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排序方式: 共有623条查询结果,搜索用时 15 毫秒
81.
Lemay SG van den Broek DM Storm AJ Krapf D Smeets RM Heering HA Dekker C 《Analytical chemistry》2005,77(6):1911-1915
We report a new technique for fabricating electrodes for electrochemical applications with lateral dimensions in the range 15-200 nm and a reproducible, well-defined geometry. This technique allows determining the electrode size by electron microscopy prior to electrochemical measurements and without contamination of the metal electrode. We measured the diffusion-limited current with stepped-current voltammetry and showed that its dependence on electrode size can be quantitatively understood if the known geometry of the electrodes is explicitly taken into account. 相似文献
82.
83.
Hendrik Schbe 《Quality and Reliability Engineering International》1994,10(3):229-236
In this paper a stochastic approach to consequence tree analysis is considered. A consequence tree is a set of events logically combined by OR and AND connections that occur in sequence, some being prerequisites for others. Consequence trees are applicable to failure propagation in plants. Facilitating paths and inhibiting cuts are defined and considered. The distribution of the time the system needs to reach a certain top event is obtained. Probability weights are defined that can be used to obtain the weakest link in the consequence tree. 相似文献
84.
85.
Despite considerable research effort, the use of physics-based modelling to predict frictional behaviour is still a debatable
question in modern tribological research. This article presents a dry-friction model, based on physical phenomena such as
adhesion, elastic–plastic contact and deformation. This contribution offers a means to simulate all kinds of frictional behaviour
that is observed in experimental research. The contact of two bodies through their surfaces is transformed into the contact
of a body that is provided with asperities and containing material and geometrical information of both of the mating surfaces,
and a counter profile, holding solely geometrical information. The local adhesion between the asperity tips and the counter
profile, together with the elastic–plastic behaviour of the asperities themselves, form the basis for this model. The simulation
results show qualitatively good agreement with experimental study. Friction and contact phenomena such as normal creep, increasing
static coefficient of friction with increasing dwell time, pre-sliding hysteresis with nonlocal memory, Stribeck and viscous
effect, frictional lag, stick–slip and dynamical oscillations are revealed by this model. Furthermore, future improvement
and refinement of the model is possible (and ongoing) so as to incorporate lubrication and asperity wear. 相似文献
86.
Kanchan Taori Yanxia Liu Dr. Valerie J. Paul Dr. Hendrik Luesch Prof. Dr. 《Chembiochem : a European journal of chemical biology》2009,10(10):1634-1639
Combinatorial biosynthesis meets combinatorial pharmacology, cyanobacterial style : A new antimitotic natural product with features of both dolastatins 10 and 15 was isolated from the same Floridian Symploca sp. sample that produced the histone deacetylase inhibitor largazole. Both agents in combination are more effective in inhibiting cancer cell proliferation than either agent alone.
87.
通过有限元模型升级,将有限元分析与现场测量相结合,其潜力毋庸置疑。然而,简单化的初始模型和缺少测量可能导致升级的模型参数隐藏了不准确的模型假设,而不是提高实际结构参数的评估。因此,所提出方法的目标主要是在采用非线性优化对参数进行评估之前,借助手工模型的精度消除不精确的模型简化。此外,引进多级响应目标函数,结合不同类型的测量获得参数评估的坚实基础。所提方法被用于世界上最大的Svinesund单孔桥,研究表明采用非线性模型可对模型参数进行精确评估。 相似文献
88.
89.
Hendrik R. Sikkema Bauke F. Gaastra Tjeerd Pols Bert Poolman 《Chembiochem : a European journal of chemical biology》2019,20(20):2581-2592
We are aiming for a blue print for synthesizing (moderately complex) subcellular systems from molecular components and ultimately for constructing life. However, without comprehensive instructions and design principles, we rely on simple reaction routes to operate the essential functions of life. The first forms of synthetic life will not make every building block for polymers de novo according to complex pathways, rather they will be fed with amino acids, fatty acids and nucleotides. Controlled energy supply is crucial for any synthetic cell, no matter how complex. Herein, we describe the simplest pathways for the efficient generation of ATP and electrochemical ion gradients. We have estimated the demand for ATP by polymer synthesis and maintenance processes in small cell-like systems, and we describe circuits to control the need for ATP. We also present fluorescence-based sensors for pH, ionic strength, excluded volume, ATP/ADP, and viscosity, which allow the major physicochemical conditions inside cells to be monitored and tuned. 相似文献
90.
A new colorimetric method to quantify β-1,3-1,6-glucans in comparison with total β-1,3-glucans in edible mushrooms 总被引:2,自引:0,他引:2
Jörg Nitschke Hendrik Modick Ekkehard Busch Reimund Wantoch von Rekowski Hans-Josef Altenbach Helga Mölleken 《Food chemistry》2011
Mushroom β-glucans are known for their activity as biological response modifiers and anticarcinogenic agents. β-1,3-1,6 Branched glucans with a triple helix tertiary structure are recognised as the most potent ones. In the present work, a colorimetric method for β-1,3-1,6-glucan quantification based on the dye Congo red is introduced. This method is specific for β-glucans with a triple helix. The β-1,3-1,6-glucan content of mycelia and fruiting bodies from various mushrooms was determined and compared with the total β-1,3-glucan content, measured by a fluorimetric method. The results show equal amounts of β-1,3-1,6- and total β-1,3-glucans in the analysed species but obvious differences between mycelia and fruiting bodies. On the average, 3% of mycelia and 8% of fruiting body dry mass consist of β-1,3-1,6-glucans. The average percentage of β-1,3-1,6-glucans in the total β-1,3-glucan content differs between mycelia (46%) and fruiting bodies (87%). 相似文献