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排序方式: 共有478条查询结果,搜索用时 31 毫秒
131.
This article gives a review of the results of recent dielectric and viscoelastic studies for entangled binary blends of linear cis-polyisoprenes to explain the current understanding of the equilibrium entanglement dynamics on the basis of the molecular picture of dynamic tube dilation (DTD). Comparison of dielectric and viscoelastic properties reveals that the full-DTD picture regarding the relaxed portions of the chains as a solvent fails for the high molecular weight component chain in the blends at intermediate times. This failure is related to insufficient constraint release (CR) equilibration of the entanglement segments of this chain. A partial-DTD picture properly considering this CR equilibration successfully describes the linear relaxation behavior of the blends. The dielectric and viscoelastic properties of PI under fast flow, being affected by the flow-activated CR/DTD mechanism, are also presented in order to demonstrate the usefulness of the comparison of these properties in both equilibrium and non-equilibrium states. 相似文献
132.
Masashi Kijima Hideki Hasegawa Hideki Shirakawa 《Journal of polymer science. Part A, Polymer chemistry》1998,36(15):2691-2698
Three liquid crystalline N-substituted pyrroles were synthesized from 6-(1-pyrrolyl)hexanol with phenolic derivatives having a mesogenic core of cyclohexylbenzene or biphenyl by Mitsunobu reaction. These pyrroles had two anodic peaks at 1.4 and 1.8 V (vs. SCE). The former was due to an oxidation of the pyrrole moiety and the latter was due to an oxidation of the mesogenic moiety. These pyrrole monomers were polymerized by electrochemical and chemical methods. The potentiostatic method and the chemical method using FeCl3 gave a soluble and fusible polymer, respectively. A polymer having a mesogenic core of cyclohexyl benzene obtained by the chemical method and a polymer having a mesogenic core of biphenylketone obtained by the potentiostatic method had a liquid-crystalline phase. The phase was identified as smectic A by polarizing microscopy and XRD analysis. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2691–2698, 1998 相似文献
133.
Kazuhiko Yamatoya Mayumi Shirakawa Kazutami Kuwano Junko Suzuki Osamu Baba 《Macromolecular Symposia》1997,120(1):231-236
Xyloglucan is found in the primary cell walls of higher plants, where it plays important biological roles. It also exists in certain seeds, for example tamarind, as a reserve polysaccharide. Some xyloglucan oligosaccharides possess plant growth promotion activity. We prepared hydrolyzed xyloglucan from the tamarind seed xyloglucan using endo-(1 → 4)- β -glucanase and examined its effects on lipid metabolism in rats fed a high fat diet. Among the plasma lipids, total lipid, cholesterol, triglyceride and β - lipoprotein were each reduced 14 - 17% by hydrolyzed xyloglucan. Hydrolyzed xyloglucan significantly reduced both adipose tissue weight and plasma GOT. Among the hepatic lipids, total lipid, cholesterol, triglyceride and phospholipid were significantly reduced by hydrolyzed xyloglucan. These hypolipidemic effects may be important for the treatment and prevention of geriatric diseases, including diabetes and cardiac disorders. 相似文献
134.
Keio Toi Tomoyasu Ito Toshiaki Shirakawa Isao Ikemoto 《Journal of Polymer Science.Polymer Physics》1992,30(6):549-556
Sorption and diffusion of gases (CO2, N2, and He) in a polyimide (PI2080) film were measured by using an apparatus which gives the sorption rate curves from the initial state to the equilibrium state. Nonlinear isotherms observed for CO2 sorption were interpreted successfully in terms of the dual-mode model for sorption in glassy polymers. Linear isotherms observed for N2 and He seemed to obey Henry's law. Two diffusion coefficients (DI and DE) were obtained using the short-time method and the long-time method for a Fickian diffusion model, together with the equilibrium solubility (Ce) from each experiment. The initial sorption rate curves agreed with the calculated curves using DI, however near sorption equilibrium the curves are in accord with the calculated curves using DE. These observations suggest that some relaxation process is superimposed on the diffusion process. The non-Fickian transport data were correlated successfully with a model that combines time-dependent diffusion and the Fickian model. 相似文献
135.
Youhei Kotsuchibashi Yumi Kuboshima Kazuya Yamamoto Takao Aoyagi 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):6142-6150
In this thesis, we studied the convenient synthesis and characterizations of thermo‐responsive materials with double response. To achieve these, AB‐type diblock copolymers comprising of poly(N‐isopropylacrylamide) (NIPAAm) segment and poly(NIPAAm‐co‐(N‐(hydroxymethyl)acrylamide) (HMAAm)) one were designed. That was synthesized in one‐pot using an atom transfer radical polymerization (ATRP) technique. Poly(NIPAAm‐co‐HMAAm)s synthesized separately showed sensitive thermo‐response and the cloud point was completely tunable by the composition of HMAAm. As expected, the block copolymers exhibited double thermo‐responsive profiles in aqueous solution. The responsive behavior was discussed by precise trace by 1H NMR and turbidity measurements. From these results, we could confirm almost independent dehydration of each segment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6142–6150, 2008 相似文献
136.
This paper deals with the complete characterization of solutions to an elliptic system of variational inequalities. The latter model arises in the study of the long-time behavior of shape memory materials and is suitable of describing a variety of experimentally observed phenomena. 相似文献
137.
Treatment of magnesium alkylidene carbenoids, which were generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesium chloride at −78 °C in toluene, with N-lithio nitrogen-containing heterocycles (e.g., indole, indazole, phenothiazine, and phenoxazine) gave N-alkenylated products in moderate to good yields. The intermediate of this reaction was found to be the alkenyl anion, which could be trapped with iodoalkanes using CuI as a catalyst to give the heterocycles having fully substituted alkenes on the nitrogen. The alkenyl anion intermediate could be trapped also with benzoyl chloride and phenyl isocyanate. This reaction offers a quite novel and direct N-alkenylation of nitrogen-containing heterocycles. 相似文献
138.
Jun Dong A. Shirakawa K.-I. Ueda A.A. Kaminskii 《Applied physics. B, Lasers and optics》2007,89(2-3):359-365
The microchip laser performance of Yb:YAG crystals doped with different ytterbium concentrations (CYb=10, 15, and 20 at. %) has been investigated at ambient temperature without active cooling of the gain media. Efficient laser
oscillation for a 1-mm-thick YAG doped with 10 at. % Yb3+ ions was achieved at 1030 and 1049 nm with slope efficiencies of 85% and 81%, correspondingly. The laser performance of heavy-doped
Yb:YAG crystals was limited by the thermal population at terminated lasing level and thermal lens effect at room temperature
without sufficient cooling of the samples. The laser emitting spectra of Yb:YAG microchip lasers with different Yb concentrations
and output couplings are addressed with the local temperature rise, due to the absorption of the pump power inside the gain
media under different pump levels.
PACS 42.55.Xi; 42.70.Hj; 42.55.Rz 相似文献
139.
Saori Ishizu Mizuki Sekiya Ken-ichi Ishibashi Yumi Negami Masafumi Ata 《Journal of nanoparticle research》2008,10(2):229-254
The societal impacts of nanotechnology have attracted growing attention in the United States and Europe in recent years. In
Japan, the National Institute of Advanced Industrial Science and Technology (Technology Information Department) has played
a central role in promoting discussions on this topic by collecting information from Japan and overseas, creating a network
of the interested parties, and providing a forum for discussion. This paper presents a summary of recent activities in Japan
relating to the societal impacts of nanotechnology, fro the launch of the “Nanotechnology and Society” open forum (August
2004) until the “Nanotechnology Debate” discussion forum (February 2007), and outlines the policy recommendations that came
out of a project entitled “Research on Facilitation of Public Acceptance of Nanotechnology” (March 2006). 相似文献
140.
J.?LuEmail author H.?Yagi K.?Takaichi T.?Uematsu J.-F.?Bisson Y.?Feng A.?Shirakawa K.-I.?Ueda T.?Yanagitani A.A.?Kaminskii 《Applied physics. B, Lasers and optics》2004,79(1):25-28
A high-power, continuous-wave 0.6% Nd3+-doped ceramic Y3Al5O12 (Nd:YAG) laser has been developed. 110 W laser output at 1064 nm was obtained, with a slope efficiency of about 41%. The M2 factor was found to be around 6. The laser performance of the ceramic laser material was found to compare favorably with that obtained with single crystal Nd:YAG. PACS 42.55.-f; 42.55.Xi; 42.70.Hj 相似文献