Model-based Aeroservoelastic Design and Load Alleviation of Large Wind Turbine Blades

This paper presents an aeroservoelastic modeling approach for dynamic load alleviation in large wind turbines with trailing-edge aerodynamic surfaces. The tower, potentially on a moving base, and the rotating blades are modeled using geometrically non-linear composite beams, which are linearized around reference conditions with arbitrarily-large structural displacements. Time-domain aerodynamics are given by a linearized 3-D unsteady vortexlattice method and the resulting dynamic aeroelastic model is written in a state-space formulation suitable for model reductions and control synthesis. A linear model of a single blade is used to design a Linear-Quadratic-Gaussian regulator on its root-bending moments, which is finally shown to provide load reductions of about 20% in closed-loop on the full wind turbine non-linear aeroelastic model

Electronic spin drift in graphene field effect transistors

We studied the drift of electron spins under an applied DC electric field in single layer graphene spin valves in a field effect transport geometry at room temperature. In the metallic conduction regime ($n \simeq 3.5 \times 10^{16}$ m$^{-2}$), for DC fields of about $\pm$70 kV/m applied between the spin injector and spin detector, the spin valve signals are increased/decreased, depending on the direction of the DC field and the carrier type, by as much as $\pm$50%. Sign reversal of the drift effect is observed when switching from hole to electron conduction. In the vicinity of the Dirac neutrality point the drift effect is strongly suppressed. The experiments are in quantitative agreement with a drift-diffusion model of spin transport.Comment: 4 figure

Controlling the efficiency of spin injection into graphene by carrier drift

Electrical spin injection from ferromagnetic metals into graphene is hindered by the impedance mismatch between the two materials. This problem can be reduced by the introduction of a thin tunnel barrier at the interface. We present room temperature non-local spin valve measurements in cobalt/aluminum-oxide/graphene structures with an injection efficiency as high as 25%, where electrical contact is achieved through relatively transparent pinholes in the oxide. This value is further enhanced to 43% by applying a DC current bias on the injector electrodes, that causes carrier drift away from the contact. A reverse bias reduces the AC spin valve signal to zero or negative values. We introduce a model that quantitatively predicts the behavior of the spin accumulation in the graphene under such circumstances, showing a good agreement with our measurements.Comment: 4 pages, 3 color figure

Setting positive end-expiratory pressure:The use of esophageal pressure measurements

Purpose of reviewTo summarize the key concepts, physiological rationale and clinical evidence for titrating positive end-expiratory pressure (PEEP) using transpulmonary pressure (PL) derived from esophageal manometry, and describe considerations to facilitate bedside implementation.Recent findingsThe goal of an esophageal pressure-based PEEP setting is to have sufficient PLat end-expiration to keep (part of) the lung open at the end of expiration. Although randomized studies (EPVent-1 and EPVent-2) have not yet proven a clinical benefit of this approach, a recent posthoc analysis of EPVent-2 revealed a potential benefit in patients with lower APACHE II score and when PEEP setting resulted in end-expiratory PLvalues close to 0 ± 2 cmH2O instead of higher or more negative values. Technological advances have made esophageal pressure monitoring easier to implement at the bedside, but challenges regarding obtaining reliable measurements should be acknowledged.SummaryEsophageal pressure monitoring has the potential to individualize the PEEP settings. Future studies are needed to evaluate the clinical benefit of such approach.</p

Setting positive end-expiratory pressure:The use of esophageal pressure measurements

Purpose of reviewTo summarize the key concepts, physiological rationale and clinical evidence for titrating positive end-expiratory pressure (PEEP) using transpulmonary pressure (PL) derived from esophageal manometry, and describe considerations to facilitate bedside implementation.Recent findingsThe goal of an esophageal pressure-based PEEP setting is to have sufficient PLat end-expiration to keep (part of) the lung open at the end of expiration. Although randomized studies (EPVent-1 and EPVent-2) have not yet proven a clinical benefit of this approach, a recent posthoc analysis of EPVent-2 revealed a potential benefit in patients with lower APACHE II score and when PEEP setting resulted in end-expiratory PLvalues close to 0 ± 2 cmH2O instead of higher or more negative values. Technological advances have made esophageal pressure monitoring easier to implement at the bedside, but challenges regarding obtaining reliable measurements should be acknowledged.SummaryEsophageal pressure monitoring has the potential to individualize the PEEP settings. Future studies are needed to evaluate the clinical benefit of such approach.</p

[Editorial] Molecular mechanisms of memory consolidation, reconsolidation, and persistence

In the last decades there have been significant advances in our understanding of the cellular and subcellular mechanisms underlying changes in synaptic connectivity that subserve memory formation. The so called Theory of Synaptic Plasticity and Memory has gathered a wealth of experimental support from different areas of neuroscience to become the main phenomenological description of memory at the behavioural level. This special issue of neural plasticity compiles some of the most recent advances in our understanding of the mechanisms underlying formation and persistence of different types of memories from invertebrates to humans. Contributions from different laboratories around the world pinpoint hot topics in this area of memory research, highlighting growing avenues for future research.Fil: Merlo, Emiliano. University of Cambridge; Reino Unido. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bekinschtein, Pedro Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Sietse, Jonkman. Icahn School of Medicine at Mount Sinai; Estados UnidosFil: Medina, Jorge Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas; Argentin

Linear scaling between momentum and spin scattering in graphene

Spin transport in graphene carries the potential of a long spin diffusion length at room temperature. However, extrinsic relaxation processes limit the current experimental values to 1-2 um. We present Hanle spin precession measurements in gated lateral spin valve devices in the low to high (up to 10^13 cm^-2) carrier density range of graphene. A linear scaling between the spin diffusion length and the diffusion coefficient is observed. We measure nearly identical spin- and charge diffusion coefficients indicating that electron-electron interactions are relatively weak and transport is limited by impurity potential scattering. When extrapolated to the maximum carrier mobilities of 2x10^5 cm^2/Vs, our results predict that a considerable increase in the spin diffusion length should be possible