Electric field gradient in nanostructured SnO2 studied by means of PAC spectroscopy using 111Cd or 181Ta as probe nuclei

Electric quadrupole interactions were studied in pure and Mn-doped powder samples and thin films of SnO₂ using perturbed γγ angular correlation spectroscopy (PAC). The powder samples were prepared by Sol gel method and the thin film were prepared on the Si (100) substrate by sputtering technique using Sn in the oxygen atmosphere. The samples were characterized by x-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy. The thickness of the film was 100 nm. The average particle size of the SnO₂ powder samples was determined to be smaller than 60 nm. The radioactive ¹¹¹In and ¹⁸¹Hf tracers were introduced in the powder samples during the sol gel chemical process. Radioactive ¹¹¹In was implanted on the SnO₂ thin films using the University of Bonn ion implanter (BONIS). PAC measurements were carried out in a four BaF₂ detector spectrometer in the temperature range of 77–973 K for samples annealed at different temperatures. The PAC results for both nuclear probes show the presence of two electric quadrupole interactions. The major fractions in both cases correspond to the substitutional sites in the rutile phase of SnO₂. The results are compared with previous PAC measurements.     

Dreiphasige Emulsionen

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Ueber Entstehung von Liesegang'schen Ringen bei der serologischen Präzipitation

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Zur Hydrodynamik von Systemen veränderlicher Viskosität,III

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Untersuchungen von Formaldehydeiweiß

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Novel triazolopeptides: chirospecific synthesis and conformational studies of proline derived analogs

Replacing the backbone amide function by a heterocyclic bioisostere, [3+2] azide-alkyne cycloaddition has been applied for the construction of biologically relevant peptidomimetics. Starting from aminoalkynoates, triazole formation was accomplished by addition of hydrazoic acid. NMR studies displayed that the newly developed 4,5-triazolopeptides, which incorporate a biomimetic triazole NH-function as polar constraint element, showed a substantially higher tendency to form a cis-prolyl-geometry than a comparable native peptide sequence.     

A contribution to the theory of the capillary viscometer

Summary A general arrangement of a capillary viscometer is examined with a non-steady flow of aNewtonian liquid. The flow is determined by a pressure dependent upon the time. The velocity is found as a function of the pressure gradient or the length coordinate and the time. The result can serve for the determination of the viscosity.Three illustrative examples are given.

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Zusammenfassung Der allgemeine Aufbau eines Kapillar-Viskosimeters wird an Hand des nichtstationären Fließens einer Newtonschen Flüssigkeit überprüft. Das Fließen wird durch einen zeitabhängigen Druck bestimmt. Die Geschwindigkeit ergibt sich danach als Funktion des Druckgradienten oder der Längen-Koordinate und der Zeit. Das Ergebnis kann zur Bestimmung der Viskosität dienen. Drei Beispiele dienen der Erläuterung.

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