bluuebunny/crossref_metadata_2025 huggingface dataset:
Zebrafish: gaining popularity in lipid research
Authors: Hölttä-Vuori Maarit , Salo Veijo T. V. , Nyberg Lena , Brackmann Christian , Enejder Annika , Panula Pertti , Ikonen Elina
Published: June 2010

Zebrafish are an increasingly popular vertebrate model organism in which to study biological phenomena. It has been widely used, especially in developmental biology and neurobiology, and many aspects of its development and physiology are similar to those of mammals. The popularity of zebrafish relies on its relatively low cost, rapid development and ease of genetic manipulation. Moreover, the optical transparency of the developing fish together with novel imaging techniques enable the direct visualization of complex phenomena at the level of the entire organism. This potential is now also being increasingly appreciated by the lipid research community. In the present review we summarize basic information on the lipid composition and distribution in zebrafish tissues, including lipoprotein metabolism, intestinal lipid absorption, the yolk lipids and their mobilization, as well as lipids in the nervous system. We also discuss studies in which zebrafish have been employed for the visualization of whole-body lipid distribution and trafficking. Finally, recent advances in using zebrafish as a model for lipid-related diseases, including atherosclerosis, obesity, diabetes and hepatic steatosis are highlighted. As the insights into zebrafish lipid metabolism increase, it is likely that zebrafish as a model organism will become an increasingly powerful tool in lipid research.
Demand Indicators for Adventure Tourism Packages in Costa Rica: An Exploratory Analysis
Authors: Villalobos-Céspedes Daniel , Galdeano-Gómez Emilio , Tolón-Becerra Alfredo
Published: June 2010

This paper analyzes the management of international tourist demand for adventure activities in Costa Rica and Valle Central. In particular, tourist demand for activities such as hiking, bird watching, nature observation and visits to volcanoes, among others, is not being met by tour operators and travel agencies. These activities are being offered without knowledge of the best combined option or packages. Taking as reference the Survey for Non-resident Tourists, this study analyzes the global trend of preferences of the visitors during the period 2001-2007, including how these tourists would organize their holiday given the opportunity to do so. To this end, we develop a combinatory analysis with probability measures to assess levels of the demand preferences and the efficient management of the suppliers. The results show the combinations of different adventure tourism activities which are considered more appealing, as well as providing orientation for agents in this sector to improve management.
Development of asymmetric double probe formula and its application for collisional plasmas
Authors: Saito S. , Razzak M. A. , Takamura S. , Talukder M. R.
Published: June 2010

The ratio of the electron and ion saturation currents in single probe I-V characteristics for microwave-sustained plasma jets at atmospheric pressure are found to be much smaller than the value expected from the standard high-pressure single probe theory providing an over estimation of electron temperatures. By assuming that the single probe characteristic behaves as an asymmetric double probe when the electron to ion saturation current ratio is reduced, the whole characteristics may be fitted and significantly lower electron temperatures may be derived. In this study, asymmetric double probe theory for collisional plasmas is developed and employed to microwave-sustained helium plasma jets in order to estimate the plasma parameters (electron temperature and plasma density) at atmospheric pressure avoiding the overestimation of electron temperature.
Multiscaling for systems with a broad continuum of characteristic lengths and times: Structural transitions in nanocomposites
Authors: Pankavich S. , Ortoleva P.
Published: June 2010

The multiscale approach to N-body systems is generalized to address the broad continuum of long time and length scales associated with collective behaviors. A technique is developed based on the concept of an uncountable set of time variables and of order parameters (OPs) specifying major features of the system. We adopt this perspective as a natural extension of the commonly used discrete set of time scales and OPs which is practical when only a few, widely separated scales exist. The existence of a gap in the spectrum of time scales for such a system (under quasiequilibrium conditions) is used to introduce a continuous scaling and perform a multiscale analysis of the Liouville equation. A functional-differential Smoluchowski equation is derived for the stochastic dynamics of the continuum of Fourier component OPs. A continuum of spatially nonlocal Langevin equations for the OPs is also derived. The theory is demonstrated via the analysis of structural transitions in a composite material, as occurs for viral capsids and molecular circuits.
Range-separated density-functional theory with random phase approximation applied to noncovalent intermolecular interactions
Authors: Zhu Wuming , Toulouse Julien , Savin Andreas , Ángyán János G.
Published: June 2010

Range-separated methods combining a short-range density functional with long-range random phase approximations (RPAs) with or without exchange response kernel are tested on rare-gas dimers and the S22 benchmark set of weakly interacting complexes of Jurečka et al. [Phys. Chem. Chem. Phys. 8, 1985 (2006)]. The methods are also compared to full-range RPA approaches. Both range separation and inclusion of the Hartree–Fock exchange kernel largely improve the accuracy of intermolecular interaction energies. The best results are obtained with the method called RSH+RPAx, which yields interaction energies for the S22 set with an estimated mean absolute error of about 0.5–0.6 kcal/mol, corresponding to a mean absolute percentage error of about 7%–9% depending on the reference interaction energies used. In particular, the RSH+RPAx method is found to be overall more accurate than the range-separated method based on long-range second-order Møller–Plesset (MP2) perturbation theory (RSH+MP2).
The calibration of carbon nanotube based bionanosensors
Authors: Adhikari S. , Chowdhury R.
Published: June 2010

We derive the calibration constants necessary for using single-walled carbon nanotubes (CNTs) as nanoscale mass sensors. The CNT resonators are assumed to be either in cantilevered or in bridged configurations. Two cases, namely, when the added mass can be considered as a point mass and when the added mass is distributed over a larger area is considered. Closed-form transcendental equations have been derived for the frequency shift due to the added mass. Using the energy principles, generalized nondimensional calibration constants have been derived for an explicit relationship between the added mass and the frequency shift. A molecular mechanics model based on the universal force field potential is used to validate the new results presented. The results indicate that the distributed nature of the mass to be detected has considerable effect on the performance of the sensor.
Al–Si alloy formation in narrow p-type Si contact areas for rear passivated solar cells
Authors: Urrejola Elias , Peter Kristian , Plagwitz Heiko , Schubert Gunnar
Published: June 2010

For high efficiency silicon solar cells, the rear surface passivation by a dielectric layer has significant advantages compared to the standard fully covered Al back-contact structure. In this work the rear contact formation of the passivated emitter and rear cell device structure is analyzed. Contrary to expected views, we found that the contact resistivity of fine screen printed Al fingers alloyed on narrow p-type Si areas depends on the geometry of the Al–Si alloy formation below the contacts, and decreases by reducing the contact area, while the contact resistance remains constant. At the solar cell level, the reduction in the contact resistivity leads to a minimization of the fill factor losses. At the same time, narrow Al–Si alloy formations increased the passivated area below the contacts, improving the optical properties of the rear side, reducing the short-circuit current and open-circuit voltage losses. Scanning electron microscopy analysis of the Al–Si alloy geometry is performed, in order to understand its influence on the contact resistivity. The analysis presented in this article has application in Al–Si alloying processes and advanced solar cells concepts, like back-contact and rear passivated solar cells.
Resistive switching characteristics and mechanisms of Pt-embedded SrZrO3 memory devices
Authors: Lin Meng-Han , Wu Ming-Chi , Lin Chen-Hsi , Tseng Tseung-Yuen
Published: June 2010

The effects of embedded Pt (E-Pt) metal layer on the resistive switching characteristics and mechanisms of SrZrO3 (SZO) memory devices are investigated in this study. The E-Pt is shown by transmission electron microscopy observation to thermally diffuse into SZO thin film to form E-Pt clusters and no chemical reaction occurs between Pt and SZO during 600 °C postannealing process. The carrier transport of high resistance state current of 600 °C E-Pt devices is dominated by Ohmic conduction and Frenkel–Poole (F–P) emission in the low- and high-voltage region, respectively, which is quite different from that of without E-Pt memory devices being principally dominated by F–P emission. Furthermore, the forming voltage and turn-on voltage of E-Pt devices are significantly lowered to −3.5 V and |2.3| V, respectively, due to the reduction in effective thickness of SZO thin films caused by E-Pt clusters formed, which benefit the future development of resistive random access memory devices in practical application.
Piezoelectric and dielectric aging of Bi0.5(Na0.82K0.18)0.5TiO3 lead-free ferroelectric thick films
Authors: Zhang Haibo , Jiang Shenglin , Xiao Jianzhong , Kajiyoshi Koji
Published: June 2010

Ferroelectric Bi0.5(Na0.82K0.18)0.5TiO3 (NKBT) thick films have been prepared using screen printing on Pt electroded alumina substrates. The room-temperature dielectric constant of resulting 60 μm thick NKBT film reaches as high as 823 at 1 kHz and the depolarization temperature, Td, locates at 130 °C. The effect of amplitude and frequency of the applied ac field and the aging temperature as well as the Bi excess on the dielectric and piezoelectric aging characteristics are systemically studied. The results show that the dielectric and piezoelectric aging are associated with the reorientation of defect dipoles which stabilized the non-180° domain walls. By this reorientation the domain wall motions are clamped by a time dependent force resulting in the observed decrease in the dielectric and piezoelectric properties during the aging procedural. Moreover, the aging in NKBT thick films exhibits strong frequency dependence, which is caused by that the reorientation and alignment of the defect dipoles with the local polar domains provide a pinning field to the micropolar region, where the regions with larger micropolar volume will experience stronger pinning potential. The NKBT thick films added with 0.5 mol % Bi2O3 exhibit relative lower aging rate of the dielectric constant and piezoelectric coefficient, resulting from the compensation of the Bi3+ vacancies by the addition of small amount of excess Bi2O3.
Ferroelectric field effect transistors using very thin ferroelectric polyvinylidene fluoride copolymer films as gate dielectrics
Authors: Gerber A. , Fitsilis M. , Waser R. , Reece Timothy J. , Rije E. , Ducharme Stephen , Kohlstedt H.
Published: June 2010

We report electrical characterization of memory elements consisting of a p-type silicon field-effect transistor incorporating a ferroelectric polymer Langmuir–Blodgett film into the gate insulator to produce bistability through polarization hysteresis. The thin gate insulator, consisting of a 10 nm thick silicon oxide layer and a 35 nm thick ferroelectric polymer film, enabled bistable operation at 4 V. Device hysteresis as a function of gate voltage was evident both in the device capacitance, which was measured between the gate and drain, and in the source-drain conductance. The ferroelectric film polarization was not saturated, even up to operating voltages of 10 V. This is likely the reason for the short state retention of less than 10 s at room temperature. The hysteresis vanished as the sample was heated toward the ferroelectric-paraelectric phase transition temperature, showing that the bistability was due to ferroelectric polarization reversal.
Plasmonic racetrack resonator with high extinction ratio under critical coupling condition
Authors: Wang Xiaolei , Wang Pei , Chen Chunchong , Chen Junxue , Lu Yonghua , Ming Hai , Zhan Qiwen
Published: June 2010

In this paper, an ultracompact plasmonic racetrack resonator based on single mode metal-insulator-metal plasmonic gap waveguide with high coupling efficiency is investigated both analytically and numerically. The coupling properties of a plasmonic waveguide to a racetrack resonator at 1.55 μm wavelength are studied with various coupling lengths. An extinction ratio of −34.5 dB and a free-spectral range of 303 nm at the critical coupling point can be achieved. Such a plasmonic resonator design provides a promising realization for highly effective modulators and wide band filters.
Paramagnetism in single-phase Sn1−xCoxO2 dilute magnetic semiconductors
Authors: Ghosh S. , De Munshi D. , Mandal K.
Published: June 2010

Transition metal (TM) Co doped SnO2 dilute magnetic semiconductor (DMS) in both nano- and bulk state are prepared by solvothermal and mechanosyhtesis route, respectively. Contraction in unit cell volume of tetragonal rutile SnO2 after Co doping and redshift in energy band gap compared to that of undoped SnO2 ensures the incorporation of smaller Co2+ ions replacing larger host cations Sn4+. Vibrating sample magnetometer measurements show that paramagnetism is the intrinsic magnetic property in single-phase Sn1−xCoxO whereas non-DMS related ferromagnetism is associated only with the corresponding nanostructures. Paramagnetism is also confirmed by thermal dependence of magnetization M (T) and magnetic susceptibility (χ) measurement in between 80≤T≤350 K.
A gyrofluid description of Alfvénic turbulence and its parallel electric field
Authors: Bian N. H. , Kontar E. P.
Published: June 2010

Anisotropic Alfvénic fluctuations with k∥/k⊥⪡1 remain at frequencies much smaller than the ion cyclotron frequency in the presence of a strong background magnetic field. Based on the simplest truncation of the electromagnetic gyrofluid equations in a homogeneous plasma, a model for the energy cascade produced by Alfvénic turbulence is constructed, which smoothly connects the large magnetohydrodynamics scales and the small “kinetic” scales. Scaling relations are obtained for the electromagnetic fluctuations, as a function of k⊥ and k∥. Moreover, a particular attention is paid to the spectral structure of the parallel electric field which is produced by Alfvénic turbulence. The reason is the potential implication of this parallel electric field in turbulent acceleration and transport of particles. For electromagnetic turbulence, this issue was raised some time ago in Hasegawa and Mima [J. Geophys. Res. 83, 1117 (1978)].
Parametric upconversion of lower hybrid wave by runaway electrons in tokamak
Authors: Kuley Animesh , Tripathi V. K.
Published: June 2010

A kinetic formalism of parametric decay of a large amplitude lower hybrid pump wave into runaway electron mode and an upper sideband mode is investigated. The pump and the sideband exert a ponderomotive force on runaway electrons, driving the runaway mode. The density perturbation associated with the latter beats with the oscillatory velocity due to the pump to produce the sideband. The finite parallel velocity spread of the runaway electrons turns the parametric instability into a stimulated Compton scattering process where growth rate scales as the square of the pump amplitude. The large phase velocity waves thus generated can potentially generate relativistic electrons.
Nonstationary statistical theory for multipactor
Authors: Anza S. , Vicente C. , Gil J. , Boria V. E. , Gimeno B. , Raboso D.
Published: June 2010

This work presents a new and general approach to the real dynamics of the multipactor process: the nonstationary statistical multipactor theory. The nonstationary theory removes the stationarity assumption of the classical theory and, as a consequence, it is able to adequately model electron exponential growth as well as absorption processes, above and below the multipactor breakdown level. In addition, it considers both double-surface and single-surface interactions constituting a full framework for nonresonant polyphase multipactor analysis. This work formulates the new theory and validates it with numerical and experimental results with excellent agreement.
Obtaining true transverse relaxation time distributions in high-field NMR measurements of saturated porous media: Removing the influence of internal gradients
Authors: Mitchell J. , Chandrasekera T. C. , Gladden L. F.
Published: June 2010

It is well known that nuclear magnetic resonance (NMR) transverse relaxation measurements of porous media at high magnetic field strengths provide only an effective relaxation time T2,eff, as opposed to the true T2, due to molecular diffusion through magnetic field gradients induced by the magnetic susceptibility contrast between the adsorbent and the adsorbate. Here, we deconvolve the diffusion and surface relaxation contributions to measurements of T2,eff and thus obtain the true T2 relaxation time distribution. This technique is applicable within the short time diffusion regime where the diffusion exponent varies as tE3, while the surface relaxation exponent varies as tE, where tE is the echo time in a standard Carr–Purcell Meiboom–Gill measurement. We demonstrate this technique on measurements of water in contact with glass spheres across a range of magnetic field strengths from B0=50 mT to 7.4 T. A direct measurement of T2,eff suggests that the transverse relaxation rate increases with field strength, in contrast to theoretical predictions. We show that when the effects of the susceptibility induced gradients, which are known to increase with magnetic field strength, are deconvolved from the T2,eff measurement, the true T2 relaxation rate does indeed decrease with increasing field strength. We also apply the T2 correction in multidimensional NMR experiments using the example of a T1−T2 relaxation correlation. Here, the correction is essential in order to obtain the true T1/T2 ratio as a function of magnetic field strength, which provides a measure of mobility for surface-adsorbed species; without this correction, we see surface residence times overestimated by up to two orders of magnitude. This novel approach enables the accurate determination of T2 distributions, and hence T1/T2 ratios, on high-field spectrometers that would have previously been deemed inappropriate for the study of liquids in porous media because of the intrinsic susceptibility effects.
Is the Weibel instability enhanced by the suprathermal populations or not?
Authors: Lazar M. , Schlickeiser R. , Poedts S.
Published: June 2010

The kinetic instabilities of the Weibel type are presently invoked in a large variety of astrophysical scenarios because anisotropic plasma structures are ubiquitous in space. The Weibel instability is driven by a temperature anisotropy which is commonly modeled by a bi-axis distribution function, such as a bi-Maxwellian or a generalized bi-Kappa. Previous studies have been limited to a bi-Kappa distribution and found a suppression of this instability in the presence of suprathermal tails. In the present paper it is shown that the Weibel growth rate is rather more sensitive to the shape of the anisotropic distribution function. In order to illustrate the distinguishing properties of this instability a product-bi-Kappa distribution is introduced, with the advantage that this distribution function enables the use of different values of the spectral index in the two directions, κ∥≠κ⊥. The growth rates and the instability threshold are derived and contrasted with those for a simple bi-Kappa and a bi-Maxwellian. Thus, while the maximum growth rates reached at the saturation are found to be higher, and the threshold is drastically reduced making the anisotropic product bi-Kappa (with small Kappas) highly susceptible to the Weibel instability. This effect could also raise questions on the temperature or the temperature anisotropy that seems to be not an exclusive source of free energy for this instability, and definition of these notions for such Kappa distributions must probably be reconsidered.
Interfacial barrier in manganite junctions with different crystallographic orientations
Authors: Gao W. W. , Wei A. D. , Sun J. R. , Shang D. S. , Wang J. , Zhao T. Y. , Shen B. G.
Published: June 2010

We performed a comprehensive study on the La1−xCaxMnO3/SrTiO3:Nb junctions with different hole content and film thickness. It is found that the interfacial barrier, which determines the physical properties of the junctions, shows a strong dependence on crystallographic orientation, and it is substantially higher for the (110) than for the (100)-orientated junctions. The difference in barrier height is further found to exhibit a systematic variation with Ca content and film thickness (t). It reduces from ∼0.09 to 0.02 eV for a x increase from 0.1 to 1 with a fixed t=200 nm, and experiences a growth by ∼0.06 eV corresponding to the variation in t from 10 to 160 nm for a constant x=0.33. Similar phenomena have been observed in the La0.67Ba0.33MnO3/SrTiO3:Nb junctions. In the scenario of different polarity mismatches at the (100) and (110) interfaces in the two series of junctions, these results can be qualitatively understood.
Influence of edges on the exchange bias properties of ferromagnetic/antiferromagnetic nanodots
Authors: Baltz V. , Gaudin G. , Somani P. , Dieny B.
Published: June 2010

For ferromagnetic (F)/antiferromagnetic (AF) nanodots contributions of AF spins to exchange bias is discussed. The relative weights of AF entities located at the dot edges, at the F/AF interface and in the AF grains were obtained by comparing the blocking temperature distribution of an array of nanodots with that of corresponding continuous film. Due to grain cutting, the grain size distribution is altered. We show here that the dot edges constitute additional locations for the formation of spin-glasslike AF regions at the F/AF interface. The result of patterning is thus twofold and weakens the dot ability to resist thermally activated magnetization reversal.
Semiclassical initial value approximation for Green’s function
Authors: Kay Kenneth G.
Published: June 2010

A semiclassical initial value approximation is obtained for the energy-dependent Green’s function. For a system with f degrees of freedom the Green’s function expression has the form of a (2f−1)-dimensional integral over points on the energy surface and an integral over time along classical trajectories initiated from these points. This approximation is derived by requiring an integral ansatz for Green’s function to reduce to Gutzwiller’s semiclassical formula when the integrations are performed by the stationary phase method. A simpler approximation is also derived involving only an (f−1)-dimensional integral over momentum variables on a Poincaré surface and an integral over time. The relationship between the present expressions and an earlier initial value approximation for energy eigenfunctions is explored. Numerical tests for two-dimensional systems indicate that good accuracy can be obtained from the initial value Green’s function for calculations of autocorrelation spectra and time-independent wave functions. The relative advantages of initial value approximations for the energy-dependent Green’s function and the time-dependent propagator are discussed.
The effect of cooling rates on the apparent fragility of Zr-based bulk metallic glasses
Authors: Evenson Zach , Gallino Isabella , Busch Ralf
Published: June 2010

We investigate the behavior of the kinetic fragility parameter D∗ as different cooling rates are applied to samples of the Zr57Cu15.4Ni12.6Al10Nb5 and Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 bulk metallic glass formers. The glassy samples are heated into the supercooled liquid region using differential scanning calorimetry (DSC) and cooled back into the glassy state with sets of different cooling rates, qC. The shifts in the glass transition are measured by determining the onset glass transition temperature, Tgonset, as well as the limiting fictive temperature, Tf′, upon reheating with a set of heating rates, qH. We then model the data by assuming a Vogel–Fulcher–Tammann-type behavior in the structural relaxation time, τ, and observe an apparent increase in the kinetic fragility parameter for slower cooling rates. These results show that fragilities calculated from DSC scans, where qH=qC are in good agreement with those from equilibrium viscosity data recently obtained by three-point beam-bending.
Elastic wave velocities of silica glass at high temperatures and high pressures
Authors: Yokoyama Ayako , Matsui Masanori , Higo Yuji , Kono Yoshio , Irifune Tetsuo , Funakoshi Ken-ichi
Published: June 2010

The elastic compressional (P) and shear (S) wave velocities of silica glass at simultaneous high pressures and high temperatures were measured using a combination of ultrasonic interferometry, in situ synchrotron x-ray diffraction, and radiographic techniques in a large-volume Kawai-type multianvil apparatus. We found no first-order amorphous-amorphous transformation throughout the pressure and temperature conditions between 2 and 5 GPa and up to 1173 K, contrary to previous studies suggested by piston cylinder experiments or molecular dynamics simulations. For each of the 650 and 800 K isothermal runs, the P and S wave velocities initially decreased with increasing pressure, reaching minimum values at around 3–4 GPa, followed by increases with pressure up to 6.1 GPa; on successive decompression to ambient pressure, both velocities changed irreversibly due to permanent densification, and no minima were observed in both velocities. We also found that, in a second compression-decompression cycle at 800 K, the densified silica glass was compressed reversibly (elastically) within errors without further irreversible densification. Using the measured P and S wave velocities in such reversible (elastic) compression regions as a function of pressure, we found the density of silica glass increases with temperature from 300 to 800 K at all the measured pressure range up to 6.1 GPa, providing a direct evidence of a negative thermal expansion of silica glass at high pressures.
Illumination uniformity of a capsule directly driven by a laser facility with 32 or 48 directions of irradiation
Authors: Temporal M. , Canaud B. , Laffite S. , Le Garrec B. J. , Murakami M.
Published: June 2010

The uniformity of the illumination of a spherical capsule directly driven by laser beams has been assessed numerically. Two schemes characterized by 32 and 48 directions of irradiation with associated a single laser beam or a bundle of laser beams characterized by a super-Gaussian intensity profile are considered. The calculations take into account beam imperfections as power imbalance and pointing errors. It is found that the optimum laser intensity profile, which minimizes the illumination uniformity, depends on the beams’ imperfections. A comparison between both schemes shows that the 48 beams configuration allows better illumination uniformity than the 32 beams’ configuration.
20 T portable bipolar magnetic pulser
Authors: Wolf Cruz R. R. , Dias A. L. B. , Bonfim M. J. C.
Published: June 2010

High magnetic fields are required for the study of hard magnetic materials and, in many cases, the reversal of these fields is essential. This paper describes a portable pulse generator capable of producing bipolar magnetic fields up to 20 T into a copper coil. The peak current around 7 kA is achieved by discharging two capacitor banks through a combination of thyristors and fast diodes. Each pulse polarity has a semisinusoidal shape with 18 μs base width. Pulse triggering is computer controlled and magnetic measurements are done by an induction coil or Kerr effect acquired by a sampling oscilloscope. The whole apparatus weighs less than 2 kg. Hysteresis loops of NdFeB magnets were done to demonstrate the viability of the system.
Reduced room-temperature ferromagnetism in intermediate conducting regime of V doped ZnO
Authors: Liu S. H. , Hsu H. S. , Venkataiah G. , Qi X. , Lin C. R. , Lee J. F. , Liang K. S. , Huang J. C. A.
Published: June 2010

The mechanism of room temperature (RT) ferromagnetism for low doping concentration of 2.5% V in ZnO have been systematically discussed by measuring structural, electrical, and magnetic properties. The evolution of the Curie temperature from above RT in insulated V:ZnO powders to 270 K in semiconducting samples was observed with increasing carrier concentration by using different hydrogenated annealing treatment. The results provide a direct observation that the free carriers suppress the ferromagnetism and might be associated the phenomena of charge-transfer and interaction between bound magnetic polarons.
Band alignment at Sb2S3/Cu(In,Ga)Se2 heterojunctions and electronic characteristics of solar cell devices based on them
Authors: Kieven D. , Grimm A. , Lauermann I. , Rissom T. , Klenk R.
Published: June 2010

Band offsets at Sb2S3/Cu(In,Ga)Se2 heterojunctions have been studied by x-ray and ultraviolet photoemission spectroscopy. The valence and conduction band offset have been estimated to −(0.6±0.3) eV and (0.2±0.3) eV, respectively. This result suggests Sb2S3 as a potential buffer layer material for chalcopyrite based solar cells. However, Cu(In,Ga)Se2/Sb2S3/ZnO solar cells have been investigated. While the open circuit voltage ranged up to ∼0.4–0.5 V, the short circuit current was limited to ∼1.8–4.9 mA/cm2. A photocurrent of about 30 mA/cm2 was found for negative bias. On the basis of bias dependent quantum efficiency measurements and calculations, limiting mechanisms are discussed.
Boron diffusion in magnetic tunnel junctions with MgO (001) barriers and CoFeB electrodes
Authors: Kurt H. , Rode K. , Oguz K. , Boese M. , Faulkner C. C. , Coey J. M. D.
Published: June 2010

Boron diffusion out of the CoFeB layers in model systems with thick CoFeB and MgO layers grown by radiofrequency sputtering or electron-beam evaporation and in MgO-based magnetic tunnel junctions (MTJs) is probed after annealing by x-ray photoemission spectroscopy (XPS) and electron energy loss spectroscopy. Successive interfaces are exposed by ion milling the stacks, layer by layer, in the XPS system. Despite the presence of thick CoFeB and a high annealing temperature of 400 °C, we found no boron in the MgO or at the MgO/CoFe interfaces. Similar results are also obtained in the MTJs.
Size controlled synthesis of Ge nanocrystals in SiO2 at temperatures below 400 °C using magnetron sputtering
Authors: Zhang B. , Shrestha S. , Green M. A. , Conibeer G.
Published: June 2010

A simple and silicon process-compatible technique is reported for the synthesis of Ge nanocrystals (Ge-ncs) at low temperatures below 400 °C, which is much lower than the typical growth temperatures. The Ge-ncs were found to form only within a temperature window between 350 and 420 °C. The underlying mechanism has been explained by a competitive process between Volmer–Weber growth and oxidation reaction. We further implemented this technique in the fabrication of multilayered Ge-ncs which exhibited controllable crystallite size with high crystallization quality. The low temperature technique developed in this work would allow production of Ge-ncs and relative devices on low cost substrates, such as glass.
Transition of stable rectification to resistive-switching in Ti/TiO2/Pt oxide diode
Authors: Huang Jiun-Jia , Kuo Chih-Wei , Chang Wei-Chen , Hou Tuo-Hung
Published: June 2010

We have fabricated a Ti/TiO2/Pt oxide diode with excellent rectifying characteristics by the asymmetric Schottky barriers at the Ti/TiO2 (0.13 eV) and the TiO2/Pt (0.73 eV) interfaces. Instead of homogeneous conduction, the current transport is governed by the localized oxygen-deficient TiO2 filaments. In addition, the reproducible resistive-switching exists in the same structure, triggered by the forming process. The transition between two modes is ascribed to the destruction of the interface barriers at forming. The rectification stable up to 125 °C and 103 cycles under ±3 V sweep without interference with resistive-switching shows satisfactory reliability of TiO2 diodes for one diode-one resistor memory devices.
Tuning of magnetism in ferromagnetic thin films by reversing the functional groups of molecular underlayer
Authors: Tai Jung-Chi , Huang Jang-Chang , Chang Yin-Ming , Li Kai-Shin , Hong Jhen-Yong , Wong Sheng-Syun , Chiang Wen-Chung , Lin Minn-Tsong
Published: June 2010

We demonstrate a molecular approach of tuning the magnetic properties of ferromagnetic (FM) thin films by reversing the functional groups of the organic underlayer. For the CoFe/Langmuir–Blodgett (LB) film system, we find that the coercivity of CoFe thin films (from 4 to 10 nm) made on hydrophobic surfaces is significantly enhanced whereas that on hydrophilic surfaces remains unchanged, as compared with the films directly on glass substrates. These findings suggest an alternative way for tuning the magnetic properties of the FM layer by LB film in which the functional groups play an important role.
Predissociation dynamics of N2O+ at the A Σ2+ state: Three pathways to form NO+(Σ1+) revealed from ion velocity imaging
Authors: Wang Hua , Zhou Xiaoguo , Liu Shilin , Jiang Bo , Dai Dongxu , Yang Xueming
Published: June 2010

The predissociation dynamics of nitrous oxide ion (N2O+) at its first excited state A Σ2+ has been investigated with ion velocity imaging by probing the NO+ fragments. The parent ion N2O+, prepared at the ground state X Π2(000) through (3+1) resonance-enhanced multiphoton ionization (REMPI) of jet-cooled N2O molecules at 360.55 nm, was excited to different vibrational levels of the A Σ2+ state in a wavelength range of 280–320 nm, and then predissociated to form NO+ and N fragments. The internal energy distribution of the NO+ fragment was determined from its ion velocity images. With the help of potential energy surfaces (PESs) of N2O+, three dissociation pathways have been proposed to interpret the three kinds of NO+ fragments with different internal state distributions: (1) the A Σ2+ state couples to a dissociative 1 Σ4− state via a bound 1 Π4 state to form the NO++N(S4) channel, where NO+ fragment is rotationally hot; (2) the A Σ2+ state couples to dissociative states Σ2−/Δ2 via the 1 Π4 state to form the NO++N(D2) channel, where NO+ fragment is also rotationally hot; (3) the A Σ2+ state couples to the high energy region of the ground state X Π2 and then dissociates to form the NO++N(D2) channel, where NO+ is rotationally cold.
Bias-induced oxygen adsorption in zinc tin oxide thin film transistors under dynamic stress
Authors: Chen Yu-Chun , Chang Ting-Chang , Li Hung-Wei , Chen Shih-Ching , Lu Jin , Chung Wan-Fang , Tai Ya-Hsiang , Tseng Tseung-Yuen
Published: June 2010

This study investigates the effects of bias-induced oxygen adsorption on the electrical characteristic instability of zinc tin oxide thin film transistors in different ambient oxygen partial pressures. When oxygen pressure is largest, the threshold voltages showed the quickest increase but the slowest recovery during the stress phase and recovery phase, respectively. This finding corresponds to the charge trapping time constant and recovery time constant, which are extracted by fitting the stretched-exponential equation and which exhibit a relationship with oxygen pressure. We suggest that the gate bias reduces the activation energy of oxygen adsorption during gate bias stress.
Effect of electrode configurations on the process-induced imprint behavior of epitaxial Pb(Zr0.52Ti0.48)O3 capacitors
Authors: Chen Feng , Tan Xuelian , Huang Zhen , Xuan Xiaofeng , Wu Wenbin
Published: June 2010

By using La0.7Sr0.3MnO3 (L) and SrRuO3 (S) electrodes, epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) capacitors with different electrode configurations, i.e., L/PZT/L (from top to bottom) (a), S/PZT/S (b), S/PZT/L (c), and L/PZT/S (d), have been fabricated and the process-induced imprint was investigated. All as-grown capacitors are nearly imprint-free; however, after being annealed at 10−5 Torr of O2 the capacitors a (b) show a large negative (positive) imprinted polarization (P) state at zero electric-field (E), the capacitors c give strongly pinched P-E hysteresis loops, and the capacitors d are highly resistant to imprint failure. We show evidence that the internal fields could be attributed to the various oxygen-loss-related strain gradients at PZT top and bottom interfaces, induced during the annealing.
Local and Green, Global and Fair: The Ethical Foodscape and the Politics of Care
Authors: Morgan Kevin
Published: June 2010

The core values of the ethical foodscape—ecological integrity and social justice—can assume very different political forms unless they are fashioned into a coherent and progressive narrative of sustainability. This paper explores the politics of sustainability through the prism of three major issues. First, the carbon-labelling controversy is used to highlight the potential conflict between green campaigners (who extol the benefits of local food) and social justice campaigners (who support fairly traded food from afar). Second, school-food reform is used to demonstrate that local and global food, far from being mutually exclusive options, can both be part of the constitution of a sustainable food system if global food is framed in cosmopolitan terms. Third, the paper engages with the politics of care literature to explore a question that underlies the above issues, namely, how and why we care for others. It is argued that ethical consumerism, a key part of a progressive narrative of care, is not sufficient to counter the challenge of climate change—the greatest threat to ecological integrity and social justice.
Slines, Entropy, and Environmental Exploration
Authors: Stamps Arthur E
Published: June 2010

This paper addresses the question of how to create environments that people will want to explore. Four environmental properties (slines, entropy, floor area, and shape) were tested for exploration time in three experiments that included thirty-eight virtual environments and sixty participants. Slines had the strongest effect on exploration time ( r = 0.36), followed by entropy ( r = 0.34). Floor area and shape had much smaller effects on exploration time ( r = 0.10 and r = 0.09, respectively). Possibilities for future research are discussed.
Second Homes within Irish Housing Booms and Busts: North-South Comparisons, Contrasts, and Debates
Authors: Norris Michelle , Paris Chris , Winston Nessa
Published: June 2010

We examine the expansion of second home ownership in the two jurisdictions on the island of Ireland—the Republic of Ireland and Northern Ireland. The phenomenon has emerged more recently here than in many other countries. While the growth of second homes in Ireland can be explained by many of the factors which have contributed to rising second home ownership internationally, local factors distinguish the two jurisdictions both from each other and from other cases. We compare and contrast the situation in the two jurisdictions, while also locating them in an international context. We assess the impact of second homes on local communities, housing markets, and the environment in Ireland and highlight the key public policy issues arising in each jurisdiction.
Ensuring Local Community Interests in Market-Oriented Urban Planning? The Role of Local Politicians
Authors: Hanssen Gro S
Published: June 2010

In this paper I discuss the role of local politicians in representing, mediating, and balancing growth interests and local community interests in Norway, a country that has introduced market-oriented reforms in urban planning, giving private developers a prominent role. On the basis of a broad survey and qualitative case studies I found that local community actors predominantly confront local politicians, not planners or developers, to have their voices heard. Local community actors have few institutionalized arenas for their voices in the early phases, as mandatory involvement (public hearings, complaints) is to be found only in later phases. Thus, the arenas are predominantly accommodating ‘passive participation’, the opportunity to react and protest only on already formulated proposals. Local politicians have an important role in channelling citizen input into decision making, even if the contact is mostly informal. Developers are given the proactive, constructive role, as almost all municipalities studied have institutionalized arenas for interaction between planners and developers.
Depth Perception through Circular Movements of Dots
Authors: Ito Hiroyuki
Published: June 2010

Elements that move with velocity gradients have been shown to give the impression of depth. In this study, it was found that dots in circular motion around a line of sight give a depth impression corresponding to the gradients of the angular velocities of circular motion on a screen. The results of two experiments show that depth perception through circular motion is as effective as that through expansion or spiral motion, but less effective than that through lateral motion parallax when the local speed distributions on the screen are matched. The present depth effect shows that expansion – contraction, spiral, and circular motions are a continuum in terms of producing depth effects; they differ from lateral motion parallax.
Analysis and Explanation of the Thiéry–Wundt Illusion
Authors: Day Ross H , Kimm Andrew C
Published: June 2010

The midpoint of the axis of bisection in a triangle appears to be displaced toward the apex so that the apical extent seems to be shorter than the basal extent, an effect originally reported in 1895 by Thiéry and later in 1898 by Wundt and, therefore, referred to here as the Thiéry–Wundt illusion. Following a demonstration strongly suggesting that the illusion is yet another version of the Müller-Lyer effect in a stimulus figure with inward-directed angles, four exploratory experiments designed to throw more light on this group of illusions are reported. The first showed that the effect occurs in an open angle, between converging lines that do not meet to form an apex, between converging stepped lines, and when one of the converging lines is removed, leaving a single oblique line. The other three experiments showed that the illusion also occurs in an open semicircle and a rectangular bracket, is weakened by the addition of a complete or partial baseline to form a triangle, and weakly but reliably when the angle is minimally formed from dots marking the ends of oblique lines. On the basis of these data, Judd's version of the conventional Müller-Lyer figure, and informal but easily repeatable observations, it is concluded that the Thiéry–Wundt illusion is, like other variants of the Müller-Lyer group of illusions, due to a process of directional biasing—an extension of the concept of biasing proposed originally by Morgan et al (1990, Vision Research30 1793–1810).
Does Left–Right Orientation Matter in the Perceived Expressiveness of Pictures? A Study of Bewick's Animals (1753–1828)
Authors: Bennett Kate M , Latto Richard , Bertamini Marco , Bianchi Ivana , Minshull Sarah
Published: June 2010

Strong claims have been made about the importance of orientation in visual art. Although there have been a few studies whether left or right oriented pictures are more aesthetically pleasing, there have been no empirical studies whether the meaning and expressiveness of pictures depend on orientation. Thomas Bewick (1753–1828) made explicit decisions about whether the main protagonist in his pictures should face left or right and did so to express particular meaning. In three experiments we examined whether orientation changes the expressiveness of an image. In experiment 1 participants viewed eight of Bewick's animal wood engravings facing either in their original orientation or reversed, in a between-subjects design. They rated each print on ten characteristics, for example: docile–wild, clumsy–agile, and weak–strong. The original received more extreme ratings, across characteristics, than the reversal. Experiment 2 confirmed this result with participants from Italy. In experiment 3, using a within-subjects design, participants viewed ten wood engravings of dogs and rated them on characteristics specifically identified by Bewick. Again, the ratings of the original orientation were more extreme. Thus, in agreement with Bewick, we conclude that orientation affects expressiveness.
Status of the New Zealand cave weta (Rhaphidophoridae) genera Pachyrhamma, Gymnoplectron and Turbottoplectron
Authors: Cook Lorraine D. , Trewick Steven A. , Morgan-Richards Mary , Johns Peter M.
Published: June 2010

The New Zealand Rhaphidophoridae Walker, 1869 comprise 18 endemic genera (including 8 that are monotypic). Although there are many new species to be described, rationalisation at the genus level is also required due to inconsistencies in their current systematics. Even the largest and best known taxa, including those that occupy cave systems and are the most frequently encountered by people, require taxonomic revision. These cave weta include species assigned to three poorly differentiated genera, Pachyrhamma Brunner v. Wattenwyl, 1888, Gymnoplectron Hutton, 1897 and Turbottoplectron Salmon, 1948, that are best known from North Island New Zealand. We used mitochondrial DNA sequence data to examine their relationships using representatives of each genus. The results indicate that a single genus Pachyrhamma would be appropriate for all, as Gymnoplectron and Turbottoplectron nest phylogenetically within it. There are insufficient morphological, spatial or ecological reasons to justify retention of all three. However, we also note that species level diversity does not correlate with genetic or spatial diversity; some species are genetically well partitioned and widespread while others have narrow ranges in single cave systems and are closely related to one another.