bluuebunny/crossref_metadata_2025 huggingface dataset:
Microjetting from wave focusing on oscillating drops
Authors: Thoroddsen S. T. , Etoh T. G. , Takehara K.
Published: May 2007

We present experimental observations of microjetting from an oscillating drop. The jet is generated by the focusing of axisymmetric capillary waves that overturn and collide at an apex of the drop. These jets are up to two orders of magnitude smaller than the original drops. We present two widely different configurations that produce such microjets. The first occurs on a satellite drop, produced by the pinch-off of a water drop from a vertical nozzle. The large oscillations following the contraction of the satellite bridge focus waves at the bottom, sending out a 30μm jet at 9.9m∕s. The second jet arises when a water drop, containing surfactants, falls onto and passes through a hemispherical soap film. The gentle deformation of the drop creates a surface wave that focuses at its top, shooting out a tiny jet and entrapping a small bubble inside the drop. This jet is 16±5μm in diameter and emerges at 6.3m∕s. In this configuration, the soap film wraps around the drop and acts as a sensor of the air flow, revealing that the liquid jet is preceded by a localized faster-moving air jet. The jetting in both configurations is quite robust and occurs even for slightly asymmetric conditions. These microjets appear for much lower values of the Reynolds and Weber numbers than previously observed, suggesting that free-surface jetting is not limited to the inviscid capillary-inertial regime, which has been the focus of much of the theoretical work.
High-beta steady-state research with integrated modeling in the JT-60 Upgrade
Authors: Ozeki T. ,   JT-60 Team
Published: May 2007

Improvement of high-beta performance and its long sustainment was obtained with ferritic steel tiles in the JT-60 Upgrade (JT-60U) [T. Fujita et al., Phys. Plasmas 50, 104 (2005)], which were installed inside the vacuum vessel to reduce fast ion loss by decreasing the toroidal field ripple. When a separation between the plasma surface and the wall was small, high-beta plasmas reached the ideal wall stability limit, i.e., the ideal magnetohydrodynamics stability limit with the wall stabilization. A small rotation velocity of 0.3% of the Alfvén velocity was found to be effective for suppressing the resistive wall mode. Sustainment of the high normalized beta value of βN=2.3 has been extended to 28.6s (∼15 times the current diffusion time) by improvement of the confinement and increase in the net heating power. Based on the research in JT-60U experiments and first-principle simulations, integrated models of core, edge-pedestal, and scrape-off-layer (SOL) divertors were developed, and they clarified complex features of reactor-relevant plasmas. The integrated core plasma model indicated that the small amount of electron cyclotron (EC) current density of about half the bootstrap current density could effectively stabilize the neoclassical tearing mode by the localized EC current accurately aligned to the magnetic island center. The integrated edge-pedestal model clarified that the collisionality dependence of energy loss due to the edge-localized mode was caused by the change in the width of the unstable mode and the SOL transport. The integrated SOL-divertor model clarified the effect of the exhaust slot on the pumping efficiency and the cause of enhanced radiation near the X-point multifaceted asymmetric radiation from edge. Success in these consistent analyses using the integrated code indicates that it is an effective means to investigate complex plasmas and to control the integrated performance.
Conditional statistics for passive-scalar mixing in a confined rectangular turbulent jet
Authors: Feng H. , Olsen M. G. , Fox R. O. , Hill J. C.
Published: May 2007

Experimental results for the conditional statistics, such as the velocity conditioned on a conserved scalar and the scalar conditioned on velocity, in a confined liquid-phase rectangular jet are presented and analyzed for a data set collected using simultaneous particle image velocimetry and planar laser-induced fluorescence. The joint velocity-scalar probability density function (PDF) is not joint Gaussian in this flow, as the PDF of the conserved scalar is accurately described by a beta-PDF. The conditional mean velocity is found to agree with a linear model when the scalar is close to its local mean value. A gradient PDF model is found to give poor predictions for the streamwise conditional velocity. However, the improved gradient PDF model predicts both the streamwise and transverse conditional velocities well. A linear model for the scalar fluctuation conditioned on velocity is also tested against the experimental data, showing that this model only obtains good approximations when the joint velocity-scalar PDF approaches a joint Gaussian at farther downstream locations in this flow.
An inverse problem for Gibbs fields with hard core potential
Authors: Koralov Leonid
Published: May 2007

It is well known that for a regular stable potential of pair interaction and a small value of activity one can define the corresponding Gibbs field (a measure on the space of configurations of points in Rd). In this paper we consider a converse problem. Namely, we show that for a sufficiently small constant ρ¯1 and a sufficiently small function ρ¯2(x), x∈Rd, that is equal to zero in a neighborhood of the origin, there exist a hard core pair potential and a value of activity such that ρ¯1 is the density and ρ¯2 is the pair correlation function of the corresponding Gibbs field.
Temperature dependences of microwave-enhanced critical current in wide tin films
Authors: Dmitriev V. M. , Zolochevshiĭ I. V. , Bezuglyĭ E. V.
Published: May 2007

The temperature dependences of the critical current of wide and narrow tin films irradiated with microwaves are investigated experimentally and analyzed. It is found that a high-frequency electromagnetic field stabilizes the current state of a wide film with respect to the entry of Abrikosov vortices into the film. The stabilizing effect of the irradiation increases with the radiation frequency. The fact that the enhancement of superconductivity is a general effect and is observed for uniform (narrow films) and nonuniform (wide films) distributions of the superconducting current over the film width made it possible to extend, in part, Éliashberg’s theory to wide films.
Manifestation of coherent and spin-dependent effects in the conductance of ferromagnets adjoining a superconductor
Authors: Chiang Yu. N. , Shevchenko O. G. , Kolenov R. N.
Published: May 2007

Electrotransport was investigated in the macroscopic ferromagnets (F) Fe and Ni in the presence of F∕In interfaces with different area. The measurements were performed in two configurations—with a constant current flowing parallel and perpendicular to the interfaces. It was found that the transition of In into the superconducting (S) state is accompanied by an increase of the resistance of the ferromagnets. In the first configuration the increase concerned the change of the resistance of the region between the boundaries of the potential probes (superconducting “mirrors”) and was of the order of the typical, weakly localized, contribution to the conductivity of ferromagnets from subgap singlet excitations, arising with Andreev reflection, for macroscopic distances between the “mirrors” at the coherence length characteristic for metals with a strong difference of the energy dispersion of the spin subbands. In the second configuration, where the conductivity of the F/S interface is also included in the measurements, the nonequilibrium resistive contribution of the latter, associated with the spin polarization of the region of the ferromagnet under the interface, was studied. The observed increase of the resistance corresponded to the theoretically predicted magnitude of the change occurring in the resistance of a single-domain region with spin-polarized electrons as a result of spin accumulation on the F/S interface under the conditions of limitations of Andreev reflections. The coefficients of current polarization and the coherence length in the exchange field were found for Fe and Ni from the experiemental data and the lower limit of the spin relaxation length was found for the samples investigated.
On the form of a moving boundary of a region of magnetic instability
Authors: Bespalov E. V. , Vyatkin V. S. , Efremov V. P. , Krasnoperov E. P.
Published: May 2007

When a magnetic instability collapses, a wave separating the stable and unstable state propagates along the superconductor. An induction method is used to determine the configuration of the interface of these states. For a 0.16mm in diameter Nb–Ti wire the moving boundary is 1.7–2.4mm long, depending on the magnetic field.
Spontaneous magnetization and characteristics of temperature-induced magnetization of planar Co∕Si nanostructures
Authors: Vas’kovskiĭ V. O. , Patrin G. S. , Velikanov D. A. , Svalov A. V. , Shchegoleva N. N.
Published: May 2007

The magnetic properties of planar Co∕Si nanostructures with different nominal thicknesses of the magnetic (2–42nm) and nonmagnetic (0.3–10nm) constituent layers are studied in the temperature range 4.2–300K. It is established that in the presence of Si layers the spontaneous magnetization of Co decreases and its temperature dependence changes, and magnetic hysteresis is modified. The interlayer influence is interpreted as being due to the diffusion of Si into the Co layers, which results in the formation of magnetically disordered boundary interfaces with low average magnetization. The depth of the interfaces depends on the nominal thickness of the Si layers and is estimated to reach 1.6nm. A qualitative explanation of the characteristics of the magnetization of the experimental objects under the influence of a magnetic field and temperature is given in a model where the interfaces have a granular microstructure. Electron-microscope observations confirm some assumptions of the proposed model.
Entanglement dynamics of a 3-qubit system in a magnetic field
Authors: Ivanchenko E. A.
Published: May 2007

A closed system of equations for the local Bloch vectors and spin correlation functions of three magnetic qubits with exchange interaction, which are in an arbitrary, time-dependent, external magnetic field, is obtained using decomplexification of the Liouville–Neuman equations. A numerical comparative analysis of entanglement measures is performed as a function of the initial conditions and modulation of the magnetic field. The investigation could find applications for the analysis of interference experiments and manipulation of quantum qubits.
Electric conductivity of metallic oblate or prolate nanoparticles
Authors: Grigorchuk N. I. , Tomchuk P. M.
Published: May 2007

The kinetic method is used to study the electric conductivity of a metallic nanometer-size particle with the shape of an oblate or prolate ellipsoid of revolution at frequencies above and below the characteristic free transit rate of an electron between the walls of the particle. The boundary condition chosen for this problem is diffusive reflection of an electron from the inner surface of the particle. Analytical expressions for the dependence of the electric conductivity on the degree of prolateness or oblateness of the particle and its orientation with respect to the direction of the incident radiation are obtained for the case where the incident wavelength is long compared to the characteristics dimensions of the particle. The dependence of the transverse and longitudinal components of the electric conductivity on the dimensions of the particle and on the frequency of the electromagnetic radiation is investigated. For a particle with large eccentricity these components are found to be in correspondence with known results for thin films and thin wires.
Thermally stimulated transformations in cryovacuum water ices
Authors: Drobyshev A. , Aldiyarov A. , Zhumagaliuly D. , Kurnosov V. , Tokmoldin N.
Published: May 2007

There is still no general consensus about the mechanism and nature of structural transformations in cryovacuum water ices. There are different interpretations of the behavior of the cryoprecipitates with respect to the proposed glass transition in the sequence of transformations and with respect to the values of the glass transition temperature Tg. The results of an experimental investigation of thermally stimulated polyamorphous and polymorphous transformations in cryovacuum condensed films of water ices, formed at substrate temperature 16K, are presented. The investigations are performed in the frequency interval 4200–400cm−1 using a modified cryovacuum IR spectrophotometer. A method developed by the present authors for observing the transformations of the films of the cryoprecipitates at a fixed frequency of the IR spectrometer is used. Data giving more accurate temperature intervals of the existence and transformations of different forms of amorphous solid water are obtained: high and low density and “restrained” amorphous phases and their transitions into a crystalline (cubic and hexagonal) state. It is concluded that the glass-transition temperature Tg lies in the temperature interval 136–138K. These results agree well with the results obtained by P. Jennsikens et al.
Low-temperature properties of orientationally degenerate (OH)− centers in proton-conducting oxides
Authors: Ivanov M. A. , Fishman A. Ya. , Tsidil’kovskiĭ V. I.
Published: May 2007

It is shown that the presence of proton-associated dipole centers (OH)− can cause glass-like properties to appear at low temperatures in the oxides ABO3−y doped with cations with a lower valence. These properties are due to the splitting of the orientationally degenerate states of (OH)− dipolar centers as a result of proton tunneling and random crystal fields. It is established that deuterium or tritium substituted for hydrogen can cause unusual and anomalously large isotopic effects in the contributions of degenerate centers to the thermodynamic properties and the absorption of elastic and electromagnetic waves.
Jumplike deformation in normal and superconducting states: The solid solution Al–Li
Authors: Grigorova T. V. , Isaev N. V. , Pustovalov V. V. , Fomenko V. S. , Shumilin S. É.
Published: May 2007

Low-temperature jumplike deformation (LTJD) of the solid solution Al–3.8at.% Li is studied at 0.52K in the normal (N) and superconducting (S) states. The magnitude of the plasticization effect at the NS transition is used to estimate the local heating of the sample. It is shown that the local heating is insufficient to change the sign of the temperature sensitivity of the deforming stress that explains the influence of the electronic state of the sample on the development of the LTJD on the basis of the thermal concept. Analysis of the statistics of the stress jumps showed that the amplitude density distribution of jumps into the N state is described by a power law with exponent α=1.3±0.2. The power law is considered to be an indication of self-organization of criticality in dislocation dynamics and the development of LTJD a manifestation of avalanche-like motion of dislocation pileups.
Direct observation of free excitons in the luminescence spectra of xenon clusters
Authors: Vakula V. L. , Danil’chenko A. G. , Doronin Yu. S. , Kovalenko S. I. , Libin M. Yu. , Samovarov V. N.
Published: May 2007

The first observation of luminescence due to surface and volume excitons for free clusters of inert gases is reported. The experiments are performed on xenon clusters formed in an ultrasonic stream emerging into vacuum. The optical investigations are supplemented by electron diffraction measurements to clarify the effect of the structure of the clusters on their optical spectra.
Electron-electron scattering in the spin polarized transport: A feasibility of observing spin drag
Authors: Takahashi Yutaka , Hirose Fumihiko , Sato Yuuki , Kawaguchi Hitoshi
Published: May 2007

The effect of electron-electron scattering on the electron transport in spin-polarized, two-dimensional electron gas is studied in semiconductor heterostructures. We numerically calculate the mobilities and diffusion coefficients for spin-up and spin-down electrons separately in high-quality heterostructures of GaAs at the temperatures below 10K and the electron sheet density of 2×1011cm−2. The contribution from the electron-electron scattering leads to the characteristic temperature dependence of the transport coefficients both in the field-driven transport (mobilities) and the transport driven by the density gradient (diffusion coefficients), which may help us to detect the effect termed “spin drag” in the experiment. We also find that the reduction of the electron energy arising from the many-particle correlations affects the density-driven transport. It competes with spin drag in a certain condition.
Time-resolved diffraction measurements of electric-field-induced strain in tetragonal lead zirconate titanate
Authors: Daniels John E. , Finlayson Trevor R. , Studer Andrew J. , Hoffman Mark , Jones Jacob L.
Published: May 2007

The dynamic electric-field-induced strain in piezoelectric ceramics enables their use in a broad range of sensor, actuator, and electronic devices. In piezoelectric ceramics which are also ferroelectric, this macroscopic strain is comprised of both intrinsic (piezoelectric) and extrinsic (non-180° domain switching) strain components. Extrinsic contributions are accompanied by hysteresis, nonlinearity, and fatigue. Though technologically significant, direct measurement of these mechanisms and their relative contributions to the macroscopic response has not yet been achieved at driving frequencies of interest. Here we report measurements of these mechanisms in ceramic lead zirconate titanate during application of subcoercive cyclic driving electric fields using an in-situ stroboscopic neutron diffraction technique. Calculations are made from the diffraction measurements to determine the relative contributions of these different strain mechanisms. During applied electric field square waves of +0.5Ec unipolar and ±0.5Ec bipolar, at 1 Hz, non-180° domain switching is found to contribute 34% and 40% of the macroscopically measured strain, respectively.
Vibrational overtone spectrum of matrix isolated cis, cis-HOONO
Authors: Zhang Xu , Nimlos Mark R. , Ellison G. Barney , Varner Mychel E. , Stanton John F.
Published: May 2007

Cis, cis-peroxynitrous acid is known to be an intermediate in atmospheric reactions between OH and NO2 as well as HOO and NO. The infrared absorption spectra of matrix-isolated cc-HOONO and cc-DOONO in argon have been observed in the range of 500–8000cm−1. Besides the seven fundamental vibrational modes that have been assigned earlier for this molecule [Zhang et al., J. Chem. Phys. 124, 084305 (2006)], more than 50 of the overtone and combination bands have been observed for cc-HOONO and cc-DOONO. Ab initio CCSD(T)/atomic natural orbital anharmonic force field calculations were used to help guide the assignments. Based on this study of the vibrational overtone transitions of cis, cis-HOONO that go as high as 8000cm−1 and the earlier paper on the vibrational fundamentals, we conclude that the CCSD(T)/ANO anharmonic frequencies seem to correct to ±35cm−1. The success of the theoretically predicted anharmonic frequencies {υ} in assigning overtone spectra of HOONO up to 8000cm−1 suggests that the CCSD(T)/ANO method is producing a reliable potential energy surface for this reactive molecule.
Electrical charge transport and energy conversion with fluid flow during electrohydrodynamic conduction pumping
Authors: Feng Yinshan , Seyed-Yagoobi Jamal
Published: May 2007

The electrohydrodynamic (EHD) conduction pumping takes advantage of the electrical Coulomb force exerted on dielectric liquid by externally applied electric field(s). The conduction term here represents a mechanism for electric current flow in which charged carriers are produced not by injection from electrodes or induction from electric fields, but by dissociation of neutral electrolytic species within the dielectric liquid. The EHD conduction pumping can be applied to drive both isothermal liquid and two-phase fluids without the degradation of the working fluid electric properties. Such nonmechanical and low-power-consumption pumping mechanism can be utilized for active flow generation/control under both terrestrial and microgravity conditions. So far, the majority of conducted studies has been focused mainly on the experimental realization of the EHD conduction pumping phenomenon and the computational fluid dynamics simulation verification. More fundamental studies, such as theoretical analysis with convection terms included, generalized nondimensional modeling, and pumping efficiency prediction, are required for a complete understanding of this new EHD pumping phenomenon. An asymptotic nondimensional theoretical model for the EHD conduction pumping has been presented in this paper, with the fluid convection taken into account. The theoretical analysis provided here reveals the effects of flow convection on the EHD conduction pumping and the associated energy transport/conversion during the pumping process. Based on the asymptotic model, the pumping efficiency of the EHD conduction pumping is analytically derived and compared with the experimental data. Such results help clarify the capabilities and limitations corresponding to the nature of the EHD conduction pumping.
Transition to turbulence in a tall annulus submitted to a radial temperature gradient
Authors: Lepiller Valérie , Prigent Arnaud , Dumouchel Fabien , Mutabazi Innocent
Published: May 2007

We have investigated the transition to turbulence in a water flow confined inside a tall vertical cylindrical annulus submitted to a radial temperature gradient using the space-time diagrams technique. As soon as a small radial temperature gradient is applied to the annular flow, the radial stratification of density induces a torque that produces a large convection cell. The first instability of this flow occurs via a supercritical bifurcation and gives rise to axisymmetric rolls localized in the middle of the system. Just above the onset, the pattern contains spatiotemporal defects. For large values of the control parameter, we have observed a coexistence of turbulent bursts and laminar domains. We have measured the turbulent fraction and have performed a statistical analysis of the laminar and turbulent zones, and have found that they bear the main characteristics of spatiotemporal intermittency.
Generalized Jarzynski’s equality in inhomogeneous Markov chains
Authors: Ge Hao , Qian Min
Published: May 2007

A rigorous mathematical theory of generalized Jarzynski’s equality in inhomogeneous Markov chains is given. Then, we explain its physical meaning and applications through several previous work including the original works of Jarzynski [Phys. Rev. Lett. 78, 2690 (1997); Phys. Rev. E 56, 5018 (1997); J. Stat. Phys. 96, 415 (1999); J. Stat. Phys. 98, 77 (2000)] and Crooks [J. Stat. Phys. 90, 1481 (1998); Phys. Rev. E 60, 2721 (1999); Phys. Rev. E 61, 2361 (2000)], Hatano-Sasa equality [Phys. Rev. E 86, 3463 (2001)], and the Gibbs free energy differences in stoichiometric chemical systems. By the way, we also consider the denumerable case.
Thermal convection in a rotating porous layer using a thermal nonequilibrium model
Authors: Malashetty M. S. , Swamy Mahantesh , Kulkarni Sridhar
Published: May 2007

Linear stability of a rotating fluid-saturated porous layer heated from below and cooled from above is studied when the fluid and solid phases are not in local thermal equilibrium. The extended Darcy model, which includes the time derivative and Coriolis terms, is employed as a momentum equation. A two-field model that represents the fluid and solid phase temperature fields separately is used for energy equation. The onset criterion for both stationary and oscillatory convection is derived analytically. It is found that a small interphase heat transfer coefficient has significant effect on the stability of the system. There is a competition between the processes of rotation and thermal diffusion that causes the convection to set in through the oscillatory mode rather than the stationary one. The rotation inhibits the onset of convection in both stationary and oscillatory mode. In addition, the effect of porosity modified conductivity ratio, Darcy-Prandtl number, and the ratio of diffusivities on the stability of the system is investigated. A weak nonlinear theory based on the truncated representation of Fourier series method is used to find the Nusselt number. The effect of thermal nonequilibrium on heat transfer is brought out. The transient behavior of the Nusselt number is also investigated by solving the finite amplitude equations using Runge-Kutta method.
Optical gain, loss, and transparency current in high performance mid-infrared interband cascade lasers
Authors: Soibel Alex , Mansour Kamjou , Qiu Yueming , Hill Cory J. , Yang Rui Q.
Published: May 2007

The net modal gain, optical loss, and transparency current of high-performance, narrow ridge waveguide interband cascade (IC) lasers have been measured using the Hakki–Paoli technique in the temperature range from T=78 to 270 K. In this temperature range, the optical loss of IC lasers increases from αw≈17 cm−1 at T=78 K to αw≈35 at T=270 K, the transparency current density rises from Itr=10 to 330 A∕cm2, and the differential gain decreases from gd≈2.2 cm∕A to gd≈0.06 cm∕A with a characteristic temperature of T0=130 K. The implications of these observed characteristics for IC lasers are discussed.
Optical properties of self-assembled Cu2O nanocrystals embedded in a polyimide layer
Authors: Jung J. H. , Kim T. W. , Song M. S. , Kim Y.-H. , Yoo K. H.
Published: May 2007

Self-assembled Cu2O nanoparticles embedded in a polyimide (PI) matrix were formed by curing Cu thin films with PI precursor layers. Transmission electron microscopy images and selected area electron diffraction patterns showed that Cu2O nanocrystals were created inside the PI layer. The excitonic peaks corresponding to the transitions from the electronic sublevel to the heavy-hole sublevel in the Cu2O nanocrystals embedded in the PI layer shifted to the lower energy side with increasing curing time, and this behavior is attributed to a decrease in the confinement effects because the size of the nanocrystals increases with the curing time. The activation energy of the electrons confined in the ground state of the Cu2O nanocrystals embedded in the PI layer, as obtained from the temperature-dependent photoluminescence spectra, was larger than that of those confined in the excited state. The present results can help us to improve understanding of the optical properties of Cu2O nanocrystals embedded in a PI layer.
The magnetic field and temperature dependences of proton spin-lattice relaxation in proteins
Authors: Goddard Yanina , Korb Jean-Pierre , Bryant Robert G.
Published: May 2007

The nuclear magnetic relaxation dispersion profiles of lyophilized globular proteins were measured in the frequency range of 10kHz–30MHz at temperatures from 156to302K. The existent theory of proton relaxation in immobilized protein systems was critically tested and expended to include contributions of rapid motions of protein side-chain groups. The new theory takes into account the strong coupling between the side-chain protons and the protein backbone, when correlation function cannot be written as a product of the contributions. The measurements showed that while the relaxation rate constant of the protein backbone protons is a linear function of the absolute temperature the side-chain groups exhibit an exponential temperature dependence corresponding to an activated process. Measurements carried out on simple homopolypeptides, polyglycine and polyalanine, provide strong support of the proposed new theory.
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transition of benzo[g,h,i]perylene in supersonic jets and rare gas matrices
Authors: Rouillé G. , Arold M. , Staicu A. , Krasnokutski S. , Huisken F. , Henning Th. , Tan X. , Salama F.
Published: May 2007

The study of the S1(A11)←S0(A11) transition of benzo[g,h,i]perylene (BghiP, C22H12) in supersonic jets and solid rare gas matrices is reported. In the jet-cooled spectrum, the origin band position is located at 25027.1±0.2cm−1, the assignment being supported by the analysis of vibrational shifts and rotational band contours. Except for the origin band, which is weak, all bands are attributed to the fundamental excitation of nontotally symmetric b1 vibrational modes of S1. The intensity pattern is interpreted as a consequence of the weak oscillator strength of the electronic transition combined with intensity-borrowing through vibronic interaction between the S1(A11) and S2(B11) states. The spectra of the S1(A11)←S0(A11) and S2(B11)←S0(A11) transitions have also been measured for BghiP in solid neon and argon matrices. The comparison of the redshifts determined for either transition reveals that the polarizability of BghiP is larger in its S2 than in its S1 state. Bandwidths of 2.7cm−1 measured in supersonic jets, which provide conditions relevant for astrophysics, are similar to those of most diffuse interstellar bands. The electronic transitions of BghiP are found to lie outside the ranges covered by present databases. From the comparison between experimental spectra and theoretical computations, it is concluded that the accuracy of empirical and ab initio approaches in predicting electronic energies is still not sufficient to identify astrophysically interesting candidates for spectroscopic laboratory studies.
A clean radiation environment for opacity measurements of radiatively heated material
Authors: Xu Yan , Zhang Jinyan , Yang Jiamin , Pei Wenbing , Ding Yongkun , Lai Donxian , Men Guangwei , Luo Zheng
Published: May 2007

A clean x-ray radiation environment is essential for detailed measurements of the opacity of high-temperature radiatively heated material. A lot of laser energy is usually needed to heat a large hohlraum to produce such a clean x-ray radiation environment. A type of target is proposed that uses low-density, low-Z foam to provide a passage to radiation while isolating the sample from the disturbance from laser produced, high-temperature, high-Z plasma and heating by reflected laser light. With a smaller hohlraum, less laser energy is needed to produce high-temperature x-ray radiation for sample heating. Experiments have been done to check the proposal. The recorded clean Al self-emission spectra proved there was no gold plasma in the view-way to disturb the measurement. This type of hohlraum can provide a high-quality work-table for opacity measurement even in a relatively small laser facility.
Influence of magnetic shear on impurity transport
Authors: Nordman H. , Fülöp T. , Candy J. , Strand P. , Weiland J.
Published: May 2007

The magnetic shear dependence of impurity transport in tokamaks is studied using a quasilinear fluid model for ion temperature gradient (ITG) and trapped electron (TE) mode driven turbulence in the collisionless limit and the results are compared with nonlinear gyrokinetic results using GYRO [J. Candy and R. E. Waltz, J. Comput. Phys 186, 545 (2003)]. It is shown that the impurity transport is sensitive to the magnetic shear, in particular for weak, negative, and large positive shear where a strong reduction of the effective impurity diffusivity is obtained. The fluid and gyrokinetic results are in qualitative agreement, with the gyrokinetic diffusivities typically a factor 2 larger than the fluid diffusivities. The steady state impurity profiles in source-free plasmas are found to be considerably less peaked than the electron density profiles for moderate shear. Comparisons between anomalous and neoclassical transport predictions are performed for ITER-like profiles [R. Aymar, P. Barabaschi, and Y. Shimomura, Plasma Phys. Controlled Fusion 44, 519 (2002)].
Infrared absorption of gaseous ClCS detected with time-resolved Fourier-transform spectroscopy
Authors: Chu Li-Kang , Han Hui-Ling , Lee Yuan-Pern
Published: May 2007

A transient infrared absorption spectrum of gaseous ClCS was detected with a step-scan Fourier-transform spectrometer coupled with a multipass absorption cell. ClCS was produced upon irradiating a flowing mixture of Cl2CS and N2 or CO2 with a KrF excimer laser at 248nm. A transient band in the region of 1160–1220cm−1, which diminished on prolonged reaction, is assigned to the C–S stretching (ν1) mode of ClCS. Calculations with density-functional theory (B3P86 and B3LYP/aug-cc-pVTZ) predict the geometry, vibrational wave numbers, and rotational parameters of ClCS. The rotational contour of the spectrum of ClCS simulated based on predicted rotational parameters agrees satisfactorily with experimental observation; from spectral simulation, the band origin is determined to be at 1194.4cm−1. Reaction kinetics involving ClCS, CS, and CS2 are discussed.
Compressional wave generation in droplets of water deposited on a quartz crystal: Experimental results and numerical calculations
Authors: Couturier G. , Boisgard R. , Jai C. , Aimé J. P.
Published: May 2007

The generation of shear and compressional waves in liquids by AT-cut quartz crystals has received much attention in the past; however, this is not the case for droplets deposited onto quartz crystals. In this paper, we investigate the compressional wave generation in droplets and use different techniques to correlate the compressional wave generation to the shape of the droplets using frequency and dissipation measurements in an oscillator circuit while using a video camera to record the shape during evaporation. A good correlation between eigenmodes predicted by a finite element method and those obtained experimentally are observed.
Ag nanoshell-induced dual-frequency electromagnetic wave absorption of Ni nanoparticles
Authors: Lee Chung-Che , Chen Dong-Hwang
Published: May 2007

The electromagnetic wave absorption properties of the epoxy resin composites containing Ni, Ag, and Ni–Ag core-shell nanoparticles were studied. Interestingly, Ni–Ag core-shell nanoparticles showed a dual-frequency absorption property in 2–18 and 18–40GHz, although Ni nanoparticles exhibited absorption only in 18–40GHz and no absorption was observed for Ag nanoparticles in the whole frequency range. The additional absorption of Ni–Ag core-shell nanoparticles in 2–18GHz might be due to the lags of polarization between the core/shell interfaces, which contributed to the dielectric loss. The frequency dependences of permittivity and permeability and the absorber thickness effect were also investigated.
Effect of removing the no-virtual-pair approximation on the correlation energy of the He isoelectronic sequence
Authors: Watanabe Yoshihiro , Nakano Haruyuki , Tatewaki Hiroshi
Published: May 2007

The correlation energies (CEs) for the He-like ions are studied with the virtual-pair approximation (VPA) and with the no-virtual-pair approximation (NVPA). In contrast to the nonrelativistic CEs, the CEs calculated with relativity fell sharply as the nuclear charge Z increased, although the CE calculated with the NVPA was considerably lower than with the VPA for the heavier atoms. It is shown that CE calculated with a Hylleraas-type function implicitly includes the effects of the excitations into negative-energy states, which corresponds to the VPA. The present results verify that the strong dependence on Z of the CE of He-like ions is an essential effect of the relativity.
Optimized effective potential method for individual low-lying excited states
Authors: Glushkov V. N. , Levy M.
Published: May 2007

This paper presents an optimized effective potential (OEP) approach based on density functional theory (DFT) for individual excited states that implements a simple method of taking the necessary orthogonality constraints into account. The amended Kohn-Sham (KS) equations for orbitals of excited states having the same symmetry as the ground one are proposed. Using a variational principle with some orthogonality constraints, the OEP equations determining a local exchange potential for excited states are derived. Specifically, local potentials are derived whose KS determinants minimize the total energies and are simultaneously orthogonal to the determinants for states of lower energies. The parametrized form of an effective DFT potential expressed as a direct mapping of the external potential is used to simplify the OEP integral equations. A performance of the presented method is examined by exchange-only calculations of excited state energies for simple atoms and molecules.
Wide frequency range capacitive detection of loss in a metallic cantilever using resonance and relaxation modes
Authors: Richert Ranko
Published: May 2007

The impedance of a capacitor which embraces a charged cantilever is used to measure the mechanical properties of the cantilever material. The technique has been tested with an amorphous metallic specimen, but is applicable for many other solids. The material damping can be measured at the resonance frequency of the cantilever via the width of the resonance curve or by recording the ring-down behavior. Additionally, several decades in frequency are accessible below the resonance frequency, where values as low as ν=0.03Hz are achieved easily. The data are analyzed with a single equation that captures the damping at all frequencies in terms of the material specific Young’s modulus E and its loss angle tanδ=E″∕E′.
Accurate particle position measurement from images
Authors: Feng Y. , Goree J. , Liu Bin
Published: May 2007

The moment method is an image analysis technique for subpixel estimation of particle positions. The total error in the calculated particle position includes effects of pixel locking and random noise in each pixel. Pixel locking, also known as peak locking, is an artifact where calculated particle positions are concentrated at certain locations relative to pixel edges. We report simulations to gain an understanding of the sources of error and their dependence on parameters the experimenter can control. We suggest an algorithm, and we find optimal parameters an experimenter can use to minimize total error and pixel locking. For a dusty plasma experiment, we find that a subpixel accuracy of 0.017pixel or better can be attained. These results are also useful for improving particle position measurement and particle tracking velocimetry using video microscopy in fields including colloids, biology, and fluid mechanics.
Catalytic chemiluminescence properties of boehmite “nanococoons”
Authors: Cao Huaqiang , Zhang Lei , Liu Xiangwen , Zhang Sichun , Liang Yu , Zhang Xinrong
Published: May 2007

There have been great interest in constructing advanced nanostructures due to the potential profit of achieving nanodevices with interesting properties; much effort has been devoted to combining biology and nanotechnology to synthesize superstructures, in shapes of higher complexity than those of low-dimensional nanostructures. The advanced nanostructures can function from sensing to emitting light or storing information. Here the authors demonstrate the self-organization of boehmite nanorods into the cocoonlike nanostructures by using glycine as reactant. The growth mechanism is described. The boehmite (γ-AlOOH) nanococoons exhibit excellent sensitivity to ethanol vapor with rapid, stable, and reversible characteristics as catalytic chemiluminescence nanosensors.
Evidence for trap-limited transport in the subthreshold conduction regime of chalcogenide glasses
Authors: Ielmini Daniele , Zhang Yuegang
Published: May 2007

The study of the temperature dependence of subthreshold conduction in amorphous chalcogenide materials reveals a voltage dependent activation energy, which can be attributed to trap-limited conduction. The authors find that the features of subthreshold conduction regime (subthreshold slope and activation energy) can be quantitatively explained by a simple conduction model for Poole-Frenkel transport in the presence of a high concentration of traps. This analysis allows for an accurate prediction of the temperature and voltage dependence of subthreshold current in amorphous chalcogenides, and offers a simple scheme for estimating the average distance between traps in the disordered material.
Conductivity-dependency-free in-plane poling for Mach-Zehnder modulator with highly conductive electro-optic polymer
Authors: Song Reem , Yick Andrew , Steier William H.
Published: May 2007

This letter presents the in-plane poling in electro-optic (EO) polymer modulators with conductivity dependency of core and claddings eliminated. A Mach-Zehnder (MZ) modulator with a highly conductive EO polymer, AJLS102/APC, is realized and poled by the in-plane coplanar waveguide poling electrode. Vπ of 7.7V in a single-arm poled MZ (3.8V for push-pull operation) is achieved and the evaluated r33 is 65pm∕V. Combined with the r33’s of the previously measured single layers and MZ modulators using two other EO polymers, this experiment proves that the r33 proportional to the single layer r33 can be achieved in an in-plane MZ device regardless of the material conductivities.
Passive in vivo elastography from skeletal muscle noise
Authors: Sabra Karim G. , Conti Stephane , Roux Philippe , Kuperman W. A.
Published: May 2007

Measuring the in vivo elastic properties of muscles (e.g., stiffness) provides a means for diagnosing and monitoring muscular activity. The authors demonstrated a passive in vivo elastography technique without an active external radiation source. This technique instead uses cross correlations of contracting skeletal muscle noise recorded with skin-mounted sensors. Each passive sensor becomes a virtual in vivo shear wave source. The results point to a low-cost, noninvasive technique for monitoring biomechanical in vivo muscle properties. The efficacy of the passive elastography technique originates from the high density of cross paths between all sensor pairs, potentially achieving the same sensitivity obtained from active elastography methods.
Ytterbium and chromium doped composite Y3Al5O12 ceramics self-Q-switched laser
Authors: Dong Jun , Shirakawa Akira , Ueda Ken-ichi , Yagi Hideki , Yanagitani Takagimi , Kaminskii Alexander A.
Published: May 2007

Composite Yb:Y3Al5O12∕Cr:Y3Al5O12 ceramics were fabricated by using vacuum sintering technique and nanocrystalline technology. Self-Q-switched composite Yb:Y3Al5O12∕Cr:Y3Al5O12 ceramic lasers with pulse energy of 125μJ and peak power of over 105kW at repetition rate of 3.8kHz have been demonstrated. Nearly diffraction-limited beam quality with M2 less than 1.35 was achieved in this composite Yb:Y3Al5O12∕Cr:Y3Al5O12 ceramic self-Q-switched lasers.
Design of molecular wires based on one-dimensional coordination polymers
Authors: Alexandre Simone S. , Soler José M. , Sanz Miguel Pablo J. , Nunes R. W. , Yndurain Félix , Gómez-Herrero Júlio , Zamora Félix
Published: May 2007

The authors report the results of ab initio calculations for the structural and electronic properties of one-dimensional coordination polymers with the general formula [M(6-MP)2]n (where 6-MP=6-mercaptopurinate, and M=MnII, FeII, CoII, NiII, and CuII). A common stable structure, consistent with the experimental data for [Cd(6-MP)2]n, is found for all metal cations studied, with the exception of MnII. Polymers containing FeII, NiII, and CoII are found to be ferromagnetic semiconductors, while [Cu(6-MP)2]n shows a Peierls-unstable paramagnetic metallic phase that undergoes a transition to a ferromagnetic semiconductor one under small stretching.
Ordered Ni nanohole arrays with engineered geometrical aspects and magnetic anisotropy
Authors: Navas D. , Hernández-Vélez M. , Vázquez M. , Lee W. , Nielsch K.
Published: May 2007

Ni nanohole arrays are prepared by a replication process involving sputtering, polymer molding pressing, and electroplating techniques, using anodic alumina membranes as templates. Nanohole diameter to interhole distance ratio is engineered by suitable template processing. From the analysis of the magnetization curves for increasing nanohole diameter, it is concluded that coercivity increases due to the pinning of domain walls to nanoholes, while in-plane anisotropy decreases owing to local shape anisotropy effects.
2-phosphor-converted white light-emitting diodes using oxynitride/nitride phosphors
Authors: Xie Rong-Jun , Hirosaki Naoto , Kimura Naoki , Sakuma Ken , Mitomo Mamoru
Published: May 2007

Green α-sialon:Yb2+ and red Sr2Si5N8:Eu2+ oxynitride/nitride phosphors have been demonstrated as potential downconversion luminescent materials for white light-emitting diodes (LEDs). In this letter, the authors attempt to fabricate white LEDs by combining α-sialon:Yb2+ and Sr2Si5N8:Eu2+ with a blue LED die and report their optical properties. These two phosphors lend themselves for use in 2-phosphor-converted white LEDs with promising properties: a wide range of tunable correlated color temperature (2700–6700K), acceptable color rendering index (82–83), and luminous efficacy (17–23lm∕W). These LEDs are acceptable for general lighting.
Superhydrophobic spiral Co3O4 nanorod arrays
Authors: Guo Zhi-guang , Liu Wei-min
Published: May 2007

The authors report a facile method for the fabrication of a superhydrophobic surface with spiral Co3O4 nanorod arrays on a glass wafer plated Au. The resulting surface shows superhydrophobicity with a static contact angle of about (162±1.6)° and a sliding angle of around (5±2)°. This functionalized, nanostructured surface provides enhanced understanding of the effect of the surface roughness and solid surface fraction on superhydrophobicity, rendering them well suited for various potential applications such as in catalysts, dyes or inks, coatings, fillers, and microreactors.
Charge redistribution at YBa2Cu3O7-metal interfaces
Authors: Schwingenschlögl U. , Schuster C.
Published: May 2007

Charge redistribution at interfaces is crucial for electronic applications of high-Tc superconductors, since the band structure is modified on a local scale. The authors address the normal-state electronic structure of YBa2Cu3O7 (YBCO) at an YBCO-metal contact by first principles calculations for prototypical interface configurations. They derive quantitative results for the intrinsic doping of the superconducting CuO2 planes due to the metal contact. Their findings can be explained in terms of a band-bending mechanism, complemented by local screening effects. The authors determine a net charge transfer of 0.09–0.13 electrons in favor of the intraplane Cu sites, depending on the interface orientation.
Vacuum ultraviolet laser pulsed field ionization-photoelectron study of allyl radical CH2CHCH2
Authors: Xing Xi , Reed Beth , Lau Kai-Chung , Ng C. Y. , Zhang Xu , Barney Ellison G.
Published: May 2007

The pulsed field ionization-photoelectron (PFI-PE) spectrum of allyl radical CH2CHCH2 (C3H5) in the energy range of 65200–66600cm−1 has been measured using vacuum ultraviolet laser. Based on the simulation of the rotational structures resolved in the vibrational PFI-PE bands of C3H5+(X̃A11;00+andν7+=1), the ionization energies (IEs) of C3H5(X̃A22;00) to form C3H5+(X̃A11;00+andν7+=1) are determined to be 65584.6±2.0cm−1 (8.13146±0.00025eV) and 66020.9±2.0cm−1 (8.18556±0.00025eV), respectively, where ν7+(a1) is the symmetric C–C–C bending mode of C3H5+(X̃A11). These values are compared to IE(C3H5) values obtained in previous experimental and high-level ab initio quantum theoretical studies.