Linear amplification

The tube of Figure 2-2 can be operated as an ionization chamber, as a proportional counter, or as a Geiger counter. The tube output differs radically from one case to another. Because of these differences, the electronic circuitry associated with the tube must also be different for each case if the pulses from the tube are to be reliably selected and counted. In particular, the circuitry will have to differ in characteristics such as stability, amount of amplification, and time of response. In all cases, linear amplification (amplifier output always proportional to tube output) is desirable. 

Linear amplification, 59 Line designation, 30-34 Line intensity, location of maximum of, 282, 283... 

If distinct peaks cannot be detected with linear amplification gain, change the detector to log amplification. Larger particles, such as E. coli and zymosan, may require log fluorescence amplification gain. 

For every decade of input, the output changes about 120 mV. In commercial logarithmic amplifiers, a subsequent linear amplification stage further amplifies the output voltage to a preset value. A typical input-output characteristic of a commercial logarithmic amplifier is shown in Fig. 11.4. 

Liu CL, Schreiber SL, Bernstein BE. Development and validation of a T7-based linear amplification for genomic DNA. BMC Genomics 2003 4 19. 

Park PJ, Cao YA, Lee SY et al. Current issues for DNA microarrays platform comparison, double linear amplification, and universal RNA reference. JBiotechnol 2004 112 225-245. 

Analyze on a flow cytometer (see Notes 9 and 10). This type of staining can be analyzed on any of the modem flow cytometers with the proviso that the machine is equipped with a pulse processing facility to enable the discrimination of cell doublets. The most commonly used flow cytometer is the Becton Dickinson FACScan. In this machine, PI should be collected into FL3 rather than FL2 to overcome any crossover of the FITC into the FL2 channel The FL3 detector should be routinely set around 400, whereas FL1 is usually set at around 500 in linear amplification Controls, without either BrdU or the monoclonal antibody, should be included whenever possible to determine the lower limits of detection of the DNA precursor. At least 10,000 events should be analyzed, but more might be required in the case of slowly proliferating (low BrdU incorporation) tissues or tumors. 

The methods outlined below include protocols for direct and indirect immunofluorescence staining, that can be adapted easily for the cell type of interest as indicated in the relevant notes. The principal approaches to flow cytometric analysis, standardization and calibration are then given, followed by two more detailed protocols illustrating quantitation using direct immunofluorescence, and a competitive binding assay, which demonstrates the application of linear amplification of fluorescence. 

This method illustrates well the precision with which antibody binding can be measured by flow cytometry, and the use of linear amplification of the fluorescence signal. 

The basic hearing-aid circuit is a linear amplifier, and the simplest hearing aid consists of a microphone, amplifier, and receiver (output transducer). In addition to being commonly prescribed on its own, the linear hearing aid also forms the fundamental building block for more-advanced designs. Thus many of the problems associated with linear amplification will also affect other processing approaches when implemented... 

Lippmann et al., 1981] Lippmann, R., Braida, L., and Durlach, N. (1981). Study of multichannel amplitude compression and linear amplification for persons with sensorineural hearing loss, J. Acoust. Soc. Am., 69 524-534. 

Multi-channel compression systems divide the speech spectrum into several frequency bands, and provide a compression amplifier for each band. The compression may be independent in each of the bands, or the compression control signals and/or gains may be cross-linked. Independent syllabic compression has not been found to offer any consistent advantage over linear amplification [Braida et al., 1979][Lippmann et al., 1981][Walker et al., 1984], One problem in multi-channel compression systems has been the unwanted phase and amplitude interactions that can occur in the filters used for frequency analysis/synthesis [Walker et al., 1984] and which can give unwanted peaks or notches in the system frequency response as the gains change in each channel. 

Braida et ah, 1979] Braida, L., Durlach, N., Lippmann, R., Hicks, B., Rabinowitz, W., and Reed, C. (1979). Hearing aids - a review of past research on linear amplification, amplitude compression and frequency lowering. In ASHA Monogr. 19. Am. Speech-Lang.-Hearing Assn. 

Fig. 3.9. The effect of changes in the photomultiplier tube voltage and amplifier gain on the appearance of six signals with intensities in the relationship of 1 2 10 20 100 200 to each other. A Linear amplification. B Logarithmic amplification, (continued on next page)...

Fig. 3.11. Intensity signals from fluorescent beads (of five different intensities) acquired with linear amplification (top) and logarithmic amplification (bottom). Log amplification permits all five intensities to be on scale (that is, within the 1024 channel range). Additionally, the spread (the CY) and the peak height of the distributions for each bead are visually similar with a log but not with a linear amplifier. From Givan (2001).

Figure 3-6 Discriminator settings for simultaneous detection of 5H and, 4C in linear amplification (e.g., Packard Inst.) at left, and logarithmic amplification (e.g., Beckman), at right.

If two PGR primers include elements that cannot be replicated, an exponential expansion is reduced to arithmetic accumulation. However, if multiple nested sets of internal primers (also nonreplicable) are included, product accumulation (at least in theory) can approach that of PCR. This process is known as linked linear amplification. It requires a polymerase, several sets of nested primer pairs, and thermal cycling similar to PCR. ... 

Phillips J, Eberwine JH. Antisense rna amplification a linear amplification method for analyzing the mrna population from single living cells. Methods 1996 10 283-8. 

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