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.

Tectonic stress and magma chamber size as controls on dike propagation : Constraints from the 1975-1984 Krafla rifting episode

Abstract: [1] The best-studied dike intrusion events on a divergent plate boundary occurred along the Krafla segment of the northern rift zone in Iceland from 1975–1984. Seismic and geodetic measurements there showed that a central magma chamber fed dikes that propagated laterally many times the thickness of the lithosphere. The patterns of dike length, dike width, caldera subsidence, and lava extrusion strongly suggest that dike propagation is affected by tectonic stresses that change with each dike intrusion event and that magma pressures are linked to the dike opening. These observations have inspired us to develop a quantitative model for the lateral propagation of basaltic dikes away from a magma chamber. We assume dikes propagate as long as there is sufficient driving pressure, defined as the difference between magma pressure and tectonic stress at the dike tip. The opening dike and the magma chamber are treated as a closed system for a given dike intrusion event. During an event, magma pressure is reduced linearly with the magma volume withdrawn from the chamber. Relative tectonic tension in the lithosphere is reduced linearly as the dike width increases. A dike begins propagation when the driving pressure equals the “breakout” pressure needed to force the magma out of the chamber. It stops when the driving pressure reaches a minimum value. Generally, the dike width is proportional to this “stopping” pressure, and a reasonable value gives a width of 1 m. Besides the breakout and stopping pressures, the propagation distance depends on the initial distribution of tectonic stress and the thickness of the lithosphere cut by a dike. The intrusion of a dike changes the tectonic stress distribution so that subsequent dikes may propagate different distances and directions than the first dike. After a period of magma chamber refilling, a new dike can initiate if the breakout pressure is reached. For an idealized spreading segment the tectonic stress field evolves to produce a sequence of dikes propagating in one direction followed by a sequence of dikes propagating in the opposite direction. The first dike in each sequence should be the longest followed by successively shorter dikes. When tectonic stresses close to a magma chamber have been largely relieved, then extrusion of magma may start. The model pattern of dike propagation and extrusion is consistent with data from the Krafla episode. Magma chamber size should have a major effect on magmatic systems in other tectonic settings with larger magma chambers producing longer characteristic dikes.

Risk of second cancer among women with breast cancer.

Abstract: A large number of women survive a diagnosis of breast cancer. Knowledge of their risk of developing a new primary cancer is important not only in relation to potential side effects of their cancer treatment, but also in relation to the possibility of shared etiology with other types of cancer. A cohort of 525,527 women with primary breast cancer was identified from 13 population-based cancer registries in Europe, Canada, Australia and Singapore, and followed for second primary cancers within the period 1943-2000. We used cancer incidence rates of first primary cancer for the calculation of standardized incidence ratios (SIRs) of second primary cancer. Risk of second primary breast cancer after various types of nonbreast cancer was also computed. For all second cancer sites combined, except contralateral breast cancer, we found a SIR of 1.25 (95% CI = 1.24-1.26) on the basis of 31,399 observed cases after first primary breast cancer. The overall risk increased with increasing time since breast cancer diagnosis and decreased by increasing age at breast cancer diagnosis. There were significant excesses of many different cancer sites; among these the excess was larger than 150 cases for stomach (SIR = 1.35), colorectal (SIR = 1.22), lung (SIR = 1.24), soft tissue sarcoma (SIR = 2.25), melanoma (SIR = 1.29), non-melanoma skin (SIR = 1.58), endometrium (SIR = 1.52), ovary (SIR = 1.48), kidney (SIR = 1.27), thyroid gland (SIR = 1.62) and leukaemia (SIR = 1.52). The excess of cancer after a breast cancer diagnosis is likely to be explained by treatment for breast cancer and by shared genetic or environmental risk factors, although the general excess of cancer suggests that there may be additional explanations such as increased surveillance and general cancer susceptibility.

High Latitude Dust in the Earth System

Abstract: Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (> or = 50degN and > or = 40degS) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 sq km and contribute at least 80-100 Tg/yr1 of dust to the Earth system (approx. 5% of the global dust budget); both are projected to increase under future climate change scenarios.

Discovery of common variants associated with low TSH levels and thyroid cancer risk

Abstract: To search for sequence variants conferring risk of nonmedullary thyroid cancer, we focused our analysis on 22 SNPs with a P < 5 × 10(-8) in a genome-wide association study on levels of thyroid stimulating hormone (TSH) in 27,758 Icelanders. Of those, rs965513 has previously been shown to associate with thyroid cancer. The remaining 21 SNPs were genotyped in 561 Icelandic individuals with thyroid cancer (cases) and up to 40,013 controls. Variants suggestively associated with thyroid cancer (P < 0.05) were genotyped in an additional 595 non-Icelandic cases and 2,604 controls. After combining the results, three variants were shown to associate with thyroid cancer: rs966423 on 2q35 (OR = 1.34; P(combined) = 1.3 × 10(-9)), rs2439302 on 8p12 (OR = 1.36; P(combined) = 2.0 × 10(-9)) and rs116909374 on 14q13.3 (OR = 2.09; P(combined) = 4.6 × 10(-11)), a region previously reported to contain an uncorrelated variant conferring risk of thyroid cancer. A strong association (P = 9.1 × 10(-91)) was observed between rs2439302 on 8p12 and expression of NRG1, which encodes the signaling protein neuregulin 1, in blood.

T‐cell subpopulations in the blood and skin of patients with psoriasis

Abstract: SUMMARY Monoclonal antibodies were used to determine, simultaneously, the proportions of T-cell populations in the peripheral blood and in the skin lesions of fifty-one patients with psoriasis. The results were analysed in relation to the extent, age and clinical type of the skin lesions. In the group of patients with extensive lesions, a significant reduction in the number of total T (TT) and T helper/inducer-cells, (TH), but not in T suppressor/cytotoxic cells (Ts) was observed in the peripheral blood. Furthermore, the skin TH/TS ratio was greater in late guttate and in chronic plaque lesions than the corresponding ratio in the blood. These findings suggest that there is an active selective recruitment of TH cells into established psoriatic lesions. In contrast, the TH/TS ratio in early guttate lesions was the same as in the blood, and significantly lower than in the plaque lesions. An additional finding was a decrease of TS, and a corresponding increase of null cells in the blood of patients with chronic plaque psoriasis. These observations provide further evidence for the participation of T cells in the pathogenesis of psoriasis.