We describe an asymptotic analysis of the coupled nonlinear system of equations describing time-dependent three-dimensional monoenergetic neutron transport and isotopic depletion and radioactive decay. The classic asymptotic diffusion scaling of Larsen and Keller [1], along with a consistent small scaling of the terms describing the radioactive decay of isotopes, is applied to this coupled nonl...

background: miniature neutron sources with high neutron flux have abundant applications in medicine, industry and researches. the most important general characteristic of miniature neutron sources is their diameter which is 3mm in average. in this research, we have surveyed and designed an am-be miniature neutron source fabrication. materials and methods: this investigation resulted in creation...

Similar to LaCoO4.14, La2-xSrxCuO4±δ shows oxygen diffusion at moderate temperatures. The Oxygen Isotope Back Exchange (OIBE) experiments are done in order to investigate the effect of strontium on the oxygen diffusion in as grown single crystals of La2-xSrxCuO4±δ (x =0, 0.05, 0.1, 0.15). Neutron diffraction data collected at TriCS@SINQ are in agreement with diffusion measurements achieved by o...

β-Eucryptite (LiAlSiO4) is known to show super-ionic conductivity above 700 K. We performed inelastic neutron scattering measurements in β-eucryptite over 300-900 K and calculated the phonon spectrum using classical molecular dynamics (MD) simulations. The MD simulations were used to interpret the inelastic neutron spectra at high temperatures. The calculated diffusion coefficient for Li showed...

The self-diffusion of myoglobin in concentrated solutions was investigated up to volume fractions of 0.4 by neutron back-scattering spectroscopy. The quasi-elastic spectrum can be decomposed into two Lorentz curves: (1) a narrow line, where the width increases with Q, which is assigned to translational diffusion, and (2) a broad Q-independent line, reflecting proteininternal motions. The appare...

We have investigated the diffusion coefficient of nano-meter-sized domains on a vesicle composed of saturated phospholipids, unsaturated phospholipids and cholesterols by means of neutron spin echo spectroscopy. The obtained diffusion coefficient was examined from a viewpoint of the hydrodynamic model of Brownian objects in a fluid membrane.

We show that the widely used parabolic approximation to the Equation of State (EOS) of asymmetric nuclear matter leads systematically to significantly higher core-crust transition densities and pressures. Using an EOS for neutron-rich nuclear matter constrained by the isospin diffusion data from heavy-ion reactions in the same sub-saturation density range as the neutron star crust, the density ...

With the use of theory developed earlier, bulk effects in ultracold neutron coherent inelastic scattering are considered both for solid and liquid target samples related to energy and momentum exchange with phonon and diffusion-like modes. For the neutron in a material trap, differential and integral probabilities for the energy transfer per bounce are presented in a simple analytic form which ...

The development of a stochastic cellular automata model for low-density highly concentrated neutron sources is presented. The model was implemented for purely reflecting and absorbing media with no fission source. Results of numerical experiments for one benchmark case with the new model is compared to a traditional neutron diffusion calculation. Similarities and differences of the model with M...