Extensive signals

J/cm2. As previously reported (1), excitation at 532 nm resulted in a shorter lifetime (86 4 microseconds) even at the lowest fluence used (0.1 J/cm2), where, with extensive signal averaging, a final signal-to-noise ratio of about 20 was obtained. As noted above the observed fluorescence decays at 532 nm became increasing non-exponential with increasing laser fluence. 

The signal hypothesis was proposed by Blobel and Sabatini pardy to explain the distinction between free and membrane-bound polyribosomes. They found that proteins synthesized on membrane-bound polyribosomes contained a peptide extension (signal peptide)... 

Stopped-flow experiments, illustrated by pathway A of Figure 7.8, are better suited for sample components present at low concentrations since a separated analyte can be selected and held in the NMR probe allowing extensive signal averaging. Execution of stopped-flow acquisition requires calibration of the exact length of time it takes... 

The spectrum may exhibit extensive signal overlap, a problem common with biomolecules. 

Tire immune response depends not only upon recognition of foreign antigens but also upon an extensive signaling network and upon a series of specialized... 

In running the experiment, averaging data in order to improve signal-to-noise ratio is one of the most important features of computer-aided experiments. During the last few years several results have only become possible by extensive signal averaging. One has to keep in mind that most pulse radiolysis experiments utilize concentrations of a few micromol and that absorptivity is already very low, so low that it extends beyond the limits of commercially available steady-state photospectrometer. In some cases quite a few of averages need to be performed because noise reduction is proportional to the square root of the number of experiments. 

Figure 3. (A) C H) NMR spectrum of D-glucose-l- C free in refolding buffer (B) 0.5 mM receptor and 0.1 mM D-glucose-l- C and (C) 0.5 mM receptor and 2 mM D-glucose-1- C. The small resonances to the right of the free a-sugar in the bottom trace appear to be natural abundance carbon signals from impurities or fold over which are observed after extensive signal averaging.

To obtain spectra of very dilute molecular beams with low laser intensities requires extensive signal averaging. Using ion counting techniques the molecular beam intensity is measured with the laser on and off over many thousands of cycles of a mechanical chopper to obtain the absolute fraction of molecular loss. Signal to noise is limited only by the counting statistics. 

Certain relations between intensive and extensive signals are of fundamental significance for system (or transducer) design. According to [3], these relations can be summarized as follows ... 

Extensive signals behave in an additive manner. In consequence, it is not possible to measure extensive signals such as mass or volume in small parts of a system, and therefore sensors for extensive signals cannot easily be miniaturized. For sensors based on microtechnologies, which are normally preferred for mass production due to cost considerations, extensive signals are difficult to handle because there is often no simple level of standardization for batch-oriented fabrication processes. How this problem may be solved is shown in the next section. 

If an extensive signal is to be measured with a low-cost microdevice that can be batch-manufactured, the signal has to first be converted into an intensive signal. For example, the mass flow (extensive) in a tube may be represented by the mass-flow density (intensive) at a small region within the tube. To ensure correct correlation between mass-flow density and mass flow, however, the tube itself becomes an essential part of the measuring setup. Consequently, such sensors are often not testable before their manufacturing process is entirely complete. The stage of production at which a sensor can be tested is cmcial, because it can be ten times cheaper to discard a sensor chip than to discard the complete sensor. 

FlDs with a reduced tip angle increased by a factor of 1.74 for ibuprofen and 1.54 for maleic acid relative to the SIN obtained with 64 FIDs and a 90° tip angle. This is again attributed to the differences in Ti for the two molecules and leads to an inflated ibuprofen concentration (63.1 mM compared to 56.6mM). While the error might be less if the relaxation times are nearly the same for the standard and the analyte, in many quantitation experiments a 90° tip angle and repetition time of >5ri are used, especially if extensive signal averaging is not required. ... 

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