Dystrophin-like dys-1 gene is expressed and required in muscle tissue, playing a vital role in gravisensing in caenorhabditis elegans (c. elegans). To date, microRNA (miRNA)-mediated epigenetic mechanism in microgravi...
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Dystrophin-like dys-1 gene is expressed and required in muscle tissue, playing a vital role in gravisensing in caenorhabditis elegans (c. elegans). To date, microRNA (miRNA)-mediated epigenetic mechanism in microgravity-induced muscular atrophy remains to be elucidated. In the present study, we first analyzed mRNA and miRNA expression profiles in space-flown dys-1(cx18) mutants and wild type worms (wt) of c. elegans. The results showed that spaceflight and microgravity have fewer effects on mRNA and miRNA expression in dys-1 mutant than in wt worms. mRNA and miRNA expression patterns of dys-1 mutants were changed by microgravity. Hierarchical clustering analysis showed that the alterations of genes function on neuromuscular system under space environment. Seven miRNAs (cel-miR-52, 56, 81, 82, 84, 124 and 230) have 18 significant anti-correlated target genes under space environment. RT-qPcR analysis confirmed that miR-52 and cdh-3, miR-84 and lin-14, miR-124 and mgl-3 in dys-1 mutants reversely altered under microgravity environment and in simulated microgravity experiment. Locomotion ability was only reduced in F0 wt worms but not in dys-1 mutants as well as their F1 offspring after simulated microgravity. We observed expression alterations of 7 neuromuscular genes (unc-27, nlp-22, flp-1, egl-5, flp-4, mgl-3, unc-94) in F0 wt worms, which might be involved in the regulation of locomotion ability of c. elegans. This study provides important insights to reveal the mechanism in the pathogenesis of muscular atrophy induced by microgravity.
To maintain the thermal stability of Sic nanowires during Siccoating fabrication process, carbon and Sic double protective layers were covered on the surface of nanowires. And Sic nanowires with double protective lay...
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To maintain the thermal stability of Sic nanowires during Siccoating fabrication process, carbon and Sic double protective layers were covered on the surface of nanowires. And Sic nanowires with double protective layers toughened Siccoating were prepared by pack cementation. The results showed that after introducing the Sic nanowires with double protective layers, the fracture toughness of the Siccoating was increased by 88.4 %. The coating protected c/c for 175 h with a mass loss of 3.67 %, and after 51 thermal shock cycles, the mass losses of the oxidized coating were 3.96 %. The double protective layers are beneficial to improve the thermal stability of nanowires, leading to good fracture toughness and thermal shock resistance of Siccoating. Sic nanowires consume the energy of crack propagation by fracture, pullout and bridging, leading to an increase in fracture toughness.
In this study, niobium-based alloy c103 is joined to carbon fibre-reinforced Sic (c/Sic) composite utilising commercially available Ticusil & REG;and cusil & REG;alloy braze filler material. Various characteri...
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In this study, niobium-based alloy c103 is joined to carbon fibre-reinforced Sic (c/Sic) composite utilising commercially available Ticusil & REG;and cusil & REG;alloy braze filler material. Various characterisation techniques are employed to investigate the interfacial microstructures and evolution mechanism of c/Sic-c103 junctions. Lap shear strength (LSS) is used to evaluate the mechanical performance of the brazed joints. The results show that adding Ti promotes the growth of "nails", a phenomenon favourable for robust joint quality. However, high Ti content deteriorates the bond strength due to the formation of significant brittle intermetallic phases, causing premature delamination of the joints. The response surface methodology (RSM) is employed to examine the interactions among various operating parameters. To attain the high LSS value, the high temperature, intermediate reaction time, and low cooling rate are necessary for a Ticusil-based joint, whereas high temperature, low reaction time, and increased cooling rate are preferred for a cusil-based joint.
c/c-Siccomposites are promising candidates for heavy-duty tracked vehicle brake discs. A third-body layer (TBL) can be formed on the surface of c/c-Sic self-mated brake discs, which has an important impact on tribolo...
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c/c-Siccomposites are promising candidates for heavy-duty tracked vehicle brake discs. A third-body layer (TBL) can be formed on the surface of c/c-Sic self-mated brake discs, which has an important impact on tribological behavior and wear mechanism of brake discs. Herein, the formation conditions and evolution process of TBL and its effect on friction and wear properties were investigated. An appropriate braking pressure and speed (P and V) are beneficial to the cutting of asperities and refinement of wear debris on the contact surface, which are preconditions for the formation of original TBL. The original TBL can be formed under the P center dot V of 12, 15, and 16, which effectively improve braking stability and reduce the wear rate. During the continuous braking process, the original TBL undergoes growth, stabilization, destruction, and regeneration. Under the frictional heat and compressive stress, wear debris gradually evolves into a uniform and dense TBL. The average coefficient of friction and wear rate reach to the lowest value of .446 and 38.5 x 10(-3) cm(3)/MJ, respectively. A continuous high temperature in the later stages of braking leads to severe oxidative wear. The newly formed TBL covers the original surface to form a multilayered structure, indicating the TBL undergoes destruction and regeneration.
In order to improve the mechanical and ablative resistance of c/ccomposites, (Hf-Ta-Zr)c single-phase solid solution ceramics were introduced into c/ccomposites by polymer infiltration and pyrolysis (PIP) to fabrica...
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In order to improve the mechanical and ablative resistance of c/ccomposites, (Hf-Ta-Zr)c single-phase solid solution ceramics were introduced into c/ccomposites by polymer infiltration and pyrolysis (PIP) to fabricate (Hf-Ta-Zr)c modified c/ccomposites (HTZ). Their mechanical property and ablation resistance were studied. The results showed that HTZ achieved simultaneous enhancement of mechanical property and ablative resis-tance. Their flexural strength and modulus could reach 219.34 MPa and 24.82 GPa, respectively. In addition, the mass and linear ablation rate of HTZ were 0.379 mg/s and 0.667 mu m/s, respectively after the 90 s oxyacetylene ablation. A dense Hf-Ta-Zr-O multiphase oxide layer was formed on the surface of the HTZ during ablation process, which protected the interior modified c/ccomposites from ablation. Our work expands a rational design of modified c/ccomposites and broaden the application of solid solution ceramic in the field of ultra-high temperature ablation resistance for carbon or ceramic-based composites.
c/c-BN composites containing different contents of h-BN particles were prepared by chemical vapor infiltration (cVI), presenting different microstructures and pyrolyticcarbon (Pyc) textures. The effects of different ...
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c/c-BN composites containing different contents of h-BN particles were prepared by chemical vapor infiltration (cVI), presenting different microstructures and pyrolyticcarbon (Pyc) textures. The effects of different micro-structures and Pyc textures on the thermo-physical properties and their phonon mechanisms at 30-900 degrees c were investigated. The temperature dependence of heat capacity follows Debye's phonon theory, especially in the low -temperature section (30-300 degrees c) and the temperature dependence of thermal conductivity is determined by heat capacity and mean free length of phonon. Due to the higher texture of h-BN and regenerative laminar Pyc (ReL-Pyc), h-BN addition causes higher Debye temperature (Theta D) and high sensitivity of thermal conductivity to temperature. Besides, h-BN addition significantly changes the microstructure of composites such as pore struc-ture, Pyc morphology, crack distribution and fiber/Pyc interface bonding state, causing the transformation of thermal conductivity from anisotropy to isotropy. Finally, based on the different microstructures of composites, the microstructure model and thermal resistance formulas of composites were established and coincident with the experimental results.
The multi-directional laminate ccF800H/Ac631 bismaleimide composite material was exposed for a long time under the thermal-cycling environment (-60 degrees c similar to+180 degrees c), and the mass loss rate, FTIR spe...
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The multi-directional laminate ccF800H/Ac631 bismaleimide composite material was exposed for a long time under the thermal-cycling environment (-60 degrees c similar to+180 degrees c), and the mass loss rate, FTIR spectra, DMA, tensile strength were tested. The fatigue stress level was determined according to the tensile strength and the fatigue performance of the before and after the thermal-cycling environment was tested. Macroscopic visual inspection and ultrasonicc-scan were used to characterize and analyze the fatigue damage of composite materials. The results show that with the increase in the number of thermal cycles, the mass loss of the composite material started with increased rapidly and then basically flat. The c/BMI composites underwent obvious thermal oxygen aging. After thermal-cycling, it would lead to changes in dynamic mechanical properties by a certain degree of post-curing, physical aging, and local interface debonding in composite materials. With the thermal cycles increased the composite material tensile strength first increased slightly and then decreased rapidly. After 300 thermal cycles, the composite materials occurred slightly damaged, and the fatigue life was apparently reduced compared with the original state. The fatigue failure modes of composite materials are mainly fiber fracture and multi-directional laminate delamination. At high stress levels, the stiffness of the specimen after thermal-cycling are lower decrease compared with original specimens, more stress levels would lead to more II stage rate of stiffness decline, and stiffness degradation curve and hysteretic energy recovery curve had enough effect to characterize damage effect of material environment induced by thermal-cycling environment factors.
作者：
chatterjee, SubhasishKean Univ
Dorothy & George Hennings Coll Sci Math & Technol Dept Chem & Phys Union NJ 07083 USA
Diamond nanoparticles represent an elegant class of nanoscale materials with promising applications in nanotechnology. Solid-state NMR is a powerful technique for investigating the atomic-level structure and dynamics ...
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Diamond nanoparticles represent an elegant class of nanoscale materials with promising applications in nanotechnology. Solid-state NMR is a powerful technique for investigating the atomic-level structure and dynamics of nanomaterials in their natural state. The present study illustrates the application of high-resolution c-13 NMR to nanomaterials characterization, and the fundamental c-13 spin-lattice relaxation times highlight the spatial arrangement of surface-associated paramagneticcenters around the core sp3 carbon assembly of diamond nanoparticles, delineating the unique size-dependent physicochemical characteristics of diamond nanoparticles.
coP has attracted increasing attention due to its high theoretical capacity for lithium storage. However, coP suffers from a large volume expansion during cycling, which leads to electrode pulverization and poor cycle...
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coP has attracted increasing attention due to its high theoretical capacity for lithium storage. However, coP suffers from a large volume expansion during cycling, which leads to electrode pulverization and poor cycle stability. In addition, the conductivity of coP is poor, resulting in undesirable rate performance. To solve this problem, the coP/ccomposite was prepared based on the in-situ phosphating heat treatment technology of co-BTc MOF. The as prepared coP/c exhibits a good lithium storage specificcapacity and a cycle stability, which is attributed by the synergistic effect of the porous nanostructure and carbon frame. The porous nanostructure of the coP/c allows the electrolyte to easily penetrate into the interior, which increases the number of electrochemical reaction sites while effectively mitigating the volume expansion during lithiation and improving electrical conductivity. Thanks to the special structures, the discharge specificcapacity of the Lithium-ion batteries (LIBs) based the coP/c as anode materials is 645.7 mAh g(-1) after 200 cycles at a current density of 200 mA g(-1). This work demonstrates that the coP/c has a great potential as a next generation anode material for LIBs.
Obtaining coatings with excellent ablation resistance is a longstanding challenge for the ablation protection of carbon/carbon (c/c) composites. In this work, a single phase Hf0.75Zr0.25N solid solution ultra-high tem...
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Obtaining coatings with excellent ablation resistance is a longstanding challenge for the ablation protection of carbon/carbon (c/c) composites. In this work, a single phase Hf0.75Zr0.25N solid solution ultra-high temperature ceramic (UHTc) coating was proposed, and prepared on the surface of c/ccomposites by chemical vapor deposition (cVD) for the first time. The results revealed that the hardness and Young's modulus of Hf0.75Zr0.25N coating are higher than those of HfN and ZrN coatings, reaching 33.35 GPa and 316.42 GPa, respectively. After ablation for 180 s under oxygen acetylene flame with a temperature exceeding 2200 & DEG;c, the Hf0.75Zr0.25N coating retained its structural integrity and exhibited lower ablation (Rm: 0.26 mg/s;Rh: 0.32 & mu;m/s). This is mainly attributed to the formation of the dense Hf-Zr-O oxide scale promoted by the oxidation sintering reaction during ablation. The above results indicate the nitride solid solution UHTc has great potential as ablation resistance coating at ultra-high temperatures.
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