Concurrent infall of satellites: Collective effects changing the overall picture

A variety of new physical processes have proven to play an important role in orbital decay of a satellite galaxy embedded inside a dark matter halo but this is not fully understood. Our goal is to assess if the orbital history of a satellite remains unchanged during a concurrent sinking. For this purpose we analyze the impact that the internal structure of the satellites and their spatial distribution inside the host halo may have on the concurrent sinking process due to both mass loss and the combined effect of self-friction, which have not been studied before for concurrent sinking. We set up a set of N-body simulations that include multiple satellites, sinking simultaneously in a host halo and we compare them with models including a single satellite. The main result of our work is that the satellite's accretion history differs from the classical isolated view when we consider the collective effects. The accretion history of each satellite strongly depends on the initial configuration, the number of satellites in the halo at the time of infall and the internal properties of each satellite. We observe that compact satellites in a flat configuration fall slower than extended satellites that have lost mass, showing a non-reported behavior of self-friction. We find that such effects are maximized when satellites are located in a flat configuration. We show that in a flat configuration similar to the Vast Polar Structure, deviations in the apocenters can be of about 30% with respect to the isolated case, and up to 50% on the eccentricities. We conclude that ignoring the collective effects produced by the concurrent sinking of satellite galaxies may lead to large errors in the determination of the merger progenitors properties, making it considerably more challenging to trace back the accretion event. Timing constrains on host density profile may be modified by the effects discussed here.Comment: A&A, Forthcoming article Received: 29 March 2022 / Accepted: 26 September 2022 6 pages, 6 figure

Attacking Group Protocols by Refuting Incorrect Inductive Conjectures

Automated tools for finding attacks on flawed security protocols often fail to deal adequately with group protocols. This is because the abstractions made to improve performance on fixed 2 or 3 party protocols either preclude the modelling of group protocols all together, or permit modelling only in a fixed scenario, which can prevent attacks from being discovered. This paper describes Coral, a tool for finding counterexamples to incorrect inductive conjectures, which we have used to model protocols for both group key agreement and group key management, without any restrictions on the scenario. We will show how we used Coral to discover 6 previously unknown attacks on 3 group protocols

Use of sonic tomography to detect and quantify wood decay in living trees.

Premise of the studyField methodology and image analysis protocols using acoustic tomography were developed and evaluated as a tool to estimate the amount of internal decay and damage of living trees, with special attention to tropical rainforest trees with irregular trunk shapes.Methods and resultsLiving trunks of a diversity of tree species in tropical rainforests in the Republic of Panama were scanned using an Argus Electronic PiCUS 3 Sonic Tomograph and evaluated for the amount and patterns of internal decay. A protocol using ImageJ analysis software was used to quantify the proportions of intact and compromised wood. The protocols provide replicable estimates of internal decay and cavities for trees of varying shapes, wood density, and bark thickness.ConclusionsSonic tomography, coupled with image analysis, provides an efficient, noninvasive approach to evaluate decay patterns and structural integrity of even irregularly shaped living trees

Stellar occultations enable milliarcsecond astrometry for Trans-Neptunian objects and Centaurs

Trans-Neptunian objects (TNOs) and Centaurs are remnants of our planetary system formation, and their physical properties have invaluable information for evolutionary theories. Stellar occultation is a ground-based method for studying these small bodies and has presented exciting results. These observations can provide precise profiles of the involved body, allowing an accurate determination of its size and shape. The goal is to show that even single-chord detections of TNOs allow us to measure their milliarcsecond astrometric positions in the reference frame of the Gaia second data release (DR2). Accurated ephemerides can then be generated, allowing predictions of stellar occultations with much higher reliability. We analyzed data from stellar occultations to obtain astrometric positions of the involved bodies. The events published before the Gaia era were updated so that the Gaia DR2 catalog is the reference. Previously determined sizes were used to calculate the position of the object center and its corresponding error with respect to the detected chord and the International Celestial Reference System (ICRS) propagated Gaia DR2 star position. We derive 37 precise astrometric positions for 19 TNOs and 4 Centaurs. Twenty-one of these events are presented here for the first time. Although about 68\% of our results are based on single-chord detection, most have intrinsic precision at the submilliarcsecond level. Lower limits on the diameter and shape constraints for a few bodies are also presented as valuable byproducts. Using the Gaia DR2 catalog, we show that even a single detection of a stellar occultation allows improving the object ephemeris significantly, which in turn enables predicting a future stellar occultation with high accuracy. Observational campaigns can be efficiently organized with this help, and may provide a full physical characterization of the involved object.Comment: 16 pages, 28 figures. The manuscript was accepted and is to be publishe

Malformaciones vasculares: Manejo mediante técnicas de radiología intervencional y satisfacción de los pacientes Vascular malformations

Introducción: Las anomalías vasculares son una patología frecuente en la población general, y son causa de deterioro de la calidad de vida de los pacientes que las padecen. En los últimos años, las técnicas mínimamente invasivas de radiología intervencional se han convertido en una alternativa eficaz para el tratamiento de estos pacientes. El objetivo del presente estudio es mostrar nuestra experiencia en el manejo de malformaciones vasculares con estas técnicas en la Clínica Alemana de Santiago y evaluar la satisfacción de los pacientes con este manejo. Material y Métodos: Evaluación del seguimiento de todos los pacientes con malformaciones vasculares tratados en la Unidad de Radiología Intervencional desde el año 2006 hasta junio del año 2009. Los pacientes fueron clasificados en base a la hemodinamia de la malformación vascular (alto flujo vs. bajo flujo). Se evaluaron las complicaciones, y se realizó una encuesta sobre la satisfacción de los pacientes con el tratamiento. Resultados: Ochenta y siete pacientes (253 procedimientos) fueron incluidos en el estudio, 36 hombres y 51 mujeres, todos con seguimiento completo en este periodo. La edad promedio de ellos fue de 20,6 años. En más del 50% de los pacientes la anomalía vascular se ubicó en la cara o extremidades inferiores. Un 28% (25 pacientes) presentó malformación de alto flujo (pura o mixta) y 72% (62 pacientes) de bajo flujo (malformaciones vasculares, linfangiomas o mixtas). En promedio, cada paciente se realizó 2,9 procedimientos (1-10). Del total de procedimientos realizados, hubo 4 complicaciones mayores (1,65%), una de ellas con secuelas estéticas producto de necrosis de la zona. El promedio de satisfacción fue de un 7,95 en una escala de 1 a 10, siendo significativamente mayor en pacientes con malformaciones de bajo flujo (8,27) que en los de alto flujo (7,16) (p Background: Vascular anomalies are prevalent in the general population and may produce significant impairment in quality of life. In recent years, minimally invasive interventional radiology techniques have become an efficient alternative for the treatment of these patients. The aim of this study was to present our experience in the management of vascular malformations with such techniques at Clínica Alemana in Santiago, Chile, and assess the satisfaction of patients with this management. Material and Methods: Evaluation of the follow-up of patients with vascular malformations treated in the Interventional Radiology Unit at our center since June - 2006 to June - 2009. Patients were classified according to the hemodynamics of the lesions (high vs low-flow). Complications and patient satisfaction with the treatment were assessed. Results: Eighty-seven patients (253 procedures) were included in the study, 36 men and 51 women, all with complete follow-up during the period of the study. Their average age was 20.6 years. In over 50% of the patients the vascular anomaly was located on the face or the lower extremities. Twenty-eight percent (25 patients) had a high-flow malformation (pure or mixed) and 62 (72%) had a low-flow lesion (vascular malformation, lymphangioma or mixed). On average, each patient underwent 2.9 procedures (1-10). There were 4 major complications (1.65%), one of which was predominantly cosmetic with necrosis in the area of the lesion. The average satisfaction rate was 7.95 (on a rating scale of 1 to 10). Satisfaction was significantly higher in patients with low-flow malformations (8.27) than in those with high-flow lesions (7.16). (p < 0.05) Discussion: Treatment of vascular malformations using interventional radiology techniques is an effective alternative, with good prospects of clinical improvement, patient satisfaction and low complication rates