The role of Sb in the molecular beam epitaxy growth of 1.30–1.55 μm wavelength GaInNAs/GaAs quantum well with high indium content

Sb-assisted GaInNAs/GaAs quantum wells (QWs) with high (42.5%) indium content were investigated systematically. Transmission electron microscopy, reflection high-energy electron diffraction and photoluminescence (PL) measurements reveal that Sb acts as a surfactant to suppress three-dimensional growth. The improvement in the 1.55 μm range is much more apparent than that in the 1.3 μm range, which can be attributed to the difference in N composition. The PL intensity and the full-width at half maximum of the 1.55 μm single-QW were comparable with that of the 1.3 μm QWs.     

Structure theorem for dual quasi-hopf bicomodules and its application

We present a structure theorem for dual quasi-Hopf bicomodules, and also obtain the structure theorem C ≌ D ? H for dual quasi-Hopf module coalgebras, where H is a dual quasi-Hopf algebra, C a right H-module coalgebra, and D a left H-comodule coalgebra in the tensor category ^H M induced from C, and D ? H the smash coproduct introduced by Bulacu and Nauwelaerts.     

Almost periodic sequence solutions of a discrete Lotka–Volterra competitive system with feedback control

In this paper, we consider a discrete Lotka–Volterra competitive system with feedback control. Assuming that the coefficients in the system are almost periodic sequences, we obtain the existence and uniqueness of the almost periodic solution which is uniformly asymptotically stable.     

Preferential binding specificity of silver cation to a single nucleobase over base pairs evaluated by abasic site-containing DNA

The binding specificity of silver cations to abasic (AP) site-containing DNA was electrochemically investigated by comparison with the fully matched DNA without the AP site. AP site-containing DNA is designed in a way that only the nucleotide opposite the AP site is variable to allow for coexistence of an unpaired nucleotide and a number of DNA base pairs. The surface of a gold electrode was modified by AP site-containing DNA duplex on which Ag⁺ binding specificity was evaluated. Electrochemical investigations on the AP-DNA-modified electrodes reveal that Ag⁺ preferentially associates to the unpaired nucleotides instead of the coexisted base pairs and shows sequence-dependant binding, especially stronger for purines than for pyrimidines. Additionally, the hydrogen bond pattern moieties of the unpaired nucleotides should be involved in Ag⁺ binding evidenced by a decrease of the redox signal when introducing a ligand with its hydrogen bond moiety complementary to the nucleotide deoxycytidine. This is the first attempt to make a comparison in one DNA molecule for metal ion binding to coexisted unpaired nucleotide and DNA base pairs. The present method demonstrates an easy way for investigating binding specificity of heavy metal ions to AP site in the presence of coexisted DNA base pairs.     

Preparation of strontium chloride hexahydrate by batch‐cooling crystallization: Control of crystal size and morphology

The effects of initial supersaturation, cooling rate, and stirring rate on the morphology of strontium chloride hexahydrate (SrCl₂·6H₂O) crystals were investigated by batch‐cooling crystallization, providing optimal operating conditions. Uniform needle‐like crystals with a length of 1200.50 μm and a width of 100.92 μm on average were obtained. The corresponding aspect ratio of length to width was about 11.90. Moreover, the morphological modification of SrCl₂·6H₂O crystals using cetyltrimethylammonium chloride (CTAC) was studied. When 20.30 mmol·L⁻¹ of CTAC was added, the length and width of crystals were 792.71 μm and 233.25 μm, respectively, and the corresponding aspect ratio decreased to 3.40. The shape of SrCl₂·6H₂O crystal changed to granule‐like, probably because of the strong interaction of CTAC with the SrCl₂·6H₂O facets with a denser distribution of Cl⁻ ions. This study offers a simple, flexible, and highly efficient approach to regulate the morphology of SrCl₂·6H₂O crystals and opportunities for multiple applications of SrCl₂·6H₂O.     

Optimization of Adiponitrile Hydrolysis in Subcritical Water Using an Orthogonal Array Design

A study of the hydrolysis of adiponitrile (ADN) was performed in subcritical water to research the dependence on experimental conditions. An L₂₅(5⁶) orthogonal array design (OAD) with six factors at five levels using statistical analysis was employed to optimize the experimental conditions for each product in which the interactions between the variables were temporarily neglected. The six factors were adiponitrile concentration (ADN c, wt%), temperature (T), time (t h), percentage of additives (reactant/additive, wt/wt%), additives (A), and pressure (p, MPa). The effects of these parameters were investigated using the analysis of variance (ANOVA) to determine the relationship between experimental conditions and yield levels of different products. The results showed that (ADN c) and T had a significant influence on the yields of adipamide, adipamic acid, and adipic acid at p<0.05. Time was the statistically significant factor for the yield of 5-cyanovalermic acid at p<0.05 and (ADN c) was the significant factor for the yield of 5-cyanovaleramide at p<0.1. Finally, five supplementary experiments were conducted under optimized conditions predicted by the Taguchi method; the results showed that the yield obtained of each product was no lower than that of the highest in the 25 experiments. Carbon balance was calculated to demonstrate the validity of the experimental technique and the reliability of the results. Based on the experimental results, a possible reaction mechanism was proposed.     

SYNTHESES AND OPTOELECTRONIC PROPERTIES OF A HEXA-ARMED FLUORENE-BENZENE COPOLYMER BASED ON 2,4,6,8,10,12-HEXABENZYL-2,4,6,8,10,12-HEXAAZAISOWURTZITANE CAGED-CORE

A novel kind of hexa-armed fluorene-benzene copolymer based on a hexaazaisowurtzitane core was synthesized through Suzuki coupling polycondensation.The introduction of this bulky caged-core could not only enhance the photoluminescence quantum efficiency,but also improve the electroluminescence properties,especially suppress the common green-color emission of polyfluorenes(PFs) material during device operation.These features can be attributed to the successful suppression of PF's chain aggregation which p...     

化学与防火涂料

通过介绍当前我国防火涂料的种类、用途及使用对象,揭示其中的化学知识;对当前我国防火涂料的发展现状进行了分析,并根据防火涂料的发展现状对其今后的发展方向进行了探讨.     

基于加权改进的AR模型的负载预测研究

负载预测在故障管理中有着十分重要的作用,通过对CPU负载以及内存使用率的预测可以对系统进行实时监控,预知未来时间段资源的可用性,发出异常告警;文中提出一种加权改进的自回归模型,通过对最小二乘法求出的参数进行加权处理,结合时间序列分析理论,建立一个负载预测模型,用于CPU负载和内存使用率的预测;实验证明,对AR模型的参数进行加权的方法优化了参数估计,预测误差减小了60%~80%。     

Poria Acid,Triterpenoids Extracted from Poria cocos,Inhibits the Invasion and Metastasis of Gastric Cancer Cells

Background: Poria cocos (P. cocos) is an important medicinal fungus in traditional Chinese medicine. Poria acid (PA), a triterpenoid compound, is an effective component of traditional Chinese medicine P. cocos. This experiment investigated the anti-gastric cancer biological activity of PA in vitro. Methods: The effect of PA on the viability of gastric cancer cells was detected by the thiazolyl blue (MTT) assay. Cell adhesion assays were used to detect changes in the adhesion of cells treated after PA (0, 20, 40, and 80 µmol/L). The ability of cell invasion and migration were detected by Transwell assays and wound healing assays. A high-content imaging system was used to dynamically record the motility of the gastric cancer cells after PA (0, 20, 40, and 80 µmol/L) treatment. Western blotting was used to detect the expression of epithelial–mesenchymal transformation (EMT), invasion and migration related proteins. Results: The MTT assay showed that the proliferation of gastric cancer cells was significantly inhibited after PA treatment. Cell adhesion experiments showed that the adhesion of gastric cancer cells was significantly decreased after PA treatment. Compared with the control group, the wound healing area of the gastric cancer cells treated with different concentrations of PA decreased. The Transwell assay showed that the number of gastric cancer cells passing through the cell membrane were significantly reduced after PA treatment. In addition, after PA treatment, the cells’ movement distance and average movement speed were significantly lower than those of the control group. Finally, PA can significantly alter the expression of EMT-related proteins E-cadherin, N-cadherin, and Vimentin and decreased the expressions of metastasis-related proteins matrix metalloproteinase (MMP) 2, MMP-9 and tissue inhibition of matrix metalloproteinase (TIMP)1 in the gastric cancer cells. Conclusions: Triterpenoids from P. cocos have significant biological activity against gastric cancer, and the mechanism may be involved in the process of epithelial–mesenchymal transformation.