Photochemical route for preparing atomically dispersed Pd-1/TiO2 catalysts on (001)-exposed anatase nanocrystals and P25

单原子分散催化剂由于其独特的结构和性质,在催化研究中己展现出巨大的潜力,成为了催化研究的前沿领域.传统的催化剂制备方法(例如共沉积,浸渍法等)在; 单原子分散催化剂的制备中卓有成效,但不断涌现的新方法能够制备出传统方法不能制备的新型单原子分散催化剂.最近,光化学方法由于其步骤简单和制备条件温; 和的优点而引起了广泛关注.; 在之前的研究中我们揭示了光化学法制备单原子分散催化剂的分子机制.我们发现,紫外光照的作用在于将二氧化钛纳米片表面的乙二醇基激发生成乙二醇自由基,; 后者不仅有利于氯钯酸根中氯离子的脱除,还可通过Pd-O键将钯原子锚定在载体上,形成了独特的钯-乙二醇-二氧化钛的界面.根据对光化学法制备技术的理; 解,本文将光化学法拓展到其他二氧化钛体系,成功制备了基于(001)面暴露的锐钛矿纳米晶和商用二氧化钛P25的单原子分散钯催化剂.通过吸附和紫外光; 照,可以在室温下简单地制备单原子分散钯催化剂.扩展X射线吸收精细结构实验表明,紫外光照的作用是促进钯原子上氯离子的离去和更多Pd-O键的形成.与; 通过其它方法制备的催化剂相比,光化学法制备的两种Pd_1/TiO_2催化剂在苯乙烯的催化氢化反应中表现出更高的活性和稳定性.转化频率TOF为商用; Pd/C催化剂的6倍.; 单原子分散催化剂为研究催化反应中复杂的界面效应提供了理想的模型体系.由于CO的催化氧化反应性能对金属活性中心的化学配位环境高度敏感,因此我们选择; 它作为模型反应以研究光化学法制备的单原子分散催化剂之间的差异.; 结果发现,两种载体制备的单原子分散钯催化剂都具有很好的催化CO氧化低温活性,373; K时CO转化率均可高达96%.其中,负载在(001)面暴露的锐钛矿纳米晶的催化剂在343 K时TOF高达6.7*10~(-3); s~(-1),比有文献报道的活性最高的Pd/La-修饰Al_2O_3催化剂在相同条件下高3.3倍,是目前Pd基催化剂在催化CO氧化反应中的活性最; 佳记录.这可能是由于二氧化钛的载体效应引起的.虽然两种催化剂的催化活性相当,但Pd/P25的表观活化能比Pd/TiO_2(NC)高一倍左右.两种; 催化剂的金属都以单原子态分布,催化CO氧化反应的机制却可能完全不同.这说明单原子分散催化剂的性能与载体的表面性质密切相关.本文为单原子催化中载体; 的选择和原子尺度的界面调控提供了新的研究思路.Atomically dispersed catalysts have shown promising prospects in catalysis studies. Among all of the developed methods for synthesizing atomically dispersed catalysts, the photochemical approach has recently aroused much attention owing to its simple procedure and mild preparation conditions involved. In the present study, we demonstrate the application of the photochemical method to synthesize atomically dispersed Pd catalysts on (001)-exposed anatase nanocrystals and commercial TiO2 (P25). The as -prepared catalysts exhibit both high activity and stability in the hydrogenation of styrene and catalytic oxidation of CO. (C) 2017, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.XAFS station of the Shanghai Synchrotron Radiation Facility (SSRF); [BL14W1]; National postdoctoral program for innovative talents; [BX201600093

Corrected Navier-Stokes equations for compressible flows

For gas flows, the Navier-Stokes (NS) equations are established by mathematically expressing conservations of mass, momentum and energy. The advantage of the NS equations over the Euler equations is that the NS equations have taken into account the viscous stress caused by the thermal motion of molecules. The viscous stress arises from applying Isaac Newton's second law to fluid motion, together with the assumption that the stress is proportional to the gradient of velocity1. Thus, the assumption is the only empirical element in the NS equations, and this is actually the reason why the NS equations perform poorly under special circumstances. For example, the NS equations cannot describe rarefied gas flows and shock structure. This work proposed a correction to the NS equations with an argument that the viscous stress is proportional to the gradient of momentum when the flow is under compression, with zero additional empirical parameters. For the first time, the NS equations have been capable of accurately solving shock structure and rarefied gas flows. In addition, even for perfect gas, the accuracy of the prediction of heat flux rate is greatly improved. The corrected NS equations can readily be used to improve the accuracy in the computation of flows with density variations which is common in nature.Comment: 13 pages, 7 figure

Transcriptome analysis of Deinagkistrodon acutus venomous gland focusing on cellular structure and functional aspects using expressed sequence tags

BACKGROUND: The snake venom gland is a specialized organ, which synthesizes and secretes the complex and abundant toxin proteins. Though gene expression in the snake venom gland has been extensively studied, the focus has been on the components of the venom. As far as the molecular mechanism of toxin secretion and metabolism is concerned, we still knew a little. Therefore, a fundamental question being arisen is what genes are expressed in the snake venom glands besides many toxin components? RESULTS: To examine extensively the transcripts expressed in the venom gland of Deinagkistrodon acutus and unveil the potential of its products on cellular structure and functional aspects, we generated 8696 expressed sequence tags (ESTs) from a non-normalized cDNA library. All ESTs were clustered into 3416 clusters, of which 40.16% of total ESTs belong to recognized toxin-coding sequences; 39.85% are similar to cellular transcripts; and 20.00% have no significant similarity to any known sequences. By analyzing cellular functional transcripts, we found high expression of some venom related genes and gland-specific genes, such as calglandulin EF-hand protein gene and protein disulfide isomerase gene. The transcripts of creatine kinase and NADH dehydrogenase were also identified at high level. Moreover, abundant cellular structural proteins similar to mammalian muscle tissues were also identified. The phylogenetic analysis of two snake venom toxin families of group III metalloproteinase and serine protease in suborder Colubroidea showed an early single recruitment event in the viperids evolutionary process. CONCLUSION: Gene cataloguing and profiling of the venom gland of Deinagkistrodon acutus is an essential requisite to provide molecular reagents for functional genomic studies needed for elucidating mechanisms of action of toxins and surveying physiological events taking place in the very specialized secretory tissue. So this study provides a first global view of the genetic programs for the venom gland of Deinagkistrodon acutus described so far and an insight into molecular mechanism of toxin secreting. All sequences data reported in this paper have been submitted into the public database [GenBank: DV556511-DV565206]

Association Between Cancer Prevalence and Different Socioeconomic Strata in the US: The National Health and Nutrition Examination Survey, 1999–2018

BackgroundInequality in health outcomes in relation to Americans' socioeconomic status (SES) is rising. American Cancer Society depicts that the most common cancers are diagnosed in men and women in 2021. We aim to study socioeconomic inequalities in related cancers to investigate whether the cancer prevalence differs within the family income to poverty ratio (PIR).MethodsThe study investigated data from adults aged 20–85 years participated in the 1999–2018 National Health and Nutrition Examination Survey (NHANES) who had complete data available on PIR and cancer or malignancy information (n = 49,720). Participants were stratified into 3 categories of PIR: high income (PIR ≥ 4), middle income (>1 and <4), or at or below the federal poverty level (≤1).ResultsThe prevalence of prostate cancer was higher in the middle-income (3.61% [n = 464]) and high-income groups (3.36% [n = 227]) than in the low-income group (1.83% [n = 84], all p < 0.001). The prevalence of breast cancer was higher in middle-income (2.86% [n = 390]) and high-income participants (3.48% [n = 218]) than in low-income participants (2.00% [n = 117], all p < 0.001). Compared with the low-income group in men (0.48% [n = 22]), a higher prevalence of colon and rectum cancer occurs in the middle-income (0.87% [n = 112], p = 0.012) and high-income groups (0.89% [n = 58], p = 0.018). The prevalence of lung cancer in women was lower in high-income participants than middle-income participants (0.10% [n = 6] vs. 0.29% [n = 39], p = 0.014).ConclusionsIncreasing disparities in cancer prevalence were identified across all socioeconomic categories analyzed in this study. To ensure the sustainable development goals, it is a global health priority to understand inequalities in health and to target interventions accordingly

Interfacing with silica boosts the catalysis of copper

厦门大学化学化工学院郑南峰教授团队长期致力于研究固体功能材料的表界面化学行为，在分子水平上实现对固体功能材料的化学性能的调控与优化。得益于固体表面物理化学国家重点实验室的多学科合作以及能源材料化学协同创新中心的多单位优势互补，郑南峰教授课题组通过与校内外多个课题组的密切合作，近期在功能材料的可控制备、复杂表界面结构的高分辨表征和表界面过程分子机制的深入理解等方面取得系列重要进展，相关成果近期均在Nature Communications发表。 与厦门大学傅钢、袁友珠教授以及中国科学院物理研究所谷林研究员密切合作，历时五年，在多相催化的金属-载体界面效应研究方面取得重要进展。SiO2被广泛用作工业负载型金属催化剂的载体，多被视为惰性载体，在催化过程中仅起到分散金属的作用。郑南峰教授领衔的合作研究打破这个催化领域的“定式”。他们发现了“惰性”载体SiO2与Cu之间存在可以数量级提升酯基加氢催化性能的活性界面，揭示了相关界面效应的分子作用机制，并应用于指导实用铜催化剂的制备。【Abstract】Metal-support interaction is one of the most important parameters in controlling the catalysis of supported metal catalysts. Silica, a widely used oxide support, has been rarely reported as an effective support to create active metal-support interfaces for promoting catalysis. In this work, by coating Cu microparticles with mesoporous SiO2, we discover that Cu/SiO2 interface creates an exceptional effect to promote catalytic hydrogenation of esters. Both computational and experimental studies reveal that Cu–Hδ− and SiO–Hδ+ species would be formed at the Cu–O–SiOx interface upon H2 dissociation, thus promoting the ester hydrogenation by stablizing the transition states. Based on the proposed catalytic mechanism, encapsulting copper phyllosilicate nanotubes with mesoporous silica followed by hydrogen reduction is developed as an effective method to create a practical Cu nanocatalyst with abundant Cu-O-SiOx interfaces. The catalyst exhibits the best performance in the hydrogenation of dimethyl oxalate to ethylene glycol among all reported Cu catalysts.We thank the National Key R&D Program of China (2017YFA0207302, 2017YFA0207303, 2017YFA0206801), the NNSF of China (21731005, 21420102001, 21721001, 21333008, 21373167, 21573178), and the Fundamental Research Funds for the Central Universities (20720160046) for financial support. 研究工作得到了科技部、国家自然科学基金委和教育部，中科院先导项目，国家重点研发计划，分子反应动力学国家重点实验室开放课题基金等项目的资助