Tape sealants—New solutions for sealing nonregimented gaps

Physico-mechanical properties of the developed tape sealant VGM-L are presented. It is shown that the sealant makes it possible to obtain a reliable and stable sealed seam in joint surfaces working in the temperature range from ?60 to +130°C. The method of sealant preparation is described.     

Solid scintillator "Ready Cap" for measurement with a liquid scintillation counter--spectra and counting efficiencies for 15 different radionuclides

"Ready Cap", a small plastic container coated with solid scintillator has recently been introduced (Beckman Instruments, Inc.). Pulse height spectra and counting efficiencies obtained with a liquid scintillator and Ready Cap using a liquid scintillator counter were compared for 15 different radionuclides. For radionuclides emitting low-energy beta-rays or characteristic X-rays, the spectra for Ready Cap shifted toward the higher energy side compared with the spectra for the liquid scintillator. This tendency was reversed for the nuclides emitting higher-energy beta-radiations (36Cl and 32P). Generally, counting efficiencies both in Ready Cap and in liquid scintillator increased with increase in the energy of beta- or X-rays. For some nuclides, Ready Cap gave higher counting efficiencies and for others it gave lower values than in the liquid scintillator. However, the differences were not large within each nuclide. The use of Ready Cap is recommended for measurements of radionuclides when liquid scintillation cocktails have no means of waste disposal under the present Japanese radioisotope regulation.     

Radioactivity measurement with a plastic scintillation vial

Liquid scintillation counting is widely used to measure radioactivity, but it generates radioactive organic liquid waste. Not to generate the liquid waste using a liquid scintillation counter, novel counting method with a plastic scintillation vial was designed. The counting efficiency for ³²P was 10–40% and that for ¹²⁵I was 4–8%. The efficiency depended on the sample volume. The color quenching effect was negligible. No radioactive liquid waste was generated by this method. In addition, you can reuse the measured sample.     

Coincidence counting for PGNAA applications: Is it the optimum method?

Summary One of the main advantages of γ-γ coincidence counting is the reduction of the background spectrum, pulse pile-up, and summing effects (for simple schemes). For prompt gamma-ray neutron activation analysis (PGNAA), the sources of background include the gamma-rays from the natural background, from surrounding materials, from the neutron source, and from detector neutron activation. While this counting approach effectively increases the signal-to-noise (S/N) ratio, it also decreases the signal counting rate. This adds some practical limitations to using this approach. In this work, two examples are presented for the efficient use of the coincidence counting approach.     

Enhanced Sealing by Hydrophobic Modification of Alaska Pollock‐Derived Gelatin‐Based Surgical Sealants for the Treatment of Pulmonary Air Leaks

Pulmonary air leaks are medical complications of thoracic surgery for which fibrin sealant is the main treatment. In this study, innovative sealants based on hydrophobically modified Alaska pollock‐derived gelatin (hm‐ApGltn) and a poly(ethylene)glycol‐based 4‐armed cross‐linker (4S‐PEG) have been developed and their burst strengths have been evaluated using fresh rat lung. The developed sealants show higher lung burst strength compared with the nonmodified original ApGltn (Org‐ApGltn)‐based sealant and a commercial fibrin sealant. The maximum burst strength of the hm‐ApGltn‐based sealant is 1.6‐fold higher than the Org‐ApGltn‐based sealant (n = 5, p < 0.05), and 2.1‐fold higher than the commercial fibrin sealant (n = 5, p < 0.05). Cell culture experiments show that modification of ApGltn with cholesteryl or stearoyl groups effectively enhances anchoring to the cell surface. In addition, binding constants between hm‐ApGltn and extracellular matrix proteins such as fibronectin and fibrillin are increased. Therefore, the new hm‐ApGltn/4S‐PEG‐based sealant has the potential for applications in thoracic surgery.

     

An innovative method for dead time correction in nuclear spectroscopy

All nuclear spectroscopy systems, whether measuring charged particles, X-rays, or gamma-rays, exhibit dead time losses during the counting process due to pulse processing in the electronics. Several techniques have been employed in an effort to reduce the effects of dead time losses on a spectroscopy system including live time clocks and loss-free counting modules. Live time extension techniques give accurate results when measuring samples in which the activity remains roughly constant during the measuring process (i.e., the dead time does not change significantly during a single measurement period). The loss-free counting method of correcting for dead time losses, as introduced by HARMS and improved by WESTPHAL (US Patent No. 4,476,384) give better results than live time extension techniques when the counting rate changes significantly during the measurement. However, loss-free counting methods are limited by the fact that an estimation of the uncertainty associated with the spectral counts can not be easily determined, because the corrected data no longer obeys Poisson statistics. Therefore, accurate analysis of the spectral data including the uncertainty calculations is difficult to achieve. The Ortec® DSPEC ^PLUS implements an improved zero dead time method that accurately predicts the uncertainty from counting statistics and overcomes the limitations of previous loss-free counting methods. The uncertainty in the dead-time corrected spectrum is calculated and stored with the spectral data (Patent Pending). The GammaVision-32® analysis algorithm has been improved to propagate this uncertainty through the activity calculation. Two experiments are set up to verify these innovations. The experiments show that the new method gives the same reported activity and associated uncertainties as the well-proven Gedcke-Hale live time clock. It is thus shown that over a wide range of dead times the new ZDT method tracks the true counting rate as if it had zero dead time, and yields an accurate estimation of the statistical uncertainty in the reported counts.     

Aqueous Systems for Liquid Scintillation Counting: Use of Hydrotropes

Liquid hydrotropic systems, i.e., mixtures of hydrotropes and water‐forming hydrophilic and hydrophobic regions, allow the solubilization of organic scintillators in essentially aqueous media. Such systems were applied to liquid scintillation counting with 4‐[4‐(5‐phenyloxazol‐2‐yl)benzyl]morpholine as scintillator, a 2,5‐diphenyloxazole (PPO) derivative that proved well‐soluble in acidic hydrotrope systems. Its fluorescence properties were studied. Phenylalanine labeled with ³H or ¹⁴C was used to test counting. While ¹⁴C counting worked acceptably, ³H counting was comparatively inefficient, probably due to the short lifetime of β‐particles in aqueous environments.     

Method for rapid tritiated water extraction from environmental samples

We have developed a thermal vacuum desorption process to rapidly extract water from environmental samples for tritium analysis. Thermal vacuum desorption allows for extraction of the moisture from the sample within a few hours in a form and quantity suitable for liquid scintillation counting and allows detection of tritium at the levels of <2 Bq/l of milk, <0.5 Bq/g of vegetation, and <0.5 Bq/g of soil. We developed a prototype unit that can process batches of twenty or more samples within 24 hours. Early data shows that a high percentage of water is extracted reproducibly without enrichment or depletion of the tritium content. The quench coefficient of the extracted water is low allowing for accurate, direct liquid scintillation counting. In most samples, good comparison has been observed with results using freeze-dry lyophilization as the water extraction method     

Simultaneous determination of35S and14C in double-labelled organic compounds by liquid scintillation counting

An isotope analytical method for the simultaneous determination of³⁵S and¹⁴C in double-labelled organic compounds by liquid scintillation counting is described. The sample is burned in a stream of oxygen. Sulfur oxides are converted to sulfuric acid and separated from other combustion products, including carbon-14 dioxide, on a heated quartz wool column previously wetted with hydrogen peroxide. Carbon dioxide is collected from the gas stream by an absorbent suitable for liquid scintillation counting. The residual sulfuric acid is rinsed off the column with water and the aqueous solution obtained is mixed with a liquid scintillation cocktail for radioactivity measurement. The final solutions ready for counting are obtained in less than fifteen minutes, quantitative collection recovery is achieved and no cross contamination occurs.     

An efficient inexpensive multisleeve liquid scintillation counting system

This paper reports a method that conserves greatly on the cost of counting radioactive samples for liquid scintillation counting. It accomplishes this by using several glass sleeves that are much more inexpensive than conventional counting and/or minivials, and because volumes of counting fluid are reduced the cost of the counting fluid is also markedly reduced. The usual vial system (A) uses 15 ml of counting fluid with 37% efficiency for tritum; the minivial uses .75 ml with 37% efficiency while 0.15 and 30 μl volumes gave approximately 21% efficiency. Another feature of this system is the capacity to reuse the outer sleeve(s) and dispose of the smaller counting vessel. This means that less counting fluid and glass will have to be disposed of in the environment.     

2DE‐based approach for estimation of number of protein species in a cell

Insufficient sensitivity of methods for detection of proteins at a single molecule level does not yet allow obtaining the whole image of human proteome. But to go further, we need at least to know the proteome size, or how many different protein species compose this proteome. This is the task that could be at least partially realized by the method described in this article. The approach used in our study is based on detection of protein spots in 2DE after staining by protein dyes with various sensitivities. As the different protein spots contain different protein species, counting the spots opens a way for estimation of number of protein species. The function representing the dependence of the number of protein spots on sensitivity or LOD of protein dyes was generated. And extrapolation of this function curve to theoretical point of the maximum sensitivity (detection of a single smallest polypeptide) allowed to counting the number of different molecules (polypeptide species) at the concentration level of a single polypeptide per proteome. Using this approach, it was estimated that the minimal numbers of protein species for model objects, Escherichia coli and Pirococcus furiosus, are 6200 and 3400, respectively. We expect a single human cell (HepG2) to contain minimum 70 000 protein species.     

Development of a method for the determination of 226Ra by liquid scintillation counting

Liquid scintillation counting has not been widely applied to a-particle detection because of its poor energy resolution and variable background. In the present work, a time saving and reasonably accurate method for determination of ²²⁶Ra in water has been developed, using liquid scintillation spectrometry and pulse-shape analysis. The effect of three levels of chemical quench on the spillover of alpha interactions into the beta window and vice versa was assessed. The advantages of liquid scintillation in comparison with other methods (radon emanation) for determination of ²²⁶Ra are the high counting efficiency (~100%) and the easier sample preparation, with no need for sample preconcentration.     

Removal of the impurities from environmental water samples for tritium measurement by liquid scintillation counting

Liquid scintillation counting is the most popular method for tritium measurement, however, it takes much time and a lot of doing to distill off the impurities before mixing the sample water and liquid scintillation cocktail. We have investigated the possibility of an alternative method to the distillation. We have found out that the filtration can be an alternative to distillation for the environmental water samples before electrolytic enrichment.     

Fast,selective and sensitive methods for the determination of lead-210 in phosphogypsum and phosphate ore

Two methods are presented for a fast, accurate and precise determination of²¹⁰Pb in industrial samples with a calcium-phosphate and-sulphate matrix. One method combinessolid-liquid extraction on a Pb-selective column Sr^*Spec (Eichrom) with gamma-ray spectrometry of²¹⁰Pb and can be applied to samples >10 g for aselective ²¹⁰Pb determination. The yield is determined gravimetrically. The detection limit is 380 mBq for a 24 h counting period. The other method combineschromatography on Sr^*Spec with liquid scintillation counting of²¹⁰Pb for asensitive ²¹⁰Pb determination and can be applied to samples of up to 1 g. The yield is determined on-line by the UV signal of PbEDTA. The detection limit is 70 mBq for a 2 h counting period. Aspects of accuracy, precision, selectivity, sensitivity and the application of both methods to phosphogypsum and phosphate ores are presented.     

On-stream nuclear activation of trace uranium and thorium using a 14 MeV neutron generator

A method for the continuous on-stream determination of trace concentrations of uranium and thorium in flowing streams is developed. The 14 MeV neutron generator was used for irradiation and the delayed neutron counting technique was employed in counting the induced neutron activity. The dependence of the minimum detectable concentration on the irradiation, decay and counting times, liquid flow-rate and the background was studied. At optimal conditions, uranium and thorium concentrations were determined down to 20 and 100 ppm, respectively. The interference of the neutron emitting nuclide^17m O was reduced to an insignificant level by optimizing the decay time.     

Methodology for rapid tritium determination in urine

Summary The present work proposes a methodology for a rapid determina-tion of the tritium content in urine. The urine is treated with active carbon and tritium is determined by liquid scintillation counting. Different kinds of active carbon were experimented for the metabolites removal from urine samples. The counting efficiency was calculated by a quench curve using yellow food dye as a quenching agent. It was obtained a procedure which maintained a good reproducibility, low uncertainty and detection limit of 7 Bq/l (10 ml of urine, 120 minutes of counting time and efficiency of 23.9%).     

Simple measurement of14C in the environment using a gel suspension method

A simple analytical method for environmental¹⁴C with a low background liquid scintillation counter was developed. We used a new gelling agent, N-lauroyl-L-glutamic-α,γ-dibutylamide, for the liquid scintillation counting of¹⁴C as CaCO₃ (gel suspension method). Our procedure for sample preparation was much simpler than that of conventional methods and required no special equipment. The samples prepared with the standard sample of CaCO₃ were measured to evaluate the self absorption of the sample, the optimum condition of counting and the detection limit. Our results indicated that the newly developed technique could be efficiently applied for the monitoring of environmental¹⁴C.     

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.     

<Emphasis Type="Italic">ABCD</Emphasis>-<Emphasis Type="Italic">Tool</Emphasis>, a software suite for the analysis of α/β spectra from liquid scintillation counting

This paper presents the alpha/beta complete deconvolution tool (ABCD-Tool), a C++ application for the analysis of spectra from liquid scintillation counting (LSC) measurements. In addition to the basic algorithms for standard gross alpha/beta analysis and the determination of the counting efficiency, the software implements a recent unfolding technique based on Fourier transforms, which gives precise and reliable results even in the case of complex, strongly overlapping spectra. The application is designed to be used with alpha/beta spectra generated from Perkin Elmer Wallac Quantulus 1220. However, future upgrades are scheduled in order to extend the compatibility to spectra from other LSC instruments in commerce.     

Ultraviolet photolysis of urine for suppression of color quenching prior to liquid scintillation counting of tritium

In order to reduce the color quenching in the measurement of tritium in urine by liquid scintillation counting , UV irradiation was applied to decompose the organic substances in the sample. Urine was decolorized under UV irradiation in the presence of hydrogen peroxide. As a result, color quenching was considerably suppressed and higher counting efficiency of tritium was obtained. This UV treatment made it possible to increase the urine content in the sample from 2 to 40% (v/v) without significant decrease of counting efficiency. Either higher sensitivity or shorter analysis time was achieved in the tritium measurement by the augmentation of urine content. When the measurement time was 30 min, the detection limit of tritium defined as 3s was 0.03 Bq/ml. At the expense of some sensitivity (set at a detection limit of 0.3 Bq/ml), the measurement time was shortened to 0.5 min. These results will make a great improvement to routine tritium monitoring as well as to emergency monitoring in mass tritium exposure.