Let R be a commutative ring with non-zero identity. The cozero-divisor graph of R, denoted by , is a graph with vertices in , which is the set of all non-zero and non-unit elements of R, and two distinct vertices a an...Let R be a commutative ring with non-zero identity. The cozero-divisor graph of R, denoted by , is a graph with vertices in , which is the set of all non-zero and non-unit elements of R, and two distinct vertices a and b in are adjacent if and only if and . In this paper, we investigate some combinatorial properties of the cozero-divisor graphs and such as connectivity, diameter, girth, clique numbers and planarity. We also study the cozero-divisor graphs of the direct products of two arbitrary commutative rings.展开更多
The tree-ring cores of Tianshan spruces collected from nine sites in the Urumqi River drainage of the middle Tianshan Mountains were used to establish three types of the tree-ring width chronologies over the last 370 ...The tree-ring cores of Tianshan spruces collected from nine sites in the Urumqi River drainage of the middle Tianshan Mountains were used to establish three types of the tree-ring width chronologies over the last 370 years, using the international standard method of dendrochronology. Our study demonstrates that dendrochronology can be better used to reconstruct the number of the precipitation day than to reconstruct the precipitation amount in middle Tianshan Mountains. It is found that the residual chronology among the three tree-ring width chronologies has the best relationship with number of spring precipitation days from May 20 to June 8. The chronologies at Haxionggou B site and Zaierdegou site in the Urumiqi drainage have the highest correlation with the observed number of spring precipitation days at Daxigou meteorological station, and are used to reconstruct the spring precipitation days over the last 370 years in the drainage. The main significant decreasing trend of the number of the spring precipitation days occurred during 1665—1717, while the significant increasing trends happened during 1805—1841 and 1914—1943. The reconstructed series of the number of spring precipitation days has quasi-periodic variations of 3.3, 2.1, 2.5, 12.3 and 32.0 years with the dominated short periodical changes. The long cycle of 32 years is shown quite clearly in the 10-year smoothed sequence. The maximum spring precipitation days occurred mainly in the 1630s, 1840s and 1940s, while the lowest number of spring precipitation days for the 10-year average occurred in the 1710s.展开更多
The trend toward designing large hydrophobic molecules for lead optimization is often associated with poor drug-likeness and high attrition rates in drug discovery and development. Structural simplification is a power...The trend toward designing large hydrophobic molecules for lead optimization is often associated with poor drug-likeness and high attrition rates in drug discovery and development. Structural simplification is a powerful strategy for improving the efficiency and success rate of drug design by avoiding 'molecular obesity'. The structural simplification of large or complex lead compounds by truncating unnecessary groups can not only improve their synthetic accessibility but also improve their pharmacokinetic profiles, reduce side effects and so on. This review will summarize the application of structural simplification in lead optimization. Numerous case studies, particularly those involving successful examples leading to marketed drugs or drug-like candidates, will be introduced and analyzed to illustrate the design strategies and guidelines for structural simplification.展开更多
文摘Let R be a commutative ring with non-zero identity. The cozero-divisor graph of R, denoted by , is a graph with vertices in , which is the set of all non-zero and non-unit elements of R, and two distinct vertices a and b in are adjacent if and only if and . In this paper, we investigate some combinatorial properties of the cozero-divisor graphs and such as connectivity, diameter, girth, clique numbers and planarity. We also study the cozero-divisor graphs of the direct products of two arbitrary commutative rings.
基金supported by the National Key Basic Research Project(Grant No.G200O48701)the National Natural Science Foundation(Grant No.40265002)+1 种基金the Project(Grant No.2002CCA04600)the Xinjiang Commission of Science and Technology(Grant No.980103002).
文摘The tree-ring cores of Tianshan spruces collected from nine sites in the Urumqi River drainage of the middle Tianshan Mountains were used to establish three types of the tree-ring width chronologies over the last 370 years, using the international standard method of dendrochronology. Our study demonstrates that dendrochronology can be better used to reconstruct the number of the precipitation day than to reconstruct the precipitation amount in middle Tianshan Mountains. It is found that the residual chronology among the three tree-ring width chronologies has the best relationship with number of spring precipitation days from May 20 to June 8. The chronologies at Haxionggou B site and Zaierdegou site in the Urumiqi drainage have the highest correlation with the observed number of spring precipitation days at Daxigou meteorological station, and are used to reconstruct the spring precipitation days over the last 370 years in the drainage. The main significant decreasing trend of the number of the spring precipitation days occurred during 1665—1717, while the significant increasing trends happened during 1805—1841 and 1914—1943. The reconstructed series of the number of spring precipitation days has quasi-periodic variations of 3.3, 2.1, 2.5, 12.3 and 32.0 years with the dominated short periodical changes. The long cycle of 32 years is shown quite clearly in the 10-year smoothed sequence. The maximum spring precipitation days occurred mainly in the 1630s, 1840s and 1940s, while the lowest number of spring precipitation days for the 10-year average occurred in the 1710s.
基金supported by the National Natural Science Foundation of China (Grant No. 81725020 to Chunquan Sheng and No. 21602252 to Shengzheng Wang)the Innovation Program of Shanghai Municipal Education Commission (Grant No. 2019-0107-00-07-E00073 to Chunquan Sheng, China)the Hong Kong Scholars Program (Grant No. XJ201713 to Shengzheng Wang, China)
文摘The trend toward designing large hydrophobic molecules for lead optimization is often associated with poor drug-likeness and high attrition rates in drug discovery and development. Structural simplification is a powerful strategy for improving the efficiency and success rate of drug design by avoiding 'molecular obesity'. The structural simplification of large or complex lead compounds by truncating unnecessary groups can not only improve their synthetic accessibility but also improve their pharmacokinetic profiles, reduce side effects and so on. This review will summarize the application of structural simplification in lead optimization. Numerous case studies, particularly those involving successful examples leading to marketed drugs or drug-like candidates, will be introduced and analyzed to illustrate the design strategies and guidelines for structural simplification.
