6,219 research outputs found
Correlated fluctuations in the exciton dynamics and spectroscopy of DNA
The absorption of ultraviolet light creates excitations in DNA, which
subsequently start moving in the helix. Their fate is important for an
understanding of photo damage, and is determined by the interplay of electronic
couplings between bases and the structure of the DNA environment. We model the
effect of dynamical fluctuations in the environment and study correlation,
which is present when multiple base pairs interact with the same mode in the
environment. We find that the correlations strongly affect the exciton
dynamics, and show how they are observed in the decay of the anisotropy as a
function of a coherence and a population time in a non-linear optical
experiment
Predicting the Success of Invasive Species in the Great Bay Estuarine Researve
The University of New Hampshire Zoology Department reports on a study designed to continue monitoring the distribution of invasive species in the Great Bay Estuary and to carry out laboratory experiments designed to test the effects of salinity on ascidian mortality and determine predators of ascidian species. Researchers collected presence/absence and abundance data of invasive species at four sites within the Great Bay Estuarine System. The report gives a brief description of the results of the monitoring program to compare results obtained from 2006 to 2007 and to assess the response of ascidians to varying salinity and predators. This report specifically includes monitoring data from 2007 and results of laboratory and field experiments examining the effects of salinity and predators on ascidian distribution
Does settlement plate material matter? The influence of substrate type on fouling community development
Benthic community composition and ascidian abundance can differ dramatically between adjacent man-made and natural substrates. Although multiple factors, including light exposure, surface orientation, predation exposure, and habitat type, are known to contribute to these patterns, few studies have directly tested the influence of substrate identity on community development. We compared fouling communities on settlement plates composed of commonly occurring natural (granite) and artificial (concrete, high density polyethylene, and PVC) marine materials deployed from late May to mid November 2014 from a floating dock in Newcastle, NH. We sought to determine if observed patterns resulted from differential recruitment onto substrate materials or post-settlement survival and growth. To do this, half of the plates were cleaned during bi-weekly examinations, and half were left un-cleaned. Preliminary analyses indicate that community composition differs between substrate types. These results will help us understand how substrate features contribute to non-native species establishment and habitat dominance, and may inform decisions regarding material usage in marine construction. These findings also underline the importance of settlement substrate choice in scientific studies, as plate material may influence experimental conclusions
On finite-size Lyapunov exponents in multiscale systems
We study the effect of regime switches on finite size Lyapunov exponents
(FSLEs) in determining the error growth rates and predictability of multiscale
systems. We consider a dynamical system involving slow and fast regimes and
switches between them. The surprising result is that due to the presence of
regimes the error growth rate can be a non-monotonic function of initial error
amplitude. In particular, troughs in the large scales of FSLE spectra is shown
to be a signature of slow regimes, whereas fast regimes are shown to cause
large peaks in the spectra where error growth rates far exceed those estimated
from the maximal Lyapunov exponent. We present analytical results explaining
these signatures and corroborate them with numerical simulations. We show
further that these peaks disappear in stochastic parametrizations of the fast
chaotic processes, and the associated FSLE spectra reveal that large scale
predictability properties of the full deterministic model are well approximated
whereas small scale features are not properly resolved.Comment: Accepted for publication in Chao
Phase behaviour of charged colloidal sphere dispersions with added polymer chains
We study the stability of mixtures of highly screened repulsive charged
spheres and non-adsorbing ideal polymer chains in a common solvent using free
volume theory. The effective interaction between charged colloids in an aqueous
salt solution is described by a screened-Coulomb pair potential, which
supplements the pure hard-sphere interaction. The ideal polymer chains are
treated as spheres that are excluded from the colloids by a hard-core
interaction, whereas the interaction between two ideal chains is set to zero.
In addition, we investigate the phase behaviour of charged colloid-polymer
mixtures in computer simulations, using the two-body (Asakura-Oosawa pair
potential) approximation to the effective one-component Hamiltonian of the
charged colloids. Both our results obtained from simulations and from free
volume theory show similar trends. We find that the screened-Coulomb repulsion
counteracts the effect of the effective polymer-mediated attraction. For
mixtures of small polymers and relatively large charged colloidal spheres, the
fluid-crystal transition shifts to significantly larger polymer concentrations
with increasing range of the screened-Coulomb repulsion. For relatively large
polymers, the effect of the screened-Coulomb repulsion is weaker. The resulting
fluid-fluid binodal is only slightly shifted towards larger polymer
concentrations upon increasing the range of the screened-Coulomb repulsion. In
conclusion, our results show that the miscibility of dispersions containing
charged colloids and neutral non-adsorbing polymers increases, upon increasing
the range of the screened-Coulomb repulsion, or upon lowering the salt
concentration, especially when the polymers are small compared to the colloids.Comment: 25 pages,13 figures, accepted for publication on J.Phys.:Condens.
Matte
Dimensional crossover of the fundamental-measure functional for parallel hard cubes
We present a regularization of the recently proposed fundamental-measure
functional for a mixture of parallel hard cubes. The regularized functional is
shown to have right dimensional crossovers to any smaller dimension, thus
allowing to use it to study highly inhomogeneous phases (such as the solid
phase). Furthermore, it is shown how the functional of the slightly more
general model of parallel hard parallelepipeds can be obtained using the
zero-dimensional functional as a generating functional. The multicomponent
version of the latter system is also given, and it is suggested how to
reformulate it as a restricted-orientation model for liquid crystals. Finally,
the method is further extended to build a functional for a mixture of parallel
hard cylinders.Comment: 4 pages, no figures, uses revtex style files and multicol.sty, for a
PostScript version see http://dulcinea.uc3m.es/users/cuesta/cross.p
Natural Notation for the Domestic Internet of Things
This study explores the use of natural language to give instructions that
might be interpreted by Internet of Things (IoT) devices in a domestic `smart
home' environment. We start from the proposition that reminders can be
considered as a type of end-user programming, in which the executed actions
might be performed either by an automated agent or by the author of the
reminder. We conducted an experiment in which people wrote sticky notes
specifying future actions in their home. In different conditions, these notes
were addressed to themselves, to others, or to a computer agent.We analyse the
linguistic features and strategies that are used to achieve these tasks,
including the use of graphical resources as an informal visual language. The
findings provide a basis for design guidance related to end-user development
for the Internet of Things.Comment: Proceedings of the 5th International symposium on End-User
Development (IS-EUD), Madrid, Spain, May, 201
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