251 research outputs found
Moroccan Leishmania infantum: genetic diversity and population structure as revealed by multi-locus microsatellite typing
Low energy neutron propagation in MCNPX and GEANT4
Simulations of neutron background from rock for underground experiments are
presented. Neutron propagation through two types of rock, lead and hydrocarbon
material is discussed. The results show a reasonably good agreement between
GEANT4, MCNPX and GEANT3 in transporting low-energy neutrons.Comment: 9 Figure
Neutron- and muon-induced background in underground physics experiments
Background induced by neutrons in deep underground laboratories is a critical
issue for all experiments looking for rare events, such as dark matter
interactions or neutrinoless 2-beta decay. Neutrons can be produced either by
natural radioactivity, via spontaneous fission or (alpha,n) reactions, or by
interactions initiated by high-energy cosmic rays. In all underground
experiments, Monte Carlo simulations of neutron background play a crucial role
for the evaluation of the total background rate and for the optimization of
rejection strategies. The Monte Carlo methods that are commonly employed to
evaluate neutron-induced background and to optimize the experimental setup, are
reviewed and discussed. Focus is given to the issue of reliability of Monte
Carlo background estimates.Comment: 10 pages, 8 figures. Presented in the IV ILIAS Annual Meeting.
Accepted for publication on EPJ
First measurement of low intensity fast neutron background from rock at the Boulby Underground Laboratory
A technique to measure low intensity fast neutron flux has been developed.
The design, calibrations, procedure for data analysis and interpretation of the
results are discussed in detail. The technique has been applied to measure the
neutron background from rock at the Boulby Underground Laboratory, a site used
for dark matter and other experiments, requiring shielding from cosmic ray
muons. The experiment was performed using a liquid scintillation detector. A
6.1 litre volume stainless steel cell was filled with an in-house made liquid
scintillator loaded with Gd to enhance neutron capture. A two-pulse signature
(proton recoils followed by gammas from neutron capture) was used to identify
the neutron events from much larger gamma background from PMTs. Suppression of
gammas from the rock was achieved by surrounding the detector with high-purity
lead and copper. Calibrations of the detector were performed with various gamma
and neutron sources. Special care was taken to eliminate PMT afterpulses and
correlated background events from the delayed coincidences of two pulses in the
Bi-Po decay chain. A four month run revealed a neutron-induced event rate of
1.84 +- 0.65 (stat.) events/day. Monte Carlo simulations based on the GEANT4
toolkit were carried out to estimate the efficiency of the detector and the
energy spectra of the expected proton recoils. From comparison of the measured
rate with Monte Carlo simulations the flux of fast neutrons from rock was
estimated as (1.72 +- 0.61 (stat.) +- 0.38 (syst.))*10^(-6) cm^(-2) s^(-1)
above 0.5 MeV.Comment: 37 pages, 24 figures, to be published in Astroparticle Physic
Phlebotomus sergenti in a Cutaneous Leishmaniasis Focus in Azilal Province (High Atlas, Morocco): Molecular Detection and Genotyping of Leishmania tropica, and Feeding Behavior
International audienceBackground Phlebotomus (Paraphlebotomus) sergenti is at least one of the confirmed vectors for the transmission of cutaneous leishmaniasis caused by Leishmania tropica and distributed widely in Morocco. This form of leishmaniasis is considered largely as anthroponotic, although dogs were found infected with Leishmania tropica, suggestive of zoonosis in some rural areas. Methodology and Findings This survey aimed at (i) studying the presence of Leishmania in field caught Phlebotomus sergenti, (ii) investigating genetic diversity within Leishmania tropica and (iii) identifying the host-blood feeding preferences of Phlebotomus sergenti. A total of 4,407 sand flies were collected in three rural areas of Azilal province, using CDC miniature light traps. Samples collected were found to consist of 13 species: Phlebotomus spp. and 3 Sergentomyia spp. The most abundant species was Phlebotomus sergenti, accounting for 45.75% of the total. 965 female Phlebotomus sergenti were screened for the presence of Leishmania by ITS1-PCR-RFLP, giving a positive rate of 5.7%(55/965), all being identified as Leishmania tropica. Nucleotide heterogeneity of PCR-amplified ITS1-5.8S rRNA gene-ITS2 was noted. Analyses of 31 sequences obtained segregated them into 16 haplotypes, of which 7 contain superimposed peaks at certain nucleotide positions, suggestive of heterozygosity. Phlebotomus sergenti collected were found to feed on a large variety of vertebrate hosts, as determined by Cytochrome b sequencing of the DNA from the blood meals of 64 engorged females. Conclusion Our findings supported the notion that Phlebotomus sergenti is the primary vector of Leishmania tropica in this focus, and that the latter is genetically very heterogeneous. Furthermore, our results might be suggestive of a certain level of heterozygosity in Leishmania tropica population. This finding, as well as the feeding of the vectors on different animals are of interest for further investigation
Machine-Related Backgrounds in the SiD Detector at ILC
With a multi-stage collimation system and magnetic iron spoilers in the
tunnel, the background particle fluxes on the ILC detector can be substantially
reduced. At the same time, beam-halo interactions with collimators and
protective masks in the beam delivery system create fluxes of muons and other
secondary particles which can still exceed the tolerable levels for some of the
ILC sub-detectors. Results of modeling of such backgrounds in comparison to
those from the e+ e- interactions are presented in this paper for the SiD
detector.Comment: 29 pages, 34 figures, 7 table
Moroccan Leishmania infantum: Genetic Diversity and Population Structure as Revealed by Multi-Locus Microsatellite Typing
Leishmania infantum causes Visceral and cutaneous leishmaniasis in northern Morocco. It predominantly affects
children under 5 years with incidence of 150 cases/year. Genetic variability and population structure have been
investigated for 33 strains isolated from infected dogs and humans in Morocco. A multilocus microsatellite typing
(MLMT) approach was used in which a MLMtype based on size variation in 14 independent microsatellite markers
was compiled for each strain. MLMT profiles of 10 Tunisian, 10 Algerian and 21 European strains which belonged to
zymodeme MON-1 and non-MON-1 according to multilocus enzyme electrophoresis (MLEE) were included for
comparison. A Bayesian model-based approach and phylogenetic analysis inferred two L.infantum sub-populations;
Sub-population A consists of 13 Moroccan strains grouped with all European strains of MON-1 type; and subpopulation
B consists of 15 Moroccan strains grouped with the Tunisian and Algerian MON-1 strains. Theses subpopulations
were significantly different from each other and from the Tunisian, Algerian and European non MON-1
strains which constructed one separate population. The presence of these two sub-populations co-existing in
Moroccan endemics suggests multiple introduction of L. infantum from/to Morocco; (1) Introduction from/to the
neighboring North African countries, (2) Introduction from/to the Europe. These scenarios are supported by the
presence of sub-population B and sub-population A respectively. Gene flow was noticed between sub-populations A
and B. Five strains showed mixed A/B genotypes indicating possible recombination between the two populations.
MLMT has proven to be a powerful tool for eco-epidemiological and population genetic investigations of Leishmania.The fieldwork and data collection was granted by Pastur Institute in Morocco for Dr. Meryem Lemrani. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Identification of backgrounds in the EDELWEISS-I dark matter search experiment
This paper presents our interpretation and understanding of the different
backgrounds in the EDELWEISS-I data sets. We analyze in detail the several
populations observed, which include gammas, alphas, neutrons, thermal sensor
events and surface events, and try to combine all data sets to provide a
coherent picture of the nature and localisation of the background sources. In
light of this interpretation, we draw conclusions regarding the background
suppression scheme for the EDELWEISS-II phase
Risk and protective factors for drug dependence in two Moroccan high-risk male populations
Background Substance use is linked to biological, environmental, and social factors. This study provides insights on protective and risk factors for drug dependence in two Moroccan, high-risk, male samples. Methods Data from the “Mental and Somatic Health without borders” (MeSHe) survey were utilized in the present study. The MeSHe survey assesses somatic and mental health parameters by self-report from prison inmates (n = 177) and outpatients from an addiction institution (n = 54). The “Drug dependence” and the “No drug dependence” groups were identified based on the Arabic version of the Drug Use Disorder Identification Test’s (DUDIT) validated cutoff for identifying individuals with drug dependence, specifically in Morocco. Results The majority of participants who had at least high school competence (67.6%), were living in a partnership (53.7%), were a parent (43.1%), and/or had a job (86.8%) belonged to the “No drug dependence” group, while the presence of mental health problems was typical among the “Drug dependence” group (47.4%). A multivariable regression model (χ2 (df = 5, N = 156) = 63.90, p < 0.001) revealed that the presence of depression diagnosis remains a significant risk factor, while a higher level of education, having a child, and being employed are protective factors from drug dependence. Discussion Findings support the importance of increasing academic competence and treating depression as prevention from the persistence of drug addiction in male high-risk populations
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