共查询到20条相似文献,搜索用时 31 毫秒
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《Fuel》1987,66(7):935-946
The application of l.c.-m.s., using both quadrupole and magnetic sector mass spectrometers, to the analysis of aromatic fractions of hydropyrolysis tars and a Gray-King tar, is described. The results are compared with those obtained by g.c.-m.s. and probe mass spectrometric methods such as field desorption, desorption chemical ionization and low ionizing voltage probe. The molecular weight range observed by l.c.-m.s. is much greater than that observed by g.c.-m.s. and is similar to those observed by probe methods. The proportion of the aromatic fractions eluted from the NH2-bonded silica column by hexane is not known, but some polar molecules are retained and can be eluted by increasing solvent polarity. The results indicate the presence of extensive homologous series of aliphatics and aromatics with carbon numbers exceeding C50. The extent of alkylation decreases with increasing severity of the method used to prepare the tar. 相似文献
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E.R. Andrew 《Polymer》1985,26(2):190-192
The dynamical behaviour of four solid polypeptides (α-chymotrypsin, insulin, lysozyme, ribonuclease A) has been investigated by proton magnetic relaxation. The interpretation was supplemented by measurements on the constituent amino acids, and on dipeptides, tripeptides and homopolypeptides. The following motions were identified and characterized: methyl group reorientation, segmental motion, sidechain motion, proline ring puckering, reorientation of water molecules in the structure. Slow motions were investigated through measurements of the dipolar relaxation time TID. 相似文献
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T. J. Potts T. C. Smith B. N. Rockwood D. L. Henry E. H. Tenent Jr. W. J. Johnson R. T. Doughtie Jr. F. W. Quackenbush E. A. Epps Jr. P. Van Entwistle V. E. Munsey C. L. Hoffpauir J. L. Clough M. P. Etheredge K. E. Holt 《Journal of the American Oil Chemists' Society》1959,36(11):545-549
Conclusions The results obtained in this collaborative study show that none of the methods tested offer sufficient advantages in precision
and accuracy to warrant selection as an official method to the exclusion of other methods studied.
Also the precision of all methods tested show these methods to be inadequate for checking crude fiber specification limits
set up by the N.S.P.A. on soybean oil meal. This statement would also apply to any other product where specification limits
on crude fiber are narrower than the precision shown in Table VI.
Ease and speed for manipulation are also an important criterion for choosing an official method. A poll of committee members
showed no definite preference for any one method studied; every method received the support of two or more of the committee
members.
The Liaison Committee is still hopeful that a method can be devised that will give a precision in line with trade specifications
and practices. The committee will continue to work toward the development of such a method. 相似文献
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