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151.
Chung‐Yang Chuang Trong‐Ming Don Wen‐Yen Chiu 《Journal of polymer science. Part A, Polymer chemistry》2009,47(11):2798-2810
In this research, thermo‐ and pH‐responsive nanoparticles with an average diameter of about 50–200 nm were synthesized via the surfactant‐free emulsion polymerization. The thermal/pH dual responsive properties of these nanoparticles were designed by the addition of a pH sensitive monomer, acrylic acid (AA), to be copolymerized with N‐isopropylacrylamide (NIPAAm) in a chitosan (CS) solution. The molar ratio of CS/AA/NIPAAm in the feed was changed to investigate its effect on structure, morphology, thermal‐ and pH‐responsive properties of the nanoparticles. It was found that CS‐PAA‐PNIPAAm nanoparticles could be well dispersed in the aqueous solution and carried positive charges on the surface. The addition of thermal‐sensitive NIPAAm monomer affected the polymerization mechanism and interactions between CS and AA. The particle size of the nanoparticles was found to be varied with the composition of NIPAAm monomer in the feed. The synthesized nanoparticles exhibited stimuli‐responsive properties, and their mean diameter thus could be manipulated by changing pH value and temperature of the environment. The nanoparticles showed a continuous release of the encapsulated doxycycline hyclate up to 10 days during an in vitro release experiment. The environmentally responsive nanoparticles are expected to be used in many fields such as drug delivery system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2798–2810, 2009 相似文献
152.
The reduction of ReCl4(THF)2 in the presence of excess t-butylisocyanide by sodium amalgam produces pentakis(t-butylisocyanide)chlororhenium(I), which has been converted to the corresponding methyl and ethyl derivatives. The reaction of pentakis(trimethylphosphine)chlororhenium(I) with ButNC gives partially substituted complexes, ReCl(CNBut)2(PMe3)3 and ReCl(CNBut)3(PMe3)2. The structures of both compounds have been determined by X-ray methods. Octahedral ReCl(CNBut)2(PMe3)3 has trans isocyanide groups with one linear [C---N---C = 175(1)°] and one slightly bent [C---N---C = 159(1)°]. The Re---C bond lengths are equal within experimental error [2.004(7), 2.003(7)Å]. In the octahedral ReCl(CNBut)3(PMe3)2, for which the structure is not well defined, due to disorder, the unique isocyanide trans to chlorine is considerably bent at the nitrogen atom [C---
---C = 141(6)°] and appears to show the shortest Re---C bond length, 1.94(5) vs 2.02(5)Å for the other two isocyanides which are mutually trans. Protonation of these two isocyanide complexes with fluoroboric acid gives, respectively, the salts [ReCl(CNBut)CNHBut(PMe3)3]BF4 and [ReCl(CNBut)2CNHBut(PMe3)2]BF4, whose configurations have been determined by NMR spectroscopy. The reduction by sodium amalgam of Cr2(CO2Me)4 in tetrahydrofuran in presence of ButNC gives a high yield of Cr(CNBut)6 while similar reduction of the dimeric tungsten(II) complex of the anion (mhp) of 2-methyl-6- hydroxypyridine gives W(CNBut)6. Interaction of W2(mhp)4 in methanol-ether with ButNC gives a tungsten(I) complex W2(η-mhp)2(ButNC)4, which may be an intermediate in the reductive cleavage reaction. Interaction of cis-PtMe2(PMe3)2 with ButNC leads only to replacement of one PMe3 group to give the complex cis-PtMe2(PMe3)(CNBut). 相似文献
153.
From electrical resistivity measurements on PdH samples we have separated out the optical and acoustic phonon contributions. The onset of optical resistivity coincides with the occurence of superconductivity, supporting the recent evidence that optical phonons play the major role in the formation of superconductivity in PdH system. 相似文献
154.
Y. C. Chiu H. J. Hwang 《Colloids and surfaces. A, Physicochemical and engineering aspects》1994,90(2-3):155-165
Vitamin E is widely used in pharmaceutical, food and cosmetic preparations. This paper discusses methods of preparing a vitamin E emulsion by using sodium N-lauroylsarcosinate (SNLS) ionic surfactant. The amount of vitamin E dissolved in water was analyzed by turbidity and UV absorption measurements. The emulsion droplet size was determined by laser light scattering. Microemulsions with small particle size and high resistance to oxidation in air can be obtained by solubilizing vitamin E in SNLS solution. The dissolution is rapid and the surfactant solution has high solubilization power. At 0.7% surfactant concentration, the saturation value is 1 g vitamin E per gram of surfactant. The micellar dissociation concentration (MDC) of the surfactant can be estimated from a vitamin saturation—surfactant concentration curve. Dissolution mechanisms at different surfactant concentrations are interpreted by use of the MDC and CMC (critical micellar concentration) concepts. 相似文献
155.
A general high yield synthesis for W2(O2CR)4 compounds is proposed based on eqn (1), wherein a WW triple bond is converted to a quadruple bond, and this has been established for RMe, Et and t-Bu.W2Et2(NMe2)4 + 4RCOOCOR → W2(O2CR)4 + 4RCONMe2 + C2H4 + C2H6 (1) 相似文献
156.
A new space-time model for hadron-nucleus collisions is proposed, where particles at the instant of creation are not only immature but their maturity rate is enhanced in the presence of other hadronic matter, as in a nucleus. With only one free parameter, the model can explain dnAp/dν, dnAπ/dν, RAp(EL), and the A-dependences of σinpA and σinπA. 相似文献
157.
158.
Lue-Yung Chow Chiu Swadesh R. Samanta 《Journal of Quantitative Spectroscopy & Radiative Transfer》1981,25(3):253-264
Photoionization of H2(1Σg+) in a vibrational υ″ and rotational N″ state into H2+(2Σg+) in a vibrational υ′ and rotational N′ state is studied theoretically. The differential cross section, after summing over the final states, is expressed in the well-known simple form of . Parallel expressions are obtained for H2+ in a specific υ′ state (in terms of σ(υ′) and β(υ′)) and for H2+ in a rotational fine level υ′N′ (in terms of σ(υ′N′) and β(υ′N′)). Asymmetry parameters β, β(υ′) and β υ′N′), which are expressed in terms of Racah and Clebsch-Gordan coefficients and electronic transition moments, can be reduced approximately to 2 lineary polarized light and to -1 for unpolarized light. Using single-center electronic wave functions and including partial eaves l = 1, 3, and 5, σ(υ′) and β(υ′) are computed as a function of υ′ at 584 Å. The computed σ(υ′) divided by the Frank-Condon overlap, in agreement with experimental results, increases monotonically with υ′; σT and β are computed in the incident photon energy range of 600–4000 Å and the results compare favorably with previous calculations. 相似文献
159.
Shan-Tao?Lai Ying-Nan?Chiu Ricardo?LetelierEmail author 《Journal of mathematical chemistry》2005,37(1):1-16
Labarthes primitive L-patterns for the 3nj-symbols, where n=3,4,5,6,7, are reported. It is shown that, any L-patterns of the angular momentum recoupling coefficients can be expressed in terms of linear combinations of the primitive L-patterns and how the 3nj-symbols can be calculated from the expressions presented here.AMS subject classification: 81QShan-Tao Lai–Permanent Address for reprint requestYing-Nan ChiuAlso– Institute of Atomic and Molecular Sciences, Academia Sinica,Taipei, Taiwan, R.O.C. 相似文献
160.