Detectors direct

In TOF-SARS [9], a low-keV, monoenergetic, mass-selected, pulsed noble gas ion beam is focused onto a sample surface. The velocity distributions of scattered and recoiled particles are measured by standard TOF methods. A chaimel electron multiplier is used to detect fast (>800 eV) neutrals and ions. This type of detector has a small acceptance solid angle. A fixed angle is used between the pulsed ion beam and detector directions with respect to the sample as shown in figure Bl.23.4. The sample has to be rotated to measure ion scattering... 

In contrast, solute property detectors directly measure some physico-chemical property of the eluate species... 

Principles and Characteristics Mass-spectral analysis methods may be either indirect or direct. Indirect mass-spectral analysis usually requires some pretreatment (normally extraction and separation) of the material, to separate the organic additives from the polymers and inorganic fillers. The mass spectrometer is then used as a detector. Direct mass-spectrometric methods have to compete with separation techniques such as GC, LC and SFC that are more commonly used for quantitative analysis of polymer additives. The principal advantage of direct mass-spectrometric examination of compounded polymers (or their extracts) is speed of analysis. However, quite often more information can be... 

Where process equipment is provided with fixed-temperature detectors, these should be located as near as possible to the potential fire source for example, above flammable liquid pump seals, immediately over a solvent draw-off point, or mounted above a crude tank mixer stuffing box. As a general rule, fixed-temperature detectors directed at a potential hazard should be considered only for process equipment where specific fire problems are anticipated. 

The light detector is usually made of an extremely thin optical fiber, whose tip is much smaller than the diameter of a human hair. The light diffused by the sample is collected by the tip of the needle and next conduced to an electronic detector. The detector converts the incoming light intensity into an electrical pulse feeding the computer. In some cases, instead of the optical fiber, the sensor extremity can be just a simple very small solid-state detector directly converting directly the light into an electric pulse. 

Eluate from a chromatography column can be passed through a plasma to atomize and ionize its components and measure selected elements by atomic emission spectroscopy or mass spectrometry. An atomic emission detector directs eluate through a helium plasma in a microwave cavity. Every element of the periodic table produces characteristic emission that can be detected by a photodiode array polychromator (Figure 20-14). Sensitivity for sulfur can be 10 times better than the sensitivity of a flame photometric detector. 

When a. and are very small, Q Q , the scattering plane is nearly parallel to the surface, and diffracting net planes are perpendicular to it. The scattering geometry being defined by the incident beam and detector directions, one has... 

By adding a multiangle light-scattering [1] detector directly into the separation line, as shown schematically in Fig. 1, the eluting molar masses are determined ab-... 

A quantitative analysis of the degradation of the sample substantially requires the use of an on-line absolute detector such as light scattering (SEC-LS). In this case, the on-line LS detector directly measures, without calibration, the molar mass of the sample. The characterization of a series of narrow MMD standards with increasing and known molar mass evidences the degradation of the sample. The simple direct comparison of the known molar mass of the standards and the... 

FIG U RE 14.1 Geometry of scattering for an incident wave from the negative x-axis with propagation direction defined by the incident wave vector k. and with polarization (pol.) parallel to z. Light is scattered to the detector in the direction of the scattering wave vector k. Scattered polarization will be in the direction of the projection of the incident polarization onto the plane p, which is perpendicular to the detector direction. 

Btoautographic determinations, where test organisms, tissue homogenates or cell organelles are applied in aggr or gelatine solution as detectors directly on the ... 

Each improvement or discovery in the field of radiation sources (lasers for exemple) or in the field of detectors monodimensional and area detectors) directly brings up new steps forwards in our knowledge of matter. 

One of the most important techniques for kinetic studies at high temperatures to emerge during the post war years has been the shock tube (2). Two modes for its operation have been in common use. One is to observe chemical reactions, via spectroscopic detectors, directly behind the incident shock wave. A second is to use the shock wave reflected from the end of the shock tube to heat a gas mixture for longer times (1 to 10 msec) and then analyze the products chemically. Because the reflected shock wave has a peculiar time-temperature history, it does not yield very precise or accurate rate constants. 

The quantification of whole vims particles in the presence of subunits bearing the same epitope using the same mAb as capture and detector (direct sandwich ELISA). 

SS, 3 X 2nun). A Nal detector continuously measures the passing activity through the sample loop. A GC run is remotely started at the moment that the sample loop is filled with [ NJ-NHs. The GC is equipped with a Haysep P column (SS, mesh 80-100, O.D. 1/8). The GC run is started at 90°C, and after 1 minute, the temperature is increased with 10°C/min to 130°C. The products are analysed by a thermal conductivity detector (TCD). A Nal detector, directed at the TCD, monitors labelled products. Behind the TCD detector, a heated electrical 3-way valve selects a small part from the [ NJ-NHg peak. Depending on the experiment, a pulse time of 2-10 s is used to inject the labelled gaseous ammonia into the reactant stream. The required specific activity of the radioactive ammonia pulse is 0.1 MBq/ml minimum to meet the statistical requirements of the positron emission profiling experiments. 

To get simultaneous SAXS and WAXS patterns, the WAXS could be monitored only in a limited range using a tilted detector. By using a horizontal tensile direction the vertically arranged WAXS detector monitors mainly the equatorial scattering of the sample. To follow also quick changes exclusively in the crystalline phase WAXS measurements were performed alternatively with the WAXS detector directly in the beam behind the sample and a sampling rate of 1 s. 

Solid-state detectors directly convert the absorbed gamma ray energy into collection of electric charge and do not need photomultiplier tubes. Since the PMT is a bulky and expensive component, this represents a significant breakthrough. Cadmium zinc telluride is an attractive solid-state detec-... 

The CCD detector permits not only simultaneous background correction but complete correction of spectral interferences such as structured background from molecular species such as OH and NO. The resolution permits collection of the spectra from these species and removal of them from the absorbance of the sample. Direct-line overlap can also be corrected, if the matrix has an additional absorption line within the registered spectral range of the detector. Direct-line overlap is rare and usually is due to line-rich matrices such as Fe, so the system can reliably correct for the direct overlap of Fe on Zn, for example. 

---