8,903 research outputs found
The Dhāraṇī of Mahāvyutpatti #748: Origin and Formation
This paper aims to identify the sources of a list of twelve dhāraṇīs included in Rubric 748 of the Mahāvyutpatti. It produces evidence connecting this group with three similar dhāraṇī enumerations transmittted in the Ratnamegha, Tathāgataguṇajñānācintyaviṣayāvatāranirdeśa and Tathāgatamahākaruṇānirdeśa. The exposition of
the Tathāgatamahākaruṇānirdeśa is particularly valuable since it preserves one of the earliest and most detailed discussions of dhāraṇī practice in Mahāyāna sūtras.
The Ratnamegha is closest to the Mahāvyutpatti and thus the most likely source for its list
s/alpha/Fe Abundance Ratios in Halo Field Stars: Is there a Globular Cluster Connection?
We try to understand the s- and r-process elements vs Ti/Fe plots derived by
Jehin et al. (1999) for mildly metal-poor stars within the framework of the
analytical semi-empirical models for these elements by Pagel & Tautvaisiene
(1995, 1997). Jehin et al. distinguished two Pop II subgroups: IIa with
alpha/Fe and s-elements/Fe increasing together, which they attribute to pure
SNII activity, and IIb with constant alpha/Fe and a range in s/Fe which they
attribute to a prolonged accretion phase in parent globular clusters. However,
their sample consists mainly of thick-disk stars with only 4 clear halo
members, of which two are `anomalous' in the sense defined by Nissen & Schuster
(1997). Only the remaining two halo stars (and one in Nissen & Schuster's
sample) depart significantly from Y/Ti (or s/alpha) ratios predicted by our
model.Comment: 6 pages, 5 figures To appear in: Roma-Trieste Workshop 1999: `The
Chemical Evolution of the Milky Way: Stars vs Clusters', Vulcano Sept. 1999.
F. Giovanelli & F. Matteucci (eds), Kluwer, Dordrech
Modelling of errors in databases
A lot of time and energy are expended assembling national databases containing information about health care processes and outcomes. Unfortunately, given the complexity of the data gathering procedures involved, errors occur. This inevitably leads to problems when it comes to the analysis of data from such sources. Indeed, sometimes it is very much a matter of faith that summary statistics represent a true reflection of the facts. On the assumption that one knows the rates at which different forms of errors occur, mathematical modelling methods can be used to obtain estimates of the effects of such errors on the estimates that would be derived for summary statistics associated with an erroneous data base
Galactic archaeology: IMF and depletion in the "thin disk"
We determine the initial mass function (IMF) of the ``thin disk'' by means of
a direct comparison between synthetic stellar samples (for different matching
choices of IMF, star formation rate SFR and depletion) and a complete
(volume-limited) sample of single stars near the galactic plane (|z| < 25pc),
selected from the Hipparcos catalogue (d < 100pc, M_v < +4.0). Our synthetic
samples are computed from first principles: stars are created with a random
distribution of mass M_* and age t_* which follow a given (genuine) IMF and
SFR(t_*). They are then placed in the HR diagram by means of a grid of
empirically well-tested evolution tracks. The quality of the match (synthetic
versus observed sample) is assessed by means of star counts in specific regions
in the HR diagram. 7 regions are located along the MS (main sequence, mass
sensitive), while 4 regions represent different evolved (age-sensitive) stages
of the stars. The counts of evolved stars, in particular, give valuable
evidence of the history of the ``thin disk'' (apparent) star formation and lift
the ambiguities in models restricted to MS star counts.Comment: 10 pages, 3 figures, submitted to MNRA
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