Science Communication & Education | Duke Research Blog

Diffusion a la Chocolate Lava Cake

February 21st, 2013

By Ashley Yeager

Note: This is the second post in a four-part, monthly series that will give readers recipes to try in their kitchen and learn a little chemistry and physics along the way. Read the first post here.

Making chocolate lava cakes demonstrates the diffusion of heat. Credit: Ashley Yeager, Duke.

Between bites of hot lava cake and vanilla ice cream, freshmen taking Chemistry and Physics of Cooking talk about diffusion. Their conversation isn’t so esoteric that an outsider wouldn’t understand.

Instead, it’s a simple chat about how long to cook a cake based on how heat moves.

Understanding diffusion is a way to make sense of cooking times, says chemistry and physics professor Patrick Charbonneau, who is leading the class along with chef Justine de Valicourt.

Diffusion of matter is how particles in a liquid, gas or solid intermingle and move from a region of higher concentration to one of lower concentration.

Heat diffusion describes how hot particles warm up cooler particles around them, which allows the inside of a dish to cook, even though only the outside is heated.

Before turning his students loose in a kitchen in Smith Warehouse to eat a product of this process, Charbonneau and his teaching fellows had the group work through the equations that describe diffusion.

“Solving the diffusion equations of heat gives you a first estimate of how long to bake a cake or cook a turkey,” Charbonneau says. The cooking time for lava cake is especially critical in order to get the outside it to bake, while the inside remains gooey, de Valicourt adds.

In class, the students calculated that to make a muffin-sized lava cake with ingredients at room temperature in an oven at 400°F (204°C) would take about 10 minutes. In the lab, they found that the calculation was fairly accurate, but for a more exact estimate of cooking time, they needed to factor in the temperature of melted chocolate chips in their recipe.

“Still, with the cooking time being not so mysterious, it’s one fewer thing left to chance,” Charbonneau says, adding, “then you can be more creative with the recipe in other ways.”

He and de Valicourt, who have partnered with the Alicia Foundation to offer the Chemistry and Physics of Cooking class, have provided the following recipe for experimenting with diffusion and hot lava cake.

Hot Lava Cake –

Ingredients:
60g (1/3 c) dark chocolate chips
60 g (1/2 stick) butter
60 g (1/4 c) sugar
3 eggs (or 2 egg and 45mL (3tbs) coconut milk)
30 g (1/4 c) flour
small pinch salt
Non-stick cooking spray

Materials:
1 bowl (bain-marie)*
4 ramekin dishes or 1 muffin tin
2 medium bowls
1 scale (if weighing ingredients)
1 sieve
1 cooking thermometer (optional)

* You can make a bain-marie by placing a bowl over a saucepan of simmering water.

Instructions:

1. Preheat the oven to 400°F/204°C.
2. Melt chocolate and butter on bain-marie. Stir. Do not boil the water or the chocolate could burn.
3. Combine eggs and sugar (and coconut milk) in a medium bowl and whisk until bubbly.
4. Combine flour and salt in another bowl and pass it through the sieve.
5. With one person whisking and another pouring, slowly add the chocolate mixture to the egg mixture.
6. Add the flour and salt to the wet ingredients and whisk well.
7. Spray ramekins or muffin tin with non-stick cooking spray.
8. Fill the ramekins or muffin tin a little more than halfway full.
9. Place the ramekins or tin in the oven on the middle rack.
10. Bake until the cakes start growing. The interior of the lava cake should be around 158-176°F/70-80°C and the outside around 203-212°F/95-100°C – ie until the edges of the cake are set, but the center is still a liquid – about 7 to 10 minutes (less for smaller cakes).

Close Encounters of the Twitter Kind

January 30th, 2013

By Ashley Yeager

Astrophysicist Katie Mack and other researchers are starting to join Twitter to do better science. Image courtesy of: mediabistro.com

Before launching into dark matter’s effects on particle physics in the early universe, astrophysicist Katie Mack of the University of Melbourne in Australia took a little detour Wednesday to talk about Twitter.

The social media tool is helping her “do better science and learn about new science,” she said during her Jan. 30 seminar at Duke.

The talk materialized from a tweet she had posted a few days ago about attending ScienceOnline, an annual, Raleigh-based conference for scientists and communicators talking and writing about science on the Internet.

Duke physicist Mark Kruse, who joined Twitter in October after the 2012 Council for the Advancement of Science Writers meeting, saw Mack’s tweet about coming to the Triangle and then contacted her to see if she would like to speak about her research.

She said yes, obviously, and explained during her talk that the invitation, as well as the other networking she has done on Twitter, got her to thinking about why all physicists (and scientists) should use the site.

@AstroKatie shares her top reasons scientists should be on Twitter. Credit: Katie Mack, U. of Melbourne.

Here is a paraphrased list of her top five reasons:

1. You can see what scientific breakthroughs people are getting excited about.
2. You can keep track of science discoveries outside of your field.
3. You can share your work with a broader audience.
4. You can connect with other scientists in and outside your field, building your professional network.
5. You can connect and share your work with the public.

Clearly Mack’s invitation to speak at Duke illustrates her third point about Twitter. Now, she said, she looks forward to attending her first ScienceOnline meeting to build on those points and learn new ways of using the tool to connect with other scientists and science enthusiasts.

You can follow Mack at @astrokatie, Kruse at @markckruse and ScienceOnline at @ScienceOnline (or #scio13) if you’re already on Twitter.

And, if you’re a Duke researcher not yet on Twitter but want to be, check it out here, then contact the university’s news office if you’ve got questions.

Cooking up chemistry with candy

January 23rd, 2013

By Ashley Yeager

Note: This is the first in a four-part, monthly series that will give readers recipes that they can try in their kitchen and also learn a little chemistry and physics along the way.

Making sucre à la crème (left) and soft toffee (right) illustrates the fundamental principles of changing a liquid to a solid. Credit: Ashley Yeager, Duke.

A dozen freshmen pull on pieces of fresh, soft toffee, popping the candy into their mouths and licking it from their teeth as chef Justine de Valicourt talks about making the treats in a tiny kitchen on the second floor of Smith Warehouse.

Eating toffee and other sweets doesn’t usually spark a discussion about chemistry. But, as the students learn, the core of the eating experience is entirely about chemistry and some physics too, says professor Patrick Charbonneau.

He is leading a freshman seminar, called the Chemistry and Physics of Cooking, and in this particular class, he, de Valicourt and a team of teaching assistants work with the students to explore phase transitions – such as the change of liquid water to ice – by making two traditional Québécois desserts, sucre à la crème and soft toffee.

Both desserts have the same ingredients — maple syrup, butter and cooking cream. But, the experience of eating them is entirely different. One, the toffee, is stretchy, chewy and sticky, while the other, the sucre à la crème, is more crumbly and smooth.

The way the sugar molecules in solution cool down into a solid structure is what determines the final texture of a candy or chocolate, Charbonneau says.

During the lab, the students cool one mixture of syrup, butter and cream quickly and then whisk it. The stirring motion forces the sugar molecules to bump into each other, creating seeds of crystallization, which continue to grow and eventually clump together to give the sucre à la crème its solid, crumbly texture.

The students mix and heat the ingredients, then let them cool slowly, leaving the candy to set for at least three hours. Not whisked or stirred, it solidifies without forming too many large crystals, giving it a glassier appearance and a stickier, chewy texture, a signature feature of toffee.

Making these candies is pretty basic, easy enough that anyone could try it in a home kitchen, Charbonneau says, adding that he and de Valicourt have provided the recipes as a way to reach beyond the classroom and give more than just their students an introduction to cooking and, of course, the chemistry behind it too.

Sucre à la crème –

Ingredients:
1 can of maple syrup (540mL)
45 ml (3 tbsp.) of butter (plus some to grease the mold)
250 ml (1 cup) of cooking cream 35%

Materials:
1 medium saucepan
1 candy thermometer
1 wooden spoon
1 square mold
1 whisk
1 bucket of cold water

Instructions:

1. Put all ingredients in the saucepan. Stir.
2. Heat on the stove to 118°C (244°F) – 120°C (248°F). Be careful not to touch the bottom of the pan with the thermometer, which will give an incorrect reading.
3. Put the saucepan in the bucket of cold water and let the mixture cool down to 55°C (131°F) – 60°C (140°F) in the center. Do not stir the mixture.
4. Once cooled in the water, whisk the mixture to make a creamy pale paste. Pour in the mold and cut it before it gets too hard.
5. Let it rest 30 min in the fridge.

Soft toffee –

Ingredients:
1 can of maple syrup (540mL)
45 ml (3 tbsp.) of butter (plus some to grease the mold)
250 ml of cooking cream 35%

Materials:
1 medium saucepan
1 candy thermometer
1 wooden spoon
1 square mold

Instructions:
1. Put all ingredients in the saucepan. Stir.
2. Heat on the stove to 118°C (244°F) – 120°C (248°F). Be careful not to touch the bottom of the pan with the thermometer, which will give an incorrect reading.
3. Pour into the greased mold, let it cool down slowly, without disturbing it for 3-8 hours.

From the basement, female physicists shaped Duke and German science

December 5th, 2012

By Ashley Yeager

German physicist Hedwig Kohn (April 5, 1887 – 1964) in her laboratory, circa 1912. Image courtesy of: the Jewish Women’s Archive.

Physicist Hedwig Kohn‘s brother was murdered in a Nazi concentration camp in 1941.

Yet, when she trained young German physicists at Duke University a little more than 10 years later, she bore no resentment against them. Those students later returned to Germany and helped educate the country’s students in quantum mechanics.

Kohn fled Nazi Germany with the help of several prominent scientists in 1940, teaching first at the Women’s College in Greensboro, now UNC–Greensboro, and then at Wellesley College in Massachusetts. In 1952, she retired from teaching and accepted a research associate position working with physicist Hertha Sponer at Duke.

“It’s important that Kohn’s and Sponer’s tenure at Duke not be forgotten,” said physicist Brenda Winnewisser, an adjunct professor at The Ohio State University. The women’s lives and their research helped shape the physics department’s early encouragement of women interested in science.

Winnewisser, who earned her Ph.D. in physics at Duke in 1965, spoke briefly about Sponer and mostly about Kohn during a Nov. 28 physics colloquium. During her talk, Winnewisser recounted Kohn’s history, explained how she saved Kohn’s letters and photographs from destruction and described how she is using the archived information to write Kohn’s biography, a book called Hedwig Kohn: A Passion for Physics.

In her lab, which was in the subbasement of the Duke physics building, Kohn measured the absorption features and concentrations of atomic species in flames. The research was a continuation of what she had worked on from 1912 until 1933, when the Nazis stripped her of her privilege to do research and teach because of her being Jewish and female.

Still, the Nazis couldn’t take away the quality or importance of her work, which had a resurgence in citations in the 1960s as researchers began to test rocket designs and study plasmas, Winnewisser said. She added that Kohn also had an “indirect impact on improving quantum mechanics education in Germany after World War II.”

Three of the four physicists Kohn mentored at Duke returned to Germany to teach at prominent universities, bringing with them what they had learned from Kohn about flames, absorption and also quantum mechanics. “Kohn gave them the technical basis for successful careers,” Winnewisser said.

Her biography of Kohn, who died in 1964, is slated for release by Biting Duck Press in the spring of 2014.

Soft Matter, Or Just Marshmallows?

November 16th, 2012

By Ashley Mooney

When a chemist whisks cake batter, he’s not just thinking about the deliciousness that awaits. Whisking can actually induce chemical reactions integral to the texture of the dessert.

In a class being taught next term, Patrick Charbonneau, assistant professor of chemistry and physics, will help students apply science to creating edible masterpieces. For example, they will make two traditional Quebec desserts as an experiment in phase transitions. The ingredients in both are essentially the same, Charbonneau said, but one requires whisking while the other rests as it cools.

Students will measure the stiffness of marshmallows using chocolate bars, maybe it will end in a gooey s’more.

“By whisking you actually induce micro-crystallization and in the other one you remain in the glass phase, so the texture is completely different,” he said. “They’re going to be cooking—these are real desserts and real recipes—but the science is very controlled.”

Charbonneau works in a sub-discipline of chemistry called “soft matter,” but this doesn’t just mean marshmallows. The subject combines aspects of chemistry, physics, chemical engineering and material sciences—and fits perfectly with the science of cooking.

“The demos [in the class] are centered on food, so one of the cool ones is this material properties experiment measuring the [stiffness] of marshmallows using a chocolate bar,” Charbonneau said. “The chocolate bars are calibrated—you know their weight—and you just need a ruler to measure how much the marshmallow compresses.”

Although Charbonneau usually teaches an advanced physical chemistry course, he said he rediscovered old cuisine—and the science behind it—with the help of his friend from college and chef Justine de Valicourt, who is a visiting artist at Duke. De Valicourt has an undergraduate degree in biomedical sciences, but opted for culinary school rather than medical school. She will teach the cooking components of the seminar.

The class will meet once a week in spring semester for two and a half hours, with the first half dedicated to theory and food-centric demos, followed by cooking experiments and a dinner run by de Valicourt.

While cooking may make science more appealing to the non-scientists at Duke, Charbonneau said a basic understanding of chemistry is required in order to discuss the material in detail.

“Sure there’s the detailed chemical reaction when you’re browning something, but browning is not the entire thing,” he said. “There are some structural issues, and taste is something that is much more complicated than just a chemical that touches a receptor—there’s a texture, there’s a look.”

Since there is limited space in the kitchen—and thus limited space in the class—Charbonneau said he hopes he can make the topic more accessible to the Duke community through de Valicourt’s office hours and a final banquet.

“The students from the class will help with the cooking and serving of the banquet,” he said. “It’s the chef’s job to be able to teach them (how to cook properly) and to supervise them, so that should be fun. Hopefully we’ll be able to reach as many people as possible. We got amazing support from everybody in the administration that we talked to. I’m very grateful.”

Since bringing together a chef, a chemist and class space took a “special alignment of the planets to make it happen,” the class—which is being taught for the first time in the spring—may also be its only run.

“The chef is here for a semester, and I would never have dared—because I’m a theorist—to do a thing like this without her or the TA’s,” Charbonneau said. “I do hope though that some of the material we’ve built up will be able to be used as a special topic in general chemistry. I would like to have a module where I would be able to reuse the demonstrations and the content, and maybe even bring in a local chef at that point who would be interested. That’s one way to project it in the future.”

For those interested, the course is called Chemistry and Physics of Cooking, listed as Chem 89.

“It’s listed under chemistry, but it’s really about chemistry and physics,” Charbonneau said. “We’re looking at more physical chemistry—physics processes, denaturing of proteins. We’re also looking at the material science idea, such as viscosity, elasticity—viscoelastic moments, which chemists would never talk about… in a general chemistry class.”

Film Presents Alan Turing In Full; Duke Preview Monday

October 24th, 2012

Guest post by Pender M. McCarter, Trinity College (1968), Senior Public Relations Counselor, IEEE-USA/Washington

A scene from the movie “Codebreaker” about the life of Alan Turing.

Alan Turing has been hailed as a digital Darwin, an Einstein and a Newton who helped to “catapult civilization in to the digital age.” The British mathematician laid the groundwork for everything we do with computers today, according to Apple co-founder Steve Wozniak. The Turing Machine incorporated all the basic aspects of computer input and output. His 1950 paper, “Computing Machinery and Intelligence,” posited that computers can be programmed to mimic human behavior. And at the end of his life, Turing wrote about pattern formation in biology, what he called morphogenesis, that could be observed in animal stripes and spirals and even exist in ecosystems and galaxies. Turing is best known for leading the British Bletchley Park code breakers team that cracked Germany’s Naval Enigma Code, helped end World War II, and saved perhaps millions of lives.

Yet until recently Turing’s contributions have been little known or appreciated outside of the sci-tech community. And his personal life as a gay man has generally been glossed over. In 2012, the centenary of Alan Turing’s birth, hundreds of events have been held worldwide. A new film, Codebreaker, presents Turing’s personal and professional life without flinching, including how his sexual nature contributed to his extraordinary achievements and tragic downfall.

The drama documentary emphasizes that the support and encouragement Turing enjoyed with other eccentric and brilliant technologists at Bletchley Park motivated and sustained him. When he lost this community after World War II, at a time when there was a craving for normalcy and scant tolerance for non-conformists, Turing learned how unforgiving the world could be.

The drama scenes in Codebreaker center on the psychotherapy sessions Turing participated in during the last 18 months of his life. In these final months, Turing faced persecution as a gay man under the same 19^th century British laws that were used to prosecute Oscar Wilde. In 1954, at the age of 41, Turing committed suicide leaving us to wonder about potential future accomplishments in a more accepting and tolerant time. In 2009, former British Prime Minister Gordon Brown apologized posthumously to Turing: “We’re sorry; you deserved so much better.”

Codebreaker will be screened at the Duke Center for LGBT Life (02 West Union Building) on Monday, Oct. 29, from 7-8:30 p.m., with underwriting from IEEE-USA, the Washington-based office of the IEEE, the world’s largest professional association for the advancement of technology. The drama documentary will be introduced by Executive Producer Patrick Sammon, who will also answer questions about the film.

Here’s a link to the trailer: http://www.turingfilm.com/

Science Under the Stars!

October 23rd, 2012

By Pranali Dalvi

The 8^th annual Science under the Stars, held in the lower lobby of the French Family Science Center, brought together several Duke departments, research groups, and organizations. Kids of all ages were busy participating in hands-on science activities.

Bioluminescence demo by Dr. Hendricks

Lab administrator Dr. Diane Hendricks had a station to illuminate the bioluminescent properties of Pyrocystis fusiformis, a marine dinoflagellate. Dinoflagellates bioluminesce when their cell wall is exposed to sheer stress, which triggers the light response. When asked why dinoflagellates glow, some kids hypothesized that dinoflagellates glow to look larger and more threatening so they can ward off predators. Scientists mistakenly thought so for a while, too. However, scientists now favor the burglar alarm hypothesis, based on the idea that the enemy of my enemy is my friend.

“Rather than trying to scare away the predators, they are actually attracting the predators of their predators,” Dr. Hendricks explained. Because the color blue is most easily seen in the ocean, many sea creatures bioluminesce blue. As a memento of Dr. Hendricks’s demo, kids were able to take home glowsticks of various colors!

The physics department showed students how to make Oobleck. Oobleck is a mixture of 2 parts corn starch and 1 part water. It displays shear thickening behavior, meaning that its viscosity – or resistance to flow – increases with shear rate. When the shear rate is low, the corn starch grains can easily move past one another and oobleck flows easily. However, under high shear stress, the corn starch grains pack tightly together and prevent the flow of grains past one another.

The process of preparing oobleck

Oobleck is an example of a non-Newtonian fluid. Non-Newtonian fluids are those whose resistance to flow changes according to the force that is applied to the fluid. One application of non-Newtonian fluids is in the soles of running shoes. The sheer thickening fluid hardens in response to the forces exerted during running or walking.

A favorite stop for the kids was CSI Durham presented by the Department of Evolutionary Anthropology and Anatomy. Students were required to perform cranial, pelvic, and femoral assessments to identify who the “missing victim” was. The skull and pelvis have distinct features in males versus females, and the femoral head and length diameter predict stature pretty accurately.

The event was sponsored by the Chemistry Department and organized by Dr. Kenneth Lyle.

Refereed physics for Twitter and Facebook, maybe

October 19th, 2012

By Ashley Yeager

These library stacks of science journals are going out of style as more publishers opt for online-only, open access formats. Credit: UCSF.

When journal publishers send peer-reviewed tweets, they’ll have truly entered the digital age. They’re not there yet, but that doesn’t mean they’re not trying, said Gene Sprouse, editor-and-chief of the American Physical Society(APS) and a physics professor at Stony Brook University.

Sprouse, speaking at an Oct. 17 physics colloquium, described how the Internet is changing the way scientists share their research. They used to submit papers to journals, have their ideas vetted by other scientists, and then see their arguments and data in print — or not. He said it has been this way since the 1660s when the first journal, Philosophical Transactions, was first published.

But with online journals available right on researchers’ desktop and open-access digital archives, such as arXiv.org, journal editors, like those at the helm of magazines and newspapers, are trying to figure out how to shift print publications online while still making a profit.

“Eventually print journals will disappear,” Sprouse said, explaining that sans paper, authors and publishers could include new types of content like movies and active graphics in their articles. But even with new media features, “what physicists want is rapid acceptance of their paper into a prestigious journal with no hassles during peer review. They want attention for their work, and they want it widely distributed.”

To meet those demands in the new media landscape, APS has developed a Creative Commons license for authors to share their articles on their personal web sites and encourages them to publish pre-prints in online digital archives, such as arXiv.org.

Hoping to merge the prestige of the “baby Nature” journals – Nature Photonics, Nature Optics, Nature Physics, etc. – with the open-access model of the Public Library of Science, or PLOS, journals, the society has also created Physical Review X.

It’s the society’s first online-only, fully open-access journal. The one-year-old publication, which charges authors $1,500 per accepted article, is already comparable in prestige to APS’s other leading journal, Physical Review Letters. The difference is that now authors have an open-access journal to submit to at APS, which is important as more funders push researchers to submit to that type of publication, Sprouse said.

The society isn’t ignoring Twitter and Facebook either. When asked when the society would post the first refereed physics tweet, Sprouse said he couldn’t really say because he personally doesn’t use social media. But, APS, he added quickly, is working on its social media strategy and would “welcome any advice from those of you exploring that realm.”