Dark Matter, Dark Energy and the solution of the strong CP problem

The strong CP problem was solved by Peccei & Quinn by introducing axions, a viable candidate for Dark Matter (DM). Here the PQ approach is modified so to yield also Dark Energy (DE). DM and DE arise, in fai proportions, from a single scalar field, without tuning any extra parameter. In the present epoch, they are weakly coupled. Fluctuations have a fair evolution. The model is also fitted to the WMAP1 release, using a Markov Chain Monte Carlo technique, and performs as well as $\Lambda$CDM, coupled or uncoupled DE. Best--fit cosmological parameters for different models are mostly within 2--$\sigma$ level. Here, the main peculiarity of the model is to favor high values of the Hubble parameter.Comment: Proceeding of the workshop dsu2006, "The Dark Side of th Universe", Madrid, June 20-24, 200

Neutral-cluster implantation in polymers by computer experiments

In this work we perform atomistic model potential molecular dynamics simulations by means of state-of-the art force-fields to study the implantation of a single Au nanocluster on a Polydimethylsiloxane substrate. All the simulations have ben performed on realistic substrate models containing up to 4.6 millions of atoms having depths up to 90 nm and lateral dimensions up to 25 nm. We consider both entangled-melt and cross-linked Polydimethylsiloxane amorphous structures. We show that even a single cluster impact on the Polydimethylsiloxane substrate remarkably changes the polymer local temperature and pressure. Moreover we observe the presence of craters created on the polymer surface having lateral dimensions comparable to the cluster radius and depths strongly dependent on the implantation energy. Present simulations suggest that the substrate morphology is largely affected by the cluster impact and that most-likely such modifications favor the the penetration of the next impinging clusters

The multimode covering location problem

In this paper we introduce the Multimode Covering Location Problem. This is a generalization of the Maximal Covering Location Problem that consists in locating a given number of facilities of different types with a limitation on the number of facilities sharing the same site. The problem is challenging and intrinsically much harder than its basic version. Nevertheless, it admits a constant factor approximation guarantee, which can be achieved combining two greedy algorithms. To improve the greedy solutions, we have developed a Variable Neighborhood Search approach, based on an exponential-size neighborhood. This algorithm computes good quality solutions in short computational time. The viability of the approach here proposed is also corroborated by a comparison with a Heuristic Concentration algorithm, which is presently the most effective approach to solve large instances of the Maximal Covering Location Problem

Sulla storia degli studi di frattura in Italia

History of studies of fracture is inherently intermingled with the history of technology developments. In the beginning very little was written about. We must credit Leonardo and Galileo as the first ones that wrote about the problem and on how to measure and foresee rupture loads. Later, nineteenth century italian scientists distinguished themselves in attempting to establish material laws and multiple stresses rupture criteria. A review of the works of past centuries italian scientists is presented, along with a critical comparison with the work of other past european scientists

Valores pragmáticos de formas personales y no personales del verbo en muestras de lengua escrita del español de la región NEA

La identificación de exponentes funcionales de formas personales (pretérito perfecto, condicional simple e imperativo) y no personales (infinitivo, gerundio y participio) del verbo en muestras de lengua escrita del español de la región NEA. En esta propuesta tomamos en consideración formas verbales personales y no personales de un corpus formado por muestras de lengua escrita de la comunidad de habla de Resistencia, obtenido en sus medios de comunicación. Observamos este trabajo es una de las acciones de proyectos de investigación, finalizados y en curso, de la Universidad Nacional del Nordeste, cuyo propósito final es el de aportar información para la elaboración una gramática comunicativa del español de la región NEA, que sea de utilidad para la enseñanza del español como lengua materna y extranjera. Para la descripción y explicación del modo en que efectivamente usan estas formas los integrantes de la comunidad de habla en cuestión, nos valemos del método comunicativo, puesto que éste ubica tanto a los interlocutores como a la interacción que existe entre ellos, en el centro del análisis. Partimos de una exploración bibliográfica, relacionada con los usos de estas formas verbales en el español en general, para luego -teniendo en cuenta esta información- abordar el análisis de nuestro corpus desde distintas perspectivas, pero fundamentalmente desde el punto de vista pragmático-discursivo. Actualmente, en nuestra comunidad de habla, no se registran antecedentes de análisis de fenómenos de variación lingüística realizados a partir de muestras de usos tanto orales como escritos. Por ello, nos proponemos describir y explicar registros sociales y su adecuación al contexto, con el fin de sistematizar el estado actual de la lengua y los usos en el español de Resistenci

Evaluation of vegetation post-fire resilience in the Alpine region using descriptors derived from MODIS spectral index time series

In this study a method based on the analysis of MODerate-resolution Imaging Spectroradiometer (MODIS) time series is proposed to estimate the post-fire resilience of mountain vegetation (broadleaf forest and prairies) in the Italian Alps. Resilience is defined herewith as the ability of a dynamical system to counteract disturbances. It can be quantified by the amount of time the disturbed system takes to resume, in statistical terms, an ecological functionality comparable with its undisturbed behavior. Satellite images of the Normalized Difference Vegetation Index (NDVI) and of the Enhanced Vegetation Index (EVI) with spatial resolution of 250m and temporal resolution of 16 days in the 2000-2012 time period were used. Wildfire affected areas in the Lombardy region between the years 2000 and 2010 were analysed. Only large fires (affected area >40ha) were selected. For each burned area, an undisturbed adjacent control site was located. Data pre-processing consisted in the smoothing of MODIS time series for noise removal and then a double logistic function was fitted. Land surface phenology descriptors (proxies for growing season start/end/length and green biomass) were extracted in order to characterize the time evolution of the vegetation. Descriptors from a burned area were compared to those extracted from the respective control site by means of the one-way analysis of variance. According to the number of subsequent years which exhibit statistically meaningful difference between burned and control site, five classes of resilience were identified and a set of thematic maps was created for each descriptor. The same method was applied to all 84 aggregated events and to events aggregated by main land cover. EVI index results more sensitive to fire impact than NDVI index. Analysis shows that fire causes both a reduction of the biomass and a variation in the phenology of the Alpine vegetation. Results suggest an average ecosystem resilience of 6-7 years. Moreover, broadleaf forest and prairies show different post-fire behavior in terms of land surface phenology descriptors. In addition to the above analysis, another method is proposed, which derives from the qualitative theory of dynamical systems. The (time dependent) spectral index of a burned area over the period of one year was plotted against its counterpart from the control site. Yearly plots (or scattergrams) before and after the fire were obtained. Each plot is a sequence of points on the plane, which are the vertices of a generally self-intersecting polygonal chain. Some geometrical descriptors were obtained from the yearly chains of each fire. Principal Components Analysis (PCA) of geometrical descriptors was applied to a set of case studies and the obtained results provide a system dynamics interpretation of the natural process.JRC.H.3 - Forest Resources and Climat

Modeling Gross Primary Production of Agro-Forestry Ecosystems by Assimilation of Satellite-Derived Information in a Process-Based Model

In this paper we present the results obtained in the framework of a regional-scale analysis of the carbon budget of poplar plantations in the northern Italy. We explored the ability of the processbased model BIOME-BGC to estimate the gross primary production (GPP) of these agro-forestry ecosystems exploiting eddy covariance and satellite data using an inverse modeling approach. We present a modified version of BIOME-BGC (named PROSAILH-BGC) which was coupled with the radiative transfer models PROSPECT and SAILH with the aims of i) improving the BIOME-BGC description of the radiative transfer regime within the canopy and ii) allowing the assimilation of remotely-sensed vegetation indexes time series, such as MODIS NDVI, into the BIOME-BGC. In summary, this study showed that assimilation of eddy covariance and remote sensing data in a process model can provide important information for estimating the carbon budget at regional scale.JRC.H.2 - Climate chang