Artefacts subtraction

High-speed cyclic voltammetry10 can easily be done at microelectrodes, increasing the range of rate constants accessible by the technique. This is because of the reduced capacitive contribution at microelectrodes— sweep rates of up to 106Vs-1 at microelectrodes have been reported. Nevertheless capacitive current subtraction is essential at these rates and instrumental artefacts can appear, which must be taken into account. 

In friction force microscopy, laser light interference may lead to artefacts that are often eliminated by subtracting trace and retrace (after scan line shift correction). 

Quality On each transient only the desired signal is detected, avoiding the need for signal addition/subtraction in the steps of a phase cycle. Difference artefacts are thus not encountered, and the ti-noise often associated with these in 2D spectra is reduced, providing cleaner spectra. 

Optimising difference experiments Minimising subtraction artefacts... 

Figure 8.28. NOE difference artefacts shown by an asterisk in the difference spectrum (b), arise when two similar, but not quite identical, signals are subtracted in an attempt to reveal the genuine NOEs (N). The artefacts can be attenuated a little through the use of line-broadening window functions (c, lb = 1 Hz).

A long-known solution to the background problem is to record alternating spectra with and without illumination, and then subtract them. Apart from the degradation of the sensitivity by a factor of V5 because CIDNP is only acquired in one-half of the spectra but the noise in all of them, this is plagued by the usual artefacts of... 

The use of FTIR spectrometers is now almost universal. The accuracy, sensitivity and reproducability of the new instrumentation have facilitated the development of a range of new data processing methods such as spectral subtraction, deconvolution, curve resolving etc., and new sampling techniques, but it is essential to remember that the underlying principles of infrared spectroscopy have not changed. The precautions necessary to avoid spectral artefacts are thus an important aspect of the work. 

The electrical bandwidth ranged from d.c. to 1 MHz the dwell time of the transient recorder was 2 /xs. The fluorescence artefact was subtracted. 

The same principle goes for biological organisms of any kind, for human artefacts, and even for human ideas. Additions consist of births and in-migrants subtractions of deaths and out-migrants. The rate of additions and subtractions to a population, however, is going to depend upon its own size and the size of the other populations of the ecosystem. (Boulding, 1983)... 

The acquisition of blank (baseline) runs for comparison with the kinetic data set is to be recommended. Data obtained from suitable blank runs should be subtracted from the main kinetic data in order to correctly define the CD change of interest (i.e. to correct for any CD offset together with any pressure induced artefact present immediately after mixing). 

Widespread species (e.g. Inga edulis Mart.) were coded for only the area from which they were sampled, which subtracts real ambiguity from the analysis because a clade may then be distinctly geographically distributed, but only as an artefact of not including all possible areas of occurrence for the constituent species. 

A common approach for UP spectra in the literature is the data treatment by subtraction of spectra (particularly the underlying support) in order to make changes in electron density better visible, i.e. [29]. This approach is omitted in this thesis, as this often based on incomparable spectra (due to changing operation conditions of the EES experimental setup) and results in artefact peaks, with no physical meaning [8]. 

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