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112 results on '"Nahum, Avi"'

13. Effect of a nasogastric tube on esophageal pressure measurement in normal adults

Author

Niknam, Jamshid, Chandra, Amitt, Adams, Alexander B., Nahum, Avi, Ravenscraft, Sue A., and Marini, John J.

Subjects
Respiration -- Measurement, Esophagus -- Measurement, Health, Measurement
Abstract

We studied the correspondence betwen fluctuations of esophageal pressure measured before and after placement of a nasogastric (NG) tube in six normal volunteers. Flow, airway pressure, and esophageal pressure data [...]

Published
1994

19. Increased hydrogen peroxide in the expired breath of patients with acute hypoxemic respiratory failure

Author

Sznajder, J. Iasha, Fraiman, Ana, Hall, Jesse B., Sanders, William, Schmidt, Gregory, Crawford, Gregory, Nahum, Avi, Factor, Phillip, and Wood, Lawrence D.H.

Subjects
Respiratory insufficiency, Metabolites, Hydrogen peroxide, Acute respiratory distress syndrome, Health, Diseases
Abstract

Acute hypoxemic respiratory failure (AHRF) can result from diverse lung insults. Toxic oxygen metabolites have been implicated in this clinical condition and in animal models of pulmonary edema. Hydrogen peroxide [...]

Published
1989

49. High-performance displacement chromatography

Author

Horváth, Csaba, Nahum, Avi, and Frenz, John H.

Abstract

The potential of the displacement mode of liquid chromatography for preparative-scale separations has been investigated by using microparticulate packed columns and instrumentation typically employed in analytical high-performance liquid chromatography (HPLC). Although the physico-chemical basis of the technique has long been established, its development was handicapped by lack of efficient chromatographic systems and suitable tools to monitor column effluent and gather data required for analysis and design of the displacement chromatographic process and for selection of suitable displacers. The availability of novel solid stationary phases with adequate properties to facilitate rapid sorption kinetics, the possibility of monitoring the effluent of the “fractionator” liquid chromatograph by an auxiliary ”analyzer“ unit as well as the relatively easy evaluation of appropriate adsorption isotherms by using the HPLC equipment, however, provide a basis to advance the displacement mode of liquid chromatography for preparative separations with analytical columns. After a brief review of the principles of the technique the dual chromatographic system used in the experiments for fractionation and analysis is described. Expressions for the efficiency of separation are given and factors affecting the development of the “displacement train” containing the separated feed components are enumerated. The interplay between the nature and concentration of displacer, the column length, amount of feed, flow-rate as well as the nature and concentration of the components of the mixture to be fractionated is discussed qualitatively. Fractionation of mixtures containing phenolic compounds or adenosine and inosine on columns packed with octadecyl-silica bonded phases (reversed-phase chromatography) is used to exemplify the effect of the operating conditions on the afficacy of the separation. The results are related to the adsorption isotherms of the substances that were measured by frontal analysis and found to follow the Langmuir model. The results suggest that upon accumulation of a sufficient amount of data on adsorptivities in chromatographic systems of interest high-performance displacement chromatography offers a promising approach to the use of ubiquitous HPLC equipment for preparative-scale separations with analytical columns.

Published
1981
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