Impact of rotation shifts on autonomic nervous system in shift workers as assessed by short term - Heart Rate Variability and other autonomic function tests.

OBJECTIVE : The objective of the study was to assess the autonomic imbalance in night shift workers when compared to regular day workers using short term HRV and other cardiac autonomic function tests. METHODS : The study was conducted in Physiology Research Laboratory, Department of Physiology, PSG IMS&R, Coimbatore. 30 day shift workers and 30 night shift workers were included in the study. The short term heart rate variability was assessed using a Biopac. Lead II electrocardiogram was recorded for a minimum of 5 minutes using a computerized physiograph (NEVIQURE- Digital ECG recorder). The analysis of the HRV was done with the aid of Finland software. Using this HRV analysis, time domain parameters and frequency domain parameters were determined. The other cardiac autonomic function tests were conducted in the research laboratory. The data obtained was subjected to statistical analysis using unpaired t-test. RESULTS : The mean RR interval showed a highly significant decrease and the mean HR showed a highly significant increase in the night shift workers when compared to the day workers. The RMSSD and the pNN50 were significantly low in night workers. Regarding the frequency domain measures the VLF showed a significant increase while the HF showed a significant decrease in the night shift workers. Among the other cardiac autonomic function tests the Valsalva ratio showed a significant decrease among the night shift workers. CONCLUSION : The night shift induces sympathetic over-activity and reduced cardiovagal activity in shift workers. However the delayed effects of shift work and adaptation of the workers to the night shift has to be further explored

Flexure and Shear Study of Deep Beams using Metakaolin Added Polypropylene Fibre Reinforced Concrete

Structural elements like walls of bunkers, load bearing walls in buildings, pile caps, plate elements in folded plates behave as deep beams. Beams whose span (L) to depth (D) ratio is reasonably small can be said as a deep beam. Beams with large depth, supported by individual columns, often used as transfer girders in tall buildings, long span structures etc are commonly referred to as deep beams. Deep beams are used for architectural buildings where the span is very large without any intermediate columns such as marriage halls, assembly halls, auditoriums, theatres etc. According to IS456-2000, a beam is said to be as a deep beam when the ratio of effective span to overall depth (L/D) is less than 2.0 for simply supported members and 2.5 for continuous members. The design of such structural elements requires innovative procedures to serve the functionality coupled with durability. In deep beams, the bending stress distribution across any transverse section deviates appreciably from the straight line distribution assumed as in the simple beam theory. So, assumption of “Plane section before bending remains plane after bending” does not become valid and the neutral axis does not lies at the mid depth. In deep beams, the ultimate failure due to shear is generally brittle in nature, in disparity to the ductile behavior and progressive failure with large number of cracks as observed in normal beams. In this paper, flexural strength of M20 and M30 graded concrete deep beams with the addition of a combination of 0%,10%,20% metakaolin as a partial replacement for cement and 0%,2.5%,5% polypropylene fibre is found out and mode of failure is observed for each case. Mix designs for M20 and M30 graded concrete are carried out in worksheets and the proportions of cement, sand, coarse aggregate are calculated based on the tests conducted on cement and aggregates. Cubes are casted and 7 days compressive strengths for those cubes are tested using compressive testing machine and the mix proportions are used