This Week at Physics

<< Fall 2013 Spring 2014 Fall 2014 >>

Events During the Week of February 2nd through February 9th, 2014

Monday, February 3rd, 2014

Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:15 pm
Place: 5242 Chamberlin Hall
Abstract: Please visit the following link for more details:
    http://cmb.physics.wisc.edu/journal/index.html
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Le Zhang (lzhang263@wisc.edu)
Host: Peter Timbie
Add this event to your calendar

Faculty Candidate Seminar
CANCELED--Mechanics and self-organization of motor-driven filamentous assemblies: from swimming sperm to active gels
Time: 4:00 pm
Place: 4274 Chamberlin Hall
Speaker: Daniel Chen, Brandeis University
Abstract: A fascinating feature of living matter is that mechanical tasks at large length scales are routinely accomplished with exquisite precision by the cooperative action of millions of nanometer-sized molecular motors and fibers. Examples range from cellular motility and division to muscle actuation. From a technological standpoint, it would be highly desirable to spawn materials that could inherit, at least in part, this ability. In this vein, I will describe two biological motor-driven filamentous assemblies that exemplify these remarkable properties and our efforts to both fundamentally understand them and to create new functional materials with them. In first part I will describe the creation of active gels comprised of purified microtubules and motor proteins that consume chemical energy in the form of ATP. Unlike equilibrium polymer gels, these gels are capable of continuous structural remodeling that can drive internal fluid flows and macroscopic motility. In the second part I describe a new experimental platform to measure ATP consumption in swimming sea urchin sperm at the single-cell level. These measurements provide new insight into long-standing questions about mechanical regulation of periodic beating in flagella. Together, these systems highlight the need for new approaches from soft matter physics to understand the unique stress-structure-dynamics relationships intrinsic to motor-driven biological materials.
Host: Pupa Gilbert/Sue Coppersmith
Add this event to your calendar

Tuesday, February 4th, 2014

Chaos & Complex Systems Seminar
Predicting fate
Time: 12:05 pm
Place: 4274 Chamberlin Hall (refreshments will be served)
Speaker: Jim Blair, Milton and Edgewood College
Abstract: Large quantities of agrochemicals are applied to farm fields every year. What happens to them? How are they transported and transformed? How long do they last in the soil? How rapidly do they move through soil to reach the ground water? Where do they end up? This has been studied after the chemicals have been applied. In this talk I will describe the development of a series of laboratory procedures that attempt to predict the environmental fate of new agrochemicals before they are applied. Topics include: Radio-labels and Liquid Scintillation Counting The Three Faces of Fate Material Balance Does History Matter? MCPA, Dow, and St. Croix Factory Farms and Frankenfoods
Host: Clint Sprott
Add this event to your calendar

Special Plasma Physics Seminar
Spectral Line Profile Modeling Under the Action of Dynamic Electric and Static Magnetic Fields
Time: 12:05 pm
Place: 5280 Chamberlin Hall
Speaker: Elijah Martin, North Carolina State University
Add this event to your calendar

"Physics Today" Undergrad Colloquium (Physics 301)
Garage Physics Projects
Time: 1:20 pm
Place: 2223 Chamberlin
Speaker: Duncan Carlsmith, UW Madison Department of Physics
Add this event to your calendar

Faculty Candidate Seminar
Searching for dark matter with bubble chambers
Time: 4:00 pm
Place: Chamberlin Hall 4274
Speaker: Hugh Lippincott
Abstract: The PICO Collaboration (formed from the recent merger of the Chicago-based COUPP and the Canadian-based PICASSO experiments) uses bubble chambers to search for dark matter particles. Unlike the bubble chambers of the 1960s and 1970s, PICO chambers are operated in only mildly superheated conditions, rendering them insensitive to the minimum ionizing particles that typically constitute the largest background in dark matter searches. The bubble chamber allows for rejection of other backgrounds as well - for example, alpha decays can be discriminated from signal events because they sound louder. The result is a detector with minimal backgrounds that can be scaled to large masses. I will introduce the field of direct detection of dark matter and discuss the status of PICO, including results from the COUPP-4 detector and a progress report on COUPP-60 and PICO-2L, two chambers recently commissioned in the deep underground site of SNOLAB.
Host: Dasu and Everett
Add this event to your calendar

Wednesday, February 5th, 2014

Faculty Candidate Seminar
From colloids to bacteria: anisotropy in self-organizing systems at the mesoscopic scale
Time: 4:00 pm
Place: 5280 Chamberlin Hall
Speaker: Kun Zhao, UCLA
Abstract: Many complex mesoscopic systems, ranging from synthetic colloids to active biological cells, exhibit a rich variety of pattern-forming behavior. In this talk, I will show you how anisotropy in two model systems, anisotropic shaped colloids and bacterial communities, affect complex pattern formation. During the directed self-assembly of colloidal systems, shape anisotropy can greatly influence resulting structures. We have developed a technique called roughness controlled depletion attraction which allows us to probe the phase space of 2D Brownian systems for a variety of anisotropic shapes such as triangles, squares, and other polygons. We have discovered several unanticipated effects, such as local chiral symmetry breaking in a triatic liquid crystal phase of uniform triangles. Anisotropy also plays a large role in the formation of bacterial communities called biofilms. Biofilms are a major human health hazard as well as being an impediment in many industrial and medical settings. By using condensed matter techniques, we present for the first time the dynamics of colony formation at early stages of biofilm development for Pseudomonas aeruginosa. We found that Pseudomonas aeruginosa does not follow an isotropic random walk as commonly assumed, but instead obeys a new form of polysaccharide-guided dynamics such that the distribution of surface visitation follows a power law. This power low behavior may benefit bacteria social organization during biofilm formation.
Host: Pupa Gilbert/Sue Coppersmith
Add this event to your calendar

Thursday, February 6th, 2014

R. G. Herb Condensed Matter Seminar
Electrically controlled spin qubits in coupled quantum dot systems
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Vanita Srinivasa, UMD
Abstract: The spins of electrons confined in semiconductor quantum dots represent versatile building blocks for solid-state quantum information processing devices. Within these systems, manipulation via electric fields enables both rapid control and protection from noise. I will describe our theoretical investigations of single-electron and multi-electron quantum dot systems with electrically controllable spin relaxation, highly tunable exchange interactions, and quantum gates robust against charge noise. These features yield approaches for rapid single-spin initialization as well as for controllably coupling donor electron spin qubits in silicon.

Host: Coppersmith
Add this event to your calendar

NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Searching for Q-balls with the High Altitude Water Cherenkov Observatory
Time: 2:30 pm
Place: 4274 Chamberlin Hall
Speaker: Peter Karn, UC Irvine
Abstract: The High Altitude Water Cherenkov (HAWC) Observatory is a gamma-ray experiment currently under construction at Sierra Negra in Mexico. When complete it will consist of a 22,000 square meter array of 300 water Cherenkov detectors. Although HAWC is designed to study gamma rays from galactic and extra-galactic sources, the large volume of instrumented water (each tank holds ~188,000 liters) gives the opportunity to search for rare objects. One such target is the Q-ball, a very massive, subrelativistic particle that can have a large baryon number and can be stable since their creation in the early universe. If stable, Q-balls would make up some of the dark matter of the universe, but their large mass means their flux is very low. HAWC has a flexible data acquisition system which, with a dedicated trigger algorithm for non-relativistic species, allows a search for Q-balls traversing the detector. The Q-ball trigger, simulation, and analysis will be presented.
Host: Vandenbroucke
Add this event to your calendar

Astronomy Colloquium
Measuring Magnetic Fields Near and Far via the Zeeman Effect
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Tim Robishaw, Dominion Radio Astrophysical Observatory
Abstract: The Zeeman effect is the only observational tool that allows us to directly measure the magnetic field strength and direction in the interstellar medium. We provide an overview of ongoing projects in which we are using the Zeeman splitting of the 21-cm line and the 18-cm hydroxyl (OH) transitions in order to probe astrophysical magnetic fields. We will highlight the first detection of extragalactic Zeeman splitting in the OH<br>
megamaser emission from starburst galaxies. Results will be shown from a southern survey of Zeeman splitting in OH masers in our Milky Way's spiral arms that suggest field reversals relative to the field directions probed by Faraday rotation. We will also discuss previous measurements of the Zeeman effect in Galactic 21-cm radio emission, some of the instrumental challenges involved in such measurements, and plans for a large-scale<br>
survey underway on the 64-m Parkes telescope and the 26-m John A. Galt Telescope at the Dominion Radio Astrophysical Observatory.
Add this event to your calendar

Friday, February 7th, 2014

Theory Seminar (High Energy/Cosmology)
Top Portal Dark Matter
Time: 2:00 pm
Place: 5280 Chamberlin Hall
Speaker: Christopher Jackson, University of Texas at Arlington
Abstract: With the recent discovery of the Higgs boson, much of the attention in the particle physics community has turned to illuminating the true nature of dark matter. Out of the numerous possible scenarios studied in the literature, one interesting scenario involves the case where dark matter (much like the Higgs boson) has enhanced couplings to the most massive particles in the Standard Model (e.g., W and Z bosons, top quarks and/or the Higgs boson itself). In this talk, I will discuss one particular model where dark matter couples exclusively to the right-handed top quark (which we dub aEurooeTop portal dark matteraEuro or TPDM). In this situation, the possibility of detecting dark matter in direct-detection experiments such as LUX is highly suppressed and one must turn to other types of searches. I will present the results of a preliminary study on the feasibility of detecting TPDM either at the LHC or through indirect searches. In particular, I will show that this type of model has very interesting signatures in gamma rays.
Host: Jordi Salvadó Serra
Add this event to your calendar

Physics Department Colloquium
Quantum Optics with Microwave Photons
Time: 3:30 pm
Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
Speaker: Maxim Vavilov, University of Wisconsin Department of Physics
Abstract: Recent experiments revealed the quantum nature of electromagnetic fields of superconducting circuits at microwave frequencies.

Individual quanta of these fields are photons with energy a few million times smaller than the energy of an optical photon and are extremely hard to detect. A promising device for microwave photon detection is based on Josephson junctions. Even a single microwave photon with tiny energy is sufficient to switch a junction from the superconducting to voltage state, and detection of a photon reduces to observation of voltage pulses across the junction.

In this talk, I will present a theoretical model of a Josephson junction interacting with a quantized electromagnetic field and show that such Josephson photon detectors have relatively high efficiency of detection of microwave photons. I will discuss application of such detectors to qubit readout for quantum information processing and to studies of photon emission statistics by quantum electronic devices.
Poster: http://www.physics.wisc.edu/twap/posters/2014/3281.pdf
Add this event to your calendar

Saturday, February 8th, 2014

Wonders of Physics
Physics of Dimensions
Time: 1:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott and colleagues, UW Department of Physics
Abstract: The 31st annual presentation of the popular outreach program for the public. Advanced free tickets are recommended.
Host: Clint Sprott
Add this event to your calendar

Sunday, February 9th, 2014

Wonders of Physics
Physics of Dimensions
Time: 1:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott and colleagues, UW Department of Physics
Abstract: The 31st annual presentation of the popular outreach program for the public. Advanced free tickets are recommended.
Host: Clint Sprott
Add this event to your calendar

Wonders of Physics
Physics of Dimensions
Time: 4:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott and colleagues, UW Department of Physics
Abstract: The 31st annual presentation of the popular outreach program for the public. Advanced free tickets are recommended.
Host: Clint Sprott
Add this event to your calendar


"This Week at Physics" poster: http://www.physics.wisc.edu/twap/posters/2014/2014-02-03.pdf

©2013 Board of Regents of the University of Wisconsin System