17837 research outputs found
Sort by
Assessing the potential for trophic transfer of microplastics through the Thames food web
Get PDFMonitoring of plastic pollution focuses on macroplastics (>2.5 cm), with microplastics (<5 mm) only quantified in ad-hoc research studies. When microplastics are studied, it is only in flagship species and little is known about food web interactions with microplastics. Using the River Thames as a case study, this thesis establishes an ecosystem-wide assessment of macro- and microplastics. Such an approach has yet to be utilised elsewhere. This thesis provides evidence for the trophic transfer of microplastics and, through examination of macroplastics, highlights potential sources of microplastics. Furthermore, the present research demonstrates that macroplastic monitoring alone is insufficient to identify all major sources of plastic in the environment. Macroplastic is dominated by single-use products, in particular food packaging with rainfall contributing to inputs of sewage-related debris. Microplastic concentrations in sediment range from 0.2 to 2.6 particles per gram, with fibres being most abundant both in biota and sediment. Microplastics are readily ingested, with marine mammals as top predators (e.g., Halichoerus grypus and Phocoena phoceona) consuming the most (102 items on average). When organism size is accounted for, however, Corophium volutator and Hediste diversicolor ingests higher concentrations. Therefore, benthic infauna are exposed to the greatest microplastic concentrations. Eriocheir sinensis (Chinese mitten crab) are also highly contaminated, accumulating large tangles of plastic in the gastric mill. Over 90% of individuals contain tangles, many of which were made of over 100 plastic fibres. Microplastic colour and polymer type varies between the environment and biota with a greater proportion of coloured fibres and cellulosic particles present in the digestive tract. The results suggest that microplastics can be transferred to predators, but biomagnification is unlikely. The evidence provided supports the use of an ecosystem approach to plastic monitoring in addition to the use of model species and can provide insight into products posing the greatest risk. This evidence can be used to influence policy, product design and disposal
Aspect Perception and the Homeric Inhabitants of Hades
Get PDFHomeric epic contains many ambiguous images of the entity that inhabits Hades. In one way, Homer gives different names to this inhabitant: namely, νεκύς, ψυχή, and εἴδωλον. In another way, the ghost appears seemingly contradictory. In the Nekyia, the shades, at some moments, seem almost human and corporeal: they can drink, run, speak, and recognise the living by themselves. By contrast, at other moments, they are insubstantial, they screech like bats, and they cannot communicate with the living without drinking from a pool of blood. Scholars have suggested that these diverse descriptions are the product of compositional strata, metaphorical models, or poetic license. But few of these studies concentrate sufficiently on how the poet or characters try to make sense of the dead through these ambiguous presentations.1In this thesis, I propose that a phenomenological and psychological model, “aspect perception”, can disambiguate these seemingly confusing and contradictory descriptions of the wraith. Coined by Ludwig Wittgenstein, aspect perception is the idea that properties of a stimulus inform our perception of the percept. Wittgenstein uses Jastrow’s duck-rabbit image to show how the Gestalt’s properties lead us to think that the picture is either of a duck or of a rabbit. Inspired by this study, my aim is to show that the ghost’s characteristics impel both the poetic narrator and characters not only to form diverse conceptions of the wraith, but also to describe the shade inconsistently as human and inhuman. In order to demonstrate this, I argue that the inhabitant of Hades is an entity that has opposing qualities. It is a shade that can appear simultaneously corporeal and incorporeal, sentient and insentient. It is these properties, and ultimately this mode of perception, which account for these inconsistencies and ambiguities.<br/
Police Use of TASER:A systematic review of potential decision factors, including officer crewing levels
Get PDFGame-theoretic statistics and safe anytime-valid inference
Get PDFSafe anytime-valid inference (SAVI) provides measures of statistical evidence and certainty—e-processes for testing and confidence sequences for estimation—that remain valid at all stopping times, accommodating continuous monitoring and analysis of accumulating data and optional stopping or continuation for any reason. These measures crucially rely on test martingales, which are nonnegative martingales starting at one. Since a test martingale is the wealth process of a player in a betting game, SAVI centrally employs game-theoretic intuition, language and mathematics. We summarize the SAVI goals and philosophy, and report recent advances in testing composite hypotheses and estimating functionals in nonparametric settings
Evaluating the Impact of Experimental Assumptions in Automated Fault Localization
Get PDFMuch research on automated program debugging often assumes that bug fix location(s) indicate the faults' root causes and that root causes of faults lie within single code elements (statements). It is also often assumed that the number of statements a developer would need to inspect before finding the first faulty statement reflects debugging effort. Although intuitive, these three assumptions are typically used (55% of experiments in surveyed publications make at least one of these three assumptions) without any consideration of their effects on the debugger's effectiveness and potential impact on developers in practice. To deal with this issue, we perform controlled experimentation, split testing in particular, using 352 bugs from 46 open-source C programs, 19 Automated Fault Localization (AFL) techniques (18 statistical debugging formulas and dynamic slicing), two (2) state-of-the-art automated program repair (APR) techniques (GenProg and Angelix) and 76 professional developers. Our results show that these assumptions conceal the difficulty of debugging. They make AFL techniques appear to be (up to 38%) more effective, and make APR tools appear to be (2X) less effective. We also find that most developers (83%) consider these assumptions to be unsuitable for debuggers and, perhaps worse, that they may inhibit development productivity. The majority (66%) of developers prefer debugging diagnoses without these assumptions twice as much as with the assumptions. Our findings motivate the need to assess debuggers conservatively, i.e., without these assumptions
Data sources:
Access Repository Dashboard
Do you manage Royal Holloway - Pure? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!