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Search Results: 1 - 10 of 87 matches for " Isolda; "
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On the pointwise convergence to initial data of heat and Poisson problems for the Bessel operator
Isolda Cardoso
Mathematics , 2015,
Abstract: We find optimal integrability conditions on the initial data $f$ for the existence of solutions $e^{-t\Delta_{\lambda}}f(x)$ and $e^{-t\sqrt{\Delta_{\lambda}}}f(x)$ of the heat and Poisson initial data problems for the Bessel operator $\Delta_{\lambda}$ in $\mathbb{R}^{+}$. We also characterize the most general class of weights $v$ for which the solutions converge a.e. to $f$ for every $f\in L^{p}(v)$, with $1\le p<\infty$. Finally, we show that for such weights and $1
Es la violencia de género y el acceso a la justicia un asunto de Derechos Humanos
Heredia de Salvatierra,Isolda;
Revista Venezolana de Estudios de la Mujer , 2006,
Abstract: the problem of access to justice for women who suffer violence is the subject of this article, and the reflection is made on whether this is a matter of human rights. from the description of the gender violence is considered the international and national juridical framework of women?s human rights. the question raised is the following: what is happening in venezuela? the author concludes giving some suggestions.
Aplicaciones de la biogeografía histórica a la distribución de las plantas mexicanas
Luna-Vega, Isolda;
Revista mexicana de biodiversidad , 2008,
Abstract: biogeographical patterns of the mexican flora are explained based on 3 different theories, considering number of species, endemisms, and relations among areas: 1) dispersalist theory, where mexico has been considered as the receiver of elements of different sources or geographic areas, considering that it is located in the transition zone between the nearctic and neotropical regions, which along the autochthonous ones form a complex mixture of species with different origins, both spatial and temporal, 2) vicariant theory, that proposes a close relationship between the earth's history and the history of the biota, so that the number of species and their distribution may be explained by the complex geologic history of mexico, and 3) pleistocenic glaciations, which explain the recent distributional patterns of plants based on ecological and historical arguments, based on paleoclimatic changes of the recent past. a continuous debate within historical biogeography has high lighted the importance of biogeography as source of evidence for taxonomy and vice versa. historical biogeography has a close relationship with systematics, but is an independent discipline within comparative biology. biogeography is undergoing a conceptual revolution that is causing a revision of its fundamentals and methods. the utilization of different methods in an integrative manner in the same analysis may maximize the advantages of each one.
Aplicaciones de la biogeografía histórica a la distribución de las plantas mexicanas Historical biogeography applied to the distribution of Mexican plants
Isolda Luna-Vega
Revista mexicana de biodiversidad , 2008,
Abstract: Los patrones biogeográficos de laflora mexicana, tanto en número de especies como de endemismos y relaciones entre áreas, han sido explicados a la luz de 3 teorías: 1) la dispersalista, donde México se considera receptor de elementos de diferentes fuentes o áreas geográficas, sobre todo si se toma en cuenta que está ubicado en la zona de transición entre la regiones neártica y neotropical que, junto con los autóctonos, han constituido un complejo mosaico de especies con diferentes orígenes, tanto espaciales como temporales; 2) la teoría de la vicarianza, que propone que hay una estrecha correspondencia entre la historia de la Tierra y la historia de la biota, por lo que el número de especies y su distribución tendrían que explicarse esencialmente de acuerdo con la compleja historia geológica de México y 3) el efecto de las glaciaciones pleistocénicas, que mediante eventos ecológicos e históricos explica los patrones contemporáneos de la distribución, con base en los cambios paleoclimáticos del pasado reciente. El debate fundamental al interior de la biogeografía histórica ha recaído en la importancia que tiene como fuente de evidencia para la taxonomía y viceversa. La biogeografía histórica, aunque posee una estrecha relación con la sistemática, es una disciplina independiente dentro de la biología comparada, que puede operar paralelamente a esta última. La biogeografía está en un proceso de revolución conceptual que ha propiciado la revisión de sus fundamentos y métodos. La utilización de diferentes métodos de una manera integrativa en un mismo análisis permite maximizar las bondades de cada uno de ellos. Biogeographical patterns of the Mexican flora are explained based on 3 different theories, considering number of species, endemisms, and relations among areas: 1) dispersalist theory, where Mexico has been considered as the receiver of elements of different sources or geographic areas, considering that it is located in the transition zone between the Nearctic and Neotropical regions, which along the autochthonous ones form a complex mixture of species with different origins, both spatial and temporal, 2) vicariant theory, that proposes a close relationship between the earth's history and the history of the biota, so that the number of species and their distribution may be explained by the complex geologic history of Mexico, and 3) pleistocenic glaciations, which explain the recent distributional patterns of plants based on ecological and historical arguments, based on paleoclimatic changes of the recent past. A continuous debate within historical biog
Explicit fundamental solutions of some second order differential operators on Heisenberg groups
Isolda Cardoso,Linda Saal
Mathematics , 2012,
Abstract: Let $p,q,n$ be natural numbers such that $p+q=n$. Let $\FF$ be either $\CC$, the complex numbers field, or $\HH$, the quaternionic division algebra. We consider the Heisenberg group $N(p,q,\FF)$ defined as $N(p,q,\FF)=\FF^{n}\times \mathfrak{Im}\FF$, with group law given by $$(v,\zeta)(v',\zeta')=(v+v', \zeta+\zeta'-{1/2} \mathfrak{Im} B(v,v')),$$ where $B(v,w)=\sum_{j=1}^{p} v_{j}\bar{w_{j}} - \sum_{j=p+1}^{n} v_{j}\bar{w_{j}}$. Let $U(p,q,\FF)$ be the group of $n\times n$ matrices with coefficients in $\FF$ that leave invariant the form $B$. In this work we compute explicit fundamental solutions of some second order differential operators on $N(p,q,\FF)$ which are canonically associated to the action of $U(p,q,\FF)$.
Evaluation of the corrosion resistance of AISI 316 stainless steel filters
Barbosa, Luzinete Pereira;Costa, Isolda;
Materials Research , 2005, DOI: 10.1590/S1516-14392005000200013
Abstract: in this investigation, the corrosion resistance of aisi 316 ss filters prepared with powders in the size ranges 74-44 μm and 210-105 μm and compacted with pressures of 300 mpa and 400 mpa has been evaluated in naturally aerated 0.5 m h2so4 solution at 25 °c. weight loss of filters manufactured with compacting pressure of 400 mpa were significantly higher than that of filters compacted at 300 mpa. the filter compacted at 400 mpa had higher carbon and nitrogen contents compared to those compacted at 300 mpa. the former also had chromium rich precipitates and oxides in the grain boundaries. the pores in filters compacted at 400 mpa were smaller than in filters compacted at 300 mpa. smaller pores favor the formation of concentration cells and consequently, increased crevice corrosion.
Análisis de trazos para establecer áreas de conservación en la faja volcánica transmexicana
Torres Miranda,Andrés; Luna Vega,Isolda;
Interciencia , 2006,
Abstract: the transmexican volcanic belt is recognized as a province based on geologic, tectonic, geomorphologic and biogeographic characteristics. the belt is a volcanic arch extending from the pacific coast in jalisco and nayarit states to the atlantic coast in veracruz. its formation began in the middle miocene, with a final episode in the last pliocene-quaternary, where most of the volcanic complex was formed. a trace analysis of 136 organisms (birds, mammals, reptiles, ferns and oaks) was undertaken, and 8 generalized traces and 15 nodes were found. six of them were found in the cuencas de toluca-mexico-puebla region. several of the nodes found were reported in previous works, and many of them coincide with priority terrestrial regions and important bird conservation areas. using complementarity analysis, four conservation priority areas are proposed, following the criteria of conserving the lowest number of areas with a large number of species. these areas are, in order of importance: valle de méxico-sierra de chichinautzin-sierra nevada corridor, cofre de perote-ca?ón de río blanco corridor, volcán de san juan node, and pátzcuaro node.
The effect of hydrogen peroxide on the electrochemical behaviour of Ti-13Nb-13Zr alloy in Hanks' solution
Assis, Sérgio Luiz de;Costa, Isolda;
Materials Research , 2006, DOI: 10.1590/S1516-14392006000400014
Abstract: titanium alloys are largely used for biomedical applications mainly due to their high corrosion resistance resulting from the protective oxide film formed on their surface. the literature, however, has pointed out discrepancies between in vitro tests and in vivo tests. these discrepancies have been ascribed to hydrogen peroxide (h2o2) generated by inflammatory reactions. in this investigation the electrochemical behaviour of a ti-13nb-13zr alloy, which was developed as material for implants, has been evaluated in hanks' solution, with and without h2o2. the evolution of the electrochemical behavior was monitored by electrochemical impedance spectroscopy (eis) and the results were fitted to an equivalent circuit that simulates an oxide film as a duplex layer structure composed of an inner barrier layer and an outer porous layer. in the solution without h2o2, the oxide film was very stable during the whole test period. on the other hand, in the solution with h2o2, the eis results varied significantly, indicating a progressive decrease in the barrier layer resistance until 35 days which was followed by the restoration of the barrier layer protective characteristics against corrosion, either due to its growth or to its self-healing after partial consumption of the oxidant agent. the oxide film formed on the ti alloy samples after 125 days of immersion in hanks' solution, either with or without h2o2 was analyzed by xps. the xps results revealed the presence of tio and tio2 on the samples immersed in the two electrolytes, however, ti2o3 was only found on the samples exposed to the h2o2 containing solution.
The effect of polarisation on the electrochemical behavior of Ti-13Nb-13Zr alloy
Assis, Sérgio Luiz de;Costa, Isolda;
Materials Research , 2007, DOI: 10.1590/S1516-14392007000300014
Abstract: the effect of potentiostatic polarisation on the electrochemical behavior of the ti-13nb-13zr alloy was investigated by electrochemical impedance spectroscopy (eis) and potentiodynamic polarisation curves in hanks' solution at 37 °c. potentiodynamic polarisation curves show a passive behavior with a slight current increase as potentials around 1300 mv(sce). based on these curves, different potentials were chosen to perform potentiostatic eis experiments. eis experimental data were interpreted using different equivalent circuits associated with the duplex nature of the oxide layer. the fitting procedure evidenced the thickening of a defective oxide layer with the applied potentials, corresponding to key points in the potentiodynamic polarisation curves.
Apresenta o: pessoa e ambiente, as duas faces da mesma moeda
Isolda de Araújo Günther
Paidéia (Ribeir?o Preto) , 2008, DOI: 10.1590/s0103-863x2008000100003
Abstract:
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