Signal distribution

Fig. 10. Exploded view of a monolithic multicomponent ceramic substrate. Layers (a) signal distribution (b) resistor (c) capacitor (d) circuit protection ...

Data relative to the HNMR spectra of iron derivatives of H3OEC are reported in Table 13. The spectra of the mononuclear complexes Fe(OEC)L (L = Cl, Ph, Py) are typical of paramagnetic species with broad unresolved signals distributed over a large spectral width. 

Figure 2. Relief (a), LF signal distribution (b), and corresponding cross-sections along the white line (c), (d). Constant line slope was subtracted in (c).

As indicated in Fig. 5, the signal is spread out over several elements of the read-out electrode. The role of a position sensitive read-out system is to determine the centroid of the signal distribution. 

The device of Fig. 14 is only a one-dimensional detector. For two-dimensional detectors, several schemes for the localization of avalanches are feasible. However, this needs a careful study of the signal distribution as is shown by the results obtained at CERN... 

Dr. Currie has described this in simple terms "Our basic task is to distinguish the blank or background from a true signal at the detection limit. [That] can be done, provided that the signals are random. Independent, and stationary. To completely specify the false positive (a) and false negative (g) risks, we must know the form of the [signal] distribution and its parameters. For most analytical situations we assume the distribution to be normal (Gaussian), and the dispersion parameter Is simply the Imprecision (standard deviation)."... 

Since the choice of pulse sequence for acquiring the matrix of free induction decays governs the distribution of signals in the resultant 2D spectrum, many different types of 2D NMR experiment are possible, with signal distribution in f and f2 reflecting a variety of different NMR parameters. Several previous reviewsl have offered a simple introduction to 2D NMR methods the aim of this chapter is to provide an overview of work in this field up to July, 1980, and to describe in a little more detail some of the technical features peculiar to these experiments. In the limited space available, experimental aspects will be emphasized at the expense of a full discussion of the spin physics involved the basic mechanisms of most of the experiments to be discussed have been treated fairly extensively in the 1iterature. "3... 

The core of a two-dimensional NMR experiment is the sequence of radiofrequency pulses used to obtain the matrix of time-domain signals S(tj,t2), since it is this which governs the signal distribution in the final spectrum. In the preceding section, one of the earliest high-resolution 2D NMR experiments was used to exemplify the basic features of two-dimensional methods. The details of the experimental methods and data manipulations used are deferred to the next section this section sets out to make a brief summary of the many different types of 2D spectrum that may be produced, and the many and various pulse sequences used to generate them. 

Figure 3. Proton 2D J spectrum for the AX subsystem of thiouracil, signal distribution in f2 showing the usual two doublets, and in fl showing separated doublets for the A and the X protons.

Although no general solution to the problem of the "phasetwist" line shape has yet been presented, in certain cases the antisymmetric part of the real term of Equation 10 can be cancelled out by adding 2D spectra which have the same signal distribution, but the opposite sense of phase rotation in their line shapes. This is particularly simple for spectra that are symmetrical about f = 0, since a simple mirror image provides the necessary partner ... 

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