522 research outputs found
Structure of the Coulomb and unitarity corrections to the cross section of pair production in ultra-relativistic nuclear collisions
We analyze the structure of the Coulomb and unitarity corrections to the
single pair production as well as the cross section for the multiple pair
production. In the external field approximation we consider the probability of
pair production at fixed impact parameter between colliding
ultra-relativistic heavy nuclei. We obtain the analytical result for this
probability at large as compared to the electron Compton wavelength. We
estimate also the unitary corrections to the total cross section of the
process.Comment: 10 pages, 2 figures, RevTeX, references correcte
Nonequilibrium stabilization of charge states in double quantum dots
We analyze the decoherence of charge states in double quantum dots due to
cotunneling. The system is treated using the Bloch-Redfield generalized master
equation for the Schrieffer-Wolff transformed Hamiltonian. We show that the
decoherence, characterized through a relaxation and a dephasing time
, can be controlled through the external voltage and that the
optimum point, where these times are maximum, is not necessarily in
equilibrium. We outline the mechanism of this nonequilibrium-induced
enhancement of lifetime and coherence. We discuss the relevance of our results
for recent charge qubit experiments.Comment: 5 pages, 5 figure
Goodness-of-fit test for nonparametric regression models: Smoothing spline ANOVA models as example
Nonparametric regression models do not require the specification of the functional form between the outcome and the covariates. Despite their popularity, the amount of diagnostic statistics, in comparison to their parametric counterparts, is small. We propose a goodness-of-fit test for nonparametric regression models with linear smoother form. In particular, we apply this testing framework to smoothing spline ANOVA models. The test can consider two sources of lack-of-fit: whether covariates that are not currently in the model need to be included, and whether the current model fits the data well. The proposed method derives estimated residuals from the model. Then, statistical dependence is assessed between the estimated residuals and the covariates using the HSIC. If dependence exists, the model does not capture all the variability in the outcome associated with the covariates, otherwise the model fits the data well. The bootstrap is used to obtain p-values. Application of the method is demonstrated with a neonatal mental development data analysis. We demonstrate correct type I error as well as power performance through simulations
Macroscopic quantum superpositions in highly-excited strongly-interacting many-body systems
We demonstrate a break-down in the macroscopic (classical-like) dynamics of
wave-packets in complex microscopic and mesoscopic collisions. This break-down
manifests itself in coherent superpositions of the rotating clockwise and
anticlockwise wave-packets in the regime of strongly overlapping many-body
resonances of the highly-excited intermediate complex. These superpositions
involve many-body configurations so that their internal interactive
complexity dramatically exceeds all of those previously discussed and
experimentally realized. The interference fringes persist over a time-interval
much longer than the energy relaxation-redistribution time due to the
anomalously slow phase randomization (dephasing). Experimental verification of
the effect is proposed.Comment: Title changed, few changes in the abstract and in the main body of
the paper, and changes in the font size in the figure. Uses revTex4, 4 pages,
1 ps figur
Wavelet analysis of epileptic spikes
Interictal spikes and sharp waves in human EEG are characteristic signatures
of epilepsy. These potentials originate as a result of synchronous,
pathological discharge of many neurons. The reliable detection of such
potentials has been the long standing problem in EEG analysis, especially after
long-term monitoring became common in investigation of epileptic patients. The
traditional definition of a spike is based on its amplitude, duration,
sharpness, and emergence from its background. However, spike detection systems
built solely around this definition are not reliable due to the presence of
numerous transients and artifacts. We use wavelet transform to analyze the
properties of EEG manifestations of epilepsy. We demonstrate that the behavior
of wavelet transform of epileptic spikes across scales can constitute the
foundation of a relatively simple yet effective detection algorithm.Comment: 4 pages, 3 figure
Fronts dynamics in the presence of spatio-temporal structured noises
Front dynamics modeled by a reaction-diffusion equation are studied under the
influence of spatio-temporal structured noises. An effective deterministic
model is analytical derived where the noise parameters, intensity, correlation
time and correlation length appear explicitely. The different effects of these
parameters are discussed for the Ginzburg-Landau and Schl\"ogl models. We
obtain an analytical expression for the front velocity as a function of the
noise parameters. Numerical simulations results are in a good agreement with
the theoretical predictions.Comment: 11 pages, 6 figures; REVTEX; to be published in Phys.Rev.E, july 200
Vortex dynamics and states of artificially layered superconducting films with correlated defects
Linear resistances and -characteristics have been measured over a wide
range in the parameter space of the mixed phase of multilayered a-TaGe/Ge
films. Three films with varying interlayer coupling and correlated defects
oriented at an angle from the film normal were investigated.
Experimental data were analyzed within vortex glass models and a second order
phase transition from a resistive vortex liquid to a pinned glass phase.
Various vortex phases including changes from three to two dimensional behavior
depending on anisotropy have been identified. Careful analysis of
-characteristics in the glass phases revealed a distinctive and
-dependence of the glass exponent . The vortex dynamics in the
Bose-glass phase does not follow the predicted behavior for excitations of
vortex kinks or loops.Comment: 16 pages, 10 figures, 3 table
Blood BTEXS and heavy metal levels are associated with liver injury and systemic inflammation in Gulf states residents
Introduction: Exposures to volatile organic compounds and metals have previously been associated with liver diseases including steatohepatitis, although more data are needed. Benzene, toluene, ethylbenzene, xylenes, styrene (BTEXS) and metals were measured in blood samples collected between May 2012–July 2013 from volunteers participating in home visits for the Gulf Long-term Follow-up (GuLF) Study. This cross-sectional analysis evaluates associations of exposure biomarkers with serum liver injury and adipocytokine biomarkers in a sample of 214 men. Methods: Adult nonsmoking men without a history of liver disease or heavy alcohol consumption were included. The serologic disease biomarkers evaluated were the hepatocellular injury biomarker, cytokeratin 18 [whole (CK18 M65) and caspase-cleaved fragment (CK18 M30)]; and adipocytokines. Confounder-adjusted beta coefficients were determined using linear regression models for the overall sample (primary endpoints) and for obesity-classified sub-groups (secondary endpoints). A product interaction term between the exposure of interest and a dichotomized indicator of obesity was included to determine the disease modifying effects of obesity on the biomarker associations. Results: The study sample was 57% white and 51% obese. In the overall sample, lead was positively associated with CK18 M30 (β = 21.7 ± 6.0 (SE), p = 0.0004); IL-1β (β = 32.8 ± 5.2, p < 0.0001); IL-6 (β = 72.8 ± 18.3, p = 0.0001); and IL-8 (β = 140.8 ± 42.2, p = 0.001). Cadmium exposures were associated with increased IL-1β (β = 77.8 ± 26.3, p = 0.003) and IL-8 (β = 419.5 ± 201.2, p = 0.04). There were multiple significant interactions between obesity and exposure to lead, cadmium, benzene and toluene in relation to outcome biomarkers. Among obese participants (n = 108), benzene, lead, and cadmium were each positively associated with CK18 M30, IL-1β, IL-6, and IL-8. In obese subjects, lead was also inversely associated with leptin, and toluene was positively associated with IL-1β. Conclusion: For the overall sample, heavy metal exposures were associated with liver injury (lead only) and/or systemic inflammation (lead and cadmium). Obesity modified the associations between BTEXS and heavy metal exposures on several of the outcome variables. In the obesity subgroup, liver injury was positively associated with lead, cadmium and benzene exposures; systemic inflammation was increased with lead, cadmium, benzene, and toluene exposures; and leptin was inversely associated with lead exposures. The cross-sectional design of this study makes it difficult to determine causality, and all results should be interpreted cautiously. Nonetheless, the potential impact of exposures to lead, cadmium, benzene and toluene in steatohepatitis, an obesity-associated inflammatory liver disease, warrants further investigation
Acute and longer-term cardiovascular conditions in the Deepwater Horizon Oil Spill Coast Guard Cohort
Introduction: In 2010, the U.S. Coast Guard (USCG) led a clean-up response to the Deepwater Horizon (DWH) oil spill. Human studies evaluating acute and longer-term cardiovascular conditions associated with oil spill-related exposures are sparse. Thus, we aimed to investigate prevalent and incident cardiovascular symptoms/conditions in the DHW Oil Spill Coast Guard Cohort. Methods: Self-reported oil spill exposures and cardiovascular symptoms were ascertained from post-deployment surveys (n = 4,885). For all active-duty cohort members (n = 45,193), prospective cardiovascular outcomes were classified via International Classification of Diseases, 9th Edition from military health encounter records up to 5.5 years post-DWH. We used log-binomial regression to calculate adjusted prevalence ratios (aPRs) and 95% confidence intervals (CIs) in the cross-sectional analyses and Cox Proportional Hazards regression to calculate adjusted hazard ratios (aHR) and 95% CIs for incident cardiovascular diagnoses during 2010–2015 and stratifying by earlier (2010–2012) and later (2013–2015) time periods. Results: Prevalence of chest pain was associated with increasing levels of crude oil exposure via inhalation (aPRhigh vs. none = 2.00, 95% CI = 1.16–3.42, p-trend = 0.03) and direct skin contact (aPRhigh vs. none = 2.72, 95% CI = 1.30–5.16, p-trend = 0.03). Similar associations were observed for sudden heartbeat changes and for being in the vicinity of burning oil exposure. In prospective analyses, responders (vs. non-responders) had an elevated risk for mitral valve disorders during 2013–2015 (aHR = 2.12, 95% CI = 1.15–3.90). Responders reporting ever (vs. never) crude oil inhalation exposure were at increased risk for essential hypertension, particularly benign essential hypertension during 2010–2012 (aHR = 2.00, 95% CI = 1.08–3.69). Responders with crude oil inhalation exposure also had an elevated risk for palpitations during 2013–2015 (aHR = 2.54, 95% CI = 1.36–4.74). Cardiovascular symptoms/conditions aPR and aHR estimates were generally stronger among responders reporting exposure to both crude oil and oil dispersants than among those reporting neither. Conclusions: In this large study of the DWH oil spill USCG responders, self-reported spill clean-up exposures were associated with acute and longer-term cardiovascular symptoms/conditions
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