Modification of Low Refractive Index Polycarbonate for High Refractive Index Applications

Polycarbonates and polythiourethanes are the most popular materials in use today, for optical applications. Polycarbonates are of two types which fall in the category of low refractive index and medium refractive index. The present paper describes the conversion of low refractive index polycarbonates into high refractive index material by the use of a high refractive index monomer, polythiol, as an additive. Novel polycarbonates, where the properties of refractive index and Abbe number can be tailor made, have been obtained. Thermal studies and refractive index determination indicate the formation of a new polymer with improved properties and suitable for optical applications

A vital and disregarded anatomical landmark: Descending sigmoid colon flexure

Background: During the colonoscopy, colon tortuosity is a vital factor to complete the procedure successfully. Endoscopy can be difficult in cases with acute angle bending of adjacent colon segments.  Aim: To assess the relationship of descending sigmoid colon flexure to vital anatomical points on CT in adult subjects. Methods: 114 adult subjects with CT examination of the abdominopelvic region were retrospectively analyzed. In 114 subjects, the angle between proximal sigmoid and descending colon was evaluated in degrees along with descending-sigmoid flexure position concerning the anterior aspect of the 5th lumbar vertebra, the median plane, and left anterior superior iliac spine. Results: Descending sigmoid flexure was seen in all 114 subjects. the LV-DSF was significantly higher in male subjects, with a distance of 123.7±23.1mm compared to female subjects where it was 115.6±21.2. This was statistically significant with p<0.005. MP-DSF in male subjects was 97.8±15.6mm which was significantly higher than the female subjects having MP-DSF of 88.8±14.0mm. The minimum to maximum for males and females respectively were 52-149 and 44-116 which was a statistically significant difference with p<0.001. However, for ASIS-DSF, the distance did not differ significantly between males and females with p=0.54 Conclusions