A new growth method for CdTe: A breakthrough toward large areas

CdTe and CdZnTe are well-investigated II-VI semiconductors, mainly used as substrates for the HgCdTe-IR detection and as detectors for x-ray and γ-ray detection. For both applications, the demand is toward larger and larger dimensions to make larger infrared (IR) and x-ray and γ-ray arrays. This paper presents a new method to grow large dimension CdTe (or CdZnTe), mainly devoted to x-ray and γ-ray detection. This method is based on solvent evaporation from Te-rich solution made of cadmium and tellurium (optionally zinc); it operates in an open tube, and growth proceeds in a crucible maintained at a constant temperature. At the end of growth, a disc of CdTe (or CdZnTe) is obtained, the thickness of which is in the range 1–10 mm. The 65-mm-diameter discs appear as polycrystals with large grains. The electrical properties strongly depend on the presence of voluntarily introduced dopants to obtain high-resistivity material. Two different impurities are commonly used to obtain resistivity in the 10¹⁰ Ωcm range: aluminum and chlorine. Characterization of both doped materials and results of detectors under x-ray and γ-ray illumination will be given; spectrometric grade performance has been obtained and will be presented. The originally 65-mm-diameter crucible can be scaled up to 300 mm in diameter; this will be discussed in the paper.     

Balancing the risk of dioxins and polychlorinated biphenyls (PCBs) and the benefit of long-chain polyunsaturated fatty acids of the n-3 variety for French fish consumers in western coastal areas

A study of 401 fish-eating adults living in a coastal region of France was undertaken to establish exposure to dioxins/polychlorinated biphenyls and the intake of long-chain polyunsaturated fatty acids of the n-3 variety. Fish consumption was estimated using food frequency diaries and the dioxin/polychlorinated biphenyl data collected by the French control authorities was used to calculate dietary exposure. The results showed that for a group of adult subjects selected because of their consumption of fish, 60% achieved the nutritional recommendation for long-chain n-3 polyunsaturated fatty acids and 79% were exposed to total dioxins below the toxicological threshold of 14 pg kg^?1 body weight week^?1. Nevertheless, only 41% of these subjects had an optimal balance between the risk and benefit of eating fish, because 19% were meeting the nutritional recommendation but exceeding the toxicological threshold, whereas 38% were exposed below the toxicological threshold but failed to reach the recommended intake of long-chain n-3 polyunsaturated fatty acids. Similar results were found regarding the balance between long-chain n-3 polyunsaturated fatty acids and polychlorinated biphenyls even if a toxicological threshold was not established for these compounds. The results show that meeting the nutritional requirements of 0.5 mg day^?1 of long-chain n-3 polyunsaturated fatty acids is compatible with respect to toxicological thresholds, while an intake higher than 1.5 g day^?1 is likely to lead to a dietary exposure above the provisional tolerable weekly intake for dioxins.     

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.     

Estimation of the dietary intake of pesticide residues, lead, cadmium, arsenic and radionuclides in France

Estimation of the dietary exposure of French consumers to 10 pesticides (omethoate, oxydemeton, phosalon, phosphamidon, triazophos, dicofol (op'+pp'), parathion ethyl, dichlorvos, procymidon and vinchlozolin), three heavy metals (lead, cadmium and arsenic) and three radionuclides (¹³⁴caesium, ¹³⁷caesium and ¹³¹iodine) from collected duplicate portion in mass catering establishments in 1998/1999 are reported, and compared with those from previous French studies as well as those from other countries. Dietary exposure estimates appear to be reassuring, in that Estimated Daily Intake (EDI) estimates are generally low, representing at maximum only 4% of the Acceptable Daily Intake (ADI) for pesticide residues and 28% of the Provisional Tolerable Weekly Intake (PTWI) for heavy metals. Moreover, none of the three radionuclides has been found in duplicate meals. When comparisons are possible, estimated dietary exposures for heavy metals are lower than those from previous French studies and similar or above those from other countries.     

Mycotoxin contamination of sorghum and its contribution to human dietary exposure in four sub-Saharan countries

This research aimed at evaluating the safety, and the type, level and prevalence of mycotoxins in grain sorghum of four sub-Saharan African (SSA) countries (Burkina Faso, Ethiopia, Mali and Sudan). A multi-analyte LC-MS/MS method for quantification of 23 mycotoxins (nivalenol, deoxynivalenol, fusarenon X, neosolaniol, 3-acetyl deoxynivalenol, 15-acetyl deoxynivalenol, diacetoxyscirpenol, roquefortine C, HT-2 toxin, alternariol, T-2 toxin, FB1, FB2, FB3, zearalenone, aflatoxin G₁, aflatoxin G₂, aflatoxin B₁, aflatoxin B₂, sterigmatocystin, OTA, altenuene, alternariol monomethylether) was applied to different sorghum matrices. Of the 1533 analysed samples, 33% were contaminated with at least one of the following mycotoxins: aflatoxins, fumonisins, sterigmatocystin, Alternaria toxins, OTA and zearalenone. Country of origin, colour, source and collection period of sorghum samples significantly influenced the type, level and prevalence of mycotoxins. Sterigmatocystin (15%), fumonisins (17%) and aflatoxins (13%) were the most prevalent. FB1 (274 ± 585 µg/kg) had the highest mean concentration followed by FB2 (214 ± 308 µg/kg) while diacetoxyscirpenol (8.12 ± 19.2 µg/kg) and HT-2 (11.9 ± 0.00 µg/kg) had the lowest concentrations. Neosolaniol, fusarenon-X, 3-acetyl deoxynivalenol, 15-acetyl deoxynivalenol, T-2 toxin, nivalenol and roquefortine C were not detected in any of the samples. Sudan had the lowest prevalence and mean concentration of all mycotoxins. Pink sorghum had the highest concentrations of fumonisins and aflatoxins. Mycotoxins from Aspergillus spp. and Alternaria spp. are the mycotoxins of concern in SSA grain sorghum with regard to prevalence, concentration and possible health risk from exposure. Based on the performed risk characterisation, daily consumption of sorghum containing aflatoxins, alternariol, alternariol monomethyl ether, sterigmatocystin and OTA could result in exceeding the established health-based guidance values for these toxins.     

Assessment of seasonality in exposure to dioxins, furans and dioxin-like PCBs by using long-term food-consumption data

According to the European Food Safety Authority (EFSA) guidance related to uncertainties in dietary exposure assessment, exposure assessment based on short-term food-consumption surveys, such as 24-h recalls or 2-day records, tend to overestimate long-term exposure because of the assumption that the dietary pattern will be similar day after day over a lifetime. The aim of this study was to make an assessment of dietary exposure to polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), also called 'dioxins' and 'dioxin-like PCBs', using long-term household purchase and consumption survey data collected by TNS-Secodip. Weekly purchases of the major dioxins and dl-PCB vector products of these contaminants were collected for 328 single-person households, who participated at TNS-Secodip consumption surveys from 2003 to 2005 and who were single-person households in order to estimate better their consumption. These data were combined with average contamination levels of food products. Weekly gross average exposure was estimated at 10.2 pg toxic equivalent (WHO TEQ) kg(-1) bw week(-1) (95% confidence interval [9.6, 10.9]). According to the typical shape of the distribution of individual weekly exposures, it is sensible to fit an exponential law to these data. The mean was therefore 12.1 pg WHO TEQ kg(-1) bw week(-1). This value is higher than the arithmetic mean because it better takes into account inter-individual variability. It was estimated that about 20% of persons in this sample were exceeding the current health-based guidance value mainly due to high consumption of seafood and/or dairy products. Thanks to long survey duration (3 years) and the weekly recording of food consumption, it was possible to demonstrate the actual seasonality of dietary exposure to dioxins and dl-PCBs with a maximum between March and September; similar seasonality is observable for fish consumption. Autoregressive integrated moving average (ARIMA) models were adjusted to the time series and it was demonstrated that the number of times the upper limit of confidence intervals exceeds the provisional tolerable weekly intake (PTWI) is about 15 weeks per year on average. Finally, compared with the results obtained from data collected in the short-term surveys (1 week), this study does not suggest that short-term consumption surveys tend to overestimate the long-term exposure.     

An optimised method for material identification using a photon counting detector

X-ray photon counting detectors have become a competitive alternative to energy integrating systems in certain domains. However, processing methods currently used in radiography for investigating the composition of an object are an extension of dual energy methods and have started to show their limits with an increasing number of counting windows (bins). Thus, in a context of material recognition for homeland security, this study aims to introduce a new data processing method suitable for any type of detector, in integrating or counting mode, regardless of the number of bins. Additionally, a criterion to quantify the influence of the number of counting windows as well as the influence of their threshold position has been developed.The optimisation process is conducted in simulation by considering ideal detectors, and the results, for detectors with m=2, 3, 4 and 5 counting windows, are compared to those obtained with an analytical criterion developed in the literature and adapted to our study context. Both methods give identical results. In the final part, the performances of a spectrometric detector (energy windows width of 1 keV) and of optimised systems with m=2, 3, 4 and 5 bins are analysed for homogeneous plastic identification. The results show an increase in performance with increase in bin number until the performance level of the spectrometric detector is reached.Moreover, a discussion on the optimisation robustness as a function of material thickness to be identified is presented. The spectrometric detector, which does not require any optimisation of the bins thresholds, appears then to be a candidate of choice for material recognition when using X-ray photon counting detectors.     

Human pancreatic lipase: an exposed hydrophobic loop from the C-terminal domain may contribute to interfacial binding

Epitope mapping was performed using four anti-HPL monoclonal antibodies (mAb's 81-23, 146-40, 315-25, and 320-24) directed against human pancreatic lipase (HPL). Three HPL mutants produced in insect cells were tested for this purpose: (i) N-HPL, which consists of only the N-terminal domain of HPL, (ii) HPL(-lid), in which a short loop consisting of 5 amino acid residues replaces the full-length 23-residue lid domain present in HPL, and (iii) N-GPLRP2/C-HPL chimera, a chimeric mutant consisting of the N-terminal domain of the guinea pig pancreatic lipase related protein 2 (GPLRP2) fused to the C-terminal domain of HPL. The C-terminal domain of HPL (C-HPL) was prepared in a pure form after performing chymotryptic digestion of HPL. The mAb 146-40 recognizes HPL, HPL(-lid), and N-HPL but not GPLRP2, N-GPLRP2/C-HPL chimera, or the C-HPL. The antibody mAb 146-40 therefore specifically recognizes the N-terminal domain of HPL, and the epitope recognized does not include the amphiphilic lid. On the other hand, mAb's 81-23, 315-25, and 320-24 react specifically to the C-terminal domain of HPL, since they recognize HPL, HPL(-lid), the N-GPLRP2/C-HPL chimera, and the C-HPL but not N-HPL or GPLRP2. It was further established that these three mAb's recognize the same conformational epitope, the structure of which is stabilized by the N-terminal domain in the presence of SDS at concentrations greater than its critical micellar concentration. This conformational epitope was found to be located in the vicinity of Met 397 and Arg 414. These two residues delineate a highly exposed peptide stretch extending from the HPL C-terminal domain, which includes a hydrophobic surface loop (beta5'). Kinetic studies on the HPL/mAb's complexes showed that the lipase activity was much lower in these complexes than in HPL. The results of the present study suggest for the first time that the beta5' loop from the C-terminal domain may be involved in the interaction of HPL with a lipid/water interface.     

Pancreatic lipase-related protein 1 (PLRP1) is present in the pancreatic juice of several species

Pancreatic lipase-related protein 1 (PLRP1) was purified from human, canine, porcine and rat pancreatic juices. The four PLRP1s were identified using microsequencing methods after performing gel filtration on Ultrogel AcA-54 followed by chromatography on Heparin-Sepharose cation-exchanger. Polyclonal antibodies specific to human PLRP1 (HPLRP1) were raised in the rabbit using a synthetic decapeptide from HPLRP1. The results of Western blotting analysis showed that these antibodies recognized native HPLRP1 and recombinant HPLRP1 produced by insect cells, and cross-reacted only with rat PLRP1 (RPLRP1). No significant lipolytic activity was observed with native canine PLRP1 and recombinant HPLRP1 on various glycerides, phospholipid and vitamin esters, or on cholesterol esters. It was established for the first time that this protein is secreted in variable amounts by the adult exocrine pancreas of several species.