Nonlinear aeroelastic modeling via conformal mapping and vortex method for a flat-plate airfoil in arbitrary motion

A nonlinear aerodynamic modeling based on conformal mapping is presented to obtain semi-analytical formulas for the unsteady aerodynamic force and pitching moment on a flat-plate airfoil in arbitrary motion. The aerodynamic model accounts for large amplitudes and non-planar wake and is used to study the aeroelastic behavior of a flat-plate airfoil elastically connected to a support. The fluid is assumed to be inviscid and incompressible, while the flow is assumed to be attached, planar, and potential. Within these hypotheses, conformal mapping and a complex-potential representation of unsteady aerodynamics are used to simplify the theoretical formulation. The vorticity shed at the trailing edge is discretized in desingularized point vortices in order to allow free-wake dynamics. The unsteady aerodynamic model is validated with classical linearized formulations based on the assumption of small disturbances, and with experimental data and theoretical predictions for a large-amplitude pitch-up, hold, pitch-down maneuver. The aeroelastic model is then used to simulate the response of a flat-plate airfoil to sudden starts and body-vortex interactions. Numerical results show that the proposed approach can be an effective tool to model the aeroelastic behavior of an arbitrarily-moving wing section in a time-dependent potential stream of incompressible fluid

An analytical study of the self-induced inviscid dynamics of two-dimensional uniform vortices

The self-induced dynamics of a uniform planar vortex in an isochoric, inviscid fluid is analytically investigated, by writing a new nonlinear integrodifferential problem which describes the time evolution of the Schwarz function of its boundary. In order to overcome the difficulties related to the nonlinear nature of the problem, an approximate solution of the above problem is proposed in terms of a hierarchy of linear integral equations. In particular, the solution at the first order is here investigated and applied to a class of uniform vortices, the kinematics of which is well known. A rich mathematical phenomenology has been found behind the approximate dynamics. In particular, the motion of certain branch points and the consequent changes in the algebraic structure of the Schwarz function appear to be its key features. The approximate solutions are finally compared with the contour dynamics simulations of the vortex motion. The agreement is satisfactory up to times of the order of a quarter of the eddy turnover time, while it becomes more and more qualitative at later times. Eventually, the physical meaning of the approximate solutions is lost, the corresponding vortex boundaries becoming non-simple curves

Kinetics of MgWO4 Formation in the Solid State Reaction between MgO and WO3

The solid state reaction of MgWO4 formation from MgO (single crystals) and WO3 was investigated in the temperature range 800 - 985 °C under both air and argon atmosphere. The techniques employed for the kinetic study (contact and thermogravimetric methods) allowed to point out that the process follows the linear rate law in the early stages and the parabolic one in the subsequent stages. From inert marker experiments, kinetic determinations under the two different atmospheres and conductivity measurements, it was possible to state that the reaction is governed by a cation counterdiffusion mechanis

On the Mechanism of CaWO4 Formation in the Solid State from CaO and WO3

The formation in the solid state of CaWO4 from CaO (single crystal) or Ca3WO6 and WO3 was investigated by the contact method between 800 and 1000 °C in air and in argon. The results obtained indicate that these reactions are governed by the diffusion of the W6+ and O2- ions. From the CaWO4 structure, along with the lattice disorder predominant in this compound (0 vacancies and 0 interstitials) and the values of ionic mobilities, it was possible to state that the oxygen diffusion, via V0 2·, represents the rate - determining step in the considered reaction

Kinetics of Formation of SrWO4 in the Solid State Reaction Between WO3 and SrCO3

The solid state reaction WO3 + SrCO3 → SrWO4 + CO2 was studied with the reactants in form both of separate pellets and of powder mixtures. As for pellets, by an application of Wagner's method it was possible to state that the governing process is the cation counterdiffusion involving W6+ and Sr2+. Thermogravimetric measurements in the temperature range 663° - 755 °C on equimolar powder mixtures and with SrCO3 in a specially prepared spherulitic form were interpreted using Dünwald- Wagner's equatio

Kinetics and Mechanism of Solid State Reactions in the Agl-TlI System

The kinetics of the solid state reactions AgI + TiI → AgTlI2 (I) Agl + AgTl2I3 → 2 AgTlI2 (II) AgTlI2 + Til → AgTl2I3 (III) are investigated with reactant pellets by the contact method. With the aid of inert marker experiments and transport number determinations it was possible to state that the governing mechanism is the cation counter-diffusion in all cases and that the rate determining step is the diffusion of Tl+. The experimental reaction rate constants agree reasonably with those calculated on the basis of the Wagner's thermodynamic theory

Shwachman Diamond Syndrome: an emergency challenge

Shwachman Diamond Syndrome is a rare congenital disorder characterized by pancreatic insufficiency, bone marrow dysfunction and skeletal abnormalities. No specific test is available for a definitive diagnosis for SDS. In the presence of clinical features of SDS, pancreatic insufficiency should be tested for or lipomatosis radiologically demonstrated. New directions might be found in genetic analysis. Sometimes, a life-threatening event may be the first clinical manifestation of the syndrome

Shwachman Diamond Syndrome: an emergency challenge

Shwachman Diamond Syndrome is a rare congenital disorder characterized by pancreatic insufficiency, bone marrow dysfunction and skeletal abnormalities. No specific test is available for a definitive diagnosis for SDS. In the presence of clinical features of SDS, pancreatic insufficiency should be tested for or lipomatosis radiologically demonstrated. New directions might be found in genetic analysis. Sometimes, a life-threatening event may be the first clinical manifestation of the syndrome

Interleukin and neurotrophin up-regulation correlates with severity of H1N1 infection in children: a case–control study

Summary Objective To evaluate the correlation between cytokine and neurotrophin expression and clinical findings, disease severity, and outcome of children with H1N1 influenza infection. Methods A prospective observational clinical study was performed on 15 children with H1N1 infection, 15 controls with lower respiratory tract infections (LRTI), and 15 non-infected children. Plasma levels of interleukin (IL)-1β, IL-6, and neurotrophic factor (nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), and glial derived neurotrophic factor (GDNF)) were measured using immunoenzymatic assays. Results Significantly higher levels of IL-1β, IL-6, BDNF, and NGF were detected in patients with H1N1 infection compared to LRTI controls, while there was no significant variation in GDNF in the two groups. IL-1β, IL-6, BDNF, and NGF levels were significantly higher in H1N1 patients with more severe clinical manifestations compared to H1N1 patients with mild clinical manifestations. Of note, IL-6 was significantly correlated with the severity of respiratory compromise and fever, while NGF up-regulation was associated with the duration of cough. No correlation was found between interleukin and neurotrophic factor expression and outcome. Conclusions H1N1 infection induces an early and significant IL-1β, IL-6, BDNF, and NGF up-regulation. The over-expression of these molecular markers is likely to play a neuroimmunomodulatory role in H1N1 infection and may contribute to airway inflammation and bronchial hyper-reactivity in infected children

Development of a repressible mycobacterial promoter system based on two transcriptional repressors

Tightly regulated gene expression systems represent invaluable tools for studying gene function and for the validation of drug targets in bacteria. While several regulated bacterial promoters have been characterized, few of them have been successfully used in mycobacteria. In this article we describe the development of a novel repressible promoter system effective in both fast- and slow-growing mycobacteria based on two chromosomally encoded repressors, dependent on tetracycline (TetR) and pristinamycin (Pip), respectively. This uniqueness results in high versatility and stringency. Using this method we were able to obtain an ftsZ conditional mutant in Mycobacterium smegmatis and a fadD32 conditional mutant in Mycobacterium tuberculosis, confirming their essentiality for bacterial growth in vitro. This repressible promoter system could also be exploited to regulate gene expression during M. tuberculosis intracellular growt