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951.
Li Changjun; Li Zheng; Evans David J.; Zhang Tie 《IMA Journal of Numerical Analysis》2003,23(4):581-592
Golub et al. (2001, BIT, 41, 7185) gave a generalizedsuccessive over-relaxation method for the augmented systems.In this paper, the connection between the SOR-like method andthe preconditioned conjugate gradient (PCG) method for the augmentedsystems is investigated. It is shown that the PCG method isat least as accurate (fast) as the SOR-like method. Numericalexamples demonstrate that the PCG method is much faster thanthe SOR-like method. 相似文献
952.
Many natural products contain carbohydrate moieties that contribute to their biological activity. Manipulation of the carbohydrate domain of natural products through multiple glycosylations to identify new derivatives with novel biological activities has been a difficult and impractical process. We report a practical one‐pot enzymatic approach with regeneration of cosubstrates to synthesize analogues of vancomycin that contain an N‐alkyl glucosamine, which exhibited marked improvement in antibiotic activity against a vancomycin‐resistant strain of Enterococcus. 相似文献
953.
A new synthetic method for the manufacture of glutaric dialdehyde is investigated. Glutaric dialdehyde was prepared by the
addition-hydrolysis reaction of benzimidazolium salt with saturated dihalide as the di-Grignard reagent. The yield of glutaric
dialdehyde by this method can reach 73%. Both infrared spectra and melting point of the compound were consistent with those
reported earlier.
Translated from Journal of Northwest University (Natural Science Edition), 2005, 35(2) (in Chinese) 相似文献
954.
ZhengBin Zhang Chunying Liu Peifeng Li Zhenzhen Wu Cai Lin Huawei Huang Lei Xing Liansheng Liu 《Frontiers of Chemistry in China》2006,1(1):86-97
Many food algae and red tide algae were cultivated in the f/2 medium, and the nitric oxide (NO) concentration of the medium
and the cell density were determined. The experiments on algae were conducted when different concentrations of NO were added
into the medium using two methods. The results show that low concentrations of NO were self-produced by marine algae during
the exponential growth period and were about nmol/L level. But at the end of the period, i.e., 2 or 3 days before the cell
density reaches the maximum, an NO peak appeared, with the NO concentration reaching 10 nmol/L. The NO threshold concentration
exists according to the influence of exogenous NO on the marine phytoplankton growth. One type is the threshold concentration
that can promote algae growth, and its value is between 10 and 1 nmol level, or even lower. The other type can inhibit the
phytoplankton growth, which is about μmol level or higher. The results indicate that red tide algae are far more sensitive
to NO than are food algae. The fundamental experimental outcome above may provide a new clue for red tide chemical forecast
by inspecting the NO change. 相似文献
955.
本文对于用电荷交换方法或低杂波涨落的方法测量高能α粒子作了简短的评述,建议用核反应13C(α,n)16O测量氘-氚聚变等离子体中的高能α粒子,并提出了一种减少杂质污染,增加穿透深度的方法。 相似文献
956.
本探讨了高等代数与解析几何进行一体化教学的必要性,研究了高等代数与解析几何进行一体化教学以后教学内容的协调性与教学手段的合理性,强调了数学实验在高等代数与解析几何一体化教学中的重要性。 相似文献
957.
第二类Fredholm积分方程的泰勒展开解法 总被引:3,自引:0,他引:3
本进一步发展了用Taylor公式求解第二类Fredholm积分方程的方法,并给出了近似解的误差精度分析. 相似文献
958.
959.
960.
§1 IntroductionAt present,boundary value problems (BVPs) are widely investigated with variousmethods and techniques. BVPs with integral boundary conditions constitute a veryinteresting class of problems such as multipoint,three-point,four-point and nonlocalboundary value problems which are considered by many authors.And the existence ofpositive solutions for these problems becomes the subjectof many papers[1—6] .In a recentpaper[7] ,the authors have studied the existence of positive solut… 相似文献