Shock absorbing support and restraint means Patent

Shock absorbing couch for body support under high acceleration or deceleration force

Ultrasonic detection and identification of fabrication defects in composites

Methods for deliberate fabrication of porosity into carbon/epoxy composite panels and the influence of three-dimensional stitching on the detection of porosity were investigated. Two methods of introducing porosity were investigated. Porosity was simulated by inclusion of glass microspheres, and a more realistic form of porosity was introduced by using low pressure during consolidation. The panels were ultrasonically scanned and the frequency slope of the ultrasonic attenuation coefficient was used to evaluate the two forms of porosity. The influence of stitching on the detection of porosity was studied using panels which were resin transfer molded from stitched plies of knitted carbon fabric and epoxy resin

Magnetic susceptibility of a CuO2 plane in the La2CuO4 system: I. RPA treatment of the Dzyaloshinskii-Moriya Interactions

Motivated by recent experiments on undoped La2CuO4, which found pronounced temperature-dependent anisotropies in the low-field magnetic susceptibility, we have investigated a two-dimensional square lattice of S=1/2 spins that interact via Heisenberg exchange plus the symmetric and anti-symmetric Dzyaloshinskii-Moriya anisotropies. We describe the transition to a state with long-ranged order, and find the spin-wave excitations, with a mean-field theory, linear spin-wave analysis, and using Tyablikov's RPA decoupling scheme. We find the different components of the susceptibility within all of these approximations, both below and above the N'eel temperature, and obtain evidence of strong quantum fluctuations and spin-wave interactions in a broad temperature region near the transition.Comment: 20 pages, 2 column format, 22 figure

Design of a high efficiency cyclone for collection of rare and low concentration airborne pathogens

Recent serious outbreaks of pathogens such as Chalara Fraxinea, (Ash Dieback) demonstrate the vulnerability of UK’s forests, woods, and trees. Early detection of threats is critical in the fight against such tree pests and pathogens. This requires a process for collecting and analysing the spores which is robust, flexible and can be deployed rapidly, but which also has sufficient sensitivity to detect the earliest precursors. The work presented here describes a newly-developed high-efficiency detection apparatus and is part of an ongoing BBRSC project to improve the UK’s biosecurity. Our automatic spore system is capable of collecting and analysing Chalara Fraxinea using a novel cyclonic pathogen collector. Cyclones are an effective way to separate small particles (spores) from large quantities of surrounding air and store them for analysis. Our system incorporates a purpose-designed high efficiency cyclone directly integrated with a low power custom impeller to maximise volumetric air sampling while minimising the power requirement. 3D printing was used extensively to validate theoretical models and the particle collection and retention capability of this series of prototypes was evaluated experimentally within our Aerosol test chamber. We found that we could collect greater than 90% of particulate in the target size range, thus providing a front-end to a detection platform. Our system is capable of operating autonomously and at low power, with a high sensitivity to ambient particles. The final system design incorporates the use of multiple cyclone storage vessels ensuring complete isolation of each sample, eradicating cross-contamination, and facilitating automated handling of the sample inside the same apparatus. COTS – commercial off the shelf components were incorporated into the cyclone to make a series of cost effective collection vessels. Early collection and detection of pathogens in-situ represents a considerable advance in surveillance and monitoring of pathogens strengthening UK biosecurity for the future

Development of an automated smart trap for wheat pathogens

National surveys show fungicide use on wheat continues to increase despite fluctuations in disease pressure, reaching a 30 year high in 2012 (Defra). Septoria tritici is the most significant foliar disease in UK wheat causing between £43M to £53M in yield losses annually; Yellow and brown rust are more sporadic but have caused significant losses during high disease years. In all cases control is by fungicide application costing £82M annually (GFK Kynetec 2013). Effective disease management relies on either prophylactic pesticide use or significant manual intervention and time consuming assessment of crop disease indicators by farmers and agronomists. Furthermore indications are that current levels of pesticide use could lead to increased risk of pesticide resistance, if this should occur it is estimated that wheat yields could reduce by up to 20%. To address this we have developed a prototype integrated and automated spore detection system, designed for unattended field application, to monitor and identify the presence of Septoria, brown and yellow rust. The prototype system incorporates novel cyclonic pathogen collection, on-board sample processing and isothermal DNA amplification chemistry (LAMP). We present the engineering design, optimisation and evaluation of our prototype system reporting on successfully completed laboratory testing and initial field trial results. This prototype will be the basis for the development of a commercially available system which, in addition to inoculum detection, will be capable of providing growers/agronomists with real-time information on inoculum moving into a crop enabling more effective timing and selection of fungicide application, and thus better control, increased yield, and improved environmental stewardship

Influence of van der Waals forces on the adsorption structure of benzene on silicon studied using density functional theory

Two different adsorption configurations of benzene on the Si(001)-(2 x 1) surface, the tight-bridge and butterfly structures, were studied using density functional theory. Several exchange and correlation functionals were used, including the recently developed van der Waals density functional (vdW-DF), which accounts for the effect of van der Waals forces. In contrast to the Perdew-Burke-Ernzerhof (PBE), revPBE, and other generalized-gradient approximation functionals, the vdW-DF finds that, for most coverages, the adsorption energy of the butterfly structure is greater than that of the tight-bridge structure

Constraining the History of the Sagittarius Dwarf Galaxy Using Observations of its Tidal Debris

We present a comparison of semi-analytic models of the phase-space structure of tidal debris with observations of stars associated with the Sagittarius dwarf galaxy (Sgr). We find that many features in the data can be explained by these models. The properties of stars 10-15 degrees away from the center of Sgr --- in particular, the orientation of material perpendicular to Sgr's orbit (c.f. Alard 1996) and the kink in the velocity gradient (Ibata et al 1997) --- are consistent with those expected for unbound material stripped during the most recent pericentric passage ~50 Myrs ago. The break in the slope of the surface density seen by Mateo, Olszewski & Morrison (1998) at ~ b=-35 can be understood as marking the end of this material. However, the detections beyond this point are unlikely to represent debris in a trailing streamer, torn from Sgr during the immediately preceding passage ~0.7 Gyrs ago, but are more plausibly explained by a leading streamer of material that was lost more that 1 Gyr ago and has wrapped all the way around the Galaxy. The observations reported in Majewski et al (1999) also support this hypothesis. We determine debris models with these properties on orbits that are consistent with the currently known positions and velocities of Sgr in Galactic potentials with halo components that have circular velocities v_circ=140-200 km/s. The best match to the data is obtained in models where Sgr currently has a mass of ~10^9 M_sun and has orbited the Galaxy for at least the last 1 Gyr, during which time it has reduced its mass by a factor of 2-3, or luminosity by an amount equivalent to ~10% of the total luminosity of the Galactic halo. These numbers suggest that Sgr is rapidly disrupting and unlikely to survive beyond a few more pericentric passages.Comment: 19 pages, 5 figures, accepted to Astronomical Journa

Climate-driven Shifts in Quantity and Seasonality of River Discharge over the past 1000 Years from the Hydrographic Apex of North America

Runoff generated from high elevations is the primary source of freshwater for western North America, yet this critical resource is managed on the basis of short instrumental records that capture an insufficient range of climatic conditions. Here we probe the effects of climate change over the past ~1000 years on river discharge in the upper Mackenzie River system based on paleoenvironmental information from the Peace-Athabasca Delta. The delta landscape responds to hydroclimatic changes with marked variability, while Lake Athabasca level appears to directly monitor overall water availability. The latter fluctuated systematically over the past millennium, with the highest levels occurring in concert with maximum glacier extent during the Little Ice Age, and the lowest during the 11th century, prior to medieval glacier expansion. Recent climate-driven hydrological change appears to be on a trajectory to even lower levels as high-elevation snow and glacier meltwater contributions both continue to decline

Magnetic susceptibility study of hydrated and non-hydrated NaxCoO2-yH2O single crystals

We have measured the magnetic susceptibility of single crystal samples of non-hydrated NaxCoO2 (x ~ 0.75, 0.67, 0.5, and 0.3) and hydrated Na0.3CoO2-yH2O (y ~ 0, 0.6, 1.3). Our measurements reveal considerable anisotropy between the susceptibilities with H||c and H||ab. The derived anisotropic g-factor ratio (g_ab/g_c) decreases significantly as the composition is changed from the Curie-Weiss metal with x = 0.75 to the paramagnetic metal with x = 0.3. Fully hydrated Na0.3CoO2-1.3H2O samples have a larger susceptibility than non-hydrated Na0.3CoO2 samples, as well as a higher degree of anisotropy. In addition, the fully hydrated compound contains a small additional fraction of anisotropic localized spins.Comment: 6 pages, 5 figure