Influence of contact pressure, cross-shear and counterface material on the wear of PEEK and CFR-PEEK for orthopaedic applications

Total joint replacement is a successful surgical intervention for the treatment of the degeneration of many joints, particularly the hip and knee. As the demand for joint replacement grows, and the life expectancy of the population increases, the performance requirements of these implants also changes. New materials, to improve longevity and enhance performance have been explored including PEEK and CFR-PEEK. This study investigated whether CFR-PEEK and PEEK were appropriate materials for total joint replacement by examining wear performance in simple configuration studies articulating against cobalt chrome under a range of cross-shear and contact pressure conditions. Simple geometry pin on plate studies were conducted for one million cycles for each test condition, with the contact pressure and cross-shear conditions representing a range in which the material may need to operate in-vivo. The wear factor for PEEK was significantly higher than CFR-PEEK and conventional polyethylene under all test conditions. Both PEEK and CFR-PEEK wear were influenced by contact pressure, with the highest wear factors for both materials measured at the highest pressure conditions. PEEK appeared to have a cross-shear dependent wear response, but this was not observed for the CFR-PEEK material. This study has further characterised the wear performance of two materials that are gaining interest for total joint replacement. The wear performance of the PEEK material showed poorer wear performance compared to polyethylene when articulating with a metal counterface, but the performance of the CFR-PEEK material suggested it may provide a suitable alternative to polyethylene in some applications. The wear performance of CFRPEEK was poorer than polyethylene when it was used as the plate, when there was translation of the contact zone over the surface of the CFR-PEEK plate. This has implications for applications in low conforming contacts, such as lower conformity knee replacement

Hindrance of heavy-ion fusion at extreme sub-barrier energies in open-shell colliding systems

The excitation function for the fusion-evaporation reaction 64Ni + 100Mo has been measured down to a cross section of ∼5 nb. Extensive coupled-channels calculations have been performed, which cannot reproduce the steep falloff of the excitation function at extreme sub-barrier energies. Thus, this system exhibits a hindrance for fusion, a phenomenon that has been discovered only recently. In the S-factor representation introduced to quantify the hindrance, a maximum is observed at Es = 120.6 MeV, which corresponds to 90% of the reference energy Esref, a value expected from systematics of closed-shell systems. A systematic analysis of Ni-induced fusion reactions leading to compound nuclei with mass A = 100-200 is presented in order to explore a possible dependence of fusion hindrance on nuclear structure

First evidence of fusion hindrance for a small Q-value system

The excitation function for the fusion-evaporation reaction 28Si + 64Ni has been measured down to a cross section of 25 nb. This is the first observation of fusion hindrance at extreme sub-barrier energies for a system with a small, negative Q-value (- 1.78 MeV). This result is further proof that heavy-ion fusion hindrance, reported earlier only for systems with large, negative Q-values, is a general phenomenon. The measured behavior can be reproduced by coupled-channels calculations with a modified ion-ion potential incorporating the effects of nuclear incompressibility

ISSCR standards for the use of human stem cells in basic research

The laboratory culture of human stem cells seeks to capture a cellular state as an in vitro surrogate of a biological system. For the results and outputs from this research to be accurate, meaningful, and durable, standards that ensure reproducibility and reliability of the data should be applied. Although such standards have been previously proposed for repositories and distribution centers, no widely accepted best practices exist for laboratory research with human pluripotent and tissue stem cells. To fill that void, the International Society for Stem Cell Research has developed a set of recommendations, including reporting criteria, for scientists in basic research laboratories. These criteria are designed to be technically and financially feasible and, when implemented, enhance the reproducibility and rigor of stem cell research

A common NKCC2 mutation in Costa Rican Bartter's syndrome patients : evidence of a founder effect

Contains fulltext : 25474___.PDF (publisher's version ) (Open Access

Skin grafts from genetically modified α-1,3-galactosyltransferase knockout miniature swine: a functional equivalent to allografts

Burn is associated with a considerable burden of morbidity worldwide. Early excision of burned tissue and skin grafting of the resultant wound has been established as a mainstay of modern burn therapy. However, in large burns, donor sites for autologous skin may be limited. Numerous alternatives, from cadaver skin to synthetic substitutes have been described, each with varying benefits and limitations. We previously proposed the use of genetically modified (alpha-1,3-galactosyl transferase knockout, GalT-KO) porcine skin as a viable skin alternative. In contrast to wild type porcine skin, which has been used as a biologic dressing following glutaraldehyde fixation, GalT-KO porcine skin is a viable graft, which is not susceptible to loss by hyperacute rejection, and undergoes graft take and healing, prior to eventual rejection, comparable to cadaver allogeneic skin. In the current study we aimed to perform a detailed functional analysis of GalT-KO skin grafts in comparison to allogeneic grafts for temporary closure of full thickness wounds using our baboon dorsum wound model. Grafts were assessed by measurement of fluid loss, wound infection rate, and take, and healed appearance, of secondary autologous grafts following xenograft rejection. Comparison was also made between fresh and cryopreserved grafts. No statistically significant difference was identified between GalT-KO and allogeneic skin grafts in any of the assessed parameters, and graft take and function was not adversely effected by the freeze–thaw process. These data demonstrate that GalT-KO porcine grafts are functionally comparable to allogeneic skin grafts for temporary closure of full thickness wounds, and support their consideration as an alternative to cadaver allogeneic skin in the emergency management of large burns

Gynecologic Cancer InterGroup (GCIG) Consensus Review for Uterine Serous Carcinoma

Biological, physical and clinical aspects of cancer treatment with ionising radiatio