罗氏沼虾幼苗体内一种极小病毒的序列测定与分析

从患罗氏沼虾幼苗肌肉白浊病的幼虾体内分离到两种病毒颗粒,诺达病毒(MrNV)和直径只有15nm的小病毒颗粒(extrasmallvirus,XSV),本文通过建立病毒cDNA文库获得XSV基因组的部分序列,在此基础上合成探针,用从病虾组织中提取的总PNA进行Northern杂交,结果表明XSV基因组至少包括两条RNA片段.利用不同的方法对XSV的两端序列进行克隆和测定,分别得到了872、831和662bp3个相互重叠的序列片段,这3个序列的阅读框编码一个相同的大小在17×103左右的蛋白.     

Tandem silylformylation-allyl(crotyl)silylation: a new approach to polyketide synthesis

Tandem intramolecular silylformylation-allyl(crotyl)silylation reactions have been developed that allow the highly efficient synthesis of polyketide fragments. The substrates are subjected to Rh(I)-catalyzed silylformylation to afford β-(diallyl)silyl aldehydes which undergo spontaneous uncatalyzed allylsilylation. This unusual spontaneous allylsilylation reaction is driven by strain release Lewis acidity, which arises from the ∼95° O-Si-C bond angle in the oxasilacyclopentane product of the silylformylation reaction. The methodology has been developed both for alkene and alkyne substrates, may be used to establish as many as three stereocenters, and has been shown to be amenable to use in an iterative fashion.     

Long-Term Prediction of Creep Strain of Expanded Polystyrene

Data obtained in investigating the creep of expanded polystyrene in compression are discussed. An analysis of the results of creep tests 65–608 days long showed that the creep can be predicted for 50 years based on experiments of less duration than the 605 days indicated in EN 13163. For this purpose, it is suggested to employ a 95-fold extrapolation in time if the creep curves are described by a power function (as recommended by EN 13163) or a 50-fold extrapolation if the exponential equation proposed in the present paper is used. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 795–802, November–December, 2005.     

中小企业集群竞争力模型研究

以模糊综合评判作为理论基础,结合AHP方法和专家法,建立了中小企业集群竞争力层次结构模型和中小企业竞争力综合评判模型。     

Nonlinear rheological behavior of silica filled solution‐polymerized styrene butadiene rubber

The reinforcement and nonlinear viscoelastic behavior have been investigated for silica (SiO₂) filled solution‐polymerized styrene butadiene rubber (SSBR). Experimental results reveal that the nonlinear viscoelastic behavior of the filled rubber is similar to that of unfilled SSBR, which is inconsistent with the general concept that this characteristic comes from the breakdown and reformation of the filler network. It is interesting that the curves of either dynamic storage modulus (G′) or loss tangent (tan δ) versus strain amplitude (γ) for the filled rubber can be superposed, respectively, on those for the unfilled one, suggesting that the primary mechanism for the Payne effect is mainly involved in the nature of the entanglement network in rubbery matrix. It is believed there exists a cooperation between the breakdown and reformation of the filler network and the molecular disentanglement, resulting in enhancing the Payne effect and improving the mechanical hysteresis at high strain amplitudes. Moreover, the vertical and the horizontal shift factors for constructing the master curves could be well understood on the basis of the reinforcement factor f(φ) and the strain amplification factor A(φ), respectively. The surface modification of SiO₂ causes a decrease in f(φ), which is ascribed to weakeness of the filler–filler interaction and improvement of the filler dispersion. However, the surface nature of SiO₂ hardly affects A(φ). © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2594‐2602, 2007     

原始地应力及力学参数的测定

本文根据孔壁应力解除法获得的量测应变,提出了采用最优化方法直接确定岩体的泊松比和原始地应力。实例表明,这样获得的原始地应力更符合实际——对应最小的量测残差。     

变参数波振器中小信号增益公式

利用微扰展开技术推导出变参数波振器的小信号增益两个近似求积表达式并将其计算结果与数值模拟结果进行了比较,二者吻合很好。利用近似解析式对小信号增益进行了初步探讨,得到了电子入射能量可低于初始谐振能,能散度允许范围受波振器设计影响以及降低锥度改变率可提高小信号增益等新结论。     

Simple Constructions of Almost k-wise Independent Random Variables

We present three alternative simple constructions of small probability spaces on n bits for which any k bits are almost independent. The number of bits used to specify a point in the sample space is (2 + o(1)) (log log n + k/2 + log k + log 1/?), where ? is the statistical difference between the distribution induced on any k bit locations and the uniform distribution. This is asymptotically comparable to the construction recently presented by Naor and Naor (our size bound is better as long as ? < 1/(k log n)). An additional advantage of our constructions is their simplicity.     

试论中小企业在台湾经济发展中的作用

在台湾经济发展过程中，中小企业始终发挥着重要的作用。这不仅是因为台湾中小企业自身具备灵活与弹性的特质，能够适应各种内外经济环境，起着大企业所不能起的填补经济活动中的空缺的作用，而且中小企业之间能自发形成各种协作关系，台湾行政当局加以有组织地推动经济合作，使中小企业始终发挥重要作用。研究中小企业在台湾经济发展中的作用对我们在工业化过程中，如何扶持中小企业，使它促进经济协调发展，有一定的借鉴意义。     

某类一阶非线性双曲型方程的Cauchy问题

本文考虑一类具实际物理背景的一阶非线性双曲型方程，证明了解的存在唯一及正则性。