The evolution of shear key design for bridges is accompanied by research on structural earthquake resistance. However, the vast majority of pounding forces, responses, and corresponding data for the study and design of shear keys have been based on expensive experimentalism and imprecise empiricism approaches for decades. Hence, strengthening theoretical study on seismic performance of shear key is essential. In this paper, a "Beam-Spring-Beam + Concentrated Mass" continuum dynamic model is proposed. Meanwhile, the transient wave function expansion method and the mode superposition method are applied to determine the analytical expression of the dynamic response from the girder and pier system (pier and cap beam). Furthermore, the combined transient internal force method and Duhamel integration method are introduced to assess the elastic pounding process. Through programming and numerical analysis, a series of pounding response data related to the shear key under various working circumstances will be explored. As mentioned above, the proposed theoretical method can optimize shear key design and boost the reliability of seismic limiting devices in the future. •Establishing a feasible "Beam-Spring-Beam + Concentrated Mass" continuum model of girders and piers based on a two-span continuous girder bridge.•Deriving the analytical solutions of responses by conducting the response equations under horizontal seismic excitation (containing orthonormality verification).•Simulating the pounding process by embedding elastic pounding calculation methods into Continuum Model.
Southeast Asian countries including Malaysia play a major role in global drug trade and abuse. Use of amphetamine-type stimulants has increased in the past decade in Malaysia. This study aimed to apply wastewater-based epidemiology for the first time in Kuala Lumpur, Malaysia, to estimate the consumption of common illicit drugs in urban population. Influent wastewater samples were collected from two wastewater treatment plants in Kuala Lumpur in the summer of 2017. Concentrations of twenty-four drug biomarkers were analyzed for estimating drug consumption. Fourteen drug residues were detected with concentrations of up to 1640 ng/L. Among the monitored illicit drugs, 3,4-methylenedioxy-methamphetamine (MDMA) or ecstasy had the highest estimated per capita consumptions. Consumption and dose of amphetamine-type stimulants (methamphetamine and MDMA) were both an order of magnitude higher than those of opioids (heroin and codeine, methadone and tramadol). Amphetamine-type stimulants were the most prevalent drugs, replacing opioids in the drug market. The prevalence trend measured by wastewater-based epidemiology data reflected the shift to amphetamine-type stimulants as reported by the Association of Southeast Asian Nations Narcotics Cooperation Center. Most of the undetected drug residues were new psychoactive substances (NPSs), suggesting a low prevalence of NPSs in the drug market.
As the only endemic neotropical parrot to have recently lived in the northern hemisphere, the Carolina parakeet (Conuropsis carolinensis) was an iconic North American bird. The last surviving specimen died in the Cincinnati Zoo in 1918 [1]. The cause of its extinction remains contentious: besides excessive mortality associated to habitat destruction and active hunting, their survival could have been negatively affected by its range having become increasingly patchy [2] or by the exposure to poultry pathogens [3, 4]. In addition, the Carolina parakeet showed a predilection for cockleburs, an herbaceous plant that contains a powerful toxin, carboxyatractyloside, or CAT [5], which did not seem to affect them but made the birds notoriously toxic to most predators [3]. To explore the demographic history of this bird, we generated the complete genomic sequence of a preserved specimen held in a private collection in Espinelves (Girona, Spain), as well as of a close extant relative, Aratinga solstitialis. We identified two non-synonymous genetic changes in two highly conserved proteins known to interact with CAT that could underlie a specific dietary adaptation to this toxin. Our genomic analyses did not reveal evidence of a dramatic past demographic decline in the Carolina parakeet; also, its genome did not exhibit the long runs of homozygosity that are signals of recent inbreeding and are typically found in endangered species. As such, our results suggest its extinction was an abrupt process and thus likely solely attributable to human causes.