4,127 research outputs found

    A study of the toxic principle in red clover

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    A report on Department of Agricultural Chemistry research project 247, Forage Poisoning--P. [2].Digitized 2007 AES.Includes bibliographical references (page 12)

    Multiply Folded Graphene

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    The folding of paper, hide, and woven fabric has been used for millennia to achieve enhanced articulation, curvature, and visual appeal for intrinsically flat, two-dimensional materials. For graphene, an ideal two-dimensional material, folding may transform it to complex shapes with new and distinct properties. Here, we present experimental results that folded structures in graphene, termed grafold, exist, and their formations can be controlled by introducing anisotropic surface curvature during graphene synthesis or transfer processes. Using pseudopotential-density functional theory calculations, we also show that double folding modifies the electronic band structure of graphene. Furthermore, we demonstrate the intercalation of C60 into the grafolds. Intercalation or functionalization of the chemically reactive folds further expands grafold's mechanical, chemical, optical, and electronic diversity.Comment: 29 pages, 10 figures (accepted in Phys. Rev. B

    The Mid-Infrared Instrument for the James Webb Space Telescope, VII: The MIRI Detectors

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    The MIRI Si:As IBC detector arrays extend the heritage technology from the Spitzer IRAC arrays to a 1024 x 1024 pixel format. We provide a short discussion of the principles of operation, design, and performance of the individual MIRI detectors, in support of a description of their operation in arrays provided in an accompanying paper (Ressler et al. (2015)). We then describe modeling of their response. We find that electron diffusion is an important component of their performance, although it was omitted in previous models. Our new model will let us optimize the bias voltage while avoiding avalanche gain. It also predicts the fraction of the IR-active layer that is depleted (and thus contributes to the quantum efficiency) as signal is accumulated on the array amplifier. Another set of models accurately predicts the nonlinearity of the detector-amplifier unit and has guided determination of the corrections for nonlinearity. Finally, we discuss how diffraction at the interpixel gaps and total internal reflection can produce the extended cross-like artifacts around images with these arrays at short wavelengths, ~ 5 microns. The modeling of the behavior of these devices is helping optimize how we operate them and also providing inputs to the development of the data pipeline

    The medical licensing examination debate

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    National licensing examinations are typically large-scale examinations taken early in a career or near the point of graduation, and, importantly, success is required to subsequently be able to practice. They are becoming increasingly popular as a method of quality assurance in the medical workforce, but debate about their contribution to patient safety and the improvement of healthcare outcomes continues. A systematic review of the national licensing examination literature demonstrates that there is disagreement between assessment experts about the strengths and challenges of licensing examinations. This is characterized by a trans-Atlantic divide between the dominance of psychometric reliability assurance in North America and the wider interpretations of validity, to include consequences, in Europe. We conclude that the debate might benefit from refocusing to what a national licensing examination should assess: to achieve a balance between assessing a breadth of skills and the capacity for such skills in practice, and focusing less on reproducibility

    The International Landscape of Medical Licensing Examinations: A Typology Derived From a Systematic Review

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    Background National licensing examinations (NLEs) are large-scale examinations usually taken by medical doctors close to the point of graduation from medical school. Where NLEs are used, success is usually required to obtain a license for full practice. Approaches to national licensing, and the evidence that supports their use, varies significantly across the globe. This paper aims to develop a typology of NLEs, based on candidacy, to explore the implications of different examination types for workforce planning. Methods A systematic review of the published literature and medical licensing body websites, an electronic survey of all medical licensing bodies in highly developed nations, and a survey of medical regulators. Results The evidence gleaned through this systematic review highlights four approaches to NLEs: where graduating medical students wishing to practice in their national jurisdiction must pass a national licensing exam before they are granted a license to practice; where all prospective doctors, whether from the national jurisdiction or international medical graduates, are required to pass a national licensing exam in order to practice within that jurisdiction; where international medical graduates are required to pass a licensing exam if their qualifications are not acknowledged to be comparable with those students from the national jurisdiction; and where there are no NLEs in operation. This typology facilitates comparison across systems and highlights the implications of different licensing systems for workforce planning. Conclusion The issue of national licensing cannot be viewed in isolation from workforce planning; future research on the efficacy of national licensing systems to drive up standards should be integrated with research on the implications of such systems for the mobility of doctors to cross borders

    Very Luminous Carbon Stars in the Outer Disk of the Triangulum Spiral Galaxy

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    Stars with masses in the range from about 1.3 to 3.5 Mo pass through an evolutionary stage where they become carbon stars. In this stage, which lasts a few Myr, these stars are extremely luminous pulsating giants. They are so luminous in the near-infrared that just a few of them can double the integrated luminosity of intermediate-age (0.6 to 2 Gyr) Magellanic Cloud clusters at 2.2 microns. Astronomers routinely use such near-infrared observations to minimize the effects of dust extinction, but it is precisely in this band that carbon stars can contribute hugely. The actual contribution of carbon stars to the outer disk light of evolving spiral galaxies has not previously been morphologically investigated. Here we report new and very deep near-IR images of the Triangulum spiral galaxy M33=NGC 598, delineating spectacular arcs of carbon stars in its outer regions. It is these arcs which dominate the near-infrared m=2 Fourier spectra of M33. We present near-infrared photometry with the Hale 5-m reflector, and propose that the arcs are the signature of accretion of low metallicity gas in the outer disk of M33.Comment: 4 pages, 4 figures. Revised version submitted to A&A Letter

    Nucleon Edm from Atomic Systems and Constraints on Supersymmetry Parameters

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    The nucleon EDM is shown to be directly related to the EDM of atomic systems. From the observed EDM values of the atomic Hg system, the neutron EDM can be extracted, which gives a very stringent constraint on the supersymmetry parameters. It is also shown that the measurement of Nitrogen and Thallium atomic systems should provide important information on the flavor dependence of the quark EDM. We perform numerical analyses on the EDM of neutron, proton and electron in the minimal supersymmetric standard model with CP-violating phases. We demonstrate that the new limit on the neutron EDM extracted from atomic systems excludes a wide parameter region of supersymmetry breaking masses above 1 TeV, while the old limit excludes only a small mass region below 1 TeV.Comment: 10 pages, 7 figure file
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