940 resultados para The Black President
Resumo:
Drawing on longitudinal data from the Early Childhood Longitudinal Study, Kindergarten Class of 1998–1999, this study used IRT modeling to operationalize a measure of parental educational investments based on Lareau’s notion of concerted cultivation. It used multilevel piecewise growth models regressing children’s math and reading achievement from entry into kindergarten through the third grade on concerted cultivation and family context variables. The results indicate that educational investments are an important mediator of socioeconomic and racial/ethnic disparities, completely explaining the black-white reading gap at kindergarten entry and consistently explaining 20 percent to 60 percent and 30 percent to 50 percent of the black-white and Hispanic-white disparities in the growth parameters, respectively, and approximately 20 percent of the socioeconomic gradients. Notably, concerted cultivation played a more significant role in explaining racial/ethnic gaps in achievement than expected from Lareau’s discussion, which suggests that after socioeconomic background is controlled, concerted cultivation should not be implicated in racial/ethnic disparities in learning.
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The objective of this descriptive-exploratory study was to identify the health beliefs of black individuals with hypertension regarding the barriers and benefits of diet for controlling the disease, including the sociodemographic factors associated with the health beliefs surrounding diet control. One hundred and six black adults with hypertension were interviewed using a specific instrument. The data were analyzed considering the percentages, frequency of the cases, scores and prevalence ratio. The global analysis of beliefs showed a preponderance of beliefs regarding the benefits of diet control. It was observed that men, younger individuals, lack of a partner and low educational level and income were related to the beliefs regarding the benefits of adopting a healthy diet. In conclusion, health promotion among the black population requires an interdisciplinary approach and specific health policies addressing this populations' needs, aimed at preventive and curative aspects.
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Predation of Caiman yacare (Spix, 1825) (Crocodilia, Alligatoridae) by Busarellus nigricollis (Latham, 1790) (Accipitriformes, Accipitridae) in the Taiama Ecological Station, Alto Pantanal, State of Mato Grosso. The Black-collared Hawk Busarellus nigricollis is an Accipitridae commonly seen on river banks, lagoon shores, and marshy areas. It feeds mainly on fishes and aquatic insects. It hunts from dead tree branches at forest edges or emergent trunks in flooded areas. Detailed information about the Black-collared Hawk food habits is scarce. In this study, we describe the predation of Caiman yacare (Pantanal alligator) by an individual of B. nigricollis. The event was observed on 20 August 2010 at 10: 14 am, in the Taiama Ecological Station, municipality of Caceres, Alto Pantanal, state of Mato Grosso. The B. nigricollis individual was seen leaving the Paraguay River carrying a juvenile C. yacare around 40 cm long. The prey was torn apart and given to a Black-collared Hawk nestling sitting atop a nest in flooded forest, ca. 15 m way from the river bank. This is the first published record of Pantanal alligator predation by the Black-collared Hawk.
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The following varieties of natural quartz, as the blue, the green, the red, the pink, the black, the sulphurous and the milky quartz, have been investigated concerning their thermoluminescence properties. For comparison sake natural colorless alpha quartz has been include. Since X-rays diffraction analysis has shown that all of them have the same crystal structure as the alpha quartz, it is expected that no great change in the TL property should be found, however, that was not the case. The TL peaks at 110, 175, 220, 325 and 375 degrees C observed in the alpha quartz are not found in all the varieties of quartz, for instance, the sulphurous quartz presented only 110 degrees and 245 degrees peaks, the pink one presented just 110, 220 and 375 degrees C peaks and so on. In respect to TL response as function of gamma ray dose a quite varied behavior has been observed and discussed. (C) 2012 Elsevier B.V. All rights reserved.
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Abstract Background The family Accipitridae (hawks, eagles and Old World vultures) represents a large radiation of predatory birds with an almost global distribution, although most species of this family occur in the Neotropics. Despite great morphological and ecological diversity, the evolutionary relationships in the family have been poorly explored at all taxonomic levels. Using sequences from four mitochondrial genes (12S, ATP8, ATP6, and ND6), we reconstructed the phylogeny of the Neotropical forest hawk genus Leucopternis and most of the allied genera of Neotropical buteonines. Our goals were to infer the evolutionary relationships among species of Leucopternis, estimate their relationships to other buteonine genera, evaluate the phylogenetic significance of the white and black plumage patterns common to most Leucopternis species, and assess general patterns of diversification of the group with respect to species' affiliations with Neotropical regions and habitats. Results Our molecular phylogeny for the genus Leucopternis and its allies disagrees sharply with traditional taxonomic arrangements for the group, and we present new hypotheses of relationships for a number of species. The mtDNA phylogenetic trees derived from analysis of the combined data posit a polyphyletic relationship among species of Leucopternis, Buteogallus and Buteo. Three highly supported clades containing Leucopternis species were recovered in our phylogenetic reconstructions. The first clade consisted of the sister pairs L. lacernulatus and Buteogallus meridionalis, and Buteogallus urubitinga and Harpyhaliaetus coronatus, in addition to L. schistaceus and L. plumbeus. The second clade included the sister pair Leucopternis albicollis and L. occidentalis as well as L. polionotus. The third lineage comprised the sister pair L. melanops and L. kuhli, in addition to L. semiplumbeus and Buteo buteo. According to our results, the white and black plumage patterns have evolved at least twice in the group. Furthermore, species found to the east and west of the Andes (cis-Andean and trans-Andean, respectively) are not reciprocally monophyletic, nor are forest and non-forest species. Conclusion The polyphyly of Leucopternis, Buteogallus and Buteo establishes a lack of concordance of current Accipitridae taxonomy with the mtDNA phylogeny for the group, and points to the need for further phylogenetic analysis at all taxonomic levels in the family as also suggested by other recent analyses. Habitat shifts, as well as cis- and trans-Andean disjunctions, took place more than once during buteonine diversification in the Neotropical region. Overemphasis of the black and white plumage patterns has led to questionable conclusions regarding the relationships of Leucopternis species, and suggests more generally that plumage characters should be used with considerable caution in the taxonomic evaluation of the Accipitridae.
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This experimental thesis concerns the study of the long-term behaviour of ancient bronzes recently excavated from burial conditions. The scientific interest is to clarify the effect of soil parameters on the degradation mechanisms of ancient bronze alloy. The work took into consideration bronzes recovered from the archaeological sites in the region of Dobrudja, Romania. The first part of research work was dedicated to the characterization of bronze artefacts using non destructive (micro-FTIR, reflectance mode) and micro-destructive (based on sampling and analysis of a stratigraphical section by OM and SEM-EDX) methods. Burial soils were geologically classified and analyzed by chemical methods (pH, conductivity, anions content). Most of objects analyzed showed a coarse and inhomogeneous corroded structure, often made up of several corrosion layers. This has been explained by the silt nature of soils, which contain low amount of clay and are, therefore, quite accessible to water and air. The main cause of a high dissolution rate of bronze alloys is the alternate water saturation and instauration of the soil, for example on a seasonal scale. Moreover, due to the vicinity of the Black Sea, the detrimental effect of chlorine has been evidenced for few objects, which were affected by the bronze disease. A general classification of corrosion layers was achieved by comparing values of the ratio Cu/Sn in the alloy and in the patina. Decuprification is a general trend, and enrichment of copper within the corrosion layers, due to the formation of thick layers of cuprite (Cu2O), is pointed out as well. Uncommon corrosion products and degradation patterns were presented as well, and they are probably due to peculiar local conditions taking place during the burial time, such as anaerobic conditions or fluctuating environmental conditions. In order to acquire a better insight into the corrosion mechanisms, the second part of the thesis has regarded simulation experiments, which were conducted on commercial Cu-Sn alloys, whose composition resembles those of ancient artefacts one. Electrochemical measurements were conducted in natural electrolytes, such as solutions extracted from natural soil (sampled at the archaeological sites) and seawater. Cyclic potentiodynamic experiments allowed appreciating the mechanism of corrosion in both cases. Soil extract’s electrolyte has been evaluated being a non aggressive medium, while artificial solution prepared by increasing the concentration of anions caused the pitting corrosion of the alloy, which is demonstrated by optical observations. In particular, electrochemical impedance spectroscopy allows assessing qualitatively the nature of corroded structures formed in soil and seawater. A double-structured layer is proposed, which differ, in the two cases, for the nature of the internal passive layer, which result defectiveness and porous in case of seawater.
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Linear dispersal systems, such as coastal habitats, are well suited for phylogeographic studies because of their low spatial complexity compared to three dimensional habitats. Widely distributed coastal plant species additionally show azonal and often essentially continuous distributions. These properties, firstly, make it easier to reconstruct historical distributions of coastal plants and, secondly, make it more likely that present distributions contain both Quaternary refugia and recently colonized areas. Taken together this makes it easier to formulate phylogeographic hypotheses. This work investigated the phylogeography of Cakile maritima and Eryngium maritimum, two species growing in sandy habitats along the north Atlantic Ocean and the Mediterranean Sea coasts on two different spatial scales using AFLP data. The genetic structure of these species was investigated by sampling single individuals along most of their distributions from Turkey to south Sweden. On a regional scale the population genetic structure of both species was also studied in detail in the Bosporus and Dardanelles straits, the Strait of Gibraltar and along a continuous stretch of dunes in western France. Additionally, populations of C. maritima were investigated in the Baltic Sea/Kattegat/North Sea area. Over the complete sampling range the species show both differences and similarities in their genetic structure. In the Mediterranean Sea, both species contain Aegean Sea/Black Sea and west Mediterranean clusters. Cakile maritima additionally shows a clustering of Ionian Sea/Adriatic Sea collections. Further, both species show a subdivision of Atlantic Ocean/North Sea/Baltic Sea material from Mediterranean. Within the Atlantic Ocean group, C. maritima from the Baltic Sea and the most northern Atlantic localities form an additional cluster while no such substructure was found in E. maritimum. In all three instances where population genetic investigations of both species were performed in the same area, the results showed almost complete congruency of spatial genetic patterns. In the Aegean/Black Sea/Marmara region a subdivision of populations into a Black Sea, a Sea of Marmara and an Aegean Sea group is shared by both species. In addition the Sea of Marmara populations are more close to the Aegean Sea populations than they are to the Black Sea populations in both cases. Populations from the Atlantic side of the Strait of Gibraltar are differentiated from those on the Mediterranean side in both species, a pattern that confirms the results of the wide scale study. Along the dunes of West France no clear genetic structure could be detected in any of the species. Additionally, the results from the Baltic Sea/North Sea populations of C. maritima did not reveal any geographical genetic pattern. It is postulated that the many congruencies between the species are mainly due to a predominantly sea water mediated seed dispersal in both species and their shared sandy habitat. The results are compared to hypothetical distributions for the last glacial maximum based on species specific temperature requirements. It is argued that in both species the geographical borders of the clusters in the Mediterranean area were not affected by quaternary temperature changes and that the Aegean/Black Sea/Marmara cluster, and possibly the Ionian Sea/Adriatic Sea cluster in C. maritima, is the result of sea currents that isolate these basins from the rest of the sampled areas. The genetic gap in the Strait of Gibraltar between Atlantic Ocean and Mediterranean Sea populations in both species is also explained in terms of sea currents. The existence of three subgroups corresponding to the Aegean Sea, Black Sea and Sea of Marmara basins is suggested to have arisen due to geographical isolation during periods of global sea regressions in the glacials. The population genetic evidence was inconclusive regarding the Baltic Sea cluster of C. Maritima from the wide scale study. The results of this study are very similar to those of an investigation of three other coastal plant species over a similar range. This suggests that the phylo-geographic patterns of widespread coastal plants may be more predictable than those of other terrestrial plants.
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Three published papers are resumed in this thesis. Different aspects of the semiclassical theory of gravity are discussed. In chapter 1 we find a new perturbative (yet analytical) solution to the unsolved problem of the metric junction between two Friedmann-Robertson-Walker using Israel's formalism. The case of an expanding radiation core inside an expanding or collapsing dust exterior is treated. This model can be useful in the "landscape" cosmology in string theory or for treating new gravastar configurations. In chapter 2 we investigate the possible use of the Kodama vector field as a substitute for the Killing vector field. In particular we find the response function of an Unruh detector following an (accelerated) Kodama trajectory. The detector has finite extension and backreaction is considered. In chapter 3 we study the possible creation of microscopic black holes at LHC in the brane world model. It is found that the black hole tidal charge has a fundamental role in preventing the formation of the horizon.
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The aim of this work is to explore, within the framework of the presumably asymptotically safe Quantum Einstein Gravity, quantum corrections to black hole spacetimes, in particular in the case of rotating black holes. We have analysed this problem by exploiting the scale dependent Newton s constant implied by the renormalization group equation for the effective average action, and introducing an appropriate "cutoff identification" which relates the renormalization scale to the geometry of the spacetime manifold. We used these two ingredients in order to "renormalization group improve" the classical Kerr metric that describes the spacetime generated by a rotating black hole. We have focused our investigation on four basic subjects of black hole physics. The main results related to these topics can be summarized as follows. Concerning the critical surfaces, i.e. horizons and static limit surfaces, the improvement leads to a smooth deformation of the classical critical surfaces. Their number remains unchanged. In relation to the Penrose process for energy extraction from black holes, we have found that there exists a non-trivial correlation between regions of negative energy states in the phase space of rotating test particles and configurations of critical surfaces of the black hole. As for the vacuum energy-momentum tensor and the energy conditions we have shown that no model with "normal" matter, in the sense of matter fulfilling the usual energy conditions, can simulate the quantum fluctuations described by the improved Kerr spacetime that we have derived. Finally, in the context of black hole thermodynamics, we have performed calculations of the mass and angular momentum of the improved Kerr black hole, applying the standard Komar integrals. The results reflect the antiscreening character of the quantum fluctuations of the gravitational field. Furthermore we calculated approximations to the entropy and the temperature of the improved Kerr black hole to leading order in the angular momentum. More generally we have proven that the temperature can no longer be proportional to the surface gravity if an entropy-like state function is to exist.
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The analysis of apatite fission tracks is applied to the study of the syn- and post-collisional thermochronological evolution of a vast area that includes the Eastern Pontides, their continuation in the Lesser Caucasus of Georgia (Adjara-Trialeti zone) and northern Armenia, and the eastern Anatolian Plateau. The resulting database is then integrated with the data presented by Okay et al. (2010) for the Bitlis Pütürge Massif, i.e. the western portion of the Bitlis-Zagros collision zone between Arabia and Eurasia. The mid-Miocene exhumation episode along the Black Sea coast and Lesser Caucasus of Armenia documented in this dissertation mirrors the age of collision between the Eurasian and Arabian plates along the Bitlis suture zone. We argue that tectonic stresses generated along the Bitlis collision zone were transmitted northward across eastern Anatolia and focused (i) at the rheological boundary between the Anatolian continental lithosphere and the (quasi)oceanic lithosphere of the Black Sea, and (ii) along major pre-existing discontinuities like the Sevan-Akera suture zone.The integration of both present-day crustal dynamics (GPS-derived kinematics and distribution of seismicity) and thermochronological data presented in this paper provides a comparison between short- and long-term deformation patterns for the entire eastern Anatolia-Transcaucasian region. Two successive stages of Neogene deformation of the northern foreland of the Arabia-Eurasia collision zone can be inferred. (i) Early and Middle Miocene: continental deformation was concentrated along the Arabia-Eurasia (Bitlis) collision zone but tectonic stress was also transferred northward across eastern Anatolia, focusing along the eastern Black Sea continent-ocean rheological transition and along major pre-existing structural discontinuities. (ii) Since Late-Middle Miocene time the westward translation of Anatolia and the activation of the North and Eastern Anatolian Fault systems have reduced efficient northward stress transfer.
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General Relativity is one of the greatest scientific achievementes of the 20th century along with quantum theory. These two theories are extremely beautiful and they are well verified by experiments, but they are apparently incompatible. Hints towards understanding these problems can be derived studying Black Holes, some the most puzzling solutions of General Relativity. The main topic of this Master Thesis is the study of Black Holes, in particular the Physics of Hawking Radiation. After a short review of General Relativity, I study in detail the Schwarzschild solution with particular emphasis on the coordinates systems used and the mathematical proof of the classical laws of Black Hole "Thermodynamics". Then I introduce the theory of Quantum Fields in Curved Spacetime, from Bogolubov transformations to the Schwinger-De Witt expansion, useful for the renormalization of the stress energy tensor. After that I introduce a 2D model of gravitational collapse to study the Hawking radiation phenomenon. Particular emphasis is given to the analysis of the quantum states, from correlations to the physical implication of this quantum effect (e.g. Information Paradox, Black Hole Thermodynamics). Then I introduce the renormalized stress energy tensor. Using the Schwinger-De Witt expansion I renormalize this object and I compute it analytically in the various quantum states of interest. Moreover, I study the correlations between these objects. They are interesting because they are linked to the Hawking radiation experimental search in acoustic Black Hole models. In particular I find that there is a characteristic peak in correlations between points inside and outside the Black Hole region, which correpsonds to entangled excitations inside and outside the Black Hole. These peaks hopefully will be measurable soon in supersonic BEC.
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Nowadays the environmental issues and the climatic change play fundamental roles in the design of urban spaces. Our cities are growing in size, many times only following immediate needs without a long-term vision. Consequently, the sustainable development has become not only an ethical but also a strategic need: we can no longer afford an uncontrolled urban expansion. One serious effect of the territory industrialisation process is the increase of urban air and surfaces temperatures compared to the outlying rural surroundings. This difference in temperature is what constitutes an urban heat island (UHI). The purpose of this study is to provide a clarification on the role of urban surfacing materials in the thermal dynamics of an urban space, resulting in useful indications and advices in mitigating UHI. With this aim, 4 coloured concrete bricks were tested, measuring their emissivity and building up their heat release curves using infrared thermography. Two emissivity evaluation procedures were carried out and subsequently put in comparison. Samples performances were assessed, and the influence of the colour on the thermal behaviour was investigated. In addition, some external pavements were analysed. Albedo and emissivity parameters were evaluated in order to understand their thermal behaviour in different conditions. Surfaces temperatures were recorded in a one-day measurements campaign. ENVI-met software was used to simulate how the tested materials would behave in two typical urban scenarios: a urban canyon and a urban heat basin. Improvements they can carry to the urban microclimate were investigated. Emissivities obtained for the bricks ranged between 0.92 and 0.97, suggesting a limited influence of the colour on this parameter. Nonetheless, white concrete brick showed the best thermal performance, whilst the black one the worst; red and yellow ones performed pretty identical intermediate trends. De facto, colours affected the overall thermal behaviour. Emissivity parameter was measured in the outdoor work, getting (as expected) high values for the asphalts. Albedo measurements, conducted with a sunshine pyranometer, proved the improving effect given by the yellow paint in terms of solar reflection, and the bad influence of haze on the measurement accuracy. ENVI-met simulations gave a demonstration on the effectiveness in thermal improving of some tested materials. In particular, results showed good performances for white bricks and granite in the heat basin scenario, and painted concrete and macadam in the urban canyon scenario. These materials can be considered valuable solutions in UHI mitigation.
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Automatic design has become a common approach to evolve complex networks, such as artificial neural networks (ANNs) and random boolean networks (RBNs), and many evolutionary setups have been discussed to increase the efficiency of this process. However networks evolved in this way have few limitations that should not be overlooked. One of these limitations is the black-box problem that refers to the impossibility to analyze internal behaviour of complex networks in an efficient and meaningful way. The aim of this study is to develop a methodology that make it possible to extract finite-state automata (FSAs) descriptions of robot behaviours from the dynamics of automatically designed complex controller networks. These FSAs unlike complex networks from which they're extracted are both readable and editable thus making the resulting designs much more valuable.
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Clothes offer us a commentary on the individual who wears them, and one of those comments deals with gender. Clothing is fundamental to gender, turning male and female bodies into men and women. In the nineteenth century the preoccupation with appear- ances was greater than in previous periods thanks to changes in the social system and a reformulation of gender roles, as well as the popularity of physiognomic theory. Given this increased sensitivity to the gaze, it is curious that men would uniformly adopt the black suit as their garment of choice. This revolution in male fashion was born from contradic- tory motives. On the one hand, the man in black attempted to avoid the gaze so as not to be anyone’s object of desire. An exception to this rule was the elegante, for whom fashion was a way of life. The elegante became a frequent target of the satirical press, which ques- tioned his masculinity. On the other hand, the black suit came simbolize the power of the ascendant middle class because it recalled Spain’s most important monarchs, such as Carlos V and Felipe II. The black suit thus became a polysemic signifier, and the man who wore it attempted, impossibly, to be both the subject and object of the gaze.
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This project attempts to contribute to the various discourses within the black womanist tradition. In 1983, Alice Walker published her landmark collection of essays entitled In Search of Our Mother Gardens: Womanist Prose. At the outset of the volume, Walker defines the core concept of womanism. After a poetic four-part definition of the term womanist, Walker concludes by stating, 'womanist is to feminist as purple to lavender' (Phillips 19). Although this analogy is critically engaged, the scholarly discourse that emerged in response to Walker's proposition shapes the intellectual inner workings of this project. Certain established concepts (such as ancestral mediation or the laying on of hands) work in conjunction with my own concepts of 'wom(b)anism' and 'the communal womb' to frame the interpretive discussions throughout these pages. Wom(b)anism and the communal womb both emerge from the black feminist and womanist traditions, especially via the role of ancestral mediation but also within the contested discourses on womanism itself. I apply the two concepts (wom(b)anism and the communal womb) to my readings of Haile Gerima's Sankofa, Gloria Naylor's The Women of Brewster Place, and Gayl Jones' Corregidora. The relationship between the community and women's wombs across each of these texts construct a narrative that features ancestral mediation (or intervention), various acts of violence committed against women's bodies, and the complicated circumstances through which women heal themselves andtheir communities.