Search results for "fluid"

Lipids of the Plant Plasma Membrane

2010

The plasma membrane (PM) is arguably the most diverse membrane of the plant cell. Furthermore, the protein and lipid composition of the PM varies with cell type, developmental stage, and environment. Physical properties of lipids and associate proteins allow the formation of a barrier that is selectively permeable to macromolecules and solutes. As the plasma membrane delineates the interface between the cell and the environment, it is the primary part of signal recognition and transduction into intracellular responses for nutritional uptake/distribution, environmental responses, and developmental signaling. Many essential PM functions are carried out by proteinaceous components. However, PM…

Laboratori virtual d'ensenyament-aprenentatge: solució numèrica de les equacions de conservació mitjançant volums finits aplicades a superfícies este…

2014

En este treball es presenta el disseny d’un Laboratori virtual d’ensenyament-aprenentatge per a la resolució d’un problema model de Transferència de la Calor en la matèria d’Enginyeria Tèrmica del II curs del Grau d’Enginyer de Tecnologies Industrials de la Universidad Rey Juan Carlos de Madrid. En l’àmbit de la Dinàmica de Fluids Computacional i per mitjà de l’ús del programari de simulació d’Ansys Fluent s’introduïx l’alumne al disseny, modelatge del sistema, resolució, anàlisi i validació del model. El resultat d’esta experiència d’aprenentatge és no sols la mera resolució del problema, inabordable amb mètodes didàctics tradicionals, sinó el desenvolupament de la combinació de destreses,…

Identification and transcriptional profile of Lactobacillus paracasei genes involved in the response to desiccation and rehydration

2020

International audience; Lactobacillus paracasei is able to persist in a variety of natural and technological environments despite physico-chemical perturbations, in particular alternations between desiccation and rehydration. However, the way in which it adapts to hydric fluctuations and the genetic determinants involved are not clearly understood. To identify the genes involved in adaptation to desiccation, an annotated library of L. paracasei random transposon mutants was screened for viability after desiccation (25% relative humidity, 25 °C). We found 16 genes that have not been described as being involved in this response. Most of them are linked to either the transport of molecules or …

Current challenges and perspectives in gas fluxes biotreatment

2020

Abstract Nowadays, there is a wide variety of bioreactor configurations to treat specific pollutants from gas streams; however, biotechnologies share benchmark aspects that are herein described. In this chapter, the reader is introduced to the biological gas treatment field by means of a historical overview on how the initial devices used for gas treatment evolved to the innovative systems that are currently applied worldwide. The technical and operational fundamentals of biofilters, biotrickling filters, bioscrubbers, and emerging technologies such as two-phase partitioning bioreactors, multistage systems, and membranes are included. Perspectives and key research niches in the field are al…

Boundary-layer Flows Past an Hemispherical Roughness Element: DNS, Global Stability and Sensitivity Analysis

2015

Abstract We investigate the full three-dimensional instability mechanism arising in the wake of an hemispherical roughness element immersed in a laminar Blasius boundary layer. The inherent three-dimensional flow pattern beyond the critical Reynolds number is characterized by coherent vortical structures called hairpin vortices. Direct numerical simulation is used to analyze the formation and the shedding of hairpin packets inside the shear layer. The first bifurcation characteristics are investigated by global stability tools. We show the spatial structure of the linear direct and adjoint global eigenmodes of the linearized Navier-Stokes operator and use structural sensitivity analysis to …

Physical Aspects of the Atmospheric Aerosol

1982

The atmospheric aerosol is a trace substance of the troposhere as well as the trace gases. Therefore a number of similiarities should be expected. As an example a common model on residence time is developed and discussed in its results. The residence time connects the content of a reservoir (size distribution for aerosols) with its source strength or removal rate. This is presented for the aerosol. In addition other physical properties of the tropospheric aerosol like optical, electrical and water uptake properties are discussed.

Transnational Social Networks—Current Perspectives

2012

“[T]here is something mysterious about social networks. We live surrounded by them, but usually cannot see more than one step beyond the people we are directly connected to, if that. It is like being stuck in a traffic jam surrounded by cars and trucks. The traffic helicopter can see beyond our immediate surroundings and suggest routes that might extricate us. Network analysis is like that helicopter. It allows us to see beyond our immediate circle.” (Kadushin, 2012: 4)

Regional variations in the chemical and helium–carbon isotope composition of geothermal fluids across Tunisia

2011

Abstract Tunisia has numerous thermo-mineral springs. Previous studies have shown that their chemical composition and occurrence are strongly influenced by the regional geology. However little work has been done so far to study the isotopic composition of volatiles associated with these geothermal manifestations. Here, we report on the results of an extensive survey of both natural hot springs and production wells across Tunisia, aimed at investigating the spatial distribution of thermal fluids' geochemical characteristics and He–C isotopic composition. The chemistry of the analyzed samples highlights the heterogeneity of the water mineralization processes in Tunisia, as a consequence of th…

Predictive Study of Heat Transfer to an Incompressible Fluid Past a Downstream-Facing Step in Turbulent Flow

1988

A dynamic subgrid-scale tensorial eddy viscosity model

1999

In the Navier-Stokes equations the removal of the turbulent fluctuating velocities with a frequency above a certain fixed threshold, employed in the Large Eddy Simulation (LES), causes the appearance of a turbulent stress tensor that requires a number of closure assumptions. In this paper insufficiencies are demonstrated for those closure models which are based on a scalar eddy viscosity coefficient. A new model, based on a tensorial eddy viscosity, is therefore proposed; it employs the Germano identity [1] and allows dynamical evaluation of the single required input coefficient. The tensorial expression for the eddy viscosity is deduced by removing the widely used scalar assumption of the …