bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic and electronic anisotropy in single crystalline YMn4Al8
Authors: Kim J. Y. , Park J. G. , Cho B. K. , Janssen Y.
Published: June 2006

On a single crystal of YMn4Al8, we investigated specific heat and temperature-dependent magnetization M(T) and resistivity ρ(T) with field and current, respectively, parallel and perpendicular to the c axis. A few features are observed on single crystals and not on polycrystalline samples. While we found no noticeable anisotropy in M(T), there is a significant anisotropy in ρ(T), i.e., ρ‖(T)>ρ⊥(T) for T>43K and ρ‖(T)<ρ⊥(T) for T<43K, where ρ‖(T) and ρ⊥(T) are ρ(T)’s with current parallel and perpendicular to the c axis, respectively. In addition, a significant increase of γ, an electronic specific heat contribution, is found at low temperatures, resulting in γ(T=2K)=130mJ∕molK2.
Asymmetric field variation of magnetoresistance in Permalloy honeycomb nanonetwork
Authors: Tanaka M. , Saitoh E. , Miyajima H. , Yamaoka T.
Published: June 2006

The magnetic properties of two-dimensional network comprising a Permalloy wire-based honeycomb structure were investigated by magnetic force microscopy and magnetoresistance measurement. These results indicate that the magnetization of the wire behaves homogenously like a binary bit and that the magnetic interaction at the vertex governs this magnetization. This allows us to achieve a magnetoelectronic device, based on the magnetic interaction among the wires.
Reduction in intermediate layer thickness of CoCrPt–SiO2 perpendicular recording media by using Ru–SiO2
Authors: Takekuma I. , Araki R. , Igarashi M. , Nemoto H. , Tamai I. , Hirayama Y. , Hosoe Y.
Published: June 2006

A Ru–SiO2 intermediate layer was introduced between the Ru and recording layers to reduce the intermediate layer thickness of CoCrPt–SiO2 perpendicular recording media. A structural analysis revealed that the Ru–SiO2 intermediate layer enhanced the oxide segregation in the initial growth region of the recording layer. A micromagnetic simulation and magnetic property measurements indicated that the Ru–SiO2 intermediate layer reduced the intergranular exchange coupling in the initial growth region of the recording layer without magnetic anisotropy degradation. We reduced the intermediate layer thickness down to 9.1nm by using the Ru–SiO2 intermediate layer while maintaining the signal-to-noise ratio.
Field dependence of the barrier to magnetization reversal of a Stoner-Wohlfarth particle
Authors: Bennett L. H. , Della Torre E. , deWit R. , Kahler G. , Watson R. E.
Published: June 2006

It is well known that the energy barrier for magnetization reversal, EB, varies quadratically with the magnetic field for the Stoner-Wohlfarth model. However, the enthalpy H (switching energy) required to reverse the magnetization is the sum of EB and the work Wf done by the Néel fluctuation field. The sum of these two terms gives an enthalpy of reversal. If the fluctuation field is uniaxial and parallel to the holding field, then the enthalpy barrier for switching is linear in the holding field. The linearity is consistent with certain experimental results. If the fluctuation field is anisotropic, then for the same size field, the probability of the particle’s switching will depend upon the direction of that field. The paper discusses the holding field variation of the energy barrier for different fluctuation field directions.
Design of the tunnel contacts and the transport region of all-electrical spin-injection-detection devices
Authors: Van Dorpe P. , Vanheertum R. , Boukari H. , Van Roy W. , Borghs G.
Published: June 2006

The design of an all-electrical spin-injection-detection device is discussed. It is shown that the use and the design of tunnel barriers cannot simply be copied from the spin light-emitting diodes, where they have already been demonstrated. Using one-dimensional and two-dimensional self-consistent simulations, the doping levels of the tunnel contacts and the spin-transport region are engineered to obtain an optimal tunnel barrier resistance and an optimal current distribution in the spin-transport region.
Mn
–
Ir
∕
Fe
–
Si
exchange-coupled multilayer film with plural ferromagnetic resonance absorptions for wideband noise filter
Authors: Sonehara M. , Ishikawa T. , Sugiyama T. , Sato T. , Yamasawa K. , Miura Y.
Published: June 2006

Mn – Ir ∕ Fe – Si exchange-coupled multilayer films for a wideband and gigahertz band noise filters are fabricated and evaluated. The Fe–Si film has characteristics of high saturation magnetization of 19kG, low magnetostriction of the order of 10−6, and high resistivity of 73μΩcm. When the exchange bias magnetic field is introduced to the Fe–Si layers by the effect of Mn–Ir∕Fe–Si exchange-coupling, the ferromagnetic resonance (FMR) frequency of the multilayer film is higher than the natural frequency of the single Fe–Si film. In addition, the multilayer film which has different thicknesses in each Fe–Si layer has plural FMR frequencies. The multiple FMR frequency gives the film characteristic of wideband energy absorption. The FMR absorption bandwidth of the multilayer film which has three FMR frequencies is about three times wider than that of a single FMR film. Therefore, the multilayer film with plural FMR frequencies has an advantage in wideband noise absorption and will be a useful material for the wideband and gigahertz frequency range noise filterings.
Neutron and Mössbauer studies of FeCr2Se4
Authors: Kang Ju Hong , Kim Sam Jin , Lee Bo Wha , Kim Chul Sung
Published: June 2006

Fe Cr 2 Se 4 has been studied with x-ray and neutron diffraction techniques, superconducting quantum interference device magnetometer, and Mössbauer spectroscopy. The crystal structure of FeCr2Se4 at 295K is monoclinic (space group I2∕m), with the lattice parameters a=6.267Å, b=3.617Å, c=11.822Å, and β=90.69°, and its magnetic structure is found to be C-type ordering. The Mössbauer spectra were obtained at various temperatures ranging from 4.2to295K. Magnetic hyperfine and electric quadrupole interactions at 4.2K have been fitted, yielding the following results: Hhf=108.8kOe, θ=72°, φ=90°, η=0, ΔEQ=(1∕2)e2qQ[1+(1∕3)η2]1∕2=−1.65mm∕s, and R=−2.25. Our study strongly suggests that the quadrupole interaction of FeCr2Se4 is larger than the magnetic dipole interaction.
Structural effects on exchange in nanocluster perpendicular recording media
Authors: Zhou J. , Skomski R. , Sellmyer D. J.
Published: June 2006

Nanostructured FePt:M (M=C,Ag,Cu) perpendicular magnetic recording media are investigated by numerical simulations and model calculations. Both intra- and intergranular exchanges are considered, and it is assumed that the interaction through the matrix is mediated by conduction electrons. Several limits, including free-electron-like Ruderman-Kittel-Kasuya-Yosida interactions, are considered. The atomic modeling yields effective intergranular coupling strengths that depend on both cluster radius and distance, on the magnetic properties of the clusters, and on the electronic nature of the medium. In the simulations, the exchange is approximated by a thin shell with reduced exchange and zero anisotropy. The simulations show that intergranular exchange reduces the coercivity of the system, and the magnetization reversal proceeds in a regime between localized nucleation and discrete domain-wall pinning, depending on the intergranular exchange. Coercivity and loop-shape reduction also depend on the geometry of the particle system.
Influence of postdeposition annealing on the structural and optical properties of cosputtered Mn doped ZnO thin films
Authors: Yadav Harish Kumar , Sreenivas K. , Gupta Vinay
Published: June 2006

The influence of postgrowth annealing on the structural and optical properties of rf cosputtered Mn doped ZnO thin films deposited on glass substrate at room temperature has been investigated. All as deposited Zn1−xMnxO films are highly textured, with the c axis of the wurtzite structure along the growth direction. The as grown films are in a state of compressive stress and a reduction in stress with postgrowth annealing treatment are observed. The band gap of Mn doped ZnO films (3.34eV) is slightly larger than the pure ZnO film (3.30eV) and is found to decrease with an increase in annealing temperature for all the samples. The optical dispersion of refractive index with photon energy in Zn1−xMnxO films with varying x and different annealing temperature is studied in the light of single oscillator and Pikhtin-Yas’kov [Sov. Phys. Semicond. 15, 81 (1981)] model, respectively.
Direct probe of anisotropy field dispersion in perpendicular media
Authors: Ju Ganping , Zhou Hong , Chantrell Roy , Lu Bin , Weller Dieter
Published: June 2006

A complex transverse alternating-current (ac) susceptibility (χT) technique based on magneto-optical detection has been developed with sufficient sensitivity for thin film recording media. The technique has been used to measure the dispersions in grain size and anisotropy field in perpendicular magnetic recording media. Applying a direct-current (dc) field perpendicular to the easy axis effectively reduces the thermal energy barrier, which leads to thermally activated switching on the time scale of the ac field applied in the easy-axis (perpendicular) direction. The dc field dependence of the resulting imaginary transverse ac susceptibility Im(χT) is sensitive to dispersions in both the grain size and the anisotropy field. The sensitivity has been used to extract the amount of both dispersions. It has been found that the extracted grain size dispersion values agree well with those obtained from plane-view transmission electron microscopy micrographs.
Effects of Si doping on normal incidence InAs∕In0.15Ga0.85As dots-in-well quantum dot infrared photodetectors
Authors: Attaluri R. S. , Annamalai S. , Posani K. T. , Stintz A. , Krishna S.
Published: June 2006

The effects of doping on InAs∕In0.15Ga0.85As quantum dots-in-well infrared photodetectors have been studied by measuring the dark current, photocurrent, and spectral response. A significant reduction of dark current with decrease in doping concentration in the quantum dots has been observed. However, the photocurrent of the detectors increases with the doping. By measuring the background limited infrared photodetector temperature, we find that the optimum sheet doping concentration in these detectors is n=3×1010cm−2 (corresponding to about one electron per dot).
Cyclic actuation of Ni–Mn–Ga composites
Authors: Gans Eric , Carman Greg P.
Published: June 2006

Planar (2-2) and fibular (1-3) composites were fabricated by embedding single crystal Ni49.9Mn29.1Ga21.0 in a polyurethane resin. Magnetic and mechanical testing was performed on all samples. Mechanical testing showed the twin boundary yield stress to be 1.0 and 0.3MPa for the monolithic and composites, respectively. Magnetic testing was performed to determine the magnetic field induced strain as a function of increasing compressive preloads (from 0to2.0MPa). Actuation strains without an external preload are 4.9% for the monolithic and 1.0% for the composite samples. The composite samples show considerable cyclic strain without the application of a compressive loading, unlike the monolithic material. A rule of mixture model is presented to predict the strain output of the composite samples under a magnetic field and explain the reduced twin boundary yield stress.
Transition from unstable electrostatic confinement to stable magnetic confinement in a helicon reactor operating with Ar∕SF6 gas mixtures
Authors: Corr C. S. , Plihon N. , Chabert P.
Published: June 2006

Two types of instabilities were previously identified in inductive discharges having an expanding chamber when negative ions are present: (i) the source instability, occurring in the neighborhood of the capacitive-to-inductive (E to H) transition, and (ii) the downstream instability, which was shown to be the periodic formation and propagation of double layers. These unstable double layers were found over the entire parameter space (pressure/power) of interest, and they were born at the interface of the source and diffusion chambers. They acted as an internal electrostatic barrier separating a low-electronegativity, high-electron-density plasma upstream (in the source) and a high-electronegativity, low-electron-density plasma downstream. In this paper we have investigated the effect of adding a static axial magnetic field, classically used to increase the confinement and the plasma heating via helicon wave propagation. This had the following consequences: (i) the unstable double layers, and therefore the axial electrostatic confinement, were suppressed in a large part of the parameter space, and (ii) the magnetic confinement leads to a radially stratified plasma, the center being a low-electronegativity, high-density plasma and the edges being essentially an ion-ion plasma.
Optical activation of Eu ions in nanoporous GaN films
Authors: Vajpeyi A. P. , Tripathy S. , Wang L. S. , Foo B. C. , Chua S. J. , Fitzgerald E. A. , Alves E.
Published: June 2006

A systematic optical activation study of Eu-implanted nanoporous GaN films has been carried out as a function of ion dose and annealing temperature. The nanoporous GaN films are prepared by photoelectrochemical etching of n-type GaN films in HF-based electrolyte. Eu ions are implanted in both n-type GaN and n-type porous GaN films at 200keV with doses ranging from 5×1014to5×1015cm−2. For the implantation damage recovery and optical activation of Eu3+ ions, rapid thermal annealing is performed in the temperature range of 900–1200°C under nitrogen ambient. The surface morphology of implanted porous GaN after different processing steps is characterized by scanning electron microscopy and the results show that porous morphology remains uniform even after ion implantation and high temperature processing. Microphotoluminescence and micro-Raman techniques have been used to investigate the optical properties of these Eu-implanted nanoporous films. Postimplantation annealing of both as-grown GaN and porous GaN films leads to the observation of strong photoluminescence (PL) peak around 622nm, which is associated with the D05–F27 intraionic transition of Eu3+ ions. We have observed that PL intensity of Eu-related luminescence peaks increases with annealing temperature up to 1100°C. In addition, due to efficient light extraction by surface nanostructuring, Eu-implanted porous GaN films show much stronger luminescence when compared to Eu-implanted as-grown GaN. Raman spectral analyses also indicate the optimum annealing condition for the implantation damage recovery and the compressive stress state in the Eu-implanted films.
Tunneling magnetoresistance of Co2MnGe∕Al2O3∕Co junctions
Authors: Verduijn E. A. , Westerholt K.
Published: June 2006

We report on the fabrication and characterization of magnetic tunnel junctions using the Heusler compound Co2MnGe as the bottom electrode and Co as counter electrode. The Co2MnGe phase in the cubic L21 structure belongs to the group of Heusler alloys with theoretically predicted full spin polarization at the Fermi level. From the maximum tunnelling magnetoresistance of 27% at low temperatures we derive a spin polarization P=36% for the Heusler alloy. We compare the properties of the Co2MnGe∕Al2O3∕Co junction with that of a Co∕Al2O3∕Co reference junction prepared under the same conditions and discuss the possible origin of the loss of full spin polarization for the Heusler alloy in the junction.
High quality YBa2Cu3O7−δ films with controllable in-plane orientations grown on yttria-stabilized zirconia substrates
Authors: Lin P. A. , Lo R. L. , Chi C. C.
Published: June 2006

The pulsed-laser deposition (PLD) technique was used to grow high TC superconducting YBa2Cu3O7−δ (YBCO) films on both virgin and ion-bombarded yttria-stabilized zirconia (YSZ) substrates. To pattern high TC films for device applications, the ion milling technique is often used to turn virgin YSZ substrates into ion-bombarded substrates. Multilayered processes require the growth of high TC films on these ion-bombarded substrates. The purpose of this work was to investigate the growing conditions for these two kinds of substrate surfaces. We found that high quality 0° in-plane orientation films can be grown on either substrate when the growth temperature is about 810°C. The thin film grown at this temperature has TC of about 90.3K and JC of about 4×106Acm−2 at 77K. On virgin substrates, the in-plane orientations of YBCO films grown within the temperature range of 790–730°C exhibit a mixture of 0° and 45° domains. As the growth temperature decreases, the dominant orientation shifts gradually from 0° to 45°. On the other hand, on ion-bombarded YSZ substrates, the in-plane orientation of YBCO films grown within the same temperature range shows that the 45° domain is more prominent. Furthermore, 9° subpeaks appear around the 0° peak on ion-bombarded YSZ substrates. At a lower growth temperature of around 690°C, only the 45° domain exists on the virgin substrate, while a small amount of 0° domain is present with the majority of 45° domain on the ion-bombarded substrate. The TC and JC of the films grown at around 690°C on virgin substrates are as good as films grown at high temperatures, despite the difference in the in-plane orientations.
Nonconservative Ostwald ripening of a dislocation loop layer under inert nitrogen-rich SiO2∕Si interfaces
Authors: Skarlatos D. , Tsouroutas P. , Vamvakas V. Em. , Tsamis C.
Published: June 2006

In this work we perform a systematic study of the dissolution of a dislocation loop layer under the influence of inert SiO2∕Si and nitrogen-rich SiO2∕Si interfaces. The composition of the dislocation loop layer was just after its formation 10%–20% Frank dislocation loops and 90%–80% perfect prismatic loops. During subsequent inert (N2) ambient annealing the differences of the kinetics between the two loop populations have been studied as a function of the interface type. It has been shown that during the nonconservative Ostwald ripening process the defect band loses interstitials mainly due to the dissolution of perfect prismatic loops, while Frank loops remain almost unaffected by the presence of both interfaces. In parallel a competition between the interface and the population of Frank loops in absorbing the interstitials released by the prismatic loops took place. The nitrogen-rich SiO2∕Si interface has been proved in general a less effective interstitial sink than the common one and under specific annealing conditions less effective even than the small Frank loops population.
Saturated gain in GaN epilayers studied by variable stripe length technique
Authors: Mickevičius J. , Tamulaitis G. , Shur M. S. , Fareed Q. , Zhang J. P. , Gaska R.
Published: June 2006

Optical gain in GaN epilayers was investigated by using the variable stripe length (VSL) technique. The light amplification was studied for the propagation directions along and perpendicular to the layer surface. Experimental stripe length and excitation intensity dependencies were measured and saturation of gain modes and appearance of new modes was observed. The limitations of the VSL technique due to gain saturation and one-dimensional light propagation model are discussed. Gain peak values up to ∼7500cm−1 (which is the limit of applicability of the VSL technique) have been demonstrated in GaN epilayers grown on AlN buffer layers deposited on sapphire by migration enhanced metal-organic chemical vapor deposition.
The effect of nanoparticles on rough surface adhesion
Authors: DelRio Frank W. , Dunn Martin L. , Boyce Brad L. , Corwin Alex D. , de Boer Maarten P.
Published: June 2006

Particulates can strongly influence interfacial adhesion between rough surfaces by changing their average separation. In a cantilever beam adhesion test structure, a compressive zone exists just beyond the crack tip, which may act to deform such particles. To explore this phenomenon quantitatively, we compared finite element method calculations of the interface to load-displacement experiments of individual particles. Below a certain threshold density, we show that the stress distribution at the interface is sufficient to deform individual particles. In this regime, the adhesion is controlled by the intrinsic surface roughness and under dry conditions is mainly due to van der Waals forces across extensive noncontacting areas. Above this threshold density, however, the particles introduce a topography that is more significant than the intrinsic surface roughness. As a result, the interfacial separation is governed by the particle size and the adhesion is lower but stochastic in nature. We demonstrate that the particles on the micromachined surfaces are silicon carbide (SiC). The cantilever test structures were fabricated using standard surface micromachining techniques, which consisted of depositing, patterning, and etching two polycrystalline silicon (polysilicon) layers separated by a tetraethylorthosilicate (TEOS) sacrificial oxide layer. High temperature annealing in the fabrication process allows residual carbon in the TEOS sacrificial oxide layer to migrate to the polysilicon surface and form the SiC particles.
An x-ray topographic study of diamond anvils: Correlation between defects and helium diffusion
Authors: Dewaele Agnès , Loubeyre Paul , André Ramesh , Härtwig Jürgen
Published: June 2006

X-ray topographic images of several dozens of diamonds have been recorded before and after their use as anvils in a diamond anvil high pressure cell. The aim of this study is to better understand and prevent the breakage of diamond anvils when they are used in contact with a helium sample. Indeed, helium is a good hydrostatic medium for very high pressure studies but many anvils are subjected to helium embrittlement. X-ray topographic observations suggest that helium atoms enter the diamond anvil by a diffusion process enhanced by subsurface strains and/or extended preexisting defects and nonhydrostatic stress. Then these atoms open cracks during nonhydrostatic load of the diamond anvil. The diamond anvils can be classified into three types depending on the nature of the defects. An associated criterion for the selection of stones resistant to helium is proposed.
Array of cobalt nanoparticles in silica: Synthesis and effects of thermal annealing
Authors: Jacobsohn L. G. , Thompson J. D. , Misra A. , Schulze R. K. , Hundley M. F. , Nastasi M.
Published: June 2006

The synthesis, characterization, and the effects of isochronal annealing of nearly monodispersive three-dimensional arrays of Co nanoparticles are presented. Samples were obtained by alternating electron beam evaporation of Co and SiO2 layers 0.5 and 20nm thick, respectively, onto fused silica. Transmission electron microscopy (TEM) revealed the presence of 3.2nm diameter Co particles with a size dispersion standard deviation of 16%. Annealing at temperatures up to 800°C was carried out in vacuum for 5min. Field and zero-field cooled measurements of the magnetic susceptibility monitored the effects of annealing on the magnetic behavior. Two temperature regimes were observed. One, up to 700°C with an activation energy of 0.062eV where no significant particle size change was observed, was tentatively related to bonding ordering within the particles. The other regime, with an activation energy of 0.67eV, was attributed to Co diffusion and reflected particle growth as observed by TEM. These results were supported by exchange bias anisotropy and x-ray photoelectron spectroscopy measurements.
Crystal-liquid crystal binary phase diagrams
Authors: Dayal Pratyush , Matkar Rushikesh A. , Kyu Thein
Published: June 2006

We propose a new theoretical scheme for the binary phase diagrams of crystal-liquid crystal mixtures by a combination of a phase field model of solidification, the Flory-Huggins theory for liquid-liquid mixing and Maier-Saupe-McMillan (FH-MSM) model for nematic and smectic liquid crystal orderings. The phase field theory describes the crystal phase transition of anisotropic organic crystal and/or side chain liquid crystalline polymer crystals while the FH-MSM model explains isotropic, nematic and smectic-A phase transitions. Self-consistent calculations reveal several possible phase diagram topologies of the binary crystal-liquid crystal mixtures. The calculated phase diagrams were found to accord well to the reported experimental results.
Statistical mechanical theory for steady state systems. V. Nonequilibrium probability density
Authors: Attard Phil
Published: June 2006

The phase space probability density for steady heat flow is given. This generalizes the Boltzmann distribution to a nonequilibrium system. The expression includes the nonequilibrium partition function, which is a generating function for statistical averages and which can be related to a nonequilibrium free energy. The probability density is shown to give the Green-Kubo formula in the linear regime. A Monte Carlo algorithm is developed based upon a Metropolis sampling of the probability distribution using an umbrella weight. The nonequilibrium simulation scheme is shown to be much more efficient for the thermal conductivity of a Lennard-Jones fluid than the Green-Kubo equilibrium fluctuation method. The theory for heat flow is generalized to give the generic nonequilibrium probability densities for hydrodynamic transport, for time-dependent mechanical work, and for nonequilibrium quantum statistical mechanics.
Conical and glancing Jahn-Teller intersections in the cyclic trinitrogen cation
Authors: Mozhayskiy Vadim A. , Babikov Dmitri , Krylov Anna I.
Published: June 2006

The ground and electronically excited states of cyclic N3+ are characterized at the equilibrium D3h geometry and along the Jahn-Teller distortions. Lowest excited states are derived from single excitations from the doubly degenerate highest occupied molecular orbitals (HOMOs) to the doubly degenerate lowest unoccupied molecular orbitals (LUMOs), which give rise to two exactly and two nearly degenerate states. The interaction of two degenerate states with two other states eliminates linear terms and results in a glancing rather than conical Jahn-Teller intersection. HOMO-2→LUMOs excitations give rise to two regular Jahn-Teller states. Optimized structures, vertical and adiabatic excitation energies, frequencies, and ionization potential (IP) are presented. IP is estimated to be 10.595eV, in agreement with recent experiments.
Vacuum ultraviolet laser pulsed field ionization-photoelectron study of cis-dichloroethene
Authors: Lau K.-C. , Woo H. K. , Wang P. , Xing X. , Ng C. Y.
Published: June 2006

The vacuum ultraviolet (VUV) laser pulsed field ionization photoelectron (PFI-PE) spectrum of cis-dichloroethene (cis-ClCHCHCl) has been measured in the energy region of 77600–79500cm−1. On the basis of the semiempirical simulation of the origin PFI-PE band, we have obtained the IE(cis-ClCHCHCl) to be 77899.5±2.0cm−1 (9.65839±0.00025eV). The assignment of the vibrational bands resolved in the VUV-PFI-PE spectrum are guided by high-level ab initio calculations of the vibrational frequencies for cis-ClCHCHCl+ and the Franck-Condon factors for the ionization transitions. Combining the results of the present VUV-PFI-PE measurement and the recent VUV-infrared-photoinduced Rydberg ionization study [P. Wang et al., J. Chem. Phys. 124, 064310 (2006)], the vibrational frequencies for eleven of the twelve vibrational modes of cis-ClCHCHCl+ have been experimentally determined: ν1+(a1)=181cm−1, ν2+(a2)=277cm−1, ν3+(b2)=580cm−1, ν4+(b1)=730cm−1, ν5+(a1)=810cm−1, ν6+(a2)=901cm−1, ν8+(a1)=1196cm−1, ν9+(b2)=1348cm−1, ν10+(a1)=1429cm−1, ν11+(b2)=3067cm−1, and ν12+(a1)=3090cm−1). These values are compared to theoretical anharmonic vibrational frequencies obtained at the MP2/6-311G(2df,p) and CCSD(T)/6-311G(2df,p) levels. The IE prediction for cis-ClCHCHCl has also been calculated with the wave function based CCSD(T)/CBS method, which involves the approximation to the complete basis set (CBS) and the high-level correlation corrections. The theoretical IE(cis-ClCHCHCl)=9.668eV thus obtained is found to have a deviation of less than 10meV with respect to the experimental IE value.
Radial breathinglike mode of the collapsed single-walled carbon nanotube bundle under hydrostatic pressure
Authors: Wu Gang , Yang Xiaoping , Dong Jinming
Published: June 2006

Using the first-principles calculations we have studied the vibrational modes and Raman spectra of a (10, 10) single-walled carbon nanotube (SWNT) bundle under hydrostatic pressure. Detailed analysis shows that the original radial breathing mode (RBM) of the SWNT bundle disappears after the structural phase transition (SPT). And significantly a RBM-like mode appears at about 509cm−1, which could be considered as a fingerprint of the SPT happened in the SWNT bundle, and further used to determine the microscopic structure of the bundle after the SPT.
Mass transport and alloying during InN growth on GaN by molecular-beam epitaxy
Authors: Liu Y. , Xie M. H. , Wu H. S. , Tong S. Y.
Published: June 2006

During Stranski-Krastanov (SK) growth of InN on GaN by molecular-beam epitaxy, a mass transport is noted from the two-dimensional wetting layer and/or the surface excess metal adlayers to the SK islands when the excess nitrogen flux is used for deposition. The extent of mass transport depends on the material coverage. For growth under the excess indium flux condition, no such mass transport is observed.
Imaging defects in strained-silicon thin films by glancing-incidence x-ray topography
Authors: Black D. R. , Woicik J. C. , Erdtmann M. , Langdo T. A.
Published: June 2006

X-ray topographical images from thin (⩽50nm) strained-Si films grown on relaxed, planarized crystalline SiGe-on-Si (001) virtual substrates have been imaged by glancing-incidence monochromatic x-ray topography. This extremely asymmetric diffraction geometry, utilizing (311) diffraction planes, can limit penetration into the sample to as little as 6nm and allows separate images from the thin strained-Si film, the SiGe layer, and the base Si wafer to be recorded at different angles above the critical angle. Strain fields from the misfit dislocations in the SiGe layer penetrate the Si wafer and act as a template for the defect structure of the strained-Si films, even after an ex situ planarization step was inserted during the growth of the SiGe layer. This defect structure remains in the strained-Si film throughout the fabrication of strained-Si-on-insulator substrates.
Does the most stable formic acid tetramer have π stacking or C–H⋯O interactions?
Authors: Karpfen Alfred , Thakkar Ajit J.
Published: June 2006

Density functional theory (DFT), Møller-Plesset (MP) perturbation theory, and coupled-cluster calculations are used to examine low-energy minima on the potential energy surface of the formic acid tetramer (HCOOH)4. The potential energy surface is rather flat with respect to rotation of one of the dimers, relative to the other dimer in an aligned stack, about the axis passing through the inversion centers of the dimers. Our best calculations suggest that an aligned π-π stack of two dimers is very likely to be the global minimum but there are two other π-π stacks within 0.5kcal∕mol. Moreover, a fourth π-π stack, a planar association of two dimers held together by C–H⋯O interactions, and a bowl structure all lie within 1kcal∕mol of the lowest-energy structure.
Influence of defects on nanotube transistor performance
Authors: Neophytou Neophytos , Kienle Diego , Polizzi Eric , Anantram M. P.
Published: June 2006

We study the effect of vacancies and charged impurities on the performance of carbon nanotube transistors by self-consistently solving the three-dimensional Poisson and Schrödinger equations. We find that a single vacancy or charged impurity can decrease the drive current by more than 25% from the ballistic current. The threshold voltage shift in the case of charged impurities can be as large as 40mV.
Charge-carrier mobility in an organic semiconductor thin film measured by photoinduced electroluminescence
Authors: Klenkler Richard A. , Xu Gu , Aziz Hany , Popovic Zoran D.
Published: June 2006

With existing methods it is difficult to measure the mobility of semiconducting thin films that have submicron thickness and submicrosecond charge-carrier transit time. To simplify these measurements we demonstrate a technique that is a combination of the time-of-flight and transient electroluminescence methods. The technique is fundamentally optical in that it decouples the carrier transient signal from the device charging circuit and hence removes the RC time constant constraint that limits existing methods. The technique was applied to measure electron mobility in a tris(8-hydroxyquinoline) aluminum (AlQ3) thin film. Results agree well with mobility values obtained using other methods.
The first eigenvalue of a closed manifold with positive Ricci curvature
Authors: Ling Jun
Published: June 2006

We give a new estimate on the lower bound for the first positive eigenvalue of the Laplacian on a closed manifold with positive Ricci curvature in terms of the lower bound of the Ricci curvature and the largest interior radius of the nodal domains of eigenfunctions of the eigenvalue.
Quasi-translations and counterexamples to the Homogeneous Dependence Problem
Authors: de Bondt Michiel
Published: June 2006

In this article, the author gives counterexamples to the Linear Dependence Problem for Homogeneous Nilpotent Jacobians for dimension 5 and up. This problem has been formulated as a conjecture/problem by several authors in connection to the Jacobian conjecture. In dimension 10 and up, cubic counterexamples are given. In the construction of these counterexamples, the author makes use of so-called quasi-translations, a special type of invertible polynomial maps. Quasi-translations can also be seen as a special type of locally nilpotent derivations.
Counting abelian group structures
Authors: Clarke Francis
Published: June 2006

A bijective proof is given of a recurrence for the function counting the number of binary operations which endow a finite set with the structure of an abelian group. The proof depends on a lemma in “labelled homological algebra” and provides a simple route to a “curious result” of Philip Hall.
Characterizations of isometric isomorphisms between uniform algebras via nonlinear range-preserving properties
Authors: Hatori Osamu , Miura Takeshi , Takagi Hiroyuki
Published: June 2006

Let

T
T

be a surjective mapping from a uniform algebra

A
A

on a compact Hausdorff space

X
X

onto a uniform algebra on a compact Hausdorff space

Y
Y

. Suppose that

f
g
(
X
)
=
T
(
f
)
T
(
g
)
(
Y
)

fg(X)=T(f)T(g)(Y)

holds for every

f
,
g
∈
A

f,g\in A

. Then we have that

T
T

is an almost isometric isomorphism, which is a generalization of results of Molnár (2002) and Rao and Roy (2005).
On the Manin-Mumford conjecture for abelian varieties with a prime of supersingular reduction
Authors: Ito Tetsushi
Published: June 2006

We give a short proof of the “prime-to-

p
p

version” of the Manin-Mumford conjecture for an abelian variety over a number field, when it has supersingular reduction at a prime dividing

p
p

, by combining the methods of Bogomolov, Hrushovski, and Pink-Roessler. Our proof here is quite simple and short, and neither

p
p

-adic Hodge theory nor model theory is used. The observation is that a power of a lift of the Frobenius element at a supersingular prime acts on the prime-to-

p
p

torsion points via nontrivial homothety.
Altered tachykinergic influence on gastric mechanical activity in mdx mice
Authors: Mulè F. , Amato A. , Vannucchi M. G. , Faussone‐pellegrini M. S. , Serio R.
Published: June 2006

Abstract  This study investigated whether alterations in gastric activity in dystrophic mdx mouse can be attributed to dysfunctions of tachykinins. Endoluminal pressure was recorded and the expression of neuronal nitric oxide synthase (nNOS), NK1 and NK2 neurokinin receptors was investigated by immunohistochemistry. SR48968, NK2 receptor antagonist, but not SR140333, NK1 receptor antagonist, decreased the tone only in mdx gastric preparations. In the presence of N‐nitro‐l‐arginine methyl ester (l‐NAME), inhibitor of NOS, SR48968 reduced the tone also in normal stomach. [Sar9, Met(O2)11]‐SP, agonist of NK1 receptors, caused tetrodotoxin‐sensitive relaxations, antagonized by SR140333 or l‐NAME, with no difference in the potency or efficacy between normal and mdx preparations. [β‐Ala8]‐NKA(4‐10), an NK2 receptor agonist, induced SR48968‐sensitive contractions in both types of preparations, although the maximal response of mdx tissues was significantly lower than normal preparations. Immunohistochemistry demonstrated a consistent reduction of nNOS and NK2 receptor expression in mdx stomach smooth muscle cells and no change in nNOS and NK1 receptor expression in neurones. In conclusion, in mdx stomach the activation of NK2 receptors plays a role in the development of the tone, associated with a reduced NO production by muscular nNOS. The hypo‐responsiveness to NK2 receptors could depend on the reduced expression of these receptors.
Differential display proteomic analysis of Picea meyeri pollen germination and pollen‐tube growth after inhibition of actin polymerization by latrunculin B
Authors: Chen Yanmei , Chen Tong , Shen Shihua , Zheng Maozhong , Guo Yiming , Lin Jinxing , Baluška František , Šamaj Jozef
Published: June 2006

To investigate roles of the actin cytoskeleton in growth of the pollen tube of Picea meyeri, we used the actin polymerization inhibitor latrunculin B (LATB) under quantitatively controlled conditions. At low concentrations, LATB inhibited polymerization of the actin cytoskeleton in the growing pollen tube, which rapidly inhibited tip growth. The proteomic approach was used to analyse protein expression‐profile changes during pollen germination and subsequent pollen‐tube development with disturbed organization of the actin cytoskeleton. Two‐dimensional electrophoresis and staining with Coomassie Brilliant Blue revealed nearly 600 protein spots. A total of 84 of these were differentially displayed at different hours with varying doses of LATB, and 53 upregulated or downregulated proteins were identified by mass spectrometry. These proteins were grouped into distinct functional categories including signalling, actin cytoskeleton organization, cell expansion and carbohydrate metabolism. Moreover, actin disruption affected the morphology of Golgi stacks, mitochondria and amyloplasts, along with a differential expression of proteins involved in their functions. These findings provide new insights into the multifaceted mechanism of actin cytoskeleton functions and its interaction with signalling, cell‐expansion machinery and energy‐providing pathways.
Fatigue behaviour of nickel–titanium superelastic wires and endodontic instruments
Authors: BAHIA M. G. A. , GONZALEZ B. M. , BUONO V. T. L.
Published: June 2006

Endodontic files made of nickel–titanium (NiTi) superelastic wires can be employed in rotary techniques for cleaning and shaping curved root canals, suffering tensile–compressive strain cycles with maximum amplitudes between 3 and 5%. The aim of this work was to study the fatigue behaviour of this material under such high deformation conditions, using NiTi instruments and superelastic wires taken from their production line. One hundred load–unload tensile cycles in the superelastic regime (4% elongation) were applied to NiTi wires. New endodontic instruments were fatigue‐tested simulating the geometrical conditions found in their clinical use. It was found that only small changes took place in the parameters describing the mechanical behaviour of the cycled wires. The measured average number of cycles to failure varies inversely with the maximum tensile strain amplitude in the fatigue tests (r= 0.993).
Invasional meltdown 6 years later: important phenomenon, unfortunate metaphor, or both?
Authors: Simberloff Daniel
Published: June 2006

Cases in which introduced species facilitate one another's establishment, spread, and impacts are increasingly noted, and several experimental studies have provided strong evidence of a population‐level impact. However, a full ‘invasional meltdown’, in which interspecific facilitation leads to an accelerating increase in the number of introduced species and their impact, has yet to be conclusively demonstrated. The great majority of suggested instances of ‘invasional meltdown’ remain simply plausible scenarios of long‐term consequences based on short‐term observations of facilitatory interactions between individuals of two species. There is a particular dearth of proven instances in which two invasive species each enhance the impact and/or probability of establishment and spread of the other. By contrast, in many authenticated cases, at least one partner is aided. The metaphor of meltdown focused attention on facilitation in invasion and has probably helped inspire recent studies. As have other metaphors from invasion biology and other sciences, ‘meltdown’ has struck a responsive chord with writers for the lay public; some have stretched it well beyond its meaning as understood by invasion biologists. There is no evidence that this hyperbole has impeded scientific understanding or caused loss of scientific credibility.
The different other – towards an including ethics of care
Authors: Myhrvold Trine
Published: June 2006

Abstract  The aim of this article is to continue the discussion about factors of importance for an including ethics of care. A further polarization between partiality and impartiality does not seem a relevant approach. What is important is to direct attention both to the other and to the third person, which requires an acknowledgement of responsibility that extends beyond established relationships. Thus, we need to draw attention not only to the vulnerability existing within every seriously ill or injured person, but to factors of importance for marginalization of groups like refugees, people suffering from serious mental illness, and substance misusers, to mention some in the Western world. Marginalized groups are groups experiencing a discrepancy between need of health care and care given. They are not given proper priority in the distribution of resources, and they may experience ignorance when they first meet the healthcare system as patients.

Efforts to understand what circumstances can lead to inadequate inclusion indicate that the elements of differentness and extensive losses of life contexts which may be causing feelings of hopelessness and helplessness in the health professionals, are key factors posing challenges to empathy both within and beyond established relationships, besides geographical distance. Groups of people who have suffered extensive loss in their life contexts may be threatening for us, as they reflect our own fears, and remind us of our own vulnerability.

I raise the question: How can we contribute to meeting the need for an ethics of care that extends beyond the familiar to the unfamiliar both in established and non‐established relationships?
Chronic polyneuropathy and Lyme disease
Authors: Mygland Å. , Skarpaas T. , Ljøstad U.
Published: June 2006

Infection of the peripheral nervous system with Borrelia burgdorferi can present as a cranial neuropathy or radiculopathy with cerebrospinal fluid (CSF) pleocytosis and intrathecal antibody production against B. burgdorferi, or as an asymmetric peripheral neuropathy with acrodermatitis chronica atrophicans (ACA) and normal CSF findings. According to North American studies, it can also present as a symmetric chronic polyneuropathy without ACA or other Lyme manifestations. Our purpose was to investigate the prevalence of B. burgdorferi antibodies in patients presenting with isolated chronic polyneuropathy (PN) in a European region with high incidence of Lyme disease. Sera from 209 PN patients and 247 healthy blood donors from Vest‐Agder County, Norway, were examined. Borrelia burgdorferi antibodies were detected in 43 (21%) PN patients and in 45 (18%) healthy blood donors (P = 0.553). The prevalence of B. burgdorferi antibodies was similar (P = 0.311) in cryptogenic PN (24/102, 24%) and PNs of identified etiologies (19/107, 18%). PN patients with B. burgdorferi antibodies had normal spinal fluid white cell count and they did not differ clinically or electrophysiologically from PN patients without antibodies. None of 20 antibody‐positive PN patients responded to antimicrobial treatment. The study shows that, in Europe, chronic distal PN without ACA or other Lyme manifestations is very rarely caused by a B. burgdorferi infection.
European Federation of Neurological Societies/Peripheral Nerve Society guideline on management of paraproteinaemic demyelinating neuropathies: report of a joint task force of the European Federation of Neurological Societies and the Peripheral Nerve Society*
Authors: Hadden R. D. M. , Nobile‐Orazio E. , Sommer C. , Hahn A. , Illa I. , Morra E. , Pollard J. , Hughes R. A. C. , Bouche P. , Cornblath D. , Evers E. , Koski C. L. , Léger J. M. , Van den Bergh P. , Van Doorn P. , Van Schaik I. N.
Published: June 2006

Background. Paraprotein‐associated neuropathies have heterogeneous clinical, neurophysiological, neuropathological and haematological features. Objectives. To prepare evidence‐based and consensus guidelines on the clinical management of patients with both a demyelinating neuropathy and a paraprotein (paraproteinaemic demyelinating neuropathy, PDN). Methods. Search of MEDLINE and the Cochrane library, review of evidence and consensus agreement of an expert panel. Recommendations. In the absence of adequate data, evidence based recommendations were not possible but the panel agreed the following good practice points: (1) Patients with PDN should be investigated for a malignant plasma cell dyscrasia. (2) The paraprotein is more likely to be causing the neuropathy if the paraprotein is immunoglobulin (Ig)M, antibodies are present in serum or on biopsy, or the clinical phenotype is chronic distal sensory neuropathy. (3) Patients with IgM PDN usually have predominantly distal and sensory impairment, with prolonged distal motor latencies, and often anti‐myelin associated glycoprotein antibodies. (4) IgM PDN sometimes responds to immune therapies. Their potential benefit should be balanced against their possible side‐effects and the usually slow disease progression. (5) IgG and IgA PDN may be indistinguishable from chronic inflammatory demyelinating polyradiculoneuropathy, clinically, electrophysiologically, and in response to treatment. (6) For POEMS syndrome, local irradiation or resection of an isolated plasmacytoma, or melphalan with or without corticosteroids, should be considered, with haemato‐oncology advice.
Higher Variability of Phosphene Thresholds in Migraineurs Than in Controls: A Consecutive Transcranial Magnetic Stimulation Study
Authors: Antal A , Arlt S , Nitsche MA , Chadaide Z , Paulus W
Published: June 2006

The aim of this study was to characterize the temporal course of phosphene thresholds (PT) using transcranial magnetic stimulation (TMS) in control subjects and in subjects with migraine and to observe whether changes in PT over time can predict a subsequent migraine attack. PTs were measured in 16 migraineurs [nine with aura (MA) and seven without aura (MoA)] and nine controls five times over an approximately 10-week period. Mean PTs were not significantly different between migraineurs and controls; however, there was a trend in MA showing lower thresholds. The minimum threshold values were also smaller in MA subjects than in MoA or control subjects. Generally, PTs had higher variance in migraineurs than in controls, revealing a significant increase in standard deviation of PTs in MA subjects. There was no significant difference of thresholds from the first to the last stimulation in controls and in MoA subjects, but the 3rd, 4th and 5th measurements of MA subjects were significantly lower than their first measurements. Four migraineurs experienced headache within 1 day after one of the measurements. They had either very low or very high PTs compared with the PT values which were not followed by a migraine attack. Our results imply that migraineurs show a higher variability among PT measurements over time than controls, revealing unstable excitability levels in these patients. Additionally, both particularly high and low PTs might predict a subsequent headache in some individuals.