131 research outputs found
The Nab Experiment: A Precision Measurement of Unpolarized Neutron Beta Decay
Neutron beta decay is one of the most fundamental processes in nuclear
physics and provides sensitive means to uncover the details of the weak
interaction. Neutron beta decay can evaluate the ratio of axial-vector to
vector coupling constants in the standard model, , through
multiple decay correlations. The Nab experiment will carry out measurements of
the electron-neutrino correlation parameter with a precision of and the Fierz interference term to
in unpolarized free neutron beta decay. These results, along with a more
precise measurement of the neutron lifetime, aim to deliver an independent
determination of the ratio with a precision of that will allow an evaluation of and sensitively
test CKM unitarity, independent of nuclear models. Nab utilizes a novel, long
asymmetric spectrometer that guides the decay electron and proton to two large
area silicon detectors in order to precisely determine the electron energy and
an estimation of the proton momentum from the proton time of flight. The Nab
spectrometer is being commissioned at the Fundamental Neutron Physics Beamline
at the Spallation Neutron Source at Oak Ridge National Lab. We present an
overview of the Nab experiment and recent updates on the spectrometer,
analysis, and systematic effects.Comment: Presented at PPNS201
The Glycosylphosphatidylinositol-PLC in Trypanosoma brucei Forms a Linear Array on the Exterior of the Flagellar Membrane Before and After Activation
Bloodstream forms of Trypanosoma brucei contain a glycosylphosphatidylinositol-specific phospholipase C (GPI-PLC) that cleaves the GPI-anchor of the variable surface glycoprotein (VSG). Its location in trypanosomes has been controversial. Here, using confocal microscopy and surface labelling techniques, we show that the GPI-PLC is located exclusively in a linear array on the outside of the flagellar membrane, close to the flagellar attachment zone, but does not co-localize with the flagellar attachment zone protein, FAZ1. Consequently, the GPI-PLC and the VSG occupy the same plasma membrane leaflet, which resolves the topological problem associated with the cleavage reaction if the VSG and the GPI-PLC were on opposite sides of the membrane. The exterior location requires the enzyme to be tightly regulated to prevent VSG release under basal conditions. During stimulated VSG release in intact cells, the GPI-PLC did not change location, suggesting that the release mechanism involves lateral diffusion of the VSG in the plane of the membrane to the fixed position of the GPI-PLC
Influence of Helium and Nitrogen Gases on the Properties of Cold Gas Dynamic Sprayed Pure Titanium Coatings
Escalas concorrentes para a mensuraçãoda qualidade percebida: uma comparação entre a Servqual e a RSQ
Double Label Immuno Fluorescence Studies on Nanometer Filaments and Micro Tubules During Mitosis in Endothelial Cells
The Microtubule Organizing Centers, Mtocs, Are Surrounded by the 10-Nanometer Filament Ring of Endothelial-Cells in Interphase and Mitosis
Ten-nanometer filaments and mitosis: maintenance of structural continuity in dividing endothelial cells.
By indirect immunofluorescence the behavior of the 10-nm filaments was studied at various stages of mitosis in guinea pig vascular endothelial cells. Interphase cells contain a ring of 10-nm filaments that encircles the nucleus and is maintained in a plane parallel to the substrate. During prophase and metaphase the cells round up and the 10-nm filament ring becomes wavy though still a closed structure. As anaphase progresses the ring then elongates into a rectangle that contains the spindle apparatus and chromosomes. In late telophase, cytokinesis cleaves the 10-nm filaments into crescents at the site of the contractile ring. These crescents then close into rings in the daughter cells. If cytokinesis is inhibited with 5 microgram of cytochalasin B per ml, then cleavage of the 10-nm filaments is blocked and the daughter nuclei remain surrounded by the parent ring. At no point during mitosis does the array of 10-nm filaments undergo major disassembly. These results indicate that, in contrast to the other major cytoplasmic structures, ventral microfilament bundles and cytoplasmic microtubules, which disassemble and reassemble during mitosis, 10-nm filaments remain intact throughout this process. The possibility is discussed that these filaments may function in transport of organelles and structural proteins, and provide the daughter cells with topological information about placement and assembly of these elements within the microtrabecular lattice
The Distribution of 10nm Filaments and Microtubules in Endothelial-Cells During Mitosis - Double-Label Immunofluorescence Study
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