Densitometers

It is known and widely applied a method, when the spatial model of object is formed by a set of plane sections or tomographic slices. An experienced sample, created in Californian University and reffered to as Dynamic Cardiac 3D densitometer, is constructed by this principle [2]. The serial model of this tomograph of the company Imatron Associates appeared on the market in the end 1983r.[13]. On this basis a line of computer tomographs has been created. 

Boyd D.P., Gould R.G., Quinu J.R, Sparks R., Stanly J.H., Herrmansfedt W.B. A proposed dynamic cardiac 3-D densitometer for early detection and evaluation of heart disease., IEEE Trans. Nucl. Sci., V. NS-26, 1979, p.2724-2727. 

The diagnostic system DK-ID comrising the X-ray densitometer and special equipment for speciments prepare is designed in MSIA Spectrum . This system is actively used by several Russian companies dealing with forestry. The fact of efficient radiographic tomography use, when inspecting the conditions of trees in the forests is also known. 

Fig. 2. Tic densitometer scans showing the resolution of isoproterenol on a hpflc siUca-gel plate obtained using a mobile phase consisting of 6.8 mM (1 R)-(—)-ammonium-10-camphorsu1fonic acid in 75 25 (v/v) methylene chioride methano1. (a) 254 nm, (b) 275 m, (c) 300 nm.

Eig. 15. Micro densitometer tracings of x-ray line exposures with line widths of (a) 10 and (b) 1000 p.m. 

Guidelines for uniform density and dot gain limits have been estabHshed. These criteria ate the standards used to control the press. A densitometer is used to measure these standards and measurements ate made on sheets removed as the press is mnning. The operator then uses these measurements to guide press adjustments, primarily ink flows, to correct the printed result to standard (8). 

For semiquantitative or quantitative analyses, the separated dyes can be measured with a reflectance densitometer or they can be extracted from the plate or paper and measured by transmittance spectrophotometry. 

To quantitate proteins from staining, a densitometer aided by computer software is used to evaluate band areas of samples compared to band areas of a standard curve. Amido black, Coomassie Brilliant Blue, and silver stains are all appHcable for use in quantification of proteins. 

Direct Mass Measurement One type of densitometer measures the natural vibration frequency and relates the amplitude to changes in density. The density sensor is a U-shaped tube held stationaiy at its node points and allowed to vibrate at its natural frequency. At the curved end of the U is an electrochemical device that periodically strikes the tube. At the other end of the U, the fluid is continuously passed through the tube. Between strikes, the tube vibrates at its natural frequency. The frequency changes directly in proportion to changes in density. A pickup device at the cui ved end of the U measures the frequency and electronically determines the fluid density. This technique is usefiil because it is not affec ted by the optical properties of the fluid. However, particulate matter in the process fluid can affect the accuracy. 

Head meters with density compensation. Head meters such as orifices, venturis, or nozzles can be used with one of a variety of densitometers [e.g., based on (a) buoyant force on a float, (b) hydrauhc couphug, (c) voltage output from a piezoelectric ciystal, or (d) radiation absolution]. The signal from the head meter, which is proportional to pV" (where p = fluid density aud V = fluid velocity), is multiphed by p given by the densitometer. The square root of the produc t is proportional to the mass flow rate. 

Velocity meters with density compensation. The signal from the velocity meter (e.g., turbine meter, electromagnetic meter, or sonic velocity meter) is multiplied by the signal from a densitometer to give a signal proportional to the mass flow rate. 

Daniell cell 64 d.c. arc source 763, 771 Dead-stop end points 635 Decantation 119 Decomposition potential 504 Degreasing agent 80 Delves cup 788 Demasking agents 312, 334 Densitometers 231, 232 Depolariser anodic, 515 cathodic, 509... 

The apparent and partial molar volumes of aggregated sodium octyl, decyl, dodecyl, and tetradecyl sulfate molecules have been studied in detail by Vass et al. [144] from densities measured by a vibrating capillary densitometer in normal and 99.85% heavy water at 25°C and by Vass [130] from density, small-angle scattering, and positron annihilation measurements. 

Thin-layer chromatography (TLC) is used both for characterization of alcohol sulfates and alcohol ether sulfates and for their analysis in mixtures. This technique, combined with the use of scanning densitometers, is a quantitative analytical method. TLC is preferred to HPLC in this case as anionic surfactants do not contain strong chromophores and the refractive index detector is of low sensitivity and not suitable for gradient elution. A recent development in HPLC detector technology, the evaporative light-scattering detector, will probably overcome these sensitivity problems. 

In the following, an example from Chapter 4 will be used to demonstrate the concept of statistical ruggedness, by applying the chosen fitting model to data purposely corrupted by the Monte Carlo technique. The data are normalized TLC peak heights from densitometer scans. (See Section 4.2) ... 

A characteristic color is then formed, which is then ready by reflection on a densitometer (60). The principle of this system is shown in Figure 41. 

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