http://www.umbc.edu/blogs/physics/ Announcements for the Department of Physics at UMBC en Copyright 2009 Wed, 09 Dec 2009 03:31:00 -0500 http://www.sixapart.com/movabletype/ http://blogs.law.harvard.edu/tech/rss Cloud and Aerosol Properties from IR and Lidar Dr. Anne Garnier
LATMOS France Location: Physics Bldg., room 401]]> http://www.umbc.edu/blogs/physics/2009/12/seminar_wednesday_december_2_2009_at_330_pm.html http://www.umbc.edu/blogs/physics/2009/12/seminar_wednesday_december_2_2009_at_330_pm.html Seminars, Colloquia & Talks Wed, 09 Dec 2009 03:31:00 -0500 TBA Dr. Ozlem Celik
University of Maryland Baltimore County (CRESST) Location: Physics Bldg., room 401]]> http://www.umbc.edu/blogs/physics/2009/12/seminar_wednesday_december_9_2.html http://www.umbc.edu/blogs/physics/2009/12/seminar_wednesday_december_9_2.html Seminars, Colloquia & Talks Wed, 02 Dec 2009 03:30:00 -0500 No Seminar - Thanksgiving Holiday ]]> http://www.umbc.edu/blogs/physics/2009/11/seminar_wednesday_november_25_2009_.html http://www.umbc.edu/blogs/physics/2009/11/seminar_wednesday_november_25_2009_.html Seminars, Colloquia & Talks Wed, 25 Nov 2009 03:30:00 -0500 You are all invited to attend Nathan's PhD defense. Date: Monday, November 23, 2009 Time: 10:00 am Location: PHYS 401 TITLE: Application of satellite laser altimetry data to studies of sea ice properties and processes ABSTRACT: Sea ice plays an important role in the global climate system by impacting the energy balance of the Earth as well as affecting the oceanic and atmospheric circulations. Recently, large changes have been observed in the Earth's areal coverage of sea ice. However, little is currently known about sea ice thickness particularly at the scales needed for climate research. Spaceborne remote sensing provides the necessary global scale of coverage, but the retrieval of sea ice thickness from space has not been possible until recently with the launch of satellite altimeters of high accuracy and precision. The Ice, Cloud, and land Elevation Satellite (ICESat) is one such laser altimeter with the potential to retrieve sea ice freeboard, which, when combined with snow depth retrievals and the assumption of hydrostatic balance allows for the determination of sea ice thickness. The goal of this study is to use data from ICESat to provide sea ice thickness values at the global scale and high spatial resolution needed for climate studies. The work presented in this thesis includes the validation and improvement of ICESat data products, development and validation of sea ice freeboard retrieval algorithms using the ICESat data products, and the development of a method to combine ICESat freeboard retrievals with a snow depth data set to determine sea ice thickness at the 70 m spatial resolution of ICESat. The ICESat data set is used to study sea ice thickness, heat exchange, and ice production in the Arctic Ocean for the 2003-2008 time period. Despite the thinning of the Arctic sea ice cover over the 2003-2008 time period, mean ice growth rates for consecutive fall and winter measurement periods remained relatively constant. An increased ice growth rate which may be expected from a thinner ice cover appeared to be balanced by warmer temperatures. An increased ocean-atmosphere heat flux is also observed due to the thinning of the sea ice cover. ]]> http://www.umbc.edu/blogs/physics/2009/11/phd_defense_-_nathan_kurtz.html http://www.umbc.edu/blogs/physics/2009/11/phd_defense_-_nathan_kurtz.html Notable Achievements Mon, 23 Nov 2009 08:02:50 -0500 History and Optics of 3D Movies Dr. Todd Pittman
University of Maryland Baltimore County The 3-D movie experience has improved quite a bit since the “golden era” of the 1950’s…the special effects are now so realistic that you are almost guaranteed to spill your popcorn when the monster jumps off the screen! In this talk I will review the basic operating principles of modern 3-D movie systems, which are built upon the clever use of a few key concepts from undergraduate optics. Location: Physics Bldg., room 401]]> http://www.umbc.edu/blogs/physics/2009/11/seminar_wednesday_november_18_2009_at_330_pm.html http://www.umbc.edu/blogs/physics/2009/11/seminar_wednesday_november_18_2009_at_330_pm.html Seminars, Colloquia & Talks Wed, 18 Nov 2009 03:30:00 -0500 Nestor successfully defended his masters thesis on November 13, 2009 TITLE: Broad band terahertz time domain spectroscopy on polymers and organic electro-optic polymers ABSTRACT: Several polymers and two organic polymer composites were studied using terahertz time domain spectroscopy and analyzed using Duvillaret’s method and a dynamic range analysis to determine their credible bandwidth. Terahertz time domain spectroscopy is a technique that allows us to determine the real index of refraction and the absorption of nonconductive materials in the terahertz band. These polymers are used as hosts to build organic composites for terahertz generation through optical rectification and detection via electro-optic (EO) sampling. Knowledge of their optical parameters is important when considering them as hosts for emitters and detectors. Also, the knowledge of these parameters over a wide bandwidth is important in the determination of the degree of phase matching that these materials can have, for a given center wavelength of an optical pump pulse. Broad bandwidth and a clear spectrum were achieved with an air-plasma emitter and an organic EO polymer sensor. In this thesis a bandwidth that goes from 0.7 to 9 THz for the real index of refraction and for the absorption coefficient for the majority of the polymers, is reported.]]> http://www.umbc.edu/blogs/physics/2009/11/ms_defense_nestor_valdes.html http://www.umbc.edu/blogs/physics/2009/11/ms_defense_nestor_valdes.html Notable Achievements Fri, 13 Nov 2009 08:47:29 -0500 Confessions of a Converted Lecturer Dr. Eric Mazur
Harvard University I thought I was a good teacher until I discovered my students were just memorizing information rather than learning to understand the material. Who was to blame? The students? The material? I will explain how I came to the agonizing conclusion that the culprit was neither of these. It was my teaching that caused students to fail! I will show how I have adjusted my approach to teaching and how it has improved my students' performance significantly. Location: LH 5 (ECS Bldg)]]> http://www.umbc.edu/blogs/physics/2009/11/seminar_wednesday_november_11_2009_at_600_pm.html http://www.umbc.edu/blogs/physics/2009/11/seminar_wednesday_november_11_2009_at_600_pm.html Seminars, Colloquia & Talks Wed, 11 Nov 2009 06:00:00 -0500 Nonlinear Optics at the Nanoscale Dr. Eric Mazur
Harvard University We explore nonlinear optical phenomena at the nanoscale by launching femtosecond laser pulses into long silica nanowires. Using evanescent coupling between wires we demonstrate a number of nanophotonic devices. At high intensity the nanowires produce a strong supercontinuum over short interaction lengths (less than 20 mm) and at a very low energy threshold (about 1 nJ), making them ideal sources of coherent white-light for nanophotonic applications. The spectral broadening reveals an optimal fiber diameter to enhance nonlinear effects with minimal dispersion. We also present a device that permits a number of all-optical logic operations with femtosecond laser pulses in the nanojoule range. Location: Physics Bldg., Room 401]]> http://www.umbc.edu/blogs/physics/2009/11/seminar_wednesday_november_11_2009_at_330_pm.html http://www.umbc.edu/blogs/physics/2009/11/seminar_wednesday_november_11_2009_at_330_pm.html Seminars, Colloquia & Talks Wed, 11 Nov 2009 03:30:00 -0500 TBA
Location: Physics Bldg., Room 401]]> http://www.umbc.edu/blogs/physics/2009/11/seminar_wednesday_november_4_2009_at_330_pm.html http://www.umbc.edu/blogs/physics/2009/11/seminar_wednesday_november_4_2009_at_330_pm.html Seminars, Colloquia & Talks Wed, 04 Nov 2009 03:30:00 -0500 The Fermi Gamma-Ray Space Telescope and the Search for Dark Matter Yvonne Edmonds
Stanford University The Fermi Gamma-Ray Space Telescope launched in June 2008 opening a new window on the highest energy sources in the universe. I will give a brief overview of how Fermi’s primary instrument, the Large Area Telescope (LAT), detects gamma-rays and its topics of study. One of the most exciting possibilities for the Fermi-LAT is the indirect detection of dark matter. Well-motivated and popular dark matter theory assumes that a significant component of dark matter is Weakly Interacting Massive Particles (WIMPs). I will go over WIMP basics, and the strategies involved in dark matter searches. Finally, I will talk about my work on the possibility to observe gamma lines from WIMP annihilation into gamma-gamma and gamma-Z final states. Detection of these lines would give convincing evidence for the existence of WIMPs and the WIMP mass. Location: Physics Bldg., Room 401]]> http://www.umbc.edu/blogs/physics/2009/10/seminar_wednesday_october_28_2009_at_330_pm.html http://www.umbc.edu/blogs/physics/2009/10/seminar_wednesday_october_28_2009_at_330_pm.html Seminars, Colloquia & Talks Wed, 28 Oct 2009 03:30:00 -0500 Lethal Landscapes: the Soviet-American history of plutonium, radiation and the communities that learned to love and then fight over the bomb Dr. Kate Brown
University of Maryland Baltimore County In 1944, brigades of construction workers, soldiers and prisoners transformed Richland, Washington from a ranch town to an ‘operators’ village’ exclusively reserved for workers at the new Hanford Engineering Works, a vast, ambling complex behind cyclone fencing that produced plutonium for the Manhattan Project. A few years later, inspired by Hanford, soldiers, prisoners and construction workers broke ground on another special city dedicated to plutonium workers. This one located in the thick, marshy forests of the southern Russian Urals. Both cities, Richland and Cheliabinsk-40*, existed to secure the secrets of plutonium. To keep the plutonium safe, plant employees were carefully-screened and closely-watched in isolated communities in remote locations. To keep the plutonium workers, engineers and scientists happy in these provincial locations, industrial leaders rewarded them handsomely and invested generously in the plutonium communities. In short, it took a village (really a small city) to produce the few kilograms of plutonium necessary for a nuclear bomb. The cities existed for four decades in relative obscurity (Richland) or outright secrecy (Cheliabinsk-40). Chernobyl changed all that. When reactor number four blew in April 1986, it gave a pulse to anti-nuclear groups that had long demanded to know what went on behind the cyclone fencing of military nuclear installations. As American and Soviet documents were de-classified, the public learned that the plants had dumped, each day, tens of thousands of curies of radiation into rivers, air and soil. As the days had accumulated into decades, the total of spilled curies mounted into the millions and then hundreds of millions. Since Chernobyl, the public memory of the plutonium cities has existed in a vortex of controversy. Commentators, residents, and activists characterize the plutonium cities variously—as radioactive and dangerous, or as safe and wholesome, “a great place to grow up.” People in towns surrounding the plutonium cities filed lawsuits for damage from what they charged were radiation-related health problems. Meanwhile, many residents in the cities fought against acknowledging a connection between the plutonium plants and local health problems. Brown argues that the contentious legacy of the plutonium cities derive from the fact that the cities were built as model modern communities with novel new security regimes. Meanwhile radiation was also a modern contaminant--undetectable without sensitive equipment and the source of illness only after long latency periods. In short, the incongruity of the comfortable and thriving plutonium cities against an invisible, radioactive geography enabled the tragedy of massive environmental contamination, enabled too the personal tragedies of contaminated bodies to go unnoticed and unheeded for decades and remain controversial to this day. Location: Physics Bldg., room 401]]> http://www.umbc.edu/blogs/physics/2009/10/seminar_wednesday_october_21_2009_at_330_pm.html http://www.umbc.edu/blogs/physics/2009/10/seminar_wednesday_october_21_2009_at_330_pm.html Seminars, Colloquia & Talks Wed, 21 Oct 2009 03:30:00 -0500 Interstellar Dust: The Universe through Rose-Colored Glasses Dr. Ulysses J. Sofia
American University Most astronomical observations are affected by interstellar dust, the submicron sized solid particles that live in the medium between stars. This is especially true as we observe increasingly distant objects with higher redshifts. The dominant method for accounting for light distortion by interstellar dust is an empirical correction which has a restricted range of validity. We are seeking to understand dust and its distorting affects in a context that is based in physics so that we may better correct for its effects on astronomical observations. We do this primarily through the study of the physical and chemical composition of dust, and radiative transfer models that relate potential dust grains to distortion effects. Data from the Hubble Space Telescope has allowed us to make great progress in this field over the past 18 years, but there are still fundamental pieces of the puzzle that do not fit together. Location: Physics Bldg., Room 401]]> http://www.umbc.edu/blogs/physics/2009/10/seminar_wednesday_october_14_2009_at_330_pm.html http://www.umbc.edu/blogs/physics/2009/10/seminar_wednesday_october_14_2009_at_330_pm.html Seminars, Colloquia & Talks Wed, 14 Oct 2009 03:30:00 -0500 How do we know whether to believe model predictions? Dr. Susan Strahan
Goddard Space Flight Center Chemistry climate models (CCMs) embody the state of our knowledge of atmospheric chemistry and physics. They are used to predict future changes in atmospheric composition and climate based on estimates of future emissions of CO2, CH4, N2O, chlorofluorocarbons (CFCs), and other trace species. Every four years, chemistry climate modeling groups participate in an international effort sponsored by the World Meteorological Organization (WMO) to predict the future state of the stratospheric ozone. 13 CCMs participated in the most recent WMO assessment and they produced a wide range of predictions for benchmarks such as the date of the disappearance of the Antarctic ozone hole and the return of northern midlatitude ozone to 1980 levels. How do we know which, if any, of the model predictions to believe? The answer lies in the use of observations to assess the ability of CCMs to represent key aspects of stratospheric circulation and chemistry. The analyses of several decades of aircraft, balloon, and satellite trace gas observations such as O3, H2O, CH4, and N2O have identified many important transport processes in the stratosphere. We use observational analyses to derive diagnostics for stratospheric transport processes, and because of them we now understand many aspects of stratospheric circulation, e.g, the rate at which air ascends in the tropical stratosphere and the existence of transport barriers in the subtropics and polar regions. Diagnostics are applied to model simulations to assess whether models realistically represent known processes. In recent years an international group of scientist has been systematically applying a growing set of stratospheric chemistry and transport diagnostic to CCMs in order to better understand their behavior and determine model credibility. This effort is providing a rational basis for distinguishing between model predictions of the future of stratospheric ozone. Location: Physics Bldg., Room 401]]> http://www.umbc.edu/blogs/physics/2009/10/seminar_wednesday_october_7_20.html http://www.umbc.edu/blogs/physics/2009/10/seminar_wednesday_october_7_20.html Seminars, Colloquia & Talks Wed, 07 Oct 2009 03:30:00 -0500 Coherent Control of Electrical Current and Terahertz Radiation Dr. Ki Yong Kim
University of Maryland College Park Sandwiched between the traditional optical and microwave regimes, far infrared or terahertz (THz) frequency has recently drawn special attention due to its ubiquitous nature, as well as its potential for molecular sensing, biomedical imaging and spectroscopy, security scanners, and plasma diagnostics. For these applications, there is a present and growing need for high-energy, compact THz sources at a tabletop-scale. In this effort, I will present our recent demonstration of high-energy (>5 microjoule), super-broadband (>75 THz) THz radiation generation using a tabletop femtosecond laser [1]. In this scheme, an ultrafast pulsed laser’s fundamental and second harmonic fields are mixed in a gas of atoms or molecules, causing them to ionize. The resulting plasma can generate a directional electron current and simultaneous far-field THz radiation, all coherently controlled by the laser field amplitudes and relative phase. By controlling the relative phase, we can also switch the output energy between THz and harmonics. Location: Physics Bldg., room 401]]> http://www.umbc.edu/blogs/physics/2009/09/seminar_wednesday_september_30_2009_at_330_pm.html http://www.umbc.edu/blogs/physics/2009/09/seminar_wednesday_september_30_2009_at_330_pm.html Seminars, Colloquia & Talks Wed, 30 Sep 2009 03:30:00 -0500 Er:YAG is a 2.46-level laser Dr. Jeffrey O. White
Army Research Laboratory For a high power solid state laser in the 1.6 micron spectral region, Er3+ is a natural choice for the active ion. One advantage is the possibility of low-quantum-defect pumping with diode lasers. A disadvantages is the presence of upconversion. I will discuss recent modeling and experiments on lasing, and z-scan measurements of upconversion. 'Level parameters' will be proposed for quantitative comparison of rare-earth-doped solid-state laser media, operating temperatures, pump and laser wavelengths. Location: Physics Bldg., Room 401]]> http://www.umbc.edu/blogs/physics/2009/09/seminar_wednesday_september_23_1.html http://www.umbc.edu/blogs/physics/2009/09/seminar_wednesday_september_23_1.html Seminars, Colloquia & Talks Wed, 23 Sep 2009 03:30:00 -0500