Microstructure and tensile properties of squeeze cast magnesium-aluminum-strontium alloys

It has been demonstrated that die cast Mg-AI-Sr alloys have enhanced high temperature properties and are capable of replacing certain existing aluminum power train components. However, due to the inherent nature of die casting, i.e. high porosity content and other defects, automotive applications of Sr-containing magnesium die casting are very limited. Squeeze casting has a super ability to eliminate porosity and other casting defects. However, there is a general lack of understanding concerning the microstructure and tensile properties of squeeze-cast Mg-Al-Sr alloys. This thesis describes the findings of experimental investigation in obtaining an in-depth understanding on the effect of pressure levels and strontium contents on tensile properties and microstructure of squeeze cast Mg-Al-Sr alloys. The results have shown that the ultimate tensile strength (UTS), yield strength (YS) and elongation (Ef) of squeeze cast Mg-Al-Sr alloys increase with increasing applied pressures but decrease as the strontium content increases

頭部構造と各層内血流変化が光マッピング画像に及ぼす影響

Optical mapping has been applied to image brain activation two-dimensionally along the head surface by detecting the intensity changes of light that passes through the brain. In optical mapping for imaging brain activity, it is assumed that the head tissue is spatially homogeneous and temporally invariable except the activated region in the brain. However, in the superficial layers above the brain, the tissues are inhomogeneous and vary hemodynamically. Furthermore, light propagation and the optical pathlength inside the head are highly dependent on the anatomy and physiology in the head. In particular, the spatial variations in the thickness of skull and cerebrospinal fluid (CSF) layers, the existence of the blood vessels and the hemodynamic changes in the superficial layers such as the CSF and skin layers would have significant influences on light propagation and would result in the difference in the mapping images. However, itis difficult to know these influences by in vivo experiments. The aim of this study is to investigate these influences by numerical and experimental methods. Three-dimensional head models are used to simulate light propagation in the head by solving the photon diffusion equation using the finite element method (FEM), and the optical mapping images are constructed from the simulated measurement data. Tissue-mimicking phantoms with spatially varying thickness and changeable optical properties of head layers were also developed and multi-channel near-infrared spectroscopy (NIRS) experiments were performed on the dynamic phantoms. In the numerical simulations and phantom experiments, the changes in the optical densities (ΔOD) due to activated regions are obtained to construct the mapping images, and the light path probability distributions between one pair of source and detector are calculated to show the sensitivity of the tissue regions to the mapping images. As theresults, the influences of (1) the spatial variations of the skull and CSF layers and (2) the blood volume changes in the skin and CSF layers on the mapping images of brain activities are investigated quantitatively. The optical mapping for the single or multiple activated regions and the effects of the position of the activated regions relative to theprobe arrays on mapping images are also discussed. The quantitative results about the influences of the superficial layers in this study provide information for compensating the optical mapping images among different individuals or different head regions in an individual. In vivo experiments considering the influences of structural and hemodynamic differences in the superficial layers onoptical mapping remain as a future subject.電気通信大学201

Salvianolic acid B Relieves Oxidative Stress in Glucose Absorption and Utilization of Mice Fed High-Sugar Diet

Purpose: To evaluate the influence of Salvianolic acid B (Sal B) on  oxidative stress in mice administrated with glucose, sucrose and high-sugar diet.Methods: 40 Kunming mice were divided into four groups of 10. After a fast of 12 h, mice were treated by oral infusion respectively with physiological saline, 20 % glucose, 20 % sucrose, and 20 % glucose + 0.002 % Sal B. Blood glucose and levels of reactive oxygen species (ROS) were  determined at 0, 0.5, 1.0, 1.5, and 2.0 h after administration. Another 3 groups of 10 Kunming mice each were fed with normal diet, high-sugar diet (20 % sucrose, HSD) and HSD + 0.002 % Sal B. Four weeks later, the levels of ROS as well as antioxidant enzyme activity were determined.Results: Blood ROS showed the first peak at 0.5 h and a higher peak at 1.5 h after high glucose administration. ROS were mainly produced in liver and pancreas with the utilization of glucose. Sal B administration prevented increase in blood glucose and significantly (p < 0.05) reduced ROS produced in the process of glucose absorption and utilization, especially the latter. Sal B decrease oxidative stress induced by HSD through scavenging ROS associated with increased activity of antioxidant enzymes.Conclusion: This study demonstrates that Sal B can decrease oxidative stress in glucose absorption and utilization in HSD mice. Thus, the findings provide a basis for a potential interventional strategy for protecting against oxidative damage induced by HSD.Keywords: Salvianolic acid B, Blood glucose, Reactive oxygen species, Oxidative stress, Sugar di

Decision Engineering Analysis of Fraud Information Disclosure after China's Share-Splitting Reform

AbstractThis paper outlines a dynamic game model to analyze the fraud information disclosure by listed companies in China since the share-splitting reform in 2005. By analyzing the conditions of coalition-proof Nash equilibrium between large shareholders and the manager, exogenous variables’ effects on the equilibrium as well as the first-order condition of the maximum utility of the supervisory department, it is concluded that efficient capital markets require a high supervising probability and intensity of penalty to the “insider” and shortened the intervals between supervising conducts as well. Moreover, there exists a unique optimum incentive stock option ratio over which fraud information disclosure becomes more rampant. This results in a higher intensity of penalty to the manager given more stock option incentive and, in contrast, a higher intensity of penalty to large shareholders of a well managed and efficiently capital-structured company once fraud information disclosure is detected. The model's conclusions are consistent with the facts of listed companies in China. Finally, the model makes sharp suggestions for the mechanism design of stock option incentive as well as suggestions for the supervisory department to achieve efficiency of capital markets in China

Synthesis and Characterization of Different Crystalline Calcium Silicate Hydrate: Application for the Removal of Aflatoxin B1 from Aqueous Solution

Different crystalline calcium silicate hydrates (CSH) were synthesized under specific hydrothermal conditions and several methods were used to analyze samples. Amorphous calcium silicate hydrates (ACSH) mainly consists of disordered calcium silicate hydrate gel (C-S-H gel) and crystalline calcium silicate hydrates (CCSH) consists of crystallized tobermorite. The adsorption of carcinogenic aflatoxin B1 (AFB1) onto ACSH and CCSH was investigated. The adsorption kinetics was studied using pseudo-first-order and pseudo-second-order kinetic models and intraparticle diffusion model. The pseudo-second-order model provided the best correlation and the intraparticle diffusion controlled the adsorption process of AFB1 onto CCSH. Adsorption isotherm parameters were obtained from Langmuir and Freundlich and the adsorption data fitted to Freundlich much better. Based on the results of N2 adsorption/desorption, adsorption kinetics, and adsorption isotherms, the adsorption mechanism of AFB1 onto CCSH was developed. All results indicate that CCSH has a great potential to be a safe, easy-made, and cost-effective material for the control of AFB1 contamination

Functional evaluation of Asp76, 84, 102 and 150 in human arsenic(III) methyltransferase (hAS3MT) interacting with S-adenosylmethionine

AbstractWe prepared eight mutants (D76P, D76N, D84P, D84N, D102P, D102N, D150P and D150N) to investigate the functions of residues Asp76, 84, 102 and 150 in human arsenic(III) methyltransferase (hAS3MT) interacting with the S-adenosylmethionine (SAM)-binding. The affinity of all the mutants for SAM were weakened. All the mutants except for D150N completely lost their methylation activities. Residues Asp76, 84, 102 and 150 greatly influenced hAS3MT catalytic activity via affecting SAM-binding or methyl transfer. Asp76 and 84 were located in the SAM-binding pocket, and Asp102 significantly affected SAM-binding via forming hydrogen bonds with SAM