Physics and Astronomy Colloquium Series
Winter 2013

Date

Talk

Thursday
10 January

John Moustakas

Siena College

"One galaxy, two; red galaxy, blue: Mapping the Evolution of Galaxy Bimodality over Half the Age of the Universe."

Astronomers have discovered that in the nearby Universe there are two basic types of galaxies: star-forming spiral galaxies like our own Milky Way Galaxy, and elliptical, or round galaxies that stopped forming new stars long ago. However, we still do not understand why the galaxy population is bimodal, nor how the relative numbers of star-forming and elliptical galaxies have changed with cosmic time. In this talk, I will discuss a new survey in which we find dramatic changes in the galaxy population over the last 8 billion years, and I will present some of the main explanations for how and why we think the galaxy population is bimodal.

Thursday
17 January

No Colloquium

Thursday
24 January

Note change in location

Joint Colloquium with Mechanical Engineering: 12:40PM Olin 115 (Lunch at 12:20PM in Olin Rotunda)

Ed Fenimore

Los Alamos National Laboratory

"Gamma Ray Bursts, one reason why “astronomical” is an adjective"

A few times a day, somewhere in a galaxy far, far away, a special type of massive star gives birth to a black hole, ejecting material in a jet that moves very close to the speed of light. During their fleeting existence, these jets literally flood much of the universe with gamma rays. Their power output can be a significant fraction of the total power produced by all the stars in all the galaxies in the entire universe. Gamma-ray bursts were discovered at Los Alamos 40 years ago as a part of the nuclear nonproliferation efforts. They resisted explanation until engineering solutions were found that could locate them to an accuracy where their host could be identified. This includes autonomous, self-tasking satellites that provide coordinates to robotic telescopes on the ground. The Swift satellite has contributed to unraveling the mysteries behind these largest explosions since the big bang, including one event so huge, it affected the Earth’s atmosphere.

Dinner Discussion at 5:00PM Breazzano House

"Student Opportunities for Space Research at Los Alamos"

Los Alamos, due to its role in monitoring treaties to prevent the spread of nuclear weapons, has been deeply involved in basic space research since the 1960’s. Los Alamos was the first to launch multiple satellites that were capable of distinguishing temporal variations from spatial variations in space radiation. That led to the discovery of gamma-ray bursts and x–ray bursts as well as many features of the solar wind and magnetosphere. A robust program in astrophysics was developed with the Pioneer Venus Orbiter, the Japanese Ginga satellite, the HETE satellite, and most recently, the Swift satellite. We also flew planetary missions to orbit the moon, asteroids, Mars, and Mercury. Our most recent mission is the Curiosity Rover currently exploring the surface of Mars. We have built a series of satellites to study the magnetospheres of the Earth and other planets such as Saturn. We also put two experiments (x-rays and EMP) on every GPS Satellite. Los Alamos has 10,000 employees with a long history of the participation of students from all over the world. With ~ 1500 to 2000 students a year, Los Alamos probably has the largest population of students in the country outside of universities. In the space science research, students do not often directly participate in the construction of the satellites, they have been deeply involved in the modeling the missions pre-flight, flight operations, and the analysis of the data. Students are involved with all the major scientific efforts at Los Alamos: biology, environmental studies, chemistry, particle physics, materials, computer science, and theoretical physics.

Sponsored by Physics & Astronomy, Mechanical Engineering, Becker Career Center, Society of Physics Students

Thursday
31 January

Bradley Olsen

MIT

"New Physics in Materials Engineered from Proteins"

Polymer physics has provided a rich field of exploration for physicists, where the statistics of chain configuration, the thermodynamics of mixing in molecules with large spatial extent, and the multiscale dynamics of these systems have proven intriguing. Furthermore, because of their nanometer length scale and relatively slow dynamics, polymers have served as valuable models for phenomena such as nucleation and crystallization. However, most of the effort to date in polymer physics treats polymers as repetitive sequences of one or a small number of monomers. The ability to engineer polymers from the set of 20 amino acids using genetic engineering techniques dramatically expands the capability for sequence control, providing new challenges for polymer physicists. In particular, these artificially engineered proteins and synthetic polypeptides have attracted widespread interest as building blocks for polymer hydrogels. The biophysical properties of the proteins, such as molecular recognition abilities, folded chain structures, and sequence dependent thermodynamic behavior, enable advances in functional, responsive, and tunable gels. The design of polymer hydrogels that incorporate protein domains will be discussed, highlighting new challenges in polymer physics that are presented by this emerging class of materials. Within our own lab, we focus on engineering responsive and nanostructured materials based upon proteins, enabling transitions in these materials could potentially enable gels that have both shear-thinning injectable phases and tough phases to be produced as novel injectable biomaterials. To prepare a gel with such transitions, a triblock copolymer with thermoresponsive polymer endblocks and an artificially engineered protein gel midblock is designed. Poly(N-isopropylacrylamide) (PNIPAM) endblock association forms a large length scale network, while association of coiled-coil repeat domains within the protein midblock leads to self-assembly of a short length scale network. Temperature is used to trigger a transition from a single network protein hydrogel phase to a two network phase with both protein and block copolymer networks present. The formation of the second network is shown to produce a 5 to 15-fold increase in the elastic modulus, where the magnitude of modulus enhancement depends strongly on the molecular design. A second approach to biomaterial toughening is explored through engineering both topological entanglements and physical associations into the gel to produce two distinct length and timescales of network interaction. Oxidation of cysteine residues in proteins enables chain extension through protein end coupling, producing polymer gelators of high molecular weight that are not easily achievable directly by protein expression.

Thursday
7 February

Anne Starace

National Renewable Energy Laboratory

"Nanofluid heat capacities, nanofluid synthesis, and the search for high-temperature, high-heat-capacity heat-transfer fluids"

In this work we study the addition of both nano- and micro-particles to improve the thermophysical properties of heat transfer fluids (HTFs) and methods to generate such fluids. The affect of the addition of nanoparticles on the heat capacity of a fluid was measured with differential scanning calorimetry. It was found that the heat capacity of the nanofluid was typically the weighted average of its components. In order to significantly increase the effective heat capacity of a fluid via particle addition, a high loading of particles and the use of particles which undergo phase transitions are often required. In addition to desired high heat capacity, the heat transfer fluids for the next generation of concentrating solar and nuclear power plants need to operate at temperatures above 600⁰C. In order to make composite HTFs for use above 600⁰C, particle-stabilization, instead of stabilization with organic surfactants, is necessary. We mixed, at high temperatures, many combinations of dispersed phase, dispersion media (continuous phase) and stabilizing particles and found indirect evidence of particle-stabilization in some cases. While the addition of nanoparticles does not seem promising to produce large increases in heat capacity, it does hold promise for increasing the thermal conductivity of HTFs as well as for creating direct-absorption fluids. Thus, simple synthesis of nanofluids is desired. We synthesized nanofluids via the shearing (through sonication) of bulk material into nanoparticle in the desired base fluid. The affects of temperature, nanoparticle material, and surfactants on nanoparticle size and size distribution were analyzed.

Thursday
14 February

Pot Luck Luncheon

No Colloquium

Thursday
21 February

Founder's Day

No Colloquium

Thursday
28 February

Matt Bellis

Siena College

"Searching for baryon-number violation in the BaBar dataset"

From 1999-2008, the BaBar experiment collected data from electron-positron collisions running at the Upsilon(4S) resonance. This provided analysts with 1 billion B mesons with which to probe a wide variety of physics. This talk will give an overview of a search for baryon number violation in B meson decays using the dataset. This process is a signature of many Grand Unified Theories and would indicate new physics beyond the standard model. The results of this search will be presented and the history and efficacy of blind searches will be discussed.

Thursday
7 March

Talk with Electrical and Computer Engineering - details to follow.

Thursday
14 March

Greg Schwanbeck '03

Westwood High School

"How Technology is Changing Physics Education, and Why Teach High School Physics"

Technology is driving significant change in all areas of education, and high school physics is no exception. Students can collaborate on and conduct labs virtually “within the cloud,” teachers can extend their instruction beyond the classroom walls by leveraging students’ ubiquitous mobile devices, and video can drive and improve problem-solving skills. Physics teacher, educational technology enthusiast, and Union class of 2003 graduate Greg Schwanbeck will share some of these ways that technology has changed how he has taught physics over the past decade, address why one would want to teach high school physics, and discuss how to take the first few steps to become a teacher.

Schedule for Spring 2013