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161.
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Kiesel N Schmid C Weber U Tóth G Gühne O Ursin R Weinfurter H 《Physical review letters》2005,95(21):210502
Linear-optics quantum logic operations enabled the observation of a four-photon cluster state. We prove genuine four-partite entanglement and study its persistency, demonstrating remarkable differences from the usual Greenberger-Horne-Zeilinger (GHZ) state. Efficient analysis tools are introduced in the experiment, which will be of great importance in further studies on multiparticle entangled states. 相似文献
164.
Lanthanum-europium-copper oxides of composition La2?x Eu x CuO4 with structures related to those of the high temperature superconducting oxides have been prepared by solid state reactions between the component oxides in air. The X-ray powder diffraction data demonstrate that an orthorhombic to tetragonal structural transformation occurs at compositions betweenx=0.5 andx=0.8. The151Eu Mössbauer spectra show that europium is present in all phases as Eu3+. Thermal analysis studies in hydrogen show that a two-step reduction process occurs in the lanthanum-europium-copper oxides with the orthorhombic type structure.151Eu Mössbauer spectroscopy shows that the process does not involve the reduction of the lanthanide ion. 相似文献
165.
Clive S. Penkett Rupert O. Sims Lee Kingston Lauriane Dray Jason Lai Peter B. Hitchcock 《Tetrahedron》2006,62(14):3423-3434
Substituted benzene derived meta photocycloadducts have been shown to undergo a fragmentation/arylation reaction under Heck reaction conditions to give bridged bicyclo[3.2.1] compounds in a highly atom-efficient manner. When an anisole derived meta photocycloadduct is used, a bridgehead ketone is generated. However, if an alkylbenzene derived meta photocycloadduct is used, a bridgehead alkene is formed. This strategy has been used to create novel enol ether and transient allyl silane compounds. 相似文献
166.
Russell RJ Murray JB Lentzen G Haddad J Mobashery S 《Journal of the American Chemical Society》2003,125(12):3410-3411
The ribosome is an important target for aminoglycoside antibiotics; however, the clinical effectiveness of aminoglycosides has diminished due to bacterial resistance mechanisms. Here we report the X-ray structure of a novel synthetic aminoglycoside bound to the A site of the ribosome, its target for manifestation of activity. The structure validates the in silico design paradigms for the antibiotic and reveals the molecular interactions made by this novel antibiotic in prokaryotes. 相似文献
167.
Abstract— The absolute action spectrum has been determined for photoenzymatic splitting of cyclobutadipyrimidines ("pyrimidine dimers") from natural DNA, and from the synthetic polydeoxyribonucleotides poly(dA)·poly(dT) (forming only cyclobutadithymine) and poly(dG)·poly(dC) (forming only cyclobutadicytosine). These action spectra differ strikingly from each other, even when using the same enzyme preparations. On the other hand, the action spectrum for splitting cyclobutadithymine in natural DNA containing "dimers" of only this one type closely resembles the action spectrum for splitting the total mixture of "dimer" types in natural DNA, and is entirely different from the spectrum for splitting of the same photoproduct from poly(dA)·poly(dT). These results mean that the action spectrum is not simply the absorption spectrum of a chromophore carried by the photoreactivating enzyme, nor is it solely determined by the nature of the substrate photoproduct. It is at least partly determined by the over-all polynueleotide structure (viz. exact helical dimensions, pattern of neighboring bases to the "dimers," or both), affecting a ground state interaction between the enzyme and substrate in the enzyme-substrate complex. 相似文献
168.
The feasibility of mode-selective excitation with broadband femtosecond laser pulses is demonstrated for toluene in liquid phase. A learning-loop optimal control scheme was applied to a stimulated Raman excitation process. Modifications of the phase shape of one of the exciting pulses resulted in dramatic changes of the mode distribution reflected in coherent anti-Stokes Raman spectra. An evolutionary algorithm guided the coherent excitation process to a selective enhancement or suppression of one or more vibrational modes over the complete coherence lifetime spanning several picoseconds. New ways of spectral filtering as well as exciting possibilities of mode-selective studying of chemical reaction dynamics are indicated. 相似文献
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170.
Günther J. Redhammer Georg Roth Gerold Tippelt Manfred Bernroider Werner Lottermoser Georg Amthauer Rupert Hochleitner 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(3):i24-i28
The structure of the basic iron phosphate rockbridgeite [iron manganese zinc tris(phosphate) pentahydroxide] was reinvestigated with special emphasis on the cation distribution deduced from new X‐ray and 57Fe Mössbauer data. Rockbridgeite is orthorhombic, space group Cmcm, and shows three different Fe sites, one with symmetry, another with m symmetry and the third in a general position. One phosphate group has the P atom on a site with m symmetry, while the other has the P atom at a site with mm symmetry. Two Fe sites are fully occupied by ferric iron, while Mn3+ and Fe2+ are situated at a third, principally Fe, site. Structural data, bond‐valence sums and polyhedral distortion parameters suggest a new interpretation of the rockbridgeite 57Fe Mössbauer spectrum. 相似文献