VARIATIONS

This study is set out to evaluate the suitability of three Nigerian sand types, river, quarry, and coastal for mortar production, focusing on their impact on compressive strength and material properties, particularly the chloride content in coastal sand. The aim is to provide standardized data on local aggregates to enhance construction quality and sustainability in Nigeria, addressing the current lack of such data. A laboratory-based experimental design was conducted, employing standard methods to ensure reliability and repeatability. Six 50-mm mortar cubes per sand type were cast, cured, and tested for compressive strength at 7 and 28 days using a calibrated compression testing machine, following international standards (e.g., ASTM C109). The physical properties (e.g., particle size distribution, shape) and chemical properties (e.g., chloride content in coastal sand) of each sand type were analyzed using standard laboratory techniques, such as sieve analysis and chemical titration. All procedures were repeated to ensure consistency, with results analyzed at a 95% confidence level to assess their reliability.Coastal sand exhibited the highest compressive strength due to its well-graded particles, and low chloride content because it was desalinated, followed by quarry sand with slightly lower strength due to possible dust or angularity issues. River sand showed the lowest strength due to residual impurities, and grading which affected mortar integrity. The analysis identified the optimal sand type for mortar production and provided insights into the influence of material properties, with final data presented to determine statistical significance at the 95% conf dence level. Overall, the study aims to inform standardized guidelines for aggregate use in Nigeria, promoting cost effective and sustainable construction practices.

This study was carried out to determine the variation in keratometric reading using autorefractor before and after cataract surgery in St Teresa Specialist and Laser Eye Center, Edo State. This was a prospective study of one hundred (n = 100) cataract patients (50 males and 50 females) aged between 35-98 years, scheduled for cataract surgery between November to January 2022. Autorefractor (with in built keratometer ) was used to measure the flat meridian (K1) and steep meridian (K2). Cornea astigmatism (CA) was gotten by taking the difference in both meridian. The data collected was analyzed using the statistical package for social sciences (SPSS) version 22.0 and Descriptive statistics (frequencies, percentages, mean and standard deviation) was used to summarize the variables. There was a statistically significant variation in K1 and K2 values before cataract surgery, one and four weeks after cataract surgery.( p<0.001 for K1 before,one week and four weeks after surgery,also p<0.001 for K2 before surgery,one week and four weeks after surgery.) The study also showed that there was no significant difference in cornea astigmatism (CA) before the surgery and one week after the surgery(p=0.412). There was significant difference in CA before the surgery and four weeks after the surgery (p=0.010).There was also significant difference in CA one week after the surgery when compared to four weeks after the surgery (p=0.008).From the study,it was revealed that there is a statistically significant variation that exit in K1 and K2 values before and after cataract surgery as well as cornea astigmatism.