Leyyal-i ızdırap

Ahmet Rasim'in Servet-i Fünun'da tefrika edilen Leyyal-i Izdırap adlı roman

Surface pretreatments for medical application of adhesion

Medical implants and prostheses (artificial hips, tendono- and ligament plasties) usually are multi-component systems that may be machined from one of three material classes: metals, plastics and ceramics. Typically, the body-sided bonding element is bone. The purpose of this contribution is to describe developments carried out to optimize the techniques , connecting prosthesis to bone, to be joined by an adhesive bone cement at their interface. Although bonding of organic polymers to inorganic or organic surfaces and to bone has a long history, there remains a serious obstacle in realizing long-term high-bonding strengths in the in vivo body environment of ever present high humidity. Therefore, different pretreatments, individually adapted to the actual combination of materials, are needed to assure long term adhesive strength and stability against hydrolysis. This pretreatment for metal alloys may be silica layering; for PE-plastics, a specific plasma activation; and for bone, amphiphilic layering systems such that the hydrophilic properties of bone become better adapted to the hydrophobic properties of the bone cement. Amphiphilic layering systems are related to those developed in dentistry for dentine bonding. Specific pretreatment can significantly increase bond strengths, particularly after long term immersion in water under conditions similar to those in the human body. The bond strength between bone and plastic for example can be increased by a factor approaching 50 (pealing work increasing from 30 N/m to 1500 N/m). This review article summarizes the multi-disciplined subject of adhesion and adhesives, considering the technology involved in the formation and mechanical performance of adhesives joints inside the human body

Radiopaque polymeric spinal cages: a prototype study

Back pain, originating from degeneration of intervertebral discs, is often alleviated by the insertion of one or more interbody fusion cages. The function of the cage is to restore the height between two adjacent vertebrae and to mediate osseous fusion. Most commercial cages consist of titanium or a titanium alloy, while polymeric cages, mostly consisting of polyether-etherketone (PEEK), are also in use. Titanium is known for its excellent biocompatibility. Titanium cages can be located easily with imaging techniques based on X-ray absorption (e.g. CT scans). However, they introduce artefacts in magnetic resonance (MR images). PEEK cages, on the other hand, do not show up in CT images. For this reason, small metallic markers are usually incorporated. The markers reveal the position of the cage, albeit indirectly. PEEK cages are clearly and integrally seen on MR images, as they are essential free of water. There are no artefacts or disturbances; this feature, as well as its strength, makes PEEK particularly attractive for the construction of cages. Here, we introduce new allpolymeric cages on the basis of an iodine-containing methacrylic copolymer (I-copolymer). This material has been prepared from methylmethacrylate and 2-[4-iodobenzoyl]-oxo-ethylmethacrylate. Copolymerisation of both monomers results in a high molecular weight material. Cytocompatibility experiments reveal that the material contains no toxic leachables and that cells can well adhere to and proliferate on the I-copolymer. Compression experiments at physiologically relevant strains disclose mechanical characteristics comparable to PEEK. The advantage of cages prepared from this I-copolymer over commercially available cages is that the present cage contains no metallic components, implying that it is compatible with MR imaging, and the presence of the iodine atoms ensures X-ray visibility