A feature extracting and meshing approach for sheet-like structures in rocks

Meshing rock samples with sheet-like structures based their CT scanned volumetric images, is a crucial component for both visualization and numerical simulation. In rocks, fractures and veins commonly exist in the form of sheet-like objects (e.g. thin layers and distinct flat shapes), which are much smaller than the rock mass dimensions. The representations of such objects require high-resolution 3D images with a huge dataset, which are difficult and even impossible to visualize or analyze by numerical methods. Therefore, we develop a microscopic image based meshing approach to extract major sheet-like structures and then preserve their major geometric features at the macroscale. This is achieved by the following four major steps: (1) extracting major objects through extending, separation and recovering operations based on the CT scanned data/microscopic images; (2) simplifying and constructing a simplified centroidal Voronoi diagram on the extracted structures; (3) generating triangular meshes to represent the structure; (4) generating volume tetrahedron meshes constrained with the above surface mesh as the internal surfaces. Moreover, a shape similarity approach is proposed to measure and evaluate how similar the generated mesh models to the original rock samples. It is applied as criteria for further mesh generation to better describe the rock features with fewer elements. Finally, a practical CT scanned rock is taken as an application example to demonstrate the usefulness and capability of the proposed approach

Pure spin current in a two-dimensional topological insulator

We predict a mechanism to generate a pure spin current in a two-dimensional topological insulator. As the magnetic impurities exist on one of edges of the two-dimensional topological insulator, a gap is opened in the corresponding gapless edge states but another pair of gapless edge states with opposite spin are still protected by the time-reversal symmetry. So the conductance plateaus with the half-integer values $e^2/h$ can be obtained in the gap induced by magnetic impurities, which means that the pure spin current can be induced in the sample. We also find that the pure spin current is insensitive to weak disorder. The mechanism to generate pure spin currents is generalized for two-dimensional topological insulators.Comment: 5 pages, 6 figure

Recent progress in the differentiation of bone marrow derived mesenchymal stem cells (BMMSCs) to cardiomyocyte- like cells and their clinical application

Bone marrow mesenchymal stem cells (BMMSCs) are one of the cells found in bone marrow stromal. A large number of studies have shown that BMMSCs cannot only differentiate into hematopoietic stromal cells, but can migrate and position themselves in multiple non-hematopoietic organizations and differentiate into the corresponding tissue cells; this characteristic demonstrates their multilineage differentiation potential. In different conditions, BMMSCs can differentiate into bone, cartilage, fat, cardiomyocyte, endothelial cells and nerve cell, etc. Because BMMSCs are easy to acquire, they can proliferate in vitro, have multi-differentiation potential after implantation in vivo, and therefore have wide application prospects for the treatment of cardiovascular disease as the ideal seed cells. This review focuses on the biological characteristics of BMMSCs, the induction and differentiation of cardiomyocyte-like cells and the application in the cardiovascular field.Key words: Bone marrow mesenchymal stem cells (BMMSCs), cardiomyocyte-like cells, cardiovascular disease

Genome-wide examination of chlorophyll metabolic genes in maize and phylogenetic analysis among different photosynthetic organisms

Chlorophyll (Chl) is the key pigment involved in photosynthesis. Analysis of the expression pattern of Chl metabolic genes will contribute to our understanding of photosynthesis. Also, the genes coding for Chl metabolism are ideal targets for revealing the evolution relationships of photosynthetic organisms. In this study, we summarized the Chl metabolic pathway in higher plants and conducted in silico expression analysis of related genes in maize. Phylogenetic analysis revealed that the evolution of Chl metabolic genes proceeded in a certain direction. Moreover, the diversity of some rate-limiting enzymes might have played a positive role in the evolution of Chl metabolism.Kew words: Chlorophyll, maize, metabolism, phylogeny, photosynthesis

A Cellular Automata Model with Probability Infection and Spatial Dispersion

In this article, we have proposed an epidemic model by using probability cellular automata theory. The essential mathematical features are analyzed with the help of stability theory. We have given an alternative modelling approach for the spatiotemporal system which is more realistic and satisfactory from the practical point of view. A discrete and spatiotemporal approach are shown by using cellular automata theory. It is interesting to note that both size of the endemic equilibrium and density of the individual increase with the increasing of the neighborhood size and infection rate, but the infections decrease with the increasing of the recovery rate. The stability of the system around the positive interior equilibrium have been shown by using suitable Lyapunov function. Finally experimental data simulation for SARS disease in China and a brief discussion conclude the paper

Production of mirror fermions via eγe\gamma and epep collisions in the littlest Higgs model with T-parity

One of the important features of the littlest Higgs model with T-parity, called the $LHT$ model, is that it introduces the mirror fermions, which are the T-parity partners of the standard model fermions. In this paper, we discuss production of the mirror quark associated with mirror neutrino via $e\gamma$ and $ep$ collisions. We find that, in wide range of the parameter space, the mirror quark can be copiously produced at the International $e^{+}e^{-}$ Linear Collider $(ILC)$ and $ep$ collider $(THERA)$ experiments. The production rates of certain signal events, which are related the main two-body decay modes of the mirror quark, are also calculated.Comment: 19 pages, 11 figure

CONTROL STRATEGIES FOR VHTR GAS-TURBINE SYSTEM WITH DRY COOLING

ABSTRACT An original control strategy for very high temperature reactor (VHTR) gas-turbine system with dry cooling against ambient air temperature fluctuation was established in order to enable the freedom of site selection wherever desired without significant drawbacks on the performance. First, the operability of power conversion system and degradation of power generation efficiency were examined considering not only the thermodynamics but also the mechanical efficiency of compressor based on detailed performance map derived from experimental data. Second, control simulations for large ambient temperature fluctuations were conducted by system analysis code with the built-in control strategy. In addition, the sensitivity of power generation efficiency for typical steam cycle with dry cooling to ambient air temperature changes was assessed for the comparison. It was shown that the design goal can be effectively met simply by monitoring and controlling a few of key operating parameters such as reactor outlet temperature, primary coolant pressure. Furthermore, distinctive advantages of the VHTR gas-turbine system over nuclear power plant employing Rankine cycle was demonstrated when installing in inland area. INTRODUCTION Site Selection for nuclear power plants with water cooling is mired by their adverse thermal impact on the aquatic environment and consumption of large water quantity from their waste heat discharge. In addition, Fukushima nuclear plant accident elevated the importance of reactor safety against location-specific external events (e.g. tsunami), which resulted in the uncontrolled release of radioactive materials from the Fukushima plant to the environment. Although dry cooling which ultimately discharge the waste heat to the atmosphere is preferable in order to solve above issues simultaneously, several disadvantages, e.g. efficiency penalty on hottest days, high investment cost of cooling towers, etc., are preventing the penetration of the technology to curren

An improvement of isochronous mass spectrometry: Velocity measurements using two time-of-flight detectors

Isochronous mass spectrometry (IMS) in storage rings is a powerful tool for mass measurements of exotic nuclei with very short half-lives down to several tens of microseconds, using a multicomponent secondary beam separated in-flight without cooling. However, the inevitable momentum spread of secondary ions limits the precision of nuclear masses determined by using IMS. Therefore, the momentum measurement in addition to the revolution period of stored ions is crucial to reduce the influence of the momentum spread on the standard deviation of the revolution period, which would lead to a much improved mass resolving power of IMS. One of the proposals to upgrade IMS is that the velocity of secondary ions could be directly measured by using two time-of-flight (double TOF) detectors installed in a straight section of a storage ring. In this paper, we outline the principle of IMS with double TOF detectors and the method to correct the momentum spread of stored ions.Comment: Accepted by Nuclear Inst. and Methods in Physics Research,