Particulates natural

If we think in terms of the particulate nature of light (wave-particle duality), the number of particles of light or other electi omagnetic radiation (photons) in a unit of frequency space constitutes a number density. The blackbody radiation curve in Fig. 1-1, a plot of radiation energy density p on the vertical axis as a function of frequency v on the horizontal axis, is essentially a plot of the number densities of light particles in small intervals of frequency space. 

For example, the measured pressure exerted by an enclosed gas can be thought of as a time-averaged manifestation of the individual molecules random motions. When one considers an individual molecule, however, statistical thermodynamics would propose its random motion or pressure could be quite different from that measured by even the most sensitive gauge which acts to average a distribution of individual molecule pressures. The particulate nature of matter is fundamental to statistical thermodynamics as opposed to classical thermodynamics, which assumes matter is continuous. Further, these elementary particles and their complex substmctures exhibit wave properties even though intra- and interparticle energy transfers are quantized, ie, not continuous. Statistical thermodynamics holds that the impression of continuity of properties, and even the soHdity of matter is an effect of scale. 

Experiments like those described in Figures 14-3 to 14-6 establish that the electron is a negatively charged particle and that it is present in all substances. Further confirmation of the particulate nature of electricity comes from experiments that were conducted by an American physi-... 

Studies of black-body radiation led to Planck s hypothesis of the quantization of electromagnetic radiation. The photoelectric effect provides evidence of the particulate nature of electromagnetic radiation. 

Harrison, A. G., Treagust, D. F. (2002). The particulate nature of matter Challenges to understanding the submicroscopic world. In J. Gilbert, K., O. de Jong, R. Justi, D. F. Treagust J. H. Van Driel (Eds.), Chemical education Towards research-based practice (pp. 189-212). Dordrecht Kluwer. 

Novick, S., Nussbaum, J. (1978). Junior high school pupils understanding of the particulate nature of matter An interview study. Science Education, 62(3), 273-281. 

Brook, A., Briggs, H., Driver, R. (1984). Aspects of secondary students understanding of the particulate nature of matter. University of Leeds Centre for Studies in Science and Mathematics Education. 

Haidar, A., Abraham, M. (1991). A comparison of applied and theoretical knowledge of concepts based on the particulate nature of matter. Journal of Research in Science Teaching, 28, 919-938. 

Having students draw their mental model of the product of the reaction reveals misconceptions in understanding of the particulate nature of matter which could then be addressed in the classroom. 

Onwu, G., Randall, E. (2006). Some aspects of students understanding of a representational model of the particulate nature of chemistry in three different countries. Chemistry Education Research andPractice, 7(4), 226-239. 

Despite this much-discussed theoretical background, the number of concrete studies comparing historical ideas and students conceptions is fairly low in chemistiy education. Furthermore, most studies cited deal with isolated topics. Systematic overviews concerning basic ideas like micro-macro thinking, chemical reaction, the particulate nature of matter, energy conversions etc. are mostly not available, except for van Driel et al. (1998) and the case of the chemical equilibrium. 

Ozmen (2004, especially for chemical bonding) and Coll und Treagust (2003, chemistiy of metals) can help to develop a first overview. Numerous authors (e g. Pfund, 1975 Schldpke, 1991 Griffith and Preston, 1992 Mas et al., 1987) describe parallels between students conceptions and historical scientific ideas. Schldpke (1991), for example, points out similarities between students conceptions concerning properties of matter and ideas in alchemist thinking. Lee, Eichinger, Anderson, Berkheimer, and Blakeslee (1993) mentions semblances between the ideas of Aristotle and students conceptions about general aspects of the particulate nature of matter and the horror vacui . 

Paracel sus(1493-1511) This kind of non-atomic particulate nature of matter. The idea of... 

Gabel, D. (1993). Use of the particulate nature of matter in developing conceptual understanding. Journal of Chemical Education, 70(3), 193-197. 

One approach where the characteristics of the liposomal carrier system are well matched to the intended therapeutic application is the delivery of drugs to the MPS. Because of their particulate nature, the major route of clearance of liposomes, when administered in vivo by a variety of routes, is phagocytosis by MPS cells, especially macrophages in liver and spleen. Obviously, this "natural" fate of liposomes in vivo is an advantage if one attempts to treat diseases... 

A number of aspects related to the potential toxicity of liposomes has to be considered. They include effects due to (1) their particulate nature, (2) the individual components, and (3) a changed distribution of the encapsulated drug. 

Figure 6.18 A stereoscan of a fracture surface of a dental silicate cement. The debonded glass particle is to be identified by its pitted surface, the result of selective acid attack. Note the particulate nature of the matrix (Wilson et at., 1972).

Pharmacists should also take a dim view of changes in the particle size, size distribution, or particulate nature of semisolid suspensions. They are the consequence of crystal growth, changes in crystalline habit, or the reversion of the crystalline materials to a more stable polymorphic form. Any crystalline alteration can lead to a pronounced reduction in the drug-delivery capabilities and therapeutic utility of a formulation. Thus, products exhibiting such changes are seriously physically unstable and unusable. 

The sunblocks zinc oxide, titanium dioxide, and iron oxide are inorganic chemicals that are not absorbed into the skin. These substances consist of opaque particles that reflect both visible and ultraviolet light. In addition, zinc oxide blocks virtually the entire UVA and UVB spectrum and thus offers overall protection. The particulate nature of these sunblocks enhances their effectiveness at reflecting sunlight. The smaller the particle size, the greater the surface area available for reflection, and the more effective the sun protection offered by the formulation. 

The use of BRMs to treat human disease has its origins in the use of bacterial toxins to treat cancer by William B. Coley.73 These early studies resulted in the use of microbi-ally-derived substances such as BCG, Picibanil, carbohydrates from plants or fungi such as Krestin and Lentinan, other products such as Biostim and Broncho-Vaxom, as well as thymic extracts (Table 9.4). However, the lot-to-lot variation in the manufacture of these drugs has dampened enthusiasm. Equally, the focus on MOAs in drug development strategies has also dampened developmental efforts. The particulate nature of some BRMs can also result in pulmonary thrombosis and respiratory distress following i.v. injection. However, BRMs are commonly used to treat bladder cancer and derivatives of natural products are routinely used clinically. 

Figure 12.5 The photoelectric effect. Light with photons of energy hc/k approaches from the left, strikes the atoms in the metal, and ejects a photoelectron with a kinetic energy equal to the photon energy minus the work function of the metal. This demonstrates the particulate nature of light.

Nanoclay particles by virtue of their particulate nature are emerging as effective heterogeneous nucleating agents for polyesters. The nanoclay particles in PET/montmorillonite nanocomposites impart to PET a higher crystallization rate without the need for expensive nucleating agents. 

Butters G (ed) Particulate nature of PVG (1982) Applied Science, London... 

The particulate nature of the trapped metal results in each growing crystal of metal becoming a microelectrode that enlarges the active surface area of the electrode. Thus the deposition rate is maintained as concentration of metals in solution declines. 

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