Nonlinear Regression Analysis Program Research Articles

Modeling of Thin Layer Drying Kinetics of Salted Fish Fillets (Tilapia Zilli) in a Direct Passive Solar Dryer.

An empirical thin layer drying model for modeling the salted fish filets in a direct passive solar dryer was developed. The experiment was conducted in a factorial form arranged in a completely randomized design (CRD) with three treatments replicated five times. The model got evolved from Wang and Singh model. The statistical analysis was done with a non linear regression analysis program (NLRP). From the result it is evident that the new model was found best to describe the drying process of salted fish filets over the conditions tested (temperature 20 to35.1 0 C, Relative Humidity54 to100% ). Results also showed that the new model in this work was the best in terms of explaining the drying kinetics of the fish fillets with χ 2 , SE R 2 , and P values ranging from, 2.22x10 -6 to 0.001176 ,0.008171 to 0.010844 ,0.9978 to 0.9981 and 0.0226 to 0.2151 respectively.

Nonlinear Regression Analysis for Programming and Engineering Application

Aiming at the calculating the flow of cutthroat flume in Hydraulic Engineering, the test data is processed through the nonlinear regression analysis program which is based on the principle of least square method. With 33 equations of various functions including linear, power function curve and exponential curve to be selected as the mathematical model, the regression analysis is taken through 33 equations. Comparing the regression coefficient from analysis, the optimal mathematical model is selected as the empirical formula, which has great significance in guiding the practical engineering.

Relationship between the γ and some parameters of Fe-based bulk metallic glasses

Abstract The relationship between γ (T x/(T g + T l)) of Fe-based bulk metallic glasses (BMGs) and three parameters (i. e., electronegativity difference, atomic size parameter and heat of mixing) is studied in this paper. The conclusion can be drawn from the available experimental data in the literature that parameter γ has a close correlation to three parameters in Fe-based BMGs. It can be expressed as follows: γ = 0.40334 − 0.20242 × Δx 2 − 0.1209 × δ2 + 3.7395 × 10−6 × ΔH 2. The function can be obtained by a nonlinear regression analysis program and it can be used to find new Fe-based BMGs alloys.

Molecular Basis of Glucagon-like Peptide 1 Docking to Its Intact Receptor Studied with Carboxyl-terminal Photolabile Probes

The glucagon-like peptide 1 (GLP1) receptor is a member of Family B G protein-coupled receptors and represents an important drug target for type 2 diabetes. Despite recent solution of the structure of the amino-terminal domain of this receptor and that of several close family members, understanding of the molecular basis of natural ligand GLP1 binding to its intact receptor remains limited. The goal of this study was to explore spatial approximations between specific receptor residues within the carboxyl terminus of GLP1 and its receptor as normally docked. Therefore, we developed and characterized two high affinity, full-agonist photolabile GLP1 probes having sites for covalent attachment in positions 24 and 35. Both probes labeled the receptor specifically and saturably. Subsequent peptide mapping using chemical and proteinase cleavages of purified wild-type and mutant GLP1 receptor identified that the Arg(131)-Lys(136) segment at the juxtamembrane region of the receptor amino terminus contained the site of labeling for the position 24 probe, and the specific receptor residue labeled by this probe was identified as Glu(133) by radiochemical sequencing. Similarly, nearby residue Glu(125) within the same region of the receptor amino-terminal domain was identified as the site of labeling by the position 35 probe. These data represent the first direct demonstration of spatial approximation between GLP1 and its intact receptor as docked, providing two important constraints for the modeling of this interaction. This should expand our understanding of the molecular basis of natural agonist ligand binding to the GLP1 receptor and may be relevant to other family members.

Conformational Mobility in the Active Site of a Heme Peroxidase

Conformational mobility of the distal histidine residue has been implicated for several different heme peroxidase enzymes, but unambiguous structural evidence is not available. In this work, we present mechanistic, spectroscopic, and structural evidence for peroxide- and ligand-induced conformational mobility of the distal histidine residue (His-42) in a site-directed variant of ascorbate peroxidase (W41A). In this variant, His-42 binds "on" to the heme in the oxidized form, duplicating the active site structure of the cytochromes b but, in contrast to the cytochromes b, is able to swing "off" the iron during catalysis. This conformational flexibility between the on and off forms is fully reversible and is used as a means to overcome the inherently unreactive nature of the on form toward peroxide, so that essentially complete catalytic activity is maintained. Contrary to the widely adopted view of heme enzyme catalysis, these data indicate that strong coordination of the distal histidine to the heme iron does not automatically undermine catalytic activity. The data add a new dimension to our wider appreciation of structure/activity correlations in other heme enzymes.

Observation of a hybrid random ping-pong mechanism of catalysis for NodST: a mass spectrometry approach.

An efficient enzyme kinetics assay using electrospray ionization mass spectrometry (ESI-MS) was initially applied to the catalytic mechanism investigation of a carbohydrate sulfotransferase, NodST. Herein, the recombinant NodST was overexpressed with a His(6)-tag and purified via Ni-NTA metal-affinity chromatography. In this bisubstrate enzymatic system, an internal standard similar in structure and ionization efficiency to the product was chosen in the ESI-MS assay, and a single point normalization factor was determined and used to quantify the product concentration. The catalytic mechanism of NodST was rapidly determined by fitting the MS kinetic data into a nonlinear regression analysis program. The initial rate kinetics analysis and product inhibition study described support a hybrid double-displacement, two-site ping-pong mechanism of NodST with formation of a sulfated NodST intermediate. This covalent intermediate was further isolated and detected via trypsin digestion and Fourier transform ion cyclotron resonance mass spectrometry. To our knowledge, these are the first mechanistic data reported for the bacterial sulfotransferase, NodST, which demonstrated the power of mass spectrometry in elucidating the reaction pathway and catalytic mechanism of promising enzymatic systems.

Model for the Anaerobic Growth of Aeromonas hydrophila K144

The combined effects of temperature (5 to 42°C), NaCl (0.5 to 4.5%), pH (5.3 to 7.3), and NaNO2 (0 to 200 μg/ml) on the anaerobic growth of Aeromonas hydrophila K144 were studied in brain heart infusion broth using a modified central composite design. Variable combinations were tested in triplicate anaerobic flasks (nitrogen atmosphere in sealed trypsinizing flasks); viable cell counts were made at intervals during incubation by surface plating on tryptic soy agar. Growth curves were generated using the Gompertz equation in conjunction with a nonlinear regression analysis program. Values for the four Gompertz parameters (A, C, B, and M) were obtained for the variable combinations tested. Using response surface techniques, regressions were performed on Ln (B), Ln (M), Sqrt (B), and Sqrt (1/M); quadratic and cubic equations containing the four variables of temperature, NaCl, pH, and NaNO2 were developed to yield predictive values for the B and M Gompertz values. Goodness of fit evaluation of the models was determined by R2 values. Comparison of predicted and observed values of B and M and evaluation of predicted lag and generation times indicated that the quadratic model gave the best fit. Overall, the variable combinations interacted to affect the generation and lag times. The results indicate that pH, salt level, and nitrite level can be manipulated to decrease the growth of A. hydrophila when combined with low temperature incubation and anaerobic conditions.

Multiple-dose non-linear regression analysis program. Aminoglycoside dose prediction.

The ability of a new multiple-dose non-linear regression analysis program to predict steady-state aminoglycoside peak and trough serum concentrations was evaluated. 30 patients receiving either amikacin (7), gentamicin (10) or tobramycin (13) were studied. A standard method of prediction which requires the collection of 3 or 4 serum samples during a dosing interval and a predictive method which relies upon population-based estimates of pharmacokinetic parameters were compared with the new approach which requires the collection of 2 serum samples. There were no significant differences between the methods which utilised serum concentration data with regard to predictive precision (mean prediction error of about 10%). These methods were more precise than the population-based method (p less than 0.01, mean prediction error 29.1%). None of the methods produced biased estimates. These results indicate that when the regression program is employed, valid estimates of pharmacokinetic parameters and prediction of steady-state serum concentrations can be obtained with fewer serum samples than have been recommended.

Statistical study of the model-independent method to describe the blood disappearance profile of intravenously administered drugs.

The applicability of the model-independent method to pharmacokinetic analysis was statistically studied. For this purpose, two kinds of data were used, i.e., plasma disappearance data for warfarin (a typical example of a triple-exponential decay) and for amoxicillin (double-exponential decay). By using statistical analysis with least-squares fitting (SALS), a nonlinear regression analysis program, curve fittings were carried out with respect to those data sets. In the case of the warfarin data, the triple-exponential equation was superior to the model-independent one in terms of both the residual sum of squares and an information criterion (AIC). However, very little difference between the two could be seen by eye when the results were drawn on graph paper. In the case of the amoxicillin data, the model-independent equation was statistically superior to the double-exponential one. The applicability of this model-independent method to pharmacokinetic analysis was thus confirmed.

Application of Nonlinear Regression Analysis to the use of Enzymes in The Determination of Substrate Concentrations

ABSTRACT A modified nonlinear regression analysis program (originally reported by R.G. Duggleby (1981) Anal. Biochem. 110, 9–18) in BASIC for microcomputers and a modified spectrophotometer are described. Their application in the routine determination of concentrations of certain substances by the use of specific enzymes is detailed. Results are given that show the utility of the system for glucose determination by the hexokinase reaction, and its lack of utility for lactate determination using lactate dehydrogenase.

Heterogeneous nucleation in the crystallization of polyolefins: Part 2. Kinetics of crystallization of nucleated polypropylene

The kinetics of isothermal crystallization of nucleated polypropylene has been determined by depolarization measurement or dilatometry. The depolarization measurement was preferred, being faster and more reliable than dilatometry. For the evaluation of the recorded crystallization curves a non-linear regression analysis program was used fitting the data into the Avrami equation. An indication is given of some limitations in the applicability of this equation. Various experimental conditions may cause deviations in the crystallization kinetics from this equation. It is shown that in the analysis according to Avrami induction times become irrelevant. The nucleation density is highly dependent on the temperature of crystallization. Although the nucleation is for the larger part instantaneous, the density increases roughly by a factor of 10 at an increase in the degree of supercooling of 4°C. The temperature of melting prior to crystallization has no influence on the nucleation density, provided orientations in the melt have been relaxed. The nucleation density found was not proportional to the content of nucleating agent in the concentration series used, probably owing to the methods of preparation.