The spread zones, Dr. Renfrew said, are mostly the result of recent dispersals caused by agricultural inventions.
When the anchor bolt's pre-tight torque is 300 N m, with the increase of anchor bolt's pre-tight force, the anchor bolt's prestress spread range increases at roadway roof and two side coal walls, and in roadway's top coal, the spread zones can basically join and form one large zone.
We determined rhamnolipid content in cultures supplemented with 1, 2 and 4% glucose using both oil-spreading zone method and orcinol sulfuric acid method.
Oil-spreading assay was applied for estimation of surfactant activity quantitatively following the method by Morikawa et al. (2000) with a minor modification for better preservation of the round shape of the oil-spreading zone (OSZ).
Oil-spreading analyses indicated that areas of oil-spreading zone in supernatant of ZS1 cultures containing 0.5, 1, 2 and 4% glucose supplements were 25, 50, 170, and 250 cm2/μl, respectively.
The level of rhamnolipid determined by orcinol sulfuric method was found to be much higher than that by oil-spreading zone when concentration of glucose supplements was 2% or higher (p < 0.01) (Fig. 4f).
To test the surfactant activity, 5 μl supernatant was added on to the center of the crude oil raft and waited for 30 s to allow formation of the oil-spreading zone (OSZ).
Based on a standard curve (see "Materials and methods"), the sizes of oil-spreading zone could be approximated to concentrations of rhamnolipids RL7-11 at 4.7, 9.3, 30, and 44 g/l.
Maximum yield of ZS1 cultures supplemented with 1, 2, and 4% glycerol was 7.5, 18.5 and 30 g/l (respectively) based on both oil-spreading zone (Morikawa et al. 2000) and orcinol sulfuric acid methods (Abalos et al. 2001) (Fig. 4e).
