Frontal Surface Area Research Articles

Physical Modelling Tests With Flexible Woody Vegetation Mimics

Riparian forests in front of dikes can dampen incoming waves and thereby contribute to flood safety. In real-scale flume experiments with live pollard willow trees (forming a 40-m-long forest), it was observed that during storm conditions, a maximum reduction of 20 % in incoming wave height could be achieved (van Wesenbeeck, et al., 2022). Notably, this amount of wave damping occurred at a water depth of 3 meters, aligning with the section of the trees with the maximum frontal-surface area. For a larger water depth, measured wave damping however declined. This is potentially partly caused by the natural tapering form of the trees. Typically, trees are characterized by smaller branch diameters and more flexible branches higher up in the canopy (McMahon & Kronauer, 1976); and flexible vegetation mimics are known to dampen less than rigid mimics due to motion (Van Veelen, T, Reeve, & Karunarathna, 2020). Hence, both the frontal-surface area and branch rigidity decrease along the height of the willow trees, potentially leading to less wave damping by the forest when subject to large waves at higher water levels.

Integrating mangrove growth and failure in coastal flood protection designs

Mangrove forests reduce wave attack along tropical and sub-tropical coastlines, decreasing the wave loads acting on coastal protection structures. Mangrove belts seaward of embankments can therefore lower their required height and decrease their slope protection thickness. Wave reduction by mangroves depends on tree frontal surface area and stability against storms, but both aspects are often oversimplified or neglected in coastal protection designs. Here we present a framework to evaluate how mangrove belts influence embankment designs, including mangrove growth over time and failure by overturning and trunk breakage. This methodology is applied to Sonneratia apetala mangroves seaward of embankments in Bangladesh, considering forest widths between 10 and 1000 m (cross-shore). For water depths of 5 m, wave reduction by mangrove forests narrower than 1 km mostly affects the slope protection and the bank erodibility, whereas the required embankment height is less influenced by mangroves. Sonneratia apetala trees experience a relative maximum in wave attenuation capacity at 10 years age, due to their large submerged canopy area. Once trees are more than 20 years old, their canopy is emergent, and most wave attenuation is caused by trunk and roots. Canopy emergence exposes mangroves to wind loads, which are much larger than wave loads, and can cause tree failure during cyclones. These results stress the importance of including tree surface area and stability models when predicting coastal protection by mangroves.

GRAY MATTER CORRELATES OF ANXIETY, DEPRESSION, AND GAIT SPEED IN OLDER ADULTS WITH CHRONIC PAIN

Abstract Chronic pain and its comorbidities, (e.g., anxiety, depression, slow gait speeds) are a widespread, disabling condition prevalent among older adults. Worse anxiety and depression have been associated with slower gait speeds in individuals with chronic pain, and each comorbidity has been associated with structural gray matter changes; however, results are inconclusive or limited. Further investigation into these relationships may provide insight into neural mechanisms through which anxiety and depression contribute to slow gait speeds in this population. Therefore, the aim of this study was to identify gray matter measures associated with anxiety, depression, and gait speed in older adults with chronic pain. Participants (n = 31) walked across a GAITRite mat to obtain gait speed, and completed the State-Trait Anxiety Inventory (STAI), Center for Epidemiologic Studies Depression Scale (CES-D), and a T1-weighted anatomical scan. STAI score (mean = 7, β = - 0.015, p = 0.010) and CES-D score (mean = 30, β = - 0.014, p = 0.016) were significantly associated with gait speed. CES-D score was associated with left cuneus gyrus (β = 0.017, p = 0.0002) and frontal inferior sulcus surface area (β = 0.019, p = 0.002). Gait speed was associated with right inferior temporal gyrus surface area (β = 0.436, p = 0.019). STAI score was not associated with any measure. In conclusion, anxiety and depression symptoms contribute to gait slowing in older adults with chronic pain but without clinical depression or anxiety. This relationship, however, is not reflected in each comorbidity’s structural neural correlates.

Associations Between Family History of Alcohol and/or Substance Use Problems and Frontal Cortical Development From 9 to 13 Years of Age: A Longitudinal Analysis of the ABCD Study

BackgroundPrevious investigations that have examined associations between family history (FH) of alcohol/substance use and adolescent brain development have been primarily cross-sectional. Here, leveraging a large population-based sample of youths, we characterized frontal cortical trajectories among 9- to 13-year-olds with (FH+) versus without (FH−) an FH and examined sex as a potential moderator. MethodsWe used data from 9710 participants in the Adolescent Brain Cognitive Development (ABCD) Study (release 4.0). FH+ was defined as having ≥1 biological parents and/or ≥2 biological grandparents with a history of alcohol/substance use problems (n = 2433). Our primary outcome was frontal cortical structural measures obtained at baseline (ages 9–11) and year 2 follow-up (ages 11–13). We used linear mixed-effects models to examine the extent to which FH status qualified frontal cortical development over the age span studied. Finally, we ran additional interactions with sex to test whether observed associations between FH and cortical development differed significantly between sexes. ResultsFor FH+ (vs. FH−) youths, we observed increased cortical thinning from 9 to 13 years across the frontal cortex as a whole. When we probed for sex differences, we observed significant declines in frontal cortical thickness among boys but not girls from ages 9 to 13 years. No associations were observed between FH and frontal cortical surface area or volume. ConclusionsHaving a FH+ is associated with more rapid thinning of the frontal cortex across ages 9 to 13, with this effect driven primarily by male participants. Future studies will need to test whether the observed pattern of accelerated thinning predicts future substance use outcomes.

Evaluating the patella bone for sex estimation in Northwest Indian subjects: A radiological study

ObjectivesIn forensic identification, pelvis, post cranial bones especially long bones and skull are considered best for sex estimation. But there are circumstances where these bones cannot be recovered for establishing the correct biological profile of unknown human skeletal remains. In those cases, other skeletal bones should be investigated for sex estimation. The goal of the present study was to validate whether the patellar bone measurements through CT scan can be used for the sex estimation in Northwest Indian subjects. Materials and methodsThis study comprises of 344 subjects (179 males and 165 females) between the age group of 18- 80 years. Eight variables of patella were selected in the study for sex estimation using CT scan images of patella. ResultsAll the variables were statistically significant with p-value< 0.05 for indicating the sex. Univariate and multivariate discriminant function analysis (direct and stepwise method) were applied for sex estimation. The overall accuracy rate of classifying sex was 88.4% for multivariate stepwise discriminant function analysis and 87.8% for multivariate direct discriminant function analysis. Total perimeter of patella (TPP) was found to be the best variable for sex estimation with overall accuracy rate of 84.9%. ConclusionThe present study emphasized on the most dimorphic variables of patella in Northwest Indian subjects. New variables of patella namely Patellar Femoral Distance (PFD), Patellar Apex Angle (PAA), Frontal Surface Area of patella (FSA) and Total Perimeter of Patella (TPP) were added in the study of Indian subjects. This brought an overall accuracy rate of classification above 85%. The study confirmed that patellar bone's linear and angular measurements can be used for forensic identification casework.

Cortical and subcortical structural differences in psychostimulant-free ADHD youth with and without a family history of bipolar I disorder: a cross-sectional morphometric comparison

Although attention-deficit/hyperactivity disorder (ADHD) and a family history of bipolar I disorder (BD) are associated with increased risk for developing BD, their neuroanatomical substrates remain poorly understood. This study compared cortical and subcortical gray matter morphology in psychostimulant-free ADHD youth with and without a first-degree relative with BD and typically developing healthy controls. ADHD youth (ages 10-18 years) with (‘high-risk’, HR) or without (‘low-risk’, LR) a first-degree relative with BD and healthy comparison youth (HC) were enrolled. High-resolution 3D T1-weighted images were acquired using a Philips 3.0 T MR scanner. The FreeSurfer image analysis suite was used to measure cortical thickness, surface area, and subcortical volumes. A general linear model evaluated group differences in MRI features with age and sex as covariates, and exploratory correlational analyses evaluated associations with symptom ratings. A total of n = 142 youth (mean age: 14.16 ± 2.54 years, 35.9% female) were included in the analysis (HC, n = 48; LR, n = 49; HR, n = 45). The HR group exhibited a more severe symptom profile, including higher mania and dysregulation scores, compared to the LR group. For subcortical volumes, the HR group exhibited smaller bilateral thalamic, hippocampal, and left caudate nucleus volumes compared to both LR and HC, and smaller right caudate nucleus compared with LR. No differences were found between LR and HC groups. For cortical surface area, the HR group exhibited lower parietal and temporal surface area compared with HC and LR, and lower orbitofrontal and superior frontal surface area compared to LR. The HR group exhibited lower left anterior cingulate surface area compared with HC. LR participants exhibited greater right pars opercularis surface area compared with the HC. Some cortical alterations correlated with symptom severity ratings. These findings suggest that ADHD in youth with a BD family history is associated with a more a severe symptom profile and a neuroanatomical phenotype that distinguishes it from ADHD without a BD family history.

Understanding the Importance of Drag Coefficient Assessment for a Deeper Insight into the Hydrodynamic Profile of Swimmers.

The main objective of this study was to confirm that the passive drag coefficient is less dependent on swimming speed than the passive drag, Froude, and Reynolds numbers, even as swimming speed increases. The sample consisted of 12 young proficient non-competitive swimmers (seven males and five females: 20.4 ± 1.9 years). Passive drag was measured with a low-voltage isokinetic engine at 1.2, 1.4, 1.6 and 1.8 m/s. The frontal surface area was measured using digital photogrammetry. Passive drag showed significant differences with a strong effect size over the four towing speeds measured (F = 116.84, p < 0.001, η2 = 0.91) with a quadratic relationship with speed. The Froude and Reynolds numbers had similar trends, but with linear relationships. Conversely, the passive drag coefficient showed non-significant differences across the four towing speeds (F = 3.50, p = 0.062, η2 = 0.33). This strongly suggests that the passive drag coefficient should be the variable of choice for monitoring the hydrodynamic profile of swimmers rather than the absolute value of passive drag.

The Physical Properties of Arabica and Robusta Coffee Beans from Temanggung and Lampung

The development of processes and handling techniques, packing, and transportation of coffee beans all benefit from knowledge of the physical attributes of coffee beans. This research was done to describe the physical characteristics of green and roasted Temanggung and Lampung coffee beans. The findings revealed that Robusta roasted beans from Lampung with a moisture content of 1.70% had the highest values of bean dimensions, geometric mean diameter, arithmetic mean diameter, equivalent mean diameter, frontal surface area, surface area, and volume. Arabica green beans from Lampung and Temanggung had the highest shape index and density values, whereas Arabica roasted beans from Lampung had the highest aspect ratio and sphericity values. Arabica green beans from Temanggung and Arabica roasted beans from Lampung had moisture contents of 6.46% and 2.69%, respectively. Meanwhile, Robusta green beans from Lampung had the greatest scores for mass and porosity. To offer somewhat full information on the design factors involved in the roasting profile of a coffee roaster, other engineering properties should be investigated in future studies.

IMPROVING ANALYTICAL WAVE DAMPING MODELS FOR WOODY VEGETATION

Including vegetation in front of dikes is a promising addition to stand-alone hard infrastructures for the safety against flooding. Vegetation dampens the incoming waves, alters velocity structures and enhances sedimentation. Besides this, it provides other ecosystem benefits such as increasing biodiversity and scenic values. However, these cannot be implemented yet as we need more accurate ways of predicting wave damping, especially during storm conditions. We need both hydraulic and vegetation measurements, where the latter is difficult for woody vegetation as they consist of more complex structures (i.e., branch densities, angles and tapering) than grassy vegetation. Part of the Woody project aims to improve existing analytical models for wave damping by woody vegetation. We will mainly focus on accurate vegetation input (i.e., frontal-surface area and flexibility) as well as quantifying the impact of these parameters on wave damping, and how to implement this in small-scale physical models. Thereto we also aim to identify possible scale effects during scaled physical modelling. Finally, these findings will be implemented in existing analytical formulations.

Agreement between Different Methods to Measure the Active Drag Coefficient in Front-Crawl Swimming.

The aim of this study was to analyze the agreement of the active drag coefficient measured through drag and propulsion methods. The sample was composed of 18 swimmers (nine boys: 15.9 ± 0.9 years; nine girls: 15.3 ± 1.2 years) recruited from a national swimming team. The velocity perturbation method was used as the drag measurement system and the Aquanex system as the propulsion system. For both sexes combined, the frontal surface area was 0.1128 ± 0.016 m2, swim velocity 1.54 ± 0.13 m.s-1, active drag 62.81 ± 11.37 N, propulsion 68.81 ± 12.41 N. The level of the active drag coefficient agreement was calculated based on the mean values comparison, simple linear regression, and Bland Altman plots. The mean data comparison revealed non-significant differences (p > 0.05) between methods to measure the active drag coefficient. Both the linear regression (R2 = 0.82, p < 0.001) and Bland Altman plots revealed a very high agreement. The active drag coefficient should be the main outcome used in the interpretation of the swimmers' hydrodynamic profile, because it is less sensitive to swimming velocity. Coaches and researchers should be aware that the active drag coefficient can also be calculated based on propulsion methods and not just based on drag methods. Thus, the swimming community can now use different equipment to measure the hydrodynamics of their swimmers.

Structural brain alterations associated with suicidal thoughts and behaviors in young people: results from 21 international studies from the ENIGMA Suicidal Thoughts and Behaviours consortium

Identifying brain alterations associated with suicidal thoughts and behaviors (STBs) in young people is critical to understanding their development and improving early intervention and prevention. The ENIGMA Suicidal Thoughts and Behaviours (ENIGMA-STB) consortium analyzed neuroimaging data harmonized across sites to examine brain morphology associated with STBs in youth. We performed analyses in three separate stages, in samples ranging from most to least homogeneous in terms of suicide assessment instrument and mental disorder. First, in a sample of 577 young people with mood disorders, in which STBs were assessed with the Columbia Suicide Severity Rating Scale (C-SSRS). Second, in a sample of young people with mood disorders, in which STB were assessed using different instruments, MRI metrics were compared among healthy controls without STBs (HC; N = 519), clinical controls with a mood disorder but without STBs (CC; N = 246) and young people with current suicidal ideation (N = 223). In separate analyses, MRI metrics were compared among HCs (N = 253), CCs (N = 217), and suicide attempters (N = 64). Third, in a larger transdiagnostic sample with various assessment instruments (HC = 606; CC = 419; Ideation = 289; HC = 253; CC = 432; Attempt=91). In the homogeneous C-SSRS sample, surface area of the frontal pole was lower in young people with mood disorders and a history of actual suicide attempts (N = 163) than those without a lifetime suicide attempt (N = 323; FDR-p = 0.035, Cohen’s d = 0.34). No associations with suicidal ideation were found. When examining more heterogeneous samples, we did not observe significant associations. Lower frontal pole surface area may represent a vulnerability for a (non-interrupted and non-aborted) suicide attempt; however, more research is needed to understand the nature of its relationship to suicide risk.

Gender-related association among childhood maltreatment, brain structure and clinical features in bipolar disorder

Bipolar disorder (BD) and exposure to childhood maltreatment (CM), which is present at high rates in BD, are both associated with hippocampus and prefrontal cortex structural alterations thought to contribute to clinical features. Gender-related differences are implicated in BD for CM exposure, brain structure and clinical features. However, relationships among these factors in BD are understudied. This study aimed to investigate associations among gender, CM, hippocampus and prefrontal gray matter structure and clinical features in BD. Childhood trauma questionnaire, structured clinical assessments and 3 Tesla structural magnetic resonance imaging were obtained for 236 adults (18–63 years, 32.0 ± 12.6): 119 with BD (58.8% women) and 117 healthy controls (HCs, 50.4% women). Women with BD reported higher CM severity than men with BD and HCs (B=-14.34, 95% confidence intervals (CI)[-22.71,-5.97], p<.001). CM and gender showed a significant interaction for left hippocampus (B=-7.41, 95% CI[-14.10,-0.71], p<.05); CM severity was negatively associated with left hippocampus only in women with BD. In women with BD, CM was associated with post-traumatic stress disorder comorbidity (B = 25.68, 95% CI[15.11,36.25], p<.001). In men with BD, CM severity was associated with lower left frontal pole (B=-0.71, 95% CI[-1.14,-0.28], p<.05) and right superior frontal (B=-17.78, 95% CI[-30.66,-4.90], p<.05) surface area; the latter related to earlier age of first mood symptoms (B = 33.97, 95% CI[7.61, 60.33], p<.05). Findings support gender-related effects of CM on frontotemporal structure and clinical features of BD. The findings bring novel perspectives for gendered pathophysiological models of effects of CM in BD.

The dimensional and morphological assessment of frontal air sinus in different ages, genders and ethnicities (Arabian-Caucasian and Han-Chinese sub-populations).

This study aimed to assess the dimensional and morphological measurements of the frontal air sinuses in different ages and genders in the two ethnicities. This retrospective study included 360 subjects (160 males and 200 females) of both ethnicities. Subjects were divided based on age and gender into four groups, including an equal number of both males and females, for each age and ethnic group. The frontal air sinus dimensions were measured utilizing lateral cephalometric radiographs and computed using Winceph version 9.0 software. The frontal air sinus dimensions were compared between age groups in both genders and between ethnicity using an independent sample t test. The relationship between the frontal air sinus dimensions and subjects' age was evaluated using Pearson's correlation coefficient. The frontal air sinuses measurements were larger in males than females in both ethnicities, except for the frontal sinus index, which was found to be larger in females than males. The frontal air sinus surface area and height showed statistically significant differences between the two age groups in both ethnicities (P < 0.05). The Arabian-Caucasian patients had a larger frontal sinus surface area, height, and depth than the Han-Chinese patients in both age groups. The size of the frontal air sinus increases with age; and continues to expand after the age of 20years. Based on the Arabian-Caucasian and Han-Chinese sub-population findings, the frontal sinus is an effective tool for determining gender and appears to have potential in ethnicity identification.

Morphological and dimensional variations of the frontal air sinuses in a group of adolescent Caucasians and Chinese in different skeletal malocclusions: a cross-sectional cephalometric study.

This study aimed to evaluate the morphological and dimensional variations of the frontal air sinuses in a group of adolescent Caucasians and Chinese with different skeletal malocclusions in both genders. This retrospective study included 290 adolescent Caucasians and Chinese patients with 145 each. Each sample included 90 females and 55 males and was categorized based on ANB angle in reference to each population norms into 65 skeletal class I, 50 skeletal class II, and 30 skeletal class III malocclusions. All linear, angular, and surface area measurements of the frontal air sinuses were evaluated using lateral cephalometric radiographs and calculated using Winceph version 8 software. The frontal air sinus parameters were compared between genders and the two ethnic groups using an independent sample t-test. ANOVA with Tukey's post hoc tests were used to compare the frontal air sinus parameters between the three skeletal malocclusions. The frontal air sinus width and surface area were found to be significantly greater in Caucasians when compared with Chinese patients. According to gender, the frontal air sinus length, width, and surface area, as well as the glabella convexity, were greater in males than females, while the frontal air sinus index (length/width) was significantly greater in females than males in both ethnic groups. In both ethnic groups, the frontal air sinus surface area was significantly greater in skeletal class III malocclusion when compared to skeletal class I and class II malocclusions in Caucasians (P = 0.0022) and Chinese (P = 0.0097). There was a weak-to-moderate correlation between the frontal air sinus parameters and the nasio, sella, and glabella positions (R = -0.56 to 0.62). The frontal air sinus dimensions and surface area varied greatly in between ethnic groups, genders, and malocclusion types. The frontal air sinus parameters were correlated with nasion, sella, and glabella positions. These findings could assist orthodontists, ENT specialist, and forensic medical investigators to focus on the size of frontal sinus during treatment planning, the relationship between the size of frontal air sinus and malocclusions, and age determination.

Engineering properties of the cashew nut in context of designing post-harvest handling and processing machinery

The determination of the engineering properties of the cashew nut is essential as the basis for the design and development of appropriate and optimum post-harvest handling and processing machinery. The present study examined the physical, mechanical and colour properties of cashew nuts (n = 100) at a moisture content of 7.63% (wet basis) derived from Central Java, Indonesia. The main characteristics included the length, width, thickness, mass, volume, and density. The derivative properties consisted of the geometric diameter, arithmetic diameter, surface area, frontal surface area, transverse area, shape index, sphericity, bulk density, and porosity. The mechanical properties included the static friction, static and dynamic angle of repose, and compressive load (in four orientations). It was identified that the cashew nut from Central Java was dominant with a small-medium size with an average mass of 5.42 ± 0.99 g. This cashew nut was thicker, but shorter in length than the cashew nuts from India, Nigeria, and Ivory Coast. The results of the stepwise regression analysis determined that the volume had the most substantial relationship with the mass (R&lt;sup&gt;2&lt;/sup&gt; = 0.949), the bulk density had the highest correlation with the mass (R&lt;sup&gt;2&lt;/sup&gt; = 0.968), and the porosity showed a high correlation with the true density and mass (R&lt;sup&gt;2&lt;/sup&gt; = 0.997). The highest friction, static angle of repose, and-dynamic angle of repose occurred on the surface plywood, and the lowest was on the stainless-steel surface. In the context of designing appropriate cashew nut cracking equipment, it was recommended to provide the impact parallel to the longitudinal axis orientation due to the minimum compressive load (reduce the power requirement). Furthermore, the cashew nut colour properties of the L*, a*, b* coordinates were 35.988, 0.427, 1.718, respectively.

Diminished frontal pole size and functional connectivity in young adults with high suicidality

BackgroundSuicide rates among young people have been increasing in recent years, yet no validated methods are available for identifying those who are at greatest risk for suicide. Abnormalities in the medial prefrontal cortex have been previously observed in suicidal individuals, but confounding factors such as treatment and chronic illness may have contributed to these findings. Thus, in this study we tested whether the size of the medial prefrontal cortex is altered in suicidal young adults who have received no treatment with psychotropic medications. MethodsSuicidality was evaluated using the Suicide Behaviors Questionnaire-Revised (SBQ-R) and surface areas of four regions-of-interest (ROIs) within the medial prefrontal cortex were measured using magnetic resonance imaging (MRI) in a cohort of college students (n = 102). In addition, a secondary seed-based functional connectivity analysis was conducted using resting-state functional MRI data. Areas and functional connectivity of the medial prefrontal cortex of young adults with high suicidality (HS; SBQ-R score > 7; n = 20) were compared to those with low suicidality (LS; SBQ-R score = 3, n = 37). ResultsCompared to the LS group, the HS group had a significantly lower surface area of the right frontal pole (p < 0.05, Bonferroni-corrected) and significantly lower functional connectivity of the right frontal pole with the bilateral inferior frontal cortex (p < 0.001, Monte-Carlo corrected). LimitationThese findings require replication in a larger sample and extension in younger (adolescent) populations. ConclusionDiminished frontal pole surface area and functional connectivity may be linked to elevated levels of suicidality in young people.

Quantifying Frontal-Surface Area of Woody Vegetation: A Crucial Parameter for Wave Attenuation

The last years, capacity of vegetation to reduce wave impact is receiving considerable attention. To predict wave attenuation processes within vegetation fields reliable estimates of vegetation parameters are needed. This proves to be difficult for woody vegetation as it consists of complex branch structures, characterized by varying branch densities, diameters and angles. State of the art physical and numerical models effectively use a single value for the diameter, bv and density, N of vegetation, which is unrepresentative for complex vegetation, such as trees. Trees can be better described by the projected frontal-surface area, Av. Hence, this work compares methods to quantify the Av in space for a pollard willow forest, and determines suitability of these methods for predicting wave attenuation using a spectral wave model (SWAN). We use data from manual measurements and Terrestrial Laser Scans (TLS), to estimate the vertical distribution of Av; and data from large-scale flume experiments performed on a willow forest to verify model sensitivity to Av inferences. As a baseline for comparison, tree models that describe the structure of the trees in various degrees of complexity are compiled. The most realistic tree model is used to quantify potential errors in TLS and basic manual measurements of N and bv. An initial comparison shows that the TLS data underestimates Av, which indicates that conducting manual measurements is more suitable to quantify a homogeneous forest. We found that the TLS suffers from shadowing effects (i.e., blockage of laser beams) and we recommend to apply a correction factor to improve its measurements. Furthermore, we identified the impact that the different methods to determine Av have on the estimation of wave attenuation using SWAN; in addition we verified the model results with data from large-scale flume experiments performed on the willow forest. The modeled sensitivity tests indicate large differences in wave attenuation and, consequently, a wide range (0.94–1.70) of bulk drag coefficients, C~D, for the various methods applied. This shows the variation of outcome between measuring methods and highlights the importance of stating the selected method for reliable frontal-surface area estimations, and consequently for reliable wave attenuation predictions.

Vision-Based System for Automated Estimation of the Frontal Area of Swimmers: Towards the Determination of the Instant Active Drag: A Pilot Study.

Swimmers take great advantage by reducing the drag forces either in passive or active conditions. The purpose of this work is to determine the frontal area of swimmers by means of an automated vision system. The proposed algorithm is automated and also allows to determine lateral pose of the swimmer for training purposes. In this way, a step towards the determination of the instantaneous active drag is reached that could be obtained by correlating the effective frontal area of the swimmer to the velocity. This article shows a novel algorithm for estimating the frontal and lateral area in comparison with other models. The computing time allows to obtain a reasonable online representation of the results. The development of an automated method to obtain the frontal surface area during swimming increases the knowledge of the temporal fluctuation of the frontal surface area in swimming. It would allow the best monitoring of a swimmer in their swimming training sessions. Further works will present the complete device, which allows to track the swimmer while acquiring the images and a more realistic model of conventional active drag ones.

Modelling wave attenuation by saltmarsh using satellite-derived vegetation properties

Saltmarshes are increasingly recognised an important asset in coastal management as they dissipate wave energy and thus reduce the potential for coastal flooding. The frontal surface area (FSA) and the drag coefficient (Cd) are parameters commonly used in wave attenuation models to express the resistance of vegetation structure to incident waves. The FSA of vegetation represents the vertical surface area facing incoming waves which is calculated as the product of height, diameter and density whereas Cd is often used as tunable parameter that represents the vegetation-wave interactions that relies on both vegetation properties and wave conditions. Despite their importance in numerical modelling, substantial uncertainty remains in obtaining these parameters in the field due to the time-intensive and relatively expensive nature of data collection. An alternative structural vegetation parameter that can be included in wave attenuation models is the leaf area index (LAI). The primary advantage of the LAI is that it can be readily derived from satellite imagery, and thus provides a low-cost, fast alternative to field data collection. However, to date, its incorporation in widely-used coastal engineering models is lacking. The aim of this paper is to verify the use of remote-sensed LAI in numerical wave models as an alternative to FSA. Here, the widely used XBeach model for simulating storm impacts on a range of coastal systems is applied to two open coast sites with extensive saltmarsh; Chesapeake Bay, USA, and Brancaster, UK. To assess the performance of wave attenuation modelling using both methods, we compared the use of remote-sensed LAI from satellite imagery and field-based FSA as inputs into the model. The LAI-based model provides similar levels of accuracy as the FSA-based model. Likewise, higher uncertainties related to plant height, diameter, and density were found in the FSA-based model than in the LAI-based model. Therefore, the LAI-based model provides the advantage of a low-cost and fast method to accurately estimate and predict wave attenuation by vegetation using numerical models such as XBeach. Our practical application in the Brancaster site exemplifies an easy and fast approach to obtaining structural parameters of saltmarsh vegetation and estimating wave attenuation between natural and artificial saltmarshes as well as between seasons.

Perceived Discrimination and Superior Frontal Cortex Surface Area in Children: Sex Differences

Background: Limited knowledge exists on the role of Perceived Discrimination (PD) as a social determinant and risk factor that influences children’s brain development and whether this association is different for male and female children. Aim: To examine the association between PD, the superior frontal cortex, and sex differences in a national sample of 9/10-year-old children in the US. Methods: This cross-sectional study included 8,719 children from the Adolescent Brain Cognitive Development (ABCD) study. The exposure variable was PD, and the outcome variables were the right and left superior frontal cortex surface areas, measured using structural MRIs. Covariates included: age, family structure, parental education, household income, stressful life events, financial stress, neighborhood poverty, and neighborhood toxins/pollutants (lead, PM2.5, and NO2). We used a mixed-effect regression model for data analysis to adjust to the nested nature of the ABCD data. Results: There was an inverse association between PD and superior frontal cortex surface area in children. We found a statistically significant interaction between PD and the superior frontal cortex, indicating a more prominent inverse association between PD and superior frontal cortex surface area in males than females. Similar findings were observed for the right and left hemispheres. Conclusion: High levels of PD may be a more salient determinant of superior frontal cortex surface area for male than female children. Sex may alter the relevance of high PD for the brain development of US children. More research is needed on the mechanism by which sex differences emerge in the association between PD and brain development.