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Search Results: 1 - 10 of 461656 matches for " A. Leriche "
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Mechanical Properties of Porosity-Free Beta Tricalcium Phosphate (β-TCP) Ceramic by Sharp and Spherical Indentations  [PDF]
D. Chicot, A. Tricoteaux, J. Lesage, A. Leriche, M. Descamps, E. Rguiti-Constantin
New Journal of Glass and Ceramics (NJGC) , 2013, DOI: 10.4236/njgc.2013.31004
Abstract: Instrumented indentation has been developed for determining the mechanical properties of materials but an accurate determination of these properties requires attention on contact stiffness analysis, indentation size effect, elastic modulus mode of calculation, role of stress distribution around the indent and its introduction in expanding cavity models for tensile mechanical properties determination. In the present work, models for hardness, elastic modulus and plastic properties determination by indentation are briefly reviewed and applied for the characterization of a porosity-free β-TCP bioceramic. As a main result the elastic modulus is found to be equal to 162 GPa resulting from the application of different approaches based on the use of various sharp and spherical indenters. Additionally, Martens and contact macrohardnesses were found to be independent on the dwell-time and equals to 4.1 and 6.3 GPa, respectively. Finally, models based on Hollomon’s and Ludwik’s laws as well as expanding cavity models were critically analyzed in light of their capacity to determine the yield stress and to represent the behavior law of the material. As a main result, the yield stress of the β-TCP is found to be equal to 2 GPa.
The role of transition metal ions on HOx radicals in clouds: a numerical evaluation of its impact on multiphase chemistry
L. Deguillaume, M. Leriche, A. Monod,N. Chaumerliac
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2004,
Abstract: A new modelling study of the role of transition metal ions on cloud chemistry has been performed. Developments of the Model of Multiphase Cloud Chemistry (M2C2; Leriche et al., 2001) are described, including the transition metal ions reactivity emission/deposition processes and variable photolysis in the aqueous phase. The model is then applied to three summertime scenarios under urban, remote and marine conditions, described by Ervens et al. (2003). Chemical regimes in clouds are analyzed to understand the role of transition metal ions on cloud chemistry and especially, on HxOy chemistry, which consequently influences the sulphur and the VOCs chemistry in droplets. The ratio of Fe(II)/Fe(III) exhibits a diurnal variation with values in agreement with the available measurements of Fe speciation. In the urban case, sensitivity tests with and without TMI chemistry, show an enhancement of OH concentration in the aqueous phase when TMI chemistry is considered.
Microbiology and atmospheric processes: chemical interactions of Primary Biological Aerosols
L. Deguillaume,M. Leriche,P. Amato,P. A. Ariya
Biogeosciences Discussions , 2008,
Abstract: This paper discusses the influence of bioaerosols on atmospheric chemistry and vice versa through microbiological and chemical properties and processes. Several studies have shown that biological matter represents a significant fraction of air particulate matter and hence affects the microstructure and water uptake of aerosol particles. Moreover, airborne micro-organisms can transform chemical constituents of the atmosphere by metabolic activity. Recent studies have emphasized the viability of bacteria and metabolic degradation of organic substances in cloud water. On the other hand, the viability and metabolic activity of airborne micro-organisms depend strongly on physical and chemical atmospheric parameters such as temperature, pressure, radiation, pH value and nutrient concentrations. In spite of recent advances, however, our knowledge of the microbiological and chemical interactions of primary biological particles in the atmosphere is rather limited. Further targeted investigations combining laboratory experiments, field measurements, and modelling studies will be required to characterize the chemical feedbacks, microbiological activities at the air/snow/water interface supplied to the atmosphere.
The role of transition metal ions on HOx radicals in clouds: a numerical evaluation of its impact on multiphase chemistry
L. Deguillaume,M. Leriche,A. Monod,N. Chaumerliac
Atmospheric Chemistry and Physics Discussions , 2003,
Abstract: A new modelling study of the role of transition metal ions on cloud chemistry has been performed. Developments of the Model of Multiphase Cloud Chemistry (M2C2; Leriche et al., 2001) are described, including the transition metal ions reactivity emission/deposition processes and variable photolysis in the aqueous phase. The model is then applied to three summertime scenarios under urban, remote and marine conditions, described by Ervens et al. (2003). Chemical regimes in clouds are analyzed to understand the role of transition metal ions on cloud chemistry and especially, on HxOy chemistry, which consequently influences the sulphur and the VOCs chemistry in droplets. The ratio of Fe(II)/Fe(III) exhibits a diurnal variation with values in agreement with the available measurements of Fe speciation. In the urban case, sensitivity tests with and without TMI chemistry, show an enhancement of OH concentration in the aqueous phase when TMI chemistry is considered.
UDNS or LES, That Is the Question  [PDF]
Christoph Bosshard, Michel O. Deville, Abdelouahab Dehbi, Emmanuel Leriche
Open Journal of Fluid Dynamics (OJFD) , 2015, DOI: 10.4236/ojfd.2015.54034
Abstract: In the framework of the spectral element method, a comparison is carried out on turbulent first-and second-order statistics generated by large eddy simulation (LES), under-resolved (UDNS) and fully resolved direct numerical simulation (DNS). The LES is based on classical models like the dynamic Smagorinsky approach or the approximate deconvolution method. Two test problems are solved: the lid-driven cubical cavity and the differentially heated cavity. With the DNS data as benchmark solutions, it is shown that the numerical results produced by the UDNS calculation are of the same accuracy, even in some cases of better quality, as the LES computations. The conclusion advocates the use of UDNS and calls for improvement of the available algorithms.
El alcoholismo: papel del receptor opioide u en los procesos neurales de reforzamiento
Mariana Leriche,Milagros Méndez
Salud mental , 2001,
Abstract:
Cambio estructural y financiamiento para el desarrollo, hacia una erradicación de la pobreza
Cristian E. Leriche Guzmán
El Cotidiano , 2009,
Abstract: El conjunto de reflexiones que presento a continuación refleja la temática que he venido escribiendo en El Cotidiano desde sus primeros números y que se condensan en la problemática del desarrollo económico, su financiamiento y su repercusión en el nivel de vida, que en México se muestra en el indicador de pobreza. Lamentablemente las características pesimistas, o por decir lo menos escépticas, de mis escritos respecto al desarrollo del país y las políticas económicas implementadas, es lo acertado de ellos.
Microbiology and atmospheric processes: chemical interactions of primary biological aerosols
L. Deguillaume, M. Leriche, P. Amato, P. A. Ariya, A.-M. Delort, U. P schl, N. Chaumerliac, H. Bauer, A. I. Flossmann,C. E. Morris
Biogeosciences (BG) & Discussions (BGD) , 2008,
Abstract: This paper discusses the influence of primary biological aerosols (PBA) on atmospheric chemistry and vice versa through microbiological and chemical properties and processes. Several studies have shown that PBA represent a significant fraction of air particulate matter and hence affect the microstructure and water uptake of aerosol particles. Moreover, airborne micro-organisms, namely fungal spores and bacteria, can transform chemical constituents of the atmosphere by metabolic activity. Recent studies have emphasized the viability of bacteria and metabolic degradation of organic substances in cloud water. On the other hand, the viability and metabolic activity of airborne micro-organisms depend strongly on physical and chemical atmospheric parameters such as temperature, pressure, radiation, pH value and nutrient concentrations. In spite of recent advances, however, our knowledge of the microbiological and chemical interactions of PBA in the atmosphere is rather limited. Further targeted investigations combining laboratory experiments, field measurements, and modelling studies will be required to characterize the chemical feedbacks, microbiological activities at the air/snow/water interface supplied to the atmosphere.
What caused extreme ozone concentrations over Cotonou in December 2005?
A. Minga, V. Thouret, M. Saunois, C. Delon, D. Ser a, C. Mari, B. Sauvage, A. Mariscal, M. Leriche,B. Cros
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2010,
Abstract: This paper reports the first record of extreme ozone measurements in Africa. As part of the AMMA program, the ozone vertical profile recorded on 20 December over Cotonou presents exceptionally high ozone concentrations with up to 295 ppb at 1 km altitude. Retroplumes from the Flexpart model show that the air masses sampled at 1 km over Cotonou on this day came from the burning area situated north-east of Cotonou and passed over Lagos, Nigeria, which is highly impacted by urban pollution. We used the Master Mechanism box model to simulate the chemical composition of the plume during its transit. We find that neither the biomass burning emissions of ozone precursors nor additional urban emissions from Lagos are high enough to simulate more than 120–150 ppb of ozone. The only way to reach almost 300 ppb of ozone within a few hours is to feed the air mass with large amounts of reactive VOCs as those recorded in the vicinity of petrochemical area. Sensitivity tests show that 250–600 ppb of VOCs combined with 35–80 ppb of NOx allow the ozone concentrations to be higher than 250 ppb. Nigeria is the first African country with gas extraction and petrochemical industries, and petrochemical explosions frequently happen in the vicinity of Lagos. The hypothesis of a petrochemical explosion in this area is the most likely scenario which could explain the 295 ppb ozone maximum measured over Cotonou, downwind of Lagos.
Linking Climate Suitability, Spread Rates and Host-Impact When Estimating the Potential Costs of Invasive Pests
Darren J. Kriticos, Agathe Leriche, David J. Palmer, David C. Cook, Eckehard G. Brockerhoff, Andréa E. A. Stephens, Michael S. Watt
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0054861
Abstract: Biosecurity agencies need robust bioeconomic tools to help inform policy and allocate scarce management resources. They need to estimate the potential for each invasive alien species (IAS) to create negative impacts, so that relative and absolute comparisons can be made. Using pine processionary moth (Thaumetopoea pityocampa sensu lato) as an example, these needs were met by combining species niche modelling, dispersal modelling, host impact and economic modelling. Within its native range (the Mediterranean Basin and adjacent areas), T. pityocampa causes significant defoliation of pines and serious urticating injuries to humans. Such severe impacts overseas have fuelled concerns about its potential impacts, should it be introduced to New Zealand. A stochastic bioeconomic model was used to estimate the impact of PPM invasion in terms of pine production value lost due to a hypothetical invasion of New Zealand by T. pityocampa. The bioeconomic model combines a semi-mechanistic niche model to develop a climate-related damage function, a climate-related forest growth model, and a stochastic spread model to estimate the present value (PV) of an invasion. Simulated invasions indicate that Thaumetopoea pityocampa could reduce New Zealand’s merchantable and total pine stem volume production by 30%, reducing forest production by between NZ$1,550 M to NZ$2,560 M if left untreated. Where T. pityocampa is controlled using aerial application of an insecticide, projected losses in PV were reduced, but still significant (NZ$30 M to NZ$2,210 M). The PV estimates were more sensitive to the efficacy of the spray program than the potential rate of spread of the moth. Our novel bioeconomic method provides a refined means of estimating potential impacts of invasive alien species, taking into account climatic effects on asset values, the potential for pest impacts, and pest spread rates.
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