bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence-Based Diagnostic Treatment and Treatment Planning for Adult Stuttering: A Case Study
Authors: Ellis Lee W. , Beltyukova Svetlana A.
Published: November 2012

This case study describes and evaluates an approach to diagnostic treatment and treatment planning that incorporates principles of evidence-based practice and findings from recent research on efficacious treatments of stuttering. A 22-year-old woman with severe stuttering participated in eight diagnostic treatment sessions in which experts used a simplified ABA single-subject design to assess effects of treatment procedures on her stuttering. Professionals selected treatment procedures based on available evidence regarding the procedures, the clinician’s experience with the procedures, and the client’s preferences. They assessed treatment procedures such as prolonged speech, smooth speech, regulated breathing, self-imposed time out, cancellation and speech using the SpeechEasy. Researchers measured the patient’s outcomes using a measure of stuttering frequency, client self-ratings of stuttering severity, naturalness, rate and effectiveness, and the client’s summary of her overall impressions about the procedures. Researchers analyzed stuttering frequency and client self-ratings using visual inspection and Rasch analysis. Analyzing results, researchers found major differences in the client’s responsiveness to the various treatment procedures. The diagnostic treatment process, which emphasized aspects of client self-evaluation and self-management, helped the client reach conclusions about treatment on her own. The client report measures and simplified ABA format in this study seemed adequate for helping to document differential effects of the treatment procedures and to facilitate treatment planning. Findings support further clinical application and research using this evidence-based approach to diagnostic treatment and treatment planning.
Treatment of Stuttering in a School-Age Child: A Description of a Single Case-Study
Authors: Daniels Derek E.
Published: November 2012

In this article, I will provide support for a broad-based treatment approach with school-age children who stutter. Treatments for stuttering have traditionally prioritized speech modification techniques. However, school-age children who stutter experience a range of self-defeating thoughts and emotions about speaking. In this article, I present data from a case study of one school-age child who stutters. The participant experienced three semesters of treatment from a university clinic. Experts applied a broad-based treatment approach that included both speech and stuttering modification techniques and strategies for managing psychosocial aspects of stuttering. Results suggest that successful therapeutic outcomes depended on a broad-based approach of addressing the participant’s speech, attitudes, and emotions. Clinical implications are discussed.
Navigating Medical Speech-Language Pathology Reports for Children With TBI
Authors: Allison Kristen M. , Turkstra Lyn S.
Published: November 2012

Many children with TBI return to school without the benefit of a formal transition team, so it falls to the school-based SLP to identify an appropriate plan when the student returns to school. Optimally, the school-based SLP can communicate with the hospital-based SLP to discuss medical factors that will affect school performance, but administrative constraints often limit the ability of medical SLPs to communicate directly with school-based SLPs or attend school meetings. As a result of these constraints, school-based SLPs may have only the hospital SLP's report to guide them in identifying appropriate assessment and intervention plans for the child. Medical reports can be challenging to navigate, as each area of practice has its own jargon and the goals and methods used in medical settings differ substantially from those in schools. In this article, we deconstruct a typical medical SLP report and discuss ways to use information in the report to identify appropriate services for children with TBI who are returning to school.
Taking Care of Children After Traumatic Brain Injury
Authors: Haarbauer-Krupa Julie
Published: November 2012

Purpose: The purpose of this article is to inform speech-language pathologists in the schools about issues related to the care of children with traumatic brain injury.

Method: Literature review of characteristics, outcomes and issues related to the needs serving children.

Results: Due to acquired changes in cognition, children with traumatic brain injury have unique needs in a school setting.

Conclusions: Speech-Language Pathologists in the school can take a leadership role with taking care of children after a traumatic brain injury and coordination of medical and educational information.
Management of Unilateral Vocal Fold Paralysis/Paresis: A Laryngologist's Perspective
Authors: Courey Mark
Published: November 2012

This manuscript is a follow up to a panel presentation on “Vocal Fold Paresis & Paralysis: Controversies in Evaluation & Management,” which was held during the 2011 American Speech-Language-Hearing Association (ASHA) Convention in San Diego, California. In addition to me, the other members of the panel included Sarah L. Schneider, MS, CCC-SLP, Director, Speech-Language Pathology Service, UCSF Voice and Swallowing Center; Nelson Roy, PhD, Professor, Speech & Language Pathology, Department of Communication Sciences & Disorders, University of Utah; and Marshall Smith, MD, Professor of Otolaryngology, Department of Surgery, University of Utah. During the panel, I was tasked with presenting the reasons for controversies in the diagnosis and management of vocal fold paralysis. In this manuscript, I will summarize my portion of that presentation and will provide additional information on management options for unilateral vocal fold paralysis (UVFP) from the perspective of a laryngologist.
Treatment of Combined Spinal Deformity in Patient with Ollier Disease and Abnormal Vertebrae
Authors: Ryabykh S. О. , Gubin A. V. , Prudnikova О. G. , Kobyzev А. Е.
Published: November 2012

We report staged treatment of severe combined spinal deformity in an 11-year-old patient with Ollier disease and abnormal cervical vertebra. Combined scoliosis with systemic pathology and abnormal vertebrae is a rare condition and features atypical deformity location and rapid progression rate and frequently involves the rib cage and pelvis, disturbing the function of chest organs and skeleton. Progressive deformity resulted in cachexia and acute respiratory failure. A halo-pelvic distraction device assembled of Ilizarov components was employed for a staged surgical treatment performed for lifesaving indications. After vital functions stabilized, the scoliosis curve of the cervical spine was corrected and fixed with a hybrid system of transpedicular supporting points, connecting rods, and connectors that provided staged distraction during growth. The treatment showed good functional and cosmetic result.
Nachrichten aus der internationalen Fachliteratur
Authors: Fath Roland , Grade Marian , Baust Holger , Lichert Frank , Achenbach Johannes , Grätzel von Grätz Philipp , Kriegeskorte Volker , Weiß Maria
Published: November 2012

In dieser Rubrik fassen wir Nachrichten aus der Wissenschaft kurz und prägnant für Sie zusammen. In der aktuellen Ausgabe mit folgenden Themen:
Die Einwilligungsfähigkeit des Patienten
Authors: Erhard Daniela
Published: November 2012

Keine Behandlung ohne Aufklärung und Einwilligung des Patienten. Doch wer ist eigentlich einwilligungsfähig? Und was, wenn es jemand nicht ist? Ein Überblick über Definitionen, Vorgehen in der Praxis und rechtliche Regelungen.
Geriatrische Patienten – Typische Probleme und ihre Behandlung
Authors: Frohnhofen Helmut , Willschrei Heinz Peter
Published: November 2012

Nur wenn man die geriatrischen Probleme dieser Patienten rechtzeitig erkennt und auf die dadurch bedingten Bedürfnisse eingeht, kann man das Risiko von Komplikationen und ungünstigen Krankenhausverläufen reduzieren. Zu den häufigsten Problemen älterer Patienten, die im Beitrag erläutert werden, zählen die Altersgebrechlichkeit (Frailty), die Störung der Kognition (Demenz-Syndrome), der unsichere Gang mit Sturzrisiko, verordnete oder tolerierte Bettruhe mit dem Risiko eines Dekubitus, unerkannter und unbehandelter Schmerz, Polypharmazie, Mangelernährung und ein gestörter Schluckakt. Parameter der Funktionalität und Kognition müssen frühzeitig in ein umfassendes Behandlungskonzept integriert werden.Das geriatrische Assessment deckt sowohl Probleme wie auch Ressourcen und Potenziale auf.
Medikamente in der Schwangerschaft – Welche Substanzen eignen sich im Akutfall?
Authors: Nauheimer Dirk
Published: November 2012

Eine Vielzahl an Medikamenten passiert leicht die Plazenta und stellt während der Schwangerschaft wie auch peripartal ein potenzielles Risiko für Fetus oder Neugeborenen dar. Trotz aller Zurückhaltung lässt es sich nicht immer vermeiden, während der Schwangerschaft Medikamente zu verordnen. Häufig notwendig wird dies im Rahmen von ungeplanten Krankenhausaufenthalten oder zur Geburtshilfe. Neben den geburtshilflichen Eingriffen stellen sich jedes Jahr etwa 0.5–2% der Schwangeren zu nichtgynäkologischen Eingriffen in der Klinik vor. Daher ist das Wissen um die mütterlichen physiologischen Veränderungen während der Schwangerschaft sowie um mögliche negative Einflüsse häufig verwendeter Medikamente im klinischen Alltag auf Mutter und Fetus von besonderer Bedeutung. Dieser Beitrag beschäftigt sich mit den physiologischen Veränderungen in der Schwangerschaft und den Auswirkungen verschiedener Substanzen mit dem Ziel, die Anwendung im akuten Anwendungsbereich für Mutter und Fetus so sicher wie möglich zu gestalten.
Isolated Hadamard matrices from mutually unbiased product bases
Authors: McNulty Daniel , Weigert Stefan
Published: November 2012

A new construction of complex Hadamard matrices of composite order d = pq, with primes p, q, is presented which is based on pairs of mutually unbiased bases containing only product states. For product dimensions d < 100, we illustrate the method by deriving many previously unknown complex Hadamard matrices. We obtain at least 12 new isolated matrices of Butson type, with orders ranging from 9 to 91.
Finite amplitude vibrations of a sharp-edged beam immersed in a viscous fluid near a solid surface
Authors: Grimaldi Emma , Porfiri Maurizio , Soria Leonardo
Published: November 2012

In this paper, we study finite amplitude bending vibrations of a slender thin beam immersed in a quiescent viscous liquid and oscillating near a solid surface. We focus on the regime of low Knudsen and squeeze numbers and moderately large Keulegan-Carpenter number, for which neither squeeze film models nor unsteady Stokes hydrodynamics are suitable to describe the flow physics. In this case, the distributed hydrodynamic loading experienced by the oscillating beam is represented by a complex-valued hydrodynamic function, which explicitly depends on the Keulegan-Carpenter number to account for convection-driven nonlinearities in the fluid-structure interaction. We conduct a parametric study on the two-dimensional computational fluid dynamics of a rigid lamina oscillating in the vicinity of a solid surface to establish a handleable semianalytical formula for the hydrodynamic function in terms of the key nondimensional parameters. We validate the proposed modeling approach through experiments on centimeter-size compliant cantilevers vibrating underwater under base excitation at varying distances from a rigid wall.
Role of the dielectric mismatch on the properties of donors in semiconductor nanostructures bounded by air
Authors: Corfdir Pierre , Lefebvre Pierre
Published: November 2012

We compute by envelope function calculations the binding energy EB of donor atoms in thin slabs of semiconductor bounded by air, accounting for the dielectric mismatch between air and the semiconductor. We detail how EB depends on the donor-site and on the thickness of the slab. We show that due to the competition between surface and dielectric mismatch effects, EB does not monotonically decrease from the center to the surface of the nanostructures. Finally, we discuss our results in regard to recent photoluminescence experiments performed on ensemble and single GaN nanowires.
Theoretical and experimental study of the backward-wave radiation using resonant-type metamaterial transmission lines
Authors: Xu He-Xiu , Wang Guang-Ming , Qi Mei-Qing , Xu Zhi-Ming
Published: November 2012

We investigate theoretically and experimentally the backward radiation of a type of negative-refractive-index (NRI) resonant-type metamaterial transmission lines (TL). The NRI TL goes beyond the bulk metamtaterials made of original split-ring resonator/wire and the NRI TLs using inter-digital capacitors and shorted stub inductors. The operation mechanism is investigated in depth behind a general composite right/left handed concept based on a TL theory and is interpreted from the perspective of field distributions, showing that the antiparallel phase and group velocities give rise to the full-space beam scanning peppery from backward, through broadside and finally to forward as frequency increases. In addition, we discuss the possible realizations by using complementary split ring resonators and other electrically smaller fractal-shaped resonators with different configurations. The fractal strategy certainly fulfills the challenging necessity of drastically increasing left handed capacitances and inductances in the homogenization process. In all cases, the resultant radiation is analogous to the reversed Cherenkov radiation. Moreover, the comprehensive theory established for a generic type of TL metamaterial paves the way for a round of antenna design, which is of a reference value.
Nuclear fusion of deuterons with light nuclei driven by Coulomb explosion of nanodroplets
Authors: Ron Shlomo , Last Isidore , Jortner Joshua
Published: November 2012

Theoretical-computational studies of table-top laser-driven nuclear fusion of high energy (up to 15 MeV) deuterons with 7Li, 6Li, T, and D demonstrate the attainment of high fusion yields. The reaction design constitutes a source of Coulomb exploding deuterium nanodroplets driven by an ultraintense, near-infrared, femtosecond Gaussian laser pulse (peak intensity 2 × 1018–5 × 1019 W cm−2) and a solid, hollow cylindrical target containing the second reagent. The exploding nanodroplets source is characterized by the deuteron kinetic energies, their number, and the laser energy absorbed by a nanodroplet. These were computed by scaled electron and ion dynamics simulations, which account for intra-nanodroplet laser intensity attenuation and relativistic effects. The fusion yields Y are determined by the number of the source deuterons and by the reaction probability. When laser intensity attenuation is weak within a single nanodroplet and throughout the nanodroplets assembly, Y exhibits a power law increase with increasing the nanodroplet size. Y is maximized for the nanodroplet size and laser intensity corresponding to the "transition" between the weak and the strong intensity attenuation domains. The dependence of Y on the laser pulse energy W scales as W2 for weak assembly intensity attenuation, and as W for strong assembly intensity attenuation. This reaction design attains the highest table-top fusion efficiencies (up to 4 × 109 J−1 per laser pulse) obtained up to date.
The break-up of Ekman theory in a flow subjected to background rotation and driven by a non-conservative body force
Authors: Duran-Matute M. , Di Nitto G. , Trieling R. R. , Kamp L. P. J. , van Heijst G. J. F.
Published: November 2012

We present an experimental/numerical study of a dipolar flow structure in a shallow layer of electrolyte driven by electromagnetic forcing and subjected to background rotation. The aim of this study is to determine the influence of a non-conservative body force on the range of applicability of the classical Ekman boundary layer theory in rapidly rotating systems. To address this question, we study the response of the flow to the three control parameters: the magnitude of the forcing, the rotation rate of the system, and the shallowness of the layer. This response is quantified taking into account the magnitude of the flow velocity (represented by the Reynolds number), the symmetry between both vortex cores, and the vertical profile of the horizontal velocity. As in the case without background rotation, the response of the flow exhibits two scaling regimes (a linear and a nonlinear regime) in which the flow exhibits different vertical profiles of velocity. The transition between the two regimes occurs when the convective acceleration becomes of the same order as the viscous damping. This suggests that the applicability of the Ekman theory depends on the existence of a balance between the forcing and the damping due to the Ekman layers and does not depend solely on the value of the Rossby number as for decaying flows. On the other hand, the cyclone/anticyclone asymmetry is governed exclusively by the Rossby number.
Non-linear magnetohydrodynamic simulations of density evolution in Tore Supra sawtoothing plasmas
Authors: Nicolas T. , Sabot R. , Garbet X. , Lütjens H. , Luciani J.-F. , Guimaraes-Filho Z. , Decker J. , Merle A.
Published: November 2012

The plasma density evolution in sawtooth regime on the Tore Supra tokamak is analyzed. The density is measured using fast-sweeping X-mode reflectometry which allows tomographic reconstructions. There is evidence that density is governed by the perpendicular electric flows, while temperature evolution is dominated by parallel diffusion. Postcursor oscillations sometimes lead to the formation of a density plateau, which is explained in terms of convection cells associated with the kink mode. A crescent-shaped density structure located inside q = 1 is often visible just after the crash and indicates that some part of the density withstands the crash. 3D full MHD nonlinear simulations with the code XTOR-2F recover this structure and show that it arises from the perpendicular flows emerging from the reconnection layer. The proportion of density reinjected inside the q = 1 surface is determined, and the implications in terms of helium ash transport are discussed.
Diffusion of multiple species with excluded-volume effects
Authors: Bruna Maria , Chapman S. Jonathan
Published: November 2012

Stochastic models of diffusion with excluded-volume effects are used to model many biological and physical systems at a discrete level. The average properties of the population may be described by a continuum model based on partial differential equations. In this paper we consider multiple interacting subpopulations/species and study how the inter-species competition emerges at the population level. Each individual is described as a finite-size hard core interacting particle undergoing Brownian motion. The link between the discrete stochastic equations of motion and the continuum model is considered systematically using the method of matched asymptotic expansions. The system for two species leads to a nonlinear cross-diffusion system for each subpopulation, which captures the enhancement of the effective diffusion rate due to excluded-volume interactions between particles of the same species, and the diminishment due to particles of the other species. This model can explain two alternative notions of the diffusion coefficient that are often confounded, namely collective diffusion and self-diffusion. Simulations of the discrete system show good agreement with the analytic results.
Heteroepitaxial growth and characterization of ZnO films on Gd3Ga5O12 garnet substrates
Authors: Ono Yosuke , Matsui Hiroaki , Tabata Hitoshi
Published: November 2012

ZnO (0001) films have been grown epitaxially on (111) and (001) planes of Gd3Ga5O12 (GGG) substrates, which have different orientations and symmetries. The X-ray diffraction revealed that the out-of-plane and in-plane epitaxial relations of ZnO films on the GGG (111) substrates [ZnO/GGG (111)] were the [0001]ZnO || [001]GGG and [10 − 10]ZnO || [1 − 12]GGG ± 21°, while ZnO films on the GGG (001) substrates [ZnO/GGG (001)] showed the out-of-plane and in-plane epitaxial relations with the [0001]ZnO || [001]GGG and [10 − 10]ZnO || [100]GGG, [010]GGG. The mosaic spread of ZnO/GGG (001) along the in-plane and out-of-plane directions was larger than that of ZnO/GGG (111), which was closely related to a number of dislocations generated in the ZnO lattices. These mosaic structures mainly determined crystal quality of ZnO films, as also confirmed by transmittance electron microscopy (TEM). Moreover, high-resolution TEM showed that the lattice of ZnO along the [0001] direction was connected with lattices of GGG along the [111] and [001] directions without interface buffer layers. Finally, crystalline quality of ZnO films was also clarified by temperature-dependent photoluminescent spectroscopy. This study contributes to provide a new device concept on oxide semiconductor/garnet interfaces.
A piezo motor based on a new principle with high output force, rigidity and integrity: The Tuna Drive
Authors: Liu Xiaolong , Lu Qingyou
Published: November 2012

We present a linear piezoelectric motor as simple as one piezoelectric scanner tube (PST) spring-clamping a central shaft at both ends with roughly equal clamping forces. The clamping points are aligned with ±X electrodes at one end and ±Y electrodes at the other end. Thus, the ±X (or ±Y) push-pull motions of the PST can cause the push-pull motions of the clamping points on the shaft (called push-pull rubbing), which reduces the total dynamic friction force at one (or the other) end of the PST. This new piezo motor advances one step by fast push-pull rubbing at one end while slowly retracting the PST followed by fast push-pull rubbing at the other end while slowly elongating the PST. Apart from the obvious advantages of simplicity, rigidity, integrity, etc., we will also show that this motor can produce a large output force, which we believe is because of the huge drop of the clamping friction force when the push-pull rubbing occurs.
High aspect ratio nanoneedle probes with an integrated electrode at the tip apex
Authors: Comstock David J. , Elam Jeffrey W. , Pellin Michael J. , Hersam Mark C.
Published: November 2012

Many nanoscale characterization techniques require high aspect ratio nanoneedle probes with an integrated electrode that is electrically insulated everywhere except at the tip apex. We report the utilization of electron beam induced deposition, focused ion beam milling, and atomic layer deposition to fabricate such probes at the sub-100 nm length scale. This fabrication method is highly reproducible and enables precise control of the probe dimensions. Subsequent electrodeposition at the integrated electrode enables customized functionalization of the tip apex. These probes have clear applications in scanning electrochemical microscopy-atomic force microscopy, magnetic force microscopy, apertureless near-field optical microscopy, and tip-enhanced Raman spectroscopy.
Field-induced lattice deformation contribution to the magnetic anisotropy
Authors: Paes V. Z. C. , Mosca D. H.
Published: November 2012

Elastic and magnetoelastic effects are important to understand physical properties of many magnetic systems. Particularly, the influence of field-induced lattice deformation in the magnetic anisotropy and non-linear terms are commonly needed to describe the magnetic behavior of nanosystems. In this work, we exploit the contribution of field-induced lattice deformation to magnetic anisotropy for systems with hexagonal and cubic structures. Analytical expressions for changes in the first- and second-order magnetic anisotropy constants were obtained for systems which experience general and biaxial strains. Our estimates using bulk parameters available for ferromagnetic materials suggest that field-induced anisotropy contributions can become comparable to magnetocrystalline anisotropy, if the system possesses a strong magnetoelastic response.
The x-ray absorption spectroscopy model of solvation about sulfur in aqueous L-cysteine
Authors: Sarangi Ritimukta , Frank Patrick , Benfatto Maurizio , Morante Silvia , Minicozzi Velia , Hedman Britt , Hodgson Keith O.
Published: November 2012

The environment of sulfur in dissolved aqueous L-cysteine has been examined using K-edge x-ray absorption spectroscopy (XAS), extended continuum multiple scattering (ECMS) theory, and density functional theory (DFT). For the first time, bound-state and continuum transitions representing the entire XAS spectrum of L-cysteine sulfur are accurately reproduced by theory. Sulfur K-edge absorption features at 2473.3 eV and 2474.2 eV represent transitions to LUMOs that are mixtures of S–C and S–H σ* orbitals significantly delocalized over the entire L-cysteine molecule. Continuum features at 2479, 2489, and 2530 eV were successfully reproduced using extended continuum theory. The full L-cysteine sulfur K-edge XAS spectrum could not be reproduced without addition of a water-sulfur hydrogen bond. Density functional theory analysis shows that although the Cys(H)S⋯H–OH hydrogen bond is weak (∼2 kcal) the atomic charge on sulfur is significantly affected by this water. MXAN analysis of hydrogen-bonding structures for L-cysteine and water yielded a best fit model featuring a tandem of two water molecules, 2.9 Å and 5.8 Å from sulfur. The model included a Scys⋯H–Ow1H hydrogen-bond of 2.19 Å and of 2.16 Å for H2Ow1⋯H–Ow2H. One hydrogen-bonding water-sulfur interaction alone was insufficient to fully describe the continuum XAS spectrum. However, density functional theoretical results are convincing that the water-sulfur interaction is weak and should be only transient in water solution. The durable water-sulfur hydrogen bond in aqueous L-cysteine reported here therefore represents a break with theoretical studies indicating its absence. Reconciling the apparent disparity between theory and result remains the continuing challenge.
Fabrication of samples for scanning probe experiments on quantum spin Hall effect in HgTe quantum wells
Authors: Baenninger M. , König M. , Garcia A. G. F. , Mühlbauer M. , Ames C. , Leubner P. , Brüne C. , Buhmann H. , Molenkamp L. W. , Goldhaber-Gordon D.
Published: November 2012

We present a fabrication process for devices on HgTe quantum wells through which the quantum spin Hall regime can be reached without the use of a top-gate electrode. We demonstrate that a nominally undoped HgTe quantum well can be tuned from p-type to n-type, crossing through the quantum spin Hall regime, using only a back-gate hundreds of microns away. Such structures will enable scanning probe investigations of the quantum spin Hall effect that would not be possible in the presence of a gate electrode on the surface of the wafer. All processes are kept below 80 °C to avoid degradation of the heat-sensitive HgTe quantum wells.
Electronic band structure and effective mass parameters of Ge1-xSnx alloys
Authors: Lu Low Kain , Yang Yue , Han Genquan , Fan Weijun , Yeo Yee-Chia
Published: November 2012

This work investigates the electronic band structures of bulk Ge1-xSnx alloys using the empirical pseudopotential method (EPM) for Sn composition x varying from 0 to 0.2. The adjustable form factors of EPM were tuned in order to reproduce the band features that agree well with the reported experimental data. Based on the adjusted pseudopotential form factors, the band structures of Ge1-xSnx alloys were calculated along high symmetry lines in the Brillouin zone. The effective masses at the band edges were extracted by using a parabolic line fit. The bowing parameters of hole and electron effective masses were then derived by fitting the effective mass at different Sn compositions by a quadratic polynomial. The hole and electron effective mass were examined for bulk Ge1-xSnx alloys along specific directions or orientations on various crystal planes. In addition, employing the effective-mass Hamiltonian for diamond semiconductor, band edge dispersion at the Γ-point calculated by 8-band k.p. method was fitted to that obtained from EPM approach. The Luttinger-like parameters were also derived for Ge1-xSnx alloys. They were obtained by adjusting the effective-mass parameters of k.p method to fit the k.p band structure to that of the EPM. These effective masses and derived Luttinger parameters are useful for the design of optical and electronic devices based on Ge1-xSnx alloys.
Static and dynamic properties of poly(3-hexylthiophene) films at liquid/vacuum interfaces
Authors: Yimer Yeneneh Y. , Tsige Mesfin
Published: November 2012

All-atom molecular dynamics simulations are used to study static and dynamic properties of poly(3-hexylthiophene) (P3HT) films at liquid/vacuum interfaces with regards to their dependence on both temperature and molecular weight. The static properties of the films are characterized by calculating specific volume, interfacial width, orientational ordering of the hexyl groups, and surface tension. The specific volume found to be a monotonically decreasing function of the molecular weight while its dependence on temperature follows the Simha-Somcynsky's equation of state. The orientational ordering calculations show the hexyl groups protruding from the vacuum side of the interface, where the degree of order at the interface is found to be strongly dependent on both temperature and molecular weight. The surface tension values show a linear dependence on temperature and the molecular weight dependence is equally described by both M−2/3 and M−1 power law models. The dynamic properties are quantified by calculating diffusion coefficients for the chain centers-of-mass and thiophene ring segments as well as first-order and second-order end-to-end vector autocorrelations and chain backbone torsion autocorrelation. All calculated dynamic properties show strong dependence on both temperature and molecular weight. All the autocorrelations are well described by Kohlrausch-Williams-Watts equation. Our detailed analysis of the static and dynamic properties of P3HT films show that the calculated static and dynamic properties data can be fit with well-known polymer models.
K-shell spectroscopy of silicon ions as diagnostic for high electric fields
Authors: Loetzsch R. , Jäckel O. , Höfer S. , Kämpfer T. , Polz J. , Uschmann I. , Kaluza M. C. , Förster E. , Stambulchik E. , Kroupp E. , Maron Y.
Published: November 2012

We developed a detection scheme, capable of measuring X-ray line shape of tracer ions in μm thick layers at the rear side of a target foil irradiated by ultra intense laser pulses. We performed simulations of the effect of strong electric fields on the K-shell emission of silicon and developed a spectrometer dedicated to record this emission. The combination of a cylindrically bent crystal in von Hámos geometry and a CCD camera with its single photon counting capability allows for a high dynamic range of the instrument and background free spectra. This approach will be used in future experiments to study electric fields of the order of TV/m at high density plasmas close to solid density.
Measurement of bunch length in Indus-1 storage ring using fast photodiode
Authors: Garg Akash Deep , Nathwani R. K. , Holikatti A. C. , Kumar Karnewar Akhilesh , Tyagi Y. , Yadav S. , Puntambekar T. A. , Navathe C. P.
Published: November 2012

The length of electron bunches in a storage ring is an important parameter for both synchrotron radiation users and accelerator physicists. Several methods are used for measurements of bunch length using electronic and optical instruments. We have measured temporal profile of synchrotron radiation emitted from dipole magnet of Indus-1 by using fast photodiode. Bunch length is calculated by assuming gaussian profile for the particles inside bunch. The results show that bunch length is increasing with the decrease of gap voltage of RF cavity. These measurements were carried out at low beam current; at high voltage results are in close agreement with theory and the values estimated using ZAP code. In the second experiment, the results show that bunch length increases with the increase of beam current inside the bunch, and above threshold current, it follows Chao-Gareyte scaling law. The longitudinal broadband impedance for Indus-1 SRS was estimated using Keil-Schnell criterion and results were compared with theoretical estimated values using ZAP code.
Quadrupole effects in photoabsorption in ZnO quantum dots
Authors: Maikhuri Deepti , Purohit S. P. , Mathur K. C.
Published: November 2012

Electronic transitions in the quantum confined states in the conduction band of spherical ZnO semiconductor quantum dot are studied. Photoabsorption spectra and oscillator strengths have been obtained for various sizes of quantum dot using effective mass approximation. Electric quadrupole effect has been included in addition to the electric dipole effect. The nonlinear contribution to photoabsorption spectra has also been studied. Results for transition energies of the quantum confined states are found to be in good agreement with the available experimental data.
Micellar shape anisotropy and optical indicatrix in reentrant isotropic—nematic phase transitions
Authors: Simões M. , Palangana A. J. , Gobato R. , Santos O. R.
Published: November 2012

In this work, we will show that the concept of nematic order parameter and a generalization of the concept of optical indicatrix, largely used in optics of anisotropic crystals, can be joined to give a new geometrical representation to the anisotropies found in lyotropic liquid crystals. Our theoretical approach will be illustrated using refractive index data of reentrant isotropic—calamitic (discotic) nematic phase transitions of potassium laurate, decanol, and heavy water mixtures.
Why and how does native topology dictate the folding speed of a protein?
Authors: Rustad Mark , Ghosh Kingshuk
Published: November 2012

Since the pioneering work of Plaxco, Simons, and Baker, it is now well known that the rates of protein folding strongly correlate with the average sequence separation (absolute contact order (ACO)) of native contacts. In spite of multitude of papers, our understanding to the basis of the relation between folding speed and ACO is still lacking. We model the transition state as a Gaussian polymer chain decorated with weak springs between native contacts while the unfolded state is modeled as a Gaussian chain only. Using these hamiltonians, our perturbative calculation explicitly shows folding speed and ACO are linearly related when only the first order term in the series is considered. However, to the second order, we notice the existence of two new topological metrics, termed COC1 and COC2 (COC stands for contact order correction). These additional correction terms are needed to properly account for the entropy loss due to overlapping (nested or linked) loops that are not well described by simple addition of entropies in ACO. COC1 and COC2 are related to fluctuations and correlations among different sequence separations. The new metric combining ACO, COC1, and COC2 improves folding speed dependence on native topology when applied to three different databases: (i) two-state proteins with only α/β and β proteins, (ii) two-state proteins (α/β, β and purely helical proteins all combined), and (iii) master set (multi-state and two-state) folding proteins. Furthermore, the first principle calculation provides us direct physical insights to the meaning of the fit parameters. The coefficient of ACO, for example, is related to the average strength of the contacts, while the constant term is related to the protein folding speed limit. With the new scaling law, our estimate of the folding speed limit is in close agreement with the widely accepted value of 1 μs observed in proteins and RNA. Analyzing an exhaustive set (7367) of monomeric proteins from protein data bank, we find our new topology based metric (combining ACO, COC1, and COC2) scales as N0.54, N being the number of amino acids in a protein. This is in remarkable agreement with a previous argument based on random systems that predict protein folding speed depends on exp (− N0.5). The first principle calculation presented here provides deeper insights to the role of topology in protein folding and unifies many parallel arguments, seemingly disconnected, demonstrating the existence of universal mechanism in protein folding kinetics that can be understood from simple polymer physics based principles.
Proton emission from cone-in-shell fast-ignition experiments at Omega
Authors: Sinenian N. , Theobald W. , Frenje J. A. , Stoeckl C. , Séguin F. H. , Li C. K. , Petrasso R. D. , Stephens R. B.
Published: November 2012

Measurements of energetic protons from cone-in-shell fast-igniton implosions at Omega have been conducted. In these experiments, charged-particle spectrometers were used to measure a significant population (>1013) of energetic protons (7.5 MeV max.), indicating the presence of strong electric fields. These energetic protons, observed in directions both transverse and forward relative to the direction of the short-pulse laser beam, have been used to study aspects of coupling efficiency of the petawatt fast-ignitior beam. Approximately 5% of the laser energy coupled to hot electrons was lost to fast ions. Forward going protons were less energetic and showed no dependence on laser intensity or whether the cone tip was intact when the short-pulse laser was fired. Maximum energies of protons emitted transverse to the cone-in-shell target scale with incident on-target laser intensity (2–6×1018W-cm−2), as described by the ponderomotive scaling (∝I1/2). It is shown that these protons are accelerated from the entire cone, rather than from the cone tip alone. These protons were used to estimate the lower limit on the hot-electron temperature, which was found to be hotter than the ponderomotive scaling by factors of 2–3.
The simplest equivalent circuit of a pulsed dielectric barrier discharge and the determination of the gas gap charge transfer
Authors: Pipa A. V. , Koskulics J. , Brandenburg R. , Hoder T.
Published: November 2012

The concept of the simplest equivalent circuit for a dielectric barrier discharge (DBD) is critically reviewed. It is shown that the approach is consistent with experimental data measured either in large-scale sinusoidal-voltage driven or miniature pulse-voltage driven DBDs. An expression for the charge transferred through the gas gap q(t) is obtained with an accurate account for the displacement current and the values of DBD reactor capacitance. This enables (i) the significant reduction of experimental error in the determination of q(t) in pulsed DBDs, (ii) the verification of the classical electrical theory of ozonizers about maximal transferred charge qmax, and (iii) the development of a graphical method for the determination of qmax from charge-voltage characteristics (Q-V plots, often referred as Lissajous figures) measured under pulsed excitation. The method of graphical presentation of qmax is demonstrated with an example of a Q-V plot measured under pulsed excitation. The relations between the discharge current jR(t), the transferred charge q(t), and the measurable parameters are presented in new forms, which enable the qualitative interpretation of the measured current and voltage waveforms without the knowledge about the value of the dielectric barrier capacitance Cd. Whereas for quantitative evaluation of electrical measurements, the accurate estimation of the Cd is important.
Evolution of ultrashort laser pulse in large amplitude plasma waves
Authors: Bu Zhigang , Ji Peiyong
Published: November 2012

The propagation and evolution of an ultrashort laser pulse in a large amplitude plasma wave are investigated based on the photon kinetic theory. The photon number distribution function for a laser pulse in the phase space is analytically obtained by solving the photon kinetic equation in the background plasma wave. And then, the behavior of the laser pulse can be described by combining the single photon dynamics and the photon number distribution function. The evolutions of the photon number density in the coordinate and frequency domain space are discussed, and broadening or compressing of the laser pulse is also displayed in this paper. In particular, the frequency shift of the entire laser pulse is analyzed, which reflects a way of energy transformation between the laser pulse and the plasma wave.
In-plane electric fields in magnetic islands during collisionless magnetic reconnection
Authors: Chen Li-Jen , Daughton William , Bhattacharjee Amitava , Torbert Roy B. , Roytershteyn Vadim , Bessho Naoki
Published: November 2012

Magnetic islands are a common feature in both the onset and nonlinear evolution of magnetic reconnection. In collisionless regimes, the onset typically occurs within ion-scale current layers leading to the formation of magnetic islands when multiple X lines are involved. The nonlinear evolution of reconnection often gives rise to extended electron current layers (ECL) which are also unstable to formation of magnetic islands. Here, we show that the excess negative charge and strong out-of-plane electron velocity in the ECL are passed on to the islands generated therein, and that the corresponding observable distinguishing the islands generated in the ECL is the strongly enhanced in-plane electric fields near the island core. The islands formed in ion-scale current layers do not have these properties of the ECL-generated islands. The above result provides a way to assess the occurrence and importance of extended ECLs that are unstable to island formation in space and laboratory plasmas.
Charged electret deposition for the manipulation of high power microwave flashover delay times
Authors: Stephens J. , Beeson S. , Dickens J. , Neuber A.
Published: November 2012

A quasi-permanent charged electret is embedded into the radiation window of a high power microwave system. It was experimentally observed that the additional electrostatic field introduced by the electret alters the delay times associated with the development of plasma at the window surface, resulting from high power microwave excitation. The magnitudes of both the statistical and formative delay times are investigated in detail for different pressures. Experimental observations are related to calculated discharge parameters using known E/p dependent properties.
Dust negative ion acoustic shock waves considering dust size distribution effect
Authors: Ma Yi-Rong , Wang Cang-Long , Zhang Jian-Rong , Sun Jian-An , Duan Wen-Shan , Yang Lei
Published: November 2012

A multi-ion dusty plasma containing hot isothermal electrons, ions (light positive ions and heavy negative ions), and extremely and negatively charged dust grains is studied in the present paper. The dust negative ion acoustic shock waves have been investigated by employing the reductive perturbation method. How the dust size distribution affects the height and the thickness of the nonlinear shock wave is studied. It is noted that the different dust size distribution has different shock wave form and different moving speed.
On the formulation of a density matrix functional for Van der Waals interaction of like- and opposite-spin electrons in the helium dimer
Authors: Mentel Ł. M. , Sheng X. W. , Gritsenko O. V. , Baerends E. J.
Published: November 2012

Whereas a density functional that incorporates dispersion interaction has remained elusive to date, we demonstrate that in principle the dispersion energy can be obtained from a density matrix functional. In density matrix functional theory one tries to find suitable approximations to the two-particle reduced density matrix (2RDM) in terms of natural orbitals (NOs) and natural orbital occupation numbers (ONs). The total energy is then given as a function(al) of the NOs and ONs, i.e., as an implicit functional of the 1RDM. The left-right correlation in a (dissociating) bond, as well as various types of dynamical correlation, can be described accurately with a NO functional employing only J and K integrals (JK-only functional). We give a detailed analysis of the full CI wavefunction of the He2 dimer, from which the dispersion part of the two-particle density matrix is obtained. It emerges that the entirely different physics embodied in the dispersion interaction leads to an essentially different type of exchange-correlation orbital functional for the dispersion energy (non-JK). The distinct NO functionals for the different types of correlation imply that they can be used in conjunction without problems of double counting. Requirements on the (primitive) basis set for Van der Waals bonding appear to be more modest than for other types of correlation.
Optimized coordinates for anharmonic vibrational structure theories
Authors: Yagi Kiyoshi , Keçeli Murat , Hirata So
Published: November 2012

A procedure to determine optimal vibrational coordinates is developed on the basis of an earlier idea of Thompson and Truhlar [J. Chem. Phys. 77, 3031 (1982)]10.1063/1.444226. For a given molecule, these coordinates are defined as the unitary transform of the normal coordinates that minimizes the energy of the vibrational self-consistent-field (VSCF) method for the ground state. They are justified by the fact that VSCF in these coordinates becomes exact in two limiting cases: harmonic oscillators, where the optimized coordinates are normal, and noninteracting anharmonic oscillators, in which the optimized coordinates are localized on individual oscillators. A robust and general optimization algorithm is developed, which decomposes the transformation matrix into a product of Jacobi matrices, determines the rotation angle of each Jacobi matrix that minimizes the energy, and iterates the process until a minimum in the whole high dimension is reached. It is shown that the optimized coordinates are neither entirely localized nor entirely delocalized (or normal) in any of the molecules (the water, water dimer, and ethylene molecules) examined (apart from the aforementioned limiting cases). Rather, high-frequency stretching modes tend to be localized, whereas low-frequency skeletal vibrations remain normal. On the basis of these coordinates, we introduce two new vibrational structure methods: optimized-coordinate VSCF (oc-VSCF) and optimized-coordinate vibrational configuration interaction (oc-VCI). For the modes that become localized, oc-VSCF is found to outperform VSCF, whereas, for both classes of modes, oc-VCI exhibits much more rapid convergence than VCI with respect to the rank of excitations. We propose a rational configuration selection for oc-VCI when the optimized coordinates are localized. The use of the optimized coordinates in VCI with this configuration selection scheme reduces the mean absolute errors in the frequencies of the fundamentals and the first overtones/combination tones from 104.7 (VCI) to 10.7 (oc-VCI) and from 132.4 (VCI) to 8.2 (oc-VCI) cm−1 for the water molecule and the water dimer, respectively. It is also shown that the degree of coupling in the potential for ethylene is reduced effectively from four modes to three modes by the transformation from the normal to optimized coordinates, which enhances the accuracy of oc-VCI with low-rank excitations.
Thermal stability of thermoelectric materials via in situ resistivity measurements
Authors: Lukas K. C. , Liu W. S. , Jie Q. , Ren Z. F. , Opeil C. P.
Published: November 2012

An experimental setup for determining the electrical resistivity of several types of thermoelectric materials over the temperature range 20 < T < 550 °C is described in detail. One resistivity measurement during temperature cycling is performed and explained for Cu0.01Bi2Te2.7Se0.3 and a second measurement is made on Yb0.35Co4Sb12 as a function of time at 400 °C. Both measurements confirm that the materials are thermally stable for the temperature range and time period measured. Measurements made during temperature cycling show an irreversible decrease in the electrical resistivity of Cu0.01Bi2Te2.7Se0.3 when the measuring temperature exceeds the maximum sample fabrication temperature. Several other possible uses of such a system include but are not limited to studying the effects of annealing and/or oxidation as a function of both temperature and time.