Shallow Depth Research Articles

Empowering geological data analysis with specialized software GIS modules

This research is devoted to the development of a geographic information system (GIS) for the analysis of geological data. It presents two specialized software modules designed to solve complex geological problems related to potential progress to disturbed masses and magnetotelluric sounding. These modules are integrated into the QGIS environment, offering efficient data processing and analysis capabilities, contributing to a deeper understanding of geological structures. The study presents a mathematical model for the problem of magnetotelluric sounding (MTS) and the continuation of potentials towards the perturbed masses, demonstrating numerical results using the developed algorithm. To confirm the accuracy of the model, a comparative analysis was carried out with empirical data for various chemical elements, which showed high accuracy, especially at shallow depths, with an error rate of less than 2%. In addition, the study highlights the importance of powerful GIS for the analysis and interpretation of geological data, including geochemical, geophysical and remote sensing information. The advanced functionality of QGIS simplifies data processing and visualization, which makes it an invaluable tool for geologists and researchers.

Determination of kilovoltage x-ray therapy depth doses with open-ended applicators.

The purpose of this work was to determine percentage depth dose (PDD) curves for kilovoltage x-rays from the WOmed-T105 unit, with open-ended steel applicators and beam qualities ranging from 0.5 to 4.2mm Al. Measurements were made with parallel plate chambers in a water phantom, with extrapolation based on a fifth order polynomial used to estimate the surface dose. Measurements were also made with parallel plate chambers in a plastic water phantom, with thin plastic sheets used to obtain detailed measurements at shallow depths (less than 1mm). Monte Carlo simulations were performed using the EGSnrc package, with two different sources as input: a SpekPy simulation of the x-ray beam and a full simulation of the x-ray tube, treatment head and applicators. Results showed that all four methods (two measurements and two simulations) agreed within the measurement uncertainty at depths greater than 2mm. At shallow depths, significant differences were noted. At depths less than 0.1mm, the full Monte Carlo simulation and the solid water measurements showed a sharp spike in surface dose which is attributed to electron contamination, which was not seen in the SpekPy Monte Carlo simulation or the extrapolated water measurements. At depths between 0.1mm and 2mm, beyond the range of contaminant electrons, the extrapolated water measurements underestimate the dose by up to 13% compared to the full Monte Carlo simulation and the solid water measurements, attributed to fluorescent photons generated in the applicators. This work demonstrates that for open-ended applicators, measurement of depth doses in water with extrapolation of surface dose has the potential to significantly underestimate the dose at shallow depths between the surface and 2mm, even after eliminating electron contamination from the beam.

Comparative study of lesions obtained with radiofrequency between irrigated ablation catheter with flexible tip and non-irrigated catheter in ex vivo porcine heart slices

Abstract Background Lesion formation through radiofrequency (RF) is related to various parameters, including power, contact force, duration of energy delivery and temperature. Notably, the characteristics of the lesions differ when comparing irrigated to non-irrigated catheters. Non-irrigated catheter lesions present a larger surface area and shallower depth, while irrigated catheters induce deeper lesions with higher volumes. Particularly, flexible-tip open-irrigated catheter exhibit unique irrigation characteristics and the resulting lesions may show a reduced surface area but extend deeper into the tissue. Main drawbacks of using non-irrigated catheter are the risk of clot formation and of steam pops, both possibly avoidable with an irrigated catheter. Purpose The aim of the study was to demonstrate that flexible-tip open-irrigated catheter generate lesions with a smaller surface area and deeper extension when compared to non-irrigated catheter. Methods An ex vivo model consisting of porcine heart slices in a warmed saline chamber was used. A flexible-tip open-irrigated ablation catheter and a non-irrigated catheter were positioned with a stable tissue contact weight ranging from 10 to 20 g of force in perpendicular position. RF was delivered at powers of 20, 30 and 40 Watt for 60s. Lesion dimensions were analyzed. The occurrence of steam pop was registered. Results The ablations were conducted using flexible-tip open-irrigated (n=55) and non-irrigated (n=39) catheters in a power-control mode. Superficial length and width of lesions were greater with the non-irrigated catheter than with the irrigated catheter, irrespective of the power delivered (superficial length: p=0,0001 at 20W, p=0,002 at 30 W and p=0,0001 at 40 W; superficial width: p=0,001 at 20 W, p=0,019 at 30 W and p=0,003 at 40 W). When computing superficial areas, lesions performed with the non-irrigated catheter were significantly wider, regardless of the power delivered (p=0,001 at 20 W, p=0,005 at 30 W and p=0,001 at 40 W). The irrigated catheter determined significantly greater values of lesion maximum depth at high power delivery (40 W, p=0.007). No steam pop was observed using the irrigated ablation catheter, while 12 steam pops occurred with the non-irrigated catheter. Conclusions This study highlights that RF ablation using flexible-tip open-irrigated catheter has the potential to generate smaller lesion areas when compared to a non-irrigated tip. Furthermore, it may contribute to decrease steam pops, even with escalating power output. This irrigated catheter might be a preferable choice when precision is crucial, particularly in determining superficial area of lesions. Specifically, it might be advantageous for procedure as atrioventricular nodal reentry tachycardia (AVNRT) ablation, minimizing the risk of iatrogenic conduction disturbance related to RF delivery in the region of the compact AV node, located superficially at a millimeter distance from the ablation site.Experiment setting, lesion measurementsLesion superficial area

Evaluating the applicability of magnetic resonance sounding for groundwater exploration at selected locations in Aswan, Egypt

ABSTRACT Magnetic resonance sounding (MRS) was performed to evaluate its applicability for characterising groundwater at selected locations in Aswan Governorate, Egypt. The MRS mainly detects a weak but noticeable alternating magnetic field as MRS signals when the proton spin in groundwater produces non-magnetic moments and rotates around the geomagnetic field, indicating the detection of groundwater. The MRS system was first correlated at a piezometer with a known water table depth (~80 m). Subsequently, three MRS sounding stations with unknown water tables were tested at Qism Aswan at ~ 18 km from the piezometer using NUMIS Auto magnetic resonance sounding system following the MRS site common practices. The MRS data were subjected to adaptive notch filtering to remove spiky noise and potential power line harmonics, and finally enhance the MRS signals at the selected stations. The water depth (~75–95 m) estimated from the MRS data around the piezometer largely coincides with the actual depth (~80 m) at the piezometer itself. A transient electromagnetic (TEM) profile performed near the measured MRS stations indicates no water content. Unlike the MRS data for NNL-1, the data for NNL-2 and NNL-3 match well with TEM data at shallow depths. The evaluation generally indicates that the MRS method is applicable for groundwater exploration at the selected piezometer and the other three stations. However, the method necessarily requires additional denoising efforts to comprehensively characterise groundwater occurrence and aquifer parameters.

Safety and efficacy of very high-power short ablation in superior vena cava isolation in patients with atrial fibrillation

Abstract Backgrounds The superior vena cava (SVC) plays an important role in non-pulmonary vein (PV) foci to trigger atrial fibrillation (AF) and thus are occasionally isolated. A major complication in SVC isolation is phrenic nerve injury, and a shallower ablation depth might be less likely to cause complications. Recently, very high power short ablation (vHPSD) has been demonstrated to be effective in PV isolation. On the other hand, vHPSD has been reported to have shallower depth than the low-power ablation strategies, suggesting concerns about insufficient ablation in thicker myocardial sites. The vHPSD might be effective and safe in SVC isolation thinner than myocardium, however, the details were not elucidated. Purpose This study was aimed to examine the safety and efficacy of vHPSD strategy in SVC isolation, compared retrospectively with low power ablation strategies. Methods Patients with AF who were undergoing first-time SVC isolation were included. An activation map was performed from the SVC to the right atrium during sinus rhythm, and a circumferential isolation line was designed by the CARTO system at a height of 1.5cm above the earliest site. The site and extent of capture of the phrenic nerve by pacing on the circumferentially designed ablation line were recorded. The first step was to perform circumferential ablation except for the sites where the phrenic nerve was captured. If the SVC isolation was completed, the procedure was completed. If the isolation was inadequate, the sites of capture of the phrenic nerve were also ablated. Two groups of patients were analyzed: those performing vHPSD (n=27, vHPSD group) with a power of 90 watts for 3 seconds or those using lower-power (n=20, LP group) limited to 20-40 watts. Results Forty-seven patients who underwent the initial SVC isolation were evaluated. We analyzed all 351 points in the vHPSD group and all 364 points in the LP group with ablation of SVC. No differences were found in the distance of the SVC circumference on the isolation line (vHPSD: 71±10 vs. LPLD: 71±11mm, p=0.95) or the extent of phrenic nerve capture (12±7 vs. 12±9mm, p=0.82). All patients in the vHPSD group were successfully isolated first-pass; the first-pass isolation rate tended to be higher than in the LP group (100% vs. 85%, p=0.07). Differences were observed in temperature rise (49±4 vs. 28±4 degrees, p<0.001) and impedance drop (12±4 vs. 7±5Ω, p<0.001), although there were no differences in the contact force (15±8 vs. 15±7g, p= 0.73). The vHPSD group achieved SVC isolation with a shorter procedure time (9±4 vs. 17±5 min, p<0.001) and fewer ablation points (13±4 vs. 18±4, p<0.001) compared to the LP group. In the vHPSD cases, ATP was administered after isolation, but no dormant conduction was observed. Only in one case in the LP group, transient phrenic nerve injury was observed. Conclusion The vHPSD for SVC isolation might be safe and result in shorter procedure time and fewer ablation points.

A novel haemodilution chip mounted on the total thrombus-formation analysis system, a flow chamber system, enables stable analysis of platelet products under low platelet concentration/high shear conditions.

The total thrombus-formation analysis system (T-TAS) can quantitatively analyse the contribution of platelets to haemostasis using reconstituted blood samples. However, it is unsuitable in cases with low platelet counts. We introduced a haemodilution (HD) chip with a shallow chamber depth, adapted to low platelet counts and high shear conditions (1500 s-1). Blood samples were prepared by mixing red blood cell products, standard human plasma and platelet products; the final platelet count was 50 × 103/μL. Aggregation tests were performed by using the aggregation inducers collagen, adenosine diphosphate (ADP) and ristocetin. Samples with 2-, 4- and 9-day-old platelet products (N = 10) were evaluated. The HD chip enabled the stable analysis of the haemostatic function of all samples at a platelet count of 50 × 103/μL. Haemostatic function was correlated with ADP aggregation (time to 10 kPa [T10]: r = -0.53; area under the curve for 30 min: r = 0.40) and storage period (T10: r = 0.44). The HD chip-mounted T-TAS can stably analyse haemostatic function under low platelet counts and high shear conditions; this approach is expected to serve as a bridge to in vivo haemostatic tests with experimental animals.

Morphometric fingerprints and downslope evolution in bathymetric surveys: insights into morphodynamics of the Congo canyon-channel

Submarine canyons and channels are globally important pathways for sediment, organic carbon, nutrients and pollutants to the deep sea, and they form the largest sediment accumulations on Earth. However, studying these remote submarine systems comprehensively remains a challenge. In this study, we used the only complete-coverage and repeated bathymetric surveys yet for a very large submarine system, which is the Congo Fan off West Africa. Our aim is to understand channel-modifying features such as subaqueous landslides, meander-bend evolution, knickpoints and avulsions by analyzing their morphometric characteristics. We used a new approach to identify these channel-modifying features via morphometric fingerprints, which allows a systematic and efficient search in low-resolution bathymetry data. These observations have led us to identify three morphodynamic reaches within the Congo Canyon-Channel. The upper reach of the system is characterized by landslides that can locally block the channel, storing material for extended periods and re-excavating material through a new incised channel. The middle reach of the system is dominated by the sweep and swing of meander bends, although their importance depends on the channel’s age, and the time since the last up-channel avulsion. In the distal and youngest part of the system, an upstream migrating knickpoint is present, which causes multi-stage sediment transport and overspill through an underdeveloped channel with shallow depths. These findings complement previous less-detailed morphometric analyses of the Congo Canyon-Channel, offering a clearer understanding of how submarine canyon-channels can store sediment (due to channel-damming landslides, meander point bars, levee building due to overspill), re-excavate that sediment (via thalweg incision, meander propagation, knickpoint migration) and finally transport it to the deep sea. This improved understanding of the morphodynamics of the Congo Canyon-Channel may help to understand the evolution of other submarine canyon-channels, and assessment of hazards faced by seabed infrastructure such as telecommunication cables.

Characteristic deviations of the optic disc and macula in optic nerve hypoplasia based on OCT.

The purpose of this study was to evaluate the optic disc and macula in a large cohort of patients with different severity of optic nerve hypoplasia (ONH) using high-resolution spectral domain optical coherence tomography (SD-OCT). In total, 36 patients (52 ONH eyes and 17 fellow eyes in unilateral cases) and 45 healthy right eyes from 45 controls were evaluated. All patients underwent an examination to confirm the diagnosis. SD-OCT images of the disc and macula were obtained and analysed both quantitatively and qualitatively. OCT in ONH eyes demonstrated a shorter disc diameter (1061 ± 375 μm vs. 1751 ± 221 μm, p < 0.001), shallower mean cup depth (427 ± 171 μm vs. 551 ± 152 μm, p = 0.01), thinner ganglion cell complex (GCC) perifoveally (47.3 ± 13.0 μm, 60.8 ± 6.0 μm, p < 0.001) and reduced foveal depth (61 ± 36 μm, 119 ± 19 μm, p < 0.001) compared to control eyes. Qualitative analysis showed that 1/3rd of ONH eyes lacked signs of an optic cup, and 2/3rd had reduced or no sign of a foveal pit. Fellow eyes had shorter disc diameter (1446 ± 404 μm vs. 1751 ± 221 μm, p = 0.004) and reduced foveal depth (93 ± 27 μm vs. 119 ± 19 μm, p < 0.001) but similar GCC thickness (60.8 ± 7.1 μm vs. 60.8 ± 6.0 μm, p = 0.738) compared to controls. Disc diameter showed the best correlation with visual acuity in ONH eyes (ρ = 0.517, p < 0.001). ONH eyes have reduced GCC thickness and reduced or no foveal pit. Fellow eyes in presumed unilateral cases have a smaller disc diameter and reduced foveal depth compared to controls, suggesting the possibility of subclinical/mild disease. However, GCC thickness was normal. The correlation between structure and visual function is not always straightforward.

Analysis of the Combined Effect of Major Influencing Parameters for Designing High-Performance Single (sBHE) and Double (dBHE) U-Tube Borehole Heat Exchangers

In this paper, a comprehensive analysis of the combined effect of major influencing parameters on heat transfer in a single U-tube BHE (sBHE) and a double U-tube BHE (dBHE) with two independent circuits was performed by using a validated numerical heat transfer model. Geometrical parameters, such as shank spacing (with maximum, average, and minimum values), borehole diameter (large, medium, and small borehole sizes), and borehole depth (shallow, average, and deep borehole depths) as well as the thermal conductivity of soil and grout, which ranges from minimum to high values, were considered. The combined impact of these parameters was included under the following four major cases: (1) the combined effect of borehole depth, borehole size, and shank spacing; (2) the combined effect of borehole depth and soil and grout thermal conductivity; (3) the combined effect of soil and grout thermal conductivity and borehole size; and (4) the combined effect of soil thermal conductivity, borehole size, and shank spacing. Each of these major cases has nine different design options for both sBHEs and dBHEs. A series of results of heat transfer per unit borehole depth were generated for all the considered various cases. With the given parameters, the BHE case that provides the highest heat transfer among the various cases of sBHEs and dBHEs were obtained.

Seismic moment tensor solutions and geophysical settings in the Philippine Sea basin mapped by GMT

The study is focused on mapping geophysical settings on the margins of the Philippine Sea Plate (PSP). Active volcanism and seismic situation along the margins of the Philippine Sea Basin (PSB) shows earthquake events demonstrating high seismicity of the region caused by tectonic plate subduction. The aim was to perform cartographic mapping of the earthquake events using Generic Mapping Tools (GMT) modules, to analyze seismic situation through visualization of the geophysical datasets. The data was processed by GMT using multi-source data: GEBCO, CMT and ISC seismic data. Technically, a set of GMT modules was used ('psmeca', 'psvelo', 'grdtrack', 'grdimage') for data modelling and mapping. An application of GMT functionality is presented by selected code snippets with selected code snippets for 'psmeca' and 'psvelo', 'img2grd', 'img2grd' modules. Current paper presents a report on the cartographic techniques applied for geophysical mapping. Centroid moment tensor solutions are visualized for shallow depth earthquakes of Mw &lt;10 along the PSB margins from 1976 to 2010. Earthquakes along the tectonic plate subduction zone are shown by GMT. Data from Global Centroid-Moment-Tensor (CMT) Project. Presented and explained GMT code snippets contribute to the development of methods in geological mapping using GMT scripting toolset, for visualizing focal mechanisms.

The effect of bedding thickness on interlocking block pavement performance

ABSTRACT An interlocking block pavement (IBP) comprises discrete blocks, joints, bedding sand, and base and subbase layers. The thickness of the bedding sand layer gives significant impact on IBP performance. However, previous laboratory model tests have often overlooked the geotechnical properties of paving materials and the deformation characteristics of the sublayers, leading to conflicting recommendations regarding appropriate thickness. This study performed laboratory tests on IBP models with varying bedding thicknesses (30, 50, and 80 mm), considering the geotechnical properties (relative density, shear strength, and stress–strain behaviour) of the paving materials. In addition, a novel two-dimensional (2D) model chamber with a transparent wall was designed for particle image velocimetry (PIV) analysis to assess the overall deformation of the sublayers. The test results demonstrated that a bedding thickness of 50 mm exhibited higher load-dispersion ability, allowing the blocks to settle and rotate appropriately and achieving a full interlocking effect. Consequently, the deflection in the sublayer was distributed over a wide area at shallow depths. However, a bedding thickness of 30 mm provided a better performance in terms of resistance to deflection, imposing a higher stress on the base layer.

Detection method for structural defects of U-shaped hanging ring for power fittings based on magnetic leakage principle

The U-shaped hanging ring of electric power fittings is usually installed outdoors and operates in harsh environments. Under the combined effect of the weight of the conductor and wind load, the bending part at the bottom of the U-shaped hanging ring often experiences wear and cracks due to friction contact, which can easily lead to accidents such as the detachment of transmission lines. Traditional methods for detecting structural defects in ferromagnetic materials, such as ultrasonic testing, eddy current testing, and manual testing, are affected by environmental factors, have a shallow measurement depth, and are difficult to quantify. In order to solve the above problems, this paper proposes a measurement method for detecting structural defects in the U-shaped hanging ring of electric power fittings based on the principle of magnetic leakage. The magnetic leakage signal characteristics of U-shaped hanging ring defects under different excitation structural parameters and different defect types are analyzed. The method of arranging magnetic leakage signal measurement points is studied. The detection of defect parameters is achieved based on the characteristic quantity of the magnetic leakage signal under different defect conditions. Finally, the method is analyzed and verified through examples. The results show that this method can achieve quantitative detection of defect parameters in the U-shaped hanging ring under uniform structural defect and crack structural defect, and has the advantages of high measurement accuracy and small error. The research results of this paper can provide a scientific theoretical basis for the inspection and replacement of transmission line fittings in engineering, which is of great engineering significance for ensuring the safe and stable operation of the power grid.

High Sulphidation Mineralization and Advanced Argillic Alteration within Concealed Gajah Tidur Porphyry, Grasberg District, Papua

High sulphidation (HS) mineralization and associated advanced argillic alteration have been intersected by three drill holes below the Grasberg porphyry Cu-Au deposit, known as the Gajah Tidur prospect. The prospect is located between 1,500 ̶ 2,750 m level, in Grasberg District, Papua, Indonesia. The holes are of KL98-10-21, KL98-10-22, and GRD39-08 which intersected 3.4 Ma Gajah Tidur monzonite, Grasberg Igneous Complex, the wall rocks of Kembelangan, and New Guinea Limestone Group. This research aims to determine the characteristics of high sulphidation mineralization associated with advanced argillic alteration at Gajah Tidur. Petrographic, XRD, SEM, fluid inclusion, and XRF (geochemical) analyses were applied to identify the mineralogy, geochemistry, and ore fluid properties. The major element plots show a differentiated intrusion. The alteration consists of potassic materials composed of biotite and K-feldspar, overprinted by phyllic and advanced argillic ones typified by alunite, pyrophyllite, and kaolinite. The high sulphidation mineralization characterized by pyrite-covellite, chalcopyrite-chalcocite, enargite, and digenite is also present. Fluid inclusion homogenization temperature of mineralized quartz vein ranges from 393 to 542°C, indicating a magmatic fluid origin predominantly. Two distinct porphyry systems, consisting of the Gajah Tidur Cu-Mo and the Main Grasberg Cu-Au porphyry systems are emplaced at the Gajah Tidur level. Advanced argillic is less intense compared to a pervasive phyllic alteration, overprinting the stockwork and surrounding rocks, emplaced at the upper part of quartz stockwork. It is possibly associated with a late stage of Gajah Tidur porphyry hydrothermal fluids which became cooler and highly acidic. Similar to other porphyry systems such as Oyu Tolgoi in Mongolia, the Gajah Tidur porphyry did not have its hydrothermal fluid ascent to the surface to form lithocap. Instead, the ascending fluids cooled at shallower depths resulting in the formation of advanced argillic alteration.

Preliminary Investigation into Using Resistance Techniques to Assess Concrete Curing

Concrete curing is a critical stage during construction for volume stability, long-term strength development, and ultimate durability. Poor curing can lead to shrinkage, scaling, and other durability issues. Proper concrete curing maintains sufficient moisture in the concrete and allows continuous hydration. Curing for concrete pavements often involves the application of a membrane-forming curing compound to help minimize moisture evaporation and promote desirable concrete property development. However, assessing the application rate of curing compounds and effectiveness on freshly paved concrete is difficult, as most evaluation methods are performed on hardened concrete and are not applicable or difficult to assess for fresh concrete in the field. This study proposes electrical resistance as a measure to assess the drying behavior of fresh concrete to quantify the effectiveness of curing. The findings of this study demonstrate that resistance is able to distinguish between samples with and without curing compounds and significant differences in drying observed between the surface and relatively shallow depths. In addition, the testing techniques were able to differentiate between the quality and rate of curing compound application and evaluate performance across a variety of environmental conditions. These findings indicate that a resistance-based approach could be a low-cost and non-destructive technique to evaluate the effectiveness of curing compound applications in real-time.

Two-Photon Absorption Aggregation-Induced Emission Luminogen/Paclitaxel Nanoparticles for Cancer Theranostics.

Multifaceted nanoplatforms integrating fluorescence imaging and chemotherapy have garnered acknowledgment for their potential potency in cancer diagnosis and simultaneous in situ therapy. However, some drawbacks remain for traditional organic photosensitizers, such as poor photostability, short excitation wavelength, and shallow penetration depth, which will greatly lower the chemotherapy treatment efficiency. Herein, we present lipid-encapsulated two-photon active aggregation-induced emission (AIE) luminogen and paclitaxel (PTX) nanoparticles (AIE@PTX NPs) with bright red fluorescence emission, excellent photostability, and good biocompatibility. The AIE@PTX NPs exhibit dual functionality as two-photon probes for visualizing blood vessels and tumor structures, achieving penetration depth up to 186 and 120 μm, respectively. Furthermore, the tumor growth of the HeLa-xenograft model can be effectively prohibited after the fluorescence imaging-guided and PTX-induced chemotherapy, which shows great potential in the clinical application of two-photon cell and tumor fluorescence imaging and cancer treatment.

QUEST-DMC: Background Modelling and Resulting Heat Deposit for a Superfluid Helium-3 Bolometer

AbstractWe report the results of radioactivity assays and heat leak calculations for a range of common cryogenic materials, considered for use in the QUEST-DMC superfluid $$^3$$ 3 He dark matter detector. The bolometer, instrumented with nanomechanical resonators, will be sensitive to energy deposits from dark matter interactions. Events from radioactive decays and cosmic rays constitute a significant background and must be precisely modelled, using a combination of material screening and Monte Carlo simulations. However, the results presented here are of wider interest for experiments and quantum devices sensitive to minute heat leaks and spurious events, thus we present heat leak per unit mass or surface area for every material studied. This can inform material choices for other experiments, especially if underground operation is considered – where the radiogenic backgrounds will dominate even at shallow depths.

Effect of the One-to-Many Relationship between the Depth and Spectral Profile on Shallow Water Depth Inversion Based on Sentinel-2 Data

In shallow water, Sentinel-2 multispectral imagery has only four visible bands and limited quantization levels, which easily leads to the occurrence of the same spectral profile but different depth (SSPBDD) phenomenon, resulting in a one-to-many relationship between water depth and spectral profile. Investigating the impact of this relationship on water depth inversion models is the main objective of this paper. The Stumpf model and three machine learning models (Random Forest, Support Vector Machine, and Mixture Density Network) are employed, and the performance of these models is analysed based on the spatial distribution of the training dataset and the input information composition of these models. The results show that the root mean square errors (RMSEs) of the depth inversion of Random Forest and Support Vector Machine are significantly affected by the spatial distribution of the training dataset, while minimal effects are observed for the Stumpf model and the Mixture Density Network model. The SSPBDD phenomenon is widespread in Sentinel-2 images at all depths, particularly between 5 m and 15 m, with most of the depth maximum difference of the SSPBDD pixels ranging from 0 to 5 m. The SSPBDDs phenomenon can significantly reduce the inversion accuracy of any model. The number and the depth maximum difference of the SSPBDDs pixels are the main influencing factors. However, by increasing the visible spectral information and the spatial neighbourhood information in the input layer of machine learning models, the inversion accuracy and stability of the models can be improved to a certain extent. Among the models, the Mixture Density Network achieves the best inversion accuracy and stability.

Barite-bearing “septarian concretions” (upper Cretaceous – Paleocene) from the Biban area (north Algeria)

The "septarian barite concretions" have garnered significant interest worldwide. This study presents the first detailed investigation of these sedimentary structures in Algeria, with a primary focus on elucidating their genesis through petrography, SEM-EDS, major and trace elements (including REEs), and sulfur isotope analysis. The sampled concretions occur in Upper Cretaceous-Paleocene marl layers from the Biban area, primarily in two main sectors (Koudiat Djebassa and Sidi Ziane), situated within the Southern Tellian Atlas in Northern Algeria (Maghrebides). While these barite concretions exhibit diverse morphologies, our analysis focuses specifically on oblate ellipsoidal concretions. The flattened shape of these concretions may stem from compressed echinoid tests or small, oblate septarian cracked concretions representing the flattened cores. Notably, these concretions feature an outer cortex of radial fibrous barite crystals, measuring centimeters in thickness. Petrographic examination coupled with SEM-EDS analysis suggests that concretion growth occurred from porewaters in unconsolidated, soft sediments at shallow burial depths beneath the sediment-water interface, manifesting in three growth episodes: (i) an initial stage characterized by primarily thin lamellar barite crystals intertwining to form rosette-like structures in concretion cores, (ii) a later stage marked by radial-fibrous barite crystal growth in concretion margins, and (iii) the filling of septarian cracks by barite. The presence of terrigenous sediment, particularly abundant in rosette-like barite crystals, indicates growth within highly porous sediment. Conversely, the radial fibrous outer cortex is related to an effective displacive growth mode. The δ34S values of the barite concretions (ranging from 16 ‰ to 24.4 ‰), consistent with seawater values, which document that seawater was the primary sulfur source. Furthermore, REE geochemistry further supports the seawater origin of diagenetic fluids rather than a hydrothermal one. Concretions are suggested to have formed in organic-rich, fine-grained sediments at shallow depth below the sea floor, in sedimentation halts, and as a result of microbial degradation of organic matter. Barium was supplied to porewaters within the methanogenic zone, precipitating as barite when, migrating upwards, reached the boundary with the overlying sulfidic zone.

Detached eddy simulation of hydrokinetic turbine wake in shallow water depths

Detached eddy simulations (DES) have been performed for flow over a solitary hydrokinetic turbine for two different tip-speed ratios λ = 3.64 and 6.15 and three different tip-clearances (δ = 0.1D, 0.2D, and 0.35D) to elucidate the effect of air-water interface on the turbine performance and wake recovery in shallow water conditions. The power predictions show good agreement with experimental data for λ = 3.64, but a large 12% error for λ = 6.15. The interface introduced unsteadiness in the power predictions, which increased with λ. The interface did not affect the mean power predictions for lower λ significantly, but reduced power for higher λ. The two-phase simulations for λ = 6.15 showed significant improvement in wake deficit and near-wake TKE prediction compared to the single-phase simulations. The improved predictions were identified because the interface causes early tip vortex entanglement and TKE burst. The DES predictions also show turbulence anisotropy maps consistent with the experimental data. Analysis reveals that turbulence is one-dimensional, dominated by streamwise fluctuations behind the blade tip region; two-dimensional, dominated by transverse and spanwise fluctuations in the TKE burst region; and approaches three-dimensional isotropy in the fully developed wake region. Detailed analysis of the vortical structures and wake characteristics reveals that the interface significantly affects the vortex advection, breakdown, and wake evolution. In particular, they enhance the wake deficit, which slows down the advection of the tip vortex filaments, causing an early vortex entanglement. The tip vortices show interaction with vortices generated underneath the interface, but these interactions seem localized. The tip vortex breakdown was identified due to instabilities generated during vortex entanglement and interaction with interface vortices for λ = 6.15 case, and because of tip and root vortex interaction for λ = 3.64. Although the two-phase simulations are encouraging compared to the single-phase case, TKE is still underpredicted in the near-wake region, possibly because of turbulence or rotating interface modeling issues. Two-phase simulations also predict significantly higher swirl, which needs further investigation.

Distribution and ecology of shallow-water black corals across a depth gradient on Galápagos rocky reefs

AbstractAntipathes galapagensis is a prevalent habitat-forming black coral in subtidal ecosystems of the Galápagos Marine Reserve (GMR). Despite their ecological importance and status as a CITES-regulated order, little is known about their depth distribution, population structure and ecology in the GMR. Surveys were conducted in 2021 and 2022 at 9 sites in the central Galápagos Archipelago to investigate how black coral densities, occupancy, size, habitat utilization, and epizoan overgrowth varied between 2.0 and 20.0 m depth. The shallowest black corals occurred at 3.4 m depth, one of the shallowest occurrences of an Antipathes spp. in the world. Coral density increased with depth, with a maximum density of 5.2 colonies per m2 observed across the depth range surveyed. Occupancy modeling also yielded curves with increasing probabilities of black coral presence with depth at all sites. Colony height increased with depth at 8 out of 9 sites and was positively correlated with coral density at 6 of 9 sites. Overall, 47% of colonies surveyed occupied cryptic habitats and 53% were attached to exposed substrate, but black coral habitat usage patterns varied with depth at 5 of 9 sites. At these sites, colonies on shallower transects (5.0, 10.0 m depth) more frequently displayed cryptic habitat usage while colonies along the deeper transects (15.0, 20.0 m) were more often exposed. In general, coral density, probability of occupancy, height, and exposed habitat utilization increased with depth, while the average degree of overgrowth and number of epibiont taxa were unrelated to depth. Five hypotheses regarding factors potentially limiting the shallow (upper) depth distribution of A. galapagensis—ranging from negative impacts of the physical environment to high predation on exposed substrates—are presented for future testing. These results provide a comprehensive ecological characterization of Galápagos black coral populations that can be used to assess the impact of future environmental change and applied to management decisions for this key marine foundation species in the GMR.