PKS 1510-089: a rare example of a flat spectrum radio quasar with a very high-energy emission

The blazar PKS 1510-089 is an example of flat spectrum radio quasars. High-energy emissions from this class of objects are believed to have been produced by inverse Compton radiation with seed photons originating from the broad line region. In such a paradigm, a lack of very high-energy emissions is expected because of the Klein-Nishina effect and strong absorption in the broad line region. Recent detection of at least three such blazars by Cherenkov telescopes has forced a revision of our understanding of these objects. We have aimed to model the observed spectral energy distribution of PKS 1510-089 from the high-energy flares in March 2009, during which very high-energy emission were also detected by H.E.S.S. We have applied the single-zone internal shock scenario to reproduce the multiwavelength spectrum of PKS~1510-089. We have followed the evolution of the electrons as they propagate along the jet and emit synchrotron and inverse Compton radiation. We have considered two sources of external photons: the dusty torus and the broad line region. We have also examined the effects of the gamma-gamma absorption of the high-energy photons both in the AGN environment (the broad line region and the dusty torus), as well as while traveling over cosmological distances: the extragalactic background light. We have successfully modeled the observed spectrum of PKS 1510-089. In our model, the highest energy emission is the result of the Comptonization of the infrared photons from the dusty torus, thus avoiding Klein-Nishina regime, while the bulk of the emissions in the GeV range may still be dominated by the Comptonization of radiation coming from the broad line region.Comment: Accepted for publication in A&

Causes, prevention, and interventions regarding classroom disruptions in digital teaching: A systematic review

Digitization and the Sars-CoV-2 pandemic are accelerating the use of digital tools in teaching. Therefore, this systematic literature review offers an overview of international studies with a particular focus on classroom disruptions and their causes, as well as on prevention and intervention strategies in digital settings. Selecting out of over 700 published articles from the last 20 years, the results show that, although the research on classroom management in general is numerous, the connection between digitization and classroom disruptions has received little attention so far. Studies of different methodological orientations have been conducted, but strongly teacher-focused. Also, there are conceptual inaccuracies leading to a variety of different findings and interpretations. Thus, this article provides a definition of the term digital teaching and critically discusses the classification of new findings, their emplacement in existing research, as well as their potential to expand existing models. Furthermore, the results summarize causes of disruptions in digital teaching, their possible prevention and intervention strategies

Pluralisme logique, tolérance et empirisme

Dans les débats actuels sur le pluralisme logique, il est souvent fait référence à Carnap qui opéra, au début des années trente, un tournant pluraliste, corrélatif de l’adoption de son fameux principe de tolérance. À l’époque, il renonçait ainsi à l’universalisme logique dont Frege, Russell et Wittgenstein avaient été les principaux représentants, et il donnait une nouvelle orientation à sa philosophie empiriste. Nous cherchons ici à caractériser l’empirisme carnapien dans le contexte du pluralisme et de la tolérance, en montrant quelles difficultés il rencontre et en indiquant quelques solutions possibles

Counting unlabelled toroidal graphs with no K33-subdivisions

We provide a description of unlabelled enumeration techniques, with complete proofs, for graphs that can be canonically obtained by substituting 2-pole networks for the edges of core graphs. Using structure theorems for toroidal and projective-planar graphs containing no K33-subdivisions, we apply these techniques to obtain their unlabelled enumeration.Comment: 25 pages (some corrections), 4 figures (one figure added), 3 table

Characterization and enumeration of toroidal K_{3,3}-subdivision-free graphs

We describe the structure of 2-connected non-planar toroidal graphs with no K_{3,3}-subdivisions, using an appropriate substitution of planar networks into the edges of certain graphs called toroidal cores. The structural result is based on a refinement of the algorithmic results for graphs containing a fixed K_5-subdivision in [A. Gagarin and W. Kocay, "Embedding graphs containing K_5-subdivisions'', Ars Combin. 64 (2002), 33-49]. It allows to recognize these graphs in linear-time and makes possible to enumerate labelled 2-connected toroidal graphs containing no K_{3,3}-subdivisions and having minimum vertex degree two or three by using an approach similar to [A. Gagarin, G. Labelle, and P. Leroux, "Counting labelled projective-planar graphs without a K_{3,3}-subdivision", submitted, arXiv:math.CO/0406140, (2004)].Comment: 18 pages, 7 figures and 4 table