bluuebunny/crossref_metadata_2025 huggingface dataset:
A paracrine network regulates the cross-talk between human lung stem cells and the stroma
Authors: Ruiz E. Josue , Oeztuerk-Winder Feride , Ventura Juan-Jose
Published: January 2014

The signals that regulate stem cell self-renewal and differentiation in the lung remain elusive. Lung stem cells undergo self-renewal or lineage commitment to replenish tissue, depending on cross-talk with their environment. This environment, also known as the niche, includes mesenchymal and endothelial tissues. Here we define molecular mechanisms involved in the interaction between human lung Lgr6+ stem cells (LSCs) and fibroblasts in a functional microenvironment. We reveal a central role for p38α MAPK in establishing and maintaining such cross-talk, acting in both cell types. In LSCs, p38α induces the expression of SDF-1, which activates the stroma. p38α is essential for fibroblast activation and induction of cytokine expression, in particular TNFα. This paracrine network induces a hierarchical activation leading to the recruitment of endothelium, establishing a functional microenvironment. Disruption of this cross-talk abrogates proper LSC differentiation in vivo and may lead to lung dysfunction and disease.
Trading Network Predicts Stock Price
Authors: Sun Xiao-Qian , Shen Hua-Wei , Cheng Xue-Qi
Published: January 2014

Stock price prediction is an important and challenging problem for studying financial markets. Existing studies are mainly based on the time series of stock price or the operation performance of listed company. In this paper, we propose to predict stock price based on investors' trading behavior. For each stock, we characterize the daily trading relationship among its investors using a trading network. We then classify the nodes of trading network into three roles according to their connectivity pattern. Strong Granger causality is found between stock price and trading relationship indices, i.e., the fraction of trading relationship among nodes with different roles. We further predict stock price by incorporating these trading relationship indices into a neural network based on time series of stock price. Experimental results on 51 stocks in two Chinese Stock Exchanges demonstrate the accuracy of stock price prediction is significantly improved by the inclusion of trading relationship indices.
How dolphins see the world: A comparison with chimpanzees and humans
Authors: Tomonaga Masaki , Uwano Yuka , Saito Toyoshi
Published: January 2014

Bottlenose dolphins use auditory (or echoic) information to recognise their environments and many studies have described their echolocation perception abilities. However, relatively few systematic studies have examined their visual perception. We tested dolphins on a visual-matching task using two-dimensional geometric forms including various features. Based on error patterns, we used multidimensional scaling to analyse perceptual similarities among stimuli. In addition to dolphins, we conducted comparable tests with terrestrial species: chimpanzees were tested on a computer-controlled matching task and humans were tested on a rating task. The overall perceptual similarities among stimuli in dolphins were similar to those in the two species of primates. These results clearly indicate that the visual world is perceived similarly by the three species of mammals, even though each has adapted to a different environment and has differing degrees of dependence on vision.
Mysterious abrupt carbon-14 increase in coral contributed by a comet
Authors: Liu Yi , Zhang Zhao-feng , Peng Zi-cheng , Ling Ming-xing , Shen Chuan-Chou , Liu Wei-guo , Sun Xiao-chun , Shen Cheng-de , Liu Ke-xin , Sun Weidong
Published: January 2014

A large and sudden increase in radiocarbon (14C) around AD 773 are documented in coral skeletons from the South China Sea. The 14C increased by ~ 15‰ during winter and remain elevated for more than 4 months, then increased and dropped down within two months, forming a spike of 45‰ high in late spring, followed by two smaller spikes. The 14C anomalies coincide with an historic comet collision with the Earth's atmosphere on 17 January AD 773. Comas are known to have percent-levels of nitrogen by weight and are exposed to cosmic radiation in space. Hence they may be expected to contain highly elevated 14C/12C ratios, as compared to the Earth's atmosphere. The significant input of 14C by comets may have contributed to the fluctuation of 14C in the atmosphere throughout the Earth's history, which should be considered carefully to better constrain the cosmic ray fluctuation.
Polysaccharide electrospun fibers with sulfated poly(fucose) promote endothelial cell migration and VEGF-mediated angiogenesis
Authors: Rujitanaroj Pim-On , Aid-Launais Rachida , Chew Sing Yian , Le Visage Catherine
Published: January 2014

This study demonstrates the potential of fucoidan-incorporated pullulan–dextran fibers as tunable reservoirs for VEGF delivery to promote angiogenesis.
Peptoids for biomaterials science
Authors: Lau King Hang Aaron
Published: January 2014

Reports of peptoid structures and interfaces highlighting their potential as synthetically convenient, multifunctional, modular and precisely tunable biomaterials are reviewed.
Poly(3-alkylthiophene)s show unexpected second-order nonlinear optical response
Authors: Deckers S. , Vandendriessche S. , Cornelis D. , Monnaie F. , Koeckelberghs G. , Asselberghs I. , Verbiest T. , van der Veen M. A.
Published: January 2014

Poly(3-hexylthiophene)s show upon oligomerization an unexpectedly significant second-order nonlinear optical response.
The cobalt corrole catalyzed hydrogen evolution reaction: surprising electronic effects and characterization of key reaction intermediates
Authors: Mahammed Atif , Mondal Biswajit , Rana Atanu , Dey Abhishek , Gross Zeev
Published: January 2014

The proton-activating intermediate in the cobalt corrole catalyzed hydrogen evolution reaction was characterized and a surprising effect of macrocycle halogenation was uncovered.
Organometallic carbonyl clusters: a new class of contrast agents for photoacoustic cerebral vascular imaging
Authors: Kong Kien Voon , Liao Lun-De , Lam Zhiyong , Thakor Nitish V. , Leong Weng Kee , Olivo Malini
Published: January 2014

The strong photoacoustic signal of a water soluble osmium carbonyl cluster allowed it to be employed as a contrast agent to image the cerebral vasculature of a rat. The high stability and low toxicity of such a compound make it an excellent candidate in such biomedical applications.
Self-sorting of dynamic metallosupramolecular libraries (DMLs) via metal-driven selection
Authors: Kocsis Istvan , Dumitrescu Dan , Legrand Yves-Marie , van der Lee Arie , Grosu Ion , Barboiu Mihail
Published: January 2014

“Metal-driven” selection between finite mononuclear and polymeric metallosupramolecular species can be quantitatively achieved.
Cooperation between the surface hydroxyl groups of Ru–SiO2@mSiO2and water for good catalytic performance for hydrogenation of quinoline
Authors: Zhang Lei , Wang Xiaoyan , Xue Ying , Zeng Xiaojun , Chen Hua , Li Ruixiang , Wang Shanling
Published: January 2014

A new core–shell catalyst showing excellent performance and stability was used in the hydrogenation of quinoline in water.
Extracellular matrix density promotes EMT by weakening cell–cell adhesions
Authors: Kumar Sandeep , Das Alakesh , Sen Shamik
Published: January 2014

This paper probes the influence of extracellular matrix density on cell–cell adhesion and its relevance to EMT.
Preparation and characterization of nano-1,1-diamino-2,2-dinitroethene (FOX-7) explosive
Authors: Gao Bing , Wu Peng , Huang Bing , Wang Jun , Qiao Zhiqiang , Yang Guangcheng , Nie Fude
Published: January 2014

Two kinds of nano FOX-7 particle sizes, elementary particles of about 30–90 nm and 100–200 nm, were prepared by the USEA method.
A mechanical nanogate based on a carbon nanotube for reversible control of ion conduction
Authors: He Zhongjin , Corry Ben , Lu Xiaohua , Zhou Jian
Published: January 2014

Ion conduction in nanofluidic devices can be reversibly controlled by regulating the ion hydration state with an AFM-tip deformable nanogate.
Noninvasive label-free nanoplasmonic optical imaging for real-time monitoring of in vitro amyloid fibrogenesis
Authors: Lee Sung Sik , Lee Luke P.
Published: January 2014

We utilize nanoplasmonic optical imaging as the noninvasive and label-free method in order to monitorin vitroamyloid fibrogenesis in real-time, which is considered as the primary pathological mechanism of Alzheimer's disease.
Solution-processed Cu2ZnSnS4 absorbers prepared by appropriate inclusion and removal of thiourea for thin film solar cells
Authors: Park Si-Nae , Sung Shi-Joon , Son Dae-Ho , Kim Dae-Hwan , Gansukh Mungunshagai , Cheong Hyeonsik , Kang Jin-Kyu
Published: January 2014

Effective adding/removal of organic chemicals to/from CZTS precursor thin films for preparing uniform CZTS thin films with optimal photovoltaic properties was achieved by pre-annealing of CZTS precursors containing thiourea.
Tailoring porosities and electrochemical properties of composites composed of microfibrillated cellulose and polypyrrole
Authors: Carlsson Daniel O. , Mihranyan Albert , Strømme Maria , Nyholm Leif
Published: January 2014

The porosities of composites of polypyrrole and nanocellulose can be tailored from 30 to 98% with ∼10% increments enabling the electrochemical behavior of the materials to be readily controlled.
Identification of TP53-induced glycolysis and apoptosis regulator (TIGAR) as the phosphoglycolate-independent 2,3-bisphosphoglycerate phosphatase
Authors: Gerin Isabelle , Noël Gaëtane , Bolsée Jennifer , Haumont Olivier , Van Schaftingen Emile , Bommer Guido T.
Published: January 2014

The p53-induced protein TIGAR [TP53 (tumour protein 53)-induced glycolysis and apoptosis regulator] is considered to be a F26BPase (fructose-2,6-bisphosphatase) with an important role in cancer cell metabolism. The reported catalytic efficiency of TIGAR as an F26BPase is several orders of magnitude lower than that of the F26BPase component of liver or muscle PFK2 (phosphofructokinase 2), suggesting that F26BP (fructose 2,6-bisphosphate) might not be the physiological substrate of TIGAR. We therefore set out to re-evaluate the biochemical function of TIGAR. Phosphatase activity of recombinant human TIGAR protein was tested on a series of physiological phosphate esters. The best substrate was 23BPG (2,3-bisphosphoglycerate), followed by 2PG (2-phosphoglycerate), 2-phosphoglycolate and PEP (phosphoenolpyruvate). In contrast the catalytic efficiency for F26BP was approximately 400-fold lower than that for 23BPG. Using genetic and shRNA-based cell culture models, we show that loss of TIGAR consistently leads to an up to 5-fold increase in the levels of 23BPG. Increases in F26BP levels were also observed, albeit in a more limited and cell-type dependent manner. The results of the present study challenge the concept that TIGAR acts primarily on F26BP. This has significant implications for our understanding of the metabolic changes downstream of p53 as well as for cancer cell metabolism in general. It also suggests that 23BPG might play an unrecognized function in metabolic control.
Electric field induced sheeting and breakup of dielectric liquid jets
Authors: Khoshnevis Ahmad , Tsai Scott S. H. , Esmaeilzadeh Esmaeil
Published: January 2014

We report experimental observations of the controlled deformation of a dielectric liquid jet subjected to a local high-voltage electrostatic field in the direction normal to the jet. The jet deforms to the shape of an elliptic cylinder upon application of a normal electrostatic field. As the applied electric field strength is increased, the elliptic cylindrical jet deforms permanently into a flat sheet, and eventually breaks-up into droplets. We interpret this observation—the stretch of the jet is in the normal direction to the applied electric field—qualitatively using the Taylor-Melcher leaky dielectric theory, and develop a simple scaling model that predicts the critical electric field strength for the jet-to-sheet transition. Our model shows a good agreement with experimental results, and has a form that is consistent with the classical drop deformation criterion in the Taylor-Melcher theory. Finally, we statistically analyze the resultant droplets from sheet breakup, and find that increasing the applied electric field strength improves droplet uniformity and reduces droplet size.
Recent development of RIKEN 28 GHz superconducting electron cyclotron resonance ion source
Authors: Higurashi Y. , Ohnishi J. , Ozeki K. , Kidera M. , Nakagawa T.
Published: January 2014

Over the past two years, we have tried to improve the performance of the RIKEN superconducting electron cyclotron resonance ion source using several methods. For the production of U vapor, we chose the sputtering method because it is possible to install a large amount of material inside the plasma chamber and thus achieve long-term operation without a break, although it is assumed that the beam intensity is weaker than in the oven technique. We also used an aluminum chamber instead of a stainless steel one. Using these methods, we successfully produced ∼180 eμA of U35+ and ∼230 eμA of U33+ at the injected radio frequency (RF) power of ∼4 kW (28 GHz). Very recently, to further increase the beam intensity of U35+, we have started to develop a high temperature oven and have successfully produced a highly charged U ion beam. In this contribution, we report on the beam intensity of highly charged U ions as a function of various parameters (RF power and sputtering voltage) and discuss the effects of these parameters on the beam stability in detail.
Refinement of the experimental dynamic structure factor for liquid para-hydrogen and ortho-deuterium using semi-classical quantum simulation
Authors: Smith Kyle K. G. , Poulsen Jens Aage , Cunsolo A. , Rossky Peter J.
Published: January 2014

The dynamic structure factor of liquid para-hydrogen and ortho-deuterium in corresponding thermodynamic states (T = 20.0 K, n = 21.24 nm−3) and (T = 23.0 K, n = 24.61 nm−3), respectively, has been computed by both the Feynman-Kleinert linearized path-integral (FK-LPI) and Ring-Polymer Molecular Dynamics (RPMD) methods and compared with Inelastic X Ray Scattering spectra. The combined use of computational and experimental methods enabled us to reduce experimental uncertainties in the determination of the true sample spectrum. Furthermore, the refined experimental spectrum of para-hydrogen and ortho-deuterium is consistently reproduced by both FK-LPI and RPMD results at momentum transfers lower than 12.8 nm−1. At larger momentum transfers the FK-LPI results agree with experiment much better for ortho-deuterium than for para-hydrogen. More specifically we found that for k ∼ 20.0 nm−1 para-hydrogen provides a test case for improved approximations to quantum dynamics.
Ion sources for ion implantation technology (invited)
Authors: Sakai Shigeki , Hamamoto Nariaki , Inouchi Yutaka , Umisedo Sei , Miyamoto Naoki
Published: January 2014

Ion sources for ion implantation are introduced. The technique is applied not only to large scale integration (LSI) devices but also to flat panel display. For LSI fabrication, ion source scheduled maintenance cycle is most important. For CMOS image sensor devices, metal contamination at implanted wafer is most important. On the other hand, to fabricate miniaturized devices, cluster ion implantation has been proposed to make shallow PN junction. While for power devices such as silicon carbide, aluminum ion is required. For doping processes of LCD fabrication, a large ion source is required. The extraction area is about 150 cm × 10 cm, and the beam uniformity is important as well as the total target beam current.
Characteristics of plasma grid bias in large-scaled negative ion source
Authors: Kisaki M. , Tsumori K. , Ikeda K. , Nakano H. , Osakabe M. , Nagaoka K. , Takeiri Y. , Kaneko O.
Published: January 2014

The electron density was measured at various bias voltages to understand how the plasma grid bias affects the electron near the plasma grid in large-scaled negative ion sources. It was found that the response of the electron to the bias voltage changes depending on negative ion production processes. The electron density remarkably decreases with increasing the bias voltage in the pure-volume plasma. On the other hand, the electron density depends on the bias voltage weakly in the Cs-seeded plasma. In addition, it was observed that the response of the co-extracted electron current to the bias voltage has similar trend to that of the electron density.
Thermal decomposition of energetic materials viewed via dynamic x-ray radiography
Authors: Smilowitz L. , Henson B. F. , Romero J. J. , Oschwald D.
Published: January 2014

We describe the evolution of solid density, leading up to ignition in the slow thermal decomposition of the solid organic secondary explosive octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine. This work describes an x-ray radiographic diagnostic, allowing the study of solid density in a fully encased explosive heated to thermal explosion. The result of this study is the ability to observe and manipulate the ignition volume in a thermal explosion.
Elemental diffusion during the droplet epitaxy growth of In(Ga)As/GaAs(001) quantum dots by metal-organic chemical vapor deposition
Authors: Chen Z. B. , Lei W. , Chen B. , Wang Y. B. , Liao X. Z. , Tan H. H. , Zou J. , Ringer S. P. , Jagadish C.
Published: January 2014

Droplet epitaxy is an important method to produce epitaxial semiconductor quantum dots (QDs). Droplet epitaxy of III-V QDs comprises group III elemental droplet deposition and the droplet crystallization through the introduction of group V elements. Here, we report that, in the droplet epitaxy of InAs/GaAs(001) QDs using metal-organic chemical vapor deposition, significant elemental diffusion from the substrate to In droplets occurs, resulting in the formation of In(Ga)As crystals, before As flux is provided. The supply of As flux suppresses the further elemental diffusion from the substrate and promotes surface migration, leading to large island formation with a low island density.
Giant magnetoelectric effect at low frequencies in polymer-based thin film composites
Authors: Kulkarni A. , Meurisch K. , Teliban I. , Jahns R. , Strunskus T. , Piorra A. , Knöchel R. , Faupel F.
Published: January 2014

A polymer-based magnetoelectric 2-2 composite was fabricated in a thin film approach by direct spin coating of polyvinylidenefluoride-co-trifluoroethylene onto a Metglas substrate without the usage of an adhesive for the mechanical coupling between the piezoelectric and magnetostrictive materials. For a prototype single-sided clamped cantilever, a magnetoelectric coefficient as high as 850 V cm−1 Oe−1 is observed at its fundamental bending mode resonance frequency at 27.8 Hz and a detection limit of 10 pTHz−1/2 at its second bending mode resonance frequency at 169.5 Hz.
Analytic cubic and quartic force fields using density-functional theory
Authors: Ringholm Magnus , Jonsson Dan , Bast Radovan , Gao Bin , Thorvaldsen Andreas J. , Ekström Ulf , Helgaker Trygve , Ruud Kenneth
Published: January 2014

We present the first analytic implementation of cubic and quartic force constants at the level of Kohn–Sham density-functional theory. The implementation is based on an open-ended formalism for the evaluation of energy derivatives in an atomic-orbital basis. The implementation relies on the availability of open-ended codes for evaluation of one- and two-electron integrals differentiated with respect to nuclear displacements as well as automatic differentiation of the exchange–correlation kernels. We use generalized second-order vibrational perturbation theory to calculate the fundamental frequencies of methane, ethane, benzene, and aniline, comparing B3LYP, BLYP, and Hartree–Fock results. The Hartree–Fock anharmonic corrections agree well with the B3LYP corrections when calculated at the B3LYP geometry and from B3LYP normal coordinates, suggesting that the inclusion of electron correlation is not essential for the reliable calculation of cubic and quartic force constants.
Chaotic advection at large Péclet number: Electromagnetically driven experiments, numerical simulations, and theoretical predictions
Authors: Figueroa Aldo , Meunier Patrice , Cuevas Sergio , Villermaux Emmanuel , Ramos Eduardo
Published: January 2014

We present a combination of experiment, theory, and modelling on laminar mixing at large Péclet number. The flow is produced by oscillating electromagnetic forces in a thin electrolytic fluid layer, leading to oscillating dipoles, quadrupoles, octopoles, and disordered flows. The numerical simulations are based on the Diffusive Strip Method (DSM) which was recently introduced (P. Meunier and E. Villermaux, “The diffusive strip method for scalar mixing in two-dimensions,” J. Fluid Mech. 662, 134–172 (2010)) to solve the advection-diffusion problem by combining Lagrangian techniques and theoretical modelling of the diffusion. Numerical simulations obtained with the DSM are in reasonable agreement with quantitative dye visualization experiments of the scalar fields. A theoretical model based on log-normal Probability Density Functions (PDFs) of stretching factors, characteristic of homogeneous turbulence in the Batchelor regime, allows to predict the PDFs of scalar in agreement with numerical and experimental results. This model also indicates that the PDFs of scalar are asymptotically close to log-normal at late stages, except for the large concentration levels which correspond to low stretching factors.
Dynamic correlations in Brownian many-body systems
Authors: Brader Joseph M. , Schmidt Matthias
Published: January 2014

For classical Brownian systems driven out of equilibrium, we derive inhomogeneous two-time correlation functions from functional differentiation of the one-body density and current with respect to external fields. In order to allow for appropriate freedom upon building the derivatives, we formally supplement the Smoluchowski dynamics by a source term, which vanishes at the physical solution. These techniques are applied to obtain a complete set of dynamic Ornstein-Zernike equations, which serve for the development of approximation schemes. The rules of functional calculus lead naturally to non-Markovian equations of motion for the two-time correlators. Memory functions are identified as functional derivatives of a unique space- and time-nonlocal dissipation power functional.
Co-condensation of nonane and D2O in a supersonic nozzle
Authors: Pathak Harshad , Wölk Judith , Strey Reinhard , Wyslouzil Barbara E.
Published: January 2014

We study the unary and binary nucleation and growth of nonane–D2O nanodroplets in a supersonic nozzle. Fourier Transform Infrared spectroscopy measurements provide the overall composition of the droplets and Small Angle X-ray Scattering experiments measure the size and number density of the droplets. The unary nucleation rates Jmax of nonane, 9.4 × 1015 < Jmax /cm−3 s−1 < 2.0 × 1016, and those of D2O, 2.4 × 1017 < Jmax /cm−3 s−1 < 4.1 × 1017, measured here agree well with previous results. In most of the binary condensation experiments new particle formation is dominated by D2O, but the observed nucleation rates are decreased by up to a factor of 6 relative to the rates measured for pure D2O, an effect that can be partly explained by non-isothermal nucleation theory. The subsequent condensation of D2O is inhibited both by the increased temperature of the binary droplets relative to the pure D2O droplets, and because the binary droplet surface is expected to be comprised largely of nonane. For the one case where nonane appears to initiate condensation, we find that the nucleation rate is about 50% higher than that observed for pure nonane at comparable pv0, consistent with significant particle formation driven by D2O.
Precision control of multiple quantum cascade lasers for calibration systems
Authors: Taubman Matthew S. , Myers Tanya L. , Pratt Richard M. , Stahl Robert D. , Cannon Bret D.
Published: January 2014

We present a precision, 1-A, digitally interfaced current controller for quantum cascade lasers, with demonstrated temperature coefficients for continuous and 40-kHz full-depth square-wave modulated operation, of 1–2 ppm/ °C and 15 ppm/ °C, respectively. High precision digital to analog converters (DACs) together with an ultra-precision voltage reference produce highly stable, precision voltages, which are selected by a multiplexer (MUX) chip to set output currents via a linear current regulator. The controller is operated in conjunction with a power multiplexing unit, allowing one of three lasers to be driven by the controller, while ensuring protection of controller and all lasers during operation, standby, and switching. Simple ASCII commands sent over a USB connection to a microprocessor located in the current controller operate both the controller (via the DACs and MUX chip) and the power multiplexer.
Structures, electrical properties, and leakage current behaviors of un-doped and Mn-doped lead-free ferroelectric K0.5Na0.5NbO3 films
Authors: Wang Lingyan , Ren Wei , Shi Peng , Wu Xiaoqing
Published: January 2014

Lead-free ferroelectric un-doped and doped K0.5Na0.5NbO3 (KNN) films with different amounts of manganese (Mn) were prepared by a chemical solution deposition method. The thicknesses of all films are about 1.6 μm. Their phase, microstructure, leakage current behavior, and electrical properties were investigated. With increasing the amounts of Mn, the crystallinity became worse. Fortunately, the electrical properties were improved due to the decreased leakage current density after Mn-doping. The study on leakage behaviors shows that the dominant conduction mechanism at low electric field in the un-doped KNN film is ohmic mode and that at high electric field is space-charge-limited and Pool-Frenkel emission. After Mn doping, the dominant conduction mechanism at high electric field of KNN films changed single space-charge-limited. However, the introduction of higher amount of Mn into the KNN film would lead to a changed conduction mechanism from space-charge-limited to ohmic mode. Consequently, there exists an optimal amount of Mn doping of 2.0 mol. %. The 2.0 mol. % Mn doped KNN film shows the lowest leakage current density and the best electrical properties. With the secondary ion mass spectroscopies and x-ray photoelectron spectroscopy analyses, the homogeneous distribution in the KNN films and entrance of Mn element in the lattice of KNN perovskite structure were also confirmed.
Atomistic study of porosity impact on phonon driven thermal conductivity: Application to uranium dioxide
Authors: Colbert Mehdi , Ribeiro Fabienne , Tréglia Guy
Published: January 2014

We present here an analytical method, based on the kinetic theory, to determine the impact of defects such as cavities on the thermal conductivity of a solid. This approach, which explicitly takes into account the effects of internal pore surfaces, will be referred to as the Phonon Interface THermal cONductivity (PITHON) model. Once exposed in the general case, this method is then illustrated in the case of uranium dioxide. It appears that taking properly into account these interface effects significantly modifies the temperature and porosity dependence of thermal conductivity with respect to that issued from either micromechanical models or more recent approaches, in particular, for small cavity sizes. More precisely, it is found that if the mean free path appears to have a major effect in this system in the temperature and porosity distribution range of interest, the variation of the specific heat at the surface of the cavity is predicted to be essential at very low temperature and small sizes for sufficiently large porosity.
Non-perturbative calculation of molecular magnetic properties within current-density functional theory
Authors: Tellgren E. I. , Teale A. M. , Furness J. W. , Lange K. K. , Ekström U. , Helgaker T.
Published: January 2014

We present a novel implementation of Kohn–Sham density-functional theory utilizing London atomic orbitals as basis functions. External magnetic fields are treated non-perturbatively, which enable the study of both magnetic response properties and the effects of strong fields, using either standard density functionals or current-density functionals—the implementation is the first fully self-consistent implementation of the latter for molecules. Pilot applications are presented for the finite-field calculation of molecular magnetizabilities, hypermagnetizabilities, and nuclear magnetic resonance shielding constants, focusing on the impact of current-density functionals on the accuracy of the results. Existing current-density functionals based on the gauge-invariant vorticity are tested and found to be sensitive to numerical details of their implementation. Furthermore, when appropriately regularized, the resulting magnetic properties show no improvement over standard density-functional results. An advantage of the present implementation is the ability to apply density-functional theory to molecules in very strong magnetic fields, where the perturbative approach breaks down. Comparison with high accuracy full-configuration-interaction results show that the inadequacies of current-density approximations are exacerbated with increasing magnetic field strength. Standard density-functionals remain well behaved but fail to deliver high accuracy. The need for improved current-dependent density-functionals, and how they may be tested using the presented implementation, is discussed in light of our findings.
Definition and determination of the triplet-triplet energy transfer reaction coordinate
Authors: Zapata Felipe , Marazzi Marco , Castaño Obis , Acuña A. Ulises , Frutos Luis Manuel
Published: January 2014

A definition of the triplet-triplet energy transfer reaction coordinate within the very weak electronic coupling limit is proposed, and a novel theoretical formalism is developed for its quantitative determination in terms of internal coordinates The present formalism permits (i) the separation of donor and acceptor contributions to the reaction coordinate, (ii) the identification of the intrinsic role of donor and acceptor in the triplet energy transfer process, and (iii) the quantification of the effect of every internal coordinate on the transfer process. This formalism is general and can be applied to classical as well as to nonvertical triplet energy transfer processes. The utility of the novel formalism is demonstrated here by its application to the paradigm of nonvertical triplet-triplet energy transfer involving cis-stilbene as acceptor molecule. In this way the effect of each internal molecular coordinate in promoting the transfer rate, from triplet donors in the low and high-energy limit, could be analyzed in detail.
Shape resonance spectra of uracil, 5-fluorouracil, and 5-chlorouracil
Authors: Kossoski F. , Bettega M. H. F. , Varella M. T. do N.
Published: January 2014

We report on the shape resonance spectra of uracil, 5-fluorouracil, and 5-chlorouracil, as obtained from fixed-nuclei elastic scattering calculations performed with the Schwinger multichannel method with pseudopotentials. Our results are in good agreement with the available electron transmission spectroscopy data, and support the existence of three π* resonances in uracil and 5-fluorouracil. As expected, the anion states are more stable in the substituted molecules than in uracil. Since the stabilization is stronger in 5-chlorouracil, the lowest π* resonance in this system becomes a bound anion state. The present results also support the existence of a low-lying \documentclass[12pt]{minimal}\begin{document}$\sigma _{\rm CCl}^*$\end{document}σ CCl * shape resonance in 5-chlorouracil. Exploratory calculations performed at selected C–Cl bond lengths suggest that the \documentclass[12pt]{minimal}\begin{document}$\sigma _{\rm CCl}^*$\end{document}σ CCl * resonance could couple to the two lowest π* states, giving rise to a very rich dissociation dynamics. These facts would be compatible with the complex branching of the dissociative electron attachment cross sections, even though we cannot discuss any details of the vibration dynamics based only on the present fixed-nuclei results.
Electrical conductivity studies in (Ag3AsS3)x(As2S3)1−x superionic glasses and composites
Authors: Studenyak I. P. , Neimet Yu. Yu. , Kranjčec M. , Solomon A. M. , Orliukas A. F. , Kežionis A. , Kazakevičius E. , Šalkus T.
Published: January 2014

Compositional, frequency, and temperature studies of impedance and electrical conductivity in (Ag3AsS3)x(As2S3)1−x superionic glasses and composites were performed. Frequency range from 10 Hz to 3 × 109 Hz and temperature interval 300–400 K were used for the measurements. Compositional dependences of electrical conductivity and activation energy are analyzed; the most substantial changes are observed with the transition from (Ag3AsS3)0.4(As2S3)0.6 glass to (Ag3AsS3)0.5(As2S3)0.5 composite. With increase of Ag3AsS3 content, the investigated materials are found to have crystalline inclusions and show the two-phase composite nature. Addition of Ag3AsS3 leads to the increase of electrical conductivity whereas the activation energy decreases.
Effects of sodium ions on trapping and transport of electrons at the SiO2/4H-SiC interface
Authors: Basile A. F. , Ahyi A. C. , Feldman L. C. , Williams J. R. , Mooney P. M.
Published: January 2014

Capacitance-voltage (C-V) and Deep-Level-Transient Spectroscopy (DLTS) measurements were performed on Metal-Oxide-Semiconductor (MOS) capacitors fabricated on 4H-SiC with the SiO2 layer grown by Sodium-Enhanced Oxidation. This technique has yielded 4H-SiC MOS transistors with record channel mobility, although with poor bias stability. The effects of the mobile positive charge on the C-V characteristics and DLTS spectra were investigated by applying a sequence of positive and negative bias-temperature stresses, which drifted the sodium ions toward and away from the SiO2/4H-SiC interface, respectively. Analytical modeling of the C-V curves shows that the drift of sodium ions in the SiO2 layer during the voltage sweep can explain the temperature dependence of the C-V curves. The effects of lateral fluctuations of the surface potential (due to a non-uniform charge distribution) on the inversion layer mobility of MOS transistors are discussed within a two-dimensional percolation model.
Mapping continuous potentials to discrete forms
Authors: Thomson Chris , Lue Leo , Bannerman Marcus N.
Published: January 2014

The optimal conversion of a continuous inter-particle potential to a discrete equivalent is considered here. Existing and novel algorithms are evaluated to determine the best technique for creating accurate discrete forms using the minimum number of discontinuities. This allows the event-driven molecular dynamics technique to be efficiently applied to the wide range of continuous force models available in the literature, and facilitates a direct comparison of event-driven and time-driven molecular dynamics. The performance of the proposed conversion techniques are evaluated through application to the Lennard-Jones model. A surprising linear dependence of the computational cost on the number of discontinuities is found, allowing accuracy to be traded for speed in a controlled manner. Excellent agreement is found for static and dynamic properties using a relatively low number of discontinuities. For the Lennard-Jones potential, the optimized discrete form outperforms the original continuous form at gas densities but is significantly slower at higher densities.
Vibrational excitations in chloromethyl radical formed by the photodissociation of chlorobromomethane
Authors: Li Qianguang , Zhu Rongshu , Lu Jinjun , Zhang Xiu , Tang Bifeng
Published: January 2014

Using velocity map ion imaging, the photodissociation of chlorobromomethane (CH2BrCl) at 233–234 nm has been studied. The total translational energy distributions and the anisotropy parameters have been determined from the ion images of the photofragments Br (2P1/2) (denoted as Br*) and Br (2P3/2) (denoted as Br) for the dominant CH2BrCl + hv → CH2Cl + Br* and CH2BrCl + hv → CH2Cl + Br channels. Using an impulsive model invoking angular momentum conservation, the vibrational energy distributions of the chloromethyl radicals have been derived from the total translational energy distributions for the two channels. The study suggests that there are a number of vibrational modes of the chloromethyl radical to be excited in both of the two photodissociation channels. In the Br* channel, the CH2 s-stretch mode v1 has the most probability of excitation. While in the Br channel, the CH2 scissors mode ν2 is attributed to the highest peak of the vibrational energy curve of the chloromethyl radical. The results further imply that, following absorption of one UV photon of 234 nm, other vibrational modes besides v5 (C–Br stretch mode) are also excited in the parent molecule.
Crystal structure of Si-doped HfO2
Authors: Zhao Lili , Nelson Matthew , Aldridge Henry , Iamsasri Thanakorn , Fancher Chris M. , Forrester Jennifer S. , Nishida Toshikazu , Moghaddam Saeed , Jones Jacob L.
Published: January 2014

Si-doped HfO2 was prepared by solid state synthesis of the starting oxides. Using Rietveld refinement of high resolution X-ray diffraction patterns, a substitutional limit of Si in HfO2 was determined as less than 9 at. %. A second phase was identified as Cristobalite (SiO2) rather than HfSiO4, the latter of which would be expected from existing SiO2-HfO2 phase diagrams. Crystallographic refinement with increased Si-dopant concentration in monoclinic HfO2 shows that c/b increases, while β decreases. The spontaneous strain, which characterizes the ferroelastic distortion of the unit cell, was calculated and shown to decrease with increasing Si substitution.
Double injection, resonant-tunneling recombination, and current-voltage characteristics in double-graphene-layer structures
Authors: Ryzhii M. , Ryzhii V. , Otsuji T. , Maltsev P. P. , Leiman V. G. , Ryabova N. , Mitin V.
Published: January 2014

We evaluate the effect of the recombination associated with interlayer transitions in ungated and gated double-graphene-layer (GL) structures on the injection of electrons and holes. Using the proposed model, we derive analytical expressions for the spatial distributions of the electron and hole Fermi energies and the energy gap between the Dirac points in GLs as well as their dependences on the bias and gate voltages. The current-voltage characteristics are calculated as well. The model is based on hydrodynamic equations for the electron and hole transports in GLs under the self-consistent electric field. It is shown that in undoped double-GL structures with weak scattering of electrons and holes on disorder, the Fermi energies and the energy gap are virtually constant across the main portions of GLs, although their values strongly depend on the voltages and recombination parameters. In contrast, the electron and hole scattering on disorder lead to substantial nonuniformities. The resonant inter-GL tunneling enables N-shaped current-voltage characteristics provided that GLs are sufficiently short. The width of the current maxima is much larger than the broadening of the tunneling resonance. In the double-GL structures with relatively long GLs, the N-shaped characteristics transform into the Z-shaped characteristics. The obtained results are in line with the experimental observations [Britnell et al., Nat. Commun. 4, 1794–1799 (2013)] and might be useful for design and optimization of different devices based on double-GL structures, including field-effect transistors and terahertz lasers.
Analysis of interfacial instability and multimode bubble formation in saturated boiling using coupled level set and volume-of-fluid approach
Authors: Hens Abhiram , Biswas Gautam , De Sudipta
Published: January 2014

The dynamics of vapor-liquid interface are important because interfacial instability determines bubble growth, detachment frequency, waiting time, shape of bubbles, and the interrelationship between bubble formation sites. In this study, a detailed numerical simulation has been performed to understand the transition in bubble release pattern and multimode bubble formation in saturated pool boiling. The interfaces drop down alternatively at the nodes and antinodes of the wavelengths dictated by Rayleigh-Taylor instability and Taylor-Helmholtz instability. Due to higher degrees of superheat, vapor jets emanate from nodes and antinodes. An attempt has been made to predict the maximum and minimum heat fluxes during saturated pool boiling.
Thermal performance prediction and energy conservation potential of earth air tunnel heat exchanger for thermal comfort in building
Authors: Kaushik S. C. , Garg Tarun , Lal Shiv
Published: January 2014

In this communication, thermal performance of building integrated “Earth Air Tunnel Heat Exchanger” (EATHE) has been studied for a composite climate of Delhi. Mathematical model and building thermal simulation software (Energy Plus) are used for prediction of indoor air temperatures. The predicted results are validated through experimental results. Energy conservation potential both for heating and cooling of EATHE has been evaluated for winter and summer months in a specific year. Quantitative assessment of CO2 mitigation has also been computed. It is observed that Coefficient of performance (COP) of EATHE is found between 6.3–13 during summer and 6.8–9.5 during winter season. The maximum drop in air temperature across the earth air tunnel is found to be 8.7 °C with air velocity of 2.69 m/s during peak summer and during winter season the room air temperature is raised by 5–7 °C. On the other hand, the system is capable of maintaining room temperature in the range of 27–30 °C during peak summer when outdoor temperature are in the range of 33–41 °C. EATHE integration with building can significantly reduce the electrical power consumption by 96.63 MWh annually, needed for space heating and cooling load. It is discovered from the study that this EATHE has potential of reducing global warming 8 by substantially mitigating CO2 to the tune of 95 tonnes annually.
Atomic-scale observation of parallel development of super elasticity and reversible plasticity in GaAs nanowires
Authors: Bao Peite , Wang Yanbo , Cui Xiangyuan , Gao Qiang , Yen Hung-Wei , Liu Hongwei , Kong Yeoh Wai , Liao Xiaozhou , Du Sichao , Hoe Tan H. , Jagadish Chennupati , Zou Jin , Ringer Simon P. , Zheng Rongkun
Published: January 2014

We report the atomic-scale observation of parallel development of super elasticity and reversible dislocation-based plasticity from an early stage of bending deformation until fracture in GaAs nanowires. While this phenomenon is in sharp contrast to the textbook knowledge, it is expected to occur widely in nanostructures. This work indicates that the super recoverable deformation in nanomaterials is not simple elastic or reversible plastic deformation in nature, but the coupling of both.
Hard X-ray nanoimaging method using local diffraction from metal wire
Authors: Takano Hidekazu , Konishi Shigeki , Shimomura Sho , Azuma Hiroaki , Tsusaka Yoshiyuki , Kagoshima Yasushi
Published: January 2014

A simple hard X-ray imaging method achieving a high spatial resolution is proposed. Images are obtained by scanning a metal wire through the wave field to be measured and rotating the sample to collect data for back projection calculations; the local diffraction occurring at the edges of the metal wire operates as a narrow line probe. In-line holograms of a test sample were obtained with a spatial resolution of better than 100 nm. The potential high spatial resolution of this method is shown by calculations using diffraction theory.
Atomically flat La-silicate/Si interface using tungsten carbide gate electrode with nano-sized grain
Authors: Tuokedaerhan K. , Kakushima K. , Kataoka Y. , Nishiyama A. , Sugii N. , Wakabayashi H. , Tsutsui K. , Natori K. , Iwai H.
Published: January 2014

Interface properties of La-silicate gate dielectrics on Si substrates with W or nano-sized grain W2C gate electrodes have been investigated. A low interface state density of 2.5 × 1011 cm−2/eV has been achieved with W2C gate electrodes, which is one third of those with W gate electrode. An interface roughness of 0.33 nm with spatial frequency comparable to the grain size of W gate electrode has been observed. Besides, an atomically flat interface of 0.12 nm has been obtained with W2C gate electrode. The origin of flat interface may be attributed to the elimination of inhomogeneous stress by grains in metal electrode.
Synthesis and electrical conductivity of multilayer silicene
Authors: Vogt P. , Capiod P. , Berthe M. , Resta A. , De Padova P. , Bruhn T. , Le Lay G. , Grandidier B.
Published: January 2014

The epitaxial growth and the electrical resistance of multilayer silicene on the Ag(111) surface has been investigated. We show that the atomic structure of the first silicene layer differs from the next layers and that the adsorption of Si induces the formation of extended silicene terraces surrounded by step bunching. Thanks to the controlled contact formation between the tips of a multiple probe scanning tunneling microscope and these extended terraces, a low sheet resistance, albeit much higher than the electrical resistance of the underlying silver substrate, has been measured, advocating for the electrical viability of multilayer silicene.
Elementary model of severe plastic deformation by KoBo process
Authors: Gusak A. , Danielewski M. , Korbel A. , Bochniak M. , Storozhuk N.
Published: January 2014

Self-consistent model of generation, interaction, and annihilation of point defects in the gradient of oscillating stresses is presented. This model describes the recently suggested method of severe plastic deformation by combination of pressure and oscillating rotations of the die along the billet axis (KoBo process). Model provides the existence of distinct zone of reduced viscosity with sharply increased concentration of point defects. This zone provides the high extrusion velocity. Presented model confirms that the Severe Plastic Deformation (SPD) in KoBo may be treated as non-equilibrium phase transition of abrupt drop of viscosity in rather well defined spatial zone. In this very zone, an intensive lateral rotational movement proceeds together with generation of point defects which in self-organized manner make rotation possible by the decrease of viscosity. The special properties of material under KoBo version of SPD can be described without using the concepts of nonequilibrium grain boundaries, ballistic jumps and amorphization. The model can be extended to include different SPD processes.
Bulk and surface half-metallicity: The case of D03-type Mn3Ge
Authors: Liu Hao , Gao G. Y. , Hu Lei , Ni Yun , Zu Fengxia , Zhu Sicong , Wang Shuling , Yao K. L.
Published: January 2014

Motivated by the experimental realization of D022-type Mn3Ge (001) films [Kurt et al. Appl. Phys. Lett. 101, 132410 (2012)] and the structural stability of D03-type Heusler alloy Mn3Ge [Zhang et al. J. Phys.: Condens. Matter 25, 206006 (2013)], we use the first-principles calculations based on the full potential linearized augmented plane-wave method to investigate the electronic and magnetic properties of D03-type Heusler alloy Mn3Ge and its (001) surface. We show that bulk D03-Mn3Ge is a half-metallic ferromagnet with the minority-spin energy gap of 0.52 eV and the magnetic moment of 1.00 μB per formula unit. The bulk half-metallicity is preserved at the pure Mn-terminated (001) surface due to the large exchange split, but the MnGe-terminated (001) surface destroys the bulk half-metallicity. We also reveal that the surface stabilities are comparable between the D03-Mn3Ge (001) and the experimental D022-Mn3Ge (001), which indicates the feasibility to grow the Mn3Ge (001) films with D03 phase other than D022 one. The surface half-metallicity and stability make D03-Mn3Ge a promising candidate for spintronic applications.