The Darrieus-Landau instability in fast deflagration and laser ablation

The problem of the Darrieus-Landau instability at a discontinuous deflagration front in a compressible flow is solved. Numerous previous attempts to solve this problem suffered from the deficit of boundary conditions. Here, the required additional boundary condition is derived rigorously taking into account the internal structure of the front. The derived condition implies a constant mass flux at the front; it reduces to the classical Darrieus-Landau condition in the limit of an incompressible flow. It is demonstrated that in general the solution to the problem depends on the type of energy source present in the system. In the common case of a strongly localized source, compression effects make the Darrieus-Landau instability considerably weaker. In particular, the Darrieus-Landau instability growth rate is reduced for laser ablation in comparison with the classical incompressible case. The instability disappears completely in the Chapman-Jouguet regime of ultimately fast deflagration.Comment: 24 pages, 3 figures, version to appear in Physics of Plasma

Low vorticity and small gas expansion in premixed flames

Different approaches to the nonlinear dynamics of premixed flames exist in the literature: equations based on developments in a gas ex- pansion parameter, weak nonlinearity approximation, potential model equation in a coordinate-free form. However the relation between these different equations is often unclear. Starting here with the low vor- ticity approximation proposed recently by one of the authors, we are able to recover from this formulation the dynamical equations usually obtained at the lowest orders in gas expansion for plane on average flames, as well as obtain a new second order coordinate-free equation extending the potential flow model known as the Frankel equation. It is also common to modify gas expansion theories into phenomelogical equations, which agree quantitatively better with numerical simula- tions. We discuss here what are the restrictions imposed by the gas expansion development results on this process

Spin relaxation at the singlet-triplet crossing in a quantum dot

We study spin relaxation in a two-electron quantum dot in the vicinity of the singlet-triplet crossing. The spin relaxation occurs due to a combined effect of the spin-orbit, Zeeman, and electron-phonon interactions. The singlet-triplet relaxation rates exhibit strong variations as a function of the singlet-triplet splitting. We show that the Coulomb interaction between the electrons has two competing effects on the singlet-triplet spin relaxation. One effect is to enhance the relative strength of spin-orbit coupling in the quantum dot, resulting in larger spin-orbit splittings and thus in a stronger coupling of spin to charge. The other effect is to make the charge density profiles of the singlet and triplet look similar to each other, thus diminishing the ability of charge environments to discriminate between singlet and triplet states. We thus find essentially different channels of singlet-triplet relaxation for the case of strong and weak Coulomb interaction. Finally, for the linear in momentum Dresselhaus and Rashba spin-orbit interactions, we calculate the singlet-triplet relaxation rates to leading order in the spin-orbit interaction, and find that they are proportional to the second power of the Zeeman energy, in agreement with recent experiments on triplet-to-singlet relaxation in quantum dots.Comment: 29 pages, 14 figures, 1 tabl

Dynamics of the O. felineus Infestation Intensity and Egg Production in Carcinogenesis and Partial Hepatectomy in the Setting of Superinvasive Opisthorchiasis

Clinical and experimental studies have shown that opisthorchii tend to evade tumour growth foci to colonize more distant areas of the liver. When modelling tumours with various carcinogens in the setting of superinvasive opisthorchiasis, the intensity of invasion is reduced both before the formation of neoplasms (>120 days) and after the development of tumours of various histogeneses (liver, pancreas, and stomach) (>240 days). Egg production was observed to increase with the decrease in the number of parasites in the liver. The smallest changes in the infestation intensity indicators and egg production were observed in the experimental stomach tumours (p>0.05). A partial hepatectomy in the setting of opisthorchiasis did not affect the number of parasites in the ecological niche (liver) or the production of eggs by the helminth. With the deterioration of the vegetation state, parasite clumps of opisthorchii increase egg production under the conditions of distress

Hypereosinophilic Syndrome, Cardiomyopathies, and Sudden Cardiac Death in Superinvasive Opisthorchiasis

Cardiovascular pathology in patients with superinvasive opisthorchiasis is characterized by severe changes in haemodynamics and myocardial metabolism, impaired automatism, excitability, and conduction of the heart muscle. An analysis of 578 cases (medical and outpatient records and reports of pathoanatomical and forensic autopsies) recorded in healthcare facilities treating opisthorchiasis patients with a hyperendemic focus was carried out. We identified a set of cardiac changes in patients with hypereosinophilic syndrome associated with superinvasive opisthorchiasis infection, classified the pathological processes in accordance with ICD-10, and described their pathogenesis