Optical fibers, characterization with

Most Kaminsky catalysts contain only one type of active center. They produce ethylene—a-olefin copolymers with uniform compositional distributions and quite narrow MWDs which, at their limit, can be characterized by M.Jratios of about 2.0 and MFR of about 15. These features of the catalysts determine their first appHcations in the specialty resin area, to be used in the synthesis of either uniformly branched VLDPE resins or completely amorphous PE plastomers. Kaminsky catalysts have been gradually replacing Ziegler catalysts in the manufacture of certain commodity LLDPE products. They also faciUtate the copolymerization of ethylene with cycHc dienes such as cyclopentene and norhornene (33,34). These copolymers are compositionaHy uniform and can be used as LLDPE resins with special properties. Ethylene—norhornene copolymers are resistant to chemicals and heat, have high glass transitions, and very high transparency which makes them suitable for polymer optical fibers (34). 

Most recently, an in vivo investigation of a NIR Con A RET system was reported and the host response characterized.114 In this work, Cy-7-labeled Con A and Alexa Flour 647-labeled dextran system were entrapped with a hollow microdialysis fiber immobilized on the tip of an optical fiber. The device was characterized in vitro, the result of which indicated a response range of 36 150 mg/dL. More important, the device was implanted subcutaneously and evaluated in vivo for 16 days. Results were promising, as the implant readout retained a high degree of correlation with blood glucose fluctuations (as measured by blood-draw methods). An increase in response time was observed at the end of the experimental period, with fibrous encapsulation cited as the cause. 

Weckhuysen and coworkers (Nijhuis et al., 2003) described equipment suitable for parallel Raman and UV-vis spectroscopic measurements. Openings on the opposite sides of a furnace allowed acquisition of Raman and UV-vis spectra through optical grade windows in a tubular quartz reactor. UV-vis spectra were recorded at 823 K. Gas-phase analysis was achieved with mass spectrometry and gas chromatography. A more advanced version of the design (Nijhuis et al., 2004) accommodates four optical fiber probes, placed at 10-mm vertical spacing along the tubular reactor. The temperature that the fibers can withstand is 973 K the reported spectra characterize samples at 823 K. 

Approximate versions of the translational EPR state, wherein the -function correlations are replaced by finite-width (Gaussian) distributions, have been shown to characterize the quadratures of the two optical-field outputs of parametric down-conversion, or of a fiber interferometer with Kerr nonlinearity. Such states allow for various schemes of continuous-variable quantum information processing such as quantum teleportation [Braunstein 1998 (b) Furu-sawa 1998] or quantum cryptography [Silberhorn 2002], A similar state has also been predicted and realized using collective spins of large atomic samples [Polzik 1999 Julsgaard 2001]. It has been shown that if suitable interaction schemes can be realized, continuous-variable quantum states of the original EPR type could even serve for quantum computation. 

Based on the theories of geometric and wave optics, light propagates within optical fibers in the form of orthogonal modes. The light power distribution, in MM fibers, can be analyzed and characterized by using geometric and wave optics. In order to evaluate the MPD, within MM fibers, the wave equation, which is a second-order differential equation, has to be solved in cylindrical coordinate system. A summary of the MPD analysis is presented next, with an example on application to chemical and biosensors. 

Figure 4.14 Fluorescence confocal image of (a) P3DDT + PEO fibers (b) SEM image of a sample of fibers (c) fluorescence confocal image of P3DDT fibers (PEO was removed by washing with acetonitrile) (d) SEM image from the same sample of fibers. (Reprinted with permission from Synthetic Metals, Electrospun polyalkylthiophene/polyethyleneoxide fibers Optical characterization by A. Bianco, C. Bertarelli, S. Frisk et al., 157, 276-281. Copyright (2007) Elsevier Ltd)...

For the optical characterization, the samples were cut directly from the extruded material. Absorption spectra were recorded on a Perkin-Elmer Lambda 9 spectrophotometer and on an Ocean Optics fiber optic spectrometer. The reflectance spectra were recorded using the fiber optics spectrometer with a reflectance probe. 

Simoes E, Abe I, Oliveira J, Frazao O, Caldas P, Pinto JL. Characterization of optical fiber long period grating refractometer with nanocoating. Sens Actuators B 2010 153 335-9. 

Beltran-Perez, G. Lopez-Huerta, F. Munoz-Aguirre, S. CastiUo-Mixcoatl, J. Palomino-Merino, R. Lozada-Morales, R. Portillo-Moreno, O. Fabrication and characterization of an optical fiber pH sensor using sol-gel deposited Ti02 film doped with organic dyes. Sens. Actuators, B 2006, B120, 74—78. 

The fibers were characterized with respect to their density, specific surface area, pore size distribution, microstructure (SEM), and tensile strength (using a special device to ensure fracture of the filaments and not fracture at the spanning clamps fixing the filaments). One example of supercritically dried filaments is shown in Figure 9.11. The filaments are white, soft and ductile with a diameter of 250 pm and in this respect their optical appearance is not different from the monoliths. It would be interesting to use the method of Cai et al. [28] described above in order to investigate whether transparent filaments can be produced. 

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