Shape evolution of electrodeposited copper bumps with high peclet numbers

We report the shape evolution of initial copper bumps at Peclet numbers higher than a hundred. The role of vortices and of penetration flow within the cavity was discussed with numerical fluid dynamics computation to obtain a bump with a single hump at the center. The current distributions, or flux profiles, were calculated at the diffusion controlled overpotential and were compared with the electrodeposited bump shapes. For the 100 mu m cavity width, the vortices increase at the upstream corners with Peclet numbers 1410 and 7311. The vortices are the local resistance of mass transfer to the cathode. These vortices cause the hollows in flux profiles at the upstream corner with these Peclet numbers. The penetration flow collides with the photoresist sidewall and the vortices decrease at downstream corners. These decreased vortices cause the increase in flux profile at downstream corners. For a 30 pm cavity width a single large vortex forms for the higher Peclet number 44,500 and a single hump in flux is achieved.</p

RecO-mediated DNA homology search and annealing is facilitated by SsbA

Bacillus subtilis RecO plays a central role in recombinational repair and genetic recombination by (i) stimulating RecA filamentation onto SsbA-coated single-stranded (ss) DNA, (ii) modulating the extent of RecA-mediated DNA strand exchange and (iii) promoting annealing of complementary DNA strands. Here, we report that RecO-mediated strand annealing is facilitated by cognate SsbA, but not by a heterologous one. Analysis of non-productive intermediates reveals that RecO interacts with SsbA-coated ssDNA, resulting in transient ternary complexes. The self-interaction of ternary complexes via RecO led to the formation of large nucleoprotein complexes. In the presence of homology, SsbA, at the nucleoprotein, removes DNA secondary structures, inhibits spontaneous strand annealing and facilitates RecO loading onto SsbA–ssDNA complex. RecO relieves SsbA inhibition of strand annealing and facilitates transient and random interactions between homologous naked ssDNA molecules. Finally, both proteins lose affinity for duplex DNA. Our results provide a mechanistic framework for rationalizing protein release and dsDNA zippering as coordinated events that are crucial for RecA-independent plasmid transformation

Batch grinding kinetics of Ethenzamide particles by fluidized-bed jet-milling

Ethenzamide solids as a representative active pharmaceutical ingredient (API) were batch-ground by means of a fluidized-bed jet-mill which is a relatively new equipment and promising for production in the pharmaceutical field. Thus, the characteristic grinding mechanism was investigated. As a result, the variation of the residual ratio with grinding time after milling was expressed simply by a mathematical model using only the first Kapur function, and it was consistent with experimental data satisfactorily. As the shape of the function was much different from that of inorganic compound and peculiar to API, a cubic function with respect to particle diameter was defined newly and well fitted to the experimental data. The function was also found to be affected by the operating parameters as the grinding gas pressure, the charge weight of raw material and the linear velocity at the grinding nozzle. According to the assessments of the breakage and the selection functions derived from the first Kapur function, it was found that the grinding mechanism of Ethenzamide particles was related with particle attrition mainly