PubMed · 14771083
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M KREPSKY. 1950. The impedance angle and thyroid dysfunction.. https://pubmed.ncbi.nlm.nih.gov/14771083/
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The most significant biotic and abiotic stress agents of water extremity, salinity, and infection lead to wood decay and modifications of moisture and ion content, and density. This strongly influences the (di-)electrical and mechanical properties and justifies the application of geophysical imaging techniques. These are less invasive and have high resolution in contrast to classical methods of destructive, single-point measurements for inspecting stresses in trees and soils. This review presents some in situ and in vivo applications of electric, radar, and seismic methods for studying water status and movement in soils, roots, and tree trunks. The electrical properties of a root-zone are a consequence of their moisture content. Electrical imaging discriminates resistive, woody roots from conductive, soft roots. Both types are recognized by low radar velocities and high attenuation. Single roots can generate diffraction hyperbolas in radargrams. Pedophysical relationships of water content to electrical resistivity and radar velocity are established by diverse infiltration experiments in the field, laboratory, and in the full-scale 'GeoModel' at Kiel University. Subsurface moisture distributions are derived from geophysical attribute models. The ring electrode technique around trunks images the growth ring structure of concentric resistivity, which is inversely proportional to the fluid content. Healthy trees show a central high resistivity within the dry heartwood that strongly decreases towards the peripheral wet sapwood. Observed structural deviations are caused by infection, decay, shooting, or predominant light and/or wind directions. Seismic trunk tomography also differentiates between decayed and healthy woods.
Intraluminal impedance monitoring is a new technique that can be used to detect the flow of liquids and gas through hollow viscera. In combination with manometry, it is used for esophageal function testing and while manometry provides information on contractile activity, impedance provides information on esophageal bolus transit. This is especially useful in patients with nonobstructive dysphagia. However, impedance monitoring appears to be less suitable for the evaluation of patients with achalasia. When used in combination with esophageal pH monitoring, impedance monitoring makes gastroesophageal reflux monitoring more complete because it allows recognition of both acidic and weakly acidic reflux episodes. The results of several studies suggest that impedance-pH monitoring is useful in the evaluation of patients with PPI-resistant typical reflux symptoms, chronic unexplained cough, excessive belching, and rumination.
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