We discuss an implementation of an efficient algorithm for the numerical computation of Fourier transforms of bandlimited functions defined on the rotation group SO(3). The implementation is freely available on the web. The algorithm described herein uses O(B 4 ) operations to compute the Fourier coefficients of a function whose Fourier expansion uses only (the O(B 3 )) spherical harmonics of degree at most B. This compares very favorably with the direct O(B 6 ) algorithm derived from a basic quadrature rule on O(B 3 ) sample points. The efficient Fourier transform also makes possible the efficient calculation of convolution over SO(3) which has been used as the analytic engine for some new approaches to searching 3D databases (Funkhouser et al.fast SO(3) algorithm can be improved to give an algorithm of complexity O(B 3 log 2 B), but at a cost in numerical reliability. Numerical and empirical results are presented establishing the empirical stability of the basic algorithm. Examples of applications are presented as well.
The Functional Magnetic Resonance Imaging Data Center (fMRIDC) (http://www.fmridc.org) was established in the Autumn of 1999 with the objective of creating a mechanism by which members of the neuroscienti¢c community may more easily share functional neuroimaging data. Examples in other sciences o¡er proof of the usefulness and bene¢t that sharing data provides through encouraging growth and development in those ¢elds. By building a publicly accessible repository of raw data from peerreviewed studies, the Data Center hopes to create a similarly successful environment for the neurosciences.In this article, we discuss the continuum of data-sharing e¡orts and provide an overview of the scienti¢c and practical di¤culties inherent in managing various fMRI data-sharing approaches. Next, we detail the organization, design and foundation of the fMRIDC, ranging from its current capabilities to the issues involved in the submitting and requesting of data. We discuss how a publicly accessible database enables other ¢elds to develop relevant tools that can aid in the growth of understanding of cognitive processes. Information retrieval and meta-analytic techniques can be used to search, sort and categorize study information with a view towards subjecting study data to secondary`meta-' and`mega-analyses'. In addition, we detail the technical and policy challenges that have had to be addressed in the formation of the Data Center. Among others, these include: human subject con¢dentiality issues; ensuring investigator's rights; heterogeneous data description and organization; development of search tools; and data transfer issues. We conclude with comments concerning the future of the fMRIDC e¡ort, its role in promoting the sharing of neuroscienti¢c data, and how this may alter the manner in which studies are published.
We have developed a multiscale algorithm for elastic (or molded) alignment of images. There is a wide array of medical applications of elastic (as opposed to strictly rigid) alignment: Subtraction of previous images from current ones to identify changes is perhaps the most obvious. We present preliminary results of this molding technique on a variety of images, and conclude with some closing remarks about this and future directions and goals of this work.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.