Development of Ni-Sr(V,Ti)O3-δ Fuel Electrodes for Solid Oxide Fuel Cells

A series of strontium titanates-vanadates (STVN) with nominal cation composition Sr1-xTi1-y-zVyNizO3-δ (x = 0–0.04, y = 0.20–0.40 and z = 0.02–0.12) were prepared by a solid-state reaction route in 10% H2–N2 atmosphere and characterized under reducing conditions as potential fuel electrode materials for solid oxide fuel cells. Detailed phase evolution studies using XRD and SEM/EDS demonstrated that firing at temperatures as high as 1200 °C is required to eliminate undesirable secondary phases. Under such conditions, nickel tends to segregate as a metallic phase and is unlikely to incorporate into the perovskite lattice. Ceramic samples sintered at 1500 °C exhibited temperature-activated electrical conductivity that showed a weak p(O2) dependence and increased with vanadium content, reaching a maximum of ~17 S/cm at 1000 °C. STVN ceramics showed moderate thermal expansion coefficients (12.5–14.3 ppm/K at 25–1100 °C) compatible with that of yttria-stabilized zirconia (8YSZ). Porous STVN electrodes on 8YSZ solid electrolytes were fabricated at 1100 °C and studied using electrochemical impedance spectroscopy at 700–900 °C in an atmosphere of diluted humidified H2 under zero DC conditions. As-prepared STVN electrodes demonstrated comparatively poor electrochemical performance, which was attributed to insufficient intrinsic electrocatalytic activity and agglomeration of metallic nickel during the high-temperature synthetic procedure. Incorporation of an oxygen-ion-conducting Ce0.9Gd0.1O2-δ phase (20–30 wt.%) and nano-sized Ni as electrocatalyst (≥1 wt.%) into the porous electrode structure via infiltration resulted in a substantial improvement in electrochemical activity and reduction of electrode polarization resistance by 6–8 times at 900 °C and ≥ one order of magnitude at 800 °C.

Nitrogen management under increased atmospheric CO2 concentration in cucumber (Cucumis sativus L.): ameliorating environmental impacts of fertilization

In the last years, the atmospheric CO2 concentration has increased significantly, and this increase can cause changes in various physiological and biochemical processes of plants. However, the response of plants to elevated CO2 concentration (e[CO2]) will be different depending on the nitrogen form available and the plant species. Therefore, hydroponic trials on cucumber plants, with two CO2 concentrations (400 and 1000 ppm) and two nitrogen sources (NO3−/NH4+; 100/0 and 90/10), were conducted. Physiological parameters—such as gas exchange, GS, GOGAT and GDH activities, cation composition, soluble sugar and starch content- were measured. The results showed that when plants were grown with NH4+ and e[CO2], parameters such as photosynthesis rate (ACO2), instantaneous water use efficiency (WUEi), the content of NH4+, Ca2+ and Mg2+, and the concentration of starch, were higher than in control plants (irrigated with nitrate as sole nitrogen source and ambient CO2 concentration (a[CO2])). Furthermore, an improvement in N assimilation was observed when the GS/GOGAT pathway was enhanced under these conditions (NH4+ and e[CO2]). Thus, our results contribute to the reduction of the negative environmental impacts of the use of nitrogen fertilizers on this crop, both by reducing nitrogen leakage (eutrophication) and greenhouse gas emissions.

Grguricite, CaCr2(CO3)2(OH)4.4H2O, a new alumohydrocalcite analogue

The occurrence and characterisation of a new member of the dundasite group are reported. Grguricite, ideally CaCr2(CO3)2(OH)4⋅4H2O, is the Cr analogue of alumohydrocalcite, CaAl2(CO3)2(OH)4⋅4H2O and occurs as lilac crusts of very fine-grained crystalline aggregates in the Pb–Ba–V mineralisation found at the Adeghoual Mine, Mibladen, Morocco (32°46′0″N, 4°37′59″W). The identification was based upon a close match with the powder X-ray diffraction data for alumohydrocalcite, the confirmation of anion components identified by Raman spectroscopy and the cation composition determined by electron-probe microanalysis. The empirical formula based upon 14 oxygen atoms per formula unit is Ca0.84Pb0.03Cr1.65Al0.39Mg0.02(CO3)2(OH)4⋅4H2O, with carbonate, hydroxyl and water contents set to those of the alumohydrocalcite stoichiometry. The fine-grained nature of the crystals (c. 0.5 μm × 0.1 μm × 5 μm) precluded a single-crystal X-ray study and both density and optical determinations. Grguricite is triclinic with space group P${\bar 1}$. Unit-cell parameters refined from the powder diffraction data are: a = 5.724(2), b = 6.5304(9), c = 14.646(4) Å, α = 81.682(1), β = 83.712(2), γ = 86.365(2)°, V = 537.8(2) Å3 and Z = 2. The five strongest peaks in the powder pattern are [dhkl, Å (I/Imax)(hkl)]: 6.222(100)(011), 3.227(87)(020), 6.454(63)(010), 2.883(58)(005, 023, 121) and 7.208(45)(002). The mineral is named after Australian geologist Ben Grguric.

Geochemistry of contrasting stream types, Taylor Valley, Antarctica

The McMurdo Dry Valley region is the largest ice-free area of Antarctica. Ephemeral streams flow here during the austral summer, transporting glacial meltwater to perennially ice-covered, closed basin lakes. The chemistry of 24 Taylor Valley streams was examined over the two-decade period of monitoring from 1993 to 2014, and the geochemical behavior of two streams of contrasting physical and biological character was monitored across the seven weeks of the 2010–2011 flow season. Four species dominate stream solute budgets: HCO3–, Ca2+, Na+, and Cl–, with SO42–, Mg2+, and K+ present in significantly lesser proportions. All streams contain dissolved silica at low concentrations. Across Taylor Valley, streams are characterized by their consistent anionic geochemical fingerprint of HCO3 > Cl > SO4, but there is a split in cation composition between 14 streams with Ca > Na > Mg > K and 10 streams with Na > Ca > Mg > K. Andersen Creek is a first-order proglacial stream representative of the 13 short streams that flow <1.5 km from source to gage. Von Guerard is representative of 11 long streams 2–7 km in length characterized by extensive hyporheic zones. Both streams exhibit a strong daily cycle for solute load, temperature, dissolved oxygen, and pH, which vary in proportion to discharge. A well-expressed diurnal co-variation of pH with dissolved oxygen is observed for both streams that reflects different types of biological control. The relative consistency of Von Guerard composition over the summer flow season reflects chemostatic regulation, where water in transient storage introduced during times of high streamflow has an extended opportunity for water-sediment interaction, silicate mineral dissolution, and pore-water exchange.

Modern Features of the Transformation of the World and Russian Labor Markets

The article is devoted to the assessment of the impact of modern digital technologies on the world and Russian labor market. The relevance of the chosen problem is explained by the fact that the achieved level of digital development of society has a signifi cant impact on the size of labor markets, the qualifi cation composition of workers, the demand for certain professions. The article presents the results of the analysis of the impact of digital technology on the growth of Russia’s GDP, the contribution of individual factors of growth in value added of diff erent sectors of the economy, including the sectoral dimension, the dynamics of digital technologies across regions of the country. The article presents the results of studies characterizing new trends in the labor market, formed as a response to the increasingly active penetration of the digital economy in the socioeconomic sphere of society.