This Perspective is focused on the photocatalytic activity of gold nanoparticles supported on titania (Au/TiO2). Titania is the most widely used photocatalyst, but its limited activity under visible light irradiation has motivated the quest for modified titania materials absorbing visible light. The review starts by justifying how doping with metallic elements is a related strategy, but different, to that leading to the use of Au/TiO2 in photocatalysis. Data supporting and confirming the photoactivity of gold nanoparticles in colloidal solutions are briefly presented to justify the possibility of gold photosensitization of titania by electron injection into the conduction band. After describing the most common procedures used to prepare Au/TiO2, the central part of this article is focused on the photocatalytic activity reported for Au/TiO2 for hydrogen generation, dye decoloration, phenol decomposition and carboxylic acid degradation, among other processes. Emphasis is given to the role that parameters like Au loading, particle size, surface area, spatial structuring and others play on the photocatalytic activity. One important issue has been to distinguish those reports using visible light from those other in which direct titania excitation by UV light has been used. These Au/TiO2 photocatalysts can find real applications in the near future for environmental remediation and for hydrogen generation.

Titania supported gold nanoparticles as photocatalyst

Additive manufacturing of biomaterials.

We sought to establish the incidence of joint failure secondary to adverse reaction to metal debris (ARMD) following metal-on-metal hip resurfacing in a large, three surgeon, multicentre study involving 4226 hips with a follow-up of 10 to 142 months. Three implants were studied: the Articular Surface Replacement; the Birmingham Hip Resurfacing; and the Conserve Plus. Retrieved implants underwent analysis using a co-ordinate measuring machine to determine volumetric wear. There were 58 failures associated with ARMD. The median chromium and cobalt concentrations in the failed group were significantly higher than in the control group (p < 0.001). Survival analysis showed a failure rate in the patients with Articular Surface Replacement of 12.8% [corrected] at five years, compared with < 1% at five years for the Conserve Plus and 1.5% at ten years for the Birmingham Hip Resurfacing. Two ARMD patients had relatively low wear of the retrieved components. Increased wear from the metal-on-metal bearing surface was associated with an increased rate of failure secondary to ARMD. However, the extent of tissue destruction at revision surgery did not appear to be dose-related to the volumetric wear.

/pdf/adverse-reaction-to-metal-debris-following-hip-resurfacing-1wusrbjnk6.pdf

Adverse reaction to metal debris following hip resurfacing: THE INFLUENCE OF COMPONENT TYPE, ORIENTATION AND VOLUMETRIC WEAR

Friction of cartilage on metal, metal on cartilage and cartilage on cartilage contact configurations, within a mixed lubrication regime, was measured using synovial fluid, Ringer's solution or with no lubricant present. The main test variable was the period of stationary loading which ranged from 5 s to 45 min, prior to sliding and consequently measuring friction. The coefficient of friction rose gradually with increasing stationary loading time, up to a value of approximately 0.3 at 45 min for all the contact configurations. Following the re-application of load, after short periods of load removal, friction was also found to drop sharply. The flow of liquid in the biphasic cartilage and load carriage by the fluid phase was highlighted as being an important factor in reducing friction within the mixed or boundary lubrication regime. Movement of the contact zone over the cartilage counterface ensured very low friction as the slider moved over fully hydrated cartilage. For the cartilage--cartilage contacts synovial fluid significantly reduced friction compared to Ringer's solution. This was attributed to an effective boundary lubrication action, which was not as effective for the cartilage--metal contacts.

The influence of loading time and lubricant on the friction of articular cartilage.

Ultra-high molecular weight polyethylene (UHMWPE) is the most common bearing material in total joint arthroplasty due to its unique combination of superior mechanical properties and wear resistance over other polymers. A great deal of research in recent decades has focused on further improving its performances, in order to provide durable implants in young and active patients. From “historical”, gamma-air sterilized polyethylenes, to the so-called first and second generation of highly crosslinked materials, a variety of different formulations have progressively appeared in the market. This paper reviews the structure–properties relationship of these materials, with a particular emphasis on the in vitro and in vivo wear performances, through an analysis of the existing literature.

/pdf/ultra-high-molecular-weight-polyethylene-influence-of-the-3v7f7qhgba.pdf

Ultra-High Molecular Weight Polyethylene: Influence of the Chemical, Physical and Mechanical Properties on the Wear Behavior. A Review

https://sensorprod.com/news/white-papers/2009-02_imf/wp_imf-2009-02.pdf

Influence of the meniscus on friction and degradation of cartilage in the natural knee joint.

Lubrication mechanisms and contact mechanics have been analysed in a new generation of ‘cushion form’ bearings for artificial hip joints, which comprise low elastic modulus layers on the articulating surfaces. Comparisons have been made with ‘ hard’ bearings used in existing prostheses and also with the natural hip joint. Lubricating film thicknesses are enhanced by larger contact areas and lower contact pressures. For a fixed contact area, simultaneous changes in layer thickness and radial clearance have been shown to have a small effect on elastohydrodynamic film thickness. Hard bearings designed with the same contact area as the cushion bearings produced a similar film thickness, but lubricant film thickness is not optimized in current designs. The main advantage of using a cushion bearing with low elastic modulus layers was found to be associated with microelastohydrodynamic lubrication. Careful selection of the elastic modulus is important in order to ensure that this lubrication regime was effective...

Design Considerations for Cushion Form Bearings in Artificial Hip Joints

Development of computational wear simulation of metal-on-metal hip resurfacing replacements.

Glycosaminoglycans (GAGs) have been shown to be responsible for the interstitial fluid pressurization of articular cartilage and hence its compressive stiffness and load-bearing properties. Contradictory evidence has been presented in the literature on the effect of depleting GAGs on the friction properties of articular cartilage. The aim of this study was to investigate the effect of depleting GAGs on the friction and deformation characteristics of articular cartilage under different tribological conditions. A pin-on-plate machine was utilized to measure the coefficient of friction of native and chondroitinase ABC (CaseABC)-treated articular cartilage under two different models: static (4 mm/s start-up velocity) and dynamic (4 mm/s sliding velocity; 4 mm stroke length) under a load of 25 N (0.4 MPa contact stress) and with phosphate-buffered saline as the lubricant. Indentation tests were carried out at 1 N and 2 N loads (0.14 MPa and 0.28 MPa contact stress levels) to study the deformation characteristics of both native and GAG-depleted cartilage samples. CaseABC treatment rendered the cartilage tissue soft owing to the loss of compressive stiffness and a sulphated-sugar assay confirmed the loss of GAGs from the cartilage samples. CaseABC treatment significantly increased (by more than 50 per cent) the friction levels in the dynamic model (p < 0.05) at higher loading times owing to the loss of biphasic lubrication. CaseABC treatment had no effect on friction in the static model in which the cartilage surfaces did not have an opportunity to recover fluid because of static loading unlike the cartilage tissue in the dynamic model, in which translation of the cartilage surfaces was involved, ensuring effective biphasic lubrication. Therefore the depletion of GAGs had a smaller effect on the coefficient of friction for the static model. Indentation tests showed that GAG-depleted cartilage samples had a lower elastic modulus and higher permeability than native tissue. These results corroborate the role of GAGs in the compressive and friction properties of articular cartilage and emphasize the need for developing strategies to control GAG loss from diseased articular cartilage tissue.

The effect of glycosaminoglycan depletion on the friction and deformation of articular cartilage.

Crosslinked ultra-high molecular weight polyethylene (UHMWPE) has been developed and introduced into clinical practice in order to reduce wear in the hip. Zero wear of highly crosslinked UHMWPE in vitro has been reported by some groups using lubricants with high concentrations of serum proteins in hip simulators. In contrast, some clinical studies have reported finite wear rates. The aim of this study was to compare the wear rates, wear surfaces, and wear debris produced by UHMWPE with different levels of crosslinking in a hip joint simulator, with lower, more physiologically relevant concentrations of protein in the lubricant. The UHMWPEs were tested in the Leeds ProSim hip joint simulator against cobalt-chromium (CoCr) femoral heads. The wear particles were isolated and imaged using a field emission gun scanning electron microscope (FEGSEM) at high resolution. The highly crosslinked UHMWPEs had significantly lower wear volumes than the non-crosslinked UHMWPEs. No significant difference was found in the percentage number and percentage volume of the particles in different size ranges from any of the materials. They had similar values of specific biological activity. The functional biological activity (FBA), which takes into account the wear volume and specific biological activity, showed that the highly crosslinked UHMWPEs had lower FBAs due to their lower wear volume.

Wear and biological activity of highly crosslinked polyethylene in the hip under low serum protein concentrations

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Z M Jin

Author Tools

Chat about Author