用200nm铜颗粒在空气中快速压力辅助烧结及连续无压退火提高结合强度

为了设计一种有效且适用于功率器件的烧结结合工艺,提出一种两步工艺,使用约200 nm的铜颗粒基浆料形成具有高温可持续性和优越导热性的粘结层.该工艺涉及在空气中快速压力辅助烧结和在氮气气氛中连续无压退火.当使用20％(质量分数)的羟基丁二酸和80％(质量分数)的乙二醇混合物浆料时,在300℃、5 MPa烧结30 s后的剪...     

Oil resistance and low-temperature characteristics of plasticized nitrile butadiene rubber compounds

The mechanical properties and oil resistance of nitrile butadiene rubber as an automotive material are investigated under low-temperature conditions. We discuss the effects of various plasticizers, such as dioctyl adipate, adipic acid ester, polyether ester, and adipic acid polyester. The mechanical properties after thermal oxidation aging, as well as oil resistance and low-temperature characteristics of the compounds, are measured using a moving die rheometer, universal testing machine, differential scanning calorimeter, low-temperature retraction tester, and gehman torsional stiffness tester. We focus on how the oil resistance and low-temperature characteristics are affected by the plasticizer type and plasticizer content. The results demonstrate that nitrile butadiene rubber compounds are affected by the low molecular weight and viscosity of the plasticizer. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47851.     

Continuous fractionation of fly ash particles by SPUTT for the investigation of PCDD/Fs levels in different sizes of insoluble particles

A combined analytical method has been developed to characterize the size dependent levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) contained in fly ash particles from a municipal solid waste incinerator (MSWI). Gravitational SPLITT fractionation (GSF), a relatively new technique for the fast and continuous separation of micron sized particles, was used to fractionate a fly ash sample, directly collected from a bag-filter house of MSWI in Korea, into six different size groups (<1.0, 1.0-2.5, 2.5-5.0, 5.0-10, 10-20, and 20-53 microm in diameter) in water solution, and the resulting fractions are examined by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) in order to determine the concentration of PCDD/Fs according to these particle sizes. The results from SPLITT fractionation show that approximately 54% of the fly ash particles (sieved fraction <53 microm) by weight have been found to be smaller than 5.0 microm excluding the water soluble matter in the sample. From the HRGC/HRMS measurements, particle fractions in the size range of PM 1.0-2.5 and 2.5-5.0 appear to carry about 76 and 79 ng/g of PCDD/Fs which are relatively larger than those found in other diameter ranges. Principal component analysis (PCA) shows that particles larger than 5.0 microm are clustered into a group predominantly containing low chlorinated dioxins and fractions smaller than 5.0 microm into another group with lower chlorinated furans. This study demonstrated that the combining GSF with a secondary analytical method such as HRGC/HRMS has the potential to obtain size dependent information of particulate materials in relation to their production processes, chemical compositions, environmental fates, and other factors.     

Biodegradable membranes for the controlled release of progesterone. 1. Characterization of membrane morphologies coagulated from PLGA/progesterone/DMF solutions

Biodegradable membranes containing progesterone as a drug were prepared from ternary, poly(d,l‐lactide‐co‐glycolide)/progesterone/dimethylformamide, solutions. The homogeneous solutions, after cast on glass plates, were solidified to result in a solid membrane structure by three different solvent‐removal processes: solvent evaporation under vacuum, solvent extraction via immersion into the nonsolvent bath, or vapor exposure at high humidity condition. Impregnation characteristics of progesterone in the prepared membranes varied significantly, depending on the removal processes used. When a cast solution was solidified by exposure at the environment of 70% relative humidity, progesterone was separated from a membrane structure with the morphology of flake‐like shapes, and thermal analysis of the prepared membrane showed the clear, endothermic peak of the drug. Vitrification of a cast solution by solvent evaporation under vacuum induces both the uniform drug dispersion in the polymer matrix, with the drug forming spherical structures, and the strong interaction between the drug and the matrix, as identified by a broadened melting endotherm of the drug. When coagulated at thermodynamic nonequilibrium conditions through rapid exchange between dimethyformamide and water, the cast solution film results in a membrane structure consisting of the drug distributed nonuniformly in the polymer matrix. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 60–67, 2000     

Histone Demethylase KDM7A Contributes to the Development of Hepatic Steatosis by Targeting Diacylglycerol Acyltransferase 2

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. While the development of NAFLD is correlated with aberrant histone methylation, modifiers of histone methylation involved in this event remain poorly understood. Here, we studied the functional role of the histone demethylase KDM7A in the development of hepatic steatosis. KDM7A overexpression in AML12 cells upregulated diacylglycerol acyltransferase 2 (DGAT2) expression and resulted in increased intracellular triglyceride (TG) accumulation. Conversely, KDM7A knockdown reduced DGAT2 expression and TG accumulation, and significantly reversed free fatty acids-induced TG accumulation. Additionally, adenovirus-mediated overexpression of KDM7A in mice resulted in hepatic steatosis, which was accompanied by increased expression of hepatic DGAT2. Furthermore, KDM7A overexpression decreased the enrichment of di-methylation of histone H3 lysine 9 (H3K9me2) and H3 lysine 27 (H3K27me2) on the promoter of DGAT2. Taken together, these results indicate that KDM7A overexpression induces hepatic steatosis through upregulation of DGAT2 by erasing H3K9me2 and H3K27me2 on the promoter.     

Targeted Induction of Endogenous VDUP1 by Small Activating RNA Inhibits the Growth of Lung Cancer Cells

Recent studies have reported that small double-strand RNAs (dsRNAs) can activate endogenous genes via an RNA-based promoter targeting mechanism termed RNA activation (RNAa). In the present study, we showed that dsVDUP1-834, a novel small activating RNA (saRNA) targeting promoter of vitamin D₃ up-regulated protein 1 (VDUP1) gene, up-regulated expression of VDUP1 at both mRNA and protein levels in A549 lung cancer cells. We also demonstrated that dsVDUP1-834 inhibited cell proliferation in A549 lung cancer cells. Further studies showed that dsVDUP1-834 induced cell-cycle arrest by increasing p27 and p53 and decreasing cyclin A and cyclin B1. In addition, knockdown of VDUP1 abrogated dsVDUP1-834-induced up-regulation of VDUP1 gene expression and related effects. The activation of VDUP1 by dsVDUP1-834 was accompanied by an increase in dimethylation of histone 3 at lysine 4 (H3K4me2) and acetylation of histone 3 (H3ac) and a decrease in dimethylation of histone 3 at lysine 9 (H3K9me2) at the target site of VDUP1 promoter. Moreover, the enrichment of Ago2 was detected at the dsVDUP1-834 target site, and Ago2 knockdown significantly suppressed dsVDUP1-834-mediated inhibition of cell proliferation and modulation of cell-cycle regulators. Taken together, the results presented in this report demonstrate that dsVDUP1-834 induces VDUP1 gene expression by epigenetic changes, resulting in cell growth inhibition and cell-cycle arrest. Our results suggest that targeted induction of VDUP1 by dsVDUP1-834 might be a promising therapeutic strategy for the treatment of lung cancer.     

Synthesis of Kisspeptin-Mimicking Fragments and Investigation of their Skin Anti-Aging Effects

In recent years, a number of active materials have been developed to provide anti-aging benefits for skin and, among them, peptides have been considered the most promising candidate due to their remarkable and long-lasting anti-wrinkle activity. Recent studies have begun to elucidate the relationship between the secretion of emotion-related hormones and skin aging. Kisspeptin, a neuropeptide encoded by the KISS1 gene, has gained attention in reproductive endocrinology since it stimulates the reproductive axis in the hypothalamus; however, the effects of Kisspeptin on skin have not been studied yet. In this study, we synthesized Kisspeptin-10 and Kisspeptin-E, which are biologically active fragments, to mimic the action of Kisspeptin. Next, we demonstrated the anti-aging effects of the Kisspeptin-mimicking fragments using UV-induced skin aging models, such as UV-induced human dermal fibroblasts (Hs68) and human skin explants. Kisspeptin-E suppressed UV-induced 11 beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) stimulation leading to a regulation of skin aging related genes, including type I procollagen, matrix metalloproteinases-1 (MMP-1), interleukin-6 (IL-6), and IL-8, and rescued the skin integrity. Taken together, these results suggest that Kisspeptin-E could be useful to improve UV-induced skin aging by modulating expression of stress related genes, such as 11β-HSD1.     

Improved Synchronization Criteria for Chaotic Neural Networks with Sampled-data Control Subject to Actuator Saturation

International Journal of Control, Automation and Systems - In this paper, the synchronization problem for chaotic neural networks with sampled-data control and actuator saturation is investigated....     

Engineering of the catalytic site of xylose isomerase to enhance bioconversion of a non-preferential substrate

Mutation in active site would either completely eliminate enzyme activity or may result in an active site with altered substrate-binding properties. The enzyme xylose isomerase (XI) is sterospecific for the α-pyranose and α-fructofuranose anomers and metal ions (M1 and M2) play a pivotal role in the catalytic action of this enzyme. Mutations were created at the M2 site of XI of Thermus thermophilus by replacing D254 and D256 with arginine. Mutants D254R and a double mutant (D254R/D256R) showed complete loss of activity while D256R showed an increase in the specificity on D-lyxose, L-arabinose and D-mannose which are non-preferential substrates for XI. Both wild type (WT) and D256R showed higher activity at pH 7.0 and 85°C with an increase in metal requirement. The catalytic efficiency Kcat/Km (S(-1) mM(-1)) of D256R for D-lyxose, L-arabinose and D-mannose were 0.17, 0.09 and 0.15 which are higher than WT XI of T.thermophilus. The altered catalytic activity for D256R could be explained by the possible role of arginine in catalytic reaction or the changes in a substrate orientation site. However, both the theories are only assumptions and have to be addressed with crystal study of D256R.     

Plastic limit loads for cracked large bore branch junction

This paper reports plastic limit loads for a cracked large bore branch junction, based on three-dimensional finite element limit analyses using elastic-perfectly plastic materials. Part-through surface and through-wall cracks are postulated in the intersection. For loading conditions, internal pressure and (in-plane and out-of-plane) bending to the branch pipe and to the run pipe are considered. The effect of the crack on limit loads is found to be significant for internal pressure and bending to the branch pipe, but not for bending to the run pipe. The large geometry change effect for bending to the branch pipe is briefly discussed.