Load mitigation for wind turbines by a passive aeroelastic device

This paper conducts a preliminary investigation of a novel passive concept for the mitigation of loads on wind turbines. The device, which can be implemented as a flap or a pitching blade tip, moves passively in response to blade vibrations, opposing them, thereby yielding an attenuation of loads. In comparison to active load mitigation devices, such as active flaps, this solution has the advantage of not requiring sensors nor actuators, resulting in a particularly simple implementation, with potential benefits in manufacturing and maintenance costs, as well as in reliability and availability.The paper first describes the novel passive device, here implemented by means of a flap, highlighting its main characteristics. A proof of concept of the new idea is then given by a simulation study conducted with the combination of a sectional model of the flap and an aeroservoelastic multibody model of the rest of the machine. Results, obtained for a 10. MW wind turbine, indicate the ability of the passive flap in attenuating blade vibrations in a significant frequency range, which in turn yield a reduced fatigue damage to the structure without noticeable effects in terms of power production and ultimate loads

Articulated blade tip devices for load alleviation on wind turbines

This paper investigates the load alleviation capabilities of an articulated tip device, where the outermost portion of the blade can rotate with respect to the rest of the blade. Passive, semi-passive and active solutions are developed for the tip rotation. In the passive and semi-passive configurations tip pitching is mainly driven by aerodynamic loads, while for the active case the rotation is obtained with an actuator commanded by a feedback control law. Each configuration is analyzed and tested using a high-fidelity aeroservoelastic simulation environment, by considering standard operative conditions as well as fault situations. The potential benefits of the proposed blade tip concepts are discussed in terms of performance and robustness

Synchronized onset of nuclear and cell surface modifications in U937 cells during apoptosis

In this study we investigated the relationship between nuclear and cell surface modifications (i.e. blebbing, phosphatidylserine [PS] and sugar residues exposure) in a monocytic cell line, U937, during apoptosis induced by oxidative stress (1mM H2O2) or inhibition of protein synthesis (10 mg/ml puromycin). Dying cells were simultaneously observed for nuclear modifications, presence of superficial blebs and plasma membrane alterations. Morphological analysis performed by conventional fluorescence microscopy, or by transmission and scanning electron microscopy showed that the courses of nuclear and membrane alterations occured concomitantly, but the phenotype was dependent on the stage of the apoptotic process and the type of apoptogenic inducer used. The progression of apoptosis in U937 cells beyond early stages resulted in the extensive formation of blebs which concomitantly lost some typical markers of apoptosis, such as PS and sugar residues. Therefore, the modality by which the nucleus condenses, or the amount and the pattern of distribution of PS on the cell surface were, for each cell line, strictly related to the apoptogenic inducer. The morphological data reported in the present paper should lead to a more precise quantification of apoptosis by improving the detection of apoptotic cells in vivo (i.e. in tissue, organs), which is a crucial point in the evaluation of efficiency of antiproliferative drugs, such as antiblastic or immunosuppressive compounds

From the Ancient Diets to the Recent Acquisitions on the Role of Brain Inflammation in Epilepsy, Are there Any Links?

Recent studies put in evidence the role of brain inflammation in the pathogenetic mechanisms of seizures. It has been reported that an intestinal inflammation may be able to migrate to the brain, thus an intestinal inflammation could be the original cause of epilepsy, as osteopaths believed in the '20s. We attempted to demonstrate the role of gut-brain axis in epilepsy on the basis of recent acquisitions

pH-Dependent structuring and fluorescence properties of tryptophan-derived polyamidoamino acids

The binding sites of proteins often contain tryptophan residues, whose fluorescent properties may be altered upon ligand binding. Conformational changes within the binding site can result in either fluorescence quenching or enhancement, which may be utilized to quantitatively investigate protein-ligand interactions. Amphoteric fluorescent (L)-, (D)- and (D,L)-tryptophan-deriving polyamidoamino acid (PAAC) homopolymers and their copolymers with glycine and arginine PAAC copolymers were synthesized by the polyaddition of N,N'-methylenebisacrylamide (MBA) with (L)-, (D)- and (D,L)-tryptophan and, respectively, glycine- and (L)-arginine/(L)-tryptophan mixtures. The polymerization reaction was run at 50\ub0C and pH>10 for 7 days under nitrogen atmosphere. All polymers were characterized by NMR spectrometry, UV-Visible spectroscopy, dynamic light scattering (DLS), steady state and time-resolved fluorescence (TRF) spectroscopy. Solubility in aqueous systems at different pH\u2019s was determined by measuring the transmittance at 450 nm. Homopolymers showed similar pH-dependent solubility patterns, with steep solubility drop at pH < 8. Volumetric particle size distribution obtained by DLS analysis showed hydrodynamic radii (Rh) 48 100 nm and negligible changes with pH. Fluorescence quantum yield of the MBA-L-tryptophan measured at 10-5 M repeating unit concentration decreased from 6 to 4 % from pH 11 to 8 respectively. Excitation and emission spectra showed maxima at 279 nm and 370 nm respectively, the latter showing a 20 nm blue shift by decreasing pH from 11 to 8. The excited-state lifetimes of the MBA-(L)-tryptophan at the maximum emission wavelength decreased from \u3c41 = 0.90 ns, \u3c42 = 4.40 ns to \u3c41 = 0.81 ns, \u3c42 = 3.49 ns passing from pH 11 to 8, with a population redistribution in favour of the shortest time. PAAC copolymers were synthesized under the same conditions of the homopolymers. The solubility curves in water of copolymers showed complete solubility for tryptophan content up to 20 % on a molar basis. For tryptophan content up to 30 and 40%, transmittance dropped down, respectively, to 60 % and 5 % in the pH range 2-7. DLS measurements at different pH\u2019s showed average volume particle size 2.5 nm in the range considered. Preliminary TRF spectroscopy data proved that PAAC copolymers were endowed with pH-dependent emission properties. Moreover, significant fluorescence quantum yield was detected at the tryptophan content as low as 5 %. Finally, preliminary circular dichroism measurements showed pH-dependent patterns. In conclusion, tryptophan-based PAAC polymers displayed tunable amphiphilicity, chirality and self-assembly properties

pH-Dependent structuring and fluorescence properties of tryptophan-derived polyamidoamino acids

The binding sites of proteins often contain tryptophan residues, whose fluorescent properties may be altered upon ligand binding. Conformational changes within the binding site can result in either fluorescence quenching or enhancement, which may be utilized to quantitatively investigate protein-ligand interactions. Amphoteric fluorescent (L)-, (D)- and (D,L)-tryptophan-deriving polyamidoamino acid (PAAC) homopolymers and their copolymers with glycine and arginine PAAC copolymers were synthesized by the polyaddition of N,N'-methylenebisacrylamide (MBA) with (L)-, (D)- and (D,L)-tryptophan and, respectively, glycine- and (L)-arginine/(L)-tryptophan mixtures. The polymerization reaction was run at 50\ub0C and pH>10 for 7 days under nitrogen atmosphere. All polymers were characterized by NMR spectrometry, UV-Visible spectroscopy, dynamic light scattering (DLS), steady state and time-resolved fluorescence (TRF) spectroscopy. Solubility in aqueous systems at different pH\u2019s was determined by measuring the transmittance at 450 nm. Homopolymers showed similar pH-dependent solubility patterns, with steep solubility drop at pH < 8. Volumetric particle size distribution obtained by DLS analysis showed hydrodynamic radii (Rh) 48 100 nm and negligible changes with pH. Fluorescence quantum yield of the MBA-L-tryptophan measured at 10-5 M repeating unit concentration decreased from 6 to 4 % from pH 11 to 8 respectively. Excitation and emission spectra showed maxima at 279 nm and 370 nm respectively, the latter showing a 20 nm blue shift by decreasing pH from 11 to 8. The excited-state lifetimes of the MBA-(L)-tryptophan at the maximum emission wavelength decreased from \u3c41 = 0.90 ns, \u3c42 = 4.40 ns to \u3c41 = 0.81 ns, \u3c42 = 3.49 ns passing from pH 11 to 8, with a population redistribution in favour of the shortest time. PAAC copolymers were synthesized under the same conditions of the homopolymers. The solubility curves in water of copolymers showed complete solubility for tryptophan content up to 20 % on a molar basis. For tryptophan content up to 30 and 40%, transmittance dropped down, respectively, to 60 % and 5 % in the pH range 2-7. DLS measurements at different pH\u2019s showed average volume particle size 2.5 nm in the range considered. Preliminary TRF spectroscopy data proved that PAAC copolymers were endowed with pH-dependent emission properties. Moreover, significant fluorescence quantum yield was detected at the tryptophan content as low as 5 %. Finally, preliminary circular dichroism measurements showed pH-dependent patterns. In conclusion, tryptophan-based PAAC polymers displayed tunable amphiphilicity, chirality and self-assembly properties

Rotorcraft Flight Envelope Protection by Model Predictive Control

A novel flight envelope protection method is presented. The approach is based on a model predictive receding horizon formulation, which computes at each instant in time the future extremal control inputs that would lead the vehicle to ride the flight envelope boundary without ever exceeding it. The extremal inputs are then used for pilot cueing. The calculation of the extremal inputs is based on the constrained optimization of a quadratic figure of merit for a reduced-order linear parameter varying model of the vehicle. The model accounts for the cross-couplings among the inputs that characterize the flight mechanics of rotorcraft vehicles and spans the entire flight envelope of interest by piecewise linear interpolation of given trim points. The approach leads to a convex optimization problem, which can be computed very efficiently in real time using a deterministic number of operations. A heuristic modification to the limits of the critical parameters, driven by a reduced-order nonlinear model of the vehicle, is used for online solution adaptation against possible model mismatch. The new approach is demonstrated by numerical simulation of multiple complex pilot-in-the-loop aggressive maneuvers