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Proper mechanical stability in retained austenite is a crucial factor for medium Mn steel to attain high strength and excellent ductility. In this paper, intercritical annealing and quenching and partitioning (IA & Q&P) processes are applied to medium Mn steel, to obtain retained austenite with proper mechanical stability. The effect of intercritical annealing temperature on mechanical stability of retained austenite is studied using interrupted tests. Moreover, from the perspective of usage of medium Mn steel, the mechanical stability of retained austenite at uniaxial tension and plane strain states is further investigated, to understand the transformation of retained austenite. Results indicate that high intercritical annealing temperature (680 °C) caused the austenite to transform immediately, due to the limited resistance of austenite to martensite transformation, caused by low carbon (C) content. This low C content also led to low stacking-fault energy, which may be another way to promote the transformation of austenite. Additionally, due to the high Schmid factor, caused by enhanced grain rotation and strain state, the retained austenite has relatively low stability at the early stage of the plane strain state. With increasing martensite surrounding the austenite, the retained austenite achieves high mechanical stability at the later stage of the plane strain state. [ABSTRACT FROM AUTHOR]

Candida albicans (C. albicans) is a common cause of vulvovaginal candidiasis (VVC). In this paper, the genetic diversity and molecular epidemiology of 173 C. albicans strains were investigated by multilocus sequence typing (MLST). A total of 52 diploid sequence types (DSTs) were recognized, and 27 (51.9%) of which have not been reported in the MLST database. Genotyping was performed on the multiple isolates collected from patients with recurrent VVC (RVVC, referring to VVC which attacks more than 4 times in one year) in different acute infectious phases. The results showed that 59.1% (26/44) of the patients suffered a relapse, with DST 79 (65.4%) as the dominant genotype. The etiology of the remaining 40.9% (18/44) of patients was reinfection, and the main genotypes included DST 79 (33.3%), DST 124 (8.6%) and DST 1895 (8.6%). DST 79 (45%) and DST 1395 (7.5%) were the main isolates of VVC patients, while DST 79 (24.1%), DST 727 (6.9%), DST 732 (6.9%) and DST 1867 (6.9%) were the main types of healthy volunteers. The results of the genotypes between RVVC patients and other groups were statistically different. Furthermore, cluster analysis was carried out on 1468 isolates, among which 1337 were downloaded from the MLST database, 130 were divided into 8 Clades in the present study and the remaining one was taken as a singleton. 92.3% isolates from relapse patients, 58.3% isolates from re-infected patients, 77.5% isolates from VVC patients and 51.7% isolates from volunteers were distributed in Clade 1. The analysis of the genotypes of multiple isolates from RVVC patients further demonstrated that point mutation and loss of heterozygosity contributed to the microevolution of C. albicans. • The etiology of RVVC was reinfection or relapse can be identified by genotyping. • The genotype of relapse RVVC patients was significantly different from other groups(reinfection,VVC and volunteers). • Further demonstrated that point mutation and loss of heterozygosity contributed to the microevolution of C. albicans. [ABSTRACT FROM AUTHOR]

The decrease in mechanical properties of high-strength steel after welding is an important issue affecting the wide application of high-strength steel. Air-hardening steel is a high-strength steel suitable for lower body structural parts such as subframes. Its application process involves welding, hot forming and other processes. The present work investigates the microstructure and mechanical properties of the air-hardening steel laser welded joint that is air-cooled after hot forming in the two-phase zone (800 °C). The microstructure was characterized by electron backscattered diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that during hot forming, the welded joint transforms from martensite to ferrite and acicular martensite, and the base metal transforms from ferrite to polygonal martensite and ferrite. The difference in martensite morphology between the welded joint and the base metal is attributed to the nucleation positions of austenite. The structural evolution of the welded joint and the base metal is accompanied with the annihilation and reproduction of dislocations, which results in significant changes in hardness. The hardness value dropped from the highest 430 HV to 271 HV in the welded joint, while increased from the lowest 184 HV to 203 HV in the base metal. After hot forming, the tensile strength of the welded sample is reduced by only 36 MPa, and the total elongation is slightly decreased by about 1.5% compared with the unwelded sample. The welded joint and the base metal have similar plastic deformation capabilities, since the acicular martensite in the welded joint displays good plastic deformation ability, and the dislocation density of the welded joint and the base metal is similar. Overall, the microstructure and dislocation density of the air-hardening steel welded joint after hot forming are similar to those of the base metal, which is responsible for the good mechanical properties of air-hardening steel welded joint. • The rules of microstructure evolution of welded joints during hot forming are proposed. • After hot forming, the strength and plasticity of the welded specimen are basically no loss compared with the unwelded specimen. [ABSTRACT FROM AUTHOR]

ZnO–graphene nanocomposites were synthesized by a one-pot method at room temperature, using graphene oxide as starting material, Zn powder as a precursor of ZnO and as reducing agent in mildly alkaline conditions, followed by post-treatment with potassium hydroxide solution. It is found that the ZnO nanoparticles (average diameter ∼14nm) were dispersed evenly on the graphene sheets. The resulting nanocomposites exhibited excellent capacitative performance (192Fg−1, 20.8kWkg−1) and fluorescent effect. [Copyright &y& Elsevier]

Abstract In the present study, Polonium-210 (210Po) is studied in TSP and coal combustion samples for its potential application in tracing air pollutants. A significant seasonal variation of atmospheric 210Po in Beijing was observed: winter > autumn > summer > spring. During the combustion of coal, 210Po was highly enriched in fly ash but was depleted in bottom ash. Using selenium (Se) as an indicator of coal combustion, significantly positive correlation between 210Po and Se in TSP samples (r2 = 0.705) revealed that coal combustion was a primary source of atmospheric 210Po in Beijing. The mean emission factor of 210Po from industry sector was found to be the highest (1.15 Bq kg−1), followed by the residential (0.308 Bq kg−1) and coal-fired power plant (0.0776 Bq kg−1) sectors. The annual emission inventories of 210Po from three coal consumer sectors (residential, coal-fired power plant, and industry) in 2016 in Beijing were estimated to be 1.49, 0.0729, and 1.36 GBq, respectively. The ratio of radioactive 210Po and stable element Se (210Po/Se) was creatively used as a combined indicator or fingerprint of coal combustion emission, which will contribute to the development of radioisotope tracer technology based on nuclide fingerprint database in the source identification of air pollutants. Graphical abstract Image 1 Highlights • 210Po was characterized in TSP and coal combustion samples to trace the air pollutants. • A significant seasonal variation of atmospheric 210Po was observed. • 210Po was highly enriched in fly ash while was depleted in bottom ash. • Coal combustion emission was a primary source of atmospheric 210Po in Beijing. • The ratio of 210Po/Se could be a novel indicator of coal combustion emission. [ABSTRACT FROM AUTHOR]

Abstract: The surface functional groups of thermally reduced graphene nanosheets (TRG) prepared by vacuum promoted thermal expansion of graphene oxide are tailored by progressive carbonization. The residual carbon ratios after annealing at various temperatures from 250 to 1000°C increase progressively from 44.3 to 84.8%. The oxygen containing functional groups are intensively removed at higher annealing temperature. The thermally stable phenols, ethers, and carbonyls become the major components in 1000°C annealed TRG. Though the starting material G250 owns a high specific capacitance of 170.5F/g, the value decreases to only 47.5F/g when the annealing temperature is increased to 1000°C. The oxygen containing functional groups can enhance the capacitance performance of TRGs by introducing abundant pseudocapacitance active sites through reversible Faradic redox reactions. The correlation between the structural evolution and electrochemical performance of TRGs provides new insight for designing graphene based electrodes with controllable properties for advanced supercapacitors. [Copyright &y& Elsevier]

Graphene oxide–carbon fiber/phenolic resin, chemically-reduced graphene oxide–carbon fiber/phenolic resin, and thermally-reduced graphene oxide–carbon fiber/phenolic resin composites were prepared by blending a graphene oxide suspension in an ethanol solution of phenolic resin with carbon fibers, followed by vacuum drying and hot pressing. The effects of the type of graphene oxide on structure, compressive performance and friction properties of the composites were investigated. Results showed that the compressive properties of the composites were greatly improved with a 0.1 mass graphene oxide % loading compared with the pure carbon fiber/phenolic resin composite. The compressive strength and modulus of the thermally-reduced graphene oxide/phenolic resin/carbon fiber composites were increased by 178.9%, 129.5%, respectively, and the highest energy storage modulus of the chemically-reduced graphene oxide/phenolic resin/carbon fiber composite was increased by 75.2% compared with the pure carbon fiber/phenolic resin composite. The glass transition temperatures of all the composites containing graphene oxide decreased. [New Carbon Materials 2012;27(5):377–84] [ABSTRACT FROM AUTHOR]

Abstract: A free-standing graphene oxide film (GOF) obtained by self-assembly at a liquid/air interface was annealed in a confined space between two stacked substrates to form a free-standing highly conductive graphene film. Characterization indicates that the oxygen-containing functional groups (e.g. epoxy, carboxyl, and carbonyl) were removed as small molecules (e.g. H2O, CO2, and CO) during the annealing, meanwhile the size of sp2 domains in the film was decreased. When annealed between two stacked wafers, random interlayer expansion and fractional movement in the GOF were suppressed by the pressure-induced friction, which helps preserve the morphology of the film. The conjugation in the basal plane of graphene and π–π interactions between well stacked graphene sheets favor the transportation of charge carriers in the film, to produce a good electrical conductivity of the resulting free-standing reduced GOF (increased from 1.26×10−5 to 272.3S/cm). [Copyright &y& Elsevier]