On the invariant causal characterization of singularities in spherically symmetric spacetimes

The causal character of singularities is often studied in relation to the existence of naked singularities and the subsequent possible violation of the cosmic censorship conjecture. Generally one constructs a model in the framework of General Relativity described in some specific coordinates and finds an ad hoc procedure to analyze the character of the singularity. In this article we show that the causal character of the zero-areal-radius (R=0) singularity in spherically symmetric models is related with some specific invariants. In this way, if some assumptions are satisfied, one can ascertain the causal character of the singularity algorithmically through the computation of these invariants and, therefore, independently of the coordinates used in the model.Comment: A misprint corrected in Theor. 4.1 /Cor. 4.

On the Papapetrou field in vacuum

In this paper we study the electromagnetic fields generated by a Killing vector field in vacuum space-times (Papapetrou fields). The motivation of this work is to provide new tools for the resolution of Maxwell's equations as well as for the search, characterization, and study of exact solutions of Einstein's equations. The first part of this paper is devoted to an algebraic study in which we give an explicit and covariant procedure to construct the principal null directions of a Papapetrou field. In the second part, we focus on the main differential properties of the principal directions, studying when they are geodesic, and in that case we compute their associated optical scalars. With this information we get the conditions that a principal direction of the Papapetrou field must satisfy in order to be aligned with a multiple principal direction of the Weyl tensor in the case of algebraically special vacuum space-times. Finally, we illustrate this study using the Kerr, Kasner and pp waves space-times.Comment: 24 pages, LaTeX2e, IOP style. To appear in Classical and Quantum Gravit

Omni-Channel Intensity and Shopping Value as Key Drivers of Customer Satisfaction and Loyalty

Omni-channel retailing consists of the complete alignment of the different channels and touchpoints that generate a seamless experience for consumers, allowing them to move freely through all channels. The consumer's perception of a seamless and consistent omni-channel experience is called intensity. This study reveals that this intensity in the shopping experience can offer value to consumers, and that intensity and shopping value also influence satisfaction and loyalty. We propose a relationship model that had been tested in a quantitative study with PLS, with a representative sample of buyers who had used the Click and Collect system. The main contribution of this study is to the literature on the analysis of omni-channels from the consumer experience perspective, through an in-depth analysis of the concepts of intensity and shopping value, as well as their relationship with satisfaction and loyalty. The results revealed the existence of a positive relationship between intensity and shopping value, and between these two variables and satisfaction and loyalty. Keywords: omni-channel; intensity; shopping value; satisfaction; loyalt

Tracking of learning level on design and safety skills in two core subjects of the chemical engineering degree at UPV

[EN] Chemical engineers develop their profession in areas in which design of processes and safety of installations, equipment and procedures designed are especially relevant due to the impact and consequences that a failure of these items represent. Therefore, curriculum of chemical engineers chemical engineering should include these disciplines as a valuable skill. In the Universitat Politècnica of València (UPV), design and safety competence training is worked in the curriculum of chemical engineering degree through several subjects. "Experimentation in Chemical Engineering III" (EIq3) from 3rd course, semester B and "Industrial Processes of Chemical Engineering" (PIIQ) from 4th course semester A, are core courses specially focussed on the development of several activities to work these skills. In EIq3 students design a production process to obtain oil from almond for cosmetic purposes. This design project includes: lab work to study and understand the stages of the production process and its performance, drawing of block and flow diagram of the process by using Autocad and recommendation of basic safety measures in the installation. In the following semester, students of PIIQ study different production processes and design a process to obtain olive oil. This design includes drawing of block and flow diagram of the full process, selection and justification of safety measures needed and its implementation in the installation through its drawing in the flow diagram. Safety is also strengthened through an activity of safety presentation about an item related to the installation that students should prepare and defense. This work collects and analyses the evolution of the learning level and its deepness into safety and design skills through the analysis of the results obtained along the several control points stablished in EIq3 and PIIQ courses. These control points are: deliverables of academic works at the beginning of EIq3, assessment of design project and written exam at the end of EIq3 and academic results at the end of PIIQ of several academic years. Progressive work along these two consecutive courses in safety and design skills have allowed to obtain a deeper degree of learning in these disciplines and better results in a medium term compared with the previous academic years in which these activities and methodology were not performed in both subjects.García-Fayos, B.; Sancho, M.; Arnal Arnal, JM. (2019). Tracking of learning level on design and safety skills in two core subjects of the chemical engineering degree at UPV. IATED. 6484-6491. https://doi.org/10.21125/inted.2019.1571S6484649

Development of a rubric for the evaluation of "design and project" competence in an experimental subject of chemical engineering degree

[EN] "Experimentation in Chemical Engineering III" is the last experimental core course of the Chemical Engineering Degree at the Universitat Politècnica València (UPV). It is a practical course of 4.5 ECTS which is taught in the 2nd semester of the 3rd year, in which students perform experimental sessions related to the subject "Separation Processes¿ taught in the previous semester. The subject has to work the competence "Design and Project", both in its specific and transversal approach. In order to develop suitably such competence, in 2016 it was requested an ¿Innovation and Education Improvement Project¿ (PIME), through the Institute of Education Sciences of the UPV, with the aim of integrate the Project Oriented Learning (POL) as the main methodology. The Project was implemented during the academic year 2017-2018 and the main objective was to perform experimental sessions to obtain data that would be used in the design project. Transition to POL methodology implied the design and development of new activities [1] and a change in the way that the evaluation was performed. The design project was the main learning product obtained and it is used to assess the development of the ¿Design and project¿ competence in the students. The tool used to evaluate the design project is a rubric. Rubric includes the evaluation criteria and their different levels of achievement and scoring, and allows a more homogeneous assessment by all the lecturers that evaluate the project. This paper describes the development process of the rubric and presents the final version which is currently used in the subject after two years of implementation that includes several changes made. This work will also describe the way that score of each item contributes to the final grade of the project and of the competence. The rubric presented can be applied to other subjects in which similar design projects would be performed, after adapting it to the particular context of each subject.Sancho, M.; García-Fayos, B.; Arnal Arnal, JM. (2019). Development of a rubric for the evaluation of "design and project" competence in an experimental subject of chemical engineering degree. IATED. 6395-6403. https://doi.org/10.21125/inted.2019.1552S6395640

Application of ultrafiltration for drinking water production in decentralised systems: 20 years of the AQUAPOT project

[EN] Access to drinking water is a basic human right which has become an international goal. However, despite the efforts made in the framework of the Millennium Development Goals of the United Nations, about 700 million people are still without access to an adequate source of drinking water in rural areas of developing countries, especially in Africa Sub-Saharan. The AQUAPOT project, developed by the "Instituto Universitario de Seguridad, Radiofisica y Medioambiental (ISIRYM)" of the "Universitat Politecnica de Valencia (UPV)", both in Spain, has been focused research on the design, development and installation of decentralised drinking water systems as an alternative to existing water management systems in developing areas. AQUAPOT systems are based on ultrafiltration technology and have been successfully applied in different localities in Ecuador and Mozambique to produce safe drinking water for human consumption. The present paper describes the main actions carried out within the project AQUAPOT over the last 20 years. It describes the main features of the installed plants and the protocol to choose the best location; it also shows the main results achieved within the project, and discusses the lessons learned throughout the years in relation to the operation of the plants as well as the quality of the treated water.Arnal Arnal, JM.; García-Fayos, B.; Sancho, M. (2018). Application of ultrafiltration for drinking water production in decentralised systems: 20 years of the AQUAPOT project. Desalination and Water Treatment. 103:296-306. https://doi.org/10.5004/dwt.2018.21989S29630610

General approach to the study of vacuum space-times with an isometry

In vacuum space-times the exterior derivative of a Killing vector field is a 2-form (named here as the Papapetrou field) that satisfies Maxwell's equations without electromagnetic sources. In this paper, using the algebraic structure of the Papapetrou field, we will set up a new formalism for the study of vacuum space-times with an isometry, which is suitable to investigate the connections between the isometry and the Petrov type of the space-time. This approach has some advantages, among them, it leads to a new classification of these space-times and the integrability conditions provide expressions that determine completely the Weyl curvature. These facts make the formalism useful for application to any problem or situation with an isometry and requiring the knowledge of the curvature.Comment: 24 pages, LaTeX2e, IOP style. To appear in Classical and Quantum Gravit

Evaluation of macrophage plasticity in brown and white adipose tissue

There are still questions about whether macrophage differentiation is predetermined or is induced in response to tissue microenvironments. C2D macrophage cells reside early in the macrophage lineage in vitro, but differentiate to a more mature phenotype after adoptive transfer to the peritoneal cavity (PEC-C2D). Since C2D macrophage cells also traffic to adipose tissue after adoptive transfer, we explored the impact of white adipose tissue (WAT), brown adipose tissue (BAT) and in vitro cultured adipocytes on C2D macrophage cells. When PEC-C2D macrophage cells were cultured with preadipocytes the cells stretched out and CD11b and Mac-2 expression was lower compared to PEC-C2D macrophage cells placed in vitro alone. In contrast, PEC-C2D cells co-cultured with adipocytes maintained smaller, round morphology and more cells expressed Mac-2 compared to PEC-C2D co-cultured with preadipocytes. After intraperitoneal injection, C2D macrophage cells migrated into both WAT and BAT. A higher percentage of C2D macrophage cells isolated from WAT (WAT-C2D) expressed Ly-6C (33%), CD11b (11%), Mac-2 (11%) and F4/80 (29%) compared to C2D macrophage cells isolated from BAT (BAT-C2D). Overall, BAT-C2D macrophage cells had reduced expression of many cytokine, chemokine and receptor gene transcripts when compared to in vitro grown C2D macrophages, while WAT-C2D macrophage cells and PEC-C2D up-regulated many of these gene transcripts. These data suggest that the C2D macrophage phenotype can change rapidly and distinct phenotypes are induced by different microenvironments

Quasinormal modes for the charged Vaidya metric

The scalar wave equation is considered in the background of a charged Vaidya metric in double null coordinates $(u,v)$ describing a non-stationary charged black hole with varying mass $m(v)$ and charge $q(v)$. The resulting time-dependent quasinormal modes are presented and analyzed. We show, in particular, that it is possible to identify some signatures in the quasinormal frequencies from the creation of a naked singularity.Comment: 4 pages. Prepared for the proceedings of the Spanish Relativity meeting (ERE2010), Granada, Spain, September 6-10, 201

Fluvial geomorphological dynamics and land use changes: impact on the organic carbon stocks of soil and sediment

The drainage basin of the Turrilla river (SE of Spain) went through important land cover changes since 1950s; from mainly an agrarian scenario in 1956 to other depopulated and forested in 2015. This study analyzes the effects of land use changes on fluvial dynamics and their relationship with the organic carbon (OC) stock in fluvial sedimentary deposits as well as in the soil of the basin. Methods included a fluvial geomorphological analysis and a land use change analysis in combination with OC databases of soil and sediment. Results showed that the fluvial channel experienced important morphological changes related to different erosion processes and stabilization of fluvial deposits, induced by land use changes in the drainage area. The active channel decreased 63% in the study period, while bank erosion and gully erosion increased (34% and 21 %, respectively). Alluvial fans and alluvial plain were also extended (21% and 7 %, respectively) and alluvial bars were colonized by vegetation. Sediment was impoverished in OC compared to catchment soils (0.24 enrichment ratio sediment/soil). However the increase of OC stock (Mg ha-1) was very similar between soil (25 %) and sediment (23 %). The total reservoir of OC (Mg) increased 27% in sediments and 25% in the catchment soils. Results show the large influence of geomorphological dynamics on the OC reservoir at the catchment scale. A very high potential of fluvial sediments to increase OC sinks was observed, particularly in scenarios where the active channel is narrowed and the fluvial channel is encroached with vegetation, facilitating the input of OC in sediment. The potential of sediment to sequester organic carbon could be very useful in planning and management of fluvial sedimentary zones in climate change mitigation policies. © 2019, Universidad Austral de Chile. All rights reserved.Este estudio ha recibido apoyo financiero del proyecto DISECO (CGL2014-55405-R) del Plan Nacional de Ciencia del Ministerio de Economía y Competitividad de España, del proyecto SOGLO (P7/24 IAP BELSPO) del gobierno de Bélgica. AHM recibió apoyo financiero para una estancia en la Universidad Nacional de Córdoba (Argentina) del Banco de Santander mediante el Convenio Becas de Intercambio Latinoamérica (Programa ILA). CBF recibió apoyo financiero para dos estancias en el extranjero del programa Salvador de Madariaga 2017 (Ministerio de Educación, Cultura y Deporte, Gobierno de España) y del programa Jiménez de la Espada 2017 (Fundación Séneca, Agencia de Ciencia y Tecnología de la Región de Murcia). MAB fue parcialmente financiada por un contrato Juan de la Cierva-Incorporación (Ref: IJCI-2015-23500). Todas estas estancias permitieron el trabajo continuado en la redacción de este artículo