42 research outputs found
Neutron - Mirror Neutron Oscillations: How Fast Might They Be?
We discuss the phenomenological implications of the neutron (n) oscillation
into the mirror neutron (n'), a hypothetical particle exactly degenerate in
mass with the neutron but sterile to normal matter. We show that the present
experimental data allow a maximal n-n' oscillation in vacuum with a
characteristic time much shorter than the neutron lifetime, in fact as
small as 1 sec. This phenomenon may manifest in neutron disappearance and
regeneration experiments perfectly accessible to present experimental
capabilities and may also have interesting astrophysical consequences, in
particular for the propagation of ultra high energy cosmic rays.Comment: 4 pages, 1 figure; revtex; matches paper published by P.R.
Instabilities in neutrino-plasma density waves
One examines the interaction and possible resonances between supernova
neutrinos and electron plasma waves. The neutrino phase space distribution and
its boundary regions are analyzed in detail. It is shown that the boundary
regions are too wide to produce non-linear resonant effects. The growth or
damping rates induced by neutrinos are always proportional to the neutrino flux
and .Comment: 9 pages, a few words modified to match PRD publicatio
Classical Nambu-Goldstone fields
It is shown that a Nambu-Goldstone (NG) field may be coherently produced by a
large number of particles in spite of the fact that the NG bosons do not couple
to flavor conserving scalar densities like . If a flavor
oscillation process takes place the phases of the pseudo-scalar or flavor
violating densities of different particles do not necessarily cancel each
other. The NG boson gets a macroscopic source whenever the total (spontaneously
broken) quantum number carried by the source particles suffers a net increase
or decrease in time. If the lepton numbers are spontaneously broken such
classical NG (majoron) fields may significantly change the neutrino oscillation
processes in stars pushing the observational capabilities of neutrino-majoron
couplings down to GeV.Comment: 11 pages, updated, to appear in PR
Neutrino helicity asymmetries in leptogenesis
It is pointed out that the heavy singlet neutrinos characteristic of
leptogenesis develop asymmetries in the abundances of the two helicity states
as a result of the same mechanism that generates asymmetries in the standard
lepton sector. Neutrinos and standard leptons interchange asymmetries in
collisions with each other. It is shown that an appropriate quantum number,
B-L', combining baryon, lepton and neutrino asymmetries, is not violated as
fast as the standard B-L. This suppresses the washout effects relevant for the
derivation of the final baryon asymmetry. One presents detailed calculations
for the period of neutrino thermal production in the framework of the singlet
seesaw mechanism.Comment: 11 pages, 1 figure, revtex, matches PRD versio
Antioxidant activity of sugar molasses, including protective effect against DNA oxidative damage
Extracts were obtained from molasses, a byproduct of the sugar industry, via a number of chromatographic steps. Their antioxidant capacity was studied, including the inhibitory effect upon DNA oxidative damage;the phenolic compound profile there of was ascertained as well. Two extracts exhibited significant antioxidant features,
expressed by their capacity to decolorize ABTS radical cation and to scavenge hydroxyl free radicals (via deoxyribose
assay). Those 2 extracts also brought about protection against induced DNA oxidative damage (via decreasing DNA scission, as assessed by electrophoresis).The phenolic compounds syringic acid,p-hydroxybenzoic acid, vanillic acid, p-hydroxybenzaldehyde, and ferulic acid were positively identified and quantified
RAB3A Regulates Melanin Exocytosis and Transfer Induced by Keratinocyte-Conditioned Medium
Funding: We would like to thank our group for the critical reading of the manuscript and the NMS microscopy and cell culture facilities, as well as José Belo’s group, for the kind gift of mouse embryonic fibroblasts. This study was supported by Fundação para a Ciência e a Tecnologia (Portugal) through grant PTDC/BIA-CEL/29765/2017 and PhD fellowships to LCC, MVN, LBL and AF (2020.08812.BD, PD/BD/137442/2018, SFRH/BD/131938/2017 and PD/BD/ 135506/2018, respectively). This work was developed with the support from the research infrastructure PPBI-POCI-01-0145-FEDER-022122, cofinanced by Fundação para a Cieˆncia e a Tecnologia (Portugal) and Lisboa2020, under the PORTUGAL2020 agreement (European Regional Development Fund). This article was supported by the LYSOCIL project, which has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement number 811087. This work was also supported by iNOVA4Health e UIDB/04462/2020 and UIDP/04462/2020 and by the Associated Laboratory LS4FUTURE (LA/P/0087/2020), two programs financially supported by Fundação para a Ciência e a Tecnologia/Ministério da Ciência, Tecnologia e Ensino Superior (Portugal).Skin pigmentation is imparted by melanin and is crucial for photoprotection against UVR. Melanin is synthesized and packaged into melanosomes within melanocytes and is then transferred to keratinocytes (KCs). Although the molecular players involved in melanogenesis have been extensively studied, those underlying melanin transfer remain unclear. Previously, our group proposed that coupled exocytosis/phagocytosis is the predominant mechanism of melanin transfer in human skin and showed an essential role for RAB11B and the exocyst tethering complex in this process. In this study, we show that soluble factors present in KC-conditioned medium stimulate melanin exocytosis from melanocytes and transfer to KCs. Moreover, we found that these factors are released by differentiated KCs but not by basal layer KCs. Furthermore, we found that RAB3A regulates melanin exocytosis and transfer stimulated by KC-conditioned medium. Indeed, KC-conditioned medium enhances the recruitment of RAB3A to melanosomes in melanocyte dendrites. Therefore, our results suggest the existence of two distinct routes of melanin exocytosis: a basal route controlled by RAB11B and a RAB3A-dependent route, stimulated by KC-conditioned medium. Thus, this study provides evidence that soluble factors released by differentiated KCs control skin pigmentation by promoting the accumulation of RAB3A-positive melanosomes in melanocyte dendrites and their release and subsequent transfer to KCs.publishersversionpublishe
Hereditary breast cancer and ancestry in the Madeira archipelago: An exploratory study
Access to genetic testing and counselling in remote areas such as the Madeira archipelago, in the Northern Atlantic Ocean, may be complex. Different counselling methods, including telegenetics, should be explored. In this study, we characterise the Hereditary Breast/Ovarian Cancer (HBOC) families with Madeira ancestry enrolled in our programme. Of a total of 3, 566 index patients tested between January 2000 and June 2018, 68 had Madeira ancestry and 22 were diagnosed with a pathogenic germline variant (PV). As in the whole group, BRCA2 PV were more frequent in Madeira patients (68.4%: c.9382C>T (26.3%), c.658_659del (21%), c.156_157insAlu (10.5%), c.793+1G>A (5.3%) and c.298A>T (5.3%). However, the most frequently diagnosed PV in Madeira patients was the BRCA1 c.3331_3334del (31.6%). BRCA1/2 detection rates were 27.9% and 10.5% for Madeira and the whole group, respectively. This study is the first characterisation of HBOC patients with Madeira ancestry. A distinct pattern of BRCA1/2 variants was observed, and the geographic clustering of BRCA1 c.3331_3334del variant may support the possibility of a founder mutation previously described in Northern Portugal. The high detection rate observed reinforces the need to reduce gaps in access to genetic testing in Madeira and other remote areas. According to current guidelines, timely identification of HBOC patients can contribute to their ongoing care and treatment
Plasma wave instabilities induced by neutrinos
Quantum field theory is applied to study the interaction of an electron
plasma with an intense neutrino flux. A connection is established between the
field theory results and classical kinetic theory. The dispersion relation and
damping rate of the plasma longitudinal waves are derived in the presence of
neutrinos. It is shown that Supernova neutrinos are never collimated enough to
cause non-linear effects associated with a neutrino resonance. They only induce
neutrino Landau damping, linearly proportional to the neutrino flux and
.Comment: 18 pages, 3 figures, title and references correcte
Neutrino Oscillations: a source of Goldstone fields
It is proved that true Goldstone bosons develop coherent fields whenever the
associated charges of the matter particles are not conserved in a macroscopic
scale. The sources of the Goldstone fields are the time rates of quantum number
violation. The case of neutrino flavour oscillations is studied with
application to Supernovae. It is shown that if the Lepton numbers break at the
Fermi scale, the neutrino potentials and oscillation patterns change in the
periods of largest neutrino fluxes. In this way, electron anti-neutrino to muon
anti-neutrino oscillations may occur in the first instants of neutrino
emission.Comment: 12 pages, LATeX with RevTex, 1 figure, reference [4] corrected, to
appear in Phys. Rev. D 1 (1998
Leptogenesis via Collisions: Leaking Lepton Number to the Hidden Sector
We propose a lepto-baryogenesis mechanism in which the non-zero B-L of the
universe is produced in out-of-equilibrium, lepton number and CP violating
scattering processes that convert ordinary particles into particles of some
hidden sector. In particular, we consider the processes mediated by the heavy Majorana neutrinos of the seesaw
mechanism, where and are ordinary lepton and Higgs doublets and
, their hidden counterparts. Such a leptogenesis mechanism is
effective even if the reheating temperature is much smaller than the heavy
neutrino masses. In particular, it can be as low as GeV.Comment: 4 pages, revtex, 2 figures; as to appear in PRL, supplemented with an
additional remar