Jet mixing time of liquids tM in a rotating vessel was observed from the pulse response curve of electric conductivity. The ratio of mixing time to mean residence time, tM/tR, was well correlated with the dimensionless angular velocity Ω*, which was equal to the ratio of tangential velocity at the vessel wall to jet velocity at the nozzle hole. For the present experimental conditions, tM/tR showed a minimum value of about 0.2 regardless of jet nozzle angle, and the minimum value appeared at Ω* = 0.2–0.3. The observed response curves were classified into five types by shape. The transition of shape to shape depended only on Ω* regardless of jet flow rate, and the transition point agreed well with the Ω* value giving the minimum value of tM/tf. The ratio of mixing time to apparent circulation time, tM/tAC was 5 to 9 for the non-rotating condition (Ω* = 0), and these values were almost the same, 5 to 6, for the ratio of mixing time to circulation time in an agitated vessel with impeller. tM/tAC increases stepwise with increase of Ω* where the position of the step agrees with that of the transition of the shape of response curve.
A servo motor widely used in robot technology was applied to a mixing operation. Periodic interruption of rotation, upward and downward movement and a co-reverse periodic rotation of the impeller were very effective in the liquid mixing. They were especially effective in the high viscosity liquid using a conventional disk turbine impeller. When the periodic interruption of rotation and the co-reverse periodic rotation were used, they were effective at a higher switch frequency for liquid mixing. The larger moving speed and length were effective. In addition, the mixing performance was improved further by the synergy effect of the combination of the co-reverse periodic rotation and upward and downward movement of impeller. Moreover, the mixing performance was improved from unsteady speed mixing at low Reynolds number.
Northern and Southern blots are the most commonly used techniques for the confirmation of presence and expression of target genes. Molecular tools available for this purpose include radioisotope-, enzyme- and hapten-labeled nucleic acid probes. In particular, the use of enzyme-labeled probes are easy and safe, and do not require bound/free processes after hybridization associated with an antibody-based detection system. However, there are few approaches that enable the post-transcriptional modification of RNA with enzymes or proteins. In this study, we applied the Cu(I)-catalyzed [3 + 2] azide-alkyne cycloaddition (CuAAC) reaction to the labeling of an RNA strand with enzymes. The C-5 position of UTP was modified with an alkyne group and alkyne-bearing RNA was prepared by in vitro transcription using T7 RNA polymerase. Surface amino groups of bacterial alkaline phosphatase (BAP) were randomly derivatized with azide groups at different modification ratios. The CuAAC reaction occurred selectively between the alkyne-modified RNA and the azide-modified enzyme. The RNA probe conjugated with BAP using this technique could detect a specific RNA by dot blot northern hybridization.
