bluuebunny/crossref_metadata_2025 huggingface dataset:
The protective role of prosocial behaviors on antisocial behaviors: The mediating effects of deviant peer affiliation
Authors: Carlo Gustavo , Mestre Maria Vicenta , McGinley Meredith M. , Tur‐Porcar Ana , Samper Paula , Opal Deanna
Published: March 2014

Prosocial behaviors, actions intended to help others, may serve a protective function against association with deviant peers and subsequent delinquent and antisocial behaviors. The present study examined the relations among specific types of prosocial behaviors, deviant peer affiliation, and delinquent and aggressive behaviors. Six hundred and sixty‐six adolescents (46% girls; M age = 15.33, SD = .47) from Valencia, Spain completed questionnaires of prosocial behaviors, affiliation with deviant peers, antisocial behaviors, and aggression. Results showed that antisocial behaviors were negatively related only to specific forms of prosocial behaviors. Further analyses showed that deviant peer affiliation mediated the relations between compliant prosocial behavior and delinquency and aggression. Although altruism was not directly related to delinquency and aggression, it was indirectly linked to the behaviors via deviant peer affiliation. Discussion focuses on the relevance of specific forms of prosocial behaviors to antisocial behaviors and the risk of deviant peers for prosocial youth.
The relationship between emotional problems and subsequent school attainment: A meta‐analysis
Authors: Riglin Lucy , Petrides K.V. , Frederickson Norah , Rice Frances
Published: March 2014

Longitudinal studies have provided mixed findings regarding the relationship between emotional problems and subsequent poor school attainment. A meta‐analysis of 26 community‐based studies of children and adolescents was performed. Results revealed a prospective association between emotional problems and poor school attainment. More consistent associations were found for depression than anxiety. Moderator analyses indicated that some of the heterogeneity between studies may be due to age and gender, with reduced heterogeneity particularly notable for school grades during early adolescence and for anxiety by gender. Findings suggest that early identification and provision of support for young people with emotional problems may be helpful for improving academic outcomes such as school attainment.
Predicción de la satisfacción y el bienestar en el trabajo: hacia un modelo de organización saludable en Colombia
Authors: Nader Martín , Peña Bernate Sandra Patricia , Sánchez Santa-Bárbara Emilio
Published: March 2014

En el presente artículo se incluyen los datos correspondientes a un estudio realizado con 240 trabajadorescolombianos, que tuvo como objetivo principal determinar si la percepción del clima social, la descripcióndel trabajo (significación, responsabilidad y conocimiento de resultados) y la experiencia de fluidez (Flow)permiten predecir la satisfacción y el bienestar en el trabajo. Se dise˜naron 2 modelos teóricos, uno deellos con efectos directos del clima social y la descripción del trabajo sobre la satisfacción y el bienestar, yotro con la variable flow como mediadora, estimados mediante ecuaciones estructurales. Los resultadosmostraron que la percepción del clima social es un buen predictor de satisfacción en las organizaciones.Asimismo, el flow predice de manera precisa y amplia el sentirse satisfecho en el trabajo.
Cómo una microempresa logró un desarrollo de productos ágil y generador de valor empleando Lean
Authors: Barón Maldonado Diana Isabel , Rivera Cadavid Leonardo
Published: March 2014

El propósito del presente artículo es mostrar un ejemplo de cómo una microempresa puede hacer quesu desarrollo de productos sea más ágil, flexible y generador de valor empleando Lean. Se tomaron comoreferentes el proceso genérico de desarrollo de productos, el proceso de desarrollo tradicional en el sectorde confecciones, el sistema Toyota de desarrollo de productos y el antiguo sistema de desarrollo de laempresa. Se destacan el rol del lugar de reunión virtual y el papel del ingeniero jefe en el nuevo sistemade desarrollo de productos. Como resultado se obtuvo un sistema más enfocado en el cliente, con mejorvelocidad de respuesta y producción Justo a Tiempo.
Composite Scale of Morningness: Psychometric properties, validity with Munich ChronoType Questionnaire and age/sex differences in Poland
Authors: Jankowski K.S.
Published: March 2014

The present study aimed at testing psychometric properties of the Composite Scale of Morningness (CSM) and validating it with mid sleep on free days (MSF) derived from the Munich ChronoType Questionnaire (MCTQ) in Poland, along with analyzing age and sex differences in the CSM and MSF. A sample of 952 Polish residents (62.6% females) aged between 13 and 46 was tested. Additionally, a sample of 33 university students were given MCTQ and filled in a sleep diary for 8 days. MSF derived from MCTQ was related to the one from sleep diary (r = .44). The study revealed good reliability of the CSM (α = .84) and its validity: greater morningness preference was associated with earlier MSF from MCTQ (r = –.52). CSM scores were distributed over its full range, with a mean of 34, and did not differ between sexes, although females were earlier than males by 23 minutes in MSF. Regarding age, eveningness estimated with both CSM and MSF was greatest in subjects aged 16–18 years, and a shift toward eveningness during puberty and a shift back toward morningness in older age was observed. The Polish version of the CSM consisted of two components of morningness. Cutoff scores were: for evening types (lower 10%) 24 or less, for morning types (upper 10%) 43 or more. The Polish CSM presents good psychometric properties, which are similar to those reported in other language versions, and also presents sex/age patterns similar to those found previously.
Physiological evidence of a deficit to enhance the empathic response in schizophrenia
Authors: Corbera S. , Ikezawa S. , Bell M.D. , Wexler B.E.
Published: March 2014

Empathy is crucial for maintaining effective social interactions. Research has identified both an early-emotional sharing and a late-cognitive component of empathy. Although considered a functionally vital social cognition process, empathy has scarcely been studied in schizophrenia (SZ). We used event-related potentials (ERPs) to study the temporal dynamics of empathic response in 19 patients with SZ and 18 matched healthy controls (HC) using an empathy for physical pain paradigm. Participants responded to pictures of hands in neutral and painful situations in an active empathic condition and one manipulated by task demands. Additionally, subjective ratings of the stimuli and empathic self-reports were collected. People with SZ had (1) decreased early-emotional ERP responses to pictures of others in pain; (2) decreased modulation by attention of late-cognitive ERP responses; (3) lower ratings of perspective taking and higher ratings of personal distress which were both related to decreased modulation of late-cognitive empathic responses; (4) a significant relationship between high affective overlap between somebody else's pain and their own pain and decreased modulation of late-cognitive empathic responses; (5) a distinct relationship between regulatory deficits in late-cognitive empathy and functioning. Patients had present but reduced early and late empathy-related ERPs. Patients also reported increased personal distress when faced with distress in others. The late ERP responses are thought to be associated with self-regulation and response modulation. The magnitude of these late responses was inversely associated with reported levels of personal distress in both patients and controls. Additionally, regulatory deficits in cognitive empathy were highly related with deficits in functioning. Decreased ability to regulate one's own emotional engagement and response to emotions of others may be an important source of distress and dysfunction in social situations for patients with schizophrenia.
Determinants of Physical Activity in America: A First Characterization of Physical Activity Profile Using the National Health and Nutrition Examination Survey (NHANES)
Authors: Kao Ming‐Chih Jeffrey , Jarosz Renata , Goldin Michael , Patel Amy , Smuck Matthew
Published: March 2014

Objectives

To develop and implement methodologies for characterizing accelerometry‐derived patterns of physical activity (PA) in the United States in relation to demographics, anthropometrics, behaviors, and comorbidities using the National Health and Nutrition Examination Survey (NHANES) dataset.

Design

Retrospective analysis of nationally representative database.

Setting

Computer‐generated modeling in silico.

Participants

A total of 6329 adults in the United States from the NHANES 2003‐2004 database.

Methods

To discover subtle multivariate signal in the dynamic and noisy accelerometry data, we developed a novel approach, termed discretized multiple adaptive regression and implemented the algorithm in SAS 9.2 (SAS Institute, Cary, NC).

Main Outcome Measurements

Demographic, anthropometric, comorbidity, and behavioral variables.

Results

The intensity of PA decreased with both increased age and increased body mass index. Both greater education and greater income correlate with increased activity over short durations and reduced activity intensity over long durations. Numerous predictors demonstrated effects within activity ranges that may be masked by use of the standard activity intensity intervals. These include age, one of the most robust variables, where we discovered decreasing activities inside the moderate activity range. It also includes gender, where women compared with men have increased proportions of active times up to the center of light activity range, and income greater than $45,000, where a complex effect is seen with little correspondence to existing cut‐points.

Conclusions

The results presented in this study suggest that the method of multiple regression and heat map visualization can generate insights otherwise hidden in large datasets such as NHANES. A review of the provided heat maps reveals the trends discussed previously involving demographic, anthropometric, comorbidity, and behavioral variables. It also demonstrates the power of accelerometry to expose alterations in PA. Ultimately, this study provides a US population‐based norm to use in future studies of PA.
Anthropological and Historical Perspectives on India's Working Classes
Authors: SANCHEZ ANDREW , STRÜMPELL CHRISTIAN
Published: March 2014

With reference to original ethnographic and historical research on India, the papers collected in this forum suggest conceptual refinements that might re-centre the study of class in regional scholarship. Through discussions of class politics in industrial, construction and agricultural contexts, the authors interrogate the conceptual oppositions between stably employed fordist labour forces and the ‘working poor’ that have often constrained ethnographic and historical analyses of India's working classes. Inspired by Marxist historiography, this forum engages with the historically contingent emergence of Indian working classes through different types of labour, gender and ethnic struggles, and considers the complex political boundaries that are produced by such processes.
Electrochemical characteristics of nanostructured platinum electrodes – a cyclic voltammetry study
Authors: Daubinger P. , Kieninger J. , Unmüssig T. , Urban G. A.
Published: March 2014

This article describes the electrochemical phenomena occurring at nanostructured platinum electrodes with high electrochemically active surface areas.
Beyond the molecular orbital conception of electronically excited states through the quantum theory of atoms in molecules
Authors: Ferro-Costas David , Pendás Ángel Martín , González Leticia , Mosquera Ricardo A.
Published: March 2014

Application of QTAIM electron density analysis and energy partitioning based on it provide quantitative support for qualitative predictions derived from the MO paradigm, as well as further descriptions for electron density rearrangements in electronically excited states.
Soft-template-carbonization route to highly textured mesoporous carbon–TiO2 inverse opals for efficient photocatalytic and photoelectrochemical applications
Authors: Quan Li Na , Jang Yoon Hee , Stoerzinger Kelsey A. , May Kevin J. , Jang Yu Jin , Kochuveedu Saji Thomas , Shao-Horn Yang , Kim Dong Ha
Published: March 2014

A significantly enhanced visible light photocatalytic activity was demonstrated for highly ordered mesoporous carbon–TiO2 inverse opal nanostructures.
Simultaneous 3-dimensional elemental imaging with LIBS and LA-ICP-MS
Authors: Chirinos Jose R. , Oropeza Dayana D. , Gonzalez Jhanis J. , Hou Huaming , Morey Mark , Zorba Vassilia , Russo Richard E.
Published: March 2014

Laser Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) are used simultaneously for spatially resolved mapping of major and trace elements and isotopes within aBastnäsiterare earth ore sample.
CO2 hydrogenation to dimethyl ether over CuO–ZnO–Al2O3/HZSM-5 prepared by combustion route
Authors: Zhang Yajing , Li Debao , Zhang Sujuan , Wang Kangjun , Wu Jing
Published: March 2014

CuO–ZnO–Al2O3 was prepared by a combustion method and then mixed with HZSM-5 to perform direct synthesis of DME from CO2.
Sound Production Treatment: Effects of Blocked and Random Practice
Authors: Wambaugh Julie L. , Nessler Christina , Wright Sandra , Mauszycki Shannon C.
Published: March 2014

Purpose

This investigation was designed to further the development of a treatment for acquired apraxia of speech (AOS), Sound Production Treatment (SPT), by examining the effects of blocked and random practice.

Method

A multiple-baseline design across participants and behaviors was used with 6 speakers with chronic AOS and aphasia. Accuracy of production of target sounds in treated and untreated words produced in probe sessions served as the primary dependent variable. Stimulus generalization was also measured to phrase production and sentence completion. Participants received SPT applied with blocked presentation of treatment words (
SPT-blocked
) and SPT applied with random presentation of treatment words (
SPT-random
).

Results

Increases in accuracy of articulation of target sounds in treated words were observed for all participants for both conditions of treatment. SPT-random appeared to be associated with better maintenance for 2 participants. Generalization to untreated words was positive for all participants for SPT-random and SPT-blocked. Stimulus generalization effects varied across participants and measurement conditions; patterns of generalization did not appear to be associated with treatment condition.

Conclusions

There may be an advantage for SPT-random for some speakers with AOS. Findings from the nonspeech motor learning literature may not translate directly to the treatment of AOS.

Supplemental Material

https://doi.org/10.23641/asha.6170213
Effects of Intensive Phonomotor Treatment on Reading in Eight Individuals With Aphasia and Phonological Alexia
Authors: Brookshire C. Elizabeth , Conway Tim , Pompon Rebecca Hunting , Oelke Megan , Kendall Diane L.
Published: March 2014

Purpose

The aim of this study was to investigate effects of a multimodal treatment of phonology, phonomotor treatment, on the reading abilities of persons with aphasia (PWA) with phonological alexia.

Method

In a retrospective, single-group design, this study presents pre-, post-, and 3-months posttreatment data for 8 PWA with phonological alexia. Participants completed 60 hr of phonomotor treatment over 6 weeks. Wilcoxon signed-ranks tests and group effect sizes comparing pre-, immediately post-, and 3-months posttreatment performance on tests of phonological processing and reading were performed.

Results

Group data showed phonological processing and oral reading of real words and nonwords improved significantly posttreatment; these gains were maintained 3 months later. No group improvement was found for reading comprehension; however, one individual did show improvement immediately post- and 3-months posttreatment.

Conclusions

This study provides support that phonomotor treatment is a viable approach to improve phonological processing and oral reading for PWA with phonological alexia. The lack of improvement with comprehension is inconsistent with prior work using similar treatments (Conway et al., 1998; Kendall et al., 2003). However, this difference can, in part, be accounted for by differences in variables, such as treatment intensity and frequency, outcome measures, and alexia severity.
Synchronous digitization for high dynamic range lock-in amplification in beam-scanning microscopy
Authors: Muir Ryan D. , Sullivan Shane Z. , Oglesbee Robert A. , Simpson Garth J.
Published: March 2014

Digital lock-in amplification (LIA) with synchronous digitization (SD) is shown to provide significant signal to noise (S/N)and linear dynamic range advantages in beam-scanning microscopy measurements using pulsed laser sources. Direct comparisons between SD-LIA and conventional LIA in homodyne second harmonic generation measurements resulted in S/N enhancements consistent with theoretical models. SD-LIA provided notably larger S/N enhancements in the limit of low light intensities, through the smooth transition between photon counting and signal averaging developed in previous work. Rapid beam scanning instrumentation with up to video rate acquisition speeds minimized photo-induced sample damage. The corresponding increased allowance for higher laser power without sample damage is advantageous for increasing the observed signal content.
Phase behavior of the 38-atom Lennard-Jones cluster
Authors: Sehgal Ray M. , Maroudas Dimitrios , Ford David M.
Published: March 2014

We have developed a coarse-grained description of the phase behavior of the isolated 38-atom Lennard-Jones cluster (LJ38). The model captures both the solid-solid polymorphic transitions at low temperatures and the complex cluster breakup and melting transitions at higher temperatures. For this coarse model development, we employ the manifold learning technique of diffusion mapping. The outcome of the diffusion mapping analysis over a broad temperature range indicates that two order parameters are sufficient to describe the cluster's phase behavior; we have chosen two such appropriate order parameters that are metrics of condensation and overall crystallinity. In this well-justified coarse-variable space, we calculate the cluster's free energy landscape (FEL) as a function of temperature, employing Monte Carlo umbrella sampling. These FELs are used to quantify the phase behavior and onsets of phase transitions of the LJ38 cluster.
Large piezoelectric coefficient and ferroelectric nanodomain switching in Ba(Ti0.80Zr0.20)O3-0.5(Ba0.70Ca0.30)TiO3 nanofibers and thin films
Authors: Jalalian A. , Grishin A. M. , Wang X. L. , Cheng Z. X. , Dou S. X.
Published: March 2014

Currently available low-dimensional piezoelectric materials show a low piezoelectric coefficient d33 of merely 100 pm V−1 with Pb(Zr, Ti)O3-based materials at the high end. Here, we report very large piezoelectricity in Ba(Ti0.80Zr0.20)O3-0.5(Ba0.70Ca0.30)TiO3 (BTZ-0.5BCT) lead-free nanostructures sintered as thin films (d33 = 140 pm V−1) and nanofibers (d33 = 180 pm V−1). The influences of lateral size, geometry, and the clamping effect on the piezoelectric performance were investigated for both thin films and nanofibers. Combining a high piezoelectric coefficient with environmental benefits, the BTZ-0.5BCT nanostructures provide the superior functions sought for highly efficient piezoelectric devices and electromechanical systems.
Alternating magnetic field assisted magnetization reversal in ferromagnetic antidot
Authors: Huang Hao-Ting , Ger Tzong-Rong , Huang Chen-Yu , Liao Kuei-Tien , Wang Pei-Jen , Lai Jun-Yang , Chen Jiann-Yeu , Lai Mei-Feng
Published: March 2014

Although the effects of high-frequency electromagnetic waves on magnetization reversal have been extensively studied, the influence of a low-frequency ac field on magnetization reversal has seldom been examined. In this study, we measured the magnetoresistance and examined the magnetic switching process of Permalloy antidot thin films under an alternating magnetic field with a frequency of 25 kHz. When no alternating magnetic field was present, the transitional field of the antidot thin films decreased as the angle of the direct magnetic field increased. When an alternating magnetic field was present, the transitional field exhibited the same trend. We compared the magnetization process of the antidot thin films with and without the alternating magnetic field and determined that the alternating field can facilitate the transition of magnetization, specifically, by lowering the transitional field with the highest variation rate (33.73%).
Curvature dependence of the interfacial heat and mass transfer coefficients
Authors: Glavatskiy K. S. , Bedeaux D.
Published: March 2014

Nucleation is often accompanied by heat transfer between the surroundings and a nucleus of a new phase. The interface between two phases gives an additional resistance to this transfer. For small nuclei the interfacial curvature is high, which affects not only equilibrium quantities such as surface tension, but also the transport properties. In particular, high curvature affects the interfacial resistance to heat and mass transfer. We develop a framework for determining the curvature dependence of the interfacial heat and mass transfer resistances. We determine the interfacial resistances as a function of a curvature. The analysis is performed for a bubble of a one-component fluid and may be extended to various nuclei of multicomponent systems. The curvature dependence of the interfacial resistances is important in modeling transport processes in multiphase systems.
Molecular dynamics simulations of polyelectrolyte brushes under poor solvent conditions: Origins of bundle formation
Authors: He Gui-Li , Merlitz Holger , Sommer Jens-Uwe
Published: March 2014

Molecular dynamics simulations are applied to investigate salt-free planar polyelectrolyte brushes under poor solvent conditions. Starting above the Θ-point with a homogeneous brush and then gradually reducing the temperature, the polymers initially display a lateral structure formation, forming vertical bundles of chains. A further reduction of the temperature (or solvent quality) leads to a vertical collapse of the brush. By varying the size and selectivity of the counterions, we show that lateral structure formation persists and therefore demonstrate that the entropy of counterions being the dominant factor for the formation of the bundle phase. By applying an external compression force on the brush we calculate the minimal work done on the polymer phase only and prove that the entropy gain of counterions in the bundle state, as compared to the homogeneously collapsed state at the same temperature, is responsible for the lateral microphase segregation. As a consequence, the observed lateral structure formation has to be regarded universal for osmotic polymer brushes below the Θ-point.
Oxidation of ligand-protected aluminum clusters: An ab initio molecular dynamics study
Authors: Alnemrat Sufian , Hooper Joseph P.
Published: March 2014

We report Car-Parrinello molecular dynamics simulations of the oxidation of ligand-protected aluminum clusters that form a prototypical cluster-assembled material. These clusters contain a small aluminum core surrounded by a monolayer of organic ligand. The aromatic cyclopentadienyl ligands form a strong bond with surface Al atoms, giving rise to an organometallic cluster that crystallizes into a low-symmetry solid and is briefly stable in air before oxidizing. Our calculations of isolated aluminum/cyclopentadienyl clusters reacting with oxygen show minimal reaction between the ligand and O2 molecules at simulation temperatures of 500 and 1000 K. In all cases, the reaction pathway involves O2 diffusing through the ligand barrier, splitting into atomic oxygen upon contact with the aluminum, and forming an oxide cluster with aluminum/ligand bonds still largely intact. Loss of individual aluminum-ligand units, as expected from unimolecular decomposition calculations, is not observed except following significant oxidation. These calculations highlight the role of the ligand in providing a steric barrier against oxidizers and in maintaining the large aluminum surface area of the solid-state cluster material.
Variational symmetries, conserved quantities and identities for several equations of mathematical physics
Authors: Donchev Veliko
Published: March 2014

We find variational symmetries, conserved quantities and identities for several equations: envelope equation, Böcher equation, the propagation of sound waves with losses, flow of a gas with losses, and the nonlinear Schrödinger equation with losses or gains, and an electro-magnetic interaction. Most of these equations do not have a variational description with the classical variational principle and we find such a description with the generalized variational principle of Herglotz.
Investigations of segregation phenomena in highly strained Mn-doped Ge wetting layers and Ge quantum dots embedded in silicon
Authors: Prestat E. , Porret C. , Favre-Nicolin V. , Tainoff D. , Boukhari M. , Bayle-Guillemaud P. , Jamet M. , Barski A.
Published: March 2014

In this Letter, we investigate manganese diffusion and the formation of Mn precipitates in highly strained, few monolayer thick, Mn-doped Ge wetting layers and nanometric size Ge quantum dot heterostructures embedded in silicon. We show that in this Ge(Mn)/Si system manganese always precipitates and that the size and the position of Mn clusters (precipitates) depend on the growth temperature. At high growth temperature, manganese strongly diffuses from germanium to silicon, whereas decreasing the growth temperature reduces the manganese diffusion. In the germanium quantum dots layers, Mn precipitates are detected, not only in partially relaxed quantum dots but also in fully strained germanium wetting layers between the dots.
Peptide dynamics by molecular dynamics simulation and diffusion theory method with improved basis sets
Authors: Hsu Po Jen , Lai S. K. , Rapallo Arnaldo
Published: March 2014

Improved basis sets for the study of polymer dynamics by means of the diffusion theory, and tests on a melt of cis-1,4-polyisoprene decamers, and a toluene solution of a 71-mer syndiotactic trans-1,2-polypentadiene were presented recently [R. Gaspari and A. Rapallo, J. Chem. Phys. 128, 244109 (2008)]. The proposed hybrid basis approach (HBA) combined two techniques, the long time sorting procedure and the maximum correlation approximation. The HBA takes advantage of the strength of these two techniques, and its basis sets proved to be very effective and computationally convenient in describing both local and global dynamics in cases of flexible synthetic polymers where the repeating unit is a unique type of monomer. The question then arises if the same efficacy continues when the HBA is applied to polymers of different monomers, variable local stiffness along the chain and with longer persistence length, which have different local and global dynamical properties against the above-mentioned systems. Important examples of this kind of molecular chains are the proteins, so that a fragment of the protein transthyretin is chosen as the system of the present study. This peptide corresponds to a sequence that is structured in β-sheets of the protein and is located on the surface of the channel with thyroxin. The protein transthyretin forms amyloid fibrils in vivo, whereas the peptide fragment has been shown [C. P. Jaroniec, C. E. MacPhee, N. S. Astrof, C. M. Dobson, and R. G. Griffin, Proc. Natl. Acad. Sci. U.S.A. 99, 16748 (2002)] to form amyloid fibrils in vitro in extended β-sheet conformations. For these reasons the latter is given considerable attention in the literature and studied also as an isolated fragment in water solution where both experimental and theoretical efforts have indicated the propensity of the system to form β turns or α helices, but is otherwise predominantly unstructured. Differing from previous computational studies that employed implicit solvent, we performed in this work the classical molecular dynamics simulation on a realistic model solution with the peptide embedded in an explicit water environment, and calculated its dynamic properties both as an outcome of the simulations, and by the diffusion theory in reduced statistical-mechanical approach within HBA on the premise that the mode-coupling approach to the diffusion theory can give both the long-range and local dynamics starting from equilibrium averages which were obtained from detailed atomistic simulations.
High-pressure synthesis and compressive behavior of tantalum nitrides
Authors: Yusa Hitoshi , Kawamura Fumio , Taniguchi Takashi , Hirao Naohisa , Ohishi Yasuo , Kikegawa Takumi
Published: March 2014

WC- and NaCl-type tantalum mononitrides and hexagonal Ta5N6 were prepared at high pressure and temperature, and their compressive behaviors were examined using in situ high-pressure X-ray diffraction. Comparison of the formula volumes of the tantalum mononitrides indicated that the NaCl type was the densest phase. The P–V data showed that the WC-type structure had the highest bulk modulus value (K0 = 351(1) GPa). An analysis of the compression properties in terms of the crystallographic characteristics of the structures indicated that a prismatic polyhedral array with face-sharing connectivity was responsible for the incompressible nature of these tantalum nitrides.
Anisotropic surface phonon dispersion of the hydrogen-terminated Si(110)-(1×1) surface: One-dimensional phonons propagating along the glide planes
Authors: Matsushita Stephane Yu , Matsui Kazuki , Kato Hiroki , Yamada Taro , Suto Shozo
Published: March 2014

We have measured the surface phonon dispersion curves on the hydrogen-terminated Si(110)-(1×1) surface with the two-dimensional space group of p2mg along the two highly symmetric and rectangular directions of \documentclass[12pt]{minimal}\begin{document}$\overline{\Gamma \rm X}$\end{document}ΓX¯ and \documentclass[12pt]{minimal}\begin{document}$\overline{\Gamma \rm X^\prime }$\end{document}ΓX′¯ using high-resolution electron-energy-loss spectroscopy. All the essential energy-loss peaks on H:Si(110) were assigned to the vibrational phonon modes by using the selection rules of inelastic electron scattering including the glide-plane symmetry. Actually, the surface phonon modes of even-symmetry to the glide plane (along \documentclass[12pt]{minimal}\begin{document}$\overline{\Gamma \rm X}$\end{document}ΓX¯) were observed in the first Brillouin zone, and those of odd-symmetry to the glide plane were in the second Brillouin zone. The detailed assignment was made by referring to theoretical phonon dispersion curves of Gräschus et al. [Phys. Rev. B 56, 6482 (1997)]. We found that the H–Si stretching and bending modes, which exhibit highly anisotropic dispersion, propagate along \documentclass[12pt]{minimal}\begin{document}$\overline{\Gamma \rm X}$\end{document}ΓX¯ direction as a one-dimensional phonon. Judging from the surface structure as well as our classical and quantum mechanical estimations, the H–Si stretching phonon propagates by a direct repulsive interaction between the nearest neighbor H atoms facing each other along \documentclass[12pt]{minimal}\begin{document}$\overline{\Gamma \rm X}$\end{document}ΓX¯, whereas the H–Si bending phonon propagates by indirect interaction through the substrate Si atomic linkage.
Research Update: Mesoporous sensor nanoarchitectonics
Authors: Ariga Katsuhiko , Yamauchi Yusuke , Ji Qingmin , Yonamine Yusuke , Hill Jonathan P.
Published: March 2014

In this short review, we have selected three main subjects: (i) mesoporous materials, (ii) sensing applications, and (iii) the concept of nanoarchitectonics, as examples of recent hot topics in nanomaterials research. Mesoporous materials satisfy the conditions necessary not only for a wide range of applications but also for ease of production, by a variety of simple processes, which yield bulk quantities of materials without loss of their well-defined nanometric structural features. Sensing applications are of general importance because many events arise from interaction with external stimuli. In addition to these important features, nanoarchitectonics is a concept aimed at production of novel functionality of whole units according to concerted interactions within nanostructures. For the combined subject of mesoporous sensor nanoarchitectonics, we present recent examples of research in the corresponding fields categorized according to mechanism of detection including optical, electrical, and piezoelectric sensing.
Cryogenically cooled octupole ion trap for spectroscopy of biomolecular ions
Authors: Boyarkin Oleg V. , Kopysov Vladimir
Published: March 2014

We present here the design of a linear octupole ion trap, suitable for collisional cryogenic cooling and spectroscopy of large ions. The performance of this trap has been assessed using ultraviolet (UV) photofragmentation spectroscopy of protonated dipeptides. At the trap temperature of 6.1 K, the vibrational temperature of the ions reaches 9.1 K, although their estimated translational temperature is ∼150 K. This observation suggests that, despite the significant translational heating by radio-frequency electrical field, vibrational cooling of heavy ions in the octupole is at least as efficient as in the 22-pole ion traps previously used in our laboratory. In contrast to the 22-pole traps, excellent radial confinement of ions in the octupole makes it convenient for laser spectroscopy and boosts the dissociation yield of the stored ions to 30%. Overlap of the entire ion cloud by the laser beam in the octupole also allows for efficient UV depletion spectroscopy of ion–He clusters. The measured electronic spectra of the dipeptides and the clusters differ drastically, complicating a use of UV tagging spectroscopy for structural determination of large species.
Phase transitions in a reaction-diffusion model on a line with boundaries
Authors: Khorrami Mohammad , Aghamohammadi Amir
Published: March 2014

A one-dimensional model on a line of length L is investigated, which involves particle diffusion as well as single particle annihilation. There are also creation and annihilation at the boundaries. The static and dynamical behaviors of the system are studied. It is seen that the system could exhibit a dynamical phase transition. For small drift velocities, the relaxation time does not depend on the absorption rates at the boundaries. This is the fast phase. For large velocities, the smaller of the absorption rates at boundaries enter the relaxation rate and makes it longer. This is the slow phase. Finally, the effect of a random particle creation in the bulk is also investigated.
Kinetic equilibria of relativistic collisionless plasmas in the presence of non-stationary electromagnetic fields
Authors: Cremaschini Claudio , Tessarotto Massimo , Stuchlík Zdeněk
Published: March 2014

The kinetic description of relativistic plasmas in the presence of time-varying and spatially non-uniform electromagnetic (EM) fields is a fundamental theoretical issue both in astrophysics and plasma physics. This refers, in particular, to the treatment of collisionless and strongly-magnetized plasmas in the presence of intense radiation sources. In this paper, the problem is investigated in the framework of a covariant gyrokinetic treatment for Vlasov–Maxwell equilibria. The existence of a new class of kinetic equilibria is pointed out, which occur for spatially-symmetric systems. These equilibria are shown to exist in the presence of non-uniform background EM fields and curved space-time. In the non-relativistic limit, this feature permits the determination of kinetic equilibria even for plasmas in which particle energy is not conserved due to the occurrence of explicitly time-dependent EM fields. Finally, absolute stability criteria are established which apply in the case of infinitesimal symmetric perturbations that can be either externally or internally produced.
Enhanced magnetoresistance induced by oxygen deficiency in La0.4Ca0.6MnO3-δ oxides
Authors: Triki M. , Dhahri E. , Hlil E. K. , Garden J. L.
Published: March 2014

We report electrical features and magnetoresistance behavior of the oxygen deficient La0.4Ca0.6MnO3-δ perovskites (δ = 0, 0.15, and 0.2). These samples will be referred to as S0, S15, and S20, respectively. The dependence of electrical transport on temperature and magnetic field is systematically investigated between 2 K and 400 K in magnetic field ranging up to 5 T. The parent compound shows a stable charge ordering/antiferromagnetic state with a semiconductor-like behavior in all considered temperature range. The variable range hopping and thermally activated hopping models are found to fit well with the electrical resistivity data at low and high temperatures, respectively. Oxygen deficiency tends to weaken the charge ordering and induce ferromagnetism and metallicity at low temperature. Metal insulator transition appears at higher fields for lower oxygen deficit (S15 sample) and without field for the S20 sample. The resistivity data for S15 sample are discussed in the framework of the variable-range hopping model. Abnormal transport properties were observed in the S20 sample, characterized by the double metal-insulator transitions and low minimum behavior. These results are discussed in terms of phenomenological percolation model, based on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions. While the parent compound shows no magnetoresistance, a large magnetoresistance is observed in the deficient samples at low temperature reaching 90% and 75% at 2 T for S15 and S20 samples, respectively. Noticeably, these values reached 98% and 91% at 5 T. The appearance of colossal magnetoresistance is attributed to the spin dependent hopping between spin clusters and/or ferromagnetic domains.
Numerical study of underwater shock wave by a modified method of characteristics
Authors: Li Xiaojie , Zhang Chengjiao , Wang Xiaohong , Hu Xiaofei
Published: March 2014

This paper introduces a modified method of characteristics as well as its application to simulation of a 1D spherical underwater explosion. To check the performance of the modified method, corresponding codes for computer calculation are developed to simulate the underwater explosion problem which is a typical isentropic flow problem. In applying the modified method, shock wave is calculated based on the Rankine-Hugoniot conservation relations. Artificial viscosity is not used in the simulation, and thus the corresponding influence of artificial viscosity is not introduced into the simulation. The work is mainly focused on underwater shock wave and secondary shock wave. The results simulated with the modified method are compared with other results from experiment and AUTODYN software, and the comparisons show that the modified method results are coincident with the experimental results in acceptable accuracy. Compared with the AUTODYN results, the modified method results are consistent with the experimental results better in far field. The formation and propagation of the secondary shock and the position of the gas-water interface are well captured, and the variations in flow field can be obtained. On the basis of the comparisons, it can be demonstrated that the modified method of characteristics can be applied to the simulation of 1D isentropic flow problems effectively.
Collisionless microinstabilities in stellarators. III. The ion-temperature-gradient mode
Authors: Plunk G. G. , Helander P. , Xanthopoulos P. , Connor J. W.
Published: March 2014

We investigate the linear theory of the ion-temperature-gradient (ITG) mode, with the goal of developing a general understanding that may be applied to stellarators. We highlight the Wendelstein 7X (W7-X) device. Simple fluid and kinetic models that follow closely from existing literature are reviewed and two new first-principle models are presented and compared with results from direct numerical simulation. One model investigates the effect of regions of strong localized shear, which are generic to stellarator equilibria. These “shear spikes” are found to have a potentially significant stabilizing affect on the mode; however, the effect is strongest at short wavelengths perpendicular to the magnetic field, and it is found to be significant only for the fastest growing modes in W7-X. A second model investigates the long-wavelength limit for the case of negligible global magnetic shear. The analytic calculation reveals that the effect of the curvature drive enters at second order in the drift frequency, confirming conventional wisdom that the ITG mode is slab-like at long wavelengths. Using flux tube simulations of a zero-shear W7-X configuration, we observe a close relationship to an axisymmetric configuration at a similar parameter point. It is concluded that scale lengths of the equilibrium gradients constitute a good parameter space to characterize the ITG mode. Thus, to optimize the magnetic geometry for ITG mode stability, it may be fruitful to focus on local parameters, such as the magnitude of bad curvature, connection length, and local shear at locations of bad curvature (where the ITG mode amplitude peaks).
Cavity enhanced terahertz modulation
Authors: Born N. , Scheller M. , Koch M. , Moloney J. V.
Published: March 2014

We present a versatile concept for all optical terahertz (THz) amplitude modulators based on a Fabry-Pérot semiconductor cavity design. Employing the high reflectivity of two parallel meta-surfaces allows for trapping selected THz photons within the cavity and thus only a weak optical modulation of the semiconductor absorbance is required to significantly damp the field within the cavity. The optical switching yields to modulation depths of more than 90% with insertion efficiencies of 80%.
Kinetic theory of the electron bounce instability in two dimensional current sheets—Full electromagnetic treatment
Authors: Tur A. , Fruit G. , Louarn P. , Yanovsky V.
Published: March 2014

In the general context of understanding the possible destabilization of a current sheet with applications to magnetospheric substorms or solar flares, a kinetic model is proposed for studying the resonant interaction between electromagnetic fluctuations and trapped bouncing electrons in a 2D current sheet. Tur et al. [A. Tur et al., Phys. Plasmas 17, 102905 (2010)] and Fruit et al. [G. Fruit et al., Phys. Plasmas 20, 022113 (2013)] already used this model to investigate the possibilities of electrostatic instabilities. Here, the model is completed for full electromagnetic perturbations. Starting with a modified Harris sheet as equilibrium state, the linearized gyrokinetic Vlasov equation is solved for electromagnetic fluctuations with period of the order of the electron bounce period. The particle motion is restricted to its first Fourier component along the magnetic field and this allows the complete time integration of the non local perturbed distribution functions. The dispersion relation for electromagnetic modes is finally obtained through the quasineutrality condition and the Ampere's law for the current density. It is found that for mildly strechted current, undamped modes oscillate at typical electron bounce frequency with wavelength of the order of the plasma sheet half thickness. As the stretching of the plasma sheet becomes more intense, the frequency of these normal modes decreases and beyond a certain threshold in ε = Bz/Blobes, the mode becomes explosive with typical growth rate of a few tens of seconds. The free energy contained in the bouncing motion of the electrons may trigger an electromagnetic instability able to disrupt the cross-tail current in a few seconds. This new instability–electromagnetic electron-bounce instability–may explain fast and global scale destabilization of current sheets as required to describe substorm phenomena.
Cavity-enhanced resonant tunneling photodetector at telecommunication wavelengths
Authors: Pfenning Andreas , Hartmann Fabian , Langer Fabian , Höfling Sven , Kamp Martin , Worschech Lukas
Published: March 2014

An AlGaAs/GaAs double barrier resonant tunneling diode (RTD) with a nearby lattice-matched GaInNAs absorption layer was integrated into an optical cavity consisting of five and seven GaAs/AlAs layers to demonstrate cavity enhanced photodetection at the telecommunication wavelength 1.3 μm. The samples were grown by molecular beam epitaxy and RTD-mesas with ring-shaped contacts were fabricated. Electrical and optical properties were investigated at room temperature. The detector shows maximum photocurrent for the optical resonance at a wavelength of 1.29 μm. At resonance a high sensitivity of 3.1×104 A/W and a response up to several pA per photon at room temperature were found.
Velocity boundary conditions at a tokamak resistive wall
Authors: Strauss H. R.
Published: March 2014

Velocity boundary conditions appropriate for magnetohydrodynamic simulations have been controversial recently. A comparison of numerical simulations of sideways wall force in disruptions is presented for Dirichlet, Neumann, Robin, and DEBS boundary conditions. It is shown that all the boundary conditions give qualitatively similar results. It is shown that Dirichlet boundary conditions are valid in the small Larmor radius limit of electromagnetic sheath boundary conditions.
Bistable nanofacet structures on vicinal AlN(0001) surfaces
Authors: Funato Mitsuru , Hayashi Yuki , Kawakami Yoichi
Published: March 2014

We demonstrate that the AlN vicinal surfaces with bunched steps are composed of (0001) and (11¯0m) nanofacets and have distinct stable structures for the growth-induced and thermal-etching-induced bunches. The index m is nearly four times greater for the growth surface than that for the etched surface. Furthermore, the stable nanofacet planes depend on the vicinal angles, suggesting that the growth and etching conditions are not primary factors to determine the nanofacet structures. The experimentally revealed step structures are well accounted for by the elastic balance model with consideration of the residual surface stress.
Comparison of thermal oxidation and plasma oxidation of 4H-SiC (0001) for surface flattening
Authors: Deng Hui , Endo Katsuyoshi , Yamamura Kazuya
Published: March 2014

The thermal oxidation and water vapor plasma oxidation of 4H-SiC (0001) were investigated. The initial oxidation rate of helium-based atmospheric-pressure plasma oxidation was six times higher than that of thermal oxidation. The oxide-SiC interface generated by plasma oxidation became flatter with increasing thickness of the oxide, whereas the interface generated by thermal oxidation was atomically flat regardless of the oxide thickness. Many pits were generated on the thermally oxidized surface, whereas few pits were observed on the surface oxidized by plasma. After the oxide layer generated plasma oxidation was removed, an atomically flat and pit-free SiC surface was obtained.
On the existence of motion-induced heat flux due to thermoelastic waves in a one-dimensional solid rod
Authors: Semperlotti Fabio , Sen Mihir
Published: March 2014

In this Letter, we show the existence of motion-induced heat transfer in homogeneous isotropic solids due to the propagation of thermoelastic waves. In particular, using the linearized governing equations for thermoelastic waves, we show that heat transfer in a one-dimensional rod is not only due to conduction but also to the local particle displacement a phenomenon which, in principle, is similar to advective heat transfer in fluids. It is found that the time-averaged heat transfer is dependent on both the material properties and the external excitation parameters. This mechanism can potentially be useful in ultrasonic welding and in the development of solid state refrigerators or heat pumps.