59 research outputs found
Effect of latent and symptomatic infections by Colletotrichum godetiae on oil quality
Anthracnose, caused by Colletotrichum spp., is the main olive fruit disease. Colletotrichum can severely infect olive fruit with a negative impact on the oil quality. However, the relationship between visible infections of Colletotrichum spp. and olive oil quality is unclear and the influence of latent infections is unknown. This study considers Colletotrichum spp. latent infections and visible infections as factors affecting the quality of olive oil. IAbsorbance in UV (K232 and K270), free acidity, and peroxide index were evaluated in oils from fruit with latent and symptomatic infections by Colletotrichum godetiae of the cvs. Arbequina, Hojiblanca, and Picual. Olive oil samples from i) latent infected fruit at three maturity stages and after two incubation periods and from ii) sets of oils from mixtures of healthy and infected symptomatic fruit were used to determine the impact of the disease on oil quality. Oils from latent infected fruit of cv. Arbequina showed higher acidity than control oils (Pâ=â0.012). Linear and exponential models were fitted to relate the oil quality parameters to the proportion of symptomatic fruit. Acidity was the most affected parameter, mainly in oils from cv. Arbequina. The thresholds of the percentage of affected fruits causing the loss of category in the quality of the oil varied greatly according to cultivar, with âArbequinaâ being the most sensitive
Fermion Masses and Mixing in Intersecting Branes Scenarios
We study the structure of Yukawa couplings in intersecting D6-branes wrapping
a factorizable 6-torus compact space T^6. Models with MSSM-like spectrum are
analyzed and found to fail in predicting the quark mass spectrum because of the
way in which the family structure for the left-handed, right-handed quarks and,
eventually, the Higgses is `factorized' among the different tori. In order to
circumvent this, we present a model with three supersymmetric Higgs doublets
which satisfies the anomaly cancellation condition in a more natural way than
the previous models, where quarks were not treated universally regarding their
branes assignments, or some particular branes were singled out being invariant
under orientifold projection. In our model, the family structures for the left,
right quarks, left leptons and the Higgses arise from one of the tori and can
naturally lead to universal strength Yukawa couplings which accommodate the
quark mass hierarchy and the mixing angles.Comment: 21 pages, latex, matches the Phys. Rev. D versio
Diversity of Colletotrichum Species Associated with Olive Anthracnose Worldwide
Olive anthracnose caused by Colletotrichum species causes dramatic losses of fruit yield and oil quality worldwide. A total of 185 Colletotrichum isolates obtained from olives and other hosts showing anthracnose symptoms in Spain and other olive-growing countries over the world were characterized. Colony and conidial morphology, benomyl-sensitive, and casein-hydrolysis activity were recorded. Multilocus alignments of ITS, TUB2, ACT, CHS-1, HIS3, and/or GAPDH were conducted for their molecular identification. The pathogenicity of the most representative Colletotrichum species was tested to olive fruits and to other hosts, such as almonds, apples, oleander, sweet oranges, and strawberries. In general, the phenotypic characters recorded were not useful to identify all species, although they allowed the separation of some species or species complexes. ITS and TUB2 were enough to infer Colletotrichum species within C. acutatum and C. boninense complexes, whereas ITS, TUB2, ACT, CHS-1, HIS-3, and GADPH regions were necessary to discriminate within the C. gloesporioides complex. Twelve Colletotrichum species belonging to C. acutatum, C. boninense, and C. gloeosporioides complexes were identified, with C. godetiae being dominant in Spain, Italy, Greece, and Tunisia, C. nymphaeae in Portugal, and C. fioriniae in California. The highest diversity with eight Colletotrichum spp. was found in Australia. Significant differences in virulence to olives were observed between isolates depending on the Colletotrichum species and host origin. When other hosts were inoculated, most of the Colletotrichum isolates tested were pathogenic in all the hosts evaluated, except for C. siamense to apple and sweet orange fruits, and C. godetiae to oleander leaves
Dynamics of coupled bosonic systems with applications to preheating
Coupled, multi-field models of inflation can provide several attractive
features unavailable in the case of a single inflaton field. These models have
a rich dynamical structure resulting from the interaction of the fields and
their associated fluctuations. We present a formalism to study the
nonequilibrium dynamics of coupled scalar fields. This formalism solves the
problem of renormalizing interacting models in a transparent way using
dimensional regularization. The evolution is generated by a renormalized
effective Lagrangian which incorporates the dynamics of the mean fields and
their associated fluctuations at one-loop order. We apply our method to two
problems of physical interest: (i) a simple two-field model which exemplifies
applications to reheating in inflation, and (ii) a supersymmetric hybrid
inflation model. This second case is interesting because inflation terminates
via a smooth phase transition which gives rise to a spinodal instability in one
of the fields. We study the evolution of the zero mode of the fields and the
energy density transfer to the fluctuations from the mean fields. We conclude
that back reaction effects can be significant over a wide parameter range. In
particular for the supersymmetric hybrid model we find that particle production
can be suppressed due to these effects.Comment: 23 pages, 16 eps-figures, minor changes in the text, references
added, accepted for publication in PR
Gauging Away the Strong CP Problem
We propose a new solution to the strong-CP problem. It involves the existence
of an unbroken gauged symmetry whose gauge boson gets a Stuckelberg
mass term by combining with a pseudoscalar field . The latter has
axion-like couplings to so that the theta parameter may
be gauged away by a gauge transformation. This system leads to mixed
gauge anomalies and we argue that they are cancelled by the addition of an
appropriate Wess-Zumino term, so that no SM fermions need to be charged under
. We discuss scenarios in which the above set of fields and couplings
appear. The mechanism is quite generic, but a natural possibility is that the
the symmetry arises from bulk gauge bosons in theories with extra
dimensions or string models. We show that in certain D-brane Type-II string
models (with antisymmetric tensor field strength fluxes) higher dimensional
Chern-Simons couplings give rise to the required D=4 Wess-Zumino terms upon
compactification. In one of the possible string realizations of the mechanism
the gauge boson comes from the Kaluza-Klein reduction of the
eleven-dimensional metric in M-theory.Comment: 21 pages, latex, one eps figure; v2 improved discussio
Constraints from Inflation on Scalar-Tensor Gravity Theories
We show how observations of the perturbation spectra produced during
inflation may be used to constrain the parameters of general scalar-tensor
theories of gravity, which include both an inflaton and dilaton field. An
interesting feature of these models is the possibility that the curvature
perturbations on super-horizon scales may not be constant due to non-adiabatic
perturbations of the two fields. Within a given model, the tilt and relative
amplitude of the scalar and tensor perturbation spectra gives constraints on
the parameters of the gravity theory, which may be comparable with those from
primordial nucleosynthesis and post-Newtonian experiments.Comment: LaTeX (with RevTex) 19 pages, 8 uuencoded figures appended, also
available on WWW via http://star.maps.susx.ac.uk/index.htm
On Physical Equivalence between Nonlinear Gravity Theories
We argue that in a nonlinear gravity theory, which according to well-known
results is dynamically equivalent to a self-gravitating scalar field in General
Relativity, the true physical variables are exactly those which describe the
equivalent general-relativistic model (these variables are known as Einstein
frame). Whenever such variables cannot be defined, there are strong indications
that the original theory is unphysical. We explicitly show how to map, in the
presence of matter, the Jordan frame to the Einstein one and backwards. We
study energetics for asymptotically flat solutions. This is based on the
second-order dynamics obtained, without changing the metric, by the use of a
Helmholtz Lagrangian. We prove for a large class of these Lagrangians that the
ADM energy is positive for solutions close to flat space. The proof of this
Positive Energy Theorem relies on the existence of the Einstein frame, since in
the (Helmholtz--)Jordan frame the Dominant Energy Condition does not hold and
the field variables are unrelated to the total energy of the system.Comment: 37 pp., TO-JLL-P 3/93 Dec 199
Leptogenesis from a sneutrino condensate revisited
We re--examine leptogenesis from a right--handed sneutrino condensate, paying
special attention to the term associated with the see--saw Majorana mass.
This term generates a lepton asymmetry in the condensate whose time average
vanishes. However, a net asymmetry will result if the sneutrino lifetime is not
much longer than the period of oscillations. Supersymmetry breaking by thermal
effects then yields a lepton asymmetry in the standard model sector after the
condensate decays. We explore different possibilities by taking account of both
the low--energy and Hubble terms. It will be shown that the desired baryon
asymmetry of the Universe can be obtained for a wide range of Majorana mass.Comment: 17 revtex pages, 3 figures, 1 table. Slightly modified and references
added. Final version accepted for publication in Phys. Rev.
Gauge and Scheme Dependence of Mixing Matrix Renormalization
We revisit the issue of mixing matrix renormalization in theories that
include Dirac or Majorana fermions. We show how a gauge-variant on-shell
renormalized mixing matrix can be related to a manifestly gauge-independent one
within a generalized scheme of renormalization. This
scheme-dependent relation is a consequence of the fact that in any scheme of
renormalization, the gauge-dependent part of the mixing-matrix counterterm is
ultra-violet safe and has a pure dispersive form. Employing the unitarity
properties of the theory, we can successfully utilize the afore-mentioned
scheme-dependent relation to preserve basic global or local symmetries of the
bare Lagrangian through the entire process of renormalization. As an immediate
application of our study, we derive the gauge-independent renormalization-group
equations of mixing matrices in a minimal extension of the Standard Model with
isosinglet neutrinos.Comment: 31 pages, LaTeX, uses axodraw.st
Challenges for Sustained Observing and Forecasting Systems in the Mediterranean Sea
The Mediterranean community represented in this paper is the result of more than 30 years of EU and nationally funded coordination, which has led to key contributions in science concepts and operational initiatives. Together with the establishment of operational services, the community has coordinated with universities, research centers, research infrastructures and private companies to implement advanced multi-platform and integrated observing and forecasting systems that facilitate the advancement of operational services, scientific achievements and mission-oriented innovation. Thus, the community can respond to societal challenges and stakeholders needs, developing a variety of fit-for-purpose services such as the Copernicus Marine Service. The combination of state-of-the-art observations and forecasting provides new opportunities for downstream services in response to the needs of the heavily populated Mediterranean coastal areas and to climate change. The challenge over the next decade is to sustain ocean observations within the research community, to monitor the variability at small scales, e.g., the mesoscale/submesoscale, to resolve the sub-basin/seasonal and inter-annual variability in the circulation, and thus establish the decadal variability, understand and correct the model-associated biases and to enhance model-data integration and ensemble forecasting for uncertainty estimation. Better knowledge and understanding of the level of Mediterranean variability will enable a subsequent evaluation of the impacts and mitigation of the effect of human activities and climate change on the biodiversity and the ecosystem, which will support environmental assessments and decisions. Further challenges include extending the science-based added-value products into societal relevant downstream services and engaging with communities to build initiatives that will contribute to the 2030 Agenda and more specifically to SDG14 and the UN's Decade of Ocean Science for sustainable development, by this contributing to bridge the science-policy gap. The Mediterranean observing and forecasting capacity was built on the basis of community best practices in monitoring and modeling, and can serve as a basis for the development of an integrated global ocean observing system
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