What is in store for the 5th edition? No new chapters; the table of contents will look similar to the 4th edition. But there are hundreds—no, thousands—of small changes, additions, improvements, and upgrades. We’ve included many new up-to-date references, and lots of new homework problems. Regular readers of this blog may see some familiar additions, which were introduced here first. We tried to cut as well as add material to keep the book the same length. We won’t know for sure until we see the page proofs, but we think we did a good job keeping the size about constant.

We found several errors in the 4th edition when preparing the 5th. This week I updated the errata for the 4th edition, to include these mistakes. You can find the errata at the book website, www.oakland.edu/~roth/hobbie.htm. I won’t list here the many small typos we uncovered, and all the misspellings of names are just too embarrassing to mention in this blog. You can see the errata for those. But let me provide some important corrections that readers will want to know about, especially if using the book for a class this fall or next winter (here in Michigan we call the January-April semester "winter"; those in warmer climates often call it spring).

- Page 78: In Problem 61, we dropped a key minus sign: “90 mV” should be “-90 mV”. This was correct in the 3rd edition (Hobbie), but somehow the error crept into the 4th (Hobbie and Roth). I can’t figure out what was different between the 3rd and 4th editions that could cause such mistakes to occur.

- Page 137: The 4th edition claimed that at a synapse the neurotransmitter crosses the synaptic cleft and “enters the next cell”. Generally a neurotransmitter doesn’t “enter” the downstream cell, but is sensed by a receptor in the membrane that triggers some response.

- Page 338: I have already told you about the mistake in the Bessel function identity in Problem 10 of Chapter 12. For me, this was THE MOST ANNOYING of all the errors we have found.

- Page 355: In Problem 12 about sound and hearing, I used an unrealistic value for the threshold of pain, 10
^{-4}W m^{-2}. Table 13.1 had it about right, 1 W m^{-2}. The value varies between people, and sometimes I see it quoted as high as 10 W m^{-2}. I suggest we use 1 W m^{-2}in the homework problem. Warning: the solution manual (available to instructors who contact Russ or me) is based on the problem as written in the 4th edition, not on what it would be with the corrected value.

- Page 355: Same page, another screw up. Problem 16 is supposed to show how during ultrasound imaging a coupling medium between the transducer and the tissue can improve transmission. Unfortunately, in the problem I used a value for the acoustic impedance that is about a factor of a thousand lower than is typical for tissue. I should have used
*Z*_{tissue}= 1.5 × 10^{6}Pa s m^{-1}. This should have been obvious from the very low transmission coefficient that results from the impedance mismatch caused by my error. Somehow, the mistake didn’t sink in until recently. Again, the solution manual is based on the problem as written in the 4th edition.

- Page 433: Problem 30 in Chapter 15 is messed up. It actually contains two problems, one about the Thomson scattering cross section, and another (parts a and b) about the fraction of energy due to the photoelectric effect. Really, the second problem should be Problem 31. But making that change would require renumbering all subsequent problems, which would be a nuisance. I suggest calling the second part of Problem 30 as Problem "30 ½".

- Page 523: When discussing a model for the T1 relaxation time in magnetic resonance imaging, we write “At long correlation times T1 is proportional to the Larmor frequency, as can be seen from Eq. 18.34.” Well, a simple inspection of Eq. 18.34 reveals that T1 is proportional to the SQUARE of the Larmor frequency in that limit. This is also obvious from Fig. 18.12, where a change in Larmor frequency of about a factor of three results in a change in T1 of nearly a factor of ten.

- Page 535: In Chapter 18 we discuss how the blood flow speed
*v*, the repetition time*T*, and the slice thickness_{R}*Δz*give rise to flow effects in MRI. Following Eq. 18.56, we take the limit when*v*is much greater than*"T*/_{R}*Δz*". I always stress to my students that units are their friends. They can spot errors by analyzing if their equation is dimensionally correct. CHECK IF THE UNITS WORK! Clearly, I didn’t take my own advice in this case.

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