Showing 1751 - 1760 of 5709 Items
Computing word length in alternate presentations of thompson's group F
Date: 2009-12-01
Creator: Matthew Horak, Melanie Stein, Jennifer Taback
Access: Open access
- We introduce a new method for computing the word length of an element of Thompson's group F with respect to a "consecutive" generating set of the form Xn = {x0,x1, ⋯, xn}, which is a subset of the standard infinite generating set for F. We use this method to show that (F, Xn) is not almost convex, and has pockets of increasing, though bounded, depth dependent on n. © 2009 World Scientific Publishing Company.
Art of John Sloan, 1871-1951: A Loan Exhibition and an Introductory Display of Paintings in the Hamlin Bequest to Bowdoin College
Date: 1962-01-01
Access: Open access
- Exhibition catalogue for Bowdoin College Museum of Art, January 20-February 28, 1962.
Parole lievitanti: La panificazione spirituale di S. Caterina di Bologna This record is embargoed.
- Embargo End Date: 2027-05-19
Date: 2022-01-01
Creator: Katherine Aiello McKee
Access: Embargoed
The development of begging calls in Yellow Warblers
Date: 2015-05-01
Creator: Jackson F Bloch
Access: Open access
- Nestling birds use begging calls to solicit resources from adults. Efficient transmission of calls is necessary for motivating parental feeding and outcompeting siblings. However, ambient acoustic masking and costs such as predation may influence the structure of the calls. While many interspecific comparisons of begging behavior have been made, the ontogeny of calls is understudied. In this study, Yellow Warbler (Setophaga petechia) begging calls were recorded and analyzed at different stages of nestling development to document changes in acoustic structure and gain insight into the selective forces that influence call development. Begging calls increased in peak frequency, frequency range, and amplitude during the 5-day recording period. Call duration did not change with age. Call structure did not differ between nestlings living in distinct acoustic environments. As begging calls increase in amplitude with age, perhaps due to increased food needs and competition from nestmates, nestlings may compensate for increased predation risk by increasing the peak frequency of the calls. Higher frequency calls attenuate more quickly than do low frequency calls and fall outside the frequency range of maximum hearing sensitivity for some potential predators. Previous studies on warbler begging have shown that nestlings of ground-nesting warblers, which are subject to higher rates of predation, beg at higher frequencies than do nestlings of tree-nesting warblers. This study supports the hypothesis that changes to begging call structure during development mirror the differences in call structure of species under different predation risks.
Identification of the determinants for the specific recognition of single-strand telomeric DNA by Cdc13
Date: 2006-01-24
Creator: Aimee M. Eldridge, Wayne A. Halsey, Deborah S. Wuttke
Access: Open access
- The single-strand overhang present at telomeres plays a critical role in mediating both the capping and telomerase regulation functions of telomeres. The telomere end-binding proteins, Cdc13 in Saccharomyces cerevisiae, Pot1 in higher eukaryotes, and TEBP in the ciliated protozoan Oxytricha nova, exhibit sequence-specific binding to their respective single-strand overhangs. S. cerevisiae telomeres are composed of a heterogeneous mixture of GT-rich telomeric sequence, unlike in higher eukaryotes which have a simple repeat that is maintained with high fidelity. In yeast, the telomeric overhang is recognized by the essential protein Cdc13, which coordinates end-capping and telomerase activities at the telomere. The Cdc13 DNA-binding domain (Cdc13-DBD) binds these telomere sequences with high affinity (3 pM) and sequence specificity. To better understand the basis for this remarkable recognition, we have investigated the binding of the Cdc13-DBD to a series of altered DNA substrates. Although an 11-mer of GT-rich sequence is required for full binding affinity, only three of these 11 bases are recognized with high specificity. This specificity differs from that observed in the other known telomere end-binding proteins, but is well suited to the specific role of Cdc13 at yeast telomeres. These studies expand our understanding of telomere recognition by the Cdc13-DBD and of the unique molecular recognition properties of ssDNA binding. © 2006 American Chemical Society.