Removal of artifacts

Third morphological treatment removal of artifacts (small objects less than 20 pixels in size)... 

Figure 4.7 Removal of artifacts (i.e., connected objects less than 20 pixels in area).

Artifact removal and/or linearization. A common form of artifact removal is baseline correction of a spectrum or chromatogram. Common linearizations are the conversion of spectral transmittance into spectral absorbance and the multiplicative scatter correction for diffuse reflectance spectra. We must be very careful when attempting to remove artifacts. If we do not remove them correctly, we can actually introduce other artifacts that are worse than the ones we are trying to remove. But, for every artifact that we can correctly remove from the data, we make available additional degrees-of-freedom that the model can use to fit the relationship between the concentrations and the absorbances. This translates into greater precision and robustness of the calibration. Thus, if we can do it properly, it is always better to remove an artifact than to rely on the calibration to fit it. Similar reasoning applies to data linearization. 

There are various approaches to the data-reduction task. An often used one consists of computing the modulus of the complex phase-detector signal. This removes all offset imperfections as well as any receiver phase misad-justment, bringing us theoretically to what we would have by summing the outputs of two independent, ideal diode detectors. In this case, however, the original signals are still available and can be used to check various aspects of data quality, carry out additional corrections (such as removal of noise-rectification artifacts), or submitted to alternative evaluation algorithms. 

However, we have observed that values obtained with crude extracts were only qualitative. Often, they did not accurately estimate the quantities of the individual enzymes present. Inhibitors were typically present that caused the underestimation of certain enzymes ie.g., ligninases Table II) and that could potentially mask less dominant enzymes. Also, certain polysaccharidases e.g., hemicellulases) were often overestimated due to the action of non-specific or synergistic enzymes e.g., other hemicellulases or cellulases) (9,14), This artifact resulted in low apparent recovery of a given activity and only moderate increases in specific activity upon purification of the major corresponding enzyme present, in spite of the fact that SDS polyacrylamide gels indicated good recovery and substantial removal of contaminants (14),... 

It is found that multiplication of the Fourier transform of the data by a carefully chosen window function is very effective in removing the artifacts around peaked functions. This process is called apodization. Apodization with the triangular window function is often applied to Fourier transform spectroscopy interferograms to remove the ringing around the infrared... 

Fig. 17 Effectiveness in removing the artifacts from the spectrum of multiplying the interferogram by the proper window function before extending the interferogram by a finite number of points, (a) Cosine interferogram of Fig. 13(a) premultiplied by the triangular window function of Fig. 14(b) before extending by 50 data points, (b) Restored spectral line.

One important application of electrolytic treatment is the removal of harmful anions, such as chloride and sulphide, from the mineralized archaeological artifacts. The negative polarization of the system repels the negatively charged species out of the cathode. The process is often accompanied by the formation of either gas or soluble species in the electrolyte. This kind of treatment was carried out to increase the rate of extraction of chlorides from iron (see Fig. 6.1) [295], copper [296], and aluminium [297] mineralized objects. 

Fig. 6.1 Curve showing the chloride egress (filled squares, left axis) from the artifact (dosed in solution), and corresponding variations of the rest potential (open squares, right axis) of the object. After 500h, a potential U = —1.52V was apphed, which accelerated the rate of removal of Cl (after [295])...

The spectral quality and the efficiency of the basic COSY and the DQ-filtered COSY experiments may be improved with the use of field gradients instead of phase cycling for coherence selection, which remove spectral artifacts and make time consuming phasecycling superfluous. 

Load the spectrum of peracetylated glucose D NMRDATA GLUCOSE 1D H GH 001999.1 R. Expand the central region and locate the spike at the carrier frequency, which appears in the middle of the spectrum. Use the Adjust Point option to remove this artifact. 

Lambert-Beer equation (equation 14). With the provision of a reference HO absorption spectrum, and with care to avoid local instrumental artifacts that affect the two beams differently, this design allows the removal of extraneous atmospheric absorption features without requiring assignment to known absorbing species. 

Saponification is a purification procedure to remove unwanted lipids and chlorophylls. It has to be omitted when alkali-labile carotenoids (e.g., astaxanthin, fucoxanthin) or carotenoid esters are to be analyzed. To prevent the formation of artifacts produced by aldol condensation between acetone and carotenals, all traces of acetone have to be removed prior to saponification (41). 

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