1,463 research outputs found

    SAVER: Surface Autonomous Vehicle for Emergency Rescue

    Get PDF
    The design, fabrication, and testing of an unmanned surface vehicle for the NASA Micro-G NExT SAVER challenge. This device features a radio direction finding phase array to autonomously navigate to an emergency distress beacon to deliver emergency supplies

    Two Stellar Components in the Halo of the Milky Way

    Full text link
    The halo of the Milky Way provides unique elemental abundance and kinematic information on the first objects to form in the Universe, which can be used to tightly constrain models of galaxy formation and evolution. Although the halo was once considered a single component, evidence for its dichotomy has slowly emerged in recent years from inspection of small samples of halo objects. Here we show that the halo is indeed clearly divisible into two broadly overlapping structural components -- an inner and an outer halo -- that exhibit different spatial density profiles, stellar orbits and stellar metallicities (abundances of elements heavier than helium). The inner halo has a modest net prograde rotation, whereas the outer halo exhibits a net retrograde rotation and a peak metallicity one-third that of the inner halo. These properties indicate that the individual halo components probably formed in fundamentally different ways, through successive dissipational (inner) and dissipationless (outer) mergers and tidal disruption of proto-Galactic clumps.Comment: Two stand-alone files in manuscript, concatenated together. The first is for the main paper, the second for supplementary information. The version is consistent with the version published in Natur

    Muscle recruitment patterns during the prone leg extension

    Get PDF
    BACKGROUND: The prone leg extension (PLE) is a clinical test used to evaluate the function of the lumbopelvis. It has been theorized that a normal and consistent pattern of muscle activation exists. Previous research has found two contradictory patterns of muscle activation during PLE in normal individuals. One study shows an almost simultaneous activation of the lower erector spinae and hamstring muscle group with a delayed activation of the gluteus maximus, while the second describes the order of activation being ipsilateral erector spinae (to the leg being extended), hamstrings, contralateral erector spinae and gluteus maximus. Due to the different conclusions from these two studies and the lack of quantified muscle onset times, expressed in absolute time this study attempted to quantify the muscle onset times (in milliseconds) during the prone leg extension, while noting if a consistent order of activation exists and whether a timing relationship also exists between the gluteus maximus and contralateral latissimus dorsi. METHODS: 10 asymptomatic males (Average height: 175.2 cm (SD 6.5), Average Weight 75.9 kg (SD 6.5), Average Age: 27.1(SD 1.28)) and 4 asymptomatic females (Average height 164.5 (SD 2.9), weight: 56.2 (SD 8.9), Average Age: 25 (SD 1)) performed the prone leg extension task while the myoelectric signal was recorded from the bilateral lower erector spinae, gluteus maximus and hamstring muscle groups. Activation onsets were determined from the rectified EMG signal relative to the onset of the hamstrings muscle group. RESULTS: No consistent recruitment patterns were detected for prone leg extension among the hamstring muscle group and the erector spinae. However, a consistent delay in the Gluteus Maximus firing of approximately 370 ms after the first muscle activated was found. Five out of 14 asymptomatic subjects showed a delay in gluteus maximus firing exceeding the average delay found in previous research of subjects considered to have a dysfunctional firing pattern. CONCLUSION: A consistent pattern of activation was not found. Variability was seen across subjects. These findings suggest the PLE is not sufficient for a diagnostic test due to the notable physiological variation. An overlap between normal and potentially abnormal activation patterns may exist

    Supplier-induced demand for psychiatric admissions in Northern New England

    Get PDF
    The development of hospital service areas (HSAs) using small area analysis has been useful in examining variation in medical and surgical care; however, the techniques of small area analysis are underdeveloped in understanding psychiatric admission rates. We sought to develop these techniques in order to understand the relationship between psychiatric bed supply and admission rates in Northern New England. Our primary hypotheses were that there would be substantial variation in psychiatric admission across geographic settings and that bed availability would be positively correlated with admission rates, reflecting a supplier-induced demand phenomenon. Our secondary hypothesis was that the construction of psychiatric HSAs (PHSAs) would yield more meaningful results than the use of existing general medical hospital service areas

    A Defined and Flexible Pocket Explains Aryl Substrate Promiscuity of the Cahuitamycin Starter Unit–Activating Enzyme CahJ

    Full text link
    Cahuitamycins are biofilm inhibitors assembled by a convergent nonribosomal peptide synthetase pathway. Previous genetic analysis indicated that a discrete enzyme, CahJ, serves as a gatekeeper for cahuitamycin structural diversification. Here, the CahJ protein was probed structurally and functionally to guide the formation of new analogues by mutasynthetic studies. This analysis enabled the in vivo production of a new cahuitamycin congener through targeted precursor incorporation.Breaking the barrier: Biofilm formation is employed by pathogenic microbes to defend against antibiotic action. This study probes both structurally and functionally CahJ, a key biosynthetic adenylation enzyme involved in generation of the cahuitamycin biofilm inhibitors, and lays a foundation for the development of effective new analogues.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145379/1/cbic201800233_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145379/2/cbic201800233.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145379/3/cbic201800233-sup-0001-misc_information.pd

    Central Powering of the Largest Lyman-alpha Nebula is Revealed by Polarized Radiation

    Full text link
    High-redshift Lyman-alpha blobs are extended, luminous, but rare structures that appear to be associated with the highest peaks in the matter density of the Universe. Their energy output and morphology are similar to powerful radio galaxies, but the source of the luminosity is unclear. Some blobs are associated with ultraviolet or infrared bright galaxies, suggesting an extreme starburst event or accretion onto a central black hole. Another possibility is gas that is shock excited by supernovae. However some blobs are not associated with galaxies, and may instead be heated by gas falling into a dark matter halo. The polarization of the Ly-alpha emission can in principle distinguish between these options, but a previous attempt to detect this signature returned a null detection. Here we report on the detection of polarized Ly-alpha from the blob LAB1. Although the central region shows no measurable polarization, the polarized fraction (P) increases to ~20 per cent at a radius of 45 kpc, forming an almost complete polarized ring. The detection of polarized radiation is inconsistent with the in situ production of Ly-alpha photons, and we conclude that they must have been produced in the galaxies hosted within the nebula, and re-scattered by neutral hydrogen.Comment: Published in the August 18 issue of Nature. 1750 words, 3 figures, and full Supplementary Information. Version has not undergone proofing. Reduced and processed data products are available here: http://obswww.unige.ch/people/matthew.hayes/LymanAlpha/LabPol

    Quantum Holographic Encoding in a Two-dimensional Electron Gas

    Full text link
    The advent of bottom-up atomic manipulation heralded a new horizon for attainable information density, as it allowed a bit of information to be represented by a single atom. The discrete spacing between atoms in condensed matter has thus set a rigid limit on the maximum possible information density. While modern technologies are still far from this scale, all theoretical downscaling of devices terminates at this spatial limit. Here, however, we break this barrier with electronic quantum encoding scaled to subatomic densities. We use atomic manipulation to first construct open nanostructures--"molecular holograms"--which in turn concentrate information into a medium free of lattice constraints: the quantum states of a two-dimensional degenerate Fermi gas of electrons. The information embedded in the holograms is transcoded at even smaller length scales into an atomically uniform area of a copper surface, where it is densely projected into both two spatial degrees of freedom and a third holographic dimension mapped to energy. In analogy to optical volume holography, this requires precise amplitude and phase engineering of electron wavefunctions to assemble pages of information volumetrically. This data is read out by mapping the energy-resolved electron density of states with a scanning tunnelling microscope. As the projection and readout are both extremely near-field, and because we use native quantum states rather than an external beam, we are not limited by lensing or collimation and can create electronically projected objects with features as small as ~0.3 nm. These techniques reach unprecedented densities exceeding 20 bits/nm2 and place tens of bits into a single fermionic state.Comment: Published online 25 January 2009 in Nature Nanotechnology; 12 page manuscript (including 4 figures) + 2 page supplement (including 1 figure); supplementary movie available at http://mota.stanford.ed

    Fast Approximate Geodesics for Deep Generative Models

    Full text link
    The length of the geodesic between two data points along a Riemannian manifold, induced by a deep generative model, yields a principled measure of similarity. Current approaches are limited to low-dimensional latent spaces, due to the computational complexity of solving a non-convex optimisation problem. We propose finding shortest paths in a finite graph of samples from the aggregate approximate posterior, that can be solved exactly, at greatly reduced runtime, and without a notable loss in quality. Our approach, therefore, is hence applicable to high-dimensional problems, e.g., in the visual domain. We validate our approach empirically on a series of experiments using variational autoencoders applied to image data, including the Chair, FashionMNIST, and human movement data sets.Comment: 28th International Conference on Artificial Neural Networks, 201
    • …
    corecore