PubMed · 14917121
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
B RAJEWSKY, O HUG. 1952. [Radioactive isotopes].. https://pubmed.ncbi.nlm.nih.gov/14917121/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The porosity in porous silicon was characterized using hyperpolarized (HP) xenon as a probe. HP xenon under conditions of continuous flow allows for the rapid acquisition of xenon NMR spectra that can be used to characterize a variety of materials. Two-dimensional exchange spectroscopy (EXSY) (129)Xe NMR experiments using HP xenon were performed to obtain exchange pathways and rates of xenon mobility between pores of different dimensions within the structure of porous silicon and to the gas phase above the sample. Pore sizes are estimated from chemical shift information and a model for pore geometry is presented.
Primary and secondary kinetic and equilibrium isotope effects are calculated with density-functional methods for the dianionic methanolysis of the native (unsubstituted) and thio-substituted ethylene phosphates.
Rice (Oryza sativa L.) is a typical silicon (Si)-accumulating plant, but the mechanism responsible for the translocation from the root to the shoot is poorly understood. In this study, the form of Si in xylem sap was identified by (29)Si-nuclear magnetic resonance (NMR) spectroscopy. In rice (cv. Oochikara) cultured in a monosilicic acid solution containing 0.5 mM Si, the Si concentration in the xylem reached 6 mM within 30 min. In the (29)Si-NMR spectra of the xylem sap, only one signal was observed at a chemical shift of -72.6 ppm, which is consistent with that of monosilicic acid. A (1)H-NMR study of xylem sap did not show any significant difference between the wild-type rice and mutant rice defective in Si uptake, and the components of the xylem sap were not affected by the Si supply. The Si concentration in the xylem sap in vitro decreased from an initial 18 mM to 2.6 mM with time. Addition of xylem sap to a solution containing 8 mM Si did not prevent the polymerization of silicic acid. All these results indicate that Si is translocated in the form of monosilicic acid through the xylem and that the concentration of monosilicic acid is high in the xylem only transiently.