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41.
Abachi S Abbott B Abolins M Acharya BS Adam I Adams DL Adams M Ahn S Aihara H Alitti J Álvarez G Alves GA Amidi E Amos N Anderson EW Aronson SH Astur R Avery RE Baarmand MM Baden A Balamurali V Balderston J Baldin B Banerjee S Bantly J Bartlett JF Bazizi K Bendich J Beri SB Bertram I Bezzubov VA Bhat PC Bhatnagar V Bhattacharjee M Bischoff A Biswas N Blazey G Blessing S Bloom P Boehnlein A Bojko NI Borcherding F Borders J Boswell C Brandt A Brock R Bross A Buchholz D Burtovoi VS Butler JM 《Physical review letters》1996,77(25):5011-5015
42.
Abachi S Abbott B Abolins M Acharya BS Adam I Adams DL Adams M Ahn S Aihara H Alitti J Álvarez G Alves GA Amidi E Amos N Anderson EW Aronson SH Astur R Avery RE Baden A Balamurali V Balderston J Baldin B Bantly J Bartlett JF Bazizi K Bendich J Beri SB Bertram I Bezzubov VA Bhat PC Bhatnagar V Bhattacharjee M Bischoff A Biswas N Blazey G Blessing S Bloom P Boehnlein A Bojko NI Borcherding F Borders J Boswell C Brandt A Brock R Bross A Buchholz D Burtovoi VS Butler JM Carvalho W Casey D 《Physical review letters》1996,76(18):3271-3276
43.
44.
The paper provides the complete list of local models forZ 2 l -invariant generic germs of Lagrangian submanifolds of dimension ≦3. Classification is done directly for genrating functions of Lagrangian submanifolds and contains both elementary singularities and non-elementary ones with continuous moduli. The results demonstrate, in particular, that in contrast to the non-equivariant case the classification of equivariant Lagrangian singularities is not subordinated to the classification of symmetric functions up to the right equivariant equivalences. 相似文献
45.
Hexalkylditin is prepared by a Lewis acid-promoted (MgCl2) reductive reaction of bis(trialkyltin) oxide using magnesium metal as reducing agent. Hexabutyl- and hexaphenylditin are synthesized with 95% and 80% yield separately and a radical mechanism is proposed for the reaction condition. Unsymmetric ditin, Bu3Sn-SnPh3, was first synthesized by this reductive method. 相似文献
46.
PHOTOCHEMISTRY and PHOTOBIOLOGY WITHOUT LIGHT 总被引:3,自引:0,他引:3
Abstract— This review covers the literature since 1980 on chemically and enzymatically generated electronically excited species. The emphasis lies on triplet states of carbonyl products that are derived from dioxetanes and dioxetanones as precursors or from suitable enzymatic oxygenations. Singlet oxygen, an important excited state species in biological processes, is not explicitly treated. The utilization of triplet excited carbonyl products to promote photochemical and photobiological transformations by energy transfer are of primordial interest and not the photomechanistic behavior, photophysical properties and inherent photochemical reactions of such excited state species. Thus, the coverage concentrates on photodamage of DNA and RNA, the photochemistry of flavins, vitamin D, tryptophan, arachidonic acid, chlorophyll, lipid peroxidation, urocanase activation, excitation of chlorophlasts, and the aerobic oxidation of Schiff bases derived from amino acids and proteins. The potential perspectives of employing authentic dioxetanes and enzymatically generated dioxetane intermediates as effective photon equivalents in photochemotherapy, phototoxicity, photoaffinity labeling and photogenotoxicity are pointed out, in the hope of stimulating more intensive activity in this emerging and novel bioorganic and photobiological field. 相似文献
47.
Tetraphenylporphyrin-sensitized photooxygenation of 2-methyl-5-trimethylsilylfuran () affords quantitatively trimethylsilyl 2-oxo-4-pentenoate (), presumably via intramolecular Baeyer-Villiger rearrangement of the intermediary dioxirane (). 相似文献
48.
The second order optical potential for thed system is derived in the framework of the Watson formalism and applied to the calculation of the 1s-state energy shift of the atom and thed scattering lengtha
d
. The results are in good agreement with those of the Faddeev type calculations.The authors wish to thank V. B. Belyaev, R. Mach, M. G. Sapozhnikov and R. A. Eramzhyan for stimulating discussions and helpful advice. 相似文献
49.
R. N. Haward J. N. Hay I. W. Parsons G. Adam A. A. K. Owadh C. P. Boxnyak A. Aref-Azaf A. Cross 《Colloid and polymer science》1980,258(6):643-662
Summary In a tensile test ductile thermoplastics may give either uniform deformation or necking. Recently it has been found that those giving uniform deformation either, are known to have extended chain configurations in solution, or have chemical formulae with linear structures and relatively few flexible bonds. The observed differences in behaviour can be predicted from a viscosity retarded rubber elasticity model in which a constant related to chain flexibility is introduced, which quantifies the strain hardening of the material. It is argued that the early development of strain hardening generally interferes with the localization of plastic strain in shear bands or crazes (as well as in a neck) and correlates with the stress cracking performance of high density polythenes.There is now also some evidence that polymers with extended chain configurations have small values ofcp (the change in specific heat atTg) and that this figure has an apparent correlation with draw ratio for different polymers.In the case of P.V.C. however it is possible to cause a changeover from the normal necking behaviour to uniform deformation by quenching the hot material in ice water. This process is believed to eliminate a structure which develops slowly in P.V.C. and most other thermoplastics when they are annealed at temperatures near toTg. The elimination of this structure during yielding causes strain softening and also promotes plastic strain localisation.This physical ageing or annealing process is still not well understood. It almost certainly includes free volume effects but recent studies have shown that a redistribution of rotational isomers also occurs. These observation, if correct, have fundamental implications for the physics of glassy polymers.
Dedicated to Prof. Dr. Rehage on the occasion of his 60th birthday.
With 22 figures and 2 tables 相似文献
Zusammenfassung Beim Zug-Test erfolgt bei dehnbaren Thermoplasten entweder eine gleichmäßige Deformation oder eine Einschnürung. Erstere tritt auf bei Vorliegen ausgestreckter Kettenkonfigurationen in Lösung oder bei Makromolekülen linearer Struktur und relativ unbiegsamer Bindungen. Die beobachteten Unterschiede wurden anhand eines ViskositätsModells mit verminderter Gummi-Elastizität unter Zugrundelegung von Literaturdaten diskutiert. Die Kettensteifheit wird rechnerisch durch Einfügung einer Konstanten berücksichtigt; sie steht in Konkurrenz mit der Lokalisierung der plastischen Dehnung und korreliert mit dem Auftreten einer Spannungsriß-Bildung im Polyäthylen hoher Dichte. Es wird darauf hingewiesen, daß sich die spezifische Wärme von Polymeren mit ausgedehnter Kettenkonfiguration beiTg nur wenig ändert; dieser Effekt steht mit dem Dehnungsverhältnis verschiedener Polymerer in Einklang.Bei PVC kann jedoch durch Abschrecken des heißen Materials in Eiswasser ein Übergang vom normalen Einschnürungsverhalten zu einer gleichmäßigen Deformation erzielt werden; dieser Effekt ist durch die Unterdrückung einer speziellen Struktur bedingt und kann auch bei der Temperung anderer thermoplastischer Polymerer nahe beiTg auftreten.Die sich bei der physikalischen Alterung und bei der Temperung abspielenden Vorgänge lassen sich noch nicht erklären. Sie umfassen sicherlich Effekte des freien Volumens und die Rückverteilung von Rotations-Isomeren. Beobachtungen dieser Art sind von grundsätzlicher Bedeutung für die Physik glasartiger Polymerer.
Dedicated to Prof. Dr. Rehage on the occasion of his 60th birthday.
With 22 figures and 2 tables 相似文献
50.
A novel solid-state NMR concept is introduced that allows for the detection of through-space proton-proton contacts in high spectral resolution. The proposed method not only can be utilized to infer sequential assignments and backbone or side chain conformation in solid-phase polypeptides, but it also provides information about the three-dimensional arrangement of the molecule of interest. As a result, the molecular structure can be studied without additional restrictions regarding sample labeling or magic angle spinning rates. 相似文献