Location: Physics Bldg., room 401

Location: Physics Bldg., room 401

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

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)

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

Location: Physics Bldg., Room 401

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

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

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

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

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

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

Humans have been altering terrestrial ecosystems for millennia, beginning with early use of fire for hunting and leading now to the wholesale restructuring of the terrestrial biosphere for use in agriculture and settlements. This presentation will explore the global implications of land use by humans, beginning with the first farmers and then detailing the global ecological patterns created by human activities from the 1700s to the present. Anthropogenic global patterns in ecosystem and land surface processes are likely causing global changes in atmospheric pattern and process- a fruitful pathway for future research.

Location: Physics Bldg., Room 401

Trapped atomic ions are among the most promising candidates for quantum information processing. All of the fundamental quantum operations have been demonstrated on this system, and the central challenge now is how to scale the system to larger numbers of qubits. By entangling atomic qubits through both deterministic phonon and probabilistic photon interfaces, the trapped ion system can be scaled in various ways for applications in quantum communication, quantum computing, and quantum simulations. I will discuss several options and issues for such atomic quantum networks, along with state-of-the-art experimental progress.

Location: Physics Bldg., Room 401

The talk will introduce Lord Rayleigh and Gustav Mie in order to help us understand their work and character. Their research on light scattering by small objects is crucial to the understanding of radiative processes in the atmosphere, which motivated the joint investigation of the two scientists. Rayleigh worked out the details of light scattering by gases, whereas Mie set the foundation for the study of light scattering by clouds and aerosols.

Rayleigh was a talented theorist, experimenter, leader and administrator. An English landowner in the Victorian era, he had a very stable and prosperous environment. He fully took advantage of his financial situation for the benefit of science and humanity. He was an average student in middle school and developed his math skills by hard work. He always strived for economy, obtaining accurate results with cheap and simple equipment, since he worked from his own money. He touched almost every area of classical physics. The discovery of argon earned him the Nobel Prize and a number of physical phenomena and mathematical methods are named after him. Atmospheric scientists use his truly innovative and accurate results regarding light scattering by gas molecules from 1871. The answer to the fundamental question: “Why is the sky blue?” lies in his work.

A reserved academic genius, Mie led a middle class life in Germany in peaceful and during turbulent times during the first half of the 20th century. Some of his significant contributions are in field theory, general relativity and X-ray diffraction. Mie’s 1908 paper on light scattering by spherical particles (of any size) is a complete work by itself. He applies first principles, documents the computational method and its implementation, reaches numerical results, and successfully compares them to experimental work. His energetic work and studies made him a foremost expert of his day on electricity and magnetism. His textbook on electrodynamics ran into several editions. His computational method for modeling light scattering and absorption by spherical particles is used in atmospheric remote sensing today and it is the foundation and benchmark of more advanced methods for modeling radiative effects of small airborne particles.

Today, Rayleigh and Mie are linked through the importance of their work to atmospheric physics but they were two different men from different circumstances.

Location: Physics Bldg., Room 401

Today’s High Technology companies, particularly those involved in defense related research, are utilizing advances associated with physics research to an increasing extent. Many of the devices and technologies employed in advanced sensors and computing are leveraging breakthroughs in physics and related disciplines. These breakthroughs encompass quantum optics, quantum information, nano-science, solid state physics, superconductivity, materials science and many other disciplines.

Physics Bldg., room 401

There will be no seminar Wednesday, April 8, 2009

One of the first steps in spacecraft mission design is the selection of orbit and attitude scenarios that enable the science. This selection process works best when scientists and engineers begin the dialog early to understand the geometry, the science measurements, and the platform orbit and attitude accuracy. Flight Dynamics analysis helps clarify accuracies available with particular sensor complements.

This affects costs both through the hardware and through the need for initial and ongoing ground support. In the first part, this talk presents an overview of general considerations needed for orbit and attitude analysis. The second part gives an introduction to Cloud CubeSat, a very small, but very exciting student spacecraft (picosat) for side-imaging of clouds.

Location: Physics Bldg., Room 401

One, relatively new interface between biology and physics occurs within astrobiology: the quest to develop a scientific understanding of life's relationship with the physical universe (i.e. its origin(s) and likely distribution.) At present we know only one example of life, and our understanding of its origin remains patchy at best.

However, science often challenges us to extrapolate from incomplete observations of the actual into reasoned inferences of what is possible. For astrobiology, this means developing our understanding of how and why we emerged on this planet. Answers require extensive interdisciplinarity: how typical is our solar system of other star-systems in the galaxy? what properties of Earth are typical or unusual for a planet? How are these properties related to life's emergence here? What can we learn about life's boundaries by examining the biodiversity we encounter today? Once life had evolved, what aspects of our 4 billion year evolutionary history were likely or even inevitable? In this talk I will approach these questions from a biologist's perspective, showing where my own research interests lie within this bigger topic. I hope to illustrate the sorts of questions that we are learning to answer (and the assumptions we still make). I will also encourage you to help me better understand what Physics can contribute to the bigger questions.

Location: Physics Bldg., Room 401

On Earth, the vast majority of precipitation originates as snow particles in the atmosphere. At middle and high latitudes, snow falling on land contributes to snowpack; a critical source of freshwater for spring and summer months. Snow on the ground also provides an atmospheric cooling mechanism due to it's high visible-light albedo. In the middle and lower latitudes, falling snow often melts, becoming rain -- feeding our streams, rivers, and lakes. The growth and melting of snow also contributes to heating / cooling of the atmosphere through phase change, influencing atmospheric motions and stability. It is critical, especially given our changing climate, to be able to accurately measure atmospheric snow on a global basis for long time periods.

One of the key challenges to measurement is understanding how the physical characteristics a snowflake influence millimeter-wavelength observations made from a satellite-based remote sensing platform. On both the microscopic and synoptic scales, the physical aspects of the initiation, growth, and dissipation of an individual snowflake are reasonably well understood. However, when considering a precipitating cloud containing a wide variety of sizes, habits, orientations, phases, of snow, the problem of characterizing the 3-D scene in analytical fashion becomes troublesome.

In this talk I will focus the physical processes which contribute to the growth and eventual destruction of an individual snowflake, and I will describe how these individual processes are treated when considering a diverse ensemble of snow particles within, for example, a precipitating cloud. I will also briefly describe how the physical properties of snow particles influence incident electromagnetic waves at centimeter and millimeter wavelengths (~1-22 mm or 13 to 220 GHz), and the ramifications for inferring information about snow based on satellite observations at these wavelengths.

Location:
Physics Bldg., room 401

Location: Physics Bldg., room 401

Location: Physics Bldg., room 401

Modern computer games exhibit a number of elements of elementary physics. This is perhaps most visible in kinematic simulation of articulated bodies, the so-called "rag doll physics" for character animation. However, physics can also be found in fluid simulation, optical effects with participating media, and models of surface reflectance. These methods must run effectively on a range of consumer hardware, and must be fast, finishing within a fraction of the 10-30 ms time available per frame. This talk will present some of the currently popular methods and demonstrate their results, and discuss the state of consumer-level hardware to accelerate physics simulation.

Location Physics Bldg., room 401

In this talk I will describe what surface plasmon polaritons (SPPs) are, how they are excited, and how they can be used to produce both very large, and effectively negative, relative permittivities and group refractive indices. The effectively negative permittivities and refractive indices that can be produced in metal/dielectric composite nanostructures has allowed the first demonstration of 2-D cloaking in the visible part of the spectrum. The general principle and limitations of practical cloaking will also be discussed, and some of the approaches that are being considered for reducing the visibility of 3-D objects. The effectively large refractive indices that can be experienced by SPPs also allows the construction of super-resolution microscopes.

Location Physics Bldg., Room 401

The international Montreal Protocol on Substances that Deplete the Ozone Layer requires that the Parties assess the control measures on the basis of available scientific, environmental, technical, and economic information. To achieve this, the Parties are required to convene appropriate panels of experts who will report their conclusions to the Parties. The 2010 Scientific Assessment of Ozone Depletion is now underway and is the seventh in the set of major assessments prepared by the Scientific Assessment Panel as direct input to the Montreal Protocol process. This talk will highlight our current understanding of stratospheric ozone and its related science issues as we embark on this next assessment. Specific points of focus will include: ozone depleting substances, ozone observations and projections, ground level ultraviolet radiation, greenhouse gases and ozone, and scientific gaps and needs.

Location: Physics Bldg., Room 401

Due to the Thanksgiving Holiday, there will be no seminar on Wednesday, November 26, 2008.

What is a physicist? A case is made for defining a physicist as anyone with a bachelor's degree (or higher) in physics. Under this definition, a large fraction of physicists are hidden, that is, they have left, or never belonged to, the traditional lot of Ph.D. academicians. Data from the Statistical Research Center at the American Institute of Physics and from a survey of members of the national physics honor society, Sigma Pi Sigma, show the vast array of actual career paths taken by physicists. From spandex to blackberries to bioinformatics to flight control to wind energy to spintronics, physicists can be found in nearly every job sector with some of the coolest careers around.

Location: Physics Bldg., Room 401

In this talk I show results of cosmological simulations suggesting a possible identification of at least some dwarf spheroidal galaxies in the Local Group as the fossils of the first galaxies (``pre-reionization fossils''). I also revisit the problem of gas accretion onto minihalos after reionization. I show that primordial minihalos with v_{cir}<20 km/s stop accreting gas after reionization, as it is usually assumed, but in virtue of their increasing concentration and the decreasing temperature of the intergalactic medium as redshift decreases, they may have a late phase (at redshift z<2) of gas accretion and possibly star formation. As a result we expect that pre-reionization fossils have a more complex star formation history than previously envisioned. The dwarf spheroidal galaxy Leo~T fits with this scenario. Another prediction of the model is the existence of a population of gas rich minihalos that never formed stars. A subset of compact high-velocity clouds may be identified as such objects but the bulk of them may still be undiscovered.

Location: Physics Bldg., Room 401

We have made a new type of X-ray Diffractometer that uses CCD technology developed for X-ray astrophysics. The instrument provides X-ray diffraction and fluorescence information from unprepared samples. This can be used to identify minerals and provide surface texture information. The instrument is designed to minimize mass, power, and risk for planetary exploration.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.

The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) program is searching for antimatter in the galactic cosmic radiation by precisely measuring the elemental and isotopic composition of the light cosmic ray component. The experiment is a highly successful US-Japanese collaboration and over the past 15 years, the BESS payload has had eight low geomagnetic cutoff, northern latitude flights and two long duration balloon flights from Antarctica. The most recent flight of the BESS-Polar experiment was a long-duration Antarctica flight, which occurred between December 2007 and January 2008. This flight yielded 24.5 days of observation time at a time of low solar activity (solar minimum). We will review the BESS program and report the results of the antiproton and proton spectra measured in the BESS-Polar I flight, the search for cosmic antinuclei, and the status of the BESS-Polar II analysis.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.

This seminar has been cancelled! There will be no seminar on Oct. 22, 2008.

When the state of a quantum system cannot be separated into the states of its constituents, we say the system is entangled. In some cases, the presence of entanglement means that measurements on different parts of a system have correlations stronger than can be explained by any purely classical theory. Einstein derisively called this effect “spooky action at a distance,” but now we know that entanglement is a hallmark of quantum mechanics. In this talk, I will investigate entanglement in particle systems. Different types of entanglement can occur in such systems, and dynamical processes can change the amount of entanglement.

In particular, I will look at how entanglement is generated between particles by scattering, the fundamental experimental paradigm for particle physics.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.

Supercooled cloud water is in a metastable thermodynamic state and, therefore, the associated phase transition (to ice) must be irreversible. Has this irreversibility been considered? Does it matter to atmospheric scientists? I'll argue No and Yes, respectively.

We used measured temperature-dependent heat capacities of supercooled water and ice to calculate the ice-(metastable) water entropy difference and to estimate a lower bound on the amount of latent heat, liberated by the freezing droplets. The calculation is compared with tabulated values of the latent heat of fusion with surprising results. Based on a novel physical picture of the freezing process, we suggest a simple estimate for the effective latent heat, suitable for heat budget calculations of glaciating clouds. In addition, we arrive at a quadratic dependence on supercooling for the irreversible contribution to heat exchange during the freezing process. Implications for optical properties of the "hurriedly made ice" will also be discussed.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.

The Solar Shield project is a collaborative effort between the Electric Power Research Institute (EPRI) and NASA. It was launched to utilize state-of-the-art space physics models in experimental space weather forecasting. More specifically, Solar Shield is using an extensive pool of coupled space physics models hosted at the Community Coordinated Modeling Center (CCMC) at NASA/GSFC. The models propagate information obtained from solar observations to the interplanetary medium, from the interplanetary medium to the Earth’s magnetosphere and ionosphere and eventually all the way down to the surface of the Earth. Here is where geomagnetically induced currents (GIC) flowing in high-voltage power transmission systems are calculated. The two-level forecasting system provides both 2-3 day lead-time and 30-60 minute lead-time forecasts, and it is already capable of generating predictions of GIC flow at few individual nodes of the North American power transmission system.

An important special aspect of the project is the participation of the end-user, i.e. power transmission industry, in the development of the forecast products. The goal is to define a system, which, when integrated into EPRI’s SUNBURST decision support tool, will help power transmission system operators to make decisions about possible mitigation actions during “poor” space weather conditions. Industry participation will also enable quantification of the economic value of the generated GIC forecasting system. The result of the economic analysis can be used to indicate if there is a business case for transitioning the experiment into operations.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.

Many new device applications in micro- and nanotechnology require the ability to fabricate complex, 3D structures. Conventional lithographic techniques are not well suited to the creation of many such structures, which has fueled interest in the development of novel fabrication techniques. One rapidly emerging technology for 3D fabrication is multiphoton absorption polymerization (MAP). In MAP, a tightly focused laser beam is used to exposure a photoresist exclusively at the laser focal point. By moving this focal point over a desired pattern in three dimensions, arbitrarily complex structures with feature sizes as small as 100 nm can be created. I will discuss some of our recent progress in expanding the capabilities of MAP as well as in creating functional devices.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.

The extragalactic background light (EBL) that permeates the Universe in the optical-IR is essentially an integral of the light produced from the time the first stars were formed in our Universe until now. As such, it is a quantity that is very closely connected to the galaxy/ large scale structure formation in our Universe. Unfortunately, measuring the EBL has been proven practically impossible, for very simple reasons that I will discuss in the first part of my talk. Luckily, we found an unexpected, parameter-free way to break the deadlock of measuring the EBL with GLAST, NASA's new gamma-ray satellite. This will be the second part of my talk. GLAST measurements are underway and the determination will take about two years.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.

Anyone who travels has likely heard the following warning: “FAA regulations prohibit the use of portable electronic devices during takeoff or landing.” The modern aircraft contains an ever-growing array of electronic sensors used in navigation and communication. At the same, time, we have seen a rapid explosion not only in the number of handheld electronic appliances carried by passengers, but also in their frequencies of operation. This has lead to growing concern that electromagnetic radiation from such devices could interfere with navigation and communication.

One potential solution to this problem is to replace the coaxial cables and wires normally used to transmit electronic signals in the aircraft with optical fibers. Compared to coaxial cables, optical fibers are smaller, lighter, and less expensive. The bandwidth available in a single fiber is large enough to accommodate the data from thousands of coaxial cables, and the loss in optical fiber is negligible in comparison to coaxial cables, especially at microwave frequencies. Most importantly, optical fibers are completely immune to electromagnetic interference, which makes them especially attractive for avionic sensor networks. The key challenge is to find a ways to modulate and demodulate analog microwave signals onto an optical carrier without distorting or impairing the microwave signal.

In this talk, I will discuss our recent research on using phase modulation instead of more commonly-used intensity modulation to impose a microwave signal on an optical carrier. To date, there has been very little research on developing low-distortion linearized phase-modulation systems. Unlike earlier intensity-modulation schemes, which often required multiple interconnected modulators or signal pre-distortion, our system is unique in that it uses only a single electrooptic phase modulator driven by an unmodified input signal, and could entirely eliminate the third-order intermodulation distortion that usually limits the dynamic range.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.

In former times, materials were developed tuning their chemical composition to get the desired properties. Hence, material analysis was used to get the chemical composition in a broad sense. Though initially based on wet-chemistry processes, material analysis by physical methods turned into an ever-growing field. Ion Beam Analysis and Inductively Coupled Plasma Mass Spectrometry are just two examples of a field in which the detection limits, and sample sizes are being extraordinarily reduced enabling nowadays the measurement of sub-ppb levels of any element of the whole periodic table in microscopic samples. The billionaire semiconductor industry is just one of the applications of modern ultra low detection analysis by physical (dry) methods. Trace elements in materials can be used to trace archaeological technologies. Trace elements in blood serum may be used in the future to trace diseases, eventually cancer. Trace elements in aerosols can indicate its origins and transport properties. In this new era, the question whether an element is or is not present in a sample has changed to what are the elemental concentration levels and how they correlate to the bio-physical-chemical processes involved.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.

Earth reflectances are highly anisotropic. The most anisotropic signal is observed over water surfaces where the glint effect generates a reflectance that varies by several orders of magnitude as a function of the observation geometry. Over land surfaces, the variations are not as large, but nevertheless significant. The reflectance of a given target varies with the observation geometry by a factor of up to four. This anisotropy causes some difficulties for a quantitative analysis of satellite measurement time series as the variability due to the changing measurement geometry may be as large as the geophysical signal that is monitored.

The POLDER/Parasol spaceborne instrument is a great tool to monitor these effects. Indeed, it provides up to 16 measurements of the same targets, with varying view angles, as the satellite flies over it. We will present and discuss the directional reflectance measurements, and the model that was developed to reproduce the observed signatures. The model is then used to correct the time series, for a much better identification of the geophysical signal, such as the vegetation dynamic.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.