103 research outputs found
Measurement of D-s(+) and D-s(*+) production in B meson decays and from continuum e(+)e(-) annihilation at ās=10.6 GeV
This is the pre-print version of the Article. The official published version can be accessed from the links below. Copyright @ 2002 APSNew measurements of Ds+ and Ds*+ meson production rates from B decays and from qqĢ
continuum events near the Ī„(4S) resonance are presented. Using 20.8 fb-1 of data on the Ī„(4S) resonance and 2.6 fb-1 off-resonance, we find the inclusive branching fractions B(BāDs+X)=(10.93Ā±0.19Ā±0.58Ā±2.73)% and B(BāDs*+X)=(7.9Ā±0.8Ā±0.7Ā±2.0)%, where the first error is statistical, the second is systematic, and the third is due to the Ds+āĻĻ+ branching fraction uncertainty. The production cross sections Ļ(e+e-āDs+X)ĆB(Ds+āĻĻ+)=7.55Ā±0.20Ā±0.34pb and Ļ(e+e-āDs*Ā±X)ĆB(Ds+āĻĻ+)=5.8Ā±0.7Ā±0.5pb are measured at center-of-mass energies about 40 MeV below the Ī„(4S) mass. The branching fractions Ī£B(BāDs(*)+D(*))=(5.07Ā±0.14Ā±0.30Ā±1.27)% and Ī£B(BāDs*+D(*))=(4.1Ā±0.2Ā±0.4Ā±1.0)% are determined from the Ds(*)+ momentum spectra. The mass difference m(Ds+)-m(D+)=98.4Ā±0.1Ā±0.3MeV/c2 is also measured.This work was supported by DOE and NSF (USA), NSERC (Canada), IHEP (China), CEA and CNRS-IN2P3 (France), BMBF (Germany), INFN (Italy), NFR (Norway), MIST (Russia), and PPARC (United Kingdom). Individuals have received support from the Swiss NSF, A. P. Sloan Foundation, Research Corporation, and Alexander von Humboldt Foundation
The Role of Ī³-Tubulin in Centrosomal Microtubule Organization
As part of a multi-subunit ring complex, Ī³-tubulin has been shown to promote microtubule nucleation both in vitro and in vivo, and the structural properties of the complex suggest that it also seals the minus ends of the polymers with a conical cap. Cells depleted of Ī³-tubulin, however, still display many microtubules that participate in mitotic spindle assembly, suggesting that Ī³-tubulin is not absolutely required for microtubule nucleation in vivo, and raising questions about the function of the minus end cap. Here, we assessed the role of Ī³-tubulin in centrosomal microtubule organisation using three-dimensional reconstructions of Ī³-tubulin-depleted C. elegans embryos. We found that microtubule minus-end capping and the PCM component SPD-5 are both essential for the proper placement of microtubules in the centrosome. Our results further suggest that Ī³-tubulin and SPD-5 limit microtubule polymerization within the centrosome core, and we propose a model for how abnormal microtubule organization at the centrosome could indirectly affect centriole structure and daughter centriole replication
The mammalian centrosome and its functional significance
Primarily known for its role as major microtubule organizing center, the centrosome is increasingly being recognized for its functional significance in key cell cycle regulating events. We are now at the beginning of understanding the centrosomeās functional complexities and its major impact on directing complex interactions and signal transduction cascades important for cell cycle regulation. The centrosome orchestrates entry into mitosis, anaphase onset, cytokinesis, G1/S transition, and monitors DNA damage. Recently, the centrosome has also been recognized as major docking station where regulatory complexes accumulate including kinases and phosphatases as well as numerous other cell cycle regulators that utilize the centrosome as platform to coordinate multiple cell cycle-specific functions. Vesicles that are translocated along microtubules to and away from centrosomes may also carry enzymes or substrates that use centrosomes as main docking station. The centrosomeās role in various diseases has been recognized and a wealth of data has been accumulated linking dysfunctional centrosomes to cancer, Alstrom syndrome, various neurological disorders, and others. Centrosome abnormalities and dysfunctions have been associated with several types of infertility. The present review highlights the centrosomeās significant roles in cell cycle events in somatic and reproductive cells and discusses centrosome abnormalities and implications in disease
The elegans of spindle assembly
The Caenorhabditis elegans one-cell embryo is a powerful system in which to study microtubule organization because this large cell assembles both meiotic and mitotic spindles within the same cytoplasm over the course of 1Ā h in a stereotypical manner. The fertilized oocyte assembles two consecutive acentrosomal meiotic spindles that function to reduce the replicated maternal diploid set of chromosomes to a single-copy haploid set. The resulting maternal DNA then unites with the paternal DNA to form a zygotic diploid complement, around which a centrosome-based mitotic spindle forms. The early C. elegans embryo is amenable to live-cell imaging and electron tomography, permitting a detailed structural comparison of the meiotic and mitotic modes of spindle assembly
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