三峡水库应力场对水田坝断裂影响的数学-力学模型研究

水库蓄水后, 在一定空间范围内形成了应力场、应变场和渗流场。我们建立了一个数学一力学模型, 以描述水压应力场的特征。通过运用弹塑性岩土体非线性应力一应变和稳定性静力分析NOLM83二维有限元程序发现, 水库水压应力场的最大主应力从水库中心向两侧、从水库表面向深部逐渐降低。在此基础上, 研究了在未来三峡水库水压应力场影响下, 水田坝断裂的应力、应变和影响范围。研究表明, 平面影响范围为该断裂两侧5～-6km.由于岩体的浮托作用, 地表面的累积位移量少于10mm, 并向下逐渐减小。因此, 水田坝断裂完全能够承受三峡水库蓄水后产生的水压应力, 不会出现中-强度水库诱发地震, 不会影响三峡工程的安全。     

Computational assessment of material structure weaknesses in polycrystalline materials

Summary By incorporating local grain orientation, grain geometry and macroscopic elastic properties, a numerical procedure has been developed for computational prediction of mesoscopic stress and strain distributions in simulated polycrystalline material samples. The numerical procedure is developed on the basis of the concept of grain-average fields, Kröner–Kneer model, Waldvogel-Rodin algorithm and a self-adaptive method. Repeated computer tests were performed to investigate mesoscopic stress variation in the samples, and find coherent interrelations of material structure weaknesses (MSWs) with local microstructure of the samples. It was found that the stronger the single crystal elastic anisotropy, the stronger the inhomogeneity of mesoscopic stress distribution. Not only the elastic anisotropy, but also the grain geometry, may produce significant local stress disturbances. It has been found that the defined orientation-geometry factor and correlation parameter are two adequate physical quantities which account for synergetic interactions due to grain-orientation geometry-induced anisotropy. By using the two quantities, MSWs can be well correlated with local microstructure. Computer tests also show that 250–400 conjoining grains are necessary to homogenize the mesoscopic stress distribution in the considered materials.     

Coefficient characterization of linear differential equations with maximal symmetries

A characterization of the general linear equation in standard form admitting a maximal symmetry algebra is obtained in terms of a simple set of conditions relating the coefficients of the equation. As a consequence, it is shown that in its general form such an equation can be expressed in terms of only two arbitrary functions, and its connection with the Laguerre–Forsyth form is clarified. The characterizing conditions are also used to derive an infinite family of semi-invariants, each corresponding to an arbitrary order of the linear equation. Finally a simplifying ansatz is established, which allows an easier determination of the infinitesimal generators of the induced pseudo group of equivalence transformations, for all the three most common canonical forms of the equation.     

毛冬青总皂苷对AHNP诱导肝损伤大鼠骨中7种微量元素的影响

目的探讨了毛冬青总皂苷对AHNP诱导肝损伤大鼠骨中微量元素的影响。方法应用逆行胰胆管术注射牛磺胆酸钠（TAC）复制急性出血坏死性胰腺炎（AHNP）大鼠实验动物模型,进行了毛冬青总皂苷（高、低剂量）的治疗。观察了5组（假手术对照组、AHNP模型组、毛冬青总皂苷高剂量组、毛冬青总皂苷低剂量组、尼尔雌醇组、）大鼠股骨中Cu、Mn、Fe、Zn、Pb、Mg和ca等微量元素的变化。结果统计学结果显示与AHNP模型组比较,毛冬青总皂苷能提高AHNP大鼠骨质中cu、Fe、Mn、Mg、Ca等元素的含量,尼尔雌醇组中的zn含量提高,毛冬青总皂苷组中的zn含量反而下降;尼尔雌醇组与毛冬青总皂苷组中Pb含量下降明显。结论说明毛冬青总皂苷的治疗作用并不是单一的,可以认为中药毛冬青总皂苷是通过发挥对人体整体的调节作用来调节骨骼中微量元素的变化,改变骨质的代谢情况,促进骨密度的提高。     

Dominating and large induced trees in regular graphs

Recently Chen et al. [Tree domination in graphs, Ars Combin. 73 (2004) 193-203] asked for characterizations of the class of graphs and the class of regular graphs that have an induced dominating tree, i.e. for which there exists a dominating set that induces a tree.We give a somewhat negative answer to their question by proving that the corresponding decision problems are NP-complete. Furthermore, we prove essentially best-possible lower bounds on the maximum order of induced trees in connected cacti of maximum degree 3 and connected cubic graphs.Finally, we give a forbidden induced subgraph condition for the existence of induced dominating trees.     

THE INDUCED REPRESENTATION OF C^＊-GROUPOID DYNAMIC SYSTEMS

1.IntroductionandDefinitionsTheinducedrepresentationofgroupC*-algebrasfirstwasalgebraicallyintroducedbyfueffelin[3].P.Greenin[6]similiaxlyintroducedtheoneforcovariantdynamicsystem.TheinducedrepresentationofcrossedproductsbycoactionswasintroducedbyK.Mansfieldin[9].Using[8]wecanobtaintheinducedrepresentationofgrollpoidC*-algebrasin[1Ol.TherichapplicationofthesecanbefoundamongmanypapersrelativetotheC*-analysisofgroupoidandgroup.TheC*-groupoiddynamicsystemanditsreducedcrossedprod-uctwereintro…     

Quantifying the strength and durability of induced immunity to HIV infection in women engaging in unprotected sexual contacts with infected men

Evidence is accumulating that exposure to human immunodeficiency virus (HIV) can lead to an increased resistance or immunity to subsequent infection. A multirisk model that permits either induced immunity or infection to develop after heterosexual inoculation with HIV is shown to be compatible with a wide spectrum of disparate male-to-female transmission data.When the model is applied to time-dependent, HIV-seroprevalence data, the probability that an unexposed woman would remain unexposed after an unprotected contact with an infected man was estimated to be greater than 0.95 on the average. Thus, it would require at least 14 unprotected sexual contacts with HIV-infected men for 50% of an unexposed cohort of women to become exposed to the virus. This suggests that there is a low probability that HIV virions will be found to have penetrated the mucosal barriers of the reproductive tract after a contact.The model also predicts, that the average woman whose mucosal barriers have been breached by HIV has a significant probability of developing immunity to the virus rather than infection. Modelling data for a cohort of unexposed Nairobi women leads to the prediction that the probability of acquiring induced immunity per contact is about 60% of the probability of acquiring the disease per contact.The modelling results also predict that those who had developed resistance to HIV run the small, but significant risk of becoming infected nonetheless by continuing high-risk behavior. For the common contact rate of ten per month, the modelling predicts that the HIV-transmission risk per contact for unexposed women in the Nairobi cohort is 1/178 while the transmission risk for the cohort's immunized women is 1/1548. These numbers suggest that HIV infection is difficult to transmit through heterosexual intercourse on the average and that male-to-female HIV-transmission risk per contact for African women lies between 1/178 and 1/1548.Direct confirmation of the predictions in the last paragraph has been subsequently observed in two completely independent studies. The Nairobi research team recently reported that a notable number of Nairobi prostitutes previously identified to be members of the HIV-resistant group became infected nonetheless. Second, in a study of 174 sexually monogamous, discordant couples in Rakai, Uganda reporting contacts rates of nine to ten per month, the male-to-female HIV-transmission risk per contact was found to be 1/769 by direct measurement, a value that falls between the above limits of 1/178 and 1/1548 predicted by the modelling. Thus, a second major prediction of this paper has been directly confirmed, and induced immunity to HIV is limited and not absolutely protective.Circumstantial evidence suggests that the induced immunity to HIV predicted by the model could be generated and/or initiated by nonspecific innate immune responses, specific immunological responses, including IgA-mediated mucosal immunity and cytotoxic T lymphocytes (CTL) immunity, or some combination of the above. It is suggested here, that a decrease in the ability of HIV virions to penetrate the protective mucus layer of the reproductive tract may be a prerequisite, cofactor, or the principle cause of the induced immunity or resistance demonstrated to exist in this paper. The value of the probability that induced immunity to HIV will develop after a contact is shown to be a sensitive function of the woman's human leucocyte antigen (HLA) supertype profile.     

Convexities related to path properties on graphs

A feasible family of paths in a connected graph G is a family that contains at least one path between any pair of vertices in G. Any feasible path family defines a convexity on G. Well-known instances are: the geodesics, the induced paths, and all paths. We propose a more general approach for such ‘path properties’. We survey a number of results from this perspective, and present a number of new results. We focus on the behaviour of such convexities on the Cartesian product of graphs and on the classical convexity invariants, such as the Carathéodory, Helly and Radon numbers in relation with graph invariants, such as the clique number and other graph properties.     

Induced subgraphs with large degrees at end-vertices for hamiltonicity of claw-free graphs

A graph is called claw-free if it contains no induced subgraph isomorphic to K1,3. Matthews and Sumner proved that a 2-connected claw-free graph G is Hamiltonian if every vertex of it has degree at least (|V(G)|-2)/3. At the workshop C&C (Novy Smokovec, 1993), Broersma conjectured the degree condition of this result can be restricted only to end-vertices of induced copies of N (the graph obtained from a triangle by adding three disjoint pendant edges). Fujisawa and Yamashita showed that the degree condition of Matthews and Sumner can be restricted only to end-vertices of induced copies of Z₁ (the graph obtained from a triangle by adding one pendant edge). Our main result in this paper is a characterization of all graphs H such that a 2-connected claw-free graph G is Hamiltonian if each end-vertex of every induced copy of H in G has degree at least |V(G)|/3+1. This gives an affirmative solution of the conjecture of Broersma up to an additive constant.     

Central-to-axial chirality transfer and induced circular dichroism in 6,7-dihydro-5H-dibenz[c,e]azepine derivatives of α- and β-amino esters

DAZ-Xaa^∗-OMe amino ester derivatives with Xaa^∗ = d/l-Ala, d/l-Val, l-Leu, l-Ile, l-Ser, l-β³-HAla, l-β³-HVal, l-β³-HLeu, (1S,2S)/(1R,2R)-ACHC (2-aminocyclohexanecarboxylic acid) and (1S,2S)/(1R,2R)-ACPC (2-aminocyclopentanecarboxylic acid), N-blocked as 6,7-dihydro-5H-dibenz[c,e]azepines (DAZ), have been synthesized and evaluated for the determination of the absolute configuration of α- and β-amino esters through the induced circular dichroism of the biphenyl chromophore.