Were dinosaurs slow and stupid, as used to be the prevailing wisdom, or nimble and smart enough to eat an attorney, as in the 1993 film Jurassic Park? The answer depends largely on whether the T. Rex in question is cold blooded, like an alligator—although gators, in a shocking lack of professional courtesy, are fully capable of chowing down on counsel—or warm blooded, like a bird. This is because creatures capable of maintaining a constant body temperature, regardless of their environment, generally also have the energy to move fast and think quickly. There's only one sure way to settle the debate, but taking the temperature of an animal that's been extinct for 150 million years poses certain obvious problems.

Fortunately, John Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry, has mastered the art of time travel without leaving the lab. His time machine is a mass spectrometer, a device that separates atoms of different weights in a process he likens to the workings of "a good, old-fashioned television set from the days when TV sets were the size of smart cars." Atoms of a given element that have different weights are called isotopes, and in his Watson Lecture on February 29, 2012, Eiler shows how isotope analysis can not only take a dinosaur's temperature, but perhaps tell us why they died. It's CSI: Jurassic Park.

"The Isotope Time Machine" is available for download in HD from Caltech on iTunesU. (Episode 9)

PASADENA, Calif.—Mike Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy at the California Institute of Technology (Caltech), has been named a co-winner of the 2012 Kavli Prize in Astrophysics for his efforts to understand the outer solar system—work that led to the demotion of Pluto.

Brown shares the award with David Jewitt (MS '80, PhD '83) of UCLA and Jane Luu of MIT's Lincoln Laboratory; in 1992, Jewitt and Luu discovered the first object in the Kuiper belt, a collection of more than a thousand objects beyond the orbit of Neptune. Brown, who joined Caltech's faculty in 1997, has since become a leader in the search for planet-sized objects in the Kuiper belt. According to the prize citation, the three received the prize "for discovering and characterizing the Kuiper belt and its largest members, work that led to a major advance in the understanding of the history of our planetary system."

Brown's most well-known discovery came in 2005, when he found a Kuiper-belt object, later named Eris, that is about the same size as Pluto but 27 percent more massive. That finding caused astronomers to rethink the definition of a planet, resulting in the reclassification of Pluto as a dwarf planet.

"Mike spent years acquiring a massive number of images and learning how to process them to accurately detect objects that subtly shift in the sky over successive days—without knowing whether there was anything interesting to be discovered," explains Kenneth Farley, the W.M. Keck Foundation Professor of Geochemistry and chair of the Division of Geological and Planetary Sciences. "But that dedication was rewarded by the discovery of several fascinating Kuiper-belt objects, and just as important as their discovery was Mike's effort in understanding them—where they came from, how they formed, what they are made of, and what they tell us about our solar system. It is wonderful to see Mike recognized for these contributions."

"This distinguished prize is further acknowledgment of Mike's extraordinary accomplishments and pioneering research that has literally reshaped our understanding of the solar system," adds Caltech president Jean-Lou Chameau. "He is truly a 'renaissance scientist' who approaches teaching and scientific discovery with passion and charisma. We are proud of Mike and are privileged to have him on the Caltech faculty."

"It's humbling to be included alongside previous Kavli Prize winners, from the people whose incredible designs for telescopes enable all of us to make these discoveries to the very pioneers of astrophysics," says Brown. "And it's an amazing reminder that some of the mysteries of the universe are right here in our own cosmic backyard."

The Kavli Prize, which includes a scroll, a gold medal, and $1 million, recognizes scientists in astrophysics, nanoscience, and neuroscience, and has been awarded every other year since 2008. King Harald of Norway will present the prizes to the winners at a ceremony in Oslo on September 4. Caltech's Maarten Schmidt, the Francis L. Moseley Professor of Astronomy, Emeritus, won the astrophysics prize in 2008. Past winners who are Caltech alumni include Jerry Nelson (BS '65), Roger Angel (MS '66), and Richard Scheller (PhD '80).

The Kavli Prizes were initiated by and named after Fred Kavli, founder and chairman of the Kavli Foundation, which is dedicated to advancing science for the benefit of humanity, promoting public understanding of scientific research, and supporting scientists and their work.

PASADENA, Calif.—Last year, images from NASA's Mars Reconnaissance Orbiter captured sand dunes and ripples moving across the surface of Mars—observations that challenged previously held beliefs that there was not a lot of movement on the red planet's surface. Now, technology developed by a team at the California Institute of Technology (Caltech) has allowed scientists to measure these activities for the very first time.

The new method for data processing is outlined in an advance online publication of the journal Nature.

"For many years, researchers have debated whether or not the sand dunes we see on Mars are fossil features related to past climate, since it was believed that the current atmosphere is too thin to produce winds that could move sand," says Jean-Philippe Avouac, the Earle C. Anthony professor of geology at Caltech, who initiated the study. "Our new data shows that wind activity is indeed a major agent of evolution of the landscape on Mars. This is important because it tells us something about the current state of Mars and how the planet is working today, geologically."

Using the COSI-corr software (for Co-registration of Optically Sensed Images and Correlation), which was invented at Caltech, a team of researchers gathered high-resolution imagery from Mars to look at a specific field of sand dunes called Nili Patera. The images came from the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter.

The team focused on precise, subpixel measurements of movement between pairs of images. On the dunes at Nili Patera, the software automatically measured changes in the position of sand ripples from one image to another over a 105-day period, resulting in the surprising findings that the ripples are moving fast—some upwards of 4.5 meters during that time—which contributes to the total motion of the sand dunes.

"This is the first time that we have full, quantitative measurement of an entire dune field on a planetary surface, as opposed to the localized manual measurements that were done before," explains Francois Ayoub, a coauthor of the paper and a scientist engineer in Avouac's lab. "Using this technique, you could monitor other dune fields, or you could also follow a particular area over a longer time frame to see the seasonal or annual evolution of the sand dunes. This is a huge step in terms of the data that you can obtain from the surface of Mars."

The team also found that the dunes at Nili Patera appear to move similarly to those found on Earth in Victoria Valley, Antarctica. This implies that the rates of landscape modification due to wind are similar on the two planets. Interestingly enough, getting these measurements was much easier on Mars—the researchers could not quantify dune ripple migration rates on Earth using the same technique because that would require satellite imagery of our planet at a resolution that makes it classified information.

"These new measurements provide keys to interpreting the landscape and the stratigraphic record that you see exhumed when you look at the imagery—we see sediments and wonder what they mean in terms of the past geologic history," says Avouac. "The fact that you can describe the current activity of surface systems will help us understand Mars's past geological record, which is a reason that this is important."

Next, the team will focus on learning more about how the sand is actually moving on the surface of Mars.

"We would like to use this new data to tie our observations to the physics of sand transport, which are not well understood," says Sebastien Leprince, a coauthor of the study and a senior research scientist on Avouac's team. "By learning more about how the sand moves around, we may also learn more about the atmosphere on Mars."

The group also plans to use the HiRISE images paired with COSI-Corr to explore other regions of Mars and monitor for surface motion. For example, there are parts of the planet that may have glaciers covered with dust, and other places where fault lines can be seen and could be tracked for displacement.

"We are going to visit other areas on Mars to get a better view of what kind of activity there is on the planet today—geologically speaking, of course," says Avouac, who points out that while they are not looking for life on Mars, their technique is detailed enough that it would detect very small changes on the surface.

The Nature study, "Earth-like Sand Fluxes on Mars," was funded by grants from the Keck Institute for Space Studies at Caltech, NASA's Mars Data Analysis Program, and the Jet Propulsion Laboratory's Director's Research and Development Fund. Additional authors on the study are Antoine Lucas, a postdoctoral scholar in planetary science at Caltech, Nathan T. Bridges from Johns Hopkins University, and Sarah Mattson from the University of Arizona. An exclusive license to Caltech's COSI-Corr technology was recently awarded to Imagin'Labs Corporation (www.imaginlabs.com).

PASADENA, Calif.—Hiroo Kanamori, the John E. and Hazel S. Smits Professor of Geophysics, Emeritus, at the California Institute of Technology (Caltech), has been elected one of 21 new foreign associates of the National Academy of Sciences. Eighty-four new members were also announced during the 149th annual meeting of the academy in Washington, D.C. 

Foreign associates are nonvoting members of the academy who have citizenship outside the United States. Membership in the National Academy of Sciences is considered one of the most important distinctions that a scientist can achieve.

Kanamori is a leading authority on the physics of earthquakes and is known for developing a moment-magnitude scale for determining the magnitude of large earthquakes based on the amount of energy they release. He is particularly interested in the application of seismology to hazard mitigation as well as the study of tsunamis and the implementation of early-warning systems.

Kanamori earned his undergraduate and graduate degrees at the University of Tokyo (BS '59, MS '61, PhD '64) before coming to Caltech as a postdoctoral researcher in 1965. After stints at MIT and the University of Tokyo, he returned to Caltech as a full professor in 1972 and became the Smits Professor of Geophysics in 1989. He served as the director of Caltech's Seismological Laboratory from 1990 until 1998 and became the Smits Professor of Geophysics, Emeritus, in 2005.

Among other distinctions, Kanamori was made a member of the American Academy of Arts and Sciences in 1987, was given the Walter H. Bucher Medal by the American Geophysical Union in 1996, was honored by the Japanese government with the Cultural Merit Award in 2006, and was selected for the Kyoto Prize by the Inamori Foundation in 2007.

Kanamori's election brings the total number of living Caltech faculty members who belong to the National Academy of Sciences to 71. Four of those, including Kanamori, are foreign associates. In addition, three current members of the Caltech Board of Trustees are academy members.

The National Academy of Sciences is dedicated to the "furtherance of science and technology and to their use for the public good," according to its mission statement. Established by a 1863 act of Congress that was signed by President Lincoln, the academy provides scientific advice to the government "whenever called upon" by any government department.

There are now 2,152 active members and 430 foreign associates of the National Academy of Sciences. 

PASADENA, Calif.—There is an old trick for remembering the difference between stalactites and stalagmites in a cave: Stalactites hold tight to the ceiling while stalagmites might one day grow to reach the ceiling. Now, it seems, stalagmites might also fill a hole in our understanding of Earth's climate system and how that system is likely to respond to the rapid increase in atmospheric carbon dioxide since preindustrial times.

Many existing historical climate records are biased to the high latitudes— coming from polar ice cores and North Atlantic deep ocean sediments. Yet a main driver of climate variability today is El Niño, which is a completely tropical phenomenon. All of this begs the question: How do we study such tropical climate influences? The answer: stalagmites.

"Stalagmites are the ice cores of the tropics," says Jess Adkins, professor of geochemistry and global environmental science at the California Institute of Technology (Caltech). He and geochemist Kim Cobb of the Georgia Institute of Technology led a team that collected samples from stalagmites in caves in northern Borneo and measured their levels of oxygen isotopes to reconstruct a history of the tropical West Pacific's climate over four glacial cycles during the late Pleistocene era (from 570,000 to 210,000 years ago).

The results appear in the May 3 issue of Science Express. The lead author of the paper, Nele Meckler, completed most of the work as a postdoctoral scholar at Caltech and is now at the Geological Institute of ETH Zürich.

Throughout Earth's history, global climate has shifted between periods of glacial cooling that led to ice ages, and interglacial periods of relative warmth, such as the present. Past studies from high latitudes have indicated that about 430,000 years ago—at a point known as the Mid-Brunhes Event (MBE)—peak temperatures and levels of atmospheric carbon dioxide in interglacial cycles were suddenly bumped up by about a third. But no one has known whether this was also the case closer to the equator.

By studying the records from tropical stalagmites, Adkins and his team found no evidence of such a bump. Instead, precipitation levels remained the same across the glacial cycles, indicating that the tropics did not experience a major shift in peak interglacial conditions following the MBE. "The stalagmite records have glacial cycles in them, but the warm times—the interglacials—don't change in the same way as they do at high latitudes," Adkins says. "We don't know what that tells us yet, but this is the first time the difference has been recorded."

At the same time, some changes did appear in the climate records from both the high latitudes and the tropics. The researchers found that extreme drying in the tropics coincided with abrupt climate changes in the North Atlantic, at the tail end of glacial periods. It is thought that these rapid climate changes, known as Heinrich events, are triggered by large ice sheets suddenly plunging into the ocean.

"In the tropics, we see these events as very sharp periods of drying in the stalagmite record," Adkins says. "We think that these droughts indicate that the tropics experienced a more El Niño–like climate at those times, causing them to dry out." During El Niño events, warm waters from the tropics, near Borneo, shift toward the center of the Pacific Ocean, often delivering heavier rainfall than usual to the western United States while leaving Indonesia and its neighbors extremely dry and prone to forest fires. 

The fact that the tropics responded to Heinrich events, but not to the shift that affected the high latitudes following the MBE, suggests that the climate system has two modes of responding to significant changes. "It makes you wonder if maybe the climate system cares about what sort of hammer you hit it with," Adkins says. "If you nudge the system consistently over long timescales, the tropics seem to be able to continue independently of the high latitudes. But if you suddenly whack the climate system with a big hammer, the impact spreads out and shows up in the tropics."

This work raises questions about the future in light of recent increases in atmospheric carbon dioxide: Is this increase more like a constant push? Or is it a whack with a big hammer? A case could be made for either one of these scenarios, says Adkins, but he adds that it would be easiest to argue that the forcing is more like a sudden whack, since the amount of carbon dioxide in the atmosphere has increased at such an unprecedented rate.

In addition to Adkins, Cobb, and Meckler, other coauthors on the paper, "Interglacial hydroclimate in the tropical West Pacific through the late Pleistocene," are Matthew Clarkson of the University of Edinburgh and Harald Sodemann of ETH Zürich. Cobb is also a former postdoctoral scholar in Adkins's group and has been collaborating on this project since her time at Caltech. The work was supported by the National Science Foundation, the Swiss National Science Foundation, the German Research Foundation, and by an Edinburgh University Principal's Career Development PhD Scholarship.

PASADENA, Calif.—The second-largest mass extinction in Earth's history coincided with a short but intense ice age during which enormous glaciers grew and sea levels dropped. Although it has long been agreed that the so-called Late Ordovician mass extinction—which occurred about 450 million years ago—was related to climate change, exactly how the climate change produced the extinction has not been known. Now, a team led by scientists at the California Institute of Technology (Caltech) has created a framework for weighing the factors that might have led to mass extinction and has used that framework to determine that the majority of extinctions were caused by habitat loss due to falling sea levels and cooling of the tropical oceans.

The work—performed by scientists at Caltech and the University of Wisconsin, Madison—is described in a paper in the early edition of the Proceedings of the National Academy of Sciences.

The researchers combined information from two separate databases to overlay fossil occurrences on the sedimentary rock record of North America around the time of the extinction, an event that wiped out about 75 percent of marine species alive then. At that time, North America was an island continent geologists call Laurentia, located in the tropics.

Comparing the groups of species, or genera, that went extinct during the event with those that survived, the researchers were able to figure out the relative importance of several variables in dictating whether a genus went extinct during a 50-million-year interval around the mass extinction.

"What we did was essentially the same thing you'd do if confronted with a disease epidemic," says Seth Finnegan, postdoctoral scholar at Caltech and lead author of the study. "You ask who is affected and who is unaffected, and that can tell you a lot about what's causing the epidemic." 

As it turns out, the strongest predictive factors of extinction on Laurentia were both the percentage of a genus's habitat that was lost when the sea level dropped and a genus's ability to tolerate broader ranges of temperatures. Groups that lost large portions of their habitat as ice sheets grew and sea levels fell, and those that had always been confined to warm tropical waters, were most likely to go extinct as a result of the rapid climate change.

"This is the first really attractive demonstration of how you can use multivariate approaches to try to understand extinctions, which reflect amazingly complex suites of processes," says Woodward Fischer, an assistant professor of geobiology at Caltech and principal investigator on the study. "As earth scientists, we love to debate different environmental and ecological factors in extinctions, but the truth is that all of these factors interact with one another in complicated ways, and you need a way of teasing these interactions apart. I'm sure this framework will be profitably applied to extinction events in other geologic intervals."

The analysis enabled the researchers to largely rule out a hypothesis, known as the record-bias hypothesis, which says that the extinction might be explained by a significant gap in the fossil record, also related to glaciation. After all, if sea levels fell and continents were no longer flooded, sedimentary rocks with fossils would not accumulate. Therefore, the last record of any species that went extinct during the gap would show up immediately before the gap, creating the appearance of a mass extinction. 

Finnegan reasoned that this record-bias hypothesis would predict that the duration of a gap in the record should correlate with higher numbers of extinctions—if a gap persisted longer, more groups should have gone extinct during that time, so it should appear that more species went extinct all at once than for shorter gaps. But in the case of the Late Ordovician, the researchers found that the duration of the gap did not matter, indicating that a mass extinction very likely did occur. 

"We have found that the Late Ordovician mass extinction most likely represents a real pulse of extinction—that many living things genuinely went extinct then," says Finnegan. "It's not that the record went bad and we just don't recover them after that."

The team used data about North American fossils from the public Paleobiology Database as well as information about the sedimentary rock record from the Macrostrat Database developed by the University of Wisconsin, Madison. Along with Fischer and Finnegan, additional coauthors of the paper, "Climate change and the selective signature of the late Ordovician mass extinction" are Shanan Peters and Noel Heim of the University of Wisconsin, Madison. Finnegan will begin a new appointment at UC Berkeley in the fall. The work was supported by the Agouron Institute and the National Science Foundation.

PASADENA, Calif.—Many of us see a man in the moon—a human face smiling down at us from the lunar surface. The "face," of course, is just an illusion, shaped by the dark splotches of lunar maria (smooth plains formed from the lava of ancient volcanic eruptions).

Like a loyal friend, the man is always there, constantly gazing at us as the moon revolves around Earth, locked in what's called a synchronous orbit, in which the moon rotates exactly once every time it orbits Earth. But why did the moon settle into an orbit with the man—rather than the moon's crater-covered far side—facing Earth?

Previously, some scientists have thought the fact that we see the man is just the result of a coincidence, a sort of lunar coin toss, says Oded Aharonson, professor of planetary science at the California Institute of Technology (Caltech). But he and his colleagues have now found that is not the case. In the past, the moon spun around its axis faster than it does today, and their new analysis shows that the fact that the man now faces us may be a result of the rate at which the moon slowed down before becoming locked into its current orientation.

Aharonson, along with Peter Goldreich, the Lee DuBridge Professor of Astrophysics and Planetary Physics, Emeritus, and Re'em Sari of the Hebrew University of Jerusalem, describe their findings in a paper published online on February 27 in the journal Icarus.

Although the moon looks spherical, it is actually elongated, almost like a football. Not long after the moon formed just over four billion years ago, while it was still hot and largely molten, Earth's gravity began to stretch its new companion. When the moon cooled, its slightly oblong shape stuck. Today, the man in the moon occupies one of the two elongated ends. 

And the reason he faces us at all times is because the moon rotates around its axis once with each revolution around the Earth, so that the same face is always pointing earthward. A couple billion years ago, give or take, the moon rotated around its axis much more rapidly, so that the inhabitants of Earth would have seen all the different sides of the moon at various times.

Eventually, however, Earth's pull on the moon slowed down its rotation through a dissipative process first explained by Goldreich in the 1960s. Tidal forces tugged on the moon, creating another slight bulge—in addition to the moon's already-elongated shape—that moved to stay on whichever side was closest to Earth at that moment. The bulge continued to point toward Earth as the moon rotated through it, causing the moon's interior to squish and flex as the bulge changed position. The internal friction from this flexing acted as a brake that slowed the moon's spinning until its rotation rate matched its revolution rate, when it settled into a synchronous orbit.

In this way, as a result of Earth's gravity, the moon became locked into an orientation with its long axis pointing toward our planet. The question, then, is why the side that ended up facing Earth is the one with the man—especially since the reverse configuration is actually favored, the researchers say. The side of the moon without the man has higher mountains and an elevated topography, they explain. Based on a naive analysis of the physics, it might be expected for this side to face Earth, because its surface—and its mass—would be closer to Earth.

In the work described in the Icarus paper, the researchers analyzed the physics of the moon and discovered that what determines which side of the moon we see is the rate at which the moon slowed down its spinning—how fast it dissipated its rotational energy. If the moon had lost energy at a significantly different rate—say 100 times faster—than it really did, there would have been a 50/50 chance that the man would face us. In that scenario, Aharonson says, having the man face us would indeed have been merely the result of a coin flip. But, as it turns out, the moon's actual rate of energy dissipation was much slower—and that means the man in the moon had about two-to-one odds of facing us. "The coin was loaded," Aharonson says.

By tweaking the dissipation rate in computer simulations, the researchers were able to simulate moons that resulted with either the man or the mountainous far side facing us every single time. In other words, they were able to load the coin however they wanted.

"The real coincidence is not that the man faces Earth," Aharonson says. Instead, the real coincidence is that the moon's dissipation rate was just the right amount to create such fascinating physics and load the coin.

But there is a caveat, he adds. The researchers' analysis is based on the present-day moon. "In the past, when the moon first locked, it could've had different properties," Aharonson notes. If that's the case, then the explanation for why we see the man might result in different odds. But, if the moon locked into its synchronous orbit relatively recently—within the last billion years or so—then there's a good chance the researchers' analysis is fitting.

The title of the Icarus paper is "Why do we see the man in the moon?" Support was provided by NASA's Lunar Reconnaissance Orbiter project.

PASADENA, Calif.—Paul D. Asimow, professor of geology and geochemistry at the California Institute of Technology (Caltech), has been awarded the Richard P. Feynman Prize for Excellence in Teaching—Caltech's most prestigious teaching honor.

Asimow was selected for his "exceptional energy, originality, and ability to explain complicated concepts effectively," according to the award citation.

The Feynman Prize was established in 1993 "to honor annually a professor who demonstrates, in the broadest sense, unusual ability, creativity, and innovation in undergraduate and graduate classroom or laboratory teaching." Any member of the Caltech community—including faculty, students, postdoctoral scholars, alumni, or staff—may nominate a faculty member for the award. A committee appointed by the provost selects the winner.

"I'm both utterly surprised and deeply gratified, as the classes I teach are pretty small and specialized," says Asimow, who teaches Introduction to Geology and Geochemistry, and Thermodynamics of Geological Systems, among other courses. "I never expected to be considered alongside the professors who shoulder the hard work of teaching the big classes. I'm inspired by this recognition to keep putting my efforts into improving and updating what and how I teach."

Asimow says he credits his success in academia to a teacher he had as an undergrad at Harvard. "My own career path was determined by one incredible professor, James B. Thompson, Jr., who recently passed away," he notes. "I'd like to acknowledge the legacies of both Feynman and Thompson."

A member of the faculty since 1999, Asimow earned his MS and PhD at Caltech in 1993 and 1997, respectively. His research focuses on characterizing the mineralogy and melting of the earth's mantle, the formation of crust, and the nature of the core-mantle boundary.

Asimow is a member of the American Geophysical Union, the Mineralogical Society of America, the Geochemical Society, and the American Physical Society. He is the winner of the 2003 F. W. Clarke Medal of the Geochemical Society, a 2003 Alfred P. Sloan Foundation Fellow, and the recipient the 2005 James B. Macelwane Medal of the American Geophysical Union. His work was supported by a National Science Foundation CAREER grant from 2003 to 2007.

In nomination letters written by students, Asimow was commended for his enthusiasm, clarity, and depth of knowledge. Several students described him as the professor to whom graduate students in the Division of Geological and Planetary Sciences turn when confused about a paper, when they can't agree on the answer to a scientific question, or when they're starting a new project or finishing a composition. The award citation also highlighted what the committee called a "striking innovation" of Asimow's curriculum for an advanced graduate class in petrology; in that class, he "invites his students to vote on the subject matter of the course on the first day of the term, laying the foundation for the extensive teacher-student interaction that forms a critical part of his teaching style."

"He is as inspiring as he is informative, and a great role model for us aspiring professors," said June Wicks, a graduate student in geochemistry, in her letter nominating Asimow for the prize. "He pours his energy into describing concepts both precisely and thoroughly."

Asimow says that the best thing about teaching at Caltech is its dynamic, engaged, talented, and curious student population.

"It makes all the difference to a teacher when the students are able and willing to interact, question, and even challenge the professor," says Asimow. "With small class sizes and suitable encouragement, I often get a group of students that help me and help each other to explore a subject in a satisfying and complete way. That's very rewarding."

Previous winners of the Feynman Prize in the past four years are J. Morgan Kousser, professor of history and social science; Dennis Dougherty, George Grant Hoag Professor of Chemistry; Jehoshua (Shuki) Bruck, Gordon and Betty Moore Professor of Computation and Neural Systems and Electrical Engineering; and Zhen-Gang Wang, professor of chemical engineering.