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31.
3,3′-Thiobispyridine is prepared by reaction of pyridine-3-thiol with 3-bromopyridine. The base peak in the mass spectrum of 3,3′-thiobispyridine is due to the molecular ion which fragments by loss of H, HCN and CS as well as by central bond rupture. The 1,1′-dimethyl diquaternary salt of 3,3′-thiobispyridine is reduced polarographically by a one electron transfer not involving hydrogen to an unstable radical cation at a potential (Eo) of −0.72 V in the pH range 7.4–11.2. 相似文献
32.
Sylvia Marhold Ernst Koller Isabella Meyer Otto S. Wolfbeis 《Fresenius' Journal of Analytical Chemistry》1990,336(2):111-113
Summary A new fluorimetric assay for cationic surfactants is based on their capability of quenching the fluorescence of 8-octadecyloxypyrene-1,3,6-trisulfonate (PTS-18). It is specific for cationic surfactants which can be determined in the 40–400 g concentration range. The method is considered to be advantageous over former methods in that it only requires addition of the sample solution to the fluorophore solution, followed by measurement of fluorescence intensity of the probe. This is in contrast to existing methods where the detergent/dye ion pair has to be extracted before measurement. 相似文献
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M. Feil W. von Oertzen H. G. Bohlen A. Gamp R. L. Walter B. Kohlmeyer 《Zeitschrift für Physik A Hadrons and Nuclei》1973,260(4):271-282
Excitation functions for the elastic scattering of12C on14C and the reactions14C(12C, α)22Ne,14C(12C,t)23Na and14C(12C,d)24Na have been measured in the vicinity of the Coulombbarrier. Strong fluctuations of the differential cross sections as a function of incident energy are observed in the α-particle, triton and deuteron channels. The total yield in the three different channels shows correlated structures at energiesE c.m.=6.8, 7.2 and 8.3 MeV. This phenomenon is similar to the structures observed in the12C+12C reactions and indicates the possible presence of resonances in the entrance channel. 相似文献
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36.
Vinck E Van Doorslaer S Dewilde S Moens L 《Journal of the American Chemical Society》2004,126(14):4516-4517
Human neuroglobin (hNgb) and human cytoglobin (hCygb), two recently discovered members of the vertebrate globin family, are known to be able to form an intramolecular disulfide bridge. Using electron paramagnetic resonance (EPR), we show that formation of a disulfide bridge in ferric hNgb causes a considerable change in the heme pocket structure, whereas this is not so clear for ferric hCygb. The structural results can be related nicely to earlier histidine and dioxygen affinity studies of the ferrous proteins. 相似文献
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Background
Although previous studies suggest that postural control requires attention and other cognitive resources, the central mechanisms responsible for this relationship remain unclear. To address this issue, we examined the effects of altered attention on cortical activity and postural responses following mechanical perturbations to upright stance. We hypothesized that cortical activity would be attenuated but not delayed when mechanical perturbations were applied during a concurrent performance of a cognitive task (i.e. when attention was directed away from the perturbation). We also hypothesized that these cortical changes would be accompanied by alterations in the postural response, as evidenced by increases in the magnitude of anteroposterior (AP) centre of pressure (COP) peak displacements and tibialis anterior (TA) muscle activity. Healthy young adults (n = 7) were instructed to continuously track (cognitive task) or not track (control task) a randomly moving visual target using a hand-held joystick. During each of these conditions, unpredictable translations of a moving floor evoked cortical and postural responses. Scalp-recorded cortical activity, COP, and TA electromyographic (EMG) measures were collected. 相似文献39.
Sylvia Pulmannová 《International Journal of Theoretical Physics》2003,42(7):1413-1423
A noncommutative version of generalized Sasaki projections in pseudoeffect algebras is introduced. It is proved that an ideal in a pseudoeffect algebra is Riesz if and only if it is closed under the right and left Sasaki projections. In lattice ordered pseudoeffect algebras, it is shown that generalized Sasaki projections are one-element sets, and their explicit form is found. It is shown that if a supremum of a normal Riesz ideal in a lattice ordered pseudoeffect algebra exists, it is a central element. These results extend those obtained recently by Avallone and Vitolo for effect algebras. 相似文献
40.
Gejza Jenca Sylvia Pulmannová 《Proceedings of the American Mathematical Society》2003,131(9):2663-2671
We prove that for every orthocomplete effect algebra the center of forms a complete Boolean algebra. As a consequence, every orthocomplete atomic effect algebra is a direct product of irreducible ones.