Reproducing neutrino effects on the matter power spectrum through a degenerate Fermi gas approach

Modifications on the predictions about the matter power spectrum based on the hypothesis of a tiny contribution from a degenerate Fermi gas (DFG) test-fluid to some dominant cosmological scenario are investigated. Reporting about the systematic way of accounting for all the cosmological perturbations, through the Boltzmann equation we obtain the analytical results for density fluctuation, $\delta$, and fluid velocity divergence, $\theta$, of the DFG. Small contributions to the matter power spectrum are analytically obtained for the radiation-dominated background, through an ultra-relativistic approximation, and for the matter-dominated and $\Lambda$-dominated eras, through a non-relativistic approximation. The results can be numerically reproduced and compared with those of considering non-relativistic and ultra-relativistic neutrinos into the computation of the matter power spectrum. Lessons concerning the formation of large scale structures of a DFG are depicted, and consequent deviations from standard $\Lambda$CDM predictions for the matter power spectrum (with and without neutrinos) are quantified.Comment: 28 pages, 06 figure

The aftermath of urban renewal

The interest of this investigation rises from the long-term renewal plan that the local government of Bogotá launched in 2007 in the city center. Although this strategic operation pretends to work for a competitive, preserved, renewed and inclusive city center, this last aspect is subject to many controversies since several urban renewal programs historically around the world have had dire consequences from a social perspective. Among the negative effects there are two common results that have occurred in many cities around the world: Firstly, the eviction of the original population necessary to carry out demolitions that give way for new constructions and secondly, the displacement of population in the form of gentrification. Although the last two cases are of great interest to be studied in a research of this type, the scenario explored by this investigation is the ex post situation of the inhabitants that are still living in the surroundings of the renovated area. For this purpose, the case selected is the construction of the Third Millennium Park, which is part of the city renewal process, and the population of the adjacent San Bernardo neighbourhood. The main objective is to identify the benefits and drawbacks that this renewal project has implied for the residents of the mentioned neighbourhood. The population living there are the first witnesses of the positive and negative outcomes of this urban renewal process. Therefore, eight years after the inauguration of the Park, it is relevant to see if there has been a positive outcome for households, considering that there have been no significant improvements in the image of the area and no gentrification took place. Two types of households (those living in an apartment complex and in detached houses) were used to compare the different realities within the same community quantify the importance of addressing the problems of a population with similar characteristics but different needs. This is an exploratory and descriptive research, whose study approach is developed through the analysis of the household's situation affected by the renewal intervention of the Third Millennium Park. The data collection involved structured surveys to 85 households and five expert interviews. In the first case, the procedure for making the sample of households surveyed was purposive. The results obtained show that the results of this experience is questionable from a socio economic point of view. The households living in the San Bernardo neighbourhood have not had the support from the local government to change their reality of abandonment and decay. The lack of a socioeconomic policy within or linked with the urban renewal one is a reality that has been happening since the local government took the decision of demolishing El Cartucho and constructing the Third Millennium Park. From a policy perspective, the balance is similar because the renewal policy designed only attended the population living in the immediate location of where the park was constructed, ignoring the inhabitants living next to it. Therefore, it is argued that a participatory process in the design, planning and implementation of the renewal did not occur. A positive outcome of the urban renewal project was an improvement in the conditions of public space in the neighbourhood and vicinity of the park. Similarly, green areas per inhabitant rose considerably with the construction of the Park. The recommendations suggested deal mainly with the way an urban renewal policy should be designed, planned and implemented. The principal points are related to the following: The approach that an urban renewal policy should have to be successful; the importance of urban governance as a form to assure a participatory, transparent, accountable and successful process; the recognition of different groups of the population in the same community and neighbourhood that have different needs; the significance of community organization processes that facilitate the strengthening of population in dealing with the public and private sectors; the integration and articulation of policies and sectors within the public administration; and finally, the commitment of politicians to assure the continuity of policies through time

Complete Cosmic History with a dynamical Lambda(H) term

In the present mainstream cosmology, matter and spacetime emerged from a singularity and evolved through four distinct periods: early inflation, radiation, dark matter and late-time inflation (driven by dark energy). During the radiation and dark matter dominated stages, the universe is decelerating while the early and late-time inflations are accelerating stages. A possible connection between the accelerating periods remains unknown, and, even more intriguing, the best dark energy candidate powering the present accelerating stage (Lambda-vacuum) is plagued with the cosmological constant and coincidence puzzles. Here we propose an alternative solution for such problems based on a large class of time-dependent vacuum energy density models in the form of power series of the Hubble rate, Lambda=Lambda(H). The proposed class of Lambda(H)-decaying vacuum model provides: i) a new mechanism for inflation (different from the usual inflaton models), (ii) a natural mechanism for a graceful exit, which is universal for the whole class of models; iii) the currently accelerated expansion of the universe, iv) a mild dynamical dark energy at present; and v) a final de Sitter stage. Remarkably, the late-time cosmic expansion history of our class of models is very close to the concordance LambdaCDM model, but above all it furnishes the necessary smooth link between the initial and final de Sitter stages through the radiation- and matter-dominated epochs.Comment: Accepted in Phys. Rev. D. (2013

Are mesenchymal stromal cells immune cells?

Mesenchymal stromal cells (MSCs) are considered to be promising agents for the treatment of immunological disease. Although originally identified as precursor cells for mesenchymal lineages, in vitro studies have demonstrated that MSCs possess diverse immune regulatory capacities. Pre-clinical models have shown beneficial effects of MSCs in multiple immunological diseases and a number of phase 1/2 clinical trials carried out so far have reported signs of immune modulation after MSC infusion. These data indicate that MSCs play a central role in the immune response. This raises the academic question whether MSCs are immune cells or whether they are tissue precursor cells with immunoregulatory capacity. Correct understanding of the immunological properties and origin of MSCs will aid in the appropriate and safe use of the cells for clinical therapy. In this review the whole spectrum of immunological properties of MSCs is discussed with the aim of determining the position of MSCs in the immune system

Complete cosmic history with a dynamical Λ = Λ(H) term

In the present mainstream cosmology, matter and space-time emerged from a singularity and evolved through four distinct periods: early inflation, radiation, dark matter, and late-time inflation (driven by dark energy). During the radiation and dark matter dominated stages, the universe is decelerating while the early and late-time inflations are accelerating stages. A possible connection between the accelerating periods remains unknown, and, even more intriguing, the best dark energy candidate powering the present accelerating stage ( Λ -vacuum) is plagued with the cosmological constant and coincidence puzzles. Here we propose an alternative solution for such problems based on a large class of time-dependent vacuum energy density models in the form of power series of the Hubble rate, Λ = Λ ( H ) . The proposed class of Λ ( H ) -decaying vacuum model provides: (i) a new mechanism for inflation (different from the usual inflaton models), (ii) a natural mechanism for a graceful exit, which is universal for the whole class of models; (iii) the currently accelerated expansion of the universe, (iv) a mild dynamical dark energy at present; and (v) a final de Sitter stage. Remarkably, the late-time cosmic expansion history of our class of models is very close to the concordance Λ CDM model, but above all it furnishes the necessary smooth link between the initial and final de Sitter stages through the radiation- and matter-dominated epochs