检索结果-南通市图书馆

The Combinatorial Approach to Asymmetric Hydrogenation: More Miles out of Monophos

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

复旦学报（自然科学版） 2005年第5期44卷 829-830页

作者： johannes G. de Vries DSM Research DSM Pharma Chemicals-Advanced Synthesis Catalysis & Development P.O. Box 18 6160 MD Geleen The Netherlands.

In custom manufacturing time-to-market is of overriding importance. Thus, asymmetric hydrogenation will be applied only if an appropriate catalyst can be found in a very short period of time. For this reason we have build up a full-scale capability for High Throughput Experimentation, encompassing several robot systems. As ligand synthesis was the last remaining barrier we have explored, together with the University of Groningen, the use of simple monodentate ligands, such as MonoPhosTM. These ligands can be synthesised in two chemical steps, from BINOL, PCl3 and an ***, very high enantioselectivities can be obtained in the asymmetric hydrogenation of α-and β-dehydro-amino acids and esters, aromatic enamides, itaconic acid and ester[1]. See Scheme 1 and 2(at page 830).

关键词：加氢催化同质催化剂铑氨基磷酸脂

维普期刊数据库

Effect of bed load supply on sediment transport in mountain streams

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2017年第2期32卷 240-252页

作者： johannes Kammerlander Bernhard Gems Daniel Kβler Markus Aufleger Unit of Hydraulic Engineering University of Innsbruck Austrian Research Centre for Forests Department of Natural Hazards 3. BERNARD Ingenieure ZT GmbH

Mountain streams with their tributary torrents build the upper part of the fluvial *** are important regarding the transfer of sediment from headwaters to lower *** are typically steep with wide grain size distributions,ranging from fine sand up to large boulders,and a stabilized bed *** streams often are supply-limited with respect to mobile bed load,which needs to be addressed when bed load transport equations are applied to such *** better understand supply limitation,laboratory experiments highlighting the effect of bed load supply on incipient motion and bed load transport rate are *** tests were done in which fine bed load was supplied to a previously armored channel bed,with flow conditions ranging from one-third to twice the critical discharge for the bed *** flows not exceeding the critical discharge,the time series of the bed load transport rate at the downstream model boundary featured consistent patterns which are attributed to distinct phases:(i) a temporal lag,(ii) an equilibrium state,and(iii) a post-supply *** load transport occurred even at flows distinctly below that for incipient motion of the bed ***,with the mass of total bed load outflow approaching the supply amount,the mass did not exclusively consist of supplied *** coarser the supplied bed load,the more sediment was mobilized from the bed *** higher flows,processes *** bed load outflow exceeded the supply amount and the break-up of the armor layer caused a refining of the bed surface.

关键词： Bed load transport Bed load supply Mountain stream Experimental modeling

三氧化钨催化糖分子选择裂解新机理及其对生物质利用的重要意义

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Catalysis 2023年第3期46卷 1-3页

作者： johannes A.Lercher 德国慕尼黑工业大学德国加兴美国西北太平洋国家实验室美国里奇兰

糖类化合物催化转化合成燃料和化学品为现有化石路线提供了可行的替代方案.碳化钨、氧化钨和钨酸等钨基催化剂具有催化糖分子碳-碳键选择性断裂生成乙二醇、丙二醇等C_(2,3)产物的独特性能.然而,对该催化反应的机理还一直缺乏明确的认识... 详细信息

糖类化合物催化转化合成燃料和化学品为现有化石路线提供了可行的替代方案.碳化钨、氧化钨和钨酸等钨基催化剂具有催化糖分子碳-碳键选择性断裂生成乙二醇、丙二醇等C_(2,3)产物的独特性能.然而,对该催化反应的机理还一直缺乏明确的认识.最近北京大学刘海超团队报道,糖分子的羰基、α-和β-羟基与三氧化钨(WO_(3))表面的两个邻近钨原子(W-O-W结构)配位,形成一种双钨三齿螯合物;该螯合物作为反应的关键中间体,引发羰基β-位的碳-碳键断裂,从而实现糖分子的选择裂解.该新反应机理不仅为糖化学提供了新的认识,而且为糖基生物质提供了一个经乙醇醛、甘油醛等C_(2,3)中间体转化为化学品的有效策略.固体核磁表征结果表明,吸附到WO_(3)表面的^(13)Cc标记葡萄糖的C1、C2和C3三个碳原子与表面钨原子形成了C-O-W键,从而在去屏蔽作用下化学位移向低场移动,说明糖分子需要羰基以及α-和β-羟基三个官能团共同参与才具有反应活性.催化反应结果表明,含有W-O-W结构的钨基化合物均表现出催化糖分子裂解生成C_(2,3)产物的活性,例如:仲钨酸铵、磷钨酸盐和钨青铜等均相、多相催化剂都能有效地将葡萄糖转化为乙二醇.通过理论计算分别模拟L-苏阿糖和2-脱氧-L-苏阿糖在WO_(3)(001)晶面上的反应过程,发现前者形成的L-苏阿糖-三氧化钨三齿螯合物,在后续碳-碳键选择性断裂生成一分子乙醇醛和一分子表面结合的乙烯二醇中间物种过程中,只有-0.01 eV的能量变化以及0.53 eV的能垒;而2-脱氧-L-苏阿糖则不同,由于缺乏α-羟基,后续碳-碳键断裂过程中需要吸收0.20 eV的能量和克服0.62 eV的能垒.计算结果进一步证明了糖-三氧化钨三齿螯合物中间体和糖分子α-羟基在反应中发挥了至关重要的作用.刘海超团队这项开拓性的工作揭示了三氧化钨催化糖分子碳-碳键选择性断裂的新机理,扩展了教科书中对经典逆羟醛缩合反应机理的描述.在该机理指导下,来源多样、纯度不同和结构各异的糖类化合物均能够在钨基催化剂作用下经乙醇醛和甘油醛等C_(2,3)中间体转化为化学品,从而为糖基生物质高效利用提供了具有实用意义的新策略.这正如现代石油化工所普遍采用的方法,首先将石油原料经过催化裂化或水汽裂解转化为乙烯、丙烯等C_(2,3)中间体,然后进一步转化为下游丰富的化学品.因此,该项研究工作对于纤维素、半纤维素等糖基生物质的高效转化利用具有重要意义.

关键词：生物质糖三氧化钨碳–碳键断裂非经典逆羟醛缩合反应机理

维普期刊数据库

Colon capsule endoscopy: Current status and future directions

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2014年第44期20卷 16596-16602页

作者： Andrea O Tal johannes Vermehren J?rg G Albert Department of Internal Medicine I University Hospital Frankfurt

Colon capsule endoscopy(CCE; Pill Cam Colon; Given Imaging; Yoqneam, Israel) is a minimally invasive wireless technique for the visualization of the colon. With the recent introduction of the second generation colon capsule the diagnostic accuracy of CCE for polyp detection has significantly improved and preliminary data suggest it may be useful to monitor mucosal inflammation in patients with inflammatory bowel disease. Limitations include the inability to take biopsies and the procedural costs. However, given the potentially higher acceptance within an average risk colorectal cancer(CRC) screening population, its usefulness as a screening tool with regard to CRC prevention should be further evaluated.

关键词： Capsule endoscopy Endoscopy Colon capsule endoscopy Colonoscopy Colorectal cancer Colon Colonic capsule endoscopy Inflammatory bowel disease

Predicting the next move: tracking the complexity of lung cancer evolution and metastasis

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Signal Transduction and Targeted Therapy 2023年第9期8卷 3885-3887页

作者： Carina Lorenz Axel M.Hillmer johannes Brägelmann University of Cologne Faculty of Medicine and University Hospital CologneDepartment of Translational GenomicsCologneGermany University of Cologne Faculty of Medicine and University Hospital CologneMildred Scheel School of Oncology CologneCologneGermany University of Cologne Faculty of Medicine and University Hospital CologneCenter for Molecular Medicine CologneCologneGermany University of Cologne Faculty of Medicine and University Hospital CologneInstitute of PathologyCologneGermany

In a series of seven papers in Nature and Nature Medicine,the TRACERx study group presents multi-omic analyses of 421 non-small cell lung cancer(NSCLC)patients,which have yielded a comprehensive map of intratumor heterogeneity(ITH)and lung cancer evolutionary trajectories at an unprecedented level of detail.1–7 The in-depth molecular data,and their subsequent integrated analyses,hold the potential to not only shine light on lung cancer progression but also influence a broad spectrum of scientific disciplines,research fields,and clinical oncology,thereby enhancing our understanding of cancer in general.

关键词： lung cancer metastasis

Efficient training of ANN potentials by including atomic forces via Taylor expansion and application to water and a transition-metal oxide

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

npj Computational Materials 2020年第1期6卷 1205-1218页

作者： April M.Cooper johannes Kästner Alexander Urban Nongnuch Artrith School of Chemistry University of St AndrewsSt AndrewsUK Institute for Theoretical Chemistry University of StuttgartStuttgartGermany Department of Chemical Engineering Columbia UniversityNew YorkNYUSA

Artificial neural network(ANN)potentials enable the efficient large-scale atomistic modeling of complex materials with near firstprinciples *** molecular dynamics simulations,accurate energies and interatomic forces are a prerequisite,but training ANN potentials simultaneously on energies and forces from electronic structure calculations is computationally ***,we introduce an efficient alternative method for the training of ANN potentials on energy and force information,based on an extrapolation of the total energy via a Taylor *** translating the force information to approximate energies,the quadratic scaling with the number of atoms exhibited by conventional force-training methods can be avoided,which enables the training on reference datasets containing complex atomic structures.

关键词： forces enable atomic

Chronic peripheral inflammation: a possible contributor to neurodegenerative diseases

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Neural Regeneration Research 2021年第9期16卷 1711-1714页

作者： Patrick Süβ Addison J.Lana johannes C.M.Schlachetzki Department of Molecular Neurology Friedrich-Alexander-University Erlangen-NürnbergUniversity Hospital ErlangenErlangenGermany Department of Cellular and Molecular Medicine University of California San DiegoLa JollaCAUSA

The contribution of chronic peripheral inflammation to the pathogenesis of neurodegenerative diseases is an outstanding question. Sustained activation of the peripheral innate and adaptive immune systems occurs in the context of a broad array of disorders ranging from chronic infectious diseases to autoimmune and metabolic diseases. In addition, progressive systemic inflammation is increasingly recognized during aging. Peripheral immune cells could potentially modulate the cellular brain environment via the secretion of soluble molecules. There is an ongoing debate whether peripheral immune cells have the potential to migrate into the brain under certain permissive circumstances. In this perspective, we discuss the possible contribution of chronic peripheral inflammation to the pathogenesis of age-related neurodegenerative diseases with a focus on microglia, the resident immune cells of the brain parenchyma.

关键词： aging Alzheimer's disease inflammation innate immune system microglia neurodegeneration Parkinson's disease

维普期刊数据库

Experimental investigation on local shear stress and turbulence intensities over a rough non-uniform bed with and without sediment using 2D particle image velocimetry

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2020年第2期35卷 193-202页

作者： Petr Lichtneger Christine Sindelar johannes Schobesberger Christoph Hauer Helmut Habersack CD-Laboratory of Sediment Research and Management Institute of Water ManagementHydrology and Hydraulic EngineeringDepartment Water-Atmosphere-EnvironmentUniversity of Natural Resources and Life Sciences

The current work focuses on locally resolving velocities,turbulence,and shear stresses over a rough bed with locally non-uniform character.A nonporous subsurface layer and fixed interfacial sublayer of gravel and sand were water-worked to a nature-like bed form and additionally sealed in a hydraulic ***-dimensional Particle Image Velocimetry(2 D-PIV) was applied in the vertical plane of the experimental flume *** with clear water and weak sediment transport were done under slightly supercritical flow to ensure sediment transport conditions without formation of considerable sediment deposits or *** study design included analyzing the double-averaged flow parameters of the entire measurement domain and investigating the flow development at 14 consecutive vertical *** geometrical variabilities as well the presence of sediment were mainly reflected in the vertical velocity *** the vertical velocity decreased over the entire depth in presence of sediment transport,the streamwise velocity profile was reduced only within the interfacial *** the region with decelerating flow conditions,however,the streamwise velocity profile systematically increased along the entire depth *** increase in the main velocity(reduction of flow resistance)correlated with a decrease of the turbulent shear and main normal ***,effects of rough bed smoothening and drag force reduction were experimentally documented within the interfacial sublayer due to mobile ***,the current study leads to the conclusion that in nonuniform flows the maximum Reynolds stress values are a better predictor for the bed shear stress than the linearly extrapolated Reynolds stress *** is an important finding because,in natural flows,uniform conditions are rare.

关键词： Turbulence measurement Local bed shear stress Sediment transport and flow interaction Hydraulic flume experiment Particle image velocimetry

Association of inducible nitric oxide synthetase genotype and Helicobacter pylori infection gastric cancer risk may be due to faulty primer design

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2013年第3期19卷 429-430页

作者： Amin Talebi Bezmin Abadi johannes G Kusters Department of Medical Microbiology University Medical Center Utrecht3584 CX UtrechtThe Netherlands

Rafiei et al recently described an association between the presence of the C150T polymorphism of the induc-ible nitric oxide synthase(iNOS)gene and Helicobacter pylori(***)induced gastric *** we used primer-BLAST to find the polymerase chain reaction (PCR)product that would be generated by the primers used by these authors no products against any of the sequences present in the GenBank database were *** analysis of the iNOS sequences present in the GenBank suggest that the result from their study might come from a faulty primer design and may thus represent an *** they may be correct and have identified a truly interesting explanation for the mechanism whereby *** induces gastric cancer but some additional experiments would be in order to exclude the possibility of a PCR artifact.

关键词： Helicobacter pylori Polymorphism Inducible nitric oxide synthase