Date: Wednesday, September 5, 2012
Time: 9:30am
Location: PHYS 401

Title
Optical, microphysical and compositional properties of volcanic ash, soil dust, urban pollution and other aerosols.

Abstract
The microphysical properties of aerosols are of fundamental importance in the estimation and prediction of their direct and indirect forcing effects on the balance of energy of the Earth. One of the main parameters missing in current atmospheric models is the complex refractive index of aerosol particles from the ultraviolet (UV) to the short-wave infrared (SWIR) wavelength. The main objective of this project is to perform a detailed characterization of important optical and microphysical properties of aerosol particles, and create a database for these commonly missing parameters. This research proposes to investigate the geometrical size distribution, shape, material density, and imaginary part of the refractive index of different types of aerosols from UV to SWIR wavelengths. The proposed methodology includes in situ measurements using the LACO-UMBC Reflec-Nephelometer, and aerosol in situ filter collection using the LACO Aerosol Sampling Stations. Also, materials can be collected directly from the ground (like deposited volcanic ash, or dust) and brought to our laboratory for posterior re-suspension. Our experimental setup allows us to separate particles into PM10, PM2.5, or PM1.0. Particles collected on filters are analyzed by different techniques, such as Scanning Electron Microscopy (SEM) for determination of size distribution, reflectance measurements for determination of the optical absorption properties as a function of the wavelength, and Proton Induced X-ray Emission (PIXE) or X-Ray fluorescence for elemental composition. Finally, the spectral imaginary part of refractive index (from 300 to 2500nm) is derived numerically from the measurements of mass absorption coefficient, size distribution and geometrical shape of the particles, and the density of the material. The selected samples for this study include materials collected at vicinity of volcanic eruptions at Eyjafjallajökull (Iceland), Puyehue (Chile), Mont Saint Helens and Fuego Volcano (USA), dust from central Sahara at Birmoghrein (Mauritania) and Bordj Mokhtar (Algeria), and urban pollution with distinct organic and black carbon components.

Date: Thursday, September 6, 2012
Time: 10:00am
Location: PHYS 401

Title
Physical Processes Influencing the Mid-Atlantic Planetary Boundary Layer with Applications in Air Quality and Wind Energy

Abstract
Understanding the Planetary Boundary Layer (PBL) dynamics is essential in air quality, wind energy and numerical weather prediction, specifically the vertical mixing processes of heat, momentum and constituents. Currently, it is suggested to be the most important factor in modeling the lower atmosphere especially in regions of complex terrain such as the Mid-Atlantic region. In this proposal an synergy of measurements and models will be used to investigate vertical mixing processes in the Mid-Atlantic region. The utilization of a baroclinic zone as a wind resource in the Mid-Atlantic region will be analyzed by use of high resolution model runs in comparison with wind, aerosol, and other measurements. These model and data analysis aim to improve the current understanding of turbulent mixing in the complex terrain of the Mid-Atlantic Region.

In a typical solar cell, only part of the energy from absorbed light is converted to electricity. Each absorbed photon produces an electron-hole pair, i.e. exciton, which ultimately cools till it possesses only the semiconductor bandgap energy. The excess energy that is typically wasted can be harnessed by exploiting multiple exciton generation, whereby the excess energy is used to excite additional excitons. This process was recently shown to be more efficient in nanocrystals than in the bulk. We have discovered that multiple exciton generation is significantly enhanced in quasi-one-dimensional nanorods compared to nanocrystals. Devices exploiting this enhancement have the potential to show enhanced photovoltaic efficiencies. I will discuss our transient absorption measurements of multiple exciton generation in PbSe nanostructures. Complications arising from the quasi-one dimensionality of these nanostructures will be explained. Multiple exciton dynamics and lifetimes will also be discussed, as well as promising future directions.

Location: Physics Bldg., Room 401

It may seem somewhat surprising that information is governed by uncertainty. Put another way, if we know what someone is going to tell us, then there would be no need for listening. The uncertainty of that communication, entropy, is a measure of the information gained. In this presentation, I will discuss some basic concepts of entropy along with some of our recent experiments on studies of entanglement entropy and quantum imaging using compressive sensing. Lastly, I will present results on recent studies of quantum noise on compressive signals. These experiments will be couched in the ideas of entropy and the information gained as a function of the number of photons. Compressive sensing has a wide range of possible application including imaging through obscurants, hyperspectral imaging, and high resolution single pixel imaging in otherwise difficult regions of the spectrum to image. These concepts are crucial in understanding compressive sensing as a sensing paradigm. Based on these ideas, I will present details of a novel compressive sensing Lidar system.

Location: Physics Bldg., Room 401

An evolving temperature record from the Greenland Summit, at approximately 3216 m in elevation, has documented unusual periods of near and above freezing air temperatures especially in July 2012. Since August 2005, data has been collected from well-calibrated and actively-ventilated temperature sensors at a NOAA-ESRL climate observatory. Comparison of these data from a nominal 2 m height above the ice sheet surface over the past seven summers reveals several periods of unusual warmth at the highest elevations of the ice sheet during 2012. Field observations from station personnel indicate slush formed during the period of greatest warmth and an ~2 cm thick ice crust has been preserved in the snow stratigraphy. The warm temperatures at Summit were independently assessed and mapped across Greenland using a combination of SSMIS passive microwave, Oceansat scatterometer, and MODIS infrared data. http://www.nasa.gov/topics/ earth/features/greenland-melt.html

Detailed analysis of the available data indicates that temperatures rose to or above freezing for almost 6.5 hours on July 11 at Summit Station. A maximum air temperature of 1 degree C was recorded repeatedly in the 1-minute averages during this period. NOAA’s data also indicated brief periods at or above zero on July 12th and 29th as well. These anomalously warm air-temperature periods can now be compared and contrasted with equivalent-quality data from earlier records (automatic weather stations began operating in May 1987 during the GISP2 project) and used to calibrate indications of warm surface temperatures derived from satellite sensors.

Location: Physics Bldg., Room 401

As an astronomer, I typically would be classified as a "Scientist," and of course, Technology and Engineering are at the heart of how scientists collect our data. We all agree that Mathematics is the language of science. It is the inextricable nature of these four subjects that is at the heart of the STEM education movement. The predicted need for scientists and engineers in America, and the corresponding lack of interest in these subjects demonstrated by American students, lends a sense of urgency to the movement. This talk will provide a brief summary of one astronomer's journey from the telescope to STEM teacher education and highlight some areas where university STEM faculty can contribute their expertise to the inspiration of the next generation of American scientists and engineers.

Location: Physics Bldg., Room 401