The purpose of this study is to develop a mathematical model of the spiral basilar membrane in the center of the cochlea, which plays an important role in the mammalian auditory system. The basilar membrane transmits ...The purpose of this study is to develop a mathematical model of the spiral basilar membrane in the center of the cochlea, which plays an important role in the mammalian auditory system. The basilar membrane transmits sound vibrations, which are converted into electrical potential changes by the inner hair cells. The basilar membrane is thought to lie on a locally undistorted curved surface because the inner hair cells, which are arranged in an orderly fashion on the basilar membrane, respond to their location-specific frequencies. In mammals, the number of rotations of this surface and the rate of change of its width with each rotation are different. It turns out that by modifying the right helicoid, we can obtain a mathematical model that satisfies these points. In conclusion, even though the three-dimensional structure of the basilar membrane varies among species, this model can reproduce this structure. This further suggests that there are common genetic determinants of cochlear development in mammals. From a practical standpoint, this may be useful for creating cochlear implants.展开更多
Objective: To give an historical record of the research of the World Health Organization (WHO) Task Force to develop methods of male contraception; to examine the social, political, medical, pharmaceutical, funding, a...Objective: To give an historical record of the research of the World Health Organization (WHO) Task Force to develop methods of male contraception; to examine the social, political, medical, pharmaceutical, funding, and other factors that influenced progress; and to suggest reasons why such methods are only now becoming available. Design: Review of basic and clinical research over 30 years. Setting: Task force of a multinational agency and collaborating agencies. Conclusion(s): Through the involvement of many international scientists, the WHO Task Force has uniquely contributed to the exploratory phases of the research in male contraception and by its multicenter contraceptive efficacy studies has accelerated progress towards the ideal hormonal method. Despite an adverse climate involving social and political attitudes, funding constraints, and pharmaceutical industry hesitations, WHO formed coalitions with governments and international agencies to sustain research with results that apply to men in culturally diverse populations and thereby to influence activities across the whole range of global reproductive health and family planning.展开更多
选择以干冷气候为主的兰州和温暖湿润的江汉平原作为研究区域,结合其他多种指标和研究区的岩性特征,对有机碳同位素(δ13Corg)的古气候指示意义进行了初步探讨.结果表明,在兰州地区,δ13Corg值波动反映C3/C4植物比例的改变,指示温度变化...选择以干冷气候为主的兰州和温暖湿润的江汉平原作为研究区域,结合其他多种指标和研究区的岩性特征,对有机碳同位素(δ13Corg)的古气候指示意义进行了初步探讨.结果表明,在兰州地区,δ13Corg值波动反映C3/C4植物比例的改变,指示温度变化.δ13Corg值偏正时,表明C4植物含量较大,反映温度较高,而δ13Corg值偏负时,表明气候较冷;江汉平原δ13Corg值主要反映降水信息,δ13Corg值偏负时指示相对暖湿气候,δ13Corg值偏正反映气候偏干.δ13Corg等指标同时还揭示了末次盛冰期以来两地古气候类同特征:即12.0 ka BP之前气候相对偏干;在全新世晚期,气候波动中转暖.不同之处表现为:约在12.0～10.0 ka BP,当兰州气候还很干冷时,江汉平原已进入暖湿的冰后期;而在全新世早中期,当兰州气候转为暖湿时,江汉平原气候则表现为略偏干.展开更多
文摘The purpose of this study is to develop a mathematical model of the spiral basilar membrane in the center of the cochlea, which plays an important role in the mammalian auditory system. The basilar membrane transmits sound vibrations, which are converted into electrical potential changes by the inner hair cells. The basilar membrane is thought to lie on a locally undistorted curved surface because the inner hair cells, which are arranged in an orderly fashion on the basilar membrane, respond to their location-specific frequencies. In mammals, the number of rotations of this surface and the rate of change of its width with each rotation are different. It turns out that by modifying the right helicoid, we can obtain a mathematical model that satisfies these points. In conclusion, even though the three-dimensional structure of the basilar membrane varies among species, this model can reproduce this structure. This further suggests that there are common genetic determinants of cochlear development in mammals. From a practical standpoint, this may be useful for creating cochlear implants.
文摘Objective: To give an historical record of the research of the World Health Organization (WHO) Task Force to develop methods of male contraception; to examine the social, political, medical, pharmaceutical, funding, and other factors that influenced progress; and to suggest reasons why such methods are only now becoming available. Design: Review of basic and clinical research over 30 years. Setting: Task force of a multinational agency and collaborating agencies. Conclusion(s): Through the involvement of many international scientists, the WHO Task Force has uniquely contributed to the exploratory phases of the research in male contraception and by its multicenter contraceptive efficacy studies has accelerated progress towards the ideal hormonal method. Despite an adverse climate involving social and political attitudes, funding constraints, and pharmaceutical industry hesitations, WHO formed coalitions with governments and international agencies to sustain research with results that apply to men in culturally diverse populations and thereby to influence activities across the whole range of global reproductive health and family planning.
文摘选择以干冷气候为主的兰州和温暖湿润的江汉平原作为研究区域,结合其他多种指标和研究区的岩性特征,对有机碳同位素(δ13Corg)的古气候指示意义进行了初步探讨.结果表明,在兰州地区,δ13Corg值波动反映C3/C4植物比例的改变,指示温度变化.δ13Corg值偏正时,表明C4植物含量较大,反映温度较高,而δ13Corg值偏负时,表明气候较冷;江汉平原δ13Corg值主要反映降水信息,δ13Corg值偏负时指示相对暖湿气候,δ13Corg值偏正反映气候偏干.δ13Corg等指标同时还揭示了末次盛冰期以来两地古气候类同特征:即12.0 ka BP之前气候相对偏干;在全新世晚期,气候波动中转暖.不同之处表现为:约在12.0～10.0 ka BP,当兰州气候还很干冷时,江汉平原已进入暖湿的冰后期;而在全新世早中期,当兰州气候转为暖湿时,江汉平原气候则表现为略偏干.
