Meson-Meson Scattering in Relativistic Constraint Dynamics

Dirac's relativistic constraint dynamics have been successfully applied to obtain a covariant nonperturbative description of QED and QCD bound states. We use this formalism to describe a microscopic theory of meson-meson scattering as a relativistic generalization of the nonrelativistic quark-interchange model developed by Barnes and Swanson.Comment: 5 pages, 1 figure in LaTex, talk present at the First Meeting of the APS Topical Group on Hadronic Physics (Fermilab, October 24-26, 2004

Pion Interferometry for Hydrodynamical Expanding Source with a Finite Baryon Density

We calculate the two-pion correlation function for an expanding hadron source with a finite baryon density. The space-time evolution of the source is described by relativistic hydrodynamics and the Hanbury-Brown-Twiss (HBT) radius is extracted after effects of collective expansion and multiple scattering on the HBT interferometry have been taken into account, using quantum probability amplitudes in a path-integral formalism. We find that this radius is substantially smaller than the HBT radius extracted from the freeze-out configuration.Comment: 4 pages, 2 figure

Association of antihypertensive monotherapy with serum sodium and potassium levels in Chinese patients

<b>Background</b> International guidelines on management of hypertension recommend any major classes of antihypertensive drugs. However, the low prescribing rate of thiazides has been attributed to concerns about electrolyte disturbances and studies between antihypertensive drug classes and hyponatremia/hypokalemia among Chinese patients were scarce. <p></p> <b>Methods</b> From clinical databases we included 2,759 patients who received their first-ever antihypertensive monotherapy from January 2004 to June 2007 in a large territory of Hong Kong. We studied the plasma sodium and potassium levels 8 weeks after prescriptions and factors associated with hyponatremia and hypokalemia by multivariable regression analyses. <p></p> <b>Results</b> Among major antihypertensive drug classes, thiazide users had the lowest sodium level (139.6 mEq/l, 95% confidence interval (CI) 139.3, 140.0, P < 0.001) and patients-prescribed calcium channel blockers (CCBs; 3.92 mEq/l, 95% CI 3.89, 3.95) or thiazide diuretics (3.99 mEq/l, 95% CI 3.93, 4.04) had the lowest potassium levels (P < 0.001). Multivariate analysis reported that advanced age (>/=70 years, odds ratio (OR) 7.49, 95% CI 2.84, 19.8, P < 0.001), male gender (OR 2.38, 95% CI 1.45, 3.91, P < 0.001), and thiazide users (OR 2.42, 95% CI 1.29, 4.56, P = 0.006) were significantly associated with hyponatremia, while renin-angiotensin system (RAS) (OR 0.31, 95% CI 0.13, 0.73, P = 0.008) and beta-blockers (BBs) (OR 0.35, 95% CI 0.23, 0.54, P < 0.001) users were less likely to present with hypokalemia. However, the proportions having normonatremic (95.1%) and normokalemic (89.4%) levels were high. <p></p> <b>Conclusions</b> In view of the low prevalence of hyponatremia and hypokalemia associated with thiazides, physicians should not be deterred from prescribing thiazide diuretics as first-line antihypertensive agents as recommended by most international guidelines

Interventions to increase the uptake of seasonal influenza vaccination among pregnant women: A systematic review

© 2015 Elsevier Ltd.Background: Pregnant women and their infants under 6 months of age infected with influenza have a high risk of serious morbidity and mortality. Influenza vaccine during pregnancy offers 3-for-1 benefits to pregnant women, fetuses and newborn infants. Current vaccination uptake rates during pregnancy, however, are often lower than other high-risk groups and the general population. Methods: We systematically reviewed evidence on the effectiveness of interventions to improve influenza vaccination coverage in pregnant women. Risk differences (RDs) were calculated from the included studies. Results: Eleven studies were included in the review, of which four were randomized controlled trials (RCTs). Three cohort studies assessed provider-focused interventions while four RCTs and one cohort study evaluated pregnant women-focused interventions. Two cohort studies and a prospective intervention study assessed the effectiveness of bundled interventions. No study solely assessed the effectiveness of interventions to enhance access to influenza vaccination. One moderate quality RCT showed that an influenza pamphlet, with or without a verbalized benefit statement, improved the vaccination rate (RD. =0.26; RD. =0.39). The other reviewed RCTs showed discordant results, with RDs ranging from -0.15 to 0.03. Although all observational studies significantly improved vaccination rates (RDs ranged from 0.03 to 0.44), the quality of the evidence varied. Conclusions: There is a lack of effective interventions to increase the influenza vaccination rate in pregnant women. Based on the existing research, we recommend that clinicians provide influenza pamphlets to pregnant women with a verbalized statement about the benefits of influenza vaccine to newborns. Further high-quality RCTs are needed to develop successful maternal influenza vaccination programs. Increased clarity in reporting the content of interventions would help to improve the comparability and generalizability of the published studies.postprin

Delayed Slater determinant update algorithms for high efficiency quantum Monte Carlo

Within ab initio Quantum Monte Carlo simulations, the leading numerical cost for large systems is the computation of the values of the Slater determinants in the trial wavefunction. Each Monte Carlo step requires finding the determinant of a dense matrix. This is most commonly iteratively evaluated using a rank-1 Sherman-Morrison updating scheme to avoid repeated explicit calculation of the inverse. The overall computational cost is therefore formally cubic in the number of electrons or matrix size. To improve the numerical efficiency of this procedure, we propose a novel multiple rank delayed update scheme. This strategy enables probability evaluation with application of accepted moves to the matrices delayed until after a predetermined number of moves, K. The accepted events are then applied to the matrices en bloc with enhanced arithmetic intensity and computational efficiency via matrix-matrix operations instead of matrix-vector operations. This procedure does not change the underlying Monte Carlo sampling or its statistical efficiency. For calculations on large systems and algorithms such as diffusion Monte Carlo where the acceptance ratio is high, order of magnitude improvements in the update time can be obtained on both multi-core CPUs and GPUs

Relativistic Modification of the Gamow Factor

In processes involving Coulomb-type initial- and final-state interactions, the Gamow factor has been traditionally used to take into account these additional interactions. The Gamow factor needs to be modified when the magnitude of the effective coupling constant increases or when the velocity increases. For the production of a pair of particles under their mutual Coulomb-type interaction, we obtain the modification of the Gamow factor in terms of the overlap of the Feynman amplitude with the relativistic wave function of the two particles. As a first example, we study the modification of the Gamow factor for the production of two bosons. The modification is substantial when the coupling constant is large.Comment: 13 pages, in LaTe

Unification of bulk and interface electroresistive switching in oxide systems

We demonstrate that the physical mechanism behind electroresistive switching in oxide Schottky systems is electroformation, as in insulating oxides. Negative resistance shown by the hysteretic current-voltage curves proves that impact ionization is at the origin of the switching. Analyses of the capacitance-voltage and conductance-voltage curves through a simple model show that an atomic rearrangement is involved in the process. Switching in these systems is a bulk effect, not strictly confined at the interface but at the charge space region.Comment: 4 pages, 3 figures, accepted in PR

Interferometry signatures for QCD first-order phase transition in heavy ion collisions at GSI-FAIR energies

Using the technique of quantum transport of the interfering pair we examine the Hanbury-Brown-Twiss (HBT) interferometry signatures for the particle-emitting sources of pions and kaons produced in the heavy ion collisions at GSI-FAIR energies. The evolution of the sources is described by relativistic hydrodynamics with the system equation of state of the first-order phase transition from quark-gluon plasma (QGP) to hadronic matter. We use quantum probability amplitudes in a path-integral formalism to calculate the two-particle correlation functions, where the effects of particle decay and multiple scattering are taken into consideration. We find that the HBT radii of kaons are smaller than those of pions for the same initial conditions. Both the HBT radii of pions and kaons increase with the system initial energy density. The HBT lifetimes of the pion and kaon sources are sensitive to the initial energy density. They are significantly prolonged when the initial energy density is tuned to the phase boundary between the QGP and mixed phase. This prolongations of the HBT lifetimes of pions and kaons may likely be observed in the heavy ion collisions with an incident energy in the GSI-FAIR energy range.Comment: 16 pages, 4 figure

Trajectory generation for road vehicle obstacle avoidance using convex optimization

This paper presents a method for trajectory generation using convex optimization to find a feasible, obstacle-free path for a road vehicle. Consideration of vehicle rotation is shown to be necessary if the trajectory is to avoid obstacles specified in a fixed Earth axis system. The paper establishes that, despite the presence of significant non-linearities, it is possible to articulate the obstacle avoidance problem in a tractable convex form using multiple optimization passes. Finally, it is shown by simulation that an optimal trajectory that accounts for the vehicle’s changing velocity throughout the manoeuvre is superior to a previous analytical method that assumes constant speed