Spatial Density Distribution Research Articles

The spatiotemporal evolution of monogenetic scoria cones in the Paricutin-Tancítaro region, Mexico: Results from a Morpho-chronological analysis and its consequences on the distributed volcanic hazard

The Paricutin-Tancítaro region (PTR) within the Michoacán-Guanajuato monogenetic Volcanic Field (MGVF) is characterized by a large stratovolcano, Tancítaro enclosed in a dense distribution of monogenetic volcanoes, mainly scoria cones, that includes the well-known Paricutin. The succession of seismic swarms beginning 54 years after the birth of Paricutin in 1943 represents a challenge for apprising the region's volcanic and seismic hazards. In this work, we introduce a novel methodology to assess the spatiotemporal evolution of the monogenetic scoria cones and the distributed volcanic hazards. We first performed a morpho-chronometric analysis of 171 scoria cones to estimate their relative ages, which revealed an increasing trend in the rate of monogenetic eruptions over the last 120 kyr, especially in the last 20 kyr, with a current mean waiting interval between monogenetic eruptions of only 120 yr. In a second step, we estimate the spatiotemporal evolution of monogenetic volcanic activity in PTR using a Voronoi tessellation to represent the spatial density distribution of scoria cone emplacement through time to detect dynamic shifts in volcanic activity locations in the region. This approach thus reveals spatial dynamic patterns in the rates of monogenetic eruptions over time. Subsequently, a Poisson process is assumed to estimate the spatially distributed cone-forming eruption probabilities based on the morpho-chronometrically analyzed cones. Remarkably, a high spatial correlation was found between the areas with the highest probabilities and the location of the recent seismic swarms recorded in the PTR.

Efficient Proton Transfer and Charge Separation within Covalent Organic Frameworks via Hydrogen-Bonding Network to Boost H2O2 Photosynthesis.

Photocatalytic synthesis based on the oxygen reduction reaction (ORR) has shown great promise for H2O2 production. However, the low activity and selectivity of 2e- ORR result in a fairly low efficiency of H2O2 production. Herein, we propose a strategy to enhance the proton-coupled electron transfer (PCET) process in covalent organic frameworks (COFs), thereby significantly boosting H2O2 photosynthesis. We demonstrated that the construction of a hydrogen-bonding network, achieved by anchoring the H3PO4 molecular network on COF nanochannels, can greatly improve both proton conductivity and photogenerated charge separation efficiency of COFs. Thus, COF@H3PO4 exhibited superior photocatalytic performance in generating H2O2 without sacrificial agents, with a solar-to-chemical conversion efficiency as high as 0.69%. Results indicated that a much more localized spatial distribution of energy band charge density on COF@H3PO4 led to efficient charge separation, and the small energy barrier of the rate-limiting step from *OOH to H2O2 endowed COF@H3PO4 with higher 2e- ORR selectivity.

Lagrangian characterization of the southwestern Atlantic from a dense surface drifter deployment

The Southwestern Atlantic (SWA) is characterized by its large Eddy Kinetic Energy as the result of the confluence of two major western boundary currents, the northward flowing Malvinas Current (MC) and the southward flowing Brazil Current. The SWA study was addressed in the literature based on altimetry data, in situ measurements, regional models and ocean reanalysis. The present study constitutes the first effort to sample a portion of the SWA, with a dense drifter array (N = 62) deployment. The drifters, drogued at 15 m depths, were deployed across the MC and the Argentine Continental Shelf along two zonal transects located at 47°S and 47.25°S, between the 8th and the September 9, 2021. Drifters were set to deliver their position every 10 and 60 min, providing accurate Lagrangian trajectories that provide information on a large range of space and time scales of the surface currents. Three regions are clearly identified based on the analysis of the speed of the drifters, of their trajectories and of the spectral density of their velocities: the continental shelf, the slope and the open ocean. The comparison of the trajectories of the drifters with satellite altimetry images shows that, in general, drifters follow mesoscale features that are detectable in satellite altimetry maps. The analysis of the drifter trajectories also allowed us the study of submesoscale features of the flow (1–10 km) that are not observable in satellite altimetry data. Comparison with cloud-free, high-resolution color images, shows that drifter trajectories organized by the mesoscale flow might also locally follow sub-mesoscale features. In frontal regions it was found that drifter velocities double satellite altimetry geostrophic velocities, which suggests that the dynamics at those regions is largely dominated by ageostrophic components. The ageostrophic Ekman component might explain the direction of the drifters when strong winds from a given direction prevail for several days and the drifters are not in a region with large sea surface height (SSH) gradients. The joint analysis of drifters’ trajectory and SSH clearly depicts that mesoscale features on the open ocean region control the cross-shelf exchanges between the MC and open ocean regions as well as the strength and width of the MC. Finally, the spatial density distribution of the drifters during the first hours after deployment and within a small eddy also allowed us to characterize the flow in terms of its divergence, vorticity and strain, indicating that the MC is geostrophic and has a jet-like behavior while the eddy is largely ageostrophic and has a dominant vorticity component over strain. We conclude observing that the analysis of a dense array of drifters provides valuable information of the flow that cannot be attained solely based on satellite data.

Efficient computational modeling of electronic stopping power of organic polymers for proton therapy optimization

This comprehensive study delves into the intricate interplay between protons and organic polymers, offering insights into proton therapy in cancer treatment. Focusing on the influence of the spatial electron density distribution on stopping power estimates, we employed real-time time-dependent density functional theory coupled with the Penn method. Surprisingly, the assumption of electron density homogeneity in polymers is fundamentally flawed, resulting in an overestimation of stopping power values at energies below 2 MeV. Moreover, the Bragg rule application in specific compounds exhibited significant deviations from experimental data around the stopping maximum, challenging established norms.

A theoretical study of the signal enhancement mechanism of coaxial DP-LIBS

In the field of dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) research, the pursuit of methods for determining pulse intervals and other parameters quickly and conveniently in order to achieve optimal spectral signal enhancement is paramount. To aid researchers in identification of optimal signal enhancement conditions and more accurate interpretation of the underlying signal enhancement mechanisms, theoretical simulations of the spatiotemporal processes of coaxial DP-LIBS-induced plasma have been established in this work. Using a model based on laser ablation and two-dimensional axisymmetric fluid dynamics, plasma evolutions during aluminum–magnesium alloy laser ablation under single-pulse and coaxial dual-pulse excitations have been simulated. The influences of factors, such as delay time, laser fluence, plasma temperature, and particle number density, on the DP-LIBS spectral signals are investigated. Under pulse intervals ranging from 50 to 1500 ns, the time evolutions of spectral line intensity, dual-pulse emission enhancement relative to the single-pulse results, laser irradiance, spatial distribution of plasma temperature and species number density, as well as laser irradiance shielded by plasma have been obtained. The study indicates that the main reason behind the radiation signal enhancement in coaxial DP-LIBS-induced plasma is attributed to the increased species number density and plasma temperature caused by the second laser, and it is inferred that the shielding effect of the plasma mainly occurs in the boundary layer of the stagnation point flow over the target surface. This research provides a theoretical basis for experimental research, parameter optimization, and signal enhancement tracing in DP-LIBS.

Computation of the Spatial Distribution of Charge-Carrier Density in Disordered Media.

The space- and temperature-dependent electron distribution n(r,T) determines optoelectronic properties of disordered semiconductors. It is a challenging task to get access to n(r,T) in random potentials, while avoiding the time-consuming numerical solution of the Schrödinger equation. We present several numerical techniques targeted to fulfill this task. For a degenerate system with Fermi statistics, a numerical approach based on a matrix inversion and one based on a system of linear equations are developed. For a non-degenerate system with Boltzmann statistics, a numerical technique based on a universal low-pass filter and one based on random wave functions are introduced. The high accuracy of the approximate calculations are checked by comparison with the exact quantum-mechanical solutions.

Spatial variation of guanaco (Lama guanicoe) densities influenced by natural and anthropogenic variables in Southern Andean Precordillera (Argentina)

ABSTRACT The spatial distribution of ungulate densities is determined by their decisions on habitat selection, modulated by environmental characteristics and human activities. Poaching and habitat degradation are threats to the guanaco, a native herbivore of arid environments of South America. Seasonal surveys of guanacos were carried out during two independent years in mountain environments of Andean Precordillera, inside a protected area and surroundings. Field surveys and GIS analyses estimated environmental variables. Density surface models estimated spatial distribution of guanacos, based on predictions about food availability, weather, risk perception, and human activities. The current distribution of densities is mainly influenced by the availability of preferred food and water, and protection effectiveness. Twelve years ago, disturbing human activities were also relevant. High densities in great altitudes yearlong, and a winter expansion through lower altitudes, are evidence of partial migrations, related to climatic events and food declines. Selective use of Puna grasslands and association with wetlands agree with food and risk predictions. Greater densities inside than outside the protected area, and decreasing guanaco–observer distances, are evidence of continued effective protection. Density surface modeling, applied to multi-year distance sampling, highlights as a useful tool for understanding the spatial dynamics of guanaco populations, and aiding management decisions.

Prediction of viral spillover risk based on the mass action principle

Infectious zoonotic disease emergence, through spillover events, is of global concern and has the potential to cause significant harm to society, as recently demonstrated by COVID-19. More than 70% of the 400 infectious diseases that emerged in the past five decades have a zoonotic origin, including all recent pandemics. There have been several approaches used to predict the risk of spillover through some of the known or suspected infectious disease emergence drivers, largely using correlative approaches. Here, we predict the spatial distribution of spillover risk by approximating general transmission through animal and human interactions. These mass action interactions are approximated through the multiplication of the spatial distribution of zoonotic virus diversity and human population density. Although our results indicate higher risk in regions along the equator and in Southeast Asia where both virus diversity and human population density are high, it should be noted that this is primarily a conceptual exercise. We compared our spillover risk map to key factors, including the model inputs of zoonotic virus diversity estimate map, human population density map, and the spatial distribution of species richness. Despite the limitations of this approach, this viral spillover map is a step towards developing a more comprehensive spillover risk prediction system to inform global monitoring.

Critical Temperature and Critical Current Enhancement in Arrays of Josephson Junctions: A Ginzburg–Landau Perspective

The present investigation explores the spatial distribution of Cooper pair density in graph-shaped arrays of Josephson junctions using a Ginzburg–Landau approach. We specifically investigate double-comb structures and compare their properties with linear arrays as reference systems. Our findings reveal that the peculiar connectivity of the double-comb structure leads to spatial gradients in the order parameter, which can be readily detected through measurements of Josephson critical currents. We present experimental results which indicate the specific dependence of the order parameter on the branches of the graphs and are evidence of the theoretical predictions.

An incoherent Thomson scattering system for measurements near plasma boundaries.

Laser Thomson scattering (LTS) is a minimally invasive measurement technique used for determining electron properties in plasma systems. Sheath model closure validation requires minimally invasive measurements of the electron properties that traverse the boundaries between the bulk plasma, the presheath, and the plasma sheath. Several studies have probed the radial properties along the surface of discharge electrodes with laser-based diagnostics and electrostatic probes. These measurements provide valuable insight into the electron properties in this dynamic region. However, sheath model calibration requires plasma property measurements perpendicular to plasma bounding surfaces, in this case, along the electrode normal vector between discharge electrodes. This work presents the development of a discharge plasma cell and laser Thomson scattering system with a measurement volume step of 1mm normal to plasma bounding surfaces. The laser Thomson scattering measurements are made between a set of discharge electrodes separated by ∼25mm that are used to generate a pulsed argon plasma. The spatial distribution of electron temperature and density is measured at several discharge voltages between 8 and 20kV at a pressure of 8 Torr-Ar. It is determined that the system is statistically stationary and resembles a classic DC discharge plasma. The results are some of the first laser diagnostic-based "between electrode" measurements made along the plasma bounding electrode normal vector. A one-dimensional sheath model is applied to determine the near cathode electron properties, and it is determined that the edge of the presheath is probed in the high-voltage cases. As the lengths of the presheath and sheath decrease with decreasing voltage, the region recedes below the closest probed point to the cathode. To improve the performance of the diagnostic, the step size of the interrogation volume should decrease by an order of magnitude from 1mm to less than 100 μm, and the data acquisition strategy should be revised to increase the signal-to-noise ratio.

Direct observation of the transition from spin waves to the magnon Bose condensate

Bose-Einstein condensation occurs at an appropriate density of bosonic particles, depending on their mass and temperature. The transition from the semiclassical paradigm of spin waves to the magnon Bose-Einstein condensed state (mBEC) was obtained experimentally with increasing magnon density. We used the Faraday rotation effect to study the spatial distribution of the magnon density and phase far from their excitation region. A coherent magnetization precession was observed throughout the sample, which indicates the formation of a magnon BEC. It is shown that this result under experimental conditions goes beyond the applicability of the Landau-Lifshitz-Gilbert semiclassical theory.

A lift-off measurement and compensation method based on a comprehensive EMAT-PEC probe

In the field of industrial testing, lift-off fluctuations of the probe are inevitable, leading to unstable signals and inconsistent detection results, especially in electromagnetic acoustic transducer (EMAT). Besides, EMAT has a low energy utilization, since the induced pulsed eddy current (PEC) is not fully utilized during the transduction process. To address these issues, this paper proposes a novel composite detection method which is able to measure the lift-off based on PEC and compensate for the lift-off effect on EMAT using a designed comprehensive EMAT-PEC probe. A finite element (FE) model of the EMAT consisting of a permanent magnet and a type of butterfly coil is established, and the spatial distribution of the PEC density induced by the butterfly coil is analyzed. Based on this, comparison of the effectiveness among different EMAT-PEC probe configurations for lift-off detection is implemented, and an optimal EMAT-PEC probe with a compact structure is designed. This probe is capable of obtaining both EMAT signal and PEC signal synchronously through a single excitation, ensuring the accuracy and efficiency of the compensation process. The blind test is then performed to simulate the random lift-off fluctuation, and the experimental results demonstrate that the relative errors of the measured lift-off and the compensated peak amplitudes of EMAT signals are all less than 7%, verifying the effectiveness of the method. For industrial applications, based on the developed method, a probe array with different lift-off combinations is designed to simplify the calibration process, and an application in probe inclination detection is introduced, proving the method has good application foreground.

CyTRACK: An open-source and user-friendly python toolbox for detecting and tracking cyclones

This work introduces CyTRACK (Cyclone TRACKing framework), a new open-source, comprehensive and user-friendly Python toolbox for detecting and tracking cyclones in model and reanalysis datasets. The kernel of CyTRACK is based on detecting critical cyclone centres in the mean sea level pressure field at a single time slice, which are then filtered following several threshold parameters. This paper also compares ten years of CyTRACK outputs forced with the ERA5 reanalysis against best-track archives and available cyclones track datasets. The results reveal that CyTRACK can capture the inter-annual (year to year) and intra annual (seasonal cycle) variability of cyclone frequency, life cycle characteristics and spatial distribution of track densities. Largest differences were observed in the annual and seasonal frequency. In summary, CyTRACK provides a user-friendly framework for sensitivity analysis of several free parameters used to perform the tracking, and it is useful for case or climatological studies of cyclone features.

Analyzing Role of FSI in City Sprawl- Case Study: Pune City

Pune is the second-largest city in the state of Maharashtra after Mumbai, and is an important city in terms of its economic and industrial growth. Over the years Pune Municipal Corporation area has grown in concentric rings. Future growth of PMC will be mainly governed by existing transport corridors, existing and future industrial developments in and around PMC and the expansion of central business district (CBD). The aim of the research is to analyze role of FSI in city sprawl supported with a case study of Pune City. The objectives of the research are- to assess existing and proposed policies/projects undertaken in Pune City for last two decades, to understand population growth trend and its distribution within and around the city, to analyze factors contributing to intensification and spatial distribution of population density, to examine the effects of increased population density on the existing infrastructure facilities in the urban settlements and lastly to propose strategies or proposals for the selected study area. The methodology adopted for the study initiates with assessing the data collected from secondary sources. The increase in population and built-up area attributed to various factors are studied using satellite images and GIS techniques. Population and built-up density can be linked up together to understand how the former growth affects the latter. The distribution and pattern of population density helps to provide useful information in provision of necessary service infrastructure. Finally, different approaches of accommodating the future population are studied and proposed in the study. Keywords Urban sprawl; Density; Spatial Distribution; Accessibility; Urban Growth

Electric-field-driven ferromagnetic response in Janus MnReX3 (X = Se, S) monolayer via asymmetric interface orbital hybridization

Abstract Regulating spin-related electronic structures of two dimensional (2D) materials by an external electric field plays a substantial role in achieving spintronic and multistate information storage. However, electric-field-dependent ferromagnetic behavior at atomic-thick 2D materials is very difficult to be realized due to their intrinsic inversion symmetry, in which the symmetric spatial distribution of charge density makes it become insensitive to spontaneous polarization from external electric field. Herein, a new-type Janus MnReX3 (X = Se, S) monolayer with noncentrosymmetric configuration in which their orbital hybridization at internal interface can be engineered by rearranging the spatial symmetry of out-of-plane charge density. As a result, the spin exchange interaction among magnetic sites can be regulated by the electric-field-driven charge density redistribution, leading to a controllable ferromagnetic behavior at room temperature. Our results not only suggest a promising strategy to regulate the ferromagnetic response by reducing the crystal symmetry, but also provide a new insight into designing 2D magnetic materials.

Prediction and effectiveness study of fracture distribution based on an artificial neural network technology and production performance data detection method: a case study of Ordovician carbonate formation in the Tahe oilfield, Tarim Basin

To solve the difficulty of predicting the spatial distribution of fracture linear density and clarify the controlling influence of tectonic factors on the effectiveness of fractures. This article combines core, conventional logging, imaging logging, and 3D seismic volume data and uses artificial intelligence neural network technology combined with the sequential Gaussian method to establish a linear density volume prediction model for fractures in the study area. In addition, production dynamic data are applied to verify the effectiveness of the fractures. The results show that the artificial intelligence neural network technique is highly applicable with an accuracy of up to 76.8% in predicting the fracture linear density. The fracture linear density is controlled by tectonic activity, and the fracture linear density increases sharply in the areas adjacent to the main faults, the fracture superposition site, and the intersection site of multiple faults, with the fracture linear density reaching 8.65 fractures per meter in study areas. The effective distance of fracture connectivity is mostly concentrated between 550 and 670 m. When the difference in fracture density along the structural ridge is between 2 and 4 fractures/meter, the effectiveness of the fractures is strong.

Linkage between Granite Weathering and Gully Erosion in Subtropical Region

Granites, widely distributed in the Earth’s crust, undergo pedogenic processes, shaping diverse soil-mantled landscapes influenced by climatic factors in different regions. Investigating the geochemical signatures in granite weathering profiles across varying climatic conditions provides valuable insights into the intricate interplay between weathering and landscape evolution. In this study, the geochemical features, particularly major and rare earth elements, and the weathering degree of granites across temperate to subtropical regions in China were examined. The results indicated significant variations in the geochemical characteristics of granite weathering profiles, both at a pedon and regional scale (p < 0.01). With increasing hydrothermal conditions from north to south, soil pH shifted from neutral to acidic, accompanied by the leaching of major elements (K2O, Na2O, CaO, and MgO) and the enrichment of Al and Fe. The total rare earth elements (∑REEs) ranged from 75 to 352 ppm, and light rare earth elements (LREEs) from 71 to 317 ppm, exhibiting less significant variations across the study area, while heavy rare earth elements (HREEs) showed higher concentrations in the subtropical region (3 to 35 ppm). Plagioclases dominated the weathering process in temperate regions, with K-feldspar progressively increasing and, eventually, dominating from temperate to subtropic regions, resulting in a shift in clay minerals from 2:1-type in the temperate to 1:1-type in the subtropic. The chemical index of alteration (CIA) and comprehensive weathering index (W) increased from fresh rock to residual soils along the weathering profiles and from north to south across the study area, ranging from 50.72 to 97.44 and 35.11 to 70.62, respectively. The intensified granite weathering degree was significantly influenced by climatic conditions (p < 0.05), especially the multi-year average precipitation (22.4%) and relative humidity (9.1%) (p < 0.01). Gully erosion on the granite weathering mantle was concentrated in granites with a comprehensive weathering index exceeding 52.51, and the spatial variation of the granite weathering degree aligned with the spatial distribution of gully density across the study area.

Interferometer study of radial and axial density evolution and temperature in N2 gas subjected to negative and positive corona discharges

In the present paper, we propose to make an optical diagnosis by laser interferometry to determine experimentally the density of neutral particles in a coronal discharge bathing in a gaseous medium N2. We are particularly interested in the measurement of variation of the optical path and therefore of the index of refraction which allows us to highlight the variation of the density of the neutrals in the discharge, and using a computer treatment (Pearce method) the refractive index of the medium is calculated to determine the spatial distribution of density and temperature (radial and axial) at the core of the corona discharge in two different situations (positive and negative). This optical diagnosis also allowed us to quantitatively determine the phenomenon of depopulation of neutral particles. These quantitative and experimental results are interesting because they allow a good correlation between the theoretical results obtained so far

Observational features of charge distribution in Earth’s inner magnetosphere

Understanding the motion of charged particles in the electromagnetic field in the inner magnetosphere is essential for space science and space weather. Charge accumulation can occur due to the dipole magnetic and convective electric fields in this region. However, until the recent Magnetospheric Multiscale (MMS) mission, there were few means to detect charge distribution in situ. We report unambiguous in situ observation of the spatial distribution of the excess charge density in the inner magnetosphere by the MMS mission. We find that a positive (negative) charge accumulates in the dusk (dawn) side inner magnetospheres, which is contrary to the long assumed overall quasi-neutrality of space plasma. These observations and results offer insight into magnetosphere–ionosphere coupling.

Optical properties and exciton transfer between N-heterocyclic carbene iridium(III) complexes for blue light-emitting diode applications from first principles.

N-heterocyclic carbene (NHC) iridium(III) complexes are considered as promising candidates for blue emitters in organic light-emitting diodes. They can play the roles of the emitter as well as of electron and hole transporters in the same emission layer. We investigate optical transitions in such complexes with account of geometry and electronic structure changes upon excitation or charging and exciton transfer between the complexes from first principles. It is shown that excitation of NHC iridium complexes is accompanied by a large reorganization energy ∼0.7eV and a significant loss in the oscillator strength, which should lead to low exciton diffusion. Calculations with account of spin-orbit coupling reveal a small singlet-triplet splitting ∼0.1eV, whereas the oscillator strength for triplet excitations is found to be an order of magnitude smaller than for the singlet ones. The contributions of the Förster and Dexter mechanisms are analyzed via the explicit integration of transition densities. It is shown that for typical distances between emitter complexes in the emission layer, the contribution of the Dexter mechanism should be negligible compared to the Förster mechanism. At the same time, the ideal dipole approximation, although giving the correct order of the exciton coupling, fails to reproduce the result taking into account spatial distribution of the transition density. For charged NHC complexes, we find a number of optical transitions close to the emission peak of the blue emitter with high exciton transfer rates that can be responsible for exciton-polaron quenching. The nature of these transitions is analyzed.