Thermal depolarization and electromechanical hardening in Zn2+-doped Na1/2Bi1/2TiO3-BaTiO3

Na_1/2Bi_1/2TiO₃-based materials have been earmarked for one of the first large-volume applications of lead-free piezoceramics in high-power ultrasonics. Zn²⁺-doping is demonstrated as a viable route to enhance the thermal depolarization temperature and electromechanically harden (1-y)Na_1/2Bi_1/2TiO₃-yBaTiO₃ (NBT100yBT) with a maximum achievable operating temperature of 150 °C and mechanical quality factor of 627 for 1 mole % Zn²⁺-doped NBT6BT. Although quenching from sintering temperatures has been recently touted to enhance T_F-R, with quenching the doped compositions featuring an additional increase in T_F-R by 17 °C, it exhibits negligible effect on the electromechanical properties. The effect is rationalized considering the missing influence on conductivity and therefore, negligible changes in the defect chemistry upon quenching. High-resolution diffraction indicates that Zn²⁺-doped samples favor the tetragonal phase with enhanced lattice distortion, further corroborated by ²³Na Nuclear Magnetic Resonance investigations.     

Alterations in the Genomic Distribution of 5hmC in In Vivo Aged Human Skin Fibroblasts

5-Hydroxymethylcytosine (5hmC) is a functionally active epigenetic modification. We analyzed whether changes in DNA 5-hydroxymethylation are an element of age-related epigenetic drift. We tested primary fibroblast cultures originating from individuals aged 22–35 years and 74–94 years. Global quantities of methylation-related DNA modifications were estimated by the dot blot and colorimetric methods. Regions of the genome differentially hydroxymethylated with age (DHMRs) were identified by hMeDIP-seq and the MEDIPS and DiffBind algorithms. Global levels of DNA modifications were not associated with age. We identified numerous DHMRs that were enriched within introns and intergenic regions and most commonly associated with the H3K4me1 histone mark, promoter-flanking regions, and CCCTC-binding factor (CTCF) binding sites. However, only seven DHMRs were identified by both algorithms and all of their settings. Among them, hypo-hydroxymethylated DHMR in the intron of Rab Escort Protein 1 (CHM) coexisted with increased expression in old cells, while increased 5-hydroxymethylation in the bodies of Arginine and Serine Rich Protein 1 (RSRP1) and Mitochondrial Poly(A) Polymerase (MTPAP) did not change their expression. These age-related differences were not associated with changes in the expression of any of the ten-eleven translocation (TET) enzymes or their activity. In conclusion, the distribution of 5hmC in DNA of in vivo aged human fibroblasts underwent age-associated modifications. The identified DHMRs are, likely, marker changes.     

Genetic and genomic analysis of age at first insemination in Israeli dairy cattle

We performed a genetic analysis of age at first insemination, including estimation of the heritability and genetic correlations with other economic traits, and the consequences of including this trait in the Israeli selection index. The genetic factors affecting age at first insemination were determined via GWAS. Five data sets were analyzed. Data sets 1, 2, and 3 were used to compute variance components among age at first insemination, first calving age, days from first insemination to calving, and the 9 traits included in the Israel breeding index. Heritabilities for age at first insemination, calving age, and days from first insemination to calving in Israeli Holsteins as computed by REML individual animal model analyses of 273,239 Israeli Holstein cows were 0.072, 0.042, and 0.014. The estimated genetic correlation between the first 2 traits was 0.88. In addition to the fact that heritability of age at first insemination is 1.7 times the heritability for calving, the former trait has the advantage that the number of records is greater, and the records are generated earlier. Absolute values of the genetic and residual correlations between age at first insemination and the 9 traits included in the Israeli index were all less than 0.2. Data set 4 included first insemination dates of 1,181,600 calves born from 1985 through 2018. Genetic evaluations were computed by a single trait animal model. Annual phenotypic and genetic trends for age at first calving for calves born since 1985 were “positive,” that is, economically negative, at 0.320 ± 0.003 and 0.169 ± 0.005 d, respectively. Applying the GCTA-GREML software, 54% of variance in the transmitting ability of 1,585 sires could be explained by considering all 40,498 markers included in the GWAS analysis. The significant markers were mainly associated with milk production genes. The SNP UA-IFASA-8854 on chromosome 11 had the lowest probability value, 1.2 × 10^?24. This marker is located between the genes RETSAT and ELMOD3, both of which are overexpressed in human mammary glands. The gene RETSAT is reported to be essential for lipid accumulation and adipogenesis promotion. Gene enrichment analysis found that genes in the genomic region flanking significant markers are associated with vasopressin receptor activity, which was shown to mediate puberty in humans. If age at first insemination is included in the index with a weighting to account for 9% of the index, reductions of 2.8 and 2.6 d for age at first insemination and first calving age after 10 yr of selection are predicted, as compared with reductions of 1.4 and 1.1 d with the current index. Gains for the other index traits are only marginally affected. We suggest selection on age at first insemination as an alternative to selection for early calving.     

Influence of accelerated curing on the compressive strength of polymer-modified concrete

In recent building practice, rapid construction is one of the principal requisites. Furthermore, in designing concrete structures, compressive strength is the most significant of all parameters. While 3-d and 7-d compressive strength reflects the strengths at early phases, the ultimate strength is paramount. An effort has been made in this study to develop mathematical models for predicting compressive strength of concrete incorporating ethylene vinyl acetate (EVA) at the later phases. Kolmogorov-Smirnov (KS) goodness-of-fit test was used to examine distribution of the data. The compressive strength of EVA-modified concrete was studied by incorporating various concentrations of EVA as an admixture and by testing at ages of 28, 56, 90, 120, 210, and 365 d. An accelerated compressive strength at 3.5 hours was considered as a reference strength on the basis of which all the specified strengths were predicted by means of linear regression fit. Based on the results of KS goodness-of-fit test, it was concluded that KS test statistics value (D) in each case was lower than the critical value 0.521 for a significance level of 0.05, which demonstrated that the data was normally distributed. Based on the results of compressive strength test, it was concluded that the strength of EVA-modified specimens increased at all ages and the optimum dosage of EVA was achieved at 16% concentration. Furthermore, it was concluded that predicted compressive strength values lies within a 6% difference from the actual strength values for all the mixes, which indicates the practicability of the regression equations. This research work may help in understanding the role of EVA as a viable material in polymer-based cement composites.     

武汉市一般人群血清中全氟及多氟烷基化合物浓度及其影响因素研究

目的 了解武汉市一般人群血清中全氟及多氟烷基化合物(PFASs)浓度,探索血清中PFASs浓度水平的影响因素。方法 以在武汉市某医院进行一般体检的人群为研究对象(n=67),通过超高效液相色谱-三重四级杆质谱(UPLC-TQ/MS)联用仪测定外周血清中12种PFASs浓度,采用多元线性回归分析方法分析一般人口学特征和血清中PFASs浓度的关联性。结果 武汉市一般人群血清中12种PFASs的平均浓度水平为11.60 ng/mL。全氟辛烷磺酸及其盐类(PFOS)和全氟辛酸及其盐类(PFOA)的贡献率较大,分别为45.03%和31.86%。男性人群血清中PFOS、PFOA、全氟己基磺酸(PFHxS)、全氟壬酸(PFNA)等主要化合物的浓度高于女性,其β值(95%可信区间)分别为0.708(0.313,1.104)、0.518(0.069,0.967)、0.724(0.388,1.059)和0.684(0.399,0.968)。同时,发现血清中PFOS、PFHxS、PFNA浓度和年龄呈正相关,其β值(95%可信区间)分别为0.062(0.042,0.081)、0.035(0.019,0.052)和0.030(0.016,0.045)。结论 性别和年龄对血清中PFASs浓度有影响,在进行人体PFASs暴露评估中应考虑这些因素。     

退火温度对冷轧DP980钢力学性能的影响

利用连续退火模拟机对DP980试验钢进行了连续退火试验,并通过扫描电镜、电子背散射衍射、透射电镜等研究了不同退火温度下(775、800、825和850 ℃),试验钢显微组织的演变规律和力学性能的变化趋势。结果表明:试验钢的屈服强度随着退火温度的升高而不断增大(从705 MPa增大到850 MPa),抗拉强度和断后伸长率则随着退火温度的升高而不断减小(抗拉强度从1150 MPa减小到1030 MPa;伸长率从8.9%减小到5.3%),这与试验钢的显微组织构成和形态分布密切相关。此外,不同退火温度下,试验钢的加工硬化率曲线均呈现单调下降的趋势。     

12CrNi3钢外锁止套局部表面激光淬火工艺

利用半导体激光宽带对12CrNi3外锁止套局部进行表面淬火处理,并对处理后的零件进行外观检验、显微组织观察、硬度检测分析和摩擦磨损试验。试验结果表明:采取定光斑方式,激光头到工件表面扫描区域中心点距离375 mm(离焦量为0),工件倾斜22°,激光头倾斜18°,温度1350 ℃,扫描速度9 mm/s,单道扫描后表面平整性最好。表面激光淬火硬化层为750～1000 μm,最浅处为443.1 μm,硬化区组织为极细小马氏体组织,硬度达600～700 HV0.2,是基体硬度的2倍左右, 约为渗碳+淬火态硬度的1.3倍,且相变硬化区耐磨性能明显提高。     

Effect of metallurgical evolution during post-weld aging treatment on localised corrosion of resistance spot welding joints of A286 superalloy

The combined effect of resistance spot welding and precipitation hardening on the localised corrosion of A286 superalloy is studied. The specimens tested by double loop electrochemical potentiokinetic reactivation were welded in the solution treated condition, and then subjected to different precipitation hardening treatments. For both base metal and weld nugget, the maximum localised corrosion is reached when η phase is clearly observable. The fact that the localised corrosion resistance of weld nugget is different from that shown by base metal may be explained by the segregation of Ni and Ti towards the interdendritic region of weld nugget (studied by using scanning electron microscope/energy dispersive X-ray analysis).     

DP980+Z烘烤硬化值与退火温度的关系

摘要：为了研究退火温度对镀锌DP980+Z烘烤硬化值的影响，退火温度控制在760～820℃之间，系统分析退火温度对烘烤硬化值的影响。通过准静态拉伸试验机测量烘烤硬化值及抗拉强度，采用lepara试剂对组织中的马氏体进行着色，利用金相显微镜及图像处理软件测量马氏体的体积分数；采用扫描电镜观察DP980+Z的双相组织特点，并且将组织图片通过CAD转化成有限元图进行网格划分，建立代表性体积单元（RVE），通过有限元分析铁素体、马氏体强度对烘烤硬化值的影响。在同样的变形量情况下，DP980+Z的原始屈服强度越高，烘烤硬化值越高。