The fundamental solution of the unidirectional pulse propagation equation

The fundamental solution of a variant of the three-dimensional wave equation known as "unidirectional pulse propagation equation" (UPPE) and its paraxial approximation is obtained. It is shown that the fundamental solution can be presented as a projection of a fundamental solution of the wave equation to some functional subspace. We discuss the degree of equivalence of the UPPE and the wave equation in this respect. In particular, we show that the UPPE, in contrast to the common belief, describes wave propagation in both longitudinal and temporal directions, and, thereby, its fundamental solution possesses a non-causal character.Comment: accepted to J. Math. Phy

New Hypothesis for Cause of Epidemic among Native Americans, New England, 1616–1619

This epidemic may have been leptospirosis complicated by Weil syndrome

Hidden Cues in Random Line Stereograms

Successful fusion of random-line stereograms with breaks in the vernier acuity range has been interpreted to suggest that the interpolation process underlying hyperacuity is parallel and preliminary to stereomatching. In this paper (a) we demonstrate with computer experiments that vernier cues are not needed to solve the stereomatching problem posed by these stereograms and (b) we provide psychophysical evidence that human stereopsis probably does not use vernier cues alone to achieve fusion of these random-line stereograms.MIT Artificial Intelligence Laborator

The Conditional Lucas & Kanade Algorithm

The Lucas & Kanade (LK) algorithm is the method of choice for efficient dense image and object alignment. The approach is efficient as it attempts to model the connection between appearance and geometric displacement through a linear relationship that assumes independence across pixel coordinates. A drawback of the approach, however, is its generative nature. Specifically, its performance is tightly coupled with how well the linear model can synthesize appearance from geometric displacement, even though the alignment task itself is associated with the inverse problem. In this paper, we present a new approach, referred to as the Conditional LK algorithm, which: (i) directly learns linear models that predict geometric displacement as a function of appearance, and (ii) employs a novel strategy for ensuring that the generative pixel independence assumption can still be taken advantage of. We demonstrate that our approach exhibits superior performance to classical generative forms of the LK algorithm. Furthermore, we demonstrate its comparable performance to state-of-the-art methods such as the Supervised Descent Method with substantially less training examples, as well as the unique ability to "swap" geometric warp functions without having to retrain from scratch. Finally, from a theoretical perspective, our approach hints at possible redundancies that exist in current state-of-the-art methods for alignment that could be leveraged in vision systems of the future.Comment: 17 pages, 11 figure

Erythromycin-induced resistance to clindamycin in Staphylococcus aureus.

PURPOSE: To describe the incidence of erythromycin-induced resistance to clindamycin in a sample of Staphylococcus aureus isolates. METHODS: 100 erythromycin-resistant and clindamycin-sensitive S. aureus were collected as a convenience sample from February to August 2003. Inducible clindamycin resistance was identified using the D-zone disc method. RESULTS: Of the 100 Staphylococcus aureus isolates, 64 were methicillin sensitive (MSSA) and 36 were methicillin resistant (MRSA). Of the 64 MSSA isolates, 22 (34%) had inducible resistance. Of the 36 MRSA isolates, 4 (11%) had inducible resistance. Overall, 26% of these clindamycin sensitive S. aureus isolates, exhibited inducible resistance to clindamycin. CONCLUSIONS: In this sample, MSSA isolates were almost three times more likely to have inducible MLS resistance compared to MRSA isolates. Inducible resistance may compromise the efficacy of clindamycin. The frequency of inducible resistance in this series of "clindamycin sensitive" S. aureus isolates is 26%. It is likely that the true percentage of clindamycin resistance is being underestimated since testing for inducible resistance is not routinely performed