Laser ablation on vascular diseases: mechanisms and influencing factors.

Vascular diseases, such as venous insufficiency and coronary artery diseases, have been threatening the health of people. Efficient treatment with proper postoperative care is required to relieve the pain of the patients. Traditionally, venous insufficiency is treated with ligation and stripping, an open surgery whose complication rate cannot be ignored. Coronary artery disease is often treated with balloon angioplasty during which undilatable lesions may be encountered, limiting the efficacy of this approach. With advances in laser photonics and percutaneous coronary intervention procedure, laser ablation is emerging as an alternative and adjunctive therapy for these diseases. Endovenous laser ablation has the advantages of high success rate, low complication risk, and fast postoperative recovery. Laser ablation in arteries can handle uncrossable or undilatable lesions with a low incidence of serious complications. In this review, previously published research concerning vascular diseases and their therapies are analyzed in order to provide a clear explanation of the mechanisms and merits of laser ablation. For endovenous laser ablation, the main mechanisms are steam bubbles, heat conduction, and heat pipe, and three main influencing factors are wavelength, fiber types, and laser energy density. For excimer laser coronary atherectomy, the main mechanisms are photochemical, photothermal, and photomechanical effects, and three main influencing factors are catheter, medium, and laser parameters.

Pilot study on demister-based dust removal methods for boiler flue gas.

This study explores the synergistic removal effect of various schemes based on demisters on boiler flue gas dust on a pilot-scale experimental bench. The results show that the dust removal efficiency is 28.43-51.30% when demisters are put into operation alone; the larger the inlet dust concentration of demisters is, the higher the dust removal efficiency will be; but it still cannot reach the 10 mg/Nm3 ultra-low emission standard. The dust removal efficiency is 93.13% when wet electro-static precipitator and demisters are put into operation simultaneously. Furthermore, the outlet dust concentration is lower than 5 mg/Nm3, and the dust removal efficiency of the demisters themselves increases to 67.28%, which has shown a significant improvement compared with operation alone. The dust removal efficiency is 70.98-78.37% when the water-washing layer and demisters are put into operation simultaneously. Moreover, the outlet dust concentration reaches the standard of 10 mg/Nm3 when the liquid-gas ratio (L/G) is more than 3.5. This research shows that when the inlet dust concentration is ≤ 35 mg/Nm3, the method of "water-washing layer + demisters" can be used as an equivalent alternative to the wet electro-static precipitator when L/G ≥ 3.5, which has reference value for reducing the construction cost of ultra-low emission reformation.

Recent Progress of Two-Dimensional Materials for Ultrafast Photonics.

Owing to their extraordinary physical and chemical properties, two-dimensional (2D) materials have aroused extensive attention and have been widely used in photonic and optoelectronic devices, catalytic reactions, and biomedicine. In particular, 2D materials possess a unique bandgap structure and nonlinear optical properties, which can be used as saturable absorbers in ultrafast lasers. Here, we mainly review the top-down and bottom-up methods for preparing 2D materials, such as graphene, topological insulators, transition metal dichalcogenides, black phosphorus, and MXenes. Then, we focus on the ultrafast applications of 2D materials at the typical operating wavelengths of 1, 1.5, 2, and 3 µm. The key parameters and output performance of ultrafast pulsed lasers based on 2D materials are discussed. Furthermore, an outlook regarding the fabrication methods and the development of 2D materials in ultrafast photonics is also presented.

MXenes: synthesis, incorporation, and applications in ultrafast lasers.

The rapid expansion of nanotechnology and material science prompts two-dimensional (2D) materials to be extensively used in biomedicine, optoelectronic devices, and ultrafast photonics. Owing to the broadband operation, ultrafast recovery time, and saturable absorption properties, 2D materials become the promising candidates for being saturable absorbers in ultrafast pulsed lasers. In recent years, the novel 2D MXene materials have occupied the forefront due to their superior optical and electronic, as well as mechanical and chemical properties. Herein, we introduce the fabrication methods of MXenes, incorporation methods of combining 2D materials with laser cavities, and applications of ultrafast pulsed lasers based on MXenes. Firstly, top-down and bottom-up approaches are two types of fabrication methods, where top-down way mainly contains acid etching and the chief way of bottom-up method is chemical vapor deposition. In addition to these two typical ones, other methods are also discussed. Then we summarize the advantages and drawbacks of these approaches. Besides, commonly used incorporation methods, such as sandwich structure, optical deposition, as well as coupling with D-shaped, tapered, and photonic crystal fibers are reviewed. We also discuss their merits, defects, and conditions of selecting different methods. Moreover, we introduce the state of the art of ultrafast pulsed lasers based on MXenes at different wavelengths and highlight some excellent output performance. Ultimately, the outlook for improving fabrication methods and applications of MXene-based ultrafast lasers is presented.