Influence of Some Rheological Parameters On Flexure of the Oceanic Lithosphere

International audienceS U M M A R Y Rheological parameters describe properties of the lithosphere, but it is generally impossible to measure them in situ. Thus a model has to be developed to relate parameters to observables. We consider flexure of the oceanic lithosphere. A quantitative representation of a brittle-elastic-ductile rheology is based on a semi-empirical model. The non-linear problem of plate flexure is solved by the multiple-shooting algorithm using a Runge-Kutta procedure from analytical solutions for an elastic model. The bending moment and its derivatives have been deduced analytically to improve the accuracy and speed of computations. A family of numerical solutions was built that describes flexure of the oceanic lithosphere at subduction zones for various ages, strain rates, and activation energies. Relative contributions of rheological parameters are discussed. The model is then used to evaluate rheological parameters of the Kuril trench from gravity data. The strain rate estimates are found to be about 3. 10-('6*1)s-1 assuming creep activation energies between 520 kJ/mole and 550 kJ/mole for lithospheric age ranging from 90 Ma to 110 Ma

Joint inversion of teleseismic and GOCE gravity data: application to the Himalayas

Our knowledge and understanding of the 3-D lithospheric structure of the Himalayas and the Tibetan Plateau is still challenging although numerous geophysical studies have been performed in the region. The GOCE satellite mission has the ambitious goal of mapping Earth's gravity field with unprecedented precision (i.e. an accuracy of 1-2 mGal for a spatial resolution of 100 km) to observe the lithosphere and upper-mantle structure. Consequently, it gives new insights in the lithospheric structure beneath the Himalayas and the Tibetan Plateau. Indeed, the GOCE gravity data now allow us to develop a new strategy for joint gravimetry-seismology inversion. Combined with teleseismic data over a large region in a joint inversion scheme, they will lead to lithospheric velocity-density models constrained in two complementary ways. We apply this joint inversion scheme to the Hi-CLIMB (Himalayan-Tibetan Continental Lithosphere during Mountain Building) seismological network which was deployed in South Tibet and the Himalayas for a 3-yr period. The large size of the network, the high quality of the seismological data and the new GOCE gravity data set allow us to image the entire lithosphere of this active area in an innovative way. We image 3-D low velocity and density structures in the middle crust that fit the location of discontinuous low S-velocity zones revealed by receiver functions in previous geophysical studies. In the deeper parts of our velocity model we image a positive anomaly interpreted to be the heterogenous Indian lithosphere vertically descending beneath the centre of the Tibetan Platea

Wavelet-based directional analysis of the gravity field: evidence for large-scale undulations

International audienceIn the eighties, the analysis of satellite altimetry data leads to the major discovery of gravity lineations in the oceans, with wavelengths between 200 and 1400 km. While the existence of the 200 km scale undulations is widely accepted, undulations at scales larger than 400 km are still a matter of debate. In this paper, we revisit the topic of the large-scale geoid undulations over the oceans in the light of the satellite gravity data provided by the GRACE mission, considerably more precise than the altimetry data at wavelengths larger than 400 km. First, we develop a dedicated method of directional Poisson wavelet analysis on the sphere with significance testing, in order to detect and characterize directional structures in geophys-ical data on the sphere at different spatial scales. This method is particularly well suited for potential field analysis. We validate it on a series of synthetic tests, and then apply it to analyze recent gravity models, as well as a bathymetry data set independent from gravity. Our analysis confirms the existence of gravity undulations at large scale in the oceans, with characteristic scales between 600 and 2000 km. Their direction correlates well with present-day plate motion over the Pacific ocean, where they are particularly clear, and associated with a conjugate direction at 1500 km scale. A major finding is that the 2000 km scale geoid undulations dominate and had never been so clearly observed previously. This is due to the great precision of GRACE data at those wavelengths. Given the large scale of these undulations, they are most likely related to mantle processes. Taking into account observations and models from other geophysical information, as seismological tomography, convection and geochemical models and electrical conductivity in the mantle, we conceive that all these inputs indicate a directional fabric of the mantle flows at depth, reflecting how the history of subduction influences the organization of lower mantle upwellings

Faecal haemoglobin concentration is related to detection of advanced colorectal neoplasia in the next screening round

Objective: To examine associations between faecal haemoglobin concentrations below the cut-off used in colorectal cancer screening and outcomes in the next screening round.Methods: In the Scottish Bowel Screening Programme, faecal haemoglobin concentrations and diagnostic outcomes were investigated for participants with a negative result (faecal haemoglobin concentrations &lt; 80.0 µg Hb/g faeces), followed by a positive result within two years.Results: Of 37,780 participants with negative results, at the next screening round, 556 (1.5%) screened positive and 30,293 (80.2%) negative. Initial median faecal haemoglobin concentrations (2.1 µg Hb/g faeces, IQR: 0.0-13.2) were higher in those with subsequent positive results than those with subsequent negative results (0.0 µg Hb/g faeces, IQR: 0.0-1.4; p &lt; 0.0001). Using faecal haemoglobin concentrations 0.0-19.9 µg Hb/g faeces as reference, logistic regression analysis showed high adjusted odds ratios for advanced neoplasia (advanced neoplasia: colorectal cancer or higher risk adenoma) detection at the next round of 14.3 (95% CI: 8.9-23.1) in those with initial faecal haemoglobin concentrations 20.0-39.9 µg Hb/g faeces, and 38.0 (95% CI: 20.2-71.2) with 60.0-79.9 µg Hb/g faeces.Conclusions: A higher proportion of participants with faecal haemoglobin concentrations of ≥ 20 µg Hb/g faeces had advanced neoplasia detected at the next round than participants with lower faecal haemoglobin concentrations. Although most relevant when using high faecal haemoglobin concentrations cut-offs, studies of faecal haemoglobin concentrations and outcomes over screening rounds may provide strategies to direct available colonoscopy towards those at highest risk.</p

Polimorfismo do promotor do gene da leptina está associado ao aumento de leptina plasmática e IMC em mulheres brasileiras

Variants in leptin gene (LEP) have been implicated in the pathogenesis of obesity. The relationship between LEP G-2548A polymorphism and obesity-related traits was evaluated in a sample of Brazilian women (n = 228) who were randomly selected from two clinical centers in Sao Paulo city. Blood samples were collected for DNA extraction, plasma leptin and serum lipids measurements. LEP G-2548A genotypes were identified by a PCR- RFLP strategy using the endonuclease Alw44I. LEP G-2548A was associated with obesity after adjustment for covariates (age, hypertension, coronary artery disease, smoking and physical activity). Women carrying G allele had a four times higher risk of obesity than the A allele carriers (OR: 4.11, CI95%: 1.06-15.90, p = 0.041). G allele was also related to increased plasma leptin (p = 0.024) and body mass index (p = 0.027). Hypertension, hyperglycemia, dyslipidemia and coronary artery disease were associated with obesity. However LEP G-2548A polymorphism was not related to these variables. All together these data suggest that LEP G-2548A polymorphism has an important role in regulating plasma leptin levels and body mass index in women.Variantes no gene da leptina (LEP) foram implicados na patogênese da obesidade. A relação entre o polimorfismo LEP G-2548A e as características relacionadas com a obesidade foram avaliadas em mulheres brasileiras (n = 228), que foram selecionadas randomicamente de dois centros de pesquisa clínica na cidade de São Paulo. As amostras de sangue foram coletadas para extração de DNA e determinações de leptina plasmática e lipídeos séricos. Os genótipos do LEP G-2548A foram identificados pela estratégia de PCR-RFLP, empregando a endonuclease Alw44I. O polimorfismo LEP G-2548A foi associado com obesidade, após ajuste para as covariáveis: idade, hipertensão, doença arterial coronariana, tabagismo e atividade física. Mulheres com alelo G tiveram quatro vezes maior risco de obesidade que as portadoras do alelo A (OR: 4,11, CI95%: 1,06-15,90; p = 0,041). O alelo G também foi relacionado com leptina plasmática (p = 0,024) e o índice de massa corporal (p = 0,027) aumentado. A hipertensão, a hiperglicemia, a dislipidemia e a doença arterial coronariana foram associadas com obesidade. Entretanto, o polimorfismo LEP G-2548A não foi relacionado com essas variáveis. Os resultados deste estudo são sugestivos de que o polimorfismo LEP G-2548A tem papel importante na regulação da leptina plasmática e no índice de massa corporal em mulheres

Microgravimetric measurements at the 1994 international comparison of absolute gravimeters

International audienc

Infecção piógena do espaço epidural raquidiano em criança

Registro de um caso de infecção piógena do espaço epidural raquidiano, provavelmente originada de lesão purulenta da pele, o início da sintomatologia ocorrendo após traumatismo da coluna vertebral. Os autores acentuam a importância dos seguintes fatos para o diagnóstico: 1) sintomatologia neurológica limitada à lesão das estruturas contidas no canal raquidiano; 2) as diferenças citoquímicas do liqüido cefalorraquidiano colhido em punções combinadas, suboccipital e lombar; 3) os resultados da mielografia mostrando a lentidão do trânsito da substância contrastante. O tratamento clínico, à base de antibióticos em doses intensas e glicocorticóides por via oral, deu excelentes resultados, demonstrando que, nesses casos agudos, o tratamento conservador deve ser preferido à intervenção cirúrgica

Seizure recurrence in infants with neonatal convulsions a follow-up study: estudo evolutivo

Twenty three infants with neonatal seizures were followed prospectively to a mean age of 11 months. Only 2 were pre-term and birth weight ranged from 1700 to 4230 grams, with 17 male and 6 female infants. Hypoxic-ischemic encephalopathy was the most common etiology (82.6%). Focal clonic convulsions were the predominant seizure type, present in 7/16 infants in which the seizure type could be identified. All infants had a neurological examination and EEC, and 18 had a cranial ultrasonography performed at the follow-up. Anticonvulsant medication was discontinued, if follow-up EEG and neurological examination were normal. At the follow-up, seizure recurrence was observed in 7/23 (30%) infants. Abnormal EEG, neurological examination and cranial ultrasonography were statistically correlated with seizure recurrence. We conclude that infants with neonatal seizures can remain free of anticonvulsant medication provided they have normal neurological examination, EEG and cranial ultrasonography.</jats:p

Bases do desenvolvimento neurológico

E feita uma tentativa de relacionar os modernos conhecimentos da expressão genômica do sistema nervoso (SN) no homem, não sendo intensão deste artigo abordar os aspectos da evolução embrionário-fetal do SN do homem, e sim, enfocar o "equipamento neurológico" com o qual nascemos e como evolvemos para atingir a maturação. São, então, abordados os temas maturação e aprendizagem. Na maturação são ressaltados os aspectos de função e estrutura e, portanto, de mielinização do SN; no segundo aspecto - aprendizagem - são abordadas as várias teorias, dando-se ênfase à teoria do condicionamento, baseada em Pavlov. Após a revisão destas bases, o neurofenótipo da criança é dividido em 3 tipos: manifestações permanentes, manifestações reflexas transitórias e manifestações reflexas evolutivas. O neurofenótipo do RN normal se caracteriza por: 1 - atitude assimétrica tendendo ao padrão do reflexo tônico-cervical assimétrico; 2 - hipertonia generalizada em flexão dos 4 membros, contrastando com a hipotonia da musculatura paravertebral; 3 - presença, em 100% dos RN, dos reflexos miotáticos: patelares, adutores, tricipitais e naso-palpebrais, sendo obrigatória a simetria das respostas; 4 - reflexo cutâneo-plantar em extensão do hálux, com ou sem leque em 100% dos RN; 5 - atividades automáticas ou reflexas presentes em 100% dos RN; reflexo tônico-cervical assimétrico (fragmentado em 70%: completo em 30%), marcha reflexa, apoio plantar automático, sucção; 6 - reflexo dos "olhos de boneca" em 100%; 7 - reflexo fotomotor em 100%. A seguir são apresentadas as fases evolutivas do lactente normal separadas em 5 idades-chaves. Finalmente são apresentadas as conclusões do Exame Neurológico Evolutivo (ENE) do grupo de Lefèvre que mostra importantes correlações entre a maturação e certas funções, principalmente no que diz respeito, à sensibilidade pro-prioceptiva e às sensibilidades gnósicas