Migration in later life: evidence from the British Household Panel Study

This article uses data from the British Household Panel Study over the period 1991 - 2007 to examine the factors associated with residential mobility among people aged 50 and over. In line with earlier research, the likelihood of migrating, that is, changing address, is found to vary according to the demographic and socio-economic characteristics of the older person. Those in late middle age (50-59) and the oldest-old (90 and over) were most likely to move. Migration was also strongly associated with changes in partnership, health and economic status during the last 12 months, highlighting the importance of seeing migration within a life course context with certain life course events such as divorce, widowhood or retirement being important triggers for prompting a move. As divorce and remarriage become more common in later life, 'relationship driven migration' is likely to become more important, adding a new category to the classical typology of later life migration.     

Maternal Rnf12/RLIM is required for imprinted X-chromosome inactivation in mice

Two forms of X-chromosome inactivation (XCI) ensure the selective silencing of female sex chromosomes during mouse embryogenesis. Imprinted XCI begins with the detection of Xist RNA expression on the paternal X?chromosome (Xp) at about the four-cell stage of embryonic development. In the embryonic tissues of the inner cell mass, a random form of XCI occurs in blastocysts that inactivates either Xp or the maternal X?chromosome (Xm). Both forms of XCI require the non-coding Xist RNA that coats the inactive X?chromosome from which it is expressed. Xist has crucial functions in the silencing of X-linked genes, including Rnf12 (refs 3, 4) encoding the ubiquitin ligase RLIM (RING finger LIM-domain-interacting protein). Here we show, by targeting a conditional knockout of Rnf12 to oocytes where RLIM accumulates to high levels, that the maternal transmission of the mutant X?chromosome (Δm) leads to lethality in female embryos as a result of defective imprinted XCI. We provide evidence that in Δm female embryos the initial formation of Xist clouds and Xp silencing are inhibited. In contrast, embryonic stem cells lacking RLIM are able to form Xist clouds and silence at least some X-linked genes during random XCI. These results assign crucial functions to the maternal deposit of Rnf12/RLIM for the initiation of imprinted XCI.     

High star formation rates as the origin of turbulence in early and modern disk galaxies

Observations of star formation and kinematics in early galaxies at high spatial and spectral resolution have shown that two-thirds are massive rotating disk galaxies, with the remainder being less massive non-rotating objects. The line-of-sight-averaged velocity dispersions are typically five times higher than in today's disk galaxies. This suggests that gravitationally unstable, gas-rich disks in the early Universe are fuelled by cold, dense accreting gas flowing along cosmic filaments and penetrating hot galactic gas halos. These accreting flows, however, have not been observed, and cosmic accretion cannot power the observed level of turbulence. Here we report observations of a sample of rare, high-velocity-dispersion disk galaxies in the nearby Universe where cold accretion is unlikely to drive their high star formation rates. We find that their velocity dispersions are correlated with their star formation rates, but not their masses or gas fractions, which suggests that star formation is the energetic driver of galaxy disk turbulence at all cosmic epochs.     

Magnetite defines a vertebrate magnetoreceptor

The key behavioural, physiological and anatomical components of a magnetite-based magnetic sense have been demonstrated in rainbow trout (Oncorhynchus mykiss). Candidate receptor cells located within a discrete sub-layer of the olfactory lamellae contained iron-rich crystals that were similar in size and shape to magnetite crystals extracted from salmon. Here we show that these crystals, which mapped to individual receptors using confocal and atomic force microscopy, are magnetic, as they are uniquely associated with dipoles detected by magnetic force microscopy. Analysis of their magnetic properties identifies the crystals as single-domain magnetite. In addition, three-dimensional reconstruction of the candidate receptors using confocal and atomic force microscopy imaging confirm that several magnetic crystals are arranged in a chain of about 1 microm within the receptor, and that the receptor is a multi-lobed single cell. These results are consistent with a magnetite-based detection mechanism, as 1-microm chains of single-domain magnetite crystals are highly suitable for the behavioural and physiological responses to magnetic intensity previously reported in the trout.     

印染废水脱色研究进展

分别从生物处理法、化学氧化法、吸附法和电化学法等方面介绍了印染废水的处理方法和研究进展,介绍了放电等离子体技术、超临界水氧化技术、膜分离技术以及超声波技术等新兴的治污技术,分析了染料废水处理技术的研究状况。化学氧化技术使用广泛,一般常用于生物处理的前处理;吸附法的吸附效率较高,吸附过程不破坏染料的分子结构,染料可以回收利用;电化学技术不仅能去除重金属,而且能去除化学需氧量(COD)、生物需氧量(BOD)和总悬浮固体(TSS)浓度,对染料的脱色效果很好;超临界水氧化法使有毒有害的有机物完全转化,可以避免二次污染问题,氧化反应速率快,适用范围广;膜分离技术高效、节能,可实现废水的循环利用和有用物质回收;超声技术操作条件温和、降解速率快、可以单独使用或与其他水处理技术联合使用。