Bulk Nanocrystalline Thermoelectrics Based on Bi-Sb-Te Solid Solution

A nanopowder from p-Bi-Sb-Te with particles ~ 10 nm were fabricated by the ball milling using different technological modes. Cold and hot pressing at different conditions and also SPS process were used for consolidation of the powder into a bulk nanostructure and nanocomposites. The main factors allowing slowing-down of the growth of nanograins as a result of recrystallization are the reduction of the temperature and of the duration of the pressing, the increase of the pressure, as well as addition of small value additives (like MoS2, thermally expanded graphite or fullerenes). It was reached the thermoelectric figure of merit ZT=1.22 (at 360 K) in the bulk nanostructure Bi0,4Sb1,6Te3 fabricated by SPS method. Some mechanisms of the improvement of the thermoelectric efficiency in bulk nanocrystalline semiconductors based on BixSb2-xTe3 are studied theoretically. The reduction of nanograin size can lead to improvement of the thermoelectric figure of merit. The theoretical dependence of the electric and heat conductivities and the thermoelectric power as the function of nanograins size in BixSb2-xTe3 bulk nanostructure are quite accurately correlates with the experimental data.Comment: 35 pages, 24 figures, 4 tables, 52 reference

ТЕКТОНО-ГЕОФИЗИЧЕСКОЕ РАЙОНИРОВАНИЕ РАДОНОАКТИВНОСТИ ПОРОД КРИСТАЛЛИЧЕСКОГО ФУНДАМЕНТА БЕЛАРУСИ

The high degree of correlation and genetic communications between radon volume activities (RVO), main types of crystalline basement rocks, geophysical fields, and main tectonic elements has been detected. Taking into account this correlation, a map of the radon activity of the basement was designed with three types of territory marking: with RVO more than 78200 Bq/m3 , 50000–72900 Bq/m3 and 25700–44000 Bq/m3 . The particular composition of rocks, as well as structural elements of zoning of the basemenet appeared in the RVO distribution. Установлена высокая степень корреляционно-генетической связи между объемной активностью радона (ОАР) основных типов пород кристаллического фундамента, геофизическими полями и основными тектоническими элементами. На основании этой связи построена карта радоноактивности фундамента с выделением трех типов территорий: с ОАР более 78200 Бк/м3 , 50000–72900 Бк/м3 и 25700–44000 Бк/м3 . В распределении ОАР проявляются как особенности состава пород, так и элементы структурного районирования фундамента.

Conservation of freshwater bivalves at the global scale: diversity, threats and research needs

Bivalves are ubiquitous members of freshwater ecosystems and responsible for important functions and services. The present paper revises freshwater bivalve diversity, conservation status and threats at the global scale and discusses future research needs and management actions. The diversity patterns are uneven across the globe with hotspots in the interior basin in the United States of America (USA), Central America, Indian subcontinent and Southeast Asia. Freshwater bivalves are affected by multiple threats that vary across the globe; however, pollution and natural system (habitat) modifications being consistently found as the most impacting. Freshwater bivalves are among the most threatened groups in the world with 40% of the species being near threatened, threatened or extinct, and among them the order Unionida is the most endangered. We suggest that global cooperation between scientists, managers, politicians and general public, and application of new technologies (new generation sequencing and remote sensing, among others) will strengthen the quality of studies on the natural history and conservation of freshwater bivalves. Finally, we introduce the articles published in this special issue of Hydrobiologia under the scope of the Second International Meeting on Biology and Conservation of Freshwater Bivalves held in 2015 in Buffalo, New York, USA.This work was supported by FCT—Foundation for Science and Technology, Project 3599—Promote the Scientific Production and Technological Development and Thematic 3599-PPCDT by FEDER as part of the project FRESHCO: multiple implications of invasive species on Freshwater Mussel co-extinction processes (Contract: PTDC/AGRFOR/1627/2014). FCT also supported MLL under Grant (SFRH/BD/115728/2016)