Development of Powder-in-Tube Processed Iron Pnictide Wires and Tapes

The development of the PIT fabrication process of iron pnictide superconducting wires and tapes has been carried out in order to enhance their transport properties. Silver was found to be the best sheath material, since no reaction layer was observed between the silver sheath and the superconducting core. The grain connectivity of iron pnictide wires and tapes has been markedly improved by employing Ag or Pb as dopants. At present, critical current densities in excess of 3750 A/cm^2 (Ic = 37.5 A) at 4.2 K have been achieved on Ag-sheathed SrKFeAs wires prepared with the above techniques, which is the highest in iron-based wires and tapes so far. Moreover, Ag-sheathed Sm-1111 superconducting tapes were successfully prepared by PIT method at temperatures as low as 900C, instead of commonly used temperatures of 1200C. These results demonstrate the feasibility of producing superconducting pnictide composite wires, even grain boundary properties require much more attention.Comment: 4 pages, 6 figures. Submitted to ASC2010 proceeding

The Social Income Inequality, Social Integration and Health Status of Internal Migrants in China

Background: To examine the interaction between social income inequality, social integration, and health status among internal migrants (IMs) who migrate between regions in China. Methods: We used the data from the 2014 Internal Migrant Dynamic Monitoring Survey in China, which sampled 15,999 IMs in eight cities in China. The Gini coefficient at the city level was calculated to measure social income inequality and was categorized into low (0.2 \u3c Gini \u3c= 0.3), medium (0.3 \u3c Gini \u3c= 0.4), high (0.4 \u3c x \u3c = 0.5), and very high (Gini \u3e 0.5). Health status was measured based upon self-reported health, subjective well-being, and perceptions of stress and mental health. Social integration was measured from four perspectives (acculturation and integration willingness, social insurance, economy, social communication). Linear mixed models were used to examine the interaction effects between health statuses, social integration, and the Gini coefficient. Results: Factors of social integration, such as economic integration and acculturation and integration willingness, were significantly related to health. Social income inequality had a negative relationship with the health status of IMs. For example, IMs in one city, Qingdao, with a medium income inequality level (Gini = 0.329), had the best health statuses and better social integration. On the other hand, IMs in another city, Shenzhen, who had a large income inequality (Gini = 0.447) were worst in health statues and had worse social integration. Conclusion: Policies or programs targeting IMs should support integration willingness, promote a sense of belonging, and improve economic equality. In the meantime, social activities to facilitate employment and create social trust should also be promoted. At the societal level, structural and policy changes are necessary to promote income equity to promote IMs\u27 general health status

Effect of Living Arrangements on Cognitive Function in Chinese Elders: A Longitudinal Observational Study

Objective To examine how living arrangement as a social contextual factor can affect Chinese elders’ cognitive function. Setting and participants Our sample consists of 2486 Chinese elders from two waves (2014 and 2018) of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) that was administered in 22 of China’s 31 provinces using a multi-stage, disproportionate, purposive random sampling method. The CLHLS aims to better understand the determinants of healthy longevity in China and collects extensive data on a large population of fragile elders aged 80–112 in China. Outcome measures Cognitive function was measured by the Mini-Mental State Examination (MMSE). Living arrangement was divided into living in an institution, living alone and living with household members. Generalised linear regressions were carried out to examine the associations between baseline characteristics and cognitive function, while controlling age, gender and residential area. Results A total of 2486 participants were included in the study at baseline in 2014. Of these, 1162 (46.7%) were men and 1324 (53.3%) were women. The mean age at baseline was 75.07 (±8.31) years. The mean years of schooling were 2.86 (±3.68). The number (proportion) of the three living arrangements (lived in institutions, lived alone and lived with household members) were 93 (3.8%), 463 (18.6%) and 1930 (77.6%), respectively. Among all participants, cognitive function declined over time. Those who lived alone presented with the highest MMSE scores at baseline and showed the lowest decline after 4 years. Living arrangements had significant effects on decreasing cognitive function. Conclusion Chinese elders living in institutions were most vulnerable to cognitive decline. Living alone was not a risk condition in itself for the elderly in terms of cognitive decline. In addition, the benefits of living with household members to support cognitive function were not found in our study

Enhanced critical current properties in Ba0.6K0.4+xFe2As2 superconductor by over-doping of potassium

Phase-pure polycrystalline Ba0.6K0.4+xFe2As2 with were prepared using a one-step solid-state reaction method. We found that over-doping of potassium can improve critical current density (Jc). High-field Jc for samples with x = 0.1 is three times higher than that for samples with x = 0. Over-doping of K has minimal effect on the critical transition temperature (Tc). Less than 0.5 K degradations in Tc was measured for samples with x = 0.1. TEM revealed high concentration of dislocations in samples with x = 0.1, resulting in enhanced flux pining. Further analyses on magnetization loops for powder samples confirm that K over-doping can promote intra-grain Jc. Our results indicate that slight excess of K in Ba0.6K0.4Fe2As2 samples is beneficial to high-field applications.Comment: 13 pages, 4 figure

High transport critical current densities in textured Fe-sheathed Sr1-xKxFe2As2+Sn superconducting tapes

We report the realization of grain alignment in Sn-added Sr1-xKxFe2As2 superconducting tapes prepared by ex-situ powder-in-tube method. At 4.2 K, high transport critical current densities Jc of 2.5x10^4 A/cm^2 (Ic = 180 A) in self-field and 3.5x10^3 A/cm^2 (Ic = 25.5 A) in 10 T have been measured. These values are the highest ever reported so far for Fe-based superconducting wires and tapes. We believe the superior Jc in our tape samples are due to well textured grains and strengthened intergrain coupling achieved by Sn addition. Our results demonstrated an encouraging prospect for application of iron based superconductors.Comment: 14 pages, 4 figure

Superconductivity induced by doping Ru in SrFe2-xRuxAs2

Using one-step solid state reaction method, we have successfully synthesized the superconductor SrFe1-xRuxAs. X-ray diffraction indicates that the material has formed the ThCr2Si2-type structure with a space group I4/mmm. The systematic evolution of the lattice constants demonstrates that the Fe ions are successfully replaced by the Ru. By increasing the doping content of Ru, the spin-density-wave (SDW) transition in the parent compound is suppressed and superconductivity emerges. The maximum superconducting transition temperature is found at 13.5 K with the doping level of x = 0.7. The temperature dependence of DC magnetization confirms superconducting transitions at around 12 K. Our results indicate that similar to non-isoelectronic substitution, isoelectronic substitution contributes to changes in both the carrier concentration and internal pressure, and superconductivity could be induced by isoelectronic substitution.Comment: 14 pages, 4 figure

Association Between Acculturation and Body Weight Status Among Migrant Children in Guangzhou, China: A Cross-Sectional Study

Objective To assess the association between acculturation and body weight status among internal migrant children in China. Design, setting and participants A cross-sectional study was conducted among 1154 pairs of migrant children aged 11–17 years and their primary caregivers in Guangzhou, China, from April to May 2016. Measures Migrant children’s body weight status was measured by body mass index. Acculturation was measured by a questionnaire, developed and validated by the research team. The questionnaire had three dimensions with five factors, namely language, social interaction, custom, dressing and diet. Social anxiety was measured by Social Anxiety Scale for Children. Food intake was measured by the food frequency table that was developed from a previous study. Logistic regression was performed to examine the association between acculturation and overweight/obesity while controlling for migrant children’s and their caregivers’ demographic characteristics, children’s social anxiety and food intake. Results Seventy-six out of 1154 (6.6%) migrant children were overweight, and 36 (3.1%) were obese. The overall prevalence of overweight/obesity was 12.5% in boys, and 6.1% in girls (pConclusions The low levels of acculturation was associated with overweight/obesity among migrant children in Guangzhou, China. Promoting healthy acculturation and social campaign on healthy body weight may help prevent childhood overweight/obesity. Young migrant children, boys and children living with urban-to urban migrant caregivers should be the target subgroups

Direct observation of nanometer-scale amorphous layers and oxide crystallites at grain boundaries in polycrystalline Sr1-xKxFe2As2 superconductors

We report here an atomic resolution study of the structure and composition of the grain boundaries in polycrystalline Sr0.6K0.4Fe2As2 superconductor. A large fraction of grain boundaries contain amorphous layers larger than the coherence length, while some others contain nanometer-scale particles sandwiched in between amorphous layers. We also find that there is significant oxygen enrichment at the grain boundaries. Such results explain the relatively low transport critical current density (Jc) of polycrystalline samples with respect to that of bicrystal films.Comment: 12 pages, 4 figure