Shallow Profiles Research Articles

Thermodynamic and hydrological drivers of the soil and bedrock thermal regimes in central Spain

Abstract. An assessment of the soil and bedrock thermal structure of the Sierra de Guadarrama, in central Spain, is provided using subsurface and ground surface temperature data coming from four deep (20 m) monitoring profiles belonging to the Guadarrama Monitoring Network (GuMNet) and two shallow profiles (1 m) from the Spanish Meteorology Service (Agencia Estatal de Meteorología, AEMET) covering the time spans of 2015–2021 and 1989–2018, respectively. An evaluation of air and ground surface temperature coupling showed that soil insulation due to snow cover is the main source of seasonal decoupling, being especially relevant in winter at high-altitude sites. Temperature propagation in the subsurface was characterized by assuming a heat conductive regime by considering apparent thermal diffusivity values derived from the amplitude attenuation and phase shift of the annual cycle with depth. This methodology was further extended to consider the attenuation of all harmonics in the spectral domain, which allowed for analysis of thermal diffusivity from high-frequency changes in the soil near the surface at short timescales. For the deep profiles, the apparent thermal diffusivity ranges from 1 to 1.3×10-6 m2 s−1, which is consistent with values for gneiss and granite, the major bedrock components in the Sierra de Guadarrama. However, thermal diffusivity is lower and more heterogeneous in the soil layers close to the surface (0.4–0.8×10-6 m2 s−1). An increase in diffusivity with depth was observed that was generally larger in the soil–bedrock transition at 4–8 m depth. The outcomes are relevant for the understanding of soil thermodynamics in relation to other soil properties. Results with the spectral method suggest that changes in near-surface thermal diffusivity are related to changes in soil moisture content, which makes it a potential tool to gain information about soil drought and water resource availability from soil temperature data.

Mechanism and genesis of Sanmen Bay as a sink of Holocene Yangtze River sediment, Zhejiang Province, China

Introduction: The Holocene mud deposits that extend from the Yangtze River mouth to the Taiwan Strait along the Zhejiang–Fujian coast, East China Sea (ECS), have attracted considerable research attention. However, there is a lack of consensus regarding the redistribution flux of Yangtze River sediment after it enters the sea. There are many bays along the Zhejiang and Fujian coasts, but their role in the source–sink process of Yangtze River sediment is not well-documented owing to limited data.Methods: In this study, data from shallow seismic profiles, core samples, and surface sediment samples were analysed to assess the role of Sanmen Bay, the second largest bay in Zhejiang Province, in the source–sink process of Yangtze River sediments.Results: The results showed that Sanmen Bay is an important sink for Yangtze River sediments. The characteristics of the clay minerals indicate that the fine-grained sediments in Sanmen Bay are mainly derived from Yangtze River sediments. The thickness of Holocene deposits in Sanmen Bay ranges from 8.2 to 32.0 m, with an average of 23.4 m and a total sediment volume of 5.06 × 104 Mt, accounting for 1% of Yangtze River sediment in this time period. The Bayesian age-depth model based on borehole accelerator mass spectrometry (AMS) 14C dating shows that a high sedimentation rate occurred in the early and late Holocene but decreased significantly in the mid-Holocene, which is similar to that of the inner shelf of the East China Sea (ECS).Conclusion: The variation in the Holocene sedimentation rate in Sanmen Bay is related to the southward transport process and mechanism of Yangtze River sediments. The results of this study provide a basis for understanding the source–sink process of sediment in large rivers.

GIInger predicts homologous recombination deficiency and patient response to PARPi treatment from shallow genomic profiles

Homologous recombination deficiency (HRD) is a predictive biomarker for poly(ADP-ribose) polymerase 1 inhibitor (PARPi) sensitivity. Routine HRD testing relies on identifying BRCA mutations, but additional HRD-positive patients can be identified by measuring genomic instability (GI), a consequence of HRD. However, the cost and complexity of available solutions hamper GI testing. We introduce a deep learning framework, GIInger, that identifies GI from HRD-induced scarring observed in low-pass whole-genome sequencing data. GIInger seamlessly integrates into standard BRCA testing workflows and yields reproducible results concordant with a reference method in a multisite study of 327 ovarian cancer samples. Applied to a BRCA wild-type enriched subgroup of 195 PAOLA-1 clinical trial patients, GIInger identified HRD-positive patients who experienced significantly extended progression-free survival when treated with PARPi. GIInger is, therefore, a cost-effective and easy-to-implement method for accurately stratifying patients with ovarian cancer for first-line PARPi treatment.

Application of Horizontal-to-vertical Spectral Ratio with a Dense Linear Array on Prospecting Urban Underground Active Faults: a Case in The Mingguang City, Anhui Province

Reliable knowledge of sedimentary structures is beneficial for the study of active faults covered by sediments and can also provide important information for seismic hazard assessment, earthquake emergency response and urban planning. Based on the dense seismic array with a spacing of ∼ 60 m between stations and a length of ∼ 8 km, the horizontal-to-vertical spectral ratio (HVSR) curves were obtained at 133 stations with the ambient noise, and the two-dimensional sedimentary structures of the Quaternary and Neogene strata were imaged over two main faults of the Tanlu fault zone in the eastern Jiashan Basin by frequency-depth conversion. The variations (∼ 130 m) in the depth of the Quaternary and Neogene sedimentary basement directly beneath the fault zone agree well with the spatial characteristics of the fault revealed by the shallow seismic reflection profile with active sources at the same locations.

Geothermal gradients in a high-organic content landfill

Geothermal gradients in a high-organic content landfill

The stellar mass of the Gaia-Sausage/Enceladus accretion remnant

ABSTRACT The Gaia-Sausage/Enceladus (GS/E) structure is an accretion remnant that comprises a large fraction of the Milky Way’s stellar halo. We study GS/E using high-purity samples of kinematically selected stars from APOGEE DR16 and Gaia. Employing a novel framework to account for kinematic selection biases using distribution functions, we fit density profiles to these GS/E samples and measure their masses. We find that GS/E has a shallow density profile in the inner Galaxy, with a break between 15 and 25 kpc beyond which the profile steepens. We also find that GS/E is triaxial, with axis ratios 1:0.55:0.45 (nearly prolate), and the major axis is oriented about 80° from the Sun–Galactic centre line and 16° above the plane. We measure a stellar mass for GS/E of $1.45\, ^{+0.92}_{-0.51}\, \mathrm{(stat.)}\, ^{+0.13}_{-0.37} \mathrm{(sys.)}\ \times 10^{8}$ M⊙. Our mass estimate is lower than others in the literature, a finding we attribute to the excellent purity of the samples we work with. We also fit a density profile to the entire Milky Way stellar halo, finding a mass in the range of 6.7–8.4 × 108 M⊙, and implying that GS/E could make up as little as 15–25 per cent of the mass of the Milky Way stellar halo. Our lower stellar mass combined with standard stellar mass-to-halo mass relations implies that GS/E constituted a minor 1:8 mass-ratio merger at the time of its accretion.

Helicopter‐Based Ocean Observations Capture Broad Ocean Heat Intrusions Toward the Totten Ice Shelf

AbstractThe recent discovery of warm ocean water near the Totten Ice Shelf (TIS) has increased attention to the Sabrina Coast in East Antarctica. We report the result of 6‐day helicopter‐based observations conducted during the 61st Japanese Antarctic Research Expedition (JARE61), revealing warm ocean water (0.5–1°C) occupying a large previously unsampled area of the Sabrina Coast (116.5°E−120°E) below 550–600 m. Along the TIS front, we observe modified Circumpolar Deep Water (mCDW) well above freezing (∼−0.7°C), consistent with previous work. We identify glacial meltwater outflow from the TIS cavity west of 116°E. No signs of mCDW intrusions toward the Moscow University Ice Shelf cavity are observed; however, those observations were limited to only two shallow (∼330 m) profiles. We also highlight the advantages of helicopter‐based observations for accessibility, speed, maneuverability, and cost‐efficiency. The combination of ship‐ and helicopter‐based observations using the JARE61 approach will increase the potential of future polar oceanographic observations.

Groundwater Circulation in the Shallow Crystalline Aquifer of Tharisa Mine, South Africa: Evidence from Environmental Isotopes and Near-Surface Geophysics

For underground mining, efficient groundwater management is one of the critical mining economics components. The region of interest, known as Tharisa Mine, is situated on the western limb of the Bushveld Igneous Complex, which is home to South Africa’s premier platinum-group metal resources. This work aimed to provide the findings from the investigation and imaging of the near-subsurface hydrogeological architecture in a shallow profile using stable isotopes of water (18O and 2H) and radioactive water isotopes (3H). Regarding isotope data, 18O varied from −3.5 to 1.5‰; 2H from −24 to 4.7‰; and 3H from 2.0 to 3.4 T.U. Utilizing combined geophysical techniques, the results were verified. Additionally, the geophysical methods, including seismic refraction tomography, multichannel analysis of surface waves, electrical resistivity tomography, and magnetics, helped identify the fluid’s pathways and lineaments during migration to verify the isotope results. The groundwater inflow volumes into the open pit were initially determined by integrating the following findings: the delineation of fracture systems/zones and fluid migration pathways; mining activities enhance the storage and transmission ability of the aquifer; and the main sources of water in the mine include mixing of surface and deep water sources, recycling of water possibly via lineaments, and tailings dam seepages.

Shallow S-wave Velocity Profile Estimation using Surface Velocity and Microtremor HVSR with a Linear Velocity Increase Approach

We propose a simple method for 1D S-wave velocity (Vs) profile estimation using a measured surface S-wave velocity (V1) and peak frequency of the observed microtremor horizontal-to-vertical spectral ratio (HVSR). In this method, the S-wave velocity profile is presented as linear velocity increase with depth in sediments over a bedrock layer that has a given constant S-wave velocity. Thus, the profile can be parameterized with the measured surface S-wave velocity and the velocity gradient. The gradient can be estimated based on the agreement of the peak frequencies of the observed microtremor HVSR and the theoretical ellipticity of the fundamental mode of the Rayleigh wave. We examined the applicability of the proposed method using numerical tests as well as application to actual data at five sites in the Bandung Basin, Indonesia, where observed Rayleigh wave phase velocities from microtremor array surveys were available. The applicability was confirmed in numerical tests using sample models of soil profiles in the basin. Actual application indicated the appropriateness of the estimated S-wave velocity profiles due to the similarity of their theoretical Rayleigh wave phase velocities with the observed Rayleigh wave phase velocities. Since the proposed method needs prior confirmation of the linear increase of the S-wave velocity, it is suitable for use in spatial interpolation of shallow S-wave velocity profiles with simple data acquisition.

Geological hazards in the Oujiang estuary in the Zhejiang Province, China: type, distribution, and origin

Introduction: As our understanding of the ocean and its uses continues to advance, countries worldwide with ocean access are implementing new marine strategies. For example, understanding marine geological disasters can help develop the use of ocean resources and oceanic engineering.Methods: Therefore, this study used recent data from the Oujiang Estuary, a nearshore area in China, to determine its geological hazards.Results: The geological hazards were classified as active or restricted based on topography, geomorphology, shallow seismic profile, single-channel seismic profile, and geological drilling data. Active geological hazards primarily include shallow gas and active sand waves, whereas restrictive geological hazards include irregularly buried bedrock, erosion channels, steep submarine slopes, and buried paleochannels. We also evaluated the distribution characteristics and scope, such as the vertical distribution of shallow gas based on the seismic profiles, drilling rock facies, methane, and carbon dioxide contents in the top air, and the isotope values. We found that shallow gas was vertically distributed among multiple layers. The main gas-bearing layers were the clayey silt and sandy (silt) clay layers of the early Holocene and late Pleistocene strata. The shallow gas content was relatively low in the coarse sediment layer at the bottom of the late Pleistocene succession. Generally, the Holocene and late Pleistocene deposits do not contain gas, and the gas content in the middle and late Pleistocene strata (at greater depths) is relatively low.Discussion: The combined effects of the regional geological structure, sea level changes, modern hydrodynamics, and human activities have formed the geological environment of the Oujiang Estuary.

Gradient doping in Cu2ZnSnSe4 by temperature and potential induced defect steering

Kesterite materials are among the most promising emerging photovoltaic absorbers, despite the number of challenging issues this technology presents. The use of soft thermal post-deposition treatments is key to improving the CdS/kesterite interface quality. Thermal treatments can result in a low-temperature phase transition which affects the optoelectronic properties. In this work, the effects of applied voltage during a full device thermal post-deposition treatments above the critical temperature of the phase transition are explored. The applied voltage modifies the formation energy and drives in-depth migration of ionized defects, which can generate a shallow doping density gradient. Supporting the experimental findings, the effects of a shallow doping density gradient on the current–voltage curves and the external quantum efficiency are modelled using drift–diffusion calculations. The presence of bulk recombination centers in the modelling is a key aspect to precisely reproduce the experimental results. The shallow doping density gradient in opposite directions precisely matches the experimental results for opposite voltage polarizations. The effects on the band structure of the device are presented proving this as a promising strategy for improving charge carrier selectivity.This is the first time that a defect engineering approach has been proposed and successfully proven to control shallow doping density profiling and improve the charge carrier selectivity of kesterite devices. In this sense, the results and their thorough physical interpretation presented in this work will potentially open new perspectives in other photovoltaic technologies as well as in the field of materials engineering.

Environmental fate of chlorpyrifos in Rhodic Ferralsol grown with corn during summer and winter seasons under high-intensity rainfall

The interactions between pesticides' physicochemical properties and edaphoclimatic factors influence their distribution into the environment. Understanding how those factors interact in a changing environment is crucial for mitigating environmental and agronomic problems. Thus, a percolation lysimeter with undisturbed soil and suction lysimeters were used to conduct a field study to evaluate the distribution of chlorpyrifos sprayed in a corn crop cultivated in a Rhodic Ferralsol in simulated extreme rainfall conditions. The mobility of chlorpyrifos was evaluated under simulated precipitation (150 mm h−1), 24 h and 48 h after applying the chlorpyrifos in different phenological stages of corn during the summer and winter crops in two agricultural years. In addition, GC-ECD determined the residual concentration of chlorpyrifos in the runoff and leached samples. Finally, a laboratory adsorption study was conducted with Rhodic Ferralsol to find the chlorpyrifos adsorption capacity in different temperatures, with and without soil organic matter. Our results show that soil organic matter is essential in chlorpyrifos adsorption, responsible for approximately 5% pesticide retention, which could be 25% higher during winter. High-intensity rainfalls positively affect runoff and leaching; nevertheless, these are responsible for only 0.2% of all chlorpyrifos amounts, as the soil is the major reservoir of chlorpyrifos by retention into clays and organic matter. Furthermore, the corn growth stages directly affect chlorpyrifos transportation, with higher amounts observed in runoff and leaching during the first and last corn growth stages. Therefore, in the conditions such as high-intensity rainfall, exposed soil, shallow soil profile, and temperatures below 20 °C, attention should be paid to chlorpyrifos spray with special regard to the weather forecast, avoiding its spray near rainfall events. Further studies should be conducted in other soil classes and rainfall conditions to validate our observations.

Inaccuracies and biases of the Gaussian size deconvolution for extracted sources and filaments

A simple Gaussian size deconvolution method is routinely used to remove the blur of observed images caused by insufficient angular resolutions of existing telescopes, thereby to estimate the physical sizes of extracted sources and filaments. To ensure that the physical conclusions derived from observations are correct, it is necessary to know the inaccuracies and biases of the size deconvolution method, which is expected to work when the structures, as well as the telescope beams, have Gaussian shapes. This study employed model images of the spherical and cylindrical objects with Gaussian and power-law shapes, representing the dense cores and filaments observed in star-forming regions. The images were convolved to a wide range of angular resolutions to probe various degrees of resolvedness of the model objects. Simplified shapes of the flat, convex, and concave backgrounds were added to the model images, then planar backgrounds across the footprints of the structures are subtracted and sizes of the sources and filaments were measured and deconvolved. When background subtraction happens to be inaccurate, the observed structures acquire profoundly non-Gaussian profiles. The deconvolved half maximum sizes can be strongly under- or overestimated, by factors of up to ~20 when the structures are unresolved or partially resolved. For resolved structures, the errors are generally within a factor of ~2; although, the deconvolved sizes can be overestimated by factors of up to ~6 for some power-law models. The results show that Gaussian size deconvolution cannot be applied to unresolved structures, whereas it can only be applied to the Gaussian-like structures, including the critical Bonnor-Ebert spheres, when they are at least partially resolved. The deconvolution method must be considered inapplicable for the power-law sources and filaments with shallow profiles. This work also reveals subtle properties of convolution for structures of different geometry. When convolved with different kernels, spherical objects and cylindrical filaments with identical profiles obtain different widths and shapes. In principle, a physical filament, imaged by the telescope with a non-Gaussian point-spread function, could appear substantially shallower than the structure is in reality, even when it is resolved.

Pedogenic bayerite in andic material of Isla Santa Cruz, Galápagos archipelago

The lower part of a shallow profile on volcanic ash from Isla Santa Cruz of the Galápagos archipelago was found to contain abundant bayerite, a relatively rare Al(OH)3 polymorph, as confirmed by X-ray diffraction and Raman spectroscopy analyses. The bayerite-bearing interval consists of orange-brown colloidal material with high Al and Fe content, and it contains bayerite in the form of pervasive thin coatings along the sides of pores, including planar voids and narrow channels. Associated gibbsite seems to occur as part of the coatings. Bayerite is interpreted to have formed by rapid crystallisation from solutions derived from the Al-rich groundmass. Gibbsite is regarded as the product of an ongoing process of bayerite transformation.

Time series prediction of shallow water sound speed profile in the presence of internal solitary wave trains

The internal waves, especially the internal solitary wave (ISW) trains, cause violent perturbations of sound speed. Sound speed profile (SSPs) facilitates the pre-understanding of the sound field distribution in the experimental sea, therefore, the real-time prediction of SSPs in the presence of ISW trains are of great significance. In this paper, an orthogonal representation of SSPs that considers the background field (background SSP) variation is proposed. Based on the statistical characteristics of time-series SSPs, high-precision SSP prediction is realized by the long short-term memory recurrent neural network (LSTM). The prediction accuracy is demonstrated with the SSP data from an experiment in the South China Sea, and the mean RMSE of SSP prediction is reduced to about 1 m/s.

GRB 221009A afterglow from a shallow angular structured jet

ABSTRACT Exceptionally bright gamma-ray burst (GRB) afterglows can reveal the angular structure of their jets. GRB jets appear to have a narrow core (of half-opening angle θc), beyond which their kinetic energy drops as a power-law with angle θ from the jet’s symmetry axis, $E_{\mathrm{ k},\rm iso}(\theta)\propto [1+(\theta /\theta _\mathrm{ c})^2]^{-a/2}$. The power-law index a reflects the amount of mixing between the shocked jet and confining medium, which depends on the jet’s initial magnetization. Weakly magnetized jets undergo significant mixing, leading to shallow (a ≲ 2) angular profiles. We use the exquisite multiwaveband afterglow observations of GRB 221009A to constrain the jet angular structure using a dynamical model that accounts for both the forward and reverse shocks, for a power-law external density profile, next ∝ R−k. Both the forward shock emission, that dominates the optical and X-ray flux, and the reverse shock emission, that produces the radio afterglow, require a jet with a narrow core (θc ≈ 0.021) and a shallow angular structure (a ≈ 0.8) expanding into a stellar wind (k ≈ 2). Moreover, these data appear to favour a small fraction (ξe ≈ 10−2) of shock heated electrons forming a power-law energy distribution in both shocks.

A structured jet explains the extreme GRB 221009A.

Long-duration gamma-ray bursts (GRBs) are powerful cosmic explosions, signaling the death of massive stars. Among them, GRB 221009A is by far the brightest burst ever observed. Because of its enormous energy (Eiso ≈ 1055 erg) and proximity (z ≈ 0.15), GRB 221009A is an exceptionally rare event that pushes the limits of our theories. We present multiwavelength observations covering the first 3 months of its afterglow evolution. The x-ray brightness decays as a power law with slope ≈t-1.66, which is not consistent with standard predictions for jetted emission. We attribute this behavior to a shallow energy profile of the relativistic jet. A similar trend is observed in other energetic GRBs, suggesting that the most extreme explosions may be powered by structured jets launched by a common central engine.

A study of activated phosphorus distribution within silicon substrate for polysilicon passivating contacts based on an in-line PVD system

An in-line PVD system consisting of plasma oxidation chamber and phosphorus-doped amorphous silicon deposition chamber was used to fabricate highly-doped polysilicon passivating contact structure for commercial TOPCon solar cells, which can help to achieve simple fabrication process and excellent electrical properties. In this paper, we studied how the doping profiles of ionized phosphorus atoms in the passivating contact formed by this method varies with the deposition conditions, especially the in-diffusion profile in the silicon substrate. Increasing the RF power of plasma oxidation can prevent phosphorus from penetrating through SiOx to form a shallow profile, and reducing the power is conducive to the formation of more pinholes on SiOx, resulting in a wide profile following the shallow profile. The shallow profile effectively inhibits the surface recombination rate and thus achieve good passivation quality, while the emergence of the following wide profile helps to reduce the contact resistivity by providing more majority carrier transport channels. The 100 W condition constructed a shallow and gradually widening doping profile, exhibiting a low recombination current density of 16.5 fA/cm2 and a low contact resistivity of 1.87 mΩ·cm2. However, the SiOx thickness and density obtained at 80 W are insufficient for achieving a shallow-first-then-widen doping profile, even with adjustments to thermal activation conditions. Additionally, we found the engineering of surface microstructure on silicon wafers also has an impact on the doping profile.

Towards Sic-Based VUV Pin-Photodiodes - Investigations on 4H-SiC Photodiodes with Shallow Implanted Al Emitters

4H silicon carbide (SiC) based pin photodiodes with a sensitivity in the vacuum ultraviolet spectrum (VUV) demand newly developed emitter doping profiles. This work features the first ever reported 4H-SiC pin photodiodes with an implanted p-emitter and a noticeable sensitivity at a wavelength of 200 nm. As a first step, Aluminum doping profiles produced by low energy ion implantation in 4H-SiC were characterized by secondary-ion mass spectrometry (SIMS). Photodiodes using these shallow emitters are compared to one with a deep p-emitter doping profile employing IV characteristics and the spectral response. SIMS results demonstrate the possibility of shallow Alimplantation profiles using low implantation energies with all emitter profiles featuring characteristic I-V results. For some shallow doping profiles, a meassurable signal at the upper limit of the VUV spectrum could be demonstrated, paving the way towards 4H-SiC pin photodiodes with sensitivities for wavelengths below 200 nm.

A reinvestigation of debris disc halos

Context. Scattered-light images reveal that a significant fraction of debris discs consist of a bright ring beyond which extends a wide halo. This halo is expected and should be made of small grains collisionally produced in the ring of parent bodies (PBs) and pushed on high-eccentricity orbits by radiation pressure. It has been shown that, under several simplifying assumptions, the surface brightness (SB) of this halo should radially decrease as r−3.5 in scattered light Aims. We aim to revisit the halo phenomenon and focus on two unexplored issues: (1) how the unavoidable presence of small unbound grains, non-isotropic scattering phase functions (SPFs), and finite instrument resolution affect scattered-light SB profiles, and (2) how the halo phenomenon manifests itself at longer wavelengths in thermal emission, both on resolved images and on system-integrated spectral energy distributions (SEDs). Methods. We use a collisional evolution code to estimate the size-dependent spatial distribution of grains in a belt+halo system at steady state. We use the GRaTeR radiative-transfer code to derive synthetic images in scattered light and thermal emission, as well as SEDs. Results. We find that unbound grains account for a significant fraction of the halo’s luminosity in scattered light, and can significantly flatten the SB radial profile for the densest and brightest discs. Because halos are strongly size-segregated with radial distance, realistic size-dependent SPFs also have an effect, resulting here again in shallower SB profiles. For edge-on discs, non-resolving the vertical profile can also significantly flatten the projected SB profile. We show that roughly half of the observationally derived halo profiles found in the literature are compatible with our new results, and that roughly half of the remaining systems are probably shaped by additional processes (planets, stellar companions, etc.). We also propose that, in future observational studies, the characteristics of the PB belts and the halos should be fitted separately. In thermal emission, we find that wide halos should remain detectable up to the far-infrared (far-IR) and that, with the exception of the ~8–15 µm domain, the halo accounts for more than half of the system’s total flux up to λ ~ 80–90 µm. The contribution from the halo strongly decreases in the submm to mm but still represents a few percent of the system’s luminosity at λ ~ 1 mm. For unresolved systems, the presence of a halo can also affect the determination of the radius of the disc from its SED.