Seminars are held on Tuesdays, 3:45-4:45pm in SB 110, unless otherwise noted. Meet at 3:30 in SB 157 for refreshments (refreshments are available even on Tuesdays with no seminar!). See Calvin's Visitor Resources for maps and directions to the Science Building.

Schedules from previous semesters:Fall 2003, Spring 2003, Fall 2002, Spring 2002

Feb 4: Between Satellites and Rovers: Mars Exploration from Atmospheric Platforms Prof. Matt Heun, Calvin Engineering Department
To date, Mars has been studied exclusively from orbital and surface locations, yielding a wealth of scientific data about the red planet. However, there have ben several, less-publicized, attempts to develop observation platforms that offer both a "birds-eye" view of the planet, like satellites, and scientifically-driven mobility, like rovers. These alternative atmospheric platforms include airplanes, gliders, balloons, and airships. The political and technical challengs of designing atmospheric platforms as well as the strengths and weaknesses of each proposed approach will be discussed. And, details of a previous Mars balloon development effort will be presented.

Feb 17: Nonlinear Materials and Devices: Studies using Superconductive Thin Films. Dr. Steve Remillard '88, founder and president of Agile Devices, Inc.
A primer on superconductivity will be presented. Emphasis will be given to the way in which many branches of fundamental physics are used in describing superconductivity, including thermodynamics, electromagnetics, classical mechanics and quantum mechanics. Elements from each of these branches are used to explain the phenomenon of flux nucleation, whcih then leads to microwave nonlinearities in the material. After introducing the idea of microwave nonlinearity, we will look at how nonlinearities are measured at microwave frequencies. A "back-of-the-envelope" calculation will consider how well measurements with superconducting devices correspond to what is known about flux nucleation.

February 24: Diffusion, and How It Is Used. Dr. Jim Keener, professor of mathematics at the University of Utah. Dr. Keener is the author of Mathematical Physiology, designated "Best New Title in Mathematics" in 1998 by the Association of American Publishers.
Diffusion is one of the most important features of biological systems, especially when combined with chemical reactions. In this talk Dr. Keener will discuss some of the mathematical consequences of Fick's law of diffusion, and how several biological organisms utilize these to facilitate their existence. The examples he will describe include transport of oxygen and carbon dioxide, quorum sensing by bacteria, and detection of filament length by salmonella. (To understand this talk completely, one will need to know a little bit, but not much, about ordinary differential equations.)

March 1: Check out those hips! Engineering and Orthopedics Steve Meulink '86 Calvin BSE Graduate now working for Zimmer, Inc. of Warsaw, IN
This presentation will be an overview of hip surgery and hardware, hip design, materials and processes, and advances in minimally invasive surgery. He will also talk about what it means to be a Christian engineer or medical professional with general reflections of his college experience and subsequent career in orthopedic engineering.

March 30: Shaking Sand: Separation, Pattern Formation, and the Gas between the Grains Mason Klein '02, grad student at Harvard-Smithsonian Center for Astrophysics
Not astronomy, but almost as fun. Typically in vibrated granular media, particles separate by size, the largest rising to the top -- try it with a can of mixed nuts. But what happens when everything is the same size? I will present recent work on mixing and de-mixing in vibrated sand made of equally-sized bronze and glass spheres. It turns out that density-based pattern formation depends heavily on properties of the surrounding air or other gas. There will be pictures and movies of sand in action, as well as me trying to explain what is going on in this system.

April 23: The Physics and Circuit Applications of
Resonant Tunneling Diodes Dr. Robert Potter, Knowles Electronics
The concept of single barrier particle tunneling and the existence of quantized energy states of a particle in a box (potential well) will be reviewed. Resonant tunneling, which combines the ideas of single barrier tunneling together with quantized states in a potential well will then be introduced.
The resonant tunneling diode (RTD) is a physical realization of such an ideal, abstract resonant tunneling system, and it is usually made in semiconductor heterostructures such as GaAs/AlGaAs or InGaAs/InAlAs. Some common devices structures that employ narrow potential wells (~ 50 A) will be described along with the device’s measured current-voltage (I-V) characteristic, which is highly nonlinear and which has a region of negative differential resistance. Fine structure that is observed in the I-V characteristics of a wide well (~ 600 A) device, that can be attributed to virtual state scattering, even at room temperature, will be presented.
By sequentially growing several such RTD structures vertically, a device that has multiple regions of negative differential resistance can be fabricated. These I-V characteristics can be used to implement complex circuit functions that have greatly reduced circuit complexity when compared to conventional circuit implementations. The circuit applications of these multi-peaked devices for achieving functions such as frequency multiplication, parity bit generation, multi-level logic, and analog-to-digital conversion will be discussed.

April 27: First Fruits of Calvin's Twin Telescopes: Cool Images and New
Science Professor Larry Molnar
Almost two years ago, Calvin College received money for a new 16 inch
telescope on the Science Building and a second one (to be operated remotely) at
the Rehoboth Christian School in northwest New Mexico. This talk brings the
subject up-to-date on how the construction has gone, what innovations were
needed to make the project work, and what kind of cool images are now being
obtained by even 100-level students. It will also present a series of
observations of the binary star system U Geminorum: a bizarre system in which
one star, which has collapsed down to the size of the earth, spins around a
normal star every four hours. A stream of material is pulled off of the normal
star and forms a disk around the collapsed star. Analysis of our own
observations adds to this story an understanding of the dramatic way in which
the disk develops over time. This is a first taste of the opportunities for
astronomical research upper class students will have from now on.

May 7: Copernicus and the Tale of the Pale Blue Dot Dr. Dennis Danielson, Professor of English, University of British Columbia.
Most of us have at some point heard the claim that Copernicus, by "dethroning" earth from the center of the universe, “showed” that the Earth and Earth’s inhabitants are cosmically not very special. This claim is routinely extrapolated to function as a principle -- the “Copernican Principle” -- according to which not only is Earth merely one planet among many, but also the Milky Way is merely one galaxy among many, and perhaps what we think of as the whole cosmos is merely one universe among many. Moreover, this “principle” is enlisted to show that science trumps religion: while religion wants to enthrone Earth-dwelling human beings in the center of the universe, science authoritatively demonstrates (in more ways than one) the “mediocrity” of our place. From Fontenelle in the seventeenth century to Carl Sagan in the late twentieth, Copernicus is thus used to bring down human pride, which supposedly stems from our naive religious illusions. Unfortunately, this comic-book version of the meaning of Copernicus is all but universally accepted by many educated people, including some scientists, whose capacity to weigh evidence ought to make them capable of a more well-informed, critical view. An effort to attain such a critical view -- based on the exciting words Copernicus and his followers, and on a measure of undogmatic careful thinking -- can revitalize our perception not only of Copernicus in his own age but also of the interplay between science and metascientific assumptions today.