Effect of planting pattern on shading and phytoplankton photosynthesis in Bangladesh rice-fish farms

In the present study, a Border Planting (BP) pattern recommended by the Bangladesh Agricultural Research Council was tested against Regular Planting (RP) to assess the effect, if any, on gross phytoplankton photosynthesis and shading. A Wide Planting (WP) pattern was also included in the trial, as an extreme case, to assess the level of photosynthesis that might be obtained if some of the rice yield was sacrificed. Three rice-planting treatments, each with four replicates, using the rice variety BR16, were undertaken: (1) RP, 26 cm between rows N to S and E to W; (2) BP, 20 cm between rows N to S and alternately 21 cm and 36 cm between rows E, to W; and (3) WP, 66 cm between rows N to S and E to W. BP showed no advantage compared to RP, possibly because the rice variety used was short and thus produced relatively little shading. WP did show a benefit for phytoplankton photosynthesis, but this may not generate an increase in fish yield sufficient to justify the negative impact of rice production.

Effect of transportation stress on hepatic glycogen of Oreochromis niloticus (L.)

Oreochromis niloticus was subjected to transportation stress to investigate hepatic glycogen levels and mortality as indices of stress. Mortalities lasted up to three days after transportation, except in highly aerated samples. Heptic glycogen levels in transported fish were significantly lower in the controls. Stress appeared to be more intense when fish were transported at a high density and in a high salinity medium.

The effect of nozzle design on laser micro-machining of M2 tool steels

This paper shows how computational techniques have been used to develop axi-symmetric, straight, sonic-line, minimum length micro nozzles that are suitable for laser micro-machining applications. Gas jets are used during laser micro-machining processing applications to shield the interaction zone between laser and workpiece material, and they determine the machining efficiency of such applications. The paper discusses the nature of laser-material interactions and the importance of using computational fluid dynamics to model pressure distributions in short nozzles that are used to deliver gas to the laser-material interaction zone. Experimental results are presented that highlight unique problems associated with laser micro machining using gas jets.