Multiple jumps and vacancy diffusion in a face-centered cubic metal

The diffusion of monovacancies in gold has been studied by computer simulation. Multiple jumps have been found to play a central role in the atomic dynamics at high temperature, and have been shown to be responsible for an upward curvature in the Arrhenius plot of the diffusion coefficient. Appropriate saddle points on the potential energy surface have been found, supporting the interpretation of vacancy multiple jumps as distinct migration mechanisms.Comment: 16 page

A participatory design approach for the development of support environments in eGovernment services to citizens

The introduction of eGovernment services and applications leads to major changes in the structure and operation of public administrations. In this paper we describe the work in progress in an Italian project called “SPO.T.” aimed at the analysis, development, deployment and evaluation of tools and environments to support the people who plan, deliver, use and evaluate user-centred provision of One-Stop-Shop services to citizens. The “SPO.T.” project has focused on two requirements: 1. the support tools and environments must facilitate the active involvement of all stakeholders in the definition and evolution of eGovernment applications and services, and it is argued that through participatory design changes of structure, process and culture can be delivered effectively; 2. they must embody a set of architecturally coherent resources which reflect the new roles and relationships of public administration and which are sufficiently generic to be relevant to a wide range of local contexts across the community

Manipulating Bodily Presence Affects Cross-Modal Spatial Attention : A Virtual-Reality-Based ERP Study

Earlier studies have revealed cross-modal visuo-tactile interactions in endogenous spatial attention. The current research used event-related potentials (ERPs) and virtual reality (VR) to identify how the visual cues of the perceiver’s body affect visuo-tactile interaction in endogenous spatial attention and at what point in time the effect takes place. A bimodal oddball task with lateralized tactile and visual stimuli was presented in two VR conditions, one with and one without visible hands, and one VR-free control with hands in view. Participants were required to silently count one type of stimulus and ignore all other stimuli presented in irrelevant modality or location. The presence of hands was found to modulate early and late components of somatosensory and visual evoked potentials. For sensory-perceptual stages, the presence of virtual or real hands was found to amplify attention-related negativity on the somatosensory N140 and cross-modal interaction in somatosensory and visual P200. For postperceptual stages, an amplified N200 component was obtained in somatosensory and visual evoked potentials, indicating increased response inhibition in response to non-target stimuli. The effect of somatosensory, but not visual, N200 enhanced when the virtual hands were present. The findings suggest that bodily presence affects sustained cross-modal spatial attention between vision and touch and that this effect is specifically present in ERPs related to early- and late-sensory processing, as well as response inhibition, but do not affect later attention and memory-related P3 activity. Finally, the experiments provide commeasurable scenarios for the estimation of the signal and noise ratio to quantify effects related to the use of a head mounted display (HMD). However, despite valid a-priori reasons for fearing signal interference due to a HMD, we observed no significant drop in the robustness of our ERP measurements.Peer reviewe

Hybrid Events: Mediating Collocated Participation

This workshop invites the CSCW community to explore hybrid events – large collocated events where technology is used to support audience participation. We argue that the technology landscape has changed since the early studies in CSCW towards this context. Therefore, the research foci must similarly change and focus on studying the practices or propose alternative and novel interfaces. This workshop helps the CSCW community to consider the research agenda for the next generation of hybrid event studies. We do this by discussing the open conceptual, empirical and constructive research problems in this domain. Together with the organizers and participants, we seek to develop a research agenda and seek opportunities for further collaboration on the topic of hybrid events.Non peer reviewe

Physicality and Cooperative Design

CSCW researchers have increasingly come to realize that material work setting and its population of artefacts play a crucial part in coordination of distributed or co-located work. This paper uses the notion of physicality as a basis to understand cooperative work. Using examples from an ongoing fieldwork on cooperative design practices, it provides a conceptual understanding of physicality and shows that material settings and co-worker’s working practices play an important role in understanding physicality of cooperative design

Caloric Curves in two and three-dimensional Lennard-Jones-like systems including Long-range forces

We present a systematic study of the thermodynamics of two and three-dimensional generalized Lennard-Jones ($LJ$) systems focusing on the relationship between the range of the potential, the system density and its dimension. We found that the existence of negative specific heats depends on these three factors and not only on the potential range and the density of the system as stated in recent contributions.Comment: LaTex, 12 pages, 7 figure

Exploring Peripheral Physiology as a Predictor of Perceived Relevance in Information Retrieval

Peripheral physiological signals, as obtained using electrodermal activity and facial electromyography over the corrugator supercilii muscle, are explored as indicators of perceived relevance in information retrieval tasks. An experiment with 40 participants is reported, in which these physiological signals are recorded while participants perform information retrieval tasks. Appropriate feature engineering is defined, and the feature space is explored. The results indicate that features in the window of 4 to 6 seconds after the relevance judgment for electrodermal activity, and from 1 second before to 2 seconds after the relevance judgment for corrugator supercilii activity, are associated with the users’ perceived relevance of information items. A classifier verified the predictive power of the features and showed up to 14% improvement predicting relevance. Our research can help the design of intelligent user interfaces for information retrieval that can detect the user’s perceived relevance from physiological signals and complement or replace conventional relevance feedback

Bioinspired scattering materials: light transport in anisotropic, disordered systems

The study of light propagation in disordered media has attracted the interest of many researchers for its relevance to fundamental and applied problems, ranging from imaging through turbid media to the fabrication of white paint. Scattering in a disordered system is determined by the spatial distribution and the scattering properties of its building blocks. To date, most efforts on scattering optimisation have focused on isotropic, high refractive index systems. This thesis investigates the importance of anisotropy in increasing the scattering efficiency of a system, with a particular focus on low refractive index media and their use as sustainable, white materials. Nature provides a striking example of how to exploit anisotropy to achieve scattering optimisation: with the intra-scale chitin network of the beetle genus Cyphochilus. In this thesis, after showing that this network exhibits the highest scattering efficiency found in nature thus far, a systematic numerical investigation was performed to understand the importance of both single-particle and structural anisotropy in scattering optimisation. In particular, this numerical analysis unveiled that ensembles of anisotropic particles show higher reflectance compared to their isotropic counterpart, whilst using less material. Based on these findings, the optical properties of bioinspired, scattering systems — obtained both via polymer phase separation and a combination of sequential vacuum filtration and freeze-drying — were investigated. Notably, the reported materials achieve scattering properties comparable to those found in nature, showcasing the potential of using biopolymers to produce sustainable, biocompatible white materials. In addition, the presented bioinspired systems are an interesting platform for fundamental studies, allowing to investigate light transport in anisotropic media.European Research Council grant awarded to Dr Silvia Vignolin

Lattice-switch Monte Carlo

We present a Monte Carlo method for the direct evaluation of the difference between the free energies of two crystal structures. The method is built on a lattice-switch transformation that maps a configuration of one structure onto a candidate configuration of the other by `switching' one set of lattice vectors for the other, while keeping the displacements with respect to the lattice sites constant. The sampling of the displacement configurations is biased, multicanonically, to favor paths leading to `gateway' arrangements for which the Monte Carlo switch to the candidate configuration will be accepted. The configurations of both structures can then be efficiently sampled in a single process, and the difference between their free energies evaluated from their measured probabilities. We explore and exploit the method in the context of extensive studies of systems of hard spheres. We show that the efficiency of the method is controlled by the extent to which the switch conserves correlated microstructure. We also show how, microscopically, the procedure works: the system finds gateway arrangements which fulfill the sampling bias intelligently. We establish, with high precision, the differences between the free energies of the two close packed structures (fcc and hcp) in both the constant density and the constant pressure ensembles.Comment: 34 pages, 9 figures, RevTeX. To appear in Phys. Rev.