Constraints on leptogenesis from a symmetry viewpoint

It is shown that type I seesaw models based on the standard model Lagrangian extended with three heavy Majorana right-handed fields do not have leptogenesis in leading order, if the symmetries of mass matrices are also the residual symmetry of the Lagrangian. In particular, flavor models that lead to a mass-independent leptonic mixing have a vanishing leptogenesis CP asymmetry. Based on symmetry arguments, we prove that in these models the Dirac-neutrino Yukawa coupling combinations relevant for leptogenesis are diagonal in the physical basis where the charged leptons and heavy Majorana neutrinos are diagonal.Comment: 5 pages; a few comments added; final version to appear in Phys. Rev.

Computing the zeros of quaternion polynomials

A method is developed to compute the zeros of a quaternion polynomial with all terms of the form qkXk. This method is based essentially in Niven's algorithm [1], which consists of dividing the polynomial by a characteristic polynomial associated to a zero. The information about the trace and the norm of the zero is obtained by an original idea which requires the companion matrix associated to the polynomial. The companion matrix is represented by a matrix with complex entries. Three numerical examples using Mathematica 2.2 version are given.http://www.sciencedirect.com/science/article/B6TYJ-444G6J6-N/1/2ab1f648c1929ffc5374c2a8b11c2a7

Modulating intermolecular interactions and rheological properties in silk fibroin using ultrasound frequencies

info:eu-repo/semantics/draf

Differential equations over octonions

Differential equations with constant and variable coefficients over octonions are investigated. It is found that different types of differential equations over octonions can be resolved. For this purpose non-commutative line integration is used. Such technique is applied to linear and non-linear partial differential equations in real variables. Possible areas of applications of these results are outlined.Comment: 50 page

Intrahepatic Colangiocarcinoma

Introdução: o colangiocarcinoma intra-hepático (CCIhp) é um tumor maligno raro, normalmente diagnosticado num estadio avançado. São objectivos deste estudo avaliar os resultados da terapêutica do CCIhp e os factores prognósticos com significado estatístico na sobrevida de doentes com esta entidade nosológica tratados no nosso Serviço. Material e métodos: Vinte e um doentes submetidos a tratamento por CCIhp nos últimos anos, dos quais onze foram operados com intuitos curativos: quatro hepatectomias esquerdas, duas hepatectomias esquerdas alargadas aos segmentos V e VIII, duas hepatectomias direitas, duas bissegmentectomias e uma trissegmentectomia. Resultados: a mortalidade per-operatória foi de 0% e a pós-operatória (três meses) de 6%. As sobrevidas cumulativas aos 5 anos foram de 14% no total da população, 26% nos doentes submetidos a cirurgia com intuitos curativos e 26% para a sobrevida cumulativa livre de doença. Observou-se recidiva tumoral hepática em cinco doentes, a qual ocorreu aos 1,09 ± 0,82 anos (limites: 0,24-2,08). Os factores que influenciaram a sobrevida da globalidade dos doentes foram o tratamento cirúrgico com intuitos curativos (p=0,028), a presença de invasão vascular (p=0,002) e o valor da fosfatase alcalina no momento do diagnóstico (p=0,044). Entre os doentes operados com intuitos curativos, a presença de invasão vascular influenciou a sobrevida global (p=0,025) e a sobrevida livre de doença (p=0,002). Conclusões: A ressecção cirúrgica com intuitos curativos aumentou, de forma estatisticamente significativa, a sobrevida dos doentes com CCIhp. No entanto, sendo o diagnóstico geralmente tardio, apenas uma pequena percentagem destes doentes pode beneficiar deste tratamento.info:eu-repo/semantics/publishedVersio

Resonant leptogenesis and tribimaximal leptonic mixing with A4 symmetry

We investigate the viability of thermal leptogenesis in type-I seesaw models with leptonic flavour symmetries that lead to tribimaximal neutrino mixing. We consider an effective theory with an A4 x Z3 x Z4 symmetry, which is spontaneously broken at a scale much higher than the electroweak scale. At the high scale, leptonic Yukawa interactions lead to exact tribimaximal mixing and the heavy Majorana neutrino mass spectrum is exactly degenerate. In this framework, leptogenesis becomes viable once this degeneracy is lifted either by renormalization group effects or by a soft breaking of the A4 symmetry. The implications for low-energy neutrino physics are discussed.Comment: 14 pages, 15 figures; final version to appear in Phys. Rev.

Quaternionic eigenvalue problem

We discuss the (right) eigenvalue equation for $\mathbb{H}$, $\mathbb{C}$ and $\mathbb{R}$ linear quaternionic operators. The possibility to introduce an isomorphism between these operators and real/complex matrices allows to translate the quaternionic problem into an {\em equivalent} real or complex counterpart. Interesting applications are found in solving differential equations within quaternionic formulations of quantum mechanics.Comment: 13 pages, AMS-Te

Efeitos implícitos da pertença e identificação grupais na discriminação social

Utilizando uma metodologia não-obstrusiva, testámos a hipótese de que a associação entre estímulos visuais não salientes e a pertença grupal dos indivíduos pode interferir na escolha de uma equipa de trabalho sem que estes se apercebam dessa influência. As participantes (66 estudantes dos cursos de Psicologia e de Serviço Social) foram acolhidas por uma Psicóloga vs. Trabalhadora Social após o que deveriam escolher entre duas equipas, fisicamente semelhante vs. diferente da pessoa que as recebeu, para a continuação do mesmo estudo. Os resultados mostraram que as participantes que foram acolhidas pelo membro do exogrupo escolheram mais a equipa diferente do que as participantes acolhidas pelo membro do endogrupo sendo este efeito mediado pela identificação ao endogrupo. Os resultados são discutidos à luz de investigação anterior utilizando medidas implícitas de discriminação social.ABSTRACT: Using a non-obstrusive measure, we tested the hypothesis that the association between non-salient visual stimuli and group membership can affect the choice of a working team beyond participants’ awareness of that influence. Participants (66 Psychology and Social Service students) were received by a Psychologist vs. Social Worker. They then had to choose between two teams, physically similar to vs. different from the person who had just received them, to work with in the second phase. Results show that most participants who had been received by an out-group member chose the different team more than did participants who had been received by an in-group member. This effect was mediated by in-group identification. Results are discussed based on previous research using implicit measures of social discrimination.info:eu-repo/semantics/publishedVersio

Seasonal changes in the biochemical fate of carbon fixed by benthic diatoms in intertidal sediments

Benthic diatoms are important primary producers in intertidal marine sediments and form the basis of the food web in these ecosystems. In order to investigate the carbon flow within diatom mats, we performed in situ 13C pulse-chase labeling experiments and followed in detail the biochemical fate of carbon fixed by the diatoms for five consecutive days. These labeling experiments were done at approximately 2-monthly intervals during 1 yr in order to cover seasonal variations. The fixed carbon was recovered in individual carbohydrates including extracellular polymeric substances (EPS), amino acids, fatty acids, and nucleic acid bases. In addition, we assessed a variety of environmental parameters and photosynthetic characteristics. The fixed carbon was initially mainly stored as carbohydrate (glucose) while nitrogen-rich compounds (e.g., amino acids and RNA/DNA) were produced more slowly. During the year, the diatoms distributed the photosynthetically fixed carbon differently among the various carbon pools that were measured. In summer, the diatoms decreased carbon fixation and accumulated relatively more lipid as a storage compound (27% 6 2% vs. 12% 6 5% in other seasons). The percentage of fixed carbon that was excreted as EPS was lower in summer compared to other seasons, amounting 9% 6 4% and 21% 6 6%, respectively. Hence, it seemed that the physiology of the microphytobenthos was different during summer and caused by higher light intensity and a shift in nitrogen source

Mathematica tools for quaternionic polynomials

In this paper we revisit the ring of (left) one-sided quaternionic polynomials with special focus on its zero structure. This area of research has attracted the attention of several authors and therefore it is natural to develop computational tools for working in this setting. The main contribution of this paper is a Mathematica collection of functions QPolynomial for solving polynomial problems that we frequently find in applications.(undefined)info:eu-repo/semantics/publishedVersio