Die Bestimmung von Kupferspuren in W?ssern

Zusammenfassung Die Kupferspuren in Wässern einschließlich der Erzwässer können schnell und verläßlich photometrisch bestimmt werden, wenn man eine Lösung von Bleidiäthyldithiocarbaminat in Chloroform als Reagens verwendet. Die Bestimmung wird durch die in Wässern gewöhnlich vorkommenden Elemente nicht gestört. 0,02 g Kupfer in 1 ml Wasser können noch sicher erfaßt werden.     

HN2(2A') electronic manifold. II. Ab initio based double-sheeted DMBE potential energy surface via a global diabatization angle

A double-sheeted double many-body expansion potential energy surface is reported for the coupled 12A'/22A' states of HN2 by fitting about 6000 ab initio energies. All crossing seams are described to their full extent on the basis of converged results. The lowest adiabatic sheet is fitted with a rmsd of 0.8 kcal mol-1 with respect to the calculated energies up to 100 kcal mol-1 above the absolute minimum, and the topology of the first excited-state investigated with the aid of the upper adiabatic sheet. A new scheme that overcomes obstacles in previous diabatization methods for modeling global double-sheeted potential energy surfaces is also reported. The novel approach uses a global diabatization angle which allows the diabats to mimic both the crossing seams and atom-diatom dissociation limits.     

Control of lasing filament arrays in nonlinear liquid media

Multiple filamentation in a high concentration solution of coumarin 153 in ethanol is studied. It is shown that the output filament pattern may be controlled by placing diffractive elements (circular aperture, edge) in the input beam path. These filaments are formed in highly reproducible arrays along diffraction maxima corresponding to the element used. Experimental results are supported by numerical simulations. They confirm that diffraction-induced intensity gradients swamp modulational instability on the wavefront, forcing filaments to form along diffraction maxima. The effect of two-photon absorption by coumarin molecules on filament patterns is also investigated over a range of dye concentrations. Control results are finally exploited in the production of arrays of localized lasing filaments, which should open novel applications. The resultant lasing sources are mutually coherent and highly repeatable from shot-to-shot, as is shown by their far-field interference patterns. PACS 42.65.Tg; 52.38.Hb; 42.68.Ay     

Bone repair using mineral trioxide aggregate combined to a material carrier, associated or not with calcium hydroxide in bone defects

Mineral trioxide aggregate (MTA) is a powder aggregate containing mineral oxides with a good biological action and may facilitate the regeneration of the periodontal ligament and formation of bone. Calcium hydroxide demonstrates antibacterial properties, enhances tissue dissolution, and induces bone formation. The objective of this study was to evaluate the MTA in the bone healing process and verify if the calcium hydroxide P.A. can improve and accelerate this process. It was used forty male Wistar rats, which were divided into two groups, considering or not the use of calcium hydroxide P.A. solution before treatment. Thus, each one of these groups was divided in four groups with five animals each, according to the treatment and the defect filled by: animal's coagulum, monoolein gel, MTA in aqueous solution, and MTA combined with monoolein gel. After 10 days, the animals were perfused and the right hemimandibles removed for histological analysis. Statistical analysis of the data showed significant difference between all analyzed groups when it was made comparisons using or not calcium hydroxide P.A. (p<0.0001). There was found statistical difference between the groups that was inserted or not MTA, independently the calcium hydroxide application (p<0.05). Results showed that the MTA used was able to induce bone regeneration and had its action optimized when combined to calcium hydroxide P.A.     

An ultra-clean technique for accurately analysing Pb isotopes and heavy metals at high spatial resolution in ice cores with sub-pg g Pb concentrations

Measurements of Pb isotope ratios in ice containing sub-pg g⁻¹ concentrations are easily compromised by contamination, particularly where limited sample is available. Improved techniques are essential if Antarctic ice cores are to be analysed with sufficient spatial resolution to reveal seasonal variations due to climate. This was achieved here by using stainless steel chisels and saws and strict protocols in an ultra-clean cold room to decontaminate and section ice cores. Artificial ice cores, prepared from high purity water were used to develop and refine the procedures and quantify blanks. Ba and In, two other important elements present at pg g⁻¹ and fg g⁻¹ concentrations in Polar ice, were also measured. The final blank amounted to 0.2 ± 0.2 pg of Pb with ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb ratios of 1.16 ± 0.12 and 2.35 ± 0.16, respectively, 1.5 ± 0.4 pg of Ba and 0.6 ± 2.0 fg of In, most of which probably originates from abrasion of the steel saws by the ice. The procedure was demonstrated on a Holocene Antarctic ice core section and was shown to contribute blanks of only ∼5%, ∼14% and ∼0.8% to monthly resolved samples with respective Pb, Ba and In concentrations of 0.12 pg g⁻¹, 0.3 pg g⁻¹ and 2.3 fg g⁻¹. Uncertainties in the Pb isotopic ratio measurements were degraded by only ∼0.2%.     

Detailed 1H and 13C NMR structural assignments of four sesquiterpene lactones isolated from Eremanthus elaeagnus (Asteraceae)

A complete ¹H and ¹³C NMR analysis for a group of four sesquiterpene lactones isolated from Eremanthus elaeagnus (Asteraceae) is described in this work. ¹H NMR, ¹³C {¹H} NMR, gCOSY, gHMQC, and gHMBC experiments were performed to provide sufficient structural information to allow an unequivocal assignment. All hydrogen coupling constants were measured, clarifying all hydrogen signal multiplicities.     

Synthesis and antimicrobial activity of sulphamethoxazole-based ureas and imidazolidine-2,4,5-triones

Progression of drug resistance among bacterial and fungal pathogens justifies the development of novel antimicrobial agents. Thus, a series of novel sulphamethoxazole-based ureas and imidazolidine-2,4,5-triones have been designed and synthesised. The urea derivatives were obtained by the reaction of sulphamethoxazole and isocyanates, and their cyclisation to imidazolidine-2,4,5-triones was performed via oxalyl chloride. All synthesised derivatives were evaluated in vitro to determine their activity against gram-positive and gram-negative bacteria, fungi, Mycobacterium tuberculosis, and atypical mycobacteria and their cytotoxicity. The growth of mycobacteria was inhibited within the range of 4–1000 µM and M. tuberculosis was the least-susceptible strain. 4-(3-Heptylureido)-N-(5-methylisoxazol-3-yl)benzenesulphonamide was identified as the most promising compound because it exhibited the highest activity against atypical mycobacteria at minimum inhibitory concentrations, from 4 µM, and with acceptable toxicity (selectivity indices for M. avium and M. kansasii higher than 16 and 62.5, respectively). Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus, were inhibited at concentrations starting from 125 µM, whereas the investigated derivatives exhibited almost no antifungal potency and activity against gram-negative species.     

Niobium (V) peroxocomplexes as a catalyst of oxidation of methylphenylsulphide by hydroperoxide

The electrospray ionization-mass spectrometry (ESI-MS) method has been used for determination of the structure of niobium peroxocomplexes. The formation of mono- and bisperoxocomplexes has been established. These complexes contain Schiff bases and 8-quinolinol as ligands. Trisperoxocomplexes are formed when pyridine and 1,10-phenanthroline are used. Peroxocomplexes with Schiff bases as ligands has shown a high activity as catalysts in the methylphenylsulphide oxidation.     

Quality assessment of hydrosphere in the vicinity of Czech nuclear power plants by radioanalytical methods

Summary The paper deals with the impact of nuclear plants and radioactive waste disposal on surface and ground water quality in their vicinity using various radiometric and radioanalytical methods. The impact of nuclear power plant Temelin on activation concentrations and fission products in hydrosphere, including tritium, was detected. The annual average tritium concentrations in Vltava River correspond to the previously calculated estimates for average and minimal quaranteed flow rates. The concentrations histories of ⁹⁰Sr and ¹³⁷Cs in surface water show a decreasing trend. This trend was not influenced by the nuclear power plant pilot operation. In the case of tritium, a concentration increase trend has been already observed since the startup of pilot operation. An attempt has made interpreting the sorption and diffusion data for radionuclides of cesium, strontium and tritium and technetium as representatives of multivalent elements. Sorption and diffusion data of ¹³⁷Cs and ⁹⁰Sr in contact with natural sorbent bentonite lead to the conclusion that both diffusion and batch sorption experiments can be simulated by an exchange model. Sorption of technetium on various bentonites plus additives materials is described. Retention of technetium on these solid phases is driven by sorption of reduced form of technetium Tc(IV).