排序方式: 共有27条查询结果,搜索用时 31 毫秒
1.
The use of nuclide95Zr as radiotracer is often unfavourably influenced by the continuous accumulation of the radioactive daughter nuclide95Nb. The present paper gives a method showing how the daughter radioactivity can influence the value of the distribution coefficient
of zirconium calculated from radioactivity measurements. A simple method of continuous purification of95Zr, which yields a product of the required degree of purity, is also described. 相似文献
2.
3.
4.
5.
Elisabeth CW van Straaten Willem de Haan Hanneke de Waal Philip Scheltens Wiesje M van der Flier Frederik Barkhof Ted Koene Cornelis J Stam 《BMC neuroscience》2012,13(1):1-7
Background
This study examined the effects of dietary polyunsaturated fatty acids (PUFA) as different n-6: n-3 ratios on spatial learning and gene expression of peroxisome- proliferator-activated receptors (PPARs) in the hippocampus of rats. Thirty male Sprague?CDawley rats were randomly allotted into 3 groups of ten animals each and received experimental diets with different n-6: n-3 PUFA ratios of either 65:1, 22:1 or 4.5:1. After 10?weeks, the spatial memory of the animals was assessed using the Morris Water Maze test. The expression of PPAR?? and PPAR?? genes were determined using real-time PCR.Results
Decreasing dietary n-6: n-3 PUFA ratios improved the cognitive performance of animals in the Morris water maze test along with the upregulation of PPAR?? and PPAR?? gene expression. The animals with the lowest dietary n-6: n-3 PUFA ratio presented the highest spatial learning improvement and PPAR gene expression.Conclusion
It can be concluded that modulation of n-6: n-3 PUFA ratios in the diet may lead to increased hippocampal PPAR gene expression and consequently improved spatial learning and memory in rats. 相似文献6.
7.
8.
9.
T.J. Kotas 《International Journal of Heat and Fluid Flow》1980,2(3):105-114
In this work the concepts applicable to a method of thermodynamic analysis known as exergy analysis are defined and discussed. Expressions are obtained for exergy components of a steady stream of matter and the relationship between the exergy of a steady stream of matter and that of a closed system is derived. The concept of the standard environment is introduced, its relationship to standard chemical exergy is established, and tables of standard chemical exergy of chemical elements are presented. An idealized model of an open system interacting with the standard environment is used to show the relationship between absolute availability function and exergy. 相似文献
10.
The ears of fishes are remarkable sensors for the small acoustic disturbances associated with underwater sound. For example, each ear of the Atlantic cod (Gadus morhua) has three dense bony bodies (otoliths) surrounded by fluid and tissue, and detects sounds at frequencies from 30 to 500 Hz. Atlantic cod have also been shown to localize sounds. However, how their ears perform these functions is not fully understood. Steady streaming, or time-independent, flows near a 350% scale model Atlantic cod otolith immersed in a viscous fluid were studied to determine if these fluid flows contain acoustically relevant information that could be detected by the ear's sensory hair cells. The otolith was oscillated sinusoidally at various orientations at frequencies of 8-24 Hz, corresponding to an actual frequency range of 280-830 Hz. Phase-locked particle pathline visualizations of the resulting flows give velocity, vorticity, and rate of strain fields over a single plane of this mainly two-dimensional flow. Although the streaming flows contain acoustically relevant information, the displacements due to these flows are likely too small to explain Atlantic cod hearing abilities near threshold. The results, however, may suggest a possible mechanism for detection of ultrasound in some fish species. 相似文献