1,339 research outputs found
Evidence for short cooling time in the Io plasma torus
We present empirical evidence for a radiative cooling time for the Io plasma torus that is about a factor of ten less than presently accepted values. We show that brightness fluctuations of the torus in the extreme ultraviolet (EUV) at one ansa are uncorrelated with the brightness at the other ansa displaced in time by five hours, either later or earlier. Because the time for a volume of plasma to move from one ansa to the other is only five hours, the cooling time must be less than this transport time in order to wipe out memory of the temperatures between ansae. Most (âŒ80â85%) of the EUV emission comes from a narrow (presumably ribbonâlike) feature within the torus. The short cooling time we observe is compatible with theoretical estimates if the electron density in the ribbon is âŒ10^4/cm^3. The cooling time for the rest of the torus (which radiates the remaining 15â20% of the power) is presumably consistent with the previously derived 20âhour values. A nearlyâcontinuous heating in both longitude and time is needed to maintain the EUV visibility of the torus ribbonâa requirement not satisfied by presently available theories
Anelagem como tratamento silvicultural em oito espécies arbóreas na floresta amazÎnica.
bitstream/item/57840/1/CPATU-ComTec95.pd
Superthermal electron processes in the upper atmosphere of Uranus: Aurora and electroglow
Strong ultraviolet emissions from the upper atmosphere of Uranus suggest that both auroral and electroglow phenomena are of significant aeronomical consequences in the structure of the upper atmosphere. Combined modeling and data analysis were performed to determine the effect of electroglow and auroral phenomena on the global heat and atomic hydrogen budgets in the Uranus upper atmosphere. The results indicate that the auroral and electroglow heat sources are not adequate to explain the high exospheric temperature observed at Uranus, but that the atomic hydrogen supplied by these processes is more than sufficient to explain the observations. The various superthermal electron distributions modeled have significantly different efficiencies for the various processes such as UV emission, heating, ionization, and atomic hydrogen production, and produce quite different H2 band spectra. However, additional information on the UV spectra and global parameters is needed before modeling can be used to distinguish between the possible mechanisms for electroglow
Composição florĂstica e estrutura de uma ĂĄrea de cinco hectares de mata alta sem babaçu na Floresta Nacional do TapajĂłs.
bitstream/item/63279/1/Oriental-Doc63.pd
Teste de anelagem em espécies arbóreas na floresta amazÎnica.
bitstream/item/40147/1/Cic-Tec-75-CPATU.pd
Teste de duas modalidades de anelagem em oito espécies arbóreas na floresta amazoÎnica.
bitstream/item/57543/1/CPATU-PA178.pd
'A habitual disposition to the good': on reason, virtue and realism
Amidst the crisis of instrumental reason, a number of contemporary political philosophers including JĂŒrgen Habermas have sought to rescue the project of a reasonable humanism from the twin threats of religious fundamentalism and secular naturalism. In his recent work, Habermas defends a post-metaphysical politics that aims to protect rationality against encroachment while also accommodating religious faith within the public sphere. This paper contends that Habermasâ post-metaphysical project fails to provide a robust alternative either to the double challenge of secular naturalism and religious fundamentalism or to the ruthless instrumentalism that underpins capitalism. By contrast with Habermas and also with the ânew realismâ of contemporary political philosophers such as Raymond Geuss or Bernard Williams, realism in the tradition of Plato and Aristotle can defend reason against instrumental rationality and blind belief by integrating it with habit, feeling and even faith. Such metaphysicalâpolitical realism can help develop a politics of virtue that goes beyond communitarian thinking by emphasising plural modes of association (not merely âcommunityâ), substantive ties of sympathy and the importance of pursuing goodness and mutual flourishing
The community of advantage
This paper gives an overview of my recently published book, The Community of Advantage: A Behavioural Economistâs Defence of the Market. I explain that my stance as author is that of a behavioural economist and an economic liberal. The book is an attempt to counter the widespread belief that the findings of behavioural economics justify regulatory interventions in the economy that would previously have been thought unacceptably paternalistic. I argue that competitive markets are desirable, not as an efficient means for satisfying the given preferences of assumedly rational individuals, but as an institutional structure that provides opportunities for whatever voluntary transactions people might want to make
NG7538 IRS1 N: modeling a circumstellar maser disk
We present an edge-on Keplerian disk model to explain the main component of
the 12.2 and 6.7 GHz methanol maser emission detected toward NGC7538-IRS1 N.
The brightness distribution and spectrum of the line of bright masers are
successfully modeled with high amplification of background radio continuum
emission along velocity coherent paths through a maser disk. The bend seen in
the position-velocity diagram is a characteristic signature of differentially
rotating disks. For a central mass of 30 solar masses, suggested by other
observations, our model fixes the masing disk to have inner and outer radii of
about 270 AU and 750 AU.Comment: To appear in The Proceedings of the 2004 European Workshop: "Dense
Molecular Gas around Protostars and in Galatic Nuclei", Eds. Y. Hagiwara,
W.A. Baan, H.J. van Langevelde, 2004, a special issue of ApSS, Kluwe
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