Pronounced Gradient Research Articles

Fundamentals of Flexoelectricity, Materials and Emerging Opportunities Toward Strain-Driven Nanocatalysts.

Flexoelectricity, an intrinsic property observed in materials under nonuniform deformation, entails a coupling between polarization and strain gradients. Recent catalyst advancements have reignited interest in flexoelectricity, particularly at the nanoscale, where pronounced strain gradients promote robust flexoelectric effects. This paper comprehensively examines flexoelectricity, encompassing methodologies for precise measurement, elucidating its distinctions from related phenomena, and exploring its potential applications in augmenting catalytic properties. So far, the greatest potentials are based on lead strontium titanate (PST) and other metallic titanates such as titania (TiO2), strontium titanate (STO), barium strontium titanate (BST) sulfates (MoS2, ZnS)and halide perovskites (with archetype XPbI3). This review explores the promise of flexoelectric properties in addressing material and photocatalytic challenges, such as charge carrier recombination and ineffective surface charge separation. Additionally, it sheds light on the synergy with emerging paradigms like photo-flexo catalysis and synergistic flexo-piezo catalysis, specifically focusing on selective chemical transformations like green hydrogen production. Current limitations related to the usage of photoflexoelectricity for photocatalysis are mostly the stability of the used substance (susceptibility to photodegradation) or the voltage values, which represent the inferior potential for specific practical applications. This work underscores the indispensable role of flexoelectricity in catalysisand its capacity to steer future researchand technological advancement.

Centrifugal directional freezing and pressure infiltration: Tailoring gradient structures and mechanical properties in Al/B4C composites

Inspired by the gradient structures found in natural materials like bone, this study presents a novel fabrication method combining centrifugal freeze casting and pressure infiltration to produce Al/B4C composites with a tunable gradient layered structure, effectively addressing the challenge of achieving both high strength and toughness in metal-matrix composites. By precisely controlling key parameters such as centrifugal speed, ceramic content, particle size distribution, and freezing temperature, we achieved a gradient transition from high hardness and strength in the outer layers to lower hardness and higher toughness in the inner layers, mimicking the performance characteristics of natural materials. Specifically, higher centrifugal speeds and multi-sized ceramic particles promoted a more pronounced gradient structure, with larger particles concentrating in the outer regions for enhanced strength. While increasing ceramic content improved overall strength, it also affected toughness, highlighting the need for optimization. Freezing temperature influenced the ice-crystal structure and interlayer ceramic bridging, impacting both the gradient and overall composite properties. The optimized composites exhibited a unique combination of low density, high strength, and exceptional fracture toughness, primarily attributed to strong interfacial bonding, effective crack deflection and metal bridging, and formation of an interpenetrating structure. This study provides a versatile, cost-effective and scalable pathway for fabricating bioinspired high-performance metal–ceramic composites.

Quantifying Residual Soil Moisture through Empirical Orthogonal Functions Analysis to Support Legume-Based Cropping Systems

AbstractThis study investigates spatiotemporal variability of residual soil moisture during the OND (October-November-December) season in Ethiopia and its implications for crop productivity. Employing advanced statistical techniques, we analyze spatial and temporal distribution of soil moisture across Ethiopia from 1981 to 2020, focusing on selected crops including legumes: chickpea, field peas, common bean, soybean and alfalfa, to assess the potential of residual moisture to support post-rainy season cropping. Results indicate pronounced east-west moisture gradients, with eastern regions of Ethiopia exhibiting lower moisture levels (< 60 kg.m-2) compared to western regions (> 150 kg.m-2). The central highlands, which are pivotal for agricultural activities, demonstrate significant variability in moisture (standard deviations > 25 kg.m-2), with implications on agricultural sustainability. The northern and southeastern tips of the country are particularly vulnerable to prolonged drought, where climate change and frequent dry spells exacerbate moisture deficits, consequently impacting crop productivity. Despite these challenges, promising opportunities for future crop production emerge in the southeastern region, which is characterized by increasing moisture trend over time ($$\:\tau\:=0.59$$). Findings further indicate that residual moisture adequately meets and supports crop water requirements in the western, central, and southwestern Ethiopia. In these regions, residual moisture supports more than 90% of cropland water requirements of various crops during the initial and late-season growth stages, whereas water requirement coverage drops to less than 20% during the mid-season growth stage. Therefore, by utilizing residual soil moisture alongside supplemental irrigation, Ethiopian farmers can meet crop water needs for double cropping and enhance resilience to climate variability.

A propensity score matched analysis of transcatheter aortic valve replacement in failed bioprosthetic valves

Abstract Introduction While recently published data indicate similar long-term results of transcatheter aortic valve replacement (TAVR) compared to surgical procedures, surgical aortic valve replacement (SAVR) remains the standard of care in low-risk patients. However, since life expectancy increases, a non-negligible number of patients experience bioprosthetic valve dysfunction with the need for reintervention, but long-term data of TAVR in failed bioprosthetic valves is scarce. Purpose The aim of the study was to analyse long-term data of patients with TAVR in failed bioprosthetic valves compared to patients with native valve TAVR. The primary endpoint was 6-year all-cause mortality and the main secondary endpoint was echocardiographic valve function. Methods Patients undergoing TAVR for severe aortic valve disease between December 2012 and December 2020 were retrospectively analysed. Prior TAVR or aortic valve homografts led to exclusion from the study. A 2:1 propensity score matching by the optimal neighbor matching algorithm was performed to overcome differences in baseline characteristics. Results Between December 2012 and December 2020, 3,423 patients received TAVR for severe aortic valve disease and met inclusion criteria for the study. Of those, 3,287 patients underwent native valve TAVR, whereas 136 patients experienced bioprosthetic valve dysfunction and were treated with TAVR-in-SAV. After 2:1 propensity score matching, baseline characteristics without any relation to prior SAVR were similar between both groups. Concerning postprocedural echocardiographic function, a less pronounced gradient reduction (57.0 vs. 71.0 %, p < 0.01, Figure 1) and a higher number of patients with elevated mean pressure gradient > 20 mmHg could be found after prior SAVR (19.4 vs. 3.0 %, p < 0.01). However, there was no difference regarding 6-year all-cause mortality between both groups (log rank test p = 0.8, Figure 2). Conclusions Besides a less pronounced gradient reduction and higher mean aortic pressure gradients after TAVR-in-SAV compared to patients with native valve TAVR, no differences in 6-year all-cause mortality could be observed in a propensity score matched analysis.Reduction of mean pressure gradient6-year all-cause mortality

Exploration of chemical reaction and activation energy role of Jeffery-Hamel Jeffery fluid flow in penetrable non-parallel channels with entropy optimization

Recent research has demonstrated that non-Newtonian fluids exhibit superior heat transfer capabilities compared to conventional fluids. However, current methods for enhancing heat transfer in non-Newtonian fluids have their limitations. This study aims to address these limitations by investigating the influence of chemical reactions and activation energy on heat transfer within convergent/divergent channels, as described by the Buongiorno model. The study highlights several key outcomes like Higher convergence angles lead to pronounced concentration variations and gradients, whereas divergent channels result in more uniform concentration profiles. The parameter reflecting kinetic energy dominance over thermal energy shows that increasing this parameter decreases fluid temperature due to energy conversion to kinetic form. Additionally, a higher value enhances solute dispersion and energy transfer, while entropy generation increases with higher values, indicating greater irreversibility and energy losses. These insights are crucial for optimizing channel design in non-Newtonian fluid applications, aiding in the control of concentration gradients, management of temperature variations, and overall improvement in efficiency. Numerical computations of the proposed model were performed using the BVP4c scheme.

The global distribution and drivers of wood density and their impact on forest carbon stocks.

The density of wood is a key indicator of the carbon investment strategies of trees, impacting productivity and carbon storage. Despite its importance, the global variation in wood density and its environmental controls remain poorly understood, preventing accurate predictions of global forest carbon stocks. Here we analyse information from 1.1 million forest inventory plots alongside wood density data from 10,703 tree species to create a spatially explicit understanding of the global wood density distribution and its drivers. Our findings reveal a pronounced latitudinal gradient, with wood in tropical forests being up to 30% denser than that in boreal forests. In both angiosperms and gymnosperms, hydrothermal conditions represented by annual mean temperature and soil moisture emerged as the primary factors influencing the variation in wood density globally. This indicates similar environmental filters and evolutionary adaptations among distinct plant groups, underscoring the essential role of abiotic factors in determining wood density in forest ecosystems. Additionally, our study highlights the prominent role of disturbance, such as human modification and fire risk, in influencing wood density at more local scales. Factoring in the spatial variation of wood density notably changes the estimates of forest carbon stocks, leading to differences of up to 21% within biomes. Therefore, our research contributes to a deeper understanding of terrestrial biomass distribution and how environmental changes and disturbances impact forest ecosystems.

Analyzing the effects of shading on power output in curved photovoltaic array on airship

This study investigates the use of photovoltaic (PV) arrays on airships, focusing on challenges due to the curved structure that affects solar radiation distribution. A novel Photo-Thermal-Electric Model (PTEM), developed in MATLAB/Simulink, is introduced to simulate PV array behavior under various conditions, including the impact of solar altitude, laying angle, and airship flight attitude on power generation. PTEM's effectiveness is demonstrated through detailed power output graphs, revealing that radiation gradients significantly affect power generation, often leading to overestimations in the Photo-Thermal Model (PTM) model by 3 %–30 %. Comparative analysis shows that PTEM provides more accurate energy output estimates for individual PV modules, especially in areas with pronounced radiation gradients, differing from PTM estimates by hundreds of watts. These findings offer valuable insights for enhancing PV module lifespan and optimizing energy system designs, contributing to more efficient renewable energy solutions for long-endurance aircraft.

Thermal effects and deformation mechanisms in abrasive waterjet machining: insights from Ti-6Al-4V alloy for broader applications

As a novel cold machining method, abrasive waterjet machining (AWJM) has significant potential for processing titanium-based materials such as Ti-6Al-4V alloy. However, the thermal effects and material deformation mechanisms of AWJM remain challenging to explain. This study introduces a six-colour blackbody radiation pyrometry method that successfully monitors transient high temperatures during AWJM. The results revealed that temperatures during AWJM were not negligible, reaching up to 3602.08K, leading to material solidification and oxidation. The flash temperature exhibited transient and continuously oscillating characteristics at the microsecond scale. The combined mechanical and thermal loads created three distinct regions: the jet impact zone (elongated grains, oxide-based compositions, and material melting), the heat-affected zone (larger grains), and the base material zone. In the jet impact zone, a pronounced temperature gradient formed on the surface, promoting grain refinement. However, as the distance from the impact zone increases, the extent of grain refinement diminishes, leading to larger grain sizes. The higher kernel average misorientation values observed in and near the impact zone indicated that high-temperature conditions were insufficient for complete recrystallisation, either because of inadequate diffusion or the short duration of the elevated temperatures. This study reveals the thermal and material deformation mechanisms involved in the AWJM process. This establishes a foundational understanding of the processing of titanium-based and other heat-sensitive materials, ultimately contributing to enhanced overall material performance.

Cell Mediated Reactions Create TGF-β Delivery Limitations in Engineered Cartilage

During native cartilage development, endogenous TGF-β activity is tightly regulated by cell-mediated chemical reactions in the extracellular milieu (e.g., matrix and receptor binding), providing spatiotemporal control in a manner that is localized and short acting. These regulatory paradigms appear to be at odds with TGF-β delivery needs in tissue engineering (TE) where administered TGF-β is required to transport long distances or reside in tissues for extended durations. In this study, we perform a novel examination of the influence of cell-mediated reactions on the spatiotemporal distribution of administered TGF-β in cartilage TE applications. Reaction rates of TGF-β binding to cell-deposited ECM and TGF-β internalization by cell receptors are experimentally characterized in bovine chondrocyte-seeded tissue constructs. TGF-β binding to the construct ECM exhibits non-linear Brunauer–Emmett–Teller (BET) adsorption behavior, indicating that as many as seven TGF-β molecules can aggregate at a binding site. Cell-mediated TGF-β internalization rates exhibit a biphasic trend, following a Michaelis-Menten relation (Vmax=2.4 molecules cell-1 s-1, Km=1.7 ng mL-1) at low ligand doses (≤130ng/mL), but exhibit an unanticipated non-saturating power trend at higher doses (≥130ng/mL). Computational models are developed to illustrate the influence of these reactions on TGF-β spatiotemporal delivery profiles for conventional TGF-β administration platforms. For TGF-β delivery via supplementation in culture medium, these reactions give rise to pronounced steady state TGF-β spatial gradients; TGF-β concentration decays by ∼90% at a depth of only 500 μm from the media-exposed surface. For TGF-β delivery via heparin-conjugated affinity scaffolds, cell mediated internalization reactions significantly reduce the TGF-β scaffold retention time (160 to 360-fold reduction) relative to acellular heparin scaffolds. This work establishes the significant limitations that cell-mediated chemical reactions engender for TGF-β delivery and highlights the need for novel delivery platforms that account for these reactions to achieve optimal TGF-β exposure profiles. Statement of SignificanceDuring native cartilage development, endogenous TGF-β activity is tightly regulated by cell-mediated chemical reactions in the extracellular milieu (e.g., matrix and receptor binding), providing spatiotemporal control in a manner that is localized and short acting. However, the effect of these reactions on the delivery of exogenous TGF-β to engineered cartilage tissues remains not well understood. In this study, we demonstrate that cell-mediated reactions significantly restrict the delivery of TGF-β to cells in engineered cartilage tissue constructs. For delivery via media supplementation, reactions significantly limit TGF-β penetration into constructs. For delivery via scaffold loading, reactions significantly limit TGF-β residence time in constructs. Overall, these results illustrate the impact of cell-mediated chemical reaction on TGF-β delivery profiles and support the importance of accounting for these reactions when designing TGF-β delivery platforms for promoting cartilage regeneration.

Exploring the Impact of Heat Treatment on Residual Stress, Microstructure, and Mechanical Behavior of Laser Powder Bed Fusion Additively Manufactured Ti-6Al-2Sn-4Zr-2Mo Alloy

In the field of additive manufacturing (AM), a promising alloy that is gaining attention is the near-α Ti-6Al-2Sn-4Zr-2Mo (Ti6242) alloy. This alloy is known for its remarkable resistance to creep and corrosion at elevated temperatures. However, the production of Ti6242 components via Laser-based AM technologies faced with several challenges, such as the formation of residual stress in the as-built state that originates from the nature of these processes. Therefore, this study has a dual objective: first, to evaluate the microstructure and residual stresses in the as-built Ti6242 produced through laser powder bed fusion. Secondly, to investigate the impact of a promising post heat treatment on mitigating residual stresses, inducing alterations in the microhardness of the Ti6242 alloy and its ductility, phase transformations and microstructure evolution. The as-built specimen exhibited a significant residual stress of 1357 MPa, which was caused by the pronounced temperature gradients experienced during the fabrication process. It is interesting to note that this promising post heat treatment was highly effective in eliminating 99% of the residual stress. After heat treatment, the amount of α' present in the as-built specimen decreased. This resulted in the activation of diffusion of elements such as molybdenum, causing a proportion of the α' to decompose into the more ductile α+β structure. Additionally, it is revealed that the microstructural changes and relieved stresses from the heat treatment process caused a lower microhardness and a higher ductility under compressive loading, as the elongation and toughness reached 20.5% and 23.255 kJ/mm3 in the heat-treated samples, respectively. The outcomes of this work facilitate the use of this alloy in the production of complex shape components through laser-based AM technologies.

Correlation between shot peening coverage and surface microstructural evolution in AISI 9310 steel: An EBSD and surface morphology analysis

In this study, martensitic high-strength steel serves as the subject of investigation, with both conventional and severe shot peening experiments being conducted. The coverage levels for conventional shot peening (CSP) are set at 100 % and 200 %, while severe shot peening (SSP) sees levels of 800 % and 1200 %. For the first time, the use of kernel average misorientation (KAM) enables the calculation of geometrically necessary dislocation (GND) density after peening, facilitating the study of GND density distribution across different coverage and offering a method for the visual assessment of peening degree. Results reveal that, under CSP, the gradient distribution of grain size is relatively uniform, whereas SSP leads to a pronounced gradient in grain size distribution. Taking into account the heterogeneous distribution of the initial material microstructure, a gradient in grain size from the surface to the interior of the material will appear after the coverage reaches a certain value, which is 400 % for AISI 9310 steel. Compared with CSP, SSP will further reduce the surface roughness Sa and improve the surface quality. The research presented further understands the relationship between shot peening process parameters and martensitic steel microstructure, providing an important reference for revealing the strengthening mechanism and selecting reasonable process parameters.

On tailored microstructure in AA 2024 alloy during in-situ microwave casting

In the present study, application of microwave energy was explored for tailoring the microstructure in AA 2024 alloy through directional solidification route. Microwave transparent (alumina) and absorbing (graphite) mould materials were utilized to investigate the effect of microwave interaction (electric and magnetic field components) with AA 2024 alloy on microstructure evolution in terms of dendrite size distribution and formation of eutectic phase. Results showed more pronounced eutectic phase gradient was developed using alumina mould. On the other hand, a more uniform distribution of the eutectic phase and grain size was observed with graphite mould. The development of the eutectic phase gradient is attributed to the effective microwave interaction with the AA 2024 alloy melt during solidification. This is primarily associated with the formation of an additional flux at the solid-liquid (S/L) interface of the alloy under the effect of magnetic field and an enhancement in diffusion flux due to mass transport caused by electric field component of microwave. Formation of AlCu, Al2Cu, and Al2CuMg intermetallic phases in both alumina and graphite mould casts was confirmed. Significantly higher hardness was observed at the higher eutectic phase sites within the alumina mould cast, whereas graphite mould casts exhibited better tensile properties.

Exploring the natural ventilation potential of urban climate for high-rise buildings across different climatic zones

The natural cooling capacity of the environment can effectively reduce the building energy consumption by natural ventilation (NV). For architects, developing NV strategies requires a comprehensive understanding of the distribution characteristics of urban meteorology. This study investigates the vertical characteristics of urban local-scale meteorological parameters across climatic zones. It aims to assess the climatic potential for NV of outdoor air in high-rise buildings. Firstly, using Weather Research and Forecasting (WRF) model coupled with Local Climate Zone (LCZ) data and sounding data, the vertical distribution of meteorological parameters are explored in typical urban areas across different climatic zones. Then, based on an adaptive thermal comfort model, the climatic potential is assessed for NV in high-rise buildings via the indicator of annual natural ventilation hour (NVH). Finally, the characteristics of urban meteorology is further is analyzed in terms of its impact on the natural ventilation potential (NVP) in each climatic zone. Results indicate that air temperature decreases with height from 0 to 500 m, with more pronounced temperature gradients in compact building areas. Near the ground level, Kunming (Temperate Zone) has the most NVH, reaching 4,840 h annually. However, when building height exceeds 100 m, Guangzhou (Hot Summer and Warm Winter, HSWW) becomes more suitable for NV. In cold regions, low temperatures limit NVP during winter, while high humidity constrains it in Temperate and HSWW zones. Overall, the annual NVP in high-rise building areas exceeds that of low-rise building areas. These distribution characteristics of NVP are anticipated to promote the utilization of natural resources for sustainable urban development.

Porosity and permeability optimization of PEMFC cathode gas diffusion layer based on topology algorithm

The gas diffusion layer (GDL) is a crucial component in proton exchange membrane fuel cells (PEMFCs), significantly affecting mass transport and overall cell performance. Due to the pronounced pressure gradients and uneven mass transfer between the inlet and outlet of the serpentine flow field, this study proposes the design of a GDL with a concentration gradient to optimize performance. Leveraging topological optimization algorithms, the research focuses on enhancing the mass transport properties and improving cell efficiency. The optimization process considers the pressure distribution, oxygen concentration, and water content within the serpentine flow field as boundary conditions. By optimizing the porosity and permeability of the GDL in different regions, the study aims to enhance the GDL's mass transport capabilities. Simulation results demonstrate that initializing the porosity at 1 provides superior optimization, significantly enhancing mass transfer and overall cell performance. Although increased permeability contributes to improved mass transport, its impact is less significant compared to porosity optimization. Therefore, GDL porosity is identified as the dominant factor in enhancing cell performance, while permeability adjustments play a secondary role.

Enhancing Directional Droplet Transport via Surface Charge Gradient: Insights from Molecular Dynamics Simulations.

The phenomenon of spontaneous droplet transport has a wide range of implications in water collection, microfluidic manipulation, oil-water separation, and various other fields. Achieving efficient and controllable spontaneous droplet transport is therefore of paramount importance. This study investigates the potential of surface charge manipulation to enhance spontaneous droplet transport through comprehensive molecular dynamics simulations. Our findings reveal that the surface charge of the substrate significantly influences its wettability, reducing the contact angle of the droplet and increasing both the contact area and interaction energy. Moreover, we introduce a novel approach to enhance droplet mobility by creating a surface charge gradient on the substrate. By introducing bands with varying charges along a specific direction of the substrate, the droplet experiences a force directed toward regions of increasing charge, thereby facilitating its movement. Importantly, the driving mechanism of droplet motion is well explained by combining classical electrowetting theory with the analysis of the droplet's advancing and receding contact angles, which demonstrates that a more pronounced surface charge gradient generates greater force and enhances droplet mobility. These findings offer valuable insights into the design of microfluidic systems and related applications based on electrowetting.

Characterization of wind effect on environmental dispersion for a shallow wetland flow

The present work focuses on the dispersion of pollutants under the influence of wind and ecological degradation in a fully developed steady flow for a shallow wetland. The dispersion coefficient is determined by Aris’ method of moments and Meis’ multi-scale analysis. Based on the comparison study, the concentration profiles obtained using multi-scale analysis converge with Aris’ method of moments, indicating that both analytical approaches provide reliable and consistent descriptions of pollutant dispersion in the system. In first-order degradation reaction rates, high degradation rates lead to lower mean concentrations and potentially more pronounced concentration gradients, while low degradation rates result in higher mean concentrations. The critical length of the region influenced by the contaminated cloud is computed analytically. It shows that for the common contaminant constituent lead (Pb), initially, it increases gradually to reach the maximum; after that as time increases, it decreases to zero under wind conditions.

Elucidating nanostructural organization and photonic properties of butterfly wing scales using hyperspectral microscopy.

Biophotonic nanostructures in butterfly wing scales remain fascinating examples of biological functional materials, with intriguing open questions with regard to formation and evolutionary function. One particularly interesting butterfly species, Erora opisena (Lycaenidae: Theclinae), develops wing scales that contain three-dimensional photonic crystals that closely resemble a single gyroid geometry. Unlike most other gyroid-forming butterflies, E. opisena develops discrete gyroid crystallites with a pronounced size gradient hinting at a developmental sequence frozen in time. Here, we present a novel application of a hyperspectral (wavelength-resolved) microscopy technique to investigate the ultrastructural organization of these gyroid crystallites in dry, adult wing scales. We show that reflectance corresponds to crystallite size, where larger crystallites reflect green wavelengths more intensely; this relationship could be used to infer size from the optical signal. We further successfully resolve the red-shifted reflectance signal from wing scales immersed in refractive index liquids with varying refractive index, including values similar to water or cytosol. Such photonic crystals with lower refractive index contrast may be similar to the hypothesized nanostructural forms in the developing butterfly scales. The ability to resolve these fainter signals hints at the potential of this facile light microscopy method for in vivo analysis of nanostructure formation in developing butterflies.

Large Eddy Simulation of Cross‐Shore Hydrodynamics Under Random Waves in the Inner Surf and Swash Zones

AbstractA 3D large eddy simulation coupled with a free surface tracking scheme was used to simulate cross‐shore hydrodynamics as observed in a large wave flume experiment. The primary objective was to enhance the understanding of wave‐backwash interactions and the implications for observed morphodynamics. Two simulation cases were carried out to elucidate key processes of wave‐backwash interactions across two distinct stages: berm erosion and sandbar formation, during the early portion of a modeled storm. The major difference between the two cases was the bathymetry: one featuring a berm without a sandbar (Case I), and the other, featuring a sandbar without a berm (Case II) at similar water depth. Good agreement (overall Willmott's index of agreement greater than 0.8) between simulations and measured data in free surface elevation, wave spectrum, and flow velocities validated the model skill. The findings indicated that the bottom shear stress, represented by the Shields parameter, was significant in both cases, potentially contributing substantial sediment transport. Notably, the occurrence of intense wave‐backwash interactions were more frequent in the absence of a sandbar. These intense wave‐backwash interactions resulted in a pronounced horizontal pressure gradient, quantified by high Sleath parameters, exceeding the criteria for momentary bed failure. Additionally, a more vigorous turbulence‐bed interaction, characterized by near‐bed turbulent kinetic energy, was observed in the case lacking a sandbar, potentially augmenting sediment suspension. These insights are pivotal in understanding the mechanisms underlying berm erosion and how sandbar formation serves to protect further beach erosion.

Predicting undetected native vascular plant diversity at a global scale

Vascular plants are diverse and a major component of terrestrial ecosystems, yet their geographic distributions remain incomplete. Here, I present a global database of vascular plant distributions by integrating species distribution models calibrated to species' dispersal ability and natural habitats to predict native range maps for 201,681 vascular plant species into unsurveyed areas. Using these maps, I uncover unique patterns of native vascular plant diversity, endemism, and phylogenetic diversity revealing hotspots in underdocumented biodiversity-rich regions. These hotspots, based on detailed species-level maps, show a pronounced latitudinal gradient, strongly supporting the theory of increasing diversity toward the equator. I trained random forest models to extrapolate diversity patterns under unbiased global sampling and identify overlaps with modeled estimations but unveiled cryptic hotspots that were not captured by modeled estimations. Only 29% to 36% of extrapolated plant hotspots are inside protected areas, leaving more than 60% outside and vulnerable. However, the unprotected hotspots harbor species with unique attributes that make them good candidates for conservation prioritization.

Age-Related Blood Pressure Gradients Are Associated With Blood Pressure Control and Global Population Outcomes.

The strong relationship between blood pressure (BP) and age is well known. Limited evidence suggests that a steeper age-BP slope may be associated with an increased risk of adverse outcomes. The May Measurement Month campaign enables an investigation of geographic, socioeconomic, and sex differences in age-related BP gradients and their association with public-health outcomes. Cross-sectional, annual global BP May Measurement Month screening data were analyzed. Average systolic BP and age-related BP slopes across different age groups were calculated to assess regional, socioeconomic, and sex-stratified variations. The association of BP slopes derived from adjusted linear regression models with country-level health metrics was investigated. Age-related systolic BP gradients differed distinctly across global geographic regions, income levels, and between sexes. The steepest age gradients of BP were observed in populations from Africa and Europe. Women had lower BP levels than men at younger ages (20s and 30s) but subsequently experienced more pronounced age-related BP gradients. Geographically divergent age-related BP gradients were significantly associated with major national public health indicators. Globally, steeper age-related BP slopes were associated with poor BP control, increased disability-adjusted life years, and death rates. A steeper population age-BP slope of 1 mm Hg per 10 years was associated with a decrease in life expectancy of 3.3 years in this population (95% CI, -5.1 to -1.4; P=0.0007). Age-related BP gradients vary considerably across global populations and are associated with variability in BP-related risks and adverse outcomes across regions. Effective public health strategies may require region-specific targeting of adverse BP gradients to improve health outcomes.