New developments in CdTe and CdZnTe detectors for X and γ-ray applications

There has been considerable recent progress in II-VI semiconductor material and in methods for improving performance of the associated radiation detectors. New high resistivity CdZnTe material, new contact technologies, new detector structures, new electronic correction methods have opened the field of nuclear and x-ray imaging for industrial and medical applications. The purpose of this paper is to review new developments in several of these fields. In addition, we will present some recent results at LETI concerning first the CdTe 2-D imaging system (20 × 30 mm² with 400 × 600 pixels) for dental radiology and second the CdZnTe fast pulse correction method applied to a 5 × 5 × 5 mm³ CdZnTe detector (energy resolution = 5% for detection efficiency of 85% at 122 keV) for medical imaging.     

Optimal modalities for radiative transfer-neural network estimation of canopy biophysical characteristics: Evaluation over an agricultural area with CHRIS/PROBA observations

Neural networks trained over radiative transfer simulations constitute the basis of several operational algorithms to estimate canopy biophysical variables from satellite reflectance measurements. However, only little attention was paid to the training process which has a major impact on retrieval performances. This study focused on the several modalities of the training process within neural network estimation of LAI, FCOVER and FAPAR biophysical variables. Performances were evaluated over both actual experimental observations and model simulations. The SAIL and PROSPECT radiative transfer models were used here to simulate the training and the synthetic test datasets. Measurements of LAI, FCOVER and FAPAR were achieved over the Barrax (Spain) agricultural site for a range of crop types concurrently to CHRIS/PROBA satellite image acquisition. Results showed that the spectral band selection was specific to LAI, FCOVER and FAPAR variables. The optimal band set provided significantly improved performances for LAI, while only small differences were observed for the other variables. Gaussian distributions of the radiative transfer model input variables performed better than uniform distributions for which no prior information was exploited. Including moderate uncertainties in the reflectance simulations used in the training process improved the flexibility of the neural network in cases where simulations departed slightly from observations. Simple neural network architecture with a single hidden layer of five tangent sigmoid transfer functions was performing as good as more complex architectures if the training dataset was larger than ten times the number of coefficients to tune. Small sensitivity of performances was observed depending on the way the solution was selected when several networks were trained in parallel. Finally, comparison with a NDVI based approach showed the generally better retrieval accuracy of neural networks.     

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.     

Estimation of the distribution of the maximum theoretical intake for ten additives in France.

Three European directives imply for all member states an evaluation of food additives intakes. This paper describes the French approach, using a step-by-step procedure to evaluate, at a national level, the consumption of 10 food additives or groups of additives (E100, curcumin; E160b, annatto; E200-203, sorbic acid and salts; E210-213, benzoic acid and salts; E220-224, 226-228, sulphites; E249-250, nitrites; E297, fumaric acid; E473-474, sucrose esters and sucroglycerides; E491-492, stearoyl lactates; E952, cyclamic acid). The results are reassuring for the general population, except for sulphites.     

Thermal stability of the nanolayered Fe2AlB2 in nitrogen and argon atmospheres

The thermal stability and decomposition mechanisms of Fe₂AlB₂ powders, synthesized by reactive powder metallurgy, were studied under nitrogen (N₂) or argon (Ar) atmospheres. The effects of using different FeB precursors to synthesize the Fe₂AlB₂ and hydrochloric acid (HCl) purification treatments on the thermal stability were also investigated. When as-synthesized Fe₂AlB₂ powders are treated in dilute HCl to dissolve impurity phases, decomposition in N₂ atmospheres occurs readily above 1200 K. The decomposition reaction involves β-FeB precipitation and the liberated Al atoms reacting with the ambient N₂ to form AlN. Under Ar environments, HCl-treated Fe₂AlB₂ powders decompose and precipitate β-FeB, by the out-diffusion of Al from the nanolaminated structure. Interestingly, isothermal annealing under N₂ atmospheres revealed that Fe₂AlB₂ was more thermally stable when synthesized from lab-synthesized, instead of commercially available, FeB precursors and when the HCl treatment was avoided. The effects of the various factors on the decomposition temperature and decomposition mechanisms are discussed herein.     

Tuning Thermal Transport Through Atomically Thin Ti3C2Tz MXene by Current Annealing in Vacuum

Heat transport across vertical interfaces of heterogeneous 2D materials is usually governed by the weak Van der Waals interactions of the surface‐terminating atoms. Such interactions play a significant role in thermal transport across transition metal carbide and nitride (MXene) atomic layers due to their hydrophilic nature and variations in surface terminations. Here, the metallicity of atomically thin Ti₃C₂T_z MXene, which is also verified by scanning tunneling spectroscopy for the first time, is exploited to develop a self‐heating/self‐sensing platform to carry out direct‐current annealing experiments in high (<10^?8 bar) vacuum, while simultaneously evaluating the interfacial heat transport across a Ti₃C₂T_z/SiO₂ interface. At room temperature, the thermal boundary conductance (TBC) of this interface is found, on average, to increase from 10 to 27 MW m^?2 K^?1 upon current annealing up to the breakdown limit. In situ heating X‐ray diffraction and X‐ray photo‐electron spectroscopy reveal that the TBC values are mainly affected by interlayer and interface spacing due to the removal of absorbents, while the effect of surface termination is negligible. This study provides key insights into understanding energy transport in MXene nanostructures and other 2D material systems.     

Methodological characteristics of the national dietary surveys carried out in the European Union as included in the European Food Safety Authority (EFSA) Comprehensive European Food Consumption Database

In 2009 competent organisations in the European Union provided the European Food Safety Authority (EFSA) with data from the most recent national dietary survey at the level of individuals' consumption. Twenty different Member States provided EFSA with data from 22 different national dietary surveys, with consumption figures for adults and, when available, for children. Member States' dietary data were assembled into the EFSA Comprehensive European Food Consumption Database. In this paper an overview of the methodologies and protocols employed in the different national dietary surveys is provided. Specifically, details about dietary assessment methods, interview administration, sampling design, portion size estimation, dietary software, evaluation of under-reporting and non-dietary information collected are described. This information is crucial to evaluate the level of accuracy of food consumption data and to anticipate and acknowledge the utmost important sources of heterogeneity of national databases included in the Comprehensive Database. The Comprehensive Database constitutes a unique resource for the estimation of consumption figures across the European Union and represents a useful tool to assess dietary exposure to hazardous substances and nutrient intake in Europe. Nevertheless, the many substantial methodological differences that characterise the Comprehensive Database are acknowledged and critically discussed.     

Occurrence of total aflatoxins,ochratoxin A and deoxynivalenol in foodstuffs available on the Lebanese market and their impact on dietary exposure of children and teenagers in Beirut

Mycotoxins are fungal metabolites commonly present in food and constituting a potential threat to food safety. Total aflatoxins (AFT), ochratoxin A (OTA) and deoxynivalenol (DON) are among the most widespread mycotoxins. We assessed the occurrence of AFT, OTA and DON in some foodstuffs available on the Lebanese market and evaluated the potential risk to the health of children and teenagers in Beirut from dietary exposure to these mycotoxins. Analytical data on the contamination of raw and processed cereals and cereal-based products, pulses and nuts were collected. The mean levels of AFT, OTA and DON were calculated for each food items. Levels of dietary exposure were obtained by combining food consumption data with the mean mycotoxin levels, adopting a deterministic approach. Intakes were calculated for average and high consumers (75th and 95th percentile) among children and teenagers, and compared with the provisional tolerable daily intake (PTDI) or provisional tolerable weekly intake (PTWI) of the respective mycotoxin. The results showed that mycotoxin levels in the food samples were generally below national/European maximum limits. However, high levels of AFT, OTA and DON were found in some samples of nuts, biscuits and bread. The calculated intake for AFT exceeded its respective PTDI in all groups by a factor ranging from 3 to 7. The intakes of OTA and DON were found to be below the threshold of toxicological concern established for these mycotoxins by international expert groups, although the intake of DON in children at the highest percentile (P95) was close to its PTDI. Our study highlights the need to reconsider the maximum permissible levels of total aflatoxins in some foodstuffs and to establish regulatory guidelines regarding OTA and DON. The results also emphasise the need for routine monitoring of the levels of mycotoxin contamination in foodstuffs that are highly consumed by Lebanese children and teenagers, i.e. cereals and cereal-based products.     

Expression in insect cells and purification of a catalytically active recombinant human gastric lipase

Human gastric lipase (HGL) cDNA was synthesized by RT-PCR amplificationand cloned into the PVL 1392 baculovirus transfer vector. Therecombinant transfer vector was cotransfected with a modifiedbaculovirus DNA (Baculogold^TM) which contains a lethal deletion.Cotransfection of baculovirus DNA with the recombinant transfervector rescues the lethal deletion of this virus DNA and reconstitutesviable virus particles inside the transfected insect cells.BTI-TN-5B1-4 insect cells (also called High Five^TM cells) wereused to express recombinant HGL. The level of HGL secretionwas {small tilde}32 mg/1 of culture medium. The insect cellsalso accumulated HGL intracellularly, which indicated the existenceof rate-limiting steps in the secretion of HGL. Therefore weinvestigated the effect of replacing the HGL signal peptide(SP) by other SP of secreted proteins. The honeybee melittinSP and the human pancreatic lipase (HPL) SP were tested. Thefusion of HGL with HPL SP resulted in a 2-fold increase in theamount of lipase secreted from the insect cells. The recombinantactive HGL was not processed at the expected cleavage site ofthe natural enzyme, however, but at residue +3. On the otherhand, High Five^TM cells transfected with the vector encodingHGL fused to the melittin SP did not secrete any detectableactive HGL. Recombinant HGL was identified using the Westernblot procedure with rabbit polyclonal antibodies. The proteinmigrated with an apparent molecular mass of 45 kDa under SDS–PAGEanalysis (compared with 50 kDa in the case of natural HGL),indicating that the insect cells have only a limited capacityto glycosylate HGL. The maximum specific activities of the recombinantlipase were 434, 730 and 562 units/mg using long-chain (Intralipid^TM),medium-chain (trioctanoylglycerol) and short-chain (tributyroylglycerol)triacylglycerols, respectively.