Showing 4141 - 4150 of 5713 Items
Separation of internal and interaction dynamics for NLS-described wave packets with different carrier waves
Date: 2008-11-01
Creator: Martina Chirilus-Bruckner, Christopher Chong, Guido Schneider, Hannes Uecker
Access: Open access
- We give a detailed analysis of the interaction of two NLS-described wave packets with different carrier waves for a nonlinear wave equation. By separating the internal dynamics of each wave packet from the dynamics caused by the interaction we prove that there is almost no interaction of such wave packets. We also prove the validity of a formula for the envelope shift caused by the interaction of the wave packets. © 2008 Elsevier Inc. All rights reserved.
Seasonal acclimatization of antioxidants and photosynthesis in Chondrus crispus and Mastocarpus stellatus, two co-occurring red algae with differing stress tolerances
Date: 2004-01-01
Creator: Nissa L. Lohrmann, Barry A. Logan, Amy S. Johnson
Access: Open access
- Mastocarpus stellatus and Chondrus crispus are red macroalgae that co-dominate the lower rocky intertidal zones of the northern Atlantic coast. M. stellatus is more tolerant than C. crispus of environmental stresses, particularly those experienced during winter. This difference in tolerance has been attributed, in part, to greater contents or activities of certain antioxidants in M. stellatus. We compared the photosynthetic capacities and activities of three antioxidant enzymes - superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR) - as well as the contents of ascorbate from fronds of M. stellatus and C. crispus collected over a year. Photosynthetic capacity increased in winter, but did not differ between species in any season. The activities of the three antioxidant enzymes and the contents of ascorbate were significantly greater in tissues collected during months with mean air and water temperatures below 7.5°C ("cold" months; December, February, March, April) than in months with mean air temperatures above 11°C ("warm" months; June, July, August, October). Overall, C. crispus had significantly greater SOD and APX activities, while M. stellatus had higher ascorbate contents. Species-specific differences in GR activity depended upon mean monthly temperatures at the time of tissue collection; C. crispus had higher activities during cold months, whereas M. stellatus had higher activities during warm months. Taken together, these data indicate that increased ROS scavenging capacity is a part of winter acclimatization; however, only trends in ascorbate content support the hypothesis that greater levels of antioxidants underlie the relatively greater winter tolerance of M. stellatus in comparison to C. crispus.
Resistance to dislodgement: habitat and size-specific differences in morphology and tenacity in an intertidal snail
Date: 1993-01-01
Creator: G. C. Trussell, A. S. Johnson, S. G. Rudolph, E. S. Gilfillan
Access: Open access
- The authors quantified 1) shell size (defined as the maximum projected surface area, MPSA); 2) shell shape; 3) foot area; 4) maximum force to dislodge a snail in shear; and 5) tenacity (force per foot area required to dislodge) of the herbivorous Littorina obtusata. Wave-exposed snails were smaller (lower average MPSA), and were shorter and had larger foot area and greater dislodgement force than did protected snails of similar MPSA. The greater dislodgement force at the exposed site was due to larger foot area, not to greater tenacity. -from Authors
Bowdoin College Catalogue (1911-1912)
Date: 1912-01-01
Access: Open access
- Bowdoin College Bulletin no. 38
Origami-based impact mitigation via rarefaction solitary wave creation
Date: 2019-01-01
Creator: Hiromi Yasuda, Yasuhiro Miyazawa, Efstathios G. Charalampidis, Christopher Chong, Panayotis G., Kevrekidis, Jinkyu Yang
Access: Open access
- The principles underlying the art of origami paper folding can be applied to design sophisticated metamaterials with unique mechanical properties. By exploiting the flat crease patterns that determine the dynamic folding and unfolding motion of origami, we are able to design an origami-based metamaterial that can form rarefaction solitary waves. Our analytical, numerical, and experimental results demonstrate that this rarefaction solitary wave overtakes initial compressive strain waves, thereby causing the latter part of the origami structure to feel tension first instead of compression under impact. This counterintuitive dynamic mechanism can be used to create a highly efficient-yet reusable-impact mitigating system without relying on material damping, plasticity, or fracture.
Inbreeding shapes the evolution of marine invertebrates
Date: 2020-05-01
Creator: Kevin C. Olsen, Will H. Ryan, Alice A. Winn, Ellen T. Kosman, Jose A., Moscoso, Stacy A. Krueger-Hadfield, Scott C. Burgess, David B. Carlon, Richard K. Grosberg, Susan Kalisz, Don R. Levitan
Access: Open access
- Inbreeding is a potent evolutionary force shaping the distribution of genetic variation within and among populations of plants and animals. Yet, our understanding of the forces shaping the expression and evolution of nonrandom mating in general, and inbreeding in particular, remains remarkably incomplete. Most research on plant mating systems focuses on self-fertilization and its consequences for automatic selection, inbreeding depression, purging, and reproductive assurance, whereas studies of animal mating systems have often assumed that inbreeding is rare, and that natural selection favors traits that promote outbreeding. Given that many sessile and sedentary marine invertebrates and marine macroalgae share key life history features with seed plants (e.g., low mobility, modular construction, and the release of gametes into the environment), their mating systems may be similar. Here, we show that published estimates of inbreeding coefficients (FIS) for sessile and sedentary marine organisms are similar and at least as high as noted in terrestrial seed plants. We also found that variation in FIS within invertebrates is related to the potential to self-fertilize, disperse, and choose mates. The similarity of FIS for these organismal groups suggests that inbreeding could play a larger role in the evolution of sessile and sedentary marine organisms than is currently recognized. Specifically, associations between traits of marine invertebrates and FIS suggest that inbreeding could drive evolutionary transitions between hermaphroditism and separate sexes, direct development and multiphasic life cycles, and external and internal fertilization.
Increasing forest loss worldwide from invasive pests requires new trade regulations
Date: 2014-10-01
Creator: Bitty A. Roy, Helen M. Alexander, Jennifer Davidson, Faith T. Campbell, Jeremy J., Burdon, Richard Sniezko, Clive Brasier
Access: Open access
- Loss of forests due to non-native invasive pests (including insects, nematodes, and pathogens) is a global phenomenon with profound population, community, ecosystem, and economic impacts. We review the magnitude of pest-associated forest loss worldwide and discuss the major ecological and evolutionary causes and consequences of these invasions. After compiling and analyzing a dataset of pest invasions from 21 countries, we show that the number of forest pest invasions recorded for a given country has a significant positive relationship with trade (as indicated by gross domestic product) and is not associated with the amount of forested land within that country. We recommend revisions to existing international protocols for preventing pest entry and proliferation, including prohibiting shipments of non-essential plants and plant products unless quarantined. Because invasions often originate from taxa that are scientifically described only after their introduction, current phytosanitary regulations - which target specific, already named organisms - Are ineffective.
A simple polymerase chain reaction-based method for the construction of recombinase-mediated cassette exchange donor vectors
Date: 2008-11-01
Creator: Jack R. Bateman, C. Ting Wu
Access: Open access
- Here we describe a simple method for generating donor vectors suitable for targeted transgenesis via recombinase-mediated cassette exchange (RMCE) using the ΦC31 integrase. This PCR-based strategy employs small attB "tails" on the primers used to amplify a sequence of interest, permitting the rapid creation of transgenes for in vivo analysis. Copyright © 2008 by the Genetics Society of America.
Narrative, Identity, and Holocaust Memorialization in the United States
Date: 2020-01-01
Creator: Alexander Noah Kogan
Access: Open access
- Narratives at Holocaust memorials and museums in the United States connect the Holocaust to present-day identities and weave the Holocaust into American history. Holocaust narratives––whether at the universal, national, or local level––draw moral lessons from the past. These narratives and their moral lessons redefine what constitutes the Holocaust and are determined by the needs and sentiments of the present. The sites of remembrance in this thesis at once show the significance of the Holocaust in American identities at both national and local levels, as well as encourage an active remembrance of the past that restructures these identities. The type of active remembrance and its purpose differs at each site, but each encourages a reconsideration of the past to find potentially applicable lessons for the present.