A General Framework for Trajectory Triangulation

The multiple view geometry of static scenes is now well understood. Recently attention was turned to dynamic scenes where scene points may move while the cameras move. The triangulation of linear trajectories is now well handled. The case of quadratic trajectories also received some attention. We present a complete generalization and address the problem of general trajectory triangulation of moving points from non-synchronized cameras. Two cases are considered: (i) the motion is captured in the images by tracking the moving point itself, (ii) the tangents of the motion only are extracted from the images. The first case is based on a new representation (to computer vision) of curves (trajectories) where a curve is represented by a family of hypersurfaces in the projective space ?⁵. The second case is handled by considering the dual curve of the curve generated by the trajectory. In both cases these representations of curves allow: (i) the triangulation of the trajectory of a moving point from non-synchronized sequences, (ii) the recovery of more standard representation of the whole trajectory, (iii) the computations of the set of positions of the moving point at each time instant an image was made. Furthermore, theoretical considerations lead to a general theorem stipulating how many independent constraints a camera provides on the motion of the point. This number of constraint is a function of the camera motion. On the computation front, in both cases the triangulation leads to equations where the unknowns appear linearly. Therefore the problem reduces to estimate a high-dimensional parameter in presence of heteroscedastic noise. Several method are tested.     

Virtual Interpersonal Touch: Expressing and Recognizing Emotions Through Haptic Devices

ABSTRACT

This article examines the phenomenon of Virtual Interpersonal Touch (VIT), people touching one another via force-feedback haptic devices. As collaborative virtual environments become utilized more effectively, it is only natural that interactants will have the ability to touch one another. In the work presented here, we used relatively basic devices to begin to explore the expression of emotion through VIT. In Experiment 1, participants utilized a 2 DOF force-feedback joystick to express seven emotions. We examined various dimensions of the forces generated and subjective ratings of the difficulty of expressing those emotions. In Experiment 2, a separate group of participants attempted to recognize the recordings of emotions generated in Experiment 1. In Experiment 3, pairs of participants attempted to communicate the seven emotions using physical handshakes. Results indicated that humans were above chance when recognizing emotions via VIT but not as accurate as people expressing emotions through nonmediated handshakes. We discuss a theoretical framework for understanding emotions expressed through touch as well as the implications of the current findings for the utilization of VIT in human-computer interaction.     

Some natural flavonoids are competitive inhibitors of Caspase-1, -3 and -7 despite their cellular toxicity

A common feature of both apoptosis and inflammation is the activation of caspases. Caspases are aspartate-directed cysteine proteases that have numerous cellular targets. It has been discovered that several flavonoids are inhibitors of caspases. Flavonoids are members of a family of polyphenolic compounds from plants that have many biological properties, one of which is the ability to induce cell death. Some flavonoids are selective inhibitors of particular caspases. Since some of the inhibitory flavonoids are nevertheless cytotoxic, these results suggest that flavonoid-induced cell death may be occurring through a non-classical apoptosis pathway that is not dependent on caspase activity.     

Experimental Investigation of Wire Electrical Discharge Machining of NdFeB Permanent Magnets with an RC-Type Machine

This paper focuses on wire electrical discharge machining (WEDM) of devices made from commercially available sintered neodymium-iron-boron (NdFeB) rare-earth magnets that have been magnetized before machining. We conduct an experimental study to quantify the effects of the voltage and capacitance of an RC-type WEDM machine, as well as the magnet polarity, on slicing rate, mean kerf, and variation in kerf. We find that voltage and capacitance affect slicing rate, that voltage affects mean kerf, that no parameters tested affect the variation in kerf, and that the polarity of the magnet being machined does not affect the machining process. Linear regression is used to fit simple predictive models to the data with good agreement. Further analysis is performed to characterize the loss in permanent magnetization on the surface of the magnet due to heating during the machining process, and it is found that the outer layer of approximately 35 μm in depth is demagnetized when using the highest voltage and capacitance values tested.     

Simulation of Dynamic Earthquake Ruptures in Complex Geometries Using High-Order Finite Difference Methods

We develop a stable and high-order accurate finite difference method for problems in earthquake rupture dynamics in complex geometries with multiple faults. The bulk material is an isotropic elastic solid cut by pre-existing fault interfaces that accommodate relative motion of the material on the two sides. The fields across the interfaces are related through friction laws which depend on the sliding velocity, tractions acting on the interface, and state variables which evolve according to ordinary differential equations involving local fields. The method is based on summation-by-parts finite difference operators with irregular geometries handled through coordinate transforms and multi-block meshes. Boundary conditions as well as block interface conditions (whether frictional or otherwise) are enforced weakly through the simultaneous approximation term method, resulting in a provably stable discretization. The theoretical accuracy and stability results are confirmed with the method of manufactured solutions. The practical benefits of the new methodology are illustrated in a simulation of a subduction zone megathrust earthquake, a challenging application problem involving complex free-surface topography, nonplanar faults, and varying material properties.     

Urinary aflatoxin M1 in Port-au-Prince and a rural community in north-east Haiti

Aflatoxins (AFs) are hepatocarcinogenic mycotoxins that can contaminate grains and oil seeds in tropical and sub-tropical areas and have been detected in maize and peanut products of Haiti. The first objective was to assess human exposure to AFs among Haitians at an urban hospital (GHESKIO) and a rural health centre (HCBH). The second objective was to test the association between AF exposure and reported dietary intake of potentially contaminated foods, such as maize, peanut products and milk. Measurement of urinary AFM1 by HPLC revealed that among 367 participants 14% and 22% at GHESKIO and HCBH, respectively, had detectable AFM1. The maximum and median AFM1 concentrations for all detected samples were 700 pg AFM1 ml^–1 and 11.7 pg ml^–1, respectively. Detection of AFM1 was significantly associated with peanut consumption (p < 0.05). Controlling for diet and age group in a logit model, patients who reported peanut consumption the day of the survey and patients from HCBH had greater log odds of excreting detectable AFM1 (p < 0.001 and 0.002, respectively); females had lower log odds (p = 0.020). Recalled frequency of consuming non-dairy animal-sourced foods, an indicator of diet quality, approached significance (p = 0.056) as an inverse predictor of urinary AFM1 detection. The findings augur the need for interventions that will improve food safety in Haiti and limit exposure to AFs, particularly among rural communities.     

An Energy Stable Approach for Discretizing Hyperbolic Equations with Nonconforming Discontinuous Galerkin Methods

When nonconforming discontinuous Galerkin methods are implemented for hyperbolic equations using quadrature, exponential energy growth can result even when the underlying scheme with exact integration does not support such growth. Using linear elasticity as a model problem, we propose a skew-symmetric formulation that has the same energy stability properties for both exact and inexact quadrature-based integration. These stability properties are maintained even when the material properties are variable and discontinuous, and the elements are non-affine (e.g., curved). Additionally, we show how the nonconforming scheme can be made conservative and constant preserving with variable material properties and curved elements. The analytic stability, conservation, and constant preserving results are confirmed through numerical experiments demonstrating the stability as well as the accuracy of the method.     

Providing Dynamic Visual Information for Collaborative Tasks: Experiments With Automatic Camera Control

One possibility presented by novel communication technologies is the ability for remotely located experts to provide guidance to others who are performing difficult technical tasks in the real world, such as medical procedures or engine repair. In these scenarios, video views and other visual information seem likely to be useful in the ongoing negotiation of shared understanding, or common ground, but actual results with experimental systems have been mixed. One difficulty in designing these systems is achieving a balance between close-up shots that allow for discussion of detail and wide shots that allow for orientation or establishing a mutual point of focus in a larger space. Achieving this balance can be difficult without disorienting or overloading task participants. In this article we present results from two experiments involving three automated camera control systems for remote repair tasks. Results show that a system providing both detailed and overview information was superior to systems providing only one or the other in terms of performance but that some participants preferred the detail-only system.     

我真不是素描

<正>简单的纯白瓷块加上素描感十足的黑色包边,营造出立体插画般的视觉错觉。英国陶艺家Katharine Morling用坚硬的陶瓷创作出其他瓶瓶罐罐绝对没有的3D梦幻感。一台堪称古董级别的收银机内似乎装了太多的硬币,抽屉怎么也关不上,一旁放着订书机、记事本、笔筒等小杂物。如果不是有一圈黑色包边清晰地勾勒出轮廓,它们就像是微融的白巧克力。再仔细一看,似乎又像用柔软的纸张剪出的纸艺美物。然而轻轻敲几下,清脆