Scintillation Method Research Articles

Tritium and14C counting in tissue samples by using liquid scintillation method

The combustion method has been modified to increase the recovery of tritiated water after combustion of a tritium-labeled tissue sample. This was accomplished by cooling the bottom of the combustion flask in a dry ice-acetone bath while irradiating the top with an infrared lamp. The procedure resulted in at least 92% to 102% recovery of the tritiated water. The NCS solubilizer was found to be superior to hyamine for solubilizing(14)C labeled tissue samples. The samples yielded light yellow-colored solutions when incubated for 15 hr at 50-55C. The counting efficiency of this solution was 75% or higher.

RADIOASTRONOMICAL INVESTIGATIONS OF THE INHOMOGENEOUS STRUCTURE OF THE NEAR-SOLAR PLASMA

CONTENTS I. Introduction 424 II. Results of Study of the Solar Supercorona by the Transmission Method 425 1. Characteristics of Inhomogeneities Within the Distance Range r = (5–60)R 425 2. Influence of Scattering of Waves in the Solar Supercorona on the Observed Dimensions and Shape of the Discrete Sources of Emission 426 3. Model of Two-component Structure of the Sun's Supercorona 427 III. Study of Interplanetary Plasma by the Radio Scintillation Method 428 1. Observations of Interplanetary Scintillators 428 2. Method of Calculating the Electron Densities from Radio-Scintillation Data 429 3. Description of Radio-wave Scattering with the Aid of the Theory of the Phase Screen 430 4. Radioastronomical Observations of Solar Wind 431 5. Interpretation of Experimental Data 431 IV. Nature of the Inhomogeneous Structure of the Near-Solar Plasma 432 Conclusion 433 Cited Literature 434

The Determination of Formaldehyde in Cellulose Formals and. Methylated Cellulose Formals

It is shown that only Schiff's method is suitable for the determination of formaldehyde in methylated cellulose formals. These are intermediates in the elucidation of the struc ture of cotton cross-linked with formaldehyde. Some modifications of the usual pro cedure are recommended to obtain an accuracy of 3% relative to the amount of formaldehyde present. The modified Schiff's method was standardized with cellulose formals containing C14-formaldehyde whose activity was determined by ionization chamber assay after combustion to CO2. A routine determination of C14-formaldehyde in cellulose formals by the liquid scintillation method is also described.

A test for dispersion in F-region drifts observed by the radio star scintillation method

Records of scintillations of the source Cassiopeia A made on 38 Mc/s using three spaced interferometers have been analysed to determine whether Fourier components of different frequencies give different values of drift velocity. Such an effect is found to occur, and in most cases the speed of drift increases with frequency, while the direction of drift does not change. This effect is related to a systematic ‘skewness’ of the cross-correlation functions. The dispersion could be produced by the propagation of some type of dispersive wave through the F-region of the ionosphere, but it is considered more likely that it is produced by a variation of drift velocity along the line of sight.

The determination of doubly labeled artificial soil in detergency studies

AbstractA liquid scintillation method for the determination of carbon‐14 and tritium labeled soil on white fabric has been developed. The method involves the use of an external standard to determine the counting efficiency for each isotope. The requirement that these determinations be made on swatches of fabric complicates the analysis because of their variable antiquenching effect. The method has been appied to cotton, Dacron, nylon, and Dacron/cotton.A computer program has been written which accepts the raw counting data and performs all necessary calculations, printing out the data in a convenient form. The great convenience of the method has encouraged its application to large scale screening studies without sacrificing the precision, accuracy, or selectivity normally associated with small model systems.

Polymerization kinetics in highly viscous media

AbstractThe influence of the viscosity of the reaction medium on the rate of polymerization of styrene has been examined by adding different amounts of inert polystyrene to pure monomer and its solutions in benzene. Azobisisobutyronitrile was decomposed photochemically (λ = 365 mμ) at 25°C. or thermally at 70°C.; its rate of decomposition was followed by ultraviolet spectrometry. The rate of formation of dimethyl‐N‐cyanoisopropylketenimine (DKI) was followed by infrared spectrometry (2020 cm.−1). The initiation efficiency was determined by the scintillation method with the use of a 14Clabeled initiator. The rate of polymerization was followed dilatometrically. An increase of viscosity does not affect the rate of decomposition of the initiator; on the contrary, during the photochemical decomposition, it causes an increase of DKI concentration and an appreciable decrease of efficiency (from 0.51 to 0.30). From the point of view of the rate of photopolymerization, an increase of viscosity causes a decrease in the order of the reaction with respect to the initiator (from 0.5 to 0.3) and an increase with respect to monomer from 1.5 to 2. These results are interpreted on the basis of a decrease of termination rate constant between two growing chains in favor of a termination reaction between a growing chain and a primary radical. These effects, due to an increase of the viscosity of the solution, on the initiation and termination reactions influence the rate of polymerization in opposite direction and compensate each other to approximatively 25%.

A liquid scintillation method for measuring carbon-14 uptake in photosynthesis.

THE accurate determination of the radioactivity of stock sodium carbonate solutions and the correction of the radioactivity of membrane filtered algae to zero thickness are two of the greatest barriers to accurate productivity measurements using carbon-14.

Half-life and specific activity of 99Tc

The half-life and specific activity of 99Tc were redetermined by measuring the activity of a known weight (determined coulometrically) of 99Tc by a liquid scintillation method and found to be 2·14(±0.·05) × 10 5 years and 3·75(±0·11) × 10 4 disintegration/min per μg respectively. These results are in excellent agreement with previous values.

Liquid scintillation method for determination of solvent-extracted phosphorus-32 in foods

A method for solvent extraction of radioactive phosphorus as phospho-molybdic acid in foods is described. The use of a carrier can be eliminated due to the quantity of the stable element present in foods. The use of a liquid scintillation technique for counting is discussed, showing the effective elimination of color and chemical quench. The efficiency resulting from the liquid scintillation method of counting makes possible the detection of 10 -5 μc levels of activity in the original sample.

Sensitivity of scintillation method in gamma-ray flaw detection

Sensitivity of scintillation method in gamma-ray flaw detection

Thin-Layer Chromatographic Stability Assay for C14-Labeled Steroid in a Cream

The acetonide of 6α-fluoro-16α-hydroxyhydrocortisone, prepared from C14-labeled acetone, was formulated as a cream. Initial assays were made by a conventional tetrazolium method and also by a thin-layer chromatographic separation and subsequent scintillation measurement of the C14-labeled steroid. The cream samples were aged under accelerated conditions, and subsequent assays by the two methods were compared to the initial results. Small assay interferences caused by the aging of the formulation were demonstrated on the tetrazolium method. The techniques used illustrated advantages of the thin-layer chromatographic scintillation method for the early evaluation of a proposed stability method for a cream formulation. The acetonide of 6α-fluoro-16α-hydroxyhydrocortisone, prepared from C14-labeled acetone, was formulated as a cream. Initial assays were made by a conventional tetrazolium method and also by a thin-layer chromatographic separation and subsequent scintillation measurement of the C14-labeled steroid. The cream samples were aged under accelerated conditions, and subsequent assays by the two methods were compared to the initial results. Small assay interferences caused by the aging of the formulation were demonstrated on the tetrazolium method. The techniques used illustrated advantages of the thin-layer chromatographic scintillation method for the early evaluation of a proposed stability method for a cream formulation.

A plastic scintillator method for the radioassay of H 3- and C 14-labelled ompounds on filter paper

A simple and efficient technique for the radioassay of H 3- and C 14-labelled ompounds on filter paper is described. The technique onsists in laying a paper tissue soaked in a solution of plastic scintillator in benzene at a oncentration of ∼200 g/l, and placed onto each side of the filter paper supporting the activity. The sample is then held for a few minutes in benzene vapour to prevent premature evaporation of the solvent and dried at a temperature of about 60°C. The dried sample is then placed vertically in an otherwise empty ounting vial and ounted in a onventional Tri-Carb liquid scintillation spectrometer. Efficiencies of about 20 per cent were obtained for tritiated non-polar ompounds, and of about 10 per cent for tritiated polar ompounds. The use of dioxan as a solvent for the plastic scintillator appears to be advantageous when ounting tritiated polar ompounds on filter paper. The assay of C 14-labelled ompounds on filter paper gave exceptionally good results using this technique.

Improvements in thermal neutron scintillation detectors for time-of-flight studies

Scintillation methods of detecting thermal neutrons are reviewed and ways of preparing and using the organic borate/zincsulphide scintillator are described which lead to a marked improvement in efficiency. In particular, a method of pulse-shape discrimination is described, based on a pronounced difference in pulse sha[es from ZnS(Ag) excited by alpha-particles and electrons. Methods of measuring detector efficiency or neutron flux are reviewed and a simple method is shown to be satisfactory to 1 2 % accuracy. Using these techniques a thermal neutron efficiency of 42% is observed in the presence of 5mR/h gamma radiation, or 52% in the absence of gamma background. Some tests have been carried out on lithium glass scintillators showing that with small area detectors in applications where the gamma background is low, high efficiencies can be achieved, but where gamma backgrounds are high the zincsulphide type is preferable.

Counting of weak β-emitters in bacterial cells by means of the liquid scintillation method

Liquid scintillation counting has been used to determine the C 14 and S 35 radioactivity of bacterial cells. A simple method for incorporating the cell material into the scintillation solution is described. This method involves the digestion of the cells with formamide and permits the incorporation of up to 10–11 mg cells (determined as dry solids) into 15 ml of a scintillation solution consisting of 10 ml 0.3% PPO in toluene and 5 ml ethanol. With smaller amounts of cells, viz., 6–7 mg, a simple autolysis of the cells at 60°C was found to be sufficient to bring the cell material into the scintillation solution. Various compositions of the scintillation solutions were investigated with respect to the counting efficiency of C 14 and S 35 in bacterial cells.

The measurement of aqueous solutions of metallic radioisotopes by liquid scintillation methods

The measurement of aqueous solutions of metallic radioisotopes by liquid scintillation methods

γ−γ angular correlation measurement on the 0,337→1,10 MeV cascade in the decay of Fe59

By applying the scintillation method and sum-coincidence circuit the authors carried out γ−γ angular correlation measurements on the smallest intensity 0,337→1,10 MeV cascade in the decay of Fe59, after having reproduced the results known for the 0,145→1,29 MeV cascade. For the 0,337→1,10 MeV cascade the angular correlation function isW(ν)=1−(0,451±0,156)P 2 (cos ν), which for the 1,43, 1,29 and 1,10 MeV levels excludes the spin assignments 3/2, 5/2, 7/2; 5/2, 3/2, 7/2; 3/2, 1/2, 7/2 and 5/2, 1/2, 7/2.

Investigation of the decay scheme of Cr 51

The energy distribution of γ-rays arising from the decay of Cr 51 was investigated by the scintillation method. Besides the well-known, most intense transition of 323 keV, we also found the 323 keV and 320 keV cascade transitions of low intensity. At 150 keV a new γ-transition in cascade with the line of 323 keV was found. A cross-over transition of 470 keV energy was observed in parallel with the cascade.

Internal source scintillation spectrometry

Abstract The investigation of L/K, K/β + ratios, β spectral shapes and extranuclear processes by internal source scintillation methods is considered. A description is given of the well-type method which can eliminate escape corrections in such determinations. Source distribution and activation effects which bear on this type of spectrometry are also mentioned.

On the quantitative assay of radiochromatograms by liquid scintillation counting

It is possible to obtain accurate results with the normal liquid scintillation method for the assay of radioactive paper strips, if the solubility of the radioactive compound being measured in the scintillation fluid is taken into account. A technique for taking this soiubility into account is described which involves the replacement of the radioactive paper strip in the sample container by an inactive paper strip and the use of a standard radioactive paper strip. The ratio of efficiencies for activity in solution and on the strip was determined for three different papers. (D.L.C.)

Assay of Tritium, Carbon-14 and Sulphur-35 in Wool by Liquid-Scintillation Counting

A procedure is described for the assay of biosynthetically labeled wool directly by the liquid scintillation method. Results are reported for the assay of samples clipped from three sheep that had received intravenous injections of H/ sup3/-lysine, C¹⁴-phenylalanine, or S³⁵-cystine respectively. (C.H.)