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181.
Rat pancreatic juice (RPJ) reduced the mean uptake of 57CoB12 bound to rat intrinsic factor (IF) by perfused rat intestinal segments from 30.1 +/- 2.4 (pg 57CoB12 per cm intestine +/- S.E.M.) to 26.7 +/- 2.4 (p less than 0.05). RPJ activated with enterokinase reduced the uptake from 22.8 +/- 2.8 to 16.1 +/- 1.9 (p less than 0.05). RPJ also reduced the uptake from 15.8 +/- 2.3 to 8.3 +/- 2.0 (p less than 0.01) in segments from partially pancreatectomized rats. Rat bile abolished the inhibitory effect of RPJ. The results indicate that in the absence of bile the exocrine pancreatic secretion is capable of inhibiting the intestinal uptake of vitamin B12. 相似文献
182.
Self—sensitized and Rose Bengal—sensitized photo—oxidation of 4, 4′-bisacetamidostilbene (BAAS) in solution gives p—acetamidobenzaldehyde and p—acetamidobenzoic acid via the reaction of singlet oxygen with the trans isomer (la). The rate of the photo—oxidation is retarded in the presence of effective singlet oxygen quenchers. On the other hand, cls—BAAS (lb) is more stable to visible light under the conditions of Rose Bengal—sensitized photo—oxidation than trans—stilbene. 相似文献
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Extraction of a plasma time-activity curve from dynamic brain PET images based on independent component analysis 总被引:1,自引:0,他引:1
Naganawa M Kimura Y Ishii K Oda K Ishiwata K Matani A 《IEEE transactions on bio-medical engineering》2005,52(2):201-210
A compartment model has been used for kinetic analysis of dynamic positron emission tomography (PET) data [e.g., 2-deoxy-2-18F-fluoro-D-glucose (FDG)]. The input function of the model [the plasma time-activity curve (pTAC)] was obtained by serial arterial blood sampling. It is of clinical interest to develop a method for PET studies that estimates the pTAC without needing serial arterial blood sampling. For this purpose, we propose a new method to extract the pTAC from the dynamic brain PET images using a modified independent component analysis [extraction of the pTAC using independent component analysis (EPICA). Source codes of EPICA are freely available at http://www5f.biglobe.ne.jp/?kimura/Software/top.html]. EPICA performs the appropriate preprocessing and independent component analysis (ICA) using an objective function that takes the various properties of the pTAC into account. After validation of EPICA by computer simulation, EPICA was applied to human brain FDG-PET studies. The results imply that the EPICA-estimated pTAC was similar to the actual measured pTAC, and that the estimated blood volume image was highly correlated with the blood volume image measured using 15O-CO inhalation. These results demonstrated that EPICA is useful for extracting the pTAC from dynamic PET images without the necessity of serial arterial blood sampling. 相似文献
185.
Atomic nanotube welders: boron interstitials triggering connections in double-walled carbon nanotubes 总被引:1,自引:0,他引:1
Endo M Muramatsu H Hayashi T Kim YA Van Lier G Charlier JC Terrones H Terrones M Dresselhaus MS 《Nano letters》2005,5(6):1099-1105
Here we demonstrate that the incorporation of boron (B) atoms between double-walled carbon nanotubes (DWNTs) during thermal annealing (1400-1600 degrees C) results in covalent nanotube "Y" junctions, DWNT coalescence, and the formation of flattened multiwalled carbon nanotubes (MWNTs). These processes occur via the merging of adjacent tubes, which is triggered by B interstitial atoms. We observe that B atom interstitials between DWNTs are responsible for the rapid establishment of covalent connections between neighboring tubes (polymerization), thereby resulting in the fast annealing of the carbon cylinders with B atoms embedded in the newly created carbon nanotube network. Once B is in the lattice, tube faceting (polygonization) starts to occur, and the electronic properties are expected to change dramatically. Therefore, B atoms indeed act as atomic nanotube fusers (or welders), and this process could now be used in assembling novel electronic nanotube devices, nanotube networks, carbon nanofoams and heterojunctions exhibiting p-type electronic properties. 相似文献
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Jiwang Yan Takuya Kaneko Kazunori Uchida Nobuhito Yoshihara Tsunemoto Kuriyagawa 《The International Journal of Advanced Manufacturing Technology》2010,50(9-12):991-1002
A two-step electrodischarge machining method was proposed for fabricating microgrooves with varied cross-sections on hard materials. Firstly, tungsten tool electrodes were shaped by wire electrodischarge grinding, and then the resulting tool electrodes were used to electrodischarge machine microgrooves on stainless steel. Preliminary experimental results showed that, in the first step, a sharp tool electrode with surface roughness of 0.3 µmRa could be achieved, and the surface roughness of the resulting groove was 0.16 µmRa in the second step. Voltage strongly affects the machining speed. A high voltage (>70 V) was preferable for improving the material removal rate. However, significant tool wear took place when using a high condenser capacitance at high voltages. To suppress tool wear, a high voltage and a small capacitance should be used. As test pieces, microgrooves having rectangular, triangular, circular and semi-closed cross-sections were fabricated. 相似文献