21,438 research outputs found
The efficacy of emamectin benzoate against infestations of Lepeophtheirus salmonis on farmed Atlantic salmon (Salmo salar L) in Scotland, 2002-2006
No full textInfestations of the parasitic copepod Lepeophtheirus salmonis, commonly referred to as sea lice, represent a major challenge to commercial salmon aquaculture. Dependence on a limited number of theraputants to control such infestations has led to concerns of reduced sensitivity in some sea lice populations. This study investigates trends in the efficacy of the in-feed treatment emamectin benzoate in Scotland, the active ingredient most widely used across all salmon producing regions. Study data were drawn from over 50 commercial Atlantic salmon farms on the west coast of Scotland between 2002 and 2006. An epi-informatics approach was adopted whereby available farm records, descriptive epidemiological summaries and statistical linear modelling methods were used to identify factors that significantly affect sea lice abundance following treatment with emamectin benzoate (SLICEH, Schering Plough Animal Health). The results show that although sea lice infestations are reduced following the application of emamectin benzoate, not all treatments are effective. Specifically there is evidence of variation across geographical regions and a reduction in efficacy over time. Reduced sensitivity and potential resistance to currently available medicines are constant threats to maintaining control of sea lice populations on Atlantic salmon farms. There is a need for on-going monitoring of emamectin benzoate treatment efficacy together with reasons for any apparent reduction in performance. In addition, strategic rotation of medicines should be encouraged and empirical evidence for the benefit of such strategies more fully evaluated
Factors associated with changing efficacy of emamectin benzoate against infestations of Lepeophtheirus salmonison Scottish salmon farms
No full textThe availability and use of medicines to control infestations of sea lice on Atlantic salmon, Salmosalar L., farms in Scotland has changed considerably in the last decade (Lees, Gettinby & Revie 2008b). Whereas hydrogen peroxide and organophosphate compounds were used widely throughout the 1990s and in the early 2000s, only two therapeutants have remained in common use since 2005: topical cypermethrin (Excis; Novartis Animal Health, Camberley, UK) and an oral formulation of emamectin benzoate (SLICE; Schering Plough Animal Health, Uxbridge, UK)
Model selection with application to gamma process and inverse Gaussian process
No full textThe gamma process and the inverse Gaussian process are widely used in condition-based maintenance. Both are suitable for modelling monotonically increasing degradation processes. One challenge for practitioners is determining which of the two processes is most appropriate in light of a real data set. A common practice is to select the one with a larger maximized likelihood. However, due to variations in the data, the maximized likelihood of the “wrong” model could be larger than that of the “right” model. This paper proposes an efficient and broadly applicable test statistic for model selection. The construction of the test statistic is based on the Fisher information. Extensive numerical study is conducted to indicate the conditions under which the gamma process can be well approximated by the inverse Gaussian process, or the other way around
Confidence in assessing the effectiveness of bath treatments for the control of sea lice on Norwegian salmon farms
No full textThe salmon louse Lepeophtheirus salmonis is the most important ectoparasite of farmed salmonids in the Northern hemisphere, having a major economic and ecological impact on the sustainability of this sector of the aquaculture industry. To a large extent, control of L. salmonis relies on the use of topical delousing chemical treatments in the form of baths. Improvements in methods for the administration and assessment of bathtreatments have not kept pace with the rapid modernization and intensification of the salmon industry. Bathtreatments present technical and biological challenges, including best practice methods for the estimation of the effect of licetreatment interventions. In this communication, we compare and contrast methods to calculate and interpret treatmenteffectiveness at pen and site level. The methods are illustrated for the calculation of the percentage reduction in mean abundance of mobile lice with a measure of confidence. Six different methods for the calculation of confidence intervals across different probability levels were compared. We found the quasi-Poisson method with a 90% confidence interval to be informative and robust for the measurement of bathtreatment performance
What is the value of a standard?
No full textStandards play a critical role in the procurement of defence, and other, systems. Choosing the most appropriate standard is important but has become more topical given the UK Ministry of Defence policy of “as civilian as possible, as military as necessary”. Whereas historically managers might have selected from classes of defence standards, this choice set is now increased to include civil standards. We develop a model that has been commissioned by the UK Defence Standardisation whose responsibilities include supporting project teams on the selection of standards. Our model is based on an extension of Bayesian Belief Networks, called an Influence Diagram, which allows decisions and consequences to be represented as well as uncertain-ties. We have developed an initial model for a real case to assess the feasibility and use. We outline the con-text of the defence procurement project in our case study and describe the reasoning underpinning the model structure. We have found that it is possible to develop a simple model that captures the views of multiple stakeholders and informs a reasoned choice about the value of alternative standards
MV Farnella Cruises 8, 9/82, 26 February - 26 March 1982. Geophysical studies in the Nares Abyssal Plain and the King's Trough Flank. Recovery of tide gauges deployed in December 1981
Full text linkThe use of prevalence as a measure of lice burden: a case study of Lepeophtheirus salmonis on Scottish Atlantic salmon, Salmo salar L., farms
No full textThis study investigates the benefits of using prevalence as a summary measure of sea lice infestation on farmed Atlantic salmon, Salmo salar L. Aspects such as sampling effort, the relationship between abundance and prevalence arising from the negative binomial distribution, and how this relationship can be used to indicate the degree of aggregation of lice on a site at a given time point are discussed. As a case study, data were drawn from over 50 commercial Atlantic salmon farms on the west coast of Scotland between 2002 and 2006. Descriptive statistics and formal analysis using a linear modelling technique identified significant variations in sea lice prevalence across year class, region and season. Supporting evidence of a functional relationship between prevalence and abundance of sea lice is provided, which is explained through the negative binomial distribution
The effects of topic complexity and familiarity on cognitive and physical moves in a thesaurus-enhanced search environment
No full textThis paper presents an evaluation of the effects of search topic characteristics on cognitive and physical search moves within the interface of a thesaurus-enhanced information retrieval environment. Topic characteristics examined here are topic complexity, topic familiarity, search type and prior topic search experience. The data gathering techniques adopted in this investigation included pre- and post-search questionnaires, transaction logs and post-session interviews. Thirty academic staff and postgraduate researchers from the Faculty of Veterinary Medicine at the University of Glasgow participated in this study. Each participant conducted three searches based on their research information needs. The results show that complex topics are associated with significantly more cognitive and physical moves. However, it is perhaps equally important to note that the results indicate that variation in the other topic characteristics did not demonstrate any significant difference in the number of cognitive or physical moves
RV Farnella Cruises 1 and 2, 19 September - 5 November 1981. Geophysical studies of the continental margin on the eastern edge of the Grand Banks
Full text linkEvaluation of elicitation methods to quantify Bayes linear models
No full textThe Bayes linear methodology allows decision makers to express their subjective beliefs and adjust these beliefs as observations are made. It is similar in spirit to probabilistic Bayesian approaches, but differs as it uses expectation as its primitive. While substantial work has been carried out in Bayes linear analysis, both in terms of theory development and application, there is little published material on the elicitation of structured expert judgement to quantify models. This paper investigates different methods that could be used by analysts when creating an elicitation process. The theoretical underpinnings of the elicitation methods developed are explored and an evaluation of their use is presented. This work was motivated by, and is a precursor to, an industrial application of Bayes linear modelling of the reliability of defence systems. An illustrative example demonstrates how the methods can be used in practice
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