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1.
The angular variations of the five-fold differential cross section obtained by using different wave functions of helium are
compared with experimental data. It is found that in the coplanar geometry two kinematical arrangements, (i) equal energy
sharing between the two ejected electrons with one of them ejected along the momentum transfer direction and the other along
varying direction and (ii) the Bethe ridge condition with fixed sum of ejected electron energies and varying angle between
them, are very sensitive to e-e correlations contained in the target wave function. This comparison has been used to show
that open-shell class of wave functions better incorporate e-e correlations than the closed-shell class. 相似文献
2.
M. F. Barakat M. M. Abdel-Hamid 《Journal of Radioanalytical and Nuclear Chemistry》1996,211(2):461-471
The various aspects of valency stabilization of polyvalent ions during -radiolysis have been further investigated. Ce(IV) ions, which are normally reduced in their aqueous solution, were found to be stabilized for increasing periods of time when they were irradiated in the presence of increasing amounts of bromate ions. It was found that the addition of about fifteen times excess of bromate ions to a 10–3 N Ce(IV) solution stabilized the cerium ions in the tetravalent state for about 120 hours during irradiation at a dose rate of 336 Gy/h. Increasing the amount of bromate used resulted in a subsequent increase in the protection time. It has been also noted that while bromate ions protected Ce(IV) in solution, the latter ions showed a clear protective effect on the bromate used, i.e., there is a mutual protective effect. The probable mechanisms, conditions and limitations of the protection process have been discussed. Based on the data obtained in the present work, it has been suggested that the protection of Ce(IV) ions by bromate ions in aqueous solutions during -radiolysis is very probably due to the preferential interaction of bromate with the reducing radiolysis products of water which are capable of reducing Ce(IV) to Ce(III). 相似文献
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The source of the biotin sulfur atom remains a contested point in studies of biotin synthase (BioB) in vitro. Recent reports that BioB has an intrinsic pyridoxal phosphate (PLP)-dependent cysteine desulfurase activity were tested by depleting Escherichia coli cells of PLP. The BioB-dependent conversion of dethiobiotin to biotin proceeded in these cells irrespective of the presence or absence of PLP. 相似文献
9.
Nasser?Mohammed?HosnyEmail author Abdel-Hamid?M.?Shallaby 《Transition Metal Chemistry》2007,32(8):1085-1090
Coordination compounds of MnII, CuII, FeIII and ZnII ions with 4-acetylpyridine nicotinoylhydrazone (4-APNH) were synthesized and characterized by elemental analyses, molar conductivity,
magnetic moments, i.r., u.v./vis., m.s., 1H-n.m.r. and thermal analyses. I.r. spectra show that the ligand can act either in the enol form as monovalent bidentate or
in the keto form as neutral bidentate depending on the metal salt used. Octahedral structures are proposed for Fe complex
and square – planar for the Cu complex, while tetrahedral structures were suggested for Zn and Mn complexes on the basis of
magnetic and spectral evidences. Semi-empirical calculations ZINDO/1 have been used to study the molecular geometry and the
harmonic vibrational spectra with the purpose to assist the experimental assignment of the complexes.
In memory of the late Professor Dr. Abdel Hamid M. Shallaby 2/5/2006 相似文献
10.
Mohammed K. Abdel-Hamid Jonathan Coates Celia Miländer Brian W. Skelton Anthony C. Willis 《Tetrahedron letters》2009,50(50):6947-8550
The allylation of indigo results in the one-step synthesis of two unique complex heterocyclic systems: a spiroindoline-pyridoindolone arising from the addition of three allyl moieties and a fused pyridoindolo-azepinoindolone generated from the addition and subsequent cyclisation of two allyl moieties. The structures of these novel heterocycles are assigned unambiguously using extensive NMR experiments and by X-ray crystallographic analysis. The distribution of the products is influenced by the use of thermal versus microwave heating. 相似文献