Assessing temporary speed restrictions and associated unavailability costs in railway infrastructure

This paper analyses the occurrence of temporary speed restrictions in railway infrastructure associated with railway track geometry degradation. A negative binomial regression model is put forward to estimate the expected number of temporary speed restrictions, controlling for the main quality indicators of railway track geometry degradation and for the maintenance and renewal actions/decisions. The prediction of temporary speed restrictions provides a quantitative way to support the assessment of unavailability costs to railway users. A case study on the Lisbon–Oporto Portuguese line is explored, comparing three statistical models: the Poisson, the ‘over-dispersed’ Poisson and the proposed negative binomial regression. Main findings suggest that the main quality indicators for railway track geometry degradation are statistically significant variables, apart from the maintenance and renewal actions. Finally, a discussion on the impacts of the unavailability costs associated with temporary speed restrictions is also provided in a regulated railway context.info:eu-repo/semantics/acceptedVersio

Topological Reverberations in Flat Space-times

We study the role played by multiply-connectedness in the time evolution of the energy E(t) of a radiating system that lies in static flat space-time manifolds M_4 whose t=const spacelike sections M_3 are compact in at least one spatial direction. The radiation reaction equation of the radiating source is derived for the case where M_3 has any non-trivial flat topology, and an exact solution is obtained. We also show that when the spacelike sections are multiply-connected flat 3-manifolds the energy E(t) exhibits a reverberation pattern with discontinuities in the derivative of E(t) and a set of relative minima and maxima, followed by a growth of E(t). It emerges from this result that the compactness in at least one spatial direction of Minkowski space-time is sufficient to induce this type of topological reverberation, making clear that our radiating system is topologically fragile. An explicit solution of the radiation reaction equation for the case where M_3 = R^2 x S^1 is discussed, and graphs which reveal how the energy varies with the time are presented and analyzed.Comment: 16 pages, 4 figures, REVTEX; Added five references and inserted clarifying details. Version to appear in Int. J. Mod. Phys. A (2000

Synergy of farnesol and antibiotics against planktonic versus biofilm cells of Staphylococcus epidermidis

Staphylococcus epidermidis is the most frequent cause of nosocomial sepsis and catheter-related infections, in which biofilm formation is considered to be one of the main virulence mechanisms. Moreover, their increased resistance to conventional antibiotic therapy enhances the need to develop new therapeutical agents. Farnesol, a quorum-sensing molecule in Candida albicans, has been described as impairing bacterial growth. The goal of this study was to evaluate the synergistic effect of farnesol and antibiotics on planktonic and biofilm cells of S. epidermidis strains (1457 and 9142). To accomplish that, three antibiotics with different mechanisms of action were tested: vancomycin (cell wall synthesis inhibitor), tetracycline (Protein synthesis inhibitor) and rifampicin (RNA synthesis inhibitor). A 24 h kinetic study was performed using these antibiotics at the peak serum concentration along with farnesol at concentrations of 30, 100, 200 and 300 μM. To evaluate planktonic cells viability, it was used two tests: a rapid colorimetric method that is based on the reduction of tetrazolium salt (XTT) to measure mitochondrial cellular activity and standard colony forming units enumeration (CFU). The growth inhibition effect of farnesol and/or antibiotics on biofilm cells of S. epidermidis was assessed by XTT, CFU enumeration and Crystal Violet, which measures total biomass of biofilm. In planktonic as well as in biofilm cells, both strains of S. epidermidis studied were much less susceptible to farnesol than to all the antibiotics tested. All the antibiotics were highly effective against planktonic cells. Biofilm cells were much less susceptible than planktonic cultures to vancomycin, tetracycline and rifampicin. In planktonic cells it was not observed a synergistic effect of farnesol and any of the antibiotics used, except for the strain 9142 when treated with vancomycin. In biofilms, there was a synergistic effect of farnesol and all antibiotics, expressed by the reduction of biomass and mitochondrial cellular activity of biofilm cells. The susceptibility of biofilm cells to farnesol and antibiotics was higher when the antibiotic tested was rifampicin, followed by tetracycline and finally by vancomycin

Reforço de edifícios existentes de betão armado com contraventamentos metálicos

Foi calibrado um modelo numérico refinado para a reprodução do comportamento de estruturas existentes de betão armado, e do seu reforço por contraventamento, face a solicitações sísmicas. Estes modelos foram calibrados com base numa série de ensaios

Farnesol as a prospective antimicrobial agent against Staphylococcus epidermidis

Objectives: Staphylococcus epidermidis is now among the most important pathogenic agents responsible for bloodstream nosocomial infections and for biofilm formation on indwelling medical devices. Its increasing resistance to common antibiotics is a challenge for the development of new antimicrobial agents. Accordingly, the goal of this study was to evaluate the effect of farnesol, a natural sesquiterpenoid, on Staphylococcus epidermidis biofilm cells and compare this one with the effect of vancomycin, one of the most frequently used antibiotics to treat resistant nosocomial infections. Another aim of this work was to determine if subjecting S. epidermidis cells to farnesol they acquire resistance. Methods: A 24 h kinetic study was performed using vancomycin at the peak serum concentration (40mg/L) and farnesol at concentrations of 30, 100, 200 and 300 microM. The growth inhibition effect of farnesol and vancomycin on biofilm cells of S. epidermidis was assessed by XTT (the reduction of this tetrazolium salt is a measure of cellular activity and is easily assessed by colorimetry) and Crystal Violet, which measures total biomass of biofilm. The biofilm cells were analysed by confocal laser scanning microscopy after being stained with Live/Dead. Resistance to farnesol and vancomycin was tested growing S. epidermidis planktonic cells in sub-inhibitory concentrations of farnesol and vancomycin and then subjecting these cells to inhibitory concentrations of both antimicrobial agents during 24 hours. After that, cellular activity was assessed by XTT. This was repeated for 5 consecutive days. Results: Both tested agents act at the cell wall level, vancomycin inhibits the biosynthesis of bacterial cell wall, while farnesol is considered to disrupt the normal barrier function of the cell membrane. Interestingly, farnesol at a concentration higher than 200 microM displayed the same or higher effectiveness of vancomycin at peak serum concentration. In fact, the response of the strains tested was very similar for both farnesol (>200 microM) and vancomycin. Regarding cells resistance to farnesol, the results point out to a slight increase of tolerance but not to an acquired resistance, because the percentage of inhibition was steady along the time. Conclusions: Overall, the results indicate a potential antibacterial effect of farnesol against S. epidermidis, and therefore the possible action of this molecule on the prevention of S. epidermidis related infections

Causal Anomalies in Kaluza-Klein Gravity Theories

Causal anomalies in two Kaluza-Klein gravity theories are examined, particularly as to whether these theories permit solutions in which the causality principle is violated. It is found that similarly to general relativity the field equations of the space-time-mass Kaluza-Klein (STM-KK) gravity theory do not exclude violation of causality of G\"odel type, whereas the induced matter Kaluza-Klein (IM-KK) gravity rules out noncausal G\"odel-type models. The induced matter version of general relativity is shown to be an efficient therapy for causal anomalies that occurs in a wide class of noncausal geometries. Perfect fluid and dust G\"odel-type solutions of the STM-KK field equations are studied. It is shown that every G\"odel-type perfect fluid solution is isometric to the unique dust solution of the STM-KK field equations. The question as to whether 5-D G\"odel-type non-causal geometries induce any physically acceptable 4-D energy-momentum tensor is also addressed.Comment: 16 page. LaTex file. To appear in Int. J. Mod. Phys. A (1998

Measurement errors and uncertainty estimation of an experimental set up using a 2D PIV technique

The study of the flow interaction and the heat transfer between air jets and a surface is of paramount importance in industrial processes that apply multiple air jet impingement. To ensure a good performance of the process, high heat transfer rates and uniformization of the flow over the target plate are required. To perform this analysis, a PIV technique was implemented for the measurement of the velocity fields of the flow. However, as any real experiment, the values recorded by the PIV method are subjected to several errors that compromise the reliability and accuracy of the measurements. These errors can have different sources, from the installation and alignment to the particles seeding and calibration procedure. To determine an interval that contains the measurement error, the uncertainty quantification is crucial. In that sense, this paper focus on the identification of measurement errors and uncertainty quantification of an experimental set up specially built for the analysis of the interaction between a non-isothermal jets and non-flat surfaces moving perpendicularly to the jet axis. To ensure the reliability of the results, preliminary tests were performed to guarantee a uniform and stable flow and to determine the range and conditions of operation. In addition, this work presents an analysis of the system, and the source of errors are identified, quantified and, when possible, corrected. The particle seeding, which consists of olive oil droplets, is characterized and its efficiency for the flow tracking is analysed. The test facility was tested to fully characterize the flow field in terms of mean velocity profile and turbulence intensity over a wide range of Reynolds numbers and temperature. Several velocity fields are then measured until convergence of the flow quantities is reached. The combination of these measurements with high spatial resolution and low measurement errors allow to obtain accurate and precise measurement values.Portuguese Foundation for Science and Technology (FCT) through the Research Grant PD/BD/128216/2016. This work has been supported by FCT within the Project Scope UID/CEC/00319/2019 (ALGORITMI) and Project Scope UID/EMS/04077/2019 (METRICS)

Cell adhesion molecules involved in the leukocyte recruitment induced by venom of the snake Bothrops jararaca.

It has been shown that Bothrops jararaca venom (BjV) induces a significant leukocyte accumulation, mainly neutrophils, at the local of tissue damage. Therefore, the role of the adhesion molecules intercellular adhesion molecule-1 (ICAM-1), LECAM-1, CD18, leukocyte function-associated antigen-1 (LFA-1) and platelet endothelial cell adhesion molecule-1 (PECAM-1) on the BjV-induced neutrophil accumulation and the correlation with release of LTB4, TXA2, tumor necrosis factor-alpha, interleukin (IL)-1 and IL-6 have been investigated. Anti-mouse LECAM-1, LFA-1, ICAM-1 and PECAM-1 monoclonal antibody injection resulted in a reduction of 42%, 80%, 66% and 67%, respectively, of neutrophil accumulation induced by BjV (250 microg/kg, intraperitoneal) injection in male mice compared with isotype-matched control injected animals. The anti-mouse CD18 monoclonal antibody had no significant effect on venom-induced neutrophil accumulation. Concentrations of LTB(4), TXA(2), IL-6 and TNF-alpha were significant increased in the peritoneal exudates of animals injected with venom, whereas no increment in IL-1 was detected. This results suggest that ICAM-1, LECAM-1, LFA-1 and PECAM-1, but not CD18, adhesion molecules are involved in the recruitment of neutrophils into the inflammatory site induced by BjV. This is the first in vivo evidence that snake venom is able to up-regulate the expression of adhesion molecules by both leukocytes and endothelial cells. This venom effect may be indirect, probably through the release of the inflammatory mediators evidenced in the present study