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101.
Machuca F de León SG Centeno A Fierro JL 《Journal of colloid and interface science》2001,237(2):290-293
The equilibrium parameters for the adsorption of Mo(VI) on gamma-Al(2)O(3) and of Co(II) and Pt(IV) on MoO(3)/gamma-Al(2)O(3) were determined. The adsorption isotherms were performed from aqueous solutions of the corresponding precursors on two different alumina supports. According to the classification given by Giles, L-type-shaped, subgroup 2, adsorption curves were found for the system Mo on gamma-Al(2)O(3), L-type, subgroup 1, for the Pt on MoO(3)/gamma-Al(2)O(3), and S-type for Co on the MoO(3)/gamma-Al(2)O(3) system. Numerical calculations were carried out for all the isotherms to find the equilibrium parameters. These constants are being used to model the development of Pt, Co, and Mo profiles on MoO(3)/gamma-Al(2)O(3) or gamma-Al(2)O(3) extrudates, respectively, which belong to the new generation of noble-metal-MoO(3)/gamma-Al(2)O(3)-supported catalysts to be used in oil-refining processes. Copyright 2001 Academic Press. 相似文献
102.
Boris U. Stambuk Mary Ann Franden Arjun Singh Min Zhang 《Applied biochemistry and biotechnology》2003,106(1-3):255-263
The kinetics and regulation of d-xylose uptake were investigated in the efficient pentose fermentor Candida succiphila, and in Kluyveromyces marxianus, which assimilate but do not ferment pentose sugars. Active high-affinity (K
m
∼ 3.8 mM; V
max ∼ 15 nmol/[mg·min]) and putative facilitated diffusion low-affinity (K
m
∼ 140 mM; V
max ∼ 130 nmol/[mg·min]) transport activities were found in C. succiphila grown, respectively, on xylose or glucose. K. marxianus showed facilitated diffusion low-affinity (K
m
∼ 103 mM; V
max ∼ 190 nmol/[mg·min]) transport activity when grown on xylose under microaerobic conditions, and both a low-affinity and an
active high-affinity (K
m
∼ 0.2 mM; V
max ∼ 10 nmol/[mg·min]) transport activity when grown on xylose under fully aerobic conditions. 相似文献
103.
Summary The complexones EDTA, DCTA and EGTA were investigated as eluting agents at various pH-values for the simultaneous separation of 9 cations and 6 anions using ion chromatography on a silica gel based anion exchanger (Nucleosil 10-Anion II). 1,2-Diaminocyclohexanetetraacetic acid (DCTA) proved to be the best eluting agent. UV spectrophotometry was used for both direct and indirect detection of the anions and anionic metal complexes and a detailed study was carried out with respect to selectivity of detection. This was facilitated by referring to the UV absorption spectra of the anions and metal complexes involved. By choice of a suitable wavelength between 203 and 270 nm and taking into account pH effects, a number of selective determinations were possible. Examples include Pb and Cu in the presence of excess of Ca and Mg as well as nitrate, nitrite and bromide in a large excess of chloride and sulphate. Some examples of detection limits are (g/l) nitrate 2, Fe(III) 3, Cu 9 and Pb 12 (sample volume 20 l, direct UV-detection). The Chromatographie behaviour of Fe(II) and Fe(III) was studied and discussed. Drinking water was analysed for chloride, nitrate and sulphate as well as Ca and Mg using DCTA in the eluent. Complete analyses can be carried out in less than 15 min.
Herrn Prof. Dr. R. Neeb zum 60. Geburtstag gewidmet 相似文献
Herrn Prof. Dr. R. Neeb zum 60. Geburtstag gewidmet 相似文献
104.
Vyacheslav Ya. Sosnovskikh Boris I. Usachev Mikhail I. Kodess 《Tetrahedron letters》2004,45(39):7351-7354
Reactions of chromones with dilithiooximes proceed via nucleophilic 1,2-addition to give, on acidification, 4H-chromene-4-spiro-5′-isoxazoline derivatives in high yields. On treatment with concentrated H2SO4 the isoxazoline ring of this novel spiroannulated heterocyclic system opens to give α,β-unsaturated oximes, which undergo nitrosation, bromination, and the Beckmann rearrangement to the corresponding spiroisoxazolines and α,β-unsaturated amides, respectively. The latter can be obtained directly by the Beckmann rearrangement of 4H-chromene-4-spiro-5′-isoxazolines. 相似文献
105.
Ivan Gutman Sabina Gojak Niko Radulović Boris Furtula 《Monatshefte für Chemie / Chemical Monthly》2006,137(3):277-284
Summary. In a recent work it was demonstrated that in linear hexagonal chains the distribution of π-electrons into rings (as computed
by means of the Randić–Balaban method) is uniform, irrespective of the nature of the terminal fragments. We now establish that an analogous, yet somewhat
more complex, uniformity in the π-electron distribution exists also in double linear hexagonal chains, as well as in some
other benzenoid systems. 相似文献
106.
The cellular mechanism based on P-glycoprotein (PGP) for its drug pump function has become very important in multidrug resistance (MDR) research. A method has been established to characterize PGP on single K562 cell by coupling capillary electrophoresis with laser induced fluorescence detection. A permeable intact cell after the immunoassay binding with fluorescence labeling antibody was injected into the capillary and directly separated without lysis. It was found that once 5-10 optional cells were detected in batch, the PGP amount on this cell line could be outlined and calculated clearly. The PGP amount on K562 MDR cell line is 3.88 times higher than that on K562 sensitive cell line. These two cell lines with immunoassay binding were also analyzed by injection of multi-cells in order to improve the throughput. A resistance factor so called multidrug resistance multiple (MRM) was introduced to evaluate the MDR difference between cell lines. The MRM values of the cell line K562 measured by single cell analysis are well correlated with those by flow cytometry, which also prove the validity of our method in single cell analysis for the possibility of cancer diagnosis, pharmacokinetics and drug screening in future. 相似文献
107.
The association of a C3v-symmetrical calix[6]tris-amine with different concave tris-carboxylic acids of various degrees of flexibility has been explored by 1H NMR spectroscopy. In all cases, self-assembled structures directed by the selective inclusion of a neutral guest molecule were obtained, the more preorganized being stable in protic solvents. With a rigid C3-symmetrical cap, chiral guest recognition in the calixarene cavity resulted. A large tris-acidic partner gave a unique molecular ditopic receptor that is able to simultaneously accommodate two neutral molecules in two distinct hydrophobic cavities with different binding processes. 相似文献
108.
Perfluoromethyl Element Ligands. XXIX. Preparation and Spectroscopic Investigation of M(CO)4L2 Complexes (M ? Cr, Mo, W; L ? Me2PSMe, Me2PSeMe, (CF3)2PSMe, (CF3)2PSMe) The complexes M(CO)4L2 (see Inhaltsübersicht) have been prepared by the reaction of tetracarbonyl norbornadiene metal compounds M(CO)4NBD with L at room temperature or 35°C, respectively. The cis-complexes formed in the first step undergo rearrangement to trans-isomers at higher temperatures. New compounds have been characterized by analytical and spectroscopic (IR, NMR, MS) methods. 相似文献
109.
This review covers our extensive research activities in the area of fluorine containing phospha- and arsaalkenes as well as selenocarbonyls, which differ considerably in their properties and reactivities from their alkyl and aryl counterparts and thus contribute in a gratifying manner to the still growing field of unsaturated element-carbon compounds of 3rd and 4th row main group elements E. Of particular interest is the influence of the fluorine substituents and other small groups (OR, NR2) with either inductive and/or mesomeric effects on the polarity and reactivity of the EC bond. Addition reactions of proton acidic and hydridic polar HX reactants as well as [2+2], [3+2] and [4+2] cycloadditions have been thoroughly studied. The results obtained allow a classification of the EC systems within five different types, A to E, and prove a change from “normal” to “inverse” heteroalkenes in this sequence. The ligand properties of some derivatives have also been investigated in some detail. 相似文献
110.