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Metals and arsenic distribution in stray dogs' tissues around a lead-zinc mine in Kabwe, Zambia
No full textMetal contamination poses a threat to human, animal, and environmental health. The purpose of the current study was to assess the accumulation of toxic and trace metal concentrations in tissues of stray dogs in Kabwe, a town known for lead pollution due to a long history of lead and zinc mining. Brain, spleen, heart, stomach, stomach content, small intestine, kidney, liver, and bone samples were collected from 29 stray dogs (14 from locations within 3 km of the mine and 15 from sites 7 km away from the mine) after necropsy. Inductively coupled plasma mass spectrometry was used to analyze toxic metals, arsenic (As), cadmium (Cd), and lead (Pb), and trace elements, copper (Cu) and zinc (Zn). The lungs (0.117 +/- 0.114 mg/kg dry weight), kidney (7.515 +/- 8.830 mg/kg dry weight), and bone (41.68 +/- 66.83 mg/kg dry weight) were found to have the highest concentrations of As, Cd, and Pb, respectively. In contrast, higher Cu and Zn concentrations were measured in the liver than in other tissues. In all tissues analyzed, tissues sampled from dogs near the mine had significantly higher mean concentrations of Cd and Pb than dogs far away. Neither sex nor age-related differences were observed in the distribution of metals in most tissues. There were significant associations among toxic (Pb and Cd) and trace metals (Cu and Zn). In the kidney, Cd positively correlated with Pb (rho = 0.534) and Zn (rho = 0.600), whereas in the liver, Cu correlated with Zn (rho = 0.565). The current study's findings suggest that environmental pollution is still a problem in Kabwe, and environmental remediation is needed to address the pollution
Asymmetric Cyanation of α-Ketimino Ester Derivatives with Chiral Ru-Li Combined Catalysts
No full textAsymmetric cyanation of alpha-ketimino esters catalyzed by combined systems of amino acid/BINAP derivative/Ru-(II) complexes and lithium compounds was examined. The use of an appropriate combination of amino acid and BINAP ligands achieved high enantioselectivity for a variety of alpha-alkynyl (Val/XylBINAP/Ru), alpha-alkenyl (Val/TolBINAP/Ru), and alpha-aryl imino esters (Val/XylBINAP/Ru) as well as an isatin-derived cyclic imino amide (t-Leu/BINAP/Ru) to afford the alpha-cyano-alpha-amino esters and the amide with an alpha-nitrogen-substituted quaternary chiral center with up to 98% ee
動的な機械加工プロセスの表現への4次元幾何モデルの適用
No full textIn the trend of Industry 4.0, the relationship between cyber field and physical field is gradually being established and deepened. In the field of processing and manufacturing, cyber field can be used to simulate the processing. This simulation can guide the real processing from multiple aspects and be applied to various processes. In this study, the authors tried to propose a geometric modeling system for cutter-workpiece engagement (CWE) of the milling process based on four-dimensional (4D) spatio-temporal space. Different from the traditional geometric process simulation based on three-dimensional (3D) models, this study pioneered the introduction of 4D geometric models for CWE analysis. 4D spatio-temporal space has three spatial coordinate axes (x, y, z) and one time coordinate axis (t). Therefore, the 4D geometric model in the 4D spatio-temporal space also integrates all the data in space and time. This means that a 4D geometric model can represent the shape of a 3D object, as well as the movement and morphological changes of the 3D object over a period of time. In traditional 3D methods, such a dynamic process often requires a discrete data set or is derived using physical equations. The method using a 4D geometric model can integrate this dynamic process into a 4D static model, which undoubtedly improves the integrity of the data. At the same time, it also provides a more convenient method for a series of computer-based and AI-based post-processing processes, such as display and deep learning training cases. In this study, the main focus is on representing the dynamic process of tool movement and material removal in CWE. The authors believe that this process is very suitable for analysis and representation using 4D geometric models. This dissertation describes the details of this study in detail. Chapter 1 summarizes the general outline of the paper. Chapters 2 and 3 introduce the research background and foundation in the field of machining simulation and 4D geometric modeling. Chapter 4 introduces the more special tools used to build the system. Chapters 5, 6, and 7 are the main chapters of the paper, which elaborate on three CWE analysis methods based on 4D geometric models. These three methods are T-map method, 4D imprint method and 4D set operation method, and they each have different advantages and disadvantages. The entire paper will be summarized in Chapter 8. The author hopes that this dissertation can propose a new solution to CWE analysis to a certain extent, and put forward some thoughts on the application of 4D models for industry filed and graphics field
