Identification of microbial contaminants present during the curing of honeybush tea (Cyclopia)

Honeybush tea (Cyclopia) is produced over a wide area of the Western and Eastern Provinces of South Africa and exported to several countries worldwide. It is traditionally manufactured by curing honeybush material for several days at relatively high temperatures and moisture contents and this results in extensive mould and bacterial growth. This leads to a product with inferior leaf colour and organoleptic quality as well as health concerns. Unlike during the manufacture of black tea, honeybush curing temperatures do not reach levels where these contaminants are eliminated. The microbial contaminants and the minimum temperatures necessary to eliminate these organisms were thus investigated. Yeast-Glucose (YG), Yeast-Starch (YpSs) and Czapek media were evaluated for the isolation of contaminants that developed during the curing of honeybush tea. YG and YpSs gave good results, while the Czapek medium was found to be unsatisfactory for the detection of microbial contaminants. A low pH (pH 5.0) favoured mould growth, while bacteria proliferated at pH 7.0. Honeybush material fermented in a curing heap and material fermented under controlled conditions at 40 and 50 °C showed microbial contamination, but no contaminants were detected on or in material fermented at higher temperatures (60, 70 and 80 °C). Two thermophilic moulds, Humicola grisea var thermoida and Humicola lanuginosa, a thermotolerant mould, Rhizomucor pusillus, and five endospore-forming species of the genus Bacillus were isolated. The data indicated that R pusillus was the predominant microbial contaminant. © 1999 Society of Chemical Industry     

消费电子产品寿命终期的生态效益研究(一)

要改善消费电子产品寿命终期阶段的生态效益,对其作全面的评估是需要的。荷兰Delft大学倡导的环境权重再循环和生态效益(QWERTY／EE)理论,其目标是想以最小的产品寿命终期处理成本实现最大化的环境重建。本文生态效益概念的提出是基于一系列改进措施的实现,诸如改变切碎和分离装置,实现塑料和玻璃的回收利用,或对某种产品进行单独分类等。对75种之多的消费电子产品的分析清楚地显示：各种产品类别之间具有分组性能(在衡量环境和经济方面有良好的回收性)和明显区别。从这个意义上说,此评估将引发目前最实用的回收技术的进步。而且,环境权重再循环和生态效益概念,使得对当前和今后的寿命终期处理工艺进行选择和归类成为可能,并能进一步确定哪种方法可以带来最佳投资、环境收益比。对以玻璃为主体的产品中玻璃回收的增加导致了环境的明显改善。对含有贵金属的产品,贵金属的单独分类和处理,也具有同样的价值,比如手机。然而以上事实是基于经济可行的前提。其它的结论和成果对玻璃的回收利用来说只是对处于拆解状态下,并且有阴极射线管(CRT)或液晶显示器(LCD)的大型家电设备才具有生态效益。对中小尺寸的家电设备进行塑料回收利用,其额外成本相对于环境改善是很高的。在绝大多数情况下,对以金属为主体的产品只进行切碎和分离并不能导致环境或经济效益的显著改善。一般来说,提高寿命终期产品生态效益的各种方法导致了很复杂的环境、经济结果。因而,应建立寿命终期政策策略评估体系,在某些情况下还应进一步修正,来支持和提高生态效益改善措施。至于具体的结果,虽然不同的环境评估模型按不同的顺序把单个物质排序,但除了塑料回收环节外,改进措施在系统级上的结果显示出一致性。     

Erratum to: Electrochemical dissolution of metallic platinum in ionic liquids

The electrochemical dissolution of Pt in several ionic liquids (ILs) was studied. Different ILs were tested assessing their potential to dissolve Pt. Dissolution rate and current efficiency were evaluated. The main focus was on Cl containing ILs: first generation, eutectic-based ILs and second generation ILs with discrete anions. Pt dissolution only occurred in type 1 eutectic-based ILs with a max. dissolution rate of 192.2 g m^?2 h^?1 and a max. current efficiency of 99 % for the ZnCl₂–1-ethyl-3-methylimidazolium chloride IL, and 9.090 g m^?2 h^?1 and 96 % for the 1:1 ZnCl₂–choline chloride IL. The dissolution occurred through the formation of [PtCl_x]^y? complexes. To form these complexes, addition of a metal chloride was necessary. Furthermore, an IL with an electrochemical window of 1.5 V, preferably 2.0 V was required to achieve Pt dissolution. The added metal salt needed to have a higher decomposition potential than 1.5 V or should be a Pt salt.     

UV and solar light photocatalytic removal of organic contaminants in municipal wastewater

This study investigated UV and solar photocatalysis of organic pollutants in municipal wastewater using metal-ion (Ag, Cu and Fe) doped TiO₂ photocatalysts. The effects of pH and catalyst dosage on photocatalytic performance were determined. The best performance was obtained using 0.5 g/L catalyst concentration and pH 6, and the treated water met specific requirements of the drinking water quality standards (phenol ≤10 μg/L) and wastewater effluents for discharge chemical oxygen demand (COD) levels (<30 mg/L). The photocatalysts were effective under both UV and visible light, thereby overcoming the limitation of TiO₂ which is only effective under UV light.     

Performance of sewer pipe concrete mixtures with portland and calcium aluminate cements subject to mineral and biogenic acid attack

The paper reports on the performance of a series of sewer pipe concrete mixtures and cementitious lining mixtures in acid environments. Binder types based on ordinary portland cement (OPC) and calcium aluminate cement (CAC) were used, with both acid-soluble and acid-insoluble aggregates and various supplementary cementitious materials (SCM). One series of tests subjected the mixtures to pure mineral acid (hydrochloric acid, pH = 1), using a specially designed dynamic test rig. The other series of tests involved monitoring specimens placed in a live sewer under very aggressive conditions induced by acid-generating bacteria. Under mineral acid attack on concretes with conventional dolomite aggregates, OPC/silica fume concretes displayed best performance, attributed to their densified microstructure coupled with substantially improved ITZ. CAC concretes with dolomite aggregate did not perform any better than similar OPC specimens under these conditions, primarily because of their higher porosity. However, with concretes using synthetic alag^TM aggregates in mineral acid testing, CAC/alag^TM mixtures performed exceptionally well due to their homogeneous microstructure, inferred absence of an ITZ, and slower dissolution and finer size of alag^TM aggregate particles. The dynamic acid test was able to reveal differences in physical and chemical interactions between constituents in concrete mixes. Under biogenic acid conditions in the sewer, CAC concretes clearly outperformed OPC concretes. This is ascribed to the ability of CAC to stifle the metabolism of the acid-generating bacteria, thereby reducing acid generation. Thus the effects of neutralisation capacity and stifling of bacterial activity need to be distinguished in designing concrete mixtures to provide good acid resistance. Relative rates of dissolution of binder and aggregates are also important in overall performance, with uniform rates preferable in order to avoid aggregate fallout.     

The particle swarm optimization algorithm in size and shape optimization

Shape and size optimization problems instructural design are addressed using the particle swarm optimization algorithm (PSOA). In our implementation of the PSOA, the social behaviour of birds is mimicked. Individual birds exchange information about their position, velocity and fitness, and the behaviour of the flock is then influenced to increase the probability of migration to regions of high fitness. New operators in the PSOA, namely the elite velocity and the elite particle, are introduced. Standard size and shape design problems selected from literature are used to evaluate the performance of the PSOA. The performance of the PSOA is compared with that of three gradient based methods, as well as the genetic algorithm (GA). In attaining the approximate region of the optimum, our implementation suggests that the PSOA is superior to the GA, and comparable to gradient based algorithms. Received December 18, 2000     

Detection and measurement of hypercholesterolaemia in South Africans attending general practitioners in private practice--the cholesterol monitor

The synthesis and the pharmacological evaluation at metabotropic glutamate receptors of S-2-(4'-carboxy-cubyl)glycine (ACUDA, 9) are described. S-2-(4'-Carboxy-cubyl)glycine is a structurally novel group I selective antagonist for mGluR1 subtype.     

Simple technique for the measurement of the transfer impedance ofvariable length coaxial interconnecting leads

An experimental technique for the routine measurement of the transfer impedance of variable length coaxial leads was developed. Ready-made leads incorporating connectors at either end can be evaluated either for the purposes of quality control during manufacture or when performing general electromagnetic compatibility (EMC) troubleshooting. A low-cost measurement fixture is proposed and the measurement method is elementary. Lead lengths of up to a few meters in length can be measured up to frequencies of approximately 300 MHz. Measured results for RG-58 cables are presented and compared to published values to validate the method     

Chemical Characterization of Territorial Marking Fluid of Male Bengal Tiger, <Emphasis Type="Italic">Panthera tigris</Emphasis>

The territorial marking fluid of the male Bengal tiger, Panthera tigris, consists of a mixture of urine and a small quantity of lipid material that may act as a controlled-release carrier for the volatile constituents of the fluid. Using gas chromatography and gas chromatography–mass spectrometry, 98 volatile compounds and elemental sulfur were identified in the marking fluid. Another 16 volatiles were tentatively identified. The majority of these compounds were alkanols, alkanals, 2-alkanones, branched and unbranched alkanoic acids, dimethyl esters of dicarboxylic acids, γ- and δ-lactones, and compounds containing nitrogen or sulfur. Several samples of the marking fluid contained pure (R)-3-methyl-2-octanone, (R)-3-methyl-2-nonanone, and (R)-3-methyl-2-decanone, but these ketones were partly or completely racemized in other samples. The γ-lactone (S)-(+)-(Z)-6-dodecen-4-olide and the C₈ to C₁₆ saturated (R)-γ-lactones and (S)-δ-lactones were present in high enantiomeric purities. The chiral carboxylic acids, 2-methylnonanoic acid, 2-methyldecanoic acid, 2-methylundecanoic acid, and 2-ethylhexanoic acid were racemates. Cadaverine, putrescine, and 2-acetylpyrroline, previously reported as constituents of tiger urine, were not detected. The dominant contribution of some ketones, fatty acids, and lactones to the composition of the headspace of the marking fluid suggests that these compounds may be important constituents of the pheromone. Although it constitutes only a small proportion, the lipid fraction of the fluid contained larger quantities of the volatile organic compounds than the aqueous fraction (urine). The lipid derives its role as controlled-release carrier of the chemical message left by the tiger, from its affinity for the volatiles of the marking fluid. Six proteins with masses ranging from 16 to 69 kDa, inter alia, the carboxylesterase-like urinary protein known as cauxin, previously identified in the urine of the domestic cat and other felid species, were identified in the urine fraction of the marking fluid. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.