Accumulation of uranium by filamentous green algae under natural environmental conditions

The capacity of algae to concentrate uranium under natural environmental conditions is measured by a-spectrometry. Spirogyra, a filamentous green fresh-water alga, has concentrated uranium from a surface concrete ponds with elevated uranium levels (140-1140 ppb). The concentration factors (CFs) ranged from 8.9-67 with an average value of 22.Cladophora spp, a filamentous green marine alga has concentrated uranium from the marine water with a concentration factor ranged from 220–280. The average concentration factor was 250. The factors affecting the sorption process are discussed in detail. This revised version was published online in July 2006 with corrections to the Cover Date.     

Asymptotic discrimination between renewal processes

Limit theorems for the logarithm of the likelihood ratio are proven. With their help the rate of decrease in the probability of errors of the second kind in the Neumann-Pierson criterion is established.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 44, No. 10, pp. 1382–1388, October, 1992.     

Synthesis of (1R,4R,7S)- and (1S,4S,7S)-2-(4-tolylsulfonyl)-5-phenyl-methyl-7-methyl-2,5-diazabicyclo[2.2.1]heptanes via regioselective opening of 3,4-epoxy-d-proline with lithium dimethyl cuprate

The synthesis of (1S,4S,7S)- and (1R,4R,7S)-2-(4-tolylsulfonyl>5-phenylmethyl-7-rnethyl-2,5-diazabicyclo-[2.2.1]heptanes ( 20 ) and ( 22 ) from trans 4-hydroxy-L-proline is described.     

Mobilization and fractionation of137Cs in calcareous soils

Mobility of¹³⁷Cs was investigated in columns of calcareous loam and clay soils leached under river water, NH₄OAc, KCl, CaCl₂, and EDTA. Fractionation of Cs into ten sequential fractions was accomplished in the leached soils as well as in soil samples received carrier-free¹³⁷Cs and incubated for 60 d. At the end of 90 d of leaching with river water and CaCl₂, the bulk of Cs applied (>97%) was found to remain in the upper 1 cm of soil columns. On the other hand, the reduction in Cs concentration was approximately 30% with NH₄OAc, 18% with KCl, and 10 to 25% with EDTA. The major soil constituents appeared to be responsible for retaining Cs were clay, silt, and Fe oxides. The leaching consistently increased the magnitude of fractions bound to clay minerals and in most cases decreased the fractions of water soluble, exchangeable, carbonate, and organic matter.     

Spontaneous adsorption of ferrocenes on highly ordered pyrolytic graphite edges

The spontaneous adsorption of ferrocene and eight derivatives have been examined electrochemically on highly ordered pyrolytic graphite edges. All compounds give surface coverages of ca. 2×10^?8 mol/cm². Three of the adsorbed compounds give oxidation waves significantly more negative than their solution counterparts, in contrast with the other six derivatives.     

Aminopropylcellulose,synthesis and derivatization

The preparation of 3-aminopropylcellulose from cyanoethylcellulose is readily achieved. Reduction of the cyano groups with borane-dimethyl sulfide in tetrahydrofuran or a borane-tetrahy-drofuran complex proceeds quantitatively in 3 h to a corresponding 3-aminopropylcellulose. The presence of primary amine functions is confirmed by spectroscopy and a positive ninhydrin test; the concentration of amino substituents, as ascertained by titration, ranged from 1.2 to 6.4 meq/g. Because the derivatives are neither soluble nor excessively swollen in water, applications as ion-exchange resins or chromatographic supports can be envisioned. Treatment of 3-aminopropyl-cellulose with acetyl chloride, phenyl isocyanate, or p-toluenesulfonyl isocyanate produced 3-acetamido-, 3-(N′-phenyluredo)-, or 3-(N′-p-toluenesulfonyluredo)-N-propylcellulose. Alkylation with methyl chloride yielded a water-soluble quaternary ammonium salt.     

Screening of urban aerosol particulate composites for selected metal distribution and their dependence on meteorological parameters

Local atmospheric aerosol particulate samples, collected as composites on daily 6-12 hour basis, at Quaid-i-Azam University campus, Islamabad, Pakistan, using high volume sampling technique, were analysed for Pb, Na, K, Fe, Mn, Cd, Cr, Ni, Zn and Co by FAAS method. The monitoring period ran from October, 2001 through March, 2002, with a total of 105 samples collected on cellulose filters, treated in part with the HNO3-based wet digestion method for metal quantification, and for particle size distribution separately. The metal content of the aerosols was examined in relation to dependence on meteorological parameters, such as temperature, relative humidity, wind speed, sun shine and pan evaporation. Statistical correlation analysis was conducted for multiple metal pairs in aerosols, and the data were examined in relation to meteorological parameters and relevant aerosol particle size fractions. The study revealed no viable strong correlation between the meteorological parameters and metal levels; in general, however, a significant positive correlation was found for temperature. A strong positive correlation was observed for PM<25 and PM2.5-10. For coarse particles (PM10-100 and PM>100), however, a negative correlation was observed. The levels of Na, K, Fe and Zn were found in the range of 1-5 microg/m3 while those for the rest of the metals in the sub microg/m3 range. Principal component analysis and cluster analysis were performed on dataset for source identification and appointment. Largest contribution (33%) was shown by the industrial emissions followed by traffic/road dust (16.7%).     

Retention, kinetics and thermodynamics profile of cadmium adsorption from iodide medium onto polyurethane foam and its separation from zinc bulk

The sorption behaviour of 2.5 × 10⁻⁵ M solution of Cd(II) on polyurethane foam (PUF) from iodide medium have been investigated. The conditions were optimized from aqueous solutions of different pH (1-10) and of acids of varied concentration (0.01-1.0 M). The maximum concentration of KI was found to be 0.24 M and equilibration time was established to be 20 min. The data successfully followed the Freundlich and Dubinin-Radushkevich (D-R) isotherms at low metal ion concentration while Langmuir isotherm followed at higher metal ion concentration. The Freundlich parameter 1/n = 0.66 ± 0.02 have been evaluated whereas D-R isotherm yields the sorption free energy E = 10.5 ± 0.1 kJ mol⁻¹ indicating ion exchange type chemisorption. The monolayer coverage (XL) constant of Langmuir isotherm was found to be 23.7 ± 0.4 mg g⁻¹. The numerical values of thermodynamics parameters enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG) indicated the endothermic and spontaneous nature of sorption. The Scatchard plot analysis was tested to evaluate the binding sites of the PUF and stability constants of sorption were determined. On the basis of these parameters, the sorption mechanism was discussed. Among the foreign ions tested, Pb(II), Hg(II), cyanide and nitrite should be absent. The clean separation of Cd(II) from Zn(II) ions in the ratio 1:250, respectively, was achieved by column chromatography.     

Computer simulations of the solvation dynamics of Coumarin 153 in dimethylsulfoxide

We report molecular dynamics (MD) simulations of the solvation dynamics of Coumarin 153 in liquid dimethylsulfoxide using two distinct sets of partial charges for the coumarin probe. The excited state dipole moment of the coumarin and the dynamic Stokes shift in solution depend significantly on the type of charge distributions used. Nevertheless, the overall characteristics of the solvation responses obtained from both sets of charges are very similar and show good agreement with time-dependent Stokes shift experiments. Microscopic details of the solvent reorganization around the probe are discussed in light of the charge transfer upon photoexcitation.     

Synergic effect of triphenylphosphine oxide (TPPO) on the extraction of Hg(II), Se(IV), Co(II) and Mn(II) with fluorinated pyrazolone (HPMTFP)

Extraction of Hg(II), Se(IV), Mn(II) and Co(II) has been carried out with 1-phenyl-3-methyl-4-trifluoroacetyl-2-pyrazolin-5-one (HPMTFP) and triphenylphosphine oxide (TPPO) into chloroform from pH 1–10. Quantitative extraction of Hg(II), Mn(II) and Co(II) at pH 4 with equimolar 0.05M (PMTFP+TPPO) in chloroform was observed. Se(IV) remains unextracted at this pH range. The stoichiometric composition of the extracted complexes M(PMTFP)₂·nH₂O (M=Mn, Hg), M(PMTFP)₂·2TPPO (M=Mn and Co) and Co(PMTFP)₂·TPPO·H₂O at less than 0.1M TPPO has been established. The formation constantsK _m,0 andK _m,n and stability constants _m,n have been computed. The analytical method developed was applied to the IAEA standard reference material (SRM) potato fluor V-4 for the determination of these elements using NAA technique.