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  • Articles  (2,924)
  • Wiley-Blackwell  (2,924)
  • American Association for the Advancement of Science (AAAS)
  • American Chemical Society (ACS)
  • American Meteorological Society
  • 1990-1994  (2,924)
  • Technology  (2,924)
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  • Articles  (2,924)
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  • 1
    Electronic Resource
    Electronic Resource
    A new technique for quantitation of metal particulates and metal reaction products in tissues near implants (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 191-193 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tissue specimens retrieved from four regions adjacent to hip implants during revision surgery were subjected to a novel treatment to make possible the quantitative separation of residual metal particulates and metal reaction products (metal ions and metal-protein complexes). The tissues were exposed to sodium hypochlorite solution that degraded and solubilized them, liberating metal reaction products and leaving behind metal wear particles, which were separated by centrifugation. Atomic absorption spectrophotometry was used to analyze the concentrations of the separated metal ions and wear particles. Co ion concentrations were 0.05 to 0.9 mM, Cr ion concentrations were 0.04 to 2.1 mM, and Ti ion concentrations were 0.30 to 0.60 mM. The weight of Co metal particles was 0.1 to 4.9 mg/100 mg tissue, of Cr metal particles 0.07 to 2.2 mg/100 mg tissue, and of Ti particles 0.09 to 5.2 mg/100 mg tissue; one black tissue sample contained 3333 mg Ti/100 mg tissue. No correlation was found between the concentrations of these two entities in the samples examined, probably due to the complex and varied processes creating them. The procedures discussed here will result in data that can help elucidate the separate contributions of metal reaction products and metal particulates to implant loosening. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050303
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  • 2
    Electronic Resource
    Electronic Resource
    Processing and characterization of absorbable polylactide polymers for use in surgical implants (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 133-140 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Absorbable fibers of linear poly-α-hydroxy acids have been used successfully in providing temporary scaffolds for tissue regeneration. In some surgical applications, degradation rates for poly(glycolide) (PGA) are too high, but implants of poly(L-lactide) (PLLA) fibers may degrade too slowly for optimal function. Polymers produced by copolymerization of L-lactide with varying amounts of D-lactide may offer an alternative choice for absorbable fiber based implants. Poly(L/D-lactide) stereocopolymers with L/D lactide molar ratios of 95/5, 90/10, and 85/15 were considered. Melt-spun/hot-drawn fibers with L/D molar ratios of 90/10 and 85/15 and draw ratios ranging from 3.0 to 8.9 were further evaluated by mechanical testing, differential scanning calorimetry, birefringence, x-ray diffraction, and in vitro exposure to pH 7.4 phosphate buffered saline at 37°C. Fabrication was reproducible and results indicated that tensile strength, modulus, and birefringence all increased with increasing draw ratio up to a draw ratio of 6.7 and declined thereafter; elongation to failure decreased for the entire range studied. For fibers with a draw ratio of 6.7, there was a 10% relative difference in crystallinity between the 90/10 and 85/15 lactide fibers (90/10 was higher). Wet strength retention after 12 weeks in vitro exposure was approximately 10% for the 90/10 fibers and 30% for the 85/15 fibers. The intermediate wet strength retention of lactide stereocopolymer fibers when compared to reported values for PGA and PLLA fibers, suggests these materials may be useful in absorbable surgical implants for tissue repair and regeneration. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050206
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  • 3
    Electronic Resource
    Electronic Resource
    Creep behavior of hand-mixed simplex P bone cement under cyclic tensile loading (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 235-243 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Acrylic cement, used for the fixation of total hip replacements and other orthopedic implants, is a subject of renewed scientific interest as a result of recent hypotheses about dynamic, longterm mechanical failure mechanisms suspected to play a role in prosthetic loosening. Little is known, however, about the long-term mechanical behavior of cement. In this study, the dynamic creep deformation of hand mixed acrylic cement was examined in laboratory tests. Strain patterns found represented the familiar creep process consisting of a primary, a secondary, and a tertiary creep phase. Specimens dynamically loaded with a maximum stress of 3 MPa from 0 were subject to creep of about 50% of the elastic strain after 250 000 loading cycles. A linear relationship between the logarithmic values of the creep-strain and the number of loading cycles was found. Specimens exposed to higher loads showed significantly higher creep-strains. No relationship could be established between the strain levels and the porosity of the specimens. Specimens dynamically loaded with a maximal stress of 7 or 11 MPa from 0 failed during the tests. The number of loading cycles to failure was similar to fatigue strength data reported in earlier literature. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050309
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  • 4
    Electronic Resource
    Electronic Resource
    Letters to the editor (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 271-272 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050314
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  • 5
    Electronic Resource
    Electronic Resource
    Biomechanical aspects on rehydrated freeze-dried human allograft dura mater tissues (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 265-270 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Biomechanical properties of rehydrated freeze-dried human dura mater tissues were studied. Scanning electron and polarized light analysis indicated a multilayered distribution of collagen fibers in the dura mater tissue. Uniaxial tensile testing of 95 test strips permitted determination of average values for failure stress (6.65 ± 0.14 MPa), failure strain (0.15 ± 0.003), tangent modulus (69.50 ± 1.29 MPa), elongation (0.56 ± 0.01), and tangent stiffness (12.53 ± 0.24 kN/m) of the dura mater tissue. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050313
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  • 6
    Electronic Resource
    Electronic Resource
    Erratum (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 273-273 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050315
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  • 7
    Electronic Resource
    Electronic Resource
    Announcement (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 275-275 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050316
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  • 8
    Electronic Resource
    Electronic Resource
    Mixed mode fracture characterization of hydroxylapatite-titanium alloy interface (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 285-291 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Cantilever beam and four-point bend specimen geometries were used to experimentally determine the critical energy release rates for a plasma sprayed hydroxylapatite-titanium alloy (HA-Ti alloy) interface. A locus of energy release rates as a function of crack tip phase angle was determined where a 0° phase angle represented tensile opening (mode I) loading and a 90° phase angle represented in-plane shear (mode II) loading. Energy release rates were found to increase substantially with an increase in phase angle. An energy release rate of 0.108 N/mm was determined for a phase angle of 0° (mode I). Energy release rates of 0.221, 0.686, and 1.212 N/mm were determined for phase angles of 66°, 69°, and 72°, respectively. The experimental data was matched to a phenomenological model for which crack propagation depended on mode I loading alone indicating that crack propagation at the Ha-Ti alloy interface is dominated by the mode I loading alone indicating that crack propagation at the Ha-Ti alloy interface is dominated by the mode I loading component. Therefore, regions of HA coated implants that experience compressive or shear loading across the HA-Ti alloy interface may be much less likely to debond than regions that experience tensile loading. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050403
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  • 9
    Electronic Resource
    Electronic Resource
    Load transfer through a hydroxyapatite-coated canine hip implant (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 293-306 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Strain transfer near hydroxyapatite (HA) coated canine hip implants was examined using simulated anatomical loading based on in vivo strain measurements. Strain changes near implants relative to intact control values were in excess of 100% for transverse and principal strains for zero time period (immediate postimplant) specimens. They were generally smaller (100% or less) for axial, transverse, and principal minimums in the same locations for 4 months postimplantation specimens.Cortical bone loss occurred in all implanted femora. The most extensive loss, up to 47%, occurred adjacent to the proximal section of the implant. Extensive trabecular bone formation, over 300% in some regions of each femur, was noted in all implanted femora.Backscattered electron imaging along the HA-coated sections of the implants showed extensive bone bonded to the coating. Normal light and UV light micrographs showed direct bone apposition to the implant surfaces and extensive bone formation in all test animals. Microscopy revealed no evidence of any soft tissue layer between the implant and bone. Bone was typically found in direct contact with the implant surface.Histomorphometry indicated that bone formation rates in the implanted femora were elevated, up to 850%, relative to controls. Fewer formation sites were noted on the posterior and lateral (in two cases zero sites). Mineral apposition rates (MAR) from two of the dogs were slightly elevated (from 110-113%) in the implanted femora relative to controls and depressed (to about 83% of controls) in a third. © 1994 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050404
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  • 10
    Electronic Resource
    Electronic Resource
    Compressive stress relaxation behavior of irradiated ultra-high molecular weight polyethylene at 37°C (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 333-338 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The preconditioned stress relaxation behavior of irradiated ultra-high molecular weight polyethylene (UHMWPE), a commonly used bearing surface in total joint replacements (TJR), was modelled in uniaxial compression at 37°C. Twenty cylindrical specimens (10 mm dia. × 27 mm length) were machined from a compression molded plate of medical grade UHMWPE and γ-irradiated to a minimum dose of 2.5 Mrad. At an initial strain rate 1000%/s, five specimens were each tested at constant strains of 1, 2, 5 and 10%. The modified superposition principle provided a good agreement of the nonlinear viscoelastic (stress relaxation) behavior of UHMWPE (standard error of 0.0753 MPa). © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050408
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  • 11
    Electronic Resource
    Electronic Resource
    Apatite coated on organic polymers by biomimetic process: Improvement in its adhesion to substrate by NaOH treatment (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 339-347 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A dense, uniform and highly biologically active bone-like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substrate surface by the following biomimetic method at ordinary temperature and pressure. First, a substrate is set in contact with particles of bioactive CaO SiO2 based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma. Second, the substrate is soaked in another solution with ion concentrations 1.5 times those of SBF (1.5 SBF). In the present study, organic polymer substrates treated with 5 M NaOH solution were subjected to the above mentioned biomimetic process. The induction periods for the apatite nucleation on polyethyl-eneterephthalate (PET), polymethylmethacrylate (PMMA), polyamide 6 (PA6), and polyethersulfone (PESF) substrates were reduced from 24 to 12 h with the NaOH treatment. The adhesive strength of the formed apatite layer were increased from 3.5 to 8.6 MPa, from 1.1 to 3.4 MPa, and from 0.6 to 5.3 MPa with the NaOH treatment, for PET, PMMA, and PA 6, respectively. It was assumed that highly polar groups, such as carboxyl and sulfinyl ones formed by the hydrolysis of an ester group on PET and PMMA and of an amide group on PA 6, or of a sulfonyl group on PESF with the NaOH treatment, attached a large number of hydrated silica dissolved from the glass particles, to accelerate the apatite nucleation, and also to form a strong bond with the apatite. The apatite-organic polymer composites thus obtained are expected to be useful as bone-repairing as well as soft tissue-repairing materials. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/jab.770050409
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  • 12
    Electronic Resource
    Electronic Resource
    Adsorption of collagenase to particulate titanium: A possible mechanism for collagenase localization in periprosthetic tissue (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 353-360 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Osteolysis is a central feature of aseptic loosening of orthopaedic joint prostheses. This destructive process is believed to result from phagocytosis of implant wear debris by periprosthetic and synovial macrophages and the subsequent release of proinflammatory mediators, including collagenase. Isolated murine macrophages were cultured in vitro with particulate titanium in order to explore the mechanism of macrophage activation by particulate wear debris. The results, in which the amount of secreted, soluble collagenase in culture supernatants was inversely proportional to titanium concentration, suggested that titanium strongly adsorbed secreted collagenase. This inference was confirmed by direct binding assays in which particulate titanium coated with adsorbed collagenase bound an alkaline phosphatase conjugated anticollagenase antibody, but not a conjugated anti-IgG antibody. Adsorption of collagenase was not influenced by preincubation of titanium particles with albumin. The adsorbed collagenase remained enzymatically active as indicated by its ability to hydrolyze a synthetic peptide substrate. These results demonstrate that particulate titanium stimulates collagenase production by macrophages and then strongly adsorbs the secreted proinflammatory enzyme. The process of macrophage stimulation, collagenase secretion, and adsorption may represent an important mechanism for localization and concentration of collagenase in periprosthetic and synovial tissue, a mechanism that ultimately triggers bone resorption through osteoclast activation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050411
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  • 13
    Electronic Resource
    Electronic Resource
    The editor's corner: Substantially equivalent to what? (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 375-375 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050414
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  • 14
    Electronic Resource
    Electronic Resource
    A new saw technique improves preparation of bone sections for light and electron microscopy (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 369-373 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A newly developed saw technique was developed to produce sections circa 10 μm or thicker from fresh bone or dentine and from plastic embedded undecalcified bone tissue with or without implant materials. The method comprises only one step because grinding or polishing to make the sections thinner is not necessary. The bone slices can be decalcified rapidly without using aggressive solvents and used for making ultrathin sections for electron microscopy. Sections of fresh dentine of 15 to 30 μm are transparent which makes it possible to study osteoclastic resorption in vitro. Sections, 10 μm thick, with an intact interface of bone and implant material can be observed for biocompatibility studies. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050413
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  • 15
    Electronic Resource
    Electronic Resource
    Biomaterials applicability: Establishing suitable “materials' equivalency” protocols (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 377-378 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050415
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  • 16
    Electronic Resource
    Electronic Resource
    Biomaterials lubricated for minimum frictional resistance (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 175-181 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: To improve the frictional characteristics of a biomaterial, the mechanical performance of a lubricated surface was studied. In vitro friction tests showed that the coefficient of dynamic friction of the lubricated surface was about 0.01 against rabbit bladder and the coefficient of static friction increased with the preload period. The efficacy of a lubricated cystoscope was evaluated by an in vivo test simulating cystoscope operation. The maximal and the total resistance force on the cystoscope model were found to decrease with the surface lubrication. Histological study revealed that urethral damage caused by rubbing with the cystoscope model was reduced by this lubrication technique. Presumably, prolonged retention of water on the lubricated surface region prevented tissue adhesion to the foreign material. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/jab.770050211
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  • 17
    Electronic Resource
    Electronic Resource
    Announcement (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 183-183 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050212
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  • 18
    Electronic Resource
    Electronic Resource
    Masthead (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994) 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050301
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  • 19
    Electronic Resource
    Electronic Resource
    Inhibition of in vitro calcium phosphate precipitation in presence of polyurethane via surface modification and drug delivery (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 245-254 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Biomaterial associated calcification is the principal cause of the clinical failure of bioprosthetic implants. The present investigation describes the mineralization of polymeric substrate in an extracirculatory environment and the possible methods of prevention. Calcification was examined on various polyurethane films (and bioprosthetic tissue) incubated in metastable solutions of calcium phosphate and the role of polymer casting and precipitation was evaluated. The formulation and the in vitro efficacy of prolonged controlled-release chitosan matrices, containing the novel anticalcification agents, such as Fe+++ or protamine sulfate (PS), were also attempted. The in vitro release profiles of PS from chitosan beads was performed in a rotating shaker (100 rpm) in 0.1 M phosphate buffer (pH 7.4) and was monitored spectrophotometrically. The amount and percentage of drug release were much higher initially, which was controlled with the incorporation of egg phosphatidyl choline (EPC). The PS loaded chitosan beads (coincubated in calcium phosphate solution with the calcifiable polyurethane films) significantly inhibited biomaterial calcification (about 40-50% inhibition). Surface modification of polyurethanes with Fe+++ or PS also inhibited the calcification profile of the material. These findings suggest the possibility of a combination therapy for prevention of biomaterial associated calcification via surface modifications in conjunction with long-term controlled release of the anticalcifying drugs. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/jab.770050310
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  • 20
    Electronic Resource
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    Torsional properties of healed canine diaphyseal defects grafted with a fibrillar collagen and hydroxyapatite/tricalcium phosphate composite (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 277-283 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The need for alternatives to autogenous bone grafts is widely recognized. This study compared the torsional strength of canine femora 1 year after grafting with one of three forms of a collagen/hydroxyapatite/tricalcium phosphate bone grafting material (COLLAGRAFT15), autogenous bone, or no graft. The groups were compared to each other and to the unoperated contralateral femora. Results of torsional testing were evaluated for torsional strength, torsional displacement, total energy to fracture and White fracture mode. Data analysis showed lower torsional strength of the operated vs. unoperated femora with the exception of morsellized COLLAGRAFT15 material, which had higher strength. However, the only difference in the operated groups was that the morsellized COLLAGRAFT15 had greater strength than several groups including the autogenous bone group. There was no difference found in angular displacement between any of the groups. However, there was a difference in the energy to fracture in both strip forms of the COLLAGRAFT15. The final conclusion is that in this model, grafting with COLLAGRAFT15 provided torsional properties at one year postoperatively at least equivalent to autogenous bone. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/jab.770050402
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  • 21
    Electronic Resource
    Electronic Resource
    Use of a compact sandwich specimen to evaluate fracture toughness and interfacial bonding of bone (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 315-323 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The objective of the present study was to develop a reliable and statistically valid test to measure the fracture toughness of small specimens of bone, and by extension, prosthetic materials, using a compact sandwich specimen. Samples of bone were sandwiched between holders of a different material and using this specimen configuration a new technique was developed to test the fracture toughness of the bone interlayer. The effects of different speciments sizes and holder materials were investigated empirically. Using finite element analysis a correction factor was determined to account for the finite thickness of the interlayer and the analytical solutions governing the test specimen were accordingly modified. Bulk compact tension specimens of bone were tested for comparison. Both wet and dry bone were evaluated and the fracture surface morphology characterized using scanning electron microscopy. The results indicate no statistically significant differences between the fracture toughness values obtained from the compact tension and sandwich specimens. The application of this technique to the testing of interfacial bonding between bone and biomaterials is discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/jab.770050406
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  • 22
    Electronic Resource
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    Mechanical properties of vacuum-mixed acrylic bone cement (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 307-314 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The thrust of the present work was the experimental determination of the uniaxial static compressive and fully reversed tension-compression fatigue properties of CMWTM 3 acrylic bone cement whose consituents were mixed in a properietary chamber while simultaneously subjected to a vacuum. Selected indices of performance in this material are: mean static compressive strength, 81.4 MPa; mean compressive modulus of elasticity, 1.95 GPa; endurance limit, 8.1 MPa; and characteristic fatigue life (using a three-parameter Weibull fit to the fatigue test data obtained at a stress of ±10 MPa), 238 712 cycles. The difficulties in comparing results obtained using different cement formulations, preparation conditions, and test conditions are detailed. With this in mind, it is suggested that the present results are within the range of values reported by previous workers for other formulations mixed using a variety of methods. The clinical significance of the present results is discussed. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/jab.770050405
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    Ciprofloxacin attachment to porous-coated titanium surfaces (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 325-331 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A simple and effective method for attaching ciprofloxacin HCl salt to the surface of porouscoated titanium based orthopedic materials was developed. The method utilizes the electrophoretic migration of both fine ciprofloxacin HCl particles and ciprofloxacin ions to deposit the antibiotic salt on a positively biased surface. The quantity of antibiotic deposited can be easily and effectively controlled by varying the time of deposition and applied voltage. In vitro tests have indicated that the antimicrobial activity of the treated surfaces is retained for a period of 5 days. The method allows a significant amount of antibiotic to be deposited and could theoretically be used to deliver antibiotics to the tissues surrounding prosthetic devices in order to prevent postoperative infections. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/jab.770050407
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    Effects of fixation technique on displacement incompatibilities at the bone-implant interface in cementless total knee replacement in a canine model (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 349-352 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bone-implant displacements can be caused by rigid body motion and by differences in material properties of the implant and bone. In the present study of the tibial component in total knee replacement, we tested a series of tibial component fixation designs to determine how certain design features influenced the magnitude of the tangential displacement between the component and supporting bone in a canine model. The transverse expansion of the proximal tibia under static axial loading was measured in the intact tibia and then in the same bone following implantation of tibial components with different interface characteristics: cementless flat smooth, cementless flat porous-coated, cementless flat porous-coated with screws, cementless pegged porous-coated, cementless pegged porous-coated with screws, cemented pegged, and cemented pegged with screws. In all cases, the magnitude of the transverse expansion increased with higher applied loads. When the statistical analysis was restricted to the cementless interfaces, the presence/absence of the porous coating, the presence/absence of pegs, and the use of screws had no significant influence on tibial expansion. However, in an analysis including the cemented and cementless pegged components, tibial expansion was reduced with the use of screws. The magnitude of the interface motion due to these displacement incompatibilities was approximately fivefold lower than the amount of interface motion related to rigid body motion found in a separate study with the canine model. The measured expansion was similar in the intact tibiae and the implanted tibiae, suggesting that the transverse constraint in the canine proximal tibia must be provided by the surrounding cortical ring rather than the subchondral bone. © 1994 John Wiley & Sons, Inc.
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    Improved sensitivity and decreased sample size in a cytotoxicity test for biomaterials: A modified colony microassay using a microplate and crystal violet staining (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 361-367 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Modified Eagle's minimum essential medium supplemented with 5% fetal calf serum was highly sensitive to cytotoxicity and formed large control colonies in the V79 colony assay. A highly sensitive cytotoxicity test was developed using 96-well microtiter plates. Test chemicals or extracts of polyurethane materials containing the same chemicals were added 24 h after inoculation of cell suspensions. The cells were fixed and stained with crystal violet after additional culture for 6 days (V79 cells) or 10 days (Balb/3T3 cells). In terms of sensitivity and rapid quantitative measurement, this modified colony microassay, using a low cell density in 96-well microplates, was superior to various cytotxicity tests such as colony, growth inhibition, cytolethality, and agar diffusion assays. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/jab.770050412
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    Metallic wear debris in metal-backed patellar failure (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 9-16 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Eight patients with failure of metal-backed patellar components were studied for evidence of intraarticular and systemic metal deposition. Seven of the eight patients had failure of a titanium-based patellar component that then articulated with a cobaltchromium femoral component. One patient had articulation of a cobalt-chromium patellar component against a cobalt-chromium femoral component. All components failed by the same pattern of failure. Wearing of the ultra high molecular weight polyethylene was followed by displacement of the polyethylene and then metal-to-metal contact of the components.Methods for analysis of the debris included light and electron microscopy of synovial tissue and electron dispersive x-ray analysis (EDAX) of tissue. Graphite furnace atomic absorption spectroscopy (GFAAS) was done on synovial fluid and synovial tissue as well as urine and blood specimens taken at various times from implantation to patellar revision.Massive deposition of metallic debris within the knee joint was documented both histologically and by GFAAS. Titanium levels reached as high as 2776 ppm (mg/L) in the synovial fluid and as high as 917 mg/g of synovial tissue. Elevation of all the pertinent metals was seen in the tissue and body fluids. Titanium and aluminum levels were the highest. Titanium levels in the serum generally were highest near the time of implant failure. Other metal elevations were variable and could not be related to the time of failure. Synovial fluid levels of all metals and serum levels of titanium are reflective of intraarticular generation of metallic debris.This study demonstrates that in situations of failure of a device, massive intraarticular debris generation occurs and systemic transport will occur. To date no systemic consequences can be attributed to the deposition of debris and follow-up urine and blood specimens suggest that debridement and revision of the failed device results in lowering of the ion levels. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/jab.770050103
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    Characterization of polyesterurethane degradation products (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 1-7 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Microthane foam, a poly(ester)urethane, used as a covering of some breast implants (Meme or Replicon by Surgitek) degrades readily in phosphate buffer pH 7.4 producing multiple unknown products in addition to 2,4 and 2,6 toluenediamine (TDA). The cumulative weight loss of the foam in buffer was 1.5% at 1 week and 2% at 2 weeks. Multiple peak molecular weights from 105 to 665 000 were found in the aqueous foam extracts following 2 weeks of incubation at 37°C using size exclusion chromatography (SEC). TDA was measured in the foam buffer extracts by high pressure liquid chromatography (HPLC) and confirmed by gas chromatography/mass spectroscopy (GC/MS). The total cumulative levels of 2,4 TDA and 2,6 TDA measured were 3 ± 0.65 μg/g of foam and 1.13 ± 0.19 μg/g of foam following 36 days of incubation at 37 °C. Higher amounts, 8.96 μg/g of 2,4 TDA and 3.3 μg/g of 2,6 TDA, were obtained at 50 °C. The cumulative release of TDA in aqueous extracts was found to correlate linearly with time suggesting a slow but continuous production of TDA under neutral conditions. However, less than 0.2 μg/g of TDA was detected as residual TDA in the methylene chloride extracts following up to 60 days at 37 °C. PU foam extracted with methylene chloride under similar conditions showed higher foam weight loss, 4.4 and 5% at 1 and 2 weeks, respectively. The results presented in this study provide further evidence that Microthane undergoes hydrolysis under neutral conditions in aqueous solutions producing TDA and other unknown low molecular weight components and oligomers. © 1994 John Wiley & Sons, Inc.
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    Behaviour of endothelial cells cultured in the presence of polymers impregnated with adsorbable proteins (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 47-50 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The aim of this study is the in vitro evaluation of the functional modifications of human endothelial cells in the presence of Dacron® impregnated with resorbable proteins. For this purpose, human endothelial cells isolated from the umbilical vein have been put in contact for 48 h with knitted Dacron® impregnated with collagen or gelatin and with nonimpregnated knitted Dacron® and double velour Dacron®. As control, endothelial cells cultured in the absence of material were used. After the contact time, cell counts were performed. In addition, the concentrations of two proteins synthesized by endothelium, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1), were evaluated on the supernatants. In the cultures in contact with Dacron® impregnated with collagen or gelatin and in those in contact with knitted Dacron®, we have observed a smaller cell growth than that observed in cultures without materials. The synthesis of t-PA showed some significant variations between the control cultures and those in contact with the materials. PAI-1 production was significantly reduced in the cultures in contact with gelatin impregnated Dacron® and with knitted Dacron®. Double velour Dacron® caused no significant variation in any of the examined parameters. © 1994 John Wiley & Sons, Inc.
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    Masthead (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994) 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050101
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    Effect of hydroxyapatite coating on bone growth into porous titanium alloy implants under loaded conditions (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 23-37 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Titanium alloy tibial segmented defect repair devices whose stems were coated with two layers of titanium alloy beads (Ti-6A1-4V, bead diameter c. 750 μm) were implanted in six beagle dogs. In four of the animals stems had been plasma-sprayed with hydroxyapatite (HA); the other two animals received devices with uncoated stems. Devices intended for 6-month and 3-month evaluation were implanted in right and left tibiae, respectively. Because the amount of bone ingrowth into pore spaces was greater in cortical bone than in cancellous bone, stems were more stable and firmer in the cortical bone. In stems coated with HA, new bone tissue came into contact with the surface of beads in the superficial layer of the stem faster than in stems not so coated. Furthermore, new bone tissue entered into pore spaces in these stems earlier, in larger amounts, and reached more deeply, binding directly to the beads. Rate and quality of bone ingrowth did not differ between the 3-month and 6-month tibiae; in other words, optimal bone ingrowth was attained within 3 months postimplantation. © 1994 John Wiley & Sons, Inc.
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    Chemical and mechanical degradation of UHMWPE: Report of the development of an in vitro test (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 17-21 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ultra high molecular weight polyethylene (UHMWPE), used in total joint replacement implants, undergoes oxidative degradation due to gamma radiation sterilization and to exposure to oxidizing agents in the body environment. UHMWPE components also experience large stresses both on and near the articulating surface. It is hypothesized that there is a causal relationship between chemical degradation and mechanical loading of UHMWPE joint components. This report describes the development of an in vitro test to examine the combined effects of chemical environment and cyclic loading history on the chemical, physical, and mechanical properties of UHMWPE. The test apparatus consists of modular load trains, in which strings of UHMWPE test specimens can be subjected to cyclic tensile and compression load ranges, while being exposed to either control or degrading environments. Following cyclic loading for specified time intervals, the specimens can be statically loaded to determine the effect of cyclic loading and environment on the monotonic tensile and compressive stress-strain behavior of UHMWPE. To determine the appropriate control and degrading environments, gamma radiation sterilized UHMWPE specimens were maintained (unloaded) for up to 6 months in aqueous environments of distilled water and three concentrations of hydrogen peroxide (0.01, 0.1, and 1.0%) in distilled water at 37°C. Specimens were evaluated with depth from the surface for changes in density. Infrared spectroscopy (IR) analysis was conducted on selected surface sections. No significant changes in density or surface IR spectra occurred for specimens in distilled water as compared with the UHMWPE in the initial radiation sterilized condition. Specimens exposed to hydrogen peroxide solutions demonstrated changes in density and IR spectra consistent with oxidative degradation and comparable to the changes previously observed on retrieved UHMWPE components. Based on these results, distilled water was selected for the control environment. A 0.5% hydrogen peroxide solution was selected for the test environment, to produce moderate changes at a rate compatible with the maximum 12-month time period of the experiment. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/jab.770050104
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    A method for transmission electron microscopy investigation of the osteoblast/hydroxyapatite interface (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 39-45 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Neonatal rat calvaria osteoblasts were cultured on hydroxyapatite (as received or relatively-rough surface and mechanically polished to a 0.3-m̈m finish) and on glass (reference material) in Dulbecco's Modified Eagle Medium supplemented with 10% fetal bovine serum, 50 μg/mL ascorbic acid, and 10 mM β-glycerophosphate under standard, sterile, cell-culture conditions for 1, 3, 7, 14 and 21 days. At the end of the prescribed time periods, the cells were fixed and embedded in resin before removing the material substrates by exposure to acid solutions. Transmission electron microscopic examination of stained, ultrathin sections of the biological structures revealed osteoblast monolayers at 1 day of culture but multilayered cell structures at later time periods (14 and 21 days). The osteoblasts exhibited continuous contact and intimate apposition on polished hydroxyapatite and on glass; in contrast, osteoblasts on as received or rough hydroxyapatite made contact with discrete high points, spanned low regions of the material surface, and did not conform to all substrate contours. An electron dense layer (composed of mucopolysaccharides and proteins) was observed on all substrates tested after 7 days of culture. Collagen fibrils were seen interspersed among the osteoblasts as early as 3 days of culture; at later culture times, (i.e., 21 days) mineralized loci were observed in the extracellular matrix. © 1994 John Wiley & Sons, Inc.
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    Evaluation of absorbable poly(ortho esters) for use in surgical implants (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 51-64 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Recent reports describe an unfavorable noninfective inflammatory response to acidic degradation products in clinical applications of bone fixation devices fabricated from bulk hydrolyzing polyglycolides and polylactides (PGA and PLA). The work described here suggests that poly(ortho esters) (POEs) offer an alternative. By comparison, hydrophobic POEs degrade predominately via surface hydrolysis, yielding first a combination of nonacidic degradation products, followed by alcoholic and acidic products gradually over time. POE specimens proved acutely nontoxic in United States Pharmacopeia tests of cellular, intracutaneous, systemic, and intramuscular implant toxicity.Hot-molded specimens degraded slowly in saline, retaining 92% initial stiffness (1.6 GPa flexion) and retaining 80% initial strength (66 MPa flexion) in 12 weeks. Degradation was almost unaffected by decreasing saline pH from 7.4 to 5.0. This demonstrated the relative hydrophobicity of POEs, since incorporation of small amounts of acid within the polymer markedly increases the degradation rate. Degradation rates were increased substantially by dynamic mechanical loading in saline. This may be true for other degradable polymers also, but no data could be found in the literature. Presumably, tensile loading opens microcracks, allowing water to enter.Solvent cast POE films were strong in tension (30 + MPa tensile yield) and reasonably tough (12-15% elongation to yield). Higher molecular weight films (41-67 kDa) showed no degradation in mechanical properties after 31 days in physiological buffer at body temperature. A 27-kDa film offered similar initial strength and stiffness but began showing mechanical degradation at 31 days. The films showed a decrease in weight with exposure time but no change in either molecular weight or water absorption at 31 days, further supporting the observation that POE degrades by surface hydrolysis rather than by bulk hydrolysis. © 1994 John Wiley & Sons, Inc.
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    Phosphonated polyurethanes that resist calcification (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 65-77 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Cardiovascular implant mineralization involving bioprosthetic materials, such as glutaraldehyde cross linked porcine aortic valves or synthetic materials such as polyurethanes, is an important problem that frequently leads to clinical failure of bioprosthetic heart valves, and complicates long-term experimental artificial heart device implants. Novel, proprietary, calcification resistant polyetherurethanes (PEU) as an alternative to bioprosthetic materials were the subject of these investigations. A series of PEU was derivatized through a proprietary reaction mechanism to achieve covalent binding of 100 to 500 nM/mg of bisphosphonate (2-hydroxyethane bisphosphonic acid, HEBP). The stability of HEBP (physically dispersed or covalently bound) verified by studying the release kinetics in physiological buffer (pH 7.4) at 37°C, demonstrated the covalent binding reaction to be stable, efficient, and permanent. Surface (FTIR-ATR, ESCA, SEM/EDX) and bulk (solubility, GPC) properties demonstrated that the covalent binding of HEBP occurs in the soft segment of the PEU, reduces surface degradation, and does not affect the original material properties of the PEU (prior to derivatization). In vitro calcium diffusion of the derivatized PEU showed a decrease in calcium permeation as the concentration of HEBP covalent binding was increased. In vivo properties of underivatized and derivatized PEU (containing 100 nM of covalently bound HEBP) were studied with rat subdermal implants for 60 days. Explants demonstrated calcification resistance due to the covalently bound HEBP without any side effects. It is concluded that a PEU containing HEBP might serve as a calcification resistant candidate material for the fabrication of a heart valve prosthesis and other implantable devices. © 1994 John Wiley & Sons, Inc.
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    Masthead (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994) 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050201
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    FEM analysis of stress and deformation in the vicinities of arterial graft anastomosisThis work was performed at the Department of Biomedical Control, Research Institute of Applied Electricity, Hokkaido University, Sapporo, Japan. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 79-87 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Effects of compliance mismatch at end-to-end artery/graft anastomoses on the distributions of wall stresses and compliance were studied using the finite element method. The canine common carotid artery (CCA), and expanded polytetrafluoro-ethylene (EPTFE) thin-walled graft, and a newly developed polyurethane graft (HS-2) were used as the models for the host artery, stiff graft, and compliant graft, respectively. Mechanical properties of CCA and HS-2 were determined from a pressure-diameter test, those of EPTFE graft were obtained by tensile test. Nonlinear elasticity of CCA and HS-2 was incorporated by iterating a linear FEM analysis: elastic moduli of the vessel walls were changed every 5 mmHg. The results showed that, in the case of the artery/EPTFE anastomosis in which the diameters of the artery and the graft were matched at 0 mmHg, regions of high tensile and shear stresses appeared in the graft near the anastomosis at the intraluminal pressure of 100 mmHg. The stress concentrations were remarkable, even if the diameters were matched at 100 mmHg and the pressure was varied within a physiological range (60-140 mmHg). Moreover, a hypercompliant zone appeared in the arterial wall near the anastomosis in this case. On the other hand, neither high stress concentrations nor hypercompliant zone appeared near the artery/HS-2 anastomosis. Because the mechanical complications at the compliance-mismatched anastomosis might finally result in graft failure and occlusion, it is important to match the compliance of graft to that of natural arteries, particularly to improve the patency of small-calibered arterial grafts. © 1994 John Wiley & Sons, Inc.
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    Technical note. Symmetry of biomechanical properties in canine femora (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 99-101 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/jab.770050112
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    Physical properties of hyaluronic acid and hydroxypropylmethylcellulose in solution: Evaluation of coating ability (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 89-98 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Hyaluronic acid (HA) and hydroxypropylmethylcellulose (HPMC) in buffered saline are “viscoelastics” used in ophthalmic surgery to prevent mechanical damage to delicate eye structures and to form a protective coating over corneal endothelium.HA is a high molecular weight polysaccharide that exhibits decreasing viscosity at increased shear rates. HPMC is a cellulose derivative that exhibits low surface tension. This study examines the physical properties of HA and HPMC solutions and attempts to correlate these properties with the ability of those macromolecules to coat and protect ocular structures.Results presented in this article suggest mixtures of HA and HPMC exhibit low surface tension and ease of aspiration characteristics that are desired in viscoelastic materials. For this reason a blend of these two macromoleculars offers handling advantages over each of these individual macromolecules. © 1994 John Wiley & Sons, Inc.
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    Effects of metallic debris on adult bovine articular chondrocyte metabolism in vitro (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 109-115 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of this study was to examine the effects of particles, derived from metals commonly used in joint prostheses, on chondrocyte proliferation, metabolism, and morphology in vitro. Chondrocyte viability was influenced by the type and concentration of metal particle added. Cobalt was toxic to chondrocytes at all particle concentrations (0.83-0.000083%, v/v), whereas the chromium, titanium and titanium-aluminum particles only effected chondrocyte viability at high concentrations. The metabolic response of chondrocytes to particulate debris as assessed by caseinase, collagenase, and hexosaminidase activities were variable at low concentrations but were always reduced at high concentrations (0.83% v/v). Prostaglandin E2 levels in the medium showed a steady increase when particle load increased, except in the medium of chondrocytes exposed to titanium-aluminum. Scanning electron microscopy of chondrocytes exposed to titanium showed ruffled cell borders and frequent membrane blebbings. This was in contrast to chondrocytes exposed to cobalt, where the crenated appearance indicated cell death, and titanium-aluminum, where the cells appeared quiescent. These findings show that metal particles alter chondrocyte viability and metabolism and suggest that particulate debris may influence the integrity and stability of articular cartilage following hemiarthroplasty. © 1994 John Wiley & Sons, Inc.
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    Incidence of infection and analysis of contributing factors in revision joint arthroplasty over a two-year period (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 103-108 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study examined the incidence of infection and the contributing factors in 166 patients undergoing total joint revision surgery. Of these 32 (19%) had organisms grown from material taken at the local site at the time of revision surgery. Six of the culture-negative patients were clinically suspected of having an infection. With the inclusion of these six, the total incidence of infection in these revision patients was 23%. This is not the incidence of infection in total joint surgery. This is the incidence of infection in patients undergoing revision surgery for whatever reason. The cause of infection in 53% of the cases was either Staphylococcus aureus or coagulase-negative Staphylococci. The Gram-negative bacteria were implicated in only five (15%) of the cases. Many of these infections (31%) were in patients who had had the implant for greater than 7 years. Only 15% of the infections were in patients who had the implant for less than 6 months with an additional 9% being revised in the first year. There were no clinical symptoms or underlying conditions, including allergy, that distinguished the infected from the noninfected group. The infection rate was somewhat higher with the cobalt chromium alloys, somewhat less in the uncemented devices, and somewhat higher in the patients with total knee replacements than those with total hip replacements. The histopathologic analysis revealed that the presence of polymorphonuclear leukocytes (PMNS) was correlated with infection, but most patients with infection had lymphocytes rather than PMNS indicative of a chronic infection. Thus the diagnosis of infection on the basis of histopathology needs to be carefully evaluated. The presence of PMNS is diagnostic for infection, but has a high number of false negatives. The histopathologic data and the data on implantation time indicate that most of these infections are chronic infections. © 1994 John Wiley & Sons, Inc.
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    Effects of intermittent micromotion versus polymer particles on tissue ingrowth: Experiment using a micromotion chamber implanted in rabbits (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 117-123 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Both micromotion and particulate debris have been implicated in the process of aseptic loosening of joint arthroplasties and the failure of bone ingrowth into porous coated prostheses. In the present study, we compare the histological and histomorphometric results of tissue ingrowth into titanium chambers in the presence of interfacial micromotion versus phagocytosable particles of two polymers used in orthopedic surgery. The micromotion chamber, having a 1 × 1 × 5 mm transverse canal for tissue ingrowth was implanted into the proximal right tibia of five mature male New Zealand white rabbits. In the first series, the chambers were manipulated at 40 cycles per day (cpd) at 1 Hz, using an amplitude of 0.5 mm. The tissue within the chamber was harvested after 3 weeks. In the following series, fabricated particles of bone cement or highdensity polyethylene (HDPE) were mixed with the carrier, 1% sodium hyaluronate (Healon) to obtain a concentration of 108 particles/mL; this solution was implanted in the canal of the chamber but micromotion was not instituted. Histological sections from control, nonmoved chambers, or those implanted with the carrier Healon alone contained extensive trabecular and woven bone embedded in a fibrovascular stroma. The application of 40 cpd resulted in less formation of bone and more fibrous tissue within the chamber. The sections containing particles of bone cement were infiltrated by numerous foamy, mononuclear, and multinuclear histiocytes. HDPE particles were associated with more fibrosis and a less aggressive foreign body response compared to cement particles. Chambers manipulated at 40 cpd and those containing cement or HDPE particles contained less bone compared to nonmoved chambers or those containing Healon alone. Despite evoking different histological reactions, the presence of micromotion or polymer particles appears to inhibit the formation of bone in this experimental model. © 1994 John Wiley & Sons, Inc.
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    Materials and design concepts for an intervertebral disc spacer. I. Fiber-reinforced composite design (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 125-132 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The intervertebral disc is a complex joint anatomically and functionally. It may be displaced or damaged due to trauma or a disease process. To alleviate this condition, it may be necessary to remove the involved disc surgically and fuse the two adjacent vertebrae. Fusion is one option; however, replacing the damaged disc (or part thereof) with a suitable synthetic equivalent to allow near normal joint motion is more desirable. Unfortunately, the complex mechanical properties of the lumbar disc cannot be duplicated with homogeneous synthetic materials (polymers). To overcome this fundamental problem we have developed rational designs utilizing biocompatible thermoplastic elastomers of various stiffnesses (durometers) with and without fiber reinforcements. Our design consisted of three components analogous to the natural end plates, annulus, and nucleus. In this study only the fiber-reinforced design is considered. The variables examined in the present study included orientation of the fiber layers, number of fiber layers, and order of the reinforcing layers. The results of mechanical testing of the fiber reinforced disc spacer indicate that a range of compressive and torsional properties can be achieved. The results further demonstrate that properly developed, this design results in properties similar to the natural disc. Designs developed provided adequate compression and compression torsion properties for a synthetic spine disc spacer. © 1994 John Wiley & Sons, Inc.
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    Fatigue behavior of a titanium femoral hip prosthesis with proximal sleeve-stem modularity (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 195-201 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Modular hip prostheses are increasing in variety and utilization. Component stability, high endurance limit, and minimal particulate debris generation are critical for long-term clinical success. The purpose of this study was to characterize the fatigue response and evaluate the in vitro potential for component motion and wear of the S-ROMTM, a Ti-6Al-4V hip prosthesis with a modular design based on a Morse taper connection. A fatigue jig was desiged to simulate fixation of the device at the sleeve-bone interface only with distal support mainly against the lateral endosteal cortex. Two series of tests were performed in air at room temperature: one with direct vertical loading (to produce high bending moments in the coronal plane) and one with a compound loading angle directed at 15° out-of-plane (to include torsional physiological loads). Applied loads using a servohydraulic test machine ranged from 5 × BW (body weight) to 9 × BW (1 × BW = 73 kg, ≈ 160 lb) at 10 Hz on an Instron apparatus. No mechanical failures were observed on the 11-mm size stems below 6 × BW for in-plane vertical loading, and at or below 7 × BW for out-of-plane loading. Using displacement monitoring with a sensitivity of 35 μm, no measurable slippage or relative motion was detected between the stem and sleeve when they were properly assembled. Examination of the contact areas with scanning electron microscopy revealed random surface modification (an indication of fretting or burnishing) with occasional evidence of transfer of material between stem and sleeve. At loads under 7 × BW there was no visual evidence of loose wear debris in the presence of gross stability. Overall, the extent of surface change or wear was relatively small in all components tested at physiological load levels. © 1994 John Wiley & Sons, Inc.
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    Chemical stress relaxation of polyglycolic acid suture (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 215-220 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Chemical stress relaxation methods are employed to study chemical and mechanical factors influencing the degradation of uncoated polyglycolic acid (PG) sutures. Specially constructed instrumentation is used to study the kinetics of the load bearing capability of PG (DexonTM) 3-0 sutures in hydrolytic solution. The effects of pH, temperature, strain rate, and initial load on the rate of chemical stress relaxation are presented. Data show how mechanical factors such as the rate of loading (related to the speed of knot tying), as well as the final tension, are related to the rate of structural degradation. Maximum stability is observed at approximately 40°C, with slower degradation both above and below this point. Results show that the slower and tighter the suture is pulled, the greater its ability to sustain tensile loads during hydrolysis. © 1994 John Wiley & Sons, Inc.
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    Evaluation of a new absorbable lactomer® subcuticular staple (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 221-226 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The most recent advance in skin stapling is the Auto Suture® SQS®-20 disposable stapler. It approximates and everts wound edges, placing one synthetic absorbable pin in the dermis each time the instrument handle is activated. Staple wound closure was accomplished four times faster than sutural closure of the dermis. Wounds with staple pin closure exhibit superior resistance to infection than wounds approximated by dermal sutures. Although sutures provide more immediate wound security, as measured by wound breaking strength, than dermal pins, the breaking strength of wounds subjected to either dermal pins or dermal sutures were not significantly different 14 days after wounding. © 1994 John Wiley & Sons, Inc.
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    From the editor (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 255-255 
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    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050311
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    Stimulation of bone healing by transforming growth factor-beta1 released from polymeric or ceramic implants (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 141-150 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The ability of transforming growth factor-beta1 (TGF-β1) to stimulate bone healing was evaluated in a rat critical calvarial defect model. Both a low dose and a high dose of TGF-β1 were incorporated into two different types of implants: one made from a composite of poly(lactic-co-glycolic acid) (PLPG) (50:50) and demineralized bone matrix (DBM), and the other from calcium sulfate (CaSO4). Scanning electron microscopy showed that the CaSO4 implants were more porous than the PLPG/DBM samples. Both types of implants released biologically active TGF-β1 for over 300 h in vitro. The samples were implanted in a 9-mm diameter rat calvarial defect for 6 weeks along with contralateral control implants containing no TGF-β1. Microradiography and histological analysis were used to assess the bone healing in the defects. Microradiography revealed that the greatest amount of calcified bone (67.5%) was present in the CaSO4 implants containing a high dose of TGF-β1 while minimal new bone formation occurred in the PLPG/DBM implants. Histologically, the PLPG/DBM implants exhibited an inflammatory response with little mineralization or bone formation. The defects containing the PLPG/DBM implants consisted of a connective tissue stroma with large void spaces. Giant cells and numerous polymorphonuclear leukocytes were present throughout the implants. In contrast, the CaSO4 implants had only a few inflammatory cells and the presence of mineralization and true bone was a more consistent feature. These preliminary studies show that TGF-β1 is capable of inducing new bone formation. Furthermore, the materials used to deliver the growth factor can play a significant role in the bone healing process. © 1994 John Wiley & Sons, Inc.
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    Six bioabsorbable polymers: In vitro acute toxicity of accumulated degradation products (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 151-157 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bioabsorbable polymer implants may provide a viable alternative to metal implants for internal fracture fixation. One of the potential difficulties with absorbable implants is the possible toxicity of the polymeric degradation products especially if they accumulate and become concentrated. Accordingly, material evaluation must involve dose-response toxicity data as well as mechanical properties and degradation rates. In this study the toxicity and rates of degradation for six polymers were determined, along with the toxicity of their degradation product components. The polymers studied were poly(glycolic acid) (PGA), two samples of poly(L-lactic acid) (PLA) having different molecular weights, poly(ortho ester) (POE), poly(∊-caprolactone) (PCL), and poly(hydroxy butyrate valerate) (5% valerate) (PHBV). Polymeric specimens were incubated at 37°C in 0.05 M Tris buffer (pH 7.4 at 37°C) and sterile deionized water. The solutions were not changed during the incubation intervals, providing a worst-case model of the effects of accumulation of degradation products. The pH and acute toxicity of the incubation solutions and the mass loss and logarithmic viscosity number of the polymer samples were measured at 10 days, 4, 8, 12, and 16 weeks. Toxicity was measured using a bioluminescent bacteria, acute toxicity assay system. The acute toxicity of pure PGA, PLA, POE, and PCL degradation product components was also determined. Degradation products for PHBV were not tested. PGA incubation solutions were toxic at 10 days and at all following intervals. The lower molecular weight PLA incubation solutions were not toxic in buffer but were toxic by 4 weeks in water. The other materials did not produce toxic responses during the 16-week exposures. The degradation products components in order from most toxic to least toxic are: lactic acid (PLA), ∊-caproic acid (PCL), glycolic acid (PGA), cyclohexane dimethanol (POE), propionic acid (POE), 1,6 hexane diol (POE), pentaerythritol dipropionate (POE), and pentaerythritol (POE). © 1994 John Wiley & Sons, Inc.
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    Surface modification of polymeric biomaterials by albumin grafting using γ-irradiation (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 163-173 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polymeric biomaterial surfaces were modified by albumin grafting to improve their blood compatibility. Albumin molecules were functionalized by introducing double bonds using glycidyl acrylate. The functionalized albumin was covalently attached to various biomaterial surfaces such as polypropylene, polycarbonate, and poly(vinyl chloride) by γ-irradiation. Surface-induced platelet adhesion and thrombus formation on the albumin-grafted surfaces was examined using computer-enhanced video microscopy and scanning electron microscopy. The amount of the grafted albumin was dependent on the γ-irradiation dose and the concentration of albumin used for adsorption. The grafted albumin molecules remained on the surface even after exposure to blood for prolonged time periods. This approach was used to graft albumin to polymeric materials of an oxygenator. The albumin grafting resulted in a substantial improvement in blood compatibility as compared to control oxygenators. The covalent grafting of functionalized albumin by γ-irradiation obviates the need for premodification of chemically inert polymer surfaces. It is useful for albumin grafting to various biomaterial surfaces. © 1994 John Wiley & Sons, Inc.
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    Characterization of a polyepoxy compound fixed porcine heart valve bioprosthesis (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 159-162 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Concerns with the currently available bioprostheses are calcification, long-term durability, and suboptimal hemodynamic performance. It is well known that these concerns are all more or less related to the cross-linking reagent, glutaraldehyde or formaldehyde, used in fixing bioprostheses. To address these concerns, we undertook the development of a porcine bioprosthesis fixed with a polyepoxy compound. In the development of this polyepoxy compound valve, it was found that the porcine leaflets fixed with polyepoxy compound were softer and more pliable than those fixed with glutaraldehyde. In this study, a special microtoming technique was developed to section the biological tissue so that the fixation uniformity in distinct layers of porcine aortic wall could be characterized. The fixation index and the denaturation temperature measurements in distinct layers of aortic walls showed that the cross-linking density was uniform throughout the entire aortic wall for the polyepoxy compound fixed porcine valve. It was also noticed that the fixation index of the polyepoxy compound fixed aortic wall (91.5 ± 0.5, n =3) was not significantly different from that of its valvular leaflet (90.6 ± 0.8, n = 3). Similarly, the denaturation temperature of the polyepoxy compound fixed aortic wall (80.4 ± 0.9°C, n = 5) was statistically comparable to that of its valvular leaflet (79.0 ± 0.5°C, n = 5). The results of this study indicated that polyepoxy compound can adequately fix the entire porcine aortic wall as well as its valvular leaflets. In a preliminary study, three polyepoxy compound fixed valves were evaluated in the mitral position in a juvenile sheep model. At 5-month retrieval, no calcification could be visually observed in any of the explanted valves. © 1994 John Wiley & Sons, Inc.
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    New advances in electronic devices for hole detection (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 257-264 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Holes in surgical gloves are considered to be an important source of transmission of pathogens between surgeon and patient. Two new glove hole detectors have been devised to alert the surgeon to the presence of holes. These devices have been evaluated using six powder-free and seven powdered varieties of surgical gloves that were either dry or exposed to hydration. Eight of the 13 surgical gloves hydrated rapidly with water, altering their resistance to the conduction of electricity. Because the Barrier Integrity MonitorTM only has a hydration monitor, 68 false positives occurred during the evaluation, indicating to the surgeon that he/she should change gloves unnecessarily because the glove had no hole. In contrast, the Surgic Alert MonitorTM (SAMTM) had a hydration alarm as well as a glove hole detection alarm. During the 104 tests, the SAMTM device showed no false positives. In the testing of five of the rapidly hydrating types of surgical gloves, the SAMTM device could not reliably detect holes. On the basis of this study, the SAMTM device, in conjunction with gloves that resist hydration, appeared to be a reliable hole detection monitor. © 1994 John Wiley & Sons, Inc.
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    Masthead (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994) 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050401
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    Corrosion and cell culture evaluations of nickel-chromium dental casting alloys (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 203-213 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In this study, the corrosion and surface properties of four commercially available nickel-chromium dental casting alloys, were evaluated using electrochemical corrosion testing and Auger electron microscopy. The corrosion tests were conducted under cell culture conditions of 5% CO2 humidified atmosphere at 37°C in minimum essential medium (MEM) balanced salt solution, 95% MEM-5% FBS (fetal bovine serum) cell culture media, and in 95% MEM-5% FBS media after cold solution sterilization of test samples. The results of the surface and corrosion analyses were correlated to cytotoxicity and metal ion release from the alloys using agarose overlay and direct contact cell culture tests. The surface and electrochemical corrosion analyses demonstrated that the non-beryllium containing alloys were more resistant to accelerated corrosion processes as compared to the beryllium-containing alloys. All alloys demonstrated decreased corrosion rates in cell culture solutions after cold solution sterilization treatment. The corrosion products released from the nickel-based alloys failed to alter the cellular morphology and viability of human gingival fibroblasts, however they did cause reductions in cellular proliferation. The potential for accelerated corrosion and the exposure of local and systemic tissues to elevated levels of corrosion products raises concerns over the biocompatibility of these alloys. © 1994 John Wiley & Sons, Inc.
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    Polyethylene wear debris and tissue reactions in knee as compared to hip replacement prostheses (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 185-190 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Differences in bearing surface conformity and wear mechanisms suggest that the polyethylene (PE) wear debris generated by total knee replacement (TKR) prostheses should be different than that in total hip replacement prostheses (THR). To address this issue, PE wear debris and the cellular response in periprosthetic tissues from 19 failed TKRs was compared to that from 24 failed THRs using polarized light microscopy and a semiquantitative grading system. The foreign-body inflammatory reaction in the THR cases was characterized by plump macrophages with a diffuse cytoplasmic birefringence when examined under polarized light, indicating the presence of multiple submicron particles of PE. The majority of the PE particles were 〈1 μm in size and only a small fraction of the total were 〉10 μm. The foreign-body inflammatory reaction in the TKR cases was characterized by giant cells with fewer macrophages. In the TKR specimens, the size range of PE particles was broader than in the hips. PE particles between 2 and 20 μm were frequent in TKR specimens; particles 〈1 μm in length were less common than in the THR specimens. Diffuse cytoplasmic birefringence was not a characteristic of the TKR cases. These histologic differences were so consistently distinct that the source of the specimen (i.e., from a THR or TKR) could be blindly determined by light microscopy. The size distribution of the PE wear particles in these cases indicate that THRs generate a higher number of submicron PE particles and relatively few large particles while TKRs generate a broader range of particles that includes fewer submicron particles. The observed differences in the cellular responses is likely a direct result of the differences in the spectrum of PE wear particles. These differences may in part account for differences in periprosthetic bone resorption and loosening in TKRs as compared to THRs. © 1994 John Wiley & Sons, Inc.
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    Physical properties of model viscoelastic materials (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 227-234 
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    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Previous observations on polysaccharides used as viscoelastic agents in ophthalmic surgery suggest that the pseudoplasticity of solutions of hyaluronan (HA) and the low surface tension of hydroxypropylmethylcellulose (HPMC) solutions are physical properties that make these solutions useful clinically. Our laboratories are interested in correlating the physical properties of macromolecular solutions with the ability of these molecules to protect ocular structures during eye surgery. The purpose of this study is to compare the physical properties of model viscoelastics with the properties of HA and HPMC. The results of these studies suggest that polysaccharides that form extended structures in solution at low shear rates and that are characterized by large decreases in the axial ratio at high shear rates, exhibit pseudoplastic behavior. In this study pseudoplasticity is exhibited by polysaccharides with molecular weights in excess of 450 000, and is insensitive to the backbone chemistry for linear macromolecules. In addition, low surface tension is associated with charged macromolecules that have a high positive second virial coefficient. © 1994 John Wiley & Sons, Inc.
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    Masthead (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994) 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100101
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    Iterative computation of second-order derivatives of eigenvalues and eigenvectors (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 1-9 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An iterative method is introduced for computing second-order partial derivatives (sensitivities) of eigenvalues and eigenvectors of matrices which depend on a number of real design parameters. Numerical tests confirm the viability of the method and support our theoretical analysis. Alternative methods are reviewed briefly and compared with the one proposed here.
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    Semi-Loof element for plate instability (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 11-19 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the formulation of the semi-Loof element the rotation of the tangent plane is derived from the interpolation of the transverse displacement, while the rotation of the normal is interpolated separately by another set of shape functions. The geometric stiffness matrix can be formulated by use of either of the two rotation representations. It is demonstrated that the use of the tangent plane representation in the geometric stiffness matrix is far superior to the common form at present.
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    Least-squares T-elments: Equivalent FE and BE forms of a substructure-oriented boundary solution approach (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 21-32 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An efficient solution to boundary-value problems may be based on the application of a suitably truncated T-complete set of Trefftz functions over individual subdomains and on linking the fields by a least-squares procedure. Although it yields a symmetric system of linear equations, this approach as originally presented by Zielinski and Zienkiewicz is not suited for implementation into FE codes. The present paper presents two equivalent formulations, which take respectively the form of the finite (FE) and non-conventional boundary-element (BE) approach. Both allow the resulting simultaneous equations to be assembled following the standard direct stiffness methods and can readily be implemented into existing FE codes.As in the conventional p-method, the accuracy may be controlled within large limits without increasing the number of elements. The present approach allows substantial saving in computer time in comparison with the so-called hybrid-Trefftz (HT) elements, though the assumed displacement fields are identical. The practical efficiency of the new T-element approach is assessed on the problem of stress concentration in a symmetrically compressed perforated panel.
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    Generalized finite-differences solution of 3D elliptical problems involving Neumann boundary conditions (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 43-58 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A method is presented for the solution of elliptical problems defined on general-shape multiconnected three-dimensional domains approximated by means of polyhedra. The boundary conditions may be of the Neumann type. The differential operator and the normal derivative are discretized by generalized finite-difference (GFD) methods using an orthogonal non-uniform Cartesian grid. The convergence properties are analysed and the solutions of some Poisson and biharmonic problem are presented.
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    Heuristic optimization of a laminated composite plate and its comparison with a minimization method (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 59-65 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A heuristic optimization design methodology based on redesign rules for composite laminated plates is presented. It is modelled on the cyclic approach to the design process observed in designers of structural components using composites. In comparison with a simple weight minimization algorithm it gives quasioptimal ply thicknesses, but takes under ten iterations. It is thereby shown to be most suitable for initial design studies. Multiaxial combinations of in-plane loads and bending moments are considered in the design procedure.
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    Numerical investigation of a method to reduce the reheating time of steel bars (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 33-42 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Reduction of reheating time saves on energy input and increases the production rate in the steel-making process. Reductions can be achieved by allowing the centre temperature of a steel bar to be lower than the surface temperature by a small margin, before starting with the hot rolling process. This can only be done if the temperature difference does not adversely affect the quality of the final product or the rolling equipment. The paper presents numerical simulations to investigate the savings that can be obtained for various temperature differences between surface and centre temperatures to evaluate the feasibility of the concept. The results presented include the cross-sectional temperature distribution in a typical steel bar during reheating at hourly intervals as well as the effect of various differences between centre and surface temperatures on reheating time. The reheating time predicted for various steel bar sizes as well as for various differences between surface and centre temperatures are then compared against measured reheating times. To indicate the practical applicability of the concept to the hot rolling process the detailed temperature distribution in a typical steel bar, with an initial temperature difference between the surface and centre of the bar, was simulated numerically. This was compared to a similar simulation for a well soaked steel bar for which experimental measurements are also available. The numerical method used to obtain the simulations is also presented. Boundary conditions account for radiation, convection and conduction inside the steel bar. It is concluded that the concept of allowing differences between surface and centre temperatures of a steel bar during reheating holds great potential for energy savings in the steel-making process.
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    Higher-order singular isoparametric elements for crack problems (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 73-80 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Standard isoparametric finite elements can be used as singular crack-tip elements in fracture mechanical computations by placing the middle nodes in the neighbourhood of the crack tip. Such elements have already been applied to several plane and three-dimensional problems, so this method can be considered as commonly well accepted. The paper shows that singularity of order r(1 - m)/m is obtained with an nth-order isoparametric element.
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    Method of iterative linearization to solve non-linear stochastic vibration problems (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 67-71 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper, an iterative method of statistic linearization (IMSL) is presented to solve non-linear stochastic vibration equations. This method represents an improvement over the classical linearization method. The method uses the solution of the corresponding linear vibration equation as an initial value in an iterative procedure. To obtain information about essential statistical average values, the method uses a ‘boot-strapping’ procedure, which defines a pseudorandom process based on the statistical characteristics of the linear solution and then uses samples from the process to estimate them. For Gaussian input excitation, the statistical average values are obtained by theoretical analysis.
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    Conference diary (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 89-91 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    URL: http://dx.doi.org/10.1002/cnm.1640100111
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    BEM computation of DSIF in cracked viscoelastic plates (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 81-87 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Dynamic stress intensity factors of cracked linear viscolastic solids under conditions of plane stress are computed by the boundary-element method in conjunction with the numerical Laplace transform and the correspondence principle of linear viscoelasticity. Quadratic isoparametric conventional and quarter-point boundary elements are employed. The multidomain approach is used in cases where symmetry cannot be invoked. Dynamic stress intensity factors are computed for cracked viscoelastic rectangular plates subjected to suddenly applied loads, and comparisons are made against results obtained by other numerical methods.
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    Masthead (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994) 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
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    URL: http://dx.doi.org/10.1002/cnm.1640100201
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    Compound difference schemes for time-dependent equations on non-uniform nets (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 93-110 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new approach to constructing monotonous second-order-accurate schemes for time-dependent Navier-Stokes equations in the compressible case is suggested. Flows with shock waves and thin viscous boundary layers are considered. The approach joins two different schemes while each of them is appropriate for its own type of flow. The resulting scheme is constructed as a splitting one, and the approach is applied at the stage governed by the Euler equations in Lagrangian variables. The approach turns out to be fruitful also for parabolic equations with ‘viscous’ terms. The method is illustrated by the problem on compression of deuterium in a conical solid-body target with viscous heating of deuterium.
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    Eigensolution reanalysis of modified structures using perturbations and Rayleigh quotients (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 111-119 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new eigensolution reanalysis method for modified structures is developed and presented based on the usual first-order perturbation scheme and the Rayleigh quotients. By this method, the accuracies of the eigensolutions of the modified structures computed by perturbation methods are improved. A numerical example is presented and the accuracies of the usual first-order perturbation method, second-order perturbation method, William B. Bickford method and the proposed method are compared.
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    Perturbation method for computing eigenvalue bounds in structural vibration systems with interval parameters (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 121-134 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this study a perturbation method for computing the upper and lower bounds of eigenvalues of structural vibration systems with interval parameters is presented. The eigenproblem of the uncertain (interval) structure is expressed by equations consisting of the uncertainties. If the uncertainity is small in parameters, the eigensolutions of uncertain structures can be obtained efficiently by the perturbation method presented. A numerical example is given to demonstrate the validity of the method.
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    Accuracy and efficiency of multivariant finite elements for three-dimensional simulation of viscous incompressible flows (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 135-148 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The performance of the univariant finite element Q1P0 and the multivariant finite elements Q1+P0 and R2+P0 are compared for simulation of three-dimensional incompressible viscous flows. Incompressible flow vortices for the R2+P0 element are presented. For the two flows simulated, the R2+P0 element is found to be not only the most accurate but also computationally the most efficient of the three types of finite element used. For one of the two flows simulated, the pressure distribution obtained by using the Q1P0 element is found to be afflicted with the checker-board spurious pressure mode. For the uniform finite-element mesh used, the checker-board pressure mode is eliminated by taking a weighted average of the pressure over the neighbouring Q1P0 elements.
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    Conference diary (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 179-181 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    URL: http://dx.doi.org/10.1002/cnm.1640100209
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    Truncated envelope peconditioning technique (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 149-154 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the paper the use of a truncated envelope technique is discussed as a preconditioning for the conjugate gradient method for solving large linear systems of equations with symmetric positive-definite matrices. An algorithm to generate a truncated envelope is introduced. Computational experience with systems of linear equations from the Harwell-Boeing collection is presented to highlight the efficiency of this approach.
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    High-order polynomial interpolation in boundary integral equation analysis (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 167-178 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A sixth-order polynomial shape function is developed for BIE analysis. The function is applied over only three-noded elements, but with the support for the function extending over adjacent elements. This avoids the oscillations near the ends of the range which otherwise are characteristic of high-order polynomial interpolation. Various test problems are explored, and it is shown that results as accurate as those from conventional quadratic elements are obtained with larger nodal spacings, and thus giving the potential for significant reductions in matrix storage requirements and solution times.
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    Accurate finite element method for steady and quasisteady lifting aerofoil (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 155-166 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A finite element formulation based on superposition is proposed for a lifting aerofoil in incompressible potential flow. An accuracy improvement technique for the singularity at the aerofoil trailing edge is discussed. It is shown that the quarter-node quadrilateral element can be readily employed to simulate this singularity. It is also demonstrated that the circulation in the flow field can be easily represented by a single constraint equation rather than introducing an artificial cut line in the mesh. The influence of finite-element mesh size on solution accuracy and the correct form of the boundary condition have been investigated as well. Numerical examples are given for both steady and quasisteady Joukowski aerofoils of various thicknesses and at a range of incidences. In all test cases, good agreement is observed between the analytical solution and the numerical result.
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    Masthead (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994) 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
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    URL: http://dx.doi.org/10.1002/cnm.1640100301
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    A 3D element for non-linear analysis of solids (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 183-194 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An 8-node element (HMITC) for 3D non-linear analysis of solids is presented. The new element is based on an element developed by Wilson and Ibrahimbegovic, that incorporates incompatible modes, and on the method of mixed interpolation of tonsorial components. The HMITC element does not contain spurious zero energy modes and satisfies Irons' Patch Test. The numerical experimentation indicates that the HMITC has good performance even with distorted meshes.
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    Space-time oriented streamline diffusion methods for non-linear conservation laws in one dimension (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 203-215 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper we consider an explicit finite-element method, with elements adaptively oriented in space-time, for the solution of one-dimensional conservation laws, extending previous work dealing with linear convection-diffusion and incompressible flow. In particular we consider Burgers' equation and the compressible Euler equations.
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    Neural-network-based approximations for solving partial differential equations (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 195-201 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical method, based on neural-network-based functions, for solving partial differential equations is reported in the paper. Using a ‘universal approximator’ based on a neural network and point collocation, the numerical problem of solving the partial differential equation is transformed to an unconstrained minimization problem. The method is extremely easy to implement and is suitable for obtaining an approximate solution in a short period of time. The technique is illustrated with the aid of two numerical examples.
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    Cyclic symmetry in boundary elements (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 217-225 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An efficient algorithm for consideration of axial and cyclic symmetry in the boundary-element method is presented. The appropriate transformation relationships was derived. The algorithm is then implemented in a boundary element program for the analysis of 2D elastostatic problems. Through analysis of typical problems the validity of the algorithm and its implementation is verified. A high level of accuracy and substantial reduction in computer time and storage was achieved.
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    Explicit variable time-step method for implicit moving boundary problems (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 227-235 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The diffusion of oxygen into an absorbing medium as an example of an implicit moving boundary problem has been dealt with by a number of authors using various numerical techniques, and, where appropriate, approximate analytical expressions. To evaluate the time for complete absorption, extrapolation is usually employed. An unconditionally stable explicit numerical scheme that avoids the limitations of such methods is presented and tested herein. Unlike existing schemes this method is fully numerical; it avoids the large array size, generally required for existing methods, by using a variable-length time step. The time for complete absorption emerges from the final step in the normal computing procedure with no recourse to extrapolation. Furthermore, owing to the implicit condition prevailing at the moving boundary, no iterations are needed to evaluate the time step required for the moving boundary to move a single space increment. The numerical results obtained compare very favourably with those due to earlier authors.
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    Boundary-element solution of some structural-acoustic coupling problems using the multiple reciprocity method (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 237-248 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the paper we have developed a new formulation for solution of structural-acoustic coupling problems by boundary elements using the multiple reciprocity method. It is assumed that the structure is composed of plate components and is excited by the external or the internal noise source. The efficiency of the proposed formulation becomes especially remarkable if the boundary-value problem is to be solved repeatedly for different values of frequency. The accuracy of the numerical computations has been compared with the analytical solution in a test example.
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    Homogenization and effective elastoplasticity models for periodic composites (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 257-265 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Techniques for stress- and strain-controlled in situ homogenization of inelastic periodic composites are presented. The results of homogenization computations on a specific elastoplastic composite solid are then employed to validate the form of an orthotropic elastoplasticity model with a tensorial kinematic hardening law.
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    Lagrange multiplier approach for evaluation of friction in explicit finite-element analysis (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 249-255 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An algorithm for evaluation of friction in general contact-impact interfaces is described. The algorithm is based on an explicit finite-element method. Coulomb's friction law is assumed. The defence node algorithm is used such that the sticking condition can be imposed with the Lagrange multiplier method even in explicit dynamic analysis. The algorithm is supposed to be applicable in general situations, including large deformations of the contact-impact bodies and large relative sliding between the contact-impact boundaries. Numerical results are presented to demonstrate the performance of the algorithm.
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    Conference diary (1994)
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    Communications in Numerical Methods in Engineering 10 (1994), S. 275-277 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Masthead (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994) 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    General forming of transition elements (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 267-273 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A generalization of the r(1-m)/m strain singularity of higher-order isoparametric elements is presented. It is shown that, by variable placement of the side nodes between their original and singular positions, the point of singularity sensed by the element can be controlled. The transition elements have a strain singularity outside their domain. The singular and non-singular elements are elements are special cases of the general mapping. The transition elements, together with the singular isoparametric elements, can be used for solving crack problems.
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    Some geometric problems related to fracture-control in complex structures (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 279-290 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the design of members with flaws, it is necessary to keep the stress intensity factor K of any sharp crack below the fracture toughness Kcr of the materials. Stress-intensity factor equations for the more common basic specimen geometries and various loading conditions are available in the literature. The application of these equations to complex structures involves geometric problems such as the identification of the outline of each member and the sizing of the equivalent specimen for each flaw. The paper gives a response to such difficulties.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100402
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    Modified simplex optimization program (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 303-312 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple, yet storage-effective ‘linear’ programming code is given. The assumption of non-negative variables is bypassed without increasing the size of the problem. Furthermore, the objective is allowed to be summed over not just linear, but also concave, functions. A specific truss topology optimization example is shown.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100405
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    Fourth-order difference method for quasilinear Poisson equation in cylindrical symmetry (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 291-296 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: We propose in this paper a nine-point, fourth-order difference method for the numerical solution of the quasilinear Poisson equation \documentclass{article}\pagestyle{empty}\begin{document}$$ Au_{zz} + \frac{1}{r}u_r + Bu_{rr} = f\left({r,z,u,u_r,u_z} \right) $$\end{document} with appropriate boundary conditions. The method is based on five evaluations of f. The numerical results of four problems obtained using this method are listed. The results demonstrate the fourth-order accuracy of the method.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100403
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    Use of central-difference operators for solution of singularly perturbed problems (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 297-302 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Singularly perturbed second-order elliptic equations with boundary layers are considered. These may be considered as model problems for the advection of some quantity such as heat or a pollutant in a flow field or as linear approximations to the Navier-Stokes equations for fluid flow. Numerical methods composed of central-difference operators on special piece-wise-uniform meshes are constructed for the above problems. Numerical results are obtained which show that these methods give approximate solutions with error estimates that are independent of the singular perturbation parameter. An open theoretical problem is posed.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cnm.1640100404
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    Superconvergent patch recovery of finite-element solution and a posteriori L2 norm error estimate (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 313-320 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the paper we present a superconvergent patch recovery technique for obtaining higher-order-accurate finite-element solutions and thus a postprocessed type of L2 norm error estimate. Two modifications make our procedure different from the one proposed by Zienkiewicz and Zhu (1992), in which higher-order-accurate derivatives of the finite-element solution at nodes are determined. Firstly, the recovery process is made for element, not for nodes. An ‘element patch’, which represents the union of an element under consideration and the surrounding elements, is introduced. Secondly, the local error estimate is calculated directly from the improved solution for this element. Numerical tests on both 1D and 2D model problems show that this method can provide an asymptotically exact a posteriori L2 norm error estimate if the used element possesses superconvergent points for the solutions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100406
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    Universal matrices with new infinite elements for quasiharmonic equation (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 321-331 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new approach to developing serendipity quadrilateral infinite elements is presented. Using these elements universal matrices for quasiharmonic equation are developed. For a particular member of the family these matrices are independent of the size and shape of the element. Using these matrices the element stiffness matrix can be generated in a simpler manner by taking into account the size and shape of the element.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100407
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    Accelerated modified Newton-Raphson iteration-based finite-element solution of structural problems involving non-linear deformation behaviour (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 333-338 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new global secant relaxation (GSR)-method-based improvement procedure is used to improve the overall convergency performance of the modified Newton-Raphson iteration in carrying out the solution of discrete systems resulting from the finite-element discretization of a certain class of structural problems involving non-linear deformation behaviour.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100408
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    A simulation of free-surface electrohydrodynamic flow (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 339-353 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Theoretical and experimental analysis of free-surface electrohydrodynamic flow is fragmented and incomplete. Simulation studies of this phenomenon are further limited by the inherent complexities in the modelling process. In this note a mathematical model is developed to analyse free-surface electrohydrodynamic flow in two dimensions, and preliminary results of the simulation are described. The configurations examined include electrified conducting surfaces, the dielectrophoretic forces, and a conducting jet. The simulation is compared with analytical results in the first two investigations and is shown to be quite accurate. In the last simulation it is demonstrated that in the initial formation of a conducting jet, a 10 per cent increase in applied voltage results in about a 10 per cent increase in fluid velocity.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100409
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    Conference diary (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 355-357 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100410
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    Announcements (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 359-360 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100411
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    Masthead (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994) 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100501
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    Improvement on dual reciprocity boundary element method for equations with convective terms (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 361-371 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The dual reciprocity boundary element method, first proposed by Nardini and Brebbia (1982, 1985), is a powerful technique for solving elliptic partial differential equations. Adopting this approach, a singular volume integral, which needs to be evaluated with a traditional boundary element method, can be converted into a boundary integral. However, when the governing equation is of a certain type, this conversion fails due to the singularities being introduced inside the physical domain and on the boundary arising by differentiating distance functions. We avoid these artificially created singularities by constructing a transformation which leads to improved numerical results.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100502
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    Method to generate complex computational meshes efficiently (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 373-384 
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    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper demonstrates an approach to generate three-dimensional boundary-fitted computational meshes efficiently. One basic idea underlying the present study is that often similar geometries have to be meshed, and therefore an efficient mesh-adaption method, which allows adaptation of the topological mesh to the specific geometry, would be more efficient than generating all new meshes. On the other hand the mesh generation for Cartesian topologies has been shown to be a very simple task. It can be executed by connecting and removing brick elements to a basic cube. In connection with a so-called ‘Macro Command Language’, a high degree of automation can be reached when adapting topologically defined meshes to a surface. Furthermore, a high mesh quality has proved to be the key to good simulation results. During the mesh generation it is important to provide the possibility of modifiying the mesh quality and also the mesh density at any time of the meshing process. Using this generation method the meshing time is reduced - e.g. a computational mesh for a two-valve cylinder head can be generated within a few hours.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100503
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