Ecological change in shallow lakes through antifoulant biocide contamination

This study sought to determine whether tributyltin (TBT), a toxic environmental contaminant now banned from use in antifoulant paints, could have contributed to ecological degradation in shallow lakes. Anthropogenic stresses have often led to changes in ecological structure and functioning within such waterbodies, with catastrophic loss of submerged macrophytes a common phenomenon. An area that has experienced intense TBT contamination and widespread macrophyte loss, is the Broads, a popular inland navigable waterway in E. England. Development of an online SPE-LC-MSn analytical method enabled identification and quantification of contemporary organic antifoul biocides in water and sediment samples. This contemporary analysis improved understanding of the transport mechanisms that would have been responsible for dilution and dispersion of TBT. Within the River Bure study area, a distinct antifoul biocide contamination gradient was observed, that related to the level and type of boating activity. Most significantly, biocide transportation has led to areas not directly exposed to boating activity, but in hydrological connection, to become contaminated. The recent ecological histories of contaminated lakes was reconstucted using multi-proxy palaeoecological analytical techniques on cores collected using a new wide-diameter corer. Data from the radiometrically-dated cores indicated that at least twenty years of continuous TBT pollution occurred in the Broads, against a backgound of eutrophication. The pre-TBT period was characterised by presence of macrophyte remains with abundant plant-associated diatoms, cladocera and invertebrates, which switched to predominantly planktonic assemblages after initial detection of TBT. Environmental concentrations of TBT present during its active usage in antifoulant paints, would have adversely affected functionally important aquatic organisms, as indicated by ecotoxicological test data. The spatio-temporal assessment of contamination, combined with a palaeoecological approach, has been successful in reconstructing relative toxicant exposure and patterns of ecological change in the Broads. This methodology could be applied to the study of other persistent pollutants

Confirmatory factor analysis of Clinical Outocmes in Routine Evaluation (CORE-OM) used as a measure of emotional distress in people with tinnitus

BACKGROUND: People with troublesome tinnitus often experience emotional distress. Therefore a psychometrically sound instrument which can evaluate levels of distress and change over time is necessary to understand this experience. Clinical Outcomes in Routine Evaluation (CORE-OM) is a measure of emotional distress which has been widely used in mental health research. Although originally designed as a 4-factor questionnaire, factor analyses have not supported this structure and a number of alternative factor structures have been proposed in different samples. The aims of this study were to test the factor structure of the CORE-OM using a large representative tinnitus sample and to use it to investigate levels of emotional distress amongst people with a range of tinnitus experience. METHODS: The CORE-OM was completed by 342 people experiencing tinnitus who self-rated their tinnitus on a 5-point scale from ‘not a problem’ to ‘a very big problem’. Confirmatory factor analysis was used to test all ten factor models which have been previously derived across a range of population samples. Model fit was assessed using fit criterion and theoretical considerations. Mean scores on the full questionnaire and its subscales were compared between tinnitus problem categories using one-way ANOVA. RESULTS: The best fitting model included 33 of the 34 original items and was divided into three factors: negatively worded items, positively worded items and risk. The full questionnaire and each factor were found to have good internal consistency and factor loadings were high. There was a statistically significant difference in total CORE-OM scores across the five tinnitus problem categories. However there was no significant difference between those who rated their tinnitus ‘not a problem’, and ‘a small problem’ or ‘a moderate problem.’ CONCLUSION: This study found a 3-factor structure for the CORE-OM to be a good fit for a tinnitus population. It also found evidence of a relationship between emotional distress as measured by CORE-OM and perception of tinnitus as a problem. Its use in tinnitus clinics is to be recommended, particularly when emotional distress is a target of therapy

The neurobiology of HIV dementia: implications for practice in South Africa

In this review, the neuropathogenesis of HIV dementia (HIV-D) is discussed in the context of the local epidemic. HIV-D continues to be prevalent in the era of highly active anti-retroviral therapy. HIV neuro-invasion into the central nervous system may result in the development of separate HIV genotypes in an individual through compartmentalisation. The blood brain barrier continues to limit penetration of anti-retroviral drugs into the cerebrospinal fluid. Individuals with active neuro-inflammation appear to respond well to HAART. In some cases low grade neuro-degeneration persists with consequent clinical deterioration. In South Africa, the emergence of a sub-epidemic of HIV-D is being driven by various factors, including the incomplete coverage of HAART to all who need it, the late stage presentation of people living with HIV/AIDS (PLWHA) and a co-occurring methamphetamine epidemic. Differences in viral subtype do not appear to confer protection against HIV-D. Implications for PLWHA who are at risk for HIV-D in South Africa are explored, with a view to providing suggestions for improving practice and research into this area.Key words: Dementia; HIV; HAART; South Afric

A biological survey of the Blakeney Freshes: North Norfolk

Blakeney Freshes in an area of low-lying grazing marsh on the North Norfolk coast, formed by the reclamation of salt marshes behind Blakeney spit (Figures 1 & 2). The area has long been recognised for its conservation value and was identified by Ratcliffe (1977) to be a Grade 1 site in the Nature Conservation Review. Reid et al. (1989) reiterated this describing the site as being of “key importance” due to it comprising of one of the most extensive areas of oligohaline-mesohaline grazing marsh in Norfolk. The marshes are particularly noted for a range of wintering and breeding birds, but also for the aquatic flora and fauna which inhabit the 25 km of drainage ditches that form a network across the site (Foster & Jackson 2000)

Tributyltin (TBT) and the decline of the Norfolk Broads: Hickling Broad and Barton Broad

This study furthers the work of Sayer et al (2001), in which a model was presented regarding the collapse of the plant-dominated state in the aquatic ecosystem of the Norfolk Broads, E. England. The boat antifouling biocide tributyltin (TBT) was implicated as a toxic switching mechanism from evidence gathered in a palaeolimnological study of Wroxham Broad

Balancing the dilution and oddity effects: Decisions depend on body size

Background Grouping behaviour, common across the animal kingdom, is known to reduce an individual's risk of predation; particularly through dilution of individual risk and predator confusion (predator inability to single out an individual for attack). Theory predicts greater risk of predation to individuals more conspicuous to predators by difference in appearance from the group (the ‘oddity’ effect). Thus, animals should choose group mates close in appearance to themselves (eg. similar size), whilst also choosing a large group. Methodology and Principal Findings We used the Trinidadian guppy (Poecilia reticulata), a well known model species of group-living freshwater fish, in a series of binary choice trials investigating the outcome of conflict between preferences for large and phenotypically matched groups along a predation risk gradient. We found body-size dependent differences in the resultant social decisions. Large fish preferred shoaling with size-matched individuals, while small fish demonstrated no preference. There was a trend towards reduced preferences for the matched shoal under increased predation risk. Small fish were more active than large fish, moving between shoals more frequently. Activity levels increased as predation risk decreased. We found no effect of unmatched shoal size on preferences or activity. Conclusions and Significance Our results suggest that predation risk and individual body size act together to influence shoaling decisions. Oddity was more important for large than small fish, reducing in importance at higher predation risks. Dilution was potentially of limited importance at these shoal sizes. Activity levels may relate to how much sampling of each shoal was needed by the test fish during decision making. Predation pressure may select for better decision makers to survive to larger size, or that older, larger fish have learned to make shoaling decisions more efficiently, and this, combined with their size relative to shoal-mates, and attractiveness as prey items influences shoaling decisions

A wide-spectrum language for verification of programs on weak memory models

Modern processors deploy a variety of weak memory models, which for efficiency reasons may (appear to) execute instructions in an order different to that specified by the program text. The consequences of instruction reordering can be complex and subtle, and can impact on ensuring correctness. Previous work on the semantics of weak memory models has focussed on the behaviour of assembler-level programs. In this paper we utilise that work to extract some general principles underlying instruction reordering, and apply those principles to a wide-spectrum language encompassing abstract data types as well as low-level assembler code. The goal is to support reasoning about implementations of data structures for modern processors with respect to an abstract specification. Specifically, we define an operational semantics, from which we derive some properties of program refinement, and encode the semantics in the rewriting engine Maude as a model-checking tool. The tool is used to validate the semantics against the behaviour of a set of litmus tests (small assembler programs) run on hardware, and also to model check implementations of data structures from the literature against their abstract specifications

Periodic methanol masers: from a colliding wind binary (CWB) perspective

Since the discovery of periodic class II methanol masers at 6.7 and 12.2 GHz associated with high-mass star formation regions (HMSFRs), a number of possible driving mechanisms have been proposed to explain this phenomenon. Here, we apply a more realistic treatment of the original colliding wind binary (CWB) model explanation to investigate to what extent it can describe the flare profiles of the periodic methanol masers. It was found that the CWB hypothesis is feasible from an energetics standpoint, because the emission from the shocked gas does cause an outward shift of the position of the ionization front (IF). This confirms that the energy budget available from the shocked gas is enough to be the driving force behind the CWB model. The CWB model describes the light curve of the 1.25 km s−1 12.2 GHz velocity feature of G9.62 + 0.20E very well over 4000 d. The quiescent state flux density of the 1.25 km s−1 velocity feature can also be described very well by the time-dependent change in electron density (ne). The CWB model also describes the other periodic methanol masers, G22.357 + 0.066, G37.55 + 0.20, and G45.473 + 0.134, which have similar light curves, very well. This strongly suggests that these periodic methanol masers can be described by the time-dependent change in the free–free emission from some part of the background H II region against which the masers are projected

Treatment options for subjective tinnitus: Self reports from a sample of general practitioners and ENT physicians within Europe and the USA

<p>Abstract</p> <p>Background</p> <p>Tinnitus affects about 10-15% of the general population and risks for developing tinnitus are rising through increased exposure to leisure noise through listening to personal music players at high volume. The disorder has a considerable heterogeneity and so no single mechanism is likely to explain the presence of tinnitus in all those affected. As such there is no standardized management pathway nor singly effective treatment for the condition. Choice of clinical intervention is a multi-factorial decision based on many factors, including assessment of patient needs and the healthcare context. The present research surveyed clinicians working in six Westernized countries with the aims: a) to establish the range of referral pathways, b) to evaluate the typical treatment options for categories of subjective tinnitus defined as acute or chronic, and c) to seek clinical opinion about levels of satisfaction with current standards of practice.</p> <p>Methods</p> <p>A structured online questionnaire was conducted with 712 physicians who reported seeing at least one tinnitus patients in the previous three months. They were 370 general practitioners (GPs) and 365 ear-nose-throat specialists (ENTs) from the US, Germany, UK, France, Italy and Spain.</p> <p>Results</p> <p>Our international comparison of health systems for tinnitus revealed that although the characteristics of tinnitus appeared broadly similar across countries, the patient's experience of clinical services differed widely. GPs and ENTs were always involved in referral and management to some degree, but multi-disciplinary teams engaged either neurology (Germany, Italy and Spain) or audiology (UK and US) professionals. For acute subjective tinnitus, pharmacological prescriptions were common, while audiological and psychological approaches were more typical for chronic subjective tinnitus; with several specific treatment options being highly country specific. All therapy options were associated with low levels of satisfaction.</p> <p>Conclusions</p> <p>Despite a large variety of treatment options, the low success rates of tinnitus therapy lead to frustration of physicians and patients alike. For subjective tinnitus in particular, effective therapeutic options with guidelines about key diagnostic criteria are urgently needed.</p

Logics for Petri nets with propagating failures

Petri nets play a central role in the formal modelling of a wide range of complex systems and scenarios. Their ability to handle with both concurrency and resource awareness justifies their spread in the current formal development practices. On the logic side, Dynamic Logics are widely accepted as the de facto formalisms to reason about computational systems. However, as usual, the application to new situations raises new challenges and issues. The ubiquity of failures in the execution of current systems, interpreted in these models as triggered events that are not followed by the corresponding transition, entails not only the adjustment of these structures to deal with this reality, but also the introduction of new logics adequate to this emerging phenomenon. This paper contributes to this challenge by exploring a combination of two previous works of the authors, namely the Propositional Dynamic Logic for Petri Nets [1] and a parametric construction of multi-valued dynamic logics presented in [13]. This exercise results in a new family of Dynamic Logics for Petri Nets suitable to deal with firing failures.publishe