4,898 research outputs found
Constraints on Natural MNS Parameters from |U_e3|
The MNS matrix structure emerging as a result of recent neutrino measurements
strongly suggests two large mixing angles (solar and atmospheric) and one small
angle (|U_e3| << 1). Especially when combined with the neutrino mass hierarchy,
these values turn out to impose rather stringent constraints on possible flavor
models connecting the three active fermion generations. Specifically, we show
that an extremely small value of |U_e3| would require fine tuning of Majorana
mass matrix parameters, particularly in the context of seesaw models.Comment: 21 pages, ReVTeX, 2 .eps figure files, updated references and
acknowledgment
A prospective cohort study of the effects of adjuvant breast cancer chemotherapy on taste function, food liking, appetite and associated nutritional outcomes
\u27Taste\u27 changes are commonly reported during chemotherapy. It is unclear to what extent this relates to actual changes in taste function or to changes in appetite and food liking and how these changes affect dietary intake and nutritional status
Unprecedented Alexandrium blooms in a previously low biotoxin risk area of Tasmania, Australia.
During October 2012, a shipment of blue mussels (Mytilus galloprovincialis) from the poorly monitored east coast of Tasmania, Australia, was tested by Japanese import authorities and found to be contaminated with unacceptable levels of Paralytic Shellfish Toxins (PSTs; 10 mg/kg). Subsequently local oysters, scallops, clams, the viscera of abalone and rock lobsters were also found to be contaminated. This led to a global product recall and loss to the local economy of AUD 23M. Following low toxicity during 2013 and 2014 and implementation of minimal shellfish farm closures, a more severe bloom event occurred during July-November 2015 and again June-September 2016 (up to 300,000 Alexandrium cells/L; 24 mg/kg PST in mussels, 6 mg/kg in Crassostrea gigas oysters), also causing 4 human illnesses resulting in hospitalization after consumption of wild shellfish. While Alexandrium tamarense had been detected in low concentrations in southeastern Australia since 1987, all cultured strains belonged to the mostly non-toxic group 5 (now designated A. australiense; detected since 1987) and weakly toxic group 4 (A. pacificum; detected in 1997). In contrast, the 2012 to 2016 outbreaks were dominated by highly toxic group 1 (A. fundyense) never detected previously in the Australian region. Molecular analyses suggest that A. fundyense may have been a cryptic ribotype previously present in Tasmania, but newly stimulated by altered water column stratification conditions driven by changing rainfall and temperature patterns. Increased seafood and plankton monitoring of the area now include the implementation of Alexandrium qPCR, routine Neogen™ immunological and HPLC PST tests, but ultimately may also drive change in harvesting strategies and aquaculture species selection by the local seafood industry
Supersymmetric Flavor Models and the B --> phi K_S Anomaly
We consider the flavor structure of supersymmetric theories that can account
for the deviation of the observed time-dependent CP asymmetry in B --> phi K_S
from the standard model prediction. Assuming simple flavor symmetries and
effective field theory, we investigate possible correlations between sizable
supersymmetric contributions to b --> s transitions and to flavor changing
processes that are more tightly constrained. With relatively few assumptions,
we determine the properties of minimal Yukawa and soft mass textures that are
compatible with the desired supersymmetric flavor-changing effect and
constraints. We then present explicit models that are designed (at least
approximately) to realize these textures. In particular, we present an Abelian
model based on a single U(1) factor and a non-trivial extra-dimensional
topography that can explain the CP asymmetry in B --> phi K_S, while
suppressing other supersymmetric flavor changing effects through a high degree
of squark-quark alignment.Comment: 18 pages LaTeX, 3 eps figure
Weak Mixing Angle and Higgs Mass in Gauge-Higgs Unification Models with Brane Kinetic Terms
We show that the idea of Gauge-Higgs unification(GHU) can be rescued from the
constraint of weak mixing angle by introducing localized brane kinetic terms in
higher dimensional GHU models with bulk and simple gauge groups. We find that
those terms lead to a ratio between Higgs and W boson masses, which is a little
bit deviated from the one derived in the standard model. From numerical
analysis, we find that the current lower bound on the Higgs mass tends to
prefer to exceptional groups E(6), E(7), E(8) rather than other groups like
SU(3l), SO(2n+1), G(2), and F(4) in 6-dimensional(D) GHU models irrespective of
the compactification scales. For the compactification scale below 1 TeV, the
Higgs masses in 6D GHU models with SU(3l), SO(2n+1), G(2), and F(4) groups are
predicted to be less than the current lower bound unless a model parameter
responsible for re-scaling SU(2) gauge coupling is taken to be unnaturally
large enough. To see how the situation is changed in more higher dimensional
GHU model, we take 7D S^{3}/ Z_{2} and 8D T^{4}/ Z_{2} models. It turns out
from our numerical analysis that these higher dimensional GHU models with gauge
groups except for E(6) can lead to the Higgs boson whose masses are predicted
to be above the current lower bound only for the compatification scale above 1
TeV without taking unnaturally large value of the model parameter, whereas the
Higgs masses in the GHU models with E(6) are compatible with the current lower
bound even for the compatification scale below 1 TeV.Comment: 22 pages, 4 figure
Limits on excited tau leptons masses from leptonic tau decays
We study the effects induced by excited leptons on the leptonic tau decay at
one loop level. Using a general effective lagrangian approach to describe the
couplings of the excited leptons, we compute their contributions to the
leptonic decays and use the current experimental values of the branching ratios
to put limits on the mass of excited states and the substructure scale.Comment: 10 pages, 6 figures, to be published in Phys. Rev.
The coral Acropora loripes genome reveals an alternative pathway for cysteine biosynthesis in animals
The metabolic capabilities of animals have been derived from well-studied model organisms and are generally considered to be well understood. In animals, cysteine is an important amino acid thought to be exclusively synthesized through the transsulfuration pathway. Corals of the genus Acropora have lost cystathionine β-synthase, a key enzyme of the transsulfuration pathway, and it was proposed that Acropora relies on the symbiosis with dinoflagellates of the family Symbiodiniaceae for the acquisition of cysteine. Here, we identify the existence of an alternative pathway for cysteine biosynthesis in animals through the analysis of the genome of the coral Acropora loripes. We demonstrate that these coral proteins are functional and synthesize cysteine in vivo, exhibiting previously unrecognized metabolic capabilities of animals. This pathway is also present in most animals but absent in mammals, arthropods, and nematodes, precisely the groups where most of the animal model organisms belong to, highlighting the risks of generalizing findings from model organisms
The prolate-to-oblate shape transition of phospholipid vesicles in response to frequency variation of an AC electric field can be explained by the dielectric anisotropy of a phospholipid bilayer
The external electric field deforms flaccid phospholipid vesicles into
spheroidal bodies, with the rotational axis aligned with its direction.
Deformation is frequency dependent: in the low frequency range (~ 1 kHz), the
deformation is typically prolate, while increasing the frequency to the 10 kHz
range changes the deformation to oblate. We attempt to explain this behaviour
with a theoretical model, based on the minimization of the total free energy of
the vesicle. The energy terms taken into account include the membrane bending
energy and the energy of the electric field. The latter is calculated from the
electric field via the Maxwell stress tensor, where the membrane is modelled as
anisotropic lossy dielectric. Vesicle deformation in response to varying
frequency is calculated numerically. Using a series expansion, we also derive a
simplified expression for the deformation, which retains the frequency
dependence of the exact expression and may provide a better substitute for the
series expansion used by Winterhalter and Helfrich, which was found to be valid
only in the limit of low frequencies. The model with the anisotropic membrane
permittivity imposes two constraints on the values of material constants:
tangential component of dielectric permittivity tensor of the phospholipid
membrane must exceed its radial component by approximately a factor of 3; and
the membrane conductivity has to be relatively high, approximately one tenth of
the conductivity of the external aqueous medium.Comment: 17 pages, 6 figures; accepted for publication in J. Phys.: Condens.
Matte
An A4 flavor model for quarks and leptons in warped geometry
We propose a spontaneous A4 flavor symmetry breaking scheme implemented in a
warped extra dimensional setup to explain the observed pattern of quark and
lepton masses and mixings. The main advantages of this choice are the
explanation of fermion mass hierarchies by wave function overlaps, the
emergence of tribimaximal neutrino mixing and zero quark mixing at the leading
order and the absence of tree-level gauge mediated flavor violations. Quark
mixing is induced by the presence of bulk flavons, which allow for cross-brane
interactions and a cross-talk between the quark and neutrino sectors, realizing
the spontaneous symmetry breaking pattern A4 --> nothing first proposed in
[X.G.\,He, Y.Y.\,Keum, R.R.\,Volkas, JHEP{0604}, 039 (2006)]. We show that the
observed quark mixing pattern can be explained in a rather economical way,
including the CP violating phase, with leading order cross-interactions, while
the observed difference between the smallest CKM entries V_{ub} and V_{td} must
arise from higher order corrections. We briefly discuss bounds on the
Kaluza-Klein scale implied by flavor changing neutral current processes in our
model and show that the residual little CP problem is milder than in flavor
anarchic models.Comment: 34 pages, 2 figures; version published in JHE
A Phenomenological Study on Lepton Mass Matrix Textures
The three active light neutrinos are used to explain the neutrino
oscillations. The inherently bi-large mixing neutrino mass matrix and the
Fritzsch type, bi-small mixing charged lepton mass matrix are assumed. By
requiring the maximal \nu_\mu-\nu_\tau mixing for the atmospheric neutrino
problem and the mass-squared difference approperiate for the almost maximal
mixing solution to the solar neutrino problem, the following quantities are
predicted: the \nu_e-\nu_\mu mixing, V_{e3}, CP violation in neutrino
oscillations, and the effective electron-neutrino mass relevant to neutrinoless
double beta decays.Comment: 6 pages, revtex, no figures, confusing points corrected,
clarification and refernces adde
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