365 research outputs found
On the finiteness of the moments of the measure of level sets of random fields
General conditions on smooth real valued random fields are given that ensure the finiteness of the moments of the measure of their level sets. As a by product a new generalized Kac-Rice formula (KRF) for the expectation of the measure of these level sets is obtained when the second moment can be uniformly bounded. The conditions involve (i) the differentiability of the trajectories up to a certain order k, (ii) the finiteness of the moments of the k-th partial derivatives of the field up to another order, (iii) the boundedness of the joint density of the field and some of its derivatives. Particular attention is given to the shot noise processes and fields. Other applications include stationary Gaussian processes, Chi-square processes and regularized diffusion processes. AMS2000 Classifications: Primary 60G60. Secondary 60G15
An introductory study of house spiders (Araneae) in Belgium
More than 800 spiders were collected in 43 houses heated in winter, distributed mainly in the northern part of Belgium. Information required for the collections to be eligible for the project was: address, construction year, type of house, and surroundings. The spiders were qualified as âhouse spidersâ or âgarden spidersâ. Of the 93 species collected, 19 could be defined as house spiders. Pholcus phalangioides was the most common, followed by Eratigena atrica and Steatoda triangulosa. Garden spiders enter the house much more often in houses in a rural environment than in those situated in clusters, and mainly in spring. The spiders are most common in autumn when many of them are breeding. The common house spiders colonize houses shortly after their construction
Continuously varying coupled transmission lines applied to design band-pass filters
International audienceThis article presents a technique to analyze and optimize Continuously Varying Transmission Lines (CVTL's), used to design microwave band-pass filters in planar technology. For millimeters waves, radiation losses can increase quickly, especially for sharp discontinuities in planar circuits. In this approach, rather than taking account of this effect in a full-wave analysis, we generate structures without discontinuities. Moreover, the line shape is optimized to reduce spurious responses out of the band-pass. For several filters, measurements are compared with simulation results
First Isolation and Direct Evidence for the Existence of Large Small-Mammal Reservoirs of Leptospira sp. in Madagascar
Background: Leptospirosis has long been a major public health concern in the southwestern Indian Ocean. However, in Madagascar, only a few, old studies have provided indirect serological evidence of the disease in humans or animals. Methodology/Principal Findings: We conducted a large animal study focusing on small-mammal populations. Five field trapping surveys were carried out at five sites, from April 2008 to August 2009. Captures consisted of Rattus norvegicus (35.8%), R. rattus (35.1%), Mus musculus (20.5%) and Suncus murinus (8.6%). We used microbiological culture, serodiagnosis tests (MAT) and real-time PCR to assess Leptospira infection. Leptospira carriage was detected by PCR in 91 (33.9%) of the 268 small mammals, by MAT in 17 of the 151 (11.3%) animals for which serum samples were available and by culture in 9 of the 268 animals (3.3%). Rates of infection based on positive PCR results were significantly higher in Moramanga (54%), Toliara (48%) and Mahajanga (47.4%) than in Antsiranana (8.5%) and Toamasina (14%) (p = 0.001). The prevalence of Leptospira carriage was significantly higher in R. norvegicus (48.9%), S. murinus (43.5%) and R. rattus (30.8%) than in M. musculus (9.1%) (p < 0.001). The MAT detected antibodies against the serogroups Canicola and Icterohaemorrhagiae. Isolates were characterized by serology, secY sequence-based phylogeny, partial sequencing of rrs, multi-locus VNTR analysis and pulsed field gel electrophoresis. The 10 isolates obtained from nine rats were all identified as species L. interrogans serogroup Canicola serovar Kuwait and all had identical partial rrs and secY sequences. Conclusions/Significance: We present here the first direct evidence of widespread leptospiral carriage in small mammals in Madagascar. Our results strongly suggest a high level of environmental contamination, consistent with probable transmission of the infection to humans. This first isolation of pathogenic Leptospira strains in this country may significantly improve the detection of specific antibodies in human cases
Trace-element imaging at macroscopic scale in a Belgian sphalerite-galena ore using Laser-Induced Breakdown Spectroscopy (LIBS)
Laser-Induced Breakdown Spectroscopy (LIBS) is a fast in-situ analytical technique based on spectroscopic analysis of atomic emission in laser-induced plasmas. Geochemical mapping at macroscopic scale using LIBS was applied to a decimetric Zn-Pb ore sample from east Belgium, which consists of alternating sphalerite and galena bands. A range of elements was detected with
no or minimal spectral correction, including elements of interest for beneficiation such as Ge, Ag and Ga (although the detection of gallium could not be confirmed), and remediation, especially As and Tl. The comparison between LIBS and Energy Dispersive Spectroscopy (EDS) analyses showed that LIBS intensities reliably relate to elemental concentration although differences in spot size
and detection limits exist between both techniques. The elemental images of minor and trace elements (Fe, Cu, Ag, Cd, Sb, As, Tl, Ge, Ni and Ba) obtained with LIBS revealed with great detail the compositional heterogeneity of the ore, including growth zones that were not visible on the specimen. In addition, each mineral generation has a distinct trace-element composition, reflecting a geochemical sequence whose potential metallogenic significance at the district scale should be addressed in further work. Although qualitative and preliminary, the obtained LIBS dataset already produced a wealth of information that allowed to initiate discussion on some genetical and crystallochemical aspects. Above all, LIBS appears as a powerful tool for screening geochemically large samples for the selection of zones of particular interest for further analysis.LIBS Scree
Exploratory meta-analysis of anthropogenic disturbances on amphibian diversity in the Kasugho, Butembo, Mambasa and Kisangani stations in the Democratic Republic of the Congo
peer reviewedCe travail prĂ©sente les rĂ©sultats dâune mĂ©ta-analyse de quatre Ă©tudes menĂ©es sur les Amphibiens Ă Kasugho, Butembo, Mambasa et Kisangani en RĂ©publique DĂ©mocratique du Congo. Lâobjectif principal Ă©tait de vĂ©rifier le lien entre le taux dâanthropisation des habitats et la frĂ©quence des espĂšces observĂ©es afin dâidentifier dâĂ©ventuelles espĂšces indicatrices des perturbations anthropiques. Lâobservation directe a gĂ©nĂ©rĂ© 815 Amphibiens capturĂ©s dans les habitats anthropisĂ©s (Ă©tang piscicole, jachĂšre) et non anthropisĂ©s (marĂ©cage, forĂȘt secondaire, forĂȘt primaire). Sur les 37 espĂšces identifiĂ©es, 2 (Amietophrynus kisoloensis, Hoplobatrachus occipitalis) vivent uniquement dans les habitats anthropisĂ©s et 11 (Afrixalus quadrivittatus, Amietophrynus gracilipes, Arthroleptis variabilis, Cardioglossa gracilis, C. leucomystax, Hyperolius viridiflavus, Leptopelis aubryioides, L. ocellatus, Phrynobatrachus auritus, Ptychadena anchietae, P. chrysogaster) prĂ©fĂšrent uniquement les habitats non anthropisĂ©s. La plus forte similaritĂ© entre les habitats anthropisĂ©s et non anthropisĂ©s a Ă©tĂ© observĂ©e Ă Mambasa (Ă©tang piscicole, marĂ©cage, jachĂšre, forĂȘt secondaire, forĂȘt primaire) et la plus faible entre les habitats Ă Butembo (marĂ©cage, jachĂšre). Un test de Chi-carrĂ© souligne un lien entre le statut dâhabitat et les abondances dâAmphibiens. Une corrĂ©lation linĂ©aire significative confirme quâil nây a pas de relation directe entre les frĂ©quences dans les deux statuts dâhabitat. La prĂ©sente Ă©tude confirme le potentiel des Amphibiens comme indicateurs de perturbations anthropiques des Ă©cosystĂšmes
Peering into the dark (ages) with low-frequency space interferometers: Using the 21-cm signal of neutral hydrogen from the infant universe to probe fundamental (Astro)physics.
The Dark Ages and Cosmic Dawn are largely unexplored windows on the infant Universe (zâ~â200-10). Observations of the redshifted 21-cm line of neutral hydrogen can provide valuable new insight into fundamental physics and astrophysics during these eras that no other probe can provide, and drives the design of many future ground-based instruments such as the Square Kilometre Array (SKA) and the Hydrogen Epoch of Reionization Array (HERA). We review progress in the field of high-redshift 21-cm Cosmology, in particular focussing on what questions can be addressed by probing the Dark Ages at zâ>â30. We conclude that only a space- or lunar-based radio telescope, shielded from the Earth's radio-frequency interference (RFI) signals and its ionosphere, enable the 21-cm signal from the Dark Ages to be detected. We suggest a generic mission design concept, CoDEX, that will enable this in the coming decades
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