2,208 research outputs found

    Ensuring a Strong Public Health Workforce for the 21st Century: Reflections on PH WINS 2017

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    The success of any organization can be attributed to one thing: its people. This is particularly true for local health departments (LHDs) and state health agencies (SHAs), as the public health workforce is fundamental to achieving organizational goals and improving the health outcomes of populations

    Anisotropy in the Cosmic Microwave Background at Degree Angular Scales: Python V Results

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    Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m off-axis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37-45 GHz in two frequency bands. With a 0.91 deg x 1.02 deg beam the instrument fully sampled 598 deg^2 of sky, including fields measured during the previous four seasons of Python observations. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background, we place constraints on the angular power spectrum of fluctuations in eight multipole bands up to l ~ 260. The observed spectrum is consistent with both the COBE experiment and previous Python results. There is no significant contamination from known foregrounds. The results show a discernible rise in the angular power spectrum from large (l ~ 40) to small (l ~ 200) angular scales. The shape of the observed power spectrum is not a simple linear rise but has a sharply increasing slope starting at l ~ 150.Comment: 5 page

    Geophysics

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    Contains reports on three research projects

    Molecular Dynamics Simulation Study of Nonconcatenated Ring Polymers in a Melt: I. Statics

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    Molecular dynamics simulations were conducted to investigate the structural properties of melts of nonconcatenated ring polymers and compared to melts of linear polymers. The longest rings were composed of N=1600 monomers per chain which corresponds to roughly 57 entanglement lengths for comparable linear polymers. For the rings, the radius of gyration squared was found to scale as N to the 4/5 power for an intermediate regime and N to the 2/3 power for the larger rings indicating an overall conformation of a crumpled globule. However, almost all beads of the rings are "surface beads" interacting with beads of other rings, a result also in agreement with a primitive path analysis performed in the following paper (DOI: 10.1063/1.3587138). Details of the internal conformational properties of the ring and linear polymers as well as their packing are analyzed and compared to current theoretical models.Comment: 15 pages, 14 figure

    DASI First Results: A Measurement of the Cosmic Microwave Background Angular Power Spectrum

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    We present measurements of anisotropy in the Cosmic Microwave Background (CMB) from the first season of observations with the Degree Angular Scale Interferometer (DASI). The instrument was deployed at the South Pole in the austral summer 1999--2000, and made observations throughout the following austral winter. We have measured the angular power spectrum of the CMB in the range 100<l<900 with high signal-to-noise. In this paper we review the formalism used in the analysis, in particular the use of constraint matrices to project out contaminants such as ground and point source signals, and to test for correlations with diffuse foreground templates. We find no evidence of foregrounds other than point sources in the data, and find a maximum likelihood temperature spectral index beta = -0.1 +/- 0.2 (1 sigma), consistent with CMB. We detect a first peak in the power spectrum at l approx 200, in agreement with previous experiments. In addition, we detect a peak in the power spectrum at l approx 550 and power of similar magnitude at l approx 800 which are consistent with the second and third harmonic peaks predicted by adiabatic inflationary cosmological models.Comment: 8 pages, 1 figure, minor changes in response to referee comment

    Overview of the spectrometer optical fiber feed for the Habitable-zone Planet Finder

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    The Habitable-zone Planet Finder (HPF) is a highly stabilized fiber fed precision radial velocity (RV) spectrograph working in the Near Infrared (NIR): 810 - 1280 nm . In this paper we present an overview of the preparation of the optical fibers for HPF. The entire fiber train from the telescope focus down to the cryostat is detailed. We also discuss the fiber polishing, splicing and its integration into the instrument using a fused silica puck. HPF was designed to be able to operate in two modes, High Resolution (HR- the only mode mode currently commissioned) and High Efficiency (HE). We discuss these fiber heads and the procedure we adopted to attach the slit on to the HR fibers.Comment: Presented at 2018 SPIE Astronomical Telescopes + Instrumentation, Austin, Texas, USA. 18 pages, 25 figures, and 2 table

    F-theory and Dark Energy

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    Motivated by its potential use as a starting point for solving various cosmological constant problems, we study F-theory compactified on the warped product Rtime×S3×Y8\mathbb{R}_{\text{time}} \times S^3 \times Y_{8} where Y8Y_{8} is a Spin(7)Spin(7) manifold, and the S3S^3 factor is the target space of an SU(2)SU(2) Wess--Zumino--Witten (WZW) model at level NN. Reduction to M-theory exploits the abelian duality of this WZW model to an S3/ZNS^3 / \mathbb{Z}_N orbifold. In the large NN limit, the untwisted sector is captured by 11D supergravity. The local dynamics of intersecting 7-branes in the Spin(7)Spin(7) geometry is controlled by a Donaldson--Witten twisted gauge theory coupled to defects. At late times, the system is governed by a 1D quantum mechanics system with a ground state annihilated by two real supercharges, which in four dimensions would appear as "N=1/2\mathcal{N} = 1/2 supersymmetry" on a curved background. This leads to a cancellation of zero point energies in the 4D field theory but a split mass spectrum for superpartners of order Δm4DMIRMUV\Delta m_\text{4D} \sim \sqrt{M_\text{IR} M_\text{UV}} specified by the IR and UV cutoffs of the model. This is suggestively close to the TeV scale in some scenarios. The classical 4D geometry has an intrinsic instability which can produce either a collapsing or expanding Universe, the latter providing a promising starting point for a number of cosmological scenarios. The resulting 1D quantum mechanics in the time direction also provides an appealing starting point for a more detailed study of quantum cosmology.Comment: v3: 67 pages, 5 figures, reference added, typos corrected, revised analysis of superpartner masse
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