27,161 research outputs found
Renewable Energy Resources Impact on Clean Electrical Power by developing the North-West England Hydro Resource Model.
This paper describes the development of a sequential decision support system to promote hydroelectric power in North-West England. The system, composed of integrated models, addresses barriers to the installation of hydroelectric power schemes. Information is linked through an economic assessment which identifies different turbine options, assesses their suitability for location and demand; and combines the different types of information in a way that supports decision making. The system is structured into five components: the hydrological resource is modelled using Low Flows 2000, the turbine options are identified from hydrological, environmental and demand requirements; and the consequences of different solutions will be fed into other components so that the environmental impacts and public acceptability can be assessed and valued. A preliminary case study is presented on an old gunpowder works to illustrate how the resource model may be employed. Historical architectural structures, power uptake and educational instruction of hydro power technology are considered
Automated design of robust discriminant analysis classifier for foot pressure lesions using kinematic data
In the recent years, the use of motion tracking systems for acquisition of functional biomechanical gait data, has received increasing interest due to the richness and accuracy of the measured kinematic information. However, costs frequently restrict the number of subjects employed, and this makes the dimensionality of the collected data far higher than the available samples. This paper applies discriminant analysis algorithms to the classification of patients with different types of foot lesions, in order to establish an association between foot motion and lesion formation. With primary attention to small sample size situations, we compare different types of Bayesian classifiers and evaluate their performance with various dimensionality reduction techniques for feature extraction, as well as search methods for selection of raw kinematic variables. Finally, we propose a novel integrated method which fine-tunes the classifier parameters and selects the most relevant kinematic variables simultaneously. Performance comparisons are using robust resampling techniques such as Bootstrapand k-fold cross-validation. Results from experimentations with lesion subjects suffering from pathological plantar hyperkeratosis, show that the proposed method can lead tocorrect classification rates with less than 10% of the original features
When it Pays to Rush: Interpreting Morphogen Gradients Prior to Steady-State
During development, morphogen gradients precisely determine the position of
gene expression boundaries despite the inevitable presence of fluctuations.
Recent experiments suggest that some morphogen gradients may be interpreted
prior to reaching steady-state. Theoretical work has predicted that such
systems will be more robust to embryo-to-embryo fluctuations. By analysing two
experimentally motivated models of morphogen gradient formation, we investigate
the positional precision of gene expression boundaries determined by
pre-steady-state morphogen gradients in the presence of embryo-to-embryo
fluctuations, internal biochemical noise and variations in the timing of
morphogen measurement. Morphogens that are direct transcription factors are
found to be particularly sensitive to internal noise when interpreted prior to
steady-state, disadvantaging early measurement, even in the presence of large
embryo-to-embryo fluctuations. Morphogens interpreted by cell-surface receptors
can be measured prior to steady-state without significant decrease in
positional precision provided fluctuations in the timing of measurement are
small. Applying our results to experiment, we predict that Bicoid, a
transcription factor morphogen in Drosophila, is unlikely to be interpreted
prior to reaching steady-state. We also predict that Activin in Xenopus and
Nodal in zebrafish, morphogens interpreted by cell-surface receptors, can be
decoded in pre-steady-state.Comment: 18 pages, 3 figure
Structural Reorganization of Parallel Actin Bundles by Crosslinking Proteins: Incommensurate States of Twist
We construct a coarse-grained model of parallel actin bundles crosslinked by
compact, globular bundling proteins, such as fascin and espin, necessary
components of filapodial and mechanosensory bundles. Consistent with structural
observations of bundles, we find that the optimal geometry for crosslinking is
overtwisted, requiring a coherent structural change of the helical geometry of
the filaments. We study the linker-dependent thermodynamic transition of
bundled actin filaments from their native state to the overtwisted state and
map out the "twist-state'' phase diagram in terms of the availability as well
as the flexibility of crosslinker proteins. We predict that the transition from
the uncrosslinked to fully-crosslinked state is highly sensitive to linker
flexibility: flexible crosslinking smoothly distorts the twist-state of bundled
filaments, while rigidly crosslinked bundles undergo a phase transition,
rapidly overtwisting filaments over a narrow range of free crosslinker
concentrations. Additionally, we predict a rich spectrum of intermediate
structures, composed of alternating domains of sparsely-bound (untwisted) and
strongly-bound (overtwisted) filaments. This model reveals that subtle
differences in crosslinking agents themselves modify not only the detailed
structure of parallel actin bundles, but also the thermodynamic pathway by
which they form.Comment: Main Text (25 pages, 7 figures) with supporting material (12 pages, 9
figures, 2 tables
Comprehensive Observations of a Solar Minimum CME with STEREO
We perform the first kinematic analysis of a CME observed by both imaging and
in situ instruments on board STEREO, namely the SECCHI, PLASTIC, and IMPACT
experiments. Launched on 2008 February 4, the CME is tracked continuously from
initiation to 1 AU using the SECCHI imagers on both STEREO spacecraft, and is
then detected by the PLASTIC and IMPACT particle and field detectors on board
STEREO-B. The CME is also detected in situ by ACE and SOHO/CELIAS at Earth's L1
Lagrangian point. The CME hits STEREO-B, ACE, and SOHO on 2008 February 7, but
misses STEREO-A entirely. This event provides a good example of just how
different the same event can look when viewed from different perspectives. We
also demonstrate many ways in which the comprehensive and continuous coverage
of this CME by STEREO improves confidence in our assessment of its kinematic
behavior, with potential ramifications for space weather forecasting. The
observations provide several lines of evidence in favor of the observable part
of the CME being narrow in angular extent, a determination crucial for deciding
how best to convert observed CME elongation angles from Sun-center to actual
Sun-center distances.Comment: 27 pages, 10 figures, AASTEX v5.2, accepted by Ap
Linear response of a grafted semiflexible polymer to a uniform force field
We use the worm-like chain model to analytically calculate the linear
response of a grafted semiflexible polymer to a uniform force field. The result
is a function of the bending stiffness, the temperature, the total contour
length, and the orientation of the field with respect to that of the grafted
end. We also study the linear response of a worm-like chain with a periodic
alternating sequence of positive and negative charges. This can be considered
as a model for a polyampholyte with intrinsic bending siffness and negligible
intramolecular interactions. We show how the finite intrinsic persistence
length affects the linear response to the external field.Comment: 6 pages, 3 figure
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