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1.
Sanchez-sanz M; Blyth MG 《The Quarterly Journal of Mechanics and Applied Mathematics》2007,60(2):125-138
Unsteady, axisymmetric stagnation flow about a circular cylinderis examined when the far-field flow is a periodic function oftime with a fixed time average and an oscillatory part of prescribedamplitude and frequency. Solutions are computed for arbitraryvalues of the Reynolds number, quantifying the effects of surfacecurvature, and a frequency parameter based on the period ofthe far-field flow. It is found that solutions remain regularand periodic provided that the far-field amplitude lies belowa critical value. Above this value, solutions terminate in afinite-time singularity. The blow-up time is delayed by increasingthe curvature of the surface. These results are corroboratedby asymptotic predictions valid in the limits of small and largeamplitude and frequency. For large Reynolds number, the problemreduces to the two-dimensional stagnation-point flow againsta plane wall studied by previous authors. 相似文献
2.
Max Lagally 《Mathematische Annalen》1914,76(1):105-128
Ohne Zusammenfassung 相似文献
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The edge structure and stability of monolayer-high islands fabricated on Si(001) surfaces by scanning tunneling microscopy have been analyzed theoretically. In contrast to the edges of similar islands grown by depositing Si, the properties of edges of fabricated islands are determined by the length of the trench of dimers that are removed to create the island. We demonstrate the possibility of controlling the edge structure, and thus the stability, through a selective process of atom removal. 相似文献
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Fujikawa Y Akiyama K Nagao T Sakurai T Lagally MG Hashimoto T Morikawa Y Terakura K 《Physical review letters》2002,88(17):176101
The structure of Ge(105)-(1 x 2) grown on Si(105) is examined by scanning tunneling microscopy (STM) and first-principles calculations. The morphology evolution with an increasing amount of Ge deposited documents the existence of a tensile surface strain in Si(105) and its relaxation with increasing coverage of Ge. A detailed analysis of high-resolution STM images and first-principles calculations produce a new stable model for the Ge(105)-(1 x 2) structure formed on the Si(105) surface that includes the existence of surface strain. It corrects the model developed from early observations of the facets of "hut" clusters grown on Si(001). 相似文献
10.
S -nitrosothiols have many biological activities and may act as nitric oxide (NO) carriers and donors, prolonging NO half-life in vivo. In spite of their great potential as therapeutic agents, most S -nitrosothiols are too unstable to isolate. We have shown that the S -nitroso adduct of N -acetylcysteine (SNAC) can be synthesized directly in aqueous and polyethylene glycol (PEG) 400 matrix by using a reactive gaseous (NO/O2 ) mixture. Spectral monitoring of the S–N bond cleavage showed that SNAC, synthesized by this method, is relatively stable in nonbuf-fered aqueous solution at 25°C in the dark and that its stability is greatly increased in PEG matrix, resulting in a 28-fold decrease in its initial rate of thermal decomposition. Irradiation with UV light (λ= 333 nm) accelerated the rate of decomposition of SNAC to NO in both matrices, indicating that SNAC may find use for the photogeneration of NO. The quantum yield for SNAC decomposition decreased from 0.65 ± 0.15 in aqueous solution to 0.047 ± 0.005 in PEG 400 matrix. This increased stability in PEG matrix was assigned to a cage effect promoted by the PEG microenvironment that increases the rate of geminated radical pair recombination in the homolytic S–N bond cleavage process. This effect allowed for the storage of SNAC in PEG at −20°C in the dark for more than 10 weeks with negligible decomposition. Such stabilization may represent a viable option for the synthesis, storage and handling of S -nitrosothiol solutions for biomedical applications. 相似文献