595 research outputs found
Nucleosynthesis of Elements in Low to Intermediate Mass Stars through the AGB Phase
We present a review of the main phases of stellar evolution with particular
emphasis on the nucleosynthesis and mixing mechanisms in low- and
intermediate-mass stars. In addition to explicit studies of the effects of the
first, second and third dredge-up, we also discuss cool bottom processing and
hot bottom burning.Comment: 30 pages, latex, 18 figures, uses style files aipproc.cls aipproc.sty
epsf.sty ; to be published in (refereed) conference proceedings
"Astrophysical Implications of the Laboratory Study of Presolar Materials",
ed. T. Bernatowitz and E. Zinner (AIP: Sunnyside, NY), in press; also
available at http://www.maths.monash.edu.au/~boothroy
Our Sun. V. A Bright Young Sun Consistent with Helioseismology and Warm Temperatures on Ancient Earth and Mars
The relatively warm temperatures required on early Earth and Mars have been
difficult to account for via warming from greenhouse gases. We tested whether
this problem can be resolved for both Earth and Mars by a young Sun that is
brighter than predicted by the standard solar model. We computed high-precision
solar evolutionary models with slightly increased initial masses of M_i = 1.01
to 1.07 M_sun; for each mass, we considered three different mass loss
scenarios. We then tested whether these models were consistent with the current
high-precision helioseismic observations. The relatively modest mass loss rates
in these models are consistent with observational limits from young stars and
estimates of the past solar wind obtained from lunar rocks, and do not
significantly affect the solar lithium depletion. For appropriate initial
masses, all three mass loss scenarios are capable of yielding a solar flux 3.8
Gyr ago high enough to be consistent with water on ancient Mars. We find that
all of our mass-losing solar models are consistent with the helioseismic
observations. The early solar mass loss of a few percent does indeed leave a
small fingerprint on the Sun's internal structure. However, for helioseismology
to significantly constrain early solar mass loss would require higher accuracy
in the observed solar parameters and input physics, namely, by a factor of
about 3 for the observed solar surface composition, and a factor of 2 for the
solar interior opacities, the pp nuclear reaction rate, and the diffusion
constants for gravitational settling.Comment: LaTeX, 30 pages (including 13 figures); ApJ, in press. Added
figures/color figures are available at
http://www.cita.utoronto.ca/~boothroy/sun5.htm
Status of the standard vector—axial-vector model for nuclear beta decay
The complete set of experimental results on correlations in nuclear beta decay is analyzed in terms of the general Hamiltonian including scalar, vector, axial vector, and tensor interactions with an arbitrary degree of parity violation. It is concluded that the standard vector minus axial-vector model with maximal parity violation (left-handed lepton current) is compatible with the data and rigorous limits are obtained for the values of possible additional coupling constants. In the scalar and tensor case the new constraints are considerably tighter than those published before: |CS / CV| and |CS′ / CV|≤0.2, |(CS+CS′) / CV|≤0.06; |CT / CA| and |CT′ / CA|≤0.09, |(CT+CT′) / CA|≤0.01, all at the 95% confidence level. On the other hand, rather large admixtures of the right-handed lepton currents (CV′ / CV≠1 or CA′ / CA≠1) are allowed by the data. An analysis of the correlations between various coupling constants implied by the data is also performed
Is Female Attractiveness Related to Final Reproductive Success?
In order to test the assumption that female attractiveness relates to reproductive success, photographs of 47 rural
Polish women taken in their youth were rated for attractiveness, and BMI at age 18 was recorded; these measures of attractiveness
were then compared with their subsequent life histories. Facial attractiveness did not relate to number of
children or grandchildren. It also did not relate to age of marriage or husband’s education. It did relate to number of
marriages and husband’s height. BMI at age 18 did not relate significantly to any of the outcome variables. These results
suggest that although more attractive women may have married higher quality (taller) husbands and may in ancestral
population have achieved greater reproductive success this way, there is no evidence in a modern, European Catholic society
for their having greater reproductive success
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