Drawings pictorial

The next most important aspect of a molecular compound is its shape. The pictorial representations of molecules that most accurately show their shapes are images based on computation or software that represents atoms by spheres of various sizes. An example is the space-filling model of an ethanol molecule shown in Fig. C.2a. The atoms are represented by colored spheres (they are not the actual colors of the atoms) that fit into one another. Another representation of the same molecule, called a ball-and-stick model, is shown in Fig. C.2b. Each ball represents the location of an atom, and the sticks represent the bonds. Although this kind of model does not represent the actual molecular shape as well as a space-filling model does, it shows bond lengths and angles more clearly. It is also easier to draw and interpret. 

Following is a pictorial vector representation of a doublet. It shows the evolution of the components of a signal. Draw vector positions in the fourth and fifth frames, along with their directions of rotation. 

Pictorial models are a helpful part of documenting a design. Unfortunately, it is a common error to treat the pictures as the sole focus of documentation or design activities. Teams spend a real lot of money on modeling tools, draw lots of pictures using these tools, and then expect to press a button to generate well-structured, clear, explanatory documentation. Sadly, it does not usually turn out exactly that way. 

The same thing applies to larger pictorial models with associations. Some methodologists have argued that the tendency to draw models with several types and associations is antipathetic to encapsulation. This would be true if the boxes represented classes and if the lines represented their variables Each class should be separately designed, independently of the others. But when the boxes are types and the lines merely abstract attributes, the issue of encapsulation is much weaker. 

The attributes of a complex object are usually expressed in terms of types, which themselves are modeled with other attributes and so on. Drawing them pictorially shows the relationships more clearly. When an object is specified, the types of attributes are chosen for their expressiveness rather than for execution efficiency. Some of these specification types invented to help model a set of actions may never be implemented directly however, the type model must constitute a valid abstraction of the implementation, as documented in a refinement and its justification. The types that are implemented are those generated by decomposition they must exist because the design calls for them to interact with one another. 

To show this technique pictorially, for every directed association between classes, draw the link instead to a type specification (in C++, a pure abstract class in Java, an interface). The original target of the link is a subclass (Java implementor) of this specification. In Figure 16.9 we have decided that a Book is loaned not to a Member but to a BookHolder, of which Member is only one possible implementation. 

This is a very useful approach, and what follows is not meant to replace it so much as to offer a different viewpoint. In the present scheme, there are two very broad categories of structure—"fishnet" and "lattice", which can. in fact, be achieved by a variety of mechanisms. Thus, the viewpoint offered below is strongly tied to the end structure of the gel. 2uid only indirectly to chemical properties which produce them. The various structures are defined in the text, but use is also made of simple drawings. It is hoped that others will adopt the wider use of simple pictorial diagrams for the description of gel structures. 

A wavefunction ip and its eigenvalue E define an orbital. The orbital is therefore an energy level available for electrons and it implies the relevant electron distribution. In mathematical models, these distributions extend to infinity, but in a pictorial representation it is sufficient to draw the volume in which the probability of presence of the electron is rather arbitrarily around 90%. The spatial distribution of atomic and molecular orbitals have implications for processes of electron tunneling (section 4.2.1). 

Book of Art A Pictorial Encyclopedia of Painting, Drawing and Sculpture. New York Grolier, 1994. 

Fig. 7. Pictorial representation of a Covalon ei(pi, C) traveling in chain A creating plasmon wave that affects another Covalon e, (p,, tj) in chain A to move toward (p2,t2). Since at t2 the plasmon wave changes its sign, the Covalon continues to move toward (p.3, C) and so on. It is not shown in the drawing but chain A now emits its own plasmon wave back to chain A thus creating a cooperative effect.

Fig.1. Pictorial drawing of the RPMS. The beam inflector magnet is the first component at the left,followed by the bellows system and target chamber, aperature holder, quadrupole doublet, Wein filter(5 m. long),magnetic dipole and pivoting "tail" with quadrupole doublet and focal plane detectors at the right end.

Here (p,

inactive orbitals for each VB structure, L and R are the active orbitals of the left and right fragments, respectively, and the subscripts n and a stand for neutral and anionic fragments, respectively (recall that the cationic fragments have only inactive orbitals and no active ones). Note that the inactive orbitals (pi, (pi and (pi" of TVT11 are all different from each other, as are the active orbitals Ln, La, or Rn, Ra. These differences are pictorially represented in 9-11 by drawing orbitals with different sizes depending on the identity of the species as neutral, cationic or anionic. 

When you have read through all tire different types of reaction mechanism, practise drawing them out with and without the help of the book. Complete the exercises at the end of the chapter and then try to devise mechanisms for other reactions that you may know. You now have the tools to draw out in the universal pictorial language of organic chemists virtually all the mechanisms for the reactions you will meet in this book and more besides ... 

Although drawings provide a pictorial representation of uterfxxhemistrv. they are difficult to translate into words. Thus, a verbal method for indicating the three-dimensional arrangement of atoms, or configuration, at... 

The most commonly used pictorial representation for a wavefunction is called the boundary surface and it is used to give a three-dimensional perspective of most of the electron density in an orbital. Usually these shapes are drawn so that their volume contains about 95% of the electron density in a molecular orbital. It is instmctive to draw them in a process that first sketches the atomic orbitals as separated functions and then brings them together, allowing mixing to occur via the secular determinant (see (14)). 

Gerischer s distribution curves can be interpreted as representing the energy dependence of the electron transfer rate constants involving the reduced and oxidized species. Only a few electrochemical studies have attempted to evaluate the model and quantify the distributions and reorganizational parameters [17, 18]. Nevertheless, it has become common practice to draw a pictorial representation of the distributions when discussing interfacial electron transfer kinetics relevant to dye sensitization. 

Figure 4.25. Pictorial representation of a non-equilibrated surface layer, indicating the transport processes that may occur in it. Cartesian co-ordinates zl surface, counting downwards from z = 0 in the surface x parallel to the surface on the right y parallel to the surface, normal to the plane of drawing. Desorption is ignored. Further discussion in the text.

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