12 research outputs found
Social features of online networks: the strength of intermediary ties in online social media
An increasing fraction of today social interactions occur using online social
media as communication channels. Recent worldwide events, such as social
movements in Spain or revolts in the Middle East, highlight their capacity to
boost people coordination. Online networks display in general a rich internal
structure where users can choose among different types and intensity of
interactions. Despite of this, there are still open questions regarding the
social value of online interactions. For example, the existence of users with
millions of online friends sheds doubts on the relevance of these relations. In
this work, we focus on Twitter, one of the most popular online social networks,
and find that the network formed by the basic type of connections is organized
in groups. The activity of the users conforms to the landscape determined by
such groups. Furthermore, Twitter's distinction between different types of
interactions allows us to establish a parallelism between online and offline
social networks: personal interactions are more likely to occur on internal
links to the groups (the weakness of strong ties), events transmitting new
information go preferentially through links connecting different groups (the
strength of weak ties) or even more through links connecting to users belonging
to several groups that act as brokers (the strength of intermediary ties).Comment: 14 pages, 18 figure
A Kinetic-Based Model of Radiation-Induced Intercellular Signalling
It is now widely accepted that intercellular communication can cause significant variations in cellular responses to genotoxic stress. The radiation-induced bystander effect is a prime example of this effect, where cells shielded from radiation exposure see a significant reduction in survival when cultured with irradiated cells. However, there is a lack of robust, quantitative models of this effect which are widely applicable. In this work, we present a novel mathematical model of radiation-induced intercellular signalling which incorporates signal production and response kinetics together with the effects of direct irradiation, and test it against published data sets, including modulated field exposures. This model suggests that these so-called "bystander" effects play a significant role in determining cellular survival, even in directly irradiated populations, meaning that the inclusion of intercellular communication may be essential to produce robust models of radio-biological outcomes in clinically relevant in vivo situations