Seasonal Growth of Waterhyacinth in the Sacramento/San Joaquin Delta, California

Waterhyacinth ( Eichhornia crassipes (Mart.) Solms), is a serious problem in the Sacramento/San Joaquin Delta, California. There is little published information on its phenology or seasonal growth in this system. Waterhyacinths were sampled at 2 to 3 week intervals from November, 1995 to July, 1997 and the following measurements were made on individual plants: dry weight, height, number of living leaves, number of dead leaves, and the width of the largest lamina. (PDF has 4 pages.

Do tissue carbon and nitrogen limit population growth of weevils introduced to control waterhyacinth at a site in the Sacramento-San Joaquin Delta, California?

Waterhyacinth (Eichhornia crassipes(Mart.) Solms), is a serious problem in the Sacramento Delta. Two weevil species (Neochetina bruchi Hustache and N. eichhorniae Warner) have been introduced as biological control agents. The purpose of this study was to test the hypothesis that nitrogen (N) in the tissue of waterhyacinth was not sufficient to support weevil growth and reproduction. Because it grows better on plants with high N content and because it has a greater impact on the growth of high N plants, N. bruchi may be a more effective biological control agent in the Sacramento Delta

Interactions between American pondweed and monoecious hydrilla grown in mixtures

To assess the potential for monoecious hydrilla ( Hydrilla verticillata (L.f.) Royle) to invade existing aquatic plant communities, monoecious hydrilla was grown in mixtures with American pondweed ( Potamogeton nodosus Poiret). When grown with hydrilla from axillary turions, American pondweed was a stronger competitor. When grown with hydrilla from tubers, American pondweed was equally as strong a competitor as hydrilla

Seasonal Changes in Chemical Composition of Eurasion Watermilfoil (Myriophyllum spicatum L.) and Water Temperature at Two Sites in northern California: implications for Herbivory

We compared seasonal changes in Eurasian watermilfoil (Myriophyllum spicatum L.) characteristics and water temperature for a shallow poind in Davis, CA, and the Truckee River, near Tahoe City, CA. Tissue C and N were 15% lower in plants from the Truckee River than in plants from the Davis pond. Seasonal fluctuations in tissue N were also different. Mean phenolic acid content of Truckee River palnts (162yM g-1) was less than those from the shallow pond (195 yM g-1). Phenolic acid content was positively related to tissue C for Truckee River and Davis pond plants and, tissue C:N ratio for Truckee River plants. Mean monthly water temperature (1990 to 1998) for the Truckee River site was less than 20 C. Water temperatures were warmer in August and September at this site. However, Eurasian watermilfoil collected during these months was characterized by lower levels of tissue N. During a 29-month period beginning January 1994, mean monthly water temperature for the Davis pond exceeded 20 C, only during July to September 1995. Tissue N was generally greater during summer for watermilfoil growing in the pond. These results imply that Eurasian watermilfoil biological control agents may have different developmental rates in these habitats, and thus different impacts on watermilfoil populations

Investigation of Direct Force Control for Planetary Aerocapture at Neptune

In this work, a direct force control numerical predictor-corrector guidance architecture is developed to enable Neptune aerocapture using flight-heritage blunt body aeroshells. A linear aerodynamics model is formulated for a Mars Science Laboratory-derived aeroshell. The application of calculus of variations shows that the optimal angle of attack and side-slip angle control laws are bang-bang. A closed-loop numerical predictor-corrector direct force control guidance algorithm is developed and numerically simulated using the Program to Optimize Simulated Trajectories II. The Monte Carlo simulated trajectories are demonstrated to be robust to the modeled dispersions in aerodynamics, atmospheric density, and entry state. An aerocapture technology trade study demonstrates that blunt body direct force control aerocapture enables similar performance as slender body bank angle control but halves the peak g-loading

Influence of Dilute Acetic Acid Treatments on Survival of Monoecious Hydrilla Tubers in the Oregon House Canal, California

Hydrilla (Hydrilla verticillata (L.f.)Royle), a serious aquatic weed, reproduces through formation of underground tubers. To date, attacking this life-cycle stage has been problematic. The purpose of this study was to measure the impact of exposure to dilute acetic acid on monoecious hydrilla tubers under field conditions. In this field experiment, treatments were acetic acid concentration (0, 2.5, or 5%) and sediment condition (perforated or not perforated). Each of 60, 1x1 m plots (in the Oregon House Canal) were randomly assigned to one treatment. Two weeks after treatment, we collected three samples from each plot. One was washed over 2 mm wire mesh screens to separate tubers from sediment. Relative electrolyte leakage was measured for one tuber from each plot. Five additional tubers from each plot were placed in a growth chamber and sprouting monitored for four weeks. A second sample from each plot was placed in a plastic tub and placed in an outdoor tank, filled with water. These samples were monitored for tuber sprouting. Relative electrolyte leakage increased significantly for tubers exposed to 2.5% or 5% acetic acid. Effects on tubers in perforated sediment were reduced. Exposure to acetic acid inhibited tuber sprouting by 80 to 100%, in both chamber and outdoor tests. These results confirm findings from earlier laboratory/greenhouse experiments, and suggest that this approach may be useful in the management of hydrilla tuber banks in habitats where the water level can be lowered to expose the sediments

Selecting Projects for a Capstone Spacecraft Design Course from Real World Solicitations

The first decision that goes into setting the tone for a senior capstone spacecraft design course is the choice of the projects. There are several sources of ideas for design projects, including design competitions and topics set by various technical committees. A new source of design ideas comes from real world design projects. The National Aeronautics and Space Administration\u27s Office of Space Science originally released an Announcement of Opportunity in spring 2002 to solicit designs for a complete Mars mission. The Senior Capstone Spacecraft Design course in the Department of Aerospace Engineering at The Pennsylvania State University paralleled this proposal process for the spacecraft design projects for the 2002-2003 academic year. While the original announcement called for proposers to determine what kind of a flight mission they would conduct, eight specific, realistic flight missions were chosen and assigned to the eight teams in the class. Many of the important aspects of the original project were duplicated; however, a significant amount of material was deleted. This paper discusses the outcome of the year-long course, compares some of the designs developed by the students to the designs chosen in the actual NASA mission design, and draws conclusions about the advantages and disadvantages of selecting a project based from a real solicitation

Sedimentation study, Environmental Monitoring and Operations Guidance System (EMOGS), Kings Bay, Georgia and Florida : Phase III--FY 1989

Repeated side-scan sonar and multi-frequency bathymetric surveys, accompanied by accurate, high resolution, and repeatable navigation, were conducted in the vicinity of a tidal inlet to define the length and time scales associated with bedforms and channel shoaling in a structured tidal inlet. The study site, St. Mary's entrance channel along the Georgia/Florida border (Fig. I), has a dredged channel approximately 46-52 feet in depth, bordered by a large ebb tidal delta. The tidal inlet serves Cumberland Sound, Kings Bay, and associated waterways, providing a large discharge of water from the inlet that creates bedforms and channel shoaling, given the abundance of sand-sized sediment in the vicinity. The jettied inlet produces flows tht are predominately tidally-driven, whereas farther offshore the driving forces consist predominately of waves and storm-generated flows. In the channel reaches (Table 1) between these two areas, combined wave-steady flows are present, creating a myriad of scales of bedforms and shoaling patterns. This study was designed to elucidate the time and space scales of these variable bedforms and shoaling patterns, emphasizing the difference in these scales between the three different flow regimes. The results provide an important data base for quantifying shoaling processes and mechanisms in tidal inlet channels.Funding was provided by the National Oceanic Atmospheric Administration under Sea Grant No. NA860A-D-SG090

Sedimentation study, Environmental Monitoring and Operations Guidance System (EMOGS), Kings Bay, Georgia and Florida, 1988-1990 : final report

Repeated side-scan sonar and multi-frequency bathymetric surveys, accompanied by accurate, high resolution, and repeatable navigation, were conducted in the vicinity of a tidal inlet to define the length and time scales associated with bedforms and channel shoaling in a structured tidal inlet. The study site, St. Marys entrance channel along the Georgia/Florida border (Fig. 1), has a dredged channel approximately 46-52 feet in depth at a datum of mean low water (MLW), bordered by a large ebb tidal delta. The tidal inlet serves Cumberland Sound, Kings Bay, and associated waterways, providing a large discharge of water from the inlet that creates bedforms and channel shoaling, given the abundance of sand-size sediment in the vicinity. The jettied inlet produces flows that are predominantly tidally-driven, whereas farther offshore the driving forces consist predominantly of waves and storm-generated flows. In the channel reaches (Table 1) between these two areas, combined wave/steady flows are present, creating a myriad of scales of bedforms and shoaling patterns, emphasizing the difference in these scales between the three different flow regimes. The results provide an important data base for quantifying shoaling processes and mechanisms in tidal inlet channels.Funding was provided by the National Oceanic & Atmospheric Administration's Sea Grant Program through Grant NA860-A-D-090

Pressure/Temperature Logger (PTL) development and field deployment for the Great Bay, NH, tidal dynamics experiment

Durg 1992 and 1993 experiments were conducted in the shallow east side of Great Bay, New Hampshire. These experiments were conducted to better understand the morphodynamics and evolutionary tendencies of shallow tidal embayments and intertidal fiats. Hardware and software used in the collection of data are described. Discussed also are techniques used to collect data. Six pressure temperature loggers (PTL) and one current meter (TCSWG) were developed for the experiments. Both instruments are internally powered and internally recording. The instruments were developed because no company was found that manufactured a similar instrument within the price range of the project.Funding was provided by the National Science Foundation through Grant No. OCE91-02429