Self-induced and induced transparencies of two-dimensional and three- dimensional superlattices

The phenomenon of transparency in two-dimensional and three-dimensional superlattices is analyzed on the basis of the Boltzmann equation with a collision term encompassing three distinct scattering mechanisms (elastic, inelastic and electron-electron) in terms of three corresponding distinct relaxation times. On this basis, we show that electron heating in the plane perpendicular to the current direction drastically changes the conditions for the occurrence of self-induced transparency in the superlattice. In particular, it leads to an additional modulation of the current amplitudes excited by an applied biharmonic electric field with harmonic components polarized in orthogonal directions. Furthermore, we show that self-induced transparency and dynamic localization are different phenomena with different physical origins, displaced in time from each other, and, in general, they arise at different electric fields.Comment: to appear in Physical Review

Profile of cortisol, glycaemia, and blood parameters of American Bullfrog tadpoles Lithobates catesbeianus exposed to density and hypoxia stressors

The aim of this study was to evaluate alterations to the physiological profile (cortisol, glycaemia, and blood parameters) of Lithobates catesbeianus caused by the stressors density and hypoxia. The organisms were in the prometamorphosis stage and exposed to different tadpole densities: 1 tadpole/L (T1), 5 tadpoles/L (T2), and 10 tadpoles/L (T3) for 12 days. The blood was collected through the rupture of the caudal blood vessel and collected under normoxia (immediate collection) and hypoxia (after 15 minutes of air exposure) conditions. Cortisol levels rose on the fourth and eighth days of treatment and returned to basal levels by the end of the experiment. The stressor mechanisms tested did not affect glycaemia. White blood cells (total number of lymphocytes, neutrophils, and eosinophils) showed a significant difference at the twelfth day of the experiment when compared with the start of the experiment. We concluded that, under controlled conditions, a density of up to 10 tadpoles/L and air exposure for 15 minutes did not cause harmful physiological alterations during the experimental period. The answer to these stressors maybe was in another hormonal level (corticosterone)

A multi-country test of brief reappraisal interventions on emotions during the COVID-19 pandemic.

The COVID-19 pandemic has increased negative emotions and decreased positive emotions globally. Left unchecked, these emotional changes might have a wide array of adverse impacts. To reduce negative emotions and increase positive emotions, we tested the effectiveness of reappraisal, an emotion-regulation strategy that modifies how one thinks about a situation. Participants from 87 countries and regions (n = 21,644) were randomly assigned to one of two brief reappraisal interventions (reconstrual or repurposing) or one of two control conditions (active or passive). Results revealed that both reappraisal interventions (vesus both control conditions) consistently reduced negative emotions and increased positive emotions across different measures. Reconstrual and repurposing interventions had similar effects. Importantly, planned exploratory analyses indicated that reappraisal interventions did not reduce intentions to practice preventive health behaviours. The findings demonstrate the viability of creating scalable, low-cost interventions for use around the world

Витамин D-связывающий белок как многофункциональный компонент сыворотки крови

Vitamin D-binding protein (DBP) was discovered more than half a century ago as a polymorphic serum protein and is currently characterized by a variety of physiological properties. First of all, DBP carries the bulk of vitamin D metabolites circulating in the bloodstream, while albumin is the second most important transport protein, especially in patients with a low concentration of DBP in serum. Since it was discovered that only 12% of the total circulating DBP have occupied steroid binding sites, a vigorous study of other potential biological roles of DBP was initiated: actin utilization, regulation of inflammation and innate immunity mechanisms, fatty acid binding, effects on bone metabolism and participation in the tumor pathogenesis. This review focuses on the main known biological functions of DBP.Витамин D-связывающий белок (DBP) был открыт более полувека назад в качестве полиморфного белка сыворотки крови и к настоящему моменту характеризуется многообразием физиологических свойств. Прежде всего, DBP переносит основную часть циркулирующих в кровотоке метаболитов витамина D, тогда как альбумин является вторым по значимости транспортным белком, особенно у пациентов с низкой концентрацией DBP в сыворотке. Поскольку было открыто, что сайты связывания стероидов заняты лишь у 12% от общего количества циркулирующего DBP, инициировано активное изучение других потенциальных биологических ролей этого белка: утилизация актина, регуляция процессов воспаления и механизмов врожденного иммунитета, связывание жирных кислот, влияние на метаболизм костной ткани и связь с патогенезом опухолевых заболеваний. Данный обзор посвящен рассмотрению основных известных биологических функций DBP