Spot photometer

Older experimental arrangements used Earaday cups with small apertures mounted on goniometers, which could be moved around the sample to collect the back-scattered electron current directly, or spot photometers, which were directed at one dif-... 

Robert Wilhelm Bunsen, 1811-1899, German chemist who investigated the cacodyl radical, the geysers of Iceland, and the chemical action of light. Inventor of the Bunsen battery, the grease-spot photometer, ice and vapor calorimeters, the thermoregulator, the constant-level water-bath, and the filter pump. 

Once spot photometers became available (15., 16., 17, 18), many workers determined the intensity at the maximum blackening of the x-ray reflection, (the peak center). To accept this for the integrated intensity is to imply that the integrated intensity is... 

Bunsen and Roscoe used a burning magnesium wire as a light source for comparison with the intensity of sunlight. The grease-spot photometer was... 

Analyses in the pg range, e.g., in water and oil, can be carried out with thin-layer chromatography [244]. After separation on the thin-layer plates, then by Dragendorff reagent, colored spots are measured with the help of a spectral photometer at 525 nm. 

Visual comparison of diffraction spots with a graded intensity scale was by far the most used method to quantify intensities. The human eye, which is a very good comparative photometer, can estimate the relative order of blackness of a series of spots with great accuracy, but not on a true numerical scale. The origin of this method is unknown and seems almost intuitive. Many authors (8-13) suggest ways to obtain an intensity scale. 

By comparison with a film strip with a relative intensity scale for some strong hkl reflection exposed to X-rays for known increments of time, the intensity of each spot was read by hand (later by optical photometers), and a set of Miller indices hkl and intensities Ihm were collected (this would take a... 

The UV photometer has been proposed both in the German and Czech case studies to support the supplementation and validation of the risk assessment. In order to show the necessary number of uses at which the costs per analysis of UV photometer move below the costs of traditional methods, the cost function for the UV photometer has been calculated. The costs of using the UV photometer are rather high if it is used for few analyses but fall considerably with higher numbers of uses. This cost function is then compared with the linear cost function of spot sampling where the cost of laboratory analysis (list prices) have been considered. 

Figure 6.1.2 makes clear that the break-even point where the cost function of the UV photometer moves beyond the costs of classical methods is reached much earlier in the German case then in the Czech case. The figure illustrates that the break-even point where the UV photometer becomes advantageous over spot sampling lies at 17.5 analysis per year in Germany. 

Photometer, Fig. 2 DNA microarrays. The probes are complementary fragment oligonucleotides, of target DNA or mRNA spotted onto the microarray surface. This type of array is typically hybridized with target cDNAs that are labeled with fluorophores. The samples are amplified by PCR and hybridized to the microarray and then scanned in... 

The draft versions of ISO norms (1983) describe both simple techniques for on-the-spot turbidity measurement and optical turbidity meters. The diagram below illustrates the principle of a turbidity photometer for laboratory use (Dr, Lange, model LTP 3). 

A rectangular array of spots is written and the large-area CR of the projected image is measured with a photometer. The laser beam is focused to about 10x15 ym and is modulated with an A/0... 

Carbonised spots can be directly evaluated with photometers, suitably equipped for scanning, or using so-called densitometers, which are built essentially for measurements of transmission and reflection on thin solid layers. Photovolt (Firm 104) and Chromoscan (Firm 78) densitometers of various types have been those so far principally used. 

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