10,048 research outputs found
Bayesian spatial analysis of demographic survey data: an application to contraceptive use at first sexual intercourse
In this paper we analyze the spatial patterns of the risk of unprotected sexual intercourse for Italian women during their initial experience with sexual intercourse. We rely on geo-referenced survey data from the Italian Fertility and Family Survey, and we use a Bayesian approach relying on weakly informative prior distributions. Our analyses are based on a logistic regression model with a multilevel structure. The spatial pattern uses an intrinsic Gaussian conditional autoregressive (CAR) error component. The complexity of such a model is best handled within a Bayesian framework, and statistical inference is carried out using Markov Chain Monte Carlo simulation. In contrast with previous analyses based on multilevel model, our approach avoids the restrictive assumption of independence between area effects. This model allows us to borrow strength from neighbors in order to obtain estimates for areas that may, on their own, have inadequate sample sizes. We show that substantial geographical variation exists within Italy (Southern Italy has higher risks of unprotected first-time sexual intercourse), and that the spatial pattern is stable across birth cohorts. The findings are robust with respect to the specification of the prior distribution. We argue that spatial analysis can give useful insights on unmet reproductive health needs. (KEYWORDS: spatial statistical demography, contraceptive use, hierarchical Bayesian modeling, Monte Carlo Markov Chain, multilevel statistical models, Italy, FFS)Italy, contraceptive usage
Local orientational ordering in fluids of spherical molecules with dipolar-like anisotropic adhesion
We discuss some interesting physical features stemming from our previous
analytical study of a simple model of a fluid with dipolar-like interactions of
very short range in addition to the usual isotropic Baxter potential for
adhesive spheres. While the isotropic part is found to rule the global
structural and thermodynamical equilibrium properties of the fluid, the weaker
anisotropic part gives rise to an interesting short-range local ordering of
nearly spherical condensation clusters, containing short portions of chains
having nose-to-tail parallel alignment which runs antiparallel to adjacent
similar chains.Comment: 13 pages and 6 figure
Collapse of quasi-two-dimensional wet granular columns
This paper deals with the experimental characterization of the collapse of
wet granular columns in the pendular state, with the purpose of collecting data
on triggering and jamming phenomena in wet granular media. The final deposit
shape and the runout dynamics were studied for samples of glass beads, varying
particle diameter, liquid surface tension, and liquid amount. We show how the
runout distance decreases with increasing water amount (reaching a plateau for
) and increases with increasing Bond number, while the top and toe
angles and the final deposit height increase with increasing water amount and
decrease with decreasing Bond number. Dimensional analysis allowed to discuss
possible scalings for the runout length and the top and toe angles: a
satisfying scaling was found, based on the combination of Bond number and
liquid amount.Comment: 8 pages, 14 figure
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