Showing 591 - 600 of 722 Items
Measurements of semileptonic branching fractions of B mesons at the '(4S) resonance
Date: 1992-01-01
Creator: S. Henderson
K. Kinoshita
F. Pipkin
M. Procario
M., Saulnier
R. Wilson
J. Wolinski
D. Xiao
R. Ammar
P. Baringer
D. Coppage
R. Davis
P. Haas
M. Kelly
N. Kwak
Ha Lam
S. Ro
Y. Kubota
J. K. Nelson
D. Perticone
R. Poling
S. Schrenk
G. Crawford
R. Fulton
T. Jensen
D. R. Johnson
H. Kagan
R. Kass
R. Malchow
F. Morrow
J. Whitmore
Access: Open access
- We report new measurements of semileptonic branching fractions of B mesons produced at the '(4S) resonance determined by fitting the inclusive electron and muon momentum spectra to different theoretical models. Using B(B»'X"-») to denote the average of the semileptonic branching fractions for B decay to electrons and muons, we obtain B(B»'X"-»)= (10.5±0.2±0.4)% using the refined free-quark model of Altarelli et al., and B(B»'X"-»)=(11.2±0.3±0.4)% using a modified version of the form-factor model of Isgur et al., in which the D**"-» contribution is allowed to float in the fit. The average of these two results is B(B»'X"-»)=(10.8±0. 2±0.4±0.4)%, where the errors are statistical, systematic uncertainties in the measurement, and systematic uncertainties associated with the theoretical models, respectively. Semileptonic branching fractions as low as this are difficult to accommodate in theoretical models where hadronic B-meson decays arise only from spectator diagrams. We use dilepton yields to limit the uncertainty in the semileptonic branching fraction due to the possible existence of non-BB» decays of the '(4S). In addition, we tag neutral B mesons using the decays B»0'D*+- and B»0'D*+"-» to obtain the first direct measurement of semileptonic branching fractions for neutral B mesons; the average of the electron and muon results for neutral B mesons is B(B»0'X"-»)=(9.9±3.0±0.9)%. © 1992 The American Physical Society.
Measurement of baryon production in B-meson decay
Date: 1992-01-01
Creator: G. Crawford
R. Fulton
T. Jensen
D. R. Johnson
H., Kagan
R. Kass
R. Malchow
F. Morrow
J. Whitmore
P. Wilson
D. Bortoletto
D. Brown
J. Dominick
R. L. McIlwain
D. H. Miller
M. Modesitt
C. R. Ng
S. F. Schaffner
E. I. Shibata
I. P.J. Shipsey
M. Battle
H. Kroha
K. Sparks
E. H. Thorndike
C. H. Wang
M. S. Alam
I. J. Kim
W. C. Li
X. C. Lou
B. Nemati
V. Romero
Access: Open access
- Using the CLEO detector at the Cornell Electron Storage Ring, we observe B-meson decays to c+ and report on improved measurements of inclusive branching fractions and momentum spectra of other baryons. For the inclusive decay Bc+X with c+pK-+, we find that the product branching fraction B(Bc+X)B(c+pK-+)=(0.273±0.051±0.039)%. Our measured inclusive branching fractions to noncharmed baryons are B(BpX)=(8.0±0.5±0.3)%, B(BX)=(3.8±0.4±0.6)%, and B(B-X)=(0.27±0.05±0.04)%. From these rates and studies of baryon-lepton and baryon-antibaryon correlations in B decays, we have estimated the branching fraction B(Bc+X) to be (6.40.8±0.8)%. Combining these results, we calculate B(c+pK-) to be (4.3±1.0±0.8)%. © 1992 The American Physical Society.
Ds+ decays to + and +
Date: 1992-01-01
Creator: J. Alexander
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
P. C. Kim
D. L. Kreinick
J. D. Lewis
G. S. Ludwig
J. Masui
J. Mevissen
N. B. Mistry
S. Nandi
C. R. Ng
E. Nordberg
C. Grady
Access: Open access
- Using the CLEO II detector, we have accurately measured Ds decay branching ratios relative to the mode for the and states, for which there are conflicting claims; our results are 0.540.090.06 and 1.200.150.11, respectively. © 1992 The American Physical Society.
The spherical Bochner theorem on semisimple Lie groups
Date: 1975-01-01
Creator: William H. Barker
Access: Open access
- Let G be a connected semisimple Lie group with finite center and K a maximal compact subgroup. Denote (i) Harish-Chandra's Schwartz spaces by Cp(G)(0
Pectin dependent cell adhesion restored by a mutant microtubule organizing membrane protein
Date: 2021-04-01
Creator: Bruce D. Kohorn
Jacob Dexter-Meldrum
Frances D.H. Zorensky
Salem Chabout
Gregory, Mouille
Susan Kohorn
Access: Open access
- The cellulose-and pectin-rich plant cell wall defines cell structure, mediates defense against pathogens, and facilitates plant cell adhesion. An adhesion mutant screen of Arabidopsis hypocotyls identified a new allele of QUASIMODO2 (QUA2), a gene required for pectin accumulation and whose mutants have reduced pectin content and adhesion defects. A suppressor of qua2 was also isolated and describes a null allele of SABRE (SAB), which encodes a previously described plasma membrane protein required for longitudinal cellular expansion that organizes the tubulin cytoskeleton. sab mutants have increased pectin content, increased levels of expression of pectin methylesterases and extensins, and reduced cell surface area relative to qua2 and Wild Type, con-tributing to a restoration of cell adhesion.
Automorphisms of higher rank lamplighter groups
Date: 2015-12-01
Creator: Melanie Stein
Jennifer Taback
Peter Wong
Access: Open access
- Let τd(q) denote the group whose Cayley graph with respect to a particular generating set is the Diestel-Leader graph DLd(q), as described by Bartholdi, Neuhauser and Woess. We compute both Aut(τd(q)) and Out(τd(q)) for d ≥ 2, and apply our results to count twisted conjugacy classes in these groups when d ≥ 3. Specifically, we show that when d ≥ 3, the groups τd(q) have property R∞, that is, every automorphism has an infinite number of twisted conjugacy classes. In contrast, when d = 2 the lamplighter groups τ2(q) = Lq = Zq Z have property R∞ if and only if (q, 6)≠1.
Microevolution of Candida albicans in Macrophages Restores Filamentation in a Nonfilamentous Mutant
Date: 2014-12-01
Creator: Anja Wartenberg
Jörg Linde
Ronny Martin
Maria Schreiner
Fabian, Horn
Ilse D. Jacobsen
Sabrina Jenull
Thomas Wolf
Karl Kuchler
Reinhard Guthke
Oliver Kurzai
Anja Forche
Christophe d'Enfert
Sascha Brunke
Bernhard Hube
Access: Open access
- Following antifungal treatment, Candida albicans, and other human pathogenic fungi can undergo microevolution, which leads to the emergence of drug resistance. However, the capacity for microevolutionary adaptation of fungi goes beyond the development of resistance against antifungals. Here we used an experimental microevolution approach to show that one of the central pathogenicity mechanisms of C. albicans, the yeast-to-hyphae transition, can be subject to experimental evolution. The C. albicans cph1Δ/efg1Δ mutant is nonfilamentous, as central signaling pathways linking environmental cues to hyphal formation are disrupted. We subjected this mutant to constant selection pressure in the hostile environment of the macrophage phagosome. In a comparatively short time-frame, the mutant evolved the ability to escape macrophages by filamentation. In addition, the evolved mutant exhibited hyper-virulence in a murine infection model and an altered cell wall composition compared to the cph1Δ/efg1Δ strain. Moreover, the transcriptional regulation of hyphae-associated, and other pathogenicity-related genes became re-responsive to environmental cues in the evolved strain. We went on to identify the causative missense mutation via whole genome- and transcriptome-sequencing: a single nucleotide exchange took place within SSN3 that encodes a component of the Cdk8 module of the Mediator complex, which links transcription factors with the general transcription machinery. This mutation was responsible for the reconnection of the hyphal growth program with environmental signals in the evolved strain and was sufficient to bypass Efg1/Cph1-dependent filamentation. These data demonstrate that even central transcriptional networks can be remodeled very quickly under appropriate selection pressure.
A dominant allele of arabidopsis pectin-binding wall-associated kinase induces a stress response suppressed by MPK6 but not MPK3 mutations
Date: 2012-01-01
Creator: Bruce D. Kohorn
Susan L. Kohorn
Tanya Todorova
Gillian Baptiste
Kevin, Stansky
Meghan McCullough
Access: Open access
- The plant cell wall is composed of a matrix of cellulose fibers, flexible pectin polymers, and an array of assorted carbohydrates and proteins. The receptor-like Wall-Associated Kinases (WAKs) of Arabidopsis bind pectin in the wall, and are necessary both for cell expansion during development and for a response to pathogens and wounding. Mitogen Activated Protein Kinases (MPKs) form a major signaling link between cell surface receptors and both transcriptional and enzyme regulation in eukaryotes, and Arabidopsis MPK6 and MPK3 indeed have important roles in development and the response to stress and pathogens. A dominant allele of WAK2 requires kinase activity and activates a stress response that includes an increased ROS accumulation and the up-regulation of numerous genes involved in pathogen resistance, wounding, and cell wall biogenesis. This dominant allele requires a functional pectin binding and kinase domain, indicating that it is engaged in a WAK signaling pathway. A null mutant of the major plasma membrane ROS-producing enzyme complex, rbohd/f does not suppress the WAK2cTAP-induced phenotype. A mpk6, but not a mpk3, null allele is able to suppress the effects of this dominant WAK2 mutation, thus distinguishing MPK3 and MPK6, whose activity previously was thought to be redundant. Pectin activation of gene expression is abated in a wak2-null, but is tempered by the WAK-dominant allele that induces elevated basal stress-related transcript levels. The results suggest a mechanism in which changes to the cell wall can lead to a large change in cellular responses and help to explain how pathogens and wounding can have general effects on growth. The Author 2011. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS.2011 © The Author 2011. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS.
Nonlinear localized modes in two-dimensional hexagonally-packed magnetic lattices
Date: 2021-04-01
Creator: Christopher Chong
Yifan Wang
Donovan Maréchal
Efstathios G. Charalampidis
Miguel, Molerón
Alejandro J. Martínez
Access: Open access
- We conduct an extensive study of nonlinear localized modes (NLMs), which are temporally periodic and spatially localized structures, in a two-dimensional array of repelling magnets. In our experiments, we arrange a lattice in a hexagonal configuration with a light-mass defect, and we harmonically drive the center of the chain with a tunable excitation frequency, amplitude, and angle. We use a damped, driven variant of a vector Fermi-Pasta-Ulam-Tsingou lattice to model our experimental setup. Despite the idealized nature of this model, we obtain good qualitative agreement between theory and experiments for a variety of dynamical behaviors. We find that the spatial decay is direction-dependent and that drive amplitudes along fundamental displacement axes lead to nonlinear resonant peaks in frequency continuations that are similar to those that occur in one-dimensional damped, driven lattices. However, we observe numerically that driving along other directions results in asymmetric NLMs that bifurcate from the main solution branch, which consists of symmetric NLMs. We also demonstrate both experimentally and numerically that solutions that appear to be time-quasiperiodic bifurcate from the branch of symmetric time-periodic NLMs.
Pectin activation of MAP kinase and gene expression is WAK2 dependent
Date: 2009-12-01
Creator: Bruce D. Kohorn
Susan Johansen
Akira Shishido
Tanya Todorova
Rhysly, Martinez
Elita Defeo
Pablo Obregon
Access: Open access
- The angiosperm extracellular matrix, or cell wall, is composed of a complex array of cellulose, hemicelluose, pectins and proteins, the modification and regulated synthesis of which are essential for cell growth and division. The wall associated kinases (WAKs) are receptor-like proteins that have an extracellular domain that bind pectins, the more flexible portion of the extracellular matrix, and are required for cell expansion as they have a role in regulating cellular solute concentrations. We show here that both recombinant WAK1 and WAK2 bind pectin in vitro. In protoplasts pectins activate, in a WAK2-dependent fashion, the transcription of vacuolar invertase, and a wak2 mutant alters the normal pectin regulation of mitogen-activated protein kinases. Microarray analysis shows that WAK2 is required for the pectin activation of numerous genes in protoplasts, many of which are involved in cell wall biogenesis. Thus, WAK2 plays a major role in signaling a diverse array of cellular events in response to pectin in the extracellular matrix. © 2009 Blackwell Publishing Ltd.