3,878 research outputs found
The Impact of Climate Change upon the Snowmelt Hydrology of an Upland UK Catchment
No full textSnowmelt hydrology is important in the winter flow regime of upland catchments in the UK as it can attenuate the extremes of the river flow hydrograph. The sensitivity of snow accumulation and melt to changes in climate, in particular to increases in temperature, could impact upon the variability of the winter flow regime. The potential impacts of this change are increases in flood risk and decreases in low flows. Hence this project investigated the consequences of projected climatic change upon snowmelt hydrology of the Dacre Beck catchment in the English Lake District. A distributed snowmelt model was created which spatialised temperature and precipitation data across the catchment. The model accumulated snow when the temperature fell below 0°C and applied one of three temperature-index snowmelt equations to melt the accumulated snowpack. The model was driven using stochastic baseline and projected (2050s medium emissions) weather series calculated using the UKCP09 weather generator. The results showed a large future reduction in both winter snow accumulation and the magnitude of snowmelt hydrology. However, the limited hydrological process representation of the model meant it could not reliably forecast changes in the winter flow regime. Therefore the snow accumulation and melt equations were incorporated into the physically based Connectivity Runoff Model (CRUM). This improved model was calibrated to observed discharge data within a Generalised Likelihood Uncertainty Estimation (GLUE) framework before being run with a sample of baseline and projected UKCP09 weather generator series. The results showed that both high and low flows in the winter flow regime were likely to increase which contradicted previous expectations but it was unclear about the role of snowmelt hydrology in these changes. Further investigation using temperature perturbed weather series found that these changes in the winter flow regime were most likely caused by increases in rainfall which overrode the impact of changes in snowmelt hydrology
Snow sports injuries in Scotland: a case-control study.
No full textOBJECTIVES: To examine the incidence and patterns of snow sports injuries at the three largest commercial ski areas in Scotland and to identify factors associated with injury risk. METHODS: A prospective case-control study of all injured people at Cairngorm, Glenshee, and Nevis Range ski areas during the 1999-2000 winter season. Personal details, snow sports related variables, diagnosis, and treatment were recorded. Control data were collected at random from uninjured people at all three areas. Random counts were performed to analyse the composition of the on slope population. RESULTS: A total of 732 injuries were recorded in 674 people. Control data were collected from 336 people. The injury rate for the study was 3.7 injuries per 1000 skier days. Alpine skiers comprised 67% of the on slope population, snowboarders 26%, skiboarders 4%, and telemark skiers 2%. Lower limb injuries and sprains were the commonest injuries in alpine skiers and skiboarders. Snowboarders sustained more injuries to the upper limb and axial areas. Skiboarders and snowboarders had a higher incidence of fractures. After adjustment for other variables, three factors were all independently associated with injury: snowboarding (odds ratio (OR) 4.07, 95% confidence interval (CI) 1.65 to 10.08), alpine skiing (OR 3.82, CI 1.6 to 9.13), and age <16 years (OR 1.9, CI 1.14 to 3.17). More than five days of experience in the current season and at least one week of experience in total had a protective effect against injury. CONCLUSIONS: Despite a change in the composition of the alpine population at Scottish ski areas, the overall rate and pattern of injury are similar to those reported previously in comparable studies. Several factors are associated with an increased risk of injury and should be targeted in future injury prevention campaigns
The effect of an anti-malarial subsidy programme on the quality of service provision of artemisinin-based combination therapy in Kenya: a cluster-randomized, controlled trial.
No full textBACKGROUND: Many patients with suspected malaria in sub-Saharan Africa seek treatment from private providers, but this sector suffers from sub-standard medicine dispensing practices. To improve the quality of care received for presumptive malaria from the highly accessed private retail sector in western Kenya, subsidized pre-packaged artemether-lumefantrine (AL) was provided to private retailers, together with a one day training for retail staff on malaria diagnosis and treatment, job aids and community engagement activities. METHODS: The intervention was assessed using a cluster-randomized, controlled design. Provider and mystery-shopper cross-sectional surveys were conducted at baseline and eight months post-intervention to assess provider practices. Data were analysed based on cluster-level summaries, comparing control and intervention arms. RESULTS: On average, 564 retail outlets were interviewed per year. At follow-up, 43% of respondents reported that at least one staff member had attended the training in the intervention arm. The intervention significantly increased the percentage of providers knowing the first line treatment for uncomplicated malaria by 24.2% points (confidence interval (CI): 14.8%, 33.6%; adjusted p=0.0001); the percentage of outlets stocking AL by 31.7% points (CI: 22.0%, 41.3%; adjusted p=0.0001); and the percentage of providers prescribing AL for presumptive malaria by 23.6% points (CI: 18.7%, 28.6%; adjusted p=0.0001). Generally outlets that received training and job aids performed better than those receiving one or none of these intervention components. CONCLUSION: Overall, subsidizing ACT and retailer training can significantly increase the percentage of outlets stocking and selling AL for the presumptive treatment of malaria, but further research is needed on strategies to improve the provision of counselling advice to retail customers
Reformulating the rj-McMC Algorithm for 3D Inversion of Passive Seismic Data for Near-Surface Characterization
No full textGeophysical subsurface characterization techniques could, due to their non-invasive nature, play a crucial role in the design and subsequent construction of infrastructure in urban & industrial environ- ments. Geo-data specialist company Fugro sees potential in upgrading their current ambient-seismic- noise-tomography workflow, to make use of state-of-the-art inversion schemes with the main goal of increasing the quality and accuracy of the initial-site characterization delivered to clients. In this thesis I explore the feasibility of utilizing the reverse-jump Markov chain Monte Carlo (rj-McMC) algorithm for the inversion of ambient seismic noise for characterization in urban & industrial environments. Specif- ically, testing the potential of scaling down this inversion algorithm to fit in a small scale, near-surface framework. To achieve this, I first carried out analyses to evaluate the appropriate Rayleigh wave frequency range, after which realistic noise hyperparameters, suited for this reduced scale problem, were obtained. Because of the potential exploitation of in-situ borehole measurements, I reformulated the Bayesian prior within the rj-McMC algorithm to implement these constraining shear wave velocity values appropriately. I conducted extensive synthetic experiments to gain insight into the behavior of this adapted algorithm, from which it was concluded that the inherent dynamic discretization partially prevents these constraints from being implemented to their full extent. Nevertheless, promising results lead me to conclude that the use of the rj-McMC algorithm for application in near-surface urban & industrial environments is feasible.Applied Geophysics | IDEA Leagu
Delayed emesis: moderately emetogenic chemotherapy (single-day chemotherapy regimens only)
No full textPurpose An update of the recommendations for the prophylaxis of delayed emesis induced by moderately emetogenic chemotherapy discussed during the third Perugia Consensus Conference (June 2009) sponsored by MASCC-ESMO was presented. The review considered new studies published since the second consensus conference (April 2004). Methods An online search was used conducting PubMed and the search terms moderately, chemotherapy, and emesis with a restriction to papers in English. Results Overall, nine randomized controlled studies were included: four evaluating NK1 receptor antagonists, one palonosetron, and four dopamine receptor antagonists. Conclusions In patients receiving a combination of anthracycline plus cyclophosphamide treated with a combination of aprepitant, a 5-HT3 receptor antagonist and dexamethasone to prevent acute nausea and vomiting, aprepitant is suggested to prevent delayed emesis. In patients who do not receive aprepitant for the prophylaxis for acute emesis and in which palonosetron is recommended, a multiday oral dexamethasone is the preferred treatment for the prevention of delayed emesis. Levels of evidence and of consensus for both recommendations are moderate
Age patterns of severe paediatric malaria and their relationship to Plasmodium falciparum transmission intensity.
No full textBACKGROUND: The understanding of the epidemiology of severe malaria in African children remains incomplete across the spectrum of Plasmodium falciparum transmission intensities through which communities might expect to transition, as intervention coverage expands. METHODS: Paediatric admission data were assembled from 13 hospitals serving 17 communities between 1990 and 2007. Estimates of Plasmodium falciparum transmission intensity in these communities were assembled to be spatially and temporally congruent to the clinical admission data. The analysis focused on the relationships between community derived parasite prevalence and the age and clinical presentation of paediatric malaria in children aged 0-9 years admitted to hospital. RESULTS: As transmission intensity declined a greater proportion of malaria admissions were in older children. There was a strong linear relationship between increasing transmission intensity and the proportion of paediatric malaria admissions that were infants (R2 = 0.73, p < 0.001). Cerebral malaria was reported among 4% and severe malaria anaemia among 17% of all malaria admissions. At higher transmission intensity cerebral malaria was a less common presentation compared to lower transmission sites. There was no obvious relationship between the proportions of children with severe malaria anaemia and transmission intensity. CONCLUSION: As the intensity of malaria transmission declines in Africa through the scaling up of insecticide-treated nets and other vector control measures a focus of disease prevention among very young children becomes less appropriate. The understanding of the relationship between parasite exposure and patterns of disease risk should be used to adapt malaria control strategies in different epidemiological settings
Plasmodium infection and its risk factors in eastern Uganda.
No full textBACKGROUND: Malaria is a leading cause of disease burden in Uganda, although surprisingly few contemporary, age-stratified data exist on malaria epidemiology in the country. This report presents results from a total population survey of malaria infection and intervention coverage in a rural area of eastern Uganda, with a specific focus on how risk factors differ between demographic groups in this population. METHODS: In 2008, a cross-sectional survey was conducted in four contiguous villages in Mulanda, sub-county in Tororo district, eastern Uganda, to investigate the epidemiology and risk factors of Plasmodium species infection. All permanent residents were invited to participate, with blood smears collected from 1,844 individuals aged between six months and 88 years (representing 78% of the population). Demographic, household and socio-economic characteristics were combined with environmental data using a Geographical Information System. Hierarchical models were used to explore patterns of malaria infection and identify individual, household and environmental risk factors. RESULTS: Overall, 709 individuals were infected with Plasmodium, with prevalence highest among 5-9 year olds (63.5%). Thin films from a random sample of 20% of parasite positive participants showed that 94.0% of infections were Plasmodium falciparum and 6.0% were P. malariae; no other species or mixed infections were seen. In total, 68% of households owned at least one mosquito although only 27% of school-aged children reported sleeping under a net the previous night. In multivariate analysis, infection risk was highest amongst children aged 5-9 years and remained high in older children. Risk of infection was lower for those that reported sleeping under a bed net the previous night and living more than 750 m from a rice-growing area. After accounting for clustering within compounds, there was no evidence for an association between infection prevalence and socio-economic status, and no evidence for spatial clustering. CONCLUSION: These findings demonstrate that mosquito net usage remains inadequate and is strongly associated with risk of malaria among school-aged children. Infection risk amongst adults is influenced by proximity to potential mosquito breeding grounds. Taken together, these findings emphasize the importance of increasing net coverage, especially among school-aged children
The snow and the willows : the ecological responses of the alpine dwarf shrub "Salix herbacea" to climate change
No full textCurrent changes in shrub abundance in alpine and arctic tundra ecosystems are primarily driven by warming, changes in snow cover time and shifts in biotic interactions. However, while taller shrub communities are expanding, dwarf shrubs show reductions under climate warming. The aim of this thesis was to disentangle the phenological, growth and fitness response of a widespread prostrate shrub to warming and changes in snowmelt time, investigate shifts between competition and facilitation in communities along environmental stress gradients, and determine trait plasticity in response to snowmelt change. To this end, we investigated phenology, vegetative growth and reproductive traits in Salix herbacea, a widespread, long-lived alpine and arctic prostrate shrub, along its elevational and snowmelt microhabitat range over three years in Davos, Switzerland. To examine environmental drivers of trait variation, community interactions and potential for plastic responses to global changes, we used a space-for-time substitution study, a neighbor removal experiment, and reciprocal transplant experiment.
Earlier snowmelt was associated with longer phenological development periods, an increased likelihood of herbivory and fungal damage, fewer stems and no increase in end-of-season wood reserve carbohydrates. Furthermore, while early snowmelt was associated with an increased proportion of flowering stems, the number of fruiting stems was not, as fruit set decreased significantly with earlier snowmelt. Warmer temperatures at lower elevations were associated with decreases in stem number and wood low-molecular weight sugars, and increases in proportion of stems fruiting.
In the reciprocal transplant experiment, S. herbacea generally started to grow earlier, but had a longer development time and produced smaller leaves on ridges relative to snowbeds. The phenological changes did not influence clonal or sexual reproduction, but smaller leaves in early-snowmelt sites were associated with reduced sexual reproduction, a potentially maladaptive response of leaf plasticity. Clonal and sexual reproduction generally showed no response to changes in snowmelt timing. Moreover, we found no home site advantage in terms of sexual and clonal reproduction. Leaf damage probability depended on snowmelt timing and thus exposure period, but it had no short-term effect on fitness traits.
In the neighbor removal study, the majority of S. herbacea traits were controlled primarily by snowmelt timing. However, neighbour removal directly reduced the number of days required for fruit production relative to control shrubs; however, it also increased the likelihood of leaf tissue herbivory. Effects of neighbour removal also changed along the environmental gradients, with neighbour removal leading to reduced leaf size on earlier snowmelt sites, and increased fungal damage with increasing elevation.
We conclude that Salix herbacea exhibits strong reductions in performance under earlier snowmelt, with few benefits of warming temperatures. Further, plasticity in leaf traits may lead to fitness reductions under earlier snowmelt. With accelerated spring snowmelt, environmental stress will likely increase due to increasing exposure to cold temperatures and damage agents, which reduce the leaf crops and flowering probability in the following summers. However, detrimental effects of early snowmelt may be at least partly mediated by facilitative interactions by neighbours. Under climate change, we may begin to see reductions in clonal and sexual reproduction, leading to fitness declines in S. herbacea, which in turn may reduce persistence of populations in arctic and alpine ecosystems, particularly those growing on current early exposure microhabitats as spring snowmelt accelerates. The results of this thesis suggest that earlier spring snowmelt timing may represent one of the critical global change drivers reducing dwarf shrub performance in arctic and alpine tundra ecosystems
Depositional record of historic lahars in the Whangaehu Gorge, Mt. Ruapehu
No full textMt. Ruapehu is one of the most lahar prone volcanoes in the world, having both a crater lake and six small glaciers upon its 2797 m summit. The major outlet for the crater lake, the Whangaehu Gorge, has hosted over 46 historic lahars. However, the low preservation of debris flow deposits, as a result of frequent remobilisation on steep slopes, allows for the detailed description of only 9 lahar events over the last 150 years. Field investigation, historic aerial photos, two airborne LiDAR surveys and direct measurements have been utilised to describe the sedimentology, geomorphology and distribution of historic lahar deposits in the first 11 km of the Whangaehu Gorge. Inundation maps have been created for 1945, 1953, 1975, September 1995, October 1995, March 2007 and September 2007. Grain size distribution, componentry and geomorphology of the 1861, 1975, September 1995, October 1995, 1999 and 2007 lahar deposits have been compared.
The lahar deposits are massive, very poorly sorted, silty gravels that form a series of unconsolidated terraces. The limited sediment sources in the steep sided Whangaehu Gorge, including minor historic eruption products, results in significant recycling of lahar deposits. However, the deposits can be differentiated by proportions of lithological components and in some cases anthropogenic debris. The abundance of hydrothermally altered material reflects the role of Crater Lake in lahar formation, although, some of these materials (gypsum, sulphur and snow) are only temporary.
Non-cohesive debris flows and occasional snow slurry lahars have been formed by a range of triggering mechanisms associated with and independent of eruptions. Lahars have been formed in the Whangaehu Valley as the result of ejected crater lake water and associated snow melt (1975, September 1995 and September 2007), as well as the progressive displacement of lake water as a result of lava dome growth (1945) and uplift of the lake floor (1968). Inter-eruption lahars occur as a result of Crater Lake outburst floods (1861, 1953 and March 2007) and remobilisation by precipitation and the collapse of tephra laden snow (October 1995 and 1999).
The comparison of historic lahars also reflects the range of lahar magnitudes experienced historically on Ruapehu. The most recent Crater Lake outburst of March 2007, with a peak discharge of 1700-2500 m3/s is the second largest recorded lahar, behind only the eruption-generated lahar of April 1975 with a peak discharge of 5000-7500 m3/s.
Lahar mitigation can subsequently be based on lahar generation and incorporation of the vast amounts of data collected before and after the 2007 outburst flood. Recent remobilisation and phreatic activity suggest the significant under-representation of small volume events like rain-generated and snow slurry lahars in the geologic record
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