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61.
本文研究了动力系统x=x+P_n(x,y),y=y+Q_n(x,y),这里P_n(x,y),Q_n(x,y)为n次二元多项式齐式,证明了这个系统为可积系统,并且研究了这个奇点的性质。 相似文献
62.
The main results are as follows:
( i ) For the number of chord diagrams of order n, an exact formula is given.
( ii ) For the number of spine diagrams of order n, the upper and lower bounds are obtained. These bounds show that the estimation is asymptotically the best.
As a byproduct, an upper bound is obtained, for the dimension of Vassiliev knot invariants of order n, that is, 1/2 ( n -1)! for any n≥3, and 1/2( n - 1)! - 1/2( n - 2)! for bigger n . Our upper bound is based on the work of Chmutov and Duzhin and is an improvement of their bound ( n - 1)! . For n = 3, and 4,1/2( n - 1)! is already the best. 相似文献
63.
针对防汛金属网在装载过程中易出现网结断裂的情况,通过对不同编织工艺参数的试样的拉伸性能测试,分析了金属网结拉伸断裂的机理和破坏模式,为进一步研究防汛金属网的强度失效问题奠定基础。结果表明:网节的编织工艺参数对其抗拉强度影响较大。编织角越大,网节结构紧密,网丝无滑移,但一定程度上减低了网节的抗拉强度;网节编织长度小,可以充分发挥网丝的抗拉性能,但结构稳定性较差。 相似文献
64.
65.
黄瓜根结线虫拮抗菌筛选及作用机理初探 总被引:13,自引:0,他引:13
采用击倒、驱避、温室盆栽和田间小区试验相结合的方法,对已获得的多株拮抗菌株进行了防治黄瓜根结线虫(Meloidogyne incognita)的筛选实验,并对优势菌株的作用机理进行了初步研究.结果表明,在室内共同培养条件下,S506,Cm05和Ms2菌株表现优秀,对线虫的校正死亡率均在30%以上,其中S506最高,达48.8%;对线虫的驱避实验,以Cm05+S506组合最好;在连茬4,8,11 a的温室土壤上进行的盆栽和田间小区实验表明,S506的防效最高、最稳定,田间校正防效最高达85.29%,显著优于阿维菌素14.89%的防效.S506的抗线虫物质主要是胞外代谢产物. 相似文献
66.
J. Schaller U. Kämpfer S. Schürch L. Kuhn-Nentwig S. Haeberli W. Nentwig 《Cellular and molecular life sciences : CMLS》2001,58(10):1538-1545
CSTX-9 (68 residues, 7530.9 Da) is one of the most abundant toxic polypeptides in the venom of the wandering spider Cupiennius salei. The amino acid sequence was determined by Edman degradation using reduced and alkylated CSTX-9 and peptides generated by
cleavages with endoproteinase Asp-N and trypsin, respectively. Sequence comparison with CSTX-1, the most abundant and the
most toxic polypeptide in the crude spider venom, revealed a high degree of similarity (53% identity). By means of limited
proteolysis with immobilised trypsin and RP-HPLC, the cystine-containing peptides of CSTX-9 were isolated and the disulphide
bridges were assigned by amino acid analysis, Edman degradation and nanospray tandem mass spectrometry. The four disulphide
bonds present in CSTX-9 are arranged in the following pattern: 1-4, 2-5, 3-8 and 6-7 (Cys6-Cys21, Cys13-Cys30, Cys20-Cys48, Cys32-Cys46). Sequence comparison of CSTX-1 with CSTX-9 clearly indicates the same disulphide bridge pattern, which is also found in
other spider polypeptide toxins, e.g. agatoxins (ω-AGA-IVA, ω-AGA-IVB, μ-AGA-I and μ-AGA-VI) from Agelenopsis aperta, SNX-325 from Segestria florentina and curtatoxins (CT-I, CT-II and CT-III) from Hololena curta. CSTX-1/CSTX-9 belong to the family of ion channel toxins containing the inhibitor cystine knot structural motif. CSTX-9,
lacking the lysine-rich C-terminal tail of CSTX-1, exhibits a ninefold lower toxicity to Drosophila melanogaster than CSTX-1. This is in accordance with previous observations of CSTX-2a and CSTX-2b, two truncated forms of CSTX-1 which,
like CSTX-9, also lack the C-terminal lysine-rich tail.
Received 23 July 2001; accepted 31 July 2001 相似文献
67.
平凡纽结分解的个数 总被引:1,自引:1,他引:0
陶志雄 《浙江科技学院学报》2004,16(4):226-227
分解一个有n个二重点的universe的每个二重点可以得到2^n个纽结,章通过构造的方法给出了这2^n个纽结中平凡纽结个数的下界. 相似文献
68.
Herrmann A Svangård E Claeson P Gullbo J Bohlin L Göransson U 《Cellular and molecular life sciences : CMLS》2006,63(2):235-245
Cyclotides are cyclic plant proteins with potent cytotoxic effects. Here we systematically probed the importance of surface-exposed
charged amino acid residues of the cyclotide cycloviolacin O2, using a strategy involving chemical modifications. We show
that the single glutamic acid plays a key role for the cytotoxicity: methylation of this residue produced a 48-fold decrease
in potency. Virtually no change in potency was observed when masking the single arginine residue using 1,2-cyclohexanedione,
while acetylation of the two lysine residues reduced the potency 3-fold. The derivative with modifications at both arginine
and lysine residues showed a 7-fold loss of potency. In addition, we show that the activity is dependent on an intact disulfide
network and that the short sequences between the six cysteine residues, that is, the backbone loops, are devoid of cytotoxic
activity.
Received 11 October 2005; received after revision 3 November 2005; accepted 15 November 2005 相似文献
69.
王树忠 《哈尔滨商业大学学报(自然科学版)》2007,23(4):454-456
在S3中对于任何纽结K都有t(K)≤g1(K)≤h(K)≤t(K) 1成立.基于纽结K的隧道数、1-桥亏格和h-亏格三个几何不变量之间的这种关系,将S3中的纽结定义为p纽结、q纽结和r纽结三类.连同σ纽结,得到了这些纽结连通和的一些重要性质. 相似文献
70.
通过二阶常系数微分算子的零空间及其初值问题解的唯一性,引入了广义B样条曲线的概念,给出了B样条曲线的一种统一表示形式,介绍了该样条的求值算法及节点插入算法,并对其凸包性质和变差缩减性质作了分析,最后给出了相应算例。数值实验表明:该算法对任意样条都适用,且结果准确、有效。 相似文献