Cyclodextrin–poloxamer aggregates as nanocarriers in eye drop formulations: dexamethasone and amphotericin B

In this present study cyclodextrin (CD)–poloxamer aggregates were characterized and developed as ophthalmic drug carriers. The combined effect of γCD/2-hydroxypropyl-γCD (HPγCD) mixtures and poloxamer on solubilization and permeability of two model drugs, dexamethasone (Dex) and amphotericin B (AmB), was investigated. The CD–poloxamer interaction and complex aggregation were examined by ¹H nuclear magnetic resonance (¹H-NMR), their solubilizing ability by high-performance liquid chromatography, and their particle size determined by dynamic light scattering and transmission electron microscopy. Formulations containing either 1.5% w/v Dex or 0.15% w/v AmB in eye drop suspensions containing various γCD/HPγCD ratios and poloxamer 407 (P407) were prepared. The solubility of the drugs, surface tension and hemolytic effect of the eye drops and drug permeation from selected formulations were determined. The ¹H-NMR study showed that P407 formed inclusion complex with CDs by inserting its poly(propylene oxide) segment into the CD cavity. P407 and γCD interacted with each other to form nanosized aggregates, and the observed concentration of dissolved γCD and P407 progressively decreased with increasing γCD and P407 concentrations. Including a high proportion of HPγCD improved the drug solubilization and reduced the hemolytic effect. The surface tension of the formulations decreased with increasing P407 concentration. Furthermore, increasing P407 content in the formulations enhanced formation of complex aggregates with consequent slower drug release. It was concluded that the drug/γCD/HPγCD complex was stabilized by P407 through formation of multi-component aggregates. Thus, CD–poloxamer aggregates are self-assembled nanocarriers from which drug delivery characteristics can be adjusted by changing the γCD/HPγCD/P407 ratios.     

Estimation of optimum binder content of recycled asphalt incorporating a wax warm additive using response surface method

This paper presents a new approach to estimate the optimum binder content (OBC) of recycled asphalts (RAs) incorporating a warm mix additive based on the interaction effects of compaction temperature, RA content and binder content using volumetric and strength characterisation. The experimental design was developed using response surface method (RSM) based on central composite design for various compaction temperatures (130–160 °C), RA contents (30–50%) and binder contents (4.9–6.0%). Laboratory tests were performed and analysed to meet the desired volumetric and strength properties according to the Malaysian specifications for the design of dense asphalt mixtures. Statistical analysis and mathematical models proposed by RSM were used to determine the OBC. The results showed that compaction temperature is the most significant factor in determining the OBC. There are minimum differences in the OBC variation of samples incorporating different dosage of RA. The developed model can be used for quick estimation of OBC for various levels of compaction temperature and RA content.     

国内外绿色混凝土的发展动态及趋势

混凝土作为目前最大宗的土木建筑材料，在给社会带来良好的经济和社会效益，同时，也造成了严重的环境污染和生态破坏。本文分析探讨了国内外绿色混凝土发展状况及趋势。目前，开展绿色材料其相关理论的研究，从而实现材料科学与技术的持续发展，是历史发展的必然，也是材料科学的进步。在这种的背景条件下，具有环境协调和自然相适应的特性绿色混凝土应运而生。     

Coarse particulate matter and airborne endotoxin within wood stove homes

Emissions from indoor biomass burning are a major public health concern in developing areas of the world. Less is known about indoor air quality, particularly airborne endotoxin, in homes burning biomass fuel in residential wood stoves in higher income countries. A filter‐based sampler was used to evaluate wintertime indoor coarse particulate matter (PM_10‐2.5) and airborne endotoxin (EU/m³, EU/mg) concentrations in 50 homes using wood stoves as their primary source of heat in western Montana. We investigated number of residents, number of pets, dampness (humidity), and frequency of wood stove usage as potential predictors of indoor airborne endotoxin concentrations. Two 48‐h sampling events per home revealed a mean winter PM_10‐2.5 concentration (± s.d.) of 12.9 (± 8.6) μg/m³, while PM_2.5 concentrations averaged 32.3 (± 32.6) μg/m³. Endotoxin concentrations measured from PM_10‐2.5 filter samples were 9.2 (± 12.4) EU/m³ and 1010 (± 1524) EU/mg. PM_10‐2.5 and PM_2.5 were significantly correlated in wood stove homes (r = 0.36, P < 0.05). The presence of pets in the homes was associated with PM_10‐2.5 but not with endotoxin concentrations. Importantly, none of the other measured home characteristics was a strong predictor of airborne endotoxin, including frequency of residential wood stove usage.     

Residue strength,water absorption and pore size distributions of recycled aggregate concrete after exposure to elevated temperatures

In this paper, the effects of high temperature exposure of recycled aggregate concretes in terms of residual strengths, capillary water absorption capacity and pore size distribution are discussed. Two mineral admixtures, fly ash (FA) and ground granulated blast furnace (GGBS) were used in the experiment to partially replace ordinary Portland cement for concrete production. The water to cementitious materials ratio was maintained at 0.50 for all the concrete mixes. The replacement levels of natural aggregates by recycled aggregates were at 0%, 50% and 100%. The concretes were exposed separately to 300 °C, 500 °C and 800 °C, and the compressive and splitting tensile strength, capillary water coefficient, porosity and pore size distribution were determined before and after the exposure to the high temperatures. The results show that the concretes made with recycled aggregates suffered less deteriorations in mechanical and durability properties than the concrete made with natural aggregates after the high temperature exposures.     

中子星磁场研究进展

射电脉冲星，包括单星和双星，其观测特征被评论．双星脉冲星和毫秒脉冲星的短周期和弱磁场相关性暗示这些脉冲星是存在双星吸积过程的反加速脉冲星．最近提出的中子星磁场起源与演化模型进行了分析．     

Survey of users and providers of recycled water: quality concerns and directions for applied research

Users and providers of recycled water in Queensland, Australia, were canvassed to ascertain concerns about recycled water quality and directions for applied research. Some 79% of respondents had concerns about recycled water quality including microbiological components, such as viruses, parasites and bacteria, salinity related components, aggregate components, such as pH and solids, nutrients, organic components, including pesticides and endocrine disruptors, as well as quality variability. Relative differences in the proportion of concern for some quality characteristics were observed between the areas of different population density with those from the low population areas being more concerned than those from medium or high areas. Some users and providers observed changes in recycled water quality during distribution including nutrients, chlorine, solids, colour and odour. Some 52% of providers and 19% of current users propose to expand their usage and 30% of non-users propose to commence doing so in the next 5 years. Recycled water quality characteristics identified for applied research included microbiological components, organic components, nutrients and salinity.     

Efficient Parallel Graph Algorithms for Coarse-Grained Multicomputers and BSP

In this paper we present deterministic parallel algorithms for the coarse-grained multicomputer (CGM) and bulk synchronous parallel (BSP) models for solving the following well-known graph problems: (1) list ranking, (2) Euler tour construction in a tree, (3) computing the connected components and spanning forest, (4) lowest common ancestor preprocessing, (5) tree contraction and expression tree evaluation, (6) computing an ear decomposition or open ear decomposition, and (7) 2-edge connectivity and biconnectivity (testing and component computation). The algorithms require O(log p) communication rounds with linear sequential work per round (p = no. processors, N = total input size). Each processor creates, during the entire algorithm, messages of total size O(log (p) (N/p)) . The algorithms assume that the local memory per processor (i.e., N/p ) is larger than p ^ε , for some fixed ε > 0 . Our results imply BSP algorithms with O(log p) supersteps, O(g log (p) (N/p)) communication time, and O(log (p) (N/p)) local computation time. It is important to observe that the number of communication rounds/ supersteps obtained in this paper is independent of the problem size, and grows only logarithmically with respect to p . With growing problem size, only the sizes of the messages grow but the total number of messages remains unchanged. Due to the considerable protocol overhead associated with each message transmission, this is an important property. The result for Problem (1) is a considerable improvement over those previously reported. The algorithms for Problems (2)—(7) are the first practically relevant parallel algorithms for these standard graph problems. Received July 5, 2000; revised April 16, 2001.     

Experimental comparison of the switching heuristics for aggregate production planning problem

Two improved versions of the production switching heuristic(PSH), Dominant PSH and Inventory-Ratio-Based PSH are proposed. Extensive computer experiments are performed to evaluated the proposed rules. Both linear and quadratic cost functions are adopted for the comparison study. Also. the influence of seasonality is investigated on the effectiveness of each rule. The results show that the proposed rules outperform the PSH in terms of the total cost, especially when seasonality factor is significant or the unit inventory carrying cost is high.     

三维六角形粗网格中子扩散计算方法

本文介绍对于由六角形栅元组件组成的核反应堆堆芯,采用三维粗网格展开法求解中子扩散方程,推导出九点高阶近似差分方程。该方程形式上与低阶有限差分方程类似,可以采用低阶有限差分法的求解技巧求解,所建立的方法适用于两维或三维中子扩散计算,对堆芯设计和燃耗分析很有意义。