Proprietà in banda radio di nuclei galattici attivi

Questa tesi si propone di descrivere le principali proprietà di quella categoria di corpi celesti noti come AGN. La trattazione sviluppa questa analisi operando una prima divisione in sorgenti estese e sorgenti compatte, descrivendo poi nello specifico i corpi celesti appartenenti all’una o all’altra tipologia. In seguito, sono stati illustrati i vari modelli unificati, tentativi teorici orientati a descrivere questi oggetti diversi all’osservazione, come in realtà manifestazioni dello stesso oggetto. Nella sezione quarta di questa sede sono state operate le necessarie considerazioni relativistiche dovute alle alte velocità raggiunte dai getti espulsi da questo tipo di corpi. In merito a ciò è stato preso in esame il quasar a spettro piatto 4C 38.41. Osservando l’evoluzione dei suoi getti si è osservato un moto superluminale con un β_apparente ~ 9, spiegato con considerazioni di natura geometrica

Stakeholder engagement via facebook. An analysis of world’s most popular museums

Over the last few years, social media (SM) have been emphasised as a means for organisations to foster stakeholder relationship with particular stress on their potential to promote community building and dialogic engagement with online audiences. These potential benefits of SM have been claimed also with respect to cultural organisations. However, the available research evidence on SM and museums suggests that museums still struggle to exploit these tools to their full potential. This paper adds further evidence on this issue by empirically investigating whether museums are using Facebook to promote follower engagement using a sample of top-attended museums worldwide. Results suggest that the frequency and content type of posts correlate to some extent with the degree of follower reactions. Nevertheless, sample museums predominantly use SM to publish promotional contents and as a result fail to achieve a true ‘dialogic’ follower engagement

Digitalization and firm financial performance in healthcare: the mediating role of intellectual capital efficiency

The digitalization of processes in healthcare sector firms is expected to reduce costs, improve the quality of healthcare service, customer care experience, and patient safety, and attain efficiency and efficacy in project implementation. This research investigates the impact of digitalization on the financial performance of healthcare-sector firms in the European Union. The study also examines whether a firm’s intellectual capital efficiency mediates the process of digitalization’s impact on a firm’s financial performance. Using a sample of 965 firm observations from 2017 to 2021, we find that digitalization positively affects financial performance. Further analysis suggests that capital-employed efficiency fully mediates the relationship between digitalization and firm performance. Partial mediation is also reported for intellectual capital efficiency, human capital efficiency, and structural capital efficiency in the process of digitalization impacting firm performance. These findings provide fresh insight into how digitalization impacts a firm’s financial performance, establishing intellectual capital efficiency as a mediating mechanism that may explain this impact

Manipulating electronic states at oxide interfaces using focused micro X-rays from standard lab-sources

Recently, x-ray illumination, using synchrotron radiation, has been used to manipulate defects, stimulate self-organization and to probe their structure. Here we explore a method of defect-engineering low-dimensional systems using focused laboratory-scale X-ray sources. We demonstrate an irreversible change in the conducting properties of the 2-dimensional electron gas at the interface between the complex oxide materials LaAlO3 and SrTiO3 by X-ray irradiation. The electrical resistance is monitored during exposure as the irradiated regions are driven into a high resistance state. Our results suggest attention shall be paid on electronic structure modification in X-ray spectroscopic studies and highlight large-area defect manipulation and direct device patterning as possible new fields of application for focused laboratory X-ray sources.Comment: 12 pages, 4 figure

X-rays writing/reading of Charge Density Waves in the CuO2 plane of a simple cuprate superconductor

It is now well established that superconductivity in cuprates competes with charge modulations giving electronic phase separation at a nanoscale. More specifically, superconducting electronic current takes root in the available free space left by electronic charge ordered domains, called charge density wave (CDW) puddles. This means that CDW domain arrangement plays a fundamental role in the mechanism of high temperature superconductivity in cuprates. Here we report about the possibility of controlling the population and spatial organization of the charge density wave puddles in a single crystal La2CuO4+y through X - ray illumination and thermal treatments. We apply a pump - probe method based on X - ray illumination as pump and X - ray diffraction as a probe setting a writing and reading procedure of CDW puddles. Our findings are expected to allow new routes for advanced design and manipulation of superconducting pathways in new electronics.Comment: 11 Pages 4 figure

Singlet‐Triplet Excited‐State Inversion in Heptazine and Related Molecules: Assessment of TD‐DFT and ab initio Methods

We have investigated the origin of the S1-T1 energy levels inversion for heptazine, and other N-doped π-conjugated hydrocarbons, leading thus to an unusually negative singlet-triplet energy gap (DEST < 0). Since this inversion might rely on substantial doubly-excited configurations to the S1 and/or T1 wavefunctions, we have systematically applied multi-configurational SA-CASSCF and SC-NEVPT2 methods, SCS-corrected CC2 and ADC(2) approaches, and linear-response TD-DFT, to analyse if the latter method could also face this challenging issue. We have also extended the study to B-doped π-conjugated systems, to see the effect of chemical composition on the results. For all the systems studied, an intricate interplay between the singlet-triplet exchange interaction, the influence of doubly-excited configurations, and the impact of dynamic correlation effects, serves to explain the DEST < 0 values found for most of the compounds, which is not predicted by TD-DFT.The work in Alicante is supported by “Ministerio de Ciencia e Innovación” of Spain (Grant No. PID2019-106114GB–I00). Computational resources in Namur are provided by the “Consortium des Équipements de Calcul Intensif” (CÉCI), funded by the “Fonds de la Recherche Scientifiques de Belgique” (F.R.S.-F.N.R.S.) under Grant No. 2.5020.11. G.R. acknowledges a grant from the “Fonds pour la formation a la Recherche dans l’Industrie et dans l’Agriculture” (F.R.I.A.) of the F.R.S.-F.N.R.S