Microstructure, texture and tensile properties of ultrafine/nano grained magnesium alloy processed by accumulative back extrusion

An AZ31 wrought magnesium alloy was processed by employing multipass accumulative back extrusion process. The obtained microstructure, texture and room temperature tensile properties were characterized and discussed. Ultrafine grained microstructure including nano grains were developed, where the obtained mean grain size was decreased from 8 to 0.5 µm by applying consecutive passes. The frequency of both low angle and high angle boundaries increased after processing. Strength of the experimental alloy was decreased after processing, which was attributed to the obtained texture involving the major component lying inclined to the deformation axis. Both the uniform and post uniform elongations of the processed materials were increased after processing, where a total elongation of 68 pct was obtained after six-pass deformation. The contribution of different twinning and slip mechanism was described by calculating corresponding Schmid factors. The operation of prismatic slip was considered as the major deformation contributor. The significant increase in post uniform deformation of the processed material was discussed relying on the occurrence of grain boundary sliding associated with the operation of prismatic slip.Postprint (author's final draft

Analysis of microstructure effects on edge crack of thin strip during cold rolling

Edge cracks in cold rolling of the thin strip affect the strip quality and productivity significantly. In this study, an experimental and mechanical investigation on microstructures has been carried out to study the edge crack formation during cold rolling of the thin strip. The effects of the feed material microstructures on the edge crack evolution were studied employing optical microscopy and scanning electron microscopy (SEM). Experimental observation indicates that fine grain occurs in hot-rolled microstructure and coarse grain is produced in ferritic rolled microstructure. Different grain sizes affect significantly the formation mechanics of the microcrack, crack initiation, and orientation of crack extension. The grain size and grain boundaries effects on crack retardation are discussed also during edge crack initiation. During the crack growth in coarse grain, most edge crack tips will blunt, which improves the crack toughness by causing less stress concentration. Overall, the fine microstructure shows a good crack initiation resistance, whereas the coarse microstructure has a better resistance to crack propagation. This research provides additional understanding of the mechanism of microstructure influence on edge crack evolution of cold strip rolling, which could be helpful for developing defect-free thin strip

Daidzein Prevents the Increase in CD4+CD28null T Cells and B Lymphopoesis in Ovariectomized Mice: A Key Mechanism for Anti-Osteoclastogenic Effect

Estrogen deficiency leads to an upregulation of TNF-α producing T cells and B-lymphopoesis which augments osteoclastogenesis. Estrogen deficiency also increases the population of premature senescent CD4+CD28null T cells which secrete a higher amount of TNF-α thus leading to enhanced osteoclastogenesis. Isoflavonoids like daidzein and genistein are found mostly in soybeans, legumes, and peas. These share structural similarity with 17β-stradiol (E2) and have osteoprotective role. This study explores the effect of daidzein (Daid) on the proliferation of TNF-α producing T cells, premature senescent T cells and B cell lymphopoesis under estrogen deficient conditions. For this study adult Balb/c mice were treated with Daid at 10 mg/kg body weight dose by oral gavage daily post ovariectomy (Ovx). After six weeks animals were autopsied and bone marrow and spleen cells were collected for FACS analysis. Blood serum was collected for ELISA. It was observed that Ovx mice treated with Daid for six weeks show reduction in Ovx induced expansion of CD4+ T cells in bone marrow and spleen when analysed by flow cytometry. Estrogen deficiency led to increased prevalence of TNF-α secreting CD4+CD28null T cells, however, treatment with Daid increased the percentage of CD4+CD28+ T cells. Co-culture of CD4+CD28null T cells and bone marrow resulted in enhanced osteoclastogenesis as evident by increased tartarate resistant acid phosphatase (TRAP) expression, an osteoclast marker. However, treatment with Daid resulted in reduced osteoclastogenesis in CD4+CD28null T cells and bone marrow cell co-culture. Daid also regulated B lymphopoesis and decreased mRNA levels of RANKL in B220+ cells. Taken together, we propose that one of the mechanisms by which Daid prevents bone loss is by reversing the detrimental immune changes as a result of estrogen deficiency

Biodegradable, flexible silicon nanomembrane-based NO x gas sensor system with record-high performance for transient environmental monitors and medical implants

Abstract: A novel transient electronics technology that is capable of completely dissolving or decomposing in certain conditions after a period of operation offers unprecedented opportunities for medical implants, environmental sensors, and other applications. Here, we describe a biodegradable, flexible silicon-based electronic system that detects NO species with a record-breaking sensitivity of 136 Rs (5 ppm, NO2) and 100-fold selectivity for NO species over other substances with a fast response (~30 s) and recovery (~60 s). The exceptional features primarily depend on not only materials, dimensions, and design layouts but also temperatures and electrical operations. Large-scale sensor arrays in a mechanically pliable configuration exhibit negligible deterioration in performance under various modes of applied loads, consistent with mechanics modeling. In vitro evaluations demonstrate the capability and stability of integrated NOx devices in severe wet environments for biomedical applications

Positive association of the hepatic lipase gene polymorphism c.514C > T with estrogen replacement therapy response

<p>Abstract</p> <p>Background</p> <p>Hepatic lipase (HL), an enzyme present in the hepatic sinusoids, is responsible for the lipolysis of lipoproteins. Human HL contains four polymorphic sites: G-250A, T-710C, A-763G, and C-514T single-nucleotide polymorphism (SNPs). The last polymorphism is the focus of the current study. The genotypes associated with the C-514T polymorphism are CC (normal homozygous - W), CT (heterozygous - H), and TT (minor-allele homozygous - M). HL activity is significantly impaired in individuals of the TT and CT genotypes. A total of 58 post-menopausal women were studied. The subjects were hysterectomized women receiving hormone replacement therapy consisting of 0.625 mg of conjugated equine estrogen once a day. The inclusion criteria were menopause of up to three years and normal blood tests, radiographs, cervical-vaginal cytology, and densitometry. DNA was extracted from the buccal and blood cells of all 58 patients using a commercially available kit (GFX^®- Amersham-Pharmacia, USA).</p> <p>Results</p> <p>Statistically significant reductions in triglycerides (t = 2.16; n = 58; p = 0.03) but not in total cholesterol (t = 0.14; n = 58; p = 0.89) were found after treatment. This group of good responders were carriers of the T allele; the CT and TT genotypes were present significantly more frequently than in the group of non-responders (p = 0.02 or p = 0.07, respectively). However, no significant difference in HDL-C (t = 0.94; n = 58; p = 0.35) or LDL-C (t = -0.83; n = 58; p = 0.41) was found in these patients.</p> <p>Conclusions</p> <p>The variation in lipid profile associated with the C-514T polymorphism is significant, and the T allele is associated with the best response to ERT.</p

Development of fine-grained structure caused by friction stir welding process of a ZK60A magnesium alloy

yesA fine-grained microstructure average grain size of which is around 2 mm was developed in ZK60A magnesium alloy subjected to a FSW proces