Substraction, Digital

The recorded digital image is processed by a PC computer. Typical operations are image magnification, contrast stretcliing and false colouring, image substraction or addition, determination and evaluation of profiles. 

The infrared spectra of the different samples were taken with a Fourier Transform infrared spectrometer (Digilab FTS-14) using the double beam mode vs. air as reference. 150 scans per sample and 100 scans per reference, at a resolution of 4 cm-l, were taken for every sample. All spectra were stored on tape, and a digital substraction of the after- and- before UV exposure (or any other sample treatment) spectra was performed, whenever needed, by an on-line computer, thus permitting a better visualization of the spectral changes in the polymer by UV- photooxidation. 

Figure 3 Score profiles for cxlbjarde (Figure 3A) and for cox3 parde (Figure 3B) of cytochrome oxidase from Paracoccus denitrificans [14] are obtained by substraction of turn preferences from a-helix preferences (full line). Digital predictions, as outcome of the best training procedure for the SPLIT algorithm with Kyte-Doolittle hydropathy scale (Methods), are shown as bold horizontal bars at the score level 0.5. Observed location of TMH segments are shown as bold horizontal bars at the score level 0.2.

Covey AM, Brody LA, Maluccio MA, Getradjdman GJ, Brown KT (2002) Variant hepatic arterial anatomy revisited digital substraction angiography performed in 600 patients. Radiology 224 542-547... 

With the help of an additional digital memory, is stored and then sent back twice with a difference of AA to the storage oscilloscope. After substraction one obtains the second derivative. This process can be repeated if higher-order derivatives are desired. 

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