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121.
Dag Viktor Nilsson 《Mathematical Methods in the Applied Sciences》2017,40(4):1053-1080
We consider a two‐dimensional inviscid irrotational flow in a two layer fluid under the effects of gravity and interfacial tension. The upper fluid is bounded above by a rigid lid, and the lower fluid is bounded below by a rigid bottom. We use a spatial dynamics approach and formulate the steady Euler equations as a Hamiltonian system, where we consider the unbounded horizontal coordinate x as a time‐like coordinate. The linearization of the Hamiltonian system is studied, and bifurcation curves in the (β,α)‐plane are obtained, where α and β are two parameters. The curves depend on two additional parameters ρ and h, where ρ is the ratio of the densities and h is the ratio of the fluid depths. However, the bifurcation diagram is found to be qualitatively the same as for surface waves. In particular, we find that a Hamiltonian‐Hopf bifurcation, Hamiltonian real 1:1 resonance, and a Hamiltonian 02‐resonance occur for certain values of (β,α). Of particular interest are solitary wave solutions of the Euler equations. Such solutions correspond to homoclinic solutions of the Hamiltonian system. We investigate the parameter regimes where the Hamiltonian‐Hopf bifurcation and the Hamiltonian real 1:1 resonance occur. In both these cases, we perform a center manifold reduction of the Hamiltonian system and show that homoclinic solutions of the reduced system exist. In contrast to the case of surface waves, we find parameter values ρ and h for which the leading order nonlinear term in the reduced system vanishes. We make a detailed analysis of this phenomenon in the case of the real 1:1 resonance. We also briefly consider the Hamiltonian 02‐resonance and recover the results found by Kirrmann. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
122.
In this contribution, the LuGre model is extended and the effect of frictional aging is incorporated using the state variable approach. The adapted friction model is used in combination with a single-degree-of-freedom oscillator to investigate the basic effects on the stick-slip amplitude and period. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
123.
New methods for the determination of carbon in sodium using laser ablation inductively coupled plasma optical emission spectrometry
(LA-ICP-OES) and ICP-OES with pneumatic nebulisation (PN-ICP-OES) were developed. The determination was required for the study
of the carbon dioxide reaction with molten sodium at high temperatures (300–600°C). After exposition to CO2, the solidified sodium sample was subjected to direct solid analysis by LA-ICP-OES and to solution analysis. For the determination
of carbon in the sodium sample surface layer by LA-ICP-OES, three different matrices containing sodium were tested (NaCl,
NaF, and Na2B4O7 · 10H2O) as calibration pellets. The calibration dependences were improved using sodium as the internal standard. Average carbon
content in the sodium bulk sample was determined by PN-ICP-OES after the sample dissolution by water vapour. 相似文献
124.
125.
Barbieriková Z Bella M Kučerák J Milata V Jantová S Dvoranová D Veselá M Staško A Brezová V 《Photochemistry and photobiology》2011,87(1):32-44
Novel 7‐substituted 6‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐h]quinoline ( SeQ(1–6) ) and 8‐substituted 9‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐f ]quinoline derivatives ( SeQN(1–5) ) with R7, R8 = H, COOC2H5, COOCH3, COOH, COCH3 or CN were synthesized and their spectral characteristics were obtained by UV/Vis spectroscopy. Ultraviolet A photoexcitation of the selenadiazoloquinolones in dimethylsulfoxide or acetonitrile resulted in the formation of paramagnetic species coupled with molecular oxygen activation generating the superoxide radical anion or singlet oxygen, evidenced by electron paramagnetic resonance spectroscopy. The cytotoxic/photocytotoxic impact of selenadiazoloquinolones on murine and human cancer cell lines was demonstrated using the derivative SeQ5 (with R7 = COCH3). 相似文献
126.
Faraday rotation enhancement of gold coated Fe2O3 nanoparticles: comparison of experiment and theory
Understanding plasmonic enhancement of nanoscale magnetic materials is important to evaluate their potential for application. In this study, the Faraday rotation (FR) enhancement of gold coated Fe(2)O(3) nanoparticles (NP) is investigated experimentally and theoretically. The experiment shows that the Faraday rotation of a Fe(2)O(3) NP solution changes from approximately 3 rad/Tm to 10 rad/Tm as 5 nm gold shell is coated on a 9.7 nm Fe(2)O(3) core at 632 nm. The results also show how the volume fraction normalized Faraday rotation varies with the gold shell thickness. From the comparison of experiment and calculated Faraday rotation based on the Maxwell-Garnett theory, it is concluded that the enhancement and shell dependence of Faraday rotation of Fe(2)O(3) NPs is a result of the shifting plasmon resonance of the composite NP. In addition, the clustering of the NPs induces a different phase lag on the Faraday signal, which suggests that the collective response of the magnetic NP aggregates needs to be considered even in solution. From the Faraday phase lag, the estimated time of the full alignment of the magnetic spins of bare (cluster size 160 nm) and gold coated NPs (cluster size 90 nm) are found to be 0.65 and 0.17 μs. The calculation includes a simple theoretical approach based on the Bruggeman theory to account for the aggregation and its effect on the Faraday rotation. The Bruggeman model provides a qualitatively better agreement with the experimentally observed Faraday rotation and points out the importance of making a connection between component properties and the average "effective" optical behavior of the Faraday medium containing magnetic nanoparticles. 相似文献
127.
Kristina?Zubow Anatolij?Zubow Viktor?Anatolievich?ZubowEmail author 《Journal of Cluster Science》2011,22(4):603-619
It was investigated how the “wall effect” influences the cluster distribution in water and 3.5 wt.% NaCl solution being in
a glass cylinder. The cluster distribution in a mass assemble up to 2.2 million Dalton was determined in dependence on the
distance to the wall at normal atmospheric pressure. The average cluster mass, the rate of collapsed and skeletal clusters
and the number of cluster kinds depended on the distance to the wall and on stirring methods. In different liquid’s layers
and at different distances to the wall, there were registered newly appearing clusters as well as disappearing ones especially,
solvated clusters of ion pairs (SCIPs). Under non-stirring conditions, the base water cluster (H2O)12 and (NaCl·40H2O)2 are the most sensitive to the wall distance. Other SCIPs like dimers, tetramers and hexamers remain stable at stirring in
the vessel center (12 rad/s) and don’t react to wall approaching however at cylinder rotation (8.9 rad/s) these SCIPs are
sensitive to the wall. The wall nature, the distance to the wall and the constant magnetic field were concluded to influence
the cluster distribution differently. Cluster properties were assumed to be applied by sea water living organisms for their
navigation. 相似文献
128.
Abid OU Nawaz M Ibad MF Khera RA Iaroshenko V Langer P 《Organic & biomolecular chemistry》2011,9(7):2185-2191
Aryl-substituted pyridines and pyrimidines were prepared by [4+2] cycloadditions of alkynyl-substituted pyridines and -pyrimidines with electron-rich dienes. The reactions proceed by formation of a bridged cycloadduct and subsequent thermal extrusion of ethylene. The pyridine moiety plays a crucial role for the success of the reaction. 相似文献
129.
Iaroshenko VO Bunescu A Spannenberg A Supe L Milyutina M Langer P 《Organic & biomolecular chemistry》2011,9(21):7554-7558
The reaction of 1,3-bis-silyl enol ethers with 3-methoxalylchromones affords a great variety of functionalised 2,4'-dihydroxybenzophenones. These products are formed by a domino Michael/retro-Michael/Mukaiyama-aldol reaction. The synthesized compounds are promising candidates for the synthesis of the novel UV-A/B and UV-B filters. 相似文献
130.
Cvijeta Jakobušić Brala Viktor Pilepić Ivana Sajenko Ana Karković Stanko Uršić 《Helvetica chimica acta》2011,94(9):1718-1731
The effects of charged species on proton‐coupled electron‐transfer (PCET) reaction should be of significance for understanding/application of important chemical and biological PCET systems. Such species can be found in proximity of activated complex in a PCET reaction, although they are not involved in the charge transfer process. Reported here is the first study of the above‐mentioned effects. Here, the effects of Na+, K+, Li+, Ca2+, Mg2+, and Me4N+ observed in PCET reaction of ascorbate monoanions with hexacyanoferrate(III) ions in H2O reveal that, in presence of ions, this over‐the‐barrier reaction entered into tunneling regime. The observations are: a) dependence of the rate constant on the cation concentration, where the rate constant is 71 (at I = 0.0023), and 821 (at 0.5M K+), 847 (at 1.0M Na+), and 438 M ?1 s?1 (at 0.011M Ca2+); b) changes of kinetic isotope effect (KIE) in the presence of ions, where kH/kD=4.6 (at I = 0.0023), and 3.4 (in the presence of 0.5M K+), 3.3 (at 1.0M Na+), 3.9 (at 0.001M Ca2+), and 3.9 (at 0.001M Mg2+), respectively; c) the isotope effects on Arrhenius pre‐factor where AH/AD=0.97 (0.15) in absence of ions, and 2.29 (0.60) (at 0.5M Na+), 1.77 (0.29) (at 1.0M Na+), 1.61 (0.25) (at 0.5M K+), 0.42 (0.16) (at 0.001M Ca2+) and 0.16 (0.19) (at 0.001M Mg2+); d) isotope differences in the enthalpies of activation in H2O and in D2O, where ΔΔH?(D,H)=3.9 (0.4) kJ mol?1 in the absence of cations, 1.3 (0.6) at 0.5M Na+, 1.8 (0.4) at 0.5M K+, 1.5 (0.4) at 1.0M Na+, 5.5 (0.9) (at 0.001M Ca2+), and 7.9 (2.8) (at 0.001M Mg2+) kJ mol?1; e) nonlinear proton inventory in reaction. In the H2O/dioxane 1 : 1, the observed KIE is 7.8 and 4.4 in the absence and in the presence of 0.1M K+, respectively, and AH/AD=0.14 (0.03). The changes when cations are present in the reaction are explained in terms of termolecular encounter complex consisting of redox partners, and the cation where the cation can be found in a near proximity of the reaction‐activated complex thus influencing the proton/electron double tunneling event in the PCET process. A molecule of H2O is involved in the transition state. The resulting ‘configuration’ is more ‘rigid’ and more appropriate for efficient tunneling with Na+ or K+ (extensive tunneling observed), i.e., there is more precise organized H transfer coordinate than in the case of Ca2+ and Mg2+ (moderate tunneling observed) in the reaction. 相似文献