25 research outputs found
Random Sequential Adsorption on Fractals
Irreversible adsorption of spheres on flat collectors having dimension
is studied. Molecules are adsorbed on Sierpinski's Triangle and Carpet like
fractals (), and on General Cantor Set (). Adsorption process is
modeled numerically using Random Sequential Adsorption (RSA) algorithm. The
paper concentrates on measurement of fundamental properties of coverages, i.e.
maximal random coverage ratio and density autocorrelation function, as well as
RSA kinetics. Obtained results allow to improve phenomenological relation
between maximal random coverage ratio and collector dimension. Moreover,
simulations show that, in general, most of known dimensional properties of
adsorbed monolayers are valid for non-integer dimensions.Comment: 12 pages, 8 figure
Random packing of spheres in Menger sponge
Random packing of spheres inside fractal collectors of dimension 2 < d < 3 is
studied numerically using Random Sequential Adsorption (RSA) algorithm. The
paper focuses mainly on the measurement of random packing saturation limit.
Additionally, scaling properties of density autocorrelations in the obtained
packing are analyzed. The RSA kinetics coefficients are also measured. Obtained
results allow to test phenomenological relation between random packing
saturation density and collector dimension. Additionally, performed simulations
together with previously obtained results confirm that, in general, the known
dimensional relations are obeyed by systems having non-integer dimension, at
least for d < 3.Comment: 13 pages, 6 figure
Fe3O4(001) films on Fe(001): Termination and reconstruction of iron-rich surfaces
High-quality and impurity-free magnetite surfaces with (sqrt2xsqrt2)R45o
reconstruction have been obtained for the Fe3O4(001) epitaxial films deposited
on Fe(001). Based on atomically resolved STM images for both negative and
positive sample polarity and Density Functional Theory calculations, a model of
the magnetite (001) surface terminated with Fe ions forming dimers on the
reconstructed (sqrt2xsqrt2)R45o octahedral iron layer is proposed.Comment: 17 pages 4 figure
Algorithmic Complexity for Short Binary Strings Applied to Psychology: A Primer
Since human randomness production has been studied and widely used to assess
executive functions (especially inhibition), many measures have been suggested
to assess the degree to which a sequence is random-like. However, each of them
focuses on one feature of randomness, leading authors to have to use multiple
measures. Here we describe and advocate for the use of the accepted universal
measure for randomness based on algorithmic complexity, by means of a novel
previously presented technique using the the definition of algorithmic
probability. A re-analysis of the classical Radio Zenith data in the light of
the proposed measure and methodology is provided as a study case of an
application.Comment: To appear in Behavior Research Method
Hepatitis C Virus Core Protein Induces Neuroimmune Activation and Potentiates Human Immunodeficiency Virus-1 Neurotoxicity
BACKGROUND: Hepatitis C virus (HCV) genomes and proteins are present in human brain tissues although the impact of HIV/HCV co-infection on neuropathogenesis remains unclear. Herein, we investigate HCV infectivity and effects on neuronal survival and neuroinflammation in conjunction with HIV infection. METHODOLOGY: Human microglia, astrocyte and neuron cultures were infected with cell culture-derived HCV or exposed to HCV core protein with or without HIV-1 infection or HIV-1 Viral Protein R (Vpr) exposure. Host immune gene expression and cell viability were measured. Patch-clamp studies of human neurons were performed in the presence or absence of HCV core protein. Neurobehavioral performance and neuropathology were examined in HIV-1 Vpr-transgenic mice in which stereotaxic intrastriatal implants of HCV core protein were performed. PRINCIPAL FINDINGS: HCV-encoded RNA as well as HCV core and non-structural 3 (NS3) proteins were detectable in human microglia and astrocytes infected with HCV. HCV core protein exposure induced expression of pro-inflammatory cytokines including interleukin-1β, interleukin-6 and tumor necrosis factor-α in microglia (p<0.05) but not in astrocytes while increased chemokine (e.g. CXCL10 and interleukin-8) expression was observed in both microglia and astrocytes (p<0.05). HCV core protein modulated neuronal membrane currents and reduced both β-III-tubulin and lipidated LC3-II expression (p<0.05). Neurons exposed to supernatants from HCV core-activated microglia exhibited reduced β-III-tubulin expression (p<0.05). HCV core protein neurotoxicity and interleukin-6 induction were potentiated by HIV-1 Vpr protein (p<0.05). HIV-1 Vpr transgenic mice implanted with HCV core protein showed gliosis, reduced neuronal counts together with diminished LC3 immunoreactivity. HCV core-implanted animals displayed neurobehavioral deficits at days 7 and 14 post-implantation (p<0.05). CONCLUSIONS: HCV core protein exposure caused neuronal injury through suppression of neuronal autophagy in addition to neuroimmune activation. The additive neurotoxic effects of HCV- and HIV-encoded proteins highlight extrahepatic mechanisms by which HCV infection worsens the disease course of HIV infection