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Attention deficit hyperactivity disorder (ADHD) is associated with heavy metal exposure during adolescent development. However, the direct clinical evidence is limited. To investigate the possible association between environmental heavy metal exposure and ADHD, a case-control study was conducted with children aged 6-14 years in Guangzhou, China. Results showed that median concentrations of chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), molybdenum (Mo), tin (Sn), barium (Ba), and lead (Pb) in the urine of the case group were significantly higher than those of the control group. Children with ADHD had significantly higher levels of 8-OHdG and MDA compared with those from the control group. In addition, correlations between urinary Co, Ni, Cu, Mo, and Sn were significantly correlated with 8-OHdG and MDA concentrations in urine. After the case and control groups were combined together and the first quartile was used as the reference category, odds ratios (ORs) of ADHD for children increased significantly with the quartile increasing of urinary Co, Cu, and Sn. Our study provides a clinical evidence that Co, Cu, and Sn exposure, particularly Sn exposure, may be an environmental risk of the incurrence of ADHD for children. Furthermore, Co, Ni, Cu, Mo, and Sn exposures were significantly correlated with DNA and lipid damage.

Our study shows long-term exposure to ETS was associated with urinary CC-16 among children without asthma.

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The traditional small and medium enterprise management system has a low efficiency of operation and management. A small and medium enterprise management system based on a clustering algorithm is designed in this paper to address this problem. In the proposed algorithm, the management system architecture is planned. The overall framework of the management system is designed based on the architecture theory. The management module is set up to realize the design of the management system. The system operation data management storage mode is set up to shorten the staff management and execution process. A multiunit management module is used to realize the management, operation, and propaganda management of enterprise expenditure. The effectiveness of the designed system is tested using simulation-based experiments to simulate the management and operation mode of the medium- and small-sized enterprise. Experimental results show that the efficiency of the designed management system is about 34% higher than that of the traditional management method, and the operation is stable.