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This paper is devoted to study the electrochemical behavior of Pt catalyst in a polymer electrolyte fuel cell at various operating conditions and at different electric potential difference (also known as voltage) cycling applied in accelerated stress tests. The degradation of platinum is considered with respect to the Pt ion dissolution and the Pt oxide coverage of catalyst described by a one-dimensional model. In the model, degradation rate increases with temperature and decreasing particle diameter of Pt nano-particles. The theoretical study of the underlying diffusion system with the nonlinear reactions is presented by analytical methods and gives explicit solutions through a first integral of the ODE system. Numerical tests are obtained using a second order implicit-explicit scheme. The computer simulation shows that the lifetime of the catalyst depends on the voltage profile and the upper potential level. By this Pt mass loss is more significant at the membrane surface than at the gas diffusion layer.

Thin film photovoltaic (PV) technologies were quite popular in 2005-2010 due to relatively low modules costs and low need in silicon or other materials. Amorphous silicon (a-Si) thin films are well known as PV active material with wider light absorption bandgap than for crystalline silicon which allows better module operation in case of diffuse radiation. Low PV energy conversion efficiency (7-11% against 16-19% for crystalline) is a main drawback of such modules. CuInGaSe2 (CIGS) thin films have no such features for absorption bandgap, but have large efficiency (13-14% for PV module and 20,4% for laboratory scale cell). It is also known, that thin film modules have much lower temperature power coefficient, which makes their operation more reliable at hot weather. Nowadays fast progress in crystalline silicon PV technologies led to lower cost for crystalline modules and made thin film technologies less competitive. In Joint Institute for High Temperatures comparative field tests of several thin film and crystalline modules were conducted in 2015-16, using small autonomous power units (PV module, charge controller, small accumulator for charge controller feed and resistive load) as a test bed. Specific energy production for each module throughout different months and the whole test period (10.2015-10.2016) was used as a main criteria for comparison. Economic efficiency (energy production to capital costs ratio for each module type) was also estimated.

Abstract Experimental pressures as a function of temperature, density, and mole fraction x of xenon along the critical line of { x Xe+(1 − x )CO 2 } have been obtained using a precise ( p , ρ, T ) instrument in the temperature range (301.69 to 304.15) K, the density range (468.0 to 502.4) kg·m −3 , the mole fraction range (0 to 4.2067·10 −2 ), and the pressure range (7.2916 to 7.3883) MPa.

The impact of temporary storage sites for radioactive wastes in Guba Andreeva on the environmental conditions in the coastal zone of the Barents Sea after 50 years of operation is evaluated on the basis of general chronological reconstruction of the dynamics of radioactive contamination of the marine environment. The bottom deposits along the seacoast at different distances from the repository were investigated. It was found that the region of constant impact of the repository on the conditions in the marine environment is localized near the perimeter of the sanitary-protective zone. Growth of the specific activity of 137Cs, 90Sr, 238Pu, 239,240Pu is recorded in sediments layers up to the level 16–20 cm. The impact of the emission of radionuclides from the repository site is not perceptible in the seacoast zone (Motovskii Zaliv). The age of the sedimentary layers was determined: it shows that the significant concentration of 137Cs in the deposits in Motovskii Zaliv corresponds to the mid-1960s and 1986 and is associated with atmospheric fallout of radionuclides as a result of the nuclear weapons tests and the accident at the Chernobyl NPP.

Flying over the open sea is energetically costly for terrestrial birds. Despite this, over-water journeys of many birds, sometimes hundreds of kilometres long, are uncovered by bio-logging technology. To understand how these birds afford their flights over the open sea, we investigated the role of atmospheric conditions, specifically wind and uplift, in subsidizing over-water flight at a global scale. We first established that ΔT, the temperature difference between sea surface and air, is a meaningful proxy for uplift over water. Using this proxy, we showed that the spatio-temporal patterns of sea-crossing in terrestrial migratory birds are associated with favourable uplift conditions. We then analysed route selection over the open sea for five facultative soaring species, representative of all major migratory flyways. The birds maximized wind support when selecting their sea-crossing routes and selected greater uplift when suitable wind support was available. They also preferred routes with low long-term uncertainty in wind conditions. Our findings suggest that, in addition to wind, uplift may play a key role in the energy seascape for bird migration that in turn determines strategies and associated costs for birds crossing ecological barriers such as the open sea.

Reproduction in fishes is sensitive to temperature. Elevated temperatures and anomalous ‘heat waves’ associated with climate change have the potential to impact fish reproductive performance and, in some cases, even induce sex reversals. Here we examine how thermal sensitivity in the hormone pathways regulating reproduction provides a framework for understanding impacts of warmer conditions on fish reproduction. Such effects will differ depending on evolved variation in temperature sensitivity of endocrine pathways regulating reproductive processes of sex determination/differentiation, gametogenesis and spawning, as well as how developmental timing of those processes varies with reproductive ecology. For fish populations unable to shift geographical range, persistence under future climates may require changes in temperature responsiveness of the hormone pathways regulating reproductive processes. How thermal sensitivity in those hormone pathways varies among populations and species, how those pathways generate temperature maxima for reproduction, and how rapidly reproductive thermal tolerances can change via adaptation or transgenerational plasticity will shape which fishes are most at risk for impaired reproduction under rising temperatures. This article is part of the theme issue ‘Endocrine responses to environmental variation: conceptual approaches and recent developments’.

Varying the spectral composition of light is one of the ways to accelerate the growth of conifers under artificial conditions for the development of technologies and to obtain sustainable seedlings required to preserve the existing areas of forests. We studied the influence of light of different quality on the growth, gas exchange, fluorescence indices of Chl a, and expression of key light-dependent genes of Pinus sylvestris L. seedlings. It was shown that in plants growing under red light (RL), the biomass of needles and root system increased by more than two and three times, respectively, compared with those of the white fluorescent light (WFL) control. At the same time, the rates of photosynthesis and respiration in RL and blue light (BL) plants were lower than those of blue red light (BRL) plants, and the difference between the rates of photosynthesis and respiration, which characterizes the carbon balance, was maximum under RL. RL influenced the number of xylem cells, activated the expression of genes involved in the transduction of cytokinin (Histidine-containing phosphotransfer 1, HPT1, Type-A Response Regulators, RR-A) and auxin (Auxin-induced protein 1, Aux/IAA) signals, and reduced the expression of the gene encoding the transcription factor phytochrome-interacting factor 3 (PIF3). It was suggested that RL-induced activation of key genes of cytokinin and auxin signaling might indicate a phytochrome-dependent change in cytokinins and auxins activity.