4 results
Age-related brain deviations and aggression
- Nathalie E. Holz, Dorothea L. Floris, Alberto Llera, Pascal M. Aggensteiner, Seyed Mostafa Kia, Thomas Wolfers, Sarah Baumeister, Boris Böttinger, Jeffrey C. Glennon, Pieter J. Hoekstra, Andrea Dietrich, Melanie C. Saam, Ulrike M. E. Schulze, David J. Lythgoe, Steve C. R. Williams, Paramala Santosh, Mireia Rosa-Justicia, Nuria Bargallo, Josefina Castro-Fornieles, Celso Arango, Maria J. Penzol, Susanne Walitza, Andreas Meyer-Lindenberg, Marcel Zwiers, Barbara Franke, Jan Buitelaar, Jilly Naaijen, Daniel Brandeis, Christian Beckmann, Tobias Banaschewski, Andre F. Marquand
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- Journal:
- Psychological Medicine / Volume 53 / Issue 9 / July 2023
- Published online by Cambridge University Press:
- 22 April 2022, pp. 4012-4021
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- Article
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Background
Disruptive behavior disorders (DBD) are heterogeneous at the clinical and the biological level. Therefore, the aims were to dissect the heterogeneous neurodevelopmental deviations of the affective brain circuitry and provide an integration of these differences across modalities.
MethodsWe combined two novel approaches. First, normative modeling to map deviations from the typical age-related pattern at the level of the individual of (i) activity during emotion matching and (ii) of anatomical images derived from DBD cases (n = 77) and controls (n = 52) aged 8–18 years from the EU-funded Aggressotype and MATRICS consortia. Second, linked independent component analysis to integrate subject-specific deviations from both modalities.
ResultsWhile cases exhibited on average a higher activity than would be expected for their age during face processing in regions such as the amygdala when compared to controls these positive deviations were widespread at the individual level. A multimodal integration of all functional and anatomical deviations explained 23% of the variance in the clinical DBD phenotype. Most notably, the top marker, encompassing the default mode network (DMN) and subcortical regions such as the amygdala and the striatum, was related to aggression across the whole sample.
ConclusionsOverall increased age-related deviations in the amygdala in DBD suggest a maturational delay, which has to be further validated in future studies. Further, the integration of individual deviation patterns from multiple imaging modalities allowed to dissect some of the heterogeneity of DBD and identified the DMN, the striatum and the amygdala as neural signatures that were associated with aggression.
Turbulent characteristics of a shallow wall-bounded plane jet: experimental implications for river mouth hydrodynamics
- JOEL C. ROWLAND, MARK T. STACEY, WILLIAM E. DIETRICH
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- Journal:
- Journal of Fluid Mechanics / Volume 627 / 25 May 2009
- Published online by Cambridge University Press:
- 25 May 2009, pp. 423-449
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Jets arising from rivers, streams and tidal flows entering still waters differ from most experimental studies of jets both in aspect ratio and in the presence of a solid bottom boundary and an upper free surface. Despite these differences, the applicability of experimental jet studies to these systems remains largely untested by either field or realistically scaled experimental studies. Here we present experimental results for a wall-bounded plane jet scaled to jets created by flow discharging into floodplain lakes. A characteristic feature of both our prototype and experimental jets is the presence of large-scale meandering turbulent structures that span the width of the jets. In our experimental jets, we observe self-similarity in the distribution of mean streamwise velocities by a distance of six channel widths downstream of the jet outlet. After a distance of nine channel widths the velocity decay and the spreading rates largely agree with prior experimental results for plane jets. The magnitudes and distributions of the cross-stream velocity and lateral shear stresses approach self-preserving conditions in the upper half of the flow, but decrease in magnitude, and deviate from self-preserving distributions with proximity to the bed. The presence of the meandering structure has little influence on the mean structure of the jet, but dominates the jet turbulence. A comparison of turbulence analysed at time scales both greater than and less than the period of the meandering structure indicates that these structures increase turbulence intensities by 3–5 times, and produce lateral shear stresses and momentum diffusivities that are one and two orders of magnitude greater, respectively, than turbulence generated by bed friction alone.
Bedload transport of fine gravel observed by motion-picture photography
- Thomas G. Drake, Ronald L. Shreve, William E. Dietrich, Peter J. Whiting, Luna B. Leopold
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- Journal:
- Journal of Fluid Mechanics / Volume 192 / July 1988
- Published online by Cambridge University Press:
- 21 April 2006, pp. 193-217
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Motion pictures taken at Duck Creek, a clear stream 6.5 m wide and 35 cm deep near Pinedale, Wyoming, provide detailed, quantitative information on both the modes of motion of individual bedload particles and the collective motions of large numbers of them. Bed shear stress was approximately 6 Pa (60 dynes cm−2), which was about twice the threshold for movement of the 4 mm median diameter fine gravel bed material; and transport was almost entirely as bedload. The displacements of individual particles occurred mainly by rolling of the majority of the particles and saltation of the smallest ones, and rarely by brief sliding of large, angular ones. Entrainment was principally by rollover of the larger particles and liftoff of the smaller ones, and infrequently by ejection caused by impacts, whereas distrainment was primarily by diminution of fluid forces in the case of rolling particles and by collisions with larger bed particles in the case of saltating ones. The displacement times averaged about 0.2−0.4 s and generally were much shorter than the intervening repose times. The collective motions of the particles were characterized by frequent, brief, localized, random sweep-transport events of very high rates of entrainment and transport, which in the aggregate transported approximately 70% of the total load moved. These events occurred 9% of the time at any particular point of the bed, lasted 1–2 s, affected areas typically 20–50 cm long by 10–20 cm wide, and involved bedload concentrations approximately 10 times greater than background. The distances travelled during displacements averaged about 15 times the particle diameter. Despite the differences in their dominant modes of movement, the 8–16 mm particles typically travelled only about 30% slower during displacement than the 2–4 mm ones, whose speeds averaged 21 cm s−1. Particles starting from the same point not only moved intermittently downstream but also dispersed both longitudinally and transversely, with diffusivities of 4.6 and 0.26 cm2 s−1, respectively. The bedload transport rates measured from the films were consistent with those determined conventionally with a bedload sampler. The 2–4 mm particles were entrained 6 times faster on finer areas of the bed, where 8–16 mm particles covered 6% of the surface area, than on coarser ones, where they covered 12%, even though 2–4 and 4–8 mm particles covered practically the same percentage areas in both cases. The 4–8 and 8–16 mm particles, in contrast, were entrained at the same rates in both cases. To within the statistical uncertainty, the rates of distrainment balanced the rates of entrainment for all three sizes, and were approximately proportional to the corresponding concentrations of bedload.
2 - Hillslopes, Channels, and Landscape Scale
- Edited by Garrison Sposito, University of California, Berkeley
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- Book:
- Scale Dependence and Scale Invariance in Hydrology
- Published online:
- 18 January 2010
- Print publication:
- 22 October 1998, pp 30-60
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Summary
Are Landscapes Scale-invariant?
There is no doubt that channel networks display scale invariance in some respects, but this does not mean that landscapes lack distinctive scales, nor does it mean that the processes that evolve landscapes do not have scale dependence and do not impart distinctive scale-dependent morphology. Rodríguez-Iturbe and Rinaldo (1996) have summarized recent papers on channel networks and have argued for the importance of explaining the apparent scale invariance of landscape organization. Although the ubiquitous branching networks of valleys may indeed be scale-invariant or may possess attributes of multiscaling, knowledge of that cannot explain many of the fundamental issues involved in landscape form and evolution. In this chapter we focus on issues of scale and the importance of linking a process to an appropriate scale. We raise here more questions than answers, but in so doing perhaps make a case that as much as scale invariance is an appealing attribute of landscapes, understanding the controls on the actual scales of landscape features in both space and time can provide critical theoretical and practical insights into landscape processes and evolution.
Part of this discussion about scale in geomorphology is driven by the advent of computer-based analysis of digital topographic surfaces. In effect, our view of landscapes over the past 20 years has shifted from one of limited analysis of topographic contours (usually focusing on individual hillslope and river profiles or calculation of drainage density) to fully two-dimensional (or three-dimensional, depending on how one counts) grid-based investigations.