2,383 research outputs found
Inhibition of the multidrug resistance P-glycoprotein: Time for a change of strategy?
P-glycoprotein (P-gp) is a key player in the multidrug-resistant phenotype in cancer. The protein confers resistance by mediating the ATP-dependent efflux of an astonishing array of anticancer drugs. Its broad specificity has been the subject of numerous attempts to inhibit the protein and restore the efficacy of anticancer drugs. The general strategy has been to develop compounds that either compete with anticancer drugs for transport or act as direct inhibitors of P-gp. Despite considerable in vitro success, there are no compounds currently available to "block" P-gp-mediated resistance in the clinic. The failure may be attributed to toxicity, adverse drug interaction, and numerous pharmacokinetic issues. This review provides a description of several alternative approaches to overcome the activity of P-gp in drug-resistant cells. These include 1) drugs that specifically target resistant cells, 2) novel nanotechnologies to provide high-dose, targeted delivery of anticancer drugs, 3) compounds that interfere with nongenomic transfer of resistance, and 4) approaches to reduce the expression of P-gp within tumors. Such approaches have been developed through the pursuit of greater understanding of resistance mediators such as P-gp, and they show considerable potential for further application. Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics
Structural properties of crumpled cream layers
The cream layer is a complex heterogeneous material of biological origin
which forms spontaneously at the air-milk interface. Here, it is studied the
crumpling of a single cream layer packing under its own weight at room
temperature in three-dimensional space. The structure obtained in these
circumstances has low volume fraction and anomalous fractal dimensions. Direct
means and noninvasive NMR imaging technique are used to investigate the
internal and external structure of these systems.Comment: 9 pages, 4 figures, accepted in J. Phys. D: Appl. Phy
Spin-glass state of vortices in YBa2Cu3Oy and La2-xSrxCuO4 below the metal-to-insulator crossover
Highly disordered magnetism confined to individual weakly interacting
vortices is detected by muon spin rotation in two different families of
high-transition-temperature superconductors, but only in samples on the
low-doping side of the low-temperature normal state metal-to-insulator
crossover (MIC). The results support an extended quantum phase transition (QPT)
theory of competing magnetic and superconducting orders that incorporates the
coupling between CuO2 planes. Contrary to what has been inferred from previous
experiments, the static magnetism that coexists with superconductivity near the
field-induced QPT is not ordered. Our findings unravel the mystery of the MIC
and establish that the normal state of high-temperature superconductors is
ubiquitously governed by a magnetic quantum critical point in the
superconducting phase.Comment: 9 pages, 9 figure
Design study of the deepsky ultraviolet survey telescope
Preliminary mechanical design and specifications are presented for a wide field ultraviolet telescope and detector to be carried as a Spacelab payload. Topics discussed include support structure stiffness (torsional and bending), mirror assembly, thermal control, optical alignment, attachment to the instrument pointing pallet, control and display, power requirements, acceptance and qualification test plans, cost analysis and scheduling. Drawings are included
EIT and diffusion of atomic coherence
We study experimentally the effect of diffusion of Rb atoms on
Electromagnetically Induced Transparency (EIT) in a buffer gas vapor cell. In
particular, we find that diffusion of atomic coherence in-and-out of the laser
beam plays a crucial role in determining the EIT resonance lineshape and the
stored light lifetime.Comment: 5 pages, 8 figure
A network-based dynamical ranking system for competitive sports
From the viewpoint of networks, a ranking system for players or teams in
sports is equivalent to a centrality measure for sports networks, whereby a
directed link represents the result of a single game. Previously proposed
network-based ranking systems are derived from static networks, i.e.,
aggregation of the results of games over time. However, the score of a player
(or team) fluctuates over time. Defeating a renowned player in the peak
performance is intuitively more rewarding than defeating the same player in
other periods. To account for this factor, we propose a dynamic variant of such
a network-based ranking system and apply it to professional men's tennis data.
We derive a set of linear online update equations for the score of each player.
The proposed ranking system predicts the outcome of the future games with a
higher accuracy than the static counterparts.Comment: 6 figure
Hole doping dependences of the magnetic penetration depth and vortex core size in YBa2Cu3Oy: Evidence for stripe correlations near 1/8 hole doping
We report on muon spin rotation measurements of the internal magnetic field
distribution n(B) in the vortex solid phase of YBa2Cu3Oy (YBCO) single
crystals, from which we have simultaneously determined the hole doping
dependences of the in-plane Ginzburg-Landau (GL) length scales in the
underdoped regime. We find that Tc has a sublinear dependence on
1/lambda_{ab}^2, where lambda_{ab} is the in-plane magnetic penetration depth
in the extrapolated limits T -> 0 and H -> 0. The power coefficient of the
sublinear dependence is close to that determined in severely underdoped YBCO
thin films, indicating that the same relationship between Tc and the superfluid
density is maintained throughout the underdoped regime. The in-plane GL
coherence length (vortex core size) is found to increase with decreasing hole
doping concentration, and exhibit a field dependence that is explained by
proximity-induced superconductivity on the CuO chains. Both the magnetic
penetration depth and the vortex core size are enhanced near 1/8 hole doping,
supporting the belief by some that stripe correlations are a universal property
of high-Tc cuprates.Comment: 12 pages, 13 figure
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