Formation and characterization of inorganic membranes from zeolite-silica microcomposites

Small crystals of zeolites (500-1000 nm) with two- and three-dimensional channel systems (faujasite and ZSM-5 structures) were embedded in amorphous thin films derived from TEOS hydrolyzed in alcoholic solution. Scanning electron microscopy studies show that the zeolites can be quite evenly dispersed in the membrane, resulting in single layers of zeolite crystals protruding out of the amorphous matrix. In situ FT-IR studies with a series of probe molecules revealed that in most membranes the zeolites were 100% accessible from the gas phase. The membranes excluded molecules which are larger than the pore openings of the zeolite embedded in the composite

Virtual cooperativity in myoglobin oxygen saturation curve in skeletal muscle in vivo

BACKGROUND: Myoglobin (Mb) is the simplest monomeric hemoprotein and its physicochemical properties including reversible oxygen (O(2))binding in aqueous solution are well known. Unexpectedly, however, its physiological role in intact muscle has not yet been established in spite of the fact that the role of the more complex tetrameric hemoprotein, hemoglobin (Hb), in red cells is well established. Here, I report my new findings on an overlooked property of skeletal Mb. METHODS: I directly observed the oxygenation of Mb in perfused rat skeletal muscle under various states of tissue respiration. A computer-controlled rapid scanning spectrophotometer was used to measure the oxygenation of Mb in the transmission mode. The light beam was focused on the thigh (quadriceps) through a 5-mm-diameter light guide. The transmitted light was conducted to the spectrophotometer through another 5-mm-diameter light guide. Visible difference spectra in the range of 500–650 nm were recorded when O(2 )uptake in the hindlimb muscle reached a constant value after every stepwise change in the O(2 )concentration of the buffer. RESULTS: The O(2 )dissociation curve (ODC) of Mb, when the effluent buffer O(2 )pressure was used as the abscissa, was of a sigmoid shape under normal and increased respiratory conditions whereas it was of rectangular hyperbolic shape under a suppressed respiratory condition. The dissociation curve was shifted toward the right and became more sigmoid with an increase in tissue respiration activity. These observations indicate that an increase in O(2 )demand in tissues makes the O(2 )saturation of Mb more sensitive to O(2 )pressure change in the capillaries and enhances the Mb-mediated O(2 )transfer from Hb to cytochrome oxidase (Cyt. aa(3)), especially under heavy O(2 )demands. CONCLUSION: The virtual cooperativity and O(2 )demand-dependent shifts of the ODC may provide a basis for explaining why Mb has been preserved as monomer during molecular evolution

Paramagnetic artifact and safety criteria for human brain mapping

Biological effects of magnetic field and their safety criteria, especially effects of gradient magnetic field on the cerebral and pulmonary circulation during functional brain mapping are still unclear. Here we estimated that magnetically induced artifacts for the blood oxygenation level- and flow- based functional magnetic resonance imaging are less than 0.1%, and disturbance in the pulmonary circulation is less than 1.3% even if the field strength of magnetic resonance system is risen up to 10 tesla. These paramagnetic effects are considered to be small and harmless during human brain mapping

Fabrication of aligned carbon nanotube-filled rubber composite

ArticleScripta Materialia. 54(1):31-35 (2006)journal articl