Dynamic distallation

There are circumstances when a complex process may involve two competing (i.e., opposing) dynamic effects that have different time constants. One example is the increase in inlet temperature to a tubular catalytic reactor with exothermic kinetics. The initial effect is that the exit temperature will momentarily decrease as increased conversion near the entrance region depletes reactants at the distal, exit end. Given time, however, higher reaction rates lead to a higher exit temperature. 

A reversible, direct fluoroimmunosensor for human serum albumin (HS A) measurement has been described by Bright et al.(m> Antibody Fab fragments are first immobilized on small quartz plates by hinge-region thiols, and then dansylated. The immunosensor is formed by attaching the quartz plates with bound Fab to the distal end of a bifurcated fiber-optic probe, which transmits both the excitation and emission. Binding of ffSA to the immunosensor results in a three- to five-fold enhancement of dansyl fluorescence. The sensor can be reused up to 50 times, with a detection limit of about 1.8 x 10-8 M, and a somewhat limited dynamic range. 

It is now well ascertained that dendrites are capable of propagating action potentials not only in distal to proximal direction, but also in the reverse direction by back-propagation after initiation at the cell body (Ludwig and Pittman, 2003). The so-called law of dynamic polarization enunciated by Cajal (see Berlucchi, 1999) was aimed at stating the unidirectional propagation of excitations within the nervous system, and assumed that nerve impulses are conducted from the dendrite or soma to axon terminals. This dogma is now being reconsidered, not only in view of the evidence of dendrodendritic synapses, but also in view of the existence of electrical synapses in which the flow of information can be bidirectional. 

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