950 resultados para Science--History--Early works to 1800


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This paper describes an innovative approach to develop the understanding about the relevance of mathematics to computer science. The mathematical subjects are introduced through an application-to-model scheme that lead computer science students to a better understanding of why they have to learn math and learn it effectively. Our approach consists of a single one semester course, taught at the first semester of the program, where the students are initially exposed to some typical computer applications. When they recognize the applications' complexity, the instructor gives the mathematical models supporting such applications, even before a formal introduction to the model in a math course. We applied this approach at Unesp (Brazil) and the results include a large reduction in the rate of students that abandon the college and better students in the final years of our program.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Artificial selection for starvation resistance provided insight into the relationships between evolved physiological and life history trait responses following exposure to biologically induced stress. Investigations of alterations to body composition, metabolic rate, movement, and life history traits including development time, female egg production, and longevity in response to brief periods of starvation were conducted on genetically based starvation-resistant and control lines of Drosophila melanogaster. Analysis of the starvation-resistant lines indicated increased energy storage with increased triglyceride deposition and conversion of carbohydrates to lipid, as identified by respiratory quotient values. Correlations between reductions in metabolic rates and movement in the starvation-resistant lines, suggested the presence of an evolved physiological response resulting in energy conservation. Investigations of life history traits in the starvation-resistant lines indicated no significant differences in development time or reproduction between the selected and control lines. Measurements of longevity, however, indicated a significant reduction in starvation-resistant D. melanogaster lifespan. These results suggested that elevated lipid concentrations, similar to that observed with obesity, were correlated with premature mortality. Exposure of the starvation-resistant and control lines to diets supplemented with glucose, palmitic acid, and a 2:1 mixture of casein to albumin were used to investigate alterations in body composition, movement, and life history traits. Results obtained from this study indicated that increased sugar in the diet led to increased carbohydrate, glycogen, total sugar, trehalose, and triglyceride concentrations, while increased fat and protein in the diet resulted in increased soluble protein, carbohydrate, glycogen, total sugar, and trehalose concentrations. Examination of life history trait responses indicated reduced fecundity in females exposed to increased glucose concentrations. Increased supplementations of palmitic acid was consistently correlated with an overall reduction in lifespan in both the starvation-resistant and control Drosophila lines, while measurements of movement indicated increased female activity levels in flies exposed to diets supplemented with fat and protein. Analyses of the physiological and life history trait responses to starvation and dietary supplementation on Drosophila melanogaster used in the present study has implications for investigating the mechanisms underlying the development and persistence of human obesity and associated metabolic disorders.

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To evaluate the rate and degree of osseointegration at chemically modified moderately rough, hydrophilic (SLActive) and moderately rough, hydrophobic (SLA) implant surfaces during early phases of healing in a human model.

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by Isidor Blum. With special contrib. by William Rosenau ...

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by Henry Thatcher Fowler

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Recent advances in radiometric dating result in significant improvements in the geological timescale and provide better insight into the timing of various processes and evolutions within the Earth's system. However, no radiometric ages are contained within the Givetian. Consequently, the absolute ages of the Givetian Stage boundaries, as well as the stage's duration, remain poorly constrained. As an alternative, the analysis of sedimentary cycles allows for the estimation of the duration of this stage. We examined the high-resolution magnetic susceptibility signals of four Givetian outcrops in the Givet area for a possible astronomical imprint, to fully understand the rates of evolutionary and environmental change. All four sections are firmly correlated and wavelet analyses of the magnetic susceptibility signals reveal the imprint of astronomical eccentricity forcing. The highly stable 405 kyr cycles constrain the duration of the Givetian Stage at 4.35±0.45 Myr, which is in good agreement with the International Chronostratigraphic Chart (5.0 Myr). The studied sections also exhibit an imprint of obliquity, suggesting a climatic teleconnection between low and high latitudes. The corresponding microfacies curves demonstrate similar astronomical imprint, and thereby indicate that the observed 10**5 year-scale cyclicity is the result of climatic and environmental change.

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Nearly complete Paleogene sedimentary sequences were recovered by Leg 114 to the subantarctic South Atlantic. Silicoflagellate assemblages from the Paleogene and immediately overlying lower Neogene from Sites 698 (Northeast Georgia Rise), 700 (East Georgia Basin), 702 (Islas Orcadas Rise), and 703 (Meteor Rise) were examined. The described assemblage from Hole 700B represents the most complete yet described from the Paleocene, encompassing planktonic foraminifer Zones Plb (upper part) through P4 and Subchrons C25N to C23N. All lower Eocene sediments are barren as a result of diagenesis, except for a single sample from Hole 698A. Middle Eocene silicoflagellates described from Hole 702B range in age from early middle Eocene (P10) to late Eocene (PI5), with correlations to Subchrons C21N to C18N. Hole 703A contains late Eocene through early Miocene assemblages, with paleomagnetic control from Subchrons C16R to C6AAN. Leg 114 biosiliceous sequences contain exceptionally diverse assemblages of silicoflagellates. Approximately 155 species and separate morphotypes are described from the Paleogene and earliest Neogene. New taxa described from Leg 114 sediments include Bachmannocena vetula n. sp., Corbisema animoparallela n. sp., Corbisema camara n. sp., Corbisema constricta spinosa n. subsp., Corbisema delicata n. sp., Corbisema hastata aha n. subsp., Corbisema praedelicata n. sp., Corbisema scapana n. sp., Corbisema triacantha lepidospinosa n. subsp., Dictyocha deflandreifurtivia n. subsp., Naviculopsis biapiculata nodulifera n. subsp., Naviculopsis cruciata n. sp., Naviculopsis pandalata n. sp., Naviculopsis primativa n. sp., and Naviculopsis trispinosa eminula n. subsp. Taxonomic revisions were made to the following taxa: Corbisema constricta constricta emended, Corbisema disymmetrica crenulata n. comb., Corbisema jerseyensis emended, and Distephanus antarcticus n. comb. Silicoflagellate assemblages from the Paleogene and earliest Neogene of Holes 698A, 699A, 700B, 702B, and 703A are the basis of a silicoflagellate zonation spanning the interval from 63.2 to 22.25 Ma. Silicoflagellate zones recognized in this interval include the Corbisema hastata hastata Zone, Corbisema hastata aha Zone, Dictyocha precarentis Zone, Naviculopsis constricta Zone, Naviculopsis foliacea Zone, Bachmannocena vetula Zone, Dictyocha grandis Zone, Naviculopsis pandalata Zone, Naviculopsis constricta-Bachmannocena paulschulzii Zone, Bachmannocena paulschulzii Zone, Naviculopsis trispinosa Zone with subzones a and b, Corbisema archangelskiana Zone, Naviculopsis biapiculata Zone, Distephanus raupii Zone, Distephanus raupii-Corbisema triacantha Zone, and Corbisema triacantha mediana Zone.