science | technology

CATAPULTAWinter 2018

TABLE OF CONTENTS

3 - 4

15-16

6

7-8

14

11-12

5

13

17

18

Dead Stars

Regen med

AMZN GO

MUONS

Monkey

prime #’s

BLOOD moon

COLONY COLLAPSE

lizard tails

CAR - T

01 | CATAPULTA // WINTER 2018

10-11pi day

clones

WINTER 2018 // CATAPULTA | 01

EDITOR’S NOTEDoes anyone tell you anything along the lines of carpe diem, “seize the day,” or even “YOLO”? Does it ever annoy you?

We don’t blame you if it does, but those people might be on to something. According to science, population growth under limited resources might look like this (Figure 1)

So what does that mean? Basically, the dotted line is the maximum population our resources could possibly support, and the solid line tracks the organism’s total population over time. Notice how the population first grows at a rapid rate, before sharply declining after it crosses the carrying capacity.

Yay, squiggly lines! But what does that translate into for us humans if our population grows like this?

Not anything good -- the graph shows the population growing, before some cataclysm happens that causes it to fall A LOT. If this actually happens, that event could be anything from warfare to famine to whatever else. Not things we’re really looking forward to. You’re probably not looking forward to it either (or at least, you shouldn’t be). But, that should provide some incentive to make the most out of what you have now! And that’s why you should read Catapulta. Who knows, it might be your last chance.

Right: Figure 1

EDITORS IN CHIEFALFRED YAN (I)LAUREN JIANG (I)

HEAD COPY EDITORSNENA KOTSALIDIS (I)TIM LIU (II)

ASSISTANT COPYEDITORSAUSTIN WANG (II)CHRISTY JESTIN (III)

ASSOCIATE COPYEDITORSRYAN NIE (II)LINA ZHANG (III)RACHEL WENG (IV)ALICE ZHANG (IV)CINDY ZHOU (IV)

HEAD CONTENT EDITORSVICTOR CHAU (I)ASHLEY CHOU (II)

ASSISTANT CONTENT EDITORSJERRY HAN (II)JOHN LIN (IV)

ASSOCIATE CONTENT EDITORS MAHAD ABDI (II)RYAN NIE (II) AUSTIN WANG (II)JACK ZHAN (II)TRACY ZHANG (II) ALEX CHOU (V)

HEAD LAYOUT EDITORSDAVID CHEN (I)TING WEI LI (I)

ASSISTANT LAYOUTEDITORSDAVID SHEN (I)NATALIA TAM (IV)

ASSOCIATE LAYOUTEDITORSYANXI FANG (II)SAM BURFIEND (IV)ESTHER SHEN (IV)EMILINA TRAN (IV)THERESA HUANG (V)

PUZZLE EDITORHAYDEN CODIGA (I)

STAFF WRITERLIANE XU (II)

TREASURERPETER HUYNH (I)

WEBMASTERKEVIN S. QI (II)

FACULTY ADVISORMS. BATEMAN

CONGZHOU HEFAN YANGFRAN YANGHUIMIN JIKATHERINE FAULKNER

MICHAEL CHENLI YAONENA KOTSALIDISZHEJUAN WANGZHENJUAN WANG

OUR PATREON SUPPORTERS

Winter Issue Staff

PULSARSDead Stars in Space Could Replace GPS Satellites

Since early times, sailors have relied heavily on the sky to aid navigation, using visual markers like the North Star and the celestial poles to determine their whereabouts. Today, we do not often struggle with this issue, since we have the Global Positioning System (GPS) of satellites that we use daily in our cars and on our smartphones. GPS, however, relies on humans to regulate satellite timing, and the farther one gets from the satellites, the more difficult it is to pinpoint one’s location. Moreover, while GPS is accurate enough for navigation on Earth, it is not sufficient for space mis-sions that take place outside of satellite orbit. As a re-sult, a new solution has been introduced: a stellar GPS network, known as the pulsar positioning system. The premise of the pulsar positioning system is that, similar to how GPS utilizes the consistency of satellite signals to discover your location, spaceships would receive ra-diation blips, or pulsars, from dead stars that emit radi-ation at constant intervals. Instead of having to rely on Earth-orbiting satellite beacons, stellar navigation could use intergalactic beacons to explore more of space. Using the GPS system, the receiver, such as a car or a mobile device, sends radio signals from the satellites in Earth’s orbit. These satellites, adjusted with atomic clocks in order to relay signals at the same time, are all at different distances from the receiver. Therefore, each transmission reaches it at different times. From these differences in duration, the GPS system deduces its location. The highest quality consumer devices can estimate your location within about a meter in the best situations, but tall buildings and other interferences can easily throw off the system by more than 10 meters. Furthermore, because these GPS satellites orbit the Earth so rapidly (they complete two orbits a day), Einstein’s special theory of relativity necessitates that the clocks tick slower than those of Earth. For instance,

after two minutes, the GPS satellites are already diver-gent from Earth’s clocks. The only way to send the cor-rect time to the satellites is by determining the actual time from clocks on Earth and relaying the information to each satellite, which is a perpetual obligation for the Department of Defense. Conversely, even though a pulsar’s uniform sig-nals are used to keep time just like the GPS system, the math in the pulsar positioning system already accounts for relativity. Therefore, the constant conversion asso-ciated with GPS is avoided. Pulsars have the ability to keep time similar to atomic clocks and don’t shift very often between intervals relative to Earth, but when they do, the distance they travel can be predicted. To prove that the pulsar positioning system could navigate on its own, several researchers experi-mented with their radio signals. Angelo Tartaglia, a physicist at the Polytechnic University of Turin in Ita-ly, conducted a study on a software that imitates pulsar broadcasts. Tartaglia and his team tracked the trajecto-ry of the observatory to the accuracy of several hun-dred meters. Additionally, researchers with the Station Explorer for X-ray Timing and Navigation Technology experiment (SEXTANT) reported on a pulsar analysis at a news conference on January 11 during a meeting of the American Astronomical Society. SEXTANT used an array of fifty-two X-ray telescopes to measure the sig-nals from five pulsars. According to astronomer Keith Gendreau, an analysis of those signals yielded a location that was within ten kilometers of SEXTANT’s actual po-sition as it orbited Earth on a space station. Still, pulsars are weak sources and typically require large radio tele-scopes to track, so researchers are beginning to look for pulsars that emit X-rays, which provide a much brighter signal, and require smaller and lighter antennas.

03 | Mira Yu - VI CATAPULTA // WINTER 2018

The true advantage of a pulsar system lies in its ability to track a spacecraft’s movement along three dimensions and detect any deviation from its course. “It’s easy to calculate a satellite’s position along the line of sight by measuring Doppler shift —the change of frequency with an object’s speed — but more difficult to create a three-dimensional picture of a spacecraft trajectory,” says Scott Ransom, an astronomer at the National Radio Astronomy Observatory in Charlottes-ville, Virginia. In a scenario in which we are far from Earth, pulsar navigation systems could improve upon the position estimates currently formed using orbit-ing satellites, and serve as an alternative GPS system if those satellites were to malfunction.

Pulsars have the ability to keep time similar to atomic clocks and don’t shift very often between intervals relative to Earth, but when they do, the distance they travel can be predicted.

“researchers are beginning to look for pulsars that emit X-rays, which provide a much brighter signal and require smaller and lighter antennas.

“

WINTER 2018 // CATAPULTA | 04

Blue

m

oon: The second full moon in a month

What were you doing the night of January 31, 2018? If you were outside, you might have seen the first super blue blood moon visible from the United States since 1866! What does that mean? It means that on that night, the Moon shone huge, bright and RED! Why did it appear this way? The answer is found, first and foremost, in the Moon’s uneven elliptical orbit. On its path lies the perigee and apogee, the closest and farthest points from the planet, respectively. A supermoon occurs when a full moon rises on its perigee. It is hard to discern the difference in size from the ground, but a supermoon is noticeably brighter. In fact, the Moon can appear fourteen percent larger and thirty percent brighter than at its apogee during this time. The term “blue moon” refers to the rare second full moon of a month, while “blood moon,” eerie as it may sound, refers to

the Moon’s appearance during a lunar eclipse. A lunar eclipse occurs when the Earth blocks most of the Sun’s rays from reaching the Moon; the passing of the Sun’s rays through the Earth’s atmosphere gives the Moon a red-copper hue. Earth’s shadow, just as that of any other celestial body, has two parts: the umbra and the penumbra. The umbra, from the Latin word for shadow, is the smaller, darker, inner ring within the penumbra, the wider and lighter shadow invisible to the human eye. In Boston, it was possible to see a partial

eclipse just by stepping outside during the early morning hours. The best view on

the East coast, according to the National Aeronautics and Space

Administration (NASA), was right at about 6:45 A.M.

This was when the Moon was at its closest point to the viewer, making it appear much larger than when it was high in the sky.

Super Blue Blood Moon 2018

Blood moon:

When the Earth

eclipses the moon,

making it appear red

Supermoon: When a full moon rises on its perigee (when it’s nearest to the Earth),

making it appear huge

05 | John Nagasawa - II CATAPULTA // WINTER 2018

Amazon has expanded horizontally once again with the beginning of its chain of corner grocery stores, Amazon Go. These stores are bringing grocery and convenience shopping into the 21st century— with no lines to checkout. Using hundreds of sensors, cameras, weighted shelves and more, Amazon has created a store where you can walk in, take what you want and leave out the front door without having to scan each item and pay at the end. Before entering the store, the only thing customers need to do is download the Amazon Go app and link their credit card to it. From there, customers walk through a gate and begin shopping. This is where the technology comes in. When someone scans in, the store immediately starts tracking the shopper, seeing where they walk, how long they look at products, and more. Although Amazon has not officially disclosed what data they gather or how long they hold onto it, it can be assumed that it is used to plan where to place products in the future and what new products to bring into the store later on. These sensors also enable Amazon to actively monitor what products the customers take and how many with accuracy. The system is precise enough to the point where someone can load up a backpack with food as they shop and still be charged when they walk out. Yet, along with all the innovative technology being introduced into the store, there comes a serious issue which society will have to face in the future— what to do about all the current cashiers whose jobs may be at risk because of this technology. Indeed, as society continues to innovate, the job market is going to shift, but with Amazon Go, it may come sooner than expected. Overall, this is just another step from Amazon into our daily lives. And who knows, if they pick their new headquarters to be in Boston, we might just get a store as well!

Enter

ShopGo

Blood moon:

When the Earth

eclipses the moon,

making it appear red

WINTER 2018 // CATAPULTA Armen Youssoufian - II | 06

Muons: A Solution to the Problems of Fusion Power? Nuclear fusion, the process behind the energy released from the Sun, theoretically provides a consistent, safe form of electricity generation, which has no dangerous by-products and is fueled by the most abundant element in the universe. In order to induce nuclear fusion on Earth, the hydrogen nuclei must be heated to extreme temperatures and confined into incredibly high densities. This is necessary because atomic nuclei have positive electric charges and therefore repel each other. This electromagnetic repulsion is known as the Coulomb barrier and must be overcome by giving the nuclei very high velocities, confining them into a small space so that two nuclei will be able to frequently “collide”2 with one another. When deuterons (d), hydrogen nuclei with one neutron, or tritons (t), hydrogen nuclei with two neutrons, fuse, they release a great amount of energy in the form of highly energetic particles, namely helium nuclei and neutrons. After escaping from the fusion chamber, the neutrons can deposit their heat and be used to further induce nuclear reactions, which can produce more fusion fuel. The amount of energy and machinery needed to create these conditions for fusion has prevented the development of nuclear fusion power plants. There is, however, an alternative method of inducing hydrogen fusion which does not require the nuclei to be heated to these extreme temperatures at all, and it relies on the exotic sister particle of the electron: the muon (µ). Muons have the same properties as electrons3, however, they are approximately 207 times as massive. When a beam of nuclear material is fired at a gas of hydrogen molecules consisting of deuterium and tritium isotopes, the resulting high-energy collisions will result in many muons. Muons will knock away electrons and then bind a triton and deuteron together, forming a positively charged molecular heavy hydrogen ion (d-µ-t)+. Once the two nuclei have formed this exotic muonic molecule, they will be drawn very close to each other, much closer than the nuclei in standard hydrogen molecules are. This is because the muon, on account of its massive size, shields the two nuclei from the electromagnetic repulsion between them to a much greater extent than an electron would, effectively lowering the Coulomb barrier between them. Now, in very close proximity, it is likely that the triton and deuteron will bypass the reduced

“An alternative method of inducing

hydrogen fusion”

07 | Patrick Stulb - II CATAPULTA // WINTER 2018

Coulomb barrier and fuse together through a process known as quantum tunneling, resulting in an alpha particle (helium-4 nucleus) and a highly energetic neutron. The muon is also released and can continue on to catalyze more fusion. Thus, through the use of muons, the fusion of hydrogen can successfully be induced without needing to turn the hydrogen into a superheated plasma or to confine it in extreme densities using powerful electromagnet - both of which require an immense amount of energy. Muon-catalyzed fusion is unfortunately not without its own problems. There are many issues which prevent it from being a reasonable source of electricity. The main issue is keeping the fusion chamber supplied with muons. Because it is an exotic particle, muons decay very quickly, and have a small chance of becoming bound to an alpha particle, making them unable to continue

catalyzing fusion. Although calculations have shown that a net positive amount of energy could be produced, the electrical generation capacity needed to run the particle collider and

produce the continuous supply of muons (approximately four to six megawatts must be inputted to generate an additional one megawatt output) would

entail an unreasonably high capital investment. Nevertheless, should a cheaper way of creating muons be found, muon-catalyzed fusion

could potentially be a solution to our ever-growing need for electricity.

“Muon-catalyzed fusion could potentially

be a solution to our ever-

growing need for electricity.”

WINTER 2018 // CATAPULTA | 08

d+ t+

μ-

d+e-

e-

t+

He2+

n0

μ-

*diagram is not to scale and wave function shapes are simplified

**e--e- interactions are ignored for simplicity

A standard deuterium-

tritium hydrogen molecule

Arrows represent electromagnetic

interactions

A muon replaces the electrons in the deuterium-tritium

hydrogen molecule, forming (d-μ-t)+. The nuclei in (d-μ-t)+ are shielded from their EM

repulsion by the muon.

Because of the reduced Coulomb barrier, the nuclei fuse, forming a helium nucleus

and releasing the muon and a highly energetic neutron. These products are

separated by their immense heat.

PI DAYBLS Catapulta Presents

Nerdy nomswhat better time to enjoy a slice of pie than pi day?

a pie for a pie, a tooth for a toothVote to pie your favorite math and science teachers.

1 vote $1

1 slice $2

1 slice + 2 votes $3

3.14.2018Dining Hall

2:30 pm

ABOUT PI DAY

pi day is bls catapulta’s annual celebration of the number 3.14... or π: every aspiring mathlete’s best friend, not only useful for calculating the area of a circle, but also statistics, physics, engineering, quantum mechanics, and every other field you can think of.

Held in the dining hall, this event is a chance to enjoy a slice (or two, or more) of pie as well as bear witness to an epic stem (science, tech, engineering, math) teacher pieing!

so how can you participate? firstly you can buy tickets, each of which will net you a slice of delicious pie. Secondly you can vote for your favorite stem teachers to get pied in the face (runner-up will pie the winner)! a Full list of participants can be found to your right.

We hope to see you there!

09 | CATAPULTA // WINTER 2018

If that wall of text didn’t pique your curiosity, how about a few words from some of our candidates?

Name: Mr. Bilodeau

Nickname: Gerry

What I teach: The best students in the school!Favorite type of pie: Pecan

Who I want to pie in the face: Can’t think of anyone.

Bad science/math joke: What do you get when you cross a

mosquito with a mountain climber? Nothing. You can’t cross a

vector and a scalar.

Why you should vote for me: They should vote for Ms. Cojohn.

Name: Mr. Pietrangelo

Nickname: My friend used to call me Cheese in high school.

What I teach: Chemistry

Favorite type of pie: I like all pies.

Who I want to pie in the face: Donald Trump.

Bad science/math joke: Are you an exothermic reaction? Because

you spread your hotness EVERYWHERE (courtesy of Michael).

Why you should vote for me: Because I love pie, and because I

hold a grudge forever.

Name: Ms. Leung

What I teach: Math

Favorite type of pie: Don’t like pie.Who I want to pie in the face: Theresa Cojohn

Bad science/math joke: All my jokes are good, I can’t.Why you should vote for me: People shouldn’t vote for me, they

should vote for Theresa Cojohn. I got pied last year. This year is

redemption.

Name: Ms. Cojohn

Nickname: Coach Co

What I teach: Math magic

Favorite type of pie: Apple crumble

Who I want to pie in the face: Ms. LA, but I feel bad because she’s pregnant

Bad science/math joke: Parallel lines have so much in common,

it’s a shame they’ll never meet.

Also, life without geometry is pointless.

Why you should vote for me: You shouldn’t.

Name: Aaron Osowiecki

What I teach: Physics

Favorite type of pie: Apple pie

Who I want to pie in the face: My son

Bad science/math joke: A cop pulls Heisenberg over.

Cop: "Do you know how fast you were going?"Heisenberg: "No but I know where I am."Why you should vote for me: I don’t give enough homework. I’ve

been here for 19 years and haven’t gotten pied in the face yet.

Name: Ms. Jacobson Peregrino

Nickname: Ms. JP

What I teach: Earth science

Favorite type of pie: Wild berry mix

Who I want to pie in the face: Mr. Balicki

Why you should vote for me: I’m not afraid of making a big mess.

full teacher list

AndersenBalicki

BatemanBilodeau

CastellanosCojohnGalego

GayGreavesGreen

HamiltonJP

LeungMcQuade

NjokuO’DonnellOsowiecki

PelsPietrangeloSabharwal

SarkisSmith

SouthwickSpezzano

StoneWalker

Wetherby

Winter Issue // Catapulta | 10

23

57

11

17

13

19 23

29 3137

4143 47

5359

6167

71

7983 89

101

97103107

109

PRIME NUMBERS WHY DO THEY MATTER?

On December 26, 2017, a Fedex employee and a former electrical engineer from Tennessee named Jonathan Pace discovered what is now the largest known prime number. Pace is a volunteer for the Great Internet Mersenne Prime Search (GIMPS). The number, called M77232917, is 2 77,232,917-1, which spans over 23 million digits long.

FIRST OF ALL, WHAT IS A PRIME NUMBER?You have undoubtedly come across prime numbers sometime in your math class. But in case you have forgotten: according to Wolfram MathWorld, a prime number “is a positive integer, p>1 that has no positive integer divisors other than 1 and p itself.” Examples of prime numbers include 2, 5, and 13.

A Mersenne Prime is a prime number in the form of 2n-1, where n is also a prime number. Mathematicians have found that Mersenne primes have many properties. Each Mersenne prime, for example, corresponds with exactly one perfect number, which is a number that equals the sum of its divisors, excluding the number itself (e.g. 6, 28, 496). Finding Mersenne primes, unfortunately, is computationally challenging, which makes their discovery all the more significant. In fact, the discovery of 211213-1 as a prime was celebrated in Urbana,Illinois in 1963 with a special postalmeter design.

WHAT IS A MERSENNE PRIME?

11 | Liane Xu - II CATAPULTA // WINTER 2018

23

57

11

23

31

47

6167

7173

7989

97

HOW DOES GIMPS WORK?George Woltman founded the software program GIMPS in 1996. He originally developed the

software to run on Intel i386 systems, but since then, Woltman has updated it so that it can also work on new Intel and AMD processors. It uses the Lucas-Lehmer primality test, which states

that “for p an odd prime, the Mersenne number 2p-1 is prime if and only if 2p-1 divides S(p-1) where S(n+1) = (S(n))2-2, and S(1) = 4,” to ensure that the number is prime. For example, 23-1

or 7 divides S(3-1)=(S(1))2-2=16-2=14. Since its founding, thousands of volunteers have worked on millions of assignments in order to find and confirm larger Mersenne primes. Sixteen have been found through GIMPS so

far, which is incredible considering the magnitude of the numbers and the rarity of them.

There is an infinite number of primes, which the famous Greek mathematician Euclid first proved. This statement is actually known as Euclid’s theorem and is one of the most import-ant theorems in number theory. Mathematicians believe that there are an infinite number of

Mersenne primes as well.This knowledge is important because otherwise, we would be searching for prime

numbers that do not exist.

Beyond the interest of just finding greater prime numbers, there is actually a reason why prime numbers are critical in modern society. You might not know it, but it is likely that

your privacy and security relies on prime numbers. Rivest–Shamir–Adleman (RSA) encryption relies on the multiplication of two big prime numbers. The larger the

numbers are, the more difficult they are to factor and the more difficult your bank account is to hack. Most of the prime numbers presently used by banks

and companies such as Amazon are only a few hundred digits long, which are just enough to keep everything safe. The 23 million

digit prime number might be a bit of an overkill, but it never hurts to keep searching.

WHY DO WE CARE?

HOW MANY PRIMES ARE THERE?

113127

131139

149151

WINTER 2018 // CATAPULTA | 12

137

During the winter of 2006 to 2007, beekeepers all over the world started to see a 30 to 90 percent loss in their colonies as a result of a phenomenon known as colony collapse disorder, where most of the worker bees in a colony disappear simultaneously. In the US alone, there has been a steady decline in the honey bee population from five million in 1988 to 2.5 million today. Over the years, these insects have suffered from invasions of dangerous parasites like Acarapis woodi, microscopic mites that infect and lay their eggs within the trachea

as well as feed on bodily fluids. One perpetrator of colony collapse disorder is the parasitic mite Varroa destructor, which reproduces in honey bee hives. The female mites enter a hive cell and lay their eggs on the larva before the bees cover the cell in wax. When the eggs hatch, the young mites and their mother feed on the developing bee in the safety of the cell. Then the bee, which is not dead yet, chews its way through the wax, releasing the mother mites and their offspring. These mites are then free to spread across the beehive. When they are outside of the cell, they feed on the body fluids of the adult honey bees,

greatly weakening them. Pesticides have also contributed to the issue of colony collapse disorder. Neonicotinoids are a class of insecticides used throughout the agricultural world that in high doses lead to convulsions, paralysis and death; even in smaller amounts neonicotinoids may cause bees to lose their sense of location. Bees usually come in contact with these toxins by collecting pollen or consuming contaminated water, after which they often carry the toxins to the hive, ultimately

killing the whole colony. Other factors contributing to the disappearance of bees include too much genetic uniformity (when individuals are all genetically identical in a population), crop monocultures, overcrowding, and human activity. These are all major problems for bees, and, by extension, for humans as well. After all, one out of every three meals eaten by people is made possible by honey bees. If they were to die out, the thousands of plants that depend on them would follow. Honey bees are fighting for survival, and this is only one example of the catastrophic effects

that would occur if they became extinct.

COLONY

COLL

A

P

S

E

13 | Daniel Li - III CATAPULTA // WINTER 2018

The Chinese Academy of Sciences (CAS) in Shanghai has gotten closer in the process of eventually cloning humans. The same cloning techniques that scientists used to clone Dolly the Sheep in the late 1990s have been used to clone a primate closely related to humans - monkeys. The two cloned monkeys, Zhong Zhong and Hua Hua, are healthy and have been living for seven to eight weeks as of January 25, 2018. The process of cloning is not as easy as it may seem. Scientists have to remove a mature somatic cell, such as a skin cell, from the animal they wish to clone. They then transfer the DNA from the mature somatic cell to another animal’s egg cell that has its own DNA-containing nucleus removed - a process called Somatic Cell Nuclear Transfer (SCNT). Despite this long process, only a few of the clones are successful and healthy. Zhong Zhong and Hua Hua were the only two successful clones out of 127 eggs.

Nevertheless, the duo have been miracles for the scientific world as scientists

continue to learn more about primate cloning.

However, one of the scientists at CAS, Mu-ming Poo, says that this insufficient process may cause more harm than good. Poo says, “we must always consider the effect of our interference in the ecosystem and evaluate the risks.” He

went on to say that the cloning of humans is possible in the

future and that “the barrier of cloning primate species is now

overcome.” Many scientists, however, have opposed the idea of cloning humans as they claim it is unethical and that United States federal regulators would not allow the process due to several safety concerns. The mystery of cloning primates is finally approaching its conclusion. The next big question is whether or not scientists will ever make human clones.

MONKEY clones

WINTER 2018 // CATAPULTA Connor Stowe - III | 14

Imagine damaged organs regenerating and wounds healing

without leaving scars. A new field of biomaterial development called

regenerative medicine seeks to turn that dream into a reality. Regenerative

medicine, often referred to as “tissue engineering,” is the process of creating living,

functional tissue in order to repair or replace tissue or organ function lost due to age, disease,

damage, or congenital defects. It is a broad field that re-engineers damaged

tissues and incorporates research on self-healing.

Regenerative medicine stems from the idea of biomimicry: the concept that human problems can be solved through the imitation of nature. Several animals are able to regenerate whole organs that humans cannot. Some human body parts are able to self-repair after injury, such as the skin and the liver. Skin is constantly being

renewed and repaired, and the liver can grow back into its original size if it is damaged.

Humans, however, cannot regenerate limbs, while some other vertebrates

can. Fish, for example, can regenerate parts of their fins, eyes, kidneys,

hearts, and brains. Tadpoles can regenerate their limbs, tails, brains, and eye tissues; salamanders share a similar ability.

When someone loses an arm, he or she typically gets a prosthetic replacement. With regenerative medicine, however, the patient may be able to grow back his or her own

arm. Cells are the building blocks of tissues, the basic units of function in the body. Groups of

cells generate their own support structures, which

are called extracellular matrices or scaffolds (Figure 1). These

scaffolds act as templates for tissue regeneration, guiding the growth

of new tissues, and as transmitters for many signaling molecules, each

of which can set off a chain reaction that controls the cells. Researchers have successfully engineered these processes to fix damaged tissues and sometimes to create new ones.

There are two methods that scientists use to create new tissues. The first is to build a new scaffold for the patient by using a wide variety of items from proteins to biodegradable plastics. When this scaffold is created, cells can be introduced, and with the correct environment and growth factors-

REGENERATIVE MEDICINE

biomaterialscaffold

growth factors or

bioreacters

15 | Tara Kirchman - III CATAPULTA // WINTER 2018

substances that stimulate cellular growth and healing- tissues will start to develop (Figure 2). The other method is to use an existing scaffold from an organ donor. Scientists harvest cells from organ donors and grow new tissues from the leftover scaffolds. This process opens many doors in the world of personalized medicine, because a surgical patient’s discarded tissue can be combined with that patient’s own cells to make customized organs, reducing the chance of rejection of a foreign organ by the immune system.

Since regenerative medicine is a relatively new field, tissue engineering currently plays a small role in patient treatments. The United States Food and Drug Administration has approved the use of tissue engineered skins and cartilage. Organs such as supplemental bladders, small arteries, skin grafts, cartilage and even a full trachea have been implanted in patients. Professor Ioannis Yannas at the Massachusetts Institute of Technology has developed a highly porous

collagen-GAG scaffold by combining collagen with glycosaminoglycan, a polysaccharide found in many tissues of the body, and then using a controlled freeze drying process. Attempts are being made to engineer tissues and organs in vitro (in the test tube) using this method. These scaffolds, however, have limited use in human patients because the procedures are still experimental and very costly. In order for the scaffolds to become clinically and commercially viable, they need to be cost-effective and produced in small batches, rather than individually in labs.

figure 1

FF

F

figure 2

biomaterialscaffold

growth factors or

bioreacterscells

engineeredtissue

WINTER 2018 // CATAPULTA | 16

LIZARDTAILS Lizards have captivated humankind for

many millennia, inspiring mythical creatures like

dragons and wyverns. It is, however, unnecessary

to go as far as literature to find jaw-dropping lizards.

The Earth holds a stunning variety of them: from lizards

as small as just a few centimeters to the Komodo dragon, a

ten-foot goliath. Many lizards exhibit interesting and exciting traits, but there is none quite so

intriguing as the ability to undergo autotomy.

Not to be confused with autonomy, autotomy is the act of self amputation. When threatened,

many lizards are able to drop part of their tail and escape. Some species, such as the glass lizard,

have put their own spin on this adaptation. When a glass lizard loses its tail, that tail continues to

break into even smaller sections. Other species such as geckos are able to utilize their detached tail

in a different way. After their tail falls off, it continues to move, as if it were alive. This movement

distracts predators and can save the lizard’s life.

Even so, losing a tail is a huge trade-off. Not only does the tail aid in movement, but it also

has a social purpose. Most importantly, it serves as an energy reserve. Rival reptiles have actually

been observed scaring each other for the sole purpose of capturing and eating the tail.

But the most mysterious part in all of this is how the tail continues to move after it

is severed from the body. For a very long time, no movement patterns or habits were

found. There have been, however, many studies that have attempted to investigate

whether it is environmental stimulus or something else. As far as we know,

signals come from the very far end of the tail, working in a similar fashion to

our human spinal cord and our reflexes.

17 | Kevin S. Qi - II CATAPULTA // WINTER 2018

John Lin - IV | 18

CAR-T TherapyIn December 2017, Jef-

frey Zhou (’17) was named the Regional Champion of North America at the 2017

Breakthrough Junior Challenge for his video on chimeric antigen receptor T-cell

(CAR-T) therapy, a relatively new and prom-ising technique used to treat cancer.

In your body, T-cells are immune cells that assist the body in recognizing foreign agents and in coordi-

nating an immune response against them. T-cells, in most

cases, are very adept at detecting those anomalies. Cancer cells, however, can evade the detection of T-cells by dis-guising themselves as normal cells.

Cancer cells are the result of certain mutations in the cells’ DNA. These mutations are expressed as the cell un-dergoes mitosis, or cellular replication. These mutations cause the cells to divide uncontrollably, which could ulti-mately lead to cancer. Since cancer cells come from nor-mal cells, their cell membranes are very similar to those of normal cells, which makes it possible for cancer cells to avoid an immune response.

Cancer cells are the result of certain mutations in the cells’ DNA.

Artistic rendition of a T-cell equipped with

CAR proteins

Despite this, slight differences in antigens on the cell membranes can be detected. The first step is to isolate and to identify that a specific antigen has been found in the cancer cells. The next step is to de-velop the chimeric antigen receptor (CAR) protein. There are three parts to this protein: the first part is used to identify the specific antigen on the cancer cells’ membrane, the second part acts as a link between the extracellular and the intracellular part of the protein, and the last part triggers a response in the T-cell to combat the cancer cell. Once the protein is developed, scientists extract T-cells from the patient’s body and employ a lentivirus, which as a vector is able to incorporate the DNA of the protein into the DNA of a T-cell. Once the DNA of the receptor is incorporated, the protein will be present on the T-cell’s membrane. After the T-cells are mass-produced, they are injected back into the patient’s body and should work effectively in identifying and responding to cancer cells.

On August 30, 2017, the United States Food and Drug Administration (FDA) approved the first CAR-T therapy, making the treatment avail-able to young patients with acute lymphoblastic leukemia as well as to some patients with forms of Non-Hodgkin’s lymphoma. This move is a significant milestone for CAR-T therapy as well as gene therapy in general, since it was the first to be approved by the FDA. As more research is done on the topic of CAR-T therapy, more treatments will hopefully be de-veloped and approved in the future.

WINTER 2018 // CATAPULTA

NEPTUNEURANUSSATURNJUPITERVenus

MERCURY

GRAYPURPLE

BLUEGREEN

YELLOWORANGE

202520232022202120202019

POW

ERW

ALL

MODE

L YTE

SLA

SEMI

MODE

L 3MO

DEL X

MODE

L S

GRAY

PURP

LEBL

UEGR

EEN

YELL

OWOR

ANGE

2025

2023

2022

2021

2020

2019

1. The Tesla Semi is either blue or will be launched in 2023.2. The Model S will end up one planet closer to the sun than the purple payload.3. The Model S will not launch in 2023.4. Either the Model Y or the Tesla Semi will launch in 2020.5. The yellow product will not launch in 2019.6. The gray product will not go to Uranus.7. The yellow payload will be two planets farther from the sun than the Model Y.8. The Model X will not go to Uranus.9. Of the rocket to Uranus and the rocket that launches in 2021, one will carry the Powerwall and the other will carry the green payload.10. Of the Tesla Semi and the payload bound for Saturn, one is blue and the other will launch in 2025.11. The blue payload will end up one planet closer to the sun than the Model S.12. Of the Model S and the payload that will launch in 2020, one will go to Mercury and the other is yellow.13. The powerwall will go farther from the sun than the orange payload.

PUZZ

LEElon Musk might be crazy, but he knows what good P.R. is. Having sent his Tesla Roadster to Mars earlier this year, he has resolved to send a Tesla product to each of the other six planets in the solar system. Solve the puzzle to find the destination, color, and launch year for each of the six products.

NOTE: When counting the order of planets from the sun, please count only the six plan-ets listed in the puzzle.EX. Saturn is the fourth planet from the sun.

MARK THE GRID WITHX AND O

TO KEEP TRACK OF THE CLUES

Send your answer to catapultasciencebls@gmail.com for the chance to win a $15 gift card!