Polycrystalline Diamond as a Potential Material for the Hard-on-Hard Bearing of Total Hip Prosthesis: Von Mises Stress Analysis.

Due to polymeric wear debris causing osteolysis from polymer, metal ions causing metallosis from metal, and brittle characteristic causing fracture failure from ceramic in the application on bearing of total hip prosthesis requires the availability of new material options as a solution to these problems. Polycrystalline diamond (PCD) has the potential to become the selected material for hard-on-hard bearing in view of its advantages in terms of mechanical properties and biocompatibility. The present study contributes to confirming the potential of PCD to replace metals and ceramics for hard-on-hard bearing through von Mises stress investigations. A computational simulation using a 2D axisymmetric finite element model of hard-on-hard bearing under gait loading has been performed. The percentage of maximum von Mises stress to respective yield strength from PCD-on-PCD is the lowest at 2.47%, with CoCrMo (cobalt chromium molybdenum)-on-CoCrMo at 10.79%, and Al2O3 (aluminium oxide)-on-Al2O3 at 13.49%. This confirms that the use of PCD as a hard-on-hard bearing material is the safest option compared to the investigated metal and ceramic hard-on-hard bearings from the mechanical perspective.

Adopted walking condition for computational simulation approach on bearing of hip joint prosthesis: review over the past 30 years.

Bearing on artificial hip joint experiences friction, wear, and surface damage that impact on overall performance and leading to failure at a particular time due to continuous contact that endangers the user. Assessing bearing hip joint using clinical study, experimental testing, and mathematical formula approach is challenging because there are some obstacles from each approach. Computational simulation is an effective alternative approach that is affordable, relatively fast, and more accessible than other approaches in examining various complex conditions requiring extensive resources and several different parameters. In particular, different gait cycles affect the sliding distance and distribution of gait loading acting on the joints. Appropriate selection and addition of gait cycles in computation modelling are crucial for accurate and reliable prediction and analysis of bearing performance such as wear a failure of implants. However, a wide spread of gait cycles and loading data are being considered and studied by researchers as reported in literature. The current article describes a comprehensive literature review adopted walking condition that has been carried out to study bearing using computational simulation approach over the past 30 years. Many knowledge gaps related to adoption procedures, simplification, and future research have been identified to obtain bearing analysis results with more realistic computational simulation approach according to physiological human hip joints.

Computational Contact Pressure Prediction of CoCrMo, SS 316L and Ti6Al4V Femoral Head against UHMWPE Acetabular Cup under Gait Cycle.

Due to various concerns about the use of metal-on-metal that is detrimental to users, the use of metal as acetabular cup material was later changed to ultra high molecular weight polyethylene (UHMWPE). However, the wear on UHMWPE releases polyethylene wear particles, which can trigger a negative body response and contribute to osteolysis. For reducing the wear of polyethylene, one of the efforts is to investigate the selection of metal materials. Cobalt chromium molybdenum (CoCrMo), stainless steel 316L (SS 316L), and titanium alloy (Ti6Al4V) are the frequently employed materials. The computational evaluation of contact pressure was carried out using a two-dimensional axisymmetric model for UHMWPE acetabular cup paired with metal femoral head under gait cycle in this study. The results show Ti6Al4V-on-UHMWPE is able to reduce cumulative contact pressure compared to SS 316L-on-UHMWPE and CoCrMo-on-UHMWPE. Compared to Ti6Al4V-on-UHMWPE at peak loading, the difference in cumulative contact pressure to respective maximum contact pressure is 9.740% for SS 316L-on-UHMWPE and 11.038% for CoCrMo-on-UHMWPE.

Diarrhea-like condition and intestinal mucosal responses in susceptible homozygous and heterozygous F4R+ pigs challenged with enterotoxigenic Escherichia coli.

Enterotoxigenic Escherichia coli (ETEC) F4 is a major cause of diarrhea in both neonatal and young pigs. Indeed, only pigs having F4 receptors are susceptible. Among the susceptible pigs, it is yet unknown if spontaneous E. coli postweaning diarrhea (PWD) occurrence and intestinal mucosal responses to ETEC differ between genotypes. This study investigated a diarrhea-like condition and intestinal mucosal responses in F4 homo- and heterozygous susceptible weaner pigs. Sixteen weaned pigs (28 d of age) were used in a 2 × 2 factorial study with genotype (homo- or heterozygous F4R(+)) and inoculation with E. coli F4 or not as the 2 factors. Within genotype, 4 pigs were inoculated with E. coli F4 and the other 4 pigs received saline buffer on days 7 and 8 after weaning. Fecal score and DM and bacterial counts were conducted from days 7 to 12 after weaning. Blood was obtained on days 3 and 10 after weaning and at the time of killing. Four pigs were killed per day on days 14, 15, 16, and 17. Small intestine (SI) was divided into 3 parts of equal length for measurement of intestinal weight and the amount of mucosa. Lymphocyte subsets in jejunal Peyer's patches (jejPP) were analyzed using flow cytometry. Escherichia coli reduced (P = 0.05) total percentage of intestinal mucosa (on a dry basis) and had an impact on metabolomics profile of the plasma. No effect of genotype was seen on fecal score and DM, fecal shedding of hemolytic E. coli, mucosal responses, metabolomics profile, antibody responses, and lymphocyte subsets counts. This study suggests that both F4 homo- and heterozygous susceptible pigs have similar functional receptors for E. coli F4, which facilitate the adhesion of F4 to the intestinal tissue.

Radiotracer method for residence time distribution study in multiphase flow system.

[(131)I] isotope in different chemical compounds have been injected into 24in hydrocarbon transmission pipeline containing approximately 95% water, 3% crude oil, 2% gas and negligible solid material, respectively. The system is operated at the temperature around 70 degrees C enabling fluids flow is easier in the pipeline. The segment of measurement was chosen far from the junction point of the pipeline, therefore, it was reasonably to assume that the fluids in such multiphase system were separated distinctively. Expandable tubing of injector was used to ensure that the isotopes were injected at the proper place in the sense that [(131)I]Na isotope was injected into water layer and iodo-benzene, ([131])IC(6)H(5,) was injected into crude oil regime. The radiotracer selection was based on the compatibility of radiotracer with each of fluids under investigation. [(131)I]Na was used for measuring flow of water while iodo-benzene, ([131])IC(6)H(5,) was used for measuring flow of crude oil. Two scintillation detectors were used and they are put at the distances 80 and 100m, respectively, from injection point. The residence time distribution data were utilized for calculation water and crude oil flows. Several injections were conducted in the experiments. Although the crude oil density is lighter than the density of water, the result of measurement shows that the water flow is faster than the crude oil flow. As the system is water-dominated, water may act as carrier and the movement of crude oil is slowed due to friction between crude oil with water and crude oil with gas at top layer. Above of all, this result was able to give answer on the question why crude oil always arrives behind water as it is checked at gathering station. In addition, the flow patterns of the water in the pipeline calculated by Reynolds number and predicted by simple tank-in-series model is turbulence in character.