Volume 20

The effect of UV-B exposure on the seedling vigor of mung beans (Vigna radiata) was studied. Seeds were exposed to UV-B light for times of 0, 1, 2, 4, 8, 12, and 16 hours, and were then left to germinate for a total of 48 hours, including exposure time. The length of the seedling radicle and the percentage of seeds that germinated were measured. It was found that seedling vigor increased at two hours of UV-B exposure, with a gradual decrease in seedling vigor after two hours. There was no significant difference in the seedling vigor for the durations of 1, 4, and 8 hours of UV-B light exposure.

Coptis rhizome (Huang Lian) is the dried underground stem part of a plant called Coptis chinensis (Chinese goldthread), known to contain bioactive compounds with antibacterial potential, particularly berberine. This study investigated the antibacterial activity of Coptis rhizome extracts against Micrococcus luteus, a gram-positive bacterium that can cause opportunistic infections in immunocompromised individuals. Three extraction methods including aqueous, ethanol, and enzyme-assisted extraction (EAE), were evaluated to identify the approach with the strongest antibacterial activity. Based on the results obtained, aqueous extraction demonstrated the highest antibacterial activity against M. luteus among the three methods tested. This indicates that aqueous extraction is the most effective method for extracting antibacterial compounds from Coptis rhizome under the conditions of this study.

Air vortex cannons generate structurally integral, coherent rings of rotating air that propagate through a surrounding medium over measurable distances. The effect of the outlet diameter of an air vortex cannon on the mass, impulse, and average velocity of air vortices produced by the cannon was investigated experimentally. Vortices generated using six outlet diameters were analysed by measuring the impulse exerted on a force plate and the impact velocity, from which the effective vortex mass was calculated. Increasing outlet diameter resulted in a monotonic power-law increase in both vortex mass and impulse, while the average velocity reached a maximum at an intermediate outlet diameter before decreasing. These results indicate that vortex performance depends on balancing the volume of air expelled with the ability to maintain vortex coherence, suggesting the existence of an optimal outlet diameter for effective vortex formation.

The effect of fish physiology on hydrodynamics is investigated by comparing the drag coefficients of Oreochromis niloticus, which is characterized by a flat body with scales, and Clarias batrachus, which is characterized by a long, rounded body with smooth skin. The fish were towed horizontally through water using a pulley system, and their velocity was tracked. Reynolds numbers were calculated to identify the flow regime. Drag coefficients of O. niloticus and C. batrachus were measured as 0.060 ± 0.007 and 0.042 ± 0.006, respectively, with Reynolds numbers of 1.79 x 10^5 and 2.23 x 10^5. The results indicate that the round, scaleless body of the catfish generates less drag compared to the flat, scaled body of the tilapia.

We examine the effects of tube diameter on the period and decay constant of a vertically oscillating water column. Using transparent tubes with diameters ranging from 17 to 88 mm, oscillations were recorded and analyzed using video tracking. Theoretical models predict that the period is independent of both oscillation amplitude and tube diameter. The results confirm this independence, showing a constant period of approximately 1.29s. However, relative energy loss was found to increase with oscillation amplitude through a power-law relationship, with the exponent increasing with tube diameter before plateauing at a value close to 0.41; this indicates that the damping behavior becomes increasingly nonlinear as tube diameter increases, approaching a velocity dependence of drag around v^1.41 for larger tubes.