Goddard DEVELOP Students: Using NASA Remote Sensing Technology to Study the Chesapeake Bay Watershed

The DEVELOP National Program is an Earth Science research internship, operating under NASA s Applied Sciences Program. Each spring, summer, and fall, DEVELOP interns form teams to investigate Earth Science related issues. Since the Fall of 2003, Goddard Space Flight Center (GSFC) has been home to one of 10 national DEVELOP teams. In past terms, students completed a variety of projects related to the Applied Sciences Applications of National Priority, such as Public Health, Natural Disasters, Water Resources, and Ecological Forecasting. These projects have focused on areas all over the world, including the United States, Africa, and Asia. Recently, Goddard DEVELOP students have turned their attention to a local environment, the Chesapeake Bay Watershed. The Chesapeake Bay Watershed is a complex and diverse ecosystem, spanning approximately 64,000 square miles. The watershed encompasses parts of six states: Delaware, Maryland, New York, Pennsylvania, Virginia, and West Virginia, as well as the District of Columbia. The Bay itself is the biggest estuary in the United States, with over 100,000 tributaries feeding into it. The ratio of fresh water to salt water varies throughout the Bay, allowing for a variety of habitats. The Bay s wetlands, marshes, forests, reefs, and rivers support more than 3,600 plant and animal species, including birds, mammals, reptiles, amphibians, fish, and crabs. The Bay is also commercially significant. It is ranked third in the nation in fishery catch, and supplies approximately 500 million pounds of seafood annually. In addition to its abundant flora and fauna, the Chesapeake Bay watershed is home to approximately 16.6 million people, who live and work throughout the watershed, and who use its diverse resources for recreational purposes. Over the past several decades, the population throughout the watershed has increased rapidly, resulting in land use changes, and ultimately decreasing the health of the Chesapeake Bay Watershed. Over the course of 2009-2010, student teams carried out two independent research projects focused on the Chesapeake Bay Watershed. The first investigated the threat of invasive species to forests in Maryland. The second investigated the detection of winter cover crops throughout the watershed from satellite data

Modeling hydrodynamic self-propulsion with Stokesian Dynamics. Or teaching Stokesian Dynamics to swim

We develop a general framework for modeling the hydrodynamic self-propulsion (i.e., swimming) of bodies (e.g., microorganisms) at low Reynolds number via Stokesian Dynamics simulations. The swimming body is composed of many spherical particles constrained to form an assembly that deforms via relative motion of its constituent particles. The resistance tensor describing the hydrodynamic interactions among the individual particles maps directly onto that for the assembly. Specifying a particular swimming gait and imposing the condition that the swimming body is force- and torque-free determine the propulsive speed. The body’s translational and rotational velocities computed via this methodology are identical in form to that from the classical theory for the swimming of arbitrary bodies at low Reynolds number. We illustrate the generality of the method through simulations of a wide array of swimming bodies: pushers and pullers, spinners, the Taylor=Purcell swimming toroid, Taylor’s helical swimmer, Purcell’s three-link swimmer, and an amoeba-like body undergoing large-scale deformation. An open source code is a part of the supplementary material and can be used to simulate the swimming of a body with arbitrary geometry and swimming gait

Giving It Another Shot: A Reexamination of the Second or Subsequent Conviction Language of the Firearm Possession Sentencing Statute

The effects of the current interpretation of the federal firearm possession sentencing statute are severe, often mandating the imposition of de facto life sentences for first-time offenders. For example, suppose a twenty-three-year-old first-time offender was found guilty in a federal district court of robbing $500 from two financial institutions in two days and carrying a single firearm during the robbery spree. Under the Federal Sentencing Guidelines, this first-time offender would be subject to a sentence ranging between forty-one and fifty-one months for each robbery. Thus, for the substantive offenses, the sentence would total eighty-two to 102 months, or six years and ten months to eight years and six months. But because the offender was found to have been carrying a firearm, he could also be convicted of two counts of possessing a firearm in furtherance of a crime of violence, and thus subject to additional, mandatory sentences. Under the current interpretation of 18 U.S.C. 924(c) ( 924(c) ), the offender would be subject to a five- year sentence for the first firearm possession count in accordance with 924(c)(1)(A) and a twenty-five-year sentence for the second firearm possession count in the same proceeding in accordance with 924(c)(1)(C). Added together and without any adjustments by the trial judge, the total sentence for this hypothetical crime spree ranges from thirty-six years and ten months to thirty-eight years and six months. Serving his full sentence, the twenty-three-year-old first-time offender would thus be in prison until he is around sixty years old. Furthermore, the Comprehensive Crime Control Act of 1984 abolished parole in the federal prison system, so federal inmates must now serve at least eighty-five percent of their sentences. As the above hypothetical scenario reveals, criminal sentencing in federal courts is shaped by both the advisory Federal Sentencing Guidelines ( Sentencing Guidelines or Guidelines ), created by the United States Sentencing Commission, and by mandatory statutory provisions, passed by Congress. In this example, 924(c)(1)(A) mandates a minimum five-year sentence for the possession of a firearm during the commission of a violent crime or drug trafficking offense, and 924(c)(1)(C) mandates a minimum twenty-five-year sentence for possession of a firearm in the case of a a second or subsequent conviction

Measurements and Modeling of Total Solar Irradiance in X-class Solar Flares

The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment can detect changes in the total solar irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-class solar flares for the first time. Presented here is a robust algorithm for determining the radiative output in the TIM TSI measurements, in both the impulsive and gradual phases, for the four solar flares presented in Woods et al., as well as an additional flare measured on 2006 December 6. The radiative outputs for both phases of these five flares are then compared to the vacuum ultraviolet (VUV) irradiance output from the Flare Irradiance Spectral Model (FISM) in order to derive an empirical relationship between the FISM VUV model and the TIM TSI data output to estimate the TSI radiative output for eight other X-class flares. This model provides the basis for the bolometric energy estimates for the solar flares analyzed in the Emslie et al. study