Universal inversion formulas for recovering a function from spherical means

The problem of reconstruction a function from spherical means is at the heart of several modern imaging modalities and other applications. In this paper we derive universal back-projection type reconstruction formulas for recovering a function in arbitrary dimension from averages over spheres centered on the boundary an arbitrarily shaped smooth convex domain. Provided that the unknown function is supported inside that domain, the derived formulas recover the unknown function up to an explicitly computed smoothing integral operator. For elliptical domains the integral operator is shown to vanish and hence we establish exact inversion formulas for recovering a function from spherical means centered on the boundary of elliptical domains in arbitrary dimension.Comment: [20 pages, 2 figures] Compared to the previous versions I corrected some typo

A series solution and a fast algorithm for the inversion of the spherical mean Radon transform

An explicit series solution is proposed for the inversion of the spherical mean Radon transform. Such an inversion is required in problems of thermo- and photo- acoustic tomography. Closed-form inversion formulae are currently known only for the case when the centers of the integration spheres lie on a sphere surrounding the support of the unknown function, or on certain unbounded surfaces. Our approach results in an explicit series solution for any closed measuring surface surrounding a region for which the eigenfunctions of the Dirichlet Laplacian are explicitly known - such as, for example, cube, finite cylinder, half-sphere etc. In addition, we present a fast reconstruction algorithm applicable in the case when the detectors (the centers of the integration spheres) lie on a surface of a cube. This algorithm reconsrtucts 3-D images thousands times faster than backprojection-type methods

Coupling of Two Motor Proteins: a New Motor Can Move Faster

We study the effect of a coupling between two motor domains in highly-processive motor protein complexes. A simple stochastic discrete model, in which the two parts of the protein molecule interact through some energy potential, is presented. The exact analytical solutions for the dynamic properties of the combined motor species, such as the velocity and dispersion, are derived in terms of the properties of free individual motor domains and the interaction potential. It is shown that the coupling between the motor domains can create a more efficient motor protein that can move faster than individual particles. The results are applied to analyze the motion of helicase RecBCD molecules

Pressure Drop: Securitising and De-Securitising Safeguarding

This article explores how securitization theory is mobilised in contemporary social work discourse, policy and practice. We draw on recent child protection research to support our claim that a new practice issue, described previously as securitised safeguarding, has emerged. We demonstrate its emergence using securitization theory as a conceptual mode of analysis to describe how a securitised safeguarding response depicts particular families as an existential threat, which in turn, prompts a response characterised by forms of muscular liberalism. We argue that this emerging practice issue requires critical consideration and suggest it will have a significant impact on social work; one that is unlikely to be beneficial for the profession and more importantly, families being worked with. By describing a process of de-securitisation, we offer an alternative and more nuanced approach, that perceives families holistically, and mobilises a welfare safeguarding model. This more closely resembles traditional social work values of emancipation, liberation and empowerment within social work practice

Don't Forget Your ABC's: Evaluating the State-of-the-Art in Chat-Oriented Dialogue Systems

Despite tremendous advancements in dialogue systems, stable evaluation still requires human judgments producing notoriously high-variance metrics due to their inherent subjectivity. Moreover, methods and labels in dialogue evaluation are not fully standardized, especially for open-domain chats, with a lack of work to compare and assess the validity of those approaches. The use of inconsistent evaluation can misinform the performance of a dialogue system, which becomes a major hurdle to enhance it. Thus, a dimensional evaluation of chat-oriented open-domain dialogue systems that reliably measures several aspects of dialogue capabilities is desired. This paper presents a novel human evaluation method to estimate the rates of many dialogue system behaviors. Our method is used to evaluate four state-of-the-art open-domain dialogue systems and compared with existing approaches. The analysis demonstrates that our behavior method is more suitable than alternative Likert-style or comparative approaches for dimensional evaluation of these systems.Comment: Accepted to ACL 2023; first two authors contributed equall

Space Shuttle: MDAC/MMC space shuttle booster determination of stability and control characteristics and power effects at subsonic speed, Mach numbers zero and 0.26

Low speed wind tunnel tests of stability and control characteristics of space shuttle booster at subsonic speed

MASCULINE HEGEMONY AND FEMININE ALTERITY IN BAUDELAIRE'S 'A UNE MENDIANTE ROUSSE'

This is the author accepted manuscript. The final version is available from Oxford University via http://dx.doi.org/10.1093/frebul/ktu01