Seminar: Fall 2007

Seminars are held on Tuesdays, 3:45-4:45pm in SB110, unless otherwise noted. Meet at 3:30 in SB157 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: Spring 2007, Fall 2006, Spring 2006, Fall 2005, Spring 2005, Fall 2004, Spring 2004, Fall 2003, Spring 2003, Fall 2002, Spring 2002, Fall 2001, Spring 2001, Fall 2000, Spring 2000, Fall 1999.

September 18: Do Long Distance Relationships Really Work? A Study of Molecular Binding Forces Between Two Well-Separated Atoms
Students Kathy Hoogeboom and Ross Norman and Prof. Matt Walhout
In certain situations, atom-atom interactions can produce potential energy wells that support bound vibrational states of exotic, "purely long-range" dimer molecules. In these giant dimers, the two atoms behave as if they are tied together by an unusually long spring, so that they never get closer together than a few nanometers, even at the inner turning point of the vibration. This talk will summarize a theoretical model of the giant dimers and focus on experimental observations and spectroscopic measurements. The discussion will outline the technique of "photoassociation" in an atom trap and focus on the Prof. Walhout's past work with giant helium dimers as well as our ongoing study of long-range krypton molecules.

September 25: Shining a Light on Asteroid Dynamics
Student Melissa Haegert and Prof. Larry Molnar
The rate at which an asteroid spins on its axis is an observable property that can reveal much about the history and future of the asteroid belt. As many asteroids are relatively bright, the time consuming task of determining their spins is ideally suited to modest telescopes such as those of the Calvin Observatory. This seminar will report on several studies of asteroid spins recently completed or underway at the Observatory.

Among the highlights to be reported are 1) the discovery of an asteroid with a satellite companion; 2) an update on the surprising lethargy of Trojan asteroids; and 3) evidence for a billion year old collision in the inner asteroid belt that may be responsible for sending numerous projectiles on a collision course with Earth. We will also discuss the possible causes for changes in asteroid rotation rate and orbit. Remarkably, sunlight shining on the asteroids may be the key factor behind all of our highlighted results.

October 2: Two Short Talks On Optics
Prof. David Van Baak
Part 1: Generating, and Processing, Quadrature Signals in Interferometry
Students learn that the optical apparatus called a Michelson interferometer makes it possible to detect mechanical displacements as small as a wavelength of light (under a millionth of a meter). This talk shows that the interferometer can be improved to make it possible to detect displacements much smaller still, and also to detect the sign of the displacements unambiguously.
Part 2: Concretely Illustrating the Failure of Local Realism
"Entangled photons" represent a glamorous experimental capability, and they provide the entryway into the Bell inequalities, quantum computing, and quantum cryptography. This talk focuses on a new and highly accessible way to show, and to see, that directly accessible experimental results provide a way to refute the common-sense idea that photons always possess (even unknown) polarizations.

October 11: Fire and Ice: NASA's Missions to Mercury and Pluto
Dr. Tom Strikwerda, '71, Applied Physics Lab of John Hopkins University
This presentation will describe two missions being conducted by the Applied Physics Laboratory/Johns Hopkins Univ. for NASA, MESSENGER and New Horizons. APL designed and built both spacecraft as well as several of the scientific instruments, and is operating the two spacecraft via NASA's Deep Space Network. If time permits, I will also touch on several other APL missions for NASA.

October 12: Origins: A Reformed Look At Creation, Design, and Evolution
Profs. Deborah and Loren Haarsma
FaithAlive Resources, the publishing ministry of the Christian Reformed Church, asked us to write a book “for the person in the pew” on issues of origins. In this short seminar, we'll give an overview of the contents of the book and our writing approach, as well as answer audience questions. The book begins with chapters on God's governance of natural processes, doing science as part of a Christian worldview, and interpretation of scripture. Other chapters review the scientific, theological, and worldview issues around the age of the Earth, the Big Bang, biological evolution, and intelligent design. The book ends with two chapters on several scientific and theological issues around human origins. A book reception will follow at 4:15 p.m. in DeVries Hall Atrium.

October 16: Simulations of South Pole Telescope Data
Student Jessie Taylor
One of the first goals of the South Pole Telescope, a telescope recently deployed at the South Pole by a consortium of universities, is to discover thousands of galaxy clusters by using slight variations in the Cosmic Microwave Background. These clusters should begin to shed light on dark energy, the mysterious majority of the universe. Study of these clusters should also help differentiate between various cosmological models. However, the observations of the South Pole Telescope are dominated by noise, atmospheric effects and irregularities due to the instrument, completely masking the faint signal of the clusters. The data must be heavily processed in order to recover the signal. One way of testing the processing procedures is to apply them to simulated data. Therefore, there is a need for code to realistically model data produced by the telescope, including noise and instrument response. I spent this past summer modifying existing simulations to reflect these non-idealities. This talk will focus on both the motivation for the South Pole Telescope as well as the simulations I worked on.

November 6: Green Matters for Grey Matter: Building Green Learning Environments
Jordan Hoogendam '04, Green Building Consultant
Awareness and interest in green buildings has been growing exponentially in the USA since the inception of LEED (Leadership in Energy & Environmental Design) in 1998. A similar trajectory is being realized in the Canadian context, beginning in 2004 with the launch of LEED Canada. Since then, the Canadian market has been matching the growth and successes to the south.

Jordan Hoogendam (Calvin Alum, Engineering 2004), a Green Building Consultant in Ontario, Canada, will present on LEED Certification and metrics for success, as well as some of the perceived barriers to the adoption of green building practices. This presentation will draw on Hoogendam\u2019s experiences, and will include specific examples of green schools and institutions of higher learning that have adopted LEED standards. An overview of the green building industry will be given, with a focus on its growth and on opportunities for employment in "green collar" jobs. This presentation will also highlight opportunities for colleges and universities to embrace the green revolution and to prepare their graduates to excel in this quickly emerging marketplace.

November 13: Long, Long, Ago in Galaxies Far, Far Away
Prof. Deb Haarsma and Student Katie Shomsky
A galaxy cluster is made up of thousands of galaxies, each of which contains billions of stars. The space between the galaxies is filled with hot gas that emits X-rays. We studied four fields on the sky where an X-ray source suggested a galaxy cluster and near-infrared observations showed a concentration of red galaxies. Each field was observed with the Gemini Multi-Object Spectrograph on the Gemini North Telescope in Mauna Kea, Hawaii. Spectra were measured for several galaxies in each field in order to determine their distances from their redshifts. The observing technique was successful, detecting galaxies out to a redshift of 1.34 (8.89 billion lightyears). In field RXJ1603.6+4316, we found five galaxies at redshift 0.925 (7.42 billion lightyears) that are associated with the surrounding supercluster of galaxies. In field RXJ1605.6+2548, we discovered several galaxies around redshift 0.545 (5.33 billion light years), likely a moderate-mass galaxy
cluster.

November 27: Two Talks in Neuroscience
Rho kinase and the development of new nerve cell electrical excitability - a complicated story
Karin DeJong (senior Biology major)
When exposed to Nerve Growth Factor (NGF), PC12 cells become more like nerve cells - they grow long neurites and develop increased electrical excitability. The proteins Rho kinase and RhoA were known to be important for growing neurites, but it was not known if they also play a role in increasing electrical excitability. NGF treatment has numerous biochemical effects on PC12 cells, whereas Y-27632 is a drug which more selectively inhibits Rho kinase and RhoA. In our PC12 cells, Y-27632 treatment caused PC12 cells to have large electrical excitability (comparable to NGF-treated cells) but incomplete neurite outgrowth. However, other experiments show that NGF can also increase electrical excitability of PC12 cells via a RhoA-independent pathway, which complicates the story of nerve cell development.
Potassium ion currents in corneal epithelial cells, ultraviolet light, and salty tears
David Will (senior Chemistry & Biology major)
Exposure to high levels of ultraviolet (UV) light causes corneal epithelial cells to undergo apoptosis (programmed cell death). In the intact eye, corneal epithelial cells are able to survive exposure to the ambient UV light. One step in apoptosis that leads to cell death is the loss of K+ from the cell through specific ion channels. Experiments have shown that reducing the efflux of K+ inhibits apoptosis. It is also known the tears have a much higher K+ concentration than other extracellular body fluids. We hypothesize that the high K+ concentration in tears helps to reduce the efflux of K+ from corneal epithelial cells, and thereby prevent UV-induced apoptosis. Using electrophysiology patch-clamp methods, we have confirmed that UV exposure does increase K+ efflux from corneal epithelial cells and that increasing the extracellular K+ concentration reduces the K+ efflux.

December 4 : Structural basis for the conducting interface between
LaAlO3 and SrTiO3
Divine Kumah, University of Michigan Applied Physics Program
The Coherent Bragg Rod Analysis (COBRA) phase retrieval algorithm has recently been developed to obtain electron density maps with sub-angstrom resolution of thin film structures with in-plane periodicity from x-ray diffraction measurements. The physics responsible for the formation of a high-mobility, 2-dimensional, electron gas at the interface of two insulators has been the subject of considerable research and controversy since its discovery in the LaAlO3/SrTiO3 system. Using COBRA, the formation of the quasi two-dimensional electron gas is explained, based on structural considerations.