22 research outputs found
Long-term recovery of macroinvertebrate biota in grossly polluted streams: Re-colonisation as a constraint to ecological quality
No full textTo meet targets imposed by the European Water Framework Directive (2000/60/EC) it is vital that measures to improve the status of rivers are both effective and economically viable. Achievement of such aims needs robust understanding of biological responses to changes in water quality vis-à-vis mechanisms of and constraints to the colonization of previously polluted sites. This study therefore examined the long-term chemical and biological changes in historically polluted rivers to elucidate the responses of macroinvertebrate biota to improvements in chemical water quality. For three historically polluted sites in the English Midlands, data from surveys over a period of ca. 50 years were analysed. Ammonia (NH3) and 5-day biochemical oxygen demand (BOD5) were used as chemical water quality indicators. Variations in the ecological recovery of the study sites were assessed using an average pollution sensitivity score (Average Score Per Taxon) and the number of taxa present (usually to family level) present in hand-net samples. Ecological recovery varied widely and was influenced by the intensity and spatial extent of the pollution and the proximity of available sources of potential colonisers. At the site most isolated from potential sources of colonizing taxa, no clean-water macroinvertebrate taxa were recorded 30 years after the major sources of pollution ceased. Where clean-water colonisers were more readily available, significant improvements in ecological quality followed within 2–5 years of the improvements in chemical quality. Macroinvertebrate communities and hence monitoring data may thus be indicative of long past conditions or of biological isolation rather than contemporaneous chemical conditions. Combined chemical and biological data were used to explore a generic model for predicting recovery rates and success. Neither BOD5 nor NH3 were found to provide a consistent and meaningful prediction of either average pollution tolerance of macroinvertebrate taxa or of the number of taxa present. Long-term relationships between macroinvertebrate variables and chemical water quality variables, however, were non-linear, suggesting that water quality thresholds may have to be exceeded before biological recovery can occur. Even when chemical water quality has been improved substantially, the apparent ecological status of macroinvertebrate communities may not reflect reduced pollution levels attained until adequate time to allow for re-colonisation (possibly decades) has elapsed
Investigating the Degree of Crystallinity in Ultrasonically Welded Thermoplastic Composite Joints
No full textUltrasonic Welding is a fusion bonding method that can create high-strength thermoplastic composite joints at very fast speeds. This makes it a very promising method for use in the aerospace industry, though further research is required to mature it. One topic of interest is how the crystallinity of the polymer matrix in the joint is affected by the ultrasonic welding process. This thesis specifically investigated the degree of crystallinity of carbon fibre reinforced lower melting polyaryl ether ketone (LM PAEK) composite. An experimental methodology was developed to measure the temperature at different locations through the thickness of the joint, and extract samples for Differential Scanning Calorimetry analysis. The calculated degree of crystallinity was related to the temperature evolution for different locations in the joint and variation in the welding force and amplitude.Aerospace Engineerin
Modification of an Asphalt Binder with Altraflex 2006
No full textCivil Engineering and GeosciencesStructural EngineeringRoad and Railway Engineerin
Collaborative Augmented Reality Mirror Game
No full textThis report describes the development of an augmented reality game by students of the Delft University of Technology. This game, called the Augmented Reality Mirror Game, is a game that uses augmented reality technology to simulate lasers and objects with optical properties like mirrors and beam splitters. The goal of this game is to use these objects to route one or more laser beams from emitters to targets. Collaboration is an essential aspect of the game. Different players have distinct capabilities to manipulate the game world and solve the puzzles.Bachelor ProjectComputer ScienceElectrical Engineering, Mathematics and Computer Scienc
Environmental flows and European Water Framework Directive
No full text1. Environmental flows is now a widely accepted term that covers the quantity, timing, duration, frequency and quality of water flows required to sustain freshwater, estuarine and near-shore ecosystems and the human livelihoods and well-being that depend on them.
2. The Water Framework Directive (WFD) of the European Union does not use the term environmental flows explicitly, but requires member states to achieve good ecological status (GES) in all waterbodies, which is assessed by reference to aquatic biology. Nevertheless, it is accepted that ecologically appropriate hydrological regimes are necessary to meet this status. Implementing environmental flows will be a key measure for restoring and managing river ecosystems.
3. The WFD explicitly requires stakeholder involvement, but this has been interpreted as largely a dissemination exercise by national government agencies. Stakeholders are no longer involved in negotiation over ecological objectives as these are pre-set in the WFD. However, stakeholders may be more involved in reviewing standards and agreeing to measures to restore river ecosystems to the status required by the WFD.
4. The U.K. has undertaken two major projects to set environmental standards for water resources (i) to define water abstraction limits that maintain a healthy river ecosystem and (ii) to define ecologically appropriate flow releases from reservoirs.
5. Implementation of environmental flows remains a major issue, but new ideas such as time-limited licences and licence trading are being tried
Improving the nutrition of Merino ewes during pregnancy and lactation increases weaning weight and survival of progeny but does not affect their mature size
No full textLamb growth to weaning, and during the period immediately following weaning, influences post-weaning mortality and may affect mature size. The hypothesis tested in the experiments reported in this paper was that changes in the maternal liveweight of Merino ewes during pregnancy and lactation could predict the weight at weaning, post-weaning survival and mature size of their progeny. At two sites (Vic. and WA) in each of two years, a wide range in the liveweight profiles of ewes was generated during pregnancy and lactation by varying the amount of supplements fed and feed on offer grazed. Across the four experiments this resulted in progeny weights ranging from 13.8 to 28.3 kg just before weaning. Lamb growth was primarily related to the amount of feed on offer during lactation, but was also related to the liveweight change of the ewe during pregnancy. These relationships were consistent in both experiments at each site. Weaning weight was strongly associated with post-weaning survival at the Vic. site. Survival rates decreased significantly when weaning weights were below 20 kg. These results indicate that management of ewe and lamb nutrition to maximise growth of lambs before weaning and growing weaners at 30 g/day or more after weaning are important for optimal post-weaning survival. The findings also suggest that the mature size of offspring is unlikely to be adversely affected by pre-weaning nutrition within the range of nutritional scenarios during pregnancy and lactation that are likely to be experienced within the Australian sheep industry
Influence of stream flow on epilithic diatom communities and its consequence for water quality monitoring
No full textEpilithic diatom communities and relevant physico-chemical variables were studied between 3 May and 16 July 1993 in Harwood Beck, an oligotrophic stream in Upper Teesdale, and the River Browney, a lowland eutrophic river. The effect of stormflow on diatom-based water quality indices was assessed. In both rivers epilithic chlorophyll ḁ (µg cm(^-2)) was highly variable and very low after mid- June. In Harwood Beck there was a significant difference in epihthic chlorophyll a between cobbles and boulders, with the greatest difference after stormflow. Epilithic chlorophyll a in the River Browney was initially high, but declined markedly after stormflow. River Browney chlorophyll a was inversely correlated with current speed on cobbles and total inorganic nitrogen on cobbles and boulders. Uptake of inorganic nitrogen may be directly related to epilithic diatom biomass. A sharp rise in the percentage of Cocconeis placentula between mid-June and mid-July suggests that grazing may be an important factor limiting algal biomass. The possible roles of algal grazers, Cladophora glomerata and silicate concentration, in progressively limiting diatom biomass during the summer are discussed. Percentage composition changes of taxa after stormflow are generally related to taxa morphology and mode of adherance to the substrate. There were no significant differences in the percentages of the five most common taxa between cobbles and boulders. Percentage changes in taxa were not significantly correlated with nutrients, with the exception of Navicula gregaria and N. lanceolata (in the River Browney) which were inversely correlated with the concentration of total inorganic nitrogen. There appears to be a succession of dominant species, possibly related to the influence of flow and nutrient concentrations, which tended to increase during the study period. Diatom water quality indices remained relatively stable over the 10 week period. Effectively equal water quality classifications were derived from the Specific Pollution Index (SPI) and Generic Diatom Index (GDI). The zoning system proposed by Round (1993) may be broadly useful, but requires careful interpretation
Predicting the ecological consequences of river management for a riverine cyprinid fish.
No full textCurrent river management seeks to resolve a compromise between stakeholder interests, ecosystem services provision and conservation aims, especially in relation to assessment of ecosystem health. While management decisions should be evidenced-based, current population and habitat models fail to incorporate fish behaviour and the interactions between fish and their environment, thus limiting their ability to predict management-relevant, population responses to environmental change. In order to address these weaknesses, an individual-based model is developed and parameterised to predict the distribution and growth of roach (Rutilus rutilus), a common, generalist, freshwater fish; known to be typically dominant in heavily modified rivers. Such a model seeks to build on current management models and practices, with emphasis on improving recruitment of juvenile roach. Virtual forager parameters are derived from foraging experiments, published investigations, models of roach behaviour and bioenergetics. Data collected from field studies in a typical, highly modified, lowland river are used to describe the environment and initial fish population with subsequent data on fish population trends used to validate the IBM, under a pattern-oriented modelling approach; specifically growth rate and habitat distribution patterns. River management practices including the removal of in-stream aquatic macrophytes and regulation of flow regime for flood risk management are predicted as potentially damaging to roach recruitment, subsequent year-class strength and therefore, populations in subsequent years. Recommendations for more sympathetic management schemes are provided. The modelling framework described here can be used to produce robust predictions of roach population patterns in riverine habitats and allows the user to test the impact of environmental change on cyprinid fish, enabling the modelling system to be used to develop proactive, evidence-based management in light of current rates of environmental change
Diminishing benefits of urban living for children and adolescents’ growth and development
No full textOptimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified. © 2023, The Author(s)
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Marketing legal services to medium-sized companies
No full textThis thesis examines marketing and buying of legal services in the context of medium-sized companies from theoretical and empirical perspectives. The theoretical foundations for the market of legal services are laid by studying the particularities of services and their intrinsic challenges for marketing. Different ways to segment the legal market are examined, including client-led segmentation, which includes segmentation by client size, such as medium-sized companies. After studying the theoretical foundations of legal marketing, this thesis examines forces in the macro- and micro-environment responsible for driving or hindering the development of strategic marketing initiatives in law firms. Taking the standpoint of medium-sized companies as corporate buyers of legal services, the thesis also examines purchasing behaviour in the different stages of the organisational buying process. The empirical research considers both marketing and buying perspectives. Managing partners and marketing directors were interviewed regarding marketing in their organisations. The interviews covered such matters as marketing organisation, marketing information, policies, as well as strategies and tactics. Mirroring the literature review, the purchasing behaviour of decision-makers in medium-sized companies was also studied empirically
