Loss of purity by wave packet scattering at low energies

We study the quantum entanglement produced by a head-on collision between two gaussian wave packets in three-dimensional space. By deriving the two-particle wave function modified by s-wave scattering amplitudes, we obtain an approximate analytic expression of the purity of an individual particle. The loss of purity provides an indicator of the degree of entanglement. In the case the wave packets are narrow in momentum space, we show that the loss of purity is solely controlled by the ratio of the scattering cross section to the transverse area of the wave packets.Comment: 7 pages, 1 figur

The effect of dyadic interactions on learning rotate gesture for technology-naïve older adults

Older adults having limited experience with modern computing technology may find it difficult to learn touch gestures, especially the more complex rotate gesture. Social interactions, as implied by social constructivism, are assumed to be powerful in enabling older adults to acquire the skill of touch gestures. The social effect can be reinforced with the motivational effect of digital games. To verify the assumption, we conducted empirical studies with 59 older adults, who were divided into two groups: 17 Singles and 21 Dyads. They were asked to play a set of digital games on a multi-touch tabletop. Results show that on average Dyads have spent significantly longer time in the games and have performed a significantly higher number of correct rotate gestures than Singles. Future work focuses on analyzing the emotional aspect of social interactions and identifying further applications of social gaming to other ageing issue

Integrating the strengths of cognitive emotion models with traditional HCI analysis tools

This paper reports an attempt to integrate key concepts from cognitive models of emotion to cognitive models of interaction established in HCI literature. The aim is to transfer the strengths of interaction models to analysis of affect-critical systems in games, e-commerce and education, thereby increasing their usefulness in these systems where affect is increasingly recognised as a key success factor. Concepts from Scherer’s appraisal model and stimulation evaluation checks, along with a framework of emotion contexts proposed by Coulson (An everything but framework for modelling emotion. In proceeding of AAAI spring symposium on architectures for emotion, 2004), are integrated into the cycle of display-based action proposed by Norman (The design of everyday things. Basic Books, New York, 1988). Norman’s action cycle has commonly been applied as an interaction analysis tool in the field of HCI. In the wake of the recent shift of emphasis to user experience, the cognition-based action cycle is deemed inadequate to explicate affective experiences, such as happiness, joy and surprise. Models based on appraisal theories, focusing on cognitive accounts of emotion, are more relevant to understanding the causes and effects of feelings arising from interacting with digital artefacts. The paper explores the compatibility between these two genres of model, and future development of integrated analysis tools

S-wave quantum entanglement in a harmonic trap

We analyze the quantum entanglement between two interacting atoms trapped in a spherical harmonic potential. At ultra-cold temperature, ground state entanglement is generated by the dominated s-wave interaction. Based on a regularized pseudo-potential Hamiltonian, we examine the quantum entanglement by performing the Schmidt decomposition of low-energy eigenfunctions. We indicate how the atoms are paired and quantify the entanglement as a function of a modified s-wave scattering length inside the trap.Comment: 10 pages, 5 figures, to be apear in PR

Learning to drag: the effects of social interactions in touch gestures learnability for older adults

Considering the potential physical limitations of older adults, the naturalness of touch-based gestures as an interaction method is questionable. Assuming touch-based gestures are natural, they should be highly learnable and amenable to enhancement through social interactions. To investigate whether social interactions can enhance the learnability of touch gestures for older adults with low digital literacy, we conducted a study with 42 technology- naïve participants aged 64 to 82. They were paired and encouraged to play two games on an interactive tabletop with the expectation to use the drag gesture to complete the games socially. We then compared these results with a previous study of technology–naïve older adults playing the same games individually. The results of the comparisons show that dyadic interactions had some benefits for the participants in helping them to become comfortable with the drag gesture by negotiation and imitation. Further qualitative analysis suggested that playing pairs generally helped learners to comfortably explore the digital environment using the newly acquired skill

Intuitive learnability of touch gestures for technology-naïve older adults

Touch-based interactions, if intuitive and natural, should be highly learnable. However, the learnability of touch gestures as a computer interaction modality cannot be taken for granted and should be evaluated empirically. This is especially true when technology-naïve older adults are concerned, given the psychological and physical constraints associated with this age range. To investigate this issue, we conducted a study with 17 technology-naïve older adults, whose experience with technology was mostly limited to making calls with mobile phones. Specifically, the participants were presented with three simple digital games on an interactive tabletop surface and asked to play the games on their own with minimal instruction or help. The first two games required the use of a drag gesture whereas the third game required the use of a rotate gesture. The main research question was whether the older adults could learn the gestures effectively and efficiently. A set of variables such as task duration and gesture accuracy were measured. Results showed that the learnability of a drag gesture was relatively high and that the participants could transfer this skill across the games. In contrast, the learnability of a rotate gesture was low and most of the participants failed to demonstrate any improvement over the tasks of the game. These findings partially corroborate those of earlier work. Implications for future work are drawn, especially exploring the potential of social interactions between older adults for enhancing the learning effects

Climatic versus biotic constraints on carbon and water fluxes in seasonally drought-affected ponderosa pine ecosystems

We investigated the relative importance of climatic versus biotic controls on gross primary production (GPP) and water vapor fluxes in seasonally drought-affected ponderosa pine forests. The study was conducted in young (YS), mature (MS), and old stands (OS) over 4 years at the AmeriFlux Metolius sites. Model simulations showed that interannual variation of GPP did not follow the same trends as precipitation, and effects of climatic variation were smallest at the OS (50%), and intermediate at the YS (<20%). In the young, developing stand, interannual variation in leaf area has larger effects on fluxes than climate, although leaf area is a function of climate in that climate can interact with age-related shifts in carbon allocation and affect whole-tree hydraulic conductance. Older forests, with well-established root systems, appear to be better buffered from effects of seasonal drought and interannual climatic variation. Interannual variation of net ecosystem exchange (NEE) was also lowest at the OS, where NEE is controlled more by interannual variation of ecosystem respiration, 70% of which is from soil, than by the variation of GPP, whereas variation in GPP is the primary reason for interannual changes in NEE at the YS and MS. Across spatially heterogeneous landscapes with high frequency of younger stands resulting from natural and anthropogenic disturbances, interannual climatic variation and change in leaf area are likely to result in large interannual variation in GPP and NEE