Events at Physics |
Events on Tuesday, March 25th, 2008
- Chaos & Complex Systems Seminar
- Computational constraints in Hebbian learning: relationship to epileptogenesis and other neurological disorders
- Time: 12:05 pm
- Place: 4274 Chamberlin Hall
- Speaker: David Hsu, Neurology
- Abstract: The ability of the brain to absorb and incorporate within itself new ideas implies that it is a metastable system. It must continually change and yet not devolve into randomness. How does it do this, and what are the consequences? Brain activity can be represented in terms of a large collection of excitable bodies that possess both spontaneous activity and that can stimulate other bodies to become excited. I discuss a simple computer model of such a system and study (1) what is necessary for such a system to learn, and (2) what is necessary for it to maintain itself in a state capable of further learning. It turns out that the highest performing brain models that are able to maintain stable learning also show self-organized criticality. Unfortunately, the homeostatic constraints that maintain optimal brain performance also predispose the brain toward neurological disease. The relationship to epilepsy is presented, and an approach to its cure is proposed.
- Astronomy Colloquium
- Smith's Cloud: The Most Interesting Hydrogen Cloud in the Local Universe
- Time: 3:45 pm
- Place: 6515 Sterling Hall (coffee at 3:30 pm in 6521 Sterling)
- Speaker: Jay Lockman, NRAO
- Abstract: In the first part of the talk I will review the capabilities of the new Green Bank 100 meter diameter radio telescope (GBT) and briefly discuss some of the scientific programs to which it has contributed. The main part of the talk will be about Smith's Cloud. This hydrogen cloud has been known since 1963 and is usually classified as a high-velocity cloud, but only recently has its nature become clear through observations with the GBT. It is a coherent mass of gas more than 3x1 kpc in extent, contains more than a million solar masses of hydrogen, and appears to be on a trajectory to cross the Galactic plane in 20-40 Myr. It is now interacting with the gaseous halo of the Galaxy and is in the process of breaking up. It may be the prototype of a gas cloud accreting onto the Milky Way and bringing fresh gas to fuel star formation.
- Host: Snezana Stanimirovic