Social Presence in Online Discussion Forums

El uso de foros de discusión en línea como una herramienta para el aprendizaje colaborativo requiere que los estudiantes se perciban mutuamente como personas reales y generen lazos afectivos entre ellos. Se investigó la relación entre la presencia social de los participantes en un foro y sus posiciones en las redes sociales de amistad, consejo, y adversarios formadas con compañeros. Se encontró una correlación negativa entre la centralidad de los participantes en la red de adversarios con el uso de indicadores afectivos, más no con indicadores cohesivos ni interactivos. No se encontraron correlaciones significativas entre la centralidad en las redes de consejo y amistad con ninguno de los tipos de indicadores de presencia social.When using online discussion boards as a tool for collaborative learning, students should be able to perceive each other as real people and create affective bonds between them. This paper assesses the relationship between social presence indicators and participants' messages to an online discussion board and his or her centrality in the advice, friendship, and hindrance social network created by all participants. A negative correlation was found between the use of affective indicators and centrality in the hindrance networks; no significant correlations were found between the centrality in the other networks and any kind of indicator of social presence

Phase diagram study of a two-dimensional frustrated antiferromagnet via unsupervised machine learning

We apply unsupervised learning techniques to classify the different phases of the $J_1-J_2$ antiferromagnetic Ising model on the honeycomb lattice. We construct the phase diagram of the system using convolutional autoencoders. These neural networks can detect phase transitions in the system via `anomaly detection', without the need for any label or a priori knowledge of the phases. We present different ways of training these autoencoders and we evaluate them to discriminate between distinct magnetic phases. In this process, we highlight the case of high temperature or even random training data. Finally, we analyze the capability of the autoencoder to detect the ground state degeneracy through the reconstruction error.Comment: 11 pages, 15 figure

Virtually Abelian Quantum Walks

We introduce quantum walks on Cayley graphs of non-Abelian groups. We focus on the easiest case of virtually Abelian groups, and introduce a technique to reduce the quantum walk to an equivalent one on an Abelian group with coin system having larger dimension. We apply the technique in the case of two quantum walks on virtually Abelian groups with planar Cayley graphs, finding the exact solution.Comment: 10 pages, 3 figure

Adjuvants : an essential component of neisseria vaccines

Adjuvants may be classified into delivery systems and immune potentiator or modulator molecules based on their mechanism of action. Neisseria vaccines containing traditional adjuvants such as aluminium salts have existed for long time, but meningitis caused by Neisseria meningitidis serogroups, particularly serogroup B, continues to be a global health problem. Novel strategies have applied in silico and recombinant technologies to develop "universal" antigens (e.g. proteins, peptides and plasmid DNA) for vaccines, but these antigens have been shown to be poorly immunogenic even when alum adjuvanted, implying a need for better vaccine design. In this work we review the use of natural, detoxified, or synthetic molecules in combination with antigens to activate the innate immune system and to modulate the adaptive immune responses. In the main, antigenic and imune potentiator signals are delivered using nano-, micro-particles, alum, or emulsions. The importance of interaction between adjuvants and antigens to activate and target dendritic cells, the bridge between the innate and adaptive immune systems, will be discussed. In addition, nasal vaccine strategies based on the development of mucosal adjuvants and Neisseria derivatives to eliminate the pathogen at the site of infection provide promising adjuvants effective not only against respiratory pathogens, but also against pathogens responsible for enteric and sexually transmitted diseases

Influence of the feeding mechanism on deposits of square particles

In a previous paper [Hidalgo et al., Phys. Rev. Lett. 103, 118001 (2009)] it was shown that square particles deposited in a silo tend to align with a diagonal parallel to the gravity, giving rise to a deposit with very particular properties. Here we explore, both experimentally and numerically, the effect on these properties of the filling mechanism. In particular, we modify the volume fraction of the initial configuration from which the grains are deposited. Starting from a very dilute case, increasing the volume fraction results in an enhancement of the disorder in the final deposit characterized by a decrease of the final packing fraction and a reduction of the number of particles oriented with their diagonal in the direction of gravity. However, for very high initial volume fractions, the final packing fraction increases again. This result implies that two deposits with the same final packing fraction can be obtained from very different initial conditions. The structural properties of such deposits are analyzed, revealing that, although the final volume fraction is the same, their micromechanical properties notably differ

Characteristics of precipitation in the Santarém study region.

Abstract ID: 80. Publicado também on-line

Osteocyte dysfunction promotes osteoarthritis through MMP13-dependent suppression of subchondral bone homeostasis.

Osteoarthritis (OA), long considered a primary disorder of articular cartilage, is commonly associated with subchondral bone sclerosis. However, the cellular mechanisms responsible for changes to subchondral bone in OA, and the extent to which these changes are drivers of or a secondary reaction to cartilage degeneration, remain unclear. In knee joints from human patients with end-stage OA, we found evidence of profound defects in osteocyte function. Suppression of osteocyte perilacunar/canalicular remodeling (PLR) was most severe in the medial compartment of OA subchondral bone, with lower protease expression, diminished canalicular networks, and disorganized and hypermineralized extracellular matrix. As a step toward evaluating the causality of PLR suppression in OA, we ablated the PLR enzyme MMP13 in osteocytes while leaving chondrocytic MMP13 intact, using Cre recombinase driven by the 9.6-kb DMP1 promoter. Not only did osteocytic MMP13 deficiency suppress PLR in cortical and subchondral bone, but it also compromised cartilage. Even in the absence of injury, osteocytic MMP13 deficiency was sufficient to reduce cartilage proteoglycan content, change chondrocyte production of collagen II, aggrecan, and MMP13, and increase the incidence of cartilage lesions, consistent with early OA. Thus, in humans and mice, defects in PLR coincide with cartilage defects. Osteocyte-derived MMP13 emerges as a critical regulator of cartilage homeostasis, likely via its effects on PLR. Together, these findings implicate osteocytes in bone-cartilage crosstalk in the joint and suggest a causal role for suppressed perilacunar/canalicular remodeling in osteoarthritis

Effects of environmental variables on the distribution of juvenile cubomedusae Carybdea marsupialis in the coastal Western Mediterranean

[EN] Relationships between environmental factors and oscillations in jellyfish abundance, especially in the early life stages, could help to interpret past increases and also predict scenarios in a changing future. For the first time, we present cubozoan spatial and temporal distributions in the earliest stages and their relationships with different factors. Abundances ofCarybdea marsupialismedusae showed high interannual variability from 2008 to 2014 along the Denia coast (SE Spain, W Mediterranean). During 2015, samples were collected from 11 beaches along 17 km of coastline, 8 times from January to November in order to determine the effects of environmental factors on the distribution of juvenileC.marsupialis. Juveniles (<= 15 mm diagonal bell width) were present from May to July, with more sampled near shore (0-15 m). Most of them occurred in June when their numbers were unequal among beaches (average 0.05 ind m(-3), maximum 6.71 ind m(-3)). We tested distributions of juveniles over time and space versus temperature, salinity, nutrients (N, P and Si), chlorophyll-a(Chl-a), and zooplankton abundance. Temperature and cladocerans (zooplankton group) were significantly positively correlated with juvenile distribution, whereas Chl-aconcentration was weakly negative. By contrast, in 2014, high productivity areas (Chl-aand zooplankton) overlapped the maximum adult abundance (5.2 ind m(-3)). The distribution of juveniles during 2015 did not spatially coincide with the areas where ripe adults were located the previous year, suggesting that juveniles drift with the currents upon release from the cubopolyps. Our results yield important insights into the complexity of cubozoan distributions.This study has received funding through European Commission's LIFE programme [LIFE08 NAT ES64 CUBOMED.eu to C.B. from the Alicante University and V.L.F. from the Institute of Marine Science, CSIC, Spain], and from the D.G Sostenibilidad de la Costa y el Mar from the Spanish Ministry of Agriculture, Food and the Environment, the Fundacion Biodiversidad, and the D.G. Agua -Generalitat Valenciana. It has also received support from Parques Nacionales and Ajuntament de Denia. We are grateful for the collaboration of Fundació Baleària, Marina El Portet de Dénia and Marina de Dénia. This work is a contribution from the ¿Ramon Margalef¿ Environmental Research Institute (IMEM) from the University of Alicante, Spain. We are especially grateful for the sampling and laboratory support provided in the Montgó Research Station by NGO ACIF Marina Alta volunteers: Ángela Alba, Ainara Ballesteros, Miguel Escolano, Ángel Fernández, Marta Gil, Héctor Gutiérrez, Ainara Lacalle and Alba Pérez. We would also like to extend our thanks to Jordi Alventosa and Júlia Escrivá from IGIC-Polytechnic Valencia University for their contribution to nutrient analysis. Editing services were provided by Sea Pen Scientific Writing.Bordehore, C.; Fonfría, E.; Alonso, C.; Rubio-Tortosa, B.; Acevedo, M.; Canepa, A.; Falco, S.... (2020). Effects of environmental variables on the distribution of juvenile cubomedusae Carybdea marsupialis in the coastal Western Mediterranean. PLoS ONE. 15(6):1-20. https://doi.org/10.1371/journal.pone.0230768S120156Purcell, J., Uye, S., & Lo, W. (2007). Anthropogenic causes of jellyfish blooms and their direct consequences for humans: a review. 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Giardia intestinalis e estado nutricional em crianças participantes do programa de nutrição complementar, melhoramento alimentar e nutricional da Antioquia (MANA) - Instituto Colombiano de Bem-Estar Familiar (ICBF), Antióquia, Colombia, maio a outubro de 2006

A infecção pela Giardia intestinalis está amplamente distribuída no mundo apresentando a maior prevalência nos países em desenvolvimento. Em crianças, esta parasitose pode ter conseqüências graves no estado geral de saúde assim como no ganho de peso e estatura. O objetivo desta pesquisa foi estabelecer a associação entre a infecção com Giardia e o estado nutricional das crianças beneficiárias do programa de complementação alimentar - MANA. Um estudo de corte no qual foram avaliadas 2035 crianças entre os oito meses e os seis anos de idade foi realizado. A informação foi obtida a partir de questionários estruturados, medições antropométricas e exame de fezes. Os resultados mostraram que 27,6% das crianças estavam infectadas com Giardia intestinalis, das quais 8,1% apresentaram desnutrição moderada, 1,9% desnutrição grave e 14,1% franca queda no crescimento. Em conclusão, nesta população a Giardíase foi indicador de desnutrição grave.Giardia intestinalis infection is prevalent throughout the world and widely distributed in developing countries. In general, children display serious consequences to their state of health, including slow height-weight development; therefore, the main aim of this study was to determine the association between Giardia infection and the nutritional status of children who participate in the program of complementary feeding (Mejoramiento Alimentario y Nutricional de Antioquia (MANA) - Instituto Colombiano de Bienestar Familiar (ICBF)). A cross-sectional study examining the association of giardiasis with nutritional status was conducted. A total of 2035 children aged eight months to six years-old were studied. Data were collected using structured questionnaires, anthropometric measurements and laboratory analysis of blood and stool samples. Analysis of the results showed that 27.6% of children were infected with G. intestinalis, while 8.1% and 1.9% were mildly and significantly underweight, respectively, and 14.1% presented stunting. Giardiasis was statistically identified as a strong predictor of stunting in this study population