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81.
In this paper we take an approach similar to that in [13] to establish a positive mass theorem for spin asymptotically hyperbolic
manifolds admitting corners along a hypersurface. The main analysis uses an integral representation of a solution to a perturbed
eigenfunction equation to obtain an asymptotic expansion of the solution in the right order. This allows us to understand
the change of the mass aspect of a conformal change of asymptotically hyperbolic metrics.
Vincent Bonini: The first named author supported by MSRI Postdoctoral Fellowship.
Jie Qing: The second named author supported partially by NSF grant DMS 0402294.
Submitted: April 6, 2007. Accepted: September 24, 2007. 相似文献
82.
V.B. Gavrikov V.P. Likhachev J.D.T. Arruda-Neto A.L. Bonini 《The European Physical Journal A - Hadrons and Nuclei》2001,12(4):487-493
Differential and integral features of incoherent X-radiation, induced by relativistic electrons in crystals, are studied for
observation angles θγ several times greater than γ-1, where γ is the projectile Lorentz factor. The existence of sharp maxima and a minimum of the five-folded incoherent differential
cross-section as a function of the final electron angles, and a dip minimum when the cross-section is taken as a function
of the photon energies, is demonstrated. At near backward observation angles the three-folded cross-section shows a maximum
in the region of several keV photon energies. The obtained results allow us to optimize the conditions for coincidence experiments,
minimizing the incoherent contribution to the total radiation yield, and helping to analyse results of finite-size detector
experiments with crystal targets.
Received: 2 July 2001 / Accepted: 26 November 2001 相似文献
83.
Both symmetrical and nonsymmetrical trans-2,3-diaryloxiranes are regio- and stereoselectively opened by the LiBr/Amberlyst 15 system. In the case of symmetrical trans-stilbene oxide, the syn- versus anti-bromohydrins ratio ranged between 88/12 and 30/70, by varying the reaction temperature from 20 to -30 degrees C. In the case of nonsymmetrical para-substituted trans-2,3-diaryloxiranes, the regioselectivity is determined by electronic effects. If one phenyl bears a strong electron-withdrawing group (as NO2 or CF3), the nucleophilic attack is totally on the beta-carbon with respect to the substituted phenyl ring. With one phenyl bearing a strong electron-releasing group (OCH3), the regioselectivity is reversed. Ab initio calculation at the DFT/B3LYP/6-31G level, run on protonated epoxide structures, supports the formation of a cationic acyclic intermediate. Application of the method on ortho-methoxy and ortho-nitro 2,3-diaryloxiranes afforded the syn-bromohydrins in excellent yield, via regio- and stereoselective opening at either alpha- or beta-carbon, respectively. 相似文献
84.
Synthesis of a Corey's lactone analogue and a synthon for 11-deoxy-11-methyl prostaglandin and prostacyclin from the iridoid glucoside Aucubin is described. 相似文献
85.
C. C. Bonini C. Iavarone C. Trogolo Gerald A. Poulton 《Journal of mass spectrometry : JMS》1980,15(10):516-519
The mass spectral fragmentation of eleven α-hydroxybutenolide compounds (isotetronic acids) are reported. The main features are carboxyl and consecutive carbon monoxide expulsions. Masses were determined using high resolution techniques, metastable transitions were detected by defocusing experiments, and pathways were further documented by isotopic labelling experiments. 相似文献
86.
87.
Bhattacharjee S Deterding LJ Jiang J Bonini MG Tomer KB Ramirez DC Mason RP 《Journal of the American Chemical Society》2007,129(44):13493-13501
We investigated electron transfer between a tyrosyl radical and cysteine residue in two systems, oxyhemoglobin (oxyHb)/peroxynitrite/5,5-dimethyl-1-pyrroline N-oxide (DMPO) and myoglobin (Mb)/hydrogen peroxide/DMPO, using a combination of techniques including ESR, immuno-spin trapping (IST), and ESI/MS. These techniques show that the nitrone spin trap DMPO covalently binds to one or more amino acid radicals in the protein. Treating oxyHb with peroxynitrite and Mb with H2O2 in the presence of a low DMPO concentration yielded secondary Cys-DMPO radical adduct exclusively, whereas in the presence of high DMPO, more of the primary Tyr-DMPO radical adduct was detected. In both systems studied, we found that, at high DMPO concentrations, mainly tyrosyl radicals (Hb-Tyr42/Tyr24 and Mb-Tyr103) are trapped and the secondary electron-transfer reaction does not compete, whereas in the presence of low concentrations of DMPO, the secondary reaction predominates over tyrosyl trapping, and a thiyl radical is formed and then trapped (Hb-Cys93 or Mb-Cys110). With increasing concentrations of DMPO in the reaction medium, primary radicals have an increasing probability of being trapped. MS/MS was used to identify the specific Tyr and Cys residues forming radicals in the myoglobin system. All data obtained from this combination of approaches support the conclusion that the initial site of radical formation is a Tyr, which then abstracts an electron from a cysteine residue to produce a cysteinyl radical. This complex phenomenon of electron transfer from one radical to another has been investigated in proteins by IST, ESR, and MS. 相似文献
88.