TOPICAL structure

Related topics Structures and roles of fatty acids Triacylglycerols (K4) (Kl) Fatty acid breakdown (K2)... 

To summarize this topic, structure-based methods are extremely helpful in creating ideas for new scaffolds and further optimization strategies. 

The EIBC Books are referred to as spin-on books, recognizing that all the articles in these thematic volumes are destined to become part of the online content of EIBC, usually forming a new category of articles in the EIBC topical structure. We find that this provides multiple routes to finding the latest summaries of current research. 

In order to cover these novel developments, the chapters of the previous edition have not only been updated but new chapters have been added. For this purpose, the topical structure of the new edition had to be extended and is now subdivided into four parts. In Part 1, the fundamentals of the instrumentation for infrared and Raman imaging and mapping and an overview on the chemometric tools for image analysis are treated in two introductory chapters. Part 2 comprises Chapters 3-10 and describes a wide variety of applications ranging from biomedical via food, agriculture, and plants to polymers and pharmaceuticals. In Part 3, Chapters 11 and 12 describe imaging techniques operating beyond the diffraction limit, and finally Part 4 (Chapters 13-15) covers special methodical developments and their utility in specific fields. 

The topic of capillarity concerns interfaces that are sufficiently mobile to assume an equilibrium shape. The most common examples are meniscuses, thin films, and drops formed by liquids in air or in another liquid. Since it deals with equilibrium configurations, capillarity occupies a place in the general framework of thermodynamics in the context of the macroscopic and statistical behavior of interfaces rather than the details of their molectdar structure. In this chapter we describe the measurement of surface tension and present some fundamental results. In Chapter III we discuss the thermodynamics of liquid surfaces. 

The succeeding material is broadly organized according to the types of experimental quantities measured because much of the literature is so grouped. In the next chapter spread monolayers are discussed, and in later chapters the topics of adsorption from solution and of gas adsorption are considered. Irrespective of the experimental compartmentation, the conclusions as to the nature of mobile adsorbed films, that is, their structure and equations of state, will tend to be of a general validity. Thus, only a limited discussion of Gibbs monolayers has been given here, and none of such related aspects as the contact potentials of solutions or of adsorption at liquid-liquid interfaces, as it is more efficient to treat these topics later. 

Microemulsions are treated in a separate section in this chapter. Unlike macro- or ordinary emulsions, microemulsions are generally thermodynamically stable. They constitute a distinctive type of phase, of structure unlike ordinary homogeneous bulk phases, and their study has been a source of fascination. Finally, aerosols are discussed briefly in this chapter, although the topic has major differences from those of emulsions and foams. 

The plan of this chapter is as follows. We discuss chemisorption as a distinct topic, first from the molecular and then from the phenomenological points of view. Heterogeneous catalysis is then taken up, but now first from the phenomenological (and technologically important) viewpoint and then in terms of current knowledge about surface structures at the molecular level. Section XVIII-9F takes note of the current interest in photodriven surface processes. 

HIrsch A (ed) 1999 Fuiierenes and Reiated Structures (Topics in Current Chemistry 199) (Berlin Springer)... 

To get to know various databases covering the topics of bibliographic data, physicochemical properties, and spectroscopic, crystallographic, biological, structural, reaction, and patent data... 

More than 10 000 databases exist that provide a small or large amount of data on various topics (including chemistry). The contents in databases are supplied by approximately 3500 database developers (e.g., the Chemical Abstracts Service, MDL Information Systems, etc.). Since there is a variety of topics from economics to science, as well as a variety of structures of the database, only some of the vendors (-2000) offer one or more databases as either local or as online databases (Figure 5-4) [4]. Usually, databases are provided by hosts that permit direct access to more than one database. The search occurs primarily through different individual soft-... 

The Chemical Abstracts System (CAS) produces a set of various databases ranging from bibliographic to chemical structure and reaction databases. All the databases originate from the printed media of Chemical Abstracts, which was first published in 1907 and is divided into different topics. Author index, general index, chemical structure index, formula index, and index guide arc entries to the corresponding database (Table 5-3). 

Then, in the early and mid-1 990s, CAS developed SciFinder and SciFinder Sc ho lar to address the needs of professional chemists and other scientists. SciFinder was developed to allow more intelligence in data access, such as smart structure searching, research topic exploration, advanced author searching, and powerful refine and analysi.s capabilities including categorize and panorama". 

The investigation of molecular structures and of their properties is one of the most fascinating topics in chemistry. Chemistry has a language of its own for molecular structures which has been developed from the first alchemy experiments to modem times. With the improvement of computational methods for chemical information processing, several descriptors for the handling of molecular information have been developed and used in a wide range of applications. 

A most important task in the handling of molecular data is the evaluation of "hidden information in large chemical data sets. One of the differences between data mining techniques and conventional database queries is the generation of new data that are used subsequently to characterize molecular features in a more general way. Generally, it is not possible to hold all the potentially important information in a data set of chemical structures. Thus, the extraction of relevant information and the production of reliable secondary information are important topics. 

I ll e con cept of a param cter set is an iin port an t (but often in con vc-nicnl) aspect of molecular m cchan ics calculation s. Molecular m ech an ics tries (o use experirn cn la I data to replace a priori com pu-tation, but in m an y situation s the experirn en tal data is n ot kn own and a parameter is missing. Collecting parameters, verification of their validity, and the relation ship of these molecular mechanics parameters to chemical and structural moieties are all important an d difficult topics. 

Porphyrins and chlorophylls are the most widespread natural pigments. They are associated with the energy-converting processes of respiration and photosynthesis in living organisms, and the synthesis of specific porphyrin derivatives is often motivated by the desire to perform similar processes in the test tube. The structurally and biosynthetically related corrins (e.g. vitamin B,j) catalyze alkylations and rearrangements of carbon skeletons via organocobalt intermediates. The biosyntheses of these chromophores are also of topical interest. 

Each of the following reactions has been described in the chemical literature and involves an organic starting matenal somewhat more complex than those we have encountered so far Nevertheless on the basis of the topics covered in this chapter you should be able to wnte the structure of the principal organic product of each reaction... 

An important concern to chemists is synthesis the challenge of preparing a particular compound m an economical way with confidence that the method chosen will lead to the desired structure In this section we will introduce the topic of synthesis emphasiz mg the need for systematic planning to decide what is the best sequence of steps to con vert a specified sfarfmg mafenal fo a desired producf (fhe target molecule)... 

The Stvfl mechanism is an ionization mechanism The nucleophile does not participate until after the rate determining step has taken place Thus the effects of nucleophile and alkyl halide structure are expected to be different from those observed for reactions pro ceedmg by the 8 2 pathway How the structure of the alkyl halide affects the rate of Stvfl reactions is the topic of the next section... 

The article A History of the Structural Theory of Benzene—The Aromatic Sex tet and Huckel s Rule in the February 1997 issue of the Journal of Chemical Educa tion (pp 194-201) IS a rich source of additional informa tion about this topic... 

How living systems convert acetate to fats is an exceedingly complex story one that IS well understood m broad outline and becoming increasingly clear m detail as well We will examine several aspects of this topic m the next few sections focusing mostly on Its structural and chemical features... 

Analytical chemistry is inherently a quantitative science. Whether determining the concentration of a species in a solution, evaluating an equilibrium constant, measuring a reaction rate, or drawing a correlation between a compound s structure and its reactivity, analytical chemists make measurements and perform calculations. In this section we briefly review several important topics involving the use of numbers in analytical chemistry. 

A variety of experimental techniques have been employed to research the material of this chapter, many of which we shall not even mention. For example, pressure as well as temperature has been used as an experimental variable to study volume effects. Dielectric constants, indices of refraction, and nuclear magnetic resonsance (NMR) spectra are used, as well as mechanical relaxations, to monitor the onset of the glassy state. X-ray, electron, and neutron diffraction are used to elucidate structure along with electron microscopy. It would take us too far afield to trace all these different techniques and the results obtained from each, so we restrict ourselves to discussing only a few types of experimental data. Our failure to mention all sources of data does not imply that these other techniques have not been employed to good advantage in the study of the topics contained herein. 

All polymer molecules have unique features of one sort or another at the level of individual repeat units. Occasional head-to-head or tail-to-tail orientations, random branching, and the distinctiveness of chain ends are all examples of such details. In this chapter we shall focus attention on two other situations which introduce variation in structure into polymers at the level of the repeat unit the presence of two different monomers or the regulation of configuration of successive repeat units. In the former case copolymers are produced, and in the latter polymers with differences in tacticity. Although the products are quite different materials, their microstructure can be discussed in very similar terms. Hence it is convenient to discuss the two topics in the same chapter. 

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