4,284 research outputs found

    Investigation of relationships between linears, total and hazy areas, and petroleum production in the Williston Basin: An ERTS approach

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    The author has identified the following significant results. ERTS-1 imagery in a variety of formats was used to locate linear, tonal, and hazy features and to relate them to areas of hydrocarbon production in the Williston Basin of North Dakota, eastern Montana, and northern South Dakota. Derivative maps of rectilinear, curvilinear, tonal, and hazy features were made using standard laboratory techniques. Mapping of rectilinears on both bands 5 and 7 over the entire region indicated the presence of a northeast-southwest and a northwest-southeast regional trend which is indicative of the bedrock fracture pattern in the basin. Curved lines generally bound areas of unique tone, maps of tonal patterns repeat many of the boundaries seen on curvilinear maps. Tones were best analyzed on spring and fall imagery in the Williston Basin. It is postulated that hazy areas are caused by atmospheric phenomena. The ability to use ERTS imagery as an exploration tool was examined where petroleum and gas are presently produced (Bottineau Field, Nesson and Antelope anticlines, Redwing Creek, and Cedar Creek anticline). It is determined that some tonal and linear features coincide with location of present production in Redwing and Cedar Creeks. In the remaining cases, targets could not be sufficiently well defined to justify this method

    X-ray polarimetry with an active-matrix pixel proportional counter

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    We report the first results from an X-ray polarimeter with a micropattern gas proportional counter using an amorphous silicon active matrix readout. With 100% polarized X-rays at 4.5 keV, we obtain a modulation factor of 0.33 +/- 0.03, confirming previous reports of the high polarization sensitivity of a finely segmented pixel proportional counter. The detector described here has a geometry suitable for the focal plane of an astronomical X-ray telescope. Amorphous silicon readout technology will enable additional extensions and improvements.Comment: 4 pages, 4 figures, 1 tabl

    Spectrum of Sizes for Perfect Deletion-Correcting Codes

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    One peculiarity with deletion-correcting codes is that perfect tt-deletion-correcting codes of the same length over the same alphabet can have different numbers of codewords, because the balls of radius tt with respect to the Levenshte\u{\i}n distance may be of different sizes. There is interest, therefore, in determining all possible sizes of a perfect tt-deletion-correcting code, given the length nn and the alphabet size~qq. In this paper, we determine completely the spectrum of possible sizes for perfect qq-ary 1-deletion-correcting codes of length three for all qq, and perfect qq-ary 2-deletion-correcting codes of length four for almost all qq, leaving only a small finite number of cases in doubt.Comment: 23 page

    Ultrafast harmonic mode-locking of monolithic compound-cavity laser diodes incorporating photonic-bandgap reflectors

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    We present the first demonstration of reproducible harmonic mode-locked operation from a novel design of monolithic semiconductor laser comprising a compound cavity formed by a 1-D photonic-bandgap (PBG) mirror. Mode-locking (ML) is achieved at a harmonic of the fundamental round-trip frequency with pulse repetition rates from 131 GHz up to a record high frequency of 2.1 THz. The devices are fabricated from GaAs-Al-GaAs material emitting at a wavelength of 860 nm and incorporate two gain sections with an etched PBG reflector between them, and a saturable absorber section. Autocorrelation studies are reported which allow the device behavior for different ML frequencies, compound cavity ratios, and type and number of intra-cavity reflectors to be analyzed. The highly reflective PBG microstructures are shown to be essential for subharmonic-free ML operation of the high-frequency devices. We have also demonstrated that the single PBG reflector can be replaced by two separate features with lower optical loss. These lasers may find applications in terahertz; imaging, medicine, ultrafast optical links, and atmospheric sensing

    Exercise physiologists: essential players in interdisciplinary teams for noncommunicable chronic disease management

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    Noncommunicable diseases (NCDs), such as obesity and type 2 diabetes mellitus, are a growing public health challenge in Australia, accounting for a significant and increasing cost to the health care system. Management of these chronic conditions is aided by interprofessional practice, but models of care require updating to incorporate the latest evidence-based practice. Increasing research evidence reports the benefits of physical activity and exercise on health status and the risk of inactivity to chronic disease development, yet physical activity advice is often the least comprehensive component of care. An essential but as yet underutilized player in NCD prevention and management is the “accredited exercise physiologist,” a specialist in the delivery of clinical exercise prescriptions for the prevention or management of chronic and complex conditions. In this article, the existing role of accredited exercise physiologists in interprofessional practice is examined, and an extension of their role proposed in primary health care settings

    A Monitoring Campaign for Luhman 16AB. I. Detection of Resolved Near-Infrared Spectroscopic Variability

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    [abbreviated] We report resolved near-infrared spectroscopic monitoring of the nearby L dwarf/T dwarf binary WISE J104915.57-531906.1AB (Luhman 16AB), as part of a broader campaign to characterize the spectral energy distribution and temporal variability of this system. A continuous 45-minute sequence of low-resolution IRTF/SpeX data spanning 0.8-2.4 micron were obtained, concurrent with combined-light optical photometry with ESO/TRAPPIST. Our spectral observations confirm the flux reversal of this binary, and we detect a wavelength-dependent decline in the relative spectral fluxes of the two components coincident with a decline in the combined-light optical brightness of the system over the course of the observation. These data are successfully modeled as a combination of brightness and color variability in the T0.5 Luhman 16B, consistent cloud variations; and no significant variability in L7.5 Luhman 16A. We estimate a peak-to-peak amplitude of 13.5% at 1.25 micron over the full lightcurve. Using a two-spot brightness temperature model, we infer an average cloud covering fraction of ~30-55% for Luhman 16B, varying by 15-30% over a rotation period. A Rhines scale interpretation for the size of the variable features explains an apparent correlation between period and amplitude for three highly variable T dwarfs, and predicts relatively fast winds (1-3 km/s) for Luhman 16B consistent with lightcurve evolution on an advective time scale (1-3 rotation periods). Our observations support the model of a patchy disruption of the mineral cloud layer as a universal feature of the L dwarf/T dwarf transition.Comment: 11 pages, 7 figures; accepted for publication in Astrophysical Journa

    Gravitational Microlensing Events from the First Year of the Northern Galactic Plane Survey by the Zwicky Transient Facility

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    The Zwicky Transient Facility (ZTF) (Bellm et al. 2019; Graham et al. 2019; Masci et al. 2019) is currently surveying the entire northern sky, including dense Galactic plane fields. Here, we present preliminary results of the search for gravitational microlensing events in the ZTF data collected from the beginning of the survey (2018 March 20) through 2019 June 30

    Literacy under and over the desk: oppositions and heterogeneity

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    In this paper I argue that a dominant theme in New Literacy Studies research, the differences between literacy practices inside and outside school, has sometimes involved conflating ‘home literacy’ with private, unregulated ‘vernacular literacy’, and the use of an idealised abstract notion of schooled literacy to represent students’ actual everyday experience in the classroom. Drawing on linguistic ethnographic research in two British primary schools, I use examples of ‘unofficial’ and ‘official’ literacy activities from 10-11 year-olds to show that a wide range of different forms of literacy can be found in the classroom and I argue that the division between ‘vernacular’ and ‘schooled’ is not as clear-cut as is sometimes assumed. My analysis of children’s literacy activities suggests that, on the one hand, unofficial activities orientate towards and index official knowledges and the macro-level institutional order and, on the other hand, official activities are interpenetrated with informal practices and procedures. I also comment on some implications of using the New Literacy Studies ‘events and practices’ conceptual framework for understanding what is going on in classrooms
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