1,853 research outputs found

    Experimental Methods to Characterize Nonlinear Vibration of Flapping Wing Micro Air Vehicles

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    For urban combat reconnaissance, the flapping wing micro air vehicle concept is ideal because of its low speed and miniature size, which are both conducive to indoor operations. The focus of this research is the development of experimental methods best suited for the vibration testing of the wing structure of a flapping wing micro air vehicle. This study utilizes the similarity of a beam resonating at its first bending mode to actual wing flapping motion. While computational finite element analysis based on linear vibration theory is employed for preliminary beam sizing, an emphasis is placed on experimental measurement of the nonlinear vibration characteristics introduced as a result of large movement. Beam specimens fabricated from 2024-T3 aluminum alloy and IM7/5250-4 carbon-epoxy were examined using a high speed optical system and a scanning laser vibrometer configured in both three and one dimensions, respectively

    Creation and Worldwide Utilisation of New COVID-19 Online Information Hub for Genetics Health Professionals, Patients and Families

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    The current COVID-19 pandemic has unfortunately resulted in many significant concerns for individuals with genetic disorders and their relatives, regarding the viral infection and, particularly, its specific implications and additional advisable precautions for individuals affected by genetic disorders. To address this, the resulting requirement for guidance and information for the public and for genetics professionals was discussed among colleagues nationally, on the ScotGEN Steering Committee, and internationally on the Education Committee of the European Society of Human Genetics (ESHG). It was agreed that the creation of an online hub of genetics-related COVID-19 information resources would be particularly helpful. The proposed content, divided into a web page for professionals and a page for patients, was discussed with, and approved by, genetics professionals. The hub was created and provided online at www.scotgen.org.uk and linked from the ESHG’s educational website for genetics and genomics, at www.eurogems.org. The new hub provides links, summary information and representative illustrations for a wide range of selected international resources. The resources for professionals include: COVID-19 research related hubs provided by Nature, Science, Frontiers, and PubMed; clinical guidelines; the European Centre for Disease Prevention and Control; the World Health Organisation; and molecular data sources including coronavirus 3D protein structures. The resources for patients and families include links to many accessible sources of support and relevant information. Since the launch of the pages, the website has received visits from over 50 countries worldwide. Several genetics consultants have commented on usefulness, clarity, readability, and ease of navigation. Visits have originated most frequently in the United Kingdom, Kuwait, Hong Kong, Moldova, United States, Philippines, France, and Qatar. More links have been added since the launch of the hub to include additional international public health and academic resources. In conclusion, an up-to-date online hub has been created and made freely available for healthcare professionals, patients, relatives and the public, providing categorised easily navigated links to a range of worldwide resources related to COVID-19. These pages are receiving a rapidly growing number of return visits and the authors continue to maintain and update the pages’ content, incorporating new developments in this field of enormous worldwide importance

    WALLABY Early Science - I. The NGC 7162 Galaxy Group

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    We present Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY) early science results from the Australian Square Kilometre Array Pathfinder (ASKAP) observations of the NGC 7162 galaxy group. We use archival HIPASS and Australia Telescope Compact Array (ATCA) observations of this group to validate the new ASKAP data and the data reduction pipeline ASKAPsoft. We detect six galaxies in the neutral hydrogen (HI) 21-cm line, expanding the NGC 7162 group membership from four to seven galaxies. Two of the new detections are also the first HI detections of the dwarf galaxies, AM 2159-434 and GALEXASC J220338.65-431128.7, for which we have measured velocities of cz=2558cz=2558 and cz=2727cz=2727 km s−1^{-1}, respectively. We confirm that there is extended HI emission around NGC 7162 possibly due to past interactions in the group as indicated by the 40∘40^{\circ} offset between the kinematic and morphological major axes for NGC 7162A, and its HI richness. Taking advantage of the increased resolution (factor of ∼1.5\sim1.5) of the ASKAP data over archival ATCA observations, we fit a tilted ring model and use envelope tracing to determine the galaxies' rotation curves. Using these we estimate the dynamical masses and find, as expected, high dark matter fractions of fDM∼0.81−0.95f_{\mathrm{DM}}\sim0.81-0.95 for all group members. The ASKAP data are publicly available.Comment: 20 pages, 11 figures, accepted for publication in MNRA

    Effect of Spatial Charge Inhomogeneity on 1/f Noise Behavior in Graphene

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    Scattering mechanisms in graphene are critical to understanding the limits of signal-to-noise-ratios of unsuspended graphene devices. Here we present the four-probe low frequency noise (1/f) characteristics in back-gated single layer graphene (SLG) and bilayer graphene (BLG) samples. Contrary to the expected noise increase with the resistance, the noise for SLG decreases near the Dirac point, possibly due to the effects of the spatial charge inhomogeneity. For BLG, a similar noise reduction near the Dirac point is observed, but with a different gate dependence of its noise behavior. Some possible reasons for the different noise behavior between SLG and BLG are discussed.Comment: 28 pages, 3 figures + 3 supplement figure

    Risk stratification using coronary artery calcium scoring based on low tube voltage computed tomography

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    To determine if coronary artery calcium (CAC) scoring using computed tomography at 80 kilovolt-peak (kVp) and 70-kVp and tube voltage-adapted scoring-thresholds allow for accurate risk stratification as compared to the standard 120-kVp protocol. We prospectively included 170 patients who underwent standard CAC scanning at 120-kVp and 200 milliamperes and additional scans with 80-kVp and 70-kVp tube voltage with adapted tube current to normalize image noise across scans. Novel kVp-adapted thresholds were applied to calculate CAC scores from the low-kVp scans and were compared to those from standard 120-kVp scans by assessing risk reclassification rates and agreement using Kendall’s rank correlation coefficients (Τb) for risk categories bounded by 0, 1, 100, and 400. Interreader reclassification rates for the 120-kVp scans were assessed. Agreement for risk classification obtained from 80-kVp and 70-kVp scans as compared to 120-kVp was good (Τb = 0.967 and 0.915, respectively; both p < 0.001) with reclassification rates of 7.1% and 17.2%, respectively, mostly towards a lower risk category. By comparison, the interreader reclassification rate was 4.1% (Τb = 0.980, p < 0.001). Reclassification rates were dependent on body mass index (BMI) with 7.1% and 13.6% reclassifications for the 80-kVp and 70-kVp scans, respectively, in patients with a BMI < 30 kg/m2 (n = 140), and 2.9% and 7.4%, respectively, in patients with a BMI < 25 kg/m2 (n = 68). Mean effective radiation dose from the 120-kVp, the 80-kVp, and 70-kVp scans was 0.54 ± 0.03, 0.42 ± 0.02, and 0.26 ± 0.02 millisieverts. CAC scoring with reduced tube voltage allows for accurate risk stratification if kVp-adapted thresholds for calculation of CAC scores are applied

    The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

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    We present a catalog of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 GHz and/or 218 GHz in the 2008 Southern survey. Flux densities span 14-1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two sub-populations: 167 radio galaxies powered by central active galactic nuclei (AGN), and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97% of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogs. When combined with flux densities from the Australian Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index of 3.7+0.62-0.86, and includes both local galaxies and sources with redshifts as great as 5.6. Dusty sources with no counterpart in existing catalogs likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.Comment: 13 pages, 8 figures, 4 table

    The Atacama Cosmology Telescope: The LABOCA/ACT Survey of Clusters at All Redshifts

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    We present a multi-wavelength analysis of eleven Sunyaev Zel'dovich effect (SZE)-selected galaxy clusters (ten with new data) from the Atacama Cosmology Telescope (ACT) southern survey. We have obtained new imaging from the Large APEX Bolometer Camera (345GHz; LABOCA) on the Atacama Pathfinder EXperiment (APEX) telescope, the Australia Telescope Compact Array (2.1GHz; ATCA), and the Spectral and Photometric Imaging Receiver (250, 350, and 500 μm500\,\rm\mu m; SPIRE) on the Herschel Space Observatory. Spatially-resolved 345GHz SZE increments with integrated S/N > 5 are found in six clusters. We compute 2.1GHz number counts as a function of cluster-centric radius and find significant enhancements in the counts of bright sources at projected radii θ<θ2500\theta < \theta_{2500}. By extrapolating in frequency, we predict that the combined signals from 2.1GHz-selected radio sources and 345GHz-selected SMGs contaminate the 148GHz SZE decrement signal by ~5% and the 345GHz SZE increment by ~18%. After removing radio source and SMG emission from the SZE signals, we use ACT, LABOCA, and (in some cases) new Herschel SPIRE imaging to place constraints on the clusters' peculiar velocities. The sample's average peculiar velocity relative to the cosmic microwave background is 153±383 km s−1153\pm 383\,\rm km\,s^{-1}.Comment: 19 pages, 11 figures, Accepted for Publication in The Astrophysical Journa
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