Science for society

Chapter 8 presents an introduction and sections on: education and outreach in an interdisciplinary environment; science with and for the citizens; open communication and responsible citizens; science and ethics; the limits of scienc

Performance of the ATLAS electromagnetic calorimeter end-cap module 0

The construction and beam test results of the ATLAS electromagnetic end-cap calorimeter pre-production module 0 are presented. The stochastic term of the energy resolution is between 10% GeV^1/2 and 12.5% GeV^1/2 over the full pseudorapidity range. Position and angular resolutions are found to be in agreement with simulation. A global constant term of 0.6% is obtained in the pseudorapidity range 2.5 eta 3.2 (inner wheel)

... Huius de iure publico disceptationis defensionem ... ad consequenda ex utriusq. iuris peritia doctoralia privilegia atq. insig. suscipiet

Franciscus Rosellus Bruntrutensis. XXI. Ianuar. hora & loco solitisLetztes Blatt unbedrucktEnthält 79 ThesenDiss. iur. Basel, 160

Growth and characterization of fullerene nanocrystals on NaCl/Au(111)

The growth of fullerene nanocrystals, composed of only C(60), only C(70), or a mixture of both fullerenes, has been investigated by scanning tunneling microscopy (STM). The nanocrystals, formed on a NaCl ultrathin layer partially covering a Au(111) surface, have characteristic truncated-triangular or hexagonal shapes, with lateral size up to 100 nm and a typical height of two to four molecular layers. This growth mode differs considerably from the ones observed on metallic surfaces. STM images with bias-dependent submolecular resolution reveal the spatial distribution of the electronic density originating from the molecular orbitals. A comparison of the experimental results with first-principles density functional theory calculations allows us to unambiguously determine the orientation and the nature of individual fullerene molecules in the surface layer of the nanocrystals

Du vécu des personnalités dites psychopathiques à travers le Rorschach

Merceron Colette, François Perron, Rossel Frieda, Viloux Donatella. Du vécu des personnalités dites psychopathiques à travers le Rorschach. In: Bulletin de psychologie, tome 32 n°339, 1979. Psychologie clinique III. pp. 283-289

A measure of cortico-cortical potentials evoked by 10Hz direct electrical stimulation of the brain and by means of a differential recording mode of electrocorticographic signals

International audienceDirect electrical stimulation (DES) at 60 Hz is used to perform real-time functional mapping of the brain during wide-awake neurosurgery. The electrophysiological effects of DES are largely unknown, locally and at a more remote distance. Here, by lowering the DES frequency to 10 Hz and by using a differential recording mode of electro-corticographic (ECoG) signals to improve the focality, we were able to record cortico-cortical evoked potentials easily with standard current amplitude of stimulation (2 mA). DES applied at 10 Hz and differential recording of ECoG could be used to map on-line the connectivity between different sub-cortical and cortical areas with a higher spatial accuracy

How far does electrical stimulation activate white matter tracts? A computational modeling study

International audienceObjective: The aim of this study was to model how the different parameters of electrical stimulation (intensity, pulse shape, probe geometry) influence the extent of white matter activation.Methods: The electrical potentials generated by the stimulating electrodes were determined by solving Laplace equation. The temporal evolution of membrane potentials at each nodes of Ranvier of an axon was then computed by solving the coupled system of differential equations describing membrane dynamics and cable propagation.Results: Regions of unilateral propagation were observed for monophasic pulses delivered with a bipolar probe aligned along the tract. For biphasic pulses, the largest activation areas and depths were found with a high inter-electrode-distance (IED) bipolar probe, oriented orthogonally to the tract. The smallest activation areas and depths were found for bipolar stimulations with the probe aligned parallel to the tract and low IED. For isotropic white matter regions, the activation area and depth were three times larger than for anisotropic white matter tracts.Conclusions: Bipolar probes with biphasic pulses offer the greatest versatility: an orthogonal orientation acts as two monopolars (increased sensitivity when searching for a tract), whereas a parallel orientation corresponds to a single monopolar (increased specificity). Activation is more superficial when stimulating highly anisotropic tracts.Significance: This knowledge is essential for interpreting the behavorial effects of stimulation and the recordings of axono-cortical evoked potentials

The orientation of the stimulating bipolar probe modulates axono-cortical evoked potentials

International audienceDirect electrical stimulation (DES) can be applied on cortical areas and white matter pathways (WMP) for brain mapping

The difference between electrical microstimulation and direct electrical stimulation – towards new opportunities for innovative functional brain mapping?

International audienceBoth electrical microstimulation (EMS) and direct electrical stimulation (DES) of the brain are used to perform functional brain mapping. EMS is applied to animal fundamental neuroscience experiments, whereas DES is performed in the operating theatre on neurosurgery patients. The objective of the present review was to shed new light on electrical stimulation techniques in brain mapping by comparing EMS and DES. There is much controversy as to whether the use of DES during wideawake surgery is the ‘gold standard’ for studying the brain function. As part of this debate, it is sometimes wrongly assumed that EMS and DES induce similar effects in the nervous tissues and have comparable behavioural consequences. In fact, the respective stimulation parameters in EMS and DES are clearly different. More surprisingly, there is no solid biophysical rationale for setting the stimulation parameters in EMS and DES; this may be due to historical, methodological and technical constraints thathave limited the experimental protocols and prompted the use of empirical methods. In contrast, the gap between EMS and DES highlights the potential for new experimental paradigms in electrical stimulation for functional brain mapping. In view of this gap and recent technical developments in stimulator design, it may now be time to move towards alternative, innovative protocols based on the functional stimulation of peripheral nerves for which a more solid theoretical grounding exists)

Electrophysiological Effects of Direct Electrical Stimulations During Awake Brain Surgery: Methodological Considerations

International audienceIRECT electrical stimulation (DES) has long been used to perform real-time functional mapping of the brain. More recently, this technique was introduced in the neurosurgery of slow-growing and infiltrative brain tumors to guide the resection with great success. By generating transient perturbations, this method allows the real-time identification of both cortical areas and subcortical networks that are essential for the function. Thus, as much as possible, non-functional tissue can be removed while minimizing the sequelae. However, the understanding of the electrophysiological effects of DES and, in particular its remote propagation, remains an open and key question. DES can be used to probe on-line and in-vivo the spatio-temporal connectivity and the dynamics of functional networks by associating electrophysiological recordings. Such methodology has been performed using electrocorticography (ECoG) and implanted grids on the surface of grey matter for pre-surgical planning of drug resistant epileptic patients. Some of these results suggest a local cortico-cortical propagation of evoked potentials (EPs) with DES. However, the propagation through subcortical pathways and at distant sites needs more direct evidences. To investigate more remote effects of DES (i.e. cortico-subcortico-cortical EPs), electroencephalographic (EEG) recordings would be of some interest. Intra-operative EEG recordings were studied to analyze if and how stimulation currents spread at distant sites and more especially if they can be perceptible in the " controlesional " hemisphere. In other words, does DES induce EPs? Does DES modify the frequency contents included in the natural activity of the brain? We also aimed to measure the effects of DES on functional connectivity, i.e. to determine if DES modifies the correlation between the different EEG signals between the pre, intra and post-DES phases. To our knowledge, this approach has never been performed. Data were collected during an awake brain surgery (without interfering with the surgical routine) for one patient harboring a right frontal hemisphere tumor and under local anesthesia. Neural activity was recorded from the surface of the skull (EEG, sampling frequency of 2048 Hz) on 4 sites (3 controlesional sites: F3, C3 and O1 and 1 ipsilesional site: O2; the lesion was centered on F4, Fp2 and F8). DES was delivered with a bipolar electrode using standard parameters (biphasic square pulse, 60 Hz, ~ 2 mA). First we tried to measure EPs when DES is applied cortically and subcortically. To maximize the EPs while minimizing the noise and the artifacts, EEG signals were synchronized and averaged upon a given time window (500 ms). The phases when DES is applied can be recognized by the appearance of artefacts on the natural EEG activity. However, whereas EPs have been observed in ECoG [2, 3], no EP was detected in our EEG data. With a 60 Hz frequency, stimulation artefacts can hide EPs. Indeed, the nervous time of conduction is close to the stimulation period, in particular for the interhemispheric transfer (around 20 ms). Choosing a stimulation frequency lower than 60 Hz could limit artefacts and make the detection of EPs easier. In consequence it is planned to study the time-frequency content of the neural data. To reduce bias and variance problems, multitaper spectral estimation could be used. We will look for modifications of the spectrum for each period of stimulation, before, during and after DES. In addition, functional connectivity also remains to be studied by looking at the correlation between signals from various electrodes, especially between electrodes located in the ipsi vs. controlesional hemisphere. We will present the setup, the data analysis protocol and the preliminary results