Spectral encoding

Fig. 13 SPR sensors with wavelength division multiplexing, a Spectral encoding by means of a high refractive index overlayer [38]. b Spectral encoding by means of altered angles of incidence [39]. c Spectral reflectivity with two SPR dips...

Most IR and many Raman instrnments today nse an interferometer, where the spectral encoding takes place, instead of a monochromator. The Michelson interferometer is a mnltiplex system with a simple design - a fixed mirror, a moving mirror and an optical beam splitter. It is illustrated in Figure 2.12 and its use within an FTIR instrument is shown in Figure 2.13. The source radiation hits the beam splitter from where some of the light is reflected to the moving mirror and some is transmitted to the fixed mirror. The mirrors... 

Localized MR spectroscopy was developed to obtain chemical as well as spatial information. Frequency offsets (caused by the inhomogeneous susceptibility or chemical shift distribution) can be recorded by introducing a further measuring domain, called the spectral-encoding domain. Thus, the dimension of the experiment is increased by one. The spatial distribution of compounds with distinct chemical shifts can be obtained as chemical-shift-selective maps. The spatial distribution of frequency offsets can be acquired by imaging pulse sequence, such as echo-time encoding. The method is suited for the... 

Clancy NT, et al. An endoscopic structured lighting probe using spectral encoding. In Sterenborg H, Vitkin lA, editors. Novel biophotortic techniques and applications 2011. 

The sample analysis process is quite simple using a modern spectrometer coupled with a powerful computer. Infrared energy is emitted from a glowing black-body source. This beam passes through an interferometer where the spectral encoding ... 

Chon, J.W.M., Bullen, C., Zijlstra, P., and Gu, M. (2007) Spectral encoding on gold nanorods doped in a silica sol-gel matrix and its application to high-density optical data storage. Adv. Funct. Mater., 17, 875-880. 

G. M. Multiplexed DNA detection using spectrally encoded porous Si02 photonic crystal particles. Anal. Chem. 2009,81, 2618-2625. 

Photoresponsive organic and polymeric molecules have been reported as options for spectrally encoded multilayer data storage devices. For multilayer devices a two-photon induced spectral change gives high three-dimensional spatial resolution because only data bits within the focal volume experience an effect [94]. Gold nanorods are an attractive option for optical data storage. 

Flowever, if only the Darling-Deimison conplmg is important for the conpled stretches, what is its importance telling ns about the internal molecnlar motion It turns out that the right kind of analysis of the spectroscopic fitting Flamiltonian reveals a vast amonnt about the dynamics of the molecnle it allows ns to decipher the story encoded in the spectrum of what the molecule is really doing in its internal motion. We will approach this spectral cryptology from two complementary directions ... 

Several empirical approaches for NMR spectra prediction are based on the availability of large NMR spectral databases. By using special methods for encoding substructures that correspond to particular parts of the NMR spectrum, the correlation of substructures and partial spectra can be modeled. Substructures can be encoded by using the additive model greatly developed by Pretsch [11] and Clerc [12]. The authors represented skeleton structures and substituents by individual codes and calculation rules. A more general additive model was introduced... 

These pairs of encoded structures and their (R spectra are used to ti ain a counterpropagation network (see Section 9.5.5). The two-layer netwoi k pi ocesses the structural information in its upper part and the spectral information in its lower part. Thus the network learns the correlation between the structures and their (R spec tra. This prnciedine is shown in Figine 10.2-8. 

Multivariate data analysis usually starts with generating a set of spectra and the corresponding chemical structures as a result of a spectrum similarity search in a spectrum database. The peak data are transformed into a set of spectral features and the chemical structures are encoded into molecular descriptors [80]. A spectral feature is a property that can be automatically computed from a mass spectrum. Typical spectral features are the peak intensity at a particular mass/charge value, or logarithmic intensity ratios. The goal of transformation of peak data into spectral features is to obtain descriptors of spectral properties that are more suitable than the original peak list data. 

The combination of microscopic and macroscopic information is made possible by what can be called parameter imaging . In the general sense, it consists of the encoding of properties such as spectral line shifts, relaxation times, diffusion coefficients, etc., in the image by suitable combination of corresponding modules into one pulse sequence. Parameter images are to be distinguished from mere... 

Another issue of concern is the amplitude of magnetic field gradients required for solids imaging. For spectra up to a few kHz wide, standard frequency encoding schemes can be used to obtain reasonable spatial resolution. This will not work for broader lines, but it is well known that phase encoding is much more tolerant to line broadening and can be used for spectral widths in excess of 100 kHz with no major loss in spatial resolution. 

Fig. 5.5.14 Schematic diagram showing how the double-phase encoded DEPT sequence achieves both spatial and spectral resolution within the reactor, (a) A spin-echo ]H 2D image taken through the column overlayed with a grid showing the spatial location within the column of the two orthogonal phase encoded planes (z and x) used in the modified DEPT sequence. The resulting data set is a zx image with a projection along y. In-plane spatial resol-ution is 156 [Am (z) x 141 [xm (x) for a 3-mm slice thickness. The center of each volume from which the data have been acquired is identified by the intersection of the white lines. The arrow indicates the direction of flow.

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