Showing 911 - 920 of 5701 Items
Bowdoin College Catalogue (1912-1913)
Date: 1913-01-01
Access: Open access
- Bowdoin College Bulletin no. 44
From local to global behavior in competitive Lotka-Volterra systems
Date: 2003-01-01
Creator: E. C. Zeeman, M. L. Zeeman
Access: Open access
- In this paper we exploit the linear, quadratic, monotone and geometric structures of competitive Lotka-Volterra systems of arbitrary dimension to give geometric, algebraic and computational hypotheses for ruling out nontrivial recurrence. We thus deduce the global dynamics of a system from its local dynamics. The geometric hypotheses rely on the introduction of a split Liapunov function. We show that if a system has a fixed point p ∈ int R+n and the carrying simplex of the system lies to one side of its tangent hyperplane at p, then there is no nontrivial recurrence, and the global dynamics are known. We translate the geometric hypotheses into algebraic hypotheses in terms of the definiteness of a certain quadratic function on the tangent hyperplane. Finally, we derive a computational algorithm for checking the algebraic hypotheses, and we compare this algorithm with the classical Volterra-Liapunov stability theorem for Lotka-Volterra systems.
Spatially variable syn- and post-orogenic exhumation of the Appalachian Mountains from apatite and zircon (U-Th)/He thermochronology
Date: 2020-01-01
Creator: Luke Coughtry Basler
Access: Open access
- We present zircon and apatite (U-Th)/He (ZHe, closure temperature = 150-200ºC; AHe, closure temperature = 45-80ºC) results from two study regions in the Appalachians Mountains to investigate the timing, rates, and spatial trends of exhumation during Alleghanian orogenesis, Atlantic rifting, and post-rift passive margin conditions. Within West Virginia and Virginia, 10 ZHe dates along an across-orogen transect display an eastward younging trend, from ~425 million years (Ma) in the western Appalachian Plateau province, to ~250-300 Ma in the central Valley-Ridge fold-thrust belt, and 163 ± 29 Ma in the eastern Piedmont. Inverse thermal modeling of ZHe data using external geologic constraints indicates: (1) Pre-depositional cooling signatures within Pennsylvanian Appalachian Plateau rocks, suggesting provenance from recycled Taconic or Acadian basin strata, (2) Rapid Alleghanian (250-300 Ma) cooling in the Valley and Ridge province, indicating syn-orogenic uplift and exhumation, followed by a protracted period of stable syn-rift thermal conditions from ~250-150 Ma, and (3) Rapid rift-induced cooling in the Piedmont province, likely caused by rift-flank uplift and the post-rift lessening of the geothermal gradient. Within the Northern Appalachians of Vermont, four metamorphic samples yield averaged AHe dates of 100-120 Ma. Inverse thermal modeling indicates stable thermal conditions from 90 Ma to the present, limiting cooling driven by the recently recognized Northern Appalachian lithospheric thermal anomaly to < 20ºC. Modeling also indicates steady mid-Cretaceous (120-90 Ma) cooling (70 to 30ºC) coeval with passage over the Great Meteor Hotspot, although cooling rates are slower than would be expected during hotspot-induced thermal doming.
Carbon cycle studies based on the distribution of O2 in air
Date: 1999-01-01
Creator: Michael L. Bender, Mark O. Battle
Access: Open access
Bowdoin College Catalogue (1918-1919, 2nd and 3rd terms)
Date: 1919-01-01
Access: Open access
- Bowdoin College Bulletin no. 86
A new global ethic»: A history of the United Nations International Environmental Education Program, 1975-1995
Date: 2020-12-01
Creator: Charles Dorn
Access: Open access
- In 1975, the United Nations, under the auspices of its Educational, Scientific and Cultural Organization (UNESCO) and Environment Program (UNEP), established the International Environmental Education Program (IEEP). For two decades, IEEP aimed to accomplish goals ascribed to it by UNESCO member states and fostered communication across the international community through Connect, the UNESCO-UNEP environmental education newsletter. After reviewing UNESCO’s early involvement with the environment, this study examines IEEP’s development, beginning with its conceptual grounding in the 1968 UNESCO Biosphere Conference. It examines the 1972 United Nations Conference on the Human Environment held in Stockholm, moves on to the UNESCO-UNEP 1975 Belgrade Workshop, and continues with the world’s first intergovernmental conference dedicated to environmental education held in Tbilisi in 1977. The paper then uses Connect to trace changes in the form and content of environmental education. Across two decades, environmental education shifted from providing instruction about nature protection and natural resource conservation to fostering an environmental ethic through a problems-based, interdisciplinary study of the ecology of the total environment to adopting the concept of sustainable development. IEEP ultimately met with mixed success. Yet it was the primary United Nations program assigned the task of creating and implementing environmental education globally and thus offers a particularly useful lens through which to analyze changes in the international community’s understanding of the concept of the environment over time.
Poem by Mac Brower (Class of 2018)
Date: 2020-01-01
Creator: Mac Brower
Access: Open access
- This is a poem I composed while stay-at-home orders were being issued nationwide. I wrote it shortly after leaving my home in Washington, DC to live with my parents in North Carolina. The author is an alumnus from the class of 2018.
State of the Arg: Protein methylation at arginine comes of age
Date: 2001-07-13
Creator: Anne E. McBride, Pamela A. Silver
Access: Open access