Generation and Propagation of Optical Vortices

Optical vortices are singularities in phase fronts of laser beams. They are characterized by a dark core whose size may dramatically affect their behavior upon propagation. Previously, only large-core vortices have been extensively studied. The object of the research presented in this dissertation was to explore ways of generating small-core optical vortices (also called optical vortex filaments), and to examine their propagation using analytical, numerical and experimental methods. Computer-generated holography enabled us to create arbitrary distributions of optical vortex filaments for experimental exploration. We used hydrodynamic paradigms to develop an heuristic model which described the dependence of vortex motion on other vortices and the background beam, both qualitatively and quantitatively. We predicted that pair of optical vortex filaments will rotate with angular rates inversely proportional to their separation distance (just like vortices in a fluid). We also reported the first experimental observation of this novel fluid-like effect. It was found, however, that upon propagation in linear media, the fluid-like rotation was not sustained owing to the overlap of diffracting vortex cores. Further numerical studies and experiments showed that rotation angle may be enhanced in nonlinear self-defocusing media. The results presented in this thesis offer us a better understanding of dynamics of propagating vortices which may result in applications in optical switching, manipulation of micro-particles and optical limiting

Research informing policy: an analysis of an emerging blockchain-enabled collaborative economy

Depto. de Ingeniería de Software e Inteligencia Artificial (ISIA)Fac. de InformáticaFALSEUnión Europea. Horizonte 2020Joint Research Centre (JRC)unpu

Potentialities and limitations of blockchain technologies in the governance of social enterprise collectives: the case of Smart Ibérica

Depto. de Ingeniería de Software e Inteligencia Artificial (ISIA)Fac. de InformáticaTRUEUnión Europea. Horizonte 2020pu

HIIphot: Automated Photometry of HII Regions Applied to M51

We have developed a robust, automated method, hereafter designated HIIphot, which enables accurate photometric characterization of HII regions while permitting genuine adaptivity to irregular source morphology. HIIphot utilizes object-recognition techniques to make a first guess at the shapes of all sources then allows for departure from such idealized ``seeds'' through an iterative growing procedure. Photometric corrections for spatially coincident diffuse emission are derived from a low-order surface fit to the background after exclusion of all detected sources. We present results for the well-studied, nearby spiral M51 in which 1229 HII regions are detected above the 5-sigma level. A simple, weighted power-law fit to the measured H-alpha luminosity function (HII LF) above log L_H-alpha = 37.6 gives alpha = -1.75+/-0.06, despite a conspicuous break in the HII LF observed near L_H-alpha = 10^38.9. Our best- fit slope is marginally steeper than measured by Rand (1992), perhaps reflecting our increased sensitivity at low luminosities and to notably diffuse objects. HII regions located in interarm gaps are preferentially less luminous than counterparts which constitute M51's grand-design spiral arms and are best fit with a power-law slope of alpha = -1.96+/-0.15. We assign arm/interarm status for HII regions based upon the varying surface brightness of diffuse emission as a function of position throughout the image. Using our measurement of the integrated flux contributed by resolved HII regions in M51, we estimate the diffuse fraction to be approximately 0.45 -- in agreement with the determination of Greenawalt et al. (1998). Automated processing of degraded datasets is undertaken to gauge systematic effects associated with limiting spatial resolution and sensitivity.Comment: 41 pages, 14 figures, Postscript version with high-resolution figures at ftp://ftp.aoc.nrao.edu/staff/dthilker/preprint

Integration of ontologies with decentralized autonomous organizations development: A systematic literature review

This paper presents a systematic literature review of the integration of ontologies into the Decentralized Autonomous Organization (DAO) development process. The review extracted data from 34 primary studies dealing with ontologies in the blockchain domain. DAO has become a key concept for the development of blockchain-based decentralized software systems. DAOs are seen as a positive alternative for organizations interested in the adoption of decentralized, reliable and transparent governance, as well as attracting the interest of academic research. However, there is no common understanding or generally accepted formal definition of a DAO, and the guidelines that provide support for the adoption and development of DAOs are limited to a few key references that lack the computational semantics needed to enable their automated validation, simulation or execution. Thus, the objective of this paper is to provide an unbiased and up-to-date review related to the integration of ontologies within DAOs which helps to identify new research opportunities and take advantage of this integration from a blockchain-based decentralized perspective

Maintaining an affective commons through events: a practice-based study of three collaborative communities

Depto. de Ingeniería de Software e Inteligencia Artificial (ISIA)Fac. de InformáticaFALSEunpu

Comment on 'The Molecular Evolutionary Patterns of the Insulin/FOXO Signaling Pathway'

Letter to the Editor on Wang M, Wang Q, Wang Z, Zhang X, Pan Y. The molecular evolutionary patterns of the insulin/FOXO signaling pathwa

Ostrom’s crypto-principles? Towards a commons-based approach for the use of Blockchain technologies for self-governance

Fac. de InformáticaTRUEUnión Europea. Horizonte 2020pu