4,543 research outputs found
FORCES AND MOMENTS AT THE L4/L5 VERTEBRAL LEVEL WHILE FORWARD BENDING IN A SUPPORTED POSTURE
INTRODUCTION Chronic lower back pain has been associated with improper body mechanics while lifting. Forces and moments imposed on the lumbar spine have been investigated while performing a variety of lifting tasks to better understand the mechanical nature of injury to this region. Research focused on the injured patient has been sparse. The purpose of this line of study is to determine the mechanical effects at the L4/L5 vertebral level while using a supported lifting posture. METHODS Nine males (mean age 49.6± 9.7 yrs) participating in a chronic back pain program volunteered as subjects. Each subject performed two styles of lift while removing a wash cloth from a support structure constructed to simulate the dimensions of a washing machine. The lifting postures were(1) a common bowed-back lift performed with both feet in a stationary position, and (2) a rotation about the hip joint of the weight-bearing leg while the contra-lateral leg was allowed to rotate posteriorly to maintain the standing curvature of the spine ("golfer's lift"). Data was recorded using a 60 Hz S-VHS video camcorder and a Bertec force platform (500 Hz). A sagittal plane inverse dynamic model was developed and used to calculate forces and moments imparted on the L4/L5 vertebral level. Self-reported subjective ratings of lower back pain were recorded on an ordinal scale from 0 to 10. RESULTS Two profiles of lifts were identified based on the direction of the net moment at L4/L5. Negative moments, requiring a contraction of the spinal extensors to maintain equilibrium, were found in the majority of subjects while performing the bowed-back posture, while only in one subject performing the golfer's lift posture. Positive moments, resulting in an unloading of the spinal extensors, were found in the majority of subjects while performing the golfer's lift posture. Significant differences F(1.68) = 64.74, p < .001] were found between the peak L4/L5 moments for the two lifting postures. A Wilcoxon matched-pairs signed-ranks test revealed a significant increase (
Full-scale wind-tunnel investigation of a VTOL aircraft with a jet-ejector system for lift augmentation
Full scale wind tunnel investigation of VTOL AIRCRAFT with jet ejector system for lift augmentatio
The Vector Vortex Coronagraph: Laboratory Results and First Light at Palomar Observatory
High-contrast coronagraphy will be needed to image and characterize faint
extra-solar planetary systems. Coronagraphy is a rapidly evolving field, and
many enhanced alternatives to the classical Lyot coronagraph have been proposed
in the past ten years. Here, we discuss the operation of the vector vortex
coronagraph, which is one of the most efficient possible coronagraphs. We first
present recent laboratory results, and then first light observations at the
Palomar observatory. Our near-infrared H-band (centered at ~ 1.65 microns) and
K-band (centered at ~ 2.2 microns) vector vortex devices demonstrated excellent
contrast results in the lab, down to ~ 1e-6 at an angular separation of 3 lb/d.
On sky, we detected a brown dwarf companion 3000 times fainter than its host
star (HR 7672) in the Ks band (centered at ~2.15 microns), at an angular
separation of ~ 2.5 lb/d. Current and next-generation high-contrast instruments
can directly benefit from the demonstrated capabilities of such a vector
vortex: simplicity, small inner working angle, high optical throughput (>90%),
and maximal off-axis discovery space
Exchange anisotropy pinning of a standing spin wave mode
Standing spin waves in a thin film are used as sensitive probes of interface
pinning induced by an antiferromagnet through exchange anisotropy. Using
coplanar waveguide ferromagnetic resonance, pinning of the lowest energy spin
wave thickness mode in Ni(80)Fe(20)/Ir(25)Mn(75) exchange biased bilayers was
studied for a range of IrMn thicknesses. We show that pinning of the standing
mode can be used to amplify, relative to the fundamental resonance, frequency
shifts associated with exchange bias. The shifts provide a unique `fingerprint'
of the exchange bias and can be interpreted in terms of an effective
ferromagnetic film thickness and ferromagnet/antiferromagnet interface
anisotropy. Thermal effects are studied for ultra-thin antiferromagnetic
Ir(25)Mn(75) thicknesses, and the onset of bias is correlated with changes in
the pinning fields. The pinning strength magnitude is found to grow with
cooling of the sample, while the effective ferromagnetic film thickness
simultaneously decreases. These results suggest that exchange bias involves
some deformation of magnetic order in the interface region.Comment: 7 pages, 7 figure
The effect of epidural anaesthesia on peripheral resistance and graft flow following femorodistal reconstruction
Objective:To determine the extent to which epidural anaesthesia influences peripheral resistance and graft blood flow following femorocrural reconstruction.Design:Prospective, controlled study measuring blood flow, arterial pressure and peripheral resistance in femorocrural bypass grafts for 20 min following onset of epidural anaesthesia with 15ml of 0.25% bupivacaine.Patients:Twenty patients undergoing femorocrural reconstruction for critical lower-limb ischaemia with in situ long saphenous vein, under general anaesthesia. Ten patients had epidural cannulae inserted preoperatively and injected with bupivacaine after completion of the graft.Results:Peripheral resistance fell in all 10 patients receiving epidural anaesthesia from a mean (range) of 1.07 PRU (0.32–2.2) to 0.49 PRU (0.19–0.72), compared to control values of 0.95 PRU (0.39–2.0) to 0.91 PRU (0.41–1.51; P < 0.01, Wilcoxon). There was a tendency for blood pressure to fall in the study patients (not significant) but graft blood flow still increased from 98 ml min−1 (41–221) to 160 ml min−1 (101–250), compared to flow in the control patients of 101 ml min−1 (45–176) at baseline to 104 ml min−1 (56–168; p < 0.01) at 20 min.Conclusions:Epidural anaesthesia significantly decreases peripheral resistance and increases graft blood flow in femorocrural grafts and would appear, therefore, to be of benefit for patients undergoing femorodistal reconstruction
Rapid localized flank inflation and implications for potential slope instability at Tungurahua volcano, Ecuador
This is the final version. Available on open access from Elsevier via the DOI in this recordHigh rates of volcano surface deformation can be indicative of a forthcoming eruption, but can also relate to slope instability and possible flank collapse. Tungurahua volcano, Ecuador, has been persistently active since 1999 and has previously experienced catastrophic flank failures. During the ongoing eruptive activity, significant surface deformation has been observed, with the highest rates contained within the amphitheatre-shaped scar from the 3000-year-old failure on the west flank However, the cause of this asymmetric deformation and how it might relate to slope stability has not been assessed. Here, for the first time, we present a range of models to test physical processes that might produce asymmetric deformation, which are then applied to slope stability. Our models are informed by InSAR measurements of a deformation episode in November 2015, which show a maximum displacement of ~3.5 cm over a period of ~3 weeks, during which time the volcano also experienced multiple explosions and heightened seismicity. Asymmetric flank material properties, from the rebuilding of the cone, cannot explain the full magnitude and spatial footprint of the observed west flank deformation. The inflation is inferred to be primarily caused by shallow, short35 term, pre-eruptive magma storage that preferentially exploits the 3 ka flank collapse surface. Shallow and rapid pressurization from this inclined deformation source can generate shear stress along the collapse surface, which increases with greater volumes of magma. This may contribute to slope instability during future unrest episodes and promote flank failure, with general application to other volcanoes worldwide displaying asymmetric deformation patterns.Royal SocietyNatural Environment Research Council (NERC)Economic and Social Research Council (ESRC
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Studies of normal and deficient colour vision with relevance to occupational environments
The studies described in this thesis aim to assess the importance of normal colour vision in visually demanding, colour-related tasks that are often safety-critical and aim to improve our understanding of how congenital deficiencies can affect the processing of colour signals and the corresponding changes in visual performance.
The first study compares the colour vision requirements within different professional environments. 519 subjects were tested: 141 normal trichromats, 268 deutans and 110 protans. All subjects carried out the Ishihara 38-plate test, the CAD test and the Nagel anomaloscope, and sub-populations were examined with the AO-HRR plates, the Farnsworth D15, the City University test (2nd Ed.), the Holmes-Wright type A and B lanterns. Inconsistencies of outcome amongst the various tests and potential alternative practices are discussed.
The second study focuses on understanding the discrepancies in performance observed on lantern tests when the subject’s task is to report the colour of small signal lights presented against a dark background field. These conditions were simulated using a psychophysical luminance pedestal technique. Variations in the measurement of chromatic sensitivity over the visual field, as well as the detection of targets where colours are combined with luminance contrasts, are discussed and explanations considered with regard to underlying retinal physiology.
The last study investigates the use of colour signals in ATC (air traffic control) applications. The work carried out addresses current failings in acceptance criteria for applicants, and provides alternative methods of assessing suitability. The chromatic discrimination thresholds of normal trichromats and colour deficient subjects were related to performance on a set of visual search tasks selected to be more representative of typical colour usage in large field visual displays. Display parameters under which the performance of colour deficient observers could be comparable to that of normal trichromats are examined with regard to updating occupational acceptance criteria
Hypersaline microbial self-powered biosensor with increased sensitivity
The on-line, self-powered monitoring of the organic carbon content in hypersaline solutions (e.g. chemical oxygen demand, COD) based on a microbial biosensor would avoid the generation of toxic waste, originated by common COD analytical methods, and reduce the release of pollutants into the environment. Herein, a disposable cathode was applied to microbial fuel cells (MFCs) for the environmental friendly monitoring of the COD reaching a sensitivity one order of magnitude higher compared to the MFC with an air breathing cathode. Additionally, the entrapment of bacterial cells in alginate-capsules ensured a considerable linear range (up to approximately 10,000 mg COD L−1), providing opportunities for the wide application of the device to hypersaline solutions characterized by different origins and contamination levels
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