Three-body recombination in Bose gases with large scattering length

An effective field theory for the three-body system with large scattering length is applied to three-body recombination to a weakly-bound s-wave state in a Bose gas. Our model independent analysis demonstrates that the three-body recombination constant alpha is not universal, but can take any value between zero and 67.9 \hbar a^4/m, where a is the scattering length. Other low-energy three-body observables can be predicted in terms of a and alpha. Near a Feshbach resonance, alpha should oscillate between those limits as the magnetic field B approaches the point where a -> infinity. In any interval of B over which a increases by a factor of 22.7, alpha should have a zero.Comment: 8 pages, RevTex, 3 postscript figures, uses epsf.sty, rotate.sty, references added, discussion improve

On the combustion of fine iron particles beyond FeO stoichiometry: Insights gained from molecular dynamics simulations

Molecular dynamics (MD) simulations are performed to investigate the thermal and mass accommodation coefficients (TAC and MAC, respectively) for the combination of iron(-oxide) and air. The obtained values of TAC and MAC are then used in a point-particle Knudsen model to investigate the effect on the combustion behavior of (fine) iron particles. The thermal accommodation for the interactions of $\mathrm{Fe}$ with $\mathrm{N_2}$ and $\mathrm{Fe_xO_y}$ with $\mathrm{O_2}$ is investigated for different surface temperature, while the mass accommodation coefficient for iron(-oxide) with oxygen is investigated for different initial oxidation stages $Z_\mathrm{O}$, which represents the molar ratio of $\mathrm{O}/\left(\mathrm{O} + \mathrm{Fe}\right)$, and different surface temperatures. The MAC decreases almost linearly as a function of $Z_\mathrm{O}$, with a steeper slope when $Z_\mathrm{O} < 0.5$ and a gentler slope when $0.5 < Z_\mathrm{O} < 0.57$. By incorporating the MD-informed accommodation coefficients into the single iron particle model, the oxidation beyond $Z_\mathrm{O} = 0.5$ (from stoichiometric $\mathrm{FeO}$ to $\mathrm{Fe_3O_4}$) is modeled. A new temperature evolution for single iron particles is observed compared to results obtained with previously developed continuum models. Specifically, results of the present simulations show that the oxidation process continues after the particle reaching the peak temperature, while previous models predicting a maximum temperature was attained when the particle is fully oxidized to $Z_\mathrm{O} = 0.5$. Since the rate of formation slows down as the MAC decreases with an increasing oxidation stage, the rate of heat loss exceeds the rate of heat release upon reaching the maximum temperature. Finally, the effect of transition-regime heat and mass transfer on the combustion behavior of fine iron particles is investigated and discussed

Percolating Reaction-Diffusion Waves (PERWAVES) — Sounding Rocket Combustion Experiments

Percolating reaction–diffusion waves in disordered random media are encountered in many branches of modern science, ranging from physics and biology to material science and combustion. Most disordered reaction–diffusion systems, however, have complex morphologies and reaction kinetics that complicate the study of the dynamics. Flames in suspensions of heterogeneously reacting metal-fuel particles is a rare example of a reaction–diffusion wave with a simple structure formed by point-like heat sources having well-defined ignition temperature thresholds and combustion times. Particle sedimentation and natural convection can be suppressed in the free-fall conditions of sounding rocket experiments, enabling the properties of percolating flames in suspensions to be observed, studied, and compared with emerging theoretical models. The current paper describes the design of the European Space Agency PERWAVES microgravity combustion apparatus, built by the Airbus Defense and Space team from Bremen in collaboration with the scientific research teams from McGill University and the Technical University of Eindhoven, and discusses the results of two sounding-rocket flight experiments. The apparatus allows multiple flame experiments in quartz glass tubes filled with uniform suspensions of 25-micron iron particles in oxygen/xenon gas mixtures. The experiments performed during the MAXUS-9 (April 2017) and TEXUS-56 (November 2019) sounding rocket flights have confirmed flame propagation in the discrete mode, which is a pre-requisite for percolating-flame behavior, and have allowed observation of the flame structure in the vicinity of the propagation threshold

Аксіологічні виміри душпастирства у творах Іоана Золотоустого

Стаття Світлани Білоус "Аксіологічні виміри душпастирства у творах Іоана Золотоустого" присвячена пошуку джерел духовної опіки над людиною, витоки яких автор бачить у християнському середньовіччі. Життя і творча спадщина Іоана Золотоустого – яскравий приклад пояснення сутності й визначення ціннісної природи душпастирювання крізь призму поняття священства.Статья Светланы Билоус "Аксиологические измерения душпастирства в произведениях Іоана Золотоустого" посвящена поиску источников духовной опеки над человеком, истоки которіх автор видит в христианском средневековье. Жизнь и творческое наследство Иоанна Золотоустого – яркий пример объяснения сущности и определение ценностной природы душпастирства сквозь призму понятия священства.The article by Svitlana Bilous "Axiological dimensions of priesthood in the Ioan Zolotoustyi’s works" is dedicated to finding sources of spiritual care over a human, the origin of which the author sees in the Christian Middle Ages. The life and literary heredity of Ioan Zolotoustyi is a brilliant pattern of explaining the essence and definition of valuable ​​nature of pastoral care through the prism of the concept of the priesthood