Category Archives: Science: Physics, Astronomy, etc.

Penicillin, cheese allergy, and stomach cancer

penecillin molecule

The penicillin molecule is a product of the penicillin mold

Many people believe they are allergic to penicillin — it’s the most common perceived drug allergy — but several studies have shown that most folks who think they are allergic are not. Perhaps they once were, but when people who thought they were allergic were tested, virtually none showed allergic reaction. In a test of 146 presumably allergic patients at McMaster University, only two had their penicillin allergy confirmed; 98.6% of the patients tested negative. A similar study at the Mayo Clinic tested 384 pre-surgical patients with a history of penicillin allergy; 94% tested negative, and were given clearance to receive penicillin antibiotics before, during, and after surgery. Read a summary here.

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Orange showing three different strains of the penicillin mold; some of these are toxic.

This is very good news. Penicillin is a low-cost, low side-effect antibiotic, effective against many diseases including salmonella, botulism, gonorrhea, and scarlet fever. The penicillin molecule is a common product of nature, produced by a variety of molds, e.g. on the orange at right, and used in cheese making, below. It is thus something most people have been exposed to, whether they realize it or not.

Penicillin allergy is still a deadly danger for the few who really are allergic, and it’s worthwhile to find out if that means you. The good news: that penicillin is found in common cheeses suggests, to me, a simple test for penicillin allergy. Anyone who suspects penicillin allergy and does not have a general dairy allergy can try eating brie, blue, camembert, or Stilton cheese: any of cheeses made with the penicillin mold. If you don’t break out in a rash or suffer stomach cramps, you’re very likely not allergic to penicillin.

There is some difference between cheeses. Some, like brie and camembert, have a white fuzzy mold coat; this is Penicillium camemberti. it exudes penicillin — not in enough to cure gonorrhea, but enough to give taste and avoid spoilage — and to test for allergy. Danish blue and Roquefort, shown below, have a different look and more flavor. They’re made with blue-green, Penicillium roqueforti. Along with penicillin, this mold produces a small amount of neurotoxin, roquefortine C. It’s not enough to harm most people, but it could cause some who are not allergic to penicillin to be allergic to blue cheese. Don’t eat a moldy orange, by the way; some forms of the mold produce a lot of neurotoxin.

For people who are not allergic, a thought I had is that one could, perhaps treat heartburn or ulcers with cheese; perhaps even cancer? H-Pylori, the bacteria associated with heartburn, is effectively treated by amoxicillin, a penicillin variant. If a penicillin variant kills the bacteria, as seems plausible that penicillin cheese might too. Then too, amoxicillin, is found to reduce the risk of gastric cancer. If so, penicillin or penicillin cheese might prove to be a cancer protective. To my knowledge, this has never been studied, but it seems worth considering. The other, standard treatment for heartburn, pantoprazole / Protonix, is known to cause osteoporosis, and increase the risk of cancer.

A culture of Penicillium roqueforti. Most people are not allergic to it.

The blue in blue cheese is Penicillium roqueforti. Most people are not allergic.

Penicillin was discovered by Alexander Fleming, who noticed that a single spore of the mold killed the bacteria near it on a Petrie dish. He tried to produce significant quantities of the drug from the mold with limited success, but was able to halt disease in patients, and was able to interest others who had more skill in large-scale fungus growing. Kids looking for a good science fair project, might consider penicillin growing, penicillin allergy, treatment of stomach ailments using cheese, or anything else related to the drug. Three Swedish journals declared that penicillin was the most important discovery of the last 1000 years. It would be cool if the dilute form, the one available in your supermarket, could be shown to treat heartburn and/or cancer. Another drug you could study is Lysozyme, a chemical found in tears, in saliva, and in human milk, but not in cow milk. Alexander Fleming found that tears killed bacteria, as did penicillin. Lysozyme, the active ingredient of tears, is currently used to treat animals, but not humans.

Robert Buxbaum, November 9, 2017. Since starting work on this essay I’ve been eating blue cheese. It tastes good and seems to cure heartburn. As a personal note: my first science fair project (4th grade) involved growing molds on moistened bread. For an incubator, I used the underside of our home radiator. The location kept my mom from finding the experiment and throwing it out.

magnetic separation of air

As some of you will know, oxygen is paramagnetic, attracted slightly by a magnet. Oxygen’s paramagnetism is due to the two unpaired electrons in every O2 molecule. Oxygen has a triple-bond structure as discussed here (much of the chemistry you were taught is wrong). Virtually every other common gas is diamagnetic, repelled by a magnet. These include nitrogen, water, CO2, and argon — all diamagnetic. As a result, you can do a reasonable job of extracting oxygen from air by the use of a magnet. This is awfully cool, and could make for a good science fair project, if anyone is of a mind.

But first some math, or physics, if you like. To a good approximation the magnetization of a material, M = CH/T where M is magnetization, H is magnetic field strength, C is the Curie constant for the material, and T is absolute temperature.

Ignoring for now, the difference between entropy and internal energy, but thinking only in terms of work derived by lowering a magnet towards a volume of gas, we can say that the work extracted, and thus the decrease in energy of the magnetic gas is ∫∫HdM  = MH/2. At constant temperature and pressure, we can say ∆G = -CH2/2T.

With a neodymium magnet, you should be able to get about 50 Tesla, or 40,000 ampere meters At 20°C, the per-mol, magnetic susceptibility of oxygen is 1.34×10−6  This suggests that the Curie constant is 1.34 x293 = 3.93 ×10−4  At 20°C, this energy difference is 1072 J/mole. = RT ln ß where ß is the concentration ratio between the O2 content of the magnetized and un-magnetized gas.

From the above, we find that, at room temperature, 298K ß = 1.6, and thus that the maximum oxygen concentration you’re likely to get is about 1.6 x 21% = 33%. It’s slightly more than this due to nitrogen’s diamagnetism, but this effect is too small the matter. What does matter is that 33% O2 is a good amount for a variety of medical uses.

I show below my simple design for a magnetic O2 concentrator. The dotted line is a permeable membrane of no selectivity – with a little O2 permeability the design will work better. All you need is a blower or pump. A coffee filter could serve as a membrane.bux magneitc air separator

This design is as simple as the standard membrane-based O2 concentrator – those based on semi-permeable membranes, but this design should require less pressure differential — just enough to overcome the magnet. Less pressure means the blower should be smaller, and less noisy, with less energy use.  I figure this could be really convenient for people who need portable oxygen. With several stages and low temperature operation, this design could have commercial use.

On the theoretical end, an interesting thing I find concerns the effect on the entropy of the magnetic oxygen. (Please ignore this paragraph if you have not learned statistical thermodynamics.) While you might imagine that magnetization decreases entropy, other-things being equal because the molecules are somewhat aligned with the field, temperature and pressure being fixed, I’ve come to realize that entropy is likely higher. A sea of semi-aligned molecules will have a slightly higher heat capacity than nonaligned molecules because the vibrational Cp is higher, other things being equal. Thus, unless I’m wrong, the temperature of the gas will be slightly lower in the magnetic area than in the non-magnetic field area. Temperature and pressure are not the same within the separator as out, by the way; the blower is something of a compressor, though a much less-energy intense one than used for most air separators. Because of the blower, both the magnetic and the non magnetic air will be slightly warmer than in the surround (blower Work = ∆T/Cp). This heat will be mostly lost when the gas leaves the system, that is when it flows to lower pressure, both gas streams will be, essentially at room temperature. Again, this is not the case with the classic membrane-based oxygen concentrators — there the nitrogen-rich stream is notably warm.

Robert E. Buxbaum, October 11, 2017. I find thermodynamics wonderful, both as science and as an analog for society.

How Tesla invented, I think, Tesla coils and wireless chargers.

I think I know how Tesla invented his high frequency devices, and thought I’d show you, while also explaining the operation of some devices that develop from in. Even if I’m wrong in historical terms, at least you should come to understand some of his devices, and something of the invention process. Either can be the start of a great science fair project.

physics drawing of a mass on a spring, left, and of a grounded capacitor and inception coil, right.

The start of Tesla’s invention process, I think, was a visual similarity– I’m guessing he noticed that the physics symbol for a spring was the same as for an electrical, induction coil, as shown at left. A normal person would notice the similarity, and perhaps think about it for a few seconds, get no where, and think of something else. If he or she had a math background — necessary to do most any science — they might look at the relevant equations and notice that they’re different. The equation describing the force of a spring is F = -k x  (I’ll define these letters in the bottom paragraph). The equation describing the voltage in an induction coil is not very similar-looking at first glance, V = L di/dt.  But there is a key similarity that could appeal to some math aficionados: both equations are linear. A linear equation is one where, if you double one side you double the other. Thus, if you double F, you double x, and if you double V, you double dI/dt, and that’s a significant behavior; the equation z= atis not linear, see the difference?

Another linear equation is the key equation for the motion for a mass, Newton’s second law, F = ma = m d2x/dt2. This equation is quite complicated looking, since the latter term is a second-derivative, but it is linear, and a mass is the likely thing for a spring to act upon. Yet another linear equation can be used to relate current to the voltage across a capacitor: V= -1/C ∫idt. At first glance, this equation looks quite different from the others since it involves an integral. But Nicola Tesla did more than a first glance. Perhaps he knew that linear systems tend to show resonance — vibrations at a fixed frequency. Or perhaps that insight came later. 

And Tesla saw something else, I imagine, something even less obvious, except in hindsight. If you take the derivative of the two electrical equations, you get dV/dt = L d2i/dt2, and dV/dt = -1/C i . These equations are the same as for the spring and mass, just replace F and x by dV/dt and i. That the derivative of the integral is the thing itself is something I demonstrate here. At this point it becomes clear that a capacitor-coil system will show the same sort of natural resonance effects as shown by a spring and mass system, or by a child’s swing, or by a bouncy bridge. Tesla would have known, like anyone who’s taken college-level physics, that a small input at the right, resonant frequency will excite such systems to great swings. For a mass and spring,

Basic Tesla coil. A switch set off by magnetization of the iron core insures resonant frequency operation.

Basic Tesla coil. A switch set off by magnetization of the iron core insures resonant frequency operation.

resonant frequency = (1/2π) √k/m,

Children can make a swing go quite high, just by pumping at the right frequency. Similarly, it should be possible to excite a coil-capacitor system to higher and higher voltages if you can find a way to excite long enough at the right frequency. Tesla would have looked for a way to do this with a coil capacitor system, and after a while of trying and thinking, he seems to have found the circuit shown at right, with a spark gap to impress visitors and keep the voltages from getting to far out of hand. The resonant frequency for this system is 1/(2π√LC), an equation form that is similar to the above. The voltage swings should grow until limited by resistance in the wires, or by the radiation of power into space. The fact that significant power is radiated into space will be used as the basis for wireless phone chargers, but more on that later. For now, you might wish to note that power radiation is proportional to dV/dt.

A version of the above excited by AC current. In this version, you achieve resonance by adjusting the coil, capacitor and resistance to match the forcing frequency.

A more -modern version of the above excited by AC current. In this version, you achieve resonance by adjusting the coil, capacitor and resistance to match the forcing frequency.

The device above provides an early, simple way to excite a coil -capacitor system. It’s designed for use with a battery or other DC power source. There’s an electromagnetic switch to provide resonance with any capacitor and coil pair. An alternative, more modern device is shown at left. It  achieves resonance too without the switch through the use of input AC power, but you have to match the AC frequency to the resonant frequency of the coil and capacitor. If wall current is used, 60 cps, the coil and capacitor must be chosen so that  1/(2π√LC) = 60 cps. Both versions are called Tesla coils and either can be set up to produce very large sparks (sparks make for a great science fair project — you need to put a spark gap across the capacitor, or better yet use the coil as the low-voltage part of a transformer.

power receiverAnother use of this circuit is as a transmitter of power into space. The coil becomes the transmission antenna, and you have to set up a similar device as a receiver, see picture at right. The black thing at left of the picture is the capacitor. One has to make sure that the coil-capacitor pair is tuned to the same frequency as the transmitter. One also needs to add a rectifier, the rectifier chosen here is designated 1N4007. This, fairly standard-size rectifier allows you to sip DC power to the battery, without fear that the battery will discharge on every cycle. That’s all the science you need to charge an iPhone without having to plug it in. Designing one of these is a good science fair project, especially if you can improve on the charging distance. Why should you have to put your iPhone right on top of the transmitter battery. Why not allow continuous charging anywhere in your home. Tesla was working on long-distance power transmission till the end of his life. What modifications would that require?

Symbols used above: a = acceleration = d2x/dt2, C= capacitance of the capacitor, dV/dt = the rate of change of voltage with time, F = force, i = current, k = stiffness of the spring, L= inductance of the coil, m = mass of the weight, t= time, V= voltage, x = distance of the mass from its rest point.

Robert Buxbaum, October 2, 2017.

Heraclitus and Parmenides time joke

From Existential Commics

From Existential Comics; Parmenides believed that nothing changed, nor could it.

For those who don’t remember, Heraclitus believed that change was the essence of life, while  Parmenides believed that nothing ever changes. It’s a debate that exists to this day in physics, and also in religion (there is nothing new under the sun, etc.). In science, the view that no real change is possible is founded in Schrödinger’s wave view of quantum mechanics.

Schrödinger's wave equation, time dependent.

Schrödinger’s wave equation, time dependent.

In Schrödinger’s wave description of reality, every object or particle is considered a wave of probability. What appears to us as motion is nothing more than the wave oscillating back and forth in its potential field. Nothing has a position or velocity, quite, only random interactions with other waves, and all of these are reversible. Because of the time reversibility of the equation, long-term, the system is conservative. The wave returns to where it was, and no entropy is created, long-term. Anything that happens will happen again, in reverse. See here for more on Schrödinger waves.

Thermodynamics is in stark contradiction to this quantum view. To thermodynamics, and to common observation, entropy goes ever upward, and nothing is reversible without outside intervention. Things break but don’t fix themselves. It’s this entropy increase that tells you that you are going forward in time. You know that time is going forward if you can, at will, drop an ice-cube into hot tea to produce lukewarm, diluted tea. If you can do the reverse, time is going backward. It’s a problem that besets Dr. Who, but few others.

One way that I’ve seen to get out of the general problem of quantum time is to assume the observed universe is a black hole or some other closed system, and take it as an issue of reference frame. As seen from the outside of a black hole (or a closed system without observation) time stops and nothing changes. Within a black hole or closed system, there is constant observation, and there is time and change. It’s not a great way out of the contradiction, but it’s the best I know of.

Predestination makes a certain physics and religious sense, it just doesn't match personal experience very well.

Predestination makes a certain physics and religious sense, it just doesn’t match personal experience very well.

The religion version of this problem is as follows: God, in most religions, has fore-knowledge. That is, He knows what will happen, and that presumes we have no free will. The problem with that is, without free-will, there can be no fair judgment, no right or wrong. There are a few ways out of this, and these lie behind many of the religious splits of the 1700s. A lot of the humor of Calvin and Hobbes comics comes because Calvin is a Calvinist, convinced of fatalistic predestination; Hobbes believes in free will. Most religions take a position somewhere in-between, but all have their problems.

Applying the black-hole model to God gives the following, alternative answer, one that isn’t very satisfying IMHO, but at least it matches physics. One might assume predestination for a God that is outside the universe — He sees only an unchanging system, while we, inside see time and change and free will. One of the problems with this is it posits a distant creator who cares little for us and sees none of the details. A more positive view of time appears in Dr. Who. For Dr. Who time is fluid, with some fixed points. Here’s my view of Dr. Who’s physics.  Unfortunately, Dr. Who is fiction: attractive, but without basis. Time, as it were, is an issue for the ages.

Robert Buxbaum, Philosophical musings, Friday afternoon, June 30, 2017.

West’s Batman vs Zen Batmen

“Holy kleenex Batman, it was right under our noses and we blew it.” I came of age with Adam West’s Batman on TV and a relatively sane Batman in the comic books. Batman was a sort of urban cowboy: a loner, but law-abiding, honest, and polite – both to the police and to the ordinary citizen. He was good, and he was “nice.” As with future Batmen, no one died, at least not from the Batman.

bat-buddah

More recent Batmen have been not nice, and arguably not good either. They are above the law, trained in eastern monasteries by dark masters of kung fu, with a morality no one quite understands. One could say, quite literally, “He was a dark and stormy knight.”

Well, a few days ago, I found the item at left for sale on e-Bay, a plastic Batman-Buddha, and I started wondering about the meditations that produced Batman, and that Batman expounds on life and crime. It wasn’t pretty. They are not pretty. A quick check from the movie versions suggest the Zen Batman is pretty messed up, something that psychologists have noted.

Here’s a quote from the goofy, Adam West Batman of the 1960s: “Underneath this garb, we’re perfectly ordinary Americans.” Believing yourself to be normal helps improve sanity, and helps you relate to others. Calling yourself an American implies you keep American laws. Here’s another quote: “A reporter’s lot is not easy, making exciting stories out of plain, average, ordinary people like Robin and me.” It’s nice to see that the Adam West Batman feels for the other peoples’ problems, respects their professions, and does not profess to be better than they. By contrast, when a more recent Batman is asked: “What gives you the right? What’s the difference between you and me?” The Dark Knight responds, “I’m not wearing hockey pads.” This is a might-is-right approach, suggesting he’s above the law. The problem: a self-appointed vigilante is a criminal.

Here are some more quotes of the recent, eastern Batmen:
“Sometimes it’s only madness that makes us what we are.”
“That mask — it’s not to hide who I am, but to create what I am.”
“I won’t kill you, but I don’t have to save you.”

These quote are at least as messed up as the hockey pad quote above. It sometimes seems the Joker is the more sane of the two. For example, when Batman explains why he doesn’t kill: “If you kill a killer, the number of killers remains the same.” To which Joker replies: “Unless you kill more than one… but whatever you say, Batsy.”

Not a classic Batmobile, but I like the concept.

Not a classic Batmobile, but I like the concept; if that’s not Adam West, if could be.

The dark, depressive Batmen tend to leave Gotham City in shambles after every intervention, with piles of dead. West’s Batman left the city clean and whole. Given the damage, you wonder why the police call Batman or let him on the streets. Unlike West, the current Batmen never works with the police, quite. And to the extent that Robin appears at all, his relationship with Batman is more frenemy than friend or ward. Batgirl (mostly absent) has changed too. The original Batgirl, if you don’t recall, was Barbara Gordon, Commissioner Gordon’s daughter. She was a positive, female role model, with a supportive, non-sexist parent in Commissioner Gordon (an early version of Kim Possible’s dad). The current Batgirl appears only once, and is presented as the butler’s daughter. Until her appearance that day, you never see her at Wayne Manor, nor did she know quite what her dad was up to.

Here are some West Batman / Robin interactions showing an interest in Robin’s education and well-being:

“Haven’t you noticed how we always escape the vicious ensnarements of our enemies?” Robin: “Yeah, because we’re smarter than they are!”  “I like to think it’s because our hearts are pure.”

“Better put 5 cents in the meter.” Robin: “No policeman’s going to give the Batmobile a ticket.”
“This money goes to building better roads. We all must do our part.”

Robin: “You can’t get away from Batman that easy!” “Easily.” Robin: “Easily.”
“Good grammar is essential, Robin.” Robin: “Thank you.” “You’re welcome.”

Robin/Dick:”What’s so important about Chopin?” “All music is important, Dick. It’s the universal language. One of our best hopes for the eventual realization of the brotherhood of man.” Dick: “Gosh Bruce, yes, you’re right. I’ll practice harder from now on.”

“That’s one trouble with dual identities, Robin. Dual responsibilities.”

“Even crime fighters must eat. And especially you. You’re a growing boy and you need your nutrition.”

“What took you so long, Batgirl?” Batgirl: “Rush hour traffic, plus all the lights were against me. And you wouldn’t want me to speed, would you?” Robin: “Your good driving habits almost cost us our lives!” Batman: “Rules are rules, Robin. But you do have a point.”

And finally: “I think you should acquire a taste for opera, Robin, as one does for poetry and olives.”

Clearly this Batman takes an interest in Robin’s health and education, and in Batgirl’s. Robin is his ward, after all, rather a foster child, and it’s good to seem him treated as a foster child — admittedly with a foster-father whose profession is a odd.

Perhaps the most normal comment from a non-West Batman is this (it appears in many posters): “It’s not who I am underneath, but what I do that defines me.” It’s, more or less, a quote from Karl Jung (famous psychologist) and can serve as a motivator providing pride in one’s art, but job-attachment goes with suicide, e.g. when you lose your job. The far healthier approach is less identification with job; just be proud of doing good and developing virtue. West’s Batman finds Catwoman, a woman with her own moral code, odious, abhorrent, and insegrievious, and says so. The only difference between her and The Joker is the amount of damage done; he should find her insegrievious. Sorry to say, recent, Zen Batmen and Supermen are just as bad. To quote Robin: “Holy strawberries, Batman, we’re in a jam.”

Robert Buxbaum, June 26, 2017. Insegeivious is a made-up word, BTW. If we use it, it could become part of the real vocabulary.

If the wall with Mexico were covered in solar cells

As a good estimate, it will take about 130,000 acres of solar cells to deliver the power of a typical nuclear facility, 26 TWhr/year. Since Donald Trump has proposed covering his wall with Mexico with solar cells, I came to wonder how much power these cells would produce, and how much this wall might cost. Here goes.

Lets assume that Trump’s building a double wall on a strip of land one chain (66 feet) wide, with a 2 lane road between. Many US roads are designed in chain widths, and a typical, 2 lane road is 1/2 chain wide, 33 feet, including its shoulders. I imagine that each wall is slanted 50° as is typical with solar cells, and that each is 15 to 18 feet high for a good mix of power and security. Since there are 10 square chains to an acre, and 80 chains to a mile we find that it would take 16,250 miles of this to produce 26 TWhr/year. The proposed wall is only about 1/10 this long, 1,600 miles or so, so the output will be only about 1/10 as much, 2.6 TWhr/year, or 600 MW per average daylight hour. That’s not insignificant power — similar to a good-size coal plant. If we aim for an attractive wall, we might come to use Elon Musk’s silica-coated solar cells. These cost $5/Watt or $3 Billion total. Other cells are cheaper, but don’t look as nice or seem as durable. Obama’s, Ivanpah solar farm, a project with durability problems, covers half this area, is rated at 370 MW, and cost $2.2 Billion. It’s thus rated to produce slightly over half the power of the wall, at a somewhat higher price, $5.95/Watt.

Elon Musk with his silica solar panels.

Elon Musk with his, silica-coated, solar wall panels. They don’t look half bad and should be durable.

It’s possible that the space devoted to the wall will be wider than 66 feet, or that the length will be less than 1600 miles, or that we will use different cells that cost more or less, but the above provides a good estimate of design, price, and electric output. I see nothing here to object to, politically or scientifically. And, if we sell Mexico the electricity at 11¢/kWhr, we’ll be repaid $286 M/year, and after 12 years or so, Republicans will be able to say that Mexico paid for the wall. And the wall is likely to look better than the Ivanpah site, or a 20-year-old wind farm.

As a few more design thoughts, I imagine an 8 foot, chain-link fence on the Mexican side of the wall, and imagine that many of the lower solar shingles will be replaced by glass so drivers will be able to see the scenery. I’ve posited that secure borders make a country. Without them, you’re a tribal hoard. I’ve also argued that there is a pollution advantage to controlling imports, and an economic advantage as well, at least for some. For comparison, recent measurement of the Great Wall of China shows it to be 13,170 miles long, 8 times the length of Trump’s wall with China.

Dr. Robert E. Buxbaum, June 14, 2017.

A clever, sorption-based, hydrogen pump

Hydrogen-power ed fuel cells provide a lot of advantages over batteries, e.g. for drones and extended range vehicles, but part of the challenge is compressing the hydrogen. On solution I’d proposed is a larger version of this steam-powered compressor, another is a membrane reactor hydrogen generator, and a few weeks ago, I wrote about an other clever innovative solutions: an electrochemical hydrogen pump. It was a fuel cell operating backwards, pumping was very efficient and compact, but the pressure was borne by the fuel cell membranes, so the pump is only suitable at low pressure differentials. I’d now like to describe a different, very clever hydrogen pump, one that operates by metallic hydride sorption and provides very high pressure.

Hydride sorption -desorption pressures vs temperature.

Hydride sorption -desorption pressures vs temperature, from Dhinesh et al.

The basic metal hydride reaction is M + nH2 <–> MH2n. Where M is a metal or metallic alloy. While most metals will undergo this reaction at some appropriate temperature and pressure, the materials of interest are exothermic hydrides that undergo a nearly stoichiometric absorption or desorption reaction at temperatures near 1 atm, temperatures near room temperature. The plot at right presents the plateau pressure for hydrogen absorption/ desorption in several, common metal hydrides. The slope is proportionals to the heat of sorption. There is a red box shown for the candidates that sorb or desorb between 1 and 10 atmospheres and 25 and 100 °C. Sorbants whose lines pass through that box are good candidates for pump use. The ones with a high slope (high heat of sorption) in particular, if you want a convenient source of very high pressure.

To me, NaAlH4 is among the best of the materials, and certainly serves as a good example for how the pump works. The basic reaction, in this case is:

NaAl + 2H2 <–> NaAlH4

The line for this reaction crosses the 1 atm red line at about 30°C suggesting that each mol of NaAl material will absorb 2 mols of hydrogen at 1 am and normal room temperatures: 20-30°C. Assume the pump contains 100 g of NaAl (2.0 mols). We can expect it will 4 mols of hydrogen gas, about 90 liters at this temperature. If this material in now heated to 250°C, it will desorb most of the hydrogen (80% perhaps, 72 liters) at 100 atm, or 1500 psi. This is a remarkably high pressure boost; 1500 psi hydrogen is suitable for use filling the high pressure tank of a hydrogen-based, fuel cell car.

But there is a problem: it will take 2-3 hours to cycle the sober; the absorb hydrogen at low pressure, heat, desorb and cycle back to low temperature. If you only can pump 72 liters in 2-3 hours, this will not be an effective pump for automobiles. Even with several cells operating in parallel, it will be hard to fill the fuel tank of a fuel-cell car. The output is enough for electric generators, or for the small gas tank of a fuel cell drone, or for augmenting the mpg of gasoline automobiles. If one is interested in these materials, my company, REB Research will supply them in research quantities.

Properties of Metal Hydride materials; Dhanesh Chandra,* Wen-Ming Chien and Anjali Talekar, Material Matters, Volume 6 Article 2

Properties of Metal Hydride materials; Dhanesh Chandra,* Wen-Ming Chien and Anjali Talekar, Material Matters, Volume 6 Article 2

At this point, I can imagine you saying that there is a simple way to make up for the low output of a pump with 100g of sorbent: use more, perhaps 10 kg distributed over 100 cells. The alloys don’t cost much in bulk, see chart above (they’re a lot more expensive in small quantities). With 100 times more sorbent, you’ll pump 100 times faster, enough for a fairly large hydrogen generator, like this one from REB. This will work, but you don’t get economies of scale. With standard, mechanical pumps give you a decent economy of scale — it costs 3-4 times as much for each 10 times increase in output. For this reason, the hydride sorption pump, though clever appears to be destined for low volume applications. Though low volume might involve hundreds of kg of sorbent, at some larger value, you’re going to want to use a mechanical pump.

Other uses of these materials include hydrogen storageremoval of hydrogen from a volume, e.g. so it does not mess up electronics, or for vacuum pumping from a futon reactor. I have sold niobium screws for hydrogen sorption in electronic packages, and my company provides chemical sorbers for hydrogen removal from air. For more of our products, visit www.rebresearch.com/catalog.html

Robert Buxbaum, May 26, 2017. 

Future airplane catapults may not be electric

President Trump got into Hot Water with the Navy this week for his suggestion that they should go “back to god-damn steam” for their airplane catapults as a cure for cost over-runs and delays with the Navy’s aircraft carriers. The Navy had chosen to go to a more modern catapult called EMALS (electromagnetic, aircraft launch system) based on a traveling coil and electromagnetic pulses. This EMAL system has cost $5 Billion in cost over-runs, has added 3 years to the program, and still doesn’t work well. In response to the president’s suggestion (explosion), the Navy did what the rest of Washington has done: blame Trump’s ignorance, e.g. here, in the Navy Times. Still, for what it’s worth, I think Trump’s idea has merit, especially if I can modify it a bit to suggest high pressure air (pneumatics) instead of high pressure steam.


Tests of the navy EMALS, notice that some launches go further than others; the problem is electronics, supposedly.

If you want to launch a 50,000 lb jet fighter at 5 g acceleration, you need to apply 250,000 lbs of force uniformly throughout the launch. For pneumatics, all that takes is 250 psi steam or air, and a 1000 square inch piston, about 3 feet in diameter. This is a very modest pressure and a quite modest size piston. A 50,000 lb object accelerated this way, will reach launch speed (130 mph) in 1.2 seconds. It’s very hard to get such fast or uniform acceleration with an electromagnetic coil since the motion of the coil always produces a back voltage. The electromagnetic pulses can be adjusted to counter this, but it’s not all that easy, as the Navy tests show. You have to know the speed and position of the airplane precisely to get it right, and have to adjust the firing of the pushing coils accordingly. There is no guarantee of smooth acceleration like you get with a piston, and the EMALS control circuit will always be vulnerable to electromagnetic and cyber attack. As things stand, the control system is thought to be the problem.

A piston is invulnerable to EM and cyber attack since, if worse comes to worse, the valves can be operated manually, as was done with steam-catapults throughout WWII. And pistons are very robust — far more robust than solenoid coils — because they are far less complex. As much force as you put on the plane, has to be put on the coil or piston. Thus, for 5 g acceleration, the coil or piston has to experience 250,000 lbs of horizontal force. That’s 3 million Newtons for those who like SI units (here’s a joke about SI units). A solid piston will have no problem withstanding 250,000 lbs for years. Piston steamships from the 50s are still in operation. Coils are far more delicate, and the life-span is likely to be short, at least for current designs. 

The reason I suggest compressed air, pneumatics, instead of steam is that air is not as hot and corrosive as steam. Also an air compressor can be located close to the flight deck, connected to the power center by electric wires. Steam requires long runs of steam pipes, a more difficult proposition. As a possible design, one could use a multi-stage, inter-cooled air compressor connected to a ballast tank, perhaps 5 feet in diameter x 100 feet long to guarantee uniform pressure. The ballast tank would provide the uniform pressure while allowing the use of a relatively small compressor, drawing less power than the EMALS. Those who’ve had freshman physics will be able to show that 5 g acceleration will get the plane to 130 mph in only 125 feet of runway. This is far less runway than the EMALS requires. For lighter planes or greater efficiency, one could shut off the input air before 120 feet and allow the remainder of the air to expand for 200 feet of the piston.

The same pistons could be used for capturing an airplane. It could start at 250 psi, dead-ended to the cylinder top. The captured airplane would push air back into the ballast tank, or the valve could be closed allowing pressure to build. Operated that way, the cylinder could stop the plane in 60 feet. You can’t do that with an EMAL. I should also mention that the efficiency of the piston catapult can be near 100%, but the efficiency of the EMALS will be near zero at the beginning of acceleration. Low efficiency at low speed is a problem found in all electromagnetic actuators: lots of electromagnetic power is needed to get things moving, but the output work,  ∫F dx, is near zero at low velocity. With EM, efficiency is high at only at one speed determined by the size of the moving coil; with pistons it’s high at all speeds. I suggest the Navy keep their EMALS, but only as a secondary system, perhaps used to launch drones until they get sea experience and demonstrate a real advantage over pneumatics.

Robert Buxbaum, May 19, 2017. The USS Princeton was the fanciest ship in the US fleet, with super high-tech cannons. When they mis-fired, it killed most of the cabinet of President Tyler. Slow and steady wins the arms race.

summer science: a toad or turtle terrarium

Here’s an easy summer science project, one I just made: a toad habitat. It’s similar to a turtle terrarium (I’ll show how to make that too). I’d made the turtle terrarium ten years ago for my 8-year-old daughter (here’s some advice I gave her on her 16th birthday).

For this project you’ll need: a large flower-pot, fish tank, or plastic clothes bin. You’ll need some dirt for the bottom, and a small plastic bin, jar, or Tupperware for toad (or turtle) transport. You’ll also need a smallish plastic dish or tub (~6″ by 1″ deep) to serve as a lake in the toad habitat. For the turtle version you don’t need the lake, but will need a rock or brick. And that’s all, besides your toad or turtle. The easy way to get your pet is to find one by a river. If that doesn’t work, go to a pet-store and get one that is native to your area of the country. Local fauna (fauna= animals) will be heartier and cheeper, and will allow you to keep your terrarium outside if you choose. Keeping my toad outside means he (or she) can catch bugs without me having to buy them all the time. It also seems more “natural” to study animals in their natural temperature cycles. I caught my toads three weeks ago, in mid April after the last frost — I plan to set one free in the fall –the other I gave away.

For my toad habitat, I used a large, old flower-pot that I had sitting outside my house. It is 21″ across at the top and 18″ tall. I put 6″ of dirt in it. six inches is deep enough for the toad to dig in, and it left 12″ of airspace — I don’t think the toad can jump a foot in the air to get out. I made sure the soil was muddy, and had worms. Toads seem to like mud and they eat worms. Toads drink water through their skin, and may not like chlorinated water. I also added some leaves and a small flower pot for shade, and put in some bits of fruit and some bugs, and planted a single plant. My hope was to develop a colony of ants and bugs for the toads to eat. I buried my plastic water bowl, my mini-lake, slightly below ground level with the top 1/2″ above. I then went off with my toad transport to catch a toad or three in the wetlands areas near me (I live in Oak Park, MI).

Some good toad hunting spots in Keego Harbor MI

Some good toad hunting spots in Keego Harbor MI

The first place I went was the banks of the Rouge river near Lawrence Tech. Sorry to say, the area showed no signs of toads, frogs, turtles, or even fish. There was an illegally connected drain, though — not good. I plan to bring the illegal grain up with the “Friends of the Rouge” (good group). I then went to an oak swamp on the Rouge. The area was beautiful and scenic, but there was no oxygen in the water and so no fish or toads; oxygen is important for the health of a river; without it, you’ve got  a swamp. I finally hit pay-dirt in Keego Harbor, MI, see map, a rural community 10 miles away from my home. In Keego harbor I found American toads aplenty: jumping all over, and big, hollow toad-mounds by the river. The locals were friendly too. Toad catching is a good conversation starter. I put two toads in my bin with some lake water and took them home to the terrarium, see movie.

My neighbor got the other toad and put him/her in a fish-tank terrarium in his bathroom. His terrarium has a screen on top with holes small enough to keep the toad and his food from escaping. He is feeding his toad meal worms, but I don’t have a movie. Apparently they like it.

I left my pot outside, as I mentioned, so my toad can catch insects that fly by, and spiders. My toad seems to like spiders. I also tried putting in wax-worms ($1 for 12). The good thing about wax worms is they move slowly, unlike crickets (crickets cost more and can jump out). My toad ate all 12 worms in 2 days. I have not put a lid on my pot yet. Perhaps that’s a mistake. My colony of bugs seems to be breeding fast enough to make up for escapees and eating, but perhaps that’s because the toad doesn’t eat many. A fellow at the pet store sold me ten small crickets for $3.00, but I don’t think the toad ate any before they escaped. See what your toad eats; it’s science. I think my toad is a female: it doesn’t vibrate or croak at night. Male toads vibrates and croak. Toads can be gender fluid, though; somethings two “female” toads will breed. Your job is to watch, enjoy, and perhaps learn something.

The main difference between this project, and the turtle terrarium I’d made is that the turtle terrarium was mostly water, with a brick, and this is mostly mud with a lake. I made the turtle terrarium in a laundry bin, a bigger environment, and flooded it except for the brick. I bought the turtles (a red-ears and a snapping) and fed it chicken bits and dandelion leaves. As with this terrarium, I kept the turtles outside through the spring, summer, and fall, but I brought the turtles in the winter. They lasted that way for about 8 years. Toads only live for 2-3 years, and mime may be a year or two old already. I won’t be too surprised if it croaks on my watch. For now, she seems safe and hoppy.

Robert Buxbaum, May 3, 2017. Here are some other science fair projects, chemical, and biological.

A very clever hydrogen pump

I’d like to describe a most clever hydrogen pump. I didn’t invent it, but it’s awfully cool. I did try to buy one from “H2 Pump,” a company that is now defunct, and I tried to make one. Perhaps I’ll try again. Here is a diagram.

Electrolytic membrane H2 pump

Electrolytic membrane H2 pump

This pump works as the reverse of of a PEM fuel cell. Hydrogen gas is on both sides of a platinum-coated, proton-conducting membrane — a fuel cell membrane. As in a PEM fuel cell, the platinum splits the hydrogen molecules into H atoms. An electrode removes electrons to form H+ ions on one side of the membrane; the electrons are on the other side of the membrane (the membrane itself is chosen to not conduct electricity). The difference from the fuel cell is that, for the pump you apply a energy (voltage) to drive hydrogen across the membrane, to a higher pressure side; in a fuel cell, the hydrogen goes on its own to form water, and you extract electric energy.

As shown, the design is amazingly simple and efficient. There are no moving parts except for the hydrogen itself. Not only do you pump hydrogen, but you can purify it as well, as most impurities (nitrogen, CO2) will not go through the membrane. Water does permeate the membrane, but for many applications, this isn’t a major impurity. The amount of hydrogen transferred per plate, per Amp-second of current is given by Faraday’s law, an equation that also shows up in my discussion of electrolysis, and of electroplating,

C= zFn.

Here, C is the current in Amp-seconds, z is the number or electrons transferred per molecule, in this case 2, F is Faraday’s constant, 96,800, n is the number of mols transferred.  If only one plate is used, you need 96,800 Amp-seconds per gram of hydrogen, 53.8 Amp hours per mol. Most membranes can operate at well at 1.5 Amp per cm2, suggesting that a 1.1 square-foot membrane (1000 cm2) will move about 1 mol per minute, 22.4 slpm. To reduce the current requirement, though not the membrane area requirement, one typically stacks the membranes. A 100 membrane stack would take 16.1 Amps to pump 22.4 slpm — a very manageable current.

The amount of energy needed per mol is related to the pressure difference via the difference in Gibbs energy, ∆G, at the relevant temperature.

Energy needed per mol is, ideally = ∆G = RT ln Pu/Pd.

where R is the gas constant, 8.34 Joules per mol, T is the absolute temperature, Kelvins (298 for a room temperature process), ln is the natural log, and Pu/Pd is the ratio of the upstream and downstream pressure. We find that, to compress 2 grams of hydrogen (one mol or 22.4 liters) to 100 atm (1500 psi) from 1 atm you need only 11400 Watt seconds of energy (8.34 x 298 x 4.61= 11,400). This is .00317 kW-hrs. This energy costs only 0.03¢ at current electric prices, by far the cheapest power requirement to pump this much hydrogen that I know of. The pump is surprisingly compact and simple, and you get purification of the hydrogen too. What could possibly go wrong? How could the H2 pump company fail?

One thing that I noticed went wrong when I tried building one of these was leakage at the seals. I found it uncommonly hard to make seals that held even 20 psi. I was using 4″ x 4″ membranes so 20 psi was the equivalent of 320 pounds of force. If I were to get 200 psi, there would have been 3200 lbs of force. I could never get the seals to stay put at anything more than 20 psi.

Another problem was the membranes themselves. The membranes I bought were not very strong. I used a wire-mesh backing, and a layer of steel behind that. I figured I could reach maybe 200 psi with this design, but didn’t get there. These low pressures limit the range of pump applications. For many applications,  you’d want 150-200 psi. Still, it’s an awfully cool pump,

Robert E. Buxbaum, February 17, 2017. My company, REB Research, makes hydrogen generators and purifiers. I’ve previously pointed out that hydrogen fuel cell cars have some dramatic advantages over pure battery cars.