The effect of technological microdefects of structure on service life of polymer materials

Within the framework of the kinetic theory of strength, relations for estimation of durability of thermoplastic materials under stationary and non-stationary thermomechanical impacts are obtained It is shown that durability decreases linearly with increase in the natural (Napierian) logarithm of the mean size of microcracks formed during manufacturing of polymer products. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 3–6, July, 2007.     

The influence of the entrance channel on the formation and decay of the compound nucleus <Superscript>250</Superscript>No

The mass-energy and angular distributions of binary fissionlike fragments produced in the reactions ⁴⁴Ca + ²⁰⁶Pb and ⁶⁴Ni + ¹⁸⁶W, leading to the same compound nucleus ²⁵⁰No, have been measured at excitation energies of 30 and 40 MeV. The presence of the quasifission component was observed for both systems. But in the case of the ⁶⁴Ni ion, the quasifission process dominates, while in the case of the ⁴⁴Ca ion, the main process is the fusion-fission of compound nucleus ²⁵⁰No. From the angular distributions of reaction fragments, the time scales were found for quasifission and fusion-fission for both reactions.     

Groups with handles of order different from three

We obtain a test for the unsimplicity of an infinite group.Translated from Ukrainskyi Matematychnyi Zhurnal, Vol. 56, No. 8, pp. 1030–1042, August, 2004.     

Influence of Cyclodextrins on the Kinetics of Oxidation of Amino Acids and BSA by Hydrazyl Radicals

The kinetics of oxidation of amino acids (Arg, His, Lys, Phe, Thr and Tyr), a dipeptide (Gly-His), and BSA (bovine serum albumin) by two persistent water soluble free radicals of the hydrazyl type has been studied.The rate decreases in the order Arg>Lys>Tyr>Thr>HisBSAPheGly-His with bothfree radicals. Addition to the reaction mixture of - and -cyclodextrin decreases the oxidation rate, probably due to amino acidencapsulation in the cyclodextrin cavity. -Cyclodextrin protects more efficiently against oxidation than -cyclodextrin.     

The microscopic investigation of structures of moving flux lines by neutron and muon techniques

We have used a variety of microscopic techniques to reveal the structure and motion of flux line arrangements, when the flux lines in low T _c type II superconductors are caused to move by a transport current. Using small-angle neutron scattering by the flux line lattice (FLL), we are able to demonstrate directly the alignment by motion of the nearest-neighbor FLL direction. This tends to be parallel to the direction of flux line motion, as had been suspected from two-dimensional simulations. We also see the destruction of the ordered FLL by plastic flow and the bending of flux lines. Another technique that our collaboration has employed is the direct measurement of flux line motion, using the ultra-high-resolution spectroscopy of the neutron spin-echo technique to observe the energy change of neutrons diffracted by moving flux lines. The muon spin rotation (μSR) technique gives the distribution of values of magnetic field within the FLL. We have recently succeeded in performing μSR measurements while the FLL is moving. Such measurements give complementary information about the local speed and orientation of the FLL motion. We conclude by discussing the possible application of this technique to thin film superconductors.     

Statistical characteristics of two-phase gas-liquid flow in a vertical microchannel

This paper presents an experimental study of the structure of an upward gas-liquid flow in a vertical microchannel with a cross-sectional dimension of 0.67 × 2.00 mm and a length of 0.5 m. The tests were performed in the ranges of reduced rates of nitrogen 0.04–11.00 m/sec and water 0.07–0.41 m/sec. Using the method of two-beam laser scanning, we identified the main flow regimes (slug-bubble, slug, transient, emulsion, and annular) and determined the statistical characteristics of the two-phase flow. A map of flow regimes was constructed, the dependence of slug velocity on the reduced mixture velocity was obtained, and the friction factor for an upward gas-liquid flow in a microchannel was measured.     

Probing fission time scales with neutrons and GDR gamma rays

The time scales for nuclear fission have been explored using both pre-and postfission neutrons and GDR gamma rays. Four systems were investigated: 133-MeV ¹⁶O + ¹⁷⁶Yb and ²⁰⁸Pb and 104-MeV ⁴He + ¹⁸⁸Os and ²⁰⁹Bi. Fission fragments were measured in coincidence with PPACs. The neutrons were detected using eight detectors from the DEMON array, while gamma rays were measured using the US BaF2 array. The pre-and postfission gamma rays were determined using moving source fits parallel and perpendicular to the fission fragment emission directions. The time scales for fission for the neutrons were determined using the neutron clock technique. The gamma-ray data were fitted using a statistical model calculation based on the code CASCADE. The results of the fits from both data types were used to extract nuclear friction coefficients, γ, and fission time scales. The γ values ranged from 7 to 20, while the fission times were (31–105)×10^?21 s.