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D Butterfield

Publications and source records attributed to D Butterfield.

10 recordsLinked to original sources
PubMed2006

Impacts of climate change on in-stream nitrogen in a lowland chalk stream: an appraisal of adaptation strategies.

The impacts of climate change on nitrogen (N) in a lowland chalk stream are investigated using a dynamic modelling approach. The INCA-N model is used to simulate transient daily hydrology and water quality in the River Kennet using temperature and precipitation scenarios downscaled from the General Circulation Model (GCM) output for the period 1961-2100. The three GCMs (CGCM2, CSIRO and HadCM3) yield very different river flow regimes with the latter projecting significant periods of drought in the second half of the 21st century. Stream-water N concentrations increase over time as higher temperatures enhance N release from the soil, and lower river flows reduce the dilution capacity of the river. Particular problems are shown to occur following severe droughts when N mineralization is high and the subsequent breaking of the drought releases high nitrate loads into the river system. Possible strategies for reducing climate-driven N loads are explored using INCA-N. The measures include land use change or fertiliser reduction, reduction in atmospheric nitrate and ammonium deposition, and the introduction of water meadows or connected wetlands adjacent to the river. The most effective strategy is to change land use or reduce fertiliser use, followed by water meadow creation, and atmospheric pollution controls. Finally, a combined approach involving all three strategies is investigated and shown to reduce in-stream nitrate concentrations to those pre-1950s even under climate change.

Agriculture↗
PubMed2002

Steady state and dynamic modelling of nitrogen in the River Kennet: impacts of land use change since the 1930s.

Steady state and dynamic models have been developed and applied to the River Kennet system. Annual nitrogen exports from the land surface to the river have been estimated based on land use from the 1930s and the 1990s. Long term modelled trends indicate that there has been a large increase in nitrogen transport into the river system driven by increased fertiliser application associated with increased cereal production, increased population and increased livestock levels. The dynamic model INCA (Integrated Nitrogen in Catchments) has been applied to simulate the day-to-day transport of N from the terrestrial ecosystem to the riverine environment. This process-based model generates spatial and temporal data and reproduces the observed instream concentrations. Applying the model to current land use and 1930s land use indicates that there has been a major shift in the short term dynamics since the 1930s, with increased river and groundwater concentrations caused by both non-point source pollution from agriculture and point source discharges.

Agriculture↗
PubMed2002

Nutritional approaches to combat oxidative stress in Alzheimer's disease.

Alzheimer's disease (AD) brains are characterized by extensive oxidative stress. Additionally, large depositions of amyloid beta-peptide (Abeta) are observed, and many researchers opine that Abeta is central to the pathogenesis of AD. Our laboratory combined these two observations in a comprehensive model for neurodegeneration in AD brains centered around Abeta-induced oxidative stress. Given the oxidative stress in AD and its potentially important role in neurodegeneration, considerable research has been conducted on the use of antioxidants to slow or reverse the pathology and course of AD. One source of antioxidants is the diet. This review examines the literature of the effects of endogenous and exogenous, nutritionally-derived antioxidants in relation to AD. In particular, studies of glutathione and other SH-containing antioxidants, vitamins, and polyphenolic compounds and their use in AD and modulation of Abeta-induced oxidative stress and neurotoxicity are reviewed.

Journal Article↗
PubMed2001

Modelling instream nitrogen variability in the Dee catchment, NE Scotland.

The Integrated Nitrogen in CAtchments model (INCA) was applied to the River Dee, Aberdeenshire, NE Scotland. To a first approximation the model was able to simulate the annual mean streamwater NO3-N concentrations observed along the length of the main channel. This provided the basis for using INCA to subsequently explore the effects of N deposition and land use management on streamwater NO3-N concentrations and loads. On an annual timescale, the model predictions suggest that NO3-N concentrations will decrease by 5% following a 20% reduction in fertiliser application. Furthermore, model results also suggest that a 50% increase in N deposition will cause a 15% increase in the streamwater NO3-N concentrations. The utility of INCA as a tool for catchment management is discussed, current limitations are highlighted and possible improvements are suggested.

Agriculture↗
PubMed2000

Assessing the potential impacts of various climate change scenarios on the hydrological regime of the River Kennet at Theale, Berkshire, south-central England, UK: an application and evaluation of the new semi-distributed model, INCA

A new semi-distributed integrated nitrogen in catchments (INCA) model was used to attempt to assess the potential impacts of several recent Hadley Centre climate change scenarios on the hydrological flow regime of the entire River Kennet catchment to Theale, south-central England, UK. The climatically and hydrologically anomalous period 1985-1995 was used for baseline data in an attempt to: (1) represent any possible future climatic or hydrological variability not available from scenario use alone; and (2) attain maximum possible model calibration validity under future climates by simulating extremes of within-year hydrological variability. Substantial reductions in total annual runoff occurred, with an average reduction of 18.97%. Summer and late autumn soil moisture deficits (SMDs) increased in intensity, and were also found to persist for longer periods into autumn and (occasionally) winter. A generally enhanced hydrological regime of the River Kennet was simulated, with increased seasonality overall. A greater percentage of flow was observed to occur in spring and (occasionally) winter. Month-to-month variability of flow was discovered to be greater than annual changes. An average reduction in minimum annual flows of 46.03% occurred. Implications for catchment ecology and water resource requirements are briefly discussed. An evaluation of the new INCA model's performance as a tool for climate change impacts assessment is made.

Journal Article↗
PubMed1978

Cancer of the pancreas in young adults.

Two young women with cancer of the pancreas are described. The rising incidence and epidemiology of this cancer is discussed. The need for tissue diagnosis and some new aspects of treatment of pancreatic cancer relevant to these cases are presented.

Adenocarcinoma↗
PubMed1978

The results of colonic anastomoses at the Royal Melbourne Hospital.

One hundred consecutive colocolic and colorectal anastomoses are reviewed. The operative mortality was 5%, wound infection rate 27%, and faecal fistula rate 15%. These complications are shown to double the hospital bed stay. Factors affecting their occurence are examined, and recommendations are made with a view to lower this morbidity.

Adult↗
PubMed1972

Clinical, microbiological, and immunological studies in patients with immunoglobulin deficiencies and gastrointestinal disorders.

Seven patients with gastrointestinal disorders and deficiencies of serum and secretory immunoglobulins were evaluated clinically, microbiologically, and immunologically. Five patients had generalized deficiencies of immunoglobulins; two were selectively deficient. Diarrhoea and malabsorption in six of the seven patients were at least partially explained. Four of the five patients with generalized hypogammaglobulinaemia had intestinal infestation with Giardia lamblia; in three of the five, excessive numbers of anaerobic bacteria were cultured from small bowel fluids. Despite much variability in relative severity of patients' respiratory and gastrointestinal tract symptoms, deficiencies of mucosal immunocytes and immunoglobulins in nasopharyngeal and gastrointestinal tract tissues and secretions were similar. Except for one selectively IgA-deficient patient, all patients were deficient in IgE. The study characterizes in greater detail than heretofore the gastrointestinal disorders associated with immunoglobulin deficiency states.

Adolescent↗