Transition from spin glass to paramagnetism in the magnetic properties of PrAu2Si2

It is unexpected that a spin-glass transition, which generally occurs only in system with some form of disorder, was observed in the ThCr2Si2-type compound PrAu2Si2 at a temperature of 3 K. This puzzling phenomenon was later explained based on a novel dynamic frustration model that does not involve static disorder. We present the results of re-verification of the reported spin-glass behaviors by measuring the physical properties of three polycrystalline PrAu2Si2 samples annealed under different conditions. Indeed, in the sample annealed at 827 ◦C for one week, a spin-glass transition does occur at a temperature of T f~2.8 K as that reported previously in the literature. However, it is newly found that the spin-glass effect is actually more pronounced in the as-cast sample, and almost completely disappears in the well-annealed (at 850 ◦C for 4 weeks) sample. The annealing effect observed in PrAu2Si2, that is, spin glass to paramagnetism transition is discussed by comparing with earlier results reported on the same system and other isomorphic compounds.

Влияние углеродных нанотрубок на термоэлектрические свойства сплавов Гейслера p- и n-типа

This paper presents the results of studying the effect of carbon nanotubes on thermoelectric properties of p-type (Nb0.6Ta0.4)0.8Ti0.2FeSb and n-type Ti0.5Zr0.25Hf0.25NiSn half Heusler alloys. The experimental data obtained indicate a strong effect of the carbon nanotubes on electrical conductivity and Seebeck coefficient of the n-type compound, while the changes in these properties in the p-type compound were significantly less. It is suggested that a possible reason for this difference is the formation of a conducting cluster of carbon nanotubes in the sample of the n-type Heusler alloy.

Scholl Reaction of an ortho-Phenylene-bridged Cyclic Pyrrole-Thiophene Hybrid Hexamer

Scholl reaction of ortho-phenylene-bridged cyclic pyrrole-thiophene hybrid hexamer exclusively gave a cyclophane-type compound of [5]heterohelicenes in 45% yield. The structure was unambiguously revealed by X-ray diffraction analysis. This helicenophane-type compound showed sharp absorption and fluorescence spectra, reflecting its rigid structure. The reaction path was analyzed on the basis of DFT calculations. The reaction path was analyzed on the basis of DFT calculations, and it was found that the formation of 8 is thermodynamically favored and further oxidation is prohibited due to the increased strain energy.

THE ACTION OF SOME CYTOKININ-TYPE COMPOUNDS ON THE ANTIOXIDANT PROTECTION CAPACITY OF PLANTS IN CONDITIONS OF UNFAVORABLE VARIATION OF HUMIDITY AND REPEATED WATER STRESS

The effect of cytokinin-type compound on the capacity of the enzymatic and non-enzymatic system of antioxidant protection by plants in conditions of humidity fluctuation and repeated drought were studied. As subjects served the plants Glycine max (Merr) L.cultivar Nadejda, grown in the Mitcherlih vegetation pots with volume of 40 kg soil and exposed to the drought stress at the phases first trifoliate leaf and flowering – pods formation. The antioxidant protection capacity of soybeans pre-treated with cytokinin, thiourea and with the composition Polyel + phytohormones (AIA, Gb, CK)is ensured both by the intensification of the activity of antioxidant enzymes and by the increase of content of non-enzymatic substances with low molecular weight.After restoring the optimal moisture content, the plants pre-treated with thiourea and Polyel + F more fully restore their functional processes.

A New Compound Pt3Bi2S2 with Superior Performance for Hydrogen Evolution Reaction

The exploration of efficient electrocatalysts for hydrogen evolution reaction (HER) is beneficial to obtain renewable clean energy. Herein, a new parkerite-type compound Pt3Bi2S2 was synthesized, which is constructed by [PtBi4S2]...