1,721,068 research outputs found
The dark matter distribution in disc galaxies
No full textWe use high-quality optical rotation curves of nine low-luminosity disc galaxies to obtain the velocity profiles of the surrounding dark matter haloes. We find that they increase linearly with radius at least out to the edge of the stellar disc, implying that, over the entire stellar region, the density of the dark halo is about constant. The properties of the mass structure of these haloes are similar to those found for a number of dwarf and low surface brightness galaxies, but provide a more substantial evidence of the discrepancy between the halo mass distribution predicted in the cold dark matter scenario and those actually detected around galaxies. We find that the density law proposed by Burkert reproduces the halo rotation curves, with halo central densities (rho (0) similar to 1-4 x 10(-24) g cm(-3)) and core radii (r(0) similar to 5-15 kpc) scaling as rho (0) proportional to r(0)(-2/3)
Novel pumpkin seed oil-based oleogels: development and physical characterization
Full text linkThe objective of this research was to develop novel oleogels based on pumpkin seed oil and natural waxes. Crystallization and gelation of 4, 5, 6 and 8 % of beeswax and carnauba wax in pumpkin seed oil were investigated, and their physical properties were evaluated using an oleogel prepared with sunflower oil and beeswax as reference. In order to obtain a complete three-dimensional network, after a cooling stage a setting stage was necessary at 25 °C for no longer than 60 min. Oleogels produced with pumpkin seed oil and beeswax were weaker than those made with sunflower seeds; pumpkin seed oil-based oleogels structured by carnauba wax presented higher viscoelastic properties, retained more oil and were firmer than oleogels based on beeswax. Based on scaling theory, all the oleogels followed a strong-link regime and the fractal dimension of the network (D) was comparable to fats widely used in food production. Therefore, pumpkin seed oil can be used to create novel oleogels
The normalization of left populism? The paradigmatic case of Podemos
No full textAfter a hopeful electoral debut, left populism in Europe has undergone relative normalization. While the literature on new parties might regard the persistence of left populist forces as a success, we deem instead that such an outcome should be considered against the backdrop of the initial left populist hypothesis. Based on a discussion of the existing literature and ten semi-structured interviews with party members, this paper analyses the case of Podemos in Spain as a proxy to assess the fortunes of left populism in Europe at large. We describe its political trajectory and explain its failure to go mainstream by reference to the interplay between, at a macro level, the structure of political opportunities and, at a meso level, its interpretation of the populist strategy. In particular, we focus on the paradoxical effects of the representative void, on the specific and unfavorable mutations of the populist moment in Spain for Podemos, and its own organizational and strategic shortcomings.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
The distribution of dark matter in galaxies: Constant-density dark halos envelop the stellar disks
No full textIn this paper we review the main and the most recent evidence for the presence of a core radius in the distribution of the dark matter around spiral galaxies. Their rotation curves, coadded according to the galaxy luminosity, conform to an Universal profile which can be represented as the sum of an exponential thin disk term plus a spherical halo term with a flat density core. From dwarfs to giants, these halos feature a constant density region of size ro and core density po related by po = 4.5 x 10(-2) (r(o)/kpc)(-2/3)M(circle dot)pc(-3). At the highest masses po decreases exponentially, with ro revealing a lack of objects with disk masses > 10(11)M(circle dot) and central densities > 1.5 x 10-2(ro/kpc)(-3)M(circle dot)pc(-3), which implies a maximum mass of,: 2 x 10(12)M(circle dot) for halos hosting spirals. The fine structure of dark matter halos is obtained from the kinematics of a number of suitable low-luminosity disk galaxies. The inferred halo circular velocity increases linearly with radius out to the edge of the stellar disk, implying a constant dark halo density over the entire disk region. The structural properties of halos around normal spirals are similar to those around dwarf and low surface brightness galaxies; nevertheless they provide far more substantial evidence of the discrepancy between the mass distributions predicted in the Cold Dark Matter scenario and those actually detected around galaxies
Lambda CDM and the distribution of dark matter in galaxies: A constant-density halo around DDO 47
Full text linkIn this paper we present a test case for the existence of a core in the density distribution of dark halos around galaxies. DDO 47 has a rotation curve that increases linearly from the first data point, at 300 pc, up to the last one, at 5 kpc. This profile implies the presence of a (dark) halo with an (approximately) constant density over the region mapped by data. This evidences the inability of standard Lambda Cold Dark Matter scenario to account for the dark matter distribution around galaxies, and points toward the existence of an intriguing halo scale-length of homogeneity. This work adds up to the results of Blais-Ouellette et al. (2002), Trott & Webster (2002), Binney & Evans (2002), de Blok & Bosma (2002) and Bottema (2002) in suggesting that at galactic scales CDM theory should incorporate, as an intrinsic property, a "density core" feature
Platone come luogo storiografico da Cicerone ad Agostino
No full textIl saggio analizza la presenza della figura e dell'opera di Platone nella speculazione latina da Cicerone ad Agostino. Nello specifico, vengono analizzate per un verso le linee della tradizione testuale che, per il tramite di Cicerone, porta nel mondo latino solo una parte dei testi platonici, valutati in un'ottica specificatamente scettica; per un altro, viene analizzata l'incidenza che tale tradizione e più in generale la dottrina platonica ha avuto sulla produzione filosofico-teologica dei primi secoli cristiani, che ha identificato in Platone il 'princeps' di quella tradizione pagana che, come tale, andava per certi versi respinta e per altri assorbita nel nuovo mondo cristian
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