Physical Properties, Photo- and Bio-degradation of Baked Foams Based on Cassava Starch, Sugarcane Bagasse Fibers and Montmorillonite

The objectives of this work were to develop biodegradable trays from cassava starch, sugarcane fibers and Na-montmorillonite (Na-MMT) using a baking process and to study the effects of these components on the physical properties, photo- and bio-degradation of the trays. The sample F20 (produced with 20 g fiber/100 g formulation) showed the maximum yield production (100 %). All formulations resulted in well-shaped trays with densities between 0.1941 and 0.2966 g/cm³. The addition of fibers and Na-MMT resulted in less dense and less rigid trays compared to control samples (only starch). The studied processing conditions resulted in good nanoclay dispersion, leading to the formation of an exfoliated structure. The evaluation of the photo-degradation stability of the trays under UV exposure for 336 h showed that a sample produced with a specific combination of fiber and nanoclay (20 g fiber and 5 g nanoclay/100 g formulation) had the highest loss in stress at break (91 %). Biodegradation assays showed that Control trays (starch) and F20 (20 g fiber/100 g formulation) lost a greater percentage of their weight after 90 days of incubation in soil, with losses of up to 85.50 and 82.70 %, respectively.     

PCB accumulation and tissue distribution in cave salamander (Proteus anguinus anguinus, Amphibia, Urodela) in the polluted karstic hinterland of the Krupa River, Slovenia

For over two decades, a manufacturer of electrical capacitors disposed of its waste within the karstic hinterland of the Krupa River (Slovenia) resulting in the surroundings becomming heavily polluted with PCB. Albeit the extent of the contamination has been known since 1983 and the Krupa River has become one of the most PCB polluted river in Europe, the effects on the cave fauna of the region remain unknown. The most famous cave dweller of the Krupa hinterland is the endemic cave salamander Proteus anguinus anguinus. In this study we determine the levels of PCB in the tissues of the Proteus and in river sediments. The total concentration of PCB in individual tissue samples from specimens of the Krupa spring was between 165.59 μg g⁻¹ and 1560.20 μg g⁻¹ dry wt, which is at least 28-times higher than those from an unpolluted site. The kidneys contained the lowest concentration, while the highest concentration was in subcutaneous fat and tissues with high lipid contents like visceral fat and liver. Total PCB concentrations in sediment samples from the Krupa River were between 5.47 and 59.20 μg g⁻¹ dry wt showing that a high burden of PCB still remains in the region. The most abundant PCB congeners in all analyzed samples were di-ortho substituted (PCB #101, #118, #138 and #158), but higher proportion of mono-ortho PCB was present in sediments. The ability of Proteus to survive a high PCB loading in its environment and especially in its tissues is remarkable. Its partial elimination of low chlorinated and mono-ortho substituted congeners is also reported.     

Baked Foams Based on Cassava Starch Coated with Polyvinyl Alcohol with a Higher Degree of Hydrolysis

The aims of this work were to produce trays based on cassava starch, coated with polyvinyl alcohol (PVA) with a higher degree of hydrolysis (98%), and to study the effects of the coating on the mechanical and water sorption properties of the trays. Two types of PVA were tested: SELVOL? 325 (degree of polymerization?=?1000–1500) and SELVOL? 107 (degree of polymerization?=?350–650). A decrease in the water absorption capacity of 50% was observed when the coated samples were compared with the control sample after 30 min of immersion in water. It was observed in both coated samples a reduction of the initial rate of water adsorption sorption and a decrease in hydrophilicity compared with the control sample. Tensile strength and elongation were increased with application of the coatings. The use of the two types of PVA resulted in materials with similar mechanical and water sorption properties.     

Degradation of methyl-phenanthrene isomers during bioremediation of soil contaminated by residual fuel oil

Phenanthrene and methyl-phenanthrenes are major aromatic pollutants originating in particular from fuel oil. Phenanthrene is usually degraded faster than methyl-phenanthrenes under geological and environmental conditions. Here, we report a preferential and accelerated biodegradation of methyl-phenanthrenes versus phenanthrene in soil contaminated by fuel oil. The polluted soil was mixed with sawdust and sand to form a homogenized biopile. The biopile was continuously sprayed with microbial consortia isolated from crude oil?Ccontaminated soil and treated by biosurfactants and nutritive substances for biostimulation. During a 6-month bioremediation experiment, a steady increase in the relative abundance of phenanthrene compared to methyl-phenathrenes was observed by gas chromatography?Cmass spectrometry. The increase was the highest for trimethyl-phenanthrenes, with a phenanthrene/trimethyl-phenanthrenes ratio increasing from 0.42 to 2.45. By contrast, the control, non-stimulated samples showed a ratio decrease from 0.85 to 0.11. Moreover, the results showed that the level of degradability depends on the number of methyl groups.     

Distribution and availability of potentially toxic metals in soil in central area of Belgrade,Serbia

Belgrade, capital city of Serbia, has over 1,600,000 inhabitants and over 400,000 vehicles trafficking every day on its streets. The investigation of soil pollution was performed by sequential extraction analysis to investigate the availability of potentially toxic metals (Zn, Cd, Pb, Co, Ni, Cu, Cr and Mn) under different oxidation and pH conditions. All investigated metals were mainly extracted from soils with neutral or acidic extractants. Serious pollution was observed along roads and streets with high traffic frequency, but Pb and Ni pollution was the highest since their concentrations exceed both soil Serbian standard and Canadian guidance values and is characteristic for all investigated sites. Cd, Cu, Cr and Zn concentrations are moderately high since they are between Canadian guideline and Serbian standard.     

Analysis of Conditions and Organization of Work of Notebook Computer Users

Abstract

Aim. The aim of this study was to evaluate working conditions with a notebook computer (notebook) as a potential cause of musculoskeletal disorders. Material and methods. The study had 2 stages. The first one was a questionnaire survey among 300 notebook users. The next stage was an expert analysis of 53 randomly selected workstations. The questionnaire survey included questions about the participants, their working conditions, work organization and also duration of work with a notebook. Results and conclusions. The results of the research showed that most examined operators used a notebook as a basic working tool. The most important irregularities included an unadjustable working surface, unadjustable height of the seat pan and backrest, unadjustable height and distance between the armrests and no additional ergonomic devices (external keyboard, docking station, notebook stand or footstool).     

环氧化合物分子结构与致变活性的关系

由化学物质毒性效应登录(RTECS)1998年光盘系统检索获得86种环氧化合物对鼠沙门氏菌致变活性数据.应用主成分分析法从11种分子描述符中选择出5种对致变活性有明显影响的描述符:碳原子数,苯环数,氢原子数,烷基数和氧原子数.通过样本学习集训练并优化神经网络结构,建模分类预报:对于86个样本,低和高2类活性,正确分类率达到92%.结果表明:3～4个骈接苯环的环氧化物的特殊结构具有很强的致变活性.     

U型截面弯曲件失稳起皱分析

对U型截面弯曲件失稳起皱问题进行了研究,通过板材成形性能实验及起皱模拟实验,对失稳起皱原因进行了分析,为类似的异型截面弯曲件起皱的预防提供了可行的实验分析方法。     

Sustainable Development and Transition of Traditional Retailing Centers in Beijing from Consumers' Perspective

Based on the consumer questionnaires of the three traditional retailing centers,Qianmen,Wangfujing and Xidan in Beijing,this article analyzes the present features of consumer composition in the three retailing centers.What is more,the evolution course and function transition of traditional retailing centers is revealed based on the changing of consumer composition in different times.Lastly,the renewal method and development trends of traditional retailing centers are discussed based on the evaluation results in consumers' perspective.