248 research outputs found
Growth and food habits of introduced stizostedion hybrids in Cherokee Reservoir, Tennessee
Growth and food habits of young-of-year and yearling Stizostedion hybrids stocked in Cherokee Reservoir, Tennessee, were examined from July 1983 to December 1985. Growth was excellent throughout the study and hybrids averaged 296 and 442 mm at ages 1 and 2, respectively. Both young-of-year and yearling hybrids attained 90% of their annual growth by December. Condition factors (K) of hybrids increased with age (0.62- 1.17), while relative weights (Wr) were within the acceptable range (95-105) for all but three months of the first two years following introduction. Both condition indices decreased sharply during the spring and summer. Reduced abundance of appropriate-sized shad following winter and sub-optimal temperature/dissolved oxygen characteristics may negatively affect hybrids during this period. Hybrids began consuming fish immediately following stocking, with shad being the most important food item for both young-of-year and yearlings during each year of the study. Insects, primarily chironomids and Hexagenia nymphs, were consumed by hybrids during the spring and summer, but were a minor component of the total hybrid diet. Non-shad fishes were frequently collected in forage samples, but occurred rarely in the diets of hybrids. Results from prey-predator length relationships suggested that there was a decrease in the abundance of appropriate- sized shad during the late spring
Growth and food habits of introduced stizostedion hybrids in Cherokee Reservoir, Tennessee
Growth and food habits of young-of-year and yearling Stizostedion hybrids stocked in Cherokee Reservoir, Tennessee, were examined from July 1983 to December 1985. Growth was excellent throughout the study and hybrids averaged 296 and 442 mm at ages 1 and 2, respectively. Both young-of-year and yearling hybrids attained 90% of their annual growth by December. Condition factors (K) of hybrids increased with age (0.62- 1.17), while relative weights (Wr) were within the acceptable range (95-105) for all but three months of the first two years following introduction. Both condition indices decreased sharply during the spring and summer. Reduced abundance of appropriate-sized shad following winter and sub-optimal temperature/dissolved oxygen characteristics may negatively affect hybrids during this period. Hybrids began consuming fish immediately following stocking, with shad being the most important food item for both young-of-year and yearlings during each year of the study. Insects, primarily chironomids and Hexagenia nymphs, were consumed by hybrids during the spring and summer, but were a minor component of the total hybrid diet. Non-shad fishes were frequently collected in forage samples, but occurred rarely in the diets of hybrids. Results from prey-predator length relationships suggested that there was a decrease in the abundance of appropriate- sized shad during the late spring
Tag-reporting levels for red drum (Sciaenops ocellatus) caught by anglers in South Carolina and Georgia estuaries
A total of 1784 legal-size (≥356 mm TL) hatchery-produced red drum (Sciaenops ocellatus) were tagged and released to estimate tag-reporting levels of recreational anglers in South Carolina (SC) and Georgia (GA). Twelve groups of legal-size fish (~150 fish/ group) were released. Half of the fish of each group were tagged with an external tag with the message “reward” and the other half of the fish were implanted with tags with the message “100/tag. Reporting level for the “reward”tags was estimated by dividing the number of “reward” tags returned by the number of “100 reward” tags were returned. This finding indicates that only 56.7% of the fish captured with “reward” tags were reported in SC. The pattern was similar for GA where 19.1 (±10.6)% of “reward” message tags were returned as compared with 30.1 (±15.6)% for “$100 reward” message tags. This difference yielded a reporting level of 63% for “reward” tags in GA. Currently, 50% is used as the estimate for the angler reporting level in population models for red drum and a number of other coastal finfish species in the South Atlantic region of the United States. Based on results of our study, the commonly used reporting estimate may result in an overestimate of angler exploitation for red drum
Inclusive Scattering of Polarized Electrons on Polarized 3He Effects of Final State Interaction and the Magnetic Form Factor of the Neutron
Effects of final state interaction on asymmetries in inclusive scattering of
polarized electrons on polarized 3He are investigated using consistent 3He
bound state wave function and 3N continuum scattering states. Significant
effects are found, which influence the extraction of the magnetic neutron form
factor from A_T'. The enhancement found experimentally for A_TL' near the 3N
breakup threshold, which could not be explained in calculations carried through
in plane wave impulse approximation up to now, occurs now also in theory if the
full final state interaction is included.Comment: 29 pages, 5 figure
Dispersion-Theoretical Analysis of the Nucleon Electromagnetic Formfactors
Dispersion relations allow for a coherent description of the nucleon
electromagnetic form factors measured over a large range of momentum transfer,
GeV. Including constraints from unitarity and
perturbative QCD, we present a novel parametrisation of the absorptive parts of
the various isoscalar and isovector nucleon form factors. Using the current
world data, we obtain results for the electromagnetic form factors, nucleon
radii and meson couplings. We stress the importance of measurements at large
momentum transfer to test the predictions of perturbative QCD.Comment: 33 pp, RevTEX or plain LaTeX, 7 figures (in ffig.uu
Semiclassical Mechanics of the Wigner 6j-Symbol
The semiclassical mechanics of the Wigner 6j-symbol is examined from the
standpoint of WKB theory for multidimensional, integrable systems, to explore
the geometrical issues surrounding the Ponzano-Regge formula. The relations
among the methods of Roberts and others for deriving the Ponzano-Regge formula
are discussed, and a new approach, based on the recoupling of four angular
momenta, is presented. A generalization of the Yutsis-type of spin network is
developed for this purpose. Special attention is devoted to symplectic
reduction, the reduced phase space of the 6j-symbol (the 2-sphere of Kapovich
and Millson), and the reduction of Poisson bracket expressions for
semiclassical amplitudes. General principles for the semiclassical study of
arbitrary spin networks are laid down; some of these were used in our recent
derivation of the asymptotic formula for the Wigner 9j-symbol.Comment: 64 pages, 50 figure
Meeting Report: Threats to Human Health and Environmental Sustainability in the Pacific Basin
The coastal zone of the Pacific Rim is home for about one-third of the world’s population. Disproportionate growth of Far Eastern economies has produced a disproportionate share of related environmental difficulties. As the region searches for acceptable compromises between growth and environmental quality, its influence on global environmental health is certain to increase. Consequences of global environmental change such as habitat alteration, storms, and sealevel rise will be particularly acute among Pacific Rim nations. Adverse health effects from arsenic exposure in Pacific Rim nations have been used to justify drinking water standards in the United States and elsewhere. As global manufacturing in the Pacific Rim increases, the centroid of global air quality and waste management issues will shift further toward Far Eastern nations. The Eleventh International Conference of the Pacific Basin Consortium (PBC) was held in September 2005 in Honolulu, Hawaii. The purpose of the conference was to bring together individuals to discuss regional challenges to sustainable growth. The historic emphasis of the conference on hazardous wastes in relation to human health makes the PBC an ideal forum for discussing technical aspects of sustainable economic growth in the Pacific region. That role is reflected in the 2005 PBC conference themes, which included management of arsenic in potable waters, air quality, climate change, pesticides, mercury, and electronics industry waste—each with emphasis on relationships to human health. Arsenic management exemplifies the manner in which the PBC can focus interdisciplinary discussion in a single technical area. The conference program provided talks on arsenic toxicology, treatment technologies, management of arsenic-bearing residuals from water treatment, and the probable societal costs and benefits of arsenic management
Metal-substituted protein MRI contrast agents engineered for enhanced relaxivity and ligand sensitivity
Engineered metalloproteins constitute a flexible new class of analyte-sensitive molecular imaging agents detectable by magnetic resonance imaging (MRI), but their contrast effects are generally weaker than synthetic agents. To augment the proton relaxivity of agents derived from the heme domain of cytochrome P450 BM3 (BM3h), we formed manganese(III)-containing proteins that have higher electron spin than their native ferric iron counterparts. Metal substitution was achieved by coexpressing BM3h variants with the bacterial heme transporter ChuA in Escherichia coli and supplementing the growth medium with Mn3+-protoporphyrin IX. Manganic BM3h variants exhibited up to 2.6-fold higher T1 relaxivities relative to native BM3h at 4.7 T. Application of ChuA-mediated porphyrin substitution to a collection of thermostable chimeric P450 domains resulted in a stable, high-relaxivity BM3h derivative displaying a 63% relaxivity change upon binding of arachidonic acid, a natural ligand for the P450 enzyme and an important component of biological signaling pathways. This work demonstrates that protein-based MRI sensors with robust ligand sensitivity may be created with ease by including metal substitution among the toolkit of methods available to the protein engineer.National Institutes of Health (U.S.) (NIH Grant R01-DA28299 )National Institutes of Health (U.S.) (NIH NRSA Fellowship (Award F32-GM087102))California Institute of Technology (Caltech Jacobs Grant
The chronostratigraphy of the Haua Fteah cave (Cyrenaica, northeast Libya)
The 1950s excavations by Charles McBurney in the Haua Fteah, a large karstic cave on the coast of
northeast Libya, revealed a deep sequence of human occupation. Most subsequent research on North
African prehistory refers to his discoveries and interpretations, but the chronology of its archaeological
and geological sequences has been based on very early age determinations. This paper reports on the
initial results of a comprehensive multi-method dating program undertaken as part of new work at the
site, involving radiocarbon dating of charcoal, land snails and marine shell, cryptotephra investigations,
optically stimulated luminescence (OSL) dating of sediments, and electron spin resonance (ESR) dating of
tooth enamel. The dating samples were collected from the newly exposed and cleaned faces of the upper
7.5 m of the w14.0 m-deep McBurney trench, which contain six of the seven major cultural phases that
he identified. Despite problems of sediment transport and reworking, using a Bayesian statistical model
the new dating program establishes a robust framework for the five major lithostratigraphic units
identified in the stratigraphic succession, and for the major cultural units. The age of two anatomically
modern human mandibles found by McBurney in Layer XXXIII near the base of his Levalloiso-Mousterian
phase can now be estimated to between 73 and 65 ka (thousands of years ago) at the 95.4% confidence
level, within Marine Isotope Stage (MIS) 4. McBurney’s Layer XXV, associated with Upper Palaeolithic
Dabban blade industries, has a clear stratigraphic relationship with Campanian Ignimbrite tephra.
Microlithic Oranian technologies developed following the climax of the Last Glacial Maximum and the
more microlithic Capsian in the Younger Dryas. Neolithic pottery and perhaps domestic livestock were
used in the cave from the mid Holocene but there is no certain evidence for plant cultivation until the
Graeco-Roman period
- …