New Photocatalytical Reduction Systems for Mercury Speciation Analysis

近年来的研究表明，元素的不同形态与其物理化学性质和环境行为及生物效应密切相关。联用技术已经成为元素形态分析中应用最广泛的技术，而高效液相色谱（HPLC）和原子荧光光谱（AFS）通过高效的在线接口链接联合使用由于其简便、灵敏度高、选择性强、经济实用等优点已经被越来越多地应用于可蒸气发生元素的形态分析。常用的蒸气发生进样方法采用硼氢化钾/氢氧化钠－盐酸（KBH4/NaOH-HCl）体系，此体系进样效率高，但是也具有以下缺点：（1）KBH4不稳定，要现配现用；同时由于其不稳定，制备高纯的KBH4相对困难，它的使用常常引入杂质并使背景升高；（2）易受共存离子特别是过渡金属离子的干扰；（3）产生的大量氢...Recent approaches indicated that the environmental behavior and biological function as well as physicochemical property of an element depend mainly on the kind of its existing species. Hyphenated techniques combining a continuing separation technique and an element-selective and/or a structure-specific detector play an important role in elemental speciation analysis. Among these, effectively bridg...学位：理学硕士院系专业：化学化工学院化学系_分析化学学号：20032503

C–X(X = Cl, Br, I) bond dissociation energy as a descriptor for the redispersion of sintered Au/AC catalysts

负载型Au基催化剂在工业过程中具有非常广泛的潜在应用,如催化加氢/脱氢过程、精细化学品合成、能源催化转化及环境保护等过程,表现出很高的催化活性和选择性.Au基催化剂活性物种或活性中心基本由纳米粒子或化合物构成,但在应用过程中因Ostwald熟化效应或粒子迁移作用,尤其是高温高压等苛刻反应条件下,均随应用时间延长从小尺寸粒子逐渐长为大粒子,造成活性降低或完全失活,这也是负载型催化剂失活的最主要原因之一.其中因成本、稀缺等特性,负载型Au催化剂的烧结问题是影响和制约其应用的主要因素.除可通过载体改性、助剂和官能团配位稳定等方法来延缓其失活过程外,对已烧结催化剂的高效、快捷和绿色的再分散/再生过程也具有基础和应用研究的重要意义.活性炭载Au催化剂(Au/AC)广泛应用于乙炔氢氯化反应中,以期替代高毒性的汞基催化剂,但在反应过程中因高活性的Au~(3+)物种易被还原而形成Au~0物种进而烧结导致失活;如新鲜Au/AC催化剂表面的Au粒子尺寸为1-2 nm,经乙炔氢氯化反应后变为33 nm左右;随之在453 K、0.1 MPa、乙炔体积空速(GHSV)为600 h~(-1)、氯化氢与乙炔摩尔比为1.1的反应条件下,乙炔转化率从81.8%降至11.2%.如何有效对大粒子Au再分散/再生可为其应用提供有力支撑.有研究表明,气相CHI_3在甲醇羰基化反应过程中明显改变Au/AC表面的Au粒子尺寸;或采用浓盐酸或王水也可将烧结的Au/AC催化剂进行再分散/再生.但已有的Au基催化剂再分散/再生过程均伴随着强酸、强氧化或高毒性在分散剂的应用,对环境的影响及后续处理有明显的局限性,且再分散机理尚不明确.在前期工作基础上,本文采用系列卤代烃(碘代烃、溴代烃和氯代烃)对烧结的Au/AC进行再分散/再生研究.结果表明,在室温常压条件下CHI_3可以快捷高效地对烧结Au/AC催化剂进行再分散/再生,具有最优的再分散性能;通过对系列碘代烃C-I键的解离能分析,发现C-I解离能越低越有利于大粒子Au的再分散.同时,溴代烃和氯代烃对烧结的Au/AC催化剂也具有再分散能力,但比碘代烃的再分散效率低.C-X键的解离能与再分散效率有高相关性,即C-X键的解离能越低越有利于Au的再分散.总体上,三类卤代烃再分散效率高低顺序为C-I>C-Br>C-Cl.进而,通过不同分散过程中Au粒子分散状态推测了卤代烃对Au粒子的再分散机理,即卤代烃先在Au粒子表面化学吸附,然后C-X键解离,形成Au-X物种,小粒子Au在AC表面聚集并稳定,最后形成高分散Au粒子(粒径<1 nm)催化剂.以乙炔氢氯化反应考察了再生Au/AC催化剂性能,结果表明,该催化剂上乙炔转化率可达79.4%,基本恢复至初始水平,且该方法可对失活催化剂进行多次高效再生.Disintegration or redispersion of supported sintered gold nanoparticles(Au NPs) in the presence of alkyl halide can give catalyst regeneration or redispersion of sintered Au catalysts. The selectivity of alkyl halides, temperature and size distributions were investigated to elucidate the redispersion of Au NPs during halide-induced decomposition. This study proved that the alkyl halide induced the redispersion of sintered Au NPs which depended on the R–X(X = I, Br, Cl) bond dissociation energy(BDE) and thus provided a simple descriptor for the regeneration of inactive supported Au cata-lysts. A correlation between the BDE of R–X and dispersion efficiency was established. The tendency for disintegration and redispersion followed the R–X BDE of the alkyl halide. Compared to alkyl chlorides and bromides, iodides were more efficient for redispersing sintered Au NPs. As a descriptor, the BDE of R–I played a crucial role in particle redispersion. These findings provided insights into the mechanism of organic halide-induced Au NP disintegration and the effect of the halide type on the redispersion of sintered catalysts.国家自然科学基金(21403178,21473145,21503173,91545115);; 教育部创新团队发展计划(IRT_14R31);; 福建省青年教师教学科研基金(JA15003

扇聚焦等时性回旋加速器性能的改进和提高

安装了ＥＣＲ离子源及其外注入系统后，增加了离子种类、提高了束流强度。扇聚焦等时性回旋加速器（ＳＦＣ）主要工作点分布于三次谐波加速区域，为了匹配外注入系统，仔细地研究了中心区，重新设计加工了Ｄ盒及假Ｄ。为了改进ＳＦＣ性能，提高运行效率，同时进行了其它改进工作．介绍了改进后的ＳＦＣ的调束工作

Expert consensus on the management of dermatogenic chronic pruritus in children

瘙痒见于多种疾病,在儿童多由皮肤疾病导致,即皮肤源性瘙痒.持续存在的慢性瘙痒治疗困难,可对患儿的睡眠、情绪、认知、学校表现及社会家庭功能等方面产生负面影响,严重影响患儿及其家庭成员的生活质量.临床上迫切需要对儿童慢性瘙痒进行规范化管理,而目前国内外缺乏独立的儿童慢性瘙痒诊疗指南或共识.该共识根据循证医学证据及专家意见,制定了一套针对0～18岁儿童皮肤源性慢性瘙痒的管理方案,供临床医生参考.</p

近70年来中国自然地理与生存环境基础研究的重要进展与展望

自然环境是人类赖以生存和发展的基础,探索自然环境及其各要素(如地貌、气候、水文、土壤等)的特征、演变过程、地域分异规律以及驱动机制是自然地理学的重点研究内容.中国自然地理要素类型丰富且区域差异较大,为开展自然地理研究提供了难得的机遇.文章主要围绕青藏高原隆升与亚洲内陆干旱化及河流发育、高原冰冻圈环境演化、全新世多时间尺度季风与西风气候变化、湖泊与湿地、流域模型与土壤侵蚀、过去人-地关系演化、生物地理及中国三维地带性规律等几个方面,梳理了近70年来中国自然地理与生存环境研究的重大理论进展与重要贡献.在简要交代国际前沿研究进展的基础上,回顾并梳理了中国自然地理学各分支领域的研究脉络,进一步聚焦重大研究成果或具有较大争议、重大影响的学术争鸣问题,归纳目前研究现状,并进行未来工作展望.最后提出在推进生态文明建设的国家需求下,应发挥中国自然地理研究的优势,厘清自然地理要素变化的过程、规律与机制,持续推进中国自然地理研究为国家战略服务,在全球视野下做出具有中国特色的自然地理学理论贡献

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies