Spot length

A small spot containing exactly 1 fig of leucine on a thin-layer plate has evolved into a two-dimensional Gaussian zone with <7X = 1.25 mm and [Pg.140]

The size and shape of the diffraction spots vary across the film. The radial spot length is given by convolution as... 

Most studies in TLC have been qualitative, and considerable experimentation may be necessary to obtain quantitative results, although excellent commercial layers and new equipment have aided the problem. Phenolic compounds have been analyzed by spectrophotometry off the plate at 725 nm (133) by means of Folin-Ciocalteu reagent, essentially sodium tungstate and molybdate with lithium sulfate (134). Chlorophenols have been quantified after reaction with dansyl chloride and separation (135). Channel TLC (linear relationships between spot lengths and concentration between 1 and 8 pg/spot) has been used (136). The phenols in cashew nut shell liquid have been quantified by off and on the plate methods with a flying-spot scanning procedure and densitometry (137) and the distribution of unsaturateds by TLC/MS (138). Catecholamines and their metabolites in urine have been quantified (12) and determined by on the plate fluorimetry (139). Hindered phenols have been analyzed by densitometry (140). Semiquantitative determinations of the coupling products of 4,4 -... 

The choice of the slit size (width and height) depends on the shape and size of the spot. Usually, for a spot whose round shape is sharply defined, the slit width is set at 120% of the spot diameter, when the spot is oval — at 120% of the spot length, and for a band — at 50-70% of its length [13]. 

The sensitivity curves are plots of maximum achieved sensitivity as a function of thickness of the object for a given focal spot size and source to detector distance. The best attainable sensitivity in image intensifier systems is a function of tube voltage, current, scattered radiation and the screen gamma. As a first step, stainless steel plates with thicknesses ranging from 5 mm-30 mm in steps of 5 mm were chosen. These plates had a length of 950 mm and width of 280 mm. The plate is positioned very close and at the center to the LI. tube. The extraneous... 

Similarly, the focusing capability of an array is the strongest focused beam which can be steered. The simplest way to evaluate it is to test a theoretical focusing time delay law, in the near-field and in the natural direction of propagation of the array. The beam pattern characteristics depth, lateral size and length of the focal spot must be found consistent with modelling and no lobe must appear above a predetermined level. 

Dimensional measurement using lasers is illustrated by measurement of wire diameter. When a fine wire is inserted in the highly collimated beam of a laser, the light is diffracted by the wire to form a distinct line of spots perpendicular to the length of the wire. The spots appear at angles 9 with respect to the direction of the laser beam. 9 is given by... 

This result means that the reactor is insensitive if the temperature profile is concave toward the reactor length axis, and the inflection point is avoided. If the AT exceeds that permitted by the previous criterion—the limit set by RT /E— an inflection of the temperature vs., tube length will occur and thermal runaway will set in. Just before runway sets in the temperature at the hot spot can be 1.4 times higher than RT /E. 

The thrust of development is toward ever better spatial resolution, which means the smallest possible spot size on the sample compatible with adequate signal-to-noise ratio, for acquisition within a reasonable length of time. 

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