Century

Watson s vivid and outspoken account of how he and Crick discovered the structure of DNA (and won themselves a Nobel Prize) - one of the greatest scientific achievements of the century. 

A magnificent study of life, thoughr and art in 14th and 15th century France and the Netherlands, long established as a classic. 

Historical Slang Literary Terms Mathematics Twentieth Century History... 

For more than a century petroleum geologists have been looking for oil. During this period major discoveries have been made in many parts of the world. However, it is becoming increasingly likely that most of the giant fields have already been discovered and that future finds are likely to be smaller, more complex, fields. This is particularly true for mature areas like the North Sea. 

These effects were recorded in Greece around 2500 years ago and not long afterwards Democritus proposed an atomic structure for all matter. The magnetic compass seems to have taken another 1500 years to appear and magnetic theory a further half century. 

Although Gibbs published his monumental treatise on heterogeneous equilibrium in 187S, his work was not generally appreciated until the turn of the century, and it was not until many years later that the field of surface chemistry developed to the point that experimental applications of the Gibbs equation became important. 

To first order, the dispersion (a-a) interaction is independent of the structure in a condensed medium and should be approximately pairwise additive. Qualitatively, this is because the dispersion interaction results from a small perturbation of electronic motions so that many such perturbations can add without serious mutual interaction. Because of this simplification and its ubiquity in colloid and surface science, dispersion forces have received the most significant attention in the past half-century. The way dispersion forces lead to long-range interactions is discussed in Section VI-3 below. Before we present this discussion, it is useful to recast the key equations in cgs/esu units and SI units in Tables VI-2 and VI-3. 

This section will concentrate on the motions of atoms within molecules— internal molecular motions —as comprehended by the revolutionary quantum ideas of the 20th century. Necessarily, limitations of space prevent many topics from being treated in the detail they deserve. Some of these are treated in more detail in... 

The miderstanding of molecular motions is necessarily based on quaiitum mechanics, the theory of microscopic physical behaviour worked out in the first quarter of the 20th century. This is because molecules are microscopic systems in which it is impossible—or at least very dangerous —to ignore the dual wave-particle nature of matter first recognized in quaiitum theory by Einstein (in the case of classical waves) and de Broglie (in the case of classical particles). 

Knowledge of internal molecular motions became a serious quest with Boyle and Newton, at the very dawn of modem natural science. Flowever, real progress only became possible with the advent of quantum theory in the 20th century. The study of internal molecular motion for most of the century was concerned primarily with molecules near their equilibrium configuration on the PES. This gave an enonnous amount of inunensely valuable infonuation, especially on the stmctural properties of molecules. 

One of the most significant achievements of the twentieth century is the description of the quantum mechanical laws that govern the properties of matter. It is relatively easy to write down the Hamiltonian for interacting fennions. Obtaining a solution to the problem that is sufficient to make predictions is another matter. 

The existence of intennolecular interactions is apparent from elementary experimental observations. There must be attractive forces because otherwise condensed phases would not fomi, gases would not liquefy, and liquids would not solidify. There must be short-range repulsive interactions because otherwise solids and liquids could be compressed to much smaller volumes with ease. The kernel of these notions was fomuilated in the late eighteenth century, and Clausius made a clear statement along the lines of this paragraph as early as 1857 [1]. 

An older treatment that contains a wealth of references to tlie earlier literature, and an interesting history of the subject begiimmg with the work of Clairault in the mid-eighteentli century. 

At its foundation level, statistical mechanics mvolves some profound and difficult questions which are not fiilly understood, even for systems in equilibrium. At the level of its applications, however, the rules of calculation tliat have been developed over more than a century have been very successfLil. 

Flalf a century later Van Konynenburg and Scott (1970, 1980) [3] used the van der Waals equation to derive detailed phase diagrams for two-component systems with various parameters. Unlike van Laar they did not restrict their treatment to the geometric mean for a g, and for the special case of b = hgg = h g (equalsized molecules), they defined two reduced variables. 

Levelt Sengers J M H 1976 Critical exponents at the turn of the century Phys/ca A 82 319-51... 

Crutzen P J 1995 Overview of tropospheric chemistry developments during the past quarter century and a look ahead Faraday Disouss. 100 1-21... 

Ion chemistry is a product of the 20th century. J J Thomson discovered the electron in 1897 and identified it as a constituent of all matter. Free positive ions (as distinct from ions deduced to exist in solids or electrolytes) were first produced by Thomson just before the turn of the century. He produced beams of light ions, and measured their mass-to-charge ratios, in the early 1900s, culminating in the discovery of two isotopes of neon in 1912 [1]. This year also marked Thomson s discovery of which turns out to be the... 

Undeniably, one of the most important teclmological achievements in the last half of this century is the microelectronics industry, the computer being one of its outstanding products. Essential to current and fiiture advances is the quality of the semiconductor materials used to construct vital electronic components. For example, ultra-clean silicon wafers are needed. Raman spectroscopy contributes to this task as a monitor, in real time, of the composition of the standard SC-1 cleaning solution (a mixture of water, H2O2 and NH OH) [175] that is essential to preparing the ultra-clean wafers. 

Spectroscopy, or the study of the interaction of light with matter, has become one of the major tools of the natural and physical sciences during this century. As the wavelength of the radiation is varied across the electromagnetic spectrum, characteristic properties of atoms, molecules, liquids and solids are probed. In the... 

As discussed in more detail elsewhere in this encyclopaedia, many optical spectroscopic methods have been developed over the last century for the characterization of bulk materials. In general, optical spectroscopies make use of the interaction of electromagnetic radiation with matter to extract molecular parameters from the substances being studied. The methods employed usually rely on the examination of the radiation absorbed. 

Wang J, Tian B, Wang J, Lu J, Olsen C, Yarnitzky C, Olsen K, Hammerstrom D and Bennett W 1999 Stripping analysis Into the 21st century faster, smaller, cheaper, simpler and better Tina/. Chim. Acta 385 429... 

Zewail A H 1994 Femtochemistry. Uitrafast Dynamics of the chemicai Bond (Worid Scientific Series in 20th Century Chemistry, voi 3) (Singapore World Scientific)... 

We are all familiar with tire tliree states of matter gases, liquids and solids. In tire 19tli century the liquid crystal state was discovered [1 and 2] tliis can be considered as tire fourtli state of matter [3].The essential features and properties of liquid crystal phases and tlieir relation to molecular stmcture are discussed here. Liquid crystals are encountered in liquid crystal displays (LCDs) in digital watches and otlier electronic equipment. Such applications are also considered later in tliis section. Surfactants and lipids fonn various types of liquid crystal phase but this is discussed in section C2.3. This section focuses on low-molecular-weight liquid crystals, polymer liquid crystals being discussed in tire previous section. 

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