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.

Phenological response of tundra plants to background climate variation tested using the International Tundra Experiment

Abstract: The rapidly warming temperatures in high-latitude and alpine regions have the potential to alter the phenology of Arctic and alpine plants, affecting processes ranging from food webs to ecosystem trace gas fluxes The International Tundra Experiment (ITEX) was initiated in 1990 to evaluate the effects of expected rapid changes in temperature on tundra plant phenology, growth and community changes using experimental warming Here, we used the ITEX control data to test the phenological responses to background temperature variation across sites spanning latitudinal and moisture gradients The dataset overall did not show an advance in phenology; instead, temperature variability during the years sampled and an absence of warming at some sites resulted in mixed responses Phenological transitions of high Arctic plants clearly occurred at lower heat sum thresholds than those of low Arctic and alpine plants However, sensitivity to temperature change was similar among plants from the different climate zones Plants of different communities and growth forms differed for some phenological responses Heat sums associated with flowering and greening appear to have increased over time These results point to a complex suite of changes in plant communities and ecosystem function in high latitudes and elevations as the climate warms

Variants in DENND1A are associated with polycystic ovary syndrome in women of European ancestry.

Abstract: Context: A genome-wide association study has identified three loci (five independent signals) that confer risk for polycystic ovary syndrome (PCOS) in Han Chinese women. Replication is necessary to determine whether the same variants confer risk for PCOS in women of European ancestry. Objective: The objective of the study was to test whether these PCOS risk variants in Han Chinese women confer risk for PCOS in women of European ancestry. Design: This was a case-control study. Setting: The study was conducted at deCODE Genetics in Iceland and two academic medical centers in the United States. Patients: Cases were 376 Icelandic women and 565 and 203 women from Boston, MA, and Chicago, IL, respectively, all diagnosed with PCOS by the National Institutes of Health criteria. Controls were 16,947, 483, and 189 women not known to have PCOS from Iceland, Boston, and Chicago, respectively. Intervention: There were no interventions. Main Outcomes: Main outcomes were allele frequencies for seven variants in PCOS cas...

Neural Basis for Priming of Pop-Out during Visual Search Revealed with fMRI

Abstract: Maljkovic and Nakayama first showed that visual search efficiency can be influenced by priming effects. Even ‘‘pop-out’’ targets (defined by unique color) are judged quicker if they appear at the same location and/or in the same color as on the preceding trial, in an unpredictable sequence. Here, we studied the potential neural correlates of such priming in human visual search using functional magnetic resonance imaging (fMRI). We found that repeating either the location or the color of a singleton target led to repetition suppression of blood oxygen level--dependent (BOLD) activity in brain regions traditionally linked with attentional control, including bilateral intraparietal sulci. This indicates that the attention system of the human brain can be ‘‘primed,’’ in apparent analogy to repetition-suppression effects on activity in other neural systems. For repetition of target color but not location, we also found repetition suppression in inferior temporal areas that may be associated with color processing, whereas repetition of target location led to greater reduction of activation in contralateral inferior parietal and frontal areas, relative to color repetition. The frontal eye fields were also implicated, notably when both target properties (color and location) were repeated together, which also led to further BOLD decreases in anterior fusiform cortex not seen when either property was repeated alone. These findings reveal the neural correlates for priming of pop-out search, including commonalities, differences, and interactions between location and color repetition. fMRI repetition-suppression effects may arise in components of the attention network because these settle into a stable ‘‘attractor state’’ more readily when the same target property is repeated than when a different attentional state is required.

Holographic superconductors with Lifshitz scaling

Abstract: Black holes in asymptotically Lifshitz spacetime provide a window onto finite temperature effects in strongly coupled Lifshitz models. We add a Maxwell gauge field and charged matter to a recently proposed gravity dual of (2+1)-dimensional Lifshitz theory. This gives rise to charged black holes with scalar hair, which correspond to the superconducting phase of holographic superconductors with z > 1 Lifshitz scaling. Along the way we analyze the global geometry of static, asymptotically Lifshitz black holes at the arbitrary critical exponent z > 1. In all known exact solutions there is a null curvature singularity in the black hole region, and, by a general argument, the same applies to generic Lifshitz black holes.

Classification of Remote Sensing Optical and LiDAR Data Using Extended Attribute Profiles

Abstract: Extended Attribute Profiles (EAPs), which are obtained by applying morphological attribute filters to an image in a multilevel architecture, can be used for the characterization of the spatial characteristics of objects in a scene. EAPs have proved to be discriminant features when considered for thematic classification in remote sensing applications especially when dealing with very high resolution images. Altimeter data (such as LiDAR) can provide important information, which being complementary to the spectral one can be valuable for a better characterization of the surveyed scene. In this paper, we propose a technique performing a classification of the features extracted with EAPs computed on both optical and LiDAR images, leading to a fusion of the spectral, spatial and elevation data. The experiments were carried out on LiDAR data along either with a hyperspectral and a multispectral image acquired on a rural and urban area of the city of Trento (Italy), respectively. The classification accuracies obtained pointed out the effectiveness of the features extracted by EAPs on both optical and LiDAR data for classification.