Category: today i learned (til)

Every year I move into a new room on campus at Georgia Tech, I buy a package of sticky putty, hoping that it will be strong enough to hold my large posters of the periodic table and Chance the Rapper, because command strips are just way too expensive. They usually fall down in the middle of the night, waking me up in terror. Recently in my polymers class, I learned about the beauty of spider silks and how they secrete different silks to accomplish different tasks. When I googled “spider silk,” I found articles and youtube videos claiming that spider silk is stronger than steel. I wondered how spiderwebs are able to stick to walls better than my command strips, but when I accidentally run into one, it breaks easily.

After doing some research, I learned that strands of spider silk are actually made of thousands of close-packed, parallel nanostrands, and depending on the gland they are secreted from, their tensile strength is 100-400 kpsi, compared to steel, which is 40 kpsi [1]. The secret is in how the tensile strength is measured. Tensile tests consist of putting a material in tension, essentially stretching it until it breaks. Spider silk is made of semi-crystalline polymer nano strands that can stretch a lot before breaking, and having many strands stacked together makes it even stronger, while steel thread of the same diameter or density has a crystalline structure that doesn’t stretch. This scenario is analogous to breaking a single stick of strong wood versus breaking a bundle of many weaker but stretchier sticks of wood: the bundle wins.

Spiders have different glands that secrete silks with different properties as protein structures to accomplish different tasks [2]. The tubuliform gland creates the silk to make the hard outer shell for an egg sac, and the aciniform gland makes the inner lining of the egg sac. The aggregate and flagelliform glands produce the sticky droplets and capture spiral threads, respectively, to catch prey.  The major ampullate gland makes the frame of the web as well as the dragline silk that allows the spider to move around. Lastly, the pyriform silk gland is responsible for the silk that attaches the web to the walls, trees, your bedroom window, etc. Pyriform silk is described as a “protein glue” or a “glue-like cement” that holds small amino acid fibroins, which then connect larger dragline silks, and are sometimes reinforced by aciniform silk [3]. Together, all of these components create a very strong network of silks that makes the overall product very adhesive. 

In this picture from a study that took Scanning Electron Microscope (SEM) images of a single attachment point of a web, it looks like the pyriform silk is a splat of glue with the dragline silk (white arrow) stuck in it [4]. Looking closer, the “glue” looks like a network with many, smaller attachments to the surface of the wall. 

Meanwhile, the sticky putty that I use to try to hang up my posters isn’t as robust as the spider silk glue. The formula for sticky putty is a trade secret, but it is known that it works as a pressure-sensitive adhesive, so the extent of adhesion depends on the amount of pressure you apply to it, as well as the shape and geometry. So even though I add a lot of pressure to the poster when I first apply it, depending on the weight of the poster and the amount of putty I used, the poster will slowly pull the putty off the wall, depending on how much I used and the temperature of my room [5]. 

If spider silks are so strong and perform so many tasks well, why don’t we make adhesives or other high performance materials out of it? There have been many ideas for potential uses of spider silk in body armor due to its mechanical properties. It is also antimicrobial, so there are many ideas for biomedical applications, such as scaffolding for tissue generation [2]. However, spider silk is extremely difficult to harvest. This is because spiders are inherently cannibalistic and produce a small amount of silk in comparison to silk worms, which are typically used to harvest silk for textiles. Scientists have attempted to put spider genes in silkworms, but the silk they produce still isn’t of the same quality [6]. So unfortunately, I probably can’t get a spider as a pet and harvest the silk for my dorm posters. But doing all this research made me curious: How is Spiderman’s silk compared to actual spider’s silk? And where are the silk glands?

References:

[1]Hayashi, C. Y., Shipley, N. H., & Lewis, R. V. (1999). Hypotheses that correlate the sequence, structure, and mechanical properties of spider silk proteins. International journal of biological macromolecules, 24(2-3), 271-275.

[2] TED. (Dec 7, 2011). Hayashi, Cheryl: The Magnificence of Spider Silk [Video file]. Retrieved from https://www.youtube.com/watch?v=xossR6eHv3I&t=248s

[3]Hardy, John & Römer, Lin & Scheibel, Thomas. (2008). Polymeric materials based on silk proteins. Polymer. 49. 4309-4327. 10.1016/j.polymer.2008.08.006.

[4]Blasingame, Eric et al. “Pyriform spidroin 1, a novel member of the silk gene family that anchors dragline silk fibers in attachment discs of the black widow spider, Latrodectus hesperus.” The Journal of biological chemistry vol. 284,42 (2009): 29097-108. doi:10.1074/jbc.M109.021378

[5] “Blu Tack FAQs.” Blu Tack, Wayback Machine Internet Archive, 2010, web.archive.org/web/20100418062649/http://www.blutack.com/faq.htm.

[6] SciShow (Feb 4, 2019). Green, Hank: Why Can’t We Make Spider Silk? [Video file]. Retrieved from https://www.youtube.com/watch?v=UX2LHcLxjio

It is a truth universally acknowledged that any homework of significant difficulty is in want of long hours to completion. In this case, twenty hours, give or take some breaks to re-hydrate from where the tears slipped away unnoticed among the frustration and eye strain. Even then, the outcome isn’t what you wanted and you may not make the deadline at all.

May whatever powers-that-be bless professors that give their students who fail part one of a multi-part homework a working version to complete the next section.

All dramatics and literary reference aside, animation is hard. I know this for a fact, I’ve been doing frame-by-frame animation since middle school and, while that can get tedious, it is much, much more straightforward than the computer graphics assignment I was referencing above. However, I’m getting ahead of myself; this is a story about learning, frustration, trial, error, failure, success, and at the end of it all, the final product.

The first thing to note is that Computer Graphics is a known grade killing class, and has been that way for at least five years, if not since it’s conceit. You talk to any Georgia Tech student who has taken the course and they’ll tremble in horror, either fake or very real, the reaction is the same at its core. I, unfortunately, didn’t know this until after I had begun.

The second thing to note is that the professor that I had for the class was infinitely preferable to previous holders of the position, as referenced by the second paragraph.

The third thing to note is that I’m still not entirely sure what a scene graph is. Of course, I understand what it is in concept — a data structure designed to keep graphic elements organised in a certain configuration for ease of use. Say you had a character with the parts: body, head, left arm, right arm, left leg, right leg, left hand, right hand, left foot, and right foot. The graph would be organized something like this:

Body
/           |            |            |             \
Head    left arm   right arm      left leg     right leg
|               |              |            |
Left hand    right hand    left foot    right foot

The character would then be connected to the world of the scene through the Body node. Using this construction, all of the pieces of the scene graph of the character are moved relative to its parent nodes– the nodes above it and connected to it within the scene graph. It’s fairly simple for anyone with a basic knowledge of coding languages, but understanding a scene graph and implementing one are two entirely separate things. It’s the implementation where I stumbled and was left in the dust on the side of the road.

However, homework waits for no one, especially not a homework with multiple parts. Part two of the homework was to create a character using the scene graph implementation from part one, and to connect the pieces appropriately to make a recognizable image of at least ten parts and three levels like the scene graph above. This was accomplished mostly by trial, error, and begging my fellow students to take pity and help me. If there is one thing I can say about college, it really does destroy any pride you may have once had when it comes to school work.

The third and final part of the homework was to take the character from part two and create an animation in the scene graph. Camera movements, movement of at least one part of the character, and one part of the surrounding scene were required. This part came the easiest to me, but it was still an exercise in frustrated guess-and-check. Moving the camera a few degrees only to find you turned it the wrong direction, making sure that the piece of your character that you decided to move doesn’t visually disconnect itself and become a floating arm spinning into the distance.

I’ll admit, I laughed aloud at some of the things my errors caused, but it felt more hysterical than anything at the time. When your entire animation starts spinning into the endless void, you have to start laughing, or you’ll cry. Still, I lived in the TA office hours until I finally managed to create a working product. It isn’t what I wanted, not nearly as good as it could have been, but remember what I said earlier about pride. If it completes all of the requirements and doesn’t look like hot garbage, it is a success.

You can view the finished version that took 20 hours out of my life by clicking the link below.

https://dj-baker.github.io/charged-animation/

A Tale of Binge-Watching and You

After years of saying ‘I don’t need it’ or ‘it will waste my time,’ I finally caved last year and started using Netflix. My friend decided to celebrate the occasion by trying to hook me on the show, You. We huddled on her couch and watched the first two episodes together. Afterwards, she left it up to me to finish the season. However, like I tend to do with many things, I put it off. Over a month passed before I finally decided to finish the show. I sat down the following Saturday afternoon to begin episode three and came to my senses hours later when I realized I had finished the entire series. I had been so eager to feel the rush of the story and not be left on cliffhangers that I gave up my entire afternoon to gain some closure. While part of me felt a little empty inside due to forking over so much continuous time to the show, I did actually enjoy its contents and was eager to discuss it with my friend. However, I was not able to see her until 2 weeks later. When this chance finally arose for me to devour every detail of the show and its story, I suddenly started drawing up blanks. I could remember those first two episodes fairly well, but when it came to the nine episodes I watched in the same day, I could really only remember the ending and a few select events in detail. Everything else blurred together. He did what in which episode? Wait, did she actually do that? My memory was foggy and nothing stood out clearly but those first two episodes. Why did I remember those so well even though it had been well over a month since I had seen them and yet all the more recent episodes I watched were already well-faded in my memories? Besides just wasting my time, did binge-watching have some unforeseen consequences on me?

The answer is yes. A recent study has linked binge-watching to the reduction of long-term memories of basic details related to watched shows (Hattie, Horto, Horvath & Lodge, 2017). When compared to normal television viewers who tend to watch one new episode per week, binge-watchers scored lower on basic assessments regarding common details of specific episodes and characters of the shows they’ve seen. Why though does binge-watching have this effect on individuals? The science behind this is connected with memory consolidation and a little phenomenon called the temporal distinctiveness theory.

Memory Consolidation and Your Brain

Memory consolidation refers to the process of converting a temporary memory into a long-lasting one. For a memory to become permanent, the memory must be transported from the hippocampus (the part of the brain related to short-term gains and instinct) to the neocortex (part of the brain connected to rational thought/deeper thinking)(Squire, Genzel, Wixted & Morris, 2015).During this transfer, the long-term memory is established by increasing the complexity, distribution, and connectivity of the neocortex with respect to the other parts of the brain. Without this transfer and shifts in the neocortex, the initial memory becomes lost to the person within a short period of time. 

A couple of different factors can influence how well someone can consolidate a memory. For example, the amount of prior knowledge one has on a topic can influence the strength of one’s ability to make these long-term memories. Another factor that affects this process of consolidation is time, and this time factor can be explained by the temporal distinctness theory.

Temporal Distinctiveness Theory: The Gap Between Memories

Temporal distinctiveness theory essentially states that by increasing the time gap between solidifying new long-term memories, you can better recall them more distinctly at a later time (Cowan, 2008). When a single item/event has been given time to be isolated by itself, then that memory can be transferred into the neocortex as a much more distinct and identifiable memory versus if multiple consecutive memories are trying to be stored in the neocortex at once. This “downtime” for memories to be installed into the neocortex is called neutral memory consolidation (Brown, Ecker & Lewandowsky, 2014). During neutral consolidation, the brain is either doing low mental activities or sleep, giving it a chance to successfully transfer the memories from the hippocampus to the neocortex. When I watched the first two episodes of You and then gave myself time to absorb what occurred in those episodes, I was able to better create distinct long-term memories from those experiences and recall more specific details from the show. However, when I binged-watched the other nine episodes, I did not give myself time between each episode to consolidate my memories, which is why all of my memories regarding those episodes (barring the very end) were foggy and jumbled together. Binge-watching my show, while enjoyable at the time, stripped me away from my ability to better remember what happened in it in the future. 

So Netflix or TV?

We all hate that feeling of watching a captivating show on TV and then being forced to wait a week or month for its conclusion. It feels so rewarding to just get that immediate answer to a question without being forced to suffer and mull over all the possibilities of what’s going to happen to your favorite character. However, for this quick satisfaction, we relinquish part of our ability to better remember the content that we witness. Binge-watching does not give you brain the chance to transfer that event into long-term memory. Though, at the end of the day, it is still up to you to decide your viewing experience. Which part of the trade-off will you accept: binge-watching’s instantaneous enjoyment but long-term haziness, or TV’s long-lasting remembrance but painful wait time? I’ve already decided my choice for the next series on my Netflix list: Bojack Horseman season 6. I’ll be taking it one episode at a time, so I can make distinct memories to stay with me well after I finish the show. What about you?  

Citations

• Brown, G. D. A., Ecker, U. K. H. & Lewandowsky, S. (2014). Memory Without Consolidation: Temporal Distinctiveness Explains Retroactive Interference. Cognitive Science. Volume 39. Issue 7. https://doi.org/10.1111/cogs.12214 
• Cowan N. (2008). What are the differences between long-term, short-term, and working memory?. Progress in brain research, 169, 323–338. doi:10.1016/S0079-6123(07)00020-9
• Hattie, J.A.C., Horto, A. J., Horvath, J.C., & Lodge, J. M. (2017). The impact of binge-watching on memory and perceived comprehension. First Monday. Volume 22. Number 9. https://firstmonday.org/ojs/index.php/fm/article/view/7729/6532 
• Squire, L. R., Genzel, L., Wixted, J. T., & Morris, R. G. (2015). Memory consolidation. Cold Spring Harbor perspectives in biology, 7(8), a021766. doi:10.1101/cshperspect.a021766

Introduction:

To consider something toxic, it must produce “an adverse biological effect” to humans or other animals (“Basic Terminology”). For birds, several species have adverse effects on humans through touch or ingestion. The remainder of this article explores several of these species including quail, pitohui birds, and spur-winged geese.

Quail:

Sources from the Roman Empire and the Bible document epidemics caused by the consumption of quail. The disease, referred to today as coturnism, only affected humans during certain migration periods. As the birds travel west to Europe, their flesh becomes deadly, but when they returned east, the birds are no longer toxic. Scientists believe the toxicity in quails comes from their own diet. Early speculation of quail toxicity thought the birds ingested plants like hemlock or henbane, but recent researchers believe that the culprit is Stachys annua, a plant that exhibits toxicity at consistent intervals with the quail migration (Bartram & Boland).

Pitohui Birds:

The pitohui birds, native to New Guinea, have a neurotoxin originally only thought present in poison-dart frogs (found in Columbia and Central America). The toxin, present on the bird’s feathers and bodily tissue, if touched, can cause nausea, numbness, burning, and sneezing. With more exposure, the neurotoxin can lead to severe symptoms such as convulsions and contractions. (Bartram & Boland). The concentration of poison in the pitohui birds is 3-times less than that of the poison-dart frog. Contact with a frog can lead to cardiac arrest and death, but these extreme issues are much less common after contact with the pitohui birds (Ligabue-Braun & Carlini). The neurotoxins found in both pitohui birds and poison-dart frogs can only develop with appropriate diet. Poison dart frogs, when raised in captivity, no longer have the neurotoxin, and scientists assume the same is true for the birds. The specific ingredient that causes the poisonous neurotoxin remains unknown (Bartram & Boland). The low concentration of neurotoxins in pitohui birds causes some scientists to believe that the toxin developed evolutionarily to deter against parasites. Research shows that these birds have one of the lowest rates of tick infestations compared to other species in the area (Ligabue-Braun & Carlini).

Other:

There are 13 other documented bird species that can harm or kill a human because of their own diet. Spur-winged geese, for example, eat a type of beetle that contains toxic material which causes severe skin blisters and death in humans (Bartram & Boland). More research is needed in the field of toxic birds to document reactions and determine causes of toxicity.

Citations:

Bartram, S. and Boland, W. (2001), Chemistry and Ecology of Toxic Birds. ChemBioChem, 2: 809-811. doi:10.1002/1439-7633(20011105)2:11<809::AID-CBIC809>3.0.CO;2-C

“Basic Terminology.” U.S. National Library of Medicine, National Institutes of Health, toxtutor.nlm.nih.gov/01-002.html.

Ligabue-Braun, Rodrigo, and Célia Regina Carlini. “Poisonous Birds: A Timely Review.” Toxicon, vol. 99, 2015, pp. 102–108., doi:10.1016/j.toxicon.2015.03.020.

Picture Sources:

https://commons.wikimedia.org/wiki/File:Spur-winged_Goose_RWD4.jpg

https://en.m.wikipedia.org/wiki/File:Rectes_uropygialis_-_The_Birds_of_New_Guinea.jpg

https://commons.wikimedia.org/wiki/File:Stachys_annua_Sturm47.jpg

In college, it’s hard to balance sleep and studying. Many students sacrifice sleep in the hopes that that time spent studying instead will positively impact their grades. However, lack of sleep has many negative consequences, such as negatively impacting learning, memory, and performance.

Some students (yourself included) may “pull an all-nighter” (24 hours or more without sleep) before examinations in the hopes of better grades. However, many studies suggest otherwise. For instance, in one study, subjects were given the task to identify the presence of a “T” or “L” and the orientation of 3 diagonal bars. Participants that went 30 hours without sleep showed no improvement in performance, even after 2 days of post-recovery sleep. In another study, subjects were taught a motor task and then tested either after 12 hours of no sleep or 12 hours that included sleep; subjects tested with 12 hours of no sleep showed no significant change in performance. However, their performance improved by 18% after a night of sleep. Those tested within the 12 hours that included a sleep period also showed improvement in performance Another study found the average amount of sleep per night was found to be significantly correlated with GPA—students who slept for more hours each night tended to have better grades. Also, the average number of days per week that students got less than 5 hours of sleep was found to be negatively correlated, although weakly, with GPA. This supports the concept that sleep is required for learning and memory consolidation.

In conclusion, sleep is vital in aiding learning and memory consolidation. So next time you’re considering pulling an all-nighter to study for a test, reconsider doing so. Those few extra hours you’d spend studying would be better spent sleeping so you can consolidate the information you’ve learned and perform better on the next day’s test!

References