Synthesis and properties of biodegradable hydrogels of κ-carrageenan grafted acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid as candidates for drug delivery systems

Novel types of highly swelling hydrogels were prepared by grafting crosslinked polyacrylic acid-co-poly-2-acrylamido-2-methylpropanesulfonic acid (PAA-co-PAMPS) chains onto κ-carrageenan through a free radical polymerization method. Here, we propose a mechanism for κ-carrageenan-g-PAA-co-PAMPS formation and confirm the hydrogel structure using FTIR spectroscopy. The effect of grafting variables (i.e. concentration of methylenebisacrylamide (MBA), acrylic acid/-2-acrylamido-2-methylpropanesulfonic acid (AA/AMPS) weight ratio, ammonium persulfate (APS), κ-carrageenan, neutralization percent and reaction temperature) were systematically optimized to achieve a hydrogel with a maximum swelling capacity. The maximum water absorbency of the optimized final product was 1238 g/g, while poly-2-acrylamido-2-methylpropanesulfonic acid-g-κ-carrageenan and polyacrylic acid-g-κ-carrageenan hydrogels swelled to a range of 135–800 g/g. The swelling of superabsorbent hydrogels was measured in various solutions with pH values ranging from 1 to 13. In addition, the pH reversibility, on–off switching behavior and swelling kinetics in distilled water were preliminarily investigated.     

基于前向纠错的自适应网络传输机制

针对无线网络中的传输控制协议（TCP）因为丢包触发丢包重传机制而导致传输性能大幅下降的问题,提出了一种基于前向纠错的自适应传输机制（AdaptiveFEC）。该机制通过前向纠错来减少数据段的丢失,以避免触发TCP的丢包重传机制,从而达到提升TCP传输性能的目的。首先,根据当前的网络状况以及当前连接的数据传输特征确定当前时间段中的最优冗余段比例;然后,利用TCP数据段中的数据段序号信息实时进行网络状况的估计,从而根据网络波动来动态更新冗余段比例。大量实验结果说明,在20 ms的往返时延以及5%丢包率的传输环境中,相较于静态的前向纠错机制,AdaptiveFEC能够使得TCP连接的传输速率平均提升42%,当运用在文件下载的应用中时,所提机制能够使得下载速度提升至原来的两倍。     

基于分布式服务模型的遥感影像数据挖掘系统

依据遥感影像的特点及WCS标准,研究面向服务的遥感数据挖掘模式及其基于工作流的分布式系统架构。在此基础上,采用．Net体系及WSBPEL流程建模语言,设计一个遥感影像纹理关联规则的挖掘系统,并研究对大数据集的访问、网络资源占用、程序的可伸缩性等方面的实现技术,为Internet环境下遥感影像的处理提供了依据。     

基于案例推理的故障诊断算法

电力系统智能告警研究目前主要集中于规则推理领域,未能充分利用系统内历史故障的案例进行有效的分析与故障处理.本文初步研究了基于案例推理的故障诊断算法,在此基础上提出了一种基于向量计算的案例匹配算法.该算法通过对故障信息进行抽象,并与系统案例库中的案例进行相似度计算的方式,对故障信息与案例信息进行一一匹配.案例库的建立基于经过人工分析的各类历史故障信息.相似案例的故障性质、故障原因分析可对本次故障的分析、诊断和后续处理起到指导作用.     

基于PXE技术的MAXDOS实现机房系统维护

提供一种解决高校计算机机房在进行大批量计算机系统传输的高效方案,该方案主要基于Inter的PXE技术并结合MAXDOS软件实现高校计算机机房系统,软件等其他资源的备份还原。该方案配置简单易学,有很高的效率。     

Heat treatment temperature effect on the microstructure and optical properties of Dy2(WO4)3 powders

Dy₂(WO₄)₃ powders were synthesized through liquid-phase reaction. The structure transformation of Dy₂(WO₄)₃ powders were analyzed by differential scanning calorimetry (DSC), X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). The optical absorption and photoluminescence properties were characterized by UV-vis-infra diffuse reflectance spectra and fluorescence spectra. The Dy₂(WO₄)₃ host could absorb deep UV light and transfer the energy of UV light to Dy³⁺ ions, which convert the high-energy UV light to blue light (482 nm, ⁴ F _9/2→⁶ H _15/2) and yellow light (547 nm, ⁴ F _9/2→⁶ H _13/2). The Dy₂(WO₄)₃ powders could also absorb near UV light and exhibit blue and yellow emissions near 482 and 547 nm, respectively. Heat treating promoted the crystallization and regulated the micro-structure of Dy₂(WO₄)₃ hosts. The bands of W-O_d anti-symmetric stretching vibration exhibited red shift with the increasing of sintering temperature. The W-O_b-W groups tended to combine with each other to form W-O_c-W groups after heat treating. These regulation of micro-structure had influence on the luminescent color of Dy₂(WO₄)₃. The samples could emit yellow-green, white-yellow and white light under the excitation of 350 nm after being treated at 600, 800 and 1 000 °C, respectively. The prepared Dy₂(WO₄)₃ powders have potential to act as UV absorber for solar cell to improve the conversion efficiency and also exhibit potential for white light LED.     

A dually spontaneous reduction and assembly strategy for hybrid capsules of graphene quantum dots with platinum–copper nanoparticles for enhanced oxygen reduction reaction

The unique hybrid capsules of graphene quantum dots (GQDs) with platinum (Pt)–copper (Cu) nanoparticles have been prepared by a dually spontaneous reduction and assembly process of oxidized graphene quantum dots (ox-GQDs) and Pt precursor by galvanic displacement reaction on Cu microspheres. Cu@PtCu core–shell microspheres were first prepared by reaction of Cu with platinum (IV), which subsequently induced the reduction and assembly of ox-GQDs on them at room temperature. After removal of the Cu cores, the resultant capsules of PtCu@GQDs were collected. Based on the unique hybrid structure, PtCu@GQDs capsules showed remarkably enhanced catalytic activity for oxygen reduction reaction (ORR) with a 2 times higher mass activity and a 40 mV more positive onset potential than that of commercial Pt black, indicating the promise of the newly-prepared PtCu@GQDs capsules as catalysts for fuel cell applications.     

Analysis of chemical compounds and toxicological evaluation of Forsythia suspensa leaves tea

To determine the compositions of Forsythia suspensa leaves tea (FSLT) and its safety, the chemical compounds were analysed with some methods, and the toxicity was evaluated in Kunming mice and Wistar rats. The results showed that FSLT contained rich flavonoid, lignans, triperpene acids, amino acids, and mineral elements. In the acute toxicity study, none of the mice died, and no obvious poisoning symptoms were observed after 14 days in mice at the dose of 15 mg/g·body weight (bw) FSLT; in the sub-chronic toxicity, no abnormal or dead rat was found at the dose of 1, 3, and 10 mg/g·bw during 90 days feeding administration; there was no significant difference in bw and food consumption; no significant differences were found in each hematology and serum biochemistry parameter and organ/body weight ratio comparing with the control experimental group. The results revealed that the FSLT has low or no toxicity via oral administration. Therefore, FSLT is very suitable and safe to be used as a new resource food.     

Study on retrogradation of maize starch–flaxseed gum mixture under various storage temperatures

This study aimed to investigate the effect of flaxseed gum (FG) on the retrogradation of maize starch (MS) gels under different storage temperatures. In this work, MS‐FG gels with 0–0.4% FG were stored under different temperatures (–20, 4 and 20 °C). Under all storage temperatures, the addition of FG inhibited the retrogradation process of MS, suppressed the recrystallisation of starch molecules, reduced the water loss of starch gels and improved the texture of the gels. Among the three storage temperatures, ?20 °C could almost stop the starch retrogradation but leading it results in the hardest gel texture. The retrogradation of MS‐FG gels stored under 4 °C was most serious with the fastest rate of recrystallisation. When stored at 20 °C, the gels had a retrogradation degree that was lower than when they were stored at 4 °C and also had the softest texture.