同胚不可约k树的计数公式

由同胚不可约树得到同胚不可约k树的概念,并利用Polya计数定理得到了它的计数公式.     

路与圈的积图的(d,1) 全标号

研究了路与圈的积图的(d,1) 全标号问题,并给出了路与圈的积图的(d,1) 全标号数。     

X2+XY-Y2+k=0存在正整数解的条件

若二元二次方程X2+XY-Y2+k=0存在正整数解,则其每组解必为广义Fibonacci数列相邻二项,并且方程X2+XY-Y2+k=0具有广义Fibonacci数列的正整数解时,满足一定约束条件.Lucas数列作为一种广义Fibonacci数列,其相邻二项是X2+XY-Y2±5=0的正整数解.     

交换环上的Noether模

本文将交换Noether环上有限生成模的一些结果推广到任意交换环上的Noether模上.     

抽象锥中1-集压缩映射的不动点定理

设P是实Banach空间E的一个锥 ,f是PR 到P的一个 1-集压缩映射 ,且对PR中任一序列 {xn} ,若limn→∞(xn-f(xn) ) =θ,则存在u∈PR,使得u -f(u) =θ.那么当对任意满足‖f(x)‖ >R的x∈ PR,存在y∈IpR(x) ,使‖y-f(x)‖<‖x-f(x)‖ ,或都有‖f(x) -x‖≠‖f(x)‖ -R ,或存在 1<α <+∞ ,使‖f(x)‖α-Rα≤‖f(x) -x‖α,或存在 0<β<1,使‖f(x)‖β-Rβ≥‖f(x) -x‖β,或对任意 0 <λ<1,都有x≠λf(x)时 ,f在PR 中有一个不动点 .通过以上结论的给出 ,解决了一类微积分方程的解的存在性 .     

稀疏图平方图的染色数上界

图G的平方G2定义为顶点集V(G)=V(G²), 并且uv∈E(G²)当且仅当u和v之间的距离至多为2. G²的色数χ(G²)是指使得G²存在正常k顶点染色的最小整数k. 用权转移的方法证明: 如果mad(G)<4且Δ(G)≥7, 则χ(G²)≤3Δ(G)+1; 如果mad(G)≤4且Δ(G)≥8, 则χ(G²)≤3Δ(G)+5.     

The structure and functions of the presenilins

The presenilins (PSs) were new proteins discovered in 1995 to be involved, among other functions, in the molecular mechanisms leading to Alzheimers disease. These proteins have been the subject of many investigations since then to elucidate their molecular structures and functions. Until now, the conclusions about PS structure have been discordant, but the 8-TM structure has been accepted by the Alzheimers community, with the evidence for the 7-TM structure largely ignored. Here the evidence is reviewed for the 6-TM, 7-TM, 8-TM and other proposed models of PS topography and possibilities offered for the differences in interpretation of the various sets of data. The conclusion is that at this stage, the 7-TM model for cell surface PS is most likely the correct one.Received 22 December 2004; accepted 26 January 2005     

Antiproliferative effect of β-elemene in chemoresistant ovarian carcinoma cells is mediated through arrest of the cell cycle at the G2-M phase

Elemene is a natural antitumor plant drug. However, the effect of elemene on cell growth in ovarian cancer is unknown. In this study, we show that -elemene inhibited the proliferation of cisplatin-resistant human ovarian cancer cells and their parental cells, but had only a marginal effect in human ovary cells, indicating differential inhibitory effects on cell growth between ovarian cancer cells and normal ovary cells. We also demonstrated for the first time that -elemene markedly enhanced cisplatin-induced growth inhibition in resistant cells compared to sensitive cells. In addition, cell cycle analysis revealed a synergistic effect of -elemene and cisplatin on the induction of cell cycle G2-M arrest in our resistant ovarian carcinoma cells. Furthermore, we showed that treatment of these cells with both drugs downregulated cyclin B1 and Cdc2 expression, but elevated the levels of p53, p21waf1/cip1, p27kip1 and Gadd45. Finally, the combination of -elemene and cisplatin was found to increase the phosphorylation of Cdc2 and Cdc25C, which leads to a reduction in Cdc2-cyclin B1 activity. These novel findings suggest that -elemene sensitizes chemoresistant ovarian carcinoma cells to cisplatin-induced growth suppression partly through modulating the cell cycle G2 checkpoint and inducing cell cycle G2-M arrest, which lead to blockade of cell cycle progression.Received 19 January 2005; accepted 5 February 2005     

Hydra vulgaris ω10-lipoxygenase is used in vivo to synthesize new α-linolenic acid metabolites

Previous studies conducted in cytosolic extracts of the freshwater hydrozoanHydra vulgaris led to the finding of an abundant 11(R)-lipoxygenase catalyzing the peroxidation of polyunsaturated fatty acid (PUFAs) on the tenth carbon atom from the aliphatic end (10 peroxidation). Here we describe experiments aimed at identifying the actual metabolites generated in vivo by such enzymic activity. Homogenates ofH. vulgaris polyps were analyzed by HPLC. This showed the presence of three major components chromatographically identical to three metabolites obtained when incubating the homogenates with exogenous -linolenic acid (-LA). The presence, in extracts of polyps prelabelled with [¹⁴C]--linolenic acid, of radioactive metabolites displaying the same chromatographic properties, substantiated the hypothesis that the natural products isolated in vivo are derived from -LA. Gas chromatographic analyses revealed that this was the most abundant PUFA in both free and phosphoglyceride-bound fatty acid pools. [¹H]-NMR analysis of the endogenous substances, carried out in comparison with products obtained from exogenously incubated -LA, indicated that their structures were those of 9-hydroxy-, 9-hydroperoxy- and 9-keto-octadeca-10E-12Z-15Z-trienoic acids (9--HOTrE,-HPOTrE and-KOTrE).Hydra homogenates transformed 9--HPOTrE partly into 9--HOTrE and partly into 9--KOTrE. Chiral phase HPLC conducted on 9--HOTrE established that this metabolite was composed mostly of theR anantiomer. These observations, and the finding that the presence of exogenous arachidonic acid in incubated homogenates significantly reduces the production of -LA metabolites, provide strong evidence that these compounds are produced by an enzymic activity identical to the previously-describedH. vulgaris (R)-10-lipoxygenase. Further experiments suggested that -LA, acting as the native substrate for this enzyme, is mainly esterified on the 2 position ofHydra phosphoglycerides, and that the production of the -LA metabolites described here for the first time from natural sources, can be potentially enhanced in vivo by stimuli activating phospholipase A₂.     

基于双剔除门限的Switching-CFAR目标检测算法

为了解决传统的目标检测算法在非均匀噪声环境下检测性能严重下降的问题,提出了一种基于双剔除门限的Switching-CFAR（switching-constant false alarm rate based on dual censoring thresholds,DCS-CFAR）目标检测算法。基于参考窗参考单元样本期望值和测试单元,得到双重剔除功率比较门限。通过双重比较,剔除参考窗中极大值参考单元,根据剩余参考单元数,选择合适的参考单元来估计背景噪声功率,并得到功率检测门限。在Matlab环境下,通过蒙特卡洛方法和SwerlingII模型对DCS-CFAR目标检测算法的关键参数,以及在各种仿真环境下与其它目标检测算法的检测性能进行了仿真对比分析,DCS-CFAR目标检测算法在均匀背景噪声下,检测率为98.76%,接近于CA-CFAR算法;在杂波和多干扰目标环境下,检测率分别为97.83%和98.23%。在均匀和非均匀噪声环境下,DCS-CFAR检测算法均优于ACCA-CFAR和GO-CFAR算法。结果表明,提出的DCS-CFAR检测算法在均匀和非均匀噪声环境下, 均具有良好的检测性能。