Suitability and Applications of Total-Reflection X-Ray Fluorescence Spectrometry for Analytical Characterization of Nuclear Materials.

The suitability and applications of Total reflection X-ray Fluorescence (TXRF) for characterization of nuclear materials are numerous. TXRF has been successfully applied for trace, minor and major determinations of constituents in nuclear materials such as fuel, clad, control rod, coolant, etc. The two major advantages of TXRF i.e. requirement of very small sample for analysis and non-requirement of matrix matched standards, make this technique further more attractive and suitable for nuclear industry. The applications of TXRF for trace analysis in nuclear materials such as fuel, clad, coolant and control rods are described in detail along with its applications for determination of major and speciation studies in TXRF mode.

Histone acetylation: a key determinant of acquired cisplatin resistance in cancer.

Cisplatin is an alkylating class of chemotherapeutic drugs used to treat cancer patients. However, cisplatin fails in long-term treatment, and drug resistance is the primary reason for tumor recurrence. Hence, understanding the mechanism of acquirement of chemoresistance is essential for developing novel combination therapeutic approaches. In this study, in vitro cisplatin-resistant cancer cell line models were developed. Gene ontology and GSEA of differentially expressed genes between parental and resistant cells suggest that PI3K-AKT signaling, central carbon metabolism, and epigenetic-associated phenomenon alter in cisplatin-resistant cells. Further, the data showed that increased glucose transport, alteration in the activity of histone-modifying enzymes, and acetyl-CoA levels in resistant cells paralleled an increase in global histone acetylation. Enrichment of histone acetylation on effectors of PI3K-AKT and glycolysis pathway provides evidence of epigenetic regulation of the key molecules in drug resistance. Moreover, cisplatin treatment to resistant cells showed no significant changes in histone acetylation marks since drug treatment alters cell epigenome. In continuation, targeting PI3K-AKT signaling and glycolysis leads to alteration in histone acetylation levels and re-sensitization of resistant cells to chemo-drug. The data provide evidence of histone acetylation's importance in regulating pathways and cisplatin-resistant cells' cell survival. Our study paves the way for new approaches for developing personalized therapies in affecting metabolic pathways and epigenetic changes to achieve better outcomes for targeting drug-resistant cells.

A highly sensitive method for uranium quantification in water samples at ultra-trace level by total reflection X-ray fluorescence, after its direct pre-concentration on the surface of amidoxime functionalized quartz sample supports.

In this work we have developed a Total reflection X-Ray Fluorescence (TXRF) based methodology for the determination of uranium in natural water samples at ultra-trace concentration level. The methodology involves functionalization of quartz sample supports used for TXRF measurements with (3-Amidoxy) triethoxysilane, which has very high uranium uptake efficiency. (3-Amidoxy) triethoxysilane has been synthesized from (3-Cyanopropyl) triethoxysilane (CPTS). This amidoxime functionalized sample supports, simply needed to be dipped in the uranium solution for 3 h after which, it can be directly taken for TXRF measurements. The developed methodology is very fast, simple with less sample preparation steps involved. The present work utilizes Rayleigh scattered peak to construct the calibration curve for the quantification purpose. The developed methodology has improved accuracy as well as precision for the quantification of uranium at such low concentrations level. The detection limit and accuracy obtained are 0.013 ng/mL (13 ppt) and 1.9%, respectively which are the lowest using any X-Ray Fluorescence based method, to the best of our knowledge. The method was successfully applied for the U determination in natural water samples like ground water, river water and sea water.

Direct non-destructive trace and major elemental analysis in steel samples utilizing micro-focused bremsstrahlung radiation in X-ray fluorescence geometry.

Stainless steel is a very important technological material used in various industries. In this work, a simple non-destructive method is developed for major as well as trace elemental determination in stainless steel samples using micro-X-ray fluorescence (XRF) based technique. The utilization of full bremsstrahlung excitation in combination with micro-focused geometry substantially reduces the detection limit of different elements present in stainless steel. The developed methodology is capable of determining elemental concentrations down to 30-80 ppm level in stainless steel matrix without any requirement of cumbersome dissolution or separation procedure. Elements such as Si, P, S and Co were determined simultaneously at trace level using the developed micro-XRF based technique. At the same time this technique is also capable of analyzing elements which are present at percentage levels. Till now there is no such report showing the capability of lab-XRF based non-destructive technique for the analysis of both major as well trace elements down to such low concentration level to the best of our knowledge. Moreover, the methodology involved is very simple and straight forward. The analytical results obtained were very much satisfactory with good accuracy and precision.

A Direct Non-destructive Method for Determination of Sulfur in Ore Samples Using EDXRF Spectrometry.

A method has been developed for direct non-destructive energy dispersive X-ray fluorescence (EDXRF) determination of sulfur in solid uranium ores and intermediates, obtained from the alkaline recovery process for uranium from its ores. The method involves thorough grinding of a few mg of solid powder samples to fine particle size and mixing the fine powder thus obtained with a few drops of 10% collodion solution in amyl acetate to make a paste. A very small amount of this paste was transferred with the help of the pestle tip, spread uniformly in the form of thin slurry on Mylar films, and dried to make very thin sample specimens on thin Mylar film supports. These specimens were presented for EDXRF measurements. A calibration plot was made by plotting the intensity ratios of S Kα and Rayliegh scattered peak of the excitation source (Ge Kα) against sulphur percent in the certified reference materials (CRMs). It was found that the precision obtained using this methodology was within 5% (±1σ) and the deviation of the EDXRF analytical results from the expected values of CRM was within 7%. The developed method was successfully applied for the determination of sulfur in the samples obtained from the different stages of the uranium ore processing using alkaline based leaching method.

Direct non-destructive total reflection X-ray fluorescence elemental determinations in zirconium alloy samples.

The development of a direct non-destructive synchrotron-radiation-based total reflection X-ray fluorescence (TXRF) analytical methodology for elemental determinations in zirconium alloy samples is reported for the first time. Discs, of diameter 30 mm and about 1.6 mm thickness, of the zirconium alloys Zr-2.5%Nb and Zircalloy-4 were cut from plates of these alloys and mirror polished. These specimens were presented for TXRF measurements directly after polishing and cleaning. The TXRF measurements were made at the XRF beamline at Elettra synchrotron light source, Trieste, Italy, at two different excitation energies, 1.9 keV and 14 keV, for the determinations of low- and high-Z elements, respectively. The developed analytical methodology involves two complementary quantification schemes, i.e. using either the fundamental parameter method or relative sensitivity based method, allowing quantification of fifteen minor and trace elements with respect to Zr with very good precision and accuracy. In order to countercheck the TXRF analytical results, some samples were analyzed using the DC arc carrier distillation atomic emission spectrometry technique also, which shows an excellent agreement with the results of the TXRF-based methodology developed in this work. The present work resulted in a non-destructive TXRF elemental characterization methodology of metal and alloy samples avoiding the cumbersome dissolution and matrix separation which are normally required in other techniques and traditional methods of TXRF determination. In addition, the production of analytical waste could also be avoided to a large extent. Although the work was carried out for specific applications in the nuclear industry, it is equally suitable for other such samples in different industrial applications.

Universal EDXRF Method for Multi-elemental Determinations Using Fused Bead Specimens.

A systematic study on the EDXRF determination of multi-elements using fusion bead specimens and a universal calibration procedure was carried out. Beads of multi-elements were prepared by mixing MERCK multi-elemental standard solutions with the fusion flux. The elemental X-ray lines of K, Ca, Ba, Cr, Mn, Fe, Co, Ni, Cu and Zn were excited using a Ge secondary target and that of Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Pb, Bi and Sr using a Rh primary target. The relative sensitivities of the elemental X-ray lines obtained using different excitation modes were calculated using a single bead. Using this relative sensitivity, the concentration of elements in other bead samples was determined. The average precision obtained was 3% (1 s) and the average deviation from expected values, calculated on the basis of sample preparation, was 6%. In order to further countercheck the validity of this methodology, a standard soil sample received from IAEA was analyzed.

Direct Multielemental Trace Determinations in Plutonium Samples by Total Reflection X-ray Fluorescence Spectrometry Using a Very Small Sample Amount.

A simple, safe, and sensitive method for direct multielemental trace determinations in plutonium samples using total reflection X-ray fluorescence (TXRF) spectrometry has been developed. A very small volume (2 µL) of the sample solutions was deposited on TXRF supports after separation of the plutonium matrix from these solutions. Since the amount of the plutonium deposited on the supports was in the ng level only fixed on the supports and the specimen spots were not disturbed during the sample preparation, the samples could be analyzed directly without putting the instrument in a glovebox. This approach avoided a cumbersome operation of the instrument in a glovebox, which is normally utilized for Pu-based samples using other techniques. Similarly, the requirement of small amounts of the samples minimized the radiation dose to the operator as well as a cumbersome problem of management of radioactive analytical waste of plutonium samples. The samples were analyzed using the TXRF spectra of the specimens, concentration of the internal standard Se or Ga and predetermined sensitivity values. The elemental detection limits for the elements K-Sr varied from 1.06 to 0.09 ng. The elements K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Ba, Tl, and Pb were analyzed at µg/mL level. The analytical results of TXRF determinations showed average relative standard deviation (RSD) value of 4.5% (1σ, n = 3) and the TXRF determined results deviated from the expected values by 5.9% on average for samples prepared by adding multielements in plutonium solutions. Two real plutonium samples were also analyzed in similar manner. For the real plutonium sample solution the average RSD values of TXRF determinations were 10.6% (1σ, n = 3) for the elemental concentrations in the range of 0.2 to 61 µg/mL. These values are comparable with conventional trace element analytical techniques with added advantages mentioned above.

Direct Compositional Characterization of (U,Th)O2 Powders, Microspheres, and Pellets Using TXRF.

A total reflection X-ray fluorescence (TXRF) analysis method for direct compositional characterization of sintered and green (U,Th)O2 samples in different forms (e.g., pellets, powders, and microspheres) without sample dissolution has been developed for the first time. The methodology involves transfer of only a few nanograms of the sample on the TXRF sample support by gently rubbing the samples on supports or taking their tiny uniform slurry in collodion on the sample support, drying them to make thin film, and measuring the TXRF spectra of the specimens thus prepared. This approach minimizes the matrix effects. Uranium determinations from the TXRF spectra of such specimens were made with respect to thorium, considering it as an internal standard. Samples having uranium atom percent (at%) from 0 to 100 in (U,Th)O2 were analyzed for uranium in comparison to thorium. The results showed an average precision of 2.6% (RSD, 2σ, n = 8). The TXRF-determined results deviated from expected values within 5%. The TXRF results were compared with those of biamperometry with good agreement. The lattice parameters of the solid solutions were calculated using their XRD patterns. A good correlation between lattice parameters and TXRF-determined U at% and between TXRF-determined U at% and expected U at%, calculated on the basis of preparation of (U,Th)O2 solid solutions, was obtained. The developed method is capable of analyzing (U,Th)O2 samples directly with almost negligible sample preparation and is well suited for radioactive samples. The present study suggests that this method can be extended for the determination of U,Th and Pu in other nuclear fuel materials (e.g., nitrides, carbides, etc.) in the form of pellets, powders, and microspheres after suitable modifications in sample handling procedure.

Characterization of Sb-doped Bi(2)UO(6) solid solutions by X-ray diffraction and X-ray absorption spectroscopy.

The preparation and characterization of Sb-doped Bi(2)UO(6) solid solutions, in a limited composition range, is reported for the first time. The solid solutions were prepared by solid-state reactions of Bi(2)O(3), Sb(2)O(3) and U(3)O(8) in the required stoichiometry. The reaction products were characterized by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) measurements at the Bi and U L(3) edges. The XRD patterns indicate the precipitation of additional phases in the samples when Sb doping exceeds 4 at%. The chemical shifts of the Bi absorption edges in the samples, determined from the XANES spectra, show a systematic variation only up to 4 at% of Sb doping and support the results of XRD measurements. These observations are further supported by the local structure parameters obtained by analysis of the EXAFS spectra. The local structure of U is found to remain unchanged upon Sb doping indicating that Sb(+3) ions replace Bi(+3) during the doping of Bi(2)UO(6) by Sb.

Synthesis of oleic acid functionalized Fe3O4 magnetic nanoparticles and studying their interaction with tumor cells for potential hyperthermia applications.

In the present study, oleic acid (OA) functionalized Fe3O4 magnetic nanoparticles (MN) were synthesized following modified wet method of MN synthesis. The optimum amount of OA required for capping of MN and the amount of bound and unbound/free OA was determined by thermogravimetric analysis (TGA). Further, we have studied the effect of water molecules, associated with MN, on the variation in their induction heating ability under alternating current (AC) magnetic field conditions. We have employed a new approach to achieve dispersion of OA functionalized MN (MN-OA) in aqueous medium using sodium carbonate, which improves their biological applicability. Interactions amongst MN, OA and sodium carbonate were studied by Fourier transform infrared spectroscopy (FT-IR). Intracellular localization of MN-OA was studied in mouse fibrosarcoma cells (WEHI-164) by prussian blue staining and confocal laser scanning microscopy (CLSM) using nile blue A as a fluorescent probe. Results showed MN-OA to be interacting mainly with the cell membrane. Their hyperthermic killing ability was evaluated in WEHI-164 cells by trypan blue method. Cells treated with MN-OA in combination with induction heating showed decreased viability as compared to respective induction heating controls. These results were supported by altered cellular morphology after treatment of MN-OA in combination with induction heating. Further, the magnitude of apoptosis was found to be ~5 folds higher in cells treated with MN-OA in combination with induction heating as compared to untreated control. These results suggest the efficacy of MN-OA in killing of tumor cells by cellular hyperthermia.

Galvanic reactions involving silver nanoparticles embedded in cation-exchange membrane.

Galvanic reactions of Hg(2+), Rh(3+), and AuCl(4)(-) ions with Ag nanoparticles positioned near the surface and throughout the matrix of host poly(perfluorosulfonic) acid membrane have been studied.