Consolidation of Cu-based amorphous alloy powders by high-pressure torsion

We applied high-pressure torsion (HPT) for consolidation of gas-atomized metallic glass Cu₅₄Zr₂₂Ti₁₈Ni₆ powders into high-density bulk disks. The effects of the number of revolutions (N = 1–5 turns), applied pressure (2.5–10 GPa), and temperature (298–473 K) on densification and structural changes were investigated. The consolidated glassy disks showed an excellent hardness of ~5.2 GPa although a mechanical softening effect along with fragmentation in the center of HPT disks occurred at N > 3 by a couple of branching cracks. The HPT process at higher applied pressures improved the bulk density and inter-particulate bonding, resulting in higher hardness. Increasing the temperature of HPT processing enhanced the densification and deep drawability of the consolidated metallic glass. Although the HPT process did not change the crystallization temperature of the metallic glass powders, it increased the crystallization enthalpy, suggesting the free volume increase and inhibition of a significant nanocrystallization during the HPT process.     

Al-Ga-Mn-Ca-Cu合金电极碱性体系电化学性能

通过熔铸、压延、退火等一系列工艺制作了新型Al-0.017Ga-0.885Mn-0.038Ca-0.048Cu (wt.%)阳极合金,并通过了EIS、极化曲线分析研究了其在不同浓度NaOH溶液中的腐蚀行为和电化学性能。结果表明,随着NaOH浓度的增加,合金阳极的自腐蚀速率在逐渐增加,Al-0.017Ga-0.885Mn-0.038Ca-0.048Cu合金在4mol/LNaOH溶液中的腐蚀速率增长速度明显降低,放电电压在电流密度为120mA/cm2下仍能维持在1 V左右,阳极能量密度也最高,达6.056kW?h/kg,更适合不同电流密度下的连续恒流放电。且合金的恒流放电和EIS结果与腐蚀特性吻合较好。     

A rapid method for the simultaneous determination of 25 anti-hypertensive compounds in dietary supplements using ultra-high-pressure liquid chromatography

A novel, stable, simple and specific ultra-performance liquid chromatography method with ultraviolet detection (205 nm) for the simultaneous analysis of 25 anti-hypertensive substances was developed. The method was validated according to the International Conference of Harmonisation guidelines with respect to linearity, accuracy, precision, limit of detection (LOD), limit of quantitation (LOQ) and stability. From the ultra-performance liquid chromatography results, we identified the LOD and LOQ of solid samples to be 0.20–1.00 and 0.60–3.00 μg ml^?1, respectively, while those of liquid samples were 0.30–1.20 and 0.90–3.60 μg ml^?1, respectively. The linearity exceeded 0.9999, and the intra- and inter-day precisions were 0.15–6.48% and 0.28–8.67%, respectively. The intra- and inter-day accuracies were 82.25–111.42% and 80.70–115.64%, respectively, and the stability was lower than 12.9% (relative standard deviation). This method was applied to the monitoring of 97 commercially available dietary supplements obtained in Korea, such as pills, soft capsules, hard capsules, liquids, powders and tablets. The proposed method is accurate, precise and of high quality, and can be used for the routine, reproducible analysis and control of 25 anti-hypertensive substances in various dietary supplements. The work presented herein may help to prevent incidents related to food adulteration and restrict the illegal food market.     

Biotransformation of monosodium glutamate to gamma-aminobutyric acid by isolated strain Lactobacillus brevis L-32 for potentiation of pentobarbital-induced sleep in mice

In the current study, we investigated the biotransformation of monosodium glutamate (MSG) to gamma-aminobutyric acid (GABA) by the growing and resting cells from an isolated bacterial strain, Lactobacillus brevis. This strain is a high GABA-producing strain that was identified and isolated from natural kimchi. We gathered the experiment results by design of response surface methodology (RSM) for optimum condition for GABA production and results indicated the optimum culture temperature (35°C) and culture time (58 h). Using resting cells from the same culture batch in the substrate-containing buffer, approximately 3.98 g/l of GABA was produced at a conversion rate of 65.6%. GABA-treated mice showed significantly increased sleep duration compared to that of a control group (p < 0.05) in the pentobarbital-induced sleep test using a hypnotic dose. These results suggest that biotransformed GABA could potentially be used a novel nutraceutical supplement for sleep.     

Corrosion Behaviors of Zirconia Refractory by CaO–SiO2–MgO–CaF2 Slag

In this work the corrosion behaviors of zirconia refractory (partially MgO-stabilized zirconia) was investigated in CaO–SiO₂–MgO–CaF₂ slag with varying CaF₂ content at 1873 K. To figure out the corrosion mechanism, the characteristics of present slag at high temperature were examined in terms of melting temperature and vaporization behaviors. Corrosion experiment and melting temperature measurement were carried out by heating microscope (HM) and the vaporization phenomenon was investigated by thermo gravimetry–differential scanning calorimetry. After experiment, the corroded interfaces of zirconia refractory by slag were analyzed by scanning electron microscope-energy dispersive spectroscopy and electron probe microanalysis. With an addition of CaF₂, three different layers were formed at the interface of slag and zirconia refractory. Furthermore, the corrosion behaviors of zirconia refractory were found to be continuously accelerated with an increase of CaF₂ which facilitated the dissolution of intermediate compound. On the other hand, melting temperature of CaO–SiO₂–MgO–CaF₂ slag showed no continuous decrease with an increase of CaF₂. Also, considerable vaporization of fluoride gas was occurred in high CaF₂ containing slag during HM experiment which might cause a gradual change of slag composition and also environmental pollution. From the results, present study suggested that a proper amount of CaF₂ should be added when it is used for enhancing refining capacity of slag in order not to cause any severe damage of zirconia-based refractory by slag.     

Absorption of NOx in packed column (II)

An absorption efficiency of packed column removing nitrogen oxides with water and NaOH solution under atmospheric pressure was studied. The efficiency and the acidity produced by absorption of NO, were measured in a packed column. The model developed that was based on the mass-transfer information for packed column and absorption mechanism accompanying the chemical reaction was compared with experimental results. Predictions using the model presented by the previous paper (part 1) was shown well to agree with from the experimental results (part II). The efficiency of NO_x, absorption is largely dependent on the height of packing material and the partial pressure of NO_x in the feed gas. The efficiency of NO_x absorption decreases with the increase of the acidity produced by recycling of water as a scrubber liquid. For the recycle mode with an aqueous NaOH solution as a scrubber liquid, NO_x absorption efficiency is shown to be constant until all of the C_OH- in the scrubber liquid are converted into C_H+.     

Multigroup pin power reconstruction with two-dimensional source expansion and corner flux discontinuity

A pin power reconstruction method that is readily applicable to multigroup problems with superior accuracy is presented for applications involving rectangular fuel assemblies. It employs a two-dimensional (2D), fourth order Legendre expansion of the source distribution that naturally leads to a group-decoupled, 2D semi-analytic solution of the neutron diffusion equation. The four surface average currents and four corner fluxes are used as the boundary conditions to uniquely specify the homogenous solution. The corner fluxes and source expansion coefficients are iteratively determined using the condition of corner point balance and the orthogonal property of the Lengedre functions. Corner discontinuity is incorporated in the calculation of the corner fluxes which turns out to be very effective in the cases of enrichment zoning. The accuracy of the proposed method is assessed by performing the two-step core calculations for the L336C5, C5G7MOX, and MOX core transient benchmark problems and then by comparing with the direct whole-core transport solutions. The results indicate that the proposed method is as accurate as the fully analytic method and works well irrespective the number of groups. However, it is also noted that somewhat larger errors are inevitable at the peripheral assemblies near the reflector in which the error associated with a prioi generation of the homogenized cross-sections and form functions is not trivial.     

Experimental and Modeling Studies on the Chemical Vapor Infiltration with Respect to the Effects of Thermal Gradient and Other Operating Parameters

Effects of operating parameters in the thermal gradient chemical vapor infiltration of propane such as thermal gradient, diffusion, infiltrations time, and concentration of propane were studied by focusing on the visualizations of the intrinsic effects of these parameters. A uniform deposition in the preform was obtained with a gradually increasing temperature along the gas flow. The uniformity of deposition through the preform got improved with increasing deposition time. Results of numerical modeling estimated the experimental data very well when the pre-exponential factor of the overall rate of carbon deposition from propane reported by Vaidyaraman[1] was multiplied by 4. The average density of a preform increased by about 3 times from 0.38 to 1.15 g/cm3 after 60 hr deposition with a thermal gradient under the conditions of 3% propane in nitrogen and 840 to 900 ℃.     

Peptide–Peptide Co-Assembly: A Design Strategy for Functional Detection of C-peptide,A Biomarker of Diabetic Neuropathy

Diabetes-related neuropathy is a debilitating condition that may be averted if it can be detected early. One possible way this can be achieved at low cost is to utilise peptides to detect C-peptide, a biomarker of diabetic neuropathy. This depends on peptide-peptide co-assembly, which is currently in a nascent stage of intense study. Instead, we propose a bead-based triple-overlay combinatorial strategy that can preserve inter-residue information during the screening process for a suitable complementary peptide to co-assemble with C-peptide. The screening process commenced with a pentapeptide general library, which revealed histidine to be an essential residue. Further screening with seven tetrapeptide focused libraries led to a table of self-consistent peptide sequences that included tryptophan and lysine at high frequencies. Three complementary nonapeptides (9mer com-peptides), wpkkhfwgq (Trp-D), kwkkhfwgq (Lys-D), and KWKKHFWGQ (Lys-L) (as a negative control) were picked from this table for co-assembly studies with C-peptide. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) and circular dichroism (CD) spectroscopies were utilized to study inter-peptide interactions and changes in secondary structures respectively. ATR-FTIR studies showed that there is indeed inter-peptide interaction between C-peptide and the tryptophan residues of the 9mer com-peptides. CD studies of unaggregated and colloidal C-peptide with the 9mer com-peptides suggest that the extent of co-assembly of C-peptide with Trp-D is greatest, followed by Lys-D and Lys-L. These results are promising and indicate that the presented strategy is viable for designing and evaluating longer complementary peptides, as well as complementary peptides for co-assembly with other polypeptides of interest and importance. We discuss the possibility of designing complementary peptides to inhibit toxic amyloidosis with this approach.