Bremsstrahlung in Alpha-Decay

We present the first fully quantum mechanical calculation of photon radiation accompanying charged particle decay from a barrier resonance. The soft-photon limit agrees with the classical results, but differences appear at next-to-leading-order. Under the conditions of alpha-decay of heavy nuclei, the main contribution to the photon emission stems from Coulomb acceleration and may be computed analytically. We find only a small contribution from the tunneling wave function under the barrier.Comment: 12 pages, 2 Postscript figure

Ionizing radiation exposure and the development of soft-tissue sarcomas in atomic-bomb survivors

BACKGROUND: Very high levels of ionizing radiation exposure have been associated with the development of soft-tissue sarcoma. The effects of lower levels of ionizing radiation on sarcoma development are unknown. This study addressed the role of low to moderately high levels of ionizing radiation exposure in the development of soft-tissue sarcoma. METHODS: Based on the Life Span Study cohort of Japanese atomic-bomb survivors, 80,180 individuals were prospectively assessed for the development of primary soft-tissue sarcoma. Colon dose in gray (Gy), the excess relative risk, and the excess absolute rate per Gy absorbed ionizing radiation dose were assessed. Subject demographic, age-specific, and survival parameters were evaluated. RESULTS: One hundred and four soft-tissue sarcomas were identified (mean colon dose = 0.18 Gy), associated with a 39% five-year survival rate. Mean ages at the time of the bombings and sarcoma diagnosis were 26.8 and 63.6 years, respectively. A linear dose-response model with an excess relative risk of 1.01 per Gy (95% confidence interval [CI]: 0.13 to 2.46; p = 0.019) and an excess absolute risk per Gy of 4.3 per 100,000 persons per year (95% CI: 1.1 to 8.9; p = 0.001) were noted in the development of soft-tissue sarcoma. CONCLUSIONS: This is one of the largest and longest studies (fifty-six years from the time of exposure to the time of follow-up) to assess ionizing radiation effects on the development of soft-tissue sarcoma. This is the first study to suggest that lower levels of ionizing radiation may be associated with the development of soft-tissue sarcoma, with exposure of 1 Gy doubling the risk of soft-tissue sarcoma development (linear dose-response). The five-year survival rate of patients with soft-tissue sarcoma in this population was much lower than that reported elsewhere.published_or_final_versio

Anomalous enhancements of low-energy fusion rates in plasmas: the role of ion momentum distributions and inhomogeneous screening

Non-resonant fusion cross-sections significantly higher than corresponding theoretical predictions are observed in low-energy experiments with deuterated matrix target. Models based on thermal effects, electron screening, or quantum-effect dispersion relations have been proposed to explain these anomalous results: none of them appears to satisfactory reproduce the experiments. Velocity distributions are fundamental for the reaction rates and deviations from the Maxwellian limit could play a central role in explaining the enhancement. We examine two effects: an increase of the tail of the target Deuteron momentum distribution due to the Galitskii-Yakimets quantum uncertainty effect, which broadens the energy-momentum relation; and spatial fluctuations of the Debye-H\"{u}ckel radius leading to an effective increase of electron screening. Either effect leads to larger reaction rates especially large at energies below a few keV, reducing the discrepancy between observations and theoretical expectations.Comment: 6 pages, 3 figure

Radiation correction to astrophysical fusion reactions and the electron screening problem

We discuss the effect of electromagnetic environment on laboratory measurements of the nuclear fusion reactions of astrophysical interest. The radiation field is eliminated using the path integral formalism in order to obtain the influence functional, which we evaluate in the semi-classical approximation. We show that enhancement of the tunneling probability due to the radiation correction is extremely small and does not resolve the longstanding problem that the observed electron screening effect is significantly larger than theoretical predictions.Comment: 9 pages, 1 eps figure

Comparative Analysis of the Mechanisms of Fast Light Particle Formation in Nucleus-Nucleus Collisions at Low and Intermediate Energies

The dynamics and the mechanisms of preequilibrium-light-particle formation in nucleus-nucleus collisions at low and intermediate energies are studied on the basis of a classical four-body model. The angular and energy distributions of light particles from such processes are calculated. It is found that, at energies below 50 MeV per nucleon, the hardest section of the energy spectrum is formed owing to the acceleration of light particles from the target by the mean field of the projectile nucleus. Good agreement with available experimental data is obtained.Comment: 23 pages, 10 figures, LaTeX, published in Physics of Atomic Nuclei v.65, No. 8, 2002, pp. 1459 - 1473 translated from Yadernaya Fizika v. 65, No. 8, 2002, pp. 1494 - 150

Influence of the computational domain on DNS of turbulent heat transfer up to Re-tau=2000 for Pr=0.71

[EN] We present a new set of direct numerical simulation data of a passive thermal flow in a turbulent plane Poiseuille flow with constant Prandtl number Pr = 0.71, and mixed boundary conditions. Simulations were performed at Re-tau = 500, 1000, and 2000 for several computational domains in the range of l(x) = 2 pi h to 8 pi h and l(z)= pi h to 3 pi h. As a first key result we found that a length of l(x) = 2 pi h and a width of l(z) = pi is enough to accurately obtain the one-point statistics and the budgets of the thermal kinetic energy, its dissipation and the thermal fluxes. None of them collapse exactly in wall units. On the other hand, the value of the thermal Karman constant grows very slightly with the Reynolds number with a value of K-th = 0.44 for Re-tau = 2000. (C) 2018 Elsevier Ltd. All rights reserved.This work was supported by the Ministerio de Empleo y Competitividad, project ENE2015-71333-R. The computations of the new simulations were made possible by a generous grant of computing time from the Supercomputation center of the Universitat Politecnica de Valencia. We are grateful to Mr. Kawamura for providing us with copies of their original data.Lluesma-Rodriguez, F.; Hoyas, S.; Pérez Quiles, MJ. (2018). Influence of the computational domain on DNS of turbulent heat transfer up to Re-tau=2000 for Pr=0.71. International Journal of Heat and Mass Transfer. 122:983-992. https://doi.org/10.1016/j.ijheatmasstransfer.2018.02.047S98399212

Bone sarcomas in atomic bomb survivors of Hiroshima and Nagasaki

Abstract no. 1017PURPOSE/OBJECTIVE(S): Ionizing radiation‐induced bone sarcomas have traditionally been associated with exposure to high levels of ionizing radiation. The role of exposure to lower levels of ionizing radiation in the development of such lesions remains speculative. Also, the appropriate dose‐response model of radiation dose exposure to excess relative risk (ERR) in association with bone sarcomas is questionable. MATERIALS/METHODS: The data source of the longitudinal, population‐based Life Span Study (N=120,321) cohort of atomic bomb survivors of Hiroshima and Nagasaki was utilized to estimate the ERR per Gray (Gy) of ionizing radiation exposure in the development of bone sarcomas. Other factors regarding sarcoma demographics …postprin

Evidence for a narrow structure at W~1.68 GeV in eta photoproduction on the neutron

New results on quasi-free $\eta$ photoproduction on the neutron and proton bound in a deuteron target are presented. The $\gamma n \to \eta n$ quasi-free cross section reveals a bump-like structure which is not seen in the cross section on the proton. This structure may signal the existence of a relatively narrow ($M\sim 1.68$ GeV, $\Gamma \leq 30$ MeV) baryon state.Comment: Replaced with published versio