83 research outputs found
Seasonal Variations of the 7Be Solar Neutrino Flux
Measuring the 7Be solar neutrino flux is crucial towards solving the solar
neutrino puzzle. The Borexino experiment, and possibly the KamLAND experiment,
will be capable of studying the 7Be neutrinos in the near future. We discuss
(1) how the seasonal variation of the Borexino and KamLAND data can be used to
measure the 7Be solar neutrino flux in a background independent way and (2) how
anomalous seasonal variations might be used to discover vacuum neutrino
oscillations, independent of the solar model and the measurement of the
background. In particular, we find that, after three years of Borexino or
KamLAND running, vacuum neutrino oscillations can be either established or
excluded for almost all values of (sin^2 2 theta, Delta m^2) preferred by the
Homestake, GALLEX, SAGE, and Super-Kamiokande data. We also discuss how well
seasonal variations of the data can be used to measure (sin^2 2 theta, Delta
m^2) in the case of vacuum oscillations.Comment: 39 pages, 13 figures, uses psfig. Now the impact of the MSW effect on
vacuum oscillations taken into account. Conclusions unchanged. References
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Characterization of the flavonoids of the Argan tree leaves (Argania spinosa (L.) Skeels, Sapotaceae) and study of their antimicrobial activity
Quatre flavonoïdes, la quercétine, la myricétine, la quercétrine et la myricétrine ont été isolés à partir des feuilles d’Argania spinosa (L.) Skeels, Sapotaceae. Ces composés ont été séparés à l’aide de méthodes chromatogaphiques usuelles et identifiés sur la base de leurs caractéristiques spectroscopiques (UV, SM, RMN 1H et13C). La myricétine et la myricétrine ont montré une activité anti-microbienne plus importante contre les bactéries que contre les levures
Solar neutrinos and grand unification
We consider the Grand Unification (GU) scenario for neutrino masses which is
based on the see-saw mechanism with the mass of the heaviest right handed (RH)
neutrino at the GU-scale: , and on the quark-lepton
symmetry for fermions from the third generation. The scenario predicts for the
light neutrinos: eV and eV (in the case of a linear mass hierarchy of the RH neutrinos
or/and in presence of the Planck scale suppressed non-renormalizable
operators). It also predicts large mixing: . In this scenario the solar neutrinos
() undergo both the \nue \nutau resonance conversion in the
Sun and substantial \nue \numu vacuum oscillations on the way from the
Sun to the Earth. The interplay of both effects enlarges the range of neutrino
parameters which solve the -problem. In particular, mixing angle can be as small as the corresponding quark mixing:
. The scenario predicts
peculiar (oscillatory) distortion of the boron neutrino energy spectrum and
seasonal variations of signals. Manifestations of these effects in the
Super-Kamiokande and SNO experiments are studied.Comment: 36 pages, LaTeX, includes 14 figures, revised and expande
Constraints on mixing angles of Majorana neutrinos
By combining the inputs from the neutrinoless double beta decay and the fits
of cosmological models of dark matter with solar and atmospheric neutrino data,
we obtain constraints on two of the mixing angles of Majorana neutrinos, which
become stronger when coupled with the reactor neutrino data. These constraints
are strong enough to rule out Majorana neutrinos if the small angle solution of
solar neutrino puzzle is borne out.Comment: Some corrections and clarifications adde
Status of a Supersymmetric Flavour Violating Solution to the Solar Neutrino Puzzle with Three Generations
We present a general study of a three neutrino flavour transition model based
on the supersymmetric interactions which violate R-parity. These interactions
induce flavour violating scattering reactions between solar matter and
neutrinos. The model does not contain any vacuum mass or mixing angle for the
first generation neutrino. Instead, the effective mixing in the first
generation is induced via the new interactions. The model provides a natural
interpretation of the atmospheric neutrino anomaly, and is consistent with
reactor experiments. We determine all R-parity violating couplings which can
contribute to the effective neutrino oscillations, and summarize the present
laboratory bounds. Independent of the specific nature of the (supersymmetric)
flavour violating model, the experimental data on the solar neutrino rates and
the recoil electron energy spectrum are inconsistent with the theoretical
predictions. The confidence level of the -analysis ranges between and . The incompatibility, is due to the new SNO
results, and excludes the present model. We conclude that a non-vanishing
vacuum mixing angle for the first generation neutrino is necessary in our
model. We expect this also to apply to the solutions based on other flavour
violating interactions having constraints of the same order of magnitude.Comment: 17 pages, Latex fil
Quantum dynamics in strong fluctuating fields
A large number of multifaceted quantum transport processes in molecular
systems and physical nanosystems can be treated in terms of quantum relaxation
processes which couple to one or several fluctuating environments. A thermal
equilibrium environment can conveniently be modelled by a thermal bath of
harmonic oscillators. An archetype situation provides a two-state dissipative
quantum dynamics, commonly known under the label of a spin-boson dynamics. An
interesting and nontrivial physical situation emerges, however, when the
quantum dynamics evolves far away from thermal equilibrium. This occurs, for
example, when a charge transferring medium possesses nonequilibrium degrees of
freedom, or when a strong time-dependent control field is applied externally.
Accordingly, certain parameters of underlying quantum subsystem acquire
stochastic character. Herein, we review the general theoretical framework which
is based on the method of projector operators, yielding the quantum master
equations for systems that are exposed to strong external fields. This allows
one to investigate on a common basis the influence of nonequilibrium
fluctuations and periodic electrical fields on quantum transport processes.
Most importantly, such strong fluctuating fields induce a whole variety of
nonlinear and nonequilibrium phenomena. A characteristic feature of such
dynamics is the absence of thermal (quantum) detailed balance.Comment: review article, Advances in Physics (2005), in pres
In vitro antibacterial activity of some plant essential oils
BACKGROUND: To evaluate the antibacterial activity of 21 plant essential oils against six bacterial species. METHODS: The selected essential oils were screened against four gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris) and two gram-positive bacteria Bacillus subtilis and Staphylococcus aureus at four different concentrations (1:1, 1:5, 1:10 and 1:20) using disc diffusion method. The MIC of the active essential oils were tested using two fold agar dilution method at concentrations ranging from 0.2 to 25.6 mg/ml. RESULTS: Out of 21 essential oils tested, 19 oils showed antibacterial activity against one or more strains. Cinnamon, clove, geranium, lemon, lime, orange and rosemary oils exhibited significant inhibitory effect. Cinnamon oil showed promising inhibitory activity even at low concentration, whereas aniseed, eucalyptus and camphor oils were least active against the tested bacteria. In general, B. subtilis was the most susceptible. On the other hand, K. pneumoniae exhibited low degree of sensitivity. CONCLUSION: Majority of the oils showed antibacterial activity against the tested strains. However Cinnamon, clove and lime oils were found to be inhibiting both gram-positive and gram-negative bacteria. Cinnamon oil can be a good source of antibacterial agents
Common Hierarchical Lepton Mass Textures for Atmospheric and Solar Neutrino Oscillations
We propose and study a common hierarchical mass texture for both charged
lepton and neutrino sectors. The texture gives rise to a large
mixing. Also it leads to the small angle MSW
effect solution for solar neutrino data. It naturally gives a small
oscillation relevant to the CHOOZ result in
certain mass limits.Comment: 11 pages, no figures, late
Global Three-Neutrino Vacuum Oscillation fits to the Solar and Atmospheric Anomalies
We determine the three-neutrino mixing and mass parameters that are allowed
by the solar and atmospheric neutrino data when vacuum oscillations are
responsible for both phenomena. The global fit does not appreciably change the
allowed regions for the parameters obtained from effective two-neutrino fits.
We discuss how measurements of the solar electron energy spectrum below 6.5 GeV
in Super-Kamiokande and seasonal variations in the Super-Kamiokande, Ga,
and BOREXINO experiments can distinguish the different solar vacuum solutions.Comment: Revtex, 31 pages, uses epsf.sty, 14 postscript figures. Version to be
published in Phys. Rev.
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