极大代数意义下矩阵的周期分析

该文首先引进“依位置是周期的”和“最小周期”的概念,不须附加任何条件,证明了矩阵为周期阵的充要条件是其标准形中主对角线上的元素：Ａｔ,Ｉ≤ｔ≤ω,若其特征值λｔ≠－∞,则相等,并进一步证明文＾「３」中的ｄ是Ａ为λ周期阵时的最小阶。证明过程可很容易地推广到一般情况,即可证任一矩阵都是多值周期阵。     

Engineering microbes for targeted strikes against human pathogens

Lack of pathogen specificity in antimicrobial therapy causes non-discriminant microbial cell killing that disrupts the microflora present. As a result, potentially helpful microbial cells are killed along with the pathogen, altering the biodiversity and dynamic interactions within the population. Moreover, the unwarranted exposure of antibiotics to microbes increases the likelihood of developing resistance and perpetuates the emergence of multidrug resistance. Synthetic biology offers an alternative solution where specificity can be conferred to reduce the non-specific, non-targeted activity of currently available antibiotics, and instead provides targeted therapy against specific pathogens and minimising collateral damage to the host’s inherent microbiota. With a greater understanding of the microbiome and the available genetic engineering tools for microbial cells, it is possible to devise antimicrobial strategies for novel antimicrobial therapy that are able to precisely and selectively remove infectious pathogens. Herein, we review the strategies developed by unlocking some of the natural mechanisms used by the microbes and how these may be utilised in targeted antimicrobial therapy, with the promise of reducing the current global bane of multidrug antimicrobial resistance.     

论企业为何技术创新动力不足

基于一组约束条件下目标函数最大的线性规划模型，本文导出了模拟企业经济行为选择的微分方程组，揭示了旧体制下国有企业技术创新动力不足的原因。     

D to H ratio and the origin and evolution of Titan's atmosphere

A value of 1.7 x 10(-3) has been reported for the ratio of CH3D to CH4 in the stratosphere of the saturnian moon Titan. A lower value of 6 x 10(-4) for this ratio in the deeper part of Titan's atmosphere was reported by de Bergh et al. For comparison we note that the CH3D to CH4 ratio on Saturn and Jupiter is 8.7 x 10(-5) and 6.7 x 10(-5), respectively. We estimate the uncertainties in all these observations and data reduction to be about a factor of 2. Despite these uncertainties it appears that Titan's atmosphere is enriched in deuterium by a factor of > or = 3 relative to Jupiter and Saturn. Potential causative factors examined here for this enrichment are condensation to form tropospheric methane clouds, fractionation occurring over a hypothetical CH4-C2H6 ocean and between the ocean and the clathrate crust beneath, fractionation which occurred during the formation of Titan and fractionation occurring as a result of the evolution of Titan's atmosphere. We conclude that the greater part of the observed fractionation is probably derived from the formation of Titan and the subsequent evolution of Titan's atmosphere driven by photochemistry.     

Water vapour in the atmosphere of a transiting extrasolar planet

Water is predicted to be among the most abundant (if not the most abundant) molecular species after hydrogen in the atmospheres of close-in extrasolar giant planets ('hot Jupiters'). Several attempts have been made to detect water on such planets, but have either failed to find compelling evidence for it or led to claims that should be taken with caution. Here we report an analysis of recent observations of the hot Jupiter HD 189733b (ref. 6) taken during the transit, when the planet passed in front of its parent star. We find that absorption by water vapour is the most likely cause of the wavelength-dependent variations in the effective radius of the planet at the infrared wavelengths 3.6 mum, 5.8 mum (both ref. 7) and 8 mum (ref. 8). The larger effective radius observed at visible wavelengths may arise from either stellar variability or the presence of clouds/hazes. We explain the report of a non-detection of water on HD 189733b (ref. 4) as being a consequence of the nearly isothermal vertical profile of the planet's atmosphere.     

水仙鳞茎分泌物中抑制物质的分离与鉴定

首次报道了水仙鳞茎分泌液中抑制物质的分离纯化及鉴定的方法,经红外、紫外、磁核共振、及质谱等各种分析手段检测确证这种物质就是ｎａｒ－ｃｉｃｌａｓｉｎｅ（ＮＣＳ）,是一种生物碱,这种物质能明显抑制白菜种子萌发及其幼苗的生长。