Aerogel Waveplates

Optical transmission measurements were made on 98% porosity silica aerogel samples under various degrees of uniaxial strain. Uniaxially compressed aerogels exhibit large birefringence, proportional to the amount of compression, up to the 15% strain studied. The birefringence is mostly reversible and reproducible through multiple compression-decompression cycles. Our study demonstrates that uniaxially strained high porosity aerogels can be used as tunable waveplates in a broad spectral range.Comment: 7 pages, 4 figures, submitted to Optics Expres

In-vitro Effectiveness of Herbal Mouthwashes on the Force Degradation of Two Orthodontic E-chains

Background: Plaque build-up around fixed orthodontic appliances might lead to clinical problems. Even though mouthwashes are recommended during orthodontic treatment, the magnitude of force loading and unloading in elastomeric chains is significantly affected by alcohol-containing mouthwashes. Aim: To evaluate and compare the efficacy of herbal mouthwashes on the force degradation of two orthodontic E-chains. Materials and Methods: Chlorhexidine, Hiora-K and Triphala were used in the study. Ninety pieces of closed clear E-chains with five loops each of AO and 3M companies were collected and divided into three groups (n=30) namely Chlorhexidine, Hiora-K and Triphala. Each group was divided into two sub-groups based on the E-chain brands (n=15). On day 1, the original force was recorded by stretching the E-chain up to 25mm using universal testing machine and the load was recorded in kilograms and converted to grams. The E-chains were subjected to their respective mouthwashes daily for one minute. The force was again recorded on the 21st and 30th days. The obtained data were subjected to statistical analysis using SPSS 16.0 version. Results: The 3M E-chain showed a significant(p=0.000) difference compared with AO. Hiora and Triphala showed lesser force degradation than Chlorhexidine (p=0.013). Further, there was a significant (p=0.001) reduction in force degradation from baseline to the first month. Conclusion: Force degradation was more significant from the1st to the 21st day. 3M E-chain showed less force decay than AO E-chain. Hiora-K and Triphala mouthwash groups showed less force decay than the Chlorhexidine