Neutrinoless double beta decay with and without Majoron-like boson emission in a 3-3-1 model

We consider the contributions to the neutrinoless double beta decays in a $SU(3)_L\otimes U(1)_N$ electroweak model. We show that for a range of the parameters in the model there are diagrams involving vector-vector-scalar and trilinear scalar couplings which can be potentially as contributing as the light massive Majorana neutrino exchange one. We use these contributions to obtain constraints upon some mass scales of the model, like the masses of the new charged vector and scalar bosons. We also consider briefly the decay in which besides the two electrons a Majoron-like boson is emitted.Comment: Revtex, 10 pages and 8 eps figures. Extended version to be published in Physical Review

Phase diagram of the antiferromagnetic XY model in two dimensions in a magnetic field

The phase diagram of the quasi-two-dimensional easy-plane antiferromagnetic model, with a magnetic field applied in the easy plane, is studied using the self-consistent harmonic approximation. We found a linear dependence of the transition temperature as a function of the field for large values of the field. Our results are in agreement with experimental data for the spin-1 honeycomb compound BaNi_2V_2O_3Comment: 3 page

XMM-Newton observations of the low-luminosity cataclysmic variable V405 Pegasi

V405 Peg is a low-luminosity cataclysmic variable (CV) that was identified as the optical counterpart of the bright, high-latitude ROSAT all-sky survey source RBS1955. The system was suspected to belong to a largely undiscovered population of hibernating CVs. Despite intensive optical follow-up its subclass however remained undetermined. We want to further classify V405 Peg and understand its role in the CV zoo via its long-term behaviour, spectral properties, energy distribution and accretion luminosity. We perform a spectral and timing analysis of \textit{XMM-Newton} X-ray and ultra-violet data. Archival WISE, HST, and Swift observations are used to determine the spectral energy distribution and characterize the long-term variability. The X-ray spectrum is characterized by emission from a multi-temperature plasma. No evidence for a luminous soft X-ray component was found. Orbital phase-dependent X-ray photometric variability by $\sim50\%$ occurred without significant spectral changes. No further periodicity was significant in our X-ray data. The average X-ray luminosity during the XMM-Newton observations was L_X, bol simeq 5e30 erg/s but, based on the Swift observations, the corresponding luminosity varied between 5e29 erg/s and 2e31 erg/son timescales of years. The CV subclass of this object remains elusive. The spectral and timing properties show commonalities with both classes of magnetic and non-magnetic CVs. The accretion luminosity is far below than that expected for a standard accreting CV at the given orbital period. Objects like V405 Peg might represent the tip of an iceberg and thus may be important contributors to the Galactic Ridge X-ray Emission. If so they will be uncovered by future X-ray surveys, e.g. with eROSITA.Comment: A&A, in pres

Monitoramento de doenças fúngicas em cultivares de trigo no Rio Grande do Sul.

Orientador: João Leodato Nunes Maciel

Resistência do tipo antixenose em cultivares de Capsicum spp. em relação ao afídeo Aphis gossypii.

O objetivo deste estudo foi identificar fontes de resistência do tipo antixenose em cultivares de Capsicum spp. ao pulgão Aphis gossypii. Para isso dois ensaios de preferência foram realizados, em 2008, em condições de casa de vegetação com 14 cultivares comerciais sendo avaliadas. As plantas foram infestadas 60 dias após o plantio com a liberação de dez adultos de A. gossypii por planta. Os resultados mostraram diferenças significativas no número médio de A. gossypii entre as cultivares, aos dez dias após a infestação. A cultivar Cambuci foi uma das menos preferidas. Para testar a hipótese que a resistência era do tipo antixenose, bioensaios comportamentais foram conduzidos com A. gossypii usando compostos orgânicos voláteis (COVs) coletados da cultivar não-preferida Cambuci e da preferida All Big. Os pulgões foram significativamente repelidos somente pelos COVs da cultivar Cambuci infestado. Além disso, a análise de cromatografia gasosa acoplada a espectrometria de massa (CG-EM) dos COVs liberados por plantas antes e após a infestação por A. gossypii revelou que a cultivar não preferida Cambuci emitiu nove compostos a mais, após a infestação, incluindo 6-metil-5 hepten-2-ona, um semioquímico de defesa de planta envolvido em interações entre plantas e pulgões. Estes resultados sugerem que semioquímicos liberados por cultivares não-preferidas têm potencial para ser usado em programas de melhoramento visando à produção de cultivares de Capsicum spp resistentes ao A. Gossypii