9,981 research outputs found

    The Kovacs effect in the one-dimensional Ising model: a linear response analysis

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    We analyze the so-called Kovacs effect in the one-dimensional Ising model with Glauber dynamics. We consider small enough temperature jumps, for which a linear response theory has been recently derived. Within this theory, the Kovacs hump is directly related to the monotonic relaxation function of the energy. The analytical results are compared with extensive Monte Carlo simulations, and an excellent agreement is found. Remarkably, the position of the maximum in the Kovacs hump depends on the fact that the true asymptotic behavior of the relaxation function is different from the stretched exponential describing the relevant part of the relaxation at low temperatures.Comment: accepted for publication in Phys. Rev.

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

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    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

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    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

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    We determine the effect of Lorentz invariance violation in the vacuum energy and stress between two parallel plates separated by a distance LL, in the presence of a massive real scalar field. We parametrize the Lorentz-violation in terms of a symmetric tensor hμνh^{\,\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 Fc(L)=F0(L~)/dethμν\mathcal{F}_c(L)=\mathcal{F}_0(\tilde{L})/\sqrt{-{\rm det}\, h^{\,\mu\nu}}, where F0\mathcal{F}_0 is the Lorentz-invariant expression, and L~\tilde{L} is the plate separation rescaled by the component of hμνh^{\,\mu\nu} normal to the plates, L~=L/hnn\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

    Rapid determination of salbutamol in pharmaceutical preparations by chiral capillary electrophoresis

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    A fast and simple method of chiral capillary electrophoresis (CE) has been applied to the analysis of salbutamol in different pharmaceutical preparations. Using of a 25 mM acetate buffer (pH 5.0), containing 13.1 mg/mL carboxymethyl- -cyclodextrin (CM- -\ud CD), an applied voltage of 20 kV and a temperature of 25 C, the enantiomers of salbutamol could be separated in about 2 min. Three different pharmaceutical preparations (two syrups, one oral solution, and two kind of tablets) containing a racemate of salbutamol\ud were injected directly in the CE system, following dilution in dimethyl sulfoxide\ud (DMSO). Appreciable differences in the retention times were observed for salbutamol enantiomers in the different formulations studied, which were attributed to the effect of the matrix components on the electrophoretic mobility. The standard addition method\ud was used for the calibration due to the existence of matrix interferences. Finally, the stability of the enantiomers of salbutamol in the oral solution was studied calculating the enantiomeric ratio values when the solution was injected immediately after being opened in the first case and after being opened and stored in the fridge for two months in the second case

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

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    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
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