Deuteron structure and diffractive deuteron-nucleus interaction

A nonrelativistic deuteron wave function involving the D-wave state and having a correct asymptotic behavior is constructed on the basis of the experimentally measured deuteron charge form factor G _C(q) and deuteron structure function A(q). The differential cross section for elastic deuteron-nucleus scattering is calculated by using this wave function and is found to agree with experimental data at an energy of 110 MeV. Integrated cross sections for various processes involving deuteron-nucleus interactions are also calculated. The distribution in the emission angle of the center of mass of the neutron-proton system produced in the diffractive dissociation of 110-MeV deuterons in the field of ²⁰⁸Pb nuclei is obtained.     

Investigation into the dielectric relaxation of vinylidene fluoride copolymers with hexafluoropropylene

Four relaxation processes and one ferroelectric-paraelectric phase transition are revealed in vinylidene fluoride-hexafluoropropylene copolymers with different ratios of the components in the temperature range from ?100 to 150°C. The relaxation process occurring at the lowest temperature is associated with the local mobility of the chains, whereas the relaxation process at a higher temperature is due to micro-Brownian motion of segments in the amorphous phase in the glass transition range. A smeared relaxor phase transition from the polar modification of the α phase of vinylidene fluoride units to the paraelectric phase is observed in the temperature range 50–70°C. At higher temperatures, there occurs an intensive relaxation process that can be attributed to space-charge relaxation or manifestation of the normal relaxation mode.     

Influence of cobalt(III) dimethyldithiocarbamate complexes on styrene polymerization initiated by tert-butyl perbenzoate

Kinetic features of radical polymerization of styrene initiated by tert-butyl perbenzoate in the presence of tris(N,N-dimethyldithiocarbamato)cobalt(III) (CoL₃) and its adduct with iodine (CoL₃ · 2I₂) were studied. The optimal concentration ratios of the activators and tert-butyl perbenzoate, providing fast styrene polymerization at 338–368 K, were determined.     

Hydrophobicity and thermal stability of fluorinated pentaerythritol esters

Wetting angles and limits of thermal stability of esters derived from pentaerythritol and perfluoro-, ω-chloropolyfluoro-, and perfluoropolyethercarboxylic acids were studied.     

Conformational implications of some nucleotide sequences

The conformational properties of some nucleotide sequences result in their ability to bind specifically some ligands or tobe recognized by specific proteins. In order to investigate the dependence of conformational behavior of the DNA duplex on nucleotide sequence, we analyzed the interaction energy of nucleic acid bases as a function of conformational parameters and base sequence. Extended regions of minimum energy values were found for different sequences. Although these regions (valleys) largely overlap, each one shows specificity for a particular sequence. This suggests that a specific pathway of changes in conformational parameters exists for each sequence. the changes may be accompanied by considerable shifts (2–3 Å) of the atom positions and an only slight variation (1–2 kcal/mol) of energy. Even small shifts in other directions can cause a drastic energy increase. For some nucleotide sequences, the energetically preferable conformations are the B-like ones (e.g., ApA, TpA), whereas for others the A-like ones are preferable (e.g., GpG, ApT). IN general, Pyr-Pur sequences have a tendency to a larger τ and smaller H and D than Pur-Pyr sequences. A large body of experimental data on nucleic acid structure in fibers and in solutions can be explained by results obtained.     

Self-inhibition or the lack of it in the pyrolyses of neopentane and n-hexane

Published data show that in its early stages (up to 3% decomposition), the pyrolysis of n-hexane in the ranges 723–823 K and 10–100 Torr is not inhibited by the olefin products, in contrast with neopentane pyrolysis which is very strongly inhibited in similar conditions. Detailed consideration of the chain mechanisms for the two pyrolyses shows that the reactivity of the chain terminating radical towards hydrogen abstraction from an allylic C? H bond in product olefin is the factor which determines whether or not observable self-inhibition occurs. Thus, n-hexane pyrolysis, whose chain decomposition is terminated by recombination and disproportionation of ethyl, is not significantly self-inhibited, whereas that of neopentane which is terminated by recombination of methyl is very strongly inhibited because methyl is 14× more reactive than ethyl. The implications for other alkanes are briefly discussed.     

HPLC studies of isomeric chromium-N-benzoylphenylhydroxylaminates

Summary N-Benzoylphenylhydroxylarnine complexes of some metals have been investigated by HPLC. The green chromium complex formed by this reagent shows conclusive evidence of the presence of geometrical isomers. It is photosensitive and changes to a brown modification when irradiated with ultra violet or visible light. Elution behaviour of the complexes has been studied with different solvent mixtures. Attempts have been made to characterize the complexes from different measurements.

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Untersuchung von isomeren Chrom-N-benzoylphenylhydroxylaminaten durch HPLC

     

High reliability atomic absorption spectrometry of major and minor elements in biological materials

Summary Reliable analytical information is of fundamental importance for decisions of far-reaching impact in many regulatory, medical and scientific areas and disciplines. It is however at times elusive. Although the technique of atomic absorption spectrometry (AAS) as become widely established in analytical laboratories throughout the world for the determination of inorganic elements, only few AAS-based methods have reached official status and even fewer have attained reference method status. Research is underway to delineate impacts of a number of parameters on method performance to lead to protocols for standard and reference flame AAS (FAAS) methods for the reliable measurement of major and minor levels of elements of nutritional and toxicological pertinence in clinical and biological materials. Factors investigated include preparation of standards, calibration techniques, sampling and sample decomposition, solution preparation, instrumental parameters, and measurement protocols. Examples of some pronounced effects of sample decomposition and calibration techniques are presented as well as indications of the excellent performance of well-applied AAS procedures determined by use of standard reference materials and comparison with other techniques of analysis. Reference will be made to the determination of the major and minor nutrient elements Na, K, Mg, Ca, Mn, Fe, Cu and Zn in plant biological reference materials.Formerly at Plant Research Centre, Agriculture Canada, Ottawa, Ontario K1A OC6, CanadaContribution No. 1030 from Plant Research Centre