Particle composition mixture

The health effects of particulate matter (a complex mixture of solids and liquids) emissions are not yet well understood but are recognized as major contributors to health problems. Biological activity of particulate matter may be related to particle sizes and/or particle composition. Furthermore, it has generally been concluded that exposure to particulate matter may cause increased morbidity and mortality, such as from cardiovascular disease. Long-term exposure to particulate emissions is also associated with a small increase in the relative risk of lung cancer. 

Two peaks in the accumulation mode may also result if the particles are externally mixed rather than internally mixed (the latter meaning that all particles have the same composition corresponding to a mixture of the various components). That is, the composition of individual particles may not be the same as the overall bulk particle composition, with some having more hygroscopic components than others. These are referred to as externally mixed particles indeed single-particle analyses suggest that externally mixed particles are common (see Chapter 11.B.4). In this case, a... 

Fig. 1.1.13 Concentration domains of solutions containing FeClj and HCI aged at 100°C for 24 h (upper) and for 1 week (lower). N, no particle formation. Particle shapes D. double ellipsoids E, ellipsoidal 1, irregular of varying sizes R. rod-like S, spherical. Pairing of symbols indicates a mixture of corresponding particles in the suspension. Particle composition R, p-FeOOH all other particles, a-Fe2Oi. (From Ref. 65.)...

Figure 9.2 shows the correlation functions for the reactive state just below the phase transition point (Yco = 0.56 < yz). The steady state is reached in a very short time. The particle composition on the surface is a mixture of A and B particles with many empty sites in between. 

Particle composition is far more difficult to evaluate. Bulk elemental analysis [atomic absorption spectroscopy (AA) or inductively coupled plasma mass spectrometry (ICP-MS) are most common for metals] is useful in confirming the overall bimetallic composition of the sample, but provides no information regarding individual particles. Microscopy techniques, particularly Energy Dispersive Spectroscopy (EDS), has supported the assertion that bimetallic DENs are bimetallic nanoparticles, rather than a physical mixture of monometallics [16]. Provided the particle density is low... 

Synthesis of metallic nanoparticles proceeds in many ways they can be divided into physical and chemical. Physical methods include inert gas condensation, arc discharge, ion sputtering, and laser ablation. The main idea behind these methods is condensation of solid particles from the gas phase, the substrate for nanoparticle generation being pure metals (or their mixtures/alloys in the case of complex particle composition). Chemical methods, in turn, include various methods utilizing... 

A full description of an aerosol and its properties requires specification of particle composition and its dependence on particle size. Because the composition of a heterogeneous mixture is difficult to characterize, it has been customary to identify a small number of representative particle types (e.g., d Almeida et al., 1991) and treat... 

Figure 11.24 Qualitative demonstrations of the displacement and tag-along effects. Left set Influence of the feed composition. Left column Chromatograms obtained with 200 mg of a mixture of two of the epimers of a 1,1,1-trisubstituted cyclohexanone on a 250x21.4 mm column packed with 12 im silica, with 40 mL/min of a solution of n-hexane and ethyl acetate (97.5 2.5). Composition as indicated. Right column results of computer calculations. Right set Influence of the column efficiency. Top two rows, experimental data under the same experimental conditions as in (a), except average particle size of silica particles, and mixture composition 1 3. Bottom row, results of computer calculations. Reproduced with permission from ]. Newburger and G. Guiockon,. Chromatogr., 484 (1989) 153 (Figs. 6 and 8).

In geometrically similar systems there is complete similarity if all necessary dimensionless criteria derived either from differential equations or by using the pi theorem are equal. In complex precipitation processes such complete similarity is impossible. Moreover, because we want to obtain identical not similar products from the systems differing in scale, we usually want to reproduce the product quality (particle size, particle morphology), mixture composition, and structure of the suspension on a larger scale. We thus use limited similarity, which means that we lose several degrees of freedom (we cannot manipulate particle size, solution composition, viscosity, and diffu-sivity), and we obtain this way a reduced number of similarity criteria. 

Yan, H. and Barbosa-Canovas, G.V. 2000. Compression characteristics of selected food powders The effect of particle size, mixture composition, and compression cell geometry. In Selected physical properties of food powders , Doctoral Thesis, pp. 82-113. Biological Systems Engineering Department, Washington State University. 

Both nitric acid digestion and enzyme digestion were tested with liver and lung tissue as well as with cultured cells. Tissue processing with a mixture ofi protease enzymes is preferred because it is applicable to a wide range of particle compositions. Samples were visualized via fluorescence microscopy and transmission electron microscopy to validate the SdFFF results. We describe in detail the tissue preparation procedures and discuss method sensitivity compared to reported levels of nanoparticles in vivo. 

On the basis of all these considerations a model can be proposed to account for the capacity decline in LPB prototypes. According to this model, which is pictorially illustrated in Figure 6.29, the loss in capacity would be in part apparent—i.e. due to the fact that a fraction of the charging current is shunted along lithium microdendrites and thus not available for driving the electrochemical process—and in part real—i.e. associated with low diffusion kinetics and with electrical isolation of particles of the intercalation active compound in the positive electrode composite mixture. 

MMT nanoparticles are well known to be a mixture of several natural compounds with nonuniform composition and particle size [27]. For example, MMT minerals from different deposits might differ considerably in composition. This variation in composition of MMT significantly complicates the task of making functional nanocomposites with prescribed properties for targeted applications. Therefore, there is a need to develop synthetic nanofillers with prescribed particle composition, shape, and size for use as fillers in polymer nanocomposites with well-defined properties. In this area, synthetic nanodimensional silicates may provide a number of opportunities in polymer nanocomposites that is relatively little studied and poorly understood relative to the well-studied polymer nanocomposites filled with natural layered MMTs [28-32]. In contrast to the commonly used layered MMT compounds, it is envisaged that use of nanoparticles with different morphology (e.g.,... 

Coaxial spinning can also be used to form polymer-particle composite nanofibers as discussed in Chapter 6. Li et al. (2005a), in their research on decorating the interior of hoUow nanofibers with nanoparticles, used this technique very effectively. The core fluid used was a ferrofluid of magnetic iron oxide particles and the shell layer was a mixture of poly(vinyl p5u-olhdone)/ titanium isopropoxide. Extraction of the core phase of the core-shell nanofibers with octane yielded hollow, magnetically susceptible nanofibers, with their interiors decorated with oxide nanoparticles. 

Particle-particle composites, which are intimate mixtures of generics of marked physical size. An example might be earth pigments. 

For large-particle composites, upper and lower elastic modulus values depend on the moduli and volume fractions of matrix and particulate phases according to the rule-of-mixtures expressions Equations 16.1 and 16.2. 

Continuum models go one step frirtlier and drop the notion of particles altogether. Two classes of models shall be discussed field theoretical models that describe the equilibrium properties in temis of spatially varying fields of mesoscopic quantities (e.g., density or composition of a mixture) and effective interface models that describe the state of the system only in temis of the position of mterfaces. Sometimes these models can be derived from a mesoscopic model (e.g., the Edwards Hamiltonian for polymeric systems) but often the Hamiltonians are based on general symmetry considerations (e.g., Landau-Ginzburg models). These models are well suited to examine the generic universal features of mesoscopic behaviour. 

An adsorbent can be visualized as a porous soHd having certain characteristics. When the soHd is immersed in a Hquid mixture, the pores fill with Hquid, which at equilibrium differs in composition from that of the Hquid surrounding the particles. These compositions can then be related to each other by enrichment factors that are analogous to relative volatiHty in distillation. The adsorbent is selective for the component that is more concentrated in the pores than in the surrounding Hquid. 

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