Gravitational redshift of galaxies in clusters as predicted by general relativity

The theoretical framework of cosmology is mainly defined by gravity, of which general relativity is the current model. Recent tests of general relativity within the Lambda Cold Dark Matter (ΛCDM) model have found a concordance between predictions and the observations of the growth rate and clustering of the cosmic web. General relativity has not hitherto been tested on cosmological scales independently of the assumptions of the ΛCDM model. Here we report an observation of the gravitational redshift of light coming from galaxies in clusters at the 99 per cent confidence level, based on archival data. Our measurement agrees with the predictions of general relativity and its modification created to explain cosmic acceleration without the need for dark energy (the f(R) theory), but is inconsistent with alternative models designed to avoid the presence of dark matter.     

HLA-DR antigens on lymphoid cells differ from those on myeloid cells

The human HLA-D region-related loci encode antigens which are structurally homologous and functionally analogous to the murine Ia molecules in mice. In addition to a role in immune regulation, it has been shown that the human D region-associated molecules are expressed on immature haematopoietic precursors and may also be involved in the regulation of haematopoiesis. Here we present evidence that distinct 'Ia-like' antigens are found on different haematopoietic cells. Approximately half of the Ia-like molecules expressed by B cells and activated T cells have an 'epitope' which is unique to lymphocytes and is not detectable on the Ia-like molecules of haematopoietic precursors or monocytes. This kind of lineage-restricted variation in Ia expression is a potential basis for selective compartmentalization and regulation of DR-associated function.     

探讨使用野外随机取样推断随机变量概率分布的数学方法--杂草研究作为一个例子

我们在生态学研究中涉及到的大多数变量呈现出随机性,因而可以认为它们就是随机变量.概率分布是研究随机变量变化规律的基础,如何利用野外取样来推断检验随机变量的分布是本文要解决的主要问题.本文扩展了回归方法的应用,使其能用来推断一个随机变量的分布函数,并且该推断还能被统计检验.作为一个应用实例,该方法被用于确定杂草种子在特定条件下扩散的分布函数.在此条件下,该杂草种子扩散为近似的高斯(正态)分布.     

Increased methylation variation in epigenetic domains across cancer types

Tumor heterogeneity is a major barrier to effective cancer diagnosis and treatment. We recently identified cancer-specific differentially DNA-methylated regions (cDMRs) in colon cancer, which also distinguish normal tissue types from each other, suggesting that these cDMRs might be generalized across cancer types. Here we show stochastic methylation variation of the same cDMRs, distinguishing cancer from normal tissue, in colon, lung, breast, thyroid and Wilms' tumors, with intermediate variation in adenomas. Whole-genome bisulfite sequencing shows these variable cDMRs are related to loss of sharply delimited methylation boundaries at CpG islands. Furthermore, we find hypomethylation of discrete blocks encompassing half the genome, with extreme gene expression variability. Genes associated with the cDMRs and large blocks are involved in mitosis and matrix remodeling, respectively. We suggest a model for cancer involving loss of epigenetic stability of well-defined genomic domains that underlies increased methylation variability in cancer that may contribute to tumor heterogeneity.     

Globally Optimal Clusterwise Regression By Column Generation Enhanced with Heuristics,Sequencing and Ending Subset Optimization

A column generation based approach is proposed for solving the cluster-wise regression problem. The proposed strategy relies firstly on several efficient heuristic strategies to insert columns into the restricted master problem. If these heuristics fail to identify an improving column, an exhaustive search is performed starting with incrementally larger ending subsets, all the while iteratively performing heuristic optimization to ensure a proper balance of exact and heuristic optimization. Additionally, observations are sequenced by their dual variables and by their inclusion in joint pair branching rules. The proposed strategy is shown to outperform the best known alternative (BBHSE) when the number of clusters is greater than three. Additionally, the current work further demonstrates and expands the successful use of the new paradigm of using incrementally larger ending subsets to strengthen the lower bounds of a branch and bound search as pioneered by Brusco's Repetitive Branch and Bound Algorithm (RBBA).     

Localization of the c-ab1 oncogene adjacent to a translocation break point in chronic myelocytic leukaemia

The human c-ab1 oncogene maps within the region (q34-qter) of chromosome 9 which is translocated to chromosome 22, the Philadelphia (Ph') chromosome, in chronic myelocytic leukaemia (CML). The position of the Ph' chromosomal break point is shown to be variable and, in one CML patient, has been localized immediately 5' of, or within, the c-ab1 oncogene. A DNA restriction fragment corresponding to this site has been molecularly cloned and shown to represent a chimaeric fragment of DNA from chromosomes 9 and 22.     

Plate-wide stress relaxation explains European Palaeocene basin inversions

During Late Cretaceous and Cenozoic times, many Palaeozoic and Mesozoic rifts and basin structures in the interior of the European continent underwent several phases of inversion (the process of shortening a previously extensional basin). The main phases occurred during the Late Cretaceous and Middle Palaeocene, and have been previously explained by pulses of compression, mainly from the Alpine orogen. Here we show that the main phases differed both in structural style and cause. The Cretaceous phase was characterized by narrow uplift zones, reverse activation of faults, crustal shortening, and the formation of asymmetric marginal troughs. In contrast, the Middle Palaeocene phase was characterized by dome-like uplift of a wider area with only mild fault movements, and formation of more distal and shallow marginal troughs. A simple flexural model explains how domal, secondary inversion follows inevitably from primary, convergence-related inversion on relaxation of the in-plane tectonic stress. The onset of relaxation inversions was plate-wide and simultaneous, and may have been triggered by stress changes caused by elevation of the North Atlantic lithosphere by the Iceland plume or the drop in the north-south convergence rate between Africa and Europe.     

Effects of grass bug feeding and drought stress on selected lines of crested wheatgrass

The sequential effects of feeding by grass bugs ( Irbisia pacifica [Hemiptera: Miridae]) and of drought stress on the growth of 2 crested wheatgrasses (the hybrid Agropyron cristatum × desertorum and A. cristatum cv. 'Fairway') were investigated in a controlled greenhouse experiment. Growth rates of genotypes that were previously selected for resistance to grass bug feeding were not consistently greater than those of unselected genotypes when plants were exposed to bug feeding. Thus, the mechanism of resistance to bug feeding for the selected genotypes does not appear to be ""tolerance,"" i.e., rapid growth rates that allow the resistant genotypes to compensate for damage to green leaves caused by bug feeding. In addition, previous bug feeding did not exacerbate the effects of drought stress on plant growth rates; droughted plants generally had lower growth rates, independent of the presence or absence of prior bug feeding. Thus, we suspect that the selection process may have inadvertently favored green, robust plants rather than true resistance to bug feeding.