889 research outputs found

    Variational calculations for the hydrogen-antihydrogen system with a mass-scaled Born-Oppenheimer potential

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    The problem of proton-antiproton motion in the H{\rm H}--Hˉ{\rm \bar{H}} system is investigated by means of the variational method. We introduce a modified nuclear interaction through mass-scaling of the Born-Oppenheimer potential. This improved treatment of the interaction includes the nondivergent part of the otherwise divergent adiabatic correction and shows the correct threshold behavior. Using this potential we calculate the vibrational energy levels with angular momentum 0 and 1 and the corresponding nuclear wave functions, as well as the S-wave scattering length. We obtain a full set of all bound states together with a large number of discretized continuum states that might be utilized in variational four-body calculations. The results of our calculations gives an indication of resonance states in the hydrogen-antihydrogen system

    Granzyme B activates procaspase-3 which signals a mitochondrial amplification loop for maximal apoptosis

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    Granzyme B (GrB), acting similar to an apical caspase, efficiently activates a proteolytic cascade after intracellular delivery by perforin. Studies here were designed to learn whether the physiologic effector, GrB–serglycin, initiates apoptosis primarily through caspase-3 or through BH3-only proteins with subsequent mitochondrial permeabilization and apoptosis. Using four separate cell lines that were either genetically lacking the zymogen or rendered deficient in active caspase-3, we measured apoptotic indices within whole cells (active caspase-3, mitochondrial depolarization [ΔΨm] and TUNEL). Adhering to these conditions, the following were observed in targets after GrB delivery: (a) procaspase-3–deficient cells fail to display a reduced ΔΨm and DNA fragmentation; (b) Bax/Bak is required for optimal ΔΨm reduction, caspase-3 activation, and DNA fragmentation, whereas BID cleavage is undetected by immunoblot; (c) Bcl-2 inhibits GrB-mediated apoptosis (reduced ΔΨm and TUNEL reactivity) by blocking oligomerization of caspase-3; and (d) in procaspase-3–deficient cells a mitochondrial-independent pathway was identified which involved procaspase-7 activation, PARP cleavage, and nuclear condensation. The data therefore support the existence of a fully implemented apoptotic pathway initiated by GrB, propagated by caspase-3, and perpetuated by a mitochondrial amplification loop but also emphasize the presence of an ancillary caspase-dependent, mitochondria-independent pathway

    Magnetic Field Stimulated Transitions of Excited States in Fast Muonic Helium Ions

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    It is shown that one can stimulate, by using the present-day laboratory magnetic fields, transitions between the lmlm sub-levels of fast μHe+\mu He^+ ions formating in muon catalyzed fusion. Strong fields also cause the self-ionization from highly excited states of such muonic ions. Both effects are the consequence of the interaction of the bound muon with the oscillating field of the Stark term coupling the center-of-mass and muon motions of the μHe+\mu He^+ ion due to the non-separability of the collective and internal variables in this system. The performed calculations show a possibility to drive the population of the lmlm sub-levels by applying a field of a few TeslaTesla, which affects the reactivation rate and is especially important to the KαK\alpha xx-ray production in muon catalyzed fusion. It is also shown that the 2s2p2s-2p splitting in μHe+\mu He^+ due to the vacuum polarization slightly decreases the stimulated transition rates.Comment: 5 figure

    Computer analysis of cardiac radionuclide data

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    Gamma-camera tomography gives uniform in-plane and cross-plane resolution with propagation of the defect from one plane to another determined only by the usual camera-collimator resolution. These images may be reformatted by computer to portray slices in any orientation. Cross plane resolution is slightly worse than for the other methods, but it is uniform. The efficiency is less than either quadrant slant hole or seven pinhole apertures. Rotating cameras are not portable nor can they be used for dynamic studies.Both slant hole collimators and seven pinhole apertures distort the object in the depth dimension because of the limited viewing angle. The slant hole geometry provides somewhat better sampling and less plane-to-plane cross talk especially for the more distant planes. The full width half maximum of the depth response is not a sensitive indicator of this problem because the depth response function has very long tails.To date, best overall performance of the limited angle methods is offered by the 40[deg] slant hole collimator on a large field-of-view camera. This, however, is not a portable unit and has a field-of-view too small for about 10% of the patients.Seven pinhole imaging offers the advantage of having been well studied by a number of institution.87-90 A large pool of normal patient studies exists and the performance is well documented. Although the seven pinhole alone is suited to dynamic studies, any of the methods may be adapted to multigated studies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25165/1/0000603.pd

    X-ray emission during the muonic cascade in hydrogen

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    We report our investigations of X rays emitted during the muonic cascade in hydrogen employing charge coupled devices as X-ray detectors. The density dependence of the relative X-ray yields for the muonic hydrogen lines (K_alpha, K_beta, K_gamma) has been measured at densities between 0.00115 and 0.97 of liquid hydrogen density. In this density region collisional processes dominate the cascade down to low energy levels. A comparison with recent calculations is given in order to demonstrate the influence of Coulomb deexcitation.Comment: 5 pages, Tex, 4 figures, submitted to Physical Review Letter
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