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Reasonable Prediction (reasonable + prediction)
Selected AbstractsPrediction of human pharmacokinetics , improving microsome-based predictions of hepatic metabolic clearanceJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 10 2007Urban Fagerholm Physiologically based methods generally perform poorly in predicting in-vivo hepatic CL (CLH) from intrinsic clearance (CLint) in microsomes in-vitro and unbound fraction in blood (fu,bl). Various strategies to improve the predictability have been developed, and inclusion of an empirical scaling factor (SF) seems to give the best results. This investigation was undertaken to evaluate this methodology and to find ways to improve it further. The work was based on a diverse data set taken from Ito and Houston (2005). Another objective was to evaluate whether rationalization of CLH predictions can be made by replacing blood/plasma-concentration ratio (Cbl/Cpl) measurements with SFs. There were apparently no or weak correlations between prediction errors and lipophilicity, permeability (compounds with low permeability missing in the data set) and main metabolizing CYP450s. The use of CLint class (high/low) and drug class (acid/base/neutral) SFs (the CD-SF method) gives improved and reasonable predictions: 1.3-fold median error (an accurate prediction has a 1-fold error), 76% within 2-fold-error, and a median absolute rank ordering error of 2 for CLH (n = 29). This approach is better than the method with a single SF. Mean (P < 0.05) and median errors, fraction within certain error ranges, higher percentage with most accurate predictions, and ranking were all better, and 76% of predictions were more accurate with this new method. Results are particularly good for bases, which generally have higher CLH and the potential to be incorrectly selected/rejected as candidate drugs. Reasonable predictions of fu,bl can be made from plasma fu (fu,pl) and empirical blood cell binding SFs (B-SFs; 1 for low fu,pl acids; 0.62 for other substances). Mean and median fu,bl prediction errors are negligible. The use of the CD-SF method with predicted fu,bl (the BCD-SF method) also gives improved and reasonable results (1.4-fold median error; 66% within 2-fold-error; median absolute rank ordering error = 1). This new empirical approach seems sufficiently good for use during the early screening; it gives reasonable estimates of CLH and good ranking, which allows replacement of Cbl/Cpl measurements by a simple equation. [source] Quantification of Shigella IcsA required for bacterial actin polymerizationCYTOSKELETON, Issue 4 2002Juana Magdalena Abstract Shigella move through the cytoplasm of host cells by active polymerization of host actin to form an "actin tail." Actin tail assembly is mediated by the Shigella protein IcsA. The process of Shigella actin assembly has been studied extensively using IcsA-expressing Escherichia coli in cytoplasmic extracts of Xenopus eggs. However, for reasons that have been unclear, wild type Shigella does not assemble actin in these extracts. We show that the defect in actin assembly in Xenopus extracts by Shigella can be rescued by increasing IcsA expression by approximately 3-fold. We calculate that the number of IcsA molecules required on an individual bacterium to assemble actin filaments in extracts is approximately 1,500,2,100 molecules, and the number of IcsA molecules required to assemble an actin tail is approximately 4,000 molecules. The majority of wild type Shigella do not express these levels of IcsA when grown in vitro. However, in infected host cells, IcsA expression is increased 3.2-fold, such that the number of IcsA molecules on a significant percentage of intracellular wild type Shigella would exceed that required for actin assembly in extracts. Thus, the number of IcsA molecules estimated from our studies in extracts as being required on an individual bacterium to assemble actin filaments or an actin tail is a reasonable prediction of the numbers required for these functions in Shigella -infected cells. Cell Motil. Cytoskeleton 51:187,196, 2002. © 2002 Wiley-Liss, Inc. [source] Response evaluation of axially loaded fixed-head pile groups in clayey soilsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 17 2009Emilios M. Comodromos Abstract The aim of this paper is to investigate the interaction between the piles in a group with a rigid head and correlate the response of a group of piles to that of a single pile. For this purpose, a computationally intensive study using 3-D nonlinear numerical analysis was carried out for different pile group arrangements in clayey soils. The responses of the groups of piles were compared with that of a single pile and the variation of the settlement amplification factor Ra was then quantified. The influence of the number of piles, the spacing, and the settlement level on the group response is discussed. A previously proposed relationship for predicting the response of a pile group, based on its configuration and the response of a single pile, has been modified to extend its applicability for any pile spacing. The modified relationship provides a reasonable prediction for various group configurations in clayey soils. Copyright © 2009 John Wiley & Sons, Ltd. [source] Equations to predict precipitation onset and bubblepoint pressures of asphaltenic reservoir fluidsAICHE JOURNAL, Issue 7 2009J. M. del Rio Abstract A set of algebraic equations to predict upper onset-of-precipitation and bubble-point pressures of asphaltene-containing reservoir fluids in wide temperature ranges are proposed. In developing the equations, laboratory data of 11 Mexican and 12 more live oils have been analyzed, and a correlation of these data with temperature has been found. A modified least-squares regression method has been used to develop two versions of the proposed equations. In one version, a single pressure/temperature data point is required to predict the entire onset/bubble-point curves at any temperature. For oils with no experimental precipitation data available at all, a second version of the proposed expressions employs standard chromatographic data of the reservoir fluid to provide a reasonable prediction. The average absolute deviations in calculated onset and bubble-point pressures by the proposed equations are 2.53 and 0.45MPa by the one-point correlations, respectively, and 3.96 and 1.62 MPa by the compositionally-based correlations, respectively. The developed expressions are simple and can be used to provide reasonable predictions of upper onset and bubble-point pressures of asphaltenic live oils in cases where laboratory data are scarce. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Theoretical and visual study of bubble dynamics in foam injection moldingPOLYMER ENGINEERING & SCIENCE, Issue 3 2010Mehdi Mahmoodi This article presents an experimental observation and a theoretical prediction of bubble dynamics in foam injection molding process with a main focus on the cell collapse phenomenon under pressure. Using a visualizing setup, cell growth behavior under a nonisothermal condition was monitored. In conjunction with the growth behavior, dynamics of cell collapse under different pressures and the effect of growing time on collapse behavior and final cell size were studied. Theoretical simulation of bubble behavior included power law model, which predicted bubble dynamics during foaming process. The results show that collapse phenomenon strongly depends on both exerted holding pressure and growth time. The presented model can also give a reasonable prediction of growth and collapse of cells and could give insight to control of cell size in injection foaming process. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Prediction of metabolic function from limited data: Lumped hybrid cybernetic modeling (L-HCM)BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2010Hyun-Seob Song Abstract Motivated by the need for a quick quantitative assessment of metabolic function without extensive data, we present an adaptation of the cybernetic framework, denoted as the lumped hybrid cybernetic model (L-HCM), which combines the attributes of the classical lumped cybernetic model (LCM) and the recently developed HCM. The basic tenet of L-HCM and HCM is the same, that is, they both view the uptake flux as being split among diverse pathways in an optimal way as a result of cellular regulation such that some chosen metabolic objective is realized. The L-HCM, however, portrays this flux distribution to occur in a hierarchical way, that is, first among lumped pathways, and next among individual elementary modes (EM) in each lumped pathway. Both splits are described by the cybernetic control laws using operational and structural return-on-investments, respectively. That is, the distribution of uptake flux at the first split is dynamically regulated according to environmental conditions, while the subsequent split is based purely on the stoichiometry of EMs. The resulting model is conveniently represented in terms of lumped pathways which are fully identified with respect to yield coefficients of all products unlike classical LCMs based on instinctive lumping. These characteristics enable the model to account for the complete set of EMs for arbitrarily large metabolic networks despite containing only a small number of parameters which can be identified using minimal data. However, the inherent conflict of questing for quantification of larger networks with smaller number of parameters cannot be resolved without a mechanism for parameter tuning of an empirical nature. In this work, this is accomplished by manipulating the relative importance of EMs by tuning the cybernetic control of mode-averaged enzyme activity with an empirical parameter. In a case study involving aerobic batch growth of Saccharomyces cerevisiae, L-HCM is compared with LCM. The former provides a much more satisfactory prediction than the latter when parameters are identified from a few primary metabolites. On the other hand, the classical model is more accurate than L-HCM when sufficient datasets are involved in parameter identification. In applying the two models to a chemostat scenario, L-HCM shows a reasonable prediction on metabolic shift from respiration to fermentation due to the Crabtree effect, which LCM predicts unsatisfactorily. While L-HCM appears amenable to expeditious estimates of metabolic function with minimal data, the more detailed dynamic models [such as HCM or those of Young et al. (Young et al., Biotechnol Bioeng, 2008; 100: 542,559)] are best suited for accurate treatment of metabolism when the potential of modern omic technology is fully realized. However, in view of the monumental effort surrounding the development of detailed models from extensive omic measurements, the preliminary insight into the behavior of a genotype and metabolic engineering directives that can come from L-HCM is indeed valuable. Biotechnol. Bioeng. 2010;106: 271,284. © 2010 Wiley Periodicals, Inc. [source] Equations to predict precipitation onset and bubblepoint pressures of asphaltenic reservoir fluidsAICHE JOURNAL, Issue 7 2009J. M. del Rio Abstract A set of algebraic equations to predict upper onset-of-precipitation and bubble-point pressures of asphaltene-containing reservoir fluids in wide temperature ranges are proposed. In developing the equations, laboratory data of 11 Mexican and 12 more live oils have been analyzed, and a correlation of these data with temperature has been found. A modified least-squares regression method has been used to develop two versions of the proposed equations. In one version, a single pressure/temperature data point is required to predict the entire onset/bubble-point curves at any temperature. For oils with no experimental precipitation data available at all, a second version of the proposed expressions employs standard chromatographic data of the reservoir fluid to provide a reasonable prediction. The average absolute deviations in calculated onset and bubble-point pressures by the proposed equations are 2.53 and 0.45MPa by the one-point correlations, respectively, and 3.96 and 1.62 MPa by the compositionally-based correlations, respectively. The developed expressions are simple and can be used to provide reasonable predictions of upper onset and bubble-point pressures of asphaltenic live oils in cases where laboratory data are scarce. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Prediction of human pharmacokinetics , improving microsome-based predictions of hepatic metabolic clearanceJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 10 2007Urban Fagerholm Physiologically based methods generally perform poorly in predicting in-vivo hepatic CL (CLH) from intrinsic clearance (CLint) in microsomes in-vitro and unbound fraction in blood (fu,bl). Various strategies to improve the predictability have been developed, and inclusion of an empirical scaling factor (SF) seems to give the best results. This investigation was undertaken to evaluate this methodology and to find ways to improve it further. The work was based on a diverse data set taken from Ito and Houston (2005). Another objective was to evaluate whether rationalization of CLH predictions can be made by replacing blood/plasma-concentration ratio (Cbl/Cpl) measurements with SFs. There were apparently no or weak correlations between prediction errors and lipophilicity, permeability (compounds with low permeability missing in the data set) and main metabolizing CYP450s. The use of CLint class (high/low) and drug class (acid/base/neutral) SFs (the CD-SF method) gives improved and reasonable predictions: 1.3-fold median error (an accurate prediction has a 1-fold error), 76% within 2-fold-error, and a median absolute rank ordering error of 2 for CLH (n = 29). This approach is better than the method with a single SF. Mean (P < 0.05) and median errors, fraction within certain error ranges, higher percentage with most accurate predictions, and ranking were all better, and 76% of predictions were more accurate with this new method. Results are particularly good for bases, which generally have higher CLH and the potential to be incorrectly selected/rejected as candidate drugs. Reasonable predictions of fu,bl can be made from plasma fu (fu,pl) and empirical blood cell binding SFs (B-SFs; 1 for low fu,pl acids; 0.62 for other substances). Mean and median fu,bl prediction errors are negligible. The use of the CD-SF method with predicted fu,bl (the BCD-SF method) also gives improved and reasonable results (1.4-fold median error; 66% within 2-fold-error; median absolute rank ordering error = 1). This new empirical approach seems sufficiently good for use during the early screening; it gives reasonable estimates of CLH and good ranking, which allows replacement of Cbl/Cpl measurements by a simple equation. [source] Bulk High-Impact Polystyrene Process, 1MACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2007Partitions of tert -Butyl Peroctoate, Styrene in Blends Containing Polystyrene, a Rubber Abstract In relation to the bulk high-impact polystyrene process, this work investigates the partition between phases of styrene and an initiator: tert- butyl peroctoate. A Flory-Huggins model was applied for predicting the phase separation point and the partitions of styrene and tert- butyl peroctoate. For blends of styrene, polystyrene, and a styrene-butadiene diblock copolymer, the model provides reasonable predictions of a ternary equilibrium diagram. For blends of styrene, polystyrene, polybutadiene, and tert- butyl peroctoate, the partition of tert- butyl peroctoate was measured at 25,°C. At emulated conversions of 13% or lower, equilibrium was reached after 1 h of mixing time. For the higher molar masses and conversion of 16%, equilibrium was not reached after 24 h of mixing time. To fit the equilibrium measurements, the solubility parameter of tert- butyl peroctoate was adjusted. [source] Scaling of chew cycle duration in primatesAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2009Callum F. Ross Abstract The biomechanical determinants of the scaling of chew cycle duration are important components of models of primate feeding systems at all levels, from the neuromechanical to the ecological. Chew cycle durations were estimated in 35 species of primates and analyzed in conjunction with data on morphological variables of the feeding system estimating moment of inertia of the mandible and force production capacity of the chewing muscles. Data on scaling of primate chew cycle duration were compared with the predictions of simple pendulum and forced mass,spring system models of the feeding system. The gravity-driven pendulum model best predicts the observed cycle duration scaling but isrejected as biomechanically unrealistic. The forced mass,spring model predicts larger increases in chew cycle duration with size than observed, but provides reasonable predictions of cycle duration scaling. We hypothesize that intrinsic properties of the muscles predict spring-like behavior of the jaw elevator muscles during opening and fast close phases of the jaw cycle and that modulation of stiffness by the central nervous system leads to spring-like properties during the slow close/power stroke phase. Strepsirrhines show no predictable relationship between chew cycle duration and jaw length. Anthropoids have longer chew cycle durations than nonprimate mammals with similar mandible lengths, possibly due to their enlarged symphyses, which increase the moment of inertia of the mandible. Deviations from general scaling trends suggest that both scaling of the jaw muscles and the inertial properties of the mandible are important in determining the scaling of chew cycle duration in primates. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source] Operation of an industrial steam reformer under severe condition: A simulation studyTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2008J. Shayegan Abstract A rigorous two-dimensional model is developed for simulating the operation of a less-investigated type steam reformer having a considerably lower operating Reynolds number, higher tube diameter, and non-availability of extra steam in the feed compared with conventional steam reformers. Simulation results show that reasonable predictions can only be achieved when certain correlations for wall to fluid heat transfer equations are applied. In all cases, strong radial temperature gradients inside the reformer tubes have been found. Furthermore, the results show how a certain catalyst loading profile will affect the operation of the reformer. Un modèle bidimensionnel rigoureux est mis au point pour simuler le fonctionnement d'un reformeur à vapeur d'un type qui a été moins étudié, ayant un nombre de Reynolds de fonctionnement bas, un diamètre de tube élevé et une non disponibilité de vapeur excédentaire dans l'alimentation comparativement aux reformeurs de vapeur classiques. Les résultats de simulation montrent que des prédictions raisonnables peuvent être obtenues seulement lorsque certaines corrélations pour les équations de transfert de chaleur de la paroi vers le fluide sont appliquées. Dans tous les cas, de forts gradients de température radiaux dans les tubes de reformeur ont été trouvés. En outre, les résultats montrent comment un certain profil de chargement de catalyseur influe le fonctionnement du reformeur. [source] | ||||||||||||||||