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971.
A rapid, accurate and precise analytical method to determine the stoichiometry of pure, excess lithium and magnesium-doped Li1+yCoO2 materials is described. The method is based on the determination of lithium, cobalt and magnesium by flame atomic absorption spectrometry after dissolution of samples in dilute hydrochloric acid. Five-point calibration curves using aqueous standard solutions have been constructed for all the analytes. Relative standard deviation (R.S.D.) of five repeated measurements are better than 0.3% for all metals when the absorbance signal of analytes is set near the middle of the regression lines.The total oxygen content is indirectly determined by potentiometric titration of average oxidation state of cobalt. The Co3+ present in the oxide powders is reduced to Co2+ at room temperature with a known excess of 0.1 M Fe2+ solution in 6 M sulphuric and phosphoric acid mixture. The samples completely dissolved in a few minutes developing a pink coloured and clear solution. The excess of Fe2+ ions is back titrated with potassium dichromate standard solution using automated potentiometric end-point detection. The difference between the total cobalt content (found by AAS) and Co3+ (found by potentiometric titration) gives the amount of Co2+ present in the materials. The S.D. of the determined Co3+ value has been estimated to be below 0.03 mg for samples of 10-20 mg. By the proposed method the LiCoO2 is well characterised and can be applied as a standard reference material for use in lithium batteries technology. 相似文献
972.
Masao Kato Takao Shiraga Tatsumi Kimura Takashi Fukuda Hiro Matsuda Hachiro Nakanishi 《先进技术聚合物》2002,13(2):120-126
We synthesized some novel rigid NLO‐active maleimide copolymers bearing DR‐1 moieties ( PMPD , PHSD and PHND ). All copolymers exhibited high Tg's (190~197 °C), good solubilities for common solvents and excellent film‐forming properties. Dependence of film thickness on the d33 value for the poled copolymer films induced by corona poling was investigated and it was demonstrated that in less than thickness of 0.3 µm decrease of the thickness gives rise to remarkable increase in the d33 value. The poled copolymer films exhibited large d33 values (270 × 10?9 esu (film thickness 0.13 µm) for PMPD , 290 × 10?9 esu (0.12 µm) for PHSD and 350 × 10?9 esu (0.08 µm) for PHND ) as well as large r33 values (51.0 pmV?1 for PMPD and 60.4 pmV?1 for PHND ) which are significantly large compared to the value of LiNbO3 (31 pmV?1) as a typical EO material. The d33 values of the poled copolymers were kept constant even after standing 1000h at 80 °C, although a small decrease was observed at an initial stage. Further, the d33 values did not change up to ca. 123 °C upon heating at the rate of 10 °C/min in all cases. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
973.
Tian-Fu LiuHua-Kuan Lin Shou-Rong ZhuZhong-Ming Wang Hong-gen WangHong-Wei Sun Xue-Bing LengYun-Ti Chen 《Journal of Molecular Structure》2002,605(1):117-122
The Mn(II) and Zn(II) complexes of N,N′-diisopropyl-1,10-phenanthroline-2,9-dimethanamine have been synthesised, and the structure of the two complexes have been studied by X-ray crystallography. 相似文献
974.
975.
G. Matuschek J. Cyrys D. Lenoir A. Kettrup 《Journal of Thermal Analysis and Calorimetry》1993,40(2):533-535
The effect of oxydation of particulate carbon as a part of fly ash has been studied by mean of differential scanning calorimetry
(DSC) and simultaneous thermal analysis/mass spectrometry (TA/MS). The results from different carbon modifications added to
fly ash were discussed and compared to those of the pure samples.
Zusammenfassung Mittels DSC und Thermoanalyse/Massenspektrometrie wurde der Effekt der Oxidation von Kohlenstoff als Teil von Flugasche untersucht. Die durch Zusatz verschiedener Kohlenstoffarten zu Flugasche erhaltenen Ergebnisse wurden diskutiert und mit denen von reinen Proben verglichen.相似文献
976.
The adsorption properties of the new carbon materials, sibunites, which are mesoporous samples with a developed surface of pores, were studied. The isotherms of the adsorption of benzene vapor were determined to estimate the porous structure of these materials. The principal methods for calculating the parameters of the porous structure of sibunites were analyzed. The application of the BET equation even in the presence of a small number of micropores can distort the results, therefore the most suitable method for estimating the surface of mesopores is one that is based on the Dubinin—Zaverina equation. The estimation of the surface of sibunites using water vapor adsorption is demonstrated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1377–1380, August, 1993. 相似文献
977.
Bromophenol blue indicator was used in UV-visible spectrophotometric measurements to study ion association constants of alkali metal fluorides. The equilibrium constants for the ion pair formation of the alkali metal fluorides were determined as a function of ionic strength at one atmosphere pressure and 25°C. The effect of pressure on these association constants was measured at a constant total ionic strength of 1.0 mol-kg–1 over a pressure range of 1 to 2000 atmospheres at 25°C. The pressure dependences of the stoichiometric association constants of the alkali metal fluorides are given by: lnK
LiF
*
=0.77–2.47×10–4P–2.12×10–8P2; lnK
NaF
*
=0.53–1.08×10–4P–1.66×10–8P2; lnK
KF
*
=0.24–4.41×10–5P–7.15×10–8P2; lnK
RbF
*
=–0.17–8.65×10–5P–4.51×10–8P2; and lnK
CsF
*
= –0.37–1.14×10–4P–6.82×10–8P2, where P is the pressure in atmospheres. The stoichiometric molar volume and compressibility changes for ion pair formation of the alkali metal fluorides were evaluated from the pressure dependence of K
MF
*
data. The thermodynamic association constants were also calculated making use of activity coefficient data from the Pitzer equations. The partial molal volume and compressibility changes for ion pair formation of each alkali metal fluoride are reported. 相似文献
978.
Monika Tarnowska Adam Liwo Mark D. Shenderovich Inta Liepiņa Alexander A. Golbraikh Zbigniew Grzonka Anna Tempczyk 《Journal of computer-aided molecular design》1993,7(6):699-719
Summary The effect of the substitution in position 1 on the low-energy conformations of the oxytocin/vasopressin 20-membered ring was investigated by means of molecular mechanics. Three representative substitutions were considered: -mercapto-,-dimethyl)propionic acid (Dmp), (-mercapto-,-cyclopentamethylene)propionic acid (Cpp), both forming strong antagonists, and (,-dimethyl--mercapto)propionic acid (-Dmp), forming analogs of strongly reduced biological activity, with the -mercaptopropionic (Mpa) residue taken as reference. Both ECEPP/2 (rigid valence geometry) and AMBER (flexible valence geometry) force fields were employed in the calculations. Three basic types of backbone conformations were taken into account which are distinguished by the type of -turn at residues 3 and 4: 1/III, II, and I/III, all types containing one or two intra-annular hydrogen bonds. The allowed (ring-closed) disulfide-bridge conformations were searched by an algorithm formulated in terms of scanning the disulfide-bridge torsional angle C-S-S-C. The ECEPP/2 and AMBER energies of the obtained conformations were found to be in reasonable agreement. Two of the low-energy conformers of the [Mpa1]-compound agreed very well with the cyclic part of the two conformers found in the crystal structure of [Mpa1]-oxytocin. An analysis of the effect of -substitution on relative energies showed that the conformations with the N-C-CH2-CH2 (1) and C-CH2-CH2-S (1) angles of the first residue around (–100°, 60°) and (100°, –60°) are not affected; this in most cases implies a left-handed disulfide bridge. In the case of -substitution the allowed values of 1 are close to ± 60°. This requirement, being in contradiction to the one concerning -substitution, could explain the very low biological activity of the -substituted analogs. The conformational preferences of substituted compounds can largely be explained by the analysis of local interactions within the first residue. Based on the selection of the conformations which are low in energy for both the reference and -substituted compounds, two distinct types of possible binding conformations were proposed, the first one being similar to the crystal conformer with a left-handed disulfide bridge, the second one having a right-handed bridge, but a geometry different from that of the crystal conformer with the right-handed bridge. The first type of disulfide-bridge arrangement is equally favorable for both I/III and II types of backbone structure, while the second one is allowed only for the II type of backbone. No conformation of the I/III type has a low enough energy to be considered as a possible binding conformation for all of the active compounds studied in this work. 相似文献
979.
Summary A new and highly sensitive HPLC method for the simultaneous determination of pirarubicine (THP-doxorubicin) and its metabolites, adriamycin and adriamycinol, in human plasma, is described. Samples were treated by liquid-liquid extraction, the organic phase removed and the residue dissolved in methanol. Separation was on a Lichrocart Supersher RP 8 column, (250×4 mm) 4 m, with a mobile phase of acetonitrile/methanol/formate-buffer. 相似文献
980.
Andreas Manz Elisabeth Verpoorte Carlo S. Effenhauser Norbert Burggraf Daniel E. Raymond D. Jed Harrison H. Michael Widmer 《Journal of separation science》1993,16(7):433-436
Miniaturization of separation columns implies equally reduced vol- umes of injectors, detectors, and the connecting channels. Planar chip technology provides a powerful means for the fabrication of micron-sized structures such as channels. This is demonstrated by two examples. An optical absorbance detector chip exhibits the expected behavior of a 1 mm optical path length cell despite its volume of 1 nL. A capillary electrophoresis device allows integrated injections of 100 pL samples, efficiencies of 70,000 to 160,000 theoretical plates in 10 to 20 seconds, and external laser-induced fluorescence detection at any capillary length of choice between 5 and 50 mm. 相似文献