bluuebunny/crossref_metadata_2025 huggingface dataset:
Magma plumbing system of the 2000 eruption of Miyakejima volcano, Japan, deduced from volatile and major component contents of olivine‐hosted melt inclusions
Authors: Saito Genji , Morishita Yuichi , Shinohara Hiroshi
Published: November 2010

Chemical analyses of 56 olivine‐hosted melt inclusions and their host olivines from the explosive eruption of Miyakejima volcano, Japan, on 18 August 2000 were carried out by electron probe micro analyzer and secondary ion mass spectrometry in order to investigate the magma plumbing system of the eruption. The bimodal olivine core composition, relatively small rims, and diffusion profiles of the Mg‐rich olivines indicate the mixing of evolved magma and less‐evolved magma in 2 months before the eruption. The major element composition of the Mg‐poor olivine‐hosted melt inclusions (Mg‐poor OLMIs) is similar to that of the groundmass. The Mg‐rich olivine‐hosted melt inclusions (Mg‐rich OLMIs) have a SiO2‐ and K2O‐poor but Al2O3‐ and CaO‐rich composition, compared to the whole‐rock composition of the products. Most of the Mg‐rich OLMIs have slightly higher H2O (1.9–3.5 wt %) and S (0.06–0.21 wt %) contents and a lower Cl (0.04–0.07 wt %) content than the Mg‐poor OLMIs, whereas they have similar CO2 (0.003–0.025 wt %) content. These results suggest that CO2‐rich gas was added to the evolved magma in a shallow magma chamber, followed by decompression degassing in a pressure range of 30–80 MPa and the rapid ascent of the less‐evolved magma from a deep magma chamber up to a depth of about 2 km. The ratios of the H2O and S contents of the Mg‐rich OLMIs are similar to that of the volcanic gas emitted from the summit after the 2000 eruption, which suggests shallow degassing of the less‐evolved magma in the conduit since the eruption.
2005 Caribbean mass coral bleaching event: A sea surface temperature empirical orthogonal teleconnection analysis
Authors: Simonti Alicia L. , Eastman J. Ronald
Published: November 2010

This study examined the effects of climate teleconnections on the massive Caribbean coral bleaching and mortality event of 2005. A relatively new analytical procedure known as empirical orthogonal teleconnection (EOT) analysis, based on a 26 year monthly time series of observed sea surface temperature (SST), was employed. Multiple regression analysis was then utilized to determine the relative teleconnection contributions to SST variability in the southern Caribbean. The results indicate that three independent climate teleconnections had significant impact on southern Caribbean anomalies in SST and that their interaction was a major contributor to the anomalously high temperatures in 2005. The primary and approximately equal contributors were EOT‐5 and EOT‐2, which correlate most strongly with the tropical North Atlantic (TNA) and Atlantic multidecadal oscillation (AMO) climate indices, respectively. The third, EOT‐9, was most strongly related to the Atlantic meridional mode. However, although statistically significant, the magnitude of its contribution to southern Caribbean variability was small. While there is debate over the degree to which the recent AMO pattern represents natural variability or global ocean warming, the results presented here indicate that natural variability played a strong role in the 2005 coral bleaching conditions. They also argue for a redefinition of the geography of TNA variability.
Perennial snow and ice variations (2000–2008) in the Arctic circumpolar land area from satellite observations
Authors: Fontana F. M. A. , Trishchenko A. P. , Luo Y. , Khlopenkov K. V. , Nussbaumer S. U. , Wunderle S.
Published: November 2010

Perennial snow and ice (PSI) extent is an important parameter of mountain environments with regard to its involvement in the hydrological cycle and the surface energy budget. We investigated interannual variations of PSI in nine mountain regions of interest (ROI) between 2000 and 2008. For that purpose, a novel MODIS data set processed at the Canada Centre for Remote Sensing at 250 m spatial resolution was utilized. The extent of PSI exhibited significant interannual variations, with coefficients of variation ranging from 5% to 81% depending on the ROI. A strong negative relationship was found between PSI and positive degree‐days (threshold 0°C) during the summer months in most ROIs, with linear correlation coefficients (r) being as low as r = −0.90. In the European Alps and Scandinavia, PSI extent was significantly correlated with annual net glacier mass balances, with r = 0.91 and r = 0.85, respectively, suggesting that MODIS‐derived PSI extent may be used as an indicator of net glacier mass balances. Validation of PSI extent in two land surface classifications for the years 2000 and 2005, GLC‐2000 and Globcover, revealed significant discrepancies of up to 129% for both classifications. With regard to the importance of such classifications for land surface parameterizations in climate and land surface process models, this is a potential source of error to be investigated in future studies. The results presented here provide an interesting insight into variations of PSI in several ROIs and are instrumental for our understanding of sensitive mountain regions in the context of global climate change assessment.
Influence of hummocks and emergent vegetation on hydraulic performance in a surface flow wastewater treatment wetland
Authors: Keefe Steffanie H. , Daniels Joan S. (Thullen) , Runkel Robert L. , Wass Roland D. , Stiles Eric A. , Barber Larry B.
Published: November 2010

A series of tracer experiments were conducted biannually at the start and end of the vegetation growing season in a surface flow wastewater treatment wetland located near Phoenix, AZ. Tracer experiments were conducted prior to and following reconfiguration and replanting of a 1.2 ha treatment wetland from its original design of alternating shallow and deep zones to incorporate hummocks (shallow planting beds situated perpendicular to flow). Tracer test data were analyzed using analysis of moments and the one‐dimensional transport with inflow and storage numerical model to evaluate the effects of the seasonal vegetation growth cycle and hummocks on solute transport. Following reconfiguration, vegetation coverage was relatively small, and minor changes in spatial distribution influenced wetland hydraulics. During start‐up conditions, the wetland underwent an acclimation period characterized by small vegetation coverage and large transport cross‐sectional areas. At the start of the growing season, new growth of emergent vegetation enhanced hydraulic performance. At the end of the growing season, senescing vegetation created short‐circuiting. Wetland hydrodynamics were associated with high volumetric efficiencies and velocity heterogeneities. The hummock design resulted in breakthrough curves characterized by multiple secondary tracer peaks indicative of varied flow paths created by bottom topography.
Application of a Bonner sphere spectrometer for determination of the energy spectra of neutrons generated by ≈1 MJ plasma focus
Authors: Králík M. , Krása J. , Velyhan A. , Scholz M. , Ivanova-Stanik I. M. , Bienkowska B. , Miklaszewski R. , Schmidt H. , Řezáč K. , Klír D. , Kravárik J. , Kubeš P.
Published: November 2010

The spectra of neutrons outside the plasma focus device PF-1000 with an upper energy limit of ≈1 MJ was measured using a Bonner spheres spectrometer in which the active detector of thermal neutrons was replaced by nine thermoluminescent chips. As an a priori spectrum for the unfolding procedure, the spectrum calculated by means of the Monte Carlo method with a simplified model of the discharge chamber was selected. Differences between unfolded and calculated spectra are discussed with respect to properties of the discharge vessel and the laboratory layout.
Note: An anvil-preformed gasket system to extend the pressure range for large volume cubic presses
Authors: Wang Haikuo , He Duanwei , Tan Ning , Wang Wendan , Wang Jianghua , Dong Haini , Ma Huan , Kou Zili , Peng Fang , Liu Xi , Li Sicheng
Published: November 2010

An anvil-preformed gasket system has been developed to extend the pressure range for the widely used large volume cubic press without sacrificing the sample volume. The relationship of the sample chamber pressure versus press load for this system was calibrated at room temperature using transitions in Bi, Tl, and Ba. With similar sample volumes (8–11 mm in diameter and 8 mm in length), the anvil-preformed gasket system can generate pressures up to about 8.5 GPa, significantly higher than 6 GPa, which was generally the maximum pressure for the conventional anvil-gasket system. The details on the optimized design for the anvil-preformed gasket system are given in this note.
Phase synchronization between collective rhythms of globally coupled oscillator groups: Noisy identical case
Authors: Kawamura Yoji , Nakao Hiroya , Arai Kensuke , Kori Hiroshi , Kuramoto Yoshiki
Published: November 2010

We theoretically investigate the collective phase synchronization between interacting groups of globally coupled noisy identical phase oscillators exhibiting macroscopic rhythms. Using the phase reduction method, we derive coupled collective phase equations describing the macroscopic rhythms of the groups from microscopic Langevin phase equations of the individual oscillators via nonlinear Fokker–Planck equations. For sinusoidal microscopic coupling, we determine the type of the collective phase coupling function, i.e., whether the groups exhibit in-phase or antiphase synchronization. We show that the macroscopic rhythms can exhibit effective antiphase synchronization even if the microscopic phase coupling between the groups is in-phase, and vice versa. Moreover, near the onset of collective oscillations, we analytically obtain the collective phase coupling function using center-manifold and phase reductions of the nonlinear Fokker–Planck equations.
Study of high Mach number laser driven blast waves in gases
Authors: Edens A. D. , Adams R. G. , Rambo P. , Ruggles L. , Smith I. C. , Porter J. L. , Ditmire T.
Published: November 2010

A series of experiments were performed examining the evolution of blast waves produced by laser irradiation of a target immersed in gas. Blast waves were produced by illumination of wires by 1 kJ, 1 ns laser pulses from the Z-Beamlet laser at Sandia National Laboratories. The blast waves were imaged by probe laser pulses at various times to examine the trajectory, radiative precursor, and induced perturbations on the blast wave front. Well defined perturbations were induced on the blast wave front with arrays of wires placed in the gas and the results of the experiments are compared to the theoretical predictions for the Vishniac overstability. It is found that the experimental results are in general agreement with these theoretical predictions on thin blast wave shells and are in quantitative agreement in the simplest case.
Fundamental solitons in discrete lattices with a delayed nonlinear response
Authors: Maluckov A. , Hadžievski L. , Malomed B. A.
Published: November 2010

The formation of unstaggered localized modes in dynamical lattices can be supported by the interplay of discreteness and nonlinearity with a finite relaxation time. In rapidly responding nonlinear media, on-site discrete solitons are stable, and their broad intersite counterparts are marginally stable, featuring a virtually vanishing real instability eigenvalue. The solitons become unstable in the case of the slowly relaxing nonlinearity. The character of the instability alters with the increase of the delay time, which leads to a change in the dynamics of unstable discrete solitons. They form robust localized breathers in rapidly relaxing media, and decay into oscillatory diffractive pattern in the lattices with a slow nonlinear response. Marginally stable solitons can freely move across the lattice.
Determination of the minimum value of the safety factor from geodesic Alfvén eigenmodes in Joint European Torus
Authors: Elfimov A. G. , Galvão R. M. O. , Sharapov S. E. ,   JET-EFDA Contributors
Published: November 2010

An analysis of the experimental conditions under which low-frequency (70–150 kHz) Alfvén eigenmodes (AE) are excited during the monster sawtooth in Joint European Torus [F. Romanelli et al., Proceedings of the 22nd IAEA Fusion Energy Conference, Geneva, Switzerland, 2008] is presented for the specific case of a discharge with ion cyclotron heating (5 MW). Using a simplified AE model for modes excited at the Alfvén wave continuum maximum with geodesic corrections taken into account, the temporal evolution of the value of the safety factor q0 at the magnetic axis is determined. We describe a new scheme to determine the time variation of q0 that works under conditions in which other standard diagnostics, such as the motional Stark effect do not give reliable results such as during a monster sawtooth.
A typical noiseless Pockels E field sensor
Authors: Fukui Yukihito , Okumura Katsuo , Moritake Hiroshi , Murooka Yoshihiro
Published: November 2010

A new practical Pockels E field sensor has been demonstrated. By combining a ferroelectric liquid crystal and a polarization-maintaining optical fiber with the sensor, it is theoretically found that almost all of the optical and electronic noise produced in the system can be completely eliminated. This fact has been experimentally proven not only under the conditions of a uniform electric field but also those of a nonuniform electric field and with ac voltages applied to a stabilized corona discharge. It is shown that if with the new Pockels E field sensor, the smallest detectable phase change was set to be 10−5 rad, the minimum measurable E field in the electrical discharge could be reduced from 102 to 10−1 kV/m. This technique should be useful not only for the field of electrical discharge studies but also for other optical measurement applications such as length, temperature, and pressure using appropriately configured transducers.
Gyrokinetic particle simulations of reversed shear Alfvén eigenmode excited by antenna and fast ions
Authors: Deng Wenjun , Lin Zhihong , Holod Ihor , Wang Xin , Xiao Yong , Zhang Wenlu
Published: November 2010

Global gyrokinetic particle simulations of reversed shear Alfvén eigenmode (RSAE) have been successfully performed and verified. We have excited the RSAE by initial perturbation, by external antenna, and by energetic ions. The RSAE excitation by antenna provides verifications of the mode structure, the frequency, and the damping rate. When the kinetic effects of the background plasma are artificially suppressed, the mode amplitude shows a near-linear growth. With kinetic thermal ions, the mode amplitude eventually saturates due to the thermal ion damping. The damping rates measured from the antenna excitation and from the initial perturbation simulation agree very well. The RSAE excited by fast ions shows an exponential growth. The finite Larmor radius effects of the fast ions are found to significantly reduce the growth rate. With kinetic thermal ions and electron pressure, the mode frequency increases due to the elevation of the Alfvén continuum by the geodesic compressibility. The nonperturbative contributions from the fast ions and kinetic thermal ions modify the mode structure relative to the ideal magnetohydrodynamic (MHD) theory. The gyrokinetic simulations have been benchmarked with extended hybrid MHD-gyrokinetic simulations.
A Peltier cells differential calorimeter with kinetic correction for the measurement of cp(H,T) and Δs(H,T) of magnetocaloric materials
Authors: Basso Vittorio , Sasso Carlo Paolo , Küpferling Michaela
Published: November 2010

In this paper we describe and test a setup for the characterization of the magnetocaloric effect around room temperature. The setup is a differential calorimeter able to measure both the specific heat cp(H,T) under constant magnetic field H and the isothermal entropy change induced by changing H, Δs(H,T), in the room temperature range. The setup uses miniaturized Peltier cells to measure the heat flux, with resolution of about 1 μW, and power Peltier cells to regulate the temperature in the range from 243 K (−30 °C) to 343 K (+70 °C). The kinetic effects due to the heat capacity of the measuring cells are taken into account by a simple model of the heat flux diffusion in the calorimetric cell. As measurement examples, we show the characterization of the magnetocaloric effect in magnetic materials with a second order transition [without latent heat and without hysteresis, as in the La1(Fe1−x−yCoySix)13 alloy with x=0.077 and y=0.079] and with a first order transitions (with latent heat and hysteresis as in Ni50Mn36Co1Sn13). As a result we compare the entropy change Δs(H,T) derived from (i) the integration of the specific heat cp(H,T) and (ii) the direct isothermal measurements, obtaining an excellent agreement.
First-principles studies of electronic, optical, and vibrational properties of LaVO4 polymorph
Authors: Sun Liming , Zhao Xian , Li Yanlu , Li Pan , Sun Honggang , Cheng Xiufeng , Fan Weiliu
Published: November 2010

First-principles calculations of electronic, optical, and vibrational properties of LaVO4 polymorph were performed with the density functional theory plane-wave pseudopotential method. The results of the electronic structure reveal that the different coordinated structure for monoclinic LaVO4 leads to an indirect band gap, while tetragonal LaVO4 has a direct band gap. Besides, the analysis of the electronic structure shows ionic nature in La–O bonds and covalent nature in V–O bonds. From further study in chemical bonding behavior, we find that the V–O covalent bonds have four types: σ bonding, π bonding, π∗ antibonding, and σ∗ antibonding states. Various optical properties, including the dielectric function, reflectivity, absorption coefficient, refractive index, and the energy-loss spectrum as functions of the photon energy were calculated. Our calculations indicate that monoclinic LaVO4 has excellent dielectric properties along [0 0 1] direction. In the optical-frequency (ω→∞) contributed from electrons the optical properties of tetragonal LaVO4 show the isotropy, while the diagonal components of static dielectric tensors ε(0) of tetragonal LaVO4 have the εxx=εyy≠εzz relation by adding the lattice vibration contribution (ω→0) to the electronic dielectric tensor. The vibrational spectra of LaVO4 polymorph have also been calculated from first principles by the linear response method. The calculated frequencies are in good agreement with the experimental data available for these crystals obtained by the methods of infrared and Raman spectroscopies. The vibrational spectra of monoclinic and tetragonal LaVO4 crystal exhibit three groups of frequencies: the low-frequency (<240 cm−1), middle-frequency (270–450 cm−1), and high-frequency region (850–970 cm−1), according to the vibration dominated by translation of La atoms, the bending vibration of O–V–O bonds, and stretching vibration of O–V–O bonds, respectively. Our studies report on microstructure of LaVO4 polymorph, and provide useful information for the potential application of this material.
The field evaporation of deuterated titanium as a neutron generator ion source
Authors: Reichenbach B. , Johnson B. Bargsten , Schwoebel P. R.
Published: November 2010

The field evaporation of deuterated titanium films is being investigated as a deuterium ion source for deuterium-tritium neutron generators. It has been found that titanium and deuterated titanium films having thicknesses of up to at least 70 layers assume a body-centered-cubic crystal structure when grown on ⟨110⟩ oriented tungsten substrates. Deuterated titanium films having thicknesses exceeding 50 atomic layers have been controllably field evaporated from the surface of tungsten tips in less than 20 ns. At ion current densities exceeding ∼106 A/cm2 and film thicknesses greater than ∼20 layers, space charge effects decrease the ratio of D to TiDx ions to less than 1. Decreasing the evaporation rate such that ion current densities are of the order of 105 A/cm2 increases the D to TiDx ratio for the evaporation of a film thickness of greater than ∼20 layers by the reduction in space charge effects that can inhibit the dissociation of titanium-deuterium complexes. Atomic deuterium ion yields of ∼10−7 μC of D+/tip have been observed and yields of >10−6 μC of D+/tip should be possible using larger tip radii. The field evaporation of titanium from an array of microfabricated tips has been demonstrated for the first time.
Lambda shifted photonic crystal cavity laser
Authors: Schubert Martin , Suhr Troels , Ek Sara , Semenova Elizaveta S. , Hvam Jørn M. , Yvind Kresten
Published: November 2010

We propose and demonstrate an alternative type of photonic crystal laser design that shifts all the holes in the lattice by a fixed fraction of the targeted emission wavelength. The structures are realized in InGaAsP (λ=1.15) with InGaAsP quantum wells (λ=1.52) as gain material. Cavities with shifts of 1/4 and 3/4 of the emission wavelength were fabricated and characterized. Measurements show threshold behavior for several modes at room temperature. Both structures are simulated using a finite difference time domain method to identify the resonances in the spectra and calculate the mode volume of the dominant mode.
New model for assessing dose, dose rate, and temperature sensitivity of radiation-induced absorption in glasses
Authors: Gilard Olivier , Caussanel Matthieu , Duval Hervé , Quadri Gianandrea , Reynaud François
Published: November 2010

A new theoretical approach is proposed to explain the dose, dose rate and temperature sensitivity of the radiation-induced absorption (RIA) in glasses. In this paper, a βth-order dispersive kinetic model is used to simulate the growth of the density of color centers in irradiated glasses. This model yields an explanation for the power-law dependence on dose and dose rate usually observed for the RIA in optical fibers. It also leads to an Arrhenius-like relationship between the RIA and the glass temperature during irradiation. With a very limited number of adjustable parameters, the model succeeds in explaining, with a good agreement, the RIA growth of two different optical fiber references over wide ranges of dose, dose rate and temperature.
Resonance tongues in a system of globally coupled FitzHugh–Nagumo oscillators with time-periodic coupling strength
Authors: Bîrzu Adrian , Krischer Katharina
Published: November 2010

We investigate the dynamics of a population of globally coupled FitzHugh–Nagumo oscillators with a time-periodic coupling strength. While for synchronizing global coupling, the in-phase state is always stable, the oscillators split into several cluster states for desynchronizing global coupling, most commonly in two, irrespective of the coupling strength. This confines the ability of the system to form n:m locked states considerably. The prevalence of two and four cluster states leads to large 2:1 and 4:1 subharmonic resonance regions, while at low coupling strength for a harmonic 1:1 or a superharmonic 1:m time-periodic coupling coefficient, any resonances are absent and the system exhibits nonresonant phase drifting cluster states. Furthermore, in the unforced, globally coupled system the frequency of the oscillators in a cluster state is in general lower than that of the uncoupled oscillator and strongly depends on the coupling strength. Periodic variation of the coupling strength at twice the natural frequency causes each oscillator to keep oscillating with its autonomous oscillation period.
Resonant tunneling and extreme brightness from diamond field emitters and carbon nanotubes
Authors: Jarvis J. D. , Andrews H. L. , Ivanov B. , Stewart C. L. , de Jonge N. , Heeres E. C. , Kang W.-P. , Wong Y.-M. , Davidson J. L. , Brau C. A.
Published: November 2010

We report new results from field emission microscopy studies of multiwall carbon nanotubes and from energy spectrum measurements of beams from diamond field emitters. In both systems, we find that resonant tunneling through adsorbed species on the emitter surface is an important and sometimes dominant effect. For diamond emitters our observations include order-of-magnitude emission enhancement without spectral broadening, complex spectral structure, and sensitivity of that structure to the applied electric field. For carbon nanotubes we have observed electron beams from individual adsorbates which are estimated to approach the maximum beam brightness allowed by Pauli exclusion.
Spectroscopic, imaging, and probe diagnostics of laser plasma plumes expanding between confining surfaces
Authors: Yeates P. , Kennedy E. T.
Published: November 2010

Laser plasma plumes were generated in aluminum rectangular cavities of fixed depth (6 mm) and varying height (2.0, 1.5, and 1.0 mm). Space and time resolved visible emission spectroscopy, gated intensified visible imaging, and Langmuir probe diagnostics were utilized to diagnose the evolution of the confined plasma plumes in comparison to freely expanding plasma plume generated from ablation of a planar target. The constrained plasma behavior displayed a multiphase history. Early stage interactions (t<100 ns) resulted in enhanced continuum and line emission, shockwave formation and plasma plume rebound. Later phase, long duration plasma-surface interactions (t>160 ns) resulted in sustained “decay,” i.e., a rapid termination of continuum emission, in concert with decreases in peak electron density (Ne) and plasma temperature (T). This later phase originates from loss mechanisms which bleed the plasma plume of thermal energy and charged particles. These loss mechanisms increase in magnitude as the duration of the plasma-surface interaction increases. The transition from enhancement phase, originating from hydrodynamic containment, and plasma-surface collisions, to decay phase is described and occurs for each cavity at a different point in the space time history.
Gate dependent photocurrents at a graphene p-n junction
Authors: Peters Eva C. , Lee Eduardo J. H. , Burghard Marko , Kern Klaus
Published: November 2010

We have used scanning photocurrent microscopy to explore the electronic characteristics of a graphene p-n junction fabricated by local chemical doping of a graphene sheet. The photocurrent signal at the junction was found to be most prominent for gate voltages between the two Dirac points of the oppositely doped graphene regions. The gate dependence of this signal agrees well with simulations based upon the Fermi level difference between the two differently doped sections. It is concluded that the photocurrent maps are dominated by the built-in electric field, with only a minor photothermoelectric contribution.
Coupling of localized surface plasmon modes in compound structure with metallic nanoparticle and nanohole arrays
Authors: He Meng-Dong , Gong Zhi-Qiang , Li Shui , Luo Yong-Feng , Liu Jian-Qiang , Chen Xiaoshuang , Lu Wei
Published: November 2010

We have investigated the effect of the coupling of localized surface plasmon (LSP) on the transmission properties of a compound structure with metallic particle and hole arrays. It is found that the variation in longitudinal interval G between particle and hole arrays leads to the shift in transmission peak and the new transmission peak, which are due to the change in coupling strength of LSP modes and the formation of coaxial guide mode, respectively. The lateral displacement Lx (parallel to the polarization direction of incident light) results in the splitting of transmission peak, originating from the variation in coupling manner of LSP modes, while the lateral displacement Ly (perpendicular to the polarization direction of incident light) causes the reduction and redshift in transmission peak.
The effect of La in InZnO systems for solution-processed amorphous oxide thin-film transistors
Authors: Kim Doo Na , Kim Dong Lim , Kim Gun Hee , Kim Si Joon , Rim You Seung , Jeong Woong Hee , Kim Hyun Jae
Published: November 2010

Solution-processed thin-film transistors (TFTs) with La–In–Zn–O (LIZO) as an active channel layer were fabricated with various mole ratios of La. The La3+ additive affected the metal–oxygen bond and made the band gap of LIZO films wider. This behavior indicates that La3+ could play the role of carrier suppressor in InZnO (IZO) systems and significantly reduce the off-current of LIZO films. The optimum LIZO TFT occurred at a LIZO mole ratio of 0.5:5:5 and its channel mobility, threshold voltage, subthreshold swing voltage, and on/off ratio were 2.64 cm2/V s, 7.86 V, 0.6 V/dec, and ∼106, respectively.
Effects of defects and local thickness modulation on spin-polarization in photocathodes based on GaAs/GaAsP strained superlattices
Authors: Jin Xiuguang , Maeda Yuya , Sasaki Toshio , Arai Shigeo , Ishida Yoichi , Kanda Masataka , Fuchi Shingo , Ujihara Toru , Saka Takashi , Takeda Yoshikazu
Published: November 2010

The spin-polarization of electrons from the GaAs/GaAsP superlattice on a GaAs substrate (∼90%) is higher than that from the same superlattice on a GaP substrate (∼60%). Transmission electron microscopy and atomic force microscopy observations revealed that stacking faults were the main defects in the superlattice on the GaAs substrate, while local thickness modulation of the superlattice layers was prominent in the superlattice on the GaP substrate. According to the density of stacking faults and the areal ratio of the thickness modulation, it was concluded that the thickness modulation in the superlattice was the main reason for the spin-polarization reduction in the photocathode on the GaP substrate. Growth of a thin GaAs layer on a GaP substrate prior to superlattice growth eliminated the thickness modulation and the spin-polarization was recovered to 90%.
Optical studies of degradation of AlGaN quantum well based deep ultraviolet light emitting diodes
Authors: Pinos A. , Marcinkevičius S. , Yang J. , Gaska R. , Shatalov M. , Shur M. S.
Published: November 2010

Aging under high current stress of AlGaN quantum well based light emitting diodes with high and low Al content in the wells emitting at 270 nm and 335 nm, respectively, has been studied by scanning near field optical spectroscopy and far field electroluminescence, photoluminescence and time-resolved photoluminescence. In the high Al content devices emission band related to optical transitions in the cladding involving nitrogen vacancies has been found. Evolution of this band during aging suggests that the role of N vacancies is crucial in the aging process by aiding defect generation and formation of high conductivity channels.
Parametric analysis of the strain-dependent behavior of a metamaterial electric resonator
Authors: Arritt B. , Adomanis B. , Khraishi T. , Smith D.
Published: November 2010

In this paper, we describe the strain-dependent behavior of an electric-LC (ELC) resonator unit cell, commonly used in metamaterial designs. We leverage analytic expression to understand the way strain manifests itself in a change in electromagnetic (EM) response. We verify the simplified physical models using full-wave simulations and generalize the trends to accommodate the strain profile for any arbitrary plane-stress loading scenario.
Spin-dependent processes in amorphous silicon-rich silicon-nitride
Authors: Lee S.-Y. , Paik S.-Y. , McCamey D. R. , Hu J. , Zhu F. , Madan A. , Boehme C.
Published: November 2010

A study of spin-dependent charge carrier transitions in silicon-rich hydrogenated amorphous silicon-nitride (a-SiNx:H) p-i-n devices is presented. Pulsed electrically detected magnetic resonance allows us to determine the paramagnetic states that influence the photocurrent and provides insights into the nature of spin-coupling between charge carriers. We show that, in contrast to hydrogenated amorphous silicon, a-SiNx:H allows strongly spin-coupled, correlated (geminate) pairs of charge carriers to dissociate into nongeminate pairs that contribute to the photocurrent. This is discussed with regard to the application of a-SiNx:H as a photoelectrochemical electrode material.
Gyromultiplier with sectioned cavity
Authors: Bandurkin I. V. , Mishakin S. V.
Published: November 2010

A novel scheme of a self-exciting single-cavity terahertz gyromultiplier is proposed and theoretically investigated. Simulations predict a possibility to obtain a power of 75 W at the frequency of 1.3 THz from the 80 kV/0.7 A electron beam when operating at the fourth cyclotron harmonic at the relatively low magnetic field of 14 T.
Three-dimensional magnetization profile and multiaxes exchange bias in Co antidot arrays
Authors: Fettar F. , Cagnon L. , Rougemaille N.
Published: November 2010

Magnetic properties of Cu/Co/Cu trilayers deposited on nanoporous alumina membranes are investigated using a superconducting quantum interference device. Hysteresis loops of the resulting Co antidot arrays show two-step magnetization reversal. Due to oxidation when samples are exposed to air, CoO forms and exchange bias is observed, whether the cooling field is applied within or perpendicular to the surface plane. In the former case, the exchange bias changes sign close to the blocking temperature of Co/CoO. We attribute these effects to the local, crescent shape of the Co films induced by the surface morphology of the membranes, which leads to a three-dimensional magnetization distribution.
Luminescence properties of In(Zn)P alloy core/ZnS shell quantum dots
Authors: Thuy Ung Thi Dieu , Reiss Peter , Liem Nguyen Quang
Published: November 2010

Chemically synthesized InP/ZnS core/shell quantum dots (QDs) are studied using time-resolved photoluminescence spectroscopy and x-ray diffraction. Zinc stearate, which is added during the synthesis of the InP core, significantly improves the optical characteristics of the QDs. The luminescence quantum yield (QY) reaches 60%–70% and the emission is tunable from 485 to 586 nm by varying the Zn2+:In3+ molar ratio and growth temperature. The observed increased Stokes shift, luminescence decay time, and QY in the presence of Zn are rationalized by the formation of an In(Zn)P alloy structure that causes band-edge fluctuation to enhance the confinement of the excited carriers.
A route to strong p-doping of epitaxial graphene on SiC
Authors: Cheng Y. C. , Schwingenschlögl U.
Published: November 2010

The effects of Au intercalation on the electronic properties of epitaxial graphene grown on SiC{0001} substrates are studied using first principles calculations. A graphene monolayer on SiC{0001} restores the shape of the pristine graphene dispersion, where doping levels between strongly n-doped and weakly p-doped can be achieved by altering the Au coverage. We predict that Au intercalation between the two C layers of bilayer graphene grown on SiC{0001} makes it possible to achieve a strongly p-doped graphene state, where the p-doping level can be controlled by means of the Au coverage.
The Na2X Superalkali Species (X=SH, SCH3, OCH3,CN, N3) as Building Blocks in the Na2XY Salts (Y=MgCl3, Cl, NO2). An Ab Initio Study of the Electric Propertiesof the Na2XY Salts
Authors: Anusiewicz Iwona
Published: November 2010

Vertical and adiabatic ionization potentials of Na2X (X = SH, SCH3, OCH3, CN, and N3) superalkali molecules have been studied using the ab initio methods. The smallest vertical ionization potential was calculated for the Na2OCH3 system (4.365 eV). The Na2X molecules were found to be capable of forming stable [Na2X]+[Y]– salts with the species exhibiting various electron affinities (Y = MgCl3, Cl, NO2). The dipole moments, polarizabilities, and first-order hyperpolarizabilities of the Na2XY ionic salts were calculated and discussed. It was found that the Na2XNO2 molecules possess extraordinary large values of anisotropy of polarizabilities (in the 15.5–28.2 × 10–24 esu range) and the first-order hyperpolarizbilities (spanning the 597.8–1295.7 × 10–30 esu range).
Seroprevalence of herpes simplex virus type 1 and type 2 among the Indigenous population of Cape York, Far North Queensland, Australia
Authors: Brazzale Anthony G. , Russell Darren B. , Cunningham Anthony L. , Taylor Janette , McBride William J. H.
Published: November 2010

Background: The objective of this study was to obtain representative seroprevalence data for the Indigenous population of Far North Queensland by measuring the age- and sex-specific seroprevalence of the herpes simplex viruses (HSV-1 and HSV-2) in Cape York. Methods: A cross-sectional seroprevalence study was conducted using de-identified serum samples collected from Indigenous patients living in Cape York, aged 16 years or older, who sought medical care between August 2007 and May 2008. An age- and sex-stratified random sample of 270 sera was tested for the presence of antibodies to HSV-1 and HSV-2 using commercially available enzyme-linked immunosorbent assays. Indeterminate results were resolved with western blot. Results: The overall seroprevalence for the Indigenous population of Cape York was 97.8% for HSV-1 and 58.5% for HSV-2. There was a statistically significant difference in HSV-2 seroprevalence according to sex (P < 0.001). Females were more likely to be HSV-2 seropositive compared with males (72.1% and 43.8%, respectively). Conclusions: This is the first study to report on the seroprevalence of HSV-1 and HSV-2 among the Indigenous population of Cape York. This study has identified a population with an extremely high prevalence of HSV-1 and HSV-2 infection. The seroprevalence of HSV-2 in this population was found to be five times higher than that reported for the general adult Australian population. These results will be invaluable to the implementation of appropriate prevention and control strategies against HSV infection and are especially important considering the strong association between HSV-2 and the acquisition and transmission of HIV.
Should we change the focus of health promotion in sexual health clinics?
Authors: Pittrof Rudiger , Goodburn Elizabeth
Published: November 2010

The effectiveness of sexual behaviour change interventions in sexual health clinics is unknown. Risk factors for poor sexual and reproductive health such as depression, violence, alcohol and smoking in sexual health clinics are all common and can be identified easily in sexual health services. Targeting these risk factors could be as effective as traditional sexual health promotion and could have additional benefits. The authors propose a pilot to assess the cost-effectiveness and acceptability of incorporating screening and interventions for these risk factors.
HIV results by phone: can we predict who will test HIV-negative?
Authors: Wright Simon , Ryder Nathan , McNulty Anna M.
Published: November 2010

Introduction: In order to review the requirement for all patients to return for HIV test results, we sought to describe the number of cases of HIV infection detected at Sydney Sexual Health Centre among people who did not disclose known risk factors before testing. Method: The clinic database identified all HIV testing episodes between January 2004 and January 2007, along with gender, gender of sexual partners and test result. Pro-forma medical records were reviewed for each person who tested positive for gender of sexual partners, condom use, and sexual contact with a person from a country known to have a high HIV prevalence and injecting drug use. Results: During the 3-year period, a total of 13 290 HIV tests were performed. In men who have sex with men, 6194 tests were performed and 55 (0.88%) tested positive. In women and heterosexual men 7096 tests were performed, and only four (0.06%) tested positive. All four reported known risks for HIV before testing. Conclusion: Clients with no recognised risk factors for HIV are unlikely to test positive at our Australian sexual health clinic. Providing the option for low risk people to obtain their results other than face to face has advantages for both the clinic in terms of service provision and the clients in terms of time and the proportion who receive their result.
A case study in grammaticalized inflectional morphology
Authors: Hill Eugen
Published: November 2010

This paper deals with one of the oldest and most controversial problems in the historical morphology of the Germanic branch of Indo-European: the origin and historical development of the so-called ‘weak preterite’. In Germanic, the weak preterite is the only means of forming the preterite tense of a derived verb. In spite of two hundred years of research into the weak preterite and a large number of hypotheses concerning its origin, it is not even securely established how the inflectional endings of this formation should be reconstructed for the common prehistory of the attested Germanic languages. Traditionally the inflectional endings of the weak preterite are conceived of as reflecting free inflectional forms of the verb “do”, only recently having been grammaticalized as inflectional morphology for derived verbs. But it has never been possible to identify the inflectional forms in question satisfactorily within the paradigm of “do”. This paper reconsiders the evidence of the Germanic daughter languages by taking into account West Germanic irregularities previously neglected or viewed as irrelevant. It is shown that the West Germanic evidence provides a key to understanding the origin and the later developments of the weak preterite inflectional endings.
Semantic change
Authors: Beeching Kate
Published: November 2010

Functional linguists are in general agreement that semantic change may be triggered as part of the negotiation of meaning in interactional contexts: a ‘one-off’ contextual implicature generalises to become a new core meaning of a lexical item (Traugott and Dasher, 2002). In what ways, however, does the ‘one-off’ contextual implicature arise? Why would one language develop one aspect of meaning and another a different one? And how or why does it generalise and become a coded part of the structure of that particular language? Hansen (2008: 228) notes that “close crosslinguistic comparisons of the polysemies of semantically related items […] should turn out to be highly relevant” in this respect. ‘False friends’, forms deriving from a common etymon which have developed different meanings in different languages, offer useful insights. This paper presents lexicographic and spoken synchronic data on two false friends in French and English, effectivement/‘effectively’ and finalement/‘finally’, and explores the cognitive processes involved in their recruitment for interactional functions. The factors which are influential in the development of hedging usages of the terms are overviewed and the contribution that a detailed synchronic study of the semantics of false friends can make to the study of semantic change is evaluated.
Inverse perturbation for optimal intervention in gene regulatory networks
Authors: Bouaynaya Nidhal , Shterenberg Roman , Schonfeld Dan
Published: November 2010

Motivation: Analysis and intervention in the dynamics of gene regulatory networks is at the heart of emerging efforts in the development of modern treatment of numerous ailments including cancer. The ultimate goal is to develop methods to intervene in the function of living organisms in order to drive cells away from a malignant state into a benign form. A serious limitation of much of the previous work in cancer network analysis is the use of external control, which requires intervention at each time step, for an indefinite time interval. This is in sharp contrast to the proposed approach, which relies on the solution of an inverse perturbation problem to introduce a one-time intervention in the structure of regulatory networks. This isolated intervention transforms the steady-state distribution of the dynamic system to the desired steady-state distribution.

Results: We formulate the optimal intervention problem in gene regulatory networks as a minimal perturbation of the network in order to force it to converge to a desired steady-state distribution of gene regulation. We cast optimal intervention in gene regulation as a convex optimization problem, thus providing a globally optimal solution which can be efficiently computed using standard toolboxes for convex optimization. The criteria adopted for optimality is chosen to minimize potential adverse effects as a consequence of the intervention strategy. We consider a perturbation that minimizes (i) the overall energy of change between the original and controlled networks and (ii) the time needed to reach the desired steady-state distribution of gene regulation. Furthermore, we show that there is an inherent trade-off between minimizing the energy of the perturbation and the convergence rate to the desired distribution. We apply the proposed control to the human melanoma gene regulatory network.

Availability: The MATLAB code for optimal intervention in gene regulatory networks can be found online: http://syen.ualr.edu/nxbouaynaya/Bioinformatics2010.html.

Contact:  nxbouaynaya@ualr.edu

Supplementary information:  Supplementary data are available at Bioinformatics online.
NBC: the Naïve Bayes Classification tool webserver for taxonomic classification of metagenomic reads
Authors: Rosen Gail L. , Reichenberger Erin R. , Rosenfeld Aaron M.
Published: November 2010

Motivation: Datasets from high-throughput sequencing technologies have yielded a vast amount of data about organisms in environmental samples. Yet, it is still a challenge to assess the exact organism content in these samples because the task of taxonomic classification is too computationally complex to annotate all reads in a dataset. An easy-to-use webserver is needed to process these reads. While many methods exist, only a few are publicly available on webservers, and out of those, most do not annotate all reads.

Results: We introduce a webserver that implements the naïve Bayes classifier (NBC) to classify all metagenomic reads to their best taxonomic match. Results indicate that NBC can assign next-generation sequencing reads to their taxonomic classification and can find significant populations of genera that other classifiers may miss.

Availability: Publicly available at: http://nbc.ece.drexel.edu.

Contact:  gailr@ece.drexel.edu
Thermal motion of tert-butyl groups III. tert-Butyl substituents in aromatic hydrocarbons, the view from the bottom of the well
Authors: Frey Joseph , Khan Saeed I. , Knobler Carolyn B. , Lightner David A. , Maverick Emily F. , Phillips Daniel J. , Rappoport Zvi , Trueblood Kenneth N.
Published: November 2010

The rigidity of the tert-butyl group (TBG) as a substituent in aromatic hydrocarbons is investigated, with a modified Hirshfeld test of anisotropic displacement parameters (ADPs) as a primary criterion. Four new structures are analyzed, along with low-temperature studies of a previously published crowded supermesityl dimer; three of the five structures meet the primary test. Most of the TBGs meet the Hirshfeld test at 100 K, and the ADPs are improved by omitting low-order data in the final refinement. The three most precise structures yield a wide variation in libration amplitudes (and in estimated rotation barriers) for 13 unique TBGs. A similar range of values is found in analyses of structures in the Cambridge Crystallographic Database. The libration amplitudes are calculated with the program THMA14C, with each TBG as an attached rigid group (ARG). Packing analysis suggests that large ADPs, especially for some individual TBG methyl groups, correspond to voids in the crystal. Published barriers to TBG reorientation, determined by solid-state NMR spin-lattice relaxation methods, for six related crystalline compounds are compared with barriers calculated from their crystal structure data.