Velocity images from stacking depth-slowness seismic wavefields

International audienceWe present synthetic and real data examples processed using a depth imaging method for long-offset multichannel seismic data via the intercept-time-slowness (τ-p) domain. The refracted and reflected information contained in the wavefield is processed simultaneously. Our scheme uses common midpoint data that is transformed to the τ-p domain and mapped to the depth-slowness (z-p) domain using a downward continuation algorithm. The velocity function for downward continuation may be obtained iteratively from the diving ray trajectory within the slowness-depth wavefield or estimated using an independent method. Horizontal events within the z-p wavefield are isolated by applying a mute function corresponding to the downward continuation velocity function in the z-p domain. Stacking the resulting wavefield gives an image trace that may be superimposed on the velocity function to form a velocity image. Following testing on synthetic data the method is applied to two long-offset marine seismic streamer data sets with offsets up to 18 km, from the northeast Atlantic margin. These examples demonstrate the potential of the method to obtain velocity images in difficult geological locations, where conventional processing has been less successful

Antioxidant activity and total phenolic content of various extracts from Mimosa hamata Willd., Mimosaceae

Jinjani (Mimosa hamata Willd., Mimosaceae) is widely distributed in India and Pakistan, which contains several interesting bioactive constituents and possesses health promoting properties. In this study, the antioxidant activity with the total phenolic content of different successive extracts (pet. ether, chloroform, n-butanol and water) from leaves, stem, root and seeds of M. hamata were assessed in an effort to compare and validate the antioxidant potential of the particular part of the plant. The antioxidant activity was determined by 2, 2- Diphenyl-1-picrylhydrazyl (DPPH) assay and total phenolic content was estimated by using Folin-Ciocalteu’s reagent. All tested extracts possessed appreciable antioxidant potential but n-butanol extract of roots was significantly higher in total phenolic content (73.16±0.19 mg GAE/g extract) and in antioxidant assay (IC50 = 5µg/ml). It is also noteworthy that in n-butanol extract of roots higher yield (85.60%) was also observed. This study validates the antioxidant potential of the roots in M. hamata and the positive relationship between total phenolic content and antioxidant activity

Discovery of flat seismic reflections in the mantle beneath the young Juan de Fuca Plate

Crustal properties of young oceanic lithosphere have been examined extensively, but the nature of the mantle lithosphere underneath remains elusive. Using a novel wide-angle seismic imaging technique, here we show the presence of two sub-horizontal reflections at ∼11 and ∼14.5 km below the seafloor over the 0.51–2.67 Ma old Juan de Fuca Plate. We find that the observed reflectors originate from 300–600-m-thick layers, with an ∼7–8% drop in P-wave velocity. They could be explained either by the presence of partially molten sills or frozen gabbroic sills. If partially molten, the shallower sill would define the base of a thin lithosphere with the constant thickness (11 km), requiring the presence of a mantle thermal anomaly extending up to 2.67 Ma. In contrast, if these reflections were frozen melt sills, they would imply the presence of thick young oceanic lithosphere (20–25 km), and extremely heterogeneous upper mantle

Azimuthal Anisotropy at Valhall: the Helmholtz Equation Approach

International audienceWe used 6 hours of continuous vertical records from 2320 sensors of the Valhall Life of Fields Seismic network to compute 2 690 040 cross-correlation functions between the full set of sensor pair combinations. We applied the 'Helmholtz tomography' approach combined with the ambient noise correlation method to track the wave front across the network with every station considered as a virtual source. The gradient of the interpolated phase travel time gives us an estimate of the local phase speed and of the direction of wave propagation. By combining the individual measurements for every station, we estimated the distribution of Scholte's wave phase speeds with respect to azimuth. The observed cosine pattern indicates the presence of azimuthal anisotropy. The elliptic shape of the fast anisotropy direction is consistent with results of previous shear wave splitting studies and reflects the strong seafloor subsidence due to the hydrocarbon reservoir depletion at depth and is in good agreement with geomechanical modeling

Protective Effect of Quercetin Against Sulphur Mustard-inducedOxidative Stress in Mice

Sulphur mustard (SM) is a chemical warfare agent that causes serious blisters upon contactwith human skin.  SM alkylates DNA and several other macromolecules, and also induces oxidativestress.  Quercetin, a bioflavonoid has wide pharmacological actions. The protective efficacy ofquercetin (100 mg/kg, i.p. and 200 mg/kg, i.p.) was studied by administering three doses in miceagainst SM.  The first dose was administered at 30 min prior, simultaneous, 2 h post or 24 h post,and two more doses on the next two days.  SM was administered (in PEG 300) percutaneouslyat varying doses for survival and protection studies.  SM was also administered at a dose of2 LD50 (19.3 mg/kg) with and without quercetin treatment and various biochemical markers wereestimated 7 days after SM administration.  Histological examinations of vital organs were alsocarried out. The animals administered with SM died at various days depending upon the dose.The body weight decreased significantly. Quercetin protected the mice significantly, in a dose-dependent manner. The protection was better when the first dose of quercetin administered was30 min prior or simultaneously.  A significant decrease in reduced as well as oxidised glutathioneand an increase in malondialdehyde, WBC count, RBC count, and haemoglobin were observedwith 2 LD50 SM. Quercetin at 100 mg/kg and 200 mg/kg doses significantly protected the biochemicalmarkers when the first dose of quercetin administered was 30 min prior or as simultaneoustreatment.  The histological lesions induced by sulphur mustard on liver, spleen, and skin werealso significantly protected by quercetin when the first dose was administered 30 min prior oras simultaneous treatment. The present study shows that percutaneous administration of SMinduces oxidative stress and quercetin can protect it as a prophylactic agent

Adult hypertrophic pyloric stenosis due to peptic ulcer disease: a rare presentation

Primary adult hypertrophic stenosis is uncommon with an uncertain etiopathogenesis and associated gastric outlet obstruction mimics gastric carcinoma. We present a case of AHPS as sequel of peptic ulcer disease in a 72 year old male. With the advent of proton pump inhibitors as a mainstay of medical therapy, complication into gastric outlet obstruction is a rare disease today. Upper GI endoscopy revealed a distended stomach, residual food and a hyperemic bulky pylorus not accommodating the endoscope. Barium meal follow-through revealed a dilated stomach and minimal barium passing through the pylorus. Histological analysis revealed mild dysplasia at the focus with dense inflammatory infiltrates composed of lymphocytes and eosinophils in the lamina propria. No evidence of malignancy was noted, favouring chronic gastritis. The condition mimics other forms of proliferative disorders like carcinoma, gastrointestinal stromal tumors. We present the clinical findings, imaging analysis and discuss etiopathogenesis and management

New insights on the origin of Barra Volcanic Ridge System, offshore Ireland : a long distance influence of the Iceland mantle plume

Acknowledgements This project was funded by the Irish Centre for Research in Applied Geosciences (iCRAG), Science Foundation Ireland (SFI), Irish Shelf and Petroleum Studies Group (ISPSG) of the Petroleum Infrastructure Programme (PiP) and Dublin Institute for Advanced Studies (DIAS). This publication uses data and survey results acquired during a project undertaken on behalf of the Irish Shelf Petroleum Studies Group (ISPSG) of the Irish Petroleum Infrastructure programme Group 4. The ISPSG comprises: AzEire Petroleum Ltd, Cairn Energy Plc, BP Exploration Operating Company Ltd, CNOOC Petroleum Europe Limited, ENI Ireland BV, Equinor Energy Ireland Limited, Europa Oil & Gas Plc, ExxonMobil E&P Ireland (Offshore) Ltd, Husky Energy, Petroleum Affairs Division of the Department of Communications, Climate Action and Environment, Providence Resources plc, Repsol Exploración SA, Sosina Exploration Ltd, Total EP, Tullow Oil Plc and Woodside Energy (Ireland) Pty Ltd. processing is done by using ECHOS software from Paradigm. We are very thankful to Dr. J. Kim Welford for providing us with the 3D Moho map of Irelands offshore. We acknowledge the Geological Survey Ireland and the Marine Institute (INFOMAR), for providing the data for this work. We also acknowledge Schlumberger for providing an academic license of Petrel software for this study. SR further acknowledges research funding from Science Foundation Ireland (SFI) and PIP. This publication derives from research supported in part by a research grant from SFI under Grant Number 13/RC/2092 and co-funded under the European Regional Development Fund and by iCRAG industry partners. Sincere thanks to Tim Minshul, Laurent Gernigon and a third reviewer for providing helpful reviews and insightful comments on the paper, which greatly improved the quality of the manuscript.Peer reviewe

Semibrittle seismic deformation in high-temperature mantle mylonite shear zone along the Romanche transform fault

Oceanic transform faults, a key element of plate tectonics, represent the first-order discontinuities along mid-ocean ridges, host large earthquakes, and induce extreme thermal gradients in lithosphere. However, the thermal structure along transform faults and its effects on earthquake generation are poorly understood. Here we report the presence of a 10- to 15-kilometer-thick in-depth band of microseismicity in 10 to 34 kilometer depth range associated with a high-temperature (700\ub0 to 900\ub0C) mantle below the brittle lithosphere along the Romanche mega transform fault in the equatorial Atlantic Ocean. The occurrence of the shallow 2016 moment magnitude 7.1 supershear rupture earthquake and these deep microearthquakes indicate that although large earthquakes occur in the upper brittle lithosphere, a substantial amount of deformation is accommodated in the semibrittle mylonitic mantle that resides at depths below the 600\ub0C isotherm. We also observe a rapid westward deepening of this band of seismicity indicating a strong lateral heterogeneity