A radionuclide generator for the production of211Pb and its daughters

²¹¹Pb and its daughters are produced in a generator system which utilizes the distillation of the intermediate daughter²¹⁹Rn from²²³Ra. The radium is precipitated as the stearate to isolate the parent while allowing the gaseous daughter to emanate. While the yield of the system is low, approximately 10%, the radionuclidic purity is extremely high. No measurable²²³Ra is found in the product.²²³Ra is separated from its parent,²²⁷Ac, by cation exchange.Deceased.Research supported in part by the Office of Health and Environmental Research, U.S. Dept. of Energy.     

A generator system for production of medical alpha-radionuclides Ac-225 and Bi-213

A generator system, consisting of two anion- and one cation-exchange columns for production of medical α-radionuclides ²²⁵Ac and ²¹³Bi, has been developed. The first anion-exchange column was used for periodical separation of ²²⁵Ac from Th with 8 M HNO₃, while the second anion-exchange column was employed for purification of ²²⁵Ac from Ra and inactive impurities in mixed HNO₃/CH₃OH media. From anion-exchange column ²²⁵Ac was stripped with 0.1–0.2 M HNO₃ and loaded directly onto cation-exchange column, used as a generator for repeated isolation of ²¹³Bi. The cation exchange behavior of Bi and other radionuclides of the interest were studied in diluted HCl, HBr and DTPA solutions used as eluents. As result, a simple and effective method for the production and purification of ²²⁵Ac and ²¹³Bi suitable for biomedical studies was elaborated.     

An improved computer model of struvite solution chemistry

The computer model of the solution chemistry of struvite has been improved. Firstly, with ammonia as the prime calculation point in the liquid phase, the algorithm is smaller and faster. Secondly, the incorporation of distilled magnesium hydrogen phosphate in the model significantly increased the concentrations in solution. Thirdly, estimates of the activity coefficients are included. These improvements have but a marginal (5–10%) improvement in the fit. However, proceeding with this flexible modelling procedure using the symbolic manipulator, Maple, easily allows the inclusion of all possible species. The addition of associated ammonium phosphates improves the fit. The relative standard deviation of the fit of both Taylor's data and the data of Webb is improved from 0.5 to 0.2. Estimates of the association constants are included.     

Preparation of targets for nuclear chemistry experiments at DANCE

In this paper, we describe the separation chemistry and electrodepositions conducted for the preparation of ²⁴¹Am, ²⁴³Am and ²³³U targets used for cross-section measurements at DANCE. Thick, adherent deposits were prepared using molecular plating from isopropyl alcohol solutions. Improved yields and thicknesses were observed for ²⁴¹Am electrodeposition after the material was purified using TRU resin from Eichrom. Similarly, ²³³U deposits were improved after purification with an anion exchange column in 9 M HBr followed by purification using UTEVA resin from Eichrom.     

Preparation of americium targets for nuclear chemistry experiments at DANCE

Using 1 gram of ²⁴¹Am from LANL stocks, the purification steps required to obtain a solution of ²⁴¹Am from the original material are described. Part of the purified solution was submitted for purity analysis by mass spectrometry, radiochemistry and trace metals analysis. The impurities were expected to be ²³⁹Pu and ²³⁷Np. A second fraction of this material was used for electroplating three samples onto titanium disks that were suitable for insertion into an instrument package to be placed into the DANCE detector. The purification methods used, the electroplating setup and the solutions to various problems that were encountered in making these targets are discussed. The analytical results are discussed as well as the yields from the electrodeposition process. Comparison of these yields with those from similar experiments utilizing ²³⁵U and ²⁴³Am are also discussed.     

Intermetallic compounds of the heaviest elements and their homologs: the electronic structure and bonding of MM', where M=Ge, Sn, Pb, and element 114, and M'=Ni, Pd, Pt, Cu, Ag, Au, Sn, Pb, and element 114

Fully relativistic (four-component) density-functional theory calculations were performed for intermetallic dimers MM', where M=Ge, Sn, Pb, and element 114, and MM'=group 10 elements (Ni, Pd, and Pt) and group 11 elements (Cu, Ag, and Au). PbM and 114M, where M are group 14 elements, were also considered. The results have shown that trends in spectroscopic properties-atomization energies D(e), vibrational frequencies omega(e), and bond lengths R(e), as a function of MM', are similar for compounds of Ge, Sn, Pb, and element 114, except for D(e) of PbNi and 114Ni. They were shown to be determined by trends in the energies and space distribution of the valence ns(MM')atomic orbitals (AOs). According to the results, element 114 should form the weakest bonding with Ni and Ag, while the strongest with Pt due to the largest involvement of the 5d(Pt) AOs. In turn, trends in the spectroscopic properties of MM' as a function of M were shown to be determined by the behavior of the np(1/2)(M) AOs. Overall, D(e) of the element 114 dimers are about 1 eV smaller and R(e) are about 0.2 a.u. larger than those of the corresponding Pb compounds. Such a decrease in bonding of the element 114 dimers is caused by the large SO splitting of the 7p orbitals and a decreasing contribution of the relativistically stabilized 7p(1/2)(114) AO. On the basis of the calculated D(e) for the dimers, adsorption enthalpies of element 114 on the corresponding metal surfaces were estimated: They were shown to be about 100-150 kJ/mol smaller than those of Pb.     

An optimum strategy for solution chemistry using semiempirical molecular orbital method: Importance of description of charge distribution

For the purpose to execute direct dynamics calculation in solution chemistry, we propose an optimum strategy for solution chemistry using semiempirical molecular orbital (MO) method with neglect of diatomic differential overlap (NDDO) approximation with specific solution reaction parameters (SSRP), i.e., the NDDO‐SSRP method. In this strategy, the empirical parameters of the semi‐empirical MO method were optimized individually for target molecule or ion by reference to the ab initio MO calculation data for many configurations on the potential energy surface near the reaction path. For demonstration, the NDDO‐SSRP method was applied to two molecules and two ions (OH^?, H₂O, NH₃, NH₄⁺) at their equilibrium states in aqueous solution, respectively. Accordingly, it was verified that both the potential energy surface and the charge distribution of these solutes in aqueous solution are dramatically improved to reproduce themselves accurately at ab initio MO calculation level. In conclusion, it is expected that the NDDO‐SSRP method should become quite useful for dynamic and statistical applications to chemical reaction systems in solution. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

An N.M.R. study of the solution chemistry of vanadium pentafluoride

¹⁹F n.m.r. spectroscopy has been to investigate the solution chemistry of vanadium pentafluoride in a wide range of solvents. It is shown that VF₅ is a remarkably weak F^- acceptor even in the VF₅/AgF/HF system, and that it acts as a weak base in SbF₅ to give a fluxional mixed polymer.     

Synthesis of neamine libraries for RNA recognition using solution phase chemistry

Selective protection of the 6′-amino group of neamine allows the preparation of aminoglycoside libraries by reductive amination and Ugi multicomponent coupling.     

Development of a 212Pb and 212Bi generator for homolog studies of flerovium and moscovium

A simple generator using AG 50Wx8 cation exchange resin has been developed for continual elution of ²¹²Pb and ²¹²Bi from the parent radionuclide ²²⁸Th, derived from ²³²U. Using 0.4 M HCl as an eluent will elute ²¹²Bi while ²¹²Pb is eluted with 2 M HCl. The generator has shown good reproducibility of elution bands. A generator set-up in 2013 has been in continual use over 4 years demonstrating that this generator system has a long and stable lifetime. The generator system presented here has served as a long-term method for attaining no-carrier-added ²¹²Pb and ²¹²Bi radionuclides for homolog studies of flerovium and moscovium.

     

An interlaboratory test for certification of potassium chloride as a certified reference material (CRM) for solution calorimetry

The enthalpy of solution of KCl in H₂O (12000 mol·mol^–1) at 298.15 K was measured in an interlaboratory test in the G.D.R. The test material was prepared in the ASMW laboratories. The purity found on the high-precision coulometric titration of chloride was 0.9999±0.0001 g·g^–1. The consensus value of the enthalpy of solution in the test was H _s ^298.15 =17.47±0.07 kJ·mol^–1. This result is in good agreement with experimental values from recognized international scientific laboratories. The test material is applicable as a CRM.

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Zusammenfassung Die Lösungsenthalpie von KCl in Wasser (Molverhältnis 12000) bei 298.15 K wurde in einem Vergleichstest in mehreren Laboratorien der DDR gemessen. Das Testmaterial wurde in den Laboratorien des ASMW hergestellt. Eine coulometrische Präzisionstitration des Chlorids ergab seine Reinheit zu (0.9999±0.0001 g/g. Der übereinstimmende Wert für die Lösungsenthalpie wurde in dem Test zu H _s ^298.15 =(17.47±0.07) kJ mol^–1 gefunden, in guter Übereinstimmung mit experimentellen Angabe aus internationalen Laboratorien. Nach Abschluss des Testes ist das Material als bestätigter Bezugsstandard verwendbar.

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2000 / ₂ 298.75 . . ASMW. , - , 0.9999±0.0001 ·^–1. , , H _S298.15=17.47±0.01 ·^–1, , . , CRM.

     

An FTIR study of the surface chemistry of the dynamic Si(100) surface during etching in alkaline solution

In situ FTIR spectroscopy has been used in the attenuated total reflectance (ATR) mode to investigate the surface chemistry of etching Si(100) surfaces in aqueous KOH. The effect of solution concentration and electrode potential on the Si-H vibrations has been explored and the experimental results compared with density functional theory calculations. In addition. the kinetics of surface passivation of n-Si(100) has been investigated using FTIR spectroscopy.     

An extended formula of site-site Smoluchowski-Vlasov equation for electrolyte solution and infinitely dilute solution

Solvation dynamics is one of the central subjects in solution chemistry. Site-site Smoluchowski-Vlasov (SSSV) equation is a diffusion equation for molecular liquid to analytically calculate the van Hove time correlation function. However, the application has been limited to simple solvent system such as liquid water because of the difficulty in solving the equation. In this study, an extended treatment of SSSV equation is proposed, which is applicable to a wide range of solution systems including mixed solution, electrolyte solution, and infinitely dilute solution. The present treatment realizes computation of the dynamics in LiCl aqueous solution, NaCl aqueous solution, and infinitely dilute aqueous solution of Li(+) and Cs(+) at the molecular level.     

Identification of ligands for the Tau exon 10 splicing regulatory element RNA by using dynamic combinatorial chemistry

We describe the use of dynamic combinatorial chemistry (DCC) to identify ligands for the stem-loop structure located at the exon 10-5'-intron junction of Tau pre-mRNA, which is involved in the onset of several tauopathies including frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17). A series of ligands that combine the small aminoglycoside neamine and heteroaromatic moieties (azaquinolone and two acridines) have been identified by using DCC. These compounds effectively bind the stem-loop RNA target (the concentration required for 50% RNA response (EC(50)): 2-58 μM), as determined by fluorescence titration experiments. Importantly, most of them are able to stabilize both the wild-type and the +3 and +14 mutated sequences associated with the development of FTDP-17 without producing a significant change in the overall structure of the RNA (as analyzed by circular dichroism (CD) spectroscopy), which is a key factor for recognition by the splicing regulatory machinery. A good correlation has been found between the affinity of the ligands for the target and their ability to stabilize the RNA secondary structure.     

Kinetics of reactions in solution: Method for the treatment of data from non-isothermal chemical kinetic experiments

A new method is proposed for the treatment of kinetic data derived from non-isothermal kinetic experiments for the determination of the parameters of the Arrhenius equation. The results obtained from its application show the excellent precision of this method.

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Boundary element solution of the linear Poisson-Boltzmann equation and a multipole method for the rapid calculation of forces on macromolecules in solution

The Poisson-Boltzmann equation is widely used to describe the electrostatic potential of molecules in an ionic solution that is treated as a continuous dielectric medium. The linearized form of this equation, applicable to many biologic macromolecules, may be solved using the boundary element method. A single-layer formulation of the boundary element method, which yields simpler integral equations than the direct formulations previously discussed in the literature, is given. It is shown that the electrostatic force and torque on a molecule may be calculated using its boundary element representation and also the polarization charge for two rigid molecules may be rapidly calculated using a noniterative scheme. An algorithm based on a fast adaptive multipole method is introduced to further increase the speed of the calculation. This method is particularly suited for Brownian dynamics or molecular dynamics simulations of large molecules, in which the electrostatic forces must be calculated for many different relative positions and orientations of the molecules. It has been implemented as a set of programs in C++, which are used to study the accuracy and speed of this method for two actin monomers.