5,496 research outputs found
Dimensions of some affine Deligne-Lusztig varieties
This paper concerns the dimensions of certain affine Deligne-Lusztig
varieties, both in the affine Grassmannian and in the affine flag manifold.
Rapoport conjectured a formula for the dimensions of the varieties X_mu(b) in
the affine Grassmannian. We prove his conjecture for b in the split torus; we
find that these varieties are equidimensional; and we reduce the general
conjecture to the case of superbasic b. In the affine flag manifold, we prove a
formula that reduces the dimension question for X_x(b) with b in the split
torus to computations of dimensions of intersections of Iwahori orbits with
orbits of the unipotent radical. Calculations using this formula allow us to
verify a conjecture of Reuman in many new cases, and to make progress toward a
generalization of his conjecture.Comment: 51 pages, 12 figure
AN ANALYSIS OF CONSUMER PERCEPTIONS OF FRESH FISH AND SEAFOOD IN THE DELMARVA REGION
Consumer/Household Economics,
Affine Deligne-Lusztig varieties in affine flag varieties
This paper studies affine Deligne-Lusztig varieties in the affine flag
manifold of a split group. Among other things, it proves emptiness for certain
of these varieties, relates some of them to those for Levi subgroups, extends
previous conjectures concerning their dimensions, and generalizes the superset
method.Comment: 44 pages, 4 figures. Minor changes to font, references, and
acknowledgments. Improved introduction, other improvements in exposition, and
two new figures added, for a total of
Specificity Between Lactobacilli And Hymenopteran Hosts Is The Exception Rather Than The Rule
Lactobacilli (Lactobacillales: Lactobacillaceae) are well known for their roles in food fermentation, as probiotics, and in human health, but they can also be dominant members of the microbiota of some species of Hymenoptera (ants, bees, and wasps). Honey bees and bumble bees associate with host-specific lactobacilli, and some evidence suggests that these lactobacilli are important for bee health. Social transmission helps maintain associations between these bees and their respective microbiota. To determine whether lactobacilli associated with social hymenopteran hosts are generally host specific, we gathered publicly available Lactobacillus 16S rRNA gene sequences, along with Lactobacillus sequences from 454 pyrosequencing surveys of six other hymenopteran species (three sweat bees and three ants). We determined the comparative secondary structural models of 16S rRNA, which allowed us to accurately align the entire 16S rRNA gene, including fast-evolving regions. BLAST searches and maximum-likelihood phylogenetic reconstructions confirmed that honey and bumble bees have host-specific Lactobacillus associates. Regardless of colony size or within-colony oral sharing of food (trophallaxis), sweat bees and ants associate with lactobacilli that are closely related to those found in vertebrate hosts or in diverse environments. Why honey and bumble bees associate with host-specific lactobacilli while other social Hymenoptera do not remains an open question. Lactobacilli are known to inhibit the growth of other microbes and can be beneficial whether they are coevolved with their host or are recruited by the host from environmental sources through mechanisms of partner choice.National Science Foundation PRFB-1003133, DEB-0919519Texas Higher Education Coordinating Board 01923, National Institutes of Health GM067317Integrative BiologyCellular and Molecular BiologyCenter for Computational Biology and BioinformaticsBrackenridge Field Laborator
Dust Temperatures in the Infrared Space Observatory Atlas of Bright Spiral Galaxies
We examine far-infrared and submillimeter spectral energy distributions for
galaxies in the Infrared Space Observatory Atlas of Bright Spiral Galaxies. For
the 71 galaxies where we had complete 60-180 micron data, we fit blackbodies
with lambda^-1 emissivities and average temperatures of 31 K or lambda^-2
emissivities and average temperatures of 22 K. Except for high temperatures
determined in some early-type galaxies, the temperatures show no dependence on
any galaxy characteristic. For the 60-850 micron range in eight galaxies, we
fit blackbodies with lambda^-1, lambda-2, and lambda^-beta (with beta variable)
emissivities to the data. The best results were with the lambda^-beta
emissivities, where the temperatures were ~30 K and the emissivity coefficient
beta ranged from 0.9 to 1.9. These results produced gas to dust ratios that
ranged from 150 to 580, which were consistent with the ratio for the Milky Way
and which exhibited relatively little dispersion compared to fits with fixed
emissivities.Comment: AJ, 2003, in pres
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