119Sn and57Fe Mössbauer study of La2−x Sr x CuO4

Mössbauer absorption measurements were carried out for¹¹⁹Sn and⁵⁷Fe impurities in La₂CuO₄, La_1.85Sr_0.15CuO₄ and La_1.6Sr_0.4CuO₄. For all cases,⁵⁷Fe spectra at 4.2 K show magnetic hyperfine splittings. On the other hand, a magnetic hyperfine field at Sn nucleus is observed only in the case of La_1.85Sr_0.15CuO₄. The results indicate that the Cu magnetic spins are collectively fluctuating in the superconducting sample.     

Structure of the isovector dipole resonance in neutron-rich <Superscript>60</Superscript><Emphasis Type="Italic">Ca</Emphasis> nuclei and direct decay from pygmy resonance

The structure of the isovector dipole resonance in neutron-rich calcium isotope, ⁶⁰Ca, has been investigated by implementing a careful treatment of the differences of neutron and proton radii in the continuum random phase approximation (RPA). The calculations have taken into account the current estimates of the neutron skin. The estimates of the escape widths for direct neutron decay from the pygmy-dipole resonance (PDR) were shown rather wide, implicating a strong coupling to the continuum. The width of the giant-dipole resonance (GDR) was evaluated, bringing on a detailed discussion about its microscopic structure.Received: 22 September 2003, Revised: 9 February 2004, Published online: 7 September 2004PACS: 21.10.Pc Single-particle levels and strength functions - 21.60.-n Nuclear structure models and methods - 24.30.Cz Giant resonances - 24.30.Gd Other resonances     

Interface magnetism of Fe/Nd multilayers studied by Mössbauer spectroscopy

Fe/Nd multilayers with⁵⁷Fe enriched interfaces are prepared to investigate crystal structure and magnetism at the interface by Mössbauer spectroscopy. The intermixture at the interface is less than two atomic layers. The magnetic moments of interface Fe atoms align collinear and turn at a certain temperature or at a certain magnetic field with keeping the collinear structure. By annealing, the interface component with smaller hyperfine field decreases and the perpendicular magnetic anisotropy increases.     

Complementary Regions of Knot and Link Diagrams

An increasing sequence of integers is said to be universal for knots and links if every knot and link has a reduced projection on the sphere such that the number of edges of each complementary face of the projection comes from the given sequence. In this paper, it is proved that the following infinite sequences are each universal for knots and links: (3, 5, 7, . . .), (2, n, n + 1, n + 2, . . .) for each n ≥ 3, (3, n, n + 1, n + 2, . . .) for each n ≥ 4. Moreover, the finite sequences (2, 4, 5) and (3, 4, n) for each n ≥ 5 are universal for all knots and links. It is also shown that every knot has a projection with exactly two odd-sided faces, which can be taken to be triangles, and every link of n components has a projection with at most n odd-sided faces if n is even and n + 1 odd-sided faces if n is odd.     

Surface instability and primary atomization characteristics of straight liquid jet sprays

Using the detailed numerical simulation data of primary atomization, the liquid surface instability development that leads to atomization is characterized. The numerical results are compared with a theoretical analysis of liquid–gas layer for a parameter range close to high-speed Diesel jet fuel injection. For intermittent and short-duration Diesel injection, the aerodynamic surface interaction and transient head formation play an important role. The present numerical setting excludes nozzle disturbances to primarily investigate this interfacial instability mechanism and the role of jet head. The first disturbed area is the jet head region, and the generated disturbances are fed into the upstream region through the gas phase. This leads to the viscous boundary layer instability development on the liquid jet core. By temporal tracking of surface pattern development including the phase velocity and stability regime and by the visualization of vortex structures near the boundary layer region, it is suggested that the instability mode is the Tollmien–Schlichting (TS) mode similar to the turbulent transition of solid-wall boundary layer. It is also demonstrated that the jet head and the liquid core play an interacting role, thus the jet head cannot be neglected in Diesel injection. In this study, this type of boundary layer instability has been demonstrated as a possible mechanism of primary atomization, especially for high-speed straight liquid jets. The effect of nozzle turbulence is a challenging but important issue, and it should be examined in the future.