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231.
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磁场影响葡萄糖氧化酶活性的研究 总被引:5,自引:0,他引:5
以尼龙网作载体,用戊二醛交联将区区糖氧化酶(GOD)固定装成酶柱并联结于流动体系中,采用流动注射分光光度法研究磁场对固定化GOD催化活性的影响。结果表明,在0℃、5℃、45℃下以1.0×10^-2mol.L^-1的葡萄糖为底物及55℃下以0.1mol^-1的葡萄糖为底物时,0.22T静有显著提高固定化GOD的反应速度,且磁场效应与底物浓度及磁场作用时间有关。用动力学方法考察了不同强度的磁场对溶解G 相似文献
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为了研究航天员舱外活动时的手套压力和太空低温复合效应对操作力量的影响,选取最大握力和握力疲劳两个指标评价手动作业力量,其中握力疲劳采用做功能力评价.操作力量抓握试验所需的不同温度和压力是通过在低温模拟舱中利用液氮降温以及真空泵抽气实现.结果表明:戴手套对最大握力和握力疲劳的影响都非常显著;与常温常压戴手套相比,压力(29.6 kPa,39.2 kPa)单独作用对最大握力的影响显著,低温单独作用对最大握力的影响并不显著,而二者对握力疲劳的影响都非常显著;在加压和低温复合作用下,最大握力和握力疲劳会进一步受到显著影响.可见手套压力和太空低温复合效应严重降低了航天员手部力量的发挥,航天员舱外作业人-手套系统的研究需考虑复合因素的影响. 相似文献
235.
文章论述了一个航天器表面原子氧通量和遭遇量预报模式的建立,并对影响航天器表面原子氧遭遇量的主要因素进行了讨论。最后用模式计算了2003~2006年间太阳同步轨道卫星表面原子氧遭遇量的情况。 相似文献
236.
Doris Breuer Steven A. Hauck II Monika Buske Martin Pauer Tilman Spohn 《Space Science Reviews》2007,132(2-4):229-260
The interior evolution of Mercury—the innermost planet in the solar system, with its exceptional high density—is poorly known.
Our current knowledge of Mercury is based on observations from Mariner 10’s three flybys. That knowledge includes the important
discoveries of a weak, active magnetic field and a system of lobate scarps that suggests limited radial contraction of the
planet during the last 4 billion years. We review existing models of Mercury’s interior evolution and further present new
2D and 3D convection models that consider both a strongly temperature-dependent viscosity and core cooling. These studies
provide a framework for understanding the basic characteristics of the planet’s internal evolution as well as the role of
the amount and distribution of radiogenic heat production, mantle viscosity, and sulfur content of the core have had on the
history of Mercury’s interior.
The existence of a dynamo-generated magnetic field suggests a growing inner core, as model calculations show that a thermally
driven dynamo for Mercury is unlikely. Thermal evolution models suggest a range of possible upper limits for the sulfur content
in the core. For large sulfur contents the model cores would be entirely fluid. The observation of limited planetary contraction
(∼1–2 km)—if confirmed by future missions—may provide a lower limit for the core sulfur content. For smaller sulfur contents,
the planetary contraction obtained after the end of the heavy bombardment due to inner core growth is larger than the observed
value. Due to the present poor knowledge of various parameters, for example, the mantle rheology, the thermal conductivity
of mantle and crust, and the amount and distribution of radiogenic heat production, it is not possible to constrain the core
sulfur content nor the present state of the mantle. Therefore, it is difficult to robustly predict whether or not the mantle
is conductive or in the convective regime. For instance, in the case of very inefficient planetary cooling—for example, as
a consequence of a strong thermal insulation by a low conductivity crust and a stiff Newtonian mantle rheology—the predicted
sulfur content can be as low as 1 wt% to match current estimates of planetary contraction, making deep mantle convection likely.
Efficient cooling—for example, caused by the growth of a crust strongly in enriched in radiogenic elements—requires more than
6.5 wt% S. These latter models also predict a transition from a convective to a conductive mantle during the planet’s history.
Data from future missions to Mercury will aid considerably our understanding of the evolution of its interior. 相似文献
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基于AOV图及二叉树的梯形图与指令表互换算法 总被引:15,自引:0,他引:15
通过对可编程逻辑控制器(Programma blelogic contro ller,PLC)的梯形图语言及指令表语言的分析,提出了基于AOV(Activity on vertex)有向图和二叉树实现梯形图与指令表程序相互转换的算法。转换算法将梯形图映射为AOV图,并由其建立二叉树来表示指令间的逻辑关系,通过遍历二叉树实现PLC梯形图与指令表的转换。文中给出一个转换实例,介绍了算法思想及其实现步骤。该算法具有通用性,适于复杂控制逻辑的梯形图,已成功用于水电自动化监控系统中的PLC编程软件平台。 相似文献
239.
G. Kminek J.D. Rummel C.S. Cockell R. Atlas N. Barlow D. Beaty W. Boynton M. Carr S. Clifford C.A. Conley A.F. Davila A. Debus P. Doran M. Hecht J. Heldmann J. Helbert V. Hipkin G. Horneck T.L. Kieft G. Klingelhoefer M. Meyer H. Newsom G.G. Ori J. Parnell D. Prieur F. Raulin D. Schulze-Makuch J.A. Spry P.E. Stabekis E. Stackebrandt J. Vago M. Viso M. Voytek L. Wells F. Westall 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
In this paper we present the findings of a COSPAR Mars Special Regions Colloquium held in Rome in 2007. We review and discuss the definition of Mars Special Regions, the physical parameters used to define Mars Special Regions, and physical features on Mars that can be interpreted as Mars Special Regions. We conclude that any region experiencing temperatures > −25 °C for a few hours a year and a water activity > 0.5 can potentially allow the replication of terrestrial microorganisms. Physical features on Mars that can be interpreted as meeting these conditions constitute a Mars Special Region. Based on current knowledge of the martian environment and the conservative nature of planetary protection, the following features constitute Mars Special regions: Gullies and bright streaks associated with them, pasted-on terrain, deep subsurface, dark streaks only on a case-by-case basis, others to be determined. The parameter definition and the associated list of physical features should be re-evaluated on a regular basis. 相似文献
240.