Recently, I stumbled upon a delightful YouTube video of an interview with Paul Horowitz, explaining how The Art of Electronics began. I’ll keep this post brief, so you’ll have time to watch the video. The host is Limor Fried, who goes by the moniker Ladyada in honor of computer programing pioneer Ada Lovelace. Fried owns the electronics company Adafruit Industries, which is a cross between a business and an educational organization. Notice that during the interview Fried wears a “transistor man” tee shirt; I remember reading about transistor man in The Art of Electronics when I was designing a circuit in John Wikswo’s lab during graduate school.
Enjoy the video, and make The Art of Electronics your go-to book for designing circuits; or, just read it for fun.
Young (1773–1829) went to medical school and was a practicing physician. How did he learn enough math and physics to become a biological physicist? In Young’s case, it was easy. He was a child prodigy and a polymath who learned more through private study than in a classroom. As an adolescent he was studying optics and building telescopes and microscopes. As a teenager he taught himself calculus. By the age of 17 was reading Newton’s Principia. By 21 he was a Fellow of the Royal Society.
Some of his most significant contributions to biological physics were his investigations into physiological optics, including accommodation and astigmatism. In Intermediate Physics for Medicine and Biology, Russ Hobbie and I state that the “ability of the lens to change shape and provide additional converging power is called accommodation.” Robinson describes Young’s experiments that proved the changing shape of the lens of the eye is the mechanism for accommodation. For instance, he was able to rule out a mechanism based on changes in the length of the eyeball by making careful and somewhat gruesome measurements on his own eye as he changed his focus. He showed that patients whose lens had been removed, perhaps because of a cataract, could no longer adjust their focus. He also was one of the first to identify astigmatism, which Russ and I describe as “images of objects oriented at different angles… form at different distances from the lens.”
Young’s name is mentioned in IPMB once, when analyzing the wave nature of light: “Thomas Young performed some interference experiments that could be explained only by assuming that light is a wave.” The Last Man Who Knew Everything describes Young’s initial experiment, where he split a beam of light by letting it pass on each side of a thin card, with the beams recombining to form an interference pattern on a screen. Young presents his famous double-slit experiment in his book A Course of Lectures on Natural Philosophy and the Mechanical Arts. Robinson debates if Young actually performed the double-slit experiment or if for him it was just a thought experiment. In any case, Young’s hypothesis about interference fringes was correct. I’ve performed Young’s double-slit experiment many times in front of introductory physics classes. It establishes that light is a wave and allows students to measure its wavelength. Interference underlies an important technique in medical and biological physics described in IPMB: Optical Coherence Tomography.
A green laser passing through two slits 0.1 mm apart produces an interference pattern. Photo by Graham Beards, published in Wikipedia.
Was Young a better biological physicist than Helmholtz? Probably not. Was Young a better scientist? It’s a close call, but I would say yes (Helmholtz had nothing as influential as the double slit experiment). Was Young a better scholar? Almost certainly. In addition to his scientific contributions, he had an extensive knowledge of languages and helped decipher the Rosetta Stone that allowed us to understand Egyptian hieroglyphics. He really was a man who knew everything.
This blog is about physics applied to medicine and biology, but if we don’t solve the climate crisis there’s no use developing fancier ways to do medical imaging or radiation therapy; we’ll all be dead. So today I’m going to tell you about a book I just read, titled Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming. It’s the book I’ve been looking for. It analyzes all the different ways we can address global warming, and ranks them by impact and importance. Here’s how the editor Paul Hawken begins Drawdown.
The genesis of Project Drawdown was curiosity, not fear. In 2001 I began asking experts in climate and environmental fields a question: Do we know what we need to do in order to arrest and reverse global warming? I thought they could provide a shopping list. I wanted to know the most effective solutions that were already in place, and the impact they could have if scaled. I also wanted to know the price tag. My contacts replied that such an inventory did not exist, but all agreed it would be a great checklist to have, though creating one was not within their individual expertise. After several years, I stopped asking because it was not within my expertise either.
Then came 2013. Several articles were published that were so alarming that one began to hear whispers of the unthinkable: It was game over. But was that true, or might it possibly be game on? Where did we actually stand? It was then that I decided to create Project Drawdown. In atmospheric terms drawdown is that point in time at which greenhouse gases peak and begin to decline on a year-to-year basis. I decided that the goal of the project would be to identify, measure, and model one hundred substantive solutions to determine how much we could accomplish within three decades towards that end.
Many solutions are presented in Drawdown, but here I count down the top ten, ranked according to their total atmospheric carbon dioxide reduction, with a brief quote from Drawdown accompanying each.
10. Rooftop Solar
As households adopt rooftop solar… they transform generation [of electricity] and its ownership, shifting away from utility monopolies and making power production their own.
9. Silvopasture
Silvopasture is… the integration of trees and pasture or forage into a single system for raising livestock… Trees create cooler microclimates and more protective environments, and can moderate water availability. Therein lies the climatic win-win of silvopasture: As it averts further greenhouse emissions from one of the world’s most polluting sectors, it also protects against changes that are now inevitable.
8. Solar Farms
Any scenario for reversing global warming includes a massive ramp-up of solar power by mid-century. It simply makes sense: the sun shines every day, providing a virtually unlimited, clean, and free fuel at a price that never changes. Small, distributed clusters of rooftop panels are the most conspicuous evidence of the renewables revolution powered by solar photovoltaics (PV). The other, less obvious iteration of the PV phenomenon is large-scale arrays of hundreds, thousands, or in some cases millions of panels [solar farms] that achieve generating capacity in the tens or hundreds of megawatts.
7. Family Planning
Increased adoption of reproductive healthcare and family planning is an essential component to achieve the United Nations’ 2015 medium global population projection of 9.7 billion people by 2050. If investment in family planning, particularly in low-income countries, does not materialize, the world’s population could come closer to the high projection, adding another 1 billion people to the planet.
6. Educating Girls
Girls education, it turns out, has a dramatic bearing on global warming. Women with more years of education have fewer, healthier children and actively manage their reproductive health… Synchronizing investments in girls’ education with those in family planning would be complementary and mutually reinforcing. Education is grounded in the belief that every life bubbles with innate potential. When it comes to climate change, nurturing the promise of each girl can shape the future for all.
5. Tropical Forests
In recent decades, tropical forests... have suffered extensive clearing, fragmentation, degradation, and depletion of flora and fauna… One of the dominant storylines of the nineteenth and twentieth centuries was the vast loss of forestland. Its restoration and re-wilding could be the twenty-first-century story.
Whether on the farm, near the fork, or somewhere in between, efforts to reduce food waste can address emissions and ease pressure on resources of all kinds, while enabling society more effectively to supply future food demand.
2. Wind Turbines
Ongoing cost reduction will soon make wind energy the least expensive source of installed electricity capacity, perhaps within a decade.
1. Refrigerant Management
As temperatures rise, so does reliance on air conditioners. The use of refrigerators, in kitchens of all sizes and throughout “cold chains” of food production and supply, is seeing similar expansion. As technologies for cooling proliferate, evolution in refrigerants and their management is imperative.
While reading Intermediate Physics for Medicine and Biology, let’s turn up the thermostat a bit during warm days. Between chapters, let’s ditch the hamburger and eat a salad instead (and if you can’t finish it, save the rest for leftovers). Let’s make sure girls in particular are encouraged to read IPMB (or whatever else that will help with their education). And let’s write our congressional representatives and encourage them to support solar and wind energy sources.
If you don’t have the time to read Drawdown, or don’t have easy access to it, then visit the website drawdown.org or watch the videos below, which summarize the plan to reverse global warming.
“Earth teems with sights and textures, sounds and vibrations, smells and tastes, electric and magnetic fields. But every animal can only tap into a small fraction of reality’s fullness. Each is enclosed within its own unique sensory bubble, perceiving but a tiny sliver of our immense world.”
An Immense World sometimes overlaps with Intermediate Physics for Medicine and Biology. For example, both books discuss vision. Yong points out the human eye has better visual acuity than most other animals. He writes “we assume that if we can see it, they [other animals] can, and that if it’s eye-catching to us, it’s grabbing their attention… That’s not the case.” Throughout his book, Yong returns to this idea of how sensory perception differs among animals, and how misleading it can be for us to interpret animal perceptions from our own point of view.
Like IPMB, An Immense World examines color vision. Yong speculates about what a bee would think of the color red, if bees could think like humans.
Imagine what a bee might say. They are trichromats, with opsins that are most sensitive to green, blue, and ultraviolet. If bees were scientists, they might marvel at the color we know as red, which they cannot see and which they might call “ultrayellow” [I would have thought “infrayellow”]. They might assert at first that other creatures can’t see ultrayellow, and then later wonder why so many do. They might ask if it is special. They might photograph roses through ultrayellow cameras and rhapsodize about how different they look. They might wonder whether the large bipedal animals that see this color exchange secret messages through their flushed cheeks. They might eventually realize that it is just another color, special mainly in its absence from their vision.
Both An Immense World and IPMB also analyze hearing. Yong says
Human hearing typically bottoms out at around 20 Hz. Below those frequencies, sounds are known as infrasound, and they’re mostly inaudible to us unless they’re very loud. Infrasounds can travel over incredibly long distances, especially in water. Knowing that fin whales also produce infrasound, [scientist Roger] Payne calculated, to his shock, that their calls could conceivably travel for 13,000 miles. No ocean is that wide.…
Like infrasound, the term ultrasound… refers to sound waves with frequencies higher than 20 kHz, which marks the upper limit of the average human ear. It seems special—ultra, even—because we can’t hear it. But the vast majority of mammals actually hear very well into that range, and it’s likely that the ancestors of our group did, too. Even our closest relatives, chimpanzees, can hear close to 30 kHz. A dog can hear 45 kHz; a cat, 85 kHz; a mouse, 100 kHz; and a bottlenose dolphin, 150 kHz. For all of these creatures, ultrasound is just sound.
In IPMB, Russ Hobbie and I introduce the decibel scale for measuring sound intensity, or how loud a sound is. Yong uses this concept when discussing bats.
The sonar call of the big brown bat can leave its mouth at 138 decibels—roughly as loud as a siren or jet engine. Even the so-called whispering bats, which are meant to be quiet, will emit 110-decibel shrieks, comparable to chainsaws and leaf blowers. These are among the loudest sounds of any land animal, and it’s a huge mercy that they’re too high-pitched for us to hear.
Yong examines senses that Russ and I never consider, such as smell, taste, surface vibrations, contact, and flow. He wonders about the relative value of nociception [a reflex action to avoid a noxious stimulus] and the sensation of pain [a subjective feeling created by the brain].
The evolutionary benefit of nociception is abundantly clear. It’s an alarm system that allows animals to detect things that might harm or kill them, and take steps to protect themselves. But the origin of pain, on top of that, is less obvious. What is the adaptive value of suffering?
On the continuum ranging from life’s unity to diversity, Yong excels at celebrating the diverse, while Russ and I focus on how physics reveals unifying principles. I’m sometimes frustrated that Yong doesn’t delve into the physics of these topics more, but I am in awe of how he highlights so many strange and wonderful animals. There’s a saying that “nothing in biology makes sense except in light of evolution.” That’s true for An Immense World, which is a survey of how the evolution of sensory perception shapes they way animals interact, mate, hunt their prey, and avoid their predators.
Two chapters of An Immense World I found especially interesting were about sensing electric and magnetic fields. When discussing the black ghost knifefish’s ability to sense electric fields, Yong writes
Just as sighted people create images of the world from patterns of light shining onto their retinas, an electric fish creates electric images of its surroundings from patterns of voltage dancing across its skin. Conductors shine brightly upon it. Insulators cast electric shadows.
Then he notes that
Fish use electric fields not just to sense their environment but also to communicate. They court mates, claim territory, and settle fights with electric signals in the same way other animals might use colors or songs.
Although flowers are negatively charged, they grow into the positively charged air. Their very presence greatly strengthens the electric fields around them, and this effect is especially pronounced at points and edges, like leaf tips, petal rims, stigmas, and anthers. Based on its shape and size, every flower is surrounded by its own distinctive electric field. As [scientist Daniel] Robert pondered these fields, “suddenly the question came: Do bees know about this?” he recalls. “And the answer was yes.”
The chapter on sensing magnetic fields is different from the others, because we don’t yet know how animals sense these fields.
Magnetoreception research has been polluted by fierce rivalries and confusing errors, and the sense itself is famously difficult both to study and to comprehend. There are open questions about all the senses, but at least with vision, smell, or even electroreception, researchers know roughly how they work and which sense organs are involved. Neither is true for magnetoreception. It remains the sense that we know least about, even though its existence was confirmed decades ago.
If you want to read a beautifully written book that explores how much of the physics in Intermediate Physics for Medicine and Biology can be used by species throughout the animal kingdom to sense their environment, I recommend An Immense World. You’ll love it.
Umwelt: The hidden sensory world of animals. By Ed Yong.
In Table 13.1 of Intermediate Physics for Medicine and Biology, Russ Hobbie and I list the approximate intensity levels of various sounds, in decibels. The minimum perceptible sound is 0 dB, a typical office has a sound level of 50 dB, a jack hammer is 100 dB, and the loudest sound listed is a rocket launch pad at 170 dB.
Can there be even louder sounds? Yes, there can! This new homework problem lets you calculate the loudest possible sound.
Section 13.4
Problem 17 ½. Let us calculate the loudest possible sound in air.
(a) Use Eq. 13.29 to calculate the intensity of a sound in Wm−2, using 428 Pa s m−1 for the acoustic impedance of air and one atmosphere (1.01 × 105 Pa) for the pressure. This pressure is the largest that can exist for a sinusoidally varying sound wave, as an even louder sound would create a minimum pressure below zero (less than a vacuum).
(b) Use the result from part (a) to calculate the intensity in decibels using Eq. 13.34.
For those of you who don’t have a copy of IPMB at your side, here are the two equations you need
I = ½ p2/Z(13.29)
Intensity level = 10 log10(I/I0)
(13.34)
where I is the intensity, Z is the acoustic impedance, p is the pressure, I0 is the minimum perceptible intensity (10−12 W m−2), and log10 is the common logarithm.
I’ll let you do the calculation, but you should find that the loudest sound is about 191 dB. Is this really an upper limit? No, you could have a peak pressure larger than one atmosphere, but in that case you wouldn’t be dealing with a traditional sound wave (with pressure ranging symmetrically above and below the ambient pressure) but more of a nonlinear acoustic shock wave.
Krakatoa, by Simon Winchester.
Has there ever been a sound that loud? Or, more interestingly, what is the loudest sound ever heard on earth? That’s hard to say for sure, but one possibility is the 1883 eruption of the Krakatoa volcano. We know this sound was loud, because people heard it so far from where the eruption occurred.
In August 1883 the chief of police on Rodriguez was a man named James Wallis, and in his official report… for the month he noted:
On Sunday the 26th the weather was stormy, with heavy rain and squalls; the wind was from SE, blowing with a force of 7 to 10, Beaufort scale. Several times during the night (26th–27th) reports were heard coming from the eastward, like the distant roar of heavy guns. These reports continued at intervals of between three and four hours, until 3 pm on the 27th, and the last two were heard in the directions of Oyster Bay and Port Mathurie [sic].
This was not the roar of heavy guns, however. It was the sound of Krakatoa—busily destroying itself fully 2,968 miles away to the east. By hearing it that night and day, and by noting it down as any good public servant should, Chief Wallis was unknowingly making for himself two quite separate entries in the record books of the future. For Rodriguez Island was the place furthest from Krakatoa where its eruptions could be clearly heard. And the 2,968-mile span that separates Krakatoa and Rodriguez remains to this day the most prodigious distance recorded between the place where unamplified and electrically unenhanced natural sound was heard and the place where that same sound originated.
Winchester concludes
The sound that was generated by the explosion of Krakatoa was enormous, almost certainly the greatest sound ever experienced by man on the face of the earth. No manmade explosion, certainly, can begin to rival the sound of Krakatoa—not even those made at the height of the Cold War’s atomic testing years.
No one knows how many decibels Krakatoa’s eruption caused on the island itself. The sound was almost certainly in the nonlinear regime, and probably had an intensity of over 200 dB.
I was particularly fascinated by Rhodes’s tale of Wilson and James Watson as competing assistant professors at Harvard in the late 1950s. Watson advocated for molecular biology, while Wilson favored evolutionary biology. It was a battle between the unity and diversity of life. Wilson, with a job offer from Stanford in hand, was offered tenure if he would remain at Harvard. Watson—already famous for discovering the structure of DNA with Francis Crick—was livid that Wilson was to be tenured before he was. In the end, Harvard gave them both tenure (a wise decision). Decades later Wilson and Watson become friends. Listen to them discuss their rivalry in the video at the end of this post.
Readers of Intermediate Physics for Medicine and Biology will be interested in Wilson’s online high-school biology textbook Life on Earth. Physicists, mathematicians, and engineers who want to apply their field to biology or medicine always face the obstacle of learning biology. Sometimes they don’t need a deep knowledge of biology, but merely must know enough to collaborate with a biologist. Life on Earth is an excellent introduction to the field. It is free, available online, is written by a giant in the field of biology, and contains beautiful photographs and engaging videos. The only problem: it was written to be used on a Mac. I am a Mac guy, so this is not a problem for me. I don’t know if it works on a PC. Life on Earth should provide you with enough biology to understand IPMB.
Problem 37. The consumption of a finite resource is
often modeled using the logistic equation. Let y(t) be the
cumulative amount of a resource consumed and y∞ be
the total amount that was initially available at t = −∞.
Model the rate of consumption [I wish Russ and I had written “amount consumed” instead of “rate of consumption”] using Eq. 2.29 over the range
−∞ < t < ∞.
(a) Set y0 = y∞/2, so that the zero of the time axis
corresponds to when half the resource has been used.
Show that this simplifies Eq. 2.29.
(b) Differentiatey(t) to find an expression for the rate
of consumption. Sketch plots of dy/dt versus t on linear
and semilog graph paper. When does the peak rate of
consumption occur?
The answer to this exercise can be found in the IPMB solution manual. (The solution manual is available free of charge to instructors. If you need a copy, email me at roth@oakland.edu.) All exercises in the solution manual have a brief preamble, explaining the goal of the exercise and why it’s important.
2.37¶ This is not a biological example, except in the sense that if we ignore this example we humans may all end up dead. Students use a variation of the logistic equation to analyze the consumption of a finite resource (e.g., oil).
I won’t solve the entire problem in this blog post, but I will show the semilog plot from the solution manual.
A semilog plot of amount consumed (solid) and the rate of consumption (dashed) for a finite resource modeled using the logistic equation. This plot is part of the solution to Problem 37b.
The rate of consumption of the resource (dy/dt) first rises exponentially, reaches a peak, and then falls exponentially. (Remember, a straight line on a semilog plot corresponds to exponential growth or decay.) For the mathematically inclined, the dy/dt curve corresponds to a hyperbolic secant squared.
Why do I bring up this topic? Recently I read Energy: A Human History, by Richard Rhodes, a sweeping account of energy transitions that changed our world. Rhodes includes a figure that looks a little bit like this:
My rendition of a figure from the final chapter of Energy: A Human History showing the historical evolution of the world energy mix.
What a wonderful plot! It both summarizes Rhodes’s book and illustrates the power and ubiquity of Hubbert’s peak. That semilog plot from Homework Problem 37 appears over and over as one finite resource replaces another.
I should add a few qualifiers.
Historical data is noisy and the curves pictured above merely approximate a complicated behavior.
The plot begins at about the time of the industrial revolution. The population of humans was probably too small, and our technology too primitive, to apply this model before that time.
All future data (say, after 2016, the year Energy was published) is extrapolation or prediction.
Let’s hope that the Renewables curve corresponds to an infinite resource, not a finite one, so it will never reach a peak and then fall. Is that wishful thinking? I don’t know, but the figure encourages us to ask such questions.
Nuclear energy shot up much faster than would be expected right after World War II, but then the curve flattened prematurely because of fears about radiation.
Natural gas appears to be with us for the foreseeable future, unless we can wean ourselves off of it to address global warming. The use of coal is almost done (regardless of what a certain senator from West Virginia thinks), and the use of oil has reached its peak and is on its way down (now might be a good time to buy an electric car).
Climate change is the critical issue looming over the right side of the plot. We must leave many of those fossil fuels (coal, oil, gas) in the ground to prevent an environmental disaster.
Perhaps I need to add extra parts to that homework problem.
(c) Suppose at time t you discover that pollution from this finite resource is killing people, and you stop consuming it immediately. How would that change the plots you made in part (b)?
(d) What would happen if the resource is killing people but people continue to consume it nevertheless?
In the fall of 1994, I became a new assistant professor of physics at Oakland University, in the specialization of medical physics. After receiving my assignment to teach a graduate-level one-semester course in magnetic resonance imaging (MRI) for the next semester, I sat in my nearly empty office and wondered what and how to teach my students…
As I went over [the MRI books available at the time] for a possible adaptation for my course, I could not find any single book that contained what I had in mind as the four essential and inseparable components of MRI—theory, instrumentation, spectroscopy, and imaging… I eventually realized, painfully, that I would have to put together the materials myself… My lecture notes, evolved and revised substantially during the last 26 years, became the basis for this book…
The book is grouped into five parts. Part I introduces the essential comcepts in magnetic resonance, including the use of the classical description and a brief introduction of the quantum mechanical description. It also includes the description for a number of nuclear interactions that are fundamental to magnetic resonance. Part II covers the essential concepts in experimental magnetic resonance, which are common for both NMR spectroscopy and MRI. Part III describes the essential concepts in NMR spectroscopy, which should also be beneficial for MRI researchers. Part IV introduces the essential concepts in MRI. The final part is concerned with the quantitative and creative nature of MRI research…
IPMB covers some of the material in Essential Concepts, particularly that dealing with physics and imaging. Nuclear magnetic resonance spectroscopy is entirely absent in IPMB. I had not seen the material in Essential Concepts about spectroscopy since taking an organic chemistry course while an undergraduate at the University of Kansas, and even then I didn’t understand much of it. IPMB has little to say about instrumentation and I found these sections of Essential Concepts to be among the most useful for me.
Essential Concepts is full of excellent images and illustrations. Some images, such as a high-resolution picture of a pickle, I had seen before on the door to Xia’s laboratory at Oakland University. We both were members of the physics department at OU for over twenty years. In fact, if you look at the acknowledgment section of Essential Concepts, you’ll find my name—along with many others—listed as reading and commenting on a draft of the book. Of course, this was done virtually, as Xia sat in his house and I in mine during the COVID-19 pandemic. This book is one of the few good things that arose from that plague.
The Early Development of Q-Space NMR Microscopy — Yang Xia
In 1971, I was hired by Professor Harold Elford Johns to work as a medical
physicist at the Princess Margaret Hospital (PMH) in Toronto. Professor Jack
Cunningham was my immediate boss. Professor Johns was considered the
guru of Medical Physics with a world-renowned reputation for being a great
scientist, a feared graduate student supervisor, and humanitarian. Over the
years, he received multiple awards including five honorary doctorate degrees,
and Officer of the Order of Canada. He was the first medical physicist to
be inducted into the Canadian Medical Hall of Fame. Jack Cunningham
also received the Officer of the Order of Canada along with multiple other
awards, largely for his work on software development for computerized radiation treatment planning systems. Johns and Cunningham were the authors
of The Physics of Radiology, the textbook which gave me my medical physics
grounding as it did for all other young, aspiring medical physicists at that
time….
[When Van Dyk was studying for his medical physics certification exams], Professors Johns and Cunningham were working on a draft of the fourth edition of their book, The Physics of Radiology. In January, I asked Jack Cunningham if I could review the available draft of this fourth edition. Considering that they would be contributors to the certification examination questions, my guess was that some, if not all, of the questions could be answered if I knew everything in this new edition. So, I went through this draft of the book from cover to cover and I solved (at least I worked on) every problem that was posed at the end of each chapter. As part of this process, I provided Jack with some comments on some questionable things that I found in the draft. As a result, my name was listed, along with others, in the acknowledgments when the book was published in 1983.
During my early years at McGill, I became involved in the activities of the newly formed Canadian College of Physicists in Medicine (CCPM), which had begun the process of credentialling Medical Physicists in Canada. While I had Engineering, rather than Physics, training, I felt that my background had prepared me well for the roles I was playing in Diagnostic Radiology at the Neuro. Nevertheless, I felt it would do no harm to formally study radiation physics and its practical implementation in medicine, so in 1983 I embarked on a mission to devour The Physics of Radiology, by Johns and Cunningham, in preparation for the CCPM Fellowship exams in 1984. The examination process had evolved into an oral session, and a closed book examination—where three questions were selected from a previously published catalogue of questions covering all aspects of Medical Physics. Every Friday afternoon for almost a year I studied “Johns and Cunningham” with Gino Fallone, then a physicist at the Montreal General Hospital, who had also decided to take the certification examination. A gruelling process, but finally successful—we both became CCPM fellows that year.
Martin Yaffe's contribution to True Tales described a bit about Johns background and career.
Dr. Johns had been born in Chengdu, China to Canadian church missionary
parents and he had spent his early years there, roaming about small communities
in the mountains of Szechuan province with his father, a no-nonsense
disciplinarian who believed strongly in devotion to duty and hard work. He
learned to be focussed and driven to succeed at whatever was his mission.
When the family eventually returned to Canada, he brought that to his graduate
work in physics and later to the University of Saskatchewan where he
built a strong medical physics research group, concentrating on developing
and refining radiation therapy. There he developed the first (or possibly the
second—there is some debate as his unit and a competitor, built by Eldorado Mining and Refining Ltd., were used to treat patients within a week or two of
each other) cobalt-60 radiation treatment system and carried out pioneering
work on radiation dosimetry and treatment planning. Dr. Johns and his work
in Saskatchewan were actually mentioned in the film First Man, about the
astronaut Neil Armstrong whose daughter had suffered from a brain tumour.
Later, he began work on The Physics of Radiology, a textbook which he
referred to jokingly (I think) as “The Bible”. This book truly became a guide
to those working in radiation oncology all over the world and was published
in multiple languages. While the book and its various editions consumed
many of his evenings after a hard day at the lab, Johns reverse bragged that
he earned about two cents per hour on his textbook writing efforts.
I once estimated that I make about ten cents an hour for my work on IPMB. I guess the difference represents inflation.
Yaffe also reminisced on Johns’ personality and mentoring technique.
Johns had an abrupt nature, not hesitating to poke you emphatically when
he felt that you needed to think harder. Often, he would read your carefully
written document, hold it up between you and slowly rip it to shreds before
filing it in the trash bin. If it was late in the day, he would tell you to meet
him the next morning at eight to re-write.
What I learned in those sessions was how to sharply focus your thinking
on a problem and how to persist until you had a workable solution.
Dr. Johns had two more senior students at the time—Aaron Fenster… and
Don Plewes. These two and the lab technician, Dan Ostler,
more or less adopted me and provided mentoring to prepare me for my
sessions with Johns. Also, Johns used to invite me into his office when he
was working on a paper with Aaron or Don and let me watch. While he
was more respectful toward them, it was not uncommon for him to fix one
of them with his laser-like glare which he held on them for what seemed
like minutes and then say something like: “Plews” (he never pronounced the
“e” that made it rhyme with Lewis; instead he made it rhyme with “news”),
“If you sent that to a journal, they’d crap all over you”. Or, as he slowly
ripped up a piece of writing that Aaron had proudly submitted, he’d say at a
similar slow pace, “well (rrrrip) Fenster (rrrrip), your (rrrrip) writing (rrrrip) is
improving.” So, rather than feel discriminated against, I simply realized that
the standards were high, and I’d have to present my best game at all times.
The Physics of Radiology is one of those landmark textbooks (like Jackson’s Classical Electrodynamics in physics) that is a rite of passage for a student in that a field of study. As a coauthor on IPMB, I know what an honor it would be for your book to make that sort of impact. Johns and Cunningham was cited in the second edition of IPMB, but not in earlier or later editions.
The fourth edition is the last that Johns and Cunningham published. However, just last year an updatedfifth edition was prepared by a team of five authors.
to communicate what medical physics is and what medical physicists do to a broad audience including science students, graduate students and residents, experienced medical physicists and their family members, and the general public who are wondering about medical physics.
The book will consist of a series of short stories written by award-winning medical physicists—stories that are of personal interest as it relates to their careers. Each story will be unique to the author and could serve any one or more of the following purposes:
Be an inspiration to young people searching for career directions, as well as more experienced physicists who are seeking direction on leadership development.
Provide an overview of what medical physicists do with a level of description that is understandable by the non-medical physicist.
Provide lessons on life’s experiences from high-profile medical physicists who have significant experience and who are clearly at the top of the field as shown by the awards that they have won.
Be entertaining for those working in the field as well as others.
You can look at this book as a Plutarchian collection of comparative biographies, or you can focus on cross-cutting lessons that appear again and again in the various chapters. Here are some of the lessons I noticed.
The critical role of mentoring. All the authors stressed the importance of having supportive, inspirational mentors early in their career, and the satisfaction of mentoring their own students.
Crucial advances grow out of discussions at scientific meetings. Clearly the opportunity to travel and attend meetings is a part of a scientist’s career that’s highly valued, and often leads to new research directions and collaborations.
The division of their duties into three parts: research, teaching, and clinical work. The variety that arises from having these three different tasks keeps a medical physicist’s job from ever becoming dull or routine.
The challenge of the American Board of Radiology (ABR) exams. Today, these certification exams act as a gateway to a career in clinical medical physics.
The interdisciplinary nature of medical physics. Many of these authors brought expertise from one field (say, computer programming) and integrated that knowledge with other fields (say, anatomy or medical imaging).
Failures are opportunities. These scientists had their share of setbacks, but managed to overcome them and use them as springboards to success. They persisted.
The role of industry in medical physics research. Many authors tell stories of interacting with for-profit companies making imaging or therapy devices. Working with industry can be complicated and aggravating, but when successful the resulting products can have a huge impact on medical practice.
Science is an international activity. Many authors had collaborators and students from all over the world, leading to lifelong friendships.
While I enjoyed all the chapters in True Tales, my favorite was by Marcel van Herk, a Steve Wozniak-like Dutch electronics guru. He started out as a 12-year-old hobbyist who built his own computer. Van Herk writes “One of the first things I did was to design and build a completely functional relay-based full adder (a circuit that can add two 4-bitbinary numbers), soldered together while listening to Black Sabbath’s Iron Man in the living room, not totally to my mother’s liking due to the music and the spilled solder on the carpet. The parts I used were small electromechanical relays from 1950 punched card sorting machines, acquired cheaply.” He ended up developing software for the Elektacone-beam CT imaging guidance system integrated with a medical linear accelerator. While his story is fascinating, it’s not uncommon; many of these scientists traveled individual, meandering paths into medical physics, taking them from a clueless neophyte to a giant in their field. A key lesson for students is that there’s no single route to success in science, and certainly not in medical physics.
If you are considering possible careers, I urge you to read True Tale of Medical Physics. It may change your life. You may change medicine.
I am an emeritus professor of physics at Oakland University, and coauthor of the textbook Intermediate Physics for Medicine and Biology. The purpose of this blog is specifically to support and promote my textbook, and in general to illustrate applications of physics to medicine and biology.
