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Abstract: Chaotic electron transport has been explored in a variety of semiconductor structures in which the transition to chaos occurs by the gradual and progressive destruction of stable orbits in response to an increasing perturbation. There is also a much rarer type of chaos, known as non-KAM dynamics, which switches on and off abruptly when the temporal frequency of the perturbation reaches certain critical values. This type of chaotic motion is of great interest due to diverse applications in the theory of plasma physics, tokamak fusion, turbulent fluid dynamics, ion traps, and quasicrystals, but has not yet been realized in experiment. Here, we show that electrons in a superlattice miniband with a tilted magnetic field provide an experimentally-accessible non-KAM system and, moreover, that this unusual type of chaotic dynamics can produce strong resonant enhancement of the electron drift velocity. The onset of chaos is characterized by the formation of intricate “stochastic web” patterns in the electron phase space. These webs delocalize the electron orbits, thereby generating strong resonant peaks in our calculated drift velocity versus electric field characteristics. [Copyright &y& Elsevier]

Progression free survival (PFS) and tumour response (TR) have been investigated as surrogate endpoints for overall survival (OS) in advanced colorectal cancer (aCRC). Applying bvNMA to evaluate surrogate endpoints in aCRC resulted in varying correlations between treatment effects on surrogate and final outcome across treatment contrasts. For example overall, for all treatments, correlation between treatment effect on TR and PFS was -0.67 (95% CrI: -0.85, -0.41), whilst the correlation for trials of EGFRi with chemotherapy vs. chemotherapy alone was higher; 0.79 (-0.95, -0.5) and lower for anti-VEGF therapies with chemotherapy vs. chemotherapy alone; -0.43 (-0.84, 0.16). [Extracted from the article]

Building on our research as part of IMI GetREAL, we aim to develop methodology for incorporating real-world data (RWD) into decision-making in the drug development process. We use these estimates to inform a bivariate network meta-analysis (NMA) model of first and second line treatments. [Extracted from the article]

Abstract: We study the effects of inter-miniband electron tunneling and electric field domains on the current–voltage and conductance–voltage curves of biased semiconductor superlattices under the action of a magnetic field that is tilted relative to the plane of the layers. For this geometry, electrons in the superlattice minibands exhibit a unique type of stochastic semiclassical motion. At certain critical values of the electric field within the superlattice layers, the stochastic trajectories change abruptly from fully localized to completely unbounded, and map out an intricate web-like mesh of conduction channels in phase space. Delocalization of the electron paths produces a series of strong resonant peaks in the electron drift velocity versus electric field curves. We use these drift velocity characteristics to make self-consistent drift-diffusion calculations of the current–voltage and differential conductance–voltage curves of the superlattices, which reveal strong resonant features originating from the sudden delocalization of the stochastic single-electron paths. We show that this delocalization has a pronounced effect on the distribution of space charge and electric field domains within the superlattices. Inter-miniband tunneling greatly reduces the amount of space-charge buildup, thus enhancing the domain structure and both the strength and number of the current resonances. [Copyright &y& Elsevier]

Understanding how complex systems respond to change is of fundamental importance in the natural sciences. There is particular interest in systems whose classical newtonian motion becomes chaotic as an applied perturbation grows. The transition to chaos usually occurs by the gradual destruction of stable orbits in parameter space, in accordance with the Kolmogorov-Arnold-Moser (KAM) theorem-a cornerstone of nonlinear dynamics that explains, for example, gaps in the asteroid belt. By contrast, ‘non-KAM’ chaos switches on and off abruptly at critical values of the perturbation frequency. This type of dynamics has wide-ranging implications in the theory of plasma physics, tokamak fusion, turbulence, ion traps, and quasicrystals. Here we realize non-KAM chaos experimentally by exploiting the quantum properties of electrons in the periodic potential of a semiconductor superlattice with an applied voltage and magnetic field. The onset of chaos at discrete voltages is observed as a large increase in the current flow due to the creation of unbound electron orbits, which propagate through intricate web patterns in phase space. Non-KAM chaos therefore provides a mechanism for controlling the electrical conductivity of a condensed matter device: its extreme sensitivity could find applications in quantum electronics and photonics. [ABSTRACT FROM AUTHOR]