Scintillation Method Research Articles

Determination of Frequency Function of Particle Intensity in Pulsed Photon Beams

The frequency functions of photon particle intensity were experimentally determined for brems-strahlung produced by a 4MeV electron linac during a pulse width of 1.6 μsec. The measurements were carried out with a plastic scintillator and electronic integrator method, making it possible to separate multiple photons that are detected during a single linac pulse. The measured distributions were compared with the Poisson distribution with the same mean value, using the chi-square test. This method can be extended to the photon energy spectrum determination.

Present status in the field of precision liquid scintillation counting

First, a short review of some general aspects, e.g., basic mechanisms, scintillators, instrumental developments, and source preparation is given. Then, the applicability and the attainable accuracy of the liquid scintillation method for absolute measurements of the activity of β-emitters of different energy, α-emitters, and EC-nuclides are discussed. The different techniques used are described: extrapolation of the bias curve to zero bias, correction for non-detection probability, and 4 π β-γ coincidence counting and efficiency tracing using liquid scintillators as β-detectors. Finally, some special applications in the field of radionuclide metrology and the suitability of liquid scintillation counters for relative radioactivity measurements by Čerenkovradiation detection are reviewed.

Incorporation of cysteine into the cerebral neurosecretory system of adult desert locusts

Liquid scintillation counting techniques were used as a means of measuring the incorporation of 35S-cysteine into the neurosecretory system of adult female Schistocerca gregaria in different physiological conditions. The methods described were unable to measure uptake of 35S label into the cerebral neurosecretory cells but were successful in measuring incorporation rates into the storage lobes of the corpora cardiaca. The corpora cardiaca become labeled soon after injection of the 35S-cysteine, and the initial amount of label is proportional to the amount of neurosecretion within the gland. Loss of label from the hemolymph occurs very rapidly, and the 35S=cysteine concentrations become limiting for incorporation within the cerebral neurosecretory cells within the first hours of the experiment. Label within the corpora cardiaca increases instead of following the decreasing hemolymph label. The rate and time of increase of label within the corpora cardiaca therefore indicates the influx of newly labeled neurosecretion and enables comparisons to be made of neurosecretory turn-over in different females. Ten-day-old females synthesize and release neurosecretory material at a rapid rate. Immature females also synthesize and release material rapidly although at a lower rate than maturing females. Mature females have much less active neurosecretory systems than either maturing or immature females. The results from this liquid scintillation method of measuring radioactive labeling of neurosecretory systems support and amplify the results gained from autoradiographic techniques.

Determination of Frequency Function of Particle Intensity in Pulsed Photon Beams

The frequency functions of photon particle intensity were experimentally determined for brems-strahlung produced by a 4MeV electron linac during a pulse width of 1.6 μsec. The measurements were carried out with a plastic scintillator and electronic integrator method, making it possible to separate multiple photons that are detected during a single linac pulse. The measured distributions were compared with the Poisson distribution with the same mean value, using the chi-square test. This method can be extended to the photon energy spectrum determination.

University of Rome Carbon-14 Dates XI

During the last few years, we have set up the benzene scintillation method in our laboratory. C14 activity measurements are now carried out with both liquid scintillation and CO2-proportional counters. Chemical apparatus for benzene synthesis and a liquid scintillation spectrometer for low-level counting were built and are described below.

Illinois State Geological Survey Radiocarbon Dates IV

This date list includes all samples processed from December 1970 through November 1971 at the Illinois State Geological Survey Radiocarbon Dating Laboratory. The benzene liquid scintillation method of Noakes, Kim, and Stipp (1965), and Noakes, Kim, and Akers (1967) was used. A new benzene synthesis system has been completed, and several changes in the sample preparation procedure have been made since the last date list report (Coleman, 1972). A brief summary of the benzene synthesis and sample pretreatment techniques used to determine the dates reported here follows.

On the absence of phlorizin hydrolase in renal brush border membranes

The extensively studied sugar transport inhibitor, phlorizin, is a phenolic β- d-glucoside which can be hydrolyzed to phloretin and glucose by a phlorizin hydrolase present in intestinal mucosa. A sensitive and specific method has been developed to determine the presence of this enzymatic activity in other tissues. Tritiated phlorizin, labeled specifically only in the glucose moiety, was used as substrate. In order to measure any liberated [ 3H]glucose by conventional liquid scintillation methods in the presence of large amounts of tritiated phlorizin, unsplit substrate was irreversibly adsorbed onto a polystyrene ion-exchange resin to which free [ 3H]glucose does not bind. Whole homogenates from hamster and rat intestinal mucosa were found to contain the anticipated high activity of phlorizin hydrolase. On the other hand, whole kidney preparations from the rat, hamster and guinea pig possessed very low levels of activity. Furthermore, the specific activity of the β-glucosidase in a membrane preparation from rat kidney, which was enriched in brush border fragments sevenfold over the crude homogenate, was even lower than whole kidney. The conclusion is drawn that renal brush borders contain no phlorizin hydrolase; the effective inhibitor of glucose transport in the kidney is phlorizin and not the aglycone, phloretin. The possibility is evaluated that this is not the case in intestine where phloretin is generated by the same cells which actively transport sugars.

Blastogenesis of rhesus peripheral lymphocytes with competitive summation of PHA and ALS responses

Rhesus monkey peripheral lymphocytes were found to undergo consistently high levels of PHA- and ALS-induced blastogenesis when in optimum culture conditions. For mitogen-induced lymphoblastogenesis, the culture conditions were defined in terms of continuous agitation incubation, cell density and serum content of the medium. The simultaneous measurement of blastogenic responses by autoradiographic and liquid scintillation methods established a linear relationship from which the percentage of responding lymphocytes could be derived from the total thymidine incorporation levels. Phytohaemagglutinin (PHA) and heterologous anti-lymphocyte sera (ALS) induced similar proliferation kinetics and maximal blastogenic responses under these culture conditions. Optimum stimulating concentrations of both mitogens in the same cultures produced no summation of their individual blastogenic responses; however, summation occurred at suboptimal mitogen doses. PHA and ALS appeared to be mitogenically stimulating the same lymphocyte population. Furthermore, no competitive inhibition was evident during simultaneous stimulation, suggesting that their induction events were neither additive nor competitive.

Liquid scintillation quench correction using 113mindium conversion electrons as an internal standard

A method of liquid scintillation quench correction is described using 113mIn as an internal standard. A small amount of 113mIn is added to each specimen bottle. The conversion electrons of 113mIn create a sharp pulseheight spectral peak whose height is determined by spectral scanning with a narrow pulse-height window. The height of the pulse at this spectral peak is linearly related to the efficiency of light output (quench) of the liquid scintillation bottle. The specimen is counted for its beta emitter 12 to 24 hr later when the 113mIn has decayed. This internal standard method is compared with more common method of automatic external standard quench correction using an external gamma emitter. The present method should allow an inexpensive, more precise, correction through a wide range of quenches.

Primary Production and Phytoplankton in the Experimental Lakes Area, Northwestern Ontario, and other Low-Carbonate Waters, and a Liquid Scintillation Method for Determining 14C Activity in Photosynthesis

A modified 14C method is described for measuring phytoplankton production in low-carbonate waters. The procedure includes the use of the Arthur and Rigler (Limnol. Oceanogr. 12: 121–124, 1967) technique for determining filtration error, liquid scintillation counting for determining the radioactivity of membrane filters and stock 14C solutions, and gas chromatography for measuring total CO2.Primary production, chlorophyll a, and total CO2 were measured for two dates in midsummer from each of several lakes in the Experimental Lakes Area (ELA), ranging from 1 to 1000 ha in area and from 2 to 117 m in maximum depth. Phytoplankton species abundance and biomass were determined for the same dates. Production ranged from 0.02 to 2.12 gC/m3∙day and from 0.179 to 1.103 g C/m2∙day. Chlorophyll ranged from 0.4 to 44 mg/m3 and from 5 to 98 mg/m2 in the euphotic zone. The corresponding ranges for live phytoplankton biomass were 120–5400 mg/m3 and 2100–13,400 mg/m2. Chrysophyceae dominated the phytoplankton of most of the lakes.A system for classifying the lakes in terms of phytoplankton species composition and production–depth curves is developed.

Calcium-45 uptake as a measurement of freeze-thaw injury to chicken spermatozoa in the presence or absence of cryopreservatives

Liquid scintillation analysis of Ca 45 uptake from chicken seminal plasma was used to evaluate pre- and postfreeze injury in the absence or presence of cryopreservatives (DMSO, glycerol, sucrose, and glucose). Three freezing methods evaluated were: 1) direct immersion in liquid nitrogen (fast), 2) controlled freezing 1 °C per min (slow), and 3) 1 °C per min to −6 °C followed by 85 °C per min to −196 °C (slow-fast). Freezing, slow or fast, significantly increased Ca 45 uptake in the absence of any cryopreservative. A glycerol level of 12% was necessary to obtain any reduction in freeze-thaw damage with slow or fast freezing. However, a slow-fast combination resulted in a protective effect at lower glycerol levels. DMSO was completely unsuccessful as a cryopreservative with high or low cooling velocities. Neither glycerol nor DMSO affected Ca 45 transport before freezing. Glucose and sucrose stimulated Ca 45 uptake before freezing, making it difficult to evaluate freeze damage. Glucose increased the amount of damage to slow frozen spermatozoa. However, it gave some protection at the highest level (0.08 g) to fast frozen semen. Sucrose levels at or above 0.08 g reduced the amount of freeze-thaw damage from fast freezing. A higher level (0.16 g) was needed to prevent significantly the injury of slow freezing. The liquid scintillation method using Ca 45 appears to be a reliable method for evaluating freeze-thaw injury to spermatozoa.

The acridine-orange fluorescent method in PHA-stimulated lymphocytes in culture.

The effect of Phytohemagglutinine (PHA) on RNA and DNA synthesis in peripheral blood lymphocytes was investigated in vitro by measuring the degree of fluorescence in nucleus, nucleolus and cytoplasm. The results were presented in the colour microphotographs using acridine-orange fluorescent method, which has been proved useful as relatively simple for the evaluation of changes in amount of RNA and DNA in the PHA-lymphocyte. In contrast to the liquid scintillation method and radioautography, the increasing synthesis of nucleic acids is seen later but more pictorially, with excellent preservation of the cell structure.

Replication of poliovirus in human lymphocytes stimulated with specific antigens.

Human lymphocytes from donors immunized with poliovirus vaccine and tetanus toxoid supported the replication of poliovirus type 1 when stimulated with these specific antigensin vitro. The blastogenic response of lymphocytes infected with poliovirus proved to be decreased as measured by partial inhibition of DNA synthesis. The inhibition of DNA synthesis was measured by liquid scintillation and radioautographic methods. The inhibition occured when virus was added up to 4 days after initiation of specific antigenic stimulation. Tuberculin-stimulated lymphocytes from Mantoux positive donors supported the replication of measles virus and poliovirus. The blastogenic response of these infected cells was also inhibited.

Analytical flame spectroscopy of powdered samples with scintillation method of detection

Analytical flame spectroscopy of powdered samples with scintillation method of detection

On the possibility of investigating inhomogeneities of the interstellar plasma by the method of scintillation of discrete sources

On the possibility of investigating inhomogeneities of the interstellar plasma by the method of scintillation of discrete sources

Thermal decomposition of sodium-containing particles in a flame

The release of sodium atoms from compounds such as NaCl, NaBr, NaI, Na 2SO 4, and NaHCO 3 has been studied with a newly developed flame scintillation spectrophotometer. The process of vaporization of the atoms appears to be largely a surface phenomenon and is discussed in terms of surface energies of the crystals and dissociation energies of the molecules. The results indicate significance for an understanding of the flame scintillation method in its application to air chemistry, and with regard to the thermal instability of certain substances.

A new phenomenon to be taken into consideration when investigating phosphorescence by liquid scintillation method

Investigating the phosphorescence radiation in the measurement of low-energy β-memitters by liquid scintillation method a new group of phenomena was observed. In the presence of scintillator molecules the phosphorescence of the bottle, of the solvent and that of the additives increased. This phenomenon—called “the introduction of phosphopescence”—may influence the choice of the optical filter and the scintillator decisively, and necessitates the phosphorescence ce investigation of every individual components in the presence of the scintillator molecule.

The beta branching ratio and conversion coefficients in the137Cs decay

The decay of137Cs has been reinvestigated using several precision counting methods. The emission rate ofβ-particles plus internal conversion electrons was measured by the 4π-proportional counter method using vacuum evaporated sources free of self-absorption and checked by the liquid scintillation method. TheK-conversion coefficient was determined by the electron X-ray coincidence method using a magnetic spectrometer and a high resolution Si(Li) detector. TheK/(L+M+...) conversion ratio and a second less accurate value for the β-branching ratio were obtained from the recorded electron spectra. Theγ-ray emission rate of all sources was determined to within ±0.14%, on the average, with a calibrated NaI(Tl) crystal detector. As results the intensity of theβ-decay to the ground state of137Ba could be determined to (5.4±0.3)% of the137Cs decays, theK-conversion coefficient to 0.0916±0.0004, and theK/(L+M+...) conversion ratio to 4.41±0.04. From these values the γ-ray emission intensity is (85.1±0.4)% of the137Cs decays and theK X-ray emission intensity is (8.13±0.10)% of the emittedγ-rays. All errors are discussed in detail.

Alpha Counting by Liquid Scintillation Spectrometry: Plutonium-239 in Animal Tissues

A liquid scintillation method has been developed for the determination of microcurie and picocurie levels of plutonium-239 and other alpha-emitting radionuclides in animal tissues. A commercially available liquid scintillation spectrometer is used, and nearly 100% counting efficiency is achieved. Transfer losses and dilution of activity are avoided by preparation of the entire tissue sample, rather than an aliquot, in the counting vial to be used for the analysis. Organic matter is removed by alternating acid digestion with heating in a mufflle furnace. Optimal ashing conditions and instrumental parameters were determined for the analysis of plutonium in bone, liver, spleen, feces, and urine. In several comparisons of analytical results by liquid scintillation and by proportional counting, close agreement between the two methods was obtained. However, the liquid scintillation method is less laborious and time-consuming, yields closer replication of analytical values, and permits more analyses per experime...

A scintillation method of spectral analysis of gold in ores

A scintillation method of spectral analysis of gold in ores