Contact angle measurement - a reliable supportive method for screening water-resistance of ultraviolet-protecting products in vivo

Substantivity of sunscreen formulations is affected by the wash-out rate of ultraviolet-absorber and -reflector compounds in water. Water-resistance of sunscreen formulations is currently determined according to a standardized European Cosmetic Toiletry and Perfumery Association (COLIPA) protocol, encompassing the determination of a minimal erythemal dose before and after a defined immersion step in water. It can be supposed that the higher the wettability of a treated skin area, the higher is the wash-out rate of sunscreen compounds. This present report addresses the validity of determining the wettability of treated skin alone as a measure for the water-resistance of sunscreen products. The report addresses the robustness, accuracy and congruence of a recently developed wettability test, based on the measurement of the contact angle (CA) of a sessile water drop on treated skin areas. Contact angle data of 66 sunscreen formulations are compared with the corresponding results of 81 water-resistance tests, using the sun protection factor (SPF)/immersion/SPF method. Sunscreen products tested by the CA method were applied to the skin of the volar forearm of test subjects at a defined dose and drying-time, using a standardized application and recording device. Contact angles between a sessile water drop and skin were recorded by a Charge-Coupled Device (CCD) camera and subjected to automatic contour analysis. Taking the SPF/immersion/SPF method as gold standard, accuracy parameters of the CA method were determined. By using an appropriate cut-off level of CAs, the CA method has a specificity and positive-predictive value of 100%, and turns out to be a reliable screening method to identify water-resistant formulations. Based on our findings, those formulations that give CAs above 30 degrees may be categorized water-proof without further testing by the COLIPA water-resistance method.     

Applications of chitosan for improvement of quality and shelf life of foods: a review

ABSTRACT:  Chitosan is a modified, natural biopolymer derived by deacetylation of chitin, a major component of the shells of crustacean. Recently, chitosan has received increased attention for its commercial applications in the biomedical, food, and chemical industries. Use of chitosan in food industry is readily seen due to its several distinctive biological activities and functional properties. The antimicrobial activity and film-forming property of chitosan make it a potential source of food preservative or coating material of natural origin. This review focuses on the applications of chitosan for improvement of quality and shelf life of various foods from agriculture, poultry, and seafood origin.     

RAPD with microsatellite as a tool for differentiation of Candida genus yeasts isolated in brewing

Fifteen wild yeast strains were isolated in two factories of a lager brewing company in Poland. Their identification with API 32C system showed mainly the presence of Candida sake species (7/15). To differentiate the isolates, randomly amplified polymorphic DNA (RAPD) with (GTG)(5), (GAC)(5), (GACA)(4) microsatellite primers and M13 core sequence (5'-GAG GGT GGC GGT TCT-3') were chosen. The results of patterns similarity are presented as dendrograms for each RAPD analysis and for overall patterns. On the overall patterns, all isolates identified as C. sake, except Strain No. 1, were regrouped in one cluster. Collection strain C. sake CBS 617 was similar in 46% to the cluster with six isolates (Strain Nos. 3, 6, 8, 11, 13, 14). The second reference strain C. sake CBS 159 and the Strain No. 1 were regrouped with other Candida species (collection strains) showing, respectively, only 20% and 42% of similarity to other C. sake strains. The similarity based on the overall dendrogram between isolate Nos. 3, 6, 8, 11, 13, 14 and C. sake CBS 617 was 49%. Between those strains and other Candida, the similarity was only 37%.     

Source apportionment of ambient volatile organic compounds in Beijing

The ambient air quality standard for ozone is frequently exceeded in Beijing in summer and autumn. Source apportionments of volatile organic compounds (VOCs), which are precursors of ground-level ozone formation, can be helpful to the further study of tropospheric ozone formation. In this study, ambient concentrations of VOCs were continuously measured with a time resolution of 30 min in August 2005 in Beijing. By using positive matrix factorization (PMF), eight sources for the selected VOC species were extracted. Gasoline-related emissions (the combination of gasoline exhaust and gas vapor), petrochemicals, and liquefied petroleum gas (LPG) contributed 52, 20, and 11%, respectively, to total ambient VOCs. VOC emissions from natural gas (5%), painting (5%), diesel vehicles (3%), and biogenic emissions (2%) were also identified. The gasoline-related, petrochemical, and biogenic sources were estimated to be the major contributors to ozone formation potentials in Beijing.     

纤维基材料的仿生学研究动向

纤维基技术的应用对仿生学的成功发展呈现出巨大的潜力,因为宇宙成物在生长过程、多毛结构和增强纤维方面具有许多相似性.约七年前,邓肯道夫纺织技术与工艺研究所协同众位生物学家一起开创了仿生学的研发,至今方兴未艾.     

福建茉莉花茶产业分析——以福建春伦茶业有限公司为例

福建春伦茶业有限公司创建于1985年,位于茉莉花茶之乡——福州市城门经济开发区,是一家集生产、加工、销售茉莉花茶产品为主的现代化企业。企业厂房面积2．3万平方米,自有茶园基地3万余亩,茉莉花基地7000亩,年生产能力达200万公斤,年销售量在180万公斤以上,是中国茶叶行业百强企业第十三强企业,也是全国最大的茉莉花茶生产加工销售企业之一。     

An evaluation of DGT performance using a dynamic numerical model

A numerical model of the transport and dynamics of metal complexes in the resin and gel layers of a DGT (diffusive gradients in thin films) device was developed and used to investigate how the chelating resin and metal-ligand complexes in solution affect metal uptake. Decreasing the stability constant or concentration of the binding resin increases the competition for free metal ions by ligands in solution, lowering the rate of mass uptake. Such effects would be rarely observed for moderately or strongly binding resins (K> 10(12)), including Chelex, which out-compete labile ligands in solution. With weakly binding resins, strongly bound solution complexes can diffuse into the resin layer before a measurable amount of dissociation occurs, such that concentrations of bound metal at the rear and front surfaces of the resin layer are equal. With more strongly binding resins, metal mainly binds to the front surface of the resin. Only complexes with the largest binding constants penetrate the gel layer containing Chelex, buttheir lack of lability means thatthe DGT sensitivity to the complex is, in any case, very low. The slow diffusion of complexes, such as those of fulvic acids, which increases the time required to establish steady state, compromises the use of the simple DGT equation. Errors are negligible for 24 h deployments, when diffusive layer thicknesses are less than 1 mm, but 3 day deployments are required to ensure accuracy with 2.4 mm thick layers. The extent to which the commonly used equation, that accounts for the concentration and diffusion of metal-complex species, overestimates DGT uptake if the rate of dissociation is slow, was estimated.     

Modeling of copper sorption onto GFH and design of full-scale GFH adsorbers

During rain events, copper wash-off occurring from copper roofs results in environmental hazards. In this study, columns filled with granulated ferric hydroxide (GFH) were used to treat copper-containing roof runoff. It was shown that copper could be removed to a high extent. A model was developed to describe this removal process. The model was based on the Two Region Model (TRM), extended with an additional diffusion zone. The extended model was able to describe the copper removal in long-term experiments (up to 125 days) with variable flow rates reflecting realistic runoff events. The four parameters of the model were estimated based on data gained with specific column experiments according to maximum sensitivity for each parameter. After model validation, the parameter set was used for the design of full-scale adsorbers. These full-scale adsorbers show high removal rates during extended periods of time.     

煤瀝青粘结剂对碳素制品性质的影响

以一种煅烧过的延迟石油焦分别和十二种在性质上显著不同的中等软化点煤沥青混合,模压制成碳索制品。这些制品和上述的焦炭分别在1150～3000℃之间的六种温度下进行热处理。测定了这些制品和焦炭的表观密度、空气拼代密度BET表面积和晶相参数等物理性质。对碳素制品还测定了对CO_2的反应性、电阻率、热膨胀系数和抗弯强度等性质。将所有的碳素制品加热到同样的最终温度,一般只发现它们在性质上仅有微小的不同。这可能导致两种结论:一种是,煤沥青在各个热处理温度下产生具有类似性质的粘结剂碳;第二种是,由于碳素制品中沥青残碳量较少(约占15％),这些粘结剂碳在性质上的差异不足以使碳素制品在性质上产生重大的差别。在从焙烧到石墨化的温度内,可以观察到碳索制品在物理性质上发生主要的改变。这些性质的变化与固体碳素材料性质的变化具有近乎平行的关系。     

热处理强化铝合金7039

Kaiser铝及化学公司发展了一种牌号为7039的A1—zn—Mn系新型热处理强化可焊铝合金。其化学成分如表1所示。7039及其它几种铝合金的物理性能如表2所示。为了改善合金的抗腐蝕性和提高强度,合金中还加入了少量的其它元素如Cr和Mg。7039铝合金焊接以后的强度比以往常用的非热处理可焊铝合金约高