890 research outputs found
Variational calculations for the hydrogen-antihydrogen system with a mass-scaled Born-Oppenheimer potential
The problem of proton-antiproton motion in the --
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
Gruppenkonstanten fuer dampf- und natriumgekuehlte schnelle Reaktoren in einer 26-Gruppendarstellung
Granzyme B activates procaspase-3 which signals a mitochondrial amplification loop for maximal apoptosis
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
It is shown that one can stimulate, by using the present-day laboratory
magnetic fields, transitions between the sub-levels of fast
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
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 sub-levels by applying a field of a few
, which affects the reactivation rate and is especially important to the
-ray production in muon catalyzed fusion. It is also shown that
the splitting in due to the vacuum polarization slightly
decreases the stimulated transition rates.Comment: 5 figure
X-ray emission during the muonic cascade in hydrogen
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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