What motivates some members of a social group to voluntarily incur costs in order to provide for the common good? This question lies at the heart of theoretical and empirical studies of cooperative behavior. This is a...What motivates some members of a social group to voluntarily incur costs in order to provide for the common good? This question lies at the heart of theoretical and empirical studies of cooperative behavior. This is also the question that underlies the classic volunteer's dilemma model, which has been previously explored in scenarios where group members are related or interact asym- metrically. Here we present a model that combines asymmetry and relatedness, showing that the probability of volunteerism in such systems depends closely on both the degree of asymmetry and level of relatedness between interacting individuals. As has been shown in previous volunteer's dilemma models, the payoff ratio and overall group size also influence the probability of volunteerism. The probability of volunteerism decreases with increasing group size or decreasing cost-to-benefit ratio of the coplayers; in the presence of asymmetrical interactions, subordinate players were more likely to offer public goods than the dominant player. More asymmetrical interactions decrease the probability of volunteerism of the dominant player; overall volunteerism increases with increasing relatedness.展开更多
Fungi are important infectious disease-causing agents,but are often overlooked as environmental factors in disease.We review several lines of evidence that point to a potential fungal origin of sporadic amyotrophic la...Fungi are important infectious disease-causing agents,but are often overlooked as environmental factors in disease.We review several lines of evidence that point to a potential fungal origin of sporadic amyotrophic lateral sclerosis(ALS),the most common form of motor neurone disease.Approximately 90%cases of ALS are sporadic,and the aetiology of sporadic ALS is still unknown.We have previously postulated that grass or soil-associated fungal infections may be a leading cause of sporadic ALS.Herein we extend this proposal to water-associated fungi.A wide variety of fungi have been reported in drinking water including Acremonium,Alternaria,Aspergillus,Cladosporium,Fusarium,Penicillium and Trichoderma.Some of these are known to produce neurotoxic mycotoxins.Despite this,drinking water is not routinely monitored for fungal contamination.Fungal contamination could explain the close correlation between distribution of well water and cases of sporadic ALS in the United States.We propose several mechanisms by which an opportunistic fungal infection from environmental exposure(to water,soil or plants)can lead to long term neuronal degradation resulting in the hallmarks of ALS.If confirmed,the association between fungal infection and sporadic ALS could lead to novel treatment strategies for this progressive and fatal disease.展开更多
The practice of medicine in Muslim nations dates to the millennia before the advent of the religion of Islam. As far as the pre-Islamic period is concerned, what evidence is available indicates the medical evolution b...The practice of medicine in Muslim nations dates to the millennia before the advent of the religion of Islam. As far as the pre-Islamic period is concerned, what evidence is available indicates the medical evolution began nearly 6000 years ago in Mesopotamia, where medicine for the first time in history became a recognised profession. In ancient Egypt, it was practised by priest-physicians who demonstrated astonishing knowledge in various medical subjects. The origins of medicine in ancient Persia (Afghanistan, Iran, and parts of Central Asia) span the 6<sup>th</sup> century B.C. and to the Zoroastrian religious book of Avesta, which delved into such topics as preventive and clinical medicine. In reference to the account of medicine in the Arab peninsula, limited information exists. In terms of post-Islamic ages, the foundations of Islamic science were laid during the reign of the second Abbasid Caliph, al-Mansur, and the establishment of Baghdad as its capital in 762 A.D., when the Arabic translation movement commenced. During the next six centuries, medicine and other fields of science flourished, and prominent physicians such as the Bukht Yishu family, Razī, Majūsī, Avicenna, Jorjanī, Al-Zahrāwī, and other scientists emerged. In both the pre- and post-Islamic ages, Islamic medicine was heavily influenced by Mesopotamian, Egyptian, Persian, Indian, and, predominantly, Greek medicine. Nevertheless, the advancements and innovations in medical science and healthcare systems that were achieved during the early and medieval Islamic ages have indubitably made an invaluable contribution to the evolution of medicine throughout the world, and to the invention of numerous procedures and practices which are still widely performed today. Hence, the value of comprehending the pivotal role Islamic medicine played (and indeed still plays) in the progression of medical practice across the globe cannot be overstated.展开更多
基金supported by the National Natural Science Foundation of China(31170408, 71161020, 10961027)the Program for Innovative Research Team (in Science and Technology) in University of Yunnan Province+3 种基金the Natural Science Foundation of Yunnan Province (2009CD104)the West Light Foundation of the Chinese Academy of Sciencesthe Special Fund for the Excellent Youth of the Chinese Academy of Sciences (KSCX2-EW-Q-9)the State Key Laboratory of Genetic Resources and Evolution
文摘What motivates some members of a social group to voluntarily incur costs in order to provide for the common good? This question lies at the heart of theoretical and empirical studies of cooperative behavior. This is also the question that underlies the classic volunteer's dilemma model, which has been previously explored in scenarios where group members are related or interact asym- metrically. Here we present a model that combines asymmetry and relatedness, showing that the probability of volunteerism in such systems depends closely on both the degree of asymmetry and level of relatedness between interacting individuals. As has been shown in previous volunteer's dilemma models, the payoff ratio and overall group size also influence the probability of volunteerism. The probability of volunteerism decreases with increasing group size or decreasing cost-to-benefit ratio of the coplayers; in the presence of asymmetrical interactions, subordinate players were more likely to offer public goods than the dominant player. More asymmetrical interactions decrease the probability of volunteerism of the dominant player; overall volunteerism increases with increasing relatedness.
文摘Fungi are important infectious disease-causing agents,but are often overlooked as environmental factors in disease.We review several lines of evidence that point to a potential fungal origin of sporadic amyotrophic lateral sclerosis(ALS),the most common form of motor neurone disease.Approximately 90%cases of ALS are sporadic,and the aetiology of sporadic ALS is still unknown.We have previously postulated that grass or soil-associated fungal infections may be a leading cause of sporadic ALS.Herein we extend this proposal to water-associated fungi.A wide variety of fungi have been reported in drinking water including Acremonium,Alternaria,Aspergillus,Cladosporium,Fusarium,Penicillium and Trichoderma.Some of these are known to produce neurotoxic mycotoxins.Despite this,drinking water is not routinely monitored for fungal contamination.Fungal contamination could explain the close correlation between distribution of well water and cases of sporadic ALS in the United States.We propose several mechanisms by which an opportunistic fungal infection from environmental exposure(to water,soil or plants)can lead to long term neuronal degradation resulting in the hallmarks of ALS.If confirmed,the association between fungal infection and sporadic ALS could lead to novel treatment strategies for this progressive and fatal disease.
文摘The practice of medicine in Muslim nations dates to the millennia before the advent of the religion of Islam. As far as the pre-Islamic period is concerned, what evidence is available indicates the medical evolution began nearly 6000 years ago in Mesopotamia, where medicine for the first time in history became a recognised profession. In ancient Egypt, it was practised by priest-physicians who demonstrated astonishing knowledge in various medical subjects. The origins of medicine in ancient Persia (Afghanistan, Iran, and parts of Central Asia) span the 6<sup>th</sup> century B.C. and to the Zoroastrian religious book of Avesta, which delved into such topics as preventive and clinical medicine. In reference to the account of medicine in the Arab peninsula, limited information exists. In terms of post-Islamic ages, the foundations of Islamic science were laid during the reign of the second Abbasid Caliph, al-Mansur, and the establishment of Baghdad as its capital in 762 A.D., when the Arabic translation movement commenced. During the next six centuries, medicine and other fields of science flourished, and prominent physicians such as the Bukht Yishu family, Razī, Majūsī, Avicenna, Jorjanī, Al-Zahrāwī, and other scientists emerged. In both the pre- and post-Islamic ages, Islamic medicine was heavily influenced by Mesopotamian, Egyptian, Persian, Indian, and, predominantly, Greek medicine. Nevertheless, the advancements and innovations in medical science and healthcare systems that were achieved during the early and medieval Islamic ages have indubitably made an invaluable contribution to the evolution of medicine throughout the world, and to the invention of numerous procedures and practices which are still widely performed today. Hence, the value of comprehending the pivotal role Islamic medicine played (and indeed still plays) in the progression of medical practice across the globe cannot be overstated.
