Problématique de la régénération naturelle du Prunus avium au nord-ouest de la Tunisie: Influence des facteurs topographiques et édaphiques

The wild cherry (Prunus avium) is a species very appreciated in cabinet making or as root stock for the cherry tree plantations in the Tunisian northwest. Prunus avium is endangered due to its excessive use by local population. It thus seemed necessary to study the process of the natural regeneration by seed of this species. The obtained results showed that the highest rates of regeneration in small plots were observed at medium altitude (400-600 m), with low slope, exposed northward and in loamy soils. This study allowed us to conclude on the importance of the role played by the environment parameters and other climatic factors such as the minimal and maximal temperature in the natural regeneration of this species in our study zone. To be able to conserve and develop Tunisian wild cherries, we recommend using other techniques of multiplication such as cuttings of root segments. Key words: Wild cherry, Tunisia, parameters of the medium, multiplication by sowingLe merisier (Prunus avium) est une espèce très prisée en ébénisterie ou comme porte greffe pour le cerisier dans le nord-ouest tunisien. Prunus avium est menacé de disparition due à son l’utilisation abusive par la population locale. Il est donc apparu nécessaire d’étudier le processus de la régénération naturelle par semis de cette espèce. Les résultats obtenus montrent que le taux de régénération par semis le plus élevé est observé sur les placettes à moyennes altitudes (400-600 m), à faible pente, exposé vers le nord-ouest et sur des sols limoneux. Cette étude nous a permis de conclure l’importance du rôle joué par les paramètres du milieu et d’autres facteurs climatiques comme la température minimale et maximale sur la régénération naturelle de cette espèce au niveau de notre zone d’étude. Pour pouvoir conserver et mettre en valeur les merisiers tunisiens, nous préconisons d’utiliser d’autres techniques de multiplication comme le bouturage de segments de racines. Mots clés: Merisier, Tunisie, paramètres du milieu, multiplication par semi

Population dynamics of ticks infesting sheep in the arid steppes of Tunisia

This study aimed to determine tick population dynamics infesting sheep in Gafsa region (Central Tunisia). Ticks were collected monthly over a year, from October 2013 to September 2014, from 57‒64 randomly-included Barbarine-breed sheep. In total, 560 ticks were collected and identified. They belonged to two species: Rhipicephalus sanguineus sensu lato (98.6%) and Hyalomma excavatum (1.4%). Sheep were only infested from April to October with a maximum infestation prevalence (number of infested animals / number of examined animals) in August for R. sanguineus s.l. (83%), and in May for H. excavatum (7%). The highest infestation intensity (number of ticks / number of infested sheep) was 3.7 ticks per animal in August. These results should help sheep owners and veterinarians to implement efficient control programs against ticks and the pathogens they transmit

A multi-color quantum well photodetector for mid- and long-wavelength infrared detection

The authors report a two-color quantum well infrared photodetector at room temperature operating in the mid- and long-wavelength infrared detection. To this purpose, the band alignment is tailored and electronic properties are investigated for the proposed structure based on Ga1−xInxAsySb1−y/GaSb and AlxGa1−xAsySb1−y/GaSb. As accurate knowledge of band offsets is required in device modeling, we have proceeded to theoretical investigations of the band offsets for pseudo-morphically strained and lattice-matched Ga1−xInxAsySb1−y/GaSb and AlxGa1−xAsySb1−y/GaSb heterointerfaces in the whole range of alloy compositions 0 ≤ x, y ≤ 1. The carrier effective masses are deduced from the laws extracted from the k.p strain Hamiltonian laws. For the modeled heterostructure, the dark current of about 10−1 A cm−2 at ambient temperature shows the high performance of this multi-color infrared photodetector around 5 and 12.5 µm wavelengths