Hybrid extractive scintillator resin for simultaneous concentration and detection of plutonium from aqueous solutions.

A scoping study of a commercially available resin selective for aqueous plutonium (Pu), AnaLig® Pu-02, modified with scintillator was investigated as a scheme to simultaneously concentrate and detect Pu in aquatic matrices. The extractive scintillating resin was comprised of a silica base, functionalized for plutonium extraction, grafted with plastic scintillator of polyvinyl toluene (PVT) and 2-(1-naphthyl)-4-vinyl-5- phenyloxazole (vNPO) fluor. Scintillator was incorporated onto the AnaLig® Pu-02 resin in a two-step process of silanization followed by surface-polymerization. Successful modification was facilitated by grinding the resin beads prior to silanization to expose cleaved silica surface sites appropriate for scintillator grafting. The modified resin was subjected to initial characterization of batch uptake and radioluminosity measurements where a total detection efficiency of 32.5% was observed. The modified resin was then subjected to pH 1 simulants containing environmental relevant groundwater constituents of varying concentration. Concentrations of 0.001M Fe(III) interfered with Pu uptake, while concentrations of up to 0.01M Ca(II) and 0.001 mM concentration of natural uranium and thorium had minimal influence on plutonium uptake. A translucent column packed with the modified AnaLig® Pu-02 was placed in a commercial flow-cell radiation detector for real-time detection of plutonium; a total detection efficiency of 20.4% was achieved for on-line measurements. The modification of AnaLig® Pu-02 results in a minimum detection limit capable of meeting the EPA limit for gross alpha activity in drinking water given a sufficient counting time of 15 min and approximately 300 mL of solution volume.

Increase in the reduction potential of uranyl upon interaction with graphene oxide surfaces.

Coordination of uranyl (U(vi)) with carboxylate groups on functionalized graphene oxide (GO) surfaces has been shown to alter the reduction potential of the sorbed uranium ion. A quantitative measure of the reduction potential and qualitative estimation of sorption/desorption processes were conducted using cyclic voltammetry, and the proposed coordination environment was determined using the surface sensitive attenuated total reflection mode of infrared spectroscopy (ATR-FTIR). GO is a nanostructured material possessing a large amount of oxygen-containing functional groups both on basal planes and at the edges, which can form strong surface complexes with radionuclides. The presence of these functional groups on the surface of GO allows efficient immobilization of uranium due to sorption of uranyl (UO22+) to carboxylate, hydroxide, or sulfonate functional groups and the potential for enhanced reduction of U(vi) to more strongly sorbing and insoluble U(iv). Herein, binding of U(vi) to carboxylate groups on the GO surface is proposed as the primary sorption mechanism based on the FTIR study. Furthermore, the coordination of uranium with the surface increases the reduction potential of the U(vi)/U(iv) redox couple as compared to the case of the aqueous U(vi)/U(iv) species. This is consistent with the alteration of the electronic structure of the sorbed ion, which can be determined in our case due to the use of a GO-coated working electrode. Thus, GO-coated glassy carbon electrodes and other semi-conducting electrodes with high ion sorption capacities may provide a means of examining the oxidation/reduction potentials of sorbed ions.

Mobility of radionuclides in soil/groundwater system: comparing the influence of EDTA and four of its degradation products.

The adsorption behavior of 241Am, 60Co, 137Cs and 85Sr in the presence and absence of chelating ligands (ethylenediaminetetraacetic acid, ethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, iminodiaceiticacid and methyliminodiacetic acid) was investigated. Sorption affinity in the absence of chelating ligands followed: Am(III)>Co(II)>Cs(I)>Sr(II). The presence of chelating ligands generally had little effect on sorption of 85Sr and 137Cs with Kd values 110 and 690 mL g(-1), respectively. But at 0.02 M of ethylenediaminetetraacetic or hydroxyethyliminodiacetic, the Kd decreased to 5 or 63 mL g(-1), respectively, where thermochemical modeling indicated almost all 85Sr is complexed with these ligands. The Kd values for 241Am and 60Co generally decreased with increasing chelating agent concentrations. In notable cases, the Kd values for Am increased at specific concentrations of 10(-3) M for IDA, MIDA and 10(-4) M for EDDA. This is proposed to be due to formation of a ternary surface complex.

Theoretical organically bound tritium dose estimates.

This paper illustrates a theoretical approach to estimating the dose associated with the ingestion of both organically bound tritium and tissue free water tritium relative to the ingestion of only tissue free water tritium. Organically bound tritium, specifically non-exchangeable OBT, can result in an increased dose relative to that from exchangeable organically bound tritium and tissue free water tritium because of the longer biological half-life of the former resulting in a dose conversion factor that is twice that of the latter. Non-exchangeable organically bound tritium is tritium that is bound to carbon whereas exchangeable organically bound tritium is tritium bound to oxygen, nitrogen, or sulfur. Tissue free water ranges from 85+% in most fruits and vegetables down to approximately 10% in grains. The remaining edible food mass consists, in part, of exchangeable and nonexchangeable hydrogen that is incorporated into carbohydrates, proteins and fat. The potential organically bound tritium content of several common food items was calculated knowing the amount of bound and unbound hydrogen that exists in these foods and by assuming that the hydrogen to tritium ratio is the same for the "free water" and bound hydrogen compartments. The theoretical ratio of dose from ingestion of organically bound tritium and tissue free water tritium to dose from ingestion of only tissue free water tritium was calculated to be on average within 12%, 30%, and 261% of experimentally based values for fruits and vegetables, meats and eggs, and grains, respectively. The difference is attributed to the T:H ratio being a function of the kinetics associated with the assimilation of tritium into the tissues.

The weak CD8+ CTL response to an influenza hemagglutinin epitope reflects limited T cell availability.

One of the two class I MHC (H-2Kd)-restricted immunogenic regions identified on the influenza virus strain A/Japan/57 (H2N2) hemagglutinin (HA) encompasses two distinct, partially overlapping epitopes. These epitopes map to residues 204 to 212 (JHA 204-212) and 210 to 219 (JHA 210-219), respectively. When we investigated the magnitude of the CTL responses of H-2d BALB/c mice to these two epitopes, we found that the JHA 204-212 nonamer epitope is immunodominant, eliciting vigorous CTL responses in BALB/c mice immunized with A/Japan/57 virus. In contrast, the CTL response to the JHA 210-219 decamer epitope was weak and variable. The subdominance of the JHA 210-219 was not due to low affinity binding of JHA 210-219 to H-2Kd or to inefficient processing of this epitope in vivo. Rather, an analysis of CTL precursor (pCTL) frequency by limiting dilution showed that the frequency of pCTL to the JHA 210-219 epitope was at least 10-fold lower than the frequency of pCTL to the JHA 204-212 epitope, implying that the low and variable response to the JHA 210-219 epitope was due to a limited number of CD8+ T cell precursors directed to JHA 210-219. This hypothesis was further supported by the finding of limited heterogeneity in reactivity pattern displayed by short term bulk cultures of the JHA 210-219-specific CTLs for cross-reactive epitopes. Implications of these findings for vaccine design and for T lymphocyte function and repertoire development are discussed.

Recognition of an immunoglobulin VH epitope by influenza virus-specific class I major histocompatibility complex-restricted cytolytic T lymphocytes.

There are two immunogenic sites on the type A influenza A/Japan/57 (H2N2) hemagglutinin (HA) that can be recognized by class I major histocompatibility complex (MHC), H-2Kd-restricted cytolytic T lymphocytes (CTLs). One of these sites encompasses two distinct partially overlapping epitopes, which span HA residues 204-212 and 210-219. During the analysis of the fine specificity of CTL clones directed to the HA 210-219 epitope, we found that one clone 40-2 also recognized the myeloma cell line P3x63-Ag8. P3x63-Ag8 is derived from the MOPC 21 myeloma and expresses an immunoglobulin (Ig) heavy chain variable region (VH) gene which is a member of the murine 7183 VH gene family. Recognition was specific for the endogenously processed MOPC 21 heavy chain in association with the Kd molecules, since the SP2/0 derivative of P3x63-Ag8, which does not make a functional Ig H chain, is not recognized. The VH epitope recognized by clone 40-2 could be mapped to a 10 amino acid peptide spanning MOPC 21 VH residues 49-58. Cross-reactivity for the VH gene product was also demonstrable in some heterogeneous populations of CTL generated in response to influenza virus infection. These results represent the first demonstration of cross-reactivity for an endogenously processed product of a self-Ig by the CTL directed to a foreign antigen and raise the possibility that the Ig VH expression may regulate the CD8+ T cell response to foreign antigens.

Fluorescence of tetraphenyl-butadiene in the vacuum ultraviolet.

Tetraphenyl-butadiene is a useful alternative to sodium salicylate as a fluorescent wavelength converter for detectors in the vacuum uv. Measurements of the fluorescence efficiency of TPB relative to sodium salicylate over the wavelength range 735-3160 A are presented, and the application of TPB coatings to image tube detectors is discussed. Over the entire wavelength range studied TPB had a higher fluorescent efficiency than sodium salicylate.