TangiBoard: a toolkit to reduce the implementation burden of tangible user interfaces in education

The use of Tangible User Interfaces (TUI) as an educational technology has gained sustained interest over the years with common agreement on its innate ability to engage and intrigue students in active-learning pedagogies. Whilst encouraging results have been obtained in research, the widespread adoption of TUI architectures is still hindered by a myriad of implementation burdens imposed by current toolkits. To this end, this paper presents an innovative TUI toolkit: TangiBoard, which enables the deployment of an interactive TUI system using low-cost, and presently available educational technology. Apart from curtailing setup costs and technical expertise required for adopting TUI systems, the toolkit provides an application framework to facilitate system calibration and development integration with GUI applications. This is enabled by a robust computer vision application that tracks a contributed passive marker set providing a range of tangible interactions to TUI frameworks. The effectiveness of this toolkit was evaluated by computer systems developers with respect to alternate toolkits for TUI design. Open-source versions of the TangiBoard toolkit together with marker sets are provided online through research licens

Designing a marker set for vertical tangible user interfaces

Tangible User Interfaces (TUI)s extend the domain of reality-based human-computer interaction by providing users the ability to manipulate digital data using physical objects which embody representational significance. Whilst various advancements have been registered over the past years through the development and availability of TUI toolkits, these have mostly converged towards the deployment of tabletop TUI architectures. In this context, markers used in current toolkits can only be placed underneath the tangible objects to provide recognition. Albeit being effective in various literature studies, the limitations and challenges of deploying tabletop architectures have significantly hindered the proliferation of TUI technology due to the limited audience reach such systems can provide. Furthermore, available marker sets restrict the placement and use of tangible objects since if placed on top of the tangible object, the marker will interfere with the shape and texture of the object limiting the effect the TUI has on the end-user. To this end, this paper proposes the design and development of an innovative tangible marker set specifically designed towards the development of vertical TUIs. The proposed marker set design was optimized through a genetic algorithms to ensure robustness in scale invariance, the capability of being successfully detected with distances of up to 3.5 meters and a true occlusion resistance of up to 25%, where the marker is recognized and not tracked. Open-source versions of the marker set are provided through research license on www.geoffslab.com/tangiboard_marker_set

Comparison of minimally invasive parathyroidectomy under local anaesthesia and minimally invasive video-assisted parathyroidectomy for primary hyperparathyroidism: A cost analysis

Background: Primary hyperparathyroidism (PHPT) origins from a solitary adenoma in 70-95% of cases. Moreover, the advances in methods for localizing an abnormal parathyroid gland made minimally invasive techniques more prominent. This study presents a micro-cost analysis of two parathyroidectomy techniques. Patients and methods: 72 consecutive patients who underwent minimally invasive parathyroidectomy, video-assisted (MIVAP, group A, 52 patients) or "open" under local anaesthesia (OMIP, group B, 20 patients) for PHPT were reviewed. Operating room, consumable, anaesthesia, maintenance costs, equipment depreciation and surgeons/anaesthesiologists fees were evaluated. The patient's satisfaction and the rate of conversion to conventional parathyroidectomy were investigated. T-Student's, Kolmogorov-Smirnov tests and Odds Ratio were used for statistical analysis. Results: 1 patient of the group A and 2 of the group B were excluded from the cost analysis because of the conversion to the conventional technique. Concerning the remnant patients, the overall average costs were: for Operative Room, 1186,69 \u20ac for the MIVAP group (51 patients) and 836,11 \u20ac for the OMIP group (p<0,001); for the Team, 122,93 \u20ac (group A) and 90,02 \u20ac (group B) (p<0,001); the other operative costs were 1388,32 \u20ac (group A) and 928,23 \u20ac (group B) (p<0,001). The patient's satisfaction was very strongly in favour of the group B (Odds Ratio 20,5 with a 95% confidence interval). Conclusions: MIVAP is more expensive compared to the "open" parathyroidectomy under local anaesthesia due to the costs of general anaesthesia and the longer operative time. Moreover, the patients generally prefer the local anaesthesia. Nevertheless, the rate of conversion to the conventional parathyroidectomy was relevant in the group of the local anaesthesia compared to the MIVAP, since the latter allows a four-gland exploration

Consequences of anisotropy in electrical charge storage: application to the characterization by the mirror method of TiO2 rutile

This article is devoted first to anisotropic distributions of stored electric charges in isotropic materials, second to charge trapping and induced electrostatic potential in anisotropic dielectrics. On the one hand, we examine the case of anisotropic trapped charge distributions in linear homogeneous isotropic (LHI) insulators, obtained after an electron irradiation in a scanning electron microscope. This injection leads to the formation of a mirror image

Charge-Fluctuation-Induced Non-analytic Bending Rigidity

In this Letter, we consider a neutral system of mobile positive and negative charges confined on the surface of curved films. This may be an appropriate model for: i) a highly charged membrane whose counterions are confined to a sheath near its surface; ii) a membrane composed of an equimolar mixture of anionic and cationic surfactants in aqueous solution. We find that the charge fluctuations contribute a non-analytic term to the bending rigidity that varies logarithmically with the radius of curvature. This may lead to spontaneous vesicle formation, which is indeed observed in similar systems.Comment: Revtex, 9 pages, no figures, submitted to PR

Description beyond the mean field approximation of an electrolyte confined between two planar metallic electrodes

We study an electrolyte confined in a slab of width $W$ composed of two grounded metallic parallel electrodes. We develop a description of this system in a low coupling regime beyond the mean field (Poisson--Boltzmann) approximation. There are two ways to model the metallic boundaries: as ideal conductors in which the electric potential is zero and it does not fluctuate, or as good conductors in which the average electric potential is zero but the thermal fluctuations of the potential are not zero. This latter model is more realistic. For the ideal conductor model we find that the disjoining pressure is positive behaves as $1/W^3$ for large separations with a prefactor that is universal, i.e. independent of the microscopic constitution of the system. For the good conductor boundaries the disjoining pressure is negative and it has an exponential decay for large $W$. We also compute the density and electric potential profiles inside the electrolyte. These are the same in both models. If the electrolyte is charge asymmetric we find that the system is not locally neutral and that a non-zero potential difference builds up between any electrode and the interior of the system although both electrodes are grounded.Comment: 16 pages, 5 figures, added a new appendix B and a discussion on ideal conductors vs. good conductor

Critical Casimir forces for O(n){\cal O}(n) systems with long-range interaction in the spherical limit

We present exact results on the behavior of the thermodynamic Casimir force and the excess free energy in the framework of the $d$-dimensional spherical model with a power law long-range interaction decaying at large distances $r$ as $r^{-d-\sigma}$, where $\sigma<d<2\sigma$ and $0<\sigma\leq2$. For a film geometry and under periodic boundary conditions we consider the behavior of these quantities near the bulk critical temperature $T_c$, as well as for $T>T_c$ and $T<T_c$. The universal finite-size scaling function governing the behavior of the force in the critical region is derived and its asymptotics are investigated. While in the critical and under critical region the force is of the order of $L^{-d}$, for $T>T_c$ it decays as $L^{-d-\sigma}$, where $L$ is the thickness of the film. We consider both the case of a finite system that has no phase transition of its own, when $d-1<\sigma$, as well as the case with $d-1>\sigma$, when one observes a dimensional crossover from $d$ to a $d-1$ dimensional critical behavior. The behavior of the force along the phase coexistence line for a magnetic field H=0 and $T<T_c$ is also derived. We have proven analytically that the excess free energy is always negative and monotonically increasing function of $T$ and $H$. For the Casimir force we have demonstrated that for any $\sigma \ge 1$ it is everywhere negative, i.e. an attraction between the surfaces bounding the system is to be observed. At $T=T_c$ the force is an increasing function of $T$ for $\sigma>1$ and a decreasing one for $\sigma<1$. For any $d$ and $\sigma$ the minimum of the force at $T=T_c$ is always achieved at some $H\ne 0$.Comment: 13 pages, revtex, 8 figure

Three-Particle Correlations in Simple Liquids

We use video microscopy to follow the phase-space trajectory of a two-dimensional colloidal model liquid and calculate three-point correlation functions from the measured particle configurations. Approaching the fluid-solid transition by increasing the strength of the pair-interaction potential, one observes the gradual formation of a crystal-like local order due to triplet correlations, while being still deep inside the fluid phase. Furthermore, we show that in a strongly interacting system the Born-Green equation can be satisfied only with the full triplet correlation function but not with three-body distribution functions obtained from superposing pair-correlations (Kirkwood superposition approximation).Comment: 4 pages, submitted to PRL, experimental paper, 2nd version: Fig.1 and two new paragraphs have been adde