Baculovirus immediate early gene promoter based expression vectors for transient and stable transformation of insect cells

A recombinant plasmid vector was constructed in which the bacterial LacZ gene was placed under the control of a Bombyx mori baculovirus early promoter. The vector proved to be active in transfected cultured dipteran and lepidopteran cells. Co-transfection carried out with this recombinant plasmid vector and a plasmid containing the hygromycin phosphotransferase gene followed by selection with the antibiotic hygromycin B, resulted in stable transformation of cultured Drosophila melanogaster Schneider 2 cells. Southern blot analysis of the host cell's genomic DNA in combination with chromosomal in situ hybridization demonstrated that multiple copies of both plasmids were integrated in the host cell's genome.     

Adapting prior knowledge activation: Mobilisation, perspective taking, and learners’ prior knowledge

This study investigates the effects of two prior knowledge activation strategies, namely, mobilisation and perspective taking, on learning. It is hypothesised that the effectiveness of these strategies is influenced by learners’ prior domain knowledge. More specifically, mobilisation is expected to be the most effective activation strategy at lower levels of prior knowledge. Mobilisation is a bottom-up oriented strategy that serves a broad stage-setting function. It provides learners with a relevant context in which new information can be integrated, which might be especially beneficial for learners with lower levels of prior knowledge to help them extend their limited knowledge base. As prior knowledge increases, perspective taking is expected to become the most effective strategy for activating learners’ prior knowledge. Perspective taking is a top-down oriented strategy that results in the activation of a corresponding schema. This schema guides the selection and processing of information relevant to the schema, which might especially support learners with higher levels of prior knowledge to refine their already elaborated knowledge base. The effectiveness of the activation strategies (in terms of learning task performance) was indeed influenced by learners’ prior knowledge in the hypothesised direction.     

Analysis of space mapping algorithms for application to partitioned fluid–structure interaction problems

Fluid–structure interactions (FSI) play a crucial role in many engineering fields. However, the computational cost associated with high‐fidelity aeroelastic models currently precludes their direct use in industry, especially for strong interactions. The strongly coupled segregated problem—that results from domain partitioning—can be interpreted as an optimization problem of a fluid–structure interface residual. Multi‐fidelity optimization techniques can therefore directly be applied to this problem in order to obtain the solution efficiently. In previous work, it is already shown that aggressive space mapping (ASM) can be used in this context. In this contribution, we extend the research towards the use of space mapping for FSI simulations. We investigate the performance of two other approaches, generalized space mapping and output space mapping, by application to both compressible and incompressible 2D problems. Moreover, an analysis of the influence of the applied low‐fidelity model on the achievable speedup is presented. The results indicate that output space mapping is a viable alternative to ASM when applied in the context of solver coupling for partitioned FSI, showing similar performance as ASM and resulting in reductions in computational cost up to 50% with respect to the reference quasi‐Newton method. Copyright © 2015 John Wiley & Sons, Ltd.     

Cumulative probabilistic risk assessment of triazole pesticides in Belgium from 2011-2014

Pesticide residues in food can lead to harmful toxic effects when exposed. Some of these compounds have a common Mode of Action and thus elicit a similar biological response. This paper considers the triazoles, a class of widely used fungicides exhibiting the same short-term (acute) and long-term (chronic) response in humans. We examined Belgian pesticide residue data from 2011–2014 and coupled these with the results of the Belgian food consumption survey of 2004. Cumulative probabilistic risk assessment was done using the Monte Carlo Risk Assessment 8.0 web application. The European Food Safety Authority (EFSA) published a guidance document that proposes both optimistic and pessimistic scenarios for dietary exposure assessment. Other than those two, a third, more balanced, scenario was simulated and showed an exposure right in between the EFSA scenarios. In the optimistic scenario, the foods with the highest measured residues in the residue data contributed the most to the total health risk. In the balanced and pessimistic scenarios, the highest contribution to the total health risk was made by active ingredients with a high sampling rate and/or a high consumption rate. No significant trends were observed in the health risk through 2011 to 2014, and the exposure distribution showed no health risks for the extreme consumers, with one exception in 2012.     

Headspace components that discriminate between thermal and high pressure high temperature treated green vegetables: Identification and linkage to possible process-induced chemical changes

For the first time in literature, this study compares the process-induced chemical reactions in three industrially relevant green vegetables: broccoli, green pepper and spinach treated with thermal and high pressure high temperature (HPHT) processing. Aiming for a fair comparison, the processing conditions were selected based on the principle of equivalence. A comprehensive integration of MS-based metabolic fingerprinting techniques, advanced data preprocessing and statistical data analysis has been implemented as untargeted/unbiased multiresponse screening tool to uncover changes in the volatile fraction. For all vegetables, thermal processing, compared to HPHT, seems to enhance Maillard and Strecker degradation reaction, triggering the formation of furanic compounds and Strecker aldehydes. In most cases, high pressure seems to accelerate (an)aerobic thermal degradation of unsaturated fatty acids leading to the formation of aliphatic aldehydes and ketones. In addition, both thermal and HPHT processing accelerated the formation of sulfur-containing compounds. This work demonstrated that the approach is effective in identifying and comparing different process-induced chemical changes, adding depth to our perspective in terms of studying a highly complex chemical changes occurring during food processing.     

Mapping temperature uniformity in industrial scale HP equipment using enzymatic pressure–temperature–time indicators

The potential of two previously developed pressure–temperature–time indicators (pTTIs) to detect temperature differences during high pressure (HP) processing was assessed. In a first theoretical approach, numerical integration of pressure, temperature-profiles and kinetic data of inactivation of the pTTIs, Bacillus amyloliquefaciens α-amylase and Bacillus subtilis α-amylase, was applied to translate hypothetical temperature profiles under pressure into indicator read-outs. This resulted in the definition of the application window with regard to initial temperature of the pressure medium (equal to the high pressure wall), the pressure level, build-up rate and holding time. Both indicators showed great potential for use in HP pasteurization processing. Secondly, in an experimental part, the temperature uniformity in a horizontally oriented, industrial scale HP equipment was mapped for the first time, using these indicators. Differences in indicator read-outs were obtained in the radial plane of the HP vessel, and based on the kinetic data of the pTTIs, attributed to temperature differences. Of course, this temperature non-uniformity will only result in process non-uniformity if the temperature dependency of the kinetics of the target attribute (safety, quality) is sufficiently temperature sensitive in the studied pressure, temperature-range.     

Insight into the prevalence and distribution of microbial contamination to evaluate water management in the fresh produce processing industry

This study provided insight into the degree of microbial contamination in the processing chain of prepacked (bagged) lettuce in two Belgian fresh-cut produce processing companies. The pathogens Salmonella and Listeria monocytogenes were not detected. Total psychrotrophic aerobic bacterial counts (TPACs) in water samples, fresh produce, and environmental samples suggested that the TPAC is not a good indicator of overall quality and best manufacturing practices during production and processing. Because of the high TPACs in the harvested lettuce crops, the process water becomes quickly contaminated, and subsequent TPACs do not change much throughout the production process of a batch. The hygiene indicator Escherichia coli was used to assess the water management practices in these two companies in relation to food safety. Practices such as insufficient cleaning and disinfection of washing baths, irregular refilling of the produce wash baths with water of good microbial quality, and the use of high product/water ratios resulted in a rapid increase in E. coli in the processing water, with potential transfer to the end product (fresh-cut lettuce). The washing step in the production of fresh-cut lettuce was identified as a potential pathway for dispersion of microorganisms and introduction of E. coli to the end product via cross-contamination. An intervention step to reduce microbial contamination is needed, particularly when no sanitizers are used as is the case in some European Union countries. Thus, from a food safety point of view proper water management (and its validation) is a critical point in the fresh-cut produce processing industry.     

Harmonisation of food categorisation systems for dietary exposure assessments among European children

Within the European project called EXPOCHI (Individual Food Consumption Data and Exposure Assessment Studies for Children), 14 different European individual food consumption databases of children were used to conduct harmonised dietary exposure assessments for lead, chromium, selenium and food colours. For this, two food categorisation systems were developed to classify the food consumption data in such a way that these could be linked to occurrence data of the considered compounds. One system served for the exposure calculations of lead, chromium and selenium. The second system was developed for the exposure assessment of food colours. The food categories defined for the lead, chromium and selenium exposure calculations were used as a basis for the food colour categorisation, with adaptations to optimise the linkage with the food colour occurrence data. With this work, an initial impetus was given to make user-friendly food categorisation systems for contaminants and food colours applicable on a pan-European level. However, a set of difficulties were encountered in creating a common food categorisation system for 14 individual food consumption databases that differ in the type and number of foods coded and in level of detail provided about the consumed foods. The work done and the problems encountered in this project can be of interest for future projects in which food consumption data will be collected on a pan-European level and used for common exposure assessments.