Use of global sensitivity analysis in quantitative microbial risk assessment: application to the evaluation of a biological time temperature integrator as a quality and safety indicator for cold smoked salmon

The aim of this study was to apply a global sensitivity analysis (SA) method in model simplification and to evaluate (eO)^®, a biological Time Temperature Integrator (TTI) as a quality and safety indicator for cold smoked salmon (CSS). Models were thus developed to predict the evolutions of Listeria monocytogenes and the indigenous food flora in CSS and to predict TTIs endpoint. A global SA was then applied on the three models to identify the less important factors and simplify the models accordingly. Results showed that the subset of the most important factors of the three models was mainly composed of the durations and temperatures of two chill chain links, out of the control of the manufacturers: the domestic refrigerator and the retail/cabinet links. Then, the simplified versions of the three models were run with 10⁴ time temperature profiles representing the variability associated to the microbial behavior, to the TTIs evolution and to the French chill chain characteristics. The results were used to assess the distributions of the microbial contaminations obtained at the TTI endpoint and at the end of the simulated profiles and proved that, in the case of poor storage conditions, the TTI use could reduce the number of unacceptable foods by 50%.     

Comparison of ochratoxin A and deoxynivalenol in organically and conventionally produced beers sold on the Belgian market.

Beer was chosen as a cereal-derived and homogeneous product for a comparison of organic and conventional production methods in terms of mycotoxin contamination levels. Ochratoxin A (OTA, a storage mycotoxin) and deoxynivalenol (DON, a field mycotoxin) were assessed by HPLC in organically and conventionally produced beers sold in Belgium. Immunoaffinity column (OchraTest and DONPrep) purification was used prior to HPLC analysis. For in-house validation, recovery experiments, carried out with the spiked beers in the ranges of 50-200 ng OTA l-1 and 20-100 microg DON l-1, led to the overall averages of 91% (RSD = 10%, n = 9) and 93% (RSD = 5%, n = 27), respectively. Organic beers collected during 2003-2004 were more frequently OTA-contaminated (95%, n = 40) than their conventional counterparts (50%, n = 40). Conventional beers were OTA-contaminated at a mean concentration of 25 ng l-1 (range: 19-198 ng l-1), while organic beers contained a mean level of 182 ng l-1 (range: 18-1134 ng l-1). High OTA contamination above the limit of 200 ng l-1 (up to 1134 ng l-1) occasionally occurred in organically produced beers. A complementary survey performed with the same brands in 2005 did not confirm this accidental presence of excessive OTA loads (range: 3-67 ng l-1 for 10 conventional beers and 19-158 ng l-1 for 10 organic beers). Establishing a maximum of 3 microg OTA kg-1 in malt, the application of the regulation EC No. 466/2001 (entered in force before the last sampling) may be related to the observed improvement. The overall incidence of DON was 67 and 80% in conventional and organic beers, respectively. DON concentrations ranged from 2 to 22 microg DON l-1 (mean = 6 microg DON l-1) in conventional beers, while organic beers ranged from 2 to 14 microg DON l-1 (mean=4 microg DON l-1). Thus, DON in beers does not appear to be a major matter of concern. From the statistical tests, it was concluded that the variation between different batches was significant (P < 0.0001), in contrast to that observed between different brands, showing a lack of homogeneity in the raw materials. This occurs either in organically or in conventionally produced materials. Considering these results, an optimized frequency of controls according to European Regulations EC No 466/2001 and EC No 856/2005 should be recommended to reject the irregular batches.     

Self-directed learning readiness, Internet self-efficacy and preferences towards constructivist Internet-based learning environments among higher-aged adults

This article examines several research questions to establish a theory model for explaining factors that influence adult learners' preferences for constructivist Internet-based learning environments (CILE). Data were gathered from 541 individual participants enrolled in adult education institutes in Taiwan for structural equation modelling (SEM) analyses. The research results established a 10-scale instrument for assessing adult learners' preferences for CILE. Among the scales of CILE, adult students placed the highest value on relevance to life and reflective thinking, and scored the lowest for critical judgement, ease of use and student negotiation. The SEM analyses revealed that compared to Internet self-efficacy (ISE), self-directed learning readiness plays a major role in predicting adults' preferences for their learning environment, especially for the higher level of intellectual challenge. ISE plays a mediating role in the relationships between Internet usage and the participants' preferences. This result suggests that more time spent on Internet practice may increase adult learners' ISE, which may strengthen their preferences for Internet-based learning environments.     

Regions of tau implicated in the paired helical fragment core as defined by NMR

We have studied the mature Alzheimer-like fibers of tau by fluorescence and NMR spectroscopy. Assembly of the protein into paired helical filaments after incubation with heparin at 37 degrees C was verified by electron microscopy and size-exclusion chromatography. NMR spectroscopy on these mature fibers revealed different regions of residual mobility for tau: the N-terminal domain was found to maintain solution-like dynamics and was followed by a large domain of decreasing mobility; finally the core region was distinguished by a solid-like character. Heteronuclear-NOE data indicate that the decreasing mobility is due to both a slowing down of the rapid nanosecond movements and the introduction of slower movements that lead to exchange broadening. Fluorescence spectroscopy confirmed the presence of this rigid core, and some degree of protection from hydrogen exchange for those residues was observed. Hence, our data give a more precise picture of the dynamics of tau when it is integrated into mature filaments and should provide further understanding of the molecular processes that govern aggregation.     

Electroplating of copper onto a preanodized 7005Al/Al2O3(P) metal matrix composite

The electroplating of copper onto 7005Al/Al₂O_3(P) metal matrix composites (Al MMC) is difficult but becomes feasible if the composites have been preanodized in mineral acids. It is clear that phosphoric (P) acid anodizing is better than oxalic (O) or sulfuric (S) acid anodizing when the morphology of the copper coating and its adhesion to the MMC substrate are considered. Electrochemical studies, such as cyclic anodic potentiodynamic polarization (CAPP), cyclic cathodic potentiodynamic polarization (CCPP) and electrochemical impedance spectroscopy (EIS) are beneficial in delineating the influence of the anodizing pretreatment on the subsequent copper electroplating process. A positive hysteresis of the CAPP curve in phosphoric acid indicates the effective removal of oxide film from the composite. After examining the CCPP curves for the Cu-electroplating bath, for MMC pretreated in various acids, we can understand the morphological differences in the copper coatings and variations in adhesion to the anodized composite. EIS measurements confirm the d.c.-polarization results.     

Electrowinning of palladium using a modified cyclone reactor

The electrochemical behaviour of palladium in dilute acidic chloride solution was investigated using a rotating disc electrode system and the electrowinning of palladium using a modified electrochemical cyclone cell was also carried out. The effect of several variables such as applied voltage, hydrochloric acid concentration and electrolyte flow rate were studied to obtain the optimum conditions for electrowinning. More than 99% of the palladium in solution was recovered within an hour under the optimum conditions using the cyclone cell and grey powdery deposits were observed at a high applied voltage. The purity of palladium electrowon from the leach liquor was at least 99%.     

Biological nutrient removal in simple dual sludge system with an UMBR (upflow multi-layer bioreactor) and aerobic biofilm reactor.

In this study, a simple dual sludge process was developed for small sewage treatment. It is a hybrid system that consists of upflow multi-layer bioreactor (UMBR) as anaerobic and anoxic reactor with suspended growth microorganisms and post aerobic biofilm reactor with inclined plates. UMBR is a multifunction reactor that acts as primary sedimentation tank, anaerobic reactor, anoxic reactor, and thickener. The sludge blanket in the UMBR is maintained at a constant level by automatic control so that clear water (30 mg-SS/L) can flow into the post aerobic biofilm reactor. It leads to improving performance of the biofilm reactor due to preventing of excess microbial attachment on the media surface and no requirment for a large clarifier caused by low solid loading. The HRT in the UMBR and the aerobic biofilm reactor were about 5.8 h and 6.4 h, respectively. The temperature in the reactor during this study varied from 12.5 degrees C to 28.3 degrees C. The results obtained from this study show that effluent concentrations of TCOD, TBOD, SS, TN, and TP were 29.7 mg/L, 6.0 mg/L, 10.3 mg/L, 12.0 mg/L, and 1.8 mg/L, which corresponded to a removal efficiency of 92.7%, 96.4%, 96.4%, 74.9%, and 76.5%, respectively. The sludge biomass index (SBI) of the excess sludge in the UMBR was about 0.55, which means that the sludge in the UMBR was sufficiently stabilized and may not require further treatment prior to disposal.     

Improved performances of the fast reactor calculational system ERANOS-ERALIB1 due to improved a priori nuclear data and consideration of additional specific integral data

A single consistent scheme of calculational methods and nuclear data called ERANOS-ERALIB1 was produced in 1996 to calculate fast reactor neutronic parameters. It represents a significant improvement on previous schemes such as CARNAVAL-IV, PROPANE and VASCO, each of which were required in order to calculate one specific application. The nuclear data library ERALIB1 has been obtained by a consistent statistical adjustment based on 355 integral data from 71 different systems. The performance of ERALIB1 is excellent, as demonstrated during its validation for which all the k_eff SUPER-PHENIX data were reproduced to within 70 pcm.

The only restriction on this satisfactory performance is related to the rather poor prediction of the sodium void reactivity effect. This was due to very bad nuclear data for ²³Na, and the unsatisfactory methods used to calculate the sensitivity coefficients for the sodium void reactivity variation Δρ_Na. To improve the performance relative to this point and to enlarge the domain of validation several actions have been undertaken:

•a revision of the formalism and algorithms used to calculate the derivatives of Δρ_Na to the sodium cross section data,

•a significant enlargement of the integral data base related to this aspect of the sodium void effect. Compared to the initial data base established in support of ERALIB1, several additional (18) sodium void configurations corresponding to voids of different volumes at different core locations have been studied.

In order to broaden the range of application of the improved library, which will be called ERALIB1.A, significant effort has been devoted to additional configurations which have firstly been evaluated, and then if judged suitable, included in the adjustment process. They are related to two specifically targeted experimental programmes:

•a study of neutron deep penetration. Several configurations of the JANUS experimental programme (shielding constructed of separate steel, iron and sodium plates) have been analysed. With this complementary information ERALIB 1A becomes applicable for accurate predictions of shielding configurations,

•a study of steel reflectors for a fast reactor of the SUPER-PHENIX type. The measurements performed in the MASURCA (the CIRANO experimental programme) and FCA facilities include spectral indices (F25(r)/F25(0),...) at different positions in the reflector. As a consequence of these measurements, important information has been obtained for additional “secondary” structural material isotopes, such as ⁵⁷Fe, ⁶⁰Ni and ⁵³Cr.

Significant effort has also been devoted to the analysis of 29 β_eff experiments. The result of this is an improvement of the uncertainty on ν_d(E) which guarantees a prediction of β_eff with the required accuracy (3% for critical configurations, and 5% for power reactors).

The consistent statistical adjustment method by Gandini et al. (1973) has been completed. Rigorous criteria have been introduced to identify any data which are suspect and/or inconsistent in the integral data base. These data may introduce additional bias in the adjusted library, and for that reason they must be discarded before adjustment.