A Simple Apparent Resistivity Definition for Modified Central-Loop TEM System

2017 ◽  
pp. 221-232
Author(s):  
Yunfei Lu ◽  
Guoqiang Xue ◽  
Xiu Li ◽  
Zhipeng Qi
Keyword(s):  
Apparent Resistivity ◽  
Central Loop

Numerical calculation of All-Time Apparent Resistivity for Central Loop Transient Electromagnetic Method

2003 ◽  
Vol 46 (5) ◽  
pp. 998-1010 ◽  
Author(s):  
Denghai BAI ◽  
Maxwell A Meju ◽  
Jian LU ◽  
Lifeng WANG ◽  
Zhaohai HE
Keyword(s):  
Numerical Calculation ◽  
Apparent Resistivity ◽  
Electromagnetic Method ◽  
Transient Electromagnetic Method ◽  
Transient Electromagnetic ◽  
Central Loop

Multiseparation, multisystem electromagnetic depth sounding‐An extension for unification

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 56-62 ◽  
Author(s):  
Umesh C. Das
Keyword(s):  
Apparent Resistivity ◽  
Mutual Coupling ◽  
Random Noise ◽  
Field Measurements ◽  
Dipole Source ◽  
Controlled Source ◽  
Definition Of ◽  
Depth Sounding ◽  
Central Loop ◽  
The Given

A recent definition of controlled‐source electromagnetic apparent resistivity has been adopted, and it is shown that this definition is unique. It produces a single apparent resistivity value by transforming any of the given combinations of the mutual coupling ratios measured by five different source‐receiver configurations, namely, horizontal coplanar loops (HCP), vertical coplanar loops (VCP), vertical coaxial loops (VCA), electric dipole source and horizontal receiver loop (EDL), and central loop (in‐loop) configurations. Synthetic field data for the commercially available MaxMin system, which can be operated with HCP, VCP, and VCA configurations, are fabricated and they are transformed to apparent resistivities. An analysis of apparent resistivity curves so obtained reveals the requirements of the ranges of frequencies and transmitter‐receiver separations needed for given exploration depth. A concise analysis of the effect of the random noise errors in the MaxMin data on stability of apparent resistivity is carried out. From this analysis, it is expected that apparent resistivities from field measurements will be stable, even when the measurements are corrupted with random noises.

Discussion on Method of Eliminating Large Loop Source TEM Border Effect

2014 ◽  
Vol 962-965 ◽  
pp. 313-316
Author(s):  
Zi Qiang Han ◽  
Tao Liu
Keyword(s):  
Apparent Resistivity ◽  
Measurement Data ◽  
Ground Model ◽  
Correct Interpretation ◽  
Border Effect ◽  
Magnetic Dipoles ◽  
Large Loop ◽  
Tem Method ◽  
Correct Understanding ◽  
Central Loop

Large loop source TEM method has played an important role in minerals and engineering exploration. But there is a strong border effect when one explains by central loop later-time apparent resistivity. In this paper, a method was used to calculate all-time apparent resistivity by magnetic dipoles composing loop. For 1D forward data, all-time apparent resistivity was computed and compared with later-time apparent resistivity. Conclusions have been drawn that all-time apparent resistivity has no border effect on homogeneous ground model; but for complex layered model, all-time apparent resistivity border effect is reflected in vicinity of false extreme point of apparent resistivity curve, and is much weaker than later-time apparent resistivity border effect. The conclusions are conducive to a correct understanding of using all-time apparent resistivity to eliminate border effect and guide correct interpretation of measurement data.

Application of Apparent Resistivity Ratio on the Interpretation of Small Central-loop TEM Survey in Areas of Conductive Overburden

2019 ◽  
Vol 24 (3) ◽  
pp. 479-486
Author(s):  
Hu Zhao ◽  
Sheng Zhou ◽  
Rui Li ◽  
Zhenzhu Xi ◽  
Xia Long
Keyword(s):  
Apparent Resistivity ◽  
Reference Station ◽  
Ratio Method ◽  
Resistivity Ratio ◽  
Resistivity Variation ◽  
Prism Model ◽  
Central Loop ◽  
Subsurface Resistivity ◽  
Resistivity Image ◽  
Local Anomalies

Central-loop TEM sounding data are often interpretead with apparent resistivity as a function of depth. This can quickly give a qualitative understanding of the subsurface resistivity variation. However, when the resistivity contrast between anomalies and background is weak, especially when there is a conductive overburden, the apparent resistivity image is inadequate to quickly and visually identify local anomalies. As an alternative, the apparent resistivity ratios of each measured station to a reference station is proposed as a fast way to identify local conductive anomalies qualitatively. Modeling analyses are carried out on 1D layer model, 2D fault models, and a 3D prism model with conductive overburdens. The results show that the apparent resistivity ratio outperforms the apparent resistivity on intuitively reflecting the target anomaly. As an image enhancement technique, the apparent resistivity ratio performs data transformation on the original apparent resistivity data, normalizing the background response, and highlighting the anomaly. At last, the apparent resistivity ratio method is successfully applied on interpreting a small central-loop TEM survey on investigating karst structure beneath a freshwater river. It provides an alternative simple fast way for interpretation of central loop TEM measurements.

Forward modelling of circular loop source and calculation of whole area apparent resistivity based on TEM

2018 ◽  
Vol 35 (2) ◽  
pp. 183-198 ◽  
Author(s):  
Jun ZHANG ◽  
Yanging WU ◽  
Hongchun YI
Keyword(s):  
Apparent Resistivity ◽  
Forward Modelling ◽  
Circular Loop

scholarly journals Novel Three-Finger Neurotoxins from Naja melanoleuca Cobra Venom Interact with GABAA and Nicotinic Acetylcholine Receptors

Toxins ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 164
Author(s):  
Lina Son ◽  
Elena Kryukova ◽  
Rustam Ziganshin ◽  
Tatyana Andreeva ◽  
Denis Kudryavtsev ◽  
...  
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Gabaa Receptors ◽  
Binding Sites ◽  
Acetylcholine Receptors ◽  
Nicotinic Acetylcholine ◽  
High Affinity ◽  
Central Loop ◽  
Acetylcholine Binding Proteins ◽  
Α7 Nachrs

Cobra venoms contain three-finger toxins (TFT) including α-neurotoxins efficiently binding nicotinic acetylcholine receptors (nAChRs). As shown recently, several TFTs block GABAA receptors (GABAARs) with different efficacy, an important role of the TFTs central loop in binding to these receptors being demonstrated. We supposed that the positive charge (Arg36) in this loop of α-cobratoxin may explain its high affinity to GABAAR and here studied α-neurotoxins from African cobra N. melanoleuca venom for their ability to interact with GABAARs and nAChRs. Three α-neurotoxins, close homologues of the known N. melanoleuca long neurotoxins 1 and 2, were isolated and sequenced. Their analysis on Torpedocalifornica and α7 nAChRs, as well as on acetylcholine binding proteins and on several subtypes of GABAARs, showed that all toxins interacted with the GABAAR much weaker than with the nAChR: one neurotoxin was almost as active as α-cobratoxin, while others manifested lower activity. The earlier hypothesis about the essential role of Arg36 as the determinant of high affinity to GABAAR was not confirmed, but the results obtained suggest that the toxin loop III may contribute to the efficient interaction of some long-chain neurotoxins with GABAAR. One of isolated toxins manifested different affinity to two binding sites on Torpedo nAChR.

scholarly journals Corrections of surface fissure effect on apparent resistivity measurements

2014 ◽  
Vol 200 (2) ◽  
pp. 1118-1135 ◽  
Author(s):  
J. Gance ◽  
P. Sailhac ◽  
J.-P. Malet
Keyword(s):  
Apparent Resistivity ◽  
Resistivity Measurements

Apparent resistivity of azimuthal anisotropy layered media

2002 ◽  
Vol 15 (5) ◽  
pp. 526-532
Author(s):  
Ai-guo Ruan ◽  
Tong-en Mao ◽  
Qing-he Li ◽  
Shuang-cheng Ge
Keyword(s):  
Apparent Resistivity ◽  
Layered Media ◽  
Azimuthal Anisotropy
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