« Gilles Martinet : un parcours intellectuel et politique à gauche »

Le colloque qui s’est tenu à Sciences Po le 22 mars 2016 a étudié dans ses différentes dimensions le parcours intellectuel et politique d’une figure importante de la gauche française : Gilles Martinet. Marc Lazar a introduit ce colloque en rappelant la concomitance de plusieurs dates : 1916, année de la naissance de Gilles Martinet ; 2006, année de sa mort ; et 1995-1996, date de la remise des archives de Gilles Martinet au Centre d’histoire de l’Europe du Vingtième siècle (CHEVS) alors dirig..

La Ligue des droits de l’homme et la défense de la cause palestinienne (années 1960 – années 1980)

International audienceThe article looks at the evolution of the positions taken by the Ligue des droits de l’homme towards the Palestinians between the Six Day War and the early 1980s. Initially very reluctant to criticize the state of Israel and to support the Palestinians, the LDH becomes more and more critical and took into consideration the status of Palestinian refugees and their right to a sovereign state.L’article s’intéresse à l’évolution des prises de position de la Ligue des droits de l’homme à propos des Palestiniens entre la guerre des Six Jours et le début des années 1980. D’abord très réticente à critiquer l’État d’Israël et à soutenir les Palestiniens, la Ligue devient de plus en plus critique et prend en considération le statut des réfugiés palestiniens et leur droit à un État souverain

Brève de recherches: Le fonds Daniel Mayer au CHSP, par Thomas Maineult

contribution à un site webLe fonds Daniel Mayer aux Archives d’histoire contemporaine du Centre d’histoire de Sciences Po permet de saisir le parcours d’un homme politique dont la carrière fut marquée par un engagement fort et constant pour un certain nombre de causes. À travers le parcours de celui qui s’engagea très tôt en faveur de Sacco et Vanzetti et qui milita plus tard contre son propre parti pour mettre un terme au conflit algérien, c’est une fidélité à des idées qui transparaît dans ses archives. Lutte contre l’antisémitisme, militantisme à la Ligue des Droits de l’Homme, et fidélité à l’Etat d’Israël sont autant de facettes d’un même personnage. Pour l’historien qui se plonge dans les archives concernant la question du Proche-Orient, il est frappant de voir la constance des positions et l’intransigeance sur les valeurs portées par Daniel Mayer. Homme de convictions et d’action, il n’hésite pas à s’opposer au PSU qu’il a contribué à faire naître en rendant sa carte en 1967 à cause de la position du parti sur le conflit israélo-arabe. Très préoccupé par cette question, il compile ainsi notes et documents émanant d’instituts de sondage ou d’interviews données à la presse relatifs au conflit. En témoigne un sondage IFOP de juin 1971 réalisé auprès d’étudiants français montrant qu’Israël conserve encore un assez fort capital de sympathie parmi cette population. L’étude de ce fonds m’a apporté une autre vision de mon sujet de recherche et m’a obligé à ne jamais négliger les positions opposées à celles des acteurs que j’étudie. Sa volonté de voir advenir la paix au Proche-Orient se traduit donc dans son engagement politique mais aussi dans son engagement associatif. A la tête de la LDH et de la FIDH, il envoie des observateurs au Proche-Orient afin de constater les atteintes aux droits de l’homme, notamment lors des massacres de Sabra et Chatila en 1982. Homme de plusieurs fidélités, Daniel Mayer a su tout au long de sa carrière mêler éthique de conviction et éthique de responsabilité

ERT monitoring of gas injection into water saturated sands: Modelling and inversion of cross-hole laboratory data

International audienceA set of laboratory experiments were performed in order to investigate the capacity of the electrical resistivity tomography method to detect and monitor the circulation of gaseous CO2 into geological media. The experiments consisted of injecting reactive (CO2) or inert (N2) gases into reactive (carbonate) or inert (silica) sands saturated with water. The laboratory setup was a metric-scale cylindrical tank instrumented with electrodes placed on vertical rods, hence simulating a borehole to borehole monitoring network. The results demonstrated that the ERT method can efficiently detect, locate and image gas circulation plumes. Two main behaviors were identified: either an increase of the medium resistivity due to the invasion of the porous space by an electrically insulating gas phase, or a resistivity decrease induced by dissolution processes that enhance ionic concentrations in the saturating water. The observed anomalies showed varying geometric shapes depending on which type of sand was used. A 3D cellular automaton model was built and managed to reproduce different gas plume circulation patterns and the electrical resistivity response associated. This modeling work confirmed the link existing between the shapes of the resistivity anomalies, the gas plume geometry and the particle size distribution of the sand. Through a numerical sensitivity analysis, several measuring protocols were tested and developed in order to improve the imaging capacity of the electrical resistivity method. Results demonstrated that the most efficient protocol was different depending on the shape of the gas plume, thus stressing the importance of having a priori knowledge on the geological, lithological and hydraulic characteristics of the subsurface, in order to correctly assess the most likely gas plume geometry and hence design the most adapted monitoring protocol

Laboratory monitoring of CO2 injection in saturated silica and carbonate sands using spectral induced polarization

International audienceSeries of experiments were performed to study the spectral induced polarization (SIP) response of sands fully saturated with water, into which gaseous CO 2 or N 2 was injected, in the frequency range 0.5 Hz–20 kHz. Three main observations were made. (1) SIP parameters were always most affected by gas injection when the frequency of the injected signal was in the intermediate range (1 < f < 20 kHz). This point emphasizes the interest of broadening the frequency range of SIP surveys toward intermediate frequencies. It also implies that more work is needed in order to understand and quantify the parasitic effects that occur at this frequency range (EM coupling and electrode polarization). (2) Through all the experiments performed, we were able to distinguish the parameters variations caused by a reduction of the water saturation level (invasion of a resistive gas phase in the porous space) from those resulting from dissolution processes (increase of the electrical conductivity of the saturating water). (3) The quadrature conductivity σ , which is mainly linked to the capacitive properties and inductive response of the media, always shows relative variations stronger than the resistivity of the media, hence demonstrating the interest of the additional information provided by the SIP method as against the classical resistivity method

Modelling the spectral induced polarization response of water-saturated sands in the intermediate frequency range (102–105 Hz) using mechanistic and empirical approaches

International audienceThe intermediate frequency range 10 2 –10 5 Hz forms the transition range between the spectral induced polarization frequency domain and the dielectric spectroscopy frequency domain. Available experimental data showed that the spectral induced polarization response of sands fully saturated with water was particularly sensitive to variations of the saturating water electrical conductivity value in the intermediate frequency range. An empirical and a mechanistic model have been developed and confronted to this experimental data. This confrontation showed that the Maxwell Wagner polarization alone is not sufficient to explain the observed signal in the intermediate frequency range. The SIP response of the media was modelled by assigning relatively high dielectric permittivity values to the sand particle or high effective permittivity values to the media. Such high values are commonly observed in the dielectric spectroscopy literature when entering the intermediate frequency range. The physical origin of these high dielectric permittivity values is discussed (grain shape, electromagnetic coupling), and a preliminary study is presented which suggests that the high impedance values of the non-polarizable electrodes might play a significant role in the observed behaviour

Anomalies of noble gases and self-potential associated with fractures and fluid dynamics in a horizontal borehole, Mont Terri Underground Rock Laboratory

Before the excavation of the new gallery Ga08 in the Mont Terri Underground Rock Laboratory (Switzerland), which joined the existing gallery Ga04 in 2008, the end-face of gallery Ga04 was instrumented in 2007 to characterize the evolution of the rock mass with geochemical and geophysical methods. The noble gas content of a 12-m long horizontal borehole evidenced that desaturation processes occurred in the first 2 m, where pre-existing fractures accommodated the stress change during excavation of gallery Ga04 four years before. These first 2 m are associated with the so-called Excavation Damaged Zone (EDZ). As an inflow of pore water was observed in this borehole few weeks after its drilling, continuous self-potential (SP) measurements were performed to characterize its dynamics. After the drilling of new sub-horizontal boreholes in the end-face, strong localized variations of SP occurred. The comparison with the geological features of the rock mass suggests that these dynamic anomalies have to be associated with fluid circulation in pre-existing tectonic fractures that were primarily reactivated by the excavation of the gallery Ga04 and subsequently by the drilling operations

Anomalies of noble gases and self-potential associated with fractures and fluid dynamics in a horizontal borehole, Mont Terri Underground Rock Laboratory

Before the excavation of the new gallery Ga08 in the Mont Terri Underground Rock Laboratory (Switzerland), which joined the existing gallery Ga04 in 2008, the end-face of gallery Ga04 was instrumented in 2007 to characterize the evolution of the rock mass with geochemical and geophysical methods. The noble gas content of a 12-m long horizontal borehole evidenced that desaturation processes occurred in the first 2 m, where pre-existing fractures accommodated the stress change during excavation of gallery Ga04 four years before. These first 2 m are associated with the so-called Excavation Damaged Zone (EDZ). As an inflow of pore water was observed in this borehole few weeks after its drilling, continuous self-potential (SP) measurements were performed to characterize its dynamics. After the drilling of new sub-horizontal boreholes in the end-face, strong localized variations of SP occurred. The comparison with the geological features of the rock mass suggests that these dynamic anomalies have to be associated with fluid circulation in pre-existing tectonic fractures that were primarily reactivated by the excavation of the gallery Ga04 and subsequently by the drilling operations