Einige Gesetzmäßigkeiten der spontanen Umwandlung der Wasserstofform des Montmorillonits in die Aluminium-form

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Graph—theoretical approach to the calculation of physico-chemical properties of polymers

A topological extrapolation method for the calculation of various properties (melting points, refractive indices, specific rotation, etc.) of infinite linear polymers is developed. The rapid convergence of the oligomer extrapolation series results in very good agreement between calculated and experimental values. Comparison between the proposed method and other empirical or semi-empirical methods (the group addition method and the Pade-approximation) is also presented.     

Speciation of beryllium, nickel, and vanadium in soil samples from Csepel Island, Hungary

Sequential leaching methods have been used for the speciation of Be, Ni, and V in five soil samples from Csepel Island on the Danube river located near an oil-fired power plant. The concentrations of the elements of the extracts were determined by inductively coupled plasma mass spectrometry. The total efficiency (the sum of the extracted metals divided by metal fraction which is soluble in aqua regia) of the five-step method was always higher. The difference for Ni was considerable, because of the high abundance of Ni found in the moderately reducible fraction, which is absent from the three-step method. The sum of the mobile species (exchangeable, carbonatic, and easily reducible) determined by both methods, were in reasonable agreement; this was not so for the individual fractions. There were greater differences between the non-mobile fractions (moderately reducible and oxidizable), because of the presence or absence of the moderately reducible fraction. For both methods there was good correlation between the oxidizable fraction and the organic matter content of the soils.     

Topological characterization of cyclic structures

The sum of the topological distances in the molecular graph (the Wiener number) is used for a topological characterization of the condensed polycyclic molecular systems. This topological index discriminates well the isomeric cyclic molecules. In addition, it also properly reflects their structural features. On this basis the principal points of molecular cyclicity are formulated in 15 rules.     

Nanostructured electrochemical DNA biosensors for detection of the effect of berberine on DNA from cancer cells

Multi walled carbon nanotubes (MWNT) in dimethylformamide (DMF) or aqueous sodium dodecyl sulfate (SDS) solution, colloidal gold nanoparticles (GNP) in phosphate buffer solution (PBS), and a GNP–MWNT mixture in aqueous SDS solution have been investigated for chemical modification of a screen-printed carbon electrode used as the signal transducer of a dsDNA-based biosensor. Differential pulse voltammetry of the DNA redox marker and the guanine moiety anodic oxidation and cyclic voltammetry with K₃[Fe(CN)₆] as indicator revealed substantial enhancement of the response of the biosensor, particularly when MWNT in SDS solution was used. The biosensor was used in testing of berberine, an isoquinoline plant alkaloid with significant antimicrobial and anticancer activity. Berberine had a very strong, concentration-dependent, effect on the structural stability of DNA from the human cancer cells (U937 cells) whereas non-cancer cells were changed only when berberine concentrations were relatively high 75 and 50 μg mL⁻¹. Figure Schematic illustration of preparation of the nanostructured films: (a) layer-to-layer coverage (DNA/nanomaterial/SPE); (b) mixed coverage (DNA-nanomaterial/SPE)     

Compact Zernike phase contrast x-ray microscopy using a single-element optic

We demonstrate Zernike phase contrast in a compact soft x-ray microscope using a single-element optic. The optic is a combined imaging zone plate and a Zernike phase plate and does not require any additional alignment or components. Contrast is increased and inversed in an image of a test object using the Zernike zone plate. This type of optic may be implemented into any existing x-ray microscope where phase contrast is of interest.     

Untersuchung der Strukturumwandlungen des Vermiculits in saurem Medium mittels der Methode der Elektronenspinresonanz

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Einfluß der Austauschkationen auf die Acetonitril-bzw. Pyridinadsorption durch Montmorillonit

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