Realizability definition

An experimental teclmique that is usefiil for structure studies of biological macromolecules and other crystals with large unit cells uses neither the broad, white , spectrum characteristic of Lane methods nor a sharp, monocliromatic spectrum, but rather a spectral band with AX/X 20%. Because of its relation to the Lane method, this teclmique is called quasi-Laue. It was believed for many years diat the Lane method was not usefiil for structure studies because reflections of different orders would be superposed on the same point of a film or an image plate. It was realized recently, however, that, if there is a definite minimum wavelengdi in the spectral band, more than 80% of all reflections would contain only a single order. Quasi-Laue methods are now used with both neutrons and x-rays, particularly x-rays from synclirotron sources, which give an intense, white spectrum. 

The new international temperature scale, known as ITS-90, was adopted in September 1989. However, neither the definition of thermodynamic temperature nor the definition of the kelvin or the Celsius temperature scales has changed it is the way in which we are to realize these definitions that has changed. The changes concern the recommended thermometers to be used in different regions of the temperature scale and the list of secondary standard fixed points. The changes in temperature determined using ITS-90 from the previous IPTS-68 are always less than 0.4 K, and almost always less than 0.2 K, over the range 0-1300 K. 

Step-growth polymerizations can be schematically represented by one of the individual reaction steps VA + B V —> Vab V with the realization that the species so connected can be any molecules containing A and B groups. Chain-growth polymerization, by contrast, requires at least three distinctly different kinds of reactions to describe the mechanism. These three types of reactions will be discussed in the following sections in considerable detail. For now our purpose is to introduce some vocabulary rather than develop any of these beyond mere definitions. The principal steps in the chain growth mechanism are the following ... 

In use, a mantle of ice is frozen onto the outer surface of the thermometer weU. A common way to do this is to fiU the weU with cmshed dry ice until the mantle achieves a good thickness. Descriptions of the technique for doing this are given in several pubHcations and in manufacturers Hterature. The temperature of the water triple point is 0.01°C, or 273.16 K, by definition. In practice, that temperature can be realized in the ceU within 0.00015 K of the definition. In contrast, a bath of ice and water for producing the temperature 0°C is difficult to estabHsh with an accuracy better than 0.002°C. 

In order to increase the precision of realization of the base unit meter, the definition based on the wavelength of a krypton-86 radiation was replaced in 1983 by one based on the speed of light. Also added were the prefixes zetta (Z) for 10, zepto (z) for 10 , yotta (Y) for 10 , and yocto (y) for 10 . 

More definitive evidence for the formation of an oxirene intermediate or transition state was presented recently by Cormier 80TL2021), in an extension of his earlier work on diazo ketones 77TL2231). This approach was based on the realization that, in principle, the oxirene (87) could be generated from the diazo ketones (88) or (89) via the oxocarbenes 90 or 91) or from the alkyne (92 Scheme 91). If the carbenes (90) (from 88) and (91) (from 89) equilibrate through the oxirene (87), and if (87) is also the initial product of epoxidation of (92), then essentially the same mixture of products (hexenones and ketene-derived products) should be formed on decomposition of the diazo ketones and on oxidation of the alkyne this was the case. 

To reiterate the definition of chromatographic resolution a separation is achieved in a chromatographic system by moving the peaks apart and by constraining the peak dispersion so that the individual peaks can be eluted discretely. Thus, even if the column succeeds in meeting this criterion, the separation can still be destroyed if the peaks are dispersed in parts of the apparatus other than the column. It follows that extra-column dispersion must be controlled and minimized to ensure that the full performance of the column is realized. 

These are the characteristics which need to be specified and their achievement controlled, assured, improved, managed, and demonstrated. These are the characteristics which form the subject matter of the specified requirements referred to in ISO 9000. When the value of these characteristics is quantified or qualified they are termed quality requirements or requirements for quality. ISO 8402 1994 defines requirements for quality as an expression of the needs or their translation into a set of quantitatively or qualitatively stated requirements for the characteristics of an entity to enable its realization and examination. While rather verbose, this definition removes the confusion over quality requirements and technical requirements. (An additional definition is provided in Appendix A.) Technical requirements for a product or service are quality requirements. The requirements of ISO 9000 are quality system requirements. 

If a quality record was intended to be any document generated or used by the quality system, the definition would surely have indicated this. If we decompose the definition further, requirements for quality are defined in ISO 8402 as the expression of the needs or their translation into a set of quantitatively stated requirements for the characteristics of an entity to enable its realization and examination. Clearly, such a requirement would be a contract, product specification, design requirement, etc. This implies that any product verification records are quality records, but it rules out any recorded information as being a quality record. 

First, we must realize that many variables exist in any structural design. We can make a list of structural variables such as sizes, lengths of objects, materials, laminae orientations, and so on. those variables all have influence just as column length, moment of inertia, and Young s modulus influence column-buckling loads. The complete list of design variables will be called the vector Xj, and that vector will have N components. That list constitutes the definition of the structural configuration. 

As early as 1895, Knorr realized that three types of derivatives could be formed for this type of compound, corresponding to the three tautomeric structures. Other early investigators assigned an 0X0 structure to these compounds on the basis of tenuous chemical evidence, while still others discussed the tautomerism without reaching any definite conclusions. ... 

Although beyond the scope of the present discussion, another key realization that has shaped the definition of click chemistry in recent years was that while olefins, through their selective oxidative functionalization, provide convenient access to reactive modules, the assembly of these energetic blocks into the final structures is best achieved through cydoaddition reactions involving carbon-het-eroatom bond formation, such as [l,3]-dipolar cydoadditions and hetero-Diels-Al-der reactions. The copper(i)-catalyzed cydoaddition of azides and terminal alkynes [5] is arguably the most powerful and reliable way to date to stitch a broad variety... 

Operations research has occasionally been defined as the art of giving bad answers to questions that would otherwise receive worse answers. The significance of this definition is best realized by those who have looked seriously at the world about them. 

The importance of twinned crystals in demonstrating that nucleation is the relevant growth mechanism has been realized since 1949 [64, 99]6. They were first investigated extensively in polymer crystals by Blundell and Keller [82] and they have recently received increased attention as a means of establishing, or otherwise, the nucleation postulate for lamellar growth [90, 91, 95,100-102]. The diversity of opinion in the literature shows that it is very difficult to draw definite conclusions from the experimental evidence, and the calculations are often founded upon implicit assumptions which may or may not be justified. We therefore restrict our discussion to an introduction to the problem, the complicating features which make any a priori assumptions difficult, and the remaining information which may be fairly confidently deduced. 

The problem with the Arrhenius definitions is that they are specific to one particular solvent, water. When chemists studied nonaqueous solvents, such as liquid ammonia, they found that a number of substances showed the same pattern of acid-base behavior, but plainly the Arrhenius definitions could not be used. A major advance in our understanding of what it means to be an acid or a base came in 1923, when two chemists working independently, Thomas Lowry in England and Johannes Bronsted in Denmark, came up with the same idea. Their insight was to realize that the key process responsible for the properties of acids and bases was the transfer of a proton (a hydrogen ion) from one substance to another. The Bronsted-Lowry definition of acids and bases is as follows ... 

Since the early 1970s a panel convened by the International Union of Pure and Applied Chemistry and the International Union of Biochemistry and Molecular Biology has been working to formulate recommendations for carbohydrate nomenclature that meet developing needs of research and electronic data handling, while retaining links to the established literature base on carbohydrates. The realization of these endeavors is presented here in the final document Nomenclature of Carbohydrates, which provides a definitive reference for current researchers, both in the text version and in the version accessible on the World Wide Web (http //www.chem.qmw.ac.uk/iupac/2carb/), where amendments and revisions are maintained. 

Clean and Polluted Air. In the development of atmospheric chemistry, there has been an historic separation between those studying processes in the natural or unpolluted atmosphere, and those more concerned with air pollution chemistry. As the field has matured, these distinctions have begun to disappear, and with this disappearance has come the realization that few regions of the troposphere are completely unaffected by anthropogenic emissions. An operational definition of clean air could be based upon either the NMHC concentration, or upon the NOjj concentration. 

Combustion has a very long history. From antiquity up to the middle ages, fire along with earth, water, and air was considered to be one of the four basic elements in the universe. However, with the work of Antoine Lavoisier, one of the initiators of the Chemical Revolution and discoverer of the Law of Conservation of Mass (1785), its importance was reduced. In 1775-1777, Lavoisier was the first to postulate that the key to combustion was oxygen. He realized that the newly isolated constituent of air (Joseph Priestley in England and Carl Scheele in Sweden, 1772-1774) was an element he then named it and formulated a new definition of combustion, as the process of chemical reactions with oxygen. In precise, quantitative experiments he laid the foundations for the new theory, which gained wide acceptance over a relatively short period. 

As surface area and pore structure are properties of key importance for any catalyst or support material, we will first describe how these properties can be measured. First, it is useful to draw a clear borderline between roughness and porosity. If most features on a surface are deeper than they are wide, then we call the surface porous (Fig. 5.16). Although it is convenient to think about pores in terms of hollow cylinders, one should realize that pores may have all kinds of shapes. The pore system of zeolites consists of microporous channels and cages, whereas the pores of a silica gel support are formed by the interstices between spheres. Alumina and carbon black, on the other hand, have platelet structures, resulting in slit-shaped pores. All support materials may contain micro, meso and macropores (see text box for definitions). 

Numbering-up can be performed in two ways (Figure 1.4). External numhering-up is referred to as the connection of many devices in a parallel fashion [8] (a similar, but less elaborate, definition was already provided in [9, 10] see also [11] for a realized industrial example). A device in the sense as it is used here is defined as a functional element, e.g. a micro-mixing flow configuration such as an interdigital... 

Another important use of RMs is the maintenance of conventional scales. The octane number of gasoline is an example of such a scale. The scale is defined through chemicals. This definition can be realized through RMs. Another example is the pH scale, which is defined by buffers with pH = 4, pH = 7, and pH = 10. These buffers are defined as mixtures of salts, dissolved in water. These define the pH scale can be used by laboratories for the purpose of calibrating their pH meters. 

Those ions which take no part in the reaction are known as spectator ions , and from these considerations, the following definitions can be derived. A basic oxide (or hydroxide) is a metallic oxide (or hydroxide) which contains the 02 (or OFT) ion it will react with an acid to form a salt and water only. It is necessary to realize the importance of the word only in this definition, as were it to be omitted, then certain compounds which are quite different from basic metallic oxides and hydroxides would be covered by this definition. Thus, Pb(IV) oxide reacts with hydrochloric acid to produce Pb(II) chloride (a salt) and water, but does not belong to the class of bases because chlorine gas is also produced ... 

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