Transient response analysis and modeling of near wall flow conditions in a micro channel: evidence of slip flow

An experimental tool for determination of the near wall transport parameters in a micro channel, supported by flow simulation, is presented. The method is based on the transient flow response due to convective diffusion, in absence of specific adsorption. An approximately step-function type temporal solute concentration variation serves as the input signal. The associated response signal of a surface plasmon resonance sensor, acting as an integral part of a micro channel, has been taken as the output signal. It provides the flow-dependent change of the NaOH solute concentration in the channel within the optical detection and near wall distance interval 0 < d < 0.5 μm. The temporal signal evolution and response time, until an initially plain aqueous solution is replaced by the solute, varies inversely with solute concentration and flow rate. In the asymptotic limits, the near wall forced convective and diffusive channel transit times, along with the associated velocities, can be extracted and separated. A low convective near wall flow speed would account for 100% adsorption efficiency. The validity of the scaling relation for Fickian diffusive transport has been confirmed by experiments. Convective near wall flow reveals a distorted parabolic flow profile. This indicates relaxation of the no-slip condition, and presence of slip flow. Neither boundary layer formation, nor near wall micro turbulences have been observed. Eventually, a compact mathematical transient flow model, outlined in the Laplace domain for the electrical equivalent analogue circuit and applicable to the convective diffusion equation, has been developed for the flow transients.     

Effects of incorporated amaranth albumins on the functional properties of wheat dough

BACKGROUND: Recent developments in micro‐scale testing methodology and in methods modelling the effects of native forms of constituents by in vitro methods have provided a new approach to study the impact of added foreign proteins on dough end‐use quality. Amaranth (Amaranthus) is a member of the pseudo‐cereal family, whose storage proteins have superior nutritional quality due to their essential amino acid composition. The aim of this project was to study the effects of the incorporated amaranth albumin proteins on the rheological properties of the wheat dough. RESULTS: The mixing time requirements, dough strength and stability of the reconstructed dough increased proportionally with the amount (1, 3 and 5%) of amaranth albumin proteins incorporated. These results were supported by measurements on the non‐extractable polymeric protein ratio of the dough indicating the change in polymer size distribution. CONCLUSION: It was demonstrated that amaranth albumin proteins are capable of interacting with gluten proteins through disulfide bonds, showing similar effects to the individual glutenin subunits of wheat flour proteins. Improvements in dough strength and stability without a substantial increase in the mixing requirements are of great significance for developing energy saving technologies in the baking industry. Copyright © 2009 Society of Chemical Industry     

Thermal and mechanical behaviour of sisal/phenolic composites

This research proposes the development of polymeric composites reinforced with natural fibres to become stronger the damaged timber structures and proposes thermal and mechanical characterization of these composites. Fibres with larger structural applications are glass and carbon fibres but the use of natural fibres is an economical alternative and possesses many advantages such as biodegradability, low cost and is a renewable source. Woven sisal fabric was submitted to heat treatment before moulding and the influence of moisture content of fibres on the composites behaviour was observed. The paper presents mechanical characterization by tensile and flexural strength of woven sisal fabric composites, with and without thermal treatment (at 60 °C for 72 h) on the fabric, thermal characterization by TGA and the manufacturing process by compression moulding. Experimental results show to sisal/phenolic composites a tensile strength and a flexural strength value of 25.0 MPa and 11.0 MPa, respectively, independent to the use of sisal fibres with or without thermal treatment.     

Biodegradable polymers: A review about biodegradation and its implications and applications

Plastic waste pollution is a global environmental problem that could be solved by biodegradable materials. In addition, its biodegradability has been important for medical applications. In this way, the biodegradability performance has been investigated for different materials under diversified environmental conditions. In this context, this review shows the main up-to-date biodegradable polymers (from renewable sources and fossil-based), their structure and properties, and their biodegradability characteristics. Also, this review shows the effect of polymer properties and environmental conditions on biodegradability, methods of biodegradability and toxicity determination, modification processes to enhance biodegradability, and main applications of biodegradable polymers for agriculture, medical, and packaging. Finally, this review presents a discussion of the implications of biodegradation on the environment, the current context, and future perspectives of plastic biodegradation.     

Determination of the composition and thickness of chromel and alumel thin films on different substrates by quantitative energy dispersive spectroscopy analysis

Thin films of two alloys (chromel and alumel), with thickness less than 100 nm, were obtained by plasma deposition technique, namely filtered cathodic vacuum arc (FCVA). The elemental analyses were performed by quantitative energy dispersive spectroscopy (EDS) microanalysis and Rutherford backscattering spectrometry (RBS). The applicability of EDS to such thin films as these was established by analysis of films deposited on substrates of different atomic numbers, specifically vitreous carbon, silicon, copper, and tin. We found that a substrate with atomic number similar to the mean atomic number of the film constituents is best for reliable EDS results, when compared to RBS. The compatibility between quantitative EDS measurements and RBS measurements, as well as comparison between the thin film elemental composition and the bulk material composition, was assessed by statistical analysis. Good consistency between EDS and RBS measurements was found for both chromel and alumel thin films when copper was used as substrate material. We observed severely overlapping peaks in the RBS output for the case of alumel films so that EDS analysis was crucial. We also compared thickness measurements determined by EDS and RBS, and we found good agreement for the case of alumel film on copper substrate, and 15% agreement for chromel film on copper substrate.     

White tea intake interferes with the expression of angiogenic factors in the corpora lutea of superovulated rats

White tea derived from the Camellia sinensis (L.) plant has anticancer effects. Its main catechin decreases the gene expression of Vegf in tumours. However, VEGF is also the angiogenic factor of the reproductive organs. In this study, Wistar rats were divided into the following groups (n = 30): the control group (CT), which received water, and the white tea intake group (WT), for 3 months. At the end of every month, the corpora lutea (CL) of ten rats were removed to evaluate the gene expression of Vegf and its receptors (Flt‐1 and Kdr). White tea increased the relative mRNA abundance of Vegf (CT = 0.95 ± 0.06 and WT = 2.13 ± 0.19), Kdr (CT = 0.88 ± 0.06 and WT = 1.94 ± 0.32) and Flt‐1 (CT = 0.94 ± 0.06 and WT = 2.11 ± 0.22) in CL (P < 0.05). White tea increased angiogenic‐related genes in rat CL but did not alter the number of rat CL.     

Integrating product and process design in construction

Product modularity namely the notion that products can be decomposed into parts (or modules) has been widely applied in manufacturing but not in construction, precluding this industry to also benefit from it. The narrow definition of a module, which is often simplistically equated to a sub-assembly produced off-site, and the lack of integration between product and process design, which is typical in construction, are argued to be two root causes of such problem. This paper starts by discussing the operational implications of misaligned decisions in these two domains in an empirical study addressing a high-rise apartments building project. Seven guidelines are then devised using a Design Science Research (DSR) approach for integrating product (product modularity and modules) and process (work structure and work packages) design. The results indicate that product modularity can be applied for improving operations regardless of the construction method(s) used. Yet, a revised understanding of modules (as a material, a component, a non-volumetric or a volumetric sub-assembly) is needed in addition to a coordinated product and process design, particularly for traditional construction.     

On the modularization and reuse of exception handling with aspects

This paper presents an in‐depth study of the adequacy of the AspectJ language for modularizing and reusing exception‐handling code. The study consisted of refactoring existing applications so that the code responsible for implementing error‐handling strategies was moved to newly created exception handler aspects. We have performed quantitative assessments of five systems—four object‐oriented and one aspect‐oriented—based on four key quality attributes, namely separation of concerns, coupling, cohesion, and conciseness. Our investigation also included a multi‐perspective analysis of the refactored systems, including (i) the extent to which error‐handling aspects can be reused, (ii) the beneficial and harmful aspectization scenarios for exception handling, and (iii) the scalability of AOP to support the modularization of exception handling in the presence of other aspects. Copyright © 2009 John Wiley & Sons, Ltd.     

Prevalence,genetic characterization and antimicrobial resistance of Salmonella isolated from fresh pork sausages in Porto Alegre,Brazil

A total of 336 samples of fresh pork sausage randomly obtained from supermarkets and butcher shops in Porto Alegre, Brazil, were examined for the presence of Salmonella serovars. Salmonella enterica was detected in 82 (24.4%) of the samples, with a most probable number count ranging from 0.03 MPN g^?1 to 460 MPN g^?1. Strains belonging to the most isolated S. enterica serovars (Brandenburg, Panama, Derby and Typhimurium) were further characterized by XbaI-macrorestriction, resulting in a total of 17 profiles. Resistance to tetracycline was the most prevalent among the Salmonella isolates. S. panama and S. typhimurium presented the greatest number of resistance phenotypes.     

Hydrogels from silk fibroin metastable solution: Formation and characterization from a biomaterial perspective

Silk fibroin (SF) hydrogels were obtained from the dialysis of a SF metastable solution. Temperature and calcium concentration in SF solution/hydrogel were measured, as critical variables for SF gelation phenomenon. Gelation time of SF solution was increased by decreasing the dialysis temperature, whereas the residual calcium concentration was higher when higher dialysis temperatures were applied. Hydrogels obtained at 20 °C were characterized after freeze-drying. SEM micrographs showed porous structures, of ca. 20 μm (in cross-sectional area) and 5 μm (on surface). XRD indicated the presence of a β-sheet structure that is formed during SF gelation. In hydrogel formation, SF molecules in solution are dehydrated and interact by intra and intermolecular hydrogen bonds, forming a stable hydrogel. DSC measurements showed the decomposition peak for SF at 290 °C, characteristic of SF β-sheet structure, which is in accordance with the XRD results and demonstrate its high thermal resistance. SF hydrogels were found not to be toxic to cells using in vitro cytotoxicity tests. Results indicate that silk fibroin hydrogels hold promise for use in the biomaterial field.