A density functional theory study of polarons on different TiO_(2)surfaces

Polarons are widely considered to play a crucial role in the charge transport and photocatalytic performance of materials,but the mechanisms of their formation and the underlying driving factors remain a matter of controversy.This study delves into the formation of polarons in different crystalline forms of TiO_(2)and their connection with the materials'structure.By employing density functional theory calculations with on-site Coulomb interaction correction(DFT+U),we provide a detailed analysis of the electronic polarization behavior in the anatase and rutile forms of TiO_(2).We focus on the polarization properties of defect-induced and photoexcited excess electrons on various TiO_(2)surfaces.The results reveal that the defect electrons can form small polarons on the anatase TiO_(2)(101)surface,while on the rutile TiO_(2)(110)surface,both small and large polarons(hybrid-state polarons)are formed.Photoexcited electrons are capable of forming both small and large polarons on the surfaces of both crystal types.The analysis indicates that the differences in polaron distribution are primarily determined by the intrinsic properties of the crystals;the structural and symmetry differences between anatase and rutile TiO_(2)lead to the distinct polaron behaviors.Further investigation suggests that the polarization behavior of defect electrons is also related to the arrangement of electron orbitals around the Ti atoms,while the polarization of photoexcited electrons is mainly facilitated by the lattice distortions.These findings elucidate the formation mechanisms of different types of polarons and may contribute to understanding the performance of TiO_(2)in different fields.

粪菌移植治疗溃疡性结肠炎系统评价/meta分析的再评价

背景:溃疡性结肠炎(UC)发病率高且易复发。目前已有大量系统评价/meta分析探讨了粪菌移植(FMT)治疗UC的疗效和安全性,但得出的结论并不相同,然而这些研究的质量尚未得到充分评估。目的:对FMT治疗UC的系统评价/meta分析进行再评价。方法:计算机检索PubMed、Cochrane Library、Embase、Web of Science、中国知网、中国生物医学文献数据库、万方、维普等数据库,搜集FMT治疗UC的系统评价/meta分析,检索时间为建库至2023年5月。同时手工检索灰色文献并咨询专家。两名研究者交互进行文献筛选和提取资料。采用PRISMA报告清单、AMSTAR-2工具分别评估纳入研究的报告质量和方法学质量,同时基于GRADE系统对结局指标进行证据质量分级。结果:最终纳入17篇系统评价/meta分析,纳入原始研究包括随机对照试验和观察性研究,大多数研究对FMT治疗UC的有效性和安全性得出肯定结论。纳入研究的PRISMA报告清单评分为12.5~22.5分,平均为17.68分。3篇研究报告相对完整,10篇有一定缺陷,4篇有相对严重的报告缺陷。AMSTAR-2评分显示:2篇属中质量,3篇属低质量,12篇为极低质量。GRADE系统评级结果显示:8个结局指标中6个为中级,2个为低级。结论:FMT可能是一种安全有效的治疗UC的方法,但当前证据质量较低,临床证据使用者需谨慎对待以上证据。

逍遥散治疗慢性萎缩性胃炎作用机制的研究概述

慢性萎缩性胃炎临床以上腹胀痛、嗳气、消瘦为主要表现,是一种常见的难治性消化系统疾病,属于胃癌的癌前病变。目前,现代医学对慢性萎缩性胃炎尚无特异性的治疗方法,远期疗效亦不甚满意。中医药治疗慢性萎缩性胃炎具有一定优势,在缓解临床症状、改善客观指标、延缓或逆转萎缩进展、提高远期疗效等方面均取得了可观的效果。中医将本病归结为“胃脘痛”“腹胀”等范畴,本病为本虚标实证:本为脾胃虚弱,实为肝气郁结阻络,故肝郁脾虚贯穿疾病的发生及发展各个阶段。逍遥散作为调和肝脾的经典中药方剂,已被现有研究证实在治疗慢性萎缩性胃炎方面疗效确切、不良反应少、安全性高。逍遥散治疗慢性萎缩性胃炎虽有丰富的临床试验支撑,但对其作用机制的总结归纳仍较少,且主要局限于调节激素分泌、抗炎症反应、调节神经递质浓度等方面。其次,部分研究较为表浅,缺乏后期深入跟进。对降低癌变倾向的这一机制,有待进一步研究证实。最后,各机制理论之间尚不能构建清晰的网络关系,其相关调控靶点还不明确,今后可从这些方面进行深入研究。本文以探讨逍遥散治疗慢性萎缩性胃炎的相关作用机制为重点进行综述,以期为临床提供参考。