Evidence against the non-enzymatic calcium theory of tenderization

The objective of the present study was to determine whether variation in the tenderization of lamb longissimus could be attributed to variations in the rise in free calcium postmortem and sarcomere lengthening post rigor. The longissimus muscle of 10 crossbred lambs (Romney×Coopworth) was sampled at 1 and 7 days postmortem for determination of MIRINZ shear force, myofibrillar fragmentation index (MFI), sarcomere length, free calcium, and proteolysis of troponin-T. Despite considerable variation in tenderness and tenderization of the muscles, sarcomere lengthening was not observed. The concentration of free calcium at 7 days postmortem correlated significantly with the MFI (r=0.640; P<0.05) and tended to correlate with the shear force (r=−0.596; P<0.1) and degradation of troponin-T (r=0.625; P<0.1). Degradation of troponin-T was significantly correlated with tenderization (r=0.664; P<0.05). Troponin-T is a calpain substrate, but reportedly is not degraded through a direct effect from calcium. The present results, therefore, suggest that the variation in free calcium in postmortem muscle affects tenderization through an effect on the calpain system and not through a direct effect of calcium on myofibrillar proteins. Consequently, the results of this study do not support the (calcium) theory that calcium directly affects tenderization.     

Low temperature synthesis of calcium cobaltites in a solid state reaction

This paper presents synthesis of calcium cobaltites of the nominal composition of Ca₃Co₄O₉ prepared by the solid state reaction. The reaction between CaCO₃ and Co₃O₄ was investigated at 700–900 °C during 20 h and at 800 °C during 2–30 h. Mass changes, phase composition and Co⁺³, Co⁺⁴ content were examined. Stability of the calcined specimens was tested by DTA/TG. It was found that two phases: Ca₃Co₄O₉ and Ca₃Co₂O₆ were present as a result of calcinations above 800 °C. On the other hand, the temperature of 750 °C was too low for calcium cobaltites to be synthesized. Mono-phase material with Ca₃Co₄O₉ phase was obtained after calcinations at 800 °C but non-stoichiometry of the compound and its relation to the calcinations time were found. Once synthesized, the compound was stable up to 900 °C.     

Growth of calcium carbonate on non-covalently modified carbon nanotubes

The crystallization of calcium carbonate was investigated on pristine and non-covalently modified carbon nanotubes (CNTs) using the vapor diffusion technique in a calcium chloride solution. Non-covalent modification was accomplished by treating the carbon nanostructures with the amphiphilic copolymer poly(isoprene-b-acrylic acid). Calcium carbonate crystals grown on the surface and in the interstitial channels of CNT buckypapers were observed in both cases. Scanning electron microscopy analysis of the untreated CNTs showed the characteristic rhombohedral morphology of calcite crystals, while in the case of modified material spherical and ellipsoidal crystals, consisted of nanocrystallites, were observed. X-ray diffraction analysis showed the presence of calcite crystals in both cases.     

建南气田飞三段气藏精细描述与开发潜力研究

建南气田飞三段气藏属于低孔隙度、低渗透率海相碳酸盐岩储层,为了提高气藏开发效果和经济效益,必须进行气藏精细描述,建立准确的地质模型,认识储层分布规律,同时,要大力开展气藏数值模拟研究,确定合理的开采技术政策,指出开发潜力目标,编制气藏优化开发调整方案。     

Studies on impurity ion and radiofrequency electric field effects on calcium carbonate deposition

The influences of impurity ions (Mg²⁺, Zn²⁺, Fe²⁺, Fe³⁺, and Al³⁺ ) and radiofrequency (44 MHz) electric field (RF) on calcium carbonate deposition in glass capillaries were studied. Calcium carbonate was precipitated from 0.1 M CaCl₂ and Na₂CO₃ solutions (100+ 100 ml) just before the inlet to the capillary. It was found that except for Al ³⁺ ions at 0.001 M concentration, the rest of the ions studied decreased CaC0₃ deposition. A minor influence of the RF field on the deposition was found in some of the systems tested, but it was in the range of the standard deviation of the results. An increase in deposition was observed in systems without impurity ions when equimolar volumes (500 + 500 ml) of 0.0025 M solutions of CaCl₂ and Na₂CO₃ were used for the experiment.     

3D spatial distribution of the calcium carbonate caused by carbonation of cement paste

Carbonation of cement-based materials is one area of concern for the durability of concrete structures. The calcium carbonate caused by carbonation is an important indicator of carbonation degrees. The present paper, using 3D tomography data, proposes a nondestructive method to characterize the 3D spatial distributions of calcium carbonate. It allows monitoring of 3D carbonation evolutions. The evolution of the calcium carbonate distributions in a specimen of cement paste with different carbonation degrees is given using the current method. The results are compared with the average quantity of calcium carbonate determined by thermal analysis. From the sharp edge of the calcium carbonate distribution, we conclude that the accelerated carbonation in this experimental condition is a diffusion controlling process.     

Nanoindentation study of calcium silicate hydrates in concrete produced with effective microorganisms-based bioplasticizer

The mechanical properties of concrete produced with effective microorganisms (EM)-based bioplasticizer are investigated by means of statistical nanoindentation, and compared to the nanomechanical properties of concrete produced with ordinary superplasticizer (SP). The resort to nanoindentation enables to survey the elasticity, hardness and long-term logarithmic relaxation behavior of calcium silicate hydrates (C–S–H) after few minutes only. For each material, a cluster analysis of the experimental results yields groupings of indents likely performed on C–S–H with distinct packing densities. It is found that the addition of EM-based bioplasticizer improves the strength of C–S–H by enhancing the cohesion and friction of solid nanograins, and decreases the absolute rate of long-term relaxation. The statistical analysis of indentation results also suggests that EM-based bioplasticizer inhibits the precipitation of C–S–H of higher density. The findings of this work corroborate the results of a previous study which attributed an increase of homogeneity and a refinement of the crystalline structure of silicate phases to the effect of a biomodifier similar to EM-based bioplasticizer. The improvement of strength properties of C–S–H is also shown to coincide with a gain of compressive strength measured at the macroscale of EM-based concrete.     

元素迁移的模拟模型实验

从野外不同地质体上，观察到地壳中元素是以纳米微粒状态被上升气流迁移的。为了进一步研究，设计了模拟以上升气流通过矿层、矿层加盖及围岩的模型层。实验结果显示，在模型中上升气流迁移的粒子仍是纳米微粒，并且采样片上含量也是随时间积累而增加。当有水层和玻璃盖层时，部分元素仍能穿透盖层，部分元素迁移受阻挠。纯扩散实验说明纯扩散迁移也存在，不过迁移量很小。列出模型实验中用扫描探针显微术观察到的纳米微粒照片。     

Performance of plate heat exchangers during calcium sulphate fouling — investigation with an in-line filter

The uncertainty about the fouling behaviour is one of the main reasons why plate and frame heat exchangers are not more widely installed in the chemical process industry and in power generating facilities. In the present investigation, the deposition of calcium sulphate in two different plate heat exchanger geometries was investigated. The deposition process was deliberately focused on crystallisation fouling through the installation of an in-line filter and the mode of preparation of the test solution. The investigated operating parameters were solution concentration, flow velocity, and bulk and surface temperatures. The heat exchangers were opened after each experiment to record the appearance and distribution of the deposits. The key result of this investigation is the strong correlation between the plate design and the tendency for deposit formation.     

钙基吸收剂脱硫反应特性的研究

本文对两种钙基吸收剂－ＣａＯ和Ｃａ（ＯＨ）２的脱硫反应机理进行了试验研究。对两者的反应活性进行了比较，并就一些因素对脱硫活性和影响作了研究，所得结论对脱硫反应的优化，脱硫剂的选择及干法ＦＧＤ装置的开发和研制有参考意义。