Wednesday, July 27, MG 2050, 10:00 to 11:00 am

CuInSe₂ Solar Cells: Adding Ga

Alex Pudov
Colorado State University

In the fast growing market of renewable energy produced by solar cells, it is important to reduce the costs of manufacturing and increase the efficiency for existing cells. Thin-film solar cells based on the very thin CuInSe₂ (CIS) layers create a serious competition for traditional Si devices in a number of aspects, the main one being the lower costs. CIS-cell efficiencies have grown from ~5% to ~20% (approaching Si) over a couple of decades; some of this increase was due to alloying CuInSe₂ with CuGaSe₂ that has a higher band gap. I intend to discuss the basics of solar cells, the primary measurement techniques used to study them, and in particular, what happens in terms of the device physics of CIS solar cells when Ga is added.

Friday, July 22, MG 2050, 10:30 to 11:30 am

Singular Optics: Liquid Crystal Based Beam Steering Device

Liubov Kreminska
Liquid Crystal Institute, Kent State University, Ohio

(1) The spontaneous formation of patterns can be observed in many optical systems. Light waves carry information in their amplitude, phase, polarization and wavelength. In optics, transport of information is not coupled to transport of mass that leads to great experimental flexibility. Hence, a number of different types of pattern formation phenomena appear. The process of birth, evolution and annihilation of phase singularities in initially smooth laser beams caused by self-action in nonlinear media was observed experimentally and explained by numerical simulation with Gaussian lens. The pattern formation was observed in and explained by an interference of multiple waves.

(2) Digital Beam Steering Device (DBD) Based on Decoupled Birefringent Prism Deflector and Polarization Rotator is described. Each stage of the device comprises a polarization rotator and a birefringent prism deflector. The birefringent prism deflects the beam by an angle that depends on polarization of the incident beam. Rotation of linear polarization is achieved by an electrically switched twisted nematic (TN) cell. A DBD composed of N rotator-deflector pairs steers the beam into 2^N directions. As an example, a four-stage DBD deflecting normally incident laser beam within the range of ±56 mrad with 8 mrad steps is described. Redirection of the beam is achieved by switching the TN cells.

Wednesday, April 27, BT 251/2, 4:35 to 5:25 pm

Stardust: Observational Evidence of Mass-loss Processes During the Late Stages of Stellar Evolution

Angela Speck
Department of Physics and Astronomy, University of Missouri

All elements bigger than He form(ed) in stars. Intermediate-mass stars (0.8-8.0 solar masses), like the sun, are important contributors to this element generation. In the late stages of evolution, intermediate mass stars follow a path on the Hertzsprung-Russell diagram up the red giant branch and then up the asymptotic giant branch (AGB), where they begin to lose mass through a slow, massive stellar wind. This leads to the formation of circumstellar shells of dust and molecules. AGB stardust contributes significantly to the replenishment of interstellar dust, and thus plays a crucial role in galaxy evolution. In particular, these stellar dust grains are found in meteorites, which demonstrates that these grains become part of the next generations of stars and planets. One of the major issues still to be resolved: what are the physical mechanisms for the intensive mass loss experienced by AGB stars?

At the end of the AGB phase, the stellar wind has exhausted the outer stellar envelope, the star evolves off the AGB and becomes a "protoplanetary" nebula (PPN). The circumstellar shells around PPNe contain the fossil record of their previous AGB mass loss. The dust furthest from the central star represents the oldest mass loss, while material closer to the stars represents more recent mass loss. The inner radius of the dust shell represents the end of heavy mass loss and the end of the AGB phase of the star's evolution. The mass-loss rates during the AGB phase determine the density distribution of matter in these regions. For example, a constant mass-loss rate would lead to a 1/r² dust density distribution; an increasing mass-loss rate would appear as a faster than 1/r² drop-off in the dust density; while an episodic mass-loss rate would appear as discrete dust shell enhancements at particular radii from the central star. During the AGB phase, the velocity of the outflowing mass appears to be fairly constant. However, theoretical models suggest that changes in surface luminosity of the star as a result of thermal pulses from the helium burning shell should lead to variations in the mass-loss rate. Observational evidence for such episodic mass loss is seen in parsec-sized dust shells of two PPN (the Egg Nebula and AFGL 618). These far-infrared observations are presented. Radiative transfer modeling of these observations provides the radial dust density distribution and thus provides constrains on the mass-loss history.

Tuesday, April 19, BT251/2, 4:35 to 5:25 pm

Advanced Physics Seminar Presentations

Jason Stenghelle, Ikechukwu Okonkwo, Nathaniel Gonner, Uchenna Edeh
Truman State University

Physics 445: Advanced Physics Seminar is the capstone course for students in the Physics BA program. In this course students choose a topic in physics that is of particular interest to them, research that topic, and prepare both written and oral presentations on that topic. At this colloquium you will see the final presentations of the students in this course.

Ikechukwu Okonkwo: "On the Physics of the Bowed Violin String"

Nathaniel Gonner: "The Physics of Golf"

Jason Stenghelle: "Realism and Constructive Empiricism: What is the debate? Why should physicists care?"

Uchenna Edeh: "Fabrication of Integrated Circuits"

Wednesday, April 6, BT 251/2, 4:35 to 5:25 pm

Advanced Lab Presentations on Current Issues in Experimental Physics

Charles Weaver III, Amenyedu Adovor
Truman State University

Charles Weaver will speak on "Transforming the Electric Infrastructure." Since Thomas Edison started the first power grid, and subsequent power company, in the U.S., the system for delivering electricity to 300 million consumers in North America has grown to a behemoth. The grid sprawls across the United States by means of more than 200,000 miles of high-voltage wiring. It is comprised mainly of technology developed and installed during the 1950's. The presentation will focus on problems that have cropped up in the power grid over the past fifty years and possible solutions to balance the ever-growing demand for power on the grid while maintaining the quality of service since the blackout that hit the Eastern seaboard on August 14th, 2003.

Amenyedu Adovor will present "Treating Cancer with Protons." The fundamentals of cancer involve studying the fundamentals of growth. Physics offers biology tools and technique to better understand growth. One of the areas in medicine where Physics has contributed a lot in terms of technique is the area of Radiotherapy. Only months after x-rays were discovered, it was adapted to treat a patient with breast cancer. Today, proton therapy is developing into an effective treatment option for use in hospitals. Protons deposit dose locally and gradually. The dose is further increased by nuclear interaction and Coulomb scattering making protons more effective at treating tumors. This paper outlines how to develop a proton therapy treatment center in a hospital setting.

Friday, April 1, BT 251/2, 3:35 to 5:00 pm

Galileo:  A Guided Tour

Kerry Magruder
History of Science Collections, University of Oklahoma

Even elementary students have heard of Galileo, and physicists know a lot about him.  But not many people know the rewarding experience of reading Galileo for themselves, despite the fact that this founder of modern science is regarded as one of the greatest prose writers of all time.  This presentation will be a reader's guide to Galileo's works.  Come learn what he wrote, when, and why.  By touring the remarkable Galileo collection of the University of Oklahoma History of Science Collections, we will come away with a deeper understanding of who Galileo was and what he accomplished, and glean some favorite quotations along the way.  To come into touch with Galileo's words is to touch the past in an authentic, real way.  Sit back, relax, enjoy the tour and create your own Galileo reading list!

Wednesday, March 23, BT 251/2, 4:35 to 5:25 pm

Advanced Darkness: Some Experiments with Entangled Photons

Nick Peters
University of Illinois at Urbana-Champaign

According to Schrödinger, "Entanglement is the characteristic trait of quantum mechanics." But for an idea that has been around since the first half of the twentieth century, the most simple entangled quantum system—a pair of two-level systems—still yields new and interesting physics. We will discuss generation of exotic entangled photon pairs, their "concentration," and how their quantum nature enables a non-intuitive form of quantum communication called remote state preparation.

Tuesday, March 1, BH Little Theater, 7:30 to 8:30 pm

Einstein and Symmetry

William Klink
University of Iowa

One of the three papers published by Einstein in 1905, the special theory of relativity,  radically changed our notion of space and time.  In changing our notions of space and time Einstein also changed our conception of conservation laws, such as the conservation of energy.    Using some simple demonstrations I will show how Newton implicitly used symmetry ideas to account for the existence of conservation laws.  By exploring the connection between symmetry ideas and conservation laws, even with new notions of space and time, Einstein started a way of thinking about the nature of physical theories and how they are grounded in symmetry ideas, that is still used today, even in quantum theory and string theory.  I will discuss the notion of symmetry, how Einstein used it as a guide for his own work,  and show how it leads to a deeper understanding of the nature of all physical theories.

Tuesday, February 22, SUB Activities Room, 7:30 to 8:30 pm

Brownian Motion

Ian Lindevald
Truman State University

Tuesday, February 15, VH1000, 7:30 to 8:30 pm

Light Quanta: A Worldline

Michael Goggin
Truman State University

Albert Einstein's Nobel Prize-winning paper on the quantization of light will be explained. The work will be placed in the historical context in which it arose. The influence of the paper on the future development of quantum mechanics will also be presented, concluding in a discussion of wave-particle duality.

Tuesday, February 8, VH1000, 7:30 to 8:30 pm

E=mc²... What's It All About?

Peter Rolnick
Truman State University

Why are nuclear bombs, pound for pound, so much more powerful than chemical bombs? If you could convert the mass in a one-pound rock completely into energy, how much energy would that be? And what does the speed of light have to do with all of this? I will discuss the meaning and consequences of Einstein's most famous equation, and talk about the reasoning which led him to discover this important relationship.

Tuesday, February 1, VH1000, 7:30 to 8:30 pm

The Relativity of Space and Time

Ken Hahn
Truman State University

Wednesday, January 26, BT251/2, 4:35 to 5:25 pm

Summer Research Opportunities in Physics

The Physics Faculty
Truman State University

Discussion of summer research offerings: various routes for on-campus research and compensation, plus the process of locating and applying for REUs, internships, and other off-campus opportunities. Questions about the STEP program, university stipends, REU's, and interships will be answered.

Wednesday, December 1, BT251/2, 4:35 to 5:25 pm

Wavelets in Scattering Theory

Wayne Polyzou
Department of Physics and Astronomy, University of Iowa

Wavelets are orthonormal basis functions that have a fractal structure. They are used in signal processing and data compression. The most familiar application is the compression algorithm used in digital photography to make JPEG files. In this talk I will give an introduction to Daubechies wavelets, discuss how to do numerical analysis with functions that have structure on all scales, and show that wavelet methods lead to simplifications in the solution of scattering problems in relativistic quantum mechanics.

Wednesday, November 17, BT251/2, 4:35 to 5:25 pm

Student Summer Research Presentations

J D Lloyd: Magnetic Tunnel Junctions (MTJ) have shown promising results for application in the new field of spintronics, which simultaneously uses the spin and charge degrees of freedom of the electron. The surface morphology of the layers within these nano-devices was studied as a function of thickness and oxygen patial pressure.

Sarah Smith: The nature of the melting transition from vortex lattice to vortex liquid in the high temperature superconducting oxides has been a subject of major interest since their discovery. Measurement of a latent heat from the vortex lattice melting in superconducting Bi-2212 would provide clear evidence of a first order transition, but small samples and weak signals place requirements on instrumentation and technique that have not yet been satisfied. I will discuss the development and characterization of a differential, steady-state AC microcalorimeter for high-precision studies of nanogram samples of Bi-2212.

Tuesday, November 9, BT251/2, 4:35 to 5:25 pm

The Pinhole Camera

Matt Young
Department of Physics, Colorado School of Mines

Despite being great fun, the pinhole camera is a potentially useful imaging device and a good tool for introducing several concepts. It is diffraction-limited and completely free from linear distortion, and has depth of field from a few centimeters to infinity. I will use it to illustrate the transition from geometrical optics to physical optics and distinguish between far- and nearfield diffraction. I will outline how the pinhole camera and some of its relatives, such as the Fresnel zone plate and the pinspeck camera, have been used for practical (and not so practical) functions such as X-ray imaging and centimeter waveguides. Finally, I will show some bizarre photographs taken with a pinhole camera.

Tuesday, November 9, SUB Conference Room, 8:00 to 9:00 pm

Why Intelligent Design Fails

Matt Young
Department of Physics, Colorado School of Mines

"Intelligent Design" is a comparatively sophisticated version of creationism which is challenging mainstream science and science education across the nation. Matt Young, co-editor (with Taner Edis) of the recent book "Why Intelligent Design Fails," explains why this latest objection to evolution is a scientific failure.

Advanced Lab Presentations on Current Issues in Experimental Physics

Dave Rife and Chris Cook
Truman State University, Science/Physics

Students in Advanced Lab II are required to make formal presentations based on an article about some current work in experimental physics. Chris Cook will speak on "How to detect buried structures through electrical measurements." Subsurface disturbances can be detected by evaluating the electrical response on the surface of the ground, leading to an accurate image of the underlying surface. Dave Rife's presentation will be based upon "Experimental investigation of ultrasound propagation in turbulent, diffractive media," by T.A. Anderson and W.W. Durgin.

Thursday, September 30, VH 1000, 3:00 to 4:00 pm

Jamming

Andrea Liu
University of Pennsylvania

All around us things seem to be getting jammed. Before breakfast, coffee grounds and cereal jam as they refuse to flow into our filters and bowls. On the way to work, we are caught in traffic jams. In factories, the raw materials, powders, get jammed as they clog in the conduits that were designed to have them flow smoothly from one side of the factory floor to the other. Our recourse in all these situations is to pound on our containers, dashboards and conduits until the jam miraculously disappears. We are usually so irritated by the jam that we have not really noticed that the approach to jamming and the jammed state, in all of these situations, have common properties and similar behaviors that are quite different from those in systems near the liquid-solid transition.