Raymond E. Goldstein

Schlumberger Professor of Complex Physical Systems

Fellow of Churchill College

Our research group focuses on understanding nonequilibrium phenomena in the natural world, with particular emphasis on biological physics. We strive for a holistic approach in which theory and experiment seamlessly coexist, in the best tradition of DAMTP. Members of the group include theoretical and experimental physicists, applied mathematicians and biologists. Undergraduates are welcome to join us.

Much of our current research is involved with physical aspects of multicellularity. We are engaged in studies of collective dynamics, mixing, and transport in concentrated bacterial and algal suspensions, striving to understand the more general problem of interacting, self-propelled organisms. These issues touch on aspects of nonequilibrium statistical mechanics and fluid dynamics, but also have implications for specific biological phenomena such as quorum sensing. Of interest also is the role of flagella-driven flows in the evolutionary transition from unicellular to multicellular organisms (using the Volvocine green algae as a model lineage). Experimental methods include optical trapping, high-speed imaging, fluorescence microscopy, microfluidics, and particle imaging velocimetry. We use a variety of model organisms to study these processes (the bacterium B. subtilis, and algae such as Chlamydomonas and Volvox). Theoretical tools used vary from nonlinear PDEs, as in fluid mechanics and elasticity, to statistical physics and dynamical systems methods.

A new project centres around understanding the dynamics of cytoplasmic streaming, the persistent circulation of the fluid contents of large eukaryotic cells driven by the collective dynamics of motor proteins. Discovered by Bonaventura Corti in 1774, streaming has been studied intensely for over two centuries, but many fundamental questions have remained unanswered with regard to how the fluid motion impacts on cellular metabolism, homeostasis, and mixing. Using the model organisms Chara corallina and Arabidopsis thaliana we are engaged in a comprehensive experimental study of fluid dynamical and transport issues associated with streaming, using techniques from microfluidics, electrophysiology, fluid dynamics and molecular biology. At the same time, we have been developing a theoretical understanding of the unusual transport phenomena that take place in these high Peclet number flows, with their often intriguing geometry. Some of these transport issues have implications for microfluidic applications. (Image at left is copyright 2008 National Academy of Sciences U.S.A.).

A separate line of investigation focuses on a broad class of problems in the natural world involving growth by precipitation. The classic example of this is provided by cave formations such as stalactites, stalagmites, and draperies. We have developed a successful free-boundary theory for the ideal shape of stalactites by combining chemical kinetics and fluid dynamics. A related synthesis of fluid mechanics, heat transfer, and solidification led to a theory for the shapes of dripping icicles. Remarkably, these shapes have the same mathematical form far from the tip. We are currently investigating the origin of the ripples so commonly found on them, along with the great variety of non-axisymmetric shapes found in nature.

Research in our group is closely related to that of several other groups within DAMTP,
including the Biological Fluid Dynamics Group, the Institute for Theoretical Geophysics ,
the G.K. Batchelor Fluid Dynamics Laboratory, and the Cambridge Computational Biology
Institute. In addition, we expect to build strong ties with the growing efforts in Biological and
Soft Systems and Medical Physics in the Cavendish laboratory.

Partner Laboratory at the University of Arizona

Part of my group remains in the Department of Physics at the University of Arizona. In close collaboration with Prof. J.O. Kessler, we study collective dynamics in biological systems, aspects of biophysical elasticity, and the physics of multicellularity. A separate effort continues
our work on precipitative growth and the physics of speleothems. At the University of Arizona we spent a number of years developing an interdisciplinary program at the interface of Biology, Physics, and Mathematics. This was funded by the NSF IGERT Program, and administered jointly with Michael Tabor, Leslie P. Tolbert, Neil H. Mendelson, and Timothy W. Secomb. Some aspects of this program, including an interdisciplinary laboratory for biological physics, were described in an article in Physics Today with Philip C. Nelson and Thomas R. Powers.

Funding

Research at the University of Cambridge is supported by a number of sources. Chief among them is the Schlumberger Corporation, through its generous endowment of the Schlumberger Chair and the Schlumberger Chair Fund.

Specific research grants funding research in the group include:

Dr. Idan Tuval (Ph.D., UIB, 2005) a postdoctoral fellow in DAMTP, is supported by the Human Frontier Science Program in his research in biophysics, done in a collaboration between our group and the group of Prof. T.J. Pedley.

An intriguing problem in plant science is the appearance of "patchy stomatal conductance" in plant leaves, resulting in spatially varying rates of photosynthesis. Our project on "Physical and Mathematical Aspects of Inhomogeneous Photosynthetic Activity" is funded by a Research Grant from the Royal Society.

We have a major research program on the fluid dynamics and biology of cytoplasmic streaming, the persistent circulation of the contents of large eukaryotic cells driven by the action of motor proteins. This work combines in vivo and in vitro experiments with theoretical work on fluid flow and transport. It is funded in part by the grant "Microfluids of Cytoplasmic Streaming" from the Leverhulme Trust.

We are also very grateful to the Leverhulme Trust for supporting the sabbatical visit of Professor Jerry P. Gollub (Haverford) to DAMTP for the academic year 2008-2009, through a Leverhulme Visiting Professorship.

Additional funding for work on streaming comes to Dr. Marco Polin (Ph.D., New York University, 2007), a postdoctoral fellow in our group. Marco's Ph.D. research was on aspects of colloidal physics studied with holographic optical traps. His experimental research in DAMTP is supported by a Marie Curie European Fellowship for Career Development from the European Commission on the project entitled "The biophysics of cytoplasmic streaming in Chara corallina."

The second major thrust of our group is funded by the grant "Physical Aspects of Evolutionary Transitions to Multicellularity" from the Engineering and Biological Systems program of the Biotechnology and Biological Sciences Research Council (BBSRC). Using the Volvocine green algae as model systems, major goals include understanding allometric scaling laws that underlie self-propulsion and metabolism, experimental and theoretical studies of flagellar synchronization using micromanipulation and high-speed imaging techniques, and investigations into the dynamics of phototaxis in multicellular systems.

Ph.D. student Knut Drescher (B.A. Physics, Oxford, 2007) is supported by DAMTP DTA funds from the Engineering and Physical Sciences Research Council (EPSRC) in his work on multicellularity. His focus is on the dynamics of phototaxis in multicellular algae, in theory and experiment.

Ph.D. student Jan-Willem van de Meent (B.A. Physics, Leiden University, 2006) is supported by DAMTP DTA funds from the Engineering and Physical Sciences Research Council (EPSRC) and from the University of Leiden in his work on cytoplasmic streaming. Jan-Willem's work involves both theoretical and experimental components.

Work at the University of Arizona has been supported by the National Science Foundation (grant PHY0551742), the National Institutes of Health (grant R01 GM72004-01 with Charles Wolgemuth and Nyles Charon) and the Department of Energy (grant DOE-W-31-109-ENG-38 with Argonne National Laboratories, in collaboration with Igor Aranson).