bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulations of chemical vapor deposition diamond film growth using a kinetic Monte Carlo model and two-dimensional models of microwave plasma and hot filament chemical vapor deposition reactors
Authors: May P. W. , Harvey J. N. , Allan N. L. , Richley J. C. , Mankelevich Yu. A.
Published: December 2010

A one-dimensional kinetic Monte Carlo (KMC) model has been developed to simulate the chemical vapor deposition of a diamond (100) surface under conditions used to grow single-crystal diamond (SCD), microcrystalline diamond (MCD), nanocrystalline diamond (NCD), and ultrananocrystalline diamond (UNCD) films. The model considers adsorption, etching/desorption, lattice incorporation and surface migration but not defect formation or renucleation processes. Two methods have been devised for estimation of the gas phase concentrations of species at the growing diamond surface, and are used to determine adsorption rates for C1Hx hydrocarbons for the different conditions. The rate of migration of adsorbed carbon species is governed by the availability of neighboring radical sites, which, in turn, depend upon the rates of H abstraction and of surface-radical migration. The KMC model predicts growth rates and surface roughness for each of diamond types consistent with experiment. In the absence of defect formation and renucleation the average surface diffusion length, ℓ, is a key parameter controlling surface morphology. When ℓ<2, surface migration is limited by the lack of availability of surface radical sites, and the migrating surface species simply hop back and forth between two adjacent sites but do not travel far beyond their initial adsorption site. Thus, Eley–Rideal processes dominate the growth, leading to the rough surfaces seen in NCD and UNCD. The maximum or “intrinsic” surface roughness occurs for nominally zero-migration conditions (ℓ=0) with an rms value of approximately five carbon atoms. Conversely, when migration occurs over greater distances (ℓ>2), Langmuir–Hinshelwood processes dominate the growth producing the smoother surfaces of MCD and SCD. By extrapolation, we predict that atomically smooth surfaces over large areas should occur once migrating species can travel approximately five sites (ℓ∼5). β-scission processes are found to be unimportant for MCD and SCD growth conditions, but can remove up to 5% of the adsorbing carbon for NCD and UNCD growth. C1Hx insertion reactions also contribute <1% to the growth for nearly all conditions, while C2Hx (x<2) insertion reactions are negligible due their very low concentrations at the surface. Finally, the predictions for growth rate and morphology for UNCD deposition in a microwave system were found to be anomalous compared to those for all the other growth conditions, suggesting that carbonaceous particulates created in these plasmas may significantly affect the gas chemistry.
Coherent quantum phenomena in mesoscopic metallic conductors (Review Article)
Authors: Gogadze G. A.
Published: December 2010

Quantum coherent phenomena in mesoscopic cylindrical metallic conductors are examined. When pure doubly- and singly-connected normal samples are placed in a longitudinal magnetic field, interference phenomena occur which depend on the magnetic flux through the cross-section of the conductor. The period of the induced oscillations is given by the quantum of flux, hc∕e, of the normal metal. Quantum states are formed in these structures by electron collisions with the dielectric boundary of the sample. The magnetic flux is included in the expression for the quasiparticle spectrum. The proximity effect and its influence on the spectrum of quantum coherent phenomena is investigated. The behavior of cylindrical samples consisting of a superconducting (S) metal with a deposited thin pure normal (N) metal layer is analyzed. In these structures, electrons are localized in a well bounded by a dielectric on one side and by a superconductor on the other. The resulting quantized Andreev levels have the feature that in a varying field H (or temperature T) each of the levels in the well can coincide periodically with the chemical potential of the metal. As a result, the state of the system has a strong degeneracy and the density of states exhibits resonance spikes as a function of the energy of the NS sample. This makes a significant contribution to the magnetic moment. A theory of the reentrant effect for NS structures has been developed for interpreting the anomalous behavior of the magnetic susceptibility of these structures as a function of magnetic field and temperature.
450 mm dual frequency capacitively coupled plasma sources: Conventional, graded, and segmented electrodes
Authors: Yang Yang , Kushner Mark J.
Published: December 2010

Wafer diameters for microelectronics fabrication will soon transition from 300 to 450 mm at a time when excitation frequencies for capacitively coupled plasmas (CCPs) are increasing to 200 MHz or higher. Already for 300 mm tools, there is evidence that wave behavior (i.e., propagation, constructive, and destructive interference) affects the uniformity of processing. The increase in diameter to 450 mm is likely to exacerbate these effects, perhaps requiring nontraditional tool designs. This is particularly important in dual frequency (DF) CCP tools in which there are potential interactions between frequencies. In this paper, results from a two-dimensional computational investigation of Ar plasma properties in a 450 mm DF-CCP reactor, incorporating a full-wave solution of Maxwell’s equations, are discussed. As in 300 mm DF-CCP reactors, the electron density collapses toward the center of the reactor with increasing high frequency (HF), however, with more pronounced finite wavelength effects. Graded conductivity electrodes with multilayer of dielectrics are computationally demonstrated as a possible means to suppress wave effects thereby increasing plasma uniformity. Segmentation of the HF electrode also improves the plasma uniformity by making the electrical distance between the feeds and the sheath edges as uniform as possible.
Novel spray pyrolysis for dye-sensitized solar cell
Authors: Senthilnathan V. , Ganesan S.
Published: December 2010

In the area of photovoltaic, the silicon solar cell is the most popular and it has issues such as stability and scaling up cost. On the other hand, a dye-sensitized solar cell (DSSC) is one of the most promising candidates for a high-performance solar cell in the next generation, since it is fabricated by a simple manufacture process at relatively low cost. The focus of interest in this research paper is to mention the usage of maiden single and simple apparatus of spray pyrolysis thin film deposition to fabricate the electrode and counterelectrode for DSSC. It involves the novelties introduced in the instrumentation of the apparatus and the characterizations (x-ray diffraction, scanning electron microscope, and atomic force microscopy) of the prepared thin films for the fabricated DSSC. In this work, the pomegranate fruit dye is used to sensitize the nano-TiO2.
Preheating ablation effects on the Rayleigh–Taylor instability in the weakly nonlinear regime
Authors: Wang L. F. , Ye W. H. , Sheng Z. M. , Don Wai-Sun , Li Y. J. , He X. T.
Published: December 2010

The two-dimensional Rayleigh–Taylor instability (RTI) with and without thermal conduction is investigated by numerical simulation in the weakly nonlinear regime. A preheat model κ(T)=κSH[1+f(T)] is introduced for the thermal conduction [W. H. Ye, W. Y. Zhang, and X. T. He, Phys. Rev. E 65, 057401 (2002)], where κSH is the Spitzer–Härm electron thermal conductivity coefficient and f(T) models the preheating tongue effect in the cold plasma ahead of the ablation front. The preheating ablation effects on the RTI are studied by comparing the RTI with and without thermal conduction with identical density profile relevant to inertial confinement fusion experiments. It is found that the ablation effects strongly influence the mode coupling process, especially with short perturbation wavelength. Overall, the ablation effects stabilize the RTI. First, the linear growth rate is reduced, especially for short perturbation wavelengths and a cutoff wavelength is observed in simulations. Second, the second harmonic generation is reduced for short perturbation wavelengths. Third, the third-order negative feedback to the fundamental mode is strengthened, which plays a stabilization role. Finally, on the contrary, the ablation effects increase the generation of the third harmonic when the perturbation wavelengths are long. Our simulation results indicate that, in the weakly nonlinear regime, the ablation effects are weakened as the perturbation wavelength is increased. Numerical results obtained are in general agreement with the recent weakly nonlinear theories as proposed in [J. Sanz, J. Ramírez, R. Ramis et al., Phys. Rev. Lett. 89, 195002 (2002); J. Garnier, P.-A. Raviart, C. Cherfils-Clérouin et al., Phys. Rev. Lett. 90, 185003 (2003)].
Weak localization, Aharonov-Bohm oscillations, and decoherence in arrays of quantum dots
Authors: Golubev D. S. , Semenov A. G. , Zaikin A. D.
Published: December 2010

Combining scattering matrix theory with the non-linear σ-model and the Keldysh technique, we develop a unified theoretical approach for non-perturbative study of the effect of electron-electron interactions on weak localization and Aharonov-Bohm oscillations in arbitrary arrays of quantum dots. Our model embraces weakly disordered conductors, strongly disordered conductors, and metallic quantum dots. In all these cases, as T→0 the electron decoherence time saturates to a finite value determined by a universal formula which agrees quantitatively with a number of experiments. Our analysis provides overwhelming evidence in favor of electron-electron interactions as a universal mechanism for zero temperature electron decoherence in disordered conductors.
Thermoelectric properties of partly Sb- and Zn-substituted Ba8Ga16Ge30 clathrates
Authors: Cederkrantz D. , Nygren M. , Palmqvist A. E. C.
Published: December 2010

The effects on the thermoelectric properties of n-Ba8Ga16Ge30 when substituting small amounts of the Ga or Ge with Sb or Zn have been investigated. A number of syntheses were prepared in quaternary systems of Ba8Ga16Ge30 substituted with either Sb or Zn but only three samples were found to yield single phase products with nominal compositions of Ba8Ga15Sb1Ge30, Ba8Ga15Zn1Ge30 and Ba8Ga16Ge28Zn2, respectively. When Ge was substituted for Zn the resulting sample remained n-type and an increase in thermopower and a decrease in thermal conductivity were achieved. These positive effects were accompanied with an increased electrical resistivity and thus the ZT was only somewhat improved up to about 400 °C. When substituting Ga with either Sb or Zn samples remained n-type but showed decreased thermopower and increased electrical resistivity and thermal conductivity. It is thus concluded that substitution of Ga with Zn or Sb is detrimental for the thermoelectric properties of Ba8Ga16Ge30, whereas substitution of Ge with Zn appears a potent method for improving its performance.
Monodisperse magnetite nanofluids: Synthesis, aggregation, and thermal conductivity
Authors: Jiang Wei , Wang Liqiu
Published: December 2010

Magnetic nanofluids possess some unique properties that can significantly affect their thermal conductivity. We synthesize monodispersed magnetite (Fe3O4) nanofluids in toluene with the particle size from 4 to 12 nm and obtain aqueous nanofluids by a simple “one-step” phase transfer. Even without the effect of external field, the magnetic-interaction-induced self-assembled aggregation can still be significant in magnetite nanofluids. Investigation of the microstructures of self-assembled aggregation is carried out by the dynamic light scattering, which unveils the variation of aggregated configurations with particle concentration and time. Based on the calculation from the existing models, the aggregates decrease the thermal conductivity of both themselves and the entire system, mainly due to the less solid contents and weaker mobility compared with the single particles as well as the increase in interfacial thermal resistance. As the manifestation of the aggregation-structure variation, the measured thermal conductivity is of a wavelike shape as a function of particle concentration. The particle coating layers are also of importance in cluster formation so that nanofluid thermal conductivity can be manipulated for some nanofluids by changing the stabilizer used and thus controlling the particle aggregated structures. Due to the effects of temperature, viscosity and coating layers, the thermal conductivity for aqueous system varies in a different way as that for the toluene system.
Sensing small changes in a wave chaotic scattering system
Authors: Taddese Biniyam Tesfaye , Antonsen Thomas M. , Ott Edward , Anlage Steven M.
Published: December 2010

Classical analogs of the quantum mechanical concepts of the Loschmidt Echo and quantum fidelity are developed with the goal of detecting small perturbations in a closed wave chaotic region. Sensing techniques that employ a one-recording-channel time-reversal-mirror, which in turn relies on time reversal invariance and spatial reciprocity of the classical wave equation, are introduced. In analogy with quantum fidelity, we employ scattering fidelity techniques which work by comparing response signals of the scattering region, by means of cross correlation and mutual information of signals. The performance of the sensing techniques is compared for various perturbations induced experimentally in an acoustic resonant cavity. The acoustic signals are parametrically processed to mitigate the effect of dissipation and to vary the spatial diversity of the sensing schemes. In addition to static boundary condition perturbations at specified locations, perturbations to the medium of wave propagation are shown to be detectable, opening up various real world sensing applications in which a false negative cannot be tolerated.
Properties of wetting layer states in low density InAs quantum dot nanostructures emitting at 1.3 μm: Effects of InGaAs capping
Authors: Seravalli L. , Bocchi C. , Trevisi G. , Frigeri P.
Published: December 2010

In this work we study the properties of energy levels of the two-dimensional quantum system composed by wetting layers and thin capping layers in low density InAs/InGaAs quantum dot structures, that can be used as single photon sources at the fiber-optic wavelength of 1.3 μm. We show how, thanks to the low density of quantum dots, x-ray characterization of structures allows to extract thicknesses and compositions of the InAs wetting layer and the quantum well formed by the InGaAs capping layer, resulting in substantial deviations from the simplified picture of a wetting layer consisting of a 1.6 monolayer thick InAs square well. The agreement between model calculations of quantum confined energy levels based on x-ray data and photoluminescence peak energies substantiates the validity of this calculation, that also allows to investigate on carrier localization. The increase in In composition in the InGaAs capping layer results in reduced localization of heavy holes in the wetting layer, that are pushed into the InGaAs quantum well, while the electron, being already strongly delocalized in the quantum well, is relatively less affected. We discuss consequences on carriers’ overlap in the wetting layer and on spatial separation between wetting layer and quantum dot carriers and we consider implications for control of properties of quantum dot structures suitable as single photon sources in the telecommunication windows.
Passage of a monomer through a nonrigid periodical substrate formed by noninteracting particles
Authors: Iakushev Denis
Published: December 2010

The paper examines a classical system in one degree of freedom: a particle (monomer) interacting with a periodic lattice of independent, separated oscillators. The monomer can interact with oscillators via a short-range attractive potential force. The periodic lattice of oscillators may absorb the energy of the monomer launched at some initial velocity, but it does so in a very peculiar manner. The monomer velocity gradually decreases, approaching near some nonzero limit value. The limiting monomer velocities can assume discrete values only. This behavior of the monomer is accounted for by the existing resistance force that completely vanishes at certain monomer velocities.
Optoelectronic and all-optical multiple memory states in vanadium dioxide
Authors: Coy Horacio , Cabrera Rafmag , Sepúlveda Nelson , Fernández Félix E.
Published: December 2010

Vanadium dioxide exhibits a well-known insulator-to-metal transition during which several of its physical properties change significantly. A hysteresis loop develops for each of them as the material is heated and then cooled through the transition. In this work VO2/SiO2 samples were maintained—by heat sinking—at a selected temperature within the heating branch of the hysteresis loops for resistance and near-infrared transmittance, while brief thermal excursions of the VO2 film were caused by either voltage pulses applied to the film or laser light pulses irradiating the film. These pulses had durations from milliseconds to a few seconds and the resulting drops in resistance or transmittance were easily and repeatably measurable without appreciably affecting their new values. A sequence of equal-duration pulses (for either equal-voltage or equal-irradiation pulses) caused the resistance and infrared transmittance to continue to drop, each time by a smaller amount, and larger energy pulses were required in order to cause drops comparable with the initial one. The ability of the film to change the values of the measurands in this manner with additional pulses was maintained up to a limit defined by the outer hysteresis curve for the measurand in question. The results presented show that a plurality of memory “states” in VO2 can be established or “written” either by voltage pulses or by light pulses applied to the material, and queried or “read” by resistance or transmittance readings, or both. These states were found to remain stable for at least several hours, as long as temperature was kept constant, and are expected to persist indefinitely under this condition. In the all-optical case, if the same light beam is used for writing and reading the memory state, the device is an optical analog of a memristor.
Weak dissipation does not result in the disappearance of the persistent current
Authors: Gurtovoi V. L. , Ilin A. I. , Nikulov A. V. , Tulin V. A.
Published: December 2010

Recent experiments confirm a prediction made by I.O. Kulik forty years ago to the effect that energy dissipation does not suppress the equilibrium circular current observed in the normal state of superconducting rings and normal metal rings. Conflicting interpretations of the persistent current as a Brownian motion or a dissipationless current are compared from the standpoint of observations of this phenomenon when an electric potential difference is present. Distinctions between quantum phenomena at the atomic and mesoscopic levels are emphasized. It is pointed out that quantum oscillations in the magnetic field of the potential difference observed in asymmetric rings with a persistent current can be verified experimentally under thermodynamic equilibrium.
Effect of relative vapor pressure on separation of nanoscale contact in atomic force microscope
Authors: Kim Doo-In , Jeong Young-Keun , Kang Myung-Chang , Ahn Hyo-Sok , Kim Kwang Ho
Published: December 2010

The separation of nanoscale contact junction is investigated in an atomic force microscope at various relative vapor pressure conditions. Gradual increase in adhesion force is observed as the relative vapor pressure increases. However, the force-deformation behaviors of the water-mediated nanoscale contacts vary extensively with the relative vapor pressure conditions. At low relative vapor pressure (p/ps<0.06), water molecules play a role as a weak glue contributing solid extension. In contrast, at high relative vapor pressure (p/ps=0.8), the highest adhesion force is observed without indication of the solid extension. The meniscus collapses and forms a water column after solids separates at an intermediate relative vapor pressure condition (p/ps=0.4). The detailed analysis revealed the transition of adhesion mechanism from the solid-dominant adhesion to liquid-dominant adhesion as the relative vapor pressure increases.
The role of local anisotropy profiles at grain boundaries on the coercivity of Nd2Fe14B magnets
Authors: Hrkac Gino , Woodcock Thomas G. , Freeman Colin , Goncharov Alexander , Dean Julian , Schrefl Thomas , Gutfleisch Oliver
Published: December 2010

We present numerical evidence from atomistic calculations that the coercivity of high-performance NdFeB-sintered-magnets (<20% of the theoretical Stoner–Wolfarth-limit) can be explained by a distorted region of Nd2Fe14B at grain boundaries, which has a reduced local magnetic anisotropy. We show that depending on the boundary composition of fcc-NdO and hcp-Nd2O3, the thickness of this region of reduced anisotropy varies between 0.4 for fcc and 1.6 nm for the hcp phase. For NdO, the distortions are mostly confined in the fcc-NdO-phase but equally distributes in both the hcp-Nd2O3 and Nd2Fe14B. The experimentally measured coercivity of 1.25 T can be understood when taking this distortion and magnetostatic effects into account.
Electrohydrodynamic instabilities in thin liquid trilayer films
Authors: Roberts Scott A. , Kumar Satish
Published: December 2010

Experiments by Dickey et al. [Langmuir 22, 4315 (2006)] and Leach et al. [Chaos 15, 047506 (2005)] show that novel pillar shapes can be generated from electrohydrodynamic instabilities at the interfaces of thin polymer/polymer/air trilayer films. In this paper, we use linear stability analysis to investigate the effect of free charge and ac electric fields on the stability of trilayer systems. Our work is also motivated by our recent theoretical study [S. A. Roberts and S. Kumar, J. Fluid Mech. 631, 255 (2009)] which demonstrates how ac electric fields can be used to increase control over the pillar formation process in thin liquid bilayer films. For perfect dielectric films, the effect of an ac electric field can be understood by considering an equivalent dc field. Leaky dielectric films yield pillar configurations that are drastically different from perfect dielectric films, and ac fields can be used to control the location of free charge within the trilayer system. This can alter the pillar instability modes and generate smaller diameter pillars when conductivities are mismatched. The results presented here may be of interest for the creation of complex topographical patterns on polymer coatings and in microelectronics.
Measurements of impulsive reconnection driven by nonlinear Hall dynamics
Authors: Tharp T. D. , Almagri A. F. , Miller M. C. , Mirnov V. V. , Prager S. C. , Sarff J. S. , Kim C. C.
Published: December 2010

The magnetic fields associated with reconnection in the edge of the reversed field pinch configuration have been measured in the Madison Symmetric Torus. The measured magnetic field structure is compared with theoretical predictions computed in both toroidal and cylindrical geometries. The summation of multiple modes has been accomplished to reveal a complex but still coherent edge structure. Key terms of relevant Ohm’s law are accessible from magnetic field measurement and reveal the ordering [(1/ne)J×B⪢E>ηJ], which implies that two fluid effects are important in the physics governing this reconnection. Further, it is seen that the nonlinear three-wave coupling of the Hall term acts as a driving mechanism for this linearly stable mode.
Observation of an anisotropic effect of antiferromagnetic ordering on the superconducting gap in ErNi2B2C
Authors: Bobrov N. L. , Chernobay V. N. , Naidyuk Yu. G. , Tyutrina L. V. , Yanson I. K. , Naugle D. G. , Rathnayaka K. D. D.
Published: December 2010

The point-contact spectra of the Andreev reflection dV∕dI curves of the superconducting rare-earth nickel borocarbide ErNi2B2C (Tc≈11K) have been analyzed in the “one-gap” and “two-gap” approximations using the generalized Blonder-Tinkham-Klapwijk model and the Beloborod’ko model allowing for the pair-breaking effect of magnetic impurities. Experimental and calculated curves have been compared not only in shape, but in magnitude as well, which provides more reliable data for determining the temperature dependence of the energy gap (or superconducting order parameter) Δ(T). The anisotropic effect of antiferromagnetic ordering at TN≈6K on the superconducting gap/order parameter has been determined: as the temperature is lowered, Δ decreases by ∼25% in the c-direction and only by ∼4% in the ab-plane. It is found that the pair-breaking parameter increases in the vicinity of the magnetic transitions, the increase being more pronounced in the c-direction. The efficiency of the models was tested for providing Δ(T) data for ErNi2B2C from Andreev reflection spectra.
Magnetic switch of polarization in epitaxial orthorhombic YMnO3 thin films
Authors: Fina I. , Fàbrega L. , Martí X. , Sánchez F. , Fontcuberta J.
Published: December 2010

We report on the growth and characterization of epitaxial thin films of orthorhombic YMnO3. It is found that a ferroelectric polarization exists along c-axis (Pc∼90 nC/cm2) and a magnetic field induces the development of a ferroelectric polarization along a-axis (Pa) while suppressing Pc. This field-induced switching is consistent with the existence of a cycloidal magnetic order in YMnO3. This finding evidences that a noncollinear spin arrangement in thin films allows switchable electrical polarization and of tunability of their dielectric response by magnetic field.
Ultrathin Co/Pt and Co/Pd superlattice films for MgO-based perpendicular magnetic tunnel junctions
Authors: Yakushiji K. , Saruya T. , Kubota H. , Fukushima A. , Nagahama T. , Yuasa S. , Ando K.
Published: December 2010

Ultrathin [Co/Pt]n and [Co/Pd]n superlattice films consisting of 0.14–0.20-nm-thick Co and Pt(Pd) layers were deposited by sputtering. A large perpendicular magnetic anisotropy [(3–9)×106 ergs/cm3] and an ideal square out-of-plane hysteresis loop were attained even for ultrathin superlattice films with a total thickness of 1.2–2.4 nm. The films were stable against annealing up to 370 °C. MgO-based perpendicular magnetic tunnel junctions with this superlattice layer as the free layer showed a relatively high magnetoresistance ratio (62%) and an ultralow resistance-area product (3.9 Ω μm2) at room temperature. The use of these films will enable the development of gigabit-scale nonvolatile memory.
Double-nonlinear metamaterials
Authors: Yang Rongcao , Shadrivov Ilya V.
Published: December 2010

We study a double-nonlinear metamaterial composed of a mixture of both nonlinear electric and nonlinear magnetic resonators. We predict multistable behavior in such metamaterial with the possibility to control the effective index of refraction by the electromagnetic field intensity. In contrast to the structure with just one type of nonlinear inclusions, our composite material may switch properties between the transparent negative index and the transparent positive index regimes.
Feedback-resistant p-type doped InAs/InP quantum-dash distributed feedback lasers for isolator-free 10 Gb/s transmission at 1.55 μm
Authors: Zou Q. , Merghem K. , Azouigui S. , Martinez A. , Accard A. , Chimot N. , Lelarge F. , Ramdane A.
Published: December 2010

The tolerance to external optical feedback of p-type doped InAs/InP quantum-dash-based distributed feedback (DFB) lasers is investigated for different values of the Bragg-grating coupling coefficient. We show that p-doping of the active layer not only enhances the differential gain but also results in small values of the linewidth enhancement factor, both parameters contributing to an increased tolerance to external optical feedback. A −18 dB onset of coherence collapse is reported for antireflection-coated devices, demonstrating the compatibility of quantum-dash-based DFB lasers with isolator-free operation.
A numerical study of Auger recombination in bulk InGaN
Authors: Bertazzi Francesco , Goano Michele , Bellotti Enrico
Published: December 2010

Direct interband and intraband Auger recombination due to electron-electron-hole and hole-hole-electron transitions in bulk InGaN is investigated by first-order perturbation theory including Fermi statistics, realistic electronic structures obtained by nonlocal empirical pseudopotential calculations, and their corresponding wavevector-dependent dielectric functions. Our results confirm that the intraband Auger coefficient is negligible in alloy compositions relevant for solid-state lighting and indicate that the resonant enhancement associated with interband transitions for wavelengths ranging from blue to green cannot account for the efficiency droop experimentally observed in GaN-based light emitting diodes.
Liquid crystal light deflecting devices based on nonuniform anchoring
Authors: Valyukh S. , Valyukh I. , Chigrinov V. , Kwok H. S. , Arwin H.
Published: December 2010

Tunable liquid crystal light deflecting devices based on nonuniform anchoring energy are proposed. These devices have uniform thicknesses of the layers they are composed of, and beam deviation is controlled with a uniform electrical field. Potential applicability of such an approach in beam deflectors and active lenses is investigated. It is shown that the approach is a competitive alternative to liquid crystal light deflecting devices, in which the needed spatial distribution of liquid crystal molecules is achieved either due to nonuniform thickness or due to generation of nonuniform electrical field.
Systematic investigation of self-absorption and conversion efficiency of 6.7 nm extreme ultraviolet sources
Authors: Otsuka Takamitsu , Kilbane Deirdre , Higashiguchi Takeshi , Yugami Noboru , Yatagai Toyohiko , Jiang Weihua , Endo Akira , Dunne Padraig , O’Sullivan Gerry
Published: December 2010

We have investigated the dependence of the spectral behavior and conversion efficiencies of rare-earth plasma extreme ultraviolet sources with peak emission at 6.7 nm on laser wavelength and the initial target density. The maximum conversion efficiency was 1.3% at a laser intensity of 1.6×1012 W/cm2 at an operating wavelength of 1064 nm, when self-absorption was reduced by use of a low initial density target. Moreover, the lower-density results in a narrower spectrum and therefore improved spectral purity. It is shown to be important to use a low initial density target and/or to produce low electron density plasmas for efficient extreme ultraviolet sources when using high-Z targets.
Effects of rotation on stability of viscous stationary flows on a spherical surface
Authors: Ibragimov Ranis N. , Pelinovsky Dmitry E.
Published: December 2010

We study the incompressible viscous fluid flows within a thin rotating atmospheric shell. The model uses the two-dimensional Navier–Stokes equations on a spherical surface and serves as a simple mathematical description of a general atmospheric circulation caused by the difference in temperature between the equator and the poles. Linearized stability of a particular stationary flow is considered. Under the assumption of no friction and a distribution of temperature dependent only upon latitude, the stationary flow models a zonal distribution of pressure corresponding to atmospheric currents parallel to the circles of latitude. We prove analytically that the stationary flow is asymptotically stable in the time evolution of the Navier–Stokes equations. When the spherical surface is truncated between two symmetrical rings near the North and South Poles, the asymptotic stability of the stationary flow is verified numerically.
Structure of the magnetized sheath of a dusty plasma
Authors: Mehdipour H. , Denysenko I. , Ostrikov K.
Published: December 2010

A three-component fluid model for a dusty plasma-sheath in an oblique magnetic field is presented. The study is carried out for the conditions when the thermophoretic force associated with the electron temperature gradient is one of the most important forces affecting dust grains in the sheath. It is shown that the sheath properties (the sheath size, the electron, ion and dust particle densities and velocities, the electric field potential, and the forces affecting the dust particles) are functions of the neutral gas pressure and ion temperature, the dust size, the dust material density, and the electron temperature gradient. Effects of plasma-dust collisions on the sheath structure are studied. It is shown that an increase in the forces pushing dust particles to the wall is accompanied by a decrease in the sheath width. The results of this work are particularly relevant to low-temperature plasma-enabled technologies, where effective control of nano- and microsized particles near solid or liquid surfaces is required.
Closed-air induced composite wetting on hydrophilic ordered nanoporous anodic alumina
Authors: Li Zhirong , Wang Jingxia , Zhang Youzhuan , Wang Jianjun , Jiang Lei , Song Yanlin
Published: December 2010

We investigate wetting behaviors of two kinds of hydrophilic ordered nanoporous anodic alumina (PAA). The water contact angle (CA) increases at first and subsequently decreases with increasing pore diameter of PAA with closed-pore structure, while the water CA decreases monotonously on PAA with open-pore structure. These interesting wetting behaviors are mainly due to the presence/absence of closed-air in the PAA. The closed-air could prevent water from entering into the nanopores. This work offers insight to control wetting by tailoring the surface nanostructure and will be significant for applications in printing, coating, etc.
Size-dependent strain in epitaxial (001) gadolinium-doped ceria nanoislands
Authors: Solovyov Vyacheslav F. , Gibert Marta , Puig Teresa , Obradors Xavier
Published: December 2010

We report size-dependent strain in epitaxial gadolinium doped ceria nanoislands, which was determined by synchrotron x-ray diffraction. Reciprocal space sections of symmetric, (004) and asymmetric, (224) reflections are approximated by a model assuming size-dependent strain of the islands using real-space size distribution obtained by atomic force microscopy. We show that the islands smaller than 40 nm are subjected to a high level of lateral tensile strain and normal compression. The lateral to normal strain ratio determined from the reciprocal map analysis suggests that lateral tension is the primary stress generator, possibly due to oxygen vacancy ordering on the island-substrate interface.
Enhancing visibility of graphene on arbitrary substrates by microdroplet condensation
Authors: Gonçalves Hugo , Belsley Michael , Moura Cacilda , Stauber Tobias , Schellenberg Peter
Published: December 2010

In order to take advantage of the enormous potential of graphene for future electronic microcircuits and other applications it is necessary to develop reliable, rapid, and widely applicable methods to visualize graphene-based structures. We report here on a microdroplet condensation technique, which allows for quick visual identification of graphene on a variety of substrates, including some which were previously considered unsuitable for the visualization of carbon layers. The technique should also be applicable to visualize artificially patterned graphene structures which are expected to be key technologically enabling components in electronic microcircuits and other applications.
Morphologically controlled synthesis of colloidal upconversion nanophosphors and their shape-directed self-assembly
Authors: Ye Xingchen , Collins Joshua E. , Kang Yijin , Chen Jun , Chen Daniel T. N. , Yodh Arjun G. , Murray Christopher B.
Published: December 2010

We report a one-pot chemical approach for the synthesis of highly monodisperse colloidal nanophosphors displaying bright upconversion luminescence under 980 nm excitation. This general method optimizes the synthesis with initial heating rates up to 100 °C/minute generating a rich family of nanoscale building blocks with distinct morphologies (spheres, rods, hexagonal prisms, and plates) and upconversion emission tunable through the choice of rare earth dopants. Furthermore, we employ an interfacial assembly strategy to organize these nanocrystals (NCs) into superlattices over multiple length scales facilitating the NC characterization and enabling systematic studies of shape-directed assembly. The global and local ordering of these superstructures is programmed by the precise engineering of individual NC’s size and shape. This dramatically improved nanophosphor synthesis together with insights from shape-directed assembly will advance the investigation of an array of emerging biological and energy-related nanophosphor applications.
Syntaxin N-terminal peptide motif is an initiation factor for the assembly of the SNARE–Sec1/Munc18 membrane fusion complex
Authors: Rathore Shailendra S. , Bend Eric G. , Yu Haijia , Hammarlund Marc , Jorgensen Erik M. , Shen Jingshi
Published: December 2010

Intracellular membrane fusion is mediated by the concerted action ofN-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and Sec1/Munc18 (SM) proteins. During fusion, SM proteins bind the N-terminal peptide (N-peptide) motif of the SNARE subunit syntaxin, but the function of this interaction is unknown. Here, using FRET-based biochemical reconstitution andCaenorhabditis elegansgenetics, we show that the N-peptide of syntaxin-1 recruits the SM protein Munc18-1/nSec1 to the SNARE bundle, facilitating their assembly into a fusion-competent complex. The recruitment is achieved through physical tethering rather than allosteric activation of Munc18-1. Consistent with the recruitment role, the N-peptide is not spatially constrained along syntaxin-1, and it is functional when translocated to another SNARE subunit SNAP-25 or even when simply anchored in the target membrane. The N-peptide function is restricted to an early initiation stage of the fusion reaction. After association, Munc18-1 and the SNARE bundle together drive membrane merging without further involving the N-peptide. Thus, the syntaxin N-peptide is an initiation factor for the assembly of the SNARE-SM membrane fusion complex.
CRITICAL CONSUMPTION
Authors: Yates Luke S.
Published: December 2010

Critical consumption, the purchase or boycott of goods for political, ethical or environmental reasons, is regularly characterised as an example of ‘new politics’ or ‘new’ political participation. However, such analysis often neglects work from the sociology of consumption and social movement studies. This paper argues that consumers express their identity through critical consumption, in the form of a pledge of allegiance to the goals of certain social movements. Cross-national data from the European Social Survey identifies critical consumers as belonging to higher class positions and being generally older, highly educated, and more often women than men. Separating analysis of boycotting from that of buycotting, the positive purchase of goods for ethical or political reasons, suggests that buycotting is more resource-dependent and individualistic than boycotting. Substantial differences are found between the impact of people's resources in different countries, particularly between Northern and Central European countries and their Southern and Eastern counterparts. The findings thus recommend an approach to consumer politics that remains sensitive to social structural contexts between countries and different forms of consumer participation.
Low-frequency repetitive transcranial magnetic stimulation of the anterior temporal lobes does not dissociate social versus nonsocial semantic knowledge
Authors: Wong Cara , Gallate Jason
Published: December 2010

Social conceptual knowledge is imperative to communicate with, interact with, and interpret human society; however, little is known about the neural basis of social concepts. Previous research has predominantly suggested that the right anterior temporal lobe (ATL) may specifically represent social conceptual knowledge, whereas the left ATL is necessary for general semantic processing. However, this view has not always been supported by empirical studies. Employing a lateralized design and two different semantic tasks and a nonsemantic control task, we aimed to clarify some of these ambiguities by potentially dissociating left from right functionality and social from nonsocial concepts, using inhibitory repetitive transcranial magnetic stimulation (rTMS) coupled with a sham and control site stimulation ( N = 56). The results showed that stimulation of the left ATL led to overall faster processing times without affecting accuracy, whilst the right ATL and control groups did not significantly change in reaction times or accuracy. No difference occurred between social and nonsocial concepts after stimulation. This study is the first to show that inhibition of the left temporal lobe may improve performance on a semantic task and provides evidence that the ATLs may be lateralized in conceptual processing. The results do not confirm that the right temporal lobe is crucial for social conceptual processing, as inhibition did not significantly affect performance for social concepts.
Climate Change in China: Policy Evolution, Actions Taken and Options Ahead
Authors: Li Jie , Xu Jintao
Published: December 2010

This paper provides an overview of China's climate policy, including both diplomatic efforts and internal policy changes. China's policy evolution is divided into three phases, corresponding to major milestones in the international negotiation process since 1988. In addition, important domestic initiatives are summarized, including the recent policy of energy saving and emissions reduction, the clean energy programme, and the use of forests to trap carbon. The paper also points out potential directions for more substantive climate policies.
A Policy Model for Climate Change in California
Authors: Berck Peter , Xie Lunyu
Published: December 2010

California's ‘Scoping Plan’ to reduce greenhouse gas emissions relies on vehicle emissions standards, low carbon fuels, and renewable electricity, as well as a regional cap-and-trade system and other market-based instruments. The process has been guided by a computable general equilibrium (CGE) model, the Environmental Dynamic Revenue Analysis Model (E-DRAM). The model shows that the Scoping Plan measures will result in net benefits for the state economy, measured in gross state product (industrial output), employment, and personal income. Most of the benefits result from reduced energy costs. Despite aggregate net benefits, individual industrial sectors gain or lose differentially.
Climate Change Policy in Africa with Special Reference to Energy and Land Use
Authors: Köhlin Gunnar , Mekonnen Alemu , Westholm Lisa
Published: December 2010

While Africa has contributed marginally to climate change, the continent will be disproportionately affected by it, particularly the agricultural sector. Climate change demands policy action to address mitigation and adaptation needs, and it poses opportunities in implementation of international instruments. Two sectors, energy and land use, are particularly important. Over 85% of anthropogenic greenhouse gas emissions in Africa come from energy supply and agriculture. African governments will have to synchronize national development plans and strategies with adaptation and mitigation plans, as well as safeguard that adherence to the rules of international funding mechanisms do not unnecessarily constrain national development strategies.
International Emission Inequality and Per Capita Abatement Schemes
Authors: Levy Amnon , Chowdhury Khorshed , Livermore Jonathan Levy
Published: December 2010

Carbon dioxide emission inequalities between and within five income groups of countries are computed. The revealed dominant inequality between the high income groups and the low and middle income groups and its likely intensification by an internationally uniform abatement rate constitute a case for using per capita figures in assessing countries' unilateral and internationally cooperative abatements. Our analysis suggests that the cooperative expected net benefit maximizing abatement can be smaller than the unilateral abatement for weak countries and for countries with high ability and inclination to politically and economically reward other countries.
The Power and Pitfalls of Experiments in Development Economics: Some Non‐random Reflections
Authors: Barrett Christopher B. , Carter Michael R.
Published: December 2010

Impact evaluation based on randomized controlled trials (RCTs) offers a powerful tool that has fundamentally reshaped development economics by offering novel solutions to long‐standing problems of weak causal identification. Nonetheless, RCTs suffer important and underappreciated pitfalls, some of which are intrinsic to the method when applied to economic problems, others that are the result of methodological boosterism. Among the pitfalls are ethical dilemmas, uncontrollable treatments that result in a ‘faux exogeneity,’ distortion of the research agenda, and a tendency to estimate interventions' abstract efficacy rather than their effectiveness in practice. We illustrate these points through the literature on smallholder capital access and productivity growth. Ultimately, we argue for a methodological pluralism that recognizes all identification strategies' limitations.
Bootstrapping Your Fish or Fishing for Bootstraps? Precision of Welfare Loss Estimates from a Globally Concave Inverse Demand Model of Commercial Fish Landings in the U.S. Great Lakes
Authors: Hilmer Christiana E. , Holt Matthew T. , Bishop Richard C.
Published: December 2010

We extend Holt and Bishop's (2002) normalized quadratic inverse demand function by obtaining measures of precision of elasticities and consumer welfare loss estimates due to reductions in commercial landings in the U.S. Great Lakes. Even with curvature constraints imposed, confidence intervals are obtained by using the bootstrap, subsample bootstrap, and subsample jackknife.
SlideSort: all pairs similarity search for short reads
Authors: Shimizu Kana , Tsuda Koji
Published: December 2010

Motivation: Recent progress in DNA sequencing technologies calls for fast and accurate algorithms that can evaluate sequence similarity for a huge amount of short reads. Searching similar pairs from a string pool is a fundamental process of de novo genome assembly, genome-wide alignment and other important analyses.

Results: In this study, we designed and implemented an exact algorithm SlideSort that finds all similar pairs from a string pool in terms of edit distance. Using an efficient pattern growth algorithm, SlideSort discovers chains of common k-mers to narrow down the search. Compared to existing methods based on single k-mers, our method is more effective in reducing the number of edit distance calculations. In comparison to backtracking methods such as BWA, our method is much faster in finding remote matches, scaling easily to tens of millions of sequences. Our software has an additional function of single link clustering, which is useful in summarizing short reads for further processing.

Availability: Executable binary files and C++ libraries are available at http://www.cbrc.jp/~shimizu/slidesort/ for Linux and Windows.

Contact:  slidesort@m.aist.go.jp; shimizu-kana@aist.go.jp

Supplementary information:  Supplementary data are available at Bioinformatics online.