1,939 research outputs found

    The Occurrence of PCBs and Chlorinated Pesticide Contaminants in Bottlenose Dolphins (Tursiops truncatus) in a Resident Community: Comparison with Age, Gender and Birth Order

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    Tissue samples from twenty bottlenose dolphins from a stable, residential community of coastal dolphins in the western Gulf of Mexico were analyzed for toxic PCB congeners and chlorinated pesticides. The tissues analyzed (blubber and melon) were from known individuals in a long-term (27+ y) study that stranded and were recovered for necropsy. Substantial demographic data were available on these individuals and utilized in the analysis of maternal transfer of organochlorines to young. The male dolphins in this study were shown to accumulate organochlorine contaminants with age. In female dolphins the organochlorine levels were found to decline with age. These results are in agreement with previous studies, with gestational and lactational transfer accounting for the decline seen in the females. A lengthening in interreproductive interval by increasing organochlorine levels after approximately age 30 y is noted in the females. For the first time, this study quantified the organochlorine levels of the first calf of a female, testing the hypothesis that the first-born of a female receives a substantially greater organochlorine load than subsequent calves. The first-born calf (age 5.3 mo) had the highest blubber ΣPCB, total DDT, HCB, and total pesticide levels of all animals in this study. The organochlorine levels in this calf were 2-5 fold higher than in a similarly aged, fourth-born calf. All animals in this study had appreciable EPCBlevels (range 0.07 - 26.9 ug/g wet weight; 2.6 - 203.2 ug/g lipid weight), and EDDT (range 0.06 - 10.3 wet weight; 0.9 - 88.1 ug/g lipid weight). These values are in a moderate range compared to other studies, but not far below levels at which western Gulf of Mexico bottlenose dolphins evidenced mortality events in 1990 and 1992. Further monitoring of this population is warranted

    North Florida Trees

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    Artist Statement I began exploring manipulation and fabrication in the darkroom after a workshop in Alexander Diaz’s Introduction to Photography course. I have always had an affinity for nature, especially trees. I was especially moved by the barren trees seen during a cold North Florida winter. Growing up in Florida, I’m used to seeing the vast greenery brought by these trees, but there was just something about their emptiness during winter that really struck me. I wanted to capture and print them in a way that emphasized these qualities. Black and white film paired with splattering in the darkroom was a perfect medium for expressing these trees’ desolate and broken characteristics

    Theorizing the Concept of Agency in Human-Algorithmic Ensembles with a Socio-Technical Lens

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    The growing relevance of algorithmic systems, including artificial intelligence, for processes of value creation raise theoretical and practical interest in the conceptualization of actorhood and the balancing of human and technological agencies within socio-technical ensembles. Prominent theories of the IS discipline still reflect a human-centric conceptualization of agency, which we deem challenged by advances in machine learning technology. We therefore motivate a revised theorizing of the concept of agency with a socio-technical lens. For that, we apply an inductive top-down theorizing approach. In this short paper, we present the first inductive step by describing tensions, oppositions and contradictions in the discourse on agency in IS literature of the last 30 years in the AIS Senior Scholars’ Basket of journals. The preliminary findings uncover a conceptual and ontological incoherence surrounding the concept of agency in IS scholarship, and a gap between reviewed publications and the agency claims of algorithmic systems

    Approximate Inference for Robust Gaussian Process Regression

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    Gaussian process (GP) priors have been successfully used in non-parametric Bayesian regression and classification models. Inference can be performed analytically only for the regression model with Gaussian noise. For all other likelihood models inference is intractable and various approximation techniques have been proposed. In recent years expectation-propagation (EP) has been developed as a general method for approximate inference. This article provides a general summary of how expectation-propagation can be used for approximate inference in Gaussian process models. Furthermore we present a case study describing its implementation for a new robust variant of Gaussian process regression. To gain further insights into the quality of the EP approximation we present experiments in which we compare to results obtained by Markov chain Monte Carlo (MCMC) sampling

    A longitudinal study of adolescent Internet addiction: the role of conscientiousness and classroom hostility

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    Over the last decade, research on Internet Addiction (IA) has increased. However, almost all studies in this area are cross-sectional and do not examine the context in which internet use takes place. Therefore, a longitudinal study examined the role of conscientiousness (as a personality trait) and classroom hostility (as a contextual factor) in the development of IA. The participants comprised 648 adolescents and were assessed over a two-year period (while aged 16–18 years). A three-level hierarchical linear model was carried out on the data collected. Findings revealed that: (i) lower conscientiousness was associated with IA and this did not change over time; and (ii) although being in a more hostile classroom did not initially have a significant effect, it increased girls’ IA vulnerability over time and functioned protectively for boys. Results indicated that the contribution of individual and contextual IA factors may differ across genders and over time. More specifically, although the protective effect of conscientiousness appeared to hold, the over-time effect of classroom hostility increased the risk of IA for girls. These findings are discussed in relation to the psychological literature. The study’s limitations and implications are also discussed
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