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  • 1990-1994  (7)
  • 1970-1974
  • 1915-1919
  • 1992  (7)
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  • 1990-1994  (7)
  • 1970-1974
  • 1915-1919
Year
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Periodontology 2000 5 (1992), S. 0 
    ISSN: 1600-0757
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Melanin isolated from the ink sac of Sepia officinalis (Sepia melanin) has been proposed as a standard for natural eumelanin. There are no standard methods for the isolation, purification, and storage of melanins. Mild methods designed to preserve the native composition and structure of melanin are needed. The specific aim of the present work, using Sepia melanin, was to develop a mild and generally applicable protocol for the isolation and purification of melanins. It is well established that melanin polymers contain a large number of free carboxylic acid residues. These anionic residues are responsible for the cation exchange properties observed for melanins. Heating melanins with hydrochloric acid at reflux has been demonstrated to lead to extensive decarboxylation. Indeed, heat alone has been shown to cause decarboxylation, and care must be exercised to avoid such conditions. By analogy with cation exchange resins, melanins should be isolated and named according to the associated counterion (e.g., Sepia melanin—K+ form). The method reported here avoided extremes in pH and temperature, and was designed to yield melanin in the K+ form. Physical disaggregation of particulate melanin using a wet milling step was also found to facilitate removal of significant quantities of adsorbed protein. The following physical parameters were used to monitor the purification and to characterize the resultant melanin: pH, conductance, particle size, and diffuse reflectance spectroscopy.
    Type of Medium: Electronic Resource
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  • 2
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    Unknown
    London : Periodicals Archive Online (PAO)
    Journal of adolescence. 15:4 (1992) 467 
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of public health dentistry 52 (1992), S. 0 
    ISSN: 1752-7325
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previous data relating to the cost of fluoridation often do not include annualized costs or costs for labor and maintenance. The purpose of this study was to estimate accurately current costs for initiating and maintaining fluoridation and to develop a methodology that can be used to provide the cost basis for further cost-effectiveness studies. The data were collected from 44 Florida communities that had initiated community water fluoridation between 1981 and 1989. Equipment, installation, and engineering costs were derived from copies of actual invoices for equipment and services and then adjusted to 1988 dollars. The chemical costs were calculated from operational reports listing flow rate and pounds used. The cost was then adjusted according to whether the hydrofluosilicic acid was supplied as 15-gallon carboys, 55-gallon drums, in bulk, or as sodium silicofluoride or sodium fluoride. The initial cost was annualized at 2 percent and 4 percent over 15 years. Calculated operational costs included chemical costs, labor costs, and maintenance and repair costs. The operational costs were then added to the annualized depreciation costs and opportunity costs for the initial investment, to produce an estimated cost per person served. The total mean cost per person for all installations was $1.14 per year at 2 percent and $1.25 per year at 4 percent. The mean cost at 4 percent for communities of fewer than 10,000 was $2.12; for communities between 10,000 and 50,000 it was $0.68; and for communities over 50,000 it was $0.31. The total mean cost per person across all installations was $0.41 at 2 percent and 0.45 at 4 percent. The average yearly cost was related to the size of the community, the number of injection points, and the method of chemical purchase and delivery.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A 2-yr study evaluated the effects of acid precipitation on the forest floor community. Throughfall was collected at weekly intervals, acidified to pH 4.3 and 3.6, and applied to throughfall excluded 1 m2 plots in a stand of loblolly pine (Pinus taeda L.) in south Mississippi, and in a longleaf pine (P. palustris Mill.) plantation in east Texas. Control plots received ambient throughfall which ranged from pH 3.7 to 6.2 in Mississippi and pH 3.8 to 6.7 in Texas. Five plots of each treatment at each location were destructively sampled after 1 yr and the 5 remaining plots were sampled after 2 yr. Chemical analyses were conducted for all collections of throughfall and litter leachate, and for the fermentation layer, rhizosphere, and mineral soil. After 2 yr, comparisons of the pH 3.6 plots with the controls indicated significant decreases in the number, length and biomass of lateral roots, and the percent and number of ectomycorrhizae. Decreases in these root characteristics for plots subjected to applications of throughfall acidified to near-ambient pH 4.3 were also significant or bordered on significance. Numbers of herbivorous mites increased significantly with decreasing pH, but the predaceous mites appeared insensitive. Treated plots had fewer numbers of some groups of the larger invertebrates, especially earthworms, but variation was generally too great to show significance. The acid treatments had little effect on numbers of nematodes, saprophytic fungi or endomycorrhizal fungi.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 71 (1992), S. 1411-1414 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The iron-containing phases in nine precipitator ashes of widely differing composition have been analyzed by57Fe Mössbauer spectroscopy. The importance of the relative proportion of calcium ferrite to magnesioferrite in determining the ash fusion characteristics was established and a procedure developed which reproduced the observed proportion, starting from the ash chemical analysis data.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 71 (1992), S. 1503-1506 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A description is given of an Imaging Mössbauer Spectroscopy (IMS) system which can take 256 simultaneous Mössbauer spectra along a sample of up to 50 mm length. Illustration of its application to mineralogical studies is given with an analysis of the iron phases in a banded sample of jaspilite.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 71 (1992), S. 1399-1402 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Gold sorbed onto different types of flexible polyurethane foams from cyanide solution at pH 11 is shown to remain as the Au(CN)2 − ion. At least two different bonding mechanisms occur, with different recoilles fractions, and possible configurations are suggested.
    Type of Medium: Electronic Resource
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