H2 Formation on Interstellar Grains in Different Physical Regimes

An analysis of the kinetics of H2 formation on interstellar dust grains is presented using rate equations. It is shown that semi-empirical expressions that appeared in the literature represent two different physical regimes. In particular, it is shown that the expression given by Hollenbach, Werner and Salpeter [ApJ, 163, 165 (1971)] applies when high flux, or high mobility, of H atoms on the surface of a grain, makes it very unlikely that H atoms evaporate before they meet each other and recombine. The expression of Pirronello et al.\ [ApJ, 483, L131 (1997)] -- deduced on the basis of accurate measurements on realistic dust analogue -- applies to the opposite regime (low coverage and low mobility). The implications of this analysis for the understanding of the processes dominating in the Interstellar Medium are discussed.Comment: 4 pages, MN styl

Steering effects on growth instability during step-flow growth of Cu on Cu(1,1,17)

Kinetic Monte Carlo simulation in conjunction with molecular dynamics simulation is utilized to study the effect of the steered deposition on the growth of Cu on Cu(1,1,17). It is found that the deposition flux becomes inhomogeneous in step train direction and the inhomogeneity depends on the deposition angle, when the deposition is made along that direction. Steering effect is found to always increase the growth instability, with respect to the case of homogeneous deposition. Further, the growth instability depends on the deposition angle and direction, showing minimum at a certain deposition angle off-normal to (001) terrace, and shows a strong correlation with the inhomogeneous deposition flux. The increase of the growth instability is ascribed to the strengthened step Erlich Schwoebel barrier effects that is caused by the enhanced deposition flux near descending step edge due to the steering effect.Comment: 5 page

Analytical Calculation of the Neutrons Spectrum for Direct Measurement of N-N Scattering at Pulsed Reactor Yaguar

Analytical calculation of a single neutron detector counts per YAGUAR reactor pulse is presented and comparison with coincidence scheme is given.Comment: 10 pages, 3 figure

ОСОБЛИВОСТІ СІЛЬСЬКОГОСПОДАРСЬКОГО ВИКОРИСТАННЯ ДЕРНОВО-КАРБОНАТНИХ ҐРУНТІВ (РЕНДЗИН) ВОЛИНСЬКОГО ПОЛІССЯ

The features of sod-carbonate soils (rendzin) and their contiguity to Upper Cretaceous deposits within the boundaries of the Volyn Polissia are considered. The research was conducted in two areas and similar results were obtained. The term "rendziny" is briefly explained and their genesis, soil profile morphology, humus reserves, processes of humus formation and dehumification are defined. The most lasting effect of humus accumulation is noted when organic fertilizers are applied. This indicates that the use of organic and organo-mineral fertilizer systems leads to the stabilization of humus accumulation in the arable layer of the humus horizon.To maintain a high level of humus formation, it is necessary to apply organic fertilizers, and for a high degree of enrichment of humus with nitrogen, it is necessary to supplement them with mineral fertilizers. Of all the applied fertilization systems, the most optimal is the organo-mineral (combined) system (N60P60K120+8.9 t/ha of manure), which contributes to the formation of a powerful humus horizon characterized by the highest thermodynamic stability of the humus complex.The transformation of colloidal forms of humus was noted. When plowing rendzin on control (without fertilizers), the content of GH in the plowed layer decreases by 2 times, which indicates increased mineralization due to plowing. The use of fertilizer systems makes it possible to restrain PG mineralization by 16–40%, and the organo-mineral system exerts a great influence on its stabilization.     Розглянуто особливості дерново-карбонатних ґрунтів (рендзин), їхню приуроченість до верхньокрейдових відкладень у межах Волинського Полісся. Дослідження проведено на двох площах та отримано аналогічні результати. Коротко пояснено термін «рендзини» і визначено їх генезу, морфологію грунтового профілю, запаси гумусу, процеси утворення гумусу та дегуміфікації. Найбільш тривалим ефект накопичення гумусу відзначається при внесенні органічних добрив. Це свідчить про те, що застосування органічної та органо-мінеральної системи добрива призводить до стабілізації накопичення гумусу в орному шарі гумусового горизонту.Для підтримки високого рівня утворення гумусу необхідно обов'язково вносити органічні добрива, а для високого ступеня збагачення гумусу азотом необхідно доповнювати їх мінеральними добривами. З усіх застосовуваних систем удобрення найбільш оптимальною є органо-мінеральна (комбінована) система (N60P60K120+8,9 т/га гною), яка сприяє утворенню потужного гумусового горизонту, що характеризується найвищою термодинамічною стійкістю гумусового комплексу.Відзначено трансформацію колоїдних форм гумусу. При розорюванні рендзин на контролі (без добрив) вміст ПГ у орному шарі зменшується у 2 рази, що свідчить про підвищену мінералізацію внаслідок розорювання. Застосування систем добрива дозволяє стримувати мінералізацію ПГ на 16–40%, причому великий вплив на його стабілізацію чинить органо-мінеральна система

PHARMACOEPIDEMIOLOGICAL ANALYSIS OF THE TREATMENT OF PAROXYSMAL AND PERSISTENT ATRIAL FIBRILLATION IN EVERY DAY CLINICAL PRACTICE

Aim. To analyze current clinical practice in the treatment of atrial fibrillation (AF) in emergency care department of multidisciplinary hospital in 2008-2009. Material and methods. Retrospective continuous pharmacoepidemiology study was carried out. Hospital history sheets of the patients admitted to the emergency care department in the period from 01.01.2008 to 31.12.2009 were analyzed. Results. Physicians of emergency care department mainly chose strategy of sinus rhythm restoration and maintenance in patients with paroxysmal and persistent AF . To implement this strategy pharmacological cardioversion was performed in patients with stable hemodynamics. The most frequently used medicine for pharmacological cardioversion was procainamide (60% of all prescriptions). Its efficacy was about 50% as compared with this of 80% for amiodarone and propafenone. In order to maintain sinus rhythm monotherapy with beta-blockers or amiodarone was preferred. Conclusion. Overall, AF treatment corresponded to current guidelines. Physicians preferred strategy of sinus rhythm restoration and maintenance

Effect of laser heat treatment on structure and wear resistance of cobalt stellite

The structure and wear resistance of Stellite 6 alloy were studied before and after laser heat treatment. A significant refinement of the microstructure after the heat treatment is noted, the hardness the alloy changed slightly. An increase of wear resistance in shock-abrasive wear at angles of attack of 60-90° as well as metal-to-metal wear with presence of an abrasive layer is shown. © 2019 IOP Publishing Ltd. All rights reserved

The multiple quantum NMR dynamics in systems of equivalent spins with the dipolar ordered initial state

The multiple quantum (MQ) NMR dynamics in the system of equivalent spins with the dipolar ordered initial state is considered. The high symmetry of the MQ Hamiltonian is used in order to develop the analytical and numerical methods for an investigation of the MQ NMR dynamics in the systems consisting of hundreds of spins from "the first principles". We obtain the dependence of the intensities of the MQ NMR coherences on their orders (profiles of the MQ NMR coherences) for the systems of $200 - 600$ spins. It is shown that these profiles may be well approximated by the exponential distribution functions. We also compare the MQ NMR dynamics in the systems of equivalent spins having two different initial states, namely the dipolar ordered state and the thermal equilibrium state in the strong external magnetic field.Comment: 11 pages 4 figure

End states, ladder compounds, and domain wall fermions

A magnetic field applied to a cross linked ladder compound can generate isolated electronic states bound to the ends of the chain. After exploring the interference phenomena responsible, I discuss a connection to the domain wall approach to chiral fermions in lattice gauge theory. The robust nature of the states under small variations of the bond strengths is tied to chiral symmetry and the multiplicative renormalization of fermion masses.Comment: 10 pages, 4 figures; final version for Phys. Rev. Let