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991.
亚皮秒太瓦脉冲激光与物质相互作用研究进展 总被引:1,自引:0,他引:1
当前亚皮称太瓦超短冲激光技术的发展为激光与物质相互作用领域提供了许劝人心的研究机会,从激光与单个原子的相互作用到激光等离子体中的集体效应,如原子的高度离化、X射线激光、等离子体波导,等离子体粒子加速器,快速点火方案等等,文章评述了最近几年这方面的研究进展。 相似文献
992.
Abhishek Roy Michael A. Hickner Xiang Yu Yanxiang Li Thomas E. Glass James E. McGrath 《Journal of Polymer Science.Polymer Physics》2006,44(16):2226-2239
One of the integral parts of the fuel cell is the proton exchange membrane. Our research group has been engaged in the past few years in the synthesis of several sulfonated poly(arylene ether) random copolymers. The copolymers were varied in both the bisphenol structure as well as in the functional groups in the backbone such as sulfone and ketones. To compare the effect of sequence length, multiblock copolymers based on poly(arylene ether sulfone)s were synthesized. This paper aims to describe our investigation of the effect of chemical composition, morphology, and ion exchange capacity (IEC) on the transport properties of proton conducting membranes. The key properties examined were proton conductivity, methanol permeability, and water self diffusion coefficient in the membranes. It was observed that under fully hydrated conditions, proton conductivity for both random and block copolymers was a function of IEC and water uptake. However, under partially hydrated conditions, the block copolymers showed improved proton conductivity over the random copolymers. The proton conductivity for the block copolymer series was found to increase with increasing block lengths under partially hydrated conditions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2226–2239, 2006 相似文献
993.
Ta‐Tsien Li Yue‐Jun Peng Yong‐Fu Yang Yi Zhou 《Mathematical Methods in the Applied Sciences》2008,31(2):193-227
One often believes that there is no shock formation for the Cauchy problem of quasilinear hyperbolic systems (of conservation laws) with linearly degenerate characteristic fields. It has been a conjecture for a long time (see Arch. Rational Mech. Anal. 2004; 172 :65–91; Compressible Fluid Flow and Systems of Conservation Laws in Several Space Variables. Springer: New York, 1984) and it is still an open problem in the general situation up to now. In this paper, a framework to justify this conjecture is proposed, and, by means of the concept such as the strict block hyperbolicity, the part richness and the successively block‐closed system, some general kinds of quasilinear hyperbolic systems, which verify the conjecture, are given. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
994.
Xinde Tang Xiaochao Liang Qian Yang Xinghe Fan Zhihao Shen Qifeng Zhou 《Journal of polymer science. Part A, Polymer chemistry》2009,47(17):4420-4427
Novel AB2‐type amphiphilic block copolymers of poly(ethylene glycol) and poly(N‐isopropylacrylamide), PEG‐b‐(PNIPAM)2, were successfully synthesized through single‐electron transfer living radical polymerization (SET‐LRP). A difunctional macroinitiator was prepared by esterification of 2,2‐dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether (PEG). The copolymers were obtained via the SET‐LRP of N‐isopropylacrylamide (NIPAM) with CuCl/tris(2‐(dimethylamino)ethyl)amine (Me6TREN) as catalytic system and DMF/H2O (v/v = 3:1) mixture as solvent. The resulting copolymers were characterized by gel permeation chromatography and 1H NMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions (PDI < 1.15). Their phase transition temperatures and the corresponding enthalpy changes in aqueous solution were measured by differential scanning calorimetry. As a result, the phase transition temperature of PEG44‐b‐(PNIPAM55)2 is similar to that in the case of PEG44‐b‐PNIPAM110; however, the corresponding enthalpy change is much lower, indicating the significant influence of the macromolecular architecture on the phase transition. This is the first study into the effect of macromolecular architecture on the phase transition using AB2‐type amphiphilic block copolymer composed of PEG and PNIPAM. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4420–4427, 2009 相似文献
995.
Xiaoze Jiang Jingyan Zhang Yueming Zhou Jian Xu Shiyong Liu 《Journal of polymer science. Part A, Polymer chemistry》2008,46(3):860-871
Double hydrophilic diblock copolymer, poly(N,N‐dimethylacrylamide)‐b‐poly(N‐isopropylacrylamide‐co‐3‐azidopropylacrylamide) (PDMA‐b‐P(NIPAM‐co‐AzPAM), containing azide moieties in one of the blocks was synthesized via consecutive reversible addition‐fragmentation chain transfer polymerization. The obtained diblock copolymer molecularly dissolves in aqueous solution at room temperature, and can further supramolecularly self‐assemble into core‐shell nanoparticles consisting of thermoresponsive P(NIPAM‐co‐AzPAM) cores and water‐soluble PDMA coronas above the lower critical solution temperature of P(NIPAM‐co‐AzPAM) block. As the micelle cores contain reactive azide residues, core crosslinking can be facilely achieved upon addition of difunctional propargyl ether via click chemistry. In an alternate approach in which the PDMA‐b‐P(NIPAM‐co‐AzPAM) diblock copolymer was dissolved in a common organic solvent (DMF), the core‐crosslinked (CCL) micelles can be fabricated via “click” crosslinking upon addition of propargyl ether and subsequent dialysis against water. CCL micelles prepared by the latter approach typically possess larger sizes and broader size distributions, compared with that obtained by the former one. In both cases, the obtained (CCL) micelles possess thermoresponsive cores, and the swelling/shrinking of which can be finely tuned with temperature, rendering them as excellent candidates as intelligent drug nanocarriers. Because of the high efficiency and quite mild conditions of click reactions, we expect that this strategy can be generalized for the structural fixation of other self‐assembled nanostructures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 860–871, 2008 相似文献
996.
Chengzhong Cui Edward M. Bonder Frieder Jkle 《Journal of polymer science. Part A, Polymer chemistry》2009,47(23):6612-6618
A new class of amphiphilic organometallic block copolymers with cationic organoboron pendant groups was developed. Selective replacement of one of the bromine substitutents on each boryl group of the block copolymer PSBBr2‐b‐PS with an organometallic reagent ArM (ArM = 2,4,6‐trimethylphenyl copper, 4‐t‐butylphenyltrimethyl tin) followed by treatment with 2,2′‐bipyridine gave the novel block copolymers [ 3Ar ](Br)n as light yellow solid materials that show good stability in air and moisture and high solubility in most organic solvents. Their structure and composition were confirmed by multinuclear NMR, GPC, and elemental analysis. Highly regular micellar aggregates form in block‐selective solvents (e.g., MeOH, toluene) as demonstrated by 1H NMR, dynamic light scattering, and transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6612–6618, 2009 相似文献
997.
Yaohong Chen J. P. Kennedy 《Journal of polymer science. Part A, Polymer chemistry》2008,46(1):174-185
Two new telechelic amphiphilic triblock copolymers, HE3‐PEG‐b‐PDMS‐b‐PEG‐HE3 and HE3‐PEG‐b‐PDMS‐b‐PEG‐HE3, i.e., sequence‐reversed triblocks of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic polydimethylsiloxane (PDMS) segments fitted with photocrosslinkable tri[2‐(3,4‐cyclohexane oxide)ethyl‐dimethylsiloxy]silane (HE3) termini, were synthesized, characterized, photocrosslinked to amphiphilic conetworks (APCNs), and the properties of the APCNs were analyzed. APCNs in which the crosslinking sites are located in the hydrophobic domains exhibited significantly better mechanical properties than those in which the crosslinks were in the hydrophilic domains. The stiff domains formed of the UV‐crosslinkable HE3 chain‐end substituents provide not only crosslinking but reinforcement as well. The crosslinking/reinforcement efficiency was greatly enhanced by the addition of excess HE3. Water‐swollen APCNs were optically clear and exhibited mechanical properties appropriate for biomedical application. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 174–185, 2008 相似文献
998.
刘小珍 《光谱学与光谱分析》1998,18(5):614-616
本文用电感耦合等离子体原子发射光谱法,X射线荧光光谱法、红外光谱以及X射线衍射谱测定了石棉红花岗石和芝麻白花岗石的成分和光谱、根据石棉红岗石和芝麻白花岗石的X射线衍射谱,用计算机检索它们的组成,对计算机检索的结果进行对比得出,石棉红花岗石的红色是由于它含有Fe的红色矿物而产生的。 相似文献
999.
1000.
On the Block Independence in G-Inverse and Reflexive Inner Inverse of A Partitioned Matrix 总被引:1,自引:0,他引:1
Yong Hui LIU Mu Sheng WEI 《数学学报(英文版)》2007,23(4):723-730
By applying the multiple quotient singular value decomposition QQQQQ-SVD, we study the block independence in g-inverse and reflexive inner inverse of 2× 2 partitioned matrices, and prove a conjecture in [Yiju Wang, SIAM J. Matrix Anal. Appl., 19(2), 407-415(1998)]. 相似文献