954 research outputs found
Neutrino charge radius and electromagnetic dipole moments via scalar and vector leptoquarks
The one-loop contribution of scalar and vector leptoquarks (LQs) to the
electromagnetic properties (NEPs) of massive Dirac neutrinos is presented via
an effective Lagrangian approach, with emphasis on the effective neutrino
charge radius (NCR), which has never been calculated and is obtained by the
background field formalism in a Yang-Mills-like scenario for gauge LQs.
Analytical results for nonzero neutrino mass are presented in terms of both
Feynman-parameter integrals and Passarino-Veltman scalar functions, which can
be useful to obtain the NEPs of heavy neutrinos, out of which approximate
expressions are obtained for light neutrinos. For the numerical analysis we
concentrate on the only renormalizable scalar and vector LQ representations
that do not need extra symmetries to forbid tree-level proton decay.
Constraints on the parameter space consistent with current experimental data
are then discussed and it is found that the LQ representations
and could yield the largest contributions to the NEPs
provided that they have couplings to both left- and right-handed neutrinos of
the order of . For a LQ mass of TeV, the magnetic dipole moment
(MDM) of the tau neutrino can be of the order of , whereas its
neutrino electric dipole moment (EDM) can reach values as high as
- ecm. On the other hand, the NCR can reach values up to
cm regardless of the neutrino flavor and even in the absence of
right-handed neutrinos. In the latter scenario, the EDM vanishes and the
contribution to neutrino MDM would be negligible, of the order of
for the tau neutrino, whereas those for the muon and electron neutrinos
would be about two and seven orders of magnitude smaller, respectively. Our
estimates could be severely suppressed due to a possible suppression of the LQ
coupling constants.Comment: 31 pages, 11 figure
The Diameter Distribution of the Stem Villi Arteries Does Not Discriminate between Normal and Intra Uterine Growth Restricted Placentas
The distribution of the stem villi arteries and arterioles diameter was evaluated on histological sections from 6 normal (control) and 8 Intrauterine Growth Restricted (IUGR) placentas. No significant difference between the diameter distributions was found. This result can be due either to a similar pattern in vascularization or to the inadequacy of the diameter distribution in showing existing differences. Further investigation is needed to make a distinction between these two hypotheses. A multiparametric model is proposed, which predicts the diameter distribution that is expected when a few parameters (describing the vessel geometry and the tree branching structure) are varied in their normal range. The diameter distribution is shown to slightly change or not to change at all when important parameters, such as the vessel asymmetry, are changed. We conclude thatthe diameter distribution is insensitive to variation in certain placental structural parameters. A reliable analysis of the stem villi vasculature in normal and TUGR placentas cannot be based on the comparison of the respective diameter distributions alone
The Effect of Simple Melodic Lines on Aesthetic Experience: Brain Response to Structural Manipulations
This fMRI study investigates the effect of melody on aesthetic experience in listeners na\uefve to formal musical knowledge. Using simple melodic lines, whose syntactic structure was manipulated, we created systematic acoustic dissonance. Two stimulus categories were created: canonical (syntactically \u201ccorrect,\u201d in the Western culture) and modified (made of an altered version of the canonical melodies). The stimuli were presented under two tasks: listening and aesthetic judgment. Data were analyzed as a function of stimulus structure (canonical and modified) and stimulus aesthetics, as appraised by each participant during scanning. The critical contrast modified versus canonical stimuli produced enhanced activation of deep temporal regions, including the parahippocampus, suggesting that melody manipulation induced feelings of unpleasantness in the listeners. This was supported by our behavioral data indicating decreased aesthetic preference for the modified melodies. Medial temporal activation could also have been evoked by stimulus structural novelty determining increased memory load for the modified stimuli. The analysis of melodies judged as beautiful revealed that aesthetic judgment of simple melodies relied on a fine-structural analysis of the stimuli subserved by a left frontal activation and, possibly, on meaning attribution at the charge of right superior temporal sulcus for increasingly pleasurable stimuli
Vegetation reconstruction to the mid-Holocene transition in Sahel and Sahara : first palynological results of a lacustrine record from the Mega-Lake Chad
Ecophysiological modeling of photosynthesis and carbon allocation to the tree stem in the boreal forest
A better understanding of the coupling between photosynthesis and carbon allocation in the boreal forest, together with its associated environmental factors and mechanistic rules, is crucial to accurately predict boreal forest carbon stocks and fluxes, which are significant components of the global carbon budget. Here, we adapted the MAIDEN ecophysiological forest model to consider important processes for boreal tree species, such as nonlinear acclimation of photosynthesis to temperature changes, canopy development as a function of previous-year climate variables influencing bud formation and the temperature dependence of carbon partition in summer. We tested these modifications in the eastern Canadian taiga using black spruce (Picea mariana (Mill.) B.S.P.) gross primary production and ring width data. MAIDEN explains 90% of the observed daily gross primary production variability, 73% of the annual ring width variability and 20-30% of its high-frequency component (i.e., when decadal trends are removed). The positive effect on stem growth due to climate warming over the last several decades is well captured by the model. In addition, we illustrate how we improve the model with each introduced model adaptation and compare the model results with those of linear response functions. Our results demonstrate that MAIDEN simulates robust relationships with the most important climate variables (those detected by classical response-function analysis) and is a powerful tool for understanding how environmental factors interact with black spruce ecophysiol-ogy to influence present-day and future boreal forest carbon fluxes.Peer reviewe
Low-dose curcuminoid-loaded in dextran nanobubbles can prevent metastatic spreading in prostate cancer cells
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