481 research outputs found
Weakly coupled, antiparallel, totally asymmetric simple exclusion processes
We study a system composed of two parallel totally asymmetric simple
exclusion processes with open boundaries, where the particles move in the two
lanes in opposite directions and are allowed to jump to the other lane with
rates inversely proportional to the length of the system. Stationary density
profiles are determined and the phase diagram of the model is constructed in
the hydrodynamic limit, by solving the differential equations describing the
steady state of the system, analytically for vanishing total current and
numerically for nonzero total current. The system possesses phases with a
localized shock in the density profile in one of the lanes, similarly to
exclusion processes endowed with nonconserving kinetics in the bulk. Besides,
the system undergoes a discontinuous phase transition, where coherently moving
delocalized shocks emerge in both lanes and the fluctuation of the global
density is described by an unbiased random walk. This phenomenon is analogous
to the phase coexistence observed at the coexistence line of the totally
asymmetric simple exclusion process, however, as a consequence of the
interaction between lanes, the density profiles are deformed and in the case of
asymmetric lane change, the motion of the shocks is confined to a limited
domain.Comment: 14 pages, 15 figures, to appear in Phys. Rev.
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Oils Colored with Wood-Staining Fungal Pigments : Color Loss, Oxidation, and Structural Breakdown
Wood-staining fungal pigments have potential uses as colorants for wood and textiles. Traditionally, organic solvents have been used as carriers for these pigments. However, other environmentally-friendly and more readily available carriers must be found. Natural oils have the potential to carry these pigments but have demonstrated color loss over relatively short periods of time, possibly due to oxidation and/or polymerization of both the oils and pigments. The current study examined therapeutic and food grade oils (instead of finishing oils) for their potential to carry draconin red, the pigment from Scytalidium cuboideum. To track color loss over time for treated and untreated pigmented oils, a colorimeter and the CIE2000 L*a*b* color space were used. It was determined that hemp oil was a potential carrier for draconin red, as were flax seed oil and cold-pressed linseed oil when treated with β-carotene as the pigment did not degrade over time in these oils. FTIR analysis was used to determine if oxidation was occurring in the oils and if changes in draconin red could be tracked. Based on the FTIR analysis, oxidation was not likely the cause of color loss in the pigmented oils and the pigment could not be distinguished from the oils in the IR spectra. Finally, SEM was employed to determine if crystal degradation was contributing to color loss. The SEM analysis indicated, surprisingly, that the crystals of draconin red formed rather than degraded over time, so crystal breakdown was also not likely the cause of color loss. Further in-depth chemical studies are needed to determine the mechanism of color loss in pigmented natural oils
Assessing the effects of different land-use/land-cover input datasets on modelling and mapping terrestrial ecosystem services - Case study Terceira Island (Azores, Portugal)
Modelling ecosystem services (ES) has become a new standard for the quantification and assessment of various ES. Multiple ES model applications are available that spatially estimate ES supply on the basis of land-use/land-cover (LULC) input data. This paper assesses how different input LULC datasets affect the modelling and mapping of ES supply for a case study on Terceira Island, the Azores (Portugal), namely: (1) the EU-wide CORINE LULC, (2) the Azores Region official LULC map (COS.A 2018) and (3) a remote sensing-based LULC and vegetation map of Terceira Island using Sentinel-2 satellite imagery. The InVEST model suite was applied, modelling altogether six ES (Recreation/Visitation, Pollination, Carbon Storage, Nutrient Delivery Ratio, Sediment Delivery Ratio and Seasonal Water Yield). Model outcomes of the three LULC datasets were compared in terms of similarity, performance and applicability for the user. For some InVEST modules, such as Pollination and Recreation, the differences in the LULC datasets had limited influence on the model results. For InVEST modules, based on more complex calculations and processes, such as Nutrient Delivery Ratio, the output ES maps showed a skewed distribution of ES supply. Yet, model results showed significant differences for differences in all modules and all LULCs. Understanding how differences arise between the LULC input datasets and the respective effect on model results is imperative when computing model-based ES maps. The choice for selecting appropriate LULC data should depend on: 1) the research or policy/decision-making question guiding the modelling study, 2) the ecosystems to be mapped, but also on 3) the spatial resolution of the mapping and 4) data availability at the local level. Communication and transparency on model input data are needed, especially if ES maps are used for supporting land use planning and decision-making
Direct observation of the tube model in F-actin solutions
Mutual uncrossability of polymers generates topological constraints on their
conformations and dynamics, which are generally described using the tube model.
We imaged confinement tubes for individual polymers within a F-actin solution
by sampling over many successive micrographs of fluorescently labeled probe
filaments. The resulting average tube width shows the predicted scaling
behavior. Unexpectedly, we found an exponential distribution of tube curvatures
which is attributed to transient entropic trapping in network void spaces.Comment: 6 pages, 4 figure
Molecular Spiders in One Dimension
Molecular spiders are synthetic bio-molecular systems which have "legs" made
of short single-stranded segments of DNA. Spiders move on a surface covered
with single-stranded DNA segments complementary to legs. Different mappings are
established between various models of spiders and simple exclusion processes.
For spiders with simple gait and varying number of legs we compute the
diffusion coefficient; when the hopping is biased we also compute their
velocity.Comment: 14 pages, 2 figure
Limited Lifespan of Fragile Regions in Mammalian Evolution
An important question in genome evolution is whether there exist fragile
regions (rearrangement hotspots) where chromosomal rearrangements are happening
over and over again. Although nearly all recent studies supported the existence
of fragile regions in mammalian genomes, the most comprehensive phylogenomic
study of mammals (Ma et al. (2006) Genome Research 16, 1557-1565) raised some
doubts about their existence. We demonstrate that fragile regions are subject
to a "birth and death" process, implying that fragility has limited
evolutionary lifespan. This finding implies that fragile regions migrate to
different locations in different mammals, explaining why there exist only a few
chromosomal breakpoints shared between different lineages. The birth and death
of fragile regions phenomenon reinforces the hypothesis that rearrangements are
promoted by matching segmental duplications and suggests putative locations of
the currently active fragile regions in the human genome
G-protein alpha-subunits in cytosolic and membranous fractions of human neutrophils
In plasma membranes of human neutrophils, we identified two major pertussis toxin substrates of 40 kDa Mr with pI values of 5.30 and 5.37. Only the acidic of the two substrates was also present in neutrophil cytosol. Two-dimensional tryptic peptide maps revealed a high degree of homology of cytosolic and particulate substrates. Purified G-protein beta gamma-complex stimulated pertussis toxin-catalyzed [32P]ADP-ribosylation of membranous and cytosolic substrates of neutrophils less than 2-fold and 6-fold, respectively. Hydrodynamic properties of the cytosolic substrate strongly suggested that it exists as a monomer. Purified G-protein beta gamma-complex increased the s20,w value of the cytosolic substrate from 3.3 S to 4.0 S. The GTP analogue, guanosine 5'-O-(3-thiotriphosphate), promoted the release of pertussis toxin substrates from plasma membranes. An antiserum raised against a sequence specific for the Gi2 alpha-subunit reacted with 39-40 kDa proteins in plasma membranes and with an apparently single 40 kDa protein in cytosol. We conclude that neutrophil cytosol contains monomeric Gi2 alpha-subunits which--by interacting with hydrophobic beta gamma-complexes--may reversibly bind to the plasma membrane
Greedy Solution of Ill-Posed Problems: Error Bounds and Exact Inversion
The orthogonal matching pursuit (OMP) is an algorithm to solve sparse
approximation problems. Sufficient conditions for exact recovery are known with
and without noise. In this paper we investigate the applicability of the OMP
for the solution of ill-posed inverse problems in general and in particular for
two deconvolution examples from mass spectrometry and digital holography
respectively.
In sparse approximation problems one often has to deal with the problem of
redundancy of a dictionary, i.e. the atoms are not linearly independent.
However, one expects them to be approximatively orthogonal and this is
quantified by the so-called incoherence. This idea cannot be transfered to
ill-posed inverse problems since here the atoms are typically far from
orthogonal: The ill-posedness of the operator causes that the correlation of
two distinct atoms probably gets huge, i.e. that two atoms can look much alike.
Therefore one needs conditions which take the structure of the problem into
account and work without the concept of coherence. In this paper we develop
results for exact recovery of the support of noisy signals. In the two examples
in mass spectrometry and digital holography we show that our results lead to
practically relevant estimates such that one may check a priori if the
experimental setup guarantees exact deconvolution with OMP. Especially in the
example from digital holography our analysis may be regarded as a first step to
calculate the resolution power of droplet holography
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