Bimodal fission in binary and ternary spontaneous fission of 252Cf

The hot bimodal fission of ²⁵²Cf is reexamined with new high-statistics data. We constructed a γ-γ-γ coincidence cube for binary fission and LCP-gated γ-γ matrix for ternary fission. By identifying the secondary fission fragments from their γ-ray transitions, we measured the yields for various fission splits. The normal neutron yield distribution is found to be Gaussian for Xe-Ru. However, the binary fission split of Ba-Mo is found to exhibit a bimodal neutron distribution with the “hot mode” corresponding to ≈3.1% of the total yield. In α ternary fission, the first measurements of yields for specific fission splits are presented. The Te-α-Ru and Xe-α-Mo neutron yields fit well with a single mode, but the Ba-α-Zr split shows evidence for an enhanced hot mode with an intensity of ≈13.8% of the normal mode. The text was submitted by the authors in English.     

Rectangular oscillation of the sequence of partial sums of a multiple Fourier series and absence of the BMO property

Translated from Matematicheskie Zametki, Vol. 52, No. 2, pp. 152–154, August, 1992.     

New data on the ternary fission of 252Cf from the Gammasphere facility

Ternary fission of ²⁵²Cf was studied at Gammasphere using eight ΔE×E particle telescopes. Helium, beryllium, boron, and carbon light charged particles (LCPs) emitted with kinetic energy more than 9, 21, 26, and 32 MeV, respectively, were identified. The 3368-keV γ transition from the first 2⁺ excited state in ¹⁰Be was found and the population probability ratio N(2⁺)/N(0⁺) = 0.160 ± 0.025 was estimated. No evidence was found for 3368-keV γ rays emitted from a triple molecular state. For the first time, charge distributions are obtained for ternary fission fragments emitted with helium, beryllium, and carbon LCPs.     

Mass-spectrometric characteristics of glycidyl and thioglycidyl ethers

The principles of the fragmentation of the simplest glycidyl and thioglycidyl ethers under the influence of electron impact, which were discovered by comparison of the spectra of homologs using data from photoelectronic spectroscopy and optical mass spectrometry, are examined as a manifestation of the general characteristics of the fragmentation of bifunctional compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 739–745, June, 1988.     

Hydrogenation of benzene on sulfide catalysts in the presence of thiophene

The principles of benzene hydrogenation have been studied with sulfide catalysts NI/MS₂, Ni/SiO₂, M/SiO₂ and (Ni, M)/SiO₂ (M=Mo, W) obtained via metal complex precursors or by impregnation. In bimetallic catalysts active sites of benzene hydrogenation are formed upon reduction of the active component for thiophene hydrogenolysis.

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Ni/MS₂, Ni/SiO₂, M/SiO₂, (Ni,M)/SiO₂, M=Mo W, , . , .

     

Synergetic effect in thiophene hydrogenolysis on sulfied (Ni?Nb)/SiO2 catalysts

Nonadditive increase in the activity of sulfided (Ni–Nb)/SiO₂ catalysts, compared to Nb/SiO₂ and Ni/SiO₂, has been found, with the maximum synergetic effect observed at the atomic ratio =Ni/Ni+Nb=0.2.

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(Ni–Nb)/SiO₂ Nb/SiO₂ Ni/SiO₂, =Ni/(Ni+Nb)=0,2.

     

(Z)-3-p-tolylsulfinylacrylonitrile as a chiral dienophile: diels-alder reactions with furan and acyclic dienes

The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles.     

Totik's conjecture for Chrestenson and Walsh systems

Пустьf— интегрируем ая на группе \(G = \mathop \prod \limits_{k = 0}^\infty Z(p_k )\) функция и lim supp _k <∞. Дана характериза ция точекμ-сильной сумми руемости ряда Фурье ф ункцииf по системе Прайса. Это позволило установит ь слабый тип (1,1) мажоран тных операторов, связанны х с ВМО-сильнымн средними рядов по сис темам Крестенсонаp _k ≡p и Уолшаp _k ≡2. Как следствие, для частных сумм рядов по этим системам получе но: еслиf∈L ^{[0, 1]}, то для любой конс тантыA>0 справедливо $$\mathop {\lim }\limits_{n \to \infty } \frac{1}{n}\mathop \sum \limits_{k = 0}^{n - 1} \exp A|s_k (f,x) - f(x)| = 1$$ для почти всехx∈[0,1]. Тем самым установлена справедливость гипо тезы В. Тотика для этих систем.