Relative particle size

Table 13.6 contains some of the analytical techniques that allow particle size determination. Before a technique is chosen, the relative particle size and type of size information... 

Measured D/H ratios in five bulk Stardust particles (black dots sizes represent relative particle sizes), and in micron-size subareas in one particle (open circles enclosed by oval) measured by ion microprobe. The particle compositions overlap D/H ratios in comets, IDPs, and the insoluble organic matter in chondrites. Modified from McKeegan et al. (2006). 

Considered in this chapter are specific features of the catalytic behavior of metallic nanostructures of new type, produced by laser electrodispersion of metals. This method makes it possible to obtain Cu, Ni, or Pd nanoparticles whose sizes are specific to each particular metal, with the relative particle size scatter being exceedingly narrow, <10%. An important distinctive... 

According to percolation theory, the effect of a reduction in the drug particle size should be similar to an increase in the excipient particle size in a binary system It may be expected that the relative particle size of the component, but not its absolute particle size, will determine the properties of the system. 

Fig. 3.8 Comparison of relative particle sizes of inorganic pigments.

Conventional tungsten carbide powder. The particle size range of these qualities is between 1 and 10 pm (the majority between 1 and 2.5 pm). The average particle size has to be met usually within the limits of +10% relative. Particle size distributions for a given average particle size can be adjusted within certain limits already during tungsten powder reduction (see Section 5.4.4). 

Microencapsulation Processes with Their Relative Particle Size Ranges Approximate Particle/Capsule Size (pm) Approximate Payload% ... 

Balinov et al. studied the use of NMR to characterize emulsions using the NMR self-diffusion technique (66). The technique uses the phase differences in consecutive pulses to measure the diffusion length of the target molecules. As such, the technique indicates the relative particle size in an emulsion. The NMR technique was compared to optical microscopy and showed good correlation over several experiments involving aging and breaking of the emulsions. 

Table 4-26 Correlation of thermoanalytical index numbers with the averaqe relative particle size M...

Introduce a relative particle size q. For spherical particles, q is the ratio of the particle perimeter to the wavelength 2 rr 2jrr/ii... 

Table 1.2 Microencapsulation processes with their relative particle size ranges.

Yeliseyeva (14) used an oxygen etching technique to investigate the internal structure of soft acrylate particles and was able to show that the particles contained many "globules" of much smaller size. The relative particle sizes determined in this study are given in Table II. The primary particle diameters are about 10 times those... 

Keywords Controlled drug delivery, percolation theory, critical points, cellulose derivatives, polymeric matrices, relative particle size, tablet porosity, biodegradable polyurethane... 

Other factors such as polymer concentration, polymer properties, drug content, drug and excipient relative particle size, and compression pressure have been demonstrated to influence drug release [13]. 

Figure 4.12 Excipient percolation thresholds (expressed as %v/v HPMC + initial porosity)/ HPMC relative particle size versus the drug solubility in matrices containing acyclovir, theophiline, ranitidine HCl, acetaminophen, lobenzarit disodium and KCl.

Since there is a linear dependence of the percolation threshold of one component on its relative particle size, with the aim to correct the influence of the different relative particle size, the values of the excipient percolation threshold were divided by the excipient relative particle size [87]. The obtained results have been plotted against the solubility of the drugs studied in this work acetaminophen, theophylline and ranitidine-HCl. Moreover, data corresponding to hydrophilic matrices studied in previous works and containing different drugs—KCl, lobenzarit disodium and acyclovir—were also included, as it can be observed in Figure 4.12 [93, 94,96]. 

Influence of Relative Particle Size on Critical Points... 

As it as been previously explained for inert matrices, the percolation threshold shows a linear dependency on particle size that was foxmd by Caraballo et al, being the factor responsible for the change of the percolation threshold the relative particle size of the studied component [86, 87]. 

Figure 4.13 Drug percolation thresholds versus the drug relative particle size in inert matrices (KCl/ Eudragit RS-PM) and the excipient percolation thresholds versus the excipient relative particle size in hydrophilic matrices (KCI/HPMC K4M and LBD/HPMC K4M).

Iherefore, also in the case of hydrophilic matrices, lower percolation thresholds are found for smaller relative particle size of a component due to its higher percolation efficiency. 

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