41 research outputs found
Resonant leptogenesis in a predictive SO(10) grand unified model
An SO(10) grand unified model considered previously by the authors featuring
lopsided down quark and charged lepton mass matrices is successfully predictive
and requires that the lightest two right-handed Majorana neutrinons be nearly
degenerate in order to obtain the LMA solar neutrino solution. Here we use this
model to test its predictions for baryogenesis through resonant-enhanced
leptogenesis. With the conventional type I seesaw mechanism, the best
predictions for baryogenesis appear to fall a factor of three short of the
observed value. However, with a proposed type III seesaw mechanism leading to
three pairs of massive pseudo-Dirac neutrinos, resonant leptogenesis is
decoupled from the neutrino mass and mixing issues with successful baryogenesis
easily obtained.Comment: 22 pages including 1 figure; published version with reference adde
Neutrinos in 5D SO(10) Unification
We study neutrino physics in a 5D supersymmetric SO(10) GUT. We analyze
several different choices for realizing the See-Saw mechanism. We find that the
"natural" scale for the Majorana mass of right-handed neutrinos depends
critically on whether the right-handed neutrinos are located in the bulk or
localized on a brane. In the former case, the effective Majorana mass is
"naturally" of order the compactification scale, about 10^{14} GeV. Note, this
is the value necessary for obtaining a light tau neutrino mass approximately
10^{-2} eV which, within the context of hierarchical neutrino masses, is the
right order of magnitude to explain atmospheric neutrino oscillations. On the
other-hand when the right-handed neutrino is localized on the brane, the
effective Majorana mass is typically larger than the compactification scale.
Nevertheless with small parameters of order 1/10 - 1/30, an effective Majorana
mass of order 10^{14} GeV can be accommodated. We also discuss the constraints
on model building resulting from the different scenarios for locating the
right-handed neutrinos.Comment: 24 page
Altered mitochondrial function and overgeneration of reactive oxygen species precede the induction of apoptosis by 1-O-octadecyl-2-methyl-rac-glycero-3-phosphocholine in p53-defective hepatocytes
The mechanism of induction of apoptosis by the novel anti-cancer drug 1-O-octadecyl-2-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3) was investigated in p53-defective SV40 immortalized rat hepatocytes (CWSV1). Exposure to 12 uμM ET-18-OCH3 for 36 h induced apoptosis as determined using classical morphological features and agarose gel electrophoresis of genomic DNA. Increased levels of reactive oxygen species (ROS) were detected spectrophotometrically using a nitroblue tetrazolium (NBT) assay in cells treated with ET-18-OCH3. Both the increased generation of ROS and the induction of apoptosis were inhibited when cells were treated concurrently with ET-18-OCH3 in the presence of the antioxidant α-to-copherol. Similar results were achieved when cells were switched acutely to choline-deficient (CD) medium in the presence of the antioxidant. The possible role of mitochondria in the generation of ROS was investigated. Both ET-18-OCH3 and CD decreased the phosphatidylcholine (PC) content of mitochondrial and associated membranes, which correlated with depolarization of the mitochondrial membrane as analyzed using 5,5′,6,6′-tetramethylbenzimidazolcarbocyanine iodide (JC-1), a sensitive probe of mitochondrial membrane potential. Rotenone, an inhibitor of the mitochondrial electron transport chain, significantly reduced the intracellular level of ROS and prevented mitochondrial membrane depolarization, correlating with a reduction of apoptosis in response to either ET-18-OCH3 or CD. Taken together, these results suggest that the form of p53-independent apoptosis induced by ET-18-OCH3 is mediated by alterations in mitochondrial membrane PC, a loss of mitochondrial membrane potential, and the release of ROS, resulting in completion of apoptosis
U(2)-like Flavor Symmetries and Approximate Bimaximal Neutrino Mixing
Models involving a U(2) flavor symmetry, or any of a number of its
non-Abelian discrete subgroups, can explain the observed hierarchy of charged
fermion masses and CKM angles. It is known that a large neutrino mixing angle
connecting second and third generation fields may arise via the seesaw
mechanism in these models, without a fine tuning of parameters. Here we show
that it is possible to obtain approximate bimaximal mixing in a class of models
with U(2)-like Yukawa textures. We find a minimal form for Dirac and Majorana
neutrino mass matrices that leads to two large mixing angles, and show that our
result can quantitatively explain atmospheric neutrino oscillations while
accommodating the favored, large angle MSW solution to the solar neutrino
problem. We demonstrate that these textures can arise in models by presenting a
number of explicit examples.Comment: 20 pages RevTex4, 2 figure
Choline deficiency induces apoptosis in SV40-immortalized CWSV-1 rat hepatocytes in culture
Immortalized CWSV-1 rat hepatocytes, in which p53 protein is inactivated by SV40 large T antigen, had increased numbers of cells with strand breaks in genomic DNA (terminal dUTP end labeling) when grown in 0 μM choline (67-73% of cells) than when grown in 70 μM choline (2-3% of cells). Internucleosomal fragmentation of DNA (DNA ladders) was detected in cells grown with 5 μM and 0 μM choline for 72 h. Cells treated with 0 or 5 μM choline for 72 h detached from the substrate in high numbers (58% of choline deficient cells vs. 1.4% of choline sufficient cells detached) exhibited a high incidence of apoptosis (apoptotic bodies were seen in 55-75% of cells; 67-73% had DNA strand breaks), and an absence of mitosis and proliferating cell nuclear antigen (PCNA) expression. Cells undergoing DNA fragmentation had functioning mitochondria. At 24 h, cells grown in 0 or 5 μM choline synthesized DNA more rapidly than those grownin 70 μM choline. By 72 h, the cells grown in 0 or 5 μM choline were forming DNA much more slowly than control cells (assessed by thymidine incorporation, PCNA expression, and mitotic index). Western blot analysis showed that p53 in the nucleus of cells was detected in direct association with SV40 T-antigen, and was therefore likely to be inactive. We conclude that choline deficiency kills CWSV-1 hepatocytes in culture by inducing apoptosis via what may be a p53-independent process, and that this process begins in viable cells before they detach from the culture dish
CP Violation in a Supersymmetric SO(10) x U(2)_{F} Model
A model based on SUSY SO(10) combined with U(2) family symmetry constructed
recently by the authors is generalized to include phases in the mass matrices
leading to CP violation. In contrast with the commonly used effective operator
approach, -dimensional Higgs fields are utilized to construct the
Yukawa sector. R-parity symmetry is thus preserved at low energies. The
symmetric mass textures arising from the left-right symmetry breaking chain of
SO(10) give rise to very good predictions for quark and lepton masses and
mixings. The prediction for agrees with the average of current
bounds from BaBar and Belle. In the neutrino sector, our predictions are in
good agreement with results from atmospheric neutrino experiments. Our model
favors both the LOW and QVO solutions to the solar neutrino anomaly; the matrix
element for neutrinoless double beta decay is highly suppressed. The leptonic
analog of the Jarlskog invariant, , is predicted to be of
.Comment: RevTeX4; 7 pages; typos corrected; clarification remarks added; more
references added. To appear in Physical Review
Minimal Mixing of Quarks and Leptons in the SU(3) Theory of Flavour
We argue that flavour mixing, both in the quark and lepton sector, follows
the minimal mixing pattern, according to which the whole of this mixing is
basically determined by the physical mass generation for the first family of
fermions. So, in the chiral symmetry limit when the masses of the lightest (
and ) quarks vanish, all the quark mixing angles vanish. This minimal
pattern is shown to fit extremely well the already established CKM matrix
elements and to give fairly distinctive predictions for the as yet poorly known
ones. Remarkably, together with generically small quark mixing, it also leads
to large neutrino mixing, provided that neutrino masses appear through the
ordinary ``see-saw'' mechanism. It is natural to think that this minimal
flavour mixing pattern presupposes some underlying family symmetry, treating
families of quarks and leptons in a special way. Indeed, we have found a local
chiral family symmetry model which leads, through its dominant
symmetry breaking vacuum configuration, to a natural realization of the
proposed minimal mechanism. It can also naturally generate the quark and lepton
mass hierarchies. Furthermore spontaneous CP violation is possible, leading to
a maximal CP violating phase , in the framework of the
MSSM extended by a high-scale chiral family symmetry.Comment: 52 pages, LaTex, no figures; some typos corrected; journal versio
Quark and Lepton Mass Matrices in the SO(10) Grand Unified Theory with Generation Flipping
We investigate the SO(10) grand unified model with generation flipping. The
model contains one extra matter multiplet and it mixes with the
usual matter multiplets when the SO(10) is broken down to SU(5).
We find the parameter region of the model in which the observed quark masses
and mixings are well reproduced. The resulting parameter region is consistent
with the observation that only have a source of hierarchies and
indicates that the mixing between second and third generations tends to be
large in the lepton sector, which is consistent with the observed maximal
mixing of the atmospheric neutrino oscillation. We also show that the model can
accommodate MSW and vacuum oscillation solutions to the solar neutrino deficit
depending on the form of the Majorana mass matrix for the right-handed
neutrinos.Comment: 28 pages, Late
A texture of neutrino mass matrix in view of recent neutrino experimental results
In view of recent neutrino experimental results such as SNO, Super-Kamiokande
(SK), CHOOZ and neutrinoless double beta decay , we
consider a texture of neutrino mass matrix which contains three parameters in
order to explain those neutrino experimental results. We have first fitted
parameters in a model independent way with solar and atmospheric neutrino mass
squared differences and solar neutrino mixing angle which satisfy LMA solution.
The maximal value of atmospheric neutrino mixing angle comes out naturally in
the present texture. Most interestingly, fitted parameters of the neutrino mass
matrix considered here also marginally satisfy recent limit on effective
Majorana neutrino mass obtained from neutrinoless double beta decay experiment.
We further demonstrate an explicit model which gives rise to the texture
investigated by considering an gauge group with two
extra real scalar singlets and discrete symmetry. Majorana
neutrino masses are generated through higher dimensional operators at the scale
. We have estimated the scales at which singlets get VEV's and M by
comparing with the best fitted results obtained in the present work.Comment: Journal Ref.: Phys. Rev. D66, 053004 (2002
Four Light Neutrinos in Singular Seesaw Mechanism with Abelian Flavor Symmetry
The four light neutrino scenario, which explains the atmosphere, solar and
LSND neutrino experiments, is studied in the framework of the seesaw mechanism.
By taking both the Dirac and Majorana mass matrix of neutrinos to be singular,
the four neutrino mass spectrum consisting of two almost degenerate pairs
separated by a mass gap eV is naturally generated. Moreover the
right-handed neutrino Majorana mass can be at GeV scale unlike
in the usual singular seesaw mechanism. Abelian flavor symmetry is used to
produce the required neutrino mass pattern. A specific example of the flavor
charge assignment is provided to show that maximal mixings between the
and are respectively attributed to the
atmosphere and solar neutrino anomalies while small mixing between two pairs to
the LSND results. The implication in the other fermion masses is also
discussed.Comment: Firnal version to appear in PR