Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg

© 2018, The Author(s). High-pressure torsion (HPT) processing was applied to cast pure magnesium, and the effects of the deformation on the microstructure, hardness, tensile properties and corrosion resistance were evaluated. The microstructures of the processed samples were examined by electron backscatter diffraction, and the mechanical properties were determined by Vickers hardness and tensile testing. The corrosion resistance was studied using electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results show that HPT processing effectively refines the grain size of Mg from millimeters in the cast structure to a few micrometers after processing and also creates a basal texture on the surface. It was found that one or five turns of HPT produced no significant difference in the grain size of the processed Mg and the hardness was a maximum after one turn due to recovery in some grains. Measurements showed that the yield strength of the cast Mg increased by about seven times whereas the corrosion resistance was not significantly affected by the HPT processing

Default risk, state ownership and the cross-section of stock returns: evidence from China

We apply a structural model to estimate firm-level default risk in China and investigate the stock return predictability of default risk and the moderating effects of state ownership for the sample period from 2003 to 2015. We show unique evidence that in China, default risk is positively associated with expected stock returns and state ownership matters considerably to the return predictability of default risk. We find investors of state-owned enterprises (SOEs) are not compensated appropriately in China despite of their higher default risk exposure. Our empirical evidence supports the conjecture on shareholder advantages and suggests that a strong bargaining power of equity holders would have a negative impact on stock returns

A functional variant in the Stearoyl-CoA desaturase gene promoter enhances fatty acid desaturation in pork

There is growing public concern about reducing saturated fat intake. Stearoyl-CoA desaturase (SCD) is the lipogenic enzyme responsible for the biosynthesis of oleic acid (18:1) by desaturating stearic acid (18:0). Here we describe a total of 18 mutations in the promoter and 3′ non-coding region of the pig SCD gene and provide evidence that allele T at AY487830:g.2228T>C in the promoter region enhances fat desaturation (the ratio 18:1/18:0 in muscle increases from 3.78 to 4.43 in opposite homozygotes) without affecting fat content (18:0+18:1, intramuscular fat content, and backfat thickness). No mutations that could affect the functionality of the protein were found in the coding region. First, we proved in a purebred Duroc line that the C-T-A haplotype of the 3 single nucleotide polymorphisms (SNPs) (g.2108C>T; g.2228T>C; g.2281A>G) of the promoter region was additively associated to enhanced 18:1/18:0 both in muscle and subcutaneous fat, but not in liver. We show that this association was consistent over a 10-year period of overlapping generations and, in line with these results, that the C-T-A haplotype displayed greater SCD mRNA expression in muscle. The effect of this haplotype was validated both internally, by comparing opposite homozygote siblings, and externally, by using experimental Duroc-based crossbreds. Second, the g.2281A>G and the g.2108C>T SNPs were excluded as causative mutations using new and previously published data, restricting the causality to g.2228T>C SNP, the last source of genetic variation within the haplotype. This mutation is positioned in the core sequence of several putative transcription factor binding sites, so that there are several plausible mechanisms by which allele T enhances 18:1/18:0 and, consequently, the proportion of monounsaturated to saturated fat.This research was supported by grants from the Spanish Ministry of Science and Innovation (AGL2009-09779 and AGL2012-33529). RRF is recipient of a PhD scholarship from the Spanish Ministry of Science and Innovation (BES-2010-034607). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of manuscript

Complex pattern of environmental changes and organic matter preservation in the NE Ordos lacustrine depositional system (China) during the T-OAE (Early Jurassic)

The lower Toarcian black shale and mudstone succession of the Anya section in the northeastern Ordos Basin records a climatically controlled evolution of the lacustrine system during the negative carbon isotope excursion (NCIE) of the Toarcian oceanic anoxic event (T-OAE; ca. 183 Ma). In the Anya section, petrography integrated with climate proxies (Sr/Cu and Rb/Sr) and weathering indices (weathering index of Parker, chemical index of weathering and plagioclase index of alteration), suggests that a warm-humid climate with sporadic semihumid-semiarid intervals developed during the early Toarcian and was coincident with strong chemical weathering. Sr/ Ba and S/TOC ratios suggest that the Anya section's rocks were generally deposited in freshwater. Four phases (phases A, B, C and D) in lake evolution are distinguished from the variation in petrographical and geochemical proxies providing clues about the drivers of environmental change and organic matter accumulation in the lacustrine basin. Phases A and C have a high preservation of organic matter derived from lake plankton (Type II -III kerogens), were characterized by anoxia, and coincided with high primary productivity. On the contrary, phases B and D indicate a low primary productivity and suboxic-oxic conditions, with a lower organic matter content of predominantly higher land plant origin (Type III kerogen). The accumulation of organic matter was mainly controlled by changes in primary productivity and redox conditions that were tightly linked to the local sedimentary evolution of the Ordos Basin and to global and regional climate. During the early Toarcian NCIE, the accumulation of organic-poor sediment and terrestrial organic matter may have been driven by enhanced sea-sonality, superimposing on local lake level changes. As a consequence, the peak of the T-OAE carbon cycle perturbation does not coincide with lacustrine black shale deposition and/or peak anoxia in this continental depositional system. This emphasizes the significance of local or regional environmental change on the carbon sequestration within lacustrine systems