ABSTRACT
Rotating backward extrusion (RBE) is one of severe plastic deformation (SPD) methods used to produce cylindrical components with a very large strain by a single pass. In this study, the microstructure and texture evolution in the different regions of Mg-12Gd-4Y-2Zn-0.5Zr (wt.%) alloys via RBE process were investigated by using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron back-scatter diffraction (EBSD). The results showed that the cup-shaped sample formed by RBE process exhibited typical gradient microstructure expanding from its inner wall to outer wall along the radial direction (RD). The average grain size of the RBEed sample decreased when the radius decreased from the edge region to the center region along the RD, which was attributed to the different strains and strain rates in the different regions. It also could be observed that the center region showed highest deformation and the edge region exhibited the lowest deformation in the RBEed sample along the RD. In addition, the grain refinement mechanisms of the experimental alloy containing long-period stacking ordered (LPSO) phases after RBE with 100 N were continuous dynamic recrystallization (CDRX), discontinuous dynamic recrystallization (DDRX) and particle stimulated nucleation (PSN).
ABSTRACT
Objective Studies have shown that circular RNA (circRNA) is a molecular sponge of microRNA (miRNA) and can be used for the treatment and diagnosis of liver diseases. Therefore, this study aims to further investigate the expression profile of circRNA and its effect on autophagy in rat liver regeneration. Methods Based on the high-throughput sequencing in regenerated liver of 0 hour, 2, 6, 12, 24, 30, 36, 72, 120 and 168 hours after 2/3 hepatectomy in 60 rats, the expression profiles of circRNAs, miRNAs and mRNA were analyzed and their relationship were predicted by miRanda aug 2010 software. Furthermore, according to gene function → miRNA function → circRNA function, circRNAs and miRNAs that regulating autophagy were obtained in liver regeneration and compting endogenous (ceRNA) network was constructed. Results There were 102 circRNAs, 42 miRNAs and 153 mRNAs associated with autophagy involved in liver regeneration. Using bioinformatics analysis, 44 types of circRNAs, 13 types of miRNAs and 17 types of mRNA were found to interact with each other, and their co-expression network was constructed. Conclusion In this study, we screened out the circRNAs, miRNAs and mRNAs related to autophagy in liver regeneration and built the interaction network map.
ABSTRACT
The rotating backward extrusion (RBE) process, as a new severe plastic deformation (SPD) process, is based on conventional backward extrusion and rotation, which meets the requirement of modern industrial development with its high performance and production efficiency. However, there is little research on the microstructure evolution and texture modification of the RBE process. Thus, in this study, the effect of different rotating revolutions, e.g., n = 5, n = 10, and n = 50, on the microstructure and texture development for the RBE process based on the AZ80 magnesium (Mg) alloy were investigated at 653 K. The results disclose that the rotating revolution is an influencing processing parameter on the deformation of the RBE process. The grain refining ability is enhanced with the increase of the rotating revolutions, and the minimum grain size of the cup bottom, shearing zone, and cup wall can reach to 16.7 µm, 15.6 µm, and 13.0 µm, respectively, under the condition of n = 50. Furthermore, with the increase in the rotating revolutions, the microstructure of the alloy becomes more uniform and the proportion of dynamic recrystallization (DRX) is also increased. The maximum DRX fractions of the sample for the cup bottom and cup wall are 95.4% and 86.8%, respectively, at n = 50. The DRX mechanism of the RBE process is determined by the continuous DRX and discontinuous DRX. In addition, the texture can be significant weakened during the RBE process, especially at the cup bottom, where the maximum pole intensity can be reduced from 17.6 at n = 10 to 6.5 at n = 50, which can be attributed to the higher proportion of new DRXed grains whose orientations are more random compared with the deformed grains.
ABSTRACT
Various multilayered thin films are extensively used as the basic component of some micro-electro-mechanical systems, requiring an efficient measurement method for material parameters, such as Young's modulus, residual stress, etc. This paper developed a novel measurement method to extract the Young's moduli and residual stresses for individual layers in multilayered thin films, based on the first resonance frequency measurements of both cantilever beams and doubly-clamped beams. The fabrication process of the test structure, the corresponding modeling and the material parameter extraction process are introduced. To verify this method, the test structures with gold/polysilicon bilayer beams are fabricated and tested. The obtained Young's moduli of polysilicon films are from 151.38 GPa to 154.93GPa, and the obtained Young's moduli of gold films are from 70.72 GPa to 75.34GPa. The obtained residual stresses of polysilicon films are from -14.86 MPa to -13.11 MPa (compressive stress), and the obtained residual stresses of gold films are from 16.27 to 23.95 MPa (tensile stress). The extracted parameters are within the reasonable ranges, compared with the available results or the results obtained by other test methods.
ABSTRACT
L-arabinose isomerase (L-AI) can isomerize L-arabinose and D-galactose into L-ribulose and D-tagatose, respectively, which is currently the most effective biological catalyst for D-tagatose production. The crystal structure of L-AI has been solved recently and its gene has been cloned, sequenced and overex- pressed. L-AI improved by protein engineering will be the dominant enzyme for industrial production of D-tagatose. This paper reviewed researches on protein structure and function, properties and application in D-tagatose production of L-AI, and the long-term potential development of L-AI was prospected.
ABSTRACT
An extracellar fibrinolytic strain was isolated from fermented shrimp paste. In addition to general physiological and biochemical properties, the strain was identified by 16S rDNA sequence and systematic analysis. The results showed that 16S rDNA sequence of the strain had high similarity with AY601723 and AB195282, suggesting that the strain is a subspecies of Bacillus sp. It was named as Bacillus sp. nov. SK006 by CCTCC. The medium composition and fermentation conditions for fibrinolytic enzyme production were also optimized in the research.
ABSTRACT
Thermostable L-arabinose isomerase (L-AI) is the most potential enzyme for the biological production of D-tagatose from D-galactose, a novel functional factor. Gene araA encoding the L-arabinose isomerase from Bacillus stearothermophilis IAM 11001 was cloned and expressed in Escherichia coli. The araA gene of 1491 bp has 95% identity with L-AI from Thermus sp. IM6501. The GenBank accession number for the nucleotide sequence of this araA gene determined in this work is EU394214.The bacterium was induced by IPTG and analyzed by SDS-PAGE, approximately 59 kDa exogenous protein was observed on the SDS-PAGE. The recombinant L-AI was purified to electrophoretical homogeneity with affinity chromatography, and the activity of recombinant L-AI was also studied. The bioconversion rate of D-galactose to D-tagatose reached 39.4% after 24h whole cell reaction.
ABSTRACT
Rare sugars were defined as monosaccharides and their derivatives that rarely exist in nature. They played an important role in food, health, medicine and etc A strategy for bioproduction of rare sugars, namely Izumoring, was described. By the Izumoring method, all monosaccharides and polyols could be linked, using enzymatic reaction with D-tagatose 3-epimerase, aldose isomerases and polyol dehydrogenases. Izumoring for hexoses, pentoses and tetroses were designed respectively. According to this strategy, the bioproduction routes of various rare sugars, using microbial and enzymatic reactions, could be obtained. In addition, the future research tendency of biotransformation of rare sugars was put forward.
ABSTRACT
To investigate the structure disruption of BSA (1mg/ml, dissolved in PBS) induced by ultrasonication and the French press. The BSA solution was passed through the French press and received ultrasound irradiation, and then detected by HPLC(High-performance liquid chromatography),DLS(Dynamic Light Scattering),CD(Circular Dichroism)and nondenaturing SDS-PAGE. Detection results showed that BSA was polymerized after ultrasound irradiation and the polymerization can be reduced by adding mannitol (free radical scavenger). This means that the free radical play an important role in this process. However, the BSA passing through the French press for several times wasn’t polymerized, and the secondary structure was somewhat destroyed. These results suggested that ultrasound irradiation and French press destroy the molecular structure in different manners, so that the suitable cell lyses methods should be selected according to the characteristics of the protein.
