Showing 4651 - 4660 of 5701 Items

Landscape in Maine 1820-1970: A Sesquicentennial Exhibition

Date: 1970-01-01

Creator: James Morton

Access: Open access

Catalog of an exhibition held at the Colby College Art Museum, April 4-May 10; the Bowdoin College Museum of Art, May 21-June 28; and the Carnegie Gallery, University of Maine, Orono, July 8-August 30. Sponsored by the Maine Federation of Women's Clubs.


Quantification of dendritic and axonal growth after injury to the auditory system of the adult cricket gryllus bimaculatus

Date: 2013-09-27

Creator: Alexandra Pfister, Amy Johnson, Olaf Ellers, Hadley W. Horch

Access: Open access

Dendrite and axon growth and branching during development are regulated by a complex set of intracellular and external signals. However, the cues that maintain or influence adult neuronal morphology are less well understood. Injury and deafferentation tend to have negative effects on adult nervous systems. An interesting example of injury-induced compensatory growth is seen in the cricket, Gryllus bimaculatus. After unilateral loss of an ear in the adult cricket, auditory neurons within the central nervous system (CNS) sprout to compensate for the injury. Specifically, after being deafferented, ascending neurons (AN-1 and AN-2) send dendrites across the midline of the prothoracic ganglion where they receive input from auditory afferents that project through the contralateral auditory nerve (N5). Deafferentation also triggers contralateral N5 axonal growth. In this study, we quantified AN dendritic and N5 axonal growth at 30 h, as well as at 3, 5, 7, 14, and 20 days after deafferentation in adult crickets. Significant differences in the rates of dendritic growth between males and females were noted. In females, dendritic growth rates were non-linear; a rapid burst of dendritic extension in the first few days was followed by a plateau reached at 3 days after deafferentation. In males, however, dendritic growth rates were linear, with dendrites growing steadily over time and reaching lengths, on average, twice as long as in females. On the other hand, rates of N5 axonal growth showed no significant sexual dimorphism and were linear. Within each animal, the growth rates of dendrites and axons were not correlated, indicating that independent factors likely influence dendritic and axonal growth in response to injury in this system. Our findings provide a basis for future study of the cellular features that allow differing dendrite and axon growth patterns as well as sexually dimorphic dendritic growth in response to deafferentation. © 2013 Pfister, Johnson, Ellers and Horch.


Field information links permafrost carbon to physical vulnerabilities of thawing

Date: 2012-08-16

Creator: Jennifer W. Harden, Charles D. Koven, Chien Lu Ping, Gustaf Hugelius, A., David McGuire, Phillip Camill, Torre Jorgenson, Peter Kuhry, Gary J. Michaelson, Jonathan A. O'Donnell, Edward A.G. Schuur, Charles Tarnocai, Kristopher Johnson, Guido Grosse

Access: Open access

Deep soil profiles containing permafrost (Gelisols) were characterized for organic carbon (C) and total nitrogen (N) stocks to 3m depths. Using the Community Climate System Model (CCSM4) we calculate cumulative distributions of active layer thickness (ALT) under current and future climates. The difference in cumulative ALT distributions over time was multiplied by C and N contents of soil horizons in Gelisol suborders to calculate newly thawed C and N. Thawing ranged from 147 PgC with 10 PgN by 2050 (representative concentration pathway RCP scenario 4.5) to 436 PgC with 29 PgN by 2100 (RCP 8.5). Organic horizons that thaw are vulnerable to combustion, and all horizon types are vulnerable to shifts in hydrology and decomposition. The rates and extent of such losses are unknown and can be further constrained by linking field and modelling approaches. These changes have the potential for strong additional loading to our atmosphere, water resources, and ecosystems. © 2012. American Geophysical Union. All Rights Reserved.


Hands to Work and Hearts to God: The Shaker Tradition in Maine

Date: 1969-01-01

Creator: Theodore Elliot

Access: Open access

"Catalogue [published] on the occasion of an exhibition [at Bowdoin] of Shaker art, furniture, and objects, mostly of Maine manufacture, now at Sabbathday Lake"--Foreword


Rockwell Kent Collection

Date: 1972-01-01

Creator: Richard V. West

Access: Open access

Includes an essay by Richard V. West.


Report of the President, Bowdoin College 1997-1998

Date: 1998-01-01

Access: Open access



Report of the President, Bowdoin College 1902-1903

Date: 1903-01-01

Access: Open access




Free limits of Thompson's group F

Date: 2011-12-01

Creator: Azer Akhmedov, Melanie Stein, Jennifer Taback

Access: Open access

We produce a sequence of markings Sk of Thompson's group F within the space Gn of all marked n-generator groups so that the sequence (F, Sk) converges to the free group on n generators, for n ≥ 3. In addition, we give presentations for the limits of some other natural (convergent) sequences of markings to consider on F within G3, including (F, {x0, x1, xn}) and (F, {x0, x1, x0n}) © 2011 Springer Science+Business Media B.V.


Bounding right-arm rotation distances

Date: 2007-03-01

Creator: Sean Cleary, Jennifer Taback

Access: Open access

Rotation distance measures the difference in shape between binary trees of the same size by counting the minimum number of rotations needed to transform one tree to the other. We describe several types of rotation distance where restrictions are put on the locations where rotations are permitted, and provide upper bounds on distances between trees with a fixed number of nodes with respect to several families of these restrictions. These bounds are sharp in a certain asymptotic sense and are obtained by relating each restricted rotation distance to the word length of elements of Thompson's group F with respect to different generating sets, including both finite and infinite generating sets. © World Scientific Publishing Company.