Non-Collinear Magnetism due to Orbital Degeneracy and Multipolar Interactions

The origin of non-collinear magnetism under quadrupolar ordering is investigated with CeB6 taken as a target system. The mode-mixing effect among 15 multipoles is analyzed based on the Ginzburg-Landau free energy. Then the lower magnetic transition temperature and the order parameters are derived within the mean-field approximation. In the presence of pseudo-dipole-type interactions for the next-nearest neighbors, the observed pattern of non-collinear ordering is indeed stabilized for certain set of interaction parameters. The stability of the phase III' in the magnetic field is also explained, which points to the importance of the next-nearest-neighbor octupole-octupole interaction. Concerning the phase IV in CexLa1-xB6 with x ~ 0.75, a possibility of pure octupole ordering is discussed based on slight modifications of the strength of interactions.Comment: 12 pages, 7 figures, 3 tables, to appear in J. Phys. Soc. Jpn. 70 (6) (2001

Lattice Dynamics of LaFeAsO_{1-x}F_{x} and PrFeAsO_{1-y} via Inelastic X-Ray Scattering and First-Principles Calculation

The lattice dynamics of LaFeAsO_{1-x}F_{x} (x=0, 0.1) and PrFeAsO_{1-y} (y~0.1) are investigated using inelastic x-ray scattering and ab-initio calculation. Measurements of powder samples provide an approximation to the phonon DOS, while dispersion is measured from a single crystal of PrFeAsO_{1-y}. A model that agrees reasonably well with all of the data at room temperature is built from results of ab-initio calculations by softening the strength of the Fe-As bond by 30%.Comment: 4 pages, 4 figures; some changes of the text and a revision of figure

Controlled Micro/Nanodome Formation in Proton-Irradiated Bulk Transition-Metal Dichalcogenides

At the few-atom-thick limit, transition-metal dichalcogenides (TMDs) exhibit strongly interconnected structural and optoelectronic properties. The possibility to tailor the latter by controlling the former is expected to have a great impact on applied and fundamental research. As shown here, proton irradiation deeply affects the surface morphology of bulk TMD crystals. Protons penetrate the top layer, resulting in the production and progressive accumulation of molecular hydrogen in the first interlayer region. This leads to the blistering of one-monolayer thick domes, which stud the crystal surface and locally turn the dark bulk material into an efficient light emitter. The domes are stable (>2-year lifetime) and robust, and host strong, complex strain fields. Lithographic techniques provide a means to engineer the formation process so that the domes can be produced with well-ordered positions and sizes tunable from the nanometer to the micrometer scale, with important prospects for so far unattainable applications

Assessing the Healthfulness of Campus Dining Environments Using “Full Restaurant Evaluation Supporting a Healthy (FRESH) Dining Environment” Tool

This audit assessed dining halls/cafeterias (DH), fast food (FF), sit-down (SD) and delivery restaurants. Healthfulness of Foods subscale (HEFS) consisted of 12 items assessing menu descriptions, food preparation and healthful foods availability; (a¼.813) (total possible points were 60). Dining Environment Supports subscale (DESS) consisted of 10 items assessing nutrition information/labeling, signage/posters, portion/cup sizes, pricing, etc. (a¼.753) (total possible points were 50). Each criterion was scored using a five-point semantic-differential scale, a score of “1” provided little or no support for selecting healthy foods, and “5” provided extensive options or high support for healthy food selection. Research assistants were trained and completed interrater reliability \u3e 80% before data collection. Inter-class correlations (ICC), non-parametric, and ANOVA with Fisher’s LSD post hoc statistics were conducted. Through 15 schools 362 dining venues were evaluated (14.6% DH, 55% FF, 26% SD, 4.4% delivery). ICC results were appropriate [.89 to .99] For DH, FF, SD, and delivery; average HEFS scores were 29.45 12.17, 19.67 7.75, 24.0 9.64, 18.47 4.79 respectively; and average DESS scores were 22.10 5.27, 18.8 4.53, 20.27 4.95, 16.333.75, respectively. Between the 15 schools there were significant differences on both the HEFS and the DESS scores F (13,338) ¼ 2.893, p\u3c.05 and DESS score F (13,339) ¼ 1.902, p\u3c.05. This simplified FRESH dining environment audit effectively assessed the healthfulness of the foods and the environmental supports, and determined differences in the overall FRESH dining environment on college campuses