Seismic reflection data, calcium/iron ratios, stable istopes, and magnetic susceptibility of sediment cores from the Pen Duick Escarpment, Gulf of Cadiz

Here we present a case study of three cold-water coral mounds in a juvenile growth stage on top of the Pen Duick Escarpment in the Gulf of Cadiz; Alpha, Beta and Gamma mounds. Although cold-water corals are a common feature on the adjacent cliffs, mud volcanoes and open slope, no actual living cold-water coral has been observed. This multidisciplinary and integrated study comprises geophysical, sedimentological and (bio)geochemical data and aims to present a holistic view on the interaction of both environmental and geological drivers in cold-water coral mound development in the Gulf of Cadiz. Coring data evidences (past or present) methane seepage near the Pen Duick Escarpment. Several sources and pathways are proposed, among which a stratigraphic migration through uplifted Miocene series underneath the escarpment. The dominant morphology of the escarpment has influenced the local hydrodynamics within the course of the Pliocene, as documented by the emplacement of a sediment drift. Predominantly during post-Middle Pleistocene glacial episodes, favourable conditions were present for mound growth. An additional advantage for mound formation near the top of Pen Duick Escarpment is presented by seepage-related carbonate crusts which might have offered a suitable substrate for coral settling. The spatially and temporally variable character and burial stage of the observed open reef frameworks, formed by cold-water coral rubble, provides a possible model for the transition from cold-water coral reef patches towards juvenile mound. These rubble "graveyards" not only act as sediment trap but also as micro-habitat for a wide range of organisms. The presence of a fluctuating Sulphate-Methane Transition Zone has an important effect on early diagenetic processes, affecting both geochemical and physical characteristics, transforming the buried reef into a solid mound. Nevertheless, the responsible seepage fluxes seem to be locally variable. As such, the origin and evolution of the cold-water coral mounds on top of the Pen Duick Escarpment is, probably more than any other NE Atlantic cold-water coral mound province, located on the crossroads of environmental (hydrodynamic) and geological (seepage) pathways.

Convection-diffusion in MHD: Comparison of primitive variable and vector potential solutions of the magnetic induction equation

Abstract not available

Emergent Antiferromagnetism Out Of The Hidden-order" State In Uru2si2: High Magnetic Field Nuclear Magnetic Resonance To 40 T."

Very high field (29)Si-NMR measurements using a fully (29)Si-enriched URu(2)Si(2) single crystal were carried out in order to microscopically investigate the hidden order (HO) state and adjacent magnetic phases in the high field limit. At the lowest measured temperature of 0.4 K, a clear anomaly reflecting a Fermi surface instability near 22 T inside the HO state is detected by the (29)Si shift, (29)K(c). Moreover, a strong enhancement of (29)K(c) develops near a critical field H(c) ≃ 35.6 T, and the ^{29}Si-NMR signal disappears suddenly at H(c), indicating the total suppression of the HO state. Nevertheless, a weak and shifted (29)Si-NMR signal reappears for fields higher than H(c) at 4.2 K, providing evidence for a magnetic structure within the magnetic phase caused by the Ising-type anisotropy of the uranium ordered moments.

Feasibility And Reproducibility Of Diffusion-weighted Magnetic Resonance Imaging Of The Fetal Brain In Twin-twin Transfusion Syndrome.

The aim of this study is to test the feasibility and reproducibility of diffusion-weighted magnetic resonance imaging (DW-MRI) evaluations of the fetal brains in cases of twin-twin transfusion syndrome (TTTS). From May 2011 to June 2012, 24 patients with severe TTTS underwent MRI scans for evaluation of the fetal brains. Datasets were analyzed offline on axial DW images and apparent diffusion coefficient (ADC) maps by two radiologists. The subjective evaluation was described as the absence or presence of water diffusion restriction. The objective evaluation was performed by the placement of 20-mm(2) circular regions of interest on the DW image and ADC maps. Subjective interobserver agreement was assessed by the kappa correlation coefficient. Objective intraobserver and interobserver agreements were assessed by proportionate Bland-Altman tests. Seventy-four DW-MRI scans were performed. Sixty of them (81.1%) were considered to be of good quality. Agreement between the radiologists was 100% for the absence or presence of diffusion restriction of water. For both intraobserver and interobserver agreement of ADC measurements, proportionate Bland-Altman tests showed average percentage differences of less than 1.5% and 95% CI of less than 18% for all sites evaluated. Our data demonstrate that DW-MRI evaluation of the fetal brain in TTTS is feasible and reproducible.