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Abstract Very long baseline interferometry (VLBI) provides the highest-resolution images in astronomy. The sharpest resolution is nominally achieved at the highest frequencies, but as the observing frequency increases, so too does the atmospheric contribution to the system noise, degrading the sensitivity of the array and hampering detection. In this paper, we explore the limits of high-frequency VLBI observations usingngehtsim, a new tool for generating realistic synthetic data.ngehtsimuses detailed historical atmospheric models to simulate observing conditions, and it employs heuristic visibility detection criteria that emulate single- and multifrequency VLBI calibration strategies. We demonstrate the fidelity ofngehtsim’spredictions using a comparison with existing 230 GHz data taken by the Event Horizon Telescope (EHT), and we simulate the expected performance of EHT observations at 345 GHz. Though the EHT achieves a nearly 100% detection rate at 230 GHz, our simulations indicate that it should expect substantially poorer performance at 345 GHz; in particular, observations of M87* at 345 GHz are predicted to achieve detection rates of ≲20% that may preclude imaging. Increasing the array sensitivity through wider bandwidths and/or longer integration times—as enabled through, e.g., the simultaneous multifrequency upgrades envisioned for the next-generation EHT—can improve the 345 GHz prospects and yield detection levels that are comparable to those at 230 GHz. M87* and Sgr A* observations carried out in the atmospheric window around 460 GHz could expect to regularly achieve multiple detections on long baselines, but analogous observations at 690 and 875 GHz consistently obtain almost no detections at all. 

Cloud computing services have enjoyed explosive growth over the last decade. Users are typically businesses and government agencies who are able to scale their storage and processing requirements, and choose from pre-defined services (e.g. specific software-as-a-service applications). But with this outsourcing has also come the potential for data breaches targeted at the end-user, typically consumers (e.g. who purchase goods at an online retail store), and citizens (e.g. who transact information for their social security needs). This paper briefly introduces U.S.-based cloud computing regulation, including the U.S. Health Insurance Portability and Accountability Act (HIPPA), the Gramm Leach Bliley Act (GLBA), and the U.S. Stored Communications Act (SCA). We present how data breach notification (DBN) works in the U.S. by examining three mini-case examples: the 2011 Sony PlayStation Network data breach, the 2015 Anthem Healthcare data breach, and the 2017 Equifax data breach. The findings of the paper show that there is a systemic failure to learn from past data breaches, and that data breaches not only affect business and government clients of cloud computing services but their respective end-user customer base. Finally, the level of sensitivity of data breaches is increasing, from cloud computing hacks on video game platforms, to the targeting of more lucrative network and computer crime abuses aiming at invasive private health and financial data. 

This paper is about stakeholders in the cloud computing value-chain. Early cloud computing literature focused on the technical aspect of the technology and viewed the provider and customer as essential value-chain stakeholders. The more users that use cloud services, the potential for data breaches increases. The review of the literature was carried out using a social-technical approach. Socio-technical theory encapsulates the social, technical and environmental dimensions of a system. The outcomes of the search indicated that there are two pertinent stakeholder types: operational and non-operational. Operational stakeholders include cloud providers, customers, enablers, resellers and third-party providers. Non-operational stakeholders include regulators, legislators, courts, non-government organisations, law enforcement, industry-standard bodies and end-users. The end-users are critically important in the cloud value-chain in that they rely on online services for everyday activities and have their data compromised. The cloud value-chain presents that cloud services encapsulate more than just technology services. The paper considers the complex stakeholder relationships and data breach issues, indicating the need for a better socio-technical response from the stakeholders within the value-chain.