Research the phytoplankton dynamics regimes depending on nutrient transformation processes in coastal systems

The paper describes the construction of a three-dimensional mathematical model of biogeochemical processes, considering the salinity and temperature influence on the phytoplankton populations’ development. The paper proposes a new difference scheme for solving convection-diffusion-reaction problems at large values of the Peclet grid number (2<Pe≤20), which is a linear combination of the central and the upwind leapfrog difference schemes. The three-layer difference scheme is more accurate than the traditional upwind leapfrog difference scheme for problems where convection prevails over diffusion. The construction of discrete equations for solving the problem of biogeochemical cycles on the basis of the scheme considering the filling of cells is described. The stationary regimes of phytoplankton dynamics problem were researched considering the transformation of phosphorus, nitrogen and silicon forms. Results of software complex, which allows to simulate biogeochemical processes in the Azov Sea, were described. The software package allows to forecast the dynamics of the Azov Sea ecosystem development in the conditions of modern salinization.The reported study was funded by RFBR, project number 20-01-00421

(Vyacheslavite U4+(PO4)(OH).nH2O - a new uranium phosphate.

Vyacheslavite is found in the zone of secondary enrichment of a U deposit and occurs in veinlets as dense green aggregates on quartz crystals; SEM shows elongated lamellar crystals = or &lt;8 mu m long. Under the microscope the crystals are weakly pleochroic in shades of green and have alpha 1.700, beta 1.726-1.729, gamma 1.729-1.731, 2Valpha small; parallel extinction; electron microdiffraction indicates orthorhombic symmetry. Indexed XRD powder data are tabulated; strongest lines 6.19(10), 2.69(7), 4.56(6), 4.13(6), 3.68(5), 2.71(5) A; a 6.96, b 9.10 c = or &lt; 12.38 A; space group CmCm, Cmc21 or C2cm; Dcalc 5.09/cm3. Microprobe analysis gave UO2 69.75-67.63, CaO 0.5-0.55, P2O5 16.9-17.1, H2O (by diff.) 12.85-14.72, corresponding with the formula U4+(PO4)(OH).nH2O where n approx 2.5. The name is for Vyacheslava G. Melkova.-R.A.H

(Vyacheslavite U4+(PO4)(OH).nH2O - a new uranium phosphate.

Vyacheslavite is found in the zone of secondary enrichment of a U deposit and occurs in veinlets as dense green aggregates on quartz crystals; SEM shows elongated lamellar crystals = or &lt;8 mu m long. Under the microscope the crystals are weakly pleochroic in shades of green and have alpha 1.700, beta 1.726-1.729, gamma 1.729-1.731, 2Valpha small; parallel extinction; electron microdiffraction indicates orthorhombic symmetry. Indexed XRD powder data are tabulated; strongest lines 6.19(10), 2.69(7), 4.56(6), 4.13(6), 3.68(5), 2.71(5) A; a 6.96, b 9.10 c = or &lt; 12.38 A; space group CmCm, Cmc21 or C2cm; Dcalc 5.09/cm3. Microprobe analysis gave UO2 69.75-67.63, CaO 0.5-0.55, P2O5 16.9-17.1, H2O (by diff.) 12.85-14.72, corresponding with the formula U4+(PO4)(OH).nH2O where n approx 2.5. The name is for Vyacheslava G. Melkova.-R.A.H

Notable Reactivity of Acetonitrile Towards Li2O2 LiO2 Probed by NAP XPS During Li O 2 Battery Discharge

One of the key factors responsible for the poor cycleability of Li–O2 batteries is a formation of byproducts from irreversible reactions between electrolyte and discharge product Li2O2 and/or intermediate LiO2. Among many solvents that are used as electrolyte component for Li–O2 batteries, acetonitrile (MeCN) is believed to be relatively stable towards oxidation. Using near ambient pressure X-ray photoemission spectroscopy (NAP XPS), we characterized the reactivity of MeCN in the Li–O2 battery. For this purpose, we designed the model electrochemical cell assembled with solid electrolyte. We discharged it first in O2 and then exposed to MeCN vapor. Further, the discharge was carried out in O2 + MeCN mixture. We have demonstrated that being in contact with Li–O2 discharge products, MeCN oxidizes. This yields species that are weakly bonded to the surface and can be easily desorbed. That’s why they cannot be detected by the conventional XPS. Our results suggest that the respective chemical process most probably does not give rise to electrode passivation but can decrease considerably the Coulombic efficiency of the battery