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At least 19 recordsLinked to original sources
PubMed1985

Effect of air-scattered beta particles on instrument and dosimeter response.

Air-scattered beta particles are responsible for many of the inaccuracies encountered when readings are obtained with many types of beta survey instruments and personnel dosimeters. The ratio of beta particles scattered at various angles to beta's coming directly from the source increases as the distance from the source increases. This ratio, at a given distance from the source, is also a function of the beta energy, becoming larger for lower-energy beta sources. Changes in this ratio cause the response of beta instruments to have an apparent change in the directional response. These air-scattered beta particles are also responsible, in many cases, for a part of the apparent decrease in the efficiency of beta survey instruments when detecting low-energy beta sources. Air-scattered beta's also cause personnel dosimeters, which are not properly designed to detect them, to have responses that are low. We give experimental results to confirms the above effects. Design changes to survey instruments and dosimeters are suggested that would eliminate the errors created by the failure of the instruments to detect these air-scattered beta particles.

Air↗
PubMed1987

Differential interactions of beta particles with liquid enantiomers and internal timing of chiral molecules.

The Cerenkov and liquid scintillation technique was applied to detect differential interactions between beta particles and chiral molecules. The highly helical beta emitting 32P and the barely helical beta emitting 3H were dissolved in the liquid enantiomers of 2-phenylbutyric acid. The interactions of the beta particles with the enantiomers were compared. Differential interactions were observed in case of 32P. The stopping power of R enantiomers was greater than that of the S enantiomer. The apparent decay of 32P was faster in the S enantiomer than in the R enantiomer. It is not clear whether this is due to some mistake in measurement or reflects the postulated difference of internal timing of the two enantiomers. Since, in spite of all efforts, contamination could not totally be excluded and data are significant only to one sigma, results must be considered preliminary. The method, however, seems to be more sensitive than all previously used methods. The differential effect was always in the same direction in at least 5 replicas.

Beta Particles↗
PubMed1986

Induction of chromosome aberrations by 90Sr beta-particles in cultured human lymphocytes.

Human blood was irradiated with beta-particles from an external source of 90Sr. The source was a rolled piece of silver foil, active dimensions: 100 X 12.5 mm, incorporating 3.7 X 10(8) Bq (10 mCi) of 90Sr/90Y. After culturing for 48 h, the dicentric yield in the lymphocytes at the first metaphase was measured as a function of the dose in the blood. The aberration yield fitted the linear-quadratic function well, which is consistent with the single-track and two-track model for aberration formation at low LET radiation. The curve for 90Sr beta-rays was compared with a curve for 60Co gamma-rays. The main difference between the coefficients was in the alpha values. With respect to 60Co gamma-rays, the RBE calculated from the dose-effect relationships for dicentric production was 2.8 at the dose of 0.14 Gy; it decreased with increasing doses. The distribution of dicentrics was consistent with the Poisson distribution but showed a tendency to over-dispersion in the region of higher doses. A reason for these discrepancies is discussed.

Beta Particles↗
PubMed1978

Mean skeletal dose factors for beta-particle emitters in human bone. Part I: volume-seeking radionuclides.

Based on calculations by Whitwell and Spiers, mean skeletal dose factors for beta-particle emitters have been derived for application to dosimetry in nuclear medicine, radiobiology and radiation protection. The dose factors apply to bone-seeking radionuclides that are depostited more or less uniformly throughout the human mineralized skeleton and are defined as: (1) vDM/DB, the mean dose to the haemopoietic marrow in trabecular bone as a fraction of the "dose to bone", DB; (2) vDs/DB, the mean dose to endosteal (osteogenic) tissue lying in a zone 0--10 micron from trabecular surfaces, also as a fraction of the dose DB. Dose factors are given for three ages, 1.7, 9 and 44 years and for eight radionuclides, ranging in mean beta-particle energy from 0.05 MeV (14C) to 0.93 MeV (90Y). Dose factors, calculated for a single lumbar vertebra of an infant aged 3.5 weeks, enable approximate values of mean skeletal dose factors to be estimated for ages less than 1.7 years. Limited data are also reported on dose factors for the femoral cortex from subjects aged 9 and 50 years.

Adult↗
PubMed1978

The response of E. coli Bs-1 to tritium-beta particles under aerated and anoxic conditions.

E. coli Bs-1 cells were exposed to acute doses of tritium-beta particles by suspension in tritiated water for known lengths of time. The resulting survival rate was compared with that obtained for external irradiation with 7 MeV electrons. The o.e.r. measured for tritium-beta s was not significantly different from the value of 2.15 measured for 7 MeV electrons. The r.b.e. of the tritium beta s relative to 7 MeV electrons was 1.21 in both air and nitrogen. These results were compared with existing data for low voltage electron irradiations and with track segment studies of the effect of varying LET on the radiosensitivity of E. coli Bs-1.

Dose-Response Relationship, Radiation↗
PubMed1989

Optical imaging of the spatial distribution of beta-particles emerging from surfaces.

The multiplication in gases of ionization electrons, by the effect of the electric fields between parallel electrodes, leads to the emission of light from the molecules excited in the avalanche process. The optical imaging of this light, with intensifiers, on charge-coupled devices permits the localization, in the gaseous volume, of the entrance points of the beta-particles emitted by radioactive compounds placed close to or at the cathode electrode. Thin slices of anatomical samples labeled with 3H show detailed structures 30 microns in size. Gels carrying 32P or 35S are imaged with accuracies of the order of 0.5 mm (full width at half maximum). In comparison with photographic emulsion, the gain in time for data taking is close to a factor of 100, with the advantage of linearity and wider dynamic range in the intensity measurement and a greatly improved signal-to-noise ratio.

Animals↗
PubMed1991

Localization and quantitation of tritiated compounds in tissue sections with a gaseous detector of beta particles: comparison with film autoradiography.

Quantitative analysis of tritium polymer standards and of brain sections labeled with tritiated vasopressin was carried out by using a gaseous detector of beta particles designed for this purpose. The gaseous detector showed major advantages compared with film autoradiography: the linearity and the large dynamic range of intensity measurements as well as the short time needed for data acquisition.

Animals↗
PubMed1991

SOFI: a bidimensional detector for fast direct on-line quantification of beta particles on blots.

We present a high-speed, high-resolution beta imager developed to replace autoradiographic films currently used in molecular biology experiments. It allows the user to locate and make quantitative analyses of 32P-labeled molecules on a 25.6 x 25.6-cm flat surface. Combining new techniques--scintillating optical fibers and multianode photomultipliers--this fast imager offers several advantages when compared with recent gas detectors and flexibility for further improvements. Several biological applications will be discussed.

Animals↗
PubMed1987

Experimental and computational techniques for beta-particle dosimetry.

This paper reports the experimental and the computational techniques that were specifically developed to provide dose response data for a new method of beta dosimetry, which is reported in an accompanying article (Sh87). The specific experimental techniques consist of setting up, calibrating and obtaining backscattering and resolution corrections for a plastic-scintillator-based beta spectrometer. The computation techniques involve (1) adapting a Monte Carlo electron transport computer code to use measured beta energy distributions as input data and (2) using the code to calculate the energy deposition of these distributions of electrons in a slab of material. The energy deposition of backscattered electrons incident on the slab is also taken into account. Codes, which were developed to calculate the energy deposited by photons in LiF, are used to derive a theoretical value for the TLD response calibration factor. This factor compares well to the experimentally derived result which was obtained by exposing TLDs to a calibrated 137Cs/137mBa photon source.

Algorithms↗