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991.
Nilmini K. Abayasinghe Sibylle Glaser K. Prasanna U. Perera Dennis W. Smith 《Journal of polymer science. Part A, Polymer chemistry》2005,43(21):5257-5266
Oligoethylene‐end‐capped polylactides were synthesized through the ring‐opening polymerization of L ‐lactide with alcohol‐terminated oligoethylenes as macroinitiators. The polymerization of L ‐lactide was carried out in bulk at 130 °C in the presence of stannous octoate and primary alcohols with four different molecular weights: 350, 425, 550, and 700 g/mol. The end‐capped copolymers that formed had a number‐average molecular weight of approximately 40,000 (weight‐average molecular weight/number‐average molecular weight = 1.7) according to gel permeation chromatography and were highly crystalline in comparison with the similarly formed homopolymer of L ‐lactide. The copolymer structure was characterized by Fourier transform infrared, NMR, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and differential scanning calorimetry analysis. This work focused on developing more crystallizable and hydrolytically stable polylactide derivatives that could potentially be used as compatibilizers in polylactide–polyolefin blends or as nucleating agents for poly(L ‐lactide) or other polyesters. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5257–5266, 2005 相似文献
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993.
M. P. Dancy J. Billowes I. S. Grant D. E. Evans J. A. R. Griffith S. A. Wells D. A. Eastham J. Groves J. R. H. Smith D. W. L. Tolfree P. M. Walker 《Hyperfine Interactions》1990,59(1-4):193-196
East particle-photon coincidence techniques, developed at Daresbury with strontium isotopes, allow ultrasensitive laser fluorescence
spectroscopy of beams of radio-active isotopes which can only be produced in very low yields. The technique has now been applied
to neutron-deficient barium isotopes down to120Ba. From measured hyperfine splittings and isotope shifts, nuclear moments and changes in mean square radii have been determined.
The work has revealed an abrupt increase in the mean square radius for121Ba large enough to disrupt the systematic staggering of nuclear size seen for the series. In a recent experiment an isomeric
state of127Ba with a half-life of about 2 seconds has been produced in a very low yield; nevertheless we have succeeded in obtaining
a fluorescence spectrum. 相似文献
994.
Most writers on frequency assignment algorithms have described the details of a single algorithm, and evaluated the algorithm on selected data sets. There has been relatively little emphasis on describing the common features that are important if an algorithm is to have good performance. This paper describes the key features, with particular emphasis on algorithms for weighted fixed spectrum problems. The use of algorithms handling weighted constraints has become increasingly common in recent years. The advantages and disadvantages of weighting constraints are demonstrated. 相似文献
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997.
N. Leonard H. M. Smith L. K. Boseley A. K. Miller J. P. Potts Ch. G. Matthews A. H. Parker und W. Bersch 《Fresenius' Journal of Analytical Chemistry》1906,45(5-6):394-396
Ohne Zusammenfassung 相似文献
998.
H. B. Kellog Ada M. Kellog G. F. Smith C. A. Getz 《Analytical and bioanalytical chemistry》1937,108(9-10):335-335
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