Mapping spectral

Concepts Interaction of radiation with matter Light and matter interact by scatter and absorption. Absorption only occurs when the colour of the radiation is the same as an energy separation within the molecule, but scatter occurs at all wavelengths 

Telescopes Instruments for collecting the light from the stars either outside the Earth s atmosphere in orbit or on the Earth collecting the light through the atmospheric windows. Each telescope has a finite spatial resolution 

Atomic structure The energy levels of the electron around the atom are controlled by quantum mechanics 

Spectroscopy The absorption of radiation between two energy levels within an atom or molecule 

Selection rules Some transitions in spectroscopy are allowed and some are forbidden 

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Figure 2.7 (a) Tip-enhanced near-field Raman spectral mapping ofthe adenine nanocrystal at 30 nm intervals, (b) Raman intensity distribution of two major bands at 739 cm and 1328cm. ... 

The transformation by log double-centering has received various names among which spectral mapping [13], logarithmic analysis [14], saturated RC association model [15], log-bilinear model [16] and spectral map analysis or SMA for short [17]. 

Each of the three approaches will be applied in this section to the transformed retention times of the 23 chalcones with eight chromatographic elution methods in Table 31.2. The transformation is defined by the successive operations of logarithms, double-centering and global normalization which is typical for the method of spectral map analysis (SMA) ... 

P. J. Lewi, Spectral mapping, a technique for classifying biological activity profiles of chemical compounds. Arzneim. Forsch. (Drug Res.), 26 (1976) 1295-1300. 

P.J. Lewi, Spectral map analysis. Analysis of contrasts, especially from log-ratios. Chemom. Intell. Lab. Syst., 5 (1989) 105-116. 

According to Andersen [12] early applications of LLM are attributed to the Danish sociologist Rasch in 1963 and to Andersen himself. Later on, the approach has been described under many different names, such as spectral map analysis [13,14] in studies of drug specificity, as logarithmic analysis in the French statistical literature [15] and as the saturated RC association model [16]. The term log-bilinear model has been used by Escoufier and Junca [ 17]. In Chapter 31 on the analysis of measurement tables we have described the method under the name of log double-centred principal components analysis. 

For a detailed description of spectral map analysis (SMA), the reader is referred to Section 31.3.5. The method has been designed specifically for the study of drug-receptor interactions [37,44]. The interpretation of the resulting spectral map is different from that of the usual principal components biplot. The former is symmetric with respect to rows and columns, while the latter is not. In particular, the spectral map displays interactions between compounds and receptors. It shows which compounds are most specific for which receptors (or tests) and vice versa. This property will be illustrated by means of an analysis of data reporting on the binding affinities of various opioid analgesics to various opioid receptors [45,46]. In contrast with the previous approach, this application is not based on extra-thermodynamic properties, but is derived entirely from biological activity spectra. 

Fig. 37.4. Spectral map of the 26 opioid agonists and antagonists in 4 receptor binding tests, as described by Table 37.7 [45, 46]. Circles refer to the compounds. Squares represent the binding tests. Areas of circles and squares are proportional to the marginal mean affinities in the table. The lines that join the three poles (DHM, DADLE and EKC) of the map represent axes of contrast between the p-, 8-and K-opioid receptors. The horizontal and vertical components represent 18 and 79%, respectively, of the interaction in the data.

The spectral map shows three distinct poles of specificity. These are respectively the p-receptor (DHM), the 6-receptor (DADLE) and the K-receptor (EKC). The naloxone receptor (NAL) appears to be strongly correlated with the p-receptor (DHM) and, hence, provides little additional information. In spectral map analysis, correlation between variables, as well as similarity between compounds, is evidenced by the proximity of their corresponding symbols. The lines drawn through the three poles of the map represent bipolar axes of contrast. A contrast is defined in this context as a log ratio or, equivalently, as a difference of logarithms. For example, the horizontal axis through the p- and 8-receptors defines the p/6 contrast. Compounds that project on the right side of this axis bind more specifically to the p-receptor, while those that project on the left side possess more... 

It appears from the spectral map that the K-receptor is a highly specific receptor which produces strong contrasts in binding affinities of opioid analgesics. The contrast is most evident in ketazocine, ethylketazocine and buprenorphine which possess much more affinity for the K-receptor than for the two others. The contrast is also strong with dihydromorphine, beta-endorphin, an enkephalin analog and two experimental compounds (LY and FK) which have little or no affinity for the K-receptor. 

P.J. Lewi, Spectral mapping of drug-test specificities. In Advanced Computer-Assisted Techniques in Drug-Discovery (H. van de Waterbeemd, Ed.). VCH, Weinheim, Germany, 1994, pp. 219-253. 

G. Calomme and P.J. Lewi, Multivariate analysis of structure-activity data. Spectral map of opioid narcotics in receptor binding. Actual. Chim. Therap., S.l 1 (1984) 121-126. 

Harris, A. T. (2006). Spectral mapping tools from the earth sciences applied to spectral microscopy data. Cytometry A 69, 872-9. 

Spectral mapping Setting a spectrometer to a specific transition in an atom or molecule and mapping the sky... 

Spectral mapping Using a known transition in a molecule, such as the 155 GHz transition in CO, to map the column density or concentration of the molecule within a giant molecular cloud. 

Goldsmith P. et al. (2006). Spectral Mapping of the Taurean Molecular Cloud (in preparation)... 

G. Qros, T. Cserhati and E. Forgacs, Separation of the strength and selectivity of the microbiological effect of synthetic dyes by spectral mapping technique. Chemosphere, 52 (2003) 185-193. G. Oros, T. Cserhati and E. Forgacs, Strength and selectivity of the fungicidal effect of diazobenzene dyes. Fres. Env. Bull., 10 (2001) 319-322. 

E. Forgacs, T. Cserhati, S. Balogh, R. Kaliszan, R Haber and A. Nasal, Separation of strength and selectivity of mobile phase by spectral mapping technique. Biomed Chromatogr., 15 (2001) 348-355. 

The unified plotting of loadings and scores is a standard characteristic of two techniques plots on the factors of correspondence analysis and spectral maps These techniques are at the beginning of their use in food chemistry. 

A kind of logarithmic transform, such as In (1 -I- x), is used in spectral maps within row and column centring and global standardization (division by the standard deviation around the mean of all the values of the data matrix). 

Geologic data for asteroid 4 Vesta, (a) Spectral map of a part of the surface of Vesta as it rotates, showing the distribution of HED-like lithologies, modified from Binzel et at. (1997). (b) Interpretive geologic cross-section of Vesta, illustrating how HED meteorites might be distributed in the interior,... 

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