1,435 research outputs found
Polynuclear aromatic hydrocarbon carcinogens as antiestrogens in MCF-7 human breast cancer cells: role of the Ah receptor
Treatment of MCF-7 cells with 1.0 μM 3-methylcholanthrene (MC) caused a decrease in cell proliferation and [3H]thymidine uptake whereas no effects were observed at a lower (0.1 μM) concentration. Co-treatment of the cells with 1 nM 17β-estradiol plus 0.1 or 1.0 μ MC resulted in a significant inhibition of 17β-estradiol-induced growth and [3H]thymidine uptake. MC also inhibited the 17β-estradiol-induced secretion of the 52 kDa protein (procathepsin D) in MCF-7 cells and caused a concentration-dependent decrease in the nuclear estrogen receptor (ER) as determined by either velocity sedimentation analysis or immunoquantitation with human ER antibodies. The effects of several different polynuclear aromatic hydrocarbon (PAH) congeners on the nuclear ER in MCF-7 cells were also determined. Only those congeners which bound to the aryl hydrocarbon (Ah) receptor, namely benzo[a]pyrene, benz[a]anthracene, 7,12-dimethylbenz[a]anthracene and MC, caused a decrease in nuclear ER levels. In contrast, benzo[ghi]perylene, a congener which did not bind to the Ah receptor did not affect nuclear ER levels in MCF-7 cells. Moreover, with some congeners the decrease in nuclear ER levels could be observed without any significant induction of ethoxyresorufin O-deethylase activity, a P4501A1-dependent monooxygenase. These data suggest that the Ah receptor liganded with MC and related PAHs induced a broad spectrum of antiestrogenic responses in MCF-7 cells and complements the results of previous studies which report the antiestrogenic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and other halogenated aromatics which are also Ah receptor agonists
Using Strategy Improvement to Stay Alive
We design a novel algorithm for solving Mean-Payoff Games (MPGs). Besides
solving an MPG in the usual sense, our algorithm computes more information
about the game, information that is important with respect to applications. The
weights of the edges of an MPG can be thought of as a gained/consumed energy --
depending on the sign. For each vertex, our algorithm computes the minimum
amount of initial energy that is sufficient for player Max to ensure that in a
play starting from the vertex, the energy level never goes below zero. Our
algorithm is not the first algorithm that computes the minimum sufficient
initial energies, but according to our experimental study it is the fastest
algorithm that computes them. The reason is that it utilizes the strategy
improvement technique which is very efficient in practice
Selfconsistent gauge-invariant theory of in-plane infrared response of high-Tc cuprate superconductors involving spin fluctuations
We report on results of our theoretical study of the in-plane infrared
conductivity of the high-Tc cuprate superconductors using the model where
charged planar quasiparticles are coupled to spin fluctuations. The
computations include both the renormalization of the quasiparticles and the
corresponding modification of the current-current vertex function (vertex
correction), which ensures gauge invariance of the theory and local charge
conservation in the system. The incorporation of the vertex corrections leads
to an increase of the total intraband optical spectral weight (SW) at finite
frequencies, a SW transfer from far infrared to mid infrared, a significant
reduction of the SW of the superconducting condensate, and an amplification of
characteristic features in the superconducting state spectra of the inverse
scattering rate 1/tau. We also discuss the role of selfconsistency and propose
a new interpretation of a kink occurring in the experimental low temperature
spectra of 1/tau around 1000cm^{-1}.Comment: 9 pages with 6 figures, submitted to Physical Review
Will jets reduce the elliptic flow at LHC, while decays of resonances restore the constituent quark scaling?
Formation and evolution of the elliptic flow pattern in Pb+Pb collisions at
sqrt{s}=5.5 ATeV and in Au+Au collisions at sqrt{s}=200 AGeV are analyzed for
different hadron species within the framework of HYDJET++ Monte-Carlo model.
The model contains both hydrodynamic state and jets, thus allowing for a study
of the interplay between the soft and hard processes. It is found that jets are
terminating the rise of the elliptic flow with increasing transverse momentum.
Since jets are more influential at LHC compared to RHIC, the elliptic flow at
LHC should be weaker than that at RHIC. The influence of resonance decays on
particle elliptic flow is investigated also. These final state interactions
enhance the low-p_T part of the v_2 of pions and light baryons, and work
towards the fulfilment of idealized constituent quark scaling.Comment: 8 pages, 9 figures, 3 table
Collective and fractal properties of pion jets in the four-velocity space at intermediate energies
Experimental results are presented for study of collective and fractal
properties of soft pion jets in the space of relative four-dimensional
velocities. Significant decreasing is obtained for mean square of second
particle distances from jet axis for pion-proton interactions at initial
energies GeV in comparison with hadron-nuclear collisions at close
energies. The decreasing results in power dependence of distance variable on
collision energy for range GeV. The observation allows us to
estimate the low boundary of manifestation of color degree of freedom in pion
jet production. Cluster dimension values were deduced for pion jets in various
reactions. Fractional values of this dimension indicate on the manifestation of
fractal-like properties by pion jets. Changing of mean kinetic energy of jet
particles and fractal dimension with initial energy increasing is consistent
with suggestion for presence of color degrees of freedom in pion jet production
at intermediate energies.Comment: The conference "Physics of fundamental interactions". ITEP, Moscow,
Russia. November 23 - 27, 200
Spectroscopic distinction between the normal state pseudogap and the superconducting gap of cuprate high T_{c} superconductors
We report on broad-band infrared ellipsometry measurements of the c-axis
conductivity of underdoped RBa_{2}Cu_{3}O_{7-d} (R=Y, Nd, and La) single
crystals. Our data provide a detailed account of the spectral weight (SW)
redistributions due to the normal state pseudogap (PG) and the superconducting
(SC) gap. They show that these phenomena involve different energy scales,
exhibit distinct doping dependencies and thus are likely of different origin.
In particular, the SW redistribution in the PG state closely resembles the one
of a conventional charge- or spin density wave (CDW or SDW) system.Comment: 4 pages, 4 figure
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