Direct potentiometric determination of sodium ion in blood. II. Influence of cations.

1984 ◽  
Vol 30 (6) ◽  
pp. 865-870 ◽  
Author(s):  
P Bijster ◽  
K L Vink

Abstract We measured the emf of NaCl solutions (120-160 mmol/L), with and without the addition of KCl (5-20 mmol/L), CaCl2 (2-8 mmol/L), or MgCl2 (1-4 mmol/L). Measurements were made with a home-built cell in steady-state and with two commercial direct potentiometric analyzers about 20 s after the sample was introduced. We calculated the sodium ion activity in the mixed NaCl-KCl solutions according to different thermodynamic theories and found almost the same results. We conclude that the influence on the emf of physiological concentrations of these cations was negligible when emf measurements were made in steady-state with the home-built cell. Of the three added cations, K+ caused the greatest increase in apparent sodium ion activity (up to about 4%) when emf measurements were made with commercial analyzers, owing to low salt-bridge concentration and the short measuring time of about 20 s.

1988 ◽  
Vol 254 (4) ◽  
pp. E526-E531 ◽  
Author(s):  
J. Rosenblatt ◽  
R. R. Wolfe

The use of stable isotope tracers to calculate substrate kinetics in humans is favored over the use of radioactive isotopes because of their greater safety and versatility. However, potential complications not met when dealing with radioactive tracers are caused by 1) the natural occurrence of the stable isotope used as a tracer and 2) the necessity to administer the tracer in an amount that cannot be treated as "massless." We therefore found it desirable to derive a theoretically valid equation for calculating the rate of appearance, Ra, of a substrate under steady-state conditions using a stable isotope tracer. This theoretically valid equation yields results that differ from those of the equations conventionally used to calculate (endogenous) Ra in steady state. Quantitative determination of the error in one of these equations revealed that for tracers commonly used in metabolic studies the error is negligible, whereas the error made in the other equation is likely to be quite high in commonly encountered situations. Finally, to allow for proper use of different definitions of isotopic enrichment that have arisen from practical considerations, we use the results derived above to determine valid equations for Ra appropriate to the two prevalent definitions.


1967 ◽  
Vol 13 (3) ◽  
pp. 227-232 ◽  
Author(s):  
Joseph S Annino

Abstract A method has been developed for determination of sodium concentration (activity) in urine using a glass electrode designed to be especially sensitive to sodium ion activity. The urine is diluted 2:20 with Tris buffer (pH 8.0) and sodium activity measured by dipping a sodium electrode and calomel reference electrode in the diluted specimen and obtaining a millivolt reading with a sensitive pH meter. The sodium concentration is then calculated from a predetermined standard curve. Concentrations of 0-200 mEq./L. may be read using the same dilution. Blind comparisons of sodium concentrations obtained by flame photometry and by sodium ion electrode showed excellent agreement.


1964 ◽  
Vol 19 (5) ◽  
pp. 946-948 ◽  
Author(s):  
David J. Turell ◽  
James K. Alexander

One hundred and thirty determinations of metabolic rate at rest and during both steady and unsteady states of exercise have been made in human subjects. Calculation of the caloric expenditure by means of Weir's formula, by the Zuntz-Schumburg-Lusk table, and by the Cathcart-Cuthbertson table has revealed mean differences among these methods of less than 1%. The Weir formula may be utilized for all practical purposes in lieu of the tables, permitting elimination of the RQ correction factor, and thus simplifying the estimation of the energy cost of activity caloric expenditure; determination of metabolism; formula for caloric expenditure; steady-state, caloric measurement; unsteady-state, caloric measurement Submitted on December 16, 1963


2009 ◽  
Vol 40 (3) ◽  
pp. 561-573 ◽  
Author(s):  
Ueli Angst ◽  
Bernhard Elsener ◽  
Claus K. Larsen ◽  
Øystein Vennesland

Author(s):  
Stuart McKernan

For many years the concept of quantitative diffraction contrast experiments might have consisted of the determination of dislocation Burgers vectors using a g.b = 0 criterion from several different 2-beam images. Since the advent of the personal computer revolution, the available computing power for performing image-processing and image-simulation calculations is enormous and ubiquitous. Several programs now exist to perform simulations of diffraction contrast images using various approximations. The most common approximations are the use of only 2-beams or a single systematic row to calculate the image contrast, or calculating the image using a column approximation. The increasing amount of literature showing comparisons of experimental and simulated images shows that it is possible to obtain very close agreement between the two images; although the choice of parameters used, and the assumptions made, in performing the calculation must be properly dealt with. The simulation of the images of defects in materials has, in many cases, therefore become a tractable problem.


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