Indicative particles

H.L. Stalcup (Ref 28) evaluated the instru- -ment for the particle size determination of HMX used in rocket formulations. He found that Coulter Counter distribution was similar to that obtained with the Micromerograph except at the large particle end, where the Micromerograph indicated particles over lOOp compared to 32 p for the Coulter Counter. Median values were 13.5p by Micromerograph and 16 p for the Coulter Counter. The samples for the Coulter Counter were run on an as received basis, ie, while still water-isopropanol wet ... 

Using the dilatometer technique, a small sample of powder (about 1 -2 grams) is heated at constant rate in the apparatus depicted schematically in Fig. 43. Dilatation of the sample is measured by a linear voltage transducer (LVDT) contraction of the sample indicates particle-particle surface flattening and defines the minimum softening point ox sintering temperature, Ts. In... 

If smoke is introduced with air pressure, adjust it to provide a smoke outlet velocity equal to the room air velocity at that point. Operate the particle counter with the sample tube at the normal work level and at a point remote from the smoke source. Verify that the counter indicates particle concentrations less than 200 particles of 0.5 ftm or greater. 

Examples of a few oral suspensions in which a specific and well-defined particle-size specification for the drug substance is important include phenytoin suspension, car-bamazepine suspension, trimethoprim and sulfamethoxazole suspension, and hydrocortisone suspension. It is therefore a good idea to indicate particle size in the raw material specification, even though it is meant for dissolving in the processing, to better validate the manufacturing process while avoiding scale-up problems. 

FIG. 10.8 The coagulation process as a pseudochemical reaction. The filled circles indicate particles of the dispersed phase and the open ones satellite particles of the solvent. In (a) the dispersed particles are chemically identical, and in (b) the dispersed particles are different substances. 

In Figure 8, a plot of dN137/dN95 vs. D is shown together with experimental values of the ratio for indicated particle size fractions. The excellence of the fit shows that the data analysis is consistent, although it cannot be used to establish the uniqueness of the normal distribution function in describing the data. 

Several investigators have presented evidence for low molecular weight forms exhibiting urease activity. Hand (33), in 1939, obtained diffusion data indicating particles of 17,000 daltons or less that retained enzymic activity. More recently, sucrose density gradient ultracentrifugation (34)... 

As can be seen from Table 19.3, the proportion of indicative particles exceeds the proportion of unique particles, even for promptly collected FDR. The higher proportion of indicative particles detected in casework is almost certainly due to particles from nonfirearm sources, particularly single primary element ones, meeting the criteria of the classification scheme. 

From casework statistics the unique particles (those containing the combination lead, antimony and barium, and those containing antimony and barium) occur in the ratio 7 3, respectively. Approximate percentages for indicative particles are lead-only 55% lead, antimony 20% lead, barium 8% antimony-only 7% barium, calcium, silicon 5% barium-only 5%. Table 19.3 gives an indication of the levels of the primary elements in each particle type. Table 19.4 gives an indication of the levels of accompanying elements in each particle type and is the basis for note b in Table 19.5, Particle Classification Scheme. 

Table 19.4 Percentage Occurrence of Certain Accompanying Elements in Unique and Indicative Particles... 

The original particle classification scheme192 has been revised based on casework experience, research work on blank cartridges, and so forth, and a detailed analysis of 14 years of casework results. The particle classification scheme used in Northern Ireland since 1984 is given in Table 19.5. The indicative particles are in tentative order of decreasing significance. 

Fig. 8. A sample of the CaF2 that had been screened to 2 im (seen in the SEM in Fig. 7) which was processed in the CaviMax processor with recirculation as a slurry in water for 30 min. The highlighted areas indicate particles having melted necks.

Although the fly ash particle size distribution in the submicron regime is explained qualitatively by a vaporization/homogeneous nucleation mechanism, almost all of the available data indicate particles fewer in number and larger in size than predicted theoretically. Also, data on elemental size distributions in the submicron size mode are not consistent with the vapor-ization/condensation model. More nonvolatile refractory matrix elements such as A1 and Si are found in the submicron ash mode than predicted from a homogeneous nucleation mechanism. Additional research is needed to elucidate coal combustion aerosol formation mechanisms. 

Figure 8.7. Two-dimensional arrays of Au nanocrystals of 4.2 nm mean diameter. The nanocrystals were obtained by thiol-derivatizing the hydrosol. A histogram indicating particle size distribution is given (below left). The XRD pattern from this array is also shown (below right) (reproduced with permission from reference [25]).

Hemicellulose was reclaimed from industrial soda bagasse spent pulping liquor by precipitation with methanol as was done in earlier studies 2-5). The hemicellulose precipitate obtained was submitted to different degrees of washing with 50% aqueous methanol, resulting in hemicellulose preparations containing different quantities of ash and lignin. The pH of the hemicellulose was adjusted and borax or CaCh added, after which it was dried and ball-milled to the indicated particle sizes. 

Retrogradation. This has been employed as an omnibus term, to cover almost any type of desolvation. Methods should be devised to evaluate retrogradation on a more exact basis. Light scattering methods may have application to indicate particle size and molecular aggregation. 

Both the activating and Indicating particles are highly penetrating in gram-sized or smaller samples of common materials, so that errors are not generally Incurred by analytical complications due to the nature of the matrix. 

Fig. 5. Scattering curves of styrene latex samples of various indicated particle diameters obtained with the ultra small angle scattering camera of Fig. 4 [19]...

The organization of the B sections is now as follows, where bullets indicate particle sections and brackets indicate reviews. 

Indicates particles that appear in the preceding Meson Summary Table. We do not regard the other entries as being established, t Indicates that the value of / given is preferred, but needs confirmation. 

The first near-infrared polarimetrie observations of eomets by Noguehi et al. [18]. The degree of polarization is similar to that for the visible domain, indicating particle sizes 1 pm or larger. 

The size of airborne particles varies over a range roughly from a few nanometers to hundred micrometers. In particular, PMIO and PM2.5 are used to refer to the PM with the diameter of individual particles smaller than 10 and 2.5 pm, respectively. The concentration of total suspended particles (TSP) was used as one of the air quality criteria set by the US EPA until 1986. Currently, the concentrations of both PMIO and PM2.5 are used to indicate particle pollution of the ambient air in the USA. 

Fully flushed (FF) Figure 3.10 shows the FF results, in relation to COMP. As can be seen, the relationship between FF and COMP showed considerable variation. FF generally underestimates COMP. In some cases, however, FF is considerably higher than COMP. This might indicate particle release due to flushing. As a result, is low 0.29. 

---