248 research outputs found

    Global genetic homogeneity in the deep-sea foraminiferan Epistominella exigua (Rotaliida: Pseudoparrellidae)

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    Epistominella exigua is one of the most common deep-sea foraminiferal morphospecies and has a world-wide distribution. A recent molecular study revealed high genetic similarity between Arctic, Atlantic and Antarctic populations of this species. Here, we show that the small-subunit (SSU) and internal transcribed spacer (ITS) rDNA sequences of an E. exigua population from Pacific are almost identical to those reported previously from the other three oceans. This result confirms the genetic homogeneity of E. exigua, which contrasts with the prevalence of highly differentiated populations in planktonic and shallow-water benthic foraminiferans. We discuss special features of diversifications mechanisms in the deep sea that may be responsible for the lack of genetic differentiation and global distribution of some meiofauna species

    Mapping Perceptions of Burnout in the Information Technology Profession: A Study Using Social Representations Theory

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    Job-related burnout in information technology professionals is seen as a serious issue for organizations and individuals. While the substantial body of research on job stress and burnout can provide valuable insights into the prevention of burnout in IT as well as interventions, we argue that drawing upon this work should be done with caution. In particular, generalizability of the learnings beyond the occupations studied (predominantly people-oriented and/or caregiving roles) cannot be assumed. As a first step toward assessing the applicability of existing burnout research to IT, the purpose of the study described in this paper is to understand how IT professionals make sense of and assign meaning to burnout in the profession. The study uses an approach based on social representations theory, which was first formulated by French social psychologist Serge Moscovici. Social representations are defined as the shared images and concepts through which we organize our world. Transcripts from in-depth interviews of 20 IT professionals were content- analyzed and 22 key topics (concepts) identified. Quantitative methods (including analysis of similarity and analyses to determine the relational structure of the concepts) were used to create a social representations map of these professionals’ understandings of burnout. The map provides preliminary evidence of elements that are central/peripheral to those understandings, pointing to implications for the applicability of existing theory on burnout as well as priorities for future research

    Quantitative evaluation of performance of three-dimensional printed lenses

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    We present an analysis of the shape, surface quality, and imaging capabilities of custom three-dimensional (3-D) printed lenses. 3-D printing technology enables lens prototypes to be fabricated without restrictions on surface geometry. Thus, spherical, aspherical, and rotationally nonsymmetric lenses can be manufactured in an integrated production process. This technique serves as a noteworthy alternative to multistage, labor-intensive, abrasive processes, such as grinding, polishing, and diamond turning. Here, we evaluate the quality of lenses fabricated by Luxexcel using patented Printoptical© technology that is based on an inkjet printing technique by comparing them to lenses made with traditional glass processing technologies (grinding, polishing, etc.). The surface geometry and roughness of the lenses were evaluated using white-light and Fizeau interferometers. We have compared peak-to-valley wavefront deviation, root mean square (RMS) wavefront error, radii of curvature, and the arithmetic roughness average (Ra) profile of plastic and glass lenses. In addition, the imaging performance of selected pairs of lenses was tested using 1951 USAF resolution target. The results indicate performance of 3-D printed optics that could be manufactured with surface roughness comparable to that of injection molded lense

    Modernizing Biomedical Training: Replacing Live Animal Laboratories with Human Simulation

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    This chapter reviews the global trend towards a modernization of biomedical education in favor of simulation-based training methods, which studies confirm improve student learning and transference of applied skills to clinical practice, reduce laboratory costs, and spare animals from harmful procedures

    Inexact Newton Dogleg Methods

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    The dogleg method is a classical trust-region technique for globalizing Newton\u27s method. While it is widely used in optimization, including large-scale optimization via truncated-Newton approaches, its implementation in general inexact Newton methods for systems of nonlinear equations can be problematic. In this paper, we first outline a very general dogleg method suitable for the general inexact Newton context and provide a global convergence analysis for it. We then discuss certain issues that may arise with the standard dogleg implementational strategy and propose modified strategies that address them. Newton-Krylov methods have provided important motivation for this work, and we conclude with a report on numerical experiments involving a Newton-GMRES dogleg method applied to benchmark CFD problems

    Adjoint based a posteriori error estimation in Drekar::CFD.

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