2,023 research outputs found

    Applied Geology of Industrial Limestone and Dolomite

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    Indiana Geological Survey Bulletin 46The title of this report as first proposed was "What a Consulting Geologist Should Know About Industrial Limestone" because this effort was born of a request from the Indiana-Kentucky Geological Society, Inc., for a refresher course in the economic geology of limestone. The present title was adopted, however, because the completed report is understandable to anyone with some formal or informal geologic training and an interest in the applied geology of industrial limestones. Many of Indiana's mineral producers have developed a keen understanding of the geology associated with the particular deposit that they work, but because of a lack of training, they do not know how geology can be used in a broader sense to explore and exploit limestone deposits. We believe that this report will help answer some of the questions frequently asked by both the consulting geologist and the mineral producer. Consulting geologists and mineral producers certainly need to know something about industrial limestone. The total tonnage of carbonate rocks mined or consumed in the United States in 1968 was about 603 million tons and the total value about 857 million dollars (U.S. Bureau of Mines, Minerals Yearbook, 1968). To meet the need for this basic building block of our society, the deposits now being sought must be larger, purer, and more strategically situated than ever before. Once a new quarry meant the investment of a few tens of thousands of dollars. Now it is likely to mean a million or more. The producer cannot afford to make this investment in an inadequate deposit. He needs the help of a geologist, and he needs to be able to evaluate geologic information properly. To reach as broad an audience as possible, we have used a minimum of technical terms. According to custom, industrial limestone of limestone is here synonymous with limestone and dolomite unless the contest indicates otherwise. The chemical composition of limestone is important in many uses, and limestone and dolomite are often described in terms of their carbonate context. These terms are arbitrary and depend partly on the context, both in terms of use and availability of high-grade limestone. As used in this report, high-calcium limestone is limestone composed of 95 percent CaCO3. Ultra-high calcium limestone is more than 97 percent CaCO3, high-purity carbonate rock is more than 95 percent combined CaCO3 and MgCO3, and high-purity dolomite is more than 42 percent MgCO3. (Theoretically, pure dolomite would contain 45.7 percent MgCO3.)Indiana Department of Natural Resource

    Phase ordering and roughening on growing films

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    We study the interplay between surface roughening and phase separation during the growth of binary films. Already in 1+1 dimension, we find a variety of different scaling behaviors depending on how the two phenomena are coupled. In the most interesting case, related to the advection of a passive scalar in a velocity field, nontrivial scaling exponents are obtained in simulations.Comment: 4 pages latex, 6 figure

    Re-Os geochronology and coupled Os-Sr isotope constraints on the Sturtian snowball Earth

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    After nearly a billion years with no evidence for glaciation, ice advanced to equatorial latitudes at least twice between 717 and 635 Mya. Although the initiation mechanism of these Neoproterozoic Snowball Earth events has remained a mystery, the broad synchronicity of rifting of the supercontinent Rodinia, the emplacement of large igneous provinces at low latitude, and the onset of the Sturtian glaciation has suggested a tectonic forcing. We present unique Re-Os geochronology and high-resolution Os and Sr isotope profiles bracketing Sturtian-age glacial deposits of the Rapitan Group in northwest Canada. Coupled with existing U-Pb dates, the postglacial Re-Os date of 662.4 ± 3.9 Mya represents direct geochronological constraints for both the onset and demise of a Cryogenian glaciation from the same continental margin and suggests a 55-My duration of the Sturtian glacial epoch. The Os and Sr isotope data allow us to assess the relative weathering input of old radiogenic crust and more juvenile, mantle-derived substrate. The preglacial isotopic signals are consistent with an enhanced contribution of juvenile material to the oceans and glacial initiation through enhanced global weatherability. In contrast, postglacial strata feature radiogenic Os and Sr isotope compositions indicative of extensive glacial scouring of the continents and intense silicate weathering in a post–Snowball Earth hothouse

    In vitro and ex vivo testing of tenofovir shows it is effective as an HIV-1 microbicide

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    Background: Tenofovir gel has entered into clinical trials for use as a topical microbicide to prevent HIV-1 infection but has no published data regarding pre-clinical testing using in vitro and ex vivo models. To validate our findings with on-going clinical trial results, we evaluated topical tenofovir gel for safety and efficacy. We also modeled systemic application of tenofovir for efficacy. Methods and Findings: Formulation assessment of tenofovir gel included osmolality, viscosity, in vitro release, and permeability testing. Safety was evaluated by measuring the effect on the viability of vaginal flora, PBMCs, epithelial cells, and ectocervical and colorectal explant tissues. For efficacy testing, PBMCs were cultured with tenofovir or vehicle control gels and HIV-1 representing subtypes A, B, and C. Additionally, polarized ectocervical and colorectal explant cultures were treated apically with either gel. Tenofovir was added basolaterally to simulate systemic application. All tissues were challenged with HIV-1 applied apically. Infection was assessed by measuring p24 by ELISA on collected supernatants and immunohisto-chemistry for ectocervical explants. Formulation testing showed the tenofovir and vehicle control gels were >10 times isosmolar. Permeability through ectocervical tissue was variable but in all cases the receptor compartment drug concentration reached levels that inhibit HIV-1 infection in vitro. The gels were non-toxic toward vaginal flora, PBMCs, or epithelial cells. A transient reduction in epithelial monolayer integrity and epithelial fracture for ectocervical and colorectal explants was noted and likely due to the hyperosmolar nature of the formulation. Tenofovir gel prevented HIV-1 infection of PBMCs regardless of HIV-1 subtype. Topical and systemic tenofovir were effective at preventing HIV-1 infection of explant cultures. Conclusions: These studies provide a mechanism for pre-clinical prediction of safety and efficacy of formulated microbicides. Tenofovir was effective against HIV-1 infection in our algorithm. These data support the use of tenofovir for pre-exposure prophylaxis. © 2010 Rohan et al

    Demography and disorders of German Shepherd Dogs under primary veterinarycare in the UK

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    The German Shepherd Dog (GSD) has been widely used for a variety of working roles. However, concerns for the health and welfare of the GSD have been widely aired and there is evidence that breed numbers are now in decline in the UK. Accurate demographic and disorder data could assist with breeding and clinical prioritisation. The VetCompassTM Programme collects clinical data on dogs under primary veterinary care in the UK. This study included all VetCompassTM dogs under veterinary care during 2013. Demographic, mortality and clinical diagnosis data on GSDs were extracted and reported
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