Fish Poisons for Anesthesia

I stumbled across a bizzarre video in my recommended videos feed on YouTube yesterday that shows a goldfish getting surgery on his head growth blocking his vision (Note: this video is not for people who are squeamish, although there is no blood):

The video was an interesting find overall, simply because it had no actual correlation with any videos in my watch history. I haven’t watched videos on fish or surgery, so to be recommended with a video featuring both was unusual. To be honest, while I was engrossed by the goldfish surgery, what made me keep watching was the maker, Colum’s Aquaponics’, use of clove oil to sedate the fish.

This brought two thoughts to my mind. The first was that clove oil has been recommended by traditional herbal medicine for toothaches. Typical application may have entailed chewing a clove or putting it between the gums and cheek next to the painful area. According to Colgate, clove oil has also been on the rise as a form of alternative medicine for oral pain in recent times as well [1]. Clove oil contains the chemical eugenol that is responsible for its anesthetic properties and is also used in refined form for modern dental applications [2]. Eugenol is a substituted guaiacol, making it related chemically to other plant compounds like vanillin though with very different effects [3]. Seemingly unrelated, this link between analgesia in humans and anesthesia in fish makes the use of clove oil to numb a surgery appear plausible to me, though a stretch.

Fig. 1: Eugenol, a fish anesthetic found in clove oil (Wikimedia)

The second was that in ancient Hawai’i, there was a method of fishing that involved lacing a stream or tide pool with a plant tincture to sedate the fish and cause them to float to the surface. The plants used included ‘ahuhu (Tephrosia purpurea) containing the fish toxin tephrosin and ‘akia (Wikstroemia oahuensis) [4(published in 1921, source must be treated as a work of its time),5]. Looking at some pictures of ‘akia on the internet, I immediately recognized the plant to have grown all over my elementary school campus back home. That’s pretty weird to think about, but it also makes me feel like I’ve missed out on an opportunity for some fun experiments.  

Fig. 2: 'Akia plant leaves and flowers ('Imiloa)

Hawai’i is not the only place to have practiced poison fishing, though in general the practice is considered destructive and paralleled to other wide-effect fishing methods like blast-fishing. And of course, the limited reach of poison fishing would be no match for the current global demand for fish. Yet while this fishing technique has been passed by in modern times, the plants and chemicals once used for fishing may now find new applications, namely in fish anesthesia for aquatic veterinary care.

I hope you enjoyed this short blurb on the interesting topic of fish anesthesia, and be sure to leave a comment and share your thoughts on the post. These past few weeks have been busy in school, and the first wave of midterms (UPenn doesn’t understand the term “midterm”) has started to hit. I do believe I will be able to post at least every other week, however, as seems to be my current posting schedule, so be sure to look out for future posts. As always, thanks for reading!  

An Analytical Approach to Pamphlet Folding

Most of us can say we’ve endured the frustration of folding letters or pamphlets, trying as much as possible to align the corners for a straight fold only to have them wiggle freely as the crease is made. And in an office like the one I work at, half-folding pamphlets is a fairly procedural task. Whenever this work is entrusted with me, I like to build a rig like the one shown below to minimize the chances of me pulling my hair out.

Fig. 1: Makeshift pamphlet folding rig

It's easy to arrive at a tool like this based on common-sense, but we can also take a more analytical approach as to why a simple 90° corner can make paper folding so much easier. We need to start with a surface-level premise about the universe we live in; as far as we can tell, our universe is comprised of three spatial dimensions, mathematically attributed as x, y and z and experienced as length, width and height, and one temporal dimension. The temporal dimension and the other however many must exist according to string theory or what have you aren’t as important in this task as the three spatial dimensions with which we interact on a daily basis. An unfolded pamphlet can move freely through these three spatial dimensions, as throwing them out the office window will demonstrate when they flutter down to the street below. But while they are sitting on my desk waiting to be folded, they don’t budge. This is because the desk on which they sit is applying an upward force on the pamphlet stack, counteracting gravity and preventing them from moving towards the center of the earth. Balancing forces like this is the foundation of mechanics and is the way that the following discussion manifests in the physical world we live in.

So what else is there to consider? Well, three free dimensions can also be referred to as three “degrees of freedom,” a fancy term that just says a variable can change as necessary. The more degrees of freedom that exist, the harder it is to pinpoint the position of an object that moves freely, like the corner of a pamphlet. What’s also cool about the three spatial dimensions is that even though by default we orient the basis of the defined dimensions to align one direction with gravity because this simplifies calculations, linear algebra tells us that the basis vectors x, y and z are easily translatable to different positions. Now let’s take my desk, oriented by default in the x-y plane, and translate it so that it now exists in the y-z plane. This is kind of similar to if I were floating with my body parallel to the desk, which would make more sense if I were in outer space since there is not as strong a default frame of reference when gravity is not apparent. What we see now is that my desk has somehow become like a wall! Amazing! This tells us that floors, walls and ceilings are not very dissimilar from each other, the common theme being that if I beamed a ball in a closed room, it would bounce off of all surfaces because its free motion in the three spatial directions has been truncated.

Fig. 2: Designation of three spatial dimensions adjusted to rig

Let’s return to the pamphlet folding rig. The rig is comprised simply of three walls: the desk and two others constructed from a box and a paper tray. Additionally, while folding gravity acts on the pamphlets to further constrict movement in the common z dimension, or up, while keeping the dimension still partially accessible so as to get the right side of the pamphlet over the left. My hands as well work to apply force to keep the pamphlet to the left against the box and away from me towards the paper tray while creasing, limiting the x and y dimensions. If we look at the two corners of the pamphlet tucked into the rig while half-folding, all three degrees of freedom have been collapsed, the pamphlets sandwiched between one surface and my hands along all three axes. Not only are these corners restrained, but the geometry of the pamphlet then guarantees that all other corners of the pamphlet should be aligned as well. So while in practice errors on my part and in my shabby rig’s construction limit the effectiveness of this folding method, in theory restricting the three degrees of spatial freedom of the pamphlet should produce a perfect fold every time without the frustration of any dancing corners.

Fig. 3: The final folded pamphlets

While some people may not appreciate such a lengthy analysis of as simple a contraption as a corner for folding pamphlets, I think really delving into why something so common-sense works from a physics standpoint demonstrates how approaching the world from an analytical perspective provides insights that can help everyday people live better lives. I hope you enjoyed this article, and if you have any feedback or questions, leave me a comment below. I love hearing from you guys. Thanks!

Iodine Salt to Treat Radiation?

Fig. 1: Next, movie cover (derricklferguson)

Over winter break I watched the movie Next starring Nicolas Cage with my dad. In the movie, the FBI was able to link a dead woman knifed in her room to a Russian nuclear attack plan because of a few potassium iodide (KI) pills found at the crime scene. The star FBI policewoman (who is also President Coin from the Hunger Games movies!) was quick in realizing that the only reason someone would take potassium iodide pills was to combat radiation poisoning. Before this movie, I had never heard of KI being used for this purpose, and expectedly I was skeptical. Before you judge me, imagine if someone had told you that a sugar pill could prevent you from dying of stomach cancer. That is the same magnitude of ridiculousness that I felt the whole KI pill thing had to be.

But, I was wrong of course. KI supplements are an established treatment for preventing thyroid cancer, one of the biggest health impacts observed after the Chernobyl meltdown [1]. So how is it that something so simple as a salt pill, because that’s what it is, can prevent one of the most odious conditions of modern times caused by a technology that took humans thousands of years to create? Turns out it’s by inhibition [2]. KI pills for thyroid cancer prevention aren’t made up of just any iodine; they are made of the ¹²⁷I isotope, which is iodine’s only stable form [3]. Ingested iodine is taken up by the thyroid gland, and if the iodine is of a radioactive isotope the subsequently produced radiation can cause thyroid cancer. KI pills work by dumping stable ¹²⁷I into the person’s blood stream, flooding the thyroid and reducing uptake of other radioactive iodine isotopes. KI pills only work in preventing thyroid cancer caused by radioactive iodine exposure, however, not other conditions caused by general radiation exposure.

Fig. 2: ²³⁵U fission product properties (Hochel, R. C.)

So, a few other questions obviously arise from this talk of iodide pills, one of which being where do the radioactive iodine isotopes come from in the context of nuclear fission? Fission of heavy atoms results in atoms of lighter weight and free neutrons that propagate the nuclear fission reaction. Some of the fission products of ²³⁵U are various iodine isotopes, including ¹³⁵I (6.33% yield), ¹³¹I (2.83% yield) and ¹²⁹I (0.9% yield) [4]. These are clearly not the main fission products of ²³⁵U, but they can still accumulate in contaminated environments, especially where large-scale nuclear fission reactions were involved such as nuclear meltdowns and atomic bomb testing sites. Another question to answer is how do the radioactive isotopes end up being ingested by people in contaminated regions? Scientists at Dartmouth, New Hampshire were able to measure increases in ¹³⁵I concentration, an indicator also of the presence of undetectable ¹²⁹I, on land but especially in local streams a year after the 2011 Fukushima meltdown in Japan [5]. They cited the increase as due to nuclear fallout from the Fukushima incident that blew across the continent and deposited itself in groundwater sources. This implies that the radioactive iodine isotopes can be both airborne and waterborne. If everything is coated in radioactive iodine, ingestion is believably imminent. To bring us full circle, there was also a run on KI pills in 2011 on the American West Coast due to fears of radioactive iodine finding its way into homes and food supplies there as well [6]. It’s funny how analyzing a simple movie premise can take us all the way to a not-so-late nuclear disaster.

Yesterday was the first day of classes, and soon enough school will be back in full swing. I've based my schedule this semester off of a google calendar with the idea that better organization will make hectic school life just a bit easier, so we'll see how that goes. My course load is two materials science classes, one materials science lab, orgo 2 and an anthropology class on modern culture. I'm hopeful that this semester will go better than last, and I'll keep you guys updated on what goes on. If you like this article or have ideas for another, be sure to leave me a comment below. Thanks for reading!

Can the Earth's Magnetic Field Support a Space Railgun?

Fig. 1: Railgun diagram (HowStuffWorks)

In physics class, you’ve probably learned about railguns and how they use magnetic fields and current to generate a propulsive force. And if you’re anything like me, you’ve probably wondered if we can launch a person or spaceship with one, because why not? What would be even cooler is if we could do it with the earth’s ambient magnetic field. Well, let’s test this idea a little bit.

We know that the force generated by a magnetic field on a charged particle is

1.       F = d/dt(L)q x B = qv x B (L is displacement, q is charge, B is magnetic field, v is velocity)

An equivalent statement more applicable to railguns is 

2.       F = d/dt(q)L x B = IL x B          (I is current)

This change of derivative position is acceptable because it represents a change in reference frame, the displacement derivative in the frame of the charged particle and the charge derivative from a fixed external frame of reference, watching the charges flow by. In the setup of a railgun, B and I are orthogonal and the resultant vector of the cross product is in the direction of propulsion. Solving the cross product yields

3.       F = ILB 

We also know the induced current through the railgun circuit to be related to the generated emf, 

4.       Ɛ = - d/dt(Φ_B) = - d/dt(BA) = - Bd/dt(A)          (Φ_B is magnetic flux, A is area)

By geometric analysis, we know the change in area to be the fixed base length/bar length times the change in height, or

5.       d/dt(A) = L d/dt(h) = Lv          (h is height)

The full expression is

6.       Ɛ = IR = - BLv

7.       I = - BLv/R

Appending our force equation to account for induced current that works against the initial current, we get

8.       F = (I - BLv/R)LB = LBI – (L²B²/R)v

This equation is useful because by setting the magnetic force to zero we can solve for a terminal velocity,

9.       v = IR/LB

This is no good! If we’re to launch someone high into the sky, we need a constant force to produce a constant acceleration to exceed that of gravity. So what if we keep a constant effective current to counteract the current induced by propulsion? Looking at equation 8, we see that this is possible if we establish current as a time-dependent function given by

      10.   I(t) = I₀ + BLv/R                                                 (R is resistance)

      11.   I(t) = I₀ + BL(at)/R = I₀ + BL(Ft/m)/R               (from kinematic equations v=at and F=ma)

The F term here should be substituted with the constant force we predict to be generated by the current adjustment

12.   F = I₀LB

Substitution and regrouping produces

13.   I(t) = I₀(1 + (B²L²/Rm)t)          (m is mass)

This equation can be verified by substitution into equation 8. Now that our force is constant, let’s calculate what current would accelerate the average person [1] on a weightless conductive beam unaffected by air drag 1m in length enough to counteract gravity (a pretty low bar for testing viability of concept). Since the magnetic field generated by the circuit would probably diminish too close to the walls of a 1m launcher, an external field is necessary. Let’s try using the upper end of the earth’s magnetic field strength range [2].

                     14.   F = mg = I₀LB

                     15.   I₀ = mg/LB = (62kg)(9.8m/s²)/((1m)(65x10^-6 N/Am)) = 9.3x10⁶ A

That’s a lot of current, but perhaps possible? Adjusting for a spaceship weighing 1,000 times the average person 10m wide with an acceleration of 1m/s² [3], we get a figure on the scale of 1x10⁷ A. In 2014, the CERN Superconductors team was able to pass 20x10³ A through an MgB₂ superconducting wire, a world record at the time [4]. This record value is clearly magnitudes less than even the current necessary to lift a single person, let alone a spaceship. Looks like the earth's ambient field is a no-go. But! If the person were in a magnetic field of an achievable 1T even, then with currently achievable currents it should be possible to throw them at least into the sky if not into space. Hooray for space railguns!

If you liked this post or have any ideas for another, let me know by leaving a comment. Thanks for reading!

A Prediction of Marine Plastic Debris Growth

Although it is common knowledge that plastic waste finds its way to the ocean en masse as evidenced  regions of high marine debris such as the great Pacific Plastic Gyres, there are few statistics that put exactly how much plastic enters the oceans into frame. A study published in February of this year looked to do exactly that, estimating that in 2010 an approximate 4.8-12.7 million metric tons of plastic entered waterways over 192 coastal countries that year.

This estimate was generated by taking into account local statistics for waste generation per capita and population growth trends to predict the amount of trash that shoreline countries produced within a 50 km region from the coast. An approximation of 11% plastics content for the produced waste was then applied, and transformations were imposed to convert total plastic waste to mismanaged plastic waste and finally to marine plastic debris. The authors of the study state that their estimate is one to three magnitudes higher than estimates made based upon gyre plastic content and justify this by reasoning these other estimates to only account for buoyant plastics. However, this large discrepancy between the predicted value and others brings the accuracy of the estimation into question. In the materials and methods section, the described transformation from mismanaged waste to marine waste was arbitrarily set at a percentage set of 15%, 25% and 40%, values that were deemed conservative based on a described estimation for the San Francisco Bay area.

Fig. 1: Projected plastic marine debris entering the ocean from 2010 on (Article in Discussion)

The study also estimated based on the same model that a cumulative 100-250 million metric tons of plastic waste would enter the ocean by the year 2025. This range was based on an extrapolation of population growth and plastic waste content growth rates in the past, and for this reason may be brought under scrutiny considering emerging efforts to stifle plastic waste pollution. However, the numbers produced in this study still has shock value, which lends them importance. Knowing that these enormous numbers are estimated based on current and past trends should in itself be a wake-up call since the implication is that our current lifestyle is unsustainable and resonates into the foreseeable future. In other words, this study is a call to action for all countries to set measures in place that will curb marine pollution currently and protect our future oceans.

The study goes into further detail about the extent to which efforts to reduce plastic waste in the near future will affect the amount of plastic trash that ends up in the world oceans and also gives a more detailed breakdown of the contributions of each country to marine plastic debris. It is definitely worth checking out and can be found in full text here. Thanks!

Insights into Early Hominin Communication

A recent article published in Science looked to the skull shapes of early hominins, a group comprised of our now-extinct closest ancestors and ourselves, as a prediction of what sort of auditory sensitivity they were capable of, with interesting results. The shape and size of the auditory apparatus in animals affects the intensity with which each frequency register is perceived. In the study, the inner ears of early hominins, chimpanzees and modern humans were scrutinized, and the modeled ear parts of each were used to make predictions regarding the frequencies that were more easily heard, and the results were plotted as shown below. 

Fig. 1: Sensitivity to sound over a range of frequencies (article in discussion)

In the figure, the y-axis corresponds to the log of the ratio of sound power to reach the cochlea, Pcochlea, versus that of the sound source, Po, as a measure of the perceived sound intensity. The researchers conducting the study were able to show that the early hominins had a higher sensitivity to sound at around 3kHz than both chimpanzees and modern humans and generally higher sensitivity to lower frequency sounds as well, showing a decrease in sensitivity at higher frequencies that is more similar in trend to the hearing curve of chimpanzees than it is to humans. Modern humans, in contrast to the others, have a similar sensitivity curve at lower frequencies but extend hearing to higher frequency sound, dropping off near 4kHz frequency. In analyzing this finding, the researchers came to the conclusion that the adaption to a wider frequency range of hearing in modern humans was imperative for the development of consonants in human language. The researchers considered that the phonemes t, k, f and s in particular are associated with higher frequency sound and that the ability to perceive sound over a wide range of frequencies makes these sounds more distinct from each other. Since early hominins were incapable of perceiving the upper frequency range that modern humans can, the researchers postulate that communication between the early hominins would have been vowel-intensive. They make a point, however, of stating that this finding does not confirm any information about the extent to which early hominin language was used or developed; early hominins may have used a “low-fidelity social transmission” form of communication similar to that of modern chimpanzees. Nevertheless, the skulls of these early hominins have given us another insight into what life was like for some of our earliest ancestors.

The complete article on the differences in sound perception described above is available here. While the article is heavy on jargon, the results and discussion sections can be understood without fully understanding the early talk of ear anatomical differences. 

Also, please let me know your thoughts on this trial article in the comments. I am trying something new with the posts here, providing brief summaries of emerging science rather than explanatory articles of everyday phenomena. Feedback helps me decide what content I post. Thanks!

Boiling Water at High Altitudes: A Representation of American Scientific Literacy

A recent survey by the Pew Research Center found that Americans are more likely to answer correctly questions related to basic science concepts than to scientific understanding [1]. Among the bank of questions, ones such as which layer of the earth is hottest and whether uranium is used in nuclear energy were answered correctly more often than ones such as whether the amplitude of sound waves causes its loudness. The question answered incorrectly most often was whether water at higher altitudes boils at lower temperatures with only 34% of respondents knowing that, indeed, it does.

Fig. 1: Results of Pew Research Center survey (Pew Research Center, same as reference 1)

Public scientific literacy is an important goal to work towards for developed countries. As Cary Funk and Sara Kehaulani Goo of the Pew Research Center posit, the ability to understand scientific concepts is crucial to people being well enough informed about current issues such as GMOs and the energy crisis to make educated decisions in the polls. Scientific literacy also makes daily life easier by finding more efficient solutions to everyday problems.

As a small step towards improving scientific understanding, let us discuss why it is easier to boil water at higher altitudes.

Liquid water and water vapor exist in a sort of equilibrium. There are a number of factors that can shift this equilibrium, but one we interact with daily is temperature. Say you spill a glass of water. Of course, a large spill would require immediate attention, but if only a thimbleful of water was spilt, some would be inclined to let it evaporate. Evaporation involves two main processes at play. First, the water is receiving kinetic energy from its surroundings in the form of heat energy. Second, the water is in higher concentration in the spill than in the spill’s surroundings and therefore a concentration gradient is formed at the water’s surface.

So what has this all got to do with boiling water? Well, water boils when transforming into a gas. Therefore, boiling water is a phase transition described by the equilibrium between liquid water and water vapor. Besides temperature, pressure also affect liquid-gas equilibrium as described by the ideal gas equation,

                  1.       PV=nRT (P is pressure, V is volume, n is number of molecules in moles, R is the gas
                   constant, T is temperature)

LeChatelier’s principle states that a system in equilibrium will move away from an induced change. In the case of an increase in pressure, we can see that if n and T remain the same then the ideal gas law describes a shift to decrease V, volume. On the other hand, a decrease in pressure should cause a shift towards a higher V. This means that at lower pressures, water prefers to exist in a gaseous state and the equilibrium shift will cause the water to boil. This is the foundational concept of rotary evaporators, which use the concept of reduced-pressure boiling to remove solvents.

Fig. 2: Deriving atmospheric pressure in atm's (Pearson)

Now all that is left is to link pressure to altitude, which isn’t too hard. By definition, atmospheric pressure is defined as the weight of the atmosphere over an area at sea level [2]. For example, one inch of land at sea level partitions a pillar of atmosphere weighing 14.7 lbs, so atmospheric pressure in PSI is 14.7 lbs/in². A logical extension of this concept would tell us that at any altitude greater than sea level, the pillar of air would be shorter and would consequently weigh less. This is the missing link we were searching for between pressure and altitude. Putting all of the above information together, we see that a decrease in pressure causes liquid water to favor boiling and that an increase in altitude causes atmospheric pressure to decrease. Therefore, water boils easier at higher altitudes.

Scaling the results of the survey to education levels, the Pew Research Center also found a correlation between higher education and scientific knowledge. But this is not a given. Even as college students, we must all work towards insuring that we are among the scientifically literate ready to contribute educated opinions to today's social debates.