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排序方式: 共有353条查询结果,搜索用时 140 毫秒
1.
2.
Harish Seshadri 《Mathematische Zeitschrift》2004,247(3):487-503
We study closed Einstein 4-manifolds which admit S1 actions of a certain type, i.e., warped products. In particular, we classify them up to isometry when the fixed point of the S1 action satisfies certain natural geometric conditions. The proof uses the Bochner-Weitzenböck formula for 1-forms and the theory of minimal surfaces in 3-manifolds.in final form: 22 January 2003 相似文献
3.
Harish C. Bahl Stanley Zionts 《The Journal of the Operational Research Society》1987,38(12):1141-1148
Scheduling the production of several items requires the determination of production quantities in different periods in the presence of resource constraints. Several approximate and heuristic algorithms have been proposed to solve this problem. However, no method for finding an optimal solution has as yet been developed. It is shown that the problem may be solved advantageously using Benders' decomposition. The subproblem in Benders' decomposition is shown to be a transportation problem, and some strategies for solving the master problem are indicated. The paper concludes with a sample problem demonstrating the application of the method. 相似文献
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Chloramine-B has been used as an oxidizing agent in hydrochloric acid medium for the indirect volumetric estimations of hydrogen peroxide, lead dioxide, manganese dioxide, selenium dioxide, sodium formate, sodium sulphide, sodium metavanadate, potassium iodate and copper sulphate using iodine monochloride as a catalyst and pre-oxidiser. Chloroform is used as an indicator. It is coloured pink owing to the liberation of iodine during the titration and becomes light pale yellow at the end-point because of the formation of iodine monochloride. 相似文献
6.
A spectrophotometric method for the determination of cobalt and nickel using a new reagent sodium ethylthioxanthate has been described. The yellow-colored cobalt complex and red-colored nickel complex have been extracted quantitatively using carbon tetrachloride in the pH ranges 4.0–11 and 4.0–6.7, respectively. The colors of these complexes are stable and absorbances have been measured at 389 nm for cobalt and 495 nm for the nickel complexes. Few ions interfere but the method has been applied successfully for the determination of these metal ions in various complex materials. 相似文献
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Gabapentin is an anticonvulsant drug used for the treatment of epilepsy. It is not bound to plasma protein and is not metabolized. A high performance liquid chromatography–mass spectrometric micro method is described in this report for its determination from human plasma. Chromatography was performed on a 50 × 4.6 mm, 4 μm nitrile column and the parent ion detected in the positive ionization mode on single quadrupole analyzer (Q1MI) with atmospheric pressure ionization source. Extraction was carried out on C18, 100 mg/3cc cartridge using 10 μL sample volume. The mean extraction recovery was 97% and within batch and between batch coefficients of variation were <9%. Lack of interference from endogenous substances helped in achieving a highly sensitive method without the need for monitoring fragment ions. The lowest concentration injected on column for calibration curve was 195 pg (range 0.5–64 ng). The method was applied for analysis of samples from a cross-over bio-equivalence study comparing two formulations. 相似文献
9.
Biswanath Das Katta Venkateswarlu Maddeboina Krishnaiah Harish Holla 《Tetrahedron letters》2006,47(49):8693-8697
A simple, efficient and rapid method has been developed for high-yielding regioselective nuclear monobromination of aromatic and heteroaromatic compounds using NBS in the presence of sulfonic-acid-functionalized silica at room temperature. The catalyst works under heterogeneous conditions and can be recycled. 相似文献
10.
S. P. Hasilkar Keshav Chander S. G. Marathe 《Journal of Radioanalytical and Nuclear Chemistry》1990,139(2):263-271
Attempts to carry out potentiometric determination of plutonium (by AgO-oxidation method) following the determination of thorium (by complexometric EDTA titration) gave positively biased irreproducible values of plutonium. In order to understand the factors leading to the erroneous values of plutonium, the effect of varying amounts of AgO and EDTA on redox [Fe(II)/K2Cr2O7] titration in the medium consisting of 1M H2SO4 and 0,4M HNO3 was studied. When AgO (up to 200 mg) was added in the titration medium and destroyed by sulfamic acid prior to the redox titration, the dichromate tittre value (amount of standard K2Cr2O7 solution equivalent to 1 g of Fe(II) solution) showed negative bias. The bias was found to decrease with increase in time interval between AgO destruction and the redox titration. The presence of EDTA (up to 15 mg) gave positive bias in the titre value. Results on the titre values obtained under different conditions of the aqueous medium indicated the possibility of formation of unstable Ag(II)-sulfamic acid compled, which is probably responsible for the irreproducible values of plutonium. 相似文献