Media scholars have studied and critiqued search engines-and in particular the dominant commercial actor, Google-for over a decade. Several conceptual and methodological problems, such as a lack of technological transparency, have made a detailed analysis of concrete power relations and their effects difficult. This paper argues that a microeconomic approach can aid media scholars in examining the complex interactions that underpin the dynamics of information visibility unfolding around the Google search engine. Using the concept of a 'three-sided market', we characterize the business model built around google.com as the foundation of the company's success. We then argue that the combination of search and advertising services, and in particular advertising network services, creates powerful incentives to orient the results page in self-serving ways, leading to fundamental conflicts of interest exacerbated by Google's dominant position in both markets. Based on search engines' mass media-like capacity to shape public discourse, we consider the identification of economic forces both as a prerequisite for a robust critique of the current situation and as a starting point for thinking about regulatory measures.

In this paper, we aim to show the heuristic benefit of Michel Foucault's concept of "governmentality", in order to describe three logics of power and control within digital environments. These three logics -directing, constraining and framing online behaviours -are similar to Foucault's approach to power, which is understood as a means to "lead other people's behaviours", as it is in this case enacted through the mediation of technical resources, such as software, algorithms and operating systems. This paper provides three illustrations of these logics of governmentality: the way in which Google tries to direct webmasters' practices with the help of its SEO guidelines and a webmaster ranking system (governmentality by incentives); the way by which developers constrain online behaviours through websites and software (governmentality by design); the way Apple frames the work of app developers in order to institute specific standards for action and interaction within its iPhone operating system (governmentality by framing).

The genotoxicity of cobalt metal and cobalt compounds has been widely studied. Several publications show induction of chromosomal aberrations, micronuclei or DNA damage in mammalian cells in vitro in the absence of S9. Mixed results were seen in gene mutation studies in bacteria and mammalian cells in vitro, and in chromosomal aberration or micronucleus assays in vivo. To resolve these inconsistencies, new studies were performed with soluble and poorly soluble cobalt compounds according to OECD-recommended protocols. Induction of chromosomal damage was confirmed in vitro, but data suggest this may be due to oxidative stress. No biologically significant mutagenic responses were obtained in bacteria, Tk(+/-) or Hprt mutation tests. Negative results were also obtained for chromosomal aberrations (in bone marrow and spermatogonia) and micronuclei at maximum tolerated doses in vivo. Poorly soluble cobalt compounds do not appear to be genotoxic. Soluble compounds do induce some DNA and chromosomal damage in vitro, probably due to reactive oxygen. The absence of chromosome damage in robust GLP studies in vivo suggests that effective protective processes are sufficient to prevent oxidative DNA damage in whole mammals. Overall, there is no evidence of genetic toxicity with relevance for humans of cobalt substances and cobalt metal.

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