Numerical investigations on the transient aerodynamic performance characterization of a multibladed vertical axis wind turbine.

The use of vertical axis wind turbines (VAWTs) in urban environments is on the rise due to their relatively smaller size, simpler design, lower manufacturing and maintenance costs, and above all, due to their omnidirectionality. The multibladed drag-based VAWT has been identified as a design configuration with superior aerodynamic performance. Numerous studies have been carried out in order to better understand the complex aerodynamic performance of multibladed VAWTs employing steady-state or quasi-steady numerical methods. The transient aerodynamics associated with a multibladed VAWT, especially the time–history of the power coefficient of each blade, has not been reported in the published literature. This information is important for the identification of individual blade’s orientation when producing negative torque. The current study aims to bridge this gap in the literature through real-time tracking of the rotor blade's aerodynamic performance characteristics during one complete revolution. Numerical investigations were carried out using advanced computational fluid dynamics (CFD)-based techniques for a tip speed ratio of 0 to 1. The results indicate that transient aerodynamic characterization is 13% more accurate in predicting the power generation from the VAWT. While steady-state performance characterization indicates a negative power coefficient (Cp) at λ = 0.65, transient analysis suggests that this happens at λ = 0.75

La tribalidad posmoderna dentro del festival “Rock por la Vida” en Guadalajara: emoción colectiva de los asistentes del año 2007 al 2014

Este documento tiene como objetivo analizar las expresiones de los asistentes al festival ¨Rock por la Vida¨ (RXLV) en Guadalajara, a partir del concepto de Michael Maffesoli sobre la tribalidad posmoderna. Se detalla cómo es que los asistentes definen su sensibilidad o emoción colectiva, cómo van construyendo la socialidad dentro de la masa, es decir, cómo se van generando estas tribus. Se describen las experiencias de estar-juntos y se identifican las coincidencias en las emociones colectivas que se generan dentro del RXLV. This document´s objective is to analyze the expressions of those attending the festival Rock for Life in Guadalajara. From Michael Maffesoli postmodern concept of tribalism . It details how to define their collective feeling or emotion, how they build sociality within the mass , that is, how it is generating these tribus. The experience of being together are described . Coincidences in collective emotions that are generated within the RXLV are identified

Environmental adaptation, phenotypic plasticity, and associative learning in insects: the desert locust as a case study

The ability to learn and store information should be adapted to the environment in which animals operate to confer a selective advantage. Yet the relationship between learning, memory, and the environment is poorly understood, and further complicated by phenotypic plasticity caused by the very environment in which learning and memory need to operate. Many insect species show polyphenism, an extreme form of phenotypic plasticity, allowing them to occupy distinct environments by producing two or more alternative phenotypes. Yet how the learning and memories capabilities of these alternative phenotypes are adapted to their specific environments remains unknown for most polyphenic insect species. The desert locust can exist as one of two extreme phenotypes or phases, solitarious and gregarious. Recent studies of associative food–odor learning in this locust have shown that aversive but not appetitive learning differs between phases. Furthermore, switching from the solitarious to the gregarious phase (gregarization) prevents locusts acquiring new learned aversions, enabling them to convert an aversive memory formed in the solitarious phase to an appetitive one in the gregarious phase. This conversion provides a neuroecological mechanism that matches key changes in the behavioral environments of the two phases. These findings emphasize the importance of understanding the neural mechanisms that generate ecologically relevant behaviors and the interactions between different forms of behavioral plasticity

Spatiotemporal control of two-color terahertz generation

A laser pulse composed of a fundamental and properly phased second harmonic exhibits an asymmetric electric field that can drive a time-dependent current of photoionized electrons. The current produces an ultrashort burst of terahertz (THz) radiation. When driven by a conventional laser pulse, the THz radiation is emitted into a cone with an angle determined by the dispersion of the medium. Here we demonstrate that the programmable-velocity intensity peak of a spatiotemporally structured, two-color laser pulse can be used to control the emission angle, focal spot, and spectrum of the THz radiation. Of particular interest for applications, a structured pulse with a subluminal intensity peak can drive highly focusable, on-axis THz radiation

Large-eddy simulation of the tidal-cycle variations of an estuarine boundary layer

Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 115 (2010): C08003, doi:10.1029/2009JC005702.The estuarine boundary layer affected by a horizontal density gradient exhibits temporal evolution over a tidal cycle, in a manner similar to the diurnal cycle of the ocean surface mixed layer. A large eddy simulation (LES) model is developed to investigate the physics controlling the growth of the boundary layer during the flood tide and restratification during the ebb tide. Turbulent kinetic energy, momentum and salt fluxes, bottom stress, and energy dissipation rates calculated from the LES model all show a strong flood-ebb asymmetry. Analysis of the turbulent kinetic energy (TKE) budget shows a primary balance between shear production and dissipation in the well-mixed boundary layer over the tidal cycle. However, TKE transport term is found to be important across the edge of the boundary layer during the flood tide so turbulent energy generated in the bottom boundary layer can be transferred to the stratified pycnocline region. Tidal straining leads to a small and weakly convective region inside the boundary layer during the flood tide but the strain-induced buoyancy flux does not make a significant contribution to the turbulence generation. Additional LES runs are conducted by switching off the baroclinic pressure gradient term in the momentum equation and the tidal straining term in the salinity equation to show that the baroclinic pressure gradient is the main mechanism responsible for generating the flood-ebb mixing asymmetry.This work is supported by grants OCE-0451699 (M.L.), OCE-0452380 (U.P. and S.R.), and OCE-0451740 (W.R.G.) from the National Science Foundation

Effect of COVID-19 on presentations of decompensated liver disease in Scotland

BACKGROUND AND AIMS: SARS-CoV-2 and consequent pandemic has presented unique challenges. Beyond the direct COVID-related mortality in those with liver disease, we sought to determine the effect of lockdown on people with liver disease in Scotland. The effect of lockdown on those with alcohol-related disease is of interest; and whether there were associated implications for a change in alcohol intake and consequent presentations with decompensated disease. METHODS: We performed a retrospective analysis of patients admitted to seven Scottish hospitals with a history of liver disease between 1 April and 30 April 2020 and compared across the same time in 2017, 2018 and 2019. We also repeated an intermediate assessment based on a single centre to examine for delayed effects between 1 April and 31 July 2020. RESULTS: We found that results and outcomes for patients admitted in 2020 were similar to those in previous years in terms of morbidity, mortality, and length of stay. In the Scotland-wide cohort: admission MELD (Model for End-stage Liver Disease) (16 (12–22) vs 15 (12–19); p=0.141), inpatient mortality ((10.9% vs 8.6%); p=0.499) and length of stay (8 days (4–15) vs 7 days (4–13); p=0.140). In the Edinburgh cohort: admission MELD (17 (12–23) vs 17 (13–21); p=0.805), inpatient mortality ((13.7% vs 10.1%; p=0.373) and length of stay (7 days (4–14) vs 7 days (3.5–14); p=0.525)). CONCLUSION: This assessment of immediate and medium-term lockdown impacts on those with chronic liver disease suggested a minimal effect on the presentation of decompensated liver disease to secondary care

The burden of childhood atopic dermatitis in the primary care setting: a report from the Meta-LARC Consortium

Background: Little is known about the burden of AD encountered in U.S. primary care practices and the frequency and type of skin care practices routinely used in children. Objectives: To estimate the prevalence of AD and allergic comorbidities in children 0-5 years attending primary care practices in the U.S. and to describe routine skin care practices used in this population. Design: A cross-sectional survey study of a convenience sample of children under the age of 5 attending primary care practices for any reason. Setting: Ten primary care practices in five U.S. states.Results: Amongst 652 children attending primary care practices, the estimated prevalence of ever having AD was 24 % (95% CI= 21-28) ranging from 15% among those under the age of one to 38% among those aged 4- 5 years. The prevalence of comorbid asthma was higher among AD participants compared to those with no AD, 12% and 4%, respectively (p less than 0.001). Moisturizers with high water:oil ratios were most commonly used (i.e., lotions) in the non-AD population, whereas moisturizers with low water:oil content (i.e. ointments) most common when AD was present. Conclusions: Our study found a large burden of AD in the primary care practice setting in the U.S. The majority of households reported skin care practices in children without AD that may be detrimental to the skin barrier such as frequent bathing and the routine use of moisturizers with high water: oil ratios. Clinical trials are needed to identify which skin care practices are optimal for reducing the significant risk of AD in the community