The cyclical trend of local public service governance: evidence from urban water management in Spain

The level of public and private involvement in economic activity in societies has changed over time. One may talk about the existence of a cyclical trend in which the most important periods of public governance are replaced by periods in which private management dominates the situation. This phenomenon may also be observed in local areas. Some authors have pointed out the existence of an alternation in the provision of municipal services, resulting in periods dominated by governance compared to other stages dominated by private management. In order to illustrate this cyclical trend at local level, this paper intends to analyze the evolution of the governance of the Spanish water supply since the mid-nineteenth century to the present day. Recent evidence from the industry suggests the possibility that we may currently be witnessing a further change in the trend.: Local Government, urban water supply, privatization, municipalization

Assessment of the periodontal health status and gingival recession during orthodontic treatment with clear aligners and fixed appliances: A systematic review and meta-analysis

Background: The aim was to assess periodontal health maintenance and gingival recessions development in pa-tients undergoing an orthodontic treatment with clear aligners (CA) and fixed appliances (FA).Material and Methods: An electronic search in MEDLINE, Scopus, The Cochrane Library, and Web of Science was performed up to September 2022 to identify all potential articles. Two investigators independently selected the studies according to the inclusion criteria. Prospective and retrospective studies assessing the periodontal health status and gingival recession development during the orthodontic treatment with buccal FA and CA were included. Case series, cross-sectional studies, and studies with less than two months of follow-up were excluded. Two investigators independently extracted the data from included articles and assessed risk of bias across studies using the Cochrane Collaboration tool. Qualitative and quantitative analyses of the data were performed. Pairwise meta-analysis using a random-effects model were used to compare periodontal indices between FA and CA treat-ment in different follow-up periods.Results: From the 129 potential studies, finally 12 studies were included. Only 8 could be included in the quantita-tive analysis. CA seems to slightly maintain better periodontal health indices. Only plaque index in a mid-term follow-up (mean difference (MD):-0.99; 95%; Confidence interval (CI) [-1.94 to-0.03]; P=.04; I2=99%), and pocket probing depth at a long-term follow-up (MD: -0.93mm; 95% CI [-1.16 to 0.7]; P<0.0001) reported statisti-cally significant results favoring CA.Conclusions: Up to the date there is not enough evidence to conclude that CA maintains better periodontal health during an orthodontic treatment than FA

A non-perturbative approach to the scalar Casimir effect with Lorentz symmetry violation

We determine the effect of Lorentz invariance violation in the vacuum energy and stress between two parallel plates separated by a distance $L$, in the presence of a massive real scalar field. We parametrize the Lorentz-violation in terms of a symmetric tensor $h^{\,\mu\nu}$ that represents a constant background. Through the Green's function method, we obtain the global Casimir energy, the Casimir force between the plates and the energy density in a closed analytical form without resorting to perturbative methods. With regards to the pressure, we find that $\mathcal{F}_c(L)=\mathcal{F}_0(\tilde{L})/\sqrt{-{\rm det}\, h^{\,\mu\nu}}$, where $\mathcal{F}_0$ is the Lorentz-invariant expression, and $\tilde{L}$ is the plate separation rescaled by the component of $h^{\,\mu\nu}$ normal to the plates, $\tilde{L}=L/\sqrt{-h^{nn}}$. We also analyze the Casimir stress including finite-temperature corrections. The local behavior of the Casimir energy density is also discussed.Comment: 6 pages, No figure

Teaching mathematical modeling software for multiobjective optimization in chemical engineering courses

This paper expects to give undergraduate students some guidelines about how to incorporate environmental considerations in a chemical supply chain and how the introduction of these concerns have an important effect on the results obtained in the multiobjective optimization problem where both economic and environmental aspects are considered simultaneously. To extend the economic and environmental assessment outside the chemical plant and to identify the tradeoffs associated with the reality of chemical and petrochemical industries, a simplified problem of a chemical supply chain is proposed as a case study. The inclusion of environmental concerns to this economic problem make this new case study a good example for undergraduate students interested in implementing simultaneous economic and environmental considerations in the chemical process design incorporating mathematical modeling software for solving this multiobjective problem. Thus, the final objective of this paper is to show to undergraduate students how environmental together with economic considerations could have an important impact in the logistics of a supply chain and how multiobjective optimization could be used to make better decisions in the design of chemical processes including its supply chain. To reach our purpose, the Pareto curve of the supply chain is obtained using the ɛ-constraint method. In addition, the tradeoffs of this multiobjective optimization have been identified and analyzed and ultimately a good decision based on the set of ‘equivalent’ optimal solutions for this chemical supply chain problem determined.Spanish Ministry of Education and Science (CTQ2009-14420)

Performance assessment and modeling of an SWRO pilot plant with an energy recovery device under variable operating conditions

This research was co-funded by the ERDF and the ACLIEMAC Project (MAC2/3.5b/380) of the INTERREG V-A MAC 2014-2020 program.Reverse osmosis (RO) is one of the most widespread desalination technologies in use today due to its good performance and reliability. Given that it is an energy intensive technology, using variable renewable energy sources (VRES) to power RO systems is an interesting option. Work with the RO system under variable operating conditions is one of the strategies that can be employed to take advantage of all the energy that is available at any given time from an off-grid renewable system. However, this will entail additional challenges in terms of, among other factors, plant maintenance and permeate production rate and quality. In grid-connected seawater RO (SWRO) desalination plants, energy recovery devices (ERD) are commonly used to increase energy efficiency performance. In these cases, the ERD usually operates under constant operating conditions. This work aims to assess the performance of an SWRO system with an ERD under widely variable operating conditions. The SWRO system has six membrane elements in pressure vessels. The ERD is a Pelton turbine connected to a generator to measure the energy produced by the turbine. An artificial neural network (ANN) based model was developed to estimate the performance of the SWRO-ERD system under variable operating conditions. According to the results, power savings of between 2.9 and 6.08 kW can be achieved for a wide range of operating conditions, allowing an increase in the produced permeate flux (Qp). The proposed ANN-based model is able to estimate Qp and permeate electrical conductivity with error intervals of 1.56 x 10-6 -8.49 x 10-2 m3 h-1 and 8.33 x 10-5 -31.06 mu S cm-1, respectively. The experimental data and the developed model could help to obtain a better performance pre-diction of VRES-powered SWRO systems that are operating under variable operating conditions and with ERDs.Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUEEuropean Regional Development Fund (ERDF)ACLIEMAC Project of the INTERREG V-A MAC 2014-2020 programpu