“Вибране” Миколи Воробйова

Braided rivers have complicated and dynamic bar patterns, which are challenging tofully understand and to predict both qualitatively and quantitatively. Linear theoryignores nonlinear processes that dominate fully developed bars, whereas natural riverpatterns are determined by the combined effects of boundary conditions, initial conditionssuch as planimetric forcing by fixed banks and the physical processes. Here we determinethe capability of a state-of-the-art physics-based morphological model to r eproducemorphology and dynamics characteristic of braided rivers and determine the modelsensitivity to generally used constitutive relations for flow and sediment transport. We usethe 2-D depth-averaged morphodynamic model Delft3D, which includes the necessaryspiral flow and bed slope effects on morphology. We present idealized scenarios with thesmallest possible number of enforced details in the planform and boundary conditions inorder to allow free development of bars driven by the physical processes in the model.We analyze bar and channel shapes and dynamics quantified by a number ofcomplementary metrics and compare these with imagery, field data captured in empiricalrelations, flume experiments, and predictions by linear analyses. The results show that thechosen set of boundary conditions and physics in the numerical model is sufficient toproduce many morphological characteristics and dynamics of a braided river butinsufficient for long-term modeling. Initially, braiding intensity with low-amplitude barsis high in agreement with linear analysis. In a second stage when bars merge, split, andincrease amplitude up to the water surface, the shape, size, and dynamics of individualbars compare well to those in natural rivers. However, long-term modeling results in areduction of bar and channel dynamics and formation of exaggerated bar height andlength. This suggests that additional processes, such as physics-based bank erosion, orenforced fluctuations in boundary conditions, such as spatial-temporal dischargevariation, are necessary for the simulation of a dynamic equilibrium river. The mostimportant outcome is that the modeled pattern of bars and channels is highly sensitive tothe constitutive relation for bed slope effects that is used in many morphological models.Regardless of this sensitivity and present model limitations of many models, this studyshows that physics-based modeling of sand-bed braided improves our understanding andprediction of morphological patterns and dynamics in sand-bed braided rivers

The Challenge of Generating Causal Hypotheses Using Network Models

Statistical network models based on Pairwise Markov Random Fields (PMRFs) are popular tools for analyzing multivariate psychological data, in large part due to their perceived role in generating insights into causal relationships: a practice known as causal discovery in the causal modeling literature. However, since network models are not presented as causal discovery tools, the role they play in generating causal insights is poorly understood among empirical researchers. In this paper, we provide a treatment of how PMRFs such as the Gaussian Graphical Model (GGM) work as causal discovery tools, using Directed Acyclic Graphs (DAGs) and Structural Equation Models (SEMs) as causal models. We describe the key assumptions needed for causal discovery and show the equivalence class of causal models that networks identify from data. We clarify four common misconceptions found in the empirical literature relating to networks as causal skeletons; chains of relationships; collider bias; and cyclic causal models

Bifurcation instability and chute cutoff development in meandering gravel-bed rivers

Chute cutoffs reduce sinuosity of meandering rivers and potentially cause a transition from a single to a multiple channel river. The channel bifurcation of the main channel and the mouth of the incipient chute channel controls sediment and flow partitioning and development of the chute. Recent channel bifurcation models suggest that upstream bend radius, gradient advantage, inlet step, and upstream sediment supply at the bifurcation are important factors in the evolution of bifurcations. Our objective is to unravel the relative importance of these factors for chute cutoff success and development. We compare results from a morphodynamic three-dimensional (3D) model and a one-dimensional (1D) model with nodal-point relation with field observations of chute cutoffs in a meandering gravel-bed river. The balance between increased gradient advantage and flow curvature upstream of the chute channel bifurcation was systematically investigated with the 1D model. The 3D model runs and the field observations show the development of two types of chute cutoffs: a scroll-slough cutoff and a bend cutoff. The morphodynamic 3D model demonstrates that chutes are initiated when flow depth exceeds the floodplain elevation. Overbank flow and a significant gradient advantage result in a bend cutoff. The outcome of the 1D model shows that channel curvature at the bifurcation determines the success or failure of the chute cutoff when the chute channel is located at the inner bend, as in the case of scroll-slough cutoffs. We conclude that chute initiation depends on floodplain characteristics, i.e., floodplain elevation, sediment composition, and the presence of vegetation. Chute cutoff success or failure is determined by the dynamics just upstream of the channel bifurcation and location of the chute channel in the bend, which determines channel curvature and gradient advantage. These findings have ramifications for the prediction of chute cutoff in a wide range of rivers under natural and managed conditions and for the understanding of stratigraphy and architecture of deposits

Emotional reactivity and cognitive performance in aversively motivated tasks: a comparison between four rat strains

<p>Abstract</p> <p>Background</p> <p>Cognitive function might be affected by the subjects' emotional reactivity. We assessed whether behavior in different tests of emotional reactivity is correlated with performance in aversively motivated learning tasks, using four strains of rats generally considered to have a different emotional reactivity.</p> <p>Methods</p> <p>The performance of male Brown Norway, Lewis, Fischer 344, and Wistar Kyoto rats in open field (OF), elevated plus-maze (EPM), and circular light-dark preference box (cLDB) tasks, which are believed to provide measures of emotional reactivity, was evaluated. Spatial working and reference memory were assessed in two aversively motivated learning and memory tasks: the standard and the "repeated acquisition" versions of the Morris water maze escape task, respectively. All rats were also tested in a passive avoidance task. At the end of the study, levels of serotonin (5-HT) and <it>5</it>-hydroxyindoleacetic acid, and 5-HT turnover in the hippocampus and frontal cortex were determined.</p> <p>Results</p> <p>Strain differences showed a complex pattern across behavioral tests and serotonergic measures. Fischer 344 rats had the poorest performance in both versions of the Morris water escape task, whereas Brown Norway rats performed these tasks very well but the passive avoidance task poorly. Neither correlation analysis nor principal component analysis provided convincing support for the notion that OF, EPM, and cLDB tasks measure the <it>same </it>underlying trait.</p> <p>Conclusions</p> <p>Our findings do not support the hypothesis that the level of emotional reactivity modulates cognitive performance in aversively motivated tasks. Concepts such as "emotional reactivity" and "learning and memory" cannot adequately be tapped with only one behavioral test. Our results emphasize the need for multiple testing.</p

Radicalization patterns and modes of attack planning and preparation among lone-actor terrorists: an exploratory analysis

This article explores the link between radicalization patterns and modes of attack planning and preparation among lone-actor terrorists. Building on theorized patterns of lone-actor radicalization, we discuss and compare their modes of pre-attack behavior, including target and weapon choice, observance of operational security measures, likeliness of engaging in leakage behavior, and the overall amount of time devoted to these activities. This exploratory study builds upon a dataset of thirty-three lone-actor terrorist cases in North-America and Europe between 1986 and 2015. The analysis suggests that specific patterns of radicalization are linked to systematic differences in modes of attack planning and preparation. The results provide insights into the heterogeneity of terrorist involvement and tentatively suggest the potential importance for law-enforcement agencies in using case-specific knowledge on radicalization patterns to inform forecasts of likely pre-attack behaviors.Seventh Framework Programme (FP7)No. 608354 (PRIME) FP7-SEC-2013-1Security and Global Affair

From nature to lab: scaling self-formed meandering and braided rivers

River morphodynamics and sediment transportRiver morphology and morphodynamic

Clarification on protected area management efforts in Madagascar during periods of heightened uncertainty and instability

In early May 2022, Eklund and colleagues published an article in Nature Sustainability in which they attempted to demonstrate that the early 2020 lockdown imposed in Madagascar by the emerging COVID-19 pandemic had a direct impact on Protected Areas (PAs), with an increase in the number of fires, which then stabilized once the lockdown was over. The authors, undoubtedly in good faith but based on an incomplete understanding of the situation on the ground, were attempting to draw the attention of the international community and donors to the need to maintain and strengthen PA management efforts. Their contribution, while highlighting a real and urgent need, does not, however, do justice to Madagascar’s PA managers, who, in collaboration with the populations living in the vicinity of parks and reserves, maintained and in some instances increased efforts to ensure the integrity of parks and reserves during the COVID-19 period. Following the publication of this paper, we contacted the authors as well as the editors of Nature Sustainability in a collegial effort to draw their attention to the errors identified in the analysis and to point out how this led to a misinterpretation of what actually transpired during the lockdown. We submitted a carefully worded and argued rebuttal for possible publication in Nature Sustainability, which we regarded as justified given the nature and significance of the considerations we had carefully presented

The Challenge of Generating Causal Hypotheses Using Network Models

Statistical network models based on Pairwise Markov Random Fields (PMRFs) are popular tools for analyzing multivariate psychological data, in large part due to their perceived role in generating insights into causal relationships: a practice known as causal discovery in the causal modeling literature. However, since network models are not presented as causal discovery tools, the role they play in generating causal insights is poorly understood among empirical researchers. In this paper, we provide a treatment of how PMRFs such as the Gaussian Graphical Model (GGM) work as causal discovery tools, using Directed Acyclic Graphs (DAGs) and Structural Equation Models (SEMs) as causal models. We describe the key assumptions needed for causal discovery and show the equivalence class of causal models that networks identify from data. We clarify four common misconceptions found in the empirical literature relating to networks as causal skeletons; chains of relationships; collider bias; and cyclic causal models

Biofuels from waste to road transport

Biofuels from Waste to Road (WASTE2ROAD) is an EU funded project under the Grant Agreement No. 818120 within the LC-SC3-RES-21-2018 call, “Development of next generation biofuels and alternative renewable fuel technologies for road transport”, as a Research and Innovation Action of the European Union’s Horizon 2020 Programme. The project started in the fall 2018 and will run for 4 years. In 2014, total waste production in the EU amounted to 2.5 billion tons. From this total only a limited (albeit increasing) share (36%) was recycled, while the rest was landfilled or burned, of which some 600 million tons could have been recycled or reused. Conversion of all sustainably available biogenic wastes and residues to biofuels could provide 27% of total transport fuel by 2050, achieving around 2.1 gigatons of CO2 emission reductions per year. The increasing demand for biofuels[1] implies the need for the transformation of diverse bio-resources into liquid fuels, and includes transformation of the biogenic part of municipal and industrial wastes into such biofuels. This clearly is a stepping stone to achieve the European goals[2] but it also poses challenges, such as 1) diversity and inhomogeneity of wastes throughout Europe (variable composition depending on the type of waste and geographical location), 2) the complexity of the conversion of wastes compared to fossil oils, 3) the technological aspects of co-refining and 4) high overall costs with moderate process performance. [1] https://www.iea.org/publications/freepublications/publication/Biofuels_Roadmap_WEB.pdf [2] https://europeanclimate.org/wp-content/uploads/2014/02/WASTED-final.pdf Please click Additional Files below to see the full abstract

Deep Brain Stimulation of the Pallidum is Effective and Might Stabilize Striatal D2 Receptor Binding in Myoclonus–Dystonia

Purpose: To assess clinical efficacy of deep brain stimulation (DBS) of the pallidum in Myoclonus–Dystonia (M–D) patients, and to compare pre- and post-operative striatal dopamine D2 receptor availability. Methods: Clinical parameters were scored using validated rating scales for myoclonus and dystonia. Dopamine D2 receptor binding of three patients was studied before surgery and approximately 2 years post-operatively using 123-I-iodobenzamide Single Photon Emission Computed Tomography. Two patients who did not undergo surgery served as controls. Results: Clinically, the three M–D patients improved 83, 17, and 100%, respectively on the myoclonus rating scale and 78, 23, and 65% on the dystonia rating scale after DBS. Dopamine D2 receptor binding did not change after surgery. In the two control subjects, binding has lowered further. Conclusion: These findings confirm that DBS of the pallidum has beneficial effects on motor symptoms in M–D and suggest this procedure might stabilize dopamine D2 receptor binding