14,243 research outputs found
Differential Input from the Amygdaloid Body to the Ventromedial Hypothalamic Nucleus in the Rat
Differential amygdaloid afferents to anterior dorsal, anterior ventral, posterior dorsal and posterior ventral subdivisions of the ventromedial hypothalamic nucleus (VMH) were studied by means of retrograde transport of horseradish peroxidase (HRP). Injections of tracer confined to the VMH subdivisions mentioned, and enhancement of tracer uptake and transport were achieved by iontophoretic delivery of an HRP solution containing poly-L-α-ornithine. It was shown that the medial, central, basolateral, basomedial, lateroposterior and intercalated nuclei of the amygdala constitute afferent input sources to the ventromedial nucleus in a topographic pattern related to the various subdivisions of the VMH. This topographically organized amygdala-VMH projection is discussed against the background of the functional role that both amygdala and VMH play in the control of feeding, apart from various other autonomous functions that both brain centers are known to be concerned with.
Biquadratic antisymmetric exchange and the magnetic phase diagram of magnetoelectric CuFeO
Biquadratic {\it antisymmetric} exchange terms of the form , where is the
unit vector connecting sites and and , due partially to
magnetoelectric coupling effects, are shown to be responsible for the spin-flop
helical phase in CuFeO at low magnetic field and temperature. Usual
biquadratic {\it symmetric} exchange, likely due to magnetoelastic coupling, is
found to support the stability of axial magnetic states at higher fields in
this nearly-Heisenberg like stacked triangular antiferromagnet. A model
Hamiltonian which also includes substantial interplane and higher-neighbor
intraplane exchange interactions, reproduces the unique series of observed
commensurate and incommensurate periodicity phases with increasing applied
magnetic field in this highly frustrated system. The magnetic field-temperature
phase diagram is discussed in terms of a Landau-type free energy.Comment: 7 pages, 9 figure
Leptogenesis with Almost Degenerate Majorana Neutrinos
We investigate the leptogenesis with almost degenerate neutrinos, in the
framework of democratic mass matrix, which naturally explains the large mixing
angles for neutrino oscillations as well as quark masses and mixing matrix. We
find that the baryon asymmetry in the present universe is explained via the
decays of right-handed neutrinos produced nonthermally by the inflaton decay.
The model predicts neutrinoless double beta decays accessible in near future
experiments.Comment: 17 pages, LaTeX, 2 figure
Lepton Flavor Violation in Supersymmetric SO(10) Grand Unified Models
The study for lepton flavor violation combined with the neutrino oscillation
may provide more information about the lepton flavor structure of the grand
unified theory. In this paper, we study two lepton flavor violation processes,
and , in the context of supersymmetric SO(10)
grand unified models. We find the two processes are both of phenomenological
interest. In particular the latter may be important in some supersymmetric
parameter space where the former is suppressed. Thus, Z-dacay may offer another
chance for looking for lepton flavor violation.Comment: 26 pages, 10 figure
Lepton-nucleus scattering in the impulse approximation regime
We discuss theoretical calculations of electron- and neutrino-nucleus
scattering, carried out using realistic nuclear spectral functions and
including the effect of final state interactions. Comparison between electron
scattering data and the calculated inclusive cross sections off oxygen shows
that the Fermi gas model fails to provide a satisfactory description of the
measured cross sections, and inclusion of nuclear dynamics is needed. The role
of Pauli blocking in charged-current neutrino induced reactions at low is
also analyzed.Comment: To be published in the Proceedings of NUFACT05 (Nucl. Phys. B,
Proceedings Supplements
Dynamical mass generation by source inversion: Calculating the mass gap of the Gross-Neveu model
We probe the U(N) Gross-Neveu model with a source-term . We
find an expression for the renormalization scheme and scale invariant source
, as a function of the generated mass gap. The expansion of this
function is organized in such a way that all scheme and scale dependence is
reduced to one single parameter d. We get a non-perturbative mass gap as the
solution of . In one loop we find that any physical choice for d
gives good results for high values of N. In two loops we can determine d
self-consistently by the principle of minimal sensitivity and find remarkably
accurate results for N>2.Comment: 13 pages, 3 figures, added referenc
Nearly Bi-Maximal Neutrino Mixing, Muon g-2 Anomaly and Lepton-Flavor-Violating Processes
We interpret the newly observed muon g-2 anomaly in the framework of a
leptonic Higgs doublet model with nearly degenerate neutrino masses and nearly
bi-maximal neutrino mixing. Useful constraints are obtained on the rates of
lepton-flavor-violating rare decays ,
and as well as the - conversion ratio .
We find that , and
depend crucially on possible non-zero but samll values of the
neutrino mixing matrix element , and they are also sensitive to the
Dirac-type CP-violating phase. In particular, we show that , and are approximately in the ratio if is much larger than , and in the
ratio if is much lower than , where and are the corresponding mass-squared
differences of atmospheric and solar neutrino oscillations.Comment: LaTex 6 pages (2 PS figures). Phys. Rev. D (in printing
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