Preparation and characterization of chitosan‐based dispersions

Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry     

Active application of primer acid on acid‐treated enamel: Influence on the bond effectiveness of self‐etch adhesives systems

Aim: Evaluate the composite‐to‐enamel bond after passive or active application of self‐etching primer systems on polished or pre‐etched enamel with phosphoric acid. Materials and Methods: Two self‐etch adhesives systems (SEAS) were used: Clearfil SE Bond and Easy Bond. Third human molars were divided into 8 groups (N = 10). The crown of each tooth was sectioned into halves and the mesial/distal surfaces were used. The adhesives were actively or passively applied on enamel with or without prior phosphoric‐acid etching. Resin composite cylinders were built after adhesive application. After stored in relative humidity for 24 hr/37°C the specimens were subjected to microshear test in universal testing a machine at a crosshead speed of 0.5 mm/minute. The results were analyzed with three‐way ANOVA and the Tukey test. The enamel‐etching pattern was evaluated under SEM. Results: The 2‐step SEAS system presented significantly higher adhesive bond strength means (47.37 MPa) than the 1‐step (36.87 MPa). A poor enamel‐ etching pattern was observed in active mode showing irregular and short resin tags, however there was not compromised the bond strength. Conclusion: Active or passive application produced similar values of bond strength to enamel regardless of enamel pretreatment and type of SEAS.     

Anthropomorphisms in multimedia learning: Attract attention but do not enhance learning?

Anthropomorphizing graphical elements in multimedia learning materials improves learning outcomes. The reasons for enhanced learning are unclear. We extended a seminal anthropomorphism study in order to examine whether the effect of anthropomorphisms on learning outcomes, both immediate and delayed, is caused by the anthropomorphized elements' effects on attention distribution or by elevated positive affective–motivational states. The study had a partial 3 × 2 design (the materials' graphics: schematic vs. black‐and‐white anthropomorphisms vs. colourful anthropomorphisms × eye tracker: present vs. absent). The participants were university students (N = 181). Unexpectedly, we found no significant effect of anthropomorphisms on learning outcomes. Anthropomorphisms significantly affected attention distribution during initial fixations but not overall. Modest effect on enjoyment was found, but no such effect was detected as concerns flow and generalized positive affect. We also found that the eye tracker's mere presence had slight adverse effects on learners, but these effects did not compromise learning.     

A robotic DNA purification protocol and real-time PCR for the detection of Campylobacter jejuni in foods

Primers designed to amplify a Campylobacter jejuni cadF gene sequence were used in an SYBR Green I real-time PCR assay as an alternative to conventional bacteriological methods for the rapid detection of C. jejuni in foods. Twenty-five grams of chicken skin (breast and thigh) was contaminated by adding approximately 1, 10, or 50 CFU of C. jejuni ATCC 35560. Twenty-five grams of pork and 25-ml aliquots of milk were also inoculated with 1 and 10 CFU of the pathogen. The samples were incubated in Bolton broth for different periods at 37 and 42 degrees C under microaerophilic conditions. Using a commercial robotic DNA purification system, DNA was extracted and purified from 1-ml aliquots of the enrichment cultures before and after centrifugation of the 250-ml enrichment broth at 15,900 x g for 10 min at 4 degrees C. The DNA was used as the template in a real-time PCR assay. C. jejuni was detected after 12 h of enrichment from samples inoculated with about 50 CFU/25-g sample. After centrifugation, an enrichment step of 8 h was sufficient to allow detection of pathogen in samples inoculated with 10 CFU/25 g. However, 24 h of enrichment was necessary to detect pathogen in samples inoculated with approximately 1 CFU/25 g. The real-time PCR protocol developed in this study significantly reduced the detection time of C. jejuni in foods.     

A Perinatal Palatable High-Fat Diet Increases Food Intake and Promotes Hypercholesterolemia in Adult Rats

The main goal of the present study was to evaluate the long-term effects of a perinatal palatable high-fat diet on the food intake and cholesterol profile of adult rats. Male Wistar rats (aged 22 days) were divided into two groups according to their mother’s diet during gestation and lactation (C _p, n = 10; pups from control mothers; and HL_p n = 10; pups from mothers fed a palatable high-fat diet). At the 76th day, pups were housed individually for 14 days, and daily food consumption was determined during a period of 6 days. Blood from 100-day-old rats was sampled by cardiac puncture. Fasting (12 h) serum glucose, total cholesterol, LDL-C, HDL-C, triglycerides (TG), and VLDL-C levels were determined. The measurement of food intake was higher in the animals submitted to a hyperlipidic diet during the perinatal period. Serum total cholesterol, LDL-C, HDL-C, TG, VLDL-C and glycemia were increased in the HL_p group compared to the control group. Our findings show that an early life environment with a high-fat diet can contribute to metabolic disease in later life.     

Survey and comparison of message authentication solutions on wireless sensor networks

Security is an important concern in any modern network. This also applies to Wireless Sensor Networks (WSNs), especially those used in applications that monitor sensitive information (e.g., health care applications). However, the highly constrained nature of sensors imposes a difficult challenge: their reduced availability of memory, processing power and energy hinders the deployment of many modern cryptographic algorithms considered secure. For this reason, the choice of the most memory-, processing- and energy-efficient security solutions is of vital importance in WSNs. To date, a number of extensive analyses comparing different encryption algorithms and key management schemes have been developed, while very little attention has been given to message authentication solutions. In this paper, aiming to close this gap, we identify cipher-based Message Authentication Codes (MACs) and Authenticated Encryption with Associated Data (AEAD) schemes suitable for WSNs and then evaluate their features and performance on a real platform (TelosB). As a result of this analysis, we identify the recommended choices depending on the characteristics of the target network and available hardware.     

Aerobic degradation of 2,4-dinitrotoluene by individual bacterial strains and defined mixed population in submerged cultures

The degradation efficiencies of isomeric mononitrotoluenes (2- and 4-NTs) and dinitrotoluenes (2,4-DNT and 2,6-DNT) by either individual bacterial strains (Bacillus cereus NDT4, Pseudomonas putida NDT1, Pseudomonas fluorescens NDT2, and Achromobacter sp. NDT3) or their mixture were compared in submerged batch cultivations. The mixed culture degraded 2,4-DNT nearly 50 times faster than any of the individual strains. The mixed culture also demonstrated significantly shorter lag periods in 2,4-DNT degradation, a lack of nitrite or organic intermediates accumulation in the liquid medium and the ability to degrade a broader spectrum of nitrotoluenes over a wider concentration range. The presence of both readily degradable 2-NT (or 4-NT) and poorly degradable 2,6-DNT in the medium negatively affected 2,4-DNT biodegradation. However, the mixed bacterial culture still effectively degraded 2,4-DNT with only slightly lower rates under these unfavorable conditions, thus showing potential for the remediation of 2,4-DNT contaminated sites.     

Detection of Campylobacter jejuni in naturally contaminated chicken skin by melting peak analysis of amplicons in real-time PCR

Contamination of poultry by Campylobacter spp. is a significant source of human diarrheal diseases. Traditional methods currently used to detect Campylobacter in foods are time-consuming and labor-intensive. In this study, primers designed for the Campylobacter jejuni cadF gene sequence were used in a SYBR Green I real-time PCR assay as an alternative to a conventional bacteriological method for the rapid detection of C. jejuni from poultry. Twelve portions of chicken purchased from two local grocery stores and 39 portions obtained from a commercial processing plant were examined. Samples of the skin were enriched in Bolton broth at 37 degrees C for 3 h and then at 42 degrees C for 9, 21, or 45 h under microaerobic conditions. DNA was extracted from 1-ml aliquots of the enrichment cultures using 1% Triton X-100. The DNA was used as the template in a real-time polymerase chain reaction (PCR) assay. After 24 h of enrichment, C. jejuni was isolated from 13 samples and all of the positive cultures were also detected by the real-time PCR procedure. C. jejuni was detected by both methods from samples artificially contaminated with 1 or 10 CFU of C. jejuni per 10 g, after 24 h of enrichment. The real-time PCR method was found to be sensitive and specific. It significantly reduced the time required for the detection of C. jejuni in poultry following enrichment of samples.     

Comparison of Consumer Attitudes Between Cyprus and Latvia: An Evaluation of Effect of Setting on Consumer Preferences in the Water Industry

Models approaching consumer expectations of their water supplier from a risk perspective suggest that consumers primarily and overwhelmingly want safe drinking water supply. In this study consumer preferences in the water sector are investigated in two contrasting case studies: Cyprus, where there have been significant quantity and continuity of supply issues, and Riga, where there have been water quality issues. While water quality is undoubtedly the main priority of water consumers in Riga, in Cyprus consumers indicate that they prioritise a more reliable service even though many are sufficiently dissatisfied with water quality that they do not drink the tap water. The analysis of consumer attitudes in the two case studies suggests that when water supply is unreliable, reliability takes precedence; once it is reliable quality issues come to the fore.