Questions for Discussion

What are the dimensions in mass M, length L, and time t of a diffusion coefficient  

What volume is implied when defining a mass transfer coefficient  

Give an example for a diffusion coefficient which is the same in all directions. Give an example when it isn t. 

When a silicon chip is doped with boron, does the doping involve diffusion  

Does the wafting of smells of a pie baking in the oven involve diffusion  

---

You may wish to repeat this activity several times. Following are some questions for discussion ... 

Furthermore, an important protective action of ascorbic acid is its ability to act synergistically with TOH in the inhibition of various oxidation reactions (McCay, 1985 Craw and Depew, 1985 Bendich et al., 1986 Burton and Ingold, 1986 Niki, 1987a,b). Packer et al. (1979) have shown in pulse radiolysis studies that in solution (TO) reacts rapidly with ascorbic acid (K 1.55 x 10 M s" ) to yield TOH again. This synergism seems to function in liposomal membranes as well (Scarpa et al., 1984 Doha et al., 1985 Niki et al., 1985). Some studies indicate that ascorbic acid helps to maintain tissue levels of TOH in vivo (Hruba et al, 1982 Bendich et al, 1984). However, by contrast, other in vivo studies found no evidence for an interaction between TOH and ascorbic acid (Yen et al, 1985 Burton et al, 1990). Thus, the interaction of TOH and ascorbate remains an open question for discussion. 

DIRECTIONS (Items 16-18) This case history is followed by questions for discussion. Write out brief answers (two to five sentences) and then compare your answers with those given at the end of the Answers section. 

Our generalized understanding of skin regeneration still leaves questions for discussion. At the same time it is evident that human skin is one of the indicators of health and HA is... 

Question for discussion Consider the situation shown in Figure 9-11, where t]kvlc/kc 1 and rj < 1. Is it legitimate to say that the reaction is controlled by internal transport, i.e., by pore diffusion, for this case ... 

Emphasis on Solving Problems The emphasis is on the solution of problems, and the text contains many example problems, questions for discussion, and appendices. Very few derivations and proofs are required of the student. The approach to problem-solving is to start each new problem from first principles. No attempt is made to train the student to use pre-prepared charts and graphs. 

---