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71.
Let M be a compact Riemannian manifold, E a Riemannian vector bundle on M and Σ the sphere subbundle of E. We look for embeddings of Σ into E admitting prescribed mean curvatures of various types. To cite this article: P. Cherrier, A. Hanani, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 525–528. 相似文献
72.
We prove existence, uniqueness and regularity results for the global solutions of the semilinear wave equations. In particular,
we show existence of regular self-similar solutions. Also, we build some finite-energy asymptotically self-similar solutions.
Received: 20 September 1999; in final form: 10 May 2000 / Published online: 25 June 2001 相似文献
73.
Corine Mathonire Hirokazu Kobayashi Rmy Le Bris Abdellah Kaïba Isabelle Bord 《Comptes Rendus Chimie》2008,11(6-7):665-672
The optical and photomagnetic properties of [{CuII(bipy)2}2{MoIV(CN)8}]·9H2O·CH3OH (1) have been reinvestigated. A comparison between spectra in solution and in the solid state revealed the presence of an intervalence band (or Metal–Metal Charge Transfer, hereafter noted MMCT) at 570 nm. The photomagnetic properties have been performed in a Superconducting QUantum Interference Device at 10 K with irradiation in the range of the MMCT: 488 nm, 520 nm and 647 nm at 10 K. An important increase of the magnetic signal has been measured after 1 h of irradiation at 488 nm, whereas a weaker increase has been obtained for the irradiation at 520 nm in the same conditions. Moreover, after an excitation at 488 nm, an irradiation at 647 nm has induced a decrease of the magnetic moment, which corresponds to a partial deexcitation. The complete characterization of the photoproduct has been realised after an irradiation of 4 h at 488 nm. The photomagnetic properties have shown an increase of the paramagnetism of 1 at low temperature. After a thermal heating at 300 K, the material goes back to its initial state before irradiation. It is the first time that a fully reversible photomagnetic behaviour for the compound [{CuII(bipy)2}2{MoIV(CN)8}]·9H2O·CH3OH has been described. The observed properties have been discussed in terms of an electron transfer mechanism Mo → Cu. 相似文献
74.
A regiodivergent synthesis of ring a C-prenylflavones 总被引:1,自引:0,他引:1
Capitalizing on the use of orthogonal protecting groups and the development of a modified Robinson flavone synthesis that avoids harsh acidic conditions, a regioselective synthesis of 6- and 8-prenylflavones from the same prenylated disilylated phloracetophenone (9) has been developed, targeting cannflavin B (1d), the COX-inhibiting principle of marijuana, and its unnatural isomer isocannflavin B (1e) as model compounds. 相似文献
75.
Nonlinear dynamic of composite stiffened panels to parametric and three-to-one internal resonances is investigated. The ordinary differential equation of two mode shapes is established by using Galerkin method and the condition of three-to-one internal resonance between the first mode (1,3) and the second mode (3,1) is examined near the principal resonance 2:1 of the first mode. Then, the nonlinear behavior of the two buckling mode shapes is analyzed using a perturbation analysis. We show the existence of jump phenomena for the two modes indicating a complex dynamic of the structure near the three-to-one internal resonance for the HM Graphite/epoxy materials. 相似文献
76.
77.
Nuno M.M. Moura Maria A.F. Faustino Maria G.P.M.S. Neves Augusto C. Tomé El Mostapha Rakib Abdellah Hannioui Souad Mojahidi Steffen Hackbarth Beate Röder Filipe A. Almeida Paz Artur M.S. Silva José A.S. Cavaleiro 《Tetrahedron》2012,68(39):8181-8193
2-Vinyl-5,10,15,20-tetraphenylporphyrinatozinc(II) reacts with nitrile imines, generated in situ from ethyl hydrazono-α-bromoglyoxylates, affording the corresponding pyrazolines in good to excellent yields. Treatment of pyrazoline derivatives with DDQ affords the corresponding pyrazole derivatives with moderate to excellent yields. When the hydrolysis of ester group in the pyrazoline derivatives was considered, it was observed the concomitant oxidation of the heterocyclic unit, which allowed directly obtaining porphyrin-pyrazole derivatives with a carboxylic group, in very good yields.The photophysical properties of the pyrazoline and pyrazole porphyrin derivatives show that the influence of the heterocyclic substituents is limited by the tendency of these molecules to aggregate. All other properties and especially the triplet kinetics remain unaffected. The adducts with low tendency to aggregate showed very high singlet oxygen yield, which makes these compounds interesting for their use as photosensitizers for PDT. 相似文献
78.
Samiha Dergal Samah Al-Qaisi Habib Rached Abdellah Ouerdane 《International journal of quantum chemistry》2024,124(8):e27371
The stabilities, mechanical, electronic, and magnetic properties of the new equiatomic quaternary Heusler alloy (EQHA) RuTiCrSi were investigated using the Kohn-Sham DFT (KS-DFT) calculations within the generalized gradient approach (GGA), the modified version of the exchange potential introduced by Becke and Johnson in addition to the GGA (mBJ-GGA), and Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional. The ground-state equilibrium energy reveals that the ferromagnetic with type 2 structure is the more stable. The RuTiCrSi is energetically, mechanically, and dynamically stable. The calculated self-consistent total magnetic moment is 2 μB and agrees well with the Slater-Pauling rule of . The electronic structure results from mBJ-GGA and HSE06 functionals show a half-metallic behavior. A high Curie temperature is obtained using the mean-field approximation. The thermoelectric response was calculated using the semi-classical Boltzmann transport equation under constant relaxation time. The maximum value of Seebeck coefficient is observed at the ambient temperature of . It was also observed that the power factor increases significantly as temperature rises. Therefore, the new EQHA RuTiCrSi seems to be a potential candidate for spintronic thermoelectric applications. 相似文献
79.
Cesar Auguste Badji Jean Dorland Lynda Kheloul Dimitri Brard Pascal Richomme Abdellah Kellouche Claudio Roberto Azevedo de Souza Antnio Loureno Bezerra Sylvia Anton 《Molecules (Basel, Switzerland)》2021,26(15)
Essential oils of aromatic plants represent an alternative to classical pest control with synthetic chemicals. They are especially promising for the alternative control of stored product pest insects. Here, we tested behavioral and electrophysiological responses of the stored product pest Tribolium confusum, to the essential oil of a Brazilian indigenous plant, Varronia globosa, collected in the Caatinga ecosystem. We analyzed the essential oil by GC-MS, tested the effects of the entire oil and its major components on the behavior of individual beetles in a four-way olfactometer, and investigated responses to these stimuli in electroantennogram recordings (EAG). We could identify 25 constituents in the essential oil of V. globosa, with anethole, caryophyllene and spathulenole as main components. The oil and its main component anethole had repellent effects already at low doses, whereas caryophyllene had only a repellent effect at a high dose. In addition, the essential oil abolished the attractive effect of the T. confusum aggregation pheromone. EAG recordings revealed dose-dependent responses to the individual components and increasing responses to the blend and even more to the entire oil. Our study reveals the potential of anethole and the essential oil of V. globosa in the management of stored product pests. 相似文献
80.
Z. Tahri F. Luchez I. Yordanov O. Poizat A. Moissette V. Valtchev S. Mintova M. Mostafavi V. De Waele 《Research on Chemical Intermediates》2009,35(4):379-388
The process of formation and the subsequent aggregation of silver atoms (Ag0) in nanosized zeolite beta (BEA) are studied by transient absorption spectroscopy. The zeolite nanocrystals are stabilized
in aqueous colloidal suspensions with a narrow particle size distribution in the range 30–60 nm. The reduction of silver cations
is initiated either by pulse radiolysis of the aqueous suspension or by photoinduced electron transfer using an organic electron
donor adsorbed in the zeolite framework. The silver atom in BEA nanosized crystals is found to be stable on the microsecond
timescale. 相似文献