266 research outputs found
Numerical Simulations of Pinhole and Single Mode Fibre Spatial Filters for Optical Interferometers
We use a numerical simulation to investigate the effectiveness of pinhole
spatial filters at optical/IR interferometers and to compare them with
single-mode optical fibre spatial filters and interferometers without spatial
filters. We show that fringe visibility measurements in interferometers
containing spatial filters are much less affected by changing seeing conditions
than equivalent measurements without spatial filters. This reduces visibility
calibration uncertainties, and hence can reduce the need for frequent
observations of separate astronomical sources for calibration of visibility
measurements. We also show that spatial filters can increase the
signal-to-noise ratios of visibility measurements and that pinhole filters give
signal-to-noise ratios within 17% of values obtained with single-mode fibres
for aperture diameters up to 3r_0. Given the simplicity of the use of pinhole
filters we suggest that it represents a competitive, if not optimal, technique
for spatial filtering in many current and next generation interferometers.Comment: 7 pages, 7 postscript figures. Accepted by MNRA
Ethoarchaeology and Elementary Technology of Unhabituated Wild Chimpanzees at Assirik, Senegal, West Africa
Like other wild chimpanzees (Pan troglodytes), the savanna-dwelling apes of Assirik, Senegal, West Africa, make and use tools and so have an elementary technology. Unlike their more famous counterparts elsewhere in Africa, these apes are not observable at close range. Instead, they are amenable to etho-archaeological study, in which the indirect data of artifacts, remnants, and fecal contents add to the sparse behavioral data. These open-country hominoids show 15 behavioral patterns that appear to be material culture, in the minimal sense of socially learned behavioral diversity. These can be divided into subsistence (N = 7), social (5) and maintenance (3) activities shown at customary, habitual, or present levels of frequency. Some patterns, such as Termite Fish or Baobab Crack, leave behind assemblages of hundreds of artifacts or remnants in predictable contexts at enduring worksites. Other patterns are rare and ephemeral and are known only from anecdotal data. Almost all artifacts and remnants are non-lithic, and so their perishability limits their discovery and analysis. Maximally productive use of such data depends on close collaboration between archaeology and primatolog
Tracing the evolution of nearby early-type galaxies in low density environments. The Ultraviolet view from GALEX
We detected recent star formation in nearby early-type galaxies located in
low density environments, with GALEX Ultraviolet (UV) imaging. Signatures of
star formation may be present in the nucleus and in outer rings/arm like
structures. Our study suggests that such star formation may be induced by
different triggering mechanisms, such as the inner secular evolution driven by
bars, and minor accretion phenomena. We investigate the nature of the (FUV-NUV)
color vs. Mg2 correlation, and suggest that it relates to "downsizing" in
galaxy formation.Comment: Conference "UV Universe 2010" S. Petersburg 31 May - 3 June, 2010
Accepted for publication in Astrophysics & Space Science . The final
publication is available at http://www.springerlink.co
Modelling Effects of Tariff Liberalisation on India’s Key Export Sectors: Analysis of the EU–India Free Trade Agreement
Trade agreements are increasingly being negotiated between developed and emerging economy partners. An example is the EU–India Free Trade Agreement (FTA) for which negotiations began in 2007. There has been a debate on the potential effects of the proposed FTA and how this can impact on India’s key export sectors. Our study addresses this aspect from a global computable general equilibrium (CGE) modelling perspective. Using the Global Trade Analysis Project (GTAP) framework, we analyse trade and welfare impacts of the proposed FTA between the EU and India. Two scenarios are modelled: first, complete and immediate elimination of tariff on all goods traded and second, selective tariff elimination on textiles, wearing apparel and leather goods—products in which India has a comparative advantage. Results under both scenarios show that India enjoys positive welfare effects though there is a possibility of trade diversion. Under scenario 1, India loses due to a negative terms of trade (ToT) effect. Under scenario 2, with selective sectoral liberalisation, gains are mainly concentrated in the textiles, wearing apparel and leather sectors. There is a positive output effect from change in demand for factors of production, suggesting that the proposed FTA could lead to relocation of labour-intensive production to India
The Kent State "2π" Neutron Polarimeter
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Performance of a Neutron Polarimeter to Measure the Electric Form Factor of the Neutron
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
'Education, education, education' : legal, moral and clinical
This article brings together Professor Donald Nicolson's intellectual interest in professional legal ethics and his long-standing involvement with law clinics both as an advisor at the University of Cape Town and Director of the University of Bristol Law Clinic and the University of Strathclyde Law Clinic. In this article he looks at how legal education may help start this process of character development, arguing that the best means is through student involvement in voluntary law clinics. And here he builds upon his recent article which argues for voluntary, community service oriented law clinics over those which emphasise the education of students
The Interaction of αB-Crystallin with Mature α-Synuclein Amyloid Fibrils Inhibits Their Elongation
αB-Crystallin is a small heat-shock protein (sHsp) that is colocalized
with α-synuclein (αSyn) in
Lewy bodies—the pathological hallmarks of Parkinson's
disease—and is an inhibitor of αSyn amyloid
fibril formation in an ATP-independent manner in vitro. We have
investigated the mechanism underlying the inhibitory action of sHsps, and here
we establish, by means of a variety of biophysical techniques including
immunogold labeling and nuclear magnetic resonance spectroscopy, that
αB-crystallin interacts with
αSyn, binding along the length of mature amyloid
fibrils. By measurement of seeded fibril elongation kinetics, both in solution
and on a surface using a quartz crystal microbalance, this binding is shown to
strongly inhibit further growth of the fibrils. The binding is also demonstrated
to shift the monomer-fibril equilibrium in favor of dissociation. We believe
that this mechanism, by which a sHsp interacts with mature amyloid fibrils,
could represent an additional and potentially generic means by which at least
some chaperones protect against amyloid aggregation and limit the onset of
misfolding diseases
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
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