Super- and Sub-critical Regions in Shocks driven by Radio-Loud and Radio-Quiet CMEs

White-light coronagraphic images of Coronal Mass Ejections (CMEs) observed by SOHO/LASCO C2 have been used to estimate the density jump along the whole front of two CME-driven shocks. The two events are different in that the first one was a "radio-loud" fast CME, while the second one was a "radio quiet" slow CME. From the compression ratios inferred along the shock fronts, we estimated the Alfv\'en Mach numbers for the general case of an oblique shock. It turns out that the "radio-loud" CME shock is initially super-critical around the shock center, while later on the whole shock becomes sub-critical. On the contrary, the shock associated with the "radio-quiet" CME is sub-critical at all times. This suggests that CME-driven shocks could be efficient particle accelerators at the shock nose only at the initiation phases of the event, if and when the shock is super-critical, while at later times they lose their energy and the capability to accelerate high energetic particles.Comment: 7 pages, 5 figures. In press on the "Journal of Advanced Research", Cairo University Pres

Descent among the Wayú. Concepts and social meanings

Alla luce dei dati etnografici raccolti sul campo dall'autore, l'articolo rilegge e integra le descrizioni e le interpretazioni delle categorie di discendenza e di parentela tra i Wayuu della Guajira colombiana, proponendo inoltre l'inserimento del caso wayuu all'interno della comparazione teorica dei modelli di organizzazione sociale nelle società indigene dei bassopiani sudamericani

Lexical Ambiguity in Nouns: Frequency Dominance and Declensional Classes

The existence of differences in lexical processing between ambiguous and unambiguous words is still controversial. Many factors seem to play a role in determining different ambiguity effects in word recognition, such as ambiguity type, experimental paradigm, frequency dominance, etc. The aim of this study is to investigate the role played by frequency dominance and declensional class in recognizing Italian homonymous nouns, namely, forms with multiple unrelated meanings. We report the results of two visual lexical decision experiments, in which these factors are manipulated. An ambiguity disadvantage effect is found for words belonging to two different declensional classes (Exp. 2, e.g., conte), while an absence of processing differences is reported for ambiguous words within the same declensional class (Exp. 1, e.g., credenza). Moreover, an interaction between condition and frequency is found: the inhibitory effects are stronger for ambiguous nouns with two frequency-balanced meanings than for ambiguous nouns with a strongly dominant meaning. The results are compatible with the idea that several factors should be taken into account in order to disentangle competing accounts of lexical ambiguity processing. We discuss these results in terms of how variables such as frequency dominance and declensional class affect the activation of lexical representations and play a role in determining different ambiguity effects in lexical acces

Descent among the Wayú. Concepts and social meanings

Descent among the Wayú. Concepts and social meanings. Taking the contemporary rethinking of the descent notion in Lowland South American ethnography as a starting point, the article provides an analysis of matrilineal descent among the Wayú. Using new ethnographical data, special attention is paid to indigenous concepts and to the way matrilineal descent articulates with other principles of social classification. By virtue of the role that matrilineal descent plays in defining territoriality and in feuds, the Wayú offer a very interesting case for rethinking the theoretical and comparative debate about the indigenous societies of Lowland South America and for reflecting on the complexity of the interactions between structure and history in this area.La filiation chez les Wayú. Notions indigènes et significations sociales. Reconsidérant le débat contemporain sur la notion de filiation (descent) dans l’ethnographie des Basses Terres sud-américaines, l’article fait une analyse de la filiation matrilinéaire chez les Wayú et de son articulation avec les autres principes indigènes de classification sociale. Les concepts wayú de la filiation matrilinéaire sont présentés en tenant compte de nouvelles données ethnographiques. Une attention particulière est portée sur le rôle de la filiation matrilinéaire dans la définition de la territorialité et dans les vengeances. Par leurs caractéristiques, les Wayú offrent un cas très intéressant pour le débat théorique et comparatif sur les sociétés indigènes des Basses Terres sud-américaines et pour la réflexion sur la complexité des interactions entre la structure et l’histoire dans cette aire.Conceptos y significados sociales de la descendencia entre los wayú. Retomando el debate contemporáneo acerca del concepto de descendencia en la etnografía de las Tierras Bajas Suramericanas, el artículo presenta un análisis de la matrilinealidad entre los wayú y de la forma en que ésta se articula con los otros principios de clasificación social. A través de los datos etnográficos aquí presentados, se propone una nueva interpretación de las categorías indígenas de matrilinealidad, que es aplicada al replanteamiento de la cuestión de la relación entre descendencia matrilineal, territorialidad y venganza en esta sociedad indígena. Por dichos rasgos, los wayú brindan un caso cuya consideración resulta útil tanto para el desarrollo futuro del debate teórico y comparativo acerca de las sociedades indígenas de las Tierras Bajas suramericanas, como para el estudio de las interacciones entre estructura e historia en esta área

Stellar Mass Function of Active and Quiescent Galaxies via the Continuity Equation

The continuity equation is developed for the stellar mass content of galaxies and exploited to derive the stellar mass function of active and quiescent galaxies over the redshift range z â¼ 0-8. The continuity equation requires two specific inputs gauged from observations: (i) the star formation rate functions determined on the basis of the latest UV+far-IR/submillimeter/radio measurements and (ii) average star formation histories for individual galaxies, with different prescriptions for disks and spheroids. The continuity equation also includes a source term taking into account (dry) mergers, based on recent numerical simulations and consistent with observations. The stellar mass function derived from the continuity equation is coupled with the halo mass function and with the SFR functions to derive the star formation efficiency and the main sequence of star-forming galaxies via the abundance-matching technique. A remarkable agreement of the resulting stellar mass functions for active and quiescent galaxies of the galaxy main sequence, and of the star formation efficiency with current observations is found; the comparison with data also allows the characteristic timescales for star formation and quiescence of massive galaxies, the star formation history of their progenitors, and the amount of stellar mass added by in situ star formation versus that contributed by external merger events to be robustly constrained. The continuity equation is shown to yield quantitative outcomes that detailed physical models must comply with, that can provide a basis for improving the (subgrid) physical recipes implemented in theoretical approaches and numerical simulations, and that can offer a benchmark for forecasts on future observations with multiband coverage, as will become routinely achievable in the era of JWST

Super-and sub-critical regions in shocks driven by radio-loud and radio-quiet CMEs

Abstract White-light coronagraphic images of Coronal Mass Ejections (CMEs) observed by SOHO/LASCO C2 have been used to estimate the density jump along the whole front of two CME-driven shocks. The two events are different in that the first one was a ''radio-loud'' fast CME, while the second one was a ''radio quiet'' slow CME. From the compression ratios inferred along the shock fronts, we estimated the Alfve´n Mach numbers for the general case of an oblique shock. It turns out that the ''radio-loud'' CME shock is initially super-critical around the shock center, while later on the whole shock becomes sub-critical. On the contrary, the shock associated with the ''radio-quiet'' CME is sub-critical at all times. This suggests that CME-driven shocks could be efficient particle accelerators at the shock nose only at the initiation phases of the event, if and when the shock is super-critical, while at later times they lose their energy and the capability to accelerate high energetic particles

FIRST COMPLETE DETERMINATION OF PLASMA PHYSICAL PARAMETERS ACROSS A CORONAL MASS EJECTION-DRIVEN SHOCK

We report on the study of a fast coronal mass ejection (CME)-driven shock associated with the solar eruption of 2002 March 22. This event was observed in the intermediate corona both in white light and the extreme ultraviolet (EUV) by the LASCO and UVCS instruments on board the Solar and Heliospheric Observatory ,a s well as in metric and decametric wavelengths through space- and ground-based radio observatories. Clear signatures of shock transit are (1) strong type II emission lanes observed after the CME initiation, (2) strong Ovi λλ1032, 1037 line profile broadenings (up to ∼2 × 10 7 K) associated with the shock transit across the UVCS slit field of view, and (3) a density enhancement located in LASCO images above the CME front. Since the UVCS slit was centered at 4.1 R� , in correspondence with the flank of the expanding CME, this observation represents the highest UV detection of a shock obtained so far with the UVCS instrument. White-light and EUV data have been combined in order to estimate not only the shock compression ratio and the plasma temperature, but also the strength of the involved coronal magnetic fields, by applying the Rankine–Hugoniot equations for the general case of oblique shocks. Results show that, for a compression ratio X = 2.06 as derived from LASCO data, the coronal plasma is heated across the shock from an initial temperature of 2.3 × 10 5 Ku p to 1.9 × 10 6 K, while at the same time the magnetic field undergoes a compression from a pre-shock value of ∼0.02 G up to a post-shock field of ∼0.04 G. Magnetic and kinetic energy density increases at the shock are comparable (in agreement with the idea of equipartition of energy), and both are more than two times larger than the thermal energy density increase. This is the first time that a complete characterization of pre- and post-shock plasma physical parameters has been derived in the solar corona