GHz is demonstrated for a device with a 2.2μm emitter width and a 850μm length between cleaved Fabry–Perot facets (which is the performance of an exploratory device and not near the limits).
Nonlinear absorption edge properties of 1.3-μm GaInNAs saturable absorbers
Authors: Grange R. , Rutz A. , Liverini V. , Haiml M. , Schön S. , Keller U.
Published: September 2005

GaInNAs 1.3-μm quantum-well saturable absorber mirrors are characterized with spectrally resolved nonlinear reflectivity measurements over 70nm around the broadened band edge. All important parameters such as saturation fluence Fsat, modulation depth ΔR, and nonsaturable loss ΔRns are obtained relative to the photoluminescence (PL) peak. Fsat has a minimum of 4μJ∕cm2 10nm above the PL peak and ΔR scales with the linear absorption even in the bandtail. The product ΔR∙Fsat important to suppress Q-switching instabilities in mode-locked lasers decreases linearly with wavelength and reaches a minimum 20nm above the PL peak. We observed wavelength-independent nonsaturable losses of only about 10% of the maximum linear absorption. These results increase the understanding of optical and electronic properties of GaInNAs around the band edge.
Exposition of semiconducting and ferromagnetic properties of pulsed-laser-deposited thin films of LaFe1−xNixO3 (x=0.3, 0.4, and 0.5)
Authors: Choudhary R. J. , Kumar Ravi , Khan M. Wasi , Srivastava J. P. , Patil S. I. , Arora S. K. , Shvets I. V.
Published: September 2005

We have explored the possibility of ferromagnetic semiconducting property in the epitaxial thin films of LaFe1−xNixO3 (x=0.3, 0.4, and 0.5) grown on (001) oriented LaAlO3 substrate. We observe that substitution of Ni in the series leads to the increase in conductivity of the samples with conduction being controlled by the disorder-induced localization of charge carriers. All these samples show ferromagnetic behavior at room temperature while their magnetization decreases with increase in Ni concentration in the composition. The results have been explained on the basis of the close interplay between the electrical and magnetic properties.
Programmable organic thin-film devices with extremely high current densities
Authors: Graves-Abe Troy , Sturm J. C.
Published: September 2005

Thin (12nm) organic films consisting of self-assembled multilayers of 11-mercaptoundecanoic acid were contacted by gold electrodes. The devices could be operated as a programmable memory by applying low-voltage pulses to increase the conductivity by 103 and then high-voltage pulses to reverse the increase; the conductivity of the stored state could be read nondestructively by applying a still-lower voltage pulse. Programmed states remained stable for longer than three months and devices were functional for more than 104 programming cycles. Current-voltage measurements of the devices revealed negative differential resistance with enormous current densities characteristic of metallic conduction (up to 107A∕cm2). These results are promising for application in dense, high-speed memory arrays, where resistance-capacitance delays can be minimized by large current densities.
Dielectric properties of Sb2O3-doped BaFe12O19 ferrite
Authors: Brahma P. , Banerjee S. , Chakravorty D.
Published: September 2005

Dielectric measurements were carried out on specimens with compositions BaO.(6−x)Fe2O3.xSb2O3 with x having values of 0.0, 0.025, 0.1, and 0.3. Sb2O3 doping increases the dielectric permittivity drastically. Two loss peaks of similar activation energies were observed. The analysis showed that these arose because of the presence of Fe2+–Fe3+ and Sb3+–Sb5+ pairs, respectively, in the system. The experimental data could be analyzed satisfactorily in terms of Cole-Cole relaxation formalism. The relaxation distribution parameter α was found to be much larger in the case of Sb3+–Sb5+ pair than that due to Fe2+–Fe3+ pair.
Electrospraying from nanofluidic capillary slot
Authors: Arscott Steve , Troadec David
Published: September 2005

We present here an original electrospray emitter tip based on a nanofluidic capillary slot. The nanofabrication involves focused ion beam etching to form the slot which has a cross-section of 50×300nm and a length of 4μm. The liquid is deformed into the nanofluidic capillary slot by capillary action; the electrospray is produced by the application of a low voltage. Using a water–methanol–formic acid solution, we have observed an electrospray onset voltage of 125V. At a measured electrospray current of 1nA, the unforced flow-rate is estimated to be 110pLmin−1.
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Schottky diodes operated at 800°C for hydrogen sensing
Authors: Song Junghui , Lu Wu , Flynn Jeffrey S. , Brandes George R.
Published: September 2005

Schottky diodes on AlGaN∕GaN heterostructures with Pt catalytic metal are fabricated and characterized from 200to800°C for H2 sensing. Over this large range of temperature, the forward current of Schottky diodes increases with exposure to H2 gas, which is attributed to the reduction of Schottky barrier heights resulting from hydrogen absorption in the catalytic metal. The results indicate that AlGaN∕GaN heterostructure Schottky diodes are capable of high-temperature operation for H2 sensing up to 800°C. As temperature increases, the hydrogen detection sensitivity of Pt–AlGaN∕GaN Schottky diodes improves due to the more effective H2 dissociation. When the testing ambient is changed from N2 to 5% H2/95% N2, the value of the Schottky barrier height decreases by 11 and 120meV at 200 and 800°C, respectively.
Photoluminescence properties of single Mn-doped CdS nanocrystals studied by scanning near-field optical microscopy
Authors: Ishizumi Atsushi , Matsuda Kazunari , Saiki Toshiharu , White C. W. , Kanemitsu Yoshihiko
Published: September 2005

We have fabricated Mn-doped CdS (CdS:Mn) nanocrystals embedded in Al2O3 matrices by sequential ion implantation and studied their photoluminescence (PL) properties by a scanning near-field optical microscope (SNOM). In the PL spectra of CdS:Mn nanocrystals measured by the SNOM, several sharp PL lines and a broad PL band were observed. The sharp PL lines are related to bound excitons at shallow impurities in CdS nanocrystals. The Mn-related PL spectrum is very broad even in single nanocrystals at low temperatures, and both the peak energy and the spectral width of the PL band depend on the excitation laser intensity. The PL properties of single CdS:Mn nanocrystals are discussed.
Morphological evolution of metal nanoparticles on surfaces of carbon nanotubes
Authors: Zhong Jianxin , Stocks G. Malcolm
Published: September 2005

We propose a model to elucidate the morphological evolution of metal nanoparticles grown on surfaces of carbon nanotubes. The model is based on the concept of bending-strain-induced self-organization of nanoparticles on curved surfaces. Criteria are derived within the continuum elasticity theory for predicting the size and shape of metal nanoparticles. Applications of these criteria to different metals show good agreement with experimental results.
Functional analysis of
fruitless
gene expression by transgenic manipulations of
Drosophila
courtship
Authors: Villella Adriana , Ferri Sarah L. , Krystal Jonathan D. , Hall Jeffrey C.
Published: September 2005

A
gal4
-containing enhancer–trap called
C309
was previously shown to cause subnormal courtship of
Drosophila
males toward females and courtship among males when driving a conditional disrupter of synaptic transmission (

shi
TS

). We extended these manipulations to analyze all features of male-specific behavior, including courtship song, which was almost eliminated by driving

shi
TS

at high temperature. In the context of singing defects and homosexual courtship affected by mutations in the
fru
gene, a
tra
-regulated component of the sex-determination hierarchy, we found a
C309
/

tra
F

combination also to induce high levels of courtship between pairs of males and “chaining” behavior in groups; however, these doubly transgenic males sang normally. Because production of male-specific FRU
M
protein is regulated by TRA, we hypothesized that a
fru
-derived transgene encoding the male (
M
) form of an
I
nhibitory
R
NA (

fru
MIR

) would mimic the effects of

tra
F

; but
C309
/

fru
MIR

males exhibited no courtship chaining, although they courted other males in single-pair tests. Double-labeling of neurons in which GFP was driven by
C309
revealed that 10 of the 20 CNS clusters containing FRU
M
in wild-type males included coexpressing neurons. Histological analysis of the developing CNS could not rationalize the absence of

tra
F

or

fru
MIR

effects on courtship song, because we found
C309
to be coexpressed with FRU
M
within the same 10 neuronal clusters in pupae. Thus, we hypothesize that elimination of singing behavior by the
C309
/

shi
TS

combination involves neurons acting downstream of FRU
M
cells
Attitudes to Error and Patient Safety
Authors: Webster Craig S. , Grieve Diana J.
Published: September 2005

The vast majority of patients clearly benefit from modern health care. However, the rate of injury and death inadvertently caused by medical treatment remains too high, and exacts enormous human and financial costs. Organisational change is not solely a technological issue however, and the attitudes of clinicians are critical to the successful improvement of safety and the effective re‐design of procedures and equipment. We purposively surveyed a group of clinicians for whom treatment‐caused harm is of particular concern in order to better understand some of the difficulties involved in technological change and the potential attitudinal barriers to safety improvement.
Inter‐firm Migration of Tacit Knowledge: Law and Policy1
Authors: van Caenegem William
Published: September 2005

Much knowledge is diffused by the exchange of property rights in intangibles. But tacit knowledge, not being subject to property rights, is instead diffused by migration of knowledgeable individuals between firms. The law impacts significantly on this diffusion mechanism, in particular those rules that determine the use individuals may make of their tacit knowledge after migration to a different firm. The general principle underlying the relevant law is that individuals are free to migrate with all their tacit knowledge. Nonetheless there are some narrow exceptions to this principle. That these exceptions remain narrow and carefully policed by the courts is important because imposing too many restraints on use of tacit knowledge post‐term would have a negative impact on real innovation.
Should the Knowledge‐based Economy be a Savant or a Sage? Wisdom and Socially Intelligent Innovation
Authors: Rooney David , McKenna Bernard
Published: September 2005

Discourse about knowledge‐based economies rarely moves beyond the commercialization of science and engineering, and is locked in the discursive limits of functionalism. We argue that these discourses limit the scope of what knowledge‐based economies might achieve because they are uninformed by an adequate conception of knowledge. In particular, knowledge management and knowledge‐based economy discourse has not included the axiological dimension of knowledge that leads to wisdom. Taking an axiological perspective, we can discuss policy frameworks aimed at producing the social structures needed to bring fully formed and fully functioning knowledge societies into being. We argue that while the dominant discourse of industrial modernity remains rationalist, functionalist, utilitarian and technocratic, knowledge‐based economies will resemble a savant rather than a sage. A wisdom‐based renaissance of humanistic epistemology is needed to avoid increasing social dysfunction and a lack of wisdom in complex technological societies.
Japonica Rice: Intellectual Property, Scientific Publishing and Data‐sharing1
Authors: Rimmer Matthew
Published: September 2005

This article examines a series of controversies within the life sciences over data sharing. Part 1 focuses upon the agricultural biotechnology firm Syngenta publishing data on the rice genome in the journal Science, and considers proposals to reform scientific publishing and funding to encourage data sharing. Part 2 examines the relationship between intellectual property rights and scientific publishing, in particular copyright protection of databases, and evaluates the declaration of the Human Genome Organisation that genomic databases should be global public goods. Part 3 looks at varying opinions on the information function of patent law, and then considers the proposals of Patrinos and Drell to provide incentives for private corporations to release data into the public domain.
Hydrogen bonding of the undecahydro-thiocyanato-closo-dodecaborate anion with proton donors
Authors: Filippov Oleg A. , Filin Andrey M. , Teplitskaya Lylia N. , Belkova Natalia V. , Shmyrova Yulia V. , Sivaev Igor B. , Bregadze Vladimir I. , Epstein Lina M. , Shubina Elena S.
Published: September 2005

The interaction of (Bu4N)2[B12H11SCN] (1) with various proton donors (MeOH, indole, pyrazole, imidazole, PhOH, 4-NO2C6H4OH, CF3CH2OH, (CF3)2CHOH and (CF3)3COH) was investigated by IR spectroscopy at 190 – 290 K in dichloromethane. Both the hydride hydrogen and the nitrogen atom of the SCN group of 1 acted as proton-accepting sites. IR spectral evidence of BH ···· HO and N ···· HO hydrogen-bond formation was obtained by changes in the acid νXH stretches as well as in the νBH and νCN bands of the hydride. Spectral and thermodynamic characteristics of the H-complexes were determined. Interaction with NH-acids was also examined. The electronic effects of the SCN group and the boron cage on the proton-accepting properties of both sites in 1 were analyzed by comparison with previously studied hydrogen bonding to (Bu4N)2[B12H12] and (Bu4N)[SCN]. Both types of hydrogen bonds in the model complexes of [B12H11SCN]2− HOCF3 were studied using the B3LYP/6-31G(d,p) approximation.
Warning Signals, Wind Speeds and What Next: A Pilot Project for Disaster Preparedness among Residents of Central Vietnam's Lagoons
Authors: Ramaprasad Jyotika
Published: September 2005

This paper describes a pilot disaster preparedness campaign for Central Vietnam. Central Vietnam is highly prone to water related disasters, which result in an enormous loss of lives and livelihood and make sustainable development almost impossible. Residents in the lagoons of Central Vietnam, who are particularly vulnerable because of their proximity to water, were the target audience for this project. The project first built social marketing capacity among Vietnamese government officials and community leaders, and then used their input as well as secondary and primary research to prepare the campaign.

The significance of the project lies in the fact that this may be one of the first projects in Vietnam to systematically plan a campaign based on social marketing principles. These principles are new in Vietnam, a communist country that has only recently introduced economic reform. The project thus signals the greater acceptance of nonstructural and particularly social marketing/communication approaches to disaster preparedness, where in the past the emphasis has been on structural solutions such as building dykes and dams. The project is also part of a shift that is taking place in disaster mitigation where disaster relief, the mainstay to date, is now coupled with disaster preparedness.
The Concept of Commitment as a Basis for Social Marketing Efforts: Conversion Model as a Case
Authors: Hjelmar Ulf
Published: September 2005

This article examines how social marketers and researchers can concentrate social marketing efforts around a crucial mechanism in behavior change, the notion of commitment. Citizens are committed to different forms of behavior and the success of social marketing depends upon the ability to change this commitment. This is illustrated in a case study about environmentally sustainable behaviors that is analyzed using a research tool, the Conversion Model™, based on the concept of commitment.