896 research outputs found
Invasion Percolation Between two Sites
We investigate the process of invasion percolation between two sites
(injection and extraction sites) separated by a distance r in two-dimensional
lattices of size L. Our results for the non-trapping invasion percolation model
indicate that the statistics of the mass of invaded clusters is significantly
dependent on the local occupation probability (pressure) Pe at the extraction
site. For Pe=0, we show that the mass distribution of invaded clusters P(M)
follows a power-law P(M) ~ M^{-\alpha} for intermediate values of the mass M,
with an exponent \alpha=1.39. When the local pressure is set to Pe=Pc, where Pc
corresponds to the site percolation threshold of the lattice topology, the
distribution P(M) still displays a scaling region, but with an exponent
\alpha=1.02. This last behavior is consistent with previous results for the
cluster statistics in standard percolation. In spite of these discrepancies,
the results of our simulations indicate that the fractal dimension of the
invaded cluster does not depends significantly on the local pressure Pe and it
is consistent with the fractal dimension values reported for standard invasion
percolation. Finally, we perform extensive numerical simulations to determine
the effect of the lattice borders on the statistics of the invaded clusters and
also to characterize the self-organized critical behavior of the invasion
percolation process.Comment: 7 pages, 11 figures, submited for PR
Improvement in the Adsorption of Anionic and Cationic Dyes From Aqueous Solutions: A Comparative Study Using Aluminium Pillared Clays and Activated Carbon
The aim of this work was to evaluate the adsorption properties of anionic dye Reactive Black 5 (RB5) and cationic dye Methylene Blue (MB) from salted aqueous solution using natural clay, aluminum pillared clay (Al-PILC), and activated carbon. The textural properties of the materials were obtained by N2 adsorption at 77 K and the structural properties of natural and pillared clays were determined by X-ray diffraction. The effect of pH, contact time, initial concentration of dye, and influence of the addition of NaCl were evaluated by batch adsorption. Adsorption isotherms of Al-PILC, in different salt concentration were compared with natural clay and activated carbon. The adsorption isotherms were well fitted by the Langmuir and Langmuir-Freundlich models. The process of pillaring only improved the adsorption of the anionic dye RB5. Depending on the system adsorbent/adsorbate analyzed, the salt concentration can either help or hinder dye adsorption. We found that a special morphology formed during the process of pillaring greatly increased adsorption of the MB cationic dye in the range of high salt concentrations. This unexpected result may help in developing new pillarization strategies to treat effluents with high salt content.Fil: Aguiar, J. E.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Bezerra, B. T. C.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Siqueira, A. C. A.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Barrera Diaz, Deicy Amparo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Física Aplicada; ArgentinaFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Física Aplicada; ArgentinaFil: Azevedo, D. C. S.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Lucena, S. M. P.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Silva Jr., I. J.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; Brasi
On dynamic network entropy in cancer
The cellular phenotype is described by a complex network of molecular
interactions. Elucidating network properties that distinguish disease from the
healthy cellular state is therefore of critical importance for gaining
systems-level insights into disease mechanisms and ultimately for developing
improved therapies. By integrating gene expression data with a protein
interaction network to induce a stochastic dynamics on the network, we here
demonstrate that cancer cells are characterised by an increase in the dynamic
network entropy, compared to cells of normal physiology. Using a fundamental
relation between the macroscopic resilience of a dynamical system and the
uncertainty (entropy) in the underlying microscopic processes, we argue that
cancer cells will be more robust to random gene perturbations. In addition, we
formally demonstrate that gene expression differences between normal and cancer
tissue are anticorrelated with local dynamic entropy changes, thus providing a
systemic link between gene expression changes at the nodes and their local
network dynamics. In particular, we also find that genes which drive
cell-proliferation in cancer cells and which often encode oncogenes are
associated with reductions in the dynamic network entropy. In summary, our
results support the view that the observed increased robustness of cancer cells
to perturbation and therapy may be due to an increase in the dynamic network
entropy that allows cells to adapt to the new cellular stresses. Conversely,
genes that exhibit local flux entropy decreases in cancer may render cancer
cells more susceptible to targeted intervention and may therefore represent
promising drug targets.Comment: 10 pages, 3 figures, 4 tables. Submitte
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Factors associated with smoking in pregnancy
The aim of this cross-sectional study was to identify factors related to smoking during pregnancy. The sample included 267 puerperae hospitalized in the maternity unit of a university hospital in Porto Alegre/RS. The data were collected through a self-applied instrument and statistically analyzed. The majority of the puerperae (51.3%) were between 18 and 25 years old, 55.4% were nonsmokers, 25.5% were smokers, 19.1% had recently ceased smoking (in abstinence). The nonsmokers had more consultations than the smokers and the abstinent smokers (p=0.025). The number of women who had more than one child was higher among smokers than among nonsmokers and abstinent smokers (p=0.002). Women were more likely to stop smoking before pregnancy when they had a partner who was a nonsmoker (p=0.007). Several factors influence smoking and smoking cessation and these are important in prenatal interventions aimed at pregnant women and their partners
Higher-Spin Fermionic Gauge Fields and Their Electromagnetic Coupling
We study the electromagnetic coupling of massless higher-spin fermions in
flat space. Under the assumptions of locality and Poincare invariance, we
employ the BRST-BV cohomological methods to construct consistent
parity-preserving off-shell cubic 1-s-s vertices. Consistency and
non-triviality of the deformations not only rule out minimal coupling, but also
restrict the possible number of derivatives. Our findings are in complete
agreement with, but derived in a manner independent from, the
light-cone-formulation results of Metsaev and the string-theory-inspired
results of Sagnotti-Taronna. We prove that any gauge-algebra-preserving vertex
cannot deform the gauge transformations. We also show that in a local theory,
without additional dynamical higher-spin gauge fields, the non-abelian vertices
are eliminated by the lack of consistent second-order deformations.Comment: 44 pages; references added, minor changes made, to appear in JHE
gcType : a high-quality type strain genome database for microbial phylogenetic and functional research
Taxonomic and functional research of microorganisms has increasingly relied upon genome-based data and methods. As the depository of the Global Catalogue of Microorganisms (GCM) 10K prokaryotic type strain sequencing project, Global Catalogue of Type Strain (gcType) has published 1049 type strain genomes sequenced by the GCM 10K project which are preserved in global culture collections with a valid published status. Additionally, the information provided through gcType includes >12 000 publicly available type strain genome sequences from GenBank incorporated using quality control criteria and standard data annotation pipelines to form a high-quality reference database. This database integrates type strain sequences with their phenotypic information to facilitate phenotypic and genotypic analyses. Multiple formats of cross-genome searches and interactive interfaces have allowed extensive exploration of the database's resources. In this study, we describe web-based data analysis pipelines for genomic analyses and genome-based taxonomy, which could serve as a one-stop platform for the identification of prokaryotic species. The number of type strain genomes that are published will continue to increase as the GCM 10K project increases its collaboration with culture collections worldwide. Data of this project is shared with the International Nucleotide Sequence Database Collaboration. Access to gcType is free at http://gctype.wdcm.org/
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