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61.
Masahiro Manabe Toshihiro Ochi Hideo Kawamura Hajime Katsu-ura Masaki Shiomi Mandeep Singh Bakshi 《Colloid and polymer science》2005,283(7):738-746
The partial molar volumes (Va) of 1-alkanols (carbon number, m=5, 6, 7) in - and -cyclodextrin (CD) solutions at 5.00 mmol kg–1 have been determined as a function of alkanol concentration (Ca) between 293.2 and 308.2 K by using a dilatometer. It has been observed that with an increase in Ca, Va increased in -CD solution but decreased in -CD solution, asymptotically to a value of Va in CD-free water. The dependence of Va on Ca provided the binding constant (K) of 1:1 complex, the volume change in complex formation, and the partial molar volume of complex itself. The complex formation mechanism has been discussed on the basis of these values and their carbon number dependences in the respect of geometric behavior, hydrophobic interaction, and van der Waals interaction. It is concluded that the CD cavity in water is not rigid but flexible for fitting in nicely with guest molecule. 相似文献
62.
用 PCA 及 PLS 分步处理分光光度数据,有效降低了计算的维数。以该法对不同酸度体系的5-Br-PADAP-钴、镍、铜、锌分光光度数据进行了处理,定量分析结果良好。 相似文献
63.
Toshio Fuchigami 《Journal of fluorine chemistry》2007,128(4):311-316
Recent studies on solvent effects on electrochemical partial fluorination are reviewed. At first, the historical background and some problems of electrochemical fluorination in organic solvents like acetonitrile (MeCN) are briefly mentioned. Ethereal solvents like dimethoxyethane (DME) and a mixture of DME and MeCN were found to improve both the yield and current efficiency for electrochemical fluorination since these solvent systems effectively suppress anode passivation and overoxidation of fluorinated products once formed during the electrolysis. It was also found that DME stabilizes radical cationic intermediates of 4-arylthio-1,3-dioxolan-2-ones and 3-phenylthiophthalide leading to α-fluorination while dichloromethane (CH2Cl2) destabilizes them leading to fluorodesulfurization. On the other hand, imidazolium ionic liquids and liquid fluoride salts like Et4NF·4HF and Et3N·5HF exhibited similar effects to CH2Cl2. Selective fluorination of hardly oxidizable phthalide was also achieved using a combination of two kinds of ionic liquids (imidazolium triflate and liquid fluoride salts). 相似文献
64.
65.
M Pavan 《Analytica chimica acta》2004,515(1):167-181
Interest is growing in decision making strategies and several techniques are now available. The assessment of priorities is a typical premise before final decisions are taken. Total and partial order ranking (POR) strategies, which from a mathematical point of view are based on elementary methods of discrete mathematics, appear as an attractive and simple tool to asses priorities. Despite the well-known total ranking strategies, which are scalar methods combining the different criteria values into a global index which always ranks elements in an ordered sequence, the partial order ranking is a vectorial approach which recognises that not all the elements can be directly compared with all the others. In fact when many criteria are considered, contradictions in the ranking are bound to exist and the higher the number of criteria, the higher the probability that contradictions in the ranking occur. The Hasse diagram technique (HDT) is a very useful tool to perform partial order ranking. The results of the partial order ranking are visualised in a diagram, called Hasse diagram. Incomparable elements are located at the same geometrical height and as high as possible in the diagram, thus incomparable elements are arranged in levels. The quality of a ranking procedure has to be evaluated by a deep analysis and by several indices, i.e. scalar functions that describe features of an ordered set and allow comparison among different rankings. For this purpose, new indices for ranking analysis are proposed here, compared with the ones found in literature and tested on theoretical examples and on real data. 相似文献
66.
The densities of aqueous solutions of the phosphonium halides, Bu
4-n
Ph
n
PX(n=0–4), some of which were synthesized from the phosphines, were measured at 15, 25 and 35°C. Partial molal volumes at infinite dilution,
, and B
v
coefficients for the apparent molal volumes were determined at each temperature. For the first four cations
varies little with n. For all salts B
v
are negative but become less negative with increasing n. The temperature dependence of B
v
is positive for butyl-rich salts (n<2) but negative for phenyl-rich salts (n>1). Also it appears that
is relatively large for phenyl-rich cations in comparison with that for butyl-rich cations. 相似文献
67.
Densities of boldine + alcohol binary mixtures were measured over the whole accessible range of boldine compositions at temperatures from 283.15 to 333.15 K using an Anton-Paar digital vibrating glass tube densimeter. The binary systems studied include, as a solvent, seven normal alcohols from n-C1 to n-C6, n-C8, and isopropanol. The density of these systems has been found an increasing function of the boldine composition. A new methodology based on density data of solutions of solid solutes with normal alcohols is described in order to determine solid molar volume of pure solutes. This methodology was validated with pure solid naphthalene molar volumes data at 298.15 K, with an average uncertainty of 6%. 相似文献
68.
Martínez-Pla JJ Martín-Biosca Y Sagrado S Villanueva-Camañas RM Medina-Hernández MJ 《Journal of chromatography. A》2004,1048(1):111-118
Capillary electrophoresis (CE) is a powerful technique for enantiomer separations due to its intrinsic high separation efficiencies, speed of analysis, low reagent consumption and small sample requirements. However, some chiral selectors present strong background UV absorption providing high detection limits. The present paper deals with the application of the partial-filling technique to the separation of bupivacaine enantiomers by capillary electrophoresis using human serum albumin (HSA) as chiral selector. In this procedure the cationic surfactant cetyltrimethylammonium bromide (CTAB) was used as a dinamic capillary coating in order to reduce the electro-osmotic flow and detect both bupivacaine enantiomers out of the chiral selector plug. Several experimental conditions such as CTAB concentration, pH, HSA concentration and plug length, background electrolyte concentration, temperature and voltage were studied. Under the selected conditions it is possible to detect the separated enantiomers out of the HSA plug in less than 4 min using 50 mM Tris pH 8 as background electrolyte with 50 microM CTAB, at 30 degrees C and using a separation voltage of 25 kV. The proposed methodology was then validated for analytical purposes and applied to the analysis of pharmaceutical preparations commercially available. The results obtained with the proposed methodology were in good agreement with those declared by the manufacturers. The simplicity, sample throughput, accuracy, reproducibility and low cost of the proposed method make it suitable for the control of the enantiomeric composition of bupivacaine in pharmaceuticals. 相似文献
69.
Bei-sheng Kang Mao-chun Hong Ting-bin Wen Han-qin Liu Jia-xi Lu 《Journal of Cluster Science》1995,6(3):379-401
Simple fragments of transition metal 1,2-bidentate thiolates, the so-called building blocks of the general compositions ML3, ML2, ML, M(O)L2, ML2L, MLL, etc. have been proposed to constitute the di-, tri- and tetranuclear complexes concerned in this review. Structureal regularities and characteristics have been discussed and summarized according to the thiolato ligands edt and pdt, bdt and tdt, mp, and mpo, and mpp, respectively.Abbreviations H2mpo
o-mercaptophenol
- Hmpo
2-mercaptopyridine-N-oxide
- R2dtc
N,N-dialkyldithiocarbamate
- Haet
2-aminoethanethiol
- H2bdt
o-benzenedithiol
- H2pdt
1,2-propanedithiol
- H2tdt
toluene-3,4-dithiol
- Hmpp-mppH
bis-(3-hydroxy-2-pyridyl)disulfide
- Hmp-mpH
bis-(2-oxyphenyl)disulfide
- H2edt
1,2-ethanedithiol
- dppe
1,2-bis(diphenylphosphino)ethane
- H2tedt
3,4,5,6-tetrachlorobenzene-1,2-dithiol
- H2tpdt
3-thiapentane-1,5-dithiol
- H2mnt
maleonitriledithiol
- Him
imidazole
- Bz
benzyl
- py
pyridine 相似文献
70.
We have performed Monte Carlo simulations of hard spheres under gravity. Vertical boundaries are hard walls, which are well separated with each other. On the other hand, the periodic boundary condition is imposed in the horizontal direction. While we previously reported enhancement of crystallinity as well as crystallization due to gravity, we present here the results that demonstrate the succession of a defect. In case that the crystal formed at the bottom of the system includes kinds of stacking disorders for the (0 0 1) growth, twin band structure develops as mediated by a stacking disorder succeeded in the crystal formed in the fluid region which lies on the bottom crystal. In case that the stacking structure along horizontal direction changes from the (1 1 1) stacking to the (0 0 1) stacking, twin band structure in the (0 0 1) stacking region develops as succeeded in the crystal transformed. The twin band structure also becomes large with its upward growth. 相似文献