The strange-sea quark spin distribution in the nucleon from inclusive and semi-inclusive deep-inelastic scattering

We propose new method which allows determination of the strange-sea quark spin distribution in the nucleon through measurement of various inclusive and semi-inclusive polarized deep inelastic electron–proton or muon–proton reactions. It is shown, that using combinations of inclusive data and semi-inclusive data containing neutral pions in the final state, it is possible to extract the strange-sea quark spin distribution. Similar result can be obtained for charged pions and some other hadrons also.     

Synthesis of derivatives of 4,5-dihydrofuran,furan, and hexahydrobenzofuran from conjugated alkenynes

The regiochemistry of the reaction of 1,2- and 1-substituted derivatives of 1-buten-3-yne and its 4- and 2,4-substituted derivatives of the isoprenoid type with acetoacetic ester and acetylacetone in the presence of the manganese(III) acetate-copper(II) acetate oxidative system was studied. Derivatives of 4,5-dihydrofuran, furan, and hexahydrobenzofuran were obtained.Communication 137 from the series Reactions of unsaturated compounds. See [1] for communication 136.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 24, No. 3, pp. 317–323, March, 1988.     

Kinetics of propylene oxidation in the region of negative temperature coefficients of the rate

Kinetic regularities in the consumption of initial reactants and the accumulation of propylene oxidation products has been studied in the region of negative temperature coefficients of the maximum reaction rate (T=648–723 K). It has been revealed that for prolynene-enriched mixtures (C₃H₆:O₂=3:1) at P-20.66 kPa, the reaction rate is practically independent of the temperature, whereas for poor mixtures (C₃H₆:O₂=1:5) it decreases with increasing temperature.

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a (T=648–723K). , (C₃H₆:O₂=3:1) P=20,66 , (C₃H₆:O₂=1:5) .

     

Synthesis of Allyl 2-Dialkylamino-4-pentenoates and Their Analogs via Stevens Rearrangement

Stevens rearrangement of ammonium salts containing an allyloxycarbonylmethyl group in benzene in the presence of sodium phenoxide yields allyl 2-dialkylamino-4-pentenoates. The rearrangement in the presence of sodium methoxide is accompanied by transesterification to afford methyl 2-dialkylamino-4-pentenoates.     

On Coverings of Tori with Cubes

Doklady Mathematics - We obtain new bounds and exact values of the minimum number of cubes with side length $$\varepsilon \in (0,\;1)$$ covering the torus...     

Spiky structure of coherent emission from optically thick media

The spiky structure of the spontaneous emission from praseodymium ions in the LaF₃ lattice on the ³P₀-³H₆ transition under coherent pulsed excitation of the adjacent ³H₄-³P₀ transition has been studied experimentally and theoretically. The experimental results are in good agreement with the theoretical conclusions based on analysis of the emission dynamics of an excited ensemble of three-level systems in the mean field approximation. The generation of a spiky structure is interpreted as the emission of a cnoidal wave pulse. The recorded random pattern of time intervals between the spikes reflects the sensitivity of the cnoidal wave period to fluctuations in the system. The developed theory has been found to be related to models of deterministic chaotic dynamics.     

Photoelectric properties of nInSb-nPbTe-nCdTe isotype structure prepared by vacuum pulsed-laser deposition technique

With use of the vacuum pulsed-laser deposition technique an isotype nInSb-nPbTe-nCdTe structure is fabricated. Spectral dependence of photoresponse of the obtained structure is studied at the temperature 120 K. In the curve of spectral dependence a change in the sign of photoresponse is observed for both zero bias and external voltage. Qualitative explanation of this phenomenon is given.     

The characteristics of neutrino-nuclear reactions at <Emphasis Type="Italic">E</Emphasis><Subscript><Emphasis Type="Italic">ν</Emphasis></Subscript> = 1–3 GeV

The characteristics of the charged-current neutrino—nuclear interactions are investigated for the first time at E _ν = 1–3 GeV using the data obtained with SKAT propane-freon bubble chamber irradiated in the neutrino beam at the Serpukhov accelerator. The E _ν dependence of the mean multiplicities of different types of secondary particles and their multiplicity, momentum, and angular distributions are measured. The text was submitted by the authors in English.     

Optical transmission spectra of a silicate glass containing nanocrystallites of cadmium sulphoselenide

The optical transmission spectra of CdSe _x S_1-x doped low viscosity silicate glass are experimentally studied. Glass samples were subjected to one- or multi-step heat treatment for different lengths of time. We have followed the modification of the absorption spectra after each heat treatment. The red shift of the absorption edge and the accompanying change of coloration from orange to red are explained by size-quantization effects in the energy spectrum of electrons and holes in semiconductor nanoparticles thermally developed in low viscosity glass matrix. X-ray diffraction data show no stoichiometry changes during the heat treatment processes. Crystallites composition ( ) defined from the diffraction peaks was very close to the value estimated from the position of absorption edge.Received: 14 March 2003, Published online: 9 September 2003PACS: 79.60.Jv Interfaces; heterostructures; nanostructures - 78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity) - 78.40.Fy Semiconductors