1,035 research outputs found
Effect of increased opacifier on mechanical properties of Polymethyl methacrylate (PMMA)
No full textThe required properties of injectable materials for kyphoplasty and vertebroplasty are complex and in certain aspects contradictory. They include injectability, appropriate working times, sufficient strength to support the physiological loads, stiffness that does not produce a stress concentration in the adjacent vertebrae and radiopacity so that the whereabouts of all the bone cement can be seen. As yet the prefect material fulfulling all these requirements has not been developed, but various attempts have been made. In this chapter the two groups of materials being used for kyphoplasty and vertebroplasty; polymethalmethacrylate based cements and calcium phosphate and calcium sulfate materials, are reviewed. The polymethalmethacrylate based cements remain for the rest of the patient’s life, whereas the calcium phosphate and calcium sulfate will gradually be resorbed and should be replaced with new bone
Finite element analysis of the implanted proximal tibia: A relationship between the initial cancellous bone stresses and implant migration
No full textThe cancellous bone stresses within the implanted proximal tibia were examined using a three-dimensional anatomical finite element model. Three versions of a proximal tibial prosthesis were examined: an all polyethylene press-fit design; a metal backed, stemmed press-fit design and a (horizontally) cemented metal backed, stemmed design. All three designs had published migration and survivorship data. The objectives of the study were (i) to compare the stresses generated by each of the tibial components, (ii) examine the influence of the resected surface morphology and (iii) compare the initial cancellous bone stresses with the published migration and survivorship data. The all polyethylene prosthesis generated the highest cancellous bone stresses. Addition of a metal backing and a stem reduced the stresses, but the cemented device produced the lowest cancellous bone stresses. The surface morphology had a significant effect on the cancellous bone stresses generated by press-fit prostheses. As the bone-prosthesis contact area decreased, the peak cancellous bone stresses increased by as much as 243%. The surface morphology had no effect on the cancellous bone stresses generated by the cemented implant. Good correlation was found between the predicted cancellous bone stresses and the migration and survivorship data, with the implant generating the highest cancellous bone stresses migrating the most and having the poorest survival rates at 5 year. The results support the hypothesis that the progressive failure of cancellous bone is a mechanism of implant migration regardless of the method of fixation and the implantation site
Stress and strain distribution within the intact femur: compression or bending?
No full textThe aim of this research was to test the hypothesis that the intact femur is loaded predominately in compression. The study was composed of two parts: a finite element analysis of the intact femur to assess if a compressive stress distribution could be achieved in the diaphyseal region of the femur using physiological muscle and joint contact forces; a simple radiological study to assess the in vivo deflections of the femur during one legged stance. The results of this investigation strongly support the hypothesis that the femur is loaded primarily in compression, and not bending as previously thought. The finite element analysis demonstrated that a compressive stress distribution in the diaphyseal femur can be achieved, producing a stress distribution which appears to be consistent with the femoral cross-sectional geometry. The finite element analysis also predicted that for a compressive load case there would be negligible deflections of the femoral head. The radiological study confirmed this, with no measurable in vivo deflection of the femur occurring during one legged stance
Cancellous bone stresses surrounding cemented and press fit femoral components of a freeman hip prosthesis in relation to clinical migration
No full textBioactive ceramic-reinforced composites for bone augmentation
Get PDFBiomaterials have been used to repair the human body for millennia, but it is only since the 1970s that man-made composites have been used. Hydroxyapatite (HA)-reinforced polyethylene (PE) is the first of the ‘second-generation’ biomaterials that have been developed to be bioactive rather than bioinert. The mechanical properties have been characterized using quasi-static, fatigue, creep and fracture toughness testing, and these studies have allowed optimization of the production method. The in vitro and in vivo biological properties have been investigated with a range of filler content and have shown that the presence of sufficient bioactive filler leads to a bioactive composite. Finally, the material has been applied clinically, initially in the orbital floor and later in the middle ear. From this initial combination of HA in PE other bioactive ceramic polymer composites have been developed
K.E. Løgstrups tanker tangeret
No full textIn his philosophical dissertation that can be translated as K.E. Løgstrup. A Modern Prophet (1992), Hans Hauge proposed the thesis that the philosophy of Løgstrup, from first to last, tales leave of any epistemological foundation. In this critical evaluation, the author supports the interpretation by Hauge that Løgstrup's appeal to ontology in fact refers to ever changing life situations with each of their own characteristics. However, one has to distinguish between epistemologies. Already in 1933, Løgstrup opposed Husserl's epistemology of the transcendental ego. But only much later, Løgstrup criticized Heidegger for his universalization of the regional ontology of historicity. This metaphysical "Kehre" can be dated between January and September 1969. Furthermore, in his late philosophy, Løgstrup not simply abandoned epistemology. Rather, he developed a non-foundational epistemology on the basis of an interplay between historical understanding, rooted in the need for self-preservation, and the "useless", albeit penetrating sense qualities of the world.</jats:p
Author index
No full textThe index have been scanned in colour with a HP Scanjet 5590; 300dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.Since. the issue of the "Author and Subject Index to the Government Veterinary Reports of
the Transvaal and Union of South Africa 1903-1932" which appeared in June 1937, thirty five
volumes consisting of one hundred and twenty-six numbers of the "Onderstepoort Journal of
Veterinary Research" and two supplements have been puJlished. These represent a written record
of research work done in veterinary science and allied disciplines in the Republic of South Africa
during the past thirty-six years. Many subjects have been covered by many authors and the task of
fmding a particular reference in these volumes is no easy one. As a result an author and subject
index has been compiled to cover volumes 1 to 35 and it is hoped that this will be of material
benefit to research workers all over the world
Artificial intervertebral discs
No full textOver recent years, several models of the artificial intervertebral disc (IVD) have been designed and developed to restore the normal kinematics and load-bearing behaviour of the natural IVD, involving the use of metals, ceramics and polymers. This chapter first describes the structure–properties relationship of the natural IVD, and deals with the state of the art of artificial discs made of conventional materials. Then, it highlights the role of polymer-based composite biomaterials, underlining the possibility to design multifunctional devices with tailored mechanical properties. Accordingly, a biomimetic approach and the engineering of a pilot-scale device production process for a total, customized, artificial IVD with appropriate biological, transport and mechanical properties, have also been reported. Finally, future trends and strategies are discussed, emphasizing the importance to design of advanced materials and customized implants
February 15, 1905 Page three Robert Ball is not true name Foster has scheme for new customs positions
No full textMurder suspect Robert Ball is said to be Charles R. Mains, formerly of MichiganBall, Robert; Deppe, William; Mains, Charles R.; Hulbert, Stephen F.; Falkenburg, F.A.; Hadlock, Samuel; Larsen, James; Eisenbeis, K.E.; Rogers, Jerry S.; Tanner, Minnie Adelila; Tanner, T.J.; Foster, Addison Gardner, 1837-1917; Calhoun, Scott;Tanner, Minnie Adelia;German ship Neck; torpedo boat destroyer Paul Jones
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