Entropy in an expanding universe

The question of how the observed evolution of organized structures from initial chaos in the expanding universe can be reconciled with the laws of statistical mechanics is studied, with emphasis on effects of the expansion and gravity. Some major sources of entropy increase are listed. An expanding "causal" region is defined in which the entropy, though increasing, tends to fall further and further behind its maximum possible value, thus allowing for the development of order. The related questions of whether entropy will continue increasing without limit in the future, and whether such increase in the form of Hawking radiation or radiation from positronium might enable life to maintain itself permanently, are considered. Attempts to find a scheme for preserving life based on solid structures fail because events such as quantum tunneling recurrently disorganize matter on a very long but fixed time scale, whereas all energy sources slow down progressively in an expanding universe. However, there remains hope that other modes of life capable of maintaining themselves permanently can be found.     

非编码RNAs调控家禽骨骼肌生长发育的表观遗传机制研究进展

肉、蛋、奶是畜牧业最主要的三大产品,其中,肉的需求量是最高的。肌肉是动物躯体的重要组成部分,仅骨骼肌就已占全身体质量的40%左右。骨骼肌在调节动物新陈代谢、机体运动、能量储存和健康等方面至关重要,是机体功能正常运转的必要组分。骨骼肌发育过程极其复杂,主要包括体节细胞增殖分化、成肌细胞增殖分化、肌管成熟以及肌纤维形成等环节,整个过程受许多遗传因子调控,其中,由微小RNAs(miRNAs)、长链非编码RNAs(lncRNAs)、环状RNAs(circRNAs)等几种类型构成的非编码RNAs(ncRNAs)可以通过靶向关键因子调控骨骼肌发育过程。本文介绍了各类ncRNAs的特征与功能,总结了近年来有关ncRNAs在家禽肌肉生长发育中的研究,阐述ncRNAs在骨骼肌生长发育进程中的表观遗传调控机制,为改善家禽生长发育提供参考。     

Evolution of yeast noncoding RNAs reveals an alternative mechanism for widespread intron loss

The evolutionary forces responsible for intron loss are unresolved. Whereas research has focused on protein-coding genes, here we analyze noncoding small nucleolar RNA (snoRNA) genes in which introns, rather than exons, are typically the functional elements. Within the yeast lineage exemplified by the human pathogen Candida albicans, we find--through deep RNA sequencing and genome-wide annotation of splice junctions--extreme compaction and loss of associated exons, but retention of snoRNAs within introns. In the Saccharomyces yeast lineage, however, we find it is the introns that have been lost through widespread degeneration of splicing signals. This intron loss, perhaps facilitated by innovations in snoRNA processing, is distinct from that observed in protein-coding genes with respect to both mechanism and evolutionary timing.     

Mapping the universe

Maps of the galaxy distribution in the nearby universe reveal large coherent structures. The extent of the largest features is limited only by the size of the survey. Voids with a density typically 20 percent of the mean and with diameters of 5000 km s(-1) are present in every survey large enough to contain them. Many galaxies lie in thin sheet-like structures. The largest sheet detected so far is the "Great Wall" with a minimum extent of 60 h(-1) Mpc x 170 h(-1) Mpc, where h is the Hubble constant in units of 100 km s(-1) Mpc(-1). The frequent occurrence of these structures is one of several serious challenges to our current understanding of the origin and evolution of the large-scale distribution of matter in the universe.     

拓宽中宁枸杞市场的研究分析

以宁夏中宁县为例,在分析中宁县枸杞市场现存问题的基础上,探讨了影响枸杞市场机制的几个因素,提出对拓宽枸杞市场的建议,以两高一优的绿色产品占领市场,转变市场营销观念,拓宽市场销售渠道,以产业化推动市场化发展,开拓新的国内国际市场,加强从业人员培训等对拓宽枸杞产业发展的建议.