bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of inertia and charge relaxation on electrohydrodynamic drop deformation
Authors: Lanauze Javier A. , Walker Lynn M. , Khair Aditya S.
Published: November 2013

We quantify the transient deformation of a droplet immersed in a weakly conductive (leaky dielectric) fluid upon exposure to a uniform DC electric field. Capillary forces are assumed to be sufficiently large that the drop only slightly deviates from its equilibrium spherical shape. In particular, we account for transient (or linear) fluid inertia via the unsteady Stokes equations, and also account for a finite electrical relaxation time over which the drop interface charges. The temporal droplet deformation is governed by two dimensionless groups: (i) the ratio of capillary to momentum diffusion time scales: an Ohnesorge number Oh and (ii) the ratio of charge relaxation to momentum diffusion time scales, which we denote by Sa. If charge and momentum relaxation occur quickly compared to interface deformation, Sa ≪ 1 and Oh ≫ 1 for the droplet and medium, a monotonic deformation is acquired. In contrast, Sa > 1 and Oh < 1 for either phase can lead to a non-monotonic development in the deformation. Numerical values for the deformation are calculated by inverting an analytical expression obtained in the Laplace domain, and are corroborated by asymptotic expansions at early and late times. The droplet and medium behave as perfect dielectrics at early times, which always favors an initial prolate (parallel to the applied field) deformation. As a consequence, for a final oblate (normal to the applied field) deformation, there is a shape transition from prolate to oblate at intermediate times. This transition is caused by the accumulation of sufficient charge at the interface to generate electrical and viscous shear stresses. Notably, after the transition, there may be an “overshoot” in the deformation, i.e., the magnitude exceeds its steady-state value, which is proceeded by an algebraic tail describing the arrival towards the final, steady deformation. Our work demonstrates that transient inertia or a non-zero electrical relaxation time can yield non-monotonic electrohydrodynamic drop deformation.
Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties
Authors: Yang Yang , Wang Ziyu , Ding Yi , Lu Zhihong , Sun Haoliang , Li Ya , Wei Jianhong , Xiong Rui , Shi Jing , Liu Zhengyou , Lei Qingquan
Published: November 2013

This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz–1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67) is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.
Droplet size distributions in turbulent emulsions: Breakup criteria and surfactant effects from direct numerical simulations
Authors: Skartlien R. , Sollum E. , Schumann H.
Published: November 2013

Lattice Boltzmann simulations of water-in-oil (W/O) type emulsions of moderate viscosity ratio (≃1/3) and with oil soluble amphiphilic surfactant were used to study the droplet size distribution in forced, steady, homogeneous turbulence, at a water volume fraction of 20%. The viscous stresses internal to the droplets were comparable to the interfacial stress (interfacial tension), and the droplet size distribution (DSD) equilibrated near the Kolmogorov scale with droplet populations in both the viscous and inertial subranges. These results were consistent with known breakup criteria for W/O and oil-in-water emulsions, showing that the maximum stable droplet diameter is proportional to the Kolmogorov scale when viscous stresses are important (in contrast to the inviscid Hinze-limit where energy loss by viscous deformation in the droplet is negligible). The droplet size distribution in the inertial subrange scaled with the known power law ∼d−10/3, as a consequence of breakup by turbulent stress fluctuations external to the droplets. When the turbulent kinetic energy was sufficiently large (with interfacial Péclet numbers above unity), we found that turbulence driven redistribution of surfactant on the interface inhibited the Marangoni effect that is otherwise induced by film draining during coalescence in more quiescent flow. The coalescence rates were therefore not sensitive to varying surfactant activity in the range we considered, and for the given turbulent kinetic energies. Furthermore, internal viscous stresses strongly influenced the breakup rates. These two effects resulted in a DSD that was insensitive to varying surfactant activity.
Scanning probe image wizard: A toolbox for automated scanning probe microscopy data analysis
Authors: Stirling Julian , Woolley Richard A. J. , Moriarty Philip
Published: November 2013

We describe SPIW (scanning probe image wizard), a new image processing toolbox for SPM (scanning probe microscope) images. SPIW can be used to automate many aspects of SPM data analysis, even for images with surface contamination and step edges present. Specialised routines are available for images with atomic or molecular resolution to improve image visualisation and generate statistical data on surface structure.
Theoretical and experimental analysis of a linear accelerator endowed with single feed coupler with movable short-circuit
Authors: Forno Massimo Dal , Craievich Paolo , Penco Giuseppe , Vescovo Roberto
Published: November 2013

The front-end injection systems of the FERMI@Elettra linac produce high brightness electron beams that define the performance of the Free Electron Laser. The photoinjector mainly consists of the radiofrequency (rf) gun and of two S-band rf structures which accelerate the beam. Accelerating structures endowed with a single feed coupler cause deflection and degradation of the electron beam properties, due to the asymmetry of the electromagnetic field. In this paper, a new type of single feed structure with movable short-circuit is proposed. It has the advantage of having only one waveguide input, but we propose a novel design where the dipolar component is reduced. Moreover, the racetrack geometry allows to reduce the quadrupolar component. This paper presents the microwave design and the analysis of the particle motion inside the linac. A prototype has been machined at the Elettra facility to verify the new coupler design and the rf field has been measured by adopting the bead-pull method. The results are here presented, showing good agreement with the expectations.
A TE01 mode generator for testing high power transmission devices
Authors: Wu Zewei , Li Hao , Fu Hua , Li Tianming , Xu Jianhua
Published: November 2013

To verify the performance of high power waveguide transmission devices such as the miter bend, the waveguide taper, and the quasi-optical mode converter by the low power measurement, a TE01 mode generator, converts the rectangular waveguide TE10 mode into the cylindrical waveguide TE01 mode, for Ka-band is designed, fabricated, and measured. The proposed generator consists of a TE10 to TE20 rectangular waveguide mode converter and a rectangular TE20 to circular TE01 mode converter. The converting process in each section is analyzed and the working principles are discussed. Two prototypes are built and tested. The back-to-back transmission measured results agree well with the numerical calculations. The measured optimum transmissions are 97% with a 1-dB bandwidth from 29.2 GHz to 31.6 GHz. The angle-independent transmissions demonstrate high mode purity and the presence of TE01 mode confirmed by the far-field measurement. The proposed mode generator features high conversion efficiency, high mode purity, and moderate broad bandwidth.
Generalized lock-in amplifier for precision measurement of high frequency signals
Authors: Fu Siyuan , Sakurai Atsunori , Liu Liang , Edman Fredrik , Pullerits Tõnu , Öwall Viktor , Karki Khadga Jung
Published: November 2013

We herein formulate the concept of a generalized lock-in amplifier for the precision measurement of high frequency signals based on digital cavities. Accurate measurement of signals higher than 200 MHz using the generalized lock-in is demonstrated. The technique is compared with a traditional lock-in and its advantages and limitations are discussed. We also briefly point out how the generalized lock-in can be used for precision measurement of giga-hertz signals by using parallel processing of the digitized signals.
Multi-charged heavy ion acceleration from the ultra-intense short pulse laser system interacting with the metal target
Authors: Nishiuchi M. , Sakaki H. , Maeda S. , Sagisaka A. , Pirozhkov A. S. , Pikuz T. , Faenov A. , Ogura K. , Kanasaki M. , Matsukawa K. , Kusumoto T. , Tao A. , Fukami T. , Esirkepov T. , Koga J. , Kiriyama H. , Okada H. , Shimomura T. , Tanoue M. , Nakai Y. , Fukuda Y. , Sakai S. , Tamura J. , Nishio K. , Sako H. , Kando M. , Yamauchi T. , Watanabe Y. , Bulanov S. V. , Kondo K.
Published: November 2013

Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. Al ions are accelerated up to 12 MeV/u (324 MeV total energy). To our knowledge, this is far the highest energy ever reported for the case of acceleration of the heavy ions produced by the <10 J laser energy of 200 TW class Ti:sapphire laser system. Adding to that, thanks to the extraordinary high intensity laser field of ∼1021 W cm−2, the accelerated ions are almost fully stripped, having high charge to mass ratio (Q/M).
Two dimensional nonlinear frequency-mixing photo-acoustic imaging of a crack and observation of crack phantoms
Authors: Mezil Sylvain , Chigarev Nikolay , Tournat Vincent , Gusev Vitalyi
Published: November 2013

A two-dimensional imaging of a crack by nonlinear frequency-mixing photo-acoustic method is reported. The imaging contrast is due to nonlinear photo-thermo-acoustic processes taking place in case of simultaneous excitation by lasers of thermo-elastic and acoustic waves in the vicinity of the cracks. The images are obtained by scanning of two co-focused laser beams in region of crack location. The first cw laser beam, modulated in intensity at low frequency fL, generates a thermo-elastic wave, which is able to strongly periodically modulate the local crack rigidity up to complete closing/opening of the crack. The second cw laser beam, intensity modulated at much higher frequency fH, generates an acoustic wave incident on the breathing crack. The crack rigidity is also influenced by the stationary non-modulated inhomogeneous thermal stresses caused by the stationary heating of the sample by both lasers. The main contribution to imaging contrast comes from the strong dependence of the reflectivity of acoustic waves on the crack rigidity. The modulation of crack rigidity by thermo-elastic wave leads to the parametric modulation of the reflected acoustic waves and the generation in the spectrum of the acoustic field of the side lobes, which are separated from fH by the integer number of fL. Scan images of a crack with an amplitude dynamics up to 40 dB and a spatial resolution better than 100 μm, are obtained through the mapping of nonlinear side lobe amplitudes. The observed dependences of the images on the power of the lasers are discussed and the physical explanation of the appearance of crack phantom images at high level of optical excitation is proposed. For comparison and elucidation of spatial resolution issues related to this imaging method, the one-dimensional images, obtained with one laser beam focus position fixed and the second beam focus position scanning, are also presented and discussed.
Impact of ammonia on the electrical properties of p-type Si nanowire arrays
Authors: Li Chuanbo , Zhang Chunqian , Fobelets Kristel , Zheng Jun , Xue Chunlai , Zuo Yuhua , Cheng Buwen , Wang Qiming
Published: November 2013

The electrical properties of vertically upstanding p-type silicon nanowires arrays in the ambience of NH3 are studied. It is found that, the introducing of ammonia lowers their conductivity. By investigating the absorption and desorption processes of ammonia on nanowires (NW) surfaces, the current modulations of Si NWAs are interpreted in terms of band bending at the NW edge due to injections of negative carriers from ammonia.
Carrier-envelope phase- and spectral control of fractional high-harmonic combs
Authors: Raith Philipp , Ott Christian , Meyer Kristina , Kaldun Andreas , Laux Martin , Ceci Matteo , Anderson Christopher P. , Pfeifer Thomas
Published: November 2013

We experimentally and numerically control high-harmonic generation (HHG) by time delaying variable segments of a few-cycle driving laser spectrum. In this configuration combs of fractional high harmonics can be produced by interference of two temporally spaced attosecond pulse trains. We explain the observed beating of the high-harmonic intensity with the time delay and study the influence of the spectral segmentation on the high harmonics. By the implementation of additional carrier-envelope phase (CEP) control, we extend the control configuration and demonstrate independent multi-parameter controllability of HHG purely enabled by the CEP and the time delay between two spectral segments. We present how specific properties of the fractional harmonics can be optimized. Analyzing the measured fractional harmonic combs by a spectral interferometry method, we find that the relative phase between the two contributing attosecond pulse trains can be freely set by the CEP of the driving laser field. We also discuss how, in the future, this method can be applied to simultaneously measure transient dispersion and absorption in the extreme ultraviolet spectral region.
Stability of imploding shocks generated by underwater electrical explosion of cylindrical wire array
Authors: Kozlov M. , Gurovich V. Tz. , Krasik Ya. E.
Published: November 2013

The results of two-dimensional hydrodynamic simulations of the dynamics and stability of azimuthal non-uniformities in converging shock waves generated by an underwater explosion of a cylindrical wire array and their effect on the cumulation of energy in the vicinity of the converging axis are presented. It has been shown that in spite of the fact that such non-uniformities are always weakly unstable, for a broad range of experimentally relevant regimes these non-uniformities remain small and do not significantly affect the cumulation of energy. Only the non-uniformities with wavelengths comparable to the distance from the axis of convergence exhibit substantial growth that considerably attenuates the energy cumulation.
Modulating the field-effect passivation at the SiO2/c-Si interface: Analysis and verification of the photoluminescence imaging under applied bias method
Authors: Haug Halvard , Olibet Sara , Nordseth Ørnulf , Stensrud Marstein Erik
Published: November 2013

In this paper, we study the surface passivation properties of thermally oxidized silicon wafers with controlled surface band bending, using a recently developed characterization technique combining calibrated photoluminescence imaging with the application of an external voltage over the rear side passivation layer. Various aspects of the technique and possible errors in the determination of the effective surface recombination velocity are discussed, including lateral carrier diffusion, leakage currents, and optical effects related to the presence of metal electrodes on the investigated samples. In order to quantitatively describe the recombination activity at the SiO2/c-Si interface and the effect of fixed charges in the oxide layer, the measured effective carrier lifetime vs. voltage curves have been analyzed in the framework of an extended Shockley-Read Hall recombination model. Furthermore, the results have been compared with corresponding results from microwave detected photoconductance decay measurements after depositing corona charges. We find an excellent agreement between the two techniques and between complementary measurements of the oxide charge density. Photoluminescence imaging under applied bias gives fast and repeatable measurements and allows for simultaneous data collection from multiple areas on the sample, and has thus been proven to be powerful tool for quantitative characterization of surface passivation layers.
Incident shock Mach number effects on Richtmyer-Meshkov mixing in a heavy gas layer
Authors: Orlicz G. C. , Balasubramanian S. , Prestridge K. P.
Published: November 2013

Experiments were performed at the horizontal shock tube facility at Los Alamos National Laboratory to study the effect of incident shock Mach number (M) on the development of Richtmyer-Meshkov instability after a shock wave impulsively accelerates a varicose-perturbed, heavy-gas curtain. Three cases of incident shock strength were experimentally investigated: M = 1.21, 1.36, and 1.50. We discuss the state of the mixing and the mechanisms that drive the mixing at both large and small scales by examining the time evolution of 2D density fields derived from quantitative planar laser-induced fluorescence measurements. Several differences in qualitative flow features are identified as a result of Mach number variation, and differences in vortex interaction, observed using particle image velocimetry, play a critical role in the development of the flow field. Several quantities, including mixing layer width, mixing layer area, interface length, instantaneous mixing rate, the density self-correlation parameter, probability density functions of the density field, and mixing progress variables are examined as a function of time. These quantities are also examined versus time scaled with the convection velocity of the mixing layer. A higher incident Mach number yields greater mixing uniformity at a given downstream location, while a lower Mach number produces a greater amount of total mixing between the two gases, suggesting possible implications for optimization in applications with confined geometries.
Pi and sigma double conjugations in boronyl polyboroene nanoribbons: Bn(BO)2− and Bn(BO)2 (n = 5−12)
Authors: Zhai Hua-Jin , Chen Qiang , Bai Hui , Lu Hai-Gang , Li Wei-Li , Li Si-Dian , Wang Lai-Sheng
Published: November 2013

A series of boron dioxide clusters, BxO2− (x = 7−14), have been produced and investigated using photoelectron spectroscopy and quantum chemical calculations. The dioxide clusters are shown to possess elongated ladder-like structures with two terminal boronyl (BO) groups, forming an extensive series of boron nanoribbons, Bn(BO)2− (n = 5−12). The electron affinities of Bn(BO)2 exhibit a 4n periodicity, indicating that the rhombic B4 unit is the fundamental building block in the nanoribbons. Both π and σ conjugations are found to be important in the unique bonding patterns of the boron nanoribbons. The π conjugation in these clusters is analogous to the polyenes (aka polyboroenes), while the σ conjugation plays an equally important role in rendering the stability of the nanoribbons. The concept of σ conjugation established here has no analogues in hydrocarbons. Calculations suggest the viability of even larger boronyl polyboroenes, B16(BO)2 and B20(BO)2, extending the boron nanoribbons to ∼1.5 nm in length or possibly even longer. The nanoribbons form a new class of nanowires and may serve as precursors for a variety of boron nanostructures.
Modeling multiple-frequency electron cyclotron resonance heating
Authors: Spencer J. Andrew , Kim Charlson , Kim Jin-Soo , Evstatiev Evstati G. , Svidzinski Vladimir , Cluggish Brian
Published: November 2013

Electron cyclotron resonance (ECR) heating influences two of the main parameters (electron temperature and, indirectly, density) that determine the charge state of the ions produced in an ECR ion source (ECRIS). Therefore, various schemes to optimize ECR heating in the ECRIS have been pursued such as multiple-frequency heating, the radio-frequency tuning effect, volume heating, or wide-band heating. We investigate two-frequency ECR heating of electrons in a simple magnetic mirror field by right handed circularly polarized waves with infinite phase velocity. The study shows a heating barrier different from the well-know adiabatic barrier. Study also revealed a mechanism whereby multiple frequencies give improved heating. A preliminary interpretation of the study is presented.
Communication: The Rosenfeld-Tarazona expression for liquids’ specific heat: A numerical investigation of eighteen systems
Authors: Ingebrigtsen Trond S. , Veldhorst Arno A. , Schrøder Thomas B. , Dyre Jeppe C.
Published: November 2013

We investigate the accuracy of the expression of Rosenfeld and Tarazona (RT) for the excess isochoric heat capacity, \documentclass[12pt]{minimal}\begin{document}$C_{V}^{{\rm ex}} \propto T^{-2/5}$\end{document}CV ex ∝T−2/5, for 18 model liquids. Previous investigations have reported no unifying features of breakdown for the RT expression. Here, liquids with different stoichiometric composition, molecular topology, chemical interactions, degree of undercooling, and environment are investigated. The RT expression is a better approximation for liquids with strong correlations between equilibrium fluctuations of virial and potential energy, i.e., “Roskilde-simple” liquids [T. S. Ingebrigtsen, T. B. Schrøder, and J. C. Dyre, Phys. Rev. X 2, 011011 (2012)]. This observation holds even for molecular liquids under severe nanoscale confinement which does not follow from the original RT bulk hard-sphere fluid perturbation theory arguments. The density dependence of the specific heat is predicted from the isomorph theory for Roskilde-simple liquids, which in combination with the RT expression provides a complete description of the specific heat's density and temperature dependence.
Heterodyne pump probe measurements of nonlinear dynamics in an indium phosphide photonic crystal cavity
Authors: Heuck M. , Combrié S. , Lehoucq G. , Malaguti S. , Bellanca G. , Trillo S. , Kristensen P. T. , Mørk J. , Reithmaier J. P. , de Rossi A.
Published: November 2013

Using a sensitive two-color heterodyne pump-probe technique, we investigate the carrier dynamics of an InP photonic crystal nanocavity. The heterodyne technique provides unambiguous results for all wavelength configurations, including the degenerate case, which cannot be investigated with the widely used homodyne technique. A model based on coupled mode theory including two carrier distributions is introduced to account for the relaxation dynamics, which is assumed to be governed by both diffusion and recombination.
Communication: Transfer ionization in a thermal reaction of a cation and anion: Ar+ with Br− and I−
Authors: Shuman Nicholas S. , Miller Thomas M. , Johnsen Rainer , Viggiano Albert A.
Published: November 2013

We present experimental evidence that reactions of argon cations Ar+ with the halogen anions Br− and I− do not occur exclusively by mutual neutralization, but also produce the cations Br+ or I+ ions by transfer ionization (TI). The experiments were carried out in flowing-afterglow plasmas at gas temperatures between and 300 and 500 K, and employed a variant of the Variable Electron and Neutral Density Attachment Mass Spectrometry method. The measured TI rate coefficients are 1.9 ± 0.6 × 10−9 cm3 s−1 and $1.1\, \pm\; _{0.3}^{0.8}$1.1±0.30.8 × 10−9 cm3 s−1 for the Br− and I− reactions, respectively. We find that the TI rate coefficients decline with temperature as T−0.5 to T−1. No indication of TI was found in the reaction with Cl−, where it is endoergic.
Inductively heated synthesized graphene with record transistor mobility on oxidized silicon substrates at room temperature
Authors: Tao Li , Lee Jongho , Li Huifeng , Piner Richard D. , Ruoff Rodney S. , Akinwande Deji
Published: November 2013

We report chemical vapor-deposited (CVD) graphene field-effect transistors (GFETs) on conventional SiO2/Si substrate with high-performance comparable to GFETs on boron nitride under practical ambient conditions. The fabricated GFET statistics reveal maximum carrier mobility of ∼17 800 cm2/V-s. Intrinsic graphene features such as three-region output characteristics including soft current saturation have also been observed, in addition to over ten-fold gate modulation. Low-temperature studies indicate that impurity scattering is the limiting transport mechanism. Our results on graphene, synthesized by an inductively heated CVD system, suggest that the prospects of GFETs on oxidized silicon are comparable to those on ideal surfaces, e.g., hBN at room temperature.
Room temperature thermo-electric pumping in mid-infrared light-emitting diodes
Authors: Santhanam Parthiban , Huang Duanni , Ram Rajeev J. , Remennyi Maxim A. , Matveev Boris A.
Published: November 2013

We present measurements of mid-infrared light-emitting diodes generating photons above the conventional limit of 100% electrical-to-optical power conversion efficiency. At low forward bias, lattice heat is absorbed via thermo-electric effects in the carrier injection process and released radiatively through recombination, so the diode acts as a thermodynamic heat pump. Experiments support an effective temperature model for electro-luminescence in the cooling regime and refute alternative interpretations of existing results. Although non-radiative recombination limits the power density available above unity efficiency, experiments confirm the phenomenon at room temperature.
Methods for quantifying the influences of pressure and temperature variation on metal hydride reaction rates measured under isochoric conditions
Authors: Voskuilen Tyler G. , Pourpoint Timothée L.
Published: November 2013

Analysis techniques for determining gas-solid reaction rates from gas sorption measurements obtained under non-constant pressure and temperature conditions often neglect temporal variations in these quantities. Depending on the materials in question, this can lead to significant variations in the measured reaction rates. In this work, we present two new analysis techniques for comparison between various kinetic models and isochoric gas measurement data obtained under varying temperature and pressure conditions in a high pressure Sievert system. We introduce the integral pressure dependence method and the temperature dependence factor as means of correcting for experimental variations, improving model-measurement fidelity, and quantifying the effect that such variations can have on measured reaction rates. We use measurements of hydrogen absorption in LaNi5 and TiCrMn to demonstrate the effect of each of these methods and show that their use can provide quantitative improvements in interpretation of kinetics measurements.
Monolithic generators of pseudo-nondiffracting optical vortex beams at the microscale
Authors: Žukauskas Albertas , Malinauskas Mangirdas , Brasselet Etienne
Published: November 2013

We report on the fabrication and characterization of micro-optical elements with typical size of 100 μm, which enable the production of pseudo-nondiffracting optical vortex beams of arbitrary order. This is made possible from the monolithic integration of spiral phase plates and axicons into helical axicons by direct laser writing using femtosecond laser nanopolymerization. The optical performances of the fabricated three-dimensional singular microstructures are experimentally measured and compared with their expected theoretical behavior, both in intensity and phase. The proposed approach thus represents an attempt to merge the field of singular integrated optics with that of nondiffracting light fields.
Electric field induced monoclinic phase in (Na0.52K0.48)(Nb1−ySby)O3 ceramics close to the rhombohedral-orthorhombic polymorphic phase boundary
Authors: Fu Jian , Zuo Ruzhong , Gao Xingyu
Published: November 2013

The electric field induced structural transformation in (Na0.52K0.48)(Nb1−ySby)O3 ceramics near the rhombohedral (R)-orthorhombic (O) phase boundary was investigated by means of ex-situ and in-situ synchrotron x-ray diffraction and dielectric measurements. An intermediate monoclinic (M) phase was irreversibly induced from the O phase by poling, leading to a modified polarization rotation path along R-M-O. By comparison, the reversibility of R-M phase transition would cause the phase instability. Both aspects were believed to be responsible for the high piezoelectric activity near the R-O phase boundary. Moreover, enhanced piezoelectric properties were also found to correlate with the thermal stability of the induced M phase.
Ion wake formation with dust charge fluctuation in complex plasma
Authors: Bhattacharjee Saurav , Das Nilakshi
Published: November 2013

In complex plasma, the interaction mechanism among dust grains near the plasma sheath is significantly influenced by the downward ion flow towards the sheath and dust charge fluctuation over grain surface. Asymmetric ion flow towards the sheath gives rise to well known attractive wake potential in addition to repulsive Yukawa type of potential. The present work shows that the charging dynamics play a significant role in modification of plasma dielectric response function and hence the interaction mechanism among test dust particulates. The effective Debye length is found to be a characteristic of dust size and background plasma response towards the grain along with ion flow speed. The potentials thus obtained show a damping in strength of interaction in the presence of dynamical charging of dust as compared to that of constant charge dust grains. The result also shows decrease in focal length of ion lensing with increase in grain size.
Surface passivation of nano-textured silicon solar cells by atomic layer deposited Al2O3 films
Authors: Dou Bingfei , Jia Rui , Sun Yun , Li Haofeng , Chen Chen , Jin Zhi , Liu Xinyu
Published: November 2013

In the work, the surface recombination of silicon nanostructures was investigated. Silicon nanostructures were synthesized using technique of silver catalyzed chemical wet etching, and the passivation layers of SiNx and Al2O3 were deposited on the samples. The thermal atomic layer deposited Al2O3 can conformally cover the rough surface and reduce the defect density of the nanostructures. Moreover, the negative fixed charge in Al2O3 layer introduces the surface field effect passivation. The lifetime measurement result indicates that Al2O3 layers offer much better passivation effect on the silicon nanostructure surface than SiNx layers. The silicon nano-textured solar cells with SiNx and Al2O3 passivation layers were manufactured and measured. The results show that the enhanced solar cell performance was achieved by Al2O3 passivation.
Pure carbon-based Schottky diode, an implication of stretched carbon nanowire
Authors: Mandal Bikash , Sarkar Sunandan , Pramanik Anup , Sarkar Pranab
Published: November 2013

Density functional theory calculations are performed on various forms of linear carbon chains. It has been predicted that stretched carbon nanowire may be stabilized through interchain interaction thereby forming a quasi-bound state of carbon, naming parallel carbon nanowire (PCNW). The electronic structure analysis on PCNW indicates that this ladder type of structure is achieved through lateral overlap between unhybridised p orbitals of sp C atoms. Furthermore, electronic transport calculations using nonequilibrium Green's function reveal that this material can be properly utilized as Schottky barrier diode with appreciable voltage rectifying capability when connected to asymmetrical metallic contacts, which may have potential application as field effect transistor.
Decoherence and time reversibility: The role of randomness at interfaces
Authors: Sellier J. M. , Nedjalkov M. , Dimov I. , Selberherr S.
Published: November 2013

The Wigner formalism is a convenient reformulation of the Schrödinger equation that allows the simulation of transient behavior of quantum systems in the presence of general boundary conditions. Recently, a Wigner Monte Carlo technique, based on particles signs, has been generalized to two-dimensional evolution problems. In this paper, we apply this technique to study the time reversibility of the quantum evolution of a wave packet colliding with a potential wall in the presence of interface roughness, elastic, inelastic, and diffusive interactions with the environment. We show that a wall surface roughness does not necessarily involve time irreversibility. The dynamics of the packet is indeed influenced, but remains coherent, until the boundaries of the system begin to absorb information from the system. Finally, it is shown that in the presence of inelastic scattering or diffusive processes, the time-reversibility of a quantum system is destroyed, whatever the shape of the wall interface is. In particular, we show that the random nature of a process, elastic or inelastic, is responsible for the appearance of quantum decoherence.
Approximation of effective moisture-diffusion coefficient to characterize performance of a barrier coating
Authors: Nagai Shingo
Published: November 2013

We report estimation of the effective diffusion coefficient of moisture through a barrier coating to develop an encapsulation technology for the thin-film electronics industry. This investigation targeted a silicon oxide (SiOx) film that was deposited on a plastic substrate by a large-process-area web coater. Using the finite difference method based on diffusion theory, our estimation of the effective diffusion coefficient of a SiOx film corresponded to that of bulk glass that was previously reported. This result suggested that the low diffusivities of barrier films can be obtained on a mass-production level in the factory. In this investigation, experimental observations and mathematical confirmation revealed the limit of the water vapor transmission rate on the single barrier coating.
Ferroelectric functionality in SrTiO3/Si heterojunctions
Authors: Yu H. L. , Wu Y. Z. , Jiang X. F. , Cai M. Q. , Gu L. P. , Yang G. W.
Published: November 2013

By the first-principles calculations, various SrTiO3/Si interface architectures have been studied in this work and the computed results showed that the stable ferroelectricity can be realized in the SrTiO3/Si system. The Si/SrO interface architecture with the Si-O configuration showed predominately the ferroelectric nature and the height of the potential barrier between the negative and positive poled states (0.77 eV per interfacial unit cell). The presence of the covalent bond between the substrate Si and O of SrO layer adjacent to the substrate Si leads to the disappearance of the electronic dipoles at the interface, and the reason is that the Si-O configuration of the Si/SrO interface architecture exhibits ferroelectric nature. In order to further understand the influence of the interfacial bonding nature on the ferroelectricity of the oxide layer, the BaTiO3/Si heterojunction with the same interface architectures also have been studied. Indeed, the Si/BaO interface architecture with the Si-O configuration showed predominately the ferroelectric nature too. Certainly, a full SrO (or BaO) layer directly grown on the substrate Si is benefit to the realization of the ferroelectric functionality in the ferroelectric-Si heterojunction. These findings are useful for the understanding of the basic physics of the ferroelectric-Si heterojunction and the silicon-based functional oxide device design.
Significant enhancement of energy-storage performance of (Pb0.91La0.09)(Zr0.65Ti0.35)O3 relaxor ferroelectric thin films by Mn doping
Authors: Liu Yunying , Hao Xihong , An Shengli
Published: November 2013

1.5-μm-thick (Pb0.91La0.09)(Zr0.65Ti0.35)O3 (PLZT) relaxor ferroelectric (RFE) films doped by Mn from 0 to 5 mol. % were deposited on LaNiO3/Si(100) substrates via a sol-gel method. The microstructure, dielectric properties, and energy-storage performance of PLZT thin films were investigated as a function of Mn content. X-ray diffraction patterns and scanning electron microscopy indicated that all the films possessed a similar microstructure with pure perovskite phase. However, the dielectric constant, average breakdown fields, and the difference between maximum polarization and remnant polarization of the films were improved by Mn doping. A giant recoverable energy-storage density of 30.8 J/cm3 was obtained in 1 mol. % Mn-doped films. Moreover, good temperature-dependent energy-storage stability was also observed in the films. These results indicated that Mn-doping was an efficient way to optimize the energy-storage behaviors of PLZT RFE films.
Transfer-free fabrication of graphene field effect transistor arrays using solid-phase growth of graphene on a SiO2/Si substrate
Authors: Tamaoki Masato , Imaeda Hideki , Kishimoto Shigeru , Mizutani Takashi
Published: November 2013

In this study, graphene field effect transistor arrays were fabricated, using solid-phase growth of graphene on a SiO2/Si substrate. Transfer-free fabrication was made possible by the fact that the graphene was grown not on a metal catalyst film, but on an insulating SiO2 substrate. Electrical isolation process was also eliminated by employing a patterned growth of graphene. The resultant device exhibited satisfactorily good current-voltage characteristics, with a mobility of 590 cm2/V s.
Reinforcement of CVD grown multi-walled carbon nanotubes by high temperature annealing
Authors: Elumeeva K. V. , Kuznetsov V. L. , Ischenko A. V. , Smajda R. , Spina M. , Forró L. , Magrez A.
Published: November 2013

We report on the increase of the Young's modulus (E) of chemical vapor deposition (CVD) grown multi-walled carbon nanotubes (MWNTs) upon high temperature heat treatment. The post heat-treatment at 2200–2800ºC in a controlled atmosphere results in a considerable improvement of the microstructure, chemical stability and electro-physical properties of the nanotubes. The Young's modulus of MWNTs of different diameters was measured by the deflection of a single tube suspended across the hole of silicon nitride membrane and loaded by an atomic force microscope tip. Contrary to previous reports, a strong increase of E was feasible due to the improved growth conditions of pristine carbon nanotubes and to the improved heat treatment conditions. However, the elastic modulus of CVD grown MWNTs still shows strong diameter dependence resulting from the remaining structural inhomogeneities in large diameter nanotubes.
Lithium diffusion in silicon and induced structure disorder: A molecular dynamics study
Authors: Wang Huanyu , Ji Xiao , Chen Chi , Xu Kui , Miao Ling
Published: November 2013

Using molecular dynamics method, we investigate the diffusion property of lithium in different silicon structures and silicon structure's disorder extent during lithium's diffusion process. We find that the pathway and the incident angle between the direction of barrier and diffusion of lithium are also the essential factors to the lithium's diffusion property in silicon anode besides the barrier. Smaller incident angle could decrease the scattering of lithium in silicon structure effectively. Moreover, lithium diffuses easier in the Li-Si alloy structure of higher lithium concentration with deeper injection depth. The silicon's structure will be damaged gradually during the charge and discharge process. However, it will also recover to initial state to a great extent after relaxation. Therefore, the damage of lithium diffusion to silicon anode in the structure of low lithium concentration is reversible to a great degree. In addition, the silicon structure of <110> crystal orientation perform better properties in both lithium's diffusivity and structural stability.
Helioseismology plumbs new depths
Authors: Smart Ashley G.
Published: November 2013

The technique has yielded the most detailed picture to date of the subsurface flows that circulate plasma between the Sun’s equator and poles.
Ceramic nanolattices hold up under pressure
Authors: Miller Johanna L.
Published: November 2013

At the right size scale, a brittle substance becomes strong and springy.
A powerful quantum chemical method tackles a protein
Authors: Miller Johanna L.
Published: November 2013

Previously limited to systems with a mere dozen or so atoms, coupled-cluster theory can now manage hundreds.
Japan’s Fukushima site is an ongoing morass
Authors: Feder Toni
Published: November 2013

The world-scale nuclear disaster needs to be addressed by worldwide expertise, critics say.
Geoengineering researchers ponder ethical and regulatory issues
Authors: Kramer David
Published: November 2013

With interest in artificial climate intervention heating up, advocates and foes agree on the need for a governance regime to sanction experimental trials.
Breaking from tradition, some scientists self-publish
Authors: Matthews Jermey N. A.
Published: November 2013

Online platforms offer more control over the publishing process, but no editorial peer review.
NNSA touts savings from supercomputing
Authors: Kramer David
Published: November 2013

Nuclear weaponeers look toward exascale computing, but major breakthroughs in power consumption, handling of massive data sets, and other areas are needed first.
Earth’s enigmatic inner core
Authors: Buffett Bruce
Published: November 2013

The solid iron ball at the center of our planet helps power Earth’s magnetic field and may record a billion years of geological activity in the deep interior.
The Arecibo Observatory: Fifty astronomical years
Authors: Altschuler Daniel R. , Salter Christopher J.
Published: November 2013

Among its many accomplishments, the world’s largest single-dish telescope has detailed properties of the ionosphere, spotted the first planets discovered outside our solar system, and helped confirm the general theory of relativity.
Swimming in the desert
Authors: Ding Yang , Li Chen , Goldman Daniel I.
Published: November 2013

Physicists and colleagues from various disciplines are just beginning to study how organisms and robots move within and on granular media. An old theory from fluid mechanics can help guide them.
Reconstitution of long and short patch mismatch repair reactions using
Saccharomyces cerevisiae
proteins
Authors: Bowen Nikki , Smith Catherine E. , Srivatsan Anjana , Willcox Smaranda , Griffith Jack D. , Kolodner Richard D.
Published: November 2013

Significance

This study demonstrates mismatch repair (MMR) reactions reconstituted in vitro with purified
Saccharomyces cerevisiae
proteins. Biochemical analysis of MMR in vitro showed that MMR required mispair binding by the MutS homolog 2–MutS homolog 6 complex and corresponded to the Exonuclease 1-dependent subpathway of MMR. The reactions observed involved the formation of long excision tracts whose length was consistent with the length of MMR-dependent gene conversion tracts in vivo. The availability of this reconstituted MMR reaction now allows the wealth of mutations affecting MMR generated from the genetic analysis of
S. cerevisiae
MMR mechanisms in vivo to be used in biochemical reconstitution studies whose ultimate goal is to reconstitute MMR linked to both DNA replication and recombination.
The calculability of communicative intentions through pragmatic reasoning
Authors: Sanders Robert E. , Wu Yaxin , Bonito Joseph A.
Published: November 2013

We provide conceptual and empirical support for the core tenet in pragmatic theory that speakers make their communicative intention about the pragmatic meaning of their utterances recognizable to hearers. First, we attribute skepticism about this tenet to conceptualizing communicative intentions as private cognitive states that hearers cannot reliably discern. We show it is more parsimonious to conceptualize communicative intention as arising from communally shared knowledge of discursive means to ends that is the basis for pragmatic reasoning about utterance meaning by speaker and hearer alike. Second, we address skepticism based on experiments interpreted as finding an egocentric bias where people regard communicative intentions as more obvious to others than they are. We report two original experiments we carried out that found that participants as third party observers and as communicators routinely engaged in pragmatic reasoning about the meaning of utterances in context that took others’ perspectives into account.
How the intentionality of emotion can be traced to the intensionality of emotion
Authors: Mondal Prakash
Published: November 2013

In this paper a connection between intentionality, intensionality, language and emotion will be drawn up through a demonstration of an intimate relationship between the intentionality of emotion and intensionality in language. What will be shown is that the intentionality of emotion can ultimately be traced to the intensionality of emotional contexts. For this purpose, emotive predicates will be categorized in terms of their intensional behavior and regularities. They will then be brought forward for an explication of why and how far the intentionality of emotion is unique. The insights derived from the relevant analyses will then be employed for the implications and ramifications that might be thrown upon the fabric of emotion and language within the space of cognition.
Multivoiced decisions
Authors: Greco Morasso Sara
Published: November 2013

This paper sets out to explore the relation between social argumentation and inner debate by taking into account suggestions from argumentation studies and from social and discursive psychology. It develops Dascal’s (2005) claim that there are metonymical and structural relations between the two realms of debate by substantiating it with data taken from international migrants’ inner debates at moments of difficult decisions. The data are drawn from the experience of migrating mothers who have to decide whether to go back or to remain in their host country (the UK). I show that others are present in migrants’ multivoiced decisions in two important senses: first, inner debates can be reconstructed as critical discussions (van Eemeren and Grootendorst 1984). Second, the locus from analogy has the special function of allowing the comparison between the migrant’s experience and someone else’s experience.
Speaker’s meaning and non-cancellability
Authors: Feng Guangwu
Published: November 2013

This article intends to reveal the unity between intention and other Gricean notions of signification, cancellability, and context. We argue that the total signification of an utterance is ultimately determined by speaker’s intention. We start with Grice’s conception of meaningNN and then proceed to argue that what is actually meant (both what is said and what is implicated) is hard to cancel without rendering the whole utterance self-contradictory. It is noted that cancelling p be differentiated from correcting p. It is also noted that contextual factors do not bear upon implicatures though a hearer or an analyst relies heavily on them for inference or interpretation. We suggest that any Gricean account of meaning be ontologically clear that it is the speaker’s intention that we are really invoking and consequently capture the metaphysics of meaning in order to remove the fallacy that the meaning of an utterance is its interpretation.