ABSTRACT
This study investigates the short-to-medium-term impact of Covid-19-related fiscal stimulus relief packages on reducing investor uncertainty expectations in eight major economies. We use three measures of volatility to assess investor uncertainty: implied volatility, volatility index, and realized kernel volatility of ETFs in each country. The data covers a three-year period from January 2019 to December 2021. Our findings indicate an increase in all three measures of volatility in the post-Covid to pre-stimulus period, which decreases after the announcement of the stimulus packages. The results show that, on average, the stimulus announcements alleviate investor uncertainty and facilitate economic recovery. However, the effectiveness of the stimulus packages varies across countries but not across sectors. Our results remain robust to several checks, including alternate econometric specifications, such as the Arellano-Blundell-Bond estimation for dynamic panel data. © 2023 Elsevier B.V.
ABSTRACT
In this study, three greenhouse gases (CO2, CH4, and N2O) and one conventional gas (CO) were observed at a roadside station in Shenzhen from September, 2019 to July, 2020. The average concentration of CO2, CH4, N2O, and CO was (430.8±6.1)×10-6, (2318.5±137.9)×10-9, (332.6±1.6)×10-9, and (333.4±121.2)×10-9, respectively. Seasonal variation of CO2 and CO were high in winter and low in summer, Seasonal variation of CH4 and N2O were high in autumn and low in summer. The high concentration in autumn and winter is due to the long-distance transmission of fossil fuel emissions during the heating period, and the low concentration in summer is mainly due to the reduction of long-distance transmission sources and the enhancement of sinks such as plant photosynthesis and photochemical reactions. The diurnal variation of CO2 concentration showed a two-peak and one-valley pattern, which was mainly affected by plant photosynthesis and morning and evening traffic peak;The diurnal variation of CO concentration showed a two-peak pattern, which was mainly affected by the morning and evening traffic peaks. The diurnal variation of CH4 and N2O concentration was high at night and low at day, which was mainly affected by daytime photochemical reaction. Among them, the concentration of CO2 and CO is more sensitive to the emission of traffic sources. In addition, this study compared the COVID-19 lockdown period in 2020 with the same period in 2021, and the results showed that the concentration of CO2, CH4, N2O, and CO decreased by 3.1%, 10.6%, 0.5% and 13.9%, respectively, indicating that traffic control can play an important role in reducing urban greenhouse gas emissions. © 2022, Editorial Board of China Environmental Science. All right reserved.
ABSTRACT
COVID-19 is a severe global epidemic in human history. Even though there are particular medications and vaccines to curb the epidemic, tracing and isolating the infection source is the best option to slow the virus spread and reduce infection and death rates. There are three disadvantages to the existing contact tracing system: 1. User data is stored in a centralized database that could be stolen and tampered with, 2. User's confidential personal identity may be revealed to a third party or organization, 3. Existing contact tracing systems [1] [2] only focus on information sharing from one dimension, such as location-based tracing, which significantly limits the effectiveness of such systems. We propose a global COVID-19 information sharing and risk notification system that utilizes the Blockchain, Smart Contract, and Bluetooth. To protect user privacy, we design a novel Blockchain-based platform that can share consistent and non-tampered contact tracing information from multiple dimensions, such as location-based for indirect contact and Bluetooth-based for direct contact. Hierarchical smart contract architecture is also designed to achieve global agreements from users about how to process and utilize user data, thereby enhancing the data usage transparency. Furthermore, we propose a mechanism to protect user identity privacy from multiple aspects. More importantly, our system can notify the users about the exposure risk via smart contracts. We implement a prototype system to conduct extensive measurements to demonstrate the feasibility and effectiveness of our system.
ABSTRACT
BACKGROUND: Whilst the COVID-19 diagnostic test has a high false-negative rate, not everyone initially negative is re-tested. Michigan Medicine, a primary regional centre, provided an ideal setting for studying testing patterns during the first wave of the pandemic. OBJECTIVES: To identify the characteristics of patients who underwent repeated testing for COVID-19 and determine if repeated testing was associated with downstream outcomes amongst positive cases. METHODS: Characteristics, test results, and health outcomes for patients presenting for a COVID-19 diagnostic test were collected. We examined whether patient characteristics differed with repeated testing and estimated a false-negative rate for the test. We then studied repeated testing patterns in patients with severe COVID-19-related outcomes. RESULTS: Patient age, sex, body mass index, neighbourhood poverty levels, pre-existing type 2 diabetes, circulatory, kidney, and liver diseases, and cough, fever/chills, and pain symptoms 14 days prior to a first test were associated with repeated testing. Amongst patients with a positive result, age (OR: 1.17; 95% CI: (1.05, 1.34)) and pre-existing kidney diseases (OR: 2.26; 95% CI: (1.41, 3.68)) remained significant. Hospitalization (OR: 7.88; 95% CI: (5.15, 12.26)) and ICU-level care (OR: 6.93; 95% CI: (4.44, 10.92)) were associated with repeated testing. The estimated false-negative rate was 23.8% (95% CI: (19.5%, 28.5%)). CONCLUSIONS: Whilst most patients were tested once and received a negative result, a meaningful subset underwent multiple rounds of testing. These results shed light on testing patterns and have important implications for understanding the variation of repeated testing results within and between patients.