1,721,373 research outputs found
Abrasion-corrosion of cast CoCrMo in simulated hip joint environments
No full textMetal-on-metal (MoM) hip joint replacements have been increasingly used for younger and more
active patients in recent years due to their improved wear performance compared to conventional
metal-on-polymer bearings. MoM bearings operate at body temperature within a corrosive joint
environment and therefore are inevitably being subjected to wear and corrosion as well as the
combined action of tribo-corrosion. Issues such as metal sensitivity/metallosis associated with high
levels of metal ion release triggered by the wear and corrosion products remain critical concerns.
During the past few decades, significant research has been conducted into understanding the
wear/lubrication mechanisms within the MoM hip joints in order to improve their performance and
thereby prolonging their life. However, not much attention has been given to the combined effect of
wear and corrosion of such devices in the hip joint environment, in addition, the role of third body
particles and the effects of proteins have not been well understood.In this work, a systemic approach is presented for the first time for the mapping of abrasion and
tribo-corrosion performance of a cast CoCrMo (F75) in simulated hip joint environments. The
effects of third body particles have been studied in the MoM context using 4 ?m SiC, 1 ?m and 300
nm Al2O3, as well as sub-micron BaSO4. Modified tribo-testers (micro-abrasion,
nanoindenter/scratching) incorporating a novel electrochemical cell have been used to monitor the
abrasion-corrosion behaviour of the alloy in situ. The effects of solution chemistry, abrasives size /
concentration and presence of proteins on the wear / corrosion level, wear-corrosion mechanisms,
and the depassivation/repassivation kinetics of the CoCrMo have been explored. A variety of surface
and sub-surface characterization techniques have been employed to identify the microstructual wear
mechanism interactions. Results show that the change of protein concentration (0, 25% and 50%
bovine serum) and pH (pH 7.4 and pH 4.0) of the test solutions can significantly influence the
protein adsorption behaviour, which subsequently influence the wear rates (synergy), wear
mechanisms as well as the wear-induced corrosion currents of the CoCrMo. For abrasion-corrosion
tests, reducing abrasive size from 4 ?m to 300 nm and/or abrasive volume concentration from 0.238
vol% to 0.006 vol% results in different abrasion-corrosion wear mechanisms (rolling or grooving
abrasion) and the average wear-induced corrosion currents show a linear correlation with wear rates
for 4 ?m and 1 ?m abrasives. For low volume concentration (< 0.03 vol%) slurries containing
bovine serum, organo-metallic conglomerates have been found within the wear scars. These
conglomerates help separate the surfaces, impose less damage to the surface passive film and polish
the wear scars through a chemical mechanical polishing mechanism. In addition, tribo-corrosion
tests at micro-/nano- scales reveal the effects of single abrasive particle on the surface/sub-surface
microstructual change. This investigation has revealed the nanoscale wear mechanisms that generate
nanoscale wear debris, the mechanical mixing of the surface nanostructure with adsorbed denatured
protein and also the slip/dislocation systems that are present near and on abraded surfaces that are
likely to disrupt the surface passive films. The findings give a better understanding of the evolution
of the sub-surface nanocrystalline structures and tribo-layers formation seen for the retrieved
implants. This near surface nanostructure layer and phase transformation might offer better wear
resistance through these inherent self-protecting mechanisms (i.e. increased hardness); conversely, it
may become the precursors to debris ejection and enhanced ion-release into the CoCrMo joints.This work established an experimental technique that gives greater understanding of the tribocorrosion
behaviour of cast CoCrMo in simulated hip joint environments. In particular, the roles of
third body abrasive particles and proteins have been addressed, which are relevant to clinical
applications. The material multi-scale wear mechanisms as well as the evolution of the surface / subsurface
microstructures and tribo-layers have been elucidated, which provide new insights into the in
vivo wear mechanisms of CoCrMo. The findings of this study may provide some important
indications for improved MoM joint materials, design, manufacture and evaluation
The curious effects of integrating bimetallic active centres within nanoporous architectures for acid-catalysed transformations
Full text linkThe resourceful combination of distinct Mg, Zn and Si active-sites within a single aluminophosphate framework, via simultaneous isomorphous substitution, has afforded unique bimetallic nanoporous heterogeneous catalysts. Unique site-specific interactions have been engineered, at the molecular level, to facilitate catalytic modifications and optimize product yield. By the dextrous incorporation of individual transition-metal active centres, we are able to intricately control the precise nature of the Brønsted acid sites, thereby influencing their catalytic behaviour for the industrially relevant acid-catalysed Beckmann rearrangement of cyclohexanone oxime and isopropylation of benzene
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
An international Delphi consensus statement on metabolic dysfunction-associated fatty liver disease and risk of chronic kidney disease
No full textBACKGROUND: With the rising global prevalence of fatty liver disease related to metabolic dysfunction, the association of this common liver condition with chronic kidney disease (CKD) has become increasingly evident. In 2020, the more inclusive term metabolic dysfunction-associated fatty liver disease (MAFLD) was proposed to replace the term non-alcoholic fatty liver disease (NAFLD). The observed association between MAFLD and CKD and our understanding that CKD can be a consequence of underlying metabolic dysfunction support the notion that individuals with MAFLD are at higher risk of having and developing CKD compared with those without MAFLD. However, to date, there is no appropriate guidance on CKD in individuals with MAFLD. Furthermore, there has been little attention paid to the link between MAFLD and CKD in the Nephrology community.METHODS AND RESULTS: Using a Delphi-based approach, a multidisciplinary panel of 50 international experts from 26 countries reached a consensus on some of the open research questions regarding the link between MAFLD and CKD.CONCLUSIONS: This Delphi-based consensus statement provided guidance on the epidemiology, mechanisms, management and treatment of MAFLD and CKD, as well as the relationship between the severity of MAFLD and risk of CKD, which establish a framework for the early prevention and management of these two common and interconnected diseases.</p
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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