Chromate removal as influenced by the structural changes of soil components upon carbonization at different temperatures.

Surface fire could induce heat transferring into the soil, creating a carbonized environment, which may alter the chemical compositions of soil organic matters (SOM). In the study, a surface soil was carbonized at up to 600 °C with limited air to simulate soils experiencing a surface fire, and Cr(VI) removal on the carbonized soils was investigated. NMR and FTIR analyses demonstrated a remarkable change of SOM structures at 300-400 °C. TGA-MS spectra indicated that (e.g. C(2)H(4), CH(3)OH and C(3)H(8)) were the major components in the evolved gases from the pyrolyzed soil. A maximum amount of Cr(VI) removal (ca. 4 mg g(-1) soil) occurred for the 200 °C-carbonized soils, attributed mainly to a significant increase of Cr(VI) reduction by 0.1 M KCl extractable organic carbon (EOC) with abundant carboxylic groups. Nonetheless, the formation of aromatic C upon carbonization of the soil at >400 °C may be responsible for Cr(VI) reduction.

Comparison between carotid duplex sonography and angiography in the diagnosis of extracranial internal carotid artery occlusion.

To determine the diagnostic accuracy of extracranial internal carotid artery (ICA) occlusion by carotid duplex sonography and ophthalmic flow direction, we compared both carotid sonograms and angiograms in 82 cases of ischemic cerebrovascular disease. A total of 157 carotid arteries were available for comparison. The overall diagnostic accuracy of ICA occlusion by duplex scanning was 96% (sensitivity, 83%; specificity, 98%; positive predictive value, 91%), by ophthalmic flow examination, 95% (sensitivity, 79%; specificity, 98%; positive predictive value 86%), and by combined study, 98% (sensitivity, 96%; specificity, 98%; positive predictive value 92%). We recommend that the ophthalmic flow examination should be used in combination with other sonographic methods in detecting extracranial carotid artery disease. The combined study gives higher diagnostic accuracy than the single method. When an occlusion or a tight stenosis is uncertain on carotid sonograms, color Doppler or angiography is indicated for further confirmation.