排序方式: 共有45条查询结果,搜索用时 46 毫秒
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Mohamed Abdel-Rehim Mohamed Kamel Moustapha Hassan 《Journal of separation science》1995,18(12):757-759
The effect of ammonia on the electron capture detector (ECD) response has been investigated. Nitrogen with different ammonia concentrations (5–20%) was used as make-up gas. Compared to pure nitrogen, the ECD response decreased when the ammonia concentration in the make-up gas was 5%. However, the response increased when the ammonia concentration was 20%. The response factor of 4-chlorophenol increased 4 fold when ammonia was 20%. Also, di- and tri-chlorophenols increased by 30–50%. The nitroaromatic compounds responses increased by about 2–3.7 times with 20% ammonia in the make-up gas. The signal-to-noise (S/N) increased when 20% ammonia in nitrogen was used as make-up gas compared to pure nitrogen. Also, the detector linearity increased by 50% with ammonia. 相似文献
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Moustapha B Marina GA Raúl FO Raquel CM Mahinda M 《Molecules (Basel, Switzerland)》2011,16(11):9397-9403
A phytochemical study of the methanol-soluble fraction of an aqueous extract of a sample of Psittacanthus calyculatus collected from the host plant Prosopsis laevigata (Smooth Mesquite) using several techniques, including co-chromatography coupled with UV detection, chromatographic purifications and IR, NMR and MS studies, resulted in the identification of gallic acid, two flavonol-3-biosides and the nonprotein amino acid N-methyl-trans-4-hydroxy-L-proline. 相似文献
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This paper is devoted to the study of essential self-adjointness of a relativistic Schrödinger operator with a singular homogeneous potential. From an explicit condition on the coefficient of the singular term, we provide a sufficient and necessary condition for essential self-adjointness. 相似文献
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Yuheng Cao Aaron L Nsakanda Moustapha Diaby 《The Journal of the Operational Research Society》2015,66(7):1140-1154
Coalition loyalty programmes (CLPs) are owned and operated as for-profit enterprises. We consider the ordering decisions of rewards that arise in this context, under a general setting in which not only is the demand for rewards uncertain, but also the CLP firm offers bonus points, a very common cooperative promotion mechanism used in loyalty programmes. The rewards are acquired either at a wholesale ‘discounted’ cost or at a wholesale ‘non-discounted’ cost by the CLP firm from its multiple commercial partners and supplied to customers seeking to redeem their accumulated ‘reward points’, subject to commercial partners’ capacities for offering rewards, the firm’s overall budget for purchasing rewards, and its control policy on points liability. We formulate the problem as a stochastic linear programme with recourse and solve it using a sampling-based heuristic solution procedure previously discussed in the literature. We report on the managerial applicability of our model in dealing with the redemption budget spending resulting from changes in demand variability, changes in the redemption budget, and the control of liability levels within a reasonable range. 相似文献