Testing Propositions Derived from Twitter Studies: Generalization and Replication in Computational Social Science

Replication is an essential requirement for scientific discovery. The current study aims to generalize and replicate 10 propositions made in previous Twitter studies using a representative dataset. Our findings suggest 6 out of 10 propositions could not be replicated due to the variations of data collection, analytic strategies employed, and inconsistent measurements. The study’s contributions are twofold: First, it systematically summarized and assessed some important claims in the field, which can inform future studies. Second, it proposed a feasible approach to generating a random sample of Twitter users and its associated ego networks, which might serve as a solution for answering social-scientific questions at the individual level without accessing the complete data archive.published_or_final_versio

Playing with networks : How economists explain

Peer reviewe

Impact of the Topology of Global Macroeconomic Network on the Spreading of Economic Crises

Throughout economic history, the global economy has experienced recurring crises. The persistent recurrence of such economic crises calls for an understanding of their generic features rather than treating them as singular events. The global economic system is a highly complex system and can best be viewed in terms of a network of interacting macroeconomic agents. In this regard, from the perspective of collective network dynamics, here we explore how the topology of the global macroeconomic network affects the patterns of spreading of economic crises. Using a simple toy model of crisis spreading, we demonstrate that an individual country's role in crisis spreading is not only dependent on its gross macroeconomic capacities, but also on its local and global connectivity profile in the context of the world economic network. We find that on one hand clustering of weak links at the regional scale can significantly aggravate the spread of crises, but on the other hand the current network structure at the global scale harbors higher tolerance of extreme crises compared to more “globalized” random networks. These results suggest that there can be a potential hidden cost in the ongoing globalization movement towards establishing less-constrained, trans-regional economic links between countries, by increasing vulnerability of the global economic system to extreme crises

Neutrophils: the forgotten cell in JIA disease pathogenesis

Juvenile idiopathic arthritis (JIA) has long been assumed to be an autoimmune disease, triggered by aberrant recognition of "self" antigens by T-cells. However, systems biology approaches to this family of diseases have suggested complex interactions between innate and adaptive immunity that underlie JIA. In particular, new data suggest an important role for neutrophils in JIA pathogenesis. In this short review, we will discuss the new data that support a role for neutrophils in JIA, discuss regulatory functions that link neutrophils to adaptive immune responses, and discuss future areas of investigation. Above all else, we invite the reader to re-consider the use of the term "autoimmunity" as applied to the family of illnesses we collectively call JIA

Utilization of fluorescent probe association for simultaneous assessment of plasmatic, acrosomal, and mitochondrial membranes of rooster spermatozoa

This experiment was designed with the objective of developing a simple, practical, and high repeatability technique for the simultaneous evaluation of the integrity of the plasmatic and acrosomal membranes, as well as funcional mitochondria of domestic fowl spermatozoa using an association of fluorescent probes. Four ejaculates (motility > 80% and abnormal morphology < 10%) from each of six Ross male broiler breeder (n=24) were diluted in TALP sperm medium (25x10(6) spermatozoa/mL) and split into two aliquots, and one of these aliquots was flash frozen in liquid nitrogen and thawed to damage all cellular membranes. Three treatments were prepared from these aliquots, with the following ratios of Fresh semen:Flash frozen semen: 100:0 (T100), 50:50 (T50), and 0:100 (T0). A 150-µL aliquot of diluted semen was placed in a microcentrifuge tube with the addition of 2-µL PI, 2-µL MITO, and 50-µL FITC-PSA, and incubated at 38.5º C/8 min in the dark. An 8-µL sample was placed on a slide, coverslipped, and examined by epifluorescence microscopy. Each sample had 200 cells counted and classified based on the fluorescence emitted by each probe. By regression analysis, plasma membrane integrity, as detected by PI, was determined as: v=4.17+0.82X (R²=0.95). Acrosome integrity, as detected by FITC-PSA, generated the equation: v=4.19+0.84X (R²=0.96). Functional mitochondria was estimated by the equation v=3.20+0.83X (R²=0.96). This is an efficient technique to simultaneously evaluate plasmatic, acrosomal, and mitochondrial membranes in fowl sperm. It is suggested that its application in flow cytometry systems allows this methodology to be applied in large scale