Effect of spacing and skew-angle on clear-water scour at pier alignments

Pier alignments, defined as single-row pier groups, displayed normal to main bridges’ axes, are frequently used to support bridge decks. Different alignments configurations, characterized by different combinations of piers’ shape and spacing and skew-angle of the alignment to the flow direction, lead to different interactions with the flow field and to different scour depths. Twenty six long lasting – 7 to 15 days – laboratory experiments were run under steady clear-water flow conditions, close to the threshold condition of beginning of sediment motion, to address the effect of pier spacing and skew-angle on the equilibrium scour depth. Alignments consisted of four cylindrical piers spaced of 1, 2, 3, 4.5 and 6 pier diameters; tested skew-angles were 0◦, 15◦, 30◦, 45◦ and 90◦. The main contribution of the paper derives from the long duration of the experiments. The functional relation of issued equilibrium scour depth with pier spacing and skew-angle is established and the dependence of the traditional group correction factor on the same variables is defined

Erosões localizadas junto de alinhamentos de pilares cilindricos

É conhecido o facto de os pilares fundados em leitos aluvionares poderem dar origem a cavidades de erosão que, em circunstâncias excepcionais, induzem a queda desses pilares e o colapso ou a rotura parcial das pontes em que se integram. A previsão da profundidade de equilíbrio de cavidades de erosão constitui-se, por isso, num aspecto importante do projecto de pontes. Este desiderato, não sendo de concretização trivial para pilares isolados, é mais complexo no caso de alinhamentos de pilares, em face das interacções de vórtices e da interdependência de cavidades de erosão que tais alinhamentos originam. Este estudo centra-se na caracterização de cavidades de erosão junto de alinhamentos de pilares constituídos por quatro pilares cilíndricos. Analisa-se, em concreto, o efeito do espaçamento entre pilares e o efeito do ângulo de enviesamento. O estudo foi realizado para a situação mais desfavorável de profundidade e de velocidade do escoamento de aproximação, definida para a condição de início de movimento do material do fundo. Concluiu-se que, para ângulos de enviesamento de 0º e 15º, a profundidade de erosão é cerca de 15% superior à que se observa num pilar isolado e quase não varia com o espaçamento. Em contrapartida, para ângulos de 30º, 45º e 90º, as cavidades de erosão são sucessivamente menos profundas à medida que o espaçamento aumenta. Para espaçamentos (entre eixos de pilares) iguais ou superiores a seis vezes o diâmetro dos pilares, a profundidade de erosão é praticamente independente do ângulo de enviesamento. Quando o espaçamento é igual ao diâmetro do pilar, os alinhamentos podem ser tratados como um pilar de secção rectangular e topos arredondados que envolva os pilares justapostos; excluindo esta situação de espaçamento, as maiores profundidades de erosão obtêm-se para o ângulo de enviesamento de 30º. Pôde constatar-se que existem métodos de cálculo da profundidade de erosão para alinhamentos de pilares que podem conduzir a previsões largamente por defeito

Clear-water scour at pile groups

Groups of piles are frequently used as bridge foundations. Different group configurations, characterized by different pile spacing, skew-angle, number, and arrangement of pile group columns interact differently with the flow field and lead to different scour patterns and equilibrium scour depth. There have been a number of past studies on the characterization of scouring at pile groups, but most of them report short duration scour experiments. A priori, such short durations may be postulated to inherently carry important uncertainties into existing scour predictors. In this study, 75 long-duration laboratory tests were run under steady, clear-water flow close to the threshold for initiation of sediment motion, to address the effect of time, pile spacing, skew-angle and number of pile group columns on the equilibrium scour depth. Pile groups consisted of matrical arrangements of one, two, or three columns of four rows, with spacings of 1, 2, 3, 4.5, and 6 pile diameters; the tested skew-angles were 0, 15, 30, 45, and 90°. Important contributions were achieved on (1) the impact of the duration of tests on the shape of the scour hole as well as on the precision of coefficients involved in current predictors, (2) the most unfavorable skew angle, (3) the behavior of collapsed pile groups, (4) the maximum scour depth at pile groups composed of a single alignment, and (5) the performance of two current predictors of scour depth at pile groups. Two formulations of a predictor for the calculation of an aggregated pile group factor are suggested

Planeamento da manutenção preventiva usando algoritmos genéticos

Dadas as dificuldades intrínsecas à elaboração de planos de manutenção preventiva adequados à utilização dos equipamentos, este artigo apresenta uma metodologia baseada no critério do custo mínimo para determinar os intervalos óptimos de manutenção preventiva em função da utilização do equipamento. A optimização do modelo desenvolvido foi realizada recorrendo à utilização de algoritmos genéticos, tendo a sua implementação sido efectuada utilizando a plataforma computacional Matlab. Para facilitar a interface entre o utilizador e a plataforma computacional implementada foi desenvolvida uma interface gráfica utilizando a ferramenta de interface visual (GUIDE) disponível na plataforma computacional Matlab. Com o objectivo de avaliar a robustez da metodologia proposta, foi utilizado como caso de estudo um equipamento chiller condensado a ar, responsável pela climatização de uma escola secundária, sendo apresentados os correspondentes resultados obtidos e efectuada a sua análise crítica. Os resultados obtidos permitem antever o sucesso da metodologia proposta na definição de planos de manutenção preventiva de equipamentos em função da sua utilização, minimizando o seu custo. Given the inherent difficulties of develop preventive maintenance plans appropriate to the use of equipment, this paper presents a methodology based on the minimum cost criterion for determining the optimal intervals of preventive maintenance as a function of the equipment use. The optimization of the model developed was carried out through the use of genetic algorithms, and their implementation was performed using the computing platform Matlab. To facilitate the interface between the user and the computer platform implemented a graphical user interface was developed using the visual interface tool (GUIDE) available in the Matlab computing platform. In order to assess the robustness of the proposed methodology, it was used as a case study a condensed chiller equipment to air, responsible for the air conditioning of a secondary school and presented the corresponding results obtained and made its critical analysis. The results obtained allow us to predict the success of the proposed methodology in the definition of preventive maintenance plans of equipment depending on its use, minimizing its cost.info:eu-repo/semantics/publishedVersio

Excitotoxic lesions in the central nucleus of the amygdala attenuate stress-induced anxiety behavior

The extended amygdala, composed by the amygdaloid nuclei and the bed nucleus of the stria terminalis (BNST), plays a critical role in anxiety behavior. In particular, the link between the central nucleus of the amygdala (CeA) and the BNST seems to be critical to the formation of anxiety-like behavior. Chronic unpredictable stress (CUS) exposure is recognized as a validated animal model of anxiety and is known to trigger significant morphofunctional changes in the extended amygdala. Quite surprisingly, no study has ever analyzed the role of the CeA in the onset of stress-induced anxiety and fear conditioning behaviors; thus, in the present study we induced a bilateral excitotoxic lesion in the CeA of rats that were subsequently exposed to a chronic stress protocol. Data shows that the lesion in the CeA induces different results in anxiety and fear-behaviors. More specifically, lesioned animals display attenuation of the stress response and of stress-induced anxiety-like behavior measured in the elevated-plus maze (EPM) when compared with stressed animals with sham lesions. This attenuation was paralleled by a decrease of stress-induced corticosterone levels. In contrast, we did not observe any significant effect of the lesion in the acoustic startle paradigm. As expected, lesion of the CeA precluded the appearance of fear behavior in a fear-potentiated startle paradigm in both non-stressed and stressed rats. These results confirm the implication of the CeA in fear conditioning behavior and unravel the relevance of this brain region in the regulation of the HPA axis activity and in the onset of anxiety behavior triggered by stress.Ana P. Ventura-Silva, Ana C. Ferreira, Miguel M. Carvalho and Filipa L. Campos were supported by Fundação para a Ciência e Tecnologia (FCT) grants

Variable delay-to-signal: a fast paradigm for assessment of aspects of impulsivity in rats

Testing impulsive behavior in rodents is challenging and labor-intensive. We developed a new behavioral paradigm-the Variable Delay-to-Signal (VDS) test-that provides rapid and simultaneous assessment of response and decision impulsivity in rodents. Presentation of a light at variable delays signals the permission for action (nose poke) contingent with a reward. 2 blocks of 25 trials at 3 s delay flank a block of 70 trials in which light is presented with randomly selected 6 or 12 s delays. Exposure to such large delays boosts the rate of premature responses when the delay drops to 3 s in the final block, an effect that is blunted by an acute methamphetamine challenge and that correlates with the delay-discounting (DD) paradigm (choice impulsivity). Finally, as expected, treatment with the NMDA antagonist MK-801 caused a generalized response increase in all VDS blocks. The pharmacological validation, particularly with methamphetamine which has a well established dual effect on response and decision impulsivity, and the correlations between the impulsive behavior in the DD and VDS paradigms, suggests that the later is able to provide, in a single session, a multi-dimensional assessment of impulsive behavior.The work wa ssupported by a fellowship “SFRH/BPD/80118/2011” funded by FCT—Portuguese Foundation for Science and Technology and by FEDER funds through Operational program for competitivity factors—COMPETE and by national funds through FCT—Foundation for Science and Technology to projects PTDC/SAU-NEU/108557/2008 and PTDC/SAUNSC/111814/2009

Clear-water scour at comparatively large cylindrical piers

New long-duration clear-water scour data were collected at single cylindrical piers with the objective of investigating the effect of sediment coarseness, Dp=D50 (Dp = pier diameter; D50 = median grain size) on the equilibrium scour depth and improving the scour depth time evolution modeling by making use of the exponential function suggested in the literature. Experiments were carried out for the flow intensity close to the threshold condition of initiation of sediment motion, imposing wide changes of sediment coarseness and flow shallowness, d=Dp (d = approach flow depth). The effect of sediment coarseness on the equilibrium scour depth was identified; existing predictors were modified to incorporate this effect for U=Uc ≈ 1.0; Dp=D50 > ≈60 and d=Dp ≥ 0.5; the complete characterization of a known scour depth time evolution model was achieved for U=Uc ≈ 1.0, 60 < Dp=D50 < 500 and 0.5 ≤ d=Dp ≤ 5.0

Behavioral characterization of the 6-hydroxidopamine model of Parkinson's disease and pharmacological rescuing of non-motor deficits

BACKGROUND: Parkinson's disease (PD) is a chronic neurodegenerative condition that is characterized by motor symptoms as a result of dopaminergic degeneration, particularly in the mesostriatal pathway. However, in recent years, a greater number of clinical studies have focused on the emergence of non-motor symptoms in PD patients, as a consequence of damage on the mesolimbic and mesocortical dopaminergic networks, and on their significant impact on the quality of life of PD patients. Herein, we performed a thorough behavioral analysis including motor, emotional and cognitive dimensions, of the unilateral medial forebrain bundle (MFB) 6-hydroxidopamine (6-OHDA)-lesioned model of PD, and further addressed the impact of pharmacological interventions with levodopa and antidepressants on mood dimensions. RESULTS: Based on apomorphine-induced turning behaviour and degree of dopaminergic degeneration, animals submitted to MFB lesions were subdivided in complete and incomplete lesion groups. Importantly, this division also translated into a different severity of motor and exploratory impairments and depressive-like symptoms; in contrast, no deficits in anxiety-like and cognitive behaviors were found in MFB-lesioned animals. Subsequently, we found that the exploratory and the anhedonic behavioural alterations of MFB-lesioned rats can be partially improved with the administration of both levodopa or the antidepressant bupropion, but not paroxetine. CONCLUSIONS: Our results suggest that this model is a relevant tool to study the pathophysiology of motor and non-motor symptoms of PD. In addition, the present data shows that pharmacological interventions modulating dopaminergic transmission are also relevant to revert the non-motor behavioral deficits found in the disease.We would like to acknowledge the funds attributed by Fundacao Calouste de Gulbenkian to A.J. Salgado under the scope of the The Gulbenkian Program to Support Research in the Life Sciences, and Portuguese Foundation for Science and Technology: Ciencia 2007 Program to A.J. Salgado; the PhD scholarships to M. M. Carvalho (SFRH/BD/51061/2010) and F. L. Campos (SFRH/BD/47311/2008), and the Post-Doctoral Fellowship to A.J. Rodrigues (SFRH/BPD/33611/2009) We want to further acknowledge Carina Cunha, Fabio Teixeira, Joao Bessa and Joao Cerqueira for their contribution to this work

Exposure to Ketamine Anesthesia Affects Rat Impulsive Behaviour

Introduction: Ketamine is a general anesthetic (GA) that activates several neurotransmitter pathways in various part of the brain. The acute effects as GA are the most well-known and sought-after: to induce loss of responsiveness and to produce immobility during invasive procedures. However, there is a concern that repeated exposure might induce behavioral changes that could outlast their acute effect. Most research in this field describes how GA affects cognition and memory. Our work is to access if general anesthesia with ketamine can disrupt the motivational behavior trait, more specifically measuring impulsive behavior. Methods: Aiming to evaluate the effects of exposure to repeat anesthetic procedures with ketamine in motivational behavior, we tested animals in a paradigm of impulsive behavior, the variable delay-to-signal (VDS). In addition, accumbal and striatal medium spiny neurons morphology was assessed. Results: Our results demonstrated that previous exposure to ketamine deep-anesthesia affects inhibitory control (impulsive behavior). Specifically, ketamine exposed animals maintain a subnormal impulsive rate in the initial periods of the delays. However, in longer delays while control animals progressively refrain their premature unrewarded actions, ketamine-exposed animals show a different profile of response with higher premature unrewarded actions in the last seconds. Animals exposed to multiple ketamine anesthesia also failed to show an increase in premature unrewarded actions between the initial and final periods of 3 s delays. These behavioral alterations are paralleled by an increase in dendritic length of medium spiny neurons of the nucleus accumbens (NAc). Conclusions: This demonstrates that ketamine anesthesia acutely affects impulsive behavior. Interestingly, it also opens up the prospect of using ketamine as an agent with the ability to modulate impulsivity trait.Fundação para a Ciência e Tecnologia (FCT) grant SFRH/SINTD/60126/2009info:eu-repo/semantics/publishedVersio