Chemometric approaches in environmental problems concerning PCDD and PCDF. Data interpretation and source correlation. Mechanisms of formation and destruction in MSW combustion process

Summary The role of multivariate analysis methods in evaluating, rationalizing, and working out complex environmental problems is discussed. The discussion is organized in two sections; a literature analysis of the application of chemometric methods to PCDD/PCDF data interpretation and source correlation and a review of the role of chemometric methods in analysing the results obtained by the Authors studying PCDD/PCDF formation and destruction mechanisms in MSW combustion processes.     

Analysis and modeling for time-dependent behavior of polymers exhibited in nanoindentation tests

Through the arrangement of the applied load, experimental nanoindentation results of polymethylmethacrylate (PMMA) and polyurethane (PU) employed to establish a mechanical model. The proposed model consists of irreversible delayed plastic (viscoplastic) deformation, irreversible viscous deformation, and reversible delayed elastic (viscoelastic) deformations. The phase lag exhibited between the responding depth and the oscillating load is found to be linear proportional to frequency in the range of 1-50 Hz. The residual cavity profile of the PMMA scanned by an atomic force microscope gives a validity of accommodation assumption applied in the present model. The effects of overshooting, which occurred in the dwelling process, are also discussed.     

Vertical migration of 85Sr, 137Cs and 131I in various arable and undisturbed soils

The vertical migration of ⁸⁵Sr, ¹³⁷Cs and ¹³¹I in some arable and undisturbed single-contaminated soils was studied by gamma-spectrometry measurements under lysimetric laboratory conditions during irrigation of the soil profiles with wet atmospheric precipitation for about one year, except ¹³¹I. A new simple exponential compartment (box) model was derived, which makes it possible to calculate the migration rate constants and migration rates in the individual soil layers (vertical sections) as well as the total vertical migration rate constants and total vertical migration rates of radionuclides in the bulk soil horizon. The relaxation times of radionuclides in respective soil horizons can also be evaluated.     

New pi-extended water-soluble squaraines as singlet oxygen generators

[graph: see text] Condensation of squaric acid with a number of differently substituted 2-pyrrolyl derivatives afforded three new classes of squaraines. Their sharp and intense absorption bands in the biological window (700-900 nm), inherent singlet oxygen generation capabilities, together with proper functionalization allowing good water solubility make them suitable candidates as new non-porphyrinic singlet oxygen photosensitizers for photodynamic therapy (PDT).     

Gravimetric separation of titanium and zirconium from Niobium with Phenylacetylhydroxamic acid

Phenylacetylhydroxamic acid is used to separate titanium and zirconium from niobium in an oxalate medium at pH 6.5–7.5 in presence of ammonium chloride at room temperature. The method is accurate when the ratio of (TiO₂ + ZrO₂) : Nb₂O₅ is 10 : 1 to 1 : 1 ; when the niobium concentration is higher, reprecipitation is necessary. Tantalum, citrate, tartrate, lactic acid, EDTA, and a large excess of oxalate interfere.     

Application of multiparameter equations to calculation of the mutual solubility in water-organic solvent binary systems

The solubility of organic liquids in water and of water in organic liquids is primarily determined by the capability of organic liquids for hydrogen bonding. Adequate generalization of the solubility data is possible only with multiparameter equations taking also into account other properties of organic components, including the cohesion and molar volume.     

Synthesis and studies of CuHg(NCX)4 (X = S,Se) and their complexes and application of the softness parameter in the elucidation of their structure

Complexes of CuHg(NCS)₄, CuHg(NCS)₂ (NCSe)₂ and CuHg(NCSe)₄ with tetrahydrofuran, dioxane, pyridine, 2-aminopyridine, nicotinamide, bipyridine and phenanthroline have been prepared and comparative studies made. Bipyridine and phenanthroline form cationic—anionic [CuL₃]²⁺ [Hg(SCN)₄]^2? (L = bipy, phen) complexes with CuHg(NCS)₄ and dinuclear bridged complexes with CuHg(NCSe)₄ and CuHg(NCS)₂ (NCSe)₂. For other ligands the nature of the complexes is binuclear or polynuclear. The comparative stability of the -XCN- bridge (X = S, Se) is CuHg(NCSe)₄ > CuHg(NCS)₂ (NCSe)₂ > CuHg(NCS)₄.     

Paper chromatography in the separation of ions

Summary A study has been made of the separation of alkali and alkaline earth metals. With mixtures of solvents, such as ethyl cellosolve, water and hydrochloric acid and acetone, water and hydrochloric acid in the ratio of 702010 and at different temperatures, a complete separation of alkaline earth metals was effected. Of the alkali metals only lithium, sodium and potassium could be separated from each other but rubidium and caesium always accompanied potassium.