330 research outputs found
The Role of DNA Topoisomerase II In Drug Resistance and Sensitivity.
Intrinsic or acquired resistance of human tumors to chemotheraphy is often multifactorial. One of the factors involved in resistance is the nuclear enzyme DNA topoisomerase II (TopoII) which is known to be the target of a variety of cytotoxic drugs which are widely used in the clinic. A factor complicating TopoII research is the presence of two TopoII isoforms in human cells which are called TopoIIa and b. In this thesis the role of these isoforms in resistance in small cell lung carcinoma cell line models is examined and the regulation of TopoII expression in human ovarian tumors is investigated. ....
Zie: Summary and conclusions
Critical theories for the pseudogap Kondo problem
We discuss quantum phase transitions in the pseudogap Kondo problem, which
describes a magnetic moment coupled to conduction electrons with a power-law
density of states, rho(omega) ~ |omega|^r. We show that different perturbative
expansions, together with renormalization group techniques, provide effective
low-energy field theories for the relevant critical fixed points. In
particular, we review expansions near the lower-critical and upper-critical
dimensions of the problem, being r=0 and r=1, respectively.Comment: 2 pages, 1 fig, submitted to SCES04 proceeding
From genome-wide association studies to disease mechanisms:celiac disease as a model for autoimmune diseases
Celiac disease is characterized by a chronic inflammatory reaction in the intestine and is triggered by gluten, a constituent derived from grains which is present in the common daily diet in the Western world. Despite decades of research, the mechanisms behind celiac disease etiology are still not fully understood, although it is clear that both genetic and environmental factors are involved. To improve the understanding of the disease, the genetic component has been extensively studied by genome-wide association studies. These have uncovered a wealth of information that still needs further investigation to clarify its importance. In this review, we summarize and discuss the results of the genetic studies in celiac disease, focusing on the "non-HLA" genes. We also present novel approaches to identifying the causal variants in complex susceptibility loci and disease mechanisms
Hidden Integrability of a Kondo Impurity in an Unconventional Host
We study a spin-1/2 Kondo impurity coupled to an unconventional host in which
the density of band states vanishes either precisely at (``gapless'' systems)
or on some interval around the Fermi level (``gapped''systems). Despite an
essentially nonlinear band dispersion, the system is proven to exhibit hidden
integrability and is diagonalized exactly by the Bethe ansatz.Comment: 4 pages, RevTe
Intestinal Barrier Function in Gluten-Related Disorders
Gluten-related disorders include distinct disease entities, namely celiac disease, wheat-associated allergy and non-celiac gluten/wheat sensitivity. Despite having in common the contact of the gastrointestinal mucosa with components of wheat and other cereals as a causative factor, these clinical entities have distinct pathophysiological pathways. In celiac disease, a T-cell mediate immune reaction triggered by gluten ingestion is central in the pathogenesis of the enteropathy, while wheat allergy develops as a rapid immunoglobulin E- or non-immunoglobulin E-mediated immune response. In non-celiac wheat sensitivity, classical adaptive immune responses are not involved. Instead, recent research has revealed that an innate immune response to a yet-to-be-defined antigen, as well as the gut microbiota, are pivotal in the development in this disorder. Although impairment of the epithelial barrier has been described in all three clinical conditions, its role as a potential pathogenetic co-factor, specifically in celiac disease and non-celiac wheat sensitivity, is still a matter of investigation. This article gives a short overview of the mucosal barrier of the small intestine, summarizes the aspects of barrier dysfunction observed in all three gluten-related disorders and reviews literature data in favor of a primary involvement of the epithelial barrier in the development of celiac disease and non-celiac wheat sensitivity
Kondo physics in a dissipative environment
We report nonperturbative results for the interacting quantum-critical
behavior in a Bose-Fermi Kondo model describing a spin-1/2 coupled both to a
fermionic band with a pseudogap density of states and to a dissipative bosonic
bath. The model serves as a paradigm for studying the interplay between Kondo
physics and low-energy dissipative modes in strongly correlated systems.Comment: 2 pages, 2 figures. Proceedings of The International Conference on
Strongly Correlated Electron Systems (SCES'07), accepted for publication in
Physica
Exactly Solvable Model of Superconducting Magnetic Alloys
A model describing the Anderson impurity in the Bardeen-Cooper-Schriffer
superconductor is proven to exhibit hidden integrability and is diagonalized
exactly by the Bethe ansatz.Comment: 10 pages, RevTEX, Phys. Lett. A. (in press
Metallic Ferromagnetism in the Kondo Lattice
Metallic magnetism is both ancient and modern, occurring in such familiar
settings as the lodestone in compass needles and the hard drive in computers.
Surprisingly, a rigorous theoretical basis for metallic ferromagnetism is still
largely missing. The Stoner approach perturbatively treates Coulomb
interactions when the latter need to be large, while the Nagaoka approach
incorporates thermodynamically negligible electrons into a half-filled band.
Here, we show that the ferromagnetic order of the Kondo lattice is amenable to
an asymptotically exact analysis over a range of interaction parameters. In
this ferromagnetic phase, the conduction electrons and local moments are
strongly coupled but the Fermi surface does not enclose the latter (i.e. it is
small). Moreover, non-Fermi liquid behavior appears over a range of frequencies
and temperatures. Our results provide the basis to understand some
long-standing puzzles in the ferromagnetic heavy fermion metals, and raises the
prospect for a new class of ferromagnetic quantum phase transitions.Comment: 21 pages, 9 figures, including Supporting Informatio
Do quantum dots allow one access to pseudogap Kondo physics?
For the last decade, tunable quantum dot systems have allowed the
investigation of Kondo physics wherein the quenching of a single spin on an
artificial atom affects the conductance. The pseudogap Kondo model featuring a
density of states = C, introduced by Withoff
and Fradkin in 1990 was predicted to exhibit Kondo-like physics above a
critical value of the Kondo coupling, J, which several groups have shown by
numerical renormalization group (RG) is finite for r. Gonzalez-Buxton
{\it{et al}} showed that the strong coupling limit of the particle-hole
symmetric model leads to a non-trivial phase shift at low
temperatures indicating incomplete screening of the local moment, while away
from particle-hole symmetry one generically flows towards a ground state with
. We examine the implications of this model for quantum dots
whose leads are Fermi-liquid-like, yet possess a tunneling density of states
which is suppressed at the Fermi energy as a power law.Comment: 2 pages, 1 figure, poster to be presented at SCES'04 Karlsruhe July
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