Interdisciplinary Research Projects
The Center for Polymer Studies Research Group is devoted to research in
polymer studies and statistical mechanics. Each year, a series of public
seminars brings speakers from over twenty countries to the Boston
University campus. The center's computational program involves the
development and application of modern methods of statistical mechanics:
series, Monte Carlo, and renormalization group. There are diverse
efforts focused on researching Alzheimer's disease, cardiac dynamics,
networks, economics, and liquid water. The experimental program is
largely concerned with studying the structure of polymers at the
molecular level, primarily using the techniques of Raman and Fourier
transform infrared spectroscopy to probe the molecular structure and
molecular conformation of polymers. Particular emphasis is placed on the
application of this technique to polymer gels and to biological
polymers. Another area of active investigation concerns structural
studies of biological polymers, and of natural and model cell membrane
systems.
 Featured
CPS Research Links:
Several faculty are affiliated with several research groups and projects
outside the center. Experimental Condensed
Matter Physics and Polymer Physics (Rama Bansil), Molecular Biophysics
(Kenneth J. Rothschild), Theoretical Condensed
Matter Physics and Polymer Physics (William Klein and Sidney
Redner).
Research projects under active
investigation within the center include:
- Complexity and Coupled Networks. In the past several decades,
there has been a radical shift in the way much of science is done, and
an emphasis on applying network science and complexity to real-world
problems (including cyberinfrastructures and computational and database
approaches). In social, political and defense systems, among others,
there is growing appreication that what happens in one network
significantly affects another network. For example, infrastructures show
a large number of interdependencies: physical interdependency when
energy, material or people flow from one infrastructure to another;
cyber interdependency when information is transmitted or exchanged;
geographic interdependency signaling the co-location of infrastructure
elements; logical interdependency that signals financial, political
coordination, and other interactions. One area of focus is the exploration of the
new kinds of vulnerabilities that coupled networks create and the kinds
of countermeasures that can be developed against such threats (Buldyrev
et al. 2010). For example, modern defense
systems utilize network theory to protect core defense components (i.e.,
hubs).
- Physical Mechanisms in Liquid
Water.
Water is an anomolous liquid. In addition, water is
ubiquitous, important for everything from protein folding to quenching
thirst. Water has a number of unusual properties that cannot that
distinguish if from other liquids. For example: (i) Density Maximum in
the liquid state (i.e., ice floats!), (ii) Growth of Isothermal
compressability on cooling (cold water is more "sqeezeable" than warm
water), (iii) Formation of Hydrogen bond networks (see image).
The
hydrogen bond network is believed to be responsible for the anamolous
behaviour of water. In order to explain the strange behavior of water,
researchers have started to look in the supercooled (liquid below the
freezing point) and stretched (negative pressure) regions for
answers. It appears that many of the anomalous properties can be
explained by the behavior at supercooled temperatures, including the
possiblity of a second low temperature critical point. At temperatures
below this possible critical point, there exist TWO liquid phases, one
high-density and one low-density (strong bond network). This is
analogous to cooling steam below the high temperature critical point
where a high density fluid (liquid water) and a low density fluid (water
vapor) condense out. For more information, see Francis Starr's Simulation of Water.
- Econophysics. Econophysics is an interdisciplinary research
field, applying theories and methods originally developed by physicists
in order to solve problems in economics, usually those including
uncertainty or stochastic processes and nonlinear dynamics. One driving
force behind econophysics arising at this time was the availability of
huge amounts of financial data, starting in the 1980s. It became
apparent that traditional methods of analysis were
insufficient—standard economic methods dealt with homogeneous
agents and equilibrium, while many of the more interesting phenomena in
financial markets fundamentally depended on heterogeneous agents and
far-from-equilibrium situations. The term was coined by H. Eugene
Stanley in the mid 1990s, to describe the large number of papers written
by physicists in the problems of (stock and other) markets, and first
appeared in a conference on statistical physics in Calcutta in 1995 and
its following publications. The inaugural meeting on Econophysics was
organised 1998 in Budapest. Currently, the almost regular meeting series
on the topic include: Econophysics Colloquium, ESHIA/ WEHIA,
ECONOPHYS-KOLKATA, APFA. For more information see: (i)
Gene Stanley on January 10, 2003 NPR's "Science Friday", (ii) Introduction
to Econophysics by Mantegna and Stanley (Cambridge University Press,
1999), and (iii) Econophysics
and the Current Economic Turmoil, a guest editorial by Gene Stanley
for APS News (Vol. 17, No. 11, December 8, 2008).
- Physiologic Dynamics. Center members study a broad range of
topics at the interface of statistical physics and medicine. Topics
include the exploration of fractal characteristics of cardiac dynamics,
fluid flow through respiratory systems and branching patterns, circadian
rhythm in human gait activity, complexity in scale-invariant neural
signals. One of our
main contributions is to the NIH sponsored PhysioNet which offers collections
of recorded physiologic signals and open-source software to the science
research community.
-
Statistical Mechanics Study of Alzheimer's Disease. Alzheimer
disease is a progressive neurodegenerative disorder of the central
nervous system. The exact causes of the disease are unknown. The
symptoms are familiar: loss of memory and other cognitive functions and
eventually loss of control of bodily functions. The most obvious change
in the brain of Alzheimer's disease patients is the loss of neurons. In
addition, Alzheimer's victims have formations of senile plaques and
neurofibrilary tangles, neither of which is present in normal brains.
In a collaborative research between physicists from the Center for
Polymer Studies at Boston University and neurologists from the
Massachusetts General Hospital, researchers are studying immunostained
pictures of senile plaques, neuronal bodies, dendrites and tangles,
taken by confocal microscope. The pictures are then analyzed using
methods of statistical physics. The overall purpose of the research is
to find out the mechanisms of the growth of senile plaques, to
understand how the neuronal architecture is altered in the disease, and
to quantify changes in the geometry of dendrites as compared to the
dendrites in the cortex of healthy brains. New experimental advances
applied to the understanding of the molecular origin of Alzheimer's
disease have pointed to important clues that implicate small molecular
assemblies of the protein Ab in neuronal impairment and later
death. Using tools derived from computational physics, researchers from
the Center for Polymer Studies are studying the initial stages of Ab
aggregation that may lead to the formation of the toxic oligomers. The
endpoint of their research is to investigate the oligomer topology and
3D composition in order to aid in drug development to target oligomer
formation. See also the Density Correlation Analysis of
the Brain Cortex Architecture Java applet along with a downloadable
Java application and associated examples as well as Luis Cruz-Cruz's Alzheimer's
Disease.
There are several other topics under study, including Long-Range Correlations in DNA
Base Pair Sequences., Theories of Diffusion-Limited
Aggregation , and Physics of Disordered
Media.
For more information about these efforts, please contact
Center for Polymer Studies Director Gene
Stanley (e-mail).
Image Notes: The first image shows fracturing in a disordered
network. The second image is a close-up of a computer model of liquid water.
water.
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