Buckling Resistance of Axially Restrained Chord Members of Grid Structure at Elevated Temperatures

This paper investigates the behavior of large span grid structure exposed to a localized fire. The localized fire may generate hot smoke and thus induce non-uniform temperature distribution in the grid structure. The thermal expansion of the heated members tend to be axially restrained by the adjacent cold members thus inducing additional forces on the critical members of the grid structure. The buckling resistance of axially restrained member at elevated temperature may be obtained based on second order analysis of member with initial lateral imperfection by considering force equilibrium at deformed geometry and cross section resistance being reached. The critical temperature of the member is reached when the axial force reaches its buckling resistance. It is found that the critical temperature of members with initial lateral imperfection was higher than that without such imperfection for chord members with large slenderness ratio and high axial restraint

A self-supported, flexible, binder-free pseudo-supercapacitor electrode material with high capacitance and cycling stability from hollow, capsular polypyrrole fibers

Flexible energy devices with high performance and long-term stability are highly promising for applications in portable electronics, but remain challenging to develop. As an electrode material for pseudo-supercapacitors, conducting polymers typically show higher energy storage ability over carbon materials and larger conductivity than transition-metal oxides. However, conducting polymer-based supercapacitors often have poor cycling stability, attributable to the structural rupture caused by the large volume contrast between doping and de-doping states, which has been the main obstacle to their practical applications. Herein, we report a simple method to prepare a flexible, binder-free, self-supported polypyrrole (PPy) supercapacitor electrode with high cycling stability through using novel, hollow PPy nanofibers with porous capsular walls as a film-forming material. The unique fiber structure and capsular walls provide the PPy film with enough free-space to adapt to volume variation during doping/de-doping, leading to super-high cycling stability (capacitance retention > 90% after 11000 charge-discharge cycles at a high current density of 10 A g-1) and high rate capability (capacitance retention ∼ 82.1% at a current density in the range of 0.25-10 A g-1)

Characterization and activity of N doped TiO2 supported VPO catalysts for NO oxidation

AbstractNitrogen (N) doped TiO2 supported vanadium phosphorus oxide (VPO) catalysts were prepared and tested for catalytic oxidation of NO. The experimental results showed that 0.1V(5)PO/TiN(1) was the optimal catalyst for NO oxidation and the NO conversion could reach 61% at temperature of 350°C. The physico–chemical properties of 0.1V(5)PO/TiN(1) catalyst were characterized by Brunauer–Emmett–Teller measurements (BET), Photoluminescence (PL), X–ray photoelectron spectroscopy (XPS), Infrared spectroscopy measurements of NH3 adsorbed on catalysts (NH3–IR), and Infrared Fourier transform spectroscopy (FTIR). The PL and XPS spectra revealed that the oxygen storage capacity and catalytic activity of VPO/Ti catalyst can be improved by nitrogen doping. The H2–TPR profile also indicated that V(5)PO/TiN(1) catalyst had a superior redox property. Activity test results and FTIR spectra showed that 0.1V(5)PO/TiN(1) catalysts had a superior resistivity to SO2 and the NO oxidation rate is above 50% at temperature of 350°C when SO2 concentration is 200ppm to 800ppm

Oxidative Stress Regulated Iron Regulatory Protein IRP2 Through FBXL5-Mediated Ubiquitination-Proteasome Way in SH-SY5Y Cells

Iron regulatory protein 2 (IRP2) plays a key role in the cellular iron homeostasis and could be regulated by a variety of factors, such as oxidative stress, hypoxia and iron, etc. IRP2 depletion results in neurodegenerative movement disorder with the loss of neurons and accumulations of iron. Since oxidative stress extensively exists in several neurodegenerative diseases where iron accumulation also exists, it is important to clarify the mechanisms underlying the effects of oxidative stress on IRP2 expression and its consequence. 200 and 300 μM H2O2 could result in the reduced cell viability in SH-SY5Y cells. The intracellular levels of reactive oxygen species (ROS) were increased by 52.2 and 87.3% with 200 and 300 μM H2O2 treatments, respectively. The decreased levels of mitochondrial transmembrane potential (ΔΨm) were only observed in 300 μM H2O2-treated group. The protein levels of IRP2, but not for its mRNA levels, were observed decreased in both groups, which resulted in the lower TfR1 expression and decreased iron uptake in these cells. Pretreatment with MG132, the decreased IRP2 levels caused by H2O2 treatment could be antagonized. The protein levels of F box and leucine-rich repeat protein 5 (FBXL5), the only E3 ligase of IRP2, were observed decreased accordingly. When knockdown the intracellular FBXL5 levels by si-FBXL5, the protein levels of IRP2 were found increased with H2O2 treatment. Our results suggest that FBXL5 is involved in the degradation of IRP2 under oxidative stress in dopaminergic-like neuroblastoma cells, which implies that its role in the neuronal regulation of IRP2 in neurodegenerative diseases

stability evaluation of coated lipase

Objective The study was conducted to evaluate the stability of commercial coated lipase (CT-LIP) in vitro. Methods The capsules were tested under different conditions with a range of temperature, pH, dry heat treatment and steaming treatment, simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) in this work, respectively. Free lipase (uncoated lipase, UC-LIP) was the control group. Lipase relative activities measured in various treatments were used as a reference frame to characterize the stability. Results The lipase activities were decreased with increasing temperatures (p<0.05), and there was a markedly decline (p<0.01) in lipase comparative activities of UC-LIP at 80°C compared with CT-LIP group. Higher relative activities of lipase were observed in CT-LIP group compared with the free one under acidic ambient (pH 3 to 7) and an alkaline medium (pH 8 to 12). Residual lipase activities of CT-LIP group were increased (p<0.05) by 5.67% and 35.60% in dry heat and hydrothermal treatments, respectively. The lipase relative activity profile of CT-LIP was raised at first and dropped subsequently (p<0.05) compared with constantly reduced tendency of UC-LIP exposed to both SGF and SIF. Conclusion The results suggest that the CT-LIP possesses relatively higher stability in comparison with the UC-LIP in vitro. The CT-LIP could retain the potential property to provide sustained release of lipase and thus improved its bioavailability in the gastrointestinal tract

Plasmoid ejection and secondary current sheet generation from magnetic reconnection in laser-plasma interaction

Reconnection of the self-generated magnetic fields in laser-plasma interaction was first investigated experimentally by Nilson {\it et al.} [Phys. Rev. Lett. 97, 255001 (2006)] by shining two laser pulses a distance apart on a solid target layer. An elongated current sheet (CS) was observed in the plasma between the two laser spots. In order to more closely model magnetotail reconnection, here two side-by-side thin target layers, instead of a single one, are used. It is found that at one end of the elongated CS a fan-like electron outflow region including three well-collimated electron jets appears. The ($>1$ MeV) tail of the jet energy distribution exhibits a power-law scaling. The enhanced electron acceleration is attributed to the intense inductive electric field in the narrow electron dominated reconnection region, as well as additional acceleration as they are trapped inside the rapidly moving plasmoid formed in and ejected from the CS. The ejection also induces a secondary CS

Development and performance optimization of a new composite sealing material prepared by drilling cuttings

A highly efficient composite sealing material was prepared using drilling cuttings as the base material and a binder, a coagulant, and other additives as auxiliaries. A four-factor, three-level orthogonal test was designed based on the response surface method (RSM), and a response surface regression model was constructed using compressive strength, fluidity, expansion rate, and setting time as performance indexes to analyze the effects of each factor on material performance and optimize the material proportion. The samples were prepared by simulating the grouting process, the permeability of the samples was measured, and the sealability of the material was verified by analyzing the material microscopic morphology. Results showed that the regression model had a high level of confidence and accuracy and could predict the test results accurately within the range of the test. The effects of the interaction between factors on material performance were also examined. The low permeability of the sealing material samples verified the material’s feasibility. Gradual optimization of material performance revealed that the optimal proportion was 52.6% drill cuttings, 44.3% binder, 0.6% coagulant promoter, and 2.5% expansive agent. Under these conditions, the error between the predicted and test values of each material property was less than 5%, and the comprehensive performance was superior. These findings verify the accuracy of RSM and its applicability to the optimization of material performance. This work provides reasonable theoretical guidance for the preparation of drilling cuttings composite (DC) materials in practical engineering

Metal-bonded perovskite lead hydride with phonon-mediated superconductivity up to 46 K under atmospheric pressure

In the search for high-temperature superconductivity in hydrides, a plethora of multi-hydrogen superconductors have been theoretically predicted, and some have been synthesized experimentally under ultrahigh pressures of several hundred GPa. However, the impracticality of these high-pressure methods has been a persistent issue. In response, we propose a new approach to achieve high-temperature superconductivity under atmospheric pressure by implanting hydrogen into lead to create a stable few-hydrogen metal-bonded perovskite, Pb$_4$H. This approach diverges from the popular design methodology of multi-hydrogen covalent high critical temperature ($T_c$) superconductors under ultrahigh pressure. By solving the anisotropic Migdal-Eliashberg (ME) equations, we demonstrate that perovskite Pb$_4$H is a typical phonon-mediated superconductor with a $T_c$ of 46 K, which is six times higher than that of bulk Pb (7.22 K) and higher than that of MgB$_2$ (39 K). The high $T_c$ can be attributed to the strong electron-phonon coupling (EPC) strength of 2.45, which arises from hydrogen implantation in lead that induces several high-frequency optical phonon modes with a relatively large phonon linewidth resulting from H atom vibration. The metallic-bonding in perovskite Pb$_4$H not only improves the structural stability but also guarantees better ductility than the widely investigated multi-hydrogen, iron-based, and cuprate superconductors. These results suggest that there is potential for the exploration of new high-temperature superconductors under atmospheric pressure and may reignite interest in their experimental synthesis soon.Comment: 6 pages, 4 figure