Optimization of friction-stir welding of 6061-T6 aluminum alloy

In this work, two simple but effective strategies were proposed to optimize friction-stir welding of 6061-T6 aluminum alloy. The first one involved an optimization of welding variables to provide a combination of a relatively high welding temperature and the shortest possible thermal cycle during friction-stir welding. This inhibited precipitation coarsening in the heat-affected zone and resulted in considerable residual stres

Analysis of doctors’ appeals on the issues of countering doping in sports

Objective: the main topics of the doctors’ questions were the preparation of medical documents for a TUE application, the determination of the anti­doping status of various substances and methods, as well as the use of dietary supplements in sports.Materials and methods: an analysis was carried out of more than 400 appeals of doctors providing medical assistance to athletes of various levels on the issues of countering doping in sports. The aim of the work was to identify ways to improve educational and informational activities aimed at improving the quality of medical documents for TUE applications.Results: the need for continuous work to improve the level of doctors’ knowledge in countering doping in sports was confirmed, including clarification of the procedure for using documents from anti­doping organizations, the need to use TUE guidelines for physicians and the specifics of prescribing substances prohibited only during the competitive period

Inter-year variation in pup production of Caspian seals (Pusa caspica) 2005-2012 determined from aerial surveys

Assessing species abundance and reproductive output is crucial for evaluations of population dynamics, conservation status and the development of management objectives. The Caspian seal (Pusa caspica) is a key predator in the Caspian Sea ecosystem and is listed as “Endangered” by IUCN. Here we report on fixed-wing aerial strip transect surveys of the breeding population on the Caspian Sea winter ice field carried out in February 2005-2012. Potential detection biases were estimated by applying a Petersen mark-recapture estimator to the counts from double photographic observations. We also tested for effects of weather conditions on count results, and for correlations between pup production and ice conditions and net primary productivity (npp). Fluctuations in pup production estimates were observed among years, ranging from 8,200 pups (95% CI 7,130-9342) in 2010 to 34,000 (95% CI 31,275-36,814) in 2005. Total adults on the ice ranged from 14,500 in 2010 to 66,300 in 2012. We did not detect significant associations between pup production and either ice summary data (ice season length, and ice area) or npp. The observed inter-year variation may be partly due to underlying biological drivers influencing the fecundity of the population, although measurement errors arising from observation bias, plus variation in survey timing and weather conditions may also have contributed. Identifying the potential drivers of Caspian seal population dynamics will require extending both the survey time series and the quality of supporting data. However, inter-year fluctuations should still cause concern that the population may be vulnerable to environmental variability and ecosystem dynamics

Excited-State Electronic Structure with Configuration Interaction Singles and Tamm–Dancoff Time-Dependent Density Functional Theory on Graphical Processing Units

Excited-state calculations are implemented in a development version of the GPU-based TeraChem software package using the configuration interaction singles (CIS) and adiabatic linear response Tamm–Dancoff time-dependent density functional theory (TDA-TDDFT) methods. The speedup of the CIS and TDDFT methods using GPU-based electron repulsion integrals and density functional quadrature integration allows full ab initio excited-state calculations on molecules of unprecedented size. CIS/6-31G and TD-BLYP/6-31G benchmark timings are presented for a range of systems, including four generations of oligothiophene dendrimers, photoactive yellow protein (PYP), and the PYP chromophore solvated with 900 quantum mechanical water molecules. The effects of double and single precision integration are discussed, and mixed precision GPU integration is shown to give extremely good numerical accuracy for both CIS and TDDFT excitation energies (excitation energies within 0.0005 eV of extended double precision CPU results)

Multiple Sulfur Isotope Evidence for Bacterial Sulfate Reduction and Sulfate Disproportionation Operated in Mesoarchaean Rocks of the Karelian Craton

Sulfur isotope in sulfides from the Paleoarchean and the Neoarchean sedimentary rocks evidence microbial sulfur metabolism in Archean sulfur cycle. However, sulfur metabolism for the Mesoarchean interval is less obvious since evidence for a large range in sulfur isotope values has not yet been observed in Mesoarchean samples. We report the results of multiple sulfur isotope measurements for sulfide minerals from ~2.8 Ga sedimentary rocks in the southeastern part of the Karelian Craton. In situ isotope analysis of sulfide grains have been performed using a femtosecond laser-ablation fluorination method. Sulfide samples studied here yielded Δ33S values between −0.3 and +2.7‰ and δ34S values between −10 and +33‰. The Δ33S dataset was interpreted to indicate the incorporation of sulfur from two coexisting sulfur pools, photolytic sulfate and photolytically derived elemental sulfur. We suggest that the relative contributions of these Δ33S different pools to the pyritic sulfur could be controlled by the metabolic activity of coexisting sulfate-reducing and sulfur-disproportionating bacteria during pyrite formation. We therefore suggest the operation of different metabolic pathways of sulfur in Mesoarchean sedimentary environments

Investigation of properties of nitride and silicon oxide films grown by plasma-chemical deposition on a silicon substrate

The research has been carried out on dependence of mechanical stress on the modes of deposition of silicon nitride and oxide films obtained by plasma excited chemical vapour deposition of the layers from the gas phase (PECVD). The connection has been determined between the key parameters of the deposition, such as operating pressure in the chamber, working gas consumption, deposition rate and the level of internal mechanical stresses