Differential Absorption Technique Research Articles

Chemical equilibrium constants by differential ultrasonic absorption

In 1953 Kurtze and Tamm observed a reduction of sound absorption in MgSO4 solutions upon the addition of NaCl. From this reduction it is possible to determine the concentration of (NaSO4) ion pairs. A new equilibrium dissociation constant KD=0.073 is obtained, considerably lower than the accepted value of KD=0.019. The differential ultrasonic absorption technique is a new independent approach to the study of chemical equilibria that has proved to be very useful for the study of a difficult unsymmetrical electrolyte. Two recent experimental papers using independent techniques, electrical conductance and potentiometric measurements, support the new value. The technique should be useful for the study of many other equilibria. [This paper represents results of research sponsored by the Office of Naval Research and the National Science Foundation Grant GA 18763.]

Detection Method of Ozone in Atmosphere Using Differential Absorption Technique with CO2 Laser

The measurement of the absorption lines of ozone using the emission lines of the (00°1–02°0) band of CO2 laser was discussed. As the result of experiment, it was made obvious that the absorption cross section of ozone pressurized up to 760 Torr was (2.4±0.08)×10-19 cm2 at the frequency of 1052.1956 cm-1 corresponding to the P(14) laser line of the (00°1–02°0) band. By the use of this value, the minimum detectable concentration of ozone was estimated for the long path absorption. Accordingly, it was concluded that the concentration of 0.1 ppm in ambient atmosphere would be able to be detected by using the laser power of only 0.3 µW for the path length of 500 m.

Remote measurement of NO2 emission from a chemical factory by the differential absorption technique

Using the differential absorption method the NO2 concentration within the plume of a smoke stack and over the area of a chemical factory was measured.

Detection of Prostaglandin Induction of Erythrocyte Sickling

Abstract Sickle cell crisis may be precipitated by pregnancy or infection, conditions in which prostaglandin concentrations can be elevated. We have investigated the effects of exogenous prostaglandins on whole blood and isolated, washed erythrocytes from patients with sickle cell anemia disease. Differential counting, light scattering, and optical absorption techniques indicate that prostaglandin E2 can induce and potentiate sickling of these cells under conditions of reduced oxygen tension. Absorption characteristics of sickle cell hemoglobin indicate that prostaglandin E2 affects hemoglobin only in an intact cell. These initial results suggest that prostaglandin E2 may represent a cofactor initiating or enhancing sickle cell crisis. A new application of a light-scattering technique appears a valuable method for continuous monitoring of the sickling process

Thermodynamics and kinetics of G·C base pairing in the isolated extra arm of serine-specific transfer RNA from yeast

The extra arm of serine-specific tRNA has been isolated and its helix-coil transition investigated. The oligonucleotide, which according to its clover-leaf structure contains 4 G·C base pairs, has a transition mid-point of 84±1° at pH 6.8 and an ionic strength of 0.11 M; the mid-point's ionic strength dependence is only 5° per factor of ten in the Na + concentration. The extra arm's helix-coil transition has a ΔH of 43.6±4 kcal/mole. Kinetic measurements show a negative activation energy for helix formation, which indicates that helix nucleation involves the formation of more than one base pair. Data from several defined double helices are used to correlate the G·C content in the melting regions of ribonucleotides with the dispersion of hypochromicity, as determined by a differential absorption technique.

The coupling of conformational transitions in alanine specific transfer ribonucleic acid from yeast studied by a modified differential absorption technique.

A high precision differential absorption technique has been developed for the detailed experimental analysis of the complex melting behaviour of specific tRNAs. This technique allows the resolution of overlapping transitions which have been observed in a study of the interaction of Mg2+ ions with tRNAAla (yeast). On the basis of these experimental observations a strong coupling between two adjacent transitions in tRNAAla is proposed and discussed with respect to the structure of tRNAAla. The sedimentation coefficient of tRNAAla as a function of temperature up to 80° has been studied in detail. The wavelength dependences of the hyperchromicities of various transitions in tRNA and tRNA half molecules are discussed with regard to A · U and G · C pairs melting in these processes. From a comparison of the melting behaviour of tRNAAla, tRNATyr, tRNASer, and tRNAPhe in the presence and the absence of Mg2+ ions it is shown that tRNAAla is best suited for detailed studies of conformational changes in tRNA.

Thermodynamic properties of the three conformational transitions of alanine specific transfer RNA from yeast

The melting behavior of alanine specific tRNA was studied by a modified differential absorption technique. It was found that the melting proceeds in three resolvable steps, 1, 2, 3. Steps 1 and 3 were interpreted as single processes, step 2 as two superimposed transitions. The corresponding reaction enthalpies were determined to be ΔH (1) = 40 ± 10, ΔH (2) = 2 · (65 ± 10) and ΔH (3) = 70 ± 10 kcal/mole, and are discussed on the basis of the “clover-leaf” model. Only the ionic strength dependence of steps 2 and 3 agrees with other double-stranded nucleic acids. Step 1 produces a smaller change in sedimentation coefficient than step 2.

Mesospheric electron number densities at 35°S latitude

The mean noon profile of mesopheric electron number density has been obtained at a location of 35°S, 173°E for the week preceding the total solar eclipse of May 31, 1965, and immediately after the eclipse. Values of electron number density increased monotonically, within the experimental errors of the order of 50%, from 85/cm³ at 70 km to 1200/cm³ at 90 km. Diurnal variations of nonsolar origin were detected, possibly owing to a pressure fluctuation. Data obtained by the radio-wave differential absorption technique using partial reflections were compared with data obtained by Faraday rotation techniques from a series of rocket firings conducted by National Aeronautics and Space Administration. The results obtained by the two techniques were in satisfactory agreement.

Chemical Use of the Absorption of Soft γ-Rays, β-Ray-excited X-Rays and K-Capture X-Rays. I. Improvement in Fundamental Technique and Introduction of a Differential Absorption Method

Abstract Studies for the improvement of fundamental techniques for the chemical use of the absorption of soft γ-rays, β-ray-excited X-rays and K-capture X-rays were undertaken. The exponential absorption curve, which is essential for the measurement of the accurate absorption coefficient and for many quantitative works, was obtained by the use of a proper detection method and the differential absorption technique, even in the presence of some photons having various energies. The relationship between the absorption coefficient thus obtained and the photon energy proved to agree with the theoretical result.