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.

Yukawa Alignment in a Multi Higgs Doublet Model: An effective approach

In the two Higgs doublet model, natural flavour conservation can be achieved through the use of a discrete Z2 symmetry. A less restrictive condition is the requirement of alignment in the Yukawa sector. So far, alignment has been an anzatz, not rooted in a specific model. In this letter we present a model for alignment, which starts with 2+N Higgs doublets, with natural flavour conservation imposed by a discrete symmetry. Only two of these scalars couple to the fermions, the other N scalars are in a hidden sector. Assuming that the two scalar doublets coupled to fermions are heavy, their decoupling leads to an effective Yukawa interaction. The latter connects the fermions and the scalars of the hidden sector, and exhibits the same Yukawa coupling matrix for each of the N scalars.Comment: 7 page

A 2d in vivo approach to study photosynthesis in grape berry

Is argued that fruit photosynthesis serves mainly as a respiratory CO2 refixation mechanism [1] but its contribution to growth and metabolism, localization and dynamics during fruit development are poorly known. Unlike the leaves, fruit volume imposes a constraint to photosynthesis by limiting light penetration. However, the patterns of chlorophyll distribution are apparently independent of a light intensity gradient. Microscopic observations of transversal slices of green stage grape berries (6-8 weeks after fruit set) of Alvarinho cultivar, revealed that exocarp cells, mesocarp cells next to vascular bundles, and seed coat cells present higher chlorophyll contents than inner mesocarp cells. The photosynthetic activity was determined on this material by Imaging-PAM fluorometry, a powerful tool for 2D mapping of in vivo photosynthesis. In 2 mm-thick grape berry discs, chlorophyll fluorescence parameters were estimated (Fv/Fm and II), and rapid light curves (RLC) were performed. Exocarp and seed coats of green berries showed the highest Fv/Fm values (ca. 0.6-0.7), and mesocarp cells around 85% of that value. Exocarp from mature grapes maintained Fv/Fm values during maturation, but in mesocarp and seed coats this value strongly decreased. ETRr were very sensitive to increasing light intensities and decreased with grape berry maturation. Our future prospects include the implication of photosynthesis on grape berry solute contents (sugars, acids), fruit and seed development.Fundação para a Ciência e a Tecnologia (research project no. PTDC/AGR-ALI/100636/2008

Research methodologies focused on urban planning and mathematical issues

This article aims to present an interdisciplinary approach about the research methodologies used at the civil engineering research field, in the domains of urban planning and mathematics. Actually, there are some similarities in between the research process features of urban planning and mathematics. In fact, these both scientific subjects follow analogous tasks in their research process, which have the same starting point with the definition of the research problem and the final phase, based on the proposed solution. It joins scholars from the department of civil engineering and architecture, experts in spatial analysis and scholars form the department of mathematics of the University of Beira Interior. Two case studies will be presented as examples of the application of these methodological approaches, both of them focused on the urban planning researches, associated with postgraduate teachings, one is related to a PhD thesis and the other one relates to a master degree dissertation.info:eu-repo/semantics/publishedVersio

In vitro cultures of grape tissues: new possibilities to study grape berry physiology

Grape berries suffer important morphological, biochemical and physiological changes during its development and maturation. It is known that photoassimilates translocated from leaves serve as the major source of carbon and energy to support fruit needs, but recent findings revealed that, at least in the green phase, grape berries show high photosynthetic activity especially in the exocarp. The contribution of fruit photosynthesis for fruit growth and production of organic compounds is far from being understood. In this study photomixotrophic cell suspensions were established as an in vitro model to complement the study grape berry photosynthesis. Calli of CSB (Cabernet Sauvignon Berry) cells derived from the inner tissues of the grape berry were sub-cultured in liquid modified MS medium supplemented with 2% sucrose and different hormonal combinations, one auxin (NAA) and three cytokinins (BAP, ZEA and KIN) at two different final concentrations (0.5 and 1 g mL-1). Two different growth light intensities (45- 60 and 80-105 mol m-1 s-1) were also tested. Chlorophyll fluorescence PAM fluorometry was used to evaluate the photochemical efficiency (Fv/Fm) of all suspensions and chlorophyll content was also determined. Results showed that the cytokinin type was crucial to induce the photosynthetic phenotype, but Fv/Fm was low when compared to the value exhibited by grape berry skin. To further study the photoautrophy of the grape berry tissues new callus cultures were established from the exocarp tissues of the fruit, harvested at the green stage (Alvarinho cv). Portions of detached exocarp were cultured on B5 solid medium supplemented with different hormonal combinations (NAA or 2,4-D with BAP or ZEA) at different concentrations (0.1 or 0.2 g mL-1 for auxins and 0.2 or 0.4 g mL-1 for cytokinins). Only two combinations were responsive but both induced pale green calli with higher growth rates. To our knowledge, this is a pioneer study on calli production from the exocarp of the grape berry from the Portuguese variety Alvarinho. This approach opens good perspectives to study in more detail the physiology of these cells, namely the role of photosynthesis on cell growth and metabolite production. Moreover, it will allow to investigate the impact of several environmental factors on fruit photosynthesis, such as temperature, light and water potential.Fundação para a Ciência e a Tecnologia (research project no. PTDC/AGR-ALI/100636/2008

Fruit photosynthesis: more to know about where, how and why

Not only leaves but also other plant organs and structures typically considered as carbon sinks, including stems, roots, flowers, fruits and seeds, may exhibit photosynthetic activity. There is still a lack of a coherent and systematized body of knowledge and consensus on the role(s) of photosynthesis in these “sink” organs. With regard to fruits, their actual photosynthetic activity is influenced by a range of properties, including fruit anatomy, histology, physiology, development and the surrounding microclimate. At early stages of development fruits generally contain high levels of chlorophylls, a high density of functional stomata and thin cuticles. While some plant species retain functional chloroplasts in their fruits upon subsequent development or ripening, most species undergo a disintegration of the fruit chloroplast grana and reduction in stomata functionality, thus limiting gas exchange. In addition, the increase in fruit volume hinders light penetration and access to CO2, also reducing photosynthetic activity. This review aimed to compile information on aspects related to fruit photosynthesis, from fruit characteristics to ecological drivers, and to address the following challenging biological questions: why does a fruit show photosynthetic activity and what could be its functions? Overall, there is a body of evidence to support the hypothesis that photosynthesis in fruits is key to locally providing: ATP and NADPH, which are both fundamental for several demanding biosynthetic pathways (e.g., synthesis of fatty acids); O2, to prevent hypoxia in its inner tissues including seeds; and carbon skeletons, which can fuel the biosynthesis of primary and secondary metabolites important for the growth of fruits and for spreading, survival and germination of their seed (e.g., sugars, flavonoids, tannins, lipids). At the same time, both primary and secondary metabolites present in fruits and seeds are key to human life, for instance as sources for nutrition, bioactives, oils and other economically important compounds or components. Understanding the functions of photosynthesis in fruits is pivotal to crop management, providing a rationale for manipulating microenvironmental conditions and the expression of key photosynthetic genes, which may help growers or breeders to optimize development, composition, yield or other economically important fruit quality aspects.This research was funded by FCT—Portuguese Foundation for Science and Technology, via a grant provided to AG (PD/BD/128275/2017), under the Doctoral Programme “Agricultural Production Chains—from fork to farm” (PD/00122/2012), and by the European Social Funds and the Regional Operational Programme Norte 2020. FCT also supported the work via CITAB and CBMA research units under the projects UIDB/04033/2020 and UIDB/04050/2020, respectively. The work was also support by project I&D&I “AgriFood XXI”, ref. NORTE-01-0145-FEDER-000041, co-financed by the European Regional Development Fund (FEDER), through NORTE 2020 (Northern Regional Operational Program 2014/2020). This work was also supported by CESAM (UIDP/50017/2020 + UIDB/50017/2020 + LA/P/0094/2020). Ric C. H. De Vos was financed by the business unit Bioscience of Wageningen University and Research Centre

Leptonic mixing, family symmetries, and neutrino phenomenology

Tribimaximal leptonic mixing is a mass-independent mixing scheme consistent with the present solar and atmospheric neutrino data. By conveniently decomposing the effective neutrino mass matrix associated to it, we derive generic predictions in terms of the parameters governing the neutrino masses. We extend this phenomenological analysis to other mass-independent mixing schemes which are related to the tribimaximal form by a unitary transformation. We classify models that produce tribimaximal leptonic mixing through the group structure of their family symmetries in order to point out that there is often a direct connection between the group structure and the phenomenological analysis. The type of seesaw mechanism responsible for neutrino masses plays a role here, as it restricts the choices of family representations and affects the viability of leptogenesis. We also present a recipe to generalize a given tribimaximal model to an associated model with a different mass-independent mixing scheme, which preserves the connection between the group structure and phenomenology as in the original model. This procedure is explicitly illustrated by constructing toy models with the transpose tribimaximal, bimaximal, golden ratio, and hexagonal leptonic mixing patterns

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

Changes in microphytobenthos fluorescence over a tidal cycle: implications for sampling designs

Intertidal microphytobenthos (MPB) are important primary producers and provide food for herbivores in soft sediments and on rocky shores. Methods of measuring MPB biomass that do not depend on the time of collection relative to the time of day or tidal conditions are important in any studies that need to compare temporal or spatial variation, effects of abiotic factors or activity of grazers. Pulse amplitude modulated (PAM) fluorometry is often used to estimate biomass of MPB because it is a rapid, non-destructive method, but it is not known how measures of fluorescence are altered by changing conditions during a period of low tide. We investigated this experimentally using in situ changes in minimal fluorescence (F) on a rocky shore and on an estuarine mudflat around Sydney (Australia), during low tides. On rocky shores, the time when samples are taken during low tide had little direct influence on measures of fluorescence as long as the substratum is dry. Wetness from wave-splash, seepage from rock pools, run-off, rainfall, etc., had large consequences for any comparisons. On soft sediments, fluorescence was decreased if the sediment dried out, as happens during low-spring tides on particularly hot and dry days. Surface water affected the response of PAM and therefore measurements used to estimate MPB, emphasising the need for care to ensure that representative sampling is done during low tide