X-radiation of the moon and Roentgen cosmic background according to data of AMS ''Luna-12''

Satellite measurements of lunar soft X radiation, and Roentgen cosmic backgroun

X-Ray Polarization of Solar Flares Measured with Rhessi

The degree of linear polarization in solar flares has not yet been precisely determined despite multiple attempts to measure it with different missions. The high energy range in particular has very rarely been explored, due to its greater instrumental difficulties. We approached the subject using the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) satellite to study 6 X-class and 1 M-class flares in the energy range between 100 keV and 350 keV. Using RHESSI as a polarimeter requires the application of strict cuts to the event list in order to extract those photons that are Compton scattered between two detectors. Our measurements show polarization values between 2% and 54%, with errors ranging from 10% to 26% in 1 sigma level. In view of the large uncertainties in both the magnitude and direction of the polarization vector, the results can only reject source models with extreme properties.Comment: 26 pages, 11 figures, accepted for publication by Solar Physic

Genetic Structure, Nestmate Recognition and Behaviour of Two Cryptic Species of the Invasive Big-Headed Ant Pheidole megacephala

info:eu-repo/semantics/publishe

Record of new host plants associated to the invasive mealybug species Paracoccus marginatus Williams and Granara de Willink (Hemiptera: Pseudococcidae) in the Center and Littoral regions of Cameroon.

Published online: 07 Jan 2021The papaya mealybug (PM) is a known notorious polyphagous insect pest of many plant species and has always been found associated with a new host/s in newly invaded areas. This pest recently invaded West and Central Africa. Surveys were conducted randomly from July 2014 to May 2018 to determine the host range of this pest in the Center and Littoral regions in Cameroon. Plants infested by PM were recognized by the presence of black sooty mould, leaf deformation and/or chlorosis. A standard infestation scale was used to evaluate the infestation level on each plant. After collection, infested plants were pressed, dried and identified at the national Herbarium. A total of 52 plant species (only one undetermined) belonging to 23 families were found infested by PM associated with other mealybug or with two species of mealybugs with a percentage of (79.2%, N = 75) and (20.8%, N = 75) respectively. Two plant families (out of 23 identified) and 18 plant species (out of 52 infested) were reported as host plants for the first time. The Euphorbiaceae, Malvaceae and Solanaceae are the most infested families. In addition to plant species from its native zone (tropical America), PM has established new associations with plants from tropical Africa. Carica papaya and ten additional plants were categorized as favored hosts of P. marginatus. These results will be very useful to develop appropriate management options for PM in West and Central Africa

M-CLANN: Multi-class Concept Lattice-Based Artificial Neural Network for Supervised Classification

International audienc

Une approche basée sur les treillis de Galois pour la construction des réseaux de neurones

National audienc

CLANN : Concept Lattice-based Artificial Neural Networks for supervised classification

12 pagesInternational audienc

Une étude des algorithmes de constructions d'architecture des réseaux de neurones multicouches

National audienc

Field abundance and nest structure of the ant Anoplolepis tenella associated with the African root and tuber scale in the Congo Basin

Anoplolepis tenella is a ground-dwelling ant of the tropical forest zone of Central Africa. It is associated with the African root and tuber scale (ARTS), Stictococcus vayssierei Richard, an emerging cassava pest in the zone. Developing sustainable and effective methods to control ARTS requires basic knowledge of the biology of A. tenella and the nature of interactions between the two insects. A study on the nest distribution and composition of A. tenella in various vegetation types prevailing in Central and South Provinces of Cameroon was conducted from April 2002 to June 2005. The results show that nests are generally built at the base of ARTS infested plants (96.2%; N = 469) - mainly under cassava plants (93.8%; N = 469).  Densities of A. tenella nests are higher in cassava fields (1600 nests per ha) compared with their densities in fallows (400 nests per ha), in secondary forest (90 nests per ha), and in primary forest (50 nests per ha). As with nest of other subterranean ants, the internal structure of A. tenella nest consists of cavities inter connected by a set of galleries. Relatively low percentage (13.7%, N = 51) of nests were queen-less, while those with queens were strongly polygynous (up to seven queens per nest) and with an estimate of 476 ± 255 (Mean ± SD) workers per nest. The brood (larvae and pupae) of sexual individuals appears in the nests from June to August, while sexual individuals can be found in the nests from June to September. Nuptial flights occurred between August and September. The high densities of the nests in disturbed areas in addition to polygyny are indications that A. tenella may share some characteristics with tramp ant species