Supersonic flow past a wedge on a flat plate. Laminar boundary layer separation and reattachment

Supersonic laminar flow past a two-dimensional “flat-plate/wedge“ configuration is numerically investigated. The pressures at the boundary layer separation and reattachment points are calculated over wide Mach and Reynolds number ranges. The minimum angles of the wedge surface inclination at which a return flow occurs are determined. The results are presented in the form of generalized Mach-number-dependences of the theoretical pressure on the wedge surface initiating boundary layer separation and the pressure at the boundary layer reattachment point.     

Limiting state of an elastoplastic orthotropic plate with a periodic system of collinear cracks

A modified Dugdale model is used to study the fracture of an orthotropic elastoplastic plate with a periodic system of rectilinear cracks. The material of the plate obeys a general yield criterion. The general form of solution is obtained in terms of Kolosov-Muskhelishvili potentials. The size of the plastic zone is expressed in terms of the external load and geometrical parameters. The equations for the determination of the stresses in the plastic zone and the crack opening displacement are derived. The effect of anisotropy on the formation of the plastic zones at the crack tip is examined __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 5, pp. 80–88, May 2007.     

Numerical investigation of the first transition in the three-dimensional problem of convective flow in a porous medium

The branching off of steady-state regimes from mechanical equilibrium is studied for the problem of filtration convection in a parallelepiped. The conditions for the geometric parameters under which stable continuous families of steady-state regimes develop are found. The stability of equilibria of the family with respect to three-dimensional perturbations is analyzed in a numerical experiment using a finite-difference method.     

Effect of the grain size on the macroscopic response of aluminum to shock loading

Shock tests of two lots of a 1420 aluminum-lithium alloy are performed. The mean grain size is 24 μm in the first lot and 1.6 μm in the second lot obtained by the method of equal-channel angular pressing. Two characteristics of dynamic strength of the material were determined in experiments on the high-velocity impact of flat samples: threshold of dynamic stability with respect to compression on the fore front of the compression pulse and spall strength of the material. The materials of both types have an identical threshold of dynamic stability with respect to compression, whereas the spall strength of the microcrystalline alloy is 20% greater than the spall strength of the polycrystalline alloy. The reason is the consumption of energy on structure formation in the coarse-grain material in passing to a larger-scale structural level (in the case with a fine-grain material, such a structure is available in the initial state). The experiments reveal the presence of a second plastic front whose amplitude is approximately 10% of the first plastic front. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 135–146, November–December, 2007.     

悬索在考虑1:3内共振情况下的动力学行为

研究了悬索在受到外激励作用下考虑1∶3内共振情况下的两模态非线性响应.对于一定范围内悬索的弹性-几何参数而言,悬索的第三阶面内对称模态的固有频率接近于第一阶面内对称模态固有频率的三倍,从而导致1∶3内共振的存在.首先利用Galerkin方法把悬索的面内运动方程进行离散,然后利用多尺度法对离散的运动方程进行摄动得到主共振情况下的平均方程.接下来对平均方程的稳态解、周期解以及混沌解进行了研究.最后利用Runge-Kutta法研究了悬索两自由度离散模型的非线性响应.     

Electrochemical Characterization of Egyptian Blue Pigment in Wall Paintings Using the Voltammetry of Microparticles Methodology

The solid state voltammetric response of Egypt blue, Han blue and ploss blue pigments upon attachment to graphite electrodes in contact with aqueous phosphate buffer at pH 7.0 is studied by voltammetry of microparticles and scanning electrochemical microscopy. Such voltammetric responses, combined with those for synthetic specimens consisting of binary mixtures of the pigment and SiO₂ or CaCO₃ as well as ternary ones of CaCO₃ and SiO₂ mixtures allow for the identification of the pigment and the support in samples from wall paintings using different electrochemical parameters, in particular upon performing the Tafel and modified Tafel analysis of voltammetric peaks. Identification of Egypt blue in microsamples of murals from a Roman archaeological site in Castulo (Jaén, Spain) is discussed.     

Electrogenerated Fe(I) Porphyrins: Efficient Electrocatalysts for Reductive Dechlorination of DDT in N,N′‐Dimethylformamide

Two iron(I) porphyrins were electrogenerated and then utilized as catalysts for the reductive dechlorination of 1,1‐bis(4‐chlorophenyl)‐2,2,2‐trichloroethane (DDT) in N,N′‐dimethylformamide. No reaction is observed between DDT and the Fe(III) or Fe(II) forms of the porphyrin, but the electrogenerated Fe(I) porphyrin efficiently catalyzes the electroreduction of DDT to give (1,1‐bis(4‐chlorophenyl)‐2,2‐dichloroethane) DDD, (1,1‐bis(4‐chlorophenyl)‐2,2‐dichloroethylene) DDE and (1,1‐bis(4‐chlorophenyl)‐2‐dichloroethane) DDMU as determined by GC‐MS analysis. The reductive dechlorination was monitored by electrochemistry, controlled potential electrolysis and spectroelectrochemistry and a mechanism for the reaction involving the reduced porphyrins and DDT is proposed. Comparisons are also made between the catalytic properties of metalloporphyrins containing iron, cobalt and manganese central metal ions under the same solution conditions.     

A Ready‐to‐Use Electrochemical Kit Design for the Diagnosis of Single Nucleotide Polymorphisms

In this study, for the first time a model electrochemical kit was constructed for the detection of a functional polymorphism in catechol‐O‐methyl transferase (COMT) gene which is important for diagnosis of neuropsychiatric disorders as Alzheimer disease. The disposable pencil graphite electrode (PGE) is designed as a “kit” and the probe DNA covered PGE can detect single nucleotide polymorphisms (SNPs) from real samples based on the guanine oxidation signal even after 5 months of kit preparation (150 days durability).The detection limit (S/N=3) of the biosensor was calculated as 1.18 pmol of synthetic target sequence and 6.09×10⁵ molecules of real samples in 30 min detection time.     

18O同位素标记定量肽段串联体蛋白质结合同位素稀释-多反应监测质谱的蛋白质绝对定量新方法

建立了定量肽段串联体蛋白质(concatamers of Q peptides, QconCATs)结合¹⁸O同位素标记-多反应监测质谱的蛋白质绝对定量新方法。首先对QconCAT重组蛋白质进行了纯度表征,十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)表征结果表明重组蛋白质的纯度在99%以上,相对分子质量约为63.4 kDa。对QconCAT重组蛋白质酶切后的肽段混合物进行质谱分析,并经pFind和pLabel软件处理,验证了目标肽段。还考察了QconCAT重组蛋白质的酶切效率和¹⁸O标记效率,并对QconCAT蛋白质结合¹⁸O标记-同位素稀释-多反应监测质谱方法进行了评价。实验结果表明,采用该方法对腾冲嗜热厌氧菌(Thermoanaerobacter tengcongensis, TTE)中选定蛋白质的肽段进行绝对含量测定时,相对标准偏差小于20%,准确度较高,说明该方法可用于复杂生物样本中蛋白质的绝对定量。更重要的是所建方法不仅解决了细胞培养氨基酸稳定同位素标记(SILAC)技术的重标试剂价格昂贵的问题,也为定量蛋白质组学提供了一种新的方法。