High Resistivity Regions Research Articles

Analysis on heat transfer enhancement mechanism in a cross-wavy primary surface heat exchanger based on advection thermal resistance method

This paper numerically investigates the flow and heat transfer characteristics in the primary surface heat exchanger (PSHE) with cross-wavy (CW) structures. The comprehensive performance affected by hydraulic diameters is evaluated. Moreover, the airflow shuttling behavior at the mixing area of CW-type PSHE is discussed, showing rapid heat transfer enhancement. The advection thermal resistance method and local thermal resistance analysis is proposed, while the impacts of longitudinal pitch and flowrates are considered. Results show that the case with a large hydraulic diameter displays much better comprehensive performance at lower flowrates. When raising the hydraulic diameter from 1.58 mm to 15.8 mm, the heat transfer rate per unit pumping power grows by 36.1 %. However, the priority of large channel is gradually disappeared after increasing the flowrates. Meanwhile, the larger longitudinal pitch of the CW channel may result in pronounced improvement on the heat transfer performance due to the presence of airflow shutting behavior at the mixing area as well as the secondary flow near the channel boundary layers. When no airflow shuttling exists, very high advection thermal resistance region can be observed due to the formation of boundary layers. It can be recognized that the case with airflow shuttling behavior can display similar heat transfer improvement compared to that with increasingly high Reynolds numbers, yet the pressure loss is rarely increased.

Local strain inhomogeneities during electrical triggering of a metal–insulator transition revealed by X-ray microscopy

Electrical triggering of a metal-insulator transition (MIT) often results in the formation of characteristic spatial patterns such as a metallic filament percolating through an insulating matrix or an insulating barrier splitting a conducting matrix. When MIT triggering is driven by electrothermal effects, the temperature of the filament or barrier can be substantially higher than the rest of the material. Using X-ray microdiffraction and dark-field X-ray microscopy, we show that electrothermal MIT triggering leads to the development of an inhomogeneous strain profile across the switching device, even when the material does not undergo a pronounced, discontinuous structural transition coinciding with the MIT. Diffraction measurements further reveal evidence of unique features associated with MIT triggering including lattice distortions, tilting, and twinning, which indicate structural nonuniformity of both low- and high-resistance regions inside the switching device. Such lattice deformations do not occur under equilibrium, zero-voltage conditions, highlighting the qualitative difference between states achieved through increasing temperature and applying voltage in nonlinear electrothermal materials. Electrically induced strain, lattice distortions, and twinning could have important contributions in the MIT triggering process and drive the material into nonequilibrium states, providing an unconventional pathway to explore the phase space in strongly correlated electronic systems.

Application of Multi-Near-Surface Geophysical Surveys for Geothermal Spring: A Case Study in Kon Tum Province, Vietnam

The occurrence of geothermal spring not only enhances human health, but also plays a crucial role in generating community’s revenue that boosts up the standard living of locals. An endeavor has been made to delineate the prospective areas of geothermal spring in Kon Tum province, Vietnam by the utilization of joint-geophysical techniques. The blended mode as mentioned is opted for its superiority in providing the rapidassesments of temperature in shallow temperature survey, comprehensive understanding the subsurface structure in electrical resistivity tomography in copporating with the validation in well log interpretation. The results found that the overlapping region of high temperature (35°C) region and low resistivity (200 Ωm) is observed in the east in the vicinity of Dlak Bla river, and it probably broadens to the west of the study area. The outcome of geophysical approaches strongly concur with the well log interpretation, revealing the presence of water-bearing zone encountered in fractured granite. The results also corroborated the existence of concealing fault F5 as a branch of the NE-SW fault F2 which is favorable for creating a route to form the geothermal spring. The output of this research could be considered as an intentive consultation for Kon Tum’s planners and makers on expanding the investigation and exploitation.

Bolometric IR photoresponse based on a 3D micro-nano integrated CNT architecture.

A new 3D micro-nano integrated M-shaped carbon nanotube (CNT) architecture was designed and fabricated. It is based on vertically aligned carbon nanotube arrays composed of low-density, mainly double-walled CNTs with simple lateral external contacts to the surroundings. Standard optical lithography techniques were used to locally tailor the width of the vertical block structure. The complete sensor system, based on a broadband blackbody absorber region and a high-resistance thermistor region, can be fabricated in a single chemical vapor deposition process step. The thermistor resistance is mainly determined by the high junction resistances of the adjacent aligned CNTs. This configuration also provides low lateral thermal conductivity and a high temperature coefficient of resistance (TCR). These properties are advantageous for new bolometric sensors with high voltage responsivity and broadband absorption from the infrared (IR) to the terahertz spectrum. Preliminary performance evaluations have shown current and voltage responsivities of 2 mA/W and 30 V/W, respectively, in response to IR (980 nm) absorption for a 20 × 20 μm2 device. The device exhibits an exceptionally fast response time of ≈0.15 ms, coupled with a TCR of -0.91 %/K. These attributes underscore its high operating speed and responsivity, respectively. In particular, the device maintains excellent thermal stability and reliable operation at elevated temperatures in excess of 200 °C, extending its potential utility in challenging environmental conditions. This design allows for further device miniaturization using optical lithography techniques. Its unique properties for mass production through large-scale integration techniques make it important for real-time broadband imaging systems.

Angular dependence of resistance and critical current of a Bi-2223 superconducting joint

Low resistance and high critical current are prerequisites for superconducting joints used in persistent-mode magnets. Herein, we use a joint resistance evaluation system, previously developed by us, to systematically evaluate the angular dependence of resistance and critical current of a Bi-2223 superconducting joint in a closed-loop sample. The current decay is measured by rotating the sample incrementally. The time dependence of the loop current is evaluated at 4 K, 0.15–0.28 T, and magnetic field angles ranging from 90° to 0, wherein 90° corresponds to the direction parallel to the tape surface. The results suggest that the resistance and critical current of the joint depend on the angle of the magnetic field. The evaluated critical current increases as the angle increases. The angular dependence of resistance can be divided into three regions: low-resistance, transition, and high-resistance regions. The low-resistance region exists at high angles close to 90°. In this region, the decay of the loop current is small, and the persistent current continues to flow. Furthermore, the joint resistance is less than 1.4 × 10−13 Ω. In the transition region, the joint resistance significantly increases by three orders of magnitude with sample rotation. This significant increase is attributed to an increase in the perpendicular component of the magnetic field, which decreases the critical current of the joint. At lower angles, the joint resistance remains high, ranging from 10−11 to 10−10 Ω. A significant decay in the loop current is observed in the high-resistance region. Based on these findings, we conclude that the design of a persistent-mode magnet must consider not only the magnitude but also the direction of the magnetic field applied to superconducting joints.

Polymerization force–regulated actin filament–Arp2/3 complex interaction dominates self-adaptive cell migrations

Cells migrate by adapting their leading-edge behaviors to heterogeneous extracellular microenvironments (ECMs) during cancer invasions and immune responses. Yet it remains poorly understood how such complicated dynamic behaviors emerge from millisecond-scale assembling activities of protein molecules, which are hard to probe experimentally. To address this gap, we establish a spatiotemporal "resistance-adaptive propulsion" theory based on the interactions between Arp2/3 complexes and polymerizing actin filaments and a multiscale dynamic modeling system spanning from molecular proteins to the cell. We quantitatively find that cells can accurately self-adapt propulsive forces to overcome heterogeneous ECMs via a resistance-triggered positive feedback mechanism, dominated by polymerization-induced actin filament bending and the bending-regulated actin-Arp2/3 binding. However, for high resistance regions, resistance triggers a negative feedback, hindering branched filament assembly, which adapts cellular morphologies to circumnavigate the obstacles. Strikingly, the synergy of the two opposite feedbacks not only empowers the cell with both powerful and flexible migratory capabilities to deal with complex ECMs but also enables efficient utilization of intracellular proteins by the cell. In addition, we identify that the nature of cell migration velocity depending on ECM history stems from the inherent temporal hysteresis of cytoskeleton remodeling. We also show that directional cell migration is dictated by the competition between the local stiffness of ECMs and the local polymerizing rate of actin network caused by chemotactic cues. Our results reveal that it is the polymerization force-regulated actin filament-Arp2/3 complex binding interaction that dominates self-adaptive cell migrations in complex ECMs, and we provide a predictive theory and a spatiotemporal multiscale modeling system at the protein level.

Integration of Geophysical Methods to Study Deep Structure of the Angara Fault, the Largest in the Baikal Rift

Abstract —The Angara regional fault which is transversal to the Baikal basin totals about 150 km in length and ranks as a major strike-slip fault with the normal component in the seismically active rift zone. Given that its vicinities represent an area with high population density, the emphasis needs to be placed primarily on the study of its structural features. At this, the Angara fault has been poorly studied by geophysical methods. Results of the specialized mapping carried out in the 1990s revealed the block structure of the Angara fault zone, however without a reliable identification of the fault plane, which leaves its position still to be debatable. To establish the Angara fault plane and studying its deep structure, the integration of such geophysical methods as magnetotelluric (MT) sounding, radon emanation and fieldwalking magnetic surveys was required. Their application in the study of the deep structure of the southern parts of the Angara fault allowed revealing anomalies in all of the measured fields, accordingly. The anomaly-forming object, which the authors associate with the deep penetrated Angara fault plane, was expressed in the most distinct way by the magnetotelluric data (as a high-resistivity region (ER = 8500 Ohm∙m) relative to the host rock) and radon emanation survey (radon volumetric activity index RAI ≥ 20). The fact that the magnetic field received only minor distortions from the object may indicate either moderate magnetic characteristics of the latter or a significant occurrence depth. The identified anomaly-forming object localized within the crystalline basement tends to be more sharply expressed in the left bank of the Irkutsk Reservoir, while in the upper part of the cross-section it is overprinted by rocks of the sedimentary cover.

Microscale mapping of thermal contact resistance using lock-in thermography

This paper proposes a new thermal contact resistance distribution measurement method using lock-in thermography. This method was used to evaluate a two-dimensional local thermal contact resistance distribution. To be able to measure the distribution, a uniform intensity laser heating system was developed. The developed system has a top-hat intensity distribution with a diameter of 30 mm. By combining this heat source and the lock-in thermography, a new measurement instrument was developed, which can evaluate local temperature behavior in the frequency domain, including the information of the contact interface in high spatial resolution of about 70 μm. Additionally, a new thermal contact resistance measurement principle was constructed based on a one-dimensional heat transfer equation that considers the reflected and transmitted temperature waves at the boundary and contact interface. The thermal contact resistance was acquired as a solution to the inverse problem of the temperature response done by fitting analyses. The validation of this method was performed quantitatively with two samples made of two bonded isotropic graphite plates. The one sample has an intentional defect area that has a slightly higher thermal resistance. The other sample has the known thermal contact resistance value measured with a validated method. Based on the results, the measurement value agreed with the referenced value. Also, the defect area was quantitatively detected clearly as a high thermal resistance region. Furthermore, as a practical example, the measurement method was applied for two different contact interface roughness samples consisting of aluminum alloys and thermal grease. Consequently, it was revealed and visualized that the contact interface with a rough surface has a high thermal resistance spot.

Wall Tension and Tubular Resistance in Kidney Cystic Conditions.

The progressive formation of single or multiple cysts accompanies several renal diseases. Specifically, (i) genetic forms, such as adult dominant polycystic kidney disease (ADPKD), and (ii) acquired cystic kidney disease (ACKD) are probably the most frequent forms of cystic diseases. Adult dominant polycystic kidney disease (ADPKD) is a genetic disorder characterized by multiple kidney cysts and systemic alterations. The genes responsible for the condition are known, and a large amount of literature focuses on the molecular description of the mechanism. The present manuscript shows that a multiscale approach that considers supramolecular physical phenomena captures the characteristics of both ADPKD and acquired cystic kidney disease (ACKD) from the pathogenetic and therapeutical point of view, potentially suggesting future treatments. We first review the hypothesis of cystogenesis in ADPKD and then focus on ACKD, showing that they share essential pathogenetic features, which can be explained by a localized obstruction of a tubule and/or an alteration of the tubular wall tension. The consequent tubular aneurysms (cysts) follow Laplace's law. Reviewing the public databases, we show that ADPKD genes are widely expressed in various organs, and these proteins interact with the extracellular matrix, thus potentially modifying wall tension. At the kidney and liver level, the authors suggest that altered cell polarity/secretion/proliferation produce tubular regions of high resistance to the urine/bile flow. The increased intratubular pressure upstream increases the difference between the inside (Pi) and the outside (Pe) of the tubules (∆P) and is counterbalanced by lower wall tension by a factor depending on the radius. The latter is a function of tubule length. In adult dominant polycystic kidney disease (ADPKD), a minimal reduction in the wall tension may lead to a dilatation in the tubular segments along the nephron over the years. The initial increase in the tubule radius would then facilitate the progressive expansion of the cysts. In this regard, tubular cell proliferation may be, at least partially, a consequence of the progressive cysts' expansion. This theory is discussed in view of other diseases with reduced wall tension and with cysts and the therapeutic effects of vaptans, somatostatin, SGLT2 inhibitors, and potentially other therapeutic targets.

Tracking supercritical geothermal fluid distribution from continuous seismic monitoring

Continuous seismic monitoring could play a pivotal role in deep geothermal energy exploration. We monitored seismicity near geothermal production areas of the Kuju volcanic complex with a dense seismic network and automated event detection. Most events were shallow (less than 3 km below sea level) and distributed along a boundary between regions of high and low resistivity and S-wave velocity, interpreted as a lithological boundary or related fracture zone. Deeper events located on top of subvertical conductors may reflect fracturing associated with magmatic fluid intrusion. A correlation may exist between seismicity and heavy rainfall three days prior to increased pore pressure in pre-existing fractures. Our findings support the presence of supercritical geothermal fluids and demonstrate the importance of continuous seismic monitoring in supercritical geothermal energy exploration.

Constraints on ground deformation processes at the Tulu Moye volcanic complex, Main Ethiopian Rift

Tulu Moye is an actively deforming volcanic complex with a geothermal field in the Main Ethiopian Rift. We use InSAR between 2014 and 2022, integrated with other geophysical data, to investigate the temporal and spatial characteristics of the deformation signal in the area, and to model its source. Velocity maps and time series analysis show a deformation signal consistent with uplift at a velocity of up to 50 mm/yr in the satellite Line-of-Sight (LOS) in 2014–2017, then decreasing to 12 mm/yr until 2022. The centre of deformation is located about 10 km west of a main geothermal drilling site at Tulu Moye, between the Bora, Berecha, and Tulu Moye volcanoes, with a NW-SE elongation direction. Our best-fit model suggests that the deformation is caused by an 8.7 km by 1.2 km sill situated ∼7.7 km below the surface (∼5.9 km below sea-level), elongate in the N54°W direction and dipping S11°W, and experienced an average velocity of volume change of ∼8.9 × 106 m3/yr in 2014–2017. The surface projection of the sill overlaps with local transverse faults and hydrothermal manifestations. The sill is ∼1–2 km below clusters of microseismic swarms and a region of high resistivity, both indicating hydrothermal fluid flow. The location and geometry of the sill correlates with the upper edge of high conductivity interpreted as a zone of partial melt, and we therefore attribute the uplift at the Tulu Moye volcanic complex to inflow of magma in the sill. We also suggest that the transverse caldera rims faults may restrict magma flow, and also facilitate both vertical and lateral hydrothermal fluid flow.

Tunable transport properties of dual-gated InAs/GaSb core/shell nanowires

Dual-gate structures were fabricated on a single high-quality InAs/GaSb core/shell nanowire, enabling control of the band structure and Fermi level in the crossed bandgap heterostructure. The nanowire was grown using the molecular-beam-epitaxy method in a pure crystal phase for both the core and the shell. We demonstrated clear ambipolar transport characteristics derived separately from n-type InAs and p-type GaSb. A relatively high resistance region was found between n- and p-type conduction regions; the entrance to an energy gap was thus indicated. The gap's size varied with the electric fields of dual gates and could even be closed; after closure, a weak and non-vanishing energy gap appeared. The reopened energy gap was considerably suppressed in an in-plane magnetic field only when the field was perpendicular to the axis of the nanowire (i.e., the current direction) and was identified as an electron–hole interaction induced hybridization gap.

Novel Solution to Back Flashovers on High Voltage Transmission Lines: The Embedded Ground Conductor

It is well known that for high voltage transmission lines in the range of 245 kV–525 kV, particularly in regions of high ground resistivity, lightning back flashover problems could be a major concern. Line arresters have been used successfully to address the problem. Underbuilt ground wires have been proposed as a viable alternative. The present paper shows that the full potential of additional ground wires could be achieved by optimizing their position on the tower. Such optimization often results in a preferred position at the level, or higher than the attachment height of the lower phase conductors; therefore the designation Embedded Ground Conductor. An essential requirement is that such positioning does not infringe in any way on the dielectric integrity of the electrical clearances and, under the influence of induced charge, does not become a source of positive streamers that may lead to additional radio or audible noise. It is found that a streamer- inhibited conductor, when properly placed, fully satisfies the above requirements. It is determined that for 245 kV, 345 kV and 420 kV lines, a streamer-inhibited embedded conductor could improve the back flashover rate by a factor of 10 or more

Nanoscale Mapping of Carrier Mobilities in the Ballistic Transports of Carbon Nanotube Networks.

Much progress has been made in the nanoscale analysis of nanostructures, while the mapping of key charge transport properties such as a carrier mobility remains a challenge, especially for one-dimensional systems. Here, we report the nanoscale mapping of carrier mobilities in carbon nanotube (CNT) networks and show that charge transport behaviors varied depending on network structures. In this work, the spatial distribution of localized charge transport properties such as mobilities and charge trap densities in CNT networks were mapped via a scanning noise microscopy. The mobility map was obtained from the conductivity maps measured at different back-gate biases, showing up to two orders of mobility variations depending on localized network structures. Furthermore, from the maps, correlations between mobility/conductivity and charge trap density were analyzed to determine charge transport mechanisms. In metallic CNT networks, the regions with rather high (low) or low (high) charge trap densities (mobilities) exhibited a diffusive or ballistic transport behavior, respectively. Interestingly, semiconducting CNT networks also exhibited a gradual transition from a diffusive to a ballistic transport behavior as the CNT mobility was increased by reaching the on-state with negative gate biases. The mapping of the cross-patterned CNT network showed that metallic CNT electrodes could achieve a good electrical contact with semiconducting CNTs without high contact resistance regions. Since this method allowed one to map versatile charge transport properties such as mobility, conductivity, and charge trap density, it can be a powerful tool for basic research about charge transport phenomena and practical device applications.

Application of the depth-averaged liquid film model to the annular flow regime in BWR fuel assemblies

The flow regime found in the downstream half of the BWR assembly can be described as an annular film flow with a central core of vapour with suspended droplets. This study presents the application of the fluid film model available in STAR-CCM+ to analyze the interplay between the vapour flow and the liquid film dynamics. The film model, based on depth-averaged equations, can be used to simulate film depth and velocity over complex geometries. Built on sound mathematical basis and applied to a wide variety of areas, the fluid film model, however, has not been widely used to study annular flow in nuclear fuel assemblies. Applying this model to a simplified geometry of a single rod with different gaps, the basic relationship between the vapour velocity, liquid film thickness and velocity distribution along the circumference of the rod is clarified. The minimum vapour velocity required to transport a liquid film along the surface of a fuel rod of a specific length against gravity was found using first-principles force balances. The model was then applied to a real, but simplified assembly geometry where the resulting flow pattern was primarily affected by the presence of part length rods. The minimum velocity required to transport a liquid film along the fuel rods in the assembly against gravity was found to be close to the range of velocities obtained using sub-channel codes. Strong circumferential variation in the wall shear across a short arc-length was observed for some fuel rods. The variation in wall shear also results in a corresponding variation in film velocity and film thickness and presumably has a strong impact on the local heat and mass-transfer characteristics. Cross flow from high resistance regions in the assembly towards lower resistance regions has a strong impact in terms of variations in the film thickness on the rods that are the furthest away from the low resistance paths.The modelling palette for the depth-averaged film model contains several features that can extend the validity of the modelling used in this study, such as the presence of droplets in the vapour core, deposition of droplets on to the film, heat transfer and boiling, and the influence of spacers in disrupting the liquid film. These features were not considered in this study and remain avenues for future work. The use of time-averaged turbulence modelling results in damping of unsteadiness of the vapour flow and perturbations in the film thickness. For better estimates of unsteady effects use of turbulence models such as the Large Eddy Simulation method is recommended. Current state-of-the-art in predicting dispersed annular flow using liquid film models is limited to single rods. The generalized depth-averaged film model can be applied to complex geometries including the effect of spacers.

Uncovering Topological Edge States in Twisted Bilayer Graphene.

Twisted bilayer graphene (t-BLG) has recently been introduced as a rich physical platform displaying flat electronic bands, strongly correlated states, and unconventional superconductivity. Studies have hinted at an unusual Z2 topology of the moiré Dirac bands of t-BLG. However, direct experimental evidence of this moiré band topology and associated edge states is still lacking. Herein, using superconducting quantum interferometry, we reconstructed the spatial supercurrent distribution in t-BLG Josephson junctions and revealed the presence of edge states located in the superlattice band gaps. The absence of edge conduction in high resistance regions just outside the superlattice band gap confirms that the edge transport originates from the filling of electronic states located inside the band gap and further allows us to exclude several other edge conduction mechanisms. These results confirm the unusual moiré band topology of twisted bilayer graphene and will stimulate further research to explore its consequences.

Multidimensional minimum-work control of a 2D Ising model.

A system's configurational state can be manipulated using dynamic variation of control parameters, such as temperature, pressure, or magnetic field; for finite-duration driving, excess work is required above the equilibrium free-energy change. Minimum-work protocols in multidimensional control-parameter space have the potential to significantly reduce work relative to one-dimensional control. By numerically minimizing a linear-response approximation to the excess work, we design protocols in control-parameter spaces of a 2D Ising model that efficiently drive the system from the all-down to all-up configuration. We find that such designed multidimensional protocols take advantage of more flexible control to avoid control-parameter regions of high system resistance, heterogeneously input and extract work to make use of system relaxation, and flatten the energy landscape, making accessible many configurations that would otherwise have prohibitively high energy and, thus, decreasing spin correlations. Relative to one-dimensional protocols, this speeds up the rate-limiting spin-inversion reaction, thereby keeping the system significantly closer to equilibrium for a wide range of protocol durations and significantly reducing resistance and, hence, work.

SPICE model for complementary resistive switching devices based on anti-serially connected quasi-static memdiodes

This paper reports the use of the Quasi-static Memdiode Model (QMM) for simulating Complementary Resistive Switching (CRS) devices. CRS arises from the anti-serial connection of two memristors and it is used for generating low and high-resistance regions in the I-V characteristic with the aim of mitigating the sneak-path conduction problem in crossbar arrays. Here, the use of the QMM for CRS in the form of a six terminal subcircuit is explored. While two terminals of the subcircuit correspond to the conventional input and output pins of the CRS structure, the rest provide information about the voltage at the central node, the low-voltage conductance of each device, and the low-voltage conductance of the whole structure. Special attention is paid to the simulation of the so-called table with legs hysteresis loop (resistance at fixed bias vs. write voltage), which is often invoked in connection with devices that exhibit switching activity at the two interfaces of a single dielectric layer. Because of the internal potential drop distribution, the switching process takes place alternately at one side of the structure or the other giving rise to a pseudo-CRS behavior. The flexibility of the proposed approach is demonstrated through a series of fitting exercises that involve experimental data reported in the literature. The model script for the SPICE simulator is also provided.

Basal stress controls ice-flow variability during a surge cycle of Hagen Bræ, Greenland

AbstractBasal conditions play an essential role in the dynamics of outlet glaciers, but direct observations at the bed of glaciers are challenging to obtain. Instead, inverse methods can be used to infer basal parameters from surface observations. Here, we use a simple ice-flow model as a forward model in an inversion scheme to retrieve the spatio-temporally variable basal stress parameter for Hagen Bræ, North Greenland, from 1990 to 2020. Hagen Bræ is a surge-type glacier with up to an order of magnitude variability of winter velocities near the grounding line. We find that downstream changes in the basal stress parameter can explain most of the variation of flow velocity, and we further identify a region of high resistance ~20–40 km from the grounding line. We hypothesise that this region of high resistance plays an important role in controlling glacier discharge.

Groundwater aquifer detection using the time-domain electromagnetic method: A case study in Harrat Ithnayn, northwestern Saudi Arabia

Eight time-domain electromagnetic profiles were carried out in Harrat Ithnayn, northwestern Saudi Arabia, to detect potential groundwater-bearing aquifers in the area. The collected data were processed and analyzed, with the results inferred or extrapolated between one-dimensional vertical soundings to obtain two-dimensional resistivity sections of the subsurface geological setting. We found that the resistivity values change laterally and vertically throughout the area. High resistivity values (greater than 100 Ohm-m) occupy most of the sections down to depths of approximately 100–150 m, whereas the low-resistivity regions of the section appear to be shallower than 100 m toward the west in the northern part of Harrat Ithnayn. The high-resistivity regions correspond to the Harrat basalts and are underlain by low resistivity (down to a few Ohm-m) in the saturated zones. There are also localized regions of low resistivity at depths of approximately 20–30 m, indicating shallow local groundwater aquifers. Aquifer thickness varies from approximately 50 to more than 100 m. In the southern part, the resistivity sections indicate that the main aquifer is at a depth of 150–200 m (possibly near 170 m) below the basalt. A saturated zone or shallow aquifer approximately 20–30 m thick also exists at a depth of approximately 15 m. In both the shallow and deep aquifers, the resistivity values indicate that there is good quality fresh water.