Sorption and Desorption Characteristics of Tylosin in Three Louisiana Soils and Clay Minerals

Tylosin, a macrolide class and widely used antibiotic in animal production, could contaminate environment through manure application to soil and further to river and ground water. Tylosin transport and movement in the environment are largely determined by its sorption and desorption in soils, which are poorly understood so far. Therefore, the purpose of this study was to determine (1) the optimal conditions for tylosin stability, (2) sorption and desorption characteristics of tylosin by poultry litter-impacted three Louisiana soils and (3) sorption and desorption of tylosin by selected clay minerals, the main components of soil which have strong potential application in environmental clean-up. To this end, tylosin stability was evaluated in terms of light exposure (light and dark), solvents (H2O and 0.01M CaCl2), pH (4.5 to 7.5), and temperature (4 oC and 25 oC) conditions. Sorption and desorption of tylosin were carried out at different pHs with three Louisiana soils namely Briley, Ruston and Savannah with or without organic matter being removed. For clay minerals, tylosin sorption and desorption were carried out with montmorillonite, kaolinite and illite. Tylosin in 0.01M CaCl2 was stable under light at pH 4.5, 6.0 and 7.5, and at 25 oC for about 12 days. Tylosin sorption was well described by the Freundlich equation, with sorption in the order of Briley \u3e Savannah \u3e Ruston. Tylosin sorption was affected by pH, with higher sorption at acid pH for Briley, and at pH 6 to 7 for Ruston and Savannah, but with low sorption as pH further increased. Removal of organic matter dramatically increased tylosin sorption and changed sorption pattern at lower pH \u3c 6. Tylosin desorption was in the order of Ruston \u3e Briley \u3e Savannah, with higher desorption under acid conditions, and lower desorption between pH 6.0 to 7.5. Tylosin was strongly sorbed by monotmorillonite followed by illite and kaolinite, and desorption in the order of illite \u3e kaolinite \u3e montmorillonite. The results indicated that both pH and organic matter significantly affected tylosin sorption and desorption behaviors in soil and three clay minerals exhibited different degree of sorption strength as reflected by the difference in desorption

Self-Adaptive On Demand Geographic Routing Protocols for Mobile Ad Hoc Networks

Abstract — It has been a big challenge to develop routing protocol that can meet different application needs and optimize routing paths according to the topology change in mobile ad hoc networks. Basing their forwarding decisions only on the local topology, geographic routing protocols have drawn a lot of attentions in recent years. However, inaccurate local topology knowledge and the outdated destination position information can lead to inefficient geographic forwarding and even routing failure. Proactive local position distribution can hardly adapt to the traffic demand. It is also difficult to pre-set protocol parameters correctly to fit in different environments. We have developed two self-adaptive on-demand geographic routing schemes. The local topology is updated in a timely manner according to network dynamics and traffic demands. Our route optimization scheme adapts the routing path according to both topology changes and actual data traffic requirements. Each node can determine and adjust the protocol parameter values independently according to different network environments, data traffic conditions and node’s own requirements. Our simulation studies have shown that the proposed routing protocols are more robust and outperform the existing geographic routing protocol. Specifically, the packet delivery latency is reduced almost four times as compared to GPSR at high mobility

Chinese digestive surgery interns’ learning quality and English reading proficiency during COVID-19 pandemic: Comparison between face-to-face versus WeChat teaching and learning

Gastrointestinal clinical teaching is of vital important for gastrointestinal surgery interns. However, during COVID-19 pandemic, due to frequent lockdowns and essential social distancing policy implemented in China, face-to-face teaching was interrupted significantly. To find a cost-effective way to deliver medical education to ensure that teaching and learning would be continued and uninterrupted, many social media tools and mobile applications have been used in medical teaching and learning. WeChat has been frequently employed in teaching and learning in many disciplines in Chinese universities due to its powerful functions and free cost. This study compared Chinese digestive surgery interns' learning quality, English reading proficiency, and learning satisfaction in two teaching conditions: the traditional face-to-face teaching versus WeChat teaching via an experiment. The study recruited 60 final year clinical medical students, who were randomly and equally assigned into two groups: traditional face-to-face teaching versus WeChat teaching. Interns' learning quality and learning satisfaction were measured by Likert-scale questionnaires; and their English reading proficiency was measured by the reading section in a standardized English test. The results showed that interns in WeChat group had significantly higher learning quality on understanding mechanisms and current knowledge by both self-assessment and peer-assessment. WeChat group also outperformed face-to-face group on inferencing, details, and main ideas in English reading. With regard to learning satisfaction, WeChat group were higher on learning interests, learning objectives, learning format, and English reading proficiency than face-to-face group. However, interns did not differ in terms of their learning satisfaction on medical skills, which might indicate that WeChat had limitations on training interns’ medical practical ability