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991.
The Advanced Photon Source (APS) looks forward to a period of growth in the coming years. Meanwhile, in April 2006, the APS reorganized its divisions, creating an X-ray Science Division (XSD), bringing science at the APS on a par with the accelerator, and sharing engineering and support services. The machine division, the Accelerator Systems Division, now includes all of the groups that operate and develop the machine and focus on future accelerator research. 相似文献
992.
993.
Stephan Faust Martin Goschütz Sebastian A. Kaiser Thomas Dreier Christof Schulz 《Applied physics. B, Lasers and optics》2014,116(1):183-194
Single crystal of La3Ga5.5Ta0.5O14 (LGT) containing intentionally 0.5 % of Ho3+ and 1 % of Yb3+ was grown by the Czochralski method. Examination of chemical composition of the grown crystal revealed that luminescent holmium and ytterbium ions are preferably retained in the melt and their actual concentrations are 0.12 and 0.24 %, respectively. Spectroscopic investigation performed encompassed IR host absorption spectra and Raman spectra at room temperature, optical absorption and luminescence spectra of Ho3+ and Yb3+ at room temperature and at 5 K, and luminescence decay curves at room temperature. It was found that all spectral bands recorded show important inhomogeneous line broadening. This feature was attributed to structural disorder inherent to the crystal lattice in which pentavalent Ta5+ ions occupy octahedral Ga(1) sites together with trivalent Ga3+ ions. Despite small concentrations of luminescent ions, the occurrence of nonradiative interaction that feeds the 5I6 and 5I7 levels of Ho3+ ions by transfer of an excitation from the 2F5/2 level of Yb3+ ions was evidenced. Based on examination of spectroscopic parameters evaluated, it was concluded that LGT:Ho, Yb may be considered as a potential intermediate-gain laser active material able to emit infrared radiation from the 5I7 → 5I8 transition of Ho3+ around 2 micrometres upon laser-diode pumping into Yb3+ absorption band. 相似文献
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996.
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
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998.
Ru–bis(pyridine)pyrazolate (bpp)‐Based Water‐Oxidation Catalysts Anchored on TiO2: The Importance of the Nature and Position of the Anchoring Group
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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
999.
Micromechanical fast quasi‐static detection of α and β relaxations with nanograms of polymer
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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
1000.
Stephan Ritter 《Physik in unserer Zeit》2011,42(4):166-167