35,670 research outputs found

    The cost of systemic corticosteroid-induced morbidity in severe asthma : a health economic analysis

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    The study data-set was supported by the Respiratory Effectiveness Group through their academic partnership with Optimum Patient Care. Ciaran O'Neill was funded under a HRB Research Leader Award (RL/13/16).Peer reviewedPublisher PD

    Piezoelectric copolymer hydrophones for ultrasonic field characterization

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    Hydrophones to be used in the characterization of medical ultrasonic transducers have been fabricated using a new polyvinylidene fluoride/trifluoroethylene (VF2/VF3) copolymer. The copolymer has an advantage over VF2 in that it does not require prestretching before poling. Thin copolymer films can be cast from solution and then poled using the corona discharge method. As there is a need for small‐diameter hydrophones to provide good spatial resolution in measuring highly focused ultrasonic beams, hydrophones with diameter as small as 0.1 mm have been made. Both needle‐type and line hydrophones have been tested and their performance reported. In the case of line hydrophones, the output signal is proportional to the line integral of the acoustic pressure and a computer tomographic technique has been used to reconstruct the beam profiles

    Track and capture of the orbiter with the space station remote manipulator system

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    Results of the first study using the real-time, man-in-the-loop Systems Engineering Simulator (SES) for track and capture of the Space Shuttle Orbiter with the space station manipulator are presented. The objectives include evaluation of the operational coordination required between the orbiter pilot and the space station manipulator operator, evaluation of the locations and required number of closed-circuit television cameras, and evaluation of the orbiter grapple fixture clearance geometry. The SES is a premium quality real-time facility with full fidelity orbiter and space station crew workstations and cockpits

    Survival of fossils under extreme shocks induced by hypervelocity impacts

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    Experimental data are shown for survival of fossilized diatoms undergoing shocks in the GPa range. The results were obtained from hypervelocity impact experiments which fired fossilized diatoms frozen in ice into water targets. After the shots, the material recovered from the target water was inspected for diatom fossils. Nine shots were carried out, at speeds from 0.388 to 5.34?km?s?1, corresponding to mean peak pressures of 0.2–19?GPa. In all cases, fragmented fossilized diatoms were recovered, but both the mean and the maximum fragment size decreased with increasing impact speed and hence peak pressure. Examples of intact diatoms were found after the impacts, even in some of the higher speed shots, but their frequency and size decreased significantly at the higher speeds. This is the first demonstration that fossils can survive and be transferred from projectile to target in hypervelocity impacts, implying that it is possible that, as suggested by other authors, terrestrial rocks ejected from the Earth by giant impacts from space, and which then strike the Moon, may successfully transfer terrestrial fossils to the Moon

    The periodic standing-wave approximation: eigenspectral computations for linear gravity and nonlinear toy models

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    The periodic standing wave approach to binary inspiral assumes rigid rotation of gravitational fields and hence helically symmetric solutions. To exploit the symmetry, numerical computations must solve for ``helical scalars,'' fields that are functions only of corotating coordinates, the labels on the helical Killing trajectories. Here we present the formalism for describing linearized general relativity in terms of helical scalars and we present solutions to the mixed partial differential equations of the linearized gravity problem (and to a toy nonlinear problem) using the adapted coordinates and numerical techniques previously developed for scalar periodic standing wave computations. We argue that the formalism developed may suffice for periodic standing wave computations for post-Minkowskian computations and for full general relativity.Comment: 21 pages, 10 figures, RevTe
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