Investigations of Phytoplankton Diversity in Chesapeake Bay

Characterizing the diversity of a community in relation to environmental conditions and ecosystem functions are core concepts in ecology. While decades of research have led to a growing comprehension of diversity in many ecosystems, our understanding in aquatic habitats and microbial organisms remains relatively limited. Phytoplankton represent a diverse and important group that contribute approximately half of global primary productivity and are intrinsically connected to changing environmental conditions, especially in systems as dynamic as estuaries. To better understand the ecological processes governing phytoplankton composition and diversity, spatial and temporal patterns of environmental parameters and their relation to the algal community of Chesapeake Bay were analyzed using data collected over a 25 year period (1985-2009). The phytoplankton community of Chesapeake Bay, containing 1480 taxa was characterized as one of high richness and low evenness, with a single species accounting for at least half of the biomass in almost one third of all samples examined. High gamma-diversity was attributed to seasonal succession of dominant flora and spatial heterogeneity along the estuarine gradient with high species turnover between salinity regions. Alpha-diversity was greatest in freshwater and polyhaline regions, and minimal in lower mesohaline waters. Multivariate ordination analysis identified regional differences corresponded to salinity, turbidity, and nutrient gradients, with lowest richness in regions of intermediate salinity, total nitrogen and phosphorus concentrations and highest dissolved organic nitrogen. Temporal factors included negative impacts of streamflow related nutrient increases leading to greater algal abundance and lower diversity particularly within the polyhaline Bay. Results indicate that greater algal biomass was associated with higher richness and lower evenness, and may be associated with lower ecosystem stability, with greater variance in inter-annual phytoplankton biomass. To address short-term environmental variability including nutrient loading, daily sampling of the Lafayette River, was conducted in spring 2006. During consecutive blooms of Cryptomonas sp. and Gymnodinium instriatum up to 99% of total biomass was due to the individual bloom species, although species richness was not significantly reduced. Time lag correlations indicated that the Cryptomonas sp. bloom was related to precipitation related increases in dissolved inorganic nitrogen concentrations, while the G. instriatum bloom followed periods of reduced nitrogen concentrations that were accompanied by an algal community of high richness and low evenness. Based on its connectivity to both environmental and biological variables, phytoplankton diversity is recognized as a significant indicator of ecosystem condition, with high species richness and evenness as potential goals for restoration efforts

Two-dimensional bin packing: Innovations and statistical analysis.

In this thesis, we introduce and analyze a new two dimensional bin packing algorithm. We focus on the problem of packing rectangles with known dimensions into a fixed width, infinite height bin so as to minimize the total height of the packing. To analyze the algorithm we use statistical methods to compare the known optimal pack heights with the pack heights obtained by the algorithm on a set of randomly generated test problems. This gives us a general technique to not only analyze a single algorithm, but also one which may be used to compare existing algorithms. The method to generate test problems is another contribution of this thesis.Dept. of Economics, Mathematics, and Statistics. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1997 .B72. Source: Masters Abstracts International, Volume: 37-01, page: 0271. Adviser: Richard Caron. Thesis (M.Sc.)--University of Windsor (Canada), 1997

A teleoperated unmanned rotorcraft flight test technique

NASA and the U.S. Army are jointly developing a teleoperated unmanned rotorcraft research platform at the National Aeronautics and Space Administration (NASA) Langley Research Center. This effort is intended to provide the rotorcraft research community an intermediate step between wind tunnel rotorcraft studies and full scale flight testing. The research vehicle is scaled such that it can be operated in the NASA Langley 14- by 22-Foot Subsonic Tunnel or be flown freely at an outside test range. This paper briefly describes the system's requirements and the techniques used to marry the various technologies present in the system to meet these requirements. The paper also discusses the status of the development effort

The social origin of violent behavior

This study examines the social origins of extremely violent behavior. Numerous explanations of violent offenders have focused on biological, psychological, environmental or a combination of these factors to explain violence. Most explanations of violent behavior fail to take a holistic approach to understand the cause of violent behavior. This study is an analysis of the applicability of the violentization theory. Data was obtained through in-depth semi-structured interviews from six violent offenders in a residential treatment faciIity in the Midwest. Findings indicate that for most offenders, the violentization theory is consistent with their social experiences. However, two exceptions pertained to the violentization process where the individuals stopped their journey along this socialization of violence. Further analysis revealed that the violentization process often starts within the home due to the violent subjugation by family members. The further along some are in the violentization process, the more consistent and violent their crimes are. This study finds that the violentization theory can be used to develop public policy programs aimed at stopping individuals from progressing through these stages

Demonstration and Validation of the Use of Passive Samplers for Monitoring Soil Vapor Intrusion to Indoor Air

This thesis documents a demonstration/validation of passive diffusive samplers for assessing soil vapor, indoor air and outdoor air concentrations of volatile organic compounds (VOCs) at sites with potential human health risks attributable to subsurface vapor intrusion to indoor air. The study was funded by the United States (U.S.) Department of Defense (DoD) and the U.S. Department of the Navy (DoN). The passive samplers tested included: SKC Ultra and Ultra II, Radiello®, Waterloo Membrane Sampler (WMS), Automated Thermal Desorption (ATD) tubes, and 3M OVM 3500. The program included laboratory testing under controlled conditions for 10 VOCs (including chlorinated ethenes, ethanes, and methanes, as well as aromatic and aliphatic hydrocarbons), spanning a range of properties and including some compounds expected to pose challenges (naphthalene, methyl ethyl ketone). Laboratory tests were performed under conditions of different temperature (17 to 30 oC), relative humidity (30 to 90 % RH), face velocity (0.014 to 0.41 m/s), concentration (1 to 100 parts per billion by volume [ppbv]) and sample duration (1 to 7 days). These conditions were selected to challenge the samplers across a range of conditions likely to be encountered in indoor and outdoor air field sampling programs. A second set of laboratory tests were also conducted at 1, 10 and 100 parts per million by volume (ppmv) to evaluate concentrations of interest for soil vapor monitoring using the same 10 VOCs and constant conditions (80% RH, 30 min exposure, 22 oC). Inter-laboratory testing was performed to assess the variability attributable to the differences between several laboratories used in this study. The program also included field testing of indoor air, outdoor air, sub-slab vapor and deeper soil vapor at several DoD facilities. Indoor and outdoor air samples were collected over durations of 3 to 7 days, and Summa canister samples were collected over the same durations as the passive samples for comparison. Subslab and soil vapor samples were collected with durations ranging from 10 min to 12 days, at depths of about 15 cm (immediately below floor slabs), 1.2 m and 3.7 m. Passive samplers were employed with uptake rates ranging from about 0.05 to almost 100 mL/min and analysis by both thermal desorption and solvent extraction. Mathematical modeling was performed to provide theoretical insight into the potential behavior of passive samplers in the subsurface, and to help select those with uptake rates that would minimize the risk of a negative bias from the starvation effect (which occurs when a passive sampler with a high uptake rate removes VOC vapors from the surroundings faster than they are replenished, resulting in biased concentrations). A flow-through cell apparatus was tested as an option for sampling existing sub-surface probes that are too small to accommodate a passive sampler or sampling a slip-stream of a high-velocity gas (e.g., vent-pipes of mitigation systems). The results of this demonstration show that all of the passive samplers provided data that met the performance criteria for accuracy and precision (relative percent difference less than 45 % for indoor air or 50% for soil vapor compared to conventional active samples and a coefficient of variation less than 30%) under some or most conditions. Exceptions were generally attributable to one or more of five possible causes: poor retention of analytes by the sorbent in the sampler; poor recovery of the analytes from the sorbent; starvation effects, uncertainty in the uptake rate for the specific combination of sampler/compound/conditions, or blank contamination. High (or positive) biases were less common than low biases, and attributed either to blank contamination, or to uncertainty in the uptake rates. Most of the passive samplers provided highly reproducible results throughout the demonstrations. This is encouraging because the accuracy can be established using occasional inter-method verification samples (e.g., conventional samples collected beside the passive samples for the same duration), and the field-calibrated uptake rates will be appropriate for other passive samples collected under similar conditions. Furthermore, this research demonstrated for the first time that passive samplers can be used to quantify soil vapor concentrations with accuracy and precision comparable to conventional methods. Passive samplers are generally easier to use than conventional methods (Summa canisters and active ATD tubes) and minimal training is required for most applications. A modest increase in effort is needed to select the appropriate sampler, sorbent and sample duration for the site-specific chemicals of concern and desired reporting limits compared to Summa canisters and EPA Method TO-15. As the number of samples in a given program increases, the initial cost of sampling design becomes a smaller fraction of the overall total cost, and the passive samplers gain a significant cost advantage because of the simplicity of the sampling protocols and reduced shipping charges

Degradation of Atrazine, Metolachlor, and Pendimethalin in Pesticide‐Contaminated Soils: Effects of Aged Residues on Soil Respiration and Plant Survival

This study was conducted to determine the effects of pesticide mixtures on degradation patterns of parent compounds as well as effects on soil microbial respiration. Bioavailability of residues to sensitive plant species was also determined. Soil for this study was obtained from a pesticide‐contaminated area within an agrochemical dealer site. Degradation patterns were not affected by the presence or absence of other herbicides in this study. Atrazine concentrations were significantly lower at 21 through 160 days aging time compared to day 0 concentrations. Metolachlor and pendimethalin concentrations were not significantly different over time and remained high throughout the study. Microbial respiration was suppressed in treated soils from day 21 to day 160. Soybean and canola were the most successful plant species in the germination and survival tests. Generally, with increased aging of pesticides in soil, germination time decreased. Survival time of plants increased over time for some treatments indicating possible decreased bioavailability of pesticide residues. In some cases, survival time decreased at the longer 160‐day aging period, possibly indicating a change in bioavailability, perhaps as the result of formation of more bioavailable and phytotoxic metabolites. No interactive effects were noted for mixtures of pesticides compared to individually applied pesticides in terms of degradation of the parent compound or on seed germination, plant survival, or microbial respiration

Lattice Optics Optimization for Recirculatory Energy Recovery Linacs with Multi-Objective Optimization

Beamline optics design for recirculatory linear accelerators requires special attention to suppress beam instabilities arising due to collective effects. The impact of these collective effects becomes more pronounced with the addition of energy recovery (ER) capability. Jefferson Lab’s multi-pass, multi-GeV ER proposal for the CEBAF accelerator, ER@CEBAF, is a 10- pass ER demonstration with low beam current. Tighter control of the beam parameters at lower energies is necessary to avoid beam break-up (BBU) instabilities, even with a small beam current. Optics optimizations require balancing both beta excursions at high-energy passes and overfocusing at low-energy passes. Here, we discuss an optics optimization process for recirculatory energy-recovery linacs (ERLs) using multi-objective evolutionary search methods.https://digitalcommons.odu.edu/gradposters2022_sciences/1015/thumbnail.jp

Factor Structure and Gender Invariance Testing for the Sport Anxiety Scale-2 (SAS-2)

This study aimed to provide further psychometric validation of the Sport Anxiety Scale-2 (SAS-2) by assessing the factor structure, invariance across gender, and convergent and divergent validity of the SAS-2 by correlating both related (i.e., anxiety sensitivity, brief fear of negative evaluation, intolerance of uncertainty, and negative affect) and unrelated constructs (i.e., positive affect, self-confidence). A total of 542 current and former competitive athletes completed a questionnaire through Amazon’s Mechanical Turk system. All data were collected via online survey. Participants were randomly assigned to an exploratory factor analysis (n = 271) and confirmatory factor analysis group (n = 271). Results indicated that both exploratory and confirmatory factor analyses supported the three-factor model of anxiety involving somatic anxiety, worry, and concentration disruption. Additionally, this study found the SAS-2 to be reliable, gender invariant, and have strong construct validity. Our findings extend the generalizability of the SAS-2 in more varied populations of athletic backgrounds