1,721,099 research outputs found
A finite element and experimental investigation of the femoral component mechanics in a total hip arthroplasty
No full textTotal hip arthroplasty (THA) is a successful surgical technique that can be used for the effective treatment of fractured neck of femur, osteoarthritis, tumours, avascular necrosis, failed internal fixation, developmental dysplasia and rheumatoid arthritis. Revision surgery is necessary if loosening allows relative motion between the femoral stem and femur, causing pain and mechanical instability of the THA. The large number of revision operations undertaken each year as a result of implant failure emphasises the need for better biomechanical understanding of the femoral implant system. During 2001-02 in Australia 26,689 hip replacement operations were performed, with 3,710 of these being revision operations. The Exeter stem is the most commonly used cemented stem for primary and revision hip replacement in Australia. It is therefore very important to understand the mechanics of this clinically successful implant. Few studies have presented a through investigation into the mechanics of the Exeter stem from a fundamental perspective. \ud
\ud
\ud
\ud
To address these issues, mechanical and finite element (FE) methods were used to conduct experiments and numerical investigations into the mechanics of the Exeter stem. The femur geometry, for both the experimental and FE studies, was based upon the Sawbones model 3303 medium left third generation femur. The stem orientation for all specimens of the study was replicated from the orientation achieved by the senior surgeon implanting into the Sawbones femur. Test rigs were designed specifically to constrain the femur for the purposes of loading and stability measurements. \ud
\ud
\ud
\ud
The experimental investigation was used to investigate the torsional mechanical stability of the stem and to monitor this stability following periods of cyclic loading, using a resultant hip contact force, while monitoring the distal migration of the stem. The experimental investigation was also able to provide data for the validation of the finite element model. The resultant hip contact force was represented experimentally by a cyclic load of 1Hz applied to the head of the implant. The specimen was tested for four days. The loading regime for the initially implanted specimen involved the application of load for 6 hours a day, allowing the specimen to relax under no load for 18 hours a day. The mechanical stability of the initially implanted specimen was tested prior to the application of the cyclic load and immediately after the loading periods, prior to relaxation. Further tests were undertaken to assess the mechanical stability of the stem following the removal and reimplantation of the same stem without the use of additional bone cement (a procedure used surgically when only the acetabular component requires replacement). The reimplanted specimens were tested for a further two days following reimplantation. The six hours of loading for the reimplanted specimen was achieved using three, two hour loading periods. The stability of the reimplaned stem was assessed following each loading period. \ud
\ud
\ud
\ud
Initial studies found that the material properties of the Sawbones femurs were highly temperature dependent. If the temperature of the short glass fibre reinforced (SGFR) epoxy used for the cortical bone analogue was increased from room temperature to body temperature there was a reduction in the Young's modulus of up to 37 percent. This finding led to further investigation into the strain state of the femur for varus and neutral stem orientations to reduce femur failure during cyclic loading. The strains of the varus stem orientation were found to be higher than the strains of the neutral stem. The experiments investigating the mechanical stability under cyclic loading continued using the neutral stem orientation. \ud
\ud
\ud
\ud
For the neutral stem orientation it was found that there was no perceivable variation in the torsional stiffness of the initially implanted system during the cyclic loading period even though distal migration was observed. Torsional stiffness was observed to be compromised immediately after reimplantation. However, the torsional stiffness of the reimplanted specimen was recovered within the first two hour loading period. No perceivable variation in the torsional stiffness was observed between the initially implanted specimens and the reimplanted specimens following the first two hours of loading. \ud
\ud
\ud
\ud
The finite element model (FEM) found good agreement with the experimental investigation in terms of measured strain at two of three rosette positions and failure of the cortical bone. Trends for the stress-strain state of the stem showed good agreement with the clinical findings of failure and wear of the stem. The stress-strain state of the cement predicted the expected compressive and hoop stresses once debonding of the stem-cement interface had progressed. Strain on the surface of the femur was well predicted for pure torsional loading. The FEM has provided a valuable tool for future investigation of the effect of factors such as implant positioning on femoral component mechanics.\ud
\ud
\ud
\ud
The experimental and finite element models developed within the scope of this project have provided a powerful analysis tool for the investigation of the femoral component mechanics in THA. Application of the model to clinically relevant problems has given valuable insight into the mechanisms behind the success of this particular implant type. Models such as this will provide information on implant failure modes that will further lead to an increased implant life expectancy and a reduction in the number of revision operations performed
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
- …
