Within-Event Spatially Distributed Bedload: Linking Fluvial Sediment Transport to Morphological Change

Maps of apparent bedload velocity are presented along with maps of associated channel change. Apparent bedload velocity is the bias in acoustic Doppler current profiler (aDcp) bottom track (Doppler sonar) due to near-bed particle motion (Rennie et al. 2002). The apparent bedload velocity is correlated to bedload transport (Rennie and Villard 2004), and thus serves as an indicator of local bedload transport. Spatially distributed aDcp surveys in a river reach can be used to generate maps of channel bathymetry, water velocity, bed shear stress, and apparent bedload velocity (Rennie and Church 2010). It is possible to relate the observed spatial patterns of bedload and forcing flow. In this paper, the technique is used to measure bedload flux pathways during two sequential aDcp spatial surveys conducted in a Rees River, New Zealand braid bar diffluence-confluence before and after a major flood event that inundated the entire braid plain. The aDcp surveys were complemented with terrestrial laser scans (TLS) of the bar topography. Linking aDcp bathymetry and TLS topography allowed for generation of complete digitial elevation models (DEMs) of the reach, from which morphological change between surveys were determined. Most intriguingly, the primary bedload pathway observed during the first survey resulted in sufficient deposition during the major flood event to fill and choke off an anabranch. This is perhaps the first direct field measurement of spatially distributed bedload and corresponding morphological change

The effects of land use and topographic changes on sediment connectivity in mountain catchments

Understanding the evolution of sediment connectivity associated with different land use and topographic changes is a prerequisite for a better understanding of sediment budgets and sediment transport processes. We used the Index of Sediment Connectivity (IC) developed by Cavalli et al. (2013) based on the original approach by Borselli et al. (2008) to study the effects of decadal-scale land use and topographic changes on sediment connectivity in mountain catchments. The input variables of the IC (i.e. land cover and topography) were derived from historical aerial photos using Structure from Motion-Multi View Stereo algorithms (SfM-MVS). The method was applied in different sub-catchments of the Upper River Cinca Catchment (Central Pyrenees), representative of three scenarios: (a) Land cover changes; (b) Topographic changes in agricultural fields (terracing); and (c) Topographic changes associated with infrastructure (road construction). In terms of land cover changes, results show that although connectivity is increased in some areas due to the establishment of new field crops, for most of the study area connectivity decreased due to afforestation caused by rural abandonment. Topographic changes due to the establishment of agricultural terraces affected connectivity to a larger degree than land cover changes. Terracing generally reduced connectivity due to the formation of flat areas in step-slopes, but in certain points, an increase in connectivity caused by the topographic convergence produced by terraces was observed. Finally, topographic changes associated with road construction greatly modified surface flow directions and the drainage network, resulting in changes in connectivity that may affect erosional processes nearby. The methodology used in this paper allows to study the effects of real decadal-scale land use and topographic changes on sediment connectivity and also evaluating and disentangling those changes. Furthermore, this approach can be a useful tool to identify potential risks associated with morphological and land use changes, involving road infrastructures

Drones and Digital Photogrammetry: From Classifications to Continuums for Monitoring River Habitat and Hydromorphology

Recently, we have gained the opportunity to obtain very high-resolution imagery and topographic data of rivers using drones and novel digital photogrammetric processing techniques. The high-resolution outputs from this method are unprecedented, and provide the opportunity to move beyond river habitat classification systems, and work directly with spatially explicit continuums of data. Traditionally, classification systems have formed the backbone of physical river habitat monitoring for their ease of use, rapidity, cost efficiency, and direct comparability. Yet such classifications fail to characterize the detailed heterogeneity of habitat, especially those features which are small or marginal. Drones and digital photogrammetry now provide an alternative approach for monitoring river habitat and hydromorphology, which we review here using two case studies. First, we demonstrate the classification of river habitat using drone imagery acquired in 2012 of a 120 m section of the San Pedro River in Chile, which was at the technological limits of what could be achieved at that time. Second, we review how continuums of data can be acquired, using drone imagery acquired in 2016 from the River Teme in Herefordshire, England. We investigate the precision and accuracy of these data continuums, highlight key current challenges, and review current best practices of data collection, processing, and management. We encourage further quantitative testing and field applications. If current difficulties can be overcome, these continuums of geomorphic and hydraulic information hold great potential for providing new opportunities for understanding river systems to the benefit of both river science and management

Hydraulic validation of two-dimensional simulations of braided river flow with spatially continuous aDcp data

Gravel‐bed braided rivers are characterized by shallow, branching flow across low relief, complex, and mobile bed topography. These conditions present a major challenge for the application of higher dimensional hydraulic models, the predictions of which are nevertheless vital to inform flood risk and ecosystem management. This paper demonstrates how high‐resolution topographic survey and hydraulic monitoring at a density commensurate with model discretization can be used to advance hydrodynamic simulations in braided rivers. Specifically, we detail applications of the shallow water model, Delft3d, to the Rees River, New Zealand, at two nested scales: a 300 m braid bar unit and a 2.5 km reach. In each case, terrestrial laser scanning was used to parameterize the topographic boundary condition at hitherto unprecedented resolution and accuracy. Dense observations of depth and velocity acquired from a mobile acoustic Doppler current profiler (aDcp), along with low‐altitude aerial photography, were then used to create a data‐rich framework for model calibration and testing at a range of discharges. Calibration focused on the estimation of spatially uniform roughness and horizontal eddy viscosity, νH, through comparison of predictions with distributed hydraulic data. Results revealed strong sensitivity to νH, which influenced cross‐channel velocity and localization of high shear zones. The high‐resolution bed topography partially accounts for form resistance, and the recovered roughness was found to scale by 1.2–1.4 D84 grain diameter. Model performance was good for a range of flows, with minimal bias and tight error distributions, suggesting that acceptable predictions can be achieved with spatially uniform roughness and νH.Field campaigns were primarily funded by NERC Grant NE/G005427/1 and NERC Geophysical Equipment Facility Loan 892 as well as NSERC and CFI (Canada) grants to Colin Rennie. Damia Vericat was supported by a Ramon y Cajal Fellowship (RYC‐2010‐06264) funded by the Spanish Ministry of Science and Innovation during the preparation of this manuscript. Numerical simulations were undertaken during a visit by Richard Williams to NIWA. This visit was funded by the British Hydrology Society and an Aberystwyth University Postgraduate Studentship. Murray Hicks and Richard Measures were funded by NIWA core funding under the Sustainable Water Allocation Programme

Incidence of the temperature on the hydrophobic effect of alanine dissolved in water

El efecto hidrofóbico ocupa un lugar central en el estudio del plegamiento de las proteínas desde mediados del siglo pasado, cuando W. Kauzmann lo propuso como el principal responsable del colapso de éstas a su conformación nativa compacta, bajo condiciones fisiológicas normales. Experimentalmente se observa, que al variarle la temperatura al sistema se puede desplegar y replegar a una proteína, sin intervención de ningún otro elemento externo. Esto revela la importancia que presenta estudiar la influencia de la temperatura sobre ambos aspectos del efecto hidrofóbico: la hidratación hidrofóbica (estructura del agua alrededor de un aminoácido apolar) y la interacción hidrofóbica (el efecto neto que el medio acuoso ejerce sobre dos aminoácidos apolares disueltos en él). En este trabajo consideramos un sistema formado por alanina disuelta en agua y calculamos las funciones de distribución radial alanina–agua y alanina–alanina, para cuatro temperaturas diferentes (4C, 25C, 50C y 75C). Para esto, utilizamos dos técnicas distintas y a la vez complementarias: (1) una teoría mecánico–estadística de líquidos clásicos, y (2) simulación numérica mediante dinámica molecular. De nuestros resultados se observa que al aumentar la temperatura, la hidratación disminuye y la interacción hidrofóbica alanina–alanina se hace más intensa.The hydrophobic effect has played a central role in the study of proteins folding since W. Kauzmann proposed it as the main responsible for their collapse to the compact native conformation under normal physiological conditions. By changing the medium temperature a protein can be unfolded and folded again to its native conformation, without any other external action. This reveals the importance of studying the influence of the temperature on both aspects of the hydrophobic effect: the hydrophobic hydration and the hydrophobic interaction. In this work we consider a system formed by alanine residues dissolved in water and calculate the alanine-water and alanine-alanine radial distribution functions, at four different temperatures (4C, 25C, 50C and 75C). We use two complementary theoretic techniques: (1) a statistical mechanics theory of classical liquids, and (2) numerical simulations by molecular dynamics. From our results we conclude that when temperature is increased then the residue hydration diminishes and the alanine-alanine hydrophobic interaction becomes more intense.Instituto de Física de Líquidos y Sistemas BiológicosGrupo de Aplicaciones Matemáticas y Estadísticas de la Facultad de Ingenierí

Modelo numérico para describir la incidencia del isoproterenol en la fosforilación de una proteína involucrada en la regulación de la contracción cardíaca

En este trabajo presentamos un modelo teórico que ayuda a sostener una hipótesis acerca de la influencia de la droga estimulante isoproterenol sobre la relajación y contracción cardíaca. Nuestros resultados indican que el isoproterenol no sólo participa favoreciendo la fosforilación, sino que además reduce la actividad de la proteína que cataliza la desfosforilación del fosfolambán.Grupo de Aplicaciones Matemáticas y Estadísticas de la Facultad de Ingenierí

Nonmonotonic reversible branch in four model granular beds subjected to vertical vibration

We present results from four independent models of a granular assembly subjected to tapping. We find that the steady-state packing fraction as a function of the tapping intensity is nonmonotonic. In particular, for high tapping intensities, we observe an increase of the packing fraction with tapping strength. This finding challenges the current understanding of compaction of granular media since the steady-state packing fraction is believed to decrease monotonically with increasing tapping intensity. We propose an explanation of our results based on the properties of the arches formed by the particles.Instituto de Física de Líquidos y Sistemas BiológicosGrupo de Aplicaciones Matemáticas y Estadísticas de la Facultad de Ingenierí

The interface structure of n-alkylthiolate self-assembled monolayers on coinage metal surfaces

The current state of understanding of the structure of the metal/thiolate interface of n-alkylthiolate self-assembled monolayers (SAMs) on Cu(111), Ag(111) and Au(111) is reviewed. On Cu(111) and Ag(111) there is now clear evidence that adsorbate-induced reconstruction of the outermost metal layer occurs to a less atomically-dense structure, with the S head-group atom bonded to four-fold and three-fold coordinated hollow sites, respectively, and that intermolecular interaction plays some role in the periodicity of the resulting SAMs. On the far more heavily-studied Au(111) surface, the detailed interface structure remains controversial, but there is growing evidence for the role of Au-adatom-thiolate moieties in the layer ordering