Radioactivity Methods Research Articles

Investigation of geochemical correlation between radioactive and rare earth elements; case study of Baghak mine, NE of Iran

In several uranium (U) prospecting projects in Iran, particularly Central Iran, the association and enrichment of rare earth elements (REEs) are known as the usual features. Sometimes the association of REEs and U with high economic perspective has caused that the relation between the rare earth and radioactive elements is taken into consideration in other types of mineralization, and if there is any relation, radioactivity will be applied in the exploration of REEs. In the current work, sampling from Baghak anomaly in the Sangan mines is carried out based on the radioactivity and radiation measurement methods (as the optimal sampling pattern). In fact, the goal of this work is to survey the presence or absence of such a relation in a skarn mine, which is a different case study from Central Iran. In the case of presence, this will lead to a new exploration method and sampling pattern for REEs. The mineralogical studies (based on the optical and electronic microscopic observations), statistical investigations, and geochemical analyses are applied in this research work. The results obtained from the statistical studies show that the Baghak anomaly due to involving a significant amount of U, Ce, and La and a high concentration of REEs can be considered as one of the important mines. Spider diagrams and their geochemical investigations include the features that are typical of the subduction-related magmas in the calcalkaline volcanic arcs of the continental active margins. The chondrite-normalized REE pattern shows the enrichment of LREE, and a positive pattern close to flat HREE due to the entry of LREE ions into the allanites network. The mineralogical study results also confirm that REEs (especially Ce) are accumulated as a solid solution in the allanite minerals. Moreover, from the mineralogical, geochemical, and statistical analyses, it can be observed that in addition to the presence of such a relation in the mentioned mineralization (Central Iran mineralizations), there is an acceptable correlation between these elements in the Baghak iron-skarn mineralization. Eventually, it can be said that the idea and introduced method for the exploration of REEs in this work could present a new viewpoint to the decision-makers of this industry.

Luminal leptin inhibits intestinal sugar absorption in vivo

We have previously demonstrated that leptin inhibits galactose absorption in rat intestinal everted rings and that leptin receptors are present in the apical membrane of the enterocytes. This adipocyte-derived hormone is also secreted by gastric mucosal cells and is able to reach the intestinal lumen. The goal of the present study was to prove whether luminal leptin acts on intestinal sugar absorption in vivo both at low (basal state) and high sugar concentration (post-prandial state). In vivo intestinal sugar absorption in rat was measured with recirculating and single-pass perfusion systems. Sugar disappearance in the perfusate was measured by radioactivity and biochemical methods. Luminal leptin effect on intestinal absorption mediated by sodium-dependent glucose transporter 1 (SGLT1) and glucose transporter 2 (GLUT2) as well as intestinal permeability (mannitol absorption) was determined. Luminal leptin inhibited intestinal sugar absorption at low galactose concentrations, which indicates that leptin regulates SGLT1 activity in vivo. The inhibition was reversed in the absence of hormone in the intestinal lumen, suggesting that it was produced by post-translational regulation processes. At high luminal glucose concentrations, leptin also inhibited the phloretin-insensitive component of sugar absorption mediated by SGLT1. There was no significant effect on the apical GLUT2 component of absorption. Leptin did not modify in vivo intestinal permeability determined with (14)C-mannitol. These observations support the view that gastric leptin exerts a regulatory role on intestinal sugar absorption in the postprandial state by modifying the active component of absorption.

Comparative detection of bacterial adhesion to Caco-2 cells with ELISA, radioactivity and plate count methods

Different methods are used to study bacterial adhesion to intestinal epithelial cells, which is an important step in pathogenic infection as well as in probiotic colonization of the intestinal tract. The aim of this study was to compare the ELISA-based method with more conventional plate count and radiolabeling methods for bacterial adhesion detection. An ELISA-based assay was optimized for the detection of Bifidobacterium longum and Escherichia coli O157:H7, which are low and highly adherent bacteria, respectively. In agreement with previous investigations, a percentage of adhesion below 1% was obtained for B. longum with ELISA. However, high nonspecific background and low positive signals were measured due to the use of polyclonal antibodies and the low adhesion capacity with this strain. In contrast, the ELISA-based method developed for E. coli adhesion detected a high adhesion percentage (15%). For this bacterium the three methods tested gave similar results for the highest bacterial concentrations (6.8 Log CFU added bacteria/well). However, differences among methods increased with the addition of decreased bacterial concentration due to different detection thresholds (5.9, 5.6 and 2.9 Log CFU adherent bacteria/well for radioactivity, ELISA and plate count methods, respectively). The ELISA-based method was shown to be a good predictor for bacterial adhesion compared to the radiolabeling method when good quality specific antibodies were used. This technique is convenient and allows handling of numerous samples.

Immunological detection of in vivo aflatoxin B1–DNA adduct formation in rats, rainbow trout and coho salmon

Immunological detection of carcinogen-DNA adducts in organs or tissues should prove a particularly useful approach for monitoring carcinogen exposure, for characterization of carcinogen binding to DNA and for investigating DNA repair processes in vivo. In one of a series of experiments aimed at raising antibodies against several carcinogen-modified DNAs, rabbits were immunized in our laboratory with aflatoxin B1 (AFB1)-modified DNA. After the titer and specificity of the antibodies produced were checked against standards by the enzyme-linked immunosorbent assay (ELISA) method, they were used to investigate DNA extracted from livers of rats and rainbow trout (Salmo mykiss) injected with tritium-labeled AFB1 at doses of 1-2 mg/kg (rats) or 0.1-0.5 mg/kg (rainbow trout). Adduct levels were compared using both radioactivity and ELISA methods. Positive DNA binding could be detected in both rats and rainbow trout by the immunological method at similar levels to those estimated with the radioactive analysis. To throw light on possible mechanisms underlying the wide variation in response to aflatoxins among salmonid fish, DNA extracted from the livers of rainbow trout (susceptible species) and coho salmon (Oncorhynchus kisutch) (less susceptible species) were compared following AFB1 treatment. A high rate of DNA binding was observed in rainbow trout, whereas significantly lower values were evident in coho salmon, suggesting a direct relationship between binding levels and susceptibility to mycotoxin carcinogenicity.

Distribution of the novel anticancer drug candidate brequinar sodium (DuP 785, NSC 368390) into normal and tumor tissues of nude mice bearing human colon carcinoma xenografts

The distribution of the novel anticancer drug candidate Brequinar Sodium (DuP 785, NSC 368390) was studied in control mice and mice implanted subcutaneously with human colon carcinoma xenografts. Mice were given radiolabeled 14C-Brequinar Sodium intravenously. Brequinar concentrations in blood and various tissues were determined at 1, 6, and 24 h after drug administration. Within 1 h Brequinar distributed to the tumor and all other tissues studied. The tumor-to-blood drug concentration ratios ranged from 0.19 to 0.41. Radioactivity in the liver and small intestine at 1 h accounted for 17% and 13%, respectively, of the dose given. Elimination rates of Brequinar from all tissues were approximately equal to that from blood. Comparison of blood concentrations determined by both radioactivity and HPLC methods suggests that the intact drug is probably the only form in the blood.

Uric acid metabolism in normal subjects and in gouty patients by chromatographic measurement of 14C-uric acid in plasma and urine

The turnover kinetics of uric acid were determined in a group of 25 subjects, including 6 controls, 17 gouty patients, and 2 subjects with asymptomatic hyperuricemia. According to their daily urate excretion while on a purine-free diet, the gouty patients (none of whom had evidence of tophi at the time of the study) were classified as follows: five overexcretor patients (“metabolic” gout), six normo-excretor patients (“renal” gout), and six borderline patients. Uric acid-2- 14C was used as the tracer, and the uric acid radioactivity in plasma and urine samples was measured after column chromatography through a polyacrylamide gel that specifically adsorbs uric acid. The experimental data of plasma disappearance curves and urine radioactivities of 14C-uric acid (followed up to 3 days after injection) were analyzed by the noncompartmental approach and by the urine/plasma ratio method, in order to calculate the total removal rate of uric acid, its distribution volumes, and the removal rate of uric acid through the renal route. The monocompartmental approach and the urine specific radioactivity methods were also employed to compute the uric acid turnover data, and the results were compared with those of noncompartmental analysis. The overexcretor patients were found to have normal metabolic clearance rate and fractional catabolic rate values, but significantly higher-than-normal total turnover rate values ( p < 0.005), whereas the normo-excretors had normal total turnover rate values but significantly lower metabolic clearance rate and fractional catabolic rate values compared to the controls ( p < 0.001). Uric acid excretion through the kidneys was found to be about two-thirds of the total removal both in the control subjects and in the gouty patients. The results obtained allowed the exclusion of any significant delay in the excretion of uric acid through the kidneys. The use of monocompartmental analysis led to a significant overestimation of both the total turnover rate ( p < 0.005) and the total pool of uric acid ( p < 0.001), and the urine specific radioactivity approach implied a significant overestimation of the total turnover rate ( p < 0.001). The gouty patients as a whole had a significantly larger-than-normal ( p < 0.001) total pool of uric acid, however determined. On the basis of the results obtained, a metabolic differentiation was made possible for the two pathophysiologic types of gout. In fact, the metabolic gout patients were all characterized by normal metabolic clearance rate values and increased total pool values, whereas the renal gout patients were all characterized by reduced metabolic clearance rate values and increased total pool values.

Proteins at liquid interfaces: I. Kinetics of adsorption and surface denaturation

The rates of change of film pressure (π) and surface concentration (Γ) of protein during the adsorption of β-casein, bovine serum albumin (BSA), and lysozyme at the air-water interface have been monitored by the Wilhelmy plate and surface radioactivity methods, respectively. The increases in π and Γ for the relatively flexible β-casein molecule occur simultaneously with both parameters attaining their steady-state values at about the same time. In contrast, π and Γ follow different time courses for the globular lysozyme molecule; Γ can reach a steady state value while π is still increasing significantly. The kinetics indicate that initially adsorption is diffusion-controlled but at higher surface coverages there is an energy barrier to adsorption. Under these conditions, the ability of the protein molecules to create space in the existing film and penetrate and rearrange in the surface is rate-determining. Two kinetic regions exist: the relaxation time τ 1 (typically ∼2 hr when Γ ∼2 mg m −2) describes the adsorption when both π and Γ are increasing whereas τ 2 (in the range 1–8 hr for all three proteins) relates to the situation when π is increasing at constant Γ because the protein molecules are changing conformation in the surface.

Proteins at liquid interfaces: II. Adsorption isotherms

Adsorption isotherms for the three proteins β-casein, bovine serum albumin, and lysozyme at the air-water and oil-water interfaces have been determined independently using ellipsometry and surface radioactivity methods; the surface pressure and surface potential were also monitored. Saturated monolayer coverage occurs via irreversible adsorption of 2–3 mg M −2 of protein; the resultant films generate surface pressures of about 20 mN m −1 and are 50–60 Å thick. Molecules adsorbed in the first layer dominate the film pressures so that further adsorption causes no change in the pressure although the film thickness can increase to more than 100 Å. The molecules which give rise to this increase in film thickness are reversibly adsorbed with respect to aqueous substrate exchange. The experimental isotherm data and the Langmuir adsorption isotherm are in close agreement at low protein concentrations. However, comparison with the Gibbs adsorption equation is not valid, although reasonable agreement can be achieved if some account is taken of the fact that the protein molecules in the first layer are irreversibly adsorbed.

Past and Future of Concrete Quality Evaluation

This paper examines the current practice, the recent developments, and the future prospects of various methods and techniques used for the quality evaluation of representative concrete and in-place concrete. Special attention is given to trends that will dominate the field in the future. Recent advances in accelerated test methods, ultrasonic testing, radioactivity methods, probe tests, pull-out tests, and rapid analysis of fresh concrete have been reviewed. The maturity concept, and its future role in the evaluation of concrete quality are mentioned. There is a great potential in the concrete industry for accelerated test methods and various nondestructive and partially destructive methods of testing in-place concrete.

The radioimmunoassay of steroid conjugates

The determination of steroid hormones and their metabolites by radioimmunoassay is now well established. Conventionally the steroid is converted into a derivative which introduces a carboxylic acid group and this group is joined covalently as a hapten to a carrier protein. Many steroids, both endogenous and exogenous, are excreted as glucuronides; such conjugates already have the carboxylic acid group necessary for covalent linkage and can be linked directly to protein. Several steroid-glucuronosyl-BSA complexes have been prepared and have been used as antigens in rabbits. Antisera thus produced bind steroid glucuronides with high specificity and they can be used to determine steroid glucuronides without preliminary hydrolysis. The development of this type of assay has been limited by the non-availability of labelled steroid conjugates of high specific radioactivity and general methods for the preparation of these radioligands have now been established. Conjugates treated in this way include; oestrone-3-, oestradiol-3, oestradiol-17β-, oestriol-3-, oestriol-16α-, dehydroepiandrosterone-3β and testosterone-17β-glucuronides. The work is currently being extended to include other steroid conjugates the determination of which has clinical importance.

Radioimmunoassay of protein hormones—techniques and clinical applications

Radioimmunoassay (RIA) has been applied to the measurement of a wide variety of protein and polypeptide hormones. Satisfactory performance of such assays requires the availability of the highly purified radioactively labelled antigen, of a specific antibody and of an effective method of separating antibodybound and unbound labelled antigen. Radioactive labelling is frequently performed with 125 I. Techniques for the separation of bound and free antigen include the use of precipitants of globulin, solid-phaseadsorbents which bind free radioactivity, and chromatographic and electrophoretic methods. Several approaches have been employed for the calculation of results obtained, with a growing trend to automatic data processing. The services of a laboratory specializing in RIA can provide assistance in equivocal clinical situations, e.g. in patients with borderline tests of thyroid function.

Radiative capture cross sections in medium-weight and heavy nuclei

Induced radioactivity methods have been used to measure radiative capture cross sections of alpha particles in 139La (bombarding energy 10–36 MeV), tritons in 138Ba (6–13 MeV), deuterons in 139La and 30Si (6–18 MeV) and protons in 82Se and 100Mo (5–50 and 5–20 MeV, respectively). The results are diffucult to reconcile with statistical theory. The direct radiative capture cross section calculated for the two proton capture reactions when enhanced by the particle-hole interaction approximates the experimental data over the entire energy range.

Radiative proton capture cross-sections in heavy nuclei

Induced radioactivity methods have been used to measure radiative capture cross-sections in Te 130, for protons of bombarding energy 5 to 20 MeV, Ce 142 (5–50 MeV) and Bi 209 (30–150 MeV). The results are compared with statistical theory predictions.

Tritiated bilirubin: preparation and physiological studies.

A procedure is described for the preparation of tritiated bilirubin by the Wilzbach technique, either directly (preparation W) or in conjunction with irradiation from a Co60 source (preparation C-W). After equilibration of the preparations with polar and nonpolar solvents to remove labile tritium and repeated precipitation, the constant specific activities were 110 µc/mg (W) and 30 µc/mg (C-W), respectively. Radiochemical purity of the bilirubin-H3 preparations and their azobilirubin-H3 derivatives was demonstrated by paper chromatography. Bilirubin-H3 and a high dose of carrier bilirubin were injected simultaneously into rats and the comparative bilirubin levels in serum and bile were determined by radioactivity and colorimetric methods. After 75 min, 20–30% of the initial label remained in the serum as nonbilirubin radioactivity. Pre-equilibration in vitro of bilirubin-H3 with albumin removed the protein-labile tritium. It was concluded that the adsorption of bilirubin to serum protein may involve hydrogen binding at an aliphatic group on the bilirubin molecule. In serum and bile the distribution of the bilirubin-H3 (pre-equilibrated with albumin in vitro) was identical to the distribution of bilirubin measured colorimetrically. The half-life for disappearance of bilirubin from serum in these rats was 25–35 min.

( N– Z) dependence of radiative deuteron capture cross-sections

Induced radioactivity methods have been used to determine the radiative deuteron capture cross-sections for Ni 58 and Cr 54 in the range of deuteron energies 3.5–4.5 MeV. When combined with previous measurements 1) of the Zn 64(d,γ) cross-section these results give the (d, γ) cross-sections for nuclei with N– Z = 2, 4 and 6. If there is a strong contribution to the cross-sections from direct electric dipole capture they should be proportional to the deuteron penetration factor and to ( N– Z) 2/ A 2. No evidence is found for such a direct contribution. For Ni 58( N– Z = 6) at a deuteron energy of 4.5 MeV σ (d, γ) = 295±45 μb and σ(d, p) = 75±12 mb. These cross-sections are consistent with an interpretation in terms of the statistical decay of a compound nucleus, the radiative probability being determined from photodisintegration data.

Systematics of Neutron Separation Energies

Photoneutron thresholds for 73 isotopes have been measured by radioactivity and neutron detection methods using a 25-Mev betatron. The neutron separation energies inferred from the observed thresholds are in general agreement with the values predicted from mass data and reaction energies. Several discrepancies are observed between threshold and neutron binding energies where ground state transitions require a spin change $&gt;~\frac{7}{2}$. For these nuclei, the threshold energies are consistent with neutron emission leaving the residual nucleus in an excited state.

Radiative deuteron capture Zn 64(d, γ)Ga 66

Induced radioactivity methods have been used to observed radiative deuteron capture in Zn 64 for deuteron energies of 3.5–4.5 MeV. Observations were made with NaI(Tl) gamma-ray spectrometers used singly and in coincidence and the 9.5 hour Ga 66 activity was identified in the presence of an intense 245 day Zn 65 activity resulting from the Zn 64 (d, p) and (d, n) reactions. At a deuteron energy of 4.5 MeV, σ(d, γ) = 80±12 μb and σ(d, n+d, p) = 0.16±0.02 b. The cross section ratio, σ(d, γ)/ σ(d, n+d, p) = 0.50±0.08×10 −3, is constant for 3.5–4.5 MeV deuterons. The magnitudes of the cross sections and their variation with energy are consistent with an interpretation in terms of the statistical decay of a compound nucleus, the radiative probability being calculated from photodisintegration data.

The stages in a process of severe metallic wear

In order to provide information about the basic processes involved in the wear of metals, a detailed study has been made of a severe type of wear. The particular system chosen was the wear of brass against a harder material under conditions in which the debris produced is metallic. Using radioactivity methods, transfer of metal between the rubbing surfaces was determined concurrently with measurements of the total wear. In experiments at various loads, the relationship between the rates of transfer and wear was studied. Particle-size distributions of the wear debris were obtained and compared with size distributions of the transferred fragments. It is concluded that wear occurs via a layer of transferred metal and that there is no direct production of loose wear particles. The wear process has at least two distinct stages; namely, the removal of metal from the wearing surface by transfer, and the formation of wear debris from the transferred layer on the opposing member. The magnitude of the applied load determines primarily the scale of the phenomena rather than the rate at which they occur.

Measurement of Moisture Content and Density of Soil Masses Using Radioactivity Methods

AbstractThis paper deals with the application of methods involving the scattering of neutrons and gamma rays to the measurement of moisture content and density of granular materials. The measurement of moisture content is based on the principle that when fast neutrons emitted from a radioactive source collide with hydrogen atoms they are slowed down to a much greater extent than by collisions with other atoms. The number of slow neutrons thus produced is a measure of the number of hydrogen atoms present in the vicinity of the source. Water is the principal contributor of hydrogen atoms in a soil medium. A probe, containing a source of fast neutrons and a slow neutron detector, is inserted into the soil. The probe is connected by a cable to a suitably calibrated scaling instrument, and the moisture content determined from the count rate.The density of a soil is measured with a probe that is similar but provided with a source and a detector of gamma radiation. The gamma rays emitted from this source are scattered by collisions with electrons of atoms in their path. The higher the density of the surrounding medium, the greater the scattering. In the range of densities normally occurring in soils, greater scattering results in fewer gamma rays returning to the detector. Thus, the density of the medium can also be related to the count rate obtained with the scaling instrument.The advantages of the radioactivity methods are that continuous or repeated measurements of moisture content and density at any desired depth can be made, and that measurements are integrated over a large volume of soil, so that representative values are obtained. In addition, water may be detected in the solid or vapor states as well as in the liquid state. The soil undergoes a minimum of disturbance because the probe is lowered into an access tube slightly greater than 1 inch in diameter. Measurements can be made in a short time; once the access tube has been placed, it takes an average of about six minutes to determine both moisture content and density at a given depth. The instruments are not influenced by ordinary temperature changes. The method appears to be relatively independent of soil type, so that a single calibration curve for moisture content, and one for density, may be applicable to a wide range of materials.A description of the theory of scattering of neutrons and gamma rays is included in this report as well as a discussion of the various types of sources and detectors which can be employed in the procedure. Field and laboratory tests utilizing these instruments are described, and the accuracy of test results discussed.It is concluded that application of this method will provide a rapid, simple and accurate means for measuring moisture content and density of soils or similar granular materials. On this basis, recommendations for future research and more extensive applications of the method are reviewed.

Age of extremely ancient pegmatites from south-eastern Manitoba.

IN the determination of the geological ages of minerals by radioactivity methods, much attention is being given to those ages which are of the greatest antiquity. There are several reasons for this. The age of the oldest mineral sets a minimum value for the age of the earth; also a probable minimum age is set for the solar system and extra-terrestrial matter in general. A bottom ‘rung’ is given for any stratigraphical age column, and these great ages are of value when attempting to draw up possible maximum life-spans for the evolution of living organisms to their present state of complexity. In areas of extreme antiquity, suitable minerals may be used for the indirect determination of the decay constants of potassium1; furthermore, areas of greatest age are the most suitable places for seeking possible undetected radioactivities (for example, indium-115 2). Consequently, it is highly desirable that these greatest ages be known accurately and that several checks be made.