Rayonnement en ondes métriques et décimétriques des orages

This article presents the result of the current knowledge on the very high frequency electromagnetic radiation of lightning. A phenomenology analysis of the new results obtained from the study of triggered lightning in New Mexico (TRIP 82) and at Saint-Privat-d’ Allier in Haute-Loire, France (1983) is first described. The authors then present the spectral and temporal characteristics of the VHF/UHF radiation which can be applied to the electromagnetic compatibility of systems. From a synthesis of the experimental and theoretical contributions, they propose a reflection on the lightning initiation process and on the mechanisms generating lightning radiation.     

Determination of the si-conducting polymer interfacial properties using A-C impedance techniques

A study was made of the interfacial properties of Poly(pyrrole) (PP) deposited electrochemically onto single crystal p-Si surfaces. The interfacial properties are dependent upon the counterions. The formation of “Quasi-Ohmic” and “non-Ohmic” contacts, respectively, of PP(C1O₄) and PP films doped with other counterions (BF₄ and para-toluene sulfonate) with p-Si, are explained in-terms of the conductivity of these films and the flat band potential,V _fb, of PP relative to that ofp-Si. The PP film seems to passivate or block intrinsic surface states present on thep-Si surface. The differences in the impedance behavior of para-toluene sulfonate doped and C1O₄ doped PP are compared.     

Combined Effects of Electron-Beam Irradiation and Storage Time on the Chemical and Antioxidant Parameters of Wild Macrolepiota procera Dried Samples

Mushrooms are very perishable foods due to their high susceptibility to moisture loss, changes in color and texture, or microbiological spoilage. Drying is considered as the most appropriate method to prevent these alterations, but it has some limitations, such as shrinkage, enzymatic and non-enzymatic browning reactions, and oxidation of lipids and vitamins. According to previous studies, irradiation might effectively attenuate the undesirable changes caused by drying process, ensuring also higher shelf-life of mushrooms and their decontamination. Electron-beam irradiation presents some technological advantages, since it allows higher dose rates and the possibility to be used in most foods/or thin products in a short period. Herein, the combined effects of electron-beam irradiation (0, 0.5, 1 and 6 kGy) and storage time (0, 6 and 12 months) were evaluated by measuring changes in nutritional parameters, namely, free sugars, tocopherols, fatty acids and antioxidant activity. As indicated by linear discriminant analysis, storage time had a higher effect on all the evaluated parameters, except fatty acids, which suffer significant changes with both factors. Overall, the obtained results indicate that electron-beam irradiation might be considered as a suitable technique, allowing long-lasting conservation periods while reducing changes induced by drying treatment.     

Juice from king palm (Archontophoenix alexandrae) leaf sheathes: chemical characterisation and use in soft drink formulation

The heart of palm is a food extracted from several species of palm trees. Only 10–20% of the raw material is transformed into canned hearts of palm, therefore this agro‐industry generates a large quantity of solid residue. The aim of this work was to extract and characterise a juice produced from this solid residue. This extract is compared with the traditional fruit juices (orange and pineapple juices), obtaining higher contents of minerals, such as magnesium (22.80 mg/100 g) and potassium (276.90 mg/100 g), phenolic compounds (gallic, 3,4‐dihydroxybenzoic, chlorogenic, syringic and caffeic acids) and high free radical scavenging capacity (expressed as 2,2‐diphenyl‐1‐picrylhydrazyl), which suggest high antioxidant activity. Additionally, a new soft drink was formulated using this king palm juice as its main ingredient. The soft drink samples formulated with this juice had high sensory acceptability and high intention of consumption, which suggests an important and low‐cost application for this industrial residue.     

Cultivars, culture conditions, and harvest time influence phenolic and ascorbic acid contents and antioxidant capacity of strawberry (Fragaria x ananassa)

Strawberries are a good source of micronutrients, especially antioxidant phenolics. More information is needed to better exploit the health-promoting effect of such fruits. Several studies focused on the effects of genotype, cultural practices, and seasonal variation on the antioxidant potential of strawberries, but often yielding contradictory results and/or focusing on only 1 source of variability. In the present study, we showed that total phenolic compounds, ascorbic acid, and antioxidant capacity strongly differed between genotypes of strawberry. The precise results revealed the importance of genetic background for the antioxidant capacity and for the content of total phenolics (with up to 3.3-fold variations). Other parameters may also influence the antioxidant capacity in strawberry such as harvest time, culture conditions, and environmental factors. Moreover, in this study, the harvesting time (at the same ripening stage) appeared to be very important, more important than genotype. Variations of the antioxidant capacity of up to 4.1-folds were observed following the harvesting time of "Elsanta" cultivar. PRACTICAL APPLICATION: This article compares the antioxidant capacity and the content in ascorbic acid and phenolic compounds of strawberries of different varieties and of fruits harvested from April to December at the same ripening stage. The importance of strawberry antioxidant capacity resides in its benefits for human health.