91 research outputs found
Impact of increased numbers of intensive care consultants on outcome in a central London teaching hospital
Velocity Measurements within High Velocity Air-Water Jets
High velocity turbulent jets are often used in hydraulic structures to dissipate energy and to induce or enhance air entrainment. Examples include ski jumps and bottom aeration devices. This article presents new air concentration and velocity measurements performed in the flow development region of high velocity water jets. The measurements were obtained using a two-tips conductivity probe. The data are compared with analytical air concentration profiles derived from the diffusion equation, and theoretical velocity profiles of turbulent shear layers. The results highlight that the lower jet interface defined as C = 90% coincides with the streamline of maximum velocity gradient
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What is carbon? Conceptualising carbon and capabilities in the context of community sequestration projects in the global South
Carbon has been described as a ‘surreal commodity.’ While carbon trading, storage, sequestration, and emissions have become a part of the contemporary climate lexicon, how carbon is understood, valued, and interpreted by actors responsible for implementing carbon sequestration projects is still unclear. In this review paper, we are concerned with how carbon has come to take on a range of meanings. In particular, we appraise what is known about the situated meanings that people involved in delivering, and participating in, carbon sequestration projects in the global South assign to this complex element. There has been some reflection on the new meanings conferred on carbon via the neoliberal processes of marketisation and on how these processes interact with historical and contemporary narratives of environmental change. But less is known about how these meanings are (re)produced and (re)interpreted locally. We review how carbon has been defined both as a chemical element and as a tradable, marketable commodity. We discuss the implications these global meanings might have for situated understandings, particularly linked to climate change narratives, among communities in the global South. We consider how the concept of carbon capabilities, alongside theoretical notions of networks, assemblages, and local knowledges of the environment and nature, might be useful in beginning to understand how communities engage with abstract notions of carbon. We discuss the implications of specific values attributed to carbon, and therefore to different ecologies, for wider conceptualizations of how nature is valued, and climate is understood. We review in particular how this may impact on community interactions with carbon sequestration projects. Knowing more about how people understand, value, and know carbon allows policies to be better informed and practices more effectively targeted at engaging local populations meaningfully in carbon-related projects
Analytical model for the calculation of lateral velocity distributions in potential cross-sections
[EN] The hydraulic modeling of water depth and flow velocities in open channel flows that were fitted by power-law cross-section stand out for their versatility, allowing their use in numerous practical applications, both in natural and artificial channels. The determination of the hydraulic variables of depth and average velocity has been widely studied in potential cross-sections; however, the variation seen in these variables along the cross-section was not found in the literature. Knowledge of this variation allows the development of studies (e.g. to know the approximate damage in different areas of the cross-section, to analyse sediment transport, or other applications in river hydraulics). This paper presents a methodology which allows calculation of the hydraulic variables in any area of a power-law cross-section. The methodology is applied to symmetrical cross-sections, comparing its generated results with the obtained values by different computational hydraulic codes, which are thoroughly accepted by scientific community, such as CES, HEC-RAS and IBER. The obtained predictions of hydraulic parameters (using the explicit formulation described in this research) present very low errors when compared with results of other models, with great computational cost. These errors reach a root mean square error (RMSE) of 0.13 and 0.05 in the determination of velocities' lateral distribution and the ratio between velocity and average velocity. These values indicate a very successful validation for the analysed symmetrical sections.[ES] La modelización hidráulica de calados y velocidades de flujo, en cauces con secciones que admiten
una representación de tipo potencial, se destaca por su versatilidad, permitiendo su utilización en
numerosas aplicaciones prácticas tanto en canales naturales como artificiales. El cálculo de las
variables hidráulicas (calado y velocidad media) ha sido ampliamente estudiado para este tipo de
secciones. Sin embargo, en la literatura técnica no se han encontrado estudios que muestren la
variación de estas magnitudes a lo largo de la sección transversal. El conocimiento de esta variación
permite desarrollar estudios (ejemplo: conocer de manera aproximada los daños en diferentes zonas
de la sección, analizar el transporte de sedimentos, estudiar los procesos de erosión u otras aplicaciones en hidráulica fluvial). Presentamos una metodología que permite el cálculo de las variables
hidráulicas en cualquier zona de una sección tipo potencial. La metodología es aplicada a secciones
simétricas, comparando los resultados generados con los obtenidos por diferentes códigos
hidráulicos computacionales ampliamente aceptados por la comunidad científica (p-e- CES, HECRAS e IBER). Las predicciones de los parámetros hidráulicos obtenidas (usando la formulación
explícita descrita en este artículo) presentan errores muy bajos, en comparación con otros modelos
con mayor costo computacional. Estos errores alcanzan un valor promedio para la raíz del error
cuadrático medio (RMSE) en el cálculo de la distribución lateral de velocidades de 0.13 y de 0.05, en el
cálculo de la relación de velocidades respecto a la velocidad media. Estos valores indican una
validación muy satisfactoria para las secciones simétricas analizadas.Sánchez-Romero, F.; Pérez-Sánchez, M.; López Jiménez, PA. (2018). Modelo analítico para el cálculo de distribuciones de velocidad laterales en secciones tipo potencial-ley. RIBAGUA - Revista Iberoamericana del Agua. 5(1):29-47. doi:10.1080/23863781.2018.1442189S29475
Disordered microbial communities in asthmatic airways.
A rich microbial environment in infancy protects against asthma [1], [2] and infections precipitate asthma exacerbations [3]. We compared the airway microbiota at three levels in adult patients with asthma, the related condition of COPD, and controls. We also studied bronchial lavage from asthmatic children and controls.We identified 5,054 16S rRNA bacterial sequences from 43 subjects, detecting >70% of species present. The bronchial tree was not sterile, and contained a mean of 2,000 bacterial genomes per cm(2) surface sampled. Pathogenic Proteobacteria, particularly Haemophilus spp., were much more frequent in bronchi of adult asthmatics or patients with COPD than controls. We found similar highly significant increases in Proteobacteria in asthmatic children. Conversely, Bacteroidetes, particularly Prevotella spp., were more frequent in controls than adult or child asthmatics or COPD patients.The results show the bronchial tree to contain a characteristic microbiota, and suggest that this microbiota is disturbed in asthmatic airways
Can the discharge of a hyperconcentrated flow be estimated from paleoflood evidence?
Many flood events involving water and sediments have been characterized using classic hydraulics principles, assuming the existence of critical flow and many other simplifications. In this paper, hyperconcentrated flow discharge was evaluated by using paleoflood reconstructions (based on paleostage indicators [PSI]) combined with a detailed hydraulic analysis of the critical flow assumption. The exact location where this condition occurred was established by iteratively determining the corresponding cross section, so that specific energy is at a minimum. In addition, all of the factors and parameters involved in the process were assessed, especially those related to the momentum equation, existing shear stresses in the wetted perimeter, and nonhydrostatic and hydrostatic pressure distributions. The superelevation of the hyperconcentrated flow, due to the flow elevation curvature, was also estimated and calibrated with the PSI. The estimated peak discharge was established once the iterative process was unable to improve the fit between the simulated depth and the depth observed from the PSI. The methodological approach proposed here can be applied to other higher-gradient mountainous torrents with a similar geomorphic configuration to the one studied in this paper. Likewise, results have been derived with fewer uncertainties than those obtained from standard hydraulic approaches, whose simplifying assumptions have not been considered. © 2011 by the American Geophysical Union.This work was funded by the Spanish Ministry of Science and Innovation within the framework of the CICYT Dendro-Avenidas project (CGL2007-62063) and the MAS Dendro-Avenidas project (CGL2010-19274). We are especially grateful to Robert D. Jarrett, Vern Manville, and one anonymous reviewer for their comments and helpful suggestions on previous versions of this manuscript.Bodoque, J.; Eguibar Galán, MÁ.; Diez-Herrero, A.; Gutierrez-Perez, I.; Ruiz-Villanueva, V. (2011). Can the discharge of a hyperconcentrated flow be estimated from paleoflood evidence?. Water Resources Research. 47(W12535). doi:10.1029/2011WR010380S47W12535Alcoverro, J., Corominas, J., & Gómez, M. (1999). The Barranco de Arás flood of 7 August 1996 (Biescas, Central Pyrenees, Spain). Engineering Geology, 51(4), 237-255. doi:10.1016/s0013-7952(98)00076-3Alexandrov, Y., Laronne, J. B., & Reid, I. (2007). Intra-event and inter-seasonal behaviour of suspended sediment in flash floods of the semi-arid northern Negev, Israel. Geomorphology, 85(1-2), 85-97. doi:10.1016/j.geomorph.2006.03.013BAAS, J. H., & BEST, J. L. (2008). The dynamics of turbulent, transitional and laminar clay-laden flow over a fixed current ripple. 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Experimental Study of Fine Sand Particle Settling in Turbulent Open Channel Flows over Rough Porous Beds
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