1
|
Gase AC, Bangs NL, Saffer DM, Han S, Miller PK, Bell RE, Arai R, Henrys SA, Kodaira S, Davy R, Frahm L, Barker DH. Subducting volcaniclastic-rich upper crust supplies fluids for shallow megathrust and slow slip. Sci Adv 2023; 9:eadh0150. [PMID: 37585538 PMCID: PMC10431706 DOI: 10.1126/sciadv.adh0150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 07/17/2023] [Indexed: 08/18/2023]
Abstract
Recurring slow slip along near-trench megathrust faults occurs at many subduction zones, but for unknown reasons, this process is not universal. Fluid overpressures are implicated in encouraging slow slip; however, links between slow slip, fluid content, and hydrogeology remain poorly known in natural systems. Three-dimensional seismic imaging and ocean drilling at the Hikurangi margin reveal a widespread and previously unknown fluid reservoir within the extensively hydrated (up to 47 vol % H2O) volcanic upper crust of the subducting Hikurangi Plateau large igneous province. This ~1.5 km thick volcaniclastic upper crust readily dewaters with subduction but retains half of its fluid content upon reaching regions with well-characterized slow slip. We suggest that volcaniclastic-rich upper crust at volcanic plateaus and seamounts is a major source of water that contributes to the fluid budget in subduction zones and may drive fluid overpressures along the megathrust that give rise to frequent shallow slow slip.
Collapse
Affiliation(s)
- Andrew C. Gase
- Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA
| | - Nathan L. Bangs
- Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA
| | - Demian M. Saffer
- Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA
| | - Shuoshuo Han
- Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA
| | - Peter K. Miller
- Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA
| | - Rebecca E. Bell
- Department of Earth Science and Engineering, Imperial College London, London, UK
| | - Ryuta Arai
- Research Institute for Marine Geodynamics, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
| | | | - Shuichi Kodaira
- Research Institute for Marine Geodynamics, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
| | - Richard Davy
- Department of Earth Science and Engineering, Imperial College London, London, UK
| | - Laura Frahm
- Department of Earth Science and Engineering, Imperial College London, London, UK
| | | |
Collapse
|
2
|
Barnes PM, Wallace LM, Saffer DM, Bell RE, Underwood MB, Fagereng A, Meneghini F, Savage HM, Rabinowitz HS, Morgan JK, Kitajima H, Kutterolf S, Hashimoto Y, Engelmann de Oliveira CH, Noda A, Crundwell MP, Shepherd CL, Woodhouse AD, Harris RN, Wang M, Henrys S, Barker DH, Petronotis KE, Bourlange SM, Clennell MB, Cook AE, Dugan BE, Elger J, Fulton PM, Gamboa D, Greve A, Han S, Hüpers A, Ikari MJ, Ito Y, Kim GY, Koge H, Lee H, Li X, Luo M, Malie PR, Moore GF, Mountjoy JJ, McNamara DD, Paganoni M, Screaton EJ, Shankar U, Shreedharan S, Solomon EA, Wang X, Wu HY, Pecher IA, LeVay LJ. Slow slip source characterized by lithological and geometric heterogeneity. Sci Adv 2020; 6:eaay3314. [PMID: 32232148 PMCID: PMC7096157 DOI: 10.1126/sciadv.aay3314] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Accepted: 01/02/2020] [Indexed: 05/31/2023]
Abstract
Slow slip events (SSEs) accommodate a significant proportion of tectonic plate motion at subduction zones, yet little is known about the faults that actually host them. The shallow depth (<2 km) of well-documented SSEs at the Hikurangi subduction zone offshore New Zealand offers a unique opportunity to link geophysical imaging of the subduction zone with direct access to incoming material that represents the megathrust fault rocks hosting slow slip. Two recent International Ocean Discovery Program Expeditions sampled this incoming material before it is entrained immediately down-dip along the shallow plate interface. Drilling results, tied to regional seismic reflection images, reveal heterogeneous lithologies with highly variable physical properties entering the SSE source region. These observations suggest that SSEs and associated slow earthquake phenomena are promoted by lithological, mechanical, and frictional heterogeneity within the fault zone, enhanced by geometric complexity associated with subduction of rough crust.
Collapse
Affiliation(s)
- Philip M. Barnes
- National Institute of Water and Atmospheric Research (NIWA), Wellington 6021, New Zealand
| | | | - Demian M. Saffer
- Department of Geosciences and Center for Geomechanics, Geofluids, and Geohazards, The Pennsylvania State University, University Park, PA 16802, USA
| | - Rebecca E. Bell
- Basins Research Group, Imperial College London, Exhibition Road, Kensington SW7 2AZ, UK
| | - Michael B. Underwood
- Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801, USA
| | - Ake Fagereng
- School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3AT, UK
| | - Francesca Meneghini
- Dipartimento di Scienze della Terra, Università degli Studi di Pisa, via. S. Maria, 53, Pisa 56126, Italy
| | - Heather M. Savage
- Department of Earth and Planetary Sciences, University of California, 1156 High St., Santa Cruz, CA 95064, USA
| | - Hannah S. Rabinowitz
- Department of Earth, Environmental, and Planetary Sciences, Brown University, 324 Brook Street, Providence, RI 02912, USA
| | - Julia K. Morgan
- Department of Earth Science, Rice University, 6100 South Main Street, MS-126, Houston, TX 77005-1892, USA
| | - Hiroko Kitajima
- Department of Geology and Geophysics, Texas A&M University, MS 3115 TAMU, College Station, TX 77845, USA
| | - Steffen Kutterolf
- GEOMAR, Helmholtz Center for Ocean Research, Kiel, Wischhofstrasse 1-3, Kiel 24148, Germany
| | - Yoshitaka Hashimoto
- Department of Natural Environmental Science, Faculty of Science, Kochi University, Akebonocyo 2-5-1, Kochi 780-8520, Japan
| | - Christie H. Engelmann de Oliveira
- Programa de Pós-Graduação em Geologia, Universidade do Vale do Rio dos Sinos, Avenida Unisinos 950, São Leopoldo RS 93.022-000, Brazil
| | - Atsushi Noda
- Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan
| | | | | | - Adam D. Woodhouse
- School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
| | - Robert N. Harris
- College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Ocean Administration Building, 104, 101 SW 26th Street, Corvallis, OR 97331-5503, USA
| | - Maomao Wang
- College of Oceanography, Hohai University, 1 Xikang Road, Nanjing, Jiangsu Province 210093, P.R. China
| | | | | | - Katerina E. Petronotis
- International Ocean Discovery Program, Texas A&M University, College Station, TX 77845, USA
| | - Sylvain M. Bourlange
- Ecole Nationale Superieure de Geologie—Laboratoire GeoRessources, Universite de Lorraine, 2 rue du Doyen Marcel Roubault, BP 10162, 54505 Vandoeuvre-les-Nancy Cedex, France
| | | | - Ann E. Cook
- School of Earth Sciences, Ohio State University, 317 Mendenhall Lab, 125 S. Oval Mall, Columbus, OH 43202, USA
| | - Brandon E. Dugan
- Department of Geophysics, Colorado School of Mines, 1318 Maple Street, Bldg. 6, Golden, CO 80401, USA
| | - Judith Elger
- GEOMAR, Helmholtz Center for Ocean Research, Kiel, Wischhofstrasse 1-3, Kiel 24148, Germany
| | - Patrick M. Fulton
- Department of Earth and Atmospheric Sciences, Cornell University, 3126 Snee Hall, Ithaca, NY 14853-1504, USA
| | - Davide Gamboa
- Instituto Português do Mar e da Atmosfera, I.P. (IPMA), Rua C ao Aeroporto, 1749-077 Lisboa, Portugal
| | - Annika Greve
- Institute for Marine-Earth Exploration and Engineering, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Shuoshuo Han
- Institute for Geophysics, University of Texas, 10100 Burnet Road, Austin, TX 78758, USA
| | - Andre Hüpers
- MARUM Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Leobener Strasse 8, Bremen 28359, Germany
| | - Matt J. Ikari
- MARUM Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Leobener Strasse 8, Bremen 28359, Germany
| | - Yoshihiro Ito
- Disaster Prevention Research Institute, Kyoto University, Gokasyo, Uji, Kyoto 611-0011, Japan
| | - Gil Young Kim
- Korea Institute of Geoscience and Mineral Resources (KIGAM), 124 Gwahang-no, Yuseong-gu, Daejeon 305-350, Republic of Korea
| | - Hiroaki Koge
- Marine Geology Research Group, GSJ, AIST Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan
| | - Hikweon Lee
- Korea Institute of Geoscience and Mineral Resources (KIGAM), 124 Gwahang-no, Yuseong-gu, Daejeon 305-350, Republic of Korea
| | - Xuesen Li
- College of Earth Science, Guilin University of Technology, 12 Jian gan Road, Guilin City 541004, P.R. China
| | - Min Luo
- Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, P.R. China
| | - Pierre R. Malie
- Geosciences Montpellier Laboratory, Université Montpellier, CC.60, Place E. Bataillon, 34095 Montpellier Cédex 5, France
| | - Gregory F. Moore
- Department of Earth Sciences/SOEST, University of Hawaii at Manoa, 1680 East-West Road, Honolulu, HI 96822, USA
| | - Joshu J. Mountjoy
- National Institute of Water and Atmospheric Research (NIWA), Wellington 6021, New Zealand
| | - David D. McNamara
- Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Jane Herdman Building, 4 Brownlow Street, Liverpool L69 3GP, UK
| | | | - Elizabeth J. Screaton
- Department of Geological Sciences, University of Florida, Gainesville, FL 32611, USA
| | - Uma Shankar
- Department of Geophysics, Banaras Hindu University, Institute of Science, Varanasi Uttar Pradesh 221005, India
| | - Srisharan Shreedharan
- Department of Geosciences and Center for Geomechanics, Geofluids, and Geohazards, The Pennsylvania State University, University Park, PA 16802, USA
| | - Evan A. Solomon
- School of Oceanography, University of Washington, Seattle, WA 98195-7940, USA
| | - Xiujuan Wang
- Key Laboratory of Marine Geology and Environment, Chinese Academy of Sciences, Nanhai Road 7, Qingdao, Shandong 266071, P.R. China
| | - Hung-Yu Wu
- Institute for Marine-Earth Exploration and Engineering, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Ingo A. Pecher
- School of Environmental and Marine Sciences, University of Auckland, Private Bag 92091, Auckland 1142, New Zealand
| | - Leah J. LeVay
- International Ocean Discovery Program, Texas A&M University, College Station, TX 77845, USA
| | - IODP Expedition 372 Scientists
- International Ocean Discovery Program, Expedition 372, Creeping Gas Hydrate Slides and Hikurangi LWD, 26 November 2017 to 4 January 2018; see the Supplementary Materials for a list of participants
| |
Collapse
|
3
|
Fredrickson ED, Belova EV, Battaglia DJ, Bell RE, Crocker NA, Darrow DS, Diallo A, Gerhardt SP, Gorelenkov NN, LeBlanc BP, Podestà M. Suppression of Alfvén Modes on the National Spherical Torus Experiment Upgrade with Outboard Beam Injection. Phys Rev Lett 2017; 118:265001. [PMID: 28707924 DOI: 10.1103/physrevlett.118.265001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Indexed: 06/07/2023]
Abstract
In this Letter we present data from experiments on the National Spherical Torus Experiment Upgrade, where it is shown for the first time that small amounts of high pitch-angle beam ions can strongly suppress the counterpropagating global Alfvén eigenmodes (GAE). GAE have been implicated in the redistribution of fast ions and modification of the electron power balance in previous experiments on NSTX. The ability to predict the stability of Alfvén modes, and developing methods to control them, is important for fusion reactors like the International Tokamak Experimental Reactor, which are heated by a large population of nonthermal, super-Alfvénic ions consisting of fusion generated α's and beam ions injected for current profile control. We present a qualitative interpretation of these observations using an analytic model of the Doppler-shifted ion-cyclotron resonance drive responsible for GAE instability which has an important dependence on k_{⊥}ρ_{L}. A quantitative analysis of this data with the hym stability code predicts both the frequencies and instability of the GAE prior to, and suppression of the GAE after the injection of high pitch-angle beam ions.
Collapse
Affiliation(s)
- E D Fredrickson
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - E V Belova
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - D J Battaglia
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - R E Bell
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - N A Crocker
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - D S Darrow
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - A Diallo
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - S P Gerhardt
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - N N Gorelenkov
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - B P LeBlanc
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - M Podestà
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| |
Collapse
|
4
|
Kubota S, Majeski R, Peebles WA, Bell RE, Boyle DP, Kaita R, Kozub T, Lucia M, Merino E, Nguyen XV, Rhodes TL, Schmitt JC. A frequency-modulated continuous-wave reflectometer for the Lithium Tokamak Experiment. Rev Sci Instrum 2017; 88:053502. [PMID: 28571454 DOI: 10.1063/1.4981811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The frequency-modulated continuous-wave reflectometer on LTX (Lithium Tokamak Experiment) and the data analysis methods used for determining electron density profiles are described. The diagnostic uses a frequency range of 13.1-33.5 GHz, for covering a density range of 0.21-1.4×1013 cm-3 (in O-mode polarization) with a time resolution down to 8 μs. The design of the diagnostic incorporates the concept of an "optimized" source frequency sweep, which minimizes the large variation in the intermediate frequency signal due to a long dispersive transmission line. The quality of the raw data is dictated by the tuning characteristics of the microwave sources, as well as the group delay ripple in the transmission lines, which can generate higher-order nonlinearities in the frequency sweep. Both effects are evaluated for our diagnostic and best practices are presented for minimizing "artifacts" generated in the signals. The quality of the reconstructed profiles is also improved using two additional data analysis methods. First, the reflectometer data are processed as a radar image, where clutter due to echoes from the wall and backscattering from density fluctuations can be easily identified and removed. Second, a weighed least-squares lamination algorithm POLAN (POLynomial ANalysis) is used to reconstruct the electron density profile. Examples of density profiles in LTX are presented, along with comparisons to measurements from the Thomson scattering and the λ = 1 mm interferometer diagnostics.
Collapse
Affiliation(s)
- S Kubota
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - R Majeski
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - W A Peebles
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - R E Bell
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - D P Boyle
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - R Kaita
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - T Kozub
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - M Lucia
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - E Merino
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - X V Nguyen
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - T L Rhodes
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - J C Schmitt
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| |
Collapse
|
5
|
Menard JE, Wang Z, Liu Y, Bell RE, Kaye SM, Park JK, Tritz K. Rotation and kinetic modifications of the tokamak ideal-wall pressure limit. Phys Rev Lett 2014; 113:255002. [PMID: 25554890 DOI: 10.1103/physrevlett.113.255002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Indexed: 06/04/2023]
Abstract
The impact of toroidal rotation, energetic ions, and drift-kinetic effects on the tokamak ideal wall mode stability limit is considered theoretically and compared to experiment for the first time. It is shown that high toroidal rotation can be an important destabilizing mechanism primarily through the angular velocity shear; non-Maxwellian fast ions can also be destabilizing, and drift-kinetic damping can potentially offset these destabilization mechanisms. These results are obtained using the unique parameter regime accessible in the spherical torus NSTX of high toroidal rotation speed relative to the thermal and Alfvén speeds and high kinetic pressure relative to the magnetic pressure. Inclusion of rotation and kinetic effects significantly improves agreement between measured and predicted ideal stability characteristics and may provide new insight into tearing mode triggering.
Collapse
Affiliation(s)
- J E Menard
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA
| | - Z Wang
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA
| | - Y Liu
- Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB, United Kingdom
| | - R E Bell
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA
| | - S M Kaye
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA
| | - J-K Park
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA
| | - K Tritz
- Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
6
|
Pablant NA, Bell RE, Bitter M, Delgado-Aparicio L, Hill KW, Lazerson S, Morita S. Tomographic inversion techniques incorporating physical constraints for line integrated spectroscopy in stellarators and tokamaks. Rev Sci Instrum 2014; 85:11E424. [PMID: 25430331 DOI: 10.1063/1.4891977] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Accurate tomographic inversion is important for diagnostic systems on stellarators and tokamaks which rely on measurements of line integrated emission spectra. A tomographic inversion technique based on spline optimization with enforcement of constraints is described that can produce unique and physically relevant inversions even in situations with noisy or incomplete input data. This inversion technique is routinely used in the analysis of data from the x-ray imaging crystal spectrometer (XICS) installed at the Large Helical Device. The XICS diagnostic records a 1D image of line integrated emission spectra from impurities in the plasma. Through the use of Doppler spectroscopy and tomographic inversion, XICS can provide profile measurements of the local emissivity, temperature, and plasma flow. Tomographic inversion requires the assumption that these measured quantities are flux surface functions, and that a known plasma equilibrium reconstruction is available. In the case of low signal levels or partial spatial coverage of the plasma cross-section, standard inversion techniques utilizing matrix inversion and linear-regularization often cannot produce unique and physically relevant solutions. The addition of physical constraints, such as parameter ranges, derivative directions, and boundary conditions, allow for unique solutions to be reliably found. The constrained inversion technique described here utilizes a modified Levenberg-Marquardt optimization scheme, which introduces a condition avoidance mechanism by selective reduction of search directions. The constrained inversion technique also allows for the addition of more complicated parameter dependencies, for example, geometrical dependence of the emissivity due to asymmetries in the plasma density arising from fast rotation. The accuracy of this constrained inversion technique is discussed, with an emphasis on its applicability to systems with limited plasma coverage.
Collapse
Affiliation(s)
- N A Pablant
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - R E Bell
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - M Bitter
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | | | - K W Hill
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - S Lazerson
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - S Morita
- National Institute for Fusion Science, Toki 509-5292, Gifu, Japan
| |
Collapse
|
7
|
Faust I, Delgado-Aparicio L, Bell RE, Tritz K, Diallo A, Gerhardt SP, LeBlanc B, Kozub TA, Parker RR, Stratton BC. Two-dimensional AXUV-based radiated power density diagnostics on NSTX-U. Rev Sci Instrum 2014; 85:11D856. [PMID: 25430269 DOI: 10.1063/1.4890254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A new set of radiated-power-density diagnostics for the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak have been designed to measure the two-dimensional poloidal structure of the total photon emissivity profile in order to perform power balance, impurity transport, and magnetohydrodynamic studies. Multiple AXUV-diode based pinhole cameras will be installed in the same toroidal angle at various poloidal locations. The local emissivity will be obtained from several types of tomographic reconstructions. The layout and response expected for the new radially viewing poloidal arrays will be shown for different impurity concentrations to characterize the diagnostic sensitivity. The radiated power profile inverted from the array data will also be used for estimates of power losses during transitions from various divertor configurations in NSTX-U. The effect of in-out and top/bottom asymmetries in the core radiation from high-Z impurities will be addressed.
Collapse
Affiliation(s)
- I Faust
- MIT - Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
| | | | - R E Bell
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - K Tritz
- The Johns Hopkins University, Baltimore, Maryland 21209, USA
| | - A Diallo
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - S P Gerhardt
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - B LeBlanc
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - T A Kozub
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - R R Parker
- MIT - Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
| | - B C Stratton
- MIT - Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
| |
Collapse
|
8
|
Delgado-Aparicio L, Bell RE, Faust I, Tritz K, Diallo A, Gerhardt SP, Kozub TA, LeBlanc BP, Stratton BC. High-resolution tangential absolute extreme ultraviolet arrays for radiated power density measurements on NSTX-U. Rev Sci Instrum 2014; 85:11D859. [PMID: 25430272 DOI: 10.1063/1.4894835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The radiated-power-density diagnostic on the equatorial midplane for the NSTX-U tokamak will be upgraded to measure the radial structure of the photon emissivity profile with an improved radial resolution. This diagnostic will enhance the characterization and studies of power balance, impurity transport, and MHD. The layout and response expected of the new system is shown for different plasma conditions and impurity concentrations. The effect of toroidal rotation driving poloidal asymmetries in the core radiation from high-Z impurities is also addressed.
Collapse
Affiliation(s)
| | - R E Bell
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - I Faust
- MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
| | - K Tritz
- The Johns Hopkins University, Baltimore, Maryland 21209, USA
| | - A Diallo
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - S P Gerhardt
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - T A Kozub
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - B P LeBlanc
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - B C Stratton
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| |
Collapse
|
9
|
Krysa J, Fraser S, Saha P, Fuller M, Bell RE, Carrell TWG, Modarai B, Taylor PR, Zayed HA. Quality improvement framework for major amputation: are we getting it right? Int J Clin Pract 2012; 66:1230-4. [PMID: 23163504 DOI: 10.1111/j.1742-1241.2012.02905.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
INTRODUCTION The quality improvement framework for major amputation was developed with the aim of improving outcomes and reducing the perioperartive mortality to less than 5% by 2015. The aim of the study was to assess our compliance with the framework guidelines and look for the reasons for non-compliance. METHOD All major amputations performed between 2008 and 2010 were included. The following data were collected: presence of infection ± tissue loss, status of arterial supply, revascularisation attempts, time to surgery, type of amputation, morbidity and mortality. RESULTS A total of 81 patients were included (42 BKAs, 39 AKAs). Ninety percentage had formal preoperative arterial investigations and 84% had an attempted revascularisation procedure. Patients who were transferred late from non-vascular units (n = 12) had a 30-day mortality of 50% whereas patients who presented directly to our unit had a 30-day mortality of 7.2%. The number of amputations has decreased over the last 3 years from 34 to 21 per year, coinciding with the doubling of crural revascularisation procedures performed (from 60 to 120 per year). Ten patients underwent a revision from BKA to AKA because of an inadequate profunda femoris artery (PFA), whereas all those with a healed BKA stump either had a good PFA or a named crural vessel. CONCLUSION The overall number of amputations is decreasing from year to year. By doubling our crural revascularisation procedures we are saving more limbs. Thirty-day mortality is higher than expected, particularly in patients who present late. Expeditious referral may potentially improve the mortality rate among this group of patients.
Collapse
Affiliation(s)
- J Krysa
- Department of Vascular Surgery, Guy's and St Thomas' NHS Foundation Trust, London, UK.
| | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Perkins RJ, Hosea JC, Kramer GJ, Ahn JW, Bell RE, Diallo A, Gerhardt S, Gray TK, Green DL, Jaeger EF, Jaworski MA, LeBlanc BP, McLean A, Maingi R, Phillips CK, Roquemore L, Ryan PM, Sabbagh S, Taylor G, Wilson JR. High-harmonic fast-wave power flow along magnetic field lines in the scrape-off layer of NSTX. Phys Rev Lett 2012; 109:045001. [PMID: 23006093 DOI: 10.1103/physrevlett.109.045001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Indexed: 06/01/2023]
Abstract
A significant fraction of high-harmonic fast-wave (HHFW) power applied to NSTX can be lost to the scrape-off layer (SOL) and deposited in bright and hot spirals on the divertor rather than in the core plasma. We show that the HHFW power flows to these spirals along magnetic field lines passing through the SOL in front of the antenna, implying that the HHFW power couples across the entire width of the SOL rather than mostly at the antenna face. This result will help guide future efforts to understand and minimize these edge losses in order to maximize fast-wave heating and current drive.
Collapse
Affiliation(s)
- R J Perkins
- Princeton Plasma Physics Laboratory, Princeton, New Jersey, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Podestà M, Bell RE. A real-time velocity diagnostic for NSTX. Rev Sci Instrum 2012; 83:033503. [PMID: 22462918 DOI: 10.1063/1.3692752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A new system for fast measurements of the plasma toroidal velocity has been installed on the National Spherical Torus Experiment, NSTX [M. Ono et al., Nucl. Fusion 40, 557 (2000)]. The diagnostic, based on active charge-exchange recombination spectroscopy, can measure at up to six radial locations with maximum sampling rate of 5 kHz. The system is interfaced in real time with the NSTX plasma control system, in order to feed back on plasma velocity by means of actuators such as neutral beams and external coils. The paper describes the design criteria and implementation of the diagnostic. Examples from the initial tests of the system during neon glows are also discussed.
Collapse
Affiliation(s)
- M Podestà
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | | |
Collapse
|
12
|
Maingi R, Kaye SM, Skinner CH, Boyle DP, Canik JM, Bell MG, Bell RE, Gray TK, Jaworski MA, Kaita R, Kugel HW, LeBlanc BP, Mansfield DK, Osborne TH, Sabbagh SA, Soukhanovskii VA. Continuous improvement of H-mode discharge performance with progressively increasing lithium coatings in the National Spherical Torus Experiment. Phys Rev Lett 2011; 107:145004. [PMID: 22107204 DOI: 10.1103/physrevlett.107.145004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Indexed: 05/31/2023]
Abstract
Lithium wall coatings have been shown to reduce recycling, improve energy confinement, and suppress edge localized modes in the National Spherical Torus Experiment. Here, we show that these effects depend continuously on the amount of predischarge lithium evaporation. We observed a nearly monotonic reduction in recycling, decrease in electron transport, and modification of the edge profiles and stability with increasing lithium. These correlations challenge basic expectations, given that even the smallest coatings exceeded that needed for a nominal thickness of the order of the implantation range.
Collapse
Affiliation(s)
- R Maingi
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Ren Y, Kaye SM, Mazzucato E, Guttenfelder W, Bell RE, Domier CW, LeBlanc BP, Lee KC, Luhmann NC, Smith DR, Yuh H. Density gradient stabilization of electron temperature gradient driven turbulence in a spherical tokamak. Phys Rev Lett 2011; 106:165005. [PMID: 21599377 DOI: 10.1103/physrevlett.106.165005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2010] [Indexed: 05/30/2023]
Abstract
In this Letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k(⊥)ρ(s) ≲ 10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of 2 decrease in the plasma effective thermal diffusivity.
Collapse
Affiliation(s)
- Y Ren
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Guttenfelder W, Candy J, Kaye SM, Nevins WM, Wang E, Bell RE, Hammett GW, LeBlanc BP, Mikkelsen DR, Yuh H. Electromagnetic transport from microtearing mode turbulence. Phys Rev Lett 2011; 106:155004. [PMID: 21568568 DOI: 10.1103/physrevlett.106.155004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Indexed: 05/30/2023]
Abstract
This Letter presents nonlinear gyrokinetic simulations of microtearing mode turbulence. The simulations include collisional and electromagnetic effects and use experimental parameters from a high-β discharge in the National Spherical Torus Experiment. The predicted electron thermal transport is comparable to that given by experimental analysis, and it is dominated by the electromagnetic contribution of electrons free-streaming along the resulting stochastic magnetic field line trajectories. Experimental values of flow shear can significantly reduce the predicted transport.
Collapse
Affiliation(s)
- W Guttenfelder
- Princeton Plasma Physics Laboratory, Princeton New Jersey 08543, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Berkery JW, Sabbagh SA, Betti R, Bell RE, Gerhardt SP, LeBlanc BP, Yuh H. Effect of collisionality on kinetic stability of the resistive wall mode. Phys Rev Lett 2011; 106:075004. [PMID: 21405523 DOI: 10.1103/physrevlett.106.075004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Indexed: 05/30/2023]
Abstract
The impact of collisionless, energy-independent, and energy-dependent collisionality models on the kinetic stability of the resistive wall mode is examined for high pressure plasmas in the National Spherical Torus Experiment. Future devices will have decreased collisionality, which previous stability models predict to be universally destabilizing. In contrast, in kinetic theory reduced ion-ion collisions are shown to lead to a significant stability increase when the plasma rotation frequency is in a stabilizing resonance with the ion precession drift frequency. When the plasma is in a reduced stability state with rotation in between resonances, collisionality will have little effect on stability.
Collapse
Affiliation(s)
- J W Berkery
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | | | | | | | | | | | | |
Collapse
|
16
|
Yuh HY, Kaye SM, Levinton FM, Mazzucato E, Mikkelsen DR, Smith DR, Bell RE, Hosea JC, LeBlanc BP, Peterson JL, Park HK, Lee W. Suppression of electron temperature gradient turbulence via negative magnetic shear in NSTX. Phys Rev Lett 2011; 106:055003. [PMID: 21405404 DOI: 10.1103/physrevlett.106.055003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Indexed: 05/30/2023]
Abstract
Negative magnetic shear is found to suppress electron turbulence and improve electron thermal transport for plasmas in the National Spherical Torus Experiment (NSTX). Sufficiently negative magnetic shear results in a transition out of a stiff profile regime. Density fluctuation measurements from high-k microwave scattering are verified to be the electron temperature gradient (ETG) mode by matching measured rest frequency and linear growth rate to gyrokinetic calculations. Fluctuation suppression under negligible E×B shear conditions confirm that negative magnetic shear alone is sufficient for ETG suppression. Measured electron temperature gradients can significantly exceed ETG critical gradients with ETG mode activity reduced to intermittent bursts, while electron thermal diffusivity improves to below 0.1 electron gyro-Bohms.
Collapse
Affiliation(s)
- H Y Yuh
- Nova Photonics Inc., Princeton, New Jersey 08540, USA.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Soukhanovskii VA, Roquemore AL, Bell RE, Kaita R, Kugel HW. Spectroscopic diagnostics for liquid lithium divertor studies on National Spherical Torus Experiment. Rev Sci Instrum 2010; 81:10D723. [PMID: 21033916 DOI: 10.1063/1.3478749] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The use of lithium-coated plasma facing components for plasma density control is studied in the National Spherical Torus Experiment (NSTX). A recently installed liquid lithium divertor (LLD) module has a porous molybdenum surface, separated by a stainless steel liner from a heated copper substrate. Lithium is deposited on the LLD from two evaporators. Two new spectroscopic diagnostics are installed to study the plasma surface interactions on the LLD: (1) A 20-element absolute extreme ultraviolet (AXUV) diode array with a 6 nm bandpass filter centered at 121.6 nm (the Lyman-α transition) for spatially resolved divertor recycling rate measurements in the highly reflective LLD environment, and (2) an ultraviolet-visible-near infrared R=0.67 m imaging Czerny-Turner spectrometer for spatially resolved divertor D I, Li I-II, C I-IV, Mo I, D(2), LiD, CD emission and ion temperature on and around the LLD module. The use of photometrically calibrated measurements together with atomic physics factors enables studies of recycling and impurity particle fluxes as functions of LLD temperature, ion flux, and divertor geometry.
Collapse
Affiliation(s)
- V A Soukhanovskii
- Lawrence Livermore National Laboratory, Livermore, California 94551, USA.
| | | | | | | | | |
Collapse
|
18
|
Battaglia DJ, Shafer MW, Unterberg EA, Bell RE, Hillis DL, LeBlanc BP, Maingi R, Sabbagh S, Stratton BC. Simulation of a tangential soft x-ray imaging system. Rev Sci Instrum 2010; 81:10E533. [PMID: 21034060 DOI: 10.1063/1.3478883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Tangentially viewing soft x-ray (SXR) cameras are capable of detecting nonaxisymmetric plasma structures in magnetically confined plasmas. They are particularly useful for studying stationary perturbations or phenomenon that occur on a timescale faster than the plasma rotation period. Tangential SXR camera diagnostics are planned for the DIII-D and NSTX tokamaks to elucidate the static edge magnetic structure during the application of 3D perturbations. To support the design of the proposed diagnostics, a synthetic diagnostic model was developed using the CHIANTI database to estimate the SXR emission. The model is shown to be in good agreement with the measurements from an existing tangential SXR camera diagnostic on NSTX.
Collapse
Affiliation(s)
- D J Battaglia
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Maingi R, Bell RE, Canik JM, Gerhardt SP, Kaye SM, Leblanc BP, Osborne TH, Bell MG, Fredrickson ED, Lee KC, Menard JE, Park JK, Sabbagh SA. Triggered confinement enhancement and pedestal expansion in high-confinement-mode discharges in the national spherical torus experiment. Phys Rev Lett 2010; 105:135004. [PMID: 21230781 DOI: 10.1103/physrevlett.105.135004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2010] [Indexed: 05/30/2023]
Abstract
We report observation of a new high performance regime in discharges in the National Spherical Torus Experiment, where the H mode edge "pedestal" temperature doubles and the energy confinement increases by 50%. The spontaneous transition is triggered by a large edge-localized mode, either natural or externally triggered by 3D fields. The transport barrier grows inward from the edge, with a doubling of both the pedestal pressure width and the spatial extent of steep radial electric field shear. The dynamics suggest that 3D fields could be applied to reduce edge transport in fusion devices.
Collapse
Affiliation(s)
- R Maingi
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Canik JM, Maingi R, Evans TE, Bell RE, Gerhardt SP, Leblanc BP, Manickam J, Menard JE, Osborne TH, Park JK, Paul SF, Snyder PB, Sabbagh SA, Kugel HW, Unterberg EA. On demand triggering of edge localized instabilities using external nonaxisymmetric magnetic perturbations in toroidal plasmas. Phys Rev Lett 2010; 104:045001. [PMID: 20366719 DOI: 10.1103/physrevlett.104.045001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2009] [Indexed: 05/29/2023]
Abstract
The application of nonaxisymmetric magnetic fields is shown to destabilize edge-localized modes (ELMs) during otherwise ELM-free periods of discharges in the National Spherical Torus Experiment (NSTX). Profile analysis shows the applied fields increased the temperature and pressure gradients, decreasing edge stability. This robust effect was exploited for a new form of ELM control: the triggering of ELMs at will in high performance H mode plasmas enabled by lithium conditioning, yielding high time-averaged energy confinement with reduced core impurity density and radiated power.
Collapse
Affiliation(s)
- J M Canik
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Berkery JW, Sabbagh SA, Betti R, Hu B, Bell RE, Gerhardt SP, Manickam J, Tritz K. Resistive wall mode instability at intermediate plasma rotation. Phys Rev Lett 2010; 104:035003. [PMID: 20366652 DOI: 10.1103/physrevlett.104.035003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Indexed: 05/29/2023]
Abstract
Experimental observation of resistive wall mode (RWM) instability in the National Spherical Torus Experiment (NSTX) at plasma rotation levels intermediate to the ion precession drift and ion bounce frequencies suggests that low critical rotation threshold models are insufficient. Kinetic modifications to the ideal stability criterion yield a more complex relationship between plasma rotation and RWM stability. Good agreement is found between an experimental RWM instability at intermediate plasma rotation and the RWM marginal point calculated with kinetic effects included, by the MISK code. By self-similarly scaling the experimental plasma rotation profile and the collisionality in the calculation, resonances of the mode with the precession drift and bounce frequencies are explored. Experimentally, RWMs go unstable when the plasma rotation is between the stabilizing precession drift and bounce resonances.
Collapse
Affiliation(s)
- J W Berkery
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Black SA, Carrell TWG, Bell RE, Waltham M, Reidy J, Taylor PR. Long-term surveillance with computed tomography after endovascular aneurysm repair may not be justified. Br J Surg 2009; 96:1280-3. [DOI: 10.1002/bjs.6732] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Abstract
Background
There is a common perception that a large number of secondary interventions are needed following endovascular aortic aneurysm repair.
Methods
Prospective data were collected for a cohort of 417 consecutive elective patients undergoing infrarenal aortic endograft repair between April 2000 and May 2008. The rate of secondary interventions, associated morbidity and need for reintervention following surveillance imaging were analysed.
Results
The male : female ratio was 11 : 1, median age 76 (range 40–93) years and median aneurysm diameter 6·1 (5·3–11) cm. The overall 30-day mortality rate was 1·7 per cent (seven of 417). Secondary interventions were performed in 31 patients (7·4 per cent), of which six (1·4 per cent) were detected by surveillance. Endoleaks requiring reintervention occurred in 12 patients (2·9 per cent; ten type I and two type III endoleaks). Limb ischaemia secondary to graft occlusion occurred in 17 patients (4·1 per cent); extra-anatomical bypass was needed in 15 patients (3·6 per cent) and the remaining two had an amputation. Graft explantation following late infection was required in two patients (0·5 per cent).
Conclusion
Endoluminal repair of infrarenal aortic aneurysms can be performed with a low reintervention rate. The value of prolonged surveillance seems limited and current surveillance protocols may require revision.
Collapse
Affiliation(s)
- S A Black
- Department of Vascular Surgery, Guy's and St Thomas' Hospital, London, UK
| | - T W G Carrell
- Department of Vascular Surgery, Guy's and St Thomas' Hospital, London, UK
| | - R E Bell
- Department of Vascular Surgery, Guy's and St Thomas' Hospital, London, UK
| | - M Waltham
- Department of Vascular Surgery, Guy's and St Thomas' Hospital, London, UK
| | - J Reidy
- Department of Interventional Radiology, Guy's and St Thomas' Hospital, London, UK
| | - P R Taylor
- Department of Vascular Surgery, Guy's and St Thomas' Hospital, London, UK
| |
Collapse
|
23
|
Khalique Z, Lyons OTA, Clough RE, Bell RE, Reidy JF, Schwarze U, Byers PH, Taylor PR. Successful endovascular repair of acute type B aortic dissection in undiagnosed Ehlers-Danlos syndrome type IV. Eur J Vasc Endovasc Surg 2009; 38:608-9. [PMID: 19695909 DOI: 10.1016/j.ejvs.2009.07.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 07/14/2009] [Indexed: 11/17/2022]
Abstract
A 61-year-old man presented with an acute type B aortic dissection for which a stent-graft was introduced. He remains complication-free 4 years onwards and has since been diagnosed with Ehlers-Danlos syndrome type IV (EDS IV). His particular mutation is predicted to result in lesser levels of normal collagen and may explain his favourable outcome from endovascular intervention. Understanding the genotype-phenotype correlation may influence the choice of therapy offered to patients with EDS IV.
Collapse
Affiliation(s)
- Z Khalique
- Department of Vascular Surgery, Guy's & St Thomas' NHS Foundation Trust, London, UK
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Maingi R, Osborne TH, Leblanc BP, Bell RE, Manickam J, Snyder PB, Menard JE, Mansfield DK, Kugel HW, Kaita R, Gerhardt SP, Sabbagh SA, Kelly FA. Edge-localized-mode suppression through density-profile modification with lithium-wall coatings in the National Spherical Torus Experiment. Phys Rev Lett 2009; 103:075001. [PMID: 19792649 DOI: 10.1103/physrevlett.103.075001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Indexed: 05/28/2023]
Abstract
Reduction or elimination of edge localized modes (ELMs) while maintaining high confinement is essential for future fusion devices, e.g., the ITER. An ELM-free regime was recently obtained in the National Spherical Torus Experiment, following lithium (Li) evaporation onto the plasma-facing components. Edge stability calculations indicate that the pre-Li discharges were unstable to low-n peeling or ballooning modes, while broader pressure profiles stabilized the post-Li discharges. Normalized energy confinement increased by 50% post Li, with no sign of ELMs up to the global stability limit.
Collapse
Affiliation(s)
- R Maingi
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Smith DR, Kaye SM, Lee W, Mazzucato E, Park HK, Bell RE, Domier CW, Leblanc BP, Levinton FM, Luhmann NC, Menard JE, Yuh H. Observations of reduced electron Gyroscale fluctuations in national spherical torus experiment H-mode plasmas with large ExB flow shear. Phys Rev Lett 2009; 102:225005. [PMID: 19658873 DOI: 10.1103/physrevlett.102.225005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Indexed: 05/28/2023]
Abstract
Electron gyroscale fluctuation measurements in National Spherical Torus Experiment H-mode plasmas with large toroidal rotation reveal fluctuations consistent with electron temperature gradient (ETG) turbulence. Large toroidal rotation in National Spherical Torus Experiment plasmas with neutral beam injection generates ExB flow shear rates comparable to ETG linear growth rates. Enhanced fluctuations occur when the electron temperature gradient is marginally stable with respect to the ETG linear critical gradient. Fluctuation amplitudes decrease when the ExB flow shear rate exceeds ETG linear growth rates. The observations indicate that ExB flow shear can be an effective suppression mechanism for ETG turbulence.
Collapse
Affiliation(s)
- D R Smith
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Clough RE, Bell RE, Salter R, Taylor PR. Letter to the Editor re: indication for intervention in chronic type B aortic dissection. Eur J Vasc Endovasc Surg 2009; 37:498-9. [PMID: 19217808 DOI: 10.1016/j.ejvs.2009.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Accepted: 01/07/2009] [Indexed: 11/19/2022]
|
27
|
Clough RE, Black SA, Lyons OT, Bell RE, Zayed H, Carrell T, Waltham M, Sabharwal T, Reidy J, Taylor PR. Endovascular management of mycotic aortic aneurysms. Br J Surg 2009. [DOI: 10.1002/bjs.6510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- R E Clough
- Guy's and St Thomas' NHS Foundation Trust, London
| | - S A Black
- Guy's and St Thomas' NHS Foundation Trust, London
| | - O T Lyons
- Guy's and St Thomas' NHS Foundation Trust, London
| | - R E Bell
- Guy's and St Thomas' NHS Foundation Trust, London
| | - H Zayed
- Guy's and St Thomas' NHS Foundation Trust, London
| | - T Carrell
- Guy's and St Thomas' NHS Foundation Trust, London
| | - M Waltham
- Guy's and St Thomas' NHS Foundation Trust, London
| | - T Sabharwal
- Guy's and St Thomas' NHS Foundation Trust, London
| | - J Reidy
- Guy's and St Thomas' NHS Foundation Trust, London
| | - P R Taylor
- Guy's and St Thomas' NHS Foundation Trust, London
| |
Collapse
|
28
|
Abstract
A new diagnostic, aimed at energy-resolved measurements of the spatial and temporal dynamics of fast ions in NSTX plasmas, is described. It is based on active charge-exchange recombination spectroscopy. The fast-ion signal is inferred from light emitted in the wavelength range of the D(alpha) line by fast ions recombining with an injected neutral beam. Two complementary systems are operational. The first system, based on a spectrometer coupled to a charge coupled device detector, has 16 channels with space, time, and energy resolution of 5 cm, 10 ms, and 10 keV, respectively. The second system monitors the energy-integrated fast-ion signal on time scales of approximately 20 micros at three different radii. Signals are measured by a multianode photomultiplier tube. For both systems, each channel includes two paired views, intercepting and missing the neutral beam for a direct subtraction of the background signal not associated with fast ions. Examples of signals from the 2008 NSTX run are presented.
Collapse
Affiliation(s)
- M Podestà
- Department of Physics and Astronomy, University of California Irvine, California 92697, USA
| | | | | | | |
Collapse
|
29
|
Abstract
PURPOSE We have evaluated the efficacy of endovascular repair of distal aortic arch aneurysms (DAAA) causing recurrent laryngeal nerve palsy. MATERIAL AND METHODS Eight patients (five male and three female) with median age of 72 years (range: 59-80) presented with left recurrent laryngeal nerve palsy associated with DAAA. All patients were considered unfit for open surgery. The median aneurysm size was 5.9 cm (range: 5-7.3). Thirteen stents were deployed: eight Gore, four Endofit and one Talent. Epidural anaesthesia was used in all patients. The left subclavian artery was covered in all and the left common carotid in three who had a preliminary right to left carotid-carotid bypass. Routine follow-up (FU) was with computed tomography (CT) at 3-6 months and yearly thereafter. RESULTS Exclusion of the aneurysm sac was achieved in all patients. Thirty-day mortality was 0%, with no paraplegia or stroke. Early complications included: rupture of the external iliac artery (one) and common femoral artery thrombectomy (one). One patient died of unknown cause at 17 months. The mean FU in the remaining seven patients was 21 months (range: 6-51). Aneurysm size decreased in five, was unchanged in one and increased in one. Three patients had improvement in voice quality postoperatively. One patient had a recurrent type 1 endoleak which was restented twice. No late deaths have occurred. CONCLUSION Though technically the procedures involved were more complicated, endovascular repair of DAAA causing aorto-vocal syndrome is safe and offers a realistic alternative to open surgery. Hoarseness of the voice can improve postoperatively and is associated with reduction in aortic sac diameter.
Collapse
Affiliation(s)
- J P Morales
- Department of Vascular Surgery, Guy's & St. Thomas' NHS Foundation Hospital, St. Thomas' Hospital, London, UK
| | | | | | | | | |
Collapse
|
30
|
Mazzucato E, Smith DR, Bell RE, Kaye SM, Hosea JC, LeBlanc BP, Wilson JR, Ryan PM, Domier CW, Luhmann NC, Yuh H, Lee W, Park H. Short-scale turbulent fluctuations driven by the electron-temperature gradient in the national spherical torus experiment. Phys Rev Lett 2008; 101:075001. [PMID: 18764544 DOI: 10.1103/physrevlett.101.075001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Indexed: 05/26/2023]
Abstract
Measurements with coherent scattering of electromagnetic waves in plasmas of the National Spherical Torus Experiment indicate the existence of turbulent fluctuations in the range of wave numbers k perpendicular rho(e)=0.1-0.4, corresponding to a turbulence scale length nearly equal to the collisionless skin depth. Experimental observations and agreement with numerical results from a linear gyrokinetic stability code support the conjecture that the observed turbulence is driven by the electron-temperature gradient.
Collapse
Affiliation(s)
- E Mazzucato
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Solomon WM, Kaye SM, Bell RE, Leblanc BP, Menard JE, Rewoldt G, Wang W, Levinton FM, Yuh H, Sabbagh SA. Momentum-transport studies in high E x B shear plasmas in the National Spherical Torus Experiment. Phys Rev Lett 2008; 101:065004. [PMID: 18764464 DOI: 10.1103/physrevlett.101.065004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Indexed: 05/26/2023]
Abstract
Experiments have been conducted at the National Sperical Torus Experiment (NSTX) to study both steady state and perturbative momentum transport. These studies are unique in their parameter space under investigation, where the low aspect ratio of NSTX results in rapid plasma rotation with ExB shearing rates high enough to suppress low-k turbulence. In some cases, the ratio of momentum to energy confinement time is found to exceed five. Momentum pinch velocities of order 10-40 m/s are inferred from the measured angular momentum flux evolution after nonresonant magnetic perturbations are applied to brake the plasma.
Collapse
Affiliation(s)
- W M Solomon
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Morales JP, Taylor PR, Bell RE, Chan YC, Sabharwal T, Carrell TWG, Reidy JF. Neurological Complications Following Endoluminal Repair of Thoracic Aortic Disease. Cardiovasc Intervent Radiol 2007; 30:833-9. [PMID: 17508247 DOI: 10.1007/s00270-007-9017-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2006] [Accepted: 11/14/2006] [Indexed: 11/26/2022]
Abstract
Open surgery for thoracic aortic disease is associated with significant morbidity and the reported rates for paraplegia and stroke are 3%-19% and 6%-11%, respectively. Spinal cord ischemia and stroke have also been reported following endoluminal repair. This study reviews the incidence of paraplegia and stroke in a series of 186 patients treated with thoracic stent grafts. From July 1997 to September 2006, 186 patients (125 men) underwent endoluminal repair of thoracic aortic pathology. Mean age was 71 years (range, 17-90 years). One hundred twenty-eight patients were treated electively and 58 patients had urgent procedures. Anesthesia was epidural in 131, general in 50, and local in 5 patients. Seven patients developed paraplegia (3.8%; two urgent and five elective). All occurred in-hospital apart from one associated with severe hypotension after a myocardial infarction at 3 weeks. Four of these recovered with cerebrospinal fluid (CSF) drainage. One patient with paraplegia died and two had permanent neurological deficit. The rate of permanent paraplegia and death was 1.6%. There were seven strokes (3.8%; four urgent and three elective). Three patients made a complete recovery, one had permanent expressive dysphasia, and three died. The rate of permanent stroke and death was 2.1%. Endoluminal treatment of thoracic aortic disease is an attractive alternative to open surgery; however, there is still a risk of paraplegia and stroke. Permanent neurological deficits and death occurred in 3.7% of the patients in this series. We conclude that prompt recognition of paraplegia and immediate insertion of a CSF drain can be an effective way of recovering spinal cord function and improving the prognosis.
Collapse
Affiliation(s)
- J P Morales
- Department of Vascular Surgery, Guy's and St. Thomas' Foundation Hospital NHS Trust, Lambeth Palace Road, London, UK
| | | | | | | | | | | | | |
Collapse
|
33
|
Chan YC, Morales JP, Rocker MD, Bell RE, Carrell TWG, Reidy JF, Taylor PR. Hybrid repair of type B dissecting aneurysm with associated Kommerell's diverticulum. Acta Chir Belg 2007; 107:211-4. [PMID: 17515274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Endovascular therapy has revolutionised vascular surgery. Complex open surgical procedures may be replaced with a combination of extra-anatomical reconstruction and endovascular treatment. This minimally invasive approach is associated with a lower peri-operative morbidity and mortality than open repair. We describe a novel 2-stage treatment in a patient with Type B thoracic aortic dissection with subsequent aneurysmal dilatation and the added difficulty of a concomitant aneurysmal aberrant right subclavian artery (Kommerell's diverticulum).
Collapse
Affiliation(s)
- Y C Chan
- Department of Vascular & Endovascular Surgery, Guy's & St. Thomas' NHS Foundation Hospital, 1st Floor North Wing, St. Thomas' Hospital, Lambeth Palace Road, London SE1 7EH, UK
| | | | | | | | | | | | | |
Collapse
|
34
|
Menard JE, Bell RE, Gates DA, Kaye SM, LeBlanc BP, Levinton FM, Medley SS, Sabbagh SA, Stutman D, Tritz K, Yuh H. Observation of instability-induced current redistribution in a spherical-torus plasma. Phys Rev Lett 2006; 97:095002. [PMID: 17026371 DOI: 10.1103/physrevlett.97.095002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2006] [Indexed: 05/12/2023]
Abstract
A motional Stark effect diagnostic has been utilized to reconstruct the parallel current density profile in a spherical-torus plasma for the first time. The measured current profile compares favorably with neoclassical theory when no large-scale magnetohydrodynamic instabilities are present in the plasma. However, a current profile anomaly is observed during saturated interchange-type instability activity. This apparent anomaly can be explained by redistribution of neutral beam injection current drive and represents the first observation of interchange-type instabilities causing such redistribution. The associated current profile modifications contribute to sustaining the central safety factor above unity for over five resistive diffusion times, and similar processes may contribute to improved operational scenarios proposed for ITER.
Collapse
Affiliation(s)
- J E Menard
- Princeton Plasma Physics Laboratory, Princeton, New Jersey, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Sabbagh SA, Bell RE, Menard JE, Gates DA, Sontag AC, Bialek JM, LeBlanc BP, Levinton FM, Tritz K, Yuh H. Active stabilization of the resistive-wall mode in high-beta, low-rotation plasmas. Phys Rev Lett 2006; 97:045004. [PMID: 16907583 DOI: 10.1103/physrevlett.97.045004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2006] [Indexed: 05/11/2023]
Abstract
The resistive-wall mode is actively stabilized in the National Spherical Torus Experiment in high-beta plasmas rotating significantly below the critical rotation speed for passive stability and in the range predicted for the International Thermonuclear Experimental Reactor. Variation of feedback stabilization parameters shows mode excitation or suppression. Stabilization of toroidal mode number unity did not lead to instability of toroidal mode number two. The mode can become unstable by deforming poloidally, an important consideration for stabilization system design.
Collapse
Affiliation(s)
- S A Sabbagh
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Zhu W, Sabbagh SA, Bell RE, Bialek JM, Bell MG, LeBlanc BP, Kaye SM, Levinton FM, Menard JE, Shaing KC, Sontag AC, Yuh H. Observation of plasma toroidal-momentum dissipation by neoclassical toroidal viscosity. Phys Rev Lett 2006; 96:225002. [PMID: 16803317 DOI: 10.1103/physrevlett.96.225002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Indexed: 05/10/2023]
Abstract
Dissipation of plasma toroidal angular momentum is observed in the National Spherical Torus Experiment due to applied nonaxisymmetric magnetic fields and their plasma-induced increase by resonant field amplification and resistive wall mode destabilization. The measured decrease of the plasma toroidal angular momentum profile is compared to calculations of nonresonant drag torque based on the theory of neoclassical toroidal viscosity. Quantitative agreement between experiment and theory is found when the effect of toroidally trapped particles is included.
Collapse
Affiliation(s)
- W Zhu
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Jones KG, Bell RE, Sabharwal T, Aukett M, Reidy JF, Taylor PR. Treatment of Mycotic Aortic Aneurysms with Endoluminal Grafts. Eur J Vasc Endovasc Surg 2005; 29:139-44. [PMID: 15649719 DOI: 10.1016/j.ejvs.2004.11.008] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2004] [Indexed: 02/07/2023]
Abstract
PURPOSE To report the benefit of endoluminal repair of mycotic aortic aneurysms and highlight the need for a registry. METHODS Nine patients (five female) were identified over 5 years (1998-2003) as having presumed mycotic aortic aneurysms (12 in total) suitable for endoluminal grafting. A total of nine thoracic and three abdominal were grafted and followed up for a median of 36 months. RESULTS Six of the aneurysms have resolved and one was converted to an open repair. There was one early death from rupture of a second undiagnosed aneurysm and two late deaths from rupture due to persistent inflammation. Long-term antibiotics have not been mandatory to ensure survival. CONCLUSIONS Mycotic aortic aneurysms of the thoracic and abdominal aorta do benefit from endoluminal repair, particularly when arising in previously normal aortic tissue. Endoluminal grafting also has a role in the palliation of secondarily infected aortas and so to prove its efficacy in the treatment of all these rare cases a registry is required.
Collapse
Affiliation(s)
- K G Jones
- Department of Vascular Surgery, Guy's and St Thomas' Hospital, London SE1 7EH, UK
| | | | | | | | | | | |
Collapse
|
38
|
Abstract
Stroke is a devastating complication of coronary artery bypass surgery. It increases the mortality and morbidity of the operation, and prolongs the length of hospital stay. Functional disability from the stroke may dramatically reduce the quality of life post-operatively, and some patients will require permanent institutional care. Although there are many causes of stroke extra-cerebral carotid stenosis is the most important predictor of stroke for patients undergoing coronary artery bypass grafting (CABG). If patients are identified before coronary intervention, they may benefit from treatment of their carotid disease. Carotid endarterectomy can be performed before or simultaneously with coronary artery bypass. However, carotid angioplasty with stenting and cerebral protection may offer a superior method to conventional surgery in this high-risk group of patients.
Collapse
Affiliation(s)
- P R Taylor
- Guy's & St Thomas' Hospital, London SE1 7EH, UK.
| | | |
Collapse
|
39
|
Abstract
Intervention is currently reserved in acute aortic dissection for Stanford Type A and for complications of Type B. Endovascular techniques such as fenestration of the intimal flap and stenting of vessel origins have been used to alleviate end-organ ischaemia due to compromised branches. The introduction of stent grafts has offered a realistic alternative to surgery for Type B dissections. Closure of the primary entry tear encourages thrombosis of the false lumen, which is associated with good long-term outcome. Many questions remain unanswered and randomised controlled trials need to be performed to establish the role of stent grafts in uncomplicated Type B dissections, and the use of bare stents to encourage thrombosis of the more distal false lumen. Improvements in the design and engineering of stent grafts may help to establish endoluminal repair as the first line treatment of aortic dissection.
Collapse
Affiliation(s)
- P R Taylor
- Guy's & St Thomas' Hospital, London SE1 7EH, UK.
| | | | | |
Collapse
|
40
|
Taylor PR, Bell RE, Reidy JF. Aortic transection due to blunt trauma: evolving management using endovascular techniques. Int J Clin Pract 2003; 57:652. [PMID: 14627171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
|
41
|
|
42
|
Abstract
BACKGROUND Thoracic stent grafts offer an alternative to open surgery for thoracic aortic disease, but their long-term durability is unknown. This report includes mid-term follow-up for commercially available thoracic devices. METHODS Data were collected prospectively for a series of endoluminal grafts used to treat thoracic aortic pathology. RESULTS Between July 1997 and October 2002, 67 patients received thoracic stent grafts. Elective procedures incurred a 30-day mortality rate of 2 per cent (one of 42 patients) and urgent repair 16 per cent (four of 25). Paraplegia affected three (4 per cent) of 67 patients and three patients had a stroke. The median follow-up was 17 (range 2-64) months; four patients were lost. There were six late deaths, two from aneurysm rupture (rupture of a mycotic aneurysm at 5 months and stent migration at 28 months). Other device-related complications comprised three proximal endoleaks, one of which required open surgical correction with removal of the stent graft, and two distal endoleaks, which were successfully treated with distal extension cuffs. CONCLUSION In the mid term, endoluminal repair of thoracic aortic pathology appears to be a safe alternative to open surgery, but continued surveillance is essential.
Collapse
Affiliation(s)
- R E Bell
- Department of General and Vascular Surgery, Guy's and St Thomas' Hospital, London, UK
| | | | | | | | | |
Collapse
|
43
|
Bell RE, Taylor PR, Aukett M, Sabharwal T, Reidy JF. Results of urgent and emergency thoracic procedures treated by endoluminal repair. Eur J Vasc Endovasc Surg 2003; 25:527-31. [PMID: 12787694 DOI: 10.1053/ejvs.2002.1926] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
INTRODUCTION emergency surgery on the thoracic aorta is associated with a high mortality. Endovascular treatment for these patients may offer a realistic alternative to open surgery. METHOD between 1997 and 2002 data was collected prospectively on all patients who underwent urgent or emergency endoluminal repair for thoracic aortic pathology. All patients had ruptured or were at risk of rupture, and had been assessed as high risk for open surgery. RESULTS twenty-four patients required urgent/emergency stent grafts. The median age was 74 (range 17-90). Indications included: trauma (transection in 3 and traumatic dissection in 1), acute symptomatic type B dissection (4), symptomatic degenerative aneurysms (7), false aneurysms associated with infection (6), Takayasu's vasculitis causing rupture of the descending thoracic aorta (1), symptomatic aneurysm associated with chronic dissection (1) and a secondary aorto-oesophageal fistula (1). The 30-day survival was 83.3% (20/24) and the survival at 1 year was 70.8% (17/24). The median follow-up was 13.5 months (range 2-57). The complications included: transient paraplegia (1), non-disabling stroke (1), distal endoleak treated with an extension cuff (1) and a proximal endoleak (1) which required removal of the graft at open surgery. CONCLUSION endoluminal repair of thoracic aortic disease requiring urgent/emergency treatment has encouraging results with low morbidity and mortality rates compared with open surgery. Long-term follow-up is required to assess the durability of the grafts.
Collapse
Affiliation(s)
- R E Bell
- Department of General and Vascular Surgery, Guy's and St Thomas' Hospital, Lambeth Palace Road, London, U.K
| | | | | | | | | |
Collapse
|
44
|
Abstract
INTRODUCTION Reductions in surgical training and the increases in medical gastroenterology have raised concerns that surgeons may not be adequately trained in upper gastrointestinal (GI) endoscopy. METHOD To evaluate this problem, a questionnaire was sent to all current surgical specialist registrars (SpRs) in the South Thames East Region. RESULTS There was an 82% (52/63) response rate. Only 50% (26/52) of trainees had received more than 6 months' training in upper GI endoscopy. 83% (43/52) were in posts which did not provide adequate elective exposure for training. 50% (26/52) were required to provide an emergency service, despite a paucity of experience and less than 50% were able to perform therapeutic injection. In the main, emergency endoscopy is performed with substandard equipment, poor facilities, and untrained staff. CONCLUSIONS Surgical trainees are poorly trained and do not have the necessary skills to provide an emergency service for upper GI haemorrhage. Emergency endoscopy facilities are severely under resourced.
Collapse
Affiliation(s)
- R E Bell
- Department of Surgery, William Harvey Hospital, Ashford, Kent, UK.
| | | | | |
Collapse
|
45
|
Bell RE. Textbook of endovascular procedures J. F. Dyet, D. F. Ettles, A. A. Nicholson and S.D. Wilson 285 × 220 mm. Pp 501. Illustrated. 2000. Edinburgh: Churchill Livingstone. Br J Surg 2002. [DOI: 10.1046/j.0007-1323.2001.t-03-02010.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- R E Bell
- Department of Surgery, Guy's and St. Thomas' Hospital, Lambeth Palace Road, London SE1 7EH, UK
| |
Collapse
|
46
|
Taylor PR, Bell RE, Reidy JF. Surgical repair of ruptured thoracic and thoraco abdominal aortic aneurysms (Br J Surg 2002; 89: 442-5). Br J Surg 2002; 89:1067-8. [PMID: 12153639 DOI: 10.1046/j.1365-2168.2002.02169_3.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
47
|
Bell RE, Taylor PR. Screening for peripheral vascular disease: why don't we do it? Int J Clin Pract 2002; 56:412-3. [PMID: 12166536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/26/2023] Open
|
48
|
Maingi R, Bell MG, Bell RE, Bush CE, Fredrickson ED, Gates DA, Kaye SM, Kugel HW, LeBlanc BP, Menard JE, Mueller D, Sabbagh SA, Stutman D, Taylor G, Johnson DW, Kaita R, Maqueda RJ, Ono M, Paoletti F, Paul SF, Peng YKM, Roquemore AL, Skinner CH, Soukhanovskii VA, Synakowski EJ. Characteristics of the first H-mode discharges in the national spherical torus experiment. Phys Rev Lett 2002; 88:035003. [PMID: 11801067 DOI: 10.1103/physrevlett.88.035003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2001] [Indexed: 05/23/2023]
Abstract
We report observations of the first low-to-high ( L-H) confinement mode transitions in the National Spherical Torus Experiment. The H-mode energy confinement time increased over reference discharges transiently by 100-200%, as high as approximately 100 ms. This confinement time is approximately 2 times higher than predicted by a multimachine scaling. Thus the confinement time of spherical tori has been extended to a record high value, leading to an eventual revision of confinement scalings. Finally, the power threshold for H-mode access is >10x higher than predicted by an international scaling from conventional aspect-ratio tokamaks, which could lead to new understanding of H-mode transition dynamics.
Collapse
Affiliation(s)
- R Maingi
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Bell RE, McLaughlin RE. Ionising radiation (medical exposure) regulations (Northern Ireland) 2000 and their implications for Accident and Emergency (A&E) doctors in training. Ulster Med J 2001; 70:19-21. [PMID: 11428319 PMCID: PMC2449209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
With the introduction of the Ionising Radiation (Medical Exposure) Regulations (Northern Ireland) 2000 (IRMER) the medical practitioner faces greater accountability when requesting radiological investigations. The referrer (usually a doctor or dentist) must supply sufficient medical data to justify radiation exposure to a patient. These regulations can lead to criminal prosecution if breached. Our objectives were to identify the level of unjustified requests for plain abdominal radiography among A&E doctors and whether there is a statistically significant difference in the justification of request between doctors of differing experience. We reviewed and prepared statistical analysis of 100 A&E request forms for plain abdominal radiography. Royal College of Radiologist Guidelines were used as a "Gold standard" for justification of the investigation. A&E doctors of less than six months experience are at greater risk of breaching these regulations when requesting plain abdominal films, when compared to more experienced doctors. This is a serious issue which should be addressed at undergraduate and pre-registration level in addition to ongoing audit.
Collapse
|
50
|
Tillich M, Bell RE, Paik DS, Fleischmann D, Sofilos MC, Logan LJ, Rubin GD. Iliac arterial injuries after endovascular repair of abdominal aortic aneurysms: correlation with iliac curvature and diameter. Radiology 2001; 219:129-36. [PMID: 11274547 DOI: 10.1148/radiology.219.1.r01ap15129] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To determine the relationship between iliac arterial tortuosity and cross-sectional area and the occurrence of iliac arterial injuries following transfemoral delivery of endovascular prostheses for repair of abdominal aortic aneurysms. MATERIALS AND METHODS Iliac arterial curvature values and orthogonal cross-sectional areas were determined from helical computed tomographic (CT) data acquired in 42 patients prior to transfemoral delivery of aortic stent-grafts. The curvature and luminal cross-sectional area orthogonal to the median centerline were quantified every millimeter along the median centerline of the iliac arteries. An indicator of global iliac tortuosity, the iliac tortuosity index, was defined as the sum of the curvature values for all points with a curvature of 0.3 cm(-1) or greater, and cross-sectional area (CSA) was indexed for all points as the mean cross-sectional diameter (D = 2 radical[CSA/pi]). Following stent-graft deployment, helical CT data were analyzed for the presence of iliac arterial dissections independently by two reviewers. RESULTS Eighteen dissections were detected in 16 patients. The iliac tortuosity index was significantly larger in iliac arteries with dissections (35.5 +/- 20.8 [mean +/- SD]) when compared with both nondissected contralateral iliac arteries in the same patients (26.1 +/- 21.0, P =.001) and iliac arteries in patients without any iliac arterial injury (20 +/- 9, P =.009). The tortuosity index was higher ipsilateral to the primary component delivery in 10 of 11 iliac dissections that developed along the primary component delivery route. CONCLUSION A high degree of iliac arterial tortuosity appears to impart greater risk for the development of iliac arterial injuries in patients undergoing transfemoral delivery of endovascular devices.
Collapse
Affiliation(s)
- M Tillich
- Department of Radiology, Stanford University School of Medicine, S-072B, 300 Pasteur Dr, Stanford, CA 94305-5105, USA
| | | | | | | | | | | | | |
Collapse
|