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With the increases in traffic, axle loads and travelling speed, the dynamic monitoring of railway tracks and structures is becoming more and more important to ensure a high level of safety and comfort. This situation is particularly critical at transition zones where rapid changes of track stiffness occur. This paper presents a contactless system to measure track displacements and its application in an embankment/underpass transition zone, located on the Northern line of the Portuguese railway network where the Alfa Pendular tilting train travels at a maximum speed of 220 km/h. The system is based on a diode laser module and a position sensitive detector (PSD). The PSD receives the laser beam emission and the detection of the centre of gravity of the beam spotlight on the PSD area enables the calculation of the displacement. Before field application, static and dynamic laboratory validation tests were performed in order to evaluate the system performance for different laser to PSD distances, and an accuracy of 0.01 mm was achieved using data acquisition rates of up to 15 kHz. The optical measuring system proved to be an efficient and flexible way to measure absolute and relative rail displacements in the field, enabling the detection of track deformability differences along the transition zone, even for the passage of trains at high speed (220 km/h).

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Background and objective: Studies have shown that the rate of propofol infusion may influence the predicted propofol concentration at the effect site (Es). The aim of this study was to evaluate the Es predicted by the Marsh pharmacokinetic model (ke0 0.26 min −1 ) in loss of consciousness during fast or slow induction. Method: The study included 28 patients randomly divided into two equal groups. In slow induction group (S), target-controlled infusion (TCI) of propofol with plasma, Marsh pharmacokinetic model (ke0 0.26 min −1 ) with target concentration (Tc) at 2.0-g mL −1 were administered. When the predicted propofol concentration at the effect site (Es) reached half of Es value, Es was increased to previous Es + 1 g mL −1 , successively, until loss of consciousness. In rapid induction group (R), patients were induced with TCI of propofol with plasma (6.0 g mL −1 ) at effect site, and waited until loss of consciousness.Results: In rapid induction group, Tc for loss of consciousness was significantly lower compared to slow induction group (1.67 ± 0.76 and 2.50 ± 0.56 g mL −1 , respectively, p = 0.004). Conclusion: The predicted propofol concentration at the effect site for loss of consciousness is different for rapid induction and slow induction, even with the same pharmacokinetic model of propofol and the same balance constant between plasma and effect site.Estudo comparativo entre indução rápida e lenta de propofol em infusão alvo-controlada: concentração de propofol prevista no local de ação. Ensaio clínico aleatório Resumo Justificativa e objetivo: Estudos mostraram que a taxa de infusão de propofol pode influenciar na concentração prevista de propofol no local de ação (Ce). O objetivo deste estudo foi avaliar a Ce prevista pelo modelo farmacocinético de Marsh (ke0 0,26 min −1 ) na perda da consciência durante indução rápida ou lenta. Método: Participaram deste estudo 28 pacientes, divididos aleatoriamente em dois grupos iguais. No grupo indução lenta (L), foram induzidos com propofol em infusão alvo-controlada (IAC) plasmática, modelo farmacocinético de Marsh (ke0 0,26 min −1 ), com concentração alvo (Ca) em 2,0 g.ml −1 . Quando a concentração de propofol prevista no local de ação (Ce) atingia metade do valor da Ca, aumentava-se a Ca para Ca anterior + 1 g.ml −1 . Assim sucessivamente até o momento da perda da consciência do paciente. No grupo indução rápida (R), os pacientes foram induzidos com propofol em IAC plasmática com Ca em 6,0 g.ml −1 e aguardava-se a perda da consciência do paciente. Resultados: No grupo indução rápida, a Ce na perda da consciência foi significativamente mais baixa em relação ao grupo de indução lenta (1,67 ± 0,76 e 2,50 ± 0,56 g.ml −1 , respectivamente, p = 0,004). Conclusão: A concentração prevista de propofol no local de ação durante a perda da consciência é diferente numa indução rápida e numa indução lenta, até com o mesmo modelo farmacocinético de propofol e a mesma constante de equilíbrio entre o plasma e o local de ação.