bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of rate and state friction formalism and flash melting to thin permanent slip zones of major faults
Authors: Sleep Norman H.
Published: May 2010

Strain within certain major exhumed fault zones concentrated within a ∼1 mm wide permanent slip zone. A surrounding 10 mm thick fault core is strongly damaged. Concentration of seismic strain rate within a very thin zone is expected both for rate and state friction and weakening of the slip zone by flash melting at real contacts. In both cases, the material at the rupture tip begins with a strength that is far above that for steady state sliding. The permanent slip zone is slightly weaker than its surroundings and begins to slip with a strain rate faster than the surrounding core. Damage from strain thus weakens the sliding zone more than the fault core further concentrating strain rate toward a minimum thickness that depends on the finite size of grains. Flash heating involves a weakening velocity that is the product of a material property, the weakening strain rate, and the slip zone thickness. There is a minimum strength associated with a sliding velocity ∼15 m s−1, where stresses at the crack tip just exceed the elastic limit. Higher sliding velocities imply large inelastic strains near the rupture tip that would add to macroscopic friction. Lower sliding velocities imply higher coefficients of friction, as flash weakening is velocity weakening. The width of the PSZ should organize to a finite value so its weakening velocity is that needed to give the sliding velocity for minimum strength.
Hydrothermal fluid flow within a tectonically active rift‐ridge transform junction: Tjörnes Fracture Zone, Iceland
Authors: Lupi M. , Geiger S. , Graham C. M.
Published: May 2010

We investigate the regional fluid flow dynamics in a highly faulted transform area, the Tjörnes Fracture Zone in northern Iceland which is characterized by steep geothermal gradients, hydrothermal activity, and strong seismicity. We simulate fluid flow within the Tjörnes Fracture Zone using a high‐resolution model that was based on the available geological and geophysical data and has the aim to represent the complex geological structures and the thermodynamical processes that drive the regional fluid flow in a physically realistic way. Our results show that convective heat flow and mixing of cold and saline seawater with deep hydrothermal fluids controls the large‐scale fluid flow. The distribution of faults has a strong influence on the local hydrodynamics by focusing flow around clusters of faults. This explains the nature of isolated upflow zones of hot hydrothermal fluids which are observed in the Tjörnes Fracture Zone. An important emergent characteristic of the regional fluid flow in the Tjörnes Fracture Zone are two separate flow systems: one in the sedimentary basins, comprising more vigorous convection, and one in the crystalline basement, which is dominated by conduction. These two flow systems yield fundamental insight into the connection between regional hydrothermal fluid flow and seismicity because they form the basis of a toggle switch mechanism that is thought to have caused the hydrogeochemical anomalies recorded at Húsavik before and after the 5.8 M earthquake in September 2002.
Potential effects of pollen from stacked Bt maize on non-target Lepidoptera in agrarian systems
Authors: Schuppener Mechthild , Slusarenko Alan , Rauschen Stefan
Published: May 2010

The cultivation of genetically engineered (GE) maize expressing Lepidopteran specific Bt proteins poses potential risk for non-target butterflies. Pollen is dispersed by wind in the surroundings of maize fields, deposited on weeds and taken up by non-target butterfly lavae. While MON810 contains low concentrations of Bt protein in pollen, this is not necessarily true for new GE maize lines.Species appropriate for a post market environmental monitoring (PMEM) should (i) have a small host range to ensure a comprehensive inventory, (ii) be representative and (iii) be common in agrarian landscapes. Rare species seem to be inappropriate (Aviron et al. 2009). We selected the Small Tortoiseshell (Aglais urticae) and the Peacock (Inachis io) the larvae of which are monophage on the Stinging nettle (Urtica dioica). We analysed the suitability of these species for PMEM by mapping patches of U. dioica and populations of the butterflies in two different agrarian regions of Germany during maize anthesis.There was high temporal variability in the occurrence of butterflies and in the spatial distribution of U. dioica patches. In general, methods and species used seem to be appropriate for PMEM.
Spin excitations in layered cuprates: a Fermi-liquid approach
Authors: Eremin I. , Manske D.
Published: May 2010

We review some important aspects of the doping dependence of many physical properties of the high-Tc cuprates based on a Fermi liquid-like approach. In particular, we show that the spin-fluctuation mechanism of superconductivity on the basis of a microscopic Eliashberg approach supports the idea that the symmetry of the superconducting order parameter is of the dx2−y2 -wave type. Furthermore, the renormalization of the quasiparticle spectrum caused by the scattering on spin fluctuations results in the so-called kink feature seen in ARPES. The peculiar momentum dependence of the spin fluctuations will result in a strong anisotropy of the renormalization at different parts of the first Brillouin zone and thus will lead to a strong anisotropy of the kink. Another important achievement of the microscopic Eliashberg approach is that the spin excitation spectrum renormalizes strongly below Tc due to the occurrence of superconductivity with a dx2−y2 -wave order parameter, which yields to the formation of the so-called resonance peak that can be viewed as a spin exciton. The topology of the Fermi surface and the momentum dependence of the superconducting gap explains the peculiar dispersion of the resonance peak, in good agreement with experiments.
Microwave Spectral Tables I. Diatomic Molecules
Authors: Lovas Frank J. , Tiemann Eberhard
Published: May 2010

All of the rotational spectral lines observed and reported in the open literature for 83 diatomic molecules have been tabulated. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty, and reference are given for each transition reported. In addition to rectifying a number of misprints and errors in the literature cited, the spectral lines for approximately 20 molecules have been reanalyzed to produce a comprehensive and consistent analysis of all the data extracted from various literature sources. The derived molecular properties, such as rotational constants, hyperfine structure constants, electric dipole moments, rotational g-factors and internuclear distances are listed with one standard deviation uncertainties for all species.
Ground Levels and Ionization Potentials for Lanthanide and Actinide Atoms and Ions
Authors: Martin W. C. , Hagan Lucy , Reader Joseph , Sugar Jack
Published: May 2010

Values of the first four ionization potentials of the lanthanides (Z=57–71) and of Hf have been compiled. All except the value for neutral Hf are based on spectroscopic data. The spectroscopic designations of the ground levels of the neutral through triply ionized atoms (Z=57–72) are also tabulated. A similar compilation for the actinides (Z=89–103) lists Sugar's recent values for the first ionization potentials through No (Z=102). Accurate spectroscopic ionization potentials have been determined for only two of the actinide ions (Ac+ and Th3+). The ground-level designations for the neutral through triply ionized actinides are given where they are known or can be predicted with near certainty. A selection of references to the most complete and most recent work on the analyses of the optical spectra of the neutral through triply ionized lanthanide and actinide elements is included.
Real Z2-bigradings, Majorana modules, and the standard model action
Authors: Tolksdorf Jürgen
Published: May 2010

The action functional of the standard model of particle physics is intimately related to a specific class of first order differential operators called Dirac operators of Pauli type (“Pauli–Dirac operators”). The aim of this article is to carefully analyze the geometrical structure of this class of Dirac operators on the basis of real Dirac operators of simple type. On the basis of simple type Dirac operators, it is shown how the standard model action (STM action) may be viewed as generalizing the Einstein–Hilbert action in a similar way that the Einstein–Hilbert action is generalized by a cosmological constant. Furthermore, we demonstrate how the geometrical scheme presented allows to naturally incorporate also Majorana mass terms within the standard model. For reasons of consistency, these Majorana mass terms are shown to dynamically contribute to the Einstein–Hilbert action by a “true” cosmological constant. Due to its specific form, this cosmological constant can be very small. Nonetheless, this cosmological constant may provide a significant contribution to dark matter/energy. In the geometrical description presented, this possibility arises from a subtle interplay between Dirac and Majorana masses.
On the mixing property for a class of states of relativistic quantum fields
Authors: Jäkel Christian D. , Narnhofer Heide , Wreszinski Walter F.
Published: May 2010

Let ω be a factor state on the quasilocal algebra A of observables generated by a relativistic quantum field, which, in addition, satisfies certain regularity conditions [satisfied by ground states and the recently constructed thermal states of the P(ϕ)2 theory]. We prove that there exist space- and time-translation invariant states, some of which are arbitrarily close to ω in the weak  ∗ topology, for which the time evolution is weakly asymptotically Abelian.
The split algebras and noncompact Hopf maps
Authors: Hasebe Kazuki
Published: May 2010

We develop a noncompact version of the Hopf maps based on the split algebras. The split algebras consist of three species: split-complex numbers, split quaternions, and split octonions. They correspond to three noncompact Hopf maps that represent topological maps between hyperboloids in different dimensions with hyperboloid bundle. We realize such noncompact Hopf maps in two ways: one is to utilize the split-imaginary unit, and the other is to utilize the ordinary imaginary unit. Topological structures of the hyperboloid bundles are explored, and the canonical connections are naturally regarded as noncompact gauge field of monopoles.
Determination of layer-thickness variation in periodic multilayer by x-ray reflectivity
Authors: Jiang Hui , Zhu Jingtao , Xu Jing , Wang Xiaoqiang , Wang Zhanshan , Watanabe Makoto
Published: May 2010

A method basically determining individual layer thicknesses in actual periodic multilayers has been developed, that solves simultaneous equations of positions of peaks appearing in wavelet transform curve of x-ray grazing incidence reflectivity. The determination was demonstrated on a Ni/C periodic multilayer fabricated by magnetron sputtering. Using the layer thicknesses obtained by the method, further accurate of thickness, roughness, and density of each layer was performed by Parratt’s model. The special feature that the topmost and bottom-most layers were thicker than other layers was clearly observed. The former is attributed to oxidation and the latter is attributed to the effect of deposition on thick substrate. The mean fluctuations of other layers are 2.6% in C layers and 4.2% in Ni layers attributed to random fluctuations at deposition. Numerical analysis and statistical hypothesis tests have been carried out to discuss noncumulative and cumulative layer-thickness fluctuations in fabrication process.
Dependence of the properties of phase change random access memory on nitrogen doping concentration in Ge2Sb2Te5
Authors: Fang Lina Wei-Wei , Zhao Rong , Li Minghua , Lim Kian-Guan , Shi Luping , Chong Tow-Chong , Yeo Yee-Chia
Published: May 2010

The dependence of the electrical properties of Ge2Sb2Te5 on nitrogen doping concentration was investigated, which was explained based on the trends in the materials properties of nitrogen-doped Ge2Sb2Te5. The effect of nitrogen doping in Ge2Sb2Te5 on the crystallization temperature and changes upon annealing with various nitrogen concentrations were thus exploited to explain the trends. X-ray diffraction analysis corroborates the necessity to transform to the metastable face-centered-cubic phase, and showed that direct conversion to the stable hexagonal-close-packed phase which occurs at higher nitrogen concentrations could adversely affect device performance. Approaches for enhancement of thermal stability and reduction in reset current in phase change memory devices were also discussed.
White luminescence from single-layer devices of nonresonant polymer blends
Authors: Brovelli Sergio , Guan Hao , Winroth Gustaf , Fenwick Oliver , Di Stasio Francesco , Daik Rusli , Feast W. James , Meinardi Francesco , Cacialli Franco
Published: May 2010

Poly(9,9′-dioctyl fluorene) (F8) and poly(4,4′-diphenylene diphenylvinylene) (PDPV) are conjugated polymers with optical transitions that are nonresonant thanks to the particular structural features of PDPV that yield a very large Stokes’ shift (∼1.14 eV) between absorption and emission spectra. We present steady-state and time-resolved photoluminescence (PL) experiments showing that F8:PDPV blends are “optically disconnected” systems for which the emission spectra and PL quantum yields are the linear combination of the contributions of the individual constituents with weights given by the respective absorption coefficients and concentration in the films. Single-layer light-emitting diodes incorporating F8:PDPV blends show white electroluminescence resulting from the simultaneous exploitation of the spectral features of both blend constituents (Commission Internationale de l’Eclairage, CIE, coordinates: x=0.27 and y=0.36, in the case of 8:2 F8:PDPV molar ratio).
Dynamics simulation of N2 scattering onto W(100,110) surfaces: A stringent test for the recently developed flexible periodic London–Eyring–Polanyi–Sato potential energy surface
Authors: Martin-Gondre L. , Crespos C. , Larregaray P. , Rayez J. C. , van Ootegem B. , Conte D.
Published: May 2010

An efficient method to construct the six dimensional global potential energy surface (PES) for two atoms interacting with a periodic rigid surface, the flexible periodic London–Eyring–Polanyi–Sato model, has been proposed recently. The main advantages of this model, compared to state-of-the-art interpolated ab initio PESs developed in the past, reside in its global nature along with the small number of electronic structure calculations required for its construction. In this work, we investigate to which extent this global representation is able to reproduce the fine details of the scattering dynamics of N2 onto W(100,110) surfaces reported in previous dynamics simulations based on locally interpolated PESs. The N2/W(100) and N2/W(110) systems are chosen as benchmarks as they exhibit very unusual and distinct dissociative adsorption dynamics although chemically similar. The reaction pathways as well as the role of dynamic trapping are scrutinized. Besides, elastic/inelastic scattering dynamics including internal state and angular distributions of reflected molecules are also investigated. The results are shown to be in fair agreement with previous theoretical predictions.
Nonlocal formulation of the Reynolds equation for rarefied gas flow with steep pressure variation
Authors: Shen Sheng , Yang Ronggui , Chen Gang , Crone Robert M. , Anaya-Dufresne Manuel
Published: May 2010

The current formulation of the Reynolds equation for lubrication problems in the rarefied gas flow regime breaks down when the pressure varies rapidly in the flow direction, which could often happen in the complicated modern hard-disk drive air bearings. In this paper the effect of rapid pressure change in a small distance is examined using a new nonlocal formulation of rarefied Poiseuille flow. The new formulation couples the pressure distribution and the velocity distributions via the Reynolds equation. Detailed numerical strategies required to solve the nonlocal pressure field are explained by analyzing a particular slider structure. Comparisons of the pressure field calculated using the proposed nonlocal formulation with the pressure predicted by the local formulation reveal significant differences between them in the region of large pressure variation. The nonlocal effect discussed in this paper could be significant for certain disk-drive air-bearing design that involves large pressure variations.
Higher-order eigenmodes of qPlus sensors for high resolution dynamic atomic force microscopy
Authors: Tung Ryan C. , Wutscher Thorsten , Martinez-Martin David , Reifenberger Ronald G. , Giessibl Franz , Raman Arvind
Published: May 2010

The time response of tuning-fork based sensors can be improved by operating them at higher eigenmodes because a measurement takes at least one oscillation cycle in dynamic force microscopy and the oscillation period of the second eigenmode is only about one sixth of the fundamental mode. Here we study the higher-order eigenmodes of quartz qPlus sensors [Bettac et al., Nanotechnology 20, 264009 (2009); Giessibl and Reichling, Nanotechnology 16, S118 (2005); Giessibl, Appl. Phys. Lett. 76, 1470 (2000); and Giessibl, Appl. Phys. Lett. 73, 3956 (1998)], their equivalent stiffness, and piezoelectric sensitivity, while paying special attention to the influence of the mass and rotary inertia of the sensing tip which is attached to the end of the qPlus quartz cantilever. A combination of theoretical modeling and scanning laser Doppler vibrometry is used to study the eigenmodes of qPlus sensors with tungsten tips. We find that the geometry of tungsten tips can greatly influence the shape, equivalent stiffness, and piezoelectric sensitivity of the second eigenmode of the quartz cantilever. At a critical tip length it is possible to theoretically achieve infinite equivalent stiffness and infinite piezoelectric sensitivity when the tip becomes a perfect node of vibration and beyond this critical tip length the second eigenmode loses its vibration node and the trajectory of the tip reverses with respect to the beam curvature. The findings have major implications for optimizing tip geometry for high-resolution imaging with qPlus sensors using higher eigenmodes.
Investigation of vortex shedding behind a porous square cylinder using lattice Boltzmann method
Authors: Babu V. , Narasimhan Arunn
Published: May 2010

Incompressible, two-dimensional flow around a porous square cylinder placed in an infinite stream is simulated using the d2q9i model of the lattice Boltzmann method. The Reynolds number (based on the height of the cylinder) is kept at 100. The porosity ϕ of the cylinder is varied from 0.25 to 0.9 and permeability through the Darcy number Da from 0.0001 to 0.1. The velocity data at a point downstream of the cylinder are collected at each time step. Discrete Fourier transform analysis of this data is carried out to extract the dominant frequencies of the unsteady flow field behind the cylinder. Strouhal numbers (St) calculated using these dominant frequencies are compared with those of corresponding solid cylinder to bring out the effect of the porous medium on the wake structure and the vortex shedding. At Re=100, as the nondimensional permeability Da is increased from the solid cylinder limit, more flow results through the porous cylinder. The reduction in the value of the dominant frequency with increasing porous medium permeability Da and porosity ϕ indicates a substantial reduction in the vortex shedding. Corresponding static pressure plots and St values corroborate this observation at Re=100 and 200.
Kinetic model for ion pressure perturbations in inhomogeneous laser-matter interactions
Authors: Keskinen M. J.
Published: May 2010

A Boltzmann–Vlasov Fokker–Planck model is used to characterize the evolution of ion pressure perturbations from nonuniform laser deposition in a plasma slab. It is found that significant reduction and smoothing of ion pressure perturbations from nonuniform optically smoothed single beam laser deposition can be achieved on hydrodynamic time scales over a range of scale sizes. In addition, it is observed that the ion Fokker–Planck model predicts more smoothing of the ion pressure perturbations from the critical to ablation surface than the ion fluid model.
A high-efficiency spin-resolved photoemission spectrometer combining time-of-flight spectroscopy with exchange-scattering polarimetry
Authors: Jozwiak C. , Graf J. , Lebedev G. , Andresen N. , Schmid A. K. , Fedorov A. V. , El Gabaly F. , Wan W. , Lanzara A. , Hussain Z.
Published: May 2010

We describe a spin-resolved electron spectrometer capable of uniquely efficient and high energy resolution measurements. Spin analysis is obtained through polarimetry based on low-energy exchange scattering from a ferromagnetic thin-film target. This approach can achieve a similar analyzing power (Sherman function) as state-of-the-art Mott scattering polarimeters, but with as much as 100 times improved efficiency due to increased reflectivity. Performance is further enhanced by integrating the polarimeter into a time-of-flight (TOF) based energy analysis scheme with a precise and flexible electrostatic lens system. The parallel acquisition of a range of electron kinetic energies afforded by the TOF approach results in an order of magnitude (or more) increase in efficiency compared to hemispherical analyzers. The lens system additionally features a 90° bandpass filter, which by removing unwanted parts of the photoelectron distribution allows the TOF technique to be performed at low electron drift energy and high energy resolution within a wide range of experimental parameters. The spectrometer is ideally suited for high-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES), and initial results are shown. The TOF approach makes the spectrometer especially ideal for time-resolved spin-ARPES experiments.
Growth, microstructure, and field-emission properties of synthesized diamond film on adamantane-coated silicon substrate by microwave plasma chemical vapor deposition
Authors: Tiwari Rajanish N. , Chang Li
Published: May 2010

Diamond nucleation on unscratched Si surface is great importance for its growth, and detailed understanding of this process is therefore desired for many applications. The pretreatment of the substrate surface may influence the initial growth period. In this study, diamond films have been synthesized on adamantane-coated crystalline silicon {100} substrate by microwave plasma chemical vapor deposition from a gaseous mixture of methane and hydrogen gases without the application of a bias voltage to the substrates. Prior to adamantane coating, the Si substrates were not pretreated such as abraded/scratched. The substrate temperature was ∼530 °C during diamond deposition. The deposited films are characterized by scanning electron microscopy, Raman spectrometry, x-ray diffraction, and x-ray photoelectron spectroscopy. These measurements provide definitive evidence for high-crystalline quality diamond film, which is synthesized on a SiC rather than clean Si substrate. Characterization through atomic force microscope allows establishing fine quality criteria of the film according to the grain size of nanodiamond along with SiC. The diamond films exhibit a low-threshold (55 V/μm) and high current-density (1.6 mA/cm2) field-emission (FE) display. The possible mechanism of formation of diamond films and their FE properties have been demonstrated.
Three-stage evolution of dynamic hysteresis scaling behavior in 63PbTiO3−37BiScO3 bulk ceramics
Authors: Yu Gang , Dong Xianlin , Wang Genshui , Cao Fei , Chen Xuefeng , Nie Hengchang
Published: May 2010

The ferroelectric hysteresis loops of 63PbTiO3−37BiScO3 ceramics were measured under sinusoidal electric fields in the range of frequency from 0.1 to 100 Hz and field from 5 to 55 kV/cm. The fitting results showed two linear relations existed between the logarithm of hysteresis area ⟨A⟩ and the logarithm of the amplitude of field E0 in the first and third field region. In the second region, no linear relation existed due to polarization reversal. These three-stage behaviors were distinct from the existing two-stage behaviors. The slopes in the third stage increase with the increasing of frequency, which can be attributed to dielectric loss under high frequency.
Voltage oscillation associated with nonlinear conductivity in the organic conductor α-(BEDT-TTF)2I3
Authors: Tamura Kozo , Ozawa Tatsuhiko , Bando Yoshimasa , Kawamoto Tadashi , Mori Takehiko
Published: May 2010

Characteristic voltage oscillation phenomenon is observed in an organic conductor α-[bis(ethylenedithio)tetrathiafulvalene]2I3, in the nonlinear conductivity region below the metal-insulator transition at 135 K. The oscillation, which is clearly visible in the wave form, appears only when the current is applied in the direction of the charge alternation in the two-dimensional stripe charge order. The frequency of order 10 kHz increases linearly with the applied current. These aspects are interpreted from the viewpoint of collective motion of the two-dimensional charge order.
Unraveling dielectric and electrical properties of ultralow-loss lead magnesium niobate titanate pyrochlore dielectric thin films for capacitive applications
Authors: Zhu X. H. , Defaÿ E. , Suhm A. , Fribourg-Blanc E. , Aïd M. , Zhu J. L. , Xiao D. Q. , Zhu J. G.
Published: May 2010

PbO – MgO – Nb 2 O 5 – TiO 2 (PMNT) pyrochlore thin films were prepared on Pt-coated silicon substrates by radio-frequency magnetron sputtering and postdeposition annealing method. Very interestingly, these pyrochlore-structured PMNT thin films exhibited ultralow dielectric losses, with a typical loss tangent as low as 0.001, and relatively high dielectric constants, typically εr∼170. It was found that the relative permittivity slightly but continuously increased upon cooling without any signature of a structural phase transition, displaying a quantum paraelectriclike behavior; meanwhile, the PMNT pyrochlore thin films did not show any noticeable dielectric dispersion in the real part of permittivity over a wide temperature range (77–400 K). Their dielectric responses could, however, be efficiently tuned by applying a dc electric field. A maximum applied bias field of 1 MV/cm resulted in a ∼20% tunability of the dielectric permittivity, giving rise to a fairly large coefficient of the dielectric nonlinearity, ∼2.5×109 J C−4 m−5. Moreover, the PMNT pyrochlore films exhibited superior electrical insulation properties with a relatively high breakdown field (Ebreakdown∼1.5 MV/cm) and a very low leakage current density of about 8.2×10−7 A/cm2 obtained at an electric field intensity as high as 500 kV/cm.
Performance analysis of a vacuum thermionic refrigerator with external heat transfer
Authors: Chen Lingen , Ding Zemin , Sun Fengrui
Published: May 2010

A model of a vacuum thermionic refrigerator with external heat transfer is proposed. The general expressions for cooling load and coefficient of performance (COP) are derived using the combination of finite time thermodynamics and nonequilibrium thermodynamics. The optimum regions of cooling load and COP are obtained and the effect of the heat reservoir temperature on the optimal performance of the device is analyzed by detailed numerical examples. The effects of work function on the cooling load and COP performances of the thermionic device are also investigated. By comparing the results obtained herein with those using the traditional analysis without considering external heat transfer, it is shown that the present analysis is more practical for real vacuum thermionic devices. The results may provide guidelines for the design and application of practical thermionic refrigerators
The dependence of the virtual cathode in a Polywell™ on the coil current and background gas pressure
Authors: Carr Matthew , Khachan Joe
Published: May 2010

Floating potential measurements have been carried out on a Polywell™ inertial electrostatic confinement device that uses magnetic cusps to trap electrons and establish a virtual cathode. In particular, the dependence of the floating potential on the coil current and background gas pressure was studied. The magnetic field coils were driven by a pulsed current supply and it was found that the virtual cathode could only be established within a narrow range of currents. In addition, it was shown that the magnitude of the floating potential increased with decreasing background gas pressure. It is conjectured that the depth of the virtual cathode and its lifetime are dependent on the magnitude of the injected electron current.
Thin films flowing down inverted substrates: Two dimensional flow
Authors: Lin Te-Sheng , Kondic Lou
Published: May 2010

We consider free surface instabilities of films flowing on inverted substrates within the framework of lubrication approximation. We allow for the presence of fronts and related contact lines and explore the role which they play in instability development. It is found that a contact line, modeled by a commonly used precursor film model, leads to free surface instabilities without any additional natural or excited perturbations. A single parameter D=(3 Ca)1/3cot α, where Ca is the capillary number and α is the inclination angle, is identified as a governing parameter in the problem. This parameter may be interpreted to reflect the combined effect of inclination angle, film thickness, Reynolds number, and fluid flux. Variation of D leads to change in the wavelike properties of the instabilities, allowing us to observe traveling wave behavior, mixed waves, and the waves resembling solitary ones.
Electrometry using the quantum Hall effect in a bilayer two-dimensional electron system
Authors: Ho L. H. , Taskinen L. J. , Micolich A. P. , Hamilton A. R. , Atkinson P. , Ritchie D. A.
Published: May 2010

We discuss the development of a sensitive electrometer that utilizes a two-dimensional electron gas (2DEG) in the quantum Hall regime. As a demonstration, we measure the evolution of the Landau levels in a second, nearby 2DEG as the applied perpendicular magnetic field is changed, and extract an effective mass for electrons in GaAs that agrees within experimental error with previous measurements.
Strain-enhanced photoluminescence from Ge direct transition
Authors: Cheng T.-H. , Peng K.-L. , Ko C.-Y. , Chen C.-Y. , Lan H.-S. , Wu Y.-R. , Liu C. W. , Tseng H.-H.
Published: May 2010

Strong enhancement of Ge direct transition by biaxial-tensile strain was observed. The reduction in band gap difference between the direct and indirect valleys by biaxial tensile strain increases the electron population in the direct valley, and enhances the direct transition. The band gap reduction in the direct and indirect valleys can be extracted from the photoluminescence spectra and is consistent with the calculations using k⋅p and deformation potential methods for conduction bands and valence bands, respectively.
An optofluidic volume refractometer using Fabry–Pérot resonator with tunable liquid microlenses
Authors: Chin L. K. , Liu A. Q. , Lim C. S. , Lin C. L. , Ayi T. C. , Yap P. H.
Published: May 2010

This letter reports the development of an optofluidic Fabry–Pérot (FP) resonator, which consists of a microcavity and a pair of liquid microlenses. The microcavity forms part of the microchannel to facilitate sample injection. The liquid microlenses are used for efficient light coupling from the optical fiber to the microcavity. The liquid microlens collimates the diverging light from the optical fiber into the FP cavity, which provides real-time tuning to obtain the highest possible finesse up to 18.79. In volume refractive index measurement, a sensitivity of 960 nm per refractive index unit (RIU) and a detection range of 0.043 RIU are achieved.
Laser-driven plasma jets propagating in an ambient gas studied with optical and proton diagnostics
Authors: Gregory C. D. , Loupias B. , Waugh J. , Dono S. , Bouquet S. , Falize E. , Kuramitsu Y. , Michaut C. , Nazarov W. , Pikuz S. A. , Sakawa Y. , Woolsey N. C. , Koenig M.
Published: May 2010

The results of an experiment to propagate laser-generated plasma jets into an ambient medium are presented. The jets are generated via laser irradiation of a foam-filled cone target, the results and characterization of which have been reported previously [Loupias et al., Phys. Rev. Lett. 99, 265001 (2007)] for propagation in vacuum. The introduction of an ambient medium of argon at varying density is seen to result in the formation of a shock wave, and the shock front displays perturbations that appear to grow with time. The system is diagnosed with the aid of proton radiography, imaging the perturbed structure in the dense parts of the shock with high resolution.
Locality properties of the energy flux in magnetohydrodynamic turbulence
Authors: Domaradzki J. Andrzej , Teaca Bogdan , Carati Daniele
Published: May 2010

The scale locality functions, originally introduced by Kraichnan for hydrodynamic turbulence, are computed from results of direct numerical simulations of forced magnetohydrodynamic turbulence. It is found that asymptotically the dynamics is dominated by local interactions, but the locality is much weaker than in hydrodynamic turbulence, which is characterized by the scaling exponent of 4/3. Specifically, in magnetohydrodynamic turbulence, two distinct exponents are observed, 1/3 and 2/3. Despite that, direct numerical simulation results reported in this paper exhibit strong coupling between large scales from the forcing band and smallest resolved scales because the locality is too weak to achieve decoupling for the numerical resolution available.
Hyperfine fields in nanocrystalline Fe–Zr–B probed by F57e nuclear magnetic resonance spectroscopy
Authors: Miglierini Marcel , Lančok Adriana , Kohout Jaroslav
Published: May 2010

In nanocrystalline Fe90Zr7B3, hyperfine fields belonging to the amorphous residual matrix are distinguished from those of bcc-Fe nanograins by nuclear magnetic resonance spectroscopy on F57e nuclei. With this technique, the nanograins located in magnetic domains can be distinguished from those positioned in domain walls. Structural features of core and surface regions of both types of nanograins are described. Presence of small (∼0.2%) inclusions of Zr was identified in the core of nanograins.
Single DNA molecule detection in an optical trap using surface-enhanced Raman scattering
Authors: Rao Satish , Raj Saurabh , Balint Stefan , Fons Carlota Bardina , Campoy Susana , Llagostera Montserrat , Petrov Dmitri
Published: May 2010

Raman spectra from single DNA molecules in their natural aqueous environment are presented. A DNA molecule that is anchored between two optically trapped dielectric beads is suspended in a solution with nanosized silver colloid particles. The nonspecific binding of the metal to the DNA enhances the Raman scattering that is excited by a near-infrared beam. A Raman spectrum is first recorded followed by a force-extension curve that verifies the presence of a single DNA molecule.
Electrically enhanced infrared photoluminescence in Cr:ZnSe
Authors: Jaeck Julien , Haidar Riad , Pardo Fabrice , Pelouard Jean-Luc , Rosencher Emmanuel
Published: May 2010

A sixfold enhancement of infrared (IR) photoluminescence (PL) from thick single crystal Cr:ZnSe under electrical excitation is reported. The baseline PL signal is obtained under a charge-transfer band optical seeding. The electrically enhanced IR signal is localized in the vicinity of the cathode and is shown to be likely related to hole concentration. The various mechanisms involved in this IR light emission will be discussed.
Anisotropic conductivity of doped graphene due to short-range nonsymmetric scattering
Authors: Vasko F. T.
Published: May 2010

The conductivity of doped graphene is considered taking into account scattering by short-range nonsymmetrical defects, when the longitudinal and transverse components of conductivity tensor appear to be different. The calculations of the anisotropic conductivity tensor are based on the quasiclassical kinetic equation for the case of monopolar transport at low temperatures. The effective longitudinal conductivity and the transverse voltage, which are controlled by orientation of sample and by gate voltage (i.e., doping level), are presented.
Conduction band discontinuity and electron confinement at the SixGe1−x/Ge interface
Authors: Mazzeo G. , Yablonovitch E. , Jiang H. W. , Bai Y. , Fitzgerald E. A.
Published: May 2010

Germanium rich heterostructures can constitute a valid alternative to Silicon for the confinement of single electron spins. The conduction band discontinuity in SiGe/Ge heterostructures grown on pure germanium substrate is predicted to allow the confinement of electrons in the germanium, and the conduction band profile of germanium rich heterostructures allow the implementation of g-factor modulation devices not possible in Silicon. We here prove that electrons can indeed be trapped at the Si0.1Ge0.9/Ge interface and we measure the height of the energy barrier to 0.55±0.05 eV by measuring the tunneling time of electrons as a function of the electric field.
Carrier dynamics of terahertz emission based on strained SiGe/Si single quantum well
Authors: Hung K. M. , Kuo J.-Y. , Hong C. C. , Cheng H. H. , Sun G. , Soref R. A.
Published: May 2010

We report analysis of the carrier distribution during terahertz emission process with carrier–phonon interaction based on p-doped strained SiGe/Si single quantum-well. The results of this analysis show that a considerable number of carriers can penetrate the phonon wall to become “hot” carriers on an approximately picosecond timescale. These hot carriers relax after the removal of the applied voltage, generating a “second” emission in the measurement. This investigation provides an understanding of the carrier dynamics of terahertz emission and has an implication for the design of semiconductor terahertz emitters.
Enhanced conversion efficiencies for pillar array solar cells fabricated from crystalline silicon with short minority carrier diffusion lengths
Authors: Yoon Heayoung P. , Yuwen Yu A. , Kendrick Chito E. , Barber Greg D. , Podraza Nikolas J. , Redwing Joan M. , Mallouk Thomas E. , Wronski Christopher R. , Mayer Theresa S.
Published: May 2010

Radial n+–p+ junction solar cells composed of densely packed pillar arrays, 25-μm-tall and 7.5 μm in diameter, fabricated from p-type silicon substrates with extremely short minority carrier diffusion lengths are investigated and compared to planar cells. To understand the two times higher AM 1.5 efficiencies of the pillar array cells, dark and light I-V characteristics as well as spectral responses are presented for the two structures. The higher pillar array cell efficiencies are due to the larger short-circuit currents from the larger photon absorption thickness and the shorter carrier collection length, with a significant additional contribution from multiple reflections in the structure.
A polymeric micro-optical interface for flow monitoring in biomicrofluidics
Authors: Sapuppo Francesca , Llobera Andreu , Schembri Florinda , Intaglietta Marcos , Cadarso Victor J. , Bucolo Maide
Published: May 2010

We describe design and miniaturization of a polymeric optical interface for flow monitoring in biomicrofluidics applications based on polydimethylsiloxane technology, providing optical transparency and compatibility with biological tissues. Design and ray tracing simulation are presented as well as device realization and optical analysis of flow dynamics in microscopic blood vessels. Optics characterization of this polymeric microinterface in dynamic experimental conditions provides a proof of concept for the application of the device to two-phase flow monitoring in both in vitro experiments and in vivo microcirculation investigations. This technology supports the study of in vitro and in vivo microfluidic systems. It yields simultaneous optical measurements, allowing for continuous monitoring of flow. This development, integrating a well-known and widely used optical flow monitoring systems, provides a disposable interface between live mammalian tissues and microfluidic devices making them accessible to detection/processing technology, in support or replacing standard intravital microscopy.
Model for thermoacoustic emission from solids
Authors: Hu Hanping , Zhu Tao , Xu Jun
Published: May 2010

A model for the thermoacoustic (TA) emission in both low and high frequency ranges is derived by fully coupled thermal-mechanical analysis. Accordingly, it has been theoretically confirmed that there exists a very wide range of constant (flat) amplitude-frequency response mostly in ultrasonic region for TA emission from any solid, and its existence conditions and frequency range as well as calculation formula are clarified and particularly given. The theory developed in this work agrees well with the experimental results, and is applicable to a variety of TA emission problems.
Uniaxial strain modulated band gap of ZnO nanostructures
Authors: Li S. , Jiang Q. , Yang G. W.
Published: May 2010

Influence of the uniaxial strain on the electronic structures of ZnO nanowires (NWs) and nanotubes (NTs) has been studied using the density functional theory. It was found that the uniaxial compress strain can lead to a band gap transition from direct to indirect band for both ZnO NWs and NTs. Under the same strain, the phase transition of the thick NW is easier than that of the thin one, and the phase transition of NWs seems easier than that of NTs. These results suggested the uniaxial strain can be used to tune the band structures of ZnO nanostructures, which may be help for design of ZnO-based nanodevices.
Optical sensing of square lattice photonic crystal point-shifted nanocavity for protein adsorption detection
Authors: Lu Tsan-Wen , Lin Pin-Tso , Sio Kuan-Un , Lee Po-Tsung
Published: May 2010

We propose a point-shifted D0 nanocavity formed by locally modulating four central air holes in square lattice photonic crystal for optical sensing application. Three defect modes in this nanocavity, including monopole, whispering-gallery, and dipole modes, are identified in experiments. We also apply a chemical treatment on InGaAsP surface to form a 1-octadecanethiol linking monolayer, which enables the following protein adsorption. In experiments, the wavelength shifts of lasing modes in the D0 nanocavity due to the protein adsorption are observed and agree with the simulation results. This can be a practical tool for label-free molecule detection in biomedical researches.
Multidisciplinary care needs in an Australian tertiary teaching hospital
Authors: To Timothy H. M. , Davies Owen J. , Sincock Jackie , Whitehead Craig
Published: May 2010

Background.The ageing of the Australian population is placing increasing demand on the nation’s healthcare system. This study set out to describe the level of need for multidisciplinary care in an Australian tertiary hospital setting. Methods.A cross-sectional audit by case note review of all patients on acute medical and surgical wards in an Australian tertiary hospital. The primary outcome was an identified need for multidisciplinary assessment and intervention. Results.A total of 60% of the 295 inpatients audited required multidisciplinary care. Of those who were admitted to geriatric and rehabilitation units, 84% required multidisciplinary care. Patients in acute medical and surgical units also had substantial multidisciplinary care needs. Age was a significant influence with 79% of those aged 86 and above having multidisciplinary care needs, whilst only 38% of those aged 55 or less required multidisciplinary care. Difficulties with mobility, need for assistance with self-care, and continence problems were associated with higher requirement for multidisciplinary care. Conclusions.In the hospital population, significant multidisciplinary care needs exist. These needs are not limited to inpatients that are elderly or admitted to geriatric or rehabilitation units. This has implications for planning, funding, provision of health care resources, and training of medical and allied health staff. What is known about the topic?Multidisciplinary care is the collaboration of health care staff from a variety of disciplines. This approach has been attributed to reductions in mortality and the duration of length of stay in hospital. Multidisciplinary care is widely applied to older patients and those requiring rehabilitation. However, multidisciplinary care is less frequently adopted in other areas, suggesting that some patients requiring this approach may not receive it. What does this paper add?The findings of this study demonstrate that the need for multidisciplinary care extends beyond aged care and rehabilitation patients. Although the majority of aged care and rehabilitation patients required multidisciplinary care, a significant number of patients in medical and surgical units also needed this approach. What are the implications for practitioners?A need exists for a multidisciplinary approach to be utilised more widely in the hospital setting. Collaboration between allied health and medical staff may require consideration in the allocation of resources for patient care. This also has implications for the training of medical and allied health staff both now and in the future.
Postoperative infection rates in foot and ankle surgery: a clinical audit of Australian podiatric surgeons, January to December 2007
Authors: Butterworth Paul , Gilheany Mark F. , Tinley Paul
Published: May 2010

Background.Surgical site infections are one of the most common post-operative complications encountered by foot and ankle surgeons. The incidence reported in the literature varies between 0.5 and 6.5%. The results of a 12-month Australia-wide clinical audit analysing the rates of postoperative infections in association with podiatric surgery are presented. Methods.De-identified patient data was collected from nine podiatric surgeons Australia-wide. Infections were identified according to Australian Council on Health Care Standards (ACHS) definitions and data was entered no earlier than thirty days post procedure. Results.A total of 1339 patient admissions and 2387 surgical procedures were reported using the International Classification of Diseases (ICD-10) and Medicare Benefit Schedule (MBS) coding systems. The overall infection rate was 3.1% and the rate of infection resulting in hospital re-admission was 0.25%. Conclusions.The benchmark results presented in this paper suggest that infection rates associated with podiatric surgery are well within accepted industry standards as stated in recent literature. What is known about the topic?The rates of infection in foot and ankle surgery have been reported in international literature to vary between 0.5 and 6.5%. No such data has been published to date, which describes the rate of infection following podiatric surgery in Australia. What does this paper add?This paper provides benchmark data on complication rates associated with Australian podiatric surgeons. Such data also informs health and hospital managers who may be considering podiatric surgery as an option for providing foot surgery services within the public hospital system. What are the implications for practitioners?This paper challenges podiatric surgeons to consider their own practice and whether it is a reflection of best practice.