Search

The endeavor to understand the human brain has seen more progress in the last few decades than in the previous two millennia. Still, our understanding of how the human brain relates to behavior in the real world and how this link is modulated by biological, social, and environmental factors is limited. To address this, we designed the Healthy Brain Study (HBS), an interdisciplinary, longitudinal, cohort study based on multidimensional, dynamic assessments in both the laboratory and the real world. Here, we describe the rationale and design of the currently ongoing HBS. The HBS is examining a population-based sample of 1,000 healthy participants (age 30–39) who are thoroughly studied across an entire year. Data are collected through cognitive, affective, behavioral, and physiological testing, neuroimaging, bio-sampling, questionnaires, ecological momentary assessment, and real-world assessments using wearable devices. These data will become an accessible resource for the scientific community enabling the next step in understanding the human brain and how it dynamically and individually operates in its bio-social context. An access procedure to the collected data and bio-samples is in place and published on https://www.healthybrainstudy.nl/en/data-and-methods/access. Trail registration: https://www.trialregister.nl/trial/7955.

Turbidity currents in the submarine seascape are what river flows are in terrestrial landscapes. While rivers transport sediment from the mountains through valleys towards the sea, turbidity currents transport sediment from the shallow marine realms through canyons towards the deeper abyssal plains. The large scale architecture of both systems is remarkably similar. Yet, there are some fundamental differences between rivers and turbidity currents, the most fundamental one being their density difference; the density of river water is thousand times denser than its surrounding air, while the density of a turbidity current can never be more than twice as dense as its ambient water. In addition, rivers do not depend on their sediment load to flow, while turbidity (density) currents do need the sediment derived excess density to flow. These physical differences change their morphodynamics on the bedform scale. Present day high-resolution seafloor observations show that turbidity current path ways are covered with bedforms that are fundamentally different from those that occur in river channels. In this chapter we point out these differences and present a 3D bedform stability diagram for turbidites.

This study aims to resolve process-facies links at both bed and environmental scales for the channel lobe transition zone (CLTZ). Data comes from existing experimental and modern CLTZ studies and from new outcrop studies. The experiments show that the CLTZ architecture of supercritical turbidity currents is complex and different from their counterparts where flows are subcritical throughout. Supercritical CLTZ’s are characterised by erosive channels formed by supercritical turbidity currents, by offset stacked lobes deposited from subcritical turbidity currents and by hydraulic jump related mouth bar deposits and upslope onlapping backfill deposits at the down slope end of the transition zone. Erosive channels and backfill features can be resolved by high resolution seismic data, yet evidence for supercritical flow must come from facies analysis of core data. Outcrop examples of the CLTZ from the Tabernas submarine fan (SE Spain) and the Llorenc del Munt deep-water delta slope (N. Spain) are used to establish such links between seismic scale architecture and facies recognised in cores. The outcrops described here were mapped as transition zone, and show 100 m sized, spoon-shaped scours filled with sediment containing sandy to gravelly backsets up to 4 m in height. Their facies and architecture is indicative of deposition by hydraulic jumps, can be recognized from cores, and is a good proxy for further predicting CLTZ architecture constructed by supercritical turbidity currents.

Palaeo shoreline is a commonly used proxy for palaeo sea level, but only if deposition is continuous and constant will shoreline trajectory T(l) completely capture sea-level time-series E(t). Artificial deltas were generated in the Eurotank flume facility under stepwise tectonic subsidence, periodic sea-level fluctuation and two periodic water-discharge scenarios, one in-phase and the other out-of-phase with sea level. Independent input variables tectonic subsidence Y, sea level E and water discharge Q (controlling sediment supply S) were varied and dependent output variable shoreline trajectory Twas monitored. These experiments confirm that deposition is discontinuous even for continuous sediment supply, and this hinders the inference of sea-level curve from shoreline trajectory. These results justify the here-developed methodology for converting shoreline trajectory from the space domain to the time domain, thereby improving the accuracy of the inferred sea-level curve. © 2015 John Wiley & Sons Ltd.

Sequence-stratigraphic models for fourth to sixth order, glacio-eustatic sequences based only on relative sea-level variations result in simplified and potentially false interpretations. Glacio-eustatic sealevel variations form only one aspect of cyclic climate variation; other aspects, such as variations in fluvial water discharge, vegetation cover, weathering and sediment supply can lead to variable sediment yield, thus adding complexity to sequence-stratigraphic patterns normally attributed to sealevel variations. Analogue flume models show a significant impact of water discharge on the timing and character of sequence boundaries, and on changes in the relative importance of systems tracts, as expressed in sediment volumes. Four deltas, generated under the influence of an identical sea-level curve, and affected by different water-discharge cycles were generated in the Eurotank facility: (1) constant discharge; (2) high-frequency discharge variations (HFD); (3) discharge leading sea level by a quarter phase; (4) discharge lagging sea level by a quarter phase. HFD shift the parasequence stacking pattern consistently but do not alter large-scale delta architecture. Water-discharge changes that lead sea-level changes result in high sediment yield during sea-level rise and in the poor development of maximum flooding surfaces. Delta-front erosion during sea-level fall is expressed by multiple, small channels related to upstream avulsions, and does not result in an incised valley that efficiently routs sediment to the shelf edge. When water-discharge changes lag sea-level changes, sediment yield is high during falling sea level and results in rapid progradation during forced regression. Erosion from incised valleys is strong on the proximal delta top and dissipates towards the delta front. The combination of high discharge and sea-level fall provides the most efficient mode of valley incision and sediment transport to the shelf edge. During sea-level rise, low water discharge results in sediment starvation and well-developed maximum flooding surfaces. Water-discharge variations thus alter sequence-stratigraphic patterns and provide an alternative explanation to the amplitude of sea-level fall for generating either type 1 or 2 erosional unconformities.

Supercritical-flow phenomena are fairly common in modern sedimentary environments, yet their recognition and analysis remain difficult in the stratigraphic record. This fact is commonly ascribed to the poor preservation potential of deposits from high-energy supercritical flows. However, the number of flume data sets on supercritical-flow dynamics and sedimentary structures is very limited in comparison with available data for subcritical flows, which hampers the recognition and interpretation of such deposits. The results of systematic flume experiments spanning a broad range of supercritical- flow bedforms (antidunes, chutes-and-pools and cyclic steps) developed in mobile sand beds of variable grain sizes are presented. Flow character and related bedform patterns are constrained through time-series measurements of bed configurations, flow depths, flow velocities and Froude numbers. The results allow the refinement and extension of some widely used bedform stability diagrams in the supercritical-flow domain, clarifying in particular the morphodynamic relations between antidunes and cyclic steps. The onset of antidunes is controlled by flows exceeding a threshold Froude number. The transition from antidunes to cyclic steps in fine to medium-grained sand occurs at a threshold mobility parameter. Sedimentary structures associated with supercritical bedforms developed under variable aggradation rates are revealed by means of combining flume results and synthetic stratigraphy. The sedimentary structures are compared with examples from field and other flume studies. Aggradation rate is seen to exert an important control on the geometry of supercritical-flow structures and should be considered when identifying supercritical bedforms in the sedimentary record.

The morphology of delta deposits in crater lakes on Mars is indicative of upstream (e.g., flow discharge and sediment properties) and downstream (e.g., basin characteristics) parameters, from which the hydrological conditions at the time of formation can be inferred. To investigate the influences of these parameters on delta morphology, we experimentally created deltas in crater-shaped basins by feeding a range of constant flow discharges over a feeder channel of various sand textures. We reproduced three categorically different types of deltas including most of the types that have been identified on Mars. Our most striking observation is that water level behavior (itself a unique function of flow discharge, basin size and hypsometry, and basin floor permeability) can explain most delta morphologies observed on Mars. Stepped, retrograding deltas formed during water level rise, prograding deltas formed during water level still stand, and during water level fall deltas were partially destroyed by erosion. On Mars numerous retrograding and prograding deltas were preserved, most of them without indications of channel incisions or other fluvial modification. We conclude that the main difference between a single-foreset prograding delta and a multiple-foreset retrograding delta is the behavior of the water level in the basin. These simple delta morphologies cannot be reconciled with long-duration hydrological activity, because that would imply crater lake fluctuations due to inherent complex water level histories along with complex sediment delivery histories. Our experiments and numerical verifications demonstrate that such deltas preferentially form during one aqueous event, which parsimoniously argues for short-duration hydrological activity.

Contains fulltext : 103469.pdf (Publisher’s version ) (Closed access)

Bodems die planten beschermen tegen bodemziekten en -plagen? Ze bestaan. De kunst is om dit verschijnsel in alle bodems op te roepen. Stap voor stap ontrafelen onderzoekers van Wageningen UR het mechanisme en ontwikkelen ze praktische toepassingen.