31 research outputs found
One step electrodeposition of Ag-decorated ZnO nanowires
The final publication is available at Springer via http://dx.doi.org/10.1007/s10008-016-3476-0.A new route for synthesizing Ag-decorated ZnO nanowires (NWs) on conductive glass substrates using a one-step electrodeposition technique is described here. The structural, optical, and photoelectrochemical properties of Ag-decorated ZnO nanowires were studied in detail using techniques such X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, UV-visible spectroscopy, photoluminescence, and photoelectrochemical measurements. Both pure and Ag-decorated ZnO nanowires were found to crystallize in the wurtzite structure, irrespective of their Ag contents. Increasing the Ag content from pure ZnO NWs to 3% Ag ZnO NWs decreases the photoluminescence intensity, shifts the optical band gap to the red, and increases the photocurrent up to threefold. This behavior was attributed to the surface plasmon resonance effect induced by the Ag nanoparticles, which inhibits charge recombination and improves charge transport on the ZnO surface.B.S. acknowledges the Nanomaterials and Systems Laboratory for Renewable Energies, Research and Technology Centre of Energy Technoparc Borj Cedria for financial support. This work was supported by the Ministerio de Economia y Competitividad (ENE2013-46624-C4-4-R) and the Generalitat Valenciana (Prometeus 2014/044).Slimi, B.; Ben Assaker, I.; Kriaa, A.; MarÃ, B.; Chtourou, R. (2017). One step electrodeposition of Ag-decorated ZnO nanowires. 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Synthesis and characterization of perovskite FAPbBr(3-x) I (x) thin films for solar cells
[EN] FAPbI3, FAPbBr3, and FAPbBr3-xIx perovskite thin films were produced in a single step from a solution containing a mixture of FAI, PbI2, FABr, and PbBr2 (FA = formamidinium). FAPbBr3-xIx perovskite thin films were deposited onto ITO-coated glass substrates by spin coating. X-ray diffraction analyses confirmed that these thin-film perovskites crystallize in the cubic phase (Pm-3 m) for all composition range 0 B x B 3. Mixed lead perovskites showed a high absorbance in the UV¿Vis range. The optical band gap was estimated from spectral absorbance measurements. It was found that the onset of the absorption edge for FAPbBr3¿xIx thin films ranges between 1.47 and 2.20 eV for x = 0 and x = 3, respectively. Photoluminescence emission energies for mixed halide perovskites were also dependent on their composition and presented intermediate values from 810.4 nm for FAPbI3 to 547.3 nm for FAPbBr3.This work was supported by Ministerio de Economia y Competitividad (ENE2016-77798-C4-2-R) and Generalitat valenciana (Prometeus 2014/044).Slimi, B.; Mollar GarcÃa, MA.; Ben Assaker, I.; Kriaa, A.; Chtourou, R.; MarÃ, B. (2017). Synthesis and characterization of perovskite FAPbBr(3-x) I (x) thin films for solar cells. Monatshefte für Chemie - Chemical Monthly. 148(5):835-844. https://doi.org/10.1007/s00706-017-1958-0S835844148
Activation of TRPC1 Channel by Metabotropic Glutamate Receptor mGluR5 Modulates Synaptic Plasticity and Spatial Working Memory
Group I metabotropic glutamate receptors, in particular mGluR5, have been implicated in various forms of synaptic plasticity that are believed to underlie declarative memory. We observed that mGluR5 specifically activated a channel containing TRPC1, an isoform of the canonical family of transient receptor potential (TRPC) channels highly expressed in CA1-3 regions of the hippocampus. TRPC1 is able to form tetrameric complexes with TRPC4 and/or TRPC5 isoforms. TRPC1/4/5 complexes have recently been involved in the efficiency of synaptic transmission in the hippocampus. We therefore used a mouse model devoid of TRPC1 expression to investigate the involvement of mGluR5-TRPC1 pathway in synaptic plasticity and memory formation. Trpc1-/- mice showed alterations in spatial working memory and fear conditioning. Activation of mGluR increased synaptic excitability in neurons from WT but not from Trpc1-/- mice. LTP triggered by a theta burst could not maintain over time in brain slices from Trpc1-/- mice. mGluR-induced LTD was also impaired in these mice. Finally, acute inhibition of TRPC1 by Pico145 on isolated neurons or on brain slices mimicked the genetic depletion of Trpc1 and inhibited mGluR-induced entry of cations and subsequent effects on synaptic plasticity, excluding developmental or compensatory mechanisms in Trpc1-/- mice. In summary, our results indicate that TRPC1 plays a role in synaptic plasticity and spatial working memory processes
Evaluation of Spatially Targeted Strategies to Control Non-Domiciliated Triatoma dimidiata Vector of Chagas Disease
Chagas disease is one of the most important parasitic diseases in Latin America. Since the 1980's, many national and international initiatives have contributed to eliminate vectors developing inside human domiciles. Today's challenge is to control vectors that are non-adapted to the human domicile, but still able to transmit the parasite through regular short stay in the houses. Here, we assess the potential of different control strategies applied in specific spatial patterns using a mathematical model that reproduces the dynamic of dispersion of such ‘non-domiciliated’ vectors within a village of the Yucatan Peninsula, Mexico. We show that no single strategy applied in the periphery of the village, where the insects are more abundant, provides satisfying protection to the whole village. However, combining the use of insect screens in houses at the periphery of the village (to simultaneously fight insects dispersing from the garden and the forest), and the cleaning of the peri-domicile areas of the centre of the village (where sylvatic insects are absent), would provide a cost-effective control. This type of spatially mixed strategy offers a promising way to reduce the cost associated with the repeated interventions required to control non-domiciliated vectors that permanently attempt to infest houses
Optimization of Control Strategies for Non-Domiciliated Triatoma dimidiata, Chagas Disease Vector in the Yucatán Peninsula, Mexico
Chagas disease is the most important vector-borne disease in Latin America. Residual insecticide spraying has been used successfully for the elimination of domestic vectors in many regions. However, some vectors of non-domestic origin are able to invade houses, and they are now a key challenge for further disease control. We developed a mathematical model to predict the temporal variations in abundance of non-domiciliated vectors inside houses, based on triatomine demographic parameters. The reliability of the predictions was demonstrated by comparing these with different sets of insect collection data from the Yucatan peninsula, Mexico. We then simulated vector control strategies based on insecticide spraying, insect, screens and bednets to evaluate their efficacy at reducing triatomine abundance in the houses. An optimum reduction in bug abundance by at least 80% could be obtained by insecticide application only when doses of at least 50 mg/m2 were applied every year within a two-month period matching the house invasion season by bugs. Alternatively, the use of insect screens consistently reduced bug abundance in the houses and offers a sustainable alternative. Such screens may be part of novel interventions for the integrated control of various vector-borne diseases
Characterization of the Dispersal of Non-Domiciliated Triatoma dimidiata through the Selection of Spatially Explicit Models
Chagas disease is one of the most important neglected diseases in Latin America. Although insecticides have been successfully sprayed to control domiciliated vector populations, this strategy has proven to be ineffective in areas where non-domiciliated vectors immigrating from peridomestic or sylvatic ecotopes can (re-)infest houses. The development of strategies for the control of non-domiciliated vectors has thus been identified by the World Health Organization as a major challenge. Such development primarily requires a description of the spatio-temporal dynamics of infestation by these vectors, and a good understanding of their dispersal. We combined for the first time extensive spatio-temporal data sets describing house infestation dynamics by Triatoma dimidiata inside one village, and spatially explicit population dynamics models. The models fitted and predicted remarkably the observed infestation dynamics. They thus provided both key insights into the dispersal of T. dimidiata in this area, and a suitable mathematical background to evaluate the efficacy of various control strategies. Interestingly, the observed and modelled patterns of infestation suggest that interventions could focus on the periphery of the village, where there is the highest risk of transmission. Such spatial optimization may allow for reducing the cost of control, compensating for repeated interventions necessary for non-domiciliated vectors
Modeling the Dynamic Transmission of Dengue Fever: Investigating Disease Persistence
Dengue is the most rapidly spreading mosquito-borne viral disease in the world and approximately 2.5 billion people live in dengue endemic countries. In Brazil it is mainly transmitted by Aedes aegypti mosquitoes. The wide clinical spectrum ranges from asymptomatic infections or mild illness, to the more severe forms of infection such as dengue hemorrhagic fever or dengue shock syndrome. The spread and dramatic increase in the occurrence of dengue cases in tropical and subtropical countries has been blamed on uncontrolled urbanization, population growth and international traveling. Vaccines are under development and the only current disease control strategy is trying to keep the vector quantity at the lowest possible levels. Mathematical models have been developed to help understand the disease's epidemiology. These models aim not only to predict epidemics but also to expand the capacity of phenomena explanation. We developed a spatially explicit model to simulate the dengue transmission in a densely populated area. The model involves the dynamic interactions between humans and mosquitoes and takes into account human mobility as an important factor of disease spread. We investigated the importance of human population size, human renewal rate, household infestation and ratio of vectors per person in the maintenance of sustained viral circulation
Estimating Contact Process Saturation in Sylvatic Transmission of Trypanosoma cruzi in the United States
Although it has been known for nearly a century that strains of Trypanosoma cruzi, the etiological agent for Chagas' disease, are enzootic in the southern U.S., much remains unknown about the dynamics of its transmission in the sylvatic cycles that maintain it, including the relative importance of different transmission routes. Mathematical models can fill in gaps where field and lab data are difficult to collect, but they need as inputs the values of certain key demographic and epidemiological quantities which parametrize the models. In particular, they determine whether saturation occurs in the contact processes that communicate the infection between the two populations. Concentrating on raccoons, opossums, and woodrats as hosts in Texas and the southeastern U.S., and the vectors Triatoma sanguisuga and Triatoma gerstaeckeri, we use an exhaustive literature review to derive estimates for fundamental parameters, and use simple mathematical models to illustrate a method for estimating infection rates indirectly based on prevalence data. Results are used to draw conclusions about saturation and which population density drives each of the two contact-based infection processes (stercorarian/bloodborne and oral). Analysis suggests that the vector feeding process associated with stercorarian transmission to hosts and bloodborne transmission to vectors is limited by the population density of vectors when dealing with woodrats, but by that of hosts when dealing with raccoons and opossums, while the predation of hosts on vectors which drives oral transmission to hosts is limited by the population density of hosts. Confidence in these conclusions is limited by a severe paucity of data underlying associated parameter estimates, but the approaches developed here can also be applied to the study of other vector-borne infections