Showing 2191 - 2200 of 5708 Items
Animal-to-animal variability in the phasing of the crustacean cardiac motor pattern: An experimental and computational analysis
Date: 2013-01-01
Creator: Alex H. Williams, Molly A. Kwiatkowski, Adam L. Mortimer, Eve Marder, Mary Lou, Zeeman, Patsy S. Dickinson
Access: Open access
- The cardiac ganglion (CG) of Homarus americanus is a central pattern generator that consists of two oscillatory groups of neurons: "small cells" (SCs) and "large cells" (LCs). We have shown that SCs and LCs begin their bursts nearly simultaneously but end their bursts at variable phases. This variability contrasts with many other central pattern generator systems in which phase is well maintained. To determine both the consequences of this variability and how CG phasing is controlled, we modeled the CG as a pair of Morris-Lecar oscillators coupled by electrical and excitatory synapses and constructed a database of 15,000 simulated networks using random parameter sets. These simulations, like our experimental results, displayed variable phase relationships, with the bursts beginning together but ending at variable phases. The model suggests that the variable phasing of the pattern has important implications for the functional role of the excitatory synapses. In networks in which the two oscillators had similar duty cycles, the excitatory coupling functioned to increase cycle frequency. In networks with disparate duty cycles, it functioned to decrease network frequency. Overall, we suggest that the phasing of the CG may vary without compromising appropriate motor output and that this variability may critically determine how the network behaves in response to manipulations. © 2013 the American Physiological Society.
Recent decreases in fossil-fuel emissions of ethane and methane derived from firn air
Date: 2011-08-11
Creator: Murat Aydin, Kristal R. Verhulst, Eric S. Saltzman, Mark O. Battle, Stephen A., Montzka, Donald R. Blake, Qi Tang, Michael J. Prather
Access: Open access
- Methane and ethane are the most abundant hydrocarbons in the atmosphere and they affect both atmospheric chemistry and climate. Both gases are emitted from fossil fuels and biomass burning, whereas methane (CH 4) alone has large sources from wetlands, agriculture, landfills and waste water. Here we use measurements in firn (perennial snowpack) air from Greenland and Antarctica to reconstruct the atmospheric variability of ethane (C 2H 6) during the twentieth century. Ethane levels rose from early in the century until the 1980s, when the trend reversed, with a period of decline over the next 20 years. We find that this variability was primarily driven by changes in ethane emissions from fossil fuels; these emissions peaked in the 1960s and 1970s at 14-16 teragrams per year (1 Tg = 10 12 g) and dropped to 8-10 Tg yr -1 by the turn of the century. The reduction in fossil-fuel sources is probably related to changes in light hydrocarbon emissions associated with petroleum production and use. The ethane-based fossil-fuel emission history is strikingly different from bottom-up estimates of methane emissions from fossil-fuel use, and implies that the fossil-fuel source of methane started to decline in the 1980s and probably caused the late twentieth century slow-down in the growth rate of atmospheric methane. © 2011 Macmillan Publishers Limited. All rights reserved.
Bowdoin College Catalogue (1964-1965)
Date: 1965-01-01
Access: Open access
- Bowdoin College Bulletin no. 354
General relativistic binary merger simulations and short gamma-ray bursts
Date: 2006-01-01
Creator: J.A. Faber, T.W. Baumgarte, S.L. Shapiro, K. Taniguchi
Access: Open access
A Moderated-Mediation Model of Emerging Adult and Parent Religiosity, Externalizing Behavior, and Parenting Style
Date: 2021-01-01
Creator: Benjamin M. Simonds
Access: Open access
- The present study investigated whether emerging adult religiosity mediated the relationship between high parental religiosity and low levels of offspring externalizing, and whether these pathways are moderated by aspects of authoritative parenting (i.e., acceptance, firm control, and psychological autonomy). Surveys were completed by 275 emerging adults aged 18-25, including scales assessing their religiosity, the religiosity of their parents, the style of parenting in which they were raised, and their own engagement in externalizing behaviors. Results indicated a correlation between high levels of parental and emerging adult religiosity, and a marginal relationship between high parental religiosity and reduced offspring externalizing. However, emerging adult religiosity was not related to externalizing, such that no mediation model could be tested. Psychological autonomy granting moderated the relationship between parental religiosity and emerging adult externalizing: low parental religiosity was associated with high levels of emerging adult externalizing only in parents who exhibited low levels of psychological autonomy granting, while high parental religiosity was related to low emerging adult externalizing regardless of psychological autonomy granting. The results indicate a complex relationship between parenting, externalizing, and religiosity.
Functionality of Candida albicans She3 in the mRNA transport of Saccharomyces cerevisiae Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2021-01-01
Creator: Sheikh Omar Kunjo
Access: Access restricted to the Bowdoin Community
The Role of the Golgi ELMO Proteins in Cell Adhesion in Arabidopsis thaliana
Date: 2021-01-01
Creator: Wesley James Hudson
Access: Open access
- Proper growth and development of plant cells is dependent upon successful cell adhesion between cells, and this is mostly mediated by pectin in the plant cell wall. Previously, the Kohorn Laboratory identified a non-enzymatic Golgi protein named ELMO1 as it is required for cell adhesion, likely acting as a scaffold for cell wall polymer synthesis. Plants with mutant ELMO1 demonstrate a weak defective cellular adhesion phenotype as well as reduced mannose content in the cell wall. ELMO1 has homologous proteins in at least 29 different vascular plants. These homologues have 2 possible deletions in their amino acid sequence, but protein modeling determined that these variations will not affect protein structure. There are 5 homologous ELMO1 proteins in Arabidopsis thaliana that have been aptly named ELMO2, ELMO3, ELMO4, ELMO5. elmo2-/-mutants revealed no mutant adhesion phenotypes, while elmo1-/-elmo2-/-double mutants revealed strong defects in adhesion. Confocal microscopy of propidium iodide-stained seedlings confirmed the lack of a phenotype for elmo2-/-mutants and showed disorganized gapping cells for the elmo1-/-elmo2-/-mutant. Additionally, while elmo2-/-did not have any change to root or hypocotyl length, elmo1-/-elmo2-/- mutants were significantly shorter in both regards. Taken together, these data support that ELMO2 and ELMO1 are partially redundant.