Derivation of a multilayer approach to model suspended sediment transport: application to hyperpycnal and hypopycnal plumes

We propose a multi-layer approach to simulate hyperpycnal and hypopycnal plumes in flows with free surface. The model allows to compute the vertical profile of the horizontal and the vertical components of the velocity of the fluid flow. The model can describe as well the vertical profile of the sediment concentration and the velocity components of each one of the sediment species that form the turbidity current. To do so, it takes into account the settling velocity of the particles and their interaction with the fluid. This allows to better describe the phenomena than a single layer approach. It is in better agreement with the physics of the problem and gives promising results. The numerical simulation is carried out by rewriting the multi-layer approach in a compact formulation, which corresponds to a system with non-conservative products, and using path-conservative numerical scheme. Numerical results are presented in order to show the potential of the model

Formal deduction of the Saint-Venant-Exner model including arbitrarily sloping sediment beds and associated energy

In this work we present a deduction of the Saint-Venant-Exner model through an asymptotic analysis of the Navier-Stokes equations. A multi-scale analysis is performed in order to take into account that the velocity of the sediment layer is smaller than the one of the fluid layer. This leads us to consider a shallow water type system for the fluid layer and a lubrication Reynolds equation for the sediment one. This deduction provides some improvements with respect to the classical Saint-Venant-Exner model: (i) the deduced model has an associated energy. Moreover, it allows us to explain why classical models do not have an associated energy and how to modify them in order to recover a model with this property. (ii) The model incorporates naturally a necessary modification that must be taken into account in order to be applied to arbitrarily sloping beds. Furthermore, we show that this modification is different of the ones considered classically, and that it coincides with a classical one only if the solution has a constant free surface. (iii) The deduced solid transport discharge naturally depends on the thickness of the moving sediment layer, what allows to ensure sediment mass conservation. Moreover, we include a simplified version of the model for the case of quasi-stationary regimes. Some of these simplified models correspond to the generalization of classical ones such as Meyer-Peter$\&$M\"uller and Ashida-Michiue models. Three numerical tests are presented to study the evolution of a dune for several definition of the repose angle, to see the influence of the proposed definition of the effective shear stress in comparison with the classical one, and by comparing with experimental data.Comment: 44 pages, sumbitted to Advances in Water Resources 17 july 201

Understanding how organizational culture typology relates to organizational unlearning and innovation capabilities

This study focuses on the link between organizational unlearning and innovation capabilities and explores how this relationship might be managed within an innovative firm. In order to gain a clearer insight into to the influence of a firm’s culture on organizational unlearning and its innovation capabilities, a research model was developed that employs the Competing Values Framework (Cameron & Quinn, 1999). In this model, the influence of a firm’s cultural typology on unlearning and innovation is conceptualized and hypotheses are developed. The model was tested empirically using a sample of 145 firms drawn from the Spanish automotive components manufacturing sector and the relationships between the constructs were assessed using the partial least squares path-modeling approach. The results reveal that each distinct organizational culture exerts a different impact on the innovation and unlearning outcome variables. In particular, an adhocracy culture is associated closely with innovation capabilities while a market culture exerts a significant influence on organizational unlearnin

Possible ring material around centaur (2060) Chiron

We propose that several short duration events observed in past stellar occultations by Chiron were produced by rings material. From a reanalysis of the stellar occultation data in the literature we determined two possible orientations of the pole of Chiron's rings, with ecliptic coordinates l=(352+/-10) deg, b=(37+/-10) deg or l=(144+/-10) deg, b=(24+/-10) deg . The mean radius of the rings is (324 +/- 10) km. One can use the rotational lightcurve amplitude of Chiron at different epochs to distinguish between the two solutions for the pole. Both imply lower lightcurve amplitude in 2013 than in 1988, when the rotational lightcurve was first determined. We derived Chiron's rotational lightcurve in 2013 from observations at the 1.23-m CAHA telescope and indeed its amplitude is smaller than in 1988. We also present a rotational lightcurve in 2000 from images taken at CASLEO 2.15-m telescope that is consistent with our predictions. Out of the two poles the l=(144+/-10) deg, b=(24+/-10) deg solution provides a better match to a compilation of rotational lightcurve amplitudes from the literature and those presented here. We also show that using this preferred pole, Chiron's long term brightness variations are compatible with a simple model that incorporates the changing brightness of the rings as the tilt angle with respect to the Earth changes with time. Also, the variability of the water ice band in Chiron's spectra in the literature can be explained to a large degree by an icy ring system whose tilt angle changes with time and whose composition includes water ice, analogously to the case of Chariklo. We present several possible formation scenarios for the rings from qualitative points of view and speculate on the reasons why rings might be common in centaurs. We speculate on whether the known bimodal color distribution of centaurs could be due to presence of rings and lack of them

Defining risk factors associated with difficult peripheral venous Cannulation: A systematic review and meta-analysis

Peripheral venous catheterization is a common technique in hospitals which is not always successful, resulting in multiple punctures and degradation of the vessels. This scenario, which we have termed 'difficult peripheral venous access', is associated to delays in care, obtention of samples or diagnosis, as well as a higher use of central catheters. This study intends to identify risk factors associated to the incidence of 'difficult peripheral venous access' in adults at hospital. We designed a systematic review of published studies (protocol PROSPERO 2018 CRD42018089160). We conducted structured electronic searches using key words and specific vocabulary, as well as directed searches in several databases. After validity analysis, we selected 7 studies with observational methodology. We found great variability in the definition of 'difficult peripheral venous access' and in the variables proposed as risk factors. Statistically significant factors through studies include demographic and anthropometric variables (gender, Body Mass Index), as well as medical and health conditions (diabetes, renal insufficiency, parenteral drug abuse, cancer chemotherapy), together with variables related to the vein or vascular access (vein visibility and palpability, vessel diameter, previous history of difficulty). Some studies have also considered variables related to the professional performing the technique. Meta-analyses were carried out for gender and obesity as potential risk factors. Only obesity appeared as a statistically significant risk factor with OR of 1.48; 95% CI (1.03 to 1.93; p = 0.016). Methodological heterogeneity prevented the development of further meta-analyses. It is essential to design future studies with diverse hospital populations, in which a wide selection of potential risk factors can be studied in a unique analysis. Our work identifies the most relevant variables that should be included in those studies

Cortistain is expressed in a distinct subset of cortical interneurons

Cortistatin is a presumptive neuropeptide that shares 11 of its 14 amino acids with somatostatin. In contrast to somatostatin, administration of cortistatin into the rat brain ventricles specifically enhances slow wave sleep, apparently by antagonizing the effects of acetylcholine on cortical excitability. Here we show that preprocortistatin mRNA is expressed in a subset of GABAergic cells in the cortex and hippocampus that partially overlap with those containing somatostatin. A significant percentage of cortistatin-positive neurons is also positive for parvalbumin. In contrast, no colocalization was found between cortistatin and calretinin, cholecystokinin, or vasoactive intestinal peptide. During development there is a transient increase in cortistatin-expressing cells in the second postnatal week in all cortical areas and in the dentate gyrus. A transient expression of preprocortistatin mRNA in the hilar region at P16 is paralleled by electrophysiological changes in dentate granule cells. Together, these observations suggest mechanisms by which cortistatin may regulate cortical activity

Advanced trajectory generator for two carts with RGB-D sensor on circular rail

This paper presents a motorised circular rail that generates the motion of two carts with an RGB-D sensor each. The objective of both carts' trajectory generation is to track a person's physical rehabilitation exercises from two points of view and his/her emotional state from one of these viewpoints. The person is moving freely his/her position and posture within the circle drawn by the motorised rail. More specifically, this paper describes the calculation of trajectories for safe motion of the two carts on the motorised circular rail in detail. Lastly, a study case is offered to show the performance of the described control algorithms for trajectory generation.- This work was partially supported by Ministerio de Ciencia, Innovacion y Universidades, Agencia Estatal de Investigacion (AEI) / European Regional Development Fund (FEDER, UE) under DPI2016-80894-R grant