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1.
Under intrinsic and extrinsic curvature assumptions on a Riemannian spin manifold and its boundary, we show that there is
an isomorphism between the restriction to the boundary of parallel spinors and extrinsic Killing spinors of non-negative Killing constant. As a corollary, we prove that a complete Ricci-flat spin manifold with mean-convex boundary
isometric to a round sphere, is necessarily a flat disc.
Received: 2 February 2002; in final form: 1 August 2002 /
Published online: 1 April 2003
Mathematics Subject Classification (1991): 53C27, 53C40, 53C80, 58G25
The authors would like to thank Lars Andersson for helpful discussions and for bringing to our knowledge the information
regarding Remark 4. We are also grateful to the referee for pointing out that Corollary 5 and Corollary 6 are only valid when
the boundary is at least 2-dimensional.
Research of S. Montiel is partially supported by a Spanish MCyT grant No. BFM2001-2967 相似文献
2.
M D Montiel A Carracedo I Lopez-Rodriguez M S Rodriguez-Calvo L Concheiro E Huguet M Gené 《Electrophoresis》1988,9(6):268-272
Orosomucoid (ORM) polymorphism was investigated by different methods including isoelectric focusing in acid pH ranges followed by silver staining, print immunofixation of desialyzed ORM, fixation using a lectin from the sea-weed Codium tomentosum, isoelectric focusing followed by immunofixation in miniaturized gels and isoelectric focusing in immobilized pH gradients. Population genetics studies were carried out in Galicia (NW Spain) and two new ORM variants were found. 相似文献
3.
Generator‐collector Voltammetry at Dual‐plate Gold‐gold Microtrench Electrodes as Diagnostic Tool in Ionic Liquids 下载免费PDF全文
Miguel Angel Montiel Jesus Iniesta Andrew J. Gross Thies Thiemann Frank Marken 《Electroanalysis》2016,28(5):1068-1076
Ionic liquids provide high viscosity solvent environments with interesting voltammetric characteristics and new electrochemical mechanisms. Here, a gold‐gold dual‐plate microtrench electrode is employed in generator‐collector mode to enhance viscosity‐limited currents in ionic liquids due to fast feedback within small inter‐electrode gaps (5 μm inter‐electrode gap, 27 μm microtrench depth) and to provide a mechanistic diagnosis tool. Three redox systems in the ionic liquid BMIm+BF4? are investigated: (i) ferrocene oxidation, (ii) oxygen reduction, and (iii) 2‐phenyl‐naphthyl‐1,4‐dione reduction. Both transient and steady state voltammetric responses are compared. Asymmetric diffusion processes, reaction intermediates, and solubility changes in the ionic liquid are revealed. 相似文献
4.
Fernández EJ Laguna A López-de-Luzuriaga JM Monge M Montiel M Olmos ME 《Inorganic chemistry》2005,44(5):1163-1165
The reaction of the complex [Au2Ag2(C6F5)4)N[triple bond]CCH3)2]n (1) with 1 equiv of CuCl in the presence of 1 equiv of pyrimidine ligand leads to the formation of the heteronuclear Au(I)-Cu(I) organometallic polymer [Cu{Au(C6F5)2}(N[triple bond]CCH3)(mu2-C4H4N2)]n (2) through a transmetalation reaction. Complex 2 displays unprecedented unsupported Au(I)...Cu(I) interactions of [Au(C6F5)2]- units with the acid Cu(I) sites in a [Cu(N[triple bond]CCH3)(mu2-pyrimidine)]n+(n) polymeric chain. Complex 2 has a rich photophysics in solution and in the solid state. 相似文献
5.
M. Judith Percino Víctor M. Chapela Ling-Fa Montiel Enrique Pérez-Gutiérrez José Luis Maldonado 《Chemical Papers》2010,64(3):360-367
An efficient Knoevenagel route using green chemistry conditions was applied for the synthesis of halogen- and cyano- substituted
pyridinevinylene compounds. Absorption and fluorescence emission spectra of these conjugated compounds were recorded and compared
in order to evaluate the effect of substituents on the electronic properties of pyridinevinylene compounds. The substituents
studied were terminal Cl and F, two or three aromatic rings, as well as a cyano group attached to a C=C double bond. The compounds
synthesized are: (E)-2-(4-fluorostyryl)pyridine, (E)-2-(4-chlorostyryl)pyridine, (E)-4-(4-chlorostyryl)pyridine, 2,3-diphenylacrylonitrile, 3-phenyl-2-(pyridin-2-yl)acrylonitrile, 3-phenyl-2-(pyridin-3-yl)acrylonitrile,
2-phenyl-3-(pyridin-2-yl)acrylonitrile, 3,3′-(1,4-phenylene)bis(2-phenylacrylonitrile), 3,3′-(1,4-phenylene)bis(2-(pyridin-2-yl)acrylonitrile),
and 3,3′-(1,4-phenylene)bis(2-(pyridin-3-yl)acrylonitrile). The solvent-free method used in this work allows obtaining each
compound by controlling the reaction temperature. The compounds were characterized by infrared spectroscopy and 1H-NMR spectroscopy. 相似文献
6.
Hijazi Oussama Montiel Sebastin Roldn Antonio 《Annals of Global Analysis and Geometry》2003,23(3):247-264
We give a sharp extrinsic lower bound for the first eigenvaluesof the intrinsic Dirac operator of certain hypersurfaces boundinga compact domain in a spin manifold of negative scalar curvature.Limiting-cases are characterized by the existence, on the domain,of imaginary Killing spinors. Some geometrical applications, as anAlexandrov type theorem, are given. 相似文献
7.
We report the direct electrochemistry of cytochrome c at screen printed graphite electrodes which exhibits quasi-reversible voltammetric responses without the need for any chemical or electrochemical pre-treatment, use of mediators or nanomaterials. Through voltammetric studies and X-ray photoelectron spectroscopy (XPS) it is shown that carbonyl and carboxylic surface oxygenated species likely residing at edge plane like- sites/defects of the graphite comprising the screen printed electrodes are responsible for the favourable interaction of the cytochrome c with that of the screen printed electrochemical sensing platform. 相似文献
8.
R. Valenzuela G. Alvarez H. Montiel M.P. Gutirrez M.E. Mata-Zamora F. Barrn A.Y. Snchez I. Betancourt R. Zamorano 《Journal of magnetism and magnetic materials》2008,320(14):1961-1965
A low-field non-resonant microwave absorption has recently been observed in a variety of magnetically ordered materials at low DC fields (−1000 Oe HDC+1000 Oe), which is known as low-field microwave absorption (LFA). It has been shown that LFA is essentially similar to giant magnetoimpedance (GMI), and clearly different from ferromagnetic resonance (FMR). LFA strongly depends on the anisotropy field of the sample. In contrast with FMR (which can be described as the homogeneous precession of spins in the saturated state), LFA can be thought as a spin rotation process occurring during the magnetic saturation. In this work, we present a detailed study of the basic features of LFA in several types of materials: ferrites and amorphous microwires and ribbons; in particular the effects sample shape, temperature up to the Curie transition, the influence of easy axis and the effects of annealings. These examples show that once LFA is fully understood, it can become a powerful characterization tool. 相似文献
9.
10.
A total synthesis of natural bisabolane sesquiterpenes curcuphenol ( 1 ) and xanthorrhizol ( 2 ) was developed by using the substituted acetophenones 4 and 5 , respectively, as starting materials. The acetyl group of the latter was activated through ethoxycarbonylation to carry out the prenylation, which was performed successfully to give their respective precursors 11a and 11b , and 21 that were converted into the corresponding natural sesquiterpenes 1 and 2 , respectively, over four steps and in high overall yields. 相似文献