Mechanical properties of iron processed by severe plastic deformation

In the present study, the mechanical properties of Fe processed via severe plastic deformation (equal-channel angular pressing (ECAP)) at room temperature were investigated for the first time. The grain size of annealed Fe, with an initial grain size of about 200 μm, was reduced drastically during ECAP. After eight passes, the grain size reaches 200 to 400 nm, as documented by means of transmission electron microscopy (TEM). The value of microhardness during pressing increases 3 times over that of the starting material after the first pass and increases slightly during subsequent pressing for higher-purity Fe. Examination of the value of microhardness after eight passes as a function of post-ECAP annealing temperature shows a transition from recovery to recrystallization, an observation that resembles the behavior reported for heavily deformed metals and alloys. The tensile and compression behaviors were examined. In tension, a drop in the engineering stress-engineering strain curve beyond maximum load was observed both in the annealed Fe and the ECAP Fe. This drop is related to the neck deformation. The fracture surface, examined by scanning electron microscopy (SEM), shows vein patterns, which is different from the dimples found on the fracture surface of annealed Fe. In compression, an initial strain-hardening region followed by a no-strain-hardening region was observed in the ECAP Fe. The yield strength in tension of the ECAP Fe was observed to be higher than that in compression. The strengthening mechanisms and softening behavior are discussed.     

Obtaining shorter regular expressions from finite-state automata

We consider the use of state elimination to construct shorter regular expressions from finite-state automata (FAs). Although state elimination is an intuitive method for computing regular expressions from FAs, the resulting regular expressions are often very long and complicated. We examine the minimization of FAs to obtain shorter expressions first. Then, we introduce vertical chopping based on bridge states and horizontal chopping based on the structural properties of given FAs. We prove that we should not eliminate bridge states until we eliminate all non-bridge states to obtain shorter regular expressions. In addition, we suggest heuristics for state elimination that leads to shorter regular expressions based on vertical chopping and horizontal chopping.     

Numerical modelling for scattering of waves in three-dimensional cracked material

In this paper, a mathematical model is proposed for the problem of the scattering of plane waves in a three-dimensional cracked materials. Instead of obtaining closed-form solutions as in conventional theoretical analysis methods, this approach, called the Equivalent Nodal Force (ENF) method formulates the mechanical effects of cracks as an equivalent nodal force in a numerical procedure, and physically translates cracked material into an equivalent continuous one. Several mechanical relations between waves and cracks are evident from this method. Also the results of several numerical calculations are presented and these are compared with those obtained by the conventional methods.     

部分种子成分的特征X射线在等效生物材料中衰减的测定

用Ｓｉ（Ｌｉ）探测器实现了Ｎａ、Ｍｇ、Ｓ、Ｃｌ的特征Ｘ射线在有机膜中的相对衰减以及与Ｏ、Ｋ元素的特征Ｘ射线能量相当的Ｘ射线或轫致辐射在有机膜中的相对衰减，分别得出了它们减的数学描述，并把实验得到不同能量的Ｘ射线在有机膜中的质量吸收系数与Ｂｅｒｋｅｌｅｙ的ＯＣＧ软件计算出的结果相比，相关都小于３０％。     

高峰值功率重频脉冲固体激光器

综述了高峰值功率重频脉冲固体激光器的发展现状，对其中的Ｑ开关、腔倒空、锁模等窄脉冲技术和放大技术进行了分析，展示了高峰值功率重频脉冲固体激光器的发展前景。     

扑炎痛的合成新法

以水杨酸和对硝基苯酚为原料,在三氯氧磷存在下进行酯化,然后催化加氢还原硝基,最后用乙酐进行二酰化制得扑炎痛,三步收率分别为80.8％、90.4％和88.5％。     

Selective monitoring of peptidase activities with synthetic polypeptide substrates and polyion-sensitive membrane electrode detection

A novel method to monitor specific peptidase activities in biological samples as complex as undiluted plasma/blood is described. The approach is based on the design of synthetic polypeptide substrates in which di- or triarginine sequences are linked to each other via one or more other amino acids recognized specifically by the peptidase to be determined. Detection of chymotrypsin and renin activities using synthetic substrates P4 (F-R-R-R-F-V-R-R-F-NH2) and P5 (R-R-R-L-L-R-R-L-L-R-R-R), respectively, serves to demonstrate the principles of this new assay system. A polyion-sensitive membrane electrode, prepared by doping polymer films with dinonylnaphthalene-sulfonate (DNNS), is shown to exhibit significant nonequilibrium electromotive force (EMF) responses toward these and other polycationic substrates at microgram/milliliter levels under physiological conditions. The same electrode, however, exhibits much smaller total EMF response toward the shorter fragments of the synthetic peptides generated by peptidase activity; hence, the addition of peptidase to a solution containing the synthetic substrate yields a change in electrode EMF response, the rate of which is proportional to the activity of peptidase present. Other synthetic polycationic peptides as well as natural polycationic peptides (e.g., protamine) that lack specific cleavage sites for chymotrypsin and renin, yet are detected by the DNNS-based membrane electrode, do not elicit any significant change in EMF response in the presence of the peptidases, confirming the feasibility and utility of the proposed bioanalytical method.     

Changes in mitochondrial calcium concentration during the cardiac contraction cycle

OBJECTIVE: The aim was to examine whether mitochondrial Ca2+ fluxes are high enough to change mitochondrial and cytosolic calcium concentration during the contraction cycle. METHODS: Isolated guinea pig ventricular myocytes were stimulated with paired voltage clamp pulses until contractions were maximal (2 mM [Ca2+]o, 36 degrees C). At defined times of diastole or systole, the cells were shock frozen. Electron-probe microanalysis measured the concentration of total calcium in mitochondria (sigma Ca(mito)) and surrounding cytosol (sigma Cac). Other experiments were performed to evaluate DNP sensitive mitochondrial Ca2+ uptake from depolarisation induced [Ca2+]c transients (K5indo-1 fluorescence). RESULTS: At end of diastole, sigma Ca(mito) was 446 mumol.litre-1. During systole, sigma Ca(mito) increased with a 20 ms delay. A peak sigma Ca(mito) of 1050 mumol.litre-1 was measured 40 ms after start of systole, while 95 ms after start of systole sigma Ca(mito) had fallen to 530 mumol.litre-1. From the changes in sigma Ca(mito) the rates of net mitochondrial Ca2+ flux were estimated at 100 nmol.s-1 x mg-1 protein for Ca2+ influx and 36 nmol.s-1 x mg-1 protein for Ca2+ egress. Decay of sigma Ca(mito) was coupled to a rise in sigma Na(mito). sigma Cl(mito) and sigma K(mito) rose and fell in parallel with sigma Ca(mito), suggesting Ca2+ activation of mitochondrial anion and cation channels. Activation of the non-specific permeability can be excluded. Block of mitochondrial Ca2+ uptake with DNP (100 microM) or FCCP (10 microM) increased the amplitude of the [Ca2+]c transients for 1-3 min by about 50%; evaluation of mitochondrial Ca2+ uptake from DNP sensitive difference signals, however, was hampered by sequestration of mitochondrial Ca2+ into the sarcoplasmic reticulum. CONCLUSIONS: Mitochondrial calcium content changes during each individual contraction cycle; a substantial amount of calcium is taken up during the systole and released during later systole and diastole.