Macroscopic view

As we have seen, the third law of thermodynamics is closely tied to a statistical view of entropy. It is hard to discuss its implications from the exclusively macroscopic view of classical themiodynamics, but the problems become almost trivial when the molecular view of statistical themiodynamics is introduced. Guggenlieim (1949) has noted that the usefiihiess of a molecular view is not unique to the situation of substances at low temperatures, that there are other limiting situations where molecular ideas are helpfid in interpreting general experimental results ... 

This leads us to a cracial point in thinking about micro-macro relations The closeness of the linkage between the microscopic and the macroscopic view of the world. As the example of the macromolecnlar theory shows, the same observations can be explained by dilferent theories. In other words, the cotmection between phenomena and scientific theories is not an nnambiguous one. Although one theory fits better with the observed facts than the other, the constraction of the model always remains a theoretical construction to explain phenomena. On the other hand, theories can influence the macroscopic reality as well. The polymer theory, for example, can be used to design polymers. 

The distance scale associated within the glass transition is related to the method used. For example, thermal and mechanical techniques provide macroscopic views of the glass transition, whereas spectroscopy techniques yield a molecular-level view. Thus, it is not surprising to find that molecular-level techniques, such as NMR, may result in lower Tg values compared to those obtained using a macroscopic technique, such as DSC. Both Tg values are correct, but not necessarily equal, given the different points of view the two methods are probing. 

Therefore, you should structure the macroscopic view of the development around type models, frameworks, packages, and refinements. 

Note that the terms macroscopic and microscopic constants do not imply that these quantities measure macroscopic or microscopic quantities, respectively. Here, in the macroscopic view we have simply grouped the two microscopic species (0, 1) and (1, 0) into one species denoted by (1). Both of these constants can be macroscopic or microscopic, depending on whether we study the binding per molecule or per one mole of molecules. 

Up to this point we have taken a very microscopic view of the propagation of beams of particles through material. We have described the degradation of the intensity and the energies of the beams in terms of individual interactions. Now we will take a more macroscopic view from the standpoint of the absorber. 

Statistical mechanics provides a bridge between the properties of atoms and molecules (microscopic view) and the thermodynmamic properties of bulk matter (macroscopic view). For example, the thermodynamic properties of ideal gases can be calculated from the atomic masses and vibrational frequencies, bond distances, and the like, of molecules. This is, in general, not possible for biochemical species in aqueous solution because these systems are very complicated from a molecular point of view. Nevertheless, statistical mechanmics does consider thermodynamic systems from a very broad point of view, that is, from the point of view of partition functions. A partition function contains all the thermodynamic information on a system. There is a different partition function... 

Now we will switch over to a macroscopic view, looking at the average force and pressure, rather than the instantaneous values. Collisions with the right wall (and thus force on the wall) happen every time the molecule makes a round trip between the left and right walls, thus traveling a total distance 2L the time between collisions is then 2L/Vy. So the average force on the right wall from these collisions is the momentum transferred to the wall per unit time ... 

Fig. 24 Images of a cast PMMA sample after testing in IPA at AK = 0.6 MPa Vm Left Macroscopic view of crack branching along main crack front, right SEM picture of fracture surface...

Thus, if the F in Eq. (4.147) is the electric force that stimulates conduction, then this equation is the molecular basis of the fundamental relation used in the macroscopic view of conduction [see Eq. (4.122)], i.e.,... 

Figure 1 Autoradiogram of skin treated by the passive application of H-estradiol, in dimethylsulfoxide, for 2 hours. The exposure time was 81 days. (A) A macroscopic view illustrating the regions of the epidermis, hair shafts, and sebaceous glands with the highest levels of radioactivity is shown. (The arrow points at a sebaceous gland.) Penetration gradients of radioactivity are apparent between the epidermis and dermis (B-C) and regions of hair shafts and the hypodermis (D-E). The scale bar is 25 pm. (Reprinted with permission from Ref. 11.)...

On the one hand, the thermodynamic realities of the ITIES, e.g., electrocapillarity and standard ion transfer potential, have been well established. On the other hand, our knowledge of charge transfer kinetics is less solid. Although traditional macroscopic concepts appear to be applicable at least as a first approximation, there is still a rift between macroscopic views and microscopic understanding. 

Molecular modeling has reached into many domains of science and technology. One area that has a rich history of applied theory is polymer science. Indeed, many aspects of statistical thermodynamics were developed in an attempt to understand polymer systems. Unfortunately, many theories provide only macroscopic views of polymer systems and are sometimes out of date. 

We have been focusing on a microscopic view of the nervous system as we considered how drugs might act at the level of the single neuron. We now turn to the larger picture and consider a macroscopic view of the nervous system. The structure of the nervous system is outlined in Figure 3.3. The major distinction is between the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS... 

In the next section, the entropy change for this process from the macroscopic view will be calculated to be... 

Over recent decades, a couple of intermolecular interaction patterns have been identified and refined in order to facilitate understanding of supramolecular processes. The decomposition of a whole interaction pattern into individual contributions is somewhat artificial - only the total interaction energy is well defined - but it is required for our classical, macroscopic view and understanding of these processes. The following list of interaction types contains a few important ones but cannot be considered complete (for instance, magnetic fields or reversibly built and broken covalent bonds are completely neglected) ... 

We can estimate the effective pressure from the potential profile molecules confined in the slitlike pore of 1 nm in width are presumed to be exposed to the high pressure of 100 MPa. Also application of the Laplace equation to estimate the pressure difference across the adsorbed liquid-gas interface gives 20 MPa for N2 and 140 MPa for H20[17]. Therefore, the graphitic micropore can offer the high pressure field from the macroscopic view. 

This, too, was the view of Duhem (Needham, 1996). There are many similarities in Ost-wald s and Duhem s understanding of chemical structure. For Duhem s views, see Needham (1998, pp. 50—55). See, also, Needham (1999a) on the ontological implications of the macroscopic view represented by thermodynamics. 

Popov E (1993) Light diflfaction by relief gratings a microscopic and macroscopic view. In Wolf E (ed) Progress in optics, vol 31. Elsevier, Amsterdam, pp 139-187... 

In choosing between these two models, one needs to consider the specific process. The use of mass transfer coefficients represents a lumped, more global view of the many process parameters that contribute to the rate of transfer of a species from one phase to another, while diffusion coefficients are part of a more detailed model. The first gives a macroscopic view, while the latter gives a more microscopic view of a specific part of a process. For this reason, the second flux equation is a more engineering representation of a system. In addition, most separation processes involve complicated flow patterns, limiting the use of Pick s Law. A description of correlations to estimate values of k for various systems is contained in Appendix B. 

Observations of the composition and behavior of matter are based on a macroscopic view. Matter that is large enough to be seen is called macroscopic, so all of your observations in chemistry, and everywhere else, start from this perspective. The macroscopic world is the one you touch, feel, smell, taste, and see. The properties of iron shown in Figure 1.3 are seen from a macroscopic perspective. But if you want to describe and understand the structure of iron, you must use a different perspective—one that allows you to see what can t be seen. What you can see of the New York City World Trade Center, shown in Figure 1.5, is similar to a macroscopic perspective. The actual structure of the building is hidden from view. 

In the same way, the appearance and properties of a piece of matter are the result of its structure. Although you may get hints of the actual structure from a macroscopic view, you must go to a submicroscopic perspective to understand how the hidden structure of matter influences its behavior. 

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