14,559 research outputs found

    An Automated Method for Tracking Clouds in Planetary Atmospheres

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    We present an automated method for cloud tracking which can be applied to planetary images. The method is based on a digital correlator which compares two or more consecutive images and identifies patterns by maximizing correlations between image blocks. This approach bypasses the problem of feature detection. Four variations of the algorithm are tested on real cloud images of Jupiter’s white ovals from the Galileo mission, previously analyzed in Vasavada et al. [Vasavada, A.R., Ingersoll, A.P., Banfield, D., Bell, M., Gierasch, P.J., Belton, M.J.S., Orton, G.S., Klaasen, K.P., Dejong, E., Breneman, H.H., Jones, T.J., Kaufman, J.M., Magee, K.P., Senske, D.A. 1998. Galileo imaging of Jupiter’s atmosphere: the great red spot, equatorial region, and white ovals. Icarus, 135, 265, doi:10.1006/icar.1998.5984]. Direct correlation, using the sum of squared differences between image radiances as a distance estimator (baseline case), yields displacement vectors very similar to this previous analysis. Combining this distance estimator with the method of order ranks results in a technique which is more robust in the presence of outliers and noise and of better quality. Finally, we introduce a distance metric which, combined with order ranks, provides results of similar quality to the baseline case and is faster. The new approach can be applied to data from a number of space-based imaging instruments with a non-negligible gain in computing time

    Modeling plan-form deltaic response to changes in fluvial sediment supply

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    This study focuses on the effects of changes in fluvial sediment supply on the plan-form shape of wave-dominated deltas. We apply a one-line numerical shoreline model to calculate shoreline evolution after (I) elimination and (II) time-periodic variation of fluvial input. Model results suggest four characteristic modes of wave-dominated delta development after abandonment. The abandonment mode is determined by the pre-abandonment downdrift shoreline characteristics and wave climate (which are, in turn, determined by previous delta evolution). For asymmetrical deltas experiencing shoreline instability on the downdrift flank, time-periodic variation in fluvial input influences the evolution of downdrift-migrating sandwaves. The frequency and magnitude of the riverine "forcing" can initiate a pattern that migrates away from the river mouth, interacting with the development of shoreline sandwaves. Model results suggest that long-period signals in fluvial delivery can be shredded by autogenic sand waves, whereas shorter-term riverine fluctuations can dominate the signal of the autogenic sandwaves. The insights provided by these exploratory numerical experiments provide a set of hypotheses that can be further tested using natural examples

    A Cloud Tracking Tool for Planetary Orbiter Images

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    During their operations phase, planetary missions continuously produce a wealth of data that tend to overwhelm research teams. Spectral imagers, in particular, produce data cubes in which the wavelength dimension adds to the two spatial dimensions. Tracking of atmospheric features in order to derive winds and the construction of global maps from such large data volumes becomes particularly time-consuming if done manually. This highlights the importance of automated procedures capable of analysing sequences of data cubes with minimal user interaction. A tool for cloud tracking for such a purpose is currently under development in our group. In its present state it is based on synthetic images and uses a simple method of multiple matrix comparison to derive wind components. Deriving winds from data from the Venus Express - Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) instrument will be a possible application. We shall present an overview of the method, its benchmarking and the current status and future development of the project

    Some New Developments in Psychiatry

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    New management issues for commonly occurring psychiatric syndromes are discussed in this editorial. . South African Family Practice Vol. 49 (6) 2007: pp. 1

    Vacuum Energy: Cosmological Constant or Quintessence?

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    For a flat universe presently dominated by smooth energy, either cosmological constant (LCDM) or quintessence (QCDM), we calculate the asymptotic collapsed mass fraction as function of the present ratio of smooth energy to matter energy R0\mathcal R_0. Identifying the normalized collapsed fraction as a conditional probability for habitable galaxies, we observe that the observed present ratio R0‚ąľ2\mathcal R_0 \sim 2 is likely in LCDM, but more likely in QCDM. Inverse application of Bayes' Theorem makes the Anthropic Principle a predictive scientific principle: the data implies that the prior probability for R0\mathcal R_0 must be essentially flat over the anthropically allowed range. Interpreting this prior as a distribution over {\em theories} lets us predict that any future theory of initial conditions must be indifferent to R0\mathcal R_0. This application of the Anthropic Principle does not demand the existence of other universes.Comment: 17 pages AAS LATEX, including 2 tables, 3 figures (Postscript

    Bacterial Infections of the Central Nervous System

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    Purpose of Review:: Bacterial infections of the central nervous system are neurologic emergencies. Prompt recognition and treatment are essential not only to prevent mortality, but also to decrease neurologic sequelae. This article focuses on the two most common central nervous system bacterial infections, bacterial meningitis and spinal epidural abscess. Recent Findings:: Two outbreaks of serogroup B meningococcal disease have occurred on US college campuses. The meningococcal vaccine given to young adults does not contain serogroup B. Summary:: In bacterial meningitis and in bacterial spinal epidural abscess, the identification of and eradication of the pathogen with antimicrobial therapy is the easy part. It is the recognition of the disorder, the understanding of which diagnostic studies to obtain and their limitations, and the management of the neurologic complications that require the expertise of a neurologist

    High-fidelity ion-trap quantum computing with hyperfine clock states

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    We propose the implementation of a geometric-phase gate on magnetic-field-insensitive qubits with ŌÉ^z\hat{\sigma}^z-dependent forces for trapped ion quantum computing. The force is exerted by two laser beams in a Raman configuration. Qubit-state dependency is achieved by a small frequency detuning from the virtually-excited state. Ion species with excited states of long radiative lifetimes are used to reduce the chance of a spontaneous photon emission to less than 10‚ąí8^{-8} per gate-run. This eliminates the main source of gate infidelity of previous implementations. With this scheme it seems possible to reach the fault tolerant threshold.Comment: 4 pages, 1 figur

    Redaction automatique de commentaires a partir de bases de données statistiques

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    The critical period for the development of tactile sensitivity

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    Includes bibliographical references.The focus of this project was to ascertain whether or not there is a critical period, or "Window of Opportunity" in the development of the sense of touch, and its impact on an individual's braille reading ability. A proposed solution to this problem is needed in order to evaluate the need for beginning braille instruction as early as possible or tactile sensitivity training in low vision readers with the potential to lose their sight later on in life. The theoretical aspectsof tactile sensitivity are first discussedto provide a background into the exploration of this topic. The research study designed to probe this issue is then discussed,along with the research findings. Finally, conclusions from this study are analyzed, aswell as their implications for future research.B.S.Ed. (Bachelor of Science in Education

    Municipal Law

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