Parallel detectors with

The latest trend is to smaller beads in smaller columns, as this saves eluent and shortens the time for a chromatographic analysis. This argument can be correct if only one suitable detector is used. However, these modern small columns are not optimal for a combination of detectors. So-called multiple detection is a combination of some detectors with different measurement principles (differential refractometer, spectral photometer, light-scattering detector, on-line viscometer) behind the last column, mostly in series, seldom in a branched ( parallel ) order. In this way, the tedious preparative fractionation of a polymer sample can often be avoided. 

The diffractometer has gradually evolved in terms of maximum power of sealed X-ray tubes, rotating anodes, new X-ray optics, better detector efficiency, position-sensitive detection and, lately, real-time multiple-strip (RTMS) fast X-ray detection, which replaces a single detector by an integrated array of parallel detectors to provide an up to 100-fold increase in efficiency compared with traditional detectors without compromise on resolution. Time-resolved powder diffraction is... 

Each serie of measurements consisted of two parallel samples with counting during and after sampling, one with the screen diffusion battery and the second as the reference sample, so that the fractional free radon daughters could be calculated. The radon daughters are collected on a membrane filter (filter diameter 25 mm, pore diameter 1.2 ym) and the decays of Po-218 and Po-214 are counted by means of alpha spectrometry with a surface barrier detector (area 300 mn ). 

The dispersive (+ n, - m ) mode has already been seen clearly with the duMond diagrams, Figure 2.10. Here, the curves are no longer identical and the crystals must be displaced from the parallel position in order to get simultaneous diffraction. As the crystals are displaced, so the band of intersection moves up and down the curve. When the curves become very different, the K 1 and K 2 intensities are traced out separately. Then the peaks are resolved in the rocking curve, and if no better beam conditioner is available it is important in such cases to remove the K 2 component with a slit placed after the beam conditioner. A slit placed in front of the detector, with the detector driven at twice the angular speed of the specimen, also works very well. This is in effect a low resolution triple-axis measurement. 

Charpak, G., Dominik, W., Santiard, J. C., Sauli, F. and Solomey, N. (1989). Gaseous detectors with parallel electrodes and anode mesh planes. Nud. Inst. Methods 274, 275-290. 

Second detector confirmation is another compound confirmation technique. Two detectors with selectivity to different functional groups are connected in series to one column or in parallel to two columns. For example, two detectors, a UV/VIS detector and a fluorometer, connected in series to the HPLC column are used in the EPA Method 8310 for analysis of PAH compounds. If the second detector is connected to a second column of a dissimilar polarity, then the confirmation becomes even more reliable. An example of such a configuration is organophosphorus pesticides analysis the samples may be initially analyzed with an NPD, and then confirmed on a different column with an ECD or a FPD. 

The actual system consisted of two parallel rows with 10 SAR elements each [141]. The channels underwent a linear change of the width and depth to turn and reshape the flow. The mixer was an element that was intended to be integrated in a system comprising a mixing unit, reaction channel and an optical detector with crossed cylindrical lenses and optical fibers. 

OIDs are now available which can be used as parallel light detectors with up to 2000 channels in the linear mode of operation and many tens of thousands in the two-dimensional mode of... 

Figure 5.1b represents the corrected data from the detector, with intensity contours plotted as a function of the scattering vector perpendicular (Q.) and parallel (Q.) to the layers. As shown in Figure 5.1a, the samples were mounted with the clay layers horizontal to the ground, and the scattering pattern in Figure 5.1b consists of two lobes of intensity above and below the plane of the layers in the gel, defined as the Ay-plane in Figure 5.1a. If the layers were perfectly parallel, then coherent...

As already mentioned, area (or position sensitive) detectors were first developed for neutron crystallography, since neutrons are scarce and expensive and it is important both to shorten the experiment and to use aU neutrons scattered by a sample in various directions, rather than waste all but one reflection at a time. Besides 2D scintillation detectors, there are banana ID multiwire detector and 2D detectors with two mutually perpendicular sets of parallel wires. The latter design is usefiil for time-of-ffight experiments because of ideal time resolution once an ioiuzation discharge induces current in one or more wires, we instantly know both the place and time of its arrival. 

The diffusion-layer imaging technique which was developed by McCreery is another method for studying intermediates in the diffusion layer [71-75]. A laser beam is directed in a parallel direction through the diffusion layer of the electrode and the light is then magnified and focused on a diode-array detector. With this method, spatial resolution of the diffusion layer of 1.25 pm is achieved, and concentration profiles in the diffusion layer are mapped. A detailed description of mass transport processes as well as the kinetics and spectra of intermediates can be obtained. Diffusion coefficients and extinction coefficients for, for example, the benzophenone radical anion were measured with this technique [74, 75]. 

One day, Jim (Lovelock) poked a hole in one of the tritium foils and the plane parallel detector was ready to test.. .. A mixture of components containing different functional groups along with 2 or 3 hydrocarbons was prepared and injected onto a capillary column. Positive deflections were recorded for the hydrocarbons and a series of negative deflections for the ketones, aldehydes, alcohols and particularly the halogenated substances. The electron capture detector came into being with full force. 

Figure 2.36. Diffractometer associating a position sensitive detector with aflat plate sample and a parallel beam...

Figure 11.19 Schematic diagram of a quadrupole mass analyzer. Four cylindrical or parabolic metal rods are held in a parallel configuration with fixed or oscillating electric fields applied, as negative or positive, to opposing pairs of rods. The frequency and field strength can be so adjusted that only one ion of a given m/z can make the journey down the axis between the rods to the detector. The electric fields can be gradually adjusted or scanned (over a matter of mseconds) to allow a series of ions to reach the detector, thus giving the mass spectrum.

Fig. 6.14 FIA configurations with two detectors for development of kinetic methods, (a) Serial configuration (b) parallel configuration with single injection and splitting of sample (c) parallel configuration with dual injection. R, reagent C, carrier S, sample D, detector W, waste.

The Solid Angle for a Disk Source Parallel to a Detector with a Circular Aperture... 

Consider a disk source parallel to a detector with a circular aperture (Fig. 8.9). Starting with Eq. 8.4, one may obtain an expression involving elliptic integrals or the following equation in terms of Bessel functions ... 

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