Electronic transport properties of amorphous NiTi alloys

Measurements of electrical resistivity, magnetoresistance and Hall effect on amorphous Ni_100–x Ti _x alloys withx=39, 43, 60, 65, 70, and 76 are presented. The resistivity at 4.2 K is in the range 210 cm to 325 cm. The Hall coefficient turns out to be negative for low Ti contents and positive for high Ti contents with values around –6×10^–11 m³/As and +7×10^–11 m³/As, respectively. At low temperatures, the temperature and magnetic field dependences of the quantities measured are analysed and discussed in terms of weak localisation and electron-electron interaction effects.     

The action of operator semigroups on the topological dual of the Beurling-Björck space

We investigate the action of a class of operator semigroups on generalized functions of almost exponential growth, proving that these generalized functions are admissible initial conditions for the associated heat equation.     

Analogs of the dihydroceramide desaturase inhibitor GT11 modified at the amide function: synthesis and biological activities

Dihydroceramide desaturase is the last enzyme in the biosynthesis of ceramide de novo. The cyclopropene-containing sphingolipid GT11 is a competitive inhibitor of dihydroceramide desaturase. The biological effects of chemical modification of the GT11 amide linkage are reported in this article. Either N-methyl substitution or replacement of the amide alpha-carbonyl methylene by oxygen result in inactive compounds. In contrast, both urea (3) and thiourea (4) analogs of GT11, as well as three alpha-ketoamides (5-7), did inhibit the desaturation of N-octanoylsphinganine to N-octanoylsphingosine, although with significantly lower potency than GT11. Furthermore, the alpha-ketoamides 5-7 inhibit the acidic ceramidase with similar potencies (IC50 52-83 microM). Inhibition of the neutral/alkaline ceramidase by these compounds requires around 20-fold higher concentrations. Structure-activity relationships and the biological interest of these compounds are discussed.     

Experimental evidence for anomalous beta-gamma directional correlation in Au198

Some anomalies in the longitudinal polarization and the beta shape of the non-unique first forbidden beta decay from Au¹⁹⁸ initiated this careful experiment on the beta-gamma directional correlation of the same decay. The authors found evidence that also the differential beta-gamma directional correlation shows an anomalous behaviour at beta energies below 200 keV. The anisotropy of the 0.96 MeV beta to 0.411 MeV gamma cascade at low energies, instead of decreasing with decreasing beta energy, is increasing sharply below 200 keV beta energy. Instrumental effects can be excluded as demonstrated with allowed transitions, which show the expected behaviour in the same energy region.     

Unexpected coupling between an eta5-indenyl ligand and alkenyl-vinylidene fragments: synthesis of unprecedented (eta6-indene)ruthenium(II) metallacycles

Vinylidene complexes [Ru[=C=C(H)CR1R2CH2C(Me)=CH2](eta5-C9H7)(PPh3)2][BF4] undergo an intramolecular coupling between the alkenyl-vinylidene fragment and the eta5-indenyl ligand to afford indene-metallacyclic compounds (6a,b) in which the resulting functionalised indene group is eta6-coordinated to the metal.     

First high thermally stable organo-inorganic 3D polymer scandium derivative as a heterogeneous Lewis acid catalyst

Sc2(OOCC2H4COO)2.5(OH), a new hybrid organic-inorganic polymer, has been hydrothermally obtained; the crystal structure of this material has been established by single crystal X-ray diffraction; having high thermal stability it can be used as an effective Lewis acid catalyst and can be easily recycled and reused without any appreciable loss in activity.