Generation of 13.9-mJ Terahertz Radiation from Lithium Niobate Materials.

Extremely strong-field terahertz (THz) radiation in free space has compelling applications in nonequilibrium condensed matter state regulation, all-optical THz electron acceleration and manipulation, THz biological effects, etc. However, these practical applications are constrained by the absence of high-intensity, high-efficiency, high-beam-quality, and stable solid-state THz light sources. Here, the generation of single-cycle 13.9-mJ extreme THz pulses from cryogenically cooled lithium niobate crystals and a 1.2% energy conversion efficiency from 800 nm to THz are demonstrated experimentally using the tilted pulse-front technique driven by a home-built 30-fs, 1.2-Joule Ti:sapphire laser amplifier. The focused peak electric field strength is estimated to be 7.5 MV cm-1 . A record of 1.1-mJ THz single-pulse energy at a 450 mJ pump at room temperature is produced and observed that the self-phase modulation of the optical pump can induce THz saturation behavior from the crystals in the substantially nonlinear pump regime. This study lays the foundation for the generation of sub-Joule THz radiation from lithium niobate crystals and will inspire more innovations in extreme THz science and applications.

Simulation study of the effects of interstitial fluid pressure and blood flow velocity on transvascular transport of nanoparticles in tumor microenvironment.

BACKGROUND AND OBJECTIVE: Although nanoparticle preparations have great potential in the treatment of tumors, nanoparticle preparations have not achieved the desired therapeutic effect. The reason is that the abnormal tumor microenvironment prevents nanoparticles from effective concentrating and reaching tumor area. Therefore, it's very necessary to better understand the effect of the abnormal tumor microenvironment on the transvascular transport of nanoparticles to overcome this critical problem. METHODS: In this paper, a tumor abnormal vascular-interstitial model was established, and the transvascular transport process of nanoparticles was simulated in the model by computational fluid dynamics (CFD) modeling. RESULTS: The simulation results showed that the transport efficiency of nanoparticles decreased with increasing interstitial fluid pressure (IFP), and nanoparticles could not cross the blood vessel wall when the IFP approached the blood vessel wall pressure. Interestingly, the transport efficiency of nanoparticles first increased with blood flow velocity, and then decreased with blood flow velocity. CONCLUSIONS: The results showed that with the continuous malignant development of tumors, the ability of nanoparticles to passively diffuse has almost disappeared. The enhanced permeability and retention (EPR) effect of the nanoparticles disappeared with the disappearance of the pressure gradient inside the tumor. These results provided guidance for future research on the vascular transport pathways and mechanisms of nanoparticles.