Shape Of Size Distribution Research Articles

Assessment of Triploid Watermelon Cultivars Grown in Georgia for Yield and Quality Parameters

Watermelon is the most important vegetable crop grown during the spring season; therefore, it is imperative that we screen and identify top-performing cultivars for growers. Research experiments were conducted at the University of Georgia, Tifton Vegetable Park Research Farm, during Spring 2022 and Spring 2023. The study compared commercially available large seedless watermelon (Citrullus lanatus L.) cultivars to assess their performance to determine marketable and unmarketable yields, average fruit weight, fruit size distribution, quality parameters, and hollow heart. The six top-yielding cultivars were Excursion, ACX 6177, Miramonte, El Capitan, Sierra Nevada, and Jetski. These high-performing cultivars had total yields that averaged more than 60,000 lb/acre. Of these cultivars, Excursion, Sierra Nevada, and El Capitan had a high percentage of 30/36 count watermelons, whereas cultivars ACX 6177, Miramonte, and Jetski had a large percentage of 45/60 count watermelons. ‘Powerhouse’ and ‘Captivation’ performed the worst, with lower average fruit weights and total yields. In terms of fruit quality, ‘Jetski’, ‘Warrior’, ‘Captivation’, ‘Sierra Nevada’, ‘Embasy’, and ‘Powerhouse’ had the highest soluble solid content among all the cultivars. However, all cultivars had an average soluble solid content of more than 10%, which represented “very good internal quality” according to the US Department of Agriculture standards. ‘Warrior’ and ‘Captivation’ had significantly higher hollow hearts in the fruits compared to those of all other cultivars. In summary, ‘Excursion’, ‘El Capitan’, ‘Miramonte’, ‘Sierra Nevada’, ‘ACX 6177’, and ‘Jetski’ are recommended for commercial cultivation in southern Georgia based on their high yield, sweetness, and low hollow heart incidence, with options available for growers based on desired fruit size distribution, rind color, and fruit shape, whereas ‘Warrior’, ‘Powerhouse’ and ‘Captivation’ performed poorly in terms of yield and/or hollow heart vulnerability.

Droplet contact numbers and contact probabilities in liquid‐liquid dense‐packed zones

AbstractDense‐packed zones (DPZs) are crucial in designing equipment for liquid‐liquid phase separation processes, as the DPZ height affects apparatus size. This article presents an open‐access simulation approach to determine droplet contact numbers and probabilities, which are vital for modeling the deformation and coalescence of polydisperse droplets in a DPZ. The simulation is applied to three technical cases to assess how droplet size distribution (DSD) shapes impact contact numbers and probabilities. Sensitivity analysis reveals that broader DSDs and larger droplet classes lead to higher contact numbers. In contrast, contact probability is primarily determined by droplet class diameter and its number probability within the DSD, showing an almost linear relationship. These results highlight the significance of DSD shape and droplet class diameter in predicting droplet contact numbers and probabilities in DPZs, providing valuable insights for future modeling of liquid‐liquid phase separation.

Cloud Droplet Size Distributions Governed by Condensation, Collision–Coalescence, and Sedimentation. Part II: Analytical Expressions for Size Distribution Shape and Asymptotic Behavior for Large-Droplet Tails

Abstract Droplet growth via condensation and collision–coalescence has been investigated in the limit of very weak coalescence growth: a collector-mode approximation emerges for coalescence growth that consists solely of droplets in the tail collecting droplets near the main mode of the cloud droplet size distribution and that does not deplete the mode. In this second part, the approximation is formalized, leading to a simplified form of the collision–coalescence term in the equation governing the evolution of the droplet size distribution. This form allows for analytical solutions for transient growth and for steady-state distributions representing a balance between condensation, collision–coalescence growth, and removal by sedimentation. The solutions lead to an expression for the drizzle growth time, formally, the finite time in which a droplet approaches infinite size. The drizzle growth time is related to a transition radius at which droplet growth switches from condensation-dominated to coalescence-dominated. The solutions also provide a dimensionless group that governs the steady-state distribution shape, which is referred to as the drizzle number. The solutions are checked by comparing to a Monte Carlo model developed in part 1, and it is found that the analytical solution is excellent when the drizzle number is much greater than unity, which is the typical situation for the microphysical conditions achievable in a convection–cloud chamber. The steady-state size distribution has the form of a modified gamma distribution, with a transition to a power-law tail at a sufficiently large radius. The solutions are not only formally valid for a convection–cloud chamber but can also be extended to shallow, mixed-layer clouds such as mixing fogs.

Multiple losses of aKRAB from PRDM9 coincide with a teleost-specific intron size distribution

BackgroundPrimary transcripts are largely comprised of intronic sequences that are excised and discarded shortly after synthesis. In vertebrates, the shape of the intron size distribution is largely constant; however, most teleost fish have a diverged log-bimodal ‘teleost distribution’ (TD) that is seen only in teleosts. How the TD evolved and to what extent this was affected by adaptative or non-adaptive mechanisms is unknown.ResultsHere, we show that the TD has evolved independently at least six times and that its appearance is linked to the loss of the aKRAB domain from PRDM9. We determined intron size distributions and identified PRDM9 orthologues from annotated genomes in addition to scanning 1193 teleost assemblies for the aKRAB domain. We show that a diverged form of PRDM9 (β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta$$\\end{document}) is predominant in teleosts whereas the α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document} version is absent from most species. Only a subset of PRDM9-α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document} proteins contain aKRAB, and hence, it is present only in a small number of teleost lineages. Almost all lineages lacking aKRAB (but no species with) had TDs.ConclusionsIn mammals, PRDM9 defines the sites of meiotic recombination through a mechanism that increases structural variance and depends on aKRAB. The loss of aKRAB is likely to have shifted the locations of both recombination and structural variance hotspots. Our observations suggest that the TD evolved as a side-effect of these changes and link recombination to the evolution of intron size illustrating how genome architectures can evolve in the absence of selection.

Investigating secondary ice production in a deep convective cloud with a 3D bin microphysics model: Part I - Sensitivity study of microphysical processes representations

Secondary ice production (SIP) is a crucial phenomenon for explaining the formation of ice crystal clouds, especially when addressing the discrepancies between observed ice crystal number concentrations and ice nucleating particles (INPs). In this study, we investigate parameterizations of three SIP processes (Hallett-Mossop, fragmentation of freezing drops, and fragmentation due to ice–ice collision) by simulating a deep convective cloud observed during the HAIC/HIWC campaign with the 3D bin microphysics scheme DESCAM (DEtailed SCAvening and Microphysics model). The simulated mean cloud properties, including particle size distributions and ice crystal number concentration are compared with in situ probe observations obtained during the campaign. Simulation excluding SIP shows a large underestimation of small ice crystals (< 1 mm diameter) for temperatures warmer than ‐30∘C. In our results, incorporating Hallett-Mossop and fragmentation due to ice–ice collision processes leads to ice crystal number concentrations close to observed values, thereby reducing discrepancies by two orders of magnitude. Our simulations also indicates that fragmentation of freezing drops affect minimally the properties of the cloud at its mature stage. Furthermore, we investigate the impact of fragments sizes resulting from SIP processes and show that the size of fragments generated from fragmentation due to ice–ice collision significantly influences the shape of ice particle size distribution. Employing various parameterizations of the ice crystal sticking efficiency reveals a notable impact on cloud properties. This study shows that SIP mechanisms are important and have to be considered for cold and mixed-phase clouds. However their parameterization lack reliability, highlighting the need for better quantifying these mechanisms. The companion paper, investigates the effects of SIP processes on the formation and the evolution of the deep convective system.

Immunomodulating melatonin-decorated silica nanoparticles suppress bacterial wilt (Ralstonia solanacearum) in tomato (Solanum lycopersicum L.) through fine-tuning of oxidative signaling and rhizosphere bacterial community

BackgroundTomato (Solanum lycopersicum L.) production is severely threatened by bacterial wilt, caused by the phytopathogenic bacterium Ralstonia solanacearum. Recently, nano-enabled strategies have shown tremendous potential in crop disease management.ObjectivesThis study investigates the efficacy of biogenic nanoformulations (BNFs), comprising biogenic silica nanoparticles (SiNPs) and melatonin (MT), in controlling bacterial wilt in tomato.MethodsSiNPs were synthesized using Zizania latifolia leaves extract. Further, MT containing BNFs were synthesized through the one-pot approach. Nanomaterials were characterized using standard characterization techniques. Greenhouse disease assays were conducted to assess the impact of SiNPs and BNFs on tomato plant immunity and resistance to bacterial wilt.ResultsThe SiNPs and BNFs exhibited a spherical morphology, with particle sizes ranging from 13.02 nm to 22.33 nm for the SiNPs and 17.63 nm to 21.79 nm for the BNFs, indicating a relatively uniform size distribution and consistent shape across both materials. Greenhouse experiments revealed that soil application of BNFs outperformed SiNPs, significantly enhancing plant immunity and reducing bacterial wilt incidence by 78.29% in tomato plants by maintaining oxidative stress homeostasis via increasing the activities of antioxidant enzymes such as superoxide dismutase (31.81%), peroxidase (32.9%), catalase (32.65%), and ascorbate peroxidase (47.37%) compared to untreated infected plants. Additionally, BNFs induced disease resistance by enhancing the production of salicylic acid and activating defense-related genes (e.g., SlPAL1, SlICS1, SlNPR1, SlEDS, SlPD4, and SlSARD1) involved in phytohormones signaling in infected tomato plants. High-throughput 16 S rRNA sequencing revealed that BNFs promoted growth of beneficial rhizosphere bacteria (Gemmatimonadaceae, Ramlibacter, Microscillaceae, Anaerolineaceae, Chloroplast and Phormidium) in both healthy and diseased plants, while suppressing R. solanacearum abundance in infected plants.ConclusionOverall, these findings suggest that BNFs offer a more promising and sustainable approach for managing bacterial wilt disease in tomato plants.Graphical

The effects of processing parameters on the shape of particle size distribution and grinding rate in a stirred mill

The study of particle size distribution (PSD) of materials is a crucial aspect of mineral processing. It not only determines the appropriate beneficiation process and equipment but also has a significant impact on the grade and recovery of concentrate. This study utilizes a pin-stirred mill for the wet fine grinding of limonite to examine four different widths of PSD functions and compares their quantitative descriptions of the PSD. Skewness is a parameter introduced to quantitatively describe the asymmetry of the PSD. This study aims to investigate the effect of the stirrer speed, the density and the size of the grinding media on the shape of the PSD and on the grinding rate. The results show that a lower stirrer speed and a lower density of the grinding media result in a narrower and a more symmetrical PSD of the grinding products. Moreover, the time-dependent approach succeeds in simulating and proving the evolution behavior of the median particle size. It was found that the optimum mixing ratio of the grinding media can effectively adjust the shape of the PSD and improve the grinding efficiency.

Feasibility study of the paper sludge properties in manufacturing recycled filler

The mineralization of inorganic components in paper sludge offers potential for their re-use in various fields. This study synthesized carbonates based on the minerals present in paper sludge and aimed to investigate the control of particle size distribution and particle shape of the synthesized carbonates. First, the physicochemical and thermal properties of paper mill sludge and ash were evaluated using a spectrophotometer, XRF, and TGA. Paper sludge ash was obtained by incinerating the paper sludge, followed by a carbonation reaction using CO2 gas injection and pH neutralization to produce recycled fillers. The average particle size, crystal lattice structure, and morphology of the recycled fillers were analyzed using a particle size analyzer, XRD, and FE-SEM. The results indicate that the recycled filler produced from coating paper sludge exhibited similar brightness and morphology to conventional paper-based fillers, suggesting its potential to replace commercial PCC (Precipitated Calcium Carbonate). In contrast, the recycled filler manufactured using old corrugated container mill sludge was deemed unsuitable due to its low hydration activity.

Modeling and validation of multi-objective optimization for mixed xylene hybrid distillation/crystallization process

Innovative hybrid distillation/crystallization processes offer significant energy saving and cost reduction for the separation of isomer mixtures. Despite of the enormous potential of hybrid separation processes, they are not widely exploited in industrial applications due to the complexity of the design and multi-objective optimization of these highly integrated processes. In this study, the mixed xylene hybrid scheme was first simulated to provide the initial value of non-dominated sorted genetic algorithm-III. The operating parameters were then optimized through the Python-Aspen platform. Coupled with the online monitoring tool, a rigorous melt crystallization experiment was developed to track crystal size distribution (CSD) and crystal shape. By comparing the optimized results with the original ones, the total annual cost and CO2 emissions were, respectively, reduced by 5.35 % and 12.80 %. Through the experimental validation, the accuracy of the simulation-based crystallization CSD prediction method was discussed, and the potential and challenges of this novel method were proposed. This work aims to minimize the total annual cost and CO2 emissions of the mixed xylene hybrid process simultaneously and explore the feasibility of CSD prediction method by extracting two-dimensional crystal size information from online microscopic images.

Development of a Spectrum-Based Scheme for Simulating Fine-Grained Sediment Transport in Estuaries

Fine-grained cohesive sediments in estuaries play a critical role in sediment transport and biogeochemical cycles in estuaries. Due to the convergence of marine saltwater and freshwater runoff, combined with periodic tidal cycles, fine-grained sediments exhibit intricate flocculation processes that are challenging to simulate. A size-resolved flocculation module using a bin-based scheme aids in modeling these processes but is hindered by high computational costs. In this study, we develop a new spectrum-based scheme based on the spectral shape of floc size distribution from the original bin-based scheme to expedite modeling execution. This new scheme is implemented in the Stony Brook Parallel Ocean Model (sbPOM) and applied to simulate fine-grained sediment transport in the Hudson River estuary. The effectiveness of this spectrum-based scheme is assessed by comparing its simulations with observations and results from the original bin-based scheme. The findings indicate that the new scheme can simulate the evolution of suspended sediment concentration well at a specific point by comparisons with in-situ observations. Specifically, the results of the 50 paired experiments show an average percentage difference of 1.86% and an average speedup ratio of 4.51 times compared to the original bin-based scheme. In summary, the new spectrum-based scheme offers significant acceleration benefits for the size-resolved flocculation module and has the potential for widespread application in simulating fine-grained sediments in estuaries.

Microstructure and performances of rigid polyurethane foam prepared using double‐effect baking powder as a foaming agent

AbstractThe preparation of rigid polyurethane foam with uniform pore size is extremely challenging. In this work, double‐effect baking powder was used as foaming agent, and rigid polyurethane foam with regular morphology was successfully prepared through semi‐prepolymerization. The rigid polyurethane foam apertures with regular morphology were controlled by the secondary release of CO2 when the content of baking powder is 0.30 part. Combined with theoretical calculation and experimental test, it is found that the particle size distribution, wall thickness, and hole shape are uniform, regular, thin, polygonal, and few broken holes. The compression strength, contact angle, and surface energy of the rigid polyurethane foam are 33.36 kPa, 109.6°, and 21.8 mJ/m2 after adding 0.20 part of double‐effect baking powder, respectively. By adjusting the amount of double‐acting baking powder, the porosity, mechanical properties and foam rate of the polyurethane foams could be significantly improved. Due to the molecular solvation effect, rigid polyurethane foams will deform in the water and oil due phase, but it can remain stable for a long time at room temperature without solvent. It provides a new method for the preparation of rigid polyurethane foam, which is expected to be widely used in transportation and other fields.Highlights Baking powder was firstly used as a foaming modifier for rigid polyurethane. Baking powder releases CO2 twice to ensure uniform structure of polyurethane cell. Rigid polyurethane foam has long‐term stability and regular, uniform cell holes. The porosity and mechanical properties of foams could be significantly improved. Foaming mechanism of rigid polyurethane using baking powder was firstly revealed.

Porosity and hydraulic conductivity of gap graded natural sand considering shape parameters

Gap graded natural sand is widely used in hydraulic structures, foundation treatment and recharge well fillers, and it’s also common in geological structures such as landslide deposits. In order to study the influence of grain shape on its pore and permeability characteristics, river sand in Yichang (YS), standard sand in Henan (HS) and standard smooth glass beads (BZ) are selected as test materials, and the grain shape parameters of three materials are analyzed on multiple scales. Then tests on porosity and hydraulic conductivity of gap graded natural sand were conducted. On this basis, a numerical model considering grain size distribution, coarse grain content and grain shape was established. The results showed that the average values of the shape parameters increased or decreased with the increase of grain size, and the coefficients of variation for the parameters were between 0.026 and 0.208. The shape parameters showed a negative skewness distribution, but the absolute value of the skewness coefficient was small (0.254–0.616). Grain size distribution and grain shape are the main factors controlling the porosity and hydraulic conductivity of gap graded natural sand. The minimum values of porosity and hydraulic conductivity appear at about 70 % and 30 % of large grains, respectively. The closer the grains are to the sphere, the closer the material is stacked, and the smaller the porosity value is. The grain size ratio has a significant effect on the minimum porosity of the mixture and the minimum porosity increases with the increase of the grain size ratio. The porosity of gap graded natural sand obtained by numerical method is accurate, and the error is within 10 %. The hydraulic conductivity is obtained by deriving fluid grid information and the results show that the simulated value of hydraulic conductivity is highly matched with the experimental value, and the error range is roughly between 10 % and 30 %.

Connectivity of random hypergraphs with a given hyperedge size distribution

This article discusses random hypergraphs with varying hyperedge sizes, admitting large hyperedges with size tending to infinity, and heavy-tailed limiting hyperedge size distributions. The main result describes a threshold for the random hypergraph to be connected with high probability, and shows that the average hyperedge size suffices to characterise connectivity under mild regularity assumptions. Especially, the connectivity threshold is in most cases insensitive to the shape and higher moments of the hyperedge size distribution. Similar results are also provided for related random intersection graph models.

Evolution of grain size distribution in the circumgalactic medium

Abstract In order to theoretically understand dust properties in the circumgalactic medium (CGM), we construct a dust evolution model that incorporates the evolution of grain size distribution. We treat the galaxy and the CGM as separate one-zone objects, and consider the mass exchange between them. We take into account dust production and interstellar dust processing for the galaxy based on our previous models, and newly incorporate sputtering in the hot phase and shattering in the cool phase for the CGM. We find that shattering increases the dust destruction (sputtering) efficiency in the CGM. The functional shape of the grain size distribution in the CGM evolves following that in the galaxy, but it is sensitive to the balance between sputtering and shattering in the CGM. For an observational test, we discuss the wavelength dependence of the reddening in the CGM traced by background quasar colors, arguing that, in order to explain the observed reddening level, a rapid inflow from the CGM to the galaxy is favored because of quick dust/metal enrichment. Small grain production by shattering in the CGM also helps to explain the rise of dust extinction toward short wavelengths.

Locally narrow droplet size distributions are ubiquitous in stratocumulus clouds.

Marine stratocumulus clouds are the "global reflectors," sharply contrasting with the underlying dark ocean surface and exerting a net cooling on Earth's climate. The magnitude of this cooling remains uncertain in part owing to the averaged representation of microphysical processes, such as the droplet-to-drizzle transition in global climate models (GCMs). Current GCMs parameterize cloud droplet size distributions as broad, cloud-averaged gammas. Using digital holographic measurements of discrete stratocumulus cloud volumes, we found cloud droplet size distributions to be narrower at the centimeter scale, never resembling the cloud average. These local distributions tended to form pockets of similar-looking cloud regions, each characterized by a size distribution shape that is diluted to varying degrees. These observations open the way for new modeling representations of microphysical processes.

Particle size dependence of nanoclustered ceria abrasives on surface activity and chemical mechanical planarization performance

The particle size of cerium oxide (ceria) abrasives plays a crucial role in the design and development of advanced self-stopping slurries for the chemical mechanical planarization (CMP) process in semiconductor device manufacturing. However, a lack of ceria nanoparticles (NPs) with a narrow size distribution and uniform shape poses challenges in investigating the fundamental principles of the relationship between abrasive size and CMP performance. In this study, we thoroughly investigated the effect of ceria NP size on the removal rate (RR) of silicon oxide using uniform-sized nanoclustered (NC) ceria NPs with three diameters: 51.4 nm (NC51), 68.6 nm (NC69), and 108.0 nm (NC108). While all three types of ceria NPs shared a crystallinity of ∼ 70.6 %, they exhibited distinct physicochemical characteristics. As the particle size decreased, the specific surface area and chemical activity (i.e., Ce3+/Ce4+) increased by 155 % and 69 %, respectively. In the CMP process, where direct contact between the abrasives and wafer occurs, the abrasive size influences CMP performance. Experimentally, NC51 achieved the highest RR among the three slurries, along with complex size-dependent contact properties and chemical activities. These experimental results offer significant insights into precise semiconductor manufacturing in a practical manner.

On collisional drop breakup in orographic rain

Collisional drop breakup is one of the important processes during evolution of the rain drops and leads to modified shape of the drop size distribution (DSD), which is a primary parameter in rain retrieval in remote sensing techniques. Though several experimental and observational studies have been performed in the recent past on this aspect, the impact of the same in natural rain, particularly in orographic rain, is still poorly represented. The present study aims to examine and identify the rain conditions in which collisional drop breakup is prominent and is capable of modifying the shape of DSD in orographic rain over north-eastern India. The 2-min averaged DSDs from four hilly locations are studied in both stratiform and convective rain types separately using ground-based DSD measurements. Even though drop breakup in intense to moderate rain seemed to be in notable percentage (0.2% - 11.2%), the low intensity rain also showed a considerable break-up signature (2.5% - 9%), depending upon the locations. The overall results showed that collisional breakup was more prominent in convective rain (1%–11%) than in stratiform rain (4%–5%), however, breakup is also seen primarily during stratiform rain in two of the locations. The Z-R coefficients are found to be significantly different for the break-up and non-break up cases. For breakup cases, both convective and stratiform rainfall shows an increase in intercept parameter for all locations. For stratiform rain types, the coefficient a and b ranged from 307.6 to 321.4 (167.1–178.7) and 1.27–1.37 (1.31–1.34) for rain with break-up (without break-up), respectively. In the case of convective rain, the coefficients were found to be in the range of 377.5–654.7 (270.4–641.3) and 1.28–1.42 (1.14–1.31) with break-up (without break-up), respectively. The results suggest that collisional breakup is an important process in orographic rain over North-Eastern India and it has to be taken care of, while studying rainfall over these regions, particularly in conventional radar derived quantitative precipitation estimates (QPE).

Embedding and cross-sectioning as a sample preparation procedure for accurate and representative size and shape measurement of nanopowders

Reliable measurement of the size of polydisperse, complex-shaped commercial nanopowders is a difficult but necessary task, e.g., for regulatory requirements and toxicity risk assessment. Suitable methods exist for the accurate characterization of the size of non-aggregated, stabilized, spherical and monodisperse nanoparticles. In contrast, industrial nanoscale powders usually require dedicated sample preparation procedures developed for the analysis method of choice. These nano-powders tend to agglomerate and/or aggregate, a behavior which in combination with an innate broad particle size distribution and irregular shape often significantly alters the achievable accuracy of the measured size parameters. The present study systematically tests two commercially available nanoscale powders using different sample preparation methods for correlative analysis by scanning electron microscopy, dynamic light scattering, Brunauer–Emmet–Teller method and differential mobility analysis. One focus was set on the sample preparation by embedding nanoparticles in carbon-based hot-mounting resin. Literature on this topic is scarce and the accuracy of the data extracted from cross sections of these particles is unclearly stated. In this paper systematic simulations on the deviation of the size parameters of well-defined series of nanoparticles with different shapes from the nominal value were carried out and the contributing factors are discussed.

A dislocation-density-based crystal plasticity model for FCC nanocrystalline metals incorporating thermally-activated depinning from grain boundaries

A novel dislocation-density-based crystal plasticity model for nanocrystalline face-centered cubic metals is developed based on the thermally-activated mechanism of dislocations depinning from grain boundaries. Dislocations nucleated from grain boundary dislocation sources are assumed to be the primary carriers of plasticity in the nanocrystals. The evolution of the dislocation density thereby involves a competition between the nucleation of dislocations from grain boundary defect structures, such as ledges, and the absorption of dislocations into the grain boundary via diffusion processes. This model facilitates the simulation of plastic deformation in nanocrystalline metals, with consideration of the initial microstructure resulting from a particular processing method, to be computed as a direct result of dislocation-mediated plasticity only. The exclusion of grain boundary-mediated plasticity mechanisms in the formulation of the crystal plasticity model allows for the exploration of the fundamental role dislocations play in nanocrystalline plasticity. The combined effect of average grain size, grain size distribution shape, and initial dislocation density on the mechanical performance and strain-rate sensitivity are explored with the model. Further, the influence of the grain boundary diffusivity on post-yielding strain-hardening behavior is investigated to discern the impact that the choice of processing route has on the resulting deformation response of the material.

In situ measurements of perturbations to stratospheric aerosol and modeled ozone and radiative impacts following the 2021 La Soufrière eruption

Abstract. Stratospheric aerosols play important roles in Earth's radiative budget and in heterogeneous chemistry. Volcanic eruptions modulate the stratospheric aerosol layer by injecting particles and particle precursors like sulfur dioxide (SO2) into the stratosphere. Beginning on 9 April 2021, La Soufrière erupted, injecting SO2 into the tropical upper troposphere and lower stratosphere, yielding a peak SO2 loading of 0.3–0.4 Tg. The resulting volcanic aerosol plumes dispersed predominately over the Northern Hemisphere (NH), as indicated by the CALIOP/CALIPSO satellite observations and model simulations. From June to August 2021 and May to July 2022, the NASA ER-2 high-altitude aircraft extensively sampled the stratospheric aerosol layer over the continental United States during the Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) mission. These in situ aerosol measurements provide detailed insights into the number concentration, size distribution, and spatiotemporal variations of particles within volcanic plumes. Notably, aerosol surface area density and number density in 2021 were enhanced by a factor of 2–4 between 380–500 K potential temperature compared to the 2022 DCOTSS observations, which were minimally influenced by volcanic activity. Within the volcanic plume, the observed aerosol number density exhibited significant meridional and zonal variations, while the mode and shape of aerosol size distributions did not vary. The La Soufrière eruption led to an increase in the number concentration of small particles (&lt;400 nm), resulting in a smaller aerosol effective diameter during the summer of 2021 compared to the baseline conditions in the summer of 2022, as observed in regular ER-2 profiles over Salina, Kansas. A similar reduction in aerosol effective diameter was not observed in ER-2 profiles over Palmdale, California, possibly due to the values that were already smaller in that region during the limited sampling period in 2022. Additionally, we modeled the eruption with the SOCOL-AERv2 aerosol–chemistry–climate model. The modeled aerosol enhancement aligned well with DCOTSS observations, although the direct comparison was complicated by issues related to the model's background aerosol burden. This study indicates that the La Soufrière eruption contributed approximately 0.6 % to Arctic and Antarctic ozone column depletion in both 2021 and 2022, which is well within the range of natural variability. The modeled top-of-atmosphere 1-year global average radiative forcing was −0.08 W m−2 clear-sky and −0.04 W m−2 all-sky. The radiative effects were concentrated in the tropics and NH midlatitudes and diminished to near-baseline levels after 1 year.