Stellar and nuclear-physics constraints on two r-process components in the early Galaxy

Proceedings of "Nuclei in the Cosmos 2000", Aarhus, DanmarkComment: 3 pages, 2 figures; to be publ. in Nucl. Phys.

Genetic factors of obesity and eating disorders: Copy number variations (CNV) involving SH2B1

Context : It is now clearly shown that genetic factors in association with environment play a key role in obesity and eating disorders. This project studies the clinical symptoms and molecular abnormalities in patients carrying a strong hereditary predisposition to obesity and eating behavior disorders. We have previously published the association between the 16:29.5-30.1 deletion and a very penetrant form of morbid obesity and macrocephaly. We have also demonstrated the association between the reciprocal 16:29.5-30.1 duplication and underweight and small head circumference. These 2 studies demonstrate that gene dosage of one or several genes in this region regulates BMI as well as brain growth. At present, there are no data pointing towards particular candidate genes. We are currently investigating a second non-overlapping recurrent CNV encompassing SH2B1, upstream of the aforementioned rearrangement. SNPs in this gene have been associated with BMI in GWAS studies and mice models confirmed this association. Bokuchova et al have reported an association between deletions encompassing this gene and severe early onset obesity, as well as insulin resistance. We are currently collecting and analyzing data to fully characterize the phenotype and the transcriptional patterns associated with this rearrangement. Aims : 1. Identify carriers of any CNVs in the greater 16p11.2 region (between 16:28MB and 32MB) in the EGG consortium. 2. Perform association studies between SNPs in the greater 16p11.2 region (16:28-32MB) and anthropometric measures with adjusted "locus-wide significance", to identify or prioritize candidate genes potentially driving the association observed in patients with the CNVs (and thus worthy of further validation and sequencing). 3. Explore associations between GSV genome-wide and brain volume. 4. Explore relationship between brain volumes (whole brain and regional for those who underwent brain MRI), head circumference and BMI. 5. Extrapolate this procedure to other regions covered by the Metabochip. Methods : - Examine and collect clinical informations, as well as molecular informations in these patients. - Analysis of MRI data in children and adults with BMI > 2SD. Compare changes to MRI data obtained in patients with monogenic forms of obesity (data from Lausanne study) and to underweight (BMI<-2SD) individuals from EGG. - Test whether opposite extremes of the phenotypic distribution may be highly informative Expected results : This is a highly focused study, pertaining to approximately 1 0/00 of the human genome. Yet it is clear that if successful, the lessons learned from this study could be extrapolated to other segments of the genome and would need validation and replication by additional studies. Altogether they will contribute to further explore the missing heritability and point to etiologic genes and pathways underlying these important health burdens

Nuclear Structure Studies at ISOLDE and their Impact on the Astrophysical r-Process

The focus of the present review is the production of the heaviest elements in nature via the r-process. A correct understanding and modeling requires the knowledge of nuclear properties far from stability and a detailed prescription of the astrophysical environment. Experiments at CERN/ISOLDE have played a pioneering role in exploring the characteristics of nuclear structure in terms of masses and beta-decay properties. Initial examinations paid attention to far unstable nuclei with magic neutron numbers related to r-process peaks, while present activities are centered on the evolution of shell effects with the distance from the valley of stability. We first show in site-independent applications the effect of both types of nuclear properties on r-process abundances. Then, we explore the results of calculations related to two different `realistic' astrophysical sites, (i) the supernova neutrino wind and (ii) neutron star mergers. We close with a list of remaining theoretical and experimental challenges needed to overcome for a full understanding of the nature of the r-process, and the role CERN/ISOLDE can play in this process.Comment: LATEX, 38 pages, 16 figures, submitted to Hyperfine Interaction

A tentative 4- isomeric state in Sr-98

Annual Report 2001, Institut fuer Kernchemie, Johannes-Gutenberg-Universitaet, Mainz, GermanyComment: 3 pages, 1 figur

Charged-Particle and Neutron-Capture Processes in the High-Entropy Wind of Core-Collapse Supernovae

The astrophysical site of the r-process is still uncertain, and a full exploration of the systematics of this process in terms of its dependence on nuclear properties from stability to the neutron drip-line within realistic stellar environments has still to be undertaken. Sufficiently high neutron to seed ratios can only be obtained either in very neutron-rich low-entropy environments or moderately neutron-rich high-entropy environments, related to neutron star mergers (or jets of neutron star matter) and the high-entropy wind of core-collapse supernova explosions. As chemical evolution models seem to disfavor neutron star mergers, we focus here on high-entropy environments characterized by entropy $S$, electron abundance $Y_e$ and expansion velocity $V_{exp}$. We investigate the termination point of charged-particle reactions, and we define a maximum entropy $S_{final}$ for a given $V_{exp}$ and $Y_e$, beyond which the seed production of heavy elements fails due to the very small matter density. We then investigate whether an r-process subsequent to the charged-particle freeze-out can in principle be understood on the basis of the classical approach, which assumes a chemical equilibrium between neutron captures and photodisintegrations, possibly followed by a $\beta$-flow equilibrium. In particular, we illustrate how long such a chemical equilibrium approximation holds, how the freeze-out from such conditions affects the abundance pattern, and which role the late capture of neutrons originating from $\beta$-delayed neutron emission can play.Comment: 52 pages, 31 figure