The Dynamics of a Mobile Phone Network

The empirical study of network dynamics has been limited by the lack of longitudinal data. Here we introduce a quantitative indicator of link persistence to explore the correlations between the structure of a mobile phone network and the persistence of its links. We show that persistent links tend to be reciprocal and are more common for people with low degree and high clustering. We study the redundancy of the associations between persistence, degree, clustering and reciprocity and show that reciprocity is the strongest predictor of tie persistence. The method presented can be easily adapted to characterize the dynamics of other networks and can be used to identify the links that are most likely to survive in the future

To each according to its degree: The meritocracy and topocracy of embedded markets

A system is said to be meritocratic if the compensation and power available to individuals is determined by their abilities and merits. A system is topocratic if the compensation and power available to an individual is determined primarily by her position in a network. Here we introduce a model that is perfectly meritocratic for fully connected networks but that becomes topocratic for sparse networks-like the ones in society. In the model, individuals produce and sell content, but also distribute the content produced by others when they belong to the shortest path connecting a buyer and a seller. The production and distribution of content defines two channels of compensation: a meritocratic channel, where individuals are compensated for the content they produce, and a topocratic channel, where individual compensation is based on the number of shortest paths that go through them in the network. We solve the model analytically and show that the distribution of payoffs is meritocratic only if the average degree of the nodes is larger than a root of the total number of nodes. We conclude that, in the light of this model, the sparsity and structure of networks represents a fundamental constraint to the meritocracy of societiesSupport from the MIT Media Lab Consortia, Fundación Caja Madrid (Spain), UAM-Santander (Spain) and CONICYT grants: Anillo en Complejidad Social SOC-1101 and Fondecyt 1110351 is gratefully acknowledge

To Each According to its Degree: The Meritocracy and Topocracy of Embedded Markets

A system is said to be meritocratic if the compensation and power available to individuals is determined by their abilities and merits. A system is topocratic if the compensation and power available to an individual is determined primarily by her position in a network. Here we introduce a model that is perfectly meritocratic for fully connected networks but that becomes topocratic for sparse networks-like the ones in society. In the model, individuals produce and sell content, but also distribute the content produced by others when they belong to the shortest path connecting a buyer and a seller. The production and distribution of content defines two channels of compensation: a meritocratic channel, where individuals are compensated for the content they produce, and a topocratic channel, where individual compensation is based on the number of shortest paths that go through them in the network. We solve the model analytically and show that the distribution of payoffs is meritocratic only if the average degree of the nodes is larger than a root of the total number of nodes. We conclude that, in the light of this model, the sparsity and structure of networks represents a fundamental constraint to the meritocracy of societies.MIT Media Lab Consortiu

Características físico-químicas y estabilidad oxidativa de aceites de diferentes ecotipos de ricino peruano

The aim of this research was to assess the physico-chemical properties and shelf-life of oils press-extracted at two temperatures (60 °C and 80 °C) from five Peruvian castor bean ecotypes. A wide variation for all traits was observed. Low acidity index, low peroxide index and absence of p-anisidine were recorded. The total tocopherol contents ranged from 798 to 1040 mg/kg. A higher antioxidant capacity was detected in methanolic extracts than in hexane extract. From the Rancimat performed at 150-170 °C, the predicted shelf-life at 25 °C ranged from 0.15 to 8.93 years; the higher extraction temperature led to a longer shelf-life, probably because of enzyme inactivation.El objetivo de esta investigación fue estudiar las propiedades fisicoquímicas y la vida útil de aceite de ricino extraido a presión a dos temperaturas (60 y 80 °C) de cinco ecotipos peruanos. Se notó una amplia variación para todas las características. Se observaron bajos índice de acidez, bajo índice de peróxido y ausencia de p-anisidina. El contenido total de tocoferoles osciló entre 798 y 1040 mg/kg. Se detectó una mayor capacidad antioxidante en los extractos en metanol que en los extractos en hexano. A partir del Rancimat realizado a 150-170 °C, la vida útil prevista a 25 °C osciló entre 0.15 y 8.93 años; la mayor temperatura de extracción condujo a una vida útil más larga, probablemente debido a inactivación de las enzimas. &nbsp

Influencia de la presencia de compuestos superficiales de P sobre la funcionalización de carbones activos con HNO3

La funcionalización con ácido nítrico es un método ampliamente estudiado para la incorporación de grupos funcionales de oxígeno en la superficie de carbones activos, tales como grupos carboxilos, anhídridos, lactonas y fenoles. Sin embargo, también incorpora, en menor medida, grupos funcionales nitrogenados. Estos grupos funcionales de N son capaces de mejorar las propiedades de adsorción y/o catalíticas de diferentes carbones activos. Por otro lado, la activación química con ácido fosfórico produce carbones activos con una cantidad importante de grupos superficiales de fósforo de gran estabilidad, que les confiere una elevada resistencia a la oxidación y acidez, que los hace muy interesantes en diferentes aplicaciones catalíticas. En este trabajo se va a estudiar la influencia de la presencia de estos grupos de fósforo en la funcionalización de carbones activos con ácido nítrico.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Bicarbonate-Triggered In Vitro Capacitation of Boar Spermatozoa Conveys an Increased Relative Abundance of the Canonical Transient Receptor Potential Cation (TRPC) Channels 3, 4, 6 and 7 and of CatSper-γ Subunit mRNA Transcripts

Sperm capacitation is a stepwise complex biochemical process towards fertilization. It includes a crucial early calcium (Ca2+) transport mediated by CatSper channels and Canonical Transient Potential Channels (TRPC). We studied the relative abundance of mRNA transcripts changes of the CatSper β, γ and δ subunits and TRPC-channels 1, 3, 4, 6 and 7 in pig spermatozoa, after triggering in vitro capacitation by bicarbonate ions at levels present in vivo at the fertilization site. For this purpose, we analyzedfive5 ejaculate pools (from three fertile adult boars) before (control-fresh samples) and after in vitro exposure to capacitation conditions (37 mM NaHCO3, 2.25 mM CaCl2, 2 mM caffeine, 0.5% bovine serum albumin and 310 mM lactose) at 38 °C, 5% CO2 for 30 min. In vitro capacitation using bicarbonate elicits an increase in the relative abundance of mRNA transcripts of almost all studied Ca2+ channels, except CatSper-δ and TRPC1 (significantly reduced). These findings open new avenues of research to identify the specific role of each channel in boar sperm capacitation and elucidate the physiological meaning of the changes on sperm mRNA cargo