Faculty Scholarship
Showing 21 - 30 of 733 Items
Individual differences in EEG correlates of recognition memory due to DAT polymorphisms
Date: 2017-12-01
Creator: Paolo Medrano, Erika Nyhus, Andrew Smolen, Tim Curran, Robert S., Ross
Access: Open access
- Introduction: Although previous research suggests that genetic variation in dopaminergic genes may affect recognition memory, the role dopamine transporter expression may have on the behavioral and EEG correlates of recognition memory has not been well established. Objectives: The study aims to reveal how individual differences in dopaminergic functioning due to genetic variations in the dopamine transporter gene influences behavioral and EEG correlates of recognition memory. Methods: Fifty-eight participants performed an item recognition task. Participants were asked to retrieve 200 previously presented words while brain activity was recorded with EEG. Regions of interest were established in scalp locations associated with recognition memory. Mean ERP amplitudes and event-related spectral perturbations when correctly remembering old items (hits) and recognizing new items (correct rejections) were compared as a function of dopamine transporter group. Results: Participants in the dopamine transporter group that codes for increased dopamine transporter expression (10/10 homozygotes) display slower reaction times compared to participants in the dopamine transporter group associated with the expression of fewer dopamine transporters (9R-carriers). 10/10 homozygotes further displayed differences in ERP and oscillatory activity compared to 9R-carriers. 10/10 homozygotes fail to display the left parietal old/new effect, an ERP signature of recognition memory associated with the amount of information retrieved. 10/10 homozygotes also displayed greater decreases of alpha and beta oscillatory activity during item memory retrieval compared to 9R-carriers. Conclusion: Compared to 9R-carriers, 10/10 homozygotes display slower hit and correct rejection reaction times, an absence of the left parietal old/new effect, and greater decreases in alpha and beta oscillatory activity during recognition memory. These results suggest that dopamine transporter polymorphisms influence recognition memory.
Atmospheric potential oxygen: New observations and their implications for some atmospheric and oceanic models
Date: 2006-03-01
Creator: Mark Battle, Sara Mikaloff Fletcher, Michael L. Bender, Ralph F. Keeling, Andrew C., Manning, Nicolas Gruber, Pieter P. Tans, Melissa B. Hendricks, David T. Ho, Caroline Simonds, Robert Mika, Bill Paplawsky
Access: Open access
- Measurements of atmospheric O2/N2 ratios and CO2 concentrations can be combined into a tracer known as atmospheric potential oxygen (APO ≈ O2/N2 + CO2) that is conservative with respect to terrestrial biological activity. Consequently, APO reflects primarily ocean biogeochemistry and atmospheric circulation. Building on the work of Stephens et al. (1998), we present a set of APO observations for the years 1996-2003 with unprecedented spatial coverage. Combining data from the Princeton and Scripps air sampling programs, the data set includes new observations collected from ships in the low-latitude Pacific. The data show a smaller interhemispheric APO gradient than was observed in past studies, and different structure within the hemispheres. These differences appear to be due primarily to real changes in the APO field over time. The data also show a significant maximum in APO near the equator. Following the approach of Gruber et al. (2001), we compare these observations with predictions of APO generated from ocean O2 and CO2 flux fields and forward models of atmospheric transport. Our model predictions differ from those of earlier modeling studies, reflecting primarily the choice of atmospheric transport model (TM3 in this study). The model predictions show generally good agreement with the observations, matching the size of the interhemispheric gradient, the approximate amplitude and extent of the equatorial maximum, and the amplitude and phasing of the seasonal APO cycle at most stations. Room for improvement remains. The agreement in the interhemispheric gradient appears to be coincidental; over the last decade, the true APO gradient has evolved to a value that is consistent with our time-independent model. In addition, the equatorial maximum is somewhat more pronounced in the data than the model. This may be due to overly vigorous model transport, or insufficient spatial resolution in the air-sea fluxes used in our modeling effort. Finally, the seasonal cycles predicted by the model of atmospheric transport show evidence of an excessive seasonal rectifier in the Aleutian Islands and smaller problems elsewhere. Copyright 2006 by the American Geophysical Union.
Matrix model approach to the N = 2 U (N) gauge theory with matter in the fundamental representation
Date: 2003-01-01
Creator: Stephen G. Naculich, Howard J. Schnitzer, Niclas Wyllard
Access: Open access
- We use matrix model technology to study the N = 2 U (N) gauge theory with Nf massive hypennultiplets in the fundamental representation. We perform a completely perturbative calculation of the periods ai and the prepotential F(a) up to the first instanton level, finding agreement with previous results in the literature. We also derive the Seiberg-Witten curve and differential from the large-M solution of the matrix model. We show that the two cases Nf < N and N ≤ Nf < 2N can be treated simultaneously. © SISSA/ISAS 2003.
Trumpet slices in Kerr spacetimes
Date: 2014-12-29
Creator: Kenneth A. Dennison, Thomas W. Baumgarte, Pedro J. Montero
Access: Open access
- We introduce a new time-independent family of analytical coordinate systems for the Kerr spacetime representing rotating black holes. We also propose a (2+1)+1 formalism for the characterization of trumpet geometries. Applying this formalism to our new family of coordinate systems we identify, for the first time, analytical and stationary trumpet slices for general rotating black holes, even for charged black holes in the presence of a cosmological constant. We present results for metric functions in this slicing and analyze the geometry of the rotating trumpet surface.
Electronic branching ratio of the lepton
Date: 1992-01-01
Creator: R. Ammar, P. Baringer, D. Coppage, R. Davis, M., Kelly, N. Kwak, H. Lam, S. Ro, Y. Kubota, M. Lattery, J. K. Nelson, D. Perticone, R. Poling, S. Schrenk, R. Wang, M. S. Alam, I. J. Kim, B. Nemati, V. Romero, C. R. Sun, P. N. Wang, M. M. Zoeller, G. Crawford, R. Fulton, K. K. Gan, H. Kagan, R. Kass, J. Lee, R. Malchow, F. Morrow, M. K. Sung
Access: Open access
- Using data accumulated by the CLEO I detector operating at the Cornell Electron Storage Ring, we have measured the ratio R=( e» e ) 1 where " 1 is the decay rate to final states with one charged particle. We find R=0.2231 0.0044 0.0073 where the first error is statistical and the second is systematic. Together with the measured topological one-charged-particle branching fraction, this yields the branching fraction of the lepton to electrons, Be=0.192 0.004 0.006. © 1992 The American Physical Society.
Inclusive (2P) production in (3S) decay
Date: 1991-01-01
Creator: R. Morrison, D. Schmidt, M. Procario, D. R. Johnson, K., Lingel, P. Rankin, J. G. Smith, J. Alexander, M. Artuso, C. Bebek, K. Berkelman, D. Besson, T. E. Browder, D. G. Cassel, E. Cheu, D. M. Coffman, P. S. Drell, R. Ehrlich, R. S. Galik, M. Garcia-Sciveres, B. Geiser, B. Gittelman, S. W. Gray, D. L. Hartill, B. K. Heltsley, K. Honscheid, J. Kandaswamy, N. Katayama, D. L. Kreinick, J. D. Lewis, G. S. Ludwig
Access: Open access
- Using the CsI calorimeter of the CLEO II detector, the spin triplet b(2P) states are observed in (3S) radiative decays with much higher statistics than seen in previous experiments. The observed mass splittings are not described well by theoretical models, while the relative branching ratios agree with predictions that include relativistic corrections to the radiative transition rates. © 1991 The American Physical Society.
Coordination of distinct but interacting rhythmic motor programs by a modulatory projection neuron using different co-transmitters in different ganglia
Date: 2013-05-01
Creator: Molly A. Kwiatkowski, Emily R. Gabranski, Kristen E. Huber, M. Christine Chapline, Andrew E., Christie, Patsy S. Dickinson
Access: Open access
- While many neurons are known to contain multiple neurotransmitters, the specific roles played by each co-transmitter within a neuron are often poorly understood. Here, we investigated the roles of the co-transmitters of the pyloric suppressor (PS) neurons, which are located in the stomatogastric nervous system (STNS) of the lobster Homarus americanus. The PS neurons are known to contain histamine; using RT-PCR, we identified a second co-transmitter as the FMRFamide-like peptide crustacean myosuppressin (Crust-MS). The modulatory effects of Crust-MS application on the gastric mill and pyloric patterns, generated in the stomatogastric ganglion (STG), closely resembled those recorded following extracellular PS neuron stimulation. To determine whether histamine plays a role in mediating the effects of the PS neurons in the STG, we bath-applied histamine receptor antagonists to the ganglion. In the presence of the antagonists, the histamine response was blocked, but Crust-MS application and PS stimulation continued to modulate the gastric and pyloric patterns, suggesting that PS effects in the STG are mediated largely by Crust-MS. PS neuron stimulation also excited the oesophageal rhythm, produced in the commissural ganglia (CoGs) of the STNS. Application of histamine, but not Crust-MS, to the CoGs mimicked this effect. Histamine receptor antagonists blocked the ability of both histamine and PS stimulation to excite the oesophageal rhythm, providing strong evidence that the PS neurons use histamine in the CoGs to exert their effects. Overall, our data suggest that the PS neurons differentially utilize their co-transmitters in spatially distinct locations to coordinate the activity of three independent networks. © 2013. Published by The Company of Biologists Ltd.
Measurement of gross photosynthesis, respiration in the light, and mesophyll conductance usingh2 18o labeling
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.
Incidence, size and spatial structure of clones in second-growth stands of coast redwood, Sequoia sempervirens (Cupressaceae)
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.
Intron Size Correlates Positively with Recombination Rate in Caenorhabditis elegans
Date: 2004-03-01
Creator: Anuphap Prachumwat, Laura DeVincentis, Michael F. Palopoli
Access: Open access
- A negative correlation between intron size and recombination rate has been reported for the Drosophila melanogaster and human genomes. Population-genetic models suggest that this pattern could be caused by an interaction between recombination rate and the efficacy of natural selection. To test this idea, we examined variation in intron size and recombination rate across the genome of the nematode Caenorhabditis elegans. Interestingly, we found that intron size correlated positively with recombination rate in this species.