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991.
Heather Davis Walter Skrzypek Arshad Khan 《Journal of polymer science. Part A, Polymer chemistry》1994,32(12):2267-2274
The iodine binding capacity (IBC) of amylopectin (AP, from potatoes) is determined to be around 0.38% (w/w) of the total AP in the solution. The mass of iodine bound comprises about 13.6% of the mass of AP involved with the complex, suggesting that with every four iodine atoms bound there are 23 anhydroglucose residues (AGU). Since our previous study indicates that four iodine atoms within the helix of 11 AGUs form a chromophore unit in the API complex, only 48% of the AGUs (11 out of 23) in the AP molecule are directly involved with the iodine. The heat of reaction for the API complex formation is determined to be around ?47 kJ/mol of I–I units bound and is significantly lower in magnitude than that of the amylose-iodine (AI) complex [Biopolymers, 31 , 57 (1991)]. A possible mechanism has been proposed for the formation of AI and API complexes with fixed compositions. © 1994 John Wiley & Sons, Inc. 相似文献
992.
A highly oxygenated, novel pentacyclic bis-oxa-bridged compound 8 was synthesized with remarkable efficiency starting from readily available tetrachloro-5,5-dimethoxyclopentadiene and 1,4-cyclohexadiene in three steps. The ruthenium-catalyzed oxidation of 2:1 bis-adduct 1 followed by a one-pot transformation of the resulting bis-alpha-diketone 3 furnished (after esterification) the title compound in an overall yield of 29.1%. The versatility of this simple method was further demonstrated with other norbornyl alpha-diketones to obtain the corresponding strained oxa-bridged derivatives. 相似文献
993.
The role of anion-exchange resin beads in the initiation of reactions of tertiary amines with 2,4-dinitrophenylhydrazine has been explored. This reagent has been used for the selective detection and determination of aliphatic amines. Radiochemical studies have been performed to show that the coloured species is adsorbed but not exchanged on ion-exchange beads. A model for the interaction is proposed. 相似文献
994.
V. Lange M. A. Khan U. Eichmann W. Sandner 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,18(4):319-324
We report on the spectroscopy of highly excited strontium ions after resonant multistep laser excitation. The states observed belonged to then s (26≦n≦79),n d (25≦n≦83),n f (28≦n≦86) andn g (30≦n≦81) series of Sr+. A least squares fit has been applied to determine the quantum defects and their linear energy dependence in each series, together with the ionisation limit of Sr+. The analysis of our data lead to a revised value for this ionisation limit of 88 965.18±0.02 cm?1, with respect to the ground state of the Sr+ ion. Analysis of the non core-penetratingn g states yielded experimental values for the dipole and quadrupole polarizability of Sr++, which are in satisfactory agreement with previous calculations. 相似文献
995.
M. M. Taqui Khan Debabrata Chatterjee H. C. Bajaj 《Reaction Kinetics and Catalysis Letters》1993,49(1):81-85
Selective oxidation of cyclohexane to cyclohexanone was carried out in a RuCl3-pyridine-acetic acid-KHSO5 mixture. This system yields 2.8% of cyclohexanone (based on oxone concentration) under the conditions employed. Mechanistic postulate for the oxidation reaction involves the formation of a carbene intermediate (Ru=C) prior to the ketone formation. 相似文献
996.
997.
998.
The synthesis and structures and thermal properties of two compounds: {(H2O)2K--(H2O)3-Co(H2O)3}2[V10O28] (1) and {(H2O)2K--(H2O)3-Ni(H2O)3}2[V10O28] (2) are described. These compounds have been prepared by the reaction of aqueous solutions (pH=3.5) of KVO3with MCl2·6H2O (M=Co, Ni) at 70–72°C. The isomorphous structures of the two compounds consist of interlinked chains composed of arrays of {V10O28} clusters which are joined through {(H2O)2K--(H2O)3-M(H2O)3} bridges. Thermogravimetric studies revealed the complete removal of all water molecules in multiple steps in the temperature range 90–208°C. 相似文献
999.
N. G. Zaitseva C. Deptula Kim Sen Khan O. Knotek P. Mikeć V. A. Khalkin 《Journal of Radioanalytical and Nuclear Chemistry》1988,121(2):307-321
Absorption of carrier-free T1 from nitric acid solutions of lead by ammonium 12-molybdophosphate fixed in the matrix of porous Teflon (AMP-sorbent) has been investigated. Effective separation of T1 and Pb is shown to take place. Elution processes of T1 from AMP-sorbent have been investigated. It is found that complete extraction of T1 is achieved upon dissolving AMP in concentrated ammonia. Further purification and concentration of T1 are performed by means of cation exchange chromatography on Dowex-50 or KU-2 resins. Investigation of high temperature behaviour of T1 ultramicroamounts in Pb melt showed that T1 is quantitatively separated out into the gas phase when fluorinating additions of PbF2 or NaF solid salts covering the melt surface are used. The volatile compounds of radiothallium formed were transported by a stream of inert gas (He or N2) from the evaporation zone to the thermochromatographic column, where they were sorbed on the surface in a limited zone with the maximum at 240 °C. Liquid and gas thermochromatographic methods for separation of carrier free radiothallium from protonirradiated lead material have been developed. The radiochemical, chemical and radionuclidic purity of T1 samples complies with requirements of nuclear medicine for201T1 product. Both methods ensure 95% chemical yield of T1 and take about two hours each. 相似文献
1000.
M. Ali A. H. Khan A. K. M. Wahiduzzaman M. A. Malek 《Journal of Radioanalytical and Nuclear Chemistry》1997,219(1):81-87
The trace element concentrations of eight elements (Ca, Cr, Mn, Fe, Ni, Cu, Zn and Pb) in the scalp hair of 49 normal and 55 malnourished children of the Bangladesh population, in the age group of 1 to 5 years were analyzed by the external beam PIXE method to establish their baseline values in normal children for pre-diagnostic screening of deficiency and excess in malnutrition. The results of this investigation show that the ranges of trace elements in hair are somewhat wide. For example, the normal Zn level has the range of 63–377 g·g–1 for 49 subjects. The reasons for these large individual deviations are unknown till now. The average of the elemental concentrations between normal and malnourished groups are compared (t-test,p<0.05). A correlation study has been done on each pair of original data by a non-parametric Speaman's rank test. The frequency distributions of the elements are presented and the results are compared with the data reported in the literature. A substantive correspondence between the present data in hair of both the study groups and the literature values from different countries have been observed but they did not show any regular dependence on the nutritional status of the subjects. Only the low Cu content in the hair of malnourished group can possibly be linked with nutritional disorders as evidenced from this study.Part of a Ph.D. Thesis. 相似文献