There has been a growing interest in screening programs designed to detect chronic progressive cancers in the asymptomatic stage, with the expectation that early detection will result in a better prognosis. One key el...There has been a growing interest in screening programs designed to detect chronic progressive cancers in the asymptomatic stage, with the expectation that early detection will result in a better prognosis. One key element of early detection programs is a screening test. An accurate screening test is more effective in finding cases with early-stage diseases. Sensitivity, the conditional probability of getting a positive test result when one truly has a disease, represents one measure of accuracy for a screening test. Since the true disease status is unknown, it is not straightforward to estimate the sensitivity directly from observed data. Furthermore, the sensitivity is associated with other parameters related to the disease progression. This feature introduces additional numerical complexity and limitations, especially when the sensitivity depends on age. In this paper, we propose a new approach that, through combinatorial manipulation of probability statements, formulates the age-dependent sensitivity. This formulation has an exact and simple expression and can be estimated based on directly observable probabilities. This approach also helps evaluate other parameters associated with the natural history of disease more accurately. The proposed method was applied to estimate the mammography sensitivity for breast cancer using the data from the Health Insurance Plan trial.展开更多
为保护和修复青藏高原生态系统,我国在青藏高原实施了一系列政策与生态工程。全面掌握生态系统恢复状况对科学制定区域生态系统保护与恢复策略具有重大意义。本文选取植被净初级生产力、植被覆盖度、水源涵养、土壤保持和防风固沙5个指...为保护和修复青藏高原生态系统,我国在青藏高原实施了一系列政策与生态工程。全面掌握生态系统恢复状况对科学制定区域生态系统保护与恢复策略具有重大意义。本文选取植被净初级生产力、植被覆盖度、水源涵养、土壤保持和防风固沙5个指标,利用地面和遥感数据并结合生态系统服务和权衡的综合评估(Integrated valuation of ecosystem services and trade-offs,InVEST)模型、修正的通用水土流失方程(Revised universal soil loss equation,RUSLE)和修正风蚀方程(Revised wind erosion equation,RWEQ)等方法,评估2000—2019年青藏高原生态系统恢复程度与恢复潜力。结果表明:青藏高原生态系统功能逐步提升,但部分地区仍有退化趋势。其中,生态系统基本稳定的面积最大,占比为42.03%;青藏高原植被覆盖度恢复潜力指数为29.57%。其中,植被覆盖度恢复潜力指数较大的地区主要位于青藏高原中西部。政府未来应因地制宜,对水热环境较好且恢复潜力大的地区积极采取相关措施,对生态恢复潜力大但恢复难度较高的地区采取人工修复和自然恢复相结合的方法,提高生态工程效率。展开更多
利用地面和遥感数据,采用GIS分析与模型模拟等方法,计算并分析了2000—2019年长江上游生态系统宏观结构、生态系统质量和生态系统服务的时空变化状况,利用相关分析法定量评估了生态系统服务的权衡与协同关系,并讨论了生态系统变化对生...利用地面和遥感数据,采用GIS分析与模型模拟等方法,计算并分析了2000—2019年长江上游生态系统宏观结构、生态系统质量和生态系统服务的时空变化状况,利用相关分析法定量评估了生态系统服务的权衡与协同关系,并讨论了生态系统变化对生态系统服务的影响。结果表明:(1)长江上游聚落生态系统面积增加显著,农田和荒漠面积明显减少,陆地生态系统以草地、森林和农田之间转换为主。(2)2000—2019年,长江上游生态系统质量和服务总体稳定向好,部分区域转差。植被固碳量整体呈增加趋势,局部降低,多年递增速率为1.65 Tg/a;土壤保持服务功能呈波动中上升趋势,多年递增速率为2.20 t hm^(-2)a^(-1);水源涵养服务功能轻微下降,部分年际间变化较大。(3)长江上游生态系统的植被固碳与土壤保持、水源涵养与土壤保持之间以协同关系为主,植被固碳与水源涵养之间的权衡和协同关系比例相近。(4)气候是影响生态系统服务变化的主导因素,人类活动影响生态系统服务变化,最终改变生态系统服务之间的协同与权衡关系。展开更多
Microtubule catalyzes the mechanochemical cycle of kinesin,a kind of molecular motor,through its crucial roles in kinesin's gating,ATPase and force-generation process.These functions of microtubule are realized th...Microtubule catalyzes the mechanochemical cycle of kinesin,a kind of molecular motor,through its crucial roles in kinesin's gating,ATPase and force-generation process.These functions of microtubule are realized through the kinesin-microtubule interaction.The binding site of kinesin on the microtubule surface is fixed.For most of the kinesin-family members,the binding site on microtubule is in the groove betweenα-tubulin andβ-tubulin in a protofilament.The mechanism of kinesin searching for the appropriate binding site on microtubule is still unclear.Using the molecular dynamics simulation method,we investigate the interactions between kinesin-1 and the different binding positions on microtubule.The key non-bonded interactions between the motor domain and tubulins in kinesin's different nucleotide-binding states are listed.The differences of the amino-acid sequences betweenα-andβ-tubulins make kinesin-1 binding to theα–βgroove much more favorable than to theβ–αgroove.From these results,a two-step mechanism of kinesin-1 to discriminate the correct binding site on microtubule is proposed.Most of the kinesin-family members have the conserved motor domain and bind to the same site on microtubule,the mechanism may also be shared by other family members of kinesin.展开更多
As a new type of nerve regulation technology, Vagus Nerve Stimulation is currently used in the treatment of nervous system diseases. Auricular Vagus Nerve Stimulation has become one of the research hotspots in this fi...As a new type of nerve regulation technology, Vagus Nerve Stimulation is currently used in the treatment of nervous system diseases. Auricular Vagus Nerve Stimulation has become one of the research hotspots in this field, because there is no implantation risk. However, there is no unified standard for the treatment parameters of aVNS for nervous system diseases. In this paper, the research progress of the anatomical structure and parameters of the vagus nerve and its role in nervous system diseases are reviewed to provide basis for further research.展开更多
文摘There has been a growing interest in screening programs designed to detect chronic progressive cancers in the asymptomatic stage, with the expectation that early detection will result in a better prognosis. One key element of early detection programs is a screening test. An accurate screening test is more effective in finding cases with early-stage diseases. Sensitivity, the conditional probability of getting a positive test result when one truly has a disease, represents one measure of accuracy for a screening test. Since the true disease status is unknown, it is not straightforward to estimate the sensitivity directly from observed data. Furthermore, the sensitivity is associated with other parameters related to the disease progression. This feature introduces additional numerical complexity and limitations, especially when the sensitivity depends on age. In this paper, we propose a new approach that, through combinatorial manipulation of probability statements, formulates the age-dependent sensitivity. This formulation has an exact and simple expression and can be estimated based on directly observable probabilities. This approach also helps evaluate other parameters associated with the natural history of disease more accurately. The proposed method was applied to estimate the mammography sensitivity for breast cancer using the data from the Health Insurance Plan trial.
文摘为保护和修复青藏高原生态系统,我国在青藏高原实施了一系列政策与生态工程。全面掌握生态系统恢复状况对科学制定区域生态系统保护与恢复策略具有重大意义。本文选取植被净初级生产力、植被覆盖度、水源涵养、土壤保持和防风固沙5个指标,利用地面和遥感数据并结合生态系统服务和权衡的综合评估(Integrated valuation of ecosystem services and trade-offs,InVEST)模型、修正的通用水土流失方程(Revised universal soil loss equation,RUSLE)和修正风蚀方程(Revised wind erosion equation,RWEQ)等方法,评估2000—2019年青藏高原生态系统恢复程度与恢复潜力。结果表明:青藏高原生态系统功能逐步提升,但部分地区仍有退化趋势。其中,生态系统基本稳定的面积最大,占比为42.03%;青藏高原植被覆盖度恢复潜力指数为29.57%。其中,植被覆盖度恢复潜力指数较大的地区主要位于青藏高原中西部。政府未来应因地制宜,对水热环境较好且恢复潜力大的地区积极采取相关措施,对生态恢复潜力大但恢复难度较高的地区采取人工修复和自然恢复相结合的方法,提高生态工程效率。
文摘利用地面和遥感数据,采用GIS分析与模型模拟等方法,计算并分析了2000—2019年长江上游生态系统宏观结构、生态系统质量和生态系统服务的时空变化状况,利用相关分析法定量评估了生态系统服务的权衡与协同关系,并讨论了生态系统变化对生态系统服务的影响。结果表明:(1)长江上游聚落生态系统面积增加显著,农田和荒漠面积明显减少,陆地生态系统以草地、森林和农田之间转换为主。(2)2000—2019年,长江上游生态系统质量和服务总体稳定向好,部分区域转差。植被固碳量整体呈增加趋势,局部降低,多年递增速率为1.65 Tg/a;土壤保持服务功能呈波动中上升趋势,多年递增速率为2.20 t hm^(-2)a^(-1);水源涵养服务功能轻微下降,部分年际间变化较大。(3)长江上游生态系统的植被固碳与土壤保持、水源涵养与土壤保持之间以协同关系为主,植被固碳与水源涵养之间的权衡和协同关系比例相近。(4)气候是影响生态系统服务变化的主导因素,人类活动影响生态系统服务变化,最终改变生态系统服务之间的协同与权衡关系。
基金supported by the Natural Science Foundation of Hebei Province of China(Grant No.A2020202007)the National Natural Science Foundation of China(Grant No.11605038)。
文摘Microtubule catalyzes the mechanochemical cycle of kinesin,a kind of molecular motor,through its crucial roles in kinesin's gating,ATPase and force-generation process.These functions of microtubule are realized through the kinesin-microtubule interaction.The binding site of kinesin on the microtubule surface is fixed.For most of the kinesin-family members,the binding site on microtubule is in the groove betweenα-tubulin andβ-tubulin in a protofilament.The mechanism of kinesin searching for the appropriate binding site on microtubule is still unclear.Using the molecular dynamics simulation method,we investigate the interactions between kinesin-1 and the different binding positions on microtubule.The key non-bonded interactions between the motor domain and tubulins in kinesin's different nucleotide-binding states are listed.The differences of the amino-acid sequences betweenα-andβ-tubulins make kinesin-1 binding to theα–βgroove much more favorable than to theβ–αgroove.From these results,a two-step mechanism of kinesin-1 to discriminate the correct binding site on microtubule is proposed.Most of the kinesin-family members have the conserved motor domain and bind to the same site on microtubule,the mechanism may also be shared by other family members of kinesin.
文摘As a new type of nerve regulation technology, Vagus Nerve Stimulation is currently used in the treatment of nervous system diseases. Auricular Vagus Nerve Stimulation has become one of the research hotspots in this field, because there is no implantation risk. However, there is no unified standard for the treatment parameters of aVNS for nervous system diseases. In this paper, the research progress of the anatomical structure and parameters of the vagus nerve and its role in nervous system diseases are reviewed to provide basis for further research.
