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71.
A study is presented for the non linear evolution of a self gravitating distribution of matter coupled to a massless scalar
field. The characteristic formulation for numerical relativity is used to follow the evolution by a sequence of light cones
open to the future. Bondian frames are used to endow physical meaning to the matter variables and to the massless scalar field.
Asymptotic approaches to the origin and to infinity are achieved; at the boundary surface interior and exterior solutions
are matched guaranteeing the Darmois–Lichnerowicz conditions. To show how the scheme works some numerical models are discussed.
We exemplify evolving scalar waves on the following fixed backgrounds: (a) an atmosphere between the boundary surface of an
incompressible mixtured fluid and infinity; (b) a polytropic distribution matched to a Schwarzschild exterior; (c) a Schwarzschild–Schwarzschild
spacetime. The conservation of energy, the Newman–Penrose constant preservation and other expected features are observed. 相似文献
72.
Iryna Antonyshyn Ana M. Barrios Jimnez Olga Sichevych Ulrich Burkhardt Igor Veremchuk Marcus Schmidt Alim Ormeci Ioannis Spanos Andrey Tarasov Detre Teschner Gerardo Algara‐Siller Robert Schlgl Yuri Grin 《Angewandte Chemie (International ed. in English)》2020,59(38):16770-16776
The production of hydrogen via water electrolysis is feasible only if effective and stable catalysts for the oxygen evolution reaction (OER) are available. Intermetallic compounds with well‐defined crystal and electronic structures as well as particular chemical bonding features are suggested here to act as precursors for new composite materials with attractive catalytic properties. Al2Pt combines a characteristic inorganic crystal structure (anti‐fluorite type) and a strongly polar chemical bonding with the advantage of elemental platinum in terms of stability against dissolution under OER conditions. We describe here the unforeseen performance of a surface nanocomposite architecture resulting from the self‐organized transformation of the bulk intermetallic precursor Al2Pt in OER. 相似文献
73.
Chemical Engineering of Photoactivity in Heterometallic Titanium–Organic Frameworks by Metal Doping 下载免费PDF全文
Dr. Neyvis Almora‐Barrios Dr. Josep Albero Dr. A. Rabdel Ruiz‐Salvador Dr. Javier González‐Platas Prof. Hermenegildo García Dr. Carlos Martí‐Gastaldo 《Angewandte Chemie (International ed. in English)》2018,57(28):8453-8457
We report a new family of titanium–organic frameworks that enlarges the limited number of crystalline, porous materials available for this metal. They are chemically robust and can be prepared as single crystals at multi‐gram scale from multiple precursors. Their heterometallic structure enables engineering of their photoactivity by metal doping rather than by linker functionalization. Compared to other methodologies based on the post‐synthetic metallation of MOFs, our approach is well‐fitted for controlling the positioning of dopants at an atomic level to gain more precise control over the band‐gap and electronic properties of the porous solid. Changes in the band‐gap are also rationalized with computational modelling and experimentally confirmed by photocatalytic H2 production. 相似文献
74.
Giancarlo Richard Salazar-Banda Géssica de Oliveira Santiago Santos Isabelle Maria Duarte Gonzaga Aline Resende Dória Katlin Ivon Barrios Eguiluz 《Current Opinion in Electrochemistry》2021
This review provides a current opinion about the most recent advances in the development of novel materials (i.e., anodes and cathodes), as well as new synthesis methodologies, which have been used in water and wastewater treatment by electrochemically driven oxidation technologies. The first section focuses on the advances to produce novel anodic materials comprising the active anodes — which play a key role in direct and indirect oxidation and the nonactive materials — which attract attention due to their high capacity to generate hydroxyl radicals. The second section describes recent progress on the novel emerging cathodic materials that are directly related to in situ electrogeneration of oxidants and are commonly applied in the electro-Fenton technology. Finally, the perspectives and prospects of these novel electrode materials for environmental applications are given. 相似文献
75.
Aguilà D Barrios LA Roubeau O Teat SJ Aromí G 《Chemical communications (Cambridge, England)》2011,47(2):707-709
Molecular chains of four Co(II) ions stabilized by a bis-β-diketone/pyridyl ligand may be isolated or linked into molecular pairs of two semi-independent such units. 相似文献
76.
Luis F Repollés A Martínez-Pérez MJ Aguilà D Roubeau O Zueco D Alonso PJ Evangelisti M Camón A Sesé J Barrios LA Aromí G 《Physical review letters》2011,107(11):117203
We show that a chemically engineered structural asymmetry in [Tb2] molecular clusters renders the two weakly coupled Tb3+ spin qubits magnetically inequivalent. The magnetic energy level spectrum of these molecules meets then all conditions needed to realize a universal CNOT quantum gate. A proposal to realize a SWAP gate within the same molecule is also discussed. Electronic paramagnetic resonance experiments confirm that CNOT and SWAP transitions are not forbidden. 相似文献
77.
78.
We use Galerkin least-squares terms and biorthogonal wavelet bases to develop a new stabilized dual-mixed finite element method for second-order elliptic equations in divergence form with Neumann boundary conditions. The approach introduces the trace of the solution on the boundary as a new unknown that acts also as a Lagrange multiplier. We show that the resulting stabilized dual-mixed variational formulation and the associated discrete scheme defined with Raviart–Thomas spaces are well-posed and derive the usual a priori error estimates and the corresponding rate of convergence. Furthermore, a reliable and efficient residual-based a posteriori error estimator and a reliable and quasi-efficient one are provided. 相似文献
79.
80.
Bretanha LC Teixeira VE Ritter M Siqueira GM Cunico W Pereira CM Freitag RA 《Ultrasonics sonochemistry》2011,18(3):704-707
The alternative synthesis of 12 1,2,4-oxadiazoles using ultrasound irradiation from trichloroacetoamidoxime and acyl chlorides is reported. Seven of them are novel compounds. The 3-trichloromethyl-5alkyl(aryl)-1,2,4-oxadiazoles have been synthesised in better yields and shorter reaction times compared to the conventional method. This protocol can be applicable for preparation of 1,2,4-oxadiazoles containing aryl or alkyl groups attached at their C-5 side-chain. 相似文献