Particulate profiles

The soil type and its particulate profile determine the potential for transfer of pesticide to worker. This criterion is linked, however, to rainfall. Those areas with extended dry periods and a large quantity of particulate matter below 50 u should receive closer attention. 

Figure 4. Particulate profiles as observed in a laboratory flume and as computed for a sedimenting environment. (Observed data as described in Ref. 14.) = 7,875 ppm, = 4,471 ppm (Q) Cq = 3,983 ppm,...

Some solid materials are very intractable to analysis by standard methods and cannot be easily vaporized or dissolved in common solvents. Glass, bone, dried paint, and archaeological samples are common examples. These materials would now be examined by laser ablation, a technique that produces an aerosol of particulate matter. The laser can be used in its defocused mode for surface profiling or in its focused mode for depth profiling. Interestingly, lasers can be used to vaporize even thermally labile materials through use of the matrix-assisted laser desorption ionization (MALDI) method variant. 

Figure 1 shows the particulate loading of a pipe containing gas and particulates where the nonuniformity induced by a disturbance, ie, a 90° bend, is obvious (2). A profile of concentration gradients in a long, straight, horizontal pipe containing suspended soHds is shown in Figure 2. Segregation occurs as a result of particle mass. Certain impurities, eg, metal-rich particulates, however, occur near the bottom of the pipe others, eg, oily flocculates, occur near the top (3). Moreover, the distribution may be affected by Hquid-velocity disturbances and pipe roughness.

Figure 3.28 shows 3D-SIMS distributions of the elements Si, Al,Ti, and Cr. The Cr distribution is shown from the bottom, to illustrate the rough interface. It is apparent that the interfaces are not smooth. This is the reason for the slowly decreasing Cr signal in the depth profile. As is apparent in the 3D-distribution, the different depth profiles of Si,Ti, and A1 in the layer are a result of respective particulate inclusions. 

Fig. 4.11. Characteristic intensity profiles for three different kinds of concentration (a) bulk type (b) particulate type and (c) thin-layer type. The critical angle d>c is determined by total reflection at the substrate ([4.21], after Ref [4.44]).

Fig. 1. TG spectra of carbon particulates with Fig. 2. TPR profiles measured for various Lao.gCso MnOj catalyst heating rate=l K/min. perovskite type oxides heating rate=10 K/min,...

In the present work, such a systematic approach to the physical characterization of pharmaceutical solids is outlined. Techniques available for the study of physical properties are classified as being associated with the molecular level (properties associated with individual molecules), the particulate level (properties pertaining to individual solid particles), and the bulk level (properties associated with an ensemble of particulates). Acquisition of this range of physical information yields a total profile of the pharmaceutical solid in question, whether it is an active drug, an excipient, or a blend of these. The development of a total profile is a requirement for successful manufacture of any solid dosage form. 

The vertical scavenging model also allows one to predict the distribution of particulate radionuclide profiles. Following Craig et al. [53] the particulate phase activity would be given by the solution of the equation ... 

Figure 3. (a) The concentration depth profiles of particulate lt0Pb in the sea water... 

Figure 4. Particulate 2I0Pb distribution in profiles from the Antarctic and the Atlantic (data from Refs. 45 and 55). The near constancy of particulate mPb abundance with depth is difficult to explain by the vertical scavenging model of...

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