Isolated factorizations and their applications in simplicial affine semigroups

We introduce the concept of isolated factorizations of an element of a commutative monoid and study its properties. We give several bounds for the number of isolated factorizations of simplicial affine semigroups and numerical semigroups. We also generalize $\alpha$-rectangular numerical semigroups to the context of simplicial affine semigroups and study their isolated factorizations. As a consequence of our results, we characterize those complete intersection simplicial affine semigroups with only one Betti minimal element in several ways. Moreover, we define Betti sorted and Betti divisible simplicial affine semigroups and characterize them in terms of gluings and their minimal presentations. Finally, we determine all the Betti divisible numerical semigroups, which turn out to be those numerical semigroups that are free for any arrangement of their minimal generators

Rpd3L and Hda1 histone deacetylases facilitate repair of broken forks by promoting sister chromatid cohesion

Genome stability involves accurate replication and DNA repair. Broken replication forks, such as those encountering a nick, lead to double strand breaks (DSBs), which are preferentially repaired by sister-chromatid recombination (SCR). To decipher the role of chromatin in eukaryotic DSB repair, here we analyze a collection of yeast chromatin-modifying mutants using a previously developed system for the molecular analysis of repair of replication-born DSBs by SCR based on a mini-HO site. We confirm the candidates through FLP-based systems based on a mutated version of the FLP flipase that causes nicks on either the leading or lagging DNA strands. We demonstrate that Rpd3L and Hda1 histone deacetylase (HDAC) complexes contribute to the repair of replication-born DSBs by facilitating cohesin loading, with no effect on other types of homology-dependent repair, thus preventing genome instability. We conclude that histone deacetylation favors general sister chromatid cohesion as a necessary step in SCR

LMI-based control design to enhance robustness of synchronous power controller

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Synchronous power controller (SPC) has emerged as a suitable technique to equip grid-connected inverters with grid supporting functionalities such as inertial emulation and frequency/voltage support by mimicking the behavior of synchronous machines. Although the feasibility of the SPC has been experimentally verified under various operating conditions, parameter tuning for the SPC to ensure a stable inverter system has not been adequately addressed in the literature. To fill this gap, this paper presents a robust control design for the SPC to ensure its stable operation under the grid impedance variation. The proposed design procedure consists of system modelling and robust optimal parameter selection by using linear matrix inequality approach. The effectiveness of the proposed control design is proven by means of simulations and experiments.Peer ReviewedPostprint (author's final draft

Analysis of risk disclosure in Spanish firms

Treball de Final de Grau en Finances i Comptabilitat. Codi: FC1049. Curs acadèmic 2014-2015En la última década se ha ido denunciado por los usuarios la falta de divulgación de riesgo por parte de las empresas en sus estados financieros. Una mayor divulgación de riesgos tiene como consecuencia una serie de ventajas que benefician tanto a usuarios como a las empresas, como reducciones de coste de capital. El objetivo de este estudio es comprobar si las empresas divulgan más información sobre riesgo en periodos de crisis financiera o en periodos de prosperidad económica. También se explican las diferentes tendencias sobre la divulgación de información sobre diferentes tipos de riesgo en los años estudiados. Para ello se ha analizado una muestra de empresas españolas no financieras del IBEX-35 en el año 2006 y 2011 utilizando una metodología nueva propuesta en el estudio de Cabedo y Tirado (2009). Los resultados obtenidos demuestran que estas empresas si han divulgado más información en periodos de crisis.In the last decade the users have been denounced the lack of information about risk disclosure in the financial statements of the companies. One increase disclosure of risks translates directly in a high number of advantages that benefit both users as firms, like capital cost reductions. The objective of this study is to check if companies disclose more risk disclosure in financial crisis or in periods of economic prosperity. Furthermore, the behaviour of different trends about the types of risk is explained also in this study. For it has been analysed a sample of non-financial Spanish companies that listed in IBEX-35 in 2006 and 2011 using a new methodology proposed in the study of Cabedo and Tirado (2009). The results obtained show that these companies have disclosed more information about risk in times of crisis, i.e. more in 2011 than 2006

Synchronous frequency support of photovoltaic power plants with inertia emulation

©2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Grid stability is one of the main concerns in renewable energies. The lack of inertia and their low capability to provide frequency support has created the need for implementing new control strategies to solve this problem. In current networks, frequency and voltage support are performed through synchronous generators, which provide an inherent grid support due to the inertia presented in their mechanical rotors. Based on the same concept, renewable energies based on power converters have introduced synchronous controllers to emulate the dynamic behavior of synchronous generators and provide voltage and frequency support. However, most synchronous control strategies integrate their controllers as an add-on firmware embedded in each power converter, without presenting a coordinated synchronous performance when several converters operate in a PV power plant. The aggregation of several power converters operating with a coordinated synchronous response would be advantageous in these cases, since they can provide a harmonic response with an automatic power distribution when grid support is required. This paper presents a synchronous control strategy for photovoltaic power plants, which manages several power converters as an aggregated synchronous system.Peer ReviewedPostprint (author's final draft

Simple regular black hole with logarithmic entropy correction

A simple regular black hole solution satisfying the weak energy condition is obtained within Einstein--non--linear electrodynamics theory. We have computed the thermodynamic properties of this black hole by a careful analysis of the horizons and we have found that the usual Bekenstein--Hawking entropy gets corrected by a logarithmic term. Therefore, in this sense our model realizes some quantum gravity predictions which add this kind of correction to the black hole entropy. In particular, we have established some similitudes between our model and a quadratic generalized uncertainty principle. This similitude has been confirmed by the existence of a remnant, which prevents complete evaporation, in agreement with the quadratic generalized uncertainty principle case

Do European Stock Markets Affect Latin American Stock Markets?

In this study, we examine the response of Latin American stock markets to movements in European stock markets using VAR models. Our results vary depending on the openness of the country in terms of international trade. We find evidence that Latin American stock markets are responsive to changes in the stock market from Spain. Additionally, during the second and third subperiods, Spain has much stronger ties with Brazil, and this might explain why Brazil responds more to the shocks originating from Spain than from France. In conclusion, this study uncovers two important findings. First, Spain influences Latin American markets but these responses are not homogeneous across markets. Second, the influence of Spain has different magnitude in the three subperiods.Emerging Markets, Latin America, Stock Markets Interdependence, VAR

Integrated series transformer in cascade converters for photovoltaic energy systems

This paper proposes a novel configuration for photovoltaic applications based on a cascade converter topology. The series connection between modules is achieved through the magnetic core of the integrated series transformer, therefore an inherent isolation is provided without the requirement of a dc-dc conversion stage. Such isolation approach between each module allows operation at high voltage levels without harming the PV panel insulation. The main principles that support this proposal, as well as, simulation results are presented to validate the configuration.Peer ReviewedPostprint (author's final draft