bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical mechanical polishing: Theory and experiment
Authors: Zhao Dewen , Lu Xinchun
Published: December 2013

For several decades, chemical mechanical polishing (CMP) has been the most widely used planarization method in integrated circuits manufacturing. The final polishing results are affected by many factors related to the carrier structure, the polishing pad, the slurry, and the process parameters. As both chemical and mechanical actions affect the effectiveness of CMP, and these actions are themselves affected by many factors, the CMP mechanism is complex and has been a hot research area for many years. This review provides a basic description of the development, challenges, and key technologies associated with CMP. We summarize theoretical CMP models from the perspectives of kinematics, empirical, its mechanism (from the viewpoint of the atomic scale, particle scale, and wafer scale), and its chemical-mechanical synergy. Experimental approaches to the CMP mechanism of material removal and planarization are further discussed from the viewpoint of the particle wear effect, chemical-mechanical synergy, and wafer-pad interfacial interaction.
Imagerie du syndrome de Lemierre chez l'enfant et l'adolescent
Authors: Trachsel Lysiane , Cherpillod Jacques , Maestre Leonor Alamo , Gudinchet François
Published: December 2013

Ziel: Die Rolle der Radiologie in der Behandlung des Lemierre-Syndrom zu bestimmen und die typischen Merkmale dieser seltenen, aber potenziell tödlichen Krankheit zu beschreiben. Patienten und Methode: Retrospektive Aktenanalyse von Lemierre-Syndrom diagnostizierten Patienten im CHUV (2005–2011). Ziel war eine spezifische Semiologie zu definieren. Resultate: Thrombosen der Vena jugularis interna lassen sich durch US, CT und MRI darstellen und septische Embolien durch CT. Beschreibung der Komplikationen durch CT und MRI. Schlussfolgerung: Die Thrombose der Vena jugularis interna kann durch US, CT und MRI visualisiert werden. Zur Darstellung septischer Lungenembolien eignet sich die CT. Diese Funde sollten die Diagnose und eine frühzeitige aggressive Behandlung des potenziell tödlichen Lemierre-Syndroms ermöglichen.
The Political Psychology of Protest
Authors: van Stekelenburg Jacquelien
Published: December 2013

We live in contentious times. Why are people prepared to sacrifice wealth, a pleasant and carefree life, or sometimes even their lives for a common cause? This question brings us to the individual level of analysis, and therefore to political psychology. People live in a perceived world. Indeed, this is what a political psychology of protest is about – trying to understand why people who are seemingly in the same socio-political configuration respond so differently. I will illustrate this point with an overview of state-of-the-art theoretical approaches and up-to-date empirical evidence. Discussed are grievances, efficacy/cynicism, identification, emotions, and social embeddedness. Most recent approaches combine these concepts into one model comprising two routes: An efficacy route steered by social embeddedness and a grievances route steered by cynicism. The working of the model is illustrated by empirical evidence from contemporary events such as migrants, collective action, demonstrating diasporas, and Social Media protests. Each of these illustrations exemplifies how different aspects of the socio-political context as dual identification, group status, and virtual embeddedness affect individuals’ protest behavior. As such the paper aims to provide an overview of political psychological work that may contribute to the understanding of our contentious times.
Twenty-Five Years of Research on Violence in Digital Games and Aggression Revisited
Authors: Bushman Brad J. , Huesmann L. Rowell
Published: December 2013

In this commentary, we first analyze Elson and Ferguson’s (2013) attempt to offer a theory that would explain why exposure to family, community, school, and media violence could be related to increased aggression, but not cause such aggression. We conclude that the “new” theory they offer is not very “new.” It differs from dominant social learning theories only in its claim that the relation between exposure to violence and aggression is almost entirely due to people who are genetically or biologically predisposed to be aggressive also exposing themselves to more violence. We show this assertion is strongly contradicted by existing experimental and longitudinal data. We also show that Elson and Ferguson’s so-called “exhaustive review” of empirical data on the topic is seriously flawed; that their claim that effect sizes are trivial is not supported by the math; and that their claim that scholars who believe that violent video games cause aggression are an “extreme” group in a divided field is contradicted by surveys that show the vast majority of researchers believe violent video games increase aggression. We point out that their claim that scholars who believe in media violence effects are having a “moral panic” has no theoretical or empirical support, whereas the contrasting argument that researchers who produce violent media themselves, or use it extensively, are biased by the force of cognitive consistency and experience a “reactance” of “regulatory panic” does have support from psychological theory.
Stress as Necessary Component of Realistic Recovery in Animal Models of Experimental Stroke
Authors: Walker Frederick R , Jones Kimberley A , Patience Madeleine J , Zhao Zidan , Nilsson Michael
Published: December 2013

Over the last decade there has been a considerable effort directed toward reformulating the standard approach taken to preclinically model stroke and stroke recovery. The principal objective of this undertaking has been to improve the success with which preclinical findings can be translated. Although several advancements have already been introduced, one potentially critical feature that appears to have been overlooked is psychological stress. Stroke is well recognized to produce high levels of stress in patients, and ongoing exposure to stress is recognized to deleteriously interfere with recovery. The presence of high levels of stress (distress) in stroke patients is also relevant because nearly all clinically deployed neurorestorative interventions occur against this background. Somewhat perplexingly, however, we could find no preclinical stroke studies concerned with investigating the efficacy of putative neurorestorative compounds that did so in the presence of stress. The following article will make the case that failure to recognize or compensate for the effects of ongoing stress in standard preclinical experimental models of recovery is likely to result in overestimation of the effectiveness of pharmacological or behavioral neurorestorative interventions.
Transplantation of Neural Stem Cells That Overexpress Sod1 Enhances Amelioration of Intracerebral Hemorrhage in Mice
Authors: Wakai Takuma , Sakata Hiroyuki , Narasimhan Purnima , Yoshioka Hideyuki , Kinouchi Hiroyuki , Chan Pak H
Published: December 2013

Previous studies have shown that intraparenchymal transplantation of neural stem cells (NSCs) ameliorates neurologic deficits in animals with intracerebral hemorrhage (ICH). However, massive grafted cell death after transplantation, possibly caused by a hostile host brain environment, lessens the effectiveness of this approach. We focused on the effect of oxidative stress against grafted NSCs and hypothesized that conferring antioxidant properties to transplanted NSCs may overcome their death and enhance neuroprotection after ICH. Copper/zinc-superoxide dismutase (SOD1) is a specific antioxidant enzyme that counteracts superoxide anions. We investigated whether genetic manipulation to overexpress SOD1 enhances survival of grafted NSCs and accelerates amelioration of ICH. Neural stem cells that overexpress SOD1 were administered intracerebrally 3 days after ICH in a mouse model. Histologic and behavioral tests were examined after ICH. Copper/zinc-superoxide dismutase overexpression protected the grafted NSCs via a decrease in production of reactive oxygen species. This resulted in an increase in paracrine factors released by the NSCs, and an increase in surviving neurons in the striatum and a reduction in striatal atrophy. In addition, SOD1 overexpression showed progressive improvement in behavioral recovery. Our results suggest that enhanced antioxidative activity in NSCs improves efficacy of stem cell therapy for ICH.
Inhibiting Mitochondrial β-Oxidation Selectively Reduces Levels of Nonenzymatic Oxidative Polyunsaturated Fatty Acid Metabolites in the Brain
Authors: Chen Chuck T , Trépanier Marc-Olivier , Hopperton Kathryn E , Domenichiello Anthony F , Masoodi Mojgan , Bazinet Richard P
Published: December 2013

Schönfeld and Reiser recently hypothesized that fatty acid β-oxidation is a source of oxidative stress in the brain. To test this hypothesis, we inhibited brain mitochondrial β-oxidation with methyl palmoxirate (MEP) and measured oxidative polyunsaturated fatty acid (PUFA) metabolites in the rat brain. Upon MEP treatment, levels of several nonenzymatic auto-oxidative PUFA metabolites were reduced with few effects on enzymatically derived metabolites. Our finding confirms the hypothesis that reduced fatty acid β-oxidation decreases oxidative stress in the brain and β-oxidation inhibitors may be a novel therapeutic approach for brain disorders associated with oxidative stress.
Hydrocephalus after Intraventricular Hemorrhage: The Role of Thrombin
Authors: Gao Feng , Liu Fuyi , Chen Zhi , Hua Ya , Keep Richard F , Xi Guohua
Published: December 2013

Previous studies demonstrated that thrombin is an important factor in brain injury after intracerebral hemorrhage. This study investigated the effect of thrombin on hydrocephalus development in a rat intraventricular hemorrhage (IVH) model. There were three parts in this study. First, male Sprague–Dawley rats had an injection of 200  μL saline, autologous blood or heparinized blood, into the right lateral ventricle. Second, rats had an injection of 50  μL saline or 3U thrombin into the right lateral ventricle. Third, rats had an injection of thrombin (3U) with a protease-activated receptor-1 (PAR-1) antagonist, SCH79797 (0.15 nmol), or vehicle into the right lateral ventricle. Lateral ventricle volumes were measured by magnetic resonance imaging and the brains were used for immunohistochemistry and western blot analyses. Intraventricular injection of autologous blood induced hydrocephalus from day 1 to 28. Heparinized blood injection resulted in less hydrocephalus at all time points compared with blood injection alone ( P<0.05). Intraventricular injection of thrombin caused significant hydrocephalus, ventricular wall damage, and periventricular blood–brain barrier disruption. Thrombin-induced hydrocephalus was reduced by co-injection of the PAR-1 antagonist SCH79797 ( P<0.05). In conclusion, thrombin contributes to hydrocephalus development after IVH and thrombin-induced hydrocephalus is through PAR-1.
Isolation and purification ofent-pimara-8(14),15-diene from engineeredAspergillus nidulansby accelerated solvent extraction combined with HPLC
Authors: Bromann K. , Viljanen K. , Moreira V. M. , Yli-Kauhaluoma J. , Ruohonen L. , Nakari-Setälä T.
Published: December 2013

This paper describes a purification method for tricyclic diterpene hydrocarbonent-pimara-8(14),15-diene produced inAspergillus nidulansand reports an antioxidant activity for this compound.
OpenFluor– an online spectral library of auto-fluorescence by organic compounds in the environment
Authors: Murphy Kathleen R. , Stedmon Colin A. , Wenig Philip , Bro Rasmus
Published: December 2013

An online repository of published organic fluorescence spectra has been developed, which can be searched for quantitative matches with any set of unknown spectra.
Efficient three-component coupling reactions catalyzed by Cu0-nanoparticles stabilized on modified montmorillonite
Authors: Borah Bibek Jyoti , Borah Subrat Jyoti , Saikia Lakshi , Dutta Dipak Kumar
Published: December 2013

In situgeneration of Cu0-nanoparticles into the nanopores of environmentally benign modified montmorillonite clay and their catalytic performance in three component (A3) coupling reactions of aldehyde, amine and alkyne to synthesize propargylamines with excellent yields and selectivity.
Structural and magnetic conformation of a cerocene [Ce(COT′′)2]− exhibiting a uniconfigurational f1 ground state and slow-magnetic relaxation
Authors: Le Roy Jennifer J. , Korobkov Ilia , Kim Jee Eon , Schelter Eric J. , Murugesu Muralee
Published: December 2013

Magnet-like behaviour, in the form of slow relaxation of the magnetization, was observed for a monometallic cerium(iii) sandwich complex.
An insight into the role of the surfactant CTAB in the formation of microporous molecular sieves
Authors: Xu Dongdong , Feng Ji , Che Shunai
Published: December 2013

ZSM-5 was synthesized by CTAB as a structure-directing agent (SDA). The surfactant head groups can serve as SDAs for zeolites and the long chains become isolated and occupy the micropores, which were more rigid and did not undergo decomposition.
Microfluidic reactors for photocatalytic water purification
Authors: Wang Ning , Zhang Xuming , Wang Yu , Yu Weixing , Chan Helen L. W.
Published: December 2013

Recent studies utilize microfluidics to solve the fundamental problems of photocatalysis. Here the mechanisms and reactor designs are reviewed comprehensively.
Clean room-free rapid fabrication of roll-up self-powered catalytic microengines
Authors: Zhao Guanjia , Ambrosi Adriano , Pumera Martin
Published: December 2013

Standard laboratories in the world can easily fabricate the high-tech rolled-up micromotors, simply provided a magnetron sputtering machine is available.
Simulations of hydrogen sorption in rht-MOF-1: identifying the binding sites through explicit polarization and quantum rotation calculations
Authors: Pham Tony , Forrest Katherine A. , Hogan Adam , McLaughlin Keith , Belof Jonathan L. , Eckert Juergen , Space Brian
Published: December 2013

Grand canonical Monte Carlo simulations of H2 sorption were performed in the metal–organic framework rht-MOF-1. The binding sites were revealed by combining simulation and inelastic neutron scattering data.
Silver nanoparticle–ionic silsesquioxane: a new system proposed as an antibacterial agent
Authors: Schneid Andressa C. , Roesch Eliane W. , Sperb Fernanda , Matte Ursula , da Silveira Nádya P. , Costa Tania M. H. , Benvenutti Edilson V. , de Menezes Eliana W.
Published: December 2013

Ionic silsesquioxane applied as a stabilizer of small size silver nanoparticle aqueous dispersions showing antibacterial activity at very low concentration.
Highly stable solution-processed ZnO thin film transistors prepared via a simple Al evaporation process
Authors: Kang Tae Sung , Kim Tae Yoon , Lee Gyu Min , Sohn Hyun Chul , Hong Jin Pyo
Published: December 2013

The possible nature of the improved device stability is proposed by employing the formation of Al nanoparticles (NPs) on the back channel of a ZnO film and a partial Al atom (ion) impregnation process.
Modeling of neutrals in the Linac4 H− ion source plasma: Hydrogen atom production density profile and Hα intensity by collisional radiative model
Authors: Yamamoto T. , Shibata T. , Ohta M. , Yasumoto M. , Nishida K. , Hatayama A. , Mattei S. , Lettry J. , Sawada K. , Fantz U.
Published: December 2013

To control the H0 atom production profile in the H− ion sources is one of the important issues for the efficient and uniform surface H− production. The purpose of this study is to construct a collisional radiative (CR) model to calculate the effective production rate of H0 atoms from H2 molecules in the model geometry of the radio-frequency (RF) H− ion source for Linac4 accelerator. In order to validate the CR model by comparison with the experimental results from the optical emission spectroscopy, it is also necessary for the model to calculate Balmer photon emission rate in the source. As a basic test of the model, the time evolutions of H0 production and the Balmer Hα photon emission rate are calculated for given electron energy distribution functions in the Linac4 RF H− ion source. Reasonable test results are obtained and basis for the detailed comparisons with experimental results have been established.
Frequency sweep rate dependence on the dielectrophoretic response of polystyrene beads and red blood cells
Authors: Adams T. N. G. , Leonard K. M. , Minerick A. R.
Published: December 2013

Alternating current (AC) dielectrophoresis (DEP) experiments for biological particles in microdevices are typically done at a fixed frequency. Reconstructing the DEP response curve from static frequency experiments is laborious, but essential to ascertain differences in dielectric properties of biological particles. Our lab explored the concept of sweeping the frequency as a function of time to rapidly determine the DEP response curve from fewer experiments. For the purpose of determining an ideal sweep rate, homogeneous 6.08 μm polystyrene (PS) beads were used as a model system. Translatability of the sweep rate approach to ∼7 μm red blood cells (RBC) was then verified. An Au/Ti quadrapole electrode microfluidic device was used to separately subject particles and cells to 10Vpp AC electric fields at frequencies ranging from 0.010 to 2.0 MHz over sweep rates from 0.00080 to 0.17 MHz/s. PS beads exhibited negative DEP assembly over the frequencies explored due to Maxwell-Wagner interfacial polarizations. Results demonstrate that frequency sweep rates must be slower than particle polarization timescales to achieve reliable incremental polarizations; sweep rates near 0.00080 MHz/s yielded DEP behaviors very consistent with static frequency DEP responses for both PS beads and RBCs.
Orbital-free bond breaking via machine learning
Authors: Snyder John C. , Rupp Matthias , Hansen Katja , Blooston Leo , Müller Klaus-Robert , Burke Kieron
Published: December 2013

Using a one-dimensional model, we explore the ability of machine learning to approximate the non-interacting kinetic energy density functional of diatomics. This nonlinear interpolation between Kohn-Sham reference calculations can (i) accurately dissociate a diatomic, (ii) be systematically improved with increased reference data and (iii) generate accurate self-consistent densities via a projection method that avoids directions with no data. With relatively few densities, the error due to the interpolation is smaller than typical errors in standard exchange-correlation functionals.
Nonequilibrium energy spectrum in the subgrid-scale one-equation model in large-eddy simulation
Authors: Horiuti Kiyosi , Tamaki Takahiro
Published: December 2013

The subgrid-scale (SGS) modeling in large-eddy simulation (LES) which accounts for the effect of unsteadiness and nonequilibrium state in the SGS is considered. Unsteadiness is incorporated by considering the spectral evolution in the forced homogeneous isotropic turbulence using the transport equation for the SGS energy. As for the unfiltered spectrum, perturbative expansion of the Kovasnay spectral model about the Kolmogorov −5/3 energy spectrum which constitutes a base equilibrium state in the inertial subrange, yields the extra components with −7/3 and −9/3 powers. It is shown that these spectra are actually extracted in the direct numerical simulation (DNS) data and these components govern the unsteady energy transfer. As for the SGS real-space representation of the spectral model, we consider the SGS one-equation model. The perturbation expansion is applied to the one-equation model by setting the base SGS energy as the standard Smagorinsky model, which assumes the equilibrium state in the SGS and its spectral counterpart is the Kolmogorov −5/3 spectrum. The solution yields the terms whose spectral counterparts are the components with −7/3 and −9/3 powers. These additional terms are induced by temporal variations of the base SGS energy. In the temporal variations of the grid-scale energy, SGS energy, SGS production term, and SGS dissipation which are obtained by applying the filter to the DNS data, it is shown that these quantities lag in time in this order. This time-lag is not realized in the standard Smagorinsky model and the one-equation model because the SGS dissipation is defined so that it instantaneously adjusts to the SGS energy. In the one-equation model, the direction of the energy cascade in the initial period is opposite to that obtained in the DNS data. To retrieve correct time-lag and direction of energy transfer, we relax this instantaneous adjustment and propose the nonequilibrium Smagorinsky model. In this nonequilibrium model, the SGS energy incurred by the −7/3 spectrum is added to the base Smagorinsky energy. Assessment in actual LES shows that the time-lag predicted using the standard Smagorinsky and the one-equation models is inaccurate, whereas good agreement with the DNS data is achieved in the nonequilibrium Smagorinsky model. Extraction of the grid-scale nonequilibrium energy spectrum yields the −7/3 and −9/3 components in addition to the base −5/3 spectrum. In the nonequilibrium Smagorinsky model, continuation of the grid-scale spectra into the SGS is established for the −5/3 and −7/3 components. As a result, the unsteady energy transfer is more accurately predicted, whereas the standard Smagorinsky model does not have the SGS counterpart for the −7/3 component. Feasibility of employing the eddy-viscosity approximation to account for the transfer in the period in which −9/3 spectrum prevails is discussed.
Phase diagrams of block copolymer melts by dissipative particle dynamics simulations
Authors: Gavrilov Alexey A. , Kudryavtsev Yaroslav V. , Chertovich Alexander V.
Published: December 2013

Phase diagrams for monodisperse and polydisperse diblock copolymer melts and a random multiblock copolymer melt are constructed using dissipative particle dynamics simulations. A thorough visual analysis and calculation of the static structure factor in several hundreds of points at each of the diagrams prove the ability of mesoscopic molecular dynamics to predict the phase behavior of polymer systems as effectively as the self-consistent field-theory and Monte Carlo simulations do. It is demonstrated that the order-disorder transition (ODT) curve for monodisperse diblocks can be precisely located by a spike in the dependence of the mean square pressure fluctuation on χN, where χ is the Flory-Huggins parameter and N is the chain length. For two other copolymer types, the continuous ODTs are observed. Large polydispersity of both blocks obeying the Flory distribution in length does not shift the ODT curve but considerably narrows the domains of the cylindrical and lamellar phases partially replacing them with the wormlike micelle and perforated lamellar phases, respectively. Instead of the pure 3d-bicontinuous phase in monodisperse diblocks, which could be identified as the gyroid, a coexistence of the 3d phase and cylindrical micelles is detected in polydisperse diblocks. The lamellar domain spacing D in monodisperse diblocks follows the strong-segregation theory prediction, D/N1/2 ∼ (χN)1/6, whereas in polydisperse diblocks it is almost independent of χN at χN < 100. Completely random multiblock copolymers cannot form ordered microstructures other than lamellas at any composition.
The fluctuation-dissipation theorem for stochastic kinetics—Implications on genetic regulations
Authors: Yan Ching-Cher Sanders , Hsu Chao-Ping
Published: December 2013

The Fluctuation-Dissipation theorem (FDT) connects the “memory” in the fluctuation in equilibrium to the response of a system after a perturbation, which has been a fundamental ground in many branches of physics. When viewing a cell as a stochastic biochemical system, the cell's response under a perturbation is related to its intrinsic steady-state correlation functions via the FDT, a theorem we derived and present in this work. FDT allows us to use the noise to derive dynamic response and infer dynamic properties in the system. We tested FDT's validity with gene regulation models and found that it is limited to the linear response. For an indirect regulation pathway where unknown components may exist, FDT still works within the linear response region. Thus, FDT may be used for systems with partial knowledge, and it is potentially possible to identify the existence of unobserved components. With FDT, the dynamic response can be composed of steady-state measurements without the complete detailed knowledge for the regulation or kinetics. The response function derived can give important insights into the dynamics and time scales of the system.
Temperature dependence of the crystal-liquid interfacial free energy and the endpoint of the melting line
Authors: Baidakov Vladimir G. , Protsenko Sergey P. , Tipeev Azat O.
Published: December 2013

The crystal–liquid interfacial free energy γ has been calculated as a function of the crystal orientation in a molecular dynamics experiment in a system of Lennard-Jones (LJ) particles with a cutoff radius of the potential $r_c^* = r_c /\sigma = 6.78$rc*=rc/σ=6.78 at a triple-point temperature $T_t^* = k_B T_t /\varepsilon = 0.692$Tt*=kBTt/ɛ=0.692 and temperatures above (in the region of the stable coexistence of liquid and solid phases) and below (metastable continuation of the coexistence curve of liquid and solid phases) the temperature $T_t^* $Tt*. At $T^* = T_t^* $T*=Tt*, for determining γ use was made of the method of cleaving potential. The temperature dependence of γ on the crystal–liquid coexistence curve has been determined by the Gibbs-Cahn thermodynamic integration method. In the region of stable phase coexistence ($T^* > T_t^* $T*>Tt*) good agreement with the data of Davidchack and Laird [J. Chem. Phys. 118, 7651 (2003)] has been obtained with respect to the character of the temperature dependence of γ and the orientation anisotropy. In the region of metastable phase coexistence ($T^* < T_t^* $T*<Tt*) at the approach to the endpoint of the melting line ($T_K^* = 0.529$TK*=0.529) (the existence of which was established first by Baidakov and Protsenko [Phys. Rev. Lett. 95, 015701 (2005)]) the interfacial free energy decreases, approaching at $T^* = T_K^* $T*=TK* the orientation-averaged value $\gamma _{0K}^* = \gamma _{0K} \sigma ^{{\kern 1pt} 2} /\varepsilon = 0.365$γ0K*=γ0Kσ2/ɛ=0.365. The paper discusses the behavior of the excess interfacial energy, excess interfacial entropy and excess interfacial stress on the metastable extension of the melting line and close to $T^* = T_K^* $T*=TK*.
Logarithmic scaling in the longitudinal velocity variance explained by a spectral budget
Authors: Banerjee T. , Katul G. G.
Published: December 2013

A logarithmic scaling for the streamwise turbulent intensity \documentclass[12pt]{minimal}\begin{document}$\sigma _u^2/{{u_*}^2}=B_1-A_1\break\ln \left({z}/{\delta }\right)$\end{document}σu2/u*2=B1−A1lnz/δ was reported across several high Reynolds number laboratory experiments as predicted from Townsend's attached eddy hypothesis, where u* is the friction velocity and z is the height normalized by the boundary layer thickness δ. A phenomenological explanation for the origin of this log-law in the intermediate region is provided here based on a solution to a spectral budget where the production and energy transfer terms are modeled. The solution to this spectral budget predicts A1 = (18/55)Co/κ2/3 and B1 = (2.5)A1, where Co and κ are the Kolmogorov and von Kármán constants. These predictions hold when very large scale motions do not disturb the k−1 scaling existing across all wavenumbers 1/δ < k < 1/z in the streamwise turbulent velocity spectrum Eu(k). Deviations from a k−1 scaling along with their effects on A1 and B1 are discussed using published data and field experiments.
Three-chain B6n+14 cages as possible precursors for the syntheses of boron fullerenes
Authors: Lu Haigang , Li Si-Dian
Published: December 2013

Using the first principle methods, we proposed a series of three-chain boron cages B6n+14 (n = 1–12) which are mainly built by fusing three boron semi-double-rings. Their simple geometric structures (approximate D3 or C3 symmetry) facilitate their bottom-up syntheses from the hexagonal B7 and the double-chain boron clusters, such as B2, B4, B6, B8H2, B10H2, B12H2, and the double ring B20. The spherical shapes of these three-chain boron cages show that they could be taken as the possible precursors to further synthesize the boron fullerenes, such as B80. Therefore, these three-chain boron cages provide a possible synthesis pathway of the boron fullerenes from the experimentally synthesized small planar boron clusters.
Binding and interlayer force in the near-contact region of two graphite slabs: Experiment and theory
Authors: Gould Tim , Liu Ze , Liu Jefferson Zhe , Dobson John F. , Zheng Quanshui , Lebègue S.
Published: December 2013

Via a novel experiment, Liu et al. [Phys. Rev. B 85, 205418 (2012)] estimated the graphite binding energy, specifically the cleavage energy, an important physical property of bulk graphite. We re-examine the data analysis and note that within the standard Lennard-Jones model employed, there are difficulties in achieving internal consistency in the reproduction of the graphite elastic properties. By employing similar models which guarantee consistency with the elastic constant, we find a wide range of model dependent binding energy values from the same experimental data. We attribute some of the difficulties in the determination of the binding energy to: (i) limited theoretical understanding of the van der Waals dispersion of graphite cleavage, (ii) the mis-match between the strong bending stiffness of the graphite-SiO2 cantilever and the weak asymptotic inter-layer forces that are integrated over to produce the binding energy. We find, however, that the data do support determination of a maximum inter-layer force that is relatively model independent. We conclude that the peak force per unit area is 1.1 ± 0.15 GPa for cleavage, and occurs at an inter-layer spacing of 0.377 ± 0.013 nm.
Stress-induced transformations at low temperatures in a Ni45Co5Mn36In14 metamagnetic shape memory alloy
Authors: Niitsu K. , Xu X. , Umetsu R. Y. , Kainuma R.
Published: December 2013

The martensitic transformation behavior in a Ni45Co5Mn36In14 was investigated at low temperatures. Almost perfect superelasticity was confirmed below 200 K. The reverse transformation finishing stress monotonically decreased with decreasing temperature and the forward transformation starting stress changed from a decrease to an increase at ∼125 K. The temperature dependence of equilibrium stress had the same tendency as that of equilibrium magnetic field, allowing the thermal transformation arrest temperature to be determined. The temperature dependence of hysteresis in stress-induced transformation was also similar to that in magnetic-field-induced transformation, and the levels of dissipation energy yielded by the stress and magnetic field were intrinsically equivalent.
The role of oxygen in the uptake of deuterium in lithiated graphite
Authors: Taylor C. N. , Dadras J. , Luitjohan K. E. , Allain J. P. , Krstic P. S. , Skinner C. H.
Published: December 2013

We investigate the mechanism of deuterium retention by lithiated graphite and its relationship to the oxygen concentration through surface sensitive experiments and atomistic simulations. Deposition of lithium on graphite yielded 5%–8% oxygen surface concentration and when subsequently irradiated with D ions at energies between 500 and 1000 eV/amu and fluences over 1016 cm−2 the oxygen concentration rose to between 25% and 40%. These enhanced oxygen levels were reached in a few seconds compared to about 300 h when the lithiated graphite was allowed to adsorb oxygen from the ambient environment under equilibrium conditions. Irradiating graphite without lithium deposition, however, resulted in complete removal of oxygen to levels below the detection limit of XPS (e.g., <1%). These findings confirm the predictions of atomistic simulations, which had concluded that oxygen was the primary component for the enhanced hydrogen retention chemistry on the lithiated graphite surface.
Spatial distribution of the electrical conductivity in highly filled polymers: Experiment, modeling, and application to bipolar plates
Authors: Planes E. , Gloaguen F. , Albérola N. , Flandin L.
Published: December 2013

A large variety of composites for electrical applications are developed worldwide on a daily basis. Most of these materials are made from carbonaceous fillers dispersed in polymers. The optimization of the formulations is complex and depends on parameters that are difficult to identify ab initio. The results might also be very sensitive to the processing conditions. There is therefore a need for a fast and accurate method to measure the electrical properties of samples with unfamiliar geometric features and without altering their shape. A four point probes method is incremented that fulfills all the above mentioned requirements. An analytical model is proposed that extends Uhlirs theory and permits to quickly determine the resistivity distribution. Experimental and theoretical approaches were performed to validate the method. An example is proposed with the measurement of samples initially designed for fuel cell-bipolar plates-application.
In-growth of an electrically active defect in high-purity silicon after proton irradiation
Authors: Nylandsted Larsen A. , Juul Pedersen H. , Christian Petersen M. , Privitera V. , Gurimskaya Y. , Mesli A.
Published: December 2013

Defect-related energy levels in the lower half of the band gap of silicon have been studied with transient-capacitance techniques in high-purity, carbon and oxygen lean, plasma-enhanced chemical-vapor deposition grown, n-and p-type silicon layers after 2-MeV proton irradiations at temperatures at or just below room temperature. The in-growth of a distinct line in deep-level transient spectroscopy spectra, corresponding to a level in the band gap at EV + 0.357 eV where EV is the energy of the valence band edge, takes place for anneal temperatures at around room temperature with an activation energy of 0.95 ± 0.08 eV. The line disappears at an anneal temperature of around 450 K. The corresponding defect is demonstrated not to contain boron, carbon, oxygen, or phosphorus. Possible defect candidates are discussed.
Polarization dependent color switching by extra-ordinary transmission in H-slit plasmonic metasurface
Authors: Mandal P. , Anantha Ramakrishna S. , Patil Raj , Venu Gopal Achanta
Published: December 2013

An array of H-shaped subwavelength slits in a plasmonic film has a polarization dependent extra-ordinary transmission due to shape anisotropy. Non-overlapping extra-ordinary transmission bands for the orthogonal linear polarization states of the input light are used to demonstrate a polarization dependent color switch. The fabricated array of submicron sized H-slits on a gold film displayed two transmission bands for the linear x- and y-polarized light at visible (650–850 nm) and near-infra-red (1150–1450 nm) bands, respectively. The relative transmitted light in these two bands can be controlled by changing the linear polarization state of the input radiation from 0° to 90°.
Development of spectrally selective imaging system for negative hydrogen ion source
Authors: Ikeda K. , Nakano H. , Tsumori K. , Kisaki M. , Nagaoka K. , Osakabe M. , Takeiri Y. , Kaneko O.
Published: December 2013

A spectrally selective imaging system has been developed to obtain a distribution of Hα emissions at the extraction region in a hydrogen negative ion source. The diagnostic system consisted of an aspherical lens, optical filters, a fiber image conduit, and a charge coupled device detector was installed on the 1/3-scaled hydrogen negative ion source in the National Institute for Fusion Science. The center of sight line passes beside the plasma grid (PG) surface with the distance of 11 mm, and the viewing angle has coverage 35 mm from the PG surface. Two dimensional Hα distribution in the range up to 20 mm from the PG surface was clearly observed. The reduction area for Hα emission caused by beam extraction was widely distributed in the extraction region near the PG surface.
Effect of reduction of trap charge carrier density in organic field effect transistors by surface treatment of dielectric layer
Authors: Dagar Janardan , Yadav Vandana , Tyagi Priyanka , Kumar Singh Rajiv , Suman C. K. , Srivastava Ritu
Published: December 2013

In this work, we have studied the effect of surface treatment of SiO2 dielectric layer on the reduction of the trap charge carrier density at dielectric/semiconducting interface by fabricating a metal–insulator–semiconductor (MIS) device using α, ω-dihexylcarbonylquaterthiophene as semiconducting layer. SiO2 dielectric layer has been treated with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) to modify the chemical group acting as charge traps. Capacitance-voltage measurements have been performed on MIS devices fabricated on SiO2 and HMDS treated SiO2. These data have been used for the calculation of trap charge carrier density and Debye length at the dielectric-semiconductor interface. The calculated trap charge carrier density has been found to reduce from (2.925 ± 0.049) × 1016 cm−3 to (2.025 ± 0.061) × 1016 cm−3 for the MIS device with HMDS treated SiO2 dielectric in comparison to that of untreated SiO2. Next, the effect of reduction in trap charge carrier density has been studied on the performance of organic field effect transistors. The improvement in the device parameters like mobility, on/off ratio, and gate leakage current has been obtained with the effect of the surface treatment. The charge carrier mobility has been improved by a factor of 2 through this treatment. Further, the influence of the treatment was observed by atomic force microscope and Fourier transform infrared spectroscopy techniques.
Room-temperature perpendicular magnetic anisotropy of MgO/Fe/MgO ultrathin films
Authors: Kozioł-Rachwał A. , Skowroński W. , Ślęzak T. , Wilgocka-Ślęzak D. , Przewoźnik J. , Stobiecki T. , Qin Q. H. , van Dijken S. , Korecki J.
Published: December 2013

We used the anomalous Hall effect to study the magnetic properties of MgO/Fe(t)/MgO(001) structures in which the Fe thickness t ranged from 4 Å to 14 Å. For the iron deposited at 140 K, we obtained perpendicular magnetization at room temperature below the critical thickness of tc = (9 ± 1) Å. In the vicinity of tc, the easy magnetization axis switched from an out-of-plane orientation to an in-plane orientation, and the observed spin-reorientation transition was considered in terms of the competition among different anisotropies. The perpendicular magnetization direction was attributed to magnetoelastic anisotropy. Finally, the temperature-dependent spin-reorientation transition was analyzed for Fe thicknesses close to tc.
Communication: A new paradigm for structure prediction in multicomponent systems
Authors: Schebarchov D. , Wales D. J.
Published: December 2013

We analyse the combinatorial aspect of global optimisation for multicomponent systems, which involves searching for the optimal chemical ordering by permuting particles corresponding to different species. The overall composition is presumed fixed, and the geometry is relaxed after each permutation in order to relieve local strain. From ideas used to solve graph partitioning problems we devise a deterministic search scheme that outperforms (by orders of magnitude) conventional and self-guided basin-hopping global optimisation. The search is guided by the energy gain from either swapping particles i and j (ΔEij) or changing the identity of particles i (ΔEi). These quantities are derived from the underlying (arbitrary) energy function, hence not constituting external bias, and for site-separable force fields each ΔEi can be approximated simply and efficiently. In our self-guided variant of basin-hopping, particles are weighted by an approximate ΔEi when randomly selected for an exchange, yielding a significant improvement for segregated multicomponent systems with modest particle size mismatch.
Preplasma effects on the generation of high-energy protons in ultraintense laser interaction with foil targets
Authors: Zheng F. L. , Wu S. Z. , Zhang H. , Huang T. W. , Yu M. Y. , Zhou C. T. , He X. T.
Published: December 2013

It is shown that the intense quasistatic electric and magnetic fields self-generated near the axis of the laser-driven channel in an appropriately profiled preplasma during ultraintense laser interaction with a thin target can create dense relativistic electron bunches. The latter easily penetrate through the target and can greatly enhance the sheath field at the rear, resulting in significant increase in the laser-to-ion energy conversion efficiency and the maximum energy of the target normal sheath accelerated ions. Particle-in-cell simulations show that with a hydrogen targets a proton beam of peak energy ∼38 MeV and energy conversion efficiency ≥6.5% can be produced by a linearly polarized 5 × 1019 W/cm2 laser. An analytical model is also proposed and its results agree well with those of the simulations.
Magnetization damping of an L1-FeNi thin film with perpendicular magnetic anisotropy
Authors: Ogiwara Misako , Iihama Satoshi , Seki Takeshi , Kojima Takayuki , Mizukami Shigemi , Mizuguchi Masaki , Takanashi Koki
Published: December 2013

We studied on the magnetic damping constants (α) for L10-FeNi and disordered FeNi employing three kinds of measurement methods. An L10-FeNi thin film exhibited high perpendicular magnetic anisotropy of 7.1 × 106 erg cm−3. At magnetic fields (H) lower than 2 kOe, α was estimated to be 0.091 ± 0.003. However, it was reduced down to 0.013 ± 0.001 with H, indicating that extrinsic contributions enhance α. The intrinsic α = 0.013 ± 0.001 was comparable to α = 0.009 ± 0.002 for the disordered FeNi. This suggests that L10-FeNi is a candidate achieving high magnetic anisotropy and low magnetization damping simultaneously.
Elevated temperature dependent transport properties of phosphorus and arsenic doped zinc oxide thin films
Authors: Cai B. , Nakarmi M. L. , Oder T. N. , McMaster M. , Velpukonda N. , Smith A.
Published: December 2013

Elevated temperature dependent Hall effect measurements were performed in a wide temperature range from 80 to 800 K to study transport properties of zinc oxide (ZnO) thin films heavily doped with phosphorus (P) and arsenic (As), and grown on sapphire substrates by RF magnetron sputtering. Double thermal activation processes in both P- and As-doped ZnO thin films with small activation energy of ∼0.04 eV and large activation energy of ∼0.8 eV were observed from variable temperature Hall effect measurements. The samples exhibited n-type conductivities throughout the temperature range. Based on photoluminescence measurements at 11 K and theoretical results, the large activation energy observed in the temperature dependent Hall effect measurement has been assigned to a deep donor level, which could be related to oxygen vacancy (VO) in the doped ZnO thin films.
Influences of semiconductor morphology on the mechanical fatigue behavior of flexible organic electronics
Authors: Lee Young-Joo , Uk Lee Yong , Yeon Han-Wool , Shin Hae-A-Seul , Evans Louise A. , Joo Young-Chang
Published: December 2013

The influence of crystalline morphology on the mechanical fatigue of organic semiconductors (OSCs) was investigated using 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) as a crystalline OSC and poly(triarylamine) (PTAA) as an amorphous OSC. During cyclic bending, resistances of the OSCs were monitored using the transmission-line method on a metal-semiconductor-metal structure. The resistance of the TIPS-pentacene increased under fatigue damage in tensile-stress mode, but no such degradation was observed in the PTAA. Both OSCs were stable under compressive bending fatigue. The formation of intergranular cracks at the domain boundaries of the TIPS-pentacene was responsible for the degradation of its electrical properties under tensile bending fatigue.
Shape of isolated domains in lithium tantalate single crystals at elevated temperatures
Authors: Shur V. Ya. , Akhmatkhanov A. R. , Chezganov D. S. , Lobov A. I. , Baturin I. S. , Smirnov M. M.
Published: December 2013

The shape of isolated domains has been investigated in congruent lithium tantalate (CLT) single crystals at elevated temperatures and analyzed in terms of kinetic approach. The obtained temperature dependence of the growing domain shape in CLT including circular shape at temperatures above 190 °C has been attributed to increase of relative input of isotropic ionic conductivity. The observed nonstop wall motion and independent domain growth after merging in CLT as opposed to stoichiometric lithium tantalate have been attributed to difference in wall orientation. The computer simulation has confirmed applicability of the kinetic approach to the domain shape explanation.
A monolithic polarization-independent frequency-filter system for filtering of photon pairs
Authors: Ahlrichs Andreas , Berkemeier Christoph , Sprenger Benjamin , Benson Oliver
Published: December 2013

We set up a long-term stable filtering system that consists of cascaded monolithic Fabry-Pérot filters to enhance the suppression and free spectral range. An effective free spectral range of hundreds of GHz allows the system to be used as a high resolution monochromator, with a linewidth of 192 MHz. As an important application a single mode is filtered from photon pairs generated by a parametric down-conversion source, and their indistinguishability is proven by measuring the Hong-Ou-Mandel effect with a visibility of 96%. We report that undesired birefringence, which is often encountered with monolithic cavities, can be avoided by stress-free mounting.
Microfluidic device for generating a stepwise concentration gradient on a microwell slide for cell analysis
Authors: Weibull Emilie , Matsui Shunsuke , Sakai Manabu , Andersson Svahn Helene , Ohashi Toshiro
Published: December 2013

Understanding biomolecular gradients and their role in biological processes is essential for fully comprehending the underlying mechanisms of cells in living tissue. Conventional in vitro gradient-generating methods are unpredictable and difficult to characterize, owing to temporal and spatial fluctuations. The field of microfluidics enables complex user-defined gradients to be generated based on a detailed understanding of fluidic behavior at the μm-scale. By using microfluidic gradients created by flow, it is possible to develop rapid and dynamic stepwise concentration gradients. However, cells exposed to stepwise gradients can be perturbed by signals from neighboring cells exposed to another concentration. Hence, there is a need for a device that generates a stepwise gradient at discrete and isolated locations. Here, we present a microfluidic device for generating a stepwise concentration gradient, which utilizes a microwell slide's pre-defined compartmentalized structure to physically separate different reagent concentrations. The gradient was generated due to flow resistance in the microchannel configuration of the device, which was designed using hydraulic analogy and theoretically verified by computational fluidic dynamics simulations. The device had two reagent channels and two dilutant channels, leading to eight chambers, each containing 4 microwells. A dose-dependency assay was performed using bovine aortic endothelial cells treated with saponin. High reproducibility between experiments was confirmed by evaluating the number of living cells in a live-dead assay. Our device generates a fully mixed fluid profile using a simple microchannel configuration and could be used in various gradient studies, e.g., screening for cytostatics or antibiotics.