Computed tomography (CT) contrast and radiosensitization usually increase with particle sizes of gold nanoparticles (AuNPs), but there is a huge challenge to improve both by adjusting sizes under the requirements of in vivo application. Here, we report that AuNPs have great size-dependent enhancements on CT imaging as well as radiotherapy (RT) in the size range of 3-50 nm. It is demonstrated that AuNPs with a size of ∼13 nm could simultaneously possess superior CT contrast ability and significant radioactive disruption. The Monte Carlo method is further used to evaluate this phenomenon and indicates that the inhomogeneity of gold atom distributions caused by sizes may influence secondary ionization in whole X-ray interactions. In vivo studies further indicate that this optimally sized AuNP improves real-time CT imaging and radiotherapeutic inhibition of tumors in living mice by effective accumulation at tumors with prolonged in vivo circulation times compared to clinically used small-molecule agents. These results suggest that ∼13 nm AuNPs may serve as multifunctional adjuvants for clinical X-ray theranostic application.

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PurposeThe purpose of this paper is to empirically study the impact of the coronavirus disease 2019 (COVID-19) on food prices in China and provides policy implications for crisis management for other countries who are still under the crisis of COVID-19 and for the future in China and beyond as well.Design/methodology/approachThis paper first designed a theoretical model of market equilibrium, which shows that the impact of COVID-19 on food prices is linked to the impact difference on demand and supply in response to the COVID-19 crisis. Then we collected the representative prices data for four major food products (rice, wheat flour, pork and Chinese cabbages) from three provinces (Shandong as a producing base, Beijing as a consumption base and Hubei as the epicenter), and set up an iGARCH model.Findings(1) No significant impact on rice and wheat flour prices, (2) significantly positive impact on cabbages prices and (3) various impact on pork prices. Note that the outbreak and the severity of COVID-19 have different impacts. The outbreak itself may have a relatively large impact on pork and cabbage prices, which may result from social panic, while the magnitude of the impact of severity is relatively small, and some are negative, perhaps due to more reduced demand during the quarantine.Practical implicationsChina always puts food security in its prior position of policy agenda and has been preparing for the worst scenario of the food security crisis. In the anti-COVID-19 campaign, China's local governments developed many measures to ensure food provision for each consumer. Hence, the impact of COVID-19 on food prices is minor. However, the outbreak of COVID-19 crisis could cause social panic in some scenarios where consumers may hoard food. Eventually, it may form a vicious cycle to push up food prices. This will be a challenging policy issue in crisis management for almost all governments.Originality/valueThis paper provides empirical evidence on the impact of COVID-19 on food prices in China. China has basically contained the COVID-19 in the whole country, and no major food crisis occurred during this process. The results will provide information on crisis management for other countries that are still under the COVID-19 crisis, and for future China and beyond.

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