Convex Hull Area Research Articles

Integrating dynamic high-throughput phenotyping and genetic analysis to monitor growth variation in foxtail millet

BackgroundFoxtail millet [Setaria italica (L.) Beauv] is a C4 graminoid crop cultivated mainly in the arid and semiarid regions of China for more than 7000 years. Its grain highly nutritious and is rich in starch, protein, essential vitamins such as carotenoids, folate, and minerals. To expand the utilisation of foxtail millet, efficient and precise methods for dynamic phenotyping of its growth stages are needed. Traditional foxtail millet monitoring methods have high labour costs and are inefficient and inaccurate, impeding the precise evaluation of foxtail millet genotypic variation.ResultsThis study introduces a high-throughput imaging system (HIS) with advanced image processing techniques to enhance monitoring efficiency and data quality. The HIS can accurately extract a range of key growth feature parameters, such as plant height (PH), convex hull area (CHA), side projected area (SPA) and colour distribution, from foxtail millet images. Compared with traditional manual measurements, this HIS improved data quality and phenotyping of the key foxtail millet growth traits. High-throughput phenotyping combined with a genome-wide association study (GWAS) revealed genetic loci associated with dynamic growth traits, particularly plant height (PH), in foxtail millet. The loci were linked to genes involved in the gibberellic acid (GA) synthesis pathway related to PH.ConclusionThe HIS developed in this study enables the efficient and dynamic monitoring of foxtail millet phenotypic traits. It significantly improves the quality of data obtained for phenotyping key growth traits. The integration of high-throughput phenotyping with GWAS provides new insights into the genetic underpinnings of dynamic growth traits, particularly plant height, by identifying associated genetic loci in the GA synthesis pathway. This methodological advancement opens new avenues for the precise phenotyping and exploration of genetic resources in foxtail millet, potentially enhancing its utilisation.

An approach to apply the Jaya optimization algorithm to the nesting of irregular patterns

Abstract The problem of nesting frequently arises in the industrial environment, and it has a strong ecological and economic impact in the manufacturing processes. It basically consists of placing a set of pieces (polygons) on a material sheet, making sure that the pieces do not overlap and that they do not exceed the boundaries of the sheet. With regard to irregular 2D polygons, the problem is NP-complete. Therefore, different heuristics have been developed so as to cope with the problem. In this paper, the application of the Jaya metaheuristic algorithm to the nesting problem is proposed. This algorithm has been already applied to several engineering problems and has generally demonstrated better results than most metaheuristic algorithms. In this paper, the Jaya algorithm has been adapted to the specific features of the nesting problem so as to optimize the placement of pieces on a sheet, with the objective of minimizing material waste and computational time. The results of our experimentation demonstrate the algorithm's effectiveness in reducing the convex hull area across various datasets, showing potential in solving complex, irregular shape nesting problems. This research provides a new application of the Jaya algorithm and opens ways for future work in optimization techniques and parameter-free heuristic algorithms for nesting.

Rice homolog of Arabidopsis Xylem NAC domain 1 (OsXND1), a NAC transcription factor regulates drought stress responsive root system architecture in indica rice.

Rice yield is greatly constrained by drought stress. In Arabidopsis, XYLEM NAC DOMAIN 1 (XND1) gene regulates the xylem formation, efficiency of water transport, and the delicate equilibrium between drought tolerance and resistance to pathogens. However, diversity and the role of rice homologs of OsXND1 is not reported so far. This study hypothesized that the rice homolog of OsXND1 also regulates drought stress tolerance through modulation of root architecture. Initially, phylogenetic analysis identified two OsXND1 homologs (Os02g0555300 and Os04g0437000) in rice. Further, 14 haplotypes were identified in the OsXND1 of which Hap1 and Hap3 were major haplotypes. The association analysis of OsXND1 with 16 different traits, including 10 root traits, showed three SNPs (Chr02:20972728-Promoter variant; Chr02:20972791-5' UTR variant, and Chr02:20973745-3' UTR variant) were significantly associated with root area, root surface area, total root length, and convex hull area only under drought stress in indica rice. Besides, the superior haplotype of OsXND1 increased the root area, root surface area, total root length, and convex hull area by 46%, 40%, 38%, and 42%, respectively, under drought stress conditions. Therefore, the identified superior haplotype of OsXND1 can be utilized in haplotype breeding programs for the improvement of drought tolerance in rice.

Biogeographic dynamics of graptolites during the Late Ordovician Mass Extinction in South China

Studying the temporal and spatial distributions and dynamics of fossils is crucial for understanding macroevolution processes in geological history. Biodiversity data provide an overview of faunal changes during extinction events, but it cannot differentiate the impact of extinction events on different species. Biogeographic study complements these data by offering more detailed insights into evolutionary patterns. A dataset of 704 graptolite occurrence records for the Late Ordovician Mass Extinction (LOME) was compiled from 60 localities in South China. The geographic distributions of 26 species across four graptolite biochrons (from late Katian to Hirnantian) were quantitatively reconstructed using ArcGIS. Two types of geographic range indexes, including convex hull areas and maximum distribution distances, were calculated for each species in each time slice. Based on the variations in the geographic ranges, the graptolites can be divided into three types. The geographic ranges of the first type shrank before the extinction, that of the second type expanded before the extinction but shrank during the extinction, and that of the third type expanded during the extinction. The first two types include Diplograptina species; and the third of Neograptina species. The study revealed that the extinction event affected all diplograptid graptolite species, as evidenced by the rate of decrease in geographic ranges. Interestingly, the impact of the major extinction appeared to be uniform across all graptolite species, irrespective of their initial geographic range size. The distribution centers of the graptolite species remained relatively stable and predominantly surrounded the center of the sea during the LOME. The substantial reduction in the geographic ranges of diplograptid species might be due to the global factors rather than local sea level decline.

Genetic analysis of cassava brown streak disease root necrosis using image analysis and genome-wide association studies.

Cassava brown streak disease (CBSD) poses a substantial threat to food security. To address this challenge, we used PlantCV to extract CBSD root necrosis image traits from 320 clones, with an aim of identifying genomic regions through genome-wide association studies (GWAS) and candidate genes. Results revealed strong correlations among certain root necrosis image traits, such as necrotic area fraction and necrotic width fraction, as well as between the convex hull area of root necrosis and the percentage of necrosis. Low correlations were observed between CBSD scores obtained from the 1-5 scoring method and all root necrosis traits. Broad-sense heritability estimates of root necrosis image traits ranged from low to moderate, with the highest estimate of 0.42 observed for the percentage of necrosis, while narrow-sense heritability consistently remained low, ranging from 0.03 to 0.22. Leveraging data from 30,750 SNPs obtained through DArT genotyping, eight SNPs on chromosomes 1, 7, and 11 were identified and associated with both the ellipse eccentricity of root necrosis and the percentage of necrosis through GWAS. Candidate gene analysis in the 172.2kb region on the chromosome 1 revealed 24 potential genes with diverse functions, including ubiquitin-protein ligase, DNA-binding transcription factors, and RNA metabolism protein, among others. Despite our initial expectation that image analysis objectivity would yield better heritability estimates and stronger genomic associations than the 1-5 scoring method, the results were unexpectedly lower. Further research is needed to comprehensively understand the genetic basis of these traits and their relevance to cassava breeding and disease management.

Tree species diversity mapping from spaceborne optical images: The effects of spectral and spatial resolution

AbstractIncreasingly available spaceborne sensors provide unprecedented opportunities for large‐scale, timely and continuous tree species diversity (TSD) monitoring. However, given differences in spectral and spatial resolutions, the choice of sensor is not always straightforward. In this work, we investigated the effects of spatial and spectral resolutions for four spaceborne sensors (RapidEye, Landsat‐8, Sentinel‐2 and PlanetScope) on TSD mapping in an area of approximately 4000 km2 within the Black Forest, Germany. We employed a random forest (RF) regression model to predict Shannon–Wiener diversity based on seven types of spectral heterogeneity metrics (texture, coefficient of variation, Rao's Q, convex hull volume, spectral angle mapper, convex hull area and spectral species diversity) and a full survey dataset from 135 one‐ha sample plots. We compared the RF model's performance across sensors and spatial resolutions. Our results demonstrated that the Sentinel‐2‐based TSD model achieved the highest accuracy (mean R2: 0.477, mean root‐mean‐square error (RMSE): 0.274). The RapidEye‐based TSD model produced lower accuracy (mean R2: 0.346, mean RMSE: 0.303), but it was better than the PlanetScope‐ and Landsat‐based TSD models. The 10 m (for Sentinel‐2 and RapidEye) and 15 m (for PlanetScope) were the best spatial resolutions for predicting TSD. The NIR band was the most favourable spectral band for predicting TSD. Texture metrics and Rao's Q outperformed the other spectral heterogeneity metrics. Our results highlighted that spaceborne optical imagery (especially Sentinel‐2) can be successfully used for large‐scale TSD mapping but that the choice of sensors can significantly affect the resulting mapping accuracy in temperate montane forests.

Non-numerical features fail to predict numerical performance in real-world stimuli

It has been proposed that humans use non-numerical features (such as convex hull and surface area) to estimate the number of objects in a scene. This would be an evolutionarily advantageous strategy if such features truly patterned with number in the world, but this has never been empirically tested. Here, we quantify the strength of the relationship between number and non-numerical features in two relevant image sets: the illustrations from children’s counting books, and real-world photographs. We find that non-numerical features are much less predictive of the number of objects in counting books than in photographs, despite the former being specifically designed for use in teaching children about numbers. Then, across three behavioral experiments, we ask whether the stronger relationship in photographs predicts better number estimation performance in adults (N = 120) and in children (N = 94; M age = 7;2 years). Our experiments reveal that number estimation is easier from the counting books than the photographs, even though non-numerical features are less predictive of number in books. This analysis uses real-world stimuli and draws into question the claim that non-numerical features are intrinsically involved in number extraction.

Research on visual size and visual alignment optimization of icon set design

The industry's relevant guidelines on icon design point out that in the design of icon sets, designers should adjust the size and position of each icon, instead of simply unifying the size and position by icon bounding box, to ensure consistency in visual size and visual alignment. However, existing guidelines provide vague answers on specifically adjusting different icons, leaving designers to rely on subjective experience and intuition for adjustments. To explore the general pattern of visual size and alignment between different icons, we first measured the visual size and alignment of different icons through subjective experiments, analyzed the data to find the influencing factors. Next, we constructed a visual size optimization model composed of these factors and proposed an optimization method based on the reference square. Then, we measured the difference between icons’ visual alignment and bounding box alignment through experiments. Finally, we used expert evaluation to test the model's effectiveness in visual size consistency. We have reached the following conclusions: (1) For icons with the same convex hull, the perceived visual size is consistent; (2) To unify the icon visual size using a reference square as the standard, there are two factors affecting the visual size adjustment: the convex hull area of the icon and the convex hull area outside the bounds of the reference square. (3) The visual size optimization model helps slightly improve the visual alignment consistency of icons. These conclusions and the visual size optimization model contribute to establishing more rigorous icon design standards and developing plugins to enhance the quality and efficiency of icon design.

Effects of artificial reef and fishing moratorium on trophic structure of biological community in the Pearl River Estuary marine ranch based on stable isotopes

Deployment of artificial reefs (ARs) has become popular technique to create new hard-bottom habitats, increase biodiversity and richness for fisheries. We compared the faunal community structure and food web structure associated with before and after fishing moratorium between ARs and non-ARs in Wanshan Island, Pearl River Estuary using stable isotope techniques. Community composition showed higher differences between ARs and non-ARs. The range of δ13C and δ15N of different functional groups can distinguish the pelagic and benthic trophic pathways of the food web in reef-or-not area before and after fishing moratorium. The isotopic niches of entire faunal, as well as individual functional groups, overlapped less between ARs and non-ARs in Wanshan Island, which makes the isotopic functional indices non-equivalent. The total convex hull area (TA) of ARs was larger than that of non-ARs, indicating that nutrient pathways of ARs were more diverse. Overall, however, these results suggest that trophic structure was convergence between ARs and non-ARs, and differences before and after fishing moratorium, possibly due to seasonal differences. Finally, it was shown that the construction of ARs had a weak effect on the restoration of fishery resources in this area, which might be related to lack of further management, or even similar community composition to non-ARs areas.

Discovery and Characterisation of Forward Line Formations at Centre Bounces in the Australian Football League.

The extent of player formation usage and the characteristics of player arrangements are not well understood in Australian football, unlike other team-based invasion sports. Using player location data from all centre bounces in the 2021 Australian Football League season; this study described the spatial characteristics and roles of players in the forward line. Summary metrics indicated that teams differed in how spread out their forward players were (deviation away from the goal-to-goal axis and convex hull area) but were similar with regard to the centroid of player locations. Cluster analysis, along with visual inspection of player densities, clearly showed the presence of different repeated structures or formations used by teams. Teams also differed in their choice of player role combinations in forward lines at centre bounces. New terminology was proposed to describe the characteristics of forward line formations used in professional Australian Football.

CORRELATIONS OF GPS-BASED COMMUNITY MOBILITY METRICS BETWEEN PERSONS WITH DEMENTIA AND FAMILY CAREGIVERS

Abstract Currently, the majority of dementia care is provided at home by informal caregivers. Most informal caregivers share a routine with their loved ones and change their activity patterns to adapt to a new routine of persons with dementia (PWDs). Given the dementia caregiving context, caregivers’ mobility behaviors and PWDs’ mobility may be positively associated. This study aimed to characterize patterns of GPS-derived community mobility in dementia dyads and examine relationships between PWDs’ and caregivers’ mobility patterns. Six dyads wore a GPS data logger inside and outside the home for 8-11 days. Twelve participants generated valid GPS track files (N=110). Four temporal and spatial mobility metrics were derived from GPS data (total distance, time use, median speed, and convex hull area). Then we calculated Pearson correlation coefficients between PWDs and their caregivers over all tracks. All dyads made active out-of-home trips, indicated by mean daily distance (range: 6,198 - 115,592m for PWDs; 5,125 - 108,857m for caregivers). Median speed of movement ranged from 0.09 to 1.29 km/hour for PWDs, and from 0.21 to 0.97 km/hour for caregivers. The mean size of convex hull over the monitoring period indicates a limited space usage level in both PWDs and caregivers, meaning restricted community mobility despite relatively large distance trips. The correlation coefficient was positive and significant for each metric (r = 0.70-0.97, p < .001). These results suggest substantial agreement in the mobility metrics between PWD and their caregivers, indicating a high level of dyadic effects of a partner’s experience of community mobility.

Complexity, Performance, and Search Efficiency: An Eye-Tracking Study on Assembly-Based Tasks among Construction Workers (Pipefitters)

Past studies have used eye-tracking glasses to analyze people’s perception of visual stimuli, usually regarding wayfinding, safety, or visual appeal. Some industries, such as the automotive industry, studied the effects of visual stimuli on task completion. However, the architecture and construction industries have mainly conducted eye-tracking experiments with surveys or search tasks instead of performing a task. This paper uses eye-tracking glasses to analyze people’s perception of visual stimuli while completing tangible tasks that simulate real-world applications. This research studies how people look at visual stimuli that influence their ability to interpret drawings with varying degrees of complexity, assess task completion performance, and inspect how people search for information. Twenty pipefitters wore eye-tracking glasses to record their eye movement patterns while completing a model pipe spool assembly. The eye-tracking glasses and Visual Eyes software measured visit metrics, fixations, fixation durations, convex hull coverage, assembly time, rework, and errors. Unlike previous studies, convex hull areas are calculated and used to measure search efficiency. This research found that people interacted more frequently with more complex visual stimuli but did not necessarily require more time to complete a task. People with lower search efficiency visited the drawings more frequently than people with higher search efficiency. People with higher search efficiency made fewer mistakes, redid less work, and completed tasks quicker than those with lower search efficiency. Search efficiency was found to be a good predictor of task performance.

Drone Helps Privacy: Sky Caching Assisted $k$-Anonymity in Spatial Querying

As wireless and mobile devices are prevalent and resource-rich, users can frequently query point-of-interests and enjoy diverse location-based services (LBSs) in infrastructure-based wireless networks. However, users often trade their location privacy with services by sharing their location information with an LBS server, without knowing that the server can fully be trusted. In this article, we propose a sky caching-aided spatial querying scheme with the support of a flying drone. The basic idea is that both the user and its drone collaboratively generate a set of dummy locations to hide the current location of the user from the server. We also propose cache admission control techniques to efficiently cache the queried results to minimize the number of duplicated cached copies. The location privacy is analyzed and measured in terms of the location obfuscation and the size of the convex hull area that consists of dummy locations resided within the cloaking areas of user and drone. We conduct extensive simulation experiments using the OMNeT++ for performance evaluation and comparison. The simulation results show that the proposed approach can reduce the number of queries sent to the server, extend the cloaking area, and improve the location privacy of users significantly.

Phenotypic Variability of Root System Architecture Traits for Drought Tolerance among Accessions of Citron Watermelon (Citrullus lanatus var. citroides (L.H. Bailey).

Citron watermelon (Citrullus lanatus var. citroides) is a drought-tolerant cucurbit crop widely grown in sub-Saharan Africa in arid and semi-arid environments. The species is a C3 xerophyte used for multiple purposes, including intercropping with maize, and has a deep taproot system. The deep taproot system plays a key role in the species’ adaptation to dry conditions. Understanding the root system development of this crop could be useful to identify traits for breeding water-use efficient and drought-tolerant varieties. This study compared the root system architecture of citron watermelon accessions under water-stress conditions. Nine selected and drought-tolerant citron watermelon accessions were grown under non-stress (NS) and water stress (WS) conditions using the root rhizotron procedure in a glasshouse. The following root system architecture (RSA) traits were measured: root system width (RSW), root system depth (RSD), convex hull area (CHA), total root length (TRL), root branch count (RBC), total root volume (TRV), leaf area (LA), leaf number (LN), first seminal root length (FSRL), seminal root angle (SRA), root dry mass (RDM), shoot dry mass (SDM), root–shoot mass ratio (RSM), root mass ratio (RMR), shoot mass ratio (SMR) and root tissue density (RTD). The data collected on RSA traits were subjected to an analysis of variance (ANOVA), correlation and principal component analyses. ANOVA revealed a significant (p < 0.05) accession × water stress interaction effect for studied RSA traits. Under WS, RDM exhibited significant and positive correlations with RSM (r = 0.65), RMR (r = 0.66), RSD (r = 0.66), TRL (r = 0.60), RBC (r = 0.72), FSRL (r = 0.73) and LN (r = 0.70). The principal component analysis revealed high loading scores for the following RSA traits: RSW (0.89), RSD (0.97), TRL (0.99), TRV (0.90), TRL (0.99), RMR (0.96) and RDM (0.76). In conclusion, the study has shown that the identified RSA traits could be useful in crop improvement programmes for citron watermelon genotypes with enhanced drought adaptation for improved yield performance under drought-prone environments.

Deciphering endurance capacity of mango tree (Mangifera indica L.) to desiccation stress using modern physiological tools

• Mango plant can maintain its canopy coolness during desiccation period by its ability to with draw water during water limiting conditions. • Mango plant can maintain its carboxylation capacity during hotter period of the day. • Crucial components of photosynthesis, PSII efficiency is maintained during desiccation period, thereby preventing the plants from desiccation damage and providing tolerance mechanisms. • Mango plant can maintain its structural attributes (mainly by maintaining turgidity due to water retention capacity) such as convex hull area, which also supports desiccation tolerance mechanisms. Capacity of mango tree to withstand drought (absence of soil moisture) can be attributed to stress resilient physiological processes inside the cell and also at whole plant level. To test this hypothesis, photosynthetic traits were recorded over the period of time. Further, desiccation tolerance of photosystem II (PSII) in excised mango leaves were measured by employing chlorophyll fluorescence imaging system. Beside this, the capacity of mango tree to keep its canopy cool was monitored in every 10 min interval throughout the day during dry and rainy season in the field by employing thermal imaging system. Finally, phenomics platform was used to monitor depletion of tissue moisture level as well as changes in structural attributes during desiccation in excised shoots of the tree. It was inferred that mango tree can maintain its carboxylation efficiency over the period of time. IR studies confirmed that mango tree maintained its canopy coolness during dry season. In addition, the chlorophyll fluorescence experiments revealed that mango leaves retained 50% of initial PSII efficiency for as many as 4 days after desiccation and chlorophyll fluorogram also depicted the observations. Phenomics studies concluded that mango twig retained tissue water content even up to the 164 h of desiccation with gradual decrease in canopy area. Hence, it is interpreted that these physiological resilience are amongst the various reasons for evergreen feature of mango tree which has tendency to survive severe soil moisture deficit particularly during the summer in tropical and subtropical regions, which has been revealed for first time using phenomics platform.

Quantification of spatial subclonal interactions enhancing the invasive phenotype of pediatric glioma.

SummaryDiffuse midline gliomas (DMGs) are highly aggressive, incurable childhood brain tumors. They present a clinical challenge due to many factors, including heterogeneity and diffuse infiltration, complicating disease management. Recent studies have described the existence of subclonal populations that may co-operate to drive pro-tumorigenic processes such as cellular invasion. However, a precise quantification of subclonal interactions is lacking, a problem that extends to other cancers. In this study, we combine spatial computational modeling of cellular interactions during invasion with co-evolution experiments of clonally disassembled patient-derived DMG cells. We design a Bayesian inference framework to quantify spatial subclonal interactions between molecular and phenotypically distinct lineages with different patterns of invasion. We show how this approach could discriminate genuine interactions, where one clone enhanced the invasive phenotype of another, from those apparently only due to the complex dynamics of spatially restricted growth. This study provides a framework for the quantification of subclonal interactions in DMG.

The effect of visual parameters on nonsymbolic numerosity estimation varies depending on the format of stimulus presentation

The extent to which the approximate number sense is based on the estimation of continuous visual properties has been widely discussed. Some investigators have hypothesized that humans are able to estimate numerosity directly and independently of visual cues. Other investigators have posited that numerosity can be processed only via the estimation of non-numeric visual properties. The latter theory is confirmed by the existence of the congruency effect, that is, greater accuracy in congruent trials where visual properties were positively correlated with numerosity compared with that in incongruent trials. In this study, we tested the assumption that the congruency effect, reflecting the bias in numerosity estimation due to the estimation of visual cues, varies depending on the format of the stimulus presentation and object heterogeneity. The study involved a sample of pupils in Grades 5–9 from Kyrgyzstan (N = 764; 48% girls; mean age = 13.06 years), whereby participants performed a nonsymbolic comparison test in four formats of stimulus presentation: paired/homogeneous, paired/heterogeneous, mixed/homogeneous, and mixed/heterogeneous. Compared arrays of figures might be congruent or incongruent for one visual parameter (convex hull or cumulative area), whereas another visual parameter was held constant for two arrays. The results of generalized linear mixed-effect models demonstrated that the largest congruency effect occurred in a paired format with homogeneous figures. The congruency effect was insignificant in the mixed/heterogeneous format. The results also revealed that the effects of the convex hull and cumulative area varied in different formats of stimulus presentations.

Federated Learning-Based Localization With Heterogeneous Fingerprint Database

Fingerprint-based localization plays an important role in indoor location-based services, where the position information is usually collected in distributed clients and gathered in a centralized server. However, the overloaded transmission as well as the potential risk of divulging private information burdens the application. Owning the ability to address these challenges, federated learning (FL)-based fingerprinting localization comes into people’s sights, which aims to train a global model while keeping raw data locally. However, in distributed machine learning (ML) scenarios, the unavoidable database heterogeneity usually degrades the performance of existing FL-based localization algorithm (FedLoc). In this letter, we first characterize the database heterogeneity with a computable metric, i.e., the area of convex hull, and verify it by experimental results. Then, a novel heterogeneous FL-based localization algorithm with the area of convex hull-based aggregation (FedLoc-AC) is proposed. Extensive experimental results, including real-word cases are conducted. We can conclude that the proposed FedLoc-AC can achieve an obvious prediction gain compared to FedLoc in heterogeneous scenarios.

The Influence of the Recording Time in Modelling the Swimming Behaviour of the Freshwater Inbenthic Copepod Bryocamptus pygmaeus

The analysis of copepod behaviour gained an increasing impetus over the past decade thanks to the advent of computer-assisted video analysis tools. Since the automated tracking consists in detecting the animal’s position frame by frame and improving signals corrupted by strong background noise, a crucial role is played by the length of the video recording. The aim of this study is to: (i) assess whether the recording time influences the analysis of a suite of movement descriptive parameters; (ii) understand if the recording time influences the outcome of the statistical analyses when hypotheses on the effect of toxicants/chemicals on the freshwater invertebrate behaviour are tested. We investigated trajectory parameters commonly used in behavioural studies—swimming speed, percentage of activity and trajectory convex hull—derived from the trajectories described by the inbenthic–interstitial freshwater copepod Bryocamptus pygmaeus exposed to a sub-lethal concentration of diclofenac. The analyses presented in this work indicate that the recording time did not influence the outcome of the results for the swimming speed and the percentage of activity. For the trajectory convex hull area, our results showed that a recording session lasting at least 3 min provided robust results. However, further investigations are needed to disentangle the role of concurrent factors, such as the behavioural analysis of multiple individuals simultaneously, whether they are of the same or opposite sex and the implications on sexual behaviour, competition for resources and predation.

Influence of coronal hole morphology on the solar wind speed at Earth

Context.It has long been known that the high-speed stream (HSS) peak velocity at Earth directly depends on the area of the coronal hole (CH) on the Sun. Different degrees of association between the two parameters have been shown by many authors. In this study, we revisit this association in greater detail for a sample of 45 nonpolar CHs during the minimum phase of solar cycle 24. The aim is to understand how CHs of different properties influence the HSS peak speeds observed at Earth and draw from this to improve solar wind modeling.Aims.The CHs were extracted based on the Collection of Analysis Tools for Coronal Holes which employs an intensity threshold technique applied to extreme-ultraviolet filtergrams. We first examined all the correlations between the geometric characteristics of the CHs and the HSS peak speed at Earth for the entire sample. The CHs were then categorized in two different groups based on morphological criteria, such as the aspect ratio and the orientation angle. We also defined the geometric complexity of the CHs, a parameter which is often neglected when the formation of the fast solar wind at Earth is studied. The quantification of complexity was done in two ways. First, we considered the ratio of the maximum inscribed rectangle over the convex hull area of the CH. The maximum inscribed rectangle provides an estimate of the area from which the maximum speed of the stream originates. The convex hull area is an estimate of how irregular the CH boundary is. The second way of quantifying the CH complexity was carried out by calculating the CH’s fractal dimension which characterizes the raggedness of the CH boundary and internal structure.Methods.When treating the entire sample, the best correlations were achieved between the HSS peak speed observed in situ, and the CH longitudinal extent. When the data set was split into different subsets, based on the CH aspect ratio and orientation angle, the correlations between the HSS maximum velocity and the CH geometric characteristics significantly improved in comparison to the ones estimated for the whole sample. By further dividing CHs into subsets based on their fractal dimension, we found that the Pearson’s correlation coefficient in the HSS peak speed – CH area plot decreases when going from the least complex toward the most complex structures. Similar results were obtained when we considered categories of CHs based on the ratio of the maximum inscribed rectangle over the convex hull area of the CH. To verify the robustness of these results, we applied the bootstrapping technique. The method confirmed our findings for the entire CH sample. It also confirmed the improved correlations, compared to the ones found for the whole sample, between the HSS peak speed and the CH geometric characteristics when we divided the CHs into groups based on their aspect ratio and orientation angle. Bootstrapping results for the CH complexity categorizations are, nonetheless, more ambiguous.Results.Our results show that the morphological parameters of CHs such as the aspect ratio, orientation angle, and complexity play a major role in determining the HSS peak speed at 1 AU. Therefore, they need to be taken into consideration for empirical models that aim to forecast the fast solar wind at Earth based on the observed CH solar sources.