Oscillatory melting temperature of the vortex smectic phase in layered superconductors

We report on transport measurements of YBa 2Cu 3O (7-delta) single crystals with different oxygen contents in the geometry B, J ||ab (J perpendicularB). Our data show that the vortices become confined between the Cu-O planes below a well-defined temperature at which the effective size 2xi of the vortex core is approximately equal to the period of the Cu-O layers. This confinement strongly increases the vortex liquid freezing temperature. A new melting line is found separating a vortex liquid and a smectic phase, which shows an oscillatory field dependence reflecting differences between commensurate and incommensurate smectic states.     

Synthesis of Novel Chiral Diol Ligands for the Enantioselective Reactions

The chiral diols ((,(,((,((-Tetraaryl-1,3-dioxolane-4,5-dimethanols) have been used for the formation of cyclic titanates and similar derivatives of Mg, Al and Zr. These complexes of oxophilic metal centers were employed in catalytic and stiochiometric enantioselective reactions such as enantioselective addition reactions of carbon-centered nucleophiles to aldehydes1, [2+2] cycloadditions2, and Diels-Alder reactions3. So far, the two hydrogen atoms of all this type of diols are in trans form…     

The diffraction of elastic waves by an imperfect fusion bond

We consider diffraction by a semi-infinite crack located alonga fusion interface between two differing elastic media. Twotypes of crack, namely open and partially closed cracks, areinvestigated. An open crack is modelled by a stress-free contactboundary condition and a partially closed crack is modelledby a spring contact boundary condition. For the latter, thejump in the stress across the crack is assumed to be proportionalto the jump in the displacement across the crack. This situationarises in, for example, a K-weld where the fine grain of theparent material (for example, ferritic or forged austeniticsteel) is in stark contrast with the coarse-grained weld metal(for example, austenitic weld metal). In the metal weld thedirection of the grain axis varies through the metal. However,diffraction is a local phenomenon and so the austenitic steelis assumed to have a zonal axis so that it may be modelled bya transversely isotropic composite. The ferritic or forged austeniticsteel will be modelled as an isotropic material.     

Quasidefinite Matrizen

Zusammenfassung Mit Quasidefinitheit bezeichnen wir eine Verallgemeinerung des Begriffs der Semidefinitheit von Matrizen. Für symmetrische Matrizen fallen beide Begriffe zusammen. Daher ist Quasidefinitheit eine Eigenschaft der speziellen Matrix und nicht zugleich der zugehörigen quadratischen Form. Nach Vorbereitungen in Abschnitt 1 bringen wir in Abschnitt 2 die grundlegenden Eigenschaften quasidefiniter Matrizen und in Abschnitt 3 eine weitere Eigenschaft, die mit der Optimierungstheorie in Zusammenhang steht.     

Ion-beam formation and track modification of InAs nanoclusters in silicon and silica

The implantation formation of InAs nanoclusters in silicon and silica and their modification via irradiation with Xe ions with an energy of 167 MeV and a fluence of 3 × 10¹⁴ cm^–2 are studied. It is found that post-implantation annealing and irradiation with high-energy ions alter the size and shape of nanoclusters and cause structural transformations within them. The ordering of nanoclusters and their elongation along the trajectory of Xe ions in a SiO₂ matrix is observed.