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Search Results: 1 - 10 of 37289 matches for " Jean Pierre; Rocha "
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The impact of local extinction on genetic structure of wild populations of lima beans (Phaseolus lunatus) in the Central Valley of Costa Rica: consequences for the conservation of plant genetic resources
Barrantes,Daniel; Macaya,Gabriel; Guarino,Luigi; Baudoin,Jean Pierre; Rocha,Oscar J;
Revista de Biología Tropical , 2008,
Abstract: plant populations may experience local extinction and at the same time new populations may appear in nearby suitable locations. species may also colonize the same site on multiple occasions. here, we examined the impact of local extinction and recolonization on the genetic structure of wild populations of lima beans (phaseolus lunatus) in the central valley of costa rica. we compared genetic diversity from the samples taken from the populations before and after extinction at 13 locations using microsatellite markers. locations were classified according to the occurrence of extinction episodes during the previous five years into three groups: 1) populations that experienced extinction for more than one year, and were later recolonized (recolonized), 2) populations that did not experience local extinction (control), and 3) populations that did not experience local extinction during the study, but were cut to experimentally simulate extinction (experimental). our data did not show a clear tendency in variation in allele frequencies, expected heterozygosity, and effective number of alleles within and between groups of populations. however, we found that the level of genetic differentiation between samples collected at different times at the same location was different in the three groups of populations. recolonized locations showed the highest level of genetic differentiation (mean fst= 0.2769), followed by control locations (mean fst= 0.0576) and experimental locations (mean fst= 0.0189). similar findings were observed for nei?s genetic distance between samples (di,j= 0.1786, 0.0400, and 0.0037, respectively). our results indicate that genetic change in lima beans depends on the duration and frequency of local extinction episodes. these findings also showed that control populations are not in equilibrium. implications of these results for the establishment of conservation strategies of genetic resources of lima beans are discussed. rev. biol. trop. 56 (3): 1023-1041. e
Mitochondrial DNA variation of Triatoma infestans populations and its implication on the specific status of T. melanosoma
Monteiro, Fernando A;Pérez, Ruben;Panzera, Francisco;Dujardin, Jean-Pierre;Galv?o, Cleber;Rocha, Deyse;Noireau, Francois;Schofield, Chris;Beard, Charles B;
Memórias do Instituto Oswaldo Cruz , 1999, DOI: 10.1590/S0074-02761999000700037
Abstract: dna sequence comparison of 412 base-pairs fragments of the mitochondrial cytochrome b gene was used to infer the genetic structure of nine geographical triatoma infestans populations and their phylogenetic relationship with t. melanosoma and t. brasiliensis. t. infestans and t. melanosoma were compared by morphometry, allozyme and cytogenetic analyses, as well as subjected to reciprocal crosses, in order to clarify the taxonomic status of the latter. no differences were found to distinguish the two species and the crosses between them yielded progeny. t. infestans populations presented four haplotypes that could be separated in two clusters: one formed by the samples from bolivia (andes and chaco) and the other formed by samples from argentina and brazil. silvatic and domestic t. infestans populations from bolivia (andes) were genetically identical.
Can land use changes alter carbon, nitrogen and major ion transport in subtropical brazilian streams?
Silva, Daniela Mariano Lopes da;Ometto, Jean Pierre Henry Balbaud;Lobo, Gré de Araújo;Lima, Walter de Paula;Scaranello, Marcos Augusto;Mazzi, Edmar;Rocha, Humberto Ribeiro da;
Scientia Agricola , 2007, DOI: 10.1590/S0103-90162007000400002
Abstract: several studies in tropical watersheds have evaluated the impact of urbanization and agricultural practices on water quality. in brazil, savannas (known regionally as cerrados) represent 23% of the country's surface, representing an important share to the national primary growth product, especially due to intense agriculture. the purpose of this study is to present a comprehensive evaluation, on a yearly basis, of carbon, nitrogen and major ion fluxes in streams crossing areas under different land use (natural vegetation, sugar cane and eucalyptus) in a savanna region of se brazil. eucalyptus and sugar cane alter the transport of the investigated elements in small watersheds. the highest concentration of all parameters (abiotic parameters, ions, dissolved organic carbon doc - and dissolved inorganic carbon - dic) were found in sugar cane watersheds (scw). the observed concentrations of major cations in eucalyptus watersheds (ew) (mg, ca, k, na), as well as din and doc, were found frequently to be intermediate values between those of savanna watersheds (sw) and scw, suggesting a moderate impact of eucalyptus plantations on the streamwater. same trends were found in relation to ion and nutrient fluxes, where the higher values corresponded to scw. it is suggested that sugar cane plantations might be playing an important role in altering the chemistry of water bodies.
Block Layering Approach in TAST Codes  [PDF]
Zahoor Ahmed, Jean Pierre Cances, Vahid Meghdadi
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2010, DOI: 10.4236/ijcns.2010.310105
Abstract: Threaded Algebraic Space Time (TAST) codes developed by Gamal et al. is a powerful class of space time codes in which different layers are combined and separated by appropriate Diophantine number . In this paper we introduce a technique of block layering in TAST codes, in which a series of layers (we call it Block layers) has more than one transmit antenna at the same time instant. As a result we use fewer layers (Diophantine numbers) for the four transmit antennas scheme, which enhances the coding gain of our proposed scheme. In each block layer we incorporate Alamouti’s transmit diversity scheme which decreases the decoding complexity. The proposed code achieves a normalized rate of 2 symbol/s. Simulation result shows that this type of codes outperforms TAST codes in certain scenarios.
Volatility Forecasting of Market Demand as Aids for Planning Manufacturing Activities  [PDF]
Jean-Pierre Briffaut, Patrick Lallement
Journal of Service Science and Management (JSSM) , 2010, DOI: 10.4236/jssm.2010.34045
Abstract: The concepts and techniques designed and used for pricing financial options have been applied to assist in scheduling manufacturing activities. Releasing a manufacturing order is viewed as an investment opportunity whose properties are similar to a call option. Its value can be considered as the derivative of the market demand mirrored in the selling price of the manufactured products and changes over time following an Itô process. Dynamic programming has been used to derive the optimal timing for releasing manufacturing orders. It appears advisable to release a manufacturing when the unit selling price come to a threshold P* given by the relation P* = β/(β–1) C with C = unit cost price. β is a parameter whose value depends on the trend parameter α and the volatility σ of the selling price, the discount rate ρ applicable to the capital appreciation relevant to the business context under consideration. The results have been successfully applied to the evolution of the quarterly construction cost index in France over ten years.
Chaos Appearance during Domain Wall Motion under Electronic Transfer in Nanomagnets  [PDF]
Donfack Gildas Hermann, Jean-Pierre Nguenang
World Journal of Condensed Matter Physics (WJCMP) , 2013, DOI: 10.4236/wjcmp.2013.33022
Abstract:

In this paper, we study the likelihood of chaos appearance during domain wall motion induced by electronic transfer. Considering a time-varying current density theory, we proceed to a numerical investigation of the dynamics. Using the dissipation parameter, amplitude and frequency of current density as control parameters; we show how periodic regime as well as chaotic regime can be exhibited in nanomagnetic systems. Numerical results allow setting up the periodicity and quasi-periodicity of system and chaotic phenomena occurring during magnetization switching process in nanomagnet through electronic transfer.

Traceability in Acceptance Testing  [PDF]
Jean-Pierre Corriveau, Wei Shi
Journal of Software Engineering and Applications (JSEA) , 2013, DOI: 10.4236/jsea.2013.610A005
Abstract:

Regardless of which (model-centric or code-centric) development process is adopted, industrial software production ultimately and necessarily requires the delivery of an executable implementation. It is generally accepted that the quality of such an implementation is of utmost importance. Yet current verification techniques, including software testing, remain problematic. In this paper, we focus on acceptance testing, that is, on the validation of the actual behavior of the implementation under test against the requirements of stakeholder(s). This task must be as objective and automated as possible. Our first goal is to review existing code-based and model-based tools for testing in light of what such an objective and automated approach to acceptance testing entails. Our contention is that the difficulties we identify originate mainly in a lack of traceability between a testable model of the requirements of the stakeholder(s) and the test cases used to validate these requirements. We then investigate whether such traceability is addressed in other relevant specification-based approaches.

DNA Nano Devices as a Biased Random Walk Process: A Case Study of Isothermal Ratchet?  [PDF]
Jean-Pierre Aimé, Juan Elezgaray
Materials Sciences and Applications (MSA) , 2015, DOI: 10.4236/msa.2015.65045
Abstract: Computation and amplification processes based on Networks of Chemical Reactions are at the heart of our understanding of the regulation and error correction of life systems. The recent advances in DNA nanotechnology, with the creation of the modular structures origamis and the development of dynamical networks using the toe hold mediated strand displacement, open fertile areas to construct Hierarchical Cascades of Chemical Reactions with an increasing complexity inspired from systems in biology. DNA strands have the great advantage to design autonomous and homogeneous Networks of Chemical Reactions leaving aside companion chemical reactions as it occurs in biological systems. In the present paper, we use the Fokker Planck equation to extract predictions that address a wider class of systems beyond the case of diluted solutions. We introduce the concept of toehold strength and output strength that leads to an exponential square dependence of the toehold strength divided by the output strength on the escape rate and the probability for the output strand to leave the gate. We highlight the influence of the boundary conditions that may have an important consequence in confined environment when modular structures like origamis are employed.
Skeletal involvement in the pathogenesis and outcomes of rheumatoid arthritis and osteoarthritis
Jean-Pierre Pelletier
Arthritis Research & Therapy , 2012, DOI: 10.1186/ar3571
Abstract: In RA, increased osteoclastic activity is responsible for the development of focal osteopenia/erosion and systemic osteoporosis. The increased osteoclast activity in RA has been demonstrated to be linked to a dysregulation of pathways including cell-cell interactions, cytokines, and the receptor activator of nuclear factor κB (RANK)/RANK ligand (RANKL) system. Recent studies have shown that joint erosion in RA is linked to a decrease in long-term physical function.Under OA conditions, the subchondral bone is the site of numerous dynamic morphological changes. These changes are associated with a number of local abnormal biochemical pathways related to the altered metabolism of osteoblasts and osteoclasts. At the early stages of the disease process, increased bone loss and resorption is observed with subchondral bone associated with local production of catabolic factors including cathepsin K and MMP-13. Moreover, OA osteoblasts present an abnormal phenotype resulting in increased production of growth hormones and catabolic factors. In addition, factors such as osteoprotegerin (OPG) and RANKL have been found to be expressed and modulated over time in human OA subchondral bone. Their synthesis varies from being reduced in early OA to being increased in the late stages of the disease. This finding may explain that in the early stages of OA, bone remodeling favors resorption and in the more advanced stages of the disease, bone formation is predominant.Magnetic resonance imaging (MRI) studies in knee OA patients have shown that the subchondral bone is frequently the site of signal alterations-bone marrow lesions (BML) - indicative of a great variety of morphological changes. BML and cartilage loss have been linked in several studies. Moreover, studies have identified, in OA patients, a number of risk factors for total knee replacement including BMLs.The paradigms regarding the role of bone lesions in arthritic diseases raise a number of important questions. A comprehensive
rich: An R Package to Analyse Species Richness
Jean-Pierre Rossi
Diversity , 2011, DOI: 10.3390/d3010112
Abstract: The paper describes rich, a new R package to perform species richness estimation and comparison. Species richness is the simplest surrogate for the more complex concept of species biodiversity. It is relatively easy to assess although estimations strongly depend on sampling intensity with the consequence that richness estimations should be standardized to perform valid comparisons. The R package rich allows such corrections as well as the computation of various statistics and implements different randomization tests to compare cumulative and average species richness of two communities. These tests are useful for ranking sites or communities which is a classical goal in restoration ecology and conservation biology.
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