Dust extinction and absorption: the challenge of porous grains

In many models of dusty objects in space the grains are assumed to be composite or fluffy. However, the computation of the optical properties of such particles is still a very difficult problem. We analyze how the increase of grain porosity influences basic features of cosmic dust -- interstellar extinction, dust temperature, infrared bands and millimeter opacity. Porous grains can reproduce the flat extinction across the 3 - 8 \mkm wavelength range measured for several lines of sight by {\it ISO} and {\it Spitzer}. Porous grains are generally cooler than compact grains. At the same time, the temperature of very porous grains becomes slightly larger in the case of the EMT-Mie calculations in comparison with the results found from the layered-sphere model. The layered-sphere model predicts a broadening of infrared bands and a shift of the peak position to larger wavelengths as porosity grows. In the case of the EMT-Mie model variations of the feature profile are less significant. It is also shown that the millimeter mass absorption coefficients grow as porosity increases with a faster growth occurring for particles with Rayleigh/non-Rayleigh inclusions. As a result, for very porous particles the coefficients given by two models can differ by a factor of about 3. It is found that an increase of porosity leads to an increase of extinction cross sections at some wavelengths and a decrease at others depending on the grain model. However, this behaviour is sufficient to reproduce the extinction curve in the direction of the star $\sigma$ Sco using current solar abundances. In the case of the star $\zeta$ Oph our model requires larger amounts of carbon and iron in the dust-phase than is available.Comment: Astronomy and Astrophysics (accepted; 11 pages, 11 figures

Отражение сочетания генотипов по полиморфным локусам COMT Val158Met и MAOA -uVNTR в психологических особенностях девушек

In recent years, much research on psychological features of carriers of different genes has been done. Studying the role of combinations of various genes in the formation of personal traits is the next step in the understanding of the specificity of the influence of genes on personality traits. The MAOA and COMT genes of the monoaminergic system are the subject of research of psychologists because of their impact on the duration of stay of neurotransmitters-monoamines in the synaptic space, and hence their potential impact on the duration and intensity of emotional reactions. Taking into account the constancy of this influence the authors assumed that these genes could be associated with stable personality characteristics, which was confirmed by not numerous scientific studies.The paper presents the results of the study, which involved 115 girls at the age from 18 to 30. The procedure of genotyping with the discrimination of polymorphic loci of MAOA -uVNTR and COMT Val158Met was the first stage of the experiment. The psychodiagnostic stage included the study of personality traits of the participants: the level of aggression, types of legitimized aggression, types of behavior in the conflict, formal and dynamic properties of individuality, and tendency to various forms of deviant behavior. The results of the study enabled to make psychological portraits of carriers of various combinations of genes. The carriers of the combination of the high-activity forms of the studied genes had the sanguine temperament, high aggression, intellectual speed, and flexibility. The carriers of the combination of the MAOA M heterozygous genotype and the low-activity genotype of AA COMT had the melancholic temperament, low level of aggression, intellectual speed, and flexibility. In the present study the authors made the assumption that the COMT A allele was associated with the tendency to suppression of aggression; the COMT G allele was probably associated with the preference for open forms of aggressive behavior and a high level of general activity. The COMT heterozygous genotype was associated with a low level of aggression; the MAOA L genotype was associated with a high level of aggression.Изучению психологических особенностей обладателей различных генов посвящены многие современные исследования. Следующим шагом на пути познания специфики оказываемого генами воздействия на личностные черты является изучение роли сочетаний различных генов в формировании последних. Гены моноаминергической системы MAOA и COMT являются предметом исследования психологов по причине оказываемого влияния на длительность пребывания нейромедиаторов-моноаминов в синаптическом пространстве, а значит – потенциального воздействия на продолжительность, интенсивность эмоциональных реакций. Принимая во внимание постоянство этого влияния, мы предполагаем, что данные гены могут быть ассоциированы и с устойчивыми личностными характеристиками, что находит подтверждение в немногочисленных современных научных изысканиях.В статье представлены результаты исследования, в котором приняли участие 115 девушек в возрасте 18–30 лет. Первым этапом эксперимента явилась процедура генотипирования с выделением полиморфных локусов генов MAOA -uVNTR и COMT Val158Met. Психодиагностический этап включал в себя изучение личностных особенностей участниц: уровня агрессивности, видов легитимизированной агрессии, типов поведения в конфликте, формально-динамических свойств индивидуальности, склонности к различным формам девиантного поведения.По результатам исследования составлены психологические портреты носителей различных сочетаний генов. Показано, что обладательницы комбинации высокоактивных форм изучаемых генов имеют сангвинический тип темперамента, высокую агрессивность, интеллектуальную скорость и пластичность. Носители сочетания гетерозиготного генотипа MAOA M с низкоактивным генотипом AA COMT являются обладателями меланхолического темперамента, имеют низкий уровень агрессивности, интеллектуальной скорости и пластичности. В работе высказано предположение об ассоциации аллеля А гена COMT со склонностью к подавлению агрессии, в то время как аллель G COMT, вероятно, связан у девушек с предпочтением открытых форм агрессивного поведения и высоким уровнем общей активности. Гетерозиготный генотип COMT ассоциирован с низким уровнем агрессивности, а генотип MAOA L – с высоким

Low-frequency dynamics of disordered XY spin chains and pinned density waves: from localized spin waves to soliton tunneling

A long-standing problem of the low-energy dynamics of a disordered XY spin chain is re-examined. The case of a rigid chain is studied where the quantum effects can be treated quasiclassically. It is shown that as the frequency decreases, the relevant excitations change from localized spin waves to two-level systems to soliton-antisoliton pairs. The linear-response correlation functions are calculated. The results apply to other periodic glassy systems such as pinned density waves, planar vortex lattices, stripes, and disordered Luttinger liquids.Comment: (v2) Major improvements in presentation style. One figure added (v3) Another minor chang

Mechanistic aspects of reactions of triphenylphosphine with electron-deficient alkenes in acetic acid solution

Kinetic data provide evidence that proton transfer to the carbanion centre of a phosphonium zwitterion is the rate-determining step in quarternization reactions of triphenylphosphine with electron-deficient alkenes in acetic acid solution. This conclusion is based on the third-order rate equation, the reactivity of the alkenes, and solvent isotope effects in deuteroacetic acid. Copyright © 2013 John Wiley & Sons, Ltd