Extracting the hierarchical organization of complex systems

Extracting understanding from the growing ``sea'' of biological and socio-economic data is one of the most pressing scientific challenges facing us. Here, we introduce and validate an unsupervised method that is able to accurately extract the hierarchical organization of complex biological, social, and technological networks. We define an ensemble of hierarchically nested random graphs, which we use to validate the method. We then apply our method to real-world networks, including the air-transportation network, an electronic circuit, an email exchange network, and metabolic networks. We find that our method enables us to obtain an accurate multi-scale descriptions of a complex system.Comment: Figures in screen resolution. Version with full resolution figures available at http://amaral.chem-eng.northwestern.edu/Publications/Papers/sales-pardo-2007.pd

Trastornos de conducta infantiles en medios socioeconómicos diferentes.

Se tomó una muestra de dos niveles socioeconómicos distintos, a la que se le aplicó un cuestionario sobre estas conductas y los factores de riesgo descritos para estos trastornos. Los resultados se analizaron con el programa estadístico EPI-INFO. Se encontraron importantes diferencias entre los dos grupos

Trastornos de conducta infantiles en medios socioeconómicos diferentes.

Se tomó una muestra de dos niveles socioeconómicos distintos, a la que se le aplicó un cuestionario sobre estas conductas y los factores de riesgo descritos para estos trastornos. Los resultados se analizaron con el programa estadístico EPI-INFO. Se encontraron importantes diferencias entre los dos grupos

Mesoscopic structure conditions the emergence of cooperation on social networks

We study the evolutionary Prisoner's Dilemma on two social networks obtained from actual relational data. We find very different cooperation levels on each of them that can not be easily understood in terms of global statistical properties of both networks. We claim that the result can be understood at the mesoscopic scale, by studying the community structure of the networks. We explain the dependence of the cooperation level on the temptation parameter in terms of the internal structure of the communities and their interconnections. We then test our results on community-structured, specifically designed artificial networks, finding perfect agreement with the observations in the real networks. Our results support the conclusion that studies of evolutionary games on model networks and their interpretation in terms of global properties may not be sufficient to study specific, real social systems. In addition, the community perspective may be helpful to interpret the origin and behavior of existing networks as well as to design structures that show resilient cooperative behavior.Comment: Largely improved version, includes an artificial network model that fully confirms the explanation of the results in terms of inter- and intra-community structur

New Trends for the Processing of Poly(Methyl Methacrylate) Biomaterial for Dental Prosthodontics

Rehabilitation of masticatory function in patients with absent teeth with removable dentures is an established form of treating partial or complete dentition in edentulous patients. The developments in recent decades with dental implants dominate current dental research. However, medical contraindications, a negative attitude toward implants, or financial limitations on the part of the patients limit their universal applicability, so the rehabilitation with dental prostheses still makes up a significant portion of everyday clinical practice. Conversely, removable dentures are used in the critical conditions of the oral cavity. There are about 500 strains of microorganisms in the mouth, which form the biofilm in an acidic environment causing several issues, such as denture stomatitis, deterioration of the periodontal status of the remaining teeth, or carious lesions in the supporting teeth. Therefore, it is very important to choose a suitable material for the prosthesis. Poly(methyl methacrylate) (PMMA) is an acrylic resin usually used with a long tradition for prosthetic purposes. The aim of this chapter is to present the trends for the processing of PMMA. It includes the chemical synthesis, conventional thermal processing of this acrylic resin, the new processing technique assisted with ultrasound, the antibacterial effect on PMMA with nanoparticles, and the cytotoxicity, genotoxicity, and mutagenesis of this material

Biological Control of Fusarium oxysporum in Tomato Seedling Production with Mexican Strains of Trichoderma

The problems and limitations of the control of diseases caused by phytopathogens through the use of fungicides, make the biological control present as an alternative method in the production of tomato plants in greenhouse, which is limited by the incidence of Fusarium oxysporum Schlechtend.:Fr., being the most worldwide destructive disease. The objective of the present investigation was to evaluate the effect of three Mexican strains of the genus Trichoderma against F. oxysporum on the production of tomato seedlings under greenhouse conditions, as well as to determine the antagonistic effect of the strains used. The Trichoderma harzianum strain had the highest antagonistic activity (81.50%) and the highest growth rate (1.25 cm/day), proving to be the most aggressive strain to control F. oxysporum. in addition the results of the interaction of the dual cultures paired, presented a visible overgrowth zone with hyphae of Trichoderma spp. Seeds inoculated with T. harzianum showed a survival of 84% and a mortality of 16%, lower than the control group, which present a mortality of 58%; however, the treatment inoculated with F. oxysporum had the highest incidence of “disease” with 83%, the lowest survival (17%) and a decrease of the green biomass with respect to the control

Surface texturing of aluminium alloy AA2024-T3 by picosecond laser: Effect on wettability and corrosion properties

The effects of laser texturing on the corrosion and wettability of AA2024-T3 using an IR Nd:Vanadate picosecond (ps) laser was studied. Three types of texture patterns were generated: dimples with 5% and 50% area density (percentage of surface area textured); cross groove patterns with an area density of 64%; and concentric ring patterns with an area density of 70%. For the higher area densities, the surface character changed from hydrophilic to hydrophobic. The evolution of the open circuit potential over time, potentiodynamic polarization curves and electrochemical impedance spectroscopy were then investigated and analysed. The results revealed that ultrashort ps laser surface texturing did not modify the corrosion behaviour of AA 2024-T3 in the test solution.This work was supported by the Spanish Ministry of Science and Innovation [SMOTI MAT2009-13751] and the Spanish Ministry of Economy and Competitiveness [MAT2013-48224-C2-1-R-MUNSUTI].Peer Reviewe