We show that Nearest-Neighbour Interaction (NNI) textures for the quark mass matrices can be obtained through the introduction of an Abelian flavour symmetry. The minimal realisation requires a Z 4 symmetry in the context of a two Higgs doublet model. It is further shown that the NNI textures can be in agreement with all present experimental data on quark masses and mixings, provided one allows for deviations of Hermiticity in the quark mass matrices at the 20% level.

A flavour symmetry based on Z4 is analysed in the context of SU(5) Grand Unification with the standard fermionic content plus three right-handed neutrinos. The role of Z4 is to forbid some Yukawa couplings of up-and down-quarks to Higgs scalars such that the quark mass matrices Mu, M d have Nearest-Neighbour-Interaction (NNI) structure, once they are generated through the electroweak symmetry breaking. It turns out in this framework that Z4 is indeed the minimal discrete symmetry and its implementation requires the introduction of at least two Higgs quintets, which leads to a two Higgs doublet model at low energy scale. Due to the SU(5) unification, it is shown that the charged lepton mass matrix develops also NNI form. However, the effective neutrino mass matrix exhibits a non parallel pattern, in the framework of the type-I seesaw mechanism. Analysing all possible zero textures allowed by gauge-horizontal symmetry SU(5) × Z4, it is seen that only two patterns are in agreement with the leptonic experimental data and they could be further distinguished by the light neutrino mass spectrum hierarchy. It is also demonstrated that Z4 freezes out the possibility of proton decay through exchange of colour Higgs triplets at tree-level.

All quark mass matrices with texture zeroes obtained through weak basis transformations are confronted with the experimental data. The reconstruction of the quark mass matrices M u and M d at the electroweak scale is performed in a weak basis where the matrices are Hermitian and have a maximum of three vanishing elements. The same procedure is also accomplished for the Yukawa coupling matrices at the grand unification scale in the context of the Standard Model and its minimal supersymmetric extension as well as of the two Higgs doublet model. The analysis of all viable power structures on the quark Yukawa coupling matrices that could naturally appear from a Froggatt-Nielsen mechanism is also presented.

We study one-loop radiative neutrino mass models in which one of the beyond-the-standard model fields is either a hypercharge-zero fermion quintet (minimal dark matter) or a hyperchargezero scalar septet. By systematically classifying all possible one-loop such models we identify various processes that render the neutral component of these representations (dark matter) cosmologically unstable. Thus, our findings show that these scenarios are in general not reconcilable with dark matter stability unless tiny couplings or additional ad hoc symmetries are assumed, in contrast to minimal dark matter models where stability is entirely due to the standard model gauge symmetry. For some variants based on higher-order loops we find that α 2 reaches a Landau pole at rather low scales, a couple orders of magnitude from the characteristic scale of the model itself.Thus, we argue that some of these variations although consistent with dark matter stability and phenomenological constraints are hard to reconcile with perturbativity criteria.

Biodiesel from animal fats with methanol and ethanol was produced in the presence of sodium methoxide and sodium ethoxide as catalysts. Two samples of pork fats and one natural beef tallow were directly transesterified with a good final product yield: 87.7, 86.7 and 86.3% for methanolysis, and 78.4, 82.6 and 82.7% for ethanolysis, respectively. Methyl ester content was also determined, being higher than 96.5 mass% for all the samples prepared. The presence of natural C17:0 in animal fats makes it necessary to correct the method proposed in the standard EN 14103 (2003). Biodiesel density at 15 °C of the samples was between 870 and 876 kg/m 3 , within the acceptance range of standard EN 14214, and the dynamic viscosity at 40 °C of the produced biodiesels was in the range of 4.5 to 5.16 mm 2 /s, also fulfilling requirements of EN 14214 standard. The iodine value is much lower than the superior limit established by EN 14214 standard but oxidation stability (OSI) is lower than the required limit, 6 h, of the standard, which can be attributed to the lack of natural antioxidants in tallows.