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  • 1
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in hydrolytic, respiratory,catabolic and lipid biosynthetic activities depend at least in part on successional changes in the microfloral populations of allochthonous plant litter incubated in a semi-tropical estuary. Initial colonization is by populations which have a high content of muramic acid relative to the adenosine triphosphate (ATP) and which are progressively displaced by a microflora with a lower ratio of muramic acid to ATP. Scanning electron micrography of the plant-litter microflora shows a succession of forms, with an initial bacterial colonization and its progressive displacement by more complex forms. Estimates of the microbial mass and the rates of phospholipid synthesis suggest that the detrital microflora has a relatively slow growth rate compared to its growth potential.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Cell and Developmental Biology 11 (1995), S. 35-71 
    ISSN: 1081-0706
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 34 (1996), S. 0 
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: A chemical barrier is a permeable zone of reactive materials emplaced in the subsurface to remove ground-water contaminants while allowing clean ground water to pass through. Because dissolved ferric chloride hydrolyzes to amorphous ferric oxyhydroxide when it contacts calcite (CaCO3), it may be viable to emplace a zone of amorphous ferric oxyhydroxide (an absorbent for U, Mo, and other inorganic contaminants) into calcite-bearing geologic units by injecting ferric chloride through wells. For a chemical barrier to be successful, it must remain permeable and must be immobile.This investigation monitored chemical compositions, hydraulic conductivity, and iron mobility in laboratory columns and in a two-dimensional tank to determine the viability of injecting ferric chloride to form an amorphous ferric oxyhydroxide chemical barrier. We introduced a ferric chloride solution (1,345 mg/l [0.024 m] Fe) to calcite-bearing alluvial gravel to form a chemical barrier of amorphous ferric oxyhydroxide, followed by solutions contaminated with U and Mo. The simulated chemical barriers decreased U and Mo concentrations to less than 0.05 mg/1 (2.1×10-7 m) and 0.01 (1.0×10-7 m), respectively; however, the breakthrough front is spread out with concentrations increasing to more than regulatory guideline values sooner than predicted. The hydraulic conductivity of calcite-bearing alluvial gravel decreased substantially during ferric chloride introduction because of the formation of carbon dioxide but increased to within factors of 1 to 5 of the original value as synthetic ground water flowed through the system. Amorphous ferric oxyhydroxide that formed in these experiments remained immobile at flow rates exceeding those typical of ground water. These laboratory results, in conjunction with site-specific characterization data, can be used to design chemical barriers emplaced by injection of ferric chloride.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 269-279 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The trachea is a rather simple structure, and partly because of this simplicity, many attempts have been made to effect replacement with various types of prosthetic tubes. Unfortunately, the basic design of the trachea is not easily duplicated, and thus far there is no completely satisfactory prosthetic replacement. A series of porous and non-porous ceramics implanted in muscle tissue of rabbits indicated that rigid, porous materials can be compatible with soft, viable tissue. A prosthesis of porous ceramic rings and alternate bands of Dacron mesh was constructed and employed to bridge 6-cm defects created in the tracheas of mongrel dogs. After 6 months an asymptomatic animal was sacrificed. Firm fixation was accomplished and the lumen was completely patent, but histological sections demonstrated that ingrowth and scarring did not satisfactorily contain bacterial infection. Encouragement of epithelial regeneration or some artificial barrier is necessary for successful implants. Work in progress includes devices using both methods to provide this barrier.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 6 (1972), S. 347-374 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In this investigation, ceramics were studied to determine their role as rigid, abrasive implants in soft, living tissue. Discs and tubes of three ceramics, CaO·Al2O3, CaO·TiO2, and CaO·ZrO2, were introduced as porous and non-porous structures into muscle and connective tissue sites in rabbits. The animals were observed grossly to determine the duration of redness and swelling following surgery, and samples were retrieved at 1 week, 3 months, 6 months, and 9 months after implantation. A mild, acute inflammatory response immediately followed the implantation of all three materials in both the porous and non-porous forms. Histological sections of the ceramics and surrounding tissue, cut and stained for light microscopy, demonstrated the absence of inflammatory cells and revealed the normal morphology and organization of the cells present around all types of implants tested. Tissue around discs of porous ceramics healed faster and exhibited thinner fibrous encapsulations than with impervious discs of the same material. Healthy fibrous connective tissue with an ample blood supply occupied those implants with pores of 45-100 mμ, and even more rapidly filled the samples with a 100- to 150-μ pore size. The tissue ingrowth and tight adherence to the porous samples was believed responsible for the more moderate response to porous implants. No adverse responses of any kind were observed, except in a very few, atypical specimens.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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