Carbon tax and low-carbon credit: Which policy is more beneficial to the capital-constrained manufacturer's remanufacturing activities?

Remanufacturing has attracted much attention for its enormous potential in resource recycling and low-carbon emission reduction. To investigate the effects of different government intervention policies on remanufacturing and carbon emissions, two profit maximization models of the capital-constrained manufacturer under carbon tax and low-carbon credit policies are constructed respectively. Then, through theoretical and numerical analyses, some significant findings are drawn: (1) Both carbon tax and low-carbon credit policies can encourage capital-constrained manufacturers to produce more remanufactured products, but which intervention policy is more advantageous also depends on the carbon emission cost of new products or financing cost of the remanufactured products. (2) Although carbon tax policy can effectively control carbon emissions, it is always at the expense of both capital-constrained manufacturers and consumers; while low-carbon credit policy can help capital-constrained manufacturers achieve the goal of win-win economic and environmental benefits when the remanufacturing carbon savings advantages are more apparent. (3) From the perspective of consumer benefits, carbon tax is more advantageous when the consumer willingness to pay for remanufactured products is higher; otherwise, low-carbon credit policy should be implemented. (4) The higher the environmental damage coefficient is, the more it can highlight the advantages of the two intervention policies in social welfare enhancement, especially the carbon tax policy; and when the environmental damage coefficient is given, the stronger the consumers' willingness to pay for remanufactured products is, the more it is conducive to reducing the negative effects caused by the carbon tax or low-carbon credit policy in social welfare enhancement, or increasing the corresponding positive effects. Based on above findings, some managerial insights and policy implications are provided to capital-constrained manufacturers and policy-makers.

Challenges in simulating and modeling the airborne virus transmission: A state-of-the-art review.

Recently, the COVID-19 virus pandemic has led to many studies on the airborne transmission of expiratory droplets. While limited experiments and on-site measurements offer qualitative indication of potential virus spread rates and the level of transmission risk, the quantitative understanding and mechanistic insights also indispensably come from careful theoretical modeling and numerical simulation efforts around which a surge of research papers has emerged. However, due to the highly interdisciplinary nature of the topic, numerical simulations of the airborne spread of expiratory droplets face serious challenges. It is essential to examine the assumptions and simplifications made in the existing modeling and simulations, which will be reviewed carefully here to better advance the fidelity of numerical results when compared to the reality. So far, existing review papers have focused on discussing the simulation results without questioning or comparing the model assumptions. This review paper focuses instead on the details of the model simplifications used in the numerical methods and how to properly incorporate important processes associated with respiratory droplet transmission. Specifically, the critical issues reviewed here include modeling of the respiratory droplet evaporation, droplet size distribution, and time-dependent velocity profile of air exhaled from coughing and sneezing. According to the literature review, another problem in numerical simulations is that the virus decay rate and suspended viable viral dose are often not incorporated; therefore here, empirical relationships for the bioactivity of coronavirus are presented. It is hoped that this paper can assist researchers to significantly improve their model fidelity when simulating respiratory droplet transmission.

[Effects of ketamine and splenectomy on cognition and synaptic plasticity in hippocampus of senile rats].

OBJECTIVE: To study the effects of ketamine anesthesia and surgery on cognition and synaptic structure in hippocampus of senile rats. METHODS: Fifty-six rats aged 18 months were randomly divided into 3 groups: Groups C (control group), A (ketamine 40 mg/kg, i.p.) and O (ketamine anesthesia & splenectomy). Morris water maze test was used to observe cognition at Days 1, 3 & 7 after ketamine anesthesia or operation respectively. Accordingly Groups A and O were divided into 3 subgroup, i.e. A1, A3, A7 and O1, O3, O7. The time of Morris water maze test was recorded and the synaptic structure was measured in the polymorphic layer of the rat hippocampal field CA3. RESULTS: Compared to Group C, the latency period and swimming distance significantly increased in Groups A1, O1 and O3 (P < 0.05), and the numbers passing the original platform decreased significantly in Groups O1 and O3 (P < 0.01). The latency period was significantly longer in Group O1 than that in Group A1 (P < 0.05) while the swimming distance was unchanged. Compared to Group C, the width of synaptic cleft (P < 0.01) increased, the length and area of postsynaptic densities (P < 0.05 or P < 0.01) as well as synaptic curvature (P < 0.01) decreased in Groups O1 and O3. The percentage of perforated synapses also decreased in Groups O1 and O3. CONCLUSION: Surgical injury can impair cognition of senile rats and the synaptic plasticity might be involved in postoperative cognitive dysfunction.