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Cloud federation is an emergent Cloud-computing paradigm that allows services from different Cloud systems to be aggregated in a single pool. To support secure data-sharing in a Cloud federation, anonymisation services that obfuscate sensitive datasets under differential privacy have been recently proposed. However, by outsourcing data protection to the Cloud, data owners lose control over their data, raising privacy concerns. This is even more compelling in multi-query scenarios where maintaining privacy amounts to controlling the allocation of so-called privacy budget. In this paper we propose a blockchain-based approach that enables data owners to control the anonymisation process, and enhances the security of the services. Our approach relies on blockchain to validate the usage of privacy budget and adaptively change its allocation via smart contracts, depending on the privacy requirements provided by data owners. Prototype implementation with the Hyperledger permissioned blockchain validates our approach with respect to privacy guarantee and practicality. Cloud federation builds up interconnectivity and cooperation among already deployed clouds, enabling organisations to achieve various business goals, such as controlled sharing of data, services and optimisation of computing resources usage 1-3. To support secure sharing of federated data, anonymisation services have been proposed as a building component of Federation-as-a-Service (FaaS), 3-4 a recent Cloud federation solution. This component implements differential privacy in order to obfuscate the result of statistical queries towards sensitive datasets, 5 enabling its privacy-preserving sharing. Offering this service in the context of a Cloud federation has benefits-access to multiple data sources and different service providers-but raises significant challenges for privacy management: sensitive datasets

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Using panel data on 47 African countries from 1980-2013, this paper investigates the effects of aid on Africa's economic growth from the perspective of political stability. We find that international aid can promote economic growth in Africa, but the effectiveness of aid depends on countries' political stability. Further, the intensity of aid affects its effectiveness. When the aid-GDP ratio is between 0 and 69 per cent, aid can promote economic growth in recipient countries, and when this ratio is 27 per cent, the marginal impact of aid on economic growth is maximized. The findings of this paper suggest that providers of aid should avoid providing a substantial amount of aid to countries at risk of political unrest, and they must determine the optimal scale of aid based on the economic development of recipient countries in order to enable aid to generate better results. Recipient countries should maintain social and political stability and ensure that they do not develop an excessive dependence on aid so that they can achieve the self-sustainable development of their own economies.

Airborne PM2.5 and PM10 samples were collected in summertime (August 2015) and wintertime (December 2015-January 2016) in an industrial complex area in Hefei, China. The average concentrations of PM2.5 and PM10 (90.5 and 114.5 μg/m, respectively) were higher than the regulated levels of China National Ambient Air Quality Standard (grade I) and the WHO Ambient (outdoor) Air Quality and Health Guideline Value. Seasonal variations in PM2.5/PM10 indicated that the secondary sources of particulate matters, formed by gas-to-particle conversion, were enhanced in summer due to longer time of solar radiation and higher temperature. The total concentrations of PM2.5- and PM10-associated PAHs were 5.89 and 17.70 ng/m in summer as well as 63.41 and 78.26 ng/m in winter, respectively. Both PM2.5- and PM10-associated PAHs were dominated by 4- to 6-ring PAHs, suggesting that the fossil fuel combustion and vehicle emissions were the primary sources of PAHs in atmospheric particulate matters in Hefei. The total concentration of PAHs had a slightly higher correlation coefficient with PM2.5 (R = 0.499, P < 0.05) than PM10 (R = 0.431, P > 0.05), indicating the higher association tendency of PAHs with PM2.5. The coefficient of divergence analysis showed that the compositions of PAH were quite different between summer and winter. Total BaP equivalent concentration (BaP-TEQ) for particulate-bound PAHs in winter (58.87 ng/m) was higher than that in summer (5.53 ng/m). In addition, particulate-bound PAHs in winter had an inhalation cancer risk (ICR) value of 2.8 × 10, which was higher than the safe range (10-10).