Intergrain and intragrain superconductivity in Sn- and Sb-doped Bi1.7Pb0.3Sr2Cu3Oy

Measurements of the resistivity and current dependent resistivity for small current densities ranging from 0.03 A/cm² to 3.0 A/cm² were performed with two Sn-doped and two Sb-doped polycrystalline Bi_1.7Pb_0.3Sr₂Ca₂Cu₃O_y samples in magnetic fields up to 1.7 T. Features in the temperature derivative of the resistivity curves were associated with the presence of a superconducting transition between superconducting grains, coupled by weak links with a distribution of critical currents and critical temperatures, and the superconducting transition within grains. The transition between grains was more strongly suppressed in temperature with the application of a magnetic field in samples with weaker coupling between grains. The presence of a transition in a magnetic field due to weak links between grains was verified at 77 K by the observation of a current dependent resistivity in a magnetic field.     

Über die Bedeutung der Keimbildungs- und Kristallisations-geschwindigkeit bei Fällung von Aluminiumhydroxid mit relativ großer Oberfläche,die auch bei dem entsprechenden α-Al2O3 vorhanden ist

Ohne Zusammenfassung

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Influence of Inoculation and cristallization velocity at the precipitation of aluminum hydroxide with great surface persisting in the corresponding -Al₂O₃

     

A comparison of molecular orbital methods for the analysis of the He(I) photoelectron spectra of n-alkenes

The two highest vertical ionization potentials are calculated by the Fenske-Hall, MINDO/1, and MINDO/3 molecular orbital methods for an extensive series of n-alkenes. It is found that the Fenske-Hall method gives a better correlation with the corresponding experimental photoelectron spectral data and is the most useful for the interpretation and understanding of these results. When MINDO/3 was used for calculations by the ΔSCF method, it was not possible to obtain satisfactory agreement with the photoelectron spectroscopic measurements. Finally, the relevant findings of other calculational procedures such as ab initio and SPINDO are given.     

Properties of interfacial films formed by succinylated legumin from faba beans (Vicia faba L.)

The influence of succinylation on the interfacial behaviour and emulsifying properties of the main storage protein (legumin) from faba beans was studied. Results of surface tension measurements and surface shear rheometry and properties of n-decane-water emulsions indicate an increased interfacial activity by succinylation whereby the 65% succinylated legumin was the most active derivative.

The equilibrium surface pressure Π_e increased from 16.6 to 20.21 mN m⁻¹ and the critical association concentration, i.e. the subphase concentration at which the plateau of Π_e was reached, strongly decreased with succinylation from 76.6 × 10⁻⁶ to 0.84 × 10⁻⁶ g ml⁻¹. Spread and adsorbed films of legumin exhibited purely viscous behaviour under shear stress whereby the viscosity strongly increased with succinylation (from 7.93 to 93.36 μN s m⁻¹). The droplet size of legumin-stabilized emulsions decreased and the coalescence stability increased with succinylation. The comparison with acetylated legumin supports the view that the dissociated but rather globular subunit is the most interfacially active component of acylated legumin.     

Expanding the world of endohedral fullerenes--the Tm3N@C2n (39< or =n< or =43) clusterfullerene family

A new family of endohedral fullerenes, based on an encaged trithulium nitride (Tm(3)N) cluster, was synthesised, isolated and characterised by HPLC, mass spectrometry, and visible-NIR and FTIR spectroscopy. Tm(3)N clusterfullerenes with cages as small as C(76) and as large as C(88) were prepared and six of them were isolated. Tm(3)N@C(78) is a small clusterfullerene. The two isomers of Tm(3)N@C(80) (I and II) were the most abundant structures in the fullerene soot. Tm(3)N@C(82), Tm(3)N@C(84), and Tm(3)N@C(86) represent a new series of higher clusterfullerenes. All six isolated Tm(3)N clusterfullerenes were classified as large energy-gap structures with optical energy gaps between approximately 1.2 and approximately 1.75 eV. Tm(3)N@C(80) (I) and Tm(3)N@C(80) (II) were assigned to the C(80) cages C(80):7 (I(h)) and C(80):6 (D(5h)). For Tm(3)N@C(78), the analysis pointed to an elliptical carbon cage with C(78):1 (D(3)) or C(78):4 (D(3h)) being the probable structures.     

Katalasemodelle mit Erdalkalicarbonaten als Träger

Zusammenfassung Spuren von Co²⁺, Ag²⁺- oder Mn²⁺-Ionen katalysieren stark den H₂O₂-Zerfall, wenn sie sich auf Erdalkalicarbonat-Trägern befinden, wofür CaCO₃ und BaCO₃ sich weit besser eignen als SrCO₃. Weniger wirksam waren Cu²⁺ und Fe³⁺, während die Ionen Ni²⁺, Cd²⁺ und [Fe(CN)₆]^4– sich fast indifferent in diesem System verhielten.