Le totémisme chez les indigènes de l’Australie

Les indigènes de l’Australie, dont l’étude a été si négligée jusqu’ici par la Science sociale, ont au contraire été l’objet de nombreux travaux de la part des écoles sociologiques et anthropologiques. C’est que, pour ces dernières, ils ne représenteraient pas seulement un état social simple, mais l’état social primitif par lequel toute l’humanité a dû passer. Si l’on admet ce postulat, on comprend l’intérêt immense que présentent ces sauvages ; c’est chez eux qu’il faut aller pour retrouver l..

Design of three step joint typologies: review of european standardized approaches

When assessing timber roof structures on-site for any restoration project, engineers can be faced with elements that, over time, were poorly preserved, especially damaged joints in contact with moist masonry walls. Before dealing with any intervention technique, the mechanical behaviour of such carpentry connections must be properly understood. Therefore, it has to be determined how the joints fail, which parameters (i.e. geometrical configurations and mechanical properties of the joint) influence the appearance conditions of failure modes, and the way how the internal forces are distributed within the connection. Therefore, the present paper aims at overviewing three different typologies of Step Joints (SJ) which can often be encountered within traditional timber carpentries between the rafter and the tie beam: the Single Step Joint, the Double Step Joint, and the Single Step Joint with Tenon-Mortise. Regarding each SJ typology, some design rules and geometrical recommendations can be gathered from European Standards and from authors of works on the subject, but no design equation is conventionally defined. Hence, new design models have been determined through the Analytical Campaign for the investigated Step Joints according to their geometrical parameters and to both failure modes: the shear crack in the tie beam and the crushing at the front-notch surface. In order to check the reliability of new design models and the emergence conditions of both failure modes, future experiments and numerical analysis on the three SJ typologies are going to be performed.This work was partly financed in the framework of the Portuguese Public Procurement Code, LOTE 3ES2 – Escola Secundária de Loulé e Olhão. This work was financed by FEDER funds through the Competitively Factors Operational Programme – COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of the project PTDC/EPH-PAT/2401/2014 and PhD Scholarships SFRH/BD/128580/2017.info:eu-repo/semantics/publishedVersio

Functional MRI during hippocampal deep brain stimulation in the healthy rat brain

Deep Brain Stimulation (DBS) is a promising treatment for neurological and psychiatric disorders. The mechanism of action and the effects of electrical fields administered to the brain by means of an electrode remain to be elucidated. The effects of DBS have been investigated primarily by electrophysiological and neurochemical studies, which lack the ability to investigate DBS-related responses on a whole-brain scale. Visualization of whole-brain effects of DBS requires functional imaging techniques such as functional Magnetic Resonance Imaging (fMRI), which reflects changes in blood oxygen level dependent (BOLD) responses throughout the entire brain volume. In order to visualize BOLD responses induced by DBS, we have developed an MRI-compatible electrode and an acquisition protocol to perform DBS during BOLD fMRI. In this study, we investigate whether DBS during fMRI is valuable to study local and whole-brain effects of hippocampal DBS and to investigate the changes induced by different stimulation intensities. Seven rats were stereotactically implanted with a custom-made MRI-compatible DBS-electrode in the right hippocampus. High frequency Poisson distributed stimulation was applied using a block-design paradigm. Data were processed by means of Independent Component Analysis. Clusters were considered significant when p-values were <0.05 after correction for multiple comparisons. Our data indicate that real-time hippocampal DBS evokes a bilateral BOLD response in hippocampal and other mesolimbic structures, depending on the applied stimulation intensity. We conclude that simultaneous DBS and fMRI can be used to detect local and whole-brain responses to circuit activation with different stimulation intensities, making this technique potentially powerful for exploration of cerebral changes in response to DBS for both preclinical and clinical DBS

Functional connectivity changes during epileptogenesis: a longitudinal rs-fMRI study

1. INTRODUCTION Temporal lobe epilepsy (TLE) is the most common form of epilepsy in adults. Research has shown that abnormal functional brain networks could be involved in the development of epilepsy and its comorbidities [1]. Gaining more insight into these networks can be useful for the development of new therapies. Resting-state functional magnetic resonance imaging (rs-fMRI) can visualize changes in functional networks on a whole-brain level [2]. In this study, we aim to map changes in functional networks during epileptogenesis in the intraperitoneal kainic acid (IPKA) rat model for TLE using longitudinal resting-state fMRI and graph theory. 2. MATERIALS AND METHODS Twenty-four adult male Sprague-Dawley rats (276 ± 15 g body weight) were used in this study. Seventeen animals were intraperitoneally injected with kainic acid (KA) according to the protocol of Hellier et al. [3] resulting in status epilepticus (SE). The other 7 animals were injected with saline and used as a control group. Rs-fMRI images were acquired before the KA injections and at 5 time points during the development of epilepsy. At each time point an anatomical image and three resting-state fMRI images were acquired on a 7T system, while the animals were anesthetized with medetomidine. The fMRI images were corrected for slice timing and motion, normalized, smoothed and band-pass filtered using SPM12. The Pearson correlation coefficient was calculated between the fMRI time series of 38 regions of interest (ROIs) and stored in a correlation matrix. After applying different thresholds to remove the weakest connections, several network measures were calculated using a graph theoretical network analysis toolbox (GRETNA), and plotted as a function of time to visualize how the properties of the functional networks change during epileptogenesis. 3. RESULTS AND DISCUSSION In the IPKA rat model the correlation coefficients shift to smaller values during epileptogenesis, indicating that network connections progressively become weaker. Clustering coefficient and local efficiency decrease during epileptogenesis, indicating a decrease in segregation or local interconnectivity in the functional brain network. Characteristic path length increases and global efficiency decreases during epileptogenesis, indicating a decrease in integration or overall communication efficiency. In the next phase of this study, EEG monitoring will be used to characterize the severity of epilepsy in these rats to investigate how changes in functional brain networks during epileptogenesis correlate with epilepsy severity