46 results
4 Evaluating Plasma GFAP for the Detection of Alzheimer’s Disease Dementia
- Madeline Ally, Henrik Zetterberg, Kaj Blennow, Nicholas J. Ashton, Thomas K. Karikari, Hugo Aparicio, Michael A. Sugarman, Brandon Frank, Yorghos Tripodis, Ann C. McKee, Thor D. Stein, Brett Martin, Joseph N. Palmisano, Eric G. Steinberg, Irene Simkina, Lindsay Farrer, Gyungah Jun, Katherine W. Turk, Andrew E. Budson, Maureen K. O’Connor, Rhoda Au, Wei Qiao Qiu, Lee E. Goldstein, Ronald Killiany, Neil W. Kowall, Robert A. Stern, Jesse Mez, Michael L. Alosco
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- Journal:
- Journal of the International Neuropsychological Society / Volume 29 / Issue s1 / November 2023
- Published online by Cambridge University Press:
- 21 December 2023, pp. 408-409
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Objective:
Blood-based biomarkers represent a scalable and accessible approach for the detection and monitoring of Alzheimer’s disease (AD). Plasma phosphorylated tau (p-tau) and neurofilament light (NfL) are validated biomarkers for the detection of tau and neurodegenerative brain changes in AD, respectively. There is now emphasis to expand beyond these markers to detect and provide insight into the pathophysiological processes of AD. To this end, a reactive astrocytic marker, namely plasma glial fibrillary acidic protein (GFAP), has been of interest. Yet, little is known about the relationship between plasma GFAP and AD. Here, we examined the association between plasma GFAP, diagnostic status, and neuropsychological test performance. Diagnostic accuracy of plasma GFAP was compared with plasma measures of p-tau181 and NfL.
Participants and Methods:This sample included 567 participants from the Boston University (BU) Alzheimer’s Disease Research Center (ADRC) Longitudinal Clinical Core Registry, including individuals with normal cognition (n=234), mild cognitive impairment (MCI) (n=180), and AD dementia (n=153). The sample included all participants who had a blood draw. Participants completed a comprehensive neuropsychological battery (sample sizes across tests varied due to missingness). Diagnoses were adjudicated during multidisciplinary diagnostic consensus conferences. Plasma samples were analyzed using the Simoa platform. Binary logistic regression analyses tested the association between GFAP levels and diagnostic status (i.e., cognitively impaired due to AD versus unimpaired), controlling for age, sex, race, education, and APOE e4 status. Area under the curve (AUC) statistics from receiver operating characteristics (ROC) using predicted probabilities from binary logistic regression examined the ability of plasma GFAP to discriminate diagnostic groups compared with plasma p-tau181 and NfL. Linear regression models tested the association between plasma GFAP and neuropsychological test performance, accounting for the above covariates.
Results:The mean (SD) age of the sample was 74.34 (7.54), 319 (56.3%) were female, 75 (13.2%) were Black, and 223 (39.3%) were APOE e4 carriers. Higher GFAP concentrations were associated with increased odds for having cognitive impairment (GFAP z-score transformed: OR=2.233, 95% CI [1.609, 3.099], p<0.001; non-z-transformed: OR=1.004, 95% CI [1.002, 1.006], p<0.001). ROC analyses, comprising of GFAP and the above covariates, showed plasma GFAP discriminated the cognitively impaired from unimpaired (AUC=0.75) and was similar, but slightly superior, to plasma p-tau181 (AUC=0.74) and plasma NfL (AUC=0.74). A joint panel of the plasma markers had greatest discrimination accuracy (AUC=0.76). Linear regression analyses showed that higher GFAP levels were associated with worse performance on neuropsychological tests assessing global cognition, attention, executive functioning, episodic memory, and language abilities (ps<0.001) as well as higher CDR Sum of Boxes (p<0.001).
Conclusions:Higher plasma GFAP levels differentiated participants with cognitive impairment from those with normal cognition and were associated with worse performance on all neuropsychological tests assessed. GFAP had similar accuracy in detecting those with cognitive impairment compared with p-tau181 and NfL, however, a panel of all three biomarkers was optimal. These results support the utility of plasma GFAP in AD detection and suggest the pathological processes it represents might play an integral role in the pathogenesis of AD.
5 Antemortem Plasma GFAP Predicts Alzheimer’s Disease Neuropathological Changes
- Madeline Ally, Henrik Zetterberg, Kaj Blennow, Nicholas J. Ashton, Thomas K. Karikari, Hugo Aparicio, Michael A. Sugarman, Brandon Frank, Yorghos Tripodis, Brett Martin, Joseph N. Palmisano, Eric G. Steinberg, Irene Simkina, Lindsay Farrer, Gyungah Jun, Katherine W. Turk, Andrew E. Budson, Maureen K. O’Connor, Rhoda Au, Wei Qiao Qiu, Lee E. Goldstein, Ronald Killiany, Neil W. Kowall, Robert A. Stern, Jesse Mez, Bertran R. Huber, Ann C. McKee, Thor D. Stein, Michael L. Alosco
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- Journal:
- Journal of the International Neuropsychological Society / Volume 29 / Issue s1 / November 2023
- Published online by Cambridge University Press:
- 21 December 2023, pp. 409-410
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Blood-based biomarkers offer a more feasible alternative to Alzheimer’s disease (AD) detection, management, and study of disease mechanisms than current in vivo measures. Given their novelty, these plasma biomarkers must be assessed against postmortem neuropathological outcomes for validation. Research has shown utility in plasma markers of the proposed AT(N) framework, however recent studies have stressed the importance of expanding this framework to include other pathways. There is promising data supporting the usefulness of plasma glial fibrillary acidic protein (GFAP) in AD, but GFAP-to-autopsy studies are limited. Here, we tested the association between plasma GFAP and AD-related neuropathological outcomes in participants from the Boston University (BU) Alzheimer’s Disease Research Center (ADRC).
Participants and Methods:This sample included 45 participants from the BU ADRC who had a plasma sample within 5 years of death and donated their brain for neuropathological examination. Most recent plasma samples were analyzed using the Simoa platform. Neuropathological examinations followed the National Alzheimer’s Coordinating Center procedures and diagnostic criteria. The NIA-Reagan Institute criteria were used for the neuropathological diagnosis of AD. Measures of GFAP were log-transformed. Binary logistic regression analyses tested the association between GFAP and autopsy-confirmed AD status, as well as with semi-quantitative ratings of regional atrophy (none/mild versus moderate/severe) using binary logistic regression. Ordinal logistic regression analyses tested the association between plasma GFAP and Braak stage and CERAD neuritic plaque score. Area under the curve (AUC) statistics from receiver operating characteristics (ROC) using predicted probabilities from binary logistic regression examined the ability of plasma GFAP to discriminate autopsy-confirmed AD status. All analyses controlled for sex, age at death, years between last blood draw and death, and APOE e4 status.
Results:Of the 45 brain donors, 29 (64.4%) had autopsy-confirmed AD. The mean (SD) age of the sample at the time of blood draw was 80.76 (8.58) and there were 2.80 (1.16) years between the last blood draw and death. The sample included 20 (44.4%) females, 41 (91.1%) were White, and 20 (44.4%) were APOE e4 carriers. Higher GFAP concentrations were associated with increased odds for having autopsy-confirmed AD (OR=14.12, 95% CI [2.00, 99.88], p=0.008). ROC analysis showed plasma GFAP accurately discriminated those with and without autopsy-confirmed AD on its own (AUC=0.75) and strengthened as the above covariates were added to the model (AUC=0.81). Increases in GFAP levels corresponded to increases in Braak stage (OR=2.39, 95% CI [0.71-4.07], p=0.005), but not CERAD ratings (OR=1.24, 95% CI [0.004, 2.49], p=0.051). Higher GFAP levels were associated with greater temporal lobe atrophy (OR=10.27, 95% CI [1.53,69.15], p=0.017), but this was not observed with any other regions.
Conclusions:The current results show that antemortem plasma GFAP is associated with non-specific AD neuropathological changes at autopsy. Plasma GFAP could be a useful and practical biomarker for assisting in the detection of AD-related changes, as well as for study of disease mechanisms.
The Vicissitudes of Nature: From Spinoza to Freud by Richard J. Bernstein (Polity Press, 2023). ISBN 9781509555192
- Thomas Stern
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- Journal:
- Philosophy / Volume 99 / Issue 1 / January 2024
- Published online by Cambridge University Press:
- 31 October 2023, pp. 128-132
- Print publication:
- January 2024
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Rhizobium radiobacter pseudo-outbreak linked to tissue-processing contamination
- Rebecca A. Stern, Kelly C. Byrge, Thomas R. Talbot
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- Journal:
- Antimicrobial Stewardship & Healthcare Epidemiology / Volume 3 / Issue 1 / 2023
- Published online by Cambridge University Press:
- 20 October 2023, e178
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A cluster of Rhizobium radiobacter isolates isolated from six unique surgical tissue cultures prompted an investigation ultimately identifying a pseudo-outbreak linked to errant laboratory tissue processing with contaminated, nonsterile saline. Timely response and multidisciplinary collaboration led to tangible system-level interventions and avoidance of unnecessary antibiotic exposures.
Identifying barriers to compliance with a universal inpatient protocol for Staphylococcus aureus nasal decolonization with povidone-iodine
- Rebecca A. Stern, Bryan D. Harris, Mary DeVault, Thomas R. Talbot
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 44 / Issue 7 / July 2023
- Published online by Cambridge University Press:
- 26 September 2022, pp. 1167-1170
- Print publication:
- July 2023
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Academic hospital nurses were surveyed to assess adherence barriers to a universal povidone-iodine nasal decolonization protocol to prevent Staphylococcus aureus infection. Low training rates, inadequate supplies, documentation and tracking challenges, patient refusal, and burnout contributed to suboptimal adherence. Prioritizing education is essential but alone is insufficient for successful protocol adoption.
Nietzsche's Ethics
- Thomas Stern
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- Published online:
- 18 December 2019
- Print publication:
- 02 January 2020
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This Element explains Nietzsche's ethics in his late works, from 1886 onwards. The first three sections explain the basics of his ethical theory – its context and presuppositions, its scope and its central tension. The next three sections explore Nietzsche's goals in writing a history of Christian morality (On the Genealogy of Morality), the content of that history, and whether he achieves his goals. The last two sections take a broader look, respectively, at Nietzsche's wider philosophy in light of his ethics and at the prospects for a Nietzschean ethics after Nietzsche.
5 - Diamonds and the Mantle Geodynamics of Carbon
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- By Steven B. Shirey, Karen V. Smit, D. Graham Pearson, Michael J. Walter, Sonja Aulbach, Frank E. Brenker, Hélène Bureau, Antony D. Burnham, Pierre Cartigny, Thomas Chacko, Daniel J. Frost, Erik H. Hauri, Dorrit E. Jacob, Steven D. Jacobsen, Simon C. Kohn, Robert W. Luth, Sami Mikhail, Oded Navon, Fabrizio Nestola, Paolo Nimis, Mederic Palot, Evan M. Smith, Thomas Stachel, Vincenzo Stagno, Andrew Steele, Richard A. Stern, Emilie Thomassot, Andrew R. Thomson, Yaakov Weiss
- Edited by Beth N. Orcutt, Isabelle Daniel, Université Claude-Bernard Lyon I, Rajdeep Dasgupta, Rice University, Houston
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- Book:
- Deep Carbon
- Published online:
- 03 October 2019
- Print publication:
- 17 October 2019, pp 89-128
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Summary
The science of studying diamond inclusions for understanding Earth history has developed significantly over the past decades, with new instrumentation and techniques applied to diamond sample archives revealing the stories contained within diamond inclusions. This chapter reviews what diamonds can tell us about the deep carbon cycle over the course of Earth’s history. It reviews how the geochemistry of diamonds and their inclusions inform us about the deep carbon cycle, the origin of the diamonds in Earth’s mantle, and the evolution of diamonds through time.
Simulation-based research in emergency medicine in Canada: Priorities and perspectives
- Timothy Chaplin, Brent Thoma, Andrew Petrosoniak, Kyla Caners, Tamara McColl, Chantal Forristal, Christa Dakin, Jean-Francois Deshaies, Eliane Raymond-Dufresne, Mary Fotheringham, David Ha, Nicole Holm, James Huffman, Ann-Marie Lonergan, George Mastoras, Michael O'Brien, Marie-Rose Paradis, Nicholas Sowers, Errol Stern, Andrew K. Hall
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 22 / Issue 1 / January 2020
- Published online by Cambridge University Press:
- 26 September 2019, pp. 103-111
- Print publication:
- January 2020
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Objective
Simulation plays an integral role in the Canadian healthcare system with applications in quality improvement, systems development, and medical education. High-quality, simulation-based research will ensure its effective use. This study sought to summarize simulation-based research activity and its facilitators and barriers, as well as establish priorities for simulation-based research in Canadian emergency medicine (EM).
MethodsSimulation-leads from Canadian departments or divisions of EM associated with a general FRCP-EM training program surveyed and documented active EM simulation-based research at their institutions and identified the perceived facilitators and barriers. Priorities for simulation-based research were generated by simulation-leads via a second survey; these were grouped into themes and finally endorsed by consensus during an in-person meeting of simulation leads. Priority themes were also reviewed by senior simulation educators.
ResultsTwenty simulation-leads representing all 14 invited institutions participated in the study between February and May, 2018. Sixty-two active, simulation-based research projects were identified (median per institution = 4.5, IQR 4), as well as six common facilitators and five barriers. Forty-nine priorities for simulation-based research were reported and summarized into eight themes: simulation in competency-based medical education, simulation for inter-professional learning, simulation for summative assessment, simulation for continuing professional development, national curricular development, best practices in simulation-based education, simulation-based education outcomes, and simulation as an investigative methodology.
ConclusionThis study summarized simulation-based research activity in EM in Canada, identified its perceived facilitators and barriers, and built national consensus on priority research themes. This represents the first step in the development of a simulation-based research agenda specific to Canadian EM.
LO45: Simulation-based research in emergency medicine in Canada: priorities and perspectives
- T. Chaplin, B. Thoma, A. Petrosoniak, K. Caners, T. McColl, C. Forristal, C. Dakin, J. Deshaies, E. Raymond-Dufresne, M. Fotheringham, D. Ha, N. Holm, J. Huffman, A. Lonergan, G. Mastoras, M. O'Brien, M. Paradis, N. Sowers, E. Stern, A. Hall
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 21 / Issue S1 / May 2019
- Published online by Cambridge University Press:
- 02 May 2019, pp. S23-S24
- Print publication:
- May 2019
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Introduction: Simulation has assumed an integral role in the Canadian healthcare system with applications in quality improvement, systems development, and medical education. High quality simulation-based research (SBR) is required to ensure the effective and efficient use of this tool. This study sought to establish national SBR priorities and describe the barriers and facilitators of SBR in Emergency Medicine (EM) in Canada. Methods: Simulation leads (SLs) from all fourteen Canadian Departments or Divisions of EM associated with an adult FRCP-EM training program were invited to participate in three surveys and a final consensus meeting. The first survey documented active EM SBR projects. Rounds two and three established and ranked priorities for SBR and identified the perceived barriers and facilitators to SBR at each site. Surveys were completed by SLs at each participating institution, and priority research themes were reviewed by senior faculty for broad input and review. Results: Twenty SLs representing all 14 invited institutions participated in all three rounds of the study. 60 active SBR projects were identified, an average of 4.3 per institution (range 0-17). 49 priorities for SBR in Canada were defined and summarized into seven priority research themes. An additional theme was identified by the senior reviewing faculty. 41 barriers and 34 facilitators of SBR were identified and grouped by theme. Fourteen SLs representing 12 institutions attended the consensus meeting and vetted the final list of eight priority research themes for SBR in Canada: simulation in CBME, simulation for interdisciplinary and inter-professional learning, simulation for summative assessment, simulation for continuing professional development, national curricular development, best practices in simulation-based education, simulation-based education outcomes, and simulation as an investigative methodology. Conclusion: Conclusion: This study has summarized the current SBR activity in EM in Canada, as well as its perceived barriers and facilitators. We also provide a consensus on priority research themes in SBR in EM from the perspective of Canadian simulation leaders. This group of SLs has formed a national simulation-based research group which aims to address these identified priorities with multicenter collaborative studies.
Developments Towards Imaging Nanoscale Biology with XFELs: Some Recent Examples and a Glance to the Future
- Adrian P. Mancuso, Andrew Aquila, Richard Bean, Johan Bielecki, Carsten Fortmann-Grote, Klaus Giewekemeyer, Yoonhee Kim, Ruslan Kurta, Romain Letrun, Masoud Mehrjoo, Marc Messerschmidt, Grant Mills, Adam Round, Tokushi Sato, Joachim Schulz, Marcin Sikorski, Stephan Stern, Patrik Vagovic, Thomas Tschentscher
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- Journal:
- Microscopy and Microanalysis / Volume 24 / Issue S2 / August 2018
- Published online by Cambridge University Press:
- 10 August 2018, pp. 72-75
- Print publication:
- August 2018
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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. Mendola, Christopher Menzel, Michael J. Meyer, Christian B. Miller, David W. Miller, Peter Millican, Robert N. Minor, Phillip Mitsis, James A. Montmarquet, Michael S. Moore, Tim Moore, Benjamin Morison, Donald R. Morrison, Stephen J. Morse, Paul K. Moser, Alexander P. D. Mourelatos, Ian Mueller, James Bernard Murphy, Mark C. Murphy, Steven Nadler, Jan Narveson, Alan Nelson, Jerome Neu, Samuel Newlands, Kai Nielsen, Ilkka Niiniluoto, Carlos G. Noreña, Calvin G. Normore, David Fate Norton, Nikolaj Nottelmann, Donald Nute, David S. Oderberg, Steve Odin, Michael O’Rourke, Willard G. Oxtoby, Heinz Paetzold, George S. Pappas, Anthony J. Parel, Lydia Patton, R. P. Peerenboom, Francis Jeffry Pelletier, Adriaan T. Peperzak, Derk Pereboom, Jaroslav Peregrin, Glen Pettigrove, Philip Pettit, Edmund L. Pincoffs, Andrew Pinsent, Robert B. Pippin, Alvin Plantinga, Louis P. Pojman, Richard H. Popkin, John F. Post, Carl J. Posy, William J. Prior, Richard Purtill, Michael Quante, Philip L. 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. Wolterstorff, Rega Wood, W. Jay Wood, Paul Woodruff, Alison Wylie, Gideon Yaffe, Takashi Yagisawa, Yutaka Yamamoto, Keith E. Yandell, Xiaomei Yang, Dean Zimmerman, Günter Zoller, Catherine Zuckert, Michael Zuckert, Jack A. Zupko (J.A.Z.)
- Edited by Robert Audi, University of Notre Dame, Indiana
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- The Cambridge Dictionary of Philosophy
- Published online:
- 05 August 2015
- Print publication:
- 27 April 2015, pp ix-xxx
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- Edited by Carla Bagnoli, Università degli Studi di Modena, Italy
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- Constructivism in Ethics
- Published online:
- 05 July 2013
- Print publication:
- 18 July 2013, pp vii-x
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- Edited by Fiona Ritchie, McGill University, Montréal, Peter Sabor, McGill University, Montréal
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- Shakespeare in the Eighteenth Century
- Published online:
- 05 August 2012
- Print publication:
- 19 April 2012, pp ix-xi
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5 - Static Multipoint Networks
- Thomas E. Stern, Columbia University, New York, Georgios Ellinas, University of Cyprus, Krishna Bala
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- Multiwavelength Optical Networks
- Published online:
- 05 June 2012
- Print publication:
- 08 December 2008, pp 324-431
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Summary
In static networks essentially all functionality resides in the network access stations (NASs). The performance of the network is therefore determined by how the NASs provide logical connectivity and throughput to satisfy the network's traffic requirements. This chapter explores the performance issues in static networks, viewing them all as special cases of shared media, as described in Section 5.1. Existing and potential uses of shared media abound, the most important of these being to provide efficient local access for end users to a larger optical network. The multiplexing and multiple-access techniques required to achieve multipoint logical connectivity in these networks are treated in Section 5.2. Sections 5.3 through 5.6 deal with capacity allocation and control to serve prescribed traffic requirements. We first point out some general flow conservation constraints that must be satisfied in any shared-channel system. Then the problems of traffic scheduling and control are discussed in settings with increasing degrees of complexity: dedicated connections (Section 5.4), demand-assigned connections (Section 5.5), and packet switching in the optical layer (Section 5.6). Section 5.7 discusses network access applications of static multipoint architectures. These include broadcast star-based and wavelength-router-based passive optical networks (PONs) that provide the foundation of fiber to the home/premises. In these applications the static network is the link between the end user and an optical core or metropolitan area network.
Shared Media: The Broadcast Star
The simplest form of a transparent optical network, the static network, was defined in Chapter 3 as a collection of fixed (passive) splitting/combining nodes without wavelength selectivity, interconnected by fibers that provide full or partial connectivity among a set of NASs.
E - An Algorithm for Minimum-Interference Routing in Linear Lightwave Networks
- Thomas E. Stern, Columbia University, New York, Georgios Ellinas, University of Cyprus, Krishna Bala
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- Multiwavelength Optical Networks
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- 05 June 2012
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- 08 December 2008, pp 893-895
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Summary
Given a source s and destination d for a point-to-point connection on a selected waveband in an LLN, the Min-Int algorithm presented here attempts to find a minimum-interference optical path p = 〈s, d〉 for that connection on the given waveband. The exact sense in which interference is minimized requires some explanation and is defined in Section E.3.
The Image Network
The approach used to find a path that minimizes interference is based on shortest path calculations, where the path “length” takes into account weights or “lengths” representing currently active interfering signals. These weights are associated with nodes rather than links. A useful way of visualizing the node-weighting procedure is shown in the image network of Figure E.1. In the network shown in the figure, each node of the original network is “blown up” to create additional intranodal links between each input/output port pair. This is nothing more than a representation of the internal structure of the LDC on the chosen waveband (see Figure 2.19[b]). The image network of Figure E.1 corresponds to the state of activity in the network of Figure 6.55. Two optical connections, (1, 1*) and (2, 2*), are active, with signal S1 transmitted from station 1 to 1* and signal S2 transmitted from station 2 to 2*.
We shall denote an internodal link from node i to node j by (i, j) and assign it a positive weight d(i, j).
D - A Limiting-Cut Heuristic
- Thomas E. Stern, Columbia University, New York, Georgios Ellinas, University of Cyprus, Krishna Bala
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- Multiwavelength Optical Networks
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- 08 December 2008, pp 890-892
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Summary
The concept of the limiting cut, introduced in Section 6.3.1.2, stems from the Min Cut–Max Flow relation in multicommodity flow problems. We first give a brief summary of this problem and then present a heuristic for finding limiting cuts.
The Multicommodity Flow Problem and Limiting Cuts
In the most common version of the multicommodity flow problem, a set of demands are prescribed between source-destination node pairs in a network with a given topology and link capacities. (Each source-destination demand is known as a commodity, and the network can be anything—gas pipelines, airline routes, highways, and so on.) The basic issue is whether the prescribed demands can be satisfied within the capacity constraints; that is, whether all commodities can be routed through the network (in a bifurcated manner if necessary) so that the total flow of all commodities on each link does not exceed its capacity. If so, the demands are said to be feasible.
In wavelength-routed networks (WRNs), the commodities (demands) are LCs, each requiring one λ-channel, so the capacity of a cut Ci is FiW, where Fi is the number of fiber pairs in the cut and W is the number of available wavelengths. Because a channel in a WRN is a single point-to-point entity, bifurcated routing is not permitted in a WRN. (An exception would be a case in which several λ-channels are required to carry the flow on one LC.)
The relations between cut capacities and feasible demands were stated in Section A.1.8 for the single-commodity case. In the multicommodity case, which is of interest here, the relations are considerably more complex.
F - Synopsis of the SONET Standard
- Thomas E. Stern, Columbia University, New York, Georgios Ellinas, University of Cyprus, Krishna Bala
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- Multiwavelength Optical Networks
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- 08 December 2008, pp 896-899
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Summary
SONET, the acronym for synchronous optical network, is currently the prevailing standard for high-speed digital transmission in North America. Introduced in the 1980s, it replaced an earlier standard, the plesiochronous digital hierarchy (PDH), which had been in place for more than two decades prior to the introduction of the SONET standard [Ballart+89]. The most frequently used lower levels of the PDH system are the DS1 (1.544 Mbps, designed to carry 24 64-Kbps digitized voice signals plus synchronizing overhead) and DS3, running at 44.736 Mbps. An architecture similar to SONET, the synchronous digital hierarchy (SDH), is currently used in Europe and Japan, replacing an earlier European hierarchy similar to the PDH system. SONET can carry PDH bit streams as well as many other types of digital traffic (e.g., ATM cells) as part of its payload. One of the most important features of SONET is its highly organized protection capability [Wu92].
The basic building block (i.e., the first level) of the SONET signal hierarchy is called the synchronous transport signal-level 1 (STS-1). STS-1 has a bit rate of 51.84 Mbps and is divided into two portions, transport overhead and information payload, and the transport overhead is divided further into line and section overheads. (A line is composed of one or more sections in series, separated by electronic regenerators.) The line overhead is terminated at SONET terminals and add/drop multiplexers (ADMs), and the section overhead is terminated at regenerators.
Index
- Thomas E. Stern, Columbia University, New York, Georgios Ellinas, University of Cyprus, Krishna Bala
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- Multiwavelength Optical Networks
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- 08 December 2008, pp 915-966
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8 - Survivability: Protection and Restoration
- Thomas E. Stern, Columbia University, New York, Georgios Ellinas, University of Cyprus, Krishna Bala
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- Multiwavelength Optical Networks
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- 08 December 2008, pp 647-713
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Summary
Survivability against failures, including failure recovery, is important in any telecommunications network but is highly critical for high-bandwidth optical networks. As more traffic is concentrated on fewer routes, the number of customers that can be potentially affected by a failure is increased. An analysis of failures in the Public Switched Telephone Network over a two-year period in the 1990s showed that human error, acts of nature, and overloads were the major sources of failure. The impact of the failures was measured in terms of how many times a particular failure occurred, duration of the outage, and number of customers and number of customer minutes affected during that outage. During that period, the average number of customers affected due to cable cuts or cable component failures was 216,690, costing 2,643 million in customer minutes. Similarly, the average number of customers affected by each equipment failure was 1,836,910, costing 3,544.3 million in customer minutes . Cable cuts and hardware/equipment failures account for approximately half of the failures encountered in the network during that period.
Fiber cuts are considered one of the most common failures in fiber-optic networks. Furthermore, the use of WDM over these fibers produces an extremely high volume of traffic on a cable. Commercially available fiber-optic transmission systems can run at 10 Gbps or more per channel with 80 or more channels (wavelengths) per fiber. This translates to more than 800 Gbps per fiber.
Contents
- Thomas E. Stern, Columbia University, New York, Georgios Ellinas, University of Cyprus, Krishna Bala
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- Book:
- Multiwavelength Optical Networks
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- 05 June 2012
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- 08 December 2008, pp vii-xvi
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