bluuebunny/crossref_metadata_2025 huggingface dataset:
Research Issues for Nursing and Midwifery Contributions in Emergencies
Authors: Weiner Elizabeth
Published: May 2011

This special report was prepared as a white paper for the First World Health Organization (WHO) Consultation on Nursing and Midwifery Contributions in Emergencies held in Geneva on 22–24 November 2006. Pertinent issues related to research of nurses and midwives were identified based on prior international conferences. Using this information, gaps between the current and proposed state of preparedness research activities were identified. Global perspective recommendations were made for consideration by the WHO and other nursing organizations. Finally, possible discussion questions were posed that were used during the consultation, but could also be used in other international nursing conferences.
When the Others Matter
Authors: Gerger Gernot , Leder Helmut , Faerber Stella J. , Carbon Claus-Christian
Published: May 2011

Although innovativeness is an important variable in product design, we know little about its appreciation. We studied how appreciation of innovativeness and its dynamics depends on the heterogeneity of the context in which it appears. We employed a test-retest design in which appreciation of car interior designs was tested before and after repeated evaluations. We tested heterogeneous stimulus sets (highly and lowly innovative designs together; Experiment 1) and homogeneous stimulus sets (highly or lowly innovative designs; Experiment 2). The known effect ( Carbon, Hutzler, & Minge, 2006 ; Carbon & Leder, 2005 ) of a selective increase in attractiveness ratings for highly innovative stimuli after repeated evaluations was only obtained for heterogeneous sets. In homogeneous sets, both highly and lowly innovative interiors were rated similarly and showed similar dynamics. Experiment 3 was a shorter version of Experiment 1, which ruled out differences in experimental design (more ratings and longer duration in Experiment 1) as the cause of the differences. High innovativeness was found to show a specific increase in attractiveness ratings only when innovativeness was made apparent by presenting stimuli in heterogeneous sets. Thus, awareness of variation in innovativeness as a relevant stimulus dimension is a key feature regarding its effect on appreciation.
Magnitude estimation using initial P‐wave amplitude and its spatial distribution in earthquake early warning in Taiwan
Authors: Lin Ting‐Li , Wu Yih‐Min , Chen Da‐Yi
Published: May 2011

We collected the strong‐motion accelerograms from thirteen crustal earthquakes in Taiwan recorded by the Taiwan Strong Motion Instrumentation Program (TSMIP) stations to find the empirical relationship between the areas of high initial P‐wave displacement and the corresponding earthquake magnitudes. We found that the logarithm of the area has a linear relation to the corresponding earthquake magnitude in Mw for study earthquakes with magnitudes between 5.4 and 6.5. We propose that this relationship might be able to rapidly define earthquake magnitude without knowing the earthquake location in regions with sufficient seismic station coverage and might have practical application in earthquake early warning (EEW) and rapid reporting systems.
Suppressors of cytokine signaling inhibit effector T cell responses during Mycobacterium tuberculosis Infection
Authors: Srivastava Varsha , Vashishta Mohit , Gupta Shashank , Singla Rupak , Singla Neeta , Behera Dighamber , Natarajan Krishnamurthy
Published: May 2011

Protective immune responses during Mycobacterium tuberculosis (M. tuberculosis) infection are regulated at multiple levels and critically dependent on the balance in the secretion of pro‐inflammatory and regulatory cytokines. A key factor that governs this balance at the cellular level is suppressors of cytokine signaling (SOCS). We recently demonstrated that toll‐like receptor 2 and dendritic cell (DC)‐SIGNR1 differentially regulate SOCS1 expression in DCs during M. tuberculosis infection. This consecutively regulated IL‐12 production and determined M. tuberculosis survival. In this study, we characterized the role of SOCS1 in regulating effector responses from CD4+ and CD8+ T cells during M. tuberculosis infection. Our data indicate that T cells from M. tuberculosis‐infected mice show increased and differential association of SOCS1 with CD3 and CD28, when compared with uninfected mice. While SOCS1 displays increased association with CD3 than CD28 in CD4+ T cells; SOCS1 is associated more with CD28 than CD3 in CD8+ T cells. Further, SOCS1 shows increased association with IL‐12 and IL‐2 receptors in both CD4+ and CD8+ T cells from infected mice when compared with naive mice. Silencing SOCS1 in T cells increased signal transduction from T cell receptor (TCR) and CD28 with enhanced activation of key signaling molecules and proliferation. Significantly, SOCS1‐silenced T cells mediated enhanced clearance of M. tuberculosis inside macrophages. Finally, adoptive transfer of SOCS1‐silenced T cells in M. tuberculosis‐infected mice mediated significant reduction in M. tuberculosis loads in spleen. These results exemplify the negative role played by SOCS1 during T cell priming and effector functions during M. tuberculosis infection.
When versatility matters: activins/inhibins as key regulators of immunity
Authors: Aleman‐Muench G R , Soldevila G
Published: May 2011

Activins and inhibins are members of the transforming growth factor‐β superfamily that have been considered crucial regulators of cell processes, such as differentiation, proliferation and apoptosis, in different cell types. Initial studies about the function of activin A in the immune system focused on the regulation of hematopoiesis in the bone marrow under homeostatic and inflammatory conditions. Recent data provide a more comprehensive understanding about the role of activins/inhibins in the immune system. Novel findings included in this review point out the important requirement of activin/inhibin signaling to maintain the balance between homeostatic and inflammatory signals that are required for the optimal development and function of immune cells. The purpose of this review is to highlight the versatile nature of activins/inhibins as key regulators of both the innate and adaptive immune responses.
Alzheimer's disease is TH17 related autoimmune disease against misfoded beta amyloid
Authors: Hu Wan-Jiung
Published: May 2011

Alzheimer's disease is a common neurodegenerative disorder. However, its exact etiology is still unknown. There were several mechanisms proposed such as the tau hypothesis and amyloid hypothesis. However, there is evidence challenging the above two hypotheses. Here, I propose the immune-amyloid hypothesis as a mechanism for Alzheimer's disease. Th17 related autoimmunity contributes to the disease pathogenesis. Accumulation of misfolded beta amyloid can trigger heat shock protein which in turn induces TH17 immunity. By microarray analysis of peripheral blood mononuclear cells, there is up-regulation of many TH17 related molecules after Alzheimer's disease. After knowing the exact disease pathogenesis, we can develop new therapeutic strategies to prevent or treat the detrimental disorder.
The remarkable diversity of plant PEPC (phosphoenolpyruvate carboxylase): recent insights into the physiological functions and post-translational controls of non-photosynthetic PEPCs
Authors: O'Leary Brendan , Park Joonho , Plaxton William C.
Published: May 2011

PEPC [PEP (phosphoenolpyruvate) carboxylase] is a tightly controlled enzyme located at the core of plant C-metabolism that catalyses the irreversible β-carboxylation of PEP to form oxaloacetate and Pi. The critical role of PEPC in assimilating atmospheric CO2 during C4 and Crassulacean acid metabolism photosynthesis has been studied extensively. PEPC also fulfils a broad spectrum of non-photosynthetic functions, particularly the anaplerotic replenishment of tricarboxylic acid cycle intermediates consumed during biosynthesis and nitrogen assimilation. An impressive array of strategies has evolved to co-ordinate in vivo PEPC activity with cellular demands for C4–C6 carboxylic acids. To achieve its diverse roles and complex regulation, PEPC belongs to a small multigene family encoding several closely related PTPCs (plant-type PEPCs), along with a distantly related BTPC (bacterial-type PEPC). PTPC genes encode ~110-kDa polypeptides containing conserved serine-phosphorylation and lysine-mono-ubiquitination sites, and typically exist as homotetrameric Class-1 PEPCs. In contrast, BTPC genes encode larger ~117-kDa polypeptides owing to a unique intrinsically disordered domain that mediates BTPC's tight interaction with co-expressed PTPC subunits. This association results in the formation of unusual ~900-kDa Class-2 PEPC hetero-octameric complexes that are desensitized to allosteric effectors. BTPC is a catalytic and regulatory subunit of Class-2 PEPC that is subject to multi-site regulatory phosphorylation in vivo. The interaction between divergent PEPC polypeptides within Class-2 PEPCs adds another layer of complexity to the evolution, physiological functions and metabolic control of this essential CO2-fixing plant enzyme. The present review summarizes exciting developments concerning the functions, post-translational controls and subcellular location of plant PTPC and BTPC isoenzymes.
Influence of bias voltage on dielectric relaxation of nanocrystalline anatase TiO2 using modulus formalism
Authors: Prakash T. , Ramasamy S. , Murty B. S.
Published: April 2011

Dielectric relaxation in sol–gel-derived anatase titanium oxide nanocrystals (6, 9, and 20 nm) has been investigated using impedance spectroscopy in a wide frequency range from 1 Hz to 1 MHz as a function of applied DC bias voltage, ranging from 0 to 4.2 V in a periodic interval of 0.3 V. Under the equilibrium condition, around three order of magnitude variations in the dielectric relaxation time (τ) was observed for the grain size if reduced to 6 nm from 20 nm. An unambiguous evidence for the absence of such a crystallite size effect was experimentally observed in higher biased conditions because of grain boundary Schottky potential barrier height suppression. These experimental results obey the “grain boundary double Schottky barrier model.”
Built-in electric fields and valence band offsets in InN/GaN(0001) superlattices: First-principles investigations
Authors: Shieh C. C. , Cui X. Y. , Delley B. , Stampfl C.
Published: April 2011

Based on all-electron density functional theory calculations, we systematically investigate the built-in electric fields and valence band offsets in wurtzite InN/GaN(0001) superlattices, where their correlations with biaxial strain, as well as the superlattice geometry, are determined. Both the built-in electric fields (several MV/cm) and the valence band offsets (0.16 –1.1 eV) are found to be strongly dependent on the superlattice geometry and strain growth conditions. Spontaneous polarization and strain-induced piezoelectric polarization are comparable in contribution to the macroscopic electric field. Relative to the fully relaxed superlattices, tensile (compressive) strain significantly weakens (strengthens) the magnitude of the electric field, and decreases (increases) the value of the valence band offset. The results will be valuable in relation to practical heterojunction-based device optimization and design.
Anharmonic rovibrational analysis for disilacyclopropenylidene (Si2CH2)
Authors: Lu Tongxiang , Wilke Jeremiah J. , Yamaguchi Yukio , Schaefer Henry F.
Published: April 2011

The global minimum on the Si2CH2 electronic singlet potential energy surface has been theoretically predicted to be a peculiar hydrogen bridged (Si⋅⋅⋅H⋅⋅⋅Si) disilacyclopropenylidene structure (Si2CH2). An accurate quartic force field for Si2CH2 has been determined employing ab initio coupled-cluster theory with single and double excitations and a perturbative treatment for triple excitations [CCSD(T)], in combination with the correlation consistent core-valence quadruple zeta (cc-pCVQZ) basis set. The vibration–rotation coupling constants, equilibrium and zero-point vibration corrected rotational constants, centrifugal distortion constants, and harmonic and fundamental vibrational frequencies for six isotopologues of Si2CH2 are predicted using vibrational second-order perturbation theory (VPT2). The anharmonic corrections for the vibrational motions involving the H bridged bonds are found to be more than 5% with respect to the corresponding harmonic vibrational frequencies. In this light, an experimental detection and characterization of disilacyclopropenylidene (Si2CH2) is highly desired.
Formation of a long-lived hot field reversed configuration by dynamically merging two colliding high-β compact toroids
Authors: Guo H. Y. , Binderbauer M. W. , Barnes D. , Putvinski S. , Rostoker N. , Sevier L. , Tuszewski M. , Anderson M. G. , Andow R. , Bonelli L. , Brandi F. , Brown R. , Bui D. Q. , Bystritskii V. , Ceccherini F. , Clary R. , Cheung A. H. , Conroy K. D. , Deng B. H. , Dettrick S. A. , Douglass J. D. , Feng P. , Galeotti L. , Garate E. , Giammanco F. , Glass F. J. , Gornostaeva O. , Gota H. , Gupta D. , Gupta S. , Kinley J. S. , Knapp K. , Korepanov S. , Hollins M. , Isakov I. , Jose V. A. , Li X. L. , Luo Y. , Marsili P. , Mendoza R. , Meekins M. , Mok Y. , Necas A. , Paganini E. , Pegoraro F. , Pousa-Hijos R. , Primavera S. , Ruskov E. , Qerushi A. , Schmitz L. , Schroeder J. H. , Sibley A. , Smirnov A. , Song Y. , Steinhauer L. C. , Sun X. , Thompson M. C. , Van Drie A. D. , Walters J. K. , Wyman M. D. ,   TAE Team
Published: May 2011

A high temperature field reversed configuration (FRC) has been produced in the newly built, world’s largest compact toroid (CT) facility, C-2, by colliding and merging two high-β CTs produced using the advanced field-reversed θ-pinch technology. This long-lived, stable merged state exhibits the following key properties: (1) apparent increase in the poloidal flux from the first pass to the final merged state, (2) significantly improved confinement compared to conventional θ-pinch FRCs with flux decay rates approaching classical values in some cases, (3) strong conversion from kinetic energy into thermal energy with total temperature (Te + Ti) exceeding 0.5 keV, predominantly into the ion channel. Detailed modeling using a new 2-D resistive magnetohydrodynamic (MHD) code, LamyRidge, has demonstrated, for the first time, the formation, translation, and merging/reconnection dynamics of such extremely high-β plasmas.
Miniature infrared gas sensors using photonic crystals
Authors: Pergande Daniel , Geppert Torsten M. , Rhein Andreas von , Schweizer Stefan L. , Wehrspohn Ralf B. , Moretton Susanne , Lambrecht Armin
Published: April 2011

We present an optical gas sensor based on the classical nondispersive infrared technique using ultracompact photonic crystal gas cells. The ultracompact device is conceptually based on low group velocities inside a photonic crystal gas cell and low-reflectivity antireflection layers coupling light into the device. Experimentally, an enhancement of the CO2 infrared absorption by a factor of 2.6 to 3.5 as compared to an empty cell, due to slow light inside a 2D silicon photonic crystal gas cell, was observed; this is in excellent agreement with numerical simulations. We show that, theoretically, for an optimal design enhancement factors of up to 60 are possible in the region of slow light. However, the overall transmission of bulk photonic crystals, and thus the performance of the device, is limited by fluctuations of the pore diameter. Numerical estimates suggest that the positional variations and pore diameter fluctuations have to be well below 0.5% to allow for a reasonable transmission of a 1 mm device.
Magnetism in Co80-xFexB20: Effect of crystallization
Authors: Lavrijsen R. , Paluskar P. V. , Loermans C. T. J. , van Kruisbergen P. A. , Kohlhepp J. T. , Swagten H. J. M. , Koopmans B. , Snoeck E.
Published: May 2011

We report on the change in the structural and magnetic properties of magnetically soft ternary Co80-xFexB20 alloys as a function of composition, thickness, and annealing temperature. Compositions high in cobalt show a significant change in coercivity after annealing. This is explained using the random anisotropy model by relating the magnetic exchange length to the grain size of the crystallites. The presented results are a systematic study explaining trends seen in the transition from soft to hard magnetic behavior, providing insight into why the soft CoFeB alloys have been so successful recently in spintronic devices.
Modeling of aerosol formation in a turbulent jet with the transported population balance equation-probability density function approach
Authors: Di Veroli G. Y. , Rigopoulos S.
Published: April 2011

Processes involving particle formation in turbulent flows feature complex interactions between turbulence and the various physicochemical processes involved. An example of such a process is aerosol formation in a turbulent jet, a process investigated experimentally by Lesniewski and Friedlander [Proc. R. Soc. London, Ser. A 454, 2477 (1998)]. Polydispersed particle formation can be described mathematically by a population balance (also called general dynamic) equation, but its formulation and use within a turbulent flow are riddled with problems, as straightforward averaging results in unknown correlations. In this paper we employ a probability density function formalism in conjunction with the population balance equation (the PBE-PDF method) to simulate and study the experiments of Lesniewski and Friedlander. The approach allows studying the effects of turbulence-particle formation interaction, as well as the prediction of the particle size distribution and the incorporation of kinetics of arbitrary complexity in the population balance equation. It is found that turbulence critically affects the first stages of the process, while it seems to have a secondary effect downstream. While Lesniewski and Friedlander argued that the bulk of the nucleation arises in the initial mixing layer, our results indicate that most of the particles nucleate downstream. The full particle size distributions are obtained via our method and can be compared to the experimental results showing good agreement. The sources of uncertainties in the experiments and the kinetic expressions are analyzed, and the underlying mechanisms that affect the evolution of particle size distribution are discussed.
A strategy for reducing gross errors in the generalized Born models of implicit solvation
Authors: Onufriev Alexey V. , Sigalov Grigori
Published: April 2011

The “canonical” generalized Born (GB) formula [C. Still, A. Tempczyk, R. C. Hawley, and T. Hendrickson, J. Am. Chem. Soc. 112, 6127 (1990)] is known to provide accurate estimates for total electrostatic solvation energies ΔGel of biomolecules if the corresponding effective Born radii are accurate. Here we show that even if the effective Born radii are perfectly accurate, the canonical formula still exhibits significant number of gross errors (errors larger than 2kBT relative to numerical Poisson equation reference) in pairwise interactions between individual atomic charges. Analysis of exact analytical solutions of the Poisson equation (PE) for several idealized nonspherical geometries reveals two distinct spatial modes of the PE solution; these modes are also found in realistic biomolecular shapes. The canonical GB Green function misses one of two modes seen in the exact PE solution, which explains the observed gross errors. To address the problem and reduce gross errors of the GB formalism, we have used exact PE solutions for idealized nonspherical geometries to suggest an alternative analytical Green function to replace the canonical GB formula. The proposed functional form is mathematically nearly as simple as the original, but depends not only on the effective Born radii but also on their gradients, which allows for better representation of details of nonspherical molecular shapes. In particular, the proposed functional form captures both modes of the PE solution seen in nonspherical geometries. Tests on realistic biomolecular structures ranging from small peptides to medium size proteins show that the proposed functional form reduces gross pairwise errors in all cases, with the amount of reduction varying from more than an order of magnitude for small structures to a factor of 2 for the largest ones.
Intensification of surface enhanced Raman scattering of thiol-containing molecules using Ag@Au core@shell nanoparticles
Authors: Singh Prerna , Thuy Nguyen T. B. , Aoki Yoshiya , Mott Derrick , Maenosono Shinya
Published: May 2011

In this paper, we study the relationship between nanoparticles’ structure/composition and the chemical nature of the molecules to be identified in surface enhanced Raman scattering (SERS) spectroscopy. Three types of nanoparticles (NPs) were synthesized, including Ag, Au, and silver coated by gold (Ag@Au), in order to study the resulting enhancement effects. When a rhodamine 6G dye molecule was used to assemble the NPs, it was found that Ag NPs exhibited the highest enhancement activity. However, when a thiol containing 3-amino-1,2,4-triazole-5-thiol molecule was used to assemble the NPs, it was found that the Ag@Au NPs exhibited high Raman activity as well as the Ag NPs. The results give insight into how the chemical properties of the molecules to be analyzed play an important role in the SERS detection. An additional parameter of the analysis reveals the relative stability of the three types of NP probes synthesized with regard to oxidation in the presence of different mediating molecules and varying salt concentrations. The results are of interest in designing and employing NP probes to detect biological molecules using colorimetric and SERS based approaches.
Nano-ripple formation on different band-gap semiconductor surfaces using femtosecond pulses
Authors: Chakravarty U. , Ganeev R. A. , Naik P. A. , Chakera J. A. , Babu M. , Gupta P. D.
Published: April 2011

Nano-ripple formation from ultrashort laser pulse irradiation of semiconductors of different band gaps has been studied using a Ti-sapphire laser with 8 mJ energy, 45 fs pulse duration and 800 nm wavelength (1.5eV) at a fluence in the range of ∼100 mJ/cm2 −1J/cm2. The effects of the number of laser shots, angle of incidence, laser polarization, fluence, incident laser wavelength, bandgap, and ambient medium on the ripple period, have been studied. Depending upon the experimental parameters nano-ripple sizes varied in the range of λ-λ/9. The studies clearly show that narrower nano-ripples are formed from wide bandgap semiconductors. In addition, the width of the nano-ripples decreases with the laser wavelength and fluence. The observed results are explained considering the transient metallic nature of the semiconductor surface on irradiation with intense femtosecond pulse which excites surface plasmon leading to the nano-ripple formation. The critical role of the surface plasma electron density in deciding ripple period is identified which helps in generation of narrow sub-wavelength nano-ripples.
Three-dimensional effects of curved plasma actuators in quiescent air
Authors: Wang Chin-Cheng , Durscher Ryan , Roy Subrata
Published: April 2011

This paper presents results on a new class of curved plasma actuators for the inducement of three-dimensional vortical structures. The nature of the fluid flow inducement on a flat plate, in quiescent conditions, due to four different shapes of dielectric barrier discharge (DBD) plasma actuators is numerically investigated. The three-dimensional plasma kinetic equations are solved using our in-house, finite element based, multiscale ionized gas (MIG) flow code. Numerical results show electron temperature and three dimensional plasma force vectors for four shapes, which include linear, triangular, serpentine, and square actuators. Three-dimensional effects such as pinching and spreading the neighboring fluid are observed for serpentine and square actuators. The mechanisms of vorticity generation for DBD actuators are discussed. Also the influence of geometric wavelength (λ) and amplitude (Λ) of the serpentine and square actuators on vectored thrust inducement is predicted. This results in these actuators producing significantly better flow mixing downstream as compared to the standard linear actuator. Increasing the wavelengths of serpentine and square actuators in the spanwise direction is shown to enhance the pinching effect giving a much higher vertical velocity. On the contrary, changing the amplitude of the curved actuator varies the streamwise velocity significantly influencing the near wall jet. Experimental data for a serpentine actuator are also reported for validation purpose.
Runaway electron preionized diffuse discharges in atmospheric pressure air with a point-to-plane gap in repetitive pulsed mode
Authors: Shao Tao , Zhang Cheng , Niu Zheng , Yan Ping , Tarasenko Victor F. , Baksht Evgeni Kh. , Kostyrya Igor D. , Shutko V.
Published: April 2011

This paper presents the results of the experimental studies of a pulsed discharge in atmospheric pressure air in an inhomogeneous electric field for various parameters of voltage pulses. It is shown that in a wide range of experimental conditions, including those with a positive electrode of small curvature radius, a diffuse discharge is ignited in the gap. In particular, a diffuse discharge is ignited at a pulse repetition frequency of 1 kHz and a voltage pulse amplitude of ∼25 and ∼40 kV across a high-resistance load. With voltage pulses of ∼ 220 kV in amplitude and low repetition frequencies, an extended (∼70 cm) diffuse discharge is observed in gaps of 13–40 mm. It is confirmed that the diffuse form of discharges in an inhomogeneous electric field at increased pressures is attributed to the generation of runaway electrons and x-rays.
Simulation of ferromagnetic resonance spectra of linear chains of magnetite nanocrystals
Authors: Charilaou Michalis , Winklhofer Michael , Gehring Andreas U.
Published: May 2011

Ensembles of linear chains of stable single domain magnetite crystals, as found in magnetotactic bacteria, exhibit a distinctly asymmetric ferromagnetic resonance (FMR) signal, with a pronounced high-field minimum and two or three low-field maxima in the derivative spectrum. To identify the microscopic origin of these traits, we have simulated FMR spectra of dilute suspensions of linear chains oriented randomly in space by modeling the chain as a Stoner−Wohlfarth-type rotation ellipsoid whose long axis coincides with an easy [111] axis of the cubic magnetocrystalline anisotropy system. The validity of the model is examined by comparing the results with explicit calculations of the interactions among the particles in the chain. The single ellipsoid model reproduces the experimentally observed FMR traits and can be related to the explicit chain model by adjusting the contribution to the uniaxial anisotropy along the chain axis to account for the magnetostatic interactions. Finally, we provide a practical approximation for simulating and fitting the FMR spectra of one-dimensional assemblies.
State-resolved investigation of the photodesorption dynamics of NO from (NO)2 on Ag nanoparticles of various sizes in comparison with Ag(111)
Authors: Mulugeta Daniel , Watanabe Kazuo , Menzel Dietrich , Freund Hans-Joachim
Published: April 2011

The translational and internal state energy distributions of NO desorbed by laser light (2.3, 3.5, and 4.7 eV) from adsorbed (NO)2 on Ag nanoparticles (NPs) (mean diameters, D = 4, 8, and 11 nm) have been investigated by the (1 + 1) resonance enhanced multiphoton ionization technique. For comparison, the same experiments have also been carried out on Ag(111). Detected NO molecules are hyperthermally fast and both rotationally and vibrationally hot, with temperatures well above the sample temperature. The translational and rotational excitations are positively correlated, while the vibrational excitation is decoupled from the other two degrees of freedom. Most of the energy content of the desorbing NO is contained in its translation. The translational and internal energy distributions of NO molecules photodesorbed by 2.3, 3.5, and in part also 4.7 eV light are approximately constant as a function of Ag NPs sizes, and they are the same on Ag(111). This suggests that for these excitations a common mechanism is operative on the bulk single crystal and on NPs, independent of the size regime. Notably, despite the strongly enhanced cross section seen on NP at 3.5 eV excitation energy in p-polarization, i.e., in resonance with the plasmon excitation, the mechanism is also unchanged. At 4.7 eV and for small particles, however, an additional desorption channel is observed which results in desorbates with higher energies in all degrees of freedom. The results are well compatible with our earlier measurements of size-dependent translational energy distributions. We suggest that the broadly constant mechanism over most of the investigated range runs via a transient negative ion state, while at high excitation energy and for small particles the transient state is suggested to be a positive ion.
Fluctuations in the ensemble of reaction pathways
Authors: Mazzola G. , Beccara S. a , Faccioli P. , Orland H.
Published: April 2011

The dominant reaction pathway is a rigorous framework to microscopically compute the most probable trajectories, in nonequilibrium transitions. In the low-temperature regime, such dominant pathways encode the information about the reaction mechanism and can be used to estimate nonequilibrium averages of arbitrary observables. On the other hand, at sufficiently high temperatures, the stochastic fluctuations around the dominant paths become important and have to be taken into account. In this work, we develop a technique to systematically include the effects of such stochastic fluctuations, to order kBT. This method is used to compute the probability for a transition to take place through a specific reaction channel and to evaluate the reaction rate.
Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media
Authors: Hauet T. , Hellwig O. , Park S.-H. , Beigné C. , Dobisz E. , Terris B. D. , Ravelosona D.
Published: April 2011

We have used ion irradiation to tune switching field and switching field distribution (SFD) in polycrystalline Co/Pd multilayer-based bit pattern media. Light He+ ion irradiation strongly decreases perpendicular magnetic anisotropy amplitude due to Co/Pd interface intermixing, while the granular structure, i.e., the crystalline anisotropy, remains unchanged. In dot arrays, the anisotropy reduction leads to a decrease in coercivity (HC) but also to a strong broadening of the normalized SFD/HC (in percentage), since the relative impact of misaligned grains is enhanced. Our experiment thus confirms the major role of misorientated grains in SFD of nanodevice arrays.
Exact equipotential profile mapping: A self-validating method
Authors: Filip L. D. , David Carey J. , Silva S. R. P.
Published: April 2011

A general method for mapping the equipotential profile surrounding a conductive cylindrically symmetric high aspect ratio structure, such as a carbon nanotube or a Spindt tip, is devised. The surface of the object is replaced by a discrete set of charges located on the symmetry axis. The overall electrostatic potential must satisfy a set of boundary conditions imposed on the original surface. The optimum number of charges is determined through an iterative self-validating process such that the obtained equipotential mimics the surface of the object. The method is exemplified by calculating the electric field enhancement factor for rounded cones and cylinders resembling Spindt tips and carbon nanotubes, respectively.
Theoretical investigation on the existence of inverse and direct magnetocaloric effect in perovskite EuZrO3
Authors: Alho B. P. , Nóbrega E. P. , de Sousa V. S. R. , Carvalho A. Magnus G. , de Oliveira N. A. , von Ranke P. J.
Published: April 2011

We report on the magnetic and magnetocaloric effect calculations in antiferromagnetic perovskite-type EuZrO3. The theoretical investigation was carried out using a model Hamiltonian including the exchange interactions between nearest-neighbor and next-nearest-neighbor for the antiferromagnetic ideal G-type structure (the tolerance factor for EuZrO3 is t = 0.983, which characterizes a small deformation from an ideal cubic perovskite). The molecular field approximation and Monte Carlo simulation were considered and compared. The calculated magnetic susceptibility is in good agreement with the available experimental data. For a magnetic field change from zero to 2 T a normal magnetocaloric effect was calculated and for a magnetic field change from zero to 1 T, an inverse magnetocaloric effect was predicted to occur below T = 3.6 K.
Anomalous diffusion of oligomerized transmembrane proteins
Authors: Schmidt Ulrich , Weiss Matthias
Published: April 2011

Transmembrane proteins frequently form (transient) oligomers on biomembranes, e.g., while participating in protein sorting and signaling events. Using coarse-grained membrane simulations we show here that transmembrane proteins show a subdiffusive motion on short time scales when being part of a linear oligomer, i.e., a flexible polymer, embedded in a two-dimensional membrane. Our results are in agreement with previous experimental observations. They further indicate that polymers of transmembrane proteins are well described by predictions from Rouse theory in two dimensions even in the presence of hydrodynamic interactions.
A natural orbital functional for multiconfigurational states
Authors: Piris M. , Lopez X. , Ruipérez F. , Matxain J. M. , Ugalde J. M.
Published: April 2011

An explicit formulation of the Piris cumulant \documentclass[12pt]{minimal}\begin{document}$\mathbf{\lambda }\left(\bm {\Delta },\bm {\Pi }\right)$\end{document}λΔ,Π matrix is described herein, and used to reconstruct the two-particle reduced density matrix (2-RDM). Then, we have derived a natural orbital functional, the Piris Natural Orbital Functional 5, PNOF5, constrained to fulfill the D, Q, and G positivity necessary conditions of the N-representable 2-RDM. This functional yields a remarkable accurate description of systems bearing substantial (near)degeneracy of one-particle states. The theory is applied to the homolitic dissociation of selected diatomic molecules and to the rotation barrier of ethylene, both paradigmatic cases of near-degeneracy effects. It is found that the method describes correctly the dissociation limit yielding an integer number of electrons on the dissociated atoms. PNOF5 predicts a barrier of 65.6 kcal/mol for the ethylene torsion in an outstanding agreement with Complete Active Space Second-order Perturbation Theory (CASPT2). The obtained occupation numbers and pseudo one-particle energies at the ethylene transition state account for fully degenerate π orbitals. The calculated equilibrium distances, dipole moments, and binding energies of the considered molecules are presented. The values obtained are accurate comparing those obtained by the complete active space self-consistent field method and the experimental data.
The stretching of single poly-ubiquitin molecules: Static versus dynamic disorder in the non-exponential kinetics of chain unfolding
Authors: Chatterjee Debarati , Cherayil Binny J.
Published: April 2011

Static disorder has recently been implicated in the non-exponential kinetics of the unfolding of single molecules of poly-ubiquitin under a constant force [Kuo, Garcia-Manyes, Li, Barel, Lu, Berne, Urbakh, Klafter, and Fernández, Proc. Natl. Acad. Sci. U.S.A. 107, 11336 (2010)10.1073/pnas.1006517107]. In the present paper, it is suggested that dynamic disorder may provide a plausible, alternative description of the experimental observations. This suggestion is made on the basis of a model in which the barrier to chain unfolding is assumed to be modulated by a control parameter r that evolves in a parabolic potential under the action of fractional Gaussian noise according to a generalized Langevin equation. The treatment of dynamic disorder within this model is pursued using Zwanzig's indirect approach to noise averaging [Acc. Chem. Res. 23, 148 (1990)]. In conjunction with a self-consistent closure scheme developed by Wilemski and Fixman [J. Chem. Phys. 58, 4009 (1973)10.1063/1.1679757; ibid. 60, 866 (1974)10.1063/1.1681162], this approach eventually leads to an expression for the chain unfolding probability that can be made to fit the corresponding experimental data very closely.
Pressure-energy correlations in liquids. V. Isomorphs in generalized Lennard-Jones systems
Authors: Schrøder Thomas B. , Gnan Nicoletta , Pedersen Ulf R. , Bailey Nicholas P. , Dyre Jeppe C.
Published: April 2011

This series of papers is devoted to identifying and explaining the properties of strongly correlating liquids, i.e., liquids with more than 90% correlation between their virial W and potential energy U fluctuations in the NVT ensemble. Paper IV [N. Gnan et al., J. Chem. Phys. 131, 234504 (2009)10.1063/1.3265957] showed that strongly correlating liquids have “isomorphs,” which are curves in the phase diagram along which structure, dynamics, and some thermodynamic properties are invariant in reduced units. In the present paper, using the fact that reduced-unit radial distribution functions are isomorph invariant, we derive an expression for the shapes of isomorphs in the WU phase diagram of generalized Lennard-Jones systems of one or more types of particles. The isomorph shape depends only on the Lennard-Jones exponents; thus all isomorphs of standard Lennard-Jones systems (with exponents 12 and 6) can be scaled onto a single curve. Two applications are given. One tests the prediction that the solid-liquid coexistence curve follows an isomorph by comparing to recent simulations by Ahmed and Sadus [J. Chem. Phys. 131, 174504 (2009)]10.1063/1.3253686. Excellent agreement is found on the liquid side of the coexistence curve, whereas the agreement is less convincing on the solid side. A second application is the derivation of an approximate equation of state for generalized Lennard-Jones systems by combining the isomorph theory with the Rosenfeld-Tarazona expression for the temperature dependence of the potential energy on isochores. It is shown that the new equation of state agrees well with simulations.
Density functional theory of inhomogeneous liquids. IV. Squared-gradient approximation and classical nucleation theory
Authors: Lutsko James F.
Published: April 2011

The squared-gradient approximation to the modified-core Van der Waals density functional theory model is developed. A simple, explicit expression for the SGA coefficient involving only the bulk equation of state and the interaction potential is given. The model is solved for planar interfaces and spherical clusters and is shown to be quantitatively accurate in comparison to computer simulations. An approximate technique for solving the SGA based on piecewise-linear density profiles is introduced and is shown to give reasonable zeroth-order approximations to the numerical solution of the model. The piecewise-linear models of spherical clusters are shown to be a natural extension of classical nucleation theory and serve to clarify some of the nonclassical effects previously observed in liquid–vapor nucleation. Nucleation pathways are investigated using both constrained energy-minimization and steepest-descent techniques.
Embedded density functional theory for covalently bonded and strongly interacting subsystems
Authors: Goodpaster Jason D. , Barnes Taylor A. , Miller Thomas F.
Published: April 2011

Embedded density functional theory (e-DFT) is used to describe the electronic structure of strongly interacting molecular subsystems. We present a general implementation of the Exact Embedding (EE) method [J. Chem. Phys. 133, 084103 (2010)] to calculate the large contributions of the nonadditive kinetic potential (NAKP) in such applications. Potential energy curves are computed for the dissociation of Li+–Be, CH3–CF3, and hydrogen-bonded water clusters, and e-DFT results obtained using the EE method are compared with those obtained using approximate kinetic energy functionals. In all cases, the EE method preserves excellent agreement with reference Kohn–Sham calculations, whereas the approximate functionals lead to qualitative failures in the calculated energies and equilibrium structures. We also demonstrate an accurate pairwise approximation to the NAKP that allows for efficient parallelization of the EE method in large systems; benchmark calculations on molecular crystals reveal ideal, size-independent scaling of wall-clock time with increasing system size.
Coherent control of indirect photofragmentation in the weak-field limit: Control of transient fragment distributions
Authors: Shu Chuan-Cun , Henriksen Niels E.
Published: April 2011

We demonstrate theoretically that laser-induced coherent quantum interference control of asymptotic states of dissociating molecules is possible – even in the (one-photon) weak-field limit starting from a single vibrational eigenstate – when resonances are in play. This is illustrated for the NaI molecule, where it is shown that the probability of observing atomic fragments as well as the distribution of their relative momenta can be changed by a phase modulated pulse with a fixed bandwidth. This type of control is restricted to finite times during the indirect fragmentation.
Use of correlated potential harmonic basis functions for the description of the 4He trimer and small clusters
Authors: Das Tapan Kumar , Chakrabarti Barnali , Canuto Sylvio
Published: April 2011

A correlated many-body basis function is used to describe the 4He trimer and small helium clusters (4HeN) with N = 4 − 9. A realistic helium dimer potential is adopted. The ground state results of the 4He dimer and trimer are in close agreement with earlier findings. But no evidence is found for the existence of Efimov state in the trimer for the actual 4He-4He interaction. However, decreasing the potential strength we calculate several excited states of the trimer which exhibit Efimov character. We also solve for excited state energies of these clusters which are in good agreement with Monte Carlo hyperspherical description.
Single crystal silicon capacitors with low microwave loss in the single photon regime
Authors: Weber S. J. , Murch K. W. , Slichter D. H. , Vijay R. , Siddiqi I.
Published: April 2011

We have fabricated superconducting microwave resonators in a lumped element geometry using single crystal silicon dielectric parallel plate capacitors with C>2 pF. Aluminum devices with resonant frequencies between 4.0 and 6.5 GHz exhibited an average internal quality factor Qi of 2×105 in the single photon excitation regime at T=20 mK. Attributing the observed loss solely to the capacitive element, our measurements place an upper bound on the loss tangent of the silicon dielectric layer of tan δi=5×10−6. This level of loss is an order of magnitude lower than is currently observed in structures incorporating amorphous dielectric materials, thus making single crystal silicon capacitors an attractive, robust route for realizing long-lived quantum circuits.
Free-energy landscape of nucleation with an intermediate metastable phase studied using capillarity approximation
Authors: Iwamatsu Masao
Published: April 2011

Capillarity approximation is used to study the free-energy landscape of nucleation when an intermediate metastable phase exists. The critical nucleus that corresponds to the saddle point of the free-energy landscape as well as the whole free-energy landscape can be studied using this capillarity approximation, and various scenarios of nucleation and growth can be elucidated. In this study, we consider a model in which a stable solid phase nucleates within a metastable vapor phase when an intermediate metastable liquid phase exists. We predict that a composite critical nucleus that consists of a solid core and a liquid wetting layer as well as pure liquid and pure solid critical nuclei can exist depending not only on the supersaturation of the liquid phase relative to that of the vapor phase but also on the wetting behavior of the liquid surrounding the solid. The existence of liquid critical nucleus indicates that the phase transformation from metastable vapor to stable solid occurs via the intermediate metastable liquid phase, which is quite similar to the scenario of nucleation observed in proteins and colloidal systems. By studying the minimum-free-energy path on the free-energy landscape, we can study the evolution of the composition of solid and liquid within nuclei which is not limited to the critical nucleus.
H(D) → D(H) + Cu(111) collision system: Molecular dynamics study of surface temperature effects
Authors: Vurdu Can D. , Güvenç Ziya B.
Published: April 2011

All the channels of the reaction dynamics of gas-phase H (or D) atoms with D (or H) atoms adsorbed onto a Cu(111) surface have been studied by quasiclassical constant energy molecular dynamics simulations. The surface is flexible and is prepared at different temperature values, such as 30 K, 94 K, and 160 K. The adsorbates were distributed randomly on the surface to create 0.18 ML, 0.28 ML, and 0.50 ML of coverages. The multi-layer slab is mimicked by a many-body embedded-atom potential energy function. The slab atoms can move according to the exerted external forces. Treating the slab atoms non-rigid has an important effect on the dynamics of the projectile atom and adsorbates. Significant energy transfer from the projectile atom to the surface lattice atoms takes place especially during the first impact that modifies significantly the details of the dynamics of the collisions. Effects of the different temperatures of the slab are investigated in this study. Interaction between the surface atoms and the adsorbates is modeled by a modified London–Eyring–Polanyi–Sato (LEPS) function. The LEPS parameters are determined by using the total energy values which were calculated by a density functional theory and a generalized gradient approximation for an exchange-correlation energy for many different orientations, and locations of one- and two-hydrogen atoms on the Cu(111) surface. The rms value of the fitting procedure is about 0.16 eV. Many different channels of the processes on the surface have been examined, such as inelastic reflection of the incident hydrogen, subsurface penetration of the incident projectile and adsorbates, sticking of the incident atom on the surface. In addition, hot-atom and Eley-Rideal direct processes are investigated. The hot-atom process is found to be more significant than the Eley-Rideal process. Furthermore, the rate of subsurface penetration is larger than the sticking rate on the surface. In addition, these results are compared and analyzed as a function of the surface temperatures.
Tuning magnetocaloric effect with nanocrystallite size
Authors: Mathew S. P. , Kaul S. N.
Published: April 2011

We demonstrate that the average nanocrystallite size and size distribution can be used as control parameters to respectively tune the peak value and the width-at-half-maximum of the isothermal magnetic entropy change or the adiabatic temperature change during the magnetization process (magnetocaloric effect) such that a reasonably large relative cooling power, conducive to magnetic refrigeration, is achieved.