The effects of temperature,chlorine and acids on the survival of Listeria and Salmonella strains associated with uncooked shrimp carapace and cooked shrimp flesh

The purpose of this study was to assess the influence of the association of Listeria and Salmonella with shrimp surfaces on the effects of temperature, chlorine and acids on their survival. Planktonic, attached and colonized cells of Listeria monocytogenes Scott A, L. monocytogenes V7, Salmonella Senftenberg 1734b and S. Typhimurium ATCC 14028 were challenged with high (50°, 60° and 70 °C) and low (4 °C) temperature, 100 ppm sodium hypochlorite solution, and acetic, hydrochloric and lactic acids (pH 4.0). Attached and colonized Listeria and Salmonella showed significantly greater (p < 0.05) resistance to heat (∼1.3–2.6 fold increase in D-values), hypochlorite (∼6.6 ≥ 40.0 fold) and acids (∼4.0–9.0 fold) than their planktonic counterparts. There were no significant differences (p > 0.05) in the survival of planktonic, attached or colonized cells of Listeria and Salmonella stored under refrigerated conditions. The association of Listeria and Salmonella with shrimp surfaces enhances their resistance to heat, chlorine and acids. Both attachment to, and subsequent colonization of, shrimp surfaces by pathogens may reduce the efficacy of methods used in their control. Strategies to reduce attachment of these pathogens to shrimp are required to assure safety of this product.     

Optimization of transesterification of castor oil with ethanol using a central composite rotatable design (CCRD)

In the present study, the synthesis of fatty acid esters from castor oil using an alkaline catalyst was optimized. The variables reaction time, catalyst amount and oil:ethanol molar ratio were studied using a central composite rotatable design. The effects and significance of the models on the response variable and on ethyl biodiesel yield derived from pure castor oil were evaluated using a response surface curve and analysis of variance. All the variables significantly affected the reaction yield, the amount of catalyst being the most effective. The highest yield was obtained using an oil:ethanol molar ratio of 1:11, 1.75% KOH and a reaction time of 90 min.     

Determination of Uncertainty in Transition Velocity Estimates for Ceramic Materials

The uncertainty of transition velocity estimates made for five armor ceramic materials was quantified by applying Bayesian hypothesis testing to the McCauley Wilantewicz method. Likelihood functions of the ceramic plasticity parameter and estimated transition velocity for each material were determined through analysis of load–hardness probability spaces. Parameters of these functions were analyzed to quantify variability in expected material performance. The applied statistical methodology enabled formation of probability of penetration curves that indicated how the certainty of interface defeat varied as a function of impact velocity. Qualitative and quantitative analysis of results increases the utility of the McCauley Wilantewicz method as a screening tool for ceramic materials by providing additional information regarding the variability of expected material performance. Information revealed by this statistical approach could potentially be harnessed to drive future material development by indicating microstructural states more likely to result in desirable material behavior.     

Solution blow spun titania nanofibers from solutions of high inorganic/organic precursor ratio

In this work titania nanofibers were produced from different precursor solutions by solution blow spinning. Hydrophilic polyvinylpyrrolidone, hydrophobic poly(vinyl acetate) and amorphous and semi-crystalline poly(lactic acid) polymers were used with green-solvents and titanium isopropoxide as the inorganic precursor. Hybrid nanofibers with high inorganic loading content were successfully produced from all precursor solutions. The fibers were calcined at different annealing temperatures for evaluation of phase transitions. The minimum temperature to obtain pure titania fiber was found to be 500 °C, as assessed by thermal characterization. Anatase was the unique polymorph formed at this annealing temperature. This is of paramount importance due to its photocatalytic character. Calcination at high temperatures showed that rutile slightly appeared at 600 °C for the polyvinylpyrrolidone-based system and showed a strong peak at 700 °C for all systems, co-existing with anatase as minor phase. The use of amorphous and semicrystalline poly(lactic acid) polymers did not influence the anatase crystal size and phase conversion. This was found to be dependent on the annealing temperature and medium acidity, as currently found in powder synthesis.     

Mechanism of superacid catalyzed alkane activation: theoretical ab initio studies of pentacoordinated carbonium ion rearrangement

A theoretical ab initio study of the interconversion of pentacoordinated carbonium ions was carried out. For the isobutonium cations it was found that the respective C-carbonium ions were lower in energy than the H-isobutonium ions. Nevertheless, the interconversion of the 1-H-isobutonium cation in the C-isobutonium ion is a barrierless process. This suggests that product arisen from C–C protonation in liquid superacid and zeolite catalyzed alkane activation may be formed by protonation in the outer and more accessible primary C–H bonds of isobutane, rather than by direct protonation of the inner and more steric demanding C–C bonds. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of nitrate on the reduction of Reactive Red 2 by mesophilic anaerobic sludge.

This research aimed to evaluate the effect of nitrate on anaerobic azo dye reduction by using mesophilic bioreactors, in the absence (reactor R2) and in the presence (reactor R1) of redox mediators. The azo dye Reactive Red 2 (RR2) and the redox mediator anthraquinone-2,6-disulphonate (AQDS) were selected as model compounds. The results showed that the bioreactors were efficient on RR2 reduction, in which ethanol showed to be a good electron donor to sustain dye reduction under anaerobic conditions. The redox mediator AQDS increased the rates of reductive decolourisation, but its effect was not so remarkable compared to the previous experiments conducted. Contrary to the raised hypothesis that the nitrate addition could decrease decolourisation rates and catalytic properties of the redox mediators, no effect of nitrate was observed in the bioreactors, suggesting that the presence of nitrate in textile wastewaters will not decrease the capacity of anaerobic reactors supplemented or not with redox mediators to decolourize azo dyes.     

Control of Microbial Adhesion as a Strategy for Food and Bioprocess Technology

Bacteria and other microorganisms have a natural tendency to adhere to surfaces as a survival mechanism. This can occur in many environments, including the living host, industrial systems, and natural waters. The general outcome of bacterial colonization of a surface is biofilm formation, which consists of microorganisms immobilized in a variety of polymeric compounds generally referred to as extracellular polymeric substances. Bacterial adhesion to a solid surface is a crucial step in the biofilm process. This step is dependent upon van der Waals, electrostatic, and acid–base interactions. These interactions are influenced by physicochemical properties of the substratum and the bacterial surface, such as hydrophobicity, surface charge, and electron donor–electron acceptor properties. In addition, the roughness of the substratum and the microbiological characteristics of the cell surface, such as cellular appendages and production of exopolysaccharides, can affect the adherence process. To date, many strategies have been developed to decrease the adherence of bacteria to surfaces. Surface modification with the addition of the suitable compounds makes surfaces less attractive for microorganisms and therefore prevents bacterial adherence and biofilm formation.     

Designing an effective management system for enterprises: Concepts and verification

In this article lean and agile manufacturing are considered as separate organizational strategies of enterprise management. Therefore, a model of these strategies for business situations as well as assigning modern concepts and methods of management to these strategies and business segments has been proposed. This model, called LABDM (lean agile business development model), has been provisionally verified in small‐ and medium‐sized enterprises from the gas engineering industry in the Wielkopolska province in Poland. In 17 enterprises of this industry the use of modern concepts and methods of management have been studied. With the help of the rough sets theory, a set of concepts and methods that are crucial for the effective enterprises has been identified. By comparing these concepts and methods to the LABDM, the model's rationality is proven. In conclusion, the LABDM can be used as a tool when considering a lean or agile strategy, and modern concepts and methods that are associated with these strategies. © 2008 Wiley Periodicals, Inc.     

Far infrared measurements of bulk and surface phonons in GaAs/AlAs superlattices

We have used far-infrared oblique-incidence reflection spectroscopy to study bulk phonon polaritons, and attenuated total reflection (ATR) spectroscopy to study surface phonon polaritons, in long-period GaAs/Al_xGa_1?xAs and short-period GaAs/AlAs superlattices. Results on the former are in good agreement with an effective-medium bulk-slab model of the dielectric tensor of the superlattice; results on the latter are analysed in terms of a model that contains dielectric-tensor contributions from the confined optic phonons.