Electrochemical evidence of catalysis of oxygen reduction at the polarized liquid–liquid interface by tetraphenylporphyrin monoacid and diacid

Cyclic voltammetry is used to study the role of 5,10,15,20-tetraphenyl-21H,23H-porphine (H2TPP) in the reduction of molecular oxygen by decamethylferrocene (DMFc) at the polarized water|1,2-dichloroethane (DCE) interface. It is shown that this rather slow reaction proceeds remarkably faster in the presence of tetraphenylporphyrin monoacid (H3TPP+) and diacid (H4TPP2+), which are formed in DCE by the successive transfer of two protons from the acidified aqueous phase. A mechanism is proposed, which includes the formation of adduct between H3TPP+ or H4TPP2+ and O2 that is followed by electron transfer from DMFc to the adduct leading to the observed production of DMFc+ and to the regeneration of H2TPP or H3TPP+, respectively

Scheduling of Behavioral VHDL by Retiming Techniques

Abstract In this paper we present a new approach to the scheduling of behavioral VHDL descriptions for control-ow dominated applications containing a large number of nested conditionals and data dependent loops. The proposed algorithm is able to schedule and re-schedule descriptions for optimization subject to various cost functions. The timing of the I/O signals can be c ompletely xed, partially xed o r left to the scheduler. In this case the algorithm produces a schedule such that the number of clock cycles required f o r a c omplete execution of the behavioral description is minimized. Scheduling is performed a s a b ehavioral VHDL code transformation and allows taking advantage of all the power of commercial RT synthesis systems. The corresponding problem is solved b ased on an analogy to the retiming problem on RT-level networks which can be solved i n p olynomial time. The eciency of our approach is demonstrated on various examples