Blood flow and oxygen delivery to human brain during functional activity: Theoretical modeling and experimental data

Coupling of cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) in physiologically activated brain states remains the subject of debates. Recently it was suggested that CBF is tightly coupled to oxidative metabolism in a nonlinear fashion. As part of this hypothesis, mathematical models of oxygen delivery to the brain have been described in which disproportionately large increases in CBF are necessary to sustain even small increases in CMRO2 during activation. We have explored the coupling of CBF and oxygen delivery by using two complementary methods. First, a more complex mathematical model was tested that differs from those recently described in that no assumptions were made regarding tissue oxygen level. Second, [15O] water CBF positron emission tomography (PET) studies in nine healthy subjects were conducted during states of visual activation and hypoxia to examine the relationship of CBF and oxygen delivery. In contrast to previous reports, our model showed adequate tissue levels of oxygen could be maintained without the need for increased CBF or oxygen delivery. Similarly, the PET studies demonstrated that the regional increase in CBF during visual activation was not affected by hypoxia. These findings strongly indicate that the increase in CBF associated with physiological activation is regulated by factors other than local requirements in oxygen.

Estudo e aplicação de guias de ondas integrados ao substrato em frequências de micro-ondas.

Esse trabalho de pesquisa apresenta um estudo detalhado sobre guias de ondas integrados ao substrato (SIW) operando em frequências de micro-ondas com base na teoria de guias de ondas retangulares (RWG). O estudo sobre guias SIW associa equações apresentadas na literatura e utiliza simulações eletromagnéticas para desenvolver um procedimento de projeto bem definido. É considerada a integração entre guias SIW e linhas de transmissão de microfita, projetando-se transições entre essas duas estruturas com o propósito de prover casamento de impedância e de viabilizar a caracterização em frequências de micro-ondas. São apresentadas considerações sobre processos de fabricação de circuitos SIW em substratos constituídos por laminados de alta frequência. Uma vez estabelecidos os procedimentos de fabricação e os critérios de projeto, a tecnologia SIW é aplicada ao projeto de três guias de ondas SIW nas bandas S e X, que foram fabricados empregando laminados de alta-frequência. Foram projetados dois filtros SIW passa-faixa empregando cavidades ressonantes e postes metálicos indutivos. Os dois filtros operam na frequência central de 10,61 GHz, sendo que um deles tem banda de passagem de 7,5%e é de 3ª ordem e o outro filtro tem banda de passagem de 15%, sendo de 5ª ordem. Foram realizadas comparações entre o desempenho simulado e experimental das estruturas SIW projetadas. Os resultados de simulações eletromagnéticas e experimentais demonstraram boa concordância. Os projetos em tecnologia SIW apresentados neste trabalho de pesquisa possuem perdas de retorno melhores que 10 dB na banda de operação e perdas por inserção de 1,0 dB a 1,5 dB. É apresentada a análise da sensibilidade do desempenho dos guias de ondas e filtros SIW projetados a desvios dimensionais típicos do processo de fabricação por microfresagem mecânica. Com os resultados experimentais e de simulação foi possível validar os procedimentos de projeto e de fabricação de circuitos SIW operando em frequências de micro-ondas.

Rules and orders relating to a Professor of the Mathematicks, of Natural and Experimental Philosophy, in Harvard College, 18 January 1726

This folder contains a single document describing the "rules and orders" of the Hollis Professor of Mathematics and Natural Philosophy. The document begins by defining the subjects to be taught by the Hollis Professor including natural and experimental philosophy, elements of geometry, and the principles of astronomy and geography. It then outlines the number of public and private lectures to be given to students, how much extra time the professor should spend with students reviewing any difficulties they may encounter understanding class subject matter discussed, and stipulates that the professor's duties shall be restricted solely to his teaching activities and not involve him in any religious activities at the College or oblige him to teach any additional studies other than those specified for the Hollis Professor of Mathematics and Natural Philosophy. Furthermore, the rules establish the professor's salary at £80 per year and allow the professor to receive from students, except those students studying theology under the Hollis Professor of Divinity, an additional fee as determined by the Corporation and Board of Overseers, to supplement his income. Moreover, the rules assert that all professorship candidates selected by the Harvard Corporation must be approved by Thomas Hollis during his lifetime or by his executor after his death. Finally, the rules state that the Hollis professor take an oath to the civil government and declare himself a member of the Protestant reformed religion. This document is signed by Thomas Hollis and four witnesses, John Hollis, Joshua Hollis, Richard Solly, and John Williams.

Bulletin / Ontario Agricultural College and Experimental Farm.

124-125

Die EU-Volksabstimmungen in Österreich, Finnland, Schweden und Norwegen. Verlauf, Ergebnisse Motive und Folgen = The EU referendums in Austria, Finland, Sweden and Norway. Results, motives and consequences. Institute for Advanced Studies Political Science Series No. 23, 1995

This paper analysis the 1994 EU referenda in Austria, Finland, Sweden and Norway in a comparative perspective. It shows that the results were, to some extent at least, related to how pronounced the respective elite consensus was on the necessity or desirability of EU membership. It also shows that in all cases the main motivation of the Yes voters was economic. The paper goes on to analyse the regional and social variations in voting patterns. In the concluding chapter some of the medium- and longterm effects of the referenda debates and results on Austrian, Finnish and Swedish government policy within the EU are outlined.