Joint inversion of receiver functions, surface wave dispersion, and magnetotelluric data

We present joint inversion of magnetotelluric, receiver function, and Raleigh wave dispersion data for a one‐dimensional Earth using a multiobjective genetic algorithm (GA). The chosen GA produces not only a family of models that fit the data sets but also the trade‐off between fitting the different data sets. The analysis of this trade‐off gives insight into the compatibility between the seismic data sets and the magnetotelluric data and also the appropriate noise level to assume for the seismic data. This additional information helps to assess the validity of the joint model, and we demonstrate the use of our approach with synthetic data under realistic conditions. We apply our method to one site from the Slave Craton and one site from the Kaapvaal Craton. For the Slave Craton we obtain similar results to our previously published models from joint inversion of receiver functions and magnetotelluric data but with improved resolution and control on absolute velocities. We find a conductive layer at the bottom of the crust, just above the Moho; a low‐velocity, low‐resistivity zone in the lithospheric mantle, previously termed the Central Slave Mantle Conductor; and indications of the lithosphere‐asthenosphere boundary in terms of a decrease in seismic velocity and resistivity. For the Kaapvaal Craton both the seismic and the MT data are of lesser quality, which prevents as detailed and robust an interpretation; nevertheless, we find an indication of a low‐velocity low‐resistivity zone in the mantle lithosphere. These two examples demonstrate the potential of joint inversion, particularly in combination with nonlinear optimization methods

Structure and evolution of the intracratonic Congo Basin

Surface wave tomography, heat flow, and crustal thickness measurements have demonstrated that the thickness of the continental lithosphere varies by at least a factor of 2. Since the thermal time constant of the lithosphere depends upon the square of its thickness, subsidence records of extensional sedimentary basins offer a potential way of extending these observations into the past. Here we examine the Congo basin, a large and iconic intracratonic sedimentary basin in Central Africa. This roughly circular basin covers an area in excess of 1.4 × 106 km2 with more than 5 km thickness of sedimentary rocks, the oldest parts of which are late Precambrian in age. First, we assess the thickness of the lithosphere. We have estimated its thickness across Africa using maps of shear wave velocity obtained by inversion of fundamental and higher-mode surface waveforms. The Congo Basin sits on 220 ± 30 km thick lithosphere and appears to be part of a southern core to the continent encompassing both Archean cratons and Proterozoic mobile belts. This thickness is consistent with published estimates from kimberlites. Reappraisal of legacy seismic reflection images demonstrates that the sedimentary section is underlain by a Late Precambrian rift zone and that the basin is still subsiding today. Subsidence modeling of two deep wells is consistent with uniform extension and cooling of the lithosphere by a factor of 1.2 during latest Precambrian and Cambrian time; we argue that the exceptional 0.55 Ga history of the basin is a direct consequence of the lithospheric thermal time constant being a factor of 4 longer than normal. Today, the basin coincides with a long-wavelength −30 to −40 mGal gravity anomaly. We interpret this gravity anomaly as the surficial manifestation of 400–600 m of recent mantle convective drawdown in response to the onset of upwelling plumes around the flanks of the southern African continent. The alternative explanation, that it is the static manifestation of locally thick lithosphere, is inconsistent with global trends of mantle density depletion. Our interpretation is consistent with fast seismic velocities observed throughout the sublithospheric upper mantle underneath the basin and recent geodynamic modeling

Prospective Investigation of Pesticide Applicators' Health (PIPAH) study: a cohort study of professional pesticide users in Great Britain

PURPOSE: The purpose of the study is to monitor the exposure and health of workers in Great Britain who use pesticides as a part of their job, and to gain a better understanding of the relationship between long-term exposure to pesticides and health. PARTICIPANTS: Study participants are professional pesticide users who are certified in the safe use of pesticides or who were born before 1965 and apply pesticides under 'grandfather rights'. Overall response rate was 20%; participants are mostly male (98%) and the average age is 54 years, ranging from 17 to over 80 years. FINDINGS TO DATE: Participants have completed a baseline general questionnaire and three follow-up questionnaires on the use of pesticides. These data will enable investigations into the relationship between occupational pesticide exposure and health outcomes taking into account non-occupational confounding factors. FUTURE PLANS: There is no set end date for data collection. Recruitment into the cohort will continue, and for the foreseeable future there will be annual pesticide use questionnaires and five yearly follow-up general questionnaires.The intention is to validate the pesticide use questionnaire, and to develop a crop/job exposure matrix (C/JEM) which can be updated regularly. This C/JEM will be able to look at general categories of pesticide, such as insecticides, structurally related pesticides, such as organochlorines, or individual active ingredients. Data collected on use of personal protective equipment and method of application will provide information on how potential exposure to pesticide during application may have been modified. The study will be able to estimate changes in individual pesticide use over time, and to examine the associations between pesticide use and both baseline and long-term health outcomes.The cohort members will be linked to national databases for notification of hospital episode statistics, cancer incidence and mortality for follow-up of health outcomes

Velocity-conductivity relations for cratonic lithosphere and their application : example of Southern Africa

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013): 806–827, doi:10.1002/ggge.20075.Seismic velocity is a function of bulk vibrational properties of the media, whereas electrical resistivity is most often a function of transport properties of an interconnected minor phase. In the absence of a minor conducting phase then the two should be inter-relatable primarily due to their sensitivity to temperature variation. We develop expressions between shear wave velocity and resistivity for varying temperature, composition, and water content based on knowledge from two kimberlite fields: Jagersfontein (Kaapvaal Craton) and Gibeon (Rehoboth Terrane). We test the expressions through comparison between a new high-resolution regional seismic model, derived from surface wave inversion of earthquake data from Africa and the surrounding regions, and a new electrical image from magnetotelluric (MT) data recorded in SAMTEX (Southern African Magnetotelluric Experiment). The data-defined robust linear regression between the two is found to be statistically identical to the laboratory-defined expression for 40 wt ppm water in olivine. Cluster analysis defines five clusters that are all geographically distinct and tectonically relate to (i) fast, cold, and variably wet Kaapvaal Craton, (ii) fast and wet central Botswana, (iii) slow, warm, and wet Rehoboth Terrane, (iv) moderately fast, cold, and very dry southernmost Angola Craton, and (v) slow, warm, and somewhat dry Damara Belt. From the linear regression expression and the MT image we obtain predicted seismic velocity at 100 km and compare it with that from seismic observations. The differences between the two demonstrate that the linear relationship between Vs and resistivity is appropriate for over 80% of Southern Africa. Finally, using the regressions for varying water content, we infer water content in olivine across Southern Africa.We wish to again acknowledge the three main funding agencies, the U.S. National Science Foundation’s Continental Dynamics Program (grant EAR0455242 to RLE), the South African Department of Science and Technology (grant to South African Council for Geoscience), and Science Foundation Ireland (grant 05/RGP/GEO001 to AGJ), for their support. Industry support for SAMTEX from De Beers Group Services, BHP Billiton and Rio Tinto Mining and Exploration resulted in a program far more extensive than originally conceived. S.F. has been supported by the NERC New Investigator grant NE/G000859/1. M.M. wishes to thank Science Foundation Ireland (grant 08/RFP/GEO1693 SAMTEX to AGJ) for support. J.F. wishes to thank Enterprise Ireland (grant Topo-Med to AGJ), Science Foundation Ireland (grant 10/IN.1/I3022 IRETHERMto AGJ), and the JAE-DOC Programme from Spanish CSIC, cofunded by FSE for support.2013-10-0

Techniques for the endovascular management of complications following lower limb percutaneous transluminal angioplasty

AbstractObjectives: to determine the incidence of early complications following percutaneous transluminal angioplasty and to describe their management and outcome. Materials: five hundred and fifty consecutive patients undergoing angioplasty of 648 limbs, containing 1053 anatomical segments during a two year period were reviewed retrospectively. Results: early complications affected 109 segments (10%) in 92 limbs (14%) of 84 patients (15%). Of the 109 segments affected by early complications, 106 (97%) were managed by endovascular techniques with surgery being required on only three (3%) occasions. There were no deaths attributable to angioplasty. Conclusions: although early complications occur in 14% of limbs undergoing percutaneous transfemoral angioplasty, the majority (97%) can be managed by endovascular techniques.Eur J Vasc Endovasc Surg 25, 125–130 (2003

Amelioration of type 1 diabetes following treatment of non-obese diabetic mice with INGAP and lisofylline

Type 1 diabetes mellitus results from the autoimmune and inflammatory destruction of insulin-producing islet β cells, rendering individuals devoid of insulin production. Recent studies suggest that combination therapies consisting of anti-inflammatory agents and islet growth-promoting factors have the potential to cause sustained recovery of β cell mass, leading to amelioration or reversal of type 1 diabetes in mouse models. In this study, we hypothesized that the combination of the anti-inflammatory agent lisofylline (LSF) with an active peptide fragment of islet neogenesis associated protein (INGAP peptide) would lead to remission of type 1 diabetes in the non-obese diabetic (NOD) mouse. We treated groups of spontaneously diabetic NOD mice with combinations of LSF, INGAP peptide, or control saline parenterally for up to 6 weeks. Our results demonstrate that the mice receiving combined treatment with LSF and INGAP peptide exhibited partial remission of diabetes with increased plasma insulin levels. Histologic assessment of pancreata in mice receiving combined therapy revealed the presence of islet insulin staining, increased β cell replication, and evidence of Pdx1-positivity in ductal cells. By contrast, diabetic animals showed severe insulitis with no detectible insulin or Pdx1 staining. We conclude that the novel combination treatment with LSF and INGAP peptide has the potential to ameliorate hyperglycemia in the setting of established type 1 diabetes via the recovery of endogenous β cells and warrant further studies

Role of the 12-lipoxygenase pathway in diabetes pathogenesis and complications

12-lipoxygenase (12-LOX) is one of several enzyme isoforms responsible for the metabolism of arachidonic acid and other poly-unsaturated fatty acids to both pro- and anti-inflammatory lipid mediators. Mounting evidence has shown that 12-LOX plays a critical role in the modulation of inflammation at multiple checkpoints during diabetes development. Due to this, interventions to limit pro-inflammatory 12-LOX metabolites either by isoform-specific 12-LOX inhibition, or by providing specific fatty acid substrates via dietary intervention, has the potential to significantly and positively impact health outcomes of patients living with both type 1 and type 2 diabetes. To date, the development of truly specific and efficacious inhibitors has been hampered by homology of LOX family members; however, improvements in high throughput screening have improved the inhibitor landscape. Here, we describe the function and role of human 12-LOX, and mouse 12-LOX and 12/15-LOX, in the development of diabetes and diabetes-related complications, and describe promise in the development of strategies to limit pro-inflammatory metabolites, primarily via new small molecule 12-LOX inhibitors

12-Lipoxygenase Inhibitor Improves Functions of Cytokine-Treated Human Islets and Type 2 Diabetic Islets

Context: The 12-lipoxygenase (12-LO) pathway produces proinflammatory metabolites, and its activation is implicated in islet inflammation associated with type 1 and type 2 diabetes (T2D). Objectives: We aimed to test the efficacy of ML355, a highly selective, small molecule inhibitor of 12-LO, for the preservation of islet function. Design: Human islets from nondiabetic donors were incubated with a mixture of tumor necrosis factor α , interluekin-1β, and interferon-γ to model islet inflammation. Cytokine-treated islets and human islets from T2D donors were incubated in the presence and absence of ML355. Setting: In vitro study. Participants: Human islets from organ donors aged >20 years of both sexes and any race were used. T2D status was defined from either medical history or most recent hemoglobin A1c value >6.5%. Intervention: Glucose stimulation. Main Outcome Measures: Static and dynamic insulin secretion and oxygen consumption rate (OCR). Results: ML355 prevented the reduction of insulin secretion and OCR in cytokine-treated human islets and improved both parameters in human islets from T2D donors. Conclusions: ML355 was efficacious in improving human islet function after cytokine treatment and in T2D islets in vitro. The study suggests that the blockade of the 12-LO pathway may serve as a target for both form of diabetes and provides the basis for further study of this small molecule inhibitor in vivo