Adsorption of H2O on H-ZSM-5 was studied by FT-IR in
the presence of gaseous H2O in the temperature
range between 293 and 423 K. Conversion of monomeric
hydrogen-bonded H2O to dimeric species was
clearly observed in IR spectra measured at 373 K by increasing the
equilibrium pressure of H2O. Polymeric
water was also formed by further increase of H2O pressure
at the expenses of dimeric species. The frequencies
and the relative intensities of IR bands due to dimeric species agree
with the quantum-chemical results
for H5O2
+ species.
Reversible posterior leukoencephalopathy syndrome is one of the most serious complications of immunosuppressive therapy. The clinical features include headache, altered mental functioning, seizures, cortical blindness and other visual disturbances, with hypertension. The neuroimaging studies reveal predominant posterior leukoencephalopathy. Usually, antihypertensive therapy and reduction or withdrawal of immunosuppressive agents have been reported to resolve the neurological deficits and imaging abnormalities within a few weeks. We discuss here a 51-year-old woman with nephrotic syndrome who developed acute leukoencephalopathy during combination therapy with prednisolone and cyclosporine. She developed severe headache, visual disturbance, consciousness disturbance, and generalized tonic clonic convulsion. A computed tomography scan (CT) revealed low-density areas in the subcortices of the parietal and occipital lobes. Magnetic resonance imaging (MRI) disclosed a high signal intensity area on T2-weighted images and a low signal intensity area on T1-weighted images in the same lesions. Follow-up brain CT and MRI were performed several times. Three weeks after the first study, these lesions had completely resolved, but she had persistent altered consciousness for more than 1 year.
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