1,360 research outputs found

    Chemical species concentration measurement via wireless sensors

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    This paper describes studies carried out to investigate the viability of using wireless cameras as a tool in monitoring changes in air quality. A camera is used to monitor the change in colour of a chemically responsive polymer within view of the camera as it is exposed to varying chemical species concentration levels. The camera captures this image and the colour change is analyzed by averaging the RGB values present. This novel chemical sensing approach is compared with an established chemical sensing method using the same chemically responsive polymer coated onto LEDs. In this way, the concentration levels of acetic acid in the air can be tracked using both approaches. These approaches to chemical plume tracking have many applications for air quality monitoring

    Simulating Radiating and Magnetized Flows in Multi-Dimensions with ZEUS-MP

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    This paper describes ZEUS-MP, a multi-physics, massively parallel, message- passing implementation of the ZEUS code. ZEUS-MP differs significantly from the ZEUS-2D code, the ZEUS-3D code, and an early "version 1" of ZEUS-MP distributed publicly in 1999. ZEUS-MP offers an MHD algorithm better suited for multidimensional flows than the ZEUS-2D module by virtue of modifications to the Method of Characteristics scheme first suggested by Hawley and Stone (1995), and is shown to compare quite favorably to the TVD scheme described by Ryu et. al (1998). ZEUS-MP is the first publicly-available ZEUS code to allow the advection of multiple chemical (or nuclear) species. Radiation hydrodynamic simulations are enabled via an implicit flux-limited radiation diffusion (FLD) module. The hydrodynamic, MHD, and FLD modules may be used in one, two, or three space dimensions. Self gravity may be included either through the assumption of a GM/r potential or a solution of Poisson's equation using one of three linear solver packages (conjugate-gradient, multigrid, and FFT) provided for that purpose. Point-mass potentials are also supported. Because ZEUS-MP is designed for simulations on parallel computing platforms, considerable attention is paid to the parallel performance characteristics of each module. Strong-scaling tests involving pure hydrodynamics (with and without self-gravity), MHD, and RHD are performed in which large problems (256^3 zones) are distributed among as many as 1024 processors of an IBM SP3. Parallel efficiency is a strong function of the amount of communication required between processors in a given algorithm, but all modules are shown to scale well on up to 1024 processors for the chosen fixed problem size.Comment: Accepted for publication in the ApJ Supplement. 42 pages with 29 inlined figures; uses emulateapj.sty. Discussions in sections 2 - 4 improved per referee comments; several figures modified to illustrate grid resolution. ZEUS-MP source code and documentation available from the Laboratory for Computational Astrophysics at http://lca.ucsd.edu/codes/currentcodes/zeusmp2

    The Lyman Alpha Reference Sample. VIII. Characterizing Lyman-Alpha Scattering in Nearby Galaxies

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    We examine the dust geometry and Ly{\alpha} scattering in the galaxies of the Lyman Alpha Reference Sample (LARS), a set of 14 nearby (0.02 < zz < 0.2) Ly{\alpha} emitting and starbursting systems with Hubble Space Telescope Ly{\alpha}, H{\alpha}, and H{\beta} imaging. We find that the global dust properties determined by line ratios are consistent with other studies, with some of the LARS galaxies exhibiting clumpy dust media while others of them show significantly lower Ly{\alpha} emission compared to their Balmer decrement. With the LARS imaging, we present Ly{\alpha}/H{\alpha} and H{\alpha}/H{\beta} maps with spatial resolutions as low as ∌\sim 40 pc, and use these data to show that in most galaxies, the dust geometry is best modeled by three distinct regions: a central core where dust acts as a screen, an annulus where dust is distributed in clumps, and an outer envelope where Ly{\alpha} photons only scatter. We show that the dust that affects the escape of Ly{\alpha} is more restricted to the galaxies' central regions, while the larger Ly{\alpha} halos are generated by scattering at large radii. We present an empirical modeling technique to quantify how much Ly{\alpha} scatters in the halo, and find that this "characteristic" scattering distance correlates with the measured size of the Ly{\alpha} halo. We note that there exists a slight anti-correlation between the scattering distance of Ly{\alpha} and global dust properties.Comment: 32 pages, 51 figures, accepted to Ap

    The Lyman Alpha Reference Sample: III. Properties of the Neutral ISM from GBT and VLA Observations

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    We present new H I imaging and spectroscopy of the 14 UV-selected star-forming galaxies in the Lyman Alpha Reference Sample (LARS), aimed for a detailed study of the processes governing the production, propagation, and escape of Lyα\alpha photons. New H I spectroscopy, obtained with the 100m Green Bank Telescope (GBT), robustly detects the H I spectral line in 11 of the 14 observed LARS galaxies (although the profiles of two of the galaxies are likely confused by other sources within the GBT beam); the three highest redshift galaxies are not detected at our current sensitivity limits. The GBT profiles are used to derive fundamental H I line properties of the LARS galaxies. We also present new pilot H I spectral line imaging of 5 of the LARS galaxies obtained with the Karl G. Jansky Very Large Array (VLA). This imaging localizes the H I gas and provides a measurement of the total H I mass in each galaxy. In one system, LARS 03 (UGC 8335 or Arp 238), VLA observations reveal an enormous tidal structure that extends over 160 kpc from the main interacting systems and that contains >>109^9 M⊙_{\odot} of H I. We compare various H I properties with global Lyα\alpha quantities derived from HST measurements. The measurements of the Lyα\alpha escape fraction are coupled with the new direct measurements of H I mass and significantly disturbed H I velocities. Our robustly detected sample reveals that both total H I mass and linewidth are tentatively correlated with key Lyα\alpha tracers. Further, on global scales, these data support a complex coupling between Lyα\alpha propagation and the H I properties of the surrounding medium.Comment: Preprint form, 16 figures, accepted in Ap

    Efficacy of depth jumps to elicit a post-activation performance enhancement in junior endurance runners

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    Objectives: To determine the effect of performing depth jumps (DJ) pre-exercise on running economy (RE) and time to exhaustion (TTE) at the speed associated with maximal oxygen uptake (sV˙O2max) in a group of high-performing junior middle-distance runners. Design: Randomized crossover study. Methods: Seventeen national- and international-standard male distance runners (17.6 ± 1.2 years, 63.4 ± 6.3 kg, 1.76 ± 0.06 m, 70.7 ± 5.2 mL kg−1 min−1) completed two trials. Following a 5 min warm-up at 60% V˙O2max, participants performed a 5 min run at 20%Δ below oxygen uptake corresponding with lactate turn-point to determine pre-intervention RE. Participants then completed either six DJ from a box equivalent to their best counter-movement jump (CMJ) or a control condition (C) involving body weight quarter squats. After a 10 min passive recovery, another 5 min sub-maximal run was performed followed by a run to exhaustion at sV˙O2max. Results: Compared to the C trial, DJ produced moderate improvements (−3.7%, 95% confidence interval for effect size: 0.25–1.09) in RE, which within the context of minimal detectable change is considered possibly beneficial. Differences in TTE and other physiological variables were most likely trivial (ES: <0.2). Individual responses were small, however a partial correlation revealed a moderate relationship (r = −0.55, p = 0.028) between change in RE and CMJ height. Conclusions: The inclusion of a set of six DJ in the warm-up routine of a well-trained young male middle-distance runner is likely to provide a moderate improvement in RE

    The Lyman alpha reference sample. VII. Spatially resolved Hα\alpha kinematics

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    We present integral field spectroscopic observations with the Potsdam Multi Aperture Spectrophotometer of all 14 galaxies in the z∌0.1z\sim 0.1 Lyman Alpha Reference Sample (LARS). We produce 2D line of sight velocity maps and velocity dispersion maps from the Balmer α\alpha (Hα\alpha) emission in our data cubes. These maps trace the spectral and spatial properties of the LARS galaxies' intrinsic Lyα\alpha radiation field. We show our kinematic maps spatially registered onto the Hubble Space Telescope Hα\alpha and Lyman α\alpha (Lyα\alpha) images. Only for individual galaxies a causal connection between spatially resolved Hα\alpha kinematics and Lyα\alpha photometry can be conjectured. However, no general trend can be established for the whole sample. Furthermore, we compute non-parametric global kinematical statistics -- intrinsic velocity dispersion σ0\sigma_0, shearing velocity vshearv_\mathrm{shear}, and the vshear/σ0v_\mathrm{shear}/\sigma_0 ratio -- from our kinematic maps. In general LARS galaxies are characterised by high intrinsic velocity dispersions (54\,km\,s−1^{-1} median) and low shearing velocities (65\,km\,s−1^{-1} median). vshear/σ0v_\mathrm{shear}/\sigma_0 values range from 0.5 to 3.2 with an average of 1.5. Noteworthy, five galaxies of the sample are dispersion dominated systems with vshear/σ0<1v_\mathrm{shear}/\sigma_0 <1 and are thus kinematically similar to turbulent star forming galaxies seen at high redshift. When linking our kinematical statistics to the global LARS Lyα\alpha properties, we find that dispersion dominated systems show higher Lyα\alpha equivalent widths and higher Lyα\alpha escape fractions than systems with vshear/σ0>1v_\mathrm{shear}/\sigma_0 > 1. Our result indicates that turbulence in actively star-forming systems is causally connected to interstellar medium conditions that favour an escape of Lyα\alpha radiation.Comment: 26 pages, 15 figures, accepted for publication in A&

    Modelling hepatitis C infection acquired from blood transfusions in the UK between 1970 and 1991 for the Infected Blood Inquiry

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    The Statistics Expert Group was convened at the request of the Infected Blood Inquiry to provide estimates of the number of infections and deaths from blood-borne infections including hepatitis B virus, human immunodeficiency virus, hepatitis C virus (HCV) and variant Creutzfeldt Jakob disease, as a direct result of contaminated blood and blood products administered in the United Kingdom of Great Britain and Northern Ireland (UK). In the absence of databases of HCV infections and related deaths for all nations of the UK, a statistical model was required to estimate the number of infections and subsequent deaths from HCV acquired from blood transfusions from January 1970 to August 1991. We present this statistical model in detail alongside the results of its application to each of the four nations in the UK. We estimated that 26 800 people (95% uncertainty interval 21 300–38 800) throughout the UK were chronically infected with HCV because of contaminated blood transfusions between January 1970 and August 1991. The number of deaths up to the end of 2019 that occurred as a result of this chronic infection is estimated to be 1820 (95% uncertainty interval 650–3320)

    Silent Phase of Johne’s Disease in Experimentally Infected Goats – A Study on New and Established Diagnostic Approaches Using Specific and Non-Specific Parameters

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    The current gold standard diagnostic test for Johne’s disease (JD) is detecting Mycobacterium avium subsp. paratuberculosis (MAP) from fecal samples via culture and/or PCR. Other commercially available JD diagnostic tests focus on the detection of specific antibodies within the serum or milk of infected ruminants. These tests have a high specificity but low their sensitivity and usually fail to diagnose the disease until later stages of the disease. The ideal diagnostic test should detect infected animals already during the silent phase. Here, we evaluate the use of new and established approaches to define the silent phase of JD in experimentally infected goats. None of the established diagnostic tests or new approaches for the detection of humoral and cellular immune responses were positive during the first year of infection. Only the characterization of various subsets of peripheral blood leukocytes and the weight development gave some indication for the presence of a chronic, but silent, infection. Weight differences were present throughout the first year. In addition, some of the subsets of leukocytes (WC1+ T cells, MHC class II+ leukocytes, CD1+ leukocytes, CD14+ granulocytes, and CD14+/MHC class II+ granulocytes) demonstrated significant differences, but only at certain time points
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