6,136 research outputs found
River, delta and coastal morphological response accounting for biological dynamics
Abstract. Management and construction can increase resilience in the face of climate change, and benefits can be enhanced through integration of biogenic materials including shells and vegetation. Rivers and coastal landforms are dynamic systems that respond to intentional and unintended manipulation of critical factors, often with unforeseen and/or undesirable resulting effects. River management strategies have impacts that include deltas and coastal areas which are increasingly vulnerable to climate change with reference to sea level rise and storm intensity. Whereas conventional assessment and analysis of rivers and coasts has relied on modelling of hydrology, hydraulics and sediment transport, incorporating additional biological factors can offer more comprehensive, beneficial and realistic alternatives. Suitable modelling tools can provide improved decision support. The question has been whether current models can effectively address biological responses with suitable reliability and efficiency. Since morphodynamic evolution exhibits its effects on a large timescale, the choice of mathematical model is not trivial and depends upon the availability of data, as well as the spatial extent, timelines and computation effort desired. The ultimate goal of the work is to set up a conveniently simplified river morphodynamic model, coupled with a biological dynamics plant population model able to predict the long-term evolution of large alluvial river systems managed through bioengineering. This paper presents the first step of the work related to the application of the model accounting for stationary vegetation condition. Sensitivity analysis has been performed on the main hydraulic, sedimentology, and biological parameters. The model has been applied to significant river training in Europe, Asia and North America, and comparative analysis has been used to validate analytical solutions. Data gaps and further areas for investigation are identified
Critical exponents in Ising spin glasses
We determine accurate values of ordering temperatures and critical exponents
for Ising Spin Glass transitions in dimension 4, using a combination of finite
size scaling and non-equilibrium scaling techniques. We find that the exponents
and vary with the form of the interaction distribution, indicating
non-universality at Ising spin glass transitions. These results confirm
conclusions drawn from numerical data for dimension 3.Comment: 6 pages, RevTeX (or Latex, etc), 10 figures, Submitted to PR
Spectral Analysis of Guanine and Cytosine Fluctuations of Mouse Genomic DNA
We study global fluctuations of the guanine and cytosine base content (GC%)
in mouse genomic DNA using spectral analyses. Power spectra S(f) of GC%
fluctuations in all nineteen autosomal and two sex chromosomes are observed to
have the universal functional form S(f) \sim 1/f^alpha (alpha \approx 1) over
several orders of magnitude in the frequency range 10^-7< f < 10^-5 cycle/base,
corresponding to long-ranging GC% correlations at distances between 100 kb and
10 Mb. S(f) for higher frequencies (f > 10^-5 cycle/base) shows a flattened
power-law function with alpha < 1 across all twenty-one chromosomes. The
substitution of about 38% interspersed repeats does not affect the functional
form of S(f), indicating that these are not predominantly responsible for the
long-ranged multi-scale GC% fluctuations in mammalian genomes. Several
biological implications of the large-scale GC% fluctuation are discussed,
including neutral evolutionary history by DNA duplication, chromosomal bands,
spatial distribution of transcription units (genes), replication timing, and
recombination hot spots.Comment: 15 pages (figures included), 2 figure
Dynamic Simulations of the Kosterlitz-Thouless Phase Transition
Based on the short-time dynamic scaling form, a novel dynamic approach is
proposed to tackle numerically the Kosterlitz-Thouless phase transition. Taking
the two-dimensional XY model as an example, the exponential divergence of the
spatial correlation length, the transition temperature and all
critical exponents are computed. Compared with Monte Carlo simulations in
equilibrium, we obtain data at temperatures nearer to .Comment: to appear in Phys. Rev. E in Rapid Communicatio
Universal Finite Size Scaling Functions in the 3D Ising Spin Glass
We study the three-dimensional Edwards-Anderson model with binary
interactions by Monte Carlo simulations. Direct evidence of finite-size scaling
is provided, and the universal finite-size scaling functions are determined.
Monte Carlo data are extrapolated to infinite volume with an iterative
procedure up to correlation lengths xi \approx 140. The infinite volume data
are consistent with a conventional power law singularity at finite temperature
Tc. Taking into account corrections to scaling, we find Tc = 1.156 +/- 0.015,
nu = 1.8 +/- 0.2 and eta = -0.26 +/- 0.04. The data are also consistent with an
exponential singularity at finite Tc, but not with an exponential singularity
at zero temperature.Comment: 4 pages, Revtex, 4 postscript figures include
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Adults with probable Developmental Coordination Disorder selectively process early visual, but not tactile information during action preparation. An electrophysiological study.
Developmental coordination disorder (DCD) is a neurodevelopmental condition affecting motor coordination in children and adults. Here, EEG signals elicited by visual and tactile stimuli were recorded while adult participants with and without probable DCD (pDCD) performed a motor task. The task cued reaching movements towards a location in visible peripersonal space as well as an area of unseen personal space. Event-related potentials elicited by visual and tactile stimuli revealed that visual processing was strongly affected by movement preparation in the pDCD group, even more than in controls. However, in contrast to the controls, tactile processing in unseen space was unaffected by movement preparation in the pDCD group. The selective use of sensory information from vision and proprioception is fundamental for the adaptive control of movements, and these findings suggest that this is impaired in DCD. Additionally, the pDCD group showed attenuated motor rhythms (beta: 13-30Hz) over sensorimotor regions following cues to prepare movements towards unseen personal space. The results reveal that individuals with pDCD exhibit differences in the neural mechanisms of spatial selection and action preparation compared to controls, which may underpin the sustained difficulties they experience. These findings provide new insights into the neural mechanisms potentially disrupted in this highly prevalent disorder
Fully Frustrated Ising System on a 3D Simple Cubic Lattice: Revisited
Using extensive Monte Carlo simulations, we clarify the critical behaviour of
the 3 dimensional simple cubic Ising Fully Frustrated system. We find two
transition temperatures and two long range ordered phases. Within the present
numerical accuracy, the transition at higher temperature is found to be second
order and we have extracted the standard critical exponent using finite size
scaling method. On the other hand, the transition at lower temperature is found
to be first order. It is argued that entropy plays a major role on determining
the low temperature state.Comment: 14 pages 14 figures iop style include
New stopping criteria for segmenting DNA sequences
We propose a solution on the stopping criterion in segmenting inhomogeneous
DNA sequences with complex statistical patterns. This new stopping criterion is
based on Bayesian Information Criterion (BIC) in the model selection framework.
When this stopping criterion is applied to a left telomere sequence of yeast
Saccharomyces cerevisiae and the complete genome sequence of bacterium
Escherichia coli, borders of biologically meaningful units were identified
(e.g. subtelomeric units, replication origin, and replication terminus), and a
more reasonable number of domains was obtained. We also introduce a measure
called segmentation strength which can be used to control the delineation of
large domains. The relationship between the average domain size and the
threshold of segmentation strength is determined for several genome sequences.Comment: 4 pages, 4 figures, Physical Review Letters, to appea
The Sloan Lens ACS Survey. IX. Colors, Lensing and Stellar Masses of Early-type Galaxies
We present the current photometric dataset for the Sloan Lens ACS (SLACS)
Survey, including HST photometry from ACS, WFPC2, and NICMOS. These data have
enabled the confirmation of an additional 15 grade `A' (certain) lens systems,
bringing the number of SLACS grade `A' lenses to 85; including 13 grade `B'
(likely) systems, SLACS has identified nearly 100 lenses and lens candidates.
Approximately 80% of the grade `A' systems have elliptical morphologies while
~10% show spiral structure; the remaining lenses have lenticular morphologies.
Spectroscopic redshifts for the lens and source are available for every system,
making SLACS the largest homogeneous dataset of galaxy-scale lenses to date. We
have developed a novel Bayesian stellar population analysis code to determine
robust stellar masses with accurate error estimates. We apply this code to
deep, high-resolution HST imaging and determine stellar masses with typical
statistical errors of 0.1 dex; we find that these stellar masses are unbiased
compared to estimates obtained using SDSS photometry, provided that informative
priors are used. The stellar masses range from 10^10.5 to 10^11.8 M and
the typical stellar mass fraction within the Einstein radius is 0.4, assuming a
Chabrier IMF. The ensemble properties of the SLACS lens galaxies, e.g. stellar
masses and projected ellipticities, appear to be indistinguishable from other
SDSS galaxies with similar stellar velocity dispersions. This further supports
that SLACS lenses are representative of the overall population of massive
early-type galaxies with M* >~ 10^11 M, and are therefore an ideal
dataset to investigate the kpc-scale distribution of luminous and dark matter
in galaxies out to z ~ 0.5.Comment: 20 pages, 18 figures, 5 tables, published in Ap
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