Showing 551 - 560 of 5831 Items
Date: 2004-07-01
Creator: Vladimir Douhovnikoff, Adelaide M. Cheng, Richard S. Dodd
Access: Open access
- The ecology and evolutionary potential of coast redwood (Sequoia sempervirens) is significantly influenced by the important role clonal spread plays in its reproduction and site persistence. In nine second-growth stands, amplified fragment length polymorphisms (AFLPs) were used to identify redwood clonal architecture. Clones (multistem genets) dominated sites by representing an average of 70% of stems measured, ranging in size from two to 20 stems. As a result, a relatively small number of genets can monopolize a disproportionate amount of site resources, are more likely to persist over time, and have greater on-site genetic representation. Clones were not limited to fairy-ring structures, but consisted of a wide range of shapes including concentric rings, ring chains, disjunct, and linear structures. Between-ramet distances of up to 40 m were measured, indicating that clonal reproduction is not limited to basal stump resprouting. Clonal structure in second-growth stands was similar to earlier reports from old growth, emphasizing the importance of site persistence and long-term, gradual site development. Smaller ramet numbers per genet in old growth is probably due to local within-genet self thinning. Management and conservation of redwoods will benefit from a better understanding of the dynamics and structure of clonal spread in these forests.
Date: 1994-01-01
Creator: Y. Kubota, M. Lattery, J. K. Nelson, S. Patton, D., Perticone, R. Poling, V. Savinov, S. Schrenk, R. Wang, M. S. Alam, I. J. Kim, B. Nemati, J. J. O'Neill, 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
Access: Open access
- Using the CLEO II detector, we have obtained evidence for a new meson decaying to D0K+. Its mass is 2573.2-1.6+1.7±0.8±0.5 MeV/c2 and its width is 16-4+5±3 MeV/c2. Although we do not establish its spin and parity, the new meson is consistent with predictions for an L=1, S=1, JP=2+ charmed strange state. © 1994 The American Physical Society.
Date: 2021-02-17
Creator: Kellen Delaney, Mengzhou Hu, Tessa Hellenbrand, Patsy S. Dickinson, Michael P., Nusbaum, Lingjun Li
Access: Open access
- The crab Cancer borealis nervous system is an important model for understanding neural circuit dynamics and modulation, but the identity of neuromodulatory substances and their influence on circuit dynamics in this system remains incomplete, particularly with respect to behavioral state-dependent modulation. Therefore, we used a multifaceted mass spectrometry (MS) method to identify neuropeptides that differentiate the unfed and fed states. Duplex stable isotope labeling revealed that the abundance of 80 of 278 identified neuropeptides was distinct in ganglia and/or neurohemal tissue from fed vs unfed animals. MS imaging revealed that an additional 7 and 11 neuropeptides exhibited altered spatial distributions in the brain and the neuroendocrine pericardial organs (POs), respectively, during these two feeding states. Furthermore, de novo sequencing yielded 69 newly identified putative neuropeptides that may influence feeding state-related neuromodulation. Two of these latter neuropeptides were determined to be upregulated in PO tissue from fed crabs, and one of these two peptides influenced heartbeat in ex vivo preparations. Overall, the results presented here identify a cohort of neuropeptides that are poised to influence feeding-related behaviors, providing valuable opportunities for future functional studies.
Date: 2018-05-01
Creator: Paul P.G. Gauthier, Mark O. Battle, Kevin L. Griffin, Michael L. Bender
Access: Open access
- A fundamental challenge in plant physiology is independently determining the rates of gross O2 production by photosynthesis and O2 consumption by respiration, photorespiration, and other processes. Previous studies on isolated chloroplasts or leaves have separately constrained net and gross O2 production (NOP and GOP, respectively) by labeling ambient O2 with 18O while leaf water was unlabeled. Here, we describe a method to accurately measure GOP and NOP of whole detached leaves in a cuvette as a routine gas-exchange measurement. The petiole is immersed in water enriched to a d18O of ;9,000 , and leaf water is labeled through the transpiration stream. Photosynthesis transfers 18O from H2O to O2. GOP is calculated from the increase in d18O ofO2 as air passes through the cuvette. NOP is determined from the increase in O2/N2. Both terms are measured by isotope ratio mass spectrometry. CO2 assimilation and other standard gas-exchange parameters also were measured. Reproducible measurements are made on a single leaf for more than 15 h. We used this method to measure the light response curve of NOP and GOP in French bean (Phaseolus vulgaris) at 21% and 2% O2. We then used these data to examine the O2/CO2 ratio of net photosynthesis, the light response curve of mesophyll conductance, and the apparent inhibition of respiration in the light (Kok effect) at both oxygen levels. The results are discussed in the context of evaluating the technique as a tool to study and understand leaf physiological traits.
Date: 1993-01-01
Creator: R. Ammar, S. Ball, P. Baringer, D. Coppage, N., Copty, R. Davis, N. Hancock, M. Kelly, N. Kwak, H. Lam, Y. Kubota, M. Lattery, J. K. Nelson, S. Patton, D. Perticone, R. Poling, V. Savinov, S. Schrenk, R. Wang, M. S. Alam, I. J. Kim, B. Nemati, J. J. O'Neill, H. Severini, C. R. Sun, M. M. Zoeller, G. Crawford, M. Daubenmeir, R. Fulton, D. Fujino, K. K. Gan
Access: Open access
- We have observed the decays B0→K*(892)0γ and B-→K*(892)-γ, which are evidence for the quark-level process b→sγ. The average branching fraction is (4.5±1.5±0.9) ×10-5. This value is consistent with standard model predictions from electromagnetic penguin diagrams. © 1993 The American Physical Society.
Date: 1993-01-01
Creator: M. Procario, S. Yang, D. S. Akerib, B. Barish, M., Chadha, S. Chan, D. F. Cowen, G. Eigen, J. S. Miller, J. Urheim, A. J. Weinstein, D. Acosta, M. Athanas, G. Masek, B. Ong, H. Paar, M. Sivertz, A. Bean, J. Gronberg, R. Kutschke, S. Menary, R. J. Morrison, S. Nakanishi, H. N. Nelson, T. K. Nelson, J. D. Richman, H. Tajima, D. Schmidt, D. Sperka, M. S. Witherell, R. Ballest
Access: Open access
- Using the CLEO II detector at CESR we have studied D0 decays into final states with a K̄0 or K̄*0, and have measured branching ratios for the decay modes D0→(K̄0K̄*0)π0,η, η′. These results are compared with predictions of various charm decay models, and contributions of final-state interactions are discussed. © 1993 The American Physical Society.
Date: 1971-01-01
Access: Open access
- Bowdoin College Bulletin no. 378