The Everhart Lecture Series is a forum to encourage interdisciplinary interaction among graduate students and faculty, to share ideas about recent research developments, problems and controversies, and to recognize exemplary presentation and research abilities. Lecturers discuss scientific topics at a level suitable for graduate students and faculty from all fields while addressing current research issues.
Each fall, three graduate student Everhart lecturers are selected to present their work to the Caltech community. Speakers receive a $500 honorarium and recognition at graduation.
The recording and streaming of the Everhart Lecture Series in previous years can be viewed online at the Caltech Today Theater in the 'Science and Technology' section. To view the entire archive of the Everhart lectures, please visit graduate students in the Caltech Today Theater.Nominations and applications for 2007-2008 Everhart lecturers will be accepted until Tuesday, November 13, 2007, and must include six copies of the following:
If you would like to nominate a graduate student regardless of whether they are presently completing an application, please do so! Simply send a nomination letter as described above, and include the student's contact information so that we can inform them of the nomination and encourage them to apply.
Nominees will be interviewed and asked to present a brief version of their talk to a selection committee composed of graduate students. Final selections will be made by early December. Selection will be based on the following criteria, weighted approximately equally:
The application form is here. Send applications and nominations
to:
Everhart Lecture Series Committee
c/o Celia Shiau
MC 139-74
Please email the ELS committee chair, Celia Shiau for inquiries.
Interviews will be scheduled during 20-minute time slots on November 28th and 29th from 6pm until 11pm. Please keep your schedule free during these times.
Many exotic celestial phenomena produce X-rays---supernovae, black holes and neutron stars are but a few examples. Study of the X-ray sky has brought much new knowledge to astronomy, especially in the past decade, with the launch of new X-ray telescopes in space. These telescopes employ focusing technology---X-ray mirrors to concentrate large amounts of light onto compact `X-ray digital cameras'---which results in unprecedented sharpness, colors and sensitivity. While these focusing telescopes detect low-energy X-rays (analogous to red-colored light in the visible band), no equivalent instrument exists today for high-energy X-rays---the `orange' through `violet' of the X-ray band. Our experiment, the High Energy Focusing Telescope (HEFT), is developed to satisfy exactly this need.
HEFT is among the first generation of focusing telescopes sensitive to high-energy X-rays. The instrument consists of several coaligned telescopes---X-ray mirrors and `X-ray digital cameras'---on a balloon-borne pointing platform. Both the X-ray mirrors and cameras are new technologies developed by our collaboration and by others over the past decade. If placed on a satellite, a high-energy X-ray telescope with HEFT technologies will be a thousand times more sensitive than any high-energy X-ray instrument currently in space, enabling new scientific studies that are not feasible with current space technologies. After a decade of hardware development, HEFT was launched for the first time in May, 2005.
In this talk, I shall explain the significance of high-energy X-rays in observational astronomy, describe the new technologies for focusing high-energy X-rays, and present the maiden flight of HEFT, including our latest scientific results.
Bacteria have ruled the planet for billions of years, yet only in the last few years have we learned that these organisms spend much of their lives as surface-associated communities, or biofilms. These biofilms are extremely resilient to changes in environmental conditions and can be up to a hundred times more resistant to antibiotics and antimicrobial agents. This lifestyle strategy allows the bacteria to survive well in diverse environments. However, they can also adversely affect humans, forming biofilms in pipelines, as plaque on teeth, on the surfaces of medical implants and causing life-threatening infections in the lungs of patients with cystic fibrosis. We are only starting to understand how bacteria live in these communities, how the communities are organized, how they get enough nutrients and what makes them so resilient. Bacteria in biofilm communities are nutrient limited, but instead of dying as free-swimming cells might, we have found that cells in all regions of the biofilm continue to live and produce energy. This means that all cells are potentially capable of responding to changes and interacting with their environment over long periods of time. In this seminar, I will discuss how we are working to understand the metabolic state of these quiescent cells, a growth state that has important implications for bacterial survival in natural and man-made environments, yet one that has remained largely unexplored.
As the science of materials has evolved, we have gained the ability to make unusual alloys that do not exist in nature but have properties advantageous in practical applications. As we enter a generation where greater demands are being put upon material functionality, particularly in biomedical and small-scale applications, it is increasingly important that we are able to characterize and understand how these materials work. Establishing a relationship between the microscopic behavior of a material and its macroscopic properties facilitates the development of these types of new materials and the prediction of their behavior in practical applications.
One prominent example of this type of engineered material is nitinol. Nitinol is a mixture of Nickel and Titanium that has the ability to elastically "stretch" far beyond most metals (superelasticity) and also has the ability to remember a previous shape when heated (the shape memory effect). It achieves this by changing the geometry of its crystalline structure. This transformation between phases is the fundamental mechanism behind its unique properties, but there is little experimental data characterizing how this transformation proceeds. By using a relatively new technique called Digital Image Correlation (DIC), we have succeeded in getting the first quantitative understanding of how this transformation mechanism nucleates and proceeds. This talk will introduce the shape memory effect and superelasticity, describe the physics behind these phenomena, and discuss the current and future applications of these materials.
Decision-making under uncertainty is a fundamental activity at every societal level with examples as diverse as people saving for retirement, companies pricing insurance, and countries evaluating military, social, and environmental risks. The choices can vary greatly in the amount of information available to the decision-maker about the outcome probabilities. Standard decision theory, however, precludes agents from taking into account uncertainty about probabilities. This prediction was rejected decisively by the introduction of a thought experiment called the "Ellsberg Paradox."
Much work has been done in the ensuing decades to resolve the paradox by relaxing the axioms underlying the standard model, with little attention paid to the actual decision-making apparatus -- the brain. Recent advances in technology have allowed us to peer inside the minds of decision-makers. We used a combination of data from functional brain imaging and patients with focal brain damage to study the Ellsberg paradox. Our study shows that standard theory is wrong on both the behavioral and neural levels. More generally, it shows the value of combining ideas and tools from social and biological sciences.
Einstein never did accept quantum mechanics. In a paper co-authored by Rosen and Podolsky in 1935, he objected to the role of quantum mechanics as a complete description of nature. But it was that paper which established the concept of quantum entanglement, a purely quantum mechanical correlation among various components of a physical system. For two components of a physical system linked by quantum entanglement, acting on one will affect the state of the other, irrespective of the distance between them. Quantum entanglement turns out to be the key resource in the new science of quantum information.
At the heart of quantum information science are distributed quantum networks. In quantum networks, quantum information is generated, processed, and stored locally in quantum nodes. These nodes are linked by quantum channels that transport quantum states from site to site with high fidelity by way of quantum teleportation. Even with relatively modest processing capabilities, the envisioned quantum "internet" could be used to accomplish tasks that are otherwise impossible within the realm of classical communication and computation, such as secret sharing, secure multi-party computation, and quantum metrology. Besides an introduction to the concepts of quantum entanglement and teleportation, I will talk about the effort in our group towards the realization of a quantum repeater architecture for large-scale quantum networks (to nettle Einstein, if he is watching us).
The astonishing diversity of life reflects the ongoing evolution of myriad molecular components such as genes and the proteins they encode. Strangely, even within the same organism, some proteins evolve rapidly while others barely change. For decades, functional differences between proteins have been thought to cause evolutionary rate differences, but our work reveals that protein function plays at best a minor role. Instead, we have uncovered a surprising alternative: the cellular machinery that synthesizes proteins from genes is sloppy, defective proteins cost dearly, and the speed of a gene's evolution depends on how costly it is to change. At a time when challenges to Darwinian evolution abound, our attack on this controversial problem provides an eye-opening view of how evolution science really works.
Stromatolites—laminated, enigmatically shaped cones and domes that dominated carbonate reefs for the first 80% of Earth's history—may be the oldest macroscopic record of life on Earth. If and how microbes contributed to the formation of many ancient stromatolites has puzzled geologists for decades. To develop criteria for the recognition of uniquely microbial signatures in rocks, we precipitated calcium carbonate in the presence and absence of various modern microorganisms under chemical conditions relevant for the early Earth. Using this approach, we showed that anoxygenic photosynthetic bacteria could have built stromatolites even before the rise of modern stromatolite builders—cyanobacteria. Our work disproved the paradigm that microbial sulfate reduction, a metabolism important for the formation of modern stromatolites, was responsible for the formation of similar structures billions of years ago. We also developed criteria to constrain the microbial origin of a previously unconfirmed biosignature—sub-micron-sized pores that occur in rapidly precipitating carbonate rocks. These insights into how microbes shape rocks are critical to the search for microbial biosignatures on the early Earth and other planets.
Central to the advancement of our understanding of quantum physics and to the development of the tantalizing quantum computer is the quest to devise ever better ways to manipulate atoms and photons in our laboratories. The atom chip—a device reminiscent of a computer circuit board but designed for cold neutral atoms—is an important new addition to the toolboxes of quantum physics and nanotechnology. We have fabricated and employed these devices to couple single atoms to photons, to investigate the newly discovered dilute-gas Bose-Einstein condensates, and for creating an atom mirror from an ordinary computer hard drive. Quantum computer hardware and atom laser manipulation are but a few promising atom chip applications.
Fewer than 30,000 genes orchestrate the workings of human cells. These genes encode the proteins which conduct the myriad activities necessary for life. Chemical modifications of these proteins play a critical role in regulating their cellular functions. We study one such modification, known as O-GlcNAc glycosylation. The addition of this single sugar, β-N-acetylglucosamine (GlcNAc), to proteins has been linked to nutrient sensing and gene expression. Moreover, the enzyme that transfers the sugar is abundant in the brain, and the modification has been linked to neurodegenerative disease. Understanding this dynamic modification has been hampered by the difficulty in detecting it. To address this challenge, we developed a strategy which incorporates a mutant enzyme and unnatural substrate for rapid and sensitive detection of O-GlcNAc-modified proteins. Coupling our approach to mass spectrometry yielded the first direct, wide-scale identification of O-GlcNAc proteins in the brain. Our studies have identified O-GlcNAc on proteins associated with neurotransmitter release and the formation of nerve cell structures important for learning and memory. Currently, we are investigating the dynamic regulation of O-GlcNAc in the brain in an attempt to understand its role in nerve cell function and neurodegeneration.
The Interplanetary Transport Network: Space Transportation Architecture for the 21st Century
The competing gravitational pull between celestial bodies creates a vast array of low-energy passageways that winds around the sun, planets and moons. Space travel along these corridors would slash the amount of fuel needed to explore and develop our solar system. We have shown how to identify and traverse these passageways, which are associated with Lagrange points, regions of balance near a planet or moon. We have laid the groundwork for a new kind of space transportation architecture for the exploration of Mars, the asteroids, and the outer solar system, including a mission to assess the possibility of life on Jupiter's icy moons.
Stalking the Exciton Condensate: Exotic Behavior of Electrons under Extreme Conditions
For over 40 years, scientists have sought the Bose-Einstein condensation (BEC) of excitons. BEC is responsible for many novel effects when achieved in liquid helium (creating superfluidity), in electron pairs (producing superconductivity—the lack of electrical resistance in metals), and most recently in alkali atoms (for which the 2001 Nobel prize was awarded). But the BEC of excitons has remained elusive. Excitons are fragile particles, bound pairs of electrons and holes with a predilection for annihilating one another, making the formation of a BEC difficult. In our lab we have created stable excitons in neighboring layers of two-dimensional electron gases embedded in highly-engineered semiconductor crystals. We have observed superfluid-like flow of these excitons, evidence that the long-sought exciton condensation has finally been achieved.
Cancerous Stem Cells: Insights into the Origins of Human Brain Tumors
Brain tumors are the most common solid cancer and most frequent cause of cancer death in children. Despite decades of research, the regimen of surgery, radiation, and chemotherapy remains the principle therapy available to patients. The deleterious effects of these traditional treatments, along with the lack of effective tumor-specific treatments and diagnostic tools, lead to high morbidity and mortality rates. Recent advances in leukemia research have identified bone marrow-derived stem cells as a source for those cancers. Based on this work, we have taken a novel approach to identifying the origins of brain tumors. We found that brain tumor-derived stem cells share similar properties with neural stem cells--they both give rise to neurons and glia, produce similar proportions of cell types, and self-renew--but differ in that they proliferate extensively and differentiate into abnormal cells that may contribute to tumorigenesis. These findings suggest that targeting tumor-derived stem cells is a promising approach to treating brain tumors.
Eitan Grinspun (Computer Science): "Multiresolution in Graphics and Simulation: From Wrinkles in Valentines Day Balloons to Folds in the Brain"
Sarah Heilshorn (Chemistry and Chemical Engineering): "Protein Engineering: A Novel Approach to Creating New Biomaterials"
Ian Swanson (Physics): "Tangled Science: Unraveling the Superstring Mystery"
Joshua Bloom (Astrophysics): "Toward the Origin of Gamma-Ray Bursts, the Biggest Bangs in the Universe"
Benjamin Weiss (Planetary Science): "Ancient Magnetism, Panspermia, and the Evolution of Mars"
Ramesh Srinivasan (Chemistry and Chemical Engineering): "Catching Molecules in the Act: Ultrafast Diffraction of Transient Structures in Real Time"
Questions? Contact els@caltech.edu.