students and professor

Past Events

  • 12/7/2016

    Physics & Astronomy Seminar--High Precision, Not High Energy: Looking for Exotic Physics Using Atoms and Molecules

    Dr. Chad Orzel, Assoc. Prof., Union College is presenting.

    The Standard Model of particle physics is one of the most successful theories in the history of science, but we know from phenomena like matter-antimatter asymmetry, dark matter and dark energy, and neutrino masses that the Standard Model is not complete. While the best-known searches for physics beyond the Standard Model involve particle accelerators and huge detectors, there are smaller experiments in labs around the world looking for signs of new physics with atoms, molecules, and lasers. While the effects of exotic particles are tiny at the atomic scale, the unparalleled precision of modern spectroscopic techniques makes it possible to detect even such minuscule effects. These measurements provide some of the tightest constraints we know of on physics beyond the Standard Model.

    Snacks at 3 PM in the first floor atrium. 

  • 11/22/2016

    Physics & Astronomy Seminar--Observational Tests of Stellar Physics

    Dr. Philip Rosenfield, National Science Foundation Postdoctoral Fellow, Harvard-Smithsonian Institute for Astrophysics

    Stellar evolution models are fundamental to nearly all studies in astrophysics. They are used to interpret the light from distant galaxies, to derive the star formation histories of nearby galaxies, and to understand fundamental parameters of exoplanets. Despite the success in using stellar evolution models, some important aspects of stellar physics remain poorly constrained and their uncertainties rarely addressed. In this talk, I will discuss how I use Hubble Space Telescope observations of star clusters and nearby galaxies to better understand the physics of stars.

    Lunch will be served. 

  • 11/16/2016

    Physics & Astronomy Seminar--Tracking the maturation of organelles and signaling cluster with quantitative super-resolution microscopy

    Dr. Elias Puchner, Assistant Professor, Physics & Nanotechnology, University of Minnesota-Twin Cities, is presenting.  

    Quantitative Super-Resolution Microscopy is evolving into a powerful biophysical technique to study biological processes below the optical diffraction limit. However, a deeper understanding of the biological structures under investigation is often limited by the inability to quantify their molecular composition while resolving their size and shape. I will present our solution to this challenge, an intracellular calibrated Photoactivated Localization Microscopy (PALM) approach, that can measure the size of individual organelles with 20nm resolution as well as count the absolute numbers of molecules they contain. 

    Using this technique, we simultaneously characterized the size of individual vesicles in the yeast endocytic pathway and the number of accessible PI3P binding sites they contain. The analysis of many steady-state super-resolution snapshots revealed a characteristic vesicle maturation trajectory of composition and size as well as mechanistic information indicating that PI3P production precedes fusion into larger endosomes. Colocalization analysis with known markers of vesicle maturation showed that these regulatory proteins (clathrin, Vps21, Ypt7) associate with different regions of the observed endosome maturation trajectory. I will conclude by presenting ongoing technical developments from my new lab to correct for movement of organelles during PALM imaging in live cells.

    In addition I will present the application of single molecule tracking to study the spatial clustering and change in diffusion of signaling complexes, which presents an additional regulatory layer that actively tunes pathway gain. We demonstrate that clustering of the signaling complex itself activates the pathway bypassing receptor activation and that the degree of clustering correlates with the adaptive output. 

    Snacks at 3 PM, OLRI atrium.

  • 11/10/2016

    Stand Back--I'm going to try Science

    Physics and astronomy majors, You are cordially invited to the annual physics and astronomy summer research information session on Thursday, November 10, from 12 to 1 pm, in Olin-Rice room 350 (please note the unusual location).

    Learn all about interesting, paid summer research opportunities both here at Macalester and at other institutions. Participation in a research project is a transforming experience that is an essential part of your training to become a professional physicist. It is also a graduation requirement.

    So come to the meeting and have some pizza as well!

  • 11/9/2016

    Physics & Astronomy Seminar: First Direct Detections of Gravitational Waves

    Dr. Vuk Mandic, Associate Professor, School of Physics & Astronomy, University of Minnesota will present.

    During their first observation run the Advanced LIGO gravitational-wave detectors recorded signatures of mergers of binary black hole systems. These events mark the beginning of gravitational-wave astrophysics, enabling a new approach to studying various astrophysical phenomena. I will describe the LIGO detectors and the events they recorded, and I will discuss the implications of these observations as well as our expectations for future observations.

  • 11/3/2016

    Physics & Astronomy Seminar: Little Big Bangs at the Relativistic Heavy Ion Collider

    Prof. Marzia Rosati, Iowa State University, Physics Dept. will speak on 3 November, 4:30 PM, 100 OLRI (Please note: different day, time, place from usual Physics/Astronomy seminars).

    The Relativistic Heavy Ion Collider facility at Brookhaven National Laboratory on Long Island, NY collides gold (Au) nuclei at an energy of 200 GeV per colliding nucleon pair with the goal of creating and studying the `quark-gluon plasma' (QGP) in the laboratory. The QGP is a unique state of strongly interacting matter that is predicted to exist at temperatures in excess of 1011 ºK when the protons and neutrons in nuclear matter dissolve, releasing the normally confined quarks and gluons. This deconfined phase of matter is similar to conditions in the early universe when it was only a few microseconds old.  In this talk I will  review the remarkable and unexpected results from RHIC and what they may tell us about the properties of hot, strongly interacting nuclear matter.

  • 10/27/2016

    Extra Public Observing Night

    This week there will be an extra Public Observing Night due to the Fall Sampler! Same time, same place: 8:30 to 10:30 pm in Olin-Rice 404 (use southwest staircase). Bring a pf, bring friends, bring yourself.

  • 10/14/2016

    Physics & Astronomy Seminar--Non-Equilibrium Quantum Phenomena: Rydberg Bosons, Dirac Fermions and Beyond

    Dr. Jigang Wang, Assoc. Professor, Dept. of Physics & Astronomy, Ames Lab, Iowa State U. will speak.

    The challenge to push the gigahertz switching speed-limit of today’s electronic devices into the terahertz regime underlies the entire field of information processing, storage, communication as well as integrated multi-functional systems. One key fundamental issue is how photoexcitations evolve in time into Coulomb-bound, collective excitations and unbound charge carrier transport. Up to now, the initial quantum dynamics following photoexcitation remains inaccessible in many newly–discovered, exotic materials despite of their significant potential for photovoltaic, quantum and optoelectronic technologies. In this talk, I will discuss to implement an emerging theme: use ultrashort and low-energy laser pulses to both probe and control non-equilibrium quantum dynamics under salient conditions of femtosecond in time and milli-electron volts (terahertz) in energy. I will elaborate two recent examples in our program, from the quantum formation pathways in the birth of Rydberg bosons in the hybrid perovskites to control coherent Dirac fermion transport in topological insulators. Finally I will briefly discuss long-term vision and far-reaching consequence of this cross-cutting theme in future science and technology.

  • 10/13/2016

    Extra Public Observing Night

    This week there will be an extra Public Observing Night -  OLRI 404 (use southwest staircase). Bring a pf, bring friends, bring yourself!

  • 10/10/2016

    Public Observing Night

    Love to look at the stars? Come to Public Observing Night! Check out Macalester's very own 16 inch telescope and gaze at such varied objects as Neptune, the Owl Cluster, the Albireo binary system, and more (weather permitting). (Take the southwest stairs). 

  • 10/7/2016

    Distinguished Alumni Lecture: Biniyam Taddese

    Biniyam Taddese, PhD, '06 majored in Physics, Math and Computer Science and will be speaking in Libby Shoops' Computer Systems Organization class

  • 10/7/2016

    Distinguished Alumni Lecture: Biniyam Taddese

    Biniyam Taddese, PhD, '06 majored in Physics, Math and Computer Science and will be speaking in James Heyman's Modern Physics class 

  • 10/5/2016

    Joint Physics & Chemistry Seminar--Quantum Dot Photocatalysis

    Dr. Emily Weiss, Chemical Physicist, Department of Chemistry, Northwestern University will speak. 

    This talk, based on the research by Stephen C. Jensen, Stephanie Bettis Homan, and Emily Weiss, will describe the use of cadmium sulfide quantum dots (CdS QDs) – single crystals of CdS with diameters of ~3 nm – as visible-light photocatalysts for the reduction of nitrobenzene to aniline through six sequential photoinduced, proton-coupled electron transfers in water. Transient absorption spectroscopy and nuclear magnetic resonance (NMR) are used to analyze the mechanisms of molecular adsorption to the QD, and to show us how the environment at the surface of the QD promotes chemical transformations.

    Snacks at 3:00 PM.

  • 9/19/2016

    Physics & Astronomy Seminar--The Visible-to-Shortwave-Infrared Spectrum of Atmospheric Polarization: Modeling, Applications, and Future Growth

    Laura M. Dahl & Wataru Nakagawa, Electrical & Computer Engineering, Montana State 

    Environmental remote sensing and military sensing use optical polarization imaging to retrieve atmospheric properties for climate studies and to identify man-made objects in space, in the air, or on the ground. Knowledge of the polarization state of natural skylight is important to growing applications using polarimetric sensing. Polarization adds an additional dimension beyond basic image intensity and color for enhanced target detection. Skylight becomes partially polarized when sunlight is scattered in the atmosphere and our research focuses on how skylight polarization changes from the visible-to-shortwave-infrared. We have studied how skylight polarization can be used to detect poorly resolved airplanes in flight during daytime partly cloudy and smoky conditions and in other conditions. 

  • 9/12/2016

    Public Observing Nights

    Did you know that Macalester has an observatory? And that we open it to the public? Come check out the night sky with Physics and Astronomy! We hold Public Observing Nights on alternate Mondays and Wednesdays from 8:30 pm until 10:30 pm. So come up tonight to Olin-Rice 404 (use the southwest stairwell) and admire the stars!

  • 9/1/2016

    Physics & Astronomy Informational Session

    The force is strong with us. And weak. And gravitational. And electromagnetic. 

    Join the Department of Physics & Astronomy for an informational session about the physics major. Faculty members, students, and the Physics and Astronomy Club will provide a wealth of information about the power of physics. Pizza and pop provided.

  • 6/3/2016

    Professor Sung Kyu Kim Retirement Celebration

    A special invitation only retirement dinner and celebration honoring the career of physics and astronomy Professor Sung Kyu Kim will be held Friday, June 3. Invitations for the event were mailed in March. Contact Lisa Ziemba, reunion assistant, at for more information.

    6 p.m.
    Reception, Dinner & Program, followed by a Dessert Social

    Cost: $30 per person
    Beef will be served as the entrée. Please include any dietary restrictions with your response.

    Register online here by Friday, May 13

    Share your memories. Contribute to our memory book to thank Professor Kim for his dedicated service to the college by sharing your stories, photos, tributes, and well wishes. To be included, email or mail your contributions to Kristine Spangard by April 15, 2016. or Macalester College Physics/Astronomy, 1600 Grand Avenue, St. Paul, MN 55105-1899

  • 4/13/2016

    Physics & Astronomy Senior Honors Thesis Presentation

    Noah Lupu-Gladstein will present his honors thesis, "Converting Heat into Electricity: Characterization of a Thermoelectric Nanomaterial."

    Thermoelectric devices are an emerging green technology that turn heat into electricity or vice versa without any moving parts. They have not yet seen widespread use outside of niche applications because thermoelectric materials are either too costly or too inefficient. Copper Selenide (Cu2Se) has one of the highest thermoelectric efficiencies of any bulk material and it can be synthesized inexpensively via solution-deposition. I characterized thin-films of solution-deposited Cu2Se nanoparticles and found that when the material is annealed at a high enough temperature, it transforms from a nanomaterial into a thin metal film.

  • 4/4/2016

    Physics & Astronomy Senior Honors Thesis Presentation

    Hannah Johlas will present her Honors Thesis, "The Effects of Foundation Damping on Structural Demands in Yaw-Misaligned Offshore Wind Turbines."

    Large offshore wind turbines (OWTs) offer an attractive renewable energy option for the coastal U.S., but their support structures’ high costs remain a concern. Current OWT designs largely ignore damping from foundation-soil interactions, although small increases in damping can significantly reduce the materials cost for OWT support structures. I examine how incorporating foundation damping into turbine models affects structural demands in the monopile-supported NREL 5 MW OWT, using simulations in the aeroelastic code FAST for various yaw errors, wind and wave loads, and levels of foundation damping. I find that including foundation damping in OWT design guidelines could moderately reduce the maximum structural demands required of designs, consequently lowering the cost of OWTs.

  • 3/31/2016

    Physics & Astronomy Seminar--The Thirty Meter Telescope: Entering the "Giant Telescope" Era

    Dr. Warren Skidmore of the Thirty Meter Telescope Consortium will speak about the Thirty Meter Telescope (TMT) project: the exciting scientific questions that drive the building of a giant telescope; how the observatory is designed to support a range of scientific studies; and the engineering solutions that have been developed to overcome the problems of constructing and operating a giant diffraction limited observatory.

    Refreshments at 4:15. 

  • 3/31/2016

    EnviroThursday - "The Sun Doesn't Always Shine and the Wind Doesn't Always Blow: Managing Intermittent Renewable Energy on the Grid"

    Speaker:  Jim Doyle, Professor, Physics and Astronomy Dept., Macalester College

    Climate change mitigation will require dramatic reduction of fossil fuel use in favor of renewable energy technologies.  Because of their relatively low and decreasing costs, the most viable renewable energy options for the near term are solar and wind power.  Current electric grid technology requires that energy production is closely matched to energy demand.  However, both wind and solar are intermittent as well as unpredictable, making large scale integration of these technologies with the electric grid problematic.  In this talk we will review proposals to solve this “load balancing” problem, such as energy storage and geographical expansion of the grid, and the technological and economic issues associated with these proposals.  Preliminary results of our own modeling efforts will also be presented.

    Refreshments provided.

  • 3/23/2016

    Physics & Astronomy Senior Capstone Presentations

    Physics & Astronomy Senior Capstone Presentations resume with Ari Weiland speaking on "Protein Adsorption using a Lattice Toy Model" and Kovas Zygas on "Photovoltaic applications of ZnO thin films generated by thermal oxidation of metallic Zn." 

    Refreshments at 3 p.m. in Olin-Rice atrium.

  • 3/9/2016

    Physics & Astronomy Senior Capstone Presentations

    Physics & Astronomy Senior Capstone Presentations continue with Christian Stewart speaking on "The Effects of Hydrazine Surface Doping on CVD Graphene Films" and Ian Wyse on "Rotational and Hyperfine Analysis of AuS." 

    Refreshments at 3 p.m. in Olin-Rice atrium.

  • 3/4/2016

    Physics & Astronomy Seminar: Dark Matter Search with CALET

    Dr. Holger Motz, Waseda University, Tokyo, Japan, will present. 

    "The CALET (Calorimetric Electron Telescope) cosmic-ray detector was installed on the International Space Station in August 2015. Its primary objective is the direct measurement of the electron+positron flux in the TeV-region. With an excellent proton rejection capability and a large aperture, it will provide good statistics even well above one TeV, while also featuring an energy resolution of 2%, which enables it to detect fine structures in the spectrum. Such structures may originate from Dark Matter annihilation or decay, making indirect Dark Matter search one of CALET's main science objectives among others, such as identification of signatures from nearby supernova remnants by observation of TeV electrons, and measurement of the heavy nuclei spectra to study the cosmic ray acceleration and diffusion mechanisms. The increase of the positron fraction above 10 GeV discovered by the PAMELA mission and measured in detail by AMS-02 could be explained by an extra source emitting equal amounts of electrons and positrons, with Dark Matter and nearby pulsar wind nebulae the prime candidates for this source. Current data is in agreement with a wide range of scenarios with either type of extra source or a combination. In which way the CALET measurement is expected to constrain these, and the potential to identify a Dark Matter signature if it should exist in the spectrum are going to be explained."

  • 3/2/2016

    Colloquium: On the Alleged Incommensurability of Newtonian and Relativistic Mass

    Join the Physics and Philosophy Departments as they welcome Professor Samuel Fletcher, University of Minnesota as he presents his talk titled: "On the Alleged Incommensurability of Newtonian and Relativistic Mass."

  • 2/24/2016

    Physics & Astronomy Senior Capstone Presentations

    This week's Physics & Astronomy senior capstone presentations feature Asra Nizami speaking on "Adding functionality to Astropy: a community Python library for astronomers" and Beni Jonathan Pazár speaking on "Increasing the acceptance of H4e- events without losing statistical significance."

    Refreshments at 3 p.m. in Olin-Rice atrium.

  • 2/17/2016

    Physics & Astronomy Senior Capstone Presentations

    John Carlson will speak on "Dissociative Excitation of H2 in an RF Plasma" and Alexander Stowell will speak on "Langmuir Probe Measurements of an H2 RF Plasma." 

    Refreshments at 3 PM, OLRI atrium. 

  • 2/10/2016

    Physics & Astronomy Senior Capstone Presentations

    Liam DiZio will speak on "Elastic Block Modeling of Fault Slip Rates across Southern California," and Chris Bisbee will speak on "Energetic Behavior of Resistive Random-Access Memory Cells." 

    Refreshments at 3 PM, OLRI first floor atrium.

  • 2/5/2016

    Physics Seminar-Towards Quantum Computing

    Vlad Pribiag, assistant professor of Physics, University of Minnesota, Twin Cities is speaking on: 

    As computers become more and more powerful, the dimensions of their electronic components are rapidly shrinking. As a result, understanding and harnessing quantum mechanical phenomena at the nanoscale is becoming increasingly important. In this talk, I will discuss novel quantum materials and devices that could become the basis for future electronics, including possible quantum computers.

  • 11/30/2015

    Physics & Astronomy Seminar-Nuclear Fusion: Building A Star On Earth

    Ted Strait of General Atomics is presenting. 

    Nuclear fusion powers the stars, and is a potential future energy source here on earth.  One approach to realizing this potential makes use of magnetic fields to confine the fuel, a plasma with a temperature of 100,000,000 K.  This talk will discuss the scientific challenges of magnetic confinement fusion, with results from recent research at DIII-D, the largest tokamak fusion experiment in the US.

  • 11/23/2015

    The Arch and the Scaffold: How Einstein Found the Field Equations of General Relativity

    The Philosophy and Physics Departments join together to celebrate the 100th anniversary of the landmark first presentation of "Einstein's field equations" in a seminar by Professor Michel Janssen, History of Science, University of Minnesota: “The Arch and the Scaffold: How Einstein Found the Field Equations of General Relativity.”

    November 25, 2015 marks the centenary of Einstein’s first presentation of the so-called Einstein field equations. These equations form the capstone on Einstein’s general theory of relativity. General relativity makes gravity part of the structure of space-time and the Einstein field equations govern how matter curves space-time. In his later years, Einstein often claimed that he had found the field equations in November 1915 simply by choosing the mathematically most natural candidate. In 1912-13, he had already considered equations close to the ones he published three years later. He had given up on them back then because of difficulties with their physical interpretation. He had settled for equations constructed specifically to avoid such difficulties. In Einstein’s later recollections, the ensuing three years of work on these physically sensible but mathematically inelegant equations had largely been a waste of time. Progress, as he saw it, had resumed only when he had abandoned these equations and once again put his trust in the mathematics. Einstein’s writings at the time, we argue, tell a different story. In our reconstruction of events, the inelegant equations of 1913 served as the scaffold for the magnificent arch erected in November 1915. 

    Refreshments will be served at 3 PM in the OLRI Atrium. All are welcome!

  • 11/18/2015

    Macalester Physics Majors: REU Results

    Two Macalester physics majors will present the results of their REU projects:

    • Sam Erickson will discuss "Life in a Corporate Product Development Lab at 3M."
    • Kelsey Harmatta will speak on "Altering Fate: Attempting to Control Neural Stem Cell Division from Inside and Out."

    Snacks at 3 PM, OLRI Atrium. 

  • 11/11/2015

    Physics Seminar--Why is the Bulk Resistivity of Topological Insulators so Small?

    Tianran Chen, Assistant Professor of Physics at West Chester University is speaking. 

    As-grown topological insulators (TIs) are typically heavily doped n-type crystals. Compensation by acceptors is used to move the Fermi level to the middle of the band gap, but even then TIs have a frustratingly small bulk resistivity. We show that this small resistivity is the result of band bending by poorly screened fluctuations in the random Coulomb potential. Using numerical simulations of a completely compensated TI, we find that the bulk resistivity has an activation energy of just 0.15 times the band gap, in good agreement with experimental data. At lower temperatures activated transport crosses over to variable range hopping with a relatively large localization length. Using this theory, we can also explain the anomalously small thermopower of topological insulators as measured in experiments.

    Snacks at 3:00 PM in OLRI Atrium.

  • 11/4/2015

    Physics & Astronomy Summer Research Opportunity Information Session

    "Studying the Mysteries of the Universe" 

    Summer Research Opportunities for Students

    Interested in doing physics and astronomy research in summer 2016? This session will be an informational meeting about both on-campus and off-campus summer research opportunities.  We will discuss what options are available and the application procedures.

    Find your ideal research project!

    Snacks at 3 PM

  • 10/28/2015

    Physics & Astronomy Seminar-Precise Results from Lattice QCD

    Professor Claude Bernard, Department of Physics, Washington University in St. Louis will speak.

    This seminar is an introduction to QCD, the theory of the Strong Interactions, and to lattice methods for computing nonperturbative QCD effects with a particular focus on the systematic error in lattice calculations, and how it can be reduced using various versions of chiral perturbation theory. The discussion then covers the progress in the field over the past decade or so.  Calculations of QCD effects on Weak Interaction process are emphasized.  Such calculations make possible stringent tests of the Standard Model of particle physics.  Precise results, many of them quite recent, by the MILC and Fermilab/MILC collaborations are described.  Some of these results were predictions that have since been confirmed by experiment.

  • 10/21/2015

    Joint Physics & Chemistry Seminar with Professor David Jonas

    Professor David Jonas of the University of Colorado, Boulder will speak in this joint physics/chemistry seminar. Professor Jonas uses lasers to probe the motions of electrons and nuclei on extremely short time scales.  This has enabled his group to probe the details of energy transfer in photosynthesis and to develop optical methods that determine analyte concentrations without prior calibration (i.e., prior determination of molar absorptivities).  Professor Jonas' work brings together physical chemistry, analytical chemistry, and physics.

  • 10/15/2015

    Physics & Astronomy Seminar-Nanofabrication for Astronomy: Small Features for Small Wavelengths

    Randal McEntaffer, Associate Professor of Astronomy, Univ.of Iowa will speak.

    In the coming decades, the field of X-ray astronomy desires to accomplish several key science goals.  Current X-ray observatories are incapable of addressing many of these including detailing the distribution of hot matter in the Universe.  A large fraction of baryonic matter is theorized to exist in between galaxies.  Detection of this matter and characterizing feedback mechanisms from galaxies are substantial advancements of our understanding that can be realized through soft X-ray spectroscopy.  Future X-ray missions require diffraction gratings with high throughput and high spectral resolving power to achieve these goals.  Recent advances in grating fabrication methods have enabled reflection gratings to obtain the necessary performance requirements. I will discuss these novel fabrication methods and detail our progress in fabricating custom grating groove profiles.  These gratings have demonstrated very high X-ray diffraction efficiency and spectral resolving power during X-ray testing.  I will detail these results and describe current and future space based applications of spectrometers based on such gratings.

  • 10/9/2015

    Alyson Brooks, distinguished science alum, lecture

    Alyson Brooks PhD, ’00, majored in physics and is a professor at Rutgers University in the Physics/Astronomy Dept. She will speak in Modern Astronomy with John Cannon as part of the Student Research Poster Session.

  • 10/8/2015

    Physics & Astronomy Seminar--Solving Cold Dark Matter's "Small Scale Crisis"

    Dr. Alyson Brooks, Mac '00, Assistant Professor at Rutgers is speaking.

    A cosmological model in which the Universe is dominated by cold dark matter (CDM) and dark energy has been hugely successful in describing the observed evolution and large scale structure of our Universe.  However, at small scales (in the smallest galaxies and at the centers of larger galaxies), a number of observations seem to conflict with the predictions of CDM galaxy formation theory. These small scales, though, are also regions dominated by gas and stars. I will show results from high resolution cosmological galaxy simulations that include gas, stars, and dark matter to show that the physics of ordinary matter can significantly alter the dark matter structure of galaxies, possibly solving CDM's small scale problems.

    Departmental TEA at 3 PM, OLRI Atrium.

  • 9/30/2015

    Physics & Astronomy Seminar-Macalester Physics Majors: REU Results

    Two Macalester physics majors will present the results of their REU projects. 

    • Hannah Johlas will speak on "The Effects of Foundation Damping on Structural Demands in Yaw-misaligned Offshore Wind Turbines."

    • Noah Lupu-Gladsten will speak on "Upgrading the Largest Machine Ever Built: Radiation Hardness Testing of a New Integrated Circuit for the ATLAS Inner Tracker."

    A departmental tea will be held at 3 p.m. in the Olin-Rice atrium

  • 9/23/2015

    Astronomy & Physics Seminar-Shining a Light on Compact Object Mergers: Recent Progress Modeling Kilonovae

    Jennifer Barnes, Mac ‘09, Ph.D. Candidate, University of California-Berkeley, Department of Astronomy

    In the final stages of a violent compact object merger, a small amount of mater is unbound from the system. This material, if sufficiently neutron-rich, could produce heavy elements via rapid neutron capture (the r-process). The freshly synthesized heavy nuclei would then decay to stability, radioactively powering a dim electromagnetic (EM) transient called a kilonova.  Kilonovae offer a chance to probe heavy element production and the chemical enrichment of the Universe. They are also promising EM counterparts to the gravitational wave signals produced by mergers, which gravity wave detectors expect to observe in the next decade. A major challenge to kilonova modeling arises from uncertainties in how the exotic heavy elements in the ejecta interact with light and matter. I will present recent work modeling kilonovae, discuss how these results are informing the search for r-process transients, and outline the role kilonovae will play in the era of multi‐messenger astronomy.  

    Snacks at 3 PM, OLRI Atrium.

  • 9/16/2015

    Physics & Astronomy Seminar: Probing the Extreme Edges of Galaxy Formation with ALFALFA

    Dr. Elizabeth Adams, Post-Doc Researcher, Astron Netherlands Institute for Radio Astronomy, Dwingeloo.

    The ALFALFA HI survey has detected rare but extremely interesting HI sources that probe the extreme limits of systems that are able to form stars. These sources include the ultra-compact high velocity clouds (UCHVCs), some of which may represent gas-rich but (nearly) starless Local Group galaxies; the low-mass gas-rich SHIELD dwarf galaxies; and the "Almost-Dark" HI sources, which are clearly extragalactic HI detections that have no discernible optical counterpart in extant optical surveys. I will discuss these different source populations and how they are interconnected, highlighting one system, AGC 226067, that bridges the three categories. I will also focus in particular on the UCHVCs as candidate Local Group galaxies highlighting one particular source, AGC 198606, for which HI observations with WSRT and deep WIYN/ODI optical imaging strongly support the hypothesis that it represents gas in a nearby dark matter halo.

  • 9/9/2015

    Physics & Astronomy Seminar--Macalester Physics Majors: REU Results

    Two Macalester Physics Majors present the results of their REU projects:

    Elliot Weiss will speak on “Evaluating Phase Estimation Techniques in Accelerated MR Imaging.”

    Ian Luebbers will speak on "A Solar Mystery: Tracing Radioactive Dust Grains from Supernovae to the Solar Nebula."

    Departmental TEA at 3 PM in the OLRI Atrium. 

  • 9/3/2015

    Physics & Astronomy Information Session: Collide with a Physics Major!

    First and second year students: Join the faculty and current students of the Department of Physics & Astronomy to learn about being a physics major.

    Great information, plus pizza and pop!

  • 4/21/2015

    Physics & Astronomy Senior Honors Thesis Presentation

    Ned Molter will speak on "Constraining the Properties of the Metal-Poor ISM with Interferometric CO Observations of Low Metallicity Dwarf Galaxies."  Metal deficient dwarf galaxies are critical test beds for theories about the structure of star forming clouds at low metallicity, the chemical evolution of the interstellar medium, and the conditions in the early Universe. Ned presents new high-resolution interferometric observations of the CO J = 1 - 0 emission line in five nearby metal poor dwarf irregular galaxies taken with the CARMA array.

  • 4/16/2015

    Physics & Astronomy Seminar--Constraining Dark Matter

    Dr. Kassahun Haileyesus Betre, Mac ’07, PhD ‘14, Postdoc Teaching Fellow, Stanford University, Department of Physics.

    "The Standard Model is a consistent theory all the way up to the Grand Unified Theory (GUT) scale. Nebulous principles such as naturalness have been used in the past to predict the scale where new physics is expected to arise below the GUT scale. In light of recent results from the LHC, the reliability of these principles has been questioned. As a result, we need other approaches of motivating and bounding the scale of new physics.

    "I will show that the principle of Perturbative Unitarity, which has been used effectively to constrain various new physics scales in the past can be combined with reasonable assumptions about dark matter in any Beyond the Standard Model physics that incorporates dark matter to place interesting bounds on the scale of new physics."

    Refreshments at 4:00 PM

  • 4/14/2015

    Physics & Astronomy Senior Honors Thesis Presentation

    Charlotte Martinkus will speak on "Do Tidal Interactions Trigger Starbursts in Dwarf Galaxies?" Starburst dwarf galaxies are galaxies experiencing a period of intense star formation. These are extensively studied systems, though the mechanism that triggers the starbursts is poorly understood. Tidal interactions and gas accretion are thought to be potential starburst trigger mechanisms, although internal, secular drivers have not been ruled out. If starbursts are a result of external perturbations, then one would expect to see signatures of interaction in the gaseous disk of the galaxy. To examine this hypothesis, we study newly-obtained deep, wide-field HI maps from the Green Bank Telescope (GBT) of a sample of nine well-studied nearby starburst dwarf galaxies to search for signs of interactions, such as diffuse gas emission and potential companions. 

  • 4/9/2015

    Physics & Astronomy Senior Capstone Presentations

    Rhyan Foo Kune will speak on "Modelling Transient Terahertz Magneto-Spectroscopy Measurements of p-type CVD Graphene."

    Coco Zhang will also speak.

    Refreshments at 4 PM, OLRI first floor atrium.

  • 4/2/2015

    Physics & Astronomy Senior Capstone Presentation

    Andrew Banman will present "Mid-Infrared Excitation of Graphene" and Erik Alfvin will present "The Role of Cold Gas in Low-level Supermassive Black Hole Activity."

    Refreshments at 4:00 PM.

  • 3/31/2015

    Physics & Astronomy Seminar--How Kinematics & Geometry of the ISM Affects Lyman-a Radiative Transfer and Escape

    Thøger Emil Rivera-Thorsen, Ph.D. candidate, Stockholm University, Sweden is speaking.

    Lyman-Alpha, the transition between the ground state and the first excited state in hydrogen, is a very strong emission feature in young, star forming galaxies, and therefore of great importance in observing the Universe at high redshifts. However, we cannot trust what we see: complex radiative transfer effects and absorption by dust mean that the fraction of Lyα that escapes the ISM of a galaxy may do so far away from where it was initially emitted. The Lyman Alpha Reference Sample is a team effort to learn more about which processes govern Lyα escape. In this talk, I present high-resolution, Far-UV spectroscopy of the 14 galaxies of the sample obtained with the Cosmic Origins Spectrograph at the Hubble Space Telescope. Analysis of these spectra and comparison of our findings with results from HST imaging and optical spectroscopy from SDSS can help us reveal how kinematics and geometry of the ISM influences Lyα on its way out of the galaxy.

  • 3/26/2015

    Physics & Astronomy Seminar--The Three LITTLE Dwarfs: Evolutionary tales uncovered by stars

    Dr. Megan Johnson, CSIRO, Australia.

    In popular cosmology models, dwarf galaxies are the “building blocks” of giant galaxies and are assumed to be disks. Yet, observationally, even the basic structure of dwarf irregular (dIrr) galaxies remains controversial. Studies of the projected minor-to-major axis ratios in dIrrs provide inconclusive evidence for their three dimensional shape.  Fortunately, the stellar velocity dispersion, together with rotational information, is a diagnostic of how kinematically hot a system is, and, therefore, of its structure.  Here, I present recent results from a kinematic study of three nearby dwarf irregular galaxies.  We use longslit optical spectroscopy to obtain intrinsic stellar velocities and velocity dispersions of NGC 1569, DDO 168, and DDO 46, which are part of the LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes; The HI Nearby Galaxy Survey) survey.  

  • 3/12/2015

    Physics & Astronomy Senior Capstone Presentations

    Brittany Ehmann will speak on "Ultrafast Photoconductivity Measurements of a Thermoelectric Nanocomposite: Tellurium Nanowire/PEDOT:PSS."

    Jaren Willard will also speak.

    Refreshments at 4 PM, OLRI first floor atrium.

  • 3/5/2015

    Physics & Astronomy Senior Capstone Presentation

    Senior Alex Boldin speaking on "Analysis of Spin Polarization in Half Metallic Heusler Alloys" and senior Dan Shi speaking on "Investigating Color Management Technologies."

  • 2/26/2015

    Physics Seminar--Lithium Ion Batteries: Where we are and where we need to go

    Kaitlin Tyler, from the Materials Science and Engineering Department at the University of Illinois Urbana-Champaign, will speak on the topic of lithium ion batteries: "Batteries are used in many different aspects of our lives. Lithium ion batteries have been highly talked about in recent years as a solution for the problems with battery technology. Despite these claims, there is still a ways to go as far as Li-ion battery research is concerned. This presentation will highlight the underlying motivations for using lithium ion based batteries and what research is currently happening to improve on this technology." 

    Refreshments at 4 PM in OLRI atrium.

  • 2/19/2015

    Physics & Astronomy Seminar-Kilonovae: The Glow from Merging Neutron Stars

    Jennifer Barnes, Mac '09, UC-Berkeley, Dept. of Physics will speak: In the final stages of a violent compact object merger, a small amount of matter is dynamically ejected from the system. This material, if sufficiently neutron rich, could produce heavy elements via rapid neutron capture (the r-process). The freshly synthesized heavy nuclei would then decay to stability, radioactively powering a dim electromagnetic transient called a kilonova. Kilonovae offer a clue to the as-yet undetermined site of r-process production. They are also a promising EM counterpart to the gravitational wave signals from merging neutron stars, which Advanced LIGO/Virgo expect to detect routinely in the near future. A major challenge to modeling kilonovae is calculating the opacities of the heavy elements present in the merger ejecta. Barnes will discuss new models of r-process opacities, present recent radiation transport simulations of kilonovae, and explain how these results are informing the search for r-process transients.

  • 2/12/2015

    Physics & Astronomy Seminar-From Researcher to Editor: Exoplanets and Magazines

    Mac alum and associate editor at Astronomy magazine, Dr. Korey Haynes '09 (PhD, George Mason University ‘14) will talk about her recent dissertation work characterizing hot Jupiter exoplanets. She used the Hubble Space Telescope to successfully search a half-dozen of these planets' atmospheres for signs of water. In one of these planets, she found the first spectral evidence for titanium oxide, the molecule suspected of causing temperature inversions in hot Jupiter atmospheres. She will also discuss her new position as an associate editor at Astronomy magazine, what an editing job entails, and how a PhD in astronomy led her to a job in magazine publishing.

    Refreshments at 4 PM in OLRI atrium.

  • 2/10/2015

    Physics & Astronomy Seminar: Magnetism at the Nanoscale

    E. Dan Dahlberg, School of Physics and Astronomy, Univ. of MN. Prof. Dahlberg is one of the pioneers and foremost authorities on magnetism at the nanoscale, which has profound implications for fundamental physics, applications in information technology, and biological physics.

    Major breakthroughs in micromagnetics have resulted from the development of new magnetic imaging techniques.  Through the powerful magnetic force microscope (MFM), a variant of the atomic force microscope, we can understand the domain structure and magnetization reversal in nanometer-sized particles.  I will present an introduction to micromagnetics research and description of MFM with a demonstration of the basic principle and discuss one of the magnetic materials we study, magnetite crystals. Lastly we will discuss the magnetic states and the magnetization reversal process in magnetosome chains.

    Snacks at 3:00!