Variations saisonnières de la contamination microbienne de la zone urbaine d'une lagune tropicale estuarienne

Vingt-six campagnes bimensuelles ont été réalisées au cours d'un cycle annuel (juillet 1987-juillet 1988) pour estimer le degré de contamination fécale des eaux (de surface et à l'interface eau/sédiment) de la zone urbaine (Abidjan) de la lagune Ebrié (Côte d'Ivoire). Les dénombrements de #E. coli, des entérocoques et #C. perfringens ont été couplés à une caractérisation physique des eaux (salinité, pH, température) et à une estimation de leur richesse en éléments nutritifs (N-NH4, P-PO4). Dans un contexte estuarien naturellement eutrophe, les apports domestiques de la ville d'Abidjan se traduisent par une hypereutrophie des eaux et par un très important accroissement du degré de contamination fécale principalement des eaux de surface. Cette pollution est en moyenne 500 fois vis-à-vis de #E. coli et 70 fois pour les entérocoques supérieure à celle observée pour une zone estuarienne rurale de référence. Cette très forte pollution bactérienne d'origine humaine (rapport #E. coli/entérocoques >40), rend impropre à la baignade les eaux lagunaires d'Abidja

Ecology of halophilic vibrios in an eutrophic tropical estuary

La distribution de #V. parahaemolyticus et le biotype apparenté #V. alginolyticus a été étudiée dans la zone urbaine de la lagune Ebrié (Abidjan, Côte d'Ivoire) au cours d'un cycle annuel. Au total 501 échantillons (eau de surface et de l'interface eau/sédiment) ont été bactériologiquement analysés pour la présence de ces vibrions halophiles. En tout, 16% de #V. parahaemolyticus$et 16$ ont été isolés des eaux de surface et du fond. Aucune différence majeure n'existe entre les populations des vibrions dans les eaux de surface et du fond. L'occurence saisonnière de ces espèces dans les échantillons ne montre aucune différence majeure entre les saisons de pluies et de crue et la saison sèche. Les fréquences d'isolement groupées en classes de salinité montrent que les 2 espèces sont présentes dans les eaux dont la salinité varie entre 0 et 35%, bien que les plus hautes fréquences d'isolement s'obtiennent quand la salinité est autour de 25%. Aucune corrélation significative entre #V. parahaemolyticus et #V. alginolyticus avec #E. coli et #Enterococcus n'a été observée. (Résumé d'auteur

Are parenting practices associated with the same child outcomes in Sub-Saharan African countries as in high income countries? A review and synthesis

Introduction: There is increasing interest in the transferability of parenting interventions from high-income countries (HICs) to low-income countries (LICs) in order to improve child development and health outcomes. This is based on the premise that associations between parenting practices and child outcomes are similar in both settings. Many parenting interventions in HICs are evidence-based, but less evidence exists on associations of parenting practices with child outcomes in LICs, in particular, sub-Saharan African (SSA) countries. This review synthesises evidence on the association of parenting practices with child outcomes in SSA in order to compare findings with those from HICs. Methods: We searched electronic databases—Web of Science, ASSIA, Embase, IBSS and PsycINFO—to identify studies from SSA that reported quantitative associations between parenting practices and child health or psychosocial outcomes (eg, sexual and reproductive health (SRH), mental health, conduct disorders). Due to inconsistent conceptual framing of parenting across studies, we used a modified version of the international WHO classification of parenting dimensions to guide synthesis of the results. Results: Forty-four studies met our inclusion criteria. They were conducted in 13 SSA countries and included cross-sectional and longitudinal studies, and were predominantly descriptive studies rather than intervention research. Synthesis of results showed that associations between patterns of parenting (‘positive’/‘harsh’) and child outcomes (including SRH, mental health and conduct disorders) in studies from SSA were broadly similar to those found in HICs. Conclusions: These findings suggest that the impacts of parenting practices on child outcomes are similar across contrasting global regions and, therefore, parenting interventions from HICs might be successfully transferred to SSA, subject to appropriate adaptation. However, this review also highlights the paucity of evidence in this area and the urgent need for higher quality studies to confirm these findings to help develop effective parenting interventions in SSA

Efficient Computations of Encodings for Quantum Error Correction

We show how, given any set of generators of the stabilizer of a quantum code, an efficient gate array that computes the codewords can be constructed. For an n-qubit code whose stabilizer has d generators, the resulting gate array consists of O(n d) operations, and converts k-qubit data (where k = n - d) into n-qubit codewords.Comment: 16 pages, REVTeX, 3 figures within the tex

On beach cusp formation

A system of shallow water equations and a bed evolution equation are used to examine the evolution of perturbations on an erodible, initially plane beach subject to normal wave incidence. Both a permeable (under Darcy's law) and an impermeable beach are considered. It is found that alongshore-periodic morphological features reminiscent of swash beach cusps form after a number of incident wave periods on both beaches. On the permeable (impermeable) beach these patterns are accretional (erosional). In both cases flow is ‘horn divergent’. Spacings of the cusps are consistent with observations, and are close to those provided by a standing synchronous linear edge wave. An analysis of the processes leading to bed change is presented. Two physical mechanisms are identified: concentration gradient and flow divergence, which are dominant in the lower and upper swash respectively, and their difference over a wave cycle leads to erosion or deposition on an impermeable beach. Infiltration enters this balance in the upper swash. A bed wave of elevation is shown to advance up the beach at the tip of the uprush, with a smaller wave of depression on the backwash. It is found that cusp horns can grow by a positive feedback mechanism stemming from decreased (increased) backwash on positive (negative) bed perturbations.Postprint (published version

Functional and genetic evidence that nucleoside transport is highly conserved in Leishmania species: Implications for pyrimidine-based chemotherapy

Leishmania pyrimidine salvage is replete with opportunities for therapeutic intervention with enzyme inhibitors or antimetabolites. Their uptake into cells depends upon specific transporters; therefore it is essential to establish whether various Leishmania species possess similar pyrimidine transporters capable of drug uptake. Here, we report a comprehensive characterization of pyrimidine transport in L. major and L. mexicana. In both species, two transporters for uridine/adenosine were detected, one of which also transported uracil and the antimetabolites 5-fluoruracil (5-FU) and 5F,2′deoxyuridine (5F,2′dUrd), and was designated uridine-uracil transporter 1 (UUT1); the other transporter mediated uptake of adenosine, uridine, 5F,2′dUrd and thymidine and was designated Nucleoside Transporter 1 (NT1). To verify the reported L. donovani model of two NT1-like genes encoding uridine/adenosine transporters, and an NT2 gene encoding an inosine transporter, we cloned the corresponding L. major and L. mexicana genes, expressing each in T. brucei. Consistent with the L. donovani reports, the NT1-like genes of either species mediated the adenosine-sensitive uptake of [3H]-uridine but not of [3H]-inosine. Conversely, the NT2-like genes mediated uptake of [3H]-inosine but not [3H]-uridine. Among pyrimidine antimetabolites tested, 5-FU and 5F,2′dUrd were the most effective antileishmanials; resistance to both analogs was induced in L. major and L. mexicana. In each case it was found that the resistant cells had lost the transport capacity for the inducing drug. Metabolomics analysis found that the mechanism of action of 5-FU and 5F-2′dUrd was similar in both Leishmania species, with major changes in deoxynucleotide metabolism. We conclude that the pyrimidine salvage system is highly conserved in Leishmania species - essential information for the development of pyrimidine-based chemotherapy

Drug-sensitivity and passive immunity mathematical epidemiological model for tuberculosis

Regardless of many decades of research, the widespread availability of a vaccine and more recently highly visible WHO efforts to promote a unified global control strategy, Tuberculosis remains a leading cause of infectious mortality. In this paper, a Mathematical Model for Tuberculosis Epidemic with Passive Immunity and Drug-Sensitivity is presented. We carried out analytical studies of the model where the population comprises of eight compartments: passively immune infants, susceptible, latently infected with DS-TB. The Disease Free Equilibrium (DFE) and the Endemic Equilibrium (EE) points were established. The next generation matrix method was used to obtain the reproduction number for drug sensitive () Tuberculosis. We obtained the disease-free equilibrium for drug sensitive TB which is locally asymptotically stable when < 1 indicating that tuberculosis eradication is possible within the population. We also obtained the global stability of the disease-free equilibrium and results showed that the disease-free equilibrium point is globally asymptotically stable when ≤ 1 which indicates that tuberculosis naturally dies out

Derivation of the Rules of Quantum Mechanics from Information-Theoretic Axioms

Conventional quantum mechanics with a complex Hilbert space and the Born Rule is derived from five axioms describing properties of probability distributions for the outcome of measurements. Axioms I,II,III are common to quantum mechanics and hidden variable theories. Axiom IV recognizes a phenomenon, first noted by Turing and von Neumann, in which the increase in entropy resulting from a measurement is reduced by a suitable intermediate measurement. This is shown to be impossible for local hidden variable theories. Axiom IV, together with the first three, almost suffice to deduce the conventional rules but allow some exotic, alternatives such as real or quaternionic quantum mechanics. Axiom V recognizes a property of the distribution of outcomes of random measurements on qubits which holds only in the complex Hilbert space model. It is then shown that the five axioms also imply the conventional rules for all dimensions.Comment: 20 pages, 6 figure

Schur Polynomials and the Yang-Baxter equation

We show that within the six-vertex model there is a parametrized Yang-Baxter equation with nonabelian parameter group GL(2)xGL(1) at the center of the disordered regime. As an application we rederive deformations of the Weyl character formule of Tokuyama and of Hamel and King.Comment: Revised introduction; slightly changed reference

Determining the unsaturated hydraulic conductivity of a compacted sand-bentonite mixture under constant volume and free-swell conditions

Highly compacted sand-bentonite mixtures are often considered as possible engineered barriers in deep high-level radioactive waste disposals. In-situ, the saturation of these barriers from their initially unsaturated state is a complex hydro-mechanical coupled process in which temperature effects also play a role. The key parameter of this process is the unsaturated hydraulic conductivity of the barrier. In this paper, isothermal infiltration experiments were conducted to determine the unsaturated hydraulic conductivity according to the instantaneous profile method. To do so, total suction changes were monitored at different locations along the soil specimen by using resistivity relative humidity probes. Three constant volume infiltration tests were conducted showing, unexpectedly, a decrease of the hydraulic conductivity during infiltration. One test performed under free-swell conditions showed the opposite and standard trend. These observations were interpreted in terms of microstructure changes during wetting, both under constant volume and free swell conditions