Measurement of the photoneutron flux density distribution from cylindrical targets

Measurements are performed of the density of photoneutron fluxes from cylindrical targets of²H₂O (diameter 64 and height 86 mm), Be (outer diameter 70, inner diameter 40, height 100mm), and²³⁸U (diameter 44.5 mm, height 50 mm) under the action of braking radiation from electrons with energies of 4 to 8 MeV in order to determine the effect of target form and orientation relative to the detector upon the recorded photoneutron level. The fluxes were measured by an all-wave neutron detector based on an SNM-11 counter in a paraffin retarder at an angle of 90 to the axis of the braking radiation beam for various target orientations relative to the detector. Measurement results are compared to calculations. Photoneutron fluxes from heavy water and beryllium targets of the indicated dimensions were also measured for angles of 90, 135, and 167. An isotropic nature was noted in the photoneutron fluxes from both targets.Deceased.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 5–9, September, 1989.In conclusion, the authors express their gratitude to V. I. Lunev and B. M. Yakovlev for their assistance in performing the measurements.     

Geminal conjugation in disulfides

Some aspects of the spatial and electronic structure of disulfides XSSX (X = H, Alk, Ph, Hal) are considered. It is shown that the growth of the geminal n_s-σ_SX* conjugation efficiency leads to a shortening of the SS bond that is more than three times as large as the simultaneous SX bond lengthening. The positive effective charge on the sulfur atom also increases as a result of this conjugation. These effects increase with the growth of - I and + M abilities of the substituents X. The SK_a line shifts and the HOMO bonding degree (Delta;n_S) have been measured by the X-ray fluorescence spectroscopy method for dialkyl disulfides (Alk = Me, Et, Pr, i-Pr, Bu, i-Bu, t-Bu, C₅H₁₁, C₈H₁₇, H₂NCH₂CH₂, CH₂CH  CH₂, CH₂Ph) and S₈. With the help of Δn_S values that are proportional to the n_S–σ_SC* conjugation efficiency, the sequence of the enhancement of the geminal conjugation efficiency has been established for the disulfides investigated. In the framework of the n_S–σ_SS* geminal conjugations, the shortening of the SS bonds in S₈ is explained. © John Wiley & Sons, Inc.     

1H and 13C NMR Study of the Structure of Alkylthio Enyne Alcohols and Glycols

Steric structure of some alkylthio enyne alcohols and glycols was determined by ¹H and ¹³C NMR spectroscopy. Analysis of cross peaks in the 2M NOESY spectra showed that the double bond in these compounds has Z configuration. Criteria were found which indicate the position of the hydroxy-containing substituent with respect to the triple or double bond.