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This paper studied the effects of the superheating degree and cooling intensity on the solidification structure of CP 780 slab. The results indicated that the equiaxed crystal ratio decreases with the increase of superheating degree and the cooling intensity. When the superheating degree increases from 15 to 25°C, the equiaxed crystal ratio drops sharply. While the equiaxed crystal ratio decreases slightly with an increasing superheating degree from 25°C to 55°C. It is further revealed that the superheating degree has a greater effect on the equiaxed crystal ratio compared with the influence of cooling intensity. Quantitative analysed the relationship among the equiaxed crystal ratio, the superheating degree and cooling intensity is in line with the Extreme 2D model. The accuracy of the model performance can reach 97.6% when predicting the equiaxed crystal ratio of CSP-CP 780 during CSP process. [ABSTRACT FROM AUTHOR]

A dual‐band terahertz metamaterial absorber using one‐layer periodically patterned hexagon graphene structure is proposed. By periodically loading six graphene stubs to the honeycomb hexagon graphene structure without increase of the overall size, a new high‐frequency absorption peak will be obtained to realize a dual‐band frequency response. By tuning the structural parameters or Fermi energy levels of the presented terahertz metamaterial absorber, both of the two absorption bands will be changed to the required working frequencies for design specifications. Moreover, the proposed terahertz metamaterial absorber has the properties of polarization independence and incident angle insensitivity, which are of great significance in the applications of some detecting and sensing systems. This work will be a good candidate for the design guidance of various metamaterial absorbers using graphene with single or dual absorption bands. [ABSTRACT FROM AUTHOR]

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]

As automotive steels require high safety standard for absorbing impact energy during vehicle body collision, detailed investigation of deformation behavior at shear strain state of TWIP steels is crucial. The orientation gradients, the instability of austenite diffraction peak, and microstructure of TWIP steel are investigated as a function of shear strain using transmission electron microscopy, electron back‐scatter diffraction, and X‐ray diffraction analyses of interrupted shear specimens. According to microstructural evolution results, both orientation rotation and supplementary twinning system impact the intensities of austenite diffraction peak. The decrease of γ(220) peak intensity occurs at ϵe = 0.49, since the orientations rotate mainly toward the <111> and <001> poles. The reversion of intensity of γ(220) peak happens at ϵe = 1.18, which may be caused by supplementary twinning system. Due to the kinking formed at the twin border region, orientation gradient of matrix in front of twin boundary increases significantly at ϵe = 1.18. [ABSTRACT FROM AUTHOR]

The intermolecular hydrogen bonds of mono- and dihydrated complexes of 7-(3′-Pyridyl)indole (7-3′PI) have been investigated using the time-dependent density functional theory (TD-DFT) method. The electrostatic potential analysis of monomer 7-3′PI and 7-(3′-Pyridyl)indole-water (7-3′PI-W) indicates that an intermolecular hydrogen bond between two waters can be formed for 7-(3′-Pyridyl)indole-2water (7-3′PI-2W) complex. The calculated bond lengths of the intermolecular hydrogen bonds of 7-3′PI-W and 7-3′PI-2W in the S1 state (the first excited singlet state) are all shortened compared to the ground state. By the analysis of bond length, charge population and infrared spectra, it is demonstrated that the intermolecular hydrogen bonds of 7-3′PI-W and 7-3′PI-2W are all strengthened upon electronic excitation to the S1 state. Moreover, the fluorescence of 7-3′PI-W and 7-3′PI-2W are all red-shifted to larger wavelength compared to monomer 7-3′PI. The red-shift of fluorescence peak of 7-3′PI-W and 7-3′PI-2W should be attributed to the change of hydrogen bond interaction before and after photoexcitation. Therefore, it can be concluded that the intermolecular hydrogen bonding strengthening in the excited S1 state induces the fluorescence weakening of 7-3′PI. [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]

Eight series of fluorosubstituted three-ring ester liquid crystals have been synthesized. Polarizing microscopic textural observations and DSC measurements of their phase transitions show that most are thermotropic liquid crystals with nematic and smectic A phases; furthermore, several show monotropic high order smectic phases. The results showed that the SmA phase is enhanced with the increasing number of fluoro-substituents at the para- and meta-positions of the terminal phenyl groups. The mesomorphic properties of these compounds are also affected by the direction of the ester bonds. The effect of the triple bond is also discussed. [ABSTRACT FROM AUTHOR]

Three homologous series of 4-(n-polyfluoroalkoxycarbonyl)phenyl 4-[(4-n-alkoxyphenyl)ethynyl] benzoates have been synthesized from 1,1,3-trihydroperfluoropropanol, 1,1,5-trihydroperfluoropentanol and 1,1,7-trihydroperfluoroheptanol. Polarizing microscopic textural observations and DSC measurements of the phase transitions of these compounds show that most of them are thermotropic liquid crystals with smectic A and very broad smectic C phases; furthermore, several show very narrow monotropic SmB phases. The effect of the terminal polyfluoroalkoxy and alkoxy groups on the mesomorphic behaviour is also discussed. [ABSTRACT FROM AUTHOR]

A family of 4-(1,1,7-trihydroperfluoroheptyloxycarbonyl)phenyl 4'-n-alkoxybiphenyl-4-car- boxylates has been synthesized. The compounds show the smectic A phase while the mesogens with intermediate terminal alkyl chain ( n 7-12) also exhibit a broad smectic C phase. [ABSTRACT FROM AUTHOR]

Several molecules having long semi-fluoroalkyl chains have been synthesized, and their phase transition temperatures measured by texture observation in a polarizing microscope and DSC. The SmC phase is particularly favoured in this series, especially for compounds with a long semi-fluoroalkyl chain. It was found that when the terminal hydrogen atom of the semifluoroalkyl chain of one of the compounds (D) was substituted by a chlorine atom, the liquid crystalline sequence and ranges did not change; however, the clearing and melting points and T[sub I-SmA] and T[sub SmA-SmC] increased by nearly 10°C. [ABSTRACT FROM AUTHOR]

Two chiral molecules, each having a long fluoroalkylalkoxy chain, have been synthesized. Their phase transition temperatures have been measured by texture observation in a polarizing microscope and confirmed by differential scanning calorimetry. Very broad SmC* phase is found in one of these two compounds. [ABSTRACT FROM AUTHOR]

Six compounds with semi-fluorinated chains have been synthesized. When the terminal hydrogen atom in the semi-fluoroalkoxy chain was changed to chlorine, both the clearing point and the melting point were enhanced. It was also found that the clearing points were decreased and melting points increased with the introduction of a triple bond into the cores. [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]

A reduced graphene oxide/multiwalled carbon nanotube (RGO/MWCNT) hybrid sandwiched film with different MWCNTs content was prepared by vacuum-assisted self-assembly from a complex dispersion of graphene oxide (GO) and MWCNTs followed by heat-treating at 200 °C for 1 h in a vacuum oven to reduce the GO into RGO. The free-standing RGO/MWCNT hybrid sandwiched film before heat-treatment showed a layered structure with an entangled network of MWCNTs sandwiched between the GO sheets. This unique structure not merely contribute to remove the oxygen-containing groups in GO during the heat-treatment, but also decrease the defects for electron transfer between RGO layers, which enhances the electrochemical capacitive performances of graphene-based films. A specific capacitance up to 379 F/g was achieved based on RGO/MWCNT with 30 % MWCNTs mass fraction at 0.1 A/g in a 6 M KOH electrolyte. The excellent performance of RGO/MWCNT hybrid sandwiched film signifies the importance of controlling the surface chemistry and sandwiched nanostructure of graphene-based materials. [ABSTRACT FROM AUTHOR]

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]

The high demands on lithium-ion batteries (LIBs) have increased concern about novel carbon nanomaterials with high capacity and cycling stability. Herein, twisted carbonaceous nanoribbons with high BET specific surface area of 1413 m2 g−1 were successfully synthesized using twisted 4, 4′-biphenylene bridged polybissilsesquioxane tubular nanoribbons as the starting material. Electrochemical measurement showed that the carbonaceous nanoribbon electrode not only delivered a high specific capacity of 921.1 mAh g−1 after 250 cycles at a current density of 0.1 A g−1, but also exhibited superior cycling stability and excellent rating capability. The work presents a facile way to design and fabricate good anode candidate for LIBs. [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]

Free-standing optoelectronic graphene-CdS-graphene oxide (G-CdS-GO) composite papers were prepared by vacuum-assisted self-assembly. G-CdS hybrids were first prepared by a hydrothermal method and GO acts as a dispersant which makes it easier to disperse them to form relatively stable aqueous suspensions for fabricating paper. Transmission electron microscopy shows that CdS quantum dots (QDs) with an average size of approximately 1-2 nm were distributed uniformly on the graphene sheets. Photoluminescence measurements for the as-prepared G-CdS-GO composite paper showed that the surface defect related emissions of attached CdS QDs decrease and blue shift obviously due to the change in particle size and the interaction of the surface of the CdS QDs with both the GO and the graphene sheets. The resulting paper holds great potential for applications in thin film solar cells, sensors, diodes, and so on. [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]

A theoretical rod model for investigating the polyacrylonitrile (PAN) copolymer coagulation process was presented in this work. The mass transfer rate and coagulation rate under different coagulation conditions were obtained using this method. An optical microscope with image transfer software was employed to observe the coagulation boundary of the filament. The results showed that the coagulation rate decreased continuously with the increase of bath concentration. However, with the increase of the bath concentration, the mass transfer rate decreased at the beginning of the coagulation, and as the t1/2 increased, the weight loss was greater when the bath concentration was higher. Moreover, the coagulation rate and mass transfer rate increased with the increase of the coagulation temperature, and the coagulation was most moderate when the bath temperature was 50°C. [ABSTRACT FROM AUTHOR]

Polyacrylonitrile nascent fibers, as spun into the coagulation bath, were prepared by solution polymerization and wet-spinning, and a dimethyl sulphoxide (DMSO)/H2O coagulation bath system was adopted. The effect of coagulation bath DMSO concentration on the structure and properties of the nascent fibers was studied in detail, and the diffusion coefficients of DMSO and H2O for different bath DMSO concentrations were calculated by Crank's equation to explain the structural changes of the nascent fibers, including cross-section, core/shell structure, and surface morphology. The surface morphology of nascent fibers was observed by field emission scanning electron microscopy (FESEM). The results showed that as the coagulation bath DMSO concentration increased, the diffusion coefficients gradually decreased. More circular cross-section, less core/shell structure, higher degree of crystallinity, larger crystal size, larger bulk density, and higher sound velocity of the nascent fibers were obtained when thecoagulation bath DMSO concentration was 70 wt% compared to lower or higher bath DMSO concentration. Moreover, compared with the nascent fibers spun in other bath DMSO concentrations, smoother surfaces of the nascent fibers were obtained at the bath DMSO concentration of 70 wt%. [ABSTRACT FROM AUTHOR]

A correction to the article ""A Novel for Investigating the Structural Uniformity of Polyacrylonitrile Nascent Fibers," is presented.