Characterization Methods for Fractured Glacial Tills

Author Institution: US Geological Survey, Water Resources DivisionThis paper provides a literature review of methods successfully employed to characterize finegrained and fractured or unfractured glacial deposits. Descriptions and examples are given for four major categories of characterization methods: physical, hydraulic, chemical, and indirect. Characterization methods have evolved significantly within the past ten years; however, there still exists uncertainty about the reliability of individual characterization methods applied to till deposits. Therefore, a combination of methods is best, the choice of which depends on the objectives of the work. Sampling methods, sampling scales, and reporting methods are extremely important and should be considered when interpreting and comparing results between sites. Recognition of these issues is necessary to ensure that decisions regarding the transport of fluids in fractured tills are not based on the assumption that poorly permeable tills are always an inhibitor of subsurface flow

Density of states in graphene with vacancies: midgap power law and frozen multifractality

The density of states (DoS), $\varrho(E)$, of graphene is investigated numerically and within the self-consistent T-matrix approximation (SCTMA) in the presence of vacancies within the tight binding model. The focus is on compensated disorder, where the concentration of vacancies, $n_\text{A}$ and $n_\text{B}$, in both sub-lattices is the same. Formally, this model belongs to the chiral symmetry class BDI. The prediction of the non-linear sigma-model for this class is a Gade-type singularity $\varrho(E) \sim |E|^{-1}\exp(-|\log(E)|^{-1/x})$. Our numerical data is compatible with this result in a preasymptotic regime that gives way, however, at even lower energies to $\varrho(E)\sim E^{-1}|\log(E)|^{-\mathfrak{x}}$, $1\leq \mathfrak{x} < 2$. We take this finding as an evidence that similar to the case of dirty d-wave superconductors, also generic bipartite random hopping models may exhibit unconventional (strong-coupling) fixed points for certain kinds of randomly placed scatterers if these are strong enough. Our research suggests that graphene with (effective) vacancy disorder is a physical representative of such systems.Comment: References updated onl

A Spreading Layer Origin for Dwarf Nova Oscillations

Dwarf nova outbursts often show coherent ($Q\sim10^4-10^6$) sinusoidal oscillations with the largest pulsed fraction in the extreme ultraviolet. Called dwarf nova oscillations (DNOs), they have periods of $P\approx3-40 {\rm s}$ and scale with luminosity as $P\propto L^{-\beta}$ with $\beta\approx0.1-0.2$. We propose that DNOs may be produced by nonradial oscillations in a thin hydrostatic layer of freshly accreted material, the ``spreading layer'' (SL), at the white dwarf (WD) equator. This would naturally explain a number of key properties of DNOs, including their frequency range, sinusoidal nature, sensitivity to accretion rate, and why they are only seen during outburst. In support of this hypothesis we construct a simple model that treats the SL as a cavity containing shallow surface waves, each with the same radial structure, but split into three different modes denoted by their azimuthal wavenumber, $m$. The $m=0$ latitudinally propagating mode best matches the periods and scalings associated with most DNOs, and DNOs with periods shorter than the WD Keplerian period are explained by the $m=-1$ prograde mode. We also predict a third set of oscillations, produced by the $m=1$ retrograde mode, and show its expected dependence on accretion rate.Comment: Accepted for publication in Astrophysical Journal Letters, 4 pages, 2 figure

Integrated and Modular Didactic and Methodological Concept for a Learning Factory

AbstractAs today manufacturing is not only subject to a single factory, but a network of globally distributed production sites, the goal-oriented encouragement of professional capacities is the motivation for the Learning Factory on Global Production (LGP). In this context, the design of a competency-based and action-oriented didactic and methodological concept is a prerequisite for sustainable learning results and for the development of self-determined problem solving skills. The presented paper gives an overview to the didactic and methodological design approach of the LGP. The integrated modular concept of e-learning and application in the learning factory environment supports self-directed learning and implemented by structuring the teaching/ learning process according to the model of complete action

AROUSING FEAR IN DENTAL HEALTH EDUCATION * , †

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65851/1/j.1752-7325.1965.tb00484.x.pd

A comparative analysis of parallel processing and super-individual methods for improving the computational performance of a large individual-based model

Individual-based modelling approaches are being used to simulate larger complex spatial systems in ecology and in other fields of research. Several novel model development issues now face researchers: in particular how to simulate large numbers of individuals with high levels of complexity, given finite computing resources. A case study of a spatially-explicit simulation of aphid population dynamics was used to assess two strategies for coping with a large number of individuals: the use of ‘super-individuals’ and parallel computing. Parallelisation of the model maintained the model structure and thus the simulation results were comparable to the original model. However, the super-individual implementation of the model caused significant changes to the model dynamics, both spatially and temporally. When super-individuals represented more than around 10 individuals it became evident that aggregate statistics generated from a super-individual model can hide more detailed deviations from an individual-level model. Improvements in memory use and model speed were perceived with both approaches. For the parallel approach, significant speed-up was only achieved when more than five processors were used and memory availability was only increased once five or more processors were used. The super-individual approach has potential to improve model speed and memory use dramatically, however this paper cautions the use of this approach for a density-dependent spatially-explicit model, unless individual variability is better taken into account