6,279 research outputs found

    Spurious Eccentricities of Distorted Binary Components

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    I discuss the effect of physical distortion on the velocities of close binary components and how we may use the resulting distortion of velocity curves to constrain some properties of binary systems, such as inclination and mass ratio. Precise new velocities for 5 Cet convincingly detect these distortions with their theoretically predicted phase dependence. We can even use such distortions of velocity curves to test Lucy's theory of convective gravity darkening. The observed distortions for TT Hya and 5 Cet require the contact components of those systems to be gravity darkened, probably somewhat more than predicted by Lucy's theory but clearly not as much as expected for a radiative star. These results imply there is no credible evidence for eccentric orbits in binaries with contact components. I also present some speculative analyses of the observed properties of a binary encased in a non-rotating common envelope, if such an object could actually exist, and discuss how the limb darkening of some recently calculated model atmospheres for giant stars may bias my resuts for velocity-curve distortions, as well as other results from a wide range of analyses of binary stars.Comment: 14 pp, 2 tables, 12 fig; under review by Ap

    Unsuspected Perversities in the Theory of Location

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    On an infinitely-extensible plane (with uniform customer-density) the socially-optimal configuration of firms is a regular hexagonal lattice. Will the free market necessarily produce this configuration? We argue that the currently-accepted, affirmative answer has been erroneously derived from models in which equilibrium is undefined, and in which equilibrium conditions are asserted rather than being derived from behavioural postulates. We answer the question negatively, showing that, in a standard location model: (a) many configurations, including the hexagonal, satisfy the equilibrium conditions (and in no case is zero profits a necessary condition for equilibrium); and (b) if a hexagonal configuration is initially imposed, it is much less likely to persist through successive rounds of entry than is a square or a rectangular configuration.

    Sugar beets in Iowa, 1891

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    As agreed when this co-operative work was proposed, we have collated the reports made by all the growers and have attempted to gather therefrom whatever of general interest could be found. It was sought to discover what effects, if any, upon the saccharine quality of the crop had resulted from differences in— 1. Variety of the beet. 2. Kind of soil. 3. Mode of culture (in various particulars.

    Sugar beets in Iowa, 1891, not including those grown on the station grounds

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    The proposition made in Bulletin No. 12 for an extensive investigation of the possibilities of sugar beet culture in this state, to be made jointly by the farmers of the state and the chemical section of the station, has resulted in the work whose numerical data are reported in this article. The results here recorded are almost wholly those obtained in the laboratory. The information furnished by the growers regarding the character of the soil in which the beets were grown and its treatment before planting and during growth of the crop, must be brought into condensed form before it can be of much value to the public, (even if it then be), and as it will take considerable time to do this, that portion of our report is reserved for a future bulletin

    Recent origin of low trabecular bone density in modern humans

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    Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations

    An evaluation of the stimulants and impediments to innovation within PFI/PPP projects

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    This paper identifies the theoretical stimulants and impediments associated with the implementation of PFI/PPP (Private Finance Initiative/Public Private Partnership) projects. A current defect of this procurement approach is the unintentional constraint upon the innovations incorporated into the development of PFI projects. A critical evaluation of the published literature has been utilized to synthesize a theoretical model. The paper proposes a theoretical model for the identification of potential innovation stimulants and impediments within this type of procurement. This theoretical model is then utilised to evaluate four previously completed PFI projects. These project case-studies have been examined in detail. The evaluation demonstrates how ineffective current procedures are. The application of this model before project letting could eliminate unintentional constraints and stimulate improved innovation within the process. The implementation of the model could improve the successful delivery of innovation within the entire PFI/PPP procurement process

    The Hudson Bay Lithospheric Experiment (HuBLE) : Insights into Precambrian Plate Tectonics and the Development of Mantle Keels

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    The UK component of HuBLE was supported by Natural Environment Research Council (NERC) grant NE/F007337/1, with financial and logistical support from the Geological Survey of Canada, Canada–Nunavut Geoscience Office, SEIS-UK (the seismic node of NERC), and First Nations communities of Nunavut. J. Beauchesne and J. Kendall provided invaluable assistance in the field. Discussions with M. St-Onge, T. Skulski, D. Corrigan and M. Sanborne-Barrie were helpful for interpretation of the data. D. Eaton and F. A. Darbyshire acknowledge the Natural Sciences and Engineering Research Council. Four stations on the Belcher Islands and northern Quebec were installed by the University of Western Ontario and funded through a grant to D. Eaton (UWO Academic Development Fund). I. Bastow is funded by the Leverhulme Trust. This is Natural Resources Canada Contribution 20130084 to its Geomapping for Energy and Minerals Program. This work has received funding from the European Research Council under the European Unions Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement no. 240473 ‘CoMITAC’.Peer reviewedPublisher PD

    An Optical Study of BG Geminorum: An Ellipsoidal Binary with an Unseen Primar Star

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    We describe optical photometric and spectroscopic observations of the bright variable BG Geminorum. Optical photometry shows a pronounced ellipsoidal variation of the K0 I secondary, with amplitudes of ~0.5 mag at VRI and a period of 91.645 days. A deep primary eclipse is visible for wavelengths < 4400A; a shallower secondary eclipse is present at longer wavelengths. Eclipse timings and the radial velocity curve of the K0 secondary star indicate an interacting binary where a lobe-filling secondary, M_2 ~ 0.5 Msun, transfers material into a extended disk around a massive primary, M_1 ~ 4.5 Msun. The primary star is either an early B-type star or a black hole. If it did contain a black hole, BG Gem would be the longest period black hole binary known by a factor of 10, as well as the only eclipsing black hole binary system.Comment: 27 pages, includes 8 figures and 5 tables, accepted to A
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