Observations of a barotropic planetary wave in the western North Atlantic

SOFAR float observations from 1300 m depth are used to describe a major feature of the large-scale, subthermocline velocity field observed in the western North Atlantic (31 N, 70W), during the 1978 POLYMODE Local Dynamics Experiment (LDE). The two-month-long intensive phase of the LDE was dominated by a highly polarized, oscillatory flow which had many of the characteristics of a barotropic planetary wave...

Attitude Determination from Single-Antenna Carrier-Phase Measurements

A model of carrier phase measurement (as carried out by a satellite navigation receiver) is formulated based on electromagnetic theory. The model shows that the phase of the open-circuit voltage induced in the receiver antenna with respect to a local oscillator (in the receiver) depends on the relative orientation of the receiving and transmitting antennas. The model shows that using a {\it single} receiving antenna, and making carrier phase measurements to seven satellites, the 3-axis attitude of a user platform (in addition to its position and time) can be computed relative to an initial point. This measurement model can also be used to create high-fidelity satellite signal simulators that take into account the effect of platform rotation as well as translation.Comment: 12 pages, and one figure. Published in J. Appl. Phys. vol. 91, No. 7, April 1, 200

Use of electronic medical records and biomarkers to manage risk and resource efficiencies

Peer reviewedPublisher PD

Modeling of airblast propagation through an enclosed structure

The ability to model explosively formed shock waves propagating through a structure is of particular interest to engineers concerned with structural responses to blasts. Accurate peak pressure and impulse values are critical to understanding blast loads on structures and predicting the resulting structural behavior, but are sometimes difficult to determine analytically. Experiments are necessary to determine the true structural response, but the experiments alone may not identify all the details involved in an explosive event that may be important for design purposes. When tied to experiments, computational modeling of explosive events can be an invaluable tool for an engineer. The most difficult part of modeling structural response to a close-in explosive event is capturing the fluid-structure interaction of the resulting flow of the detonation products. In this paper, we compare the results of numerical simulations of an explosive experimental event in an enclosed structure, or “attic space”, using two different computational codes, CTH and DYSMAS. Both adequately model the explosive event in attic space when compared to the experiment. We also compare the two codes’ ability to produce explosive-induced pressure-time histories in the free field. The advantage of using a coupled code like DYSMAS is that structural response can be more accurately captured than by using a hydrocode like CTH alone. The differences between the two codes’ ability to model the event are analyzed and described as well as a general description of the shock wave propagation in the attic space

Exercise-induced bronchoconstriction in athletes – A qualitative assessment of symptom perception

© 2016Background A poor relationship between perceived respiratory symptoms and objective evidence of exercise-induced bronchoconstriction (EIB) in athletes is often reported; however, the reasons for this disconnect remain unclear. The primary aim of this study was to utilise a qualitative-analytical approach to compare respiratory symptoms in athletes with and without objectively confirmed EIB. Methods Endurance athletes who had previously undergone bronchoprovocation test screening for EIB were divided into sub-groups, based on the presence or absence of EIB ± heightened self-report of dyspnoea: (i) EIB-Dys- (ii) EIB + Dys+ (iii) EIB + Dys- (iv) EIB-Dys+. All athletes underwent a detailed semi-structured interview. Results Twenty athletes completed the study with an equal distribution in each sub-group (n = 5). Thematic analysis of individual narratives resulted in four over-arching themes: 1) Factors aggravating dyspnoea, 2) Exercise limitation, 3) Strategies to control dyspnoea, 4) Diagnostic accuracy. The anatomical location of symptoms varied between EIB + Dys + athletes and EIB-Dys + athletes. All EIB-Dys + reported significantly longer recovery times following high-intensity exercise in comparison to all other sub-groups. Finally, EIB + Dys + reported symptom improvement following beta-2 agonist therapy, whereas EIB-Dys + deemed treatment ineffective. Conclusion A detailed qualitative approach to the assessment of breathlessness reveals few features that distinguish between EIB and non-EIB causes of exertional dyspnoea in athletes. Important differences that may provide value in clinical work-up include (i) location of symptoms, (ii) recovery time following exercise and (iii) response to beta-2 agonist therapy. Overall these findings may inform clinical evaluation and development of future questionnaires to aid clinic-based assessment of athletes with dyspnoea

Radiative Falloff in Neutron Star Spacetimes

We systematically study late-time tails of scalar waves propagating in neutron star spacetimes. We consider uniform density neutron stars, for which the background spacetime is analytic and the compaction of the star can be varied continously between the Newtonian limit 2M/R << 1 and the relativistic Buchdahl limit 2M/R = 8/9. We study the reflection of a finite wave packet off neutron stars of different compactions 2M/R and find that a Newtonian, an intermediate, and a highly relativistic regime can be clearly distinguished. In the highly relativistic regime, the reflected signal is dominated by quasi-periodic peaks, which originate from the wave packet bouncing back and forth between the center of the star and the maximum of the background curvature potential at R ~ 3 M. Between these peaks, the field decays according to a power-law. In the Buchdahl limit 2M/R -> 8/9 the light travel time between the center and the maximum or the curvature potential grows without bound, so that the first peak arrives only at infinitely late time. The modes of neutron stars can therefore no longer be excited in the ultra-relativistic limit, and it is in this sense that the late-time radiative decay from neutron stars looses all its features and gives rise to power-law tails reminiscent of Schwarzschild black holes.Comment: 10 pages, 7 figures, to appear in PR

Spatial Effects and GWA Mapping of Root Colonization Assessed in the Interaction Between the Rice Diversity Panel 1 and an Arbuscular Mycorrhizal Fungus

The majority of the research reported here is an output of EU project “EURoot” (FP7-KBBE-2011-5 Grant Agreement No. 289300) project. RS’s contribution was funded by FACCE-JPI NET project “GreenRice” (Sustainable and environmental friendly rice cultivation systems in Europe) and was funded by the BBSRC award BB/M018415/1.Peer reviewedPublisher PD

Predicting recovery following stroke: deep learning, multimodal data and feature selection using explainable AI

Machine learning offers great potential for automated prediction of post-stroke symptoms and their response to rehabilitation. Major challenges for this endeavour include the very high dimensionality of neuroimaging data, the relatively small size of the datasets available for learning, and how to effectively combine neuroimaging and tabular data (e.g. demographic information and clinical characteristics). This paper evaluates several solutions based on two strategies. The first is to use 2D images that summarise MRI scans. The second is to select key features that improve classification accuracy. Additionally, we introduce the novel approach of training a convolutional neural network (CNN) on images that combine regions-of-interest extracted from MRIs, with symbolic representations of tabular data. We evaluate a series of CNN architectures (both 2D and a 3D) that are trained on different representations of MRI and tabular data, to predict whether a composite measure of post-stroke spoken picture description ability is in the aphasic or non-aphasic range. MRI and tabular data were acquired from 758 English speaking stroke survivors who participated in the PLORAS study. The classification accuracy for a baseline logistic regression was 0.678 for lesion size alone, rising to 0.757 and 0.813 when initial symptom severity and recovery time were successively added. The highest classification accuracy 0.854 was observed when 8 regions-of-interest was extracted from each MRI scan and combined with lesion size, initial severity and recovery time in a 2D Residual Neural Network.Our findings demonstrate how imaging and tabular data can be combined for high post-stroke classification accuracy, even when the dataset is small in machine learning terms. We conclude by proposing how the current models could be improved to achieve even higher levels of accuracy using images from hospital scanners