ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Some important eye pathologies, such as diabetic proliferative retinopathy and retinal detachment, are strictly connected to different gel vitreus alterations. Therefore there is a strong need in ophthalmology for vitreal substitutes. Until now many synthetic and natural polymers have been tested as vitreal substitutes, but no one has proved to be an ideal vitreal substitute. An ideal vitreal substitute, apart from other characteristics, such as transparency, permanency, biocompatibility, etc. must have a rheological behaviour compatible with the surrounding tissues. The viscoelastic behaviour of different animals' gel vitreus, evaluated by means of steady shear viscosity and small-amplitude oscillatory measurements, is typical of solid-like rubbery gels with dynamic elastic modulus G′ higher than the dynamic viscous modulus G″ in the typical frequency range investigated (0.05–10 Hz). On the other hand the rheological behaviour of current or candidate vitreal substitutes (silicone oil, HPMC, high molecular weight hyaluronic acid and chemically-crosslinked hyaluronic acid), analysed with the same technique, is generally different from that of natural vitreus.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1573-4897
    Keywords: MMC ; Nickel coated graphite ; Squeeze casting ; Instable interface ; Electroplating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Metal Matrix Composites (MMC's) reinforced with continuous fibers were generally fabricated by a foil-sandwich technique or by liquid metal infiltration. Liquid metal infiltration may be used to cast final shapes in molds containing fiber preforms. It is also used to make composite wire from which may be fabricated panels and shapes by hot-press diffusion bonding or pultrusion. The major drawback of this method is that the molten matrix must wet the fiber for successful infiltration to occur, requiring special fiber surface treatments or matrix additives, and that, molten metals generally dissolve or degrade the fibers, necessitating a barrier coating on the fibers. All these problems can be solved using carbon fibers coated with metallic layers, e.g. nickel. This work analyses an easy method to produce modified carbon fibers by electroplating and the process of its recristallization. The topography of the growth front of the deposit has been studied. At temperatures higher than about 300° C an annealing under vacuum is required, because of the high reactivity of metal coating, nevertheless the heat treatment of metal deposit produces always an embrittled material.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The thermomechanical properties of fibres of two hyaluronic acid esters have been evaluated. The materials are found to be significantly different in hydrophilicity, reflected also in variations in mechanical and viscoelastic properties. Both esters show a marked decrease in strength in the swollen state.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: During the last few years, on the basis of their physico-chemical characteristics, thermoplastic materials, already used in several advanced industries, have become very attractive candidates for biomedical applications as matrix for composite femoral stems and bone plates. In the present study, the biocompatibility of a thermoplastic material, polyetherimide (PEI), was investigated both in vivo, and in vitro. Our results show that PEI did not elicit any toxic response in cell culture testing. It was possible to grow on PEI surfaces not only 3T3 fibroblasts but also human endothelial cells (HEC) from human umbelical cord, with no apparent deleterious effects on the cell viability. The attachment, spreading, and growth of cells on PEI material was followed with respect to time. Both the number of adhering HEC, and the spreading area of individual cells, increased as a function of time. The hydrogen peroxide-sensitive dye DCFH-DA was used to examine the functional activity of cells adherent to PEI or control material implants. PEI material did not induce significant DCFH oxidation until day 14, when levels of DCFH oxidation were significantly higher than observed with PDMS negative control, but lower than those observed on Pellethane positive control.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1573-4897
    Keywords: Flexural fatigue ; Glass reinforced composites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Conclusions Flexural fatigue of uniaxially and biaxially stressed IPN/glass mat composites was investigated using four point bend (4PB) and concentrically loaded (CL) specimen geometries. Regions of nearly constant bending moment between the inner spans of a 4PB beam and within the inner annulus of a CL circular plate yield quasi-uniform uniaxial and biaxial stress, respectively, on the tensile faces. The specimen dimensions were optimized for both loading geometries to give: (1) reduced specimen deflection through maximizing the ratio of the induced tensile stresses to the applied load, (2) minimized contact stresses by maximizing the induced stress with respect to the unit contact load, and (3) a large material volume exposed to the maximum cyclic stress (i.e., statistical fracture initiation). A power model was used to analyze the fatigue data for the 4PB and CL specimens. Both IPN composite materials studied fatigued more rapidly under the more severe loading conditions imposed by the CL specimen geometry. Fractography revealed that debond fracture was the dominant damage process for both geometries. The initial debond cracks were uniformly distributed throughout the stressed regions, confirming the presence of nearly uniform tensile stress. Damage localization followed after further cycling and was characterized by a locally high debond fracture density, fiber fracture, and always occurred where several glass strands crossed near the specimen surface. Final specimen failure resulted from the preferential growth of dominant cracks through the specimen thickness.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1573-4897
    Keywords: Composites ; Silicon carbide ; Wetting ; Reactivity ; Chemical oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1573-4897
    Keywords: SiC-pure Al composites ; Erosion ; Interfacial reaction ; SEM analysis ; Granulometrical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The granulometrical and morphological variations of eroded reinforcement particles during annealing for different times at several temperatures have been studied for SiC-pure Al system. The changes produced have been analysed by scanning electron microscope (SEM) after particle extraction.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Sorptions of methylene chloride and methylene chloride/n-heptane liquid solutions in poly(aryl-ether-ether-ketone) (PEEK) are analysed and interpreted assuming multiple transport mechanisms. The presence of the highly interacting methylene chloride is responsible for anomalous sorption behaviours. PEEK films immersed in methylene chloride poor n-heptane solutions sorb by non-ideal Fickian diffusion, while limiting Case II and diffusion controlled swelling accompany equilibration in progressively richer methylene chloride solutions. The optical microscopy observation of cryogenically fractured samples conditioned in pure liquid methylene chloride at 5, 20 and 36 ° C for different times, revealed the presence of a sharp moving front. Differential scanning calorimetry (DSC) indicates that the glass transition temperature of the penetrated shells was always lower than the treatment temperature. The high levels of solvent swelling and plasticization were probably responsible for the crystallinity detected in DSC thermograms and wide angle X-ray scattering (WAXS) diffractograms of the solvent treated and initially amorphous samples. The differences of WAXS diffractograms of samples crystallized by immersion in methylene chloride at 5 and 36 ° C for various times and by thermal treatment are discussed. Increasing levels of crystallinity were induced in the samples equilibrated in progressively richer methylene chloride solutions.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 25 (1990), S. 3493-3496 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The morphology of high-performance thermoplastic composites (APC-2) based on continuous carbon fibres embedded in a poly-ether-ether-ketone matrix is studied by means of scanning electron microscopy. Samples with different degrees of crystallinity obtained using different thermal treatments are investigated. The effect of the crystallinity content seems to be crucial for fibre/matrix adhesion, as can be detected by SEM analysis.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The technological process used for the production and processing of metal matrix composites (MMCs) can require contact over extended periods of time between matrix and the ceramic reinforcement or at least the permanence at high temperature and pressure of the two parts in contact. During the contact a chemical interaction takes place in the interfacial zone as a consequence of the free-energy difference existing between ceramic compound and metal. Aluminium and aluminium alloys reinforced with silicon carbide are widely utilized materials. The chemical interaction between matrix and reinforcement is not very fast but the reaction equally occurs, and a harmful layer of interfacial compound (Al4C3) is developed after a sufficiently long time. At present, the degradation of the reinforcement produced by molten matrix is the major problem for some production technologies. This problem has only been solved partially by using a coating or changing the chemical nature of the matrix. In particular, the technological problem of interfacial reaction in the SiC-Al system can be solved by adding elemental silicon to the matrix to achieve the eutectic composition. However, this expedient gives rise to a consequent significant lowering of the melting point. The problem can be overcome and the production process improved without changing the characteristics of the material by the control of processing parameters. The interfacial reaction also produces elementary silicon and this has been found as aluminium-silicon eutectic segregated at the aluminium grain boundary. An accurate description of the kinetic process can be obtained by determining the silicon content present in the matrix by original derivations obtained by means of calorimetric analysis.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...