Quantum transport of disordered Weyl semimetals at the nodal point

Weyl semimetals are paradigmatic topological gapless phases in three dimensions. We here address the effect of disorder on charge transport in Weyl semimetals. For a single Weyl node with energy at the degeneracy point and without interactions, theory predicts the existence of a critical disorder strength beyond which the density of states takes on a nonzero value. Predictions for the conductivity are divergent, however. In this work, we present a numerical study of transport properties for a disordered Weyl cone at zero energy. For weak disorder our results are consistent with a renormalization group flow towards an attractive pseudoballistic fixed point with zero conductivity and a scale-independent conductance; for stronger disorder diffusive behavior is reached. We identify the Fano factor as a signature that discriminates between these two regimes

Thymelaea Passerina, A new Weed in the United States

During a survey of the loess bluffs flora of the Missouri River border of Iowa, Morrill (1953) discovered a few individuals of an unknown weed growing on bare vertical loess south of Council Bluffs. It proved impossible to identify this plant with any of the usual American manuals. It eventually was determined to be Thymelaea passerina (L.) Coss. and Germ. Inquiries addressed to the principal American herbaria revealed that only one specimen of the plant had been previously collected in this country. This was found in a pasture in Cedar County, Nebraska, in the northeastern corner of the state

Vitis rotundifolia Michx.

https://thekeep.eiu.edu/herbarium_specimens_byname/19798/thumbnail.jp

Introduced Weedy Grasses in Iowa

Chloris verticillata Nutt., Eriochloa villosa (Thunb.) Kunth, and Miscanthus sacchariflorus (Maxim.) Hack., are reported as three grasses new to the Iowa flora

A Rapid Softening Agent for Dried Plant Structures

In the past, dried plant materials, such as fragments of herbarium specimens, have generally been softened for dissection by boiling in water. Such a process has obvious disadvantages: slowness, fire hazard, and inconvenience. Furthermore, it is impossible to apply the boiling technique to mounted herbarium specimens without removing portions of the plant. While the author was engaged in the examination of the ligules of large numbers of grass specimens, it became evident that a solution which could be applied directly to the mounted specimen to soften it in situ would be of great advantage in preventing unnecessary breakage. A little experimentation led to the formulation of the solution whose composition is stated below. It proved very satisfactory for softening most plant specimens quickly, without boiling

Pennisetum petiolare, a pseudopetiolate African Grass Adventive in lowa

Pennisetum petiolare, a grass native to the Sudan and Ethiopia and never previously reported from North America, occurred in a lawn in Ames, Iowa. The source of the seed was contaminated Niger thistle (Guizotia abyssinica) seed used in a bird feeder directly above the location of the plant. The occurrence of at least 15 other seeds or fruits as contaminants in the sample indicates that Niger thistle seed may serve as a medium for the introduction of weed seed into the United States

Morphology and Cytology of Some Hybrids Between Elymus canadensis and E. virginicus

Substances which inhibit the action of human plasma cholinesterase in vitro have been found in aqueous extracts of various members of the plant family Solanaceae. A preliminary survey of some weedy and cultivated midwestern representatives of this family revealed eleven active species in six genera: Datura, Lycopersicon, Nicotiana, Petunia, Physalis, and Solanum. A member each of the genera Capsicum and Lycium were inactive. Inhibitory substances were not found in thirty-one species representing nineteen plant families other than Solanaceae

Size-dependent fine-structure splitting in self-organized InAs/GaAs quantum dots

A systematic variation of the exciton fine-structure splitting with quantum dot size in single InAs/GaAs quantum dots grown by metal-organic chemical vapor deposition is observed. The splitting increases from -80 to as much as 520 $\mu$eV with quantum dot size. A change of sign is reported for small quantum dots. Model calculations within the framework of eight-band k.p theory and the configuration interaction method were performed. Different sources for the fine-structure splitting are discussed, and piezoelectricity is pinpointed as the only effect reproducing the observed trend.Comment: 5 pages, 5 figure

Automated sliding susceptibility mapping of rock slopes

International audienceWe present a suite of extensions for ARCVIEW GIS? (ESRI) that allows to map the spatial distribution of first-order mechanical slope-properties in hard rock terrain, e.g. for large slope areas like water reservoir slopes. Besides digital elevation data, this expert-system includes regional continuous grid-based data on geological structures that might act as potential sliding or cutoff planes for rockslides. The system allows rapid automated mapping of geometrical and kinematical slope properties in hard rock, providing the basis for spatially distributed deterministic sliding-susceptibility evaluations on a pixel base. Changing hydrostatic slope conditions and rock mechanical parameters can be implemented and used for simple predictive static stability calculations. Application is demonstrated for a study area in the Harz Mts., Germany