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At least 595 records · Page 33Linked to original sources
PubMed1980

A program library for computing the parameters of linear compartment models in pharmacokinetics.

A program library is presented with which explicit solutions of linear compartment models can be fitted to pharmacokinetic experimental data. Use is made of the fact that transport constants can be calculated from the numberical solution of such a problem without ambiguity. The non-linear regression is carried out using the Powell-method. A report of our experience with, e.g. choice of objective function, lag-time, accuracy of the numerical solution is included.

Computers↗
PubMed1988

Identification and rejection of outliers in enzyme kinetics.

A program (AICOUT) for the correct choice of the experimental value and weight for replicate enzyme kinetic determinations is given. It is based on the method of identification of outliers proposed by Kitagawa (Technometrics, 21 (1979) 193-199). The program is written in BASIC and FORTRAN77. The FORTRAN77 version of AICOUT program coupled to a FORTRAN77 version of the non-linear regression program previously published by Canela (Int J Biomed Comput, 15 (1984) 121-130) is given. This joint program leads to an improvement of precision and confidence in the estimated parameters when the suitable strategy is used. This strategy is as follows: (i) the experimental points are selected, (ii) several replicates of each point are performed, (iii) data are analyzed and outliers are rejected, (iv) normal or biweighted regression is carried out.

Algorithms↗
PubMed2004

Use of nonlinear programming to optimize performance response to energy density in broiler feed formulation.

A nonlinear programming optimization model was developed to maximize margin over feed cost in broiler feed formulation and is described in this paper. The model identifies the optimal feed mix that maximizes profit margin. Optimum metabolizable energy level and performance were found by using Excel Solver nonlinear programming. Data from an energy density study with broilers were fitted to quadratic equations to express weight gain, feed consumption, and the objective function income over feed cost in terms of energy density. Nutrient:energy ratio constraints were transformed into equivalent linear constraints. National Research Council nutrient requirements and feeding program were used for examining changes in variables. The nonlinear programming feed formulation method was used to illustrate the effects of changes in different variables on the optimum energy density, performance, and profitability and was compared with conventional linear programming. To demonstrate the capabilities of the model, I determined the impact of variation in prices. Prices for broiler, corn, fish meal, and soybean meal were increased and decreased by 25%. Formulations were identical in all other respects. Energy density, margin, and diet cost changed compared with conventional linear programming formulation. This study suggests that nonlinear programming can be more useful than conventional linear programming to optimize performance response to energy density in broiler feed formulation because an energy level does not need to be set.

Animal Feed↗
PubMed1991

Gas chromatographic system for the identification of halogenated pesticides by retention indices using n-alkanes as standards.

A gas chromatographic system for the evaluation of linear temperature-programmed retention indices allowing n-alkanes to be adopted as the reference retention markers for any type of analyte, irrespective of the atoms present in their molecules, is described. It is based on the simultaneous use of two different detectors (a flame ionization detector and a specific detector suitable for the sample components), both connected (in parallel) to the same column outlet. The performance of this system has been tested by measuring the retention indices of fifteen chlorinated pesticides under conditions of linear programming temperature, by adopting an electron-capture detector as the specific detector. The reliability of the retention indices thus determined has been proven by verifying that they can be reproduced under different chromatographic conditions.

Alkanes↗
PubMed1993

A PC program to aid in the choice of the design matrix in multiple linear regression.

A PC program, DESIGN, which can be used to evaluate and compare alternative choices of the design matrix, X, in the general linear model y = X beta + epsilon is described, illustrated and made available to interested readers. Given X, the program (1) computes various measures of the 'stability' of X and X'X and (2) determines the precisions of estimates of the model parameters, beta, and of predicted values, ŷ, at the given design points. Examples focusing on polynomial regression are given.

Data Interpretation, Statistical↗
PubMed2002

A comparison of linear and daily undulating periodized programs with equated volume and intensity for strength.

The purpose of this study was to compare linear periodization (LP) and daily undulating periodization (DUP) for strength gains. Twenty men (age = 21 +/- 2.3 years) were randomly assigned to LP (n = 10) or DUP (n = 10) groups. One repetition maximum (1RM) was recorded for bench press and leg press as a pre-, mid-, and posttest. Training involved 3 sets (bench press and leg press), 3 days per week. The LP group performed sets of 8 RM during weeks 1-4, 6 RM during weeks 4-8, and 4 RM during weeks 9-12. The DUP group altered training on a daily basis (Monday, 8 RM; Wednesday, 6 RM; Friday, 4 RM). Analysis of variance with repeated measures revealed statistically significant differences favoring the DUP group between T1 to T2 and T1 to T3. Making program alterations on a daily basis was more effective in eliciting strength gains than doing so every 4 weeks.

Adolescent↗
PubMed1989

BOOMER, a simulation and modeling program for pharmacokinetic and pharmacodynamic data analysis.

BOOMER is an improved version of an earlier non-linear regression program, MULTI-FORTE. Rather than the user writing a FORTRAN subroutine, models are defined by means of the parameters which make up the model. Models based on differential equations are specified by means of zero-order, first-order, or Michaelis-Menten-type rate constants. Doses (in units of mass) are translated into the usually observed concentration units by a reciprocal volume parameter. Integrated equation models are specified in terms of baseline terms, exponential terms, or the emax function with slope term as described by the Hill equation. Time points can be specified as parameters to specify dose times, infusion start/stop times, or lag times. With careful selection of parameters quite complex models can be specified. The user has a choice of differential equation solvers and fitting algorithms.

Computer Simulation↗
PubMed2000

A recurrent neural network for solving linear projection equations.

Linear projection equations arise in many optimization problems and have important applications in science and engineering. In this paper, we present a recurrent neural network for solving linear projection equations in real time. The proposed neural network has two layers and is amenable to parallel implementation with simple hardware. In the theoretical aspect, we prove that the proposed neural network can converge globally to the solution set of the problem when the matrix involved in the problem is positive semidefinite and can converge exponentially to a unique solution when the matrix is positive definite. In addition, we analyze the stability of the related dynamic system in detail. As an application, we show that the proposed neural network can be used directly to solve linear and convex quadratic programming problems and linear complementary problems with positive semidefinite matrices. The validity and transient behavior of the neural network are demonstrated by using three numerical examples.

Linear Models↗
PubMed1996

A novel two-site binding equation presented in terms of the total ligand concentration.

For the most frequently used two-site model, an exact binding equation is presented in terms of the total ligand concentration. This equation has been extended to analyze the spectroscopic titration experiment where the dilution of protein solution cannot be neglected, the displacement study, and the effect of non-specific binding. Thus, with a non-linear regression program, all unknown binding parameters can be determined correctly by fitting these equations to the experimental data without any data transformation. As an example of the use of the new equations, the experimental data for receptor-insulin binding were taken from literature and reanalyzed by using a non-linear regression data analysis program.

Binding Sites↗
PubMed2003

A comparison of linear and daily undulating periodized programs with equated volume and intensity for local muscular endurance.

The purpose of this study was to compare linear periodization (LP), daily undulating periodization (DUP), and reverse linear periodization (RLP) for gains in local muscular endurance and strength. Sixty subjects (30 men, 30 women) were randomly assigned to LP, DUP, or RLP groups. Maximal repetitions at 50% of the subject's body weight were recorded for leg extensions as a pretest, midtest, and posttest. Training involved 3 sets (leg extensions) 2 days per week. The LP group performed sets of 25 repetition maximum (RM), 20RM, and 15RM changing every 5 weeks. The RLP group progressed in reverse order (15RM, 20RM, 25RM), changing every 5 weeks. The DUP group adjusted training variables between each workout (25RM, 20RM, 15RM repeated for the 15 weeks). Volume and intensity were equated for each training program. No significant differences were measured in endurance gains between groups (RLP = 73%, LP = 56%, DUP = 55%; p = 0.58). But effect sizes (ES) demonstrated that the RLP treatment (ES = 0.27) was more effective than the LP treatment (control) and the DUP treatment (ES = -0.02) at increasing muscular endurance. Therefore, it was concluded that making gradual increases in volume and gradual decreases in intensity was the most effective program for increasing muscular endurance.

Adult↗
PubMed1986

MULTI-FORTE, a microcomputer program for modelling and simulation of pharmacokinetic data.

MULTI-FORTE is an expanded version of the MULTI non-linear fitting programs written by Yamaoka et al. The functions of the three original programs (including Gauss-Newton and Simplex fitting algorithms) have been combined and translated into FORTRAN 77 on the Macintosh computer for both speed and convenience. Models can be described in integrated equation form or as a system of differential equations. Bayesian estimation is also available. Improved numerical integration routines have been added including methods suitable for systems of 'stiff' differential equations (Fehlberg's 4/5 Runge-Kutta method and Gear's DIFSUB subroutine). MULTI-FORTE is a user-friendly program taking data from keyboard or disk file to produce output on screen, printer, or disk file in tables or printer-type plots.

Computer Simulation↗
PubMed2005

Simultaneous liquid chromatographic determination of doxorubicin and its major metabolite doxorubicinol in parrot plasma.

A new microscale method is reported for the determination of doxorubicin and its active metabolite, doxorubicinol, in parrot plasma. Sample workup involved acetonitrile protein precipitation, ethyl acetate extraction, followed by back extraction into HCl. Separations were achieved on a phenyl-hexyl column at 30 degrees C using acetonitrile (17%, v/v) in 0.01 M orthophosphoric acid (83%, v/v) delivered via a linear flow program. Fluorometric detection wavelengths were 235 nm (excitation) and 550 nm (emission). Calibration plots were linear (r2>0.999), and recoveries were 71-87% from 20 to 400 ng/mL. Assay imprecision was <or=8.5% and inaccuracy was <or=6.3%. The limit of quantification was 25 ng/mL.

Animals↗
PubMed1998

Discrimination between native and intentionally misfolded conformations of proteins: ES/IS, a new method for calculating conformational free energy that uses both dynamics simulations with an explicit solvent and an implicit solvent continuum model.

A new method for calculating the total conformational free energy of proteins in water solvent is presented. The method consists of a relatively brief simulation by molecular dynamics with explicit solvent (ES) molecules to produce a set of microstates of the macroscopic conformation. Conformational energy and entropy are obtained from the simulation, the latter in the quasi-harmonic approximation by analysis of the covariance matrix. The implicit solvent (IS) dielectric continuum model is used to calculate the average solvation free energy as the sum of the free energies of creating the solute-size hydrophobic cavity, of the van der Waals solute-solvent interactions, and of the polarization of water solvent by the solute's charges. The reliability of the solvation free energy depends on a number of factors: the details of arrangement of the protein's charges, especially those near the surface; the definition of the molecular surface; and the method chosen for solving the Poisson equation. Molecular dynamics simulation in explicit solvent relaxes the protein's conformation and allows polar surface groups to assume conformations compatible with interaction with solvent, while averaging of internal energy and solvation free energy tend to enhance the precision. Two recently developed methods--SIMS, for calculation of a smooth invariant molecular surface, and FAMBE, for solution of the Poisson equation via a fast adaptive multigrid boundary element--have been employed. The SIMS and FAMBE programs scale linearly with the number of atoms. SIMS is superior to Connolly's MS (molecular surface) program: it is faster, more accurate, and more stable, and it smooths singularities of the molecular surface. Solvation free energies calculated with these two programs do not depend on molecular position or orientation and are stable along a molecular dynamics trajectory. We have applied this method to calculate the conformational free energy of native and intentionally misfolded globular conformations of proteins (the EMBL set of deliberately misfolded proteins) and have obtained good discrimination in favor of the native conformations in all instances.

Computer Simulation↗
PubMed1995

A PC program for unbiased and predictive linear and quadratic discriminant analysis.

Discriminant analysis plays an important role in biological and medical research. The most popular methods of discrimination in practical applications are parametric methods like linear and quadratic discriminant analysis. However, there exist modifications of these approaches, namely unbiased and predictive discriminant analysis, which lead to reduced error rates in certain situations. In this paper a menu-driven, user-friendly PC program written in Borland Pascal 7.0 is introduced which performs unbiased and predictive linear and quadratic discriminant analysis.

Bias↗
PubMed2005

Simultaneous determination of sildenafil, vardenafil and tadalafil as forbidden components in natural dietary supplements for male sexual potency by high-performance liquid chromatography-electrospray ionization mass spectrometry.

A high-performance liquid chromatographic method coupled with ultraviolet detection and electrospray ionization mass spectrometry (HPLC-UV-ESI-MS) was developed for simultaneous determination of banned additives-sildenafil, vardenafil and tadalafil in dietary supplements for male sexual potency. The separation was achieved on a C18 column with acetonitrile and aqueous solution (20 mmol ammonium acetate, 0.2% formic acid) as mobile phase at a flow rate of I ml/min with a linear gradient program. UV detection was at 292 nm. Identification of drugs was accomplished using ESI-MS. Good linearity between response (peak area) and concentration was found over a concentration range of 0.8-80 microg/ml for sildenafil; 2.25-225 microg/ml for vardenafil; and 1.1-110 microg/ml for tadalafil, with regression coefficient is better than 0.999. The recovery of the method ranged from 93.3 to 106.1%, and the relative standard deviation varied from 2.0 to 5.6% (n = 6). The method has been successfully applied to the analysis of practical samples of natural dietary supplements.

Carbolines↗
PubMed2004

Simultaneous determination of the major isosteroidal alkaloids and their glucosides in the bulbs of Fritillaria by high performance liquid chromatography coupled with evaporative light scattering detection.

AIM: To establish an HPLC-ELSD method for the simultaneous determination of five major bioactive isosteroidal alkaloids and gluco-alkaloids in the bulbs of Fritillaria namely peimissine, imperialine, sinpeinine A, imperialine-3 beta-glucoside and yibeinoside A. METHODS: A Nova-Pak C18 column (150 mm x 3.9 mm ID) was used. The chromatography was carried out with a linear gradient programming. The mobile phase was acetonitrile-water (containing 0.1% diethylamine) and the flow rate was 1.0 mL.min-1. RESULTS: The linear range of peimissine was 13.1-288.2 mg.L-1 (r2 = 0.9975), imperialine-3 beta-glucoside 7.7-169.4 mg.L-1 (r2 = 0.9993), yibeinoside A 7.3-160.6 mg.L-1 (r2 = 0.9997), imperialine 16.5-363.0 mg.L-1 (r2 = 0.9992), sinpeinine A 8.7-191.4 mg.L-1 (r2 = 0.9942). CONCLUSION: The method is accurate with overall intra- and inter-day variation less than 5% and recovery more than 95%. The method was successfully applied to analyze five major bioactive alkaloids and gluco-alkaloids in three Fritillaria bulbs.

Alkaloids↗