Wind vane correction during yaw misalignment for horizontal-axis wind turbines

This paper investigates the accuracy of wind direction measurements for horizontal-axis wind turbines and their impact on yaw control. The yaw controller is crucial for aligning the rotor with the wind direction and optimizing energy extraction. Wind direction is conventionally measured by one or two wind vanes located on the nacelle, but the proximity of the rotor can interfere with these measurements. The authors show that the conventional corrections, including low-pass filters and calibrated offset correction, are inadequate to correct a systematic overestimation of the wind direction deviation caused by the rotor misalignment. This measurement error can lead to an overcorrection of the yaw controller and, thus, to an oscillating yaw behaviour, even if the wind direction is relatively steady. The authors present a theoretical basis and methods for quantifying the wind vane measurement error and validate their findings using computational fluid dynamics simulations and operational data from two commercial wind turbines. Additionally, the authors propose a correction function that improves the wind vane measurements and demonstrate its effectiveness in two free-field experiments. Overall, the paper provides new insights into the accuracy of wind direction measurements and proposes solutions to improve the yaw control for horizontal-axis wind turbines.</p

Pre-activated antiviral innate immunity in the upper airways controls early SARS-CoV-2 infection in children

Children have reduced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rates and a substantially lower risk for developing severe coronavirus disease 2019 compared with adults. However, the molecular mechanisms underlying protection in younger age groups remain unknown. Here we characterize the single-cell transcriptional landscape in the upper airways of SARS-CoV-2-negative (n = 18) and age-matched SARS-CoV-2-positive (n = 24) children and corresponding samples from adults (n = 44), covering an age range of 4 weeks to 77 years. Children displayed higher basal expression of relevant pattern recognition receptors such as MDA5 (IFIH1) and RIG-I (DDX58) in upper airway epithelial cells, macrophages and dendritic cells, resulting in stronger innate antiviral responses upon SARS-CoV-2 infection than in adults. We further detected distinct immune cell subpopulations including KLRC1 (NKG2A)+ cytotoxic T cells and a CD8+ T cell population with a memory phenotype occurring predominantly in children. Our study provides evidence that the airway immune cells of children are primed for virus sensing, resulting in a stronger early innate antiviral response to SARS-CoV-2 infection than in adults

A collaborative evaluation of LC-MS/MS based methods for BMAA analysis: soluble bound BMAA found to be an important fraction.

Exposure to β-Ν-methylamino-l-alanine (BMAA) might be linked to the incidence of amyotrophic lateral sclerosis, Alzheimer's disease and Parkinson's disease. Analytical chemistry plays a crucial role in determining human BMAA exposure and the associated health risk, but the performance of various analytical methods currently employed is rarely compared. A CYANOCOST initiated workshop was organized aimed at training scientists in BMAA analysis, creating mutual understanding and paving the way towards interlaboratory comparison exercises. During this workshop, we tested different methods (extraction followed by derivatization and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis, or directly followed by LC-MS/MS analysis) for trueness and intermediate precision. We adapted three workup methods for the underivatized analysis of animal, brain and cyanobacterial samples. Based on recovery of the internal standard D3BMAA, the underivatized methods were accurate (mean recovery 80%) and precise (mean relative standard deviation 10%), except for the cyanobacterium Leptolyngbya. However, total BMAA concentrations in the positive controls (cycad seeds) showed higher variation (relative standard deviation 21%-32%), implying that D3BMAA was not a good indicator for the release of BMAA from bound forms. Significant losses occurred during workup for the derivatized method, resulting in low recovery ( < 10%). Most BMAA was found in a trichloroacetic acid soluble, bound form and we recommend including this fraction during analysis

COVID-19 severity correlates with airway epithelium-immune cell interactions identified by single-cell analysis

To investigate the immune response and mechanisms associated with severe coronavirus disease 2019 (COVID-19), we performed single-cell RNA sequencing on nasopharyngeal and bronchial samples from 19 clinically well-characterized patients with moderate or critical disease and from five healthy controls. We identified airway epithelial cell types and states vulnerable to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In patients with COVID-19, epithelial cells showed an average three-fold increase in expression of the SARS-CoV-2 entry receptor ACE2, which correlated with interferon signals by immune cells. Compared to moderate cases, critical cases exhibited stronger interactions between epithelial and immune cells, as indicated by ligand–receptor expression profiles, and activated immune cells, including inflammatory macrophages expressing CCL2, CCL3, CCL20, CXCL1, CXCL3, CXCL10, IL8, IL1B and TNF. The transcriptional differences in critical cases compared to moderate cases likely contribute to clinical observations of heightened inflammatory tissue damage, lung injury and respiratory failure. Our data suggest that pharmacologic inhibition of the CCR1 and/or CCR5 pathways might suppress immune hyperactivation in critical COVID-19

Single-embryo transfer reduces clinical pregnancy rates and live births in fresh IVF and Intracytoplasmic Sperm Injection (ICSI) cycles: a meta-analysis

<p>Abstract</p> <p>Background</p> <p>It has become an accepted procedure to transfer more than one embryo to the patient to achieve acceptable ongoing pregnancy rates. However, transfers of more than a single embryo increase the probability of establishing a multiple gestation. Single-embryo transfer can minimize twin pregnancies but may also lower live birth rates. This meta-analysis aimed to compare current data on single-embryo versus double-embryo transfer in fresh IVF/ICSI cycles with respect to implantation, ongoing pregnancy and live birth rates.</p> <p>Methods</p> <p>Search strategies included on-line surveys of databases from 1995 to 2008. Data management and analysis were conducted using the Stats Direct statistical software. The fixed-effect model was used for odds ratio (OR). Fixed-effect effectiveness was evaluated by the Mantel Haenszel method. Seven trials fulfilled the inclusion criteria.</p> <p>Results</p> <p>When pooling results under the fixed-effect model, the implantation rate was not significantly different between double-embryo transfer (34.5%) and single-embryo transfer group (34.7%) (<it>P </it>= 0.96; OR = 0.99, 95% CI 0.78, 1.25). On the other hand, double-embryo transfer produced a statistically significantly higher ongoing clinical pregnancy rate (44.5%) than single-embryo transfer (28.3%) (<it>P </it>< 0.0001; OR:2.06, 95% CI = 1.64,2.60). At the same time, pooling results presented a significantly higher live birth rate when double-embryo transfer (42.5%) (P < 0.001; OR: 1.87, 95% CI = 1.44,2.42) was compared with single-embryo transfer (28.4%).</p> <p>Conclusion</p> <p>Meta-analysis with 95% confidence showed that, despite similar implantation rates, fresh double-embryo transfer had a 1.64 to 2.60 times greater ongoing pregnancy rate and 1.44 to 2.42 times greater live birth rate than single-embryo transfer in a population suitable for ART treatment.</p

Long term costs and effects of reducing the number of twin pregnancies in IVF by single embryo transfer: the TwinSing study

Contains fulltext : 87274.pdf (publisher's version ) (Open Access)BACKGROUND: Pregnancies induced by in vitro fertilisation (IVF) often result in twin gestations, which are associated with both maternal and perinatal complications. An effective way to reduce the number of IVF twin pregnancies is to decrease the number of embryos transferred from two to one. The interpretation of current studies is limited because they used live birth as outcome measure and because they applied limited time horizons. So far, research on long-term outcomes of IVF twins and singletons is scarce and inconclusive. The objective of this study is to investigate the short (1-year) and long-term (5 and 18-year) costs and health outcomes of IVF singleton and twin children and to consider these in estimating the cost-effectiveness of single embryo transfer compared with double embryo transfer, from a societal and a healthcare perspective. METHODS/DESIGN: A multi-centre cohort study will be performed, in which IVF singletons and IVF twin children born between 2003 and 2005 of whom parents received IVF treatment in one of the five participating Dutch IVF centres, will be compared. Data collection will focus on children at risk of health problems and children in whom health problems actually occurred. First year of life data will be collected in approximately 1,278 children (619 singletons and 659 twin children). Data up to the fifth year of life will be collected in approximately 488 children (200 singletons and 288 twin children). Outcome measures are health status, health-related quality of life and costs. Data will be obtained from hospital information systems, a parent questionnaire and existing registries. Furthermore, a prognostic model will be developed that reflects the short and long-term costs and health outcomes of IVF singleton and twin children. This model will be linked to a Markov model of the short-term cost-effectiveness of single embryo transfer strategies versus double embryo transfer strategies to enable the calculation of the long-term cost-effectiveness. DISCUSSION: This is, to our knowledge, the first study that investigates the long-term costs and health outcomes of IVF singleton and twin children and the long-term cost-effectiveness of single embryo transfer strategies versus double embryo transfer strategies

Voluntary disclosure of corporate strategy: determinants and outcomes. An empirical study into the risks and payoffs of communicating corporate strategy.

Business leaders increasingly face pressure from stakeholders to be transparent. There appears however little consensus on the risks and payoffs of disclosing vital information such as corporate strategy. To fill this gap, this study analyzes firm-specific determinants and organisational outcomes of voluntary disclosure of corporate strategy. Stakeholder theory and agency theory help to understand whether companies serve their interest to engage with stakeholders and overcome information asymmetries. I connect these theories and propose a comprehensive approach to measure voluntary disclosure of corporate strategy. Hypotheses from the theoretical framework are empirically tested through panel regression of data on identified determinants and outcomes and of disclosed strategy through annual reports, corporate social responsibility reports, corporate websites and corporate press releases by the 70 largest publicly listed companies in the Netherlands from 2003 through 2008. I found that industry, profitability, dual-listing status, national ranking status and listing age have significant effects on voluntary disclosure of corporate strategy. No significant effects are found for size, leverage and ownership concentration. On outcomes, I found that liquidity of stock and corporate reputation are significantly influenced by voluntary disclosure of corporate strategy. No significant effect is found for volatility of stock. My contributions to theory, methodology and empirics offers a stepping-stone for further research into understanding how companies can use transparency to manage stakeholder relations

Influence of rotor blade flexibility on the near-wake behavior of the NREL 5&thinsp;MW wind turbine

High-fidelity computational fluid dynamics (CFD) simulations of the National Renewable Energy Laboratory (NREL) 5 MW wind turbine rotor are performed, comparing the aerodynamic behavior of flexible and rigid blades with respect to local blade quantities as well as the wake properties. The main focus has been set on rotational periodic quantities of blade loading and fluid velocity magnitudes in relation with the blade tip vortex trajectories describing the development of those quantities in the near wake. The results show that the turbine loading in a quasi-steady flow field is mainly influenced by blade deflections due to gravitation. Deforming blades change the aerodynamic behavior, which in turn influences the surrounding flow field, leading to non-uniform wake characteristics with respect to speed and shape.</p

Modeling space-time correlations of velocity fluctuations in wind farms

An analytical model for the streamwise velocity space-time correlations in turbulent flows isderived and applied to the special case of velocity fluctuations in large wind farms. The modelis based on the Kraichnan-Tennekes random sweeping hypothesis, capturing the decorrelation intime while including a mean wind velocity in the streamwise direction. In the resulting model, thestreamwise velocity space-time correlation is expressed as a convolution of the pure space cor-relation with an analytical temporal decorrelation kernel. Hence, the spatiotemporal structureof velocity fluctuations in wind farms can be derived from the spatial correlations only. We thenexplore the applicability of the model to predict spatiotemporal correlations in turbulent flows inwind farms. Comparisons of the model with data from a large eddy simulation of flow in a large,spatially periodic wind farm are performed, where needed model parameters such as spatial andtemporal integral scales and spatial correlations are determined from the large eddy simulation.Good agreement is obtained between the model and large eddy simulation data showing thatspatial data may be used to model the full spatiotemporal structure of fluctuations in wind farms

Percutaneous vertebroplasty and balloon kyphoplasty in the treatment of osteoporotic vertebral fractures:a prospective randomized comparison

Purpose The purpose of this study is to compare the efficacy and safety of percutaneous vertebroplasty (PVP) and balloon kyphoplasty (BKP) in the treatment of osteoporotic vertebral compression fractures. Materials and methods Patients with osteoporotic vertebral body fractures (T4-L5) were randomized and not blinded to kyphoplasty (n = 69) or vertebroplasty (n = 70). The postoperative pain score (VAS) at 12 months was the primary end point. The radiographic results were evaluated in relation to the resolution of the fracture and the possible onset of further osteoporotic fractures during follow-up. Results A total of one hundred and thirty-nine patients were eligible for randomization (n = 70 for PVP group and n = 69 for BKP), and twenty-six patients (twenty in the BKP group and six in the PVP group) were excluded. The mean average age of patients was 73 years, and 82% of the patients were females. VAS pain score was significantly reduced after surgery in both groups, and there were no significant differences between the two groups in postoperative VAS score. There was a significant reduction in kyphotic wedge angle and improvement of the sagittal index in both groups, but there was no significant difference between the two groups. There was a significant higher risk incidence of adjacent level fractures in the vertebroplasty group. Conclusions In terms of clinical outcomes, there were no differences between the two groups. Both showed a significant clinical improvement, vertebral body height restoration and reduction in the kyphotic angle. There was a significant higher risk of adjacent level fractures in the vertebroplasty group