8,467 research outputs found

    Coordinate Confusion in Conformal Cosmology

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    A straight-forward interpretation of standard Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmologies is that objects move apart due to the expansion of space, and that sufficiently distant galaxies must be receding at velocities exceeding the speed of light. Recently, however, it has been suggested that a simple transformation into conformal coordinates can remove superluminal recession velocities, and hence the concept of the expansion of space should be abandoned. This work demonstrates that such conformal transformations do not eliminate superluminal recession velocities for open or flat matter-only FRLW cosmologies, and all possess superluminal expansion. Hence, the attack on the concept of the expansion of space based on this is poorly founded. This work concludes by emphasizing that the expansion of space is perfectly valid in the general relativistic framework, however, asking the question of whether space really expands is a futile exercise.Comment: 5 pages, accepted for publication in MNRAS Letter

    Satellite Snow Surveillance -A Down to Earth Use of Space Technology

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    In the not-too-distant future, an increasing use will be made of earth-orbiting satellites to survey our natural resources. One resource that has been observed from space since the first meteorological satellite nearly a decade ago, is the earth\u27s snow cover. Continued observation of this resource will be a prime use of satellite systems designed specifically to view the earth1 s surface; in fact, a survey of snow and ice on a world-wide scale, as planned in the International Hydrological Decade, appears economically feasible only through the use of satellite observations. Thus, snow surveillance is a really down-to-earth use of space technology. Recent studies of the use of satellite photography to map snow cover distributions in the Upper Mississippi-Missouri River Basins Region are described in this paper. The techniques presented for identifying and mapping snow distributions, and for estimating snow depths, were developed originally from TIROS photography, * and were tested on a data sample obtained from the ESSA satellites. 2 Additional research is currently in progress to determine whether these techniques developed for the relatively flat terrain of the north-central United States are also applicable to mountainous areas. This research is briefly reviewed, and the outlook for operational snow surveillance from space is discussed

    Spectroscopic membership for the populous 300 Myr-old open cluster NGC 3532

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    NGC 3532 is an extremely rich open cluster embedded in the Galactic disc, hitherto lacking a comprehensive, documented membership list. We provide membership probabilities from new radial velocity observations of solar-type and low-mass stars in NGC 3532, in part as a prelude to a subsequent study of stellar rotation in the cluster. Using extant optical and infra-red photometry we constructed a preliminary photometric membership catalogue, consisting of 2230 dwarf and turn-off stars. We selected 1060 of these for observation with the AAOmega spectrograph at the Anglo-Australian Telescope and 391 stars for observations with the Hydra-South spectrograph at the Victor Blanco Telescope, obtaining spectroscopic observations over a decade for 145 stars. We measured radial velocities for our targets through cross-correlation with model spectra and standard stars, and supplemented them with radial velocities for 433 additional stars from the literature. We also measured log g, Teff, and [Fe/H] from the AAOmega spectra. Together with proper motions from Gaia DR2 we find 660 exclusive members. The members are distributed across the whole cluster sequence, from giant stars to M dwarfs, making NGC 3532 one of the richest Galactic open clusters known to date, on par with the Pleiades. From further spectroscopic analysis of 153 dwarf members we find the metallicity to be marginally sub-solar, with [Fe/H]=-0.07. Exploiting trigonometric parallax measurements from Gaia DR2 we find a distance of 484−30+35484^{+35}_{-30} pc. Based on the membership we provide an empirical cluster sequence in multiple photometric passbands. A comparison of the photometry of the measured cluster members with several recent model isochrones enables us to confirm the 300 Myr cluster age. However, all of the models evince departures from the cluster sequence in particular regions, especially in the lower mass range. (abridged)Comment: Accepted for publication in A&A. 19 pages, 18 Figures, and 6 Table

    Expanding Space: the Root of all Evil?

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    While it remains the staple of virtually all cosmological teaching, the concept of expanding space in explaining the increasing separation of galaxies has recently come under fire as a dangerous idea whose application leads to the development of confusion and the establishment of misconceptions. In this paper, we develop a notion of expanding space that is completely valid as a framework for the description of the evolution of the universe and whose application allows an intuitive understanding of the influence of universal expansion. We also demonstrate how arguments against the concept in general have failed thus far, as they imbue expanding space with physical properties not consistent with the expectations of general relativity.Comment: 8 pages, accepted for publication in PAS

    Authors, publishers, and politicians: the quest for an Anglo-American copyright agreement, 1815-1854

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    (print) xv, 311 p. ; 23 cmPreface ix -- Acknowledgments xi -- I The Depression of 1837-43 and its Implications for the American Book Trade 1 -- II British Periodicals in America 30 -- III Copyright In and Out of Congress, 1815-42 49 -- IV Further Efforts to Influence the American Congress, 1842-51 75 -- V The Impact of Foreign Reprints on the Domestic British Book Trade 95 -- VI Efforts to Influence Parliament, 1838-44 116 -- VII The Canadian Market 138 -- VIII The British Law Courts : A Possible Remedy for the Absence of International Copyright 153 -- IX American Lobbyists in the Early 1850s 177 -- X The Organization 194 -- XI Bribery, or the Necessary Expenses of Congressional Action : November 1851-February 1853 216 -- XII The Need for Senate Ratification : February 1853-June 1854 241 -- Notes 263 -- Index 30

    Joining the Hubble Flow: Implications for Expanding Space

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    The concept of expanding space has come under fire recently as being inadequate and even misleading in describing the motion of test particles in the universe. Previous investigations have suffered from a number of shortcomings, which we seek to correct. We study the motion of test particles in the universe in detail, solving the geodesic equations of General Relativity for a number of cosmological models. In particular, we use analytic methods to examine whether particles removed from the Hubble flow asymptotically rejoin the Hubble flow, a topic that has caused confusion because of differing definitions and invalid reasoning. We conclude that particles in eternally expanding but otherwise arbitrary universes do not in general rejoin the Hubble flow

    Information Management to Mitigate Loss of Control Airline Accidents

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    Loss of control inflight continues to be the leading contributor to airline accidents worldwide and unreliable airspeed has been a contributing factor in many of these accidents. Airlines and the FAA developed training programs for pilot recognition of these airspeed events and many checklists have been designed to help pilots troubleshoot. In addition, new aircraft designs incorporate features to detect and respond in such situations. NASA has been using unreliable airspeed events while conducting research recommended by the Commercial Aviation Safety Team. Even after significant industry focus on unreliable airspeed, research and other evidence shows that highly skilled and trained pilots can still be confused by the condition and there is a lack of understanding of what the associated checklist(s) attempts to uncover. Common mode failures of analog sensors designed for measuring airspeed continue to confound both humans and automation when determining which indicators are correct. This paper describes failures that have occurred in the past and where/how pilots may still struggle in determining reliable airspeed when confronted with conflicting information. Two latest generation aircraft architectures will be discussed and contrasted. This information will be used to describe why more sensors used in classic control theory will not solve the problem. Technology concepts are suggested for utilizing existing synoptic pages and a new synoptic page called System Interactive Synoptic (SIS). SIS details the flow of flight critical data through the avionics system and how it is used by the automation. This new synoptic page as well as existing synoptics can be designed to be used in concert with a simplified electronic checklist (sECL) to significantly reduce the time to configure the flight deck avionics in the event of a system or sensor failure

    Systematic review of copper intrauterine contraception continuation in young nulliparous women based on intrauterine device type.

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    OBJECTIVES: No copper intrauterine device (IUD) type is known to better suit young nulliparous women who tend to experience higher rates of IUD discontinuation compared with their older parous counterparts. A systematic review to determine which IUDs have higher continuation rates in young nulliparous women was undertaken. DESIGN: Systematic review and meta-analyses of available evidence based on IUD type. DATA SOURCES: AMED, BNI, CINAHL, DARE, EMBASE, EMCARE, HMIC, MEDLINE, PsycINFO, PubMed, TRIP, and the Cochrane Library electronic databases were searched from inception to 11 May 2022; as well as the Bandolier, Medicines and Healthcare products Regulatory Agency, Faculty of Sexual and Reproductive Healthcare, Royal College of Obstetricians and Gynaecologists, Department of Health, National Institute for Health and Care Excellence, Scottish Intercollegiate Guidelines, WHO and Google Scholar websites. ELIGIBILITY CRITERIA: All studies on IUDs currently available in the UK or comparable (same design and size) to those available in the UK, involving nulliparous women of any age including those aged under 30. DATA EXTRACTION AND SYNTHESIS: Independently extracted data were assessed as low risk of bias using the Mixed Methods Appraisal Tool. Random effects meta-analyses of proportions were performed where data, including subgroups, were amenable to quantitative synthesis. Heterogeneity was reported using tau2 and I2 statistics, and sensitivity analyses were also performed. RESULTS: Nineteen studies involving 13 045 nulliparous women were included but the heterogeneity of participant ages, parity and IUD types made quantitative synthesis of outcome data in totality inappropriate. The highest continuation rate obtained was 91.02% (95% CI 88.01% to 93.64%) for the smaller TCu 380A at 12 months post insertion. CONCLUSIONS: Evidence for IUD use in young nulliparous women based on IUD type remains limited. Smaller sized IUD types appear better suited to this group of IUD users, however, more research is needed. PROSPERO REGISTRATION NUMBER: CRD42019120969

    Policy disconnect: A critical review of UK air quality policy in relation to EU and LAQM responsibilities over the last 20 years

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    © 2018 Elsevier Ltd This paper critically reviews United Kingdom (UK) air quality policy in relation to European and Local Air Quality Management (LAQM) responsibilities over the last 20 years. The arguments articulated in this paper highlight the gulf between national and local air quality management in the UK, including differences in legislation, legal responsibilities, scales of operation, monitoring and modelling requirements, exceedence reporting and action planning. It is argued that local authorities cannot be held responsible for the UK's failure to achieve the European Union (EU) nitrogen dioxide (NO2) limit values due to fundamental differences between local government responsibilities under LAQM and the UK compliance assessment reporting to the EU. Furthermore, unambitious and counterproductive national policies and the failure of EU light-duty vehicle type approval tests and Euro standards to reduce real-world emissions of nitrogen oxides (NOx) are the main reasons for continued NO2 limit value exceedences. This failure of EU and national air quality policies has effectively undermined local authority action to improve local air quality, resulting in delays in achieving the standards, wasted resources at local and national levels, and, ultimately, unnecessary loss of life and increased morbidity in the UK population. This paper concludes that the current emphasis that the UK government is placing on implementation of Clean Air Zones (CAZs) to achieve the Ambient Air Quality Directive (2008/50/EC) (AAQD), and avoid substantial fines imposed by the European Court of Justice (CJEU), is flawed. Based on the arguments presented in this paper, a series of recommendations is proposed for the European Union, the UK government, devolved administrations and local authorities

    Vibrational-Resonance Enhancement of Positron Annihilation in Molecules

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    A first study of positron annihilation as a function of positron energy was performed. The rate of annihilation of low-energy positrons in molecular gases was discussed. It was shown that the large observed values of annihilation rates are due to the excitation of long-lived vibrational resonances of the positron-molecule complex. The results are consistent with a theoretical model of resonant annihilation
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