bluuebunny/crossref_metadata_2025 huggingface dataset:
Maximum probability domains for the analysis of the microscopic structure of liquids
Authors: Agostini Federica , Ciccotti Giovanni , Savin Andreas , Vuilleumier Rodolphe
Published: February 2015

We introduce the concept of maximum probability domains (MPDs), developed in the context of the analysis of electronic densities, in the study of the microscopic spatial structures of liquids. The idea of locating a particle in a three dimensional region, by determining the domain where the probability of finding that, and only that, particle is maximum, gives an interesting characterization of the local structure of the liquid. The optimization procedure, required for the search of the domain of maximum probability, is carried out by the implementation of the level set method. Results for a couple of case studies are presented, to illustrate the structure of liquid water at ambient conditions and upon increasing pressure from the point of view of MPDs and to compare the information encoded in the solvation shells of sodium in water with, once again, that extracted from the MPDs.
X-ray continuum as a measure of pressure and fuel–shell mix in compressed isobaric hydrogen implosion cores
Authors: Epstein R. , Goncharov V. N. , Marshall F. J. , Betti R. , Nora R. , Christopherson A. R. , Golovkin I. E. , MacFarlane J. J.
Published: February 2015

Pressure, by definition, characterizes the conditions within an isobaric implosion core at peak compression [Gus'kov et al., Nucl. Fusion 16, 957 (1976); Betti et al., Phys. Plasmas 8, 5257 (2001)] and is a key parameter in quantifying its near-ignition performance [Lawson, Proc. Phys. Soc. London, B 70, 6 (1957); Betti et al., Phys. Plasmas 17, 058102 (2010); Goncharov et al., Phys. Plasmas 21, 056315 (2014); and Glenzer et al., Phys. Plasmas 19, 056318 (2012)]. At high spectral energy, where the x-ray emission from an imploded hydrogen core is optically thin, the emissivity profile can be inferred from the spatially resolved core emission. This emissivity, which can be modeled accurately under hot-core conditions, is dependent almost entirely on the pressure when measured within a restricted spectral range matched to the temperature range anticipated for the emitting volume. In this way, the hot core pressure at the time of peak emission can be inferred from the measured free-free emissivity profile. The pressure and temperature dependences of the x-ray emissivity and the neutron-production rate explain a simple scaling of the total filtered x-ray emission as a constant power of the total neutron yield for implosions of targets of similar design over a broad range of shell implosion isentropes. This scaling behavior has been seen in implosion simulations and is confirmed by measurements of high-isentrope implosions [Sangster et al., Phys. Plasmas 20, 056317 (2013)] on the OMEGA laser system [Boehly et al., Opt. Commun. 133, 495 (1997)]. Attributing the excess emission from less-stable, low-isentrope implosions, above the level expected from this neutron-yield scaling, to the higher emissivity of shell carbon mixed into the implosion's central hot spot, the hot-spot “fuel–shell” mix mass can be inferred.
Note: Advancement in tip etching for preparation of tunable size scanning tunneling microscopy tips
Authors: Corbett J. P. , Pandya S. G. , Mandru A.-O. , Pak J. , Kordesch M. E. , Smith A. R.
Published: February 2015

The two aspects of a scanning tunneling microscopy tip, the macroscopic profile and the nanoscale apex, can be tailored by controlling the tension during electrochemical etching and the solution-electrode contact area via acetone vapor. The apex diameter is shown to be proportional to the square root of the tension, and is demonstrated over apex diameters of 150-500 nm. The apex was found to be created in four distinct shapes where a secondary etching can reshape the tip into a single geometry. Improvement in tip height and stability of the profile are demonstrated versus a non-acetone fabrication control.
Squeezout phenomena and boundary layer formation of a model ionic liquid under confinement and charging
Authors: Capozza R. , Vanossi A. , Benassi A. , Tosatti E.
Published: February 2015

Electrical charging of parallel plates confining a model ionic liquid down to nanoscale distances yields a variety of charge-induced changes in the structural features of the confined film. That includes even-odd switching of the structural layering and charging-induced solidification and melting, with important changes of local ordering between and within layers, and of squeezout behavior. By means of molecular dynamics simulations, we explore this variety of phenomena in the simplest charged Lennard-Jones coarse-grained model including or excluding the effect a neutral tail giving an anisotropic shape to one of the model ions. Using these models and open conditions permitting the flow of ions in and out of the interplate gap, we simulate the liquid squeezout to obtain the distance dependent structure and forces between the plates during their adiabatic approach under load. Simulations at fixed applied force illustrate an effective electrical pumping of the ionic liquid, from a thick nearly solid film that withstands the interplate pressure for high plate charge to complete squeezout following melting near zero charge. Effective enthalpy curves obtained by integration of interplate forces versus distance show the local minima that correspond to layering and predict the switching between one minimum and another under squeezing and charging.
A unified and preserved Dirichlet boundary treatment for the cell-centered finite volume discrete Boltzmann method
Authors: Chen Leitao , Schaefer Laura A.
Published: February 2015

A new boundary treatment is proposed for the finite volume discrete Boltzmann method (FVDBM) that can be used for accurate simulations of curved boundaries and complicated flow conditions. First, a brief review of different boundary treatments for the general Boltzmann simulations is made in order to primarily explain what type of boundary treatment will be developed in this paper for the cell-centered FVDBM. After that, the new boundary treatment along with the cell-centered FVDBM model is developed in detail. Next, the proposed boundary treatment is applied to a series of numerical tests with a detailed discussion of its qualitative and quantitative properties. From the results, it can be concluded that the new boundary treatment is at least first-order accurate for a variety of Dirichlet boundary conditions (BCs). It can handle both the velocity and density Dirichlet BCs in a unified way and further realize some BCs that the conventional lattice Boltzmann model fails to simulate. In addition, such a boundary treatment can incorporate different lattice models without changing its framework, and it can preserve the Dirichlet BCs up to machine accuracy in different situations.
An efficient plasmonic photovoltaic structure using silicon strip-loaded geometry
Authors: Awal M. A. , Ahmed Zabir , Talukder Muhammad Anisuzzaman
Published: February 2015

We show that a silicon thin-film photovoltaic structure with silicon strips on the top and grooves on the silver back contact layer can absorb incident solar energy over a broad spectral range. The silicon strips on the top scatter the incident light and significantly help couple to the photonic modes in the smaller wavelength range. The grooves on the silver back contact layer both scatter the incident light and help couple to the photonic modes and resonant surface plasmon polaritons. We find an increase of ∼46% in total integrated solar absorption in the proposed strip-loaded structure compared to that in a planar thin film structure of same dimensions. The proposed structure offers simpler fabrication compared to similar plasmonic-inspired designs.
Novel aspects of plasma control in ITER
Authors: Humphreys D. , Ambrosino G. , de Vries P. , Felici F. , Kim S. H. , Jackson G. , Kallenbach A. , Kolemen E. , Lister J. , Moreau D. , Pironti A. , Raupp G. , Sauter O. , Schuster E. , Snipes J. , Treutterer W. , Walker M. , Welander A. , Winter A. , Zabeo L.
Published: February 2015

ITER plasma control design solutions and performance requirements are strongly driven by its nuclear mission, aggressive commissioning constraints, and limited number of operational discharges. In addition, high plasma energy content, heat fluxes, neutron fluxes, and very long pulse operation place novel demands on control performance in many areas ranging from plasma boundary and divertor regulation to plasma kinetics and stability control. Both commissioning and experimental operations schedules provide limited time for tuning of control algorithms relative to operating devices. Although many aspects of the control solutions required by ITER have been well-demonstrated in present devices and even designed satisfactorily for ITER application, many elements unique to ITER including various crucial integration issues are presently under development. We describe selected novel aspects of plasma control in ITER, identifying unique parts of the control problem and highlighting some key areas of research remaining. Novel control areas described include control physics understanding (e.g., current profile regulation, tearing mode (TM) suppression), control mathematics (e.g., algorithmic and simulation approaches to high confidence robust performance), and integration solutions (e.g., methods for management of highly subscribed control resources). We identify unique aspects of the ITER TM suppression scheme, which will pulse gyrotrons to drive current within a magnetic island, and turn the drive off following suppression in order to minimize use of auxiliary power and maximize fusion gain. The potential role of active current profile control and approaches to design in ITER are discussed. Issues and approaches to fault handling algorithms are described, along with novel aspects of actuator sharing in ITER.
Hot-electron energy relaxation time in Ga-doped ZnO films
Authors: Šermukšnis E. , Liberis J. , Ramonas M. , Matulionis A. , Toporkov M. , Liu H. Y. , Avrutin V. , Özgür Ü. , Morkoç H.
Published: February 2015

Hot-electron energy relaxation time is deduced for Ga-doped ZnO epitaxial layers from pulsed hot-electron noise measurements at room temperature. The relaxation time increases from ∼0.17 ps to ∼1.8 ps when the electron density increases from 1.4 × 1017 cm−3 to 1.3 × 1020 cm−3. A local minimum is resolved near an electron density of 1.4 × 1019 cm−3. The longest energy relaxation time (1.8 ps), observed at the highest electron density, is in good agreement with the published values obtained by optical time-resolved luminescence and absorption experiments. Monte Carlo simulations provide a qualitative interpretation of our observations if hot-phonon accumulation is taken into account. The local minimum of the electron energy relaxation time is explained by the ultrafast plasmon-assisted decay of hot phonons in the vicinity of the plasmon–LO-phonon resonance.
Phase effects due to previous pulses in time-resolved Faraday rotation measurements
Authors: Trowbridge Christopher J. , Sih Vanessa
Published: February 2015

Time-resolved Faraday rotation measurements have proved transformative in the investigation of spin dynamics in semiconductors. In materials with spin lifetimes which are on the order of, or greater than, the laser repetition time, the collective effect of spin polarization due to the whole pump pulse train becomes important. Here, we discuss a relative phase shift which results from these spins. We derive and experimentally validate a closed-form expression which describes this phase shift and characterize it throughout parameter space. A spin lifetime measurement based on this phase shift is described, and we discuss situations in which the model used must be augmented to be applicable.
Synchronization of spin-transfer torque oscillators by spin pumping, inverse spin Hall, and spin Hall effects
Authors: Elyasi Mehrdad , Bhatia Charanjit S. , Yang Hyunsoo
Published: February 2015

We have proposed a method to synchronize multiple spin-transfer torque oscillators based on spin pumping, inverse spin Hall, and spin Hall effects. The proposed oscillator system consists of a series of nano-magnets in junction with a normal metal with high spin-orbit coupling, and an accumulative feedback loop. We conduct simulations to demonstrate the effect of modulated charge currents in the normal metal due to spin pumping from each nano-magnet. We show that the interplay between the spin Hall effect and inverse spin Hall effect results in synchronization of the nano-magnets.
A full-dimensional quantum dynamics study of the mode specificity in the H + HOD abstraction reaction
Authors: Fu Bina , Zhang Dong H.
Published: February 2015

We employ the initial state-selected time-dependent wave packet approach to an atom-triatom reaction to study the H + HOD → OH + HD/OD + H2 reaction without the centrifugal sudden approximation, based on an accurate potential energy surface which was recently developed by neural network fitting to high level ab initio energy points. The total reaction probabilities and integral cross sections, which are the exact coupled-channel results, are calculated for the HOD reactant initially in the ground and several vibrationally excited states, including the bending excited state, OD stretching excited states, OH stretching excited states, and combined excitations of them. The reactivity enhancements from different initial states of HOD are presented, which feature strong bond-selective effects of the reaction dynamics. The current results for the product branching ratios, reactivity enhancements, and relative cross sections are largely improved over the previous calculations, in quantitatively good agreement with experiment. The thermal rate constant for the title reaction and the contributions from individual vibrational states of HOD are also obtained.
A parallel dipole line system
Authors: Gunawan Oki , Virgus Yudistira , Tai Kong Fai
Published: February 2015

We present a study of a parallel linear distribution of dipole system, which can be realized using a pair of cylindrical diametric magnets and yields several interesting properties and applications. The system serves as a trap for cylindrical diamagnetic object, produces a fascinating one-dimensional camelback potential profile at its center plane, yields a technique for measuring magnetic susceptibility of the trapped object and serves as an ideal system to implement highly sensitive Hall measurement utilizing rotating magnetic field and lock-in detection. The latter application enables extraction of low carrier mobility in several materials of high interest such as the world-record-quality, earth abundant kesterite solar cell, and helps elucidate its fundamental performance limitation.
Photonic surfaces for designable nonlinear power shaping
Authors: Biswas Roshni , Povinelli Michelle L.
Published: February 2015

We propose a method for designing nonlinear input-output power response based on absorptive resonances of nanostructured surfaces. We show that various power transmission trends can be obtained by placing a photonic resonance mode at the appropriate detuning from the laser wavelength. We demonstrate our results in a silicon photonic crystal slab at a laser wavelength of 808 nm. We quantify the overall spectral red shift as a function of laser power. The shift results from absorptive heating and the thermo-optic effect. We then demonstrate devices with increasing, decreasing, and non-monotonic transmission as a function of laser power. The transmission changes are up to 7.5 times larger than in unpatterned silicon. The strong nonlinear transmission is due to a combination of resonantly enhanced absorption, reduced thermal conductivity, and the resonant transmission lineshape. Our results illustrate the possibility of designing different nonlinear power trends within a single materials platform at a given wavelength of interest.
Modelling of heat assisted magnetic recording with the Landau-Lifshitz-Bloch equation and Brillouin functions
Authors: Greaves Simon John , Muraoka Hiroaki , Kanai Yasushi
Published: February 2015

Brillouin functions were used to model the temperature dependence of magnetisation in media for heat assisted magnetic recording. Although dHk/dT was higher when Brillouin functions with J = 0.5 or J = 1 were used, an earlier onset of the linear reversal mode led to a drop in dHc/dT near to Tc, resulting in wider written bits. Tracks written with a higher thermal gradient were also wider when J was small and had lower SNR.
Magnetization reversal of a Nd-Cu-infiltrated Nd-Fe-B nanocrystalline magnet observed with small-angle neutron scattering
Authors: Saito Kotaro , Ueno Tetsuro , Yano Masao , Harada Masashi , Shoji Tetsuya , Sakuma Noritsugu , Manabe Akira , Kato Akira , Keiderling Uwe , Ono Kanta
Published: February 2015

The magnetization reversal process of Nd-Fe-B nanocrystalline magnets infiltrated with Nd-Cu alloy was examined using small-angle neutron scattering (SANS). The magnetic-field dependence of SANS intensity revealed a qualitative difference between Nd-Cu-infiltrated samples and as-deformed samples. Insufficient magnetic isolation along the direction perpendicular to the nominal c-axis is expected from comparable SANS intensities for different ranges of q values along this direction. For small q values near the coercivity field, Nd-Cu-infiltrated samples show a noticeable reduction in SANS intensity along the nominal c-axis, which is parallel to the external magnetic field. This indicates less spatial fluctuation of magnetic moments in Nd-Cu-infiltrated samples, owing to magnetically isolated Nd2Fe14B grains.
Measurement of Curie temperature distribution relevant to heat assisted magnetic recording
Authors: Chernyshov Alex , Le Thanh , Livshitz Boris , Mryasov Oleg , Miller Charles , Acharya Ram , Treves David
Published: February 2015

Heat-Assisted Magnetic Recording (HAMR) is a likely successor of Perpendicular Magnetic Recording (PMR) in the Hard disk drive industry. In PMR, recording performance is strongly affected by the following distributions in magnetic granular media: magnetic anisotropy field (HK), volume/grain size, and interaction field from neighboring grains. Since HAMR writing occurs in a narrow temperature region below Curie point (Tc), additional grain-to-grain Tc variation would strongly affect HAMR recording performance. Thus, Tc distribution should be examined for successful HAMR media development. In this paper, we demonstrate a new approach of extracting HK and Tc distributions (σHK and σTc) from thermo-remanence measurements. During the measurement process, a thin film is magnetically saturated, laser heated to specific peak temperature (for a time typically of 5 μs), then cooled to room temperature and magnetic thermo-remanence is measured. Analytical fit to the experimental curves enables independent evaluation of both σTc (±0.5% absolute) and σHK (±2% absolute). Parameters of the analytical statistical model include: temperature dependencies Ms(T), HK(T); mean field effective demagnetization factor N; grain size, HK; and Tc distributions. Thermal fluctuations are taken into account using Arrhenius-Neel formalism. Here, we report experimental σTc values as a function of grain volume. Increase of σTc with grain size reduction might be a limiting factor for HAMR extendibility.
Terahertz homodyne self-mixing transmission spectroscopy
Authors: Mohr Till , Breuer Stefan , Blömer Dominik , Simonetta Marcello , Patel Sanketkumar , Schlosser Malte , Deninger Anselm , Birkl Gerhard , Giuliani Guido , Elsäßer Wolfgang
Published: February 2015

A compact homodyne self-mixing terahertz spectroscopy concept is experimentally investigated and confirmed by calculations. This method provides amplitude and phase information of the terahertz radiation emitted by a photoconductive antenna in a transmission experiment where a rotating chopper wheel serves as a feedback mirror. As a proof-of-principle experiment the frequency-dependent refractive index of Teflon is measured.
Two advanced research methods: Frequency-time-resolved microwave photoconductivity and broadband photodielectric spectroscopy
Authors: Novikov G. F.
Published: February 2015

Two known methods of research of electric properties were applied on semiconducting materials and their methodology was significantly improved to obtain quantitative data on elementary reactions of charge carriers. The resonator method of microwave photoconductivity included the measurements of the frequency dependences of photoresponse. The modified frequency- and time-resolved microwave photoconductivity method gives the opportunity to separate contributions to a photoresponse of the free electrons which did not experience capture by acceptors and structural defects, and the electrons which are again released in a free state from traps. The use of a light source (λ = 350 ÷ 2500 nm) together with a broadband dielectric spectrometer provides an effective tool (the broadband photodielectric spectroscopy—BPDS) for research of relaxation processes in semiconductors caused by excess current carriers. Examples of investigation of the photoelectric properties of CdS, CdTe, and Cu(In,Ga)Se2 received with modified methods are presented.
Formation of chemically stable GeO2 on the Ge surface with pulsed metal–organic chemical vapor deposition
Authors: Shibayama Shigehisa , Yoshida Teppei , Kato Kimihiko , Sakashita Mitsuo , Takeuchi Wakana , Taoka Noriyuki , Nakatsuka Osamu , Zaima Shigeaki
Published: February 2015

For realizing high quality Ge 3-dimensional channel devices, GeO2 deposition technique is essentially required. In the case of the formation of high-k/GeO2/Ge gate stacks by using deposition method, a high-k layer has to be directly deposited on the GeO2/Ge structure which causes the degradation of interface properties of high-k/GeO2/Ge gate stacks. Therefore, the enhancement of the chemical stability of the GeO2 interlayer is a crucial issue. Recently, the deposition technique of a GeO2 thin layer has been developed, which is called as pulsed metal-organic chemical vapor deposition (pulsed MOCVD) method from tetraethoxy-germanium and H2O. In this study, we investigate the crystalline structure and resistance towards water etching of GeO2 films formed by using pulsed MOCVD method. The GeO2 film formed by the pulsed MOCVD method shows higher water resistance and the possibility of the crystallization compared with the thermal oxidation method. Taking into account that the suppression of the GeO2 reduction during high-k layer deposition provides superior interface properties, the direct formation of chemically stable GeO2 on the Ge substrate by the pulsed MOCVD method is important for fabricating high-performance high-k/GeO2/Ge gate stacks.
Understanding short channel mobility degradation by accurate external resistance decomposition and intrinsic mobility extraction
Authors: Chu Tao , Vega Reinaldo A. , Alptekin Emre , Guo Dechao , Shang Huiling
Published: February 2015

An intrinsic short channel mobility extraction method is proposed by measuring two short-channel devices with different channel lengths and the same source/drain and contact geometry. The constant and dynamic components of external resistance are separated. Short-channel mobility degradation is observed and its origin is studied. The possible causes of the halo doping and the non-uniformity of the inversion layer charge are accounted for. The weaker temperature dependence of short channel devices indicates that the short channel mobility degradation may result from some combination of defect-induced and Coulomb-induced scattering near the S/D regions, differing in severity between NFETs and PFETs which employ, respectively, ion implant and embedded epitaxy as the primary component of S/D design.
Propensity of bond exchange as a window into the mechanical properties of metallic glasses
Authors: Jiao W. , Wang X. L. , Lan S. , Pan S. P. , Lu Z. P.
Published: February 2015

We investigated the mechanical properties of Zr-Cu-Al bulk metallic glasses, by compression experiment and molecular dynamics simulations. From the simulation, we found that the large, solvent atom, Zr, has high propensity of bond exchange compared to those of the smaller solute atoms. The difference in bond exchange is consistent with the observed disparity in mechanical behaviors: Zr-rich metallic glass exhibits low elastic modulus and large plastic strain. X-ray photoelectron spectroscopy measurements suggest that the increased propensity in bond exchange is related to the softening of Zr bonds with increasing Zr content.
Looking for Auger signatures in III-nitride light emitters: A full-band Monte Carlo perspective
Authors: Bertazzi Francesco , Goano Michele , Zhou Xiangyu , Calciati Marco , Ghione Giovanni , Matsubara Masahiko , Bellotti Enrico
Published: February 2015

Recent experiments of electron emission spectroscopy (EES) on III-nitride light-emitting diodes (LEDs) have shown a correlation between droop onset and hot electron emission at the cesiated surface of the LED p-cap. The observed hot electrons have been interpreted as a direct signature of Auger recombination in the LED active region, as highly energetic Auger-excited electrons would be collected in long-lived satellite valleys of the conduction band so that they would not decay on their journey to the surface across the highly doped p-contact layer. We discuss this interpretation by using a full-band Monte Carlo model based on first-principles electronic structure and lattice dynamics calculations. The results of our analysis suggest that Auger-excited electrons cannot be unambiguously detected in the LED structures used in the EES experiments. Additional experimental and simulative work are necessary to unravel the complex physics of GaN cesiated surfaces.
Investigation of inelastic electron tunneling spectra of metal-molecule-metal junctions fabricated using direct metal transfer method
Authors: Jeong Hyunhak , Hwang Wang-Taek , Kim Pilkwang , Kim Dongku , Jang Yeonsik , Min Misook , Xiang Dong , Song Hyunwook , Park Yun Daniel , Jeong Heejun , Lee Takhee
Published: February 2015

We measured the inelastic electron tunneling spectroscopy (IETS) characteristics of metal-molecule-metal junctions made with alkanethiolate self-assembled monolayers. The molecular junctions were fabricated using a direct metal transfer method, which we previously reported for high-yield metal-molecule-metal junctions. The measured IETS data could be assigned to molecular vibration modes that were determined by the chemical structure of the molecules. We also observed discrepancies and device-to-device variations in the IETS data that possibly originate from defects in the molecular junctions and insulating walls introduced during the fabrication process and from the junction structure.
Flow networks: A characterization of geophysical fluid transport
Authors: Ser-Giacomi Enrico , Rossi Vincent , López Cristóbal , Hernández-García Emilio
Published: February 2015

We represent transport between different regions of a fluid domain by flow networks, constructed from the discrete representation of the Perron-Frobenius or transfer operator associated to the fluid advection dynamics. The procedure is useful to analyze fluid dynamics in geophysical contexts, as illustrated by the construction of a flow network associated to the surface circulation in the Mediterranean sea. We use network-theory tools to analyze the flow network and gain insights into transport processes. In particular, we quantitatively relate dispersion and mixing characteristics, classically quantified by Lyapunov exponents, to the degree of the network nodes. A family of network entropies is defined from the network adjacency matrix and related to the statistics of stretching in the fluid, in particular, to the Lyapunov exponent field. Finally, we use a network community detection algorithm, Infomap, to partition the Mediterranean network into coherent regions, i.e., areas internally well mixed, but with little fluid interchange between them.
Noise characterization of metal-single molecule contacts
Authors: Xiang D. , Sydoruk V. , Vitusevich S. , Petrychuk M. V. , Offenhäusser A. , Kochelap V. A. , Belyaev A. E. , Mayer D.
Published: February 2015

Noise spectra of molecule-free and molecule-containing mechanically controllable break junctions were investigated. The molecule-free junctions revealed typical 1/f noise characteristics. We studied three molecules as they bridged the electrodes: 11-mercaptoundecanoicacid, 1,8-octanedithiol, and 1,4-benzenedithiol, which possess different bonding strengths. For all of them, an additional Lorentzian-shape 1/f2 noise component was registered with a characteristic frequency when the electrodes were bridged by an individual molecule. Measurements of time-dependent voltage fluctuations for the molecule-containing junctions bring out two-current state fluctuations, which in the frequency domain correspond to the 1/f2 noise. Moreover, it is revealed that characteristic frequencies of these noise components are independent of molecule bonding strengths at the interface, but correlate with the molecule weights and current amplitudes in the lock-in state, in which the electrode gap is bridged by a single molecule. We attribute the noise monitored during charge transport through a molecular junction to the current induced molecular reconfigurations and suggest that the noise analysis can be used for characterization of metal-molecule coupling.
Phase field modeling of microstructure evolution of electrocatalyst-infiltrated solid oxide fuel cell cathodes
Authors: Liang Linyun , Li Qun , Hu Jiamian , Lee Shiwoo , Gerdes Kirk , Chen Long-Qing
Published: February 2015

A phase field model is developed to examine microstructural evolution of an infiltrated solid oxide fuel cell cathode. It is employed to generate the three-phase backbone microstructures and morphology of infiltrate nano-particles [La1−xSrxMnO3 (LSM)]. Two-phase Y2O3 + ZrO2 and LSM backbones composed of 0.5–1 μm particles are first generated and then seeded with infiltrate, and evolution is compared for starting infiltrate particle diameters of 5 nm and 10 nm. The computed lifetime triple phase boundary (3PB) density of the infiltrated cathode is then compared to the cathode backbone. Results indicate that initial coarsening of infiltrate nano-particles is the primary evolution process, and infiltrate coarsening is the majority contributor to 3PB reduction. However, at all times, the infiltrated cathode possesses significantly greater 3PB length than even the uncoarsened backbone. Infiltrate particle size effects indicate that the smaller particle size produces greater 3PB length for the same infiltration amount, consistent with intuition. A maximum 3PB enhancement is reached when increasing infiltrate particle loading, and the maximum enhancement depends on infiltrate particle size. It is found that architectural degradation modes will insignificantly affect the lifetime performance of infiltrated cathodes. This work suggests that lifetime optimized particle size/loading combinations are identifiable, and can be precise if additional fundamental data become available.
Magnetoconductance anisotropy of a polymer thin film at the onset of metallicity
Authors: Zanettini S. , Dayen J. F. , Etrillard C. , Leclerc N. , Kamalakar M. Venkata , Doudin B.
Published: February 2015

Thin films of poly(2,5-bis(3-dodecyl-2-yl)-thieno[3,2-b]thiophene) (C12-PBTTT) polymer under electrolyte gating and doping are investigated as model systems for organic thin films devices approaching the metallic side of a metal-insulator (M-I) transition. For the most doped samples, with an estimated density reaching 8 × 1020 cm−3 holes and a conductivity exceeding 1000 S cm−1, a positive high-field magnetoconductance is found in a limited temperature range window and only when the field is perpendicular to the sample plane. This signature of weak localization, combined with indications of finite zero-temperature conductivity, allows us to identify delocalized metallic-like transport in these thin films, even though the conductivity decreases when cooling down the samples.
High-frequency and high-field optically detected magnetic resonance of nitrogen-vacancy centers in diamond
Authors: Stepanov Viktor , Cho Franklin H. , Abeywardana Chathuranga , Takahashi Susumu
Published: February 2015

We present the development of an optically detected magnetic resonance (ODMR) system, which enables us to perform the ODMR measurements of a single defect in solids at high frequencies and high magnetic fields. Using the high-frequency and high-field ODMR system, we demonstrate 115 GHz continuous-wave and pulsed ODMR measurements of a single nitrogen-vacancy (NV) center in a diamond crystal at the magnetic field of 4.2 T as well as investigation of field dependence (0–8 T) of the longitudinal relaxation time (T1) of NV centers in nanodiamonds.
Sub-band transport mechanism and switching properties for resistive switching nonvolatile memories with structure of silver/aluminum oxide/p-type silicon
Authors: Liu Yanhong , Li La , Wang Song , Gao Ping , Zhou Peng , Li Jinhua , Weng Zhankun , Pan Lujun , Zhang Jialiang
Published: February 2015

In this paper, we discuss a model of sub-band in resistive switching nonvolatile memories with a structure of silver/aluminum oxide/p-type silicon (Ag/AlxOy/p-Si), in which the sub-band is formed by overlapping of wave functions of electron-occupied oxygen vacancies in AlxOy layer deposited by atomic layer deposition technology. The switching processes exhibit the characteristics of the bipolarity, discreteness, and no need of forming process, all of which are discussed deeply based on the model of sub-band. The relationships between the SET voltages and distribution of trap levels are analyzed qualitatively. The semiconductor-like behaviors of ON-state resistance affirm the sub-band transport mechanism instead of the metal filament mechanism.
Fast magnetic reconnection due to anisotropic electron pressure
Authors: Cassak P. A. , Baylor R. N. , Fermo R. L. , Beidler M. T. , Shay M. A. , Swisdak M. , Drake J. F. , Karimabadi H.
Published: February 2015

A new regime of fast magnetic reconnection with an out-of-plane (guide) magnetic field is reported in which the key role is played by an electron pressure anisotropy described by the Chew-Goldberger-Low gyrotropic equations of state in the generalized Ohm's law, which even dominates the Hall term. A description of the physical cause of this behavior is provided and two-dimensional fluid simulations are used to confirm the results. The electron pressure anisotropy causes the out-of-plane magnetic field to develop a quadrupole structure of opposite polarity to the Hall magnetic field and gives rise to dispersive waves. In addition to being important for understanding what causes reconnection to be fast, this mechanism should dominate in plasmas with low plasma beta and a high in-plane plasma beta with electron temperature comparable to or larger than ion temperature, so it could be relevant in the solar wind and some tokamaks.
The Size Distribution of Employment Centers within the US Metropolitan Areas
Authors: Arribas-Bel Daniel , Ramos Arturo , Sanz-Gracia Fernando
Published: February 2015

This study tackles the description of the size distribution of urban employment centers or, in other words, the size of areas within cities with significantly high densities of workers. Certainly, there exists a branch of urban economics that has paid substantial attention to urban employment centers, but the efforts have been focused on identification methodologies. In this paper we build on such body of research and combine it with insights from the latest contributions in the sister subfield of city size distributions to push the agenda forward in terms of the understanding of these phenomena. We consider the 359 Metropolitan Statistical Areas (MSAs) in the United States in the year 2000 and reach three main conclusions: First, employment center sizes are more unevenly distributed than city sizes; second, the two functions that best describe city size distributions, namely the lognormal and the double Pareto-lognormal, also offer a good fit for the case of centers, particularly the latter; and third, several interesting statistically significant relationships (correlations) between variables related to centers and MSAs are deduced. Further experiments with a different technique of center identification suggest that the results are fairly robust to the method of choice.
Learning to argue like an expert
Authors: Awad Scrocco Diana Lin
Published: February 2015

Many scholars have argued that practicing medicine requires sophisticated rhetorical prowess (Loftus 2012; Pender 2005; Segal 2005, 2007). Although rhetorical theory can explain how novices learn to argue like experts, much work in the subfield of medical learning only implicitly draws on rhetorical notions (e.g., Barton & Eggly 2009; Heritage & Maynard 2006). This study examines conversations between faculty physician preceptors and resident physician trainees in an internal medicine clinic to consider the role of persuasion in teaching novices to argue like experts. Using Aristoteliantopoi, I reveal how the common lines of argument underlying medical teaching and learning help novice and expert physicians explain concepts, elicit interpretations, and initiate deliberation. As they synthesize and rationalize medical information, they use antecedent-and-consequence, possible-and-impossible, authority, and testimonialtopoi. This study of professional enculturation elucidates a rarely examined area of medical communication, potentially enabling preceptors to teach their tacit reasoning more explicitly to residents.
Producing written noun phrases in French
Authors: Maggio Severine , Chenu Florence , Bes de Berc Guillemette , Pesci Blandine , Lété Bernard , Jisa Harriet , Fayol Michel
Published: February 2015

This research compares the time-course of the written production of bare nouns to that of noun phrases. French adults named pictures of objects either using or not using determiners. Resulting pauses and writing rates were analyzed in relation to word-orthographic frequency, syllabic length, and phoneme-to-grapheme consistency at the end of words. More specifically, we showed that the noun production process begins as soon the determiner production is initiated (word frequency effect on latencies, length and consistency effects on determiner writing rate) and continued during the course of the noun production. When the determiner was absent, the management of writing was different: the writer slowed the production speed, probably in order to realize the lexeme processing that s/he could not do in the absence of the determiner production time. These results provided further evidence that some form of parallel processing occurs in written word production and led us to sketch the time-course of the noun spelling in written denomination of a noun phrase.
From t-bias to d-bias in Dutch
Authors: Hanssen Esther , Schreuder Robert , Neijt Anneke
Published: February 2015

Previous studies reveal that young Dutch children display a [t]-bias in the middle of words in pronunciation (e.g. van der Feest 2007; Kerkhoff 2007). First graders, however, display a 〈d〉-bias in the middle of words in their writings (Neijt & Schreuder 2007). The present study investigates children’s spelling and pronunciation of word medial d and t to examine this apparent contrast. It turned out that first graders started with a 〈t〉-bias in their spellings while later on they displayed a 〈d〉-bias. A similar development was found for pronunciation: Kindergartners displayed a [t]-bias, while second graders displayed a [d]-bias instead. Our explanation is that this change is caused by overgeneralization, due to differences between Dutch pronunciation and orthography. We conclude that the orthographic system, although learned later in life, affects children’s earlier acquired pronunciation.
Community consensus and social identity in alphabet development
Authors: Schreyer Christine
Published: February 2015

In the Huon Gulf area of Papua New Guinea, the indigenous language Jabêm was one of the languages of first contact for Lutheran German Missionaries, circa 1900. As a result, Jabêm became a language of the church and, later, a language of education. In both domains, written materials were commonly produced and generations of children were schooled in Jabêm rather than their own mother tongues. This paper discusses the relationship between Jabêm and Kala, an indigenous language spoken in six villages along the Huon Gulf Coast. Kala was without a standard orthography until recent collaborations between members of the communities and researchers from UBC Okanagan. This paper, therefore, also describes the development of the Kala standardized orthography and examines the distinct influences Jabêm has in both spoken and written domains. For instance, Jabêm’s role as a written authority retains positive connotation, which influenced the newly created Kala orthography.
Right Ventricular Long Noncoding RNA Expression in Human Heart Failure
Authors: Di Salvo Thomas G. , Guo Yan , Su Yan Ru , Clark Travis , Brittain Evan , Absi Tarek , Maltais Simon , Hemnes Anna
Published: February 2015

The expression of long noncoding RNAs (lncRNAs) in human heart failure (HF) has not been widely studied. Using RNA sequencing (RNA‐Seq), we compared lncRNA expression in 22 explanted human HF hearts with lncRNA expression in 5 unused donor human hearts. We used Cufflinks to identify isoforms and DESeq to identify differentially expressed genes. We identified the noncoding RNAs by cross‐reference to Ensembl release 73 (Genome Reference Consortium human genome build 37) and explored possible functional roles using a variety of online tools. In HF hearts, RNA‐Seq identified 84,793 total messenger RNA coding and noncoding different transcripts, including 13,019 protein‐coding genes, 2,085 total lncRNA genes, and 1,064 pseudogenes. By Ensembl noncoding RNA categories, there were 48 lncRNAs, 27 pseudogenes, and 30 antisense RNAs for a total of 105 differentially expressed lncRNAs in HF hearts. Compared with donor hearts, HF hearts exhibited differential expression of 7.7% of protein‐coding genes, 3.7% of lncRNAs (including pseudogenes), and 2.5% of pseudogenes. There were not consistent correlations between antisense lncRNAs and parent genes and between pseudogenes and parent genes, implying differential regulation of expression. Exploratory in silico functional analyses using online tools suggested a variety of possible lncRNA regulatory roles. By providing a comprehensive profile of right ventricular polyadenylated messenger RNA transcriptome in HF, RNA‐Seq provides an inventory of differentially expressed lncRNAs, including antisense transcripts and pseudogenes, for future mechanistic study.
Well-posedness of general boundary-value problems for scalar conservation laws
Authors: Andreianov Boris , Sbihi Karima
Published: February 2015

In this paper we investigate well-posedness for the problemut+div⁡φ(u)=fu_t+ \operatorname {div} \varphi (u)=fon(0,T)×Ω(0,T)\!\times \!\Omega,Ω⊂RN\Omega \subset \mathbb {R}^N, with initial conditionu(0,⋅)=u0u(0,\cdot )=u_0onΩ\Omegaand with general dissipative boundary conditionsφ(u)⋅ν∈β(t,x)(u)\varphi (u)\cdot \nu \in \beta _{(t,x)}(u)on(0,T)×∂Ω(0,T)\!\times \!\partial \Omega. Here for a.e.(t,x)∈(0,T)×∂Ω(t,x)\in (0,T)\!\times \!\partial \Omega,β(t,x)(⋅)\beta _{(t,x)}(\cdot )is a maximal monotone graph onR\mathbb {R}. This includes, as particular cases, Dirichlet, Neumann, Robin, obstacle boundary conditions and their piecewise combinations.

As for the well-studied case of the Dirichlet condition, one has to interpret theformal boundary conditiongiven byβ\betaby replacing it with the adequateeffective boundary condition. Such effective condition can be obtained through a study of the boundary layer appearing in approximation processes such as the vanishing viscosity approximation. We claim that the formal boundary condition given byβ\betashould be interpreted as the effective boundary condition given by another monotone graphβ~\tilde \beta, which is defined fromβ\betaby the projection procedure we describe. We give several equivalent definitions of entropy solutions associated withβ~\tilde \beta(and thus also withβ\beta).

For the notion of solution defined in this way, we prove existence, uniqueness andL1L^1contraction, monotone and continuous dependence on the graphβ\beta. Convergence of approximation procedures and stability of the notion of entropy solution are illustrated by several results.
Model companion of ordered theories with an automorphism
Authors: Laskowski Michael , Pal Koushik
Published: February 2015

Kikyo and Shelah showed that if

T
T

is a theory with the Strict Order Property in some first-order language

L

\mathcal {L}

, then in the expanded language

L

σ

:=

L

∪
{
σ
}

\mathcal {L}_\sigma := \mathcal {L}\cup \{\sigma \}

with a new unary function symbol

σ
\sigma

, the bigger theory

T
σ

:=
T
∪
{
“
σ

 is an 

L

-automorphism

}

T_\sigma := T\cup \{“\sigma \mbox { is an } \mathcal {L}\mbox {-automorphism}\}

does not have a model companion. We show in this paper that if, however, we restrict the automorphism and consider the theory

T
σ

T_\sigma

as the base theory

T
T

together with a “restricted” class of automorphisms, then

T
σ

T_\sigma

can have a model companion in

L

σ

\mathcal {L}_\sigma

. We show this in the context of linear orders and ordered abelian groups.
Science communication: a career where PhDs can make a difference
Authors: Irion Robert
Published: February 2015

Among careers for biologists with PhDs, science communication is one of the most diverse and rewarding pathways. Myriad options exist, from traditional journalism to new media, from writing for specialists to working in public outreach. Textbooks, mass-market books, and freelance writing that combines many of these pursuits are all viable choices. Communicating about science allows researchers to step away from the minutiae of a subdiscipline and to once again explore the breadth of science more fully through an ever-evolving array of stories. A doctoral degree can confer distinct advantages in the eyes of prospective editors and employers. Here I describe those advantages, possible career directions, and steps toward making such a transition.
Ubiquitin binding by the CUE domain promotes endosomal localization of the Rab5 GEF Vps9
Authors: Shideler Tess , Nickerson Daniel P. , Merz Alexey J. , Odorizzi Greg
Published: February 2015

Vps9 and Muk1 are guanine nucleotide exchange factors (GEFs) in Saccharomyces cerevisiae that regulate membrane trafficking in the endolysosomal pathway by activating Rab5 GTPases. We show that Vps9 is the primary Rab5 GEF required for biogenesis of late endosomal multivesicular bodies (MVBs). However, only Vps9 (but not Muk1) is required for the formation of aberrant class E compartments that arise upon dysfunction of endosomal sorting complexes required for transport (ESCRTs). ESCRT dysfunction causes ubiquitinated transmembrane proteins to accumulate at endosomes, and we demonstrate that endosomal recruitment of Vps9 is promoted by its ubiquitin-binding CUE domain. Muk1 lacks ubiquitin-binding motifs, but its fusion to the Vps9 CUE domain allows Muk1 to rescue endosome morphology, cargo trafficking, and cellular stress-tolerance phenotypes that result from loss of Vps9 function. These results indicate that ubiquitin binding by the CUE domain promotes Vps9 function in endolysosomal membrane trafficking via promotion of localization.