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1.
Woo-Soo Kim Ruth Houbertz Tae-Ho Lee Byeong-Soo Bae 《Journal of Polymer Science.Polymer Physics》2004,42(10):1979-1986
Inorganic–organic hybrid polymers have been developed and tested for evaluation in optical and electrical applications. Although hybrid inorganic–organic polymers can be synthesized by sol–gel chemistry at first, the physical properties of hybrid inorganic–organic polymers are changed during thin film-making processes, that is, photocuring and thermal curing. To investigate the effect of photoinitiator on the material properties during processing, a model system containing methacrylic groups as organically polymerizable units was selected. The conversion of CC double bond of methacrylic groups depending on some kinds of photoinitiator quantities was characterized by Fourier transform infrared spectroscopy. It was confirmed to correlate the degree of CC double bond conversion with the refractive indices. Thermodynamically, the enthalpy of the photopolymerization of hybrid polymer was investigated by UV–DSC. UV–DSC spectra showed the exothermic nature of photopolymerization of ORMOCER® to be in dependence of photoinitiator quantities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1979–1986, 2004 相似文献
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3.
Casey Chun Zhou Eric J. Stoner Kent D. Stewart L. Steven Hollis Edmund D. Matayoshi Gregory M. Brill 《Tetrahedron》2004,60(47):10611-10618
Oritavancin is a semi-synthetic glycopeptide antibiotic which is structurally related to vancomycin. When oritavancin bisphosphate is dried in vacuo with heat, a new compound forms. This new compound is stable only in the solid state and reverts to oritavancin in solution. Highly enriched samples of this compound were obtained by preparative HPLC and the structure of this compound was elucidated by using one and two-dimensional (1H and 13C) NMR spectroscopy in conjunction with computer-assisted molecular modeling. It has been determined that oritavancin adopts a conformation similar to that of vancomycin in solution, while the new compound is the unnatural R-AB-biaryl atropisomer of oritavancin. This is the first observation and isolation of an AB-biaryl atropisomer in an intact member of the vancomycin family of glycopeptide antibiotics. 相似文献
4.
Ruth Kellerhals 《Israel Journal of Mathematics》2004,143(1):361-379
Forn≥2, we quantify the Margulis constant ε(n) giving rise to a thick and thin decomposition of hyperbolicn-manifolds of finite volume. As a consequence, we obtain new universal lower bounds for the volume and Gromov's invariant
as well as a geometrical inequality between injectivity radius and diameter for compact manifolds. Finally, we concretise
the upper bound for the counting function of hyperbolic manifolds of dimension >4 as described by Burger, Gelander, Lubotzky
and Mozes.
Partially supported by Schweizerischer Nationalfonds No. 20-61379.00 and 20-67619.02. 相似文献
5.
Jacquelyn A. Carioscia Lauren Schneidewind Casey O'Brien Robert Ely Caitlin Feeser Neil Cramer Christopher N. Bowman 《Journal of polymer science. Part A, Polymer chemistry》2007,45(23):5686-5696
The ability to prepare high Tg low shrinkage thiol–ene materials is attractive for applications such as coatings and dental restoratives. However, thiol and nonacrylated vinyl materials typically consist of a flexible backbone, limiting the utility of these polymers. Hence, it is of importance to synthesize and investigate thiol and vinyl materials of varying backbone chemistry and stiffness. Here, we investigate the effect of backbone chemistry and functionality of norbornene resins on polymerization kinetics and glass transition temperature (Tg) for several thiol–norbornene materials. Results indicate that Tgs as high as 94 °C are achievable in thiol–norbornene resins of appropriately controlled chemistry. Furthermore, both the backbone chemistry and the norbornene moiety are important factors in the development of high Tg materials. In particular, as much as a 70 °C increase in Tg was observed in a norbornene–thiol specimen when compared with a sample prepared using allyl ether monomer of analogous backbone chemistry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5686–5696, 2007 相似文献
6.
A graph with n vertices that contains no triangle and no 5-cycle and minimum degree exceeding n/4 contains an independent set with at least (3n)/7 vertices. This is best possible. The proof proceeds by producing a homomorphism to the 7-cycle and invoking the No Homomorphism Lemma. For k ≥ 4, a graph with n vertices, odd girth 2k+1, and minimum degree exceeding n/(k+1) contains an independent set with at least kn/(2k+1) vertices; however, we suspect this is not best possible. © 1993 John Wiley & Sons, Inc. 相似文献
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Ahmed Iraqi Ruth C. Pegington Timothy G. Simmance 《Journal of polymer science. Part A, Polymer chemistry》2006,44(10):3336-3342
The postmodification of poly[9‐(2‐hexyldecyl)‐9H‐carbazole‐2,7‐diyl] ( P1 ) upon its reaction with N‐bromosuccinimide affords exclusive and full bromination of the 3,6‐positions of the carbazole repeat units to yield poly[3,6‐dibromo‐9‐(2‐hexyldecyl)‐9H‐carbazole‐2,7‐diyl] ( P2 ). Brominated polymer P2 can be used as a precursor for further functionalization at the 3,6‐positions with the desired functional group to afford other useful polymers. Polymer P2 has hence been reacted with copper(I) cyanide to afford poly[3,6‐dicyano‐9‐(2‐hexyldecyl)‐9H‐carbazole‐2,7‐diyl] ( P3 ). Full substitution of the bromide groups with nitrile‐functional groups has been achieved. The preparation and structural characterization of polymers P2 and P3 are presented together with studies on their electronic conjugation and photoluminescence properties. Cyclic voltammetry studies on polymer P3 indicate that the new polymer is easier to reduce (n‐dope) but more difficult to oxidize than its unsubstituted counterpart ( P1 ) as a result of the introduction of the electron‐withdrawing nitrile‐functional groups at the 3,6‐positions on the carbazole repeat units on the polymer chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3336–3342, 2006 相似文献
9.
郭冰 柳卫平 Trinczek M Lapi S Ames F Buckley K R D’Auria J M Jayamanna K Ruiz C Ruth T J 《中国物理 C》2006,30(7):675-679
加拿大TRIUMF实验室利用11C成功验证了一种产生高强度(~108ions/s)放射性束流的方法. 该方法不同于普通在线同位素分离方法, 它利用了13MeV的低能强流质子束, 可以产生一系列核天体物理实验感兴趣的高强度放射性束流. 相似文献
10.
M. E. Wrenn H. Ruth D. Burleigh N. P. Singh 《Journal of Radioanalytical and Nuclear Chemistry》1992,156(2):407-412
The literature on the normal content of uranium in urine is reviewed. The reported normal concentration has declined several orders of magnitude over the years, probably due to improvements in analytical technique rather than a real change. The lowest mean values were reported with spectrometry (mean of 23 ng/l in 12 subjects) and thermal ion mass spectrometry (3.4 ng/l in 1 subject). Even spectrometry is not sufficiently sensitive at normal levels, so that techniques such as fission track analysis or mass spectrometry must be used to obtain results above the detection limit of the technique for individual samples. 相似文献