[show abstract][hide abstract] ABSTRACT: BACKGROUND: Microcontact datasets gathered automatically by electronic devices have the potential augment the study of the spread of contagious disease by providing detailed representations of the study population's contact dynamics. However, the impact of data collection experimental design on the subsequent simulation studies has not been adequately addressed. In particular, the impact of study duration and contact dynamics data aggregation on the ultimate outcome of epidemiological models has not been studied in detail, leaving the potential for erroneous conclusions to be made based on simulation outcomes. METHODS: We employ a previously published data set covering 36 participants for 92 days and a previously published agent-based H1N1 infection model to analyze the impact of contact dynamics representation on the simulated outcome of H1N1 transmission. We compared simulated attack rates resulting from the empirically recorded contact dynamics (ground truth), aggregated, typical day, and artificially generated synthetic networks. RESULTS: No aggregation or sampling policy tested was able to reliably reproduce results from the ground-truth full dynamic network. For the population under study, typical day experimental designs -- which extrapolate from data collected over a brief period -- exhibited too high a variance to produce consistent results. Aggregated data representations systematically overestimated disease burden, and synthetic networks only reproduced the ground truth case when fitting errors systemically underestimated the total contact, compensating for the systemic overestimation from aggregation. CONCLUSIONS: The interdepedendencies of contact dynamics and disease transmission require that detailed contact dynamics data be employed to secure high fidelity in simulation outcomes of disease burden in at least some populations. This finding serves as motivation for larger, longer and more socially diverse contact dynamics tracing experiments and as a caution to researchers employing calibrated aggregate synthetic representations of contact dynamics in simulation, as the calibration may underestimate disease parameters to compensate for the overestimation of disease burden imposed by the aggregate contact network representation.
BMC Medical Informatics and Decision Making 11/2012; 12(1):132. · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: The contact networks between individuals can have a profound impact on the evolution of an infectious outbreak within a network. The impact of the interaction between contact network and disease dynamics on infection spread has been investigated using both synthetic and empirically gathered micro-contact data, establishing the utility of micro-contact data for epidemiological insight. However, the infection models tied to empirical contact data were highly stylized and were not calibrated or compared against temporally coincident infection rates, or omitted critical non-network based risk factors such as age or vaccination status.
In this paper we present an agent-based simulation model firmly grounded in disease dynamics, incorporating a detailed characterization of the natural history of infection, and 13 weeks worth of micro-contact and participant health and risk factor information gathered during the 2009 H1N1 flu pandemic.
We demonstrate that the micro-contact data-based model yields results consistent with the case counts observed in the study population, derive novel metrics based on the logarithm of the time degree for evaluating individual risk based on contact dynamic properties, and present preliminary findings pertaining to the impact of internal network structures on the spread of disease at an individual level.
Through the analysis of detailed output of Monte Carlo ensembles of agent based simulations we were able to recreate many possible scenarios of infection transmission using an empirically grounded dynamic contact network, providing a validated and grounded simulation framework and methodology. We confirmed recent findings on the importance of contact dynamics, and extended the analysis to new measures of the relative risk of different contact dynamics. Because exponentially more time spent with others correlates to a linear increase in infection probability, we conclude that network dynamics have an important, but not dominant impact on infection transmission for H1N1 transmission in our study population.
BMC Medical Informatics and Decision Making 05/2012; 12:35. · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: A particularly useful indicator of past vegetation are phytoliths, glassy products of plant metabolism which have distinctive
size and morphology based on the plant taxa which produced them; however, their analysis is a time-consuming task. Building
on investigations into mobilizing and sorting of synthetic polystyrene microspheres using a closed loop rectangular microelectromechanical
systems (MEMS) electrokinetic array, we investigate these devices’ utility for sorting natural microparticles. Using phytolith
samples extracted from archaeological sediment, we show that closed loop MEMS can separate the glassy bodies from both mineral
contaminants and each other. Also, small differences in polarization between the phytoliths cause lateral segregation between
particles of different sizes and shapes. This process facilitates manual analysis by providing a motive force to the phytoliths
that translates and rotates them, showing different configurations as they are propelled by the MEMS array. The organization
of the phytoliths into streams also opens the door to automated analysis using image processing. Phytolith assaying is therefore
feasible using a MEMS electrokinetic ring and merits additional research to explore the potential of this innovative approach.
KeywordsPhytolith analysis–Paleoenvironmental reconstruction–Microelectromechanical systems–Electrokinetic microsorting–Computer vision
Archaeological and Anthropological Sciences 04/2012; 3(4):309-323.
[show abstract][hide abstract] ABSTRACT: The growth of wireless devices with short-range communications capabilities is making research into Pocket Switched Networks (PSN)s more appealing. While some recent research has investigated the role of location in predicting the mobility patterns of autonomous agents within PSNs, little attention has been paid to the location as a resource itself. In this paper we investigate the potential for stationary nodes, acting as relay stations for mobile agents in PSNs. Using empirical datasets, we demonstrate that appropriate utilization of place as a resource can increase network performance and decrease the load on nodes which are popular because of their location rather than their mobility pattern.
IEEE 36th Conference on Local Computer Networks, LCN 2011, Bonn, Germany, October 4-7, 2011; 01/2011
[show abstract][hide abstract] ABSTRACT: By analyzing people's contact patterns over time, it is possible to build efficient delay tolerant networking (DTN) algorithms and derive important data for parameterizing and calibrating epidemiological models. Significant research has been performed in the automated acquisition of contact patterns using mobile devices such as Zigbee motes or Bluetooth-enabled cellular phones. However, the limited number of studies described to date do not capture the breadth of human experience or specifically include the acquisition of health related information. In this paper we present Flunet, a mobile contact-tracking network deployed in a Canadian university environment during flu season. Flunet tracked contact patterns of 36 participants and their proximity to 11 stationary nodes using MicaZ motes over a period of three months. Participants filled out weekly surveys on their state of health. This study is distinct from others because we incorporate health information and the impact of sub-zero temperatures on mobility patterns. This paper presents a preliminary analysis of the data set, primarily from a DTN perspective. We present fundamental attributes of the dataset, the efficiency of routing for single pass and flooding-based algorithms and a preliminary look at the relationship between network characteristics and health status.
WiOpt'10: Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks. 01/2010;
[show abstract][hide abstract] ABSTRACT: In this paper, we demonstrate long-range particle transport using linear two-phase interdigitated arrays with electrodes of equal size but with asymmetric spacing between them. We report net motion of 6 µm polystyrene spheres in an aqueous electrolyte and characterize the dependence of particle velocity on frequency, potential and phase, and show consistency with previous experiments that involved four-phase arrays producing AC electroosmotic and dielectrophoretic forces. We explore the effect of increasing the asymmetry of the electrode spacing and show that this decreases the performance of the array. We also examine the effect of increasing the overall scale of the array while maintaining geometric proportions and particle size and report that this also decreases the performance. We compare our results to previous analytical theoretical predictions and find general agreement.
Journal of Micromechanics and Microengineering 03/2008; 18(5):055007. · 1.79 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this paper, we study microparticles in liquid suspension streaming around a closed rectangular track and present lateral sorting of the particles into focused streams. The track consists of a two-phase interdigitated electrode array with symmetric electrodes but asymmetric electrode spacing. We demonstrate the ability to consistently focus an initially scattered suspension of mono-size polystyrene particles into a single narrow stream traveling around the circuit. We also demonstrate the ability of the device to separate suspensions of multiple sphere sizes into distinct streams according to size. We report that focusing positions are generally consistent for a given particle size, regardless of the presence of other particles in the suspension, and that particles sort by decreasing size from the center to the edge of the track. These results are compared with finite element analysis of the steady-state electric field and analytical approximations of the electrokinetic forces. We hypothesize that the sorting is due to a balance between phase-based and gradient-based dielectrophoretic forces.
Journal of Micromechanics and Microengineering 02/2008; 18(4):045002. · 1.79 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this paper, we describe a cumulative context computer game, where accumulated contextual information of the players" activity levels, obtained through mobile sensors, is used to modify game state. Our implementation used a statistic-based, real-time version of the classic game of chess, where the statistics of the pieces depended on the activity of the users and the environment in which they performed the activity. Users found the game engaging and fun, and almost all of the participants altered their behaviors to enhance their performance in the game. This work provides a platform for further research into meaningful integration of cumulative context in games.
Proceedings of the 2008 Conference on Future Play: Research, Play, Share, Future Play 2008, Toronto, Ontario, Canada, November 3-5, 2008; 01/2008
[show abstract][hide abstract] ABSTRACT: Heuristic evaluation – a technique where experts inspect software and determine where the application violates predetermined policies for good usability – is an effective technique for evaluating productivity software. The technique has recently been applied to video games, examining playability and usability for both single and multiplayer games. However, the severity ratings assigned to usability problems and used as a coarse categorization method for triage are still subjectively and somewhat arbitrarily assigned by evaluators, offering limited organizational value. In addition, they fail to account for the diversity found between games and game genres. In this paper we present a modified heuristic evaluation technique, which produces a prioritized list of heuristic violations based on the problem's frequency, impact, persistence, the heuristic it violates, and the game's genre. We evaluate our technique in a case study and show that the technique provides substantial value with little additional effort.
[show abstract][hide abstract] ABSTRACT: Player coordination is a key element in many multi-player real-time digital games, and control over the design of these coordination requirements is an important part of developing successful games. However, it is currently difficult to describe or analyze coordination requirements in game situations, because current frameworks and theories do not mesh with the realities of video game design. We developed a new framework (called PLATO) that can help game designers understand and manipulate coordination episodes. The framework deals with five atomic aspects of coordinated activity: Players, Locations, Actions, Time, and Objects. PLATO provides a vocabulary, methodology and diagram notation for describing and analyzing coordination. We demonstrate the framework's utility by describing coordination situations from existing games, showing how PLATO can be used to understand and redesign coordination requirements.
[show abstract][hide abstract] ABSTRACT: Obesity is a growing problem among children, due in part to their sedentary lifestyles. Time spent engaged in physical activity is decreasing, while time spent playing computer and video games is on the rise. We leverage children's interest in digital games to encourage families to engage in purposeful walking. We present a GPS-based game, played on a mobile device that uses walking as a primary gameplay mechanic. Our game, PiNiZoRo, includes a fighting game, triggered at points along a real-world route, and a map editor that allows parents and recreation specialists to create custom routes in their neighbourhoods. Results from an initial focus group with parents were positive, as they showed enthusiasm for the concept, implementation, and gameplay.
[show abstract][hide abstract] ABSTRACT: Smartphones have the potential to revolutionize health monitoring and delivery. Significant attention has been given to personal health devices and systems to help individuals and medical practitioners monitor health and treatment compliance. The data collected from these systems also has significant value to public health workers and epidemiologists. However, requirements for backend analysis and supplemental data differ between personal and public health applications. In this paper we describe iEpi, an end-to-end system for collecting, analyzing, and utilizing contextual microdata through smartphones for epidemiological and public health applications.
[show abstract][hide abstract] ABSTRACT: Contagions - either pathogens spread through contact networks or societal memes spread through social networks - impact the occurrence and character of both epidemic and endemic diseases. While computational models explore disease parameters in the context of a given contact network, these models are always subject to the caveat that reality may not be consistent with the simplified assumptions regarding contact, contagion or network structure. More - and more accurate - data on the contact dynamics between people and places could alleviate some uncertainties, and make models more robust tools for policy-makers and researchers. Properly applied, consumer electronics can serve as a valuable source of this data. Using smartphones as sensor platforms rather than personal communications devices, it is possible to record high fidelity information on a participant's location, activity level, and contacts between both people and places. This paper describes the design, architecture and a preliminary deployment of a general smartphone-based epidemiological data collection system. The dataset, gathered over one month, contains over 45 million records related to the behavioral patterns of 39 participants. We provide an initial analysis of aggregate level statistics to demonstrate the power and scope of the technique for capturing relevant data. Demonstrating the potential for such data to inform decision-making, we further perform an agent-based simulation of a flu-like illness that uses the dataset to capture aspects of both person-person and environmental (place-person) transmission. We demonstrate that the data collection is possible, valuable, and scalable and that the data can be leveraged to inform detailed models capturing more complex physical interactions than were previously feasible.