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Chapter 17 - Disorders of Intermediaries of Metabolism and Malignant Hyperthermia
- Edited by David R. Gambling, University of California, San Diego, M. Joanne Douglas, University of British Columbia, Vancouver, Grace Lim, University of Pittsburgh
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- Book:
- Obstetric Anesthesia and Uncommon Disorders
- Published online:
- 26 January 2024
- Print publication:
- 01 February 2024, pp 273-289
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Summary
Many inherited conditions result from disorders of intermediary metabolism. Many more are discovered annually using advanced gene sequencing and other tools. These diseases cause symptoms because of the accumulation of precursors, absence of the final product, excessive toxic intermediaries, or a combination of all three mechanisms. Many are fatal in childhood, but some are compatible with adult life and pregnancy. A better understanding of the enzymatic deficiencies and new technologies have made recombinant enzyme replacement therapy possible. Along with early diet manipulation, current management allows many patients to live relatively normal lives. Because fertility may not be affected, some of these conditions will be encountered by the anesthesiologist. This chapter describes diseases caused by certain enzyme deficiencies and the by-products that cause symptoms. Some are exacerbated by pregnancy and the stress of labor and delivery. The anesthesiologist plays an essential role in reducing physiologic stress and avoiding triggering agents and routines that cause severe metabolic derangements or cardiopulmonary decompensation. The final portion of the chapter describes the most recent advances in the prevention and treatment of malignant hyperthermia in pregnancy, discussing the impact on mother and baby.
Artin algebraization for pairs with applications to the local structure of stacks and Ferrand pushouts
- Part of
- Jarod Alper, Jack Hall, Daniel Halpern-Leistner, David Rydh
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- Journal:
- Forum of Mathematics, Sigma / Volume 12 / 2024
- Published online by Cambridge University Press:
- 01 February 2024, e20
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We give a variant of Artin algebraization along closed subschemes and closed substacks. Our main application is the existence of étale, smooth or syntomic neighborhoods of closed subschemes and closed substacks. In particular, we prove local structure theorems for stacks and their derived counterparts and the existence of henselizations along linearly fundamental closed substacks. These results establish the existence of Ferrand pushouts, which answers positively a question of Temkin–Tyomkin.
Foreword
- Edited by Michael Sanders, King's College London, Jonathan Breckon, King's College London
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- Book:
- The What Works Centres
- Published by:
- Bristol University Press
- Published online:
- 20 January 2024
- Print publication:
- 28 April 2023, pp xviii-xxiv
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Summary
‘What Works Centres’ are becoming an increasingly familiar part of the policy and professional landscape. In addition to the existing centres – covering more than a £250 billion expenditure – there is now a steady stream of interest in creating more.
Yet when the National Institute for Clinical Excellence (NICE) – in many ways the blueprint for later What Works Centres – was created in 1999, many doubted that it would survive to the next election. It was intended to get politicians, and the Department of Health, out of judgements about which treatments worked and for what. Yet senior figures feared that as soon as the young institution dared to say ‘no’ – that a given drug was not cost-effective – all hell would break loose.
Sure enough, it didn't take long for angry calls to be received in Whitehall from a major pharmaceutical company demanding that NICE guidance against its product be revoked. Against the expectations of many, the line was held, and the first of today's What Work Centres went on to help shape and guide the clinical practices of a generation.
At the time NICE was created, there was talk about creating a ‘social policy NICE’. Archie Cochrane himself nodded towards the need to extend such evidence-based approaches to other fields in an epilogue to his famous 1972 book Effectiveness and efficiency (Cochrane, 1972).
Yet it was not until after the 2010 election that serious work began into the wider application of the What Works approach and centres. A number of factors helped spark the decade of institution-building that followed.
First, the fiscal context sharpened minds. The UK faced a structural deficit of 8 per cent. Against this background, tough questions were being asked about what programmes and activities merited protecting – what worked and at what cost? Second, a weird part of No 10 – the Behavioural Insights Team – starting running randomised controlled trials. The rapid and practical conclusions these gave rise to helped to popularise experimental methods. Third, senior figures in the administration, including the new Cabinet Secretary Jeremy Heywood, the Cabinet Office Minister Oliver Letwin and the Chief Secretary to the Treasury Danny Alexander, came to support the idea – not least with Jeremy's decision to major on the idea at his first speech in 2012.
Surfactant- and gravity-dependent instability of two-layer channel flows: linear theory covering all wavelengths. Part 2. Mid-wave regimes
- Alexander L. Frenkel, David Halpern, Adam J. Schweiger
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- Journal:
- Journal of Fluid Mechanics / Volume 863 / 25 March 2019
- Published online by Cambridge University Press:
- 23 January 2019, pp. 185-214
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The joint effects of an insoluble surfactant and gravity on the linear stability of a two-layer Couette flow in a horizontal channel are investigated. The inertialess instability regimes are studied for arbitrary wavelengths and with no simplifying requirements on the system parameters: the ratio of thicknesses of the two fluid layers; the viscosity ratio; the base shear rate; the Marangoni number $Ma$; and the Bond number $Bo$. As was established in the first part of this investigation (Frenkel, Halpern & Schweiger, J. Fluid Mech., vol. 863, 2019, pp. 150–184), a quadratic dispersion equation for the complex growth rate yields two, largely continuous, branches of the normal modes, which are responsible for the flow stability properties. This is consistent with the surfactant instability case of zero gravity studied in Halpern & Frenkel (J. Fluid Mech., vol. 485, 2003, pp. 191–220). The present paper focuses on the mid-wave regimes of instability, defined as those having a finite interval of unstable wavenumbers bounded away from zero. In particular, the location of the mid-wave instability regions in the ($Ma$, $Bo$)-plane, bounded by their critical curves, depending on the other system parameters, is considered. The changes of the extremal points of these critical curves with the variation of external parameters are investigated, including the bifurcation points at which new extrema emerge. Also, it is found that for the less unstable branch of normal modes, a mid-wave interval of unstable wavenumbers may sometimes coexist with a long-wave one, defined as an interval having a zero-wavenumber endpoint.
Surfactant- and gravity-dependent instability of two-layer channel flows: linear theory covering all wavelengths. Part 1. ‘Long-wave’ regimes
- Alexander L. Frenkel, David Halpern, Adam J. Schweiger
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- Journal:
- Journal of Fluid Mechanics / Volume 863 / 25 March 2019
- Published online by Cambridge University Press:
- 23 January 2019, pp. 150-184
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A linear stability analysis of a two-layer plane Couette flow of two immiscible fluid layers with different densities, viscosities and thicknesses, bounded by two infinite parallel plates moving at a constant relative velocity to each other, with an insoluble surfactant monolayer along the interface and in the presence of gravity is carried out. The normal modes approach is applied to the equations governing flow disturbances in the two layers. These equations, together with boundary conditions at the plates and the interface, yield a linear eigenvalue problem. When inertia is neglected the velocity amplitudes are the linear combinations of certain hyperbolic functions, and a quadratic dispersion equation for the increment, that is the complex growth rate, is obtained, where coefficients depend on the aspect ratio, the viscosity ratio, the basic velocity shear, the Marangoni number $Ma$ that measures the effects of surfactant and the Bond number $Bo$ that measures the influence of gravity. An extensive investigation is carried out that examines the stabilizing or destabilizing influences of these parameters. Since the dispersion equation is quadratic in the growth rate, there are two continuous branches of the normal modes: a robust branch that exists even with no surfactant, and a surfactant branch that, to the contrary, vanishes when $Ma\downarrow 0$. Regimes have been uncovered with crossings of the two dispersion curves, their reconnections at the point of crossing and separations as $Bo$ changes. Due to the availability of the explicit forms for the growth rates, in many instances the numerical results are corroborated with analytical asymptotics.
Surfactant and gravity dependent instability of two-layer Couette flows and its nonlinear saturation
- Alexander L. Frenkel, David Halpern
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- Journal:
- Journal of Fluid Mechanics / Volume 826 / 10 September 2017
- Published online by Cambridge University Press:
- 03 August 2017, pp. 158-204
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A horizontal channel flow of two immiscible fluid layers with different densities, viscosities and thicknesses, subject to vertical gravitational forces and with an insoluble surfactant monolayer present at the interface, is investigated. The base Couette flow is driven by the uniform horizontal motion of the channel walls. Linear and nonlinear stages of the (inertialess) surfactant and gravity dependent long-wave instability are studied using the lubrication approximation, which leads to a system of coupled nonlinear evolution equations for the interface and surfactant disturbances. The (inertialess) instability is a combined result of the surfactant action characterized by the Marangoni number $Ma$ and the gravitational effect corresponding to the Bond number $Bo$ that ranges from $-\infty$ to $\infty$. The other parameters are the top-to-bottom thickness ratio $n$, which is restricted to $n\geqslant 1$ by a reference frame choice, the top-to-bottom viscosity ratio $m$ and the base shear rate $s$. The linear stability is determined by an eigenvalue problem for the normal modes, where the complex eigenvalues (determining growth rates and phase velocities) and eigenfunctions (the amplitudes of disturbances of the interface, surfactant, velocities and pressures) are found analytically by using the smallness of the wavenumber. For each wavenumber, there are two active normal modes, called the surfactant and the robust modes. The robust mode is unstable when $Bo/Ma$ falls below a certain value dependent on $m$ and $n$. The surfactant branch has instability for $m<1$, and any $Bo$, although the range of unstable wavenumbers decreases as the stabilizing effect of gravity represented by $Bo$ increases. Thus, for certain parametric ranges, even arbitrarily strong gravity cannot completely stabilize the flow. The correlations of vorticity-thickness phase differences with instability, present when gravitational effects are neglected, are found to break down when gravity is important. The physical mechanisms of instability for the two modes are explained with vorticity playing no role in them. This is in marked contrast to the dynamical role of vorticity in the mechanism of the well-known Yih instability due to effects of inertia, and is contrary to some earlier literature. Unlike the semi-infinite case that we previously studied, a small-amplitude saturation of the surfactant instability is possible in the absence of gravity. For certain $(m,n)$-ranges, the interface deflection is governed by a decoupled Kuramoto–Sivashinsky equation, which provides a source term for a linear convection–diffusion equation governing the surfactant concentration. When the diffusion term is negligible, this surfactant equation has an analytic solution which is consistent with the full numerics. Just like the interface, the surfactant wave is chaotic, but the ratio of the two waves turns out to be constant.
Slip-enhanced drop formation in a liquid falling down a vertical fibre
- David Halpern, Hsien-Hung Wei
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- Journal:
- Journal of Fluid Mechanics / Volume 820 / 10 June 2017
- Published online by Cambridge University Press:
- 02 May 2017, pp. 42-60
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For a liquid film falling down along a vertical fibre, classical theory (Kalliadasis & Chang J. Fluid Mech., vol. 261, 1994, pp. 135–168; Yu & Hinch J. Fluid Mech., vol. 737, 2013, pp. 232–248) showed that drop formation can occur due to capillary instability when the Bond number $G=\unicode[STIX]{x1D70C}ga^{3}/\unicode[STIX]{x1D6FE}h_{0}$ is below the critical value $G_{c}\approx 0.60$, where $\unicode[STIX]{x1D70C}$ is the fluid density, $g$ is the gravitational acceleration, $a$ is the fibre radius, $\unicode[STIX]{x1D6FE}$ is the surface tension and $h_{0}$ is the unperturbed film thickness. However, the experiment by Quéré (Europhys. Lett., vol. 13 (8), 1990, pp. 721–726) found $G_{c}\approx 0.71$, which is slightly greater than the above theoretical value. Here we offer a plausible way to resolve this discrepancy by including additional wall slip whose amount can be measured by the slip parameter $\unicode[STIX]{x1D6EC}=3\unicode[STIX]{x1D706}/h_{0}$, where $\unicode[STIX]{x1D706}$ is the slip length. Using lubrication theory, we find that wall slip promotes capillary instability and, hence, enhances drop formation. In particular, when slip effects are strong ($\unicode[STIX]{x1D6EC}\gg 1$), the transition films and the drop height scale as $(c/\unicode[STIX]{x1D6EC})^{-1/3}$ and $(c/\unicode[STIX]{x1D6EC})^{2/3}$, respectively, distinct from those found by Yu & Hinch for the no-slip case where $c$ is the travelling speed. In addition, for $\unicode[STIX]{x1D6EC}>1$, $G_{c}$ is found to increase with $\unicode[STIX]{x1D6EC}$ according to $G_{c}\approx 0.7\unicode[STIX]{x1D6EC}^{1/3}$, offering a possible explanation why the $G_{c}$ found by Quéré is slightly greater than that predicted by the no-slip model. Using the above expression, the estimated slip length in Quéré’s experiment is found to be of the order of several micrometres, consistent with the typical slip length range 1–$10~\unicode[STIX]{x03BC}\text{m}$ for polymeric liquids such as silicone oil used in his experiment. The existence of wall slip in Quéré’s experiment is further supported by the observation that the film thinning kinetics exhibits the no-slip result $h\propto t^{-1/2}$ for early times and changes to the strong slip result $h\propto t^{-1}$, where $h$ is the film thickness. We also show that when the film is ultrathin, although capillary instability can become further amplified by strong slip effects, the instability can be arrested by the equally intensified gravity draining in the weakly nonlinear regime whose dynamics is governed by the Kuramoto–Sivashinsky equation.
Slip-induced suppression of Marangoni film thickening in surfactant-retarded Landau–Levich–Bretherton flows
- David Halpern, Yen-Ching Li, Hsien-Hung Wei
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- Journal:
- Journal of Fluid Mechanics / Volume 781 / 25 October 2015
- Published online by Cambridge University Press:
- 24 September 2015, pp. 578-594
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We report that the well-known Marangoni film thickening in surfactant-laden Landau–Levich–Bretherton coating flow can be completely suppressed by wall slip. The analysis is made by mainly looking at how the deposited film thickness varies with the capillary number $Ca$ ($\ll 1$) and the dimensionless slip length ${\it\Lambda}={\it\lambda}/R$ ($\ll 1$) in the presence of a trace amount of insoluble surfactant, where ${\it\lambda}$ is the slip length and $R$ is the radius of the meniscus. When slip effects are weak at sufficiently large $Ca$ (but still $\ll 1$) such that $Ca\gg {\it\Lambda}^{3/2}$, the film thickness can still vary as $Ca^{2/3}$ and be thickened by surfactant as if wall slip were absent. However, when slip effects become strong by lowering $Ca$ to $Ca\ll {\it\Lambda}^{3/2}$, the film, especially when surface diffusion of surfactant is negligible, does not get thinner according to the strong-slip quadratic law reported previously (Liao et al., Phys. Rev. Lett., vol. 111, 2013, 136001; Li et al., J. Fluid Mech., vol. 741, 2014, pp. 200–227). Instead, the film behaves as if both surfactant and wall slip were absent, precisely following the no-slip $2/3$ law without surfactant. Effects of surface diffusion are also examined, revealing three distinct regimes as $Ca$ is varied from small to large values: the strong-slip quadratic scaling without surfactant, the no-slip $2/3$ scaling without surfactant and the film thickening along the no-slip $2/3$ scaling with surfactant. An experiment is also suggested to test the above findings.
Leadership During the Boston Marathon Bombings: A Qualitative After-Action Review
- Eric Goralnick, Pinchas Halpern, Stephanie Loo, Jonathan Gates, Paul Biddinger, John Fisher, George Velmahos, Sarita Chung, David Mooney, Calvin Brown, Brien Barnewolt, Peter Burke, Alok Gupta, Andrew Ulrich, Horacio Hojman, Eric McNulty, Barry Dorn, Leonard Marcus, Kobi Peleg
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- Journal:
- Disaster Medicine and Public Health Preparedness / Volume 9 / Issue 5 / October 2015
- Published online by Cambridge University Press:
- 22 June 2015, pp. 489-495
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Objective
On April 15, 2013, two improvised explosive devices (IEDs) exploded at the Boston Marathon and 264 patients were treated at 26 hospitals in the aftermath. Despite the extent of injuries sustained by victims, there was no subsequent mortality for those treated in hospitals. Leadership decisions and actions in major trauma centers were a critical factor in this response.
MethodsThe objective of this investigation was to describe and characterize organizational dynamics and leadership themes immediately after the bombings by utilizing a novel structured sequential qualitative approach consisting of a focus group followed by subsequent detailed interviews and combined expert analysis.
ResultsAcross physician leaders representing 7 hospitals, several leadership and management themes emerged from our analysis: communications and volunteer surges, flexibility, the challenge of technology, and command versus collaboration.
ConclusionsDisasters provide a distinctive context in which to study the robustness and resilience of response systems. Therefore, in the aftermath of a large-scale crisis, every effort should be invested in forming a coalition and collecting critical lessons so they can be shared and incorporated into best practices and preparations. Novel communication strategies, flexible leadership structures, and improved information systems will be necessary to reduce morbidity and mortality during future events. (Disaster Med Public Health Preparedness. 2015;9:489–495)
Contributors
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- By Brittany L. Anderson-Montoya, Heather R. Bailey, Carryl L. Baldwin, Daphne Bavelier, Jameson D. Beach, Jeffrey S. Bedwell, Kevin B. Bennett, Richard A. Block, Deborah A. Boehm-Davis, Corey J. Bohil, David B. Boles, Avinoam Borowsky, Jessica Bramlett, Allison A. Brennan, J. Christopher Brill, Matthew S. Cain, Meredith Carroll, Roberto Champney, Kait Clark, Nancy J. Cooke, Lori M. Curtindale, Clare Davies, Patricia R. DeLucia, Andrew E. Deptula, Michael B. Dillard, Colin D. Drury, Christopher Edman, James T. Enns, Sara Irina Fabrikant, Victor S. Finomore, Arthur D. Fisk, John M. Flach, Matthew E. Funke, Andre Garcia, Adam Gazzaley, Douglas J. Gillan, Rebecca A. Grier, Simen Hagen, Kelly Hale, Diane F. Halpern, Peter A. Hancock, Deborah L. Harm, Mary Hegarty, Laurie M. Heller, Nicole D. Helton, William S. Helton, Robert R. Hoffman, Jerred Holt, Xiaogang Hu, Richard J. Jagacinski, Keith S. Jones, Astrid M. L. Kappers, Simon Kemp, Robert C. Kennedy, Robert S. Kennedy, Alan Kingstone, Ioana Koglbauer, Norman E. Lane, Robert D. Latzman, Cynthia Laurie-Rose, Patricia Lee, Richard Lowe, Valerie Lugo, Poornima Madhavan, Leonard S. Mark, Gerald Matthews, Jyoti Mishra, Stephen R. Mitroff, Tracy L. Mitzner, Alexander M. Morison, Taylor Murphy, Takamichi Nakamoto, John G. Neuhoff, Karl M. Newell, Tal Oron-Gilad, Raja Parasuraman, Tiffany A. Pempek, Robert W. Proctor, Katie A. Ragsdale, Anil K. Raj, Millard F. Reschke, Evan F. Risko, Matthew Rizzo, Wendy A. Rogers, Jesse Q. Sargent, Mark W. Scerbo, Natasha B. Schwartz, F. Jacob Seagull, Cory-Ann Smarr, L. James Smart, Kay Stanney, James Staszewski, Clayton L. Stephenson, Mary E. Stuart, Breanna E. Studenka, Joel Suss, Leedjia Svec, James L. Szalma, James Tanaka, James Thompson, Wouter M. Bergmann Tiest, Lauren A. Vassiliades, Michael A. Vidulich, Paul Ward, Joel S. Warm, David A. Washburn, Christopher D. Wickens, Scott J. Wood, David D. Woods, Motonori Yamaguchi, Lin Ye, Jeffrey M. Zacks
- Edited by Robert R. Hoffman, Peter A. Hancock, University of Central Florida, Mark W. Scerbo, Old Dominion University, Virginia, Raja Parasuraman, George Mason University, Virginia, James L. Szalma, University of Central Florida
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- Book:
- The Cambridge Handbook of Applied Perception Research
- Published online:
- 05 July 2015
- Print publication:
- 26 January 2015, pp xi-xiv
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Notes on Contributors
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- By Charles Altieri, Faith Barrett, Alfred Bendixen, David Bergman, Edward Brunner, Stephen Burt, Susan Castillo Street, Michael C. Cohen, Robert Daly, Betty Booth Donohue, Jim Egan, Richard Flynn, Ed Folsom, Stephen Fredman, Frank Gado, Roger Gilbert, Rigoberto González, Nick Halpern, Jeffrey A. Hammond, Kevin J. Hayes, Matthew Hofer, Tyler Hoffman, Christoph Irmscher, Virginia Jackson, Joseph Jonghyun Jeon, John D. Kerkering, George S. Lensing, Mary Loeffelholz, Wendy Martin, Cristanne Miller, David Chioni Moore, Walton Muyumba, John Timberman Newcomb, Bob Perelman, Siobhan Phillips, Brian M. Reed, Elizabeth Renker, Eliza Richards, Reena Sastri, Robin G. Schulze, Mark Scroggins, David E. E. Sloane, Angela Sorby, Juliana Spahr, Willard Spiegelman, Lisa M. Steinman, Ernest Suarez, Joseph T. Thomas, Lesley Wheeler, David Wojahn
- Edited by Alfred Bendixen, Princeton University, New Jersey, Stephen Burt, Harvard University, Massachusetts
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- Book:
- The Cambridge History of American Poetry
- Published online:
- 05 December 2014
- Print publication:
- 27 October 2014, pp xi-xviii
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The influence of surfactant on the propagation of a semi-infinite bubble through a liquid-filled compliant channel
- David Halpern, Donald P. Gaver III
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- Journal:
- Journal of Fluid Mechanics / Volume 698 / 10 May 2012
- Published online by Cambridge University Press:
- 30 March 2012, pp. 125-159
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We investigate the influence of a soluble surfactant on the steady-state motion of a finger of air through a compliant channel. This study provides a basic model from which to understand the fluid–structure interactions and physicochemical hydrodynamics of pulmonary airway reopening. Airway closure occurs in lung diseases such as respiratory distress syndrome and acute respiratory distress syndrome as a result of fluid accumulation and surfactant insufficiency. This results in ‘compliant collapse’ with the airway walls buckled and held in apposition by a liquid occlusion that blocks the passage of air. Airway reopening is essential to the recovery of adequate ventilation, but has been associated with ventilator-induced lung injury because of the exposure of airway epithelial cells to large interfacial flow-induced pressure gradients. Surfactant replacement is helpful in modulating this deleterious mechanical stimulus, but is limited in its effectiveness owing to slow surfactant adsorption. We investigate the effect of surfactant on micro-scale models of reopening by computationally modelling the steady two-dimensional motion of a semi-infinite bubble propagating through a liquid-filled compliant channel doped with soluble surfactant. Many dimensionless parameters affect reopening, but we primarily investigate how the reopening pressure depends upon the capillary number (the ratio of viscous to surface tension forces), the adsorption depth parameter (a bulk concentration parameter) and the bulk Péclet number (the ratio of bulk convection to diffusion). These studies demonstrate a dependence of on , and suggest that a critical bulk concentration must be exceeded to operate as a low-surface-tension system. Normal and tangential stress gradients remain largely unaffected by physicochemical interactions – for this reason, further biological studies are suggested that will clarify the role of wall flexibility and surfactant on the protection of the lung from atelectrauma.
Contributors
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- By Giustino Albanese, Andrew Amaranto, Brandon H. Backlund, Alexander Baxter, Abraham Berger, Mark Bernstein, Marian E. Betz, Omar Bholat, Suzanne Bigelow, Carl Bonnett, Elizabeth Borock, Christopher B. Colwell, Alasdair Conn, Moira Davenport, David Dreitlein, Aaron Eberhardt, Ugo A. Ezenkwele, Diana Felton, Spiros G. Frangos, John E. Frank, Jonathan S. Gates, Lewis Goldfrank, Pinchas Halpern, Jean Hammel, Kristin E. Harkin, Jason S. Haukoos, E. Parker Hays, Aaron Hexdall, James F. Holmes, Debra Houry, Jennifer Isenhour, Andy Jagoda, John L. Kendall, Erica Kreisman, Nancy Kwon, Eric Legome, Matthew R. Levine, Phillip D. Levy, Charles Little, Marion Machado, Heather Mahoney, Vincent J. Markovchick, Nancy Martin, John Marx, Julie Mayglothling, Ron Medzon, Maurizio A. Miglietta, Elizabeth L. Mitchell, Ernest Moore, Maria E. Moreira, Sassan Naderi, Salvatore Pardo, Sajan Patel, David Peak, Christine Preblick, Niels K. Rathlev, Charles Ray, Phillip L. Rice, Carlo L. Rosen, Peter Rosen, Livia Santiago-Rosado, Tamara A. Scerpella, David Schwartz, Fred Severyn, Kaushal Shah, Lee W. Shockley, Mari Siegel, Matthew Simons, Michael Stern, D. Matthew Sullivan, Carrie D. Tibbles, Knox H. Todd, Shawn Ulrich, Neil Waldman, Kurt Whitaker, Stephen J. Wolf, Daniel Zlogar
- Edited by Eric Legome, Lee W. Shockley
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- Book:
- Trauma
- Published online:
- 07 September 2011
- Print publication:
- 16 June 2011, pp ix-xiv
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Contributors
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- By Phillip L. Ackerman, Soon Ang, Susan M. Barnett, G. David Batty, Anna S. Beninger, Jillian Brass, Meghan M. Burke, Nancy Cantor, Priyanka B. Carr, David R. Caruso, Stephen J. Ceci, Lillia Cherkasskiy, Joanna Christodoulou, Andrew R. A. Conway, Christine E. Daley, Janet E. Davidson, Jim Davies, Katie Davis, Ian J. Deary, Colin G. DeYoung, Ron Dumont, Carol S. Dweck, Linn Van Dyne, Pascale M. J. Engel de Abreu, Joseph F. Fagan, David Henry Feldman, Kurt W. Fischer, Marisa H. Fisher, James R. Flynn, Liane Gabora, Howard Gardner, Glenn Geher, Sarah J. Getz, Judith Glück, Ashok K. Goel, Megan M. Griffin, Elena L. Grigorenko, Richard J. Haier, Diane F. Halpern, Christopher Hertzog, Robert M. Hodapp, Earl Hunt, Alan S. Kaufman, James C. Kaufman, Scott Barry Kaufman, Iris A. Kemp, John F. Kihlstrom, Joni M. Lakin, Christina S. Lee, David F. Lohman, N. J. Mackintosh, Brooke Macnamara, Samuel D. Mandelman, John D. Mayer, Richard E. Mayer, Martha J. Morelock, Ted Nettelbeck, Raymond S. Nickerson, Weihua Niu, Anthony J. Onwuegbuzie, Jonathan A. Plucker, Sally M. Reis, Joseph S. Renzulli, Heiner Rindermann, L. Todd Rose, Anne Russon, Peter Salovey, Scott Seider, Ellen L. Short, Keith E. Stanovich, Ursula M. Staudinger, Robert J. Sternberg, Carli A. Straight, Lisa A. Suzuki, Mei Ling Tan, Maggie E. Toplak, Susana Urbina, Richard K. Wagner, Richard F. West, Wendy M. Williams, John O. Willis, Thomas R. Zentall
- Edited by Robert J. Sternberg, Oklahoma State University, Scott Barry Kaufman, New York University
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- Book:
- The Cambridge Handbook of Intelligence
- Published online:
- 05 June 2012
- Print publication:
- 30 May 2011, pp xi-xiv
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Stress, Work Overload, Burnout, and Satisfaction among Paramedics in Israel
- Nurit Nirel, Rachel Goldwag, Zvi Feigenberg, David Abadi, Pinchas Halpern
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- Journal:
- Prehospital and Disaster Medicine / Volume 23 / Issue 6 / December 2008
- Published online by Cambridge University Press:
- 28 June 2012, pp. 537-546
- Print publication:
- December 2008
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Introduction:
The number of paramedics in Israel is increasing. Despite this growth and important role, the emergency medical organizations lack information about the characteristics of their work.
Objective:The objective of this study was to examine the characteristics of the paramedics' work, the quality of their working lives, the factors that keep them in the profession, or conversely, draw them away from it.
Methods:Cross-sectional study conducted through telephone interviews of a random sample of 50% of the graduates of paramedic courses in Israel (excluding conscripted soldiers).
Results:The factors that attract paramedics to the profession have much to do with the essence of the job—rescuing and saving—and a love of what it involves, as well as interest and variety. Pressures at work result from having to cope with a lack of administrative support, paperwork, long hours, imbalance between work and family life, and salary. They do not come from having to cope with responsibility, the pressure of working under uncertain conditions, and the sudden transition from calm situations to emergencies. Dissatisfaction at work is caused by burnout, work overload, and poor health. Physical and mental health that impedes their ability to work is related to a sense of burnout and the intention to change professions.
Conclusions:The findings about the relationships between health, job satisfaction, and burnout, coupled with the fact that within a decade, half of the currently employed paramedics will reach an age at which it is hard for them to perform their job, lead to the conclusion that there is a need to reconsider the optimum length of service in the profession. There also is a need to form organizational arrangements to change the work procedures of aging paramedics.
Nonlinear evolution, travelling waves, and secondary instability of sheared-film flows with insoluble surfactants
- DAVID HALPERN, ALEXANDER L. FRENKEL
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- Journal:
- Journal of Fluid Mechanics / Volume 594 / 10 January 2008
- Published online by Cambridge University Press:
- 14 December 2007, pp. 125-156
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The nonlinear development of the interfacial-surfactant instability is studied for the semi-infinite plane Couette film flow. Disturbances whose spatial period is close to the marginal wavelength of the long-wave instability are considered first. Appropriate weakly nonlinear partial differential equations (PDEs) which couple the disturbances of the film thickness and the surfactant concentration are obtained from the strongly nonlinear lubrication-approximation PDEs. In a rescaled form each of the two systems of PDEs is controlled by a single parameter C, the ‘shear-Marangoni number’. From the weakly nonlinear PDEs, a single Stuart–Landau ordinary differential equation (ODE) for an amplitude describing the unstable fundamental mode is derived. By comparing the solutions of the Stuart–Landau equation with numerical simulations of the underlying weakly and strongly nonlinear PDEs, it is verified that the Stuart–Landau equation closely approximates the small-amplitude saturation to travelling waves, and that the error of the approximation converges to zero at the marginal stability curve. In contrast to all previous stability work on flows that combine interfacial shear and surfactant, some analytical nonlinear results are obtained. The Hopf bifurcation to travelling waves is supercritical for C < Cs and subcritical for C > Cs, where Cs is approximately 0.29. This is confirmed with a numerical continuation and bifurcation technique for ODEs. For the subcritical cases, there are two values of equilibrium amplitude for a range of C near Cs, but the travelling wave with the smaller amplitude is unstable as a periodic orbit of the associated dynamical system (whose independent variable is the spatial coordinate). By using the Bloch (‘Floquet’) disturbance modes in the linearized PDEs, it transpires that all the small-amplitude travelling-wave equilibria are unstable to sufficiently long-wave disturbances. This theoretical result is confirmed by numerical simulations which invariably show the large-amplitude saturation of the disturbances. In view of this secondary instability, the existence of small-amplitude periodic solutions (on the real line) bifurcating from the uniform flow at the marginal values of the shear-Marangoni number does not contradict the earlier conclusions that the interfacial-surfactant instability has a strongly nonlinear character, in the sense that there are no small-amplitude attractors such that the entire evolution towards them is captured by weakly-nonlinear equations. This suggests that, in general, for flowing-film instabilities that have zero wavenumber at criticality, the saturated disturbance amplitudes do not always have to decrease to zero as the control parameter approaches its value at criticality.
The steady motion of a semi-infinite bubble through a flexible-walled channel
- Donald P. Gaver, David Halpern, Oliver E. Jensen, James B. Grotberg
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- Journal:
- Journal of Fluid Mechanics / Volume 319 / 25 July 1996
- Published online by Cambridge University Press:
- 26 April 2006, pp. 25-65
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We performed a theoretical investigation of the progression of a finger of air through a liquid-filled flexible-walled channel - an initial model of pulmonary airway reopening. Positive pressure, Pb* drives the bubble forward, and separates flexible walls that are modelled as membranes under tension, T, supported by linearly elastic springs with elasticity K. The gap width between the walls under stress-free conditions is 2H, and the liquid has constant surface tension, γ, and viscosity, μ. Three parameters define the state of the system: Ca = μU/γ is a dimensionless velocity that represents the ratio of viscous to capillary stresses; η = T/γ is the wall tension to surface tension ratio, and γ = KH2/γ is the wall elastance parameter. We examined steady-state solutions as a function of these parameters using lubrication analysis and the boundary element method.
These studies showed multiple-branch behaviour in the Pb-Ca relationship, where Pb = Pb*/(γ/H) is the dimensionless bubble pressure. Low Ca flows (Ca [Lt ] min (1, (Γ3/η)1/2)) are dominated by the coupling of surface tension and elastic stresses. In this regime, Pb decreases as Ca increases owing to a reduction in the downstream resistance to flow, caused by the shortening of the section connecting the open end of the channel to the fully collapsed region. High Ca behaviour (max (1, (γ3/η)1/2) [Lt ] Ca [Lt ] η) is dominated by the balance between fluid viscous and longitudinal wall tension forces, resulting in a monotonically increasing Pb–Ca relationship. Increasing η or decreasing Γ reduces the Ca associated with the transition from one branch to the other. Low Ca streamlines show closed vortices at the bubble tip, which disappear with increasing Ca.
Start-up yield pressures are predicted to range from 1 [les ] Pyield*/(γ/L*) [les ] 2, which is less than the minimum pressure for steady-state reopening, Pmin/(γ/L*), where L* is the upstream channel width. Since Pyield* < Pmin*, the theory implies that low Ca reopening may be unsteady, a behaviour that has been observed experimentally. Our results are consistent with experimental observations showing that Pb* in highly compliant channels scales with γ/L*. In contrast, we find that wall shear stress scales with γ/H. These results imply that wall shear and normal stresses during reopening are potentially very large and may be physiologically significant.
List of Contributors
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- By Marcia L. Collaer, Sergio Della Sala, Eric G. Freedman, Diane F. Halpern, Mary Hegarty, Friderike Heuer, Amy E. Learmonth, Robert H. Logie, Richard E. Mayer, Akira Miyake, Daniel R. Montello, Nora S. Newcombe, Daniel Reisberg, Mike Rinck, Priti Shah, Holly A. Taylor, Barbara Tversky, Ioanna Vekiri, Michelle Vincow, David A. Waller, Christopher D. Wickens, Michelle Yeh
- Edited by Priti Shah, Akira Miyake, University of Toronto
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- Book:
- The Cambridge Handbook of Visuospatial Thinking
- Published online:
- 05 June 2012
- Print publication:
- 18 July 2005, pp vii-x
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Unsteady bubble propagation in a flexible channel: predictions of a viscous stick-slip instability
- DAVID HALPERN, SHAILESH NAIRE, OLIVER E. JENSEN, DONALD P. GAVER
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- Journal:
- Journal of Fluid Mechanics / Volume 528 / 10 April 2005
- Published online by Cambridge University Press:
- 24 March 2005, pp. 53-86
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We investigate the unsteady motion of a long bubble advancing under either prescribed pressure $p_{\rm b}$ or prescribed volume flux $q_{\rm b}$ into a fluid-filled flexible-walled channel at zero Reynolds number, an idealized model for the reopening of a liquid-lined lung airway. The channel walls are held under longitudinal tension and are supported by external springs; the bubble moves with speed $U$. Provided $p_{\rm b}$ exceeds a critical pressure $p_{\rm crit}$, the system exhibits two types of steady motion. At low speeds, the bubble acts like a piston, slowly pushing a column of fluid ahead of itself, and $U$ decreases with increasing $p_{\rm b}$. At high speeds, the bubble rapidly peels the channel walls apart and $U$ increases with increasing $p_{\rm b}$. Using two independent time-dependent simulation techniques (a two-dimensional boundary-element method and a one-dimensional asymptotic approximation), we show that with prescribed $p_{\rm b}\,{>}\,p_{\rm crit}$, peeling motion is stable and the steady pushing solution is unstable; for $p_{\rm b}\,{<}\,p_{\rm crit}$ the system ultimately exhibits unsteady pushing behaviour for which $U$ continually diminishes with time. When $q_{\rm b}$ is prescribed, peeling motion (with large $q_{\rm b}$) is again stable, but pushing motion (with small $q_{\rm b}$) loses stability at long times to a novel instability leading to spontaneous relaxation oscillations of increasing amplitude and period, for which the bubble switches abruptly between slow unsteady pushing and rapid quasi-steady peeling. This stick–slip motion is characterized using a third-order lumped-parameter model which in turn is reduced to a nonlinear map. Implications for the inflation of occluded lung airways are discussed.
Nonlinear saturation of the Rayleigh instability due to oscillatory flow in a liquid-lined tube
- DAVID HALPERN, JAMES B. GROTBERG
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- Journal:
- Journal of Fluid Mechanics / Volume 492 / 10 October 2003
- Published online by Cambridge University Press:
- 16 September 2003, pp. 251-270
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In this paper, the stability of core–annular flows consisting of two immiscible fluids in a cylindrical tube with circular cross-section is examined. Such flows are important in a wide range of industrial and biomedical applications. For example, in secondary oil recovery, water is pumped into the well to displace the remaining oil. It is also of relevance in the lung, where a thin liquid film coats the inner surface of the small airways of the lungs. In both cases, the flow is influenced by a surface-tension instability, which may induce the breakup of the core fluid into short plugs, reducing the efficiency of the oil recovery, or blocking the passage of air in the lung thus inducing airway closure. We consider the stability of a thin film coating the inner surface of a rigid cylindrical tube with the less viscous fluid in the core. For thick enough films, the Rayleigh instability forms a liquid bulge that can grow to eventually create a plug blocking the tube. The analysis explores the effect of an oscillatory core flow on the interfacial dynamics and particularly the nonlinear stabilization of the bulge. The oscillatory core flow exerts tangential and normal stresses on the interface between the two fluids that are simplified by uncoupling the core and film analyses in the thin-film high-frequency limit of the governing equations. Lubrication theory is used to derive a nonlinear evolution equation for the position of the air–liquid interface which includes the effects of the core flow. It is shown that the core flow can prevent plug formation of the more viscous film layer by nonlinear saturation of the capillary instability. The stabilization mechanism is similar to that of a reversing butter knife, where the core shear wipes the growing liquid bulge back on to the tube wall during the main tidal volume stroke, but allows it to grow back as the stoke and shear turn around. To be successful, the leading film thickness ahead of the bulge must be smaller than the trailing film thickness behind it, a requirement necessitating a large enough core capillary number which promotes a large core shear stress on the interface. The core capillary number is defined to be the ratio of core viscous forces to surface tension forces. When this process is tuned correctly, the two phases balance and there is no net growth of the liquid bulge over one cycle. We find that there is a critical frequency above which plug formation does not occur, and that this critical frequency increases as the tidal volume amplitude of the core flow decreases.