Granular Sand by Julien Chopin, PhD Candidate in Physics

Abstracts of Talks for College Visits

Members of our department have prepared talks oriented to undergraduate physics majors at New England colleges and universities. We generally require 2-4 weeks notice and are willing to drive a maximum of 3-4 hours.

Please contact Sujata Davis at 508-793-7169 to arrange a visit by one of our faculty. Also view abstracts of talks for high schools.

Charles Agosta
"Playgrounds for electrons: Organic conductors in high magnetic fields."
It is surprising that organic materials can act as good metals, but the fact that organic conductors are also superconductors at low temperature is amazing. I will discuss superconductivity and other correlated electron states found in organic conductors as well as methods for generating record breaking magnetic fields that can be used to investigate these materials.

Les Blatt
"The cookbook of the stars: How stellar processes create the periodic table."
Nuclear processes in the stars build up the entire periodic table of elements from a few primordial species produced as a direct result of the "big bang." We will look at these astrophysical processes in pictures and demonstrations to gain a better understanding of the truth of the statement "we are all bits of stardust."

Daeg Brenner
"Weighing radioactive atoms: Why are we interested and how do we do it?"
Some very light stable isotopes of medium mass elements have relatively large abundances in nature. One explanation assumes that these isotopes are produced as a result of very rapid proton capture processes that occur in violent stellar environments. To understand whether this explanation is valid, we must understand all the nuclear processes involved, many of which depend on the atomic masses. How one measures these in a laboratory on Earth will be discussed.

Harvey Gould
"What is a glass?" or "The Open Source Physics Project."
Although glasses are common materials, the nature of the glass transition is not well understood, and little is known about their structure and how this structure differs from a liquid and a crystalline solid. I will discuss the importance of these questions and recent results that give new insight into the nature of the glass transition and aging below the glass transition where the system is not in equilibrium.

Just as the switch from procedural to object-oriented programming has produced dramatic changes in commercial software design, we expect that similar changes will occur in computational physics, both in teaching and research. One of the goals of the Open Source Physics project is to develop a library of Java classes that perform much of the routine programming tasks such as input, output, animation, and user interaction. I will show how using this library makes Java programming much easier and will show examples of applets that simulate various physical systems. Harvey Gould is presently working on the third edition of Introduction to Computer Simulation Methods together with Jan Tobochnik and Wolfgang Christian.

Arshad Kudrolli
"Physics in a sand box"
Why are Brazil nuts found near the top of a can of mixed nuts? What causes an avalanche of rocks or snow? These systems are a collection of grains and examples of granular matter. The behavior of a single grain is easily understood, but the properties of a collection of grains is very complex. I will demonstrate and discuss a surprising range of collective behavior such as convection, size separation, and pattern formation displayed by granular materials.

Chris Landee
"Magnets, Data and Molecules"
The areal density for information storage on magnetic media has increased at an astonishing rate over the past three decades, with the rate approaching 60%/year since 1990. This pace has help drive the explosive development of the computer and telecommunications industries, but such a pace cannot be sustained. Well within the next decade the areal density will reach physical limits beyond which no increases are possible with current technologies. I will describe how chemists and physicists are using organic chemistry to develop molecular-based magnets, a new generation of magnetic materials with the promise to bypass the physical limits for metal-oxide recording media.

Ranjan Mukhopadhyay
"Physics of Red Blood Cells"
A human red blood cell normally assumes the shape of a flattened biconcave disc. However, it has been known for more than 50 years that, under a variety of chemical or physical treatments, the cell undergoes a sequence of dramatic (but reversible) shape transformations. Because a red blood cell has no internal structure, its shape is governed by the physics of its membrane. Using simple physical models, we can compute the full sequence of shapes; the computed shapes are in surprisingly detailed agreement with observations. I will discuss how our results make it possible to use shape transformations as a quantitative tool to probe the physics and biochemistry of cell membranes.

Send suggestions and comments to Harvey Gould.


Abstracts of Talks for High Schools

Please contact Sujata Davis at 508-793-7169 to arrange a visit.

Charles Agosta
What is super about superconductivity?
A demonstration of the new high temperature superconductors will be given. We will discuss the nature of electrical resistance in various materials and explain the differences between a conductor, semiconductor, and an insulator. In this context we will introduce the field of condensed matter physics physics, the driving science behind the microelectronics industry. We will then explain why superconductors have no electrical resistance. Next we will describe our pulsed magnetic field laboratory at Clark and explain why we needed to develop one of the strongest magnets on earth to study superconductivity. Finally, a number of applications of superconductors will be described, such as efficient electricity distribution, levitated trains, and superfast computers. Several demonstrations will highlight the main principles of the talk.

Roy Andersen
Putting the Sun in the middle of the planets
Each day we see the sun going around us. So how do we know that we are going around the sun? The answers to this question are not obvious and surprisingly, were not accepted until less than three centuries ago. The development of the idea of the sun as the center of our solar system will be explored from ancient to modern times and serve as a case study of the nature of science.

S. Leslie Blatt
The Process of Discovery
Through simple but intriguing experiments, regularities in the physical world can be discovered and hypotheses can be developed and tested. The classroom will be turned into a physics laboratory, with teams of students collaborating to develop new insights into nature in areas as diverse as light and sound, static electricity, and chaos. Materials and methods are taken from Clark University's "Discovering Physics" project, an ongoing program of innovative college-level courses and professional development workshops in science for pre-college teachers. These courses and workshops, incorporating research-generated ideas on approach and content, emphasize hands-on experiences in a cooperative, small-group learning environment. Les Blatt is on the program committee of the New England Science Center and is a member of Clark's Department of Education.

Harvey Gould
Computer simulations and real-world physics
Physicists are using the computer to do "experiments" that help them learn new physics. We will demonstrate several computer experiments that have changed the way we think about nature, including simulations of fractal patterns found in nature, chaos in complex physical systems, the physics of sandpiles, and the processes involved in biological evolution. We also will show simulations that illustrate some counterintuitive aspects of Newton's laws and other more familiar areas of physics. If time permits, we will discuss the potential impact of computers on science and teaching. Harvey Gould is co-author of Introduction to Computer Simulation Methods, second edition, an undergraduate textbook on computer simulation, and co-editor of the column, Computer Simulations, in Computers in Physics.

Arshad Kudrolli
Physics in a sand box
Why are Brazil nuts found near the top of a can of mixed nuts? What causes an avalanche of rocks or snow? These systems are a collection of grains and examples of granular matter. The behavior of a single grain is easily understood, but the properties of a collection of grains is very complex. In my talk I will demonstrate and discuss a surprising range of collective behavior such as convection, size separation and pattern formation displayed by granular materials.

Christopher Landee
Magnets in our everyday life
Magnetic materials are used by all of us, even though we may only be aware of our magnets on the kitchen refrigerator. Would you believe that there are more than twenty-five sets of magnets in a car? I will discuss the origins of magnetism, give examples of how magnetism is commonly used, and describe the exciting new uses scientists are finding for magnetism which are making our lives more productive and more interesting. Christopher Landee has been interested in magnetic materials for nearly twenty years and collaborates with Mark Turnbull of Clark's Department of Chemistry on the development of transparent, room temperature magnets.