2,795 research outputs found
What happened to the inventory overhang?
The large inventory buildup in the first half of 1997 led to media warnings of a substantially weaker economy by year's end. The authors examine the rationale for these warnings, and argue that inventory accumulation is an unreliable predictor of future economic strength.Inventories ; Business cycles
Critical Reception and Postmodern Violation of Generic Conventions in Jacques Brossard’s "Monument aux marges": L’Oiseau de feu
Québec writer Jacques-Edmond Brossard's 1989 novel, L'oiseau de feu-1. Les années d'apprentissage, first of the five-part Oiseau series, created a literary sensation as a potential monument of la science-fiction québécoise. Despite critical approbation, however, few readers endeavour beyond the series' first instalment, and the whole stands at the margins of the field both for readers and scholars. In part, the difficulty of identifying Brossard as primarily a mainstream or a science-fiction writer has estranged fans and critics of both camps. But more importantly, his series' ludic irreverence toward and self-conscious play with generic conventions – one of its many postmodern features – works against its long-term engagement of québécois/French-Canadian critics in both the mainstream and the genre milieux. Yet, this "monument aux marges" deserves more attention precisely because of its postmodernism
Mark Bould and Williams Rhys, Sf Now
Who said the Left is dead? It is alive and kicking in a major strain of science-fiction writing and criticism as witnessed in the most recent edition of the annual journal Paradoxa, edited by Mark Bould and Rhys Williams appropriately titled Sf Now. If this is a publication that is not on your radar because of its annual appearance, if you are interested in rigorous, cutting edge scholarship, you should check it out (paradoxa.com). With an international editorial board that includes such heav..
ARMD Workshop on Materials and Methods for Rapid Manufacturing for Commercial and Urban Aviation
This report documents the goals, organization and outcomes of the NASA Aeronautics Research Mission Directorates (ARMD) Materials and Methods for Rapid Manufacturing for Commercial and Urban Aviation Workshop. The workshop began with a series of plenary presentations by leaders in the field of structures and materials, followed by concurrent symposia focused on forecasting the future of various technologies related to rapid manufacturing of metallic materials and polymeric matrix composites, referred to herein as composites. Shortly after the workshop, questionnaires were sent to key workshop participants from the aerospace industry with requests to rank the importance of a series of potential investment areas identified during the workshop. Outcomes from the workshop and subsequent questionnaires are being used as guidance for NASA investments in this important technology area
A High-Frequency Search for Pulsars Within the Central Parsec of SgrA*
We report results from a deep high-frequency search for pulsars within the
central parsec of Sgr A* using the Green Bank Telescope. The observing
frequency of 15 GHz was chosen to maximize the likelihood of detecting normal
pulsars (i.e. with periods of \,ms and spectral indices of ) close to Sgr A*, that might be used as probes of gravity in the
strong-field regime; this is the highest frequency used for such pulsar
searches of the Galactic Center to date. No convincing candidate was detected
in the survey, with a detection threshold of Jy
achieved in two separate observing sessions. This survey represents a
significant improvement over previous searches for pulsars at the Galactic
Center and would have detected a significant fraction ($\gtrsim 5%) of the
pulsars around Sgr A*, if they had properties similar to those of the known
population. Using our best current knowledge of the properties of the Galactic
pulsar population and the scattering material toward Sgr A*, we estimate an
upper limit of 90 normal pulsars in orbit within the central parsec of Sgr A*.Comment: 10 pages, 7 figures, accepted for publication in the ApJ
Out of the frying pan: a young pulsar with a long radio trail emerging from SNR G315.9-0.0
The faint radio supernova remnant SNR G315.9-0.0 is notable for a long and
thin trail that extends outward perpendicular from the edge of its
approximately circular shell. In a search with the Parkes telescope we have
found a young and energetic pulsar that is located at the tip of this
collimated linear structure. PSR J1437-5959 has period P = 61 ms,
characteristic age tau_c = 114 kyr, and spin-down luminosity dE/dt = 1.4e36
erg/s. It is very faint, with a flux density at 1.4 GHz of about 75 uJy. From
its dispersion measure of 549 pc/cc, we infer d ~ 8 kpc. At this distance and
for an age comparable to tau_c, the implied pulsar velocity in the plane of the
sky is V_t = 300 km/s for a birth at the center of the SNR, although it is
possible that the SNR/pulsar system is younger than tau_c and that V_t > 300
km/s. The highly collimated linear feature is evidently the pulsar wind trail
left from the supersonic passage of PSR J1437-5959 through the interstellar
medium surrounding SNR G315.9-0.0.Comment: accepted for publication in ApJ Letter
1E 1547.0-5408: a radio-emitting magnetar with a rotation period of 2 seconds
The variable X-ray source 1E 1547.0-5408 was identified by Gelfand & Gaensler
(2007) as a likely magnetar in G327.24-0.13, an apparent supernova remnant. No
X-ray pulsations have been detected from it. Using the Parkes radio telescope,
we discovered pulsations with period P = 2.069 s. Using the Australia Telescope
Compact Array, we localized these to 1E 1547.0-5408. We measure dP/dt =
(2.318+-0.005)e-11, which for a magnetic dipole rotating in vacuo gives a
surface field strength of 2.2e14 G, a characteristic age of 1.4 kyr, and a
spin-down luminosity of 1.0e35 ergs/s. Together with its X-ray characteristics,
these rotational parameters of 1E 1547.0-5408 prove that it is a magnetar, only
the second known to emit radio waves. The distance is ~9 kpc, derived from the
dispersion measure of 830 pc/cc. The pulse profile at a frequency of 1.4 GHz is
extremely broad and asymmetric due to multipath propagation in the ISM, as a
result of which only approximately 75% of the total flux at 1.4 GHz is pulsed.
At higher frequencies the profile is more symmetric and has FWHM = 0.12P.
Unlike in normal radio pulsars, but in common with the other known
radio-emitting magnetar, XTE J1810-197, the spectrum over 1.4-6.6 GHz is flat
or rising, and we observe large, sudden changes in the pulse shape. In a
contemporaneous Swift X-ray observation, 1E 1547.0-5408 was detected with
record high flux, f_X(1-8 keV) ~ 5e-12 ergs/cm^2/s, 16 times the historic
minimum. The pulsar was undetected in archival radio observations from 1998,
implying a flux < 0.2 times the present level. Together with the transient
behavior of XTE J1810-197, these results suggest that radio emission is
triggered by X-ray outbursts of usually quiescent magnetars.Comment: Accepted for publication in ApJ Letter
Modelling systems that integrate programming language and environment mechanisms
Once we relax the assumption that it must be possible to specify programs solely in terms of text and enter them in isolation from other tools, the range of possible program development mechanisms is significantly increased. Thus, in the light of advances in the field of integrated software development environments and in view of the wider availability of suitable workstations, we should reconsider the way we perceive (and, hence design) programming languages. This paper describes on-going work aimed at exploring the role of the programming language in the context of modern software development environments. The work is currently focused on two fronts: the development of a formalism for describing both a programming language and associated environment mechanisms, and the design of environment mechanisms that support software maintenance and reuse, complementing those traditionally provided by programming languages. This paper focuses on work in the first of these two areas
Polarized radio emission from the magnetar XTE J1810-197
We have used the Parkes radio telescope to study the polarized emission from
the anomalous X-ray pulsar XTE J1810-197 at frequencies of 1.4, 3.2, and 8.4
GHz. We find that the pulsed emission is nearly 100% linearly polarized. The
position angle of linear polarization varies gently across the observed pulse
profiles, varying little with observing frequency or time, even as the pulse
profiles have changed dramatically over a period of 7 months. In the context of
the standard pulsar "rotating vector model," there are two possible
interpretations of the observed position angle swing coupled with the wide
profile. In the first, the magnetic and rotation axes are substantially
misaligned and the emission originates high in the magnetosphere, as seen for
other young radio pulsars, and the beaming fraction is large. In the second
interpretation, the magnetic and rotation axes are nearly aligned and the line
of sight remains in the emission zone over almost the entire pulse phase. We
deprecate this possibility because of the observed large modulation of thermal
X-ray flux. We have also measured the Faraday rotation caused by the Galactic
magnetic field, RM = +77 rad/m^2, implying an average magnetic field component
along the line of sight of 0.5 microG.Comment: Accepted for publication in ApJ Letters. Six pages with 4 figure
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