Numerical investigation of deep water circulation in the Faroese Channels

The overflow of dense water from the Nordic Seas through the Faroese Channels is investigated numerically using the Massachusetts Institute of Technology General Circulation Model. The model is forced by the removal of a barrier that separates different water masses in the bottom layer of the Faroe-Shetland Channel at the north-eastern boundary. An analysis of the output reveals that during its adjustment in the rotating channel the propagating flow is unstable and forms cyclonic and anti-cyclonic eddies in the Faroese Channels. The life-time of the cyclonic eddy is about 10 days, but an anti-cyclonic eddy that is formed upstream of the sill crest of the Faroe Bank Channel has a longer life-time. However, after 50 days it eventually loses its structure below 400 m due to the decay of a counter-rotating current. In the upper 400 m layer this anti-cyclonic eddy remains persistent for longer. Observational evidence of the eddy is confirmed by the tracks of experimental drifters released in the area and by the temperature and salinity fields observed in the Faroese Channels.The pinching of isotherms along the Wyville Thomson Ridge results in the concentration of cold water on the southern side of the Faroese Channels that overflows into the Rockall Trough. The model results demonstrate that the main part of the cold water outflows through the Faroe Bank Channel, rather than across the Wyville Thompson Ridge, due to Earth rotation. The apparent similarity of modelled temperature, salinity and velocity sections to recent measurements in this area adds confidence to these results.     

Kobyashevite, Cu5(SO4)2(OH)6·4H2O, a new devilline-group mineral from the Vishnevye Mountains, South Urals, Russia

A new mineral kobyashevite, Cu₅(SO₄)₂(OH)₆·4H₂O (IMA 2011–066), was found at the Kapital’naya mine, Vishnevye Mountains, South Urals, Russia. It is a supergene mineral that occurs in cavities of a calcite-quartz vein with pyrite and chalcopyrite. Kobyashevite forms elongated crystals up to 0.2 mm typically curved or split and combined into thin crusts up to 1?×?2 mm. Kobyashevite is bluish-green to turquoise-coloured. Lustre is vitreous. Mohs hardness is 2½. Cleavage is {010} distinct. D(calc.) is 3.16 g/cm³. Kobyashevite is optically biaxial (?), α 1.602(4), β 1.666(5), γ 1.679(5), 2 V(meas.) 50(10)°. The chemical composition (wt%, electron-microprobe data) is: CuO 57.72, ZnO 0.09, FeO 0.28, SO₃ 23.52, H₂O(calc.) 18.39, total 100.00. The empirical formula, calculated based on 18 O, is: Cu_4.96Fe_0.03Zn_0.01S_2.01O_8.04(OH)_5.96·4H₂O. Kobyashevite is triclinic, $ P\overline{\,1 } $ , a 6.0731(6), b 11.0597(13), c 5.5094(6)?Å, α 102.883(9)°, β 92.348(8)°, γ 92.597(9)°, V 359.87(7)?ų, Z?=?1. Strong reflections of the X-ray powder pattern [d,Å-I(hkl)] are: 10.84–100(010); 5.399–40(020); 5.178–12(110); 3.590–16(030); 2.691–16(20–1, 040, 002), 2.653–12(04–1, 02–2), 2.583–12(2–11, 201, 2–1–1), 2.425–12(03–2, 211, 131). The crystal structure (single-crystal X-ray data, R?=?0.0399) сontains [Cu₄(SO₄)₂(OH)₆] corrugated layers linked via isolated [CuO₂(H₂O)₄] octahedra; the structural formula is CuCu₄(SO₄)₂(OH)₆·4H₂O. Kobyashevite is a devilline-group member. It is named in memory of the Russian mineralogist Yuriy Stepanovich Kobyashev (1935–2009), a specialist on mineralogy of the Urals.     

Murmanite and lomonosovite as Ag-selective ionites: kinetics and products of ion exchange in aqueous AgNO3 solutions

Products and kinetics of ion exchange of heterophyllosilicate minerals lomonosovite and murmanite with aqueous AgNO₃ solutions under low-temperature conditions have been studied using scanning electron microscopy, electron microprobe analysis, single-crystal X-ray diffraction, infrared spectroscopy, ²³Na nuclear magnetic resonance spectroscopy and dynamic calorimetry. Both minerals show strong affinity for silver in cation exchange. Simplified formulae of Ag-exchanged forms of murmanite and lomonosovite are (Ag_3.0Ca_0.5Na_0.5) (Ti,Nb,Mn,Fe)_3.7?4 (Si₂O₇)₂O₄·4(H₂O,OH) and (Ag_8.2Na_1.2Ca_0.3) (Ti,Nb,Mn,Fe)_3.9?4 (Si₂O₇)₂ (PO₄)_1.9O₄·xH₂O, respectively. The reaction of ion exchange for murmanite follows the first-order kinetic model up to ca. 70–80 % conversion. The rate of the process is described by the equation k(h^?1) = 10^7.64±0.60 exp[?(12.2 ± 0.9)·10³/RT]. The average heat release value in the temperature range 39.4–72 °C is 230 J g^?1. The cation exchange is limited by processes in solid state, most probably binding of silver.     

Water exchange in fjords induced by tidally generated internal lee waves

Tidal processes are examined that control the water exchange between two basins of the Trondheimsfjord through a narrow channel with sills. For this purpose, a non-hydrostatic numerical model based on the laterally averaged Reynolds equations in the Boussinesq approximation was developed. The model takes into account the real vertical fluid stratification, variable bottom topography and variable cross-section of the fjord. Numerical experiments were performed to investigate tidally generated internal waves and their influence on the water exchange.The model produces both baroclinic tides and tidally generated lee waves. It was found that, for the Skarnsund strait which connects the Middle Fjord and the Beitstadfjord, the internal tides generated over the Skarnsund sills are very weak. Their amplitudes do not exceed 1 m.The intense short internal waves, which are identified as unsteady lee waves, comprise the basic input of the total internal wave field. These waves are generated by tidal currents at sill breaks, are trapped by topography in the generation area and grow by continuing feedback into large-amplitude waves. As the tidal flow slackens, they move upstream as freely propagating waves.As essentially nonlinear responses, the lee waves cause a nonlinear water transport. The detailed analysis of the residual currents produced by unsteady lee waves (which are propagating in both directions from the Scarnsund sills) has shown, in particular, that the residual currents can reach values as high as 0.27 m s⁻¹.It was also found that such currents exert a considerable effect on the water exchange through the Skarnsund strait between the adjacent basins. This mechanism can play an important role in water renewal and formation of the Beitasdfjord waters.     

On the use of a two-layer fluid stratification model in studies of topographically-generated baroclinic tides

Internal waves generated by a baroclinic internal wave impinging on an oceanic ridge are studied. Two stratification models are considered: a two-layer ocean model (with a density jump) and a continuously stratified ocean model (model pycnocline). The results yielded by different stratification models are compared analytically. The analysis makes possible the application of a piecewise-constant approximation of the fluid stratification to study topographically-generated baroclinic tides. Translated by V. Puchkin.     

V404 CYG/GS 2023+338: Monitoring in the Optical with Robotic Telescopes of the MASTER Global Network during the 2015 Superburst

2070 unique, homogeneous photometric and polarization observations of the microquasar in a binary system with a black hole V404 Cyg/GS2023+338 obtained in 2015 with the MASTER global network of robotic telescopes (16 robotic telescopes located at eight points on the Earth in Russia, Spain, South Africa, and Argentina) are presented. MASTER was the first telescope network to obtain optical observations of the microquasar after its gamma-ray outburst in 2015. Observations were carried out from 18:34:09 UT on June 15, 2015 until December 2015 in four polarizations and in the four standard BV RI filters. The paper presents the results of these observations and a comparative analysis of optical and X-ray data. The observations confirm the previously discovered super-long delays of the optical radiation relative to the X-ray outbursts. Possible mechanisms causing the delay in the optical variations relative to the X-ray variations are discussed. Variability of the optical polarization discovered earlier is confirmed another similar episode reported.

     

Variation of Carboneceous Atmospheric Aerosol Near St. Petersburg

Izvestiya, Atmospheric and Oceanic Physics - The results of 5-year (2013–2017) measurements of organic (OC) and elemental (EC) carbon aerosol fractions observed at the atmospheric monitoring...     

Stronadelphite from Alkaline Rocks of the Konder Massif (Khabarovsk Krai)

Geology of Ore Deposits - This paper presents the characteristics of stronadelphite Sr5(PO4)3F, identified in the eudialyte–aegirine–albite rocks of the Konder alkaline–ultrabasic...     

Nickelpicromerite,K<Subscript>2</Subscript>Ni(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>•6H<Subscript>2</Subscript>O,a new picromerite-group mineral from Slyudorudnik,South Urals,Russia

A new picromerite-group mineral, nickelpicromerite, K₂Ni(SO₄)₂?·?6H₂O (IMA 2012–053), was found at the Vein #169 of the Ufaley quartz deposit, near the town of Slyudorudnik, Kyshtym District, Chelyabinsk area, South Urals, Russia. It is a supergene mineral that occurs, with gypsum and goethite, in the fractures of slightly weathered actinolite-talc schist containing partially vermiculitized biotite and partially altered sulfides: pyrrhotite, pentlandite, millerite, pyrite and marcasite. Nickelpicromerite forms equant to short prismatic or tabular crystals up to 0.07 mm in size and anhedral grains up to 0.5 mm across, their clusters or crusts up to 1 mm. Nickelpicromerite is light greenish blue. Lustre is vitreous. Mohs hardness is 2–2½. Cleavage is distinct, parallel to {10–2}. D _meas is 2.20(2), D _calc is 2.22 g cm^?3. Nickelpicromerite is optically biaxial (+), α?=?1.486(2), β?=?1.489(2), γ?=?1.494(2), 2V_meas =75(10)°, 2V_calc =76°. The chemical composition (wt.%, electron-microprobe data) is: K₂O 20.93, MgO 0.38, FeO 0.07, NiO 16.76, SO₃ 37.20, H₂O (calc.) 24.66, total 100.00. The empirical formula, calculated based on 14 O, is: K_1.93Mg_0.04Ni_0.98S_2.02O_8.05(H₂O)_5.95. Nickelpicromerite is monoclinic, P2₁/c, a?=?6.1310(7), b?=?12.1863(14), c?=?9.0076(10) Å, β?=?105.045(2)°, V?=?649.9(1) ų, Z?=?2. Eight strongest reflections of the powder XRD pattern are [d,Å-I(hkl)]: 5.386–34(110); 4.312–46(002); 4.240–33(120); 4.085–100(012, 10–2); 3.685–85(031), 3.041–45(040, 112), 2.808–31(013, 20–2, 122), 2.368–34(13–3, 21–3, 033). Nickelpicromerite (single-crystal X-ray data, R?=?0.028) is isostructural to other picromerite-group minerals and synthetic Tutton’s salts. Its crystal structure consists of [Ni(H₂O)₆]²⁺ octahedra linked to (SO₄)^2? tetrahedra via hydrogen bonds. K⁺ cations are coordinated by eight anions. Nickelpicromerite is the product of alteration of primary sulfide minerals and the reaction of the acid Ni-sulfate solutions with biotite.     

Geophysical studies of sturgeon spawning grounds in the Lower Volga and recommendations for their remediation

The results of geophysical studies in the Lower Volga allowed the authors to reveal areas suitable for sturgeon reproduction, determine the level of sturgeon natural reproduction in different zone of the river, evaluate the productivity of spawning grounds, and give recommendations for their remediation.