4,943 research outputs found
Scattering processes could distinguish Majorana from Dirac neutrinos
It is well known that Majorana neutrinos have a pure axial neutral current
interaction while Dirac neutrinos have the standard vector-axial interaction.
In spite of this crucial difference, usually Dirac neutrino processes differ
from Majorana processes by a term proportional to the neutrino mass, resulting
in almost unmeasurable observations of this difference. In the present work we
show that once the neutrino polarization evolution is considered, there are
clear differences between Dirac and Majorana scattering on electrons. The
change of polarization can be achieved in astrophysical environments with
strong magnetic fields. Furthermore, we show that in the case of unpolarized
neutrino scattering onto polarized electrons, this difference can be relevant
even for large values of the neutrino energy.Comment: 12 pages, 5 figure
Muon anomalous magnetic moment in supersymmetric scenarios with an intermediate scale and nonuniversality
We analyze the anomalous magnetic moment of the muon (a_{\mu}) in
supersymmetric scenarios. First we concentrate on scenarios with universal soft
terms. We find that a moderate increase of a_{\mu} can be obtained by lowering
the unification scale M_{GUT} to intermediate values 10^{10-12} GeV. However,
large values of \tan \beta are still favored. Then we study the case of
non-universal soft terms. For the usual value M_{GUT}~10^{16} GeV, we obtain
a_{\mu} in the favored experimental range even for moderate \tan \beta regions
\tan\beta ~ 5$. Finally, we give an explicit example of these scenarios. In
particular, we show that in a D-brane model, where the string scale is
naturally of order 10^{10-12} GeV and the soft terms are non universal, a_{\mu}
is enhanced with low \tan\beta.Comment: Final version to appear in Phys. Rev. D. Conventions clarified,
results in the figures improve
Relic Neutralino Density in Scenarios with Intermediate Unification Scale
We analyse the relic neutralino density in supersymmetric models with an
intermediate unification scale. In particular, we present concrete cosmological
scenarios where the reheating temperature is as small as
MeV). When this temperature is associated to the decay of moduli fields
producing neutralinos, we show that the relic abundance increases considerably
with respect to the standard thermal production. Thus the neutralino becomes a
good dark matter candidate with 0.1\lsim \Omega h^2 \lsim 0.3, even for
regions of the parameter space where large neutralino-nucleon cross sections,
compatible with current dark matter experiments, are present. This is obtained
for intermediate scales GeV, and moduli masses
GeV. On the other hand, when the above temperature is
associated to the decay of an inflaton field, the relic abundance is too small.Comment: Latex, 11 pages, 2 figure
Immunity to Protozoan Parasites
Protozoan parasites cause several diseases, such as Malaria,
Leishmaniasis, and Trypanosomiasis, hampering human development worldwide. Many protozoa cause infections that
often follow chronic courses, owing to coevolution between
parasites and host immune system. The survival and transmission of pathogenic protozoa depends on their ability to evade or subvert hostâs innate and adaptive immune responses. A great challenge to research in immunology and parasitology is the development of strategies that favor immunity against protozoan parasites and prevent their evasion, chronic, or recurrent infections and associated pathologies.
This special issue includes original papers and reviews that
summarize current advances in our understanding on the
mechanisms of immunity to protozoan parasites in humans
and experimental animal models.Fil: Lopes, Marcela F. Universidade Federal do Rio de Janeiro; BrazilFil: Zamboni, Dario S. Faculdade de Medicina de Ribeirao Preto. Universidade de Sao Paulo; BrazilFil: LujĂĄn, Hugo Daniel. Universidad CatĂłlica de CĂłrdoba. Facultad de Ciencias de la Salud; ArgentinaFil: Rodrigues, Mauricio M. , Escola Paulista de Medicina; Brazi
Evolution and adaptation in pseudomonas aeruginosa biofilms driven by mismatch repair system-deficient mutators
Pseudomonas aeruginosa is an important opportunistic pathogen causing chronic airway infections, especially in cystic fibrosis (CF) patients. The majority of the CF patients acquire P. aeruginosa during early childhood, and most of them develop chronic infections resulting in severe lung disease, which are rarely eradicated despite intensive antibiotic therapy. Current knowledge indicates that three major adaptive strategies, biofilm development, phenotypic diversification, and mutator phenotypes [driven by a defective mismatch repair system (MRS)], play important roles in P. aeruginosa chronic infections, but the relationship between these strategies is still poorly understood. We have used the flow-cell biofilm model system to investigate the impact of the mutS associated mutator phenotype on development, dynamics, diversification and adaptation of P. aeruginosa biofilms. Through competition experiments we demonstrate for the first time that P. aeruginosa MRS-deficient mutators had enhanced adaptability over wild-type strains when grown in structured biofilms but not as planktonic cells. This advantage was associated with enhanced micro-colony development and increased rates of phenotypic diversification, evidenced by biofilm architecture features and by a wider range and proportion of morphotypic colony variants, respectively. Additionally, morphotypic variants generated in mutator biofilms showed increased competitiveness, providing further evidence for mutator-driven adaptive evolution in the biofilm mode of growth. This work helps to understand the basis for the specific high proportion and role of mutators in chronic infections, where P. aeruginosa develops in biofilm communities.Fil: Lujan, Adela Maria. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Centro de Investigaciones en QuĂmica BiolĂłgica de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Centro de Investigaciones en QuĂmica BiolĂłgica de CĂłrdoba; Argentina. Universidad CatĂłlica de CĂłrdoba. Instituto de Investigaciones en Recursos Naturales y Sustentabilidad JosĂ© Sanchez Labrador S. J. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto de Investigaciones en Recursos Naturales y Sustentabilidad JosĂ© Sanchez Labrador S. J.; ArgentinaFil: MaciĂĄ, MarĂa D.. Instituto de InvestigaciĂłn Sanitaria Illes Balears; EspañaFil: Yang, Liang. Technical University of Denmark; DinamarcaFil: Molin, SĂžren. Technical University of Denmark; DinamarcaFil: Oliver, Antonio. Instituto de InvestigaciĂłn Sanitaria Illes Balears; EspañaFil: Smania, Andrea. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Centro de Investigaciones en QuĂmica BiolĂłgica de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Centro de Investigaciones en QuĂmica BiolĂłgica de CĂłrdoba; Argentin
Parental and familial factors influencing physical activity levels in early adolescence: a prospective study
Parental/familial factors are important determinants of the physical activity level (PAL) in children and adolescents, but studies rarely prospectively evaluate their relationships. This study aimed to evaluate the changes in physical activity levels among adolescents from Bosnia and Herzegovina over a two-year period and to determine parental/familial predictors of PAL in early adolescence. A total of 651 participants (50.3% females) were tested at baseline (beginning of high school education; 14 years old on average) and at follow-up (approximately 20 months later). The predictors included sociodemographic characteristics (age, gender) and parental/familial factors (socioeconomic status of the family, maternal and paternal education, conflict with parents, parental absence from home, parental questioning, and parental monitoring). Physical activity levels were evidenced by the Physical Activity Questionnaire for Adolescents (PAQ-A; criterion). Boys were more active than girls, both at baseline (t-test = 3.09, p < 0.001) and at follow-up (t-test = 3.4, p < 0.001). Physical activity level decreased over the observed two-year period (t-test = 16.89, p < 0.001), especially in boys, which is probably a consequence of drop-out from the sport in this period. Logistic regression evidenced parental education as a positive predictor of physical activity level at baseline (OR [95% CI]; 1.38 [1.15â170], 1.35 [1.10â1.65]), and at follow-up (1.35 [1.11â1.69], 1.29 [1.09â1.59], for maternal and paternal education, respectively). Parents with a higher level of education are probably more informed about the importance of physical activity on health status, and thus transfer this information to their children as well. The age from 14 to 16 years is likely a critical period for maintaining physical activity levels in boys, while further studies of a younger age are necessary to evaluate the dynamics of changes in physical activity levels for girls. For maintaining physical activity levels in adolescence, special attention should be paid to children whose parents are less educated, and to inform them of the benefits of an appropriate physical activity level and its necessity for maintaining proper health and growth
Two Gallium data sets, spin flavour precession and KamLAND
We reexamine the possibility of a time modulation of the low energy solar
neutrino flux which is suggested by the average decrease of the Ga data in line
with our previous arguments. We perform two separate fits to the solar neutrino
data, one corresponding to 'high' and the other to 'low' Ga data, associated
with low and high solar activity respectively. We therefore consider an
alternative to the conventional solar+KamLAND fitting, which allows one to
explore the much wider range of the angle permitted by the
KamLAND fitting alone. We find a solution with parameters in which the 'high' and
the 'low' Ga rates lie far apart and are close to their central values and is
of comparable quality to the global best fit, where these rates lie much closer
to each other. This is an indication that the best fit in which all solar and
KamLAND data are used is not a good measure of the separation of the two Ga
data sets, as the information from the low energy neutrino modulation is
dissimulated in the wealth of data. Furthermore for the parameter set proposed
one obtains an equally good fit to the KamLAND energy spectrum and an even
better fit than the 'conventional' LMA one for the reactor antineutrino
survival probability as measured by KamLAND.Comment: V2: 15 pages, 3 eps figures, fit improved, final version to appear in
Journal of Physics
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