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Maximum Deviation (maximum + deviation)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Observer Variation in the Echocardiographic Measurement of Maximum Atrial Septal Excursion: A Comparison of M-Mode with Two-Dimensional or Transesophageal Echocardiography

ECHOCARDIOGRAPHY, Issue 10 2009

Background: Atrial septal aneurysm is typically diagnosed by transthoracic two-dimensional or transesophageal echocardiography (2DE or TEE). Such techniques are highly dependent on visual inspection which predisposes to observer variation. This study compares inter- and intraobserver variations in the measurement of maximum atrial septal excursion (MASE) obtained using transthoracic M-mode echocardiography (MME) with that obtained using 2DE or TEE. Methods: Consecutive patients with highly mobile atrial septal motion by visual inspection during 2DE or TEE were studied. MASE was estimated visually on 2DE or TEE. MME tracings were obtained with the cursor bisecting the parabola formed by the atrial septum at its maximum deviation from the midline. Electronic calipers were used to measure MASE for all echocardiographic techniques. Two observers provided two measurements each. Observer variation was determined by assessing standard deviation and confidence intervals of inter- and intraobserver differences. Results: Interobserver analysis showed standard deviations of 0.077 cm (95% CI 0.065,0.094) for MME and 0.280 cm (95% CI 0.242,0.334) for 2DE or TEE. Intraobserver analysis showed standard deviations of 0.08 cm (95% CI 0.068,0.101) for MME and 0.318 cm (95% CI 0.274,0.381) for 2DE or TEE. The mean magnitude of measured MASE was 0.44 cm higher with MME than with 2DE or TEE (95% CI 0.068,0.101). Conclusions: MME assessment of MASE is associated with substantially lower inter- and intraobserver variation than 2DE or TEE assessment. The magnitude of MASE is substantially higher with MME than with 2DE or TEE. [source]

Ab initio energy calculations and macroscopic rate modeling of hydroformylation of higher alkenes by Rh-based catalyst

AICHE JOURNAL, Issue 12 2009
Maizatul S. Shaharun
Abstract Ab initio quantum chemical computations have been done to determine the energetics and reaction pathways of hydroformylation of higher alkenes using a rhodium complex homogeneous catalyst. Calculation of fragments of the potential energy surfaces of the HRh(CO)(PPh3)3 -catalyzed hydroformylation of 1-decene, 1-dodecene, and styrene were performed by the restricted Hartree-Fock method at the second-order MØller-Plesset (MP2) level of perturbation theory and basis set of 6-31++G(d,p). Geometrically optimized structures of the intermediates and transition states were identified. Three generalized rate models were developed on the basis of above reaction path analysis as well as experimental findings reported in the literature. The kinetic and equilibrium parameters of the models were estimated by nonlinear least square regression of available literature data. The model based on H2 -oxidative addition fitted the data best; it predicts the conversion of all the alkenes quite satisfactorily with an average deviation of 7.6% and a maximum deviation of 13%. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Robust H, glucose control in diabetes using a physiological model

AICHE JOURNAL, Issue 12 2000
Robert S. Parker
A robust H, controller was developed to deliver insulin via a mechanical pump in Type I diabetic patients. A fundamental nonlinear diabetic patient model was linearized and then reduced to a third-order linear form for controller synthesis. Uncertainty in the nonlinear model was characterized by up to ±40% variation in eight physiological parameters. A sensitivity analysis identified the three-parameter set having the most significant effect on glucose and insulin dynamics over the frequency range of interest , = [0.002, 0.2] (rad/min). This uncertainty was represented in the frequency domain and incorporated in the controller design. Controller performance was assessed in terms of its ability to track a normoglycemic set point (81.1 mg/dL) in response to a 50 g meal disturbance. In the nominal continuous-time case, the controller maintained glucose concentrations within ±3.3 mg/dL of set point. A controller tuned to accommodate uncertainty yielded a maximum deviation of 17.6 mg/dL for the worst-case parameter variation. [source]

N -(p -Chlorophenyl)-3,3-diphenyl-4-(,-phenylstyryl)azetidin-2-one