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Rockfall inventories are essential to quantify a rockfall activity and characterize the hazard. Terrestrial laser scanning and advancements in processing algorithms have resulted in three-dimensional (3D) semi-automatic extraction of rockfall events, permitting detailed observations of evolving rock masses. Currently, multiscale model-to-model cloud comparison (M3C2) is the most widely used distance computation method used in the geosciences to evaluate 3D changing features, considering the time-sequential spatial information contained in point clouds. M3C2 operates by computing distances using points that are captured within a projected search cylinder, which is locally oriented. In this work, we evaluated the effect of M3C2 projection diameter on the extraction of 3D rockfalls and the resulting implications on rockfall volume and shape. Six rockfall inventories were developed for a highly active rock slope, each utilizing a different projection diameter which ranged from two to ten times the point spacing. The results indicate that the greatest amount of change is extracted using an M3C2 projection diameter equal to, or slightly larger than, the point spacing, depending on the variation in point spacing. When the M3C2 projection diameter becomes larger than the changing area on the rock slope, the change cannot be identified and extracted. Inventory summaries and illustrations depict the influence of spatial averaging on the semi-automated rockfall extraction, and suggestions are made for selecting the optimal projection diameter. Recommendations are made to improve the methods used to semi-automatically extract rockfall from sequential point clouds.

Dyslexia, or reading difficulty, is characterized by slow, inaccurate reading accompanied by executive dysfunction. Reading training using the Reading Acceleration Program improves reading and executive functions in both children with dyslexia and typical readers. This improvement is associated with increased activation in and functional connectivity between the anterior cingulate cortex, part of the cingulo-opercular cognitive-control network, and the fusiform gyrus during a reading task after training. The objective of the current study was to determine whether the training also has an effect on functional connectivity of the cingulo-opercular and fronto-parietal cognitive-control networks during rest in children with dyslexia and typical readers. Fifteen children with reading difficulty and 17 typical readers (8-12 years old) were included in the study. Reading and executive functions behavioral measures and resting-state functional magnetic resonance imaging data were collected before and after reading training. Imaging data were analyzed using a graphical network-modeling tool. Both reading groups had increased reading and executive-functions scores after training, with greater gains among the dyslexia group. Training may have less effect on cognitive control in typical readers and a more direct effect on the visual area, as previously reported. Statistical analysis revealed that compared to typical readers, children with reading difficulty had significantly greater functional connectivity in the cingulo-opercular network after training, which may demonstrate the importance of cognitive control during reading in this population. These results support previous findings of increased error-monitoring activation after reading training in children with dyslexia and confirm greater gains with training in this group.

Abstract Study Objectives Poor sleep in adolescents can increase the risk of obesity, possibly due to changes in dietary patterns. Prior neuroimaging evidence, mostly in adults, suggests that lacking sleep results in increased response to food cues in reward-processing brain regions. Needed is a clarification of the mechanisms by which food reward processing is altered by the kind of chronic sleep restriction (SR) typically experienced by adolescents. This study aimed to elucidate the impact of sleep duration on response to visual food stimuli in healthy adolescents using functional neuroimaging, hypothesizing increased reward processing response after SR compared to a well-rested condition. Methods Thirty-nine healthy adolescents, 14–17 years old, completed a 3-week protocol: (1) sleep phase stabilization; (2) SR (~6.5 h nightly); and (3) healthy sleep (HS) duration (~9 h nightly). Participants underwent functional MRI while performing a visual food paradigm. Contrasts of food versus nonfood responses were compared within-subject between conditions of SR and HS. Results Under SR, there was a greater response to food stimuli compared to HS in a voxel cluster including the left ventral tegmental area and substantia nigra. No change in food appeal rating due to the sleep manipulation was detected. Conclusions Outcomes of this study suggest that SR, as commonly experienced by healthy adolescents, results in the elevated dopaminergic drive of the reward network that may augment motivation to seek food in the context of individual food appeal and inhibitory profiles. Countermeasures that reduce food salience could include promoting consistent HS habits. Graphical Abstract

Laser scanning is routinely being used for the characterization and management of rockfall hazards. A key component of many studies is the ability to use the high-resolution topographic datasets for detailed volume estimates. 2.5-Dimensional (2.5D) approaches exist to estimate the volume of rockfall events; however these approaches require rasterization of the point cloud. These 2.5D volume estimates are therefore sensitive to picking an appropriate cell size to preserve resolution while minimizing interpolation, especially for lower volume rockfall events. To overcome the limitations of working with 2.5D raster datasets, surface reconstruction methods originating from the field of computational geometry can be implemented to assess the volume of rockfalls in 3D. In this technical note, the authors address the methods and implications of how the surface of 3D rockfall objects, derived from sequential terrestrial laser scans (TLS), are reconstructed for volumetric analysis. The Power Crust, Convex Hull and Alpha-shape algorithms are implemented to reconstruct a synthetic rockfall object generated in Houdini, a procedural modeling and animation software package. The reconstruction algorithms are also implemented for a selection of three rockfall cases studies which occurred in the White Canyon, British Columbia, Canada. The authors find that there is a trade-off between accurate surface topology reconstruction and ensuring the mesh is watertight manifold; which is required for accurate volumetric estimates. Power Crust is shown to be the most robust algorithm, however, the iterative Alpha-shape approach introduced in the study is also shown to find a balance between hole-filling and loss of detail.

White matter hyperintensities (WMH) are the most prominent imaging feature of small vessel disease (SVD). WMH and other imaging features of SVD are likely the result of ongoing insults associated with cognitive decline and cerebrovascular events. Emerging evidence suggests degradation of the neurovascular unit may underlie the pathogenesis of SVD. This prospective pilot study employed MRI in 19 subjects (68.2 ± 11.5 years of age) for diffusion-weighted imaging, applied to intravoxel incoherent motion (IVIM) modeling, to characterize microstructural and microvascular properties throughout the brain and arterial spin labeling, using multiple labeling and delay times, to measure dynamic perfusion properties including blood–brain barrier permeability (PS) in gray matter (GM). IVIM revealed WMH to have significantly greater blood volume fraction and lower pseudodiffusion and bulk diffusion than normal-appearing white matter (NAWM). IVIM parameters and PS, in canonical GM network regions, correlated with WMH volume with at least moderate effect size. Findings suggest the potential for neovascularization and evidence of restricted diffusion in WMH compared to surrounding NAWM. Regional changes in GM pertaining to the NVU scale in proportion to WMH load. Observed GM changes precede visible MR imaging abnormalities. Their early detection could elucidate SVD mechanisms of brain injury and inform future preventative measures.

Examine the effect of experimental sleep restriction (SR) on adolescents' subjective hunger and perceived appeal of sweet/dessert foods versus other foods. A secondary goal was to replicate previous findings on the effects of SR on dietary intake. Randomized cross-over sleep restriction-extension paradigm. Sleep was obtained and monitored at home. Outcome measures were gathered during office visits. 31 typically-developing adolescents aged 14-17 years. The three-week protocol consisted of a baseline week, followed randomly by five consecutive nights of SR (6.5 hours in bed) versus healthy sleep duration (HS; 10 hours in bed), a 2-night wash-out period, and a 5-night cross-over. Sleep was monitored via actigraphy. The morning after each experimental condition, teens rated their hunger, underwent a 24-hour diet recall interview, and rated the appeal of a series of pictures of sweet/dessert foods (e.g., ice cream, candy) and non-sweets (meat, eggs, fruits, vegetables). Teens rated pictures of sweet/dessert foods to be more appealing after SR than after HS (Cohen's d = .41, t = 2.07, p = .045). The sleep manipulation did not affect self-reported hunger or the appeal of non-sweet foods (p >.10). Consistent with our prior work, intake of overall calories was 11% higher and consumption of sweet/dessert servings was 52% greater during SR than HS. Adolescent SR appears to increase the subjective appeal of sweet/dessert foods, indicating a potential mechanism by which SR might contribute to weight gain and the risk for obesity and chronic illness.

Background To measure regional brain microvascular and microstructural changes in childhood-onset SLE (cSLE) using diffusion-weighted imaging (DWI) at multiple b values and investigate relationships of those measures with neurocognitive function and disease activity. Methods In this cross-sectional, case-control study, vascular volume fraction, effective diffusion, parenchymal diffusion, and blood flow parameters were regionally compared in cSLE patients and matched healthy controls. These markers of microvascular and microstructural integrity were derived by diffusion-weighted brain MRI and intravoxel incoherent motion (IVIM) modeling. Formal neurocognitive testing was completed focused on the domains of attention, visuoconstructional ability, working memory, and psychomotor speed. Test scores and measures of disease severity were regressed against regional microvascular integrity parameters among cSLE patients. Results Formal cognitive testing confirmed normal cognitive ability among all cSLE patients included in the analysis ( n  = 11). Nevertheless, reduction in blood volume fraction coincided with increased effective diffusion and flow parameters in cSLE patients vs. controls in posterior brain regions including the cuneus and precuneus. Regional microvascular measures correlated (| r | = 0.54–0.66) with neuropsychiatric scores and disease activity among cSLE patients. Conclusions There is imaging evidence, using IVIM, of degraded microvascular integrity in cSLE patients with normal cognitive ability. The observed regional changes correspond with posterior vascular border zones. These outcomes appear consistent with regional gray matter volume loss previously observed in cSLE patients with overt neurocognitive deficits, supporting the notion that adverse vascular changes precede loss of cognitive ability in cSLE. Longitudinal studies are needed to confirm the findings of this initial study.

Key to the quantification of rockfall hazard is an understanding of its magnitude-frequency behaviour. Remote sensing has allowed for the accurate observation of rockfall activity, with methods being developed for digitally assembling the monitored occurrences into a rockfall database. A prevalent challenge is the quantification of rockfall volume, whilst fully considering the 3D information stored in each of the extracted rockfall point clouds. Surface reconstruction is utilized to construct a 3D digital surface representation, allowing for an estimation of the volume of space that a point cloud occupies. Given various point cloud imperfections, it is difficult for methods to generate digital surface representations of rockfall with detailed geometry and correct topology. In this study, we tested four different computational geometry-based surface reconstruction methods on a database comprised of 3668 rockfalls. The database was derived from a 5-year LiDAR monitoring campaign of an active rock slope in interior British Columbia, Canada. Each method resulted in a different magnitude-frequency distribution of rockfall. The implications of 3D volume estimation were demonstrated utilizing surface mesh visualization, cumulative magnitude-frequency plots, power-law fitting, and projected annual frequencies of rockfall occurrence. The 3D volume estimation methods caused a notable shift in the magnitude-frequency relations, while the power-law scaling parameters remained relatively similar. We determined that the optimal 3D volume calculation approach is a hybrid methodology comprised of the Power Crust reconstruction and the Alpha Solid reconstruction. The Alpha Solid approach is to be used on small-scale point clouds, characterized with high curvatures relative to their sampling density, which challenge the Power Crust sampling assumptions.

Rockfall is a complex natural process that can present risks to the effective operation of infrastructure in mountainous terrain. Remote sensing tools and techniques are rapidly becoming the state of the practice in the characterization, monitoring and management of these geohazards. The aim of this study is to address the methods and implications of how the dimensions of three-dimensional rockfall objects, derived from sequential terrestrial laser scans (TLSs), are measured. Previous approaches are reviewed, and two new methods are introduced in an attempt to standardize the process. The approaches are applied to a set of synthetic rockfall objects generated in the open-source software package Blender. Fifty rockfall events derived from sequential TLS monitoring in the White Canyon, British Columbia, Canada, are used to demonstrate the application of the proposed algorithms. This study illustrates that the method used to calculate the rockfall dimensions has a significant impact on how the shape of a rockfall object is classified. This has implications for rockfall modelling as the block shape is known to influence rockfall runout.

Abstract Study Objectives Obstructive sleep apnea (OSA) adversely affects normal blood pressure (BP) and may disrupt circadian BP patterns. We sought to examine 24-hour circadian BP rhythms in children with OSA and healthy controls. Methods Children 5–14 years with OSA and healthy controls underwent 24-hour BP monitoring and actigraphy to quantify sleep. Shape invariant statistical models compared circadian BP patterns (e.g. times of BP peaks, time arrived at peak BP velocity [TAPV]) in the OSA and control groups. Results The analytic sample included 219 children (mild OSA: n = 52; moderate-to-severe OSA (MS-OSA): n = 50; controls: n = 117). In the morning, the MS-OSA group had earlier TAPV for DBP than controls (51 minutes, p < 0.001). TAPV in the evening was earlier for the MS-OSA group than controls (SBP: 95 minutes, p < 0.001; DBP: 28 minutes, p = 0.028). At mid-day, SBP and DBP velocity nadirs were earlier for the MS-OSA group than controls (SBP: 57 minutes, p < 0.001; DBP: 38 minutes, p < 0.01). The MS-OSA group reached most BP values significantly earlier than controls; the largest differences were 118 minutes (SBP) and 43 minutes (DBP) (p < 0.001). SBP and DBP were elevated in the MS-OSA group (hours 18–21 and 7–-12, respectively, p < 0.01) compared to controls. The MS-OSA group was prone to “non-dipping” compared to controls (SBP: odds ratio [OR] = 2.16, 95% CI: 1.09, 4.29; DBP: OR = 3.45, 95% CI: 1.21, 10.23). Conclusions Children with MS-OSA had changes in circadian BP patterns, namely earlier TAPV and BP peaks and nadirs than controls. Circadian disturbances in BP rhythms may be key to mapping the natural history of BP dysregulation in children with OSA. Graphical Abstract Graphical Abstract