Correlating the 3D melt electrospun polycaprolactone fiber diameter and process parameters using neural networks

In the present work, we developed an artificial neural networks (ANN) model to predict and analyze the polycaprolactone fiber diameter as a function of 3D melt electrospinning process parameters. A total of 35 datasets having various combinations of electrospinning writing process variables (collector speed, tip to nozzle distance, applied pressure, and voltage) and resultant fiber diameter were considered for model development. The designed stand-alone ANN software extracts relationships between the process variables and fiber diameter in a 3D melt electrospinning system. The developed model could predict the fiber diameter with reasonable accuracy for both train (28) and test (7) datasets. The relative index of importance revealed the significance of process variables on the fiber diameter. Virtual melt spinning system with the mean values of the process variables identifies the quantitative relationship between the fiber diameter and process variables.     

Cyanobacteria,Cyanotoxins, and Neurodegenerative Diseases: Dangerous Liaisons

The prevalence of neurodegenerative disease (ND) is increasing, partly owing to extensions in lifespan, with a larger percentage of members living to an older age, but the ND aetiology and pathogenesis are not fully understood, and effective treatments are still lacking. Neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis are generally thought to progress as a consequence of genetic susceptibility and environmental influences. Up to now, several environmental triggers have been associated with NDs, and recent studies suggest that some cyanotoxins, produced by cyanobacteria and acting through a variety of molecular mechanisms, are highly neurotoxic, although their roles in neuropathy and particularly in NDs are still controversial. In this review, we summarize the most relevant and recent evidence that points at cyanotoxins as environmental triggers in NDs development.     

Application of Gurson Model for Evaluation of Density‐Dependent Mechanical Behavior of Polyurethane Foam: Comparative Study on Explicit and Implicit Method

Recently, liquefied natural gas (LNG) is a focus of interest around the world for several reasons, and LNG cargo containment systems (CCS) increase in quality to prevent loss of LNG during shipping. For insulation of CCS, polyurethane foam (PUF), an outstanding insulation material, is commonly used. However, until now, although its mechanical properties are relatively good, the material is not considered as a structural member under compressive loading, principal load direction in CCS. Moreover, as PUF is a porous material by mixing and foaming, its mechanical properties depend on voids, which is a dominant parameter for density. Therefore, in the present study, nonlinear behavior of PUF is described using Gurson model with a novel technique, i.e., an acceleration factor. The model expresses the behavior through the volume fraction of voids with consideration of the density effect to evaluate structural performance using user‐defined material subroutine with explicit and implicit methods.

     

Characterization of biogenic hydroxyapatite derived from animal bones for biomedical applications

In this work, the viability of producing biogenic hydroxyapatite from bio-waste animal bones, namely bovine (cow), caprine (goat) and galline (chicken), through a heat treatment process has been investigated. The animal bones were locally sourced, cleaned to remove collagen and subsequently heat treated in air atmosphere at different temperatures ranging from 600?°C to 1000?°C. From the range of sintering temperatures investigated, it was found that hydroxyapatite derived from bovine bone showed good thermal stability while those produced from caprine and galline bones exhibited phase instability with traces of tri-calcium phosphate (TCP) being detected after heat treatment beyond 700?°C. The porous nature of the bone samples can be observed from the microstructures obtained and supported by low relative density. Heating the bovine and caprine bones at selected temperatures yielded porous HA body, having hardness values that are comparable with human cortical bone. However, the sintered galline bone sample showed higher porosity levels and low hardness when compared to the other two bone types.     

Two 3D Coordination Polymers with New Topology Based on Mixed Ligands: Synthesis,Structure, and Photoluminescence Properties

Employing tetracarboxylate and imidazole mixed ligands to react with different transition meat salts afford two new 3D coordination polymers, {[Zn₂(BPTC)(BBI)₂]·(H₂O)₃·DMSO}_n (1) and {[Cd₂(BPTC)(BBI)₂]·H₂O}_n (2) (H₄BPTC?=?biphenyl-3,3′,4,4′-tetracarboxylic acid, BBI?=?1,1′-(1,4-butanediyl)bis(imidazole)). Both these two coordination polymers are 4-connected network topologies. Compound 1 features a unprecedented 3-nodal (4,4,4)-connected network topology with the point symbol {6⁴·8²}, and 2 displays a (4,4)-connected binodal network bearing new topology with the point symbol of {7²·8⁴}2{7³·8³}. Additionally, thermal stability and photoluminescence properties of 1 and 2 were investigated.     

多孔硅场致电子发射

研究了多孔硅冷阴极的场致电子发射特性，实验表明采用电化学阳极腐蚀、氧化、蒸电极等工艺可以制备一种平面薄膜型多孔硅冷阴极。在超高真空环境下测量了多孔硅冷阴极的电子发射特性。     

半导体二极管γ瞬时辐射效应

本文研究了半导体二极管瞬时电离辐射效应,给出了在闪光X射线机上的试验结果。     

Microwave dielectric properties of Mg4Nb2O9 ceramics produced by hydrothermal synthesis

Mg₄Nb₂O₉ ceramics have been prepared by a hydrothermal synthesis in order to reduce the sintering temperature. The sintering and microwave dielectric properties of the hydrothermally processed Mg₄Nb₂O₉ were studied under various sintering temperatures ranging from 900 to 1300°C. The highest Q×f _o value of 26,069 GHz was obtained at the sintering temperature of 1300°C and is attributed to the increased density and appropriate grain growth. τ _f value of ?17.1 ppm/°C was improved by the addition of TiO₂ and τ _f value of 6.7 ppm/°C was obtained at 20 wt% TiO₂. Chemical compatibility of Mg₄Nb₂O₉ with Ag was tested to identity the possibility of using Mg₄Nb₂O₉ for an LTCC application. Since any secondary phase was not observed in the XRD pattern of the mixtures of Mg₄Nb₂O₉ and Ag powder heat treated at 900°C, it was considered that the Mg₄Nb₂O₉ system is applicable to the multilayer microwave devices using Ag as an electrode.     

Electrical characterizations of Neutron-irradiated SiC Schottky diodes

Neutrons with an average energy of 9.8±0.8 MeV were irradiated onto silicon carbide Schottky diodes. After bombardment at a fluency of 2.75×10¹¹ neutron/cm², the Schottky barrier height, ideality factor, and the leakage currents remained unchanged. The electrical properties began to deteriorate after bombardment at a fluency of 5.5×10¹¹ neutron/cm². In this study, we demonstrate that SiC SBD is robust under neutron irradiations and is well suited for space operations up to bombardments at a fluency of 2.75×10¹¹ neutron/cm². This article is dedicated to Professor Chul Soo Lee in commemoration of his retirement from Department of Chemical and Biological Engineering of Korea University.     

4-氨基-6-特丁基-3-甲硫基-1,2,4-三嗪-5(4H)-酮硫酸盐的合成工艺及活性研究

为了寻找新型的除草剂,以浓硫酸和三嗪为起始原料,采用选择性S-甲基化的方法在酸性条件下,对4-氨基-6-特丁基-3-甲硫基-1,2,4-三嗪-5(4H)-酮硫酸盐在合成过程中的各个反应参数进行优化,确定了最优反应条件。通过氢谱(1HNMR),红外光谱(IR),元素分析和熔点测定,对所合成的产物进行结构分析。采用离体含毒介质法对合成产物进行杀菌毒力活性的测定,表明对植物病害菌有良好的抑制和杀灭作用,所得数据为新型除草剂的研究提供科学依据。