24,742 research outputs found
Evidence for extended IR emission in NGC2798 and NGC6240
Extended emission at 10 and 20 microns can be used to distinguish starbursts from monsters as the underlying energy source driving the luminous infrared emission in the central regions of galaxies. The spatial extent of the mid infrared emission in the interacting galaxy NCG 2798 and the merger NGC 6240 were investigated. The 10 and 20 micron profiles of the IR source in NGC 2798 are significantly wider than beam profiles measured on a standard star, supporting a starburst interpretation of its IR luminosity. For NGC 6240 there is marginal evidence for an extended 10 micron source, suggesting that a significant fraction of its IR luminosity could be produced by a burst of star formation
On The Power of Tree Projections: Structural Tractability of Enumerating CSP Solutions
The problem of deciding whether CSP instances admit solutions has been deeply
studied in the literature, and several structural tractability results have
been derived so far. However, constraint satisfaction comes in practice as a
computation problem where the focus is either on finding one solution, or on
enumerating all solutions, possibly projected to some given set of output
variables. The paper investigates the structural tractability of the problem of
enumerating (possibly projected) solutions, where tractability means here
computable with polynomial delay (WPD), since in general exponentially many
solutions may be computed. A general framework based on the notion of tree
projection of hypergraphs is considered, which generalizes all known
decomposition methods. Tractability results have been obtained both for classes
of structures where output variables are part of their specification, and for
classes of structures where computability WPD must be ensured for any possible
set of output variables. These results are shown to be tight, by exhibiting
dichotomies for classes of structures having bounded arity and where the tree
decomposition method is considered
Decide : how much superphosphate
* A 400 per cent increase in ihe price of superphosphate has reduced the economic optimum rates of super for crops and pastures in 1975.
* Many factors, both biological and economic, must be taken into account in determining the rate of superphosphate to apply.
• DECIDE, a model developed by CSIRO and the Department of Agriculture, provides a formal system in which all these factors can be considered.
• DECIDE is based on the results of all research on superphosphate carried out in Western Australia. However, each farmer\u27s own knowledge of his farm, the soils, crops and animals is used to adapt the experimental results to get the best, easily available estimate of how much super should be applied to give maximum returns on superphosphate expenditure.
Information about DECIDE is available from all District Offices of the Department of Agriculture
Demineralization of Enamel in Primary Second Molars Related to Properties of the Enamel
Enamel structure is of importance in demineralization. Differences in porosity in enamel effect the rate of demineralization, seen between permanent and deciduous teeth. Individual differences have been shown in the mean mineral concentration values in enamel, the role of this in demineralization is not thoroughly investigated. The aim of this study was to study variations of depths of artificial lesions of demineralization and to analyze the depth in relation to variations in the chemical and mineral composition of the enamel. A demineralized lesion was created in second primary molars from 18 individuals. Depths of lesions were then related to individual chemical content of the enamel.
Enamel responded to demineralization with different lesion depths and this was correlated to the chemical composition. The carbon content in sound enamel was shown to be higher where lesions developed deeper. The lesion was deeper when the degree of porosity of the enamel was higher
A rapid and low-cost DNA extraction method for isolating Escherichia coli DNA from animal stools
The price of commercial DNA extraction methods makes the routine use of polymerase chain reaction amplification (PCR) based methods rather costly for scientists in developing countries. A guanidium thiocayante-based DNA extraction method was investigated in this study for the isolation of Escherichia coli (E. coli) DNA from goat, chicken, pig, cow and human stool samples. Two versions of the lysis buffer, with and without _-casein, were tested to alleviate PCR inhibition associated with DNA isolated from stool samples. Results obtained show that, this method using the lysis buffer containing _-casein, produces PCR ready DNA at a fraction of the cost of commercial DNA extraction kits & copy; 2011 Academic Journals
Two-Dimensional Hydrodynamic Simulations of Convection in Radiation-Dominated Accretion Disks
The standard equilibrium for radiation-dominated accretion disks has long
been known to be viscously, thermally, and convectively unstable, but the
nonlinear development of these instabilities---hence the actual state of such
disks---has not yet been identified. By performing local two-dimensional
hydrodynamic simulations of disks, we demonstrate that convective motions can
release heat sufficiently rapidly as to substantially alter the vertical
structure of the disk. If the dissipation rate within a vertical column is
proportional to its mass, the disk settles into a new configuration thinner by
a factor of two than the standard radiation-supported equilibrium. If, on the
other hand, the vertically-integrated dissipation rate is proportional to the
vertically-integrated total pressure, the disk is subject to the well-known
thermal instability. Convection, however, biases the development of this
instability toward collapse. The end result of such a collapse is a gas
pressure-dominated equilibrium at the original column density.Comment: 10 pages, 7 figures, accepted for publication in ApJ. Please send
comments to [email protected]
Renormalization-group Calculation of Color-Coulomb Potential
We report here on the application of the perturbative renormalization-group
to the Coulomb gauge in QCD. We use it to determine the high-momentum
asymptotic form of the instantaneous color-Coulomb potential and
of the vacuum polarization . These quantities are
renormalization-group invariants, in the sense that they are independent of the
renormalization scheme. A scheme-independent definition of the running coupling
constant is provided by , and of , where , and
is a finite QCD mass scale. We also show how to calculate the
coefficients in the expansion of the invariant -function , where all coefficients are scheme-independent.Comment: 24 pages, 1 figure, TeX file. Minor modifications, incorporating
referee's suggestion
Starlight Demonstration of the Dragonfly Instrument: an Integrated Photonic Pupil Remapping Interferometer for High Contrast Imaging
In the two decades since the first extra-solar planet was discovered, the
detection and characterization of extra-solar planets has become one of the key
endeavors in all of modern science. Recently direct detection techniques such
as interferometry or coronography have received growing attention because they
reveal the population of exoplanets inaccessible to Doppler or transit
techniques, and moreover they allow the faint signal from the planet itself to
be investigated. Next-generation stellar interferometers are increasingly
incorporating photonic technologies due to the increase in fidelity of the data
generated. Here, we report the design, construction and commissioning of a new
high contrast imager; the integrated pupil-remapping interferometer; an
instrument we expect will find application in the detection of young faint
companions in the nearest star-forming regions. The laboratory characterisation
of the instrument demonstrated high visibility fringes on all interferometer
baselines in addition to stable closure phase signals. We also report the first
successful on-sky experiments with the prototype instrument at the 3.9-m
Anglo-Australian Telescope. Performance metrics recovered were consistent with
ideal device behaviour after accounting for expected levels of decoherence and
signal loss from the uncompensated seeing. The prospect of complete
Fourier-coverage coupled with the current performance metrics means that this
photonically-enhanced instrument is well positioned to contribute to the
science of high contrast companions.Comment: 10 pages, 7 figures, accepted to Mon. Not. of Roy. Ast. Soc., 201
The application of useless Japanese inventions for requirements elicitation in information security
Rules of requirements elicitation in security are broken through the use of Chindōgu, by designing impractical security countermeasures in the first instance, then using these to create usable security requirements. We present a process to conceive the requirements in Chindōgu form. We evaluate the usefulness of this process by applying it in three workshops with data gathered from a European rail company, and comparing requirements elicited by this process with a set of control requirements
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