Microstructure and mechanical properties of AZ91 magnesium alloy subject to deep cryogenic treatments

AZ91 magnesium alloy was subjected to a deep cryogenic treatment. X-ray diffraction (XRD), scanning electronic microscopy (SEM), and transmission electronic microscopy (TEM) methods were utilized to characterize the composition and microstructure of the treated samples. The results show that after two cryogenic treatments, the quantity of the precipitate hardening β phase increases, and the sizes of the precipitates are refined from 8–10 μm to 2–4 μm. This is expected to be due to the decreased solubility of aluminum in the matrix at low temperature and the significant plastic deformation owing to internal differences in thermal contraction between phases and grains. The polycrystalline matrix is also noticeably refined, with the sizes of the subsequent nanocrystalline grains in the range of 50–100 nm. High density dislocations are observed to pile up at the grain boundaries, inducing the dynamic recrystallization of the microstructure, leading to the generation of a nanocrystalline grain structure. After two deep cryogenic treatments, the tensile strength and elongation are found to be substantially increased, rising from 243 MPa and 4.4% of as-cast state to 299 MPa and 5.1%.     

A common mass scale for satellite galaxies of the Milky Way

The Milky Way has at least twenty-three known satellite galaxies that shine with luminosities ranging from about a thousand to a billion times that of the Sun. Half of these galaxies were discovered in the past few years in the Sloan Digital Sky Survey, and they are among the least luminous galaxies in the known Universe. A determination of the mass of these galaxies provides a test of galaxy formation at the smallest scales and probes the nature of the dark matter that dominates the mass density of the Universe. Here we use new measurements of the velocities of the stars in these galaxies to show that they are consistent with them having a common mass of about 10(7) within their central 300 parsecs. This result demonstrates that the faintest of the Milky Way satellites are the most dark-matter-dominated galaxies known, and could be a hint of a new scale in galaxy formation or a characteristic scale for the clustering of dark matter.     

温度对二烷基二硫代甲酸钼摩擦学性能的影响

为系统了解温度对二烷基二硫代甲酸钼 (Mo DTC)减摩抗磨作用的影响 ,采用 SRV高温摩擦磨损试验机对不同温度下 Mo DTC的摩擦磨损特性进行了研究。结果表明 :Mo DTC的减摩抗磨特性与温度密切相关。 12 5℃和 2 5 0℃时 ,Mo DTC兼具减摩抗磨作用 ,在 2 5 0℃时效果尤其显著 ;32 0℃时 ,Mo DTC的抗磨作用基本丧失 ,但仍具有延缓摩擦失稳现象发生和一定程度的减摩作用。 Mo DTC的减摩抗磨特性还在一定程度上与基础油化学成份有关。根据表面分析结果认为 :2 5 0℃时 Mo DTC优异的减摩抗磨特性与缸套磨面上高含量元素 Mo,S,Zn及 P存在时形成的 Mo S2 和磷酸盐类化学质点有关     

Polycomb-mediated methylation on Lys27 of histone H3 pre-marks genes for de novo methylation in cancer

Many genes associated with CpG islands undergo de novo methylation in cancer. Studies have suggested that the pattern of this modification may be partially determined by an instructive mechanism that recognizes specifically marked regions of the genome. Using chromatin immunoprecipitation analysis, here we show that genes methylated in cancer cells are specifically packaged with nucleosomes containing histone H3 trimethylated on Lys27. This chromatin mark is established on these unmethylated CpG island genes early in development and then maintained in differentiated cell types by the presence of an EZH2-containing Polycomb complex. In cancer cells, as opposed to normal cells, the presence of this complex brings about the recruitment of DNA methyl transferases, leading to de novo methylation. These results suggest that tumor-specific targeting of de novo methylation is pre-programmed by an established epigenetic system that normally has a role in marking embryonic genes for repression.     

Estrogen receptor alpha (ESR1) gene amplification is frequent in breast cancer

Using an Affymetrix 10K SNP array to screen for gene copy number changes in breast cancer, we detected a single-gene amplification of the ESR1 gene, which encodes estrogen receptor alpha, at 6q25. A subsequent tissue microarray analysis of more than 2,000 clinical breast cancer samples showed ESR1 amplification in 20.6% of breast cancers. Ninety-nine percent of tumors with ESR1 amplification showed estrogen receptor protein overexpression, compared with 66.6% cancers without ESR1 amplification (P < 0.0001). In 175 women who had received adjuvant tamoxifen monotherapy, survival was significantly longer for women with cancer with ESR1 amplification than for women with estrogen receptor-expressing cancers without ESR1 amplification (P = 0.023). Notably, we also found ESR1 amplification in benign and precancerous breast diseases, suggesting that ESR1 amplification may be a common mechanism in proliferative breast disease and a very early genetic alteration in a large subset of breast cancers.     

A genome-wide association study for celiac disease identifies risk variants in the region harboring IL2 and IL21

We tested 310,605 SNPs for association in 778 individuals with celiac disease and 1,422 controls. Outside the HLA region, the most significant finding (rs13119723; P = 2.0 x 10(-7)) was in the KIAA1109-TENR-IL2-IL21 linkage disequilibrium block. We independently confirmed association in two further collections (strongest association at rs6822844, 24 kb 5' of IL21; meta-analysis P = 1.3 x 10(-14), odds ratio = 0.63), suggesting that genetic variation in this region predisposes to celiac disease.     

Loss of ACTN3 gene function alters mouse muscle metabolism and shows evidence of positive selection in humans

More than a billion humans worldwide are predicted to be completely deficient in the fast skeletal muscle fiber protein alpha-actinin-3 owing to homozygosity for a premature stop codon polymorphism, R577X, in the ACTN3 gene. The R577X polymorphism is associated with elite athlete status and human muscle performance, suggesting that alpha-actinin-3 deficiency influences the function of fast muscle fibers. Here we show that loss of alpha-actinin-3 expression in a knockout mouse model results in a shift in muscle metabolism toward the more efficient aerobic pathway and an increase in intrinsic endurance performance. In addition, we demonstrate that the genomic region surrounding the 577X null allele shows low levels of genetic variation and recombination in individuals of European and East Asian descent, consistent with strong, recent positive selection. We propose that the 577X allele has been positively selected in some human populations owing to its effect on skeletal muscle metabolism.     

Smart Cities and M<Superscript>3</Superscript>: Rapid Research,Meaningful Metrics and Co-Design

The research described in this paper is undertaken under the banner of the smart city, a concept that captures the way urban spaces are re-made by the incursion of new technology. Much of smart is centred on converting everyday activities into data, and using this data to generate knowledge mediated by technology. Ordinary citizens, those that may have their lives impacted by the technology, usually are not properly involved in the ‘smartification’ process. Their perceptions, concerns and expectations should inform the conception and development of smart technologies at the same extent. How to engage general public with smart cities research is the central challenge for the Making Metrics Meaningful (MMM) project. Applying a rapid participatory method, ‘Imagine’ over a five-month period (March – July) the research sought to gain insights from the general public into novel forms of information system innovation. This brief paper describes the nature of the accelerated research undertaken and explores some of the themes which emerged in the analysis. Generic themes, beyond the remit of an explicit transport focus, are developed and pointers towards further research directions are discussed. Participatory methods, including engaging with self-selected transport users actively through both picture creation and programmatically specific musical ‘signatures’ as well as group discussion, were found to be effective in eliciting users’ own concerns, needs and ideas for novel information systems.