1,041 research outputs found
Spatial aspects of tree mortality strongly differ between young and old-growth forests
Rates and spatial patterns of tree mortality are predicted to change during forest structural development. In young forests, mortality should be primarily density dependent due to competition for light, leading to an increasingly spatially uniform pattern of surviving trees. In contrast, mortality in old-growth forests should be primarily caused by contagious and spatially auto-correlated agents (e.g., insects, wind), causing spatial aggregation of surviving trees to increase through time. We tested these predictions by contrasting a three-decade record of tree mortality from replicated mapped permanent plots located in young (\u3c60-year-old) and old-growth (\u3e300-year-old) Abies amabilis forests. Trees in young forests died at a rate of 4.42% per year, whereas trees in old-growth forests died at 0.60% per year. Tree mortality in young forests was significantly aggregated, strong density dependent, and caused live tree patterns to become more uniform through time. Mortality in old-growth forests was spatially aggregated, but was density independent and did not change the spatial pattern of surviving trees. These results extend current theory by demonstrating that density-dependent competitive mortality leading to increasingly uniform three spacing in young forests ultimately transitions late in succession to a more diverse tree mortality regime that maintains spatial heterogeneity through time
Complementary Patents and Market Structure
Many high technology goods are based on standards that require several essential patents owned by different IP holders. This gives rise to a complements and a double mark-up problem. We compare the welfare effects of two different business strategies dealing with these problems. Vertical integration of an IP holder and a downstream producer solves the double mark-up problem between these firms. Nevertheless, it may raise royalty rates and reduce output as compared to non-integration. Horizontal integration of IP holders solves the complements problem but not the double mark-up problem. Vertical integration discourages entry and reduces innovation incentives, while horizontal integration always benefits from entry and innovatio
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Analysis of potential systematics
We analyze the density field of galaxies observed by the Sloan Digital Sky
Survey (SDSS)-III Baryon Oscillation Spectroscopic Survey (BOSS) included in
the SDSS Data Release Nine (DR9). DR9 includes spectroscopic redshifts for over
400,000 galaxies spread over a footprint of 3,275 deg^2. We identify,
characterize, and mitigate the impact of sources of systematic uncertainty on
large-scale clustering measurements, both for angular moments of the
redshift-space correlation function and the spherically averaged power
spectrum, P(k), in order to ensure that robust cosmological constraints will be
obtained from these data. A correlation between the projected density of stars
and the higher redshift (0.43 < z < 0.7) galaxy sample (the `CMASS' sample) due
to imaging systematics imparts a systematic error that is larger than the
statistical error of the clustering measurements at scales s > 120h^-1Mpc or k
< 0.01hMpc^-1. We find that these errors can be ameliorated by weighting
galaxies based on their surface brightness and the local stellar density. We
use mock galaxy catalogs that simulate the CMASS selection function to
determine that randomly selecting galaxy redshifts in order to simulate the
radial selection function of a random sample imparts the least systematic error
on correlation function measurements and that this systematic error is
negligible for the spherically averaged correlation function. The methods we
recommend for the calculation of clustering measurements using the CMASS sample
are adopted in companion papers that locate the position of the baryon acoustic
oscillation feature (Anderson et al. 2012), constrain cosmological models using
the full shape of the correlation function (Sanchez et al. 2012), and measure
the rate of structure growth (Reid et al. 2012). (abridged)Comment: Matches version accepted by MNRAS. Clarifications and references have
been added. See companion papers that share the "The clustering of galaxies
in the SDSS-III Baryon Oscillation Spectroscopic Survey:" titl
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: measuring structure growth using passive galaxies
We explore the benefits of using a passively evolving population of galaxies
to measure the evolution of the rate of structure growth between z=0.25 and
z=0.65 by combining data from the SDSS-I/II and SDSS-III surveys. The
large-scale linear bias of a population of dynamically passive galaxies, which
we select from both surveys, is easily modeled. Knowing the bias evolution
breaks degeneracies inherent to other methodologies, and decreases the
uncertainty in measurements of the rate of structure growth and the
normalization of the galaxy power-spectrum by up to a factor of two. If we
translate our measurements into a constraint on sigma_8(z=0) assuming a
concordance cosmological model and General Relativity (GR), we find that using
a bias model improves our uncertainty by a factor of nearly 1.5. Our results
are consistent with a flat Lambda Cold Dark Matter model and with GR.Comment: Accepted for publication in MNRAS (clarifications added, results and
conclusions unchanged
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey : baryon acoustic oscillations in the Data Releases 10 and 11 Galaxy samples
We present a one per cent measurement of the cosmic distance scale from the detections of the baryon acoustic oscillations (BAO) in the clustering of galaxies from the Baryon Oscillation Spectroscopic Survey, which is part of the Sloan Digital Sky Survey III. Our results come from the Data Release 11 (DR11) sample, containing nearly one million galaxies and covering approximately 8500 square degrees and the redshift range 0.2 < z < 0.7. We also compare these results with those from the publicly released DR9 and DR10 samples. Assuming a concordance Λ cold dark matter (ΛCDM) cosmological model, the DR11 sample covers a volume of 13 Gpc3 and is the largest region of the Universe ever surveyed at this density. We measure the correlation function and power spectrum, including density-field reconstruction of the BAO feature. The acoustic features are detected at a significance of over 7σ in both the correlation function and power spectrum. Fitting for the position of the acoustic features measures the distance relative to the sound horizon at the drag epoch, rd, which has a value of rd,fid = 149.28 Mpc in our fiducial cosmology. We find DV = (1264 ± 25 Mpc)(rd/rd,fid) at z = 0.32 and DV = (2056 ± 20 Mpc)(rd/rd,fid) at z = 0.57. At 1.0 per cent, this latter measure is the most precise distance constraint ever obtained from a galaxy survey. Separating the clustering along and transverse to the line of sight yields measurements at z = 0.57 of DA = (1421 ± 20 Mpc)(rd/rd,fid) and H = (96.8 ± 3.4 km s−1 Mpc−1)(rd,fid/rd). Our measurements of the distance scale are in good agreement with previous BAO measurements and with the predictions from cosmic microwave background data for a spatially flat CDM model with a cosmological constant.Publisher PDFPeer reviewe
Oral chondroitin sulfate and prebiotics for the treatment of canine Inflammatory Bowel Disease: a randomized, controlled clinical trial
BACKGROUND
Canine inflammatory bowel disease (IBD) is a chronic enteropathy of unknown etiology, although microbiome dysbiosis, genetic susceptibility, and dietary and/or environmental factors are hypothesized to be involved in its pathogenesis. Since some of the current therapies are associated with severe side effects, novel therapeutic modalities are needed. A new oral supplement for long-term management of canine IBD containing chondroitin sulfate (CS) and prebiotics (resistant starch, β-glucans and mannaoligosaccharides) was developed to target intestinal inflammation and oxidative stress, and restore normobiosis, without exhibiting any side effects. This double-blinded, randomized, placebo-controlled trial in dogs with IBD aims to evaluate the effects of 180 days administration of this supplement together with a hydrolyzed diet on clinical signs, intestinal histology, gut microbiota, and serum biomarkers of inflammation and oxidative stress.
RESULTS
Twenty-seven client-owned biopsy-confirmed IBD dogs were included in the study, switched to the same hydrolyzed diet and classified into one of two groups: supplement and placebo. Initially, there were no significant differences between groups (p > 0.05) for any of the studied parameters. Final data analysis (supplement: n = 9; placebo: n = 10) showed a significant decrease in canine IBD activity index (CIBDAI) score in both groups after treatment (p < 0.001). After treatment, a significant decrease (1.53-fold; p < 0.01) in histologic score was seen only in the supplement group. When groups were compared, the supplement group showed significantly higher serum cholesterol (p < 0.05) and paraoxonase-1 (PON1) levels after 60 days of treatment (p < 0.01), and the placebo group showed significantly reduced serum total antioxidant capacity (TAC) levels after 120 days (p < 0.05). No significant differences were found between groups at any time point for CIBDAI, WSAVA histologic score and fecal microbiota evaluated by PCR-restriction fragment length polymorphism (PCR-RFLP). No side effects were reported in any group.
CONCLUSIONS
The combined administration of the supplement with hydrolyzed diet over 180 days was safe and induced improvements in selected serum biomarkers, possibly suggesting a reduction in disease activity. This study was likely underpowered, therefore larger studies are warranted in order to demonstrate a supplemental effect to dietary treatment of this supplement on intestinal histology and CIBDAI
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The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the Data Release 9 Spectroscopic Galaxy Sample
We present measurements of galaxy clustering from the Baryon Oscillation
Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey III
(SDSS-III). These use the Data Release 9 (DR9) CMASS sample, which contains
264,283 massive galaxies covering 3275 square degrees with an effective
redshift z=0.57 and redshift range 0.43 < z < 0.7. Assuming a concordance
Lambda-CDM cosmological model, this sample covers an effective volume of 2.2
Gpc^3, and represents the largest sample of the Universe ever surveyed at this
density, n = 3 x 10^-4 h^-3 Mpc^3. We measure the angle-averaged galaxy
correlation function and power spectrum, including density-field reconstruction
of the baryon acoustic oscillation (BAO) feature. The acoustic features are
detected at a significance of 5\sigma in both the correlation function and
power spectrum. Combining with the SDSS-II Luminous Red Galaxy Sample, the
detection significance increases to 6.7\sigma. Fitting for the position of the
acoustic features measures the distance to z=0.57 relative to the sound horizon
DV /rs = 13.67 +/- 0.22 at z=0.57. Assuming a fiducial sound horizon of 153.19
Mpc, which matches cosmic microwave background constraints, this corresponds to
a distance DV(z=0.57) = 2094 +/- 34 Mpc. At 1.7 per cent, this is the most
precise distance constraint ever obtained from a galaxy survey. We place this
result alongside previous BAO measurements in a cosmological distance ladder
and find excellent agreement with the current supernova measurements. We use
these distance measurements to constrain various cosmological models, finding
continuing support for a flat Universe with a cosmological constant.Comment: 33 page
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: measurements of the growth of structure and expansion rate at z=0.57 from anisotropic clustering
We analyze the anisotropic clustering of massive galaxies from the Sloan
Digital Sky Survey III Baryon Oscillation Spectroscopic Survey (BOSS) Data
Release 9 (DR9) sample, which consists of 264,283 galaxies in the redshift
range 0.43 < z < 0.7 spanning 3,275 square degrees. Both peculiar velocities
and errors in the assumed redshift-distance relation ("Alcock-Paczynski
effect") generate correlations between clustering amplitude and orientation
with respect to the line-of-sight. Together with the sharp baryon acoustic
oscillation (BAO) standard ruler, our measurements of the broadband shape of
the monopole and quadrupole correlation functions simultaneously constrain the
comoving angular diameter distance (2190 +/- 61 Mpc) to z=0.57, the Hubble
expansion rate at z=0.57 (92.4 +/- 4.5 km/s/Mpc), and the growth rate of
structure at that same redshift (d sigma8/d ln a = 0.43 +/- 0.069). Our
analysis provides the best current direct determination of both DA and H in
galaxy clustering data using this technique. If we further assume a LCDM
expansion history, our growth constraint tightens to d sigma8/d ln a = 0.415
+/- 0.034. In combination with the cosmic microwave background, our
measurements of DA, H, and growth all separately require dark energy at z >
0.57, and when combined imply \Omega_{\Lambda} = 0.74 +/- 0.016, independent of
the Universe's evolution at z<0.57. In our companion paper (Samushia et al.
prep), we explore further cosmological implications of these observations.Comment: 19 pages, 11 figures, submitted to MNRAS, comments welcom
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