17,470 research outputs found

    Early detection of disease program: Evaluation of the cellular immune response

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    Surfaces of normal, cultured, and mitogen-stimulated mouse lymphoid cells were examined by scanning electron microscopy (SEM). Lymphocytes with smooth, highly villous and intermediate surfaces were observed in cell suspensions from both spleens and thymuses of normal mice and from spleens of congenitally athymic (nude) mice. Several strain-specific surface features were noted, including the spine-like appearance of microvilli on C57B1/6 lymphocytes. Although thymus cell suspensions contained somewhat more smooth cells than did spleen cell preparations, lymphocyte derivation could not be inferred from SEM examination. Studies of cells stimulated with mitogenic agents for thymus-derived lymphocytes (concanavalin A) or for bone marrow-derived lymphocytes (lipopolysaccharide) suggested that, in the mouse, development of a complex villous surface is a general concomitant of lymphocyte activation and transformation

    Hot entanglement in a simple dynamical model

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    How mixed can one component of a bi-partite system be initially and still become entangled through interaction with a thermalized partner? We address this question here. In particular, we consider the question of how mixed a two-level system and a field mode may be such that free entanglement arises in the course of the time evolution according to a Jaynes-Cummings type interaction. We investigate the situation for which the two-level system is initially in mixed state taken from a one-parameter set, whereas the field has been prepared in an arbitrary thermal state. Depending on the particular choice for the initial state and the initial temperature of the quantised field mode, three cases can be distinguished: (i) free entanglement will be created immediately, (ii) free entanglement will be generated, but only at a later time different from zero, (iii) the partial transpose of the joint state remains positive at all times. It will be demonstrated that increasing the initial temperature of the field mode may cause the joint state to become distillable during the time evolution, in contrast to a non-distillable state at lower initial temperatures. We further assess the generated entanglement quantitatively, by evaluating the logarithmic negativity numerically, and by providing an analytical upper bound.Comment: 5 pages, 2 figures. Contribution to the proceedings of the 'International Conference on Quantum Information', Oviedo, July 13-18, 2002. Discusses sudden changes of entanglement properties in a dynamical quantum mode

    Critical issues in designing and implementing temporal analytics.

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    The importance of temporality in learning has been long established, but it is only recently that serious attention has begun to be paid to the precise identification, measurement, and analysis of the temporal features of learning. From 2009 to 2016, a series of temporality workshops explored temporal concepts and data types, analysis methods for exploiting temporal data, techniques for visualizing temporal information, and practical considerations for the use of temporal analyses in particular contexts of learning. Following from these efforts, this two-part Special Section serves to consolidate research working to progress conceptual, technical and practical tools for temporal analyses of learning data. In addition, in this second and final editorial we aim to make four contributions to the ongoing dialouge around temporal learning analytics to help us move towards a clearer mapping of the research space. First, the editorial presents an overview of the five papers in Part 2 of the Special Section on Temporal Analyses, highlighting the dimensions of data types, learning constructs, analysis approaches, and potential impact. Second, it draws on the fluid relationship between ‘analyzed time’ and ‘experienced time’ to highlight the need for caution and criticality in the purposes temporal analyses are mobilized to serve. Third it offers a guide for future work in this area by outlining important questions that all temporal analyses should intentionally address. Finally, it proposes next steps learning analytics researchers and practitioners can take collectively to advance work on the use of temporal analyses to support learning

    Thermal convection in fluidized granular systems

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    Thermal convection is observed in molecular dynamic simulation of a fluidized granular system of nearly elastic hard disks moving under gravity, inside a rectangular box. Boundaries introduce no shearing or time dependence, but the energy injection comes from a slip (shear-free) thermalizing base. The top wall is perfectly elastic and lateral boundaries are either elastic or periodic. The observed convection comes from the effect of gravity and the spontaneous granular temperature gradient that the system dynamically develops.Comment: 4 pages, 5 figure

    Austral seabirds: challenges and opportunities for research and conservation

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    This paper draws together the themes of papers on procellariiform biology contained within this special issue of the Papers and Proceedings ofthe Royal Society ofTasmania which is a tribute to Irynej Skira. The role of these birds as generalised biomonitors of marine ecosystem health as well as their important interactions with commercial fisheries and human societies are major considerations. Seabird conservation faces challenges from introduced pest loss of habitat to urban development, marine pollution and climate and oceanographic changes. Studies are hampered by the difficulties of dealing with birds in remote areas (that are therefore expensive to study), a paucity of funds and problems of overlapping national and international jurisdictions in their individual home ranges or on their migration routes. There is a real need for long-term studies ofseabirds because they have delayed breeding systems, a slow rate ofreproduction, long life-spans and high adult survival. Such knowledge is important in understanding their population dynamics, the effects of changing climate, the impacts of commercial fishing, pollution, breeding habitat loss and the harvesting of chicks. The value of the long-term studies of Shorttailed Shearwaters, Puffinus tenuirostris on Fisher Island, Tasmania, is considered in the light of the importance of research investment in basic curiosity-driven research. Neglect of long-term studies and the diminishing role of local scientific journals in the dissemination of baseline data on which to build generalities are the result of changing priorities of government and other funding agencies towards shortterm output-based assessment models. Our present inability to answer the basic question of what determines seabird population abundance and distribution highlights a lack of fundamental population data in Austral seabird research. This must be addressed so that a mixture of comparative, experimental and modelling studies can be mobilised to complement descriptive studies

    Perceptual prioritization of self-associated voices

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    Information associated with the self is prioritized relative to information associated with others and is therefore processed more quickly and accurately. Across three experiments, we examined whether a new externally‐generated voice could become associated with the self and thus be prioritized in perception. In the first experiment, participants learned associations between three unfamiliar voices and three identities (self, friend, stranger). Participants then made speeded judgements of whether voice‐identity pairs were correctly matched, or not. A clear self‐prioritization effect was found, with participants showing quicker and more accurate responses to the newly self‐associated voice relative to either the friend‐ or stranger‐ voice. In two further experiments, we tested whether this prioritization effect increased if the self‐voice was gender‐matched to the identity of the participant (Experiment 2) or if the self‐voice was chosen by the participant (Experiment 3). Gender‐matching did not significantly influence prioritization; the self‐voice was similarly prioritized when it matched the gender identity of the listener as when it did not. However, we observed that choosing the self‐voice did interact with prioritization (Experiment 3); the self‐voice became more prominent, via lesser prioritization of the other identities, when the self‐voice was chosen relative to when it was not. Our findings have implications for the design and selection of individuated synthetic voices used for assistive communication devices, suggesting that agency in choosing a new vocal identity may modulate the distinctiveness of that voice relative to others

    Chalcogenide phase change materials for nanoscale switching

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    Since the demonstration of threshold switching in chalcogenide alloys over forty five years ago, phase change materials have been extensively investigated for switching and data storage applications. Phase change switching is based on the reversible change between crystalline and amorphous states of a material and in many chalcogenides this change of state takes place in nanoseconds

    The Design and Validation of the Quantum Mechanics Conceptual Survey

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    The Quantum Mechanics Conceptual Survey (QMCS) is a 12-question survey of students' conceptual understanding of quantum mechanics. It is intended to be used to measure the relative effectiveness of different instructional methods in modern physics courses. In this paper we describe the design and validation of the survey, a process that included observations of students, a review of previous literature and textbooks and syllabi, faculty and student interviews, and statistical analysis. We also discuss issues in the development of specific questions, which may be useful both for instructors who wish to use the QMCS in their classes and for researchers who wish to conduct further research of student understanding of quantum mechanics. The QMCS has been most thoroughly tested in, and is most appropriate for assessment of (as a posttest only), sophomore-level modern physics courses. We also describe testing with students in junior quantum courses and graduate quantum courses, from which we conclude that the QMCS may be appropriate for assessing junior quantum courses, but is not appropriate for assessing graduate courses. One surprising result of our faculty interviews is a lack of faculty consensus on what topics should be taught in modern physics, which has made designing a test that is valued by a majority of physics faculty more difficult than expected.Comment: Submitted to Physical Review Special Topics: Physics Education Researc
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