The collisional evolution of undifferentiated asteroids and the formation of chondritic meteoroids

Most meteorites are fragments from recent collisions experienced in the asteroid belt. In such a hyper-velocity collision, the smaller collision partner is destroyed, whereas a crater on the asteroid is formed or it is entirely disrupted, too. The present size distribution of the asteroid belt suggests that an asteroid with 100 km radius is encountered $10^{14}$ times during the lifetime of the Solar System by objects larger than 10 cm in radius; the formed craters cover the surface of the asteroid about 100 times. We present a Monte Carlo code that takes into account the statistical bombardment of individual infinitesimally small surface elements, the subsequent compaction of the underlying material, the formation of a crater and a regolith layer. For the entire asteroid, 10,000 individual surface elements are calculated. We compare the ejected material from the calculated craters with the shock stage of meteorites with low petrologic type and find that these most likely stem from smaller parent bodies that do not possess a significant regolith layer. For larger objects, which accrete a regolith layer, a prediction of the thickness depending on the largest visible crater can be made. Additionally, we compare the crater distribution of an object initially 100 km in radius with the shape model of the asteroid (21) Lutetia, assuming it to be initially formed spherical with a radius that is equal to its longest present ellipsoid length. Here, we find the shapes of both objects to show resemblance to each other.Comment: Accepted by Ap

Antimicrobial activity of an aspartic protease from Salpichroa origanifolia fruits

Abstract: Plant proteases play a fundamental role in several processes like growth, development and in response to biotic and abiotic stress. In particular, aspartic proteases (AP) are expressed in different plant organs and have antimicrobial activity. Previously, we purified an AP from Salpichroa origanifolia fruits called salpichroin. The aim of this work was to determine the cytotoxic activity of this enzyme on selected plant and human pathogens. For this purpose, the growth of the selected pathogens was analysed after exposure to different concentrations of salpichroin. The results showed that the enzyme was capable of inhibiting Fusarium solani and Staphylococcus aureus in a dose-dependent manner. It was determined that 1·2 μmol l−1 of salpichroin was necessary to inhibit 50% of conidial germination, and the minimal bactericidal concentration was between 1·9 and 2·5 μmol l−1. Using SYTOX Green dye we were able to demonstrate that salpichroin cause membrane permeabilization. Moreover, the enzyme treated with its specific inhibitor pepstatin A did not lose its antibacterial activity. This finding demonstrates that the cytotoxic activity of salpichroin is due to the alteration of the cell plasma membrane barrier but not due to its proteolytic activity. Antimicrobial activity of the AP could represent a potential alternative for the control of pathogens that affect humans or crops of economic interest. Significance and Impact of the Study: This study provides insights into the antimicrobial activity of an aspartic protease isolated from Salpichroa origanifolia fruits on plant and human pathogens. The proteinase inhibited Fusarium solani and Staphylococcus aureus in a dose-dependent manner due to the alteration of the cell plasma membrane barrier but not due to its proteolytic activity. Antimicrobial activity of salpichroin suggests its potential applications as an important tool for the control of pathogenic micro-organisms affecting humans and crops of economic interest. Therefore, it would represent a new alternative to avoid the problems of environmental pollution and antimicrobial resistance.Fil: Díaz, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján; ArgentinaFil: Rocha, Gabriela Fernanda. Universidad Nacional de Luján; ArgentinaFil: Kise, Francisco. Universidad Nacional de Luján; ArgentinaFil: Rosso, A. M.. Universidad Nacional de Luján; ArgentinaFil: Guevara, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Parisi, M.G.. Universidad Nacional de Luján; Argentin

Time series photometry of the dwarf planet ERIS (2003 UB313)

Context. The dwarf planet Eris (2003 UB313, formerly known also as "Xena") is the largest KBO discovered up to now. Despite being larger than Pluto and having many similarities to it, it has not been possible so far to detect any significant variability in its light curve, preventing the determination of its period and axial ratio. Aims. We attempt to assess the level of variability of the Eris light curve by determining its BVRI photometry with a target accuracy of 0.03 mag/frame in R and a comparable or better stability in the calibration. Methods. Eris has been observed between November 30th and December 5th, 2005 with the Y4KCam onboard the 1.0 m Yale telescope at Cerro Tololo Interamerican Observatory, Chile in photometric nights. Results. We obtain 7 measures in B, 23 in V, 62 in R, and 20 in I. Averaged B, V, and I magnitudes as colors are in agreement within ≈0.03 mag with measures from Rabinowitz et al. (2006, [arXiv:astro-ph/0605745]) taken on the same nights. Night-averaged magnitudes in R show a statistically significant variability over a range of about 0.05 ± 0.01 mag. This cannot be explained by known systematics, background objects, or some periodical variation with periods less than two days in the lightcurve. The same applies to B, V and to a lesser extent to I, due to larger errors. Conclusions. In analogy with Pluto and if confirmed by future observations, this "long term" variability might be ascribed to a slow rotation of Eris, with periods longer than 5 days, or to the effect of its unresolved satellite "Dysnomea", which may contribute for ≈0.02 mag to the total brightness.Facultad de Ciencias Astronómicas y Geofísica

“Sapos y ranas del fondo de tu casa” : Una experiencia en extensión

“Sapos y ranas del fondo de tu casa” fue un proyecto de extensión universitaria acreditado por la Universidad Nacional de La Plata llevado a cabo durante el año 2012 en escuelas rurales de Educación Primaria y Secundaria ubicadas en el Cinturón Verde-Hortícola Platense. El objetivo de esta propuesta fue el de acercar a los alumnos conocimiento sobre las diferentes especies de anfibios que habitan la zona y las problemáticas en cuanto a su conservación, haciendo especial énfasis en los problemas originados por las prácticas agrícolas de la zona. El equipo extensionista (alumnos y graduados de áreas naturales, sociales y artísticas) realizó las actividades que se desarrollaron bajo la modalidad taller, con la participación no sólo de los niños sino también de la comunidad rural (docentes y familiares). Estas fueron las primeras instancias de las actividades de educación del proyecto “Conservación de Anfibios en Agroecosistemas” que el grupo actualmente continúa desarrollando.Facultad de Ciencias Naturales y Muse

“Sapos y ranas del fondo de tu casa” : Una experiencia en extensión

“Sapos y ranas del fondo de tu casa” fue un proyecto de extensión universitaria acreditado por la Universidad Nacional de La Plata llevado a cabo durante el año 2012 en escuelas rurales de Educación Primaria y Secundaria ubicadas en el Cinturón Verde-Hortícola Platense. El objetivo de esta propuesta fue el de acercar a los alumnos conocimiento sobre las diferentes especies de anfibios que habitan la zona y las problemáticas en cuanto a su conservación, haciendo especial énfasis en los problemas originados por las prácticas agrícolas de la zona. El equipo extensionista (alumnos y graduados de áreas naturales, sociales y artísticas) realizó las actividades que se desarrollaron bajo la modalidad taller, con la participación no sólo de los niños sino también de la comunidad rural (docentes y familiares). Estas fueron las primeras instancias de las actividades de educación del proyecto “Conservación de Anfibios en Agroecosistemas” que el grupo actualmente continúa desarrollando.Facultad de Ciencias Naturales y Muse

“Sapos y ranas del fondo de tu casa” : Una experiencia en extensión

“Sapos y ranas del fondo de tu casa” fue un proyecto de extensión universitaria acreditado por la Universidad Nacional de La Plata llevado a cabo durante el año 2012 en escuelas rurales de Educación Primaria y Secundaria ubicadas en el Cinturón Verde-Hortícola Platense. El objetivo de esta propuesta fue el de acercar a los alumnos conocimiento sobre las diferentes especies de anfibios que habitan la zona y las problemáticas en cuanto a su conservación, haciendo especial énfasis en los problemas originados por las prácticas agrícolas de la zona. El equipo extensionista (alumnos y graduados de áreas naturales, sociales y artísticas) realizó las actividades que se desarrollaron bajo la modalidad taller, con la participación no sólo de los niños sino también de la comunidad rural (docentes y familiares). Estas fueron las primeras instancias de las actividades de educación del proyecto “Conservación de Anfibios en Agroecosistemas” que el grupo actualmente continúa desarrollando.Facultad de Ciencias Naturales y Muse

The Power Board of the KM3NeT Digital Optical Module: design, upgrade, and production

The KM3NeT Collaboration is building an underwater neutrino observatory at the bottom of the Mediterranean Sea consisting of two neutrino telescopes, both composed of a three-dimensional array of light detectors, known as digital optical modules. Each digital optical module contains a set of 31 three inch photomultiplier tubes distributed over the surface of a 0.44 m diameter pressure-resistant glass sphere. The module includes also calibration instruments and electronics for power, readout and data acquisition. The power board was developed to supply power to all the elements of the digital optical module. The design of the power board began in 2013, and several prototypes were produced and tested. After an exhaustive validation process in various laboratories within the KM3NeT Collaboration, a mass production batch began, resulting in the construction of over 1200 power boards so far. These boards were integrated in the digital optical modules that have already been produced and deployed, 828 until October 2023. In 2017, an upgrade of the power board, to increase reliability and efficiency, was initiated. After the validation of a pre-production series, a production batch of 800 upgraded boards is currently underway. This paper describes the design, architecture, upgrade, validation, and production of the power board, including the reliability studies and tests conducted to ensure the safe operation at the bottom of the Mediterranean Sea throughout the observatory's lifespa

Constraints to Uranus' great collision : IV. The origin of Prospero

Context: It is widely accepted that the large obliquity of Uranus is the result of a great tangential collision (GC) with an Earth size proto-planet at the end of the accretion process. The impulse imparted by the GC affected the Uranian satellite system. Nine irregular satellites (irregulars) have been discovered around Uranus. Their orbital and physical properties, in particular those of the irregular Prospero, set constraints on the GC scenario. Aims: We attempt to set constraints on the GC scenario as the cause of Uranus' obliquity as well as on the mechanisms able to generate the Uranian irregulars. Methods: Different capture mechanisms for irregulars operate at different stages on the giant planet formation process. The mechanisms able to capture before and after the GC the Uranian irregulars are analysed. Assuming that they were captured before the GC, we calculate the orbital transfer of the nine irregulars by the impulse imparted by the GC. If their orbital transfer is dynamically implausible, they should have originated after the GC. We then investigate and discuss the dissipative mechanisms able to operate later. Results: Very few transfers exist for five of the irregulars, which makes their existence unlikely before the GC. In particular Prospero could not exist at the time of the GC. Different capture mechanisms for Prospero after the GC are investigated. Gas drag by Uranus'envelope and pull-down capture are not plausible mechanisms. Capture of Prospero through a collisionless interaction seems to be difficult. The GC itself provides a mechanism of permanent capture. However, the capture of Prospero by the GC is a low probability event. Catastrophic collisions could be a possible mechanism for the birth of Prospero and the other irregulars after the GC. Orbital and physical clusterings would then be expected. Conclusions: Either Prospero originated after the GC or the GC did not occur. In the former case, the mechanism for the origin of Prospero after the GC remains an open question. An observing program able to look for dynamical and physical families is needed. In the latter case, another theory to account for Uranus' obliquity and the formation of the Uranian regular satellites on the equatorial plane of the planet would be needed.Grupo de Ciencias Planetarias (GCP

Heterogeneity in antibody range and the antigenic drift of influenza A viruses

In this paper we explore the consequences of a heterogeneous immune response in individuals on the evolution of a rapidly mutating virus. We show that several features of the incidence and phylogenetic patterns typical of influenza A may be understood in this framework. In our model, limited diversity and rapid drift of the circulating viral strains result from the interplay of two interacting subpopulations with different types of immune response, narrow or broad, upon infection. The subpopulation with the narrow immune response acts as a reservoir where consecutive mutations escape immunity and can persist. Strains with a number of accumulated mutations escape immunity in the other subpopulation as well, causing larger epidemic peaks in the whole population, and reducing strain diversity. Overall, our model produces a modulation of epidemic peak heights and patterns of antigenic drift consistent with reported observations, suggesting an underlying mechanism for the evolutionary epidemiology of influenza, in particular, and other infectious diseases, more generally