Bacterial Bio-Resources for Remediation of Hexachlorocyclohexane

In the last few decades, highly toxic organic compounds like the organochlorine pesticide (OP) hexachlorocyclohexane (HCH) have been released into the environment. All HCH isomers are acutely toxic to mammals. Although nowadays its use is restricted or completely banned in most countries, it continues posing serious environmental and health concerns. Since HCH toxicity is well known, it is imperative to develop methods to remove it from the environment. Bioremediation technologies, which use microorganisms and/or plants to degrade toxic contaminants, have become the focus of interest. Microorganisms play a significant role in the transformation and degradation of xenobiotic compounds. Many Gram-negative bacteria have been reported to have metabolic abilities to attack HCH. For instance, several Sphingomonas strains have been reported to degrade the pesticide. On the other hand, among Gram-positive microorganisms, actinobacteria have a great potential for biodegradation of organic and inorganic toxic compounds. This review compiles and updates the information available on bacterial removal of HCH, particularly by Streptomyces strains, a prolific genus of actinobacteria. A brief account on the persistence and deleterious effects of these pollutant chemical is also given.     

Effects of TiO2�CSiO2 fillers on thermal and dielectric properties of bismuth glass microcomposite dielectrics for plasma display panel

The combined effects of TiO₂ and SiO₂ fillers on thermal and dielectric properties of new lead-free environmental friendly zinc bismuth borate, ZnO?CBi₂O₃?CB₂O₃ (ZBIB) glass microcomposite dielectrics have been investigated from the viewpoint of application as rear glass dielectric layer of plasma display panels (PDPs). The interaction of fillers with glass occurred during firing has also been explored by XRD, SEM and FTIR spectroscopic analyses. All the properties are found to be regulated by the covalent character (a fundamental property) of resultant microcomposite dielectrics. In this work, the co-addition of TiO₂?CSiO₂ filler to ZBIB glass is found to be more effective to adjust the required properties to employ with PD200 glass substrate in PDP technology.     

Structure and dielectric properties of potassium niobate nano glass–ceramics

Glasses in the composition of 25K₂O-25Nb₂O₅-50SiO₂ (mol %) have been prepared by melt quenching technique and isothermally heat-treated at 800 °C for different duration (0–200 h). The formed nanocrystalline KNbO₃ phase, crystallite size and morphology are examined by X-ray diffraction, Fourier transform infrared reflection spectroscopy, field emission scanning and transmission electron microscopes. The frequency and temperature dependent dielectric constant and loss tangent are measured in the frequency and temperature ranges 0.1–1000 kHz and 200–500 °C respectively. The dielectric constant and loss tangent are found to decrease with increasing frequency and increase with increasing temperature. The dielectric constant and loss tangent versus temperature curve at different frequency revealed the phase transition of KNbO₃ from paraelectric cubic to ferroelectric tetragonal around 425 and 397 °C (Curie temperature) for nano glass–ceramics obtained after 1 and 200 h heat-treatment respectively.     

Machining damage analysis of alumina in relation to thermal shock behavior

Machining damage of alumina disks with two different finishes, C and F, was analyzed with the aim of explaining the differences in their thermal shock responses. Thermal treatments designed to simulate conditions in thermal shock testing were performed on sets of C and F disks. The damage was quantified by several techniques, including the measurement of residual stresses. The mechanical strength of as-machined disks and thermally treated disks was also determined, including fractographic analysis. A decrease in the residual stresses after thermal treatment was observed in F specimens, as was expected. Conversely, unusual behavior was observed in C disks, showing a tendency to increase the residual stresses when the disks were kept at high temperature. Several factors were discussed to explain this fact. Higher mechanical strength and a decrease in the critical flaw size was observed in thermally treated disks compared to as-machined specimens for both types of finishes.     

A deterministic crowding evolutionary algorithm to form learning teams in a collaborative learning context

The aim of forming collaborative learning teams is that participating students acquire new knowledge and skills through the interaction with their peers. To reach this aim, teachers usually utilize a grouping criterion based on the students’ roles and on forming well-balanced teams according to the roles of their members. However, the implementation of this criterion requires a considerable amount of time, effort and knowledge on the part of the teachers. In this paper, we propose a deterministic crowding evolutionary algorithm with the aim of assisting teachers when forming well-balanced collaborative learning teams. Considering a given number of students who must be divided into a given number of teams, the algorithm both designs different alternatives to divide students into teams and evaluates each alternative as regards the grouping criterion previously mentioned. This evaluation is carried out on the basis of knowledge of the students’ roles. To analyze the performance of the proposed algorithm, we present the computational experiments developed on ten data sets with different levels of complexity. The obtained results are really promising since the algorithm has reached optimal solutions for the first four data sets and near-optimal solutions for the remaining six data sets.     

Agents that Learn How to Generate Arguments from Other Agents

Learning how to argue is a key ability for a negotiator agent. In this paper, we propose an approach that allows agents to learn how to build arguments by observing how other agents argue in a negotiation context. Particularly, our approach enables the agent to infer the rules for argument generation that other agents apply to build their arguments. To carry out this goal, the agent stores the arguments uttered by other agents and the facts of the negotiation context where each argument is uttered. Then, an algorithm for fuzzy generalized association rules is applied to discover the desired rules. This kind of algorithm allows us (a) to obtain general rules that can be applied to different negotiation contexts; and (b) to deal with the uncertainty about the knowledge of what facts of the context are taken into account by the agents. The experimental results showed that it is possible to infer argument generation rules from a reduced number of observed arguments.     

Study of saturated and unsaturated permeability in natural fiber fabrics

The main goal of this work is to understand how the main processing variables are affected when glass fibers are replaced by natural fibers in reinforced plastics. In this publication, a jute fabric was characterized in terms of its saturated and unsaturated permeability. It was found that fluid absorption and swelling are mechanisms present in natural fibers that reduce both permeabilities. Fluid absorption removes fluid from the main stream as it travels through the reinforcement, acting as a sink component and thus decreasing flow velocity during the unsaturated flow. Also, the saturation of the natural fibers cause swelling, reducing the porosity and increasing flow resistance during saturated flow.