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Informant-based screening tools for dementia: an overview of systematic reviews
- Martin Taylor-Rowan, Sara Nafisi, Rhiannon Owen, Robyn Duffy, Amit Patel, Jennifer K. Burton, Terence J. Quinn
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- Journal:
- Psychological Medicine / Volume 53 / Issue 2 / January 2023
- Published online by Cambridge University Press:
- 25 May 2021, pp. 580-589
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Background
Informant-based questionnaires may have utility for cognitive impairment or dementia screening. Reviews describing the accuracy of respective questionnaires are available, but their focus on individual questionnaires precludes comparisons across tools. We conducted an overview of systematic reviews to assess the comparative accuracy of informant questionnaires and identify areas where evidence is lacking.
MethodsWe searched six databases to identify systematic reviews describing diagnostic test accuracy of informant questionnaires for cognitive impairment or dementia. We pooled sensitivity and specificity data for each questionnaire and used network approaches to compare accuracy estimates across the differing tests. We used grading of recommendations, assessment, development and evaluation (GRADE) to evaluate the overall certainty of evidence. Finally, we created an evidence ‘heat-map’, describing the availability of accurate data for individual tests in different populations and settings.
ResultsWe identified 25 reviews, consisting of 93 studies and 13 informant questionnaires. Pooled analysis (37 studies; 11 052 participants) ranked the eight-item interview to ascertain dementia (AD8) highest for sensitivity [90%; 95% credible intervals (CrI) = 82–95; ‘best-test’ probability = 36]; while the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) was most specific (81%; 95% CrI = 66–90; ‘best-test’ probability = 29%). GRADE-based evaluation of evidence suggested certainty was ‘low’ overall. Our heat-map indicated that only AD8 and IQCODE have been extensively evaluated and most studies have been in the secondary care settings.
ConclusionsAD8 and IQCODE appear to be valid questionnaires for cognitive impairment or dementia assessment. Other available informant-based cognitive screening questionnaires lack evidence to justify their use at present. Evidence on the accuracy of available tools in primary care settings and with specific populations is required.
Pre-Stroke Frailty Is Independently Associated With Post-Stroke Cognition: A Cross-Sectional Study
- Martin Taylor-Rowan, Ruth Keir, Gillian Cuthbertson, Robert Shaw, Bogna Drozdowska, Emma Elliott, Jonathan Evans, David Stott, Terence J. Quinn
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- Journal:
- Journal of the International Neuropsychological Society / Volume 25 / Issue 5 / May 2019
- Published online by Cambridge University Press:
- 01 March 2019, pp. 501-506
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Objective: Post-stroke cognitive impairment is common, but mechanisms and risk factors are poorly understood. Frailty may be an important risk factor for cognitive impairment after stroke. We investigated the association between pre-stroke frailty and acute post-stoke cognition. Methods: We studied consecutively admitted acute stroke patients in a single urban teaching hospital during three recruitment waves between May 2016 and December 2017. Cognition was assessed using the Mini-Montreal Cognitive Assessment (min=0; max=12). A Frailty Index was used to generate frailty scores for each patient (min=0; max=100). Clinical and demographic information were collected, including pre-stroke cognition, delirium, and stroke-severity. We conducted univariate and multiple-linear regression analyses with covariates forced in (covariates included were: age, sex, stroke severity, stroke-type, pre-stroke cognitive impairment, delirium, previous stroke/transient ischemic attack) to investigate the association between pre-stroke frailty and post-stroke cognition. Results: Complete data were available for 154 stroke patients. Mean age was 68 years (SD=11; range=32–97); 93 (60%) were male. Median mini-Montreal Cognitive Assessment score was 8 (IQR=4–12). Mean Frailty Index score was 18 (SD=11). Pre-stroke cognitive impairment was apparent in 13/154 (8%) patients. Pre-stroke frailty was significantly associated with lower post-stroke cognition (Standardized-Beta=−0.40; p<0.001) and this association was independent of covariates (Unstandardized-Beta=−0.05; p=0.005). Additional significant variables in the multiple regression model were age (Unstandardized-Beta=−0.05; p=0.002), delirium (Unstandardized-Beta=−2.81; p<0.001), pre-stroke cognitive impairment (Unstandardized-Beta=−2.28; p=0.001), and stroke-severity (Unstandardized-Beta=−0.20; p<0.001). Conclusions: Pre-stroke frailty may be a moderator of post-stroke cognition, independent of other well-established post-stroke cognitive impairment risk factors. (JINS, 2019, 25, 501–506)
Prevalence of pre-stroke depression and its association with post-stroke depression: a systematic review and meta-analysis
- Martin Taylor-Rowan, Oyiza Momoh, Luis Ayerbe, Jonathan J. Evans, David J. Stott, Terence J. Quinn
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- Journal:
- Psychological Medicine / Volume 49 / Issue 4 / March 2019
- Published online by Cambridge University Press:
- 15 August 2018, pp. 685-696
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Background
Depression is a common post-stroke complication. Pre-stroke depression may be an important contributor, however the epidemiology of pre-stroke depression is poorly understood. Using systematic review and meta-analysis, we described the prevalence of pre-stroke depression and its association with post-stroke depression.
MethodsWe searched multiple cross-disciplinary databases from inception to July 2017 and extracted data on the prevalence of pre-stroke depression and its association with post-stroke depression. We assessed the risk of bias (RoB) using validated tools. We described summary estimates of prevalence and summary odds ratio (OR) for association with post-stroke depression, using random-effects models. We performed subgroup analysis describing the effect of depression assessment method. We used a funnel plot to describe potential publication bias. The strength of evidence presented in this review was summarised via ‘GRADE’.
ResultsOf 11 884 studies identified, 29 were included (total participants n = 164 993). Pre-stroke depression pooled prevalence was 11.6% [95% confidence interval (CI) 9.2–14.7]; range: 0.4–24% (I2 95.8). Prevalence of pre-stroke depression varied by assessment method (p = 0.02) with clinical interview suggesting greater pre-stroke depression prevalence (~17%) than case-note review (9%) or self-report (11%). Pre-stroke depression was associated with increased odds of post-stroke depression; summary OR 3.0 (95% CI 2.3–4.0). All studies were judged to be at RoB: 59% of included studies had an uncertain RoB in stroke assessment; 83% had high or uncertain RoB for pre-stroke depression assessment. Funnel plot indicated no risk of publication bias. The strength of evidence based on GRADE was ‘very low’.
ConclusionsOne in six stroke patients have had pre-stroke depression. Reported rates may be routinely underestimated due to limitations around assessment. Pre-stroke depression significantly increases odds of post-stroke depression.
Protocol identifierPROSPERO identifier: CRD42017065544
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- By Mitchell Aboulafia, Frederick Adams, Marilyn McCord Adams, Robert M. Adams, Laird Addis, James W. Allard, David Allison, William P. Alston, Karl Ameriks, C. Anthony Anderson, David Leech Anderson, Lanier Anderson, Roger Ariew, David Armstrong, Denis G. Arnold, E. J. Ashworth, Margaret Atherton, Robin Attfield, Bruce Aune, Edward Wilson Averill, Jody Azzouni, Kent Bach, Andrew Bailey, Lynne Rudder Baker, Thomas R. Baldwin, Jon Barwise, George Bealer, William Bechtel, Lawrence C. Becker, Mark A. Bedau, Ernst Behler, José A. Benardete, Ermanno Bencivenga, Jan Berg, Michael Bergmann, Robert L. Bernasconi, Sven Bernecker, Bernard Berofsky, Rod Bertolet, Charles J. Beyer, Christian Beyer, Joseph Bien, Joseph Bien, Peg Birmingham, Ivan Boh, James Bohman, Daniel Bonevac, Laurence BonJour, William J. Bouwsma, Raymond D. Bradley, Myles Brand, Richard B. Brandt, Michael E. Bratman, Stephen E. Braude, Daniel Breazeale, Angela Breitenbach, Jason Bridges, David O. Brink, Gordon G. Brittan, Justin Broackes, Dan W. Brock, Aaron Bronfman, Jeffrey E. Brower, Bartosz Brozek, Anthony Brueckner, Jeffrey Bub, Lara Buchak, Otavio Bueno, Ann E. Bumpus, Robert W. Burch, John Burgess, Arthur W. Burks, Panayot Butchvarov, Robert E. Butts, Marina Bykova, Patrick Byrne, David Carr, Noël Carroll, Edward S. Casey, Victor Caston, Victor Caston, Albert Casullo, Robert L. Causey, Alan K. L. Chan, Ruth Chang, Deen K. Chatterjee, Andrew Chignell, Roderick M. Chisholm, Kelly J. Clark, E. J. Coffman, Robin Collins, Brian P. Copenhaver, John Corcoran, John Cottingham, Roger Crisp, Frederick J. Crosson, Antonio S. Cua, Phillip D. Cummins, Martin Curd, Adam Cureton, Andrew Cutrofello, Stephen Darwall, Paul Sheldon Davies, Wayne A. Davis, Timothy Joseph Day, Claudio de Almeida, Mario De Caro, Mario De Caro, John Deigh, C. F. Delaney, Daniel C. Dennett, Michael R. DePaul, Michael Detlefsen, Daniel Trent Devereux, Philip E. Devine, John M. Dillon, Martin C. Dillon, Robert DiSalle, Mary Domski, Alan Donagan, Paul Draper, Fred Dretske, Mircea Dumitru, Wilhelm Dupré, Gerald Dworkin, John Earman, Ellery Eells, Catherine Z. Elgin, Berent Enç, Ronald P. Endicott, Edward Erwin, John Etchemendy, C. Stephen Evans, Susan L. Feagin, Solomon Feferman, Richard Feldman, Arthur Fine, Maurice A. Finocchiaro, William FitzPatrick, Richard E. Flathman, Gvozden Flego, Richard Foley, Graeme Forbes, Rainer Forst, Malcolm R. Forster, Daniel Fouke, Patrick Francken, Samuel Freeman, Elizabeth Fricker, Miranda Fricker, Michael Friedman, Michael Fuerstein, Richard A. Fumerton, Alan Gabbey, Pieranna Garavaso, Daniel Garber, Jorge L. A. Garcia, Robert K. Garcia, Don Garrett, Philip Gasper, Gerald Gaus, Berys Gaut, Bernard Gert, Roger F. Gibson, Cody Gilmore, Carl Ginet, Alan H. Goldman, Alvin I. Goldman, Alfonso Gömez-Lobo, Lenn E. Goodman, Robert M. Gordon, Stefan Gosepath, Jorge J. E. Gracia, Daniel W. Graham, George A. Graham, Peter J. Graham, Richard E. Grandy, I. Grattan-Guinness, John Greco, Philip T. Grier, Nicholas Griffin, Nicholas Griffin, David A. Griffiths, Paul J. Griffiths, Stephen R. Grimm, Charles L. Griswold, Charles B. Guignon, Pete A. Y. Gunter, Dimitri Gutas, Gary Gutting, Paul Guyer, Kwame Gyekye, Oscar A. Haac, Raul Hakli, Raul Hakli, Michael Hallett, Edward C. Halper, Jean Hampton, R. James Hankinson, K. R. Hanley, Russell Hardin, Robert M. Harnish, William Harper, David Harrah, Kevin Hart, Ali Hasan, William Hasker, John Haugeland, Roger Hausheer, William Heald, Peter Heath, Richard Heck, John F. Heil, Vincent F. Hendricks, Stephen Hetherington, Francis Heylighen, Kathleen Marie Higgins, Risto Hilpinen, Harold T. Hodes, Joshua Hoffman, Alan Holland, Robert L. Holmes, Richard Holton, Brad W. Hooker, Terence E. Horgan, Tamara Horowitz, Paul Horwich, Vittorio Hösle, Paul Hoβfeld, Daniel Howard-Snyder, Frances Howard-Snyder, Anne Hudson, Deal W. Hudson, Carl A. Huffman, David L. Hull, Patricia Huntington, Thomas Hurka, Paul Hurley, Rosalind Hursthouse, Guillermo Hurtado, Ronald E. Hustwit, Sarah Hutton, Jonathan Jenkins Ichikawa, Harry A. Ide, David Ingram, Philip J. Ivanhoe, Alfred L. Ivry, Frank Jackson, Dale Jacquette, Joseph Jedwab, Richard Jeffrey, David Alan Johnson, Edward Johnson, Mark D. Jordan, Richard Joyce, Hwa Yol Jung, Robert Hillary Kane, Tomis Kapitan, Jacquelyn Ann K. Kegley, James A. Keller, Ralph Kennedy, Sergei Khoruzhii, Jaegwon Kim, Yersu Kim, Nathan L. King, Patricia Kitcher, Peter D. Klein, E. D. Klemke, Virginia Klenk, George L. Kline, Christian Klotz, Simo Knuuttila, Joseph J. Kockelmans, Konstantin Kolenda, Sebastian Tomasz Kołodziejczyk, Isaac Kramnick, Richard Kraut, Fred Kroon, Manfred Kuehn, Steven T. Kuhn, Henry E. Kyburg, John Lachs, Jennifer Lackey, Stephen E. Lahey, Andrea Lavazza, Thomas H. Leahey, Joo Heung Lee, Keith Lehrer, Dorothy Leland, Noah M. Lemos, Ernest LePore, Sarah-Jane Leslie, Isaac Levi, Andrew Levine, Alan E. Lewis, Daniel E. Little, Shu-hsien Liu, Shu-hsien Liu, Alan K. L. Chan, Brian Loar, Lawrence B. Lombard, John Longeway, Dominic McIver Lopes, Michael J. Loux, E. J. Lowe, Steven Luper, Eugene C. Luschei, William G. Lycan, David Lyons, David Macarthur, Danielle Macbeth, Scott MacDonald, Jacob L. Mackey, Louis H. Mackey, Penelope Mackie, Edward H. Madden, Penelope Maddy, G. B. Madison, Bernd Magnus, Pekka Mäkelä, Rudolf A. Makkreel, David Manley, William E. Mann (W.E.M.), Vladimir Marchenkov, Peter Markie, Jean-Pierre Marquis, Ausonio Marras, Mike W. Martin, A. P. Martinich, William L. McBride, David McCabe, Storrs McCall, Hugh J. McCann, Robert N. McCauley, John J. McDermott, Sarah McGrath, Ralph McInerny, Daniel J. McKaughan, Thomas McKay, Michael McKinsey, Brian P. McLaughlin, Ernan McMullin, Anthonie Meijers, Jack W. Meiland, William Jason Melanson, Alfred R. Mele, Joseph R. 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Quinn, Philip L. Quinn, Elizabeth S. Radcliffe, Diana Raffman, Gerard Raulet, Stephen L. Read, Andrews Reath, Andrew Reisner, Nicholas Rescher, Henry S. Richardson, Robert C. Richardson, Thomas Ricketts, Wayne D. Riggs, Mark Roberts, Robert C. Roberts, Luke Robinson, Alexander Rosenberg, Gary Rosenkranz, Bernice Glatzer Rosenthal, Adina L. Roskies, William L. Rowe, T. M. Rudavsky, Michael Ruse, Bruce Russell, Lilly-Marlene Russow, Dan Ryder, R. M. Sainsbury, Joseph Salerno, Nathan Salmon, Wesley C. Salmon, Constantine Sandis, David H. Sanford, Marco Santambrogio, David Sapire, Ruth A. Saunders, Geoffrey Sayre-McCord, Charles Sayward, James P. Scanlan, Richard Schacht, Tamar Schapiro, Frederick F. Schmitt, Jerome B. Schneewind, Calvin O. Schrag, Alan D. Schrift, George F. Schumm, Jean-Loup Seban, David N. Sedley, Kenneth Seeskin, Krister Segerberg, Charlene Haddock Seigfried, Dennis M. Senchuk, James F. Sennett, William Lad Sessions, Stewart Shapiro, Tommie Shelby, Donald W. Sherburne, Christopher Shields, Roger A. Shiner, Sydney Shoemaker, Robert K. Shope, Kwong-loi Shun, Wilfried Sieg, A. John Simmons, Robert L. Simon, Marcus G. Singer, Georgette Sinkler, Walter Sinnott-Armstrong, Matti T. Sintonen, Lawrence Sklar, Brian Skyrms, Robert C. Sleigh, Michael Anthony Slote, Hans Sluga, Barry Smith, Michael Smith, Robin Smith, Robert Sokolowski, Robert C. Solomon, Marta Soniewicka, Philip Soper, Ernest Sosa, Nicholas Southwood, Paul Vincent Spade, T. L. S. Sprigge, Eric O. Springsted, George J. Stack, Rebecca Stangl, Jason Stanley, Florian Steinberger, Sören Stenlund, Christopher Stephens, James P. Sterba, Josef Stern, Matthias Steup, M. A. Stewart, Leopold Stubenberg, Edith Dudley Sulla, Frederick Suppe, Jere Paul Surber, David George Sussman, Sigrún Svavarsdóttir, Zeno G. Swijtink, Richard Swinburne, Charles C. Taliaferro, Robert B. Talisse, John Tasioulas, Paul Teller, Larry S. Temkin, Mark Textor, H. S. Thayer, Peter Thielke, Alan Thomas, Amie L. Thomasson, Katherine Thomson-Jones, Joshua C. Thurow, Vzalerie Tiberius, Terrence N. Tice, Paul Tidman, Mark C. Timmons, William Tolhurst, James E. Tomberlin, Rosemarie Tong, Lawrence Torcello, Kelly Trogdon, J. D. Trout, Robert E. Tully, Raimo Tuomela, John Turri, Martin M. Tweedale, Thomas Uebel, Jennifer Uleman, James Van Cleve, Harry van der Linden, Peter van Inwagen, Bryan W. Van Norden, René van Woudenberg, Donald Phillip Verene, Samantha Vice, Thomas Vinci, Donald Wayne Viney, Barbara Von Eckardt, Peter B. M. Vranas, Steven J. Wagner, William J. Wainwright, Paul E. Walker, Robert E. Wall, Craig Walton, Douglas Walton, Eric Watkins, Richard A. Watson, Michael V. Wedin, Rudolph H. Weingartner, Paul Weirich, Paul J. Weithman, Carl Wellman, Howard Wettstein, Samuel C. Wheeler, Stephen A. White, Jennifer Whiting, Edward R. Wierenga, Michael Williams, Fred Wilson, W. Kent Wilson, Kenneth P. Winkler, John F. Wippel, Jan Woleński, Allan B. Wolter, Nicholas P. 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9 - The application of physical techniques to selected ceramic tribo-systems
- Terence F. J. Quinn, United States International University, California
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Summary
Introduction
The hardness and chemical stability of ceramics should make them ideal materials for tribo-elements that have to function under severe wear and high temperature conditions. Unfortunately, large variations in both friction and wear resistance can occur when ceramics are slid against themselves, or against a metal counterface, in the unlubricated condition. These variations have tended to prevent the widespread use of ceramics in tribo-systems. However, the recent interest in developing the ceramic diesel has tended to bring about an increase in fundamental research into the tribological properties of ceramic/ceramic and ceramic/metal tribo-systems, some of which looks very promising.
Some of the earliest work on the tribology of ceramics was carried out by Seal (1958) on diamond. Other materials include ionic crystals (Steijn, 1963), sapphire (Steijn, 1961), silicon carbide (Miyoshi and Buckley, 1979a), boron nitride (Buckley, 1978), manganese zinc-ferrite (Miyoshi and Buckley, 1981b), titanium (Nutt and Ruff, 1983), silicon nitride (Dalal, Chiu and Rabinowicz, 1975) and many other materials too numerous to mention. Since we are mainly interested in the application of physical analytical techniques to ceramic tribology, we will be very selective and discuss silicon nitride, silicon carbide and sapphire tribo-systems. Other systems may be more relevant to the reader's interest, but at least we know that various physical analytical techniques have been applied to tribo-systems with these materials as tribo-elements.
Contents
- Terence F. J. Quinn, United States International University, California
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8 - The analysis of oxidational wear in tribo-systems
- Terence F. J. Quinn, United States International University, California
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Summary
Introduction
The publication of the definitive paper by Lim and Ashby (1987) was probably the most important step towards providing tribologists with an easily applied method for estimating the type of wear mechanism most likely to occur for a given set of conditions. It is clear that mild-oxidational wear and severe-oxidational wear are very widespread in the wear mechanism map for steel (see Figure 1.5). It seems that oxidational wear is one of those areas of tribological endeavour most likely to receive an increasing amount of attention, especially in view of the interest in developing tribo-systems which can function effectively (without conventional lubrication) in high temperature environments, for example the ceramic diesel engine.
We have already discussed the oxidational theory of wear in some detail (in Section 1.4.4). In Section 6.1.4, we described how heat flow analysis in conjunction with the oxidational wear theory can be used to obtain information about temperatures (Tc) occurring at the real areas of contact, the number N of asperity contacts within those real arcs of contact and the thickness ξ of the oxide film formed at the real areas of contact. In Section 6.2.3 it was shown how proportional analysis (by X-ray diffraction) of the wear debris produced in the oxidational wear of steels, led to independent estimates of the contact temperature.
6 - The analysis of surface temperatures in tribo-systems
- Terence F. J. Quinn, United States International University, California
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Summary
Thermal aspects of sliding
Introduction
There have been many attempts to measure the temperature of the interfaces of sliding surfaces, both by direct and indirect measurements. Early direct measurements tended to involve the dynamic thermocouple, for example Shore (1925), Herbert (1926) and Furey (1964). Such measurements tend to be restrictive as regards the choice of sliding material combinations. They are also insensitive to the very rapid transients that occur during sliding. More recent direct measurements involve the use of optical photography through the transparent member of a sliding pair (Quinn and Winer, 1985) or the use of an infra-red detector (Meinders, Wilcock and Winer, 1984). We will describe both types of measurements in more detail in later sub-sections. The indirect measurements of surface temperature have tended to be a mixture of theory and experiment, for example see Ling and Pu (1964) and Archard (1959). Occasionally, temperature-dependent transitions in tribo-element phases have been used to give an indirect indication of the temperatures of sliding, for example see Quinn (1968), a paper in which the proportions of the various iron oxides in the wear debris were used to estimate the most probable temperature of formation of those oxides. We will describe the X-ray analysis of wear debris in a later sub-section (Section 6.2).
5 - The analysis of lubricant films
- Terence F. J. Quinn, United States International University, California
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Summary
The analysis of extreme-pressure lubricant films formed in the presence of typical disulphide additives
Introduction
In this section of our chapter on the analysis of lubricant films, we will be concerned with the use of physical methods of analysis to investigate the mechanisms whereby some selected disulphides provide protection under conditions of sliding which would otherwise have resulted in the breakdown or seizure of the tribo-system if the disulphides were not present as ‘extreme-pressure’ additives in the lubricant. There are, in fact, two types of extreme-pressure additives, one that prevents catastrophic failure when a tribo-system is suddenly subjected to unexpectedly high loads (such an additive is truly called an ‘extreme-pressure’ additive), and another that reduces the wear to an ‘acceptable’ level in a system designed to work close to the limits of lubrication, for example a hypoid gear system. We call the latter type of lubricant additive an ‘anti-wear’ additive, for obvious reasons. Some tribologists suggest we should drop the word ‘pressure’ in the generic word for the whole family of lubricant additives and merely call them ‘extreme-temperature’ additives. As we shall see, the temperature between the wearing interfaces is indeed an important factor in the mechanisms whereby extreme-pressure lubricant additives provide protection of those interfaces from the incidence of severe way.
References
- Terence F. J. Quinn, United States International University, California
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4 - Microscopic techniques for studying atomic structure
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Summary
Optical spectra
Description of the technique
In the simplest form of optical emission spectrometer, an electrical discharge is produced between two electrodes, at least one of which consists of, or contains, the sample to be analysed. A high voltage accelerates electrons from the cathode (the negative electrode) onto the anode, where they produce heat and the release of positive ions. Hence, some portion of the sample is vaporized by the discharge, the vaporized species become dissociated, and the resultant atoms (or ions) are excited either thermally or through collisions with each other. An excited atom or ion emits light, which is dispersed into its component wavelengths (λ) by means of a diffraction grating. In Section 2.1.4 we saw that if we place two slits in front of the sample slit source, then maxima appeared at distances from the undeviated beam that were multiples of (λDss/cz), where the reader may recall that Dss was the distance from the slits to the screen and cz was the distance between the slits (see Figure 2.7). We can write this in terms of diffraction angle Ø, since in ΔGOM of that figure, we see tan Ø = (λ/cz) for the first maximum. If the light source behind the single slit is not monochromatic but contains several wavelengths, then we would obtain several overlapping fringe patterns from each of the wavelengths present.
Frontmatter
- Terence F. J. Quinn, United States International University, California
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2 - Macroscopic physical techniques
- Terence F. J. Quinn, United States International University, California
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Summary
Optical microscopy and optical interferometry
Introduction
The availability of powerful tools for viewing surfaces at very high magnifications through the medium of highly resolved images has often caused the optical microscope to be overlooked. As we shall see, this may be related to the fact that the depth of field of an optical micrograph varies inversely with increased magnification, whereas with electron microscopy, the depth of field is almost infinite. Nevertheless, in tribology, many of the processes occur on a scale for which the optical microscope is probably the best and easiest instrument to use, especially when used in the reflection mode. Furthermore, when the optical microscope is combined with an interferometer device, we have a surface examination tool which has a vertical resolution equal to the resolution of many electron microscopes (and at a fraction of the capital outlay). We shall see how optical interferometry has indeed been used to give information about lubricant film thickness contours within the contact between a ball and a flat. These thicknesses are of the order of micrometres. Interference techniques have been used (Tolansky, 1970) to deduce the height of 40 Å steps in cleared mica. The present author has used a home-made interferometer to deduce the thickness of vacuum-evaporated films of iron used by Halliday (1960) in his work on using the contrast of electron diffraction patterns to determine thickness.
Nomenclature list
- Terence F. J. Quinn, United States International University, California
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Physical Analysis for Tribology
- Terence F. J. Quinn
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Physical Analysis for Tribology presents a unified approach to the study of wear in mechanical systems. Written by a leading expert who has studied and taught the subject both in Britain and the USA, this book will be valuable to researchers and students with a wide range of experience in tribology. The book concentrates on the methods of physical analysis and the applications of these techniques. This is then illustrated by a discussion of specific tribosystems. The early chapters provide an introduction to physical analysis that is thorough and rigorous. This prepares the reader with all the knowledge necessary to understand the subsequent discussion of applications. Although the description of systems is not exhaustive, the treatment and the theory are universal and will therefore be relevant to individual case studies. The book will appeal to tribologists from a wide variety of disciplines and will be of interest to researchers in physics, chemistry, metallurgy and mechanical engineering.
1 - Tribology
- Terence F. J. Quinn, United States International University, California
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Summary
Definitions of common tribological terms
Tribology
Tribology is a new word based on the Greek word ‘tribo’, which means ‘rubbing’. Hence tribology is the ‘study of rubbing’. The word was first used by a British Government committee (chaired by Dr Peter Jost and hence known as the ‘Jost Committee’) that produced a report, in 1966, calling for increased education and research into a subject that was estimated (at 1966 prices) to be costing the United Kingdom about £300 million per year.
The Jost Committee defined tribology as ‘the study of the science and technology of interacting surfaces in relative motion’. It was hoped that the new word might provide the basis of a more unified approach to subjects previously studied separately under titles such as ‘friction’, ‘adhesion’, ‘lubrication’ and ‘wear’. It is indeed unfortunate that, to date, the Jost Committee's awareness of the need for a more unified (that is, interdisciplinary) approach has not been shared by many tribologists. This resistance to the calls for a change in our partisan approaches to the subject is illustrated quite neatly by the fact that it has taken nearly 20 years for the Journal of Lubrication Technology (JOLT) to change its name to the Journal of Tribology (JOT), namely from 1966 to 1985.
7 - The analysis of pitting failures in tribo-systems
- Terence F. J. Quinn, United States International University, California
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- Physical Analysis for Tribology
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- 29 October 2009
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- 22 February 1991, pp 360-398
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Summary
Failure in rolling contact bearings in nominal point contact
Introduction
Czichos (1980) defines a tribo-system as one in which motion, energy and materials are transmitted, in various relative amounts, according to the required function of the system, from clearly prescribed inputs to desired outputs. Invariably, motion is a characteristic of any tribo-system. Sometimes the purpose of the system may be to change the rate of motion or to eliminate it altogether (e.g. in brakes). Such changes involve undesired outputs, such as frictional heating and the undesired removal of material from the surface through which the motion is transmitted. Gears are intended to transfer motion and power in rotating machinery, but sometimes unwanted transfer of material may also occur. The wheels of a railway engine are intended to transmit force to the rail and hence produce motion, but again we find that the unwanted transfer of material, and the loss of energy due to slip, will make the actual output somewhat different from that which was desired. Cams and tappets, valves and valve seats, piston-cylinder systems, hot and cold rolling mills, sheet-forming and wire-drawing dies, metal cutting tools, dry bearings and current collectors are further examples of tribosystems which involve some degree of transfer of motion, energy and materials. All such tribo-systems are said to have failed when the actual output deviates significantly from the intended output.
Preface
- Terence F. J. Quinn, United States International University, California
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- Physical Analysis for Tribology
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- 22 February 1991, pp vii-viii
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Summary
This book has been written with the aim of demonstrating the power of using modern techniques of physical analysis for studying the complex interactions that often occur between the contacting surfaces of tribo-systems, that is, systems involving relative motion between the various elements.
It is an interdisciplinary book, which should be of interest to tribologists whose major discipline is physics, chemistry, metallurgy or any branch of engineering involved with moving parts. Obviously, mechanical and production engineers will have more interest in tribology than (say) civil engineers or electrical engineers, but even with these disciplines, tribological problems can occur for example traction between asphalt and rubber and the wear of carbon brushes.
The book aims to be understandable by readers at all levels of technical competence with an interest in tribology. It should be of special interest to those final year undergraduate students intending to make a career in the research and development laboratories associated with the oil companies, the electricity generating industry, the aerospace companies, the steel-making and steel-forming enterprises, the automotive and diesel engine manufacturers, the railways, or any other industrial concern heavily dependent upon good tribological knowledge and practice.
Even those undergraduates destined for the production side of these industries, should find the introductory chapter on tribology useful background reading, especially if they are involved with design.
Index
- Terence F. J. Quinn, United States International University, California
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- Book:
- Physical Analysis for Tribology
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- 29 October 2009
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- 22 February 1991, pp 477-486
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3 - Microscopic physical techniques for studying atomic arrangement
- Terence F. J. Quinn, United States International University, California
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- Physical Analysis for Tribology
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- 29 October 2009
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- 22 February 1991, pp 82-147
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Summary
Basic crystallography
Introduction
Most solid substances are polycrystalline, that is, they consist of many small regions of near-perfect simple crystals (crystallites) which are generally oriented at random with respect to each other. Sometimes, however, these crystallites have preferred orientations with respect to each other. The facility for taking up preferred orientations can be a distinct advantage in metal-forming operations. It is also partly responsible for the successful operation of carbon brushes (as we shall see in Chapter 5). Separating the crystallites there are regions of very poor crystallinity, that is the atoms in these regions are not arranged in the regular arrays expected of a perfect single crystal. These regions are called ‘grain boundaries’ and they have a strong influence upon the mechanical strength of a polycrystalline solid. It is generally assumed that polycrystalline solids are isotropic as regards mechanical strength, electrical and thermal conductivity, and other physical properties relevant to the friction and wear of such solids. We shall see, however, that this assumption is not valid for materials which take up a preferred orientation upon interacting with another surface during motion. It is also not true in respect of materials that change the chemical composition of their interacting surfaces during contact, especially those materials that exhibit mild (oxidational) wear.