13,343 research outputs found
Continuity of Lyapunov Exponents for Random 2D Matrices
The Lyapunov exponents of locally constant GL(2;C)-cocycles over Bernoulli
shifts depend continuously on the cocycle and on the invariant probability. The
Oseledets decomposition also depends continuously on the cocycle, in measure
Accuracy Issues for Numerical Waveforms
We study the convergence properties of our implementation of the 'moving
punctures' approach at very high resolutions for an equal-mass, non-spinning,
black-hole binary. We find convergence of the Hamiltonian constraint on the
horizons and the L2 norm of the Hamiltonian constraint in the bulk for sixth
and eighth-order finite difference implementations.
The momentum constraint is more sensitive, and its L2 norm shows clear
convergence for a system with consistent sixth-order finite differencing, while
the momentum and BSSN constraints on the horizons show convergence for both
sixth and eighth-order systems. We analyze the gravitational waveform error
from the late-inspiral, merger, and ringdown. We find that using several
lower-order techniques for increasing the speed of numerical relativity
simulations actually lead to apparently non-convergent errors. Even when using
standard high-accuracy techniques, rather than seeing clean convergence, where
the waveform phase is a monotonic function of grid resolution, we find that the
phase tends to oscillate with resolution, possibly due to stochastic errors
induced by grid refinement boundaries. Our results seem to indicate that one
can obtain gravitational waveform phases to within 0.05 rad. (and possibly as
small as 0.015 rad.), while the amplitude error can be reduced to 0.1%. We then
compare with the waveforms obtained using the cZ4 formalism. We find that the
cZ4 waveforms have larger truncation errors for a given resolution, but the
Richardson extrapolation phase of the cZ4 and BSSN waveforms agree to within
0.01 rad., even during the ringdown.Comment: version accepted to PR
Resistance to cisplatin and paclitaxel does not affect the sensitivity of human ovarian cancer cells to antiprogestin- induced cytotoxicity
BACKGROUND: Antiprogestin compounds have been shown to be effective in blocking the growth of ovarian cancer cells of different genetic backgrounds. Herein we studied the anti-ovarian cancer effect of a series of antiprogestins sharing the chemical backbone of the most characterized antiprogestin, mifepristone, but with unique modifications in position C-17 of the steroid ring. We assessed the effect of mifepristone-like antiprogestins on the growth of ovarian cancer cells sensitive to the standard combination therapy cisplatin-paclitaxel or made double-resistant upon six cycles of pulse-selection with the drugs used at clinically relevant concentrations and exposure times.
METHODS: IGROV-1 and SKOV-3 cells were pulsed with 20 μM cisplatin for 1 h followed by 100 nM paclitaxel for 3 h once a week for six weeks. The cells that did not die and repopulate the culture after the chemotherapies were termed Platinum-Taxane-EScape cells (PTES). Parental cells were compared against their PTES derivatives in their responses to further platinum-taxane treatments. Moreover, both ovarian cancer cells and their PTES siblings were exposed to escalating doses of the various antiprogestin derivatives. We assessed cell growth, viability and sub-G1 DNA content using microcapillary cytometry. Cyclin-dependent kinase inhibitors p21(cip1) and p27(kip1) and cleavage of downstream caspase-3 substrate PARP were used to assess whether cell fate, as a consequence of treatment, was limited to cytostasis or progressed to lethality.
RESULTS: Cells subjected to six pulse-selection cycles of cisplatin-paclitaxel gave rise to sibling derivatives that displayed ~2-7 fold reduction in their sensitivities to further chemotherapy. However, regardless of the sensitivity the cells developed to the combination cisplatin-paclitaxel, they displayed similar sensitivity to the antiprogestins, which blocked their growth in a dose-related manner, with lower concentrations causing cytostasis, and higher concentrations causing lethality.
CONCLUSIONS: Antiprogestins carrying a backbone similar to mifepristone are cytotoxic to ovarian cancer cells in a manner that does not depend on the sensitivity the cells have to the standard ovarian cancer chemotherapeutics, cisplatin and paclitaxel. Thus, antiprogestin therapy could be used to treat ovarian cancer cells showing resistance to both platinum and taxanes.Fil: Gamarra Luques, Carlos Diego. University of South Dakota. Sanford School of Medicine. Division of Basic Biomedical Sciences; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Hapon, María Belén. University of South Dakota. Sanford School of Medicine. Division of Basic Biomedical Sciences; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Goyeneche, Alicia. University of South Dakota. Sanford School of Medicine. Division of Basic Biomedical Sciences; Estados UnidosFil: Telleria, Carlos Marcelo. University of South Dakota. Sanford School of Medicine. Division of Basic Biomedical Sciences; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; Argentin
Quantum phase diagram of a frustrated antiferromagnet on the bilayer honeycomb lattice
We study the spin-1/2 Heisenberg antiferromagnet on a bilayer honeycomb
lattice including interlayer frustration. Using a set of complementary
approaches, namely Schwinger bosons, dimer series expansion, bond operators,
and exact diagonalization, we map out the quantum phase diagram. Analyzing
ground state energies and elementary excitation spectra, we find four distinct
phases, corresponding to three collinear magnetic long range ordered states,
and one quantum disordered interlayer dimer phase. We detail, that the latter
phase is adiabatically connected to an "exact" singlet product ground state of
the the bilayer which exists along a line of maximum interlayer frustration.
The order within the remaining three phases will be clarified.Comment: 12 pages, 12 figure
The early stages of teaching: Teachers with good principles
The teachers in their learning process, go through different stages. Of all these phases which we are most interested in this article is the one that begins with the first contacts with the reality of the school, assuming the role reserved for vocational teachers. Teacher induction is the time period covering the early years, in which teachers have to make the transition from students to teachers. It is a period of tension and intensive learning contexts and generally unknown during which the novice teachers should acquire professional knowledge in addition to ensuring a certain balance. Induction programs for novice teachers are a real alternative to further that the first years as teachers are not frustrating year
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