825 research outputs found
Gallavotti-Cohen-Type symmetry related to cycle decompositions for Markov chains and biochemical applications
We slightly extend the fluctuation theorem obtained in \cite{LS} for sums of
generators, considering continuous-time Markov chains on a finite state space
whose underlying graph has multiple edges and no loop. This extended frame is
suited when analyzing chemical systems. As simple corollary we derive in a
different method the fluctuation theorem of D. Andrieux and P. Gaspard for the
fluxes along the chords associated to a fundamental set of oriented cycles
\cite{AG2}.
We associate to each random trajectory an oriented cycle on the graph and we
decompose it in terms of a basis of oriented cycles. We prove a fluctuation
theorem for the coefficients in this decomposition. The resulting fluctuation
theorem involves the cycle affinities, which in many real systems correspond to
the macroscopic forces. In addition, the above decomposition is useful when
analyzing the large deviations of additive functionals of the Markov chain. As
example of application, in a very general context we derive a fluctuation
relation for the mechanical and chemical currents of a molecular motor moving
along a periodic filament.Comment: 23 pages, 5 figures. Correction
Detection of curved lines with B-COSFIRE filters: A case study on crack delineation
The detection of curvilinear structures is an important step for various
computer vision applications, ranging from medical image analysis for
segmentation of blood vessels, to remote sensing for the identification of
roads and rivers, and to biometrics and robotics, among others. %The visual
system of the brain has remarkable abilities to detect curvilinear structures
in noisy images. This is a nontrivial task especially for the detection of thin
or incomplete curvilinear structures surrounded with noise. We propose a
general purpose curvilinear structure detector that uses the brain-inspired
trainable B-COSFIRE filters. It consists of four main steps, namely nonlinear
filtering with B-COSFIRE, thinning with non-maximum suppression, hysteresis
thresholding and morphological closing. We demonstrate its effectiveness on a
data set of noisy images with cracked pavements, where we achieve
state-of-the-art results (F-measure=0.865). The proposed method can be employed
in any computer vision methodology that requires the delineation of curvilinear
and elongated structures.Comment: Accepted at Computer Analysis of Images and Patterns (CAIP) 201
Tracing the Filamentary Structure of the Galaxy Distribution at z~0.8
We study filamentary structure in the galaxy distribution at z ~ 0.8 using
data from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) Redshift Survey
and its evolution to z ~ 0.1 using data from the Sloan Digital Sky Survey
(SDSS). We trace individual filaments for both surveys using the Smoothed
Hessian Major Axis Filament Finder, an algorithm which employs the Hessian
matrix of the galaxy density field to trace the filamentary structures in the
distribution of galaxies. We extract 33 subsamples from the SDSS data with a
geometry similar to that of DEEP2. We find that the filament length
distribution has not significantly changed since z ~ 0.8, as predicted in a
previous study using a \LamdaCDM cosmological N-body simulation. However, the
filament width distribution, which is sensitive to the non-linear growth of
structure, broadens and shifts to smaller widths for smoothing length scales of
5-10 Mpc/h from z ~ 0.8 to z ~ 0.1, in accord with N-body simulations.Comment: 10 pages, 8 figures, accepted for the publication in MNRA
The problems associated with the monitoring of complex workplace radiation fields at European high-energy accelerators and thermonuclear fusion facilities
The European Commission is funding within its Sixth Framework Programme a three-year project (2005-2007) called CONRAD, COordinated Network for RAdiation Dosimetry. The organisational framework for this project is provided by the European Radiation Dosimetry Group EURADOS. One task within the CONRAD project, Work Package 6 (WP6), was to provide a report outlining research needs and research activities within Europe to develop new and improved methods and techniques for the characterisation of complex radiation fields at workplaces around high-energy accelerators, but also at the next generation of thermonuclear fusion facilities. The paper provides an overview of the report, which will be available as CERN Yellow Repor
Fluctuation spectrum of fluid membranes coupled to an elastic meshwork: jump of the effective surface tension at the mesh size
We identify a class of composite membranes: fluid bilayers coupled to an
elastic meshwork, that are such that the meshwork's energy is a function
\textit{not} of the real microscopic membrane area ,
but of a \textit{smoothed} membrane's area , which corresponds to the
area of the membrane coarse-grained at the mesh size . We show that the
meshwork modifies the membrane tension both below and above the scale
, inducing a tension-jump . The
predictions of our model account for the fluctuation spectrum of red blood
cells membranes coupled to their cytoskeleton. Our results indicate that the
cytoskeleton might be under extensional stress, which would provide a means to
regulate available membrane area. We also predict an observable tension jump
for membranes decorated with polymer "brushes"
Second-generation bio-based plastics are becoming a reality - Non-renewable energy and greenhouse gas (GHG) balance of succinic acid-based plastic end products made from lignocellulosic biomass:NREU and GHG balance of succinic acid-based PBS products made from lignocellulosic biomass
Bio-based and bio-degradable plastics such as polybutylene succinate (PBS) have the potential to become sustainable alternatives to petrochemical-based plastics. Polybutylene succinate can be produced from bio-based succinic acid and 1,4-butanediol using first-generation (1G) or second-generation (2G) sugars. A cradle-to-grave environmental assessment was performed for PBS products in Europe to investigate the non-renewable energy use (NREU) and greenhouse gas (GHG) impacts. The products investigated are single-use trays and agricultural film, with incineration, industrial composting and degradation on agricultural land as end-of-life scenarios. Both end products manufactured from fully bio-based PBS and from partly bio-based PBS (made from bio-based succinic acid and fossil fuel-based 1,4 butanediol) were analysed. We examine corn (1G) as well as corn stover, wheat straw, miscanthus and hardwood as 2G feedstocks. For the cradle-to-grave system, 1G fully bio-based PBS plastic products were found to have environmental impacts comparable with their petrochemical incumbents, while 2G fully bio-based PBS plastic products allow to reduce NREU and GHG by around one third under the condition of avoidance of concentration of sugars and energy integration of the pretreatment process with monomer production. Without energy integration and with concentration of sugars (i.e., separate production), the impacts of 2G fully bio-based PBS products are approximately 15–20% lower than those of 1G fully bio-based PBS products. The environmental analysis of PBS products supports the value proposition related to PBS products while also pointing out areas requiring further research and development
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