Phasing diffuse scattering. Application of the SIR2002 algorithm to the non-crystallographic phase problem

A new phasing algorithm has been used to determine the phases of diffuse elastic X-ray scattering from a non-periodic array of gold balls of 50 nm diameter. Two-dimensional real-space images, showing the charge-density distribution of the balls, have been reconstructed at 50 nm resolution from transmission diffraction patterns recorded at 550 eV energy. The reconstructed image fits well with scanning electron microscope (SEM) image of the same sample. The algorithm, which uses only the density modification portion of the SIR2002 program, is compared with the results obtained via the Gerchberg-Saxton-Fienup HIO algorithm. In this way the relationship between density modification in crystallography and the HiO algorithm used in signal and image processing is elucidated.Comment: 7 pages, 12 figure

Philosophy as political technē: The tradition of invention in Simondon’s political thought

Gilbert Simondon has recently attracted the interest of political philosophers and theorists, despite he is rather renowned as a philosopher of technics – as the author of Of the Mode of Existence of Technical Objects – who also elaborated a general theory of complex systems in Individuation in the Light of the Notions of Form and Information. A group of scholars has developed Gilles Deleuze’s early suggestion that Simondon’s social ontology might offer the basis for a re-theorisation of radical democracy. Others, following Herbert Marcuse, have instead focused on Simondon’s analysis of the relationship between technology and society. However, only a joint study of Simondon’s two major works can reveal their implicit political stakes. As I will argue, Simondon’s anti-Aristotelianism and his anti-Heideggerian understanding of the Greek origins of philosophy, allow us to conceive philosophical thought as a ‘tradition of invention’, that is, a pedagogical technē endowed with the political task of maintaining the openness of the social system and allowing normative invention to emerge from within

Multimodal representation of optic flow in area PEc of macaque monkey.

The visual perception of self-motion is mainly provided by optic flow. Eyes usually scan the environment during locomotion, and the gaze is not always directed to the focus of expansion (FOE) of the flow field. Such eye movements change the retinal FOE position with respect to the fovea. Here, we assess if optic flow selective neurons in parietal area PEc are modulated by eye position. We recorded single neuron activity during radial optic flow stimulation in two monkeys, varying eye and retinal FOE positions. We found that the majority of PEc neurons are modulated by the FOE retinotopic position with different tuning for expansion and contraction. Although many neurons did not show any gaze field without visual stimulation, the eye position modulated optic flow responses in about half of the cells. These novel results suggest that PEc neurons integrate both visual and eye position signals, and allow us to hypothesize their role in guiding locomotion as a part of a cortical network involved in FOE representation during self-motion. Visual and eye position interaction in this area could be seen as a contribution to the building of the invariant space representation necessary to motor planning