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  • 1
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Expanding artificial implants are made of crosslinked hydorphilic polymers which imbibe body fluids and swell to a predetermined volume. The material is implanted in a dehydrated state; it then swells to fill a body cavity (i.e., vitreous cavity in the eye), or to give a form to the surrounding tissues (i.e., in plastic surgery). Such implants can be introduced in organs or tissues through a smaller incision than regular plastic and rubber implants, and have the advantage over injectable polymers in that they do not separate into globules and do not migrate from the area of implantation. The swelling equilibrium of slightly crosslinked poly (glyceryl methacrylate) [PGMA] hydrogels in salt solutions, urea, serum, and in the homogenized vitreous of the eye is given. Also, the swelling rate of PGMA in physiologic saline solution and in serum, as well as the swelling pressure-volume relationship of PGMA gels in water, is reported. The application of PGMA as an expanding implant inside the eye, and against its outer wall in retina surgery, is discussed.
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Radiopaque glass-resin composites were made for evaluation as denture base materials. The addition of silane-treated, radiopaque, powdered glass to clear poly(methyl methacrylate) resulted in composites that had greater optical translucency than commercially available pink denture base resins. These formulations could be pigmented and opacified to produce materials that simulated oral soft tissues in color and translucency.Other composites were made using various monomer, polymer and glass combinations. Those made from mixes of BIS-GMA, methyl methacrylate, poly(methyl methacrylate), and radiopaque glass had excellent translucency but handling characteristics were less than ideal.Removal of very small glass particles (less than a few μm) appeared to improve optical translucency.A radiographic survey of 12 specimens that contained from 29 to 57% of the radiopaque glass, indicated that all had sufficient radiopacity to aid in localization of swallowed or aspirated dentures made from such materials.Finishing procedures on composite specimens were more difficult and timeconsuming and did not produce surfaces as smooth as those obtained on poly(methyl methacrylate). The finished surfaces felt smooth to the tongue but might stain more easily in the mouth.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The propagation velocity and absorption coefficient of a pulse of megahertz sound was measured in 25 specimens of embalmed human skull bone. The mass densities of the specimens were also measured and their specific acoustic imped- ances calculated. The data is discussed and presented in tabular as well as graphic form.
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Physical properties were determied for radiopaque composite denture base materials consisting of poly (methyl methacrylate) as thematrix and 30, 40, and 50% by weight fo a singlane-treated barum fluoride-containing glass powder as the reinforcing filler. Specimens without glass were include for comparision.All of the materials met the requirements of Amerrican ental Association Specification No. 12 for Denture Base Polymer except that t6he material containing 50% glass had less deflection than the minimum required at the 5000-gm load in transverse testing.There was little or no difference among thematerials with respect to hardness, in denation resistance, water sorption, color stability, and resistance to drop impact.Addition of glass of the 30% level decreased the transevers strenght while 50% means with no glass. In general, the addition of glass increased the time to reach only slight effect on densities, and Young's, bulk, shear, and flexural moduli, had only slight effect on solubility and decreased the cold-cure repairability and the coefficient of linear thermal expanision.The solubility of the glass power was aboutfour times that of powdered porcelain teeth after 24 hr, and totaled 0.55% afeter 5 days.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The fatigue-crack propagation behavior of Type 316 stainless steel was studied under simulated body conditions. The fatigue specimens were immersed in circulating Ringers Solution at a temperature of 98°F. Cyclic loading was accomplished at a frequency and load waveform that corresponded to normal level walking. The concepts of linear elastic fracture mechanics were used to evaluate the fatigue behavior, and it was found that the crack-growth rate was higher under simulated body conditions than for a corresponding test conducted under ambient air conditions.
    Additional Material: 5 Ill.
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  • 7
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The transport of glucose and urea under electro-osmosis across two polyelectrolyte complex membrances and two othermembranns, for comparison, was analyzed in detail, both experimentallyand theoretically.The membranes were characterized by measurements of water content, concentration of coion and countrion in the membrane, and distribution coefficient of glucose and urea in the absence of electric current, as a function of external solution composition. In addition, fluxes of those solutes and solvent were measured as a function fo external solution composition and of electric currentThe observed phenomena were modelled by use of Fick's law of of diffusion, with electro-osmosis treated simply as bulk flow. the effect of stirring was accounted for in terms of a boundars layer mass transfer coefficient.The results indicate a good fit of the model to the data for glucose. For urea, the results indicate substantial binding of urea to the membrane matrix and anomalous behavior in he boundary layer adjacent to the membrane.
    Additional Material: 4 Ill.
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  • 9
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: One-thousand gamma particles in spherical amalgam and 1000 spherical gamma particles embedded in resin were sectioned, and the diameters for the sections were measured. Microhardness determinations were done on 50 particle sections in amaglam containing 46% mercury, 50 sections in amalgam of 52% mercury, and 50 sections of nonamalgameted particles embedded in resin.The gamma particles in amalgam seemed to have expanded as a result of their uptake of mercury. The gamma particles in amalgam had a lower hardness than the nonamalgamated particles embeded in resin. The hardness values ofthe particles were not statistically different in amalgam comtaining 46 and 52% mercury.
    Additional Material: 3 Ill.
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  • 10
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Segmented polyurethane does not indiuce acute toxcity when subjected to intracutaneous and intravascular tests with mices and rabbits. Specimens, which have been implanted in dogs for 18 months, exhibit stability heretofore unattributed tothe general class of polyurethanes. Data on tensile properties, abraxion resistance when wet, tolerance to autoclaving, results of acute toxicity test, and stablity of long-term implants are described along with appropriate means of processing the polymer into useful biomedial devices.
    Additional Material: 4 Ill.
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