A new process associated with the nonlinear optical properties of the electromagnetic vacuum, as predicted by quantum electrodynamics, is described. This can be called photon acceleration in vacuum, and corresponds to the frequency shift that takes place when a given test photon interacts with an intense beam of background radiation. PACS: 12.20.Ds, 95.30.-k

By using the relativistic top theory, we derive a relativistic top deviation equation. This equation turns out to be a generalization of the geodesic deviation equation for a pair of nearby point particles. In fact, we show that when the spin angular momentum tensor associated to the top vanishes, such a relativistic top deviation equation reduces to the geodesic deviation equation for spinless...

In this work we re-examine the opacity of the cosmic background radiation to the propagation of extremely high energy cosmic rays. We use the continuous energy loss approximation to provide spectral modification factors for several hypothesized cosmic ray sources. Earlier problems with this approximation are resolved including the effects of resonances other than the ∆. PACS numbers: 96.40,13.8...

Most segmentation methods are based on a relatively simple score, designed to lend itself to relatively efficient optimization. We take the opposite approach and suggest more complex segmentation scores that are based on a mixture of on-line and off-line learning processes and rely on rich descriptors. The score is evaluated by a segmentation process which uses exploration-exploitation to searc...

Background subtraction is a common method for detecting moving objects from static cameras able to achieve real-time performance. However, it is highly dependent on a good background model particularly to deal with dynamic scenes. In this paper a novel real-time algorithm for creating a robust and multimodal background model is presented. The proposed approach is based on an on-line clustering ...

Multiple object tracking has a broad range of applications ranging from video surveillance to robotics. In this work, we extend the application field to automated conveying systems. Inspired by tracking methods applied to video surveillance, we follow an on-line trackingby-detection approach based on background subtraction. The logistics applications turn out to be a challenging scenario for ex...

Recently several methods for background subtraction from moving camera were proposed. They use bottom up cues to segment video frames into foreground and background regions. Due to this lack of explicit models, they can easily fail to detect a foreground object when such cues are ambiguous in certain parts of the video. This becomes even more challenging when videos need to be processed online....

Despite a contemporary milieu that emphasises fluidities across gender boundaries and shifting roles, the 75 respondents in the study that informs this paper presented their food auto/biographies as a type of transformation narrative heavily influenced by the continued intersectionalities of gender and class. Respondents utilised ‘common vocabularies’ (Mills 1959) and conformed to cultural scri...

Methodological discussions in science have become increasingly common since the 1990s, particularly in fields such as economics, ecology, psychology, epidemiology, and several interdisciplinary domains – indeed in areas most faced with limited data, error, and noise. Contributors to collections on research methods, at least at some point, try to ponder, grapple with, or reflect on general issue...