Conductive Zone Research Articles

Delineation of highland saline groundwater sources in Ba'kelalan region of NE Borneo to improve the salt-making production using geochemical and geophysical approaches

The extraction of mountain salt from the saline waters is the basic livelihood of the Ba'kelalan communities of Sarawak. The current integrated approach is the first attempt to study the sources and geochemical processes of the saline groundwaters in this mountain region. Hence, in this study, saline groundwater samples from five existing wells in different seasons were analysed for hydrochemical parameters and multi-isotope composition (δ18O, δD, δ34S, δ11B and δ37Cl). The significant increase in TDS, EC and salinity was due to seasonal variation and fluctuation in water level based on hourly, daily and monthly observations. The geochemical ratios and the statistical techniques revealed that the salinity was due to the dissolution of marine evaporites as a dominant process, coupled with other factors such as water-rock interaction, ion exchange and sulphate reduction. From the isotopic signatures, it was inferred that the origin of saline groundwater was from the intense dissolution of marine evaporites such as halite dissolution and oxidation of -sulphide (pyrite). 2D electrical resistivity and seismic refraction methods were used to identify the lithological variations, depth of potential sources of saline groundwater, and the subsurface structures. It was inferred the probability of a conductive zone at a depth of 1–14 m, from which the saline groundwater plume migrates towards the perched aquifer. The presence of subsurface faults facilitated the movement of hypersaline groundwater from the saturated zone to the surface. The outcome of the study will support the dependent community to enhance their commercial salt production.

Enhancement of charging and discharging of phase change material in annular thermal energy storage unit by applying magnetic field

One of the most applicable geometries for a thermal energy storage unit is an annulus filled by phase change material (PCM). In time-sensitive applications, the charging and discharging rates of PCM are critical. In the early stage of the period, the phase change rate is high, and it becomes so low by progressing the time, especially in the pure conduction zone at the later stage. Staggering the tube increases the charging or discharging rates and decreases another. The enhancement of both the charging and discharging rates is desirable. To achieve this in the present study, to improve the heat transfer and phase change rates, the application of the magnetic field of an electric current-carrying wire at the top or the bottom of the annulus in order to induce a convection heat transfer in the nanoparticles-enhanced PCM (NePCM) is presented. The solution is validated with experimental and numerical data. The predicted result indicates that employing the wire at the top of the annulus can reduce the solidification time by 25%. The application of the magnetic field is more efficient in the charging process where the wire is employed under the annulus, which intensifies the melting rate up to 40%. Accordingly, considering the appropriate locations of the wire, a conceptual design of thermal energy storage unit under the magnetic field efficient in both charging and discharging processes is developed.

Magnetotelluric data analysis using 2D resistivity modelling in Gondang region, Bojonegoro

Previous studies in Gondang Subdistricthave identified underground mud reservoirnear a rock intrusion, while another study near Gondang Subdistrict has identified deep fault structures. This study will identify the distribution and characteristics of possible geological features in the area using magnetotelluric (MT) method to further describe the relationship between the geological features related to local geology. MT data measurements were conducted on 7 stations alonga north-south line, then modelled in 2D using nonlinear conjugate gradient algorithm. The model was used to describe the subsurface resistivity distribution and to identify the geological features. The results show 5 resistive zones (20–1250 Ω⋅m) and 4 conductive zones (≤10 Ω⋅m). The former consist of 4 vertical zones, 1 vertical zone deeper than 5 km, and 1 horizontal zone near the surface. 2 conductive zones surround a resistive zone, while 2 others stretch below the horizontal resistive zone. The vertical resistive zones are interpreted as andesite intrusions, and the horizontal one as volcanic breccia. The conductive zones are interpreted consisting of tuff and marl with possible saline water content. 3 vertical intrusions are thought to have the same source, and all vertical intrusions are suspected to co-occurr with the Pandan Volcano intrusion.

The CORRELATION BETWEEN 3-D MAGNETOTELLURIC INVERSION MODEL WITH DRILLING DATA IN PATUHA GEOTHERMAL FIELD

The Patuha geothermal field is located in West Java Province, Indonesia and developed by state owned company PT Geo Dipa Energi (Persero). The Commercial Operation Date (COD) for Patuha was in September 2014 with plant capacity of 1x60 MW. Until now, Patuha Unit I geothermal field has been running for almost 7 years. The current production wells have experienced a natural decline, which is showed by a reduction in production capacity to the initial production. This causes the steam supply to the Power Plant Unit I to be not optimal, so a make-up well program is needed. Furthermore, to support the addition of electricity production capacity from geothermal energy in Indonesia, the development of the Patuha Geothermal Field is planned to be carried out for the next Power Plant Unit’s expansion (Unit 2 and Unit 3). Nevertheless, determining the location for both make-up and development drilling might still pose high risks. This is especially because the development area (where production and injection wells are located) is only concentrated in the eastern area of the contract area. Geophysical data especially Magnetotelluric (MT) has an indispensable role considering the limited data and the limited number of existing wells that cover the entire Patuha prospect area. To understanding the subsurface feature and see the correlation between MT model with well results in Patuha Geothermal Field, MT and TDEM survey were conducted in the eastern and western parts of Patuha area with total 100 stations. Considering the complexity of the subsurface condition in volcanic area, 3-D inversion of the MT data will be the most representative approach to investigate geothermal system in Patuha Geothermal Field. An obvious subsurface resistivity distribution revealed by the 3-D inversion showed a good agreement with well results especially in mapping the temperature distribution both vertically and horizontally. Generally, the resistivity distribution consists of a conductive zone (1–10 ohm-m) at the shallow part overlying a reservoir zone with a rather higher resistivity range (20–60 ohm-m). The conductive zone (<10 ohm-m) is correlated with Base of Conductor (BOC) of the wells that indicated by the presence of the argillic mineral. Meanwhile, the resistivity value around 15-20 ohm-m is correlated with Top of Reservoir of the production or injection well which is characterized by the presence of a convective temperature. In addition, from the results of resistivity mapping there is a very good correlation also in determining of reservoir boundary which is characterized by the presence of reverse temperature from the well. These results can be used as a guidance for better development strategy and drilling prognosis for the next drilling campaign especially in the area which limited number of wells.

Large-scale magmatic–hydrothermal system of Kusatsu-Shirane Volcano, Japan, revealed by broadband magnetotellurics

Kusatsu-Shirane Volcano (KSV) is an active volcano in the central Honshu Arc, Japan, and is known for its significant hydrothermal activity and repeated phreatic eruptions over the past 200 years. On the basis of its long-term volcanic activity, an extensive magmatic–hydrothermal system is considered to have developed within the volcano, with strong impacts on volcanic processes. Previous magnetotelluric studies conducted at KSV have successfully revealed the structure of the hydrothermal system, mainly beneath the summit area. However, as the deep structure was still unclear, there was no information on the location of magma storage as a heat source to drive volcanic activity. Here we report a revised three-dimensional electrical resistivity structure model for KSV down to a depth of ~10 km below sea level (bsl), inferred from broadband magnetotelluric data (256–0.004 Hz) collected over a wider area than previous studies. The most notable feature of the model is a sub-vertical conductive zone that extends from a depth of 1.5 km below the summit area to a depth of ~10 km in the north-northwestern part of KSV. We interpret resistivity values to infer the upper half of the conductive zone (<4 km bsl) as a zone containing high-salinity brine and the lower half (>4 km bsl) as a partially molten zone. The fact that the inflation source during the unrest periods is located just beneath the brine zone indicates that the lower partially molten zone contains degassing magmas. This partially molten zone extends beneath the adjacent Shiga Volcano, suggesting that the two volcanoes could share a common magma source. The brine zone in the upper half is considered to have formed as a result of repeated magmatic intrusions during the Stage III activity of KSV since 17 ka. As this brine zone is not found beneath the presently inactive Shiga Volcano, it is considered that the formation of brine zones could be used as an indicator for evaluating recent magmatic activity and potential volcanic hazards.

Numerical modeling of NE Brazil coastal aquifer: Fault controlled conduits for seawater intrusion

Saline intrusion is a problem that mostly affects coastal aquifers around the world, either owing to anthropic and/or natural factors. The Barreiras Aquifer, which is located on Brazil's northeastern coast and of an unconfined hydraulic nature, is subject to this due to a water demand increase. This aquifer is located in an area structurally controlled by neotectonic activity. Increased complexity occurs in the form of variations in saturated thickness, hydraulic conductivity and exploited flow rates. This study aimed to construct a numerical model of dependent density flow for the Barreiras Aquifer using the SEAWAT software (USGS) and simulate saline intrusion over 20 years of pumping wells that currently exploit approximately 750 m³/h. The results can contribute to local hydrogeological management and assist managers. Simulation results with variation of recharge between dry and rainy periods and reduction of well exploitation flow rates were also obtained. The two main local faults, Boa Cica and Tabatinga, striking NW-SE and NE-SW, respectively, were simulated in a calibrated transient hydrogeological model as zones of high hydraulic conductivity (conduits) as well as in the inverse form (barriers) and offered a better fit considering the faults as zones of relatively higher hydraulic conductivities and preferred pathways for saltwater intrusion progression. A two-dimensional resistivity cross-section was used to constrain the electrical property of the NW striking fault, whether in the form of a resistive anomaly or conductive anomaly. The interpretation of the 2D geoelectric model is consistent with the conductive geoelectric anomaly associated to the Boa Cica Fault, where its transtensional nature favors wider saline contamination.

The Worth of Stochastic Inversion for Identifying Connectivity by Means of a Long‐Lasting Large‐Scale Hydraulic Test: The Salar de Atacama Case Study

AbstractUnderstanding groundwater flow involves characterizing the spatial variability of aquifer attributes and possible hydraulic connectivity structures. The latter are of crucial importance because high permeability channels may control groundwater flow and contaminant transport. In evaporitic aquifer systems, these preferential channels can consist of karst conduits, developed at different scales, as well as fault zones. These features condition the economic development of salt flats at the Central Andes. Hydraulic connectivity may affect exploitation efficiency by enhancing the inflow of less evaporated brine thus diminishing its mineral content (i.e., concentration of Li and K). In this context, we investigate if it is possible to use (tomographic) stochastic inversion (regularized pilot point method) in order to characterize the presence of connectivity structures in an evaporitic aquifer of great extension (some 1,500 km2) from head response measured at numerous observation points during a year long sequence of three hydraulic tests. Results show that, even though the solution is nonunique, the main preferential flow zones are identified. Numerous inversions yield similar fits to observed drawdowns with maximum errors of few centimeters. Preferential flow is identified not only by elongated high permeability regions, but also by a marked scale effect (model transmissivities are some 30 times larger than their local tests counterparts). The main high conductivity zones are consistent with independent information based on geophysics, isotopes, mixing ratios, piezometric data, and the expected dissolution processes.

Investigation of the Source of Groundwater Contamination Near a Farmland Using the VLF-EM and Magnetic Methods

Groundwater pollution continues to be a major problem in society where there is high level of urbanization, industrialization and conventional/inorganic farming. A detailed ground magnetic survey and VLF-EM was carried out on a site just beside a farmland to investigate the possible causes of the groundwater contamination in the area which lies within the Precambrian Basement Complex of Southwestern Nigeria. The survey was carried out using a proton precision magnetometer kept at a constant height during the survey, accompanied by Very Low Frequency - Electromagnetic Method (VLF-EM). Data for the two methods were acquired on five (5) traverses with the length of 100 m each. The distance between each traverse (inter traverse spacing) is 5 m. The VLF-EM data were interpreted qualitatively, using the Fraser and the Karous–Hjelt filters. The Fraser filtered data and relative current density pseudosections from the VLF-EM data indicate the presence of shallow and deep conductive zones that cross the farmland which are indicative of fractures. The quantitative interpretation of the data was done with a 2-D code that performs the inversion of the data. Magnetic maps were generated using Oasis Montaj, and profiles were plotted using Microsoft Excel software. From the results obtained, some major geological features were identified while linear features suspected to be fault/fractured zones, weathered zones, and bedrock depressions were delineated. Low magnetic intensity indicating presence of weak and incompetent zones were discovered. Earlier chemical analysis of both surface and groundwater collected at some depth on the farmland confirms the presence of water contamination. This knowledge supported the interpretation of the anomalies detected by VLF-EM and magnetic data as a possible cause of the contaminated groundwater flowing in connected fractures. The study concluded that the groundwater contamination originates from the farmland where some samples of the soil were found to contain nitrate chemicals resulting from fertilizer and pesticide used to enhance plant growth. Keywords: Nitrate contamination, groundwater pollution, multiple fractures, contaminant transport, fractured zone, inorganic farming DOI: 10.7176/JEES/12-6-04 Publication date: June 30 th 2022

Geophysics And Geomorphic Observation For Near-Surface Structures Mapping Of Seulimeum Fault On Lamtamot Area, Northern Sumatra

In the northern part of Sumatra Island, Indonesia, the Great Sumatran Fault, which can cause an earthquake, was divided into two segments: the Aceh and Seulimeum. An effort to reduce the risk is mapping the fault area, especially in the region that does not clearly show the sign on the surface, e.g., in the Lamtamot area, Indonesia. Electrical resistivity is widely used to study shallow structures, but the method requires more time when applied in a large area. This research explores the potential of an extremely low frequency (very low frequency-electromagnetic; VLF-EM) method to investigate the shallow fault of the Seulimeum segment. Here, the VLF-EM is compared with other geophysical methods such as resistivity and magnetic methods. For comprehensive results, the geomorphic observation that was conducted covered outcrops of the fault and trenching sites in the geophysical study for validating the model. A similar pattern of the VLF-EM and electrical resistivity data has been shown in a two-dimensional profile using data processing. The fault structure can be mapped at a distance of 20–24 m from the profile measurement, which is demonstrated by the low current density associated with the conductive zone from the VLF-EM, and low resistive anomaly in electrical resistivity. The fault can also be confirmed via magnetic intensity, which significantly increases at the same distance (20–25 m) of the VLF-EM and electrical resistivity. The geomorphic observation shows outcrops of fault activity, such as fault scarp, fractures, and faults, in the same direction as the Seulimeum segment, while scrap extends in the northwest direction up to ~20 m around the geophysical surveys. As revealed by the results, the VLF-EM method combined with other geophysical surveys and geomorphic observation can be used as a technique to image the fault that shows the shallow structure of the Seulimeum fault at 20–32 m along the profile.

Isthmus characteristics in operated congenital heart disease with atrial tachycardias

Abstract Funding Acknowledgements Type of funding sources: None. Background Patients with surgically repaired congenital heart disease (RCHD) present a high prevalence of atrial tachycardias (ATs). Although typical circuits dependent on the cavotricuspid isthmus (CTI-AFL) are the most frequent, intra-atrial re-entrant tachycardias (IART) are also common and a significant cause of recurrence. Purpose The aim of this observational study was to describe the characteristics of incisional isthmuses identified with ultrahigh-density electroanatomical mapping in patients with RCHD and to investigate their clinical significance. Methods The present investigation ambispectively examined 23 patients with RCHD. Mapping of index, induced and recurrent ATs was performed using a multipolar basket catheter and an ultra-high density mapping system. The conduction velocities (CV) and isthmus widths were calculated on isochronal and activation maps (Figure 1). Results Overall, 33 ATs in 23 patients were mapped in their entirety. 8 patients had no IART as index AT and no other zones of slow conduction. In the remaining 15 patients, 22 ATs were mapped (9 CTI-AFL/13 IART) and 27 zones of slow conduction were identified. All identified critical and/or potential incisional isthmuses had a CV≤0.625 m/sec. By trichotomizing the predictor of CV, all isthmuses (9/9) of the middle third (CV 0.075-0.133 m/sec) were critical for an IART (either index or induced) and they were significantly more frequently associated with an IART (100%) compared with the isthmuses of the upper (44.4%) and lower third (66.7%) (p=0.034). Width of critical isthmuses was significantly narrower compared to width of non-critical isthmuses (10.1±3.1 mm versus 16.3±7.3 mm, p=0.049). Among 9 induced/recurrent IARTs, critical incisional isthmus was visible at the activation map of the index AT in 6 patients (66.7%) and concealed (presented as line of block and/or collision of the wavefronts) in the remaining (33.3%). Index ATs with concealed isthmuses were significantly slower from index ATs without (U=6, p=0.047). During index ATs with cycle length &amp;lt;270 msec all critical isthmuses were visible (sensitivity 100%) (AUC=0.860, p=0.050). Conclusions The majority of isthmuses related to IARTs can be identified using ultrahigh-density activation mapping in patients with RCHD. A proportion can be overlooked due to functional block, especially during a slow index AT. CV and width of incisional isthmuses can be easily measured using novel mapping tools. Mid-range slow CV and narrow isthmus width may be predisposing factors of IART. Whether these features should promote ablation irrespective of stimulation protocol for AT induction needs further investigation. Figure 1. Isthmus CV calculation using isochronal activation mapping. Figure 2. An incisional isthmus, critical for an induced IART, was identified during a typical flutter. This isthmus had a narrow width (9.0 mm) and a mid-range slow CV (0.11 m/sec), features that may be predisposing factors for IARTs.

Modeling Monthly Nitrate Concentration in a Karst Spring with and without Discrete Conduit Flow

Understanding the coupled continuum pipe-flow framework for modeling contaminant transport in karst systems is critical for protecting water resources therein. This study simulated point and non-point source nitrate concentration in a karst spring and investigated the results generated from the flow and transport model with and without discrete conduit flow. CFPv2 and CMT3D models were integrated to address the changes in nitrate concentration at a monthly scale in a karst spring, and the results were compared with that from an equivalent porous media (EPM) model with high-hydraulic conductivity (K) zones set in the main karstified area to represent conduits. The results show that the CFPv2+CMT3D model is able to describe well the recession of nitrate concentration in spring discharge, and the relatively larger deviation (slower nitrate recession) from the observed trend for the EPM model is probably a result of the limitation of utilizing high hydraulic conductivity cells to represent conduit. Moreover, simulated hydraulic heads in poorly karstified areas from the two models both show slight differences from the observations (the head RMSE values of calibration/validation for CFPv2 and MODFLOW models are 0.16 m/0.25 m and 0.26 m/0.17 m, respectively), indicating the inclusion of conduits may not affect the simulation considerably, and the lower the proportion of karstic area, the slight effects brought from the inclusion of conduits in the model. For highly karstified areas, the CFPv2+CMT3D model could provide more accurate results (head RMSE of calibration/validation for CFPv2 and MODFLOW are 0.22 m/0.06 and 0.52 m/0.47 m, respectively), showing the coupled continuum pipe-flow framework may be more appropriate for applying to highly and maturely karstified areas where the variations in the behavior of flow and contaminant transport are more affected by turbulent flow regime.

The Thermal Response of a Packed Bed Thermal Energy Storage System upon Saturated Steam Injection Using Distributed Temperature Sensing

The effectiveness of a thermal energy storage (TES) system is typically characterized with the help of thermal stratification or temperature gradients along the direction of heat injection, which is typically the flow direction of heat transfer fluid. The steepness of temperature gradients are a direct indicator of the effectiveness or efficiency of the heat storage or dispatch process. The temperature gradient evolution along the packed bed of ceramic particles upon saturated steam injection is presented in this work. Distributed temperature sensing based on optical frequency domain reflectometry was deployed in a packed bed of ceramic particles to capture the thermal front evolution in the axial direction. The physical processes accompanying steam injection in packed beds are complex due to phase change, transitioning two-phase flow, and changes in condensate accumulation. Therefore, the variation of thermal response of the TES system for various steam injection flow rates was experimentally studied using a high-resolution distributed temperature sensing system in a chemically inert alumina particle-packed bed. Distinct zones of different heat transfer modes were observed during the steam injection experiments. A distinct conduction zone, evident from diffuse thermal fronts, was observed at low flow rates, and these thermal gradients became sharper as the flow rate increased. The diffuse thermal fronts in the heat storage media suggest a low exergy efficiency of the TES system, as energy losses started initiating before a significant fraction of the bed was saturated with steam.

A Multidisciplinary Approach for Groundwater Potential Mapping in a Fractured Semi-Arid Terrain (Kerdous Inlier, Western Anti-Atlas, Morocco)

This study is focused on developing an approach for spatial mapping of groundwater by considering four types of factors (geological, topographical, hydrological, and climatic factors), and by using different bivariate statistical models, such as frequency ratio (FR) and Shannon’s entropy (SE). The developed approach was applied in a fractured aquifer basin (Ameln Basin, Western Anti-Atlas, Morocco), to map the spatial variation of groundwater potential. Fifteen factors (15) influencing groundwater were considered in this study, including slope degree, slope aspect, elevation, topographic wetness index (TWI), slope length (LS), topographic position index (TPI), plane curvature, profile curvature, drainage density, lineament density, distance to rivers and fault network, normalized difference vegetation index (NDVI), lithology, and land surface temperature (LST). The potential maps produced were then classified into five classes to illustrate the spatial view of each potential class obtained. The predictive capacity of the frequency ratio and Shannon’s entropy models was determined using two different methods, the first one based on the use of flow data from 49 boreholes drilled in the study area, to test and statistically calibrate the predictive capacity of each model. The results show that the percentage of positive water points corresponds to the most productive areas (high water flow) (42.86% and 30.61% for the FR and SE models, respectively). On the other hand, the low water flows are consistent with the predicted unfavorable areas for hydrogeological prospecting (4.08% for the FR model and 6.12% for the SE model). Additionally, the second validation method involves the integration of 7200 Hz apparent resistivity data to identify conductive zones that are groundwater circulation zones. The interpretation of the geophysical results shows that the high-potential zones match with low apparent resistivity zones, and therefore promising targets for hydrogeological investigation. The FR and SE models have proved very efficient for hydrogeological mapping at a fractured basement area and suggest that the northern and southern part of the study area, specifically the two major fault zones (Ameln Valley in the north, and the Tighmi-Tifermit Valley in the south) has an adequate availability of groundwater, whereas the central part, covering the localities of Tarçouat, Boutabi, Tililan, and Ighalen, presents a scarcity of groundwater. The trend histogram of the evolution of positive water points according to each potentiality class obtained suggests that the FR model was more accurate than the SE model in predicting the potential groundwater areas. The results suggest that the proposed approach is very important for hydrogeological mapping of fractured aquifers, and the resulting maps can be helpful to managers and planners to generate groundwater development plans and attenuate the consequences of future drought.

PO-691-01 PHYSIOLOGIC, REALISTIC, COMPUTER MODELING OF ATRIAL FIBRILLATION TO FACILITATE THE DEVELOPMENT AND TESTING OF TREATMENT STRATEGIES

An interactive, physiologically realistic (PR), and accurate computer simulation allows multiple scenarios to be tested in a “live” environment and has become a key step in the rapid development and testing of treatment strategies for atrial fibrillation (AF). Develop an accurate model of AF that allows the user to define the regions and zones of anisotropic conduction to test the effectiveness of a variety of AF treatment strategies. A model was developed using standard electrophysiologic (EP) parameters established in the literature. An advanced implementation of the Fitzhugh-Nagumo model reproduces the action potential morphology of the human atrium enabling live simulation. To reproduce the complex conduction patterns (CCPs) of AF identified in the EP lab, a bi-layer model was implemented to represent epi- and endocardial dissociation. The model allows a user to define regions of fibrosis, zones of slow conduction, and action potential duration (APD). The user graphically draws these regions and zones with gradients that span entered max and min values of conduction velocity (CV) and APD. The EP lab experience and workflow is reproduced, with CCPs visualized on a 3D anatomy and calculated potentials displayed as 2D traces. To test the CCPs and performance of the model, isolated zones of conduction were delineated on a 3D LA model, with assigned sites of pacing and recording. Model produces accurate atrial CCPs for anatomical meshes > 20k triangles, with expected source-sink block-velocity < 5 cm/s (Figure 1). Regions of anisotropic conduction were applied to match a human AF substrate mapped by Acutus AcQMap, with PVI-block plus 2 anterior, 1 posterior, 1 roof, 1 mitral-isthmus slow conduction zones (0.1 - 50 cm/s); 1 anterior APD zone (65 - 110 ms); and anterior and posterior regions of endo-epi fibrosis (density = 25%, CV = 8 - 25 cm/s). Model produced similar CCPs to human with rotational and pivoting reentry at the same locations (Figure 2). A PR model of AF was developed that allows a user to define regions of fibrosis and zones of conduction abnormalities prominent in AF. The model can be used for developing and testing advanced treatment strategies. Clinical application is feasible, including input of procedural data to achieve optimal treatment strategies.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Efficacy of catheter ablation from the noncoronary aortic cusp of verapamil-sensitive atrial tachycardia arising near the atrioventricular node.

The efficacy of catheter ablation from the noncoronary aortic cusp (NCC) of verapamil-sensitive atrial tachycardia arising near the atrioventricular node (AVN-AT) has yet to be fully clarified. We elucidated the determinant of an effective AVN-AT ablation from the NCC. After identifying the earliest atrial activation site (EAAS) during tachycardia, the direction of the slow conduction zone (SCZ) of the reentry circuit was identified by demonstrating manifest entrainment in 26 patients with AVN-AT. Catheter ablation was initially performed from the NCC irrespective of the local activation time. If NCC ablation was ineffective, catheter ablation was performed targeting the SCZ entrance. Then the anatomical relationship between the SCZ and the successful ablation site was elucidated. NCC catheter ablation terminated AVN-AT in 14 patients (NCC group) but not in 12 (non-NCC group). Catheter ablation targeting the SCZ entrance terminated all non-NCC group ATs. The local activation time at the NCC relative to the EAAS did not differ between the NCC and non-NCC groups (10.1 ± 6.5 ms vs 11.2 ± 4.8 ms; P = .6333). The direction of the SCZ was posterior to the EAAS in all NCC group patients; however, it was posterolateral (n = 5) and lateral (n = 7) to the EAAS in the non-NCC group, suggesting that the SCZ existed in the direction of the NCC in the NCC group but was away from the NCC in the non-NCC group. A close proximity between the NCC and the SCZ of the reentry circuit, but not the local activation time at the NCC, determined the efficacy of NCC catheter ablation in AVN-ATs.

Application of Multi-Channel Analysis Surface Waves and Electrical Resistivity Tomography Methods to Identify Weak Zones at University of Mosul, Northern Iraq

Cracks have been developed in a large lecture hall on the University of Mosul Campus. These cracks exist along two sides of the building. Multi Analysis Surface Wave and Electrical Resistivity Tomography surveys were conducted at the surrounding building to investigate the nature and distribution of shallow subsurface soil/rock. The MASW’s data show three layers: the first layer is characterized by low shear wave velocity ranges between 210 and 420 m/s which is attributed to infill materials, the next layer is attributed to a river terrace (fairly competent rock) which has Vs ranging from 430m/s to 840 m/s. It is recognized by a gradual increase in mechanical characteristics as depth increases. In-depth between about 2.5m and 6.0 m the shear wave velocity drops in the top contact of this layer. The causes of low velocity may be due to weathering of the medium because of a sinkhole. The Electrical Resistivity Tomography profile shows four electrical zones, the first zone has 50-70 Ω.m. with a variable thickness from 0.5-1.5 m which indicates infill materials. The second zone has very low resistivity value, and a depth ranges 0.5m - 3.5 m, which might be interpreted to be increased clay, silt and water content (high water-saturated zone). The third zone is characterized by a high-resistivity value (&gt;100 Ω.m) that could be related to a dry conglomerate rock and gravels belong to river terraces. The fourth zone has a low-resistivity value (&lt;20 Ω.m) associated with a water-saturated marl bed. We could be definitively correlated the resistivity and velocity anomalies to sinkhole activity in were identified and characterized using combined geophysical methods. The Multi Analysis Surface Waves and Electrical Resistivity Tomography were shown to complete each other in the evaluation. The variations in Vs (low velocity) and resistivity (conductive zone) within the river terrace were detected and proposed to be indicative of dissolution and the subsidence responsible for structural damage implied by the change in the velocity and resistivity. The roughness of the top terrace surface strongly influences the nature of the velocity and resistivity values. This roughness is suggestive of dissolution or erosion.

Combination of High-Density and Coherent Mapping for Ablation of Ventricular Arrhythmia in Patients with Structural Heart Disease.

The present study describes our experience with a new mapping approach for ventricular arrhythmia (VA) ablation in patients with structural heart disease (SHD). Consecutive patients undergoing catheter ablation for recurrent VA were analyzed. High-density mapping was conducted in all patients. In patients with inducible VA, local activation time (LAT) mapping and a novel vector-based mapping algorithm were implemented to analyze arrhythmia propagation. In case of focal tachycardia, the location of earliest activation was targeted. In VAs with re-entrant mechanisms, zones of slow conduction based on coherent mapping were ablated. Substrate modification was performed when pathologic electrograms were identified. Seventy-four patients were included. Sixty-five patients (87.8%) were male. Ischemic cardiomyopathy was the underlying disease in 35 patients (47.3%) and nonischemic cardiomyopathy was the underlying disease in 39 patients (52.7%). Mean left ventricular ejection fraction was 33.8 ± 9.9%. Non-inducibility of any VA was achieved in 70 patients (94.6%). Termination of VA was achieved in 93.5% of patients with stable VA. In 4 patients (5.4%), partial success was achieved. VA (p < 0.001), ATP (p < 0.001) and shock burden (p = 0.001) were significantly reduced after ablation. Mean arrhythmia-free survival after 12 months was 85.1 ± 4.7%. High-density mapping in combination with coherent mapping may facilitate the understanding of the tachycardia mechanism, providing targets for effective ablation.

Resistivity structural imaging of the Olkaria Domes geothermal field in Kenya using 2D and 3D MT Data inversion

The 2D and 3D MT inversion from 290 soundings were analyzed to visualize the nature and extent of structural control of the Olkaria geothermal reservoir system within and outside the ring structure. The ring structure bounds the drilled geothermal field under exploitation to the east and south of Olkaria Domes. The nature of subsurface structures was classified using dimensionality analysis. The resistivity models revealed three layers varying with depth. The upper conductive layer immediately below the surface as the reservoir seal, underlain by a resistive reservoir zone at about 2.5−4km, and the deeper conductive zone at a depth of about 5.5−8km interpreted as the heat source. The resistivity structure forming a channel to the near surface, is interpreted as the hydrothermal fluid's fault pathway. The study also shows the structures resembling sill formations mapped outside the geothermal system in the Domes field, while the dykes predominate in the reservoir.

Electron Scattering in Boron Hexogonal Nitride

Investigation the effects of electron scattering in boron hexogonal nitride (h-BN) was performed. At present, material h-BN, together with graphene, is considered to be one of the most promising materials for the formation of new semiconductor devices with good characteristics for the ranges of ultrahigh and extreme high frequency bands. The main electrophysical parameters and characteristics of h-BN was considered. For this material the three valley K-M-Г band structure has been used. It is noted that the K valley has the smallest energy gap between the conductivity zone and the valence zone. Calculation of relative electron masses and parabolicity coefficients in K, M and G valleys was performed. Formulas that allow to model the main electron scattering intensities in h-BN were presented. The obtained electron scattering intensities as a function of energy and temperature were considered and analyzed. Based on the obtained characteristics, it was possible to implement a statistical multi-particle Monte Carlo method to determine the characteristics of electron transfer in the heterostructure of a semiconductor devices containing layers of hexogonal boron nitride.

Functional Assessment of Ventricular Tachycardia Circuits and Their Underlying Substrate Using Automated Conduction Velocity Mapping.

This study sought to describe the utility of automated conduction velocity mapping (ACVM) in ventricular tachycardia (VT) ablation. Identification of areas of slowed conduction velocity (CV) is critical to our understanding of VT circuits and their underlying substrate. Recently, an ACVM called Coherent Mapping (Biosense Webster Inc) has been developed for atrial mapping. However, its utility in VT mapping has not been described. Patients with paired high-density VT activation and substrate maps were included. ACVM was applied to paired VT activation and substrate maps to assess regional CV and activation patterns. A combination of ACVM, traditional local activation time maps, electrogram analysis, and off-line calculated CV using triangulation were used to characterize zones of slowed conduction during VT and in substrate mapping. Fifteen patients were included in the study. In all cases, ACVM identified slow CV within the putative VT isthmus, which colocalized to the VT isthmus identified with entrainment. The dimensions of the VT isthmus with local activation time mapping were 37.8 ± 13.7mm long and 8.7 ± 4.2mm wide. In comparison, ACVM produced an isthmus that was shorter (length: 25.1 ± 10.6mm; mean difference: 12.8; 95%CI: 7.5-18.0; P< 0.01) and wider (width: 18.8 ± 8.1mm; mean difference: 10.1; 95%CI: 6.1-14.2; P< 0.01). In VT, the CV using triangulation at the entrance (8.0 ± 3.6cm/s) and midisthmus (8.1 ± 4.3cm/s) was not significantly different (P = 0.92) but was significantly faster at the exit (16.2 ± 9.7cm/s; P< 0.01). In the paired substrate analysis, traditional local activation time isochronal mapping identified 6.3 ± 2.0 deceleration zones. In contrast, ACVM identified a median of 0 deceleration zones (IQR: 0-1; P< 0.01). ACVM is a novel complementary tool that can be used to accurately resolve complex VT circuits and identify slow conduction zones in VT but has limited accuracy in identifying slowed conduction during substrate-based mapping.