152 research outputs found
Breast cancer: Pretreatment drug resistance parameters (GSH-system, ATase, P-glycoprotein) in tumor tissue and their correlation with clinical and prognostic characteristics
Background: The identification of new factors predicting relapse, outcome and response to systemic therapy in breast cancer is warranted. The measurement of biological markers such as drug resistance parameters (DRPs), which are part of the phenotype of malignant cells and contribute to resistance to anti-cancer drugs may be a possibility, which may ultimately lead to improvement of therapeutic results. Patients and methods: The level of glutathione (GSH), activities of glutathione-S-transferase (GST), glutathione-peroxidase (GPx), 06-alkylguanine-DNA-alkyltransferase (ATase), and P-glycoprotein (PGP) were measured in tumor and adjacent tumor free tissue samples from 89 consecutive, untreated females with breast cancer and correlated with clinical and prognostic factors. Early breast cancer (EBC) was diagnosed in 56 patients, 22 patients had locally advanced (LABC) and 11 patients metastatic breast cancer. Results: All DRPs showed significantly higher expression in tumor than in tumor free tissues. GPx was positively correlated with GST (r = 0.3, P = 0.0048) and with GSH (r = 0.5, P = 0.0001) in tumor as well as in normal tissue. GST activity was significantly higher in EBC than in LABC or metastatic breast cancer (P = 0.02). GSH level was significantly higher in grade I than in grade 2 or grade 3 tumors (P = 0.01). When clinical characteristics were related to the level of DRP, âhigh' GSH was associated with age >60 years (P = 0.01) in EBC, and with grade 1-2 tumors (P = 0.05) in LABC. No differences in OS were apparent between groups of âhigh' and âlow' DRP-expression. However, the four-year estimated disease-free survival of EBC tended to be higher in patients with âhigh' GST (P = 0.10) and of LABC in patients with âhigh' GPx levels (P = 0.06). Conclusion: We conclude that âhigh' levels of DRP in tumor tissue of breast cancer patients are part of the initial phenotype of the malignant cells. Due to its high prevalence (83% in EBC, 100% in primarily metastatic breast cancer), PGP did not add to prognostic information. High levels of GSH, GST and and GPx were associated with favorable clinical characteristics and good prognosis, whereas low levels of GSH and GST activity were associated with more aggressive or more advanced diseas
Enhancement of the Binding Energy of Charged Excitons in Disordered Quantum Wires
Negatively and positively charged excitons are identified in the
spatially-resolved photoluminescence spectra of quantum wires. We demonstrate
that charged excitons are weakly localized in disordered quantum wires. As a
consequence, the enhancement of the "binding energy" of a charged exciton is
caused, for a significant part, by the recoil energy transferred to the
remaining charged carrier during its radiative recombination. We discover that
the Coulomb correlation energy is not the sole origin of the "binding energy",
in contrast to charged excitons confined in quantum dots.Comment: 4 Fig
State of the Short Dipole Model Program for the LHC
Superconducting single and twin aperture 1-m long dipole magnets are currently being fabricated at CERN at a rate of about one per month in the framework of the short dipole model program for the LHC. The program allows to study performance improvements coming from refinements in design, components and assembly options and to accumulate statistics based on a small-scale production. The experience thus gained provides in turn feedback into the long magnet program in industry. In recent models initial quenching fields above 9 T have been obtained and after a short training the conductor limit at 2 K is reached, resulting in a central bore field exceeding 10 T. The paper describes the features of recent single aperture models, the results obtained during cold tests and the plans to ensure the continuation of a vigorous model program providing input for the fabrication of the main LHC dipoles
Persistent and Coupling Current Effects in the LHC Superconducting Dipoles
One of the main issues for the operation of the LHC accelerator at CERN is the field errors generated by persistent and coupling currents in the main dipoles at injection conditions, i.e., 0.54ĂÂ T dipole field. For this reason we are conducting systematic magnetic field measurements to quantify the above effects and compare them to the expected values from measurement on strands and cables. We discuss the results in terms of DC effects from persistent current magnetization, AC effects with short time constant from strand and cable coupling currents, and long-term decay during constant current excitation. Average and spread of the measured field errors over the population of magnets tested are as expected or smaller. Field decay at injection, and subsequent snap-back, show for the moment the largest variation from magnet to magnet, with weak correlation to parameters that can be controlled during production. For this reason these effects are likely to result in the largest spread of field errors over the whole dipole production
Spin Motion in Electron Transmission through Ultrathin Ferromagnetic Films Accessed by Photoelectron Spectroscopy
Ab initio and model calculations demonstrate that the spin motion of
electrons transmitted through ferromagnetic films can be analyzed in detail by
means of angle- and spin-resolved core-level photoelectron spectroscopy. The
spin motion appears as precession of the photoelectron spin polarization around
and as relaxation towards the magnetization direction. In a systematic study
for ultrathin Fe films on Pd(001) we elucidate its dependence on the Fe film
thickness and on the Fe electronic structure. In addition to elastic and
inelastic scattering, the effect of band gaps on the spin motion is addressed
in particular.Comment: 4 pages, 5 figure
Present State of the Single and Twin Aperture Short Dipole Model Program for the LHC
The LHC model program for main dipoles is based on the design, fabrication and testing at CERN of a number of single and twin aperture 1m long magnets. So far, a number of single aperture models, each with specific characteristics, were tested at 2 K at a rate of about one per month. These magnets are the main tool used to check coil performance as a function of design and assembly options in view of optimizing and finalizing choices of components and procedures. Initial quenching field levels of 8.8 T were obtained and the short sample limit of the cable at 1.9 K was reached corresponding to a central bore field of 10 T. A few twin aperture dipole models were also built and tested, using the same structural components as for the long magnets which are now being built in industry. The paper discusses the main characteristics of the models built so far, the instrumentation developed to date and the experience obtained. Finally it describes the plans aimed at continuing a vigorous program to provide input to the long magnet program in industry
Optical manipulation of the wave function of quasiparticles in a solid
Polaritons in semiconductor microcavities are hybrid quasiparticles
consisting of a superposition of photons and excitons. Due to the photon
component, polaritons are characterized by a quantum coherence length in the
several micron range. Owing to their exciton content, they display sizeable
interactions, both mutual and with other electronic degrees of freedom. These
unique features have produced striking matter wave phenomena, such as
Bose-Einstein condensation, or parametric processes able to generate quantum
entangled polariton states. Recently, several paradigms for spatial confinement
of polaritons in semiconductor devices have been established. This opens the
way to quantum devices in which polaritons can be used as a vector of quantum
information. An essential element of each quantum device is the quantum state
control. Here we demonstrate control of the wave function of confined
polaritons, by means of tailored resonant optical excitation. By tuning the
energy and momentum of the laser, we achieve precise control of the momentum
pattern of the polariton wave function. A theoretical model supports
unambiguously our observations
Doublet structures in quantum well absorption spectra due to Fano-related interference
In this theoretical investigation we predict an unusual interaction between a
discrete state and a continuum of states, which is closely related to the case
of Fano-interference. It occurs in a GaAs/AlxGa1-xAs quantum well between the
lowest light-hole exciton and the continuum of the second heavy-hole exciton.
Unlike the typical case for Fano-resonance, the discrete state here is outside
the continuum; we use uniaxial stress to tune its position with respect to the
onset of the continuum. State-of-the art calculations of absorption spectra
show that as the discrete state approaches the continuum, a doublet structure
forms which reveals anticrossing behaviour. The minimum separation energy of
the anticrossing depends characteristically on the well width and is unusually
large for narrow wells. This offers striking evidence for the strong underlying
valence-band mixing. Moreover, it proves that previous explanations of similar
doublets in experimental data, employing simple two-state models, are
incomplete.Comment: 21 pages, 5 figures and 5 equations. Accepted for publication in
Physical Review
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