High-throughput screening and combinatorial chemistry are two of the most potent weapons ever to have been used in the discovery of new drugs. At a stroke, it seems to be possible to synthesise more molecules in a month than have previously been made in the whole of the distinguished history of organic chemistry, Furthermore, all the molecules can be screened in the same short period. However, like any weapons of immense power, these techniques must be used with care, to achieve maximum impact. The costs of implementing and running high-throughput screening and combinatorial chemistry are high, as large dedicated facilities must be built and staffed. In addition, the sheer number of chemical leads generated may overwhelm the lead optimisation teams in a hail of friendly fire. Mother nature has not entirely surrendered, as the number of building blocks that could be used to build libraries would require more atoms than there are in the universe. In addition, the progress made by the Human Genome Project has uncovered many proteins with different functions but related binding sites, creating issues of selectivity. Advances in the new field of pharmacogenomics will produce more of these challenges. There is a real need to make hi- throughput screening and combinatorial chemistry into 'smart' weapons, so that their power is not dissipated. That is the challenge for modellers, computational chemists, cheminformaticians and IT experts. In this book, we have broken down this grand challenge into key tasks.

There is a great dispar.ity between the ability of the major industrial nations to produce and distribute chemicals and our ability to comprehend the nature and potential severity of unintended consequences for man, his life support systems and the environment generally. Furthermore, the gap between our ability to produce and distribute myriad chemicals and our ability to identify, understand or predict unfavorable environmental impacts may widen. As environmental scientists we are conscious of the interrelatedness, not only of environmental systems, but of nations as well. Materials are continually moved across boundaries by human as well as natural agencies. The extent, rate and nature of transfer for most pollutants is largely unknown. We can only guess which of the numerous chemicals produced are candidates for concern. More important still is our practical ignorance of the mechanisms of chronic effects upon natural systems and of the concentrations, combinations and circumstances that may lead to irreversibilities or to serious consequences for man. We know very little also regarding the potential for or the kinds of indirect effects that might occur. With respect to the environmentltself, we know little of its assimilative capacity with regard to widely dispersed pollutants and their transformation products. But what we do know is disquieting, and a much-improved system for the evaluation and management of toxic and hazardous chemicals is needed.

High-throughput screening and combinatorial chemistry are two of the most potent weapons ever to have been used in the discovery of new drugs. At a stroke, it seems to be possible to synthesise more molecules in a month than have previously been made in the whole of the distinguished history of organic chemistry, Furthermore, all the molecules can be screened in the same short period. However, like any weapons of immense power, these techniques must be used with care, to achieve maximum impact. The costs of implementing and running high-throughput screening and combinatorial chemistry are high, as large dedicated facilities must be built and staffed. In addition, the sheer number of chemical leads generated may overwhelm the lead optimisation teams in a hail of friendly fire. Mother nature has not entirely surrendered, as the number of building blocks that could be used to build libraries would require more atoms than there are in the universe. In addition, the progress made by the Human Genome Project has uncovered many proteins with different functions but related binding sites, creating issues of selectivity. Advances in the new field of pharmacogenomics will produce more of these challenges. There is a real need to make hi- throughput screening and combinatorial chemistry into 'smart' weapons, so that their power is not dissipated. That is the challenge for modellers, computational chemists, cheminformaticians and IT experts. In this book, we have broken down this grand challenge into key tasks.

There is a great dispar.ity between the ability of the major industrial nations to produce and distribute chemicals and our ability to comprehend the nature and potential severity of unintended consequences for man, his life support systems and the environment generally. Furthermore, the gap between our ability to produce and distribute myriad chemicals and our ability to identify, understand or predict unfavorable environmental impacts may widen. As environmental scientists we are conscious of the interrelatedness, not only of environmental systems, but of nations as well. Materials are continually moved across boundaries by human as well as natural agencies. The extent, rate and nature of transfer for most pollutants is largely unknown. We can only guess which of the numerous chemicals produced are candidates for concern. More important still is our practical ignorance of the mechanisms of chronic effects upon natural systems and of the concentrations, combinations and circumstances that may lead to irreversibilities or to serious consequences for man. We know very little also regarding the potential for or the kinds of indirect effects that might occur. With respect to the environmentltself, we know little of its assimilative capacity with regard to widely dispersed pollutants and their transformation products. But what we do know is disquieting, and a much-improved system for the evaluation and management of toxic and hazardous chemicals is needed.

Terahertz physics covers one of the least explored but richest regions of the electromagnetic spectrum. Designed for independent learning, this is the first book to open up this exciting new field to students of science and engineering. Written in a clear and consistent style, the textbook focuses on an understanding of fundamental physical principles at terahertz frequencies and their applications. Part I outlines the foundations of terahertz science, starting with the mathematical representation of oscillations before exploring terahertz-frequency light, terahertz phenomena in matter and the terahertz interactions between light and matter. Part II covers components of terahertz technology, from sources of terahertz frequency radiation, through the manipulation of the radiation, to its detection. Part III deals with applications, including time-domain spectroscopy. Highlighting modern developments and concepts, the book is ideal for self-study. It features precise definitions, clear explanations, instructive illustrations, fully worked examples, numerous exercises and a comprehensive glossary.