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91.
Skaropoulos NC Yagridou HD Chrissoulidis DP 《The Journal of the Acoustical Society of America》2003,113(6):3001-3011
An exact, analytical solution is developed for the problem of acoustic-wave scattering from a cluster of ideal, gaseous, spherical bubbles in an unbounded, homogeneous, host fluid. This solution takes into account all modes of oscillation of the bubbles as well as all interactions between them; it is applicable to a wide range of bubble sizes and excitation frequencies. In the low frequency regime, the theory of this paper is shown to reduce to the "monopole" approximation, the effect of higher-order modes being non-negligible only for very small bubble-to-bubble separations. A numerical study of interactive backscattering from small clusters, comprising up to three ideal bubbles, is presented. Interactions between the bubbles are shown to produce downward shifts in the resonance frequency of the cluster, when the scattering configuration is symmetric. Furthermore, asymmetries of the scattering configuration are shown to generate sharp resonances at frequencies above the resonance of the symmetric mode. The results of this paper agree with previous theoretical and experimental work. 相似文献
92.
QM/MM calculations show that the potency of a range of inhibitors of adenosine deaminase correlates with the relative stability of the reaction intermediate at the active site, rather than with the inhibitor binding energy. 相似文献
93.
Murrie M Biner D Stoeckli-Evans H Güdel HU 《Chemical communications (Cambridge, England)》2003,(2):230-231
The role of temperature in the formation of high nuclearity nickel(II) citrate spin clusters is explored, revealing how changes in structure and hence magnetic properties can be triggered through desolvation and ligand reorganisation. 相似文献
94.
Hervé G Hahn DU Hervé AC Goodworth KJ Hill AM Hailes HC 《Organic & biomolecular chemistry》2003,1(2):427-435
Methodologies to access water soluble large ringed calixarenes in good yield using efficient synthetic procedures have been investigated. Symmetrical partial functionalisations at the lower rim are described using activated [n]ethylene glycol chains and the addition behaviour contrasted with that of bromoalkanenitriles which proceeds with no observed regioselectivity. Full functionalisations of the calixarenes bearing hydrophilic groups are then investigated and a two-step procedure established which appears to be generally applicable for the addition of different [n]ethylene glycol chains. Furthermore, difunctionalisation under different reaction conditions are described. Throughout, strategies for the characterisation of these high mass compounds are outlined. 相似文献
95.
[reaction: see text] The conjugate addition of dithiols to bis-ynones generates a versatile masked 1,3,5-triketone platform. These functional units are useful intermediates for the synthesis of oxygen-containing heterocycles commonly found in polyketide natural products. The tetrahydropyranyl fragments of the marine macrolides Lyngbouilloside and Callipeltoside A have been synthesized with use of this methodology. 相似文献
96.
The fully-oxidized surface that forms on (1 1 1) oriented Ni3Al single crystals, with and without Pt addition, at 300-900 K under oxygen pressures of ca. 10−7 Torr was studied using XPS, AES, and LEIS. Two main types of surfaces form, depending upon oxidation temperature. At low-temperature, the predominant oxide is NiO, capped by a thin layer of aluminum oxide, which we refer to generically as AlxOy. At high-temperature (i.e., 700-800 K), NiO is replaced by a thick layer of AlxOy. By comparing samples that contain 0, 10 and 20 at.% Pt in the bulk, we find that the effect of Pt is to: (1) reduce the maximum amount of both NiO and AlxOy; and (2) shift the establishment of the thick AlxOy layer to lower temperatures. Platinum also decreases the adsorption probability of oxygen on the clean surface. 相似文献
97.
Experimental evidence for surface segregation of Pt at (1 1 1) surfaces of ternary (Pt, Ni)3Al alloys is presented, based upon Auger electron spectroscopy, low energy ion scattering, and angle-resolved X-ray photoelectron spectroscopy. Density functional calculations in the dilute limit confirm that Pt segregation is energetically favored. 相似文献
98.
99.
Helen C. Aspinall Oliver BeckinghamMichael D. Farrar Nicholas Greeves Christopher D. Thomas 《Tetrahedron letters》2011,52(40):5120-5123
A diverse range of chiral and achiral oxazolyl ligands, which have many applications including catalysis and luminescent devices, are synthesized simply in three steps from readily available and inexpensive phenol and amino alcohol starting materials. The method can be applied to ligands with electron-donating/-withdrawing and sterically demanding/undemanding substituents, and can conveniently be scaled up to >25 g of product. 相似文献
100.
Abdolreza Rezaeifard Maasoumeh Jafarpour Hossein KavousiMahboubeh Alipour Helen Stoeckli-Evans 《Polyhedron》2011,30(13):2303-2309
Benzyltributylammonium periodate (BzBu3NIO4) was prepared easily in high yield in neat water. The compound crystallized with two cations and two anions per asymmetric unit and a space group of Pna21 was determined by single-crystal X-ray diffraction. It was used practically in the clean and selective epoxidation of olefins and oxygenation of saturated hydrocarbons catalyzed by manganese (III) porphyrins in water/ethanol as a green media. The catalyst could be reused without noticeable loss of activity, and the oxidant’s by-product (BzBu3NIO3) could also be reused. The efficiency of the oxidation system depends critically upon the steric hindrances and electronic structures of both the nitrogen donors and Mn-catalysts. Some evidences suggest the involvement of a high valent Mn-oxo species as well as a six-coordinate [(L)(Por)Mn-OIO3] complex in the oxidation reactions. 相似文献