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961.
碳氟链与碳氢链表面活性剂在固液界面上的吸附 总被引:1,自引:0,他引:1
全氟辛酸及其钠盐和十二烷基硫酸钠在R972上的吸附等温线均为S型或LS型,指示固液界面吸附过程中有表面疏水缔合物生成.碳氟表面活性剂的饱和吸附量显著高于碳氢表面活性剂的饱和吸附量.加电解质于液相使各体系吸附量上升.对于碳氟表面活性剂,甚至引起吸附等温线类型变化.例如,不加电解质时全氟辛酸在R972上的吸附等温线为S型,而加入HCl(c=0.05mol·dm-3)使吸附等混线变成LS型.全氟辛酸比全氟辛酸钠在R972上的吸附更强.几种表面活性剂在R972上的吸附均随温度升高而减少。应用两阶段吸附模型及通用吸附等温线公式可以很好地解释所得实验结果. 相似文献
962.
V. L. Shirokii V. A. Knizhnikov T. P. Konovalov Z. P. Zubreichuk A. A. Erdman S. E. Nefedov I. L. Eremenko A. I. Yanovskii Yu. T. Struchkov N. A. Mayer 《Russian Chemical Bulletin》1993,42(4):732-733
Co-electrolysis of potassium 1,2-dicarbadodecahydroundecaborate and indene in 0.1N sodium bromide solution in dimethylsulfoxide using iron electrodes afforded -indenyl--(3)-1,2-dicarbollyliron(III).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 764–765, April, 1993. 相似文献
963.
R. Sakamoto 《Colloid and polymer science》1984,262(10):788-792
Solvent effects on the phase separation of poly(-benzyl L-glutamate) to liquid crystal and isotropic solution have been observed in various helicogenic solvents. The temperature-composition phase diagrams have been determined for each solution. The critical concentrations,
2
*
, at which the phase separation occours have been compared in various solvents. In dimethylformamide in which the polymer is molecularly dispersed, the observed
2
*
value has agreed with that calculated by Flory's theory. In some solvents in which the polymer aggregates in a head-to-tail mode such as chloroform, the observed
2
*
values have been considerably small. It is assumed that the polymer aggregates behave as longer particles than the original particles. In dioxane in which the polymer aggregates highly both in a head-to-tail and a side-by-side modes, the
2
*
value has been a little larger than that in chloroform. In this case the relationship between the aggregation and the liquid crystal formation is so complicated that further investigation is necessary. In aromatic solvents such asm-cresol that dissolves the polymer almost molecularly, the
2
*
is smaller than that in dimethylformamide. Therefore, the intermolecular interactions between the phenyl groups in the side groups of the polymer and those in solvent molecules must be considered.The author is grateful to Mr. K. Sano and Mr. M. Watanabe for their observation of the liquid crystal formation. 相似文献
964.
The stoichiometric solubility constant of eitelite (NaMg
0.5
CO
3
+2H+ ⇄ Na++0.5Mg
2+
+CO
2
(g)+H
2
O, log*K
pso
I
=14.67±0.03 was determined at I=3 m (mol kg−1) (NaClO
4
) and 25°C. The stability of magnesium (hydrogen-)carbonato complexes in this ionic medium was explicitely taken into account.
Consequently, trace activity coefficients of free ionic species, calculated from the Pitzer model with ion-interaction parameters
from the literature, were sufficient for an evaluation of the thermodynamic solubility constants and Gibbs energies of formation
for eitelite (−1039.88±0.60), magnesite (−1033.60±0.40), hydromagnesite (−1174.30±0.50), nesquehonite (−1724.67±0.40), and
brucite (−835.90±0.80 kJ-mol
−1
). The increasing solubilities of nesquehonite and eitelite at higher sodium carbonate molalities were explained by invoking
a magnesium dicarbonato complex (Mg2++2CO
3
2−
⇄ Mg(CO3)
2
2−
, log βz = 3.90 ± 0.08). A set of ion-interaction parameters was obtained from solubility and dissociation constants for carbonic
acid in 1 to 3.5 m NaClO
4
media
which reproduce these constants to 0.02 units in log K. The following Pitzer parameters are consistent with the previously
studied formation of magnesium (hydrogen-)carbonato complexes in 3m NaClO
4
. The model and Gibbs functions of solid phases derived here reproduce original solubility data (−log [H+], [Mg
2+
]
tot
) measured in perchlorate medium within experimental uncertainty.
Presented at the XXII International Conference on Solution Chemistry, July 14–19, 1991, Linz, Austria. 相似文献
965.
Spiro-fused heterocycles were synthesized in good to high yields by a pseudo four-component reaction of an aldehyde, urea and a cyclic β-diester or a β-diamide such as Meldrum’s acid or barbituric acid derivatives using microwave irradiation under solvent-free conditions. 相似文献
966.
The goal of the present study is to test the hypothesis that LPA induces proliferation of astrocytes in hippocampus in vivo via phosphorylation of ERK 1/2. We first characterized the expression of GFAP, a special marker fiber protein of astrocytes,
in brain slices after direct injection of LPA into hippocampus by immunohistochemistry, and found that LPA induced a remarkable
proliferation of astrocytes. Then double-lablled immunofluorescence was used to detect GFAP and phosphorylation ERK 1/2 (p-ERK
1/2), LPA induced an immediate (10 min) and transient (<30 min) phosphorylation of ERK 1/2, and sequence sustained activation
of ERK 1/2 was observed, which last for at least 3 weeks after injection of LPA. Reactions are inhibited by U0126, a specific
pharmacological mitogen-activated protein kinase (MEK) inhibitor. Laser confocal scanning was used to study spatial relationship
of p-ERK and astrocytes. Amazingly, the early (<7 days) phosphorylation of ERK 1/2 is not expressed in astrocytes but in area
where neurons and/or in other cell type(s) occupied, expression of p-ERK 1/2 in astrocytes is not detected until 14 days after
LPA injection and lasts for at least 3 weeks. Taken together, these data suggest that LPA play an important role in proliferation
of astrocytes through phosphorylation of ERK 1/2 in hippocampus. It provides further proof for the functions of LPA in CNS
injury, and may contribute to clinical therapy for relative diseases. 相似文献
967.
以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高. 相似文献
968.
Dynamic light scattering experiments have been performed at various concentrations, of pharmaceutical oil-in-water microemulsions
consisting of Eutanol G as oil, a blend of a high (Tagat O2) and a low (Poloxamer 331) hydrophilic–lipophilic balance surfactant,
and a hydrophilic phase (propylene glycol/water). We probe the dynamics of these microemulsions by dynamic light scattering.
In the measured concentration range, two modes of relaxation were observed. The faster decaying mode is ascribed classically
to the collective diffusion D
c (total droplet number density fluctuation). We show that the slow mode is also diffusive and suggest that its possible origin
is the relaxation of polydispersity fluctuations. The diffusion coefficient associated with this mode is then the self-diffusion
D
s of the droplets. It was found that D
c and D
s had opposite volume fractions of oil plus surfactants (ϕ) dependence and a common limiting value D
0 for ϕ=0. Average hydrodynamic radius (R
h=10.5 nm) of droplets was calculated from D
0. R
h is supposed to compose the inner core, a surfactant film including possible solvent molecules, which migrate with the droplet.
The concentration dependence of diffusion coefficients reflects the effect of hard sphere and the supplementary repulsive
interactions which arises due to loss of entropy, when absorbed chains of surfactant intermingle on the close approach of
the two droplets. This mechanism could also explain the observed stability of our systems. The estimated extent of polydispersity
is 0.22 from the amplitude of slower decaying mode. The polydispersity in microemulsion systems is dynamic in origin. Results
indicate that the time scale for local polydispersity fluctuations is at least three orders of magnitude longer than the estimated
time between droplet collisions. 相似文献
969.
Qiang Li Pingfan Wu Yongge Wei Hongyou Guo 《Journal of organometallic chemistry》2006,691(6):1223-1228
An organic-inorganic hybrid compound, (Bu4N)2[Mo6O18(NAr)] (Ar = p-BrC6H4) has been synthesized via the DCC dehydrating protocol of the reaction of [α-Mo8O26]4− with 4-bromoaniline hydrochloride in anhydrous acetonitrile, which has been characterized by UV-Vis spectra, 1H NMR and single crystal X-ray diffraction study. By comparing the UV-Vis spectra, which were used to monitor the reaction, the optimum preparative condition for this compound was also determined. This compound crystallizes in the monoclinic space group P21/n, which is featured in a terminal para-bromophenylimido group linked to an Mo atom of a hexamolybdate cluster by a Mo-N triply bond. In addition, there are π-π dimerization of the neighboring cluster anions though the parallel aromatic rings in their crystals. 相似文献
970.
Study on oxidation of polymers treated by high LET radiation 总被引:2,自引:0,他引:2
Wang Ruiyu Ha Hongfei Wang Yugang Zhao Weijiang Yan Sha Jin Changwen Wang Guanghui Wu Jilan 《Radiation Physics and Chemistry》1998,52(1-6):251-256
The oxidation of medical silicone rubber and segmented polyether urethane which were bombarded with 11.2 MeV Si+ or F+ at the dose of 5 × 1014 ions/cm2 was studied. In XPS measurements, it was found that the oxygen concentration on the surface of the implanted polymeric membranes had been increasing in three months at least. ESR measurement showed that some free radicals existed in these membranes and their quantities decreased with time. Chemical analysis proved that peroxides were generated in the γ irradiated membranes. The reason for the increasing of oxygen concentration was that free radicals combined with oxygen in the air and produced peroxides on the membrane surface. Moreover, in order to demonstrate the radiation mechanism, low LET (γ rays) radiation of such polymeric membranes was carried out for comparison 相似文献