JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2010 | Volume:- | Issue:4 (50)|Papers Count:14

In this work, the ability of free and immobilized deactivated baker's yeast saccharomyces cerevisiae to remove uranium ions was investigated using a batch biosorption procedure with respect to the initial pH (3.0-6.0), contact time (24 h), initial ion concentration (50-400 mg/g) and presence of secondary ions (Cr (VI)). The removal of uranium was approximately 90% and 50% at low concentrations, whereas it was about 80% and 15% at high concentrations at an optimum pH of 5 and 5.5, using 1 g/l of adsorbent in 24 h of equilibration time for immobilized and free baker's yeast, respectively. Experimental results at 30°C indicated that the uptake capacity of uranium ions by immobilized baker's yeast biomass on calcium alginate was reduced by the presence of secondary ions. The experimental data obtained at the optimum have been analyzed using two two-parameter models, Langmuir and Freundlich, and one three-parameter model, Redlich–Peterson. Taking into three statistical error functions, the data were best fitted to the Redlich–Peterson model. Using the Langmuir equation, the saturated monolayer sorption capacities of uranium ions onto immobilized and free baker's yeast were 592.8 and 73 mg/g, respectively at 30°C.

153Sm-EDTMP is one of the well known radiopharmaceuticals for pain palliation of bone metastases. Despite that, it is used just in a few countries. It is due to some reasons like being costly enriched samarium that usually used as target for irradiation and short half-life of 153Sm. In this investigation, certain amounts of radiopharmaceuticals prepared by irradiation of enriched and natural samarium were injected to some normal rats. Then, the rodents were sacrificed and some of their organs were removed. All of the mentioned stages were performed in order to consider the possibility of exploiting natural samarium instead of enriched samarium by study of biodistribution of both radiopharmaceuticals in various organs especially in bone as the target tissue. At the end, the acceptable results were obtained using natural samarium in comparison with the enriched samarium from the point of view of the biodistributionstudies.

Polymeric absorbents are extensively used in the separation systems. In this paper, the preparation and characterization of a polymeric absorbent is considered.For this purpose Polyvinyl alcohol (PVA) films were prepared and then crosslinked by radiation method using gamma-ray and chemical methods by the use of Glutaraldehyde solution. In the chemical method, the reaction with and without sulphuric acid and in the radiation method the reaction in dry and also aqueous media containing acid were carried out. The gel content, water uptake and tensile properties were measured for all samples. The results showed that the radiation method in aqueous media containing acid led to the maximum gel formation. In addition, the radiation method led to the formation of films with more flexibility. Nickel and Manganese adsorptions were measured on the crosslinked films, which were obtained by the radiation and chemical methods. These measurements were made as a function of pH and also the concentration of metal ion in the solution. The maximum metal adsorption was found at pH=7. In addition, with increasing the metal ion concentration the amount of ion adsorption was increased. In general, our studies showed that an absorbent which is prepared by the radiation method is suitable for water adsorption and another formed by the chemical method is desirable in ion adsorption processes.

Zirconium molybdate gel has an excellent characteristic to be used as a column matrix material of 99mTc generators. The preparation conditions of zirconium molybdate gels will directly influence their physico-chemical characteristics and thus generator performances. In this work a series of zirconium molybdate gels were synthesized under different conditions and characterized by ICP, TGA, XRD and SEM Techniques. The effects of different parameters including pH of molybdate solution, Zr:Mo molar ratios, order of reactants addition, washing and granulating of gel on the performance of technetium-99m generators were evaluated. The experiments show that the optimum conditions for synthesis of the gel consist of: pH=4-4.5, Zr:Mo ratio of 1:1, gradual addition of molybdate solution to zirconium oxy chloride solution, no washing and grinding the resulted gel.

Gallium-67 labeled superparamagnetic iron oxide nanoparticles ([67Ga]-SPION) were prepared and evaluated for their altered biodistribution in normal rats. SPIONs with narrow size distribution were synthesized by co-precipitation technique using ferric and ferrous salts at molar ratio Fe3+/Fe2+=2:1 followed by structure identification using XRD, TGA, DSC, VSM, HRSEM, TEM and FT-IR techniques. In order to trace SPION bio-distribution, the radiolabeled iron oxide nanoparticles were prepared using 67Ga with a high labeling efficiency (over 96%, determined by RTLC method) and they also showed an excellent stability at room temperature for at least 4 days. The biodistribution of the radiolabeled SPION was checked in normal male rats up to 24 hours compared with the free Ga3+ cation biodistribution. The data strongly support the alteration of the tracer accumulation in reticuluendothelial system while the stability of the complex is highly retained. The result is promising for determining the position of the nanoparticles injected into a tissue when hyperthermia treatment/imaging is applied in biomedical fields.

One of the most important measures of therapeutic quality in Microbeam Radiation Therapy (MRT) is the Peak to Valley Dose Ratio (PVDR). This parameter is a criterion to evaluate ablation of cancerous cells and sparing of normal cells in tumor and in its surrounding region. The aim of this work is to study the influence of using gold and gadolinium nano-particles as contrast agents on dose distribution and PVDR when a phantom is irradiated by a typical micro-planar X-ray beam of European Synchrotron Radiation Facility (ESRF3). Using Geant4 computer code, a model has been designed to simulate depth dose in an intact phantom made of PMMA4 and dose distribution in a phantom containing assumed tumors in therapeutic techniques of MIMRT5 and BIMRT6. Comparison of simulated results in the intact phantom with the measured values of depth dose reveals the validity of our simulation with the designed model. To improve the efficiency of MRT, enhancement of absorbed dose in tumor tissues and sparing of normal tissues due to presence of contrast agents have been studied. The obtained results show that the enhancement is more noticeable for Au at the peak region and for Gd in the valley region. This approach of introducing contrast agents in MRT could hopefully prepare new treatment planning and improves the efficiency of tumor therapy.

The main goal of this work is designing the cavity of an accelerator and performing its calculations. By choosing “p/2” oscillation mode and using Superfish code, cavity dimensions for the desired parameters were calculated. The most important dimension for determining the resonance frequency is the radius of cylindrical cavity. The required precision for the cavity construction has been obtained by calculating the frequency variations versus the dimensions variation. Also, with the resulted electric field from Superfish code, its Fourier expansion, and considering the unidirectional components of the traveling waves, the major effect of one component in accelerating and its proper velocity have been demonstrated.

Three cation exchangers namely potassium zinc hexacyanoferrate (II) (PZF), ammonium molybdophosphate (AMP) and magnesium oxide-polyacrylonitrile composite (MgO-PAN) were synthesized. The physicochemical properties of these ion exchangers were determined using different techniques including infrared spectroscopy (IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Furthermore, the thermal stability and the effect of gamma irradiation up to 150kGy on these ion exchangers were investigated. The distribution coefficients of 90Sr, 140La and 60CO were studied for these ion exchangers by varying the pH conditions and by the use of batch method. The three prepared materials showed an increased trend in the sorption for three radionuc1ides (90Sr, 140La and 60CO) with the increasing of pH values from 1 to 7.

A new 99Mo adsorbent has been prepared with modified silica gel with zirconium oxide (SiO2/ZrO2: Na2MoO4) and used in technetium-99m generator. The adsorption behaviors of 99Mo in the form of molybdate and 99mTc in the form of pertechnetate on the new adsorbent was investigated showed that the adsorption capacity of molybdate on this generator was considerably higher than the usual generator with alumina column. Coating zirconium oxide on the surface of silica gel resulted in higher 99Mo adsorption of this compound. 99mTc is eluted with 0.9% NaCl, and the radiochemical, radiochemical and chemical purities of the eluate were checked. This generator has a great potential as compared to the traditional alumina generators.

In this study, degradation and decoloration of reactive and acid commercial dyes (C.I. Reactive Black 5 and C.I. Acid Red 151) in water under the irradiation with electron beams were investigated. Both dyes in aqueous solutions with the concentration of 100 ppm were irradiated at different doses of 1, 3, 6 and 9 kGy. The changes of the absorption spectra, degree of decoloration, pH, and chemical oxygen demand (COD) were analyzed. In addition to the influence of the absorbed dose the hydrogen peroxide additions on RB5 dye are discussed. The experimental results show that the reactive and acid dyes in aqueous solutions can be effectively degradiated by irradiation with the electron beam. The absorption bands for RB5 and AR151 decreased rapidly at 1kGy irradiation dose and disappeared almost completely at 9kGy. Also the degree of decoloration of RB5 solution at 1kGy dose and with the concentrations of H2O2 up to 5mmol/L was higher than 99.78%. Due to the production of organic and inorganic acidic anions the pH decreased during the irradiation.

Various methods of Kriging and nonlinear geostatistical methods considered as acceptable methods for resource and reserve estimations have characters such as the least estimation variance in their nature, and accurate results in the acceptable confidence levels range could be achieved if the required parameters for the estimation are determined accurately. If the determined parameters don't have the sufficient accuracy, 3-D geostatistical estimations will not be reliable any more, and by this, all the quantitative parameters of the mineral deposit (e.g. grade-tonnage variations) will be misinterpreted. One of the most significant parameters for 3-D geostatistical estimation is the anisotropy ellipsoid. The anisotropy ellipsoid is important for geostatistical estimations because it determines the samples in different directions required for accomplishing the estimation. The aim of this paper is to illustrate a more simple and time preserving analytical method that can apply geophysical or geochemical analysis data from the core-length of boreholes for modeling the anisotropy ellipsoid. By this method which is based on the distribution of covariance clouds in a 3-D sampling space of a deposit, quantities, ratios, azimuth and plunge of the major-axis, semi-major axis and the minor-axis determine the ore-grade continuity within the deposit and finally the anisotropy ellipsoid of the deposit will be constructed.

Polymethylmethacrylate-silver (pMMA/Ag) nanocomposite is synthesized by irradiating the solution of silver ions in methylmethacrylate monomer by g-ray. In this method, polymerization of the methylmethacrylate monomer and the silver ion reduction occurred simultaneously. Optical properties of the PMMA/Ag solutions are investigated using UV-Vis spectroscopy. The structural characterizations of the PMMA/Ag nanocomposite are determined by FTIR spectroscopy XRD, and SEM measurements. The SEM image shows that the Ag nanoparticles disperse in the PMMA matrix with a relatively uniform distribution. The antibacterial studies show that the PMMA/Ag nanocomposite is antibacterial against E. coli, as a model for gram-negative bacteria.