Focused time-lapse inversion of radio and audio magnetotelluric data

Geoelectrical techniques are widely used to monitor groundwater processes, while surprisingly few studies have considered audio (AMT) and radio (RMT) magnetotellurics for such purposes. In this numerical investigation, we analyze to what extent inversion results based on AMT and RMT monitoring data can be improved by (1) time-lapse difference inversion; (2) incorporation of statistical information about the expected model update (i.e., the model regularization is based on a geostatistical model); (3) using alternative model norms to quantify temporal changes (i.e., approximations of l(1) and Cauchy norms using iteratively reweighted least-squares), (4) constraining model updates to predefined ranges (i.e., using Lagrange Multipliers to only allow either increases or decreases of electrical resistivity with respect to background conditions). To do so, we consider a simple illustrative model and a more realistic test case related to seawater intrusion. The results are encouraging and show significant improvements when using time-lapse difference inversion with non l(2) model norms. Artifacts that may arise when imposing compactness of regions with temporal changes can be suppressed through inequality constraints to yield models without oscillations outside the true region of temporal changes. Based on these results, we recommend approximate l(1)-norm solutions as they can resolve both sharp and smooth interfaces within the same model. (C) 2012 Elsevier B.V. All rights reserved.

Tasavallan Presidentin radio- ja televisiopuhe Pohjolan päivän johdosta 12.4.1961

Puhe

Tasavallan Presidentin radio- ja televisiopuhe 11.9.1971

Puhe

Tasavallan Presidentin radio- ja TV-haastattelu 5.8.1970

Haastattelu

Tasavallan Presidentin radio- ja televisiopuhe 31.7.1970

Puhe

Republikens Presidents tal i radio och television 7.5.1973

Puhe

Tal med anledning av regeringsformens 40-årsjubileum (17.7.1959 i radio och TV)

Puhe

Audit report on KCCK-FM Radio, a public telecommunications entity operated by Kirkwood Community College in Cedar Rapids, Iowa for the year ended June 30, 2007

Audit report on KCCK-FM Radio, a public telecommunications entity operated by Kirkwood Community College in Cedar Rapids, Iowa for the year ended June 30, 2007

Utilisation en tomoscintigraphie d'anticorps monoclonaux radio-marqués pour la détection chez l'homme des cancers digestifs et des cancers médullaires de la thyroïde

Two 131-Iodine radiolabelled monoclonal antibodies were used to perform tomoscintigraphy in 42 patients: 11 patients bearing medullary thyroid cancers and 19 patients bearing gastrointestinal cancers received an antibody directed against carcino-embryonic antigen; 12 patients bearing gastro-intestinal cancers received an antibody directed against a non circulating antigen expressed by human colorectal cancers cell lines. Tomoscintigraphy is particularly useful for analysing the complex biodistribution of radiolabelled antibodies and the low contrast images encountered in immunoscintigraphy; the problems related to the true positive rate and to the clinical specificity of the method are discussed.