Comparison of synthetic maps from truncated jet-formation models with YSO jet observations

(abridged) Significant progress has been made in the last years in the understanding of the jet formation mechanism through a combination of numerical simulations and analytical MHD models for outflows characterized by the symmetry of self-similarity. In a previous article we introduced models of truncated jets from disks, i.e. evolved in time numerical simulations based on a radially self-similar MHD solution, but including the effects of a finite radius of the jet-emitting disk and thus the outflow. These models need now to be compared with available observational data. A direct comparison of the results of combined analytical theoretical models and numerical simulations with observations has not been performed as yet. In order to compare our models with observed jet widths inferred from recent optical images taken with HST and AO observations, we use a new set of tools to create emission maps in different forbidden lines, from which we determine the jet width as the FWHM of the emission. It is shown that the untruncated analytical disk outflow solution considered here cannot fit the small jet widths inferred by observations of several jets. Various truncated disk-wind models are examined, whose extracted jet widths range from higher to lower values compared to the observations. Thus we can fit the observed range of jet widths by tuning our models. We conclude that truncation is necessary to reproduce the observed jet widths and our simulations limit the possible range of truncation radii. We infer that the truncation radius, which is the radius on the disk mid-plane where the jet-emitting disk switches to a standard disk, must be between around 0.1 up to about 1 AU in the observed sample for the considered disk-wind solution. One disk-wind simulation with an inner truncation radius at about 0.11 AU also shows potential for reproducing the observations, but a parameter study is needed.Comment: accepted for publication in A & A, 14 pages, 21 figure

Emergence of non-twisted magnetic fields in the Sun: Jets and atmospheric response

Aims. We study the emergence of a non-twisted flux tube from the solar interior into the solar atmosphere. We investigate whether the length of the buoyant part of the flux tube (i.e. {\lambda}) affects the emergence of the field and the dynamics of the evolving magnetic flux system. Methods. We perform three-dimensional (3D), time-dependent, resistive, compressible MHD simulations using the Lare3D code. Results. We find that there are considerable differences in the dynamics of the emergence of a magnetic flux tube when {\lambda} is varied. In the solar interior, for larger values of {\lambda}, the rising magnetic field emerges faster and expands more due to its lower magnetic tension. As a result, its field strength decreases and its emergence above the photosphere occurs later than in the smaller {\lambda} case. However, in both cases, the emerging field at the photosphere becomes unstable in two places, forming two magnetic bipoles that interact dynamically during the evolution of the system. Most of the dynamic phenomena occur at the current layer, which is formed at the interface between the interacting bipoles. We find the formation and ejection of plasmoids, the onset of successive jets from the interface, and the impulsive heating of the plasma in the solar atmosphere. We discuss the triggering mechanism of the jets and the atmospheric response to the emergence of magnetic flux in the two cases.Comment: 16 pages, 15 figure

Mass Adoption of NATs: Survey and experiments on carrier-grade NATs

In recent times, the prevalence of home NATs and the widespread implementation of Carrier-Grade NATs have posed significant challenges to various applications, particularly those relying on Peer-to-Peer communication. This paper addresses these issues by conducting a thorough review of related literature and exploring potential techniques to mitigate the problems. The literature review focuses on the disruptive effects of home NATs and CGNATs on application performance. Additionally, the study examines existing approaches used to alleviate these disruptions. Furthermore, this paper presents a comprehensive guide on how to puncture a NAT and facilitate direct communication between two peers behind any type of NAT. The techniques outlined in the guide are rigorously tested using a simple application running the IPv8 network overlay, along with their built-in NAT penetration procedures. To evaluate the effectiveness of the proposed techniques, 5G communication is established between two phones using four different Dutch telephone carriers. The results indicate successful cross-connectivity with three out of the four carriers tested, showcasing the practical applicability of the suggested methods.Comment: 12 pages, 9 figure

Performances of trust among learners in the context of online social learning

This study contributes to the conversation on how to potentially make online learning more satisfying and successful. To this end, this study focuses on trusting relations because research indicates that trust binds all social relations and facilitates risk taking and deeper, more critical thinking in collaborative learning. The conceptual framework is informed by a broad literature base on trust. Qualitative, open-ended interviewing with snowball sampling is used to explore 30 learners' emergent, interactive, social construction of trust. In the tradition of qualitative research, data from these interviews were subjected to several levels of analysis to elicit findings and interpretations. The findings suggests that learners socially construct moral theories of trust, consisting of rational and affective components. The rational component shaped their assessments of others' trustworthiness. The affective component shaped a moral lens through which they viewed rational trust. The effect of this affective component is that positive affect created bonds of friendship among learners that facilitated the social appropriation of technology and transactive conflicts which contributed to deeper, critical thinking. The lack of positive affect or presence of negative affect resulted in trustcompromised learning, characterized by ongoing breaches of trust

Kaolinized rocks on the Island of Lesbos (Greece)

A description is given of the mineralogy and geology of the kaolin deposits of Lesbos (Greece) which are caused by the action of hydrothermal fluids on volcanic rocks, lavas and tuffs, having dacitic, rhyodacitic, latitic, andesitic, etc. chemism. The major deposits are Magaros-Arghenos, Aspres Petres, Stipsi and Mesotopos; the first three are located in the northern part of the island, near the centre of Petra, the last one near the southern coast and the centre of Mesotopos. Inside these deposits, through diffractometric and thermal (DTA and TG) methods and direct E. M. and S. E. M. observations, the following minerals were detected: kaolinite (type from pM to T), smectite (montmorillonite), a mixed-layer mineral of the I-MO type, open-layer illite, alunite, jarosite, cristobalite and marcasite, surely newly-formed, while quartz and feldspar are to be considered as "residual". On the whole, the deposits of Aspres Petres and Mesotopos show a rather homogeneous mineralogy, where the always present kaolin minerals can be associated with sulphates, alunite and jarosite, or with silica phases, quartz and cristobalite; the remaining deposits, instead, feature a significant "zoning". The latter has kaolin in the central part while, at the periphery, essentially smectitic minerals can be noted, mostly associated with feldspar and sometimes illitic. This diversity of alteration products is to be ascribed to the different degree of alterability and thus of acidity of the fluids altered. Indeed, the different rock permeability due to differentiated porosity and fracturing as well as temperature variations, allow the same fluids to undergo modifications, including the hypothesis of becoming enriched with ions derived from the same rocks subjected to alteration. The chemism of the original rocks does not seem to have determined any substantial influence on the formation of the altered terms. Finally, all the deposits formed "in situ" fall within the typical deposits resulted by the actions of hydrothermal fluids connected with a late volcanism. Additionally, they are arranged along the structural alignments typical of the island and of the adjoining region of Asia Minor (Turkey)