f(R)f(R) quantum cosmology: avoiding the Big Rip

Extended theories of gravity have gathered a lot of attention over the last years, for they not only provide an excellent framework to describe the inflationary era but also yields an alternative to the elusive and mysterious dark energy. Among the different extended theories of gravity, on this work we focus on metric $f(R)$ theories. In addition, it is well known that if the late-time acceleration of the universe is stronger than the one induced by a cosmological constant then some future cosmic singularities might arise, being the Big Rip the most virulent one. Following this reasoning, on this work, we analyse the Big Rip singularity in the framework of $f(R)$ quantum geometrodynamics. Invoking the DeWitt criterium, i. e. that the wave function vanishes at the classical singularity, we proof that a class of solutions to the Wheeler-DeWitt equation fulfilling this condition can be found. Therefore, this result hints towards the avoidance of the Big Rip in metric $f(R)$ theories of gravity.Comment: V1:13 pages. Dedicated to the memory of Prof. Pedro F. Gonzalez-Diaz (our former PhD supervisor). V2: 9 pages (new style), minor clarifications included, no physics changes, 6 references added. Version accepted for publication in Physical Review

Worse than a big rip?

We show that a generalised phantom Chaplygin gas can present a future singularity in a finite future cosmic time. Unlike the big rip singularity, this singularity happens for a finite scale factor, but like the big rip singularity, it would also take place at a finite future cosmic time. In addition, we define a dual of the generalised phantom Chaplygin gas which satisfies the null energy condition. Then, in a Randall-Sundrum 1 brane-world scenario, we show that the same kind of singularity at a finite scale factor arises for a brane filled with a dual of the generalised phantom Chaplygin gas.Comment: 6 pages, 4 figures, RevTeX 4. Discussion expanded and references added. Version to appear in PL

Detection of Haplosporidium pinnae from Pinna nobilis Faeces

Pinna nobilis (Linnaeus, 1758) is the largest bivalve endemic to the Mediterranean. It is distributed in a wide range of coastal environments, including estuaries. Pinna nobilis has recently become a critically endangered species (with almost 100% mortality) along the entire Spanish Mediterranean coast. This may be due to coinfections caused by Haplosporidium pinnae and bacterial pathogens such as Mycobacterium spp. We extensively sampled P. nobilis from Mar Menor lagoon (SE Spain), a site where individuals still survive. Using conventional PCR, we found Haplosporidium spp. in 7.1% of mantle and faecal DNA samples in different individuals of P. nobilis. We identified and quantified Haplosporidium pinnae in P. nobilis using Sanger sequencing and qPCR. Faecal H. pinnae detection is non-invasive, unlike biopsies. Therefore, this non-lethal and non-invasive sampling method could contribute to the welfare of living populations, particularly in eutrophic environments, where they are prone to septicaemia. The use of faecal DNA analysis could be a major advance in epidemiology and recovery assessment studies of P. nobilis.info:eu-repo/semantics/publishedVersio

El control de inventario como estrategia para el logro de rentabilidad en las mypes comerciales de la actividad ferretera ubicada en la comunidad urbana autogestionaria de Huaycán distrito de Ate - Lima, periodo 2016

La tesis que se ha desarrollado tiene como objetivo establecer los efectos del control de Inventarios de las MYPES de la actividad ferretera en la comunidad urbana autogestionaria de Huaycán perteneciente al distrito de Ate - Lima y como incide en el logro de Rentabilidad, para lo cual se utilizó la metodología de investigación científica, instrumento que sirvió para desarrollar aspectos importantes del trabajo desde su primer capítulo hasta el último.the thesis that has been developed have as an objective set the effect of control of inventories of the MYPE of activity ironmonger in the community urban self-management of huaycan belonging the distric of ate - lima and as an influence in the achivement of profitability , for the wich it was used the methodology of scientific investigation , instruments that served to developed importan aspect of the work since his first chapter until the final

Gestión de mantenimiento para reducir costos por paradas no planificadas en la flota de palas hidráulicas Hitachi en minería superficial en minera Yanacocha 2021

En Minera Yanacocha las labores o trabajos de minería superficial se ven afectados por la constante falla de flota de palas hidráulicas Hitachi. Acorde con el registro de mayo de 2021, las acciones correctivas no planificadas realizadas por la empresa tomaron un total de 85 horas de mano de obra. Por tal motivo, se desarrolló la presente investigación con el objetivo general de “Diseñar herramientas de gestión de mantenimiento para reducir costos por paradas no planificadas en la flota de palas hidráulicas Hitachi en minería superficial en Minera Yanacocha”. La investigación fue de tipo aplicada, nivel descriptivo, con un diseño no experimental, longitudinal. La muestra fue igual a la población y consistió en las excavadoras y palas hidráulicas Hitachi (2 modelo Ex-5500 y 4 palas modelo Ex-2500) para un total de 6 unidades de estudio. Durante el diagnóstico se determinó que los equipos como la pala 10 (78.25%) y la pala 7 (76.95%) presentan una disponibilidad menor a 80%, siendo los problemas en el sistema eléctrico y motor los mayores detonantes de esta situación. Se diseñó un plan compuesto por un proceso de rutina diaria de revisión, un cronograma de mantenimiento preventivo y una serie de registros para la realización de las tareas preventivas. Se estima una reducción de las fallas de hasta un 50%, lo cual, mejorará todos los indicadores de mantenimiento preventivo reflejándose en un incremento de la disponibilidad, en la cual, todos los equipos estarán sobre el 85% y la mayoría (4 de 6) sobre el 90%. Con una inversión inicial de S/. 117,639.12 y recurrente por el mismo monto, se obtuvo que el proyecto es económicamente factible con un VPN de S/. 149,016.55, una TIR de 24.6% y un IR de S/. 1.27.TesisInfraestructura, Tecnología y Medio Ambient

Road and street smart lighting control systems as a new application area of the hot-potato protocol

This paper presents the new application area of the hot-potato routing protocol, which is a “last-mile” communication network for controlling systems of road and street lighting. Four variants of the hot-potato protocol are analyzed with use of the graph theory. For the assessment of the traffic parameters the ETX parameter is used in relation to the length of the shortest path. Proposed methods are independent of the media type and can be implemented either in wireless or PLC