Simulation of the spatio-temporal extent of groundwater flooding using statistical methods of hydrograph classification and lumped parameter models

This article presents the development of a relatively low cost and rapidly applicable methodology to simulate the spatio-temporal occurrence of groundwater flooding in chalk catchments. In winter 2000/2001 extreme rainfall resulted in anomalously high groundwater levels and groundwater flooding in many chalk catchments of northern Europe and the southern United Kingdom. Groundwater flooding was extensive and prolonged, occurring in areas where it had not been recently observed and, in places, lasting for 6 months. In many of these catchments, the prediction of groundwater flooding is hindered by the lack of an appropriate tool, such as a distributed groundwater model, or the inability of models to simulate extremes adequately. A set of groundwater hydrographs is simulated using a simple lumped parameter groundwater model. The number of models required is minimized through the classification and grouping of groundwater level time-series using principal component analysis and cluster analysis. One representative hydrograph is modelled then transposed to other observed hydrographs in the same group by the process of quantile mapping. Time-variant groundwater level surfaces, generated using the discrete set of modelled hydrographs and river elevation data, are overlain on a digital terrain model to predict the spatial extent of groundwater flooding. The methodology is applied to the Pang and Lambourn catchments in southern England for which monthly groundwater level time-series exist for 52 observation boreholes covering the period 1975–2004. The results are validated against observed groundwater flood extent data obtained from aerial surveys and field mapping. The method is shown to simulate the spatial and temporal occurrence of flooding during the 2000/2001 flood event accurately

Targeted anthelmintic treatment of parasitic gastroenteritis in first grazing season dairy calves using daily live weight gain as an indicator

Control of parasitic gastroenteritis in cattle is typically based on group treatments with anthelmintics, complemented by grazing management, where feasible. However, the almost inevitable evolution of resistance in parasitic nematodes to anthelmintics over time necessitates a reappraisal of their use in order to reduce selection pressure. One such approach is targeted selective treatment (TST), in which only individual animals that will most benefit are treated, rather than whole groups of at-risk cattle. This study was designed to assess the feasibility of implementing TST on three commercial farms, two of which were organic. A total of 104 first-grazing season (FGS), weaned dairy calves were enrolled in the study; each was weighed at monthly intervals from the start of the grazing season using scales or weigh-bands. At the same time dung and blood samples were collected in order to measure faecal egg counts (FEC) and plasma pepsinogen, respectively. A pre-determined threshhold weight gain of 0.75 kg/day was used to determine those animals that would be treated; the anthelmintic used was eprinomectin. No individual animal received more than one treatment during the grazing season and all treatments were given in July or August; five animals were not treated at all because their growth rates consistently exceeded the threshold. Mean daily live weight gain over the entire grazing season ranged between 0.69 and 0.82 kg/day on the three farms. Neither FEC nor pepsinogen values were significantly associated with live weight gain. Implementation of TST at farm level requires regular (monthly) handling of the animals and the use of weigh scales or tape, but can be integrated into farm management practices. This study has shown that acceptable growth rates can be achieved in FGS cattle with modest levels of treatment and correspondingly less exposure of their nematode populations to anthelmintics, which should mitigate selection pressure for resistance by increasing the size of the refugia in both hosts and pasture

A Review of Hybrid Manufacturing

In recent years the combination of laser-based Additive Manufacturing and Computer Numerical Controlled (CNC) machining has become increasingly popular, with several machine tool manufacturers exhibiting products based on different machine tool configurations. This technology, widely known as Hybrid Manufacturing, generally exploits Directed Energy Deposition processes using powder feedstock that is fed into a melt pool created by a laser. Although Directed Energy Deposition processes predate powder bed fusion Additive Manufacturing (at least in terms of coating and repair applications), commercialization of Hybrid Manufacturing systems is still very much in its infancy. However, they do offer clear advantages, combining a high deposition rate together with the accuracy and surface finish associated with machining. This paper presents the history of the development of Hybrid Manufacturing Systems (HMS), dating back from work undertaken in the mid 1990s through to the present day. The relative merits of different material deposition approaches are compared and some of the key technical challenges which remain are highlighted and discussed.Mechanical Engineerin

The Casimir Problem of Spherical Dielectrics: Quantum Statistical and Field Theoretical Approaches

The Casimir free energy for a system of two dielectric concentric nonmagnetic spherical bodies is calculated with use of a quantum statistical mechanical method, at arbitrary temperature. By means of this rather novel method, which turns out to be quite powerful (we have shown this to be true in other situations also), we consider first an explicit evaluation of the free energy for the static case, corresponding to zero Matsubara frequency ($n=0$). Thereafter, the time-dependent case is examined. For comparison we consider the calculation of the free energy with use of the more commonly known field theoretical method, assuming for simplicity metallic boundary surfaces.Comment: 31 pages, LaTeX, one new reference; version to appear in Phys. Rev.

Potential influence of a marine heatwave on range extensions of tropical fishes in the eastern Indian Ocean—Invaluable contributions from amateur observers

Global changes to fish distributions are expected to continue in coming decades with predicted increases in ocean temperatures and the frequency of extreme climatic events. In the eastern Indian Ocean during the 2010/11 summer, sea surface temperatures 4–5 °C above average and an unseasonal, anomalously strong, Leeuwin Current (LC) triggered a “marine heatwave” along the west coast of Australia, with elevated water temperatures persisting for a further two years. Peak LC flows in summer/autumn transported pelagic early life history stages of summer-spawning coastal subtropical and tropical fishes southwards. This study examined whether the heatwave enabled the arrival, persistence and reproduction of such species in waters View the MathML source≥∼32°S using a range of available datasets. Juveniles of Chaetodon assarius, Trachinotus botla, T. baillonii, Polydactylus plebeius, Psammoperca waigiensis and Siganus sp. recruited into nearshore waters at View the MathML source≥∼32°S in 2011. Polydactylus plebeius survived until the summer of 2012/13. Trachinotus spp., P. waigiensis and Siganus sp. survived over consecutive winters, with Siganus sp. establishing a self-recruiting, breeding population two years later. A return to more typical summer water temperatures by 2013/14 was associated with an apparent recruitment failure of Siganus sp. This is a rare example of a tropical vagrant surviving to breed in temperate regions. Confirmation of range extension beyond existing limits of this and other tropical species will be primarily dependent on either continuous or intermittent recruitment from this recently established southern breeding population. Commercial fisheries catch and effort data were of limited use in this study because they were not designed to record small catches of unusual and/or non-target species. In contrast, fisheries-independent recruitment surveys recorded tropical juveniles and validated amateur observations provided important information on unusual species. The study confirmed the emerging contribution of ‘citizen scientists’ working with researchers to document climate related impacts in the marine environment

The local structure of SO2 and SO3 on Ni(1 1 1): a scanned-energy mode photoelectron diffraction study

O 1s and S 2p scanned-energy mode photoelectron diffraction (PhD) data, combined with multiple-scattering simulations, have been used to determine the local adsorption geometry of the SO2 and SO3 species on a Ni(1 1 1) surface. For SO2, the application of reasonable constraints on the molecular conformation used in the simulations leads to the conclusion that the molecule is centred over hollow sites on the surface, with the molecular plane essentially parallel to the surface, and with both S and O atoms offset from atop sites by almost the same distance of 0.65 Å. For SO3, the results are consistent with earlier work which concluded that surface bonding is through the O atoms, with the S atom higher above the surface and the molecular symmetry axis almost perpendicular to the surface. Based on the O 1s PhD data alone, three local adsorption geometries are comparably acceptable, but only one of these is consistent with the results of an earlier normal-incidence X-ray standing wave (NIXSW) study. This optimised structural model differs somewhat from that originally proposed in the NIXSW investigation

An integrated modelling approach for assessing the effect of multiscale complexity on groundwater source yields

A new multi-scale groundwater modelling methodology is presented to simulate pumped water levels in abstraction boreholes within regional groundwater models, providing a robust tool for assessing the sustainable yield of supply boreholes and improving our understanding of groundwater availability during drought. A 3D borehole-scale model, which solves the Darcy-Forchheimer equation in cylindrical co-ordinates to simulate both linear and non-linear radial flow to a borehole in a heterogeneous aquifer, is embedded within a Cartesian grid, using a hybrid radial-Cartesian finite difference method. The local-scale model is coupled to a regional groundwater model, ZOOMQ3D, using the OpenMI model linkage software, providing a flexible and efficient tool for assessing the behaviour of a groundwater source within its regional hydrogeological context during historic droughts and under climate change. The advantages of the new method are demonstrated through application to a Chalk supply borehole in the UK

Modelling boreholes in complex heterogeneous aquifers

Reliable estimates of the sustainable yield of supply boreholes are critical to ensure that groundwater resources are managed sustainably. Sustainable yields are dependent on the pumped groundwater level in a borehole, how this relates to vertical aquifer heterogeneity, and features of the borehole itself. This paper presents a 3D radial flow model (SPIDERR), based on the Darcy-Forchheimer equation, for simulating the groundwater level response in supply boreholes in unconfined, heterogeneous aquifers. The model provides a tool for investigating the causes of non-linear behaviour in abstraction boreholes, which can have a significant impact on sustainable yields. This is demonstrated by simulating a variable-rate pumping test in a Chalk abstraction borehole. The application suggests the non-linear response to pumping is due to a combination of factors: a reduction in well storage with depth due to changes in the borehole diameter, a reduction in hydraulic conductivity with depth, and non-Darcian flow

Floc formation reduces the pH stress experienced by microorganisms living in alkaline environments

The survival of microorganisms within a cementitious geological disposal facility for radioactive wastes is heavily dependent on their ability to survive the calcium dominated, hyper-alkaline conditions resulting from the dissolution of the cementitious materials. The present study shows that the formation of flocs, composed of a complex mixture of extracellular polymeric substances (EPS), provides protection against alkaline pH values up to pH 13.0. The flocs were dominated by Alishewanella and Dietzia sp, producing a mannose rich carbohydrate fraction incorporating extracellular DNA, resulting in Ca2+ sequestration. EPS provided a ~10 µm thick layer around the cells within the centre of the flocs, which were capable of growth at pH 11.0 and 11.5, maintaining internal pH values of pH 10.4 and 10.7 respectively. Survival was observed at pH 12.0, where an internal floc pH of 11.6 was observed alongside a reduced associated biomass. Limited floc survival (<2 weeks) was observed at pH 13.0.This study demonstrates that flocs are able to maintain a lower internal pH in response to the hyperalkaline conditions expected to occur within a cementitious, geological disposal facility for radioactive wastes and indicates that floc communities within such a facility would be capable of survival up to a pH of 12.0