bluuebunny/crossref_metadata_2025 huggingface dataset:
Voluntary Emotion Suppression Modifies Psychophysiological Responses to Films
Authors: Reynaud Emmanuelle , El-Khoury-Malhame Myriam , Blin Olivier , Khalfa Stéphanie
Published: July 2012

A fundamental aspect of successful social interaction is the fact people do not always experience or express emotions to their fullest extent but instead control them in a context-dependent manner. Emotion regulation involves the manipulation of subjective experience, behavior, and physiology. Previous researches have studied autonomic nervous system (ANS) responses during emotion regulation using only positive and negative stimuli without distinguishing between emotions, or it has focused on one specific emotion. Given the differences of ANS reactions to different categories of emotional stimuli, our study aims at comparing the physiological activity during emotion attending and emotion suppression using specific and distinct categories of emotions. Fifty subjects were presented with five films, inducing one of five emotions: happiness, sadness, fear, peacefulness, and disgust. While viewing the films, participants were instructed to perform an attending and a suppression task. We evaluated the following physiological measures as participants engaged in these tasks: skin conductance response (SCR), heart rate (HR), and activity of zygomatic and corrugator muscles. Performing a suppression task when viewing the happy and disgusting film clips resulted in diminished, respectively, zygomatic and corrugator muscle activities. Emotion regulation leads to a lower HR when viewing the happy film, and a higher SCR when viewing the fear-inducing film. The effects of emotional control on EMG and HR are observed on the emotions that drive the most important physiological changes in the noncontrol setting, while the increased SCR for the fear-inducing film indicates that the conscious and volitional regulation of emotion has selective effect on fear emotion as compared to happiness, disgust, sadness, and peacefulness.
The Relationship Between Valence, Task Difficulty, and the COMT Val 158 Met Polymorphism in Disengagement Processes
Authors: Gschwendtner Kathrin M. , Biehl Stefanie C. , Mühlberger Andreas , Sommer Claudia , Kübler Andrea , Reif Andreas , Herrmann Martin J.
Published: July 2012

The catechol-O-methyltransferase (COMT) Val158Met polymorphism (rs4680) moderates dopamine degradation in the prefrontal cortex. It has been shown that the Met allele is associated with an increased reactivity to negative stimuli. With regard to the tonic-phasic dopamine model it is hypothesized that this increased reactivity to negative stimuli derives from deficient disengagement from negative stimuli. The aim of this study was therefore to investigate whether this increased reactivity is reflected in prolonged disengagement from negative pictures. We used a novel forced spatial disengagement task in combination with eye tracking. This paradigm allows for varying task difficulty. Interestingly, contrary to our hypothesis, we found increased disengagement latencies for negative pictures in homozygous Val allele carriers compared to heterozygous participants. This effect was only seen in task conditions demanding less cognitive resources (prosaccade condition). We suggest that the COMT effect on emotional processing is task-specific and therefore heterosis effects can occur.
Influence of the airflow speed along transmission lines on the DC corona discharge loss, using finite element approach
Authors: Shemshadi A. , Niayesh K. , Akbari A.
Published: July 2012

Corona discharge is of great interest from the physical point of view and due to its numerous practical applications in industry and especially one of the most important sources of loss in the high voltage transmission lines. This paper provides guidelines for the amount of electric loss caused by corona phenomenon occurred around a DC high voltage wire placed between two flat plates and influence of wind speed rate on the amount of corona loss using COMSOL Multiphysics. So electric potential distribution patterns and charge density diffusion around the wire are studied in this article.
Enhancing the locality of optical interrogation with photonic-crystal fibers
Authors: Doronina-Amitonova Lyubov V. , Fedotov Il’ya V. , Ivashkina Olga I. , Zots Marina A. , Fedotov Andrei B. , Anokhin Konstantin V. , Zheltikov Aleksei M.
Published: July 2012

Small-core photonic-crystal fibers (PCFs) are shown to enhance the locality of optical interrogation in fiber-probe-based imaging. We demonstrate that, in a typical fluorescence imaging experiment, the longitudinal dimension of the interrogated region closely follows the amtan−1θd scaling with the effective mode radius am and the beam-divergence angle θd. The confinement of optical interrogation provided by small-core, high-index-step PCF probes is high enough to enable interrogation of individual neurons in a typical brain imaging experiment.
Electron transfer beyond the static picture: A TDDFT/TD-ZINDO study of a pentacene dimer
Authors: Reslan Randa , Lopata Kenneth , Arntsen Christopher , Govind Niranjan , Neuhauser Daniel
Published: July 2012

We use time-dependent density functional theory and time-dependent ZINDO (a semi-empirical method) to study transfer of an extra electron between a pair of pentacene molecules. A measure of the electronic transfer integral is computed in a dynamic picture via the vertical excitation energy from a delocalized anionic ground state. With increasing dimer separation, this dynamical measurement of charge transfer is shown to be significantly larger than the commonly used static approximation (i.e., LUMO+1–LUMO of the neutral dimer, or HOMO–LUMO of the charged dimer), up to an order of magnitude higher at 6 Å. These results offer a word of caution for calculations involving large separations, as in organic photovoltaics, where care must be taken when using a static picture to model charge transfer.
Fermi level tuning using the Hf-Ni alloy system as a gate electrode in metal-oxide-semiconductor devices
Authors: Avner Rothschild Jonathan , Cohen Aya , Brusilovsky Anna , Kornblum Lior , Kauffmann Yaron , Amouyal Yaron , Eizenberg Moshe
Published: July 2012

Hf-Ni alloys are studied as a gate electrode for metal-oxide-semiconductor devices. The Hf-Ni solid-state amorphization couple encompasses several metallurgical phenomena which are investigated at the nanoscale and are correlated with the macroscopic electrical properties of devices. The dependence of the Fermi level position on the alloy composition is studied both on SiO2 and on HfO2. In order to isolate the effects of interfacial and dielectric charges and dipoles, the dependence of the vacuum work-function values on the composition is also studied. The Fermi level positions of the alloys do not depend linearly on the average composition of the alloys and are strongly affected by Hf enrichment at the HfNix/dielectric interface and the HfNix surface. We note a constant shift of 0.4 eV in the Fermi level position on HfO2 compared to SiO2. In addition, characterization of the composition, structure, and morphology reveals Kirkendall voids formation when the bottom layer consists of Ni, and an oxygen-scavenging effect when the bottom layer is Hf.
Rotational spectra of rare isotopic species of fluoroiodomethane: Determination of the equilibrium structure from rotational spectroscopy and quantum-chemical calculations
Authors: Puzzarini Cristina , Cazzoli Gabriele , López Juan Carlos , Alonso José Luis , Baldacci Agostino , Baldan Alessandro , Stopkowicz Stella , Cheng Lan , Gauss Jürgen
Published: July 2012

Supported by accurate quantum-chemical calculations, the rotational spectra of the mono- and bi-deuterated species of fluoroiodomethane, CHDFI and CD2FI, as well as of the 13C-containing species, 13CH2FI, were recorded for the first time. Three different spectrometers were employed, a Fourier-transform microwave spectrometer, a millimeter/submillimter-wave spectrometer, and a THz spectrometer, thus allowing to record a huge portion of the rotational spectrum, from 5 GHz up to 1.05 THz, and to accurately determine the ground-state rotational and centrifugal-distortion constants. Sub-Doppler measurements allowed to resolve the hyperfine structure of the rotational spectrum and to determine the complete iodine quadrupole-coupling tensor as well as the diagonal elements of the iodine spin-rotation tensor. The present investigation of rare isotopic species of CH2FI together with the results previously obtained for the main isotopologue [C. Puzzarini, G. Cazzoli, J. C. López, J. L. Alonso, A. Baldacci, A. Baldan, S. Stopkowicz, L. Cheng, and J. Gauss, J. Chem. Phys. 134, 174312 (2011);10.1063/1.3583498 G. Cazzoli, A. Baldacci, A. Baldan, and C. Puzzarini, Mol. Phys. 109, 2245 (2011)]10.1080/00268976.2011.609142 enabled us to derive a semi-experimental equilibrium structure for fluoroiodomethane by means of a least-squares fit procedure using the available experimental ground-state rotational constants together with computed vibrational corrections. Problems related to the missing isotopic substitution of fluorine and iodine were overcome thanks to the availability of an accurate theoretical equilibrium geometry (computed at the coupled-cluster singles and doubles level augmented by a perturbative treatment of triple excitations).
Unitary group adapted state-specific multi-reference coupled cluster theory: Formulation and pilot numerical applications
Authors: Maitra Rahul , Sinha Debalina , Mukherjee Debashis
Published: July 2012

We present the formulation and the implementation of a spin-free state-specific multi-reference coupled cluster (SSMRCC) theory, realized via the unitary group adapted (UGA) approach, using a multi-exponential type of cluster expansion of the wave-operator Ω. The cluster operators are defined in terms of spin-free unitary generators, and normal ordered exponential parametrization is utilized for cluster expansion instead of pure exponentials. Our Ansatz for Ω is a natural spin-free extension of the spinorbital based Jeziorski-Monkhorst (JM) Ansatz. The normal ordered cluster Ansatz for Ω results in a terminating series of the direct term of the MRCC equations, and it uses ordinary Wick algebra to generate the working equations in a straightforward manner. We call our formulation as UGA-SSMRCC theory. Just as in the case of the spinorbital based SSMRCC theory, there are redundancies in the cluster operators, which are exploited to ensure size-extensivity and avoidance of intruders via suitable sufficiency conditions. Although there already exists in the literature a spin-free JM-like Ansatz, introduced by Datta and Mukherjee, its structure is considerably more complex than ours. The UGA-SSMRCC offers an easier access to spin-free MRCC formulation as compared to the Datta-Mukherjee Ansatz, which at the same time provides with quite accurate description of electron correlation. We will demonstrate the efficacy of the UGA-SSMRCC formulation with a set of numerical results. For non-singlet cases, there is pronounced Ms dependence of the energy for the spinorbital based SSMRCC results. Although Ms = 1 results are closer to full configuration interaction (FCI), the extent of spin-contamination is more. In most of the cases, our UGA-SSMRCC results are closer to FCI than the spinorbital Ms = 0 results.
The Hamilton-Pontryagin principle and multi-Dirac structures for classical field theories
Authors: Vankerschaver J. , Yoshimura H. , Leok M.
Published: July 2012

We introduce a variational principle for field theories, referred to as the Hamilton-Pontryagin principle, and we show that the resulting field equations are the Euler-Lagrange equations in implicit form. Second, we introduce multi-Dirac structures as a graded analog of standard Dirac structures, and we show that the graph of a multisymplectic form determines a multi-Dirac structure. We then discuss the role of multi-Dirac structures in field theory by showing that the implicit Euler-Lagrange equations for fields obtained from the Hamilton-Pontryagin principle can be described intrinsically using multi-Dirac structures. Finally, we show a number of illustrative examples, including time-dependent mechanics, nonlinear scalar fields, Maxwell's equations, and elastostatics.
Critical appraisal of excited state nonadiabatic dynamics simulations of 9H-adenine
Authors: Barbatti Mario , Lan Zhenggang , Crespo-Otero Rachel , Szymczak Jaroslaw J. , Lischka Hans , Thiel Walter
Published: July 2012

In spite of the importance of nonadiabatic dynamics simulations for the understanding of ultrafast photo-induced phenomena, simulations based on different methodologies have often led to contradictory results. In this work, we proceed through a comprehensive investigation of on-the-fly surface-hopping simulations of 9H-adenine in the gas phase using different electronic structure theories (ab initio, semi-empirical, and density functional methods). Simulations that employ ab initio and semi-empirical multireference configuration interaction methods predict the experimentally observed ultrafast deactivation of 9H-adenine with similar time scales, however, through different internal conversion channels. Simulations based on time-dependent density functional theory with six different hybrid and range-corrected functionals fail to predict the ultrafast deactivation. The origin of these differences is analyzed by systematic calculations of the relevant reaction pathways, which show that these discrepancies can always be traced back to topographical features of the underlying potential energy surfaces.
Invited Review Article: Technology for Attosecond Science
Authors: Frank F. , Arrell C. , Witting T. , Okell W. A. , McKenna J. , Robinson J. S. , Haworth C. A. , Austin D. , Teng H. , Walmsley I. A. , Marangos J. P. , Tisch J. W. G.
Published: July 2012

We describe a complete technological system at Imperial College London for Attosecond Science studies. The system comprises a few-cycle, carrier envelope phase stabilized laser source which delivers sub 4 fs pulses to a vibration-isolated attosecond vacuum beamline. The beamline is used for the generation of isolated attosecond pulses in the extreme ultraviolet (XUV) at kilohertz repetition rates through laser-driven high harmonic generation in gas targets. The beamline incorporates: interferometers for producing pulse sequences for pump-probe studies; the facility to spectrally and spatially filter the harmonic radiation; an in-line spatially resolving XUV spectrometer; and a photoelectron spectroscopy chamber in which attosecond streaking is used to characterize the attosecond pulses. We discuss the technology and techniques behind the development of our complete system and summarize its performance. This versatile apparatus has enabled a number of new experimental investigations which we briefly describe.
Universal scaling behaviour of surface tension of molecular chains
Authors: Blas F. J. , Martínez-Ruiz F. J. , Moreno-Ventas Bravo A. I. , MacDowell L. G.
Published: July 2012

We use and extend the universal relationship recently proposed by Galliero [G. Galliero, J. Chem. Phys. 133, 074705 (2010)], based on a combination of the corresponding-states principle of Guggenheim [E. A. Guggenheim, J. Chem. Phys. 13, 253 (1945)10.1063/1.1724033] and the parachor approach of Macleod [J. Macleod, Trans. Faraday Soc. 19, 38 (1923)10.1039/tf9231900038], to predict the vapour-liquid surface tension of fully flexible chainlike Lennard-Jones molecules. In the original study of Galliero, the reduced surface tension of short-chain molecules formed by up to five monomers is expressed as a unique function of the difference between the liquid and vapour coexistence densities. In this work, we extend the applicability of the recipe and demonstrate that it is also valid for predicting the surface tension of two different chainlike molecular models, namely, linear tangent chains that interact through the Lennard-Jones intermolecular potential and fully flexible chains formed by spherical segments interacting through the square-well potential. Computer simulation data for vapour-liquid surface tension of fully flexible and rigid linear Lennard-Jones, and fluid flexible square-well chains is taken from our previous works. Our results indicate that the universal scaling relationship is able to correlate short- and long-chain molecules with different degrees of flexibility and interacting through different intermolecular potentials.
Structural correlations and cooperative dynamics in supercooled liquids
Authors: Singh Murari , Agarwal Manish , Dhabal Debdas , Chakravarty Charusita
Published: July 2012

The relationships between diffusivity and the excess, pair and residual multiparticle contributions to the entropy are examined for Lennard-Jones liquids and binary glassformers, in the context of approximate inverse power law mappings of simple liquids. In the dense liquid where diffusivities are controlled by collisions and cage relaxations, Rosenfeld-type excess entropy scaling of diffusivities is found to hold for both crystallizing as well as vitrifying liquids. The crucial differences between the two categories of liquids emerge only when local cooperative effects in the dynamics result in significant caging effects in the time-dependent behaviour of the single-particle mean square displacement. In the case of glassformers, onset of such local cooperativity coincides with onset of deviations from Rosenfeld-type excess entropy scaling of diffusivities and increasing spatiotemporal heterogeneity. In contrast, for two- and three-dimensional liquids with a propensity to crystallise, the onset of local cooperative dynamics is sufficient to trigger crystallization provided that the liquid is sufficiently supercooled that the free energy barrier to nucleation of the solid phase is negligible. The state points corresponding to onset of transient caging effects can be associated with typical values, within reasonable bounds, of the excess, pair, and residual multiparticle entropy as a consequence of the isomorph-invariant character of the excess entropy, diffusivity and related static and dynamic correlation functions.
Recombination mechanisms in heteroepitaxial non-polar InGaN/GaN quantum wells
Authors: Badcock T. J. , Hao R. , Moram M. A. , Kappers M. J. , Dawson P. , Oliver R. A. , Humphreys C. J.
Published: July 2012

We report on the low temperature photoluminescence and photoluminescence excitation spectroscopy of non-polar InGaN/GaN multiple quantum well (QW) structures, grown on r-plane sapphire, containing average indium concentrations of 3%, 4.5%, and 6.5%. In the sample with the lowest indium content, two distinct emission processes are identified which are attributed to recombination from planar areas of the QWs and regions of the QWs intersected by basal-plane stacking faults (BSFs). The marked reduction in the strength of the QW exciton observed in the excitation spectra when detecting BSF-related emission is attributed to the electronic disorder in the QW due to alloy potential fluctuations which inhibits exciton transfer from the planar regions of the QW. The magnitude of this disorder increases rapidly with increasing indium fraction as is evidenced by the progressive broadening of the emission and absorption features.
Analysis of the radiative lifetime of Pr3+ d-f emission
Authors: Zych Aleksander , de Lange Matthijs , de Mello Donegá Celso , Meijerink Andries
Published: July 2012

The radiative lifetime of excited states is governed by Fermi’s Golden Rule. For many applications, the radiative decay rate is an important parameter. For example, for scintillators materials in PET scanners, a short response time is crucial and it has been realized that the d-f emission of Pr3+ is faster than for the widely applied d-f emission from Ce3+. In this paper, the radiative decay rate of d-f emission from Pr3+ is systematically investigated in a wide variety of host lattices, including scintillators materials. The variation in the decay rate is analyzed based on Fermi’s Golden Rule. The trend observed is best described using a full cavity model to correct for local-field effects and a λ3 factor to account for the energy of the transition. Still, there is a considerable scatter of the experimental data around the best fit to these data. The variation is explained by uncertainties in the refractive indices and a variation in the transition dipole moment of the d-f transition for Pr3+. Based on the results, the shortest radiative lifetime that can be achieved for Pr3+ d-f emission is predicted to be ∼6 ns.
Electronic structure of C2N2X (X = O, NH, CH2): Wide band gap semiconductors
Authors: Takarabe Kenichi , Sougawa Masaya , Kariyazaki Hiroaki , Sueoka Koji
Published: July 2012

The electronic structure of IV2V2VI class semiconductors, C2N2X (X = O, NH, CH2), was investigated using first principles calculations. The crystal structures of C2N2X are isostructural with the Si2N2O compound, sinoite. The valence of the X atom is virtually two, and thus the substitution of X (X = O, NH, CH2) is isoelectronic. From the calculated density of states, the carbon 2 p orbital does not participate in the upper valence band (VB) (0 to –5 eV). The upper valence band is dominated by the N 2 p and X 2 p orbitals. The calculated optical absorption edge shifts to a lower energy as the substitution progresses from the O atom to the CH2 group. The calculated absorption edge is 7.76, 7.07, and 6.66 eV for C2N2O, C2N2(NH), and C2N2(CH2), respectively.
Mean field theory for a reversibly crosslinked polymer network
Authors: Li Daming , Gruhn Thomas , Emmerich Heike
Published: July 2012

We present a mean field theory for melts and solutions of reversibly crosslinked polymers. In our model, crosslinks are considered as local bonds between two monomers. For a blend of A+B+AB polymers, we assume reversible crosslinks between the copolymers AB with a crosslink strength z and interaction weights ωA and ωB for monomers of type A and B, respectively. The usual mean field model for polymer blends without reversible crosslinks is recovered if z vanishes. With or without crosslinks, the A+B+AB blend can form a lamellar phase with A and B rich regions. If reversible crosslinks are enabled and ωA differs strongly from ωB, the lamellar nanophase separation of A and B monomers is accompanied by a similar segregation of crosslinked and noncrosslinked polymers. If ωA and ωB are equal, crosslinked copolymers are well mixed with the homopolymers. For a homopolymer solution with reversible crosslinks between the polymers, our calculations show that polymers and solvent molecules are separated macroscopically if the Flory-Huggins interaction parameter and the crosslink strength are suitably high or if the volume fraction of polymers or the chain length are suitably low.
Transmission crystal x-ray spectrometer covering the 6 keV–18 keV energy range with E/ΔE = 1800 instrumental resolving power
Authors: Seely John , Feldman Uri , Brown Charles , Pereira Nino , Hudson Lawrence , Glover Jack , Silver Eric
Published: July 2012

A high-resolution x-ray spectrometer utilizing a thin quartz transmission crystal and covering the 6 keV–18 keV energy range has been developed and tested. The spectrometer consists of a cylindrically bent crystal in a vacuum housing. The crystal position and the range of Bragg angles that are incident on the crystal can be adjusted to record an ≈4 keV wide spectrum in the 6 keV–18 keV range. The spectrometer is of the Cauchois type and has a compact linear geometry that is convenient for deployment at laser-produced plasma, EBIT, and other x-ray sources. Test spectra of the W L and Mo K lines from laboratory sources have linewidths as small as 11 eV, approaching the natural widths, and instrumental resolving power as high as 1800. Techniques for enhancing the energy resolution are experimentally demonstrated.
$\mathcal {N}=2$
N
=
2
supersymmetric extension of l-conformal Galilei algebra
Authors: Masterov Ivan
Published: July 2012

\documentclass[12pt]{minimal}\begin{document}$\mathcal {N}=2$\end{document} N = 2 supersymmetric extension of the l-conformal Galilei algebra is constructed. A relation between its representations in flat spacetime and in Newton-Hooke spacetime is discussed. An infinite-dimensional generalization of the superalgebra is given.
Riemann-Hilbert approach and N-soliton formula for coupled derivative Schrödinger equation
Authors: Guo Boling , Ling Liming
Published: July 2012

The coupled derivative Schrödinger equation is studied in the framework of the Riemann-Hilbert problem and a compact N-soliton solution formula is found. Taking advantage of this result, some properties for single soliton solution and asymptotic analysis of N-soliton solution are explored. As a by-product, a coupled Fokas-Lenells equation together its N-soliton solution is presented.
Quantum Painlevé-Calogero correspondence for Painlevé VI
Authors: Zabrodin A. , Zotov A.
Published: July 2012

This paper is a continuation of our previous paper where the Painlevé-Calogero correspondence has been extended to auxiliary linear problems associated with Painlevé equations. We have proved, for the first five equations from the Painlevé list, that one of the linear problems can be recast in the form of the non-stationary Schrödinger equation whose Hamiltonian is a natural quantization of the classical Calogero-like Hamiltonian for the corresponding Painlevé equation. In the present paper we establish the quantum Painlevé-Calogero correspondence for the most general case, the Painlevé VI equation. We also show how the desired special gauge and the needed choice of variables can be derived starting from the corresponding Schlesinger system with rational spectral parameter.
Structural, thermodynamical, and dynamical properties of oligomers formed by the amyloid NNQQ peptide: Insights from coarse-grained simulations
Authors: Lu Yan , Wei Guanghong , Derreumaux Philippe
Published: July 2012

Characterizing the early formed oligomeric intermediates of amyloid peptides is of particular interest due to their links with neurodegenerative diseases. Here we study the NNQQ peptide, known to display parallel β-strands in amyloid fibrils by x-ray microcrystallography, and investigate the structural, thermodynamical, and dynamical properties of 20 NNQQ peptides using molecular dynamics and replica exchange molecular dynamics simulations coupled to a coarse-grained force field. All simulations are initiated from randomized and fully dispersed monomeric conformations. Our simulations reveal that the phase transition is characterized by a change in the oligomer and β-sheet size distributions and the percentage of mixed parallel/antiparallel β-strands when the sheets are formed. At all temperatures, however, the fraction of parallel β-strands remains low, though there are many association/fragmentation events. This work and a growing body of computational studies provide strong evidence that the critical nucleus goes beyond 20 chains and reordering of the β-strands occurs in larger oligomers.
Loading device effect on protein unfolding mechanics
Authors: Yoon Gwonchan , Na Sungsoo , Eom Kilho
Published: July 2012

Single-molecule mechanical manipulation has enabled quantitative understanding of not only the kinetics of both bond rupture and protein unfolding, but also the free energy landscape of chemical bond and/or protein folding. Despite recent studies reporting the role of loading device in bond rupture, a loading device effect on protein unfolding mechanics has not been well studied. In this work, we have studied the effect of loading-device stiffness on the kinetics of both bond rupture and protein unfolding mechanics using Brownian dynamics simulations. It is shown that bond rupture forces are dependent on not only loading rate but also the stiffness of loading device, and that protein unfolding mechanics is highly correlated with the stiffness of loading device. Our study sheds light on the importance of loading device effect on the mechanically induced bond ruptures and protein unfolding.
Translocation of nanoparticles through a polymer brush-modified nanochannel
Authors: Cao Qianqian , Zuo Chuncheng , Li Lujuan , Li Yingjie , Yang Yang
Published: July 2012

A basic understanding of the transport mechanisms of nanostructures in a polymer brush-modified nanochannel as well as the brush-nanostructure interactions at molecular level is important to design and fabricate emerging smart nano/microfluidic channels. In this work, we report coarse-grained molecular dynamics simulations of the translocation of nanoparticles through a cylindrical nanochannel coated with the polymer brush. The effects of the interparticle interaction and grafting density on the distribution and electrokinetic transport of nanoparticles are addressed in detail. Analysis of the distribution and velocity profiles of nanoparticles from the simulations indicate that the location of nanoparticles along the radial direction and their migration velocity are very sensitive to the change of interparticle interaction. We find complicated transport dynamics of nanoparticles under the influence of various grafting densities. The nanoparticles show markedly different translocation behavior upon increasing the grafting density, which depends on the counterion distribution, free room within the brush, nanoparticle-polymer friction, and brush configuration. Our results may serve as a useful starting point for the transport of nanostructures in polymer-modified channels and help to guide the design of novel smart nanofluidic channels for controlling the migration behavior of nanostructures.
Microfluidic separation of live and dead yeast cells using reservoir-based dielectrophoresis
Authors: Patel Saurin , Showers Daniel , Vedantam Pallavi , Tzeng Tzuen-Rong , Qian Shizhi , Xuan Xiangchun
Published: July 2012

Separating live and dead cells is critical to the diagnosis of early stage diseases and to the efficacy test of drug screening, etc. This work demonstrates a novel microfluidic approach to dielectrophoretic separation of yeast cells by viability. It exploits the cell dielectrophoresis that is induced by the inherent electric field gradient at the reservoir-microchannel junction to selectively trap dead yeast cells and continuously separate them from live ones right inside the reservoir. This approach is therefore termed reservoir-based dielectrophoresis (rDEP). It has unique advantages as compared to existing dielectrophoretic approaches such as the occupation of zero channel space and the elimination of any mechanical or electrical parts inside microchannels. Such an rDEP cell sorter can be readily integrated with other components into lab-on-a-chip devices for applications to biomedical diagnostics and therapeutics.
Dynamics of a two-level system coupled to a bath of spins
Authors: Wang Haobin , Shao Jiushu
Published: July 2012

The dynamics of a two-level system coupled to a spin bath is investigated via the numerically exact multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) theory. Consistent with the previous work on linear response approximation [N. Makri, J. Phys. Chem. B 103, 2823 (1999)]10.1021/jp9847540, it is demonstrated numerically that this spin-spin-bath model can be mapped onto the well-known spin-boson model if the system-bath coupling strength obeys an appropriate scaling behavior. This linear response mapping, however, may require many bath spin degrees of freedom to represent the practical continuum limit. To clarify the discrepancies resulted from different approximate treatments of this model, the population dynamics of the central two-level system has been investigated near the transition boundary between the coherent and incoherent motions via the ML-MCTDH method. It is found that increasing temperature favors quantum coherence in the nonadiabatic limit of this model, which corroborates the prediction in the previous work [J. Shao and P. Hanggi, Phys. Rev. Lett. 81, 5710 (1998)]10.1103/PhysRevLett.81.5710 based on the non-interacting blip approximation (NIBA). However, the coherent-incoherent boundary obtained by the exact ML-MCTDH simulation is slightly different from the approximate NIBA results. Quantum dynamics in other physical regimes are also discussed.
Plasma-accelerated flyer-plates for equation of state studies
Authors: Fratanduono D. E. , Smith R. F. , Boehly T. R. , Eggert J. H. , Braun D. G. , Collins G. W.
Published: July 2012

We report on a new technique to accelerate flyer-plates to high velocities (∼5 km/s). In this work, a strong shock is created through direct laser ablation of a thin polyimide foil. Subsequent shock breakout of that foil results in the generation of a plasma characterized by a smoothly increasing density gradient and a strong forward momentum. Stagnation of this plasma onto an aluminum foil and the resultant momentum transfer accelerates a thin aluminum flyer-plate. The aluminum flyer-plate is then accelerated to a peak velocity of ∼5 km/s before impact with a transparent lithium fluoride (LiF) window. Simulations of the stagnating plasma ramp compression and wave reverberations within the flyer-plate suggest that the temperature at the flyer-plate impact surface is elevated by less than 50 °C. Optical velocimetry is used to measure the flyer-plate velocity and impact conditions enabling the shocked refractive index of LiF to be determined. The results presented here are in agreement with conventional flyer-plate measurements validating the use of plasma-accelerated flyer-plates for equation of state and impact studies.
Design of the reflective optics for Tore Supra ECEI system
Authors: Nam Y. , Lee W. , Yun G. S. , Park H. K. , Elbeze D. , Segui J. L. , Sabot R. , Chenevoix J. P.
Published: July 2012

A 2D electron cyclotron emission (ECE) imaging system for Tore Supra is under design for studying the MHD physics of the magnetically confined plasma such as sawteeth, tearing modes, and turbulent fluctuations. Complex beam path due to the tight access in Tore Supra led to the design of reflective optics made of 6 or more large cylindrical/flat mirrors. The total path length of the ECE beam is about 11 m, including almost 4 m inside the vacuum vessel. The imaging property of the optics has been estimated using the Gaussian beam simulation and ray transfer analysis. The possible setups for the optical alignment of the diagnostic and the operation scenarios with single- or dual-array measurement system are discussed.
Different routes from a matter wavepacket to spatiotemporal chaos
Authors: Rong Shiguang , Hai Wenhua , Xie Qiongtao , Zhong Honghua
Published: July 2012

We investigate the dynamics of a quasi-one-dimensional Bose-Einstein condensate confined in a double-well potential with spatiotemporally modulated interaction. A variety of phenomena is identified in different frequency regimes, including the self-compression, splitting, breathing-like, and near-fidelity of the matter wavepacket, which are associated with different routes for the onset of spatiotemporal chaos. The results also reveal that chaos can retain space-inversion symmetry of the system.
Filippov systems and quasi-synchronization control for switched networks
Authors: Liu Xiaoyang , Cao Jinde , Yu Wenwu
Published: July 2012

This paper is concerned with the quasi-synchronization issue of linearly coupled networks with discontinuous nonlinear functions in each isolated node. Under the framework of Filippov systems, the existence and boundedness of solutions for such complex networks can be guaranteed by the matrix measure approach. A design method is presented for the synchronization controllers of coupled networks with non-identical discontinuous systems. Moreover, a sufficient condition is derived to ensure the quasi-synchronization of switched coupled complex networks with discontinuous isolated nodes, which could be controlled by some designed linear controllers. The obtained results extend the previous work on the synchronization issue of coupled complex networks with Lipschitz continuous conditions. Numerical simulations on the coupled chaotic systems are given to demonstrate the effectiveness of the theoretical results.
Rest-wavelength fiducials for the ITER core imaging x-ray spectrometer
Authors: Beiersdorfer P. , Brown G. V. , Graf A. T. , Bitter M. , Hill K. W. , Kelley R. L. , Kilbourne C. A. , Leutenegger M. A. , Porter F. S.
Published: July 2012

Absolute wavelength references are needed to derive the plasma velocities from the Doppler shift of a given line emitted by a moving plasma. We show that such reference standards exist for the strongest x-ray line in neonlike W64+, which has become the line of choice for the ITER (Latin “the way”) core imaging x-ray spectrometer. Close-by standards are the Hf Lβ3 line and the Ir Lα2 line, which bracket the W64+ line by ±30 eV; other standards are given by the Ir Lα1 and Lα2 lines and the Hf Lβ1 and Lβ2 lines, which bracket the W64+ line by ±40 and ±160 eV, respectively. The reference standards can be produced by an x-ray tube built into the ITER spectrometer. We present spectra of the reference lines obtained with an x-ray microcalorimeter and compare them to spectra of the W64+ line obtained both with an x-ray microcalorimeter and a crystal spectrometer.
Affinity and its derivatives in the glass transition process
Authors: Garden J.-L. , Guillou H. , Richard J. , Wondraczek L.
Published: July 2012

The thermodynamic treatment of the glass transition remains an issue of intense debate. When associated with the formalism of non-equilibrium thermodynamics, the lattice-hole theory of liquids can provide new insight in this direction, as has been shown by Schmelzer and Gutzow [J. Chem. Phys. 125, 184511 (2006)]10.1063/1.2374894, by Möller et al. [J. Chem. Phys. 125, 094505 (2006)]10.1063/1.2346673, and more recently by Tropin et al. [J. Non-Cryst. Solids 357, 1291 (2011)10.1016/j.jnoncrysol.2010.11.111; Tropin et al., J. Non-Cryst. Solids 357, 1303 (2011)]10.1016/j.jnoncrysol.2010.12.005. Here, we employ a similar approach. We include pressure as an additional variable, in order to account for the freezing-in of structural degrees of freedom upon pressure increase. Second, we demonstrate that important terms concerning first order derivatives of the affinity-driving-force with respect to temperature and pressure have been previously neglected. We show that these are of crucial importance in the approach. Macroscopic non-equilibrium thermodynamics is used to enlighten these contributions in the derivation of Cp,κT, and αp. The coefficients are calculated as a function of pressure and temperature following different theoretical protocols, revealing classical aspects of vitrification and structural recovery processes. Finally, we demonstrate that a simple minimalist model such as the lattice-hole theory of liquids, when being associated with rigorous use of macroscopic non-equilibrium thermodynamics, is able to account for the primary features of the glass transition phenomenology. Notwithstanding its simplicity and its limits, this approach can be used as a very pedagogical tool to provide a physical understanding on the underlying thermodynamics which governs the glass transition process.
Pedestal magnetic field measurements using a motional Stark effect polarimeter
Authors: Lanctot M. J. , Holcomb C. T. , Allen S. L. , Fenstermacher M. E. , Luce T. C.
Published: July 2012

Temperature-controlled, 0.15 nm interference filters were installed on an edge-viewing system of the motional Stark effect (MSE) polarimeter on the DIII-D tokamak. The upgraded system provides a factor of two reduction in the bandpass compared to the previous design, and linear control of the bandpass, which is unaltered by wavelength tuning. With the new system, there is a reduced dependence of the inferred polarization angle on the filter wavelength calibration. Recent measurements from the calibrated edge-viewing system show increased agreement with other MSE arrays.
Shot noise of low energy electron field emission due to Klein tunneling
Authors: Sun S. , Ang L. K.
Published: July 2012

This paper investigates the property of shot noise for low energy electron field emission from a single-layer vertically aligned graphene sheet assuming the emission process is due to Klein tunneling. In our model, we use two different methods (relativistic WKB and transfer matrix) to calculate the transmission coefficient and thus obtain the Fano factor (γ or suppression of shot noise) as a function of temperature T, Fermi energy Ef, and local electric field F. It is found that a universal maximum value of about γ = 1/3 can be reached at low temperature limit within a certain range of local electric field.
Vibrational energy relaxation of large-amplitude vibrations in liquids
Authors: Zhang Baofeng , Stratt Richard M.
Published: July 2012

Given the limited intermolecular spaces available in dense liquids, the large amplitudes of highly excited, low frequency vibrational modes pose an interesting dilemma for large molecules in solution. We carry out molecular dynamics calculations of the lowest frequency (“warping”) mode of perylene dissolved in liquid argon, and demonstrate that vibrational excitation of this mode should cause identifiable changes in local solvation shell structure. But while the same kinds of solvent structural rearrangements can cause the non-equilibrium relaxation dynamics of highly excited diatomic rotors in liquids to differ substantially from equilibrium dynamics, our simulations also indicate that the non-equilibrium vibrational energy relaxation of large-amplitude vibrational overtones in liquids should show no such deviations from linear response. This observation seems to be a generic feature of large-moment-arm vibrational degrees of freedom and is therefore probably not specific to our choice of model system: The lowest frequency (largest amplitude) cases probably dissipate energy too quickly and the higher frequency (more slowly relaxing) cases most likely have solvent displacements too small to generate significant nonlinearities in simple nonpolar solvents. Vibrational kinetic energy relaxation, in particular, seems to be especially and surprisingly linear.
Projection of two-dimensional diffusion in a curved midline and narrow varying width channel onto the longitudinal dimension
Authors: Dagdug Leonardo , Pineda Inti
Published: July 2012

This study focuses on the derivation of a general effective diffusion coefficient to describe the two-dimensional (2D) diffusion in a narrow and smoothly asymmetric channel of varying width, in the simple diffusional motion of noninteracting pointlike particles under no external field. We present a generalization to the case of an asymmetric channel using the projection method introduced earlier by Kalinay and Percus [J. Chem. Phys. 122, 204701 (2005);10.1063/1.1899150 Kalinay and Percus Phys. Rev. E 74, 041203 (2006)]10.1103/PhysRevE.74.041203 to project the 2D diffusion equation into an effective one-dimensional generalized Fick-Jacobs equation. The expression for the diffusion coefficient given in Eq. (23) is our main result. This expression is a more general effective diffusion coefficient for narrow channels in 2D, which contains the well-known previous results as special cases, namely, those obtained by Bradley [Phys. Rev. E 80, 061142 (2009)]10.1103/PhysRevE.80.061142, and more recently by Berezhkovskii and Szabo [J. Chem. Phys. 135, 074108 (2011)]10.1063/1.3626215. Finally, we study some specific 2D asymmetric channel configurations to test and show the broader applicability of Eq. (23).
Particle Monte Carlo simulation of string-like colloidal assembly in two and three dimensions
Authors: Norizoe Yuki , Kawakatsu Toshihiro
Published: July 2012

We simulate structural phase behavior of polymer-grafted colloidal particles by molecular Monte Carlo technique. The interparticle potential, which has a finite repulsive square-step outside a rigid core of the colloid, was previously confirmed via numerical self-consistent field calculation. This model potential is purely repulsive. We simulate these model colloids in the canonical ensemble in two and three dimensions and find that these particles containing no interparticle attraction self-assemble and align in a string-like assembly, at low temperature and high density. This string-like colloidal assembly is related to percolation phenomena. Analyzing the cluster size distribution and the average string length, we build phase diagrams and discover that the average string length diverges around the region where the melting transition line and the percolation transition line cross. This result is similar to Ising spin systems, in which the percolation transition line and the order-disorder line meet at a critical point.
Improved spectral analysis for the motional Stark effect diagnostic
Authors: Ko J. , Klabacha J.
Published: July 2012

The magnetic pitch angle and the magnitude from reversed field pinch plasmas in the Madison symmetric torus (MST) have been routinely obtained from fully resolved motional Stark effect (MSE) spectrum analyses. Recently, the spectrum fit procedure has been improved by initializing and constraining the fit parameters based on the MSE model in the atomic data and analysis structure. A collisional-radiative model with level populations nlm-resolved up to n = 4 and a simple Born approximation for ion-impact cross sections is used for this analysis. Measurement uncertainty is quantified by making MSE measurements with multiple views of a single spatial location, ranging 5%–15% for typical MST operation conditions. A multi-view fit improves the goodness of fit of MSE spectral features and background.
Year round performance and economic evaluation of solar power plant for Indian tropical condition
Authors: Siva Reddy V. , Kaushik S. C. , Tyagi S. K.
Published: July 2012

In this paper, a 50 MWe design capacity solar parabolic dish concentrator Stirling engine power plant (SPDCSPP) has been modeled for analysis, where 2000 units of 25 kWe parabolic dish concentrator each considered for getting desired capacity. An attempt has been made to carryout the economic evaluation of SPDCSPP for selected Indian tropical condition. Variations of the efficiency of Stirling engine power plant at the variation of the load conditions are considered for year round performance evaluation. The developed model is examined for Indian location, i.e., Delhi. It is found that year round collector-receiver efficiency varies from 69.43% to 77.88%, and overall power plant efficiency varies from 16.86% and 25.79%. The installation cost per MWe electrical capacity is 15.32 crore rupees, and 28.10 lakhs rupees as operation and maintenance cost per MWe electrical capacity. The unit cost of electric energy generation (kWhe) is about 11.06 Indian rupees, with 30 years lifespan of the plant and 10% interest rate on investment.
Excited and ground state vibrational dynamics revealed by two-dimensional electronic spectroscopy
Authors: Caram Justin R. , Fidler Andrew F. , Engel Gregory S.
Published: July 2012

Broadband two-dimensional electronic spectroscopy (2DES) can assist in understanding complex electronic and vibrational signatures. In this paper, we use 2DES to examine the electronic structure and dynamics of a long chain cyanine dye (1,1-diethyl-4,4-dicarbocyanine iodide, or DDCI-4), a system with a vibrational progression. Using broadband pulses that span the resonant electronic transition, we measure two-dimensional spectra that show a characteristic six peak pattern from coherently excited ground and excited state vibrational modes. We model these features using a spectral density formalism and the vibronic features are assigned to Feynman pathways. We also examine the dynamics of a particular set of peaks demonstrating anticorrelated peak motion, a signature of oscillatory wavepacket dynamics on the ground and excited states. These dynamics, in concert with the general structure of vibronic two-dimensional spectra, can be used to distinguish between pure electronic and vibrational quantum coherences.