597 research outputs found
The SMC SNR 1E0102.2-7219 as a Calibration Standard for X-ray Astronomy in the 0.3-2.5 keV Bandpass
The flight calibration of the spectral response of CCD instruments below 1.5
keV is difficult in general because of the lack of strong lines in the on-board
calibration sources typically available. We have been using 1E 0102.2-7219, the
brightest supernova remnant in the Small Magellanic Cloud, to evaluate the
response models of the ACIS CCDs on the Chandra X-ray Observatory (CXO), the
EPIC CCDs on the XMM-Newton Observatory, the XIS CCDs on the Suzaku
Observatory, and the XRT CCD on the Swift Observatory. E0102 has strong lines
of O, Ne, and Mg below 1.5 keV and little or no Fe emission to complicate the
spectrum. The spectrum of E0102 has been well characterized using
high-resolution grating instruments, namely the XMM-Newton RGS and the CXO
HETG, through which a consistent spectral model has been developed that can
then be used to fit the lower-resolution CCD spectra. We have also used the
measured intensities of the lines to investigate the consistency of the
effective area models for the various instruments around the bright O (~570 eV
and 654 eV) and Ne (~910 eV and 1022 eV) lines. We find that the measured
fluxes of the O VII triplet, the O VIII Ly-alpha line, the Ne IX triplet, and
the Ne X Ly-alpha line generally agree to within +/-10 % for all instruments,
with 28 of our 32 fitted normalizations within +/-10% of the RGS-determined
value. The maximum discrepancies, computed as the percentage difference between
the lowest and highest normalization for any instrument pair, are 23% for the O
VII triplet, 24% for the O VIII Ly-alpha line, 13% for the Ne IX triplet, and
19% for the Ne X Ly-alpha line. If only the CXO and XMM are compared, the
maximum discrepancies are 22% for the O VII triplet, 16% for the O VIII
Ly-alpha line, 4% for the Ne IX triplet, and 12% for the Ne X Ly-alpha line.Comment: 16 pages, 11 figures, to be published in Proceedings of the SPIE
7011: Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray 200
Genetic Elements Involved in Zika Virus Neuropathogenesis
Zikavirus (ZIKV) is a mosquito-borne flavivirus(Fig. 1) that is closely related to Japanese encephalitis, West Nile, yellow fever, and dengue viruses. ZIKV was first discovered in Uganda in 1947, but it was not until recent outbreaks, such as through Micronesia in 2007 and through Brazil in 2015 (Fig. 2), that it has been found to be associated with neurological diseases such as Guillain-Barrésyndrome and microcephaly
A 21-year record of vertically migrating subepilimnetic populations of Cryptomonas spp.
The vertical distribution and diel migration of Cryptomonas spp. were monitored continuously for 21 years in mesotrophic Cross Reservoir, northeast Kansas, USA. The movements of these motile algae were tracked on multiple dates during JulyâOctober of each year using in situ fluorometry and optical microscopy of Lugolâs iodine-preserved samples. Episodes of subepilimnetic diel vertical migration by Cryptomonas were detected and recorded on 221 different days between 1994 and 2014, with just 2 of these years (1998 and 2013) lacking any sampling events with deep peaks sufficiently large enough to track. Whenever a subepilimnetic layer of Cryptomonas was detectable, it was generally observed to ascend toward the bottom of the epilimnion beginning approximately at sunrise; to descend toward the lake bottom during the late afternoon and evening; and to remain as a deep-dwelling population until dawn of the following day. Moreover, there was high day-to-day consistency in the absolute water column depths at which the migrating algal cells would cease their ascending or descending movement. We believe this unique and remarkable dataset comprises the most detailed record of diel migratory behavior for any planktonic freshwater alga reported for a single freshwater lake
Materiality in the future of history: things, practices, and politics
Frank Trentmann is professor of history at Birkbeck College, University of London. From 2002 to 2007, he was director of the ÂŁ5 million Cultures of Consumption research program, cofunded by the Arts and Humanities Research Council and the Economic and Social Research Council (ESRC). He is working on a book for Penguin, The Consuming Passion: How Things Came to Seduce, Enrich, and Define Our Lives, from the Seventeenth Century to the TwentyâFirst. This article is one of a pair seeking to facilitate greater exchange between history and the social sciences. Its twinââCrossing Divides: Globalization and Consumption in Historyâ (forthcoming in the Handbook of Globalization Studies, ed. Bryan Turner)âshows what social scientists (and contemporary historians) might learn from earlier histories. The piece here follows the flow in the other direction. Many thanks to the ESRC for grant number RESâ052â27â002 and, for their comments, to Heather Chappells, Steve Pincus, Elizabeth Shove, and the editor and the reviewer
Marketing Planning of Small-Sized Farms by the Fuzzy Game Theory
Walking fosters selfâefficacy, empathy, and connection, and large and small democratic actions. Such capacity seems especially the case when walking is attended by certain spatial qualities that engender, for instance, physical accessibility, a capacity to socialise, a sense of safety, or a pleasing aesthetic. Sometimes, adverse spatial alternatives dominate and then â at very least â indifference seems to loom large and spatial injustices prevail. And in the worst conditions, indifference and injustice tip over into fear and danger. This paper's orientation is towards optimism, however. Our conceptual focus is on the relationship of walking to geography and philosophical pragmatism, and on small and effective antidotes to indifference and injustice. Our empirical contributions come from a qualitative research project in Wollongong, Australia, and specifically from conversations with 25 adult residents who shared with us their experiences of regular walks in the city centre. We interpret those experiences in pragmatic terms as transactions â or experiments in what to do and how â in relation to self, others, and environs. We show how participants are affected by walks and the transactional spaces created by them, and consider how they come to care for things that might not directly concern or affect them. In the process, we discern that they experience how their actions shape and can enrich life in the city â findings that have wider salience for those interested in spatial qualities, spatial justice, and democratising impulses
Thin accretion disc with a corona in a central magnetic field
We study the steady-state structure of an accretion disc with a corona
surrounding a central, rotating, magnetized star. We assume that the
magneto-rotational instability is the dominant mechanism of angular momentum
transport inside the disc and is responsible for producing magnetic tubes above
the disc. In our model, a fraction of the dissipated energy inside the disc is
transported to the corona via these magnetic tubes. This energy exchange from
the disc to the corona which depends on the disc physical properties is
modified because of the magnetic interaction between the stellar magnetic field
and the accretion disc. According to our fully analytical solutions for such a
system, the existence of a corona not only increases the surface density but
reduces the temperature of the accretion disc. Also, the presence of a corona
enhances the ratio of gas pressure to the total pressure. Our solutions show
that when the strength of the magnetic field of the central neutron star is
large or the star is rotating fast enough, profiles of the physical variables
of the disc significantly modify due to the existence of a corona.Comment: Accepted for publication in Astrophysics & Space Scienc
Property as Legal Knowledge: Means and Ends
This article takes anthropologistsâ renewed interest in property theory as an opportunity to consider legal theory-making as an ethnographic subject in its own right. My focus is on one particular construct â the instrument, or relation of means to ends, that animates both legal and anthropological theories about property. An analysis of the workings of this construct leads to the conclusion that rather than critique the ends of legal knowledge, the anthropology of property should devote itself to articulating its own means
Researching retired ex-servicemen: reflections on ethnographic encounters
The opportunities and challenges that younger, female, civilian researchers can encounter when undertaking ethnographic research with predominantly male military veterans are relatively underexplored sociologically. This is despite a growing literature on reflexivity in military studies over the past decade. To address this gap, we draw on symbolic interactionist insights to examine the reflective account of a British, female researcher in her mid-20s, who conducted qualitative research with 20 âolderâ (aged 60+) retired servicemen from the Royal British Legion, a United Kingdom charity providing support for military veterans and their families. The study explored ex-servicemenâs embodied experiences of physical activity. The findings presented here cohere around four salient themes identified in the ethnographic reflections: (1) researcher positionality as a young, female, civilian researcher in a traditionally masculine militarised world; (2) managing distressing topics and interactional discomfort; (3) maintaining an âethic of careâ; and (4) dilemmas regarding representational issues and ex-servicemenâs embodied experiences
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