365 research outputs found

    Response to Memon

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    London Tower

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    I could hardly say that I was disillusioned as at last we stood outside and viewed for the first time the famous Tower of London, for I really didn\u27t know exactly what to expect. From stories I had heard I knew that the Tower couldn\u27t be just that-a tower; but what else? The name is misleading

    The effects of 180 years of aging on the physical and seismic properties of partially saturated sands

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    Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 126(6), (2021): e2020JB021341, https://doi.org/10.1029/2020JB021341.Constraining how the physical properties and seismic responses of recently deposited sands change with time is important for understanding earthquake site response, subsurface fluid flow, and early stages of lithification. Currently, however, there is no detailed (cm-scale) assessment of how sand's physical properties and associated seismic velocities evolve over the first two centuries after deposition. Here, we integrate sedimentation rates with seismic velocity and sediment physical properties data to assess how the vadose zone sands at Port Royal Beach, Jamaica, change within 180 years after deposition. We show that compressional and shear wave velocities increase with sediment age, whereas porosity, grain size, sorting, mineralogy, and cementation fraction remain relatively unchanged during the same period. Rock physics models (constrained by the measured physical properties) predict constant seismic velocities at all sites regardless of sediment age, though misfits between modeled and observed velocities increase with sediment age. We explain these misfits by proposing that shallow sands undergo microstructural grain reorganization that leads to a more uniform distribution of grain contact forces with time. Our results imply that beach sands undergo a previously undocumented lithification process that occurs before compaction.The Society of Exploration Geophysicists Geoscientists without Borders Grant and the Institute for Earth, Science, and Man at Southern Methodist University partially supported this work

    Comparison of Carbon and Nitrogen Content of Infected and Uninfected Snails, Succinea ovalis, and the Trematode Leucochloridium variae

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    In June, 6.7% of adult Succinea ovalis collected near Urbana, Ohio, were infected with the trematode, Leucochloridium variae. The effects of parasitism were assessed as total organic carbon (equivalent to calorific values) and as total nitrogen. The parasite represents 23.8% of total (parasite + snail tissue) dry tissue weight, 21.4% of total carbon and 19.8% of total nitrogen of infected snails. The higher C:N ratio for parasite tissue indicates a higher proportion of nonproteinaceous compounds (e.g., fats and/or carbohydrates) as compared to host tissue. There is less snail tissue in parasitized S. ovalis. The C:N ratios for parasitized and nonparasitized snail tissue suggest identical percentage compositions of proteins, fats, and carbohydrates

    Besteuerung, Inflation und Kapitalallokation : intersektorale und internationale Aspekte

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    Im Mittelpunkt der Arbeit stehen die Auswirkungen steuerlicher Abschreibungen und investitionsfördernder Massnahmen auf die intersektorale und internationale Kapitalallokation. Der Autor analysiert sowohl bestehende steuerliche Vorschriften als auch Reformvorschläge (z.B. Cash-Flow-Steuersysteme) und stellt Regelungen vor, die steuerinduzierte Fehlallokationen vermeiden

    Ecosystem Metabolism in Small Ponds: The Effects of Floating-Leaved Macrophytes

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    Small ponds constitute a significant number of standing water bodies on earth and may contribute to CO2 uptake or release into the atmosphere. Despite their importance, few studies have examined ecosystem metabolism in ponds, especially in ponds that may be dominated by floating-leaved macrophytes. In this study, we examined ecosystem metabolism by measuring changes in dissolved oxygen levels every 10 min from late May through late October for four shallow ponds (0.5–1.5 m) in east-central Minnesota, USA. Ponds had varying levels of floating-leaved macrophytes from sparse (\u3c1% coverage) to abundant (61% coverage). We found significant dierences in a number of physical/chemical factors including P, N, DOC, water temperature and light penetration. We also found significant dierence in gross primary production (GPP—average ranged from 2.2 to 5.5 mg O2/L/day), respiration (R—average ranged from 6.8 to 3.6 mg O2/L/day) and net ecosystem production (NEP—average ranged from 1.5 to 0.1 mg O2/L/day) among the ponds. On average, all of the ponds were heterotrophic (R \u3e GPP). While it appeared that floating-leaved macrophytes provided a significant impact on ecosystem metabolism, there was not a one-to-one correspondence between the amount of macrophytes and the level of ecosystem metabolism

    Brief Note: Growth of Pisidium Casertanum (Poli) in West Central Ohio

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    Author Institution: Department of Biology, University of Dayto

    Interpopulation Variation in Calcareous and Proteinaceous Shell Components in the Stream Limpet, Ferrissia rivularis

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    Natural populations of the North American stream limpet, F. rivularis, were studied in upstate New York [USA], in a set of localities whose waters have a 15-fold range of dissolved Ca (4.6-67.6 mg/liter) and also range from oligotrophy to eutrophy. Shell component analyses (CaCO3, total organic C and total N) are reported as component mass-fractions (mg/g or .mu.g/g dry weight) and as values for a standard limpet shell of 35 mm aperture length (AL). More than 2-fold differences occur between populations in all 3 components, with relatively little variation occurring within each population. Expressed per standard limpet, CaCO3 values for different populations range from 0.8-1.97 mg with no direct relationship to environmental dissolved Ca. Nominal concentration ratios of body Ca to environmental Ca range from 1953:1-29,130:1. Values for total organic C (9.13-21.0 .mu.g) and total N (2.7-6.69 .mu.g) in the shells parallel each other, all C:N ratios being relatively uniform (3.0:1-3.4:1), and indicating that the non-calcareous components are largely proteinaceous. Although alternative hypotheses predict an inverse or a direct relationship between the organic and the calcareous components, neither is shown by these populations. Genetic controls of shell secretion for the 2-major components apparently are independent, and chance dispersal has resulted in some rather inappropriate shells in certain habitats. This irregular variation in Ferrissia is 1st discussed in relation to other patterns of shell component relationships known for other freshwater mollusk, including direct relationship of the mass of shell CaCO3 to the dissolved Ca available as in Lymnaea peregra and Laevapex fuscus and the apparent regulation producing standard shell weights in L. palustris and Physa gyrina. The results are then discussed in relation to assessment of radionuclide pollution using molluscan shells from fresh waters and in their more general relationship to modes and rates of evolutionary change in freshwater faunas

    Seasonal Metabolism of the Sphaeriid Clam, Musculium partumeium (Say), from a Permanent and a Temporary Pond

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    Seasonal metabolic rates were examined for the sphaeriid clam, Musculium partumeium (Say) from a permanent and a temporary pond. For the fall-born generation from the permanent pond and for the single generation from the temporary pond, metabolic rates peak during periods of greatest growth and reproduction. Metabolic rates were consistently higher for the permanent pond population. These rates for Musculium partumeium extend the available information on the family Sphaeriidae to the genus Musculium
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