bluuebunny/crossref_metadata_2025 huggingface dataset:
High-repetition-rate, hard x-ray radiation from a laser-produced plasma: Photon yield and application considerations
Authors: Sjögren A. , Harbst M. , Wahlström C.-G. , Svanberg S. , Olsson C.
Published: March 2003

We present an experimental study of hard x rays produced in laser-produced plasmas. The laser used is a 1 kHz system, delivering 0.7 mJ for 25 fs onto a solid target. The x-ray spectrum was measured with calibrated germanium detectors, allowing a very good estimate of the absolute number of photons emitted from the plasma over a wide energy range; from 7 keV to 0.5 MeV. Assuming a bi-Maxwellian electron distribution with temperatures of 4.5 and 63 keV, theoretical calculations support the experimental findings. The imaging characteristics of the x-ray source were investigated experimentally employing image plates and theoretically based on the electron distribution.
Torsion pendulum method to evaluate the internal friction and elastic modulus of films
Authors: Li Z. S. , Fang Q. F. , Veprek S. , Li S. Z.
Published: March 2003

The formulas for the evaluation of the internal friction and shear elastic modulus of a film deposited on a cylindrical substrate using the torsion pendulum method are derived in this article. The internal friction and the shear modulus of the film, especially their variation with temperature, can be easily deduced by measuring the internal friction and the resonance frequency of the pendulum with the bare substrate and with the composite, respectively. As an example, the shear modulus and the internal friction of a TiN/Ti(C,N) multilayer film deposited on a Mo wire are measured in the temperature range from room temperature to 400 °C.
Plasma emission tomographic reconstruction in the large helical device
Authors: Liu Y. , Kostrioukov A. Yu. , Peterson B. J. ,   LHD Experiment Group
Published: March 2003

Both one-dimensional (1D) and two-dimensional (2D) tomographic reconstruction of the total radiation power distribution from the large helical device (LHD) was based on the data obtained from absolute extreme ultraviolet silicon photodiodes. Two arrays (16 and 19 channels) installed in the normal LHD cross section (constant toroidal angle) provided simple and reliable 1D poloidally symmetric radiation profile reconstruction. The data obtained from two other arrays (20 and 20 channels) were used for 2D reconstruction of the radiation distribution in a semitangential plasma cross section. Using a 2D peeling away algorithm, improved by a feedback procedure, enabled reconstruction of several Fourier harmonics at each magnetic flux surface. These measurement and analysis techniques have enabled us to visualize asymmetries in plasma emission due to pellet and gas fueling.
Experimental procedure for fundamental studies of reinforcing steel corrosion processes
Authors: Martin F. J. , Olek J.
Published: March 2003

An experimental procedure is presented for use in fundamental studies of reinforcing steel corrosion. An electrochemical corrosion cell is presented that incorporates a cement paste film cast against a polished section of reinforcing steel surface, while isolating other portions of the reinforcing steel surface from corrosion activity. The cement paste is prepared without admixed chlorides, then allowed to hydrate in a curing chamber for a period of three days prior to introduction of chlorides to the cell. The cell is transferred from a humid curing chamber to chloride solution exposure, where chlorides diffuse through the cement paste film to the steel surface and causes corrosion damage. This experimental procedure is well suited for detecting subtle changes in the passive state of reinforcing steel by either ac or dc electrochemistry. Ac impedance spectroscopy can also monitor the continuing hydration of cement paste. Chemical and microstructural analysis of the steel/cement paste interface is also possible upon disassembly of the cell.
In situ scanning tunneling microscopy of individual supported metal clusters at reactive gas pressures from 10−8 to 104 Pa
Authors: Kolmakov A. , Goodman D. W.
Published: March 2003

An experimental apparatus has been designed and an approach developed for imaging individual oxide supported nanoparticles with scanning tunneling microscopy (STM) during their nucleation, growth, alloying, and “real world” chemical, thermal, and other in situ treatments. By careful selection of the tunneling conditions and using the STM tip to index the surface, it is demonstrated that preselected individual particles can be imaged at elevated temperatures while changing the reactive gas pressure over 12 orders of magnitude. The experimental challenges due mainly to tunnel junction instabilities, a relatively weak cluster-support interaction, and sample drift are considered and strategies to overcome these obstacles proposed. Using Au and Ag clusters deposited on TiO2(110) as a model system, the potential of the method is demonstrated for exploring on a particle-by-particle basis cluster growth, alloying, thermal coarsening, and the evolution of particle morphology in a reactive gas environment. An additional advantage of the approach is that a wide cluster size distribution can be synthesized and surveyed on the same substrate. The size effects on cluster morphology therefore can be probed in situ for a wide variety of treatments on preselected clusters.
Guided self-assembly of molecular dipoles on a substrate surface
Authors: Gao Y. F. , Suo Z.
Published: March 2003

Molecules adsorbed on a substrate surface can self-assemble into a monolayer. This article models the process of self-assembly guided by an external object. The molecules are electric dipoles, diffusing on the surface at an elevated temperature. Pre-pattern a flat mask with a submonolayer of immobile atoms, which gives rise to a patterned contact potential field. Bring the mask to a small distance above the substrate. The electrostatic interaction transfers the pattern on the mask to a molecular pattern on the substrate. Similarly, one can place above the molecules a charged conducting tip, or a mask that is pre-patterned with a topographic surface. Our model includes the mobile molecular dipoles on the substrate surface, the guiding object, and the electrostatic field in the intervening space. A nonlinear diffusion equation simulates the pattern transfer process. Numerical results are presented when the guiding object is a flat metal, patterned with a submonolayer of immobile atoms.
High pressure and high temperature phase transformations in LiNbO3
Authors: Mukaide T. , Yagi T. , Miyajima N. , Kondo T. , Sata N. , Kikegawa T.
Published: March 2003

A behavior of LiNbO3 under high pressure and temperature has been studied up to 90 GPa by means of high pressure in situ x-ray observations. Recovered samples were analyzed by transmission electron microscope (TEM). When the LiNbO3 was compressed at room temperature, a transformation occurred at about 25 GPa. The powder x-ray diffraction pattern of this “room-temperature and high-pressure” (RT–HP) phase was successfully explained by the NaIO3-type structure. No further transformation was observed at room temperature up to 90 GPa and reverse transition to starting phase occurred at about 10 GPa, thus this phase was unquenchable on release of pressure. When this RT–HP phase was heated at above 30 GPa, a phase appeared which can be recovered to ambient condition. X-ray diffraction and TEM analysis of this “high-temperature and high-pressure” (HT–HP) phase clarified that this phase has hexagonal symmetry with a most likely space group of P63. The quenched sample reverts to the starting phase on heating above 650 K. This HT–HP phase is opaque, suggesting the change of electronic property. The density of these RT–HP and HT–HP phases are, respectively, 21% and 23% higher compared to the starting LiNbO3 phase at ambient condition.
Study of the elastic and elastooptic properties of Zn1−xBexSe solid solutions by Brillouin spectroscopy
Authors: Ziobrowski P. , Drozdowski M. , Szybowicz M. , Firszt F. , Łȩgowski S. , Mȩczyńska H.
Published: March 2003

We report experimental results concerning the elastic and elastooptic properties of Zn1−xBexSe solid solutions grown by the high pressure Bridgman technique. The elastic and elastooptic constants of Zn1−xBexSe crystals with different Be content have been determined at room temperature by the Brillouin scattering method.
X-ray crystal spectrometer with a charge-coupled-device detector for ion temperature measurements in the Large Helical Device
Authors: Morita Shigeru , Goto Motoshi
Published: March 2003

A Johann-type x-ray crystal spectrometer has been designed using a ray tracing calculation and constructed for ion temperature measurement in the plasma center of a large helical device (LHD) using Doppler broadening of a He-like resonance line of ArXVII, TiXXI, CrXXIII, or FeXXV. Four curved quartz (2020), (2023), (3140), and (2243) crystals are set in a quadrangular rotary crystal holder for measuring the x-ray line from such four different elements. Each of the crystals can be externally selected through a computer network. The curved crystals with a radius of 3 m are fabricated by gluing thin quartz (0.7 mmt) on an accurately ground cylindrical blue glass plate. The curvature of the crystals was checked by scanning a sharp pin along the crystal surface. As a result, an excellent agreement with the designed cylindrical curvature was obtained with an accuracy of 1 μm. A secular change of the curved crystal surface structure was found by measuring the curvature of the curved crystal fabricated 15 years earlier. A charge-coupled-device (CCD) detector is used instead of a usually used proportional counter to increase the count rate and to avoid the influence of magnetic field leakage from the LHD. The influence of magnetic fields on the proportional counter was investigated in a range of B⩽1.5 kG. The use of the CCD brought us a large increment of more than ten times in the count rate compared with the multiwire proportional counter. The ion temperature thus has been successfully observed in a time interval of 20 ms with small error bars. The lowest measured ion temperature was 0.2–0.3 keV for ArXVII and TiXXI, which indicates an excellent spectral resolution of the crystal spectrometer. Finally, the influence of the chord integration on the measured ion temperature is discussed as a function of central electron temperature and density profile with analysis from impurity transport calculations.
Mini rf-driven ion sources for focused ion beam systems
Authors: Jiang X. , Ji Q. , Chang A. , Leung K. N.
Published: March 2003

Mini rf-driven ion sources with 1.2 cm and 1.5 cm inner chamber diameter have been developed at Lawrence Berkeley National Laboratory. Several gas species have been tested including argon, krypton, and hydrogen. These mini ion sources operate in inductively coupled mode and are capable of generating high current density ion beams at tens of watts of absorbed rf power. Since the plasma potential is relatively low in the plasma chamber, these mini ion sources can function reliably without any perceptible sputtering damage of the chamber wall. The mini rf-driven ion sources will be combined with electrostatic focusing columns, and are capable of producing nanofocused ion beams for micromachining and semiconductor fabrications.
Large aperture compound lenses made of lithium
Authors: Cremer J. T. , Piestrup M. A. , Beguiristain H. R. , Gary C. K. , Pantell R. H.
Published: March 2003

We have measured the intensity profile and transmission of x rays focused by a series of biconcave parabolic unit lenses fabricated in lithium. For specified focal length and photon energy lithium compound refractive lenses (CRL) have a larger transmission, aperture size, and gain compared to aluminum, kapton, and beryllium CRLs. The lithium compound refractive lens was composed of 335 biconcave, parabolic unit lenses each with an on-axis radius of curvature of 0.95 mm. Two-dimensional focusing was obtained at 8.0 keV with a focal length of 95 cm. The effective aperture of the CRL was measured to be 1030 μm with on-axis (peak) transmissions of 27% and an on-axis intensity gain of 18.9.
Conical x-ray crystal spectrometer for time integrated and time resolved measurements
Authors: Andiel U. , Eidmann K. , Pisani F. , Witte K. , Uschmann I. , Wehrhan O. , Förster E.
Published: March 2003

We present a new x-ray spectrometer setup based on a conically curved mica crystal in the von Hámos configuration. An x-ray sensitive charge coupled device or streak camera can be easily coupled in a perpendicular orientation to the spectrally resolved x-ray line focus. Shifting the crystal along its axis of symmetry allows one to change the dispersion and the signal flux density on the detector. A large spectral range at high resolution and adjustable signal intensity is accessible with this setup.
Dynamics calculations for the Cl+C2H6 abstraction reaction: Thermal rate constants and kinetic isotope effects
Authors: Fernández-Ramos A. , Martı́nez-Núñez E. , Marques J. M. C. , Vázquez S. A.
Published: March 2003

Thermal rate constants and H/D kinetic isotope effects for the Cl+C2H6→HCl+C2H5 reaction were computed by microcanonical variational transition state theory on a high-level ab initio potential energy surface (PES). The calculations show that the reaction proceeds through a “loose” transition state, and so the consideration of variational effects is important. The PES presents a van der Waals minimum in the products side. The calculations indicate that this minimum has no effect in the forward reaction and little effect in the reverse reaction for temperatures above room temperature. The analysis of the kinetic isotope effects shows that the contribution due to tunneling is fairly small, but with an important role played by the variational effects. Classical trajectory calculations were also performed on a semiempirical PES, which was parametrized from own ab initio calculations. This method was utilized to compare the HCl relative velocity distribution with those obtained experimentally. The results show a good agreement with experiment and reinforce the reliability of the proposed mechanism for this reaction.
Self-consistent integral equation theory for solutions of finite extensible semiflexible polyelectrolyte chains
Authors: Hofmann T. , Winkler R. G. , Reineker P.
Published: March 2003

We investigate the structural and conformational properties of solutions containing semiflexible polyelectrolyte chains using a self-consistent integral equation theory approach. A one-component system is considered where the polyelectrolyte chains interact with each other via a Debye–Hückel potential. Nonelectrostatic interactions among the polymers are taken into account by a self-consistently determined solvation potential. The conformational properties of the polymer chain are determined from a variational calculation with a semiflexible reference chain. The finite chain extensibility is taken into account by constraints for the bond lengths and bond angles using Lagrangian multipliers. The scaling relation for the size of an isolated semiflexible chain with respect to chain length exhibits a transition from rodlike to excluded volume type for a given Debye screening length. For flexible chains in solution, the theory provides conformational properties which are in excellent agreement with computer simulation results. The bare chain stiffness has a pronounced influence on the conformational and structural properties of the solution. In the semidilute regime a pronounced liquidlike order is obtained for flexible polyelectrolyte chains which diminishes with increasing bare persistence length. This process is accompanied by a shift of the structural peaks to smaller length scales.
Adsorption of gold on stoichiometric and reduced rutile TiO2 (110) surfaces
Authors: Vijay Amrendra , Mills Greg , Metiu Horia
Published: March 2003

We present a density functional study of reduced and stoichiometric rutile TiO2 (110) surfaces, and of binding of gold monomers and dimers to them. On the stoichiometric TiO2 surface, a Au atom binds to either a five-coordinated Ti atom on the basal plane, or atop a bridging oxygen atom. The two sites have nearly the same binding energy, suggesting diffusion of Au across unreduced regions of TiO2 (110) will be fast. The reduction of the rutile surface, by removal of bridging oxygen atoms, causes a charge redistribution in the system, which extends far from the vacancy site. A Au atom binds strongly to the reduced surfaces: the greater the degree of reduction the stronger the binding. On all reduced surfaces, the preferred binding sites are the vacant bridging oxygen sites. Less stable is the binding to a nearby five-coordinated Ti atom. The binding of Au2 on the reduced surfaces follows a similar pattern. Specifically, if two adjacent vacant sites are available, the optimal structure involves the dimer “dissociating” to occupy them. Several other stable binding situations for gold dimers on the reduced surfaces are discussed in the text. The binding of Au to the reduced TiO2 surface involves a substantial charge transfer to gold. We argue that this will affect the chemistry in which Au will engage.
Vacuum ultraviolet mass-analyzed threshold ionization spectroscopy of p-, m-, and o-difluorobenzenes. Ionization energies and vibrational frequencies and structures of the cations
Authors: Kwon Chan Ho , Kim Hong Lae , Kim Myung Soo
Published: March 2003

Vibrational spectra of p-, m-, and o-difluorobenzene cations in the ground electronic states have been measured by vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy. From the MATI spectra, ionization energies of p-, m-, and o-difluorobenzenes to the ionic ground states have been determined to be 73 861±5, 75 332±5, and 75 003±5 cm−1, respectively. A number of vibrational modes, including fundamentals, their combinations, and overtones were distinctly observed in the MATI spectra and could be assigned successfully by comparing with the results from density functional theory calculation at the B3LYP/6-311++G (2df,2pd) level. Appearance of the overtone progression of some totally symmetric vibrations could be explained also in terms of the overlap between the geometrical changes upon ionization and normal mode eigenvectors. Excellent correlation between the experimental and calculated results suggests that p-, m-, and o-difluorobenzene cations in the ground states retain D2h, C2v, and C2v symmetries, respectively, of the corresponding neutrals.
Metastable states of ozone calculated on an accurate potential energy surface
Authors: Babikov Dmitri , Kendrick Brian K. , Walker Robert B. , T Pack Russell , Fleurat-Lesard Paul , Schinke Reinhard
Published: March 2003

A new potential energy surface for ozone is developed. It is based on high level ab initio data and includes an accurate description of the barrier region. Full quantum reactive scattering calculations using a coupled channel approach and hyperspherical coordinates are performed on this surface for various isotopic compositions of ozone. Collision lifetimes are obtained over a wide energy range, which gives the spectrum of rovibrational metastable states (scattering resonances). This spectrum is discovered to be very nonstatistical. The spectrum of resonances is dense below the isotopic zero-point-energy threshold and sparse above it. This feature is explained by the opening of additional dissociation channels at higher energies. This behavior is a general quantum mechanical effect that should occur in other triatomic molecules.
Lifetimes of electronic excited states of a molecule close to a metal surface
Authors: Corni S. , Tomasi J.
Published: March 2003

We present a model for the evaluation of the metal-induced deexcitation rate for molecules close to a metal surface. In this model, the molecule is treated quantum mechanically at the density-functional theory level and its excitations with a time-dependent density-functional theory procedure. The metal is described through its dielectric response properties. The nonlocal features of such a response are taken into account by using a modified Lindhard–Mermin dielectric constant. The presence of small random roughness on the metal surface is described with the model of Rahman and Maradudin [Phys. Rev. B 21, 504 (1980)]. Systems in which the molecule close to the metal is immersed in an homogeneous matrix or deposited on a spacer are considered. The matrix and the spacer are treated with the polarizable continuum model. The molecule–metal and the molecule–matrix (or molecule–spacer) electrostatic interactions are described by using the integral equation formalism, numerically treated with a boundary element method. As a test case, the method has been applied to the study of phosphorescence from biacetyl close to a silver surface and immersed in or deposited on solid ammonia. Our results show that nonlocal metal response and surface roughness have an important role in explaining measured lifetimes.
The electronic structure of n- and p-doped phenyl-capped 3,4-ethylenedioxythiophene trimer
Authors: de Jong M. P. , Denier van der Gon A. W. , Crispin X. , Osikowicz W. , Salaneck W. R. , Groenendaal L.
Published: March 2003

The phenyl-capped 3,4-ethylenedioxythiophene (EDOT) trimer is a well-defined oligomer of the related poly(3,4-ethylenedioxythiophene), the conjugated polymer that forms the basis of the commercialized conducting polymer “PEDOT-PSS.” EDOT-based oligomers are themselves potential candidates for applications in molecular electronics, such as organic field effect transistors and organic solar cells. Well controlled chemical doping is of importance in such applications, since it enables tuning of important properties such as the electrical conductivity, the position of the Fermi-level, the optical absorption edge, and the quantum efficiency for photovoltaic devices. The effects of chemical doping, both p-type doping with iodine, and n-type doping with lithium, on the electronic structure of condensed molecular solid films of EDOT trimer have been studied using ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy. The results are discussed in terms of parameters important for device applications.
Surface aided polarization reversal in small ferroelectric particles
Authors: Chew K.-H , Osman J. , Stamps R. L. , Tilley D. R. , Shin F. G. , Chan H. L. W.
Published: March 2003

Polarization reversal in ferroelectric particles driven by a pulsed electric field is examined theoretically using Landau–Devonshire–Khalatnikov theory. A significant reduction in reversal times is shown to be possible if certain surface properties and size criteria are met. The surface properties are also shown to control the magnitude of the applied field needed for irreversible switching. An interesting signature of surface effects is found in the switching current. The theory predicts that the switching current for small ferroelectric particles can exhibit double peaks as a function of time. The size and relative times of the peaks provide specific information on the magnitude and rate of surface reversal dynamics.
Basic characteristics of metal-ferroelectric-insulator-semiconductor structure using a high-k PrOx insulator layer
Authors: Noda Minoru , Kodama Kazushi , Kitai Satoshi , Takahashi Mitsue , Kanashima Takeshi , Okuyama Masanori
Published: March 2003

A metal-ferroelectric [SrBi2Ta2O9 (SBT)]-high-k-insulator(PrOx)-semiconductor(Si) structure has been fabricated and evaluated as a key part of metal-ferroelectric-insulatorsemiconductor-field-effect-transistor MFIS-FET memory, aiming to improve the memory retention characteristics by increasing the dielectric constant in the insulator layer and suppressing the depolarization field in the SBT layer. A 20-nm PrOx film grown on Si(100) showed both a high ε of about 12 and a low leakage current density of less than 1×10−8 A/cm2 at 1.5 MV/cm. A 400-nm SBT film prepared on PrOx/Si shows a preferentially oriented (105) crystalline structure, grain size of about 130 nm and surface roughness of 3.2 nm. A capacitance–voltage hysteresis is confirmed on the Pt/SBT/PrOx/Si diode with a memory window of 0.3 V at a sweep voltage width of 12 V. The memory retention time was about 1×104 s, comparable to the conventional Pt/SBT/SiOxNy(SiON)/Si. The gradual change of the capacitance indicates that some memory degradation mechanism is different from that in the Pt/SBT/SiON/Si structure.
Strongly charged flexible polyelectrolytes in poor solvents: Molecular dynamics simulations with explicit solvent
Authors: Chang Rakwoo , Yethiraj Arun
Published: March 2003

The behavior of salt-free solutions of charged flexible polymer molecules in poor solvents is studied using molecular dynamics simulations. The polymer molecules are modeled as chains of charged spheres, the counterions as charged spheres, and the solvent molecules are incorporated explicitly and modeled as uncharged spheres. The equilibrium static and dynamic properties are studied as a function of solvent quality. In many-chain systems, for slightly poor solvents, no peak is observed in the static structure factor at low semidilute concentrations, but a peak appears at higher concentrations. In this regime, chains form bead–necklace structures, and the counterions are strongly correlated with the polyions. When the solvent quality is decreased further, at nonzero but low polymer concentrations, the solution becomes unstable towards phase separation. The dense phase takes on spherical, cylindrical, or lamellar structures depending on the polymer concentration. The mass and charge density profiles of polyions and counterions in the dense phase are an oscillatory function of distance. The phase separation slows down the diffusion normal to the phase interface by two to three orders of magnitude, but has little effect on the diffusion parallel to the interface. These results are qualitatively different from the behavior observed in simulations where the solvent is treated implicitly via a pairwise-induced attraction between polymer beads.
Reflective in-plane switching liquid crystal displays
Authors: Sun Yubao , Zhang Zhidong , Ma Hongmei , Zhu Xinyu , Wu Shin-Tson
Published: March 2003

The performance of a reflective in-plane switching (IPS) liquid crystal display is simulated by the parameter space method. The IPS electrodes and reflectors can be separately fabricated on the top and bottom substrates. The normally black reflective in-plane switching display shows wide viewing angle, high contrast ratio, weak color dispersion, and fast response time.
Wetting of Si surfaces by Au–Si liquid alloys
Authors: Ressel B. , Prince K. C. , Heun S. , Homma Y.
Published: March 2003

The behavior of liquid Au–Si alloys on Si surfaces covered by a monolayer of gold has been investigated by ultrahigh-vacuum scanning electron microscopy. On the (111) surface, the alloy displays a constant contact angle with the surface from the eutectic temperature up to a temperature of 650 °C and thereafter the contact angle increases linearly with temperature. As observed in previous work, the shape of the liquid droplets changes from circular at lower temperature to hexagonal at higher temperature. In contrast, on the (100) surface, the contact angle increases linearly from the eutectic temperature to high temperature. The behavior of the shape of the droplets is, however, reversed: it is polygonal (octagonal) at lower temperature and becomes round at higher temperature. This behavior is explained in terms of the relative surface energy of the two surfaces and changing line tension of the liquid–solid–vapor phase line. In addition, the behavior of Au–Si droplets on vicinal and patterned surfaces of Si has been examined. The droplets cause step bunching and modify the local surface structure. Solidification of the droplets on all surfaces leads to phase separation.
Yukawa sticky m-point model of associating fluid
Authors: Kalyuzhnyi Yurij V. , Cummings Peter T.
Published: March 2003

The product-reactant Ornstein–Zernike approach, supplemented by the ideal network approximation, is formulated for the Yukawa sticky m-point (YSmP) model of associating fluid. The model is represented by the multicomponent mixture of the Yukawa hard spheres with m sticky points randomly located on the surface of each hard sphere. Extensions of the regular integral equation closures, which include polymer Percus–Yevick, polymer hypernetted chain and polymer mean spherical approximations, are presented. An analytical solution of the polymer mean spherical approximation is derived and closed form analytical expressions for the structure (contact value of the radial distribution function, structure factor) and thermodynamic (internal energy) properties of the YSmP model are obtained. Due to generality and flexibility of the model it can be used to study the properties of a number of different associating fluids, including water and aqueous solutions. By way of illustration liquid–gas phase diagrams for the model with m=0, 1, 2, 3, 4 are presented and discussed. Predictions of the theory for the liquid–gas phase diagram of the YS4P model with the parameters similar to those assumed in the frames of the statistical associating fluid theory to mimic water are in reasonably good agreement with the corresponding experimental data for water.
Accelerating molecular dynamics simulations by linear prediction of time series
Authors: Brutovsky B. , Mülders T. , Kneller G. R.
Published: March 2003

We present a molecular dynamics simulation scheme which allows to speed up molecular dynamics simulations by linear prediction of force time series. The explicit calculation of nonbonding forces is periodically replaced by linear prediction from past values. Applying our method to liquid oxygen consisting of flexible molecules we obtained real speedups between 5.4 and 6.5, compared to conventional molecular dynamics simulations. Here only the bond-stretching forces were calculated at each time step. We demonstrate that essential dynamical quantities, such as the mean-square displacement and the velocity autocorrelation function, are preserved.
Effect of illumination conditions on Czochralski-grown silicon solar cell degradation
Authors: Hashigami Hiroshi , Itakura Yu , Saitoh Tadashi
Published: March 2003

The substitutional B-interstitial O-related defects induced under an illumination, specific to B-doped Czochralski-grown silicon (Cz-Si), results in a solar cell efficiency loss of up to 3%. For a fundamental interpretation, the relationship between the solar cell performance and the minority-carrier lifetime degradation, and influence of the illumination conditions were investigated. A simulation of the cell performance degradation clearly represented that the degradation was explained as a result of the carrier diffusion length degradation. From a spectroscopic illumination investigation, the degradation was found to be independent of the stress-light wavelength. A blue light illumination on a solar cell resulted in the red response degradation, suggesting that the injected carriers activated the defect in the bulk. However, the correlation between carrier injection level and the cell performance decay time was nonlinear. The observed decay times were almost independent of the illumination intensity in the range of 1 to 100 mW/cm2. This trend appeared more significantly on cells with a higher base resistivity. From the experimental results, the role of excess carriers in the defect activation was discussed.
Magnetic and magnetotransport properties of solid phase epitaxially grown Si:Ce films
Authors: Yokota T. , Fujimura N. , Ito T.
Published: March 2003

Magnetic and magnetotransport properties of a magnetic semiconductor, Si:Ce films, were investigated. The as-deposited films exhibit n-type conduction due to their amorphous nature, with a temperature dependence of the resistivity (ρ–T) like a normal semiconductor with diamagnetic properties. By annealing at 973 K, the conduction and the magnetic susceptibility change to the p-type and become positive, respectively. The change in the magnetic susceptibility (χ–T) at a low magnetic field of 750 Oe against the measurement temperature exhibits spin-glasslike behavior showing a cusp around 38 K (Tg). The ρ–T curve increases exponentially from 273 K to 35 K, and then drastically decreases by three orders of magnitude below 33 K. Above Tg, the magnetoresistance behavior at a magnetic field below 0.5 T can be understood as that of a semiconductor caused by the Lorentz force. Below Tg, on the other hand, an extremely large magnetoresistance, which can not be explained by a Lorentz force alone, is observed.
A note on orthogonal discrete Bessel representations
Authors: Lemoine Didier
Published: March 2003

The object of this note is to bring overview of discrete Bessel representations and to highlight their differences and similarities with both the discrete Fourier transform (DFT) methods and the finite basis/discrete variable representations (FBR/DVRs). Notably, the unpublished work of Corey and Le Roy deserves special attention. Also, the work of Littlejohn and Cargo is shown to yield an interesting derivation.
Ion-imaging of the photodissociation of CF3I+
Authors: Aguirre F. , Pratt S. T.
Published: March 2003

The photodissociation of CF3I+ prepared by resonance enhanced multiphoton ionization has been studied by using velocity-map ion imaging and photoelectron spectroscopy. Photodissociation of CF3I+ between 300 and 306 nm results in dissociation to both CF3+I+ and CF3++I. As in an earlier study using time-of-flight mass spectrometry [L. D. Waits et al., J. Chem. Phys. 97, 7263 (1992)], the latter channel displays a bimodal velocity distribution, indicative of two different dissociation mechanisms. Photoelectron spectra presented here indicate that, contrary to the earlier suggestion, these dissociation processes must both occur following excitation to the A 2A1 state or to another dissociative state of the ion, and the ion images are consistent with this conclusion. The photoelectron angular distributions extracted from the ion images also provide new perspective on earlier studies of the dissociative ionization of CF3I.
Plasma characterization with terahertz time–domain measurements
Authors: Jamison S. P. , Shen Jingling , Jones D. R. , Issac R. C. , Ersfeld B. , Clark D. , Jaroszynski D. A.
Published: March 2003

Terahertz time–domain spectral techniques are applied to the characterization of a He discharge plasma. Electro-optically sampling of the electric field of a quasi-unipolar terahertz pulse transmitted through the plasma has allowed both the real and imaginary parts of the plasma permittivity to be simultaneously measured over a large spectral range. The plasma density and the collisional frequency are determined within a 30 ps duration measurement window. An anomalously high collisional frequency has been measured.
Displacement-sensitive photonic crystal structures based on guided resonance in photonic crystal slabs
Authors: Suh Wonjoo , Yanik M. F. , Solgaard Olav , Fan Shanhui
Published: March 2003

We introduce a mechanically tunable photonic crystal structure consisting of coupled photonic crystal slabs. Using both analytic theory, and first-principles finite-difference time-domain simulations, we demonstrate that a strong variation of transmission and reflection coefficients of light through such structures can be accomplished with only a nanoscale variation of the spacing between the slabs. Moreover, by specifically configuring the photonic crystal structures, high sensitivity can be preserved in spite of significant fabrication-related disorders. We expect such structures to play important roles in micromechanically tunable optical sensors and filters.
Mechanisms for retention loss in ferroelectric Pt/Pb(Zr0.4Ti0.6)O3/Pt capacitors
Authors: Kang B. S. , Yoon Jong-Gul , Kim D. J. , Noh T. W. , Song T. K. , Lee Y. K. , Lee J. K. , Park Y. S.
Published: March 2003

The switching current profiles of ferroelectric Pt/Pb(Zr0.4Ti0.6)O3/Pt capacitors were investigated after high-temperature baking to elucidate the mechanisms for retention loss. In the same-state retention, a decrease in the peak value of switching current and increase in the switching time were observed. These changes in the switching characteristics were attributed to the growth of an internal field. By comparing with the switching characteristics of a virgin capacitor and using the Merz equations, we estimated quantitatively the magnitude of the internal field. In the opposite-state retention, backswitching of polarization, triggered by the internal field, was found to be the main cause of the retention loss.
The Franz–Keldysh effect in shocked GaN:Mg
Authors: Peng H. Y. , McCluskey M. D. , Gupta Y. M. , Kneissl M. , Johnson N. M.
Published: March 2003

The band gap of uniaxially strained semi-insulating GaN:Mg has been examined using time-resolved optical transmission measurements in shock-wave experiments. For longitudinal stresses between 2.9 and 4.6 GPa, the absorption edge broadened significantly. Such a broadening is consistent with the presence of large piezoelectric fields (Franz–Keldysh effect) generated due to shock compression. For stresses greater than 4.6 GPa, however, the absorption edge remained relatively sharp. The sharp absorption onset suggests the presence of free charge carriers that screen the piezoelectric field, thereby suppressing the Franz–Keldysh effect. These observations indicate that electrical breakdown occurs at a field of 1 MV/cm. One possible mechanism that could result in free carriers is the dissociation of Mg–H complexes under the very high piezoelectric fields.
Electromigration reliability of dual-damascene Cu/porous methylsilsesquioxane low k interconnects
Authors: Lee Ki-Don , Ogawa Ennis T. , Yoon Sean , Lu Xia , Ho Paul S.
Published: March 2003

Electromigration (EM) reliability was investigated for Cu/porous low k interconnects. The porous low k dielectric was a methylsilsesquioxane (MSQ) based spin-on organosilicate material with k of 2.2. The activation energy for EM failure was found to be about 0.9 eV for Cu/porous MSQ between 208 and 367 °C, which is commonly associated with mass transport at the Cu/SiNx cap-layer interface. The threshold product of current density and line length (jL)c for Cu/porous MSQ was found to be 2500–3000 A/cm. The reduction in EM lifetime compared with Cu/oxide interconnect can be attributed to smaller back stress, due to less thermomechanical confinement of Cu/low k interconnects. Most interconnects failed by voiding at the cathode. Some lateral Cu extrusion followed by interfacial breakdown was also observed near the anode.
Intrinsic diffraction losses in photonic crystal waveguides with line defects
Authors: Andreani Lucio Claudio , Agio Mario
Published: March 2003

Intrinsic diffraction losses of linear defect modes in photonic crystal slabs are calculated for membrane-type waveguides with strong refractive index contrast. In the frequency region of high group velocity of the defect mode, the radiative losses increase with the air fraction of the lattice and decrease on increasing the channel width or the slab thickness. Close to a mini-gap in the mode dispersion, a complex frequency dependence of the losses is found. The calculated losses agree well with those measured in a Si slab [M. Lončar et al., Appl. Phys. Lett. 80, 1689 (2002)].
Activation of the Cannabinoid Receptor Type 1 Decreases Glutamatergic and GABAergic Synaptic Transmission in the Lateral Amygdala of the Mouse
Authors: Azad Shahnaz Christina , Eder Matthias , Marsicano Giovanni , Lutz Beat , Zieglgänsberger Walter , Rammes Gerhard
Published: March 2003

The endogenous cannabinoid system has been shown recently to play a crucial role in the extinction of aversive memories. As the amygdala is presumably involved in this process, we investigated the effects of the cannabinoid receptor agonist WIN 55,212-2 (WIN-2) on synaptic transmission in the lateral amygdala (LA) of wild-type and cannabinoid receptor type 1 (CB1)-deficient mice. Extracellular field potential recordings and patch-clamp experiments were performed in an in vitro slice preparation. We found that WIN-2 reduces basal synaptic transmission and pharmacologically isolated AMPA receptor- and GABAA receptor-mediated postsynaptic currents in wild-type, but not in CB1-deficient mice. These results indicate that, in the LA, cannabinoids modulate both excitatory and inhibitory synaptic transmission via CB1. WIN-2-induced changes of paired-pulse ratio and of spontaneous and miniature postsynaptic currents suggest a presynaptic site of action. Inhibition of Gi/o proteins and blockade of voltage-dependent and G protein-gated inwardly rectifying K+ channels inhibited WIN-2 action on basal synaptic transmission. In contrast, modulation of the adenylyl cyclase-protein kinase A pathway, and blockade of presynaptic N- and P/Q- or of postsynaptic L- and R/T-type voltage-gated Ca2+ channels did not affect WIN-2 effects. Our results indicate that the mechanisms underlying cannabinoid action in the LA partly resemble those observed in the nucleus accumbens and differ from those described for the hippocampus.
An initial assessment of the influence of IT on TQM: a multiple case study
Authors: Dewhurst Frank W. , Rafael Martínez‐Lorente Angel , Sánchez‐Rodríguez Cristóbal
Published: March 2003

Information technology (IT) and total quality management (TQM) have significantly impacted on most organizations and each has been widely researched. However, there is little well‐founded empirical research on the relationship between the two, particularly on the way in which TQM is influenced by IT. This paper presents an initial investigation of such relationships through an interview survey of 14 companies based in Spain. The cases indicate that there is a framework underpinning this relationship. The paper concludes with a proposal for this framework and an instrument for testing the conjectured linkages within the framework.
An empirical study of POM teaching in Spanish universities (II)
Authors: Alfalla Luque Rafaela , Machuca José A.D.
Published: March 2003

Production/operations management (POM) is today a key element for the competitivity of companies, and the demand by Spanish companies for university graduates qualified in this area is significant. Therefore, in this discipline, the correct education and training of future business managers is an evident need to be addressed; however, little is known about the current situation of POM teaching in Spanish universities. Hence, to obtain reliable and useful data, a comprehensive empirical study of the total population of university teachers of this discipline in Spain has been undertaken. The present paper concentrates first on the analysis of the characteristics of the POM faculty in Spanish universities, then considers the teaching and assessment methods and the didactic material employed in the teaching of this discipline. In both cases, a critical analysis has been made of the various problems observed, and alternative solutions have been proposed. The analysis of the content of POM programs is the subject of another article published in this journal.
Implementing enterprise resource planning systems with total quality control and business process reengineering
Authors: Schniederjans Marc J. , Kim Gyu C.
Published: March 2003

The primary objective of an enterprise resource planning (ERP) system is to help integrate an organization's business operations and processes effectively and efficiently. Not all firms have been successful in their ERP implementations and to that end research has helped to identify many factors that might be critical to a successful implementation. Such factors as the use of business process reengineering (BPR), and establishing a total quality management (TQM) culture have all shown to play important roles in ERP implementation. The focus of this survey research on US electronic manufacturing firms is to identify successful integration sequences of TQM and BPR with ERP. The findings reveal that both the sequence of implementation and the strategies selected to initiate ERP systems can significantly impact business performance successfulness.
Luxury branding on the Internet: lost opportunity or impossibility?
Authors: Dall’Olmo Riley Francesca , Lacroix Caroline
Published: March 2003

The paper addresses the issue of the use of the Internet for the management of luxury brands. We investigate luxury managers’ attitudes towards the use of the Internet to promote their brands and also assess consumers’ opinions and behaviour concerning luxury brands Web sites. Finally, we present the results of a content analysis of a number of luxury brands sites. Any discrepancies between expectations and reality are investigated. Results indicate that reality falls short of the expectations of both managers and customers and that the interactive potential of the Internet is not exploited. Furthermore, there is evidence that the Internet works best as a communication than as a customer acquisition channel for luxury brands.
Web site characteristics and business performance: some evidence from international business‐to‐business organizations
Authors: Karayanni Despina A. , Baltas George A.
Published: March 2003

This paper addresses the effectiveness of Web site capabilities. It is intended to empirically determine the importance of site properties for Internet sales performance. More specifically, we consider the relationship of characteristics such as navigability, interactivity, multimedia design and marketing communications content with sales attributed to the Internet. Advanced econometric modeling of cross‐section data on business‐to‐business firms demonstrates that interactive responsiveness of the site, enabling customized interactive programs and club membership, fast‐downloading multimedia, such as frames and animation, corporate information stressing corporate positioning and active information submission on behalf of the target audience may influence sales performance. Important implications for optimization of business‐to‐business Internet strategies are also considered.
E‐relationships – emergence and the small firm
Authors: O’Toole Thomas
Published: March 2003

The e‐business model has become an integral feature of business practice. Its existence has created an extra electronic layer to business relationships. This has facilitated close partnerships to add unique and complex electronic components to their relationships that are not easily copied by other firms. The emergence of e‐relationships is detailed and their value creating potential explored. The e‐relationship concept is then applied to the small firm. The strategic and implementation barriers that inhibit small firms from capitalising on such relationships are examined. E‐relationships are found to offer competitive advantage to few small firms. Critical to an e‐relationship’s success is the relationship orientation of the partners.
Finite strain endochronic plasticity with reference to metal tube under torsion
Authors: Khoei A.R. , Bakhshiani A. , Mofid M.
Published: March 2003

In this paper, a new rate type endochronic constitutive model is introduced to describe deformations in the finite strain range. A new material dependent objective rate of Cauchy stress is suggested based on the general form of spin tensors, defining objective stress rates. The endochronic constitutive equations are extended using the concept of corotational stress rates and additive decomposition of deformation rate. The constitutive relations are specialized for thin‐walled tubes under torsion and a procedure for solving the ordinary differential equations for cases of simple and pure torsion is developed. The axial effects for various materials, subjected to simple and pure torsion, are simulated and compared with experimental data. The results clearly indicate that the new combined rate endochronic model can be effectively used to describe the behavior of material in the finite strain range.