Enrico Ferrero

Integrating Cardiac PIP3 and cAMP Signaling through a PKA Anchoring Function of p110γ

Adrenergic stimulation of the heart engages cAMP and phosphoinositide second messenger signaling cascades. Cardiac phosphoinositide 3-kinase p110γ participates in these processes by sustaining β-adrenergic receptor internalization through its catalytic function and by controlling phosphodiesterase 3B (PDE3B) activity via an unknown kinase-independent mechanism. We have discovered that p110γ anchors protein kinase A (PKA) through a site in its N-terminal region. Anchored PKA activates PDE3B to enhance cAMP degradation and phosphorylates p110γ to inhibit PIP(3) production. This provides local feedback control of PIP(3) and cAMP signaling events. In congestive heart failure, p110γ is upregulated and escapes PKA-mediated inhibition, contributing to a reduction in β-adrenergic receptor density. Pharmacological inhibition of p110γ normalizes β-adrenergic receptor density and improves contractility in failing hearts.

COMPARISON AMONG EMPIRICAL PROBABILITY DENSITY FUNCTIONS OF THE VERTICAL VELOCITY IN THE SURFACE LAYER BASED ON HIGHER ORDER CORRELATIONS

Vertical velocity fluctuations were measured in theatmospheric surface layer by means of an ultrasonic anemometer andhigher order correlations were calculated on two time series, recordedin unstable and neutral conditions, and selected for the wholemeasurement period on the basis of the inversion test (stationaritytest). Comparisons have been made between observed and predictedcorrelations by considering Gaussian joint-PDF and Gram-Charlierseries expansions truncated to the fourth and sixth order as doneearlier by Frenkiel and Klebanoff. A bi-Gaussian PDF, given by amixture of two Gaussian PDFs, has also been considered. This lasthas been constructed assuming that either the first three or the firstfour moments are given, and the relationships between correlationfunctions of different order are derived. The departure from Gaussianbehaviour in both stability conditions is derived. Though Gram-Charlier series expansions show a good correspondence toexperimental reality, their use as non-Gaussian probabilitydistributions cannot be suggested in theoretical approaches andshould be considered with care in practical applications, due topossible occurrences of small negative probabilities. The resultsshown in this paper support the applicability of the bi-Gaussian PDFcreated using up to the fourth moment.

A simple way of computing buoyant plume rise in Lagrangian stochastic dispersion models

Abstract A simple and easy to use method to include Eulerian plume rise in Lagrangian particle models is presented. This approach takes into account the vertical variation of wind and stability. Its ability to realistically simulate plume rise and spread, both through numerical experiments under typical atmospheric conditions and by comparison with actual plumes detected by a Differential Lidar in a case study, is shown. Despite its simplicity, our method proved to describe the main plume rise characteristics in a satisfactory way and to yield a fair agreement among observed and predicted plume centreline heights and standard deviations.

Turbulence Closures In Neutral Boundary Layer Over Complex Terrain

In this work, three turbulence closure models, Mellor andYamada level 2.5, E - l and E - ∈ implemented in a circulation model, are compared in neutral condition over complex terrain. They are firstly applied to a one-dimensional case on flat terrain and then to a schematic two-dimensional valley. The simulation results, in terms of wind field and turbulent kinetic energy, are tested against measurements from a wind-tunnel experiment. The empirical constants defining the characteristic length scales of the closures are modified based on turbulence parameters estimated in the experiment. The formulation of the diffusion coefficients is analysed to explain the differences among the various closures in the simulation results. Regarding the mean flow, both on flat and complex terrain, all the closures yield satisfactory results. Concerning the turbulent kinetic energy, the best results are obtained by E - l and E - ∈ closures.

The role of wind field, mixing height and horizontal diffusivity investigated through two Lagrangian particle models

Abstract Two Lagrangian particle models, APOLLO and MILORD, were used to simulate the first ETEX experiment. The role played by wind field, mixing height h and horizontal diffusivity KH appeared to be the most important aspects to be studied. The sensitivity to the accuracy of the input advection field was studied through the application of APOLLO using different ECMWF data sets differing in space and time resolution and in being forecasted or analysed, corresponding to the real-time, emergency-like condition, and to the a posteriori benchmark simulation. The role of h and KH was investigated by running both APOLLO and MILORD with different parameterisations, and comparing the model results between them and with the available observations. The model evaluation was carried out through a set of statistical indexes computed on three hourly average concentrations paired in space and time and time-integrated concentrations. It was found that the quality of the input wind field plays a major role in predicting with sufficient accuracy the plume position and extension after the first 24xa0h from the beginning of the release. The best-model results are obtained with large values of KH (in the range of 2.5×104–4.5×104xa0m2xa0s-1), which confirms the need to enhance the horizontal diffusion, in order to include the advection fluctuations unresolved by large-scale meteorological fields. A fixed value of h in the range 1000–1500xa0m seems to be more efficient than space and time variable h computed with standard algorithms. A reasonable explanation for this result is given, based on the consideration that in the long range, particles diffuse also in the residual layer above the stable nocturnal boundary layer.

A simplified version of the correct boundary conditions for skewed turbulence in Lagrangian particle models

Abstract Recently, Thomson and Montgomery (1994, Atmospheric Environment 28 , 1981–1987) stated the correct method of treating the reflection of particle velocity at the boundaries in Lagrangian particle diffusion models for non-Gaussian turbulence. Unfortunately, this method does not have an analytical solution. Two different approximated analytical solutions are proposed and compared. It is concluded that both of them satisfy the well-mixed condition and do not appreciably depart from the correct solution. The one consuming less time is proposed.

A Lagrangian Decorrelation Time Scale in the Convective Boundary Layer

A new method for deriving the Lagrangian decorrelation time scales for inhomogeneous turbulence is described. The expression for the time scales here derived for the convective boundary layer is compared to those estimated by Hanna during the Phoenix experiment. Then the values of C0, the Lagrangian velocity structure function constant, and of Bi, the Lagrangian velocity spectrum constant, were evaluated from the Eulerian velocity spectra and from the Lagrangian time scales derived, under unstable conditions, from Taylors statistical diffusion theory. The numerical coefficient of the lateral and vertical Lagrangian spectra in the inertial subrange was found equal to 0.21, in good agreement with previous experimental estimates.

Application of a Bivariate Gamma Distribution for a Chemically Reacting Plume in the Atmosphere

The joint concentration probability density function of two reactive chemical species is modelled using a bivariate Gamma distribution coupled with a three-dimensional fluctuating plume model able to simulate the diffusion and mixing of turbulent plumes. A wind-tunnel experiment (Brown and Bilger, J Fluid Mech 312:373–407, 1996), carried out in homogeneous unbounded turbulence, in which nitrogen oxide is released from a point source in an ozone doped background and the chemical reactions take place in non-equilibrium conditions, is considered as a test case. The model is based on a stochastic Langevin equation reproducing the barycentre position distribution through a proper low-pass filter for the turbulence length scales. While the meandering large-scale motion of the plume is directly simulated, the internal mixing relative to the centroid is reproduced using a bivariate Gamma density function. The effect of turbulence on the chemical reaction (segregation), which in this case has not yet attained equilibrium, is directly evaluated through the covariance of the tracer concentration fields. The computed mean concentrations and the O3–NO concentration covariance are also compared with those obtained by the Alessandrini and Ferrero Lagrangian single particle model (Alessandrini and Ferrero, Physica A 388:1375–1387, 2009) that entails an ad hoc parametrization for the segregation coefficient.

A Lagrangian particle model with chemical reactions: application in real atmosphere

In this work, a Lagrangian particle model able to account for simple chemical reactions between NO and O3 has been improved to consider the photolysis of NO2. A system of chemical equations is numerically solved on a Eulerian grid, while the particle trajectories are moved in a Lagrangian frame. The NOx emissions of a power plant in real atmosphere, situated in a complex topography environment, have been considered as a test case. The simulated episodes refer to the diurnal time, when the ultraviolet radiation activates the NO2. Comparisons between NO/NO2’s concentrations ratio are presented in terms of scatter plots and statistical indexes analysis.

Experimental study of higher-order moments in shear-driven boundary layers with rotation

The results of laboratory wall turbulence experiments on a shear-driven rotating boundary layer are presented. The experiments were carried out in the Turin University Laboratory rotating water tank. The flow was generated by changing the rotation speed of the platform and measured by means of particle image velocimetry. In order to analyse the influence of the rotation and of surface roughness, different cases were examined. Several rotation periods were considered. The measurements were performed both over a smooth surface and over a rough-to-smooth transition. Mean flows and the higher-order moments of the velocity probability density function are shown and discussed together with a comparison of the different experimental cases, theory and large-eddy simulations.