10,842 research outputs found

    SAO/NASA joint investigation of astronomical viewing quality at Mount Hopkins Observatory: 1969-1971

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    Quantitative measurements of the astronomical seeing conditions have been made with a stellar-image monitor system at the Mt. Hopkins Observatory in Arizona. The results of this joint SAO-NASA experiment indicate that for a 15-cm-diameter telescope, image motion is typically 1 arcsec or less and that intensity fluctuations due to scintillation have a coefficient of irradiance variance of less than 0.12 on the average. Correlations between seeing quality and local meteorological conditions were investigated. Local temperature fluctuations and temperature gradients were found to be indicators of image-motion conditions, while high-altitude-wind conditions were shown to be somewhat correlated with scintillation-spectrum bandwidth. The theoretical basis for the relationship of atmospheric turbulence to optical effects is discussed in some detail, along with a description of the equipment used in the experiment. General site-testing comments and applications of the seeing-test results are also included

    Scales of the Extra Dimensions and their Gravitational Wave Backgrounds

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    Circumstances are described in which symmetry breaking during the formation of our three-dimensional brane within a higher-dimensional space in the early universe excites mesoscopic classical radion or brane-displacement degrees of freedom and produces a detectable stochastic background of gravitational radiation. The spectrum of the background is related to the unification energy scale and the the sizes and numbers of large extra dimensions. It is shown that properties of the background observable by gravitational-wave observatories at frequencies f≈10−4f\approx 10^{-4} Hz to 10310^3 Hz contain information about unification on energy scales from 1 to 101010^{10} TeV, gravity propagating through extra-dimension sizes from 1 mm to 10−1810^{-18}mm, and the dynamical history and stabilization of from one to seven extra dimensions.Comment: 6 pages, Latex, 1 figure, submitted to Phys. Re

    Improvements in prevalence trend fitting and incidence estimation in EPP 2013

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    OBJECTIVE: Describe modifications to the latest version of the Joint United Nations Programme on AIDS (UNAIDS) Estimation and Projection Package component of Spectrum (EPP 2013) to improve prevalence fitting and incidence trend estimation in national epidemics and global estimates of HIV burden. METHODS: Key changes made under the guidance of the UNAIDS Reference Group on Estimates, Modelling and Projections include: availability of a range of incidence calculation models and guidance for selecting a model; a shift to reporting the Bayesian median instead of the maximum likelihood estimate; procedures for comparison and validation against reported HIV and AIDS data; incorporation of national surveys as an integral part of the fitting and calibration procedure, allowing survey trends to inform the fit; improved antenatal clinic calibration procedures in countries without surveys; adjustment of national antiretroviral therapy reports used in the fitting to include only those aged 15–49 years; better estimates of mortality among people who inject drugs; and enhancements to speed fitting. RESULTS: The revised models in EPP 2013 allow closer fits to observed prevalence trend data and reflect improving understanding of HIV epidemics and associated data. CONCLUSION: Spectrum and EPP continue to adapt to make better use of the existing data sources, incorporate new sources of information in their fitting and validation procedures, and correct for quantifiable biases in inputs as they are identified and understood. These adaptations provide countries with better calibrated estimates of incidence and prevalence, which increase epidemic understanding and provide a solid base for program and policy planning

    The influence of rearing environment on life history and morphological traits of sailfin molly fish (P. latipinna)

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    Life history traits such as time to and size at maturity are influenced by both genetic and environmental factors. One such environmental factor may be the social environment in which a juvenile is reared. This study examined the life history traits of sailfin mollies (Poecilia latipinna) that were reared in varying social environments: in isolation, in groups with an adult male present, and in groups without an adult male present. Since females prefer larger males, we anticipated that males reared in the presence of an adult male should delay maturation and therefore mature at larger sizes in order to better compete for mates. We found that males reared with an adult male took three times longer to mature and were almost 30 percent larger than males reared without adult males or in isolation. Our results suggest that social environment has significant effects on the final size at maturity, and therefore fitness, of male sailfin mollies

    A comparative framework: how broadly applicable is a 'rigorous' critical junctures framework?

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    The paper tests Hogan and Doyle's (2007, 2008) framework for examining critical junctures. This framework sought to incorporate the concept of ideational change in understanding critical junctures. Until its development, frameworks utilized in identifying critical junctures were subjective, seeking only to identify crisis, and subsequent policy changes, arguing that one invariably led to the other, as both occurred around the same time. Hogan and Doyle (2007, 2008) hypothesized ideational change as an intermediating variable in their framework, determining if, and when, a crisis leads to radical policy change. Here we test this framework on cases similar to, but different from, those employed in developing the exemplar. This will enable us determine whether the framework's relegation of ideational change to a condition of crisis holds, or, if ideational change has more importance than is ascribed to it by this framework. This will also enable us determined if the framework itself is robust, and fit for the purposes it was designed to perform — identifying the nature of policy change

    Gravitational Waves from Mesoscopic Dynamics of the Extra Dimensions

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    Recent models which describe our world as a brane embedded in a higher dimensional space introduce new geometrical degrees of freedom: the shape and/or size of the extra dimensions, and the position of the brane. These modes can be coherently excited by symmetry breaking in the early universe even on ``mesoscopic'' scales as large as 1 mm, leading to detectable gravitational radiation. Two sources are described: relativistic turbulence caused by a first-order transition of a radion potential, and Kibble excitation of Nambu-Goldstone modes of brane displacement. Characteristic scales and spectral properties are estimated and the prospects for observation by LISA are discussed. Extra dimensions with scale between 10 \AA and 1 mm, which enter the 3+1-D era at cosmic temperatures between 1 and 1000 TeV, produce backgrounds with energy peaked at observed frequencies in the LISA band, between 10−110^{-1} and 10−410^{-4} Hz. The background is detectable above instrument and astrophysical foregrounds if initial metric perturbations are excited to a fractional amplitude of 10−310^{-3} or more, a likely outcome for the Nambu-Goldstone excitations.Comment: Latex, 5 pages, plus one figure, final version to appear in Phys. Rev. Let

    Multiple purpose wetlands

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    Presented at Water for agriculture and wildlife and the environment: win-win opportunities: proceedings from the USCID wetlands seminar on June 27-29, 1996 in Bismarck, North Dakota.Includes bibliographical referencesCreating multiple purpose wetlands on large unfragmented tracts of western grasslands affords a unique opportunity to serve both ranching and wildlife interests by simultaneously enhancing livestock performance, range condition, and waterfowl production. While surface water developments on western grasslands have long been recognized as an effective technique for improving grazing distribution, more recent data suggest that such developments also have high potential for waterfowl production. Dabbling duck productivity rates per surface acre of water in these systems are often 2-4 times higher than in more traditional habitats of the Prairie Pothole Region where waterfowl managers have traditionally focused their efforts. Throughout the Prairie Pothole Region dabbling duck recruitment appears to be severely limited by the combined influences of nesting habitat fragmentation and artificially high predator densities supported by anthropogenic landscape changes. Conversely, western grasslands are characterized by relatively large tracts of nesting cover, low density predator communities, and as a result, high duck productivity when adequate surface water is available. Recognizing the multiple benefits of created wetlands, beginning in 1992 the U.S. Fish and Wildlife Service initiated a unique statewide partnership in South Dakota to create multiple purpose wetlands on private and tribal grasslands. Emphasis was placed on creating multiple purpose wetlands on large unfragmented tracts of grassland, including for the first time, sites outside of the traditional Prairie Pothole Region. Primary partners in this program include the North American Wetlands Conservation Council, Ducks Unlimited Incorporated, Native American Tribes, the South Dakota Association of Conservation Districts, the South Dakota Department of Game, Fish and Parks, county Conservation Districts and individual landowners. Through this partnership over 450 wetlands have been created, with 30% occurring on western grasslands outside of the Prairie Pothole Region. As expected, tangible benefits noted from wetlands created through this partnership include improved grazing distribution and livestock performance, enhanced range condition and localized increases in waterfowl production. More importantly, as a result of this program many participating landowners have expressed a renewed enthusiasm for the intangible benefits of wildlife conservation. Interest in this program continues to grow providing an example of a true working partnership between agriculture and wildlife

    A meteorological report for the Mt. Hopkins Observatory: 1968-1971

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    This document is a compilation of the weather data collected at the Mt. Hopkins Observatory in southern Arizona from 1968 to 1971. It is the second meteorological report aimed at assisting scientists in the scheduling of experiments at the Observatory site

    On the use of blow up to study regularizations of singularities of piecewise smooth dynamical systems in R3\mathbb{R}^3

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    In this paper we use the blow up method of Dumortier and Roussarie \cite{dumortier_1991,dumortier_1993,dumortier_1996}, in the formulation due to Krupa and Szmolyan \cite{krupa_extending_2001}, to study the regularization of singularities of piecewise smooth dynamical systems \cite{filippov1988differential} in R3\mathbb R^3. Using the regularization method of Sotomayor and Teixeira \cite{Sotomayor96}, first we demonstrate the power of our approach by considering the case of a fold line. We quickly recover a main result of Bonet and Seara \cite{reves_regularization_2014} in a simple manner. Then, for the two-fold singularity, we show that the regularized system only fully retains the features of the singular canards in the piecewise smooth system in the cases when the sliding region does not include a full sector of singular canards. In particular, we show that every locally unique primary singular canard persists the regularizing perturbation. For the case of a sector of primary singular canards, we show that the regularized system contains a canard, provided a certain non-resonance condition holds. Finally, we provide numerical evidence for the existence of secondary canards near resonance.Comment: To appear in SIAM Journal of Applied Dynamical System
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