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At least 667 records · Page 37Linked to original sources
PubMed1995

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,4-anhydro-D-xylitol.

Described herein is a general method for the synthesis of all positional isomers of methylated and acetylated or benzoylated 1,4-anhydro-D-xylitol. The benzoates are generated simultaneously from 1,4-anhydro-D-xylitol by sequential partial methylation and benzoylation or sequential partial benzoylation and methylation. The individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation and acetylation provided the corresponding acetates. The 1H NMR spectra of the benzoates and the electron ionization mass spectra of the acetates and the tri-O-methyl derivative are reported herein as are the linear temperature programmed gas-liquid chromatography retention indices of the acetates and the tri-O-methyl derivative on three different capillary columns.

Acetates↗
PubMed1995

Synthesis and characterization of authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,4-anhydro-L-fucitol.

Described herein is the synthesis of all positional isomers of methylated and acetylated or benzoylated 1,4-anhydro-L-fucitol. The benzoates are generated simultaneously from 1,4-anhydro-L-fucitol by sequential partial methylation and benzoylation or sequential partial benzoylation and methylation. The individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation and acetylation provided the corresponding acetates. The 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tri-O-methyl derivative are reported herein as are the linear temperature programmed gas-liquid chromatography retention indices of the acetates and the tri-O-methyl derivative on three different capillary columns.

Acetates↗
PubMed1995

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,5-anhydro-D-glucitol.

Described is an efficient method for the synthesis of the sixteen positional isomers of methylated and acetylated or benzoylated 1,5-anhydro-D-glucitol. The compounds are generated simultaneously by partial methylation of 1,5-anhydro-D-glucitol and subsequent benzoylation, and the individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation of the latter and acetylation yielded the desired acetates. Reported are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tetra-O-methyl derivative. Also reported for the acetates and the tetra-O-methyl derivative are their linear temperature programmed gas-liquid chromatography retention indices on three different capillary columns.

Acetates↗
PubMed1995

Synthesis and characterization of authentic standards for the analysis of ribofuranose-containing carbohydrates by the reductive-cleavage method.

Described herein is the synthesis of all positional isomers of partially methylated and acetylated or benzoylated 1,4-anhydro-D-ribitol. The benzoates are generated simultaneously from 1,4-anhydro-D-ribitol by sequential partial methylation and benzoylation or sequential partial benzoylation and methylation. The individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation and acetylation provided the corresponding acetates. Reported herein are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tri-O-methyl derivative and also for the acetates and the tri-O-methyl derivative, their linear temperature programmed gas-liquid chromatography retention indices on three different capillary columns.

Acetates↗
PubMed1976

Improved method for measurement of serum levels of phenobarbital, carbamazepine, primidone and diphenylhydantoin by gas-liquid chromatography.

A gas-liquid chromatographic method for the simultaneous determination of phenobarbital, primidone, carbamazepine and diphenylhydantoin in human serum following therapeutic doses has been developed. After extraction with chloroform, the anticonvulsant drugs were methylated with phenyltrimethylammonium hydroxide in dimethylformamide at 85 degrees C for gas-liquid chromatography. Linear temperature programming of a 1% OV-17 column was used to achieve separation and quantitation. The procedure described in the present paper is relatively simple, highly specific and sufficiently sensitive for use in routine clinical assays.

Analysis of Variance↗
PubMed1980

A data validation program nucleus.

A data validation program designed for flexibility and user-modification is presented. It is assumed that the data to be validated consist of packets; i.e., groups of records with a common value in a record-linking field. Acceptance or rejection of data is on a packet basis. Individual field validation is specified by user-supplied tables. Multiple field checking and field interaction checking on both an intra-record and an inter-record basis may be specified by user-supplied subprograms. The program is written in PL/I using structured programming techniques. Further modifications such as record size and key positions are possible at pre-processor time.

Computers↗
PubMed1995

An exact mathematical expression for describing competitive binding of two different ligands to a protein molecule.

The dissociation constant for the binding of a spectroscopically invisible or non-radioactive ligand to its protein receptor can be determined in a competition experiment by using a structural analog that contains a reporter group. Many plotting and numerical analysis methods have been developed to calculate the binding constant of unlabeled ligand from the displacement experiments. However, a common problem with these plotting methods is that the equation transformations inevitably result in non-standard error distribution, and thus simple linear regression can not be used to extract correct values for the parameters. In the case of the numerical analysis methods, one would be faced with the possible existence of multiple solutions. In this paper, the exact mathematical expression for describing competitive binding of two different ligands to a protein molecule is presented in terms of the total concentrations of species in the system. Thus, using a commercially available non-linear regression program, all unknown parameters for describing this system can be determined by fitting the experimental data to the algebraically explicit equation without any data transformations. The distribution curves of all the species in the system can also be constructed with this equation. It is particularly useful for the cases in which the concentrations of all the species in the system are comparable to each other.

Binding, Competitive↗
PubMed1984

Evidence concerning a possible steady state rate equation for E. coli alkaline phosphatase.

Steady state data was obtained for alkaline phosphatase over a wide range of experimental conditions using two substrates, four inhibitors, two modifiers and several pH, ionic strength and temperatures values. The data was fitted by rational functions of degree 1:1, 2:2 and 3:3 using a non-linear regression program and then the F-test was used to assess the goodness of fit. A proportion of the curves could only be fitted by 2:2 functions but many of them could be adequately fitted by 1:1 functions. No statistically significant improvement in fit occurred with 3:3 functions. Data was simulated using a computer program to see what sort of curves could be generated by a two sites mechanism proposed for alkaline phosphatase and this study showed it is difficult to detect cubic terms in this rate equation. It was concluded that alkaline phosphatase does not obey Michaelis-Menten kinetics. Rather, the steady state data require a mechanism of at least second degree but do not exclude a rate equation of third degree.

Alkaline Phosphatase↗
PubMed1988

Comparison of an inductively coupled plasma-atomic emission spectrometry method for the determination of calcium, magnesium, sodium, potassium, copper and zinc with atomic absorption spectroscopy and flame photometry methods.

Serum calcium, magnesium, copper and zinc concentrations obtained from the analysis of 77 serum samples by inductively coupled plasma-atomic emission spectrometry (ICP-AES) are compared with the results obtained using atomic absorption spectroscopy (AAS). Similarly, serum sodium and potassium levels from the analysis of the same samples by ICP-AES are compared with the levels obtained by flame photometry. For each metal, we compare the results from both methods with a linear regression program that assumes error in both variables. The regression analysis shows that the ICP-AES method gives slightly higher calcium, copper, and zinc results and lower magnesium results than the AAS methods, and lower sodium and potassium results than the flame photometry method. Except for sodium, the correlation (r) between the results is very high (greater than or equal to 0.958), indicating that the ICP-AES results could be corrected to be equivalent to the atomic absorption or flame photometry results. The ICP-AES has the advantage of requiring less preparation and analysis time, and additional elements could be determined simultaneously in the same sample.

Blood Specimen Collection↗
PubMedDate not supplied

SEQUAL: an interactive computer program for sequential classification of biomedical data.

A computer program for sequential bayesian classification of patterns defined by integer and real-valued data is described. Classified patterns from a training sample are used to estimate the non-parametric (kernel) probability density functions and the a-priori class probabilities necessary to implement the bayesian classification. For each pattern and at each step in the sequential program, the 'best' feature to be measured at the next step is computed on the basis of the estimated misallocation error rate. The user can actually use the proposed feature or any other one; once the chosen feature has been measured, its value is used to allocate the pattern into the class with the highest conditional a-posteriori probability, according to the Bayes formula. The main feature of the program consists in the computation of the 'probability of reversal' at each step of the sequential procedure. The probability of reversal represents the probability that at the next step the pattern will be classified into a class different from the present one. The probability of reversal can be used as a stopping criterion, which is more efficient than other commonly used stopping rules, such as the a-posteriori Bayes probability or the estimated misallocation error rate. The program, available in FORTRAN 77 for a VAX/VMS machine, has been tested both on simulated and real data collected from patients suffering from various forms of hepatic disease.

Bayes Theorem↗
PubMed1989

Comparison of Bayesian with group sequential methods for monitoring clinical trials.

We describe some problems with applying methods based on classical sequential analysis to monitoring clinical trials. A Bayesian method is developed and the boundaries are compared with frequentist schemes. For the examples chosen, the Bayesian boundaries can be quite similar to those obtained from Pocock and O'Brien and Fleming (OBF) rules, depending on the choice of prior distribution. They converge less rapidly than OBF's but more rapidly than Pocock's. In general the Bayesian methods provide the same desirable features as frequentist methods, without sacrificing flexibility and simplicity of interpretation.

Bayes Theorem↗
PubMed1989

Analyses of group sequential clinical trials.

In the first part of this article the methodology of group sequential plans is reviewed. After introducing the basic definition of such plans the main properties are shown. At the end of this section three different plans (Pocock, O'Brien-Fleming, Koepcke) are compared. In the second part of the article some unresolved issues and recent developments in the application of group sequential methods to long-term controlled clinical trials are discussed. These include deviation from the assumptions, life table methods, multiple-arm clinical trials, multiple outcome measures, and confidence intervals.

Actuarial Analysis↗
PubMed1989

Kinetic studies of chloride inhibition in aspartate aminotransferase activity.

The inhibitive effects of chloride anion on the activity of mitochondrial aspartate aminotransferase (L-aspartate: 2-oxoglutarate-aminotransferase EC. 2.6.1.1.) from chicken (Gallus domesticus) and turkey (Maleagris gallopavo) were studied. Steady-state velocities were obtained from a wide range of chloride concentrations. The data were fitted by rational functions of 0:2 and 1:2 for chloride, using a non-linear regression program which guaranteed the fit. The goodness of fit was improved by the use of a computer program that combined model discrimination, parameter refinement and sequential design. It was concluded that chloride aspartate aminotransferase inhibition requires a minimum velocity equation of 1:2 with regard to chloride, and a plausible kinetic mechanism for this experimental result was proposed.

Animals↗
PubMed1996

Gas chromatographic determination of eugenol in ethanol extract of cloves.

An ethanolic extract of cloves was analyzed by gas chromatography directly to identify eugenol and other major phenolic compounds without previous separation of other components. Separation was performed on a fused-silica capillary column of 30 m x 0.53 mm I.D., 0.53 microns film thickness. The detector was a flame ionization detector. Helium gas at a flow-rate of 3 ml/min was used as a carrier gas. The analysis were performed with linear temperature programming. Nine components were detected and special attention was given to the major phenolic compound, eugenol.

Chromatography, Gas↗
PubMed2006

Evaluation of operating room suite efficiency in the Veterans Health Administration system by using data-envelopment analysis.

BACKGROUND: Operating room (OR) activity transcends single ratios such as cases/room, but weighting multiple inputs and outputs may be arbitrary. Data-envelopment analysis (DEA) is a novel technique by which each facility is analyzed by the weightings that optimize its score. METHODS: We performed DEA analysis of 23 Veterans Health Administration annual OR activity; 87,180 cases were performed, 24 publications generated, and 560 trainee-years of education delivered, in 168 ORs over 166,377 hours by 1,384 full-time equivalents of surgical and anesthesia providers and 523 nonproviders. RESULTS: Varying analyzed parameters produced similar efficiency rankings, with individual differences suggesting possible inefficiencies. We characterized returns to scale for efficient sites, suggesting whether patient flow might be efficiently further increased through these sites. We matched inefficient sites to similar efficient sites for comparison and suggested resource alterations to increase efficiency. CONCLUSIONS: Broader DEA application might characterize OR efficiency more informatively than conventional single-ratio rank ordering.

Anesthesiology↗