3,757 research outputs found

    Embeddings in the 3/4 range

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    We give a complete obstruction to turning an immersion of an m-dimensional manifold M in Euclidean n-space into an embedding when 3n>4m+4. It is a secondary obstruction, and exists only when the primary obstruction, due to Haefliger, vanishes. The obstruction lives in a twisted cobordism group, and its vanishing implies the existence of an embedding in the regular homotopy class of the given immersion in the range indicated. We use Goodwillie's calculus of functors, following Weiss, to help organize and prove the result.Comment: 33 pages, extensively rewritten due to incorporation of comments by the refere

    Derivatives of the identity and generalizations of Milnor's invariants

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    We synthesize work of U. Koschorke on link maps and work of B. Johnson on the derivatives of the identity functor in homotopy theory. The result can be viewed in two ways: (1) As a generalization of Koschorke's "higher Hopf invariants", which themselves can be viewed as a generalization of Milnor's invariants of link maps in Euclidean space; and (2) As a stable range description, in terms of bordism, of the cross effects of the identity functor in homotopy theory evaluated at spheres. We also show how our generalized Milnor invariants fit into the framework of a multivariable manifold calculus of functors, as developed by the author and Voli\'{c}, which is itself a generalization of the single variable version due to Weiss and Goodwillie.Comment: 25 pages, accepted for publication by the Journal of Topolog

    Application of Alternative Nucleic Acid Extraction Protocols to ProGastro SSCS Assay for Detection of Bacterial Enteric Pathogens

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    As an alternative to automated extraction, fecal specimens were processed by investigational lysis/heating (i.e., manual) and by chromatography/centrifugation (i.e., column) methods. ProGastro SSC and Shiga toxin-producing Escherichia coli (i.e., STEC) indeterminate rates for 101 specimens were 1.0% to 3.0% for automated, 11.9% for manual, and 24.8% to 37.6% for column methods. Following freeze-thaw of 247 specimens, indeterminate rates were 1.6% to 2.4% for manual and 0.8 to 5.3% for column methods. Mean processing times for manual and column methods were 30.5 and 69.2 min, respectively. Concordance of investigational methods with automated extraction was ≥98.8%

    Airframe noise of the DC-9-31

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    Airframe noise measurements are reported for the DC-9-31 aircraft flown at several speeds and with a number of flap, landing gear, and slat extension configurations. The data are corrected for wind effects, atmospheric attenuation, and spherical divergence, and are normalized to a 1 meter acoustic range. The sound pressure levels are found to vary approximately as the fifth power of flight velocity. Both lift and drag dipoles exist as a significant part of the airframe noise. The sideline data imply that a significant side-force dipole exists only for the flap- and gear-down configurations; for others, the data imply the existence of only the lift and drag dipoles. The data are compared with airframe noise predictions using the drag element and the data analysis methods. Although some of the predictions are good, further work is needed to refine the methods, particularly for the flap- and gear-down configurations

    A stable range description of the space of link maps

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    We study the space of link maps, which are smooth maps from the disjoint union of manifolds P and Q to a manifold N such that the images of P and Q are disjoint. We give a range of dimensions, interpreted as the connectivity of a certain map, in which the cobordism class of the "linking manifold" is enough to distinguish the homotopy class of one link map from another.Comment: 10 page

    Exploring goal-setting, rewards, selfmonitoring, and sharing to motivate physical activity

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    Abstract—Many people have turned to technological tools to help them be physically active. To better understand how goal-setting, rewards, self-monitoring, and sharing can encourage physical activity, we designed a mobile phone application and deployed it in a four-week field study (n=23). Participants found it beneficial to have secondary and primary weekly goals and to receive nonjudgmental reminders. However, participants had problems with some features that are commonly used in practice and suggested in the literature. For example, trophies and ribbons failed to motivate most participants, which raises questions about how such rewards should be designed. A feature to post updates to a subset of their Facebook NewsFeed created some benefits, but barriers remained for most participants. Keywords-Exercise; mobile applications; goal-setting; reminders; rewards; sharing; social networks; persuasive technology I

    The Dieppe Raid: Avoidable Disaster or Lesson in Amphibious Assault?*

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    During World War II, the Allied forces mounted an amphibious assault on the occupied French coastal town of Dieppe. Since its execution, the raid on Dieppe has become a very controversial topic. The operation had an abundance of flaws that caused many casualties. This article analyzes both issues and who, if any one should have been held responsible
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