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We investigate how a filter-medium microstructure influences filtration performance. We derive a theory that generalizes classical multiscale models for regular structures to account for filter media with more realistic microstructures, comprising random microstructures with polydisperse unidirectional fibres. Our multiscale model accounts for the fluid flow and contaminant transport at the microscale (over which the medium structure is fully resolved) and allows us to obtain macroscopic properties such as the effective permeability, diffusivity and fibre surface area. As the fibres grow due to contaminant adsorption, this leads to contact of neighbouring fibres. We propose an agglomeration algorithm that describes the resulting behaviour of the fibres upon contact, allowing us to explore the subsequent time evolution of the filter medium in a simple and robust way. We perform a comprehensive investigation of the influence of the filter-medium microstructure on filter performance in a spectrum of possible filtration scenarios.
SNP in the vitamin D receptor (VDR) gene is associated with risk of lower respiratory infections. The influence of genetic variation in the vitamin D pathway resulting in susceptibility to upper respiratory infections (URI) has not been investigated. We evaluated the influence of thirty-three SNP in eleven vitamin D pathway genes (DBP, DHCR7, RXRA, CYP2R1, CYP27B1, CYP24A1, CYP3A4, CYP27A1, LRP2, CUBN and VDR) resulting in URI risk in 725 adults in London, UK, using an additive model with adjustment for potential confounders and correction for multiple comparisons. Significant associations in this cohort were investigated in a validation cohort of 737 children in Manchester, UK. In all, three SNP in VDR (rs4334089, rs11568820 and rs7970314) and one SNP in CYP3A4 (rs2740574) were associated with risk of URI in the discovery cohort after adjusting for potential confounders and correcting for multiple comparisons (adjusted incidence rate ratio per additional minor allele ≥1·15, Pfor trend ≤0·030). This association was replicated for rs4334089 in the validation cohort (Pfor trend=0·048) but not for rs11568820, rs7970314 or rs2740574. Carriage of the minor allele of the rs4334089 SNP in VDR was associated with increased susceptibility to URI in children and adult cohorts in the United Kingdom.
Although Tennessee has Advanced Master Beef Producer (AMBP) and Beef Quality Assurance (BQA) certifications for cattle producers, currently there is no state-certified beef labeling program. A choice experiment was administered to Tennessee consumers to determine their willingness to pay for Tennessee Certified Beef (TCB) and other attributes such as labels indicating producer participation in AMBP and BQA. Random parameter logit model results indicate consumers most valued TCB steak and no-hormones-administered ground beef. Consumers also valued many labels when appearing alongside the TCB label. The impact of providing participants label definitions prior to the choice experiment was examined.
Gas production from the in vitro digestion of forage with buffered rumen fluid can be measured and used to determine forage digestibility and fermentation kinetics. Rumen micro-organisms ferment carbohydrate to gases (CO2 and CH4) and volatile fatty acids (VFA). The VFA produced also cause CO2 to be released from the C02-bicarbonate buffer. Theodorou et al. (1994) introduced the principle of measuring gas production by pressure increase using an electronic pressure transducer and sealed gas-tight culture bottles. Gases accumulate in the head space of the culture bottles as fermentation proceeds. The gas is measured and then released at regular intervals throughout the fermentation. This procedure was automated (Davies et al., 1995). The automated pressure evaluation system (APES) has advantages over the manual pressure transducer technique (Theodorou et al., 1994) in that it is less labour intensive and has been shown to be more sensitive to food characteristics (Davies et al., 1995). The APES, used in this work, has been improved to include new switches and a filtering system. It has been used here to determine the fermentation characteristics of various ruminant foods: ryegrass, wheat grain and ryegrass silage.
Sheep systems on upland permanent pastures sown with Lolium perenne/Trifolium repens, have typically been relatively intensively managed, relying on inorganic fertilizers to maintain or increase animal output. However changes in the Common Agricultural Policy have resulted in the development of agri-environment schemes to deliver environmental goals from grasslands. These schemes encourage more extensive grazing systems, and change the emphasis from animal output to issues such as increasing biodiversity. Lower stocking densities provide increased opportunities for diet selection, the development of a heterogeneous habitat and associated changes in species composition. However, will more extensive management increase botanical diversity in upland sown swards? The experiment reported here describes the effect of more extensive management combining cessation of fertilizer and lower grazing intensity on vegetation change, stocking density and lamb output over 14 years.
Differential heating applied at a single horizontal boundary forces ‘horizontal convection’, even when there is no net heat flux through the boundary. However, almost all studies of horizontal convection have been limited to a special class of problem in which temperature or heat flux differences were applied in only one direction and over the horizontal length of a box (the Rossby problem; Rossby, Deep-Sea Res., vol. 12, 1965, pp. 9–16). These conditions strongly constrain the flow. Here we report laboratory experiments and direct numerical simulations (DNS) extending the results of Griffiths & Gayen (Phys. Rev. Lett., vol. 115, 2015, 204301) for horizontal convection forced by boundary conditions imposed in a two-dimensional periodic array at a horizontal boundary. The experiments use saline and freshwater fluxes at a permeable base with the imposed boundary salinity having a horizontal length scale one quarter of the width of the box. The flow reaches a state in which the net boundary buoyancy flux vanishes and the bulk of the fluid shows an inertial range of turbulence length scales. A regime transition is seen for increasing water depth, from an array of individual coherent plumes on the forcing scale to convection dominated by emergent larger scales of overturning. The DNS explore the analogous thermally forced case with sinusoidal boundary temperature of wavenumber
, and are used to examine the Rayleigh number (
) dependence for shallow- and deep-water cases. For shallow water the flow transitions with increasing
from laminar to turbulent boundary layer regimes that are familiar from the Rossby problem and which have normalised heat transport scaling as
the Nusselt number and
the Prandtl number, in this case maintaining a stable array of coherent turbulent plumes. For deep-water and large
the laminar scaling transitions to
, with the scales of turbulence extending to the dimensions of the box. The
power law regime is explained in terms of the momentum of symmetric, inviscid large scales of motion in the interior coupled to diffusive loss of heat through stabilised parts of the boundary layer. The turbulence production is predominantly by shear instability rather than convection, with viscous dissipation distributed throughout the bulk of the fluid. These conditions are not seen in the highly asymmetric flow in the Rossby problem even at Rayleigh numbers up to six orders of magnitude greater than the transition found here. The new inertial interior regime has the rate of supply of available potential energy, and its removal by mixing of density, increasing as
, which is faster than
in the Rossby problem. Irreversible mixing is confined close to the forcing boundary and is very much larger than the viscous dissipation, which is proportional to
Limitations of access have long restricted exploration and investigation of the cavities beneath ice shelves to a small number of drillholes. Studies of sea-ice underwater morphology are limited largely to scientific utilization of submarines. Remotely operated vehicles, tethered to a mother ship by umbilical cable, have been deployed to investigate tidewater-glacier and ice-shelf margins, but their range is often restricted. The development of free-flying autonomous underwater vehicles (AUVs) with ranges of tens to hundreds of kilometres enables extensive missions to take place beneath sea ice and floating ice shelves. Autosub2 is a 3600 kg, 6.7 m long AUV, with a 1600 m operating depth and range of 400 km, based on the earlier Autosub1 which had a 500 m depth limit. A single direct-drive d.c. motor and five-bladed propeller produce speeds of 1–2 m s−1. Rear-mounted rudder and stern-plane control yaw, pitch and depth. The vehicle has three sections. The front and rear sections are free-flooding, built around aluminium extrusion space-frames covered with glass-fibre reinforced plastic panels. The central section has a set of carbon-fibre reinforced plastic pressure vessels. Four tubes contain batteries powering the vehicle. The other three house vehicle-control systems and sensors. The rear section houses subsystems for navigation, control actuation and propulsion and scientific sensors (e.g. digital camera, upward-looking 300 kHz acoustic Doppler current profiler, 200 kHz multibeam receiver). The front section contains forward-looking collision sensor, emergency abort, the homing systems, Argos satellite data and location transmitters and flashing lights for relocation as well as science sensors (e.g. twin conductivity–temperature–depth instruments, multibeam transmitter, sub-bottom profiler, AquaLab water sampler). Payload restrictions mean that a subset of scientific instruments is actually in place on any given dive. The scientific instruments carried on Autosub are described and examples of observational data collected from each sensor in Arctic or Antarctic waters are given (e.g. of roughness at the underside of floating ice shelves and sea ice).
Since their discovery, Antarctic subglacial lakes have become of great interest to the science community. It is hypothesized that they may hold unique forms of biological life and that they hold detailed sedimentary records of past climate change. According to the latest inventory, a total of 387 subglacial lakes have been identified in Antarctica (Wright and Siegert, 2011). However, exploration using scientific probes has yet to be performed. We propose a generic, formal approach to manage the operational risk of deploying probes during clean access to subglacial lake exploration. A representation of the entire probe deployment process is captured in a Markov chain. The transition from one state to the next depends on several factors, including reliability of components and processes. We use fault trees to quantify the probability of failure of the complex processes that must take place to facilitate the transition from one state to another. Therefore, the formal framework consists of integrating a Markov chain, fault trees, component and subsystem reliability data and expert judgment. To illustrate its application we describe how the approach can be used to address a series of what-if scenarios, using the intended Ellsworth Subglacial Lake probe deployment as a case study.
Livestock risk protection (LRP) insurance is a price risk management tool available to cattle producers; however, producers have been hesitant to adopt LRP. The objective of the study was to determine the monthly feeder cattle LRP contract coverage level and length maximizing the probability of the LRP net price being greater than the CME Feeder Cattle Index (CME FCI) price. The CME FCI prices were higher than the LRP net price for the majority of the contract lengths and coverage levels. Several coverage lengths and levels provided similar price protection, and there was no consistent preferred coverage length and level.
Mobile applications, or apps, have gained widespread use with the advent of modern smartphone technologies. Previous research has been conducted in the use of mobile devices for learning. However, there is decidedly less research into the use of mobile apps for health learning (eg, patient self-monitoring, medical student learning). This deficiency in research on using apps in a learning context is especially severe in the disaster health field. The objectives of this article were to provide an overview of the current state of disaster health apps being used for learning, to situate the use of apps in a health learning context, and to adapt a learning framework for the use of mobile apps in the disaster health field. A systematic literature review was conducted by using the PRISMA checklist, and peer-reviewed articles found through the PubMed and CINAHL databases were examined. This resulted in 107 nonduplicative articles, which underwent a 3-phase review, culminating in a final selection of 17 articles. While several learning models were identified, none were sufficient as an app learning framework for the field. Therefore, we propose a learning framework to inform the use of mobile apps in disaster health learning. (Disaster Med Public Health Preparedness. 2017;11:487–495)
We describe the performance of the Boolardy Engineering Test Array, the prototype for the Australian Square Kilometre Array Pathfinder telescope. Boolardy Engineering Test Array is the first aperture synthesis radio telescope to use phased array feed technology, giving it the ability to electronically form up to nine dual-polarisation beams. We report the methods developed for forming and measuring the beams, and the adaptations that have been made to the traditional calibration and imaging procedures in order to allow BETA to function as a multi-beam aperture synthesis telescope. We describe the commissioning of the instrument and present details of Boolardy Engineering Test Array’s performance: sensitivity, beam characteristics, polarimetric properties, and image quality. We summarise the astronomical science that it has produced and draw lessons from operating Boolardy Engineering Test Array that will be relevant to the commissioning and operation of the final Australian Square Kilometre Array Path telescope.
This study tested whether accurate dating by accelerator mass spectrometry (AMS) radiocarbon wiggle-matching of short tree-ring series (~30 annual rings) in the Medieval period could be achieved. Scientific dating plays a central role in the conservation of historic buildings in England. Precise dating helps assess the significance of particular buildings or elements of their fabric, thus allowing us to make informed decisions about their repair and protection. Consequently, considerable weight, both financial and legal, can be attached to the precision and accuracy of this dating. Dendrochronology is the method of choice, but in a proportion of cases this is unable to provide calendar dates. Hence, we would like to be able to use 14C wiggle-matching to provide a comparable level of precision and reliability, particularly on shorter tree-ring sequences (~30 annual growth rings) that up until now would not routinely be sampled. We present the results of AMS wiggle-matching five oak tree-ring sequences, spanning the period covered by the vast majority of surviving Medieval buildings in England (about AD 1180–1540) when currently we have only decadal and bidecadal calibration data.
The Cycadales are a group of significant global conservation concern and have the highest extinction risk of all seed plants. Understanding the synchronisation of reproductive phenology of Cycadales may be useful for conservation by enabling the targeting of pollen and seed collection from wild populations and identifying the window of fertilisation to aid in the cultivation of Cycadales. Phenological data for 11 species of Zamia were gathered from herbarium specimens. Four phenological characters were coded with monthly character states. DNA was isolated and sequenced for 26S, CAB, NEEDLY, matK and rbcL, and a simultaneous phylogenetic analysis of phenology and DNA sequence data was carried out. Three major clades were recovered: a Caribbean clade, a Central American clade and a South American clade. Eight species showed statistically significant synchronisation in microsporangiate and ovulate phenological phases, indicating the time of fertilisation. Close reproductive synchronisation was consistently observed throughout the Caribbean clade (statistically significant in four of five species) but was less consistent in the Central American clade (statistically significant in one of two species) and South American clade (statistically significant in three of four species). Ultimately, phenology is shown to be a potential driver of speciation in some clades of Zamia and in others to be a potential barrier to hybridisation.
We summarise the first year of operation of the Medium Deep Survey - a key project of the HST. Two fields in the LMC are discussed and some preliminary scientific results presented. We also comment on image deconvolution for the extragalactic fields observed as part of the Medium Deep Survey.
This paper presents a color magnitude diagram for the enigmatic cluster ω Centauri (NGC 5139 = C1328 − 472) tracing the main sequence down to V ~ 21.5. The spread in color on the upper main sequence is confirmed as intrinsic to the cluster. The CCD observations were made using the SAAO 1 m telescope with the UCL CCD camera and the RGO CCD camera at the prime focus of the AAT.