LiGaSe2 optical parametric oscillator pumped by a Q-switched Nd:YAG laser

Optical parametric oscillation is demonstrated for the first time with the chalcogenide nonlinear crystal LiGaSe2 pumped by a nanosecond Nd:YAG laser. Angle tuning provides coverage of the 4.8–9.9 μm spectral range in the mid-IR by idler pulses

Long-lived free induction decay signal in CsMnF<inf>3</inf> single crystal

Elementary excitations in antiferromagnets are magnons, and these quasiparticles with integer spin are governed by Bose statistics. In certain conditions their density can be controlled by applied radiofrequency pulse leading to the formation of Bose-Einstein condensation (BEC). We report the investigations of free induction decay signal duration in CsMnF3 under different conditions and discuss it in the framework of the magnon BEC. The observed results in CsMnF3 and previous investigations in superfluid 3He-A are compared. © Kazan Federal University (KFU)

Rippite, K2Nb2(Si4O12)O2)O(O,F), a new K-Nb-cyclosilicate from chuktukon carbonatite massif, chadobets upland, krasnoyarsk territory, russia

Rippite K2(Nb,Ti)2(Si4O12)(O,F)2, a new K-Nb-cyclosilicate, has been discovered in calciocarbonatites from the Chuktukon massif (Chadobets upland, SW Siberian Platform, Krasnoyarsk Territory, Russia). It was found in a primary mineral assemblage, which also includes calcite, fluorcalciopyrochlore, tainiolite, fluorapatite, fluorite, Nb-rich rutile, olekminskite, K-feldspar, Fe-Mn–dolomite and quartz. Goethite, francolite (Sr-rich carbonate–fluorapatite) and psilomelane (romanèchite ± hollandite) aggregates as well as barite, monazite-(Ce), parisite-(Ce), synchysite-(Ce) and Sr-Ba-Pb-rich keno-/hydropyrochlore are related to a stage of metasomatic (hydrothermal) alteration of carbonatites. The calcite–dolomite coexistence assumes crystallization temperature near 837◦C for the primary carbonatite paragenesis. Rippite is tetragonal: P4bm, a = 8.73885(16), c = 8.1277(2) Å, V = 620.69(2) Å3, Z = 2. It is closely identical in the structure and cell parameters to synthetic K2Nb2(Si4O12)O2 (or KNbSi2O7). Similar to synthetic phase, the mineral has nonlinear properties. Some optical and physical properties for rippite are: colorless; Mohs’ hardness—4–5; cleavage—(001) very perfect, (100) perfect to distinct; density (meas.)—3.17(2) g/cm3; density (calc.)—3.198 g/cm3; optically uniaxial (+); ω = 1.737-1.739; ε = 1.747 (589 nm). The empirical formula of the holotype rippite (mean of 120 analyses) is K2(Nb1.90Ti0.09Zr0.01)[Si4O12](O1.78OH0.12F0.10). Majority of rippite prismatic crystals are weakly zoned and show Ti-poor composition K2(Nb1.93Ti0.05Zr0.02)[Si4O12](O1.93F0.07). Raman and IR spectroscopy, and SIMS data indicate very low H2O content (0.09–0.23 wt %). Some grains may contain an outermost zone, which is enriched in Ti (+Zr) and F, up to K2(Nb1.67Ti0.32Zr0.01)[Si4O12](O1.67F0.33). It strongly suggests the incorporation of (Ti,Zr) and F in the structure of rippite via the isomorphism Nb5+ + O2− → (Ti,Zr)4+ + F1−. The content of a hypothetical end-member K2Ti2[Si4O12]F2 may be up to 17 mol. %. Rippite represents a new structural type among [Si4O12]-cyclosilicates because of specific type of connection of the octahedral chains and [Si4O12]8− rings. In structural and chemical aspects it seems to be in close with the labuntsovite-supergroup minerals, namely with vuoriyarvite-(K), K2(Nb,Ti)2(Si4O12)(O,OH)2·4H2O. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Investigations of inclusions in minerals and physical and chemical properties of rippite were done on state assignment of IGM SB RAS (0330-2019-0002 and 0330-2016-0005) and GIN SB RAS (AAAA-A16-116122110027-2), and the Initiative Project of Ministry of Science and Higher Education of the Russian Federation, Act 211 of the Government of the Russian Federation (agreement no. 02.A03.21.0006). Geochemical, spectroscopic and chemical studies for rippite were supported by the Russian Science Foundation (grant 19-17-00019)

Concept of teaching discipline Chemistry of an Environment

The educational space in a modern society is sharply expanded in comparison with the last centuries. Objectively occurs globalization in sphere of education. In this connection has ripened necessity more or less precise definition of frameworks of educational space at teaching discipline « Chemistry of an environment ». First of all, it is necessary to emphasize, that this discipline should give understanding about chemical compounds of all making natural the environments and about chemical reactions which proceed or can proceed in the ore

On the Connection of the Formulae for Entropy and Stationary Distribution

As it is well known in statistical physics the stationary distribution can be obtained by maximizing entropy. We show how one can reconstruct the formula for entropy knowing the formula for the stationary distribution. A general case is discussed and some concrete physical examples are considered. 1 Introduction In this paper we distinguish entropy from other functionals of distribution functions. We show for a very general case that the entropy functional is the unique functional that is maximized by the corresponding stationary distribution function under constraints given by the invariants of the associated kinetic equations. This means we prove a generalization of the so called dual to Gibb&apos;s Lemma, see Mc Kean [6]. As we will see the unique reconstruction of entropy is only possible if the dimension of the space of invariants is more than one. The physical examples we discuss are Maxwell-, Bose-Einstein-, and Fermi-Dirac distributions and constraints given by the invariants of th..