Phase transition for the Maki-Thompson rumour model on a small-world network

We consider the Maki-Thompson model for the stochastic propagation of a rumour within a population. We extend the original hypothesis of homogenously mixed population by allowing for a small-world network embedding the model. This structure is realized starting from a $k$-regular ring and by inserting, in the average, $c$ additional links in such a way that $k$ and $c$ are tuneable parameter for the population architecture. We prove that this system exhibits a transition between regimes of localization (where the final number of stiflers is at most logarithmic in the population size) and propagation (where the final number of stiflers grows algebraically with the population size) at a finite value of the network parameter $c$. A quantitative estimate for the critical value of $c$ is obtained via extensive numerical simulations.Comment: 24 pages, 4 figure

Estrategia para el aprendizaje significativo de las ciencias naturales en los niños y niñas del grado octavo de la institucion educativa departamental ¨Santa Maria¨ de Ubaté – Cundinamarca

DiagramasEn la actualidad la educación exige, no solamente que se brinde a los estudiantes una serie de conocimientos en todas las áreas, para que ellos los aprendan memorísticamente, sino que se pretende que estos conocimientos sean incorporados en su estructura cognitiva, de modo que no los olvide y los utilice en la solución problemas de su entorno.Today education requires not only it is provided to students with a range of knowledge in all areas, for them to rote learn, but it is intended that this knowledge are incorporated into their cognitive structure, so do not forget and solution used in the problems of their environment

Fortalecimiento de las habilidades en el pensamiento lógico matemático a partir del enfoque High Scope en niños y niñas de 3 a 5 años del Liceo Infantil Huellas de Colores

Los estudiantes del Liceo Infantil Huellas De Colores que oscilan entre la edades de 3 a 5 años en su proceso de aprendizaje, se les dificulta desarrollar algunas habilidades del pensamiento lógico matemático, por ende, no dan una respuesta rápida y coherente a la hora de solucionar problemas que se les presentan en su vida cotidiana, por esta razón el objetivo de esta investigación se centra en desarrollarlas a través de actividades basadas en el enfoque High Scope que potencie la observación, la comparación, la relación, la clasificación y la descripción, donde le corresponde a las docentes en formación de la Licenciatura en Pedagogía Infantil trabajar en las sesiones de clase con diversas experiencias que le faciliten desarrollar de mejor manera estas habilidades, donde al finalizar la aplicación de las actividades se emplea una escala de Lykert para evaluar el desempeño y la evolución que hayan tenido a lo largo de este proceso; la información analizada es tabulada y graficada en cuadros estadísticos, de los resultados obtenidos se redactan conclusiones y prospectivas como propuesta aplicable para el desarrollo de las Habilidades del Pensamiento Lógico Matemático de los estudiantes quienes son los beneficiarios directos de esta investigación y de las docentes en formación como las responsables de aplicarlas en el proceso de aprendizaje

Holistic approach to dissolution kinetics : linking direction-specific microscopic fluxes, local mass transport effects and global macroscopic rates from gypsum etch pit analysis

Dissolution processes at single crystal surfaces often involve the initial formation and expansion of localized, characteristic (faceted) etch-pits at defects, in an otherwise comparatively unreactive surface. Using natural gypsum single crystal as an example, a simple but powerful morphological analysis of these characteristic etch pit features is proposed that allows important questions concerning dissolution kinetics to be addressed. Significantly, quantitative mass transport associated with reactive microscale interfaces in quiescent solution (well known in the field of electrochemistry at ultramicroelectrodes) allows the relative importance of diffusion compared to surface kinetics to be assessed. Furthermore, because such mass transport rates are high, much faster surface kinetics can be determined than with existing dissolution methods. For the case of gypsum, surface processes are found to dominate the kinetics at early stages of the dissolution process (small etch pits) on the cleaved (010) surface. However, the contribution from mass transport becomes more important with time due to the increased area of the reactive zones and associated decrease in mass transport rate. Significantly, spatial heterogeneities in both surface kinetics and mass transport effects are identified, and the morphology of the characteristic etch features reveal direction-dependent dissolution kinetics that can be quantified. Effective dissolution velocities normal to the main basal (010) face are determined, along with velocities for the movement of [001] and [100] oriented steps. Inert electrolyte enhances dissolution velocities in all directions (salting in), but a striking new observation is that the effect is direction-dependent. Studies of common ion effects reveal that Ca2+ has a much greater impact in reducing dissolution rates compared to SO42−. With this approach, the new microscopic observations can be further analysed to obtain macroscopic dissolution rates, which are found to be wholly consistent with previous bulk measurements. The studies are thus important in bridging the gap between microscopic phenomena and macroscopic measurements

Genome-Wide Phylogenetic Comparative Analysis of Plant Transcriptional Regulation: A Timeline of Loss, Gain, Expansion, and Correlation with Complexity

Evolutionary retention of duplicated genes encoding transcription-associated proteins (TAPs, comprising transcription factors and other transcriptional regulators) has been hypothesized to be positively correlated with increasing morphological complexity and paleopolyploidizations, especially within the plant kingdom. Here, we present the most comprehensive set of classification rules for TAPs and its application for genome-wide analyses of plants and algae. Using a dated species tree and phylogenetic comparative (PC) analyses, we define the timeline of TAP loss, gain, and expansion among Viridiplantae and find that two major bursts of gain/expansion occurred, coinciding with the water-to-land transition and the radiation of flowering plants. For the first time, we provide PC proof for the long-standing hypothesis that TAPs are major driving forces behind the evolution of morphological complexity, the latter in Plantae being shaped significantly by polyploidization and subsequent biased paleolog retention. Principal component analysis incorporating the number of TAPs per genome provides an alternate and significant proxy for complexity, ideally suited for PC genomics. Our work lays the ground for further interrogation of the shaping of gene regulatory networks underlying the evolution of organism complexity

Étude de l’influence de la dissolution sous contrainte sur les propriétés mécaniques des solides : fluage du plâtre

The huge enhancement of the creep of plasterboard by humid environments is an old problem in the building industry, but its origin remains unknown. To understand this mechanism a three scales study (macro : mechanical behavior, micro : dissolution kinetics, nano : atomic observation) has been done. There is a strong correlation between wet plaster creep and gypsum dissolution kinetics. The concordance between this correlation and the law of deformation by pressure solution, well-known in geology, permits to propose pressure solution as one of the mechanisms responsible of wet plaster creep. The topological evolution of the cleaved surface of a gypsum single crystal during its dissolution in a flowing under-saturated aqueous solution has been observed with an atomic force microscope. The kinetics of step migration strongly depends on the saturation state of the solution, the force applied by the tip on the surface, as well as the used additives. The study of the influence of the force applied by the tip on the step velocity evidence two different dissolution enhancement regimes. At high forces (> 15 nN) a corrosive wear behavior is observed, while at low forces ( 15 nN) on observe un mécanisme d’usure de la surface, tandis qu’à faibles forces (< 10 nN) le mécanisme observé semble être la dissolution sous contrainte. L’évolution des vitesses des marches atomiques avec la force appliquée par la pointe est concordante avec une loi connue de dissolution sous contrainte

Study of the influence of pressure solution on the mechanical properties of solids : plaster creep

L’importante augmentation de fluage des plaques de plâtre en milieu humide est un vieux problème dans l’industrie du bâtiment, dont l’origine n’est pas encore établie. Afin d’en comprendre le mécanisme une étude à trois échelles (macro : réponse mécanique, micro : cinétique de dissolution et nano : observation atomique) a été réalisée. Une corrélation forte existe entre le fluage du plâtre en immersion et la cinétique de dissolution du gypse. La concordance de cette corrélation avec une loi de déformation par dissolution sous contrainte, très utilisés en géologie, permet de proposer la dissolution sous contrainte comme un des mécanismes responsables du fluage du plâtre en immersion. L’évolution de la topographie de la surface du cristal de gypse immergé dans une solution aqueuse de gypse est observée par microscopie à force atomique (AFM). La cinétique de migration des marches atomiques est très dépendante de la sous-saturation de la solution, de la force d’appui de la pointe de l’AFM ainsi que des additifs utilisés. L’étude de l’influence de la force d’appui sur les vitesses des marches met en évidence la présence de deux mécanismes complètement différents. A fortes forces (> 15 nN) on observe un mécanisme d’usure de la surface, tandis qu’à faibles forces ( 15 nN) a corrosive wear behavior is observed, while at low forces (< 10 nN) pressure solution is the observed mechanism. The step velocity evolution with the force obeys the known kinetic law of pressure solution