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The evolution of habitable zones during stellar lifetimes and its implications on the search for extraterrestrial life
- D.R. Underwood, B.W. Jones, P.N. Sleep
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- Journal:
- International Journal of Astrobiology / Volume 2 / Issue 4 / October 2003
- Published online by Cambridge University Press:
- 09 March 2004, pp. 289-299
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A stellar evolution computer model has been used to determine changes in the luminosity L and effective temperature Te of single stars during their time on the main sequence. The range of stellar masses investigated was from 0.5 to 1.5 times that of the Sun, each with a mass fraction of metals (metallicity, Z) from 0.008 to 0.05. The extent of each star's habitable zone (HZ) has been determined from its values of L and Te. These stars form a reference framework for other main sequence stars. All of the 104 main sequence stars known to have one or more giant planets have been matched to their nearest stellar counterpart in the framework, in terms of mass and metallicity, hence closely approximating their HZ limits. The limits of HZ, for each of these stars, have been compared to their giant planet(s)'s range of strong gravitational influence. This allows a quick assessment as to whether Earth-mass planets could exist in stable orbits within the HZ of such systems, both presently and at any time during the star's main sequence lifetime. A determination can also be made as to the possible existence of life-bearing satellites of giant planets, which orbit within HZs. Results show that about half of the 104 known extrasolar planetary systems could possibly have been housing an Earth-mass planet in HZs during at least the past billion years, and about three-quarters of the 104 could do so for at least a billion years at some time during their main sequence lives. Whether such Earth-mass planets could have formed is an urgent question now being investigated by others, with encouraging results.
Chapter 6 - Banana and Plantain
- Edited by Dominic Fuccillo, University of Arkansas, Linda Sears, International Plant Genetic Resources Institute, Rome, Paul Stapleton, International Plant Genetic Resources Institute, Rome
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- Book:
- Biodiversity in Trust
- Published online:
- 22 September 2009
- Print publication:
- 28 August 1997, pp 67-81
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Summary
BOTANY AND DISTRIBUTION
The genus Musa belongs to the Musaceae family, and ‘banana plant’ describes all wild species, landraces and cultivars. ‘Plantain’ describes landraces whose fruit is eaten cooked, mainly in Central and West Africa (Simmonds 1962; Stover and Simmonds 1987). Cultivated banana exhibits parthenocarpic fruit development, a marked degree of sterility, and vegetative propagation. Wild banana (Table 6.1) exhibits sexual reproduction and vegetative propagation by ratooning. Common names are numerous (Jarret 1990), and in Uganda alone Karamura and Karamura (1994) have identified 566 names used just for the subgroup Mutika/Lujugira of the AAA group.
Virtually all the cultivars derive from the Eumusa section, which Simmonds and Weatherup (1990) have divided into two subsections, Eumusa (1) and Eumusa (2). Edible banana plants derived from the Eumusa section are mainly based on the recognition of a single source for most varieties, Musa acuminata (A genome) and M. balbisiana (B genome) (Cheesman 1947,1948; Dodds and Simmonds 1948). The Australimusa section is important as a genetic source of domestication for textile fibres (Abaca or Manila hemp) and the edible Fe'i or Fehi cultivars, found only in the Pacific Islands. Callimusa and Australimusa have a basic chromosome number of 10 (2n=20) while Eumusa and Rhodochlamys have 11 (2n=22). The Simmonds and Shepherd (1955) classification associates the ploidy level (2n=2x, 3x or 4x) with a different contribution of genomes of two species.
1 - Sacrifice and holiness
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- By D.R. Jones
- Edited by S. W. Sykes
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- Book:
- Sacrifice and Redemption
- Published online:
- 10 March 2010
- Print publication:
- 28 June 1991, pp 9-21
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Summary
When in English we speak of the institution of sacrifice, we commonly refer to the system of worship which has its most characteristic and effective action in the slaughter of a victim. Sacrifice is pre-eminently bloody sacrifice. But the word has a wider connotation and comprehends the surrender to the deity of some object or possession which may be other than a beast or a bird, for the purpose of propitiation or homage. ‘sacrifice’ may also denote the victim itself or anything else that is offered. A derivative usage is its application to human self-giving. A man may sacrifice comfort or income for the sake of some higher goal, or in war may, as we say, pay the supreme sacrifice.
The picture however becomes progressively less clear as we examine the use of the word ‘sacrifice’ in the English Versions of the Bible, the Vulgate, the Septuagint, the Greek New Testament and the Hebrew of the Old Testament. Neither in the Old Testament nor in the New is there any word for the institution as a whole. Yet in the Authorized Version and the English Versions dependent upon it the noun is used up to two hundred times. In the majority of cases in the Old Testament, ‘sacrifice’ renders the Hebrew word zebah. Although the verb means ‘to kill’, this is the term for a particular sacrifice to be distinguished from the coldh or holocaust. When the two terms occur together, the English Versions, including the New English Bible and Revised English Bible (which for example in Leviticus, carefully distinguishes the zebah as ‘shared-offering’) render them as ‘sacrifice and burnt-offering’, or, in the case of the NEB ‘sacrifice and whole-offering’.