13,201 research outputs found

    Calibrated Sub-Bundles in Non-Compact Manifolds of Special Holonomy

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    This paper is a continuation of math.DG/0408005. We first construct special Lagrangian submanifolds of the Ricci-flat Stenzel metric (of holonomy SU(n)) on the cotangent bundle of S^n by looking at the conormal bundle of appropriate submanifolds of S^n. We find that the condition for the conormal bundle to be special Lagrangian is the same as that discovered by Harvey-Lawson for submanifolds in R^n in their pioneering paper. We also construct calibrated submanifolds in complete metrics with special holonomy G_2 and Spin(7) discovered by Bryant and Salamon on the total spaces of appropriate bundles over self-dual Einstein four manifolds. The submanifolds are constructed as certain subbundles over immersed surfaces. We show that this construction requires the surface to be minimal in the associative and Cayley cases, and to be (properly oriented) real isotropic in the coassociative case. We also make some remarks about using these constructions as a possible local model for the intersection of compact calibrated submanifolds in a compact manifold with special holonomy.Comment: 20 pages; for Revised Version: Minor cosmetic changes, some paragraphs rewritten for improved clarit

    Passive fetal monitoring sensor

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    An ambulatory, passive sensor for use in a fetal monitoring system is discussed. The invention is comprised of a piezoelectric polymer film, combined with a metallic mounting plate fastened to a belt, and electrically connected to a signal processing unit by means of a shielded cable. The purpose of the sensor is to receive pressure pulses emitted by a fetus inside an expectant mother. Additionally, the monitor will filter out pressure pulses arising from other sources, such as the maternal heart

    Modelling the Northeast Atlantic circulation : implications for the spring invasion of shelf regions by Calanus finmarchicus

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    The appearance in spring of the copepod Calanus finmarchicus in continental shelf waters of the northeastern Atlantic has been hypothesized to be mainly attributable to invasion from across the continental slope rather than in situ overwintering. This paper describes the application of a hydrodynamic circulation model and a particle-tracking model to Northeast Atlantic waters in order to assess the influence of the flow field and ascent migration parameters on the spring invasion of C. finmarchicus. For hydrodynamic modelling, the Hamburg Shelf-Ocean Model (HAMSOM) was applied to the North Atlantic and Nordic Seas and forced with daily mean atmospheric data. Simulated flow fields from HAMSOM serve as forcing functions for a particle-tracking model of the same region. The robustness of the simulated shelf invasion in three target boxes of the Northeast Atlantic Shelf was assessed by means of a sensitivity analysis with respect to variations in four key migration parameters: overwintering depth, ascent rate, ascent timing, and depth during residence in upper layers. The invasion of the northern North Sea and Norwegian Shelf waters is more sensitive to ascent migration parameters than invasion of the Faroese Shelf. The main reason for enhanced sensitivity of the North Sea invasion is the time and space-dependent flow structure in the Faroe-Shetland Channel. Dense aggregations of overwintering C. finmarchicus are found in the Channel, but because of the complex flow field only a proportion of the overwintering stock has the capacity to reach the North Sea

    Geomagnetic activity forcing of the Northern Annular Mode via the stratosphere

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    We consider various aspects of the link between solar-modulated geomagnetic activity and the Northern Annular Mode (NAM). Our results indicate that the geomagnetic forcing of atmospheric circulation in the Northern Hemisphere is temporally and seasonally restricted, modulated by the Quasi-Biennial Oscillation (QBO), and reliant on stratosphere-troposphere coupling. When the data are restricted to January values after 1965, for years in which the January QBO is eastwards, the correlation coefficient between the geomagnetic AA index and the NAM is 0.85. These results can account for many of the enigmatic features of Northern Hemisphere circulation.<br><br> <b>Key words.</b> Meterology and atmospheric dynamics (general circulation, climatology

    Husky Masquerade

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    Award for Best Demonstration . Abstract Face detection is the process where machines identify faces within an image or visual field. Face detection is used in analyzing emotions, and even in social networking applications, such as Snapchat. The underlying mechanism of face detection is to locate key landmarks on a person’s face. The goal is to detect faces using a webcam, find the facial landmarks of the detected faces, and overlay customized images relative to the facial landmarks. Machines need to be taught to detect faces. It is crucial to teach the program to identify the different types of jawlines. The program is provided a data model which specifies different combinations of facial landmark positions. The machine is then able to compare the objects seen in its visual field to the data model. Once the machine recognizes the landmarks, it places image overlays across the visual display or mutates the visual display. These images can be stationary across the visual field, or mobile relative to the facial landmarks. The programs built for this project are capable of detecting faces using a webcam, finding the facial landmarks of the detected faces, and overlaying customized images relative to the facial landmarks. Before the programs were created, existing software, toolboxes, and libraries were surveyed. The project’s programs closely resemble Snapchat and Instagram filters. The limitation of the programs built for this project is that they have not been optimized for smartphones; the programs work only on a laptop or a smaller computer, such as the Raspberry Pi. Hence, the programs are not widely accessible to the general public

    The Effect of Microseparation on Corrosion Rates of Metal-on-Metal Total Hip Replacements

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    The poor performance of Metal-on-Metal (MoM) bearings has to date been blamed on “adverse loading” conditions. Studies have focused on the effect of cup inclination and microseparation on gravimetric wear rates and highlighted the importance of surgical technique when implanting such devices. Up to four fold increase in the wear rates of MoM bearings subjected to microseparation has been reported during the bedding-in period. The contribution of corrosive processes to overall material degradation during adverse loading has not previously been investigated. In the present study 28 mm HC CoCrMo alloy Total Hip Replacements were tested to 1 Mcycles under standard gait and severe microseparation conditions in an electrochemically instrumented hip simulator. An order of magnitude increase in material lost as a result of oxidation was noted (0.234 to 2.044 mm3/Mcycle) during microseparation. Corrosive degradation may therefore be a much more significant contribution to poor bearing performance under adverse loading than previously considered
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