Showing 221 - 230 of 2039 Items
Evidence for penguin-diagram decays: First observation of B→K*(892)γ
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.
Study of D0 decays into K̄0 and K̄*0
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.
To what extent may peptide receptor gene diversity/complement contribute to functional flexibility in a simple pattern-generating neural network?
Date: 2019-06-01
Creator: Patsy S. Dickinson
J. Joe Hull
Alexandra Miller
Emily R. Oleisky
Andrew E., Christie
Access: Open access
- Peptides are known to contribute to central pattern generator (CPG) flexibility throughout the animal kingdom. However, the role played by receptor diversity/complement in determining this functional flexibility is not clear. The stomatogastric ganglion (STG) of the crab, Cancer borealis, contains CPGs that are models for investigating peptidergic control of rhythmic behavior. Although many Cancer peptides have been identified, their peptide receptors are largely unknown. Thus, the extent to which receptor diversity/complement contributes to modulatory flexibility in this system remains unresolved. Here, a Cancer mixed nervous system transcriptome was used to determine the peptide receptor complement for the crab nervous system as a whole. Receptors for 27 peptide families, including multiple receptors for some groups, were identified. To increase confidence in the predicted sequences, receptors for allatostatin-A, allatostatin-B, and allatostatin-C were cloned, sequenced, and expressed in an insect cell line; as expected, all three receptors trafficked to the cell membrane. RT-PCR was used to determine whether each receptor was expressed in the Cancer STG. Transcripts for 36 of the 46 identified receptors were amplified; these included at least one for each peptide family except RYamide. Finally, two peptides untested on the crab STG were assessed for their influence on its motor outputs. Myosuppressin, for which STG receptors were identified, exhibited clear modulatory effects on the motor patterns of the ganglion, while a native RYamide, for which no STG receptors were found, elicited no consistent modulatory effects. These data support receptor diversity/complement as a major contributor to the functional flexibility of CPGs.
Measurement of the τ-lepton mass
Date: 1993-01-01
Creator: R. Balest
M. Daoudi
W. T. Ford
D. R. Johnson
K., Lingel
M. Lohner
P. Rankin
J. G. Smith
J. P. Alexander
C. Bebek
K. Berkelman
D. Besson
T. E. Browder
D. G. Cassel
H. A. Cho
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
C. D. Jones
J. Kandaswamy
N. Katayama
P. C. Kim
D. L. Kreinick
Access: Open access
- Using data from the CLEO II detector at CESR, we measure the τ-lepton mass by exploiting the unique kinematics of events in which both τ's decay hadronically. The result is mτ=1777.8±0.7±1.7 MeV/c2. By comparing our result with other measurements near τ-pair threshold, we extract an upper limit on the τ-neutrino mass of 75 MeV/c2 at 95% confidence level. © 1993 The American Physical Society.
Observation of the charmed baryon c+ and measurement of the isospin mass splittings of the c
Date: 1993-01-01
Creator: 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
J. Whitmore
P. Wilson
F. Butler
X. Fu
G. Kalbfleisch
M. Lambrecht
W. R. Ross
P. Skubic
J. Snow
P. L. Wang
M. Wood
D. Bortoletto
D. N. Brown
J. Fast
R. L. McIlwain
T. Miao
D. H. Miller
Access: Open access
- We observe the c+ baryon decaying to Λc+π0 and measure the mass difference M(c+)-M(Λc+) to be 168.5±0.2 MeV/c2. We also measure the mass differences M(c++)-M(Λc+) and M(c0-M(Λc+) with improved precision and determine the isospin mass splittings M(c++)-M(c0) and M(c+)-M(c0) to be 1.1±0.4±0.1 MeV/c2 and 1.4±0.5±0.3 MeV/c2, respectively. Our results indicate that the light quark mass difference does not dominate the isospin mass splitting in c. © 1993 The American Physical Society.
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.
Extinction in competitive lotka-volterra systems
Date: 1995-01-01
Creator: Mary Lou Zeeman
Access: Open access
- It is well known that for the two species autonomous competitive Lotka-Volterra model with no fixed point in the open positive quadrant, one of the species is driven to extinction, whilst the other population stabilises at its own carrying capacity. In this paper we prove a generalisation of this result to arbitrary finite dimension. That is, for the n-species autonomous competitive Lotka-Volterra model, we exhibit simple algebraic criteria on the parameters which guarantee that all but one of the species is driven to extinction, whilst the one remaining population stabilises at its own carrying capacity. © 1995 American Mathematical Society.
Atmospheric variability of methyl chloride during the last 300 years from an Antarctic ice core and firn air
Date: 2004-01-28
Creator: M. Aydin
E. S. Saltzman
W. J. De Bruyn
S. A. Montzka
J. H., Butler
M. Battle
Access: Open access
- Measurements of methyl chloride (CH3Cl) in Antarctic polar ice and firn air are used to describe the variability of atmospheric CH3Cl during the past 300 years. Firn air results from South Pole and Siple Dome suggest that the atmospheric abundance of CH3Cl increased by about 10% in the 50 years prior to 1990. Ice core measurements from Siple Dome provide evidence for a cyclic natural variability on the order of 10%, with a period of about 110 years in phase with the 20th century rise inferred from firn air. Thus, the CH3Cl increase measured in firn air may largely be a result of natural processes, which may continue to affect the atmospheric CH3Cl burden during the 21st century. Copyright 2004 by the American Geophysical Union.
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.
Probing the mechanism of recognition of ssDNA by the Cdc13-DBD
Date: 2008-03-01
Creator: Aimee M. Eldridge
Deborah S. Wuttke
Access: Open access
- The Saccharomyces cerevisiae protein Cdc13 tightly and specifically binds the conserved G-rich single-stranded overhang at telomeres and plays an essential role in telomere end-protection and length regulation. The 200 residue DNA-binding domain of Cdc13 (Cdc13-DBD) binds an 11mer single-stranded representative of the yeast telomeric sequence [Tel11, d(GTGTGGGTGTG)] with a 3 pM affinity and specificity for three bases (underlined) at the 5′ end. The structure of the Cdc13-DBD bound to Tel11 revealed a large, predominantly aromatic protein interface with several unusual features. The DNA adopts an irregular, extended structure, and the binding interface includes a long (∼30 amino acids) structured loop between strands β2-β3 (L2-3) of an OB-fold. To investigate the mechanism of ssDNA binding, we studied the free and bound states of Cdc13-DBD using NMR spectroscopy. Chemical shift changes indicate that the basic topology of the domain, including L2-3, is essentially intact in the free state. Changes in slow and intermediate time scale dynamics, however, occur in L2-3, while conformational changes distant from the DNA interface suggest an induced fit mechanism for binding in the 'hot spot' for binding affinity and specificity. These data point to an overall binding mechanism well adapted to the heterogeneous nature of yeast telomeres. © 2008 The Author(s).