V形坡口和K形坡口Q345/SUS304异种钢对接接头残余应力和变形

以ABAQUS软件为平台,开发热-弹-塑性有限元方法模拟了V形坡口和K形坡口Q345/SUS304异种钢多层焊对接接头的温度场、残余应力和焊接变形.同时采用试验的方法测量了接头的残余应力和角变形.计算结果与试验测量结果吻合良好,验证了计算方法的妥当性.数值结果表明,不同坡口Q345/SUS304异种钢接头的Q345母材与焊缝交界处的应力分布均出现不连续性,且SUS304侧的高拉伸残余应力区明显宽于Q345侧;K形坡口开口朝向Q345侧相较于开口朝向SUS304侧的接头,Q345/焊缝交界处附近的峰值应力和高拉伸残余应力区均明显较小.试验和数值结果表明,坡口形式对接头的角变形有明显的影响.     

耐盐型聚丙烯酸钠高吸水树脂的合成研究

以过硫酸铵(APS)为引发剂,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,采用反相悬浮乳液聚合法合成了丙烯酸(AA)-丙烯酰胺(AM)-2-丙烯酰胺基辛烷基磺酸钠(NaAMC8S)三元共聚高吸水树脂,研究了引发剂含量、交联剂含量、AA中和度对树脂吸液性能的影响。结果表明:磺酸基单体NaAMC8S的加入显著提高了吸水树脂的盐水吸收能力,当引发剂含量为0.2%,交联剂含量为0.02%,中和度为75%,加入NaAMC8S为0.5%时,共聚树脂吸自来水的量为601mL/g,吸0.9%Nacl水溶液的量为154mL/g。     

The first years as independent actors in the housing market: Young households in a Swedish municipality

This study deals with young households at the beginning of their housing career. During the 1990s, a tendency of the young to leave the parental home at a later age than during previous decades was discussed. With extended education, rising housing costs and a shortage of rental housing, difficulties in finding an affordable place to live could be expected to have increased. Parental resources are of increasing importance in times of recession. The aim of this study was to follow the first steps in the housing careers of young individuals in a Swedish municipality and to investigate the time of nest-leaving and the choice of tenure for their first and second moves. Individuals aged 16–25 years in the municipality of Gävle, Sweden, were included in the study. Longitudinal data for the years 1985–1995 were used. To capture changes over time, the nest-leaving situations of two cohorts were compared. Results indicate that the individuals in the 1973 cohort leave home at a higher age than do those in the 1968 cohort. A surprisingly large share move into tenant co-operatives. Such moves, as well as moves into owner occupation, occurred mainly within Gävleborg County. Individuals moving to other municipalities outside the county moved to a larger extent into rental housing.     

澳大利亚零碳展示房

1背景简介在澳大利亚,民用住宅已经成为碳排放增长较快的板块之一.预计在2020年,民用住宅将比1990年增加61％,因此,想要达到澳大利亚的以2000年为基准,在2020年和2050年相继减排5％和80％的目标,需要对将建的和已建的民用住宅进行大量的碳减排.2007年,为了倡导民用住宅的减排和维护国家未来的持续发展,澳大利亚联邦科学院( CSIRO)的能源转型研究中心设立了澳大利亚零碳房( AusZEH)项目,致力于展示和评估适用于澳大利亚的低碳民用住宅技术.     

Real-time PCR detection of the thermostable direct hemolysin and thermolabile hemolysin genes in a Vibrio parahaemolyticus cultured from mussels and mussel homogenate associated with a foodborne outbreak

Molecular methods have become vital epidemiological tools in the detection and characterization of bacteria associated with a foodborne outbreak. We used both culture and real-time PCR to detect a Vibrio parahaemolyticus isolate associated with a foodborne outbreak. The outbreak occurred in July 2002 in Polk County, Florida, and originated at a Chinese buffet, with one person being hospitalized. The hospital isolated V. parahaemolyticus from the patient but destroyed the sample after diagnosis. From an onsite visit of the restaurant, food samples that possibly contributed to the outbreak were collected and sent to the Florida Department of Health, Tampa Branch Laboratory. Crab legs, crabsticks, and mussel samples were homogenized and incubated according to the Food and Drug Administration Bacteriological Analytical Manual culture protocol. Three sets of primers and a TaqMan probe were designed to target the tdh, trh, and tlh genes and used for real-time PCR. This study was successful in isolating V. parahaemolyticus from a mussel sample and detecting two of its genes (tdh and tlh) in food and pure culture by real-time PCR.     

Internalization and Accumulation in Dendritic Cells of a Small pH‐Activatable Glycomimetic Fluorescent Probe as Revealed by Spectral Detection

DC‐SIGN, an antigen‐uptake receptor in dendritic cells (DCs), has a clear role in the immune response but, conversely, can also facilitate infection by providing entry of pathogens into DCs. The key action in both processes is internalization into acidic endosomes and lysosomes. Molecular probes that bind to DC‐SIGN could thus provide a useful tool to study internalization and constitute potential antagonists against pathogens. So far, only large molecules have been used to directly observe DC‐SIGN‐mediated internalization into DCs by fluorescence visualization. We designed and synthesized an appropriate small glycomimetic probe. Two particular properties of the probe were exploited: activation in a low‐pH environment and an aggregation‐induced spectral shift. Our results indicate that small glycomimetic molecules could compete with antigen/pathogen for binding not only outside but also inside the DC, thus preventing the harmful action of pathogens that are able to intrude into DCs, for example, HIV‐1.     

Pressure‐Tunable Ambipolar Conduction and Hysteresis in Thin Palladium Diselenide Field Effect Transistors

Few‐layer palladium diselenide (PdSe₂) field effect transistors are studied under external stimuli such as electrical and optical fields, electron irradiation, and gas pressure. The ambipolar conduction and hysteresis are observed in the transfer curves of the as‐exfoliated and unprotected PdSe₂ material. The ambipolar conduction and its hysteretic behavior in the air and pure nitrogen environments are tuned. The prevailing p‐type transport observed at atmospheric pressure is reversibly turned into a dominant n‐type conduction by reducing the pressure, which can simultaneously suppress the hysteresis. The pressure control can be exploited to symmetrize and stabilize the transfer characteristics of the device as required in high‐performance logic circuits. The transistors are affected by trap states with characteristic times in the order of minutes. The channel conductance, dramatically reduced by the electron irradiation during scanning electron microscope imaging, is restored after an annealing of several minutes at room temperature. The work paves the way toward the exploitation of PdSe₂ in electronic devices by providing an experiment‐based and deep understanding of charge transport in PdSe₂ transistors subjected to electrical stress and other external agents.     

Distribution of the Amphipod Diporeia in Lake Superior: The Ring of Fire

Diporeia, formerly the dominant benthic macroinvertebrate in the Great Lakes, remains a keystone species in Lake Superior. Little is known, however, about fine scale amphipod distributions, especially as influenced by the production, transport and transformation of energy resources. Here, we document the distribution and abundance of Diporeia along 19 transects around the lake's perimeter. Regions of elevated density, averaging 958 ± 408 Diporeia/m² (mean ± S.D.) were observed along all transects, typically within slope habitat (depth of 30–125 m). Waters shoreward (shelf habitat, < 30 m) and lakeward (profundal habitat, > 125 m) of these regions supported significantly lower densities, averaging 239 ± 178/m² and 106 ± 59/m², respectively. Amphipods within regions of elevated density, termed here the Ring of Fire, account for two-thirds of the lakewide population while occupying only one-quarter of the benthic habitat. The Ring of Fire, observed lakewide as a band averaging 14.2 ± 9.4 km in width, is characterized as a region of transitional sediment deposition with gentle slope, proximate to nearshore locations of elevated primary production. Within the Ring of Fire exceptionally high densities are found in the south central region, where the Keweenaw Current and slope bathymetries serve to funnel production from adjoining regions of high production. Density measurements for the 173 stations sampled here are used to estimate lakewide Diporeia standing stock (22.5–37.7 trillion individuals, 4.4–7.4 Gg dry weight, 2.1–3.5 Gg C), individual and biomass density (274–460/m², 0.05–0.09 g DW/m², 0.03–0.04 gC/m²) and areal (0.02–0.03 g C/m²/yr) and total (1.6–2.6 Gg C/yr) production.