bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity analysis and assessment of prior model probabilities in MLBMA with application to unsaturated fractured tuff
Authors: Ye Ming , Neuman Shlomo P. , Meyer Philip D. , Pohlmann Karl
Published: December 2005

Previous application of maximum likelihood Bayesian model averaging (MLBMA, Neuman (2002, 2003)) to alternative variogram models of log air permeability data in fractured tuff has demonstrated its effectiveness in quantifying conceptual model uncertainty and enhancing predictive capability (Ye et al., 2004). A question remained how best to ascribe prior probabilities to competing models. In this paper we examine the extent to which lead statistics of posterior log permeability predictions are sensitive to prior probabilities of seven corresponding variogram models. We then explore the feasibility of quantifying prior model probabilities by (1) maximizing Shannon's entropy H (Shannon, 1948) subject to constraints reflecting a single analyst's (or a group of analysts') prior perception about how plausible each alternative model (or a group of models) is relative to others, and (2) selecting a posteriori the most likely among such maxima corresponding to alternative prior perceptions of various analysts or groups of analysts. Another way to select among alternative prior model probability sets, which, however, is not guaranteed to yield optimum predictive performance (though it did so in our example) and would therefore not be our preferred option, is a minimum‐maximum approach according to which one selects a priori the set corresponding to the smallest value of maximum entropy. Whereas maximizing H subject to the prior perception of a single analyst (or group) maximizes the potential for further information gain through conditioning, selecting the smallest among such maxima gives preference to the most informed prior perception among those of several analysts (or groups). We use the same variogram models and log permeability data as Ye et al. (2004) to demonstrate that our proposed approach yields the least amount of posterior entropy (residual uncertainty after conditioning) and enhances predictive model performance as compared to (1) the noninformative neutral case in which all prior model probabilities are set equal to each other and (2) an informed case that nevertheless violates the principle of parsimony.
Some self‐similar solutions in river morphodynamics
Authors: Daly E. , Porporato A.
Published: December 2005

Aggradation and degradation in one‐dimensional channels are often modeled with a simplified nonlinear diffusion equation. Different degrees of nonlinearity are obtained using the Chezy and Manning/Gauckler‐Strickler laws for the friction coefficient combined with a sediment transport equation having a generalized form of the Meyer‐Peter and Müller formula. Analytical self‐similar solutions for the “dam break” and the base‐level lowering are presented. While the linear case corresponds to the classic diffusion equation, the main effect of the nonlinearity appears to be the presence of singularities in the self‐similar solutions, related to the finite speed of propagation of perturbations.
DNA‐damage‐responsive acetylation of pRb regulates binding to E2F‐1
Authors: Markham Douglas , Munro Shonagh , Soloway Judith , O'Connor Darran P , La Thangue Nicholas B
Published: December 2005

The pRb (retinoblastoma protein) tumour suppressor protein has a crucial role in regulating the G1‐ to S‐phase transition, and its phosphorylation by cyclin‐dependent kinases is an established and important mechanism in controlling pRb activity. In addition, the targeted acetylation of lysine (K) residues 873/874 in the carboxy‐terminal region of pRb located within a cyclin‐dependent kinase‐docking site hinders pRb phosphorylation and thereby retains pRb in an active state of growth suppression. Here, we report that the acetylation of pRb K873/874 occurs in response to DNA damage and that acetylation regulates the interaction between the C‐terminal E2F‐1‐specific domain of pRb and E2F‐1. These results define a new role for pRb acetylation in the DNA damage signalling pathway, and suggest that the interaction between pRb and E2F‐1 is controlled by DNA‐damage‐dependent acetylation of pRb.
The Saccharomyces cerevisiae Sae2 protein negatively regulates DNA damage checkpoint signalling
Authors: Clerici Michela , Mantiero Davide , Lucchini Giovanna , Longhese Maria Pia
Published: December 2005

Double‐strand breaks (DSBs) elicit a DNA damage response, resulting in checkpoint‐mediated cell‐cycle delay and DNA repair. The Saccharomyces cerevisiae Sae2 protein is known to act together with the MRX complex in meiotic DSB processing, as well as in DNA damage response during the mitotic cell cycle. Here, we report that cells lacking Sae2 fail to turn off both Mec1‐ and Tel1‐dependent checkpoints activated by a single irreparable DSB, and delay Mre11 foci disassembly at DNA breaks, indicating that Sae2 may negatively regulate checkpoint signalling by modulating MRX association at damaged DNA. Consistently, high levels of Sae2 prevent checkpoint activation and impair MRX foci formation in response to unrepaired DSBs. Mec1‐ and Tel1‐dependent Sae2 phosphorylation is necessary for these Sae2 functions, suggesting that the two kinases, once activated, may regulate checkpoint switch off through Sae2‐mediated inhibition of MRX signalling.
Transcriptional regulation of the Neurospora circadian clock gene wc‐1 affects the phase of circadian output
Authors: Káldi Krisztina , González Beatriz Herreros , Brunner Michael
Published: December 2005

WHITE COLLAR‐1 (WC‐1) is the limiting component of the White Collar Complex (WCC) controlling expression of the Neurospora circadian clock protein Frequency (FRQ). Accumulation of WC‐1 is supported by FRQ on a post‐transcriptional level. Here, we show that transcription of wc‐1 is organized in a complex way. Three promoters drive transcription of wc‐1. Pdist is dependent on WCC. Pprox is independent of WCC in darkness, but inducible by light in a WCC‐dependent manner. A third promoter, Pint, is located in the wc‐1 open reading frame and promotes expression of an amino‐terminally truncated WC‐1 isoform of unknown function. Expression of wc‐1 by Pdist or Pprox alone, or by a heterologous promoter, affects the entrained phase of circadian conidiation and the response of Neurospora to light. Our results indicate that transcriptional regulation of wc‐1 is required to modulate the circadian phase of clock output.
The involvement of the Mre11/Rad50/Nbs1 complex in the generation of G‐overhangs at human telomeres
Authors: Chai Weihang , Sfeir Agnel J , Hoshiyama Hirotoshi , Shay Jerry W , Wright Woodring E
Published: December 2005

A central function of telomeres is to prevent chromosome ends from being recognized as DNA double‐strand breaks (DSBs). Several proteins involved in processing DSBs associate with telomeres, but the roles of these factors at telomeres are largely unknown. To investigate whether the Mre11/Rad50/Nbs1 (MRN) complex is involved in the generation of proper 3′ G‐overhangs at human telomere ends, we used RNA interference to decrease expression of MRN and analysed their effects. Reduction of MRN resulted in a transient shortening of G‐overhang length in telomerase‐positive cells. The terminal nucleotides of both C‐ and G‐rich strands remain unaltered in Mre11‐diminished cells, indicating that MRN is not responsible for specifying the final end‐processing event. The reduction in overhang length was not seen in telomerase‐negative cells, but was observed after the expression of exogenous telomerase, which suggested that the MRN complex might be involved in the recruitment or action of telomerase.
Redundant pathways for Cdc2 activation in Xenopus oocyte: either cyclin B or Mos synthesis
Authors: Haccard Olivier , Jessus Catherine
Published: December 2005

Xenopus oocytes are arrested in meiotic prophase I. Progesterone induces the resumption of meiotic maturation, which requires continuous protein synthesis to bring about Cdc2 activation. The identification of the newly synthesized proteins has long been a goal. Two plausible candidates have received extensive study. The synthesis of cyclin B and of c‐Mos, a kinase that activates the mitogen‐activated protein kinase pathway in oocytes, is clearly upregulated by translational control in response to progesterone. Recent studies suggest that ablation of either c‐Mos or cyclin B synthesis by antisense oligonucleotides does not block meiotic maturation. Here, however, we show that when both pathways are simultaneously inhibited, progesterone no longer triggers maturation; adding back either c‐Mos or cyclin B restores meiotic maturation. We conclude that the specific synthesis of either B‐type cyclins or c‐Mos, induced by progesterone, is required to induce meiotic maturation. The two pathways seem to be functionally redundant.
Binding at molecule/gold transport interfaces. V. Comparison of different metals and molecular bridges
Authors: Basch Harold , Ratner Mark A.
Published: December 2005

The geometric and electronic structural properties of symmetric and asymmetric metal cluster-molecule-cluster′ complexes have been explored. The metals include Au, Ag, Pd, and Al, and both benzenedithiol and the three isometric forms of dicyanobenzene are included as bridging molecules. Calculated properties such as cluster-molecule interface geometry, electronic state, degree of metal → molecule charge transfer, metal-molecule mixing in the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy region, the HOMO-LUMO gap, cluster → cluster′ charge transfer as a function of external field strength and direction, and the form of the potential profile across such complexes have been examined. Attempts are made to correlate charge transport with the characteristics of the cluster-complex systems. Indications of rectification in complexes that are asymmetric in the molecule, clusters, and molecule-cluster interfaces are discussed. The results obtained here are only suggestive because of the limitations of the cluster-complex model as it relates to charge transport.
Growth and characterization of dual-beam pulsed-laser-deposited Zn1−xCoxO thin films
Authors: Peng Y. Z. , Liew T. , Chong T. C. , Song W. D. , Li H. L. , Liu W.
Published: December 2005

Dual beam pulsed laser deposition was used to synthesize Zn1−xCoxO thin films with a large range of Co concentrations. In this paper, the influence of growth temperature on the crystal structures, magnetic properties, and semiconductor properties of these films was studied. It was found that the growth temperature has a significant effect on dopant concentration, as well as the structure and properties of the films. The optimum growth temperature is around 650°C. The thin films were of single crystal especially at low Co concentrations. Epitaxial growth of the thin films was observed. No precipitates were observed at low Co concentrations. Magnetic hysteresis loops were observed at room temperature, indicating that magnetism can be realized with Co doped into ZnO. However, the improvement was limited. The Hall resistivity tended to increase, while carrier density tended to decrease with Co concentration until a certain Co concentration (10%) is achieved. When the growth temperature was greater than 650°C, the Hall resistivity decreased, while carrier density increased. The Hall mobility increased with growth temperature. The possible reasons of the observed magnetism and semiconductor properties were also discussed.
Role of the spin magnitude of the magnetic ion in determining the frustration and low-temperature properties of kagome lattices
Authors: Pati Swapan K. , Rao C. N. R.
Published: December 2005

In view of the variety of low-temperature magnetic properties reported recently for kagome lattices with transition-metal ions in different oxidation states, we have investigated the low-energy spectrum and low-temperature thermodynamic properties of antiferromagnetic kagome lattices with varying magnitudes of site spins, employing quantum many-body Heisenberg models. The ground state and the low-lying excitation spectrum are found to depend strongly on the nature of the spin magnitude of the magnetic ions. The system remains highly frustrated if spins are half-odd-integer in magnitude, while the frustration is very weak or almost absent for integer spins or mixed-spin systems. In fact, for a mixed-spin kagome system with a certain magnitude, the whole system behaves as a classical magnet with a ferrimagnetic ground state without any frustration. These theoretical findings are consistent with a few experimental observations recently reported in the literature and would be of value in designing new kagome systems with unusual and interesting low-temperature magnetic properties.
Dynamical characterization of rotationally hindered species in liquids
Authors: Medina A. , Roco J. M. M. , Hernández A. Calvo , Velasco S.
Published: December 2005

The rotational dynamics of HCl in liquid Ar has been studied by means of molecular-dynamics simulations. We calculate the lifetimes of weakly bound HCl–Ar dimers induced by the anisotropic pair interaction. It is shown that, although lifetimes are small with respect to the reorientational decorrelation, the time interval between the breaking down and formation of the next dimer is negligibly small. Thus, with respect to the rotational dynamics of the probe, the effect is similar to that and eventually would cause a time-stable complex. This provokes a peculiar hindered rotation of the diatomic in the liquid which is macroscopically embodied in the infrared spectrum of the solution as a Q-branch nonexistent otherwise.
Effective chromophore potential, dissipative trajectories, and vibrational energy relaxation: Br2 in Ar matrix
Authors: Gühr M. , Schwentner N.
Published: December 2005

The intramolecular wave packet dynamics on the electronic B (Π03) potential of Br2 in solid argon is induced and interrogated by femtosecond pump-probe spectroscopy. An effective potential of the chromophore in the solid is derived from the wave packet period for different excitation photon energies. Deep in the potential well, it is consistent with vibrational energies from wavelength-resolved spectra. It extends to higher energies, where the vibrational bands merge to a continuum, and even beyond the dissociation limit, thus quantifying the cage effect of the argon matrix. This advantage of pump-probe spectroscopy is related to a reduced contribution of homogeneous and inhomogeneous line broadenings. The vibrational energy relaxation rates are determined by a variation of the probe window spatial position via the probe quantum energy. A very large energy loss in the first excursion of the wave packet is observed near the dissociation limit. This strong interaction with the argon matrix is directly displayed in an experimental trajectory.
Causal sites as quantum geometry
Authors: Christensen J. Daniel , Crane Louis
Published: December 2005

We propose a structure called a causal site to use as a setting for quantum geometry, replacing the underlying point set. The structure has an interesting categorical form, and a natural “tangent 2-bundle,” analogous to the tangent bundle of a smooth manifold. Examples with reasonable finiteness conditions have an intrinsic geometry, which can approximate classical solutions to general relativity. We propose an approach to quantization of causal sites as well.
Melting line of charged colloids from primitive model simulations
Authors: Hynninen Antti-Pekka , Dijkstra Marjolein
Published: December 2005

We develop an efficient simulation method to study suspensions of charged spherical colloids using the primitive model. In this model, the colloids and the co- and counterions are represented by charged hard spheres, whereas the solvent is treated as a dielectric continuum. In order to speed up the simulations, we restrict the positions of the particles to a cubic lattice, which allows precalculation of the Coulombic interactions at the beginning of the simulation. Moreover, we use multiparticle cluster moves that make the Monte Carlo sampling more efficient. The simulations are performed in the semigrand canonical ensemble, where the chemical potential of the salt is fixed. Employing our method, we study a system consisting of colloids carrying a charge of 80 elementary charges and monovalent co- and counterions. At the colloid densities of our interest, we show that lattice effects are negligible for sufficiently fine lattices. We determine the fluid-solid melting line in a packing fraction η-inverse screening length κ plane and compare it with the melting line of charged colloids predicted by the Yukawa potential of the Derjaguin-Landau-Verwey-Overbeek theory. We find qualitative agreement with the Yukawa results, and we do not find any effects of many-body interactions. We discuss the difficulties involved in the mapping between the primitive model and the Yukawa model at high colloid packing fractions (η>0.2).
Hydration number of glycine in aqueous solution: An experimental estimate
Authors: Parsons Matthew T. , Koga Yoshikata
Published: December 2005

An experimental estimate of hydration number, NH, of glycine in aqueous solution is given by using the calorimetric methodology developed by us earlier, which is briefly reviewed. We found NH to be 7±0.6 for glycine presumably in the zwitter ion form, 10±1 for sodium glycinate, and 5±0.4 for glycine hydrochloride. Both glycine and sodium glycinate seem to work purely as a hydration center without altering the nature of the bulk H2O away from the hydration shell. Glycine hydrochloride, in addition to the role of hydration center, seems also to act as a typical hydrophilic species such as polyols, urea, or polyethylene glycols. Hence, the effect of the latter on H2O is of a long range, like other hydrophilic species.
Polymer translocation: The effect of backflow
Authors: Ali I. , Yeomans J. M.
Published: December 2005

We investigate the effect of backflow on the translocation dynamics of short, flexible polymer chains threading through a small hole in a wall. We find that hydrodynamic interactions between polymer beads play an important role in determining the translocation time distribution: as a monomer moves through the hole it sets up a flow field which transfers momentum to neighboring monomers, thus helping them to move in the same direction. Translocation times are calculated by using the velocity-Verlet algorithm to solve the equations of motion of a polymer which moves in a fluid described by the stochastic rotation algorithm, a particle-based Navier-Stokes solver.
Influence of the nonlinearity and dipole strength on the amide I band of protein α-helices
Authors: Cruzeiro Leonor
Published: December 2005

Vibrational energy storage and propagation are simulated in a fully atomic model of an α-helix by combining the AMBER force field for proteins with an extended version of the Davydov/Scott model for amide I vibrational transfer [A. Scott, Phys. Rep. 217, 1 (1992)]. Dipole-dipole interactions between transition dipole moments of amide I and its on-site energies are calculated from the corresponding three-dimensional atomic positions. The comparison of the theoretically calculated absorption line shapes with the experimentally measured ones leads to a putative value of the nonlinearity parameter of −30pN.
Effect of ambient air pressure on debris redeposition during laser ablation of glass
Authors: Singh S. , Argument M. , Tsui Y. Y. , Fedosejevs R.
Published: December 2005

The effect of ambient air pressure on the redeposition of debris, ablated from the zinc borosilicate glass target using 6ns, 266nm laser pulses, has been studied for incident fluences of 3–18J∕cm2. Measurements were carried out in air at pressures ranging from 10–750Torr. Scanning electron microscopy and optical microscope observations of the target surface were made to analyze the morphology of the redeposited debris. It was found that for higher values of the laser fluence and ambient pressure, the target surface is extremely rough, with large pieces of molten glass and debris fragments deposited near and around the ablation site. The profile of the redeposited debris also shows signs of a strong shock-wave-cleaning effect and possibly a Rayleigh-Taylor instability at higher pressures. Contrary to this, under low-pressure environment the surface of the redeposited debris is cleaner and smoother, with minimal damage around the ablated crater. The measured radius of the debris field was found to be proportional to the inverse cube root of the ambient pressure, consistent with the stagnation distance of the expansion plume when energy balance with the displaced air is considered. In addition to this, the mass of the redeposited debris was estimated from the measured optical thickness of the film and compared to the ablated mass. In the range below 100Torr, both the mass of the redeposited debris and the percentage of the ablated mass which was redeposited were found to increase with the increasing fluence and the ambient air pressure.
Pump-dump iterative squeezing of vibrational wave packets
Authors: Chang Bo Y. , Sola Ignacio R.
Published: December 2005

The free motion of a nonstationary vibrational wave packet in an electronic potential is a source of interesting quantum properties. In this work we propose an iterative scheme that allows continuous stretching and squeezing of a wave packet in the ground or in an excited electronic state, by switching the wave function between both potentials with π pulses at certain times. Using a simple model of displaced harmonic oscillators and delta pulses, we derive the analytical solution and the conditions for its possible implementation and optimization in different molecules and electronic states. We show that the main constraining parameter is the pulse bandwidth. Although in principle the degree of squeezing (or stretching) is not bounded, the physical resources increase quadratically with the number of iterations, while the achieved squeezing only increases linearly.
Proton and deuteron position preferences in water clusters: An ab initio study
Authors: Anick David J.
Published: December 2005

In order to explore the effect of H-to-D substitution on the zero-point energy (ZPE) of water clusters, Hessians were computed for a database of 53 optimized (H2O)n clusters, 5⩽n⩽21, at the B3LYP∕6−311++G** level. The 53 clusters contained 1524 protons, which were sorted into 18 categories according to the type of their donor O and (if not free) acceptor O. Letting ΔZPE{H*} denote the change in ZPE when the proton H* is replaced by D, mean values for ΔZPE{H*} for the H-bonded categories ranged from −2172calmol−1 for H* in a DDAA–DDAA bond to −2118 for H* in a DAA–DDA bond. Mean value for H* free on DAA (respectively, DA) was −2018 (respectively, −1969). For DAA–DDA bonds, and for short H bonds in general, there was a strong inverse correlation between ∣ΔZPE{H*}∣ and the O–H* distance. ΔZPE for multiple H-to-D substitutions was additive, except for a cooperativity effect of −13.7 to −19.7calmol−1 when two substituted protons were in the same H2O unit and a much smaller cooperativity when one proton’s donor was the other’s acceptor. Implications of these data include a relative preference for D to occupy H bonded rather than free positions in finite water clusters, a value of 3.82 for the disproportionation equilibrium constant of mixed ice at 150 K, increased occupation by H at surface positions of mixed ice, and a larger average coordination number for liquid D2O than for liquid H2O.
Magnetization losses in multiply connected YBa2Cu3O6+x-coated conductors
Authors: Levin G. A. , Barnes P. N. , Amemiya Naoyuki , Kasai Satoshi , Yoda Keiji , Jiang Zhenan , Polyanskii A.
Published: December 2005

We report the results of a magnetization loss study in experimental multifilament, multiply connected coated superconductors exposed to time-varying magnetic field. In these samples, the superconducting layer is divided into parallel stripes segregated by nonsuperconducting grooves. In order to facilitate the current sharing between the stripes and thus increase the reliability of the striated conductors, a sparse network of superconducting bridges is superimposed on the striated film. We find that the presence of the bridges does not substantially increase the magnetization losses, both hysteresis and coupling, as long as the number of bridges per length of the sample is not large. These results indicate that it is possible to find a reasonable compromise between the competing requirements of connectivity and loss reduction in an ac-tolerant version of the high-temperature coated conductors specifically designed for ac power applications.
GaP THz wave generator and THz spectrometer using Cr:Forsterite lasers
Authors: Suto Ken , Sasaki Tetsuo , Tanabe Tadao , Saito Kyosuke , Nishizawa Jun-ichi , Ito Masahiko
Published: December 2005

We have developed a type of THz wave generator that uses Cr:Forsterite lasers as the pump and signal sources for difference frequency generation in GaP (Cr:F source system). We confirmed the generation of THz waves in the frequency range from 0.3to7.5THz, which is just similar to that obtained using the THz wave generator previously developed utilizing yttrium aluminum garnet and optical parametric oscillator (OPO) lasers (OPO source system). A peak output power of 100mW was obtained from 1.2to5THz when the power of the two input beams was 3mJ each, similar to the OPO source system. A wide measurable frequency range from below 0.6THz to over 6THz was obtained by using the Cr:F source system as the light source of a spectrometer, which has the merits of simple structure, easy maintenance, and low cost compared with the OPO source system. Although the linewidth of the Cr:F source system is greater than that of the OPO source system, the THz spectrometer still has sufficient resolution for measuring solids or liquids at room temperature.
Regarding the origin of the delayed fluorescence of conjugated polymers
Authors: Rothe Carsten , Monkman Andy
Published: December 2005

In the first part of this work we revisit and reevaluate the experimental data that lead to the assignment of the origin of the delayed fluorescence (DF) to triplet-triplet annihilation for polyfluorene and to geminate pair recombination in the case of the ladder-type polyparaphenylene (MeLPPP); the ambiguity of this classification is unveiled. Next, new data about the DF of MeLPPP under applied electric field are presented. Here, the DF intensity completely recovers once the field is turned off, which rules out geminate pairs as the origin of the DF and in turn provides clear evidence of the triplet-triplet annihilation picture. Finally, we show and discuss how recombination of space charge layers may also give rise to electric field induced delayed fluorescence, whereby the formation of these space charge layers strongly depends on device configuration and purity of the materials.
Combustion mechanism of liquid fuel spray in a gaseous flame
Authors: Nakamura Mariko , Akamatsu Fumiteru , Kurose Ryoichi , Katsuki Masashi
Published: December 2005

Two-dimensional direct numerical simulation is applied to spray flames stabilized in a laminar counterflow, and the detailed behavior is studied in terms of the droplet group combustion. The stretch ratio of the laminar counterflow is 40 l/s. n-decane (C10H22) is used as a liquid spray fuel, and a one-step global reaction is employed for the combustion reaction model. The results show that with increasing the issued liquid fuel mass fraction, two types of spray combustion appear in front of and inside the high gaseous temperature region, i.e., “premixed-like combustion” and “diffusion-like combustion,” respectively. A droplet group combustion behavior is observed in the diffusion-like combustion region. This diffusion-like combustion, however, disappears when the issued droplet size becomes small, because the droplets complete their evaporation before entering into the high gaseous temperature region. The droplet group combustion tends to reduce the gaseous temperature. This is caused mainly by the suppression of combustion reaction due to the lack of oxygen and partially by the energy exchange through the convective heat transfer between droplets and gaseous phase. The gaseous temperature reduction is promoted by the latent heat of vaporization of the droplets. The use of the parcel approach has a risk of causing a delay of combustion reaction, since the partial fuel vapor pressure increases at limited locations, which suppresses the global droplet evaporation rate.
Composite bimetallic gasket and compact mechanical anvil retainer for magnetic measurements in a diamond-anvil cell to 30GPa
Authors: Ishizuka Mamoru
Published: December 2005

A composite gasket was designed for diamond-anvil cells where the load was supported mainly by the inner part made of NiCrAl with a diameter slightly larger than the culet of the anvil. A BeCu girdle encased the NiCrAl washer and prevented it from fracturing. The thickness of the gasket was about 30μm at a pressure of 30GPa applied with a pair of diamond anvils having 500 and 550μm culets. The magnetic contribution of the composite gasket to the background signal was almost the same as that of a BeCu gasket having the same size. The diamond anvils were fixed to the pistons with four miniature screws through small BeCu rings that were press fitted to the circumference of the diamond anvils. The performance of this composite gasket together with the anvil retainer was illustrated by the measurements of the temperature dependence of the dc magnetic susceptibility of Cs2CuF4 under various pressures up to 26GPa using a superconducting quantum interference device vibrating coil magnetometer.
On unique parameters and unified formal form of hot-wire anemometric sensor model
Authors: Ligęza P.
Published: December 2005

This note reviews the extensively adopted equations used as models of hot-wire anemometric sensors. An unified formal form of the mathematical model of a hot-wire anemometric sensor with otherwise defined parameters is proposed. Those parameters, static and dynamic, have simple physical interpretation and can be easily determined. They show directly the range of sensor application. They determine the metrological properties of the given sensor in the actual medium. Hence, the parameters' values might be ascribed to each sensor in the given medium and be quoted in manufacturers’ catalogues, supplementing the sensor specifications. Because of their simple physical interpretation, those parameters allow the direct comparison of the fundamental metrological properties of various sensors and selection of the optimal sensor for the given research measurement application. The parameters are also useful in modeling complex hot-wire systems.
Polarizance of a synthetic mica crystal polarizer and the degree of linear polarization of an undulator beamline at 880eV evaluated by the rotating-analyzer method
Authors: Imazono Takashi , Hirono Toko , Kimura Hiroaki , Saitoh Yuji , Ishino Masahiko , Muramatsu Yasuji , Koike Masato , Sano Kazuo
Published: December 2005

The polarization performance of a reflection-type polarizer made with a synthetic mica (fluorophlogopite) single crystal (002) in symmetric Bragg geometry was evaluated at the photon energy of 880eV by means of the rotating-analyzer method. An experiment was performed at the undulator beamline at the SPring-8. The reflectance in the s-polarization configuration was 2.6% at an incidence angle of around 45°. As the result of the analysis based on the rotating-analyzer method, the polarizance of the polarizer and the degree of linear polarization of the incident light at 880eV were found to be 0.997±0.002 and 0.993±0.004, respectively.
Interaction potentials from periodic density-functional theory calculations: Molecular-dynamics simulations of Au clusters deposited on the TiN (001) surface
Authors: Cruz Hernández N. , Fdez. Sanz Javier
Published: December 2005

Molecular-dynamics simulations of gold particles deposited on a TiN (001) surface have been accounted for through classical pair potentials describing the atom force field. The interaction between Ti–N, Ti–Ti, N–N, Au–Au, Au–Ti, and Au–N pairs was estimated by following a procedure in which the interaction energy between two sets of atoms is estimated from density-functional calculations performed with periodic boundary conditions using plane waves as basis set. The pair potentials were expressed as the sum of two contributions: long range in a Coulomb form and a short-range term, which included the rest of the energy contributions. Simulations of the TiN (001) isolated surface reproduced the already described surface relaxation, with a rippling parameter in agreement with that found from a purely first-principles approach. Simulations of gold deposition on such surfaces showed the formation of metal clusters with well-defined fcc structure and epitaxially grown.
Impact of nitrogen incorporation on interface states in (100)Si∕HfO2
Authors: Fedorenko Y. G. , Truong L. , Afanas’ev V. V. , Stesmans A. , Zhang Z. , Campbell S. A.
Published: December 2005

The influence of nitrogen incorporation on the energy distribution of interface states in the (100)Si∕HfO2 system and their passivation by hydrogen has been studied as compared to N-free samples. The nitrogen in the (100)Si∕HfO2 entity is found to increase the trap density, most significantly, in the upper part of the Si band gap, in which energy range N prevents passivation of interface traps by hydrogen. At the same time, passivation of fast interface traps in the lower part of the band gap proceeds efficiently, provided the thickness of the nitrogen-containing interlayer is kept within a few monolayers. The minimal interface trap density below the midgap achieved after passivation in H2 is determined by the presence of slow N-related states, likely located in the insulator. As inferred from capacitance-voltage and ac conductance analysis, the lowest density of electrically active defects [(8–9)×1010eV−1cm−2 at 0.4–0.5eV from the top of the Si valence band edge] is achieved both in the N-free and N-containing (100)Si∕HfO2 structures after post-deposition anneal at 800°C in N2+5% O2 followed by passivation in molecular hydrogen at 400°C for 30min.
Breakup of Copper shaped-charge jets: Experiment, numerical simulations, and analytical modeling
Authors: Petit Jacques , Jeanclaude Véronique , Fressengeas Claude
Published: December 2005

Experimental data on the fragmentation of copper shaped-charge jets are presented and the techniques used for data processing are described. A combined numerical/analytical analysis is designed to describe shaped-charge jet breakup. The method overcomes drawbacks from exclusively numerical or analytical analyses, such as mesh sensitivity or oversimplified description. It yields predictions for break-up time, total number, and cumulative length of fragments in fairly good agreement with the experimental data. The dependence of fragmentation characteristics on the grain size in the liner is also well predicted.
Evolution of Ge∕Si(001) islands during Si capping at high temperature
Authors: Capellini G. , De Seta M. , Di Gaspare L. , Evangelisti F. , d’Acapito F.
Published: December 2005

We discuss the effect of the deposition of a Si cap layer on the composition and morphological properties of Ge(Si)∕Si(001) self-assembled islands deposited by chemical vapor deposition at 750°C. The morphological evolution of the island shape was investigated by means of atomic force microscopy and the actual island composition has been measured by means of x-ray photoemission spectroscopy and x-ray absorption spectroscopy techniques. At an early stage of Si capping, Si atoms are incorporated in the island layer. As a consequence, we observe a reverse Stranski-Krastanov growth dynamics in agreement with the volume-composition stability diagram proposed for domes, pyramids, and prepyramids in the GexSi1−x∕Si(100) system. We find that the island burying begins when the Ge average composition reaches the value x=0.28. Once the islands are buried under a thin silicon layer their composition is unaffected by subsequent silicon deposition. We conclude that strain relief, rather than thermal diffusion, is the main driving force for the observed Ge-Si alloying.
One-dimensional photonic crystals based on porous n-type silicon
Authors: Murzina T. V. , Sychev F. Yu. , Kim E. M. , Rau E. I. , Obydena S. S. , Aktsipetrov O. A. , Bader M. A. , Marowsky G.
Published: December 2005

Photonic crystals (PC) based on porous n-Si are fabricated and their structural, optical, and nonlinear optical properties are studied. The n-Si based PC composed of five pairs of layers with alternate porosity reveal a rather broad photonic band gap (PBG) of more than 100 nm and a reflectivity of up to 0.75. An average pore diameter of approximately 90 nm is found in n-Si based PC in contrast to mesoporous p-Si based PC, where pores are approximately 15 nm in diameter. Second-harmonic generation (SHG) spectroscopy reveals the enhancement of the SHG intensity by a factor of 102 at the blue edge of the PBG spectra which is attributed to the fulfillment of the phase matching conditions and the localization of the fundamental optical field in the PC.
Growth and characteristics of Ni-based Schottky-type AlxGa1−xN ultraviolet photodetectors with AlGaN∕GaN superlattices
Authors: Park Ki Yon , Kwon Bong Joon , Cho Yong-Hoon , Lee Soon Ae , Son Jeong Hwan
Published: December 2005

We investigated the structural, optical, and electrical properties of Ni-based Schottky-type AlxGa1−xN ultraviolet (UV) photodetectors. Three different types of AlxGa1−xN∕GaN heterostructures were epitaxially grown on (0001) sapphire substrates by metalorganic chemical vapor deposition. We found that the insertion of Al0.2Ga0.8N∕GaN superlattices (SLs) improved the crystal quality of AlxGa1−xN∕GaN heterostructures from photoluminescence and x-ray diffraction experiments. As a result, AlxGa1−xN UV photodetectors with Al0.2Ga0.8N∕GaN SL layers showed superior device performance with lower turn-on voltage and higher responsivity compared to those without SLs. We obtained a dark current of 0.1 nA at −5V, a responsivity of 0.097A∕W at zero bias, and a specific detectivity of D*=8×1013cmHz1∕2W−1 at λ=290nm for AlxGa1−xN UV photodetectors with Al0.2Ga0.8N∕GaN SLs.
On the spectral L2 conjecture, 3/2-Lieb-Thirring inequality and distributional potentials
Authors: Rybkin Alexei
Published: December 2005

Let H=−∂x2+V(x) be a properly defined Schrödinger operator on L2(R) with real potentials of the form V(x)=q(x)+p′(x) (the derivative is understood in the distributional sense) with some p,q∊L2(R). We prove that the absolutely continuous spectrum of H fills (0,∞) which was previously proven by Deift-Killip for V∊L2(R). We also refine the 3/2-Lieb-Thirring inequality.
A combinatorial approach for studying local operations and classical communication transformations of multipartite states
Authors: Singh Sudhir Kumar , Pal Sudebkumar Prasant , Kumar Somesh , Srikanth R.
Published: December 2005

We develop graph theoretic methods for analyzing maximally entangled pure states distributed between a number of different parties. We introduce a technique called bicolored merging, based on the monotonicity feature of entanglement measures, for determining combinatorial conditions that must be satisfied for any two distinct multiparticle states to be comparable under local operations and classical communication. We present several results based on the possibility or impossibility of comparability of pure multipartite states. We show that there are exponentially many such entangled multipartite states among n agents. Further, we discuss a new graph theoretic metric on a class of multipartite states, and its implications.
Electrical conduction in light-emitting organic polymer Schottky diodes
Authors: Rahman Faiz , Johnson Nigel P. , Slight Thomas
Published: December 2005

Schottky metal-polymer diodes, fabricated with a light-emitting polyvinylene polymer, have been studied for their electrical conduction characteristics. Radiative recombination localized at electron injection sites is seen. Device degradation at high drive voltages was observed, together with a self-passivation mechanism due to the formation of metal compounds at the periphery of electrical contacts. Reverse conduction characteristic and Schottky barrier height indicate a diffuse and extended depletion region in these devices.
Modeling nematic liquid crystals in the neighborhood of edges
Authors: Desmet Hans , Neyts Kristiaan , Baets Roel
Published: December 2005

We present a method to simplify simulation techniques for determining liquid-crystal director orientation in geometries with sharply defined edges and for surfaces with strong anchoring without preferred direction. We show analytically that close to such edges, the liquid crystal can be described by just a few parameters. After examining the solutions, it is explained how these results can avoid the numerical problems that arise when simulating such configurations.
Spatial–temporal structure of dissipative magnetic fluxes in type II superconductors
Authors: Medvedev Yu. V. , Krasnyuk I. B.
Published: December 2005

The nonlinear boundary-value problem of the penetration of a magnetic field b into a superconducting half space with resistivity ρf(b)∼bσ is investigated under the condition that the field amplitude at the boundary increases in time by a power law (b(0,t)∼(1+t)m,m>0) or in the peaking regime (b(0,t)∼(1−t/t0)m,m<0,0<t<t0). Conditions on the values of the parameters m and σ are given under which different scenarios of magnetic flux penetration can occur. The velocity of the magnetic flux front is calculated in relation to the parameters m and σ.
Pinning in nomagnetic borocarbides
Authors: Zholobenko A. N. , Mikitik G. P. , Fil’ V. D. , Fil’ D. V. , Kim J. D. , Choi E. M. , Lee S. I.
Published: December 2005

The field dependences of the Labush parameter in nonmagnetic borocarbides are measured by a method that does not require achieving a critical state. The expected values of the critical current are estimated. The values obtained are two orders of magnitude greater than the results of “direct” measurements performed on the basis of transport (magnetic) experiments. A giant peak effect, which the collective pinning model describes quantitatively well, is observed in the field dependences of the Labush parameter in Y-containing borocarbides.
Effect of nanoparticle density on narrow diameter distribution of carbon nanotubes and particle evolution during chemical vapor deposition growth
Authors: Jeong Goo-Hwan , Suzuki Satoru , Kobayashi Yoshihiro , Yamazaki Akira , Yoshimura Hideyuki , Homma Yoshikazu
Published: December 2005

Single-walled carbon nanotubes (SWNTs) were synthesized by chemical vapor deposition (CVD) using catalytic nanoparticles both on the substrates and above the substrates in order to investigate the effect of nanoparticle density on diameter-controlled SWNT growth. As the density of the catalytic nanoparticles increased, tube-diameter distribution broadened and the diameter itself also increased. SWNTs observed in this study were grown by the base-growth mechanism and their diameters were much smaller than those of the nanoparticles. Based on elaborate diameter measurements, we reasonably conjecture that the time evolution of catalytic nanoparticles during CVD growth can explain these large size differences.
Liquid-crystal diffraction gratings using polarization holography alignment techniques
Authors: Crawford Gregory P. , Eakin James N. , Radcliffe Marc D. , Callan-Jones Andrew , Pelcovits Robert A.
Published: December 2005

A method of patterning surfaces for liquid-crystal alignment using a polarization holography exposure on a linear photopolymerizable polymer alignment layer is demonstrated. Three configurations are demonstrated which include registered planar-periodic surface boundary conditions on both surfaces (true polarization gratings), planar-periodic and uniform planary surface boundary conditions, and planar-periodic and homeotropic boundary conditions. Two-dimensional polarization gratings are also demonstrated by orientating planar-periodic alignment layers orthogonally. Passive polarization gratings are also demonstrated using reactive mesogens to capture the periodic order indefinitely. The underlying structure of the configuration is discussed, including the nature of their switching transition (threshold or thresholdless), for all three configurations. A simple phenomenological model is presented to describe the Freedericksz transition for the registered planar-periodic boundary condition case.
Fast-forming boron-oxygen-related recombination center in crystalline silicon
Authors: Bothe Karsten , Schmidt Jan
Published: December 2005

The mechanism of a fast carrier lifetime degradation effect proceeding within seconds in boron-doped Czochralski silicon is investigated. The decrease in the carrier lifetime is attributed to the formation of a deep boron-oxygen-related recombination center with a strongly asymmetric electron-to-hole capture cross section ratio of 100. The center is activated in a two-step process. In a first step, the electron quasi-Fermi level has to be shifted above an energy level at EV+0.635eV before, in the second step, the actual activation occurs via a thermally activated process with an energy barrier of 0.23eV. A defect model is proposed to explain the observed activation behavior.
Magnetic properties of Li(MnyFe1−y)PO4 and its delithiated phases
Authors: Yamada Atsuo , Takei Yuki , Koizumi Hiroshi , Sonoyama Noriyuki , Kanno Ryoji
Published: December 2005

A series of synthetic (MnyFe1−y)PO4 (y<0.8) phases with negligible disorder and impurities were obtained by chemical oxidation of crystallized isotypic Li(MnyFe1−y)PO4 under optimized conditions. This enabled us to perform the comparative magnetic study along the two solid-solution lines based on inherent susceptibility data with no parasitic magnetic signals. All samples exhibit antiferromagnetism but the decrease in Néel temperature is more than seven times larger in (MnyFe1−y)PO4 than in Li(MnyFe1−y)PO4. This was discussed in terms of the asymmetric superexchange interaction by an unusual synergetic effect of Jahn-Teller distortion and edge-shared interconnection with PO4 tetrahedra.
Compact soft x-ray source using Thomson scattering
Authors: Kashiwagi Shigeru , Kuroda Ryunosuke , Oshima Takashi , Nagasawa Fumio , Kobuki Tomoaki , Ueyama Daisuke , Hama Yoshimasa , Washio Masakazu , Ushida Kiminori , Hayano Hitoshi , Urakawa Junji
Published: December 2005

A compact soft x-ray source using Thomson scattering, enabled by the combination of a picosecond laser and an electron rf gun, was developed aiming at biological studies such as those using an x-ray microscope. The x-ray source included both a photoinjector system and a picosecond laser system with a tabletop size of 2×2m2. An infrared laser beam (λ0=1047nm) was obtained from an all-solid-state mode-locked Nd:YLF laser system and injected into the photocathode of an accelerator system. A 4.2MeV electron beam was generated from a laser-driven photocathode rf gun system. The residual laser beam was amplified up to about 4.2mJ/pulse using a flash-lamp-pumped laser amplifier. Upon collision of the electron beam with the amplified laser beam, 300eV soft x rays were generated by Thomson backscattering. The stable interaction between the two beams was achieved using the same seed laser pulse for irradiating the photocathode and the scattering process with laser photons.