Juan Luis Villanueva仿真软件在S7-200 PLC教学中的应用

为了改善PLC课堂的教学效果,将Juan Luis Villanueva仿真软件用于S7-200PLC课程的日常教学。首先对Juan Luis Villanueva仿真软件做了简单介绍,之后通过实现四台电机顺序启动同时停止的例子介绍了使用仿真软件的教学过程,最后简要说明了采用仿真软件在PLC教学中的优势。     

Generalized nesbet equation for molecular calculations

The Nesbet cluster expansion for atoms and molecules is extended to much more general situations than previously assumed possible. To exemplify non-conventional uses of the equation the one-dimensional half-filled Hubbard model is evaluated; results are in good agreement with the known exact solution. A possible way of applying the same procedure to realistic hamiltonians is discussed.     

攀登科学最高峰的第三世界科学家——1970年诺贝尔化学奖得主卢伊斯·弗德里科·莱洛伊尔

阿根廷生物化学家卢伊斯·弗德里科·莱洛伊尔因发现糖核苷酸及其在碳水化合物生物合成中的作用而获1970年诺贝尔化学奖。莱洛伊尔一生不仅致力于科学研究,还积极推动阿根廷的大学和医学教育,建立了致力于科学研究的坎波马尔基金会。本文回顾了莱洛伊尔的科研成果、相关研究背景以及他的科研历程,分析了他能够获得成功的因素;讨论了名师对科研人员学术指导的重要作用、及时调节研究过程中产生的各类情绪的积极意义以及敢于大胆跨界探索对科研人员的重要性。     

Isolation of phytosterols of Dalbergia ecastophyllum (L.) Taub. (Leguminosae) and modulation of antibiotic resistance by a possible membrane effect

Globally there are a larger number of strains of microorganisms resistant to multiple drugs mainly due to misuse and indiscriminate, resulting in increased morbidity, costs inherent benefits of health care, as well as mortality rates for infections. As a result of this a large number of researches have been conducted emphasizing the antimicrobial properties of plant products. In this study, the ethanol extract and hexane fraction of Dalbergia ecastophyllum (L.) Taub. (Leguminosae) have been used to evaluate the antibacterial and antifungal activity and for modulating the resistance of antimicrobials against bacterial strains of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans and fungal strains of Candida krusei, Candida tropicalis. The antibacterial and modulatory activity was determined by microdilution. Inhibition of the growth of bacteria and fungi tested extract was ?1024. The activity was enhanced when aminoglycosides were associated with sub-inhibitory concentrations of the ethanol extract and hexane fraction of Dalbergia ecastophyllum. Therefore, it is suggested that the ethanol extract and hexane fraction of Dalbergia ecastophyllum (L.) Taub. (Leguminosae) can be used as a source of natural products with a view to changing the resistance of these microorganisms to antimicrobials.     

Berkeley and Its Physics Heritage

I first sketch the settlement of Berkeley, California, the founding of the University of California at Berkeley, and the origin of its Department of Physics. I then discuss the pivotal role that Ernest O. Lawrence (1901–1958) and his invention and subsequent development of the cyclotron played in physics at Berkeley after his arrival there in 1928 through the Second World War and beyond. I close by commenting on the Lawrence Hall of Science, the educational center and science museum conceived as a living memorial to Lawrence.     

About (k,n) stochastic matrices

We study extremals for multidimensional stochastic matrices. Some related results are also considered.