961 research outputs found

    Performance/design and product configuration requirements for the laser ranging retro-reflector (300) crew training model

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    This specification defines the performance, design, construction, and interface requirements for the Crew Training Model of the Laser Ranging Retro-Reflector (LRRR). This model is a mechanical simulation of the LRRR (300) flight configuration incorporating most visual, and all handling and manipulative features and characteristics suitable for training a space-suited astronaut on a simulated lunar surface.prepared by Leslie D. Marrus

    Apollo 15 anomalies investigation

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    The purpose of this ATM is to review and status the BxA effort with respect to the Apollo 15 Anomalies Investigation. The results of analyses and completed tests are summarized and the plans for additional testing, etc. are discussed.prepared by L. D. Marrus.UHT/Subpackage #2 Interface -- Shorting Switch Activation -- UHT/SIDE Interface -- HFE Boyd Bolts -- SIDE Connector -- Rear Curtain Cover Lanyar

    Differential localization of glutamate receptor subunits at the drosophila neuromuscular junction

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    The subunit composition of postsynaptic neurotransmitter receptors is a key determinant of synaptic physiology. Two glutamate receptor subunits, Drosophila glutamate receptor IIA (DGluRIIA) and DGluRIIB, are expressed at the Drosophila neuromuscular junction and are redundant for viability, yet differ in their physiological properties. We now identify a third glutamate receptor subunit at the Drosophila neuromuscular junction, DGluRIII, which is essential for viability. DGluRIII is required for the synaptic localization of DGluRIIA and DGluRIIB and for synaptic transmission. Either DGluRIIA or DGluRIIB, but not both, is required for the synaptic localization of DGluRIII. DGluRIIA and DGluRIIB compete with each other for access to DGluRIII and subsequent localization to the synapse. These results are consistent with a model of a multimeric receptor in which DGluRIII is an essential component. At single postsynaptic cells that receive innervation from multiple motoneurons, DGluRIII is abundant at all synapses. However, DGluRIIA and DGluRIIB are differentially localized at the postsynaptic density opposite distinct motoneurons. Hence, innervating motoneurons may regulate the subunit composition of their receptor fields within a shared postsynaptic cell. The capacity of presynaptic inputs to shape the subunit composition of postsynaptic receptors could be an important mechanism for synapse-specific regulation of synaptic function and plasticity

    State-insensitive trapping of Rb atoms: linearly versus circularly polarized lights

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    We study the cancellation of differential ac Stark shifts in the 5s and 5p states of rubidium atom using the linearly and circularly polarized lights by calculating their dynamic polarizabilities. Matrix elements were calculated using a relativistic coupled-cluster method at the single, double and important valence triple excitations approximation including all possible non-linear correlation terms. Some of the important matrix elements were further optimized using the experimental results available for the lifetimes and static polarizabilities of atomic states. "Magic wavelengths" are determined from the differential Stark shifts and results for the linearly polarized light are compared with the previously available results. Possible scope of facilitating state-insensitive optical trapping schemes using the magic wavelengths for circularly polarized light are discussed. Using the optimized matrix elements, the lifetimes of the 4d and 6s states of this atom are ameliorated.Comment: 13 pages, 13 tables and 4 figure

    Multipole (E1, M1, E2, M2) transition wavelengths and rates between states with n<= 6 in heliumlike carbon, nitrogen, oxygen, neon, silicon, and argon

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    Transition wavelengths and rates are given for E1, E2, M1, and M2 transitions between singlet and triplet S, P, D, and F states in heliumlike ions of astrophysical interest: carbon, nitrogen, oxygen, neon, silicon, and argon. All possible transitions between states with n <= 6 are considered. Wave functions and energies are calculated using the relativistic configuration-interaction (CI) method including both Coulomb and Breit interactions. For transitions to the ground state, the present theoretical wavelengths agree to five digits with precise measurements.Comment: 8 pages of text 97 pages of tables submitted to Atomic & Data Nuclear Datable

    Characterization of a novel, dominant negative KCNJ2 mutation associated with Andersen-Tawil syndrome

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    Andersen-Tawil syndrome is characterized by periodic paralysis, ventricular ectopy and dysmorphic features. Approximately 60% of patients exhibit loss-of-function mutations in KCNJ2, which encodes the inwardly rectifying K(+) channel pore forming subunit Kir2.1. Here, we report the identification of a novel KCNJ2 mutation (G211T), resulting in the amino acid substitution D71Y, in a patient presenting with signs and symptoms of Andersen-Tawil syndrome. The functional properties of the mutant subunit were characterized using voltage-clamp experiments on transiently transfected HEK-293 cells and neonatal mouse ventricular myocytes. Whole-cell current recordings of transfected HEK-293 cells demonstrated that the mutant protein Kir2.1-D71Y fails to form functional ion channels when expressed alone, but co-assembles with wild-type Kir2.1 subunits and suppresses wild-type subunit function. Further analysis revealed that current suppression requires at least two mutant subunits per channel. The D71Y mutation does not measurably affect the membrane trafficking of either the mutant or the wild-type subunit or alter the kinetic properties of the currents. Additional experiments revealed that expression of the mutant subunit suppresses native I(K1) in neonatal mouse ventricular myocytes. Simulations predict that the D71Y mutation in human ventricular myocytes will result in a mild prolongation of the action potential and potentially increase cell excitability. These experiments indicate that the Kir2.1-D71Y mutant protein functions as a dominant negative subunit resulting in reduced inwardly rectifying K(+) current amplitudes and altered cellular excitability in patients with Andersen-Tawil syndrome

    QED theory of transition probabilities and line profiles in highly-charged ions

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    A rigorous QED theory of the spectral line profiles is applied to transition probabilities in few-electron highly charged ions. Interelectron interaction corrections are included as well as radiative corrections. Parity nonconserving (PNC) amplitudes with effective weak interactions between the electrons and nucleus are also considered. QED and interelectron interaction corrections to the PNC amplitudes are derived
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