A general study of packing in oxide glass systems containing alkali

The packing fraction, defined as the ionic volume divided by the molar volume, appears to hold promise as a general measure of the structure of alkali oxide modified glasses. For modifying ions having volumes larger than oxygen (K, Rb, and Cs), the packing is dominated by the modifier as alkali oxide concentration increases and is largely independent of glass former; we define this as ionic packing. For alkali smaller than oxygen (Li and Na) the packing is controlled by the oxygen covalent network and is heavily dependent on glass former; we call this covalent packing. In this paper we compare the packing fractions of alkali borate, silicate, germanate, phosphate, and vanadate glass systems. © 2004 Elsevier B.V. All rights reserved

Management of unstable thoracolumbar spinal injuries by posterior short segment spinal fixation

Fifty patients with thoracolumbar fractures were treated operatively between July 2000 and December 2001. The average age of the patients was 33.6 years (range: 20–50 years), 36 were males and 14 were females and the follow-up averaged 59 months (range: 49–68 months). A fall from a height, usually a tree, was the most common cause of injury. Twenty six patients had unstable burst fractures and 13 had translational injury. There were 15 patients with complete neurological deficit, 17 had partial neurological lesions, while 18 had no neurological deficit. All patients were treated by posterior short segment fixation (Steffee VSP). The average pre-operative kyphotic angle was 21.48°, which improved to 12.86° in the immediate post-operative period. The loss of kyphosis averaged 3.46° (0–26°) at the final follow-up. The average pre-operative anterior vertebral body height was 44.7% (range: 36–90%), which improved to 72.0% (range: 55–97%) in the immediate post-operative period. The loss of body height averaged 3.0% (range: 1–15%) at the final follow-up. No neurological deterioration was seen, and in 24 cases a one grade or better improvement was observed. The mean pain score was 1.6, and the mean functional score was 2.8. We found that the application of posterior instrumentation resulted in a reasonable correction of the deformity with a significant reduction in recumbency-associated complications; there were, however, significant other complications