3,082 research outputs found
An HI census of Loose Groups of Galaxies
We present results from our Parkes Multibeam HI survey of 3 loose groups of
galaxies that are analogous to the Local Group. This is a survey of groups
containing only spiral galaxies with mean separations of a few hundred kpc, and
total areas of approximately 1 sq. Mpc; groups similar to our own Local Group.
We present a census of the HI-rich objects in these groups down to an M(HI),
1-sigma sensitivity ~7x10^5 M(sun), as well as the detailed properties of these
detections from follow-up Compact Array observations. We found 7 new HI-rich
members in the 3 groups, all of which have stellar counterparts and are,
therefore, typical dwarf galaxies. The ratio of low-mass to high-mass gas-rich
galaxies in these groups is less than in the Local Group meaning that the
``missing satellite'' problem is not unique. No high-velocity cloud analogs
were found in any of the groups. If HVCs in these groups are the same as in the
Local Group, this implies that HVCs must be located within ~300-400 kpc of the
Milky Way.Comment: 6 pages, to appear in the ASP proceedings of IAU Symposium 217,
"Recycling intergalactic and interstellar matter", eds. Pierre-Alain Duc,
Jonathan Braine, Elias Brink
Investing in Biodiversity Conservation: Proceedings of a Workshop
This document presents the proceedings of a one-day Workshop on Investing in Biodiversity Conservation held at the Inter-American Development Bank in Washington, D.C., on October 28, 1996. The first part of the workshop was dedicated to the presentation of key topics on biodiversity financing by five leaders in the field. The second part of the workshop was dedicated to a discussion and exchange of ideas on the role of the IDB in investing in biodiversity conservation. Three main recommendations emerged: 1) The Bank should prepare a report on on its experience in biodiversity projects and development programs with biodiversity components; 2) A task force should be formed to work on a bio-diversity policy or strategy; 3) IDB staff should be trained to understand the biodiversity concept and its implications in project preparation and implementation.Environmental Policy, Biodiversity, Natural Resources Management
Epidemiologija virusa influence konja: patogenost i prenosivost
A large-scale outbreak caused by equine influenza virus of the H3N8 subtype has occurred in each decade since an H3N8 virus was first isolated from horses in 1963. Each epidemic, and some minor outbreaks, has influenced equine influenza surveillance and vaccination policies in the UK and elsewhere. The latest widespread outbreak of equine influenza occurred in 2003. The possible reasons for infection of horses despite intensive vaccination are currently being investigated and may shed new light on the epidemiology of equine influenza.Podtip H3N8 virusa influence konja uzrokovao je velik broj epizootija svakog desetljeća otkako je 1963. godine prvi put bio izdvojen iz konja. Svaka epizootija, a i neke manje pojave, utjecale su na mjere nadzora i cijepljenja u Velikoj Britaniji i drugdje. Posljednja velika epizootija influence konja zabilježena je 2003. Mogući razlozi prijemljivosti konja usprkos stalnog cijepljenja još se istražuju i mogli bi dati novo svjetlo na epidemiologiju influence konja
Servomotor and Controller Having Large Dynamic Range
A recently developed micro-commanding rotational-position-control system offers advantages of less mechanical complexity, less susceptibility to mechanical resonances, less power demand, less bulk, less weight, and lower cost, relative to prior rotational-position-control systems based on stepping motors and gear drives. This system includes a digital-signal- processor (DSP)-based electronic controller, plus a shaft-angle resolver and a servomotor mounted on the same shaft. Heretofore, micro-stepping has usually been associated with stepping motors, but in this system, the servomotor is micro-commanded in response to rotational-position feedback from the shaft-angle resolver. The shaft-angle resolver is of a four-speed type chosen because it affords four times the resolution of a single-speed resolver. A key innovative aspect of this system is its position-feedback signal- conditioning circuits, which condition the resolver output signal for multiple ranges of rotational speed. In the preferred version of the system, two rotational- speed ranges are included, but any number of ranges could be added to expand the speed range or increase resolution in particular ranges. In the preferred version, the resolver output is conditioned with two resolver-to-digital converters (RDCs). One RDC is used for speeds from 0.00012 to 2.5 rpm; the other RDC is used for speeds of 2.5 to 6,000 rpm. For the lower speed range, the number of discrete steps of RDC output per revolution was set at 262,144 (4 quadrants at 16 bits per quadrant). For the higher speed range, the number of discrete steps per revolution was set at 4,096 (4 quadrants at 10 bits per quadrant)
On the validity of the reduced Salpeter equation
We adapt a general method to solve both the full and reduced Salpeter
equations and systematically explore the conditions under which these two
equations give equivalent results in meson dynamics. The effects of constituent
mass, angular momentum state, type of interaction, and the nature of
confinement are all considered in an effort to clearly delineate the range of
validity of the reduced Salpeter approximations. We find that for
the solutions are strikingly similar for all
constituent masses. For zero angular momentum states the full and reduced
Salpeter equations give different results for small quark mass especially with
a large additive constant coordinate space potential. We also show that
corrections to heavy-light energy levels can be accurately
computed with the reduced equation.Comment: Latex (uses epsf macro), 24 pages of text, 12 postscript figures
included. Slightly revised version, to appear in Phys. Rev.
On the instantaneous Bethe-Salpeter equation
We present a systematic algebraic and numerical investigation of the
instantaneous Bethe-Salpeter equation. Emphasis is placed on confining
interaction kernels of the Lorentz scalar, time component vector, and full
vector types. We explore stability of the solutions and Regge behavior for each
of these interactions, and conclude that only time component vector confinement
leads to normal Regge structure and stable solutions.Comment: Latex (uses epsf macro), 26 pages of text, 12 postscript figures
included
The Baryonic Tully Fisher Relation
We validate the baryonic Tully Fisher (BTF) relation by exploring the Tully
Fish er (TF) and BTF properties of optically and HI-selected disk galaxies. The
data includes galaxies from: Sakai et al. (2000) calibrator sample; McGaugh et
al. (2000: MC2000) I-band sample; and 18 newly acquired HI-selected field dwarf
galaxies observed with the ANU 2.3m telescope and the ATNF Parkes telescope
from Gurovich's thesis sample (2005).
As in MC2000, we re-cast the TF and BTF relations as relationships between
baryo n mass and W_{20}. First we report some numerical errors in MC2000. Then,
we c alculate weighted bi-variate linear fits to the data, and finally we
compare the fits of the intrinsically fainter dwarfs with the brighter galaxies
of Sakai et al. (2000). With regards to the local calibrator disk galaxies of
Sakai et al. (2000), our results suggest that the BTF relation is indeed
tighter than the T F relation and that the slopes of the BTF relations are
statistically flatter th an the equivalent TF relations. Further, for the
fainter galaxies which include the I-band MCG2000 and HI-selected galaxies of
Gurovich's thesis sample, we calc ulate a break from a simple power law model
because of what appears to be real c osmic scatter. Not withstanding this
point, the BTF models are marginally better models than the equivalent TF ones
with slightly smaller reduced chi^2.Comment: 3 pages, 3 figs, refereed conference proceeding based on an invited
talk at the Structure and Dynamics in the Local Universe, a Sydney workshop
to honour Brent Tully's 60th birthday. To appear in Publications of the
Astronomical Society of Australia, ed. J. Bland-Hawthor
Wide-field dynamic astronomy in the near-infrared with Palomar Gattini-IR and DREAMS
There have been a dramatic increase in the number of optical and radio transient surveys due to astronomical transients such as gravitational waves and gamma ray bursts, however, there have been a limited number of wide-field infrared surveys due to narrow field-of-view and high cost of infrared cameras, we present two new wide-field near-infrared fully automated surveyors; Palomar Gattini-IR and the Dynamic REd All-sky Monitoring Survey (DREAMS). Palomar Gattini-IR, a 25 square degree J-band imager that begun science operations at Palomar Observatory, USA in October 2018; we report on survey strategy as well as telescope and observatory operations and will also providing initial science results. DREAMS is a 3.75 square degree wide-field imager that is planned for Siding Spring Observatory, Australia; we report on the current optical and mechanical design and plans to achieve on-sky results in 2020. DREAMS is on-track to be one of the first astronomical telescopes to use an Indium Galium Arsenide (InGaAs) detector and we report initial on-sky testing results for the selected detector package. DREAMS is also well placed to take advantage and provide near-infrared follow-up of the LSST
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