$$\mathcal {F}_\pi $$Fπ-residuality of generalized Baumslag–Solitar groups

Archiv der Mathematik - A generalized Baumslag–Solitar group is a finitely generated group that acts on a tree with infinite cyclic edge and vertex stabilizers. A group G is residually a...     

Search for the emission of π<Superscript>0</Superscript> mesons from the neutron-induced fission of <Superscript>235</Superscript>U nuclei

A nuclear-reactor experiment on the search for the emission of neutral pions from the neutron-induced fission of ²³⁵U nuclei has been carried out. To this end, an experimental setup for searching for the emission of π⁰ mesons with high sensitivity to this process has been designed and produced. This setup consisted of two Cherenkov total-absorption spectrometers for the detection and measurements of the energy of two gamma-ray photons from π ⁰-meson decay. The spectrometers were placed at the exits of two coaxial horizontal experimental channels. To protect the detectors from low-energy β and γ rays and neutron fluxes, 3.5-m-long water filters were situated in the channels. To reject the cosmic background, large-area scintillation counters operating in the anticoincidence mode were placed over each spectrometer. The energy and time resolution of the spectrometers, as well as the efficiency of detecting charged particles by scintillation counters, were tested on the secondary electron beam of the Tomsk electron synchrotron Sirius. Runs of measurements of the effect on the operating reactor (duration of 805 h) were alternated with runs of measurements of background on the stopped reactor (duration of 403 h). Statistical processing of the experimental results yields an upper limit of ≤5.3×10 ^?12 with a 90% confidence level for the probability of the emission of neutral pions from the neutron-induced fission of ²³⁵U nuclei. This result and results of other works carried out with sources of spontaneously fissioning ²⁵²Cf nuclei show that the probabilities of the emission of π⁰ mesons from spontaneous fission and fission induced by fission-spectrum neutrons are equal to each other.     

Toward fully synthetic carbohydrate-based HIV antigen design: on the critical role of bivalency

Synthetic gp120331-335 glycopeptide fragments carrying hybrid and high-mannose type N-linked glycans were evaluated for binding to broadly neutralizing antibody 2G12 using surface plasmon resonance technology. None of the hybrid-type constructs demonstrated binding to 2G12. In the high-mannose series, the "Cys dimer" construct, presenting two undecasaccharide glycans, showed significantly higher binding than the Cys-protected monomer. The binding of the dimeric structure was further investigated in competition with recombinant gp120. The data suggest that gp120 and its designed synthetic epitope construct bind to the same site on 2G12.     

The torsion of a submanifold of a Riemannian manifold

For a submanifoldM ⁿ of a Riemannian manifoldM ^q, the concept of a torsion bivector at the point x M ⁿ for given one- and two-dimensional directions fromT _x M ⁿ is introduced using only the first and second fundamental forms ofM ⁿ. Its relation to the concept of Gaussian torsion is then established. It is proved that: 1) equality to zero of the torsion bivector is necessary and, whenM ⁿ is a nondevelopable surface of a space of constant curvature with nonzero second fundamental form, is also sufficient for the "flattening" ofM ⁿ into some totally geodesicM ⁿ⁺¹ inM ^q; 2) when n = 2, the independence of the nonzero torsion bivector of direction characterizes a minimalM ² inM ^q.Translated from Ukrainskii Geometricheskii Sbornik, No. 34, pp. 39–42, 1991.     

Secondary radiations in spacecraft shieldings

Some problems are discussed which relate to the generation of secondary radiation under the effects of heavy charged cosmic ray particles in spacecraft shielding and in biological tissue. Methods for obtaining the total and differential inelastic interaction cross sections are recommended for use in the calculation of heavy charged particle transport in the shielding. The most extensively used methods for calculating heavy charged particle passage through matter are appraised. The results of calculating cosmic ray doses in biological tissue behind shielding, which allow for the secondary particle contribution, are presented. All the calculations have been made using the set of radiation protection standards approved by the Russian State Committee for Standards. The set of standards has been verified experimentally on board satellites of the Cosmos series.     

The protopectin of the leaves and petioles of Sosnovskii's cowparsnip and heartleaf colewort

Summary 1. The protopectins of the petioles and leaves of Sosnovskii's cowparsnip and heartleaf colewort have been studied. It has been shown that the protopectins of wild-growing herbs are similar to the pectins of fruit and vegetables.2. The heterogeneity of the pectins isolated has been shown by the fractionation method. Two main fractions were obtained — neutral (weakly acidic) and acidic.M. V. Lomonosov Odessa Technological Institute of the Food Industry. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 760–763, November–December, 1977.     

Structure of a glucuronoxylan of the stems ofSymphytum asperum

The results are given of an investigation of the structure of a glucuronoxylan of the stems ofSymphytum asperum Ler. The xylan was isolated by alkaline extraction and was purified by reprecipitation via the copper complex. The polysaccharide was homogeneous according to the results of gel filtration and electrophoresis. It was shown by hydrolysis, periodate oxidation, methylation, oxidation with chromium trioxide and IR and¹³C NMR spectroscopy that the macromolecules were based on a β-(1→4)-polyxyloside chain having side chains at the second carbon atoms in the form of 4-O-Me-D-glucuronic acid. To each side chain there were not less than 12 xylose residues.     

Oxidative Ammonolysis of Vegetable Raw Materials

The influence of the composition of lignocarbohydrate vegetable raw materials, process duration (15-120 min), amount of hydrogen peroxide (0.1-0.9 g per gram of raw materials), and amount of ammonia (0.25-1.5 g per gram of raw materials) on the yield of the target product and on the nitrogen content and the content of functional groups in it in mechanochemical treatment of vegetable wastes with hydrogen peroxide in aqueous ammonia (oxidative ammonolysis) was studied. Sorption and agrochemical testing of the resulting samples as nitrogen-containing ion exchangers and fertilizers was performed.     

Dependence of the intensities of ultrasonic sidebands in the Mössbauer spectrum on the statistics of the acoustic field

The acoustic modulation of quanta is analyzed with regard for dissipation of the energy of the excited mode through resonance (having the acoustic frequency) modes. Given definite assumptions, the Rayleigh-Rice distribution function previously introduced phenomenologically is obtained for the oscillation amplitudes. It is proposed that the intensities of the ultrasonic sidebands be expressed in terms of the parameters m and , which are valid for any degree of sound coherence. The results of numerical computations are given.Translated from Izvestiya Vysshikh Uchebrnykh Zavedenii, Fizika, No. 7, pp. 54–57, July, 1979.In conclusion, the authors express their gratitude to Prof. Sh. Sh. Bashkirov for valuable comments.