Instead of running away, she stood to attention with arms akimbo and gave a serious smile. The giant wooden basket on her back almost made her fall as she tried to straighten her body. When I raised the camera, Yang J...Instead of running away, she stood to attention with arms akimbo and gave a serious smile. The giant wooden basket on her back almost made her fall as she tried to straighten her body. When I raised the camera, Yang Jiaxiu was walking along a narrow, muddy mountain path in a virgin fir forest, carrying about 50 kilograms of water. She twisted her body to pour the water into a large tank when she finally arrived at her house. Then the Miao woman put down the展开更多
Ongoing uncertainty over the relative importance of aerosol transmission of COVID-19 is in part rooted in the history of medical science and our understanding of how epidemic diseases can spread through human populati...Ongoing uncertainty over the relative importance of aerosol transmission of COVID-19 is in part rooted in the history of medical science and our understanding of how epidemic diseases can spread through human populations. Ancient Greek medical theory held that such illnesses are transmitted by airborne pathogenic emanations containing particulate matter(“miasmata”). Notable Roman and medieval scholars such as Varro, Ibn al-Khatib and Fracastoro developed these ideas, combining them with early germ theory and the concept of contagion. A widely held but vaguely defined belief in toxic miasmatic mists as a dominant causative agent in disease propagation was overtaken by the science of 19th century microbiology and epidemiology, especially in the study of cholera, which was proven to be mainly transmitted by contaminated water. Airborne disease transmission came to be viewed as burdened by a dubious historical reputation and difficult to demonstrate convincingly. A breakthrough came with the classic mid-20th century work of Wells, Riley and Mills who proved how expiratory aerosols(their “droplet nuclei”)could transport still-infectious tuberculosis bacteria through ventilation systems. The topic of aerosol transmission of pathogenic respiratory diseases assumed a new dimension with the mid-late 20th century “Great Acceleration” of an increasingly hypermobile human population repeatedly infected by different strains of zoonotic viruses, and has taken centre stage this century in response to outbreaks of new respiratory infections that include coronaviruses. From a geoscience perspective, the consequences of pandemic-status diseases such as COVID-19, produced by viral pathogens utilising aerosols to infect a human population currently approaching 8 billion, are far-reaching and unprecedented. The obvious and sudden impacts on for example waste plastic production, water and air quality and atmospheric chemistry are accelerating human awareness of current environmental challenges. As such, the “anthropause”lockdown enforced by COVID-19 may come to be seen as a harbinger of change great enough to be preserved in the Anthropocene stratal record.展开更多
The topic of"human history"is vast,as studying history involves exploring the records of past human activities.China has a long and profound tradition in historiography,with its most significant hallmark bei...The topic of"human history"is vast,as studying history involves exploring the records of past human activities.China has a long and profound tradition in historiography,with its most significant hallmark being Sima Qians Records of the Grand Historian(Shiji).The annalistic-biographical style pioneered by Shiji represents a major achievement in Chinese historiography,providing ample records of human activities.The"Annals"section documents emperors,the"Biographies"detail various figures,the"Hereditary Houses"cover aristocratic lineages,the"Treatises"describe systems,and the"Tables"present chronological sequences.The greatest strength of this biographical style is its ability to reflect the main activities of emperors,nobles,ministers,and officials.This is a proud aspect of traditional Chinese historiography,attributed to Sima Qian’s innovative framework.展开更多
In Europe, computation of displacement demand for seismic assessment of existing buildings is essentially based on a simplified formulation of the N2 method as prescribed by Eurocode 8(EC8). However, a lack of accurac...In Europe, computation of displacement demand for seismic assessment of existing buildings is essentially based on a simplified formulation of the N2 method as prescribed by Eurocode 8(EC8). However, a lack of accuracy of the N2 method in certain conditions has been pointed out by several studies. This paper addresses the assessment of effectiveness of the N2 method in seismic displacement demand determination in non-linear domain. The objective of this work is to investigate the accuracy of the N2 method through comparison with displacement demands computed using non-linear timehistory analysis(NLTHA). Results show that the original N2 method may lead to overestimation or underestimation of displacement demand predictions. This may affect results of mechanical model-based assessment of seismic vulnerability at an urban scale. Hence, the second part of this paper addresses an improvement of the N2 method formula by empirical evaluation of NLTHA results based on EC8 ground-classes. This task is formulated as a mathematical programming problem in which coefficients are obtained by minimizing the overall discrepancy between NLTHA and modified formula results. Various settings of the mathematical programming problem have been solved using a global optimization metaheuristic. An extensive comparison between the original N2 method formulation and optimized formulae highlights benefits of the strategy.展开更多
文摘Instead of running away, she stood to attention with arms akimbo and gave a serious smile. The giant wooden basket on her back almost made her fall as she tried to straighten her body. When I raised the camera, Yang Jiaxiu was walking along a narrow, muddy mountain path in a virgin fir forest, carrying about 50 kilograms of water. She twisted her body to pour the water into a large tank when she finally arrived at her house. Then the Miao woman put down the
基金supported by the Spanish Research Council (CSIC, Project COVID19 CSIC 202030E226)the Generalitat de Catalunya (SGR41)。
文摘Ongoing uncertainty over the relative importance of aerosol transmission of COVID-19 is in part rooted in the history of medical science and our understanding of how epidemic diseases can spread through human populations. Ancient Greek medical theory held that such illnesses are transmitted by airborne pathogenic emanations containing particulate matter(“miasmata”). Notable Roman and medieval scholars such as Varro, Ibn al-Khatib and Fracastoro developed these ideas, combining them with early germ theory and the concept of contagion. A widely held but vaguely defined belief in toxic miasmatic mists as a dominant causative agent in disease propagation was overtaken by the science of 19th century microbiology and epidemiology, especially in the study of cholera, which was proven to be mainly transmitted by contaminated water. Airborne disease transmission came to be viewed as burdened by a dubious historical reputation and difficult to demonstrate convincingly. A breakthrough came with the classic mid-20th century work of Wells, Riley and Mills who proved how expiratory aerosols(their “droplet nuclei”)could transport still-infectious tuberculosis bacteria through ventilation systems. The topic of aerosol transmission of pathogenic respiratory diseases assumed a new dimension with the mid-late 20th century “Great Acceleration” of an increasingly hypermobile human population repeatedly infected by different strains of zoonotic viruses, and has taken centre stage this century in response to outbreaks of new respiratory infections that include coronaviruses. From a geoscience perspective, the consequences of pandemic-status diseases such as COVID-19, produced by viral pathogens utilising aerosols to infect a human population currently approaching 8 billion, are far-reaching and unprecedented. The obvious and sudden impacts on for example waste plastic production, water and air quality and atmospheric chemistry are accelerating human awareness of current environmental challenges. As such, the “anthropause”lockdown enforced by COVID-19 may come to be seen as a harbinger of change great enough to be preserved in the Anthropocene stratal record.
文摘The topic of"human history"is vast,as studying history involves exploring the records of past human activities.China has a long and profound tradition in historiography,with its most significant hallmark being Sima Qians Records of the Grand Historian(Shiji).The annalistic-biographical style pioneered by Shiji represents a major achievement in Chinese historiography,providing ample records of human activities.The"Annals"section documents emperors,the"Biographies"detail various figures,the"Hereditary Houses"cover aristocratic lineages,the"Treatises"describe systems,and the"Tables"present chronological sequences.The greatest strength of this biographical style is its ability to reflect the main activities of emperors,nobles,ministers,and officials.This is a proud aspect of traditional Chinese historiography,attributed to Sima Qian’s innovative framework.
文摘In Europe, computation of displacement demand for seismic assessment of existing buildings is essentially based on a simplified formulation of the N2 method as prescribed by Eurocode 8(EC8). However, a lack of accuracy of the N2 method in certain conditions has been pointed out by several studies. This paper addresses the assessment of effectiveness of the N2 method in seismic displacement demand determination in non-linear domain. The objective of this work is to investigate the accuracy of the N2 method through comparison with displacement demands computed using non-linear timehistory analysis(NLTHA). Results show that the original N2 method may lead to overestimation or underestimation of displacement demand predictions. This may affect results of mechanical model-based assessment of seismic vulnerability at an urban scale. Hence, the second part of this paper addresses an improvement of the N2 method formula by empirical evaluation of NLTHA results based on EC8 ground-classes. This task is formulated as a mathematical programming problem in which coefficients are obtained by minimizing the overall discrepancy between NLTHA and modified formula results. Various settings of the mathematical programming problem have been solved using a global optimization metaheuristic. An extensive comparison between the original N2 method formulation and optimized formulae highlights benefits of the strategy.
