53 research outputs found
Behavior of the giant-dipole resonance in Sn and Pb at high excitation energ
The properties of the giant-dipole resonance (GDR) are calculated as a
function of excitation energy, angular momentum, and the compound nucleus
particle decay width in the nuclei Sn and Pb, and are compared
with recent experimental data. Differences observed in the behavior of the
full-width-at-half-maximum of the GDR for Sn and Pb are
attributed to the fact that shell corrections in Pb are stronger than
in Sn, and favor the spherical shape at low temperatures. The effects
shell corrections have on both the free energy and the moments of inertia are
discussed in detail. At high temperature, the FWHM in Sn exhibits
effects due to the evaporation width of the compound nucleus, while these
effects are predicted for Pb.Comment: 28 pages in RevTeX plus eight postscript figures. Submitted to Nucl.
Phys.
Shell Model for Warm Rotating Nuclei
In order to provide a microscopic description of levels and E2 transitions in
rapidly rotating nuclei with internal excitation energy up to a few MeV, use is
made of a shell model which combines the cranked Nilsson mean-field and the
residual surface delta two-body force. The damping of collective rotational
motion is investigated in the case of a typical rare-earth nucleus, namely \Yb.
It is found that rotational damping sets in at around 0.8 MeV above the yrast
line, and the levels which form rotational band structures are thus limited. We
predict at a given rotational frequency existence of about 30 rotational bands
of various lengths, in overall agreement with the experimental findings. The
onset of the rotational damping proceeds quite gradually as a function of the
internal excitation energy. The transition region extends up to around 2 MeV
above yrast and it is characterized by the presence of scars of discrete
rotational bands which extend over few spin values and stand out among the
damped transitions, and by a two-component profile in the
correlation. The important role played by the high-multipole components of the
two-body residual interaction is emphasized.Comment: 28 pages, LaTe
Meta-analysis of type 2 Diabetes in African Americans Consortium
Type 2 diabetes (T2D) is more prevalent in African Americans than in Europeans. However, little is known about the genetic risk in African Americans despite the recent identification of more than 70 T2D loci primarily by genome-wide association studies (GWAS) in individuals of European ancestry. In order to investigate the genetic architecture of T2D in African Americans, the MEta-analysis of type 2 DIabetes in African Americans (MEDIA) Consortium examined 17 GWAS on T2D comprising 8,284 cases and 15,543 controls in African Americans in stage 1 analysis. Single nucleotide polymorphisms (SNPs) association analysis was conducted in each study under the additive model after adjustment for age, sex, study site, and principal components. Meta-analysis of approximately 2.6 million genotyped and imputed SNPs in all studies was conducted using an inverse variance-weighted fixed effect model. Replications were performed to follow up 21 loci in up to 6,061 cases and 5,483 controls in African Americans, and 8,130 cases and 38,987 controls of European ancestry. We identified three known loci (TCF7L2, HMGA2 and KCNQ1) and two novel loci (HLA-B and INS-IGF2) at genome-wide significance (4.15 × 10(-94)<P<5 × 10(-8), odds ratio (OR) = 1.09 to 1.36). Fine-mapping revealed that 88 of 158 previously identified T2D or glucose homeostasis loci demonstrated nominal to highly significant association (2.2 × 10(-23) < locus-wide P<0.05). These novel and previously identified loci yielded a sibling relative risk of 1.19, explaining 17.5% of the phenotypic variance of T2D on the liability scale in African Americans. Overall, this study identified two novel susceptibility loci for T2D in African Americans. A substantial number of previously reported loci are transferable to African Americans after accounting for linkage disequilibrium, enabling fine mapping of causal variants in trans-ethnic meta-analysis studies.Peer reviewe
Novel Loci for Adiponectin Levels and Their Influence on Type 2 Diabetes and Metabolic Traits : A Multi-Ethnic Meta-Analysis of 45,891 Individuals
J. Kaprio, S. Ripatti ja M.-L. Lokki työryhmien jäseniä.Peer reviewe
Applications of HUGIN to Diagnosis and Control of Autonomous Vehicles
Abstract. We present an application of HUGIN to solve problems related to diagnosis and control of autonomous vehicles. The application is based on a distributed architecture supporting diagnosis and control of autonomous units. The purpose of the architecture is to assist the operator or piloting system in managing fault detection, risk assessment, and recovery plans under uncertainty. To handle uncertainty, we focus on the use of probabilistic graphical models (PGMs) as implemented in the HUGIN tool. We describe the application of PGMs to three problems of diagnosis and control of autonomous vehicles. Based on the HUGIN tool, limited memory influence diagrams (LIMIDs) are used to represent and solve complex problems of diagnosis and control of autonomous ground and underwater vehicles. In particular, we describe how battery monitoring and control problems related to an underwater and a ground vehicle are solved and how to solve the problem of assessing the quality of a sonar image related to an underwater vehicle.
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Relaxation processes in rotational motion
At few MeV above the yrast line the normally strong correlations among ..gamma..-ray energies in a rotational sequence become weaker. This observation can be interpreted as evidence for the damping of rotational motion in hot nuclei. It seems possible to relate the spreading width of the E2-rotational decay strength to the spread in frequency ..delta omega../sub 0/ of rotational bands. The origin of these fluctuations is found in: (1) fluctuations in the occupation of special single-particle orbits which contribute a significant part of the total angular momentum; and (2) fluctuations in the moment of inertia induced by vibrations of the nuclear shape. Estimates of ..delta omega../sub 0/ done making use of the hundred-odd known discrete rotational bands in the rare-earth region lead, for moderate spin and excitation energies (I approx. = 30 and U approx. = 3 to 4 MeV), to rotational spreading widths of the order of 60 to 160 keV in overall agreement with the data. 24 refs
Sand Deposits Offshore Oahu, Hawaii
The value of sand as aggregate for concrete for the construction
industry and as sediment for artificial beach replenishment at tourist destinations
on Oahu has increased following a legislative moratorium on the mining of beach
sand. Concern for future shortfalls of sand supply prompted prospecting for
offshore deposits. Sand channels extend offshore from major valleys and coastal
embayments on Oahu. Most of these accumulations join sinuous deposits of
sediment ponded on ancient terraces that parallel the coastline. Sand cores were
collected from these mapped deposits. Statistical analysis of particle size distributions
of 279 samples from these cores reveals local areas that are promising for
future exploitation. In some areas, variations of grain size can be related to water
depth and distance from shore, but in most areas, grain sizes are not simply
related to the geographic distribution of sampled sand. Along the leeward Oahu
coast, size distributions are related to depth in core : 5 ft of fine sand covers
medium and coarse sand. Comparisons between samples from different locales
reveals relationships primarily to submarine geomorphology and secondarily to
coastal wave climate
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