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161.
In a recent important breakthrough D. Christodoulou has solved a long standing problem of General Relativity of evolutionary formation of trapped surfaces in the Einstein-vacuum space-times. He has identified an open set of regular initial conditions on an outgoing null hypersurface (both finite and at past null infinity) leading to a formation a trapped surface in the corresponding vacuum space-time to the future of the initial outgoing hypersurface and another incoming null hypersurface with the prescribed Minkowskian data. In this paper we give a simpler proof for a finite problem by enlarging the admissible set of initial conditions and, consistent with this, relaxing the corresponding propagation estimates just enough that a trapped surface still forms. We also reduce the number of derivatives needed in the argument from two derivatives of the curvature to just one. More importantly, the proof, which can be easily localized with respect to angular sectors, has the potential for further developments. 相似文献
162.
Sergiu I. Vacaru 《Foundations of Physics》2013,43(6):719-732
Using Finsler brane solutions [see details and methods in: S. Vacaru, Class. Quant. Grav. 28:215001, 2011], we show that neutrinos may surpass the speed of light in vacuum which can be explained by trapping effects from gravity theories on eight dimensional (co) tangent bundles on Lorentzian manifolds to spacetimes in general and special relativity. In nonholonomic variables, the bulk gravity is described by Finsler modifications depending on velocity/momentum coordinates. Possible super-luminal phenomena are determined by the width of locally anisotropic brane (spacetime) and induced by generating functions and integration functions and constants in coefficients of metrics and nonlinear connections. We conclude that Finsler brane gravity trapping mechanism may explain neutrino super-luminal effects and almost preserve the paradigm of Einstein relativity as the standard one for particle physics and gravity. 相似文献
163.
Sergiu I. Vacaru 《International Journal of Theoretical Physics》2012,51(5):1338-1359
We study the fractional gravity for spacetimes with non-integer fractional derivatives. Our constructions are based on a formalism
with the fractional Caputo derivative and integral calculus adapted to nonholonomic distributions. This allows us to define
a fractional spacetime geometry with fundamental geometric/physical objects and a generalized tensor calculus all being similar
to respective integer dimension constructions. Such models of fractional gravity mimic the Einstein gravity theory and various
Lagrange–Finsler and Hamilton–Cartan generalizations in nonholonomic variables. The approach suggests a number of new implications
for gravity and matter field theories with singular, stochastic, kinetic, fractal, memory etc processes. We prove that the
fractional gravitational field equations can be integrated in very general forms following the anholonomic deformation method
for constructing exact solutions. Finally, we study some examples of fractional black hole solutions, ellipsoid gravitational
configurations and imbedding of such objects in solitonic backgrounds. 相似文献
164.
Lazarescu A Shova S Bartolome J Alonso P Arauzo A Balu AM Simonov YA Gdaniec M Turta C Filoti G Luque R 《Dalton transactions (Cambridge, England : 2003)》2011,40(2):463-471
Three pyridine 2,3-dicarboxylate complexes have been synthesized and characterized by IR spectroscopy, thermal analysis and single crystal X-ray diffractometry. Their magnetic properties have also been studied by EPR and magnetisation measurements. The decomposition of such complexes in air leads to the generation of mixed metal oxides, as confirmed by powder X-ray diffraction. 相似文献
165.
Sergiu Aizicovici 《Journal of Mathematical Analysis and Applications》2011,375(1):342-364
We consider a nonlinear periodic problem, driven by the scalar p-Laplacian with a concave term and a Caratheodory perturbation. We assume that this perturbation f(t,x) is (p−1)-linear at ±∞, and resonance can occur with respect to an eigenvalue λm+1, m?2, of the negative periodic scalar p-Laplacian. Using a combination of variational techniques, based on the critical point theory, with Morse theory, we establish the existence of at least three nontrivial solutions. Useful in our considerations is an alternative minimax characterization of λ1>0 (the first nonzero eigenvalue) that we prove in this work. 相似文献
166.
Sergiu P. Albu Andrei Ghicov Steffen Berger Himendra Jha Patrik Schmuki 《Electrochemistry communications》2010,12(10):1352-1355
In the present work we demonstrate the fabrication and use of a new generation of TiO2 nanotube membranes. We show that anodic oxide nanotube growth can be performed through a patterned Ti foil into an underlying Al metal layer. After the selective dissolution of the Al/alumina layer, a very well defined both side open suspended TiO2 nanotube layer can be obtained. Using lithographic patterning of the anodization area allows to achieve very large scale, flexible and well electrically connected nanotubular flow-through membranes with fast electrical switching features over the entire membrane. 相似文献
167.
Aligned self-organized TiO2 nanotubes of 15–20 µm length proved to be very promising for application in dye-sensitized solar cells. Conventional anodic nanotube layers usually show an irregular structure (nanograss) or a thin nucleation layer at the top of the nanotube array. In the present paper, we demonstrate that by a simple photoresist based method, well-defined and open TiO2 nanotube tops can be obtained which significantly enhances their performance when used in DSSCs. In fact, the layers show the highest reported solar energy conversion efficiency up to now for a pristine (particle-free) nanotube layer. 相似文献
168.
Draguta Sergiu Fonari Marina S. Bejagam Shabari Nath Storms Kathryn Lindline Jennifer Timofeeva Tatiana V. 《Structural chemistry》2016,27(4):1303-1315
Structural Chemistry - A solvent co-crystallization of three 2-aminopyridine derivatives, 2-aminopyridine (AP), 2-amino-6-methylpyridine (AMP), and 2,6-diaminopyridine (DAP) with the odd-membered... 相似文献
169.
Mirela‐Fernanda Zaltariov Maria Cazacu Sergiu Shova Angelica Vlad Iuliana Stoica Elena Hamciuc 《Journal of polymer science. Part A, Polymer chemistry》2012,50(18):3775-3787
Bis[N‐(4‐carboxyphenyl)phtalimidyl]dimethylsilane prepared by the reaction between bis(3,4‐dicarboxyphenyl)dimethylsilane anhydride and p‐aminobenzoic acid has been used to built three novel hydrogen‐bonded supramolecular polymers as a result of cocrystallization with pyridine derivatives: 4,4′‐bipyridyl ( SP1 ), 1,2‐bis(4‐pyridyl)ethylene ( SP2 ), and 4,4′‐azopyridine ( SP3 ). The structures of the dianhydride, diacid, and derived supramolecular polymers were investigated by Fourier transform infrared (FTIR) and proton magnetic resonance (1H NMR) spectroscopy. Self‐assembling was proved by the presence of the IR absorption bands around 1900 and 2400 cm?1 specific for hydrogen bond. The association constant values were estimated by using FTIR spectroscopy in solid state. According to X‐ray diffraction study, the bis(3,4‐dicarboxyphenyl)dimethylsilane anhydride ( 1 ) has an isolated molecular structure. Bis[N‐(4‐carboxyphenyl)phtalimidyl]dimethylsilane ( 2 ) molecules are associated in the crystal structure via dimeric O? H … O hydrogen bonds resulting in the wavy 1D supramolecular chain. The main packing motif for SP1 and SP3 is represented by wavy chain formed by alternating sequences of 4,4′‐bipyridyl or 4,4′‐azopyridine and bis[N(4‐carboxyphenyl)phtalimidyl]dimethylsilane molecules linked by O? H … N hydrogen bonds. Thermal behavior was studied by differential scanning calorimetry and thermogravimetric analysis. The ability for the structuration in film was emphasized by atomic force microscopy. The molecular transport ability of the reversible associations was estimated by dynamic water vapor sorption (DVS) analysis. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
170.
Does the Sign of the Cu–Gd Magnetic Interaction Depend on the Number of Atoms in the Bridge? 下载免费PDF全文
Dr. Jean‐Pierre Costes Dr. Carine Duhayon Dr. Sonia Mallet‐Ladeira Prof. Sergiu Shova Dr. Laure Vendier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):2171-2180
Several theoretical investigations with CASSCF methods confirm that the magnetic behavior of Cu–Gd complexes can only be reproduced if the 5d Gd orbitals are included in the active space. These orbitals, expected to be unoccupied, do present a low spin density, which is mainly due to a spin polarization effect. This theory is strengthened by the experimental results reported herein. We demonstrate that Cu–Gd complexes characterized by Cu–Gd interactions through single‐oxygen and three‐atom bridges consisting of oxygen, carbon, and nitrogen atoms, present weak ferromagnetic exchange interactions, whereas complexes with bridges made of two atoms, such as the nitrogen–oxygen oximato bridge, are subject to weak antiferromagnetic exchange interactions. Therefore, a bridge with an odd number of atoms induces a weak ferromagnetic exchange interaction, whereas a bridge with an even number of atoms supports a weak antiferromagnetic exchange interaction, as observed in pure organic compounds and also, as in this case, in metal–organic compounds with an active spin polarization effect. 相似文献