Using Landscape Characteristics for Targeting Habitat Conservation and Restoration: A case study of ancient semi-natural woodland in the Chiltern Hills Area of Outstanding Natural Beauty,UK

Ancient semi-natural deciduous woodland is a rare and threatened habitat cited by the European Union's Habitats Directive (92/43/EEC). Current protection of this endangered habitat in the UK takes the form of site-specific reserve designations but, if the habitat is to be conserved and enhanced, a landscape-scale selective targeting system is required. In the absence of suitable species data, physical attributes of habitat patches are used as surrogate indicators of biodiversity. Using a land-use database held on a geographical information system, values of four abiotic criteria (patch area, patch shape, nearest-neighbour distance and surrounding land use) of 48 ancient semi-natural woodland patches in part of the Chiltern Hills Area of Outstanding Natural Beauty were calculated. In order to validate the findings, three lists of floral and faunal species, indicative of ancient semi-natural woodland, were compiled, and the patches ranked according to their alpha diversity using each list. Spearman's rank correlation coefficients were calculated for patch alpha diversity and patch area (0.322 to 0.482), patch shape (0.275 to 0.465) and nearest-neighbour distance ( - 0.092 to - 0.223). Multiple regression indicated that between 15 and 22% of the variation in alpha patch diversity was explained by the abiotic factors. It is suggested that spatial targeting at the landscape scale is a valuable approach to habitat conservation.     

Parameter estimation and screening of solar cells

The aggregation (sorting) of the individual solar cells into an array is commonly based on a single operating point on the current-voltage (I-V) characteristic curve. an alternative approach for cell performance prediction and cell screening is provided by modelling the cell using an equivalent electrical circuit, in which the parameters involved are related to the physical phenomena in the device. These analytical models may be represented by a double exponential I-V characteristic with seven parameters, by a double exponential model with five parameters or by a single exponential equation with four or five parameters. In this article we address issues concerning methodologies for the determination of solar cell parameters based on measured data points of the I-V characteristic, and introduce a procedure for screening solar cells for arrays. We show that common curve-fitting techniques, e.g. least-squares, may produce many combinations of parameter values while maintaining a good fit between the fitted and measured I-V characteristics of the cell. Therefore, techniques relying on curve-fitting criteria alone cannot be used directly for cell parameterization. We propose a consistent procedure that takes into account the entire set of parameter values for a batch of cells. This procedure is based on a definition of a mean cell representing the batch, and takes into account the relative contribution of each parameter to the overall goodness of fit. the procedure is demonstrated on a batch of 50 silicon cells for Space Station Freedom.     

Characteristics of Bi-metallic Interfaces Formed During Direct Energy Deposition Additive Manufacturing Processing

Metallurgical and Materials Transactions B - Various additive manufacturing processes are being evaluated to reduce the time and cost for fabrication of low volume, complex, and multifunctional...     

Characterization of plasma electrolytic oxidation coatings on Zircaloy-4 formed in different electrolytes with AC current regime

Plasma electrolytic oxidation was undertaken on Zircaloy-4 in alkaline silicate and pyrophosphate electrolytes, with a square waveform AC current regime. The resultant coatings were examined using scanning electron spectroscopy, X-ray diffraction and nanoindentation. The coatings formed in silicate electrolyte comprised mainly a porous inner layer and a more compact outer layer, with characteristic solidification structures being evident following prolonged treatment. The coatings contained monoclinic and tetragonal ZrO₂, the latter being mainly present in the outer layer, which was of hardness up to ∼8 GPa. In contrast, extensively cracked coatings resulted from use of pyrophosphate electrolyte; the coating integrity was improved by the addition of silicate to the pyrophosphate electrolyte. The different morphologies of the coatings appeared to be related to the differing nature of the microdischarges and to the incorporation of silicon species that enhanced the formation of t-ZrO₂.     

Design,manufacture and initial operation of the beryllium components of the JET ITER-like wall

The aim of the JET ITER-like wall project was to provide JET with the plasma facing material combination now selected for the DT phase of ITER (bulk beryllium main chamber limiters and a full tungsten divertor) and, in conjunction with the upgraded neutral beam heating system, to achieve ITER relevant conditions.The design of the bulk Be plasma facing components had to be compatible with increased heating power and pulse length, as well as to reuse the existing tile supports originally designed to cope with disruption loads from carbon based tiles and be installed by remote handling. Risk reduction measures (prototypes, jigs, etc.) were implemented to maximize efficiency during the shutdown. However, a large number of clashes with existing components not fully captured by the configuration model occurred.Restarting the plasma on the ITER-like Wall proved much easier than for the carbon wall and no deconditioning by disruptions was observed. Disruptions have been more threatening than expected due to the reduced radiative losses compared to carbon, leaving most of the plasma magnetic energy to be conducted to the wall and requiring routine disruption mitigation. The main chamber power handling has achieved and possibly exceeded the design targets.     

Quantification in positron emission mammography (PEM) with planardetectors: contrast resolution measurements using a custom breastphantom and novel spherical hot-spots

The authors have previously demonstrated that their Positron Emission Mammography-1 (PEM-1) system can successfully detect small (<2 cm diameter) tumors. Images in the current system are judged qualitatively for the presence of focal uptake of ¹⁸F-FDG. The authors are presently taking steps toward quantifying the emission images. To this end they have constructed a breast phantom and developed a novel technique for fabricating very small wall-less radioactive hot-spots. The hot-spots are made by adding ¹⁸F-FDG to a 25 mg/cc solution of Agarose in water. The heated solution is poured into spherical molds which are separated upon congealing to yield robust wall-less radioactive hot-spots. The hot-spots were uniform to within 1-5 parts in 100. Less than 0.1% of the total hot-spot activity leaked into the background in 30 minutes. Contrast resolution experiments have been performed with 12 mm and 16 mm diameter hot-spots in the breast phantom containing water with various amounts of background activity. In both cases, the observed contrast values agree well with the ideal values. In the case of the 12 mm hot-spot with a 350-650 keV energy window, image contrast differed from the ideal by an average of 11%. The image contrast for 12 mm hot-spot improved by 40% and the number of detected events decreased by 35% when the low energy threshold was increased from 300 keV to 450 keV     

Exploring the biomechanics of walking and crowd “flow”

Crowd movement simulation models are generally based on aggregated speed and flow data collected more than 50 years ago. There appears to be no validated modelling capability to include the impact of recent and future changes in population demographics, resulting from an ageing population and increasing obesity rates. New analytical approaches and data gathering are required to successfully model crowd movement and safety for current and future generations. This study carried out (a) a review of the primary components of crowd movement, demographics and analytical techniques, (b) prototype experiments to investigate age-related aspects of space and potential points of contact and (c) a new predictive model for crowd flow analysis based on pedestrian biomechanics and anthropometric data. The model uses the physical space taken up by the biomechanical walking process and the spatial buffer between points of potential contact with other pedestrians to predict the speed of movement at different levels of congestion. The new analytical model was used to predict single file speeds (for people with different demographics in congested space), which compared well with published experimental data. The next steps for model development for wider “flows” and additional experiments to provide data sets for wider demographics are also proposed.     

Long wavelength GRIN-SCH MQW lasers incorporating graded GaAlInAs confinement layers

We report the growth and characterisation of the first GaAllnAs based GRIN-SCH MQW lasers operating at 1.3 and 1.6μm. In these devices, GaAllnAs barriers and either GalnAs or GaAllnAs wells have been used for the 1.6 and 1.3μm lasers, respectively, together with true continuously graded composition GaAlInAs regions for the confinement layers. The excellent structural quality of the active and confinement regions and control of wavelength uniformity has been confirmed. Buried ridge lasers fabricated from the GRIN-SCH MQW wafers lased at 1.3 and 1.6μm with CW threshold currents of 65 and 30 mA, respectively.     

Noninvasive assessment of pharmaceutical intervention during myocardial ischemia-reperfusion in a canine model using two-dimensional 31P chemical shift imaging

The metabolic effects during myocardial ischemia and sustained reperfusion of the antianginal agents diltiazem (n = 10) and propranolol (n = 10) were monitored with noninvasive phosphorus nuclear magnetic resonance spectroscopy to establish any correlation between metabolic changes and infarct size. Spectroscopy followed changes in high-energy phosphate concentrations and myocardial intracellular pH during 2 h of left anterior descending coronary artery occlusion and 3 subsequent weeks of reperfusion, in a closed chest canine infarct model. Gadolinium-DTPA enhanced magnetic resonance imaging was used to assess the extent of myocardial injury (infarct size). Microspheres were used to document the zone at risk and the success of reperfusion. Whereas diltiazem appeared to reduce the derangement in high-energy phosphates during coronary occlusion, there was no significant change in infarct size when compared with a previously studied control group. Propranolol, which produced a lesser decline in pH during occlusion and smaller pH changes during early reperfusion, was associated with a significant reduction in the degree of tissue necrosis (compared with controls). There was an inverse correlation (r = -0.51) between the change in myocardial pH (occlusion end to immediate reperfusion) and the recovery index (an index of myocardial salvage). By 1 h into reperfusion, there was a stronger inverse correlation between pH and infarct size (r = -0.75), implying a protective effect of delaying pH recovery during early reperfusion and indicating the potential use of this parameter as a predictor of tissue viability.