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61.
Interactions between two Keggin-type lacunary polyoxometalates (POMs), PW11O and SiW11O, and pre-formed citrate-protected colloidal Ag nanoparticles (NPs) were studied by surface-enhanced Raman scattering (SERS) and UV-Vis spectroscopies. Clear SERS evidence of displacing the originally surface-bound citrate ions by the subsequently added POMs indicates a stronger metal–ligand interaction between the POMs and the Ag NPs. Accompanied red-shifts in the surface plasma peak position of the Ag NPs were also observed for both POMs. The simultaneous presence of a number of SERS vibrational bands which can be assigned to vibrational modes of the POM molecule suggests that its overall structure is intact upon adsorption. Based on the SERS observations, a bonding between the penta-dentate aperture of the POMs and the Ag NP surface was proposed.Dedicated to the retirement of Michael Pope. 相似文献
62.
We report single molecule fluorescence studies of the diffusion of individual multiple fluorophore-labeled antibodies in solution, which show that a trapping potential of about 3.6 k(B)T can be obtained at laser powers below 1 mW with resonant excitation. Individual antibodies can be trapped for up to 140 ms, and bound antibodies can also be used to trap a single virion for up to 1 s. Selective resonance trapping to sort and manipulate fluorophore-labeled biomolecules and complexes may be possible. 相似文献
63.
Harutyunyan SR López F Browne WR Correa A Peña D Badorrey R Meetsma A Minnaard AJ Feringa BL 《Journal of the American Chemical Society》2006,128(28):9103-9118
The mechanism of the enantioselective 1,4-addition of Grignard reagents to alpha,beta-unsaturated carbonyl compounds promoted by copper complexes of chiral ferrocenyl diphosphines is explored through kinetic, spectroscopic, and electrochemical analysis. On the basis of these studies, a structure of the active catalyst is proposed. The roles of the solvent, copper halide, and the Grignard reagent have been examined. Kinetic studies support a reductive elimination as the rate-limiting step in which the chiral catalyst, the substrate, and the Grignard reagent are involved. The thermodynamic activation parameters were determined from the temperature dependence of the reaction rate. The putative active species and the catalytic cycle of the reaction are discussed. 相似文献
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67.
RebeccaJ. Browne DavidA. Buckingham CharlesR. Clark JosephineA. McKeon W.Gregory Jackson 《Helvetica chimica acta》2003,86(1):13-28
Properties indirectly determined, or alluded to, in previous publications on the titled isomers have been measured, and the results generally support the earlier conclusions. Thus, the common five‐coordinate intermediate generated in the OH?‐catalyzed hydrolysis of exo‐ and endo‐[Co(dien)(dapo)X]2+ (X=Cl, ONO2) has the same properties as that generated in the rapid spontaneous loss of OH? from exo‐ and endo‐[Co(dien)(dapo)OH]2+ (40±2% endo‐OH, 60±2% exo‐OH) and an unusually large capacity for capturing (R=[CoN3]/[CoOH][]=1.3; exo‐[CoN3]/endo‐[CoN3]=2.1±0.1). Solvent exchange for spontaneous loss of OH? from exo‐[Co(dien)(dapo)OH]2+ has been measured at 0.04 s?1 (k1, 0.50M NaClO4, 25°) from which similar loss from the endo‐OH isomer may be calculated as 0.24 s?1 (k2). The OH?‐catalyzed reactions of exo‐ and endo‐[Co(dien)(dapo)N3]2+ result in both hydrolysis of coordinated via an OH?‐limiting process =153 M ?1 s?1; =295 M ?1 s?1; KH=1.3±0.1 M ?1; 0.50M NaClO4, 25.0°) and direct epimerization between the two reactants =33 M ?1 s?1; =110 M ?1 s?1; 1.0M NaClO4, 25.0°). Comparisons are made with other rapidly reacting CoIII‐acido systems. 相似文献
68.
Use of experiment and an inverse method to study interface heat transfer during solidification in the investment casting process 总被引:5,自引:0,他引:5
A technique to determine the thermal boundary conditions existing during the solidification of metallic alloys in the investment casting process is presented. Quantitative information about these conditions is needed so that numerical models of heat transfer in this process produce accurate results. In particular, the variation of the boundary conditions both spatially and temporally must be known. The method used involves the application of a new inverse heat conduction method to thermal data recorded during laboratory experiments of aluminium alloy solidification in investment casting shell moulds. The resultant heat transfer coefficient for the alloy/mould interface is calculated. An experimental programme to determine requisite mould thermal properties was also undertaken. It was observed that there is significant variation of the alloy/mould heat transfer coefficient during solidification. It is found to be highly dependent on the alloy type and on the vertical position below the initial free surface of the liquid metal. The aluminium casting alloys used in this study were 413, A356, 319 (Aluminum Association designations), and commercially pure aluminium. These alloys have significantly different freezing ranges. In particular, it was found that alloys with a high freezing range solidify with rates of heat transfer to the mould which are very sensitive to metallostatic head. 相似文献
69.
C. Browne R. W. Shaffer E. Wathelet L. Ramcle A. Noll F. Bolz H. Fiedler M. D. Reuben S. Köhler F. Noss H. Sadler A. R. Matthis B. von Possaner A. Weber K. Hang K. Ramse E. Sutermeister E. Richter V. Gruenman W. Brecht E. Helmer L. K. Arnold W. Breeht F. L. Goodall J. M. Jarmus W. R. Willets 《Analytical and bioanalytical chemistry》1935,101(11-12):457-464
70.
Entanglement distillation aims at preparing highly entangled states out of a supply of weakly entangled pairs, using local
devices and classical communication only. In this note we discuss the experimentally feasible schemes for optical continuous-variable
entanglement distillation that have been presented in [D.E. Browne, J. Eisert, S. Scheel, and M.B. Plenio, Phys. Rev. A 67, 062320 (2003)] and [J. Eisert, D.E. Browne, S. Scheel, and M.B. Plenio, Annals of Physics (NY) 311, 431 (2004)]. We emphasize their versatility in particular with regards to the detection process and discuss the merits of
the two proposed detection schemes, namely photo-detection and homodyne detection, in the light of experimental realizations
of this idea becoming more and more feasible.
The text was submitted by the authors in English. 相似文献