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Conclusion The period-doubling route to chaos for a swirling vortex flow in an open cylindrical container, at an aspect ratio of 2, driven by a rotating bottom disk was recognized by using laser-Doppler velocimetry. The onset of periodic motion for the flow was found when Re was in the range between 1850 and 1900. The flow was subharmonically bifurcated into a double-period motion when Re was about 2150. When the Reynolds number was in the range from 2300 to 2400, the flow bifurcated again through the period-doubling mode. When the Reynolds number was further increased, the flow eventually showed chaotic motion. The existence of a free surface promotes the onset of periodicity, and the difference of the critical Reynolds number with and without a free surface was estimated to be about 600.This work was supported by the National Science Council of the Republic of China under grant No. NSC-82-0410-E-002-191  相似文献   
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Hwu JR  Chen CH  Hsu CI  Das AR  Li YC  Lin LC 《Organic letters》2008,10(10):1913-1916
Reaction of alkyl, acetoxy, and silyl enol ethers of 3-(organosilyl)cyclohexanone with molecular dioxygen in toluene at 110 degrees C produced the corresponding conjugated enones in yields up to 88% yield. The reaction of the same type failed on replacement of the silyl group at the C-3 position with an isopropyl group. These results indicate the existence of an unprecedented silicon-induced ene-type reaction. Its reaction mechanism, generality, limitations, and exceptions are discussed.  相似文献   
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Various (heterocyclo)carbonyl mono-oxime esters of anthraquinone were synthesized, which exhibited an ability for DNA cleavage upon UV irradiation. Their structure-activity relationship was established, in which the most potent compound was anthraquinone O-9-(1,3-benzothiazole-2-carbonyl)oxime (4j). It can produce radical species and nick DNA at the concentration as low as 1.0 μM.  相似文献   
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We demonstrate that, with appropriate staining, high-resolution X-ray microscopy can image complicated tissue structures--cerebellum and liver--and resolve large or small amounts of Au nanoparticles in these tissues. Specifically, images of tumor tissue reveal high concentrations of accumulated Au nanoparticles. PEG (poly(ethylene glycol)) coating is quite effective in enhancing this accumulation and significantly modifies the mechanism of uptake by reticuloendothelial system (RES) organs.  相似文献   
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In light of ever growing interests in noncentrosymmetric materials, a fascinating reticular chemistry is illustrated via the structure of a new family of solids where the acentric symmetry of the well-known [V(4+)(14)As(3+)(8)O(42)Cl](5-) POM cluster is manifested through the network construction of counter cations featuring slabs of Cs(+)-based half SOD β-cages.  相似文献   
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Single crystals of three new noncentrosymmetric (NCS) phosphates, α (1) and β (2) forms of Cs(3)KBi(2)Mn(4)(PO(4))(6)Cl and α-Cs(3)KBi(2)Fe(4)(PO(4))(6)Cl (3), were grown in a reactive CsCl/KCl molten-salt media. Their structures were determined by single-crystal X-ray diffraction methods showing that the α form crystallizes in the space group Cc (No. 9), which is in one of the 10 NCS polar crystal classes, m (2/m) while the β form crystallizes in P4(3) (No. 78) of another polar class, 4 (4/m). The unit cell parameters of the α form can be approximately correlated with that of the β form via the 3 × 3 orientation matrix [0.5, 0.5, 0; -0.5, 0.5, 0; 0, 0, 2 sin β]. The structures of these otherwise complicated phosphates exhibit two types of channels with circular and elliptical windows where the Cl-centered Cl(Bi(2)Cs) acentric unit is located. The neighboring acentric units are arranged in a parallel fashion in the α form, resulting in the monoclinic (Cc) lattice, but "antiparallel" in the β form, thus giving the tetragonal (P4(3)) unit cell. 1-3 feature the compatible M-O-P unit that contains four crystallographically independent MO(x) (x = 4, 5) polyhedra, which are connected to the Cl(Bi(2)Cs) acentric unit through one short and one long M(II)···Cl bond. The compositions of 1 and 2 consist of three Mn(2+) (d(5)) and one Mn(3+) (d(4)) per formula unit and that of 3 has three Fe(2+) (d(6)) and one Fe(3+) (d(5)). Bond valence sums reveal that, in the α phase, the trivalent site adopts distorted tetrahedral M(1)(3+)O(4) coordination and, in the β phase, distorted trigonal-bipyramidal M(4)(3+)O(5). Thus far, the iron phase has only been isolated in the α form presumably because of little extra stabilization energy gain if the Fe(2+) d(6) ion were to occupy the M(1)O(4) site. The possible origins pertaining to the structural differences in the α and β forms are discussed.  相似文献   
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