How do companies collaborate in open source ecosystems? An empirical study of OpenStack

OpenSourceSoftware (OSS) has come to play a critical role in the software industry. Some large ecosystems enjoy the participation of large numbers of companies, each of which has its own focus and goals. Indeed, companies that otherwise compete, may become collaborators within the OSS ecosystem they participate in. Prior research has largely focused on commercial involvement in OSS projects, but there is a scarcity of research focusing on company collaborations within OSS ecosystems. Some of these ecosystems have become critical building blocks for organizations worldwide; hence, a clear understanding of how companies collaborate within large ecosystems is essential. This paper presents the results of an empirical study of the Open Stack ecosystem, in which hundreds of companies collaborate on thousands of project repositories to deliver cloud distributions. Based on a detailed analysis, we identify clusters of collaborations, and identify four strategies that companies adopt to engage with the Open Stack ecosystem. We also find that companies may engage in intentional or passive collaborations, or may work in an isolated fashion. Further, we find that a company’s position in the collaboration network is positively associated with its productivity in Open Stack. Our study sheds light on how large OSS ecosystems work, and in particular on the patterns of collaboration within one such large ecosystem

Stable S/MAR-based episomal vectors are regulated at the chromatin level

Episomal vectors assembled from defined genetic components are a promising alternative to traditional gene therapy vectors that integrate in the host genome and may cause insertional mutations. The vector pEPI-eGFP is stably retained in the episomal state in cultured mammalian cells at low copy number for many generations without integration into the host genome. Although pEPI-eGFP is a fully engineered vector, little is known about how it interacts with the host genome and about the molecular mechanisms that are responsible for its transcriptional activity. We have analyzed the expression of the episomal reporter gene eGFP under conditions that affect the chromatin state of the genome. We have also constructed pEPI derivatives carrying a tandem array of lac operator sequences, which allows in vivo visualization and manipulation of the chromatin state of the episome. We show that changes in chromatin state of both the host and pEPI-eGFP induces changes in episomal gene activity and influences the episome’s nuclear distributions. We conclude that episomal genes are subject to control systems of the host, similarly to their counterparts in the host genome

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements