bluuebunny/crossref_metadata_2025 huggingface dataset:
Disentangling Task and Contextual Performance
Authors: Demerouti Evangelia , Xanthopoulou Despina , Tsaousis Ioannis , Bakker Arnold B.
Published: May 2014

This study among 244 employees and their colleagues working in various sectors investigated the dimensionality of self-ratings and peer-ratings of task and contextual performance, using the scales of Goodman and Svyantek (1999) . By applying the multitrait-multimethod approach, we examined the degree to which responses to performance items are influenced by the trait (task or contextual performance) and the method factors (self- or peer-ratings). Results of confirmatory factor analyses showed that while the two performance dimensions (i.e., traits) can be differentiated, responses to their items are influenced by the method factor. Specifically, peer-ratings explain more variance in task performance, while self-ratings explain more variance in contextual performance. Moreover, the measurement of task and contextual performance is invariant across self- and peer-ratings. Finally, the positive relationships between task and contextual performance on the one hand and work-related flow on the other hand are of equal strength. These findings support the validity of the performance measure but also highlight some impact of the method factors.
An Art-Based Leadership Intervention for Enhancement of Self-Awareness, Humility, and Leader Performance
Authors: Romanowska Julia , Larsson Gerry , Theorell Töres
Published: May 2014

This study represents a new cross-disciplinary approach. A year-long art-based leadership intervention was compared to conventional leadership training using a random allocation design. The study has examined whether the art-based intervention has a stronger beneficial impact on leaders’ development than the conventional program. Comparison was made utilizing leaders’ self-ratings and subordinates’ ratings of their leaders’ frequency of expressed laissez-faire leadership and capacity to cope with stress. Our findings show a striking difference in the development between the two groups. In addition to displaying less laissez-faire behavior, the leaders in the art intervention appear to have improved their self-awareness, humility, and stress coping, while contrasting results were noted in the conventional group. These findings confirm the earlier results in our research.
Facets of diazotrophy in the oxygen minimum zone waters off Peru
Authors: Loescher Carolin R , Großkopf Tobias , Desai Falguni D , Gill Diana , Schunck Harald , Croot Peter L , Schlosser Christian , Neulinger Sven C , Pinnow Nicole , Lavik Gaute , Kuypers Marcel M M , LaRoche Julie , Schmitz Ruth A
Published: May 2014

Nitrogen fixation, the biological reduction of dinitrogen gas (N2) to ammonium (NH4+), is quantitatively the most important external source of new nitrogen (N) to the open ocean. Classically, the ecological niche of oceanic N2 fixers (diazotrophs) is ascribed to tropical oligotrophic surface waters, often depleted in fixed N, with a diazotrophic community dominated by cyanobacteria. Although this applies for large areas of the ocean, biogeochemical models and phylogenetic studies suggest that the oceanic diazotrophic niche may be much broader than previously considered, resulting in major implications for the global N-budget. Here, we report on the composition, distribution and abundance of nifH, the functional gene marker for N2 fixation. Our results show the presence of eight clades of diazotrophs in the oxygen minimum zone (OMZ) off Peru. Although proteobacterial clades dominated overall, two clusters affiliated to spirochaeta and archaea were identified. N2 fixation was detected within OMZ waters and was stimulated by the addition of organic carbon sources supporting the view that non-phototrophic diazotrophs were actively fixing dinitrogen. The observed co-occurrence of key functional genes for N2 fixation, nitrification, anammox and denitrification suggests that a close spatial coupling of N-input and N-loss processes exists in the OMZ off Peru. The wide distribution of diazotrophs throughout the water column adds to the emerging view that the habitat of marine diazotrophs can be extended to low oxygen/high nitrate areas. Furthermore, our statistical analysis suggests that NO2− and PO43− are the major factors affecting diazotrophic distribution throughout the OMZ. In view of the predicted increase in ocean deoxygenation resulting from global warming, our findings indicate that the importance of OMZs as niches for N2 fixation may increase in the future.
ZebraBeat: a flexible platform for the analysis of the cardiac rate in zebrafish embryos
Authors: De Luca Elisa , Zaccaria Gian Maria , Hadhoud Marwa , Rizzo Giovanna , Ponzini Raffaele , Morbiducci Umberto , Santoro Massimo Mattia
Published: May 2014

Heartbeat measurement is important in assesssing cardiac function because variations in heart rhythm can be the cause as well as an effect of hidden pathological heart conditions. Zebrafish (Danio rerio) has emerged as one of the most useful model organisms for cardiac research. Indeed, the zebrafish heart is easily accessible for optical analyses without conducting invasive procedures and shows anatomical similarity to the human heart. In this study, we present a non-invasive, simple, cost-effective process to quantify the heartbeat in embryonic zebrafish. To achieve reproducibility, high throughput and flexibility (i.e., adaptability to any existing confocal microscope system and with a user-friendly interface that can be easily used by researchers), we implemented this method within a software program. We show here that this platform, called ZebraBeat, can successfully detect heart rate variations in embryonic zebrafish at various developmental stages and it can record cardiac rate fluctuations induced by factors such as temperature and genetic- and chemical-induced alterations. Applications of this methodology may include the screening of chemical libraries affecting heart rhythm and the identification of heart rhythm variations in mutants from large-scale forward genetic screens.
A new cosensitization method using the Lewis acid sites of a TiO2 photoelectrode for dye-sensitized solar cells
Authors: Shibayama Naoyuki , Ozawa Hironobu , Abe Masahiro , Ooyama Yousuke , Arakawa Hironori
Published: May 2014

Dye-sensitized solar cells co-sensitized with black dye and a pyridine-anchor dye showing site-selective adsorption behaviour at the TiO2 surface have been prepared for the first time to reduce competitive adsorption.
Development of a PET radiotracer for non-invasive imaging of the reactive oxygen species, superoxide, in vivo
Authors: Chu Wenhua , Chepetan Andre , Zhou Dong , Shoghi Kooresh I. , Xu Jinbin , Dugan Laura L. , Gropler Robert J. , Mintun Mark A. , Mach Robert H.
Published: May 2014

Non-invasive imaging of reactive oxygen species (ROS) in vivo was investigated using a dihydroethidium analog [18F]12 as a PET radiotracer. The data shown indicates that [18F]12 is a promising PET tracer for non-invasive imaging of ROS in vivo.
Hydride-based HPLC stationary phases: a rapidly evolving technology for the development of new bio-analytical methods
Authors: Pesek Joseph J. , Boysen Reinhard I. , Hearn Milton T. W. , Matyska Maria T.
Published: May 2014

This review focuses on the application of various silica hydride stationary phases under conditions that enable the advantages of reversed-phase, aqueous normal phase and organic normal phase selectivity to be gained.
A reusable and portable immunosensor using personal glucose meter as transducer
Authors: Zhu Xi , Zheng Hanye , Xu Huifeng , Lin Ruolan , Han Yejian , Yang Guidi , Lin Zhenyu , Guo Longhua , Qiu Bin , Chen Guonan
Published: May 2014

In this work, a portable immunosensor was developed using a personal glucose meter (PGM) as the signal transducer.
Bilayer architecture based on hexanuclear heterometal cluster units
Authors: Fang Wei-Hui , Yang Guo-Yu
Published: May 2014

An unprecedented bilayer architecture based on “head-to-head” hexanuclear heterometal clusters and linked by parallel [CuIL2] motifs has been hydrothermally made.
Synthesis of a Fe3O4–CuO@meso-SiO2 nanostructure as a magnetically recyclable and efficient catalyst for styrene epoxidation
Authors: Zhang Xiaowei , Wang Ge , Yang Mu , Luan Yi , Dong Wenjun , Dang Rui , Gao Hongyi , Yu Jie
Published: May 2014

A novel Fe3O4–CuO@meso-SiO2 composite was fabricated as a magnetically recyclable and efficient catalyst for olefin epoxidation.
Syntheses, structures and photocatalytic properties of five new praseodymium–antimony oxochlorides: from discrete clusters to 3D inorganic–organic hybrid racemic compounds
Authors: Zou Guo-Dong , Wang Ze-Ping , Song Ying , Hu Bing , Huang Xiao-Ying
Published: May 2014

Presented here are five Pr–Sb–O–Cl cluster-based compounds with structures from discrete organic-decorated cluster to 3D framework that exhibit photocatalytic H2-evolution activity and magnetic properties.
Development and characterization of custom-engineered and compacted nanoparticles as calibration materials for quantification using LA-ICP-MS
Authors: Tabersky Daniel , Luechinger Norman A. , Rossier Michael , Reusser Eric , Hametner Kathrin , Aeschlimann Beat , Frick Daniel A. , Halim Samuel C. , Thompson Jay , Danyushevsky Leonid , Günther Detlef
Published: May 2014

Flame spray synthesis was used to produce a reference nano-material with a customized composition for use in LA-ICP-MS.
Experimental design, validation and computational modeling uncover DNA damage sensing by DNA-PK and ATM
Authors: Flassig R. J. , Maubach G. , Täger C. , Sundmacher K. , Naumann M.
Published: May 2014

A computational model predicts biphasic activation of γH2AX by DNA-PKcs and ATM-P upon DNA damage, which is induced by ionizing irradiation (IR).
Viral proteins that bridge unconnected proteins and components in the human PPI network
Authors: Rachita H. R. , Nagarajaram H. A.
Published: May 2014

Viral proteins bridging unconnected components of the Hu-PPI network play a crucial role in viral replication and hence form attractive targets for therapeutic interventions.
Monolithic NPG nanoparticles with large surface area, tunable plasmonics, and high-density internal hot-spots
Authors: Zhao Fusheng , Zeng Jianbo , Parvez Arnob Md Masud , Sun Po , Qi Ji , Motwani Pratik , Gheewala Mufaddal , Li Chien-Hung , Paterson Andrew , Strych Uli , Raja Balakrishnan , Willson Richard C. , Wolfe John C. , Lee T. Randall , Shih Wei-Chuan
Published: May 2014

NPG disks as novel plasmonic nanoparticles greatly promote plasmon-matter interactions.
Enzymatically induced motion at nano- and micro-scales
Authors: Gáspár Szilveszter
Published: May 2014

In addition to their role as nature's catalysts, enzymes can be used to propel nano- and microscale objects and to pump liquid.
Block, random and palm-tree amphiphilic fluorinated copolymers: controlled synthesis, surface activity and use as dispersion polymerization stabilizers
Authors: Alaimo David , Beigbeder Alexandre , Dubois Philippe , Broze Guy , Jérôme Christine , Grignard Bruno
Published: May 2014

The architecture of novel fluorinated copolymers drastically influences their stabilizing properties and their ability to template particle formation.
NHC-catalyzed homoenolate reaction of enals and nitroalkenes: computational study of mechanism, chemoselectivity and stereoselectivity
Authors: Zhang Qi , Yu Hai-Zhu , Fu Yao
Published: May 2014

A mechanistic study on the NHC-catalyzed homoenolate reaction of enals and nitroalkenes has been performed with the aid of DFT calculations.
Total internal reflection Raman spectroscopy of poly(alpha-olefin) oils in a lubricated contact
Authors: Praveena Manimunda , Guha Kaustav , Ravishankar Abhilash , Biswas Sanjay K. , Bain Colin D. , Jayaram Vikram
Published: May 2014

A novel total internal reflection (TIR) Raman tribometer has been used to explore the physiochemical changes associated with shear-thinning in synthetic base oil.
Graphitic nanoparticles from thermal dissociation of camphor as an effective filler in polymeric coatings
Authors: Gaddam Rohit Ranganathan , Kantheti Sasidhar , Narayan Ramanuj , Raju K. V. S. N.
Published: May 2014

Formation of uniformly-sized water soluble graphitic carbon nanoparticles from the soot obtained by the incineration of camphor.
Teaching introductory quantum physics and chemistry: caveats from the history of science and science teaching to the training of modern chemists
Authors: Greca Ileana M. , Freire Olival
Published: May 2014

Finding the best ways to introduce quantum physics to undergraduate students in all scientific areas, in particular for chemistry students, is a pressing, but hardly a simple task. In this paper, we discuss the relevance of taking into account lessons from the history of the discipline and the ongoing controversy over its interpretations and foundations in the search for new ways of improving the teaching of quantum physics. We also review and discuss the recent research in science education literature that proposes new ways of introducing quantum mechanics for undergraduate students. From these discussions, we suggest some possibilities – the inclusion of philosophical interpretations and their defense; the emphasis on strictly quantum features of the systems; an emphasis on formalism, without worrying about the ultimate ontological status of mathematics; the incorporation of quantum mechanics applications into real problems; and the need to introduce complementarity when using images – which can be taken into account when devising more effective ways of teaching introductory quantum mechanics for chemistry students.
Secondary stereocontrolling interactions in chiral Brønsted acid catalysis: study of a Petasis–Ferrier-type rearrangement catalyzed by chiral phosphoric acids
Authors: Kanomata Kyohei , Toda Yasunori , Shibata Yukihiro , Yamanaka Masahiro , Tsuzuki Seiji , Gridnev Ilya D. , Terada Masahiro
Published: May 2014

Guided by computational studies, the involvement of non-classical C–H⋯O hydrogen bonds and π–π stacking interactions were found to be crucial for high stereocontrol in a chiral phosphoric acid-catalyzed reaction.
Retention of the original LLC structure in a cross-linked poly(ethylene glycol) diacrylate hydrogel with reinforcement from a silica network
Authors: Zhang Juan , Xie Zongli , Hoang Manh , Hill Anita J. , Cong Weiwei , She Feng Hua , Gao Weimin , Kong Ling Xue
Published: May 2014

A sufficient and well dispersed silica network stabilizes the nanostructure in cross-linked poly(ethylene glycol) diacrylate templated from hexagonal lyotropic liquid crystals (LLC).
High-water-content graphene oxide/polyvinyl alcohol hydrogel with excellent mechanical properties
Authors: Huang Yifu , Zhang Mingqiu , Ruan Wenhong
Published: May 2014

Boron-cross-linked graphene oxide/polyvinyl alcohol (B-GO/PVA) hydrogels with high-water-content and excellent mechanical properties are prepared by freeze/thaw and boron cross-linking methods.
Probing the unexpected behavior of AuNPs migrating through nanofibers: a new strategy for the fabrication of carbon nanofiber–noble metal nanocrystal hybrid nanostructures
Authors: Zhu Han , Du MingLiang , Zhang Ming , Zou MeiLing , Yang TingTing , Wang LiNa , Yao JuMing , Guo BaoChun
Published: May 2014

The intimate relationship of electrochemical sensors with high sensitivity and reliability has stimulated intensive research on developing versatile materials with excellent electrocatalytic activity.
Small-molecule azomethines: organic photovoltaics via Schiff base condensation chemistry
Authors: Petrus M. L. , Bouwer R. K. M. , Lafont U. , Athanasopoulos S. , Greenham N. C. , Dingemans T. J.
Published: May 2014

Small-molecule donor materials can be prepared in one step using simple condensation chemistry.
A novel luminescent monolayer thin film based on postsynthetic method and functional linker
Authors: Lu Ye , Yan Bing
Published: May 2014

A novel strategy for fabricating a visible and near-infrared light-emitting monolayer thin film is displayed. Ln3+ (Ln = Eu, Tb and Yb) complex is introduced to metal–organic frameworks (MOFs) by PSM, and then the modified MOFs are assembled onto a quartz plate by a functional linker.
Synthesis and optical properties of iron(iii) complexes of 2-benzylidene-1-indanone derivative thin films
Authors: González M. Lozano , Sánchez-Vergara M. E. , Álvarez-Bada J. R. , Chávez-Uribe M. I. , Toscano Rubén A. , Álvarez-Toledano C.
Published: May 2014

A new method to synthesize iron(iii) complexes of 2-benzyliden-1-indanone derivatives is presented.
Hypoxia-inducible regulation of placental BOK expression
Authors: Luo Daochun , Caniggia Isabella , Post Martin
Published: May 2014

BOK (BCL-2-related ovarian killer) is a member of the pro-apoptotic BCL-2 family that is highly expressed in the human placenta. BOK excess causes increased trophoblast autophagy and apoptosis in pre-eclampsia, a pathological condition of hypoxia and oxidative stress. In the present study, we identified an HRE (hypoxia-response element) at the junction of exon-1 and intron-1 (+229 to +279) in the human BOK gene, as well as an antisense transcript driven by a promoter located in intron-2. The isolated BOK-HRE bound hypoxia-inducible HIF (hypoxia-inducible factor) proteins in vitro as well as in trophoblastic JEG3 cells and was functional in its natural position as well as in front of a heterologous promoter. Being a reverted repeat, the BOK-HRE functioned in both orientations. This directionless feature of the BOK-HRE facilitates hypoxia regulation via HIF of both BOK and its antisense transcript as demonstrated by RNAi knockdown of the HIF system. Although the antisense transcript was expressed in several human carcinoma cell lines, including choriocarcinoma-derived JEG3 cells, no antisense-regulated mechanism for BOK expression was noted. Taken together, these findings indicate that hypoxia-induced expression of BOK in placental cells is regulated via HIF and is not affected by its antisense transcript.
New approach for the detection of noise‐distorted signals based on the method of S‐preparation
Authors: Timchenko Leonid I. , Kutayev Yuriy F. , Cheporniuk Serhiy V. , Kokriatskaya Nataliya I. , Yarovyy Andriy A. , Denysova Alyona E.
Published: May 2014

A classification of correlation algorithms is provided. A method of S‐preparation is discussed, which, due to the preliminary conveyor formation of correlated image convolution sums, is characterised by high noise immunity and adaptivity to uncertainty and variability of the signal clutter situation.
A radar detector with enhanced range estimation capabilities for partially homogeneous environment
Authors: Aubry Augusto , De Maio Antonio , Foglia Goffredo , Hao Chengpeng , Orlando Danilo
Published: May 2014

In this study, the authors derive an adaptive decision scheme with enhanced range estimation capabilities for point‐like targets in partially homogeneous environments. To this end, the authors jointly exploit the oversampling of the received signal and the spillover of target energy to consecutive range samples. A suitable discrete‐time model for the received signal is introduced and the so‐called two‐step generalised likelihood ratio test is derived and assessed. The performance analysis, conducted resorting to both simulated data and real recorded datasets, is aimed at assessing the effectiveness of the proposed solution, also in comparison with the existing detectors with range estimation capabilities. The illustrative examples highlight that better detection performances and increased range estimation accuracy can be achieved exploiting oversampling at the price of an additional processing cost.
Dense nitrogen-rich energetic materials: A study of 5,5′-bis(1H-tetrazolyl)amine
Authors: Laniel Dominique , Sebastiao Elena , Cook Cyril , Murugesu Muralee , Hu Anguang , Zhang Fan , Desgreniers Serge
Published: May 2014

5,5′-bis(1H-tetrazolyl)amine (BTA), a nitrogen rich molecular solid has been investigated under compression at room temperature. Powder x-ray diffraction using synchrotron radiation and micro-Raman spectroscopy were carried out to pressures up to 12.9 GPa. BTA conserves the crystalline structure of its room condition phase up to the highest pressure, i.e., an orthorhombic unit cell (Pbca). A fit of the isothermal compression data to the Birch-Murnaghan equation of state reveals the high compressibility of BTA. An analysis of the volume change with pressure yields a bulk modulus and its derivative similar to that of high-nitrogen content molecular crystals. Upon laser heating to approximately 1100 K, the sample decomposed while pressurized at 2.1 GPa, resulting in a graphitic compound. Finally, numerical simulations demonstrate that the minimum energy conformation is not experimentally observed since a higher energy conformation allows for a more stable dense packing of the BTA molecules.
Knudsen heat capacity
Authors: Babac Gulru , Reese Jason M.
Published: May 2014

We present a “Knudsen heat capacity” as a more appropriate and useful fluid property in micro/nanoscale gas systems than the constant pressure heat capacity. At these scales, different fluid processes come to the fore that are not normally observed at the macroscale. For thermodynamic analyses that include these Knudsen processes, using the Knudsen heat capacity can be more effective and physical. We calculate this heat capacity theoretically for non-ideal monatomic and diatomic gases, in particular, helium, nitrogen, and hydrogen. The quantum modification for para and ortho hydrogen is also considered. We numerically model the Knudsen heat capacity using molecular dynamics simulations for the considered gases, and compare these results with the theoretical ones.
Comment on “Rethinking first-principles electron transport theories with projection operators: The problems caused by partitioning the basis set” [J. Chem. Phys. 139, 114104 (2013)]
Authors: Brandbyge Mads
Published: May 2014

In a recent paper Reuter and Harrison [J. Chem. Phys. 139, 114104 (2013)] question the widely used mean-field electron transport theories, which employ nonorthogonal localized basis sets. They claim these can violate an “implicit decoupling assumption,” leading to wrong results for the current, different from what would be obtained by using an orthogonal basis, and dividing surfaces defined in real-space. We argue that this assumption is not required to be fulfilled to get exact results. We show how the current/transmission calculated by the standard Greens function method is independent of whether or not the chosen basis set is nonorthogonal, and that the current for a given basis set is consistent with divisions in real space. The ambiguity known from charge population analysis for nonorthogonal bases does not carry over to calculations of charge flux.
Distortion and flow of nematics simulated by dissipative particle dynamics
Authors: Zhao Tongyang , Wang Xiaogong
Published: May 2014

In this study, we simulated distortion and flow of nematics by dissipative particle dynamics (DPD). The nematics were modeled by a binary mixture that contained rigid rods composed of DPD particles as mesogenic units and normal DPD particles as solvent. Elastic distortions were investigated by monitoring director orientation in space under influences of boundary anchoring and external fields. Static distortion demonstrated by the simulation is consistent with the prediction of Frank elastic theory. Spatial distortion profile of the director was examined to obtain static elastic constants. Rotational motions of the director under influence of the external field were simulated to understand the dynamic process. The rules revealed by the simulation are in a good agreement with those obtained from dynamical experiments and classical theories for nematics. Three Miesowicz viscosities were obtained by using external fields to hold the orientation of the rods in shear flows. The simulation showed that the Miesowicz viscosities have the order of ηc > ηa > ηb and the rotational viscosity γ1 is about two orders larger than the Miesowicz viscosity ηb. The DPD simulation correctly reproduced the non-monotonic concentration dependence of viscosity, which is a unique property of lyotropic nematic fluids. By comparing simulation results with classical theories for nematics and experiments, the DPD nematic fluids are proved to be a valid model to investigate the distortion and flow of lyotropic nematics.
Calibration of a thin metal foil for infrared imaging video bolometer to estimate the spatial variation of thermal diffusivity using a photo-thermal technique
Authors: Pandya Shwetang N. , Peterson Byron J. , Sano Ryuichi , Mukai Kiyofumi , Drapiko Evgeny A. , Alekseyev Andrey G. , Akiyama Tsuyoshi , Itomi Muneji , Watanabe Takashi
Published: May 2014

A thin metal foil is used as a broad band radiation absorber for the InfraRed imaging Video Bolometer (IRVB), which is a vital diagnostic for studying three-dimensional radiation structures from high temperature plasmas in the Large Helical Device. The two-dimensional (2D) heat diffusion equation of the foil needs to be solved numerically to estimate the radiation falling on the foil through a pinhole geometry. The thermal, physical, and optical properties of the metal foil are among the inputs to the code besides the spatiotemporal variation of temperature, for reliable estimation of the exhaust power from the plasma illuminating the foil. The foil being very thin and of considerable size, non-uniformities in these properties need to be determined by suitable calibration procedures. The graphite spray used for increasing the surface emissivity also contributes to a change in the thermal properties. This paper discusses the application of the thermographic technique for determining the spatial variation of the effective in-plane thermal diffusivity of the thin metal foil and graphite composite. The paper also discusses the advantages of this technique in the light of limitations and drawbacks presented by other calibration techniques being practiced currently. The technique is initially applied to a material of known thickness and thermal properties for validation and finally to thin foils of gold and platinum both with two different thicknesses. It is observed that the effect of the graphite layer on the estimation of the thermal diffusivity becomes more pronounced for thinner foils and the measured values are approximately 2.5–3 times lower than the literature values. It is also observed that the percentage reduction in thermal diffusivity due to the coating is lower for high thermal diffusivity materials such as gold. This fact may also explain, albeit partially, the higher sensitivity of the platinum foil as compared to gold.
Second-order many-body perturbation and coupled-cluster singles and doubles study of ice VIII
Authors: Gilliard Kandis , Sode Olaseni , Hirata So
Published: May 2014

The structure, equation of state, IR, Raman, and inelastic neutron scattering (INS) spectra of high-pressure, proton-ordered phase VIII of ice are calculated by the second-order many-body perturbation and coupled-cluster singles and doubles methods. Nearly all the observed features of the pressure-dependence of the structures and spectra are reproduced computationally up to 60 GPa insofar as the anharmonic effects can be neglected. The calculations display no sign of the hypothetical isostructural transition in 2–3 GPa to phase VIII′, the existence of which has been a matter of controversy for over a decade, while they do not contradict the interpretation of the spectral anomaly at 10–14 GPa as a precursor of the VIII-X phase transition. The calculated INS spectra correct a systematic error in the peak positions of the observed spectra.
The metallization and superconductivity of dense hydrogen sulfide
Authors: Li Yinwei , Hao Jian , Liu Hanyu , Li Yanling , Ma Yanming
Published: May 2014

Hydrogen sulfide (H2S) is a prototype molecular system and a sister molecule of water (H2O). The phase diagram of solid H2S at high pressures remains largely unexplored arising from the challenges in dealing with the pressure-induced weakening of S–H bond and larger atomic core difference between H and S. Metallization is yet achieved for H2O, but it was observed for H2S above 96 GPa. However, the metallic structure of H2S remains elusive, greatly impeding the understanding of its metallicity and the potential superconductivity. We have performed an extensive structural study on solid H2S at pressure ranges of 10–200 GPa through an unbiased structure prediction method based on particle swarm optimization algorithm. Besides the findings of candidate structures for nonmetallic phases IV and V, we are able to establish stable metallic structures violating an earlier proposal of elemental decomposition into sulfur and hydrogen [R. Rousseau, M. Boero, M. Bernasconi, M. Parrinello, and K. Terakura, Phys. Rev. Lett. 85, 1254 (2000)]. Our study unravels a superconductive potential of metallic H2S with an estimated maximal transition temperature of ∼80 K at 160 GPa, higher than those predicted for most archetypal hydrogen-containing compounds (e.g., SiH4, GeH4, etc.).
Extracting magnetic anisotropy energies in Co/Pd multilayers via refinement analysis of the full magnetoresistance curves
Authors: Kachlon Yaniv , Kurzweil Noa , Sharoni Amos
Published: May 2014

We performed magnetoresistance (MR) measurements on Co/Pd multilayers with perpendicular magnetization anisotropy, as a function of external magnetic field direction and magnitude. We find that anisotropic MR for magnetization perpendicular to plane (and to the current) is surprisingly larger than the anisotropic MR when magnetization is in-plane but perpendicular to the current. We develop a refinement process for accurately and easily extracting the anisotropy energies from the full set of MR measurements. We demonstrate its effectiveness for micron-scale electrodes of the multilayers. Here, using the additional difference in MR of the out-of-plane direction, we extract both the shape anisotropy energy and perpendicular anisotropy energy.
The rate constant for radiative association of HF: Comparing quantum and classical dynamics
Authors: Gustafsson Magnus , Monge-Palacios M. , Nyman Gunnar
Published: May 2014

Radiative association for the formation of hydrogen fluoride through the A1Π → X1Σ+ and X1Σ+ → X1Σ+ transitions is studied using quantum and classical dynamics. The total thermal rate constant is obtained for temperatures from 10 K to 20 000 K. Agreement between semiclassical and quantum approaches is observed for the A1Π → X1Σ+ rate constant above 2000 K. The agreement is explained by the fact that the corresponding cross section is free of resonances for this system. At temperatures below 2000 K we improve the agreement by implementing a simplified semiclassical expression for the rate constant, which includes a quantum corrected pair distribution. The rate coefficient for the X1Σ+ → X1Σ+ transition is calculated using Breit–Wigner theory and a classical formula for the resonance and direct contributions, respectively. In comparison with quantum calculations the classical formula appears to overestimate the direct contribution to the rate constant by about 12% for this transition. Below about 450 K the resonance contribution is larger than the direct, and above that temperature the opposite holds. The biggest contribution from resonances is at the lowest temperature in the study, 10 K, where it is more than four times larger than the direct. Below 1800 K the radiative association rate constant due to X1Σ+ → X1Σ+ transitions dominates over A1Π → X1Σ+, while above that temperature the situation is the opposite.
Highly correlated configuration interaction calculations on water with large orbital bases
Authors: Almora-Díaz César X.
Published: May 2014

A priori selected configuration interaction (SCI) with truncation energy error [C. F. Bunge, J. Chem. Phys. 125, 014107 (2006)] and CI by parts [C. F. Bunge and R. Carbó-Dorca, J. Chem. Phys. 125, 014108 (2006)] are used to approximate the total nonrelativistic electronic ground state energy of water at fixed experimental geometry with CI up to sextuple excitations. Correlation-consistent polarized core-valence basis sets (cc-pCVnZ) up to sextuple zeta and augmented correlation-consistent polarized core-valence basis sets (aug-cc-pCVnZ) up to quintuple zeta quality are employed. Truncation energy errors range between less than 1 μhartree, and 100 μhartree for the largest orbital set. Coupled cluster CCSD and CCSD(T) calculations are also obtained for comparison. Our best upper bound, −76.4343 hartree, obtained by SCI with up to sextuple excitations with a cc-pCV6Z basis recovers more than 98.8% of the correlation energy of the system, and it is only about 3 kcal/mol above the “experimental” value. Despite that the present energy upper bounds are far below all previous ones, comparatively large dispersion errors in the determination of the extrapolated energies to the complete basis set do not allow to determine a reliable estimation of the full CI energy with an accuracy better than 0.6 mhartree (0.4 kcal/mol).
Convection induced by radiative cooling of a layer of participating medium
Authors: Prasanna Swaminathan , Venkateshan S. P.
Published: May 2014

Simulations and experiments have been conducted to study the effect of radiative cooling on natural convection in a horizontal layer of a participating medium enclosed between isothermal opaque wall and radiatively transparent wall and exposed to a cold background. The study is of relevance to a nocturnal boundary layer under clear and calm conditions. The focus of the study is to capture the onset of convection caused by radiative cooling. The experiments have been designed to mimic the atmospheric radiative boundary conditions, and hence decoupling convection and radiation boundary conditions. Planck number Pl and optical thickness of the layer τH are the two important parameters that govern the interaction between radiation and convection. The radiation-convection coupling is a strong function of length scale. Convection sets up within first few seconds for all the experiments. Strong plume like convection is observed for the experimental conditions used in the present study. Both simulations and experiments confirm that radiative cooling increases substantially with decrease in emissivity of the bottom wall. Radiative cooling is strongly influenced by the nongray nature of the participating medium, especially when strong emission from the medium escapes to space, in the window region of the atmosphere. Accurate representation of radiative properties is critical. Linear stability analysis of onset of convection indicates that radiation stabilizes convection as Pl decreases. The observations are similar to the case of Rayleigh Bénard convection in a radiating gas. However, for both experimental and numerical conditions, the observed Rayleigh numbers are much greater than the critical Rayleigh number. To conclude, the role of radiation is to drive and sustain convection in the unstable layer.
Sedimentation of an ellipsoidal particle in narrow tubes
Authors: Huang Haibo , Yang Xin , Lu Xi-yun
Published: May 2014

Sedimentation behaviours of an ellipsoidal particle in narrow and infinitely long tubes are studied by a multi-relaxation-time lattice Boltzmann method (LBM). In the present study, both circular and square tubes with 12/13 ⩽ D/A ⩽ 2.5 are considered with the Galileo number (Ga) up to 150, where D and A are the width of the tube and the length of major axis of the ellipsoid, respectively. Besides three modes of motion mentioned in the literature, two novel modes are found for the narrow tubes in the higher Ga regime: the spiral mode and the vertically inclined mode. Near a transitional regime, in terms of average settling velocity, it is found that a lighter ellipsoid may settle faster than a heavier one. The relevant mechanism is revealed. The behaviour of sedimentation inside the square tubes is similar to that in the circular tubes. One significant difference is that the translation and rotation of ellipsoid are finally constrained to a diagonal plane in the square tubes. The other difference is that the anomalous rolling mode occurs in the square tubes. In this mode, the ellipsoid rotates as if it is contacting and rolling up one corner of the square tube when it settles down. Two critical factors that induce this mode are identified: the geometry of the tube and the inertia of the ellipsoid.
Raman spectroscopy of solutions and interfaces containing nitrogen dioxide, water, and 1,4 dioxane: Evidence for repulsion of surface water by NO2 gas
Authors: Murdachaew Garold , Varner Mychel E. , van der Veer Wytze E. , Gerber R. Benny , Phillips Leon F.
Published: May 2014

The interaction of water, 1,4 dioxane, and gaseous nitrogen dioxide, has been studied as a function of distance measured through the liquid-vapour interface by Raman spectroscopy with a narrow (<0.1 mm) laser beam directed parallel to the interface. The Raman spectra show that water is present at the surface of a dioxane-water mixture when gaseous NO2 is absent, but is virtually absent from the surface of a dioxane-water mixture when gaseous NO2 is present. This is consistent with recent theoretical calculations that show NO2 to be mildly hydrophobic.
Elastic scattering of low-energy electrons by 1,4-dioxane
Authors: Barbosa Alessandra Souza , Bettega Márcio H. F.
Published: May 2014

We report calculated cross sections for elastic collisions of low-energy-electrons with 1,4-dioxane. Our calculations employed the Schwinger multichannel method with pseudopotentials and were carried out in the static-exchange and static-exchange plus polarization approximations for energies up to 30 eV. Our results show the presence of three shape resonances belonging to the Bu, Au, and Bg symmetries and located at 7.0 eV, 8.4 eV, and 9.8 eV, respectively. We also report the presence of a Ramsauer-Townsend minimum located at around 0.05 eV. We compare our calculated cross sections with experimental data and R-matrix and independent atom model along with the additivity rule corrected by using screening coefficients theoretical results for 1,4-dioxane obtained by Palihawadana et al. [J. Chem. Phys. 139, 014308 (2013)]. The agreement between the present and the R-matrix theoretical calculations of Palihawadana et al. is relatively good at energies below 10 eV. Our calculated differential cross sections agree well with the experimental data, showing only some discrepancies at higher energies.
Note: Broadly tunable all-fiber ytterbium laser with 0.05 nm spectral width based on multimode interference filter
Authors: Mukhopadhyay Pranab K. , Gupta Pradeep K. , Singh Amarjeet , Sharma Sunil K. , Bindra Kushvinder S. , Oak Shrikant M.
Published: May 2014

A multimode interference filter with narrow transmission bandwidth and large self-imaging wavelength interval is constructed and implemented in an ytterbium doped fiber laser in all-fiber format for broad wavelength tunability as well as narrow spectral width of the output beam. The peak transmission wavelength of the multimode interference filter was tuned with the help of a standard in-fiber polarization controller. With this simple mechanism more than 30 nm (1038 nm–1070 nm) tuning range is demonstrated. The spectral width of the output beam from the laser was measured to be 0.05 nm.
Magneto-transport and microstructure of Co2Fe(Ga0.5Ge0.5)/Cu lateral spin valves prepared by top-down microfabrication process
Authors: Ikhtiar  , Kasai S. , Itoh A. , Takahashi Y. K. , Ohkubo T. , Mitani S. , Hono K.
Published: May 2014

Heusler alloy-based lateral spin valves with ohmic contacts are prepared for the Co2Fe(Ga0.5Ge0.5)/Cu system by means of the top-down microfabrication process. The magneto-transport and microstructure are characterized to investigate the influence of the microfabrication route on the spin dependent transport of lateral spin valves systematically. A large non-local spin signal (△RS) of 17.3 mΩ is observed at room temperature, which is attributed to the highly spin-polarized Co2Fe(Ga0.5Ge0.5) ferromagnet and the clean Co2Fe(Ga0.5Ge0.5)/Cu interfaces confirmed by transmission electron microscopy. Based on the general expression of one-dimensional spin diffusion model, we discuss the importance of interfacial spin polarization in Heusler alloy-based lateral spin valves.
Epitaxial Pb(Mg1/3Nb2/3)O3-PbTiO3 (67/33) thin films with large tunable self-bias field controlled by a PbZr1−xTixO3 interfacial layer
Authors: Boota M. , Houwman E. P. , Dekkers M. , Nguyen M. , Rijnders G.
Published: May 2014

Epitaxial Pb(Mg1/3Nb2/3)O3-PbTiO3 200 nm thick, (001) oriented, perovskite phase-pure films were grown on a range of PbZr1−xTixO3 buffer layers (x = 0.2–0.8) and sandwiched between SrRuO3 electrodes on (001) SrTiO3 substrates to form a ferroelectric capacitor structure. Devices without a buffer layer or with a buffer layer of highly tetragonal PbZr1−xTixO3 show very large self-bias fields up to 1.0 × 107 V/m. These self-bias fields correlate with strain gradient layers near the bottom electrode observed in these devices only. The large self-bias was explained quantitatively in terms of the flexoelectric effect.
Vortex lattice melting of a NbSe2 single grain probed by ultrasensitive cantilever magnetometry
Authors: Bossoni L. , Carretta P. , Poggio M.
Published: May 2014

Using dynamic cantilever magnetometry, we study the vortex lattice and its corresponding melting transition in a micrometer-size crystallite of superconducting NbSe2. Measurements of the cantilever resonance frequency as a function of magnetic field and temperature respond to the magnetization of the vortex-lattice. The cantilever dissipation depends on thermally activated vortex creep motion, whose pinning energy barrier is found to be in good agreement with transport measurements on bulk samples. This approach reveals the phase diagram of the crystallite, and is applicable to other micrometer- or nanometer-scale superconducting samples.
The application of complex network time series analysis in turbulent heated jets
Authors: Charakopoulos A. Κ. , Karakasidis T. E. , Papanicolaou P. N. , Liakopoulos A.
Published: May 2014

In the present study, we applied the methodology of the complex network-based time series analysis to experimental temperature time series from a vertical turbulent heated jet. More specifically, we approach the hydrodynamic problem of discriminating time series corresponding to various regions relative to the jet axis, i.e., time series corresponding to regions that are close to the jet axis from time series originating at regions with a different dynamical regime based on the constructed network properties. Applying the transformation phase space method (k nearest neighbors) and also the visibility algorithm, we transformed time series into networks and evaluated the topological properties of the networks such as degree distribution, average path length, diameter, modularity, and clustering coefficient. The results show that the complex network approach allows distinguishing, identifying, and exploring in detail various dynamical regions of the jet flow, and associate it to the corresponding physical behavior. In addition, in order to reject the hypothesis that the studied networks originate from a stochastic process, we generated random network and we compared their statistical properties with that originating from the experimental data. As far as the efficiency of the two methods for network construction is concerned, we conclude that both methodologies lead to network properties that present almost the same qualitative behavior and allow us to reveal the underlying system dynamics.
Magnetic properties of high-symmetry CuO
Authors: Rabinovich K. S. , Samoilenko L. L. , Zhuravleva A. S. , Shneider A. G.
Published: May 2014

We investigated structural and magnetic properties of CuO-Cu2O heterostructures obtained by high-temperature annealing of copperplate. In samples synthesized at 900 °C, an antiferromagnetic alignment phase was found at the Neel temperature TN = 600 K in fields greater than 20 Oe. At lower fields, diamagnetic alignment was observed at 680 K. The cubic phase of CuO appears to be responsible for the diamagnetic transition and the high Neel temperature.
Anisotropic diffusion in a two-dimensional model with obstruction and a comparison of mean first passage time calculations
Authors: Mon K. K.
Published: May 2014

The disagreement between two different studies of the diffusion equation for two hard disks to diffuse past each other in a narrow channel remains unresolved. Two different values for the divergence exponent of the mean first passage time (MFPT) were obtained. This has motivated the proposal that the difference arises from the use of different and nonequivalent definitions for the MFPT. Doubt was raised regarding the validity of the numerical solution of the diffusion equation as an explanation for the disagreement with the dimensional reduction method. In this paper, a one disk model which partially mimics the two disks problem is studied in the infinitely anisotropic diffusion limits. Although analytical arguments predict the exact exponent to be 1/2, it has not been probed in numerical studies. Using the two algorithms, we obtain exponents from numerical solutions which are consistent with each other and the proposed exact value.
Extending plasma transport theory to strong coupling through the concept of an effective interaction potential
Authors: Baalrud Scott D. , Daligault Jérôme
Published: May 2014

A method for extending traditional plasma transport theories into the strong coupling regime is presented. Like traditional theories, this is based on a binary scattering approximation, but where physics associated with many body correlations is included through the use of an effective interaction potential. The latter is simply related to the pair-distribution function. Modeling many body effects in this manner can extend traditional plasma theory to orders of magnitude stronger coupling. Theoretical predictions are tested against molecular dynamics simulations for electron-ion temperature relaxation as well as diffusion in one component systems. Emphasis is placed on the connection with traditional plasma theory, where it is stressed that the effective potential concept has precedence through the manner in which screening is imposed. The extension to strong coupling requires accounting for correlations in addition to screening. Limitations of this approach in the presence of strong caging are also discussed.
The impact of pedestal turbulence and electron inertia on edge-localized-mode crashes
Authors: Xi P. W. , Xu X. Q. , Diamond P. H.
Published: May 2014

We demonstrate that the occurrence of Edge-Localized-Modes (ELM) crashes does not depend only on the linear peeling-ballooning threshold, but also relies on nonlinear processes. Wave-wave interaction constrains the growth time of a mode, thus inducing a shift in the criterion for triggering an ELM crash. An ELM crash requires the P-B growth rate to exceed a critical value γ>γc, where γc is set by 1/τ¯c, and τ¯c is the averaged mode phase coherence time. For 0<γ<γc, P-B turbulence develops but drives enhanced turbulent transport. We also show that electron inertia dramatically changes the instability threshold when density is low. However, P-B turbulence alone cannot generate enough current transport to allow fast reconnection during an ELM crash.