Interferometry Analysis of Cellophane Birefringence

This paper reports on a simple approach of determining the ability of a transparent material, such as cellophane to rotate the direction of polarization of a light beam. In order to determine the birefringence of such a material, a Mach-Zehnder interferometer is used to generate interference patterns when the cellophane sheet is mounted on one arm such as to intercept a portion of the laser beam. The recorded interferograms show a phase shift which is calculated to be 0.98π radians. By rotating the cellophane sheet on the object beam, the fringe separation is measured for different angles and the values used to calculate the ordinary and extraordinary refractive indices as 1.4721 ± 0.0002 and 1.4680 ± 0.0002 respectively at 632.8 nm wavelength. A surface error of approximately λ/16 (peak to valley) is measured from the recorded interferograms. Because of its sufficient birefringence and small thickness of 24 μm, cellophane can be used to fabricate special polarization pupil masks by cutting and aligning different cellophane structures appropriately.

The impact of macular surgery in different grades of epiretinal membrane

AIM：To assess the impact of macular surgery on the functional and anatomic outcomes of the patients in different grades of epiretinal membrane（ERM）.METHODS：Seventy-one eyes of 71 patients who underwent 23-gauge transconjunctival sutureless pars plana vitrectomy for primary isolated ERM were evaluated in this study.RESULTS：There were 38 females（53.5%） and 33 males（46.5%）.The average age of the patients was 68.1 y（range 42-89 y）.Mean follow up period was 14 mo（range 6-26 mo）.The cases were divided into two subgroups of cellophane maculopathy（CM） and macular pucker（MP）.An improvement was observed in the postoperative best-corrected visual acuity（BCVA）,as well as a decrement in central foveal thickness（CFT） in both groups（both of these being statistically significant;P=0.001）.In comparison between two groups,it was found that there was a significant improvement on BCVA and CFT in CM group than MP group（P=0.01）.Furthermore,the postoperative fundus findings regarding RPE alterations and macular edema were significantly higher in MP group when compared to the CM group（P=0.01）.CONCLUSION：ERM and internal limiting membrane peeling surgery can lead to a significant reduction of CFT and visual improvements in idiopathic ERM.A long-term ERM persistence will cause unrecoverable retinal damage and visual loss.

High Microplastic Contamination in Juvenile Tri-Spine Horseshoe Crabs:A Baseline Study of Nursery Habitats in Northern Beibu Gulf,China

Microplastics(MPs)are ubiquitous in marine sedimentary environments.Their occurrence in horseshoe crabs and interactions with the sedimentary environment has not been determined.In this study,MPs,mostly microfibers,were found in all extracted gastrointestinal tract(GIT)samples of the juvenile Tachypleus tridentatus from the northern Beibu Gulf,China.The MP concentrations(4–53 items ind-1)were higher than those in most marine benthic invertebrates(<15 items ind-1)reported in Chinese waters,despite their generally low level in habitat sediments(9–1818 items kg-1).The correlation between the juveniles and sediments was not evident,but the abundance in juvenile horseshoe crab GITs decreased with ages.The findings were relevant to the life-history characteristics of the species,typically with limited dispersal capability and their spending nine years or longer time living in mangrove wetlands during low tides,with apparent ontogenetic changes in their diets.These baseline data enable a better understanding of MP availability in benthic macroinvertebrates,and the ecological risks present in the ecosystems.