A genome-wide association study suggests that a locus within the ataxin 2 binding protein 1 gene is associated with hand osteoarthritis: the Treat-OA consortium

To identify the susceptibility gene in hand osteoarthritis (OA) the authors used a two-stage approach genome-wide association study using two discovery samples (the TwinsUK cohort and the Rotterdam discovery subset; a total of 1804 subjects) and four replication samples (the Chingford Study, the Chuvasha Skeletal Aging Study, the Rotterdam replication subset and the Genetics, Arthrosis, and Progression (GARP) Study; a total of 3266 people). Five single-nucleotide polymorphisms (SNPs) had a likelihood of association with hand OA in the discovery stage and one of them (rs716508), was successfully confirmed in the replication stage (meta-analysis p = 1.81×10−5). The C allele conferred a reduced risk of 33% to 41% using a case–control definition. The SNP is located in intron 1 of the A2BP1 gene. This study also found that the same allele of the SNP significantly reduced bone density at both the hip and spine (p<0.01), suggesting the potential mechanism of the gene in hand OA might be via effects on subchondral bone. The authors' findings provide a potential new insight into genetic mechanisms in the development of hand OA

Multiple Input Describing Function for Non-Linear Analysis of Ground and Air Resonance

Aeroelastic stability is a key issue that drives the design of modern rotorcraft. The robustness of stability analysis is fundamental to determine the amount of freedom a designer has in defining the key properties in specific rotorcraft problems dominated by stability. The paper presents an effective technique to investigate the effect of nonlinearities on the ground resonance stability, resorting to the multi input describing function. In this way it is possible to investigate the cases when multiple harmonics are injected into a nonlinear component, a typical condition for rotorcraft components. To show the potential of the method, an application that considers a nonlinear model for hydraulic lead-lag dampers is presented

Robust Analysis for the Investigation of Biodynamic Rotorcraft Pilot Couplings

Aircraft-Pilot Couplings, namely the adverse interaction of the pilot with the aeromechanics of aircraft, are potentially dangerous phenomena. The prediction of aircraft proneness to this type of phenomena is usually difficult prior to flight testing. Their occurrence in rotorcraft, called Rotorcraft-Pilot Couplings, received less attention until recent years. Robust stability analysis techniques borrowed from robust control theory are used in this work to develop a simple and versatile method for the investigation of the boundaries of pilot biodynamic feedthrough that guarantees the stability of the coupled system no matter how complex the vehicle model is. The proposed method is applied to the analysis of a detailed model of a medium weight helicopter, and results are discussed

Assessment of a Mid-Fidelity Numerical Approach for the Investigation of Tiltrotor Aerodynamics

The study of the complex aerodynamics that characterise tiltrotors represents a challenge for computational fluid dynamics tools. URANS numerical solvers are typically used to explore the aerodynamic features that characterise the different flight conditions of these aircraft, but their computational cost limits their applications to a few vehicle configurations. The present work explores the capabilities of a new mid-fidelity aerodynamic code that is based on the vortex particle method, DUST, to investigate the performance and flow physics of tiltrotors. With this aim, numerical simulations were performed in DUST while considering XV-15 tiltrotor configurations with increasing complexity. The study started with the investigation of a simpler configuration made up of a single wing and a proprotor. Subsequently, the full aircraft was studied in steady-level flights and its major operating flight conditions were explored—i.e., hover, conversion phase, and cruise. A thorough assessment of the code capabilities was performed by the comparison of the numerical results with high-fidelity Computational Fluid Dynamics (CFD) data. This thorough comparison showed that the mid-fidelity numerical approach implemented in DUST is suitable for capturing the flow physics related to the complex aerodynamic interactions between the proprotors and the wing along with the entire flight envelope of the tiltrotor. Moreover, a good representation of the aerodynamic performance of the vehicle was obtained, particularly for the flight conditions that are characterised by limited flow separations. The good accuracy obtained for both the performance and flow physics, combined with the relatively lower computational costs required by the mid-fidelity solver with respect to the URANS simulations, indicates that DUST could be considered a valuable tool for use in the preliminary design of novel tiltrotor configurations