Mechanisms of fragmentation of Al-W granular composites under dynamic loading

Numerical simulations of Aluminum (Al) and Tungsten (W) granular composite rings under various dynamic loading conditions caused by explosive loading were examined. Three competing mechanisms of fragmentation were observed: a continuum level mechanism generating large macrocracks described by the Grady-Kipp fragmentation mechanism, a mesoscale mechanism generating voids and microcracks near the initially unbonded Al/W interfaces due to tensile strains, and a mesoscale jetting due to the development of large velocity gradients between the W particles and adjacent Al. These mesoscale mechanisms can be used to tailor the size of the fragments by selecting an appropriate initial mesostructure for a given loading condition.Comment: 10 pages, 3 figures, submitted to AP

Potential Predation On Fish Eggs By The Lobate Ctenophore Mnemiopsis-Leidyi Within And Outside The Chesapeake Bay Plume

In Chesapeake Bay in June, the predatory lobate ctenophore Mnemiopsis leidyi and the eggs of the bay anchovy Anchoa mitchilli typically reach seasonal and localized abundance together. When examined at small vertical (1-3m), horizontal (10-50m), and temporal (6-hour) scales, the co-occurrence of M. leidyi and fish eggs (32.3-74.2% of which were A. mitchilli) was greatest in the northern reaches of the mouth of Chesapeake Bay, where the water column was stratified. Stratification to the south was effected by the Chesapeake Bay plume. With estimates of ctenophore clearance rate reported elsewhere and observed densities of ctenophores and fish eggs, potential predation was judged to be greatest in the northern reaches of the Bay mouth. The observation that co-occurrence and potential predation are greatest in areas where Chesapeake Bay water mixes with coastal shelf water implies that those fishes that spawn in low-salinity surface waters of well-stratified water columns may afford protection of their eggs from ctenophore predation

History and status of the VIMS fish collection (1951-1992)

The fish collection housed at the Virginia Institute of Marine Science of the College of William and Mary provides an important resource for taxonomic, systematic and ecological investigations of freshwater, estuarine and marine fishes. The uniqueness of the collection is in part due to its historical significance as well as a close coupling with a strong graduate program in ichthyology. The collection has internationally recognized holdings of Chesapeake Bay, middle Atlantic Bight and deep-water marine fishes, as well as freshwater fishes of the southern Appalachians. These collections have provided the basis for numerous graduate research projects and investigations by systematists from many institutions. In addition, rapidly expanding collections of early life history stages of fishes from Chesapeake Bay, middle Atlantic Bight and Caribbean localities offer an important and unique source of material for ontogenetic studies

Monitoring Relative Abundance of American Shad in Virginia Rivers 2009 Annual Report

Concern about the decline in landings of American shad (Alosa sapidissima) along the Atlantic coast prompted the development of an interstate fisheries management plan (FMP) under the auspices of the Atlantic States Marine Fisheries Management Program (ASMFC 1999). Legislation enables imposition of federal sanctions on fishing in those states that fail to comply with the FMP. To be in compliance, coastal states are required to implement and maintain fishery-dependent and fishery-independent monitoring programs as specified by the FMP. For Virginia, these requirements include spawning stock assessments, the collection of biological data on the spawning run (e.g., age-structure, sex ratio, and spawning history), estimation of total mortality, indices of juvenile abundance, biological characterization of permitted by-catch and evaluation of restoration programs by detection and enumeration of hatchery-released fish. This annual report documents continued compliance with Federal law. Since 1998, scientists at the Virginia Institute of Marine Science have monitored the spawning run of American shad in the James, York and Rappahannock rivers. The information resulting from this program is reported annually to the ASMFC, has formed the basis for a significant number of technical papers published in the professional literature, formed the basis for a recent coast-wide stock assessment and peer review for American shad (ASMFC 2007a, 2007b) and is contributing substantially to our understanding of the status and conservation of this important species. A number of individuals make significant contributions to the monitoring program and the preparation of this report. Commercial fishermen Tony Kellum, Raymond Kellum, Marc Brown and Jamie Sanders construct, set, and fish the sampling gear and offer helpful advice. They have participated in the sampling program since its beginning in 1998. Their contributions as authors of historic log books of commercial catches during the 1980s and as expert shad fishermen are essential elements of the monitoring program. We also extend our appreciation to several commercial fishers for their cooperation in our studies of by-catch of American Shad. In 2009, these individuals include: Kenneth Heath, Joseph Hinson, Demtri Hionis, George Trice, Robert Weagley, and Charles Williams. In 2009, the staff and students of the Virginia Institute of Marine Science who participated in the program were: B. Watkins, P. Crewe, A. Rhea, and R. Harris. Their dedication, consistent attention to detail and hard work in the field and in the laboratory are appreciated. B. Watkins determined ages of fish. B. Watkins and A. Rhea determined hatchery origins of fish. Fish products from the sentinel fishery are donated to the Food Bank of Newport News, Virginia. We offer thanks to the Hunters for the Hungry (Virginia Hunters Who Care) organization for their assistance

Zooplankton of the waters adjacent to the C.P. Crane Generating Station

Zooplankton populations in the Gunpowder River and its tributaries were sampled monthly from July 1979 to March 1980 in a continuation of similar studies begun in March 1979. Fourteen stations were sampled for mesozooplankton (202 ~m nets); six of these stations were also sampled for microzooplankton (concentration of pumped samples on 76 ~m netting)

Role of material properties and mesostructure on dynamic deformation and shear instability in Al-W granular composites

Dynamic experiments with Al-W granular/porous composites revealed qualitatively different behavior with respect to shear localization depending on bonding between Al particles. Two-dimensional numerical modeling was used to explore the mesomechanics of the large strain dynamic deformation in Al-W granular/porous composites and explain the experimentally observed differences in shear localization between composites with various mesostructures. Specifically, the bonding between the Al particles, the porosity, the roles of the relative particle sizes of Al and W, the arrangements of the W particles, and the material properties of Al were investigated using numerical calculations. It was demonstrated in simulations that the bonding between the "soft" Al particles facilitated shear localization as seen in the experiments. Numerical calculations and experiments revealed that the mechanism of the shear localization in granular composites is mainly due to the local high strain flow of "soft" Al around the "rigid" W particles causing localized damage accumulation and subsequent growth of the meso/macro shear bands/cracks. The "rigid" W particles were the major geometrical factor determining the initiation and propagation of "kinked" shear bands in the matrix of "soft" Al particles, leaving some areas free of extensive plastic deformation as observed in experiments and numerical calculations.Comment: 10 pages, 14 figures, submitted to Journal of Applied Physic

Evaluation of striped bass stocks in Virginia, monitoring and tagging studies, 1999-2003 Annual report, 1 September 1999 - 31 October 2000

To document continued compliance with Federal law, the Anadromous Fishes Program of the Virginia Institute of Marine Science (VIMS) has monitored the size and age composition, sex ratio and maturity schedules of the spawning striped bass stock in the Rappahannock River since December 1981 utilizing commercial pound nets and, since 1991, variable-mesh experimental gill nets. Spawning stock assessment was expanded to include the James River in 1994 utilizing 11 commercial fyke nets and variable-mesh experimental gill nets. The use of fyke nets was discontinued after 1997. In conjunction with the monitoring studies, tagging programs have been conducted in the James and Rappahannock rivers since 1987 . These studies were established to document the migration and relative contribution of these Chesapeake Bay stocks to the coastal population and to provide a means to estimate inter-year survival rates (S). With the reestablishment of fall recreational fisheries in 1993, the tagging studies were expanded to include the York River and western Chesapeake Bay to provide a direct estimation of the resultant fishing mortality (F). This document reports the results of our tagging and monitoring activities during the period 1 September 1999 through 31 October 2000. It includes an assessment of the biological characteristics of striped bass taken from the 2000 spring spawning run, estimates of annual survival based on annual spring tagging, and the results of the fall 1999 directed mortality study that is cooperative with the Maryland Department of Natural Resources. The information contained in this report is required by the Atlantic States Marine Fisheries Commission and is used to implement a coordinated management plan for striped bass in Virginia, and along the eastern seaboard

Evaluation of striped bass stocks in Virginia, monitoring and tagging studies, 1999-2003 Annual report, 1 September 2000 - 31 October 2001

This report presents the results of striped bass (Marone saxatilis) tagging and monitoring activities in Virginia during the penod 1 September 2000 through 31 October 2001. It includes an assessment of the biological characteristics of striped bass taken from the 2001 spring spawning run, estimates of annual survtval based on annual spring tagging, and the results of the fall 2000 directed mortality study that is cooperative with the Maryland Department of Natural Resources. The information contained in this report is required by the Atlantic States Marine Fisheries Commission and is used to implement a coordinated management plan for striped bass in Virginia, and along the eastern seaboard