1,939 research outputs found
Point and Line vulnerability as Bases for Predicting the Distribution of Power in Exchange Networks: Reply to Willer
Gamow-Teller sum rule in relativistic nuclear models
Relativistic corrections are investigated to the Gamow-Teller(GT) sum rule
with respect to the difference between the and transition
strengths in nuclei. Since the sum rule requires the complete set of the
nuclear states, the relativistic corrections come from the anti-nucleon degrees
of freedom. In the relativistic mean field approximation, the total GT
strengths carried by the nucleon sector is quenched by about 12% in nuclear
matter, while by about 8% in finite nuclei, compared to the sum rule value. The
coupling between the particle-hole states with the nucleon-antinucleon states
is also discussed with the relativistic random phase approximation, where the
divergence of the response function is renormalized with use of the counter
terms in the Lagrangian. It is shown that the approximation to neglect the
divergence, like the no-sea approximation extensively used so far, is
unphysical, from the sum-rule point of view.Comment: 12 pages, Brief review for Mod. Phys. Lett. A, using ws-mpla.cl
Simultaneously optimizing the interdependent thermoelectric parameters in Ce(NiCu)Al
Substitution of Cu for Ni in the Kondo lattice system CeNiAl results
in a simultaneous optimization of the three interdependent thermoelectric
parameters: thermoelectric power, electrical and thermal conductivities, where
the electronic change in conduction band induced by the extra electron of Cu is
shown to be crucial. The obtained thermoelectric figure of merit amounts
to 0.125 at around 100 K, comparable to the best values known for Kondo
compounds. The realization of ideal thermoelectric optimization in
Ce(NiCu)Al indicates that proper electronic tuning of Kondo
compounds is a promising approach to efficient thermoelectric materials for
cryogenic application.Comment: 4 pages, 4 figures. Accepted for publication in Physical Review
Josephson junction in cobalt-doped BaFe2As2 epitaxial thin films on (La, Sr)(Al, Ta)O3 bicrystal substrates
Josephson junctions were fabricated in epitaxial films of cobalt-doped
BaFe2As2 on [001]-tilt (La,Sr)(Al,Ta)O3 bicrystal substrates. 10m-wide
microbridges spanning a 30-degrees-tilted bicrystal grain boundary (BGB bridge)
exhibited resistively-shunted-junction (RSJ)-like current-voltage
characteristics up to 17 K, and the critical current was suppressed remarkably
by a magnetic field. Microbridges without a BGB did not show the RSJ-like
behavior, and their critical current densities were 20 times larger than those
of BGB bridges, confirming BGB bridges display a Josephson effect originating
from weakly-linked BGB
The Gamow-Teller States in Relativistic Nuclear Models
The Gamow-Teller(GT) states are investigated in relativistic models. The
Landau-Migdal(LM) parameter is introduced in the Lagrangian as a contact term
with the pseudo-vector coupling. In the relativistic model the total GT
strength in the nucleon space is quenched by about 12% in nuclear matter and by
about 6% in finite nuclei, compared with the one of the Ikeda-Fujii-Fujita sum
rule. The quenched amount is taken by nucleon-antinucleon excitations in the
time-like region. Because of the quenching, the relativistic model requires a
larger value of the LM parameter than non-relativistic models in describing the
excitation energy of the GT state. The Pauli blocking terms are not important
for the description of the GT states.Comment: REVTeX4, no figure
Organization of multisynaptic inputs to the dorsal and ventral dentate gyrus: retrograde trans-synaptic tracing with rabies virus vector in the rat
Behavioral, anatomical, and gene expression studies have shown functional dissociations between the dorsal and ventral hippocampus with regard to their involvement in spatial cognition, emotion, and stress. In this study we examined the difference of the multisynaptic inputs to the dorsal and ventral dentate gyrus (DG) in the rat by using retrograde trans-synaptic tracing of recombinant rabies virus vectors. Three days after the vectors were injected into the dorsal or ventral DG, monosynaptic neuronal labeling was present in the entorhinal cortex, medial septum, diagonal band, and supramammillary nucleus, each of which is known to project to the DG directly. As in previous tracing studies, topographical patterns related to the dorsal and ventral DG were seen in these regions. Five days after infection, more of the neurons in these regions were labeled and labeled neurons were also seen in cortical and subcortical regions, including the piriform and medial prefrontal cortices, the endopiriform nucleus, the claustrum, the cortical amygdala, the medial raphe nucleus, the medial habenular nucleus, the interpeduncular nucleus, and the lateral septum. As in the monosynaptically labeled regions, a topographical distribution of labeled neurons was evident in most of these disynaptically labeled regions. These data indicate that the cortical and subcortical inputs to the dorsal and ventral DG are conveyed through parallel disynaptic pathways. This second-order input difference in the dorsal and ventral DG is likely to contribute to the functional differentiation of the hippocampus along the dorsoventral axis.© 2013 Ohara et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Complex Intramolecular Mechanics of G-actin - An Elastic Network Study
Systematic numerical investigations of conformational motions in single actin
molecules were performed by employing a simple elastic-network (EN) model of
this protein. Similar to previous investigations for myosin, we found that
G-actin essentially behaves as a strain sensor, responding by well-defined
domain motions to mechanical perturbations. Several sensitive residues within
the nucleotide-binding pocket (NBP) could be identified, such that the
perturbation of any of them can induce characteristic flattening of actin
molecules and closing of the cleft between their two mobile domains. Extending
the EN model by introduction of a set of breakable links which become
effective only when two domains approach one another, it was observed that
G-actin can possess a metastable state corresponding to a closed conformation
and that a transition to this state can be induced by appropriate
perturbations in the NBP region. The ligands were roughly modeled as a single
particle (ADP) or a dimer (ATP), which were placed inside the NBP and
connected by elastic links to the neighbors. Our approximate analysis suggests
that, when ATP is present, it stabilizes the closed conformation of actin.
This may play an important role in the explanation why, in the presence of
ATP, the polymerization process is highly accelerated
Influence of Mo on the Fe:Mo:C nano-catalyst thermodynamics for single-walled carbon nanotube growth
We explore the role of Mo in Fe:Mo nanocatalyst thermodynamics for
low-temperature chemical vapor deposition growth of single walled carbon
nanotubes (SWCNTs). By using the size-pressure approximation and ab initio
modeling, we prove that for both Fe-rich (~80% Fe or more) and Mo-rich (~50% Mo
or more) Fe:Mo clusters, the presence of carbon in the cluster causes
nucleation of Mo2C. This enhances the activity of the particle since it
releases Fe, which is initially bound in a stable Fe:Mo phase, so that it can
catalyze SWCNT growth. Furthermore, the presence of small concentrations of Mo
reduce the lower size limit of low-temperature steady-state growth from ~0.58nm
for pure Fe particles to ~0.52nm. Our ab initio-thermodynamic modeling explains
experimental results and establishes a new direction to search for better
catalysts.Comment: 7 pages, 3 figures. submitte
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