16 results on '"E. Westbroek"'
Search Results
2. Path integral Monte Carlo method for the quantum anharmonic oscillator
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Marise J. E. Westbroek, Peter King, Shikhar Mittal, and Dimitri D. Vvedensky
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Coupling constant ,Physics ,05 social sciences ,Anharmonicity ,FOS: Physical sciences ,050301 education ,General Physics and Astronomy ,Markov chain Monte Carlo ,Computational Physics (physics.comp-ph) ,01 natural sciences ,symbols.namesake ,Quantum harmonic oscillator ,Quartic function ,Physics - Data Analysis, Statistics and Probability ,0103 physical sciences ,Path integral formulation ,symbols ,Statistical physics ,010306 general physics ,Ground state ,0503 education ,Physics - Computational Physics ,Data Analysis, Statistics and Probability (physics.data-an) ,Path integral Monte Carlo - Abstract
The Markov chain Monte Carlo (MCMC) method is used to evaluate the imaginary-time path integral of a quantum oscillator with a potential that includes both a quadratic term and a quartic term whose coupling is varied by several orders of magnitude. This path integral is discretized on a time lattice and calculations for the energy and probability density of the ground state and energies of the first few excited states are carried out on lattices with decreasing spacing to estimate these quantities in the continuum limit. The variation of the quartic coupling constant produces corresponding variations in the optimum simulation parameters for the MCMC method and in the statistical uncertainty for a fixed number of paths used for measurement. The energies and probability densities are in excellent agreement with those obtained from numerical solutions of Schr\"odinger's equation., Comment: Published in European Journal of Physics
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- 2018
3. Evaluation of the path integral for flow through random porous media
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Dimitri D. Vvedensky, Marise J. E. Westbroek, Peter King, Gil-Arnaud Coche, and Engineering & Physical Science Research Council (EPSRC)
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Fluids & Plasmas ,FOS: Physical sciences ,02 engineering and technology ,FLUID-FLOW ,01 natural sciences ,Dirichlet distribution ,09 Engineering ,Physics - Geophysics ,symbols.namesake ,Stochastic differential equation ,0203 mechanical engineering ,Physics, Fluids & Plasmas ,0103 physical sciences ,Fluid dynamics ,Neumann boundary condition ,010306 general physics ,01 Mathematical Sciences ,Mathematics ,Condensed Matter - Materials Science ,Science & Technology ,02 Physical Sciences ,Physics ,Mathematical analysis ,Fluid Dynamics (physics.flu-dyn) ,Materials Science (cond-mat.mtrl-sci) ,Markov chain Monte Carlo ,Physics - Fluid Dynamics ,Computational Physics (physics.comp-ph) ,Geophysics (physics.geo-ph) ,Physics, Mathematical ,Permeability (earth sciences) ,020303 mechanical engineering & transports ,Log-normal distribution ,Path integral formulation ,Physical Sciences ,CLASSICAL STATISTICAL DYNAMICS ,symbols ,NUMERICAL-SIMULATION ,Physics - Computational Physics - Abstract
We present a path integral formulation of Darcy's equation in one dimension with random permeability described by a correlated multi-variate lognormal distribution. This path integral is evaluated with the Markov chain Monte Carlo method to obtain pressure distributions, which are shown to agree with the solutions of the corresponding stochastic differential equation for Dirichlet and Neumann boundary conditions. The extension of our approach to flow through random media in two and three dimensions is discussed.
- Published
- 2018
4. Pressure statistics from the path integral for Darcy flow through random porous media
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Marise J. E. Westbroek, Peter King, Dimitri D. Vvedensky, and Gil-Arnaud Coche
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DYNAMICS ,Statistics and Probability ,Discretization ,Physics, Multidisciplinary ,MODELS ,FOS: Physical sciences ,General Physics and Astronomy ,01 natural sciences ,Darcy–Weisbach equation ,010305 fluids & plasmas ,Physics - Geophysics ,pressure ,symbols.namesake ,Stochastic differential equation ,porous media ,0103 physical sciences ,Statistics ,Neumann boundary condition ,010306 general physics ,01 Mathematical Sciences ,Mathematical Physics ,Mathematics ,Science & Technology ,02 Physical Sciences ,Darcy's law ,Physics ,Fluid Dynamics (physics.flu-dyn) ,Statistical and Nonlinear Physics ,Markov chain Monte Carlo ,random permeability ,Physics - Fluid Dynamics ,Computational Physics (physics.comp-ph) ,Geophysics (physics.geo-ph) ,Physics, Mathematical ,Permeability (earth sciences) ,Markov chain Monte Carlo method ,Modeling and Simulation ,Physical Sciences ,SIMULATION ,Path integral formulation ,Darcy equation ,symbols ,Physics - Computational Physics ,path integral - Abstract
The path integral for classical statistical dynamics is used to determine the properties of one-dimensional Darcy flow through a porous medium with a correlated stochastic permeability for several spatial correlation lengths. Pressure statistics are obtained from the numerical evaluation of the path integral by using the Markov chain Monte Carlo method. Comparisons between these pressure distributions and those calculated from the classic finite-volume method for the corresponding stochastic differential equation show excellent agreement for Dirichlet and Neumann boundary conditions. The evaluation of the variance of the pressure based on a continuum description of the medium provides an estimate of the effects of discretization. Log-normal and Gaussian fits to the pressure distributions as a function of position within the porous medium are discussed in relation to the spatial extent of the correlations of the permeability fluctuations.
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- 2019
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5. OMICS AND PROGNSTIC MARKERS
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K. Adachi, H. Sasaki, S. Nagahisa, K. Yoshida, N. Hattori, Y. Nishiyama, T. Kawase, M. Hasegawa, M. Abe, Y. Hirose, A. Alentorn, Y. Marie, S. Poggioli, H. Alshehhi, B. Boisselier, C. Carpentier, K. Mokhtari, L. Capelle, D. Figarella-Branger, K. Hoang-Xuan, M. Sanson, J.-Y. Delattre, A. Idbaih, S. Yust-Katz, M. Anderson, A. Olar, A. Eterovic, N. Ezzeddine, K. Chen, H. Zhao, G. Fuller, K. Aldape, J. de Groot, N. Andor, J. Harness, S. G. Lopez, T. L. Fung, H. W. Mewes, C. Petritsch, A. Arivazhagan, K. Somasundaram, K. Thennarasu, P. Pandey, B. Anandh, V. Santosh, B. Chandramouli, A. Hegde, P. Kondaiah, M. Rao, R. Bell, R. Kang, C. Hong, J. Song, J. Costello, R. Nagarajan, B. Zhang, A. Diaz, T. Wang, L. Bie, Y. Li, H. Liu, W. F. C. Luyo, M. H. Carnero, M. E. P. Iruegas, A. R. Morell, M. C. Figueiras, R. L. Lopez, C. F. Valverde, A. K.-Y. Chan, J. C.-S. Pang, N. Y.-F. Chung, K. K.-W. Li, W. S. Poon, D. T.-M. Chan, Y. Wang, H.-a. K. Ng, M. Chaumeil, P. Larson, H. Yoshihara, D. Vigneron, S. Nelson, R. Pieper, J. Phillips, S. Ronen, V. Clark, Z. E. Omay, A. Serin, J. Gunel, B. Omay, C. Grady, M. Youngblood, K. Bilguvar, J. Baehring, J. Piepmeier, P. Gutin, A. Vortmeyer, C. Brennan, M. N. Pamir, T. Kilic, B. Krischek, M. Simon, K. Yasuno, M. Gunel, A. L. Cohen, M. Sato, K. D. Aldape, C. Mason, K. Diefes, L. Heathcock, L. Abegglen, D. Shrieve, W. Couldwell, J. D. Schiffman, H. Colman, Q. G. D'Alessandris, T. Cenci, M. Martini, L. Ricci-Vitiani, R. De Maria, L. M. Larocca, R. Pallini, B. Theeler, F. Lang, G. Rao, M. Gilbert, E. Sulman, R. Luthra, K. Eterovic, M. Routbort, R. Verhaak, G. Mills, J. Mendelsohn, F. Meric-Bernstam, A. Yung, K. MacArthur, S. Hahn, G. Kao, R. Lustig, M. Alonso-Basanta, S. Chandrasekaran, E. P. Wileyto, E. Reyes, J. Dorsey, K. Fujii, K. Kurozumi, T. Ichikawa, M. Onishi, J. Ishida, Y. Shimazu, B. Kaur, E. A. Chiocca, I. Date, C. Geisenberger, A. Mock, R. Warta, C. Schwager, C. Hartmann, A. von Deimling, A. Abdollahi, C. Herold-Mende, O. Gevaert, A. Achrol, S. Gholamin, S. Mitra, E. Westbroek, J. Loya, L. Mitchell, S. Chang, G. Steinberg, S. Plevritis, S. Cheshier, J. Xu, S. Napel, G. Zaharchuk, G. Harsh, D. Gutman, C. Holder, R. Colen, W. Dunn, R. Jain, L. Cooper, S. Hwang, A. Flanders, D. Brat, J. Hayes, A. Droop, H. Thygesen, M. Boissinot, D. Westhead, S. Short, S. Lawler, P. Bady, S. Kurscheid, M. Delorenzi, M. E. Hegi, C. Crosby, C. Faulkner, T. Smye-Rumsby, K. Kurian, M. Williams, K. Hopkins, A. Palmer, H. Williams, C. Wragg, H. R. Haynes, K. M. Kurian, P. White, T. Oka, L. Jalbert, A. Elkhaled, R. Jensen, K. Salzman, M. Schabel, D. Gillespie, M. Mumert, B. Johnson, T. Mazor, M. Barnes, S. Yamamoto, H. Ueda, K. Tatsuno, K. Aihara, A. Bollen, M. Hirst, M. Marra, A. Mukasa, N. Saito, H. Aburatani, M. Berger, B. Taylor, S. Popov, A. Mackay, W. Ingram, A. Burford, A. Jury, M. Vinci, C. Jones, D. T. W. Jones, V. Hovestadt, S. Picelli, W. Wang, P. A. Northcott, M. Kool, G. Reifenberger, T. Pietsch, M. Sultan, H. Lehrach, M.-L. Yaspo, A. Borkhardt, P. Landgraf, R. Eils, A. Korshunov, M. Zapatka, B. Radlwimmer, S. M. Pfister, P. Lichter, A. Joy, I. Smirnov, M. Reiser, W. Shapiro, S. Kim, B. Feuerstein, C. Jungk, S. Friauf, A. Unterberg, T. A. Juratli, J. McElroy, W. Meng, A. Huebner, K. D. Geiger, D. Krex, G. Schackert, A. Chakravarti, T. Lautenschlaeger, B. Y. Kim, W. Jiang, J. Beiko, S. Prabhu, F. DeMonte, R. Sawaya, D. Cahill, I. McCutcheon, C. Lau, L. Wang, K. Terashima, S. Yamaguchi, M. Burstein, J. Sun, T. Suzuki, R. Nishikawa, H. Nakamura, A. Natsume, S. Terasaka, H.-K. Ng, D. Muzny, R. Gibbs, D. Wheeler, X.-q. Zhang, S. Sun, K.-f. Lam, K. M. Y. Kiang, J. K. S. Pu, A. S. W. Ho, G. K. K. Leung, F. Loebel, W. T. Curry, F. G. Barker, N. Lelic, A. S. Chi, D. P. Cahill, D. Lu, J. Yin, C. Teo, K. McDonald, A. Madhankumar, C. Weston, B. Slagle-Webb, J. Sheehan, A. Patel, M. Glantz, J. Connor, C. Maire, J. Francis, C.-Z. Zhang, J. Jung, V. Manzo, V. Adalsteinsson, H. Homer, B. Blumenstiel, C. S. Pedamallu, E. Nickerson, A. Ligon, C. Love, M. Meyerson, K. Ligon, L. E. Jalbert, S. J. Nelson, A. W. Bollen, I. V. Smirnov, J. S. Song, A. B. Olshen, M. S. Berger, S. M. Chang, B. S. Taylor, J. F. Costello, S. Mehta, B. Armstrong, S. Peng, A. Bapat, M. Berens, B. Melendez, M. Mollejo, P. Mur, T. Hernandez-Iglesias, C. Fiano, J. Ruiz, J. A. Rey, V. Stadler, A. Schulte, K. Lamszus, C. Schichor, M. Westphal, J.-C. Tonn, O. Morozova, S. Katzman, M. Grifford, S. Salama, D. Haussler, A. Olshen, S. Fouse, S. Nakamizo, T. Sasayama, H. Tanaka, K. Tanaka, K. Mizukawa, M. Yoshida, E. Kohmura, P. Northcott, D. Jones, S. Pfister, R. Otani, S. Takayanagi, K. Saito, S. Tanaka, M. Shin, T. Ozawa, M. Riester, Y.-K. Cheng, J. Huse, K. Helmy, N. Charles, M. Squatrito, F. Michor, E. Holland, M. Perrech, L. Dreher, G. Rohn, R. Goldbrunner, M. Timmer, B. Pollo, V. Palumbo, C. Calatozzolo, M. Patane, R. Nunziata, M. Farinotti, A. Silvani, S. Lodrini, G. Finocchiaro, E. Lopez, A. Rioscovian, R. Ruiz, G. Siordia, A. P. de Leon, C. Rostomily, R. Rostomily, D. Silbergeld, D. Kolstoe, M. Chamberlain, J. Silber, P. Roth, A. Keller, J. Hoheisel, P. Codo, A. Bauer, C. Backes, P. Leidinger, E. Meese, E. Thiel, A. Korfel, M. Weller, G. Nagae, M. Nagane, J. Z. Sanborn, T. Mikkelsen, S. Jhanwar, L. Chin, M. Nishihara, M. Schliesser, C. Grimm, E. Weiss, R. Claus, D. Weichenhan, M. Weiler, T. Hielscher, F. Sahm, B. Wiestler, A.-C. Klein, J. Blaes, C. Plass, W. Wick, G. Stragliotto, A. Rahbar, C. Soderberg-Naucler, M. Won, R. Ezhilarasan, P. Sun, D. Blumenthal, M. Vogelbaum, R. Jenkins, R. Jeraj, P. Brown, K. Jaeckle, D. Schiff, J. Dignam, J. Atkins, D. Brachman, M. Werner-Wasik, M. Mehta, J. Shen, J. Luan, A. Yu, M. Matsutani, Y. Liang, T.-K. Man, A. Trister, M. Tokita, S. Mikheeva, A. Mikheev, S. Friend, M. van den Bent, L. Erdem, T. Gorlia, M. Taphoorn, J. Kros, P. Wesseling, H. Dubbink, A. Ibdaih, P. French, H. van Thuijl, J. Heimans, B. Ylstra, J. Reijneveld, A. Prabowo, I. Scheinin, H. van Essen, W. Spliet, C. Ferrier, P. van Rijen, T. Veersema, M. Thom, A. S.-v. Meeteren, E. Aronica, H. Kim, S. Zheng, D. J. Brat, S. Virk, S. Amini, C. Sougnez, J. Barnholtz-Sloan, R. G. W. Verhaak, C. Watts, A. Sottoriva, I. Spiteri, S. Piccirillo, A. Touloumis, P. Collins, J. Marioni, C. Curtis, S. Tavare, B. Tews, T. P. C. Yeung, B. Al-Khazraji, L. Morrison, L. Hoffman, D. Jackson, T.-Y. Lee, S. Yartsev, G. Bauman, J. Fu, R. Vegesna, Y. Mao, L. E. Heathcock, W. Torres-Garcia, S. Wang, A. McKenna, C. W. Brennan, W. K. A. Yung, J. N. Weinstein, E. P. Sulman, and D. Koul
- Subjects
Abstracts ,Cancer Research ,Text mining ,Oncology ,business.industry ,Neurology (clinical) ,Computational biology ,Biology ,Omics ,business - Published
- 2013
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6. User's guide to Monte Carlo methods for evaluating path integrals
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Peter King, Stephan Dürr, Marise J. E. Westbroek, and Dimitri D. Vvedensky
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General Physics ,Monte Carlo method ,Physics, Multidisciplinary ,General Physics and Astronomy ,Social Sciences ,FOS: Physical sciences ,01 natural sciences ,010305 fluids & plasmas ,PHYSICS ,High Energy Physics - Lattice ,0103 physical sciences ,Applied mathematics ,ddc:530 ,010306 general physics ,Pseudocode ,Education, Scientific Disciplines ,Harmonic oscillator ,Condensed Matter - Statistical Mechanics ,01 Mathematical Sciences ,Physics ,Science & Technology ,02 Physical Sciences ,Statistical Mechanics (cond-mat.stat-mech) ,Numerical analysis ,High Energy Physics - Lattice (hep-lat) ,Observable ,Computational Physics (physics.comp-ph) ,Integral equation ,Education & Educational Research ,Quantum harmonic oscillator ,Path integral formulation ,Physical Sciences ,Physics - Computational Physics - Abstract
We give an introduction to the calculation of path integrals on a lattice, with the quantum harmonic oscillator as an example. In addition to providing an explicit computational setup and corresponding pseudocode, we pay particular attention to the existence of autocorrelations and the calculation of reliable errors. The over-relaxation technique is presented as a way to counter strong autocorrelations. The simulation methods can be extended to compute observables for path integrals in other settings.
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- 2017
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7. Path Integral Method for Flow through Random Porous Media
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Marise J. E. Westbroek, Dimitri D. Vvedensky, and Peter King
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symbols.namesake ,Permeability (earth sciences) ,Darcy's law ,Gaussian ,Monte Carlo method ,Path integral formulation ,Mathematical analysis ,symbols ,Geomorphology ,Randomness ,Geology ,Volumetric flow rate ,Probability measure - Abstract
One of the key problems in modelling flow in oil reservoirs is our lack of precise knowledge of the variations in flow properties across the field. At best we can infer the statistics of these variations from field observations. The challenge is to determine the statistics of the flow itself (flow rates, pressures etc.) from the statistics of the permeability variations. Conventional simulations are computationally very expensive unless smart sampling techniques or surrogate models are used. In this paper we demonstrate the use of a path integral formulation for this problem. To demonstrate how this methods works, we start with the one dimensional Darcy flow problem: q(x)=-K(x)dp(x)/dx where p(x) is the pressure, q(x) is the flow rate and K(x) is the rock permeability. The randomness of the porous medium is modelled by regarding K as a stochastic quantity which is assumed to follow Gaussian statistics. Because of the randomly varying rock structure, there is a variety of conceivable pressure realisations p(x). The path integral Z is an integral over all realisations with an appropriate probability measure. Once Z is evaluated, either analytically, or by standard Monte Carlo methods, any observable of interest, including pressure correlations can be easily obtained.
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- 2016
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8. Effect of patient's sex on early perioperative outcomes following anterior cervical discectomy and fusion.
- Author
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Alomari S, Liu A, Westbroek E, Witham T, Bydon A, and Lo SL
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- Aged, Cohort Studies, Diskectomy adverse effects, Female, Humans, Male, Retrospective Studies, Treatment Outcome, Cervical Vertebrae surgery, Spinal Fusion adverse effects
- Abstract
Objective: Differences in morbidity and mortality measures between males and females have been demonstrated for a variety of spinal surgeries, however, studies of anterior cervical discectomy and fusion (ACDF) are limited. To investigate the impact ofsexon 30-day perioperative outcomes of ACDF., Methods: Retrospective 1:1 propensity score-matched cohort study. Patients who underwent ACDF between 2016 and 2018 were reviewed from the ACS-NSQIP database.Propensity score matchingand subgroup analysis were used., Results: 21,180 patients met inclusion criteria. 11,194 patients underwent single-level ACDF and 9986 patients underwent multi-level ACDF. In the single-level group, there were 6168 (55.1%) males and 5026 (44.9%) females. In the multi-level group, there were 5033 (50.4%) males and 4953 (49.6%) females. In both single/multi-level groups, females were more likely to be of older age, be functionally dependent, and have higher BMI and lower preoperative hematocrit level. Males were more likely to be Caucasian, smokers, have myelopathy, diabetes mellitus, hypertension and bleeding disorders. In both single/multi-level groups, except for the higher incidence of urinary tract infection (UTI) in females and myocardial infarction (MI) in males, there were no significant differences in morbidity and mortality between males and females., Conclusions: Several differences in demographics and baseline health status exist between males and females undergoing ACDF. When attempting to control for comorbid conditions, we found that sex by itself is not an independent risk factor for higher perioperative morbidity or mortality in patients undergoing ACDF, except for the higher incidence of UTI in females and MI in males. These results are important findings for clinicians and spine surgeons while counseling patients undergoing this type of procedure., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier Ltd.)
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- 2021
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9. Clinical accuracy and initial experience with augmented reality-assisted pedicle screw placement: the first 205 screws.
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Liu A, Jin Y, Cottrill E, Khan M, Westbroek E, Ehresman J, Pennington Z, Lo SL, Sciubba DM, Molina CA, and Witham TF
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Objective: Augmented reality (AR) is a novel technology which, when applied to spine surgery, offers the potential for efficient, safe, and accurate placement of spinal instrumentation. The authors report the accuracy of the first 205 pedicle screws consecutively placed at their institution by using AR assistance with a unique head-mounted display (HMD) navigation system., Methods: A retrospective review was performed of the first 28 consecutive patients who underwent AR-assisted pedicle screw placement in the thoracic, lumbar, and/or sacral spine at the authors' institution. Clinical accuracy for each pedicle screw was graded using the Gertzbein-Robbins scale by an independent neuroradiologist working in a blinded fashion., Results: Twenty-eight consecutive patients underwent thoracic, lumbar, or sacral pedicle screw placement with AR assistance. The median age at the time of surgery was 62.5 (IQR 13.8) years and the median body mass index was 31 (IQR 8.6) kg/m2. Indications for surgery included degenerative disease (n = 12, 43%); deformity correction (n = 12, 43%); tumor (n = 3, 11%); and trauma (n = 1, 4%). The majority of patients (n = 26, 93%) presented with low-back pain, 19 (68%) patients presented with radicular leg pain, and 10 (36%) patients had documented lower extremity weakness. A total of 205 screws were consecutively placed, with 112 (55%) placed in the lumbar spine, 67 (33%) in the thoracic spine, and 26 (13%) at S1. Screw placement accuracy was 98.5% for thoracic screws, 97.8% for lumbar/S1 screws, and 98.0% overall., Conclusions: AR depicted through a unique HMD is a novel and clinically accurate technology for the navigated insertion of pedicle screws. The authors describe the first 205 AR-assisted thoracic, lumbar, and sacral pedicle screws consecutively placed at their institution with an accuracy of 98.0% as determined by a Gertzbein-Robbins grade of A or B.
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- 2021
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10. Influence of Sex on Early Outcomes of Elective Lumbar Fusions: An Updated Propensity-Matched and Subgroup Analysis.
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Alomari S, Liu A, Westbroek E, Witham T, Bydon A, and Larry Lo SF
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- Adult, Aged, Comorbidity, Elective Surgical Procedures adverse effects, Female, Humans, Lumbar Vertebrae surgery, Male, Middle Aged, Myocardial Infarction etiology, Propensity Score, Sex Factors, Treatment Outcome, Urinary Tract Infections etiology, Myocardial Infarction epidemiology, Postoperative Complications epidemiology, Spinal Fusion adverse effects, Urinary Tract Infections epidemiology
- Abstract
Objective: Existing data have demonstrated significant differences in morbidity and mortality measures between men and women undergoing various spinal surgeries. However, studies of lumbar fusion surgery have been limited. Thus, we investigated the effects of patient sex on 30-day perioperative outcomes after elective lumbar fusion spine surgery., Methods: Patients who had undergone lumbar fusion from 2015 to 2018 were reviewed from the American College of Surgeons National Surgical Quality Improvement Program database. Propensity score matching was used to determine whether the patient's sex had influenced the 30-day perioperative complications., Results: A total of 44,526 cases had met the inclusion criteria and were reviewed. Of the 44,526 patients, 13,715 had undergone posterior lumbar fusion, 21,993 had undergone posterior/transforaminal lumbar interbody fusion, and 8818 had undergone anterior/lateral lumbar interbody fusion. The women were more likely to be older, functionally dependent, and taking steroids for chronic conditions and to have a higher body mass index and lower preoperative hematocrit level. The men were more likely to be white, to smoke, and to have diabetes mellitus, hypertension, and bleeding disorders. In all cohorts, except for a higher incidence of urinary tract infection in the female patients and myocardial infarction in the male patients, no significant differences were found in morbidity and mortality between the sexes., Conclusions: Several differences in demographics and baseline health status were found between men and women undergoing lumbar fusion. When attempting to control for comorbid conditions using propensity score matching, we found that sex was an independent predictor of urinary tract infection in women and myocardial infarction in men across major morbidity and mortality categories in patients undergoing lumbar fusion surgery., (Copyright © 2021 Elsevier Inc. All rights reserved.)
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- 2021
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11. Automatic analysis of global spinal alignment from simple annotation of vertebral bodies.
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Doerr SA, De Silva T, Vijayan R, Han R, Uneri A, Ketcha MD, Zhang X, Khanna N, Westbroek E, Jiang B, Zygourakis C, Aygun N, Theodore N, and Siewerdsen JH
- Abstract
Purpose: Measurement of global spinal alignment (GSA) is an important aspect of diagnosis and treatment evaluation for spinal deformity but is subject to a high level of inter-reader variability. Approach: Two methods for automatic GSA measurement are proposed to mitigate such variability and reduce the burden of manual measurements. Both approaches use vertebral labels in spine computed tomography (CT) as input: the first (EndSeg) segments vertebral endplates using input labels as seed points; and the second (SpNorm) computes a two-dimensional curvilinear fit to the input labels. Studies were performed to characterize the performance of EndSeg and SpNorm in comparison to manual GSA measurement by five clinicians, including measurements of proximal thoracic kyphosis, main thoracic kyphosis, and lumbar lordosis. Results: For the automatic methods, 93.8% of endplate angle estimates were within the inter-reader 95% confidence interval ( CI 95 ). All GSA measurements for the automatic methods were within the inter-reader CI 95 , and there was no statistically significant difference between automatic and manual methods. The SpNorm method appears particularly robust as it operates without segmentation. Conclusions: Such methods could improve the reproducibility and reliability of GSA measurements and are potentially suitable to applications in large datasets-e.g., for outcome assessment in surgical data science., (© 2020 Society of Photo-Optical Instrumentation Engineers (SPIE).)
- Published
- 2020
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12. Use of Intraoperative Indocyanine Green Angiography for Feeder Vessel Ligation and En Bloc Resection of Intramedullary Hemangioblastoma.
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Molina CA, Pennington Z, Ahmed AK, Westbroek E, Goodwin ML, Tamargo R, and Sciubba DM
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- Blood Loss, Surgical prevention & control, Cervical Vertebrae, Coloring Agents, Female, Hemangioblastoma blood supply, Hemangioblastoma diagnostic imaging, Humans, Indocyanine Green, Intraoperative Care, Magnetic Resonance Imaging, Neoplasms, Multiple Primary blood supply, Neoplasms, Multiple Primary diagnostic imaging, Neurosurgical Procedures, Spinal Cord Neoplasms blood supply, Spinal Cord Neoplasms diagnostic imaging, Thoracic Vertebrae, Young Adult, von Hippel-Lindau Disease, Angiography methods, Hemangioblastoma surgery, Neoplasms, Multiple Primary surgery, Spinal Cord Neoplasms surgery
- Abstract
Background: As vascular tumors, intramedullary hemangioblastomas are associated with significant intraoperative blood loss, making them particularly challenging clinical entities. The use of intraoperative indocyanine green or other fluorescent dyes has previously been described to avoid breaching the tumor capsule, but improved surgical outcomes may result from identifying and ligating the feeder arteries and arterialized draining veins., Objective: To describe the use of combined preoperative angiography and intraoperative indocyanine green use for the identification of feeder arteries and arterialized draining veins to decrease blood loss in the resection of intramedullary hemangioblastomas., Methods: A patient with cervical myelopathy secondary to a large C3 hemangioblastoma and cervicothoracic syrinx underwent a C2-3 laminoplasty with resection of the lesion. To reduce intraoperative blood loss and facilitate safe lesion resection, the vascular architecture of the lesion was defined via preoperative digital subtraction angiography and intraoperative use of indocyanine green. The latter permitted ligation of the major and minor feeding arteries and arterialized veins prior to tumor breach, allowing for facile en bloc resection of the lesion., Results: The lesion was resected en bloc with minimal blood loss (approximately 100 mL) and without intraoperative neuromonitoring signal changes. The patient remained at neurological baseline throughout their stay., Conclusion: We present a written and media illustration of a technique for intraoperative indocyanine green use in the en bloc resection of intramedullary hemangioblastoma., (Copyright © 2019 by the Congress of Neurological Surgeons.)
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- 2019
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13. Preoperative Clinical and Radiographic Variables Predict Postoperative C5 Palsy.
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Pennington Z, Lubelski D, D'Sa A, Westbroek E, Ahmed AK, Goodwin ML, Witham TF, Bydon A, Theodore N, and Sciubba DM
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- Adult, Aged, Decompression, Surgical methods, Female, Humans, Laminectomy methods, Male, Middle Aged, Postoperative Complications epidemiology, Postoperative Period, Risk Factors, Spinal Cord surgery, Cervical Vertebrae surgery, Constriction, Pathologic surgery, Paralysis surgery, Postoperative Complications surgery
- Abstract
Background: Postoperative C5 palsy affects 8% of patients undergoing posterior cervical decompression. It is associated with a period functional disability that may exceed 12 months and increase direct care costs > $2000., Methods: All patients undergoing posterior cervical decompression at a single tertiary-care facility for degenerative conditions were evaluated for preoperative imaging, clinical presentation, surgical operation, and postoperative course. We sought to identify those variables predictive of postoperative C5 palsy., Results: Of 221 included patients (mean age, 63 years; 54% male), 12.2% experienced C5 palsy. On univariate analysis, C5 palsy was associated with foraminal diameter (P = 0.0005), spinal cord cross-sectional area (P = 0.11), number of levels undergoing laminectomy (P = 0.14), and clinical presentation of dropping objects (P = 0.07), hand clumsiness (P = 0.13), or paresthesias in the upper extremities (P = 0.08). Foraminal diameter (odds ratio, 0.31 per mm increase; 95% confidence interval, 0.16-0.60; P < 0.001) and patient report of gait disturbance (odds ratio, 0.53; 95% confidence interval, 0.33-0.85; P = 0.008) were the only significant predictors on multivariate analysis. A foraminal diameter <2 mm had 2-fold greater odds of postoperative C5 palsy. A receiver operating curve for the multivariate logistic model had an associated C-statistic of 0.7818. The absolute error of this model was 9.3% on internal validation., Conclusions: Foraminal stenosis most strongly predicted postoperative C5 palsy. A proof-of-concept model incorporating foramen size, as well as clinical complaints of paresthesias, hand clumsiness, and gait abnormality, successfully predicts the occurrence of postoperative palsy with an overall accuracy of 78%., (Copyright © 2019 Elsevier Inc. All rights reserved.)
- Published
- 2019
- Full Text
- View/download PDF
14. Contralateral approach for clipping of bilateral anterior circulation aneurysms.
- Author
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Caplan JM, Sankey E, Gullotti D, Wang J, Westbroek E, Hwang B, and Huang J
- Subjects
- Craniotomy, Female, Humans, Microsurgery, Middle Aged, Functional Laterality physiology, Intracranial Aneurysm pathology, Intracranial Aneurysm surgery, Middle Cerebral Artery, Neurosurgical Procedures methods, Surgical Instruments
- Abstract
Patients with bilateral anterior circulation aneurysms present a management challenge. These lesions may be treated in a staged manner or alternatively, for select patients, a contralateral approach may be utilized to treat bilateral aneurysms with a single surgery. In this narrated video illustration, we present the case of a 57-year-old woman with incidentally discovered bilateral aneurysms (left middle cerebral artery [MCA], left anterior choroidal artery and right MCA). A contralateral approach through a left pterional craniotomy was performed formicrosurgical clipping of all three aneurysms. The techniques of pterional craniotomy, contralateral approach, microsurgical clipping and intraoperative angiography are reviewed. The authors are grateful to Wuyang Yang, M.D. for his assistance. The video can be found here: http://youtu.be/MlPIu3hQZkg.
- Published
- 2015
- Full Text
- View/download PDF
15. BDNF Pretreatment of Human Embryonic-Derived Neural Stem Cells Improves Cell Survival and Functional Recovery After Transplantation in Hypoxic-Ischemic Stroke.
- Author
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Rosenblum S, Smith TN, Wang N, Chua JY, Westbroek E, Wang K, and Guzman R
- Subjects
- Animals, Cell Adhesion Molecules biosynthesis, Cell Differentiation, Cell Line, Cell Movement, Cell Survival, Cerebral Cortex cytology, Chemokines, CXC biosynthesis, Embryonic Stem Cells cytology, HEK293 Cells, Hippocampus cytology, Humans, Hypoxia-Ischemia, Brain pathology, Male, Mice, Mice, Inbred NOD, Mice, SCID, Neural Stem Cells cytology, Receptors, Chemokine biosynthesis, Recovery of Function, Stroke pathology, Brain-Derived Neurotrophic Factor pharmacology, Cell- and Tissue-Based Therapy methods, Embryonic Stem Cells transplantation, Hypoxia-Ischemia, Brain therapy, Neural Stem Cells transplantation, Stroke therapy
- Abstract
Intra-arterial neural stem cell (NSC) therapy has the potential to improve long-term outcomes after stroke. Here we evaluate if pretreatment of NSCs with brain-derived neurotrophic factor (BDNF) prior to transplantation improves cell engraftment and functional recovery following hypoxic-ischemic (HI) stroke. Human embryonic-derived NSCs with or without BDNF pretreatment (1 h, 100 ng/ml) were transplanted 3 days after HI stroke. Functional recovery was assessed using the horizontal ladder test. Cell engraftment was evaluated using bioluminescence imaging (BLI) and histological counts of SC121(+) cells. Fluoro-Jade C (FJC) and NeuN stains were used to evaluate neuroprotection. The effect of BDNF on NSCs was analyzed using a migration assay, immunocytochemistry, Luminex proteomic assay, and RT-qPCR.BLI analysis demonstrated significantly higher photon flux in the BDNF-treated NSC group compared to untreated NSC (p = 0.049) and control groups (p = 0.0021) at 1 week after transplantation. Immunohistochemistry confirmed increased transplanted cell survival in the cortex (p = 0.0126) and hippocampus (p = 0.0098) of animals injected with BDNF-treated NSCs compared to untreated NSCs. Behavioral testing revealed that the BDNF-treated NSC group demonstrated increased sensorimotor recovery compared to the untreated NSC and control groups (p < 0.001) over the 1-month period (p < 0.001) following transplantation. A significant improvement in performance was found in the BDNF-treated NSC group compared to the control group at 14, 21, and 28 (p < 0.05) days after transplantation. The cortex and hippocampus of the BDNF-treated NSC group had significantly more SC121(+) NSCs (p = 0.0125, p = 0.0098), fewer FJC(+) neurons (p = 0.0370, p = 0.0285), and a higher percentage of NeuN(+) expression (p = 0.0354) in the cortex compared to the untreated NSC group. BDNF treatment of NSCs resulted in significantly greater migration to SDF-1, secretion of M-CSF, VEGF, and expression of CXCR4, VCAM-1, Thrombospondins 1 and 2, and BDNF. BDNF pretreatment of NSCs results in higher initial NSC engraftment and survival, increased neuroprotection, and greater functional recovery when compared to untreated NSCs.
- Published
- 2015
- Full Text
- View/download PDF
16. Dynamic transcriptome of Schizosaccharomyces pombe shown by RNA-DNA hybrid mapping.
- Author
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Dutrow N, Nix DA, Holt D, Milash B, Dalley B, Westbroek E, Parnell TJ, and Cairns BR
- Subjects
- Chromosome Mapping, Chromosomes, Fungal metabolism, RNA Processing, Post-Transcriptional, Schizosaccharomyces metabolism, Transcription, Genetic, Untranslated Regions metabolism, Gene Expression Profiling methods, Nucleic Acid Hybridization methods, Schizosaccharomyces genetics
- Abstract
We have determined the high-resolution strand-specific transcriptome of the fission yeast S. pombe under multiple growth conditions using a novel RNA-DNA hybridization mapping (HybMap) technique. HybMap uses an antibody against an RNA-DNA hybrid to detect RNA molecules hybridized to a high-density DNA oligonucleotide tiling microarray. HybMap showed exceptional dynamic range and reproducibility, and allowed us to identify strand-specific coding, noncoding and structural RNAs, as well as previously unknown RNAs conserved in distant yeast species. Notably, we found that virtually the entire euchromatic genome (including intergenics) is transcribed, with heterochromatin dampening intergenic transcription. We identified features including large numbers of condition-specific noncoding RNAs, extensive antisense transcription, new properties of antisense transcripts and induced divergent transcription. Furthermore, our HybMap data informed the efficiency and locations of RNA splicing genome-wide. Finally, we observed strand-specific transcription islands around tRNAs at heterochromatin boundaries inside centromeres. Here, we discuss these new features in terms of organism fitness and transcriptome evolution.
- Published
- 2008
- Full Text
- View/download PDF
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