Home About us Contact
|
Home About us Contact | ||
|
|
||
Graphical Methods (graphical + methods)
Selected AbstractsWater sorption kinetics in light-cured poly-HEMA and poly(HEMA- co -TEGDMA); determination of the self-diffusion coefficient by new iterative methodsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Irini D. Sideridou Abstract The present investigation is concerned with the determination of self-diffusion coefficient (D) of water in methacrylate-based biomaterials following Fickian sorption by two new methods: the Iterative and the Graphical methods. The D value is traditionally determined by means of the initial slope of the corresponding sorption curve and the so-called Stefan's approximation. The proposed methods using equations without approximations and data resulting from the whole sorption range reach to accurate values of D, even when the sorption curve does not present an initial linear portion. In addition to D, the Graphical method allows the extrapolation of the mass of the sorbed water at equilibrium (M,), even when the equilibrium specimen's mass fluctuates around its limited value (m,). The test of the proposed procedures by means of ideal and Monte Carlo simulated data revealed that these methods are fairly applicable. The obtained D values compared with those determined by means of the Stephan's method revealed that the proposed methods provide more accurate results. Finally, the proposed methods were successfully applied to the experimental determination of the diffusion coefficient of water (50°C) in the homopolymer of 2-hydroxyethyl methacrylate (HEMA) and in the copolymer of HEMA with triethylene glycol dimethacrylate (98/2 mol/mol). These polymers were prepared by light curing (, = 470 nm) at room temperature in presence of camphorquinone and N,N -dimethylaminoethyl methacrylate as initiator. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Effect of partial recording protocols on severity estimates of periodontal diseaseJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 8 2008Albert Kingman Abstract Objectives: The study aim was to assess bias magnitudes of periodontal disease severity estimates for specific partial recording protocols (PRPs) in epidemiological studies. Material and Methods: Estimates of mean clinical attachment loss (MCAL) and mean probing pocket depth (MPPD) were derived for 20 different PRPs using full-mouth periodontal data from 1437 dentate Brazilian subjects 14,103 years old having at least four teeth. Biases, relative biases and intra-class correlations for all PRPs were evaluated. Graphical methods were used to assess how well the PRP-based estimates agreed with full-mouth scores across levels of disease. Results: Slightly higher levels of disease were evidenced on lingual than on buccal sites. Seven multi-site PRPs and the Ramfjörd PRP produced small biases in MPPD (,0.17 to 0.04 mm) and MCAL with relative biases under 8% and 4% in absolute value for MPPD and MCAL, respectively. Biases for full- and random half-mouth-based PRPs were similar. The three-site random half-mouth MB,B,DL and the Ramfjörd PRPs produced the smallest biases, with relative biases <3% in absolute value for MPPD and MCAL. Conclusions: Bias for MPPD or MCAL estimates varies by site type, number of sites per tooth and number of quadrants included in the PRP. [source] A computer method based on simulated annealing to identify aquifer parameters using pumping-test dataINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2008Yen-Chen Huang Abstract Conventional graphical or computer methods for identifying aquifer parameters have their own inevitable limitations. This paper proposes a computer method based on a drawdown model and a heuristic approach of simulated annealing (SA) to determine the best-fit aquifer parameters of the confined and unconfined aquifer systems. The drawdown model for the confined aquifer is the Theis solution and the unconfined aquifer is the Neuman solution. The estimated results of proposed method have better accuracy than those of the graphical methods and agree well with those of the computer methods based on the extended Kalman filter and Newton's method. Finally, the sensitivity analyses for the control parameters of SA indicate that the proposed method is very robust and stable in parameter identification procedures. Copyright © 2007 John Wiley & Sons, Ltd. [source] Influence of the cocatalyst structure on the statistical copolymerization of methyl methacrylate with bulky methacrylates using the zirconocene complex Cp2ZrMe2JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2005Konstantinos Kostakis Abstract Statistical copolymers of methyl methacrylate with cyclohexyl and trimethylsilyloxy ethyl methacrylate were synthesized with two different catalytic systems based on the zirconocene complex Cp2ZrMe2. The reactivity ratios of methyl methacrylate and these methacrylates were calculated with the Finemann,Ross, inverted Finemann,Ross, and Kelen,Tüdos graphical methods. The structural parameters of these copolymers were estimated from the calculation of the dyad monomer sequence fractions. Two different borate cocatalysts were employed, and their effect on the copolymerization process is discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3305,3314, 2005 [source] Zirconocene-catalyzed copolymerization of methyl methacrylate with other methacrylate monomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2004Giorgos Karanikolopoulos Abstract Statistical copolymers of methyl methacrylate (MMA) with n -butyl-, s -butyl, t -butyl-, n -hexyl-, decyl-, stearyl-, allyl-, trimethylsilyl- and trimethylsilyloxyethyl methacrylate were prepared by zirconocene-catalyzed copolymerization. The reactivity ratios of MMA copolymers with butyl-, hexyl-, and stearyl methacrylate were estimated using the Finemann,Ross, the inverted Finemann,Ross, and the Kelen,Tüdos graphical methods. Structural parameters of the copolymers were obtained from the calculated dyad sequences, derived by using the reactivity ratios. The effect of the nature of the methacrylate ester group and the catalytic system used on the copolymer structure is discussed. The glass-transition temperature (Tg) values of MMA copolymers with butyl- and hexyl methacrylate were measured and examined in the frame of several theoretical equations, allowing the prediction of these Tg values. The best fit was obtained using Barton and Johnston equations, taking the monomer sequence distribution of the copolymers into account. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3761,3774, 2004 [source] Collaboration between the top knowledge management and intellectual capital researchersKNOWLEDGE AND PROCESS MANAGEMENT: THE JOURNAL OF CORPORATE TRANSFORMATION, Issue 4 2006Ronald Dattero Recently, Serenko and Bontis published a meta-review of the knowledge management (KM) and intellectual capital (IC) literature that identified the 64 most productive KM/IC researchers. In this paper, exploratory data analysis using graphical methods and measures is performed on the collaboration patterns of these top 64 KM/IC researchers, and the resulting collaboration patterns are discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source] Kinetic analysis of bacterial bioluminescence in water,organic mediaLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 4 2001I. E. Sukovataya Abstract The interaction of luciferases from two types of luminous bacteria, Photobacterium leiognathi and Vibrio harveyi, with their substrates [the photorecovered FMNH2 and long-chain aldehydes,decanal (C10), dodecanal (C12) and tetradecanal (C14)] in water,organic media was analysed using kinetic graphical methods. Moderate concentrations of organic solvents have been demonstrated to activate the bioluminescence, while higher concentrations inhibit it. The interactions of these effectors with luciferases show different types of kinetics, which depend on concentrations of solvents, kinds of enzymes and substrates. The apparent value of the Michaelis constant, Km, for C14 of both luciferases and for C10 of luciferase V. harveyi is enhanced with increasing concentration of the organic solvent, but Km for C12 and C10 of luciferase P. leiognathi decreases. Obviously, at the specific binding of aldehydes with luciferases in the first case, hydrophobic interactions are realized, but in second, the electrostatic interactions are realized. The series of changes in parameters of bioluminescence reaction catalysed by different luciferases is obviously determined by their structural peculiarities. Copyright © 2001 John Wiley & Sons, Ltd. [source] Latent Class Model Diagnosis from a Frequentist Point of ViewBIOMETRICS, Issue 1 2003Anton K. Formann Summary. This is in response to Garrett and Zeger (2000, Biometrics56, 1055,1067) who, within the Bayesian framework, developed mainly graphical methods for latent class model diagnosis. Possible problems with this approach, and with its application to both generated and empirical data, are pointed out. The impact of the proposed tools cannot be understood by their reader, as no comparisons are made to results obtainable using established methods for latent class model diagnosis; this applies especially to overall goodness-of-fit tests, for which alternatives (bootstrap, Rudas-Clogg-Lindsay index of fit) are mentioned. Further, in one case of generated data, the methods proposed by Garrett and Zeger seem to give problematic results as to identifiability; in the case of the empirical data on major depression, they lead to accepting a suboptimal three-class model. In the latter case, one can be rather sure that an identifiable, well-fitting latent class model could have been identified,if Garrett and Zeger had also considered restricted latent class models. [source] | ||||||||||