Duke Research Blog

Following the people and events that make up the research community at Duke.

Category: Students (Page 1 of 24)

How A Zebrafish’s Squiggly Cartilage Transforms into a Strong Spine

A column of green cartilage cells divides into an alternating pattern of green cartilage and red vertebra

Our spines begin as a flexible column called the notochord. Over time, cells on the notochord surface divide into alternating segments that go on to form cartilage and vertebrae.

In the womb, our strong spines start as nothing more than a rope of rubbery tissue. As our bodies develop, this flexible cord, called the notochord, morphs into a column of bone and cartilage sturdy enough to hold up our heavy upper bodies.

Graduate student Susan Wopat and her colleagues in Michel Bagnat’s lab at Duke are studying the notochords of the humble zebrafish to learn how this cartilage-like rope grows into a mature spine.

In a new paper, they detail the cellular messaging that directs this transformation.

It all comes down to Notch receptors on the notochord surface, they found. Notch receptors are a special type of protein that sits astride cell membranes. When two cells touch, these Notch receptors link up, forming channels that allow messages to rapidly travel between large groups of cells.

Notch receptors divide the outer notochord cells into two alternating groups – one group is told to grow into bone, while the other is told to grow into cartilage. Over time, bone starts to form on the surface of the notochord and works its way inward, eventually forming mature vertebrae.

X-ray images of four zebrafish spines

Meddling with cellular signaling on the notochord surface caused zebrafish spines to develop deformities. The first and third image show healthy spines, and the second and fourth image show deformed spines.

When the team tinkered with the Notch signaling on the surface cells, they found that the spinal vertebrae came out deformed – too big, too small, or the wrong shape.

“These results demonstrate that the notochord plays a critical role in guiding spine development,” Wopat said. “Further investigation into these findings may help us better understand the origin of spinal defects in humans.”

Spine patterning is guided by segmentation of the notochord sheath,” Susan Wopat, Jennifer Bagwell, Kaelyn D. Sumigray, Amy L. Dickson, Leonie F. Huitema, Kenneth D. Poss, Stefan Schulte-Merker, Michel Bagnat. Cell, February 20, 2018. DOI: 10.1016/j.celrep.2018.01.084

Post by Kara Manke

Student Ingenuity vs. Environmental Issues (like Cow Farts)

Lots of creative and potentially life changing ideas filled the Fitzpatrick CIEMAS atrium last weekend. From devices meant to address critical environmental issues such as global warming and lion fish invasiveness, to apps that help you become more sustainable, Duke’s Blueprint tech ideation conference showcased some awesome, good ol’ student-led ingenuity.

These bright students from around Durham (mostly from Duke) competed in teams to create something that would positively impact the environment. The projects were judged for applicability, daringness, and feasibility, among other things. During the Project Expo, all teams briefly presented to viewers like a school science fair.

One of the projects I liked a lot was called Entropy—a website with your own personal plant (I named mine “Pete”) that grows or dies depending on your sustainable actions throughout the day. The user answers simple yes or no questions, such as, “did you turn off the lights today?”

You can also complete daily goals to get accessories like a hat or mustache for your plant. The website connects to Facebook, so you can track your friends’ progress and see how green they’re living. Ultimately it’s just a good, fun way to keep your sustainability in check. Pete was looking super-cute after I spammed the yes button.

Another interesting innovation posed a solution to the difficulty of catching lion fish. Humans are a lion fish’s only predator, and we hunt them by spear fishing. Since lion fish are highly invasive, catching them en-masse could seriously benefit the biodiversity of the ocean (plus, they taste delicious). So one team came up with a canopy like contraption that attracts lion fish to hang out underneath it, and then snatches them all up at once like a net. Pretty neat idea, and if it was implemented on a large scale could be a huge benefit to the Earth’s oceans (and restaurants)!

After the expo, the top seven teams were selected and given three minutes to present to the judges and audience as a whole.

Every project was astounding. “Collide-o-scope” came up with a simple Arduino-based device to transmit elephant seismic activity to train drivers nearby in order to reduce the number of train-elephant collisions in India and Sri Lanka — currently a huge problem, for both us as humans and the elephant population.

Another team, “Manatee Marker,” proposed a system of solar powered buoys to detect manatees, with the hope of reducing frequent manatee-boat accidents. Considering that manatees are quiet, basically camouflaged, and thermally invisible, this was quite an ingenious task.

Perhaps my favorite project, “Algenie” stole the show. Methane gas is a huge factor to global warming — around twenty-five times more potent as a heat-trapping gas than Carbon Dioxide — and a lot of it comes from cow farts. However, we’ve recently discovered that putting seaweed in cow feed actually lowers methane emissions almost entirely! So this team came up with a vertical, three-dimensional way to grow algae — opposed to “two-dimensionally” growing across a pond — that would maximize production. Global warming is obviously a massive issue right now and Algenie is looking to change that. They ended up getting first place, and winning a prize of $1,000 along with GoPros for every team member.

Algenie’s prototype

At the end of the day, it wasn’t about the prize money. The competition was meant to generate creative and practical ideas, while promoting making a difference. After  attending the expo I felt more aware of all the environmental issues and influenced to help out. Even if you don’t feel like spending the time drafting up a crazy buoy manatee-detecting system, you can still do your part by living sustainably day to day.

Blueprint has done an awesome job of spurring young, enthusiastic students towards helping this planet — one cow fart at a time.

Post by Will Sheehan; Will SheehanPictures from Duke Conservation Tech

“I Heart Tech Fair” Showcases Cutting-Edge VR and More

Duke’s tech game is stronger than you might think.

OIT held an “I Love Tech Fair” in the Technology Engagement Center / Co-Lab on Feb. 6 that was open to anyone to come check out things like 3D printers and augmented reality, while munching on some Chick-fil-a and cookies. There was a raffle for some sweet prizes, too.

I got a full demonstration of the 3D printing process—it’s so easy! It requires some really expensive software called Fusion, but thankfully Duke is awesome and students can get it for free. You can make some killer stuff 3D printing, the technology is so advanced now. I’ve seen all kinds of things: models of my friend’s head, a doorstop made out of someone’s name … one guy even made a working ukulele apparently!

One of the cooler things at the fair was Augmented Reality books. These books look like ordinary picture books, but looking at a page through your phone’s camera, the image suddenly comes to life in 3D with tons of detail and color, seemingly floating above the book! All you have to do is download an app and get the right book. Augmented reality is only getting better as time goes on and will soon be a primary tool in education and gaming, which is why Duke Digital Initiative (DDI) wanted to show it off.

By far my favorite exhibit at the tech fair was  virtual reality. Throw on a headset and some bulky goggles, grab a controller in each hand, and suddenly you’re in another world. The guy running the station, Mark McGill, had actually hand-built the machine that ran it all. Very impressive guy. He told me the machine is the most expensive and important part, since it accounts for how smooth the immersion is. The smoother the immersion, the more realistic the experience. And boy, was it smooth. A couple years ago I experienced virtual reality at my high school and thought it was cool (I did get a little nauseous), but after Mark set me up with the “HTC Vive” connected to his sophisticated machine, it blew me away (with no nausea, too).

I smiled the whole time playing “Super Hot,” where I killed incoming waves of people in slow motion with ninja stars, guns, and rocks. Mark had tons of other games too, all downloaded from Steam, for both entertainment and educational purposes. One called “Organon” lets you examine human anatomy inside and out, and you can even upload your own MRIs. There’s an unbelievable amount of possibilities VR offers. You could conquer your fear of public speaking by being simulated in front of a crowd, or realistically tour “the VR Museum of Fine Art.” Games like these just aren’t the same were you to play them on, say, an Xbox, because it simply doesn’t have that key factor of feeling like you’re there. In Fallout 4, your heart pounds fast in your chest as you blast away Feral Ghouls and Super Mutants right in front of you. But in reality, you’re just standing in a green room with stupid looking goggles on. Awesome!

There’s another place on campus — the Bolt VR in Edens residence hall — that also has a cutting-edge VR setup going. Mark explained to me that Duke wants people to get experience with VR, as it will soon be a huge part of our lives. Having exposure now could give Duke graduates a very valuable head start in their career (while also making Duke look good). Plus, it’s nice to have on campus for offering students a fun break from all the hard work we put in.

If you’re bummed you missed out, or even if you don’t “love tech,” I recommend checking out the Tech Fair next time — February 13, from 6-8pm. See you there.

Post By Will Sheehan

Will Sheehan

Hearing Loss and Depression Are Connected

Jessica West is a PhD candidate in sociology.

Jessica West, a PhD student in sociology at Duke, has found that hearing loss creates chronic stress but that high levels of social support – from family, friends and others – can help alleviate depression. Given that hearing loss is a growing social and physical health problem, her study suggests a need for increased vigilance regarding hearing loss among older adults, West said.

Her study was published in the November issue of Social Science & Medicine and is available here.

Here, West discusses her research.

Your research examines the correlation between hearing loss and depression. That seems a logical connection: why study it in the way you did?

Despite how common hearing loss is, it is actually quite understudied. A handful of studies have looked at the relationship between hearing loss and mental health over time, but the results from these studies are mixed: some find a relationship between hearing loss and more depressive symptoms, while others do not. On top of the mixed findings, most studies have been based overseas, and studies based in the U.S. have tended to use state-specific datasets, like the Alameda County Study, which drew from Oakland and Berkeley, CA.

I use the Health and Retirement Study, which is nationally representative of adults aged 50 and older in the U.S., and therefore more generalizable to the U.S. population.

I frame hearing loss as a physical health stressor that can impact mental health, and that social support can alter this relationship by preventing a person from experiencing stress or reducing the severity of a reaction to it. To the best of my knowledge, this is the first paper to link hearing loss to health outcomes in this way.

What might surprise people about your findings?

More than one-fifth of the people in my sample have fair to poor hearing (23.12% or 1,405 people in the first wave). Hearing loss is really common in the U.S.

Also, I found that social support is most beneficial in easing the burden of hearing loss among people with significant hearing loss. Overall, this suggests that hearing loss is a chronic stressor in people’s lives and that responses to this stressor will vary by the level of social resources that people have available to them.

What does ‘social support’ mean in real terms? What can the family and friends do for a person with hearing loss to help them?

For people with hearing loss, it’s important that they feel able to lean on, talk to, and rely on family, friends, spouses or partners, and children. And going a step further, people with hearing loss need to know that these important people in their lives truly understand the struggles they face. What this means is that people with hearing loss can benefit quite a lot from having a network of people that they feel comfortable discussing things with or reaching out to when needed.

Do people with hearing loss have adequate mental health resources or care available to them?

My research shows that social support is really important for people with hearing loss. One suggestion I make in my paper is that audiologic – or hearing — rehabilitation programs could include educational training for significant others, like spouses or friends, to emphasize the importance of supporting people with hearing impairment. Audiologists, primary care physicians, family, and friends are all key resources that could be targeted in such rehabilitation programs.

 What is your next project related to hearing loss?

 I am currently working on several projects related to hearing loss. In one, I am looking at the relationship between an individual’s hearing loss and his/her spouse’s mental health outcomes. Few population-based studies have examined the relationship between hearing loss and spousal mental health longitudinally, so I hope this study will shed light on the experience of spousal disability within marriages.

Another project I am working on looks at hearing loss from a life course perspective. In other words, I am looking at people who self-reported hearing loss before the age of 16 and seeing how their hearing loss influenced their marriages, academics and careers. A better understanding of how early life hearing loss influences later life outcomes has implications for earlier identification of hearing loss and/or the use of assistive technology to help people remain socially, academically, and economically engaged.

CITATION: West, Jessica S. 2017. “Hearing Impairment, Social Support, and Depressive Symptoms among U.S. Adults: A Test of the Stress Process Paradigm.” Social Science & Medicine 192(Supplement C):94-101.

 Read the paper 

Guest post by Eric Ferreri, News and Communications

Duke Scholars Bridge Disciplines to Tackle Big Questions

A visualization showing faculty as dots that are connected by lines

This visualization, created by James Moody and the team at the Duke Network Analysis Center, links faculty from across schools and departments who serve together on Ph.D. committees. An interactive version is available here.

When the next big breakthrough in cancer treatment is announced, no one will ask whether the researchers are pharmacologists, oncologists or cellular biologists – and chances are, the team will represent all three.

In the second annual Scholars@Duke Visualization Challenge, Duke students explored how scholars across campus are drawing from multiple academic disciplines to tackle big research questions.

“I’m often amazed at how gifted Duke faculty are and how they can have expertise in multiple fields, sometimes even fields that don’t seem to overlap,” said Julia Trimmer, Director of Faculty Data Systems and Analysis at Duke.

In last year’s challenge, students dug into Scholars@Duke publication data to explore how Duke researchers collaborate across campus. This year, they were provided with additional data on Ph.D. dissertation committees and asked to focus on how graduate education and scholarship are reaching across departmental boundaries.

“The idea was to see if certain units or disciplines contributed faculty committee members across disciplines or if there’s a lot of discipline ‘overlap.’” Trimmer said.

The winning visualization, created by graduate student Matthew Epland, examines how Ph.D. committees span different fields. In this interactive plot, each marker represents an academic department. The closer together markers are, the more likely it is that a faculty member from one department will serve on the committee of a student in the other department.

Epland says he was intrigued to see the tight-knit community of neuroscience-focused departments that span different schools, including psychology and neuroscience, neurobiology, neurology and psychiatry and behavioral Sciences. Not surprisingly, many of the faculty in these departments are members of the Duke Institute for Brain Sciences (DIBS).

Duke schools appear as dots and are connected by lines of different thicknesses

Aghil Abed Zadeh and Varda F. Hagh analyzed publication data to visualize the extent to which faculty at different Duke schools collaborate with one another. The size of each dot represents the number of publications from each school, and thickness of each line represents the number of faculty collaborations between the connected schools.

Sociology Professor James Moody and the team at the Duke Network Analysis Center took a similar approach, creating a network of individual faculty members who are linked by shared students. Faculty who sit on committees in only one field are bunched together, highlighting researchers who bridge different disciplines. The size of each marker represents the extent to which each researcher sits “between” two fields.

The map shows a set of strong ties within the natural sciences and within the humanities, but few links between the two groups. Moody points out that philosophy is a surprising exception to this rule, lying closer to the natural sciences cluster than to the humanities cluster.

“At Duke, the strong emphasis on philosophy of science creates a natural link between philosophy and the natural sciences,” Moody said.

Duke graduate student Aghil Abed Zadeh teamed up with Varda F. Hagh, a student at Arizona State University, to create elegant maps linking schools and departments by shared authorship. The size of each marker represents the number of publications in that school or department, and the thickness of the connecting lines indicate the number of shared authorships.

“It is interesting to see how connected law school and public policy school are. They collaborate with many of the sciences as well, which is a surprising fact,” Zadeh said. “On the other hand, we see Divinity school, one the oldest at Duke, which is isolated and not connected to others at all.”

The teams presented their visualizations Jan. 20 at the Duke Research Computing Symposium.

Post by Kara Manke

 

Hospital Music ‘A Reminder That There’s Life’

When William Dawson took over the Performing Arts program at Duke Hospital, he became the first full-time staff Musician in Residence and Semans/Byrd Performing Arts Coordinator. As a teacher, band director and international performer, Dawson understood the effect music could have on one’s mood and emotions. Still, he had a challenging task ahead of him – Dawson had to prove that music could make an impact in a hospital setting.

In the spring of 2014, as part of the larger Arts & Health program at Duke Hospital, the department administered a survey. Staff had the opportunity to reflect on what programs had improved their hospital experience. As it turned out, live music was one of the top patient satisfiers. Armed with the information, Arts & Health chose to expand the Performing Arts program.

The Performing Arts program differs from music therapy, where board certified professionals work one-on-one or in small groups to achieve a personalized goal. Instead, it is composed of Artists in Residence, Performing Arts Volunteers and Hospital Concerts. Throughout the week, professional musicians are assigned to hospital units to visit patients at the bedside. The professional musicians play for relaxation, company, religious services, and special events including birthdays, weddings, anniversaries and the final moments of life.

Performing Arts Volunteers are students and community members who perform in hospital lobbies and concourses. To assess the musicians’ audience, Dawson used a handheld tally counter and noted that on average, 600-800 people pass through the hospital’s heavily trafficked areas per hour. The instrumental music provides an opportunity for a shared connection, he said.

“It’s like a magic trick,” Dawson said. “I can’t tell you how many times I’ve been playing there piano and a person has cried. It’s beautiful – it’s a reminder that there’s life.”

Hospital Concerts are offered periodically by the Artists in Residence and professional organizations. Recognizing the diversity of the hospital staff and patients, Dawson ensures that performers reflect a variety of backgrounds and can cater to a wide audience.

Since becoming coordinator, Dawson has been statistically analyzing the growth of the program, because potential donors and current financial backers would like to see measurable impact. Dawson has the figures: In the 2016-2017 fiscal year, the number of bedside requests increased by 282 percent, from 109 to 416. To match demand, the number of Performing Arts Volunteers increased by 120 percent and 1,156 hours of live music were performed.

In the future, Dawson looks forward to continued program expansion. Additional funding would also enable the Uke in Duke program, a hospital in-patient instructional ukulele program, to expand and serve more patients. With Dawson’s leadership and a dedicated team of professional musicians and volunteers, the Performing Arts program has an undeniable impact.

Post by Ameya Sanyal

Researchers Get Superman’s X-ray Vision

X-ray vision just got cooler. A technique developed in recent years boosts researchers’ ability to see through the body and capture high-resolution images of animals inside and out.

This special type of 3-D scanning reveals not only bones, teeth and other hard tissues, but also muscles, blood vessels and other soft structures that are difficult to see using conventional X-ray techniques.

Researchers have been using the method, called diceCT, to visualize the internal anatomy of dozens of different species at Duke’s Shared Materials Instrumentation Facility (SMIF).

There, the specimens are stained with an iodine solution that helps soft tissues absorb X-rays, then placed in a micro-CT scanner, which takes thousands of X-ray images from different angles while the specimen spins around. A computer then stitches the scans into digital cross sections and stacks them, like slices of bread, to create a virtual 3-D model that can be rotated, dissected and measured as if by hand.

Here’s a look at some of the images they’ve taken:

See-through shrimp

If you get flushed after a workout, you’re not alone — the Caribbean anemone shrimp does too.

Recent Duke Ph.D. Laura Bagge was scuba diving off the coast of Belize when she noticed the transparent shrimp Ancylomenes pedersoni turn from clear to cloudy after rapidly flipping its tail.

To find out why exercise changes the shrimp’s complexion, Bagge and Duke professor Sönke Johnsen and colleagues compared their internal anatomy before and after physical exertion using diceCT.

In the shrimp cross sections in this video, blood vessels are colored blue-green, and muscle is orange-red. The researchers found that more blood flowed to the tail after exercise, presumably to deliver more oxygen-rich blood to working muscles. The increased blood flow between muscle fibers causes light to scatter or bounce in different directions, which is why the normally see-through shrimp lose their transparency.

Peer inside the leg of a mouse

Duke cardiologist Christopher Kontos, M.D., and MD/PhD student Hasan Abbas have been using the technique to visualize the inside of a mouse’s leg.

The researchers hope the images will shed light on changes in blood vessels in people, particularly those with peripheral artery disease, in which plaque buildup in the arteries reduces blood flow to the extremities such as the legs and feet.

The micro-CT scanner at Duke’s Shared Materials Instrumentation Facility made it possible for Abbas and Kontos to see structures as small as 13 microns, or a fraction of the width of a human hair, including muscle fibers and even small arteries and veins in 3-D.

Take a tour through a tree shrew

DiceCT imaging allows Heather Kristjanson at the Johns Hopkins School of Medicine to digitally dissect the chewing muscles of animals such as this tree shrew, a small mammal from Southeast Asia that looks like a cross between a mouse and a squirrel. By virtually zooming in and measuring muscle volume and the length of muscle fibers, she hopes to see how strong they were. Studying such clues in modern mammals helps Kristjanson and colleagues reconstruct similar features in the earliest primates that lived millions of years ago.

Try it for yourself

Students and instructors who are interested in trying the technique in their research are eligible to apply for vouchers to cover SMIF fees. People at Duke University and elsewhere are encouraged to apply. For more information visit https://smif.pratt.duke.edu/Funding_Opportunities, or contact Dr. Mark Walters, Director of SMIF, via email at mark.walters@duke.edu.

Located on Duke’s West Campus in the Fitzpatrick Building, the SMIF is a shared use facility available to Duke researchers and educators as well as external users from other universities, government laboratories or industry through a partnership called the Research Triangle Nanotechnology Network. For more info visit http://smif.pratt.duke.edu/.

Post by Robin Smith, News and Communications

Post by Robin Smith, News and Communications

Martin Brooke: Mentoring Students Toward an X Prize for Ocean Robotics

We know less about the ocean floor than the surface of the moon. As one of the most unexplored areas of the world, multiple companies have begun to incentivize ingenuity towards exploring the oceans. Among these organizations are the Gates Foundation, the National Academy of Sciences, and X Prize.

XPrize team at Duke

Martin Brooke, second from left, and the student team with their giant drone.

Martin Brooke, an Associate Professor of Electrical and Computer Engineering at Duke, is presently leading a group of students who are working on mapping the ocean floor in an efficient way for the X Prize challenge.

Brooke said “open ended problems where you don’t know what to do” inspire him to do research about ocean engineering and design.

Martin Brooke

Martin Brooke

Collaborating with professors at the Duke Marine Lab that “strap marine sensors on whales” was a simple lead-in to starting a class about ocean engineering a few years ago. His teaching philosophy includes presenting the students with problems that make them think, “we want to do this, but we have no idea how.”

Before working on a drone that drops sensor pods down into the ocean to map the ocean floor, Brooke and his students built a sensor that could be in the ocean for a month or more and take pH readings every five seconds for a previous X Prize challenge.

Addressing the issues that many fisheries faced, he told me that he met an oyster farmer in Seattle who wished that there were pH sensors in the bay because sometimes tides bring in “waves of high pH water into the sound and kill all of the oysters without warning.” Citing climate change as the cause for this rise in pH, Brooke explained how increased carbon dioxide in the air dissolves into the water and raises the acidity. Emphasizing how “there’s not enough data on it,” it’s clear that knowing more about our oceans is beneficial economically and ecologically.

Guest Post by Sofia Sanchez, a senior at North Carolina School of Math and Science

Anita Layton: A Model of STEM Versatility

Using mathematics to model the kidney and its biological systems is a field of study located at the intersection of two disciplines.

Anita Layton is a math professor at Duke. (Photo by Chris Hildreth, Duke Photography)

But for Duke’s Anita Layton, PhD, the Robert R. and Katherine B. Penn Professor of Mathematics and a professor of biomedical engineering, that just adds to the fun of it.

Growing up, with her father as the head of mathematics at her school, she was always told she was going to be a mathematician just like him. So she knew that was the last thing she wanted to do.

When Layton arrived as an undergraduate at Duke, she began a major in physics, but she seemed rather cursed when it came to getting correct results from her experiments. She settled for a BA in physics, but her academic journey was far from over. She had also taken a computer science course at Duke and fallen in love with it. If an experiment went wrong “things didn’t smell or blow up” and you could fix your mistake and move on, she said.

While pursuing her PhD in computer science at the University of Toronto, Layton was performing very math-oriented computer science, working with and analyzing numbers. However, it would be a while before biology entered the mix

While she was never good at dissections, she told me she was always good at understanding things that ‘flow’ and she came to the realization that blood is something that flows. She thought, “Hey, I can do that.

Anita Layton, Duke

Anita Layton, Ph.D.

Layton began creating programs that could solve the equations that model blood flow quickly, using her background in computer science. She then started learning about physiology, focusing on the renal system, and making models

It was a journey that took her to many different places, with pit stops and U-turns throughout many different fields. Had Layton stuck with just physics or computer science or math, she never would have ventured out and found this field that she is an expert in now.

It’s her interest in many different fields that has set Layton apart from many other people in the STEM field. In learning a wide variety of things, she has gotten better at computer science, mathematics, biology, physics, and more

When asked about what advice she would give her younger self, or any young person going into college, it would be to do just that: “Learn more things that you’re not good at.” She encouraged just taking a chemistry or biology class once in a while, or a philosophy course that makes you think in ways that you don’t normally. It’s often in those classes that you unearth things that can truly set your life in a completely different direction, Layton said, and she’s living proof of that.

Cecilia Poston, NCSSM

Cecilia Poston

Guest Post by Cecilia Poston, a senior at North Carolina School of Science and Math

Glitter and Jell-O Reveal the Science of Oobleck

A black and white image showing a circular disk dropping into a container of oobleck

Mixing black glitter with oobleck allowed researchers to track the movement of individual cornstarch particles after a sudden impact. A computer program locked onto pieces of glitter and illustrated their motion. Credit: Melody Lim.

What do gelatin and glitter have to do with serious science? For some experiments, a lot! Duke alumna Melody Lim used jiggly Jell-O and a just a pinch of glitter to solve a scientific mystery about the curious goo many like to call oobleck.

To the uninitiated, oobleck is almost magic. The simple mixture of cornstarch and water feels solid if you squeeze it, but moments later runs through your fingers like water. You can dance across a bathtub full of oobleck, but stand still for too long and you will be sucked into a goopy mess. Not surprisingly, the stuff is a Youtube favorite.

Oobleck is an example of what scientists call a non-Newtonian fluid, a liquid whose viscosity – how easily it changes shape and flows – depends upon the force that is applied. But exactly how it is that this material switches from solid to liquid and back again has remained a mystery to scientists.

A piece of gelatin being squeezed viewed through a circular polarizer

This blogger mixed up a batch of jello to see the photoelastic effect for herself. When viewed with polarized light – from an iPhone screen and a circular polarizer – the jello changes color when squeezed.

“Water is simple to understand, and so is cornstarch,” said Lim, ’16, who is currently a graduate student at the University of Chicago. “However, a combination of the two produces this ‘liquid’ that ripples and flows, solidifies beneath your feet if you run on it, then turns back into a liquid if you stop running and stand still. I wanted to know why.”

The question beguiling scientists was whether sudden impact causes the cornstarch particles to “jam” into a solid like cement, or whether the suspension remains liquid but simply moves too slowly for its liquid-like properties to be apparent — similar to what happens if you skip a rock off the surface of a lake.

“There are these two opposing pictures,” said Robert Behringer, James B. Duke Professor of Physics at Duke. “Either you squish the material and turn it into cement temporarily, or you simply transmit the stress from the impactor straight to the boundary.”

Lim did two sets of experiments to find out which way oobleck works. In one experiment, she mixed black glitter into a transparent channel filled with oobleck, and then used a high-speed camera to watch how the material responded to the impact. The glitter let her track the motion of individual particles after the disc hit.

A piece of gelatin changes color when you squeeze it.

The photoelastic effect in gelatin.

Her video shows that the particles near the impact site jam and become solid, forming what the researchers call a “mass shock” wave that travels slowly through the suspension.

In a second set of experiments, Lim placed the oobleck in a container lined with gelatin, the main ingredient in Jell-O – besides sugar and food dye, of course. Gelatin is what is called a photoelastic material, which means that applying pressure bends light that travels through it, like a prism.

“Next time you eat Jell-O, get out your sunglasses and get somebody else’s sunglasses and look between them,” Behringer said. “Because if you give it a shake you should see all these stress patterns bouncing around.”

After the metal disc hit the oobleck, the gelatin let Lim see how fast the resulting pressure wave traveled through the material and reached the boundary.

A black and white image showing pressure waves traveling through a transparent material after impact

The researchers poured oobleck into a clear container lined with gelatin, a material that bends light when a pressure is applied to it. They saw that the force of a sudden impact is rapidly transmitted through the oobleck and to the boundary with the gelatin. Credit: Melody Lim.

They found that when the impact is sudden, the pressure wave traveled to the gelatin boundary faster than the “mass shock” wave. This means that the reason oobleck appears solid after a sudden impact is because the force of the collision is quickly transmitted to a solid boundary.

“If you are running across the water, that actually puts you into an impact velocity range where the pressure wave is significantly faster than the mass shock,” Behringer said. “Whereas if you try to walk across it, the impact speeds are slow, and the system actually doesn’t have the ability to transport the momentum quickly through the material and so you just sink in.”

“If you’d told me when I started that I would line a narrow container with Jell-o, add cornstarch, water, and black glitter, drop a piece of metal on it, then publish a paper on the results, I would have laughed at you,” Lim said.

CITATION: “Force and Mass Dynamics in Non-Newtonian Suspensions,” Melody X. Lim, Jonathan Barés, Hu Zheng and Robert P. Behringer. Physical Review Letters, Nov. 3, 2017. DOI: 10.1103/PhysRevLett.119.184501

Post by Kara Manke

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