Vibrational Modes of ⁴He and H₂ Gases Adsorbed on Carbon Nanotubes

We present calculations of the breathing mode phonon frequencies of 4He and H2 physically adsorbed on the outside surface of one or more carbon nanotubes. Two geometries are considered. The first is a single, isolated nanotube, upon which the gas is adsorbed as a commensurate phase. The second is a quasi-one-dimensional groove phase nestled between two nanotubes. While the computed breathing mode frequencies depend on nanotube radius and the adsorbate, in general, they are of the same order of magnitude as those of the bare nanotubes

Simple Model of Capillary Condensation in porous media

We employ a simple model to describe the phase behavior of 4He and Ar in a hypothetical porous material consisting of a regular array of infinitely long, solid, parallel cylinders. We find that high porosity geometries exhibit two transitions: from vapor to film and from film to capillary condensed liquid. At low porosity, the film is replaced by a ``necking'' configuration, and for a range of intermediate porosity there are three transitions: from vapor to film, from film to necking and from necking to a capillary condensed phase.Comment: 14 pages, 7 figure

Bose-Einstein Condensation of Helium and Hydrogen inside Bundles of Carbon Nanotubes

Helium atoms or hydrogen molecules are believed to be strongly bound within the interstitial channels (between three carbon nanotubes) within a bundle of many nanotubes. The effects on adsorption of a nonuniform distribution of tubes are evaluated. The energy of a single particle state is the sum of a discrete transverse energy Et (that depends on the radii of neighboring tubes) and a quasicontinuous energy Ez of relatively free motion parallel to the axis of the tubes. At low temperature, the particles occupy the lowest energy states, the focus of this study. The transverse energy attains a global minimum value (Et=Emin) for radii near Rmin=9.95 Ang. for H2 and 8.48 Ang.for He-4. The density of states N(E) near the lowest energy is found to vary linearly above this threshold value, i.e. N(E) is proportional to (E-Emin). As a result, there occurs a Bose-Einstein condensation of the molecules into the channel with the lowest transverse energy. The transition is characterized approximately as that of a four dimensional gas, neglecting the interactions between the adsorbed particles. The phenomenon is observable, in principle, from a singular heat capacity. The existence of this transition depends on the sample having a relatively broad distribution of radii values that include some near Rmin.Comment: 21 pages, 9 figure

Gas Adsorption in Novel Environments, Including Effects of Pore Relaxation

Adsorption experiments have been interpreted frequently with simplified model geometries, such as ideally flat surfaces and slit or cylindrical pores. Recent explorations of unusual environments, such as fullerenes and metal-organic-framework materials, have led to a broadened scope of experimental, theoretical and simulation investigations. This paper reviews a number of such studies undertaken by our group. Among the topics receiving emphasis are these: universality of gas uptake in pores, relaxation of a porous absorbent due to gas uptake and the novel phases of gases on a single nanotube, all of which studies have been motivated by recent experiments

Gender, biography and oral history or how to tell the life of Ana María Villarreal de Santucho

Este trabajo se propone reconstruir la biografía de Ana María Villarreal de Santucho, militante del Partido Revolucionario de los Trabajadores-Ejército Revolucionario del Pueblo y esposa de su líder máximo Mario Roberto Santucho entre 1960 y 1972, cuando fue asesinada junto con otrxs quince militantes en la Base Aeronaval Almirante Zar, dependencia de la Armada argentina cercana a la ciudad de Trelew. Para ello, este estudio recurre a un acervo documental variado conformado por entrevistas, cartas personales, fotografías, expedientes judiciales, documentos políticos, prensa comercial y político partidaria.This article purposes to reconstruct the biography of Ana María Villarreal de Santucho, a militant of the Partido Revolucionario de los Trabajadores-Ejército Revolucionario del Pueblo and wife of its maximum leader, Mario Roberto Santucho, between 1960 and 1972, when she was assassinated along with others fifteen militants at the Almirante Zar Naval Air Base, a dependency of the Argentine Navy near the city of Trelew. To do this, this study recurs to a varied documentary heritage made up of interviews, personal letters, photographs, court files, political documents, commercial and political press.Fil: Andújar, Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina). Instituto de Investigaciones de Estudios de Género Universidad de Buenos Aires. Buenos Aires; ArgentinaFil: D´ Antonio, Débora. Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina). Instituto de Investigaciones de Estudios de Género Universidad de Buenos Aires. Buenos Aires; ArgentinaFil: Gatica, Mónica. Universidad Nacional de la Patagonia (Argentina). Facultad de Humanidades y Ciencias Sociales. Instituto de Investigaciones Históricas y Sociales. Comodoro Rivadavia; Argentin

Social behavior modeling based on Incremental Discrete Hidden Markov Models

12 pagesInternational audienceModeling multimodal face-to-face interaction is a crucial step in the process of building social robots or users-aware Embodied Conversational Agents (ECA). In this context, we present a novel approach for human behavior analysis and generation based on what we called "Incremental Discrete Hidden Markov Model" (IDHMM). Joint multimodal activities of interlocutors are first modeled by a set of DHMMs that are specific to supposed joint cognitive states of the interlocutors. Respecting a task-specific syntax, the IDHMM is then built from these DHMMs and split into i) a recognition model that will determine the most likely sequence of cognitive states given the multimodal activity of the in- terlocutor, and ii) a generative model that will compute the most likely activity of the speaker given this estimated sequence of cognitive states. Short-Term Viterbi (STV) decoding is used to incrementally recognize and generate behav- ior. The proposed model is applied to parallel speech and gaze data of interact- ing dyads

Diversity and neocolonialism in Big Data research: Avoiding extractivism while struggling with paternalism

The extractive logic of Big Data-driven technology and knowledge production has raised serious concerns. While most criticism initially focused on the impacts on Western societies, attention is now increasingly turning to the consequences for communities in the Global South. To date, debates have focused on private-sector activities. In this article, we start from the conviction that publicly funded knowledge and technology production must also be scrutinized for their potential neocolonial entanglements. To this end, we analyze the dynamics of collaboration in an European Union-funded research project that collects data for developing a social platform focused on diversity. The project includes pilot sites in China, Denmark, the United Kingdom, India, Italy, Mexico, Mongolia, and Paraguay. We present the experience at four field sites and reflect on the project’s initial conception, our collaboration, challenges, progress, and results. We then analyze the different experiences in comparison. We conclude that while we have succeeded in finding viable strategies to avoid contributing to the dynamics of unilateral data extraction as one side of the neocolonial circle, it has been infinitely more difficult to break through the much more subtle but no less powerful mechanisms of paternalism that we find to be prevalent in data-driven North–South relations. These mechanisms, however, can be identified as the other side of the neocolonial circle.</p