Calculated structures of asymmetric modifications of cyanospinels

Structural mechanisms of formation of low-symmetry phases of cyanospinels are described in terms of the phenomenological theory of phase transitions. These are examined for transitions from a spinel structure to two cubic and four rhombohedral phases, induced by automorphic irreducible representations 9-2 and 9-3. Atomic coordinates and the symmetry types of occupied positions in asymmetric phases are determined. Criteria for discrimination between the two as well as between the four phases are formulated. The structures of complex cyanides Tl₂Zn(CN)₄ , K₂Zn(CN)₄, K₂Hg(CN)₄, and Rb₂Hg(CN)₄ are calculated. The displacements and irreducible representations inducing transitions from spinel structures to these phases are determined. Novocherkassk State Technological University. Translated fromZhumal Struktumoi Khimii, Vol. 35, No. 5, pp. 41–49, September–October, 1994. Translated by L. Smolina     

Photothermochemical process in ammonium perchlorate crystals: II

The influence of phase transition (PT) on the process of thermal development of a latent image arising after X-ray and uv irradiation of ammonium perchlorate (AP) crystals has been studied. Despite the production of a large number of new dislocations accompanying PT, it essentially does not influence the thermal development: The developed image does not smear at PT, remaining as clear as before it. By comparing mirror-symmetric surfaces of cleavage planes of AP crystals, it has been shown that at doses of X-ray and uv irradiation sufficient for obtaining an image, no production of new dislocations was observed in AP crystals. It is suggested that latent image arises due to formation during irradiation of chlorine oxidic products of radiolysis: ClO₃, ClO₂, and ClO as well as the corresponding ions ClO^?, ClO^?₂, and ClO^?₃, i.e., initiators of AP low-temperature decomposition.     

Heteroligand Lanthanide Dialkyldithiocarbamate Complexes with 1,10-Phenanthroline: A New Approach to Synthesis and Application for the Preparation of Sulfides

A new simple method of synthesis of heteroligand complexes [Ln(Dalkdtc)₃Phen] (Ln = Eu or Er; Dalkdtc is the dialkyldithiocarbamate ion, Phen is o-phenanthroline) in an aqueous solution is described; the possibility of using the complexes as initial reagents for the synthesis of rare-earth sulfides is shown.     

Novel polycyclic pyrimidines

Methods are reported for preparing the novel pyrimidines 7,8-dihydro-9H-1,2,5-chalcodiazolo[3,4-d]thiazole[2,3-b]pyrimidin-4-ones and their N-oxides.A. V. Bogatskii Physicochemical Institute, National Academy of Sciences of Ukraine, Odessa, 270080. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1130–1132, August, 1998.     

Inhibition and labeling of enzymes and abzymes by phosphonate diesters

Reactive phosphonate diesters were designed and prepared as inhibitors of serine proteases and esterases. Inactivation of trypsin, chymotrypsin, and butyrylcholinesterase was determined by residual enzymaticactivity as well as by the release of a chromogenic or fluorogenic product of the inhibition reaction. Second-order rate constants were determined from rates of nitrophenol formation. Application of the reaction for active-site titration of enzyme preparations is demonstrated. A basic functional group present in the nitrophenyl tropane phosphonate diester was shown to confer selectivity for inactivation of try psin and chymotrypsin. Biotinylated derivatives of the phosphonate diesters were prepared to permitanalysis of proteins modified in the inhibition reaction. Labeled polypeptides were resolved by SDSPAGE, electroblotted, and detected by streptavidin-peroxidase staining. A detection limit of less than 4 ng, corresponding to 20 nM of trypsin, was demonstrated. Pretretment of enzymes with DFP or nonbiotinylated phosphonates specifically blocks the labeling. This technique permits identification of serine proteases in complex mixtures with good sensitivity and specificity.     

Homotopy of spaces of diffeomorphisms of some three-dimensional manifolds

The goal of the paper is to calculate the homotopy type of the space of diffeomorphisms for most orientable three-dimensional manifolds with finite fundamental group containing the Klein bottle. The fundamental group of such a manifold Q has the form <a, b ¦abab ^–1=1,a ^mb²ⁿ=1>. As m and n one can have any relatively prime natural numbers; these numbers m, n determine the manifold Q up to diffeomorphism. Let K be a Klein bottle lying in Q and let P be a closed tubular neighborhood in Q of this Klein bottle K. We denote by Diff_o(Q) the connected component of the space of diffeomorphisms QQ containing id Q, and by E₀(K, Q) the connected component of the space of imbeddings KQ containing the inclusion KQ; analogously we define E₀(K, P). The main results of the paper are the following two theorems. THEOREM 1. If m, n1, then the space Diff_o(Q) is homotopy equivalent with a circle. THEOREM 2. If m, n1, then the inclusion E₀(K, P) E₀(K, Q) is a homotopy equivalence. With the help of familiar results on spaces of diffeomorphisms of irreducible manifolds which are sufficiently large, Theorem 1 reduces without difficulty to Theorem 2. The main difficulty is the proof of Theorem 2. This proof develops a technique of Hatcher and the author which deals with spaces of PL-homeomorphisms and diffeomorphisms of irreducible manifolds which are sufficiently large. In the paper we use a different structure definition of the class of manifolds considered. It is easy to verify that these definitions are equivalent.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 122, pp. 72–103, 1982.