186 research outputs found
Boundary conditions in random sequential adsorption
The influence of different boundary conditions on the density of random
packings of disks is studied. Packings are generated using the random
sequential adsorption algorithm with three different types of boundary
conditions: periodic, open, and wall. It is found that the finite size effects
are smallest for periodic boundary conditions, as expected. On the other hand,
in the case of open and wall boundaries it is possible to introduce an
effective packing size and a constant correction term to significantly improve
the packing densities.Comment: 9 pages, 7 figure
Shapes for maximal coverage for two-dimensional random sequential adsorption
The random sequential adsorption of various particle shapes is studied in
order to determine the influence of particle anisotropy on the saturated random
packing. For all tested particles there is an optimal level of anisotropy which
maximizes the saturated packing fraction. It is found that a concave shape
derived from a dimer of disks gives a packing fraction of 0.5833, which is
comparable to the maximum packing fraction of ellipsoids and spherocylinders
and higher than any other studied shape. Discussion why this shape is so
beneficial for random sequential adsorption is given.Comment: 6 pages, 8 figures, 3 table
In a search for a shape maximizing packing fraction for two-dimensional random sequential adsorption
Random sequential adsorption (RSA) of various two dimensional objects is
studied in order to find a shape which maximizes the saturated packing
fraction. This investigation was begun in our previous paper [Cie\'sla et al.,
Phys. Chem. Chem. Phys. 17, 24376 (2015)], where the densest packing was
studied for smoothed dimers. Here this shape is compared with a smoothed
-mers, spherocylinders and ellipses. It is found that the highest packing
fraction out of the studied shapes is and is obtained for
ellipses having long-to-short axis ratio of , which is also the largest
anisotropy among the investigated shapes.Comment: 14 pages, 7 fiure
Synchronization in the presence of memory
We study the effect of memory on synchronization of identical chaotic systems
driven by common external noises. Our examples show that while in general
synchronization transition becomes more difficult to meet when memory range
increases, for intermediate ranges the synchronization tendency of systems can
be enhanced. Generally the synchronization transition is found to depend on the
memory range and the ratio of noise strength to memory amplitude, which
indicates on a possibility of optimizing synchronization by memory. We also
point out on a close link between dynamics with memory and noise, and recently
discovered synchronizing properties of networks with delayed interactions
Aluminium supplier selection for the automotive parts manufacturer
This paper presents a methodology for selection of the optimal sources of supply, which is also known as the problem of supplier selection. Theoretical considerations are expanded with research related to aluminium supplier selection for a hypothetical manufacturer of aluminium parts for transportation equipment located in Poland. Evaluation of five suppliers of aluminium from Poland, Germany and Slovenia has been conducted using a weighted scoring method, a strengths and weaknesses method and a graphical method. Choosing the best offer and prioritizing suppliers allows not only the most rational decision in the field of supply logistics to be taken but also the quality of service in the metallurgical industry to be improved
Tracer diffusion inside fibrinogen layers
We investigate the obstructed motion of tracer (test) particles in crowded
environments by carrying simulations of two-dimensional Gaussian random walk in
model fibrinogen monolayers of different orientational ordering. The fibrinogen
molecules are significantly anisotropic and therefore they can form structures
where orientational ordering, similar to the one observed in nematic liquid
crystals, appears. The work focuses on the dependence between level of the
orientational order (degree of environmental crowding) of fibrinogen molecules
inside a layer and non-Fickian character of the diffusion process of spherical
tracer particles moving within the domain. It is shown that in general
particles motion is subdiffusive and strongly anisotropic, and its
characteristic features significantly change with the orientational order
parameter, concentration of fibrinogens and radius of a diffusing probe.Comment: 8 pages, 12 figure
Kinetics of random sequential adsorption of two-dimensional shapes on a one-dimensional line
7 pages, 10 figuresSaturated random sequential adsorption packings built of two-dimensional ellipses, spherocylinders, rectangles, and dimers placed on a one-dimensional line are studied to check analytical prediction concerning packing growth kinetics [A. Baule, Phys. Rev. Let. 119, 028003 (2017)]. The results show that the kinetics is governed by the power-law with the exponent and for packings built of ellipses and rectangles, respectively, which is consistent with analytical predictions. However, for spherocylinders and dimers of moderate width-to-height ratio, a transition between these two values is observed. We argue that this transition is a finite size effect that arises for spherocylinders due to the properties of the contact function. In general, it appears that the kinetics of packing growth can depend on packing size even for very large packings
ClaR—a novel key regulator of cellobiose and lactose metabolism in Lactococcus lactis IL1403
In a number of previous studies, our group has discovered an alternative pathway for lactose utilization in Lactococcus lactis that, in addition to a sugar-hydrolyzing enzyme with both P-β-glucosidase and P-β-galactosidase activity (BglS), engages chromosomally encoded components of cellobiose-specific PTS (PTSCel-Lac), including PtcA, PtcB, and CelB. In this report, we show that this system undergoes regulation via ClaR, a novel activator protein from the RpiR family of transcriptional regulators. Although RpiR proteins are widely distributed among lactic acid bacteria, their roles have yet to be confirmed by functional assays. Here, we show that ClaR activity depends on intracellular cellobiose-6-phosphate availability, while other sugars such as glucose or galactose have no influence on it. We also show that ClaR is crucial for activation of the bglS and celB expression in the presence of cellobiose, with some limited effects on ptcA and ptcB activation. Among 190 of carbon sources tested, the deletion of claR reduces L. lactis growth only in lactose- and/or cellobiose-containing media, suggesting a narrow specificity of this regulator within the context of sugar metabolism
Genome-wide analysis and expression profiling of calcium-dependent protein kinases in potato (Solanum tuberosum)
Calcium-dependent protein kinases (CDPKs or CPKs), unique to plants and some protists, are involved in growth and developmental processes as well as in defence against diverse environmental stresses. CDPKs are encoded by multi-gene families. Despite extensive studies of the CDPKs in many species, information about the evolutionary history and expression patterns of the CDPK family in the staple crop potato (Solanum tuberosum) remains poorly known. In this study, we performed bioinformatics analysis of the potato whole genome sequence and identified 23 potential CDPK genes. These genes are located in eleven, of twelve, potato chromosomes. Based on the phylogenetic tree and gene structures, the CDPKs were divided into four subfamilies. To determine their expression, reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis was carried out for the CDPK genes in different organs of potato such as young and mature leaves, stems, young shoots, roots, stolons, swollen stolons, flowers and tubers. The CDPKs were expressed in all the organs analysed, but their expression patterns varied greatly. The expression of some CDPKs was strongly organ specific, for example StCPK13 and StCPK18 was found only/ mostly in flowers.
In Solanum genotypes differing in resistance to Phytophthora infestans, the expression and activity of CDPKs increased in response to a P. infestans elicitor with different kinetics and intensity. The expression levels and activity of the CDPKs correlated positively with the level of the resistance.
Our results support earlier suggestion that CDPKs are involved in potato organ development and defence against stresses. We provide new information about the CDPK gene family in the potato and a perspective on its evolutionary history and biological roles of the individual kinases
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