Evolution of Communities with Focus on Stability

Community detection is an important tool for analyzing the social graph of mobile phone users. The problem of finding communities in static graphs has been widely studied. However, since mobile social networks evolve over time, static graph algorithms are not sufficient. To be useful in practice (e.g. when used by a telecom analyst), the stability of the partitions becomes critical. We tackle this particular use case in this paper: tracking evolution of communities in dynamic scenarios with focus on stability. We propose two modifications to a widely used static community detection algorithm: we introduce fixed nodes and preferential attachment to pre-existing communities. We then describe experiments to study the stability and quality of the resulting partitions on real-world social networks, represented by monthly call graphs for millions of subscribers.Comment: AST at 42nd JAIIO, September 16-20, 2013, Cordoba, Argentina. arXiv admin note: substantial text overlap with arXiv:1311.550

Arboreal frogs, tank bromeliads and disturbed seasonal tropical forest

We investigated the relationship between arboreal frogs, tank bromeliads and landscape transformation in tropical forests of southeastern Campeche, Mexico. We surveyed frogs in six distinct habitats: slash and burn agriculture, seasonally flooded forest (bajo), aquatic habitats (lagoons and small ponds), second growth upland forest, primary forest and creek habitat using both systematic and non-systematic surveys. The highest species richness of frogs was documented in primary forest and small ponds. In contrast, no frogs were recorded in second growth forest. Similarly, tank bromeliads (Aechmea bracteata) were completely absent from early successional stages and were almost twice as abundant in seasonally flooded forest as in upland forest. The vertical distribution of A. bracteata differed between forest types, and they significantly more abundant in larger diameter trees. We examined 60 tank bromeliads during the peak of the dry season to test their use as refugia by frogs. Approximately 27% of tank bromeliads sampled had arboreal frogs belonging to three species, but 9 species have been recorded as occasional users of bromeliads in the region. There were significantly more frogs on large than on medium-sized bromeliads, and frogs were more abundant on bromeliads higher on host trees, particularly those above 3 m in height. Our results suggest that the loss of tank bromeliads from drier and less structurally complex habitats created by slash and burn agriculture and selective logging results in loss of refugia for arboreal frogs in this seasonal tropical forest. We suggest that Aechmea bracteata be a keystone species in seasonal tropical forest

Detecting Anomalous Inclusions in Soil Profiles: Encouraging the Use of Geophysics to Solve Engineering Problems

Geotechnical site investigations often do not take full advantage of geophysical methods. As examples, when delineating cemented strata and when detecting shallow cavities, investigations can be enhanced greatly for low additional cost by incorporating seismic surface-based measurements

Improved parameterization to invert Rayleigh-wave data for shallow profiles containing stiff inclusions

Inversion of shear-wave velocity profiles from phase-velocity measurements of Rayleigh-wave energy for sites containing stiff layers can be erroneous if such layers are not characterized in the starting or reference model. Incorporation of a priori knowledge then is key for converging upon a realistic or meaningful solution. Resolving soil profiles in desert regions where stiff layers cemented with calcium carbonate are intermixed with softer, uncemented media is an application for which locating shallow stiff inclusions has important implications. Identification of the stiff layers is critical for foundation design and cost estimating of excavations. A parameterization that seems adequate for this problem is to solve for anticipated high-stiffness layers embedded in a coarser (background) profile that captures the general shear-wave velocity trend of the study area. The optimization is accomplished by using simulated annealing. Uncertainty measures resulting from the inversion are helpful for describing the influence of the parameterization on final model estimates

Design of a Microgravity Hybrid Inflatable Airlock

Spacewalks, or extra-vehicular activities (EVAs), are a critical component of human space exploration for science activities and habitat construction and maintenance. For NASA's proposed lunar Gateway system, an airlock module is required for vehicle maintenance, repair, and exploration. Traditional airlock structures are fully metallic, with two chambers, known as an equipment lock and a crew lock. The larger volume, called the equipment lock, serves as the storage, logistics and electronics area, while the smaller volume, called the crew lock, serves as the volume to transition from the vacuum of space to the pressurized cabin. A traditional metallic structure design offers mass efficiency for these elements, but cannot offer volume efficiency. The potential to use an inflatable fabric pressure shell supplemented by a metallic support structure allows for efficiency in both mass and volume. Inflatable structures are being used for human habitable space modules, starting with the Bigelow Expandable Activities Module on the International Space Station. They are high-strength fabric-based structures that are compactly stowed for launch and then, once in space, they are expanded and rigidized with internal pressure. They provide significant launch volume savings over metallic structures. For Gateway, a hybrid airlock design is proposed with both metallic and inflatable structural elements, taking advantage of each material's capabilities. A metallic equipment lock serves as both a docking node and provides pressurized volume for pre-EVA activities including pre-breathe and suit donning/doffing. A rigid equipment lock offers stowage space during launch for integrated hardware and suits. Adding an integrated inflatable crew lock provides the volume required for EVAs with minimal use of launch volume. Using dual inflatable crew locks provides redundancy and the capability to move large pieces of equipment into and out of the vehicle for repair and maintenance. The inflatable crew lock is deflated and packaged in the launch shroud and expanded after installation on the Gateway. This packing capability allows additional volume to be added to the equipment lock and fully utilize the capability of the launch vehicle. This report outlines the work completed to design, analyze, and test the systems of a microgravity airlock with inflatable crew locks. In detail, it includes launch vehicles, structural sizing of the metallic equipment lock, the fabric layers of the inflatable crew lock, the internal structure of the crew lock, the space suit interface elements, the crew restraint system, the hatches and pass-throughs, the material and thermal elements, and the crew operations for the usage of the system. This paper is meant to offer a reference design for a hybrid microgravity airlock design for deep space human exploration

Valor de la escala MEESSI-AHF en el pronóstico de mortalidad intrahospitalaria en pacientes con insuficiencia cardiaca congestiva en el Hospital Guillermo Almenara Yrigoyen

Se buscará determinar el valor de la escala MEESSI-AHF en el pronóstico de mortalidad intrahospitalaria en pacientes con insuficiencia cardiaca congestiva; formaran parte aquellos que fueron atendidos en el Servicio de cardiología del Hospital Guillermo Almenara Irigoyen durante el periodo enero del 2015 – febrero del 2020 que tengan los requisitos establecidos; bajo un estudio transversal de pruebas diagnósticas. Se utilizará una muestra de 195 pacientes. En el análisis estadístico se hará uso de la prueba Chi Cuadrado (X2 ) para variables cualitativas. Se obtendrá la sensibilidad, especificidad, valor predictivo positivo y negativo. Se buscará comparar las variables intervinientes en los pacientes con insuficiencia cardíaca que fallecieron y sobrevivieron mediante la prueba Chi cuadrado y t- student dependiendo del tipo de variableTesis de segunda especialida

Behavior of early warnings near the critical temperature in the two-dimensional Ising model

Among the properties that are common to complex systems, the presence of critical thresholds in the dynamics of the system is one of the most important. Recently, there has been interest in the universalities that occur in the behavior of systems near critical points. These universal properties make it possible to estimate how far a system is from a critical threshold. Several early-warning signals have been reported in time series representing systems near catastrophic shifts. The proper understanding of these early-warnings may allow the prediction and perhaps control of these dramatic shifts in a wide variety of systems. In this paper we analyze this universal behavior for a system that is a paradigm of phase transitions, the Ising model. We study the behavior of the early-warning signals and the way the temporal correlations of the system increase when the system is near the critical point.Comment: 20 pages, 8 figures, Submitted to PLOS ONE on Oct. 20th 2014. PONE-D-14-4718