Faculty Footnotes: Mansi Kasliwal

Mansi Kasliwal is a new assistant professor but certainly not a Caltech newbie. The astronomer earned her PhD here in 2011, having helped design and build the Palomar Transient Factory (PTF), an automated widefield survey at Palomar Observatory that systematically searches for cosmic transients—powerful events like supernovae that appear in the night sky with the light of a million to a billion suns, and then fade away.

“These are extreme events where a lot of elements that we see around us are actually synthesized,” says Kasliwal.

Kasliwal continues to work with PTF and its successor, the Zwicky Transient Facility (ZTF), but is also leading a major international project devoted to chasing and studying transients using observatories around the globe. Known as GROWTH, for Global Relay of Observatories Watching Transients Happen, the project was recently granted $4.5 million through the National Science Foundation’s Partnerships in International Research and Education (PIRE) program. Its goal is to detect transients and then “stay unbeaten by sunrise.”

“We just go around the globe and keep passing the baton so that the sky remains dark,” explains Kasliwal. Here are a few more fun facts about Kasliwal:

  • She grew up in Indore, India, and came to the United States as an adventurous

Noting Kasliwal’s love of the natural sciences, a teacher in India advised Kasliwal to apply to American boarding schools. She took her advice and attended a college-prep school in Connecticut for her junior year. She spent her senior year taking classes and working with a professor at Bryn Mawr College.

  • She studied applied and engineering physics as an undergrad at Cornell.

Astrophysics was only her concentration, but at Cornell she was able to work with the late Jim Houck, the principal investigator for the infrared spectrograph on NASA’s Spitzer Space Telescope. “Spitzer was being launched, and I got to see the data start flowing in,” says Kasliwal. “From then on, I was just completely hooked.”

  • Her work has already made it into textbooks.

Kasliwal received a freshman astronomy textbook in the mail from a professor she had interned with and was astonished to find a page in it dedicated to a supernova that she had discovered. “It was one of the most awesome moments for me,” she says.

Photo credit: Caltech

Celebrating the shared legacy of Beckman and Gray

In November 2015, Caltech marked both the 25th anniversary of the Beckman Institute and the 80th birthday of chemist Harry Gray with a two-day “Invention and Imagination in the Molecular Sciences” symposium. Gray and the late Arnold Beckman (PhD ’28), former Caltech professor and chairman emeritus of the Caltech board of trustees, began a close working relationship in the late 1960s, when Gray arrived at Caltech. Beckman (above, left) congratulates Harry Gray on becoming the first Arnold O. Beckman Professor of Chemistry in 1981. Gray is also the founding director of the Beckman Institute, a multidisciplinary center for research in the chemical and biological sciences that was dedicated in 1989 with funds from the Arnold and Mabel Beckman Foundation.

Photo: Courtesy of the Caltech Archives

Pop, Focus, Destroy

A new technique developed at Caltech that uses gas-filled microbubbles for focusing light inside tissue could one day provide doctors with a minimally invasive way of destroying tumors with lasers, and lead to improved diagnostic medical imaging.

The primary challenge with focusing light inside the body is that biological tissue is optically opaque. Unlike transparent glass, the cells and proteins that make up tissue scatter and absorb light. “Our tissues behave very much like dense fog as far as light is concerned,” says Changhuei Yang, professor of electrical engineering, bioengineering, and medical engineering. “Just like we cannot focus a car’s headlight through fog, scientists have always had difficulty focusing light through tissues.”

To get around this problem, Yang and his team turned to microbubbles, commonly used in medicine to enhance contrast in ultrasound imaging. First, gas-filled microbubbles encapsulated by thin protein shells and injected into tissue are ruptured with ultrasound waves. By measuring the difference in light transmission before and after such an event, the Caltech researchers can modify the wavefront of a laser beam so that it focuses on the original locations of the microbubbles. The result, Yang explains, “is as if you’re searching for someone in a dark field, and suddenly the person lets off a flare. For a brief moment, the person is illuminated and you can home in on their location.”

If the technique is shown to work effectively inside living tissue—without, for example, any negative effects from the bursting microbubbles—it could enable a range of research and medical applications. For example, by combining the microbubbles with an antibody probe engineered to seek out biomarkers associated with cancer, doctors could target and then destroy tumors deep inside the body or detect malignant growths much sooner.

“Ultrasound and X-ray techniques can only detect cancer after it forms a mass,” Yang says. “But with optical focusing, you could catch cancerous cells while they are undergoing biochemical changes but before they undergo morphological changes.”

Photo: Courtesy of Haowen Ruan Mooseok Jang & Changhuei Yang

Tracking down the “missing” carbon from the martian atmosphere

Mars is blanketed by a mostly carbon dioxide atmosphere—one that is far too thin to prevent large amounts of water on the surface of the planet from subliming or evaporating. But many researchers have suggested that the planet was once shrouded in an atmosphere many times thicker than Earth’s. For decades that left the question, “Where did all the carbon go?”

Now scientists from Caltech and JPL think they have a possible answer. The team suggests that 3.8 billion years ago, Mars might have had only a moderately dense atmosphere. The researchers have identified a photochemical process that could have helped such an early atmosphere evolve into the current thin one without creating the problem of “missing” carbon.

“With this new mechanism, everything that we know about the martian atmosphere can now be pieced together into a consistent picture of its evolution,”says Renyu Hu, a postdoctoral scholar at JPL, a visitor in planetary science at Caltech, and lead author on the paper that appeared in Nature Communications.

When considering how the early atmosphere might have transitioned to its current state, there are two possible mechanisms for the removal of excess carbon dioxide (CO2). Either the CO2 was incorporated into minerals in rocks called carbonates or it was lost to space.

A separate study coauthored by Bethany Ehlmann, assistant professor of planetary science at Caltech, used data from several Mars-orbiting satellites to inventory carbonate rocks, showing that there are not enough carbonates in the upper crust to contain the missing carbon from a very thick early atmosphere.

To study the escape-to-space scenario, scientists examined the ratio of carbon-12 and carbon-13, two stable isotopes of the element carbon that have the same number of protons in their nuclei but different numbers of neutrons, and thus different masses. Comparing measurements from martian meteorites to those recently collected by NASA’s Curiosity rover, they found that the atmosphere is unusually enriched in carbon-13. To explain that, they describe a mechanism involving a photochemical cascade that produces carbon atoms that have enough energy to escape the atmosphere, and they show that carbon-12 is far more likely to escape than carbon-13.

“With this mechanism, we can describe an evolutionary scenario for Mars that makes sense of the apparent carbon budget, with no missing processes or reservoirs,” says Ehlmann, who is also a coauthor on the Hu study.

Photo credit: NASA/JPL-Caltech/Univ. of Arizona

Building Powerful Magnetic Fields

When certain massive stars use up all of their fuel and collapse onto their cores, explosions 10 to 100 times brighter than the average supernova occur. Astrophysicists from Caltech, UC Berkeley, the Albert Einstein Institute, and the Perimeter Institute for Theoretical Physics have used the National Science Foundation’s Blue Waters supercomputer to perform three-dimensional computer simulations to fill in an important missing piece of our understanding of what drives these blasts.

In the past, scientists have simulated the evolution of massive stars from their collapse to jet-driven explosions by factoring unrealistically large magnetic fields into their models—without explaining how they could be generated in the first place.

“That’s what we were trying to understand with this study,” says Luke Roberts, a NASA Einstein Fellow at Caltech and a coauthor on a paper reporting the team’s findings in the journal Nature. “How can you start with the magnetic field you might expect in a massive star that is about to collapse—or at least an initial magnetic field that is much weaker than the field required to power these explosions—and build it up to the strength that you need to collimate a jet and drive a jet-driven supernova?”

For more than 20 years, theory has suggested that the magnetic field of the innermost regions of a massive star that has collapsed, also known as a proto-neutron star, could be amplified by an instability in the flow of its plasma if the core is rapidly rotating, causing its outer edge to rotate faster than its center. However, no previous models could prove this process could strengthen a magnetic field to the extent needed to collimate a jet, largely because these simulations lacked the resolution to resolve where the flow becomes unstable.

Lead author on the paper Philipp Mösta—who started the work while a postdoctoral scholar at Caltech and is now a NASA Einstein Fellow at UC Berkeley—and his colleagues developed a simulation of a rapidly rotating collapsed stellar core and scaled it so that it could run on the Blue Waters supercomputer, known for its ability to provide sustained high-performance computing for problems that produce large amounts of information. The team’s highest-resolution simulation took 18 days of around-the-clock computing by about 130,000 computer processors to simulate just 10 milliseconds of the core’s evolution.

In the end, the researchers were able to simulate the so-called magnetorotational instability responsible for the amplification of the magnetic field. As theory predicted, they saw that the instability creates small patches of an intense magnetic field distributed throughout the core of the collapsed star. They found that a dynamo process connects those patches and generates currents that amplify the magnetic fields, turning them into the kind needed to power jets.

Photo: Courtesy of Mösta et al/Nature

Good Luck Green

These glowing crystals generated by Tania Darnton, a Caltech graduate student in the lab of chemist Harry Gray, are composed of the tetraphenylphosphonium (Ph4P+) salt of the compound tetrakis(diphosphonato) diplatinate(II), commonly known as Pt(POP) due to its phosphorus-oxygenphosphorus bridges. This compound is a precursor to another molecule Darnton is studying for her thesis, which is a highly luminescent derivative of Pt(POP) with possible applications in oxygen sensing thin films and catalytic electron-transfer reactions. According to Darnton, the crystals were created via the slow evaporation of a methanol solution of the compound—quite by accident, in fact. She hadn’t synthesized the Ph4P+ salt before, and after several frustrating hours of trying unsuccessfully to isolate the compound she decided to just leave the solution out and try again in the morning. When she returned the following day, she was greeted with bright green crystals, which she called a “wonderful reward” after the disappointment of the night before. Such compounds could be used in building detectors for laboratories to ensure proper atmospheric conditions for sensitive chemical reactions.

Photo: Courtesy of Tania Darnton

Triple Threat

The public high school in Blue Springs, Missouri, just outside Kansas City, graduates more than 500 seniors each year. Remarkably, the valedictorian in 2015 was the younger sister of the valedictorian in 2014—who was the younger sister of the valedictorian in 2013.

And all three are now Caltech undergraduates. These are the Butkovich sisters: junior Slava and sophomore Nina, both majoring in chemical engineering, and freshman Lazarina (“Laza”), currently deciding between chemical engineering and chemistry.

The sisters represent “a three-peat,” says Caltech admissions director Jarrid Whitney, not a package deal. “All our applicants are reviewed independently and without regard to siblings, parents, or other legacies. For three family members to receive consecutive offers of admission indicates how tremendously talented all three of them must be.”

For their part, Slava, Nina, and Laza (pictured right to left, below) find their own nearly identical trajectories unsurprising. “We were taught at a young age that science majors can do a lot of good for society,” Slava says.

In fact, according to all three, one of the biggest challenges since leaving high school has been learning to rely on something they had honestly never needed before now: study groups.

Photo credit: Caltech

The Power of Gunpowder

Although Europe represents only about 8 percent of the planet’s landmass, from 1492 to 1914, Europeans conquered or colonized more than 80 percent of the entire world. Being dominated for centuries has led to lingering inequality and long-lasting effects, including poverty and slow economic growth, in many formerly colonized countries. There are many possible explanations for why history played out this way, but few can explain why the West was so powerful for so long.

Caltech’s Philip Hoffman, the Rea A. and Lela G. Axline Professor of Business Economics and professor of history, has a new explanation: the advancement of gunpowder technology. “In 1914, really only China, Japan, and the Ottoman Empire had escaped becoming European colonies,” says Hoffman. “A thousand years ago, no one would have ever expected that result, for at that point Western Europe was hopelessly backward. It was politically weak, it was poor, and the major long-distance commerce was a slave trade led by Vikings. The political  dominance of Western Europe was an unexpected outcome and had really big consequences, so I thought: Let’s explain it.” Hoffman’s work is published in a new book titled Why Did Europe Conquer the World?

“Gunpowder was really important for conquering territory; it allows a small number of people to exercise a lot of influence,” he says. Hoffman put together an economic model of how gunpowder technology has advanced to come up with what he thinks is the real reason why the West conquered almost everyone else. His idea incorporates the model of a contest or a tournament in which your odds of winning are higher if you spend more resources on fighting.

“If you think about it, you realize that advancements in gunpowder technology—which are important for conquest—arise where political leaders fight using that technology, where they spend huge sums on it, and where they’re able to share the resulting advances in that technology,” he says. “For example, if I am fighting you and you figure out a better way to build an armed ship, I can imitate you. For that to happen, the countries have to be small and close to one another. And all of this describes Europe.” —JSC

Faculty Footnotes

There are approximately 100 billion neurons in the human brain—and the growth, development, and death of these neurons are controlled by thousands of genes. Sorting out how changes in these genes and neurons can lead to changes in behavior seems like a tall order, but that’s exactly the problem that biology research professor Carlos Lois is interested in.

His work uses songbirds as a model organism for the study of schizophrenia and autism:

“The advantage of working with birds is that they have this very natural behavior—singing—that in many ways is very similar to speech learning in humans. First, they have to listen to an adult tutor—the father bird—and after they listen, they practice until they can make a copy of the song that is very similar to what the father makes. There are not that many other animals that have this vocal learning. In humans there are a few communication-related genes that, when mutated, are associated with schizophrenia and autism. By studying mutations in those same genes in songbirds like zebra finches, we can learn how those mutations affect the bird’s ability to communicate with others—one characteristic used to diagnose these disorders.”

When he first came to Caltech to do a postdoctoral fellowship in David Baltimore’s lab, he didn’t have a driver’s license:

“When I was growing up in Spain, I lived in a big city and I didn’t need a car. Then I lived in New York and Boston. I came to Pasadena to do my postdoc and I was 28 years old and I didn’t know how to drive. I thought, ‘I’m sure I could do fine with a bicycle.’ I even went to Manhattan Beach, Santa Monica, and Zuma Beach on my bicycle, but then I decided that was enough, and I got my driver’s license.”

He loves the movies:

“I really like any sort of fiction—like novels, short stories, and especially movies. From 1986 to 2007 I’d say I watched an average of four movies every week. But when my son was born in 2007, it went from four movies per week to four movies per year. So now I mostly read fiction in novels and short stories.”

Solving the Nuclear Pore Complex

In the spring 2015 issue of this magazine, we wrote about André Hoelz, who is using X-ray crystallography to solve the architecture of one of the most elaborate structures in biology, the nuclear pore complex (“X-ray Vision,” E&S, Vol. 78, No. 1). Recently, a team led by Hoelz, assistant professor of biochemistry at Caltech, reported solving another crucial piece of that puzzle.

The nuclear pore complex (NPC) acts as a cellular gatekeeper that controls molecules trying to enter or exit the nucleus, the heart of eukaryotic cells where, among other things, genetic information is stored. For decades, scientists have been trying to figure out how the NPC can be such an effective gatekeeper—keeping out the cellular riffraff while helping to shuttle certain molecules across the nuclear envelope. This is important at least in part because the NPC is targeted by a number of diseases, including some aggressive forms of leukemia and nervous system disorders. In a paper published in Science Express on August 27, the team reported that they have solved the architecture of the pore’s inner ring, a subcomplex central to the NPC’s ability to serve as a barrier and transport facilitator. Hoelz and colleagues had previously described the atomic structure of the outer rings; now that the architectures of the inner and outer rings of the NPC are known, getting an atomic structure of those combined is “a sprint to the summit,” says Hoelz.

“When I started at Caltech, I thought it might take another 10, 20 years to do this,” he continues. “In the end, we have really only been working on this for four and a half years, and the thing is basically tackled. I want to emphasize that this kind of work is not doable everywhere. The people who worked on this are truly special, talented, and smart; and they worked day and night on this for years.”

Ultimately, Hoelz says he would like to understand how the NPC works in great detail so that he might be able to generate therapies for diseases associated with the dysfunction of the complex. —KF

Dirty Work

On the grounds of San Marino’s Huntington Library, Art Collections, and Botanical Gardens—in the private, half-acre Huntington Ranch area—nearly two dozen middle and high school students spent this past summer measuring the levels of nitrogen in the soils around them to help the ranch determine whether its dirt is up to the challenge of growing an urban garden. This hands-on research experience was part of the Community Science Academy @ Caltech, which is affiliated with Caltech’s Center for Teaching, Learning, and Outreach. At left, James Maloney (MS ’06), one of the two co-directors of the CSA@Caltech program, helps high school student Kate Samaniego gather soil samples for testing. Other projects involved conducting experiments on ant behavior, and designing and building sensor-carrying remote-controlled powered kites, which the students flew over the library grounds. —JA

Art In Aberration

This image from Caltech’s semiannual Art of Science competition highlights the beauty of scientific mistakes. Graduate student Chen Xu, who works in materials science, was attempting to plate a smooth layer of gold on top of a truss—a carefully designed lattice functioning as a cathode—for a lithium-oxygen battery, a very clean and reusable type of battery. Formed out of a polymer, the truss must be plated with gold to make it conductive. But when the precious metal was being plated onto the structure, the process went too fast and the gold formed the flowery, tree-like crystals, called dendrites, seen above. Each “bouquet” or node is about 150 microns across, or approximately double the thickness of a human hair. The photo was taken using a scanning electron microscope, a machine that shoots focused beams of electrons at a specimen and measures the scattering to get very high-resolution images.