171 research outputs found
The Effect of Exercise on Pulpal and Gingival Blood Flow in Physically Active and Inactive Subjects as Assessed by Laser Doppler
The effects of exercise on pulpal and gingival blood flow are undefined. The autonomic nervous system response suggests that they could increase or decrease with exercise, and they may be independent of each other. This study attempts to answer these questions
A Catalog of Very Isolated Galaxies from the SDSS Data Release 1
We present a new catalog of isolated galaxies obtained through an automated
systematic search. These 2980 isolated galaxies were found in approximately
2099 sq deg of sky in the Sloan Digital Sky Survey Data Release 1 (SDSS DR1)
photometry. The selection algorithm, implementing a variation on the criteria
developed by Karachentseva in 1973, proved to be very efficient and fast. This
catalog will be useful for studies of the general galaxy characteristics. Here
we report on our results.Comment: 67 pages, which includes 14 figures. Accepted for publication by A
The AMIGA sample of isolated galaxies. IV. A catalogue of neighbours around isolated galaxies
Studies of the effects of environment on galaxy properties and evolution
require well defined control samples. Such isolated galaxy samples have up to
now been small or poorly defined. The AMIGA project (Analysis of the
interstellar Medium of Isolated GAlaxies) represents an attempt to define a
statistically useful sample of the most isolated galaxies in the local (z <
0.05) Universe. A suitable large sample for the AMIGA project already exists,
the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973; 1050 galaxies),
and we use this sample as a starting point to refine and perform a better
quantification of its isolation properties. Digitised POSS-I E images were
analysed out to a minimum projected radius R > 0.5 Mpc around 950 CIG galaxies
(those within Vr = 1500 km s-1 were excluded). We identified all galaxy
candidates in each field brighter than B = 17.5 with a high degree of
confidence using the LMORPHO software. We generated a catalogue of
approximately 54 000 potential neighbours (redshifts exist for 30% of this
sample). Six hundred sixty-six galaxies pass and two hundred eighty-four fail
the original CIG isolation criterion. The available redshift data confirm that
our catalogue involves a largely background population rather than physically
associated neighbours. We find that the exclusion of neighbours within a factor
of four in size around each CIG galaxy, employed in the original isolation
criterion, corresponds to Delta Vr ~ 18000 km s-1 indicating that it was a
conservative limit. Galaxies in the CIG have been found to show different
degrees of isolation. We conclude that a quantitative measure of this is
mandatory. It will be the subject of future work based on the catalogue of
neighbours obtained here.Comment: Accepted by A&A, 10 pages, 8 figures, 4 table
Niches of marine mammals in the European Arctic
The Arctic is warming rapidly, with concomitant sea ice losses and ecosystem changes. The animals most vulnerable to Arctic food web changes are long-lived and slow-growing such as marine mammals, which may not be able to adapt rapidly enough to respond to changes in their resource bases. To determine the current extent and sources of these resource bases, we examined isotopic and trophic niches for marine mammals in the European Arctic using skin carbon (δ13C) and nitrogen (δ 15N) stable isotope (SI) compositions from 10 species: blue, fin, humpback, minke, sperm and white whales, bearded and ringed seals, walruses and polar bears, and dietary fatty acids (FAs) in polar bears, walruses and most of the whale species listed here. SI values showed clear species separation by trophic behaviour and carbon sources. Bearded seals, walruses and white whales had the smallest isotopic niches; these species are all resident High Arctic species and are likely to be particularly vulnerable to changes in Arctic ecosystems. We found clear separation between FA groupings driven by pelagic, benthic and planktonic/algal sources: pelagic FAs in all whales, benthic FAs in walruses, and copepod/algae/dinoflagellate FAs in polar bears, with some polar bear compositions approaching those of the whales and walruses. There is strong niche partitioning between study species with minimal functional redundancy, which could impact Arctic ecosystem structure and connectivity if populations of these large nutrient vectors are reduced or lost
The Photometric Properties of Isolated Early-Type Galaxies
Isolated galaxies are important since they probe the lowest density regimes
inhabited by galaxies. We define a sample of 36 nearby isolated early-type
galaxies for further study. Our isolation criteria require them to have no
comparable-mass neighbours within 2 B-band magnitudes, 0.67 Mpc in the plane of
the sky and 700 km/s in recession velocity. New wide-field optical imaging of
10 isolated galaxies with the Anglo-Australian Telescope confirms their
early-type morphology and relative isolation. We also present imaging of 4
galaxy groups as a control sample. The isolated galaxies are shown to be more
gravitationally isolated than the group galaxies. We find that the isolated
early-type galaxies have a mean effective colour of (B-R)_e = 1.54 +/- 0.14,
similar to their high-density counterparts. They reveal a similar
colour-magnitude relation slope and small intrinsic scatter to cluster
ellipticals. They also follow the Kormendy relation of surface brightness
versus size for luminous cluster galaxies. Such properties suggest that the
isolated galaxies formed at a similar epoch to cluster galaxies, such that the
bulk of their stars are very old. However, our galaxy modelling reveals
evidence for dust lanes, plumes, shells, boxy and disk isophotes in four out of
nine galaxies. Thus at least some isolated galaxies have experienced a recent
merger/accretion event which may have induced a small burst of star formation.
We derive luminosity functions for the isolated galaxies and find a faint slope
of -1.2, which is similar to the `universal' slope found in a wide variety of
environments. We examine the number density distribution of galaxies in the
field of the isolated galaxies.Comment: 16 pages, Latex, 17 figures, 6 tables, MNRAS in pres
Climate change threatens polar bear populations : a stochastic demographic analysis
Author Posting. © Ecological Society of America, 2010. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecology 91 (2010): 2883–2897, doi:10.1890/09-1641.1.The polar bear (Ursus maritimus) depends on sea ice for feeding, breeding, and movement. Significant reductions in Arctic sea ice are forecast to continue because of climate warming. We evaluated the impacts of climate change on polar bears in the southern Beaufort Sea by means of a demographic analysis, combining deterministic, stochastic, environment-dependent matrix population models with forecasts of future sea ice conditions from IPCC general circulation models (GCMs). The matrix population models classified individuals by age and breeding status; mothers and dependent cubs were treated as units. Parameter estimates were obtained from a capture–recapture study conducted from 2001 to 2006. Candidate statistical models allowed vital rates to vary with time and as functions of a sea ice covariate. Model averaging was used to produce the vital rate estimates, and a parametric bootstrap procedure was used to quantify model selection and parameter estimation uncertainty. Deterministic models projected population growth in years with more extensive ice coverage (2001–2003) and population decline in years with less ice coverage (2004–2005). LTRE (life table response experiment) analysis showed that the reduction in λ in years with low sea ice was due primarily to reduced adult female survival, and secondarily to reduced breeding. A stochastic model with two environmental states, good and poor sea ice conditions, projected a declining stochastic growth rate, log λs, as the frequency of poor ice years increased. The observed frequency of poor ice years since 1979 would imply log λs ≈ − 0.01, which agrees with available (albeit crude) observations of population size. The stochastic model was linked to a set of 10 GCMs compiled by the IPCC; the models were chosen for their ability to reproduce historical observations of sea ice and were forced with “business as usual” (A1B) greenhouse gas emissions. The resulting stochastic population projections showed drastic declines in the polar bear population by the end of the 21st century. These projections were instrumental in the decision to list the polar bear as a threatened species under the U.S. Endangered Species Act.We acknowledge primary funding for model development
and analysis from the U.S. Geological Survey and additional
funding from the National Science Foundation (DEB-0343820
and DEB-0816514), NOAA, the Ocean Life Institute and the
Arctic Research Initiative at WHOI, and the Institute of Arctic
Biology at the University of Alaska–Fairbanks. Funding for the
capture–recapture effort in 2001–2006 was provided by the U.S.
Geological Survey, the Canadian Wildlife Service, the Department
of Environment and Natural Resources of the Government
of the Northwest Territories, and the Polar Continental
Shelf Project, Ottawa, Canada
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The compensatory potential of increased immigration following intensive American mink population control is diluted by male-biased dispersal
Attempts to mitigate the impact of invasive species on native ecosystems increasingly target large land masses where control, rather than eradication, is the management objective. Depressing numbers of invasive species to a level where their impact on native biodiversity is tolerable requires overcoming the impact of compensatory immigration from non-controlled portions of the landscape. Because of the expected scale-dependency of dispersal, the overall size of invasive species management areas relative to the dispersal ability of the controlled species will determine the size of any effectively conserved core area unaffected by immigration from surrounding areas. However, when dispersal is male-biased, as in many mammalian invasive carnivores, males may be overrepresented amongst immigrants, reducing the potential growth rate of invasive species populations in re-invaded areas. Using data collected from a project that gradually imposed spatially comprehensive control on invasive American mink (Neovison vison) over a 10,000 km2 area of NE Scotland, we show that mink captures were reduced to almost zero in 3 years, whilst there was a threefold increase in the proportion of male immigrants. Dispersal was often long distance and linking adjacent river catchments, asymptoting at 38 and 31 km for males and females respectively. Breeding and dispersal were spatially heterogeneous, with 40 % of river sections accounting for most captures of juvenile (85 %), adult female (65 %) and immigrant (57 %) mink. Concentrating control effort on such areas, so as to turn them into “attractive dispersal sinks” could make a disproportionate contribution to the management of recurrent re-invasion of mainland invasive species management areas
What are the toxicological effects of mercury in Arctic biota?
This review critically evaluates the available mercury (Hg) data in Arctic marine biota and the Inuit population against toxicity threshold values. In particular marine top predators exhibit concentrations of mercury in their tissues and organs that are believed to exceed thresholds for biological effects. Species whose concentrations exceed threshold values include the polar bears (Ursus maritimus), beluga whale (Delphinapterus leucas), pilot whale (Globicephala melas), hooded seal (Cystophora cristata), a few seabird species, and landlocked Arctic char (Salvelinus alpinus). Toothed whales appear to be one of the most vulnerable groups, with high concentrations of mercury recorded in brain tissue with associated signs of neurochemical effects. Evidence of increasing concentrations in mercury in some biota in Arctic Canada and Greenland is therefore a concern with respect to ecosystem health
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