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Bowdoin College - Medical School of Maine Catalogue (1908-1909)
Date: 1909-01-01
Access: Open access
- Bowdoin College Bulletin no. 19
Bowdoin College Catalogue (1915-1916)
Date: 1916-01-01
Access: Open access
- Bowdoin College Bulletin no. 62
Atmospheric measurements of the terrestrial O2 : CO2 exchange ratio of a midlatitude forest
Date: 2019-07-10
Creator: Mark O. Battle, J. William Munger, Margaret Conley, Eric Sofen, Rebecca, Perry, Ryan Hart, Zane Davis, Jacob Scheckman, Jayme Woogerd, Karina Graeter, Samuel Seekins, Sasha David, John Carpenter
Access: Open access
- Measurements of atmospheric O2 have been used to quantify large-scale fluxes of carbon between the oceans, atmosphere and land since 1992 (Keeling and Shertz, 1992). With time, datasets have grown and estimates of fluxes have become more precise, but a key uncertainty in these calculations is the exchange ratio of O2 and CO2 associated with the net land carbon sink (B). We present measurements of atmospheric O2 and CO2 collected over a 6-year period from a mixed deciduous forest in central Massachusetts, USA (42.537 N, 72.171 W). Using a differential fuel-cellbased instrument for O2 and a nondispersive infrared analyzer for CO2, we analyzed airstreams collected within and 5m above the forest canopy. Averaged over the entire period of record, we find these two species covary with a slope of -1:081±0:007 mol of O2 per mole of CO2 (the mean and standard error of 6 h periods). If we limit the data to values collected on summer days within the canopy, the slope is -1:03±0:01. These are the conditions in which biotic influences are most likely to dominate. This result is significantly different from the value of -1.1 widely used in O2-based calculations of the global carbon budget, suggesting the need for a deeper understanding of the exchange ratios of the various fluxes and pools comprising the net sink.
Inclusive decay B→ηX
Date: 1996-01-01
Creator: Y. Kubota, M. Lattery, M. Momayezi, J. K. Nelson, S., Patton, R. Poling, V. Savinov, S. Schrenk, R. Wang, M. S. Alam, I. J. Kim, Z. Ling, A. H. Mahmood, J. J. O’Neill, H. Severini, C. R. Sun, F. Wappler, G. Crawford, C. M. Daubenmier, R. Fulton, D. Fujino, K. K. Gan, K. Honscheid, H. Kagan, R. Kass, J. Lee, M. Sung, C. White, A. Wolf, M. M. Zoeller, F. Butler
Access: Open access
- Using data samples taken at the Υ(4S) resonance and nearby continuum e+e- annihilation with the CLEO-II detector at CESR, we have measured the inclusive branching fraction B(B→ηX)=(17.6±1.1±1.2)%, and the momentum distribution of the η mesons from B meson decay. The η yield cannot be explained as arising solely from the decay of intermediate charmed mesons. © 1996 The American Physical Society.
Exclusive hadronic B decays to charm and charmonium final states
Date: 1994-01-01
Creator: M. S. Alam, I. J. Kim, B. Nemati, J. J. ONeill, H., Severini, C. R. Sun, M. M. Zoeller, G. Crawford, C. M. Daubenmier, R. Fulton, D. Fujino, K. K. Gan, K. Honscheid, H. Kagan, R. Kass, J. Lee, R. Malchow, F. Morrow, Y. Skovpen, M. Sung, C. White, F. Butler, X. Fu, G. Kalbfleisch, W. R. Ross, P. Skubic, J. Snow, P. L. Wang, M. Wood, D. N. Brown, J. Fast
Access: Open access
- We have fully reconstructed decays of both B»0 and B- mesons into final states containing either D, D*, D**, , or c1 mesons. This allows us to obtain new results on many physics topics including branching ratios, tests of the factorization hypothesis, color suppression, resonant substructure, and the B - B»0 mass difference. © 1994 The American Physical Society.
Convexity Properties of the Diestel-Leader Group Γ_3(2)
Date: 2014-05-01
Creator: Peter J Davids
Access: Open access
- The Diestel-Leader groups are a family of groups first introduced in 2001 by Diestel and Leader in [7]. In this paper, we demonstrate that the Diestel-Leader group Γ3(2) is not almost convex with respect to a particular generating set S. Almost convexity is a geometric property that has been shown by Cannon [3] to guarantee a solvable word problem (that is, in any almost convex group there is a finite-step algorithm to determine if two strings of generators, or “words”, represent the same group element). Our proof relies on the word length formula given by Stein and Taback in [10], and we construct a family of group elements X that contradicts the almost convexity condition. We then go on to show that Γ3(2) is minimally almost convex with respect to S.
Thermal fractionation of air in polar firn by seasonal temperature gradients
Date: 2001-07-01
Creator: Jeffrey P. Severinghaus, Alexi Grachev, Mark Battle
Access: Open access
- Air withdrawn from the top 5-15 m of the polar snowpack (firn) shows anomalous enrichment of heavy gases during summer, including inert gases. Following earlier work, we ascribe this to thermal diffusion, the tendency of a gas mixture to separate in a temperature gradient, with heavier molecules migrating toward colder regions. Summer warmth creates a temperature gradient in the top few meters of the firn due to the thermal inertia of the underlying firn and causes gas fractionation by thermal diffusion. Here we explore and quantify this process further in order to (1) correct for bias caused by thermal diffusion in firn air and ice core air isotope records, (2) help calibrate a new technique for measuring temperature change in ice core gas records based on thermal diffusion [Severinghaus et al., 1998], and (3) address whether air in polar snow convects during winter and, if so, whether it creates a rectification of seasonality that could bias the ice core record. We sampled air at 2-m-depth intervals from the top 15 m of the firn at two Antarctic sites, Siple Dome and South Pole, including a winter sampling at the pole. We analyzed 15N/14N, 40Ar/36Ar, 40Ar/38Ar, 18O/16O of O2, O2/N2, 84Kr/36Ar, and 132Xe/36Ar. The results show the expected pattern of fractionation and match a gas diffusion model based on first principles to within 30%. Although absolute values of thermal diffusion sensitivities cannot be determined from the data with precision, relative values of different gas pairs may. At Siple Dome, δ40Ar/4 is 66 ± 2% as sensitive to thermal diffusion as δ15N, in agreement with laboratory calibration; δ18O/2 is 83 ± 3%, and δ84Kr/48 is 33 ± 3% as sensitive as δ15N. The corresponding figures for summer South Pole are 64 ± 2%, 81 ± 3%, and 34 ± 3%. Accounting for atmospheric change, the figure for δO2/N2/4 is 90 ± 3% at Siple Dome. Winter South Pole shows a strong depletion of heavy gases as expected. However, the data do not fit the model well in the deeper part of the profile and yield a systematic drift with depth in relative thermal diffusion sensitivities (except for Kr, constant at 34 ± 4%), suggesting the action of some other process that is not currently understood. No evidence for wintertime convection or a rectifier effect is seen.
Egg Size, Breeding Phenology, and Parental Investment in Leach’s Storm Petrels Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2020-01-01
Creator: James L. O'Shea
Access: Access restricted to the Bowdoin Community