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The effects of decomposing animal remains on cave invertebrate communities
Topological derivation of shape exponents for stretched exponential relaxation
In homogeneous glasses, values of the important dimensionless
stretched-exponential shape parameter beta are shown to be determined by magic
(not adjusted) simple fractions derived from fractal configuration spaces of
effective dimension d* by applying different topological axioms (rules) in the
presence (absence) of a forcing electric field. The rules are based on a new
central principle for defining glassy states: equal a priori distributions of
fractal residual configurational entropy. Our approach and its beta estimates
are fully supported by the results of relaxation measurements involving many
different glassy materials and probe methods. The present unique topological
predictions for beta typically agree with observed values to ~ 1% and indicate
that for field-forced conditions beta should be constant for appreciable ranges
of such exogenous variables as temperature and ionic concentration, as indeed
observed using appropriate data analysis. The present approach can also be
inverted and used to test sample homogeneity and quality.Comment: Original 13 pages lengthened to 21 pages (longer introduction, added
references and discussion of new experimental data published since original
submission
Online Forum Thread Retrieval using Pseudo Cluster Selection and Voting Techniques
Online forums facilitate knowledge seeking and sharing on the Web. However,
the shared knowledge is not fully utilized due to information overload. Thread
retrieval is one method to overcome information overload. In this paper, we
propose a model that combines two existing approaches: the Pseudo Cluster
Selection and the Voting Techniques. In both, a retrieval system first scores a
list of messages and then ranks threads by aggregating their scored messages.
They differ on what and how to aggregate. The pseudo cluster selection focuses
on input, while voting techniques focus on the aggregation method. Our combined
models focus on the input and the aggregation methods. The result shows that
some combined models are statistically superior to baseline methods.Comment: The original publication is available at
http://www.springerlink.com/. arXiv admin note: substantial text overlap with
arXiv:1212.533
Spatially partitioned embedded Runge-Kutta Methods
We study spatially partitioned embedded Runge–Kutta (SPERK) schemes for partial differential equations (PDEs), in which each of the component schemes is applied over a different part of the spatial domain. Such methods may be convenient for problems in which the smoothness of the solution or the magnitudes of the PDE coefficients vary strongly in space. We focus on embedded partitioned methods as they offer greater efficiency and avoid the order reduction that may occur in non-embedded schemes. We demonstrate that the lack of conservation in partitioned schemes can lead to non-physical effects and propose conservative additive schemes based on partitioning the fluxes rather than the ordinary differential equations. A variety of SPERK schemes are presented, including an embedded pair suitable for the time evolution of fifth-order weighted non-oscillatory (WENO) spatial discretizations. Numerical experiments are provided to support the theory
Search For Oxygen in Cool DQ White Dwarf Atmospheres
We report new infrared spectroscopic observations of cool DQ white dwarfs by
using Coolspec on the 2.7m Harlan-Smith Telescope. DQs have helium-rich
atmospheres with traces of molecular carbon thought to be the result of
convective dredge-up from their C/O interiors. Recent model calculations
predict that oxygen should also be present in DQ atmospheres in detectable
amounts. Our synthetic spectra calculations for He-rich white dwarfs with
traces of C and O indicate that CO should be easily detected in the cool DQ
atmospheres if present in the expected amounts. Determination of the oxygen
abundance in the atmosphere will reveal the C/O ratio at the core/envelope
boundary, constraining the important and uncertain ^{12}C(alpha,gamma)^{16}O
reaction rate.Comment: 2 pages, 2 figures, to appear in proceedings of the 13th European
Workshop on White Dwarf
Magneto-electric coupling in zigzag graphene nanoribbons
Zigzag graphene nanoribbons can have magnetic ground states with
ferromagnetic, antiferromagnetic, or canted configurations, depending on
carrier density. We show that an electric field directed across the ribbon
alters the magnetic state, favoring antiferromagnetic configurations. This
property can be used to prepare ribbons with a prescribed spin-orientation on a
given edge.Comment: 4 pages, 5 figure
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