For each of the 650 and 800 K IWR-1-endo molecular weight isothermal runs, the P and S wave velocities initially decreased with increasing pressure, reaching minimum values at around 3-4 GPa, followed by increases with pressure up to 6.1 GPa; on successive decompression to ambient pressure, both velocities changed irreversibly due to permanent densification, and no minima were observed in both velocities. We also found that, in a second compression-decompression cycle at 800 K, the densified silica glass was compressed reversibly (elastically) within errors without further irreversible densification. Using the measured P and S wave velocities in such reversible (elastic) compression regions
as a function of pressure, we found the density of silica glass increases with temperature from 300 to 800 K at all the measured pressure range up to 6.1 GPa, providing a direct evidence of a negative thermal expansion of silica glass at high pressures. (C) 2010 American Institute of Physics. [doi:10.1063/1.3452382]“
“Purpose: To develop and demonstrate a method for regional evaluation of pulmonary perfusion and gas exchange based on intravenous injection
of hyperpolarized xenon 129 ((129)Xe) selleck chemicals llc and subsequent magnetic resonance (MR) imaging of the gas-phase (129)Xe emerging in the alveolar airspaces.
Materials and Methods: Five Fischer 344 rats that weighed 200-425 g were prepared for imaging according to an institutional animal care and use committee-approved protocol. Rats were ventilated, and a 3-F catheter was placed in the jugular (n = 1) or a 24-gauge catheter in the tail (n = 4) vein. Imaging and spectroscopy of gas-phase (129)Xe were performed after injecting 5 mL of half-normal saline saturated with (129)Xe hyperpolarized to 12%. Corresponding ventilation images were obtained CDK assay during conventional inhalation delivery
of hyperpolarized v.
Results: Injections of (129)Xe-saturated saline were well tolerated and produced a strong gas-phase (129)Xe signal in the airspaces that resulted from (129)Xe transport through the pulmonary circulation and diffusion across the blood-gas barrier. After a single injection, the emerging (129)Xe gas could be detected separately from (129)Xe remaining in the blood and was imaged with an in-plane resolution of 1 x 1 mm and a signal-to-noise ratio of 25. Images in one rat revealed a matched ventilation-perfusion deficit, while images in another rat showed that xenon gas exchange was temporarily impaired after saline overload, with recovery of function 1 hour later.
Conclusion: MR imaging of gas-phase (129)Xe emerging in the pulmonary airspaces after intravenous injection has the potential to become a sensitive and minimally invasive new tool for regional evaluation of pulmonary perfusion and gas exchange.