Vertical Gradient Research Articles

Near-natural streams: spatial factors are key in shaping multiple facets of zooplankton α and β diversity.

In near-natural basins, zooplankton are key hubs for maintaining aquatic food webs and organic matter cycles. However, the spatial patterns and drivers of zooplankton in streams are poorly understood. This study registered 165 species of zooplankton from 147 sampling sites (Protozoa, Rotifers, Cladocera and Copepods), integrating multiple dimensions (i.e., taxonomic, functional, and phylogenetic) and components (i.e., total, turnover, and nestedness) of α and β diversity. This study aims to reveal spatial patterns, mechanisms, correlations, and relative contribution of abiotic factors (i.e., local environment, geo-climatic, land use, and spatial factors) through spatial interpolation (ordinary kriging), mantal test, and analysis of variance (VPA). The study found that α diversity is concentrated in the north, while β diversity is more in the west, which may be affected by typical habitat, hydrological dynamics and underlying mechanisms. Taxonomic and phylogenetic β diversity is dominated by turnover, and metacommunity heterogeneity is the result of substitution of species and phylogeny along environmental spatial gradients. Taxonomic and phylogenetic β diversity were strongly correlated (r from 0.91 to 0.95), mainly explained by historical/spatial isolation processes, community composition, generation time, and reproductive characteristics, and this correlation provides surrogate information for freshwater conservation priorities. In addition, spatial factors affect functional and phylogenetic α diversity (26%, 28%), and environmental filtering and spatial processes combine to drive taxonomic α diversity (10%) and phylogenetic β diversity (11%). Studies suggest that spatial factors are key to controlling the community structure of zooplankton assemblages in near-natural streams, and that the relative role of localized environments may depend on the dispersal capacity of species. In terms of diversity conservation, sites with high variation in uniqueness should be protected (i) with a focus on the western part of the thousand islands lake catchment and (ii) increasing effective dispersal between communities to facilitate genetic and food chain transmission.

Unlocking the biosynthetic potential and taxonomy of the Antarctic microbiome along temporal and spatial gradients.

Extreme environments, such as Antarctica, select microbial communities that display a range of evolutionary strategies to survive and thrive under harsh environmental conditions. These include a diversity of specialized metabolites, which have the potential to be a source for new natural product discovery. Efforts using (meta)genome mining approaches to identify and understand biosynthetic gene clusters in Antarctica are still scarce, and the extent of their diversity and distribution patterns in the environment have yet to be discovered. Herein, we investigated the biosynthetic gene diversity of the biofilm microbial community of Whalers Bay, Deception Island, in the Antarctic Peninsula and revealed its distribution patterns along spatial and temporal gradients by applying metagenome mining approaches and multivariable analysis. The results showed that the Whalers Bay microbial community harbors a great diversity of biosynthetic gene clusters distributed into seven classes, with terpene being the most abundant. The phyla Proteobacteria and Bacteroidota were the most abundant in the microbial community and contributed significantly to the biosynthetic gene abundances in Whalers Bay. Furthermore, the results highlighted a significant correlation between the distribution of biosynthetic genes and taxonomic diversity, emphasizing the intricate interplay between microbial taxonomy and their potential for specialized metabolite production.IMPORTANCEThis research on antarctic microbial biosynthetic diversity in Whalers Bay, Deception Island, unveils the hidden potential of extreme environments for natural product discovery. By employing metagenomic techniques, the research highlights the extensive diversity of biosynthetic gene clusters and identifies key microbial phyla, Proteobacteria and Bacteroidota, as significant contributors. The correlation between taxonomic diversity and biosynthetic gene distribution underscores the intricate interplay governing specialized metabolite production. These findings are crucial for understanding microbial adaptation in extreme environments and hold significant implications for bioprospecting initiatives. The study opens avenues for discovering novel bioactive compounds with potential applications in medicine and industry, emphasizing the importance of preserving and exploring these polyextreme ecosystems to advance biotechnological and pharmaceutical research.

Structure and maintenance of a quasi-linear mesoscale convective system that caused torrential rain in southern Kyushu, Japan on 11 July 2021

Abstract A quasi-linear mesoscale convective system that remained nearly stationary (hereafter referred to as a stationary QLCS) for almost 8 h in southern Kyushu, Japan, caused torrential rainfall exceeding 350 mm on 11 July 2021. The stationary QLCS consisted of several rainbands organized by back-building convection. As the cold pool intensified, the system attained a more widespread structure, leaning on the upshear side. To elucidate the mechanism responsible for the upshear tilt, numerical simulations with 250-m horizontal grid spacing were conducted, including sensitivity experiments in which the evaporative cooling rates from rain were reduced to modify the cold pool intensity. Results show that the cold pool is critical to the organization of the QLCS, and the structure normal to it is mainly governed by the balance between the low-level shear magnitude and cold pool intensity, supporting the application of so-called Rotunno-Klemp-Weisman (RKW) theory to this event. The cause of the weak updraft that accompanies the leaning system over the strong cold pool was also investigated, analyzing the trajectories, vertical momentum equation, and pressure perturbation field using the anelastic equation. It is revealed that the updraft travels a longer distance through the tilted system experiencing more mixing with the ambient air, which results in less thermal buoyancy. In addition, the updraft is decelerated by the downward perturbation gradient force owing to the vertical buoyancy gradient around the sloping surface of the cold pool and the dynamical effect caused by the baroclinity-associated strong horizontal vorticity around the cold pool leading edge.

Design rules for controlling active topological defects

Topological defects play a central role in the physics of many materials, including magnets, superconductors, and liquid crystals. In active fluids, defects become autonomous particles that spontaneously propel from internal active stresses and drive chaotic flows stirring the fluid. The intimate connection between defect textures and active flow suggests that properties of active materials can be engineered by controlling defects, but design principles for their spatiotemporal control remain elusive. Here, we propose a symmetry-based additive strategy for using elementary activity patterns, as active topological tweezers, to create, move, and braid such defects. By combining theory and simulations, we demonstrate how, at the collective level, spatial activity gradients act like electric fields which, when strong enough, induce an inverted topological polarization of defects, akin to a negative susceptibility dielectric. We harness this feature in a dynamic setting to collectively pattern and transport interacting active defects. Our work establishes an additive framework to sculpt flows and manipulate active defects in both space and time, paving the way to design programmable active and living materials for transport, memory, and logic.

Simplification of Electrode Profiles for Piezoelectric Modal Sensors by Controlling Gap-Phase Length

This paper presents a method to optimize and simplify the electrode profile of a piezoelectric modal sensor. At the same time that the electrode profile is optimized to maximize the charge, a null-polarity phase is introduced. This gap-phase is modeled using the normalized norm of the spatial gradient of the polarity profile along with a two-step filtering and projection technique. High-order vibration modes generate a complex polarization profile that makes the manufacturing process difficult. The novelty of the proposed method is the addition of a constraint on the length of the interface in the topology optimization problem. This constraint simplifies the optimal designs and facilitates the fabrication process. Several examples show the simplified electrode profile that maximizes the electrical charge produced by a vibration mode, while reducing the number of different polarization regions by means of the gap-length constraint.

Spatiotemporal Patterns of White Matter Maturation after Pre-Adolescence: A Diffusion Kurtosis Imaging Study

Spatiotemporal Patterns of White Matter Maturation after Pre-Adolescence: A Diffusion Kurtosis Imaging Study

Variation in fern species richness, assemblages and morphology along a tropical riparian humidity gradient: an example from Borneo

ABSTRACT Riparian vegetation experiences a little spatial distance humidity gradient, especially in the hyper-humid tropics. In Borneo, with almost no seasons and rather constant local climatic conditions, the riparian plant species show a wide range of morphological and physiological adaptations. This study assesses the adaptation strategies of ferns along a riparian humidity gradient in the submontane forest of Sarawak, Malaysia (Borneo). The species richness and cover, morphological traits, leaf area, leaf perimeter, leaf dissection, leaf elongation ratio, and stomatal density of 63 fern species were surveyed in six study areas along six stream transects. Significant trends in species richness and species cover were identified along the six transects, and changes in morphological traits such as leaf area, leaf perimeter, and leaf dissection were also discovered. With increasing distance from the streams (i.e. decreasing humidity), ferns tended to show longer leaves and a lower stomatal density. We conclude that the morphological traits of fronds change significantly within a short tropical riparian humidity gradient. This reveals variations in the energy investment and adaptation efficiency of ferns within a tropical forest microsite.

An improved model for discrete element method simulation of spatial gradient distributions of freeze-thaw-induced damage to sandstone

The investigation into the freeze-thaw (F-T) damage holds paramount theoretical significance in comprehending the mechanisms underlying F-T disasters, predicting catastrophes, and devising engineering protection systems. F-T damage in rock evolves progressively from the surface towards the interior, however, current models exhibit conspicuous deficiencies in simulating such progressive damage. Drawing upon experimental findings concerning the evolution of F-T damage in water-saturated rock, an improved discrete element model (DEM) for rock F-T damage is developed. In this model, thermal conduction model and volume expansion theory are integrated to describe the volumetric expansion characteristics during the freezing of internal pore water, thus effectively simulating the initiation and progression characteristics of frost heave cracks. We validated this model through comparisons with theoretical analyses and experiments, exploring the effects of model parameters. Employing moment tensor, the spatial gradient distribution patterns of F-T damage in water-saturated rock from the vantage point of fracture energy was analyzed. The results reveal that at −20 °C, 20 F-T cycles are requisite for the propagation of damage from the outer layer to the center of the Sichuan sandstone samples. The extent of damage in the outer layer exceeds that of the center, with the maximum fracture energy density of the outer layer being approximately 38.7 times that of the center. This model aptly delineates the progressive development of F-T damage characteristics and holds promise for further applications in identifying and delineating F-T damage zones in cold region rock engineering.

Secondary production of the central rangeland region of the United States.

Rangelands are the dominant land use across a broad swath of central North America where they span a wide gradient, from <350 to >900 mm, in mean annual precipitation. Substantial efforts have examined temporal and spatial variation in aboveground net primary production (ANPP) to precipitation (PPT) across this gradient. In contrast, net secondary productivity (NSP, e.g., primary consumer production) has not been evaluated analogously. However, livestock production, which is a form of NSP or primary consumer production supported by primary production, is the dominant non-cultivated land use and an integral economic driver in these regions. Here, we used long-term (mean length = 19 years) ANPP and NSP data from six research sites across the Central Great Plains with a history of a conservative stocking to determine resource (i.e., PPT)-productivity relationships, NSP sensitivities to dry-year precipitation, and regional trophic efficiencies (e.g., NSP:ANPP ratio). PPT-ANPP relationships were linear for both temporal (site-based) and spatial (among site) gradients. The spatial PPT-NSP model revealed that PPT mediated a saturating relationship for NSP as sites became more mesic, a finding that contrasts with many plant-based PPT-ANPP relationships. A saturating response to high growing-season precipitation suggests biogeochemical rather than vegetation growth constraints may govern NSP (i.e., large herbivore production). Differential sensitivity in NSP to dry years demonstrated that the primary consumer production response heightened as sites became more xeric. Although sensitivity generally decreased with increasing precipitation as predicted from known PPT-ANPP relationships, evidence suggests that the dominant species' identity and traits influenced secondary production efficiency. Non-native northern mixed-grass prairie was outperformed by native Central Great Plains rangeland in sensitivity to dry years and efficiency in converting ANPP to NSP. A more comprehensive understanding of the mechanisms leading to differences in producer and consumer responses will require multisite experiments to assess biotic and abiotic determinants of multi-trophic level efficiency and sensitivity.

Rotational disturbance in laser-interferometric gravity gradiometry

Laser interferometers have been used for precise measurements of gravity and related effects. These include experiments to search for a fifth force and absolute ballistic gravimeters, which use a Michelson-type laser interferometer to measure the acceleration of a free-falling test mass. In these methods of instrumentation, the motion of free-falling test masses is measured using corner-cube laser interferometers, in which at least one retroreflector is embedded in each test mass. However carefully each of such test masses is released into free fall, a small amount of rotation is unavoidable which changes the optical path length and causes acceleration disturbance. This rotational disturbance could ultimately limit the measurement sensitivity of the laser interferometers. Various experimental and theoretical studies have been conducted to minimise the rotational disturbance in absolute ballistic gravimeters. This paper focuses on the rotational disturbance in laser-interferometric gravity gradiometers (LIGGs) that measure differential acceleration between two test masses freely falling at different heights in a vacuum. LIGGs can be configured to measure not only vertical gravity gradients, but also horizontal gradients, or gradients in both horizontal and vertical directions. However, only those to measure vertical gravity gradients have been constructed so far. Hence, in this paper, the term LIGGs specifically indicates the gravity gradiometers that measure vertical gravity gradients. Unlike absolute ballistic gravimeters, the LIGGs are, in principle, insensitive to ground vibrations; they can potentially detect some effects that are buried in seismic noise in absolute gravity data. To fully leverage this advantage of the LIGGs, it is crucial to keep the rotational disturbance to a minimum. Expressions for the rotational disturbance are derived and its magnitude is estimated based on available experimental data. The results show that the magnitude would not be more than 0.1 μGal /m in the measurement of vertical gravity gradients in a compact LIGG. Alternative designs and requirements for increasing the sensitivity of the LIGGs are also discussed.

Controllable convex interface shape during vertical gradient freeze (VGF) growth of CdZnTe crystal

A convex growth interface shape is desired but is usually hard to form during the Bridgman process of CdZnTe crystal due to its low thermal conductivity. In this work, the convex interface shape was first analyzed and the mathematical criterion was determined. Theoretical analysis indicates that a convex interface can form when the derivative of axial temperature gradient (∂2T/∂y2) near the interface is negative. The temperature profiles were then proposed according to the theoretical results, and correlative temperature gradient characteristics were presented. The 90 mm diameter CdZnTe crystal has been grown by VGF technique using the proposed temperature profiles. The experimental result shows the interface shape is always convex throughout the entire growth run, which could make a better CdZnTe single-crystalline yield possible.

Spatiotemporal variations and influencing factors of methane emissions from livestock in China: A spatial econometric analysis

In recent years, China has been implementing policies to improve the livestock industry in response to the global trend toward green and low-carbon development. These policies include the establishment of demonstration zones for high-standard agriculture, the relocation of farms to the north, etc. This study aims to investigate the impact of changes in the spatial structure of the livestock industry on methane emissions. It used panel data from 31 provinces in China from 2001 to 2021 and applied the IPCC methodology to quantify methane emissions at both the national and provincial levels. In addition, a spatial econometric model was used to analyze the impact of changes in the spatial structure of the livestock industry on methane emissions. The results show that methane from livestock in China decreased from 13.85 million tons in 2001 to 11.82 million tons in 2021. In addition, methane emissions from livestock in China show a significant spatial gradient and correlation. The Southwest has the highest methane emissions, accounting for 24 % of the total emissions. After controlling for spatial correlation and other factors in the model, it was found that the spatial structure of the livestock industry has a different influence on methane emissions both in the province and in neighboring provinces. To improve methane emission efficiency in the future, policies such as establishing functional zones for livestock farming, strengthening technological innovation and sharing for green development in agriculture, and promoting the optimization of agricultural and rural management structures should be implemented.

Predicting the vertical density structure of oceanic gravity current intrusions

Understanding the dynamics and structures in the deep ocean is one of the remaining challenges in oceanography and climate sciences. We present results from large-scale laboratory experiments of rotating down-slope gravity currents intruding into a two-layer stratified ambient, performed in the largest rotating tank in the world, the Coriolis Rotating Platform in Grenoble. By means of velocity and density measurements, we show that no mixing occurs once the current has detached from the boundary. The shape of the vertical density profile in the stratified receiving ambient enables to identify two distinct regimes: the first issued by laminar transport through Ekman dynamics, the second by turbulent transport due to intermittent dense water cascading. Vertical density gradients reveal a piece-wise linear dependence on the density anomaly for the turbulent transport, suggesting an advection-diffusion process. For the turbulent regime, the scale height is deduced and an analytical model based on the critical Froude number is proposed to predict its value. Results show that the total thickness of the intruding current is on average 2.5 times the scale height. For laminar intrusions the scale height diverges whereas the thickness of the intrusion is a few times the Ekman layer thickness. Comparing the intrusion scale height with its measured vertical extension has led to a criteria to distinguish between laminar and turbulent regimes, which is corroborated by two additional independent criteria, one based on the sign of the local vorticity and the other based on the local maxima of the vertical density gradient. The model allows us to connect laboratory experiments to deep sea observations, gravity currents and Meddies and emphasizes the importance of laboratory experiments in understanding climate dynamics.

Competing Risks for Monomorphic versus Non-Monomorphic Ventricular Arrhythmias in Primary Prevention Implantable Cardioverter Defibrillator Recipients: Global Electrical Heterogeneity and Clinical Outcomes (GEHCO) Study.

Ablation of monomorphic ventricular tachycardia (MMVT) has been shown to reduce shock frequency and improve survival. We aimed to compare cause-specific risk factors of MMVT and polymorphic ventricular tachycardia (PVT)/ventricular fibrillation (VF) and to develop predictive models. The multicenter retrospective cohort study included 2,668 patients (age 63.1±13.0 y; 23% female; 78% white; 43% nonischemic cardiomyopathy, left ventricular ejection fraction 28.2±11.1%). Cox models were adjusted for demographic characteristics, heart failure severity and treatment, device programming, and ECG metrics. Global electrical heterogeneity was measured by spatial QRS-T angle (QRSTa), spatial ventricular gradient elevation (SVGel), azimuth, magnitude (SVGmag), and sum absolute QRST integral (SAIQRST). We compared the out-of-sample performance of the lasso and elastic net for Cox proportional hazards and the Fine-Gray competing risk model. During a median follow-up of 4 years, 359 patients experienced their first sustained MMVT with appropriate ICD therapy, and 129 patients had their first PVT/VF with appropriate ICD shock. The risk of MMVT was associated with wider QRSTa (HR 1.16; 95%CI 1.01-1.34), larger SVGel (HR 1.17; 95%CI 1.05-1.30), and smaller SVGmag (HR 0.74; 95%CI 0.63-0.86) and SAIQRST (HR 0.84; 95%CI 0.71-0.99). The best-performing 3-year competing risk Fine-Gray model for MMVT (ROC(t)AUC 0.728; 95%CI 0.668-0.788) identified high-risk (> 50%) patients with 75% sensitivity, 65% specificity, and PVT/VF prediction model had ROC(t)AUC 0.915 (95%CI 0.868-0.962), both satisfactory calibration. We developed and validated models to predict the competing risks of MMVT or PVT/VF that could inform procedural planning and future RCTs of prophylactic VT ablation.

Neural-Integrated Meshfree (NIM) Method: A differentiable programming-based hybrid solver for computational mechanics

While deep learning and data-driven modeling approaches based on deep neural networks (DNNs) have recently attracted increasing attention for solving partial differential equations, their practical applications to real-world scientific and engineering problems remain limited due to the relatively low accuracy and high computational costs. In this study, we present a differentiable programming-based hybrid meshfree approach within the field of computational mechanics. This approach seamlessly integrates neural network-based deep learning architectures with physics-based meshfree discretization techniques, thus referred to as the neural-integrated meshfree (NIM) method. To effectively approximate the solution, NIM employs a hybrid scheme called NeuroPU approximation, which combines continuous DNN representations with partition of unity (PU) basis functions associated with the underlying spatial discretization. This neural-numerical hybridization not only enhances the solution representation through functional space decomposition but also reduces both the size of DNN model and the need of automatic differentiation for spatial gradient computations, leading to a significant improvement in training efficiency. Under the NIM framework, we propose two truly meshfree solvers: the strong form-based NIM (S-NIM) and the local variational form-based NIM (V-NIM). In the S-NIM solver, the strong-form governing equation is directly considered in the loss function, while the V-NIM solver employs a local Petrov–Galerkin approach that allows the construction of variational residuals based on arbitrary overlapping subdomains. This ensures both the satisfaction of underlying physics and the preservation of the meshfree property. We perform extensive numerical experiments on both stationary and transient benchmark problems to assess the effectiveness of the proposed NIM methods in terms of accuracy, scalability, generalizability, and convergence properties. Moreover, comparative analysis with other physics-informed machine learning methods demonstrates that NIM, especially V-NIM, significantly enhances both accuracy and efficiency in end-to-end predictive capabilities.

Exploring vertical gradients of radio refractivity and their significance for radio wave propagation in Abuja, Jos and Makurdi of North-Central Nigeria

Vertical radio refractivity gradients are essential for monitoring propagation conditions when designing and planning terrestrial radio links for communications in the lower atmosphere. Average data gathered from meteorological factors such as temperature, pressure, and relative humidity was used from 1980 to 2020 n this study. This study focuses on the vertical gradient of radio refractivity within the lower atmospheric layer, investigating its influence on factors like signal propagation, route clearance, and line-of-sight communication. The analysis encompasses three cities - Abuja, Makurdi, and Jos. In Figure 2 monthly average changes in the refractivity gradient are presented for Abuja. In addition, the seasonal radio refractivity gradient shows mean values of -110.000N/km for Abuja which shows that the refractivity condition is Super-Refraction, -77.553N/km for Jos which shows that the refractivity condition is Normal-Refraction and -97.209N/km for Makurdi which shows that the refractivity condition is Normal-Refraction respectively. Higher gradient values, G1, G2, and G3 were observed during the dry season (December-February) which could be attributed to dry air and steeper refractivity gradients. In contrast, lower gradient values were observed during the wet season (June-October) due to increased atmospheric moisture. Similarly, measured vertical radio refractivity gradient data, G1 N/km, G2 N/km, and G3 N/km for Jos displayed consistent fluctuations throughout the year. Similarly, measured vertical radio refractivity gradient data, G1 N/km, G2 N/km, and G3 N/km for Jos displayed consistent fluctuations throughout the year. Notably, wetter months exhibit higher refractivity gradient values, while drier months show lower values. G2 consistently records the highest gradient values, and despite varying magnitudes, the trends remain consistent. Finally, measured vertical radio refractivity gradient data, G1 N/km, G2 N/km, and G3 N/km for Makurdi indicate distinct fluctuations with the most negative values observed in November and December. The Dry Season witnesses relatively lower gradient values, while the Transition and Wet Seasons experience rising values, influenced by atmospheric shifts. The Higher negative values during the wet season suggest pronounced variations in the refractive index, affecting radio wave propagation. These findings emphasize the significance of refractivity gradient variations and their implications for radio wave behaviour particularly during different seasons.

Compositional, Structural, and Biomechanical Properties of Three Different Soft Tissue-Hard Tissue Insertions: A Comparative Review.

Connective tissue attaches to bone across an insertion with spatial gradients in components, microstructure, and biomechanics. Due to regional stress concentrations between two mechanically dissimilar materials, the insertion is vulnerable to mechanical damage during joint movements and difficult to repair completely, which remains a significant clinical challenge. Despite interface stress concentrations, the native insertion physiologically functions as the effective load-transfer device between soft tissue and bone. This review summarizes tendon, ligament, and meniscus insertions cross-sectionally, which is novel in this field. Herein, the similarities and differences between the three kinds of insertions in terms of components, microstructure, and biomechanics are compared in great detail. This review begins with describing the basic components existing in the four zones (original soft tissue, uncalcified fibrocartilage, calcified fibrocartilage, and bone) of each kind of insertion, respectively. It then discusses the microstructure constructed from collagen, glycosaminoglycans (GAGs), minerals and others, which provides key support for the biomechanical properties and affects its physiological functions. Finally, the review continues by describing variations in mechanical properties at the millimeter, micrometer, and nanometer scale, which minimize stress concentrations and control stretch at the insertion. In summary, investigating the contrasts between the three has enlightening significance for future directions of repair strategies of insertion diseases and for bioinspired approaches to effective soft-hard interfaces and other tough and robust materials in medicine and engineering.

Projected poleward migration of the Southern Ocean CO2 sink region under high emissions

The Southern Ocean is a major region of ocean carbon uptake, but its future changes remain uncertain under climate change. Here we show the projected shift in the Southern Ocean CO2 sink using a suite of Earth System Models, revealing changes in the mechanism, position and seasonality of the carbon uptake. The region of dominant CO2 uptake shifts from the Subtropical to the Antarctic region under the high-emission scenario. The warming-driven sea-ice melt, increased ocean stratification, mixed layer shoaling, and a weaker vertical carbon gradient is projected to together reduce the winter de-gassing in the future, which will trigger the switch from mixing-driven outgassing to solubility-driven uptake in the Antarctic region during the winter season. The future Southern Ocean carbon sink will be poleward-shifted, operating in a hybrid mode between biologically-driven summertime and solubility-driven wintertime uptake with further amplification of biologically-driven uptake due to the increasing Revelle Factor.

Impacts of spatial heterogeneity of anthropogenic aerosol emissions in a regionally refined global aerosol–climate model

Abstract. Emissions of anthropogenic aerosol and their precursors are often prescribed in global aerosol models. Most of these emissions are spatially heterogeneous at model grid scales. When remapped from low-resolution data, the spatial heterogeneity in emissions can be lost, leading to large errors in the simulation. It can also cause the conservation problem if non-conservative remapping is used. The default anthropogenic emission treatment in the Energy Exascale Earth System Model (E3SM) is subject to both problems. In this study, we introduce a revised emission treatment for the E3SM Atmosphere Model (EAM) that ensures conservation of mass fluxes and preserves the original emission heterogeneity at the model-resolved grid scale. We assess the error estimates associated with the default emission treatment and the impact of improved heterogeneity and mass conservation in both globally uniform standard-resolution (∼ 165 km) and regionally refined high-resolution (∼ 42 km) simulations. The default treatment incurs significant errors near the surface, particularly over sharp emission gradient zones. Much larger errors are observed in high-resolution simulations. It substantially underestimates the aerosol burden, surface concentration, and aerosol sources over highly polluted regions, while it overestimates these quantities over less-polluted adjacent areas. Large errors can persist at higher elevation for daily mean estimates, which can affect aerosol extinction profiles and aerosol optical depth (AOD). We find that the revised treatment significantly improves the accuracy of the aerosol emissions from surface and elevated sources near sharp spatial gradient regions, with significant improvement in the spatial heterogeneity and variability of simulated surface concentration in high-resolution simulations. In the next-generation E3SM running at convection-permitting scales where the resolved spatial heterogeneity is significantly increased, the revised emission treatment is expected to better represent the aerosol emissions as well as their lifecycle and impacts on climate.

The Spatial Ventricular Gradient is Associated with Inducibility of Ventricular Arrhythmias During Electrophysiology Study

Myocardial electrical heterogeneity is critical for normal cardiac electromechanical function, but abnormal/excessive electrical heterogeneity is proarrhythmic. The spatial ventricular gradient (SVG), a vectorcardiographic measure of electrical heterogeneity, has been associated with arrhythmic events over long-term follow-up, but its relationship with short-term inducibility of ventricular arrhythmias (VAs) is unclear. Determine associations between SVG and inducible VAs during electrophysiology study (EPS). Retrospective study of adults without prior sustained VA, cardiac arrest, or implantable cardioverter-defibrillator (ICD), who underwent ventricular stimulation for evaluation of syncope, non-sustained VT, and/or risk-stratification prior to primary prevention ICD implantation. 12-lead ECGs were converted into vectorcardiograms and SVG magnitude (SVGmag) and direction (azimuth and elevation) were calculated. Odds of inducible VA were regressed using logistic models. Among 143 patients (median age 66, 80% male, median LVEF 47%, 52% myocardial infarction), 34 (23.8%) had inducible VAs. Inducible patients had lower median LVEF (38 vs 50%, p<0.0001), smaller SVGmag (29.5 vs 39.4mV*ms, p=0.0099), and smaller cosine SVG azimuth (cosSVGaz) (0.64 vs 0.89, p=0.0007). When LVEF, SVGmag, and cosSVGaz were dichotomized at their medians, there was a 39-fold increase in adjusted odds (p=0.002) between patients with all low LVEF, SVGmag, and cosSVGaz (65% inducible), compared to patients with all high LVEF, SVGmag, and cosSVGaz (4% [n=1] inducible). After multivariable adjustment, SVGmag, cosSVGaz, and sex, but not LVEF or other characteristics, remained associated with inducible VAs. Assessment of electrical heterogeneity via SVG, which reflects abnormal electrophysiological substrate, adds to LVEF and identifies patients at high and low risk of inducible VA at EPS.