Influence of the Dzyaloshinskii-Moriya exchange interaction on quantum phase interference of spins

Magnetization measurements of a Mn12mda wheel single-molecule magnet with a spin ground state of S = 7 show resonant tunneling and quantum phase interference, which are established by studying the tunnel rates as a function of a transverse field applied along the hard magnetization axis. Dzyaloshinskii-Moriya (DM) exchange interaction allows the tunneling between different spin multiplets. It is shown that the quantum phase interference of these transitions is strongly dependent on the direction of the DM vector.Comment: 5 pages, 5 figure

Fabrication of Nano-Gapped Single-Electron Transistors for Transport Studies of Individual Single-Molecule Magnets

Three terminal single-electron transistor devices utilizing Al/Al2O3 gate electrodes were developed for the study of electron transport through individual single-molecule magnets. The devices were patterned via multiple layers of optical and electron beam lithography. Electromigration induced breaking of the nanowires reliably produces 1-3 nm gaps between which the SMM can be situated. Conductance through a single Mn12(3-thiophenecarboxylate) displays the coulomb blockade effect with several excitations within +/- 40 meV.Comment: 10 pages, 5 figure

Three-Loop Results in QCD with Wilson Fermions

We calculate the third coefficient of the lattice beta function in QCD with Wilson fermions, extending the pure gauge results of Luescher and Weisz; we show how this coefficient modifies the scaling function on the lattice. We also calculate the three-loop average plaquette in the presence of Wilson fermions. This allows us to compute the lattice scaling function both in the standard and energy schemes.Comment: 3 pages, LaTeX (fleqn.sty, espcrc2.sty), contribution to Lattice'97. Table caption corrected. The longer write-ups are in hep-lat/9801007 (beta function) and hep-lat/9801003 (plaquette

Physical and dynamical characterisation of low Delta-V NEA (190491) 2000 FJ10

We investigated the physical properties and dynamical evolution of Near Earth Asteroid (NEA) (190491) 2000 FJ10 in order to assess the suitability of this accessible NEA as a space mission target. Photometry and colour determination were carried out with the 1.54 m Kuiper Telescope and the 10 m Southern African Large Telescope during the object's recent favourable apparition in 2011-12. During the earlier 2008 apparition, a spectrum of the object in the 6000-9000 Angstrom region was obtained with the 4.2 m William Herschel Telescope. Interpretation of the observational results was aided by numerical simulations of 1000 dynamical clones of 2000 FJ10 up to 10^6 yr in the past and in the future. The asteroid's spectrum and colours determined by our observations suggest a taxonomic classification within the S-complex although other classifications (V, D, E, M, P) cannot be ruled out. On this evidence, it is unlikely to be a primitive, relatively unaltered remnant from the early history of the solar system and thus a low priority target for robotic sample return. Our photometry placed a lower bound of 2 hrs to the asteroid's rotation period. Its absolute magnitude was estimated to be 21.54+-0.1 which, for a typical S-complex albedo, translates into a diameter of 130+-20 m. Our dynamical simulations show that it has likely been an Amor for the past 10^5 yr. Although currently not Earth-crossing, it will likely become so during the period 50 - 100 kyr in the future. It may have arrived from the inner or central Main Belt > 1 Myr ago as a former member of a low-inclination S-class asteroid family. Its relatively slow rotation and large size make it a suitable destination for a human mission. We show that ballistic Earth-190491-Earth transfer trajectories with Delta-V < 2 km s^-1 at the asteroid exist between 2052 and 2061.Comment: 2 Tables, 11 Figures, accepted for publication in Astronomy & Astrophysic

Fractal Behaviour in the O(3) Model

We study domain formation in the two-dimensional O(3) model near criticality. The fractal dimension of these domains is determined with good statistical accuracy.Comment: 6 pages + 3 figures (concatenated PS files, uuencoded gz-compressed

Orthodontists' and laypersons' aesthetic assessment of Class III subjects referred for orthognathic surgery

This study was undertaken to compare laypersons' and professionals' perception of soft tissue profiles of Class III adults, and to evaluate which cephalometric variables are likely to influence the profile assessment score (PAS). Lateral headfilms and coloured profile photographs of 18 skeletal Class III Caucasian adult patients (10 males, 8 females with a mean age of 24.5 years) prior to surgery, and nine adult Caucasian patients (four males, five females with a mean age of 27.4 years) with a dental Class I occlusion and no major skeletal discrepancy were included in the study. The headfilms were hand traced and digitized. Various cephalometric variables were calculated by computer software. Each printed profile photograph was evaluated aesthetically by 18 laypersons and 18 orthodontists using a 10-graded visual analogue scale (VAS) and a standard profile for calibration. Intra-observer reliability was tested and no significant error was found. Paired and unpaired t-tests were used to compare the scores. The association between various cephalometric variables and the PAS was tested. In general, compared with orthodontists, laypersons were less critical in their evaluation of the Class III profiles (+0.3 grade on the VAS) as well as the reference profiles (+0.7). The reference profiles were found to be more attractive than the Class III profiles by both laypersons and orthodontists (+2.3 grades). The degree of facial concavity had a negatively predictive value for the orthodontists' and laypersons' evaluations. The degree of facial concavity together with the steepness of the mandibular plane were negatively predictive factors for the PAS given by the orthodontist