253 research outputs found
Solving problems of 4D minimal SO(10) model in a warped extra dimension
The minimal renormalizable supersymmetric SO(10) model, an SO(10) framework
with only one 10 and one 126 Higgs multiplets in the Yukawa sector, is
attractive because of its high predictive power for the neutrino oscillation
data. However, this model suffers from problems related to running of gauge
couplings. The gauge coupling unification may be spoiled due to the presence of
Higgs multiplets much lighter than the grand unification (GUT) scale. In
addition, the gauge couplings blow up around the GUT scale because of the
presence of Higgs multiplets of large representations. We consider the minimal
SO(10) model in the warped extra dimension and find a possibility to solve
these problems.Comment: 12 pages, no figure; version to appear in Phys. Rev.
A simple SO(10) GUT in five dimensions
A simple supersymmetric SO(10) GUT in five dimensions is considered. The
fifth dimension is compactified on the orbifold
possessing two inequivalent fixed points. In our setup, all matter and Higgs
multiplets reside on one brane (PS brane) where the original SO(10) gauge group
is broken down to the Pati-Salam (PS) gauge group, SU(4)_c \timesSU(2)_L
\times SU(2), by the orbifold boundary condition, while only the SO(10)
gauge multiplet resides in the bulk. The further breaking of the PS symmetry to
the Standard Model gauge group is realized by Higgs multiplets on the PS brane
as usual in four dimensional models. Proton decay is fully suppressed. In our
simple setup, the gauge coupling unification is realized after incorporating
threshold corrections of Kaluza-Klein modes. When supersymmetry is assumed to
be broken on the other brane, supersymmetry breaking is transmitted to the PS
brane through the gaugino mediation with the bulk gauge multiplet.Comment: 12 pages, 1 figure, some errors have been corrected (no change in
conclusions
Single-Molecule Analysis of Epidermal Growth Factor Signaling that Leads to Ultrasensitive Calcium Response
AbstractQuantitative relationships between inputs and outputs of signaling systems are fundamental information for the understanding of the mechanism of signal transduction. Here we report the correlation between the number of epidermal growth factor (EGF) bindings and the response probability of intracellular calcium elevation. Binding of EGF molecules and changes of intracellular calcium concentration were measured for identical HeLa human epithelial cells. It was found that 300 molecules of EGF were enough to induce calcium response in half of the cells. This number is quite small compared to the number of EGF receptors (EGFR) expressed on the cell surface (50,000). There was a sigmoidal correlation between the response probability and the number of EGF bindings, meaning an ultrasensitive reaction. Analysis of the cluster size distribution of EGF demonstrated that dimerization of EGFR contributes to this switch-like ultrasensitive response. Single-molecule analysis revealed that EGF bound faster to clusters of EGFR than to monomers. This property should be important for effective formation of signaling dimers of EGFR under very small numbers of EGF bindings and suggests that the expression of excess amounts of EGFR on the cell surface is required to prepare predimers of EGFR with a large association rate constant to EGF
Phenomenology in the Zee Model with the A_4 Symmetry
The Zee model generates neutrino masses at the one-loop level by adding
charged SU(2)_L-singlet and extra SU(2)_L-doublet scalars to the standard model
of particle physics. As the origin of the nontrivial structure of the lepton
flavor mixing, we introduce the softly broken A_4 symmetry to the Zee model.
This model is compatible with the tribimaximal mixing which agrees well with
neutrino oscillation measurements. Then, a sum rule m_1 e^{i alpha_12} + 2 m_2
+ 3 m_3 e^{i alpha_32} = 0 is obtained and it results in Delta m^2_31 < 0 and
m_3 > 1.8*10^{-2}eV. The effective mass |(M_nu)_{ee}| for the neutrinoless
double beta decay is predicted as | (M_\nu)_{ee} | > 1.7*10^{-2}eV. The
characteristic particles in this model are SU(2)_L-singlet charged Higgs bosons
s^+_alpha (alpha=xi,eta,zeta) which are made from a 3-representation of A_4.
Contributions of s^+_alpha to the lepton flavor violating decays of charged
leptons are almost forbidden by an approximately remaining Z_3 symmetry; only
BR(tau to ebar mu mu) can be sizable by the flavor changing neutral current
interaction with SU(2)_L-doublet scalars. Therefore, s^+_alpha can be easily
light enough to be discovered at the LHC with satisfying current constraints.
The flavor structures of BR(s^-_alpha to ell nu) are also discussed.Comment: 26 pages, 4 figures, version accepted by PR
Axion and Right-handed Neutrino in the Minimal SUSY SO(10) Model
The connection between the axion and right-handed neutrinos is explored in
the framework of the minimal SUSY SO(10) model. The former is related to the
Peccei-Quinn (PQ) solution to the strong CP problem and the latter is to the
light Majorana neutrinos through the see-saw mechanism. In this model, a
relative phase between and multiplets of becomes a physical degree of freedom identified with the
axion. Then, the PQ symmetry breaking scale () and the
symmetry breaking scale () coincide through the VEV of . The scalar partner of the lightest right-handed neutrino is
regarded as the inflaton, which gives a consistent density fluctuation for the
CMB.Comment: 8 pages, no figure; the version to appear in JHE
Perturbative SO(10) Grand Unification
We consider a phenomenologically viable SO(10) grand unification model of the
unification scale around GeV which reproduces the MSSM at low
energy and allows perturbative calculations up to the Planck scale or the
string scale . Both requirements strongly restrict a choice of Higgs
representations in a model. We propose a simple SO(10) model with a set of
Higgs representations and show its phenomenological viability. This model can indeed
reproduce the low-energy experimental data relating the charged fermion masses
and mixings. Neutrino oscillation data can be consistently incorporated in the
model, leading to the right-handed neutrino mass scale .
Furthermore, there exists a parameter region which results the proton life time
consistent with the experimental results.Comment: 14 pages, no figure, section5 was slightly modifie
Mis16 and Mis18 Are Required for CENP-A Loading and Histone Deacetylation at Centromeres
AbstractCentromeres contain specialized chromatin that includes the centromere-specific histone H3 variant, spCENP-A/Cnp1. Here we report identification of five fission yeast centromere proteins, Mis14–18. Mis14 is recruited to kinetochores independently of CENP-A, and, conversely, CENP-A does not require Mis14 to associate with centromeres. In contrast, Mis15, Mis16 (strong similarity with human RbAp48 and RbAp46), Mis17, and Mis18 are all part of the CENP-A recruitment pathway. Mis15 and Mis17 form an evolutionarily conserved complex that also includes Mis6. Mis16 and Mis18 form a complex and maintain the deacetylated state of histones specifically in the central core of centromeres. Mis16 and Mis18 are the most upstream factors in kinetochore assembly as they can associate with kinetochores in all kinetochore mutants except for mis18 and mis16, respectively. RNAi knockdown in human cells shows that Mis16 function is conserved as RbAp48 and RbAp46 are both required for localization of human CENP-A
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