30,745 research outputs found
Absence of synaptic regulation by phosducin in retinal slices.
Phosducin is an abundant photoreceptor protein that binds G-protein βγ subunits and plays a role in modulating synaptic transmission at photoreceptor synapses under both dark-adapted and light-adapted conditions in vivo. To examine the role of phosducin at the rod-to-rod bipolar cell (RBC) synapse, we used whole-cell voltage clamp recordings to measure the light-evoked currents from both wild-type (WT) and phosducin knockout (Pd(-/-)) RBCs, in dark- and light-adapted retinal slices. Pd(-/-) RBCs showed smaller dim flash responses and steeper intensity-response relationships than WT RBCs, consistent with the smaller rod responses being selectively filtered out by the non-linear threshold at the rod-to-rod bipolar synapse. In addition, Pd(-/-) RBCs showed a marked delay in the onset of the light-evoked currents, similar to that of a WT response to an effectively dimmer flash. Comparison of the changes in flash sensitivity in the presence of steady adapting light revealed that Pd(-/-) RBCs desensitized less than WT RBCs to the same intensity. These results are quantitatively consistent with the smaller single photon responses of Pd(-/-) rods, owing to the known reduction in rod G-protein expression levels in this line. The absence of an additional synaptic phenotype in these experiments suggests that the function of phosducin at the photoreceptor synapse is abolished by the conditions of retinal slice recordings
Pragmatic View of Short-Baseline Neutrino Oscillations
We present the results of global analyses of short-baseline neutrino
oscillation data in 3+1, 3+2 and 3+1+1 neutrino mixing schemes. We show that
the data do not allow us to abandon the simplest 3+1 scheme in favor of the
more complex 3+2 and 3+1+1 schemes. We present the allowed region in the 3+1
parameter space, which is located at between 0.82 and 2.19
at . The case of no oscillations is disfavored by about
, which decreases dramatically to about if the LSND data are
not considered. Hence, new high-precision experiments are needed to check the
LSND signal.Comment: 6 pages. Final version published in Phys. Rev. D 88, 073008 (2013
Short-Baseline Electron Neutrino Oscillation Length After Troitsk
We discuss the implications for short-baseline electron neutrino
disappearance in the 3+1 mixing scheme of the recent Troitsk bounds on the
mixing of a neutrino with mass between 2 and 100 eV. Considering the Troitsk
data in combination with the results of short-baseline nu_e and antinu_e
disappearance experiments, which include the reactor and Gallium anomalies, we
derive a 2 sigma allowed range for the effective neutrino squared-mass
difference between 0.85 and 43 eV^2. The upper bound implies that it is likely
that oscillations in distance and/or energy can be observed in radioactive
source experiments. It is also favorable for the ICARUS@CERN experiment, in
which it is likely that oscillations are not washed-out in the near detector.
We discuss also the implications for neutrinoless double-beta decay.Comment: 5 pages. Final version published in Phys.Rev. D87 (2013) 01300
Self-consistent relativistic quasiparticle random-phase approximation and its applications to charge-exchange excitations and -decay half-lives
The self-consistent quasiparticle random-phase approximation (QRPA) approach
is formulated in the canonical single-nucleon basis of the relativistic
Hatree-Fock-Bogoliubov (RHFB) theory. This approach is applied to study the
isobaric analog states (IAS) and Gamov-Teller resonances (GTR) by taking Sn
isotopes as examples. It is found that self-consistent treatment of the
particle-particle residual interaction is essential to concentrate the IAS in a
single peak for open-shell nuclei and the Coulomb exchange term is very
important to predict the IAS energies. For the GTR, the isovector pairing can
increase the calculated GTR energy, while the isoscalar pairing has an
important influence on the low-lying tail of the GT transition. Furthermore,
the QRPA approach is employed to predict nuclear -decay half-lives. With
an isospin-dependent pairing interaction in the isoscalar channel, the
RHFB+QRPA approach almost completely reproduces the experimental -decay
half-lives for nuclei up to the Sn isotopes with half-lives smaller than one
second. Large discrepancies are found for the Ni, Zn, and Ge isotopes with
neutron number smaller than , as well as the Sn isotopes with neutron
number smaller than . The potential reasons for these discrepancies are
discussed in detail.Comment: 34 pages, 14 figure
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