Civic Meaningfulness: The Political Dimension—A Reply to Lena Dominelli

This article argues, firstly, that voluntary civic practices are not doomed to fall prey to a Big Society rhetoric and a cynical politics of cuts in social spending. It all depends on how these civic practices are promoted and what kind of civic discourse is communicated through the channels of social media and public opinion. Secondly, the author highlights the political importance of connecting meaningfulness with citizenship.     

Evolutionary genetics: evolution of mate choice in the wild

Qvarnstr?m et al. test whether the preference of female collared flycatchers (Ficedula albicollis) for males with large forehead patches could have evolved as a by-product of selection acting on male patch size. They find that the crucial genetic correlation between female choice and male patch size is not significant, and conclude that preference for large patches must have been shaped directly by selection. However, their use of the patch size of a female's social partner as a measure of choice is incomplete, and will result in low estimates of the potential for direct selection to shape female preference. Their study is therefore unable to resolve the question of how female preference for large forehead patches has evolved.     

基于NSGA-Ⅱ的IPMC机器鱼动态多目标相容优化控制

实际控制问题中往往有多个控制目标需要兼顾,且多个目标通常情况下是冲突的。根据相邻控制步之间系统状态和控制输入的连续性,提出了一个基于NSGA-II的动态迭代多目标相容优化控制算法,并且这一算法有能力处理目标空间为非凸的控制问题和提高在线优化速度。考虑到IPMC驱动机器鱼在运行过程中能耗和速度两个关键且冲突的目标,建立IMPC驱动机器鱼的运动及能耗模型,将所提算法进行了应用。仿真结果表明了控制算法的有效性及其在慢复杂系统动态控制中的应用潜力。     

A mutation in APP protects against Alzheimer's disease and age-related cognitive decline

The prevalence of dementia in the Western world in people over the age of 60 has been estimated to be greater than 5%, about two-thirds of which are due to Alzheimer's disease. The age-specific prevalence of Alzheimer's disease nearly doubles every 5 years after age 65, leading to a prevalence of greater than 25% in those over the age of 90 (ref. 3). Here, to search for low-frequency variants in the amyloid-β precursor protein (APP) gene with a significant effect on the risk of Alzheimer's disease, we studied coding variants in APP in a set of whole-genome sequence data from 1,795 Icelanders. We found a coding mutation (A673T) in the APP gene that protects against Alzheimer's disease and cognitive decline in the elderly without Alzheimer's disease. This substitution is adjacent to the aspartyl protease β-site in APP, and results in an approximately 40% reduction in the formation of amyloidogenic peptides in vitro. The strong protective effect of the A673T substitution against Alzheimer's disease provides proof of principle for the hypothesis that reducing the β-cleavage of APP may protect against the disease. Furthermore, as the A673T allele also protects against cognitive decline in the elderly without Alzheimer's disease, the two may be mediated through the same or similar mechanisms.     

Skewed superstatistical distributions from a Langevin and Fokker-Planck approach

The superstatistics concept is a useful statistical method to describe inhomogeneous complex systems for which a system parameter βfluctuatesonalargespatio-temporal scale. Inthispaper weanalyze ameasuredtimeseriesofwindspeed fluctuationsandextract the superstatistical distribution function f(β) directly from the data. We construct suitable Langevin and Fokker-Planck models with a position dependent β-field and show that they reduce to standard type of superstatistics in the overdamped limit.     

DNA repair is limiting for haematopoietic stem cells during ageing

Accumulation of DNA damage leading to adult stem cell exhaustion has been proposed to be a principal mechanism of ageing. Here we address this question by taking advantage of the highly specific role of DNA ligase IV in the repair of DNA double-strand breaks by non-homologous end-joining, and by the discovery of a unique mouse strain with a hypomorphic Lig4(Y288C) mutation. The Lig4(Y288C) mouse, identified by means of a mutagenesis screening programme, is a mouse model for human LIG4 syndrome, showing immunodeficiency and growth retardation. Diminished DNA double-strand break repair in the Lig4(Y288C) strain causes a progressive loss of haematopoietic stem cells and bone marrow cellularity during ageing, and severely impairs stem cell function in tissue culture and transplantation. The sensitivity of haematopoietic stem cells to non-homologous end-joining deficiency is therefore a key determinant of their ability to maintain themselves against physiological stress over time and to withstand culture and transplantation.     

Chromosome-scale selective sweeps shape Caenorhabditis elegans genomic diversity

The nematode Caenorhabditis elegans is central to research in molecular, cell and developmental biology, but nearly all of this research has been conducted on a single strain of C. elegans. Little is known about the population genomic and evolutionary history of this species. We characterized C. elegans genetic variation using high-throughput selective sequencing of a worldwide collection of 200 wild strains and identified 41,188 SNPs. Notably, C. elegans genome variation is dominated by a set of commonly shared haplotypes on four of its six chromosomes, each spanning many megabases. Population genetic modeling showed that this pattern was generated by chromosome-scale selective sweeps that have reduced variation worldwide; at least one of these sweeps probably occurred in the last few hundred years. These sweeps, which we hypothesize to be a result of human activity, have drastically reshaped the global C. elegans population in the recent past.     

Reverse breeding in Arabidopsis thaliana generates homozygous parental lines from a heterozygous plant

Traditionally, hybrid seeds are produced by crossing selected inbred lines. Here we provide a proof of concept for reverse breeding, a new approach that simplifies meiosis such that homozygous parental lines can be generated from a vigorous hybrid individual. We silenced DMC1, which encodes the meiotic recombination protein DISRUPTED MEIOTIC cDNA1, in hybrids of A. thaliana, so that non-recombined parental chromosomes segregate during meiosis. We then converted the resulting gametes into adult haploid plants, and subsequently into homozygous diploids, so that each contained half the genome of the original hybrid. From 36 homozygous lines, we selected 3 (out of 6) complementing parental pairs that allowed us to recreate the original hybrid by intercrossing. In addition, this approach resulted in a complete set of chromosome-substitution lines. Our method allows the selection of a single choice offspring from a segregating population and preservation of its heterozygous genotype by generating homozygous founder lines.