Macalester
Past Events
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9/25/2019
Physics & Astronomy Seminar: Space Radiation and Its Effects on Microelectronic Systems
Dr. Daniel Loveless, Assistant Professor, Department of Electrical Engineering, UT Chattanooga will present a seminar, "Space Radiation and Its Effects on Microelectronic Systems."
A reliability concern of growing interest in the microelectronics community is the deleterious effect of ionizing radiation. The so-called "single events" – single particles which can penetrate semiconductor material leaving ionized charge in their wake – can cause information corruption, transient anomalies, and sometimes irreparable system failure. Single events are ubiquitous; this radiation exists in the environment external to a circuit and emanates from processing and packaging material integral to a circuit. Once only the concern of space-bound systems where increased susceptibilities to single-event effects (SEE) have been reported as device feature sizes decrease and operating frequencies increase, integrated circuit (IC) density and power scaling have propelled this issue to the forefront of reliability concerns at current technology nodes in ground-based and space-deployed electronic systems. This presentation addresses several attributes of IC scaling relevant to radiation degradation, failure modes, and vulnerability. Basic and state-of-the-art approaches for the mitigation of SEEs are presented along with examples of hardened circuits. The presentation concludes with a discussion of the latest techniques for measurement, analysis, and mitigation of transient radiation phenomena, and impacts on future technologies.
Snacks at 3 PM.
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9/19/2019
EnviroThursday - “Exploring Mars with Curiosity (the rover)”
Speaker: Dr. Dawn Sumner, Professor, Earth and Planetary Sciences, University of CA-Davis
Dawn Sumner is a member of NASA’s Mars Science Laboratory and will talk about her work helping the rover Curiosity explore ancient environments in Gale Crater on Mars.
Dawn Sumner’s research focuses on reconstructing ancient environments on early Earth and Mars and the early evolution of bacteria, including the origin of oxygenic photosynthesis. Her group studies everything from the environmental settings, geochemistry and morphology of Archean microbialites to the morphology, climate response, and genomics of modern microbial communities growing in ice-covered Antarctic lakes to the stratigraphy and geochemistry of sedimentary rocks on Mars. Sumner is a member of NASA’s Mars Science Laboratory, helping the rover Curiosity explore ancient environments in Gale Crater on Mars. She regularly shares her research and adventures with the public. Dr. Sumner is dedicated to helping students of all backgrounds prepare for careers in science as well as to creating educational and work environments that are inclusive and supportive, including through the use of feminist research and theory.
This EnviroThursday is co-sponsored by the Environmental Studies, Biology, Geology, and Physics and Astronomy Departments.
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9/18/2019
Physics & Astronomy Seminar-Fun with Physics: Student Presentations on Non-Capstone/Thesis Research
Find out what more of your physics and astronomy colleagues are doing for fun! Students will present research information and findings not related to their capstones or theses.
Snacks at 3.
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9/11/2019
Physics & Astronomy Seminar-How Do You Roll?: Student Presentations on Non-Capstone/Thesis Research
What are your physics and astronomy colleagues doing for fun? Find out at this seminar! Students will present research information and findings not related to their capstones or theses.
Snacks at 3 in the OLRI first floor Atrium.
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4/24/2019
Physics & Astronomy Capstone Presentation
Karen Perez Sarmiento presents the last Physics & Astronomy Capstone talk of the year. She will speak about her research at Fermilab.
Refreshments at 3:00 PM
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4/17/2019
Physics & Astronomy Senior Honors Thesis Presentation
Greta Helmel will present her honors thesis, "Recent Evolution of the Eta Carinae Supernova Imposter System."
The supernova imposter Eta Carinae and its surrounding Homunculus reflection nebula have been of great interest for the last several decades. As the most massive star known in our Galaxy, this object is of particular importance in understanding high mass loss episodes and final stages in the evolution of similarly massive stars. Using the most recent set of spectra from the Hubble Space Telescope STIS/CCD, we investigate changes in the behavior of the central star from 2012 to 2018, which indicate an overall brightening and a related decrease in the stellar wind density. Overall, the star appears to be slowing its development in comparison to the rapid changes it exhibited between 2004 and 2010. We also quantify the evolution of the Homunculus nebula, , determining a precise expansion rate and age estimate based on 18 years of STIS observations, one of the longest temporal baselines ever produced for this object using a single instrument.
Refreshments at 3 PM.
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4/10/2019
Physics & Astronomy Capstone Presentations
The Physics & Astronomy Department presents two more senior capstones. All are welcome!
Robert Ford ► The Neutral Hydrogen Kinematics of the Dwarf Galaxy Merger NGC 3239;
Sarah Taft ► Haro 11, Pox 186, and VCC 1313: The Enigmatic Behavior of HI Non-Emitters.
Refreshments at 3 p.m.
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4/3/2019
Physics & Astronomy Capstone Presentations
The Physics & Astronomy Department presents more senior capstones:
- Ramon Molina, "Investigation on the Electrical Properties of CdO/ZnO thin films using THz Spectroscopy"
- Robert Ford, "The Neutral Hydrogen Kinematics of the Dwarf Galaxy Merger NGC 3239"
Refreshments at 3 p.m.
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3/28/2019
Physics & Astronomy Seminar-Exploring the Coevolution of Magnetic Fields and Galaxies in Different Environments
Dr. Anna Williams, Visiting Assistant Professor, Macalester College, will present this seminar.
Galaxies are permeated with magnetic fields at all scale lengths--from protostellar disks to spiral arms. But how galaxies first acquired magnetic fields, and, in turn grow and sustain large-scale magnetic structures is not well understood. One way to unravel this problem is by observing magnetic fields in a variety of galaxy environments. Luckily, new and upgraded radio telescopes are providing a new window to the polarization universe, and greatly enhancing our ability to probe astrophysical magnetic fields. I will present the results of three observational studies focused on the coevolution of magnetic fields and galaxies in different environments: (1) a nearby spiral galaxy, NGC 6946, (2) a loose galaxy group, NGC 2563, and (3) distant disk-like galaxies at z~0.5.
Pizza provided.
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3/27/2019
Physics & Astronomy Senior Capstone Presentations
The Physics & Astronomy Department presents its senior capstone presentations.
- Sam Hollenbach, "Understanding Solar Activity During the Last 400 Years"
- Kelly Flugaur-Leavitt, "Carrier Mobility of Bismuth-Doped Perovskites"
- Dona Pantova, "UV LED Photoluminescence Measurements on GaN Sample"
Refreshments at 3:00 PM.
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3/13/2019
Physics & Astronomy Seminar "Electric-Magnetic Duality and its Modern Descendants"
The Physics & Astronomy Department presents a seminar titled "Electric-Magnetic Duality and its Modern Descendants," by Dr. Kevin Setter, Visiting Assistant Professor, Haverford College.
In the subject of electromagnetism, we learn that space is filled with a set of two arrows, the electric field and the magnetic field, the fluctuations of which are governed by a set of four Maxwell Equations. The form of these equations remains almost the same if one exchanges the electric field everywhere with the magnetic field. This simple observation turns out to lead to far-reaching implications for both modern physics and modern mathematics. In my talk, I will discuss the phenomenon of electric-magnetic duality, its generalization to nonabelian gauge theories, and surprising interconnections between physics and mathematics that have been uncovered in recent years.
Snacks at 3 PM
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3/11/2019
Physics & Astronomy Seminar-Classical Novae, Gamma-Rays, and Computation in Physics: The Work of a Transient Astronomer and Physics Educator
Dr. Thomas Finzell, post-doctoral research fellow, University of Michigan, will present "Classical Novae, Gamma-Rays, and Computation in Physics: The Work of a Transient Astronomer and Physics Educator."
Classical novae are thermonuclear events that occur on the surface of white dwarfs (burnt out stellar cores), and for nearly 40 years astronomers thought they had them figured out. But eight years ago, something unexpected happened: astronomers discovered some classical novae emit extremely energetic gamma-rays. In this talk, I will discuss how our understanding of classical novae has changed dramatically in the last decade, the new physics incorporated into our model that explain the presence of gamma-rays, and my role in effecting those changes. I will end my talk by discussing my transition from astrophysics to physics education research, and my current work studying how we can improve the way we teach physics by integrating computation into the classroom.
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3/6/2019
Physics & Astronomy Seminar: Virtual Graduate Student Round Table
Interactive Graduate Student Round Table Event! During this class period, multiple recent Macalester graduates who are now in graduate programs will be our virtual guests. These individuals will share perspectives on the realities of graduate school, from determining where to apply to succeeding once there. This will be a unique opportunity for you to learn from their recent experiences.
There will not be a rigid schedule for this event. Each of our virtual guests will speak for a few minutes about their path and their experiences. Then we will open the floor up for questions and discussion with you. Please come prepared with questions for our guests and topics you would like to discuss.
Snacks at 3 PM
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2/20/2019
Physics & Astronomy Seminar-Cancelled
Dr. Michael Rutkowski, Assistant Professor, Minnesota State University Mankato, will present a seminar "UV Astronomy: Are we entering a new Dark Age?"
Ultraviolet observations of galaxies are required to solve a number of fundamental, unanswered questions in modern astrophysics. In this topical seminar, I will discuss a number of UV-optical-near IR surveys that provide novel constraints on some of these outstanding questions. Specifically, I will highlight the utility of UV observations of 1) OVI emission in the circumgalactic medium of starburst galaxies, 2) star-forming galaxies at the rest-frame Lyman continuum regime, and 3) quiescent galaxies at intermediate redshift for understanding the cosmic history metals, reionization, and the hierarchical assembly, respectively. I will conclude with a discussion of efforts to develop new, and extend the life of existing, UV assets in space into the 2020s and (hopefully) beyond.
Snacks at 3 PM.
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2/13/2019
Surface Physics, Interfacial Electrochemistry, and Power Sources for Implantable Medical Devices
The Physics & Astronomy Department presents a seminar by Dr. Joachim Hossick-Schott, Bakken Fellow and Technical Fellow, Medtronic.
The surface was invented by the devil, according to Wolfgang Pauli. Therefore, understanding the processes between an electrode surface and adjacent media continues to be a scientifically challenging theme for many research teams around the world. The laws of physics and chemistry at the interface between an electrode surface and adjacent media determine the working principles of batteries and electrolytic capacitors. These components find ubiquitous use as electrical power sources in many electrical devices, for example in cell phones. The purpose of this talk is to highlight the surface physics and interfacial electrochemistry in batteries and electrolytic capacitors designed specifically for use in implanted medical devices.
Snacks at 3 PM.
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2/7/2019
Modern Computational Tools For Deciphering Galaxy Mergers: Andromeda's violent past and the fate of our Milky Way
Dr. Richard Anthony D'Souza, Postdoctoral Researcher, University of Michigan, presents this seminar sponsored by the Physics & Astronomy Department.
Although galaxy merging and interactions are the key, distinctive features of our picture of galaxy formation in a hierarchical Universe, they have nonetheless played a peripheral role in our observational understanding of disk-dominated Milky Way-mass galaxies. The Andromeda Galaxy (M31), our nearest large galactic neighbour, offers a unique opportunity to test how mergers affect galaxy properties. M31's stellar halo caused by the tidal disruption of satellite galaxies is the best tracer of the galaxy's accretion history. Despite a decade of effort in mapping out M31's large stellar halo, we are unable to convert M31's stellar halo into a merger history. Here we use cosmological models of galaxy formation to show that M31’s massive and metal-rich stellar halo containing intermediate age stars implies that it merged with a large (M* ~ 2.5 x 10^10 M_sun) galaxy ~2 Gyr ago.
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1/30/2019
Physics & Astronomy Seminar-The Hunt for Cosmic Monsters: Understanding Galaxies in the Confused FIR Sky
Dr. Jillian Scudder ’09, Assistant Professor, Oberlin College will present.
Observing galaxies in the Far-Infrared (FIR) gives us a unique window into the star formation rates of high redshift, dusty galaxies. These galaxies are generally thought to be forming stars at a prodigious rate, heating the internal dust reservoirs which then radiate in the FIR. It is often assumed that a bright source in the FIR belongs to a single, highly star forming galaxy, but this is impossible to verify with low resolution images. In this talk I will discuss a method of determining how many galaxies are blurred together into a single FIR detection, and what these results imply for our understanding of star formation in the earlier Universe.
Snacks at 3 PM.
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1/28/2019
Physics & Astronomy Seminar-Understanding Our Home: Simulating the Evolving Milky Way
Dr. Sarah Loebman, Hubble Fellow and Chancellor's Fellow, UC Davis will present a seminar "Understanding Our Home: Simulating the Evolving Milky Way."
We live inside a truly exciting astrophysical laboratory - the Milky Way galaxy - which provides a unique detailed perspective into the dynamics of stars and the physics of galaxy formation. Characterizing both the stellar and the dark matter content of the Milky Way and uncovering the Milky Way's formation history are key science goals of major ongoing and upcoming surveys such as APOGEE, Gaia, and LSST. However, observations of the Milky Way span a complex multi-dimensional space which necessitates sophisticated modeling to interpret. In this talk, I will highlight some of my recent achievements that utilize state-of-the-art simulations to provide deep insight into the Milky Way's content, formation, and evolution. In particular, I will discuss the Milky Way's disk and the role radial migration has played in redistributing stars within it. I will also discuss how a galaxy merger in the Milky Way's distant past impacted the movement of stars in our stellar halo today. I will conclude by discussing exciting new frontiers that Milky Way simulations are poised to tackle in the near future.
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12/11/2018
Build your own ROCKET
Ever been curious about rocket science, but didn't know where to start? Ever wanted to build and fly your own rocket? Well, now's your chance! Join High Power Rocketry at Macalester in the Idea Lab on Sunday, December 9 from 1:30-4:30 PM to construct and fly your own model rocket! Absolutely no experience necessary!!! Just grab some friends, come on over, and get ready to have a blast before finals!
Can't make it Sunday? A second session will be held on Tuesday, December 11 from 2:00-4:30 PM.
Questions? Email us at rocketry@macalester.edu
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12/9/2018
Build a your own ROCKET
Ever been curious about rocket science, but didn't know where to start? Ever wanted to build and fly your own rocket? Well, now's your chance! Join High Power Rocketry at Macalester in the Idea Lab on Sunday, December 9 from 1:30-4:30 PM to construct and fly your own model rocket! Absolutely no experience necessary!!! Just grab some friends, come on over, and get ready to have a blast before finals!
Can't make it Sunday? A second session will be held on Tuesday, December 11 from 2:00-4:30 PM.
This event is open to the community.
Questions? Email us at rocketry@macalester.edu
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12/5/2018
Physics & Astronomy Seminar "Life at Low Reynolds Number: Bugs, Walls, and Green's Functions"
Dr. William Mitchell, Visiting Assistant Professor, Macalester College, MSCS, is presenting.
The best way to develop empathy with an E. Coli, at least in the sense of mechanics, might be to try swimming through a vat of Greek yogurt. In this talk we will discuss the fluid mechanics of tiny swimmers whose locomotion relies on flagella as opposed to fins. Along the way, we will encounter scallops, biofilms, Kirchhoff rods, Green's functions, Lorentz's approach to dealing with walls, and a special cold-water swimmer named Clione antarctica.
Snacks at 3 p.m.
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11/28/2018
Physics & Astronomy Seminar "Weird Building Blocks of the Universe"
Dr. Gregory Pawloski, Associate Professor, University of Minnesota, School of Physics & Astronomy is presenting.
Neutrinos are the odd balls of the elementary particle menagerie that forms the building blocks of the universe. Because of their odd properties they can potentially be involved in interesting processes that are responsible for our universe not annihilating itself. There is currently great interest in the particle physics community to study the properties of these particles. However, because of their odd nature, their detection is challenging and extraordinary detectors are needed to study them.
Snacks at 3 p.m.
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11/14/2018
Physics & Astronomy Seminar "The Emergence of Topology in Strongly Correlated Many-body Systems"
Dr. Fiona Burnell, Assistant Professor, University of Minnesota, School of Physics & Astronomy, is presenting.
At sufficiently low temperatures, quantum mechanics plays a key role in determining materials' behaviors. Particularly in systems where interactions are important, this can lead to macroscopic physical properties that are fundamentally different from what we expect both from single-particle quantum mechanics, and from interacting classical systems. Among the possibilities are that two systems may locally look the same, but globally behave very differently. These global differences are described mathematically by a variety of topological quantities, which capture important physical differences such as statistical interactions between particles, and distinctive low-energy physics at the systems boundaries. I will describe recent developments in our understanding of interacting topological phases in the presence of global symmetries, and how these are connected to the "unusual" (or, in technical terms, anomalous) properties of their low-energy boundary states.
Snacks at 3 PM
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11/8/2018
Physics & Astronomy Summer Research Information Session
"Studying the Mysteries of the Universe"--Summer Research Opportunities: All Physics & Astronomy majors please attend this important information session!
Interested in doing physics and astronomy research in summer 2019? Join us for pizza and learn about both on-campus and off-campus summer research opportunities. We will discuss what options are available and the application procedures. Pizza lunch provided.
Find your ideal research project!
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11/7/2018
Hunting for Nature's Nuclear Forges: Where are the Heaviest Elements Made?
Dr. Jennifer Barnes '09, Einstein Fellow at Columbia University will present "Hunting for Nature's Nuclear Forges: Where are the Heaviest Elements Made?"
Electromagnetic follow-up observations of the gravitational wave-detected binary neutron star merger (NSM) GW1701817 suggested that material ejected from the accretion disk formed in the merger underwent a robust r-process nucleosynthesis, producing heavy elements like Au, Pt, and Eu. These observations seemed to answer a long-standing question about the origin of the heaviest elements in the Universe. However, the conditions that characterize the disks formed in NSMs are also found in other systems, raising the question of whether mergers are unique sites of r-process production. Of particular interest for this question is the collapse of rotating massive stars, called "collapsars." Like NSM, collapsars form accretion disks around stellar mass compact objects and are associated with ultrarelativistic outflows that give rise to gamma-ray bursts. I will discuss recent work that explored whether these collapsar disks could successfully produce the r-process, and what the signs of collapsar disk r-process nucleosynthesis might be.
Snacks at 3 PM.
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10/31/2018
Physics & Astronomy Seminar "Exploring the High-Energy Mysteries of the Sun"
Dr. Lindsay Glesener, Assistant Professor, University of Minnesota, School of Physics & Astronomy is presenting.
The Sun offers us a special window into the universe, allowing us to study the basic physics at work in many astronomical objects. There is also a practical urgency to understanding the Sun, as solar eruptions regularly hit the Earth's magnetic field with large amounts of energy, plasma, and radiation. The origin of these events lies in abrupt releases of magnetic energy on the Sun called solar flares. In this talk, I will describe some known aspects of the physics behind flares and what we hope to learn in the future with new instruments that measure high-energy radiation. I’ll also explore the routes by which telescopes are tested on suborbital platforms before they finally become ready for the limelight aboard a NASA spacecraft.
Snacks at 3 PM
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10/17/2018
Physics & Astronomy Seminar "Oh the Places You'll Go, Oh the Things You'll See...what else can you do with a Physics Degree?"
Dr. T. J. Fields,Senior Manager,Security Architecture, Cloud Security, and Identity Management, at Fiat Chrysler is presenting.
This non-traditional talk focuses on the strengths and potential weaknesses that physicists (and other students of the “hard” sciences) have when trying to seek employment outside of their academic field. Our speaker has followed such a non-physics path, and has unique insights and lessons to share about his journey and how it may apply to others.
Snacks at 3 PM
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10/10/2018
Physics, Astronomy, & Chemistry Seminar "Quantitative and Motion-Corrected Super-Resolution Imaging of Endosome Dynamics in Living Cells"
Dr. Elias Puchner, Assistant Professor, University of Minnesota is presenting “Quantitative and Motion-Corrected Super-Resolution Imaging of Endosome Dynamics in Living Cells.”
Quantitative Super-Resolution Microscopy is evolving into a powerful 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. Our solution to this challenge is an intracellular calibrated Photoactivated Localization Microscopy (PALM) approach that can be applied to simultaneously measure the size of individual organelles (with 20nm resolution) and to count the absolute numbers of molecules they contain [1]. Another limitation of PALM has been the need to fix cells in order to avoid blurring caused by motion. To address this, I will present our new live cell PALM approach, in which we use dual-color imaging to track nano-scale organelles to correct for their motion during data acquisition.
Using this intracellular calibrated PALM 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 numerous steady-state super-resolution snapshots in fixed cells revealed a characteristic vesicle maturation trajectory of composition and size as well as mechanistic information indicating that PI3P production precedes fusion into larger endosomes. In order to gain additional insights into the dynamics of endosome maturation and fusion we will present our new motion-corrected PALM results in live cells, including examples of diffusing organelles that we resolved, how their diffusion coefficient depends on their size and how they maturation to endosomes by fusion. Our dual-color live-cell PALM technique not only gives novel information about the mode of transport of these specific organelles, but provides a new avenue for quantitative super-resolution imaging in living cells. -
10/3/2018
Physics & Astronomy Seminar "Introduction to Compound Semiconductors"
Dr. Michael Haase, Lead Research Specialist at 3M will present “Introduction to Compound Semiconductors.”
Compound semiconductors are essential materials for optoelectronic devices--LEDs, laser diodes, photodetectors, photovoltaics--and for high frequency and high power electronics. This seminar will provide a technical overview of the rich field of compound semiconductor materials and devices. Some insights into internships and careers in physics in a corporate environment will also be offered.
Snacks at 3 PM, OLRI first floor atrium.
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9/26/2018
Physics & Astronomy Seminar "Seeing an Individual Star More than Half of the Way Back to the Big Bang"
Patrick Kelly, Assistant Professor, University of Minnesota,Physics & Astronomy will present.
We recently detected an individual blue supergiant star (dubbed LS1) in a multiply imaged spiral galaxy at redshift z=1.49 behind the MACS J1149 galaxy cluster (z=0.54). In the spring of 2016, the star appeared to brighten by a factor of three in Hubble Space Telescope imaging due to microlensing by a star in the intracluster medium of the foreground cluster. I will describe ongoing work to model LS1’s light curve and to draw conclusions about the stellar population in the intracluster medium, the outcomes of massive stellar evolution, and the abundance of primordial black holes.
Snacks at 3 PM
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9/19/2018
Physics & Astronomy Seminar--Nuclear Power for the Exploration and Settlement of Outer Space
Dr. Paolo Venneri (Mac '12), Director of Advanced Systems, USNC Ultra Safe Nuclear Corp. will present.
The successful exploration and settlement of outer space will require high-performance energy sources. With the growing societal awareness and excitement for space exploration, the need for the implementation of these energy sources is steadily growing. Of the energy sources currently available, nuclear fission has the most promise in terms of its ability to provide energy for long periods of time and for minimal system mass. In this seminar, I will introduce some of the basics of nuclear energy and cover a broad overview of nuclear power and propulsion for space applications along with key systems including nuclear thermal propulsion, surface fission power systems, and radioisotope power systems. In addition to a survey on space nuclear technology, we will also briefly touch on current space nuclear programs and trends driving their development.
Snacks at 3 PM
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9/12/2018
Physics & Astronomy Seminar--Signal of Opportunity Navigation for Small Spacecraft in Deep Space
Demoz Gebre-Egziabher, Professor, University of Minnesota, Aerospace Engineering & Mechanics will present.
Spacecraft navigation via naturally occurring signals (e.g., those produced by pulsars, quasars, and gamma-ray bursts) is proposed as an alternative navigation technique that could augment or eventually replace navigation via the deep space network. This technique involves using these astrophysical sources as “natural galactic GPS.” In this presentation, we describe the algorithms and sensors that will be used to enable this approach to navigation in deep space. We will also describe the Signal of Opportunity CubeSat Ranging and Timing Experiments (SOCRATES) mission that is slated to fly a prototype sensor for signal of opportunity navigation in Low Earth Orbit (LEO).
Snacks at 3 PM, first floor OLRI atrium.
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4/20/2018
Build Your Own Rocket!
Ever been curious about rocket science, but didn't know where to start? Ever wanted to build and fly your own rocket? Well, now's your chance! Join the Mac Rocketry Team in the Idea Lab on Tuesday 4/17 and Friday 4/20 from 4:30-6:30. You'll have an opportunity to learn about what we do (including last semesters successful launch and our preparation for NASA’s Space Grant Midwest High-Power Rocketry Competition in May), and to construct and fly your own model rocket! Absolutely no experience necessary!!! Just grab some friends, come on over, and get ready to have a blast!
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4/20/2018
Physics & Astronomy Senior Capstone Presentations
Paul Chery will give his capstone presentation, "Modeling Recombination in Solar Cells."
Solar cells are a competitive alternative to nonrenewable energy sources such as fossil fuels. However, the efficiency of these devices is limited by photogenerated carrier recombination. I use a numerical model to study recombination phenomena in the absorber layer of solar cells including alternate recombination models and the effects of spatial distribution of recombination centers.
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4/18/2018
Physics & Astronomy Senior Capstone Presentations
Catie Ball will present her honors thesis, "Star Formation Diagnostics in the Cosmic Eye."
Studying the properties of lensed galaxies circumvents distance-related limitations in spatial resolution and sensitivity and offers unique insights out to the high-redshift universe. We present analysis of Atacama Large sub-Millimeter Array (ALMA) and Hubble Space Telescope (HST) observations of the Cosmic Eye, a gravitationally lensed Lyman Break Galaxy at z=3.074. These observations trace the harness of stellar radiation and the nature of dust attenuation in a distant galaxy, allowing us to resolve variations in the nature of star-formation on sub-galactic scales.
Snacks at 3 p.m.
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4/17/2018
Build Your Own Rocket!
Ever been curious about rocket science, but didn't know where to start? Ever wanted to build and fly your own rocket? Well, now's your chance! Join the Mac Rocketry Team in the Idea Lab on Tuesday 4/17 and Friday 4/20 from 4:30-6:30. You'll have an opportunity to learn about what we do (including last semesters successful launch and our preparation for NASA’s Space Grant Midwest High-Power Rocketry Competition in May), and to construct and fly your own model rocket! Absolutely no experience necessary!!! Just grab some friends, come on over, and get ready to have a blast!
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4/13/2018
Physics & Astronomy Senior Honors Thesis Presentation
Elizabeth Ruvolo is presenting her honors thesis, "SHIELD: The HI Mass-Diameter Relation."
The Survey of HI in Extremely Low-mass Dwarfs (SHIELD) is a multi-wavelength galaxy survey which seeks to explore the properties of sources with extremely low-mass HI reservoirs in order to refine our understanding of galaxies and to populate understudied regions of parameter space. In this work, I use the SHIELD sample to help populate the low-mass regime of the HI mass-diameter relation.
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4/11/2018
Physics & Astronomy Senior Honors Thesis Presentation
Brian Eisner is presenting his honors thesis, "Surveying Radio Line Spectra of Nearby Galaxies."
Complex molecules have more degrees of freedom than smaller molecules, increasing the potential information yield, but simultaneously weakening the transitions. We sample the centimeter spectrum of nine nearby star-forming galaxies using the Australia Telescope Compact Array, and detect transitions from six species: recombination lines, H2CO, H2O, OH, NH3, and c-C3H2. The Next-Generation Very Large Array will be able to prove a ~150 times larger number of galaxies to sample to the same S/N ratio, and thus complex molecules should be observable in the closest galaxies with this instrument.
Snacks at 3 PM.
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4/9/2018
Physics & Astronomy Seminar--From Galaxies to Fridge Magnets: Searching for the origin of magnetic fields
The Physics & Astronomy Department presents a seminar featuring Dr. Anna Williams, a candidate for the visiting professor of physics position. Williams is a lecturer at the Univ. of Wisconsin. Please attend, then help the department evaluate the candidate with your feedback.
Magnetic fields play important roles in our everyday lives. They make our headphones work, keep reminders posted on the refrigerator, and help us get from point A to point B. Magnetic fields are also important beyond our planet where most ordinary matter is ionized and in the form of plasma. In stars, magnetic fields cause huge surface eruptions and can slow rotation. In galaxies, magnetic fields provide pressure support against gravity and affect the energy balance by accelerating and confining charged particles. Despite their prevalence, we still do not know how or when magnetic fields came about in the universe. In my talk, I will explain how astronomers observe astrophysical magnetic fields, and show how my research to detect and measure magnetic fields in galaxies helps us understand the origin of magnetic fields and their co-evolution with galaxies.
Refreshments at 4 p.m.
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4/6/2018
Physics & Astronomy Senior Honors Thesis Presentation
Theo Jacobson will present his honors thesis, "Gravitational Leptogenesis and One-Loop Effective Actions."
Inflation, the leading paradigm in modern cosmology, provides a theoretical framework for understanding the physics of the early Universe. To demonstrate its robust phenomenology, we show how one particular inflationary model provides a natural mechanism for generating the matter-antimatter asymmetry in our visible Universe. At a more formal level, we investigate how such a model can arise from more general quantum field theories.
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4/4/2018
Physics & Astronomy Senior Capstone Presentations
The Physics and Astronomy Department presents its Senior Capstone talks with:
- Masao Miazzo, "Imaging the Natural Gas of Extremely Low-mass Dwarfs"
- A. Cotter, "Actinometry of Hydrogen Plasmas"
Refreshments at 3 PM.
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4/2/2018
Physics & Astronomy Seminar
Observing & Interpreting Very High Energy Gamma Rays from Blazars
The Physics & Astronomy Department is presenting a seminar featuring Caitlin Johnson, a candidate for the visiting professor of physics position. Caitlin Johnson is a Ph.D. candidate at UC Santa Cruz. Please attend, then take this opportunity to help the department evaluate the candidate with your feedback.
Blazars, a subclass of active galactic nuclei, host powerful relativistic jets that are pointed along our line of sight. These jets produce some of the most energetic radiation observed in the universe: gamma rays. To date, questions remain about the particle physics processes responsible for creating gamma-ray emission and how they relate to overall evolution and classification of active galaxies. VERITAS, a gamma-ray telescope located in Arizona, uses a unique technique to observe gamma rays from the ground, that is if the gamma rays can actually make it to Earth.
Refreshments at 4 PM.
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3/28/2018
Physics & Astronomy Senior Honors Thesis Presentation
Alex Gordon will present his honors thesis, "A Narrowband Emission-Line Survey of the Large Magellanic Cloud."
The Large and Small Magellanic Clouds provide sites to study the interstellar medium (ISM) and its components at all scales, from small to global. The UM / CTIO Magellanic Cloud Emission-Line Survey (MCELS) is as a deep imaging survey of both of these nearby galaxies in the emission of Hα, [S ii], and [O iii]. These emission-line images are being used in detailed optical and multi-wavelength studies of planetary nebulae (PNe), H ii regions, supernova remnants (SNRs), su- perbubbles, and supergiant shells. Here we present a deep and wide view of the ∼ 104 K ionized gas in the interstellar medium of the Large Magellanic Cloud (LMC) using the MCELS data. We present large-scale flux-calibrated continuum- subtracted optical emission-line mosaics of the 8 × 8 square degree central region of the Large Magellanic Cloud created from the combination of thousands of ob- servations taken over hundreds of nights, providing a detailed view of most of the gaseous extent of the galaxy. With these mosaics in hand we conduct a systematic analysis of the [S ii] to Hα ratio of 59 known X-ray supernova remnants in the Large Magellanic Cloud. For 44 of these supernova remnants, Hα and [S ii] flux values along with [S ii] / Hα emission-line ratios have been derived. All derived [S ii] / Hα emission-line ratios ≥ 0.4, strengthening their identification as true rem- nants. We compare our values to spectroscopic values in the literature. This work has uncovered at least one previously unidentified candidate supernova remnant, triggering an ongoing spectroscopic followup campaign.
Refreshments at 3:00 PM
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3/7/2018
Physics & Astronomy Seminar--The Sunburst Arc: A Unique, Lensed Galaxy at Redshift ~2.4 with a Perforated ISM
Thøger (Emil) Rivera-Thorsen, Postdoctoral Fellow, Institute for Theoretical Astrophysics, University of Oslo is presenting.
The radiative transport and escape of Lyman alpha and UV continuum photons from distant galaxies is a critical process that bears directly on galaxy evolution and on the cosmic reionization. To explore these inter-related issues, I will present an extremely bright and extremely strongly lensed star forming galaxy at redshift 2.37 known as the "Sunburst Arc."
Snacks at 3 PM.
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2/23/2018
Physics & Astronomy Seminar: Graduate School--The Final Frontier
Wondering what the next step in your scientific career might be like? Come hear Macalester Alumni Yillikal Ayino ’12, (UMN Physics Ph.D. candidate), Minh Nguyen '14 (UMN Physics Ph.D. candidate), and Dr. Hallie Boyer ’08 (Dreyfus Postdoctoral Fellow, Carnegie Mellon and 2017 UMN Mechanical Engineering Ph.D.) talk about their research, their experiences and making the transition from Macalester to graduate school.
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12/6/2017
Physics & Astronomy Seminar--A Matter of Life and Death
Professor John Bischof, University of Minnesota Institute for Engineering in Medicine, will speak.
Gold and iron oxide nanoparticles have unique and tunable properties that allow transduction of optical (light), or radiofrequency (RF) electromagnetic fields to affect heating of biomaterials at multiple scales. This talk will explore the underlying physics and relative advantages of each form of nanoparticle heating for therapeutic treatment of cancer or other disease by heating (i.e. magnetic hyperthermia or photothermal cancer therapy). In addition, this same heating helps improve regenerative medicine by “nanowarming” vitrified (i.e. cryopreserved) biomaterials back to a transplantable state through rapid and uniform warming that avoids crystallization and cracking. This nanoparticle warming addresses an important technology bottleneck for both large systems (i.e. tissues and organs) and smaller systems (i.e. embryos and oocytes). In summary, this talk demonstrates the growing opportunities for nanoparticle heating in biomedical applications.
Snacks at 3 PM
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11/29/2017
Physics & Astronomy Seminar--Preliminary Investigations of Passive Acoustics in Lake Superior
Prof. Jay Austin, Large Lakes Observatory, Dept. of Physics & Astronomy, U of M, Duluth presents.
While a great deal of effort has been put into characterizing propagation properties and the passive (natural) acoustic soundscape of the world oceans, little if any effort has been put into the same topics with regards to freshwater systems around the world. In this talk, I will discuss the history of these sorts of observations, and present results from two deployments in Lake Superior in 2016-2017. The majority of the background signal is due to either wind/wave processes or passing vessels. These signals are used to characterize the propagation properties of the lake under different stratification conditions. Previously unobserved resonant structures and clicks of potential biological origin are discussed, as well as the possibility that they may reveal a behavioral reaction to the presence of surface vessels.
Snacks at 3 PM.
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11/27/2017
Public Observing Tonight
What's the difference between an open cluster and a globular cluster? A protoplanetary disk and a planetary nebula? Come find out at public observing night! We love the cosmos and we know you do, too! All are welcome! If the sky is cloudy, we'll still be around to chat but we won't open the 'scope.
Note: there will be no regular observing nights next semester, so we have only a few more opportunities this academic year!
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11/20/2017
Public Observing Night
Planets! Stars! Clusters! Nebulae! Galaxies! We <3 the cosmos and we know you do to! All are welcome for public observing night. If the sky is cloudy, we'll still be around to chat but we won't open the 'scope.
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11/15/2017
Physics & Astronomy Seminar--Searching for new Physics with the CMS Experiment
Julie Hogan, Assistant Professor, Bethel University, Physics & Engineering Department will present.
The Large Hadron Collider is one of the most powerful machines in the world, accelerating protons to nearly the speed of light to provide 40 million collisions per second at particle detectors such as the Compact Muon Solenoid. The CMS detector is highly versatile, featuring the largest superconducting solenoid ever built and over 100 million detection elements. CMS physicists were instrumental in the discovery of the Higgs boson in 2012 and are now searching for evidence of new physics, including heavy vector-like quarks. I'll present a recent search for vector-like quarks using W and Higgs boson jet reconstruction algorithms, and introduce a new effort to use computer vision techniques to classify jets at the high luminosity LHC.
Snacks at 3 PM.
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11/9/2017
Philosophy/Physics Colloquium
Join the Philosophy and Physics Departments for a talk by Robert DiSalle, Professor of History and Philosophy of Science Space-Time Theories at the University of Western Ontario titled “Laws & Necessities: On the Ineffective Reasonableness of Mathematics” All are welcome.
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11/9/2017
Physics & Astronomy Summer Research Information Session
Studying the Mysteries of the Universe: Summer Research Opportunities for Students.
Interested in doing physics and astronomy research in summer 2018? Join us for pizza and learn about both on-campus and off-campus summer research opportunities. We will discuss whatoptions are available and the application procedures. Find your ideal research project!
Pizza lunch provided.
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11/8/2017
Physics & Astronomy Seminar--Signatures of Particle Physics from Cosmological Inflation
Professor Marco Peloso, Minnesota Institute for Astrophysics, University of Minnesota, Physics & Astronomy Department. is presenting.
There are strong motivations to believe that the so-called "big-bang" cosmology was in reality preceded by a stage of fast and accelerated expansion, known as cosmological inflation. Inflation solves several problems of big-bang cosmology (explaining for example why the primordial universe was so homogeneous), and it provides a natural mechanism for the generation of the primordial perturbations, which seeded the present large structures in the universe (galaxies, and clusters of galaxies). Particle physics processes during inflation can leave an imprint in the primordial density perturbations (leading to characteristic patterns in the temperature anisotropies, and, possibly, to primordial black holes) and in the primordial stochastic background of gravitational waves, both at extra-galactic (thus affecting the Cosmic Microwave Background observations) and at interferometer scales (such as those probed by LIGO, and future related experiments).
Snacks at 3 PM.
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11/1/2017
Physics & Astronomy Seminar--A Materials Informatics Approach to the Study of van der Waals Materials
Postdoctoral Fellow Trevor Rhone, Harvard University, Physics Department will present.
The explosion in the recent number of proposed van der Waals (vdW) materials has increased the promise of uncovering novel physics and developing new applications for 2D atomic crystals. Though this large number of newly identified vdW materials brings the potential for discovery, immense challenges also emerge. Traditional experimental and theoretical methods for studying a large database of materials are slow and expensive. A novel approach to materials investigation is desirable. With the advent of materials informatics (the combination of statistical tools, computational methods, and materials science), one is able to efficiently screen a large database of materials and make predictions of desirable properties. I will discuss how materials informatics can be used to study 2D atomic crystals and present some initial results.
Snacks at 3 PM
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10/23/2017
Public Observing Night
Planets! Stars! Clusters! Nebulae! Galaxies! Hop on the shuttle as we explore the cosmos and ponder the infinite. All are welcome for public observing night! If the sky is cloudy we'll still be around to chat but we won't open the 'scope.
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10/18/2017
Physics & Astronomy Seminar--Magnetism & Crystal Defects: Joined at the Slip
Anna Lindquist, Visiting Assistant Professor, Geology Department, Macalester College will present.
Magnetite (Fe3O4) is the primary mineral responsible for our understanding of how Earth's magnetic field has changed over time. When sufficiently heated, it can act like a compass needle, aligning with Earth's magnetic field. Once cooled, it locks in a record of Earth's magnetic field that can last hundreds of millions of years or longer. However, like any mineral, magnetite grains vary in size and can be full of defects. These defects can affect the magnetic alignment and remagnetization of magnetite. By collecting nanometer-scale videos and images, we will be able to quantify the interactions between defects and magnetism and discuss the implications of these interactions.
Snacks at 3 PM
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10/18/2017
Skype with computational astrophysicist Dr. Jennifer Barnes '09
Dr. Jennifer Barnes will skype with Physics/Astronomy students to talk about the big news in the universe: the first observation of a neutron star merger event!
Dr. Barnes is a computational astrophysicist and an expert in compact object mergers. She will join the Macalester faculty after finishing her postdoctoral position at Columbia University. Jenni graduated from Macalester in 2009 with majors in physics and sociology, and she received her PhD degree in physics earlier this year from UC Berkeley.
Jenni is looking forward to engage with current Macalester students! Please join in an informal discussion about her research and how it relates to yesterday's exciting announcement of the first-ever observation of a neutron star merger. She will also be happy to answer any of your questions! -
10/16/2017
Public Observing Night
Crystal clear skies are expected for public observing night! Take advantage of a perfectly crisp fall evening and peep the stars. Hop on the shuttle as we explore the cosmos and ponder the infinite. All are welcome!
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10/11/2017
Physics/Astronomy & Chemistry Joint Seminar--Asteroids: Friends or Foes?
Distinguished Macalester alum, Richard Binzel '80, now Professor of Planetary Sciences and Margaret MacVicar Faculty Fellow, MIT, will present.
Asteroids make for popular disaster movies, but is there any real threat? We will look at the facts and focus on the science results delivered by physical and chemical studies of asteroids and meteorites. Richard Binzel began his forefront scientific studies of asteroids as a student at Macalester College, enabled by the dedicated teaching and the diligent telescope making of Professor Sherman W. Schultz. This work was recognized by the 1980 Apker Award from the American Physical Society.
Snacks at 3 PM
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10/9/2017
Public Observing Night
Did you know that Macalester has its very own 16 inch reflecting rooftop telescope? You're invited to come check it out at public observing night! Hop on the shuttle as we explore the cosmos and ponder the infinite. All are welcome; bring your friends, bring a date, or come alone! If the sky is cloudy we'll still be around to chat but we won't open the 'scope.
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10/2/2017
Public Observing Night
Join us for public observing night! Hop on the shuttle as we explore the cosmos and ponder the infinite. All are welcome; bring your friends, bring a date, or come alone! If the sky is cloudy we'll still be around to chat but we won't open the 'scope.