1,546 research outputs found
Anisotropic Distribution of SDSS Satellite Galaxies: Planar (not Polar) Alignment
The distribution of satellite galaxies relative to isolated host galaxies in
the Sloan Digital Sky Survey (SDSS) is investigated. Host-satellite systems are
selected using three different methods, yielding samples of ~3300, ~1600, and
\~950 satellites. In the plane of the sky, the distributions of all three
samples show highly significant deviations from circular symmetry (> 99.99%, >
99.99%, and 99.79% confidence levels, respectively), and the degree of
anisotropy is a strong function of the projected radius, r_p, at which the
satellites are found. For r_p < 100 kpc, the SDSS satellites are aligned
preferentially with the major axes of the hosts. This is in stark contrast to
the Holmberg effect, in which satellites are aligned with the minor axes of
host galaxies. The degree of anisotropy in the distribution of the SDSS
satellites decreases with r_p and is consistent with an isotropic distribution
at of order the 1-sigma level for 250 kpc < r_p < 500 kpc.Comment: ApJ Letters (in press); Discussion section substantially revised,
SDSS DR3 included in the analysis, no significant changes to the result
The properties of highly luminous IRAS galaxies
From a complete sample of 154 galaxies identified with IRAS sources in a 304 sq deg area centered on the South Galactic Pole, a subsample of 58 galaxies with L sub IR/L sub B > 3 was chosen. Low resolution spectra were obtained for 30% of the subsample and redshifts and relative emission line intensities were derived. As a class these galaxies are very luminous with = 2.9 x 10 to the 11th power L sub 0 and (L sub IR) max = 1.3 x 10 to the 12th power L sub 0. CCD images and JHK photometry were obtained for many of the subsample. The galaxies are for the most part newly identified and are optically faint, with a majority showing evidence of a recent interaction. Radio continuum observations of all galaxies of the subsample were recently obtained at 20 cm VLA with about 75% being detected in a typical integration time of about 10 minutes
Obesity in individuals with schizophrenia:a case controlled study in Scotland
We would like to thank Dr Moira Connolly, Professor Steve Lawrie and Dr Carol Robertson who, along with the authors, were part of a protocol development group funded by the NHS Research Scotland Mental Health Network (NRS MHN) formerly known as the Scottish Mental Health Research Network (SMHRN). We are grateful to the NRS MHN for funding the data acquisition and to the PCCIU for providing the data. We also thank Professor Gordon Murray for statistical advice.Peer reviewedPublisher PD
The Opacity of Nearby Galaxies from Counts of Background Galaxies: II. Limits of the Synthetic Field Method
Recently, we have developed and calibrated the Synthetic Field Method (SFM)
to derive the total extinction through disk galaxies. The method is based on
the number counts and colors of distant background field galaxies that can be
seen through the foreground object, and has been successfully applied to NGC
4536 and NGC 3664, two late-type galaxies located, respectively, at 16 and 11
Mpc. Here, we study the applicability of the SFM to HST images of galaxies in
the Local Group, and show that background galaxies cannot be easily identified
through these nearby objects, even with the best resolution available today. In
the case of M 31, each pixel in the HST images contains 50 to 100 stars, and
the background galaxies cannot be seen because of the intrinsic granularity due
to strong surface brightness fluctuations. In the LMC, on the other hand, there
is only about one star every six linear pixels, and the lack of detectable
background galaxies results from a ``secondary'' granularity, introduced by
structure in the wings of the point spread function. The success of the SFM in
NGC 4536 and NGC 3664 is a natural consequence of the reduction of the
intensity of surface brightness fluctuations with distance. When the dominant
confusion factor is structure in the PSF wings, as is the case of HST images of
the LMC, and would happen in M 31 images obtained with a 10-m diffraction-
limited optical telescope, it becomes in principle possible to improve the
detectability of background galaxies by subtracting the stars in the foreground
object. However, a much better characterization of optical PSFs than is
currently available would be required for an adequate subtraction of the wings.
Given the importance of determining the dust content of Local Group galaxies,
efforts should be made in that direction.Comment: 45 pages, 10 Postscript figure
Complexation of Cm(III) with the recombinant N-lobe of human serum transferrin studied by time-resolved laser fluorescence spectroscopy (TRLFS)
The complexation of Cm(III) with the recombinant N-lobe of human serum transferrin (hTf/2N) is investigated in the pH range from 4.0 to 11.0 using TRLFS. At pH [greater-than-or-equal] 7.4 a Cm(III) hTf/2N species is formed with Cm(III) bound at the Fe(III) binding site. The results are compared with Cm(III) transferrin interaction at the C-lobe and indicate the similarity of the coordination environment of the C- and N-terminal binding sites with four amino acid residues of the protein, two H2O molecules and three additional ligands (e.g. synergistic anions such as carbonate) in the first coordination sphere. Measurements at c(carbonate)tot = 0.23 mM (ambient carbonate concentration) and c(carbonate)tot = 25 mM (physiological carbonate concentration) show that an increase of the total carbonate concentration suppresses the formation of the Cm(III) hTf/2N species significantly. Additionally, the three Cm(III) carbonate species Cm(CO3)+, Cm(CO3)2- and Cm(CO3)33- are formed successively with increasing pH. In general, carbonate complexation is a competing reaction for both Cm(III) complexation with transferrin and hTf/2N but the effect is significantly higher for the half molecule. At c(carbonate)tot = 0.23 mM the complexation of Cm(III) with transferrin and hTf/2N starts at pH [greater-than-or-equal] 7.4. At physiological carbonate concentration the Cm(III) transferrin species II forms at pH [greater-than-or-equal] 7.0 whereas the Cm(III) hTf/2N species is not formed until pH > 10.0. Hence, our results reveal significant differences in the complexation behavior of the C-terminal site of transferrin and the recombinant N-lobe (hTf/2N) towards trivalent actinides
The role of benthic macrofauna in influencing fluxes and speciation of dissolved zinc and copper in estuarine sediments
Sediment flux experiments were carried out for sediment and water samples
collected on April 23, 2001 and June 26, 2001 from a site in the lower CFR estuary.
Benthic fluxes were determined for total dissolved copper (Cu) and zinc (Zn) and the
ligands that bind these metals. Benthic fluxes of total dissolved Cu (TDCu) ranged from
130 to -180 nmol·m-2·d-1, where a negative flux represents the migration of a species from
the sediment into the overlying water. The copper-complexing ligand fluxes ranged from
590 to -1030 nmol·m-2·d-1. Total dissolved Zn (TDZn) fluxes ranged from 56 to -300
nmol·m-2·d-1 and the Zn-complexing ligand fluxes ranged from 1220 to -980 nmol·m-2·d-1.
Fluxes of both TDCu and TDZn were several times lower than the concentration of
metal-binding ligands, suggesting that both Cu and Zn are largely complexed when they
flux from sediments. There were no significant differences (a = 0.05) between the two
seasons in the fluxes of TDZn and Zn- and Cu-complexing ligands. However, fluxes of
TDCu were significantly greater in April than in June.
The role of bioturbation in influencing benthic fluxes of these chemical species
was also investigated using Streblospio benedicti, an opportunistic species common in the
lower Cape Fear estuary. The presence of these polychaetes did not significantly affect
fluxes of metals or ligands in any of the experiments.
Speciation analysis using competitive ligand equilibration – cathodic stripping
voltammetry revealed that Cu was bound by a single strong class (L1) whose Kcond ranged
from 1013.5 to 1014.5, a result consistent with studies of Cu in this and other estuaries. Zn
speciation analyses revealed qualitatively that there are two separate ligand classes responsible for binding dissolved zinc. The conditional stability constants of the two
ligand classes are too close in value (~ 107.5) to compute values for each ligand class
Immune Profiles Vary Seasonally, But Are Not Significantly Related To Migration Distance Or Natal Dispersal, In A Migratory Songbird
A central tenet of ecoimmunology is that an organism’s environment shapes its optimal investment in immunity. For example, the benefits of acquired (relatively pathogen-specific) versus innate (non-specific) immune defences are thought to vary with the risk of encountering familiar versus unfamiliar pathogens. Because pathogen communities vary geographically, individuals that travel farther during seasonal migration or natal dispersal are predicted to have higher exposure to novel pathogens, and lower exposure to familiar pathogens, potentially favoring investment in innate immunity. During the breeding season, migratory animals’ exposure to familiar pathogens should increase, potentially favoring investment in acquired immunity. We hypothesized that song sparrows Melospiza melodia adjust their constitutive immune profiles in response to risk of encountering novel versus familiar pathogens. We predicted that individuals migrating longer distances (inferred from stable hydrogen isotope analysis of claws) and less philopatric individuals (inferred from microsatellite assignment testing) would rely more heavily on acquired than innate defences. We also predicted that reliance on acquired defences would increase throughout the early breeding season. Consistent with trade-offs between acquired and innate defences, levels of immunoglobulin Y (acquired) varied negatively with macrophage phagocytosis activity (innate). Levels of acquired relative to innate immunity did not vary significantly with migration distance or philopatry, but increased throughout the early breeding season. Macrophage phagocytosis was not significantly repeatable between years. Song sparrows appear to shift from innate defences immediately after migration, to acquired defences with increasing time at the breeding grounds. These patterns highlight the plasticity of constitutive immune defences in migratory animals
Mapping cumulative noise from shipping to inform marine spatial planning
Including ocean noise in marine spatial planning requires predictions of noise levels on large spatiotemporal scales. Based on a simple sound transmission model and ship track data (Automatic Identification System, AIS), cumulative underwater acoustic energy from shipping was mapped throughout 2008 in the west Canadian Exclusive Economic Zone, showing high noise levels in critical habitats for endangered resident killer whales, exceeding limits of “good conservation status” under the EU Marine Strategy Framework Directive. Error analysis proved that rough calculations of noise occurrence and propagation can form a basis for management processes, because spending resources on unnecessary detail is wasteful and delays remedial action
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