The Multidimensional Study of Viral Campaigns as Branching Processes

Viral campaigns on the Internet may follow variety of models, depending on the content, incentives, personal attitudes of sender and recipient to the content and other factors. Due to the fact that the knowledge of the campaign specifics is essential for the campaign managers, researchers are constantly evaluating models and real-world data. The goal of this article is to present the new knowledge obtained from studying two viral campaigns that took place in a virtual world which followed the branching process. The results show that it is possible to reduce the time needed to estimate the model parameters of the campaign and, moreover, some important aspects of time-generations relationship are presented.Comment: In proceedings of the 4th International Conference on Social Informatics, SocInfo 201

Validity of noncycloplegic refraction in the assessment of refractive errors: the Tehran Eye Study

Purpose: To determine the sensitivity and specificity of noncycloplegic autorefraction for determining refractive status compared to cycloplegic autorefraction. Methods: The target population was noninstitutionalized citizens of all ages, residing in Tehran in 2002, selected through stratified cluster sampling. From 6497 eligible residents, 70.3% participated in the study, from August to November 2002. Here, we report data on 3501 people over the age of 5 years who had autorefraction with and without cycloplegia (two drops of cyclopentolate 1.0% 5 min apart, with autorefraction 25 min after the second drop). Results: Overall, the sensitivity of noncycloplegic autorefraction for myopia was 99%, but the specificity was only 80.4%. In contrast, the sensitivity for hyperopia was only 47.9%, but the specificity was 99.4%. At all ages, noncycloplegic autorefraction overestimated myopia and underestimated hyperopia. Overestimation of myopia was highest in the 21-30 and 31-40 year groups. Underestimation of hyperopia was high up to the age of 50 (20-40%), but decreased with age, to about 8% after the age of 50, down to almost 0% after 70. The difference in mean spherical equivalent with and without cycloplegia fell from 0.71 dioptres (D) in the 5-10 age group to 0.14D in those over 70. Conclusion: Use of noncycloplegic autorefraction in epidemiological studies leads to considerable errors relative to cycloplegic measurements, except in those over 50-60. The difference between cycloplegic and noncycloplegic measurements varies with age and cycloplegic refractive category, and there is considerable individual variation, ruling out adjusting noncycloplegic measurements to obtain accurate cycloplegic refractions

Random Walks on Stochastic Temporal Networks

In the study of dynamical processes on networks, there has been intense focus on network structure -- i.e., the arrangement of edges and their associated weights -- but the effects of the temporal patterns of edges remains poorly understood. In this chapter, we develop a mathematical framework for random walks on temporal networks using an approach that provides a compromise between abstract but unrealistic models and data-driven but non-mathematical approaches. To do this, we introduce a stochastic model for temporal networks in which we summarize the temporal and structural organization of a system using a matrix of waiting-time distributions. We show that random walks on stochastic temporal networks can be described exactly by an integro-differential master equation and derive an analytical expression for its asymptotic steady state. We also discuss how our work might be useful to help build centrality measures for temporal networks.Comment: Chapter in Temporal Networks (Petter Holme and Jari Saramaki editors). Springer. Berlin, Heidelberg 2013. The book chapter contains minor corrections and modifications. This chapter is based on arXiv:1112.3324, which contains additional calculations and numerical simulation

Young Galaxy Candidates in the Hubble Frontier Fields - III. MACSJ0717.5+3745

In this paper we present the results of our search for and study of $z \gtrsim 6$ galaxy candidates behind the third Frontier Fields (FF) cluster, MACSJ0717.5+3745, and its parallel field, combining data from Hubble and Spitzer. We select 39 candidates using the Lyman Break technique, for which the clear non-detection in optical make the extreme mid-$z$ interlopers hypothesis unlikely. We also take benefit from $z \gtrsim 6$ samples selected using previous Frontier Fields datasets of Abell 2744 and MACS0416 to improve the constraints on the properties of very high-redshift objects. We compute the redshift and the physical properties, such emission lines properties, star formation rate, reddening, and stellar mass for all Frontier Fields objects from their spectral energy distribution using templates including nebular emission lines. We study the relationship between several physical properties and confirm the trend already observed in previous surveys for evolution of star formation rate with galaxy mass, and between the size and the UV luminosity of our candidates. The analysis of the evolution of the UV Luminosity Function with redshift seems more compatible with an evolution of density. Moreover, no robust $z\ge$8.5 object is selected behind the cluster field, and few $z$$\sim$9 candidates have been selected in the two previous datasets from this legacy survey, suggesting a strong evolution in the number density of galaxies between $z$$\sim$8 and 9. Thanks to the use of the lensing cluster, we study the evolution of the star formation rate density produced by galaxies with L$>$0.03L$^{\star}$, and confirm the strong decrease observed between $z$$\sim$8 and 9.Comment: 21 pages - Accepted for publication in ApJ - v2: small correction

Comparison of a User-Centered Design, Self-Management App to Existing mHealth Apps for Persons Living With HIV

Background: There is preliminary evidence that mobile health (mHealth) apps are feasible, attractive, and an effective platform for the creation of self-management tools for persons living with HIV (PLWH). As a foundation for the current study, we conducted formative research using focus groups, participatory design sessions, and usability evaluation methods to inform the development of a health management app for PLWH. The formative research resulted in identification of the following functional requirements of a mHealth app for self-management: (1) communication between providers and peers, (2) medication reminders, (3) medication log, (4) lab reports, (5) pharmacy information, (6) nutrition and fitness, (7) resources (eg, social services, substance use, video testimonials), (8) settings, and (9) search function. Objective: The purpose of this study was to conduct an ecological review of the existing apps for PLWH and to compare the functionality of existing apps with the app specifications identified in our formative work. Methods: We searched two mobile app stores (Google Play and iTunes) and found a total of 5606 apps. We reviewed the apps, narrowed our search terms, and found a total of 112 apps. Of these, we excluded 97 (86.6%) apps that were either not in English (10/112, 8.9%), not HIV focused (32/112, 28.9%), or focused only on HIV prevention (2/112, 7.8%); targeted health care providers (26/112, 23.2%); provided information only on conference schedules and events (7/112, 6.3%), fundraisers (7/112, 6.3%), specific clinics (7/112, 6.3%), international or narrow local resources (3/112, 2.7%); or were identified in the first search but were no longer on the market at the next review (4/112, 3.6%). The 15 apps meeting inclusion criteria were then evaluated for inclusion of the nine functionalities identified in our earlier work. Results: Of the 15 apps that we included in our final review, none had all of the functionalities that were identified in our formative work. The apps that we identified included the following functionalities: communication with providers and/or peers (4/15, 27%), medication reminders (6/15, 40%), medication logs (7/15, 47%), lab reports (5/15, 33%), pharmacy information (4/15, 27%), resources (7/15, 47%), settings (11/15, 73%), and search function (6/15, 40%). No apps included nutrition or fitness information. Conclusions: Currently, there are only a small number of apps that have been designed for PLWH to manage their health. Of the apps that are currently available, none have all of the desired functionalities identified by PLWH and experts in our formative research. Findings from this work elucidate the need to develop and evaluate mobile apps that meet PLWH’s desired functional specifications

The 2015 Chileno Valley glacial lake outburst flood, Patagonia

Glacial Lake Outburst Floods (GLOFs) have become increasingly common over the past century in response to climate change, posing risks for human activities in many mountain regions. In this paper we document and reconstruct the sequence of events and impact of a large GLOF that took place in December 2015 in the Chileno Valley, Patagonia. Hydrograph data suggests that the flood continued for around eight days with an estimated total discharge of 105.6 × 106 m3 of water. The sequence of events was as follows: (1) A large debris flow entered the lake from two steep and largely non-vegetated mountain gullies located northeast of the Chileno Glacier terminus. (2) Water displaced in the lake by the debris flow increased the discharge through the Chileno Lake outflow. (3) Lake and moraine sediments were eroded by the flood. (4) Eroded sediments were redistributed downstream by the GLOF. The post-GLOF channel at the lake outlet widened in some places by >130 m and the surface elevation of the terrain lowered by a maximum of 38.8 ± 1.5 m. Farther downstream, large amounts of entrained sediment were deposited at the head of an alluvial plain and these sediments produced an ~340 m wide fan with an average increase in surface elevation over the pre-GLOF surface of 4.6 ± 1.5 m. We estimate that around 3.5 million m3 of material was eroded from the flood-affected area whilst over 0.5 million m3 of material was deposited in the downstream GLOF fan. The large debris flow that triggered the GLOF was probably a paraglacial response to glacier recession from its Little Ice Age limits. We suggest that GLOFs will continue to occur in these settings in the future as glaciers further recede in response to global warming and produce potentially unstable lakes. Detailed studies of GLOF events are currently limited in Patagonia and the information presented here will therefore help to inform future glacial hazard assessments in this region

Evaluación xilológica de familias mejoradas de sauces con destino industrial maderero

El objetivo del trabajo fue la evaluación a edad temprana de la anatomía y densidad de la madera y su relacióncon el crecimiento en diámetro en 18 familias de sauces, con vistas a seleccionar clones aptos para laproducción de madera para usos sólidos y papel. Se cruzaron progenitores de ocho especies de sauces (Salixalba, S. amygdaloides, S. babylonica, S. matsudana, S. humboldtiana, S. jessoensis, S. viminalis y S. nigra),obteniéndose individuos correspondientes a 18 familias. Se seleccionaron 365 individuos dentro de las familiassobre los cuales se evaluaron las propiedades de la madera a los 3 años de edad. La familia resultó una fuentesignificativa de variación tanto para el crecimiento como para las propiedades de la madera. El crecimiento endiámetro presentó correlación positiva con la densidad de la madera (r= 0,47) y con el diámetro de vasos (r=0,73) y negativa con la frecuencia de vasos (r= -0,59). La longitud de fibras no se correlacionó significativamentecon ninguna variable medida. Por lo tanto es posible, hallar combinaciones de buen diámetro, con alta densidady altos valores de longitud de fibras. Se destacaron los cruzamientos donde intervienen como progenitorfemenino S. amygdaloides y S. matsudana, ya que demostraron las mejores combinaciones de propiedades paradiferentes destinos industriales como son: buen crecimiento en diámetro (mayores a 5cm), con altas densidadesde la madera (mayores a 0,400 g/cm3) y mayores longitudes de fibras (superiores a 700 µm). Se aconseja lapropagación de ciertas familias promisorias para aserrado y para papel.The objective of this study was to evaluate the anatomy and wood density at early age and its relation to the growth in diameter. 18 willow´s families were evaluated to select clones suitable for the production of solid wood and paper applications. Parents of eight species of willows were crossed (Salix alba, S. amygdaloides, S. babylonica, S. matsudana, S. humboldtiana, S. jessoensis, S. viminalis and S. nigra) and individuals for 18 families were taken. 365 genotypes were selected and their wood properties at the age of 3 years were evaluated. The family was a significant source of variation for both growth and for the properties of wood. Diameter growth was positively correlated with wood density (r= 0.47) and vessel diameter (r= 0.73) but it was negatively correlated with the frequency of vessels (r= -0.59). The fiber length was not significantly correlated with any measured variable. Therefore, it is possible to select clones with great diameter, high density and high fiber length. Crosses which involved S. amygdaloides and S. matsudana as female parent stood out, as they showed the best combination of properties for different industrial destinations such as: good growth in diameter (greater than 5 cm), with high wood densities (greater to 0,400 g/cm3 ) and high fiber lengths (over 700 µm). Certain promising families are recommended for sawing and paper industry.Fil: Cerrillo, Teresa. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Delta del Paraná; ArgentinaFil: Iribarren, R. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Cobas, Ana Clara. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Monteoliva, Silvia Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentin

Analyse fractale par morceaux de radiographies osseuses

- L'objectif de cette étude est de proposer, à partir du mouvement brownien fractionnaire (fBm) de paramètre H, un modèle plus général qui puisse englober des phénomènes présentant un caractère fractal par morceaux lors d'une analyse en fréquence. Ce nouveau modèle est appelé pfBm de paramètres Ho en basse fréquence, Hi en haute fréquence, ces deux régimes étant séparés par une fréquence de coupure γ. Pour Ho=Hi=H, le pfBm se réduit au fBm, lui même étant le mouvement brownien pour H=0.5. Nous pensons que le pfBm fournit ainsi un outil plus flexible que le fBm pour l'expérimentateur. Nous avons montré que ce processus a des incréments stationnaires et qu'il est autosimilaire de paramètre Ho pour les basses fréquences et de paramètre Hi pour les hautes fréquences. Nous avons alors étudié des radiographies trabéculaires osseuses qui présentent ce caractère bifractal. Les résultats montrent que l'analyse fractale par morceaux est plus efficace que l'analyse fractale standard pour diagnostiquer les modifications de la micro-architecture osseuse liées à l'ostéoporose