Três teorias e uma prática pedagógica: a história da matemática, os fundos de conhecimento e a pedagogia culturalmente relevante

O presente trabalho apresenta e discute como os professores podem utilizar de teorias da Educação na prática pedagógica da sala de aula. Para isso, esse artigo teórico apresenta a Perspectiva Sociocultural da História da Matemática, os Fundos de Conhecimento e a Pedagogia Culturalmente Relevante. Essas teorias estão embasadas na cultura dos alunos para atingirem um ensino e uma aprendizagem visando formar alunos críticos e capazes de utilizarem o que aprenderam na escola para discutir as diferenças existentes entre os grupos minoritários e majoritários na sociedade atual. É apresentada uma atividade envolvendo as três teorias

On rigidly rotating perfect fluid cylinders

The gravitational field of a rigidly rotating perfect fluid cylinder with gamma- law equation of state is found analytically. The solution has two parameters and is physically realistic for gamma in the interval (1.41,2]. Closed timelike curves always appear at large distances.Comment: 10 pages, Revtex (galley

Fractionation of potentially toxic elements in urban soils from five European cities by means of a harmonised sequential extraction procedure

The revised (four-step) BCR sequential extraction procedure has been applied to fractionate the chromium, copper, iron, manganese, nickel, lead and zinc contents in urban soil samples from public-access areas in five European cities. A preliminary inter-laboratory comparison was conducted and showed that data obtained by different laboratories participating in the study were sufficiently harmonious for comparisons to be made between cities and land types (e.g. parks, roadside, riverbanks, etc.). Analyte recoveries by sequential extraction, with respect to direct aqua regia digestion, were generally acceptable (100 ± 15%). Iron, nickel and, at most sites, chromium were found mainly in association with the residual phase of the soil matrix. Copper was present in the reducible, oxidisable and residual fractions, whilst zinc was found in all four sequential extracts. Manganese was strongly associated with reducible material as, in some cities, was lead. This is of concern because high lead concentrations were present in some soils (>500 mg kg−1) and the potential exists for remobilisation under reducing conditions. As would be expected, extractable metal contents were generally highest in older, more heavily industrialised cities. Copper, lead and zinc showed marked (and often correlated) variations in concentrations between sites within the same city whereas manganese and, especially, iron, did not. No overall relationships were, however, found between analyte concentrations and land use, nor between analyte partitioning and land use

Uniqueness in the Freedericksz transition with weak anchoring

In this paper we consider a boundary value problem for a quasilinear pendulum equation with nonlinear boundary conditions that arises in a classical liquid crystals setup, the Freedericksz transition, which is the simplest opto-electronic switch, the result of competition between reorienting effects of an applied electric field and the anchoring to the bounding surfaces. A change of variables transforms the problem into the equation x = −f(x) for ∈ (−T, T), with boundary conditions x = ± T f(x) at = ∓T, for a convex nonlinearity f. By analyzing an associated inviscid Burgers' equation, we prove uniqueness of monotone solutions in the original nonlinear boundary value problem. This result has been for many years conjectured in the liquid crystals literature, e. g. in E. G. Virga, Variational Theories for Liquid Crystals,Chapman and Hall, London, 1994 and in I. W. Stewart, The Static and Dynamic Continuum Theory of Liquid Crystals: A Mathematical Introduction, Taylor and Francis, London, 2003

Stationary Cylindrical Anisotropic Fluid

We present the whole set of equations with regularity and matching conditions required for the description of physically meaningful stationary cylindrically symmmetric distributions of matter, smoothly matched to Lewis vacuum spacetime. A specific example is given. The electric and magnetic parts of the Weyl tensor are calculated, and it is shown that purely electric solutions are necessarily static. Then, it is shown that no conformally flat stationary cylindrical fluid exits, satisfying regularity and matching conditions.Comment: 17 pages Latex. To appear in Gen.Rel.Gra

Agricultura familiar na amazônia: a trituração da capoeira como alternativa à queimada e seus efeitos sobre atributos físico-químicos do solo.

Resumo: 407

Basket Cases and Breadbaskets: Sacred Rice and Agricultural Development in Postcolonial Africa

Author's final manuscript.Based on ethnographic research among rural Diola in Guinea-Bissau, I provide a broad view of the history and interpenetration of rice in social, political, religious, and ecological domains, while chronicling the current difficulties of residents in this region who are no longer able to grown enough of it. These farmers’ experiences are unfolding at a time of revitalized attention to agricultural development in Africa, particularly under the auspices of the New Green Revolution for Africa. I examine the premises that constitute the resuscitated effort to address the plight of African farmers. I argue that the totalizing quality of rice in Diola and other rice-cultivating societies requires a development approach that takes into account dimensions of agrarian life not encapsulated by the high- modernist and anti-political orientation of the New Green Revolution for Africa

Response of CO₂ and CH₄ emissions from Arctic tundra soils to a multifactorial manipulation of water table, temperature and thaw depth

Significant uncertainties persist concerning how Arctic soil tundra carbon emission responds to environmental changes. In this study, 24 cores were sampled from drier (high centre polygons and rims) and wetter (low centre polygons and troughs) permafrost tundra ecosystems. We examined how soil CO2 and CH4 fluxes responded to laboratory-based manipulations of soil temperature (and associated thaw depth) and water table depth, representing current and projected conditions in the Arctic. Similar soil CO2 respiration rates occurred in both the drier and the wetter sites, suggesting that a significant proportion of soil CO2 emission occurs via anaerobic respiration under water-saturated conditions in these Arctic tundra ecosystems. In the absence of vegetation, soil CO2 respiration rates decreased sharply within the first 7 weeks of the experiment, while CH4 emissions remained stable for the entire 26 weeks of the experiment. These patterns suggest that soil CO2 emission is more related to plant input than CH4 production and emission. The stable and substantial CH4 emission observed over the entire course of the experiment suggests that temperature limitations, rather than labile carbon limitations, play a predominant role in CH4 production in deeper soil layers. This is likely due to the presence of a substantial source of labile carbon in these carbon-rich soils. The small soil temperature difference (a median difference of 1 ◦C) and a more substantial thaw depth difference (a median difference of 6 cm) between the high and low temperature treatments resulted in a non-significant difference between soil CO2 and CH4 emissions. Although hydrology continued to be the primary factor influencing CH4 emissions, these emissions remained low in the drier ecosystem, even with a water table at the surface. This result suggests the potential absence of a methanogenic microbial community in high-centre polygon and rim ecosystems. Overall, our results suggest that the temperature increases reported for these Arctic regions are not responsible for increases in carbon losses. Instead, it is the changes in hydrology that exert significant control over soil CO2 and CH4 emissions

Evaluation of respiratory muscle strength in overweight/obese children and adolescents

OBJECTIVE: Evaluate respiratory muscle strength in overweight/obese children and adolescents. METHODS: This cross-sectional study enrolled patients between four and 15 years old, classified according to the National Center for Health Statistics curve for body mass index (BMI): Overweight/Obese Group (OG, BMI> 85th percentile) and Normal Weight Group (NG, BMI between 5th and 85th percentile). Manuvacuometer was used to measure maximal inspiratory pressure (MaxInspP) and maximal expiratory pressure (MaxExpP). Three measurements were obtained using the maximum pulmonary effort and the higher value was considered. Variables were compared by t test chi-square test. Adjustment of possible covariants was made by analysis of covariance, being significant p<0.05. RESULTS: 69 children were included: 37 (54%) in the OG and 32 (46%) in the NG. Obese patients were younger: 9.8±2.3 versus 10.9±1.9 years (p=0.031). MaxInspP was 71.4±24.9cmH2O in the OG and 89.6±19.6cmH2O (p=0.002). MaxExpP was 71.9±24.8cmH2O in the OG and 95.6±19.6cmH2O in the NG (p<0.001). There was no difference between groups regarding gender and physical activity. After adjustment for age, only the MaxExpP was significantly different between groups (p=0.003). CONCLUSIONS: Maximal expiratory pressure was lower in overweight/obese patients, indicating that obesity may alter pulmonary mechanics.OBJETIVO: Avaliar a força muscular respiratória de crianças e adolescentes com sobrepeso ou obesidade. MÉTODOS: Estudo transversal com crianças e adolescentes entre quatro e 15 anos de idade de duas instituições de ensino fundamental e uma clínica de nutrição. As crianças foram avaliadas e classificadas em dois grupos, de acordo com a curva proposta pelo National Center for Health Statistics: sobrepeso/obesos (GSO, índice de massa corpórea (IMC) em relação à idade e ao sexo acima do percentil 85) e eutróficos (GE, IMC entre percentil 5 e 85). Para avaliar as pressões inspiratória máxima (PImax) e expiratória máxima (PEmax) foram realizadas três medidas com um manovacuômetro, considerando-se a maior medida a partir da capacidade máxima inspiratória e expiratória. Aplicou-se o teste t para as variáveis quantitativas e o qui-quadrado para as qualitativas. Para ajuste das covariáveis, foi feita a análise de covariância, sendo significante p<0,05. RESULTADOS: Foram avaliadas 69 crianças: 37 (54%) do GSO e 32 (46%) eutróficos. O GSO apresentou menor idade (9,8±2,3 versus 10,9±1,9 anos; p=0,03). A PImax foi 71,4±24,9cmH2O no GSO e 89,6±19,6cmH2O nos eutróficos (p=0,002). A PEmax foi 71,9±24,8cmH2O no GSO e 95,6±19,6cmH2O nos eutróficos (p<0,001). Não houve diferenças quanto ao sexo e à prática de atividade física. Ajustando-se os valores em relação à idade, somente a PEmax manteve-se diferente entre os grupos (p=0,003). CONCLUSÕES: A força muscular expiratória mostrou-se diminuída nesta amostra de crianças e adolescentes com sobrepeso/obesidade, indicando que a obesidade pode comprometer a mecânica pulmonar dessa população.UNIFESPUniversidade Guarulhos Unidade de Terapia Intensiva AdultoHospital Alemão Oswaldo CruzUNIFESP, EPM, São PauloSciEL