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and performances of nanodevices highly depend on the shape and quality of 2D materials, [5] various routes have been explored to synthesize high-quality controllable-shaped 2D materials. This has led to the development of different synthesis methods including mechanical exfoliation, [6] liquid-phased exfoliation, [7] and chemical vapor deposition (CVD). [8] CVD has been shown to be the most performant synthetic method, and is currently the most widely used for large-scale fabrication of high-quality 2D materials. [9] Tremendous efforts have been made to control the CVD synthetic process, for example, growing large single crystals of graphene by limiting the growth process to one nucleus, [10] fabricating wafer-scale single crystals of h-BN on liquid-gold substrates, [11] or depositing 2D transitionmetal chalcogenides via adding molten salt. [12] However, to achieve the precise control of the growth process of 2D materials, it is essential to take into account its underlying physical mechanisms. Many attempts have been made to explore the atomic mechanism and grow higher-quality materials by considering the oxygen effect, [13] the hydrogen etching, [14] the edgeenergy equilibrium, [15] the classical Wulff structure, [16] and the phase-field approach in the past years. [17] However, due to a large number of influenced factors and the underlying intricate nanoscale physical mechanisms, the precise control of the shape and quality of CVD-grown 2D materials, till now, is still regarded as a formidable challenge.Our study shows that dendritic-structured patterns commonly appear during the CVD growth processes of various 2D materials. To understand this phenomenon, we investigate the growth mechanisms in the framework of the fractal theory. [18] Although, in the past, this theory has provided an explanation for the sound of irregular or fragmented natural structures and self-similar patterns with the unfolding symmetry, [19] this theory has never been applied, to our knowledge, to the interpretation of growth mechanisms of CVD-grown 2D materials. Here, we demonstrate, both experimentally and theoretically, the existence of fractal growth mechanisms in the CVD growth process of graphene, h-BN, and molybdenum disulfide (MoS 2 ). Based on the classic diffusion-limited aggregation (DLA), [20] a typical model of the fractal theory, we develop an The precise control of the shape and quality of 2D materials during chemical vapor deposition (CVD) processes remains a challenging task, due to a lack of understanding of their underlying growth mechanisms. The existence of a fractal-growth-based mechanism in the CVD synthesis of several 2D materials is revealed, to which a modified traditional fractal theory is applied in order to build a 2D diffusion-limited aggregation (2D-DLA) model based on an atomic-scale growth mechanism. The strength of this model is validated by the perfect correlation between theoretically simulated data, predicted by 2D-DLA, and experimental results obtained from the CVD synthesis of graphene, hexagonal b...

Study Design. A retrospective study. Objective. To assess the long-term results of zero-profile spacer for 3-level anterior cervical discectomy and fusion (ACDF). Summary of Background Data. Although widely used, there are still controversies about the long-term results of zero-profile spacer, especially in multilevel cases. Methods. Cases received 3-level ACDF for cervical spondylotic myelopathy (CSM) using either zero-profile spacer (n = 27) (ZP Group), or plate and cages (n = 34) (PC Group), and with 5-year follow-up were reviewed. Neurological function and life quality were assessed by modified Japanese Orthopaedic Association (mJOA) score, Neck Disability Index (NDI), and Short-Form 36 (SF-36) score. Disc height, cervical lordosis, fusion rate, and surgical complications were observed. Results. Neurological recovery and life quality improvement were similar in both groups. Disc height and cervical lordosis (C2-7 Cobb angle) were well restored after operations, but lost in both groups during follow-up. Loss of correction (LOC) in disc height was larger in ZP Group (11.38% vs 5.71%, P < 0.05) at 5-year follow-up. LOC of cervical lordosis in ZP group constantly grew from 11.28% to 48.13% during 5-year follow-up, significantly higher than that in the PC group (from 7.43% to 14.01%) (P < 0.05). The rate of postoperative dysphagia was no statistical difference between the two groups, and symptoms were all disappeared within 1 year. There were 10 levels of adjacent segment degeneration (1 in ZP Group, and 10 in PC Group, P = 0.02). Cage subsidence (11 of 81 levels, 13.58%) and screw migration (2 of 81 levels, 2.47%) were only observed in the ZP Group. The migrated screws in one case were surgically removed. Fusion was achieved in all cases. Conclusions. In long-term follow-up of 3-level ACDF for CSM, zero-profile spacer has the similar clinical results, but loss of correction of disc height and cervical alignment were significantly higher, compared with anterior plate and cages. Level of Evidence: 3