Direct readout

No contact with the material, no moving parts to wear out or corrode Unaffected by changes in the tension or stiffness of the conveyor belt Direct readout and adaptabiUty to modem controls... 

When the operating conditions are uniform and steady (there are no fluctuations in flow rate or in concentration of CO in the gas stream), the continuous sampling method can be used. A sampling probe is placed in the stack at any location, preferably near the center. The sample is extracted at a constant sampling rate. As the gas stream passes through the sampling apparatus, any moisture or carbon dioxide in the sample gas stream is removed. The CO concentration is then measured by a nondispersive infrared analyzer, which gives direct readouts of CO concentrations. 

Advantages and disadvantages of thermal desorption are listed in Table 9.3. (Charcoal badges are also available which require no pump these are termed passive samplers .) Instruments are also available to give direct readout of atmospheric levels of pollutant. 

Portable or fixed multipoint colorimetric detectors are available which rely on paper tape impregnated with reagent. A cassette of the treated paper is driven electrically at constant speed over a sampling orifice and the stain intensity measured by an internal reflectometer to provide direct readout of concentration. Such instruments are available for a range of chemicals including those in Table 9.7. 

Fluorescence correlation spectroscopy (FCS) measures rates of diffusion, chemical reaction, and other dynamic processes of fluorescent molecules. These rates are deduced from measurements of fluorescence fluctuations that arise as molecules with specific fluorescence properties enter or leave an open sample volume by diffusion, by undergoing a chemical reaction, or by other transport or reaction processes. Studies of unfolded proteins benefit from the fact that FCS can provide information about rates of protein conformational change both by a direct readout from conformation-dependent fluorescence changes and by changes in diffusion coefficient. 

Figures 3 and 4 illustrate how G( r) changes with Keq in the fast reaction regime (tc -C to). For both figures, k and the equilibrium constant A e( = l

A significant advantage of this method is that is provides quantitative information since the IEF technique actually separates the phospho- and dephospho- forms of the protein, the ratio of these species as detected by IEF/immunoblotting is a direct readout of the protein s phosphorylation status within the cell (assuming no selective loss of one species during isolation and analysis). 

Numerous approaches have been published to improve the accuracy of IE data. However, the uncertainty of electron energy remains, causing the ionization efficiency curves not to directly approach zero at IE. Instead of being linear, they bend close to the ionization threshold and exponentially approximate zero. Even though the electron energy scale of the instrument has been properly calibrated against lEs of established standards such as noble gases or solvents, IE data obtained from direct readout of the curve have accuracies of 0.3 eV (Fig. 2.19a). 

Potassium also can be measured by ICP/AES. The wavelengths at which it can be analyzed without interference from other metals are 766.49 and 769.90 nm. Other wavelengths may be used. Potassium ion in aqueous solution can be identified quantitatively by using a potassium ion-selective electrode attached to a pH meter having an expanded millivolt scale or to a specific ion meter having a direct readout concentration scale for potassium. 

Seaman, F.C. Hurley, L.H. (1998) Molecular basis for the DNA sequence selectivity of ecteinascidin 736 and 743 evidence for the dominant role of direct readout via hydrogen bonding. J. Am. Chem. Soc., 120, 13028-41. 

Note Y denotes yes D, direct readout I, integrated collection of samples NA, not applicable and VOCs, volatile organic compounds. Source Adapted from reference 15. 

Less expensive instruments give a direct readout of absorbance and/or transmittance in analog or digital form. These instruments are suitable for single-wavelength measurements however, if a scan of absorbance vs. wavelength (Figure 5.4) is desired, some type of device to display the spectrum must be available. 

Several electrolytic-conductivity detectors are produced (Table 3.5). The Laboratory Data Control Model 701 Conducto Monitor (Fig.3.59) may be operated in either a differential mode or an absolute mode. It provides direct readout in units of specific conductance and differences as small as 0.01% in the differential mode between the carrier and the carrier plus solute can be measured. The dynamic range of linearity is 0.01-100,000 pSl 1 /cm. The detector can function in solvents ranging from distilled water to concentrated salt solutions without the necessity of changing the cell. The volume of the cell is 2.5 pi, and the nominal cell constant is 20 cm-1. This type of detector is of use mainly in high-speed ion-exchange chromatography for the detection of ionic species. 

Methane in aqueous sample determined by direct readout combustible gas detector, available commercially. 

Nametre Direct Readout Viscometer Brochure, Nametre Co. Edison, N.J., 1972. 

An Autolab Model 6300 Digital Integrator was used with the Varian GC to provide a direct readout of elution time (seconds) and relative area under each peak. A Honeywell Electronic 194 recorder displayed elution times and peak height graphically. 

The significance of deliberate or accidental changes of instrumental variables such as aspiration rate, current of the hollow cathode, wavelength, and slit width during an analysis was self-evident. The importance of background correction, especially for the low concentration levels, was another consideration. The importance of the other variables listed, such as the direct readout of concentration, was dependent upon the proper utilization of these instrumental features by the analyst. 

If you don t have a willing bed partner, you can observe your big sister s baby or anyone s pet cat or dog, and have the same thrill of discovery. Of course you can t expect an answer if you ask them if they are dreaming. But you can answer that question for yourself now that you know that the REMs that give brain-activated sleep its most popular name are a direct readout of the internal activation. Not that dreaming occurs exclusively in REM sleep. It doesn t. REM sleep just happens to provide the most ideal condition for its occurrence. 

The evaluation of selected experimental agents as MEK inhibitors was performed by measuring their ability to inhibit phosphorylation of MAP kinase IRK in murine colon 26 (C26) carcinoma cells. Since ERK1 and ERK2 represent the only known substrates for MEK, measurement of ERK phosphorylation inhibition in cells provided direct readout of cellular MEK inhibition by these agents. IC50 testing results associated with cellular inhibition of ERK phosphorylation are provided for Steps 1 and 2 intermediates and phenylamino benzhydroxamic derivatives in Table 5. 

Franklin SJ, Barton JK. Differential DNA recognition by the enantiomers of l-Rh(MGP)2phi a combination of shape selection and direct readout. Biochemistry 1998 37 16093-16105. 

Digital displays are increasingly used in preference to needle-type meters, as they are not prone to parallax errors and misreading of the absorbance scale. Some digital instruments can be calibrated to give a direct readout of the concentration of the test substance. 

Figure 2 Direct readout by P131 (white) and L145 (dark gray) in the first TA step of the PDT025 complex (see Table 1). The DNA bps is depicted in light gray. P131 and L145 contact the C2 position of the adenines in the first TA step.

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