Teaching Physics Using Virtual Reality

We present an investigation of game-like simulations for physics teaching. We report on the effectiveness of the interactive simulation "Real Time Relativity" for learning special relativity. We argue that the simulation not only enhances traditional learning, but also enables new types of learning that challenge the traditional curriculum. The lessons drawn from this work are being applied to the development of a simulation for enhancing the learning of quantum mechanics

Time-of-flight imaging of invisibility cloaks

As invisibility cloaking has recently become experimental reality, it is interesting to explore ways to reveal remaining imperfections. In essence, the idea of most invisibility cloaks is to recover the optical path lengths without an object (to be made invisible) by a suitable arrangement around that object. Optical path length is proportional to the time of flight of a light ray or to the optical phase accumulated by a light wave. Thus, time-of-flight images provide a direct and intuitive tool for probing imperfections. Indeed, recent phase-sensitive experiments on the carpet cloak have already made early steps in this direction. In the macroscopic world, time-of-flight images could be measured directly by light detection and ranging (LIDAR). Here, we show calculated time-of-flight images of the conformal Gaussian carpet cloak, the conformal grating cloak, the cylindrical free-space cloak, and of the invisible sphere. All results are obtained by using a ray-velocity equation of motion derived from Fermat’s principle

Numerical calculations of effective elastic properties of two cellular structures

Young's moduli of regular two-dimensional truss-like and eye-shape-like structures are simulated by using the finite element method. The structures are the idealizations of soft polymeric materials used in the electret applications. In the simulations size of the representative smallest units are varied, which changes the dimensions of the cell-walls in the structures. A power-law expression with a quadratic as the exponential term is proposed for the effective Young's moduli of the systems as a function of the solid volume fraction. The data is divided into three regions with respect to the volume fraction; low, intermediate and high concentrations. The parameters of the proposed power-law expression in each region are later represented as a function of the structural parameters, unit-cell dimensions. The presented expression can be used to predict structure/property relationship in materials with similar cellular structures. It is observed that the structures with volume fractions of solid higher than 0.15 exhibit the importance of the cell-wall thickness contribution in the elastic properties. The cell-wall thickness is the most significant factor to predict the effective Young's modulus of regular cellular structures at high volume fractions of solid. At lower concentrations of solid, eye-like structure yields lower Young's modulus than the truss-like structure with the similar anisotropy. Comparison of the numerical results with those of experimental data of poly(propylene) show good aggreement regarding the influence of cell-wall thickness on elastic properties of thin cellular films.Comment: 7 figures and 2 table

Correlation between safety attitudes and early adoption of cognitive aids in the German culture sphere: a multicenter survey study

Background: Cognitive Aids (checklists) are a common tool to improve patient safety. But the factors for their successful implementation and continuous use are not yet fully understood. Recent publications suggest safety culture to play a key role in this context. However, the effects on the outcome of implementation measures remain unclear. Hospitals and clinics that are involved in cognitive aid development and research might have significantly different safety cultures than their counterparts, resulting in skewed assessments of proper implementation. Therefore, the objective of this study was to assess the correlation between cognitive aid implementation and safety attitudes of staff members in early adopting and later adopting clinics. Methods: An online survey of the Safety Attitudes Questionnaire (SAQ) was carried out in German anaesthesiology departments during the initial implementation of a new checklist for emergencies during anesthesia (“eGENA” app). Subsequently an analysis between subgroups (“eGENA” app usage and occupation), with Kruskal–Wallis- and Mann–Whitney-U-Tests was carried out for the general SAQ, as well as it six subscales. Results: Departments that introduced “eGENA” app (Median 3,74, IQR 0,90) reported a significantly higher median SAQ (U (NeGENA = 6, Nnon eGENA = 14) = 70,0, z = 2,31, p = 0,02, r = 0,516) than their counterparts (Median 2,82, IQR 0,77) with significant differences in the dimensions teamwork climate, work satisfaction, perception of management and working conditions. Conclusion: Early adopters of cognitive aids are likely to show a significantly higher perception of safety culture in the SAQ. Consequently, successful implementation steps from these settings might not be sufficient in different clinics. Therefore, further investigation of the effects of safety culture on cognitive aid implementation should be conducted

VADA: A transformation-based system for variable dependence analysis

Variable dependence is an analysis problem in which the aim is to determine the set of input variables that can affect the values stored in a chosen set of intermediate program variables. This paper shows the relationship between the variable dependence analysis problem and slicing and describes VADA, a system that implements variable dependence analysis. In order to cover the full range of C constructs and features, a transformation to a core language is employed Thus, the full analysis is required only for the core language, which is relatively simple. This reduces the overall effort required for dependency analysis. The transformations used need preserve only the variable dependence relation, and therefore need not be meaning preserving in the traditional sense. The paper describes how this relaxed meaning further simplifies the transformation phase of the approach. Finally, the results of an empirical study into the performance of the system are presented

Tapered N-helical metamaterials with three-fold rotational symmetry as improved circular polarizers

Chiral helix-based metamaterials can potentially serve as compact and broadband circular polarizers. We have recently shown that the physics of structures composed of multiple intertwined helices, so called N-helices with N being an integer multiple of 4, is distinct from that of structures made of single circular helices (N = 1). In particular, undesired circular polarization conversion is strictly eliminated for N = 4 helices arranged on a square lattice. However, the fabrication of such structures for infrared/visible operation wavelengths still poses very significant challenges. Thus, we here revisit the possibility of reducing N from 4 to 3, which would ease micro-fabrication considerably. We show analytically that N = 3 helices arranged on a hexagonal lattice exhibit strictly vanishing circular polarization conversion. N = 3 is the smallest option as N = 2 obviously leads to linear birefringence. To additionally improve the circular-polarizer operation bandwidth and the extinction ratio while maintaining high transmission for the wanted polarization and zero conversion, we also investigate by numerical calculations N = 3 helices with tapered diameter along the helix axis. We find operation bandwidths as large as 2.4 octaves

2335 Evaluation of anterior chamber angle: Gonioscopy, ultrasound biomicroscopy and scheimpflug photography

Aprovat per la Comissió de Govern de 10-09-2014El termini de la suspensió serà, com a màxim, d'un any, a comptar des de l'endemà de la publicació al BO

The rise of (Chiral) 3D mechanical metamaterials

On the occasion of this special issue, we start by briefly outlining some of the history and future perspectives of the field of 3D metamaterials in general and 3D mechanical metamaterials in particular. Next, in the spirit of a specific example, we present our original numerical as well as experimental results on the phenomenon of acoustical activity, the mechanical counterpart of optical activity. We consider a three-dimensional chiral cubic mechanical metamaterial architecture that is different from the one that we have investigated in recent early experiments. We find even larger linear-polarization rotation angles per metamaterial crystal lattice constant than previously and a slower decrease of the effects towards the bulk lim