College of William & Mary: W&M Publish

    Sea Turtle Science : A Research-Based Middle and High School Classroom Resource

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    Sea turtle quick facts, biology, turtle species, nesting behavior, hatching activity, classroom activities

    Possible late Pleistocene uplift, Chesapeake Bay entrance

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    Paleontological and lithological studies of engineering borings and boring logs subaerial erosion surface of Pliocene (?)-Pleistocene age cuts across clastic sediments of pre-Yorktownian Miocene age in the subsurface and subbottom of the lower Chesapeake Bay area. When the bore-hole data are coupled with the results of subbottom echo profiling and piledriving records, it is possible to construct accurate cross sections of the buried Miocene-Pleistocene contact. The cross sections show lows in the erosion surface that may be correlated with the buried channels of the Pleistocene Elizabeth, James, York, and Susquehanna river valleys. Probable channel depths below mean low water at control points are: 100 feet (Elizabeth River, beneath Tunnel no. 1), 155 feet (James River, at Hampton Roads Tunnel), 120 feet (York River, at Yorktown), 158 feet (Susquehanna River, off Cape Charles City), and 160 feet (Susquehanna River, at Fisherman Island, Cape Charles). The channel depths of what is believed to be the buried Susquehanna River valley are less than expected when placed on a curve showing the expectable gradients of that stream during the time of the most-recent, maximum lowering of sea level (ca. 18,000 years B.P.). The discrepancy suggests uplift of that channel of approximately 170 feet in about the last 18,000 years

    Economic Aspects Of The Chesapeake Bay Oyster Fishery: Problems And The Future Or Should The Industry Be Revitalized?

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    Between 1930 and 1939, average annual landings of Crassostrea virginica from Chesapeake Bay was 32 million pounds (meat weight). During the period 1980-88, average annual landings declined to 14.6 million pounds. In 1990, landings declined to less than 3 million pounds of meats. It has been this consistent downward trend in landings, particularly since 1983, that has concerned that National Marine Fisheries Service, various state agencies, and members of the oyster industry. In response to declining harvests, the National Oceanic Atmospheric Administration Sea Grant Program in cooperation with the National Marine Fisheries Service and various state agencies and sea grant programs developed A Plan Addressing the Restoration of the American Oyster Industry. The plan recommends that roughly $3 million annually allocated between 1991 and 1995 for research dedicated to restoring the oyster industry. A proposed $15 million budget raises two important issues that must be addressed: (1) should the industry be revitalized, and (2) if so, what needs to be done. In this paper, we offer that revitalization depends upon the marketability of oysters. A nationwide survey of wholesalers conducted in 1992 suggests that consumer demand for oysters has dramatically declined. Alternatively, oysters may be nearing the end of their product life cycle or going the way of the Edsel, IBM personal computer, or Yugo. Industry revitalization efforts, therefore, must be closely linked to, at least, a generic marketing campaign directed at restoring consumer confidence in oyster products. We conclude, however, that resource enhancement efforts based on bio-remediation goals (enhancing water quality and decreasing the population of jellyfish) may be warranted, and enhancement activities rather than industry revitalization efforts should be the focus of a national research program.https://scholarworks.wm.edu/vimsbooks/1045/thumbnail.jp

    The Effect of Vaccination and Host Genetics on Transmission Dynamics of Infectious Hematopoietic Necrosis Virus and Flavobacterium Psychrophilum in Rainbow Trout (Oncorhynchus Mykiss)

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    Globally, infectious diseases are responsible for major conservation and economic losses in wild and farmed fish populations. Prevention tools, including vaccination and breeding for genetic disease resistance, are used in many systems to prevent mortality by such diseases. Studies are often done to evaluate the efficacy of a preventative method at reducing disease, but the impact on transmission is rarely studied. Protection under diverse field conditions, such as variable pathogen exposure dosages, is also not fully understood. Furthermore, there is little information on how preventative methods alter host-pathogen relationships. For example, it is largely unknown how vaccination impacts non-target pathogens that co-infect the host. These knowledge gaps make it difficult to infer the epidemiological impacts of disease prevention tools. In an attempt to fill these gaps, we investigated two leading pathogens in rainbow trout (Oncorhynchus mykiss) aquaculture: infectious hematopoietic necrosis virus (IHNV) and Flavobacterium psychrophilum. We evaluated the impacts of vaccination and genetic disease resistance on mortality and transmission across a range of challenge dosages of IHNV and F. psychrophilum to accurately reflect field variability. There was evidence of a dosage effect; as dosage increased, shedding increased and vaccine efficacy decreased. We also evaluated how vaccination and genetic disease resistance impact transmission dynamics during simultaneous and sequential co-infection of IHNV and F. psychrophilum. Our results indicate co-infected fish shed more of both pathogens than they do in single infections, and the order that the pathogen infected the host may impact transmission in both pathogens. Furthermore, vaccine efficacy may be diminished by co-infection. These studies are aimed at developing a more robust framework for inferring the efficacy of disease prevention strategies. Our results will also help to inform and improve disease management in one of the top aquaculture species in the United States

    Optical Characterization of Dynamic Exchange Coupling Interaction in Ferromagnetic Heterostructures

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    This thesis presents the optical characterization of interfacial exchange coupling interaction in ferromagnetic bilayer heterostructures. Both static and dynamic magnetic response are investigated in the exchange-coupled Co2FeAl/(Ga,Mn)As bilayer system using static magneto-optical Kerr effect (MOKE) and time-resolved magneto optical Kerr effect (TRMOKE) techniques. The goal of this thesis is to understand the underlying physics of the interfacial exchange coupling effect on the ultrafast spin dynamics in a ferromagnetic metal/ferromagnetic semiconductor bilayer heterostructure. Our finding provides a viable pathway for designing advanced semiconductor spintronic devices for ultrafast low-power spin manipulation. First, a significant enhancement of the excitation efficiency of coherent magnetization precession is observed in the ferromagnetically exchangecoupled Co2FeAl/(Ga,Mn)As bilayer heterostructures at temperatures below the Curie temperature of (Ga,Mn)As, TC = 50 K, under photoexcitation of lowfluence, near-infrared pump pulses. The coherent magnetization precession persists to room temperature, indicating that proximity-induced ferromagnetism plays an important role in the optical excitation mechanism. A subsequent simulation of the temperature-dependent precession amplitude and frequency behavior is performed based on the Landau-Lifshitz-Gilbert (LLG) equation, suggesting that the high-efficiency excitation mechanism can be attributed to the modulation of the exchange coupling field at the interfacial area, which is induced by the emergence of the dynamic exchange coupling effect between the precessing magnetizations in the two ferromagnets. Second, the Gilbert damping property of the magnetization precession in the Co2FeAl/(Ga,Mn)As bilayer system is studied. At temperatures below the Curie temperature of (Ga,Mn)As, TC = 50 K, ultrafast pump excitation creates a counter-precessing, exchange-coupled mode in the ferromagnetic bilayer. The precessing magnetization in the Co2FeAl layer transfers a pure spin current directly into the (Ga,Mn)As layer at a certain intensity of external magnetic field where the Fe(Co) spins and the Mn spins precess at the same frequency. A photo-induced enhancement of the Gilbert damping constant α is observed, indicating that spin-angular momentum is transferred at the resonance magnetic fields. This can be attributed to the effect of the interfacial dynamic exchange coupling interaction between the precessing magnetizations in two ferromagnetic layers. A corresponding phase shift of the magnetization precession is also observed at the resonance field where the Gilbert damping peak appears

    Effects Of Large Predators On The Field Culture Of The Hard Clam, Mercenaria mercenaria

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    Individuals in the clam industry h ave used fences to keep the cownose ray, Rhirioptera bonasus, out of planted areas (Lewis 2 ; Burton3 ). Tiller et al. ( 1952) indicated losses due to skates in planted holding areas and stated that One man reported the loss of 600 bushels of small clams in two nights during 1948 .... Merriner and Smith4 stated that cownose ray predation is a serious problem on oyster and clam grounds in Chesapeake Bay. From these observations it is clear that such large predators could be a significant deterrent to the culture of clams from Delaware Bay southward along the Atlantic coast. The present study continues a program designed tv evaluate methods of protecting areas seeded with young Mercenaria mercenari

    The pound-net fishery in Virginia. Part 1. History, gear description and catch

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    The pound net is one of the most important fishing gears in Virginia. Recent declines in the catch of certain economically- important species have pointed to the need for study of the fishes and the fishery and its methods. The General Assembly of Virginia has requested that the Virginia Fisheries Laboratory conduct experiments to determine the proper size mesh for nets in fixed fishing devices. A preliminary study of the pound net, embodying historical development, construction and methods of operating, and the catch trends from 1930 through 1951, was undertaken during the summer of 1953. Although the introduction of the pound net into Virginia waters about 1870 was marked by opposition and conflict, the gear was adopted and has gained importance. Little change has been made in the basic design and method of fishing, although materials and preservatives have been improved. Studies of the effects of preservatives and use of the component nets indicate variation in stated mesh sizes and the resultant need for further appraisal of definitions relative to mesh sizes and legal sizes of fishes. Of the fish species taken in ·pound nets, a few comprise the bulk of the catch and constitute the economically- important fishes. Alewives. gray sea trout, croaker, spot, shad, and butterfish have long been the principal food species, and menhaden the important nonfood item, in the catch

    Heavy Higgs searches and constraints on two Higgs doublet models

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    Since the discovery of a Higgs boson at the LHC and the measurement of many of its branching ratios, there have been numerous studies exploring the restrictions these results place on the parameter space of two Higgs doublet models. We extend these results to include the full data set and study the expected sensitivity that can be obtained with 300 fb(-1) and 3000 fb(-1) integrated luminosity. We consider searches for a heavy Standard Model Higgs boson, with a mass ranging from 200 to 400 GeV, and show that the nonobservation of such a Higgs boson can substantially narrow the allowed regions of parameter space in two Higgs doublet models

    A matricial proof of the symmetric exchange axiom for eigenvalues of principal submatrices of a complex Hermitian matrix

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    In [C.R. Johnson, B. Kroschel, M. Omladic, Eigenvalue multiplicities in principal submatrices, Linear Algebra Appl. 390 (2004)111-120] a result constraining the eigenvalues of principal submatrices of complex Hermitian matrices, based upon matroid theory, was given. Here we give a matricial proof of this result which also enables us to find a generalization of the original result. (C) 2013 Elsevier Inc. All rights reserved

    The relation between the diagonal entries and the eigenvalues of a symmetric matrix, based upon the sign pattern of its off-diagonal entries

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    It is known that majorization is a complete description of the relationships between the eigenvalues and diagonal entries of real symmetric matrices. However, for large subclasses of such matrices, the diagonal entries impose much greater restrictions on the eigenvalues. Motivated by previous results about Laplacian eigenvalues, we study here the additional restrictions that come from the off-diagonal sign-pattern classes of real symmetric matrices. Each class imposes additional restrictions. Several results are given for the all nonpositive and all nonnegative classes and for the third class that appears when n = 4. Complete description of the possible relationships are given in low dimensions. (C) 2012 Elsevier Inc. All rights reserved
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