Quantum localization and cantori in chaotic billiards

We study the quantum behaviour of the stadium billiard. We discuss how the interplay between quantum localization and the rich structure of the classical phase space influences the quantum dynamics. The analysis of this model leads to new insight in the understanding of quantum properties of classically chaotic systems.Comment: 4 pages in RevTex with 4 eps figures include

Signatures of Classical Diffusion in Quantum Fluctuations of 2D Chaotic Systems

We consider a two-dimensional (2D) generalization of the standard kicked-rotor (KR) and show that it is an excellent model for the study of 2D quantum systems with underlying diffusive classical dynamics. First we analyze the distribution of wavefunction intensities and compare them with the predictions derived in the framework of diffusive {\it disordered} samples. Next, we turn the closed system into an open one by constructing a scattering matrix. The distribution of the resonance widths ${\cal P}(\Gamma)$ and Wigner delay times ${\cal P}(\tau_W)$ are investigated. The forms of these distributions are obtained for different symmetry classes and the traces of classical diffusive dynamics are identified. Our theoretical arguments are supported by extensive numerical calculations.Comment: 20 pages; 12 figure

Combination immunotherapy and active-specific tumor cell vaccination augments anti-cancer immunity in a mouse model of gastric cancer

<p>Abstract</p> <p>Background</p> <p>Active-specific immunotherapy used as an adjuvant therapeutic strategy is rather unexplored for cancers with poorly characterized tumor antigens like gastric cancer. The aim of this study was to augment a therapeutic immune response to a low immunogenic tumor cell line derived from a spontaneous gastric tumor of a CEA424-SV40 large T antigen (CEA424-SV40 TAg) transgenic mouse.</p> <p>Methods</p> <p>Mice were treated with a lymphodepleting dose of cyclophosphamide prior to reconstitution with syngeneic spleen cells and vaccination with a whole tumor cell vaccine combined with GM-CSF (a treatment strategy abbreviated as LRAST). Anti-tumor activity to subcutaneous tumor challenge was examined in a prophylactic as well as a therapeutic setting and compared to corresponding controls.</p> <p>Results</p> <p>LRAST enhances tumor-specific T cell responses and efficiently inhibits growth of subsequent transplanted tumor cells. In addition, LRAST tended to slow down growth of established tumors. The improved anti-tumor immune response was accompanied by a transient decrease in the frequency and absolute number of CD4⁺CD25⁺FoxP3⁺T cells (Tregs).</p> <p>Conclusions</p> <p>Our data support the concept that whole tumor cell vaccination in a lymphodepleted and reconstituted host in combination with GM-CSF induces therapeutic tumor-specific T cells. However, the long-term efficacy of the treatment may be dampened by the recurrence of Tregs. Strategies to counteract suppressive immune mechanisms are required to further evaluate this therapeutic vaccination protocol.</p