bluuebunny/crossref_metadata_2025 huggingface dataset:
A method to measure the electric charge injected/extracted at the metal-dielectric interface
Authors: Neagu Eugen R.
Published: May 2008

A method was proposed to determine the sign and the value of the electric charge injected/extracted at the metal-dielectric interface. The method is based on the modification of the external electric field of a dielectric when electric charge is injected/extracted onto its surface. The lowest surface charge density measured in the presented experiments was around 1.8×10−6Cm−2. The method is insensitive to the orientational polarization. The charge carriers injection/extraction process takes place no matter if there is a conduction current through the sample.
Heisenberg algebra, umbral calculus and orthogonal polynomials
Authors: Dattoli G. , Levi D. , Winternitz P.
Published: May 2008

Umbral calculus can be viewed as an abstract theory of the Heisenberg commutation relation [P̂,M̂]=1. In ordinary quantum mechanics, P̂ is the derivative and M̂ the coordinate operator. Here, we shall realize P̂ as a second order differential operator and M̂ as a first order integral one. We show that this makes it possible to solve large classes of differential and integrodifferential equations and to introduce new classes of orthogonal polynomials, related to Laguerre polynomials. These polynomials are particularly well suited for describing the so-called flatenned beams in laser theory
Bias dependent response reversal in chemically sensitive metal oxide semiconductor capacitors
Authors: Lombardi R. , Aragón R.
Published: May 2008

Conditions for reversal of the voltage shift in chemically sensitive metal oxide semiconductor capacitors are surveyed with the pulsed illumination technique in Si∕SiO2∕Me0 capacitors, with annular Pd and Au gates under controlled H2 in N2 and NO2 in synthetic air stimuli, respectively. The polarity of the response is bias dependent. Above the threshold voltage, negative voltage shifts ensue from positive charges accumulated on the gate-dielectric interface for donor stimuli such as H2, whereas positive shifts indicate negative charge accumulation for acceptors such as NO2. Below the threshold voltage, the necessary charge compensation can be satisfied by proportional changes in the semiconductor-gate interface state population, which induce chemical shifts of opposite polarity.
Effects of a coating of spherically anisotropic material in core-shell particles
Authors: Liu D. H. , Xu C. , Hui P. M.
Published: May 2008

We study the properties of a core-shell particle with a shell of spherically anisotropic material. Such material has a matrix dielectric function that is diagonal in the spherical coordinates. The electric field in the core region is found to be enhanced when compared to an isotropic shell material of comparable dielectric constant for large anisotropy. The enhanced field can drive an enhanced nonlinear response if the core region carries an intrinsic nonlinear susceptibility. For a metallic core, the surface plasmon resonance frequency is found to depend on the degree of anisotropy or the thickness of the shell.
Theoretical analysis of texture effects on the surface morphological stability of metallic thin films
Authors: Tomar Vivek , Gungor M. Rauf , Maroudas Dimitrios
Published: May 2008

By using a nonlinear model of surface morphological evolution, linear stability analysis, and self-consistent dynamical simulations, we analyze the effects of surface crystallographic orientation of a metallic thin film on its surface morphological response to the simultaneous action of an electric field and mechanical stress. The analysis reveals improved surface morphological stability over a range of misorientation angles between the electric-field direction and “easy surface diffusion” directions; for ⟨111⟩-oriented surfaces in fcc metals, the surface morphological response is superior to that of ⟨110⟩- and ⟨100⟩-oriented surfaces. This finding provides an interpretation for the longer electromigration lifetime of {111}-textured metallic interconnects.
Enhancement of mixing and adsorption in microfluidic devices by shear-induced diffusion and topography-induced secondary flow
Authors: Lopez Mauricio , Graham Michael D.
Published: May 2008

Continuum simulations are used to assess the effects of shear-induced diffusion and secondary flow kinematics on the enhancement of mixing and adsorption during flow of suspensions in microfluidic channels. Unidirectional flow in rectangular channels is considered, as well as flow in channels with a topographically patterned wall that generates transverse flow. Patterns that lead both to chaotic and nonchaotic kinematics are considered. Effects of shear-induced diffusion due to the presence of suspended particles are incorporated via an empirical shear-rate dependent diffusivity. It is observed that for the bulk mixing case the most significant enhancement is due to convection. Channels with chaotic flow have the best mixing characteristics, followed by channels with swirling, nonchaotic flow. Only a small increase in mixing due to shear-induced diffusion is observed. For the case of adsorption from the bulk to a channel wall, on the other hand, it is observed that the most significant enhancement is due to shear-induced diffusion. Channels with secondary flows, both chaotic and nonchaotic, circulate solute-depleted fluid away from the adsorbing boundary but this is not sufficient to guarantee high fluxes toward the surface when the diffusivities are small. The most effective way to enhance adsorption is through the combination of both secondary flow and shear-induced diffusion. Secondary flow circulates fluid between bulk and boundary layer, while shear-induced diffusion enhances transport across the boundary layer. Nevertheless, under the large Peclet number conditions considered here, only a maximum of 30% of the solute is adsorbed to the surface for channels with length of 300 channel heights; for smooth channels without shear-induced diffusion this fraction is only 3%.
Where there is a valley, there is a peak: Study of ion size and image effects on nanoelectroosmotic pumping
Authors: Liu Yu , Yang Jun
Published: May 2008

With the advent of nanotechnology, nano-electro-osmosis flow (nano-EOF) has shown great promise in the next generation of lab-on-a-chip systems such as attoliter or picoliter syringes or pipettors. In order to optimize the design of such systems and to precisely control analysis processes, it is important to obtain better fundamental understanding of EOF at nanoscales. Therefore, a more comprehensive electric double layer (EDL) theory is in need to improve upon the conventional EDL theory based on the Poisson–Boltzmann (PB) equation. In this paper, the modified PB theory is utilized to investigate the flow behavior of EOF at micro- and nanoscales. The effect of ion size and the image effect are particularly emphasized. Both effects remarkably influence nano-EOF. More importantly, this study predicts a new phenomenon: two “peaks” may appear in the velocity profile of nano-EOF for some specific solid-electrolyte systems.
Solution of the Dirac equation in the rotating Bertotti–Robinson spacetime
Authors: Al-Badawi A. , Sakalli I.
Published: May 2008

The Dirac equation is solved in the rotating Bertotti–Robinson spacetime. The set of equations representing the Dirac equation in the Newman–Penrose formalism is decoupled into an axial and an angular part. The axial equation, which is independent of mass, is exactly solved in terms of hypergeometric functions. The angular equation is considered both for massless (neutrino) and massive spin-12 particles. For the neutrinos, it is shown that the angular equation admits an exact solution in terms of the confluent Heun equation. In the existence of mass, the angular equation does not allow an analytical solution, however, it is expressible as a set of first order differential equations apt for a numerical study.
Temperature-dependent spectroscopic properties of Tm3+ in germanate, silica, and phosphate glasses: A comparative study
Authors: Turri Giorgio , Sudesh Vikas , Richardson Martin , Bass Michael , Toncelli Alessandra , Tonelli Mauro
Published: May 2008

Spectroscopic properties of thulium-doped germanate, silica, and phosphate glasses were measured and compared since such glasses are of interest as materials for fiber lasers in the eye-safe wavelength region. F43 excited state fluorescence decay dynamics was investigated at temperatures from 8to300K and the results revealed a strong dependence of the F43 lifetime on the host matrix. The temperature-dependent stimulated emission cross section was obtained by using the Fuchtbauer–Ladenburg technique. In phosphate glass the fluorescent lifetime is short, making this material difficult to use for 2μm laser purposes. Tm3+-doped germanate glass shows a longer lifetime than silica, a comparable value of stimulated emission cross section and some interesting temperature-independent properties.
Dielectric relaxation in carbon black-epoxy composite materials
Authors: Achour M. E. , Brosseau C. , Carmona F.
Published: May 2008

Filled polymers have been a fertile area for modeling studies of microwave dynamics, percolation, and elasticity network formation to mention but a few. To better understand the basic concepts relevant to wave transport in filled polymers, an experimental validation is paramount for theories that predict the dielectric response and, hence, the polarization mechanisms of these heterostructures. Reproducible measurements of the effective complex permittivity, at ambient temperature, are reported in the frequency range of 200 Hz–15 MHz for series of carbon black (CB)-epoxy composites that provide a detailed and quantitative characterization of the dielectric relaxation behavior. We provide observational evidence showing that dipolar relaxation and anomalous low-frequency dispersion are likely the transport mechanisms in these samples below and above percolation, respectively. The various fractional exponents of the power-law decay of these spectral models are analyzed, and Hill plots can be used to rationalize the effective complex permittivity observations for these series of samples. Our results have important implications for designing and optimizing engineered CB/polymer materials for a broad spectrum of engineering applications, e.g., solid broadband tissue simulant materials and electromagnetic absorbers.
The stochastic dynamics of rectangular and V-shaped atomic force microscope cantilevers in a viscous fluid and near a solid boundary
Authors: Clark M. T. , Paul M. R.
Published: May 2008

Using a thermodynamic approach based upon the fluctuation-dissipation theorem, we quantify the stochastic dynamics of rectangular and V-shaped microscale cantilevers immersed in a viscous fluid. We show that the stochastic cantilever dynamics as measured by the displacement of the cantilever tip or by the angle of the cantilever tip are different. We trace this difference to contributions from the higher modes of the cantilever. We find that contributions from the higher modes are significant in the dynamics of the cantilever tip angle. For the V-shaped cantilever the resulting flow field is three-dimensional and complex in contrast to what is found for a long and slender rectangular cantilever. Despite this complexity, the stochastic dynamics can be predicted using a two-dimensional model with an appropriately chosen length scale. We also quantify the increased fluid dissipation that results as a V-shaped cantilever is brought near a solid planar boundary.
Phonon strain shift coefficients in Si1−xGex alloys
Authors: Pezzoli F. , Bonera E. , Grilli E. , Guzzi M. , Sanguinetti S. , Chrastina D. , Isella G. , von Känel H. , Wintersberger E. , Stangl J. , Bauer G.
Published: May 2008

A comprehensive study of the biaxial strain-induced shift of the Si1−xGex Raman active phonon modes is presented. High-resolution Raman measurements of Si1−xGex/Si heterostructures have been compared to x-ray diffraction data. Our approach, unlike previous works, is effective to decouple and quantify separately the effect of strain and composition on the phonon frequencies, yielding an accurate determination of the phonon strain shift coefficients in the entire composition range. Our results show that the strain shift coefficients are independent of the composition, a result which is in good agreement with theoretical calculations, performed within the framework of valence force-field theory.
A suitable model for emeraldine salt
Authors: Varela-Álvarez Adrián , Sordo José A.
Published: May 2008

A new mechanism for the formation of doped polyaniline is presented. Besides providing suitable structural and spectroscopic parameters, the new mechanism allows for the rationalization of the experimentally observed equilibrium between polaron and bipolaron defects in emeraldine salt. The magnetic behavior and the “metallic island” model for conduction in doped polyaniline are also theoretically supported by the new proposal.
Direct observation of domain wall structures in curved permalloy wires containing an antinotch
Authors: Sandweg C. W. , Wiese N. , McGrouther D. , Hermsdoerfer S. J. , Schultheiss H. , Leven B. , McVitie S. , Hillebrands B. , Chapman J. N.
Published: May 2008

The formation and field response of head-to-head domain walls in curved permalloy wires, fabricated to contain a single antinotch, have been investigated using Lorentz microscopy. High spatial resolution maps of the vector induction distribution in domain walls close to the antinotch have been derived and compared with micromagnetic simulations. In wires of 10 nm thickness the walls are typically of a modified asymmetric transverse wall type. Their response to applied fields tangential to the wire at the antinotch location was studied. The way the wall structure changes depends on whether the field moves the wall away from or further into the notch. Higher fields are needed and much more distorted wall structures are observed in the latter case, indicating that the antinotch acts as an energy barrier for the domain wall.
Gas detectors for x-ray lasers
Authors: Tiedtke K. , Feldhaus J. , Hahn U. , Jastrow U. , Nunez T. , Tschentscher T. , Bobashev S. V. , Sorokin A. A. , Hastings J. B. , Möller S. , Cibik L. , Gottwald A. , Hoehl A. , Kroth U. , Krumrey M. , Schöppe H. , Ulm G. , Richter M.
Published: May 2008

We have developed different types of photodetectors that are based on the photoionization of a gas at a low target density. The almost transparent devices were optimized and tested for online photon diagnostics at current and future x-ray free-electron laser facilities on a shot-to-shot basis with a temporal resolution of better than 100 ns. Characterization and calibration measurements were performed in the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II in Berlin. As a result, measurement uncertainties of better than 10% for the photon-pulse energy and below 20 μm for the photon-beam position were achieved at the Free-electron LASer in Hamburg (FLASH). An upgrade for the detection of hard x-rays was tested at the Sub-Picosecond Photon Source in Stanford.
Photoluminescence and surface photovoltage spectroscopy characterization of Zn1−x−yBexMgySe mixed crystals
Authors: Dumcenco D. O. , Hsu H. P. , Huang Y. S. , Firszt F. , Łęgowski S. , Męczyńska H. , Strzałkowski K. , Tiong K. K.
Published: May 2008

This paper presents an optical characterization of three Bridgman-grown Zn1−x−yBexMgySe mixed crystals in the near-band-edge interband transitions using temperature-dependent photoluminescence (PL) in the temperature range of 10–300 K and surface photovoltage spectroscopy (SPS) at room temperature. PL spectra at low temperatures of the investigated samples consist of an excitonic line, an edge emission due to radiative recombination of shallow donor-acceptor pairs, and a broad band related to recombination through deep level defects. The anomalous S-shape temperature dependence of the exciton emission peak for Zn1−x−yBexMgySe crystals with high Mg content (y=0.26) can be explained as due to localization of excited carriers caused by statistical fluctuations of local composition. The peak positions of the excitonic emission lines in PL spectra correspond quite well to the energies of the fundamental transitions determined from SPS measurements. The parameters that describe the temperature dependence of the transition energy and broadening parameter of the band-edge excitonic emission are evaluated and discussed.
Systematic investigation of the growth and structural properties of FeTiO3±δ epitaxial thin films
Authors: Popova E. , Warot-Fonrose B. , Ndilimabaka H. , Bibes M. , Keller N. , Berini B. , Bouzehouane K. , Dumont Y.
Published: May 2008

An understanding of the thin film structure and properties of ilmenite is crucial for the future study of ilmenite-hematite solid solutions for spintronics applications. Here, we report a systematic study of the FeTiO3±δ thin film structure as a function of the deposition parameters during pulsed laser ablation. The films are found to be crystalline and epitaxial on α-Al2O3(0001) substrates for a wide range of substrate temperatures and oxygen pressures. Initial stages of the film growth and in-plane lattice relaxation were investigated. The increase in the a lattice parameter of up to 6% above its bulk value was observed and is most probably due to the buckling of a few ilmenite monolayers at the film/substrate interface because of a significant compressive stress induced on the film by sapphire substrate. In spite of the absence of a diffraction peak corresponding to the ordered R3¯ phase, these films consist of pure ilmenite phase with negligible net magnetization. Film conductivity is tuned over three orders of magnitude in the studied oxygen pressure range and is comparable to that of bulk ilmenite at pressures above 10 mTorr.
Models of water imbibition in untreated and treated porous media validated by quantitative magnetic resonance imaging
Authors: Gombia M. , Bortolotti V. , Brown R. J. S. , Camaiti M. , Fantazzini P.
Published: May 2008

Fluid imbibition affects almost every activity that directly or indirectly involves porous media, including oil reservoir rocks, soils, building materials, and countless others, including biological materials. In this paper, magnetic resonance imaging (MRI) has been applied to study water imbibition in a porous medium, in which capillary properties are artificially changed. As a model system, samples of Lecce stone, a material of cultural heritage interest, were analyzed before and after treatment with a protective polymer (Silirain-50 or Paraloid PB72). By using MRI, we can visualize the presence of water inside each sample and measure the height z(t) reached by the wetting front as a function of time during experiments of capillary absorption before and after treatment. The sorptivity S, defined as the initial slope of z versus t1/2, has been determined before treatment and through both treated and untreated faces after treatment. Very good fits to the data were obtained with theoretical and empirical models of absorption kinetics, starting from the Washburn model for capillary rise, adapted by others to homogeneous porous media, and modified by us for application to a sample having a thin low-permeability layer on either surface as a result of a treatment process. This gives us parameters to quantify the effects on imbibition of the changes in the capillary properties. It is known that the Paraloid treatment preferentially affects the larger pore channels and the Silirain the smaller, and our results show this and illustrate the roles played by the different classes of pore sizes.
Substrate orientation effect on potential fluctuations in multiquantum wells of GaAs∕AlGaAs
Authors: Teodoro M. D. , Dias I. F. L. , Laureto E. , Duarte J. L. , González-Borrero P. P. , Lourenço S. A. , Mazzaro I. , Marega E. , Salamo G. J.
Published: May 2008

The photoluminescence (PL) technique as a function of temperature and excitation intensity was used to study the optical properties of multiquantum wells (MQWs) of GaAs∕AlxGa1−xAs grown by molecular beam epitaxy on GaAs substrates oriented in the [100], [311]A, and [311]B directions. The asymmetry presented by the PL spectra of the MQWs with an apparent exponential tail in the lower-energy side and the unusual behavior of the PL peak energy versus temperature (blueshift) at low temperatures are explained by the exciton localization in the confinement potential fluctuations of the heterostructures. The PL peak energy dependence with temperature was fitted by the expression proposed by Pässler [Phys. Status Solidi B 200, 155 (1997)] by subtracting the term σE2∕kBT, which considers the presence of potential fluctuations. It can be verified from the PL line shape, the full width at half maximum of PL spectra, the σE values obtained from the adjustment of experimental points, and the blueshift maximum values that the samples grown in the [311]A∕B directions have higher potential fluctuation amplitude than the sample grown in the [100] direction. This indicates a higher degree of the superficial corrugations for the MQWs grown in the [311] direction.
Nonadiabatic transitions between lambda-doubling states in the capture of a diatomic molecule by an ion
Authors: Auzinsh M. , Dashevskaya E. I. , Litvin I. , Nikitin E. E. , Troe J.
Published: May 2008

The low-energy capture of a dipolar diatomic molecule in an adiabatically isolated electronic state with a good quantum number Ω (Hund’s coupling case a) by an ion occurs adiabatically with respect to rotational transitions of the diatom. However, the capture dynamics may be nonadiabatic with respect to transitions between the pair of the Λ-doubling states belonging to the same value of the intrinsic angular momentum j. In this work, nonadiabatic transition probabilities are calculated which define the Λ-doubling j-specific capture rate coefficients. It is shown that the transition from linear to quadratic Stark effect in the ion-dipole interaction, which damps the T−1∕2 divergence of the capture rate coefficient calculated with vanishing Λ-doubling splitting, occurs in the adiabatic regime with respect to transitions between Λ-doubling adiabatic channel potentials. This allows one to suggest simple analytical expressions for the rate coefficients in the temperature range which covers the region between the sudden and the adiabatic limits with respect to the Λ-doubling states.
Very high current density package level electromigration test for copper interconnects
Authors: Roy Arijit , Tan Cher Ming
Published: May 2008

In this paper, we present quantitative analyses of the impact of Joule heating on the package level electromigration (EM) test of copper dual damascene (DD) interconnects with linewidths of 0.28 and 0.7 μm. A total of 120 samples are tested with a maximum current density of 8 MA/cm2. It is found that high test current density has a negligible impact on the estimation of activation energy and offers an opportunity to shorten the test time. However, the current density exponent is found to be a strong function of test current density, especially for interconnects with a larger linewidth. Correction due to Joule heating on the estimation of the current density exponent is described.
Spectral and nonlinear optical characteristics of nanocomposites of ZnO–CdS
Authors: Irimpan Litty , Nampoori V. P. N. , Radhakrishnan P.
Published: May 2008

In this article, we present the spectral and nonlinear optical properties of ZnO–CdS nanocomposites prepared by colloidal chemical synthesis. The optical band gap (Eg) of the material is tunable between 2.62 and 3.84 eV. The emission peaks of ZnO–CdS nanocomposites change from 385 to 520 nm almost in proportion to changes in Eg. It is possible to obtain a desired luminescence color from UV to green by simply adjusting the composition. The nonlinear optical response of these samples is studied by using nanosecond laser pulses from a tunable laser at the excitonic resonance and off-resonance wavelengths. The nonlinear response is wavelength dependent, and switching from saturable absorption (SA) to reverse SA (RSA) has been observed for samples as the excitation wavelength changes from the excitonic resonance to off-resonance wavelengths. Such a changeover in the sign of the nonlinearity of ZnO–CdS nanocomposites is related to the interplay of exciton bleach and optical limiting mechanisms. The ZnO–CdS nanocomposites show self-defocusing nonlinearity and good nonlinear absorption behavior at off-resonant wavelengths. The nonlinear refractive index and the nonlinear absorption increase with increasing CdS volume fraction at 532 nm. The observed nonlinear absorption is attributed to two photon absorption followed by weak free carrier absorption. The enhancement of the third-order nonlinearity in the composites can be attributed to the concentration of exciton oscillator strength. This study is important in identifying the spectral range and composition over which the nonlinear material acts as a RSA based optical limiter. ZnO–CdS is a potential nanocomposite material for the tunable light emission and for the development of nonlinear optical devices with a relatively small limiting threshold.
Sensitized erbium emission from silicon-rich nitride/silicon superlattice structures
Authors: Dal Negro L. , Li R. , Warga J. , Basu S. N.
Published: May 2008

Erbium-doped silicon-rich nitride/silicon superlattice structures were fabricated by direct magnetron cosputtering deposition on Si substrates. Rapid thermal annealing resulted in the nucleation of small amorphous Si clusters, which efficiently sensitize 1.54μm emission via a nanosecond-fast nonresonant energy transfer process, providing an alternative route toward the fabrication of Si-compatible devices based on Er sensitization.
Role of barrier layers in electroluminescence from SiN-based multilayer light-emitting devices
Authors: Huang Rui , Dong Hengping , Wang Danqing , Chen Kunji , Ding Honglin , Wang Xiang , Li Wei , Xu Jun , Ma Zhongyuan
Published: May 2008

We report the effects of barrier layer on the electroluminescence properties of the SiN-based multilayer light-emitting devices (LEDs). It is found that the emission efficiency is significantly enhanced by more than one order of magnitude compared to that of LED without barrier layer. Meanwhile, the emission wavelength can also be tuned from 620to510nm by controlling the Si∕N ratio of the barrier layer. The improved performance of LEDs can be attributed to the variation in the band offset between the Si-rich SiN well layer and the N-rich SiN barrier layer.
Photoinduced fluorescence enhancement in colloidal CdSeTe∕ZnS core/shell quantum dots
Authors: Yuan C. T. , Chou W. C. , Chuu D. S. , Chen Y. N. , Lin C. A. , Chang W. H.
Published: May 2008

Photoinduced fluorescence enhancement (PFE) in colloidal CdSeTe∕ZnS core/shell quantum dots (QDs) was investigated by monitoring ensemble fluorescence and single-QD fluorescence blinking behavior upon illumination. Ensemble fluorescence was increased in air and in vacuum with different enhanced factors. At the single-QD levels, fluorescence was also enhanced for some individual QDs. Relatively long on times, high quantum yields within the on times, and multilevel on states were found in fluorescence time traces. We suggest that the PFE origin from single-QD viewpoint is attributed to the contributions of surface passivation by photoinduced charged carriers and the formation of neutral core/charged shell QD states.
Optical switching in VO2 films by below-gap excitation
Authors: Rini M. , Hao Z. , Schoenlein R. W. , Giannetti C. , Parmigiani F. , Fourmaux S. , Kieffer J. C. , Fujimori A. , Onoda M. , Wall S. , Cavalleri A.
Published: May 2008

We study the photoinduced insulator-metal transition in VO2, correlating its threshold and dynamics with excitation wavelength. In single crystals, switching can only be induced with photon energies above the 670meV gap. This contrasts with the case of polycrystalline films, where formation of the metallic state can be initiated also with photon energies as low as 180meV, which are well below the bandgap. Perfection of this process may become conducive to schemes for optical switches, limiters, and detectors operating at room temperature in the mid-infrared.
Characterization of strain-induced martensite phase in austenitic stainless steel using a magnetic minor-loop scaling relation
Authors: Kobayashi Satoru , Saito Atsushi , Takahashi Seiki , Kamada Yasuhiro , Kikuchi Hiroaki
Published: May 2008

We propose a combined magnetic method using a scaling power-law rule and initial permeability in magnetic minor hysteresis loops for characterization of ferromagnetic α′ martensites in austenitic stainless steel. The scaling power law between the hysteresis loss and remanence is universal, being independent of volume fraction of strain-induced α′ martensites. A coefficient of the power law largely decreases with volume fraction, while the initial permeability linearly increases, reflecting a change in the morphology and quantity of martensites, respectively. The present method is highly effective for integrity assessment of austenitic stainless steels because of the sensitivity and extremely low measurement field.
Size-dependent trajectories of DNA macromolecules due to insulative dielectrophoresis in submicrometer-deep fluidic channels
Authors: Parikesit Gea O. F. , Markesteijn Anton P. , Piciu Oana M. , Bossche Andre , Westerweel Jerry , Young Ian T. , Garini Yuval
Published: May 2008

In this paper, we demonstrate for the first time that insulative dielectrophoresis can induce size-dependent trajectories of DNA macromolecules. We experimentally use λ (48.5 kbp) and T4GT7 (165.6 kbp) DNA molecules flowing continuously around a sharp corner inside fluidic channels with a depth of 0.4 μm. Numerical simulation of the electrokinetic force distribution inside the channels is in qualitative agreement with our experimentally observed trajectories. We discuss a possible physical mechanism for the DNA polarization and dielectrophoresis inside confining channels, based on the observed dielectrophoresis responses due to different DNA sizes and various electric fields applied between the inlet and the outlet. The proposed physical mechanism indicates that further extensive investigations, both theoretically and experimentally, would be very useful to better elucidate the forces involved at DNA dielectrophoresis. When applied for size-based sorting of DNA molecules, our sorting method offers two major advantages compared to earlier attempts with insulative dielectrophoresis: Its continuous operation allows for high-throughput analysis, and it only requires electric field strengths as low as ∼10 V/cm.
Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets
Authors: Uejio Janel S. , Schwartz Craig P. , Duffin Andrew M. , Drisdell Walter S. , Cohen Ronald C. , Saykally Richard J.
Published: May 2008

We describe an approach for characterizing selective binding between oppositely charged ionic functional groups under biologically relevant conditions. Relative shifts in K-shell x-ray absorption spectra of aqueous cations and carboxylate anions indicate the corresponding binding strengths via perturbations of carbonyl antibonding orbitals. XAS spectra measured for aqueous formate and acetate solutions containing lithium, sodium, and potassium cations reveal monotonically stronger binding of the lighter metals, supporting recent results from simulations and other experiments. The carbon K-edge spectra of the acetate carbonyl feature centered near 290 eV clearly indicate a preferential interaction of sodium versus potassium, which was less apparent with formate. These results are in accord with the Law of Matching Water Affinities, relating relative hydration strengths of ions to their respective tendencies to form contact ion pairs. Density functional theory calculations of K-shell spectra support the experimental findings.
Platinum-based inhibitors of amyloid-β as therapeutic agents for Alzheimer's disease
Authors: Barnham Kevin J. , Kenche Vijaya B. , Ciccotosto Giuseppe D. , Smith David P. , Tew Deborah J. , Liu Xiang , Perez Keyla , Cranston Greg A. , Johanssen Timothy J. , Volitakis Irene , Bush Ashley I. , Masters Colin L. , White Anthony R. , Smith Jeffrey P. , Cherny Robert A. , Cappai Roberto
Published: May 2008

Amelyoid-β peptide (Aβ) is a major causative agent responsible for Alzheimer's disease (AD). Aβ contains a high affinity metal binding site that modulates peptide aggregation and toxicity. Therefore, identifying molecules targeting this site represents a valid therapeutic strategy. To test this hypothesis, a range of L-PtCl
2
(L = 1,10-phenanthroline derivatives) complexes were examined and shown to bind to Aβ, inhibit neurotoxicity and rescue Aβ-induced synaptotoxicity in mouse hippocampal slices. Coordination of the complexes to Aβ altered the chemical properties of the peptide inhibiting amyloid formation and the generation of reactive oxygen species. In comparison, the classic anticancer drug cisplatin did not affect any of the biochemical and cellular effects of Aβ. This implies that the planar aromatic 1,10-phenanthroline ligands L confer some specificity for Aβ onto the platinum complexes. The potent effect of the L-PtCl
2
complexes identifies this class of compounds as therapeutic agents for AD.
Human biliverdin reductase is an ERK activator; hBVR is an ERK nuclear transporter and is required for MAPK signaling
Authors: Lerner-Marmarosh Nicole , Miralem Tihomir , Gibbs Peter E. M. , Maines Mahin D.
Published: May 2008

Activation of the MEK/ERK/Elk-signaling cascade is a mechanism for relaying mitogenic and stress stimuli for gene activation. MEK1 is the proximate kinase for activation of ERK1/2, and nuclear targeting of ERK1/2 is obligatory for Elk1 transcriptional activity. Human biliverdin reductase (hBVR) is a recently described Ser/Thr/Tyr kinase in the MAPK insulin/insulin-like growth factor 1 (IGF1)-signaling cascade. Using 293A cells and
in vitro
experiments, we detail the formation of a ternary complex of MEK/ERK/hBVR, activation of MEK1 and ERK1/2 kinase activities by hBVR, and phosphorylation of hBVR by ERK1/2. hBVR is nearly as effective as IGF1 in activating ERK; intact hBVR ATP-binding domain is necessary for Elk1 activation, whereas protein–protein interaction is the basis for hBVR activation of MEK1 and ERK. The two MAPK docking consensus sequences present in hBVR,
F
162
G
FP
and
K
275
KR
I
L
HC
L
G
L
(C- and D-box, respectively), are ERK interactive sites; interaction at each site is critical for ERK/Elk1 activation. Transfection with mutant hBVR-P
165
or peptides corresponding to the C- or D-box blocked activation of ERK by IGF1. Transfection with D-box mutant hBVR prevented the activation of ERK by wild-type protein and dramatically decreased Elk1 transcriptional activity. hBVR is a nuclear transporter of ERK; experiments with hBVR nuclear export signal (NES) and nuclear localization signal (NLS) mutants demonstrated its critical role in the nuclear localization of IGF-stimulated ERK for Elk1 activation. These findings, together with observations that si-hBVR blocked activation of ERK and Elk1 by IGF1 and prevented formation of ternary complex between MEK/ERK/hBVR, define the critical role of hBVR in ERK signaling and nuclear functions of the kinase.
The role of computer‐aided psychotherapy within an NHS CBT specialist service
Authors: Learmonth Despina , Trosh Jo , Rai Sadik , Sewell Janet , Cavanagh Kate
Published: May 2008

To date, the feasibility of computer‐aided psychotherapy as an intervention has only been recognised in primary care practice. The present study sought to evaluate the impact of ‘Beating the Blues’ (BtB), an established computerised cognitive behaviour therapy (CCBT) self‐help programme for the management of anxiety and depression, within an NHS CBT specialist healthcare centre. Of the 555 service users who used BtB as part of routine care, with follow‐up assessment at six to eight weeks, 71% completed all eight sessions. Statistically significant differences on the Beck Depression Inventory‐II (BDI‐II) and Beck Anxiety Inventory (BAI) were found in completer and intention‐to‐treat analyses; 50% of completers achieved reliable change on the BDI‐II and approximately 25% of completers achieved reliable and clinically significant change on both measures. Outcomes were benchmarked against outcomes in studies of routine face‐to‐face CBT. These findings provide evidence that BtB may be of value to service users in secondary mental healthcare centres, alleviating current burdens on public health and therapeutic resources. Future research directions should include examining which factors influence individuals’ decisions to try computer‐aided psychotherapy, which individuals are best suited to using these interventions, and why some users drop out prior to programme completion.
An analysis of complaints to the British Association for Counselling and Psychotherapy, 1996–2006
Authors: Khele Suky , Symons Clare , Wheeler Sue
Published: May 2008

In autumn 2006 the British Association for Counselling and Psychotherapy approved a proposal to conduct an independent audit of complaints submitted. This article represents the first stage of that audit. Case information from the professional conduct files was accessed and a total of 84 cases, considered by a pre‐hearing assessment panel to require a full hearing, were identified for this audit. The cases cover the period from October 1996 to January 2006. The information obtained was entered into a database for numerical analysis. Key findings suggest that accredited members are disproportionately complained against, as are male members of the association. The majority of complaints are made by people who are themselves involved in counselling.
The prevalence of diabetes among sexual and violent offenders and its co‐occurrence with cognitive impairment, mania, psychotic symptoms and aggressive behavior
Authors: Langevin Ron , Langevin Mara , Curnoe Suzanne , Bain Jerald
Published: May 2008

The prevalence of diabetes among 915 sexual, violent, and non‐violent non‐sex offenders was found to be more than twice the prevalence in the general population. Diabetes was most common among violent offenders and among sex offenders who victimized children. The older diabetics presented significantly more often with cognitive impairment and younger diabetics more often with manic and psychotic symptoms. Younger diabetics were significantly more likely to use force and a weapon in their offenses and were most likely to injure their victims when compared to older diabetics and younger and older non‐diabetic offenders. In more than one in four cases, the diabetes was undiagnosed at the time of their offenses prior to clinical assessment, suggesting that undiagnosed diabetes may be a possible mitigating factor in some sexual and violent offenses. Results indicate that a routine endocrine evaluation with blood tests would be a valuable addition to the assessment of violent and sexual offenders.
Ion heating in transitions to CERC in the stellarator TJ-II
Authors: Velasco J.L. , Castejón F. , Fernández L.A. , Martin-Mayor V. , Tarancón A. , Estrada T.
Published: May 2008

In TJ-II stellarator plasmas, in the electron cyclotron heating regime, an increase in the ion temperature is observed, synchronized with that of the electron temperature, during the transition to the core electron-root confinement (CERC) regime. This rise in ion temperature should be attributed to the joint action of the electron–ion energy transfer (which changes slightly during the CERC formation) and an enhancement of the ion confinement. This improvement must be related to the increase in the positive electric field in the core region. In this paper, we confirm this hypothesis by estimating the ion collisional transport in TJ-II under the physical conditions established before and after the transition to CERC. We calculate a large number of ion orbits in the guiding-centre approximation considering the collisions with a background plasma composed of electrons and ions. The ion temperature profile and the thermal flux are calculated in a self-consistent way, so that the change in the ion heat transport can be assessed.
Rad54B Targeting to DNA Double-Strand Break Repair Sites Requires Complex Formation with S100A11
Authors: Murzik Ulrike , Hemmerich Peter , Weidtkamp-Peters Stefanie , Ulbricht Tobias , Bussen Wendy , Hentschel Julia , von Eggeling Ferdinand , Melle Christian
Published: May 2008

S100A11 is involved in a variety of intracellular activities such as growth regulation and differentiation. To gain more insight into the physiological role of endogenously expressed S100A11, we used a proteomic approach to detect and identify interacting proteins in vivo. Hereby, we were able to detect a specific interaction between S100A11 and Rad54B, which could be confirmed under in vivo conditions. Rad54B, a DNA-dependent ATPase, is described to be involved in recombinational repair of DNA damage, including DNA double-strand breaks (DSBs). Treatment with bleomycin, which induces DSBs, revealed an increase in the degree of colocalization between S100A11 and Rad54B. Furthermore, S100A11/Rad54B foci are spatially associated with sites of DNA DSB repair. Furthermore, while the expression of p21WAF1/CIP1was increased in parallel with DNA damage, its protein level was drastically down-regulated in damaged cells after S100A11 knockdown. Down-regulation of S100A11 by RNA interference also abolished Rad54B targeting to DSBs. Additionally, S100A11 down-regulated HaCaT cells showed a restricted proliferation capacity and an increase of the apoptotic cell fraction. These observations suggest that S100A11 targets Rad54B to sites of DNA DSB repair sites and identify a novel function for S100A11 in p21-based regulation of cell cycle.
Regulation of Microtubule Assembly and Organization in Mitosis by the AAA+ ATPase Pontin
Authors: Ducat Daniel , Kawaguchi Shin-ichi , Liu Hongbin , Yates John R. , Zheng Yixian
Published: May 2008

To identify novel proteins important for microtubule assembly in mitosis, we have used a centrosome-based complementation assay to enrich for proteins with mitotic functions. An RNA interference (RNAi)-based screen of these proteins allowed us to uncover 13 novel mitotic regulators. We carried out in-depth analyses of one of these proteins, Pontin, which is known to have several functions in interphase, including chromatin remodeling, DNA repair, and transcription. We show that reduction of Pontin by RNAi resulted in defects in spindle assembly in Drosophila S2 cells and in several mammalian tissue culture cell lines. Further characterization of Pontin in Xenopus egg extracts demonstrates that Pontin interacts with the gamma tubulin ring complex (γ-TuRC). Because depletion of Pontin leads to defects in the assembly and organization of microtubule arrays in egg extracts, our studies suggest that Pontin has a mitosis-specific function in regulating microtubule assembly.
Signal-dependent Regulation of Transcription by Histone Deacetylase 7 Involves Recruitment to Promyelocytic Leukemia Protein Nuclear Bodies
Authors: Gao Chengzhuo , Cheng Xiwen , Lam Minh , Liu Yu , Liu Qing , Chang Kun-Sang , Kao Hung-Ying
Published: May 2008

Promyelocytic leukemia protein (PML) nuclear bodies (NBs) are dynamic subnuclear compartments that play roles in several cellular processes, including apoptosis, transcriptional regulation, and DNA repair. Histone deacetylase (HDAC) 7 is a potent corepressor that inhibits transcription by myocyte enhancer factor 2 (MEF2) transcription factors. We show here that endogenous HDAC7 and PML interact and partially colocalize in PML NBs. Tumor necrosis factor (TNF)-α treatment recruits HDAC7 to PML NBs and enhances association of HDAC7 with PML in human umbilical vein endothelial cells. Consequently, TNF-α promotes dissociation of HDAC7 from MEF2 transcription factors and the promoters of MEF2 target genes such as matrix metalloproteinase (MMP)-10, leading to accumulation of MMP-10 mRNA. Conversely, knockdown of PML enhances the association between HDAC7 and MEF2 and decreases MMP-10 mRNA accumulation. Accordingly, ectopic expression of PML recruits HDAC7 to PML NBs and leads to activation of MEF2 reporter activity. Notably, small interfering RNA knockdown of PML decreases basal and TNF-α-induced MMP-10 mRNA accumulation. Our results reveal a novel mechanism by which PML sequesters HDAC7 to relieve repression and up-regulate gene expression.
Instabilities and Self-Organization in Materials
Authors: Ghoniem Nasr , Walgraef Daniel
Published: May 2008

In materials, critical phenomena such as phase transitions, plastic deformation and fracture are intimately related to self-organization. Understanding the origin of spatio-temporal order in systems far from thermal equilibrium and the selection mechanisms of spatial structures and their symmetries is a major theme of present day research on the structure of continuous matter. Furthermore, the development of methods for producing spatially-ordered and self-assembled microstructure in solids by non-equilibrium methods opens the door to many technological applications. In order to describe and understand the behaviour of such materials, dynamical concepts related to non-equilibrium phenomena, irreversible thermodynamics, nonlinear dynamics, and bifurcation theory, are required. The generic presence of defects and their crucial influence on pattern formation and critical phenomena in extended systems is now well-established. Similar to observations in hydrodynamical, liquid crystal, and laser systems, defects in materials have a profound effect. This book is divided into two volumes. The first volume is devoted to the most basic concepts of the physics, mechanics, and mathematical theory utilized in the analysis of non-equilibrium materials. The book presents a background on material deformation, defect theory, transport processes, and the statistical mechanics and thermodynamics of phase transitions. Mathematical concepts of non-linear dynamics, such as bifurcation and instability theory, the dynamics of complex systems near pattern forming instabilities, the generic aspects of pattern formation, selection and stability are presented. Stochastic and numerical methods used in this field are also introduced. The methods and techniques developed in the first volume are applied in the second volume to specific problems in various advanced technologies.
INTRODUCTION
Authors: Ghoniem Nasr M. , Walgraef Daniel D.
Published: May 2008

This introductory chapter presents some ideas and key concepts in materials science. These include developments in the field of materials science, examples demonstrating the critical role played by material instabilities and pattern formation, the control of microstructure formation, and new materials design.
ELASTIC THEORY OF DEFECTS
Authors: Ghoniem Nasr M. , Walgraef Daniel D.
Published: May 2008

Defects play a critical role in many material phenomena, and their relationship to instabilities and pattern formation is well-established. This chapter presents a brief description of the main types of crystal defects, describing their geometry and main characteristics. It then focuses on determining their elastic field and interaction forces.
NONEQUILIBRIUM PHASE TRANSITIONS
Authors: Ghoniem Nasr M. , Walgraef Daniel D.
Published: May 2008

This chapter presents theoretical developments in the treatment of atomic clustering. The theory is applicable to atomic species, which broadly include lattice or surface atoms, molecules, impurities or point defects. The theory is applied in two general areas: on studies of nucleation and growth of precipitates during solidification of metallic alloys, and on atomic clustering on surfaces during deposition of vapour or energetic atoms.