7,522 research outputs found
Foreground separation using a flexible maximum-entropy algorithm: an application to COBE data
A flexible maximum-entropy component separation algorithm is presented that
accommodates anisotropic noise, incomplete sky-coverage and uncertainties in
the spectral parameters of foregrounds. The capabilities of the method are
determined by first applying it to simulated spherical microwave data sets
emulating the COBE-DMR, COBE-DIRBE and Haslam surveys. Using these simulations
we find that is very difficult to determine unambiguously the spectral
parameters of the galactic components for this data set due to their high level
of noise. Nevertheless, we show that is possible to find a robust CMB
reconstruction, especially at the high galactic latitude. The method is then
applied to these real data sets to obtain reconstructions of the CMB component
and galactic foreground emission over the whole sky. The best reconstructions
are found for values of the spectral parameters: T_d=19 K, alpha_d=2,
beta_ff=-0.19 and beta_syn=-0.8. The CMB map has been recovered with an
estimated statistical error of \sim 22 muK on an angular scale of 7 degrees
outside the galactic cut whereas the low galactic latitude region presents
contamination from the foreground emissions.Comment: 29 pages, 25 figures, version accepted for publication in MNRAS. One
subsection and 6 figures added. Main results unchange
Testing the Gaussianity of the COBE-DMR data with spherical wavelets
We investigate the Gaussianity of the 4-year COBE-DMR data (in HEALPix
pixelisation) using an analysis based on spherical Haar wavelets. We use all
the pixels lying outside the Galactic cut and compute the skewness, kurtosis
and scale-scale correlation spectra for the wavelet coefficients at each scale.
We also take into account the sensitivity of the method to the orientation of
the input signal. We find a detection of non-Gaussianity at per cent
level in just one of our statistics. Taking into account the total number of
statistics computed, we estimate that the probability of obtaining such a
detection by chance for an underlying Gaussian field is 0.69. Therefore, we
conclude that the spherical wavelet technique shows no strong evidence of
non-Gaussianity in the COBE-DMR data.Comment: latex file 7 pages, 6 figures, submitted to MNRA
MHD Turbulence as a Foreground for CMB Studies
Measurements of intensity and polarization of diffuse Galactic synchrotron
emission as well as starlight polarization reveal power law spectra of
fluctuations. We show that these fluctuations can arise from
magnetohydrodynamic (MHD) turbulence in the Galactic disk and halo. To do so we
take into account the converging geometry of lines of sight for the
observations when the observer is within the turbulent volume. Assuming that
the intensity of turbulence changes along the line of sight, we get a
reasonable fit to the observed synchrotron data. As for the spectra of
polarized starlight we get a good fit to the observations taking into account
the fact that the observational sample is biased toward nearby stars.Comment: 10 pages, 6 figures, Astrophyscal J., submitte
Investment of Both Essential Fatty and Amino Acids to Immunity Varies Depending on Reproductive Stage.
Tradeâoffs among the key lifeâhistory traits of reproduction and immunity have been widely documented. However, the currency in use is not wellâunderstood. We investigated how reproducing female sideâblotched lizards, Uta stansburiana, allocate lipids versus proteins when given an immune challenge. We tested whether lizards would invest more in reproduction or immunity depending on reproductive stage. Females were given stable isotopes (15Nâleucine and 13Câ1âpalmitic acid), maintained on a regular diet and given either a cutaneous biopsy or a sham biopsy (control). Stable isotopes were monitored and analyzed in feces and uric acid, skin biopsies, eggs, and toe clips. We found that lizards deposited both proteins and lipids into their healing wounds (immuneâchallenged), skin (control), and eggs (all) and that catabolism of proteins exceeded incorporation into tissue during woundâhealing. Specifically, we found that healed biopsies of wounded animals had more leucine and palmitic acid than the nonregrown skin biopsies taken from unwounded control animals. Earlier in reproduction, lizards invested relatively more labeled proteins into healing their wound tissue, but not into unwounded skin of control animals. Thus, reproduction is sometimes favored over selfâmaintenance, but only in later reproductive stages. Finally, we documented positive relationships among the amount of palmitic acid deposited in the eggs, the amount of food eaten, and the amount of palmitic acid excreted, suggesting higher turnover rates of lipids in lizards investing highly in their eggs
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A holographic system for subsea recording and analysis of plankton and other marine particles
We report here details of the design, development, initial testing and field-deployment of the HOLOMAR system for in-situ subsea holography and analysis of marine plankton and nonliving particles. HOLOMAR comprises a submersible holographic camera ("HoloCam") able to record in-line and off-axis holograms at depths down to 100 m, together with specialised reconstruction hardware ("HoloScan") linked to custom image processing and classification software. The HoloCam consists of a laser and power supply, holographic recording optics and holographic plate holders, a water-tight housing and a support frame. It utilises two basic holographic geometries, in-line and off-axis such that a wide range of species, sizes and concentrations can be recorded. After holograms have been recorded and processed they are reconstructed in full three-dimensional detail in air in a dedicated replay facility. A computer-controlled microscope, using video cameras to record the image at a given depth, is used to digitise the scene. Specially written software extracts a binarised image of an object in its true focal plane and is classified using a neural network. The HoloCam was deployed on two separate cruises in a Scottish sea loch (Loch Etive) to a depth of 100 m and over 300 holograms were recorded
Extinction and paleoecology of the Late Pleistocene cave bear from northeastern Italy: radiocarbon and stable isotope evidence
We present here the chronometric, isotopic and taphonomic evidence of cave bear from three Palaeolithic sites in north-eastern Italy: Paina, Trene and Buso doppio del Broion (Berici Hills - Vicenza). Two direct radiocarbon dates yielded an age around 24 ka BP, which make these remains the latest known representatives of the species in Europe and confirmed that demise of cave bear falls during the LGM. The carbon and nitrogen isotopic values of bone collagen do not show any marked ecological change since 33 ka BP, suggesting an essential vegetarian diet. Several bear bones preserved traces of human modification such as cut marks, which en-ables a reconstruction of the main steps of butchering process
Multidimensional natal isotopic niches refect migratory patterns in birds
7openInternationalBothNaturally occurring stable isotope ratios in animal tissues allow estimation of species trophic position and ecological niche. Measuring multiple isotopes of migratory species along flyway bottlenecks offers the opportunity to sample multiple populations and species whose tissues carry information at continental scales. We measured δ2H, δ18O, δ13C, δ15N in juvenile feathers of 21 bird species captured at a migratory bottleneck in the Italian Alps. We examined if trends in individual isotopes reflected known migratory strategies and whether dietary (δ13Câδ15N) and spatially-explicit breeding origin (δ2Hâδ18O) niche breadth (NB) differed among long-distance trans-Saharan (TS), short-distance (IP) and irruptive (IR) intra-Palearctic migrants, and whether they correlated with reported populations long-term trends. In both TS and IP groups, species δ2H declined with capture date, indicating that northern populations reached the stopover site later in the season, following a Type-I migration strategy. Values of δ2H indicated that breeding range of TS migrants extended farther north than IP and IR migrants. The breeding season was longer for IP migrants whose δ13C and δ15N values declined and increased, respectively, with time of capture. Average species dietary NB did not differ among migratory groups, but TS migrants displayed wider breeding origin niches, suggesting that long-distant migration is linked to broader ecological niches. Isotope origin NB well reflected species geographic range extent, while dietary NB did not correlate with literature accounts of speciesâ diet. We found no relationship between species breeding NB and population trends in Europe, suggesting that conditions in the breeding grounds, as inferred by stable isotopes, are not the only determinant of speciesâ long-term persistence. We demonstrate that ringing activities and isotopic measurements of passerines migrating through a bottleneck represents a unique opportunity to investigate large-scale life-history phenomena relevant to conservation.openFranzoi, A.; Larsen, S.; Franceschi, P.; Hobson, K. A.; Pedrini, P.; Camin, F.; Bontempo, L.Franzoi, A.; Larsen, S.; Franceschi, P.; Hobson, K.A.; Pedrini, P.; Camin, F.; Bontempo, L
Widely distributed breeding populations of Canada warbler (Cardellina canadensis) converge on migration through Central America
Background
To effectively conserve migratory species, the entire range encompassed by their annual life cycle needs to be considered. Most research on Nearctic-Neotropical migratory birds has focused on the breeding grounds resulting in a general lack of knowledge regarding the wintering and migratory periods. The Canada Warbler (Cardellina canadensis) has declined by 71% from 1970 to 2012, at a rate of 2.9% per year, and is listed as Threatened in Canada. As with most Nearctic-Neotropical migrants, conservation efforts outside the breeding range are limited by a poor understanding of migration routes and the connectivity between specific breeding and wintering populations.
Results
To determine migratory routes of multiple breeding populations of Canada Warblers, we directly-tracked individuals using light-level geolocators deployed at four sites across the breeding range, spanning approximately 43 degrees in longitude (Alberta, Manitoba and QuĂŠbec, Canada, and New Hampshire, USA). Twenty-five geolocators with usable data were recovered from three sites and were analyzed using FlightR to determine fall migration routes (nâ=â18) and individual wintering sites (nâ=â25). Individuals from all breeding populations took a western fall migration route at the Gulf of Mexico; with 77.8% of birds funnelling into a narrow geographic space along the western side of the Gulf of Mexico (97°W-99°W). We found no evidence for population-specific, parallel migration routes. Most individuals (72%) overwintered in Colombia. The remaining individuals overwintered in Venezuela.
Conclusions
Our results demonstrate convergence of migratory routes around a migration barrier for individuals originating from widely distributed breeding areas. Further, we suggest the potential importance of habitat around the Gulf of Mexico during migration and Andean forest in Colombia as overwintering habitat for this threatened species. Future research should be directed at understanding how these areas are used by Canada Warblers
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