Geodynamic signals detected by geodetic methods in Iceland

The geodynamics laboratory provided by Iceland’s position on an active mid-ocean ridge has been recognized for several decades. Geodetic experiments have been designed and carried out in Iceland since 1938 to verify various global geodynamic theories, such as Wegener’s theory of continental drift, the sea floor spreading hypothesis, plate tectonics, mantle plumes etc. State-of-the-art techniques have been used to obtain data on crustal displacements with ever increasing accuracy to constrain the theories. Triangulation and optical levelling were used in the beginning, later EDM-trilateration. Network GPS surveying began in 1986 and has been used extensively since then to study crustal movements. With the addition of InSAR and continuous GPS in the last decade we have made a significant stride towards the goal of giving a continuous representation of the displacement field in time and space. The largest and most persistent signal is that of the plate movements. Geodetic points in East and West Iceland move with the Eurasia and North America Plates, respectively, and the vectors are consistent with global models of plate movements. The plate boundary zones are a few tens of kilometers wide, within which strain accumulates. This strain is released in rifting events or earthquakes that have a characteristic displacement field associated with them. In the Krafla rifting episode in 1975-1984 a 100 km long section of the plate boundary in North Iceland was affected and divergent movement as large as 8-9 m was measured. The June 2000 earthquakes in the South Iceland Seismic Zone were the most significant seismic events in the last decades. Two magnitude 6.5 earthquakes and several magnitude 5 events were associated with strike-slip faulting on several parallel faults along the transform-type plate boundary. Slow post-rifting and post-seismic displacements were detected in the months and years following these events, caused by coupling of the elastic part of the crust with the visco-elastic substratum. Viscosities in the range 0.3-30 x 1018 Pa s have been estimated from the time-decay of these fields. Similar values are obtained from crustal uplift measured around the Vatnajökull glacier due to the reduced load of the glacier in the last century. Magma movements in the roots of volcanoes are reflected by deformation fields measureable around them. The volcanoes inflate or deflate in response to pressure increase or decrease in magma chambers, and intrusive bodies are revealed by bulging of the crust above them. The most active volcanoes in Iceland, Katla, Hekla, and Grímsvötn, appear to be inflating at the present time, whereas Krafla and Askja are slowly deflating. An intrusion episode was documented near the Hengill volcano in 1994-1998 and two intrusion events occurred in the Eyjafjallajökull volcano in 1994 and 1999, all of which were accompanied by characteristic deformation fields

Preimplantation genetic testing legislation and accessibility in the Nordic countries

Abstract Introduction Assisted Reproduction Technologies are in rapid development and implementation of preimplantation genetic testing (PGT) has allowed patients with genetic disorders to initiate pregnancies while minimizing or eliminating the risk of transmitting these disorders to their offspring. Testing for numeric chromosomal anomalies has been proposed as a way to increase efficacy in assisted reproduction, however this remains disputed. Legislation is lagging behind the rapid developments in this field. Material and methods We conducted a structured online survey of legislation and accessibility to Preimplantation Genetic Testing in the Nordic countries to compare the regulation and uptake of this technique. The survey was designed and answered by the authors. Results Key elements in regulation of preimplantation testing for monogenic disorders and structural rearrangements are similar in the Nordic countries although accessibility varies since only Denmark, Finland and Sweden have national clinics offering treatment. In addition, Denmark and Finland have private clinics offering PGT. Regulation is most stringent in Norway where a national board evaluates all couples seeking treatment. Treatment volumes vary between the Nordic countries with Norway and Finland having lowest treatment numbers. Preimplantation genetic testing for aneuploidy in the embryo varies between the Nordic countries where Finland and Iceland are allowed to offer this form of treatment, Denmark and Sweden only in the form of a research protocol while this form of testing is not allowed at all in Norway. Therefore the number of treatment cycles involving testing for embryo aneuploidy are lower in the Nordic countries compared to other countries where this treatment option is more common. Conclusions Science needs to inform politics regarding the rapidly evolving field of reproductive medicine and we recommend harmonization of legislation and accessibility between the Nordic countries.Peer reviewe

Remarks on identical particles in de Broglie-Bohm theory

It is argued that the topological approach to the (anti-)symmetrisation condition for the quantum state of a collection of identical particles, defined in the `reduced' configuration space, is particularly natural from the perspective of de Broglie-Bohm pilot-wave theory.Comment: RevTeX, 9 pp., to appear in Physics Letters

Integration of micro-gravity and geodetic data to constrain shallow system mass changes at Krafla Volcano, N Iceland

New and previously published micro-gravity data are combined with InSAR data, precise levelling and GPS measurements to produce a model for the processes operating at Krafla volcano, 20 years after its most recent eruption. The data have been divided into two periods: from 1990 to 1995 and from 1996 to 2003 and show that the rate of deflation at Krafla is decaying exponentially. The net micro-gravity change at the centre of the caldera is shown, using the measured Free Air Gradient, to be -85 μGal for the first and -100 μGal for the second period. After consideration of the effects of water extraction by the geothermal power station within the caldera, the net gravity decreases are -73 ± 17 μGal for the first and -65 ± 17 μGal for the second period. These decreases are interpreted in terms of magma drainage. Following a Mogi point source model we calculate the mass decrease to be ~2 x 1010 kg/yr reflecting a drainage rate of ~0.23 m3/s, similar to the ~0.13 m3/s drainage rate previously found at Askja volcano, N-Iceland. Based on the evidence for deeper magma reservoirs and the similarity between the two volcanic systems, we suggest a pressure-link between Askja and Krafla at deeper levels (at the lower crust or the crust-mantle boundary). After the Krafla fires, co-rifting pressure decrease of a deep source at Krafla stimulated the subsequent inflow of magma, eventually affecting conditions along the plate boundary in N-Iceland, as far away as Askja. We anticipate that the pressure of the deeper reservoir at Krafla will reach a critical value and eventually magma will rise from there to the shallow magma chamber, possibly initiating a new rifting episode. We have demonstrated that by examining micro-gravity and geodetic data, our knowledge of active volcanic systems can be significantly improved

Rare variants with large effects provide functional insights into the pathology of migraine subtypes, with and without aura

Migraine is a complex neurovascular disease with a range of severity and symptoms, yet mostly studied as one phenotype in genome-wide association studies (GWAS). Here we combine large GWAS datasets from six European populations to study the main migraine subtypes, migraine with aura (MA) and migraine without aura (MO). We identified four new MA-associated variants (in PRRT2, PALMD, ABO and LRRK2) and classified 13 MO-associated variants. Rare variants with large effects highlight three genes. A rare frameshift variant in brain-expressed PRRT2 confers large risk of MA and epilepsy, but not MO. A burden test of rare loss-of-function variants in SCN11A, encoding a neuron-expressed sodium channel with a key role in pain sensation, shows strong protection against migraine. Finally, a rare variant with cis-regulatory effects on KCNK5 confers large protection against migraine and brain aneurysms. Our findings offer new insights with therapeutic potential into the complex biology of migraine and its subtypes.</p

Processing unit resources in a distributed computing systems

The described program is designed for collecting, storing and processing data of distributed file system