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935 results on '"Alves, Jose A."'

202. Stochastic stability of diffeomorphisms with dominated splitting

Author

Alves, Jose F., Araujo, Vitor, and Vasquez, Carlos H.

Subjects
Mathematics - Dynamical Systems, 37D25, 37C40, 37H15
Abstract

We prove that the statistical properties of random perturbations of a nonuniformly hyperbolic diffeomorphism are described by a finite number of stationary measures. We also give necessary and sufficient conditions for the stochastic stability of such dynamical systems. We show that a certain $C^2$-open class of nonuniformly hyperbolic diffeomorphisms introduced in [Alves, J; Bonatti, C. and Viana, V., SRB measures for partially hyperbolic systems with mostly expanding central direction, Invent. Math., 140 (2000), 351-398] are stochastically stable. Our setting encompasses that of partially hyperbolic diffeomorphisms as well. Moreover, the techniques used enable us to obtain SRB measures in this setting through zero-noise limit measures., Comment: 32 pages; introduction revised and proofs detailed

Published
2004

203. Backward volume contraction for endomorphisms with eventual volume expansion

Author

Alves, Jose F., Castro, Armando, and Pinheiro, Vilton

Subjects
Mathematics - Dynamical Systems
Abstract

We consider smooth maps on compact Riemannian manifolds. We prove that under some mild condition of eventual volume expansion Lebesgue almost everywhere we have uniform backward volume contraction on every pre-orbit for Lebesgue almost every point.

Published
2004

204. On the continuity of the SRB entropy for endomorphisms

Author

Alves, Jose F., Oliveira, Krerley, and Tahzibi, Ali

Subjects
Mathematics - Dynamical Systems, 37C40, 37C75, 37D25
Abstract

We consider classes of dynamical systems admitting Markov induced maps. Under general assumptions, which in particular guarantee the existence of SRB measures, we prove that the entropy of the SRB measure varies continuously with the dynamics. We apply our result to a vast class of non-uniformly expanding maps of a compact manifold and prove the continuity of the entropy of the SRB measure. In particular, we show that the SRB entropy of Viana maps varies continuously with the map., Comment: 19 pages

Published
2004

206. Strong statistical stability of non-uniformly expanding maps

Author

Alves, Jose F.

Subjects
Mathematics - Dynamical Systems, 37C40, 37C75, 37D25
Abstract

We consider families of transformations in multidimensional Riemannian manifolds with non-uniformly expanding behavior. We give sufficient conditions for the continuous variation (in the $L^1$-norm) of the densities of absolutely continuous (with respect to the Lebesgue measure) invariant probability measures for those transformations., Comment: 21 pages

Published
2003
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207. Hyperbolic times: frequency vs. integrability

Author

Alves, Jose F. and Araujo, Vitor

Subjects
Mathematics - Dynamical Systems, 37A05, 37C40
Abstract

We consider dynamical systems on compact manifolds, which are local diffeomorphisms outside an exceptional set (a compact submanifold). We are interested in analyzing the relation between the integrability (with respect to Lebesgue measure) of the first hyperbolic time map and the existence of positive frequency of hyperbolic times. We show that some (strong) integrability of the first hyperbolic time map implies positive frequency of hyperbolic times. We also present an example of a map with positive frequency of hyperbolic times at Lebesgue almost every point but whose first hyperbolic time map is not integrable with respect to the Lebesgue measure., Comment: 18 pages

Published
2003

209. Implications of migration strategies and winter location in a migratory shorebird

Author

Alves, Jose Augusto Belchior

Subjects
591.7
Abstract

The work presented in this thesis investigates the implications of migration strategies and choice of winter location in a population of a migratory shorebird, the Icelandic Blacktailed Godwit Limosa limosa islandica. Measures of the environmental conditions experienced by individuals in different parts of the winter range are used to explore the energetic trade-offs associated with choice of winter location. The costs of migrating different distances to the Icelandic breeding grounds are also explored, as winter locations range from Britain and Ireland to Iberia. These studies suggest that winter locations in the south of the range are energetically more favourable, and that the resources available at these sites are more than sufficient to fuel migration. However, Icelandic godwits wintering in Iberia have to fly more than twice the distance to reach Iceland than their conspecifics in the north of the winter range, and models of potential flight range indicate that most birds from Iberia have to stop and refuel during spring migration. Despite this, population-wide tracking of marked individuals indicates that godwits from southern winter locations are able to reach Iceland earlier than birds from more northerly winter sites. In the Iberian winter sites, Icelandic black-tailed godwits overlap with continental black-tailed godwits (Limosa limosa limosa), but detailed field studies in Portugal indicate clear habitat segregation between these two subspecies, with Icelandic godwits primarily foraging on estuarine mudflats and continental godwits foraging in rice-fields. Estuarine prey resources vary in availability and profitability and, as in most shorebird species, female godwits are larger than males and have higher energy requirements. Thus, the extent and implications of sex differences in distribution and resource use are explored in this thesis. Finally, the impact of ongoing efforts to reduce organic inputs to the Tejo estuary, west Portugal (the main Iberian winter site), on the distribution of black-tailed godwits and their invertebrate prey are explored.

Published
2009

210. On the uniform hyperbolicity of some nonuniformly hyperbolic systems

Author

Alves, Jose F., Araujo, Vitor, and Saussol, Benoit

Subjects
Mathematics - Dynamical Systems, 58F15, 58F99
Abstract

We give sufficient conditions for the uniform hyperbolicity of certain nonuniformly hyperbolic dynamical systems. In particular, we show that local diffeomorphisms that are nonuniformly expanding on sets of total probability are necessarily uniformly expanding. We also present a version of this result for diffeomorphisms with nonuniformly hyperbolic sets.

Published
2001

212. Statistical stability for robust classes of maps with non-uniform expansion

Author

Alves, Jose F. and Viana, Marcelo

Subjects
Mathematics - Dynamical Systems, 37D25, 37D45
Abstract

We consider open sets of maps in a manifold $M$ exhibiting non-uniform expanding behaviour in some domain $S\subset M$. Assuming that there is a forward invariant region containing $S$ where each map has a unique SRB measure, we prove that under general uniformity conditions, the SRB measure varies continuously in the $L^1$-norm with the map. As a main application we show that the open class of maps introduced in [V] fits to this situation, thus proving that the SRB measures constructed in [A] vary continuously with the map., Comment: 42 pages

Published
2000

213. Random perturbations of non-uniformly expanding maps

Author

Alves, Jose F. and Araujo, Vitor

Subjects
Mathematics - Dynamical Systems, 37D25, 37H99
Abstract

We give both sufficient conditions and necessary conditions for the stochastic stability of non-uniformly expanding maps either with or without critical sets. We also show that the number of probability measures describing the statistical asymptotic behaviour of random orbits is bounded by the number of SRB measures if the noise level is small enough. As an application of these results we prove the stochastic stability of certain classes of non-uniformly expanding maps introduced in \cite{V} and \cite{ABV}., Comment: 44 pages, 2 figures

Published
2000

228. Great Lakes wave forecast system on high-resolution unstructured meshes.

Author

Abdolali, Ali, Banihashemi, Saeideh, Alves, Jose Henrique, Roland, Aron, Hesser, Tyler J., Anderson Bryant, Mary, and McKee Smith, Jane

Subjects
WIND waves, LAKES, STANDING waves, WATERSHEDS, ATMOSPHERIC models, FORECASTING, GRIDS (Cartography), OCEAN waves
Abstract

Wind-wave forecasts play a crucial role in the North American Great Lakes region towards ensuring the safety of communities, enhancement of the economy, and protection of property. Modeling wind waves in closed and relatively shallow basins with complex bathymetry like the Great Lakes is a challenge that is successfully tackled in part by using variable-resolution triangular unstructured meshes with no limits in terms of computational scalability and maximum resolution in the coastal areas. In this paper, we discuss recent advances in developing unstructured mesh capabilities as part of the spectral wave model WAVEWATCH III, in the context of National Oceanic and Atmospheric Administration (NOAA) operational requirements such as model robustness, efficiency, and accuracy. We revisit the history of developments leading to the transition from rectilinear to curvilinear grids and finally to an unstructured mesh version of NOAA's operational Great Lakes wave modeling system (GLWUv2.0). The article describes the development of the operational GLWUv2.0, from mesh design and scalability analysis to validation and verification for hindcast of storm cases and re-forecast using 4 months of retrospective simulations. In closed Great Lakes basins untouched by swell from distant sources, the atmospheric model's direct impact on wave behavior stands apart, showing reduced forecast accuracy over time, while maintaining consistent precision in accurately wind-hindcasted stormy conditions. [ABSTRACT FROM AUTHOR]

Published
2024
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231. ASYMPTOMATIC CHOLELITHIASIS: EXPECTANT OR CHOLECYSTECTOMY. A SYSTEMATIC REVIEW

Author

Alves, Jose Roberto, Klock, Diurlhane Mainara, Ronzani, Filipe Gonçalves, Santos, Sheyne Luiz dos, and Amico, Enio Campos

Subjects
Colecistectomia, Colelitíase, Cálculos biliares, Cholelithiasis, Gallbladder, Cholecystectomy, Gallstones, Vesícula biliar
Abstract

BACKGROUND: Asymptomatic cholelithiasis is a highly prevalent disease, and became more evident after the currently greater access to imaging tests. Therefore, it is increasingly necessary to analyse the risks and benefits of performing a prophylactic cholecystectomy. AIMS: To seek the best evidence in order to indicate prophylactic cholecystectomy or conservative treatment (clinical follow-up) in patients with asymptomatic cholelithiasis. METHODS: A systematic review was performed using the PubMed/Medline database, according to PRISMA protocol guidelines. The review was based on studies published between April 26, 2001 and January 07, 2022, related to individuals older than 18 years., The following terms/operators were used for search standardization: (asymptomatic OR silent) AND (gallstones OR cholelithiasis). RESULTS: We selected 18 studies eligible for inference production after applying the inclusion and exclusion criteria. Also, the Tokyo Guideline (2018) was included for better clarification of some topics less or not addressed in these studies. CONCLUSIONS: Most evidence point to the safety and feasibility of conservative treatment (clinical follow-up) of asymptomatic cholelithiasis. However, in post-cardiac transplant patients and those with biliary microlithiasis with low preoperative surgical risk, a prophylactic cholecystectomy is recommended. To establish these recommendations, more studies with better levels of evidence must be conducted. RESUMO RACIONAL: A colelitíase assintomática é uma doença altamente prevalente, e atualmente tornou-se mais evidente, após o maior acesso a exames de imagem. Portanto, é cada vez mais necessário analisar os riscos e benefícios de realizar uma colecistectomia profilática. OBJETIVOS: Buscar as melhores evidências para indicar colecistectomia profilática ou tratamento conservador (acompanhamento clínico) em pacientes com colelitíase assintomática. MÉTODOS: Foi realizada revisão sistemática, no PubMed/Medline, de acordo com as diretrizes do protocolo PRISMA, selecionando estudos publicados entre 26/04/2001 e 01/07/2022, relacionados a indivíduos maiores de 18 anos, com padronização de busca usando os seguintes termos/operadores: (Assintomático OU Silencioso) E (Cálculos biliares OU colelitíase). RESULTADOS: Foram selecionados 18 estudos elegíveis após a aplicação dos critérios de inclusão e exclusão. Além disso, a Tokyo Guideline (2018) foi incluída para melhor esclarecimento de alguns tópicos menos ou não abordados nestes estudos. CONCLUSÕES: A maioria das evidências aponta para a segurança e viabilidade do tratamento conservador (acompanhamento clínico) da colelitíase assintomática. Entretanto, em pacientes com transplante pós-cardíaco e aqueles com microlitíase biliar com baixo risco cirúrgico pré-operatório, a colecistectomia profilática é recomendada. Para estabelecer completamente estas recomendações, mais estudos com melhores níveis de evidência devem ser conduzidos.

Published
2023

235. Inoculum concentration and inoculation time for propionic acid production from whey using mixed culture of Lactobacillus helveticus and Propionibacterium freudenreichii PS-1/Concentracao de inoculo e tempo de inoculacao para producao de acido propionico usando cultura de Lactobacillus helveticus e Propionibacterium freudenreichii

Author

Ngome, Moises Tomas, Alves, Jose Guilherme Lembi Ferreira, Piccoli, Roberta Hilsdorf, Domingo, Elisangela de Carmo, Pinto, Sheyla Analia, and Bernal, Olga Lucia Mondragon

Published
2017
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238. NOAA’s Great Lakes Wave Prediction System: A Successful Framework for Accelerating the Transition of Innovations to Operations

Author

Alves, Jose-henrique, Tolman, Hendrik, Roland, Aron, Abdolali, Ali, Ardhuin, Fabrice, Mann, Greg, Chawla, Arun, Smith, Jane, Alves, Jose-henrique, Tolman, Hendrik, Roland, Aron, Abdolali, Ali, Ardhuin, Fabrice, Mann, Greg, Chawla, Arun, and Smith, Jane

Abstract

The establishment of the Great Lakes Wave forecast system is an early success story inspiring the introduction of open-innovation practices at NOAA, the United States National Oceanic and Atmospheric Administration. It shows the power of community modeling to accelerate the transition of scientific innovations to operational environmental forecasting. This paper presents an overview of wave modeling in the Great Lakes from the perspective of its societal benefits. NOAA’s operational wave modeling systems and development practices are examined, emphasizing the importance of community- and stakeholder-driven collaborative efforts to introduce innovations such as using advanced spatial grid types and physics parameterizations, leading to improved predictive skill. The success of the open-innovation approach, set in motion at NOAA by initiatives such as the Great Lakes Wave forecasting system, accelerated the transition of innovations to operations. The culture change to operational modeling efforts became part of the foundation for establishing the Unified Forecast System and, more recently, the Earth Prediction Innovation Center. Open-innovation initiatives will improve operational weather and climate forecast systems through scientific and technical innovation, reducing the devastating impacts of hazardous weather and supporting NOAA’s mission of protecting life and property and enhancing the national economy.

Published
2023
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249. The Caregiver Perspective: An Assistive AAL Platform

Author

Costa, Angelo, Magalhães, Paula, Ferreira-Alves, José, Peixoto, Tito, Simoes, Ricardo, Novais, Paulo, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Kobsa, Alfred, Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Pecchia, Leandro, editor, Chen, Liming Luke, editor, Nugent, Chris, editor, and Bravo, José, editor

Published
2014
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