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991.
New approach for chemometrics algorithm named region orthogonal signal correction (ROSC) has been introduced to improve the predictive ability of PLS models for biomedical components in blood serum developed from their NIR spectra in the 1280-1849 nm region. Firstly, a moving window partial least squares regression (MWPLSR) method was employed to locate the region due to water as a region of interference signals and to find the informative regions of glucose, albumin, cholesterol and triglyceride from NIR spectra of bovine serum samples. Next, a novel chemometrics method named searching combination moving window partial least squares (SCMWPLS) was used to optimize those informative regions. Then, the specific regions that contained the information of water, glucose, albumin, cholesterol and triglyceride were obtained. When an interested component in the bovine serum solution, such as glucose, albumin, cholesterol or triglyceride is being an analyte, the other three interests and water are considered as the interference factors. Thus, new approach for ROSC has employed for each specific region of interference signal to calculate the orthogonal components to the concentrations of analyte that were removed specifically from the NIR spectra of bovine serum in the region of 1280-1849 nm and the highest interference signal for model of analyte will be revealed. The comparison of PLS results for glucose, albumin, cholesterol and triglyceride built by using the whole region of original spectra and those developed by using the optimized regions suggested by SCMWPLS of original spectra, spectra treated OSC for orthogonal components of 1-3 and spectra treated ROSC using selected removing the highest interference signals from the spectra for orthogonal components of 1-3 are reported. It has been found that new approach of ROSC to remove the highest interference signal located by SCMWPLS improves of the performance of PLS modeling, yielding the lower RMSECV and smaller number of PLS factors. 相似文献
992.
Hydrophobic layered double hydroxides (LDHs): Selective adsorbents for liquid mixtures 总被引:1,自引:0,他引:1
The external and internal surface area of the calcium aluminum double hydroxide [Ca2Al(OH)6] NO3 ⋅ 2H2O were hydrophobized by the anionic surfactants sodium dodecylsulfate and sodium dodecyl-benzene sulfonate. The adsorption
behavior towards liquid mixtures (benzene/n-heptane and n-propanol/ toluene) was studied by determining the surface excess adsorption isotherms, the heats of immersion in these liquids,
and the basal spacing, i.e. the expansion of the interlayer space.
Both hydrophobic layered double hydroxides (LDHs) adsorbed n-hep-tane, benzene, toluene, and n-pro-panol between the layers with considerable increase of the basal spacing. Interlamellar swelling of the hydrophobizised
LDHs in n-heptane was fundamentally different to the behavior of hydrophobized 2 : 1 clay minerals (smectites, vermiculites). The surface
excess isotherms for benzene/ heptane mixtures were U-shaped and indicate preferential adsorption of benzene. Dodecylbenzene
sulfonate double hydroxide preferentially adsorbed propanol from n-propanol/ toluene mixtures but the dodecyl-sulfate derivative adsorbed both compounds.
Received: 23 January 1997 Accepted: 10 February 1997 相似文献
993.
Kinetic data for the hydrolysis of N-picolinoylimidazole (I) and 2,4-dinitrophenylpicolinate (II) in AOT [bis(2-ethylhexyl) sodium sulfosuccinate] microemulsions are used to determine for the first time the two partition constants for each substrate (i.e. K(wi) and K(oi), corresponding to the incorporation of substrate molecules from water microdroplets and the continuous medium, respectively, into the interface). Application of the pseudophase formalism to the partition constants allowed the rate constant in each phase to be determined. The rate of hydrolysis of II increased with decreasing polarity of the medium; as a result, the hydrolysis reaction took place largely at the interface. On the other hand, the rate of hydrolysis of acylimidazole I decreased with decreasing polarity, possibly as a result of changes in the resonance structures of the reagent causing the hydrolysis process to occur preferentially in water microdroplets. 相似文献
994.
Near-infrared (NIR) spectra in the region of 5000-4000 cm−1 with a chemometric method called searching combination moving window partial least squares (SCMWPLS) were employed to determine the concentrations of human serum albumin (HSA), γ-globulin, and glucose contained in the control serum IIB (CS IIB) solutions with various concentrations. SCMWPLS is proposed to search for the optimized combinations of informative regions, which are spectral intervals, considered containing useful information for building partial least squares (PLS) models. The informative regions can easily be found by moving window partial least squares regression (MWPLSR) method. PLS calibration models using the regions obtained by SCMWPLS were developed for HSA, γ-globulin, and glucose. These models showed good prediction with the smallest root mean square error of predictions (RMSEP), the relatively small number of PLS factors, and the highest correlation coefficients among the results achieved by using whole region and MWPLSR methods. The RMSEP values of HSA, γ-globulin, and glucose yielded by SCMWPLS were 0.0303, 0.0327, and 0.0195 g/dl, respectively. These results prove that SCMWPLS can be successfully applied to determine simultaneously the concentrations of HSA, γ-globulin, and glucose in complicated biological fluids such as CS IIB solutions by using NIR spectroscopy. 相似文献
995.
Various combinations of the hypernetted chain (HNC) equation with the mean spherical approximation (MSA) and the Percus-Yevick
(PY) equation are compared both for a well-known aqueous 2-2 electrolyte model solution and for real acetonitrile solutions.
Belloni's self-consistency test shows that classical HNC calculations yield the best compressibility data for the two systems
despite an apparently unrealistic g++ maximum in the case of the aqueous solution. Effective concentration-dependent potentials making use of the dependence of
the solution permittivity on electrolyte concentration are used for HNC calculations of osmotic coefficients for methanol
solutions. 相似文献
996.
997.
An achiral monomeric surfactant (sodium 10-undecenyl sulfate, SUS) and a chiral surfactant (sodium 10-undecenoyl L-leucinate, SUL) were synthesized and polymerized individually to form poly-SUS and poly-SUL. These surfactants were then copolymerized at various molar ratios to produce a variety of copolymerized surfactants (CoPSs), possessing both achiral (sulfate) and chiral (leucinate) head groups. The CoPSs, poly-SUS, poly-SUL, and sodium dodecyl sulfate were characterized using several analytical techniques. The aggregation numbers of the polymeric surfactants and the partial specific volumes were determined by the use of fluorescence quenching and density measurements, respectively. These polymeric surfactants were investigated as novel pseudostationary phases in micellar electrokinetic chromatography (MEKC) for the separation of chiral and achiral solutes. Solute hydrophobicity was found to have major influence on the MEKC retention of alkyl phenyl ketones. In contrast, hydrogen-bonding ability of benzodiazepines is the major factor that governs their retention, but hydrophobicity has an insignificant effect on MEKC retention of benzodiazepines. 相似文献
998.
Yoshihiro Sohtome Dr. Nobuko Takemura Keisuke Takada Rika Takagi Toshitsugu Iguchi Kazuo Nagasawa Prof. Dr. 《化学:亚洲杂志》2007,2(9):1150-1160
Catalytic enantio‐ and diastereoselective nitroaldol reactions were explored by using designed guanidine–thiourea bifunctional organocatalysts under mild and operationally simple biphasic conditions. These catalytic asymmetric reactions have a broad substrate generality with respect to the variety of aldehydes and nitroalkanes. Based on this catalytic nitroaldol process, straightforward syntheses of cytoxazone and 4‐epi‐cytoxazone were achieved. These catalytic nitroaldol reactions require KI as an additive for highly asymmetric induction; it operates by inhibiting the retro mode of the reaction. On the basis of studies of structure and catalytic‐activity relationships, a plausible guanidine–thiourea cooperative mechanism and a transition state of the catalytic reactions are proposed. Drastic substituent effects on the catalytic properties of this catalyst may lead to the development of new chiral surfactants. 相似文献
999.
In the present work, three polymeric surfactants were prepared and used as demulsifiers; polyalkyl phenol formaldehyde monoethanol amine ethoxylate, eo, 136(D1), polyalkyl phenol formaldehyde diethanol amine ethoxylate, eo, 37(D2) and polyalkyl phenol formaldehyde triethanol amine ethoxylate, eo, 21.5(D3). Their demulsification potency in breaking water‐in‐crude oil emulsions was investigated. In this respect, two naturally occurring Egyptian water‐in‐oil (w/o) emulsions, one of them was waxy and the other was asphaltenic, were used in order to study the demulsification power of these compounds. The data revealed that, the resolution of water from waxy crude emulsion was easier than asphaltenic crude emulsion. The demulsification efficiency increases with increasing demulsifier concentration, contact time and temperature. The interfacial tension (IFT) at the crude oil–water interface was measured, it was found that the concentration of demulsifiers required to cause a minimum IFT are always less than these indicating a maximum demulsification efficiency. All the results were discussed in relation to emulsifier chemical structure and crude oil composition. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
1000.
Ikuyoshi Tomita Toru Abe Koji Takagi Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1995,33(14):2487-2492
Block copolymers of alkoxyallenes were obtained in high yield by the two-stage living coordi-nation polymerization of two kinds of alkoxyallenes using an allylnickel catalyst. The resulting copolymers had narrow molecular weight distributions (~ 1.1), regardless of the order of the monomer additions. When an alkoxyallene-bearing hydrophilic substituent was used as a co-monomer for the block copolymerization with that bearing a hydrophobic one, the resulting copolymer showed amphiphilic properties. For example, a block copolymer obtained by the copolymerization of n-hexyloxyallene with diethylene glycol allenyl methyl ether was soluble in water as well as n-hexane. © 1995 John Wiley & Sons, Inc. 相似文献