Alumnus Arthur McDonald Wins 2015 Nobel Prize in Physics

Arthur B. McDonald (PhD '70), director of the Sudbury Neutrino Observatory (SNO) in Ontario, Canada, and Takaaki Kajita, at the University of Tokyo, Kashiwa, Japan, have shared the 2015 Nobel Prize in Physics for the discovery that neutrinos can change their identities as they travel through space.

McDonald and Kajita lead two large research teams whose work has upended the standard model of particle physics and settled a debate that has raged since 1930, when the neutrino's existence was first proposed by physicist Wolfgang Pauli. Pauli initially devised the neutrino as a bookkeeping device—one to carry away surplus energy from nuclear reactions in stars and from radioactive decay processes on Earth. In order to make the math work, he gave it no charge, almost no mass, and only the weakest of interactions with ordinary matter. Billions of them are coursing through our bodies every second, and we are entirely unaware of them.

There are three types of neutrinos—electron, muon, and tau—and they were, for many years, assumed to be massless and immutable. The technology to detect electron neutrinos emerged in the 1950s, and it slowly became apparent that as few as one-third of the neutrinos the theorists said the sun should be emitting were actually being observed. Various theories were proposed to explain the deficit, including the possibility that the detectable electron neutrinos were somehow transmuting into their undetectable kin en route to Earth.

Solving the mystery of the missing neutrinos would require extremely large detectors in order to catch enough of the elusive particles to get accurate statistics. Such sensitive detectors also require enormous amounts of shielding to avoid false readings.

The University of Tokyo's Super-Kamiokande neutrino detector, which came online in 1996, was built 1,000 meters underground in a zinc mine. Its detector, which counts muon neutrinos and records their direction of travel, found fewer cosmic-ray neutrinos coming up through the Earth than from any other direction. Since they should not be affected in any way by traveling through the 12,742-kilometer diameter of our planet, Kajita and his colleagues concluded that the extra distance had given them a little extra time to change their identities.

McDonald's SNO, built 2,100 meters deep in a nickel mine, began taking data in 1999. It has two counting systems. One is exclusively sensitive to electron neutrinos, which are the type emitted by the sun; the other records all neutrinos but does not identify their types. The SNO also recorded only about one-third of the predicted number of solar electron-type neutrinos—but the aggregate of all three types measured by the other counting systems matched the theory.

The conclusion, for which McDonald and Kajita were awarded the Nobel Prize, was that neutrinos must have a nonzero mass. Quantum mechanics treats particles as waves, and the potentially differing masses associated with muons and taus gives them different wavelengths. The probability waves of the three particle types are aligned when the particle is formed, but as they propagate they get out of synch. Therefore, there is a one-third chance of seeing any particular neutrino in its electron form. Because these particles have this nonzero mass, their gravitational effects on the large-scale behavior of the universe must be taken into account—a profound implication for cosmology.

McDonald came to Caltech in 1965 to pursue a PhD in physics in the Kellogg Radiation Laboratory under the mentorship of the late Charles A. Barnes, professor of physics, emeritus, who passed away in August 2015. "Charlie Barnes was a great mentor who was very proud of his students," says Bradley W. Filippone, professor of physics and a postdoctoral researcher under Barnes. "It is a shame that Charlie didn't get to see Art receive this tremendous honor."

A native of Sydney, Canada, McDonald received his bachelor of science and master's degrees, both in physics, from Dalhousie University in Halifax, Nova Scotia, in 1964 and 1965, respectively. After receiving his doctorate, he worked for the Chalk River Laboratories in Ontario until 1982, when he became a professor of physics at Princeton University. He left Princeton in 1989 and became a professor at Queen's University in Kingston, Canada; the same year, he became the director of the SNO. In 2006, he became the holder of the Gordon and Patricia Gray Chair in Particle Astrophysics, a position he held until his retirement in 2013.

Among many other awards and honors, McDonald is a fellow of the American Physical Society, the Royal Society of Canada, and of Great Britain's Royal Society. He is the recipient of the Killam Prize in the Natural Sciences; the Henry Marshall Tory Medal from the Royal Society of Canada, its highest award for scientific achievement; and the European Physics Society HEP Division Giuseppe and Vanna Cocconi Prize for Particle Astrophysics.

To date, 34 Caltech alumni and faculty have won a total of 35 Nobel Prizes. Last year, alumnus Eric Betzig (BS '83) received the Nobel Prize in Chemistry.

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Long-Term Contraception in a Single Shot

Caltech biologists have developed a nonsurgical method to deliver long-term contraception to both male and female animals with a single shot. The technique—so far used only in mice—holds promise as an alternative to spaying and neutering feral animals.

The approach was developed in the lab of Bruce Hay, professor of biology and biological engineering at Caltech, and is described in the October 5 issue of Current Biology. The lead author on the paper is postdoctoral scholar Juan Li.

Hay's team was inspired by work conducted in recent years by David Baltimore and others showing that an adeno-associated virus (AAV)—a small, harmless virus that is unable to replicate on its own, that has been useful in gene-therapy trials—can be used to deliver sequences of DNA to muscle cells, causing them to produce specific antibodies that are known to fight infectious diseases, such as HIV, malaria, and hepatitis C.

Li and her colleagues thought the same approach could be used to produce infertility. They used an AAV to deliver a gene that directs muscle cells to produce an antibody that neutralizes gonadotropin-releasing hormone (GnRH) in mice. GnRH is what the researchers refer to as a "master regulator of reproduction" in vertebrates—it stimulates the release of two hormones from the pituitary that promote the formation of eggs, sperm, and sex steroids. Without it, an animal is rendered infertile.

In the past, other teams have tried neutralizing GnRH through vaccination. However, the loss of fertility that was seen in those cases was often temporary. In the new study, Hay and his colleagues saw that the mice—both male and female—were unable to conceive after about two months, and the majority remained infertile for the remainder of their lives.

"Inhibiting GnRH is an ideal way to inhibit fertility and behaviors caused by sex steroids, such as aggression and territoriality," says Hay. He notes that in the study, his team also shows that female mice can be rendered infertile using a different antibody that targets a binding site for sperm on the egg. "This target is ideal when you want to inhibit fertility but want to leave the individual otherwise completely normal in terms of reproductive behaviors and hormonal cycling."

Hay's team has dubbed the new approach "vectored contraception" and says that there are many other proteins that are thought to be important for reproduction that might also be targeted by this technique.

The researchers are particularly excited about the possibility of replacing spay–neuter programs with single injections. "Spaying and neutering of animals to control fertility, unwanted behavior, and population numbers of feral animals is costly and time consuming, and therefore often doesn't happen," says Hay. "There is a strong desire in many parts of the world for quick, nonsurgical approaches to inhibiting fertility. We think vectored contraception provides such an approach."

As a next step, Hay's team is working with Bill Swanson, director of animal research at the Cincinnati Zoo's Center for Conservation and Research of Endangered Wildlife, to try this approach in female domestic cats. Swanson's team spends much of its time working to promote fertility in endangered cat species, but it is also interested in developing humane ways of managing populations of feral domestic cats through inhibition of fertility, as these animals are often otherwise trapped and euthanized.

Additional Caltech authors on the paper, "Vectored antibody gene delivery mediates long-term contraception," are Alejandra I. Olvera, Annie Moradian, Michael J. Sweredoski, and Sonja Hess. Omar S. Akbari is also a coauthor on the paper and is now at UC Riverside. Some of the work was completed in the Proteome Exploration Laboratory at Caltech, which is supported by the Gordon and Betty Moore Foundation, the Beckman Institute, and the National Institutes of Health. Olvera was supported by a Gates Millennium Scholar Award.

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Capturing the Right Odors to Study the Brain

Hong and colleagues aim to reveal neural mechanisms related to olfaction

Over the summer, Betty Hong, assistant professor of neuroscience, spent a week at the Janelia Research Campus in Ashburn, Virginia, interacting and brainstorming with other researchers from around the country interested in olfaction, our sense of smell. Invited to participate by the National Science Foundation (NSF), these 30 computational and experimental neuroscientists came up with innovative ways to approach some of the mysteries about how the brain processes odors and uses that information to guide behavior.

The five-day session was an example of the agency's new funding mechanism, the Ideas Lab. At these meetings, a multidisciplinary group of researchers is charged with generating potentially transformative proposals on a focused research topic. Now the NSF has awarded $15 million to three projects from the Olfactory Ideas Lab. Hong is coprincipal investigator on one titled "Using natural odor stimuli to crack the olfactory code." The awards expand NSF's investments in President Obama's BRAIN Initiative.

"I am grateful to have had the opportunity to be thrown together for a week with such a smart, diverse group of scientists who approach olfaction from so many different angles," says Hong (BS '02), adding that without the Ideas Lab, it is unlikely that she would have ever established collaborations with her coinvestigators. "I am also extremely grateful to the NSF for including junior investigators like myself who are just kicking off their research program. This unique funding mechanism will enable us to tackle really challenging and innovative research right at the start of our careers."

Olfactory scientists typically use simple synthetic odors involving single molecules for their experiments because natural odors—those that we smell around us every day—are too difficult to reproduce in a reliable way under controlled conditions. However, those simplified stimuli may not trigger the full range of neural computations that constitute olfaction.

Therefore, Hong and her colleagues aim to use comprehensive chemical analysis and computational methods to construct reproducible synthetic odorants in the lab that mimic naturally occurring smells in terms of eliciting typical behavioral responses in honey bees, fruit flies, and fly larvae. (Hong specializes in studies of the fruit fly Drosophila.) These synthetic odor blends can then be used to investigate how the brain processes smells and orders specific adaptive behaviors.

"We believe probing the olfactory circuit with naturalistic stimuli will reveal long-hidden computational features of the circuit," Hong explains. "Much as higher-order visual neurons only respond to complex stimuli like faces or hands, and not to simple bars and dots, we hypothesize that naturalistic odor stimuli will reveal novel features of odor space that the olfactory system encodes, which may only become apparent once appropriate sets of stimuli are used."

Along with Hong, additional principal investigators on the project are Brian Smith of Arizona State University; Aravinthan Samuel of Harvard University; and Tatyana Sharpee of the Salk Institute for Biological Studies. The project will receive $3.6 million over three years.

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Summer Interns Return with a World of Experiences

Caltech undergraduate students returned to campus this week, many after spending the summer working at companies in biotechnology, technology, and finance, among other fields. These students have had the opportunity to learn firsthand about the career opportunities and paths that may be available to them after graduation. They also had the chance to put Caltech's rigorous academic and problem-solving training to the test.

In the summer of 2015, nearly a third of returning sophomores, juniors, and seniors were placed in an internship position through Caltech's Summer Undergraduate Internship Program (SUIP). The program, run through the Institute's Career Development Center (CDC), helps connect current undergraduate students with a wide range of companies and businesses that can provide practical skills and work experiences that give the students an edge in the future job market.

Many undergraduates find paid summer internships through the CDC, says Lauren Stolper, the director of fellowships, advising, study abroad, and the CDC. The center organizes fall and winter career fairs and offers workshops related to finding internships; provides individual advising on internship options and conducting a job hunt for an internship; organizes interviews for students through its on-campus recruiting program; and provides web-based internship listings and company information through Techerlink, its online job-posting system.

Through the formal establishment of SUIP two years ago—thanks, in part, to the initiative of Craig SanPietro (BS '68, engineering; MS '69, mechanical engineering) and with seed money provided by him and three of his alumni friends and former Dabney House roommates, Peter Cross (BS '68, engineering), Eric Garen (BS '68, engineering), and Charles Zeller (BS '68, engineering)—the CDC has been able to dedicate even more time and attention to helping undergraduates secure these important positions, Stolper says.

"Through internships, students have the opportunity to learn more about the practical applications of their knowledge by contributing to ongoing projects under the guidance of professionals," says Aneesha Akram, a career counselor for internship development/advising, who oversees SUIP.

"Completing summer internships help undergraduates become competitive candidates for full-time positions," says Akram. "When it comes to recruiting for full-time positions, companies seek out candidates with previous internship experience. We have found that many large companies extend return offers and full-time conversions to students who previously interned with them."

The infographic at the above right provides a snapshot of Caltech undergraduate internships over this past summer. Students seeking internships for next summer can contact Akram or look at the CDC website for more information.

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Thursday, October 1, 2015
Cahill, Hameetman Auditorium – Cahill Center for Astronomy and Astrophysics

Launch of Engineers Week at Caltech

Friday, October 23, 2015
Winnett Lounge – Winnett Student Center

Flat Space, Deep Learning: A Workshop by Eric Mazur

Wednesday, October 21, 2015
Beckman Institute Auditorium – Beckman Institute

The Teaching and Learning Project, a National Photographic Essay on Higher Education Featuring Caltech

Tuesday, October 20, 2015 to Wednesday, October 21, 2015
Center for Student Services 360 (Workshop Space) – Center for Student Services

Guest Consultations on Teaching, with Chris Duffy

Tuesday, October 20, 2015
Dabney Hall, Lounge – Dabney Hall

Bringing Joy into Your Teaching: A Workshop by Chris Duffy

Monday, October 19, 2015
Guggenheim 101 (Lees-Kubota Lecture Hall) – Guggenheim Aeronautical Laboratory

The Future of Teaching and Learning at Caltech: An Innovation Showcase

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