Spectra fibers

Manyam, U. H. Shahriari, M. R. Morris, M. J. A complete spectrum fiber optic pH sensor based on a novel fluorescent indicator doped porous sol-gel material. Proc. SPIE- Int. Soc. Opt. Eng. 1999,3540, 10-18. 

In the first case, there is only partial instead of complete long-range three-dimensional order. Fiber spectrum features are diffuse haloes (besides sharp reflections) on the layer lines. 

As an example of the second case, we may have conformationally disordered chains, but long-range order in the positions of the chain axes (condis crystals [5]). Fiber spectrum features are the occurrence of sharp reflections on the equator only and diffuse reflections on the other layer lines. 

Finally, whenever in matter there is no long range positional but still long-range orientational order, we have ordered liquids, instead of solids. The X-ray spectral features of an ordered liquid with a smectic structure is the occurrence of one or a few meridional sharp reflections in the fiber spectrum, plus polarized halos for an ordered liquid with nematic structure the occurrence of polarized haloes, only. 

The main problem in developing fibers for IR transmission is that silica glass is not transparent in that area of the spectrum. Suitable materials include the selenides and other chalcogenide glasses (particularly for the CO2 laser light source) and the fluorohafnate glasses. In addition, materials, such as zirconium fluo-... 

Although some neural fibers respond to sweet-stimulus compounds placed on the tongue, others do not. This pattern of sensitivity is often a very complicated one. The fibers often respond to more than one, sometimes even to all, of the four taste modalities. Very rarely does a fiber respond specifically to only sweet or salty substances. Furthermore, other fibers may have an entirely different spectrum of sensitivities, and may respond strongly to one sweetener and very weakly to another. Pfaffmann reported how two fibers, one having one pattern of sensitivity to taste, and the other, a different pattern, can signal two different taste-qualities, even though... 

A supramolecular assembly of macromolecules bearing antenna dendron has been reported. Pyrazole-anchored PBE dendrons were synthesized to examine the coordination behavior to transition-metal cations (Cu, Au, Ag) [31]. Self-assembled metallacycles were found. The Cu-metallacycle further formed luminescent fibers about 1 pm in diameter. The luminescence (605 nm) occurred by the excitation of the dendron (280 nm) and the excitation spectrum was coincident with the absorption spectrum of the dendron, suggesting the antenna effect. Interestingly, the luminescence of the Cu-metallacycle fiber disappeared when the fiber was dissociated into the individual metallacycles in C2H2. 

Optical emision spectra nowadays are simply measured using a fiber optic cable that directs the plasma light to a monochromator, which is coupled to a photodetector. By rotating the prism in the monochromator a wavelength scan of the emitted light can be obtained. Alternatively, an optical multichannel analyzer can be used to record (parts of) an emission spectrum simultaneously, allowing for much faster acquisition. A spectrometer resolution of about 0.1 nm is needed to identify species. 

After the electrolysis for 5 h at —0.15 V with the bubbling of O2 into W, the amount of CO2 produced was found to be 1.6 x 10 moles. A photoabsorption spectrum of the NB after electrolysis gave a peak at 780 nm. The peak was identical with that of the one electron oxidation product of DMFC, DMFC, which had been prepared coulometrically by using a column electrode with glassy carbon fiber working electrode [40]. This fact indicates that the electrolysis product was DMFC. The DMFC produced by the electrolysis was estimated to be 3.08 x 10 moles. 

Unlike methane and the other alkanes, aromatic hydrocarbons have absorptions in the UV part of the spectrum, and thus may be detected through UV spectrometry using silica fibers. This scheme is useful for "aromatic" water pollutants such as toluenes and xylenes with their absorption bands between 250 and 300 nm. Similarly, nitrate anion can be monitored (albeit with low sensitivity) in water via its UV absorption at 250 nm. 

More fluorescence features than just the emission intensity can be used to develop luminescent optosensors with enhanced selectivity and longer operational lifetime. The wavelength dependence of the luminescence (emission spectmm) and of the luminophore absorption (excitation spectrum) is a source of specificity. For instance, the excitation-emission matrix has shown to be a powerful tool to analyze complex mixtures of fluorescent species and fiber-optic devices for in-situ measurements (e.g. 

Fig. 2.15 (a) The change in the transmission spectrum of a fiber Bragg grating coated with DH6/ PMMA in response to DNT. The sensor was exposed to saturated DNT vapor at room temperature. The measurements were taken at time intervals of one hour. The last measurement was taken after the sensor was exposed to DNT for 16 h. (b) The change of optical power at the output end of the fiber sensor for light of the wavelength of 1,562.9 nm. Reprinted from Ref. 33 with permission. 2008 American Chemical Society... 

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