Determination of Isoprene Unit Structures in Polyisoprene Rubbers

1960 ◽  
Vol 33 (2) ◽  
pp. 587-590 ◽  
Author(s):  
N. G. Kasatkina
Keyword(s):  
Rapid Determination ◽  
Model Compounds ◽  
Isoprene Unit ◽  
Gutta Percha

Abstract Conditions were selected for simple and rapid determination of the percentage of 1,4, 3,4 and 1,2 units in synthetic isoprene rubbers from the curves of the rate of their oxidation by benzoyl hydroperoxide. The content of 1,4, 3,4 and 1,2 units in synthetic isoprene rubbers was determined by comparing the curves of the rate of their oxidation by benzoyl hydroperoxide with the curves of oxidation of model compounds, i.e. limonene and gutta percha.

scholarly journals Determination of arrangement of isoprene units in pig liver dolichol by 13C-n.m.r. spectroscopy

1987 ◽  
Vol 243 (2) ◽  
pp. 481-485 ◽  
Author(s):  
Y Tanaka ◽  
H Sato ◽  
A Kageyu ◽  
T Tomita
Keyword(s):  
Chemical Structure ◽  
Reversed Phase ◽  
Hydroxyl Group ◽  
Geometric Isomers ◽  
Model Compounds ◽  
Pig Liver ◽  
Isoprene Unit ◽  
Transfer Measurement ◽  
Slight Amount

The arrangement of isoprene units in pig liver dolichol-18, -19 and -20 was determined by 1H- and 13C-n.m.r. spectroscopies. The alignment of trans and cis isoprene units was found to be in the order: dimethylallyl unit, two trans units, a sequence of 14-16 cis units, and a saturated isoprene unit terminated with a hydroxyl group, which verified the presumed chemical structure of dolichol. The absence of geometric isomers was confirmed. A slight amount of impurity was detected in each reversed-phase h.p.l.c. fraction of dolichol obtained by a conventional method. Detailed assignments of the 13C-n.m.r. spectrum were given for these dolichols by using model compounds and INEPT (insensitive nuclei enhanced by polarization transfer) measurement. The chemical structure of synthetic dolichol-19, which was prepared by the addition of a saturated isoprene unit to the polyprenol-18 isolated from Ginkgo biloba, was confirmed to be identical with that of pig liver dolichol-19.

Weak Beam Imaging and Diffraction Studies of Stacking Faults in Silicon

1976 ◽  
Vol 34 ◽  
pp. 590-591
Author(s):  
T. Y. Tan ◽  
W. K. Tice
Keyword(s):  
Fast Neutron ◽  
Rapid Determination ◽  
Stacking Faults ◽  
Imaging Method ◽  
Large Reduction ◽  
Dislocation Loops ◽  
Fringe Spacing ◽  
Weak Beam ◽  
Kinematical Theory

In studying ion implanted semiconductors and fast neutron irradiated metals, the need for characterizing small dislocation loops having diameters of a few hundred angstrom units usually arises. The weak beam imaging method is a powerful technique for analyzing these loops. Because of the large reduction in stacking fault (SF) fringe spacing at large sg, this method allows for a rapid determination of whether the loop is faulted, and, hence, whether it is a perfect or a Frank partial loop. This method was first used by Bicknell to image small faulted loops in boron implanted silicon. He explained the fringe spacing by kinematical theory, i.e., ≃l/(Sg) in the fault fringe in depth oscillation. The fault image contrast formation mechanism is, however, really more complicated.

Methods for rapid determination of pecan (Carya illinoensis) seed viability

2017 ◽  
Vol 45 (2) ◽  
pp. 455-464
Author(s):  
T.T. Xue ◽  
J. Liu ◽  
Y.B. Shen ◽  
G.Q. Liu
Keyword(s):  
Rapid Determination ◽  
Seed Viability ◽  
Carya Illinoensis
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