35 research outputs found

    Induced polarization applied to biogeophysics: recent advances and future prospects

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    This paper provides an update on the fast-evolving topic of the induced polarization (IP) method applied to biogeophysics. It emphasizes new understandings of the IP phenomena associated with biological activity, pointing out new developments and applications, and identifying existing knowledge gaps. The focus is on the use of IP as related to living organisms, including micro-organisms and plants (both roots and stems). We first discuss observed links between the IP signal and microbial cell structure, activity and biofilm formation. We provide an up-to-date conceptual model of the electrical behavior of the microbial cell and biofilm and examine the role of extracellular electron transfer mechanisms on the functionality and development of biofilms. We review the latest biogeophysical studies, including work on hydrocarbon biodegradation, contaminant sequestration, soil strengthening and peatland characterization. We then elaborate on the IP signature of the plant root zone, relying on a state-of-the-art conceptual model of the biogeophysical mechanisms of a plant root cell. The first laboratory surveys show that single roots and root system are highly polarizable. They also present encouraging results for imaging the root system embeded in a medium and gaining information on the mass density, the structure or the physiological characteristics of the root system. IP is also used to characterize wood and tree structures in the lab but also at the field scale, through tomography of the stem. Finally, we discuss up- and down-scaling between lab and field studies as well as joint interpretation. We emphasize the need for intermediate scale studies and the benefits of using IP as a time-lapse monitoring method. We conclude with the promising integration of IP in global mechanistic models to better understand and quantify subsurface biogeochemical processes

    Classificação de Muscidae (Diptera): uma proposta através da análise cladístical

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    <abstract language="eng">A cladistic analysis for 27 muscid genera is given, running the PAUP program (SWOFFORD, 1985). The 35 characters used in this study are polarized based on three outgroups of related families. A cladogram showing hypothetical phylogenetic relationships among genera and a discussion of the characters enable to propose a sequencial phylogenetic classification of Muscidae at tribal level. The following seven subfamilies and eight tribes are included: Achanthipterinae; Atherigoninae; Muscinae, with Muscini and Stomoxiini; Azeliinae, with Azeliini and Reinwardtiini; Phaoniinae; Mydaeinae, with Graphomyiini and Mydaeini and Coenosiinae, with Coenosiini and Limnophorini. Helina Robineau-Desvoidy, 1830 has not a defined position in the obtained cladogram to the considered levels. The neotropical species of Phaonia (aut.) must be separated in a new genus. The proposed classification is compared with contemporaneous classifications. The greatest congruence is found with that of SKIDMORE (1985)
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