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Search Results: 1 - 10 of 36723 matches for " Daniel Brito "
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Genetic consequences of population subdivision: the marsupial Micoureus paraguayanus (Mammalia: Didelphimorphia) as a case study
Brito, Daniel;
Zoologia (Curitiba) , 2009, DOI: 10.1590/S1984-46702009000400013
Abstract: habitat fragmentation may cause population subdivision, affecting genetic variation, leading to heterozygosity loss and increased inbreeding, and contributing to population extinction. however, some genetic models have shown that under some conditions, population subdivision can favor heterozygosity and allelic diversity, and small populations may adapt to inbreeding. here i investigate the relationship between population subdivision and genetic diversity for the marsupial micoureus paraguayanus (tate, 1931) using the program vortex. hypothetical populations of 100 and 2000 individuals were partitioned into 1, 2, 5 or 10 populations that were linked by varying rates of dispersal and also by sex-biased dispersal. results suggested that heterozygosity and allelic diversity declined rapidly when a population was subdivided. genetic and demographic stochasticity diminished the effectiveness of selection against recessive lethal alleles. dispersal partly reversed the impacts of population subdivision. however, even high rates of dispersal did not eliminate demographic fluctuations or prevent extinction. although gene flow largely prevented genetic divergence between populations, dispersal did not prevent heterozygosity from being lost more rapidly in subdivided populations than in single populations of equivalent total size. the dynamics of small, fragmented populations were critically dependent on interactions between demographic and genetic processes. populations of m. paraguayanus may have to be relatively large and continuous to avoid significant losses of genetic diversity.
A SUDAM e a crise da moderniza??o for?ada: reforma do estado e sustentabilidade na Amaz?nia
Brito, Daniel Chaves de;
Ambiente & Sociedade , 2001, DOI: 10.1590/S1414-753X2001000800005
Abstract: this article presents a study of the crisis of the politics of development of the amaz?nia. in a first level, it focus in the perspective of the state reform in the 1990s; in a second level it relates that perspective to the need of building a structure that makes possible developmental action based on proposals of sustainability. the analysis ends with the presentation of some proposals of reform made by developmental institutions (sudam/basa) and, in this context, it shows the difficulties to transform a system that has been based on patrimonial principles in its political actions.
Temporal and spatial investments in the protected area network of a megadiverse country
Rodolfo Cabral,Daniel Brito
Zoologia (Curitiba) , 2013,
Abstract: Protected area networks are the cornerstone strategy for biodiversity conservation worldwide. They are efficient even in the face of human pressures. Brazil is a megadiverse country and for this reason it should not be left out of discussions on biodiversity conservation. Here we present a temporal and spatial analysis of the historical national investments in the country's protected area network. We compare this investment in the light of international biodiversity agreements (e.g., CBD), and evaluate trends and biases in the establishment of protected areas. We obtained the following data from a database maintained by the Brazilian government: the number of protected areas, the dates when they were established, their size and category (strict protection or sustainable use). Our results show that Brazil does not meet the recommended international levels of protection, that its network coverage favors a few of its biomes only, and that the temporal flow of investments has varied greatly. Even though there is a tendency for an increase in the establishment of protected areas, there has been a noteworthy change in the categories more recent protected areas are inserted. Until the 1980's the network was comprised mostly of strict protection sites, whereas the newly created sites are mostly intended for sustainable use. This reflects a serious philosophical and practical change in the role of the national protected area network, and may affect its objectives in preserving the biodiversity of a country that plays a key role in the global biodiversity conservation scenario.
Threats to and viability of the giant anteater, Myrmecophaga tridactyla (Pilosa: Myrmecophagidae), in a protected Cerrado remnant encroached by urban expansion in central Brazil
Milena F. Diniz,Daniel Brito
Zoologia (Curitiba) , 2013,
Abstract: Urbanization poses a serious threat to wildlife populations inhabiting native vegetation remnants surrounded by the expanding urban and suburban sprawl. The close contact with human activities causes not only direct impacts, such as habitat loss, but also indirect negative effects, such as population isolation, roadkills and anthropogenic fires. The Parque Nacional de Brasília is a large Cerrado remnant almost completely surrounded by the city of Brasília, in central Brazil. Here, we use population viability analysis to model the impacts of urbanization on a population of Myrmecophaga tridactyla (Linnaeus, 1758) inhabiting that park. Our results show that roadkill mortality is by far the most serious threat to the long-term persistence of the giant anteater in the study site. The implementation of measures to better control vehicle speed in the vicinity of the park is urgently needed if we expect the giant anteater population to be effectively protected in the Parque Nacional de Brasília.
Ambivalência e medo: faces dos riscos na modernidade
Brito, Daniel Chaves de;Barp, Wilson José;
Sociologias , 2008, DOI: 10.1590/S1517-45222008000200003
Abstract: in the diagnosis of the modernity, uncertainty and insecurity - and therefore the fear - they are present elements. leaving of that verification, this work has for objective to describe the ambivalent effects of the fear on the contemporary society. in that attempt, the support of several social theories is looked for that, although they don't focus the fear, they show the constant risks of the modernization process in a certain way. on the other hand, that allows to separate the social critic, that it still tries to continue thinking the modernity with base about the conceptual premises of the western reason, of another one, that for your own fatigue proclaims your self-destruction. understands each other here that to say good-bye of the reason and to consider the autonomous movement of the modernity is to do a process that just guarantees the modernization of the fear to appear.
On the existence and structure of a mush at the inner core boundary of the Earth
Renaud Deguen,Thierry Alboussière,Daniel Brito
Physics , 2008, DOI: 10.1016/j.pepi.2007.05.003
Abstract: It has been suggested about 20 years ago that the liquid close to the inner core boundary (ICB) is supercooled and that a sizable mushy layer has developed during the growth of the inner core. The morphological instability of the liquid-solid interface which usually results in the formation of a mushy zone has been intensively studied in metallurgy, but the freezing of the inner core occurs in very unusual conditions: the growth rate is very small, and the pressure gradient has a key role, the newly formed solid being hotter than the adjacent liquid. We investigate the linear stability of a solidification front under such conditions, pointing out the destabilizing role of the thermal and solutal fields, and the stabilizing role of the pressure gradient. The main consequence of the very small solidification rate is the importance of advective transport of solute in liquid, which tends to remove light solute from the vicinity of the ICB and to suppress supercooling, thus acting against the destabilization of the solidification front. For plausible phase diagrams of the core mixture, we nevertheless found that the ICB is likely to be morphologically unstable, and that a mushy zone might have developed at the ICB. The thermodynamic thickness of the resulting mushy zone can be significant, from $\sim100$ km to the entire inner core radius, depending on the phase diagram of the core mixture. However, such a thick mushy zone is predicted to collapse under its own weight, on a much smaller length scale ($\lesssim 1$ km). We estimate that the interdendritic spacing is probably smaller than a few tens of meter, and possibly only a few meters.
Structure, diffusion and orientational freezing in lithium metasilicate
Cristian Balbuena,Carolina Brito,Daniel A. Stariolo
Physics , 2013, DOI: 10.1088/0953-8984/26/15/155104
Abstract: We report on the dynamic and structural characterization of lithium metasilicate $Li_2SiO_3$, a network forming ionic glass, by means of molecular dynamics simulations. The system is characterized by a network of $SiO_4$ tetrahedra disrupted by $Li$ ions which diffuse through the network. Measures of mean square displacement of $Si$ and $O$ atoms allow us to identify a temperature at which tetrahedra stop moving relative to each other. This temperature $T_c\approx 1500\,K$ can be characterized within the framework of mode coupling theory. At a much lower temperature $T_g\approx 1000\,K$, a change in the slope of the volume versus temperature data allows to single out the glass transition. We find signatures of both transitions in structural order parameters, related to the orientation of tetrahedra. Going down in temperature we find that, around the mode coupling transition temperature, a set of order parameters which measure the relative orientation of tetrahedra cease to increase and stay constant below $T_c$. Another well known measure of orientational order, the bond orientational order parameter, which in the studied system measures local order within single tetrahedrons, is found to continue growing below $T_c$ until $T_g$, below which it remains constant. Our results allow to relate two characteristic dynamic transitions with corresponding structural transitions, as observed in two different orientational order parameters. Furthermore, the results indicate that the network of thetrahedra continue to relax well below the point where neighboring tetrahedra cannot rearrange relative to each other, and the glass is reached only upon a process of relaxation of atoms which form the thetrahedron, as quantified by the change in the bond orientational order parameters.
'Diabetology & Metabolic Syndrome: providing an open access future for diabetes research'
Daniel Giannella-Neto, Marília de Brito Gomes
Diabetology & Metabolic Syndrome , 2009, DOI: 10.1186/1758-5996-1-1
Abstract: Among the many good reasons to launch a new open access journal devoted to publishing articles in the field of diabetes research is the fact diabetes is seen as a pandemic condition of unprecedented proportions. In 2007 there were an estimated 246 million cases of diabetes worldwide, with the Western Pacific and the European regions having the highest numbers, approximately 67 and 53 million, respectively. The prevalence of diabetes is projected to rise in both developed and developing countries. In the seven regions of the International Diabetes Federation (IDF) the estimated numbers of cases will be 380 million by 2025. In addition, in many populations, diabetes is most common among the elderly but prevalence rates will significantly rise among comparatively young and productive populations in the developing world [1].Type 2 diabetes mellitus constitutes about 85% to 95% of all diabetes cases in developed countries and accounts for an even higher percentage in developing countries mostly due to increased urbanization, westernization and economic development, which predispose to obesity due to high consumption of industrialized foods and physical inactivity [2]. Moreover, because of the inefficiency and lack of professional and material resources, the public health systems in developing countries will be facing an increasing number of people with poorly controlled diabetes more predisposed to the devastating microvascular and macrovascular consequences of the disease.In addition to the increasing numbers of diabetes cases, there are many challenges to face in optimising diabetes care. Highlighting this are studies into the factors, which can help in predicting the likelihood of achieving glycaemic control across various regions of the World. The International Diabetes Management Practice Study (IDMPS) concluded that short disease duration and use of few oral antidiabetic drugs were predictive factors for achieving HbA1C <7% in 9,901 T2DM patients recruited by 937 p
A moderniza??o na era das incertezas: crise e desafios da teoria social
Brito, Daniel Chaves de;Ribeiro, Tania Guimar?es;
Ambiente & Sociedade , 2003, DOI: 10.1590/S1414-753X2003000200009
Abstract: this article discusses the challenges posed to the modern social theories and generated by the crisis in development planning theories in view of the formation of a risk society - individual, social and environmental. in this sense, the theses formulated within the scope of the theories of development, that promised to accomplish happiness for humanity, became a normative and theoretical project of modernization-rationalization based on the certainty of its results through planning. however, as opposed to this perspective conceived under the enlightenment, the article finally presents the idea of progress parallel to an imminent situation of social risks arguing against the modern social theories and their perspective of global analysis.
Weak Diameter and Cyclic Properties in Oriented Graphs
BRITO,DANIEL; ORDAZ,OSCAR; VARELA,MARíA TERESA;
Revista Colombiana de Matemáticas , 2011,
Abstract: we describe several conditions on the minimum number of arcs ensuring that any two vertices in a strong oriented graph are joining by a path of length at most a given k, or ensuring that they are contained in a common cycle.
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