282 research outputs found
Viking Lander Atlas of Mars
Half size reproductions are presented of the extensive set of systematic map products generated for the two Mars Viking landing sites from stereo pairs of images radioed back to Earth. The maps span from the immediate foreground to the remote limits of ranging capability, several hundred meters from the spacecraft. The maps are of two kinds - elevation contour and vertical profile. Background and explanatory material important for understanding and utilizing the map collection included covers the Viking Mission, lander locations, lander cameras, the stereo mapping system and input images to this system
Strong gravitational lensing across dilaton anti-de Sitter black hole
In this work we investigate gravitational lensing effect in strong field
region around a dilaton black holes in an anti de Sitter (ADS) space. We also
analyse the dependence of the radius of the photon sphere and deflection angle
on dilaton coupling and cosmological constant in this black hole space time.
Finally the values of minimum impact parameter, the separation between the
first and the other images as well as the ratio between the flux of the first
image and the flux coming from all the other images are determined to
characterize some possible distinct signatures of such black holes.Comment: 8 pages and 3 figures. Accepted in Physical Review
Microlensing by Cosmic Strings
We consider the signature and detectability of gravitational microlensing of
distant quasars by cosmic strings. Because of the simple image configuration
such events will have a characteristic light curve, in which a source would
appear to brighten by exactly a factor of two, before reverting to its original
apparent brightness. We calculate the optical depth and event rate, and
conclude that current predictions and limits on the total length of strings on
the sky imply optical depths of \la 10^{-8} and event rates of fewer than one
event per sources per year. Disregarding those predictions but replacing
them with limits on the density of cosmic strings from the CMB fluctuation
spectrum, leaves only a small region of parameter space (in which the sky
contains about strings with deficit angle of order 0.3
milli-arcseconds) for which a microlensing survey of exposure
source-years, spanning a 20--40-year period, might reveal the presence of
cosmic strings.Comment: 4 pages, accepted for publication in MNRA
Schwarzschild black hole lensing
We study strong gravitational lensing due to a Schwarzschild black hole.
Apart from the primary and the secondary images we find a sequence of images on
both sides of the optic axis; we call them {\em relativistic images}. These
images are formed due to large bending of light near r = 3M (the closest
distance of approach r_o is greater than 3M). The sources of the entire
universe are mapped in the vicinity of the black hole by these images. For the
case of the Galactic supermassive ``black hole'' they are formed at about 17
microarcseconds from the optic axis. The relativistic images are not resolved
among themselves, but they are resolved from the primary and secondary images.
However the relativistic images are very much demagnified unless the observer,
lens and source are very highly aligned. Due to this and some other
difficulties the observation of these images does not seem to be feasible in
near future. However, it would be a great success of the general theory of
relativity in a strong gravitational field if they ever were observed and it
would also give an upper bound, r_o = 3.21 M, to the compactness of the lens,
which would support the black hole interpretation of the lensing object.Comment: RevTex, 5 eps files are included, observational difficulties are
discussed and there are some changes in presentatio
Strong Gravitational Lensing in a Charged Squashed Kaluza- Klein Black hole
In this paper we investigate the strong gravitational lensing in a charged
squashed Kaluza-Klein black hole. We suppose that the supermassive black hole
in the galaxy center can be considered by a charged squashed Kaluza-Klein black
hole and then we study the strong gravitational lensing theory and estimate the
numerical values for parameters and observables of it. We explore the effects
of the scale of extra dimension and the charge of black hole
on these parameters and observables.Comment: 17 pages, 10 figure
A frozen super-Earth orbiting a star at the bottom of the Main Sequence
We observed the microlensing event MOA-2007-BLG-192 at high angular
resolution in JHKs with the NACO adaptive optics system on the VLT while the
object was still amplified by a factor 1.23 and then at baseline 18 months
later. We analyzed and calibrated the NACO photometry in the standard 2MASS
system in order to accurately constrain the source and the lens star fluxes. We
detect light from the host star of MOA-2007-BLG-192Lb, which significantly
reduces the uncertainties in its char- acteristics as compared to earlier
analyses. We find that MOA-2007-BLG-192L is most likely a very low mass late
type M-dwarf (0.084 [+0.015] [-0.012] M\odot) at a distance of 660 [+100] [-70]
pc orbited by a 3.2 [+5.2] [-1.8] M\oplus super-Earth at 0.66 [+0.51] [-0.22]
AU. We then discuss the properties of this cold planetary system.Comment: published version A&A 540, A78 (2012) A&A, 10 pages, 7 Figure
Increased shedding of HU177 correlates with worse prognosis in primary melanoma
<p>Abstract</p> <p>Background</p> <p>Increased levels of cryptic collagen epitope HU177 in the sera of melanoma patients have been shown to be associated with thicker primary melanomas and with the nodular histologic subtype. In this study, we investigate the association between HU177 shedding in the sera and clinical outcome in terms of disease-free survival (DFS) and overall survival (OS).</p> <p>Methods</p> <p>Serum samples from 209 patients with primary melanoma prospectively enrolled in the Interdisciplinary Melanoma Cooperative Group at the New York University Langone Medical Center (mean age = 58, mean thickness = 2.09 mm, stage I = 136, stage II = 41, stage III = 32, median follow-up = 54.9 months) were analyzed for HU177 concentration using a validated ELISA assay. HU177 serum levels at the time of diagnosis were used to divide the study cohort into two groups: low and high HU177. DFS and OS were estimated by Kaplan-Meier survival analysis, and the log-rank test was used to compare DFS and OS between the two HU177 groups. Multivariate Cox proportional hazards regression models were employed to examine the independent effect of HU177 category on DFS and OS.</p> <p>Results</p> <p>HU177 sera concentrations ranged from 0-139.8 ng/ml (mean and median of 6.2 ng/ml and 3.7 ng/ml, respectively). Thirty-eight of the 209 (18%) patients developed recurrences, and 34 of the 209 (16%) patients died during follow-up. Higher HU177 serum level was associated with an increased rate of melanoma recurrence (p = 0.04) and with increasing mortality (p = 0.01). The association with overall survival remained statistically significant after controlling for thickness and histologic subtype in a multivariate model (p = 0.035).</p> <p>Conclusions</p> <p>Increased shedding of HU177 in the serum of primary melanoma patients is associated with poor prognosis. Further studies are warranted to determine the clinical utility of HU177 in risk stratification compared to the current standard of care.</p
Detection of Extrasolar Planets by Gravitational Microlensing
Gravitational microlensing provides a unique window on the properties and
prevalence of extrasolar planetary systems because of its ability to find
low-mass planets at separations of a few AU. The early evidence from
microlensing indicates that the most common type of exoplanet yet detected are
the so-called "super-Earth" planets of ~10 Earth-masses at a separation of a
few AU from their host stars. The detection of two such planets indicates that
roughly one third of stars have such planets in the separation range 1.5-4 AU,
which is about an order of magnitude larger than the prevalence of gas-giant
planets at these separations. We review the basic physics of the microlensing
method, and show why this method allows the detection of Earth-mass planets at
separations of 2-3 AU with ground-based observations. We explore the conditions
that allow the detection of the planetary host stars and allow measurement of
planetary orbital parameters. Finally, we show that a low-cost, space-based
microlensing survey can provide a comprehensive statistical census of
extrasolar planetary systems with sensitivity down to 0.1 Earth-masses at
separations ranging from 0.5 AU to infinity.Comment: 43 pages. Very similar to chapter 3 of Exoplanets: Detection,
Formation, Properties, Habitability, John Mason, ed. Springer (April 3, 2008
Planetary microlensing signals from the orbital motion of the source star around the common barycentre
With several detections, the technique of gravitational microlensing has
proven useful for studying planets that orbit stars at Galactic distances, and
it can even be applied to detect planets in neighbouring galaxies. So far,
planet detections by microlensing have been considered to result from a change
in the bending of light and the resulting magnification caused by a planet
around the foreground lens star. However, in complete analogy to the annual
parallax effect caused by the revolution of the Earth around the Sun, the
motion of the source star around the common barycentre with an orbiting planet
can also lead to observable deviations in microlensing light curves that can
provide evidence for the unseen companion. We discuss this effect in some
detail and study the prospects of microlensing observations for revealing
planets through this alternative detection channel. Given that small distances
between lens and source star are favoured, and that the effect becomes nearly
independent of the source distance, planets would remain detectable even if
their host star is located outside the Milky Way with a sufficiently good
photometry (exceeding present-day technology) being possible. From synthetic
light curves arising from a Monte-Carlo simulation, we find that the chances
for such detections are not overwhelming and appear practically limited to the
most massive planets (at least with current observational set-ups), but they
are large enough for leaving the possibility that one or the other signal has
already been observed. However, it may remain undetermined whether the planet
actually orbits the source star or rather the lens star, which leaves us with
an ambiguity not only with respect to its location, but also to its properties.Comment: 12 pages with 9 embedded figures, MNRAS accepte
Coming out with the media: the ritualization of self-disclosure in the Dutch television program Uit de Kast
Using the media to disclose one’s sexual identity has become an increasingly salient practice in recent years. Yet little is known about the reasons for the emergence of this form of self-disclosure. Based on an analysis of the Dutch television programme Uit de Kast (‘Out of the Closet’), this article relates the rise of mediated coming out practices to the ritualizing power of the media: we argue that media plays a quintessential role in transforming the socially unscripted act of coming out into a patterned, culturally meaningful performance. Our analysis reveals that the ritual work of the programme is embedded in the ways 1) the generic format of the show structures the self-disclosures, 2) the authority of the media is deployed to channel the coming out process, and 3) the programme, while controlling diversity, reinforces dominant societal values and ideologies. The case not only highlights how unprecedented ritual forms come to flourish in the current era of ‘participatory’ media culture, but also demonstrates how ritualization supports and naturalizes the claim that media is an effective agent to create order in everyday, ordinary lives
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