Environmental Science and Pollution Research - The COVID-19 pandemic is one of the contagious diseases involving all the world in 2019–2020. Also, all people are concerned about the future of... 相似文献
Pyrano[3,2-c]chromene derivatives are heterocycles with a wide range of biological properties. There is actually a need for safer synthesis of heterocycles, using for instance water as a solvent. High selectivity can also be achieved by addition of surface-active reagents to form micelles. Indeed, it is presumed that water facilitates organic reactions by the hydrophobic effect, enhanced hydrogen bonding in the transition state and cohesive energy density. Here, a simple aqueous-mediated protocol is developed for the quantitative synthesis of medicinally relevant pyrano[3,2-c]chromene derivatives by the tandem reaction of readily available reagents in cetyltrimethylammonium bromide micellar media. This new method is a modification of the three-component reaction involving Knoevenagel condensation, Michael addition and cyclization reaction. Yields of 3, 4-dihydropyrano[c]chromenes ranged from 85 to 99 % at room temperature. 相似文献
Introduction. Shoulder disorders are one of the most prevalent musculoskeletal disorders among carpet weavers. The most important cause of these disorders is muscle fatigue. The aim of the present study is to investigate the effect of carpet weaving characteristics on upper trapezius (UTr) muscle fatigue during a task cycle. Method. In this cross-sectional study, 9 women and 3 men participated. During an 80-min cycle of carpet weaving, a times-series model was applied to assess electromyography amplitude and frequency changes. Result. According to the joint analysis of electromyogram spectrum and amplitude method, the participants experienced 0% force decrease, 0.9% recovery, 18% force increase and 72% fatigue in the left UTr. Furthermore, the rates of force decrease, recovery, force increase and fatigue in the right UTr were 18%, 18%, 18% and 45%, respectively. Fatigue in the right and the left UTr was reported to be the dominant state during one carpet weaving task cycle. Conclusion. Task cycle appears to have a significant impact on UTr fatigue in participants, and UTr fatigue can be considered a serious risk factor in shoulder musculoskeletal disorders. Hence, further studies should focus on better workstations and work–rest periods during various subtasks. 相似文献
Environmental Monitoring and Assessment - Few estuaries remain unaffected by water management and altered freshwater deliveries. The Caloosahatchee River Estuary is a perfect case study for... 相似文献
Recently, an outbreak of a novel human coronavirus which is referred to as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (COVID-19) by the World Health Organization (WHO) was identified in Wuhan, China. To help combat the pandemic, a systematic review (SR) was performed to collect all available studies concerning inactivation methods, environmental survival, and control and prevention strategies. A comprehensive literature survey yielded 42 eligible studies which included in the SR. The results confirmed that the WHO recommended two alcohol-based hand rub formulations (ethanol 70–95% and 2-propanol 70–100%) had an efficient virucidal activity in less than 60 s by more and equal 4 log10 (≥ 99.99) approximately and could be used for disinfection in public health and health-care facilities. The findings indicated that SARS-CoV-1 and SARS-CoV-2 can survive under different environmental conditions between 4 and 72 h approximately. The results also demonstrate that temperature and relative humidity are important factors in the survival of SARS-CoV-2. The main strategies recommended by the WHO to avoid contracting SARS-CoV-2 are hand washing several times in the day and maintaining social distancing with others. It is important to note that the more studies require addressing, the more possible airborne transmission due to the survival of SARS-CoV-2 in aerosols for 3 h approximately. We hope that the results of the present SR can help researchers, health decision-makers, policy-makers, and people for understanding and taking the proper behavior to control and prevent further spread of SARS-CoV-2.
A new electrochemical adsorptive stripping voltammetry method was developed for the determination of trace amounts of copper in food and water samples. The study of electrochemical behavior of Cu ion indicated that Cu(II) and Schiff base formed a complex in H3BO4–NaOH buffer solution (pH?=?7.25). An accumulation potential of ?100 mV (vs Ag/AgCl) was applied while the solution was stirred for 60 s. The response curve was recorded by scanning the potential, and the peak current of ?0.31 V (vs Ag/AgCl) was recorded. The peak current and concentration of copper accorded with linear relationship in the range of 0.04–120 ng mL?1. The relative standard deviation (for 12 ng mL?1 of copper) was 1.73 %, and the detection limit was 0.007 ng mL?1. The possible interference of some common ions was studied. The proposed method was applied to the determination of copper in water, rice, wheat, tea, milk, and tomato with satisfactory results. 相似文献
Starch-g-polystyrene (Starch-g-PS)/Montmorillonite nanocomposites were prepared via free-radical graft copolymerization of styrene and starch in the presence of montmorillonite clay, by emulsion polymerization method using potassium persulfate (KPS) as an initiator/catalyst and sodium dodecylbenzensulfonate (SDBS) as an emulsifier. The nanocomposites with different clay content 0, 2.5, 5.0, 7.5 and 10 weight percent of starch were prepared and the changes in layer-stacked structures of the clay particles in the resulted nanocomposite compounds were examined by using of X-ray diffraction and FT-IR spectroscopy. Finally the thermal degradation behavior and morphology of nanocomposites were studied using thermal gravimetric analysis (TGA) and SEM, respectively. 相似文献
