409 research outputs found
Extremophiles and their application to veterinary medicine
<p/> <p>Extremophiles are organisms that can grow and thrive in harsh conditions, e.g., extremes of temperature, pH, salinity, radiation, pressure and oxygen tension. Thermophilic, halophilic and radiation-resistant organisms are all microbes, some of which are able to withstand multiple extremes. Psychrophiles, or cold-loving organisms, include not only microbes, but fish that live in polar waters and animals that can withstand freezing. Extremophiles are structurally adapted at a molecular level to withstand these conditions. Thermophiles have particularly stable proteins and cell membranes, psychrophiles have flexible cellular proteins and membranes and/or antifreeze proteins, salt-resistant halophiles contain compatible solutes or high concentrations of inorganic ions, and acidophiles and alkaliphiles are able to pump ions to keep their internal pH close to neutrality. Their interest to veterinary medicine resides in their capacity to be pathogenic, and as sources of enzymes and other molecules for diagnostic and pharmaceutical purposes. In particular, thermostable DNA polymerases are a mainstay of PCR-based diagnostics.</p
The stellar content of the isolated transition dwarf galaxy DDO210
We use Subaru Suprime-Cam and VLT FORS1 photometry of the dwarf galaxy DDO210
to study the global stellar content and structural properties of a
transition-type galaxy (with properties intermediate between dwarf irregular
and dwarf spheroidal systems). This galaxy is sufficiently isolated that tidal
interactions are not likely to have affected its evolution in any way. The
colour-magnitude diagrams of DDO210 show a red giant branch (RGB) population
(with an RGB bump), a bright asymptotic giant branch population, a red clump,
young main sequence stars and blue-loop stars. The youngest stars formed within
the last 60 Myrs and have a distinct radial distribution compared to the main
population. Whereas the overall stellar spatial distribution and HI spatial
distribution are concentric, the young stars are offset from the center of
DDO210 and are coincident with a `dent' in the HI distribution. The implied
recent star formation rate required to form the young population is
significantly higher than the derived current star formation rate, by a factor
of > 10.
Most of the stars in DDO210 are found in a red clump, and its mean I-band
magnitude suggests that the majority of stars in DDO210 have an average age of
4^{+2}_{-1} Gyr. Given this age, the colour of the RGB implies a mean
metallicity of [Fe/H] ~ -1.3. By comparing the shape of the red clump with
models for a variety of star formation histories, we estimate that an old (> 10
Gyr) stellar population can contribute ~ 20 - 30% of the stars in DDO210 at
most. The unusual star formation history of DDO210, its low mass estimate and
its isolated nature, provide insight into how star formation proceeds in the
lowest mass, unperturbed, dwarf galaxy haloes.Comment: 17 pages, 13 figures. Accepted by MNRA
Towards Enhanced Threat Intelligence Through NetFlow Distillation
Bolvedere is a hardware-accelerated NetFlow analysis platform intended to discern and distribute NetFlow records in a requested format by a user. This functionality removes the need for a user to deal with the NetFlow protocol directly, and also reduces the requirement of CPU resources as data would be passed on to a host in the known requested format
Towards malicious network activity mitigation through subnet reputation analysis
Analysis technologies that focus on partial packet rather than full packet analysis have shown promise in detection of malicious activity on net-works. NetFlow is one such emergent protocol that is used to log net-work flows through summarizing key features of them. These logs can then be exported to external NetFlow sinks and proper configuration can see effective bandwidth bottleneck mitigation occurring on net-works. Furthermore, each NetFlow source node is configurable with its own unique ID number. This feature enables a system that knows where a NetFlow source node ID number resides physically to say which network flows are occurring from which physical locations irre-spective of the IP addresses involved in these network flows
A Deep Photometric Look at Two of Andromeda's Dwarf Spheroidals: X and XVII
We use deep wide-field photometry from the Large Binocular Camera to study
the stellar and structural properties of the recently discovered Andromeda X
and Andromeda XVII (And X and And XVII) dwarf galaxies. Using the mean apparent
magnitude of the horizontal branch (HB), we derive distances of 621 +- 20 kpc
to And X and 734+- 23 kpc to And XVII, closer by >60 kpc than the previous
estimates which were based on red giant branch (RGB) observations. Thus our
results warrant against the use of the RGB tip method for determining distances
to systems with sparsely populated RGBs, and show how crucial HB observations
are in obtaining accurate distances in systems such as these. We find that And
X is a relatively faint (MV = -7.36), highly elongated (e = 0.48) system at a
distance of 174 +- 62 kpc from Andromeda. And XVII is brighter (MV = -8.61)
with an M31-centric distance of 73 kpc which makes it one of the closest
satellites to Andromeda. Both galaxies are metal-poor: we derive =-2.2
for And X, while And XVII shows = -2.0, consistent with the relation
of higher luminosity dwarfs being more metal- rich. Additionally, both galaxies
show considerable intrinsic spreads in metallicity (0.2 and 0.3 dex for And X
and And XVII respectively), consistent with multiple stellar populations.Comment: 8 pages, 6 figure
The Tidal Evolution of Local Group Dwarf Spheroidals
(Abridged) We use N-body simulations to study the evolution of dwarf
spheroidal galaxies (dSphs) driven by galactic tides. We adopt a
cosmologically-motivated model where dSphs are approximated by a King model
embedded within an NFW halo. We find that these NFW-embedded King models are
extraordinarily resilient to tides; the stellar density profile still resembles
a King model even after losing more than 99% of the stars. As tides strip the
galaxy, the stellar luminosity, velocity dispersion, central surface
brightness, and core radius decrease monotonically. Remarkably, we find that
the evolution of these parameters is solely controlled by the total amount of
mass lost from within the luminous radius. Of all parameters, the core radius
is the least affected: after losing 99% of the stars, R_c decreases by just a
factor of ~2. Interestingly, tides tend to make dSphs more dark-matter
dominated because the tightly bound central dark matter ``cusp'' is more
resilient to disruption than the ``cored'' King profile. We examine whether the
extremely large M/L ratios of the newly-discovered ultra-faint dSphs might have
been caused by tidal stripping of once brighter systems. Although dSph tidal
evolutionary tracks parallel the observed scaling relations in the
luminosity-radius plane, they predict too steep a change in velocity dispersion
compared with the observational estimates hitherto reported in the literature.
The ultra-faint dwarfs are thus unlikely to be the tidal remnants of systems
like Fornax, Draco, or Sagittarius. Despite spanning four decades in
luminosity, dSphs appear to inhabit halos of comparable peak circular velocity,
lending support to scenarios that envision dwarf spheroidals as able to form
only in halos above a certain mass threshold.Comment: 17 pages, 12 figs., accepted by Ap
The PAndAS view of the Andromeda satellite system - I. A Bayesian search for dwarf galaxies using spatial and color-magnitude information
We present a generic algorithm to search for dwarf galaxies in photometric
catalogs and apply it to the Pan-Andromeda Archaeological Survey (PAndAS). The
algorithm is developed in a Bayesian framework and, contrary to most
dwarf-galaxy-search codes, makes use of both the spatial and color-magnitude
information of sources in a probabilistic approach. Accounting for the
significant contamination from the Milky Way foreground and from the structured
stellar halo of the Andromeda galaxy, we recover all known dwarf galaxies in
the PAndAS footprint with high significance, even for the least luminous ones.
Some Andromeda globular clusters are also recovered and, in one case,
discovered. We publish a list of the 143 most significant detections yielded by
the algorithm. The combined properties of the 39 most significant isolated
detections show hints that at least some of these trace genuine dwarf galaxies,
too faint to be individually detected. Follow-up observations by the community
are mandatory to establish which are real members of the Andromeda satellite
system. The search technique presented here will be used in an upcoming
contribution to determine the PAndAS completeness limits for dwarf galaxies.
Although here tuned to the search of dwarf galaxies in the PAndAS data, the
algorithm can easily be adapted to the search for any localised overdensity
whose properties can be modeled reliably in the parameter space of any catalog.Comment: 20 pages, 16 figures, 1 table; accepted for publication in ApJ. High
res pdf available at
https://www.dropbox.com/s/7zk7pme2wunwkjv/PAndAS_dwarf_galaxies.pd
Improving Fidelity in Internet Simulation through Packet Injection
This paper describes the of extension implemented to the NKM Internet simulation system, which allows for the improved of injection of packet traffic at arbitrary nodes, and the replay of previously recorded streams. The latter function allows for the relatively easy implementation of Internet Background Radiation (IBR) within the simulated portion of the Internet. This feature thereby enhances the degree of realism of the simulation, and allows for certain pre-determined traffic, such as scanning activity, to be injected and observed by client systems connected to the simulator
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