bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly efficient deep-blue OLED with an extraordinarily narrow FHWM of 35 nm and a y coordinate <0.05 based on a fully twisting donor–acceptor molecule
Authors: Li Weijun , Yao Liang , Liu Haichao , Wang Zhiming , Zhang Shitong , Xiao Ran , Zhang Huanhuan , Lu Ping , Yang Bing , Ma Yuguang
Published: April 2014

A highly efficient deep-blue OLED with a FHWM of 35 nm and CIE coordinate of (0.161, 0.046) was obtained based on the fully twisting donor–acceptor molecule TPA–PIM.
The actin/MKL1 signalling pathway influences cell growth and gene expression through large-scale chromatin reorganization and histone post-translational modifications
Authors: Flouriot Gilles , Huet Guillaume , Demay Florence , Pakdel Farzad , Boujrad Noureddine , Michel Denis
Published: April 2014

In addition to soluble factors, mechanical constraints and extracellular matrix stiffness are important regulators of cell fate that are mediated by cytoskeletal modifications. The EMT (epithelial–mesenchymal transition) that occurs during normal development and malignant progression is a typical example of the phenotypic switch associated with profound actin remodelling and changes in gene expression. For instance, actin dynamics control motile cell functions in EMT, in part, through regulating the subcellular localization of the myocardin-related transcription factor MKL1 (megakaryoblastic leukaemia translocation 1), a co-activator of SRF (serum-responsive factor). In the present paper, we show that MKL1 participates also to the control of the cellular switch between growth and quiescence. Experimental disconnection between MKL1 and G-actin (globular actin), by using an MKL1 mutant or enhancing the F (filamentous)-/G-actin ratio, generates a widely open chromatin state and a global increase in biosynthetic activity, classically associated with cell growth. Conversely, G-actin accumulation favours nuclear condensation and cell quiescence. These large-scale chromatin changes rely upon extensive histone modifications, exemplified by that of H3K9 (H3 Lys9) shifting from trimethylation, a heterochromatin mark, to acetylation, a mark of euchromatin. The present study provides the first evidence for a global reversible hetero/euchromatinization phenomenon triggered by the actin/MKL1 signalling pathway.
Contribution to digital power factor correction controllers in high intensity discharge lamps electronic ballast applications
Authors: Diaz Francisco Javier , Lopez Victor M. , Azcondo Francisco J. , Brañas Christian , Casanueva Rosario
Published: April 2014

Utility voltage fluctuations not compensated by the low‐frequency voltage loop of the power factor correction (PFC) stage cause a perceptible variation in the light emitted by lamps, unpleasant for the human eye and known as flicker effect. A novel extension of the digital control for PFC stages analyses the input voltage, detects the fluctuations in the range of human flicker sensitivity and modifies the PFC output voltage controller to avoid their propagation to the DC bus. The purpose of the controller is to make the PFC compatible with any second stage lamp driver, assuring the mitigation of the lamp light variation caused by utility disturbances in consistent with the human eye perception. The controller is implemented in a field programmable gate array. A constant lamp luminance is achieved with this digital controller with no dependence on the next ballast stage.
Laser-driven flyer plates for shock compression science: Launch and target impact probed by photon Doppler velocimetry
Authors: Curtis Alexander D. , Banishev Alexandr A. , Shaw William L. , Dlott Dana D.
Published: April 2014

We investigated the launch and target impact of laser-driven Al flyer plates using photon Doppler velocimetry (PDV). We studied different flyer designs launched by laser pulses of different energies, pulse durations and beam diameters, that produced km s−1 impacts with transparent target materials. Laser-launching Al flyers 25–100 μm thick cemented to glass substrates is usually thought to involve laser vaporization of a portion of the flyer, which creates many difficulties associated with loss of integrity and heating of the flyer material. However, in the system used here, the launch mechanism was surprising and unexpected: it involved optical damage at the glass/cement/flyer interface, with very little laser light reaching the flyer itself. In fact the flyers launched in this manner behaved almost identically to multilayer flyers that were optically shielded from the laser pulses and insulated from heat generated by the pulses. Launching flyers with nanosecond laser pulses creates undesirable reverberating shocks in the flyer. In some cases, with 10 ns launch pulses, the thickest flyers were observed to lose integrity. But with stretched 20 ns pulses, we showed that the reverberations damped out prior to impact with targets, and that the flyers maintained their integrity during flight. Flyer impacts with salt, glass, fused silica, and acrylic polymer were studied by PDV, and the durations of fully supported shocks in those media were determined, and could be varied from 5 to 23 ns.
Variational formulation of oscillating fluid clusters and oscillator-like classification. I. Theory
Authors: Kurzeja Patrick S. , Steeb Holger
Published: April 2014

The present work develops the theoretical framework to describe oscillations of fluid clusters. The basic physical phenomena are presented and justified assumptions lead to the final set of equations for different types of oscillations (pinned/sliding). The special combination of a liquid cluster surrounded by a rigid solid matrix and a gas is investigated in more detail. Furthermore, a classification of oscillating fluid clusters is presented using a one-dimensional oscillator model. This classification includes three dynamic properties: mass, eigenfrequency, and damping whereas conceptual implementation and limitations for use in multiphase theories are clearly indicated. The frequency dependent flow profile leads to frequency dependence of the dynamic parameters. This is discussed and represented by dimensionless numbers.
Pulse transient hot strip technique adapted for slab sample geometry to study anisotropic thermal transport properties of μm-thin crystalline films
Authors: Ma Y. , Gustavsson J. S. , Haglund Å. , Gustavsson M. , Gustafsson S. E.
Published: April 2014

A new method based on the adaptation of the Pulse Transient Hot Strip technique to slab sample geometry has been developed for studying thermal conductivity and thermal diffusivity of anisotropic thin film materials (<50 μm) with thermal conductivity in the 0.01–100 W/mK range, deposited on thin substrates (i.e., wafers). Strength of this technique is that it provides a well-controlled thermal probing depth, making it possible to probe a predetermined depth of the sample layer and thereby avoiding the influence from material(s) deeper down in the sample. To verify the technique a series of measurements were conducted on a y-cut single crystal quartz wafer. A Hot Strip sensor (32-μm wide, 3.2-mm long) was deposited along two orthogonal crystallographic (x- and z-) directions and two independent pulse transients were recorded. Thereafter, the data was fitted to our theoretical model, and the anisotropic thermal transport properties were determined. Using a thermal probing depth of only 30 μm, we obtained a thermal conductivity along the perpendicular (parallel) direction to the z-, i.e., optic axis of 6.48 (11.4) W/mK, and a thermal diffusivity of 3.62 (6.52) mm2/s. This yields a volumetric specific heat of 1.79 MJ/mK. These values agree well with tabulated data on bulk crystalline quartz supporting the accuracy of the technique, and the obtained standard deviation of less than 2.7% demonstrates the precision of this new measurement technique.
Hydration of non-polar anti-parallel β-sheets
Authors: Urbic Tomaz , Dias Cristiano L.
Published: April 2014

In this work we focus on anti-parallel β-sheets to study hydration of side chains and polar groups of the backbone using all-atom molecular dynamics simulations. We show that: (i) water distribution around the backbone does not depend significantly on amino acid sequence, (ii) more water molecules are found around oxygen than nitrogen atoms of the backbone, and (iii) water molecules around nitrogen are highly localized in the planed formed by peptide backbones. To study hydration around side chains we note that anti-parallel β-sheets exhibit two types of cross-strand pairing: Hydrogen-Bond (HB) and Non-Hydrogen-Bond (NHB) pairing. We show that distributions of water around alanine, leucine, and valine side chains are very different at HB compared to NHB faces. For alanine pairs, the space between side chains has a higher concentration of water if residues are located in the NHB face of the β-sheet as opposed to the HB face. For leucine residues, the HB face is found to be dry while the space between side chains at the NHB face alternates between being occupied and non-occupied by water. Surprisingly, for valine residues the NHB face is dry, whereas the HB face is occupied by water. We postulate that these differences in water distribution are related to context dependent propensities observed for β-sheets.
Electron dynamics in complex environments with real-time time dependent density functional theory in a QM-MM framework
Authors: Morzan Uriel N. , Ramírez Francisco F. , Oviedo M. Belén , Sánchez Cristián G. , Scherlis Damián A. , Lebrero Mariano C. González
Published: April 2014

This article presents a time dependent density functional theory (TDDFT) implementation to propagate the Kohn-Sham equations in real time, including the effects of a molecular environment through a Quantum-Mechanics Molecular-Mechanics (QM-MM) hamiltonian. The code delivers an all-electron description employing Gaussian basis functions, and incorporates the Amber force-field in the QM-MM treatment. The most expensive parts of the computation, comprising the commutators between the hamiltonian and the density matrix—required to propagate the electron dynamics—, and the evaluation of the exchange-correlation energy, were migrated to the CUDA platform to run on graphics processing units, which remarkably accelerates the performance of the code. The method was validated by reproducing linear-response TDDFT results for the absorption spectra of several molecular species. Two different schemes were tested to propagate the quantum dynamics: (i) a leap-frog Verlet algorithm, and (ii) the Magnus expansion to first-order. These two approaches were confronted, to find that the Magnus scheme is more efficient by a factor of six in small molecules. Interestingly, the presence of iron was found to seriously limitate the length of the integration time step, due to the high frequencies associated with the core-electrons. This highlights the importance of pseudopotentials to alleviate the cost of the propagation of the inner states when heavy nuclei are present. Finally, the methodology was applied to investigate the shifts induced by the chemical environment on the most intense UV absorption bands of two model systems of general relevance: the formamide molecule in water solution, and the carboxy-heme group in Flavohemoglobin. In both cases, shifts of several nanometers are observed, consistently with the available experimental data.
Unbounded dynamics in dissipative flows: Rössler model
Authors: Barrio Roberto , Blesa Fernando , Serrano Sergio
Published: April 2014

Transient chaos and unbounded dynamics are two outstanding phenomena that dominate in chaotic systems with large regions of positive and negative divergences. Here, we investigate the mechanism that leads the unbounded dynamics to be the dominant behavior in a dissipative flow. We describe in detail the particular case of boundary crisis related to the generation of unbounded dynamics. The mechanism of the creation of this crisis in flows is related to the existence of an unstable focus-node (or a saddle-focus) equilibrium point and the crossing of a chaotic invariant set of the system with the weak-(un)stable manifold of the equilibrium point. This behavior is illustrated in the well-known Rössler model. The numerical analysis of the system combines different techniques as chaos indicators, the numerical computation of the bounded regions, and bifurcation analysis. For large values of the parameters, the system is studied by means of Fenichel's theory, providing formulas for computing the slow manifold which influences the evolution of the first stages of the orbit.
Tight constraints on the exchange-correlation potentials of degenerate states
Authors: Ayers Paul W. , Levy Mel
Published: April 2014

Identities for the difference of exchange-correlation potentials and energies in degenerate and nondegenerate ground states are derived. The constraints are strong for degenerate ground states, and suggest that local and semilocal approximations to the exchange-correlation energy functional are incapable of correctly treating degenerate ground states. For degenerate states, it is possible to provide both local (pointwise) equality and global inequality constraints for the exchange-correlation potential in terms of the Coulomb potential.
Kinetic and electron-electron energies for convex sums of ground state densities with degeneracies and fractional electron number
Authors: Levy Mel , Anderson James S. M. , Zadeh Farnaz Heidar , Ayers Paul W.
Published: April 2014

Properties of exact density functionals provide useful constraints for the development of new approximate functionals. This paper focuses on convex sums of ground-level densities. It is observed that the electronic kinetic energy of a convex sum of degenerate ground-level densities is equal to the convex sum of the kinetic energies of the individual degenerate densities. (The same type of relationship holds also for the electron-electron repulsion energy.) This extends a known property of the Levy-Valone Ensemble Constrained-Search and the Lieb Legendre-Transform refomulations of the Hohenberg-Kohn functional to the individual components of the functional. Moreover, we observe that the kinetic and electron-repulsion results also apply to densities with fractional electron number (even if there are no degeneracies), and we close with an analogous point-wise property involving the external potential. Examples where different degenerate states have different kinetic energy and electron-nuclear attraction energy are given; consequently, individual components of the ground state electronic energy can change abruptly when the molecular geometry changes. These discontinuities are predicted to be ubiquitous at conical intersections, complicating the development of universally applicable density-functional approximations.
Effect of mixed Ge/Si cross-linking on the physical properties of amorphous Ge-Si-Te networks
Authors: Gunasekera K. , Boolchand P. , Micoulaut M.
Published: April 2014

Amorphous GexSixTe1−2x glasses are studied as a function of composition by a combination of experimental and theoretical methods, allowing for a full description of the network structure in relationship with physico-chemical properties. Calorimetric and thermal measurements reveal that such glasses display an anomalous behavior across a range of compositions xc1=7.5% and <x<xc2=9%, in which is manifested a deep minimum in molar volume, non-reversing enthalpy, and liquid fragility. These anomalies allow defining an intermediate phase, where network rigidity onsets as the content x of Group IV atoms (Ge, Si) are increased. The structural manifestation of these anomalies is understood from  119Sn Mössbauer spectroscopy and First Principles Molecular Dynamics at selected compositions (Ge20Te80, Si20Te80, and Ge10Si10Te80). The numerical models reveal the quite different roles played by the modifier or network cross-linker Ge or Si atoms, Si being more tetrahedral in sp3 geometry, whereas Mössbauer spectroscopy shows that the nature of chemical bonding is dramatically changed around x≃ 8%. The precise evolution of the local structure and chemical bonding ultimately allows understanding the origin of the intermediate phase in these complex tellurides.
Experimental determination of radiated internal wave power without pressure field data
Authors: Lee Frank M. , Paoletti M. S. , Swinney Harry L. , Morrison P. J.
Published: April 2014

We present a method to determine, using only velocity field data, the time-averaged energy flux \documentclass[12pt]{minimal}\begin{document}$\left<\bm {J}\right>$\end{document}J and total radiated power P for two-dimensional internal gravity waves. Both \documentclass[12pt]{minimal}\begin{document}$\left<\bm {J}\right>$\end{document}J and P are determined from expressions involving only a scalar function, the stream function ψ. We test the method using data from a direct numerical simulation for tidal flow of a stratified fluid past a knife edge. The results for the radiated internal wave power given by the stream function method agree to within 0.5% with results obtained using pressure and velocity data from the numerical simulation. The results for the radiated power computed from the stream function agree well with power computed from the velocity and pressure if the starting point for the stream function computation is on a solid boundary, but if a boundary point is not available, care must be taken to choose an appropriate starting point. We also test the stream function method by applying it to laboratory data for tidal flow past a knife edge, and the results are found to agree with the direct numerical simulation. The supplementary material includes a Matlab code with a graphical user interface that can be used to compute the energy flux and power from two-dimensional velocity field data.
Dissociation dynamics of simple chlorine containing molecules upon resonant Cl K-σ* excitation
Authors: Bohinc R. , Žitnik M. , Bučar K. , Kavčič M.
Published: April 2014

A theoretical analysis of dissociation dynamics of chlorine K-σ* core-excited molecules is performed. The potential energy surfaces of HCl, Cl2, CH3Cl, CH2Cl2, CHCl3, CCl4, CFCl3, CF2Cl2, and CF3Cl are calculated along the normal vibrational modes of the ground electronic state yielding the widths of the corresponding Franck-Condon distributions. An insight into the potential energy surface of 1st σ* resonances shows that the initial dissociation dynamics of chloro(fluoro)methanes mainly involves the distancing of the carbon and the core-excited chlorine atom and is practically independent of other atoms in the molecule, which is in agreement with the recent experimental findings. The carbon atom pulls out the remaining three atoms shortly after piercing the three-atom plane resulting in a high vibrationally excited state of the fragment if the reconnection time is smaller than the lifetime of the L shell.
Auto-regressive moving average analysis of linear and discontinuous models of human balance during quiet standing
Authors: Kowalczyk Piotr , Nema Salam , Glendinning Paul , Loram Ian , Brown Martin
Published: April 2014

Linear Time Invariant (LTI) processes can be modelled by means of Auto-Regressive Moving Average (ARMA) model systems. In this paper, we examine whether an ARMA model can be fitted to a process characterised by switched nonlinearities. In particular, we conduct the following test: we generate data from known LTI and nonlinear (threshold/dead-zone) models of human balance and analyse the output using ARMA. We show that both these known systems can be fitted, according to standard criteria, with low order ARMA models. To check if there are some obvious effects of the dead-zone, we compare the power spectra of both systems with the power spectra of their ARMA models. We then examine spectral properties of three posturographic data sets and their ARMA models and compare them with the power spectra of our model systems. Finally, we examine the dynamics of our model systems in the absence of noise to determine what is the effect of the switching threshold (dead-zone) on the asymptotic dynamics.
Experimental nanocalorimetry of protonated and deprotonated water clusters
Authors: Boulon Julien , Braud Isabelle , Zamith Sébastien , Labastie Pierre , L’Hermite Jean-Marc
Published: April 2014

An experimental nanocalorimetric study of mass selected protonated (H2O)nH+ and deprotonated (H2O)n−1OH− water clusters is reported in the size range n = 20–118. Water cluster's heat capacities exhibit a change of slope at size dependent temperatures varying from 90 to 140 K, which is ascribed to phase or structural transition. For both anionic and cationic species, these transition temperatures strongly vary at small sizes, with higher amplitude for protonated than for deprotonated clusters, and change more smoothly above roughly n ≈ 35. There is a correlation between bonding energies and transition temperatures, which is split in two components for protonated clusters while only one component is observed for deprotonated clusters. These features are tentatively interpreted in terms of structural properties of water clusters.
Diradicals acting through diamagnetic phenylene vinylene bridges: Raman spectroscopy as a probe to characterize spin delocalization
Authors: González Sandra Rodríguez , Nieto-Ortega Belén , González Cano Rafael C. , Lloveras Vega , Novoa Juan J. , Mota Fernando , Vidal-Gancedo José , Rovira Concepció , Veciana Jaume , del Corro Elena , Taravillo Mercedes , Baonza Valentín G. , López Navarrete Juan T. , Casado Juan
Published: April 2014

We present a complete Raman spectroscopic study in two structurally well-defined diradical species of different lengths incorporating oligo p-phenylene vinylene bridges between two polychlorinated triphenylmethyl radical units, a disposition that allows sizeable conjugation between the two radicals through and with the bridge. The spectroscopic data are interpreted and supported by quantum chemical calculations. We focus the attention on the Raman frequency changes, interpretable in terms of: (i) bridge length (conjugation length); (ii) bridge conformational structure; and (iii) electronic coupling between the terminal radical units with the bridge and through the bridge, which could delineate through-bond spin polarization, or spin delocalization. These items are addressed by using the “oligomer approach” in conjunction with pressure and temperature dependent Raman spectroscopic data. In summary, we have attempted to translate the well-known strategy to study the electron (charge) structure of π−conjugated molecules by Raman spectroscopy to the case of electron (spin) interactions via the spin delocalization mechanism.
Two-component order parameter for quantifying clathrate hydrate nucleation and growth
Authors: Barnes Brian C. , Beckham Gregg T. , Wu David T. , Sum Amadeu K.
Published: April 2014

Methane clathrate hydrate nucleation and growth is investigated via analysis of molecular dynamics simulations using a new order parameter. This order parameter (OP), named the Mutually Coordinated Guest (MCG) OP, quantifies the appearance and connectivity of molecular clusters composed of guests separated by water clusters. It is the first two-component OP used for quantifying hydrate nucleation and growth. The algorithm for calculating the MCG OP is described in detail. Its physical motivation and advantages compared to existing methods are discussed.
Kalman filter data assimilation: Targeting observations and parameter estimation
Authors: Bellsky Thomas , Kostelich Eric J. , Mahalov Alex
Published: April 2014

This paper studies the effect of targeted observations on state and parameter estimates determined with Kalman filter data assimilation (DA) techniques. We first provide an analytical result demonstrating that targeting observations within the Kalman filter for a linear model can significantly reduce state estimation error as opposed to fixed or randomly located observations. We next conduct observing system simulation experiments for a chaotic model of meteorological interest, where we demonstrate that the local ensemble transform Kalman filter (LETKF) with targeted observations based on largest ensemble variance is skillful in providing more accurate state estimates than the LETKF with randomly located observations. Additionally, we find that a hybrid ensemble Kalman filter parameter estimation method accurately updates model parameters within the targeted observation context to further improve state estimation.
Time-dependent restricted-active-space self-consistent-field singles method for many-electron dynamics
Authors: Miyagi Haruhide , Bojer Madsen Lars
Published: April 2014

The time-dependent restricted-active-space self-consistent-field singles (TD-RASSCF-S) method is presented for investigating TD many-electron dynamics in atoms and molecules. Adopting the SCF notion from the muticonfigurational TD Hartree-Fock (MCTDHF) method and the RAS scheme (single-orbital excitation concept) from the TD configuration-interaction singles (TDCIS) method, the TD-RASSCF-S method can be regarded as a hybrid of them. We prove that, for closed-shell Ne-electron systems, the TD-RASSCF-S wave function can be fully converged using only Ne/2 + 1 ⩽ M ⩽ Ne spatial orbitals. Importantly, based on the TD variational principle, the converged TD-RASSCF-S wave function with M = Ne is more accurate than the TDCIS wave function. The accuracy of the TD-RASSCF-S approach over the TDCIS is illustrated by the calculation of high-order harmonic generation spectra for one-dimensional models of atomic helium, beryllium, and carbon in an intense laser pulse. The electronic dynamics during the process is investigated by analyzing the behavior of electron density and orbitals. The TD-RASSCF-S method is accurate, numerically tractable, and applicable for large systems beyond the capability of the MCTDHF method.
Energetic-particle-driven instabilities and induced fast-ion transport in a reversed field pinch
Authors: Lin L. , Anderson J. K. , Brower D. L. , Capecchi W. , Ding W. X. , Eilerman S. , Forest C. B. , Koliner J. J. , Liu D. , Nornberg M. D. , Reusch J. , Sarff J. S.
Published: April 2014

Multiple bursty energetic-particle (EP) driven modes with fishbone-like structure are observed during 1 MW tangential neutral-beam injection in a reversed field pinch (RFP) device. The distinguishing features of the RFP, including large magnetic shear (tending to add stability) and weak toroidal magnetic field (leading to stronger drive), provide a complementary environment to tokamak and stellarator configurations for exploring basic understanding of EP instabilities. Detailed measurements of the EP mode characteristics and temporal-spatial dynamics reveal their influence on fast ion transport. Density fluctuations exhibit a dynamically evolving, inboard-outboard asymmetric spatial structure that peaks in the core where fast ions reside. The measured mode frequencies are close to the computed shear Alfvén frequency, a feature consistent with continuum modes destabilized by strong drive. The frequency pattern of the dominant mode depends on the fast-ion species. Multiple frequencies occur with deuterium fast ions compared to single frequency for hydrogen fast ions. Furthermore, as the safety factor (q) decreases, the toroidal mode number of the dominant EP mode transits from n=5 to n=6 while retaining the same poloidal mode number m=1. The transition occurs when the m=1, n=5 wave-particle resonance condition cannot be satisfied as the fast-ion safety factor (qfi) decreases. The fast-ion temporal dynamics, measured by a neutral particle analyzer, resemble a classical predator-prey relaxation oscillation. It contains a slow-growth phase arising from the beam fueling followed by a rapid drop when the EP modes peak, indicating that the fluctuation-induced transport maintains a stiff fast-ion density profile. The inferred transport rate is strongly enhanced with the onset of multiple EP modes.
Comparing ultrafast surface and bulk heating using time-resolved electron diffraction
Authors: Streubühr C. , Kalus A. , Zhou P. , Ligges M. , Hanisch-Blicharski A. , Kammler M. , Bovensiepen U. , Horn-von Hoegen M. , von der Linde D.
Published: April 2014

From measurements of the transient Debye-Waller effect in Bismuth, we determine the buildup time of the random atomic motion resulting from the electronic relaxation after short pulse laser excitation. The surface sensitive reflection high energy electron diffraction and transmission electron diffraction yield a time constant of about 12 ps and 3 ps, respectively. The different energy transfer rates indicate relatively weak coupling between bulk and surface vibrational modes.
Calculation of state-to-state cross sections for triatomic reaction by the multi-configuration time-dependent Hartree method
Authors: Zhao Bin , Zhang Dong-H. , Lee Soo-Y. , Sun Zhigang
Published: April 2014

A framework for quantum state-to-state integral and differential cross sections of triatomic reactive scattering using the Multi-Configuration Time-Dependent Hartree (MCTDH) method is introduced, where a modified version of the Heidelberg MCTDH package is applied. Parity of the system is adopted using only non-negative helicity quantum numbers, which reduces the basis set size of the single particle functions in angular degree of freedom almost by half. The initial wave packet is constructed in the space-fixed frame, which can accurately account for the centrifugal potential. By using the reactant-coordinate-based method, the product state-resolved information can be accurately extracted. Test calculations are presented for the H + H2 reactive scattering. This work demonstrates the capability of the MCTDH method for extracting accurate state-to-state integral and differential cross sections. As an efficient scheme for high-dimensional problems, the MCTDH method may be promising for the study of product state-resolved cross sections for polyatomic reactive systems.
Anharmonic coupling between fundamental modes in tetramethylurea
Authors: Chen Yuanzheng , Men Zhiwei , Li Juntao , Li Zhanlong , Sun Shengnan , Sun Chengling , Gao Shuqin , Li Zuowei , Zhou Mi
Published: April 2014

In situ high pressure Raman spectra of tetramethylurea have been measured up to 25 GPa, liquid-solid and solid-solid phase transitions were detected at 0.2 GPa and 7.4 GPa, respectively. An unprecedented spectral phenomenon is the observation of a Fermi resonance between the fundamental modes. An exponential relationship between the intensity and the frequency difference was concluded. Pressure provides us a new way to study the correlation between Fermi resonance parameters.
Observations of strong ion-ion correlations in dense plasmas
Authors: Ma T. , Fletcher L. , Pak A. , Chapman D. A. , Falcone R. W. , Fortmann C. , Galtier E. , Gericke D. O. , Gregori G. , Hastings J. , Landen O. L. , Le Pape S. , Lee H. J. , Nagler B. , Neumayer P. , Turnbull D. , Vorberger J. , White T. G. , Wünsch K. , Zastrau U. , Glenzer S. H. , Döppner T.
Published: April 2014

Using simultaneous spectrally, angularly, and temporally resolved x-ray scattering, we measure the pronounced ion-ion correlation peak in a strongly coupled plasma. Laser-driven shock-compressed aluminum at ∼3× solid density is probed with high-energy photons at 17.9 keV created by molybdenum He-α emission in a laser-driven plasma source. The measured elastic scattering feature shows a well-pronounced correlation peak at a wave vector of k=4Å−1. The magnitude of this correlation peak cannot be described by standard plasma theories employing a linear screened Coulomb potential. Advanced models, including a strong short-range repulsion due to the inner structure of the aluminum ions are however in good agreement with the scattering data. These studies have demonstrated a new highly accurate diagnostic technique to directly measure the state of compression and the ion-ion correlations. We have since applied this new method in single-shot wave-number resolved S(k) measurements to characterize the physical properties of dense plasmas.
Channel flow of a tensorial shear-thinning Maxwell model: Lattice Boltzmann simulations
Authors: Papenkort S. , Voigtmann Th.
Published: April 2014

We discuss pressure-driven channel flow for a model of shear-thinning glass-forming fluids, employing a modified lattice-Boltzmann (LB) simulation scheme. The model is motivated by a recent microscopic approach to the nonlinear rheology of colloidal suspensions and captures a nonvanishing dynamical yield stress and the appearance of normal-stress differences and a flow-induced pressure contribution. The standard LB algorithm is extended to deal with tensorial, nonlinear constitutive equations of this class. The new LB scheme is tested in 2D pressure-driven channel flow and reproduces the analytical steady-state solution. The transient dynamics after startup and removal of the pressure gradient reproduce a finite stopping time for the cessation flow of yield-stress fluids in agreement with previous analytical estimates.
Enhanced thermoelectric performance in Cd doped CuInTe2 compounds
Authors: Cheng N. , Liu R. , Bai S. , Shi X. , Chen L.
Published: April 2014

CuIn1−xCdxTe2 materials (x = 0, 0.02, 0.05, and 0.1) are prepared using melting-annealing method and the highly densified bulk samples are obtained through Spark Plasma Sintering. The X-ray diffraction data confirm that nearly pure chalcopyrite structures are obtained in all the samples. Due to the substitution of Cd at In sites, the carrier concentration is greatly increased, leading to much enhanced electrical conductivity and power factor. The single parabolic band model is used to describe the electrical transport properties of CuInTe2 and the low temperature Hall mobility is also modeled. By combing theoretical model and experiment data, the optimum carrier concentration in CuInTe2 is proposed to explain the greatly enhanced power factors in the Cd doped CuInTe2. In addition, the thermal conductivity is reduced by extra phonon scattering due to the atomic mass and radius fluctuations between Cd and In atoms. The maximum zTs are observed in CuIn0.98Cd0.02Te2 and CuIn0.9Cd0.1Te2 samples, which are improved by over 100% at room temperature and around 20% at 600 K.
Non-perturbative modelling of energetic particle effects on resistive wall mode: Anisotropy and finite orbit width
Authors: Liu Yueqiang , Chapman I. T. , Graves J. P. , Hao G. Z. , Wang Z. R. , Menard J. E. , Okabayashi M. , Strait E. J. , Turnbull A.
Published: April 2014

A non-perturbative magnetohydrodynamic-kinetic hybrid formulation is developed and implemented into the MARS-K code [Liu et al., Phys. Plasmas 15, 112503 (2008)] that takes into account the anisotropy and asymmetry [Graves et al., Nature Commun. 3, 624 (2012)] of the equilibrium distribution of energetic particles (EPs) in particle pitch angle space, as well as first order finite orbit width (FOW) corrections for both passing and trapped EPs. Anisotropic models, which affect both the adiabatic and non-adiabatic drift kinetic energy contributions, are implemented for both neutral beam injection and ion cyclotron resonant heating induced EPs. The first order FOW correction does not contribute to the precessional drift resonance of trapped particles, but generally remains finite for the bounce and transit resonance contributions, as well as for the adiabatic contributions from asymmetrically distributed passing particles. Numerical results for a 9MA steady state ITER plasma suggest that (i) both the anisotropy and FOW effects can be important for the resistive wall mode stability in ITER plasmas; and (ii) the non-perturbative approach predicts less kinetic stabilization of the mode, than the perturbative approach, in the presence of anisotropy and FOW effects for the EPs. The latter may partially be related to the modification of the eigenfunction of the mode by the drift kinetic effects.
Installing distributed generation units and capacitors simultaneously in a distribution system considering economic issues
Authors: Hosseini S. A. , Eslami R. , Vahidi B. , Askarian Abyaneh H. , Sadeghi S. H. H. , Mohseni K.
Published: April 2014

Daily increasing demand of electrical energy and also recent developments in technology of distributed generations (DGs) have created special interest in using these units. On the other hand, capacitor insertion in the distribution feeders has been implemented by distribution companies for several years to reduce power loss and improve the voltage profile. Hence, according to the joint role of distributed generation units and capacitors, their optimal allocation will be influenced by each other. Therefore, in order to achieve the maximum benefits, this paper has discussed the optimal siting and sizing of DG resources and capacitors. One of the characteristics of the proposed method is that all technical and economical factors associated with installation of DGs and capacitors will be priced. For this purpose, all effective factors in optimal allocation and sizing of DG resources and capacitors are extracted and priced. For example, for the first time, the factor of voltage profile has been priced by the number of tapping. Using this approach, weighting the objective function parameters would be no more required. One of the other features of this paper is presenting an algorithm to determine the optimum number of DGs and capacitors. With this algorithm, power companies can find the optimum number of DGs and capacitors in the network they cover. The proposed method in this paper is tested on the 97-bus network of Bakhtar Regional Electrical Company in Iran Country.
Electrical characterization of the flowing afterglow of N2 and N2/O2 microwave plasmas at reduced pressure
Authors: Afonso Ferreira J. , Stafford L. , Leonelli R. , Ricard A.
Published: April 2014

A cylindrical Langmuir probe was used to analyze the spatial distribution of the number density of positive ions and electrons as well as the electron energy distribution function (EEDF) in the flowing afterglow of a 6 Torr N2 and N2/O2 plasma sustained by a propagating electromagnetic surface wave in the microwave regime. In pure N2 discharges, ion densities were in the mid 1014 m−3 in the pink afterglow and in the mid 1012 m−3 early in the late afterglow. In both pink and late afterglows, the ion population was much higher than the electron population, indicating non-macroscopically neutral media. The EEDF was close to a Maxwellian with an electron temperature of 0.5 ± 0.1 eV, except in the pink afterglow where the temperature rose to 1.1 ± 0.2 eV. This latter behavior is ascribed to N2 vibration-vibration pumping in the pink afterglow that increases the concentration of high N2 vibrational states and thus rises the electron temperature by vibration-electron collisions. After addition of small amounts of O2 in the nominally pure N2 discharge, the charged particles densities and average electron energy first strongly increased and then decreased with increasing O2 concentration. Based on these data and the evolution of the N2+(B) band emission intensities, it is concluded that a significant change in the positive ion composition of the flowing afterglow occurs, going from N2+ in nominally pure N2 discharges to NO+ after addition of trace amounts of O2 in N2.
Thermal rectification in pristine-hydrogenated carbon nanotube junction: A molecular dynamics study
Authors: Gordiz Kiarash , Mehdi Vaez Allaei S.
Published: April 2014

Using non-equilibrium molecular dynamics method, we investigate thermal rectification (TR) in hybrid pristine carbon nanotube (PCNT) and hydrogenated carbon nanotube (HCNT) structures. The interface thermal resistance of the junction is dependent on the direction of thermal transport, leading to TR. We show that by selecting nanotubes of smaller diameters, and/or increasing the hydrogen coverage of HCNT, the TR can be amplified. The observed TR does not decrease by increasing the system length, which presents PCNT/HCNT system as a promising thermal rectifier at room temperature.
A sustainable renewable energy mix option for the secluded society
Authors: Palanichamy C. , Naveen P. , Muthusundar S. K.
Published: April 2014

In developing countries, though electrical energy has been recognized as a noteworthy input for their economic growth and societal development, nearly 2 × 109 people lack access to electrical energy use. Many national policies were designed to provide electric service to an entire population; nevertheless, all have encountered with significant barriers. Securing a passable electric service for isolated societies with small population and large distance from the main electricity grid has been proved to be a hard-hitting challenge to the energy policy strategists. To overcome the energy barriers and the energy scarcity of the secluded society, this paper proposes a sustainable, economic, and environmental friendly energy mix option with fossil-fuelled, wind, and solar energy systems as a curative solution.
Effects of torsional degree of freedom, geometric nonlinearity, and gravity on aeroelastic behavior of large-scale horizontal axis wind turbine blades under varying wind speed conditions
Authors: Jeong Min-Soo , Cha Myung-Chan , Kim Sang-Woo , Lee In , Kim Taeseong
Published: April 2014

Modern horizontal axis wind turbine blades are long, slender, and flexible structures that can undergo considerable deformation, leading to blade failures (e.g., blade-tower collision). For this reason, it is important to estimate blade behaviors accurately when designing large-scale wind turbines. In this study, a numerical analysis considering blade torsional degree of freedom, geometric nonlinearity, and gravity was utilized to examine the effects of these factors on the aeroelastic blade behavior of a large-scale horizontal axis wind turbine. The results predicted that flapwise deflection is mainly affected by the torsional degree of freedom, which causes the blade bending deflections to couple to torsional deformation, thereby varying the aerodynamic loads through changes in the effective angle of attack. Edgewise deflection and torsional deformation are mostly influenced by the periodic gravitational force on the wind turbine blade.
Gain spectrum measurement using the segmented contact method with an integrated optical amplifier
Authors: Shahid H. , Childs D. T. D. , Majid M. A. , Kennedy K. , Airey R. , Hogg R. A. , Clarke E. , Spencer P. , Murray R.
Published: April 2014

The measurement of optical gain utilising a segmented contact and integrated optical amplifier is reported. We show that in a direct comparison of methods, the use of the integrated amplifier allows the gain spectrum to be deduced over wider spectral ranges and to lower carrier densities, as compared to the conventional segmented contact technique.
Numerical approach to generalized transmission line model and its application to Au/Sn/p-HgCdTe contact
Authors: He Kai , Li Yang , Chen Xing , Hua Hua , Gao Yan-Lin , Ye Zhen-Hua , Lin Chun , Wang Jian-Xin , Zhang Qin-Yao
Published: April 2014

A generalized transmission line model (TLM) and a compatible numerical method have been proposed to characterize metal-semiconductor contacts that exhibit nonlinear properties. This model and method have been applied to the analysis of Au/Sn/p-HgCdTe contact and have realized determination of related physical parameters by fitting experimental data. Our model's merit of avoiding the overestimation of barrier height active contact area encountered in other methods without TLM scheme is discussed. In addition, only by using this model, the transfer length can be credibly determined in the case of nonlinear contacts.
Experimental stress–strain analysis of tapered silica optical fibers with nanofiber waist
Authors: Holleis S. , Hoinkes T. , Wuttke C. , Schneeweiss P. , Rauschenbeutel A.
Published: April 2014

We experimentally determine tensile force–elongation diagrams of tapered optical fibers with a nanofiber waist. The tapered optical fibers are produced from standard silica optical fibers using a heat and pull process. Both, the force–elongation data and scanning electron microscope images of the rupture points indicate a brittle material. Despite the small waist radii of only a few hundred nanometers, our experimental data can be fully explained by a nonlinear stress–strain model that relies on material properties of macroscopic silica optical fibers. This is an important asset when it comes to designing miniaturized optical elements as one can rely on the well-founded material characteristics of standard optical fibers. Based on this understanding, we demonstrate a simple and non-destructive technique that allows us to determine the waist radius of the tapered optical fiber. We find excellent agreement with independent scanning electron microscope measurements of the waist radius.
Accurate momentum transfer cross section for the attractive Yukawa potential
Authors: Khrapak S. A.
Published: April 2014

Accurate expression for the momentum transfer cross section for the attractive Yukawa potential is proposed. This simple analytic expression agrees with the numerical results better than to within ±2% in the regime relevant for ion-particle collisions in complex (dusty) plasmas.
Direct observation of nanometer-scale strain field around CoSi2/Si interface using scanning moiré fringe imaging
Authors: Kim Suhyun , Jung Younheum , Jung Kim Joong , Byun Gwangseon , Lee Sunyoung , Lee Haebum
Published: April 2014

We report the use of scanning moiré fringe (SMF) imaging through high-angle annular dark-field scanning transmission electron microscopy (STEM) to measure the strain field around a CoSi2 contact embedded in the source and drain (S/D) region of a transistor. The atomic arrangement of the CoSi2/Si (111) interface was determined from the high-resolution (HR)-STEM images, and the strain field formed around the S/D region was revealed by nanometer-scale SMFs appearing in the STEM image. In addition, we showed that the strain field in the S/D region measured by SMF imaging agreed with results obtained via peak-pairs analysis of HR-STEM images.
Top gating of epitaxial (Bi1−xSbx)2Te3 topological insulator thin films
Authors: Yang Fan , Taskin A. A. , Sasaki Satoshi , Segawa Kouji , Ohno Yasuhide , Matsumoto Kazuhiko , Ando Yoichi
Published: April 2014

The tunability of the chemical potential for a wide range encompassing the Dirac point is important for many future devices based on topological insulators. Here, we report a method to fabricate highly efficient top gates on epitaxially grown (Bi1−xSbx)2Te3 topological insulator thin films without degrading the film quality. By combining an in situ deposited Al2O3 capping layer and a SiNx dielectric layer deposited at low temperature, we were able to protect the films from degradation during the fabrication processes. We demonstrate that by using this top gate, the carriers in the top surface can be efficiently tuned from n- to p-type. We also show that magnetotransport properties give evidence for decoupled transport through top and bottom surfaces for the entire range of gate voltage, which is only possible in truly bulk-insulating samples.
Effect of Cu doping on the resistive switching of NiO thin films
Authors: Li Jian-Chang , Hou Xue-Yan , Cao Qing
Published: April 2014

Bipolar resistive switching is observed in the GaIn/Cu:NiO film/ITO device with active layer deposited by sol-gel spin-coating. The first-principles calculations indicate that Cu dopants with valence of +1 are located at the substitutional Ni sites rather than the interstitial ones. Cu doping introduces more oxygen vacancies in the film and increases the carrier mobility, however, excessive Cu dopants may assemble at the grain boundary resulting in larger set voltage. Current–voltage measurements indicate that the trap charge limited and space charge limited conduction dominate the high resistance state, while the low resistance state follows the Ohmic mechanism. The switching is attributed to the formation/rupture of oxygen vacancy filaments.