When you first walk into Bruce Hay's genetics class, it looks like any other 21st-century college lecture hall: the professor, backed by his PowerPoint slides, faces a room full of students with iPads. However, as Hay delivers a lecture about the mechanisms that inhibit gene expression, a rectangular yellow bubble suddenly pops up on the screen below his lecture slide. It's from a student, asking a question about RNA interference. Soon another bubble pops up, this one with a link to a video that explains how microRNAs can affect the color pattern of flower petals. Other bubbles branch off from each other, and hands rise into the air.

Suddenly, you realize you're in the classroom of the future.

Those pop-up bubbles are a key component of a new interactive lecture format made possible by an app developed by two Caltech alums and brought to campus by Caltech's Center for Teaching, Learning, and Outreach (CTLO). The iPad app—produced by Su-Kam Intelligent Education Systems, or SKIES, named after cofounders Julius Su (BS '98, BS '99, PhD '07) and Victor Kam (PhD '08)—is now being used in several classes on campus.

"It's been known for a long time that lecturing—just a professor teaching and the students passively listening—is not an optimal way for students to learn. You always want to have students doing some thinking, some processing, and some recall during the lecture," says Su, who is a CTLO program manager in addition to being one of the cofounders of SKIES.

With this in mind, Su and his colleagues at CTLO have been experimenting with ways to change the traditional Caltech classroom. The SKIES app is based on one such approach—active learning, which gets students participating in a variety of ways, and is supported by a great deal of evidence indicating its effectiveness.

The wiki-like app facilitates this kind of active learning by allowing students to directly interact with lecture materials both inside and outside the classroom. The app compiles and connects notes, links, videos, and other materials—contributed by students, teaching assistants, and the professor—into a branching tree of collective knowledge stemming from an initial seed of slides or other multimedia material.

This concept of students and teachers interacting to create knowledge together is what drew Professor of Biology Bruce Hay to become one of the first users of the SKIES app in 2012.

Students can ask questions during Hay's lecture in the SKIES app. The questions or comments pop up below the lecture slide in real time.

"The big struggle that I have—and that lots of people have—is just getting students to ask questions; getting people to turn the class into more of a discussion rather than just the lecturer speaking," Hay says. "I knew that Julius and Victor were developing this prototype, and I thought, I've been teaching this same course for 15 years now and maybe this would be a good idea, to just try something new that might make it a little more interactive."

In the three years Hay has used the app in his genetics class, he says the app has done just what he'd hoped it would: provided an alternative channel by which students can participate. During class, Hay says students often add cards to his lecture slides as a form of public note-taking; for example, in one lecture, a student added a card to a particular slide, saying, "Professor Hay says this would be an excellent exam question." After class is over, he says, students often post cards with questions about the day's materials; these can then be addressed by Hay or the class's teaching assistants, either directly in class or through another branch of cards in the app.

Hay says that the app lets him monitor what students are contributing—and it allows him to promote and highlight information he considers particularly helpful and relevant to understanding the lecture material. Conversely, the app also allows students to rate how well they understand his lecture slides, as well as the cards added by TAs and other students.

"After class, I take a look at the reviews to see how well the students understood what we talked about in class that day," Hay says. "If I see that a slide is rated green [the app's version of a thumb's up], I can assume that it was pretty straightforward and understandable. But if the students have rated it red, I can add extra material to the slide, like additional text or figures. Then, in the next class, I can go back and say, 'It looks like this part was a little bit difficult. Let's just go back and review it again before we go on to the new stuff.'"

Although these continuous double checks require a bit more effort on the part of the professor and the students, they seem to be paying off: Hay says the average grades in his class went up by almost a full grade point after his first year using the app. The improvement was so noticeable, he says, "it was actually almost frightening. That was probably the biggest indication this was making a difference in terms of learning, instead of just making it fun for me and them."

In the SKIES app, students create dialogue by adding 'cards' that branch off of the professor's lecture slides.

Hay says the added content from students in the SKIES app over the past three years has enabled his course "tree" to grow and improve each term. "I'm not just repeating all the same slides every year. Many of the slides stay the same, but now I add new things, based on what the students found helpful in terms of explanations, quiz questions, and examples. So everyone is involved in making the course better," he notes.

After hearing about some of the app's early successes, other instructors across campus began using SKIES in their courses. This includes Bill Goddard, Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics, who has used SKIES to teach lectures and manage group projects in his computational and theoretical chemistry classes; Jeff Mendez, lecturer in chemistry, who has used SKIES to teach the lecture portion of his freshman solar chemistry lab; and Yaser Abu-Mostafa, professor of electrical engineering and computer science, who has used SKIES to promote and manage discussions in the in-class portion of his well-regarded Learning From Data MOOC, which has attracted over 200,000 students within and outside Caltech since its inception.

The app is also being used by many Caltech outreach programs, such as the Summer Research Connection, the Community Science Academy, and Harry Gray's Solar Army, to broaden the impact of university initiatives at the K–12 level; and is being used to teach several classes at Pasadena City College, as well as in several local middle schools and high schools.

SKIES is currently only available on iPad and iPhone, and as the app's popularity has grown, support from the Provost's Innovation in Education Fund and the Bechtel Foundation fund has allowed CTLO to expand the use of SKIES on campus through the purchase of more iPads. In the future, Su hopes that the app's reach will grow even further, both on iPads and eventually by expanding the app to work on other operating systems.

Aside from those few comments on the hardware limitations, Su says the feedback he and his colleagues at the CTLO have received from professors and students who have been using SKIES has been overwhelmingly positive.

"CTLO is continually providing Caltech faculty and TAs with evidence about what helps students learn more effectively. Active and collaborative approaches tend to work well," he says. "This app is just one way to foster more active and collaborative learning, but I think we can already see that it's providing new ways for professors to make classes even more lively and engaging for students at Caltech."

It is easy to assert offhandedly that the president made a particular decision in order to undermine Congress, or that Congress's latest bill is simply an attempt to bypass the Supreme Court. It is much harder to prove whether such arguments are accurate. After all, it is usually impossible to test such claims in a controlled manner. Still, some political scientists—such as Alexander Hirsch, a new associate professor of political science at Caltech—are using tools first developed by economists to do just that, creating mathematical models of these arguments. The models then serve as virtual laboratories that political scientists can use to test assumptions and identify implications.

Before coming to Caltech in August, Hirsch was an assistant professor of politics and public affairs at Princeton University. He earned his undergraduate degree in political science and economics at Yale University in 2003 and completed his doctoral work in political economics at Stanford Graduate School of Business in 2010.

Hirsch can often be found on campus with his dog, a goldendoodle named Baci, nearby. We recently sat down to talk with him about using models to study political behavior, why he is thrilled to be at Caltech, and where his research is headed.

What is the focus of your work?

I study simple, or toy, mathematical models of strategic behavior—game theoretic models as developed in economics, applied to political questions. The way I think about this kind of work is that when people study politics or they study elections, or they say that Obama chose to do this or the Republican Party is doing that, they're just making arguments about causal relationships. And those arguments are not really any different from the arguments that scientists make—you have assumptions, and you have implications. A and b implies c. If Obama wants a and thinks the Republican Party operates in b way, it suggests that c is the right strategic action for him to take. Those of us who use models are just subjecting those kinds of arguments to some mathematical rigor.

What do you gain from such modeling?

I think this is a valuable approach for a few reasons: First, people can be very sloppy about the arguments they make about why politics operates the way it does. Formalizing your logic forces you to be much more careful.

Writing down models also helps you discover the implications of your assumptions. People make assumptions about the preferences of political actors or how political institutions operate, and those assumptions have implications. The value of the model is not only to check whether those implications are valid, it is also to derive new implications that you didn't even imagine until you wrote down the model. Then you can use the data to actually see whether those implications come to pass.

What brought you to Caltech?

There are several things. One is that although many people don't know it, Caltech incubated this type of political-science modeling work early on, and the intellectual giants of the field were—or, in several cases are—here. It was an honor to have been invited to come and participate in that work.

One of the most appealing things to me about Caltech is that unlike many institutions of higher learning, Caltech lives and breathes research. There are other institutions that are wonderful at teaching and wonderful at research. But at Caltech it seems to me that to be wonderful at teaching means that you teach the students what the frontier of research is—that teaching and research are not different things.

An anecdote from teaching my first quarter here illustrates my point. It was around midterm time, and the students came in looking really exhausted. So I said, "Oh, I guess it's midterm time, so things are tough." And they said, "Well, actually, NSF grant deadlines are this week, so we were up all night."

Where does your passion for research come from?

My dad is a physicist and a theorist, so I grew up in a household in which academia was certainly respected as a profession. But the truth is that I wasn't really interested in pursuing an academic career for most of my childhood or even college. I gravitated a little bit more toward music and literature and stuff like that, none of which I pursued in a very serious way.

In college, I took some computer science courses and some math courses, but I was always interested in politics. Eventually, I started to take classes in economics, and I started seeing game theory taught by people who were interested in political applications. I found it very intellectually appealing that you could have these little mathematical toy models that look silly, but can say very surprising and in some cases deep things in this very controlled environment of the model.

So I saw economics and thought, "These tools are really cool and very rigorous and fun," and I saw political science and said, "These are interesting questions that I care about." So I started to gravitate in a direction where I could combine the two.

What are some of the specific topics you have researched using this approach?

I currently have a big research agenda on the incentives that legislators have to invest in developing expertise or developing new policy proposals. When will they want to put in a lot of effort versus very little effort to become an expert in an area or to develop new policies?

In one of my early papers, I also explored the idea that politicians, rather than disagreeing about what the aims of government should be, disagree about which policies will achieve those aims. I wrote down a model that said, let's imagine that politicians actually agree about what they want, but they disagree about how the world works—how to achieve those outcomes. So, for example, maybe Republicans and Democrats disagree about tax rates because they disagree about whether high taxes actually have a disincentive effect on work.

How do you write down a mathematical model about something like that?

Well, you're not trying to write a model that explains the world. You're just trying to write down the simplest possible structure that captures the types of political behaviors that you think are interesting.

In this case, the model that I wrote included just two possible policies: a and b. In the real world, of course, there are lots of possible policies, but we don't need to model all of those to try to understand what some of the political incentives are. In the model, there are two outcomes that can result from each of those policies—success or failure. I assign a utility of zero if the policy fails, and some number greater than zero if it succeeds. Then you need people to have the opportunity to learn, so you model a game in which people make the decision twice. They make their first choice and see what happened, then they use Bayes's rule—a simple mathematical theorem—to update their beliefs about which of the two alternatives is the right one, and then make the decision again.

The point is to predict patterns of what might come out of these incentives. It's not like modeling an atmospheric system; I'm not going to be able to make very precise estimates about what Congress is going to do tomorrow. It's to try to understand how these pieces fit together and what these assumptions might imply about the behavior of political actors.

What questions are you currently modeling?

There is an extensive literature in economics and in political science that tries to understand the nature of lobbying. Why does lobbying work the way it does? Why is lobbying effective? What are interest groups doing that legislators are responding to?

But there isn't a lot of literature on the lobbyists themselves. I am starting a project with Pablo Montagnes of the University of Chicago to try to understand the strategic incentives of lobbyists. Part of the focus is to try to understand the importance of the political ideology of a lobbyist. If you look at the available data, lobbyists look like passionate participants in the political process who have very real preferences about what government should look like, and not just like mercenaries who are willing to take sacks of cash to represent any interest group.

It's still very early, and we're working on the model. But we think that ideology plays a big role in what preserves a lobbyist's ability to represent you while also getting cash for it—it's what protects them from the incentive to take cash from anybody.

What do you do outside of work?

We have a very domestic life. My wife, Melanie, and I hang out with the junior faculty here. We like to eat at good restaurants. We've also been hiking a lot since we moved to L.A. We've hiked Echo Mountain maybe 12 times already. And we hang out with the dog.

Since 2007, Caltech alumnus Cesar Bocanegra (BS '95) has been the chief operating officer (COO) of DonorsChoose.org, a nonprofit that connects public school teachers with donors interested in supporting their unique classroom projects. The organization crowdsources the funding for each teacher-proposed initiative as well as arranges the purchase and shipment of any requested supplies once the fundraising goal is met. Founded in 2000, the company has had a substantial impact: approximately 62 percent of public schools in the United States have at least one teacher with a project on DonorsChoose.org. 

One of Bocanegra's focuses as COO is on the role analytics might play in growing the company's ability to improve education policy nationwide. He credits his Caltech education with giving him the tools to see what he calls the "opportunities in the data" he collects about the various requests from classrooms around the country. He hopes to use those data to inform administrators and elected officials about the needs and priorities of educators.

Read more about Cesar Bocanegra and his work with DonorsChoose.org.

Caltech's student leaders have full plates. In addition to splitting their time among responsibilities in academics, research, athletics, internships, social causes, and many other activities, they have also been elected to serve as representatives of and advocates for their peers.

However, these students say the juggling act can be a gratifying challenge. We recently spoke with Catherine Jamshidi, Connor Rosen, and Sunita Darbe about their experiences in student leadership, their goals for their organizations, and their time-management strategies.

What are your main leadership responsibilities?

Darbe: As chair of the Graduate Student Council (GSC), my job is to be the face of the graduate student body when interacting with all of the other parts of Caltech—for example, in working with the undergrads and with all of the various administrative offices and staff offices. I also try to keep an eye on what graduate students are bringing up and try to make sure that those concerns are heard by the appropriate people.

Rosen: I'm the chair of the Interhouse Committee (IHC), and the ASCIT vice president for nonacademic affairs. I deal mainly with housing, dining, issues related to how housing placements happen, and any other issues related to where people are living. IHC is also involved in the policies related to those issues, so I also serve as the intermediary between the administration and the students on these policies.

Jamshidi: As ASCIT (Associated Students of the California Institute of Technology) president, my first job is to oversee the ASCIT board of directors, which is the student government of the undergraduates. I try to be in touch with what's going on around campus, what the student body is currently concerned about, and how I can bring those concerns to the relevant administrators or members of the faculty board.

Since you are all student leaders, can you tell us what year you are and what you're studying?

Jamshidi: I'm a junior, studying computer science and business, economics, and management.

Rosen: I'm a senior majoring in chemistry. I do work on protein degradation in the biology lab of professor Alex Varshavsky.

Darbe: I'm a fourth year graduate student in materials science. I work with Harry Atwater on optics for ultrahigh-efficiency solar cells.

What were your goals when you began your term at the end of the last school year?

Darbe: Obviously the technical training at Caltech is awesome, bar none. But we also want to make sure that some of the nontechnical skills—ones that are important for professional development, but don't necessarily come through the graduate curriculum—are supported by GSC efforts. This year another one of our goals is to support and recruit a diverse student body, and we've been very pleased to see support for this at all levels in the administration.

Jamshidi: My main goal is to learn about and address what the students care about. I also went into my term expecting to be able to give good direction to the individuals on the board of directors, helping them figure out what they need to be doing in their roles.

Rosen: A lot of what the IHC works on are yearly needs that relate to the way the house system functions. The biggest of these is rotation, which is the process by which first years are assigned to a house. When I came in as IHC chair, I set goals for how efficient and effective I wanted the process to be. In the end, I wanted the students to be pleased with both with the process itself and with the outcomes. Rotation was all over and done at the beginning of the school year, and it went very well—I think we improved on the things we wanted to improve on from previous years.

How did you get involved in this leadership role, and what made you want to be a leader?

Rosen: I ended up in student government almost by accident. I love the houses, and I was very involved in my house socially, and when someone said that our house needed a president, I said, "I want to do it." As president of my house, I served on the Interhouse committee for a year before becoming chair. I like being involved because I care about the people, I care about the house, and I want to be here to help students solve their problems, so they can go back to focusing on everything else that life—and Caltech's coursework—is throwing at them.

Jamshidi: I started in student government during the third term of my freshman year. For the first two terms I was here I saw the upperclassmen who were involved, and they seemed to know everything—I wanted to be like them. And my involvement was also partially driven by boredom. I play volleyball during the fall term, and then during winter I had my first break from volleyball in a long time and I was like, "I have so much free time! What do I do now?" So I became the ASCIT secretary and I really enjoyed it.

Darbe: I was involved in GSC last year, in the capacity of organizing a professional development conference. When I see something happening and I have opinions about it, I don't like to let things sit. I like to do something about it. And fortunately, because of its small size, Caltech is an easy place to make things happen.

It sounds like these roles are time-consuming. How do you fit in time for all of the other things in your lives, like classes, research, athletics, and so on?

Jamshidi: I balance it by staying extremely organized. I schedule everything that I do, pretty much always. And if I notice that I'm spending more time on homework, I'll reschedule everything. I don't know how else I'd be able to do it.

Darbe: I can only do this role by virtue of it being a one-year commitment. It's a lot of time, but it's really rewarding, and it's really cool to see the academic institution from the other side—to sort of peek behind the curtain.

Rosen: I've always made my position in the IHC a priority. I took this on because I felt it was important, and I had a lot of things I wanted to get done in the position—things that I cared about accomplishing. It is a priority, not only in terms of when I am in class, but also when I sign up for classes. If I know I could be spending 60 hours a week on IHC commitments during a particular term, I'm not going to sign up for 60 hours of classes. For example, during rotation there was one day where I woke up at 8 a.m., went to bed at 1 a.m. the next morning, and only had a lunch break in between.

How will these leadership skills be applicable to your after-graduation plans?

Darbe: I'm interested in being a research scientist. It's not yet clear to me where the most exciting opportunity is going to be, but I think that a lot of these GSC skills are going to be very helpful. Being able to corral people, and motivate people, and run an effective meeting. And, among other things, learning how not to promise too much. So many of these skills will be very, very useful, in years to come.

Rosen: I'm applying to biology programs for graduate school right now; I definitely know that I want to stay in research. Just as Sunita said, these roles allow us to peek behind the academic curtain, and if I end up being a professor, I'll be on the inside. To know how an institution like Caltech runs at more than just the teaching level will be useful.

Jamshidi: I think the people skills I've gained as a leader will help in the future. My classes have prepared me with scientific and technical knowledge, and my leadership role has helped me develop skills like being able to work with lots of different people and learn how they're thinking. Those are important skills.

What do you think is unique about being a leader at Caltech?

Jamshidi: Caltech is so small that I feel like everyone knows me. At a larger school, people wouldn't know who I am or what I do. Often, administrators will email me random questions like, "Who do I talk to about XYZ?" and I'll redirect them. That interaction wouldn't happen at a larger school.

Rosen: It also goes the other way. Because Caltech is so small, we are able to have weekly and biweekly meetings with the vice president for student affairs. That just doesn't happen at other places. Also, I know that my job doesn't exist elsewhere because the house system is unique. That has its pros and its cons. I love the house system; it's great to be a part of. But when I'm trying to troubleshoot something, I can't ask, for example, "What did they do at MIT when something similar to this happened?" because there's no comparison to be drawn.

Caltech's new president, Thomas F. Rosenbaum, knows a thing or two about leadership. After all, he spent seven years as the provost of the University of Chicago, where he had previously served as vice president for research and for Argonne National Laboratory.

In his inaugural address on October 24, Rosenbaum spoke about what it means to lead an institute of higher education, echoing Robert A. Millikan to reflect on "the effective combination of the pure and the applied to advance knowledge and benefit society." The key elements of this successful mix "characterize the Caltech of today," he said. He went on to describe them as:

"An absolute commitment to excellence. Every appointment—student, faculty and staff—matters. Intrinsic to this strategy is the need for diversity: diversity of thought, diversity of background, diversity of experience. We must cast the net as broadly as possible to recruit and retain the most inventive and original scholars.

"Ambition. . . . We are at a time in the history of science and technology where competition for federal funds drives the system to conservatism, but the genius of Caltech is its fearlessness to try new ideas, its willingness to absorb risk and even fail if the potential is transforming discovery.

"Focus. As the constraints become more pronounced, we will be challenged even more profoundly to define areas where the Institute can be a world leader and where it cannot. We will have to forge partnerships . . . while protecting our capacity to set the intellectual agenda.

"Intimacy and intensity. This is a visceral feature of Caltech, built on an organizational structure with few disciplinary barriers and the cultural expectation of shared knowledge.

"Perspective. The arts help us to function as life thrusts us into situations where we have to conceive problems outside of the structures that define them. . . ."

While challenging to achieve, Rosenbaum said, taken together these fundamental ingredients "yield intellectual magic."

As Caltech welcomes its new president, the writers and editors behind E&S magazine thought it would be interesting to talk with other university leaders—all Caltech alumni, of course—about their roles and how they are adapting to an ever-evolving educational landscape.

Read the full story in E&S+

To fight dehydration on a hot summer day, you instinctively crave the relief provided by a tall glass of water. But how does your brain sense the need for water, generate the sensation of thirst, and then ultimately turn that signal into a behavioral trigger that leads you to drink water? That's what Yuki Oka, a new assistant professor of biology at Caltech, wants to find out.

Oka's research focuses on the study of how the brain and body work together to maintain a healthy ratio of salt to water as part of a delicate form of biological balance called homeostasis.

Recently, Oka came to Caltech from Columbia University. We spoke with him about his work, his interests outside of the lab, and why he's excited to be joining the faculty at Caltech.

Can you tell us a bit more about your research?

The goal of my research is to understand the mechanisms by which the brain and body cooperate to maintain our internal environment's stability, which is called homeostasis. I'm especially focusing on fluid homeostasis, the fundamental mechanism that regulates the balance of water and salt. When water or salt are depleted in the body, the brain generates a signal that causes either a thirst or a salt craving. And that craving then drives animals to either drink water or eat something salty.

I'd like to know how our brain generates such a specific motivation simply by sensing internal state, and then how that motivation—which is really just neural activity in the brain—goes on to control the behavior.

Why did you choose to study thirst?

After finishing my Ph.D. in Japan, I came to Columbia University where I worked on salt sensing mechanisms in the mammalian taste system. We found that the peripheral taste system has a key function for salt homeostasis in the body by regulating our salt intake behavior. But of course, the peripheral sensor does not work by itself.  It requires a controller, the brain, which uses information from the sensor. So I decided to move on to explore the function of the brain; the real driver of our behaviors.

I was fascinated by thirst because the behavior it generates is very robust and stereotyped across various species. If an animal feels thirst, the behavioral output is simply to drink water. On the other hand, if the brain triggers salt appetite, then the animal specifically looks for salt—nothing else. These direct causal relations make it an ideal system to study the link between the neural circuit and the behavior.

You recently published a paper on this work in the journal Nature. Could you tell us about those findings?

In the paper, we linked specific neural populations in the brain to water drinking behavior. Previous work from other labs suggested that thirst may stem from a part of the brain called the hypothalamus, so we wanted to identify which groups of neurons in the hypothalamus control thirst. Using a technique called optogenetics that can manipulate neural activities with light, we found two distinct populations of neurons that control thirst in two opposite directions. When we activated one of those two populations, it evoked an intense drinking behavior even in fully water-satiated animals. In contrast, activation of a second population drastically suppressed drinking, even in highly water-deprived thirsty animals.  In other words, we could artificially create or erase the desire for drinking water.

Our findings suggest that there is an innate brain circuit that can turn an animal's water-drinking behavior on and off, and that this circuit likely functions as a center for thirst control in the mammalian brain. This work was performed with support from Howard Hughes Medical Institute and National Institutes of Health [for Charles S. Zuker at Columbia University, Oka's former advisor].

You use a mouse model to study thirst, but does this work have applications for humans?

There are many fluid homeostasis-associated conditions; one example is dehydration. We cannot specifically say a direct application for humans since our studies are focused on basic research. But if the same mechanisms and circuits exist in mice and humans, our studies will provide important insights into human physiologies and conditions.

Where did you grow up—and what started your initial interest in science?

I grew up in Japan, close to Tokyo, but not really in the center of the city. It was a nice combination between the big city and nature. There was a big park close to my house and when I was a child, I went there every day and observed plants and animals. That's pretty much how I spent my childhood. My parents are not scientists—neither of them, actually. It was just my innate interest in nature that made me want to be a scientist.

What drew you to Caltech?

I'm really excited about the environment here and the great climate. That's actually not trivial; I think the climate really does affect the people. For example, if you compare Southern California to New York, it's just a totally different character. I came here for a visit last January, and although it was my first time at Caltech I kind of felt a bond. I hadn't even received an offer yet, but I just intuitively thought, "This is probably the place for me."

I'm also looking forward to talking to my colleagues here who use fMRI for human behavioral research. One great advantage about using human subjects in behavioral studies is that they can report back to you about how they feel. There are certainly advantages of using an animal model, like mice. But they cannot report back. We just observe their behavior and say, "They are drinking water, so they must be thirsty." But that is totally different than someone telling you, "I feel thirsty." I believe that combining advantages of animal and human studies should allow us to address important questions about brain functions.

Do you have any hobbies?

I play basketball in my spare time, but my major hobby is collecting fossils. I have some trilobites and, actually, I have a complete set of bones from a type of herbivorous dinosaur. It is being shipped from New York right now and I may put it in my new office.

Joanna Austin (MS '98, PhD '03) does not just go with the flow. She picks it apart and analyzes it. One of the newest faculty members in Caltech's Division of Engineering and Applied Science is a gas dynamicist, Austin studies the mechanics involved in compressible flows, those where gases reach such high speeds that the density of a fluid element changes drastically. These flows come into play in problems ranging from the logistics of a spacecraft's entry into a planet's atmosphere to the hows and whys of volcanic eruptions.

To simulate such high-speed, high-temperature conditions, Austin and her colleagues use pistons and explosives in large test tunnels to compress gases. Austin had her first experience with this kind of facility while an undergraduate at the University of Queensland, in her native Australia, where the Centre for Hypersonics houses the T4 shock tunnel. Later, as a graduate student at Caltech, Austin worked in the Explosion Dynamics Laboratory. While an assistant professor at the University of Illinois at Urbana-Champaign, she built another instrument for producing very-high-speed flows, known as the hypervelocity expansion tube (HET). In August 2014, she joined Caltech's faculty as a professor of aerospace. There, she will work with the T5 reflected shock tunnel, the next generation of the T4. She is having the HET transported to campus as well, which will create a full suite of complementary facilities.

We recently spoke with Austin about these tunnels, her research, and the challenges involved in studying high-speed flows.

What made you decide to come back to Caltech?

What it basically comes down to is that it is such an exciting and stimulating place to be, with the faculty, the students, and the facilities that are available. And I've always loved it here, so I was really thrilled to come back.

Your specialty is high-speed flows. What is your focus within that area?

My group investigates flows under conditions where the molecular processes in the gas couple with the fluid mechanics, the dynamics of the flow. That covers a range of topics, including hypervelocity flows. These are flows that are associated with objects—whether manmade or naturally occurring—entering a planet's atmosphere. We have a couple of different facilities for recreating and studying these kinds of flows.

That was another thing that was really exciting about coming back to Caltech—GALCIT already had some existing, fantastic facilities like T5. With the instrument that I built and am bringing from Illinois, the HET, we will have a really unique suite of experimental facilities.

Can you talk more about the T5 and the HET? What do they do?

Essentially what they do is produce a test gas that realistically simulates the flow over an object as it's entering an atmosphere. So if you're interested, for example, in a martian mission, we can make a model of a particular spacecraft configuration, place it in one of these two facilities, and then accelerate the gas to replicate the conditions that the model would actually experience during atmospheric entry.

Then we can make measurements and use various models to understand what happened under those conditions with regard to quantities such as heat flux, which is obviously critical to the survival of the vehicle. But we have just a one-millisecond or less window in which to make all of the measurements that we need.

What other kinds of studies do you conduct?

Another type of experiment we do involves probing the molecules themselves in a flow. So we can nonintrusively determine which molecular species are in the flow and what temperature they are at, and in that way we can inform models of the way those molecules interact.

Earlier, you provided the example of a martian mission. What work are you doing in that field?

For some of the larger vehicles that are being discussed for future Mars missions, we need to have much better models for predicting the heat flux that they will experience. For a smaller-scale vehicle, you might be able to get away with using a more protective, and therefore heavier, heat shield than you actually need. But with a larger vehicle, the mass penalty that you would pay for such a safety factor would be prohibitive. So we need to have better predictive models.

We've started working on that. I think our next step will be applying spectroscopic techniques to actually probe the molecules.

And back on Earth, what kinds of phenomena are you investigating?

We have some projects looking at bubble dynamics and the processes involved when bubbles or arrays of bubbles collapse. These come into play in various medical procedures where pulses generated by lasers selectively remove tissue but can also damage the surrounding tissue and cells.

We've also been looking at explosive volcanic eruptions. Most recently we've been interested in what happens if you send an explosive jet over different topographies, such as the side of Mount St. Helens. With 3-D printing, it's really fun, we can make physical models of the geometries of the different topographies you want to test and then run the experiment over the actual geometries.

Is there a topic within the field that most excites you?

I guess it's the umbrella topic of gas dynamics, and particularly looking at gas dynamics in reacting flows. That's the thing I really love. It's a very challenging, coupled, problem. As the fluid is going through the model that you're studying, you also have to account for the fact that the state of the fluid is changing—the gas is chemically reacting, so it's changing from reactants to products, or it's redistributing its energy states, or both. Understanding how best to model these processes, that's what excites me.

With a game-winning basket at the buzzer, the Caltech men's basketball team snapped a 55-game, four-year SCIAC losing streak with a 49-47 victory over the University of Redlands on February 3.

Read the full story on the Caltech Athletics' site.