Excellent enantio-selective enclathration of (2R,3S)-3-methyl-2-pentanol in channel-like cavity of 3-epideoxycholic acid, interpreted by the four-location model for chiral recognition

Pure (2R,3S)-3-methyl-2-pentanol is resolved from the racemates by a steroidal host; the interpretation of the recognition mechanism based on the crystal structure reveals that CH/O interaction between the host and guest plays a decisive role in enantio-selective enclathration of the small aliphatic secondary alcohol.     

156Dy as an activable yield tracer for determination of rare earth elements in biological materials by neutron activation analysis

Use of an enriched¹⁵⁶Dy isotope as an activable yield tracer for the determination of lanthanoid contents in various biological reference materials has been proposed. The method consists of preconcentration of the lanthanoid in the¹⁵⁶Dy doped samples followed by neutron irradiation and further chemical purification steps. The chemical behaviour of lanthanoid elements in the whole procedure was found, in separate runs, similar to that of the added¹⁵⁶Dy within experimental errors. Simple purification steps after irradiation allow the measurement of relatively short-lived nuclides and diminish the radiation dose received during the chemical treatment. The present results for orchard leaves (NBS SRM 1571) are generally in good agreement with the previously reported data. Some new data are obtained for other biological reference materials.     

Relation of contact densities with Mössbauer isomer shifts for 35.46 keV M1 transition of125Te

The internal conversion electron and Mössbauer isomer shifts associated with the 35.46 keV M1 transition of¹²⁵Te were observed for different metal samples into which radioactive¹²⁵I as probe atoms were introduced by means of ion-implantation. From the correlation between the Mössbauer isomer shifts and intensity ratios of O shell to N_I shell conversion electrons, a relation between 5s-electron contact densityp _5s(0) in a.u. and isomer shift δ in mm/s was deduced to bep _5s(0)=106+30.3 δ±4.3[(δ?0.30)²+0.069]^1/2, where δ was measured relative to ZnTe in mm/s. The change of the nuclear charge radius in the 35.46 keV M1 transition of¹²⁵Te was found to be ΔR/R=(0.85±0.12)×10^?4 (corresponding to Δ<r ²>=(3.7±0.5)×10^?3 fm²) when a theoretical 4s-electron contact density of 928 a.u. was used.     

Diphosphatetraazacyclooctatetraenes. II. Properties and degradations

1,5-Bis(diphenylphospha)-3,7-bis(perfluoroalkylether)-2,4,6,8- tetraazacyclooctatetraene and 1,3-bis(diphenylphospha)-5,7-bis(perfluoroalkylether) -2,4,6,8-tetraazacyclooctatetraene were found to decompose at 316°C to phospha-s-triazines. The symmetrical arrangement liberated perfluoroalkylether nitrile with concommitant formation of the corresponding diphospha-s-triazine; the unsymmetrical isomer eliminated the (C₆H₅)₂PN unit to give the monophospha-s-triazine. The thermal and oxidative stabilities of the two compounds differed widely, with the unsymmetrical isomer being significantly more stable than the symmetrical arrangement. Spectral data pertinent to these results are discussed. Both materials were found to be effective in arresting perfluoroalkylether fluid degradation in oxidizing atmospheres in the presence of metal alloys.     

Einzelschichten und Mehrfachschichten von Anthrachinonderivaten mit langen Alkylketten

Ohne Zusammenfassung     

Activation and tracer techniques for study of metallofullerenes

Advantages and uniqueness of radiochemical techniques in fullerene studies are pointed out. Some experimental data are presented on metallofullerenes production yields, HPLC elution behaviors of Y, La, Gd containing fullerenes, encapsulation of a new metal in the carbon cage, stability of the carbon cage against recoil energy, and the distribution of metallofullerenes among various organs of rats.     

Systematic behavior of mass-yield curves in low-energy fission of actinides

Mass yield curves of spontaneous fissions, thermal-neutron induced fissions, monochromatic-neutron and proton induced fissions of actinides are reviewed. Mean masses of light and heavy asymmetric mass yield peaks are listed. The subtle change of the shape of the asymmetric heavy peak is expressed in terms of the parameters of two Gaussians that fit the observed data well. One Gaussian is narrow in width and always peaks at A=133–136 while the other is broader and peaks at A=140–144. The FWHM of the heavy asymmetric peak becomes minimum for the fissioning mass A=240–245. An analysis of the projectile energy dependence of mass yield curves indicated, at least, two distinctively different behaviors, one for asymmetric products and the other for symmetric products. From the energy dependence of the peak-to-valley rations, the extra-energy required for symmetric mass division, or the difference in the fission barrier heights, in the nomeuclature of the two-mode hypothesis, is deduced for a wide range of fission nuclides.     

Radiative transition of two indirect excitons to direct exciton in thallous halides

Weak emission lines are observed at the energies far lower than the energies of edge emissions in TlCl and TlBr. They are explained as due to the radiative decay of two indirect X⁺₆ × R^?₆ excitons, both at the same M-point, by leaving one direct X⁺₆ × X^?₆ excitons through zero-phonon process.