Search results for "SHIFT"
showing 10 items of 1226 documents
3-Formyl-BODIPY Phenylhydrazone as a Chromo-Fluorogenic Probe for Selective Detection of NO2 (g)
2016
Anew colorimetric and fluorogenic probe,based on a3-formyl boron dipyrromethene (BODIPY)phe-nylhydrazone, for the sensitive and selectivedetectionNO2(g) has been prepared. The probeinsolution experi-ences aremarkablehypsochromic shift of its absorptionand fluorescence emission bands in the presence gaseousNO2(g), leading to limits of detectio noffew ppb. Theprobe also works in the solid phase, adsorbed on filterpaper strips, or chemically immobilized on the surfaceofsilica nanop articles, with limitsofdetection to the nakedeye of about 0.5 ppm.
1H,13C and19F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects
2005
Seventeen N-(mono-, di-, tri-, tetra- and penta-fluorophenyl)-N′-(3-nitrophenyl)ureas were prepared and characterized. Complete assignment of their 1H, 13C and 19F NMR data was undertaken and the correlation of the chemical shifts of the ureido protons with field-inductive and mesomeric electronic substituent parameters was studied using the Swain–Lupton model. The best correlations were obtained when the study was limited to certain substitution patterns, e.g. non-ortho, mono-ortho- and di-ortho-fluorinated ureas, which reveal probable changes in conformations caused by the degree of ortho fluorination at the phenyl ring. Additionally, there is an excellent linear cross-correlation between…
Substituent Effect in 2-Benzoylmethylenequinoline Difluoroborates Exhibiting Through-Space Couplings. Multinuclear Magnetic Resonance, X-ray Diffract…
2012
The series of nine 2-benzoylmethylenequinoline difluoroborates have been synthesized and characterized by multinuclear magnetic resonance, X-ray diffraction (XRD), and computational methods. The through-space spin-spin couplings between (19)F and (1)H/(13)C nuclei have been observed in solution. The NMR chemical shifts have been correlated to the Hammett substituent constants. The crystal structures of six compounds have been solved by XRD. For two derivatives the X-ray wave function refinement was performed to evaluate the character of bonds in the NBF(2)O moiety by topological and integrated bond descriptors.
Addressing subphthalocyanines and subnaphthalocyanines features relevant to fluorescence imaging
2018
International audience; A series of new synthetic subphthalocyanines bear structural features aimed at allowing either fluorescence activation or a bathochromic shift of the absorption band towards the near-infrared window, relevant to optical imaging. X-ray diffraction studies of four subphthalocyanines are reported. Spectrofluorimetric studies on subnaphthalocyanines and activatable subphthalocyanine pro-fluorophores are reported.
Experimental observation of temporal dispersion gratings in fiber optics
2017
We experimentally demonstrate a temporal analog to the diffraction optical grating in the Fraunhofer formalism. Using amplitude and phase temporal periodic modulations, we show that the accumulation of dispersion in fiber optics induces the development of temporally well-separated sidebands similar to the spatial orders of diffraction that are commonly observed in an optical grating operating in the far field.
Focal shift in optical waves with off-axis focus
2003
We present a formulation for a suitable description of the focal shift in optical waves that have an off-axis focus. This shift that is primarily produced along the chief axis is given in terms of the focal distance and depends only on a parameter that is named as the generalized Fresnel number. Any non-uniform, either truncated and non-apertured optical beam with off-axis focus may be considered.
Experimental and theoretical NMR and IR studies of the side-chain orientation effects on the backbone conformation of dehydrophenylalanine residue
2011
Conformation of N-acetyl-(E)-dehydrophenylalanine N', N'-dimethylamide (Ac-(E)-ΔPhe-NMe(2)) in solution, a member of (E)-α, β-dehydroamino acids, was studied by NMR and infrared spectroscopy and the results were compared with those obtained for (Z) isomer. To support the spectroscopic interpretation, the Φ, Ψ potential energy surfaces were calculated at the MP2/6-31 + G(d,p) level of theory in chloroform solution modeled by the self-consistent reaction field-polarizable continuum model method. All minima were fully optimized by the MP2 method and their relative stabilities were analyzed in terms of π-conjugation, internal H-bonds and dipole interactions between carbonyl groups. The obtained…
On ergodic operator means in Banach spaces
2016
We consider a large class of operator means and prove that a number of ergodic theorems, as well as growth estimates known for particular cases, continue to hold in the general context under fairly mild regularity conditions. The methods developed in the paper not only yield a new approach based on a general point of view, but also lead to results that are new, even in the context of the classical Cesaro means.
Some characterizations of operators satisfying a-Browder's theorem
2005
Abstract We characterize the bounded linear operators T defined on Banach spaces satisfying a-Browder's theorem, or a-Weyl's theorem, by means of the discontinuity of some maps defined on certain subsets of C . Several other characterizations are given in terms of localized SVEP, as well as by means of the quasi-nilpotent part, the hyper-kernel or the analytic core of λ I − T .
Tunable dual-wavelength thulium-doped fiber laser in the range from 2067 to 2073.5 nm
2017
A tunable dual-wavelength lineal cavity Tm-doped fiber laser is presented. The generation of the laser lines is based on the use of cascaded fiber Bragg gratings and a Hi-Bi fiber optic loop mirror.