Inhomogeneous gas model for electron mobility in high density neon gas

Experimental studies of electron mobilities in Neon as a function of the gas density have persistently shown mobilities up to an order of magnitude smaller than expected and predicted. A previously ignored mechanism (gas in--homogeneity which is negligible in the thermal mobilities for He and other gases) is found to reproduce the observed Neon mobilities accurately and simply at five temperatures with just one variable parameter. Recognizing that a gas is not a homogeneous medium, a variation in local density combined with the quantum multi--scattering theory, shifts the energy and cross section -- which in turn changes the collision probability and finally the mobilities. A lower density where a momentum transfer interaction occurs moves the mobility strongly in the same direction as the anomalous experiments. By going backwards from the observed mobilities, the collision frequency at each temperature and density is made to reproduce the experimental data by looking for the local (as opposed to average) density at which the (rare) momentum transfer interactions occur. These density deviations give a picture of the size and behavior of the wave packets for electron motion which looks very much like the often discussed wave function collapse.Comment: 18 pages, 5 figure

Fisher Waves and Front Roughening in a Two-Species Invasion Model with Preemptive Competition

We study front propagation when an invading species competes with a resident; we assume nearest-neighbor preemptive competition for resources in an individual-based, two-dimensional lattice model. The asymptotic front velocity exhibits power-law dependence on the difference between the two species' clonal propagation rates (key ecological parameters). The mean-field approximation behaves similarly, but the power law's exponent slightly differs from the individual-based model's result. We also study roughening of the front, using the framework of non-equilibrium interface growth. Our analysis indicates that initially flat, linear invading fronts exhibit Kardar-Parisi-Zhang (KPZ) roughening in one transverse dimension. Further, this finding implies, and is also confirmed by simulations, that the temporal correction to the asymptotic front velocity is of ${\cal O}(t^{-2/3})$.Comment: 8 pages, 5 figures; Papers on related work can be found at http://www.rpi.edu/~korniss/Researc

SU(3) centre vortices underpin confinement and dynamical chiral symmetry breaking

The mass function of the nonperturbative quark propagator in SU(3) gauge theory shows only a weak dependence on the vortex content of the gauge configurations. Of particular note is the survival of dynamical mass generation on vortex-free configurations having a vanishing string tension. This admits the possibility that mass generation associated with dynamical chiral symmetry breaking persists without confinement. In this presentation, we examine the low-lying ground-state hadron spectrum of the pi, rho, N and Delta and discover that while dynamical mass generation persists in the vortex-free theory, it is not connected to dynamical chiral symmetry breaking. In this way, centre vortices in SU(3) gauge theory are intimately linked to both confinement and dynamical chiral symmetry breaking. We conclude that centre vortices are the essential underlying feature of the QCD vacuum.Comment: 7 pages, 8 figues. Manuscript accepted for Publication in Phys. Rev.

(Dis)orientation and Design Preferences Within an Unfamiliar Care Environment: A Content Analysis of Older Adults’ Qualitative Reports After Route Learning

© The Author(s) 2020. Ensuring that environments are designed to cater for those with decreasing orientation, perceptual and mobility skills, is an example of how environments are being changed to become more age and dementia friendly. However, environmental design should directly involve potential users of the environment to ensure that their views are accounted for. Four open-ended questions, focusing on orientation strategies, reasons for disorientation, and design preferences, were given to 32 older adults after they had completed a route learning task through an unfamiliar environment. A Content Analysis found a strong focus on participants’ ability to memorize routes based on verbally encoding the route and on their ability to remember landmarks, with the reports linking closely to cognitive theories of navigation. Design suggestions included the importance of a homely and welcoming environment, memorable features, and access to the outdoors. The findings can be used inform age and dementia friendly design principles

Minimum drinking age laws effects on American youth 1976-1987

https://deepblue.lib.umich.edu/bitstream/2027.42/137895/1/occ28.pd

Renormalization of the singular attractive 1/r41/r^4 potential

We study the radial Schr\"odinger equation for a particle of mass $m$ in the field of a singular attractive $g^2/{r^4}$ potential with particular emphasis on the bound states problem. Using the regularization method of Beane \textit{et al.}, we solve analytically the corresponding ``renormalization group flow" equation. We find in agreement with previous studies that its solution exhibits a limit cycle behavior and has infinitely many branches. We show that a continuous choice for the solution corresponds to a given fixed number of bound states and to low energy phase shifts that vary continuously with energy. We study in detail the connection between this regularization method and a conventional method modifying the short range part of the potential with an infinitely repulsive hard core. We show that both methods yield bound states results in close agreement even though the regularization method of Beane \textit{et al.} does not include explicitly any new scale in the problem. We further illustrate the use of the regularization method in the computation of electron bound states in the field of neutral polarizable molecules without dipole moment. We find the binding energy of s-wave polarization bound electrons in the field of C$_{60}$ molecules to be 17 meV for a scattering length corresponding to a hard core radius of the size of the molecule radius ($\sim 3.37$ \AA). This result can be further compared with recent two-parameter fits using the Lennard-Jones potential yielding binding energies ranging from 3 to 25 meV.Comment: 8 page

Reproductive success through high pollinator visitation rates despite self incompatibility in an endangered wallflower

PREMISE OF THE STUDY: Self incompatibility (SI) in rare plants presents a unique challenge—SI protects plants from inbreeding depression, but requires a sufficient number of mates and xenogamous pollination. Does SI persist in an endangered polyploid? Is pollinator visitation sufficient to ensure reproductive success? Is there evidence of inbreeding/outbreeding depression? We characterized the mating system, primary pollinators, pollen limitation, and inbreeding/outbreeding depression in Erysimum teretifolium to guide conservation efforts. METHODS: We compared seed production following self pollination and within- and between-population crosses. Pollen tubes were visualized after self pollinations and between-population pollinations. Pollen limitation was tested in the field. Pollinator observations were quantified using digital video. Inbreeding/outbreeding depression was assessed in progeny from self and outcross pollinations at early and later developmental stages. KEY RESULTS: Self-pollination reduced seed set by 6.5× and quadrupled reproductive failure compared with outcross pollination. Pollen tubes of some self pollinations were arrested at the stigmatic surface. Seed-set data indicated strong SI, and fruit-set data suggested partial SI. Pollinator diversity and visitation rates were high, and there was no evidence of pollen limitation. Inbreeding depression (δ) was weak for early developmental stages and strong for later developmental stages, with no evidence of outbreeding depression. CONCLUSIONS: The rare hexaploid E. teretifolium is largely self incompatible and suffers from late-acting inbreeding depression. Reproductive success in natural populations was accomplished through high pollinator visitation rates consistent with a lack of pollen limitation. Future reproductive health for this species will require large population sizes with sufficient mates and a robust pollinator community

Epitaxial checkerboard arrangement of nanorods in ZnMnGaO4 films studied by x-ray diffraction

The intriguing nano-structural properties of a ZnMnGaO4 film epitaxially grown on MgO (001) substrate have been investigated using synchrotron radiation-based x-ray diffraction. The ZnMnGaO4 film consisted of a self-assembled checkerboard (CB) structure with perfectly aligned and regularly spaced vertical nanorods. The lattice parameters of the orthorhombic and rotated tetragonal phases of the CB structure were analyzed using H-K, H-L, and K-L cross sections of the reciprocal space maps measured around various symmetric and asymmetric reflections of the spinel structure. We demonstrate that the symmetry of atomic displacements at the phases boundaries provides the means for coherent coexistence of two domains types within the volume of the film