8,121 research outputs found
Holographic Butterfly Effect at Quantum Critical Points
When the Lyapunov exponent in a quantum chaotic system saturates
the bound , it is proposed that this system has a
holographic dual described by a gravity theory. In particular, the butterfly
effect as a prominent phenomenon of chaos can ubiquitously exist in a black
hole system characterized by a shockwave solution near the horizon. In this
paper we propose that the butterfly velocity can be used to diagnose quantum
phase transition (QPT) in holographic theories. We provide evidences for this
proposal with an anisotropic holographic model exhibiting metal-insulator
transitions (MIT), in which the derivatives of the butterfly velocity with
respect to system parameters characterizes quantum critical points (QCP) with
local extremes in zero temperature limit. We also point out that this proposal
can be tested by experiments in the light of recent progress on the measurement
of out-of-time-order correlation function (OTOC).Comment: 7 figures, 15 page
A novel scalable manufacturing platform for T-cell activation and expansion in adoptive T-cell therapy
Adoptive T cell therapy (ACT) is growing rapidly, representing the revolution in cancer treatment. However, the current manufacturing platforms are largely based on magnetic microbeads surface coated with agonist antibodies to T-cell receptors CD3 and CD28. These manufacturing platforms use expensive reagents including the viral transduction vectors, and also require multiple discrete stages and open processes with significant human interaction, contributing to the high-cost for cGMP manufacturing of these therapies. We developed a single-use, beads-free bioreactor system (Figure 1a), which provides a closed-loop T-cell activation and expansion. The perfusion-based platform also facilitates the development of the bioreactor system into a fully automated, turn-key system used in both centralized and decentralized (e.g., hospitals) manufacturing settings. The bioreactor has a unique internal structure (Figure 1b), formed by a large number of interconnected hollow spheres tightly packed in a 3D space, which yields large surface areas to increase the reactivity between the bioreactor and the T cells flowing through the bioreactor. The surfaces of the bioreactor are coated with anti-CD3 and CD28 antibodies to mimic the antigens for T activation and expansion. The feasibility of using the perfusion-based bioreactor for T-cell activation and expansion is demonstrated in Figure 2. Briefly, 20x106 PBMCs were seeded into the bioreactor system and perfused for two days during the T-cell activation phase, with the medium containing no cytokine IL2. After two-day of activation, human IL-2 was added to the system so that the total IL-2 concentration was 20 IU/mL. Then the T-cell expansion phase was carried out for three-days. On Day 5, T cells were achieved a three-time expansion after activation, which is similar to the magnetic beads-based system. However, the perfusion based bioreactor has the potential to offer multiple advantages over the current beads-based system as discussed above
Holographic Metal-Insulator Transition in Higher Derivative Gravity
We introduce a Weyl term into the Einstein-Maxwell-Axion theory in four
dimensional spacetime. Up to the first order of the Weyl coupling parameter
, we construct charged black brane solutions without translational
invariance in a perturbative manner. Among all the holographic frameworks
involving higher derivative gravity, we are the first to obtain metal-insulator
transitions (MIT) when varying the system parameters at zero temperature.
Furthermore, we study the holographic entanglement entropy (HEE) of strip
geometry in this model and find that the second order derivative of HEE with
respect to the axion parameter exhibits maximization behavior near quantum
critical points (QCPs) of MIT. It testifies the conjecture in 1502.03661 and
1604.04857 that HEE itself or its derivatives can be used to diagnose quantum
phase transition (QPT).Comment: 20 pages, 4 figures; typo corrected, added 3 references; minor
revisio
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