A new violet from Utah

journal articleA beautiful violet strikingly different from any species heretofore reported from Utah was discovered by the writer growing 011 vacant property on the outskirts of Salt Lake City at the corner of 13th South and 17th E as t streets, April 17, 1937.*' This property and neighboring areas to the east have for years been known to harbor one of the few relict colonies of Viola beckwithii t . & g . once so widely distributed over the Bonneville bench lands along the W a satch front. Growing in this same area are numerous plants of Viola purpurea venosa (Wats.) Brainard

Effect of canopy profile on solar thermal chimney performance

Solar thermal chimneys (STCs) are renewable energy power plants that require large-scale deployment to be economically competitive. This paper presents a steady-state analytical model developed to describe accurately the thermodynamics of the solar collector. The impact of different collector canopy designs on the performance is assessed. Results show that the height of the canopy has a significant effect on plant performance and that the canopy must be sufficiently high at the junction with the chimney to ensure maximum kinetic energy in the flow at the chimney inlet can be reached. A new collector profile with a partially sloped canopy is proposed. It was found to perform at similar levels of maximum power output to the best-performing existing canopy designs, and to be robust under varying environmental conditions. For ease of construction and reduction of associated costs this canopy can be built in stepped annular flat sections with only a minor loss in performance

A new polygonum from Garfield County, Utah

journal articleThe plant described below was collected 6 miles north of Escalante, Garfield Co., Utah, by W . P. Cottam, Sept. 17, 1935. It was found growing in great abundance along sandy ravines on the rocky Navajo sandstone spur which projects southward from the Aquarius Plateau. The type specimen, No. 65 0 7 , deposited in the University of Utah Herbarium, was collected at an elevation of about 7000 ft. at the specific location of T34S.R.3E

New and extended ranges for Utah Plants

journal articleThe following Utah plan ts are not included in Tidestrom's " Flora of Utah and Nevada," nor are any listed specifically for Utah in Rvdberg's " Flora of the Rocky Mountains and A djacent Plains." Specific localities are given for each species, followed by the herbaria where it may be found. The University of Utah Herbarium is designated by the letter "U " , the A. O. Garrett Herbarium by the letter "G " , and the Brigham Young University Herb arium by the letter "Y ." This list does not include a rather large number of species known to occur in Utah and listed in Tidestrom , but not specifically for Utah

One-magnon Raman scattering in La(2)CuO(4): the origin of the field-induced mode

We investigate the one-magnon Raman scattering in the layered antiferromagnetic La(2)CuO(4) compound. We find that the Raman signal is composed by two one-magnon peaks: one in the B1g channel, corresponding to the Dzyaloshinskii-Moryia (DM) mode, and another in the B3g channel, corresponding to the XY mode. Furthermore, we show that a peak corresponding to the XY mode can be induced in the planar (RR) geometry when a magnetic field is applied along the easy axis for the sublattice magnetization. The appearance of such field-induced mode (FIM) signals the existence of a new magnetic state above the Neel temperature T_N, where the direction of the weak-ferromagnetic moment (WFM) lies within the CuO(2) planes.Comment: 4 pages, 3 figure

Manipulating nanoscale structure to control functionality in printed organic photovoltaic, transistor and bioelectronic devices.

Printed electronics is simultaneously one of the most intensely studied emerging research areas in science and technology and one of the fastest growing commercial markets in the world today. For the past decade the potential for organic electronic (OE) materials to revolutionize this printed electronics space has been widely promoted. Such conviction in the potential of these carbon-based semiconducting materials arises from their ability to be dissolved in solution, and thus the exciting possibility of simply printing a range of multifunctional devices onto flexible substrates at high speeds for very low cost using standard roll-to-roll printing techniques. However, the transition from promising laboratory innovations to large scale prototypes requires precise control of nanoscale material and device structure across large areas during printing fabrication. Maintaining this nanoscale material control during printing presents a significant new challenge that demands the coupling of OE materials and devices with clever nanoscience fabrication approaches that are adapted to the limited thermodynamic levers available. In this review we present an update on the strategies and capabilities that are required in order to manipulate the nanoscale structure of large area printed organic photovoltaic (OPV), transistor and bioelectronics devices in order to control their device functionality. This discussion covers a range of efforts to manipulate the electroactive ink materials and their nanostructured assembly into devices, and also device processing strategies to tune the nanoscale material properties and assembly routes through printing fabrication. The review finishes by highlighting progress in printed OE devices that provide a feedback loop between laboratory nanoscience innovations and their feasibility in adapting to large scale printing fabrication. The ability to control material properties on the nanoscale whilst simultaneously printing functional devices on the square metre scale is prompting innovative developments in the targeted nanoscience required for OPV, transistor and biofunctional devices

Magnonic Crystal with Two-Dimensional Periodicity as a Waveguide for Spin Waves

We describe a simple method of including dissipation in the spin wave band structure of a periodic ferromagnetic composite, by solving the Landau-Lifshitz equation for the magnetization with the Gilbert damping term. We use this approach to calculate the band structure of square and triangular arrays of Ni nanocylinders embedded in an Fe host. The results show that there are certain bands and special directions in the Brillouin zone where the spin wave lifetime is increased by more than an order of magnitude above its average value. Thus, it may be possible to generate spin waves in such composites decay especially slowly, and propagate especially large distances, for certain frequencies and directions in ${\bf k}$-space.Comment: 13 pages, 4 figures, submitted to Phys Rev

Anomalous frequency and intensity scaling of collective and local modes in a coupled spin tetrahedron system

We report on the magnetic excitation spectrum of the coupled spin tetrahedral system Cu$_{2}$Te$_{2}$O$_{5}$Cl$_{2}$ using Raman scattering on single crystals. The transition to an ordered state at T$_{N}^{Cl}$=18.2 K evidenced from thermodynamic data leads to the evolution of distinct low-energy magnetic excitations superimposed by a broad maximum. These modes are ascribed to magnons with different degree of localization and a two-magnon continuum. Two of the modes develop a substantial energy shift with decreasing temperature similar to the order parameter of other Neel ordered systems. The other two modes show only a negligible temperature dependence and dissolve above the ordering temperature in a continuum of excitations at finite energies. These observations point to a delicate interplay of magnetic inter- and intra-tetrahedra degrees of freedom and an importance of singlet fluctuations in describing a spin dynamics.Comment: 7pages, 6figures, 1tabl

Nonlinear Spin Dynamics in Ferromagnets with Electron-Nuclear Coupling

Nonlinear spin motion in ferromagnets is considered with nonlinearity due to three factors: (i) the sample is prepared in a strongly nonequilibrium state, so that evolution equations cannot be linearized as would be admissible for spin motion not too far from equilibrium, (ii) the system considered consists of interacting electron and nuclear spins coupled with each other via hyperfine forces, and (iii) the sample is inserted into a coil of a resonant electric circuit producing a resonator feedback field. Due to these nonlinearities, coherent motion of spins can develop, resulting in their ultrafast relaxation. A complete analysis of mechanisms triggering such a coherent motion is presented. This type of ultrafast coherent relaxation can be used for studying intrinsic properties of magnetic materials.Comment: 1 file, LaTex, 23 page

Lattice dynamics and the electron-phonon interaction in Ca2_2RuO4_4

We present a Raman scattering study of Ca$_2$RuO$_4$, in which we investigate the temperature-dependence of the lattice dynamics and the electron-phonon interaction below the metal-insulator transition temperature ({\it T}$_{\rm MI}$). Raman spectra obtained in a backscattering geometry with light polarized in the ab-plane reveal 9 B$_{1g}$ phonon modes (140, 215, 265, 269, 292, 388, 459, 534, and 683 cm$^{-1}$) and 9 A$_g$ phonon modes (126, 192, 204, 251, 304, 322, 356, 395, and 607 cm$^{-1}$) for the orthorhombic crystal structure (Pbca$-$D$_{2h}^{15}$). With increasing temperature toward {\it T}$_{\rm MI}$, the observed phonon modes shift to lower energies and exhibit reduced spectral weights, reflecting structural changes associated with the elongation of the RuO$_6$ octahedra. Interestingly, the phonons exhibit significant increases in linewidths and asymmetries for {\it T} $>$ {\it T}$_{\rm N}$. These results indicate that there is an increase in the effective number of electrons and the electron-phonon interaction strengths as the temperature is raised through {\it T}$_{\rm N}$, suggesting the presence of orbital fluctuations in the temperature regime {\it T}$_{\rm N}$ $<$ {\it T} $<$ {\it T}$_{\rm MI}$.Comment: 6 pages, 4 figure