Ultra'soft X-ray diagnostics of short-living plasmas

Ultrasoft X-ray plasma diagnostics in IPP is realized by using X-ray diodes with Al photocathodes and submicrometer nitrocellulose filters. The X-ray detections system is suitable for measurements in a relatively broad range of radiation intensities in the spectral interval of (10–1000) eV with the time resolution of (1–10) ns under various plasma conditions. Construction, calibration and characteristic properties of the measuring apparatus are described. To illustrate its use, some results of the diagnostics of REB-heated plasma are presented.We would like to acknowledge Dr. P. unka for many helpful discussions and Dr. J. Ullschmied for cooperation in REB-heated plasma diagnostics interpretation.     

Influence of crystal-field on the thermal conductivity of PrNi5

The thermal conductivity of PrNi₅ in the temperature range 0·5 to 20 K is investigated. The analysis of crystalline electric field effect on the experimentally obtained temperature dependence of the thermal conductivity indicates that beside the main electronic component also other contributions (phonons, magnetic excitons) can take place in the heat transport in this intermetallic compound.The authors would like to thank Dr. G. Eska for lending the sample and Dr. . Jáno for his interest in the work and stimulating discussions.     

Effects of small external magnetic fields on the hyperfine field of iron in iron metal above the curie temperature: A new method for studying critical phenomena

By applying magnetic fields up to 2 kG, the equation of state and the critical dynamics of a spin system near its critical point can be studied with the Mössbauer effect. As an example, the equation of state near the Curie temperature of iron is investigated yielding the critical exponent =4.84±0.15.     

2-Amino-4,4-disubstituted-5-carboxymethyl-Δ2-1,3,4-oxadiazolin-4-ium chlorides and their recyclization in acetic anhydride

2-Methylamino-4,4-disubstituted-5-carboethoxymethyl-²-1,3,4-oxadiazolin -4-ium chlorides were obtained from the reaction of 1,1-disubstituted-4-methylsemicarbazides with ethyl propiolate in the presence of hydrochloric acid. After hydrolysis of the ester these chlorides recyclize in acetic anhydride to 1-substituted-3-acetoxy-1H-pyrazoles. The difference in the direction of ring opening with acetic anhydride in the betaines of 1,3,4-oxadiazolin-5-acetic acids and their thia-analogs has been demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1685–1688, 1992.     

Pseudo-cross-conjugated mesomeric betaines. 1. Synthesis of pseudo-cross-conjugated mesomeric betaines from quinoxaline derivatives

A new method for the synthesis of pseudo-cross-conjugated mesomeric betainic heterocyclic compounds with an angular nitrogen atom has been developed consisting in the reaction of 1,4-dielectrophile — -carbethoxy-2-(3-chloro)quinoxalylacetonitrile with azoles. Experimental regularities have been studied and a reaction mechanism has been proposed including the stage of formation of an ylide from a quaternary azolium salt. A pseudo-crossconjugated mesomeric betainic heterocyclic compound containing a thiazole ring compound has been synthesized for the first time.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1528–1533, November, 1992.     

Synthesis and investigation of the mesomorphic properties of pyran derivatives

4-[(5,6-Dihydro-2H-pyran-4-yl)methoxy]benzylidene-4-alkoxyanilines, which have the properties of smectic liquid crystals, were synthesized. The effect of the pyran ring in the benzylidene component and the length of the aliphatic radical in the aniline component on the type and thermal stability of the meso phase was ascertained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 327–328, March, 1992.     

Humulenoids from plants of the family Apiaceae spatial structure of α-apienes

A conformational analysis has been made by the method of molecular mechanics of the -apienes — natural sesquiterpenes isolated from plants of the Apiaceae family. The results of the mathematical method with the inclusion of those x-ray structural studies have shown that in the molecules under consideration it is possible to expect the predominant realization of four conformations of the 11-membered ring:₁₄A ₈ ⁷ ,¹⁴A ₇ ⁸ ,₁₄A ₇ ⁸ , and¹⁴A ₈ ⁷ . These four conformations of unsubstituted -apiene and its natural derivatives have been characterized energetically, and the barriers to their interconversions have been evaluated.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 197–202, March–April, 1992.     

Synthesis of 24-epiteasterone

Starting from ergosterol, the synthesis of the brassinosteroid 24-epiteasterone has been achieved by the use of a new scheme for introducing a 3-hydroxy-6-keto group as the result of the Birch reduction of the corresponding 5-hydroxy-⁷-3,6-dione.Institute of Bioorganic Chemistry, Belorussian Academy of Sciences, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 224–227, March–April, 1992.     

Harary-Read numbers for catafusenes: Complete classification according to symmetry

The classical Harary-Read numbers for catafusenes (catacondensed simply connected polyhexes) are reproduced without using generating functions. A complete (mathematical) solution is given for the distribution of these numbers over the different symmetry groups to which the catafusenes belong.