Spatiotemporal PET reconstruction using ML-EM with learned diffeomorphic deformation

Patient movement in emission tomography deteriorates reconstruction quality because of motion blur. Gating the data improves the situation somewhat: each gate contains a movement phase which is approximately stationary. A standard method is to use only the data from a few gates, with little movement between them. However, the corresponding loss of data entails an increase of noise. Motion correction algorithms have been implemented to take into account all the gated data, but they do not scale well, especially not in 3D. We propose a novel motion correction algorithm which addresses the scalability issue. Our approach is to combine an enhanced ML-EM algorithm with deep learning based movement registration. The training is unsupervised, and with artificial data. We expect this approach to scale very well to higher resolutions and to 3D, as the overall cost of our algorithm is only marginally greater than that of a standard ML-EM algorithm. We show that we can significantly decrease the noise corresponding to a limited number of gates

Molecular Characterization of the Gastrula in the Turtle Emys orbicularis: An Evolutionary Perspective on Gastrulation

Due to the presence of a blastopore as in amphibians, the turtle has been suggested to exemplify a transition form from an amphibian- to an avian-type gastrulation pattern. In order to test this hypothesis and gain insight into the emergence of the unique characteristics of amniotes during gastrulation, we have performed the first molecular characterization of the gastrula in a reptile, the turtle Emys orbicularis. The study of Brachyury, Lim1, Otx2 and Otx5 expression patterns points to a highly conserved dynamic of expression with amniote model organisms and makes it possible to identify the site of mesoderm internalization, which is a long-standing issue in reptiles. Analysis of Brachyury expression also highlights the presence of two distinct phases, less easily recognizable in model organisms and respectively characterized by an early ring-shaped and a later bilateral symmetrical territory. Systematic comparisons with tetrapod model organisms lead to new insights into the relationships of the blastopore/blastoporal plate system shared by all reptiles, with the blastopore of amphibians and the primitive streak of birds and mammals. The biphasic Brachyury expression pattern is also consistent with recent models of emergence of bilateral symmetry, which raises the question of its evolutionary significance

How Irish citizens negotiate foreign policy : a social representations approach to neutrality

The present study investigates the relationship between the foreign policy orientation of Irish neutrality and national identity using a social representations approach (Elcheroth, Doise, & Reicher, 2011; Moscovici, 1961/76). In four focus groups conducted in the Republic of Ireland, 22 participants discussed vignettes in which hypothetical conflicts were described. The findings pointed towards the dynamic relationship between neutrality and Irish national identity and more generally to the importance of macropolitical phenomena for identity construction. The process of categorization was key to participants' decision making regarding the hypothetical conflicts; the decision to support or oppose the Irish state's involvement in the conflicts frequently revolved around a reconsideration of the boundaries of the ingroup. Furthermore, social representations were laden with the possibility of social change; the construction of neutrality as morally ambivalent, motivated by pragmatism rather than principles, opened up a space for younger participants to resist dominant, pragmatic interpretations of the policy and offer alternatives. Theoretical and empirical implications of the findings are discussed. Taken together, the findings demonstrate the critical potential of extending a social representations approach to issues of political psychological significance