22,855 research outputs found

    Two passages in pseudo-Xenophon

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    This paper discusses textual problems in [Xenophon] Athenian Constitution 2.9 and 3.5

    On isoperimetric inequalities with respect to infinite measures

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    We study isoperimetric problems with respect to infinite measures on RnR ^n. In the case of the measure μ\mu defined by dμ=ec∣x∣2dxd\mu = e^{c|x|^2} dx, c≄0c\geq 0, we prove that, among all sets with given Ī¼āˆ’\mu-measure, the ball centered at the origin has the smallest (weighted) Ī¼āˆ’\mu-perimeter. Our results are then applied to obtain Polya-Szego-type inequalities, Sobolev embeddings theorems and a comparison result for elliptic boundary value problems.Comment: 25 page

    Quick X-ray Reflectivity using Monochromatic Synchrotron Radiation for Time-Resolved Applications

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    We describe and demonstrate a new technique for parallel collection of x-ray reflectivity data, compatible with monochromatic synchrotron radiation and flat substrates, and apply it to the in-situ observation of thin-film growth. The method employs a polycapillary x-ray optic to produce a converging fan of radiation incident onto a sample surface, and an area detector to simultaneously collect the XRR signal over an angular range matching that of the incident fan. Factors determining the range and instrumental resolution of the technique in reciprocal space, in addition to the signal-to-background ratio, are described in detail. Our particular implementation records ∼\sim5\degree{} in 2θ2\theta and resolves Kiessig fringes from samples with layer thicknesses ranging from 3 to 76 nm. Finally, we illustrate the value of this approach by showing in-situ XRR data obtained with 100 ms time resolution during the growth of epitaxial \ce{La_{0.7}Sr_{0.3}MnO3} on \ce{SrTiO3} by Pulsed Laser Deposition (PLD) at the Cornell High Energy Synchrotron Source (CHESS). Compared to prior methods for parallel XRR data collection, ours is the first method that is both sample-independent and compatible with highly collimated, monochromatic radiation typical of 3rd generation synchrotron sources. Further, our technique can be readily adapted for use with laboratory-based sources.Comment: Accepted in Journal of Synchrotron Radiatio

    Intuition and insight: two concepts that illuminate the tacit in science education

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    Tacit knowledge, that is knowledge not expressible in words, may play a role in learning science, yet it is difficult to study directly. Intuition and insight, two processes that link the tacit and the explicit, are proposed as a route to investigating tacit knowledge. Intuitions are defined as tacit hunches or feelings that influence thought with little conscious effort. This paper examines conceptualisations of intuition as embodied cognition, and as abstracted rules before examining reports of intuition in the work of scientists and in science education. Insight is described as an explicit awareness of novel relations between concepts that arrives with little conscious control. Insight is related to rapid conceptual change and the development of conceptual connections. Reports of insight in the work of scientists and in the science classroom are discussed. The manner in which insight and intuition may promote and hinder learning is considered and conditions that affect the use of both processes are suggested. Strategies that might encourage students’ use of intuition and insight in the classroom are proposed. The paper concludes with a call for a greater focus on the concept of tacit knowledge in science education and suggests areas for future research

    Posttraumatic Stress and Parenting Behaviors: The Mediating Role of Emotion Regulation

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    Maternal trauma has been linked with problematic parenting, including both harsh and permissive behaviors. However, little is known about mechanisms accounting for this association. The current study examined the potential impact of posttraumatic stress disorder (PTSD) and emotion regulation on dysfunctional parenting behaviors in a sample of community mothers. We hypothesized a mediation model wherein PTSD would be associated with dysfunctional parenting (i.e., lax and overreactive behaviors) indirectly through deficits in maternal emotion regulation. Seventy-eight community mothers of 18- to 36-month-old children were administered the Clinician Administered PTSD Scale for DSM-5 (CAPS-5) and 19 mothers met criteria for PTSD. Mothers also completed self-report measures of difficulties with emotion regulation and maternal laxness and overreactivity in parenting. Results revealed that emotion dysregulation fully mediated relations between PTSD status and lax (but not overreactive) parenting behaviors. Compared to mothers without PTSD, those with PTSD reported greater lax parenting behaviors indirectly through greater emotion dysregulation. Mothers with PTSD may struggle to parent assertively when trauma symptoms interfere with emotion regulation abilities. The current study highlights the need to design interventions focused on helping trauma-exposed mothers manage distress, ultimately aiming to enhance parenting effectiveness and improve child outcomes
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