bluuebunny/crossref_metadata_2025 huggingface dataset:
Concussion Evaluation Methods Among Washington State High School Football Coaches and Athletic Trainers
Authors: Murphy Ashley , Kaufman Marla S. , Molton Ivan , Coppel David B. , Benson John , Herring Stanley A.
Published: June 2012

Objective

To evaluate awareness of concussion assessment methods and to determine whether there are differences among Washington State high school football coaches and athletic trainers in urban versus rural school districts.

Design

A Catalyst WebQ survey link was randomly sent by e‐mail to varsity head football coaches, athletic trainers, and athletic directors in Washington State school districts.

Participants

Survey participants were high school varsity head football coaches and athletic trainers from a total of 106 Washington State high schools.

Methods

A 12‐item questionnaire on Catalyst WebQ was distributed via e‐mail. The survey inquired about use of the methods of concussion assessment, both on the field and for follow‐up; participants' concussion education training; and familiarity with Washington State's Zackery Lystedt Law.

Main Outcome Measurements

The survey examined differences in concussion management practices between rural and urban school districts and also between coaches and athletic trainers in Washington State, specifically regarding the use of the Standardized Concussion Assessment Tool 2 (SCAT2) and neurocognitive testing (NCT).

Results

Twenty‐seven of 48 respondents (56%) used the SCAT2 for on‐the‐field assessment; urban respondents were significantly more likely to use SCAT2 (P < .05). The difference between coaches and athletic trainers with respect to SCAT2 use was not significant (P = .08). NCT was used by 18 of 58 respondents (31%). This was more commonly used by those in urban districts (P < .01) and by athletic trainers (P < .01). Eleven of these 18 individuals (61%) reported that a neuropsychologist interpreted the results; the rest used other providers not specifically trained in neuropsychology. There was no statistically significant correlation between years of experience and use of the SCAT2, but those with more than 10 years of experience were less likely to use NCT (P < .01). All respondents reported being familiar with Washington State's Zackery Lystedt Law, but only 44.1% reported that the law changed their concussion management.

Conclusions

There were statistically significant differences between SCAT2 and NCT use for respondents from urban and rural districts, and also between coaches and athletic trainers, as well as NCT use among respondents with varying years of experience. Further understanding and identification of barriers that limit identification and management of concussions in high school athletes are crucial to prevent serious permanent injury. Additional education is necessary to ensure that athletic trainers and coaches are aware of current recommendations within the medical literature for the evaluation and management of concussions.
An Assessment of a Short Composite Questionnaire Designed for Use in an Interventional Spine Pain Management Setting
Authors: Burnham Robert , Stanford Gordon , Gray Lori
Published: June 2012

Objective

To evaluate the reliability, validity, responsiveness, and practicality of a short composite questionnaire designed for use in an interventional spine pain management setting.

Setting

A rural interventional spine pain management practice.

Patients

Sixty subjects undergoing spinal intervention procedures (injection or neurotomy).

Methods

The Pain Disability Quality of Life Questionnaire‐Spine (PDQQ‐S) assesses spine pain quality, related disability, and life satisfaction/quality with the use of 2 questions for each domain. To assess the PDQQ‐S, patients completed 4 questionnaires (McGill Pain Questionnaire [MPQ], Oswestry Disability Questionnaire [ODQ], Assessment of Quality of Life [AQoL], and PDQQ‐S). Patients completed the questionnaires twice before their procedure and once after their procedure.

Main Outcome Measures

Test‐retest reliability was assessed by calculating the Pearson correlation coefficient for the 2 preprocedure questionnaire completions. Validity was assessed by calculating the Pearson correlation of the pain quality, disability, and life quality/satisfaction question scores of the PDQQ‐S with the MPQ, ODQ, and AQoL, respectively. Questionnaire responsiveness was explored by calculating responsiveness ratio scores. Practicality was assessed by recording the time required to complete each questionnaire and the ease with which it was completed.

Results

Test‐retest reliability correlation scores were as follows: PDQQ‐S = 0.73; MPQ = 0.88; ODQ = 0.89; and AQoL = 0.83. Acceptable correlations existed between the pain, disability, and life quality/satisfaction domains of the PDQQ‐S and the MPQ (.50), ODQ (.71), and AQoL (−.43), respectively. Responsiveness ratio scores for the PDQQ‐S, MPQ, ODQ, and AQoL were 4.4, 1.9, 2.3, and 0.7, respectively. Compared with the other questionnaires, the PDQQ‐S required approximately one fifth the time to complete and was significantly easier to understand.

Conclusions

The PDQQ‐S demonstrates adequate reliability and validity and superior responsiveness and practicality in persons with low back pain undergoing interventional spine pain management procedures.
Influence of Directional Preference on Two Clinical Dichotomies: Acute Versus Chronic Pain and Axial Low Back Pain Versus Sciatica
Authors: Donelson Ronald , Long Audrey , Spratt Kevin , Fung Tak
Published: June 2012

Objective

To determine whether outcomes from treatment determined by subjects' directional preference (ie, reduction in back and/or leg pain, by performing a single direction of repeated end‐range lumbar movement) would vary based on pain duration, location, or neurologic status.

Design

A secondary analysis of data from a multicenter randomized clinical trial.

Setting

Eleven physical therapy departments or clinics in 5 countries, with referrals for both acute and chronic low back pain.

Subjects

Seventy‐one of 80 subjects with acute to chronic low back pain, and with and without radicular leg pain, and with or without mild neurologic deficit, were found at baseline to have a directional preference and were then treated with directional exercises that matched their directional preference.

Methods

All of the subjects were treated for 2 weeks with directional exercises and compatible posture modifications. Independent variables were pain duration, pain location, and neurologic status.

Main Outcome Measurements

Primary measures were back and leg pain intensity and function (Roland Morris Disability Questionnare). Secondary measures were activity interference, medication use, depression (Beck Depression Inventory), and a self‐report of improvement.

Results

The subjects significantly improved their back and leg pain intensity, disability, and all secondary outcome measures, but pain duration, location, and neurologic status classification did not predict treatment responsiveness. Across all pain duration categories, 91%‐100% either improved or resolved completely. There also was significant improvement across all pain location and neurologic status categories, with no significant differences across the outcome variables.

Conclusions

In subjects found to have a directional preference who then treated themselves with matching directional exercises, neither pain duration nor pain location and neurologic status predicted their uniformly good‐to‐excellent outcomes.
FX counterparty risk and trading activity in currency forward and futures markets
Authors: Levich Richard M.
Published: June 2012

The Global Financial Crisis initiated a period of market turbulence and increased counterparty risk for financial institutions. Even though the Dodd–Frank Act is likely to exempt interbank foreign exchange trading from a central counterparty mandate, market participants have the option to trade currency futures on existing futures markets which standardize counterparty risks. Evidence for the period 2005–11 indicates that the market share of currency futures trading has grown relative to the pre‐crisis period. This shift may be the result of a perceived increase in counterparty risk among banks, as well as changes in relative trading costs or changes in other institutional factors.
A Bayesian interpretation of the Federal Reserve's dual mandate and the Taylor Rule
Authors: Putnam Bluford H. , Azzarello Samantha
Published: June 2012

When the Federal Reserve was established by the US Congress in 1913, its charter mandated that the new central bank “promote an elastic currency” and the institution was given extraordinary powers to serve as a lender of last resort to the banking system. Congress was reacting to the cycle of financial panics that had beset the country since the Civil War and had worsened with the Panic of 1907. Congress sought to find a remedy to prevent runs on banks turning into full‐fledged financial crises. The term “elastic” in the opening words of the charter was intended to underscore the need for a robust banking system that could withstand shocks and not collapse upon itself. There was no mention whatsoever of a dual mandate of promoting price stability and encouraging full employment.

With prodding from the US Congress, the Federal Reserve became highly involved in the management of the economy of the United States after WWII, focusing on inflation and full employment objectives. In 1993 Professor John Taylor set forth an elegant and simple framework (aka, the Taylor Rule) for analyzing the interest rate policy of the Federal Reserve in terms of its dual mandate.

This paper examines Federal Reserve behavior from the mid‐1950s to 2011 through the lens of the Taylor Rule. Our contribution is to use a dynamic linear model with Bayesian inference to update the evolution through time of the key parameters surrounding the inflation and full employment mandates, using only the information available to the Federal Reserve at each point in time. Our findings provide a more nuanced quantitative view than is previously available in the literature of how the Federal Reserve shifted its management of its dual mandate over time and in response to different economic challenges. Moreover, our research leads to serious questions of how Federal Reserve decision making may change in the future, following the financial panic of 2008, pointing toward numerous avenues for new research.
Credit risk dynamics in response to changes in the federal funds target: The implication for firm short‐term debt
Authors: Dunbar Kwamie , Amin Abu S.
Published: June 2012

The recent credit crisis has raised a number of interesting questions regarding the role of the Federal Reserve Bank and the effectiveness of its expected and unexpected interventions in financial markets, especially during the crisis, given its mandate. This paper reviews and evaluates the impact of expected and unexpected changes in the federal funds rate target on credit risk premia. The paper's main innovation is the use of an ACH‐VAR (autoregressive conditional hazard VAR) model to generate the Fed's expected and unexpected monetary policy shocks which are then used to determine the effects of a Federal Reserve policy change on counterparty credit risk and more importantly short‐term firm debt financing. The findings answer a longstanding question sought by researchers on the effect of policy makers' announcements on firm debt financing. The results clearly show that the Federal Reserve influences short‐term debt financing through the credit channel for both expansionary and contractionary monetary policies. In particular, we find that the growth in counterparty risk appears less responsive to anticipated responses in the Fed funds rate that fail to materialize than to an unanticipated increase in the federal funds rate. Finally, we also document that the results appear to validate the Feds interventions in financial markets to stem counterparty risk and to make liquidity more readily available to firms.
Rock Climbing Rescues: Causes, Injuries, and Trends in Boulder County, Colorado
Authors: Lack Daniel A. , Sheets Alison L. , Entin Jacob M. , Christenson David C.
Published: June 2012

Objective

To describe rates and patterns of rock climbing rescue incidents, morbidity and mortality in Boulder County, CO.

Methods

Rocky Mountain Rescue Group incident reports from 1998 to 2011 were reviewed to provide a 14-year statistical account of rock climbing incidents.

Results

Rock climbing rescues in Boulder accounted for 428 of a total of 2198 (19.5%) mountain and wilderness rescue victims. Most rock climbing victims were male (78%), and 46% of victims were between the ages of 20 and 29 years; most rock climbing incidents occurred on weekend days (median time of 3:30 pm) during the spring, summer, and autumn. Technical roped climbers accounted for 58% of climbing victims, whereas unroped climbers accounted for 34%. Belay incidents accounted for 12% of climbing victims, whereas rock fall incidents accounted for 4.5% of victims. Most victims were uninjured (43% stranded or lost), whereas lower extremity injuries were the most common injury (29.5% of injured victims). A total of 5.5% of climbing victims were fatally injured (23 victims: 5 from lead falls and 9 from unroped falls).

Conclusions

The occurrence of rock climbing–related rescue victims comprised one fifth of all rescue victims in Boulder County. A large fraction of incidents and fatalities resulted from unroped climbing. Incidents of lost or uninjured stranded climbers and belay incidents account for more than half of victims, which can likely be prevented by gaining appropriate experience, seeking local information, and applying some simple safety measures for control of rope belays.
A Retrospective Review of Early Gastrointestinal Symptoms in the Prediction of Crotaline Envenomation Severity
Authors: Thornton Stephen L. , Nguyen Kenneth T. , Shenn Spondee K. , Castillo Edward M. , Clark Richard F. , Cantrell F. Lee
Published: June 2012

Objectives

Rattlesnake envenomations are cited to cause gastrointestinal (GI) symptoms, which may be indicators of systemic envenomation. We sought to identify whether the presence of early GI symptoms, defined as occurring within 4 hours of the bite, could be used to predict antivenom use or bite severity.

Methods

We performed a retrospective review of a statewide poison system's database for all cases of rattlesnake envenomation from January 2000 to December 2009. Data collected included presence of GI symptoms and antivenom use. The GI symptoms were further classified as early (within 4 hours) or late. Bite severity was determined using the minimal to moderate to severe scoring system from collected data. Data were then analyzed with a χ2 test and Fisher's exact test to evaluate for association between early GI symptoms and either antivenom use or bite severity.

Results

There were 2570 reported rattlesnake exposures in the database. Sixty-one (2.4%) of these had GI symptoms reported. Of these, 36 (59%) had symptoms develop within 4 hours of envenomation. A total of 49 patients (80%) received antivenom. Early GI symptoms were seen in 31 (63%) of patients receiving antivenom versus 5 (42%) of patients not receiving antivenom ( P = .20). Early GI symptoms were seen in 4 of 6 (66%) of the severe group, 19 of 29 (66%) of the moderate group, and 13 of 26 (50%) of the minimal group ( P = .47).

Conclusions

Gastrointestinal symptoms after rattlesnake envenomations were rarely reported in this poison center study, and the presence of early GI symptoms did not predict bite severity or the use of antivenom.
Investigation of the full configuration interaction quantum Monte Carlo method using homogeneous electron gas models
Authors: Shepherd James J. , Booth George H. , Alavi Ali
Published: June 2012

Using the homogeneous electron gas (HEG) as a model, we investigate the sources of error in the “initiator” adaptation to full configuration interaction quantum Monte Carlo (i-FCIQMC), with a view to accelerating convergence. In particular, we find that the fixed-shift phase, where the walker number is allowed to grow slowly, can be used to effectively assess stochastic and initiator error. Using this approach we provide simple explanations for the internal parameters of an i-FCIQMC simulation. We exploit the consistent basis sets and adjustable correlation strength of the HEG to analyze properties of the algorithm, and present finite basis benchmark energies for N = 14 over a range of densities 0.5 ⩽ rs ⩽ 5.0 a.u. A single-point extrapolation scheme is introduced to produce complete basis energies for 14, 38, and 54 electrons. It is empirically found that, in the weakly correlated regime, the computational cost scales linearly with the plane wave basis set size, which is justifiable on physical grounds. We expect the fixed-shift strategy to reduce the computational cost of many i-FCIQMC calculations of weakly correlated systems. In addition, we provide benchmarks for the electron gas, to be used by other quantum chemical methods in exploring periodic solid state systems.
Coulombic effects on magnetoconductivity oscillations induced by microwave excitation in multisubband two-dimensional electron systems
Authors: Monarkha Yu. P.
Published: June 2012

We develop a theory of magneto-oscillations in photoconductivity of multisubband two-dimensional electron systems which takes into account strong Coulomb interaction between electrons. In the presence of a magnetic field oriented perpendicular, internal electric fields of fluctuational origin cause fast drift velocities of electron orbit centers which affect probabilities of inter-subband scattering and the photoconductivity. For the electron system formed on the liquid helium surface, internal forces are shown to suppress the amplitude of magnetooscillations, and change positions of magnetoconductivity minima which evolve in zero-resistance states for high radiation power.
Features of the temperature dependence of pressure of solid helium at low temperatures
Authors: Lisunov A. A. , Maidanov V. A. , Rubanskii V. Y. , Rubets S. P. , Rudavskii E. Y. , Rybalko A. S. , Syrkin E. S.
Published: June 2012

A series of experiments has been performed to investigate the conditions of formation of a disordered (glass-like) state in crystals of 3He. With the help of precise measurements of pressure at constant volume it has been established that a glass phase is formed easily in rapidly cooled crystals grown under homogeneous temperature conditions in the presence of large numbers of nucleation centers. This phase can be removed only by careful annealing. This result has been found in both 3He and 4He, and is independent of type of quantum statistics and determined mainly by crystal growth conditions. An analysis of similar measurements has been performed using a different cell where during the crystal growth a directed temperature gradient was created. In this case, additional defects created as a result of deformation of the crystal were necessary to form a glass-like phase. The degree of deformation of a crystal, achievable in the experiment, was sufficient to form a glass-like phase in solid 4He, but not in a crystal of 3He where the atoms have a large amplitude of zero-point oscillations. Analyzing a temperature dependence of pressure, a study of the features of a phonon contribution to the pressure was also carried out. It was found that in both crystals 3He and 4He at different thicknesses of samples the phonon pressure differs by several times. This effect is qualitatively explained by that that in thin samples an interaction among layers of atoms becomes stronger. This leads to decreasing the phonon contribution to the thermodynamic properties of the helium crystal at low temperatures.
Features of influence of dc magnetic field pulses on a nuclear spin echo in magnets
Authors: Mamniashvili G. I. , Gegechkori T. O. , Akhalkatsi A. M. , Gavasheli C. A.
Published: June 2012

Signal intensities of a two-pulse nuclear spin echo as a function of parameters of dc magnetic field pulses are measured in the series of materials: Li0.5Fe2.5–xZnxO4 (x < 0.25) (enriched in 57Fe isotope to 96.8%), NiMnSb, Co2MnSi, La1–хСахMnO3 (x = 0.2; 0.25) and polycrystalline Co. Two types of dependences of these signals on a supplying time of such pulses with respect to the times of the exciting RF pulses are found. The mechanisms of influence of a domain structure and a dynamic frequency shift on the observed features of the investigated signals are discussed.
On a spectrum of the t–J model on a deformed lattice “necklace ladder”
Authors: Cheranovskii V. O. , Ezerskaya E. V. , Kravchenko A. A.
Published: June 2012

The effective Hamiltonians describing the lowest part of the energy spectrum in the t–J model on a lattice “necklace ladder” with a weak interaction of elementary cells are derived within the framework of perturbation theory and the formalism of cyclic spin permutations. It is shown that in a model of “necklace ladder” there are no magnetic polarons which are observed in similar rectangular ladders. A nonmonotonic dependence of the ground state spin S0 of finite ladder segments, containing L unit cells and N = 3L–1 electrons, on the value of the exchange parameter J is shown numerically. In particular, for a cycling segment with four unit cells for 0 < J < 0.02304 the spin of the ground state is equal to 11/2. An increase of J first leads to an abrupt decrease of the S0 down to a minimum value, and then to its increase up to the maximal value of S0 = 3/2, which is consistent with the qualitative estimate, proposed in the work, S0 = (L–1)/2 for large values of J. For cycling segments of the lattice “necklace ladder” containing 3L–1 electrons, for even L an exact separation of charge and spin variables in the corresponding t–J model is demonstrated.
The Raman scattering investigation of the features of low-energy electronic excitations of the terbium ion in the KTb(WO4)2 crystal
Authors: Peschanskii A. V. , Fomin V. I. , Yeremenko A. V.
Published: June 2012

Raman scattering of light in the KTb(WO4)2 single crystal is investigated in the frequency range of 3–950 cm−1 at 5 K. The ground multiplet 7F6 of Tb3+ ion is split by the crystal field with symmetry C2, and all the multiplet components are detected. It is found that the first excited electronic quasidoublet consists of two singlet levels of different symmetry and is separated from the ground quasidoublet by ∼75 cm−1. Behavior of all the detected levels is investigated in external magnetic fields H ⊥ C2 and H || C2. Spectroscopic splitting factors are determined for the ground and excited levels of the Tb3+ ion in the KTb(WO4)2 crystal. Experimental data support the view that at low temperatures the case of Ising anisotropy is realized, and the crystal under study should be considered as a system of two-level magnetic ions.
Analysis of the low-frequency spectrum of the cubic noncentrosymmetric ferrimagnet Cu2OSeO3
Authors: Kurnosov V. S. , Gnezdilov V. P. , Tsapenko V. V. , Lemmens P. , Berger H.
Published: June 2012

The IR reflectance spectra of the cubic noncentrosymmetric ferrimagnet Cu2OSeO3 (TC ≈ 60 K) were investigated in the temperature range 10–80 K. Detailed analysis of the symmetry and composition of vibrational modes was conducted on the basis of Raman scattering data and data obtained in this investigation. 68 out of 69 modes consistent with the crystal lattice symmetry were revealed. Some spectral features found in the magnetically ordered phase were studied. The bands at 280 and 421 cm−1 related to the spectrum of two-magnon light scattering were observed. Dynamic magnetoelectric coupling was found to be responsible for the intensity redistribution in the Raman and IR spectra for the threefold degenerate modes of F-symmetry (modes at 84, 205, and 269 cm−1). No change associated with magnetic ordering was observed in the symmetry of the crystal structure.
The magnetic state of a single-crystal anion-excess manganite LaMnO3+δ
Authors: Galetich I. K. , Eremenko A. V. , Pashchenko V. A. , Sirenko V. A. , Brook V. V.
Published: June 2012

The magnetic moment of the LaMnO3+δ single crystal was measured in a wide range of temperatures and magnetic fields under different cooling and measuring conditions. As a result, the nature of the magnetic state of LaMnO3+δ was defined: spin glass clusters form in it.
Conductance of a STM contact on the surface of a thin film
Authors: Khotkevych N. V. , Kolesnichenko Yu. A. , van Ruitenbeek J. M.
Published: June 2012

The conductance of a contact with a radius smaller than the Fermi wave length was investigated theoretically on the surface of a thin metal film. It is shown that quantization of the electron energy spectrum in the film leads to a step-like dependence of differential conductance G(V) as a function of applied bias eV. The distance between neighboring steps in eV equals the energy level spacing due to size quantization. We demonstrate that a study of G(V) for both positive and negative voltages maps the spectrum of energy levels above and below the Fermi surface in scanning tunneling experiments.
Magnetoplasma waves on the surface of a semiconductor nanotube with a superlattice
Authors: Ermolaev A. M. , Rashba G. I. , Solyanik M. A.
Published: June 2012

The spectra of plasma waves in the electron gas on the surface of a semiconductor nanotube with a superlattice in a parallel magnetic field have been studied using the random phase approximation. The frequencies of the long-wave intra- and inter-band magnetoplasmons in a degenerate electron gas are calculated in quantum and quasiclassical limits. If a large number of the electron levels associated with the orbital motion of electrons is filled, the magnetoplasmon frequencies exhibit the oscillations similar to the de Haas–van Alphen oscillations upon variation of nanotube parameters and the Aharonov–Bohm oscillations upon variation of the magnetic flux through the nanotube cross-section. The oscillation characteristics are determined by the ratio of the Fermi energy to the miniband width. For large values of the ratio, the beating pattern appears in the magnetoplasmon frequency dependence on the nanotube parameters. These oscillations are not present if the ratio is sufficiently small.
Electron scattering effects at physisorbed hydrogen molecules on break-junction electrodes and nanowires formation in hydrogen environment
Authors: van der Maas M. , Vasnyov S. , Hendriksen B. L. M. , Shklyarevskii O. I. , Speller S.
Published: June 2012

Physisorption of hydrogen molecules on the surface of gold and other coinage metals has been studied using distance tunneling spectroscopy. We have observed that the distance dependence of the tunnel current (resistance) displays a strong N-shaped deviation from exponential behavior. Such deviations are difficult to explain within the Tersoff–Hamann approximation. We suggest the scattering of tunneling electrons by H2 molecules as an origin for the observed effect. We have found that this phenomenon is also common for strongly adsorbed organic molecules with a single anchoring group. Pulling Au, Cu and Pt nanowires at 22 K in hydrogen environment shows that the break-junction electrodes are still connected through hydrogen–metal monoatomic chains down to very low conductance values of 10−4–10−6 G0.
The specific heat and the radial thermal expansion of bundles of single-walled carbon nanotubes
Authors: Bagatskii M. I. , Barabashko M. S. , Dolbin A. V. , Sumarokov V. V. , Sundqvist B.
Published: June 2012

The specific heat at constant pressure C(T) of bundles of single-walled carbon nanotubes (SWNTs) closed at their ends has been investigated in the temperature interval of 2–120 K. It is found that the curve C(T) has features near 5, 36, 80, and 100 K. The experimental results on the C(T) and the radial thermal expansion coefficient αR(T) of bundles of SWNTs oriented perpendicular to the sample axis have been compared. It is found that the curves C(T) and αR(T) exhibit a similar temperature behavior at T > 10 K. The temperature dependence of the Grüneisen coefficient γ(T) has been calculated. The curve γ(T) also has a feature near 36 K. Above 36 K the Grüneisen coefficient is practically independent of temperature (γ ≈ 4). Below 36 K, γ(T) decreases monotonically with lowering temperature and becomes negative at T < 6 K.
Phase magnetic segregation and magnetoresistive properties in the manganite nanocompound p-La0.8Mn1.04O3.5
Authors: Rykova A. I. , Terekhov A. V. , Cherny A. S. , Khatsko E. N. , Yeremenko A. V. , Zaleski A.
Published: June 2012

Results of comprehensive, detailed studies of the magnetic and resistive properties of the nanocompound p-La0.8Mn1.04O3.5 at temperatures of 4.2–300 K in magnetic fields up to 9 T are reported. These studies of the temperature, field, and frequency dependences of the magnetization and susceptibility indicate that, below T* ≈ 265 K the nanocomposite is in a magnetic phase-segregated state with ferromagnetic inclusions that form a superparamagnet. A unique interrelation between the magnetic resistance and the magnetization is found. The effect of aging on the magnetic and resistive properties is studied.
Effect of α-β transitions on creep in solid nitrogen
Authors: Alekseeva L. A. , Strzhemechny M. A.
Published: June 2012

The creep parameters of solid nitrogen are measured in the temperature range 32.1–39.9 K which includes the polymorphic transition point Tαβ = 35.61 K. An appreciable increase in the steady state creep rate of the samples is detected during the transition from the low-temperature cubic α-phase to the high-temperature hexagonal β-phase. This effect is explained by the fact that, despite a decrease in the number of slip planes (which could lead to increased rigidity of the crystal), two other factors play an important role in determining the enhanced plasticity of the β-phase. One of these factors is the disappearance of orientational ordering, which affects the plasticity of the material. The other factor, which is also related to the absence of orientational ordering, is a substantial difference in the structure and mobility of dislocations in these phases.
Nature of the magnetic phase transition in single-crystal LaMnO3+δ
Authors: Galetich I. K. , Eremenko A. V. , Pashchenko V. A. , Sirenko V. A. , Brook V. V.
Published: June 2012

The isotherms of the field dependences of the magnetic moment M(H) are measured at temperatures above and below the magnetic phase transition (Tc = 125 K) in single-crystal lanthanum manganite with excess oxygen (LaMnO3+δ). An analysis of these magnetic isotherms with Arrott plots and invoking the Banerjee criterion shows that the magnetic phase transition in this single crystal is a second order phase transition.
Determination of the melting threshold of TiO2 thin films processed by excimer laser irradiation
Authors: Van Overschelde O. , Delsate T. , Snyders R.
Published: June 2012

Processing surfaces by laser needs an understanding of the mechanisms generated by irradiation. In this work, to gain understanding of the mechanisms occurring during irradiation of TiO2 thin films by means of KrF excimer laser, we have performed infrared time resolved reflectivity measurements. This experimental investigation revealed modifications of the heating/cooling cycle as a function of the fluence (F). These modifications start appearing for a fluence value of about ∼0.25 J/cm2 which is associated with the melting threshold of the film. Additionally, we have solved numerically the heat equation of the system with specific boundary conditions. From these calculations, we have established the thermal history of the film during the 25 ns irradiation pulse. The data reveal that a part of the medium liquefies around a fluence of 0.23 J/cm2 in good agreement with the experimental data.
Rapid filamentation of high power lasers at the quarter critical surface
Authors: Brady C. S. , Lawrence-Douglas A. , Arber T. D.
Published: June 2012

A novel mechanism for initiating laser filamentation for intensities above 5 × 1017 W/cm2 is presented, seeded by the transient interference of an incident laser and its Raman backscattered daughter wave. For lasers propagating up short scale-length density gradients, the Raman reflectivity is peaked near the relativistically corrected quarter critical surface (RCQCS) and thus filamentation is observed to start on this surface. The filamentation at the RCQCS occurs on timescales comparable to the laser period. A series of 2D particle-in-cell (PIC) simulations confirm this physical model. Growth rates are obtained from simulations for a variety of simulation parameters and a simplified model in which the RCQCS behaves as a partially reflecting mirror, with the reflected light at double the wavelength of the incident light, is shown to reproduce the number and approximate location of filaments from PIC simulations. It was also proposed that field ionisation may alter RCQCS formation and the method of inclusion for this into the PIC simulation is presented. Additional simulations demonstrate field ionisation to have a negligible effect on the formation of the RCQCS. The implications of this filamentation mechanism for plasma experiments which require focused light of intensities above 5 × 1017 W/cm2 to propagate beyond the RCQCS are discussed.
Local unitary transformation method for large-scale two-component relativistic calculations: Case for a one-electron Dirac Hamiltonian
Authors: Seino Junji , Nakai Hiromi
Published: June 2012

An accurate and efficient scheme for two-component relativistic calculations at the spin-free infinite-order Douglas-Kroll-Hess (IODKH) level is presented. The present scheme, termed local unitary transformation (LUT), is based on the locality of the relativistic effect. Numerical assessments of the LUT scheme were performed in diatomic molecules such as HX and X2 (X = F, Cl, Br, I, and At) and hydrogen halide clusters, (HX)n (X = F, Cl, Br, and I). Total energies obtained by the LUT method agree well with conventional IODKH results. The computational costs of the LUT method are drastically lower than those of conventional methods since in the former there is linear-scaling with respect to the system size and a small prefactor.
Dynamical (e,2e) studies of tetrahydrofurfuryl alcohol
Authors: Bellm S. M. , Builth-Williams J. D. , Jones D. B. , Chaluvadi Hari , Madison D. H. , Ning C. G. , Wang F. , Ma X. G. , Lohmann B. , Brunger M. J.
Published: June 2012

Cross section data for electron scattering from DNA are important for modelling radiation damage in biological systems. Triply differential cross sections for the electron impact ionization of the highest occupied outer valence orbital of tetrahydrofurfuryl alcohol, which can be considered as an analogue to the deoxyribose backbone molecule in DNA, have been measured using the (e,2e) technique. The measurements have been performed with coplanar asymmetric kinematics at an incident electron energy of 250 eV, an ejected electron energy of 20 eV, and at scattered electron angles of −5°, −10°, and −15°. Experimental results are compared with corresponding theoretical calculations performed using the molecular 3-body distorted wave model. Some important differences are observed between the experiment and calculations.
Radio frequency charge sensing in InAs nanowire double quantum dots
Authors: Jung M. , Schroer M. D. , Petersson K. D. , Petta J. R.
Published: June 2012

We demonstrate charge sensing of an InAs nanowire double quantum dot (DQD) coupled to a radio frequency (rf) circuit. We measure the rf signal reflected by the resonator using homodyne detection. Clear single dot and DQD behavior are observed in the resonator response. rf-reflectometry allows measurements of the DQD charge stability diagram in the few-electron regime even when the dc current through the device is too small to be measured. For a signal-to-noise ratio of one, we estimate a minimum charge detection time of 350 μs at interdot charge transitions and 9 μs for charge transitions with the leads.
High energy solutions of systems of Kirchhoff-type equations in R
N
Authors: Wu Xian
Published: June 2012

In the present paper, five new critical point theorems on the product spaces are given and three existence theorems for the sequence of high energy solutions for the systems of Kirchhoff-type equations are studied.
Determination of in-depth damaged profile by Raman line scan in a pre-cut He2+ irradiated UO2
Authors: Guimbretière G. , Desgranges L. , Canizarès A. , Carlot G. , Caraballo R. , Jégou C. , Duval F. , Raimboux N. , Ammar M. R. , Simon P.
Published: June 2012

Raman measurements were carried out to probe the spectroscopic signatures of the ion beam irradiation-induced damage and their in-depth profiles on a Uranium dioxide sample previously cut and polished prior to performing a 25 MeV He2+ cyclotron beam irradiation. Raman spectra clearly show the creation of three defects bands (U1 ≈ 530, U2 ≈ 575, and U3 ≈ 635 cm−1) resulting from the ion irradiation and also some changes in the T2g peak of UO2. Their in-depth distribution inside the sample exhibits a clear increase of the damage from the surface up to the position of the implanted He.
Multiple molecule effects on the cooperativity of protein folding transitions in simulations
Authors: Lewis Jacob I. , Moss Devin J. , Knotts Thomas A.
Published: June 2012

Though molecular simulation of proteins has made notable contributions to the study of protein folding and kinetics, disagreement between simulation and experiment still exists. One of the criticisms levied against simulation is its failure to reproduce cooperative protein folding transitions. This weakness has been attributed to many factors such as a lack of polarizability and adequate capturing of solvent effects. This work, however, investigates how increasing the number of proteins simulated simultaneously can affect the cooperativity of folding transitions — a topic that has received little attention previously. Two proteins are studied in this work: phage T4 lysozyme (Protein Data Bank (PDB) ID: 7LZM) and phage 434 repressor (PDB ID: 1R69). The results show that increasing the number of proteins molecules simulated simultaneously leads to an increase in the macroscopic cooperativity for transitions that are inherently cooperative on the molecular level but has little effect on the cooperativity of other transitions. Taken as a whole, the results identify one area of consideration to improving simulations of protein folding.
Experimental laser wakefield acceleration scalings exceeding 100 TW
Authors: McGuffey C. , Matsuoka T. , Kneip S. , Schumaker W. , Dollar F. , Zulick C. , Chvykov V. , Kalintchenko G. , Yanovsky V. , Maksimchuk A. , Thomas A. G. R. , Krushelnick K. , Najmudin Z.
Published: June 2012

Understanding the scaling of laser wakefield acceleration (LWFA) is crucial to the design of potential future systems. A number of computational and theoretical studies have predicted scalings with laser power for various parameters, but experimental studies have typically been limited to small parameter ranges. Here, we detail extensive measurements of LWFA experiments conducted over a considerable range in power from 20 to 110 TW, which allows for a greater plasma density range and for a large number of data points. These measurements include scalings of the electron beam charge and maximum energy as functions of density as well as injection threshold density, beam charge, and total beam energy as functions of laser power. The observed scalings are consistent with theoretical understandings of operation in the bubble regime.
Nonlinear electrostatic excitations of charged dust in degenerate ultra-dense quantum dusty plasmas
Authors: Abdelsalam U. M. , Ali S. , Kourakis I.
Published: June 2012

The linear and nonlinear properties of low-frequency electrostatic excitations of charged dust particles (or defects) in a dense collisionless, unmagnetized Thomas-Fermi plasma are investigated. A fully ionized three-component model plasma consisting of electrons, ions, and negatively charged massive dust grains is considered. Electrons and ions are assumed to be in a degenerate quantum state, obeying the Thomas-Fermi density distribution, whereas the inertial dust component is described by a set of classical fluid equations. Considering large-amplitude stationary profile travelling-waves in a moving reference frame, the fluid evolution equations are reduced to a pseudo-energy-balance equation, involving a Sagdeev-type potential function. The analysis describes the dynamics of supersonic dust-acoustic solitary waves in Thomas-Fermi plasmas, and provides exact predictions for their dynamical characteristics, whose dependence on relevant parameters (namely, the ion-to-electron Fermi temperature ratio, and the dust concentration) is investigated. An alternative route is also adopted, by assuming weakly varying small-amplitude disturbances off equilibrium, and then adopting a multiscale perturbation technique to derive a Korteweg–de Vries equation for the electrostatic potential, and finally solving in terms for electric potential pulses (electrostatic solitons). A critical comparison between the two methods reveals that they agree exactly in the small-amplitude, weakly superacoustic limit. The dust concentration (Havnes) parameter h=Zd0nd0/ne0 affects the propagation characteristics by modifying the phase speed, as well as the electron/ion Fermi temperatures. Our results aim at elucidating the characteristics of electrostatic excitations in dust-contaminated dense plasmas, e.g., in metallic electronic devices, and also arguably in supernova environments, where charged dust defects may occur in the quantum plasma regime.
X-ray bang-time measurements at the National Ignition Facility using a diamond detector
Authors: Barrios M. A. , MacPhee A. , Regan S. P. , Kimbrough J. , Nagel S. R. , Benedetti L. R. , Khan S. F. , Bradley D. , Bell P. , Edgell D. , Collins G. W.
Published: June 2012

A chemical vapor deposition polycrystalline photoconductive diamond detector was fielded at NIF to measure the time of peak x-ray emission, or x-ray bang time, of inertial confinement fusion implosions. Imaging the capsule with a pinhole provides contrast against Hohlraum emission, allowing clear identification of the capsule component in the raw scope trace. X-ray bang time was measured to within ±41–46 ps with the internal photoconductive diamond detector.
Lower hybrid current drive at high density in the multi-pass regime
Authors: Wallace G. M. , Faust I. C. , Meneghini O. , Parker R. R. , Shiraiwa S. , Baek S. G. , Bonoli P. T. , Hubbard A. E. , Hughes J. W. , LaBombard B. L. , Lau C. , Ma Y. , Reinke M. L. , Terry J. L. , Whyte D. G. , Wright J. C. , Wukitch S. J. , Harvey R. W. , Schmidt A. E. , Smirnov A. P. , Wilson J. R.
Published: June 2012

Assessing the performance of lower hybrid current drive (LHCD) at high density is critical for developing non-inductive current drive systems on future steady-state experiments. Excellent LHCD efficiency has been observed during fully non-inductive operation (η=2.0−2.5×1019 AW–1m–2 at n¯e=0.5×1020 m–3) on Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] under conditions (ne, magnetic field and topology, and LHCD frequency) relevant to ITER [S. Shiraiwa et al., Nucl. Fusion 51, 103024 (2011)]. To extend these results to advanced tokamak regimes with higher bootstrap current fractions on C-Mod, it is necessary to increase n¯e to 1.0−1.5×1020 m−3. However, the number of current-carrying, non-thermal electrons generated by LHCD drops sharply in diverted configurations at densities that are well below the density limit previously observed on limited tokamaks. In these cases, changes in scrape off layer (SOL) ionization and density profiles are observed during LHCD, indicating that significant power is transferred from the LH waves to the SOL. Fokker-Planck simulations of these discharges utilizing ray tracing and full wave propagation codes indicate that LH waves in the high density, multi-pass absorption regime linger in the plasma edge, and SOL region, where absorption near or outside the LCFS results in the loss of current drive efficiency. Modeling predicts that non-thermal emission increases with stronger single-pass absorption. Experimental data show that increasing Te in high density LH discharges results in higher non-thermal electron emission, as predicted by the models.
A long-range electrostatic potential based on the Wolf method charge-neutral condition
Authors: Yonezawa Yasushige
Published: June 2012

Molecular simulations rely heavily on a long range electrostatic Coulomb interaction. The Coulomb potential decays inversely with distance, indicating infinite effective range. In practice, molecular simulations do not directly take into account such an infinite interaction. Therefore, the Ewald, fast multipole, and cutoff methods are frequently used. Although cutoff methods are implemented easily and the calculations are fast, it has been pointed out that they produce serious artifacts. Wolf and coworkers recently discovered one source of the artifacts. They found that when the total charge in a cutoff sphere disappeared, the cutoff error is dramatically suppressed. The Wolf method uses the charge-neutral principle combined with a potential damping that is realized using a complementary error function. To date, many molecular simulation studies have demonstrated the accuracy and reliability of the Wolf method. We propose a novel long-range potential that is constructed only from the charge-neutral condition of the Wolf method without potential damping. We also show that three simulation systems, in which involve liquid sodium-chloride, TIP3P water, and a charged protein in explicit waters with neutralized ions using the new potential, provide accurate statistical and dielectric properties when compared with the particle mesh Ewald method.
Coherent states for the nonlinear harmonic oscillator
Authors: Ghosh Subir
Published: June 2012

Wave packets for the quantum nonlinear oscillator are considered in the generalized coherent state framework. To first order in the nonlinearity parameter the coherent state behaves very similar to its classical counterpart. The position expectation value oscillates in a simple harmonic manner. The energy-momentum uncertainty relation is time independent as in a harmonic oscillator. Various features (such as the squeezed state nature) of the coherent state have been discussed.
Ab-initio studies on Li doping, Li-pairs, and complexes between Li and intrinsic defects in ZnO
Authors: Vidya R. , Ravindran P. , Fjellvåg H.
Published: June 2012

First-principles density functional calculations have been performed on Li-doped ZnO using all-electron projector augmented plane wave method. Li was considered at six different interstitial sites (Lii), including anti-bonding and bond-center sites and also in substitutional sites such as at Zn-site (Lizn) and at oxygen site (Lio) in the ZnO matrix. Stability of LiZn over Lii is shown to depend on synthetic condition, viz., LiZn is found to be more stable than Lii under O-rich conditions. Hybrid density functional calculations performed on LiZn indicate that it is a deep acceptor with (0/-) transition taking place at 0.74 eV above valence band maximum. The local vibrational frequencies for Li-dopants are calculated and compared with reported values. In addition, we considered the formation of Li-pair complexes and their role on electronic properties of ZnO. Present study suggests that at extreme oxygen-rich synthesis condition, a pair of acceptor type LiZn-complex is found to be stable over the compensating Lii + LiZn pair. The stability of complexes formed between Li impurities and various intrinsic defects is also investigated and their role on electronic properties of ZnO has been analyzed. We have shown that a complex between LiZn and oxygen vacancy has less formation energy and donor-type character and could compensate the holes generated by Li-doping in ZnO.