University of Iceland

About: University of Iceland is a education organization based out in Reykjavik, Suðurnes, Iceland. It is known for research contribution in the topics: Population & Genome-wide association study. The organization has 5423 authors who have published 16199 publications receiving 694762 citations. The organization is also known as: Háskóli Íslands.

Glycated hemoglobin measurement and prediction of cardiovascular disease

Abstract: IMPORTANCE The value of measuring levels of glycated hemoglobin (HbA(1c)) for the prediction of first cardiovascular events is uncertain. OBJECTIVE To determine whether adding information on HbA(1c ...

Carbon Storage in Basalt

Abstract: All the carbon in the atmosphere, living creatures, and dissolved in the oceans is derived from rocks and will eventually end up in rocks, the largest carbon reservoir on Earth. The carbon moves from one reservoir to another in what is called the carbon cycle ( 1 ). Humans have accelerated this cycle by mining and burning fossil fuel since the beginning of the industrial revolution, causing rising atmospheric carbon dioxide (CO2) concentrations that are the main cause of global warming. One option for mitigating high levels of global warming is to capture CO2 and safely store it for thousands of years or longer in subsurface rocks. By accelerating carbonate mineral formation in these rocks, it is possible to rebalance the global carbon cycle, providing a long-term carbon storage solution. However, this approach is both technically challenging and economically expensive.

A new method for estimating the bolometric properties of Ibc supernovae

Abstract: The bolometric properties (nickel mass, ejecta mass and kinetic energies) of 61 Ibc supernovae (SNe), including 20 gamma-ray burst and X-rayflash (GRB/XRF), 19 Ib, 13 Ic and nine Ic-BL (broad-lined) SNe are presented. All of the available BVRI photometry in the literature have been collected and used in a new method that utilizes a template supernova (SN 1998bw) and an analytical model to accurately estimate the bolometric properties of each SN. A statistical analysis of the bolometric properties is then performed, where it is found that GRB/XRF SNe are the most energetic, and eject more mass (including nickel content) than Ib, Ic and Ic-BL SNe. The results are then compared to the existing progenitor models of Ibc SNe, where it is concluded that it is highly likely that at least two progenitor channels exist for producing a Ibc SN: most Ibc SNe arise via binary interactions, where the mass of the stellar progenitor is less than what is attributed to a Wolf‐Rayet star. Conversely, the progenitors of Ic-BL and GRB/XRF are more massive than those of Ib and Ic SNe, and a key difference between GRB/XRF SNe and Ic-BL SNe is progenitor metallicity, where it is observed that the latter arise from more metal-rich progenitors. As mass loss in massive stars is influenced by metal content, theprogenitors ofIc-BLSNelosemoremass,and thereforemoreangular momentum, before exploding. It is expected that the explosion mechanism in Ic-BL and GRB/XRF SNe is ‘engine-driven’(i.e.anaccretingblackhole,oramillisecondmagnetar),buttheincreasedmass loss of Ic-BL SNe means the central engine is less powerful than in GRB/XRF SNe. Finally, it is found that the SNe that accompany GRBs and XRFs are statistically indistinguishable, and some mechanism other than metallicity is needed to explain the differences in the high-energy components in these events.

Search for cosmic-ray induced gamma-ray emission in Galaxy Clusters

Abstract: Current theories predict relativistic hadronic particle populations in clusters of galaxies in addition to the already observed relativistic leptons. In these scenarios hadronic interactions give rise to neutral pions which decay into γ rays that are potentially observable with the Large Area Telescope (LAT) on board the Fermi space telescope. We present a joint likelihood analysis searching for spatially extended γ-ray emission at the locations of 50 galaxy clusters in four years of Fermi-LAT data under the assumption of the universal cosmic-ray (CR) model proposed by Pinzke & Pfrommer. We find an excess at a significance of 2.7σ, which upon closer inspection, however, is correlated to individual excess emission toward three galaxy clusters: A400, A1367, and A3112. We discuss these cases in detail and conservatively attribute the emission to unmodeled background systems (for example, radio galaxies within the clusters).Through the combined analysis of 50 clusters, we exclude hadronic injection efficiencies in simple hadronic models above 21% and establish limits on the CR to thermal pressure ratio within the virial radius, R 200, to be below 1.25%-1.4% depending on the morphological classification. In addition, we derive new limits on the γ-ray flux from individual clusters in our sample. © 2014. The American Astronomical Society. All rights reserved.