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91.
92.
Left-handed interfaces for electromagnetic surface waves 总被引:1,自引:0,他引:1
We show that surface electromagnetic waves (SEMWs) propagating along two-dimensional (2D) interfaces separating different metamaterials can behave analogously to 3D electromagnetic waves in either usual or left-handed media, depending on the permeabilities and/or permittivities of the two materials forming the interface. We derive the conditions when SEMWs carry energy opposite to the phase velocity. In analogy to three-dimensional (3D) left-handed media, we derive both an anomalous Cherenkov emission and a reversed Doppler effect. We also predict a negative refraction at the boundary between two different interfaces, which can be useful for perfect 2D lensing. 相似文献
93.
de Carvalho PS Nachtigall FM Eberlin MN Moraes LA 《The Journal of organic chemistry》2007,72(16):5986-5993
Despite its unique structure and potential use as an important building block in organic synthesis, the title alpha-oxoketene 1 has been formed mostly under very special conditions as a short-lived species. The reactivity of 1 is, therefore, nearly unexplored. In great contrast, it seemed that its ionized gaseous form 1*+ is stable and easily accessible. In this study, we used multiple-stage pentaquadrupole mass spectrometry to probe the formation of gaseous 1*+ and explore its stability and intrinsic reactivity. With water and methanol, gaseous 1*+ was found to react similarly to solvated 1, which indicates that there is a close parallel between their reactivities. Gaseous 1*+ was also found to react promptly via polar [3 + 2] cycloadditons with various dienophiles including alkenes, alkynes, isocyanates, ketones and esters, thus forming a series of benzopyran-4-ones (flavones, 4-chromanones, 4-chromenones, benzo[1,3]dioxin-4-ones, and analogues) that are common structural units in many natural products. The present availability of 1 at room temperature and the gas-phase findings reported herein for gaseous 1*+ indicate that solvated 1 should undergo many [4 + 2] cycloadditions and functions as a versatile precursor of a variety of biologically active molecules. 相似文献
94.
95.
Nori Yamaguchi Lesley M. Hamilton Harry W. Gibson 《Angewandte Chemie (International ed. in English)》1998,37(23):3275-3279
Self-organization is the key . A series of dendritic pseudorotaxanes were efficiently constructed from complementary building blocks—namely, a three-armed, triply charged ammonium salt and the first, second, and third generations of benzyl ether dendrons bearing the dibenzo[24]crown-8 moiety. The pseudorotaxane arising from the third-generation dendron is shown in the picture. 相似文献
96.
Wenxian Zhang A.G. Kofman Jun Zhuang J.Q. You Franco Nori 《Physics letters. A》2013,377(31-33):1837-1843
Using numerical calculations, we compare the transition probabilities of many spins in random magnetic fields, subject to either frequent projective measurements, frequent phase modulations, or a mix of modulations and measurements. For various distribution functions, we find the transition probability under frequent modulations is suppressed most if the pulse delay is short and the evolution time is larger than a critical value. Furthermore, decay freezing occurs only under frequent modulations as the pulse delay approaches zero. In the large pulse-delay region, however, the transition probabilities under frequent modulations are highest among the three control methods. 相似文献
97.
We consider the relativistic deformation of quantum waves and mechanical bodies carrying intrinsic angular momentum (AM). When observed in a moving reference frame, the centroid of the object undergoes an AM-dependent transverse shift. This is the relativistic analogue of the spin-Hall effect, which occurs in free space without any external fields. Remarkably, the shifts of the geometric and energy centroids differ by a factor of 2, and both centroids are crucial for the Lorentz transformations of the AM tensor. We examine manifestations of the relativistic Hall effect in quantum vortices and mechanical flywheels and also discuss various fundamental aspects of this phenomenon. The perfect agreement of quantum and relativistic approaches allows applications at strikingly different scales, from elementary spinning particles, through classical light, to rotating black holes. 相似文献
98.
99.
Marilia I.F. BarbosaEdjane R. dos Santos Angelica E. GraminhaAndré L. Bogado Leticia R. TeixeiraHeloisa Beraldo Maria Teresa S. TrevisanJavier Ellena Eduardo E. CastellanoBernardo L. Rodrigues Márcio P. de Araujo Alzir A. Batista 《Polyhedron》2011,30(1):41-46
The complex mer-[RuCl3(dppb)(H2O)] [dppb = 1,4-bis(diphenylphosphino)butane] was used as a precursor in the synthesis of the complexes tc-[RuCl2(CO)2(dppb)], ct-[RuCl2(CO)2(dppb)], cis-[RuCl2(dppb)(Cl-bipy)], [RuCl(2Ac4mT)(dppb)] (2Ac4mT = N(4)-meta-tolyl-2-acetylpyridine thiosemicarbazone ion) and trans-[RuCl2(dppb)(mang)] (mang = mangiferin or 1,3,6,7-tetrahydroxyxanthone-C2-β-D-glucoside) complexes. For the synthesis of RuII complexes, the RuIII atom in mer-[RuCl3(dppb)(H2O)] may be reduced by H2(g), forming the intermediate [Ru2Cl4(dppb)2], or by a ligand (such as H2Ac4mT or mangiferin). The X-ray structures of the cis-[RuCl2(dppb)(Cl-bipy)], tc-[RuCl2(CO)2(dppb)] and [RuCl(2Ac4mT)(dppb)] complexes were determined. 相似文献
100.
Karina O.S. FerrazGabriele M.M. Cardoso Caryne Margotto BertolloElaine M. Souza-Fagundes Nivaldo SpezialiCarlos L. Zani Isolda C. MendesMaria A. Gomes Heloisa Beraldo 《Polyhedron》2011,30(2):315-321
Complexes [Pt(2Bz4oT)Cl], [Pt(2Bz4mT)Cl], and [Pt(2Bz4pT)Cl] were prepared with N(4)-ortho-(H2Bz4oT), N(4)-meta-(H2Bz4mT), and N(4)-para-(H2Bz4pT) tolyl-2-benzoylpyridine-derived thiosemicarbazones. The thiosemicarbazones exhibited moderate anti-proliferative activity against HepG2 (hepatoma) and UACC-62 (melanoma) cancer cell lines, but showed high anti-proliferative effect against A431 (epithelial carcinoma) cancer cell lines. Upon coordination to platinum(II) the anti-proliferative activity decreases in all cases. The cytotoxicity of the previously prepared palladium(II) analogues [Pd(2Bz4oT)Cl], [Pd(2Bz4mT)Cl], and [Pd(2Bz4pT)Cl] was also investigated. As in the case of the platinum(II) complexes, coordination to palladium(II) did not lead to activity improvement. Investigations on the mechanism of cytotoxic action against A431 cells revealed that [Pd(2Bz4oT)Cl] induced DNA fragmentation and apoptosis while H2Bz4oT did not present this effect. The high anti-proliferative effect of the thiosemicarbazones and [Pd(2Bz4oT)Cl] against A431 cells, together with the pro-apoptotic effect of [Pd(2Bz4oT)Cl] suggests that these compounds have potential as chemotherapeutic drug candidates. 相似文献