48 research outputs found
Primordial Nucleosynthesis for the New Cosmology: Determining Uncertainties and Examining Concordance
Big bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) have
a long history together in the standard cosmology. The general concordance
between the predicted and observed light element abundances provides a direct
probe of the universal baryon density. Recent CMB anisotropy measurements,
particularly the observations performed by the WMAP satellite, examine this
concordance by independently measuring the cosmic baryon density. Key to this
test of concordance is a quantitative understanding of the uncertainties in the
BBN light element abundance predictions. These uncertainties are dominated by
systematic errors in nuclear cross sections. We critically analyze the cross
section data, producing representations that describe this data and its
uncertainties, taking into account the correlations among data, and explicitly
treating the systematic errors between data sets. Using these updated nuclear
inputs, we compute the new BBN abundance predictions, and quantitatively
examine their concordance with observations. Depending on what deuterium
observations are adopted, one gets the following constraints on the baryon
density: OmegaBh^2=0.0229\pm0.0013 or OmegaBh^2 = 0.0216^{+0.0020}_{-0.0021} at
68% confidence, fixing N_{\nu,eff}=3.0. Concerns over systematics in helium and
lithium observations limit the confidence constraints based on this data
provide. With new nuclear cross section data, light element abundance
observations and the ever increasing resolution of the CMB anisotropy, tighter
constraints can be placed on nuclear and particle astrophysics. ABRIDGEDComment: 54 pages, 20 figures, 5 tables v2: reflects PRD version minor changes
to text and reference
Rising rural body-mass index is the main driver of the global obesity epidemic in adults
Body-mass index (BMI) has increased steadily in most countries in parallel with a rise in the proportion of the population who live in cities 1,2 . This has led to a widely reported view that urbanization is one of the most important drivers of the global rise in obesity 3�6 . Here we use 2,009 population-based studies, with measurements of height and weight in more than 112 million adults, to report national, regional and global trends in mean BMI segregated by place of residence (a rural or urban area) from 1985 to 2017. We show that, contrary to the dominant paradigm, more than 55 of the global rise in mean BMI from 1985 to 2017�and more than 80 in some low- and middle-income regions�was due to increases in BMI in rural areas. This large contribution stems from the fact that, with the exception of women in sub-Saharan Africa, BMI is increasing at the same rate or faster in rural areas than in cities in low- and middle-income regions. These trends have in turn resulted in a closing�and in some countries reversal�of the gap in BMI between urban and rural areas in low- and middle-income countries, especially for women. In high-income and industrialized countries, we noted a persistently higher rural BMI, especially for women. There is an urgent need for an integrated approach to rural nutrition that enhances financial and physical access to healthy foods, to avoid replacing the rural undernutrition disadvantage in poor countries with a more general malnutrition disadvantage that entails excessive consumption of low-quality calories. © 2019, The Author(s)