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71.
72.
A structure for a heterologous double-stranded molecule consisting of an oligoribonucleotide and a β-stranded oligopeptide, paired through complementary Watson-Crick-type hydrogen bonding, is proposed. The basis for such complementary pairings between oligoribonucleotides and oligopeptides is the close correspondence of the distances between the side-chains attached to the backbones of the two molecules. Both inter-nucleotide spacing and inter-amino acid side-chain spacing are approximately 3.4 Å. These kinds of interactions may have implications in protein-mediated-RNA splicing. Formation of a heterologous duplex through such a pairing mode could provide a simple coding mechanism for a reciprocal information transfer between oligonucleotides and oligopeptides. Because of its simplicity and versatility, allowing both specific and nonspecific coding, interactions via these kinds of pairing may have been relevant for prebiotic molecular evolution and for generating complex biological molecules. 相似文献
73.
王修信 《宁波大学学报(理工版)》1992,(2)
将带有纵向加劲肋的多室梯形箱形梁桥作为正交异性板折板结构考虑,采用艾瑞应力函数法给出了平面应力状态时正交异性板一般边界条件下的二维应力及位移的解析表达式一般形式。然后根据板梁在二者连接处的纵向线应变与侧向曲率两个形变协调条件解出了多室正交异性板箱形梁桥的应力分布与剪力滞后的半解析公式,使用时采用类似于有限条法的步骤计算,但输入数据和运算时间却很少。该方法兼有解析法精确条理与数值法方便灵活的特点,可推广应用于高层筒体结构和带有曲线预应力钢索的箱形梁桥等。 相似文献
74.
Hervé Moulin 《Mathematical Social Sciences》1982,3(3):243-257
Strategic decentralization of collective decision-making is considered when the agents' behaviour is non-cooperative. Specifically they use dominant, maximin risk-avert or sophisticated strategies. The existing results applying these equilibrium concepts are reviewed in three familiar economically meaningful contexts: ordinal (as in voting), random (as in bargaining) and quasilinear (as in public goods problems). 相似文献
75.
76.
One of the classical problem in computational biology is the character compatibility problem or perfect phylogeny problem. A standard formulation of this problem in terms of two closely related questions is the following. Given a data set consisting
of a finite set X and a set
of partitions induced on X by a set of characters. Is
compatible, that is, does there exist an evolutionary tree that represents (in a well-defined sense) the data? If this is the case,
is this tree unique? A fundamental result in phylogenetics states that the answer to the former of the two questions is yes
precisely if the partition intersection graph
associated to
can be made chordal by obeying a certain rule.
The main insight from this paper is that the relation graph
associated to a set
of partitions may provide a key for deciding whether such a chordalization of
exists. To prove our results, we introduce an extension of the concept of the partition intersection graph associated to
using
.
Received August 27, 2004 相似文献
77.
People may evaluate risk differently in the insurance market. Motivated by this, we examine an optimal insurance problem allowing the insured and the insurer to have heterogeneous beliefs about loss distribution. To reduce ex post moral hazard, we follow Huberman et al. (1983) to assume that alternative insurance contracts satisfy the principle of indemnity and the incentive-compatible constraint. Under the assumption that the insurance premium is calculated by the expected value principle, we establish a necessary and sufficient condition for an optimal insurance solution and provide a practical scheme to improve any suboptimal insurance strategy under an arbitrary form of belief heterogeneity. By virtue of this condition, we explore qualitative properties of optimal solutions, and derive optimal insurance contracts explicitly for some interesting forms of belief heterogeneity. As a byproduct of this investigation, we find that Theorem 3.6 of Young (1999) is not completely true. 相似文献
78.
Kai Xiong Yongping Zhu Lianshi Wang Tongmin Cai Anqiang Zhang Xiangbin Zeng 《Journal of Macromolecular Science: Physics》2013,52(7):1351-1369
Poly(ethene-co-1-butene)-graft-methyl methacrylate-acrylonitrile (PEB-g-MAN) was prepared by suspension grafting copolymerization of methyl methacrylate (MMA) and acrylonitrile(AN) onto PEB. PEB-g-MAN/SAN resin blends (ABMS) were prepared by blending PEB-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The effects of AN/(MMA+AN) feed ratio (fAN), PEB/(PEB+MMA+AN) feed ratio (fPEB) and benzoyl peroxide (BPO) dosage on the monomer conversion ratio (CR), rubber's grafting ratio (GR), grafting efficiency (GE) of the copolymerization and the toughening effect of PEB-g-MAN on the SAN resin were investigated. FTIR quantitative analysis showed that when the weight percent of AN unit in the unextracted product was 21.5 wt% with fAN of 25 wt%, the toughening effect of unextracted PEB-g-MAN on SAN resin was the highest. Gel permeation chromatography (GPC) analysis showed that when fAN was 25 wt%, the grafted copolymer had the lowest molecular weight and ABMS had highest toughness. Transmission electron microscopy (TEM) analysis showed that the highest toughness occurred when the phase structure of ABMS was cocontinuous with fAN of 25 wt%. When fAN was 25 wt% PEB-g-MAN domains have numerous small SAN domains in them, which was occlusion structure. Scanning electron microscopy (SEM) analysis indicated that the ABMS fracture surfaces had plastic flow visible, which looked like a craze fibers morphology, for the sample with highest impact strength (fAN = 25 wt%). Dynamic mechanical thermal analysis (DMA) showed that the miscibility of the PEB phase and SAN phase improved after graft copolymerization of MMA and AN onto PEB. 相似文献
79.
Kai Xiong Lianshi Wang Anqiang Zhang 《Journal of Macromolecular Science: Physics》2013,52(7):1350-1363
POE-graft-methyl methacrylate and acrylonitrile (POE-g-MAN) was prepared by graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto polyethylene-octene copolymers (POE) with suspension polymerization. POE-g-MAN/SAN resin blends (AOMS) were prepared by blending POE-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The mechanical properties, compatibility, and thermal stabilities of AOMS were studied. The notched impact strength of the blends reached 54.0 kJ/m2 when the AN/(MMA + AN) ratio (fAN) of POE-g-MAN, benzoyl peroxide dosage, and POE content in AOMS were 15 wt%, 1.0 wt%, and 25 wt%, respectively. Transmission electron microscopy analysis showed that the highest toughness occurred when the size of POE-g-MAN particles and the surface-to-surface inter-particle distance were proper. Scanning electron microscopy analysis indicated that the AOMS fracture surface had plastic flow visible, which looked like a fibril morphology when the AN/(MMA + AN) ratio (fAN) of POE-g-MAN was 15 wt%. The toughening mechanism of AOMS was shear yielding of the matrix, which endowed AOMS with remarkable toughness. Dynamic mechanical thermal analysis showed that the compatibility of the POE phase and SAN phase improved after graft copolymerization of MMA and AN onto POE. When the grafting chain polarity was appropriate, the miscibility between POE-g-MAN and SAN resin was the best. Thermogravimetry analysis showed that thermal stability of AOMS increased with increasing AN units in POE-g-MAN. 相似文献
80.
Yun-Hong Jiao Xiu-Li Wang Yu-Zhong Wang Li Chen Sheng-Mao Mu Fang Li 《Journal of Macromolecular Science: Physics》2013,52(2):351-364
Polypropylene (PP)/ethylene-octene copolymer (POE) blends with 10–50wt% POE composition were prepared using a twin-screw extruder in the melt state. Mechanical properties of PP and PP/POE blends were tested and the effect of POE content on the crystalline morphology and structure, melting and crystallization behavior, compatiblilty, phase morphology, and the interface cohesiveness of the blends were investigated by polarizing optical microscope (POM), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and scanning electron microscopy (SEM). The relationship between mechanical properties and microstructure of the PP/POE blends is discussed. The results showed that POE had a dual function of both reinforcing and toughening PP in the range from 10–40wt%, which was attributed to the integrated functions of the degree of crystallinity of the PP phase, phase morphology, and interface cohesiveness of the blend. 相似文献