Crystallization in a dense suspension of self-propelled particles

Using Brownian dynamics computer simulations we show that a two-dimensional suspension of self-propelled ("active") colloidal particles crystallizes at sufficiently high densities. Compared to the equilibrium freezing of passive particles the freezing density is both significantly shifted and depends on the structural or dynamical criterion employed. In non-equilibrium the transition is accompanied by pronounced structural heterogeneities. This leads to a transition region between liquid and solid in which the suspension is globally ordered but unordered liquid-like "bubbles" still persist

Inductively coupled plasma- and glow discharge plasma-sector field mass spectrometry

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Des guerriers pour faire la paix. L’armée américaine en Irak

Lorsque l’armée américaine prend, le 9 avril 2003, le contrôle de Bagdad, rien ne laisse présager qu’elle deviendra l’ennemi de la population irakienne. Si les troupes américaines ne reçoivent pas l’accueil triomphal espéré, leur présence est pour autant saluée par de nombreux Irakiens dans l’espoir d’éviter le retour du régime baasiste. Ils sont convaincus que leur « sort ne peut que s’améliorer après des années de souffrance  ». Quatre ans plus tard, le bilan de l’action américaine semble p..

Recognition Theory in Humanitarian Intervention

This presentation will show the limits of utilitarian models for the comprehension of war and humanitarian intervention and defend the idea that behind the concepts of interest are hidden logics of (non-)recognition between self and other. From the point of view of recognition theory, humanitarian interventions are hindered when the self holds minimized representations of others. This minimization can refer either to the existence or the status of the other. In substance, minimization allows for disengagement and the absence of emotional involvement in the existence of the Other. In the most basic existential sense, minimization means denial of the Other’s agency. Others are not “identified” as actually existing as free actors, because they do not really affect one's own life in a visible manner. More subtly, minimization of agency can be presented as an “objectification” of the Other (in the sense of not recognizing the Other as a being with needs and capabilities for reaction). This latter form of minimization is also referred to as "reification," which is the act of considering the Other as a mere object or an inanimate thing. Hence, this purely instrumental disposition towards the Other is conditioned by a vision of the world that involves the reification of the Self and the Other as well as the trivialization of violence. To a great extent, humanitarian interventions depend on the way one reacts to the pain of others and on the role one attributes to oneself – bystander or protector. We will draw illustrations from the cases of Rwanda and Libya in an attempt to compare the responses of the international community to each of them

Lattice Dynamics of Solid Cubane within the Quasi-Harmonic Approximation

Solid cubane, which is composed of weakly interacting cubic molecules, exhibits many unusual and interesting properties, such as a very large thermal expansion and a first-order phase transition at T$_{p}$=394 K from an orientationally-ordered phase of R$\bar{3}$ symmetry to a {\it non-cubic} disordered phase of the same symmetry with a volume expansion of 5.4%, among the largest ever observed. We study the lattice dynamics of solid cubane within the quasi-harmonic and rigid-molecule approximation to explain some of these unusual dynamical properties. The calculated phonon density of states, dispersion curves and thermal expansion agree surprisingly well with available experimental data. We find that the amplitude of thermally excited orientational excitations (i.e. librons) increases rapidly with increasing temperature and reaches about 35$^{\rm o}$ just before the orientational phase transition. Hence, the transition is driven by large-amplitude collective motions of the cubane molecules. Similarly the amplitude of the translational excitations shows a strong temperature dependence and reaches one tenth of the lattice constant at T=440 K. This temperature is in fair agreement with the experimental melting temperature of 405 K, indicating that the Lindemann criterion works well even for this unusual molecular solid.Comment: 15 pages, 6 figures (devoted to Prof. Ciraci in honor of his sixtieth birthday

Théories de la reconnaissance dans les relations internationales

Les théories de la reconnaissance ont été développées, ces vingt dernières années, lorsqu’une série de débats politiques et de mouvements sociaux ont attiré l’attention sur l’idée de reconnaissance. Comme le souligne A. Honneth, elles reposent sur l’idée que la qualité morale des rapports sociaux ne peut être mesurée à la seule aune de la répartition juste ou injuste des biens matériels, mais que la justice doit aussi intégrer, de manière essentielle, nos conceptions sur la manière dont les s..