Material properties of the heel fat pad across strain rates

The complex structural and material behaviour of the human heel fat pad determines the transmission of plantar loading to the lower limb across a wide range of loading scenarios; from locomotion to injurious incidents. The aim of this study was to quantify the hyper-viscoelastic material properties of the human heel fat pad across strains and strain rates. An inverse finite element (FE) optimisation algorithm was developed and used, in conjunction with quasi-static and dynamic tests performed to five cadaveric heel specimens, to derive specimen-specific and mean hyper-viscoelastic material models able to predict accurately the response of the tissue at compressive loading of strain rates up to 150 s−1. The mean behaviour was expressed by the quasi-linear viscoelastic (QLV) material formulation, combining the Yeoh material model (C10=0.1MPa, C30=7MPa, K=2GPa) and Prony׳s terms (A1=0.06, A2=0.77, A3=0.02 for τ1=1ms, τ2=10ms, τ3=10s). These new data help to understand better the functional anatomy and pathophysiology of the foot and ankle, develop biomimetic materials for tissue reconstruction, design of shoe, insole, and foot and ankle orthoses, and improve the predictive ability of computational models of the foot and ankle used to simulate daily activities or predict injuries at high rate injurious incidents such as road traffic accidents and underbody blast

The adult mouse hippocampal progenitor is neurogenic but not a stem cell

The aim of this investigation was to characterize the proliferative precursor cells in the adult mouse hippocampal region. Given that a very large number of new hippocampal cells are generated over the lifetime of an animal, it is predicted that a neural stem cell is ultimately responsible for maintaining this genesis. Although it is generally accepted that a proliferative precursor resides within the hippocampus, contradictory reports exist regarding the classification of this cell. Is it a true stem cell or a more limited progenitor? Using a strict functional definition of a neural stem cell and a number of in vitro assays, we report that the resident hippocampal precursor is a progenitor capable of proliferation and multipotential differentiation but is unable to self-renew and thus proliferate indefinitely. Furthermore, the mitogen FGF-2 stimulates proliferation of these cells to a greater extent than epidermal growth factor ( EGF). In addition, we found that BDNF was essential for the production of neurons from the hippocampal progenitor cells, being required during proliferation to trigger neuronal fate. In contrast, a bona fide neural stem cell was identified in the lateral wall of the lateral ventricle surrounding the hippocampus. Interestingly, EGF proved to be the stronger mitogenic factor for this cell, which was clearly a different precursor from the resident hippocampal progenitor. These results suggest that the stem cell ultimately responsible for adult hippocampal neurogenesis resides outside the hippocampus, producing progenitor cells that migrate into the neurogenic zones and proliferate to produce new neurons and glia

Real-time standard scan plane detection and localisation in fetal ultrasound using fully convolutional neural networks

Fetal mid-pregnancy scans are typically carried out according to fixed protocols. Accurate detection of abnormalities and correct biometric measurements hinge on the correct acquisition of clearly defined standard scan planes. Locating these standard planes requires a high level of expertise. However, there is a worldwide shortage of expert sonographers. In this paper, we consider a fully automated system based on convolutional neural networks which can detect twelve standard scan planes as defined by the UK fetal abnormality screening programme. The network design allows real-time inference and can be naturally extended to provide an approximate localisation of the fetal anatomy in the image. Such a framework can be used to automate or assist with scan plane selection, or for the retrospective retrieval of scan planes from recorded videos. The method is evaluated on a large database of 1003 volunteer mid-pregnancy scans. We show that standard planes acquired in a clinical scenario are robustly detected with a precision and recall of 69 % and 80 %, which is superior to the current state-of-the-art. Furthermore, we show that it can retrospectively retrieve correct scan planes with an accuracy of 71 % for cardiac views and 81 % for non-cardiac views

The Application of Convolutional Neural Networks to Detect Slow, Sustained Deformation in InSAR Time Series

Automated systems for detecting deformation in satellite InSAR imagery could be used to develop a global monitoring system for volcanic and urban environments. Here we explore the limits of a CNN for detecting slow, sustained deformations in wrapped interferograms. Using synthetic data, we estimate a detection threshold of 3.9cm for deformation signals alone, and 6.3cm when atmospheric artefacts are considered. Over-wrapping reduces this to 1.8cm and 5.0cm respectively as more fringes are generated without altering SNR. We test the approach on timeseries of cumulative deformation from Campi Flegrei and Dallol, where over-wrapping improves classication performance by up to 15%. We propose a mean-filtering method for combining results of different wrap parameters to flag deformation. At Campi Flegrei, deformation of 8.5cm/yr was detected after 60days and at Dallol, deformation of 3.5cm/yr was detected after 310 days. This corresponds to cumulative displacements of 3 cm and 4 cm consistent with estimates based on synthetic data

Novel Approach to Leading-Edge Vortex Suppression

A novel approach to reduce the peak lift and pitching moment on a plunging airfoil is investigated through force, moment, and velocity measurements. This approach, unlike previous investigations of delayed flow separation and leading-edge vortex suppression, uses forced separation through deployment of a minitab near the leading edge. The device can be activated for short time intervals during a gust encounter or unsteady maneuver at the expense of short-duration drag increase. Depending on the frequency and the amplitude of the wing motion and the mean angle of attack, roll-up of vorticity and the formation of a vortex can be delayed or even prevented. This change in the vortex dynamics provides effective lift and moment alleviation for post-stall angles of attack and for low reduced frequencies. In contrast, at low angles of attack, the separated shear layer may roll up for the manipulated flow, resulting in vortex shedding, and lift and nosedown pitching moment increase. These two distinct flow regimes cause decreased or increased lift force, with the most effective frequencies scaling with the reduced frequency. In contrast, the borderline between the two regions scales with the Strouhal number based on amplitude and, in particular, with the minimum effective angle of attack during the cycle. The transient response was studied by investigating impulsively started plunging oscillations. During the first cycle, lift reduction is achieved for all frequencies within the range tested

Novel Approach to Leading-Edge Vortex Suppression

A novel approach to reduce the peak lift and pitching moment on a plunging airfoil is investigated through force, moment, and velocity measurements. This approach, unlike previous investigations of delayed flow separation and leading-edge vortex suppression, uses forced separation through deployment of a minitab near the leading edge. The device can be activated for short time intervals during a gust encounter or unsteady maneuver at the expense of short-duration drag increase. Depending on the frequency and the amplitude of the wing motion and the mean angle of attack, roll-up of vorticity and the formation of a vortex can be delayed or even prevented. This change in the vortex dynamics provides effective lift and moment alleviation for post-stall angles of attack and for low reduced frequencies. In contrast, at low angles of attack, the separated shear layer may roll up for the manipulated flow, resulting in vortex shedding, and lift and nosedown pitching moment increase. These two distinct flow regimes cause decreased or increased lift force, with the most effective frequencies scaling with the reduced frequency. In contrast, the borderline between the two regions scales with the Strouhal number based on amplitude and, in particular, with the minimum effective angle of attack during the cycle. The transient response was studied by investigating impulsively started plunging oscillations. During the first cycle, lift reduction is achieved for all frequencies within the range tested

Three-dimensionality of leading-edge vortices on high aspect ratio plunging wings

To investigate the effect of sweep on the leading-edge vortex of high aspect ratio plunging wings, this article presents force, bending moment, and volumetric velocity measurements for high aspect ratio AR = 10 wings with sweep angles of 0° and 40°. The effect of the sweep angle on the bending moment is the largest at the minimum effective angle of attack. This is because as the leading-edge vortex sheds it moves inboard on the unswept wing while moving outboard on the swept wing. Where the leg of the leading-edge vortex connects with the wing there is significant three-dimensional flow. The axial velocity along the vortex filament, which may be towards to the wing tip or the wing root (reversed flow), exhibits increasing magnitude as the effective angle of attack decreases and the vortex filament deforms. Reversed axial flow along the vortex filament has the largest magnitudes for the unswept wing. In the vortex core, jetlike, wakelike, and uniform axial velocity profiles were observed. Unlike the classical vortex breakdown, the transition from the jetlike to the wakelike axial flow does not appear to be abrupt. The measurements also revealed evidence of spanwise instabilities in the leading-edge vortex filament