RESUMO
Single-crystalline silicon (sc-Si) is the dominant semiconductor material for the modern electronics industry. Despite their excellent photoelectric and electronic properties, the rigidity, brittleness, and nontransparency of commonly used silicon wafers limit their application in transparent flexible optoelectronics. In this study, a new type of Si microstructure, named single-crystalline Si frameworks (sc-SiFs), is developed, through a combination of wet-etching and microfabrication technologies. The sc-SiFs are self-supported, flexible, lightweight, tailorable, and highly transparent. They can withstand a small bending radius of less than 0.5 mm and have a transparency of up to 96% in all wavelength ranges, owing to the hollowed-out framework structures. Thus, the sc-SiFs provide a new platform for high-performance transparent flexible optoelectronics. Taking transparent flexible photodetectors (TFPDs) as an example, substrate-free and self-driven TFPDs are achieved based on the sc-SiFs. The devices exhibit superior performance compared to other reported TFPDs and reveal the great potential for integrated optoelectronic applications. The development of sc-SiFs paves the way toward the fabrication of high-performance transparent flexible devices for a host of applications, including e-skins, the Internet of Things, transparent flexible displays, and artificial visual cortexes.
RESUMO
BACKGROUND: Ulcerative colitis (UC) patients have an increased risk for the development of colorectal cancer (CRC). Our aim was to assess the risk of CRC in UC patients compared with disease extent, disease duration, and geographic variation. METHODS: In this systematic review and meta-analysis, we searched PubMed, scientific meetings, and the bibliographies of identified articles, with English language restrictions for studies published from 1988 to 2018, and assessed the risk of CRC in UC patients. Patients with Crohn's disease, family history of CRC, and colorectal adenomatous polyp (CAP) were excluded from this research. The study was registered with PROSPERO, number CRD42018102213. FINDINGS: We included 58 studies that included 267566 UC patients. Extensive UC and left-sided UC had a higher risk of CRC than proctitis UC. Geography also played a role in UC-associated CRC development. The time of malignant transformation in Asian UC patients started after 10-20 years of this disease duration. North American UC-associated CRC patients significantly increased in more than 30 years of this disease duration. CONCLUSION: In a systematic review of the literature, we found that disease extent, disease duration, and geography were strong, independent risk factors in UC-associated CRC development.
RESUMO
Nitrogen (N) leaching is a major pathway of N losses in paddy fields. Here, an experiment was conducted to assess the effects of the reduction of controlled-release urea application on grain yield and N leaching in a double-cropping paddy field. Fertilization treatments included zero-N (CK, control, 0 kg N·hm-2), conventional urea (CU, 180 kg N·hm-2), and four polymer-coated urea fertilization levels, i.e., 1.0CRU, 0.9CRU, 0.8CRU, 0.7CRU, which represented 0, 10%, 20% and 30% reduction of fertilizer inputs relative to CU, respectively. Leachate was collected at the soil depth of 60 cm using field leakage pool method. Nitrogen leaching peaked shortly after fertilization, implying that measures should be taken to prevent N leaching in the early period. Nitrogen losses from leaching were 42.3 kg N·hm-2 for 0.8CRU, and by 37.7 kg N·hm-2 for 0.7CRU, significantly lower than the leaching in CU (53.9 kg N·hm-2). Nitrogen leaching in 0.7CRU was significantly lower than that in 1.0CRU (51.3 kg N·hm-2). 11.9%-13.5% of the fertilizer N was lost via leaching across the six treatments with comparable N loss rates. Rice yields, N utilization efficiency and N harvest index were significantly higher in 0.8CRU and 0.7CRU relative to CU. Our findings suggested that the use of CRU would permit a reduction in N application by 20%-30%, which could maintain the rice yield and obtain a reduction in N leaching.