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991.
Stephan Felder Dr. Sandra Dreisigacker Dr. Stefan Kehraus Edith Neu Prof. Dr. Gabriele Bierbaum Patrick R. Wright Prof. Dr. Dirk Menche Dr. Till F. Schäberle Prof. Dr. Gabriele M. König 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(28):9319-9324
Marine myxobacteria (Enhygromyxa, Plesiocystis, Pseudoenhygromyxa, Haliangium) are phylogenetically distant from their terrestrial counterparts. Salimabromide is the first natural product from the Plesiocystis/Enhygromyxa clade of obligatory marine myxobacteria. Salimabromide has a new tetracyclic carbon skeleton, comprising a brominated benzene ring, a furano lactone residue, and a cyclohexane ring, bridged by a seven‐membered cyclic moiety. The absolute configuration was deduced from experimental and calculated CD data. Salimabromide revealed antibiotic activity towards Arthrobacter cristallopoietes. 相似文献
992.
993.
Ru–bis(pyridine)pyrazolate (bpp)‐Based Water‐Oxidation Catalysts Anchored on TiO2: The Importance of the Nature and Position of the Anchoring Group 下载免费PDF全文
Dr. Laia Francàs Dr. Craig Richmond Pablo Garrido‐Barros Dr. Nora Planas Dr. Stephan Roeser Dr. Jordi Benet‐Buchholz Dr. Lluís Escriche Dr. Xavier Sala Prof. Dr. Antoni Llobet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(15):5261-5268
Three distinct functionalisation strategies have been applied to the in,in‐[{RuII(trpy)}2(μ‐bpp)(H2O)2]3+ (trpy=2,2′:6′,2′′‐terpyridine, bpp=bis(pyridine)pyrazolate) water‐oxidation catalyst framework to form new derivatives that can adsorb onto titania substrates. Modifications included the addition of sulfonate, carboxylate, and phosphonate anchoring groups to the terpyridine and bis(pyridyl)pyrazolate ligands. The complexes were characterised in solution by using 1D NMR, 2D NMR, and UV/Vis spectroscopic analysis and electrochemical techniques. The complexes were then anchored on TiO2‐coated fluorinated tin oxide (FTO) films, and the reactivity of these new materials as water‐oxidation catalysts was tested electrochemically through controlled‐potential electrolysis (CPE) with oxygen evolution detected by headspace analysis with a Clark electrode. The results obtained highlight the importance of the catalyst orientation with respect to the titania surface in regard to its capacity to catalytically oxidize water to dioxygen. 相似文献
994.
Micromechanical fast quasi‐static detection of α and β relaxations with nanograms of polymer 下载免费PDF全文
Sanjukta Bose Silvan Schmid Tom Larsen Stephan Sylvest Keller Anja Boisen Kristoffer Almdal 《Journal of Polymer Science.Polymer Physics》2015,53(15):1035-1039
Micromechanical string resonators are used as a highly sensitive tool for the detection of glass transition (Tg or α relaxation) and sub‐Tg (β relaxation) temperatures of polystyrene (PS) and poly (methyl methacrylate) (PMMA). The characterization technique allows for a fast detection of mechanical relaxations of polymers with only few nanograms of sample in a quasi‐static condition. The polymers are spray coated on one side of silicon nitride (SiN) microstrings. These are pre‐stressed suspended structures clamped on both ends to a silicon frame. The resonance frequency of the microstrings is then monitored as a function of increasing temperature. α and β relaxations in the polymer affect the net static tensile stress of the microstring and result in measureable local frequency slope maxima. Tg of PS and PMMA is detected at 91 ±2°C and 114 ±2°C, respectively. The results match well with the glass transition values of 93.6°C and 114.5°C obtained from differential scanning calorimetry of PS and PMMA, respectively. The β relaxation temperatures are detected at 30 ± 2°C and 33 ± 2°C for PS and PMMA which is in accordance with values reported in literature. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1035–1039 相似文献
995.
Stephan Ritter 《Physik in unserer Zeit》2011,42(4):166-167
996.
Aurelia Bouchez Adam Walters Holger S.P. Müller Matthias Ordu Frank Lewen Monika Koerber Sandrine Bottinelli Christian P. Endres Stephan Schlemmer 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(11):1148-1154
The rotational spectra of the two monosubstituted 13C isotopologues of the anti conformer of ethanol have been measured between 80–800 GHz using three different spectrometers at the Cologne Laboratory Astrophysics group. The dataset was constrained for fitting with a standard Watson-S reduction Hamiltonian by rejecting transitions from high-lying states showing significant perturbation with the gauche states and by averaging some small methyl torsional splits. This treatment is compatible with the needs for a first astrophysical research for which an appropriate set of predictions is given. 相似文献
997.
Lauren E. Longobardi Dr. Timothy C. Johnstone Rosalyn L. Falconer Dr. Christopher A. Russell Prof. Dr. Douglas W. Stephan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12665-12669
The hydroboration of phosphaalkynes with Piers’ borane (HB(C6F5)2) generated unusual phosphaalkenylboranes [RCH=PB(C6F5)2]2 that persisted as dimers in both solution and the solid state. These P2B2 heterocycles underwent ring opening when subjected to nucleophiles, such as pyridine and tert‐butylisocyanide, to yield monomeric phosphaalkenylborane adducts RCH=PB(C6F5)2(L). DFT calculations were performed to probe the nature of the interaction of phosphaalkynes with boranes. 相似文献
998.
Total Synthesis of Δ12‐Prostaglandin J3: Evolution of Synthetic Strategies to a Streamlined Process 下载免费PDF全文
Prof. Dr. K. C. Nicolaou Dr. Kiran Kumar Pulukuri Ruocheng Yu Dr. Stephan Rigol Dr. Philipp Heretsch Dr. Charles I. Grove Christopher R. H. Hale Dr. Abdelatif ElMarrouni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8559-8570
The total synthesis of Δ12‐prostaglandin J3 (Δ12‐PGJ3, 1 ), a reported leukemia stem cell ablator, through a number of strategies and tactics is described. The signature cross‐conjugated dienone structural motif of 1 was forged by an aldol reaction/dehydration sequence from key building blocks enone 13 and aldehyde 14 , whose lone stereocenters were generated by an asymmetric Tsuji–Trost reaction and an asymmetric Mukaiyama aldol reaction, respectively. During this program, a substituent‐governed regioselectivity pattern for the Rh‐catalyzed C?H functionalization of cyclopentenes and related olefins was discovered. The evolution of the synthesis of 1 from the original strategy to the final streamlined process proceeded through improvements in the construction of both fragments 13 and 14 , exploration of the chemistry of the hitherto underutilized chiral lactone synthon 57 , and a diastereoselective alkylation of a cyclopentenone intermediate. The described chemistry sets the stage for large‐scale production of Δ12‐PGJ3 and designed analogues for further biological and pharmacological studies. 相似文献
999.
1000.
Dempe Stephan Dinh Nguyen Dutta Joydeep Pandit Tanushree 《Mathematical Programming》2021,188(1):227-253
Mathematical Programming - In this paper we discuss the simple bilevel programming problem (SBP) and its extension, the simple mathematical programming problem under equilibrium constraints... 相似文献