School of Humanities and Sciences
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Professor of Physics
BioWhat are the basic degrees of freedom and interactions underlying gravitational and particle physics? What is the mechanism behind the initial seeds of structure in the universe, and how can we test it using cosmological observations? Is there a holographic framework for cosmology that applies throughout the history of the universe, accounting for the effects of horizons and singularities? What new phenomena arise in quantum field theory in generic conditions such as finite density, temperature, or in time dependent backgrounds?
Professor Silverstein attacks basic problems in several areas of theoretical physics. She develops concrete and testable mechanisms for cosmic inflation, accounting for its sensitivity to very high energy physics. This has led to a fruitful interface with cosmic microwave background research, contributing to a more systematic analysis of its observable phenomenology.
Professor Silverstein also develops mechanisms for breaking supersymmetry and for stabilizing the extra dimensions of string theory to model the immense hierarchies between the cosmological horizon, electroweak, and Planck scales in nature. In addition, Professor Silverstein uses the ultraviolet completion of gravity afforded by string theory to address questions of quantum gravity, such as singularity resolution and the physics of black hole and cosmological horizons. Professor Silverstein also uses modern techniques in quantum field theory to model strongly coupled phenomena motivated by measurements in condensed matter physics.
Areas of focus:
- UV complete mechanisms and systematics of cosmic inflation, including string-theoretic versions of large-field inflation (with gravity wave CMB signatures) and novel mechanisms involving inflaton interactions (with non-Gaussian signatures in the CMB)
-Systematic theory and analysis of primordial Non-Gaussianity, taking into account strongly non-linear effects in quantum field theory encoded in multi-point correlation functions
-Long-range interactions in string theory and implications for black hole physics
- Concrete holographic models of de Sitter expansion in string theory, aimed at upgrading the AdS/CFT correspondence to cosmology
- Mechanisms for non-Fermi liquid transport and $2k_F$ singularities from strongly coupled finite density quantum field theory
- Mechanisms by which the extra degrees of freedom in string theory induce transitions and duality symmetries between spaces of different topology and dimensionality
Associate Professor of Physics and Applied Physics
Current Research and Scholarly InterestsJon's group focuses on exploring synthetic quantum matter using the unique tools available through quantum and classical optics. We typically think of photons as non-interacting, wave-like particles. By harnessing recent innovations in Rydberg-cavity- and circuit- quantum electrodynamics, the Simonlab is able to make photons interact strongly with one another, mimicking collisions between charged electrons. By confining these photons in ultra-low-loss metamaterial structures, the teams "teach" the photons to behave as though they have mass, are in traps, and are experiencing magnetic fields, all by using the structures to tailor the optical dispersion. In total, this provides a unique platform to explore everything from Weyl-semi-metals, to fractional quantum hall puddles, to Mott insulators and quantum dots, all made of light.
The new tools developed in this endeavor, from twisted fabry-perot resonators, to Rydberg atom ensembles, Floquet-modulated atoms, and coupled cavity optical mode converters, have broad applications in information processing and communication. Indeed, we are now commissioning a new experiment aimed at interconverting optical and mm-wave photons using Rydberg atoms inside of crossed optical and superconducting millimeter resonators as the transducer.
Professor of Biology
Current Research and Scholarly InterestsPlanar cell polarity, cell shape and mobility, and control of cell fate
Current Research and Scholarly InterestsCholesterol in biological membranes; genetic mechanisms & cholesterol production
Professor of Biology and, by courtesy, of Chemical and Systems Biology
Current Research and Scholarly InterestsMy overarching goal is to understand how cell growth triggers cell division. Linking growth to division is important because it allows cells to maintain specific size range to best perform their physiological functions. For example, red blood cells must be small enough to flow through small capillaries, whereas macrophages must be large enough to engulf pathogens. In addition to being important for normal cell and tissue physiology, the link between growth and division is misregulated in cancer.
Edward I. Solomon
Monroe E. Spaght Professor of Chemistry and Professor of Photon Science
Current Research and Scholarly InterestsProf. Solomon's work spans physical-inorganic, bioinorganic, and theoretical-inorganic chemistry, focusing on spectroscopic elucidation of the electronic structure of transition metal complexes and its contribution to reactivity. He has advanced our understanding of metal sites involved in electron transfer, copper sites involved in O2 binding, activation and reduction to water, structure/function correlations over non-heme iron enzymes, and correlation of biological to heterogeneous catalysis.
David and Lucile Packard Professor in Marine Science, Emeritus
Current Research and Scholarly InterestsWe examine two aspects of organism-environment interactions: How does stress from physical (e.g., temperature) and chemical (oxygen levels, pH) factors perturb organisms and how do organisms respond, adaptively, to cope with this stress? We examine evolutionary adaptation and phenotypic acclimatization using a wide variety of marine animals, including Antarctic fishes and invertebrates from intertidal habitats on the coastlines of temperate and tropical seas.
Professor of Chemical Engineering, of Materials Science and Engineering and, by courtesy, of Applied Physics
Current Research and Scholarly InterestsTheory and computation of biological processes and complex materials
Assistant Professor of Geological Sciences and, by courtesy, of Biology and Center Fellow, by courtesy, at the Woods Institute for the Environment
Current Research and Scholarly InterestsThe research interests in the Sperling Lab are Earth history and the evolution of life, and the interactions between the biosphere and the geosphere. As such this research can generally be considered paleontology, insofar as paleontology encompasses all aspects of the history of life.
Consequently, we define our research agenda by the questions we are interested in, rather than the tools used. This research incorporates multiple lines of evidence, and multiple tools, to investigate questions in the history of life. These lines of evidence include fossil data, molecular phylogenetics, sedimentary geochemistry, and developmental and ecological data from modern organisms. Ultimately, the goal is to link environmental change with organismal and ecological response through the lens of physiology.
Our field research takes place all over the world--current areas include:
-NW Canada (Yukon and Northwest Territories): Research has been conducted on the early Neoproterozoic Fifteenmile Group, Cryogenian and Ediacaran Windermere Supergroup, and on the Ordovician-Devonian Road River Group in the southern Richardson Mountains
-Southern Canadian Cordillera: Work here has focused on the early Cambrian Mural Formation and its soft-bodied fauna.
-England and Wales: Cambrian-Silurian successions in the Welsh Basin
-Namibia: Ediacaran Nama Group
-Upwelling zones: We study the oxygen minimum zone offshore California as an analogue for ancient low-oxygen oceans.
Associate Professor of Chemistry
BioResearch in the Stack group focuses on the mechanism of dioxygen activation and the subsequent oxidative reactivity with primarily copper complexes ligated by imidazoles or histamines. Specifically, the group is interested in substrate hydroxylations and full dioxygen reduction. The remarkable specificity and energy efficiency of metalloenzymes provide the inspiration for the work. Trapping and characterizing immediate species, primarily at low temperatures, provide key mechanistic insights especially through substrate reactivity along with spectroscopic and metrical correlation to DFT calculations. Our objective is to move these efficient enzymatic mechanisms into small synthetic complexes, not only to reproduce biological reactivity, but more importantly to move the oxidative mechanism beyond that possible in the protein matrix.
Daniel Stack was born, raised and attended college in Portland Oregon. He received his B.A. from Reed College in 1982 (Phi Beta Kappa), working with Professor Tom Dunne on weak nickel-pyrazine complexes. In Boston, he pursued his doctoral study in synthetic inorganic chemistry at Harvard University (Ph.D., 1988) with Professor R. H. Holm, investigating site-differentiated synthetic analogues of biological Fe4S4 cubanes. As an NSF Postdoctoral Fellow with Professor K. N. Raymond at the University of California at Berkeley, he worked on synthesizing new, higher iron affinity ligands similar to enterobactin, a bacterial iron sequestering agent. He started his independent career in 1991 at Stanford University primarily working on oxidation catalysis and dioxygen activation, and was promoted to an Associate Professor in 1998. His contributions to undergraduate education have been recognized at the University level on several occasions, including the Dinkelspiel Award for Outstanding Contribution to Undergraduate Education in 2003.
Areas of current focus include:
Copper Dioxygen Chemistry
Our current interests focus on stabilizing species formed in the reaction of dioxygen with Cu(I) complexes formed with biologically relevant imidazole or histamine ligation. Many multi-copper enzymes ligated in this manner are capable of impressive hydroxylation reactions, including oxidative depolymerization of cellulose, methane oxidation, and energy-efficient reduction of dioxygen to water. Oxygenation of such complexes at extreme solution temperatures (-125°C) yield transient Cu(III) containing complexes. As Cu(III) is currently uncharacterized in any biological enzyme, developing connections between the synthetic and biological realms is a major focus.
Surface Immobilization of Catalysts in Mesoporous Materials
In redox active biological metal sites, the ligation environment is coupled tightly to the functional chemistry. Yet, the metal sites are also site-isolated, creating species that may only have a transient existence in a homogeneous solution. Site isolation of synthetic complexes can be achieved synthetically by supporting the metal complex on a solid matrix. Movement of these complexes into silica based materials or onto electroactive carbon electrodes represent a new direction for the group in the development of bio-inspired metal-based catalysts.
Acting Dean of Research, Frank Lee and Carol Hall Professor, Senior Associate Vice Provost of Research and Professor of Genetics
Current Research and Scholarly InterestsWe use the tools of genetics, microscopy, and biochemistry to understand fundamental questions of cell biology: How are cells organized by the cytoskeleton? How do the centrosome and cilium control cell control cell signaling? How is cell division coordinated with duplication of the centrosome, and what goes wrong in cancer cells defective in this coordination?