Investigation of potential extreme load reduction for a two-bladed upwind turbine with partial pitch

This paper presents a wind turbine concept with an innovative design combining partial pitch with a two-bladed (PP-2B) turbine configuration. Special emphasis is on extreme load reduction during storm situations at standstill, but operational loads are also investigated. In order to compare the loads and dynamics of the PP-2B turbine, a partial pitch three-bladed (PP-3B) turbine and a normal pitch regulated three-bladed (3B) turbine are introduced on the basis of solidity similarity scaling. From the dynamic comparisons between two- and three-bladed turbines, it has been observed that the blade vibrations are transferred differently from the rotor to the tower. For a three-bladed turbine, blade vibrations seen in a fixed frame of reference are split with ±1P only. A two-bladed turbine has a similar split of ±1P but also includes contributions on higher harmonics (±2P, ±3P, ... etc.). Further on, frequency split is also seen for the tower vibrations, where an additional ±2P contribution has been observed for the two-bladed turbine. Regarding load comparisons, the PP-2B turbine produces larger tower load variations because of 2P excitation during the operational cases. However, extreme loads are reduced by approximately 20% for the PP-2B and 18% for the PP-3B compared with the 3B turbine for the parked condition in a storm situation. Moreover, a huge potential of 60% is observed for the reduction of the extreme tower bottom bending moment for the PP-2B turbine, when the wind direction is from ±90° to the turbine, but this also requires that the turbine is parked in a T-configuration

Active gyroscopic stabilizer to mitigate vibration in a multimegawatt wind turbine

One of the main concerns in developing large wind turbines, especially offshore, is their cost‐effectiveness versus traditional power sources. Significant dynamic loads are applied to the tower and the foundation of a multimegawatt wind turbine. Any reduction in the loads can reduce the size of the structure and, consequently, the turbine's cost. In this paper, a novel structural control application is proposed to mitigate the transmitted vibrations to a multimegawatt turbine tower to decrease the tower base shear forces and overturning moments. For this purpose, a hybrid passive/active gyro stabilizer is designed and incorporated into the NREL baseline 5‐MW wind turbine. Furthermore, two controllers, including a proportional integral differential (PID), as the baseline controller, and a nonlinear fuzzy logic controller (FLC) as the main and nonlinear controllers, have been designed and implemented to the turbine model. The structural control systems are implemented into the turbine model by cosimulating ADAMS and Simulink. The results reveal that the application of the proposed stabilizer can significantly reduce the overturning moment at the base of the tower compared to the reference NREL 5‐MW mode

Amyloid-β, p-tau, and reactive microglia load are correlates of MRI cortical atrophy in Alzheimer's disease

INTRODUCTION: The aim of this study was to identify the histopathological correlates of MRI cortical atrophy in (a)typical Alzheimer’s disease (AD) donors. METHODS: 19 AD and 10 control donors underwent post-mortem in-situ 3T-3DT1-MRI, from which cortical thickness was calculated. Upon subsequent autopsy, 21 cortical brain regions were selected and immunostained for amyloid-beta, phosphorylated-tau, and reactive microglia. MRI-pathology associations were assessed using linear mixed models. Post-mortem MRI was compared to ante-mortem MRI when available. RESULTS: Higher amyloid-beta load weakly correlated with a higher cortical thickness globally. Phosphorylated-tau strongly correlated with cortical atrophy in temporo-frontal regions. Reactive microglia load strongly correlated with cortical atrophy in the parietal region. Post-mortem scans showed high concordance with ante-mortem scans acquired <1 year before death. DISCUSSION: Distinct histopathological markers differently correlate with cortical atrophy, highlighting their different roles in the neurodegenerative process. This study contributes in understanding the pathological underpinnings of MRI atrophy patterns

Why are we not flooded by involuntary thoughts about the past and future? Testing the cognitive inhibition dependency hypothesis

© The Author(s) 2018In everyday life, involuntary thoughts about future plans and events occur as often as involuntary thoughts about the past. However, compared to involuntary autobiographical memories (IAMs), such episodic involuntary future thoughts (IFTs) have become a focus of study only recently. The aim of the present investigation was to examine why we are not constantly flooded by IFTs and IAMs given that they are often triggered by incidental cues while performing undemanding activities. One possibility is that activated thoughts are suppressed by the inhibitory control mechanism, and therefore depleting inhibitory control should enhance the frequency of both IFTs and IAMs. We report an experiment with a between-subjects design, in which participants in the depleted inhibition condition performed a 60-min high-conflict Stroop task before completing a laboratory vigilance task measuring the frequency of IFTs and IAMs. Participants in the intact inhibition condition performed a version of the Stroop task that did not deplete inhibitory control. To control for physical and mental fatigue resulting from performing the 60-min Stroop tasks in experimental conditions, participants in the control condition completed only the vigilance task. Contrary to predictions, the number of IFTs and IAMs reported during the vigilance task, using the probe-caught method, did not differ across conditions. However, manipulation checks showed that participants’ inhibitory resources were reduced in the depleted inhibition condition, and participants were more tired in the experimental than in the control conditions. These initial findings suggest that neither inhibitory control nor physical and mental fatigue affect the frequency of IFTs and IAMs.Peer reviewedFinal Published versio

Cremophor EL causes (pseudo-) non-linear pharmacokinetics of paclitaxel in patients

The non-linear plasma pharmacokinetics of paclitaxel in patients has been well established, however, the exact underlying mechanism remains to be elucidated. We have previously shown that the non-linear plasma pharmacokinetics of paclitaxel in mice results from Cremophor EL. To investigate whether Cremophor EL also plays a role in the non-linear pharmacokinetics of paclitaxel in patients, we have established its pharmacokinetics in patients receiving paclitaxel by 3-, 24- or 96-h intravenous infusion. The pharmacokinetics of Cremophor EL itself was non-linear as the clearance (Cl) in the 3-h schedules was significantly lower than when using the longer 24- or 96-h infusions (Cl175–3 h = 42.8 ± 24.9 ml h−1 m−2; Cl175–24 h = 79.7 ± 24.3; P = 0.035 and Cl135–3 h = 44.1 ± 21.8 ml h−1 m−1; Cl140–96 h = 211.8 ± 32.0; P < 0.001). Consequently, the maximum plasma levels were much higher (0.62%) in the 3-h infusions than when using longer infusion durations. By using an in vitro equilibrium assay and determination in plasma ultrafiltrate we have established that the fraction of unbound paclitaxel in plasma is inversely related with the Cremophor EL level. Despite its relatively low molecular weight, no Cremophor EL was found in the ultrafiltrate fraction. Our results strongly suggest that entrapment of paclitaxel in plasma by Cremophor EL, probably by inclusion in micelles, is the cause of the apparent nonlinear plasma pharmacokinetics of paclitaxel. This mechanism of a (pseudo-)non-linearity contrasts previous postulations about saturable distribution and elimination kinetics and means that we must re-evaluate previous assumptions on pharmacokinetics–pharmacodynamics relationships. © 1999 Cancer Research Campaig

Quality of life after stroke: Evaluation of the Greek SAQOL-39g

Background/Aims: Stroke and aphasia rehabilitation aims to improve people’s quality of life. Yet, scales for measuring health-related quality of life in stroke typically exclude people with aphasia. They are also primarily available in English. An exception is the Stroke and Aphasia Quality of Life scale (SAQOL-39g). This scale has been tested with people with aphasia; it has been adapted for use in many countries including Greece. The aim of this study was to examine the psychometric properties of the Greek SAQOL-39g. Methods: An interview-based psychometric study was carried out. Participants completed: receptive sub-tests of Frenchay Aphasia Screening Test, Greek SAQOL-39g, General Health Questionnaire-12, Frenchay Activities Index, Montreal Cognitive Assessment and Barthel Index. Results: 86 people took part; 26 provided test-retest reliability data. The Greek SAQOL-39g demonstrated excellent acceptability (minimal missing data; no floor/ceiling effects), test-retest reliability (ICC= 0.96 scale, 0.83-0.99 domains) and internal consistency (Cronbach’s alpha 0.96 scale, 0.92-0.96 domains). There was strong evidence for convergent (r=0.53-0.80 scale; 0.54-0.89 domains) and discriminant validity (r=0.52 scale; 0.04-0.48 domains). Conclusion: The Greek SAQOL-39g is a valid and reliable scale. It is a promising measure for use in stroke and aphasia treatment prioritization, outcome measurement and service evaluation