oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 1 )

2019 ( 172 )

2018 ( 201 )

2017 ( 225 )

Custom range...

Search Results: 1 - 10 of 203188 matches for " Sean P Keenan "
All listed articles are free for downloading (OA Articles)
Page 1 /203188
Display every page Item
Interfaces for noninvasive ventilation: does it matter? Interfaces para ventila o n o-invasiva: faz diferen a?
Sean P. Keenan,Brent Winston
Jornal Brasileiro de Pneumologia , 2009, DOI: 10.1590/s1806-37132009000200001
Abstract:
Wean Earlier and Automatically with New technology (the WEAN study): a protocol of a multicentre, pilot randomized controlled trial
Karen EA Burns, Maureen O Meade, Martin R Lessard, Sean P Keenan, Francois Lellouche
Trials , 2009, DOI: 10.1186/1745-6215-10-81
Abstract: A pilot weaning randomized controlled trial (RCT) is underway in the ICUs of 8 Canadian hospitals. We will randomize 90 critically ill adults requiring invasive ventilation for at least 24 hours and identified at an early stage of the weaning process to either Automated Weaning (SmartCare?) or Protocolized Weaning. The results of a National Weaning Survey informed the design of the Protocolized Weaning arm. Both weaning protocols are operationalized in Pressure Support mode, include opportunities for Spontaneous Breathing Trials, and share a common sedation protocol, oxygen titration parameters, and extubation and reintubation criteria. The primary outcome of the WEAN study is to evaluate compliance with the proposed weaning and sedation protocols. A key secondary outcome of the pilot RCT is to evaluate clinician acceptance of the weaning and sedation protocols. Prior to initiating the WEAN Study, we conducted a run-in phase, involving two patients per centre (randomizing the first participant to either weaning strategy and assigning the second patient to the alternate strategy) to ensure that participating centres could implement the weaning and sedation protocols and complete the detailed case report forms.Mechanical ventilation studies are difficult to implement; requiring protocols to be operationalized continuously and entailing detailed daily data collection. As the first multicentre weaning RCT in Canada, the WEAN Study seeks to determine the feasibility of conducting a large scale future weaning trial and to establish a collaborative network of ICU clinicians dedicated to advancing the science of weaning.ISRCTN43760151Weaning is the process during which mechanical ventilation is gradually or abruptly withdrawn. In addition, it is the time during which work of breathing is transferred from the ventilator back to the patient until fully autonomous breathing is resumed. Weaning accounts for approximately 40% of the total time spent on mechanical ventilation [1,
Comment on "Multiconfiguration Dirac-Fock energy levels and radiative rates for Br-like tungsten" by S. Aggarwal, A.K.S. Jha, and M. Mohan [Can . J. Phys. 91 (2013) 394]
K. M. Aggarwal,F. P. Keenan
Physics , 2013, DOI: 10.1139/cjp-2013-0382
Abstract: We report calculations of energy levels and oscillator strengths for transitions in W XL, undertaken with the general-purpose relativistic atomic structure package ({\sc grasp}) and flexible atomic code ({\sc fac}). Comparisons are made with existing results and the accuracy of the data is assessed. Discrepancies with the most recent results of S. Aggarwal et al. [Can. J. Phys. {\bf 91} (2013) 394] are up to 0.4 Ryd and up to two orders of magnitude for energy levels and oscillator strengths, respectively. Discrepancies for lifetimes are even larger, up to four orders of magnitude for some levels. Our energy levels are estimated to be accurate to better than 0.5% (i.e. 0.2 Ryd), whereas results for oscillator strengths and lifetimes should be accurate to better than 20%.
Mechanisms for MHD Poynting flux generation in simulations of solar photospheric magneto-convection
S. Shelyag,M. Mathioudakis,F. P. Keenan
Physics , 2012, DOI: 10.1088/2041-8205/753/1/L22
Abstract: We investigate the generation mechanisms of MHD Poynting flux in the magnetised solar photosphere. Using radiative MHD modelling of the solar photosphere with initial magnetic configurations that differ in their field strength and geometry, we show the presence of two different mechanisms for MHD Poynting flux generation in simulations of solar photospheric magneto-convection. The weaker mechanism is connected to vertical transport of weak horizontal magnetic fields in the convectively stable layers of the upper photosphere, while the stronger is the production of Poynting flux in strongly magnetised intergranular lanes experiencing horizontal vortex motions. These mechanisms may be responsible for the energy transport from the solar convection zone to the higher layers of the solar atmosphere.
Electron impact excitation of Be-like ions: a comparison of DARC and ICFT results
K. M. Aggarwal,F. P. Keenan
Physics , 2015, DOI: 10.1093/mnras/stu2727
Abstract: Emission lines of Be-like ions are frequently observed in astrophysical plasmas, and many are useful for density and temperature diagnostics. However, accurate atomic data for energy levels, radiative rates (A-values) and effective electron excitation collision strengths ($\Upsilon$) are required for reliable plasma modelling. In general it is reasonably straightforward to calculate energy levels and A- values to a high level of accuracy. By contrast, considerable effort is required to calculate $\Upsilon$, and hence it is not always possible to assess the accuracy of available data. Recently, two independent calculations (adopting the $R$-matrix method) but with different approaches (DARC and ICFT) have appeared for a range of Be-like ions. Therefore, in this work we compare the two sets of $\Upsilon$, highlight the large discrepancies for a significant number of transitions and suggest possible reasons for these.
Energy levels, radiative rates and electron impact excitation rates for transitions in C III
K. M. Aggarwal,F. P. Keenan
Physics , 2015, DOI: 10.1093/mnras/stv684
Abstract: We report energy levels, radiative rates (A-values) and lifetimes for the astrophysically-important Be-like ion C III. For the calculations, 166 levels belonging to the $n \le$ 5 configurations are considered and the {\sc grasp} (General-purpose Relativistic Atomic Structure Package) is adopted. Einstein A-coefficients are provided for all E1, E2, M1 and M2 transitions, while lifetimes are compared with available measurements as well as theoretical results, and no large discrepancies noted. Our energy levels are assessed to be accurate to better than 1\% for a majority of levels, and A-values to better than 20\% for most transitions. Collision strengths are also calculated, for which the Dirac Atomic R-matrix Code ({\sc darc}) is used. A wide energy range, up to 21 Ryd, is considered and resonances resolved in a fine energy mesh in the thresholds region. The collision strengths are subsequently averaged over a Maxwellian velocity distribution to determine effective collision strengths up to a temperature of 8.0$\times$10$^5$ K, sufficient for most astrophysical applications. Our data are compared with the recent $R$-matrix calculations of Fern{\'a}ndez-Menchero, Del Zanna \& Badnell [A\&A 566 (2014) A104], and significant differences (up to over an order of magnitude) are noted for several transitions over the complete temperature range of the results.
Radiative rates for E1, E2, M1, and M2 transitions among the 3s$^2$3p$^5$, 3s3p$^6$, and 3s$^2$3p$^4$3d configurations of Cl-like W LVIII
K. M. Aggarwal,F. P. Keenan
Physics , 2014, DOI: 10.1139/cjp-2013-0681
Abstract: We report calculations of energy levels, radiative decay rates, and lifetimes for transitions among the 3s$^2$3p$^5$, 3s3p$^6$, and 3s$^2$3p$^4$3d configurations of Cl-like W LVIII. The general-purpose relativistic atomic structure package (GRASP) has been adopted for our calculations. Comparisons are made with the most recent results of Mohan et al. [Can. J. Phys. {\bf 92} (2014) xxx] and discrepancies in lifetimes are noted, up to four orders of magnitude in some instances. Our energy levels are estimated to be accurate to better than 0.5\%, whereas results for radiative rates and lifetimes should be accurate to better than 20\%.
Radiative rates for E1, E2, M1, and M2 transitions in the Br-like ions Sr IV, Y V, Zr VI, Nb VII, and Mo VIII
K. M. Aggarwal,F. P. Keenan
Physics , 2015,
Abstract: Energies and lifetimes are reported for the lowest 375 levels of five Br-like ions, namely Sr~IV, Y~V, Zr~VI, Nb~VII, and Mo~VIII, mostly belonging to the 4s$^2$4p$^5$, 4s$^2$4p$^4$4$\ell$, 4s4p$^6$, 4s$^2$4p$^4$5$\ell$, 4s$^2$4p$^3$4d$^2$, 4s4p$^5$4$\ell$, and 4s4p$^5$5$\ell$ configurations. Extensive configuration interaction has been included and the general-purpose relativistic atomic structure package ({\sc grasp}) has been adopted for the calculations. Additionally, radiative rates are listed among these levels for all E1, E2, M1, and M2 transitions. From a comparison with the measurements, the majority of our energy levels are assessed to be accurate to better than 2\%, although discrepancies between theory and experiment for a few are up to 6\%. An accuracy assessment of the calculated radiative rates (and lifetimes) is more difficult, because no prior results exist for these ions.
Radiative rates for E1, E2, M1, and M2 transitions in F-like ions with 37 $\le$ Z $\le$ 53
K M Aggarwal,F P Keenan
Physics , 2015,
Abstract: Calculations of energy levels, radiative rates and lifetimes are reported for 17 F-like ions with 37 $\le$ Z $\le$ 53. For brevity, results are only presented among the lowest 113 levels of the 2s$^2$2p$^5$, 2s2p$^6$, 2s$^2$2p$^4$3$\ell$, 2s2p$^5$3$\ell$, and 2p$^6$3$\ell$ configurations, although the calculations have been performed for up to 501 levels in each ion. The general-purpose relativistic atomic structure package (GRASP) has been adopted for the calculations, and radiative rates (along with oscillator strengths and line strengths) are listed for all E1, E2, M1, and M2 transitions of the ions. Comparisons are made with earlier available experimental and theoretical energies, although these are limited to only a few levels for most ions. Therefore for additional accuracy assessments, particularly for energy levels, analogous calculations have been performed with the Flexible Atomic Code (FAC), for up to 72~259 levels. Limited previous results are available for radiative rates for comparison purposes, and no large discrepancy is observed for any transition and/or ion.
Energy levels, radiative rates and lifetimes for transitions in Br-like ions with 38 $\le$ Z $\le$ 42
K. M. Aggarwal,F. P. Keenan
Physics , 2014, DOI: 10.1088/0031-8949/89/12/125404
Abstract: Energy levels and radiative rates for transitions in five Br-like ions (Sr IV, Y V, Zr VI, Nb VII and Mo VIII) are calculated with the general-purpose relativistic atomic structure package ({\sc grasp}). Extensive configuration interaction has been included and results are presented among the lowest 31 levels of the 4s$^2$4p$^5$, 4s$^2$4p$^4$4d and 4s4p$^6$ configurations. Lifetimes for these levels have also been determined, although unfortunately no measurements are available with which to compare. However, recently theoretical results have been reported by Singh {\em et al} [Phys. Scr. {\bf 88} (2013) 035301] using the same {\sc grasp} code. But their reported data for radiative rates and lifetimes cannot be reproduced and show discrepancies of up to five orders of magnitude with the present calculations.
Page 1 /203188
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.