Superconductivity in the Sn-Ba-Sr-Y-Cu-O system

Since Bednorz and Muller discovered high-T(sub c) superconductivity in the La-Ba-Cu-O compound, several families of superconducting oxides have been synthesized. Here, researchers report the results of search for superconductivity in the compounds based on tin, which has a lone electron pair like Bi, Tl, Pb. The following compounds were synthesized: Sn1Ba1Sr1Cu3Ox, Sn1Ba1Ca1Cu3Ox, Sn1Ba1Mg1Cu3Ox, Sn1Sr1Ca1Cu3Ox, Sn1Sr1Mg1Cu3Ox, Sn1Ca1Mg1Cu3Ox. The initial components were oxides and carbonates of the appropriate elements. Standard firing-grinding procedure was used. Final heating was carried out at 960 C during 12 hours. Then the samples were cooled inside the furnace. All the synthesis cycles were carried out in air atmosphere. Among the synthesized compounds only Sn1Ba1Sr1Cu3Ox showed remarkable conductivity. Other compounds were practically dielectrics. Presence of a possible superconductivity in Sn1Ba1Sr1Cu3Ox was defined by using the Meissner effect. At low temperature a deviation from paramagnetic behavior is observed. The hysteresis loops obtained at lower temperatures undoubtly testify to the presence of a superconductive phase in the sample. However, the part of the superconductive phase in the Sn1Ba1Sr1Cu3Ox ceramic turned out to be small, less than 2 percent, which agrees with the estimation from magnetic data. In order to increase the content of the superconductive phase two-valent cations Ba, Sr were partially substituted by univalent (K) and three-valent ones (Y)

A green chemical method for synthesis of bromine-containing “building blocks” for the production of photovoltaic polymers

Bromine-containing derivatives of aromatic and heteroaromatic compounds are the most important "building blocks" in the assembly of modern Photovoltaic Polymers (PV). While PV is being developed to produce "green" energy, converting sunlight to electricity, the reactions for producing brominated derivatives of building blocks described in the literature are examples of obsolete and environmentally dirty technologies. More environmentally harmful than bromination with molecular bromine [1] can only be bromination by molecular bromine in a concentrated hydrobromic acid medium [2]. Using 1,1'-diphenyl (1), 9H-diphenylcarbazole (2) and thiophene (3) as examples, we successfully tested the bromination of the above objects with a mixture of potassium bromide and bromate in acetic acid as outlined in the diagram

A survey of helminths of polar bears in the Russian Arctic

The polar bear Ursus maritimus is a circumpolar species classified as vulnerable and included in the IUCN Red List. It is considered to be practically free of helminth parasites with the only species reported being Trichinella spiralis s. l. Samples of feces were collected on Chukotka coast, Wrangel Island and on ice floes in the Kara, Laptev and Chukchi seas in 2013-2015 in different seasons of the year. Coprological diagnostics was carried out using the standard flotation and sedimentation methods. In the samples collected in the snow-free period, a single sample (3.7%) was found to contain eggs of the nematode Toxascaris sp. In three out of 9 samples collected in the winter, eggs of a cestode Diphyllobothrium sp., of unidentified trematodes (presumably Heterophyidae) and of the strongylid nematode Uncinaria stenocephala were found as well as the first stage nematode larvae tentatively identified as Crenosoma sp. Viable Trichinella nativa larvae were recovered from the muscles of a female animal from north of Yakutia

Spin Content of the Quantum Soliton

The classical soliton solution, quantized by means of suitable translational and rotational collective coordinates, is embedded into the one-particle irreductible representation of the Poincare group corresponding to a definite spin. It is shown, that within the conventional quasiclassical expansion such embedding leads to a set of nontrivial consistency conditions imposed on the classical solution. The validity of these relations is considered for a number of soliton models in 2+1- and 3+1-dimensions.Comment: 10 pages, Standard LaTe