A numerically efficient variational algorithm to solve a fractional nonlinear elastic string equation

Numerical Algorithms - In this work, we propose a fractional extension of the one-dimensional nonlinear vibration problem on an elastic string. The fractional problem is governed by a hyperbolic...     

Effect of pH and gaseous ammonia flow rate on the composition and structure of ammonium uranate

Ammonium uranate was precipitated from uranyl nitrate solution using gaseous ammonia, then filtered, washed with demineralized water and dried. The influence of pH and ammonia flow rate on their composition and structure were examined by X-ray diffraction analysis, making use of additional information obtained from infrared analysis.     

Separation and detection of oxidation products of fluorodeoxyglucose and glucose by high-performance liquid chromatography-electrospray ionisation mass spectrometry

2-Deoxy-2-[18F]fluoro-D-glucose ([18F] FDG), the most popular positron emitting radiopharmaceutical, may oxidise by autoradiolysis in aqueous solution. The aim of this work was to use LC-MS for determination of the oxidation products of fluorodeoxyglucose and glucose (Glc) obtained by oxidation with Fenton's reagent. Asahipak NH2P-50 polyamide silica column and acetonitrile-0.025% aqueous ammonium formate (80:20 (v/v)) eluent were utilised with an Agilent 1100 HPLC-MS instrument. Ten major oxidation products of FDG and Glc were separated and identified by mass spectrometry: 2-fluorogluconic acid, 2-fluoroglucuronic acid, 2-oxoerythronic acid, arabinose, arabonic acid, araburonic acid, erythrose, erythrulose, gluconic acid, and glucuronic acid. The most intensive electrospray ionisation signals were found in the negative ion spectra and were due to HCOO- adducts, the other acids being in their lactone forms.     

Atmospheric pressure electrospray ionization mass spectra of glucose and 2-fluorodeoxyglucose for quantitative analysis of 2-fluorodeoxyglucose by high-performance liquid chromatography

2-Fluoro-2-deoxy-D-glucose (FDG) labeled by fluorine-18 is the most widely used radiopharmaceutical for positron emission tomography (PET). For high-performance liquid chromatography (HPLC)/MS assay and quality control, the mass spectra of FDG and glucose (Glc) in organic + water solutions were studied by flow injection analysis (FIA) and in a chromatographic eluate. In acetonitrile (MeCN) + 0.025% ammonium formate (NH(4)HCO(2)) solvent (80 : 20), electrospray ionisation (ESI) of glucose-FDG provides M.NH(4)(+) and 2M.Na(+) (M = Glc or FDG) as the most intense positive ions. Formation of the latter ions and also of M.MeCN.Na(+) and 2MeCN. Na(+) is typical of the presence of NaCl in the ESI inlet. The positive ions include heavier ions corresponding to the impurities separated by HPLC and also to the cross-ring fragmentation of complexes (2FDG. aMeCNX)L, where a = 0 or 1, L is either Na(+) or NH(4)(+) and X is a fragmented pyranose or anhydropyranose residue. The second most abundant Glc negative ion is m/z = 359 which was interpreted as (2GlcH(+))(). The negative-ion spectrum of FDG has dominating lines due to FDG.HCO(2)() ions at m/z 227 and also (2FDGH(+))() at m/z 363. The m/z 363 signal is suppressed in the presence of NaCl at a molar ratio of 4 : 1 to NH(4)HCO(2), while the ions at m/z 217 and 219, i.e. FDG.Cl(), become three times more intense than FDG.HCO(2)(). The latter ion appears to be most suitable as an analytical signal for chemical analysis of FDG at m/z 226 and 227. Limits of FDG quantitation (LOQ) of 19 ng and 21 ng were found for the 200(+) and 227() ion signals, respectively, and are wholly adequate for verification of total FDG content in radiopharmaceuticals.     

A calculation of the relative protonation energies of amines in solution

Relative protonation energies in the primary, secondary and tertiary aliphatic series of amines are calculated by a semiempirical method employing the virtual charge model. The method accounts quite well for the observed differences between the gas-phase protonation affinities and the protonation enthalpies in solution, but when allowance is made for steric shielding from the bulk solvent for “non-edge” atoms, some anomalies in the uncorrected model are removed. The calculated solute-solvent interactions are related to experimental enthalpies of solution and to trends expected from the Born model.     

Thermal studies of pre-formulates of metronidazole obtained by spray drying technique

Compatibility studies between active drugs and excipients are substantial in the pharmaceutical technology. The objective of the present work was to develop pre-formulated mixtures of metronidazole (MT) obtained by spray drying (SPDR) and their thermoanalytical characterization. Dynamic and isothermal TG, conventional DSC and DSC coupled to a photovisual system were used. DSC experiments with both techniques confirmed the homogeneity of the conventional and pre-formulated mixtures. The TG data made possible the comparison the thermal stability of the different mixtures. Similar thermal stabilities were found of the conventional and pre-formulated mixtures, with slower particles sizes of MT.     

Chemistry of dithiocarbamate derivatives of amino acids. Part II. Complexes of nickel(II) with derivatives of branched and cyclic amino acids

Summary Barium salts of the dithiocarbamate derivates of the amino acids: DL-valine, L-valine, DL-leucine, DL-isoleucine and L-proline have been synthesized. The anions have been used to obtain the corresponding nickel(II) complexes in acid form. The complexes are diamagnetic, and coordination takes place in a near-square planar geometry around the nickel(II) ion through the sulphur atoms of the dithiocarbamate moiety, the structure being confirmed by i.r.,¹H n.m.r., u.v.-vis spectros copies and by chemical analysis.No significant difference has been found between the physicochemical properties (i.r. and 'H n.m.r. spectra and magnetic properties) of the complexes prepared from the dithiocarbamate derivatives of DL- and L-valine, but d-d bands in the u.v.-vis spectra show a slight different intensity.     

The relationship between the structures of Cu(II) complexes and their chemical transformations: VII

The thermal decompositions of Cu(en)₂(NCS)X. where X^–=Cl^–, Br^–, NO ₃ ^– , BF ₄ ^– and ClO ₄ ^– , have been studied in comparison with the courses of Cu(en)₂(SCN)₂ and Cu(en)₂X₂ decomposition. It is shown that the presence of the thiocyanate group in the complexes Cu(en)₂(NCS)X is the most important factor in the decomposition course, in agreement with the fact that the anions X^– are not coordinated. or are only semicoordinated. Significant differences were found in the courses of thermal decomposition of two forms of Cu(en)₂(NCS)(BF₄) differing in the structure of their coordination polyhedra.

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Zusammenfassung Die thermische Zersetzung von Cu(en)₂(NCS)X (X=Cl Br, NO₃, BF₄ und ClO₄) wurde untersucht und mit der von Cu(en₂(SCN)₂ und Cu(en)₂X₂ verglichem. Der den Verlauf der Zersetzung entscheidend bestimmende Faktor isi die Anw esenheit der Thiocyanat-Gruppe in den Cu(en)₂(NCS)X-Komplexen, was in Übereinstimmung damit steht,. daß die Anionen X nicht oder nur teilweise koordiniert sind. Es wurden signifikante Unterschiedeim Verlauf der thermischen Zersetzung von zwei sich in der Struktur ihrer Kordinationspolyeder unter-, heidenden Formen von Cu(en)₂(NCS)(BF₄) gefunden.

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Cu(en)₂(NCS)X (X^–=Cl^–, Br^–, NO ₄ ^– , NO ₃ ^– , BF₄ ClO₄, Cu(en)₂(SCN)₂ Cu(en)₂(X)₂. , Cu(en)₂(NCS)X X Cu(en) (NCS)BF₄ i .

     

Sorption of caesium and strontium on clinoptilolite-and mordenite-containing sedimentary rocks

The sorption of caesium and strontium from its aqueous solutions by ten clinoptilolite-and mordenite-containing sedimentary materials from Slovakia, Bulgaria, Ukraine and Greece was investigated by batch-type procedure and radiotracer techniques. The concentration of the solutions, that were performed in and without the presence of competing cations (0.005 mol·dm⁻³ KCl) varied between 1·10⁻⁴ and 5·10⁻² mol·dm⁻³. The uptake and distribution coefficient (K _d ) values determined for the materials of the different origin, were correlated with their mineralogical composition and gross cation exchange capacity (CEC). The identification of the specific uptake sites was attempted on the basis of the sorption isotherms and the content of exchangeable cations. The experimental results provide information on the suitability of the individual materials for the treatment of radioactive wastes and their application as backfills in potential nuclear waste repositories.