A Strategy for Passive Control of Natural Roll-Waves in Power-Law Fluids through Inlet Boundary Conditions

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Applicability of Kinematic and Diffusive models for mud-flows: a steady state analysis

The paper investigates the applicability of Kinematic and Diffusive Wave models for mud-flows with a power-law shear-thinning rheology. In analogy with a well-known approach for turbulent clear-water flows, the study compares the steady flow depth profiles predicted by approximated models with those of the Full Dynamic Wave one. For all the models and assuming an infinitely wide channel, the analytical solution of the flow depth profiles, in terms of hypergeometric functions, is derived. The accuracy of the approximated models is assessed by computing the average, along the channel length, of the errors, for several values of the Froude and kinematic wave numbers. Assuming the threshold value of the error equal to 5%, the applicability conditions of the two approximations have been individuated for several values of the power-law exponent, showing a crucial role of the rheology. The comparison with the clear-water results indicates that applicability criteria for clear-water flows do not apply to shearthinning fluids, potentially leading to an incorrect use of approximated models if the rheology is not properly accounted for

Mechanical Systems: Symmetry and Reduction

Reduction theory is concerned with mechanical systems with symmetries. It constructs a lower dimensional reduced space in which associated conservation laws are taken out and symmetries are \factored out" and studies the relation between the dynamics of the given system with the dynamics on the reduced space. This subject is important in many areas, such as stability of relative equilibria, geometric phases and integrable systems

Impact dynamics of mud flows against rigid walls

Mud flows represent one of the major causes of natural hazards in mountain regions. Similarly to debris flows, they consist of a hyper-concentrated mixture of water and sediments flowing down a slope and may cause serious damages to people and structures. The present paper investigates the force produced by a dam-break wave of mud impacting against a rigid wall. A power-law shearthinning model is used to describe the rheology of the hyper-concentrated mixture. A onedimensional shallow water model is adopted and a second-order Finite Volume scheme is employed to numerically solve the governing equations. The results indicate that depending on the fluid rheological parameters and on the bottom slope, there exists a minimum value of the wall distance above which the peak force does not exceed the asymptotic value of the hydrostatic final condition. For two different values of the channel slope, the dimensionless value of this lower bound is individuated for several values of the power-law exponent and of a dimensionless Basal Drag coefficient. An estimation of the maximum peak force for wall distance smaller than the minimum value is also provided

A Strategy for Passive Control of Natural Roll-Waves in Power-Law Fluids through Inlet Boundary Conditions

The paper investigates the influence of the inlet boundary condition on the spatial evolution of natural roll-waves in a power-law fluid flowing in steep slope channels. The analysis is carried out numerically, by solving the von Kármán depth-integrated mass and momentum conservation equations, in the long-wave approximation. A second-order accurate scheme is adopted and a small random white-noise is superposed to the discharge at the channel inlet to generate the natural roll-waves train. Both shear-thinning and shear-thickening power-law fluids are investigated, considering uniform, accelerated and decelerated hypercritical profiles as the unperturbed condition. Independently of the unperturbed profile and of the fluid rheology, numerical simulations clearly enlighten the presence of coalescence, coarsening and overtaking processes, as experimentally observed. All the considered statistical parameters indicate that the natural roll-waves spatial evolution is strongly affected by the unperturbed profile. Compared with the uniform condition, at the beginning of roll-waves development an accelerated profile reduces the growth of the roll-waves with a downstream shift of the non-linear wave interaction. The opposite behavior is observed if the roll wave train develops over a decelerated profile. The comparison with the theoretical outcomes of the linearized near wave-front analysis allows the interpretation of this result in terms of stability of the base flow. It is shown that once the coarsening process starts to take place, the roll-waves spatial growth rate is independent of the unperturbed profile. Present results suggest that an appropriate selection of the flow depth at the channel inlet may contribute to control, either enhancing or inhibiting, the formation of a roll-waves train in power-law fluids

WATER\u2013BUDGET AS A TOOL TO EVALUATE THE SUSTAINABLE USE OF GROUNDWATER RESOURCES (ISONZO PLAIN, NE ITALY)

Water budget, hydrogeology, Soča/Isonzo River, climate chang

Corevalve vs. Sapien 3 transcatheter aortic valve replacement: A finite element analysis study

Aim: to investigate the factors implied in the development of postoperative complications in both self-expandable and balloon-expandable transcatheter heart valves by means of finite element analysis (FEA). Materials and methods: FEA was integrated into CT scans to investigate two cases of postoperative device failure for valve thrombosis after the successful implantation of a CoreValve and a Sapien 3 valve. Data were then compared with two patients who had undergone uncomplicated transcatheter heart valve replacement (TAVR) with the same types of valves. Results: Computational biomechanical modeling showed calcifications persisting after device expansion, not visible on the CT scan. These calcifications determined geometrical distortion and elliptical deformation of the valve predisposing to hemodynamic disturbances and potential thrombosis. Increased regional stress was also identified in correspondence to the areas of distortion with the associated paravalvular leak. Conclusion: the use of FEA as an adjunct to preoperative imaging might assist patient selection and procedure planning as well as help in the detection and prevention of TAVR complications

Prolonged podocyte depletion in larval zebrafish resembles mammalian focal and segmental glomerulosclerosis

Focal and segmental glomerulosclerosis (FSGS) is a histological pattern frequently found in patients with nephrotic syndrome that often progress to end-stage kidney disease. The initial step in development of this histologically defined entity is injury and ultimately depletion of podocytes, highly arborized interdigitating cells on the glomerular capillaries with important function for the glomerular filtration barrier. Since there are still no causal therapeutic options, animal models are needed to develop new treatment strategies. Here, we present an FSGS-like model in zebrafish larvae, an eligible vertebrate model for kidney research. In a transgenic zebrafish strain, podocytes were depleted, and the glomerular response was investigated by histological and morphometrical analysis combined with immunofluorescence staining and ultrastructural analysis by transmission electron microscopy. By intravenous injection of fluorescent high-molecular weight dextran, we confirmed leakage of the size selective filtration barrier. Additionally, we observed severe podocyte foot process effacement of remaining podocytes, activation of proximal tubule-like parietal epithelial cells identified by ultrastructural cytomorphology, and expression of proximal tubule markers. These activated cells deposited extracellular matrix on the glomerular tuft which are all hallmarks of FSGS. Our findings indicate that glomerular response to podocyte depletion in larval zebrafish resembles human FSGS in several important characteristics. Therefore, this model will help to investigate the disease development and the effects of potential drugs in a living organism

Caratteristiche dei dati accelerometrici registrati durante la sequenza sismica aquilana

I dati accelerometrici relativi alla sequenza sismica de L’Aquila, iniziata con l’evento del 6 Aprile alle ore 1.32 (MW 6.3), provengono dalla rete Rete Accelerometrica Nazionale (RAN), gestita dal Dipartimento della Protezione Civile (DPC) e da una rete temporanea installata il giorno dopo la scossa principale ad opera dell’Istituto Nazionale di Geofisica e Vulcanologia (INGV MI-PV). I dati del DPC sono scaricabili dalla banca dati accelerometrica italiana ITACA (http://itaca.mi.ingv.it), mentre quelli dell'INGV sono accessibili dal sito Internet http://accel.mi.ingv.it/statiche/ABRUZZO-2009/main.html. Il terremoto de L’Aquila è il terzo evento più forte che abbia prodotto registrazioni accelerometriche in Italia, dopo i terremoti dell’Irpinia (1980, MW 6.9) e del Friuli (1976, MW 6.4). Questo evento, insieme alle 12 repliche più forti (MW > 4.0) ha fornito un insieme di dati accelerometrici unico in Italia, in particolare per la presenza di un numero consistente di registrazioni in zona epicentrale ("campo vicino"). Il data set è composto da circa 300 accelerogrammi digitali (di cui 270 provenienti dalla RAN), con un ottimo rapporto segnale/rumore, registrati da circa 70 stazioni, installate in varie condizioni di sito, a distanze comprese fra 0 e 300 km. L'importanza di questo data set, non solo a livello nazionale, è legato al contributo significativo che fornisce nel colmare una lacuna nella distribuzione magnitudo-distanza dei dati strong motion italiani e mondiali, soprattutto per quanto riguarda gli eventi con meccanismo di faglia normale (Ameri et al.; 2009). I dati registrati in campo vicino provengono da un transetto composto da 6 stazioni installato dalla Protezione Civile nel 2001 nella Alta Valle dell’Aterno, con lo scopo di investigare la variabilità del moto sismico rispetto alle condizioni geologiche locali, dalla stazione AQK, installata in prossimità del centro urbano e da una stazione (AQU) appartenente alla rete broad band Mednet (http://mednet.rm.ingv.it/data.php), situata nel castello de L’Aquila. Queste stazioni distano meno di 5 km dall’epicentro dell’evento principale, ricadendo all’interno della proiezione superficiale del piano di rottura. A queste si aggiungono le registrazioni delle repliche, ottenute dalle stazioni della rete temporanea INGV, installata in area epicentrale. In questo lavoro si presenta un resoconto delle principali caratteristiche dello scuotimento del suolo verificatosi durante la sequenza sismica aquilana, attraverso l’analisi dei dati accelerometrici relativi alla scossa principale e alle due repliche più forti. Si discutono in particolare la dipendenza di diversi parametri strong motion dalla distanza, dall’azimuth e dalle condizioni di sito, e l'effetto delle caratteristiche del moto in campo vicino sulla risposta strutturalePublished57-684.1. Metodologie sismologiche per l'ingegneria sismicaN/A or not JCRreserve