Protostellar mergers in protoclusters and the origin of ultra-luminous X-ray sources

I suggest that stellar coalescence in mid-size protoclusters (M ~ 10^{3.5} - 10^{4.5} M_sun) is a possible scenario for the formation of ultra-luminous X-ray sources (ULXs). More massive super-star-clusters are not needed, since the most likely ULX mass range is only ~ 30--200 M_sun; in fact, they are very rarely found at or very near ULX positions. Protostellar envelopes and gas accretion favour captures and mergers in dense cores of embedded clusters. Moreover, protoclusters with masses ~ 10^{3.5} - 10^{4.5} M_sun are likely to disperse quickly into loose OB associations, where most ULXs are found. Sufficiently high protostellar density may be achieved when clustered star formation is triggered by galaxy collisions and mergers. Low metallicity may then be necessary to ensure that a large fraction of the stellar mass ends up in a black hole. In this scenario, most ULXs are naturally explained as the extreme end of the high-mass X-ray binary population.Comment: 4 pages, to appear in the proceedings of the IAU Symposium 230, "Populations of High Energy Sources in Galaxies", Dublin, 15-19 Aug 200

The Star as Antihero: Ricardo Darín in Carancho

El objetivo de este artículo es analizar el film Carancho (2010, Pablo Trapero) teniendo en cuenta los rasgos codificados del cine negro, especialmente aquellos relacionados con la construcción del personaje protagónico y su destino como también con los espacios que habita y en los que se desenvuelve. Se prestará particular atención a la imagen estrella de Ricardo Darín en la construcción de su personaje, un antihéroe cuya naturaleza opaca y difusa difiere de la representación clásica de la estrella cinematográfica. Para ello, emplearemos el concepto de imagen estrella de Richard Dyer y James Naremore.The purpose of this article is to explore the film Carancho (2010, Pablo Trapero), taking into account the characteristics that typify the film noir genre, particularly those related to character construction and the fate of the main character, on the one hand, and the spaces within which he moves and plays his role, on the other. Particular attention will be paid to Ricardo Darín’s star image in the construction of the protagonist of the film, an antihero whose diffuse and opaque nature differs from the classical representation of a cinematographic star. To this end, the concept of star image will be used following Richard Dyer and James Naremore, in particular.Fil: Soria, Carolina. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Environmental Dynamics in Animal Waste Reclamation in the Scaling up of Livestock in Thailand

Thailand has seen a scaling up of pig production in numbers and structure. Nonetheless, in-house separation and agricultural reclamation of pig solid waste are common practice. Waste reclamation is not taking place under small-scale farming and its environmental dynamics cannot be simply understood as a direct projection to larger scales. Scaling up has transformed the environmental significance of waste reclamation, including waste transfer from livestock to agriculture farmers. Waste transfer benefits pig farmers by trade and removal of waste by agriculture and aquaculture farmers and is key to the environmental dynamics of pig production. However, waste reclamation is not clearly defined as a management option in environmental frameworks. Waste management is mainly addressed as in-farm wastewater with limited attention to agro-environmental values of present practices. To recognise present practices in agro-environmental policies this thesis suggests a descriptive strategy focused on the transfer of waste. Such strategy would avoid command-and-control norms, avoid conflicting with an environmental culture centered in biogas technology and support knowledge transfer in agriculture. A focus on waste transfer from animal farms to agriculture [and aquaculture] plots is interpreted as off-site waste management. Off-site waste management calls for the inclusion of geographical variables beyond animal farms. This leads to an extended area of environmental influence (EAEI). Resulting environmental dynamics allows an interpretation of environment beyond resource in classical agricultural geography to a connotation where environment is also significant to agriculture and livestock because of the impacts from production. The recognition of reclamation practices and, consequently, of the integral environmental dynamics, and hence the connotation of environment, would contribute to connect livestock with agriculture through environmental geography. Intensive livestock is then defined as distribution and not location. Formalisation of reclamation practices entails the acknowledgment of agro-ecological cycles in livestock

On the Penrose inequality for dust null shells in the Minkowski spacetime of arbitrary dimension

A particular, yet relevant, particular case of the Penrose inequality involves null shells propagating in the Minkowski spacetime. Despite previous claims in the literature, the validity of this inequality remains open. In this paper we rewrite this inequality in terms of the geometry of the surface obtained by intersecting the past null cone of the original surface S with a constant time hyperplane and the "time height" function of S over this hyperplane. We also specialize to the case when S lies in the past null cone of a point and show the validity of the corresponding inequality in any dimension (in four dimensions this inequality was proved by Tod). Exploiting properties of convex hypersurfaces in Euclidean space we write down the Penrose inequality in the Minkowski spacetime of arbitrary dimension n+2 as an inequality for two smooth functions on the sphere. We finally obtain a sufficient condition for the validity of the Penrose inequality in the four dimensional Minkowski spacetime and show that this condition is satisfied by a large class of surfaces.Comment: 25 pages, 2 figures, Late

Rearrangement transformations on general measure spaces

For a general set transformation ${\cal R}$ between two measure spaces, we define the rearrangement of a measurable function by means of the Layer's cake formula. We study some functional properties of the Lorentz spaces defined in terms of ${\cal R}$, giving a unified approach to the classical rearrangement, Steiner's symmetrization, the multidimensional case, and the discrete setting of trees.Comment: 17 page

Mixed norm spaces and rearrangement invariant estimates

Our main goal in this work is to further improve the mixed norm estimates due to Fournier, and also Algervik and Kolyada, to more general rearrangement invariant (r.i.) spaces. In particular we find the optimal domains and the optimal ranges for these embeddings between mixed norm spaces and r.i. spaces