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Organ culture is an increasingly important tool in research, with advantages over monolayer cell culture due to the inherent natural environment of tissues. Successful organ cultures must retain cell viability. The aim of this study was to produce viable and non-viable osteochondral organ cultures to assess the accumulation of soluble markers in the conditioned medium for predicting tissue viability. Porcine femoral osteochondral plugs were cultured for 20 days, with the addition on day 6, of Triton X-100 (to induce necrosis), camptothecin (to induce apoptosis) or no toxic additives. Tissue viability was assessed by the tissue destructive XTT (sodium 3'-[1-[(phenylamino)-carbonyl]-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzene-sulfonic acid hydrate) assay method and LIVE/DEAD® staining of the cartilage at days 0, 6 and 20. Tissue structure was assessed by histological evaluation using haematoxylin & eosin and safranin O. Conditioned medium was assessed every 3-4 days for glucose depletion, and levels of lactate dehydrogenase (LDH), alkaline phosphatase (AP), glycosaminoglycans (GAGs), and matrix metalloproteinase (MMP)-2 and MMP-9. Necrotic cultures immediately showed a reduction in glucose consumption, and an immediate increase in LDH, GAG, MMP-2 and MMP-9 levels. Apoptotic cultures showed a delayed reduction in glucose consumption and delayed increase in LDH, a small rise in MMP-2 and MMP-9, but no significant effect on GAGs released into the conditioned medium. The data showed that tissue viability could be monitored by assessing the conditioned medium for the aforementioned markers, negating the need for tissue destructive assays. Physiologically relevant whole- or part-joint organ culture models, necessary for research and pre-clinical assessment of therapies, could be monitored this way, reducing the need to sacrifice tissues to determine viability, and hence reducing the sample numbers necessary.

Advancements in knee replacement design, material and sterilisation processes have provided improved clinical results. However, surface wear of the polyethylene leading to osteolysis is still considered the longer-term risk factor. Experimental wear simulation is an established method for evaluating the wear performance of total joint replacements. The aim of this study was to investigate the influence of simulation input conditions, specifically input kinematic magnitudes, waveforms and directions of motion and position of the femoral centre of rotation, on the wear performance of a fixed-bearing total knee replacement through a combined experimental and computational approach. Studies were completed using conventional and moderately cross-linked polyethylene to determine whether the influence of these simulation input conditions varied with material. The position of the femoral centre of rotation and the input kinematics were shown to have a significant influence on the wear rates. Similar trends were shown for both the conventional and moderately cross-linked polyethylene materials, although lower wear rates were found for the moderately cross-linked polyethylene due to the higher level of cross-linking. The most important factor influencing the wear was the position of the relative contact point at the femoral component and tibial insert interface. This was dependent on the combination of input displacement magnitudes, waveforms, direction of motion and femoral centre of rotation. This study provides further evidence that in order to study variables such as design and material in total knee replacement, it is important to carefully control knee simulation conditions. This can be more effectively achieved through the use of displacement control simulation.

Meniscal repair is widely used as a treatment for meniscus injury. However, where meniscal damage has progressed such that repair is not possible, approaches for partial meniscus replacement are now being developed which have the potential to restore the functional role of the meniscus, in stabilising the knee joint, absorbing and distributing stress during loading, and prevent early degenerative joint disease. One attractive potential solution to the current lack of meniscal replacements is the use of decellularised natural biological scaffolds, derived from xenogeneic tissues, which are produced by treating the native tissue to remove the immunogenic cells. The current study investigated the effect of decellularisation on the biomechanical tensile and compressive (indentation and unconfined) properties of the porcine medial meniscus through an experimental–computational approach. The results showed that decellularised medial porcine meniscus maintained the tensile biomechanical properties of the native meniscus, but had lower tensile initial elastic modulus. In compression, decellularised medial porcine meniscus generally showed lower elastic modulus and higher permeability compared to that of the native meniscus. These changes in the biomechanical properties, which ranged from less than 1% to 40%, may be due to the reduction of glycosaminoglycans (GAG) content during the decellularisation process. The predicted biomechanical properties for the decellularised medial porcine meniscus were within the reported range for the human meniscus, making it an appropriate biological scaffold for consideration as a partial meniscus replacement.

Early repolarization (ER), once thought to be a benign finding on electrocardiograph (ECG), has recently been associated with an increased risk of sudden cardiac death. As there are limited data in the Hispanic population, we investigated possible associations between automated ECG ER readings and overall mortality, using the classic definition involving J-point elevation with ST segment elevation.An ECG and electronic medical record (EMR) database from a regional medical center was interrogated. Inclusion criteria included Hispanic ethnicity and age over 18 from 2000 to 2011. A Cox model assessed the outcome of death. Varying morphological characteristics of ER were analyzed for high-risk features.There were n = 33,944 Hispanics of who n = 532 (1.6%) had ER with a mean follow-up period of 5.29 years. After adjustment for demographic, clinical, lifestyle, and laboratory variables, ER was not significantly related to all-cause mortality (hazard ratio [HR]: 1.18, 95% confidence interval [CI]: 0.90-1.54, P = 0.23). However, mortality risk of ER varied by gender and age (P interaction = 0.007). The risk of ER for mortality was highest for females (HR: 2.01, CI: 1.39-3.10, P = 0.001), with the highest overall risk for women over the age of 75 (HR: 2.09, CI: 1.12-3.92, P = 0.021) compared to women under age 75 (HR: 1.72, CI: 0.95-3.11, P = 0.075).ER is not associated with an increased risk of death in the overall Hispanic population. However, our analysis suggests a higher risk of overall mortality in the elderly Hispanic female population with ER.

Development of pre-clinical testing methodologies is an important goal for improving prediction of artificial replacement joint performance and for guiding future device design. Total disc replacement wear and the potential for osteolysis is a growing concern, therefore a parametric study on the effects on wear of altered kinematics and loading was undertaken. A standard ISO testing protocol was modified in order to study the wear behaviour of lumbar total disc replacements when subject to low cross shear input kinematics, reduced axial loading and smaller flexion-extension magnitude. Volumetric wear, bearing surface topography, and wear debris biological reactivity were assessed. The ISO standard results were expected, however, the very low cross shear test produced a level of wear approximately two orders of magnitude higher than that reported for zero cross shear motions on UHMWPE bearings. When the osteolytic potential of the wear particles was calculated, all total disc replacement simulations had lower predicted osteolytic potential compared to total hip replacements, as a consequence of the generally lower wear rates found.

Graphical abstract, Recently, nanometre-sized UHMWPE particles generated from hip and knee replacements have been identified in vitro and in vivo. UHMWPE particles in the 0.1–1.0 μm size range have been shown to be more biologically active than larger particles, provoking an inflammatory response implicated in late aseptic loosening of total joint replacements. The biological activity of nanometre-sized particles has not previously been studied. The biological response to clinically-relevant UHMWPE wear particles including nanometre-sized and micrometre-sized, along with polystyrene particles (FluoSpheres 20 nm, 60 nm, 200 nm and 1.0 μm), and nanometre-sized model polyethylene particles (Ceridust 3615®), was determined in terms of osteolytic cytokine release from primary human peripheral blood mononuclear cells (PBMNCs). Nanometre-sized UHMWPE wear particles, nanometre-sized Ceridust 3615® and 20 nm FluoSpheres had no significant effect on TNF-α, IL-1β, IL-6 and IL-8 release from PBMNCs at a concentration of 100 μm3 particles per cell after 12 and 24 h. The micrometre-size UHMWPE wear particles (0.1–1.0 μm) and 60 nm, 200 nm and 1.0 μm FluoSpheres caused significantly elevated osteolytic cytokine release from PBMNCs. These results indicated that particles below circa 50 nm fail to activate PBMNCs and that particle size, composition and morphology played a crucial role in cytokine release by particle stimulated macrophages.

Optimization via continuation method is a widely used approach for solving nonconvex minimization problems. While this method generally does not provide a global minimum, empirically it often achieves a superior local minimum compared to alternative approaches such as gradient descent. However, theoretical analysis of this method is largely unavailable. Here, we provide a theoretical analysis that provides a bound on the endpoint solution of the continuation method. The derived bound depends on a problem specific characteristic that we refer to as optimization complexity. We show that this characteristic can be analytically computed when the objective function is expressed in some suitable basis functions. Our analysis combines elements of scale-space theory, regularization and differential equations.

Metal-on-polyethylene total disc replacements have been an alternative to spinal fusion in the lumbar spine under certain indications for more than a decade. Recently, cervical total disc replacement has also become an alternative to cervical fusion. Knowledge acquired from years of in vitro simulator studies on other joint replacements has highlighted the risks associated with premature wear due to unforeseen adverse clinical conditions and the effect of particulate debris on surrounding natural tissues. Having no evidence of the type and composition of the lubricating fluid that will result after spinal arthroplasty, a study on the effects of lubricant serum concentration was undertaken. The wear rate was shown to be inversely proportional to protein content of the serum over a range of 50%–3% bovine serum to water concentration.

The tribological performance and biological activity of the wear debris produced has been compared for highly cross-linked polyethylene, ceramic-on-ceramic, metal-on-metal, and modified metal bearings in a series of in vitro studies from a single laboratory. The functional lifetime demand of young and active patients is 10-fold greater than the estimated functional lifetime of traditional polyethylene. There is considerable interest in using larger diameter heads in these high demand patients. Highly cross-linked polyethylene show a four-fold reduction in functional biological activity. Ceramic-on-ceramic bearings have the lowest wear rates and least reactive wear debris. The functional biological activity is 20-fold lower than with highly cross-linked polyethylene. Hence, ceramic-on-ceramic bearings address the tribological lifetime demand of highly active patients. Metal-on-metal bearings have substantially lower wear rates than highly cross-linked polyethylene and wear decreases with head diameter. Bedding in wear is also lower with reduced radial clearance. Differential hardness ceramic-on-metal bearings and the application of ceramic-like coatings reduce metal wear and ion levels.

To develop strategies to recruit and retain inactive older adults into a physical activity program.Names of 7378 older adults were obtained from 60 neighborhoods. Then, 6401 potential subjects were matched to telephone numbers and phoned. Subjects meeting the screening criteria were invited to join the program (n = 4209). Walk leaders and social support were used to enhance retention.Five hundred seventy-three subjects were recruited (260 intervention and 313 control). The respective participation rate was 12.6% (260/2056) and 14.5% (313/2153), with low attrition of 31.9% (83/260) and 24.6% (77/313).Effective recruitment and retention strategies were identified.

In broad terms, European students of the history of Latin America have concentrated their researches upon colonial policies, interactions between Europeans (and their American-born descendants) and indigenous peoples, economic and commercial structures, and political life (whether of elites or, more recently, of subaltern groups). The last two decades have witnessed a significant expansion in Britain and elsewhere of research into gender studies and cultural studies. Although the latter discipline embraces an awareness of the importance of the history of science, this has tended to be rather narrowly focussed upon travel writing, and the extent to which there were links between the promotion of scientific travel and both imperial and national projects, particularly in the eighteenth and nineteenth centuries. However, like the great British scientific travellers of the nineteenth century in Latin America, the works of cultural studies specialists tend to reveal more about European attitudes and misconceptions than Latin American reality.

Several aspects of the phenomenon of world unrest after the First World War have been scrutinized in recent years. However, little has been said of its North-African dimension in the context of British imperial interests. Drawing upon a wide range of official and private archival material this article examines the origins and nature of British concerns about conspiracies connected with followers of the Mahdi in Northern Nigeria and the Sudan. It also considers the efforts made to investigate these conspiracies against the wider backdrop of nationalist unrest in Egypt and concerns about Bolshevik intrigues world-wide. The official perception of these conspiracies as well as the various investigations into their source is also considered.

The lubricating abilities of different formulations of high molecular weight hyaluronic acid (HA), dipalmitoyl phosphatidylcholine (DPCC) and mixtures of both HA and DPCC were assessed in an in vitro model. Levels of start-up friction were determined using an osteoarthritis (OA) damaged human cartilage model set within a specially designed friction rig. To examine the long term benefits of HA, the extent of penetration of HA into cartilage tissue was investigated using fluorescently labelled HA and confocal microscopy. It was found that in this model, all formulations of HA and the majority of DPCC lubricants reduced friction (HA 5 and 10 mg ml −1 , DPPC 200 mg ml −1 reductions of 51.9%, 46.7% and 46.5% respectively), compared to a Ringers solution control. Lubrication was found not to be concentration dependant for HA formulations, but concentration was key for DPCC lubrication (100 mg ml −1 reduced friction by only 15.9%). By combining HA and DPCC (HA/DPPC; 5 mg ml −1 /100 mg ml −1 and 10 mg ml −1 /200 mg ml −1 ), a further improvement was noted (69.5% and 61.9%, respectively) as the mean levels of friction were reduced by up to a further 17% than the most effective individual formulation (HA 5 mg ml −1 ). Penetration of HA into bovine cartilage by up to 300 μm from the surface was observed over a 48 h period. It was observed that HA specifically targeted the chondrocytes as it was primarily found within the lacunae surrounding the cells.

Total disc arthroplasty offers both theoretical and practical advantages over fusion surgery as a treatment for low back pain. In the majority of cases, these relatively new devices owe much of their evolution to the success of other total joint replacements, in particular, hip and knee prostheses, which have been developed over the last four decades. The demands on these new joints are substantial, and although short-term data appear to demonstrate good outcomes in a significant proportion of patients, medium- and longer-term results are sparse. The wear performance of these devices should be emphasized as a possible cause of failure through both adverse biological reactions, such as osteolysis, and inappropriate biomechanics, similar to that observed in a small proportion but numerically significant number of hip and knee prostheses. This article reviews the current technology in terms of the performance parameters these devices are required to operate within and the evidence for future problems akin to those observed in other joint arthroplasties. The article calls for more rigorous preclinical testing and follow-up protocols, based on the technologies and procedures developed for the current range of conventional hip and knee replacements.

Despite much research, the lubrication mechanisms operating in healthy synovial joints, particularly in the boundary or mixed regimes, are still not clear. This work continued the previous research by the authors in using a finite element model to investigate the effect of a soft, biphasic, amorphous surface layer on the lubrication characteristics of articular cartilage. This model was extended and the ‘biphasic surface amorphous layer (SAL) effect’ was investigated under repetitive, dynamic loading conditions. The results of this model showed that the lubrication benefits and stress shielding conferred by the soft, biphasic SAL remained almost entirely effective, despite incomplete cartilage swelling during unloading. The reduction in friction and improved lubrication were shown to be more beneficial during rapid dynamic loading and adversely effected by slow, static loading. The very rapid recovery of the SAL was shown to play an essential role in the mechanism and was important in helping the tissue to sustain low friction under conditions of repeated dynamic loading.

The adaption of British administration for the new Middle Eastern Empire after the First World War has been studied by several historians. 1 The emergence in 1921 of the Middle East Department of t...

Grain growth behavior and solid-state single crystal growth (SSCG) in the Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 (PMN–35PT) system have been investigated with varying Li2O/PbO ratios. The effect of dislocation density on crystal growth has also been studied. For SSCG, a BaTiO3 single-crystal seed was embedded in a polycrystalline PMN–PT matrix. During annealing, a PMN–PT single crystal grew from the seed at the cost of the small matrix grains. Addition of Li2O dopant first enhanced and then reduced abnormal grain growth in the matrix. In the 2 mol% Li2O and 6 mol% PbO excess PMN–PT samples annealed at 1200°C, considerable single-crystal growth occurred without formation of abnormally large grains in the matrix. Increasing the dislocation density in the BaTiO3 seed crystal resulted in enhanced growth of single crystals. These results were explained in terms of interface reaction-controlled nucleation and growth, based on crystal growth theories.

Ultra high molecular weight polyethylene (UHMWPE) wear debris has been shown to be a major cause of long term failure of total joint replacements. Recently, crosslinking has been extensively introduced to reduce the wear of UHMWPE. In this study the wear of non-crosslinked and crosslinked UHMWPE were compared under a range of conditions. The materials examined were UHMWPE GUR 1050, non-crosslinked, moderately crosslinked--5MRad, and highly crosslinked--10MRad. The wear was examined on a multidirectional pin on plate rig. The effect of counterface roughness on wear under different kinematics was examined. The results from the different counterface conditions showed that highly crosslinked UHMWPE had significantly lower wear against both smooth and scratched counterfaces. However the reduction in wear for crosslinked polyethylene was less for scratched counterfaces. The second part of the study showed that all the UHMWPE's produced lower wear rates under lower multidirectionality because of reduced cross shear frictional forces and work. These findings are relevant to the consideration of the use of crosslinked polyethylene in the knee, where the kinematics have lower levels of cross shear and in the hip and knee against roughened metallic counterfaces.

There is currently considerable interest in the wear debris and osteolytic potential of different types of bearings used in total joint replacements. The biological activity of the wear debris is dependent on the size and volume of the particles produced. Wear volume also plays an important role in the functional biological activity of a joint replacement. In vitro studies have shown that crosslinking of ultra high molecular weight polyethylene (UHMWPE) acetabular cups and tibial trays produces a reduction in wear volume, and crosslinking has now been introduced clinically for both types of prostheses. Previous studies have identified both micron and submicron-sized polyethylene wear particles. The aim of this study was to characterize the wear and wear particles generated from moderately crosslinked GUR 1,020 GVF UHMWPE acetabular cups and tibial trays in hip and knee joint wear simulators down to 10 nanometers in size. The wear rates of the two prosthesis types were very similar at 25.6 +/- 5.3 mm(3) per million cycles for the hip prostheses and 22.75 +/- 5.95 mm(3) per million cycles for the knee prostheses. Nanometer-sized wear particles were isolated and characterized from both hip and knee simulator lubricants for the first time. Significantly higher numbers (p < 0.05) of particles in the nanometer (

Tribology of hip joints is reviewed, covering a full spectrum from natural hip joints to total hip replacements, as well as tissue engineered articular cartilage. The importance of integrated tribological studies of contact mechanics, friction, wear and lubrication, as well as fully coupled with biological considerations, has been emphasized. The exact lubrication mechanism in natural hip joints is still not clear, although the unique biphasic characteristics of articular cartilage play an important role. Tribological studies of bearing surfaces for artificial hip joint replacements are important in developing and optimizing alternative material combinations to conventional polyethylene. Recently developed tissue engineered articular cartilage has been shown to be inadequate as far as the tribological property is concerned.

There is renewed interest in metal-on-metal (MOM) total hip replacements (THRs), however, variable wear rates have been observed clinically. It is hypothesised that changes in soft tissue tensioning during surgery may alter loading of THRs during the swing phase of gait leading to changes in fluid film lubrication, friction and wear. This study aimed to assess the effect of swing phase load on the lubrication, friction and wear of MOM hip replacements. Theoretical lubrication modelling was carried out using elastohydrodynamic theory. All the governing equations were solved numerically for the lubricant film thickness between the articulating surfaces under the transient dynamic conditions with low and high swing phase loads. Friction testing was completed using a single axis pendulum simulator, simplified loading cycles were applied with low and high swing phase loads. MOM hip replacements were tested in a hip simulator, modified to provide different swing phase loading regimes; a low (100 N) and a high load (as per ISO 14242-1; 280 N). Results demonstrated that the performance of MOM bearings is highly dependent on swing phase load. Hence, changes in the tension of the tissues at surgery and variations in muscle forces may increase swing phase load, reduce lubrication, increase friction and accelerate wear. This may explain some of the variations that have been observed with clinical wear rates.

The effect of additions of up to 1 mol% Al 2 O 3 on abnormal grain growth in BaTiO 3 samples sintered at 1200 and 1250 °C has been studied. Samples with and without additions of 0.4 mol% TiO 2 were prepared. For the samples without added TiO 2 , addition of 0.1 mol% Al 2 O 3 increases the number density of abnormal grains, with further additions reducing the number density. The initial increase in number density is caused by Al 2 O 3 forming a solid solution with BaTiO 3 and releasing TiO 2 to the grain boundaries. This excess TiO 2 then reacts with BaTiO 3 to form Ba 6 Ti 17 O 40 , which promotes {1 1 1} twin formation and abnormal grain growth. Further additions of Al 2 O 3 react with BaTiO 3 , Ba 6 Ti 17 O 40 and excess TiO 2 to form Ba 4 Al 2 Ti 10 O 27 and BaAl 2 O 4 second phases, neither of which are growth sites for abnormal grains. For the samples with added TiO 2 , addition of Al 2 O 3 decreases the number of abnormal grains due to the Al 2 O 3 reacting with the excess TiO 2 and BaTiO 3 to form Ba 4 Al 2 Ti 10 O 27 and BaAl 2 O 4 instead of Ba 6 Ti 17 O 40 .

Therapeutic lubricant injections of hyaluronic acid are a relatively recent treatment for osteoarthritis. Their efficacy however, in vivo has been subject to much debate. Frictional properties of cartilage-cartilage contacts under both static and dynamic loading conditions have been investigated, using healthy cartilage and cartilage with a physically disrupted surface, with and without the addition of a therapeutic lubricant, hyaluronic acid. Most of the cartilage friction models produced typical time-dependent loading curves, with a rise in static friction with loading time. For the dynamic loading conditions the rise in friction with loading time was dependent on the spatial (and time) variation in the load on the cartilage plate. For sliding distances of 4 mm or greater, when the cartilage plate was unloaded during sliding, the dynamic friction remained low whereas, with shorter sliding distances, the dynamic friction increased with increasing loading time. Static friction was higher than dynamic friction (under the same tribological conditions). The ‘damaged’ cartilage models produced higher friction than healthy cartilage under equivalent tribological conditions. It was shown that hyaluronic acid was an effective boundary lubricant for articular cartilage under static conditions with both healthy and damaged cartilage surfaces. Hyaluronic acid was less effective under dynamic conditions. However, these dynamic conditions had low friction values with the control lubricant because of the effectiveness of the intrinsic biphasic lubrication of the cartilage. It was only under the tribological conditions in which the cartilage friction was higher and rising with increasing loading time because of depletion of the intrinsic biphasic lubrication, that the role of hyaluronic acid as an effective therapeutic lubricant was demonstrated.

OBJECTIVES: To determine the relative effects of cobblestone mat walking, in comparison with regular walking, on physical function and blood pressure in older adults. DESIGN: Randomized trial with allocation to cobblestone mat walking or conventional walking. SETTING: General community in Eugene, Oregon. PARTICIPANTS: One hundred eight physically inactive community-dwelling adults aged 60 to 92 (mean age � standard deviation 577.5 � 5.0) free of neurological and mobility-limiting orthopedic conditions. INTERVENTION: Participants were randomized to a cobblestone mat walking condition (n 554) or regular walking comparison condition (n 554) and participated in 60-minute group exercise sessions three times per week for 16 consecutive weeks. MEASUREMENTS: Primary endpoint measures were balance (functional reach, static standing), physical performance (chair stands, 50-foot walk, Up and Go), and blood pressure (systolic, diastolic). Secondary endpoint measures were Short Form-12 physical and mental health scores and perceptions of health-related benefits from exercise. RESULTS: At the 16-week posttest, differences between the two exercise groups were found for balance measures (P 5.01), chair stands (Po.001), 50-foot walk (P 5.01), and blood pressure (P 5.01) but not for the Up and Go test (P 5.14). Although significant within-group changes were observed in both groups for the secondary outcome measures, there were no differences between intervention groups. CONCLUSION: Cobblestone mat walking improved physical function and reduced blood pressure to a greater extent than conventional walking in older adults. Additional benefits of this walking program included improved health-related quality of life. This new physical activity may provide a therapeutic and health-enhancing exercise alternative for older adults. J Am Geriatr Soc 2005.

Summary In recent years there has been renewed interest in metal-on-metal (MOM) bearings for both total hip replacement and surface replacement hip arthroplasty. Short-term clinical results have been encouraging; with low wear rates and few prostheses requiring revision. This review concentrates on the factors that affect the wear of all metal devices such as specification of the alloy, processing techniques, head diameter, clearance between the components, lubrication regime, loading and surface finish. The concerns associated with MOM bearings are also discussed. These include wear particle release and dissemination, and elevated metal ion levels, which may lead to cytotoxicity, hypersensitivity and genotoxicity.

Ultra high molecular weight polyethylene (UHMWPE) wear debris is a major cause of long term failure of total joint replacements. Recently, crosslinking has been introduced in order to reduce the wear of UHMWPE. In this study the wear and wear debris of non-crosslinked and two crosslinked UHMWPE's were compared. In particular this study has focused on the characterisation of nanometre size wear debris. The UHMWPE's were tested in a multidirectional pin on plate wear simulator against smooth and scratched counterfaces. The wear particles were isolated and imaged using a field emission gun scanning electron microscope (FEGSEM) at high resolution. The use of FEGSEM revealed nanometre size particles (less than 0.1 μm) for the first time. No significant difference was found in the percentage number and percentage volume of the particles in different size ranges from any of the materials against any of the counterfaces. The specific biological activity (biological activity per unit value, SBA) was highest for the highly crosslinked material tested on the smooth counterfaces. The functional biological activity (FBA) which takes into account the wear volume and SBA showed that the highly crosslinked UHMWPE had a lower FBA for debris from both the smooth and scratched counterfaces.

Objective: To examine the relation between built environment factors (representing several dimensions of urban form of neighbourhoods) and walking activity at both the neighbourhood level and the resident level, in an older adult sample. Design, setting, participants: A cross sectional, multilevel design with neighbourhoods as the primary sampling unit and senior residents as the secondary unit. Five hundred and seventy seven residents (mean age = 74 years, SD = 6.3 years) participated in the survey, which was conducted among 56 city defined neighbourhoods in Portland, Oregon, USA. Neighbourhood level variables were constructed using geographical information systems. Resident level variables consisted of a mix of self reports and geocoded data on the built environment. Main outcome measure: Self reported neighbourhood walking. Main results: A positive relation was found between built environment factors (density of places of employment, household density, green and open spaces for recreation, number of street intersections) and walking activity at the neighbourhood level. At the resident level, perceptions of safety for walking and number of nearby recreational facilities were positively related to high levels of walking activity. A significant interaction was observed between number of street intersections and perceptions of safety from traffic. Conclusions: Certain neighbourhood built environment characteristics related to urban form were positively associated with walking activity in the neighbourhoods of senior residents. Public health promotion of walking activity/urban mobility and the design of interventions need to consider the contribution of neighbourhood level built environment influences.

Over 80% of artificial hip joints utilise polyethylene acetabular cups articulating on metal or ceramic femoral heads. Alumina ceramic heads have previously been shown to reduce polyethylene wear. However, there are concerns about the brittle nature of ceramics and this places design constraints on neck length and head size. It is therefore of interest, to investigate ceramic-like coatings on metallic heads. The aim of this study was to compare the wear of polyethylene against alumina ceramic and chromium nitride (CrN) coated CoCr femoral heads in a hip joint simulator. Three 28-mm diameter Biolox™ Forte alumina ceramic heads and three CrN coated CoCr heads were articulated against UHMWPE GUR 1020 GVF (gamma irradiated in a vacuum foil pack), acetabular cups in the Leeds II hip joint simulator. The CrN heads were coated at Ionbond Limited using arc evaporative physical vapour deposition. The wear of polyethylene against alumina ceramic was 17 mm3/million cycles and against CrN was 23 mm3/million cycles. The difference was not statistically significant. Deliberate scratching of the femoral heads after 5 million cycles did not alter the wear rate. The coated heads had a slightly higher surface roughness and a higher contact angle than the ceramic heads. The contribution of both factors to the wear rate is currently being investigated.

Metal-on-metal is one potential bearing option for total hip arthroplasty (THA). Proponents of the bearing have suggested that if the tribology is optimal, volumetric wear may occur at levels at least one order of magnitude lower than metal-on-polyethylene bearings. We present a unique postmortem case of a well fixed, metal-on-metal, McKee-Farrar total hip arthroplasty implanted 30 years previously that was clinically asymptomatic in life. Clinical and radiological examination is supplemented by tribological examination of the bearing and histopathological examination of the cement-bone interface.

The article reports on a multilevel analysis conducted to examine change in neighborhood walking activity over a 12-month period in a community-based sample of 28 neighborhoods of 303 older adults age 65 and over. The study employed a multilevel (residents nested within neighborhoods) and longitudinal (4 repeated measures over 1 year) design and a multilevel analysis of change and predictors of change in neighborhood walking activity. Results indicated a significant neighborhood effect, with neighborhood-level walking characterized by a downward trajectory over time. Inclusion of baseline variables using selected perceived neighborhood-level social- and physical-environment measures indicated that neighborhoods with safe walking environments and access to physical activity facilities had lower rates of decline in walking activity. The findings provide preliminary evidence of neighborhood-level change and predictors of change in walking activity in older adults. They also suggest the importance of analyzing change in physical activity in older adults from a multilevel or macrolevel framework.

Na2O–CaO–ZrO2–SiO2 glass compositions with ZrO2 contents of up to 20 mol% were melted. Up to 12.3 mol% ZrO2 could be dissolved into the glasses. Melting temperatures ⩾1450 °C were required to remove seed and produce a melt that could be cast. Addition of ZrO2 caused an increase in the glass transition and crystallization temperatures. Glasses crystallized at temperatures ⩾1050 °C with Keldyshite and Parakeldyshite (Na2O · ZrO2 · 2SiO2) as the crystalline phases. Addition of up to 4.6 mol% ZrO2 caused an increase in the hydrolytic resistance of the glass, with further additions having little effect. The suitability of these glasses as hosts for ZrO2-containing radioactive wastes is discussed.

Alumina and aluminosilicate flakes with compositions Al2O3, 3Al2O3⋅2SiO2 and Al2O3⋅2SiO2 have been produced from commercial raw materials using a direct current plasma spray process in air. The microstructure and phase constitution of the as-sprayed flakes were examined with optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Changes in phase constitution of the flakes with heat-treatment were examined using differential thermal analysis (DTA) and XRD of heat-treated samples. The as-sprayed Al2O3 flakes consisted of α -Al2O3 phase plus a minor γ-Al2O3 phase. The γ-phase could be removed by heat treating the flakes at 1300∘C for 2 h. The aluminosilicate flakes consisted of 3Al2O3:2SiO2 (mullite) and an amorphous phase which crystallised to 3Al2O3:2SiO2 (mullite) after heat treatment at 1100∘C for 2 h. These flakes may find applications as high temperature thermal insulation materials.

Debris-induced osteolysis due to surface wear of ultra high molecular weight polyethylene (UHMWPE) bearings is a potential long-term failure mechanism of total knee replacements (TKR). This study investigated the effect of prosthesis design, kinematics and bearing material on the wear of UHMWPE bearings using a physiological knee simulator. The use of a curved fixed bearing design with stabilised polyethylene bearings reduced wear in comparison to more flat-on-flat components which were sterilised by gamma irradiation in air. Medium levels of crosslinking further improved the wear resistance of fixed bearing TKR due to resistance to strain softening when subjected to multidirectional motion at the femoral-insert articulating interface. Backside motion was shown to be a contributing factor to the overall rate of UHMWPE wear in fixed bearing components. Wear of fixed bearing prostheses was reduced significantly when anterior-posterior displacement and internal-external rotation kinematics were reduced due to decreased cross shear on the articulating surface and a reduction in AP displacement. Rotating platform mobile bearing prostheses exhibited reduced wear rates in comparison to fixed bearing components in these simulator studies due to redistribution of knee motion to two articulating interfaces with more linear motions at each interface. This was observed in two rotating platform designs with different UHMWPE bearing materials. In knee simulator studies, wear of TKR bearings was dependent on kinematics at the articulating surfaces and the prosthesis design, as well as the type of material.

The capacity of clinically relevant wear particles from Simplex P, Endurance, Vertebroplastic and Palacos R bone cements to activate macrophages to produce cytokines and bone resorbing activity in vitro was compared. Cement particles were generated aseptically by using a pin on plate rig. The particles were irregular in shape, and there were no significant differences in the particle characteristics of the different bone cement types (mean equivalent circle diameter range 0.225–0.36 μm, mean area range 0.048–0.063 μm2, mean aspect ratio range 1.481–1.593, and mean length 0.412–0.523 μm). The volumetric concentration of particles in the 0.1- to 1.0-μm size range was 85% Palacos R, 82% Endurance, 80% Simplex P, and 77% Vertebroplastic. Particles were cultured with C3H macrophages at 100 μm3 per cell for 24 h. Cytokines were determined by enzyme-linked immunosorbent assay and bone resorption (BR) measured by Ca45 release from murine calvarias. Particles of Palacos R and Endurance stimulated enhanced production of TNF-α, IL-1-β, and IL-6 (p < 0.05; ANOVA). Simplex P particles only stimulated IL-1-β (p < 0.05; ANOVA). Vertebroplastic particles did not stimulate production of any of the cytokines. Particles of Palacos R generated the highest BR (1.38), but this did not reach statistical significance. The BRs for the other bone cements were no greater than the control. Hence, compared with the same volumetric concentrations, particles of Palacos R and Endurance were the most, and particles of Vertebroplastic were the least biologically reactive. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005

The effect of additions of up to 1 mol% Al 2 O 3 on abnormal grain growth in BaTiO 3 has been studied. For samples sintered at temperatures ≤1250 °C addition of 0.1 mol% Al 2 O 3 increases the number density of abnormal grains, with further additions reducing the number density. For samples sintered at 1350 °C, addition of Al 2 O 3 caused the primary abnormal grain size to decrease and then increase. The results are explained by considering the effect of Al 2 O 3 addition on the TiO 2 content of grain boundaries.

Simple configuration pin-on-plate tests were conducted in order to compare the wear of ultrahigh-molecular-weight polyethylene (UHMWPE) when sliding against titanium-nitride (TiN)-coated wrought cobalt-chromium (Co-Cr) plates obtained by arc evaporative physical vapour deposition (AEPVD) with that which occurs when sliding against uncoated wrought and cast Co-Cr plates. UHMWPE wear was determined for plates in their undamaged form and following simulated third-body damage to produce scratches similar to those observed on retrieved implants. In their undamaged form, the coatings produced a similar wear rate of UHMWPE to that with the uncoated Co-Cr plates. However, in their damaged form, TiN-coated plates showed significantly lower polyethylene wear than uncoated wrought Co-Cr plates (analysis of variance; α = 0.05). The TiN-coated plates prevented the generation of high scratch lips due to their higher hardness, producing much smaller Rp values (0.19 μ) than the scratched uncoated Co-Cr plates (0.92-1.15 μ). This is a probable explanation for the lower wear rate on the scratched TiN-coated plates than on the scratched uncoated wrought plates. The results of this study have illustrated the possibility of using AEPVD TiN coatings in total knee joint replacements in order to reduce polyethylene wear.

LI, F., P. HARMER, K. J. FISHER, and E. MCAULEY. Tai Chi: Improving Functional Balance and Predicting Subsequent Falls in Older Persons. Med. Sci. Sports Exerc., Vol. 36, No. 12, pp. 2046–2052, 2004. Purpose: To determine whether improved functional balance through a Tai Chi intervention is related to subsequent reductions in falls among elderly persons. Methods: Two hundred fifty-six healthy, physically inactive older adults aged 70–92 (mean age SD 77.48 4.95), recruited from a local health system in Portland, OR, participated in a 6-month randomized controlled trial, with allocation to Tai Chi or exercise stretching control, followed by a 6-month postintervention follow-up. Functional balance measures included Berg balance scale, dynamic gait index, and functional reach, assessed during the 6-month intervention period (baseline, 3-month, and 6-month intervention endpoint) and again at the 6-month postintervention follow-up. Fall counts were recorded during the 6-month postintervention follow-up period. Data were analyzed through intention-to-treat analysis of variance and logistic regression procedures. Results: Tai Chi participants who showed improvements in measures of functional balance at the intervention endpoint significantly reduced their risk of falls during the 6-month postintervention period, compared with those in the control condition (odds ratio (OR), 0.27, 95% confidence interval (CI), 0.07–0.96 for Berg balance scale; OR, 0.27, 95% CI, 0.09–0.87 for dynamic gait index; OR, 0.20, 95% CI, 0.05–0.82 for functional reach). Conclusions: Improved functional balance through Tai Chi training is associated with subsequent reductions in fall frequency in older persons. Key Words: BALANCE, FALL PREVENTION, AGING

The wear and mechanical properties of GUR 1020 (Perplas IMP 2000-2) Ultra High Molecular Weight Polyethylene (UHMWPE) subjected to gamma-irradiation in an atmosphere of acetylene, were evaluated for a range of processing conditions of irradiation, annealing and ageing. The results were compared with those obtained for the virgin UHMWPE material and material processed using conventional gamma-irradiation in nitrogen. Cross-linking produced by irradiation in acetylene, followed by subsequent annealing was found to be significantly more effective in improving the mechanical and wear properties of UHMWPE compared to when the material was irradiated in nitrogen. Gel fraction analysis on its own, while being able to detect the degree of cross-linking, was found to be insufficient in determining the effectiveness of the cross-links and the resulting mechanical properties of the UHMWPE material. The results suggest that gamma-irradiation in an atmosphere of acetylene may provide significant advantages over conventional UHMWPE processing and irradiation cross-linking techniques.

Objectives:This study examined the relationship between physical activity and self-rated health in older adults at both the neighborhood level and the resident level.Methods:A multilevel design was used that involved neighborhoods as the primary sampling unit and residents nested within each neighborhood. Residents (N = 582, mean age = 73.99 years, SD = 6.26) from 56 neighborhoods in Portland, Oregon, were surveyed on neighborhood physical activity and health status.Results:Multilevel path analysis showed a positive relationship between physical activity and health status at the neighborhood level. In addition, perceptions of neighborhood social cohesion, proximity to physical activity facilities, safety for walking, and importance of physical activity involvement, were positively related to high levels of physical activity. At the resident level, education and walking efficacy were positively associated with physical activity.Conclusions:The results provide evidence that neighborhood-level physical activity is positively linked to neighborhood-level self-rated health in older adults.

The response of murine macrophages to clinically relevant polyethylene wear particles generated from different polyethylenes at various time points and volumetric doses in vitro was evaluated. Clinically relevant ultra high molecular weight polyethylene (UHMWPE) wear debris was generated in vitro in a lubricant of RPMI 1640 supplemented with 25% (v/v) foetal calf serum using a multi-directional pin-on-plate wear rig under sterile conditions. Wear debris was cultured with C3H murine peritoneal macrophages at various particle volume (microm(3)): cell number ratios. The secretion of TNF-alpha was determined by ELISA. Initially the effect of molecular weight of UHMWPE was considered. Higher molecular weight GUR415HP was shown to have a lower wear rate than the lower molecular weight GUR1120, however a greater volume of the wear debris produced by the high molecular weight GUR415HP was in the 0.1-1.0 microm size range. Wear debris from GUR415HP produced significant levels of TNF-alpha at a concentration of 1 microm(3)/cell while at least 10 microm(3)/cell of GUR1120 wear debris per cell was needed to produce significant levels of TNF-alpha. Secondly the effects of crosslinking GUR1050 was examined when worn against a scratched counterface. The wear rate of the material was shown to decrease as the level of crosslinking increased. However the materials crosslinked with 5 and 10 Mrad of gamma irradiation produced higher percentages of 0.1-1.0 microm size wear particles than the non-crosslinked material. While the crosslinked material was able to stimulate cells to produce significantly elevated TNF-alpha levels at a particle concentration of just 0.1 microm(3)/cell only concentrations of 10 microm(3)/cell and above of the non-crosslinked wear debris were stimulatory. When the counterface was changed from scratched to smooth the wear rate for all three GUR1050 materials was further reduced. For the first time nanometre size wear particles were observed from polyethylene which reduced the percentage mass of debris in the 0.1-1.0 microm size range. For all three materials on the smooth counterface only concentrations of 50 microm(3)/cell and above were stimulatory. This study has demonstrated that molecular weight, crosslinking and counterface roughness are important factors in determining the biological activity of polyethylene.

Objectives: To determine the effectiveness of tai chi on self-rated sleep quality and daytime sleepiness in older adults reporting moderate sleep complaints. Design: Randomized, controlled trial with allocation to tai chi or exercise control. Setting: General community. Participants: One hundred eighteen women and men aged 60 to 92. Intervention: Participants were randomized into tai chi or low-impact exercise and participated in a 60-minute session, three times per week, for 24 consecutive weeks. Measurements: Primary outcome measures were the seven subscales of the Pittsburgh Sleep Quality Index (PSQI), PSQI global score, and Epworth Sleepiness Scale (ESS). Secondary outcome measures were physical performance (single leg stand, timed chair rise, 50-foot speed walk) and 12-item short form (SF-12) physical and mental summary scores. Results: Tai chi participants reported significant improvements in five of the PSQI subscale scores (sleep quality, sleep-onset latency, sleep duration, sleep efficiency, sleep disturbances) (P

This article investigates the career of a British diplomat, William Garnett, whose unusual life has until know been neglected by historians. Garnett's papers, held at Lancashire Record Office, are a particularly rich source for historians of British diplomacy, the British Foreign Office, and overseas travel in the first two decades of the twentieth century. Garnett was often outspoken and indiscreet in his private correspondence and his archive, on which this article draws, provides valuable insights into British representation and British policy in the countries to which he was posted in the period 1902–1919.

Abnormal grain growth in Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 (PMN-35PT) ceramics doped with Li2O and PbO has been investigated. Replacing the PbO dopant with up to 2 mol% Li2O caused an increase in the number of abnormal grains. For the composition containing 2 mol% Li2O and 6 mol% PbO, the amount of abnormal grain growth decreased with increasing sintering temperature. Single crystals of ∼6 mm × 6 mm × 2 mm thickness were grown from the 2 mol% Li2O, 6 mol% PbO-containing composition via the templated grain growth method. Grain growth behavior with temperature is explained in terms of the effect of Li2O on interface-reaction-controlled grain growth and the critical driving force.

The wear of existing metal-on-metal (MOM) hip prostheses (1 mm3/million cycles) is much lower than the more widely used polyethylene-on-metal bearings (30-100 mm3/million cycles). However, there remain some potential concerns about the toxicity of metal wear particles and elevated metal ion levels, both locally and systemically in the human body. The aim of this study was to investigate the wear, wear debris and ion release of fully coated surface engineered MOM bearings for hip prostheses. Using a physiological anatomical hip joint simulator, five different bearing systems involving three thick (8-12 microm) coatings, TiN, CrN and CrCN, and one thin (2 microm) coating diamond like carbon (DLC) were evaluated and compared to a clinically used MOM cobalt chrome alloy bearing couple. The overall wear rates of the surface engineered prostheses were at least 18-fold lower than the traditional MOM prostheses after 2 million cycles and 36-fold lower after 5 million cycles. Consequently, the volume of wear debris and the ion levels in the lubricants were substantially lower. These parameters were also much lower than in half coated (femoral heads only) systems that have been reported previously. The extremely low volume of wear debris and concentration of metal ions released by these surface engineered systems, especially with CrN and CrCN coatings, have considerable potential for the clinical application of this technology.

There is a need for greater understanding of setting-specific influences on physical activity to complement the predominant research paradigm of individual-centered influences on physical activity. In this study, the authors used a cross-sectional multilevel analysis to examine a range of neighborhood-level characteristics and the extent to which they were associated with variation in self-reported physical activity among older adults. The sample consisted of 582 community-dwelling residents age 65 years and older (M = 73.99 years, SD = 6.25) recruited from 56 neighborhoods in Portland, OR. Information collected from participants and neighborhood data from objective sources formed a two-level data structure. These hierarchical data (i.e., individuals nested within neighborhoods) were subjected to multilevel structural-equation-modeling analyses. Results showed that neighborhood social cohesion, in conjunction with other neighborhood-level factors, was significantly associated with increased levels of neighborhood physical activity. Overall, neighborhood-level variables jointly accounted for a substantial variation in neighborhood physical activity when controlling for individual-level variables.

There is currently much discussion about the most clinically relevant testing methods for evaluating total hip replacements. This study examined the effect of different swing phase loads, including microseparation, on the wear, friction, and wear particles of metal-on-metal (MOM) hip replacements. MOM hip replacements were tested for 5 million cycles with the use of a hip simulator; prostheses were tested with a low (100-N) and ISO (280-N) swing phase load, and under microseparation conditions. Increasing the swing phase load from 100 to 280 N in the same hip simulator increased the wear of the MOM hip replacements by over tenfold. Introducing microseparation into the gait cycle increased wear further, and stripe wear was observed on the femoral heads, accompanied by corresponding rim damage on the acetabular cups. No significant difference in wear particle size was observed between wear particles produced by low load and microseparation hip simulator conditions. Introducing microseparation into the hip simulator gait cycle increased the wear of MOM prostheses. Joint laxity and separation may lead to increased wear rates of MOM prostheses in vivo. Additionally elevated positive swing phase loads may also increase wear. Variable swing phase load conditions in vivo may contribute to variations in clinical wear rates. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 70B: 233–239, 2004

Metal-on-metal bearings offer one possible solution to problems of osteo-lysis associated with ultra high molecular weight polyethylene (UHMWPE) wear debris generated during articulation in total joint replacements. Designs using larger bearing diameters are also possible with associated improvements in both range of motion and stability. There has been considerable debate as to the optimum metallurgical structure of the cobalt chrome alloys used in these metal-on-metal bearings. This review addresses the main metallurgical design issues in metal-on-metal bearing design and reviews some recent studies from two independent academic centres. Cobalt chrome alloys with a low carbon content, when paired against themselves, have been shown to have poor wear properties under both simple configuration and simulator testing. Other cobalt chrome alloy couples with higher carbon content, whether wrought, cast or cast and heat-treated, appear to have similar performance in clinically relevant wear simulation studies. (Hip International 2004; 14: 1-10).

Ultra-high molecular weight polyethylene wear particles have been implicated as the major cause of osteolysis, implant loosening and late aseptic failure in total hip arthroplasties in vivo. This study initially screened 22 carbon-carbon composite materials as alternatives for UHMWPE in joint bearings. New bearing materials should satisfy certain criteria--they should have good wear properties that at least match UHMWPE, and produce wear particles with low levels of cytotoxic and osteolytic activity. Initial screening was based on wear resistance determined in short-term tribological pin-on-plate tests. Three materials (HMU-PP(s), HMU-RC-P(s), and SMS-RC-P(s)) which had superior wear resistance were selected for long-term testing. All materials had very low wear factors and SMS-RC-P(s), which had a wear factor of 0.08 +/- 0.56 x 10(-7) mm3/Nm, was selected for the subsequent biological testing and particle size analysis. SMS-RC-P(s) showed good biocompatibility in bulk material form and also the wear particles had low cytotoxicity for L929 fibroblasts in culture compared to metal wear particles. Wear debris size analysis by transmission electron microscopy showed that the particles were very small, with the vast majority being under 100 nm in size, similar to metal wear particles. The potential osteolytic effect of SMS-RC-P(s) wear particles was investigated by culturing particles with human peripheral blood mononuclear cells and measuring TNFalpha production. SMS-RC-P(s) did not significantly stimulate TNFalpha production at a particle volume to cell number ratio of 80:1, indicating that the debris had a low osteolytic potential. The results of this study suggest that carbon-carbon composites, particularly those composed of PAN-based fibers may be important biomaterials in the development of next generation bearing surfaces for use in total joint replacements that have very low wear rates and reduced osteolytic and cytotoxic potential.