PTFE–PMMA core–shell colloidal particles as building blocks for self‐assembled opals: synthesis,properties and optical response

A seeded surfactant‐free methyl methacrylate emulsion polymerization is employed to prepare core–shell particles with predetermined size and narrow size distribution. The particle size is determined by the ratio between methyl methacrylate (MMA, shell) and polytetrafluoroethylene (PTFE, core). Monodisperse particles in the 100–350 nm range are obtained. These particles are used to grow colloidal photonic crystals (opals) of very high optical quality, thus indirectly demonstrating the excellent control of microbead size distribution achieved by this preparation technique. The optical properties of the opals are investigated by means of reflectance and polarized‐angle‐resolved transmittance spectroscopies. These data provide a rough determination of the effective refractive index of the system, which is favorably compared with values obtained by simple effective medium models. Copyright © 2012 Society of Chemical Industry     

Comparison of a Deductive Database with a Semantic Web reasoning engine

Knowledge engineering is a discipline concerned with constructing and maintaining knowledge bases to store knowledge of various domains and using the knowledge by automated reasoning techniques to solve problems in domains that ordinarily require human logical reasoning. Therefore, the two key issues in knowledge engineering are how to construct and maintain knowledge bases, and how to reason out new knowledge from known knowledge effectively and efficiently. The objective of this paper is the comparison and evaluation of a Deductive Database system (ConceptBase) with a Semantic Web reasoning engine (Racer). For each system a knowledge base is implemented in such a way that a fair comparison can be achieved. Issues such as documentation, feasibility, expressiveness, complexity, distribution, performance and scalability are investigated in order to explore the advantages and shortcomings of each system.     

Characterization of natural rubber/gold nanoparticles SERS‐active substrate

Natural rubber/gold nanoparticles membranes (NR/Au) were studied by ultrasensitive detection and chemical analysis through surface‐enhanced Raman scattering and surface‐enhanced resonance Raman scattering in our previous work (Cabrera et al., J. Raman Spectrosc. 2012, 43, 474). This article describes the studies of thermal stability and mechanical properties of SERS‐active substrate sensors. The composites were prepared using NR membranes obtained by casting the latex solution as an active support (reducing/establishing agents) for the incorporation of colloidal gold nanoparticles (AuNPs). The nanoparticles were synthesized by in situ reduction at different times. The characterization of these sensors was carried out by thermogravimetry, differential scanning calorimetry, scanning electron microscopy (SEM) microscopy, and tensile tests. It is suggested an influence of nanoparticles reduction time on the thermal degradation of NR. There is an increase in thermal stability without changing the chemical properties of the polymer. For the mechanical properties, the tensile rupture was enhanced with the increase in the amount of nanoparticles incorporated in the material. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Roles of heat transfer modes on transient cooling by quenching process

In order to predict the metallurgical structure of the quenched part by numerical simulation, one needs the boundary condition at the part-bath interface. This last, generally of the third kind, is deduced from measurement of temperature and heat flux density of the surface of work piece. The main goal of this work is the understanding of the heat transfers mechanisms that control the cooling speed according to the size of the work piece. We developed an original device of measurement which allowed temperature and local heat flux estimating at the part-bath interface during quenching process. Experimental results have updated the prevalence of one heat transfer mode according to the more or less thermal resistive character of the quenched part. This prevalence is linked to the mean Biot number Bi _m . When Bi _m ?<?<1, heat conduction inside the work piece does not have a significant role in the cooling: the part is practically isothermal. The cooling is primarily ensured by boiling and more particularly by film boiling. Consequently the profile of cooling velocity is quasi uniform in the part. This situation favours a uniform metallurgic transformation in all the part and the absence of in temperature gradients avoids the differentials of dilation which are at the origin of residual stress fields. Conversely, when Bi _m ?>?>?1, the part has a large thermal resistance such as the temperature of the bath is quickly imposed on its surface. Then, cooling is primarily ensured by convection. In this case, the part bulk is the seat of large thermal gradients which induce a strong distribution of cooling velocity. The latter is at the origin of some differences in metallurgical structure and of a residual stress field within the part. In the intermediate value range, 0.1?<?Bi _m ?<?10, boiling and convection ensure successively the cooling, but in the boiling there is a prevalence of nucleate boiling mode which determines the reached maximum value of cooling speed located always in the close vicinity of the part-bath interface.     

Energy of defects on surfaces of copper

A cluster cutting procedure for estimating the energies of terraces, steps and kinks is tested by using ab initio and tight-binding approaches. The terrace energy is found to converge for relatively small and symmetric clusters, while step and kink energies show a slow and oscillatory convergence with size of poorly symmetric clusters.     

Experimental studies on the effect of fire accelerants during living room fires and detection of ignitable liquids in fire debris

Reconstructing the course of a fire and performing chemical analysis of ignitable liquids in fire debris is an important tool to conduct fire investigations in suspected arson cases. Here, a total of five fire tests has been performed to investigate the effect of fire accelerants on the fire development of a room fire and to prove the capability of analytical methods. Different experimental scenarios have been realized (no accelerant, accelerant applied at different positions, and different amounts of fire accelerant). Each test room was equipped with an identical set of living room furnishing. The location and amount of the fire accelerant applied löschen varied in four of five tests. One experiment was carried out without fire accelerant. Fire quantities such as mass loss (of the entire room), gas temperatures (at several locations in the room), and heat release were determined during the experiments, and chemical‐analytical studies were carried out. A headspace solid phase micro extraction procedure, using gas chromatography–mass spectrometry, was used to analyze fire debris samples to potentially detect ignitable liquids. Beside the analysis of fire debris samples, swipe soot samples were analyzed and the detectability of the fire accelerant used was demonstrated. Results show that it is possible to provide evidence of ignitable liquids in soot samples collected from walls. This allows an additional sampling strategy at potential crime scenes, besides taking fire debris samples. Copyright © 2014 John Wiley & Sons, Ltd.     

Expression of different types of [FeFe]-hydrogenase genes in bacteria isolated from a population of a bio-hydrogen pilot-scale plant

[FeFe]-hydrogenases are the enzymes responsible for high yield H₂ production during dark fermentation in bio-hydrogen production plants. The culturable bacterial population present in a pilot-scale plant efficiently producing H₂ from waste materials was isolated, classified and identified by means of 16S rDNA gene analysis. The culturable part of the mixed population consists of nine bacterial species that include non-hydrogen producers (Lactobacillus, Enterococcus and Staphylococcus) and several Clostridium that are directly responsible for H₂ production.     

Effect of ethanol on the antimicrobial properties of chlorhexidine over oral biofilm

The aim of this study was to evaluate the effect of 95% ethanol irrigation, with 5 or 10 min of action, on the antibacterial properties of 2% chlorhexidine (CHX), on oral biofilm, evaluated with confocal laser scanning microscopy (CLSM). Oral biofilm development was induced in 80 sterilized bovine dentin blocks, distributed in two groups (5 or 10 min) and 4 subgroups, according to time and the solution used: Saline (SALINE5, SALINE10); Saline followed by CHX (SALINE/CHX5, SALINE/CHX10); Ethanol (ETHANOL5, ETHANOL10), Ethanol followed by CHX (ETHANOL/CHX5, ETHANOL/CHX10). The surface of the block was dyed with Live/Dead^® BacLight. Images from different areas were analyzed by BioImage L program. The total biovolum (µm³), biovolum of live cells (green), percentage of live cells of the thickness of the biofilm visualized in CLSM and on surface biofilm were evaluated. Total biovolum and biovolum of living cells showed similar results among the different groups (p > .05). The percentage of living cells in total thickness of the biofilm also was similar among the groups (p > .05), except ETHANOL5, SALINE/CHX10, ETHANOL10, and ETHANOL/CHX10 that showed lower percentage than SALINE5 (p < .05). The ETHANOL10 and ETHANOL/CHX10 also showed lower percentage of living cells than ETHANOL/CHX5 and SALINE10 (p < .05). In relation to biofilm surface, SALINE/CHX5, SALINE/CHX10, ETHANOL5, ETHANOL10, ETHANOL/CHX5, and ETHANOL/CHX10 showed a lower percentage of living cells percentage than SALINE5 and SALINE10 groups (p < .05). Therefore, ethanol has no effect on antimicrobial properties of 2% chlorhexidine, prior when used as endodontic irrigating solution.     

Development of antibacterial silver treatments on HDPE nets for agriculture

The defense mechanism of crops associated with the use of polymeric nets and fabrics is only physical and, hence, ineffective against the bacterial contaminations. The presence of an antibacterial agent associated with the use of conventional agro‐textiles can represent a great advantage in the prevention of plant diseases and for food safety. The aim of this work was the development of antibacterial silver‐coated HDPE nets for an innovative application such as agriculture. Antibacterial coatings on high‐density polyethylene nets were obtained by a patented nanosilver deposition technique based on the in situ photo‐reduction of a silver solution. The concentration of silver deposited was defined by testing different silver solutions from a biological point of view. Moreover, in order to improve the adhesion of the silver coating to the substrate, the nets underwent low‐pressure plasma treatment before the silver deposition. The materials were characterized in terms of quality of the coating through scanning electron microscopy, and in terms of antibacterial capability on Gram positive and Gram negative bacteria through qualitative and quantitative microbiological tests. The most effective process parameters were defined and the importance of performing plasma pretreatment on this specific substrate was assessed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41623.