438 research outputs found
First Detection of Mycobacterium ulcerans DNA in Environmental Samples from South America
The occurrences of many environmentally-persistent and zoonotic infections are driven by ecosystem changes, which in turn are underpinned by land-use modifications that alter the governance of pathogen, biodiversity and human interactions. Our current understanding of these ecological changes on disease emergence however remains limited. Buruli ulcer is an emerging human skin disease caused by the mycobacterium, Mycobacterium ulcerans, for which the exact route of infection remains unclear. It can have a devastating impact on its human host, causing extensive necrosis of the skin and underlying tissue, often leading to permanent disability. The mycobacterium is associated with tropical aquatic environments and incidences of the disease are significantly higher on floodplains and where there is an increase of human aquatic activities. Although the disease has been previously diagnosed in South America, until now the presence of M. ulcerans DNA in the wild has only been identified in Australia where there have been significant outbreaks and in western and central regions of Africa where the disease is persistent. Here for the first time, we have identified the presence of the aetiological agent's DNA in environmental samples from South America. The DNA was positively identified using Real-time Polymerase Chain Reaction (PCR) on 163 environmental samples, taken from 23 freshwater bodies in French Guiana (Southern America), using primers for both IS2404 and for the ketoreductase-B domain of the M. ulcerans mycolactone polyketide synthase genes (KR). Five samples out of 163 were positive for both primers from three different water bodies. A further nine sites had low levels of IS2404 close to a standard CT of 35 and could potentially harbour M. ulcerans. The majority of our positive samples (8/14) came from filtered water. These results also reveal the Sinnamary River as a potential source of infection to humans. © 2014 Morris et al
Extending Human Perception of Electromagnetic Radiation to the UV Region through Biologically Inspired Photochromic Fuzzy Logic (BIPFUL) Systems.
Photochromic Fuzzy Logic Systems have been designed that extend human visual perception into the UV region. The systems are founded on a detailed knowledge of the activation wavelengths and quantum yields of a series of thermally reversible photochromic compounds. By appropriate matching of the photochromic behaviour unique colour signatures are generated in response differing UV activation frequencies
Evidence for Spinodal Decomposition in Nuclear Multifragmentation
Multifragmentation of a ``fused system'' was observed for central collisions
between 32 MeV/nucleon 129Xe and natSn. Most of the resulting charged products
were well identified thanks to the high performances of the INDRA 4pi array.
Experimental higher-order charge correlations for fragments show a weak but non
ambiguous enhancement of events with nearly equal-sized fragments. Supported by
dynamical calculations in which spinodal decomposition is simulated, this
observed enhancement is interpreted as a ``fossil'' signal of spinodal
instabilities in finite nuclear systems.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Letter
Response of CsI(Tl) scintillators over a large range in energy and atomic number of ions (Part I): recombination and delta -- electrons
A simple formalism describing the light response of CsI(Tl) to heavy ions,
which quantifies the luminescence and the quenching in terms of the competition
between radiative transitions following the carrier trapping at the Tl
activator sites and the electron-hole recombination, is proposed. The effect of
the delta rays on the scintillation efficiency is for the first time
quantitatively included in a fully consistent way. The light output expression
depends on four parameters determined by a procedure of global fit to
experimental data.Comment: 28 pages, 6 figures, submitted to Nucl. Inst. Meth.
Landscape Diversity Related to Buruli Ulcer Disease in Côte d'Ivoire
Buruli ulcer (BU) is one of the most neglected but treatable tropical diseases. The causative organism, Mycobacterium ulcerans, is from the family of bacteria that causes tuberculosis and leprosy. This severe skin disease leads to long-term functional disability if not treated. BU has been reported in over 30 countries mainly with tropical and subtropical climates, but Côte d'Ivoire is one of the most affected countries. M. ulcerans is an environmental bacterium and its mode of transmission to humans is still unclear, such that the disease is often referred to as the “mysterious disease” or the “new leprosy”. Here, we explored the relationship between environmental and socioeconomic factors and BU cases on a nationwide scale. We found that irrigated rice field cultures areas, and, to a lesser extent, banana fields as well as areas in the vicinity of dams used for irrigation and aquaculture purposes, represent high risk zones for the human population to contract BU in Côte d'Ivoire. This work identifies high-risk areas for BU in Côte d'Ivoire and deserves to be extended to different countries. We need now to obtain a global vision and understanding of the route of transmission of M. ulcerans to humans in order to better implement control strategies
Multifragmentation process for different mass asymmetry in the entrance channel around the Fermi energy
The influence of the entrance channel asymmetry upon the fragmentation
process is addressed by studying heavy-ion induced reactions around the Fermi
energy. The data have been recorded with the INDRA 4pi array. An event
selection method called the Principal Component Analysis is presented and
discussed. It is applied for the selection of central events and furthermore to
multifragmentation of single source events. The selected subsets of data are
compared to the Statistical Multifragmentation Model (SMM) to check the
equilibrium hypothesis and get the source characteristics. Experimental
comparisons show the evidence of a decoupling between thermal and compresional
(radial flow) degrees of freedom in such nuclear systems.Comment: 28 pages, 15 figures, article sumitted to Nuclear Physics
GENETIC EVALUATION OF SEED TRAITS FROM INTRASPECIFIC CROSSING OF GENETICALLY DISTINCT WATERMELON VARIETIES
Citrullus lanatus (Thunb.) Matsumura and Nakai (Cucurbitaceae) is an
important cucurbit crop worldwide. Global production of watermelon is
about 90 million metric tonnes per annum, making it among the top five
most consumed fresh fruits. The objective of this study was to evaluate
seed variability in different segregating populations, and determine
heritability of traits of watermelon. Interspecific crosses were made
between two cultivars of C. lanatus (Bebu and Wl\ueawl\uea Small
Seeds (WSS) were performed at Research Station of Nangui Abrogoua
University in Abidjan, C\uf4te d\u2019Ivoire. There was wide
variability between parental, F1, BC1 (first generation of
back-crossing) and F2 seeds. Seeds of all hybrid populations were
intermediate versus those of the parents. Also, crossing did not affect
F1 and F2 seed characters, but affected those of BC1 because of
maternal effects. Thus, back-crossing on Bebu cultivar produced seeds
which looked like those of Bebu; while back-crossing on WSS cultivar
produced seeds similar to those of WSS. Principal Component Analysis
(PCA) and individuals repartitioning revealed that Bebu and WSS
cultivars were genetically distinct and showed three main groups: two
groups from each parental line and one from a recombinant line
(hybrids). F2 population had a wide individual\u2019s dispersion, and
contained seeds of all other populations. High heritability was
observed for all evaluated characters.Citrullus lanatus (Thunb.) Matsumara et Nakai (Cucurbitac\ue9e) est
une importante cucurbite dans le monde entier. La production annuelle
globale est d\u2019environ 90 million de tonne, ce qui place cette
culture parmi les cinq fruits les plus consomm\ue9s crus.
L\u2019objectif de cette \ue9tude est d\u2019\ue9valuer la
variabilit\ue9 des graines de diff\ue9rentes populations en
s\ue9gr\ue9gation et de d\ue9terminer
l\u2019h\ue9ritabilit\ue9 des caract\ue8res chez
l\u2019esp\ue8ce Citrullus lanatus. Pour cela, un croisement
intersp\ue9cifique entre deux cultivars de Citrullus lanatus (Bebu et
Wl\ueawl\uea \ue0 petites graines (WSS)) a \ue9t\ue9
effectu\ue9 \ue0 la station de recherche de l\u2019Universit\ue9
Nangui Abrogoua d\u2019Abidjan (C\uf4te d\u2019Ivoire). Il existe
une variabilit\ue9 importante entre les graines parentales, F1, BC1
(premi\ue8re g\ue9n\ue9ration de back-cross) et F2. Les graines
de toutes les populations hybrides sont interm\ue9diaires \ue0
celles des parents. Aussi, le sens de croisement n\u2019affecte pas
les caract\ue8res des graines F1 et F2 mais affecte ceux des graines
BC1 \ue0 cause de l\u2019effet maternel. Ainsi, un backcross
effectu\ue9 sur le cultivar Bebu produit des graines semblables aux
graines de Bebu tandis qu\u2019un backcross effectu\ue9 sur le
cultivar WSS produit des graines semblables aux graines de WSS.
L\u2019Analyse en Composantes Principales et la r\ue9partition des
individus dans le plan permettent d\u2019observer que les cultivars
Bebu et WSS sont g\ue9n\ue9tiquement distincts et montrent trois
principaux groupes\ua0: deux groupes de chaque type parental et un
type recombinant (hybride). La population F2 a une large dispersion et
se compose des graines de toutes les autres populations. Une forte
h\ue9ritabilit\ue9 a \ue9t\ue9 observ\ue9e pour tous les
caract\ue8res \ue9valu\ue9s. En somme, la variabilit\ue9 des
graines observ\ue9es dans les populations en s\ue9gr\ue9gation
chez C. lanatus pourrait \ueatre due \ue0 des effets
g\ue9n\ue9tique
Multifragmentation in Xe(50A MeV)+Sn Confrontation of theory and data
We compare in detail central collisions Xe(50A MeV) + Sn, recently measured
by the INDRA collaboration, with the Quantum Molecular Dynamics (QMD) model in
order to identify the reaction mechanism which leads to multifragmentation. We
find that QMD describes the data quite well, in the projectile/target region as
well as in the midrapidity zone where also statistical models can be and have
been employed. The agreement between QMD and data allows to use this dynamical
model to investigate the reaction in detail. We arrive at the following
observations: a) the in medium nucleon nucleon cross section is not
significantly different from the free cross section, b) even the most central
collisions have a binary character, c) most of the fragments are produced in
the central collisions and d) the simulations as well as the data show a strong
attractive in-plane flow resembling deep inelastic collisions e) at midrapidity
the results from QMD and those from statistical model calculations agree for
almost all observables with the exception of . This
renders it difficult to extract the reaction mechanism from midrapidity
fragments only. According to the simulations the reaction shows a very early
formation of fragments, even in central collisions, which pass through the
reaction zone without being destroyed. The final transverse momentum of the
fragments is very close to the initial one and due to the Fermi motion. A
heating up of the systems is not observed and hence a thermal origin of the
spectra cannot be confirmed.Comment: figures 1 and 2 changed (no more ps -errors
Measurements of sideward flow around the balance energy
Sideward flow values have been determined with the INDRA multidetector for
Ar+Ni, Ni+Ni and Xe+Sn systems studied at GANIL in the 30 to 100 A.MeV incident
energy range. The balance energies found for Ar+Ni and Ni+Ni systems are in
agreement with previous experimental results and theoretical calculations.
Negative sideward flow values have been measured. The possible origins of such
negative values are discussed. They could result from a more important
contribution of evaporated particles with respect to the contribution of
promptly emitted particles at mid-rapidity. But effects induced by the methods
used to reconstruct the reaction plane cannot be totally excluded. Complete
tests of these methods are presented and the origins of the
``auto-correlation'' effect have been traced back. For heavy fragments, the
observed negative flow values seem to be mainly due to the reaction plane
reconstruction methods. For light charged particles, these negative values
could result from the dynamics of the collisions and from the reaction plane
reconstruction methods as well. These effects have to be taken into account
when comparisons with theoretical calculations are done.Comment: 27 pages, 15 figure
Effect of the intermediate velocity emissions on the quasi-projectile properties for the Ar+Ni system at 95 A.MeV
The quasi-projectile (QP) properties are investigated in the Ar+Ni collisions
at 95 A.MeV taking into account the intermediate velocity emission. Indeed, in
this reaction, between 52 and 95 A.MeV bombarding energies, the number of
particles emitted in the intermediate velocity region is related to the overlap
volume between projectile and target. Mean transverse energies of these
particles are found particularly high. In this context, the mass of the QP
decreases linearly with the impact parameter from peripheral to central
collisions whereas its excitation energy increases up to 8 A.MeV. These results
are compared to previous analyses assuming a pure binary scenario
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