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961.
Tomáš Malatinský Zsófia Puhová Matej Babjak Jana Doháňošová Ján Moncol Štefan Marchalín Róbert Fischer 《Tetrahedron letters》2018,59(43):3867-3871
Two new five-membered cyclic d-talo-configured nitrones were synthesized from d-mannose, and examined in 1,3-dipolar cycloadditions with vinyl acetate and vinylene carbonate. The stereoselectivity of the cycloadditions depends greatly on the protecting group of the vicinal diol attached to the nitrone C-5 carbon atom. Methyl protection resulted in limited syn/anti-selectivity, giving mixtures of the two isomeric exo-syn and exo-anti isoxazolidines in comparable amounts. On the other hand, the cyclohexylidene-substituted nitrone reacted more selectively in favour of the syn isomer. The difference in the diastereoselectivity was attributed to the specific spatial orientation of the nitrone C-5 substituent. 相似文献
962.
Stimulus‐Triggered Formation of an Anion–Cation Exciplex in Copper(I) Complexes as a Mechanism for Mechanochromic Phosphorescence
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Benjamin Hupp Dr. Jörn Nitsch Tanja Schmitt Dr. Rüdiger Bertermann Dr. Katharina Edkins Florian Hirsch Prof. Dr. Ingo Fischer Michael Auth Dr. Andreas Sperlich Priv.‐Doz. Dr. Andreas Steffen 《Angewandte Chemie (International ed. in English)》2018,57(41):13671-13675
The investigation of the mechanisms of mechanochromic luminescence is of fundamental importance for the development of materials for photonic sensors, data storage, and luminescence switches. The structural origin of this phenomenon in phosphorescent molecular systems is rarely known and thus the formulation of structure–property relationships remains challenging. Changes in the M–M interactions have been proposed as the main mechanism with d10 coinage metal compounds. Herein, we describe a new mechanism—a mechanically induced reversible formation of a cation–anion exciplex based on Cu–F interactions—that leads to highly efficient mechanochromic phosphorescence and unusual large emission shifts from UV‐blue to yellow for CuI complexes. The low‐energy luminescence is thermo‐ and vaporesponsive, thus allowing the generation of white light as well as for recovering the original UV‐blue emission. 相似文献
963.
Yuhua Zhong Luchong Zhang Andreas Fischer Liang Wang Dietmar Drummer 《高分子科学杂志,A辑:纯化学与应用化学》2018,55(1):17-23
A novel thermally conductive Polyamide 6 (PA6) with good fire resistance was prepared by introducing a phosphorous-nitrogen flame retardant (FR) and platelet-shaped hexagonal boron nitride (hBN) into the matrix. With high thermal conductivity and good flame retardancy, the material is suitable for applications in electronic and electrical devices. The limiting oxygen index (LOI) changes for various loadings content of FR. However this formulation still does not show an ideal fire resistance, due to the appearance of melt dripping behavior during the UL 94 test. With the extra introduction of 3 vol% and 5 vol% hBN, the melt dripping behavior during the burning process completely disappeared. The hBN also increased the thermal conductivity. Furthermore PA6 compounded with FR and hBN showed a better thermal stability than neat PA6. The morphology of the char residues was investigated by scanning electron microscopy (SEM). The flaky hBN acted as the framework in the char structure and the rigid hBN could effectively break the bubble-shaped char on the surface of the residues which resulted in the enhancement of the strength and compactness of the char. 相似文献
964.
Gartner B. Ackerbauer P. Breunlich W. H. Cargnelli M. Fischer A. Kammel P. King R. Kminek G. Lauss B. Marton J. Prymas W. Steininger E. Zmeskal J. Petitjean C. Chatellard D. Egger J. -P. Jeannet E. Hartmann F. J. Kosak A. Mühlbauer M. von Egidy T. Piller C. Schaller L. A. Schellenberg L. Schneuwly H. Thalmann Y. -A. Tresch S. Werthmüller A. 《Hyperfine Interactions》1996,101(1):249-255
Muon transfer from the ground state of muonic deuterium to a helium atom proceeds mainly via the formation of a muonic molecule in an excited state. A large number of decay X rays ( 6.8 keV) from these (dµHe)* molecules were observed for the4He as well as for the3He case. The time distributions of these X rays allow the determination of the ground state transfer rate. The simultaneous employment of Ge/Si-detectors and CCDs for the same target conditions allows the determination of the branching ratio of radiative to nonradiative decay for the first time. 相似文献
965.
966.
Agakichiev G Baur R Breskin A Chechik R Drees A Jacob C Faschingbauer U Fischer P Fraenkel Z Fuchs C Gatti E Glässel P Günzel T de los Heros CP Hess F Irmscher D Lenkeit B Olsen LH Panebrattsev Y Pfeiffer A Ravinovich I Rehak P Schön A Schukraft J Sampietro M Shimansky S Shor A Specht HJ Steiner V Tapprogge S Tel-Zur G Tserruya I Ullrich T Wurm JP Yurevich V 《Physical review letters》1995,75(7):1272-1275
967.
D. Eyl A. Frey H. G. Andresen J. R. M. Annand K. Aulenbacher J. Becker J. Blume-Werry Th. Dombo P. Drescher H. Fischer P. Grabmayr S. J. Hall P. Hartmann T. Hehl W. Heil J. Hoffmann J. D. Kellie F. Klein M. Meyerhoff Ch. Nachtigall M. Ostrick E. W. Otten R. O. Owens S. Plützer E. Reichert R. Rieger H. Schmieden R. Sprengard K. -H. Steffens Th. Walcher 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(2):211-214
The measurement of the polarisation transfer to the proton in the reactions $H(\vec e,e'\vec p)$ and $D(\vec e,e'\vec p)$ performed with longitudinally polarised electrons in quasi-free kinematics is presented. The coincidence measurement was executed atQ 2≈8fm ?2 using the 855 MeV, c.w. beam of the Mainz Microtron MAMI. The recoil polarisation was determined by means of a carbon analyser. The experiment shows that the binding of the nucleon does not modify the polarisationP x of the recoil proton within an error ofΔ P x/Px≈10%. The measured polarisation agrees with recent theoretical predictions. Implications for the measurement of the electric form factor of the neutron using the $D(\vec e,e'\vec n)$ reaction are discussed. 相似文献
968.
Solladié-Cavallo A Roche D Fischer J De Cian A 《The Journal of organic chemistry》1996,61(8):2690-2694
The effect of tBuP4, a strong and cation-free base, on the yield and diastereoselectivity of additions of thus formed "naked" alpha-sulfonyl carbanions to achiral butyraldehyde and chiral isopropylideneglyceraldehyde was studied. It has been found that with tBuP4 a reasonable yield ( approximately 55%) and a slightly better diastereoselectivity (72% of the anti diastreomer) are obtained with achiral and nonfunctionalized butyraldehyde while with isopropylideneglyceraldehyde the use of tBuP4 allowed us to greatly increase the yields (up to 95-100%) and the diastereoselectivities (83-89% of a single diastereomer over the four possible diastereomers). It was also shown that the extra oxygen atom in the alpha-position plays a determinant role in this effect. 相似文献
969.
970.
A. Kiejna Ph. Niedermann Ø. Fischer 《Applied Physics A: Materials Science & Processing》1990,50(3):331-338
The electron field emission from a metal covered with a thin layer of a semiconductor with electron affinity and dielectric constant is considered. The model takes into account the metal-semiconductor (Schottky) barrier of height b, the conduction current inside the semiconductor, and the band bending at the semiconductor-vacuum interface due to the external field penetration. For thick films under moderately high electric fields, the metal-semiconductor interface does not influence the emission behaviour whereas for thin films, the interface plays an important role, depending on the barrier heights. In particular, for /b<2/3 the I–V characteristics will, for strong fields, be dominated by the field emission process at the interface. In such cases important deviations from Fowler-Nordheim behaviour are found. 相似文献