985 resultados para eddy currents


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Es indudable que la tendencia del derecho público, en tiempos de globalización se caracteriza por ceder mayor participación a los particulares en la realización de obras y en la prestación de servicios públicos; por esta razón, el Estado ha incursionado en nuevas formas de realización de estos procesos en torno al nuevo sistema de compras públicas. Por lo expuesto, es importante analizar el Gobierno Electrónico y su relación con la contratación pública estatal a nivel nacional e internacional y el avance que esta ha tenido, vinculándose a la contratación pública en el proceso de gobernanza electrónica o política pública que el Estado determina o genera a fin de que se ejecute la debida y correcta aplicación de las herramientas integrantes de un gobierno electrónico con el objetivo de dinamizarlo. Así también conocer las características de la gobernanza electrónica y el gobierno electrónico en el Estado, definiendo cada uno de los elementos que integran la contratación pública electrónica, sus objetivos, los mismos que nos permiten visualizar la relación estricta entre la Gobernanza Electrónica, gobierno electrónico y contratación pública electrónica. La contratación pública electrónica en el Ecuador para su instauración y fortalecimiento ha requerido de varios actos administrativos que motiven oficialmente el uso de una plataforma electrónica, lo que ha conllevado al legislativoejecutivo y a sus instituciones a emitir instrumentos legales como acuerdos, leyes, reglamentos y resoluciones, en los cuales se determine la normativa clara para el uso y aplicación de estas herramientas de contratación; se analiza los instrumentos legales de vital importancia que sirvieron de antecedente para la construcción y funcionamiento del Sistema Nacional de Contratación Pública en el Ecuador, así como también las características actuales del mismo especialmente en relación a los procedimientos dinámicos catálogo electrónico y subasta inversa electrónica.

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El presente trabajo de investigación tiene como eje trascendental de su contenido los ingresos tributarios y su rol en las fases de la deuda pública, como componentes vinculados de la actividad financiera del Estado; la realidad financiera del Estado ecuatoriano introduce al estudio del presupuesto y la planificación nacional para vislumbrar el manejo de la deuda pública atendiendo muy especialmente a los principios de equilibrio, estabilidad presupuestaria y sostenibilidad financiera. El contenido de esta investigación convergen el análisis de la relación de los ingresos tributarios y la deuda pública en la estabilidad presupuestaria, por lo que el determinar la organización constitucional, legal de la planificación y su orientación ha sido de vital importancia, sobre todo si se intenta realizar un diagnóstico de la situación de los ingresos tributarios y el manejo de la deuda pública en Ecuador desde el año 2007 a la luz del equilibrio presupuestario y sostenibilidad financiera. Entre los métodos empleados está el dogmático que posibilitó el estudio de la actividad financiera desde la perspectiva del Derecho Financiero; el método sistemático me permitió proceder a realizar una reunión racional de los componentes de la actividad financiera del Estado y sus más importantes instrumentos. El método sincrético posibilitó el desarrollo armonioso del contenido con enfoques desarrollados desde las teorías de las finanzas públicas y la doctrina del Derecho financiero. La investigación me llevó a concluir que los recursos públicos son los medios a través de los cuales el Estado puede proveerse de ingresos, entre los cuales se reconocieron los recursos del crédito público y los recursos tributarios, es así que los ingresos tributarios son los componentes de mayor importancia en la actividad financiera pública, pues determinan la elasticidad del gasto y del endeudamiento. El ciclo de la deuda pública está conformado de tres fases: la del crédito, empréstito y de deuda pública propiamente dicha; en estas fases los ingresos tributarios tienen un rol que varía al tratarse de un crédito contraído con un acreedor nacional o un extranjero y que genera una deuda interna o externa respectivamente. Los componentes de las finanzas públicas están reflejados en el presupuesto general del Estado que a su vez está sujeto en Ecuador a la planificación nacional, conocida como Plan Nacional del Buen Vivir que encierra un conjunto ordenado de directrices y objetivos.

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Sobre el acceso a medicamentos y el derecho a la salud en el marco de la propiedad intelectual, múltiples cuestionamientos se pueden plantear, en esta tesis. Lo cierto es que a la fecha, el trabajo normativo, jurisprudencial y doctrinario que se ha suscitado entorno a él, da cuenta de una realidad que ya se había evidenciado en el Informe de la Comisión de Derechos de Propiedad Intelectual, Innovación y Salud Pública «Salud Pública, innovación y derechos de propiedad intelectual» de la Organización Mundial de la Salud en el año 2006 “una cuestión fundamental es la relación entre la combinación de políticas que podrían fomentar la innovación biomédica de interés para los países en desarrollo y la capacidad de los países para poner a disposición del público los productos de la innovación, lo que contribuiría a hacer realidad el derecho de las personas a disfrutar del más alto nivel posible de salud”. En este contexto, los Estados miembros de la Comunidad Andina como signatarios de diversos instrumentos internacionales y de las disposiciones normativas contenidas en sus Cartas Fundamentales en materia del derecho a la salud, no pueden ser ajenos a su obligación de garantizar el acceso a medicamentos para su población, así deban, entre otras posibilidades, «valerse» del régimen de flexibilidades y/o excepciones «licencias obligatorias» que consagra el régimen de protección de las innovaciones farmacéuticas «principalmente el Acuerdo sobre los Aspectos de la Propiedad Intelectual relacionados con el Comercio y/o la Decisión 486 de la Comisión de la Comunidad Andina» en procura de materializar la eficacia del derecho a la Salud. Por todo lo anterior el problema a analizar con la presente investigación académica estará orientado a demostrar cuáles son las razones por las que las flexibilidades que contiene el régimen de patentes farmacéuticas, particularmente las licencias obligatorias, resultan insuficientes o no para garantizar el acceso equitativo a los medicamentos de la población de los Estados miembros de la Comunidad Andina.

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Este trabajo analiza el anticipo mínimo del impuesto a la renta en torno a su regulación y tiene como objetivo evidenciar de qué manera su base de cálculo se desarticula del impuesto a la renta. La investigación se centra en explicar la problemática en la aplicación del sistema de anticipación en Ecuador, se utilizan varias teorías jurídicas y técnicas del tributo para estimar mejor los argumentos. Mediante un orden en el análisis separaremos su incidencia desde los elementos que componen la determinación cuantitativa, para llegar a delimitar su acaecimiento en los principios del derecho tributario y la doble tributación interna. Los resultados de este trabajo confirman la existencia de un mundo de dificultades y fricciones que genera el anticipo del impuesto a la renta. Finalmente se plantea algunas de las posibles vías de solución, confirmadas en base del éxito en otros regímenes a partir de la línea comparada.

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We use a simplified atmospheric general circulation model (AGCM) to investigate the response of the lower atmosphere to thermal perturbations in the lower stratosphere. The results show that generic heating of the lower stratosphere tends to weaken the sub-tropical jets and the tropospheric mean meridional circulations. The positions of the jets, and the extent of the Hadley cells, respond to the distribution of the stratospheric heating, with low latitude heating displacing them poleward, and uniform heating displacing them equatorward. The patterns of response to the low latitude heating are similar to those found to be associated with solar variability in previous observational data analysis, and to the effects of varying solar UV radiation in sophisticated AGCMs. In order to investigate the chain of causality involved in converting the stratospheric thermal forcing to a tropospheric climate signal we conduct an experiment which uses an ensemble of model spin-ups to analyse the time development of the response to an applied stratospheric perturbation. We find that the initial effect of the change in static stability at the tropopause is to reduce the eddy momentum flux convergence in this region. This is followed by a vertical transfer of the momentum forcing anomaly by an anomalous mean circulation to the surface, where it is partly balanced by surface stress anomalies. The unbalanced part drives the evolution of the vertically integrated zonal flow. We conclude that solar heating of the stratosphere may produce changes in the circulation of the troposphere even without any direct forcing below the tropopause. We suggest that the impact of the stratospheric changes on wave propagation is key to the mechanisms involved.

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Centred at the interface between the sea-breeze and the return flow aloft, Kelvin-Helmholtz billows (KHB) are an important feature of the turbulent structure of some sea-breeze circulations (SBCs). In other SBCs, there are no prominent KHBs observed. Factors governing the appearance of billows are determined from a database of 139 sea breezes, constructed from two years of summertime surface observations at a site on the south coast of England. Post-frontal oscillations occur in the surface data for some SBCs and are interpreted as indicating possible KHBs aloft. The SBCs are formed under a wide range of synoptic conditions, enabling various measures of possible billow occurrence to be related to properties of the large-scale, ambient flow. Consistent with laboratory experiments of density currents, KHBs are suppressed for propagation into a head wind and enhanced with a tail wind. They are also found to be enhanced for stronger ambient wind speeds, while large-scale coast-parallel flow is effective in suppressing the billows.

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The influence of surface waves and an applied wind stress is studied in an ensemble of large eddy simulations to investigate the nature of deeply penetrating jets into an unstratified mixed layer. The influence of a steady monochromatic surface wave propagating parallel to the wind direction is parameterized using the wave-filtered Craik-Leibovich equations. Tracer trajectories and instantaneous downwelling velocities reveal classic counterrotating Langmuir rolls. The associated downwelling jets penetrate to depths in excess of the wave's Stokes depth scale, δs. Qualitative evidence suggests the depth of the jets is controlled by the Ekman depth scale. Analysis of turbulent kinetic energy (tke) budgets reveals a dynamical distinction between Langmuir turbulence and shear-driven turbulence. In the former, tke production is dominated by Stokes shear and a vertical flux term transports tke to a depth where it is dissipated. In the latter, tke production is from the mean shear and is locally balanced by dissipation. We define the turbulent Langmuir number Lat = (v*/Us)0.5 (v* is the ocean's friction velocity and Us is the surface Stokes drift velocity) and a turbulent anisotropy coefficient Rt = /( + ). The transition between shear-driven and Langmuir turbulence is investigated by varying external wave parameters δs and Lat and by diagnosing Rt and the Eulerian mean and Stokes shears. When either Lat or δs are sufficiently small the Stokes shear dominates the mean shear and the flow is preconditioned to Langmuir turbulence and the associated deeply penetrating jets.

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In principle the global mean geostrophic surface circulation of the ocean can be diagnosed by subtracting a geoid from a mean sea surface (MSS). However, because the resulting mean dynamic topography (MDT) is approximately two orders of magnitude smaller than either of the constituent surfaces, and because the geoid is most naturally expressed as a spectral model while the MSS is a gridded product, in practice complications arise. Two algorithms for combining MSS and satellite-derived geoid data to determine the ocean’s mean dynamic topography (MDT) are considered in this paper: a pointwise approach, whereby the gridded geoid height field is subtracted from the gridded MSS; and a spectral approach, whereby the spherical harmonic coefficients of the geoid are subtracted from an equivalent set of coefficients representing the MSS, from which the gridded MDT is then obtained. The essential difference is that with the latter approach the MSS is truncated, a form of filtering, just as with the geoid. This ensures that errors of omission resulting from the truncation of the geoid, which are small in comparison to the geoid but large in comparison to the MDT, are matched, and therefore negated, by similar errors of omission in the MSS. The MDTs produced by both methods require additional filtering. However, the spectral MDT requires less filtering to remove noise, and therefore it retains more oceanographic information than its pointwise equivalent. The spectral method also results in a more realistic MDT at coastlines. 1. Introduction An important challenge in oceanography is the accurate determination of the ocean’s time-mean dynamic topography (MDT). If this can be achieved with sufficient accuracy for combination with the timedependent component of the dynamic topography, obtainable from altimetric data, then the resulting sum (i.e., the absolute dynamic topography) will give an accurate picture of surface geostrophic currents and ocean transports.

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The tropospheric response to midlatitude SST anomalies has been investigated through a series of aquaplanet simulations using a high-resolution version of the Hadley Centre atmosphere model (HadAM3) under perpetual equinox conditions. Model integrations show that increases in the midlatitude SST gradient generally lead to stronger storm tracks that are shifted slightly poleward, consistent with changes in the lower-tropospheric baroclinicity. The large-scale atmospheric response is, however, highly sensitive to the position of the SST gradient anomaly relative to that of the subtropical jet in the unperturbed atmosphere. In particular, when SST gradients are increased very close to the subtropical jet, then the Hadley cell and subtropical jet is strengthened while the storm track and eddy-driven jet are shifted equatorward. Conversely, if the subtropical SST gradients are reduced and the midlatitude gradients increased, then the storm track shows a strong poleward shift and a well-separated eddy-driven jet is produced. The sign of the SST anomaly is shown to play a secondary role in determining the overall tropospheric response. These findings are used to provide a new and consistent interpretation of some previous GCM studies concerning the atmospheric response to midlatitude SST anomalies.

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The Earth’s global atmospheric electric circuit depends on the upper and lower atmospheric boundaries formed by the ionosphere and the planetary surface. Thunderstorms and electrified rain clouds drive a DC current (∼1 kA) around the circuit, with the current carried by molecular cluster ions; lightning phenomena drive the AC global circuit. The Earth’s near-surface conductivity ranges from 10−7 S m−1 (for poorly conducting rocks) to 10−2 S m−1 (for clay or wet limestone), with a mean value of 3.2 S m−1 for the ocean. Air conductivity inside a thundercloud, and in fair weather regions, depends on location (especially geomagnetic latitude), aerosol pollution and height, and varies from ∼10−14 S m−1 just above the surface to 10−7 S m−1 in the ionosphere at ∼80 km altitude. Ionospheric conductivity is a tensor quantity due to the geomagnetic field, and is determined by parameters such as electron density and electron–neutral particle collision frequency. In the current source regions, point discharge (coronal) currents play an important role below electrified clouds; the solar wind-magnetosphere dynamo and the unipolar dynamo due to the terrestrial rotating dipole moment also apply atmospheric potential differences. Detailed measurements made near the Earth’s surface show that Ohm’s law relates the vertical electric field and current density to air conductivity. Stratospheric balloon measurements launched from Antarctica confirm that the downward current density is ∼1 pA m−2 under fair weather conditions. Fortuitously, a Solar Energetic Particle (SEP) event arrived at Earth during one such balloon flight, changing the observed atmospheric conductivity and electric fields markedly. Recent modelling considers lightning discharge effects on the ionosphere’s electric potential (∼+250 kV with respect to the Earth’s surface) and hence on the fair weather potential gradient (typically ∼130 V m−1 close to the Earth’s surface. We conclude that cloud-to-ground (CG) lightning discharges make only a small contribution to the ionospheric potential, and that sprites (namely, upward lightning above energetic thunderstorms) only affect the global circuit in a miniscule way. We also investigate the effects of mesoscale convective systems on the global circuit.

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This study uses large-eddy simulation (LES) to investigate the characteristics of Langmuir turbulence through the turbulent kinetic energy (TKE) budget. Based on an analysis of the TKE budget a velocity scale for Langmuir turbulence is proposed. The velocity scale depends on both the friction velocity and the surface Stokes drift associated with the wave field. The scaling leads to unique profiles of nondimensional dissipation rate and velocity component variances when the Stokes drift of the wave field is sufficiently large compared to the surface friction velocity. The existence of such a scaling shows that Langmuir turbulence can be considered as a turbulence regime in its own right, rather than a modification of shear-driven turbulence. Comparisons are made between the LES results and observations, but the lack of information concerning the wave field means these are mainly restricted to comparing profile shapes. The shapes of the LES profiles are consistent with observed profiles. The dissipation length scale for Langmuir turbulence is found to be similar to the dissipation length scale in the shear-driven boundary layer. Beyond this it is not possible to test the proposed scaling directly using available data. Entrainment at the base of the mixed layer is shown to be significantly enhanced over that due to normal shear turbulence.

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Background and purpose: Carisbamate is being developed for adjuvant treatment of partial onset epilepsy. Carisbamate produces anticonvulsant effects in primary generalized, complex partial and absence-type seizure models, and exhibits neuroprotective and antiepileptogenic properties in rodent epilepsy models. Phase IIb clinical trials of carisbamate demonstrated efficacy against partial onset seizures; however, its mechanisms of action remain unknown. Here, we report the effects of carisbamate on membrane properties, evoked and spontaneous synaptic transmission and induced epileptiform discharges in layer II-III neurones in piriform cortical brain slices. Experimental approach: Effects of carisbamate were investigated in rat piriform cortical neurones by using intracellular electrophysiological recordings. Key results: Carisbamate (50–400 mmol·L-1) reversibly decreased amplitude, duration and rise-time of evoked action potentials and inhibited repetitive firing, consistent with use-dependent Na+ channel block; 150–400 mmol·L-1 carisbamate reduced neuronal input resistance, without altering membrane potential. After microelectrode intracellular Cl- loading, carisbamate depolarized cells, an effect reversed by picrotoxin. Carisbamate (100–400 mmol·L-1) also selectively depressed lateral olfactory tract-afferent evoked excitatory synaptic transmission (opposed by picrotoxin), consistent with activation of a presynaptic Cl conductance. Lidocaine (40–320 mmol·L-1) mimicked carisbamate, implying similar modes of action. Carisbamate (300–600 mmol·L-1) had no effect on spontaneous GABAA miniature inhibitory postsynaptic currents and at lower concentrations (50–200 mmol·L-1) inhibited Mg2+-free or 4-aminopyridine-induced seizure-like discharges. Conclusions and implications: Carisbamate blocked evoked action potentials use-dependently, consistent with a primary action on Na+ channels and increased Cl- conductances presynaptically and, under certain conditions, postsynaptically to selectively depress excitatory neurotransmission in piriform cortical layer Ia-afferent terminals.

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Voltage-dependent Ca2+ channels (VDCCs) have emerged as targets to treat neuropathic pain; however, amongst VDCCs, the precise role of the CaV2.3 subtype in nociception remains unproven. Here, we investigate the effects of partial sciatic nerve ligation (PSNL) on Ca2+ currents in small/medium diameter dorsal root ganglia (DRG) neurones isolated from CaV2.3(−/−) knock-out and wild-type (WT) mice. DRG neurones from CaV2.3(−/−) mice had significantly reduced sensitivity to SNX-482 versusWTmice. DRGs from CaV2.3(−/−) mice also had increased sensitivity to the CaV2.2 VDCC blocker -conotoxin. In WT mice, PSNL caused a significant increase in -conotoxin-sensitivity and a reduction in SNX-482-sensitivity. In CaV2.3(−/−) mice, PSNL caused a significant reduction in -conotoxin-sensitivity and an increase in nifedipine sensitivity. PSNL-induced changes in Ca2+ current were not accompanied by effects on voltagedependence of activation in either CaV2.3(−/−) or WT mice. These data suggest that CaV2.3 subunits contribute, but do not fully underlie, drug-resistant (R-type) Ca2+ current in these cells. In WT mice, PSNL caused adaptive changes in CaV2.2- and CaV2.3-mediated Ca2+ currents, supporting roles for these VDCCs in nociception during neuropathy. In CaV2.3(−/−) mice, PSNL-induced changes in CaV1 and CaV2.2 Ca2+ current, consistent with alternative adaptive mechanisms occurring in the absence of CaV2.3 subunits.

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This paper discusses the risks of a shutdown of the thermohaline circulation (THC) for the climate system, for ecosystems in and around the North Atlantic as well as for fisheries and agriculture by way of an Integrated Assessment. The climate model simulations are based on greenhouse gas scenarios for the 21st century and beyond. A shutdown of the THC, complete by 2150, is triggered if increased freshwater input from inland ice melt or enhanced runoff is assumed. The shutdown retards the greenhouse gas-induced atmospheric warming trend in the Northern Hemisphere, but does not lead to a persistent net cooling. Due to the simulated THC shutdown the sea level at the North Atlantic shores rises by up to 80 cm by 2150, in addition to the global sea level rise. This could potentially be a serious impact that requires expensive coastal protection measures. A reduction of marine net primary productivity is associated with the impacts of warming rather than a THC shutdown. Regional shifts in the currents in the Nordic Seas could strongly deteriorate survival chances for cod larvae and juveniles. This could lead to cod fisheries becoming unprofitable by the end of the 21st century. While regional socioeconomic impacts might be large, damages would be probably small in relation to the respective gross national products. Terrestrial ecosystem productivity is affected much more by the fertilization from the increasing CO2 concentration than by a THC shutdown. In addition, the level of warming in the 22nd to 24th century favours crop production in northern Europe a lot, no matter whether the THC shuts down or not. CO2 emissions corridors aimed at limiting the risk of a THC breakdown to 10% or less are narrow, requiring departure from business-as-usual in the next few decades. The uncertainty about THC risks is still high. This is seen in model analyses as well as in the experts’ views that were elicited. The overview of results presented here is the outcome of the Integrated Assessment project INTEGRATION.

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We review briefly recent progress on understanding the role of surface waves on the marine atmospheric boundary layer and the ocean mixed layer and give a global perspective on these processes by analysing ERA-40 data. Ocean surface waves interact with the marine atmospheric boundary layer in two broad regimes: (i) the conventional wind-driven wave regime, when fast winds blow over slower moving waves, and (ii) a wave-driven wind regime when long wavelength swell propagates under low winds, and generates a wave-driven jet in the lower part of the marine boundary layer. Analysis of ERA-40 data indicates that the wave-driven wind regime is as prevalent as the conventional wind-driven regime. Ocean surface waves also change profoundly mixing in the ocean mixed layer through generation of Langmuir circulation. Results from large-eddy simulation are used here to develop a scaling for the resulting Langmuir turbulence, which is a necessary step in developing a parametrization of the process. ERA-40 data is then used to show that the Langmuir regime is the predominant regime over much of the global ocean, providing a compelling motivation for parameterising this process in ocean general circulation models.