Human gut microbiome viewed across age and geography

Gut microbial communities represent one source of human genetic and metabolic diversity. To examine how gut microbiomes differ among human populations, here we characterize bacterial species in fecal samples from 531 individuals, plus the gene content of 110 of them. The cohort encompassed healthy children and adults from the Amazonas of Venezuela, rural Malawi and US metropolitan areas and included mono- and dizygotic twins. Shared features of the functional maturation of the gut microbiome were identified during the first three years of life in all three populations, including age-associated changes in the genes involved in vitamin biosynthesis and metabolism. Pronounced differences in bacterial assemblages and functional gene repertoires were noted between US residents and those in the other two countries. These distinctive features are evident in early infancy as well as adulthood. Our findings underscore the need to consider the microbiome when evaluating human development, nutritional needs, physiological variations and the impact of westernization.     

The directionality of distinctively mathematical explanations

In “What Makes a Scientific Explanation Distinctively Mathematical?” (2013b), Lange uses several compelling examples to argue that certain explanations for natural phenomena appeal primarily to mathematical, rather than natural, facts. In such explanations, the core explanatory facts are modally stronger than facts about causation, regularity, and other natural relations. We show that Lange's account of distinctively mathematical explanation is flawed in that it fails to account for the implicit directionality in each of his examples. This inadequacy is remediable in each case by appeal to ontic facts that account for why the explanation is acceptable in one direction and unacceptable in the other direction. The mathematics involved in these examples cannot play this crucial normative role. While Lange's examples fail to demonstrate the existence of distinctively mathematical explanations, they help to emphasize that many superficially natural scientific explanations rely for their explanatory force on relations of stronger-than-natural necessity. These are not opposing kinds of scientific explanations; they are different aspects of scientific explanation.     

基于面向对象的物料采购系统

以一个基于面向对象的企业集成模型为研究背景，针对企业物料管理的实际，运用面向对象的系统设计方法和面向对象的程度设计语言Ｃ￣（＋＋）和ＲＯＣＫ，在计算机上实现了相应的物料采购系统。     

Fine structure and phase composition of Fe-14Mn-1.2C steel:influence of a modified mixture based on refractory metals

The effect of TiO₂, ZrO₂ and Na₃AlF₆ ultrafine powders on the fine structure and the phase composition of Fe-14Mn-1.2C steel was investigated. The introduction of the ultrafine powders into the melt influenced the grain size, the quantity, and the character of distribution of nonmetallic inclusions in the railroad frogs. The microstructure of castings was improved significantly because of the refinement of the grain structure and an increase of the grain-boundary area. After the modifying mixture was introduced into the melt, either the microtwins of one or two intersecting systems or the precipitations of ε-martensite of different types, or simultaneously the microtwins and wafers of ε-martensite, were present in each grain.     

大陆科学钻探 十年的进展与未来的挑战

科学钻探是现代地球科学研究中一个不可或缺的工具，因为它是直接获得地球深部过程信息的唯一来源，对于我们更好地认识了解我们赖以生存的星球、解决紧迫的社会经济问题具有关键性的作用。国际大陆科学钻探计划（ICDP）始于1996年，2005年在德国波茨坦召开了第二届国际大陆钻探会议。