Density Modification Research Articles

Density Modifications Toward High Mechanical Performance Nanocellulose Aerogels

ABSTRACTMechanical properties are crucial for the application of nanocellulose aerogels. In this work, a series of nanocellulose aerogels with solid content concentration gradient (0.5, 1.0, 1.5, 2.0 wt%) of precursor dispersion are prepared by freeze‐drying method, and the effect of nanocellulose solid content on the mechanical properties of nanocellulose aerogels was investigated. As the solid content concentration increased, the internal microstructure of the aerogel underwent a transition from a sparse reticular structure to a tightly arranged lamellar structure. This transition led to a substantial improvement in the mechanical properties of the aerogel. At 50% strain, the compressive strength of the aerogel increased from 8.4 to 37.56 kPa with the increase of nanofibrillar cellulose solid content. Furthermore, the specific strength, specific modulus, and compressive modulus also increased, while maintaining a low density (20.02 mg/cm3) and high porosity (98.63%). This work confirms the feasibility of structural strengthening and mechanical property enhancement of nanocellulose aerogels by density modification, which provides a guidance for the design of durability enhancement of nanocellulose aerogels for broadening their application fields.

Structural Modification Effect of Se-doped Porous Carbon for Hydrogen Evolution Coupled Selective Electrooxidation of Ethylene Glycol to Value-added Glycolic Acid.

The ethylene glycol oxidation reaction (EGOR) has attracted attention because ethylene glycol (EG), which exhibits large-scale production and a low market price, can be reformed into valuable glycolic acid (GCA) with the cogeneration of high-purity hydrogen gas during the reaction. In this study, a noble catalyst material of Pt nanoparticles supported on Se-doped porous carbon (Pt/SePC) is prepared and investigated for the selective electrochemical oxidation of EG to GCA. Pt/SePC achieved a maximum EG conversion of 94.6% and GCA selectivity of 84.4% and maintained this high performance with negligible degradation during durability tests. Furthermore, the EGOR required lower overpotential rather than the oxygen evolution reaction, thus the EGOR coupled with the hydrogen evolution reaction can reduce the cell overpotential to 0.60 V, which is much lower than that of water electrolysis (1.58 V). The effect of Se doping is investigated through experimental analyses and density functional theory (DFT) calculations, and they shows that Se modified the binding energy of Pt nanoparticles and the adsorption energy of reactants by lattice deformation and charge density modification. This study provides scientific insights and strategies for electrocatalyst design for the selective oxidation of polyols to value-added chemicals via the cogeneration of hydrogen gas.

Density modification of DNAPL using self-demulsifying colloidal biliquid aphron: Kinetics, mechanisms and influencing factors

Density-modification remediation of dense nonaqueous phase liquid (DNAPL) using colloidal biliquid aphron (CBLA) is an efficient means of enhancing flushing and avoiding the risk of downward migration of DNAPL. However, the use of demulsifier is currently necessary for CBLA to achieve density modification. This leads to issues such as low modification efficiency and the risk of secondary contamination. In this work, we developed a self-demulsifying CBLA (PO-CBLA-S) for density-modification remediation of DNAPL, eliminating the need for external demulsifiers. The self-demulsification process exhibited pseudo-secondary reaction kinetics, achieving densities below 1 g/cm3 for various DNAPLs. Groundwater chemistry parameters (pH, anions, cations, temperature, and humic acid (HA) content) were investigated for their impact on perchloroethylene (PCE) density modification. Cations were found to enhance PO-CBLA-S density modification more than anions. Both strong acidic and alkaline environments promote the density regulation of PCE by PO-CBLA-S, and temperature positively correlates with the efficiency of density modification. High concentrations of HA also have a favorable facilitating effect on the density modification. The mechanisms of self-demulsifying density modification were clarified at the microscale. Surfactant entanglement caused by internal surfactant-solvent interaction decreased the stability of PO-CBLA-S, leading to self-demulsification. This study addresses density modification challenges and provides a theoretical foundation for its groundwater remediation applications.

ARCIMBOLDO at low resolution: Verification for coiled coils and globular proteins.

Crystallography at low resolution must determine the atomic model from less experimental observations, which is challenging in the absence of a model. In addition, model bias is more severe when independent experimental data are scarce. Our methods solve the phase problem by combining the location of accurate model fragments using Phaser with density modification and interpretation of the resulting maps using SHELXE. From a partial, correct structure, the density modification process and the stereochemical constraints draw the rest of the structure, validating the result. This same principle is now exploited at low resolution. Coiled coils are important, ubiquitous structures but notoriously difficult to phase and to predict. Both correct solutions and incorrect ones are poorly discriminated by the crystallographic figures of merit as long as helices are correctly oriented. We incorporate coiled-coil verification, designed to set up competing, incompatible structural hypotheses to probe both the results and establish the power of the data to discriminate them. Efficiency of coiled-coil phasing and validation in test cases from 3 to 4 Å is demonstrated in ARCIMBOLDO_LITE, placing single helices, and in ARCIMBOLDO_SHREDDER, with fragments derived from AlphaFold models. SHELXE tracing at low resolution has been enhanced, maintaining its local character but extending the environment assessment. For non-helical structures, verification is demonstrated in the fragment location process. Its use is exemplified with the solution of the VSR1 structure at 3.5 Å, depending on LLG optimization and the emergence of new features in the electron density. Relying on verification, we have extended the use of the ARCIMBOLDO software to low resolution.

Pressure-induced collapsed tetragonal transition in optimally Na-doped CaFe2As2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{CaFe}}_{2} {\ ext{As}}_{2}$$\\end{document}

A comprehensive first-principles study on electronic structure of optimally doped Ca0.33Na0.67Fe2As2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\hbox {Ca}_{0.33}\\hbox {Na}_{0.67}\\hbox {Fe}_2\\hbox {As}_2}$$\\end{document} under hydrostatic pressures in the presence of magnetic configurations is presented. A magneto-structural transition from a tetragonal to a collapsed tetragonal phase at 3 GPa hydrostatic pressure is predicted in double-stripe antiferromagnetic configuration that corroborates experimental observations. As the system enters the non-superconducting collapsed phase, significant deviations occur in the local structural parameters compared to those at optimal Tc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\it{T}}_{c}$$\\end{document} values. This transition coincides with a sharp decrease in As density of states (DOS), accompanied by Fe magnetic moment collapse and substantial Fe square plane charge density modification. The structural transition induces a comprehensive reconstruction of the electronic structure, marked by distorted FeAs4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {FeAs}_{4}$$\\end{document} tetrahedra, potentially leading to unfavourable nesting conditions, and complete suppression of magnetism, correlating with the observed disappearance of superconductivity. Increasing pressure leads to a rise in crystal field splitting, influencing the spin-state transition in Ca0.33Na0.67Fe2As2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\hbox {Ca}_{0.33}\\hbox {Na}_{0.67}\\hbox {Fe}_2\\hbox {As}_2}$$\\end{document}, ultimately resulting in a shift from tetragonal to non-magnetic collapsed tetragonal phase as the Fe2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {Fe}^{2+}$$\\end{document} spin state transitions to a low spin state. This demonstrates the intricate interplay between crystal field splitting, external pressure, and spin dynamics, highlighting the significant impact of magneto-volume effects on the structural phase of material under pressure.

Development of polysaccharide bioplastic: Analysis of thermo-mechanical properties and different environmental implications

Despite the distinct benefits of plastics, the environmental impacts stemming from their production and accumulation in the environment have become a global concern. Therefore, the development of new technologies that mitigate these impacts is of notable importance. The present study aimed to evaluate the physicochemical properties of starch-xylan-based bioplastic, and to discuss the viability of this material in terms of applications and ecological impacts. Holocellulose, xylan, and α-cellulose were extracted from waste biomass and combined with starch for bioplastic production. Solubility in food simulants (3% acetic acid, and 90% ethanol) was performed for xylan and starch-based bioplastics. Bioplastic was evaluated to grow Aspergillus versicollor for xylanase production. The bioplastic was evaluated as a photoprotector with yeast exposed to UVC light-covered by the bioplastic for 2 h. Bioplastic disintegration was evaluated in different soil moistures and the disintegration on the surface of the compost. Liquid washes from soils exposed to bioplastic biodegradation were tested for Lactuca sativa seed germination/inhibition. Water from a local lake was exposed to bioplastic and microbial cell density modification was verified. Images of the surface of the bioplastics were obtained by scanning electron microscopy, and characterized by thermogravimetric and dynamic-mechanical analysis. The xylan addition in bioplastic led to a material with a 40–50% decreased ultraviolet light transmittance. An increase in xylan concentration reduced solubility in lipid food simulant solutions, with no fatty solubilization with 25% of xylan. It suggests potential applications in photoprotective and packaging contexts. The thermal degradation temperature of the pure starch bioplastic was 324 °C, and the addition of 10% (287 °C), 15% (286 °C), and 25% (296 °C) xylan (w/w) indicated a reduction in thermal resistance, possibly due to suboptimal interaction between polymer chains. The decrease in crystallinity in the compositions 10/90% (Xc = 20%), 15/85% xylan/starch (Xc = 21%) compared to 25/75% xylan/starch (Xc = 11%) also underscored the complexity of polymer interactions within the bioplastic matrix. Tensile strength of pure starch was 1.21 MPa, while the composition of 15/85% xylan/starch exhibited improved strength 2.99 MPa. Further investigation into the interaction between starch and xylan is warranted. Concerning the disintegration of the 25/75% xylan/starch formulation in the soil, the humidity of the soil matrix played a significant role. The disintegration occurred over 5 days and 16 days in compost (55% humidity) and soil (32.6% humidity), respectively. The results of phytotoxicity (Lactuca sativa seeds) and changes in the physicochemical and biological profile of water (smell, turbidity, phosphorus and nitrogen levels, pH, and bacterial and phytoplankton density/richness), in response to exposure to bioplastics, highlight the necessity of developing this biologically-based and biodegradable technology in concerns about potential environmental impacts. Furthermore, the present study introduces the approach of bioplastic waste recycling using enzyme production biotechnology. In line with the legitimacy of bioplastics as important materials for addressing the challenges posed by their non-biodegradable synthetic counterparts, the presented results broaden the discourse on the feasibility of this biologically based material, contributing to the development of a sustainable society.

Machine learning approaches to cryoEM density modification differentially affect biomacromolecule and ligand density quality.

The application of machine learning to cryogenic electron microscopy (cryoEM) data analysis has added a valuable set of tools to the cryoEM data processing pipeline. As these tools become more accessible and widely available, the implications of their use should be assessed. We noticed that machine learning map modification tools can have differential effects on cryoEM densities. In this perspective, we evaluate these effects to show that machine learning tools generally improve densities for biomacromolecules while generating unpredictable results for ligands. This unpredictable behavior manifests both in quantitative metrics of map quality and in qualitative investigations of modified maps. The results presented here highlight the power and potential of machine learning tools in cryoEM, while also illustrating some of the risks of their unexamined use.

15. UTILITY OF CHATGPT IN THE APPLICATION OF THREE-DIMENSIONAL RECONSTRUCTION MODELS OF THE STOMACH IN REVISIONAL BARIATRIC SURGERY

Abstract Introduction Radiological three-dimensional reconstruction from CT images is very useful in pre-surgical planning and in training for complex cases using the preoperative studies performed on the patient. In revisional bariatric surgery, there is an undiscovered field with potential applications to develop with 3D reconstruction models. Our goal is to propose the applications offered by ChatGPT with 3D reconstruction models of post-bariatric surgery anatomy, whether it be vertical gastrectomy or the gastric reservoir and gastrojejunal anastomosis in the case of bypass. Methods Three-dimensional image anatomical models of the stomach and post-bariatric surgery anatomy have been developed. CT images are obtained with the Siemens Somatom Perspective 64® device. The images are retrieved in DICOM format and processing to achieve three-dimensional reconstruction is done with the OsiriX® software, performing manual segmentation and an image density modification. ChatGPT analyzes these databases and provides us with the options that can be exploited. Results Project ideas based on ChatGPT: 1 - Surgical planning assistant. 2 - Virtual reality training simulator. 3 - Diagnostic assistant. 4 - Patient education tool. 5 - Research tool. Conclusion Obtaining three-dimensional reconstruction images of post-bariatric surgery anatomy allows us to develop models that, as guided by ChatGPT, can be applied in different aspects in revisional bariatric surgery.

Role of nonlinear structures and associated turbulence generation dayside magnetosphere reconnection sites

A numerical simulation is implemented to investigate the role of whistler wave in the presence of the ponderomotive force-driven density modification and the magnetic field perturbation due to preexisting magnetic islands. The dynamical equation governing the whistler waves is derived and solved using numerical methods to assess their role. The simulation produced results that revealed the nonlinear structures, confirming the system's turbulent characteristics. Moreover, we utilized a semi-analytical model, applying the paraxial approximation, to estimate the scale size of the current sheet, which was found to be between 2λe and λe. This measurement provides evidence of the presence of a superthin electron current sheet within reconnection sites. Qualitative consistency is established by comparing the simulation results with findings reported in the literature.

Modes and model building in SHELXE.

Density modification is a standard step to provide a route for routine structure solution by any experimental phasing method, with single-wavelength or multi-wavelength anomalous diffraction being the most popular methods, as well as to extend fragments or incomplete models into a full solution. The effect of density modification on the starting maps from either source is illustrated in the case of SHELXE. The different modes in which the program can run are reviewed; these include less well known uses such as reading external phase values and weights or phase distributions encoded in Hendrickson-Lattman coefficients. Typically in SHELXE, initial phases are calculated from experimental data, from a partial model or map, or from a combination of both sources. The initial phase set is improved and extended by density modification and, if the resolution of the data and the type of structure permits, polyalanine tracing. As a feature to systematically eliminate model bias from phases derived from predicted models, the trace can be set to exclude the area occupied by the starting model. The trace now includes an extension into the gamma position or hydrophobic and aromatic side chains if a sequence is provided, which is performed in every tracing cycle. Once a correlation coefficient of over 30% between the structure factors calculated from such a trace and the native data indicates that the structure has been solved, the sequence is docked in all model-building cycles and side chains are fitted if the map supports it. The extensions to the tracing algorithm brought in to provide a complete model are discussed. The improvement in phasing performance is assessed using a set of tests.

Adrenal and metabolic hormones demonstrate risk-reward trade-offs for African elephants foraging in human-dominated landscapes.

A key driver of the African savannah elephant population decline is the loss of habitat and associated human-elephant conflict. Elephant physiological responses to these pressures, however, are largely unknown. To address this knowledge gap, we evaluated faecal glucocorticoid metabolite (fGCM) concentrations as an indicator of adrenal activity and faecal thyroid metabolite (fT3) concentrations as an indicator of metabolic activity in relation to land use, livestock density, and human landscape modification, while controlling for the effects of seasonality and primary productivity (measured using the normalized difference vegetation index). Our best-fit model found that fGCM concentrations to be elevated during the dry season, in areas with higher human modification index values, and those with more agropastoral activities and livestock. There was also a negative relationship between primary productivity and fGCM concentrations. We found fT3 concentrations to be higher during the wet season, in agropastoral landscapes, in locations with higher human activity, and in areas with no livestock. This study highlights how elephants balance nutritional rewards and risks in foraging decisions when using human-dominated landscapes, results that can serve to better interpret elephant behaviour at the human-wildlife interface and contribute to more insightful conservation strategies.

Optical development and density modification dependence in poly (methyl methacrylate) reinforced with borax microparticles

Optical development and density modification dependence in poly (methyl methacrylate) reinforced with borax microparticles

Compact relativistic sphere with charged anisotropic matter in f(R,G) gravity

The main purpose of this research is to examine a number of interior configurations of stable anisotropic objects formed in the shape of spherical charged stars within the gravity region described by [Formula: see text], where [Formula: see text] represents the Gauss–Bonnet invariant and [Formula: see text] defines the Ricci Scalar in this scenario. The formation of these charged stars is investigated using the solutions found by Karori and Barua, among several feasible models within the theory of [Formula: see text] gravity. The study explores the behavior of these realistically charged compact stars, analyzing various physical components through the use of graphs. Furthermore, the feasibility of our model is assessed by evaluating it against different energy conditions. Additionally, topics such as density modification, stress evolution, various forces, star stability, anisotropy measurement, state parameter equations, and charge distribution are discussed.

Evidence of CME‐Magnetospheric Shock Disturbance of the D‐Region Observed in the VLF Signal

AbstractThe observation of the D‐region response to the interplanetary shock (IS) during the storm of 17 March 2015 is carried out using two very low frequency (VLF) transmitter signals (NRK and GQD) recorded at Algiers and Tunis. Data from THEMIS‐E and RBSP are used to correlate between the ground and satellite observations. The important finding is the wavy structure of the perturbations observed on the two VLF signals tens of seconds after the space detection of the shock, in concordance with the RBSP electric field measurements. The measured VLF signal amplitude and phase perturbations were: −0.65 dB, 5.81° for NRK and −0.12 dB, −126° for GQD measured at Algiers. For Tunis receiver, the perturbations were: −0.58 dB, 4.7° for NRK and 0.15 dB, −1.19° for GQD. In addition to the observations, simulations of the NRK signal perturbations were done using the long wavelength propagating capability code to determine the electron density modification that lead to the measured perturbations. The simulation results showed that the modified Wait's parameters above the NRK transmitter were: 80.391 km for h′ and 0.43 km−1 for β in the case of NRK‐Tunis path. Concerning the NRK‐Algiers path, the simulation gave 80.316 km for h′ and 0.431 km−1 for β. From these parameters values, the modified electron density was not important to explain the observed perturbations. Therefore, the IS effect could be explained by induced heating of the ionosphere due to the penetration of the electric field which leads to the changes of the ionospheric conductivity.

Characterization of Cross-Linking in Guar Gum Hydrogels via the Analysis of Thermal Decomposition Behavior and Water Uptake Kinetics

This study aimed to explore a test method for evaluating the effective cross-linking density of hydrogels. A guar gum–epichlorohydrin hydrogel (GEH) was prepared using guar gum (GG) as the raw material and epichlorohydrin (ECH) as the cross-linking agent. The thermal and mechanical properties, equilibrium swelling rate (ESR), water uptake (WU), and mass cross-linking degree of the hydrogels were assessed. Furthermore, the diffusion behavior of water molecules in the freeze-dried GEH was investigated. The experimental results showed the significance of the initial decomposition temperature (Ti) and final decomposition temperature (Tf) of the freeze-dried GEHs in determining the effective cross-linking density. The water uptake kinetics of the freeze-dried GEH was consistent with the linear fitting of the pseudo-second-order kinetic model and nonlinear fitting of the Fickian diffusion model, suggesting that chemisorption dominated the water absorption process in the GEH. Therefore, the effective cross-linking density of the hydrogels could be determined from the thermodynamic analysis and the diffusive behavior of water molecules in the gels. The thermal stability and water diffusion kinetics of the hydrogels were closely linked to the effective cross-linking density and pendant modification.

Effect of relativistic ponderomotive force on shock waves in a relativistic degenerate plasma

Abstract We investigate the effect of relativistic ponderomotive force on the propagation of shock waves in relativistic degenerate plasma, which is relevant to high-intensity laser-plasma experiments aimed at replicating extreme conditions on white dwarfs. We derive the KdV-Burger’s equation by incorporating the density modification induced by the ponderomotive force and hence demonstrate that this equation is a suitable model for shock waves affected by ponderomotive force. Unlike previous studies that use ponderomotive force as a source of nonlinearity to derive the nonlinear Schrödinger equation for envelope solitons, our study focuses on the effect of ponderomotive force on shocks produced by the intense laser. We show that the ponderomotive force can significantly modify the strength and shape of shock waves, providing insight into the underlying physics of shock waves in relativistic degenerate plasmas which may help to better understand experimental observations in this regime.

Lightweight cement pastes with hollow glass microspheres: Analytical estimation of elastic parameters

An analytical model is presented for estimation of the elastic parameters of lightweight cement pastes with hollow glass microspheres (HGMS). The microspheres consist of a siliceous spherical outer shell filled with gas, providing a density modification agent for the cement paste. The obtained lightweight cement paste is used for cementing deep wells where it is necessary to guarantee the integrity of the cement sheath to avoid fluid migration, contain the rock mass and protect the casing. The proposed micromechanical model, compared to other alternatives, results in an easy-to-use approach for obtaining an estimation of the elastic parameters of the HGMS lightweight cement. The elastic parameters are necessary for the design of the cement sheath and the analysis of its performances. The model input parameters are the elastic parameters of the cement matrix and the microspheres, as well as microspheres dimensions and volume fraction, which are easy to obtain. The model predictions are compared to experimentally evaluated elastic parameters of lightweight cement pastes. A good compatibility between predictions and experimental data is obtained, even when assuming a perfectly bounded interface between the microspheres and the cement matrix.The model also permits to take into account an imperfect interface between the microspheres and the cement matrix improving the model predictions with respect to the experimental results. The model presents an engineering tool to design lightweight cement slurries with hollow microspheres and to estimate their mechanical contribution to a cement sheath for drilling operations.

Direct phasing algorithm for protein crystals with high solvent content using low-resolution diffraction data.

Over the past decade, iterative projection algorithms, an effective approach to recovering phases from a single intensity measurement, have found application in protein crystallography to directly surmount the `phase problem'. However, previous studies have always assumed that some prior knowledge constraints (i.e. a low-resolution envelope about the protein structure in the crystal cell or histogram matching requiring a similar density distribution to the target crystal) must be known for successful phase retrieval, thus hindering its widespread application. In this study, a novel phase-retrieval workflow is proposed that eliminates the need for a reference density distribution by utilizing low-resolution diffraction data in phasing algorithms. The approach involves randomly assigning one out of 12 possible phases at 30° intervals (or two for centric reflections) to produce an initial envelope, which is then refined through density modification after each run of phase retrieval. To evaluate the success of the phase-retrieval procedure, information entropy is introduced as a new metric. This approach was validated using ten protein structures with high solvent content, demonstrating its effectiveness and robustness.

Effects of Grafting Structure on 1D One-Component Composites: An Example of Surface-Grafted Cellulose Nanofibers

This investigation explores the relationships between the structure and properties of surface-grafted cellulose nanofiber (CNF)-based one-component composites. Critical parameters, including graft density, graft chain length, and interface structure, were systematically modified. Increasing the graft density and hydrophobic modification of the CNF surface significantly improved the thermal stability. Reducing the graft chain length increased the Tg of the graft chain. The hydrophobic modification of the CNF surface decreased the Tg of the graft chains, while increasing the graft chain length resulted in a reduction in the stiffness. Conversely, decreasing the graft density led to a remarkable enhancement in the toughness and strength of the nanocomposites. The hydrophobically modified nanocomposites exhibited a decrease in modulus and an increase in elasticity. These results highlight the significant role of interfacial interaction between CNF and the grafted polymer, which is equally crucial as the graft density in determining the properties of these composites.

Improving the Accuracy of Seafloor Topography Inversion Based on a Variable Density and Topography Constraint Combined Modification Method

The use of satellite altimetry to recover marine gravity anomalies allows for the rapid acquisition of seafloor topography on a wide range of regional scales. Currently, the commonly used approaches for inverting seafloor topography have been focused on the linear correlation between gravity anomalies and seafloor topography and have disregarded the effect of density contrast between the crust and seawater on depth. Therefore, we proposed a variable density and topography constraint combined modification (VDTCCM) method by deriving Parker’s formula and the Bouguer plate formula by introducing variable density and topography factors. This method can effectively recover topography-related nonlinear terms of gravity anomalies. Subsequently, the seafloor topography of the South China Sea was estimated by applying the VDTCCM method and was defined as Seafloor topography one (ST1), and following, the accuracy was evaluated using shipborne sounding data (SSD). The results indicate that the ST1 model’s SSD-checked accuracy is 23.34% and 39.42% higher than the common international models of ETOPO1 and DTU10, respectively. Moreover, the ST1 model has advantages in mapping rugged areas, showing more detailed topographical features. Consequently, the VDTCCM method can provide beneficial references for the construction of seafloor topography models on a large regional scale using gravity anomalies recovered from satellite altimetry.